Abstract

The Cross-track Infrared Sounder (CrIS) aboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite is a spaceborne Fourier transform infrared spectrometer. The study aims to retrieve carbon dioxide (CO2) information (the CO2 profile and column-averaged dry-air mole fraction of XCO2) from June 2018 to December 2019 based on the The National Oceanic and Atmospheric Administration (NOAA)-Unique Combined Atmospheric Processing System (NUCAPS) Cloud-Cleared Radiances (CCRs) via the CrIS. The CCRs products for the CrIS with 2223 channels have been available since 22 May 2018. Characteristics of the CO2 weighting functions inform the choice of multiple channels that are around 15 μm in size that differ by latitude and season to maximize retrieval sensitivity to CO2 and minimize sensitivity to other interfering atmospheric parameters. CO2 was retrieved from these channels using an adopted nonlinear optimization algorithm. The temperature, water vapor, and ozone profiles used in the inversion process were gathered from the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5). Validations of CO2 concentrations as retrieved from CrIS showed the following conclusions: (1) The relative error of the retrieved CO2 concentrations, as compared to Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) in situ aircraft measurements, was less than 0.5%, and the root mean square errors (RMSE) were less than 0.7 ppmv (with correlation coefficients of 0.56–0.86); (2) the retrieved XCO2 from June 2018 to December 2019 correlated well with the ground-based Total Carbon Column Observing Network (TCCON) observations, and the differences were within ±0.2 ppmv. Further analysis of the temporal and spatial distribution of the retrieved CO2 at 300 hPa demonstrated a strong seasonal variation of CO2 in 0–60° N in the Northern Hemisphere with the maximum values in June–August and larger amplitudes of seasonal variation in the northeast of Asia and northeastern part of North America. The variations likely occurred due to larger sinks of atmospheric CO2 that are dominated by CO2 uptake in the summer. In the Southern Hemisphere, the CO2 displayed high concentration anomalies in the latitudinal range of 30–60° S in September–November and December–February, which probably occurred due to the lofted smoke plumes from the strong fire seasons in South America and Southern Africa.

Highlights

  • Climate change is a global issue for the international community, and it is the most serious global environmental problem that requires attention

  • The World Data Centre for Greenhouse Gases (WDCGG) released the latest report on CO2 in October of 2018, which showed that the global average CO2 concentration reached 403.3 ± 0.1 ppmv in 2016 and that the annual mean increase in CO2 was 3.3 ppmv from 2015 to 2016, which was greater than the previous increase from 2012 to 2013 [3]

  • The flight data of 10 seconds synthesis provided by the official CARIBIC website for four days met our needs

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Summary

Introduction

Climate change is a global issue for the international community, and it is the most serious global environmental problem that requires attention. The World Data Centre for Greenhouse Gases (WDCGG) released the latest report on CO2 in October of 2018, which showed that the global average CO2 concentration reached 403.3 ± 0.1 ppmv in 2016 and that the annual mean increase in CO2 was 3.3 ppmv from 2015 to 2016, which was greater than the previous increase from 2012 to 2013 [3]. Reasons for the rapid increase in CO2 mainly arise from human activities which influence the exchange of CO2 in different reservoirs. Even worse, this may lead to a ripple effect on other parts of our ecosystem, releasing more CO2 into the air from ice and permafrost near the poles.

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