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)