of 23 /23
Journal of Oceanography Vol. 48, pp. 305 to 327. 1992 Phytoplankton Pigment Distributions in Regional Upwelling around the Izu Peninsula Detected by Coastal Zone Color Scanner on May 1982 J. ISHIZAKA 1 , H. FUKUSHIMA 2 , M. KISHINO 3 , T. SAINO 4 and M. TAKAHASHI 5 1 National Institute for Resources and Environment, Tsukuba 305, Japan 2 High-Technology for Human Welfare, Tokai University, Numazu 410-03, Japan 3 The Institute of Physical and Chemical Research, Wako 351-01, Japan 4 Ocean Research Institute, University of Tokyo, Nakano-ku, Tokyo 164, Japan 5 Department of Botany, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan (Received 20 January 1992; in revised form 17 April 1992; accepted 24 April 1992) Phytoplankton pigment (chlorophyll a + pheopigments) distributions in a regional upwelling around the Izu Peninsula obtained by the Coastal Zone Color Scanner (CZCS) on May 23, 1982, were compared with ship-observed pigment and satellite sea-surface-temperature distributions. Pigment concentrations detected by the CZCS were positively correlated with the ship-observed pigment concentrations. However, they were about factor of 5 smaller when atmospheric correction parameters known for typical oceanic and land aerosol were used and when the parameters were estimated with the “clear water algorithm”. When the atmospheric correction parameters were adjusted so that a pigment concentration derived by CZCS was equivalent to a concentration obtained by the ship at a coincide location, the pattern and magnitudes of the CZCS-derived pigment distributions showed remarkable agreement with ship-observed pigment distributions. Thus, the nor- mal atmospheric correction algorithm may not be suitable for waters around Japan, and the development of better atmospheric correction methods combined with more verification programs is required. The pigment distributions showed patterns that were similar to those observed in sea-surface-temperature distri- butions. Cold water showed higher pigment concentrations, and warm water showed lower pigment concentrations. The Kuroshio, which can be identified by generally warm, low pigment water, showed a large meander which flowed offshore at Shiono-misaki, looped back onshore from Hachijo Island to Omaezaki and then flowed northeast along the Izu and Boso Peninsulas. Locally upwelled water along the Izu Peninsula was seen clearly in the sea-surface-temperature and CZCS pigment distributions as a region of cold water and high pigment concen- trations. Cold upwelled waters were also found at the eastern side of the Izu Islands, but pigment concentrations in these waters was not always high. This difference in the two upwelling regions may be caused by different physical and biological interactions. 1. Introduction Recent advances in remote sensing technology allow measurement of phytoplankton pigment (chlorophyll a + pheopigments, hereafter called “pigment”) concentrations in the surface layer of the ocean from space. The Coastal Zone Color Scanner (CZCS) was the first

Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

  • Upload
    others

  • View
    17

  • Download
    0

Embed Size (px)

Citation preview

Page 1: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Journal of OceanographyVol. 48, pp. 305 to 327. 1992

Phytoplankton Pigment Distributions in Regional Upwellingaround the Izu Peninsula Detected by Coastal Zone

Color Scanner on May 1982

J. ISHIZAKA1, H. FUKUSHIMA2, M. KISHINO3, T. SAINO4 and M. TAKAHASHI5

1National Institute for Resources and Environment, Tsukuba 305, Japan2High-Technology for Human Welfare, Tokai University, Numazu 410-03, Japan

3The Institute of Physical and Chemical Research, Wako 351-01, Japan4Ocean Research Institute, University of Tokyo, Nakano-ku, Tokyo 164, Japan

5Department of Botany, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan

(Received 20 January 1992; in revised form 17 April 1992; accepted 24 April 1992)

Phytoplankton pigment (chlorophyll a + pheopigments) distributions in a regionalupwelling around the Izu Peninsula obtained by the Coastal Zone Color Scanner(CZCS) on May 23, 1982, were compared with ship-observed pigment and satellitesea-surface-temperature distributions. Pigment concentrations detected by theCZCS were positively correlated with the ship-observed pigment concentrations.However, they were about factor of 5 smaller when atmospheric correctionparameters known for typical oceanic and land aerosol were used and when theparameters were estimated with the “clear water algorithm”. When the atmosphericcorrection parameters were adjusted so that a pigment concentration derived byCZCS was equivalent to a concentration obtained by the ship at a coincide location,the pattern and magnitudes of the CZCS-derived pigment distributions showedremarkable agreement with ship-observed pigment distributions. Thus, the nor-mal atmospheric correction algorithm may not be suitable for waters aroundJapan, and the development of better atmospheric correction methods combinedwith more verification programs is required. The pigment distributions showedpatterns that were similar to those observed in sea-surface-temperature distri-butions. Cold water showed higher pigment concentrations, and warm watershowed lower pigment concentrations. The Kuroshio, which can be identified bygenerally warm, low pigment water, showed a large meander which flowedoffshore at Shiono-misaki, looped back onshore from Hachijo Island to Omaezakiand then flowed northeast along the Izu and Boso Peninsulas. Locally upwelledwater along the Izu Peninsula was seen clearly in the sea-surface-temperature andCZCS pigment distributions as a region of cold water and high pigment concen-trations. Cold upwelled waters were also found at the eastern side of the IzuIslands, but pigment concentrations in these waters was not always high. Thisdifference in the two upwelling regions may be caused by different physical andbiological interactions.

1. IntroductionRecent advances in remote sensing technology allow measurement of phytoplankton

pigment (chlorophyll a + pheopigments, hereafter called “pigment”) concentrations in thesurface layer of the ocean from space. The Coastal Zone Color Scanner (CZCS) was the first

Page 2: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

306 J. Ishizaka et al.

sensor specifically designed for this purpose (Hovis et al., 1980; Gordon et al., 1980). This sensorwas on the Nimbus-7 satellite which was launched on November 1978 and was operated untilJune 1986. About 68,000 scenes from the world ocean, including about 4,000 scenes aroundJapan, were collected by the CZCS and are stored in an archive at the NASA Goddard SpaceFlight Center (Feldman et al., 1989; Ishizaka and Harashima, 1991). The CZCS sensor covereda region of 1636 km in each scan. This scan length allowed at least one measurement per day ofthe global ocean if the sensor power was on continuously. However, the sensor was not alwayscontinuously operated. The smallest spatial resolution of the sensor was 825 m.

During the CZCS operation, the data were compared with ship observations and accuracyof the CZCS measurements was determined. Most of the verification studies of CZCS mea-surements were conducted in waters around the U.S. coast. Errors in the measurements were onthe order of 30–40% but could be as large as a factor of 2 (Smith and Baker, 1982; Gordon et al.,1982, 1983; Gordon and Morel, 1983). Recent studies have focused on applications of CZCS datafor variety of ocean processes. These studies include using CZCS data for the statistical analysisof physical-biological interactions (cf. Abbott and Zion, 1987), estimation of primary production(cf. Platt and Sathyendranath, 1988; Sathyendranath et al., 1991a), comparisons to fisheriesdistributions, verification and improvement of physical-biological models (Ishizaka, 1990a, b,c), and estimation of processes contributing to phytoplankton concentration changes (McClainet al., 1990a). Recent applications of passive remote sensing in oceanography, including oceancolor are reviewed by Abbott and Chelton (1992).

