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A Progress Report on Combining MODIS and CALIPSO Aerosol Data for Direct
Radiative Effect Studies
Jens Redemann, Qin Zhang, Philip Russell, John Livingston, Mark Vaughan
BAERI –NASA Ames – SRI – SSAI
http://geo.arc.nasa.gov/AATS-website/
email: [email protected]
Outline A discourse on cloud edge aerosol retrievals
Goal: To devise a new, multi-instrument methodology to derive vertical
structure of F(z)
1. CALIOP observations of aerosol backscatter/extinction profiles
2. MODIS full column AOD (and cloud screening)
3. OMI aerosol absorption optical depth
4. Satellite flux measurements (CERES-like)
First step: find commonalities between coincident and collocated MODIS-
Aqua and CALIPSO observations
Study examples of cloud screening/detection methods
Make detailed comparisons of instantaneously collocated MODIS and
CALIPSO AOD retrievals, April 2007
Purpose: Provide input for CALIPSO aerosol extinction retrieval algorithm
team & define a suitable data sets for combined analysis
Conclusions
A discourse on cloud edge aerosol retrievals
2007 A-Train Conference, Lille, FR2007 A-Train Conference, Lille, FR
MODIS (500m) 553nm-AOD versus airborne sunphotometer
MODIS (500m) 553nm-AOD versus airborne sunphotometer
Subtracted cloud-adjacent pixels in along-scan direction
MODIS (500m) 1240nm-AOD versus airborne sunphotometer
CALIPSO (5km)CALIPSO (1km)
CALIPSO (333m)
MOD35 (1km)
MOD04 std3x3 (500m)
Comparison of cloud detection: MODIS vs. CALIOP
Aerosol Optical Depth comparisons One month of data, April 2007
Use CALIPSO 40km-avg. aerosol extinction profiles, and 5km aerosol
and cloud layer products
Find all (up to 4) instantaneously collocated, MYD04_L2 10x10km
aerosol retrievals traversed by CALIPSO track
Focus on over-ocean only
Apply three CALIPSO profile quality criteria:
1. Alt_top_aerosol > Alt_top_cloud
2. EQC532_flag = 0 or 1
3. Integrated attenuated backscatter @ 532 <=0.011
Stratify by MODIS cloud fraction
Break down geographically
Alt_top_aerosol > Alt_top_cloud
All three quality controls
Zonal dist. of CALIPSO and MODIS aerosol retrievals
Zonal dist. of QC CALIPSO and MODIS aerosol retrievals
Zonal dist. of CALIPSO and MODIS AOD
Important: subset of MODIS AOD along CALIPSO track has same zonal mean as global MODIS AOD => CALIPSO likely samples representative subset
2007 LMU, Redemann2007 LMU, Redemann
n= 57 r2 = 0.001y = 0.054 x + 0.116rms= 0.140, 132.3 %M aod = 0.106C aod = 0.122
n= 405 r2 = 0.063y = 0.822 x + 0.066rms= 0.148, 181.6 %M aod = 0.082C aod = 0.133
n= 548 r2 = 0.031y = 0.561 x + 0.072rms= 0.217, 131.2 %M aod = 0.165C aod = 0.164
n= 116 r2 = 0.000y = 0.014 x + 0.103rms= 0.286, 121.0 %M aod = 0.236C aod = 0.107
n= 59 r2 = 0.006y = 0.037 x + 0.077rms= 0.150, 152.9 %M aod = 0.098C aod = 0.081
n= 427 r2 = 0.015y = 0.415 x + 0.085rms= 0.141, 146.6 %M aod = 0.096C aod = 0.125
n= 707 r2 = 0.175y = 0.728 x + 0.043rms= 0.175, 100.6 %M aod = 0.174C aod = 0.169
n= 75 r2 = 0.024y = 0.155 x + 0.026rms= 0.187, 113.4 %M aod = 0.165C aod = 0.051
n= 71 r2 = 0.001y = 0.026 x + 0.084rms= 0.117, 120.7 %M aod = 0.097C aod = 0.086
n= 464 r2 = 0.038y = 0.560 x + 0.077rms= 0.168, 155.1 %M aod = 0.108C aod = 0.137
n= 1210 r2 = 0.111y = 0.660 x + 0.098rms= 0.254, 125.6 %M aod = 0.202C aod = 0.231
n= 267 r2 = 0.002y = 0.086 x + 0.115rms= 0.304, 135.6 %M aod = 0.224C aod = 0.135
n= 61 r2 = 0.009y = 0.078 x + 0.055rms= 0.071, 81.6 %M aod = 0.086C aod = 0.062
n= 441 r2 = 0.110y = 0.548 x + 0.034rms= 0.106, 91.7 %M aod = 0.115C aod = 0.097
n= 591 r2 = 0.151y = 0.237 x + 0.143rms= 0.250, 92.3 %M aod = 0.271C aod = 0.207
n= 154 r2 = 0.015y = 0.344 x + 0.052rms= 0.290, 172.4 %M aod = 0.168C aod = 0.109
