Evaluating Carbon Monoxide and Aerosol Optical Depth Simulations from CAM-Chem Using Satellite Observations

Débora Souza Alvim,Monica Tais Siqueira D’Amelio,Claudia Boian,Bushra Khalid,Júlio Barboza Chiquetto,Silvio Nilo Figueroa,Paulo Nobre,Paulo Yoshio Kubota,Jayant Pendharkar,Vinicius Buscioli Capistrano,Ariane Frassoni,Sergio Machado Corrêa,Dirceu Luis Herdies

doi:10.3390/rs13112231

Abstract

The scope of this work was to evaluate simulated carbon monoxide (CO) and aerosol optical depth (AOD) from the CAM-chem model against observed satellite data and additionally explore the empirical relationship of CO, AOD and fire radiative power (FRP). The simulated seasonal global concentrations of CO and AOD were compared, respectively, with the Measurements of Pollution in the Troposphere (MOPITT) and the Moderate-Resolution Imaging Spectroradiometer (MODIS) satellite products for the period 2010–2014. The CAM-chem simulations were performed with two configurations: (A) tropospheric-only; and (B) tropospheric with stratospheric chemistry. Our results show that the spatial and seasonal distributions of CO and AOD were reasonably reproduced in both model configurations, except over central China, central Africa and equatorial regions of the Atlantic and Western Pacific, where CO was overestimated by 10–50 ppb. In configuration B, the positive CO bias was significantly reduced due to the inclusion of dry deposition, which was not present in the model configuration A. There was greater CO loss due to the chemical reactions, and shorter lifetime of the species with stratospheric chemistry. In summary, the model has difficulty in capturing the exact location of the maxima of the seasonal AOD distributions in both configurations. The AOD was overestimated by 0.1 to 0.25 over desert regions of Africa, the Middle East and Asia in both configurations, but the positive bias was even higher in the version with added stratospheric chemistry. By contrast, the AOD was underestimated over regions associated with anthropogenic activity, such as eastern China and northern India. Concerning the correlations between CO, AOD and FRP, high CO is found during March–April–May (MAM) in the Northern Hemisphere, mainly in China. In the Southern Hemisphere, high CO, AOD, and FRP values were found during August–September–October (ASO) due to fires, mostly in South America and South Africa. In South America, high AOD levels were observed over subtropical Brazil, Paraguay and Bolivia. Sparsely urbanized regions showed higher correlations between CO and FRP (0.7–0.9), particularly in tropical areas, such as the western Amazon region. There was a high correlation between CO and aerosols from biomass burning at the transition between the forest and savanna environments over eastern and central Africa. It was also possible to observe the transport of these pollutants from the African continent to the Brazilian coast. High correlations between CO and AOD were found over southeastern Asian countries, and correlations between FRP and AOD (0.5–0.8) were found over higher latitude regions such as Canada and Siberia as well as in tropical areas. Higher correlations between CO and FRP are observed in Savanna and Tropical forests (South America, Central America, Africa, Australia, and Southeast Asia) than FRP x AOD. In contrast, boreal forests in Russia, particularly in Siberia, show a higher FRP x AOD correlation than FRP x CO. In tropical forests, CO production is likely favored over aerosol, while in temperate forests, aerosol production is more than CO compared to tropical forests. On the east coast of the United States, the eastern border of the USA with Canada, eastern China, on the border between China, Russia, and Mongolia, and the border between North India and China, there is a high correlation of CO x AOD and a low correlation between FRP with both CO and AOD. Therefore, such emissions in these regions are not generated by forest fires but by industries and vehicular emissions since these are densely populated regions.

Highlights

In the last decade, studies have shown that one of the consequences of climate change is the intensification of anthropogenic fires, which lead to changes in land cover, mainly in forested regions
The model results were compared with a priori satellite carbon monoxide (CO) observations from the Measurements of Pollution in the Troposphere (MOPITT) instrument and aerosol optical depth (AOD) from the Moderate-Resolution Imaging Spectroradiometer (MODIS)
We evaluate model simulation against observations, we present the results of the observed CO concentrations (Figure 1a, Figure 2a, Figure 3a, Figure 4a, Figure 5a) and results from experiments with CAM-TROPMAM (Figure 1b, Figure 2b, Figure 3b, Figure 4b, Figure 5b) and CAM-STRATMAM (Figure 1d, Figure 2d, Figure 3d, Figure 4d, Figure 5d) for different seasons (DJF, MAM, JJA, SON) and for the period with maximum biomass burning over South America (ASO)

Summary

Introduction

Studies have shown that one of the consequences of climate change is the intensification of anthropogenic fires, which lead to changes in land cover, mainly in forested regions. Fires produce extensive plumes of smoke, mainly in the dry season [1,2] This is alarming in the sense that significant changes in atmospheric composition and air quality may occur [3], which can be studied by using remote sensing data. Lacking aerosol optical depth (AOD) and CO concentration measurements on the surface and even at altitude can be complemented by using global remote information obtained through sounders onboard environmental satellites Studies such as those presented in [4,5] show the advantage of using information from the environmental satellite MODIS (Aqua and Terra) to detect and monitor the concentration of gases

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