Assessment of troposphere carbon monoxide variability and trend in Iraq using atmospheric infrared sounder during 2003-2016

Abstract

Background and Objective: Tropospheric Carbon Monoxide (CO) is indirect greenhouse gas and one of the most significant air pollutant produced from the biomass burning, combustion of fossil fuels and the oxidation of methane (CH4) by hydroxyl radicals (OH) or other carbonaceous gases. The aim of this study was to analyze the spatial and temporal variations of CO and to estimate its long term-trends over study area. Materials and Methods: Results of the retrieved monthly CO volume mixing ratio (VMR) obtained from Atmospheric Infrared Sounder (AIRS) data, included on the EOS Aqua satellite, from January, 2003-December, 2016 over Iraq were employed. In order to better assess the CO distribution, trend analysis used for seven stations dispersed across Iraq: Mosul, Sulaimaniyah, Rutba, Baghdad, Nukhayb, Nasiriyah and Basra. The spatial distribution analyses of the CO maps were generated employing Kriging interpolation technique. Results: The results showed a considerable variability of monthly CO in spatial and temporal scale, the monthly mean and the standard deviation of CO was 0.125±0.02 ppm for the entire period. The maximum values (0.158 ppm) were over Northern and Northwestern regions (Mosul and Rutba) in February and March and the minimum values (0.096 ppm) over Southern regions (Nasiriya and Basra) in October. The CO values during winter were higher than its values in summer season and Northern area have the highest values of CO throughout the year due to the meteorological conditions and geographic features. Trend analysis showed a negative trend for the months of the year overall selected stations refer to a considerable decreasing of CO values reached to -0.0026 ppm/year which represent about 2% of the mean value. A stagnation and stability feature was obvious from annual trend analysis during 2003-2007 and decreased in 2008 till 2016. Conclusion: The AIRS observation efficiently showed the spatial and temporal variations of CO for the considered study area.