Derivation of Tropospheric Composition from Satellites Using a 3-D CTM

A contribution to ACCENT-TROPOSAT-2, Task Group 2

Martyn Chipperfield

Institute for Atmospheric Science, School of Earth and Environment,
University of Leeds, U.K.
Tel.:  +44-(0)113-343 6459
Fax:  +44-(0)113-343 6716

The direct observation of tropospheric composition is difficult and for many species the overlying stratosphere causes a number of complications. Different methods have been employed for the removal of the stratospheric part of total column observations, including using model results. However this is limited by the accuracy of the model.

The aim of this work is to use a detailed, tested 3-D chemical transport model (TOMCAT/SLIMCAT) to improve the quantitative derivation of tropospheric composition. TOMCAT/SLIMCAT will be used to simulate the stratosphere as accurately as possible. The model already gives a reasonable simulation of the stratosphere (following on-going improvements) but in this study we will further constrain the stratosphere by assimilating longer-lived species from long-term datasets such as HALOE (see Figure). In the first instance, and in collaboration with RAL, we will use GOME data (1995 onwards), and the CTM, to derive quantitative estimates of tropospheric NO2, BrO, HCHO and SO2 over the lifetime of the mission. We will also make use of RAL access to ATSR data to account for the occurrence of clouds. We will compare our calculations with other derivations of tropospheric species from GOME. In later work (2007 onwards) we would hope to study data from other recent missions.

Figure: Zonal mean fields of CH4 from SLIMCAT CTM. Left: without assimilation. Right: with assimilation of HALOE CH4, which improves the model tracer gradients in the subtropics.


18 months objectives

Set up long-term simulations of TOMCAT/SLIMCAT with chemical data assimilation. Derivation of first year of tropospheric composition from GOME using constrained CTM.

Time schedule

 

2004

2005

2006

2007

2008

2009

All Objectives

**

**

***

***

***

**

Approximate manpower and cost

 

2004

2005

2006

2007

2008

2009

Personnel / man-years

1

1

1

1

1

1

Yearly cost (kEuro)

10

10

10

10

60

60

Likely funding agencies

U.K. Natural Environment Research Council (NERC) Studentship until 2007 (costs until then are for travel only). PDRA funding will be needed after that.

Co-workers

Dr. Richard Siddans and Dr Brian Kerridge

Rutherford Appleton Laboratory, Chilton, U.K.

Ms Lara Gunn

School of Earth and Environment, University of Leeds, U.K.

 

 


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