The first use of the CZCS for studying the waters around Japan was by Sasaki et al. (1983)who obtained pigment concentrations for the Yellow Sea. More recently, Ogishima et al. (1986)and Hiramatsu et al. (1987) have pointed out problems with using the ordinary atmosphericcorrection methods for processing CZCS images from the waters around Japan. These studieshave indicated the usefulness and problems of using satellite ocean color remote sensing aroundJapan. However, because of the limited availability of coincident ships and CZCS measurements,there has been no attempt to make comparison between satellite and ship-observed pigments(Ishizaka and Harashima, 1991). Also, although the potential usefulness of CZCS data is clear,there have been few attempts to use CZCS data to understand oceanographic processes in watersaround Japan. Matsumura and Fukushima (1988) used CZCS pigment data to categorize therelations between satellite-derived pigment and sea-surface-temperature distributions aroundJapan. Recent works relating to ocean color studies in the waters around Japan are reviewed inFukushima and Ishizaka (1992).

There is much evidence that shows that regional upwelling occurs around Japan whichresults in enhanced biological production (Takahashi et al., 1980, 1986; Takahashi and Kishi,1984; Toda, 1989). However, the upwelling patterns change rapidly, which make it difficult toobserve the spatial distributions of the upwelling and associated phytoplankton variations withship surveys. Furthermore, regional ship surveys are not sufficient to determine relationshipsbetween local upwelling events and larger scale oceanographic phenomena, such as Kuroshiomeandering. Satellites are the only tool currently available that can instantaneously observe thespatial distribution of regional upwelling as well as the larger scale ocean patterns. Infrared sea-surface-temperature images provide an overall view of upwelling patterns as regions colder thanthe surrounding area, and ocean color images give pigment distributions which may be relatedto upwelling regions. Takahashi et al. (1981) used an airborne infrared sensor to map upwellingregions and found a series of cold vortices associated with upwelling at the eastern side of Oshima

Page 3: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 307

Island. Aikoh and Takahashi (1982) used satellite infrared images from the AVHRR/NOAA-6sensor, and found similar vortices around Oshima Island. Atkinson et al. (1987a) also showedthe upwelling regions around the Izu Peninsula and Islands in May, 1982, using the infraredimages of AVHRR/NOAA-7.

In this study, CZCS-derived pigment distributions were compared with ship-observedpigment patterns from the regional upwelling around the Izu Peninsula, Japan that were measuredon May 23, 1982. The pigment distributions were described in terms of the regional upwellingand associated biological production. An infrared sea-surface-temperature (SST) image for thistime was also processed and compared with the pigment image.

The next section introduces the observations of the regional upwelling around the IzuPeninsula that were made on May 1982, and Section 3 briefly reviews the CZCS image pro-cessing procedure. Section 4 describes the results of comparisons between CZCS and ship-observed pigments obtained around the Izu Peninsula on May 23, 1982, and Section 5 describesthe oceanographic conditions of the area and the comparisons between satellite-derived pigmentand SST fields. Section 6 gives concluding remarks.

2. Regional Upwelling around Izu on May 1982Oceanographic observations were conducted between the Izu Peninsula and Oshima Island

(Fig. 1) from 22 to 26 May 1982 by the R/V Tansei Maru of the Ocean Research Institute of theUniversity of Tokyo. The observations included simultaneous measurement of SST, pigment,and nitrate plus nitrite with a continuous measuring system (Fig. 2). CTD observations and watersampling with a Rosette sampler were also made. Detailed descriptions of the samplingtechniques and the observations are found in Atkinson et al. (1987a) and Takahashi et al. (1986).

During the observation period, the Kuroshio meandered offshore at Shiono-misaki, returnedonshore from Hachijo Island to Omaezaki, and flowed northeast along the Izu Peninsula(Atkinson et al., 1987a). Upwelling was observed around Tsumeki Point on the Izu Peninsula.It has been suggested that this local upwelling was related to offshore movement of the Kuroshioin this area on 21 and 22 May subsequent onshore movement of the Kuroshio on 23 and 24 Maypushed the upwelled water nearer the coast. A second upwelling event occurred off TsumekiPoint on 25 and 26 May.

Takahashi et al. (1986) explained time changes in the surface chlorophyll a and nitrate plusnitrite in the upwelled water with a simple growth model that was based on simulated upwellingexperiments (Ishizaka et al., 1983). They concluded that phytoplankton responded to the newlyupwelled water on 21 May and grew exponentially until 23 May when the surface nutrientconcentrations become depleted, and then chlorophyll concentration gradually decreased. Abrief summary of phytoplankton growth responding to this regional upwelling can be found inIshizaka and Takahashi (1984). Also, Ishizaka et al. (1986) described phytoplankton communitychanges in the upwelled water, and Ishizaka et al. (1987) suggested that the formation of restingspores by the centric diatom, Leptocylindrus danicus, which was dominant in the upwellingregion, is a response to nutrient depletion in the later period of the upwelling.

3. CZCS Data ProcessingThere are two main steps in obtaining pigment concentrations from CZCS images; atmo-

spheric corrections and pigment estimations from the water leaving radiance. These twoprocedures are explained briefly in this section.

Page 4: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

308 J. Ishizaka et al.

Fig. 1. Large map indicates Japan and the Kuroshio path (thick arrow) for 7 May to 20 May, 1982, whichis redrawn from Atkinson et al. (1987a). The smaller map indicates the study area between the IzuPeninsula and Oshima Island. Stars show the locations of stations at which the surface water sampleswere obtained that were used for comparison with the CZCS pigment concentrations shown in Fig. 3.The lines between S1 and S4 show the cruise track along which continuous surface monitoring wasdone to obtain the pigment values that were used for comparison with the CZCS pigment values shownin Fig. 5.

3.1 Atmospheric correctionAtmospheric correction is an important aspect of processing satellite ocean color observa-

tions because the information from the surface of the ocean is only about 10% of the total radiancedetected by the satellite sensor. The remaining signal (or noise) in the satellite observations isfrom the atmosphere and needs to be removed using an appropriate algorithm. The most acceptedmethod for atmospheric correction (Gordon et al., 1983), which is used in this study, assumesthat the total radiance detected by the sensor, Lt(λ), is given by:

Lt λ( ) = Lm λ( ) + La λ( ) + t λ( )Lw λ( ), 1( )

where Lm(λ) is the radiance due to atmospheric molecular (Rayleigh) scattering, La(λ) is the

Page 5: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 309

Fig

. 2.

Sur

face

tem

pera

ture

(a)

, nit

rate

plu

s ni

trit

e (b

), a

nd p

igm

ent (

c) d

istr

ibut

ions

for

23

May

, 198

2,ob

tain

ed f

rom

con

tinu

ous

surf

ace

mea

sure

men

ts.

Dat

a w

ere

base

d on

Atk

inso

n et

al.

(19

87a)

and

Tak

ahas

hi e

t al.

(198

6).

Page 6: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

310 J. Ishizaka et al.

radiance due to aerosol particle scattering, t(λ) is the diffuse transmittance of atmosphere, Lw(λ)is the water-leaving radiance, and λ is the wavelength of channels 1–4 of the CZCS (443, 520,550, 670 nm).

