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SW o SOLAR LW o OLR
SW response
T response
ScaRaB = SW and LW broadband radiometer measuring the whole spectral ranges of the solar reflected radiation (SW), and of the longwave (LW) emission from the surface and atmosphere.
OLR History • First measurements of OLR as early as 1959
from Explorer-7 • Experiments - ERB, ERBE, ScaRaB, CERES,
GERB • First routine measurements of OLR from
operational satellites began in 1974 – NOAA scanning radiometer ( SR)- window channel
( 10-12 microns) – Linear algorithm between window radiances and total
OLR – based on radiative calculations with model atmospheres
– Evolved a few years later to a non linear algorithm which is still in use today - adjusted for different spectral interval
• SR data 1974-1978, AVHRR 1979-onward
CHANNEL Description Spectral Interval Filter
1 Visible (VIS) 0,55 — 0,65 µm Interferential
2 Solar or SW 0,2 — 4 µm Silice Filter
3 Total (T) 0,2 — 100 µm No filter
4 Infrared window (IRW) 10,5 — 12,5 µm Interferential
GERB
SCARAB
STRUMENTI
• ERB
• ERBE
• CERES (TRMM, AQUA, TERRA)
• GERB (MET8, MET9)
• SCARAB (RESURS, ADEOS, MEGHA-TROPIQUE)
• Calibrazione (intercalibrazione)
• Sampling diurno
• Calcolo del flusso a partire della radianza (identificazione della scena)
Radiance-to-flux conversionRadiance TOA flux estimate
ddsincos),,(L)(F O
2
0
2/
0
O
),,(L O )(F O
O
SAT
Angular Dependence Model (ADM)
ddsincos),,(L
),,(L),,(R
O
2
0
2/
0
OJOJ
),,(R
),,(L),,(F
OJ
OO
Flux
with
),,(R OJ where is the ADM for the ‘j’ scene
Clear-Sky Ocean CERES ADMPolar plots for the SW clear-sky ADMs at the 0°-25° SZA bin. Radii represent the VZAs and polar angles represent the AZMs. Sun is located at the 180° AZM.
Low wind (0-3 m/s)
High wind (9-12 m/s)
OLR I (zt;,)ddd
0
10
20
I (zt ;,)
B (0)T (zt ,0;,) B ( z )
T (zt , z ;,)
z d z
0
zt
N i() I (zt ,) f i( )d
i
cos()
Equator Crossing Times for NOAA Polar Orbiters
OLR: Outgoing
LW Radiation
Multi-spectral HIRS OLR Algorithm
ai=regression coefficients=local zenith angle
Ellingson et al. (1989)
OLRa0() ai()N ii
()
OLR I (zt;,)ddd
0
10
20
I (zt ;,)
B (0)T (zt ,0;,) B ( z )
T (zt , z ;,)
z d z
0
zt
N i() I (zt ,) f i( )d
i
cos()
HIS OLR Regression Model
• Channels and spectral intervals – stepwise regression based on 1600 Phillips soundings and radiation transfer model
HIRS Channel Wavelength (μm) Atmos Sensitivity
H7 13.1-13.6 Near Sfc temp
H10 7.8 – 8.5 Lower trop water vapor
H12 6.6-6.9 Upper trop water vapor
H3 14.3-14.7 Air temp- at 100mb
OLR
+ Long ‘consistent’ time series
+ 4 times/day
- Assumptions on remaining part of the LW spectrum
- No equivalent product for SW
Clear-sky OLR Anomaly (Jan 1998)
AVHRR OLR lacks sensitivity to water vapor variation, especially the upper tropo. humidity (UTH).
SW LW
Fo cosθSfc obsSat obs
LID
AR
CLO
UD
RA
DA
R
PR
EC
. R
AD
AR
SU
RF
. R
AD
AR
lidar
Cloud radar
Precipitation radar
ALTIMETER
scatterometer
Monitoraggio icebergs
SARDipole eddies in Sarichef Strait, which separates Hall and St. Matthew islands, Bering Sea, Alaska, were captured by the ERS-1 satellite in February 1992. The individual eddies have diameters of 5 to 9 km with tails of 12 to 19 km. The eddies were tidally generated, and the tidal amplitude was high at the time of the imaging. The eddies were observed only when frazil and grease ice acted as tracers.
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