First simultaneous measurements of ozone, CO, and NO_y at a high‐altitude regional representative site in the central Himalayas

Abstract

Simultaneous in situ measurements of ozone, CO, and NO y have been made for the first time at a high altitude site Nainital (29. 37°N, 79.45°E, 1958 m above mean sea level) in the central Himalayas during [2009][2010][2011]. CO and NO y levels discern slight enhancements during the daytime, unlike in ozone. The diurnal patterns are attributed mainly to the dynamical processes including vertical winds and the boundary layer evolution. Springtime higher levels of ozone (57.5 ± 12.6 ppbv), CO (215.2 ± 147 ppbv), and NO y (1918 ± 1769.3 parts per trillion by volume (pptv)) have been attributed mainly to regional pollution supplemented with northern Indian biomass burning. However, lower levels of ozone (34.4 ± 18.9 ppbv), CO (146.6 ± 71 ppbv), and NO y (1128.6 ± 1035 pptv) during summer monsoon are shown to be associated with the arrival of air mass originated from marine regions. Downward transport from higher altitudes is estimated to enhance surface ozone levels over Nainital by 6.1-18.8 ppbv. The classification based on air mass residence time, altitude variations along trajectory, and boundary layer shows higher levels of ozone (57 ± 14 ppbv), CO (206 ± 125 ppbv), and NO y (1856 ± 1596 pptv) in the continental air masses when compared with their respective values (28 ± 13 ppbv, 142 ± 47 ppbv, and 226 ± 165 pptv) in the regional background air masses. In general, positive interspecies correlations are observed which suggest the transport of air mass from common source regions (except during winter). Ozone-CO and ozone-NO y slope values are found to be lower in comparison to those at other global sites, which clearly indicates incomplete in situ photochemistry and greater role of transport processes in this region. The higher CO/NO y value also confirms minimal influence of fresh emissions at the site. Enhancements in ozone, CO, and NO y during high fire activity period are estimated to be 4-18%, 15-76%, and 35-51%, respectively. Despite higher CO and NO y concentrations at Nainital, ozone levels are nearly similar to those at other global highaltitude sites.

WRF-Chem simulated surface ozone over south Asia during the pre-monsoon: effects of emission inventories and chemical mechanisms

“…It was shown that the anthropogenic emissions and their subsequent photochemical degradation over south Asia influence air quality over the Himalayas (e.g. Ojha et al, 2012;Sarangi et al, 2014) and the Tibetan Plateau (Lüthi et al, 2015) as well as the marine environment downwind of India (e.g. Lawrence and Lelieveld, 2010).…”

“…These results indicate the need for evaluating the effects of emission inventories and chemical mechanisms on the model performance using a network of stations across south Asia, which has not been carried out thus far. We focus on the pre-monsoon season (March-May) for the study, as O 3 mixing ratios at the surface are generally the highest over most of south Asia during this period (Jain et al, 2005;Debaje et al, 2006;Reddy et al, 2010;Ojha et al, 2012;Gaur et al, 2014;Renuka et al, 2014;Bhuyan et al, 2014;Sarangi et al, 2014;Yadav et al, 2014;Sarkar et al, 2015). This is because photochemistry over south Asia is most intense during this season due to the combined effects of high pollution loading, biomass-burning emissions and a lack of precipitation.…”

Science at High-Altitude Sites of ARIES - Astrophysics and Atmospheric Sciences

“…Set-up of all these instruments is shown in Fig. 8 while their detailed descriptions are given by Sarangi et al (2014).…”

Variations in surface ozone and carbon monoxide in the Kathmandu Valley and surrounding broader regions during SusKat-ABC field campaign: Role of local and regional sources

“…These instruments are regularly subjected to zero and span tests using internal ozone generator and ozone observations from both the instruments are also inter-compared by running them side by side and using a common inlet. Further details of such inter-comparisons 20 are reported in Sarangi et al (2014). CO measurements are conducted using analyzers from two make viz., Horiba APMA-370 (at Bode and Pantnagar) and Thermo 48i (at Nainital).…”

“…Regular zero check and span check for CO instruments are performed using a primary calibration mixture from Linde UK (1150 ppbv; Sarangi et al, 2016) and secondary gas from Chemtron Science Laboratories (1790 ppbv). Multipoint calibrations (ultra-pure gases) are also carried out in different observational ranges using a zero air generator 10 (Thermo model 1160) and a dynamic gas calibrator (Thermo model 146i) (Sarangi et al, 2014).…”