The values for Lm(λ) and t(λ) can be obtained from a precalculated table which takes intoconsideration multiple scattering, polarization, and ozone effects for given zenith and azimuthangles of the sun and the satellite (Gordon et al., 1983, 1988). However, La(λ) is not easily obtainedbecause aerosol concentrations and type varies with time and space. Usually an additionalparameter, ε(λ), is used to express the spectral characteristic of aerosol scattering. Once ε(λ) isknown, and assuming Lw(670) = 0, Lw(λ) can be calculated from Eq. (1) with La(λ) obtained bythe following equation;

La λ( ) = ε λ( )La 670( ) F0 ' λ( )F0 ' 670( )

, 2( )

where F0′(λ) is the solar irradiance at the top of the atmosphere, which takes into account theeffect of ozone absorption.

The parameter, ε(λ), is related to the Angstrom exponent, α, by following equation;

ε λ( ) = λ / 670( )α, 3( )

where α can be expressed as a constant value that is dependent on aerosol types. Thisapproximation, known as Angstrom’s law, is employed by Gordon’s standard atmosphericcorrection scheme, with a slight modification in the form of a correction factor of 0.95 for ε(443),which accounts for molecular-aerosol interactions (Gordon et al., 1988).

It has been suggested that the value of α can be assumed to be 0.0 for the oceanic typeaerosols which prevail in the global oceanic areas (R. Evans, personal comm.). Esaias et al. (1986)and Feldman et al. (1989) used this method to process all of the CZCS data collected throughoutthe life time (1978–1986) of the sensor. The resultant composite images showed many interestingphytoplankton distributions (US Global Ocean Flux Study Office, 1989). For terrigenous aerosoltypes, which may be found in some coastal areas, it has been suggested to use an α value of –0.8,which means that ε(443), ε(520), and ε(550) are set to 1.32, 1.22, and 1.17, respectively (R.Evans, personal comm.).

Presently, the “clear water radiance concept” (Gordon and Clark, 1981) is the acceptedmethod for processing most regional ocean color data. This method assumes that Lw(670) = 0,and the values of ε(520) and ε(550) are calculated from a “clear water” region where pigmentconcentrations are considered to be low (<0.25 µg l–1). Typical expected values are assumed forLw(520) and Lw(550). Since Lw(443) varies even in clear water, the value of α for ε(443) iscalculated as an average of those for ε(520) and ε(550) using Angstrom’s law. This methodallows for variable aerosol characteristics between different images. However, it introduceserrors when the aerosol characteristics vary within an image and in regions where Angstrom’slaw is not valid.

3.2 In-water algorithmOnce the water-leaving radiance is known, the next step is to estimate the pigment

Page 7: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 311

(chlorophyll a + pheopigments) concentrations. The standard method for obtaining pigmentconcentrations (Gordon et al., 1983) is a simple regression between surface pigment concen-trations and the ratio of water-leaving radiance;

logC = logA + Blog Lw λ( ) / Lw 550( ){ } , 4( )

where C is the surface pigment concentration, and A and B are coefficients determined em-pirically. The wavelength, λ, switches from 443 nm to 520 nm when the pigment concentrationis greater than 1.5 µg l–1. The water-leaving radiance is affected by the subsurface pigmentconcentration as well as by the surface pigment concentration, in terms of a weighted average.Therefore, the pigment concentration between the surface and the depth at which the surface lightdecreases to 1/e (one optical depth) should be homogeneous for Eq. (4) to be valid. Also, theconcentration of suspended and dissolved materials, other than phytoplankton, which can affectthe spectral characteristic of water, should be small.

4. Comparison of CZCS and Ship-Observed Pigment Concentration

4.1 Standard atmospheric correction methodsCZCS data for the study area on 23 May, 1982 were obtained from NASA Goddard Space

Flight Center (NASA/GSFC) and initially processed with the two methods described below.First, two sets of standard epsilon values were used for the atmospheric corrections; oceanic andland aerosol values. Next, the epsilon values based on the standard atmospheric correctionalgorithm “clear water radiance concept”, which was explained in Section 3, was used. Theseepsilon values used for the processes are listed on Table 1. After epsilon values were obtained,pigment concentrations were calculated by the methods which were also described in Section 3.We used PC-SEAPAK, a user-friendly PC-based ocean color data processing system developedby GSFC (McClain et al., 1990b), to obtain the epsilon values based on the “clear water radianceconcept” and to calculate pigment concentrations using these epsilon values listed on Table 1.

Ship-observed surface pigment concentrations during May 23, 1982 varied from 0.5 to 2.3µg l–1. On the contrary, CZCS-observed pigment concentrations for the same day from locationscorresponding to the ship observation locations only varied from 0.20 to 0.25 µg l–1 using thestandard oceanic and land aerosol parameters and 0.25 to 0.30 µg l–1 using the clear water ra-diance scheme (Fig. 3). These CZCS-derived pigment concentrations were correlated with the

Epsilon r RMSE443 520 550 (n = 9) (µg l–1)

Oceanic 0.95 1.00 1.00 0.696 0.767Land 1.32 1.22 1.17 0.622 0.763Clear water 1.07 1.04 1.03 0.721 0.737Adjustment 1.43 1.17 1.13 0.827 0.290

Table 1. Epsilon values for the different atmospheric corrections used in the data processing. The resultantcorrelation coefficients (r) and root mean square errors (RMSE) that were obtained from comparisonsbetween CZCS-derived and ship-observed pigments are also shown.

Page 8: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

312 J. Ishizaka et al.

ship-observed pigment concentration at a level of r = 0.622–0.721 (Table 1). The pigment pat-terns seen in the images processed with these epsilon values were not very different from theimage processed with better set of the epsilon values described below (cf. Figs. 5 and 6).Furthermore, the patterns in the images correspond to expected patterns of oceanic pigmentdistributions. However, the CZCS-derived values were about a factor of 5 smaller than the ship-observed values (Fig. 3).

Fig. 3. (a) Ship-observed pigment concentration off Izu Peninsula on 23 May, 1982, and CZCS-derivedpigment concentration at the corresponding location. (b) Correlation between ship-observed andCZCS-derived pigment concentration. The CZCS-derived pigment concentration were processedusing four different epsilon values; oceanic, land, clear water, and adjusted values. See text for details.Arrows indicate 11:00 a.m. when the CZCS passed over the study area. The epsilon values wereadjusted to the ship-observed pigment concentrations measured at this time. The strait line on (b)indicates the values for which ship and CZCS-observed pigment concentrations are equivalent.

Page 9: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 313

4.2 Adjustment of epsilon valuesSince sea-truth pigment data were available for this study, it was possible to determine

epsilon parameters that produced CZCS-derived pigment concentrations that corresponded tothe ship-observed pigment concentrations. These epsilon values were then used to calculate thepigment concentrations for the entire CZCS image. The ship-observed pigment concentration ata hydrographic station made at 11:00 a.m. (JST) was used for this calibration because thisobservation time coincided with the satellite overpass.

A flow diagram of the method used to estimate the epsilon values at the ship location isshown in Fig. 4. First, total radiances obtained by CZCS, Lt(λ), were modeled by molecularscattering, Lm(λ), aerosol scattering, La(λ) and water leaving radiance, Lw(λ) multiplied bytransmittance, t(λ), as in Eq. (1). As described previously, Lm(λ) and t(λ) was obtained from theprecalculated table of Gordon et al. (1988). Assuming Lw(670) = 0 (Gordon et al., 1983), La(670)was calculated by Eq. (1). Next, we assumed the value of normalized water leaving radiance forthe 550 nm, nLw(550), to be 0.3 µW·cm–2·nm–1·sr–1 (Gordon et al., 1988) and the value of Lw(550)was obtained from

Lw 550( ) = nLw 550( )cosθ0exp − τ M / 2 + τOZ( ) / cosθ0{ } , 5( )

where θ0 is the solar zenith angle, and τM and τOZ are the optical thicknesses of a gas moleculeand ozone, respectively. Once Lw(550) was known, La(550) could be calculated with Eq. (1)knowing t(550) and Lm(550), and ε(550) was obtained from Eq. (2) with previously obtainedLa(670).

