Association of atmospheric pollution and instability indices: A detailed investigation over an Indian urban metropolis
Section snippets
List of acronyms
CAPE Convective Available Potential Energy LI Lifted Index NO2 nitrogen dioxide SO2 sulphur dioxide BC black carbon PM2.5 particulate matter (size < 2.5 μm) FAR false alarm rate BS Brier score CO carbon monoxide NWP numerical weather prediction PPM perfect prognostic method RPG-HATPRO Radiometer Physics GmbH-Humidity and Temperature Profiler KI K-Index TTI Total Totals Index NCEP National Center for Environmental Prediction VWSH vertical wind shear ULWS upper-level wind shear LLWS low-level wind shear SST sea surface
Experimental set-up and dataset used
Meteorological parameters and instability indices have been taken by a ground based Dicke radiometer (RPG-HATPRO) stationed at the rooftop of Institute of Radio Physics and Electronics, University of Calcutta, located at Kolkata (22°32′N, 88°20′E), India for the present study. It measures brightness temperatures at two frequency bands which are then converted to several atmospheric parameters using suitable retrieval methodologies (Chakraborty and Maitra, 2016). Table 1 indicates the brief
Variation of atmospheric instability parameters over the Indian sub-continent
Three factors emerge as important ingredients for strong convective development. They are moisture content, atmospheric instability and sufficient lifting force. As mentioned earlier, the atmospheric instability mainly refers to an irregularity in atmospheric temperature lapse rate profiles leading to localized air heating and intense updrafts on the onset of severe convective events. Saha et al. (2014) showed that the thunderstorm frequency has reduced at Kolkata in the past decade. In lieu of
Conclusions
The decrease in the CAPE, KI, TTI and increase in LI are responsible for the decrease of severe thunderstorm events during the study period. There is a sole anti-correlation between the instability indices and wind speed, which also determines the increasing stability of the atmosphere during the past 16 years. Based on the physical significances of the three instability indices, a new simpler index, KLURT index, has been designed which will be a pre-cursor for any convective phenomena and will
Acknowledgements
U.S. thankfully acknowledges the financial assistance provided by University Grants Commission (UGC), New Delhi, India, under the scheme of Dr. D.S. Kothari Post-Doctoral Fellowship (No. F.4-2/2006(BSR)/ES/15-16/0022). This work has also been partly supported under the collaboration of Banaras Hindu University, Varanasi and University of Calcutta, Kolkata. The authors acknowledge with thanks the West Bengal Pollution Control Board, Kolkata for providing us continuous pollution chart for our
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