1

Validation of OMI Ozone Profile and Tropospheric Ozone Retrievals

Xiong Liu1,2,3, Pawan K. Bhartia3, Kelly Chance2, Thomas P. Kurosu2, B.R. Bojkov1,3, Robert J.D. Spurr4, Ozonesonde Investigators

xliu@umbc.edu

1Goddard Earth Sciences and Technology Center,UMBC 2Harvard-Smithsonian Center for Astrophysics

3NASA Goddard Space Flight center 4RT Solutions Inc.

OMI Science Team MeetingJune 25, 2008

2

Outline

Introduction

Comparison with OMTO3 and OMDOAO3

Comparison of OMI ozone profiles and stratospheric ozone columns with MLS data

Comparison of OMI ozone profiles and tropospheric ozone columns with ozonesonde data

Examples of retrieved tropospheric ozone

Summary and future work

3

Introduction

OMI ozone profile retrieval (Liu et al., 2005)

Retrieve ozone at 24 ~2.5-km thick layers from 270-330 nm radiancesOptimal estimation techniqueUse ozone profile climatology by Mcpeters et al. (2007) to constrain retrievalsApply X-track and wavelength-dependent correction (assuming multiplicative) derived from 1 day’s zonal mean MLS in the tropicsDFS: 5-8 in the atmosphere with up to 2 in the troposphere.Vertical resolution: ~6-8 km FWHM in the stratosphere and ~8-15 km in the troposphere

4

Introduction

Information content in the first 0-3 km layer

DFS: 0.15-0.4 for most of the latitude range (i.e., 15-40% of ozone deviated from a priori can be retrieved at this layer)

40-80% of ozone deviated from a priori can be captured in the retrievals

5

Random (N) and Smoothing (S) Errors

N: <~2% above 22 km and within ~10% belowS+N: within 3% between 22-40 km, increase to 10% above 40 km, and to 15-30% below 20 km.SOC: 0.5-2 DU (N), 1.5-4 DU (S+N)TOC: 0.8-3 DU (N), 1.5-6 DU (S+N)TOZ: 0.2-3 DU (N), 0.5-6 DU (S+N)

6

Comparison with OMTO3and OMDOAO3

Comparison for 12 days in 2006 OMTO3: 2.5-3.3 ± 3.3-4.7 DU ( 0.9-1.1± 1.1-1.5%)OMDAO3: -1.2-3.3 ± 4.2-6.7 DU (-0.3-1.1± 1.4-2.1%)

Larger biases at high SZA

7

Comparison with MLS Ozone Profiles MLS: on-board EOS-AURA, spatiotemporally coincident with OMI MLS O3 error estimate: ~5% in the upper strat., ~10-15% in the

lower strat., ~2-3% in strat. O3 column (Froidevaux et al., 2007)

8

Comparison with MLS Ozone Profiles

Mean biases and standard deviations are within ~5% between 2-50 mb.

9

Comp. with MLS 215 hPa O3 Column

15 days of ComparisonMean Bias: -0.5-1%

Std. Dev. (Global): 2.4-2.9% Std. Dev. (Tropics): 1.8-2.6%

0-200 hPa O3 columns can be accurately derived from

OMI !!!

10

Comp. with MLS 215 hPa O3 Column

11

Comparison with Ozonesondes

Ozonesonde data: available at AURA AVDC for August 2004-March 12, 2007

For consistency, all ozonesonde data are not normalized to coincident total ozone column

Coincidence criteria: within 6 hours, 1º longitude & latitude, OMI edge pixels excluded

Focus on two latitude bands: Tropics (30ºS-30ºN), Northern Mid- Latitudes (30ºN-60ºN)

Compare profile and tropospheric O3 column (surface-200 mb)

Ozonesonde profiles are convolved with OMI averaging kernels, but not the tropospheric ozone column

12

Comparison with Ozonesondes (30ºS-30ºN)

Profile: within 15%, significant improvement throughout the troposphere

Tropospheric Ozone column (Surface-200 mb): –4.65.6 DU, high correlation (0.8)

Solid line: meanDashed line: 1

13

Comparison with Ozonesondes (30ºN-60ºN)

Within 10-20%, significant improvement in the middle and upper troposphere.

14

Comparison with Ozonesondes (30ºN-60ºN)

Northern Midlatitudes (30ºN-60ºN)Winter: 2.39.2 DU, R = 0.58Spring: 1.88.7 DU, R = 0.74Summer: -5.66.4 DU, R = 0.79Fall: 0.75.6 DU, R = 0.51

Seasonal/latitudinal dependent biases

Not from vertical resolution & radiative transfer approximation

15

“Boundary ozone” (0-3 km) Ozone over Southeast Asia

Enhanced ozone over Indonesia in Oct. 2006 relative to Oct. 2005.

Enhanced ozone over South China especially in Oct. 2006.

16

Column-Averaged O3 Mixing Ratio (July 15 – September 7, 2006)

17

Summary

Ozone profiles and tropospheric ozone are retrieved from OMI radiances. Stratospheric and tropospheric ozone columns can be very well derived from OMI data alone.

OMI ozone profiles and stratospheric ozone columns compare well with MLS, to within combined retrieval uncertainties.

OMI ozone profiles and tropospheric ozone columns compare well with ozonesonde data, but show seasonal and latitude-dependent biases.

Retrievals show signals due to pollution, biomass burning, regional and intercontinental transport, convection, and stratospheric influence.

18

Future Work

Better understand biases with respect to other correlative measurements and continue to improve retrieval algorithm

Speed up retrieval algorithm with specialized VLIDORT or linearized TOMRAD (Dave Flittner).

Make data available for the whole OMI record.

Interpret retrievals using CTMs, meteorology, in-situ and other satellite data.

Acknowledgements

OMI and MLS Science Teams Support from NASA Support from various organizations on

Ozonesonde observations