On the other hand, Lw(443) was determined from the in-water pigment algorithm, Eq. (4),with ship-observed pigment concentration, C, and with previously calculated Lw(550). We usedλ = 443 and coefficient values of 0.053 and –1.71 for log A and B, respectively, which are typicalvalues for pigment concentrations less than 1.5 µg l–1 (Gordon et al., 1983). Knowing t(443),Lw(443) and Lm(443), we obtained La(443), and ε(443) was determined similar to ε(550). Fi-nally, ε(520) was determined by Eq. (3), using an α value that is determined from ε(550). Theresulting epsilon values are shown in Table 1.

Pigment concentrations calculated with these epsilon values were significantly higher thanthose obtained using the epsilon values that correspond to standard oceanic and land aerosol andthose obtained with clear water algorithms (Fig. 3). For this analysis, the satellite-derivedpigment concentrations better matched the in situ pigment values, and the correlations were alsoimproved (Table 1). In particular, pigment samples taken within 5 hours (9:00 a.m.–3:30 p.m.)of the CZCS observations showed good agreement with the CZCS-derived pigments, althoughthe difference increased with the increased time difference (Fig. 3). Pigment concentrations fromthe hydrographic stations taken between 5:00–8:00 p.m. were underestimated by the CZCS,probably because the sampling area was at the eastern side of a region of clouds and the CZCSobservations were contaminated by cloud ringing effects that blind the sensor (Mueller, 1988;cf. Fig. 6).

The CZCS-derived pigment distributions showed large variabilities, some of which couldbe related to SST distributions (Figs. 5 and 6). In general, the variabilities in the pigmentdistributions is as expected for oceanic systems. The pigment pattern along the eastern edge ofthe Izu Peninsula was similar to the pigment pattern observed by the ship survey (Fig. 2(c)). Ittook several hours to generate these maps of sea surface parameters with the continuous

Page 10: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

314 J. Ishizaka et al.

Fig

. 4.

Flo

w d

iagr

am fo

r the

est

imat

ion

of e

psil

on v

alue

s by

the

met

hod

in w

hich

a C

ZC

S-d

eriv

ed p

igm

ent

conc

entr

atio

n ar

e as

sum

ed to

be

equi

vale

nt to

a s

hip-

obse

rved

pig

men

t con

cent

rati

on.

Page 11: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 315

observations by ship; whereas the satellite data was taken almost instantaneously. The resem-blance between these data indicated that the upwelling phenomena was stable during these hourseven the flow regime was strong. Detail comparisons between the pigment and SST images aregiven in next section.

Three onshore-offshore transects (cf. Fig. 2(c)) along which surface-pigment concentrationswere continuously measured were compared with CZCS pigment concentrations extracted alongthe same transects (Fig. 7). Similarities between the ship-observed and CZCS-derived pigmentpatterns was remarkable. The CZCS and ship-observed pigment sections showed similaronshore-offshore changes in pigment concentrations in which the pigment concentrationsgenerally decreased offshore. The first section (S1–S2) showed concentration variability ofabout 1.0 µg l–1 onshore and with a sudden decrease to 0.8 µg l–1 around S2. Pigment concen-trations along the next section (S2–S3) showed a sharp increase (>1.5 µg l–1) toward onshore, adecrease to less than 1.0 µg l–1, and an increase again at S3. The last section (S3–S4) showed agradual decrease of pigment concentration from 2.0 µg l–1 to 0.7 µg l–1 over the length of thetransect. There were slight shifts of the positions of some of the pigment fronts observed by shipand satellite. These shifts were probably caused by the short term fluctuations of the front or bythe error of navigation of ship and satellite data.

4.3 Possible reasons for the underestimationThe comparisons between the ship-observed and CZCS-derived pigment concentration

indicate that the CZCS data around Japan is useful for oceanographic studies as long as sea-truthdata are available and aerosol parameters are chosen so that ship-observed pigment concentrationsmatch satellite observations from the corresponding location. When sea-truth data are notavailable and the epsilon values are chosen from standard values or obtained from the “clearwater algorithm”, care should be taken because the absolute values of the resultant pigmentconcentrations may not be correct, although the pigment patterns may be reasonable.

Several factors may have caused the underestimation of CZCS-derived pigments whenstandard methods were used to process the data. First, the in-water algorithm that was used maynot be applicable using to this area. The standard coefficients used in Eq. (2) were originally fitusing data from coastal waters of North America (Smith and Baker, 1982; Gordon et al., 1983).Recently, it has been suggested that phytoplankton physiological or taxonomic differences maycause a mismatch of coefficients in the algorithm (Mitchell et al., 1992). This algorithm also onlyapplies for case 1 waters, which contains low concentrations of yellow substances (Gordon andMorel, 1983). Furthermore, the in-water algorithm assumes homogeneous pigment concentra-tions over the upper water column to one optical depth, and the surface upward irradiance isactually the weighted average of the surface layer. These assumptions were not necessarily validfor this area.

For this study region, it was typical that pigment maximum was found at 10–20 m rather thansurface. There was a possibility that the surface pigment concentration was overestimated by thehigher subsurface pigment concentration; however, it was not expected that the underestimationcaused by subsurface pigment. Furthermore, Sugihara et al. (1985) measured upward irradiancein this area during the same cruise, and analyzed the applicability of in-water algorithms. Theyfound that their data, which included measurements from the May 1982 cruise, data in the TokyoBay, and data off Shikoku, agreed well with the in-water algorithm of Smith and Wilson (1981).Smith and Wilson (1981) used same equation that we used in this study (Eq. (3)) but withparameter values that differed from Gordon et al. (1983), and difference of the resulted pigment

Page 12: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

316 J. Ishizaka et al.

Fig. 5. Sea-surface-temperature (a) and pigment (b) and distributions derived from the CZCS for watersaround Japan on 23 May, 1982.

Page 13: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 317

Fig

. 6.

Sea

-sur

face

-tem

pera

ture

(a) a

nd p

igm

ent (

b) d

istr

ibut

ions

der

ived

from

the

CZ

CS

for r

egio

ns a

roun

d th

e Iz

u P

enin

sula

on

23 M

ay, 1

982.

Als

osh

own

are

mag

nifi

ed i

mag

es o

f te

mpe

ratu

re (

c) a

nd p

igm

ent

(d).

Lin

es o

n th

e m

agni

fied

Im

ages

ind

icat

e th

e se

ctio

ns t

hat

wer

e ch

osen

for

the

com

pari

sons

giv

en i

n F

ig. 9

.

Page 14: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

318 J. Ishizaka et al.

concentration is about a factor of 2. We replotted (Fig. 8) the data only taken from our study areaby Sugihara et al. (1985) and found it to fit better with Gordon et al. (1983), which is the algorithmwe used in this study. Thus, the in-water algorithm was not a major reason for the error in theestimate of the CZCS-derived pigment concentrations.

