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[1] Satellite (LIS) based lightning flash grid (0.5°Â 0.5°) data for the Indian land mass region covering from 8°-33°N and 73°-86°E for a period of 4 years (1998 -2001) were used to study the diurnal variation with one hour time resolution. The analysis revealed that there exists a strong diurnal cycle in the lightning activity with a prominent peak around 1000 UTC. An examination of seasonal diurnal variation suggests that the lightning activity was found highest in premonsoon and lowest in the postmonsoon season.

This paper presents a study of spatiotemporal variation of lightning activity over Peninsular India (88-228N, 728-888E) by using monthly satellite-based lightning flash grid (18 3 18) data for a period of 10 yr (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007). The data are examined in terms of spatial, annual, and seasonal distribution of the lightning activity. It is found that lightning activity is higher over south Peninsular India and eastern India. On a seasonal time scale, the lightning activity shows two maxima-first in the month of May and then in the month of September. The lightning activity in the monsoon period is noticed to be considerable because of the occurrence of the lowlevel jet and increase in the monsoon break period. During the postmonsoon, the activity is mainly due to the presence of the convective nature of the disturbed weather during the northeast monsoon season over most parts of the east coast of south Peninsular India. The relationship between lightning activity over Peninsular India and sea surface temperature in the bordering seas (Arabian Sea and Bay of Bengal) is also examined. The results disclose a significant link between them.

This paper discussed the urban heat island (UHI) intensity and local air quality by using observational data of project of the System of Air Quality Forecasting and Research (SAFAR) over Delhi during the month of May and December 2013. It is found that UHI magnitudes ~2.2˚C and ~1.5˚C are formed at the evening traffic hours during May and December respectively. Also, intensity of UHI < 0˚C over daytime is referred as Urban Cool Island (UCI) during May and December. The diurnal PM 2.5 concentration shows a bimodal pattern with peaks at morning and evening traffic hours during May and December. The planetary boundary layer height (PBLH) values show higher in magnitude during the daytime and lower in magnitude during the night-time. Whereas, the Ground Heat Flux values are lower during the daytime and higher during the night-time. The wind speed shows lower values during the UHI and higher magnitudes during the UCI formation hours. Concentration of PM 2.5 and wind speed shows a strong negative correlation during May (r = −0.56, p = 0.002) and December (r = −0.57, p = 0.001) at C V Raman (CVR) site, however, high values in the concentration of PM 2.5 during the low wind speed favour the condition for the formation of UCI. The regression analysis indicated that PM 2.5 plays a significant role in the daytime cooling and nighttime warming over the urban areas during the low wind speed condition.

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