n= 41 r2 = 0.063y = -0.342 x + 0.109rms= 0.112, 114.8 %M aod = 0.098C aod = 0.076
n= 362 r2 = 0.025y = 0.407 x + 0.074rms= 0.154, 157.9 %M aod = 0.098C aod = 0.114
n= 900 r2 = 0.350y = 0.826 x + 0.038rms= 0.186, 65.5 %M aod = 0.284C aod = 0.273
n= 0 r2 = NaNy = 0.000 x + 0.000rms= 0.000, NaN %M aod = NaNC aod = NaN
n= 95 r2 = 0.046y = 0.513 x + 0.051rms= 0.090, 126.6 %M aod = 0.071C aod = 0.087
n= 363 r2 = 0.084y = 0.547 x + 0.068rms= 0.110, 144.8 %M aod = 0.076C aod = 0.109
n= 925 r2 = 0.046y = 0.266 x + 0.113rms= 0.247, 105.8 %M aod = 0.233C aod = 0.175
n= 149 r2 = 0.000y = 0.004 x + 0.101rms= 0.496, 146.1 %M aod = 0.339C aod = 0.102
Longitude
Latit
ude
AOD scatter info.,2007-04,Ocean Only,3-QC
180oW 120oW 60oW 0o 60oE 120oE 180oW
80oS
40oS
0o
40oN
80oN
Geographical distribution of correlation data, all cloud fractions
n= 16 r2 = 0.530y = 1.278 x + 0.015rms= 0.052, 71.5 %M aod = 0.073C aod = 0.109
n= 42 r2 = 0.199y = 0.829 x + 0.023rms= 0.050, 82.0 %M aod = 0.061C aod = 0.074
n= 54 r2 = 0.283y = 0.780 x + 0.001rms= 0.078, 67.0 %M aod = 0.117C aod = 0.092
n= 14 r2 = 0.165y = 0.274 x + 0.001rms= 0.126, 82.8 %M aod = 0.152C aod = 0.042
n= 25 r2 = 0.667y = 1.167 x + 0.006rms= 0.041, 69.6 %M aod = 0.058C aod = 0.074
n= 75 r2 = 0.169y = 0.507 x + 0.036rms= 0.050, 64.7 %M aod = 0.078C aod = 0.075
n= 234 r2 = 0.629y = 0.985 x + -0.020rms= 0.088, 53.7 %M aod = 0.164C aod = 0.142
n= 10 r2 = 0.005y = 0.016 x + 0.014rms= 0.107, 101.5 %M aod = 0.105C aod = 0.016
n= 27 r2 = 0.304y = 1.437 x + 0.000rms= 0.097, 128.3 %M aod = 0.076C aod = 0.109
n= 64 r2 = 0.011y = 0.141 x + 0.068rms= 0.066, 92.5 %M aod = 0.071C aod = 0.078
n= 212 r2 = 0.610y = 0.847 x + -0.004rms= 0.083, 52.1 %M aod = 0.159C aod = 0.131
n= 88 r2 = 0.418y = 0.433 x + 0.005rms= 0.154, 67.8 %M aod = 0.227C aod = 0.104
n= 20 r2 = 0.232y = 0.800 x + 0.022rms= 0.030, 52.5 %M aod = 0.057C aod = 0.067
n= 85 r2 = 0.305y = 0.559 x + 0.022rms= 0.050, 64.3 %M aod = 0.078C aod = 0.066
n= 264 r2 = 0.553y = 0.638 x + 0.026rms= 0.130, 52.0 %M aod = 0.250C aod = 0.186
n= 89 r2 = 0.334y = 0.342 x + 0.001rms= 0.118, 77.2 %M aod = 0.153C aod = 0.053
n= 11 r2 = 0.461y = 0.560 x + 0.027rms= 0.032, 43.2 %M aod = 0.075C aod = 0.069
n= 67 r2 = 0.250y = 0.944 x + 0.020rms= 0.066, 92.0 %M aod = 0.072C aod = 0.088
n= 293 r2 = 0.633y = 1.053 x + -0.023rms= 0.114, 38.9 %M aod = 0.292C aod = 0.285
n= 0 r2 = NaNy = 0.000 x + 0.000rms= 0.000, NaN %M aod = NaNC aod = NaN
n= 35 r2 = 0.175y = 0.694 x + 0.028rms= 0.049, 81.8 %M aod = 0.061C aod = 0.070
n= 93 r2 = 0.455y = 0.858 x + 0.022rms= 0.042, 87.3 %M aod = 0.048C aod = 0.063
n= 185 r2 = 0.415y = 0.583 x + 0.035rms= 0.116, 55.5 %M aod = 0.210C aod = 0.157
n= 45 r2 = 0.522y = 0.430 x + -0.003rms= 0.148, 72.1 %M aod = 0.205C aod = 0.085
Longitude
Latit
ude
AOD scatter info.,2007-04,Ocean Only,3-QC,FOC<0.01
180oW 120oW 60oW 0o 60oE 120oE 180oW
80oS
40oS
0o
40oN
80oN
Geographical distribution of correlation data, cloud fractions < 1%
2007 LMU, Redemann2007 LMU, Redemann
Conclusions1) Different cloud screening techniques in MODIS and CALIPSO aerosol
algorithms produce very different results, making search for collocated data complicated.
2) April 2007 AOD comparisons:
Total CALIPSO: ~ 195,000
Valid CALIPSO AOD: ~ 64,000
Valid CALIPSO and collocated MODIS AOD: ~32,000
Valid QC’ed CALIPSO and collocated MODIS AOD: ~8,500
Valid QC’ed CALIPSO and collocated MODIS AOD, FOC<1%: ~2,000
3) Most data between 0-20N
4) For “clear” conditions (FOC<1%), correlation is starting to look decent, with CALIPSO AOD lower than MYD04_L2 by about 20%
5) Largest disagreement between MODIS and CALIPSO at 30-80N
6) MODIS data collocated with CALIPSO has same zonal mean AOD as entire MODIS data set => CALIPSO likely samples representative subset