Second possibility is fluctuations in the sensor calibration. For our calculation, we used thelatest calibration parameters (R. Evans, personal comm.); however, it was discovered that therewere some short-term fluctuations in the sensor calibration in addition to the long-term trendswhich can be removed by the calibration parameters. The short-term fluctuations appear to belarge after 1981 (R. Evans, personal comm.). Presently, there is no good method for removingthe short-term fluctuations in sensor calibration, and this is difficult to evaluate whether thiscontributes to the discrepancy in estimated pigment values.

The third and most probable possibility for the underestimation is the approach used foratmospheric corrections. The set of epsilon values we derived here in order to have CZCSpigments consistent with the ship-observed data shows that the estimated value of ε(443), 1.43,is larger than the expected value of ε(443), 1.23, that is obtained from extrapolation of an α valuewhich corresponds to that obtained for ε(550). This indicates that the epsilon values we used wasnot consistent with Angstrom’s law, which is the basis for the current atmospheric correctionscheme. Fukushima et al. (1991) pointed out that large errors for pigment concentration estimationmay result to a non-power-law aerosol particle size distribution since the scattering phasefunction depends on wavelength. This will result in anomalous epsilon values which areinconsistent with Angstrom’s law. A separate investigation of channel 3 (550 nm band) showedan increase in the values of Lw(550) retrieved from around the study area, thereby suggesting thelocal presence of some aerosols with different characteristics.

Fig. 7. A comparison of continuously measured pigment concentration along the ship track and the CZCS-derived pigment concentration at corresponding locations. Pigment concentration from the CZCSwere adjusted so that the ship-observed and CZCS-derived pigment concentration at 11:00 a.m.(indicated by arrow) are equivalent.

Page 15: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 319

Fukushima et al. (in prep.; brief description in Fukushima and Ishizaka, 1992) suggested thatAngstrom’s law is not applicable for the area around Japan when yellow sand dust (Kosa) fromChinese desert regions is present. Concentration of yellow sand dust was not particularly highon May 23, 1982, and the observed optical characteristics of the atmosphere at this time wasdifferent from that typical of yellow sand dust. However, the results obtained in this studyindicate that further development of atmospheric correction algorithms specific to the regionsaround Japan is needed.

5. Comparison of CZCS Pigment Data and SST DataAfter adjusting the atmospheric correction parameters, the pigment data correlated well with

the sea-truth data, and the CZCS-derived pigment distributions showed patterns representativeof oceanographic features. In this section, comparisons between the pigment and infrared SSTdistributions are made. Sea-surface-temperature were derived from infrared images of AVHRR/NOAA-7 provided by the Tohoku University and matched to ship-observed sea-surface-tem-perature data.

5.1 Large scale comparisonThe temperature data (Fig. 5(a)) clearly showed a stream of warm water, which can be

identified as the Kuroshio. This current looped south of Japan and extended to Hachijo Island.The Kuroshio then changed to a westward direction, meandered to the northeast along theOmaezaki, Izu, and Boso Peninsulas, and separated from the coast off Katsuura. In contrast to

Fig. 8. Relationship between the ratio of the upward irradiance at 443 and 550 nm just beneath the seasurface, Eu(443)/Eu(550), and the surface pigment concentration. Redrawn from Sugihara et al. (1985).

Page 16: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

320 J. Ishizaka et al.

the warm Kuroshio water, temperatures in the southern Mikawa Bay and in Suruga and SagamiBays, and south of Nojimazaki Point were lower. There was a distinct front off Katsuura thatextended to the northeast. These patterns are consistent with a chart from the JapaneseHydrographic Office that showed the Kuroshio approaching from south of Hachijo Island, andthen flowing to the northeast along the coast of the Izu and Boso Peninsulas (Atkinson et al., 1987a).However, the SST pattern for the Kuroshio on May 23 is more similar to the chart for May 7–20 (cf. Fig. 1) than the one for May 21 to June 2 in which the Kuroshio is much further offshoreat the Izu Islands.

The pigment distribution detected by the CZCS (Fig. 5(b)) also showed large spatialvariabilities. In general, the pigment distributions corresponded to the SST distribution. Highpigment concentration occurred in low temperature regions, and low pigment concentration werefound in the high temperature areas. For example, surface pigment concentrations were relativelyhigher off Nojimazaki and at the north of the front off Katsuura which corresponded to regionsof lower-surface-temperature waters. Along the coastal side (north) of the Kuroshio, at thesouthern part of the Japanese coast, pigment concentrations were higher than the one of warmer,outside of the Kuroshio. Further westward the Kuroshio flowed around Hachijo Island andclearly separated the high pigment waters from the coast of Japan. This overall negativecorrelation between temperature and pigment around the southern Japanese islands may becaused by a general difference in nutrient availability. Low temperatures indicate low stabilitywhich results in greater nutrient availability and enhances pigment concentrations. Hightemperatures indicate increased water column stability which reduces nutrient availability andhence results in lower pigment concentrations.

5.2 Around the Izu PeninsulaMagnification of the SST image around the Izu Peninsula and northern Izu Islands (Figs. 6(a)

and (c)) showed that there was a cold plume (<20°C) along Tsumeki Point which was about 30km and 10 km along and across the peninsula, respectively. There were also several cold eddies(<21°C) with diameters of 5–10 km on the eastern side of Oshima, Toshima, Niijima, and ShikineIslands. Water temperatures around these islands were generally lower on the eastern side thanon the western side. Atkinson et al. (1987a) identified these cold water masses on the eastern sideof Izu Peninsula and the northern Izu Islands as regions of local upwelling.

The pigment image (Figs. 6(b) and (d)) showed that the cold plume off Tsumeki corre-sponded to higher pigment water, and that the colder the water, the more pigments it contains thansurrounding waters. However, the cold eddies on the eastern side of Oshima and Niijima Islandsdid not necessarily corresponded to patterns of increased pigment concentration. In particular,the cold water east of Kozu and Niijima showed relatively lower pigment concentration than thesurrounding water. Note also that there was a cloud (white region) over the Izu Peninsula, andthat water east of this cloud was relatively lower in pigment concentration than the regions northor south of this area. As described in the previous section, this underestimation of the surfacepigment concentrations may be the result of cloud ringing effects just after the sensor sees thebright objects (Mueller, 1988).

Two north-south sections of SST and pigment concentration determined by CZCS wereshown in Fig. 9. They were taken from the western and eastern sides of the northern Izu Islands,where upwelled water was observed. Surface temperature at the west of the Izu Islands wasrelatively low (20°C) at the northeast of Tsumeki Point and dropped to less than 19°C off the point(34°42′), and gradually increased (22°C) towards the south (Fig. 9(a)). Temperatures to the

Page 17: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 321

northeast of the islands were similar to those of the west and dropped to 19°C at the north (34°50′)and at the south (34°40′) of Oshima Island (Fig. 9(b)). Temperatures were higher (21.5°C) at thesouth of Oshima and lower (20.5°C) to the south, and dropped to 19°C at the east of Kozu Island(34°12′).

