HR: 08:45h
AN: A31A-04    [PDF]
TI: Improvement of the Retrieval of Surface Parameters from MOPITT Measurements and their Impact to the Retrievals of Tropospheric Carbon Monoxide Profiles
AU: * Ho, S
EM: spho@ucar.edu
AU: Gille, J C
EM: gille@ucar.edu
AU: Edwards, D P
EM: edwards@ucar.edu
AU: Warner, J
EM: juying@acd.ucar.edu
AU: Deeter, M N
EM: mnd@eos.ucar.edu
AU: Francis, G L
EM: gfrancis@ucar.edu
AU: Ziskin, D
EM: ziskin@ucar.edu
AB: Carbon monoxide (CO) is an important tropospheric trace species and can serve as a useful tracer of atmospheric transport. The Measurements of Pollution In The Troposphere (MOPITT) instrument uses the 4.7 micron CO band to measure the spatial and temporal variation of the CO profile and total column amount in the troposphere from space. Launched in 1999 on board the NASA Terra satellite, the MOPITT instrument was designed to perform with about 3-4 km vertical resolution and 22 km horizontal resolution. MOPITT is an eight-channel gas correlation radiometer; each channel generates an average (A) signal and a difference (D) signal. The thermal channel A-signals are sensitive primarily to emission from the surface, which depends on both the surface skin temperature (Ts) and emissivity (E). The D-signals are sensitive to both thermal emission/reflection and solar reflection (daytime) from the surface and target gas absorption and emission for different vertical levels. Because 4.7 micron CO bands are relatively optical thin through the atmosphere, the surface emission always provides the primary signals to the 4.7 micron thermal channels for both A- and D-signals. In the operational MOPITT CO retrieval algorithm (V3), surface skin temperature and emissivity are retrieved simultaneously with the CO profile. To obtain accurate MOPITT CO results, it is also important to retrieve surface skin temperature and surface emissivity accurately, and understand the effects of any errors in retrieved surface skin temperature and surface emissivity on retrieved CO. In this study, simulated retrieval experiments will be conducted to show the impacts of errors in retrieved surface skin temperature and surface emissivity on retrieved CO. Because MOPITT A-signals are sensitive to both surface emissivity and surface skin temperature, it requires an accurate specification of the surface skin temperature to determine surface emissivity. Therefore, the collocated MODIS surface skin temperatures (MOD11) within the MOPITT FOV are used as inputs for MOPITT 7A-signal, which is least contaminated by atmospheric absorption of CO, to compute the surface emissivity through an iterative retrieval algorithm. The monthly 1 degree-gridded averaged MOPITT 4.7 micron surface emissivity map is then used as a priori surface emissivity to constrain the surface skin temperatures obtained from the MOPITT simultaneous inversion algorithm. The validation of this monthly 1 degree-gridded averaged 4.7 micron surface emissivity map is presented and its impacts to the retrievals of surface skin temperature and tropospheric CO profiles from MOPITT measurements are also discussed.
DE: 0399 General or miscellaneous
DE: 0910 Data processing
DE: 0933 Remote sensing
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting