Diurnal, seasonal and vertical distribution of carbon monoxide levels and their potential sources over a semi-arid region, India

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Rama Gopal Kotalo
Elijabetthamma Busa
Balakrishnaiah Gugamsetty
Raja Obul Reddy Kalluri
Chakradhar Rao Tandule
Lokeswara Reddy Thotli
Manjunatha Chakala
Surya Nagi Reddy Palle

Abstract

The present study focused on the investigation of both near-surface and vertical variability of carbon monoxide (CO) concentrations and their potential sources obtained from both in situ and  Satelite Measurements of Pollution in the Troposphere (MOPITT) over a semi-arid region, Anantapur, India from January 2016 to December 2017. The diurnal variation of CO shows sharp morning (07:00-9:00 hrs) and evening peaks (07:00-9:00 hrs) associated to the local anthropogenic activities as well as the impact of mixed layer height, and low concentrations during daytime (12:00-15:00hrs). The low levels during afternoon hours may be due to increasing of mixed layer height and decrease of anthropogenic sources. The seasonal mean CO showed no obvious variation, with highest levels  observed in winter (329± 52 ppbv) followed by pre-monsoon (327 ± 57 ppbv), post-monsoon (234 ± 36 ppbv) and monsoon (192 ± 22 ppbv). The high levels of CO in the winter season attributed to increased emissions from anthropogenic sources and shallow the mixed layer height. The vertical distribution of CO showed secondary peak levels at high-pressure levels (300 hPa – 200 hPa) during winter, pre-monsoon, and post-monsoon, which indicates CO transport from different source regions. These findings  are reasonably confirmed through the air mass Concentrated Weighted Trajectory (CWT) analysis obtained from the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT). This study suggests that except monsoon, air masses transported from Indo – Gangetic Basin (IGB) region also contributes in enhancing  CO concentrations at the receptor site.

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