Pigment concentrations exceeded 2 µg l–1 at the northern part of both sections whichprobably indicated the existence of coastal water in Sagami Bay. Concentrations to the west ofthe Izu Islands were a maximum off Tsumeki Point (34°42′), which corresponded to the regionof minimum temperature (Fig. 9(b)). Pigment concentrations then gradually decreased andreached values of less than 0.5 µg l–1 toward south. In comparison, pigment concentrations to theeast of the islands showed more variability (Fig. 9(b)). Pigment concentrations were lower in thewaters associated with the cold eddies to the east of Oshima Island (34°50′, 34°40′). The cold

Fig. 9. Sea-surface-temperature and pigment concentration along the western (35°N, 139.3°E–34°N,138.8°E) and eastern (35°N, 139.7°E–34°N, 139.2°E) sides of the northern Izu Islands determined byCZCS.

Page 18: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

322 J. Ishizaka et al.

eddy to the east of Kozu Island (34°12′) did not correspond to an area of high pigment water.The cold water plume along the Izu Peninsula corresponded well to the higher pigment water

mass, and this water mass was distinguished from the water in Sagami Bay. This is consistentwith the ship observations which showed that the cold water plume was an upwelled water massand that the phytoplankton responded to the higher nutrient environment caused by the upwellingand increased in concentration (Atkinson et al., 1987a; Takahashi et al., 1986). Takahashi et al.(1986) studied the time change of the chlorophyll a and pheopigments concentrations in the coldupwelled water and found that concentrations increased during the first three days (22–24 May,1982) when nutrients were abundant and decreased next day following nutrient depletion.Satellite observations in the study on 23 May, 1982, when the chlorophyll a and pheopigmentsconcentrations were still increasing. The correspondence of the low temperature plume withhigher pigment concentrations supports the hypothesis that the phytoplankton growth was inresponse to the upwelled water mass. This also indicates that the time scale of phytoplanktongrowth was shorter than the time scale of advection or diffusion of the upwelled water.

The cold eddies observed to the eastern side (i.e. at the lee side of Kuroshio) of the northernIzu Islands correspond to the upwelled water reported by Takahashi et al. (1980). It is interestingthat these cold eddies did not contain higher pigment water, rather the pigment concentrationwere low relative to the surrounding water. Takahashi et al. (1980) also reported that cold eddiesaround the Izu Islands do not necessarily correspond to higher pigment concentration. Takahashiet al. (1986) showed that the low temperature water plume along the Izu Peninsula, whichcorresponds to higher pigment waters in this study, was actually lower in temperature and inpigment concentrations on the previous day, 22 May, 1982. The cold eddies with lower pigmentconcentrations around the Izu Islands are probably younger upwelled water. It is sill not clearwhether phytoplankton populations have sufficient time in the eddies to respond to nutrient inputby the upwelling, similar to be observed in the cold water plume along the Izu Peninsula and inthe frontal eddies of Gulf Stream (Yoder et al., 1981; McClain et al., 1984; Ishizaka, 1990a, b).It may be possible that continuous upwelling in the eddies does not allow enough time forincreased phytoplankton concentrations to develop in the eddies. The sea-surface-temperatureswere lower and pigment concentrations were higher in waters around the eddies than in waterson the western side of the islands, which may indicate possible mixing of upwelled nutrients andsubsequent phytoplankton growth in the surrounding waters.

5.3 Pigment-temperature relationshipThe relation between pigment concentration and SST on the lines discussed previously was

shown in Fig. 10. The figure also included possible mechanisms to change the relationship. Thestrong correlation between the SST and pigment concentration was found in waters in the westernside of the northern Izu Islands except for two points in the Sagami Bay. The pigmentconcentrations linearly correlated with SST from 0.2 µg l–1 at 22°C Kuroshio water to 1.3 µgl–1 at 19°C at the center of the upwelled water. Water from Sagami Bay showed higher pigmentconcentrations compared with the water in the south. The relation between the SST and pigmentconcentrations for the water in the eastern side was more widely scattered for the sametemperature range of the water.

Newly upwelled water from low-light subsurface contains relatively lower pigment andhigher nutrient concentrations. The characteristics change by growth of phytoplankton and bywarming of water temperature, and pigment concentrations and temperature increase. Ifphytoplankton grows in the upwelled water without any loss and if the warming of temperature

Page 19: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 323

Fig. 10. Correlation between sea-surface-temperature and pigment concentration along the western(35°N, 139.3°E–34°N, 138.8°E) and eastern (35°N, 139.7°E–34°N, 139.2°E) sides of the northern IzuIslands determined by CZCS. The processes that can potentially change the relationships are indicatedby the arrows. Straight line is the upper limit of pigment concentration predicted by the nutrient-temperature relationship for newly upwelled water.

is slow, the relation between pigment concentration and temperature should be close to thenegative correlation between pigment concentrations and temperature which can be expectedfrom nutrient-temperature relationship (Takahashi et al., 1986). The maximum pigment-tem-perature relationship was calculated from nitrogen-temperature relationship in the study area(Takahashi et al., 1986) and shown in Fig. 10. We assumed chlorophyll a/nitrogen ratio of 1.4µg-chl.a/µmol-N (Ishizaka et al., 1983) and constant pheopigments concentrations of 0.2 µgl–1. Pigment concentrations at the upwelling area of the western side of the Izu Islands was stilllower than expected from temperature. The lower pigment concentrations are reasonable becausethe phytoplankton growth was still persisted and because there were some loss processes ofpigment from the surface water (Takahashi et al., 1986). However, the linearity between pigmentconcentrations and temperature in the area indicated that the warming of water was not very rapidcompared with the phytoplankton growth and that the upwelled water mass was not mixed withcoastal water or old/new upwelled water mass.

Water from Sagami Bay showed higher pigment concentrations than the maximum con-centrations expected from nutrient-temperature relationship of upwelled water. The coastalwater may have different nutrient-temperature relationship because of river water input.Overestimation of pigment concentrations because of the contamination of dissolved/suspendedmaterial may also be possible for the different pigment-temperature relationship. Many of thenorthern points of the eastern section showed higher pigment concentrations. This indicates thatthe high pigment and high temperature water at the north resulted from the mixing between thecoastal and Kuroshio water. On the other hand, the variabilities of the pigment-temperaturerelation at the southern region of the eastern section was not expected from mixing of the coastalwater. This rather indicated the presence of upwelled water with different age which describedin previous section (younger upwelling eddies and older surrounding water).

Page 20: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

324 J. Ishizaka et al.

Abbott and Zion (1985) discussed the time change of the SST-pigment relationship for a 560km by 560 km region of coastal upwelling off northern California. They found a complex timeevolution of this relationship that was related to the maturation of the upwelling after a windevent. The relationship found in this study was more complicated because of the small scaleheterogeneity of water masses in the study region. Several different local upwelling eventsoccurred close each other and possibly mixed with coastal (Sagami Bay) waters. There is alsothe possibility of influences from Oyashio water which may enter the study area from north ofthe Kuroshio front.

Sathyendranath et al. (1991b) suggested that phytoplankton concentrations in the upperwater column may increase the heating rate at the surface of ocean. They estimated a monthlyheating rate in the mixed layer of the Arabian Sea associated with the phytoplankton concentra-tion obtained by the CZCS and found a significant amount of temperature increase that resultedfrom the phytoplankton. They also showed nonlinear effects of phytoplankton concentration onthe surface heating rate and pointed out that the variance structure of the biomass field isnecessary to accurately estimate the heating rate. If these arguments are true, the changes in thetemperature-pigment relationship shown in Fig. 10 or those reported by Abbott and Zion (1985)may be the result of complicated interactions between biological and physical processes. Furtherstudy is required to understand the physical-biological interactions which underlie the tempera-ture-pigment relationship.

