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How well can we measure the vertical profile of aerosol extinction?. Aerosol layers over Oklahoma as seen from Twin Otter on May 27, 2003 Photo courtesy of Roy Woods. B. Schmid [1] , R. Ferrare [2] , C. Flynn [3] , R. Elleman [4] , - PowerPoint PPT Presentation
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Aerosol layers over Oklahoma as seen from Twin Otter on May 27, 2003
Photo courtesy of Roy Woods
How well can we measure the vertical profile of aerosol extinction?
0
1
2
3
4
5
6
0 0.1 0.2 0.3Aerosol Extinction (1/km)
Alti
tude
(km
)
Neph+PSAP (453 nm) 18:34-18:52 UT
B. Schmid [1], R. Ferrare [2], C. Flynn [3], R. Elleman [4],D. Covert [4], A. Strawa [5], E. Welton [6], J. Barnard [3],
M. Bartholomew [7], M. Clayton [8], J. Eilers [5], G. Hallar [5], B. Holben [6], H. Jonsson [9], J. Michalsky [10], J. Redemann [1],
K. Ricci [11], A. Smirnov [12], D. Turner [3]
[1] Bay Area Environmental Research Institute, Sonoma, CA[2] NASA Langley Research Center, Hampton, VA
[3] Pacific Northwest National Laboratory, Richland, WA[4] University of Washington, Seattle, WA
[5] NASA Ames Research Center, Moffett Field, CA[6] NASA GSFC, Greenbelt, MD
[7] Brookhaven National Laboratory, Upton, NY [8] SAIC/NASA Langley Research Center, Hampton, VA
[9] Center for Interdisciplinary Remotely-Piloted Aircraft Studies, Marina, CA[10] NOAA/CMDL, Boulder, CO
[11] Los Gatos Research, Mountain View, CA[12] GEST/UMBC/ NASA GSFC, Greenbelt, MD
Photo courtesy Yin-Nan Lee, BNL
How do we measure the vertical profile of aerosol extinction?
Airborne:• Nepehelometer+PSAP• Cavity-Ring-Down (Cadenza) • Sunphotometry (AATS-14)
Ground based:• Raman Lidar (CARL)• MPLNET• MPLARM
Airborne in-situ measurement of
Extinction =Absorption
• Particle Soot Absorption Photometer (PSAP)
=467, 530, 660 nm• low RH• Corrections (Bond et al.,
1999, Virkkula et al, 2004)– scattering contribution– loading correction– ambient p, T
Scattering• Nephelometers
– TSI: = 450, 550, 700 nm, low RH
– RR: = 540 nm, RH=20,60,85%
• Corrections (Anderson & Ogren, 1998) – light source– angular truncation (7°-170°)– ambient RH, p, T
+
L
cR L L Lext Ray absorber( )1 1
ext c aer 1 1 1
0( )
where L = cell lengthc = speed of lightR = reflectivity of mirrors = coefficient of extinction, Rayleigh, gaseous absorbers
where = ringdown timeaer = with aerosol0 = without aerosol
Iin(t)
ring-down cavity
Iout(t)
time
Extinction from Airborne Cavity Ring-Down System
Aerosol was sampled at low RH (comparable to TSI)
Used RR-Neph measured growth curve to adjust to ambient RH
NASA Ames Airborne Tracking SunphotometerAATS-14: 354-2139 nm
Aerosol Optical Depth and H2O columnAerosol Extinction and H2O density in suitable profiles
Photo courtesy Yin-Nan Lee, BNL
Raman Lidar
• Aerosol Extinction profiles =355 nm • Unnoticed loss of sensitivity leading up to AIOP• Automated algorithms had to be modified to reduce impact of sensitivity loss.• Significant upgrades/mods were performed after AIOP resulting in significantly better performance than during any other time.
