Association of Rainfall and Stability Index with Lightning Parameter over the Indo-Gangetic Plains

Abstract

The Lightning Imaging Sensor (LIS) based satellite lightning grid data for 10 year period (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) were used to study the association of rainfall and stability index with lightning parameter over Indo-Gangetic plain (IGP) region. The spatial variation of flash rate density (FRD) is found to be (40 fl·km −2 ·yr −1 ) higher over northern region of IGP as compare to that of eastern IGP region. The annual variation of FRD exhibits bimodal distributions, while the precipitation rate shows unimodal distributions. The results show that the FRD peaked 2 months (premonsoon) in advance to the monsoon months where rainfall peak occurred due to environmental lapse rates more than 7.0ºC/km during pre-monsoon which is evident from the temperature profile for correlation coefficient between temperature (700 mb) and FRD with coefficient of 0.70, p ≤ 0.0001 during pre-monsoon.The annual variation of lifted index show negative value over March to September due to intense insolation, convective available potential energy (CAPE) and also availability of moisture. The convective cloud transform into thundercloud with the development of mixed-phase (cloud water + ice) which subsequently produce the lightning. During monsoon, seasonal thermal heating diminishes and even on revival after break monsoon period, K-index is found to be less as the orography does not allow the highly moist air of low temperature to reach to large height above freezing level. They can be referred as maritime clouds of intermediate height with moderate updraft and hence minimum lightning activity during the monsoon season. Lifted index are proved to be indicators of thunderstorm conditions. This is because that rising air parcel is much warmer than its surroundings and can accelerate rapidly and create severe thunderstorms.

Synoptic Climatology of Pre-Monsoon Severe Lightning Events in Bangladesh

“…where,Te 500 & Te 850 is the environmental temperature at 500 & 850 hPa in ºC, Tp 850 & Tp 500 is the temperature of air parcel lifted adiabatically to 850 & 500 hPa in ºC,Td 850 is the dew point temperature at 850 hPa in ºC, TT represents the total totals index value, f8 and f5 represent the 850 & 500 hPa wind speed in knots, S is the sine of the angle between the 500 & 850 hPa wind directions (i.e., the shear), ΔTe 850 − 500 is the temperature difference between 850 to 500 hPa in ºC, DD 700 is the dew point depression at 700 hPa in ºC, Z n is the height of the equilibrium level (EL) in m, Z f is the height of the level of free convection (LFC) in m, g is the acceleration due to gravity in ms − 2 , ≈ top is the top altitude of a CIN layer in m, and ≈ bottom is the bottom altitude of a CIN layer in m. The values for LCL T , LCL P and P WAT were directly taken from the daily radiosonde data records. These stability indices are a measure of the atmospheric static stability, and the values are used to quickly assess the potential of the atmosphere to produce convection and consequently severe weather (Tinmaker et al, 2017). Moreover, annual casualties had increased by a signi cant amount due to improved news coverage.…”

“…13(a) clearly shows the upper atmospheric destabilization from mid-March to May. This is because the rising air parcel is much warmer than its surroundings and can accelerate rapidly and create severe thunderstorms (Tinmaker et al, 2017). The monthly mean LI are 0.58, -2.76, and − 2.…”

“…The K Index (KI) has been proved useful in indicating the probability of air mass thunderstorms (Anderson, 1991, Holle et al, 1992, Reap, 1994, and Reap and Foster, 1979. KI values higher than 35ºC indicate high probability for the development of numerous and/ or severe thunderstorms (Tinmaker et al, 2017). Nag et al (2017) indicated that the annual, seasonal, and diurnal cycles of lightning occurrence are unique to Bangladesh and this combination does not occur elsewhere in the Indian subcontinent.…”

Spatio-temporal variability of lightning climatology and its association with thunderstorm indices over India

“…K index is proved to help indicate the air mass thunderstorm. As the K index value increases, the probability of a thunderstorm increase (Tinmaker et al, 2017). The K index is based on the temperature lapse rate, lower tropospheric humidity, and the vertical extent of the wet layer.…”

Regional variability in lightning activity over South Asia

“…These studies significantly add not only in understanding the spatio‐temporal variability of lightning activity in particular area of investigation (Lal and Pawar, 2009; Ramesh Kumar and Kamra, 2010; Tinmaker et al ., 2010, 2014, 2015; Tinmaker and Ali, 2012; Siingh et al ., 2014; Lal et al ., 2018; Mushtaq et al ., 2018) but also over the whole Indian region (Kandalgaonkar et al ., 2003; Kandalgaonkar et al ., 2005; Yoshida et al ., 2007, Ranalkar and Chaudhari (2009); Murugavel et al ., 2014; Chate et al ., 2017; Nath et al ., 2009; Tinmaker et al ., 2019). In addition, these studies deal with some particular features such as the land‐ocean contrast (Nath et al ., 2009; Kandalgaonkar et al ., 2010a; Kandalgaonkar et al ., 2010b; Chate et al ., 2017), asymmetry in eastern and western parts of India (Nath et al ., 2009; Tinmaker and Chate, 2013), effect of El‐Nino and La‐Nina events (Siingh et al ., 2017; Saha et al ., 2017a; Tinmaker et al ., 2017a, 2017b; Saha et al ., 2017b) on the lightning activity and its temporal distribution in tropical cyclones over north Indian Ocean (Ranalkar et al ., 2017). Most of these localized case studies suggest that a relationship exists between the lightning flash rate and meteorological parameters, which govern the formation and development of storms.…”