Understanding the Influence of Biomass Burning �on Tropospheric Ozone through Assimilation of TES data

Jennifer Logan �Harvard University

Dylan Jones, Mark Parrington�University of Toronto

Kevin Bowman, Helen Worden, John Worden, Greg Osterman

Jet Propulsion Laboratory�California Institute of Technology

Impact of Biomass Burning on Tropospheric O₃

TES CO, 421 mb: Nov 4-17, 2004

TES O₃, 421 mb: Nov 5-17, 2004

GEOS-Chem CO 421 mb: Nov 4-17, 2004

GEOS-Chem O₃, 421 mb: Nov 4-17, 2004

Climatological emission inventory in the model underestimates the impact biomass burning on CO and O₃ in the southern hemisphere

ppb

ppb

Objective: Assess the potential of TES data to improve O₃ in the model in a chemical data assimilation framework

Impact of Assimilation on CO and O₃ (using a sequential sub-optimal Kalman filter with TES O₃ and CO profile retrievals for Nov. 4-17, 2004)�

Change in O₃ at 7 km (assim. - without assim.)

24-hr averaged assimilated O₃ at 7 km on Nov. 17

(ppb CO)

percent

• Assimilation increases CO throughout the southern hemisphere
• Largest increases in O₃ (20-50%) are over the Indian Ocean and the Indonesian/Australian region

(ppb O3)

percent

24-hr averaged assimilated CO at 7 km on Nov. 17

Change in CO at 7 km (assim. - without assim.)

Assimilation of TES O₃ for 1 July 2005 - 1 Jan. 2006

Assimilation

Free running model

O₃ difference: assimilation - free running model

data gaps

Mean GEOS-Chem O₃ at 8 km between 20°S-equator and 180°W-180°E

• In early Sept 2005 the assimilation increases O₃ by about 20% in upper troposphere
• During the 2 week data gap in September the analysis reverts to the state of the free running model

Comparison with Ozonesonde Data at La Reunion Island (21°S, 55°E)

12 Oct 2005

17 Oct 2005

28 Oct 2005

2 Nov 2005

assimilation

free running model

sonde

• The ozone tropopause in GEOS-Chem is too low in Austral spring 2005 compared to the sonde data

​

• Assimilation of TES data reduces the bias in the model

Comparison of the O₃ Analysis with TES Observations (350 mb)

• During October the assimilation reduces the bias in the model by about a factor of 2
• Despite the reduction in the bias, the residuals for the OmA are still large

Comparison of the CO Analysis with TES Observations (350 mb)

• Following the warm-up of the TES optical bench in Dec. 2005, the assimilation significantly reduced the bias in CO in the model
• In contrast to the O₃ analysis, the CO OmA residuals are small, reflecting the longer lifetime of CO

TES OB �warm-up

Assimilation extended through 1 Sept 2006

Latitudinal Dependence of the O₃ Analysis Residuals (350 mb)

The assimilation has less impact in summer 2006 because we are propagating the forecast error variance without accounting for forecast error growth �⇒ by summer 2006 the forecast error is about 15% in the tropics and subtropics, compared to the assumed 50% error in July 2005

Larger OmA residuals in the tropics, reflecting the shorter O₃ lifetime and a lower density of TES data

20°S-0°

30°N-60°N

Conclusions

• Assimilation of TES O₃ data produces a much improved distribution of O₃ in the model, which provides greater constraints on model parameters such as the lifetime of NOx� ⇒ a better constraint on the NOx lifetime will result in improved estimates of NOx emissions from lightning and of the export of NOy from continental source regions
• In contrast to the CO analysis, the residuals in the O₃ assimilation are large, especially in the tropics, reflecting the shorter lifetime of O₃ (and the low density of the TES data)� ⇒ assimilating trace gases that are more chemical active than CO will be a challenge
• A better approach for exploiting the satellite data would be to optimize the model parameters, such as the emissions, using adjoint techniques � ⇒ work is needed to characterize the forecast errors across the range of chemical timescales in the model