6. Concluding RemarksThere are many interesting features more in the satellite-derived pigment distributions. High

pigment concentrations at the southern crest of the Kuroshio meander is one noticeable feature.The high pigments produced in this area might be in response to upwelling associated with themeander rather than transported offshore from the coast. However, identification of the actualmechanism awaits further study. In any case, the high pigment concentration at the crest of themeander and in the eastern side of the Izu Islands indicates that the Kuroshio may produce andexport organic material offshore, as suggested by Atkinson et al. (1987b). A combination ofnumerical modeling and satellite data analysis similar to that done for the southeastern U.S.continental ecosystem by Ishizaka (1990a, b, c) and other regions (cf. Ishizaka and Hofmann,1992) may be an approach for calculating primary production as well as understanding theecosystem response to the Kuroshio and its associated material flux.

In this study, CZCS-derived and ship-observed pigment concentrations in waters around IzuPeninsula, Japan, were compared and satellite pigment distributions were analyzed and comparedwith satellite sea-surface-temperature data. We found that CZCS-derived pigment concentrationswere significantly underestimated if standard pigment estimation methods were used. However,once the correct atmospheric correction parameters were obtained, the derived pigment fieldsmatched well to the distributions obtained from ship surveys, and gave detail structures ofpigment distributions for a wide area.

Further verification studies are obviously required before satellite ocean color can be usedto give accurate estimates of the pigment concentrations in the water around Japan. Presently, thedata described in this study is the only available CZCS data that can be directly compared withsea-truth pigment concentrations. Unfortunately, there is no satellite ocean color sensor availablenow. However, SeaWiFS is scheduled to be launched in 1993 by the U.S. and the JapaneseADEOS/OCTS is scheduled to be launched in 1996. It is necessary that suitable verificationprograms be in place before these ocean color sensors are in operation. The presently available

Page 21: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 325

CZCS data can be used for statistical comparisons with historical pigment and environmentaldata sets. This will provide a framework for use of the new ocean color data when it becomesavailable. The historical pigment data for the waters around Japan is poor (Ishizaka andHarashima, 1991), and routine ship operations, including research vessels, ferry boats andfishing boats, are necessary to collect additional pigment data. It is also important to have a goodinter-calibration between these varied ship operations. Such ship operation programs will alsoallow determination of whether the present in-water algorithms can be applied to the watersaround Japan. Moored optical devices, which are required for calibration of ocean color data,should be developed now so that they will be available when the new ocean color sensors arelaunched.

AcknowledgementsThis study was supported with funds by the Environmental Agency as part of a special fund

for global environmental problems. We would like to thank G. Feldman and C. R. McClain atNASA Goddard Space Flight Center for supplying the CZCS data and the PC-SEAPAKprograms. We also thank H. Kawamura at the Tohoku University and S. Saitoh at the JapanWeather Association for help for AVHRR data acquisition and processing. We would like tothank A. Harashima, S. Matsumura, and E. E. Hofmann for their helpful comments. Thanks arelikewise given to L. P. Atkinson, T. N. Lee, S. Sugihara, and T. Ishimaru for their help anddiscussions on the cruise. Special thanks are also given to the crew of the R/V Tansei Maru, OceanResearch Institute, University of Tokyo and to K. Takeda, M. Toratani, N. Kimura, and somestudents at the School of Marine Science and Technology, Tokai University, for their technicalhelp.

ReferencesAbbott, M. R. and D. B. Chelton (1992): Advances in passive remote sensing of the ocean. Rev. Geophys., 571–589.Abbott, M. R. and P. M. Zion (1985): Satellite observations of phytoplankton variability during an upwelling event.

Cont. Shelf Res., 4, 661–680.Abbott, M. R. and P. M. Zion (1987): Spatial and temporal variability of phytoplankton pigment off Northern

California during Coastal Ocean Dynamics Experiment 1. J. Geophys. Res., 92, 1745–1755.Aikoh, T. and M. Takahashi (1982): Detection of vortex motion by satellite (AVHRR/NOAA-6) and regional

upwelling off Izu-Oshima Island. J. Remote Sensing Soc. Japan, 2, 3–9.Atkinson, L. P., J. O. Blanton, C. McClain, T. N. Lee, M. Takahashi, T. Ishimaru and J. Ishizaka (1987a):

Observations of upwelling around the Izu Peninsula, Japan: May 1982. J. Oceanogr. Soc. Japan, 43, 89–103.Atkinson, L. P., J. O. Blanton and G.-A. Paffenhofer (1987b): Impact of ocean boundaries on the ocean interior. p.

147–158. Ocean margins in GOFS. U.S. GOFS Planning Report number 6. U.S. GOFS Planning andCoordination Office.

Esaias, W. E., G. C. Feldman, C. R. McClain and J. A. Elrod (1986): Monthly satellite-derived phytoplanktonpigment distribution for the North Atlantic ocean basin. EOS, 67, 835.

Feldman, G., N. Kuring, C. Ng, W. Esaias, C. McClain, J. Elrod, N. Maynard, D. Endres, R. Evans, J. Brown, S.Walsh, M. Carle and G. Podesta (1989): Ocean color. Availability of the global data set. EOS, 70, 634–641.

Fukushima, H. and J. Ishizaka (1992): Special features and applications of CZCS data in Asian waters. In OceanColour: Theory and Applications in a Decade of CZCS Experience, Kluwer Academic (in press).

Fukushima, H., M. Toratani and Y. Sugimori (1991): Effect of aerosol on satellite-derived phytoplankton pigmentconcentration: Evaluation of error under typical aerosol models. J. Fac. Mar. Sci. Tech. Tokai Univ., 32, 45–56.

Gordon, H. and D. K. Clark (1981): Clear water radiances for atmospheric correction of coastal zone color scannerimagery. Appl. Optics., 22, 4175–4180.

Gordon, H. R. and A. Y. Morel (1983): Remote Assessment of Ocean Color for Interpretation of Satellite VisibleImagery. Springer-Verlag, 114 pp.

Gordon, H. R., D. K. Clark, J. L. Mueller and W. A. Hovis (1980): Phytoplankton pigments from the Nimbus-7

Page 22: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

326 J. Ishizaka et al.

Coastal Zone Color Scanner: Comparisons with surface measurements. Science, 210, 63–66.Gordon, H. R., D. K. Clark, J. W. Brown, O. B. Brown and R. H. Evans (1982): Satellite measurement of the

phytoplankton concentration in the surface waters of a warm core Gulf Stream ring. J. Mar. Res., 40, 491–502.Gordon, H. R., D. K. Clark, J. W. Brown, O. B. Brown, R. H. Evans and W. W. Broenkow (1983): Phytoplankton

pigment concentration in the Middle Atlantic Bight: Comparison of ship determinations and CZCS estimates.Appl. Opt., 22, 20–36.

Gordon, H. R., J. W. Brown and R. H. Evans (1988): Exact Rayleigh scattering calculations for use with the Nimbus-7 Coastal Zone Color Scanner. Appl. Opt., 27, 862–871.

Hiramatsu, K., H. Fukushima, S. Matsumura and Y. Sugimori (1987): CZCS-derived pigment concentration fieldsin Japanese coastal area. Sora to Umi, 9, 1–7 (in Japanese with English abstract).

