A climate-scale satellite record for carbon monoxide: the MOPITT Version 7 product

Abstract

Abstract. The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making observations of atmospheric carbon monoxide since 2000. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the version 7 (V7) product. Improvements include (1) representation of growing atmospheric concentrations of N2O, (2) use of meteorological fields from the MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications) reanalysis for the entire MOPITT mission (instead of MERRA), (3) use of the MODIS (Moderate-Resolution Imaging Spectroradiometer) Collection 6 cloud mask product (instead of Collection 5), (4) a new strategy for radiance-bias correction and (5) an improved method for calibrating MOPITT's near-infrared (NIR) radiances. Statistical comparisons of V7 validation results with corresponding V6 results are presented, using aircraft in situ measurements as the reference. Clear improvements are demonstrated for V7 products with respect to overall retrieval biases, bias variability and bias drift uncertainty.

Satellite‐Based Analysis of CO Seasonal and Interannual Variability Over the Amazon Basin

“…MOPITT retrieval products have progressively improved as the result of improved understanding of the instrument, advances in forward modeling methods, and a variety of algorithm enhancements (Worden et al, ). Results presented in this manuscript are based on the MOPITT Version 7 (V7) “multispectral” TIR‐NIR product (Deeter et al, ). This product variant provides greater vertical resolution than either the TIR‐only or NIR‐only variants.…”

“…The MOPITT retrieval algorithm employs optimal estimation (Deeter et al, ). Through the use of a cloud mask based on collocated Moderate Resolution Imaging Spectroradiometer (MODIS) observations and MOPITT's own calibrated radiances, only clear‐sky observations are processed by the retrieval algorithm.…”

“…For each retrieved base‐10 log(VMR) profile resulting from a single MOPITT observation, the retrieval averaging kernel matrix A is produced simultaneously and is provided to users as a diagnostic. The matrix A characterizes the sensitivity of the retrieved log(VMR) profile x r t v to both the true log(VMR) profile x true and a priori log(VMR) profile x a through the relation MOPITT a priori profiles, which vary both geographically and seasonally, are based on a CO climatology for the years 2000–2009 simulated with the CAM‐chem chemical transport model (Deeter et al, ; Lamarque et al, ).…”

“…Validation results for MOPITT V7 products based on aircraft in situ profiles acquired by National Oceanic and Atmospheric Administration (NOAA) mainly over North America and over the Pacific Ocean during the HIAPER Pole‐to‐Pole Observations (HIPPO) field campaign were reported in Deeter et al (). The results demonstrated that MOPITT V7 retrieval biases are both geographically and temporally variable.…”

“…Each panel lists the overall bias, standard deviation, and correlation coefficient. Because the state vector used in the MOPITT retrieval algorithm fundamentally deals with log(VMR) values rather than VMR values directly, bias and standard deviation statistics are presented as fractional errors (%) rather than absolute errors (ppb) (Deeter et al, ). Dotted lines in each panel indicate the ideal zero‐bias line as well as fixed biases of positive and negative 10%.…”