Characteristics of tropospheric carbon monoxide profiles retrieved from MOPITT measurements
In this thesis, measurements of tropospheric carbon monoxide (CO) obtained by the Measurements of Pollution in the Troposphere (MOPITT) instrument are investigated. The MOPITT instrument and measurement techniques are discussed, and recent results from the MOPITT validation campaign are presented.;MOPITT phase I retrieved CO profile measurements are compared to in situ data obtained during the ACTO campaign. These comparison suggest that MOPITT CO profiles may possess a positive bias throughout the troposphere. The results also demonstrate the need to take into account the effects of vertical resolution and the influence of the a priori on MOPITT retrieved profiles through the use of the retrieval averaging kernels.;Comparisons of MOPITT and TOMCAT model CO profiles are also presented. The results suggest that MOPITT profiles are biased high compared to the model, and that these biases vary greatly from location to location. Simulations conducted using MOPITT operational averaging kernels to investigate the ability of the MOPITT instrument to measure layer enhancements of CO are then discussed. It is shown that MOPITT is sensitive to layer enhancements, although it is not always possible to determine the altitude of such enhancements. The seasonal cycle in MOPITT CO profile data is derived and compared to that of six CMDL surface measuring sites. A method for detecting long range transport events with anomalous CO using a regional analysis, which achieves limited success, is presented. Finally, an investigation of the combined use of the differing sensitivity of MOPITT between day and night in order to gain extra vertical information from MOPITT data is discussed. This is the first such study of its kind and the results are encouraging. Analysis shows that by examining the difference between day and night MOPITT retrieved 'surface' data it is possible, in a number of regions and seasons, to obtain further information on the vertical structure of CO. The results are validated using the TOMCAT model to represent the 'real' atmosphere. Examinations of day-night differences in phase I MOPITT data suggest that it is possible to use these differences to identify CO source regions such as biomass burning and industrialised regions.