Hovis, W. A., D. K. Clark, F. Anderson, R. W. Austin, W. H. Wilson, E. T. Baker, D. Ball, H. R. Gordon, J. L.Mueller, S. Y. El-Sayed, B. Sturm, R. C. Wrigley and C. S. Yentsch (1980): Nimbus-7 Coastal Zone ColorScanner: system description and initial imagery. Science, 210, 60–63.

Ishizaka, J. (1990a): Coupling of Coastal Zone Color Scanner data to a physical-biological model of the southeasternU.S. continental shelf ecosystem. 1. CZCS data description and Lagrangian particle tracing experiments. J.Geophys. Res., 95, 20167–20181.

Ishizaka, J. (1990b): Coupling of Coastal Zone Color Scanner data to a physical-biological model of the southeasternU.S. continental shelf ecosystem. 2. An Eulerian model. J. Geophys. Res., 95, 20183–20199.

Ishizaka, J. (1990c): Coupling of Coastal Zone Color Scanner data to a physical-biological model of the southeasternU.S. continental shelf ecosystem. 3. Nutrient and phytoplankton fluxes and CZCS data assimilation. J. Geophys.Res., 95, 20167–20181.

Ishizaka, J. and A. Harashima (1991): CZCS data number around Japan and surface chlorophyll data numbersimultaneously observed by ship. Sora to Umi, 13, 1–8 (in Japanese with English abstract).

Ishizaka, J. and E. E. Hofmann (1992): Coupling of ocean color data to physical-biological models. In Ocean Colour:Theory and Applications in a Decade of CZCS Experience, Kluwer Academic (in press).

Ishizaka, J. and M. Takahashi (1984): Production and accumulation of chlorophyll in the frontal zone of the Kuroshiobranch. Bull. Coastal Oceanogr., 21, 148–155 (in Japanese).

Ishizaka, J., M. Takahashi and S. Ichimura (1983): Evaluation of coastal upwelling effects on phytoplankton growthby simulated culture experiments. Mar. Biol., 76, 271–278.

Ishizaka, J., M. Takahashi and S. Ichimura (1986): Changes in the growth rate of different phytoplankton groupsin a localized upwelling occurring around the Izu Peninsula, Japan. J. Plankton Res., 8, 169–181.

Ishizaka, J., M. Kaichi and M. Takahashi (1987): Resting spore formation of Leptocylindrus danicus(Bacillariophyceae) during short time-scale upwelling and its significance as predicted by a simple model. Ecol.Res., 2, 229–242.

Matsumura, S. and H. Fukushima (1988): Water mass analysis using ocean color map and sea surface temperaturemap obtained by NIMBUS-7/CZCS. Sora to Umi, 10, 27–39 (in Japanese with English abstract).

McClain, C. R., L. J. Pietrafesa and J. A. Yoder (1984): Observations of Gulf Stream-induced and wind-drivenupwelling in the Georgia Bight using ocean color and infrared imagery. J. Geophys. Res., 89, 3705–3723.

McClain, C. R., J. Ishizaka and E. E. Hofmann (1990a): Estimation of the processes controlling variability inphytoplankton pigment distributions on the southeastern U.S. continental shelf. J. Geophys. Res., 95, 20213–20235.

McClain, C. R., G. Fu, M. Darzi and J. K. Firestone (1990b): PC-SEAPAK User’s Guide, Version 3.0. NASA GoddardSpace Flight Center.

Mitchell, B. G. and O. Holm-Hansen (1992): Bio-optical properties of Antarctic Peninsula waters: differentiationfrom temperate ocean models. Deep-Sea Res., 38, 1009–1028.

Mueller, J. (1988): Nimbus-7 CZCS: electronic overshoot due to cloud reflectance. Appl. Opt., 27, 438–440.Ogishima, T., H. Fukushima and Y. Sugimori (1986): Problems relating to atmospheric correction algorithm for

CZCS data in Japanese coastal area. Sora to Umi, 8, 53–63 (in Japanese with English abstract).Platt, T. and S. Sathyendranath (1988): Oceanic primary production: Estimation by remote sensing at local and

regional scales. Science, 241, 1613–1620.Sasaki, Y., I. Asanuma and K. Muneyama (1983): A study on the atmospheric correction for the satellite observation

for oceans. J. Japan Soc. Photogram. Remote Sensing, 22, 4–10 (in Japanese with English abstract).Sathyendranath, S., T. Platt, E. P. W. Horne, W. G. Harrison, S. Ulloa, R. Outerbridge and N. Hoepffner (1991a):

Estimation of new production in the ocean by compound remote sensing. Nature, 353, 129–133.

Page 23: Phytoplankton Pigment Distributions in Regional Upwelling ...svr4.terrapub.co.jp/journals/JO/pdf/4803/48030305.pdf · Phytoplankton pigment (chlorophyll a + pheopigments) distributions

Pigment Distributions in Regional Upwelling 327

Sathyendranath, S., A. D. Gouveia, S. R. Shetye, P. Ravindran and T. Platt (1991b): Biological control of surfacetemperature in the Arabian Sea. Nature, 349, 54–56.

Smith, R. C. and K. S. Baker (1982): Oceanic chlorophyll concentration as determined by satellite (CZCS). Mar.Biol., 66, 269–279.

Smith, R. C. and W. H. Wilson (1981): Ship and satellite bio-optical research in the California Bight. p. 281–294.In Oceanography from Space, ed. by J. F. R. Gower, Plenum Press, New York.

Sugihara, S., M. Kishino and N. Okami (1985): Correlation of chlorophyll concentration and suspended solids withnear-surface upward irradiance within LANDSAT Bands 4, 5 and 6. J. Oceanogr. Soc. Japan, 41, 81–88.

Takahashi, M. and M. J. Kishi (1984): Phytoplankton growth response to wind induced regional upwelling occurringaround the Izu Peninsula off Japan. J. Oceanogr. Soc. Japan., 40, 221–229.

Takahashi, M., I. Koike, T. Ishimaru, T. Saino, K. Furuya, Y. Fujita, A. Hattori and S. Ichimura (1980): Upwellingplumes in Sagami Bay and adjacent water around the Izu islands, Japan. J. Oceanogr. Soc. Japan, 36, 209–216.

Takahashi, M., Y. Yasuoka, M. Watanabe, T. Miyazaki and S. Ichimura (1981): Local upwelling associated withvortex motion off Oshima Island, Japan. p. 119–124. In Coastal Upwelling, ed. by F. A. Richards, AmericanGeophysical Union, Washington, D.C.

Takahashi, M., J. Ishizaka, T. Ishimaru, L. P. Atkinson, T. N. Lee, Y. Yamaguchi, Y. Fujita and S. Ichimura (1986):Temporal change in nutrient concentration and phytoplankton biomass in short time scale local upwellingaround the Izu Peninsula, Japan. J. Plankton Res., 8, 1039–1049.

Toda, H. (1989): Surface distributions of copepods in relation to regional upwellings around the Izu Islands insummer of 1988. J. Oceanogr. Soc. Japan, 45, 251–257.

U.S. Global Ocean Flux Study Office (1989): Ocean Color from Space. Woods Hole Oceanographic Institution,Woods Hole.

Yoder, J. A., L. P. Atkinson, T. N. Lee, H. H. Kim and C. R. McClain (1981): Role of Gulf Stream frontal eddiesin forming phytoplankton patches on the outer southeastern shelf. Limnol. Oceanogr., 26, 1103–1110.