The data assimilation of 2000-2004 carbon monoxide (CO) retrievals by the MOPITT (Measurements Of Pollution In The Troposphere) instrument onboard the NASA Terra satellite provide an opportunity for the first time to study the transport and sources of pollution including their year-to-year variations. Based on the different representations of assimilated CO in the chemistry transport model (CTM) space and at the MOPITT retrieval grid this study advocates for direct mapping of CO-sensitive radiances or characterized CO retrievals by the chemical data assimilation schemes. The comprehensive CO forecast provides a great deal of information on the vertical scales that cannot be constrained by the measured radiances. It also provides comprehensive a priori specifications for the inverse problems especially for the vertical levels and geographical regions where the radiometer begins to misplace its high sensitivity to the CO loading. Evaluation of the multi-year MOPITT retrievals and assimilated CO against in situ CO statistics showed how the data assimilation helps to diminish a priori effects in the reprocessed CO retrievals. Data analysis of the multi-year data reveal substantial inter-annual variations of CO loading in the free troposphere and call for the unbiased tracer assimilation schemes in the CTM with optimized CO surface emissions.
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 μm 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 views the earth with a pixel size 22 km by 22 km and a cross-track swath that measures a near-global distribution of CO every 3 days. In the operational MOPITT CO retrieval algorithm (V3; Version 3), surface skin temperature (Ts) and emissivity (E) are retrieved simultaneously with the CO profile. The accuracy of E and Ts is crucial for obtaining the CO retrieval within the 10% accuracy from the MOPITT measurements. However, because both Ts and E are retrieved from the same piece of information from the MOPITT measurements, the accuracy of both valuables may be limited. Extra surface skin temperature information is needed to determine surface emissivity, and vice versa. In this study, we use MODIS Ts within the MOPITT FOVs, in conjunction with those MOPITT signals most sensitive to the background scene, to compute the surface emissivity through an iterative retrieval algorithm. A monthly 1degree grid averaged 4.7 μm surface emissivity map is generated. The evaluation of the accuracy of this monthly 1 degree grid averaged 4.7 μm surface emissivity map is presented and its impacts on the retrievals of tropospheric CO profiles from the MOPITT measurements are also discussed.
The Measurements of Pollution In The Troposphere (MOPITT) instrument is designed to measure the spatial and temporal variation of the carbon monoxide (CO) profile and total column amount in the troposphere from the space. MOPITT channels are sensitive to both thermal emission from the surface and target gas absorption and emission. Surface temperature and emissivity are retrieved simultaneously with the CO profile. To obtain the desired 10% precision for the retrieved CO from MOPITT measurements, it is important to understand MOPITT CO channel sensitivity to surface temperature and emissivity and the impacts of the effects of any errors in retrieved skin temperature and emissivity on retrieved CO for various underlying surfaces. To demonstrate the impacts of the surface temperature and emissivity on the retrieval of the tropospheric CO profile, simulation studies are performed. The collocated Moderate Resolution Imaging Spectroradiometer (MODIS) surface products are used to assess the accuracy of the retrieved MOPITT surface temperature and emissivity.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.