Abstract
Abstract. The MOPITT (Measurements of Pollution in the Troposphere) satellite instrument has been making nearly continuous observations of atmospheric carbon monoxide (CO) since 2000. Satellite observations of CO are routinely used to analyze emissions from fossil fuels and biomass burning, as well as the atmospheric transport of those emissions. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the version 8 (V8) product. V8 products benefit from updated spectroscopic data for water vapor and nitrogen used to develop the operational radiative transfer model and exploit a new method for minimizing retrieval biases through parameterized radiance bias correction. In situ datasets used for algorithm development and validation include the NOAA (National Oceanic and Atmospheric Administration) and HIPPO (HIAPER Pole-to-Pole Observations) datasets used for earlier MOPITT validation work in addition to measurements from the ACRIDICON-CHUVA (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems – Cloud processes of the main precipitation systems in Brazil: A contribution to cloud resolving modeling and to the GPM (Global Precipitation Measurement)), KORUS-AQ (The Korea-United States Air Quality Study), and ATom (The Atmospheric Tomography Mission) programs. Validation results illustrate clear improvements with respect to long-term bias drift and geographically variable retrieval bias. For example, whereas bias drift for the V7 thermal-infrared (TIR)-only product exceeded 0.5 % yr−1 for levels in the upper troposphere (e.g., at 300 hPa), bias drift for the V8 TIR-only product is found to be less than 0.1 % yr−1 at all levels. Also, whereas upper-tropospheric (300 hPa) retrieval bias in the V7 TIR-only product exceeded 10 % in the tropics, corresponding V8 biases are less than 5 % (in terms of absolute value) at all latitudes and do not exhibit a clear latitudinal dependence.
Highlights
MOPITT (Measurements of Pollution in the Troposphere) is a gas correlation radiometer instrument on the National Aeronautics and Space Administration (NASA) Terra satellite which permits retrievals of carbon monoxide (CO) vertical profiles using both thermal-infrared (TIR) and near-infrared (NIR) measurements
In situ datasets used for algorithm development and validation include the NOAA (National Oceanic and Atmospheric Administration) and HIPPO (HIAPER Pole-to-Pole Observations) datasets used for earlier MOPITT validation work in addition to measurements from the ACRIDICON-CHUVA (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems – Cloud processes of the main precipitation systems in Brazil: A contribution to cloud resolving modeling and to the GPM (Global Precipitation Measurement)), KORUS-AQ (The Korea-United States Air Quality Study), and ATom (The Atmospheric Tomography Mission) programs
The remaining sections of this paper describe revisions made to the MOPITT version 8 retrieval algorithm (Sect. 2); the validation methodology and results (Sect. 3); and, the conclusions drawn from the results (Sect. 4)
Summary
MOPITT (Measurements of Pollution in the Troposphere) is a gas correlation radiometer instrument on the NASA Terra satellite which permits retrievals of CO vertical profiles using both thermal-infrared (TIR) and near-infrared (NIR) measurements. The availability of new in situ datasets (e.g., from field campaigns) has enabled the quantitative analysis of MOPITT retrieval biases in a variety of contexts As illustrated below, such in situ datasets may be used to both (1) mitigate temporally and geographically variable retrieval biases and (2) independently validate the resulting CO product. Over the MOPITT mission, validation results for V7 indicated significant long-term trends in the retrieval biases, i.e., bias drift. Similar drift values for 800 and 400 hPa retrievals are indicated in the updated bias time series plots for the V7 TIR-only product (based on in situ profiles acquired from 2000–2018) shown in Fig. 1; validation methods are described in Sect. The remaining sections of this paper describe revisions made to the MOPITT version 8 retrieval algorithm (Sect. 2); the validation methodology and results (Sect. 3); and, the conclusions drawn from the results (Sect. 4)
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