•Backscatter Lidar •Deployed during AIOP (in SMART trailer) •Aerosol Extinction profiles =523 nm •AOD anchored to AERONET, BER constant with altitude•Level 2.0 (ext. prof. when valid AERONET AOD)•Periodic overheating problems
•Backscatter Lidar •Deployed permanently at SGP•Aerosol Extinction profiles =523 nm is a new product in -stage
•AOD anchored to NIMFR, BER constant with altitude
MPLARM
Focus on data obtained in vertical profiles over SGP CF
Altitudes: ~90 – 5600 m
CIRPAS Twin OtterARM Aerosol IOP – May 2003
x y # profiles # data pointsAATS-14 Neph+PSAP 26 3484AATS-14 Cadenza 26 2856
AATS-14 MPLNET 2.0 13 587AATS-14 MPLARM 19 2073
AATS-14 Raman Lidar 11 468
AATS-14 in-situ H2O 35 6705
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
340 nmbias= 0.022, 6%rms= 0.038, 10%
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
380 nmbias= 0.022, 7%rms= 0.035, 11%
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
440 nmbias= 0.022, 8%rms= 0.032, 12%
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
501 nmbias= 0.016, 7%rms= 0.027, 11%
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
675 nmbias= 0.008, 5%rms= 0.019, 11%
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
870 nmbias= 0.002, 2%rms= 0.015, 12%
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
1020 nmbias= 0.002, 2%rms= 0.015, 14%
1 3 6 9 12 15 18-0.1
-0.05
0
0.05
0.1
1638 nmbias= -0.006, -9%rms= 0.013, 20%
AO
D: A
ER
ON
ET
min
us A
ATS
-14
Observation #
1 3 6 9 12-0.1
-0.05
0
0.05
0.1
415 nmbias= -0.004, -1%rms= 0.012, 4%
1 3 6 9 12-0.1
-0.05
0
0.05
0.1
500 nmbias= 0.006, 2%rms= 0.010, 4%
1 3 6 9 12-0.1
-0.05
0
0.05
0.1
615 nmbias= 0.007, 4%rms= 0.013, 7%
1 3 6 9 12-0.1
-0.05
0
0.05
0.1
673 nmbias= 0.001, 1%rms= 0.009, 6%
1 3 6 9 12-0.1
-0.05
0
0.05
0.1
870 nmbias= -0.002, -1%rms= 0.007, 6%
AO
D: N
IMFR
min
us A
ATS
-14
Observation #
0 2 4 6 8 10 12 14 16
0
2
4
6
8
10
12
14
16
n= 6705 r2 = 0.958y = 1.021 x + -0.224rms= 0.628, 19.4 %
in-situ - H2O Density [g/m3]
AA
TS-1
4 - H
2O D
ensi
ty [g
/m3 ]
Extinction
-0.004
0.000
0.004
0.008
0.012
0.016
0.020
0.024
0.028
Raman
Neph+P
SAP
Neph+P
SAP
MPLNET
MPLARM
Neph+P
SAP
Caden
za
Caden
za
Bias
(1/k
m)
Extinction
-50%
-40%
-30%
-20%
-10%
0%
10%
20%
30%
40%
50%
Raman
Neph+P
SAP
Neph+P
SAP
MPLNET
MPLARM
Neph+P
SAP
Caden
za
Caden
zaRela
tive
Bias
Aerosol Optical Depth
-0.03-0.02-0.010.000.010.020.030.040.050.060.070.080.09
Raman
NIMFR
Cimel
Neph+P
SAPNIM
FRCim
el
MPLNET
MPLARM
Neph+P
SAPNIM
FRCim
el
Caden
za
Neph+P
SAPCim
el
Caden
za
Bias
Diff
eren
ce
Aerosol Optical Depth
-45%
-35%
-25%
-15%
-5%
5%
15%
25%
35%
45%
55%
Raman
NIMFR
Cimel
Neph+P
SAPNIM
FRCim
el
MPLNET
MPLARM
Neph+P
SAPNIM
FRCim
el
Caden
za
Neph+P
SAPCim
el
Caden
zaBias
Diff
eren
ce
How well did past campaigns do on AATS vs Neph+PSAP comparisons?
U.S. East Coast, 1996, Bias -14% (Hegg et al., 1997, Hartley et al., 2000)
Canary Islands, 1997, Bias -20% (after inlet correction) (Schmid et al.,
2000)
Southern Africa, 2000, Bias -4% (Magi et al., 2003)
U.S. East Coast, 2001, Bias -15% Magi et al. (2004)
Eastern Asia, 2001
C-130: Bias: +6% Redemann et al., 2003
Twin Otter: Bias -13% Schmid et al., 2003
Oklahoma, 2003, Bias -14%
Aerosol IOP
Conclusions• When compared to airborne sunphotometer extinction,
in-situ measurements are biased low (2 - 4 Mm-1 VIS 12-17%, NIR 45%)
• Looking at results from 6 field campaigns, airborne Neph+PSAP measurements of extinction tend to be biased slightly low (<15%, VIS) when compared to airborne sunphotometer extinction.
• Micro-Pulse Lidar measurements biased high – MPLNET 4 Mm-1,13% – MPLARM 7 Mm-1, 24%
• Raman Lidar measurements biased high (29 Mm-1 UV 54%). We expect better agreement from a “healthier” Raman lidar.
Suggestion to AWG
• Improved Raman Lidar needs validation• Newly developed MPLARM extinction
profile algos need validation• Enhanced IAP plane will need validation
With a small amount of flight hours (i.e. AATS-14 on J-31) these objectives could be met in a cost effective way