Influences of the boundary layer evolution on surface ozone variations at a tropical rural site in India

Journal of Earth system science

M Naja2 3¹  S Lal4²  K K Reddy1³  N Ojha2 3¹  P Mahesh1³ 

[1] Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263 129, India.$$;Physical Research Laboratory, Ahmedabad, Navrangpura 380 009, India.$$;Yogi Vemana University, Kadapa, Tirupati, India.$$

关键词: Wind profiler;    boundary layer;    surface ozone;    box model;    air trajectory;    atmospheric sciences;    instruments and techniques/experiments;    modelling.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Collocated measurements of the boundary layer evolution and surface ozone, made for the first time at a tropical rural site (Gadanki 13.5°N, 79.2°E, 375 m amsl) in India, are presented here. The boundary layer related observations were made utilizing a lower atmospheric wind profiler and surface ozone observations were made using a UV analyzer simultaneously in April month. Daytime average boundary layer height varied from 1.5 km (on a rainy day) to a maximum of 2.5 km (on a sunny day). Correlated day-to-day variability in the daytime boundary layer height and ozone mixing ratios is observed. Days of higher ozone mixing ratios are associated with the higher boundary layer height and vice versa. It is shown that higher height of the boundary layer can lead to the mixing of near surface air with the ozone rich air aloft, resulting in the observed enhancements in surface ozone. A chemical box model simulation indicates about 17% reduction in the daytime ozone levels during the conditions of suppressed PBL in comparison with those of higher PBL conditions. On a few occasions, substantially elevated ozone levels (as high as 90 ppbv) were observed during late evening hours, when photochemistry is not intense. These events are shown to be due to southwesterly wind with uplifting and northeasterly winds with downward motions bringing ozone rich air from nearby urban centers. This was further corroborated by backward trajectory simulations.

【 授权许可】

Unknown