s5p tropospheric ozone product: convective cloud differential method first german s5p verification...
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S5P tropospheric ozone product:Convective Cloud Differential method
First German S5P Verification Meeting Bremen, 28 - 29 November 2013
Pieter Valks
DLR, Remote Sensing Technology Institute (IMF)
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Outline
Convective-Cloud-Differential (CCD) algorithm for S5P
Analyses of CCD method with GOME-2 data
Analyses of cloud parameters
Variability in stratospheric and upper tropospheric ozone
Tropical tropospheric ozone column
Further analyses and development for S5P
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S5P tropical tropospheric ozone with CCD method
Convective-cloud-differential (CCD)
method
above cloud and clear-sky ozone column measurements
Tropical tropospheric ozone columns (TTOC) below ~200 hPa
S5P data required:
Total ozone columns
Effective cloud fractions, cloud albedo and cloud-top pressures (OCRA and ROCINN)
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S5P cloud parameters used for CCD method
Effective cloud fraction
S5P_CLOUD_OCRA
f > 0.8 (stratospheric column)
f < 0.1 (cloud free)
Cloud pressure and albedo
S5P_CLOUD_ROCINN
CTP < 300 hPa
CTA > 0.8
(deep convective clouds)
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Stratospheric ozone column calculation
Above-cloud ozone column (ACOC) using S5P Level-2 total ozone product
Selection of S5P measurements in the tropics (20°N-20°S):
Deep convective tropical clouds (f > 0.8, CTP < 300 hPa, CTA > 0.8)
Low ozone concentrations inside cloud
East Indian Ocean / Western Pacific (70°E – 170°W)
Vac = SCD / AMFcloud (no ghost column)
Stratospheric ozone column (monthly
mean)
1.25° latitude bands
Stratospheric ozone column
independent of longitude
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Tropical tropospheric ozone column
Tropical Tropospheric Ozone Column (TTOC) S5P Level-3 product
Selection of cloud-free S5P L2 ozone measurements (f < 0.1)
Vclear = SCD / AMFclear
Monthly (weekly) mean values on a 1.25° by 2.5° lat-lon grid (20°N-20°S)
GOME-2 Tropospheric O3 Oct. 2010
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Analyses of CCD method with GOME-2 data
Analyses of cloud parameters
Variability in stratospheric and upper tropospheric ozone
Tropical tropospheric ozone column Exemplary results Comparison with ozonesonde measurements
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Cloud parameters (OCRA/ROCINN)
Frequency of deep convective clouds (f > 0.8, CTP < 300 hPa, CTA > 0.8)
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Cloud parameters (OCRA/ROCINN)
Frequency of deep convective clouds (f > 0.8, CTP < 300 hPa, CTA > 0.8)
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Cloud parameters (OCRA/ROCINN)
Histogram of cloud pressure and albedo for Eastern Indian Ocean / Western Pacific
(12.5°S - 12.5°N, 70°E – 170°W , f > 0.8)
Cloud Pressure Jan. 2008 Cloud Albedo Jan. 2008
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Cloud parameters (OCRA/ROCINN)
Histogram of cloud pressure and albedo for Eastern Indian Ocean / Western Pacific
(12.5°S - 12.5°N, 70°E – 170°W , f > 0.8)
Cloud Pressure July 2008 Cloud Albedo July 2008
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Variability in stratospheric ozone column
Monthly mean stratospheric ozone column
1.25° latitude bands between 20°S - 20°N
Assumption: stratospheric ozone column independent of longitude in tropics
Comparison of GOME-2 CCD stratospheric ozone column with ozonesondes
Comparison for 8 SHADOZ sites
Bias: ≤ 3 DU
RMS differences: 3-7 DU
Comparisons with other stratospheric ozone satellite measurements (Ziemke et al.)
TOMS CCD comparison with SAGE II (Bias: 1-4 DU; RMS differences: 4-5 DU)
OMI CCD comparison with MLS (Bias: 1-3 DU; RMS differences: 2-3 DU)
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Variability in upper tropospheric ozone
Ozone concentrations in deep convective clouds (cloud slicing technique)
Above-cloud O3 column Indian Ocean
1-3 Oct. 2007 10-20ºN/70-90ºE
Above-cloud O3 column Western Pacific
1-3 Oct. 2007 10-20ºS/160-180ºE
Mean ozone mixing ratio: ~7 ppbvMean ozone mixing ratio: 4 ~ppbv
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Variability in upper tropospheric ozone
Ozone concentrations in deep convective clouds (cloud slicing technique)
Above-cloud O3 column Indian Ocean
1-3 March 2008 0-10ºN/70-90ºE
Above-cloud O3 column Western Pacific
1-3 March 2008 0-10ºS/120-140ºE
Mean ozone mixing ratio: ~6 ppbvMean ozone mixing ratio: ~8 ppbv
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GOME-2B tropical tropospheric NO2 and ozone
Tropospheric Ozone
Tropospheric NO2
October, 2013
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GOME-2 tropical tropospheric NO2 and ozone
Tropospheric Ozone
Tropospheric NO2
September, 2010
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Comparison with ozonesonde measurements
Bias: -0.9 DU
RMS: 3.4 DU
Natal, Brazil (5ºS, 35ºW)
R: 0.89
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Comparison with ozonesonde measurements
Bias: -1.4 DU
RMS: 3.9 DU
Ascension Island (8ºS, 15ºW)
R: 0.85
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Comparison with ozonesonde measurements
Bias: -1.7 DU
RMS: 3.6 DU
American Samoa (14ºS, 171ºW)
R: 0.75
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GOME-2 tropospheric ozone ENSO index
Nino 3.4 ENSO temp. index
temperature anomalie in eastern Pacific
Ozone ENSO index
ozone column difference between western and eastern Pacific
R = 0.90
Correlation between Nino 3.4 Temp. ENSO and Ozone ENSO index
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Further analyses and development for S5P
Cloud parameters
Same cloud algorithms (OCRA/ROCINN) used for GOME-2 and S5P
Cloud selection criteria (f, CTP, CTA) to be optimized for S5P
dependent on FOV, ground pixel size, etc.
CCD method sensitive to albedo related instrument effects
(e.g. TTOC bias between GOME-2A and GOME-2B)
Spatial and temporal resolution
Temporal resolution: monthly, weekly, daily?
Valid latitude range varies with month (but only for tropics)
Spatial resolution: currently 1.25° x 2.5° lat-lon (GOME-2)
Analyse with OMI data and (simulated) S5P data
Operational processing and product format
Realistic estimates of CPU / RAM / Product size
Product format
Implementation in PDGS (Level-3 product)