Lightning Characteristics Over Humid Regions and Arid Regions and Their Association With Aerosols Over Northern India

Abstract

The association between aerosol and lightning has been investigated with long-term decadal data (2005–2014) for lightning, aerosol optical depth (AOD), relative humidity, and effective cloud droplet size. To understand the complex relationship between aerosol and lightning, two different regions with different climatic and weather conditions, a humid region R1 (22°–29° N, 89°–92° E) and an arid region R2 (23°–28° N, 70°–76° E) of northern India, were chosen for the study domain. The results show that lightning activity was observed to occur more over the humid region R1, i.e., 1141 days (1/3 of total days), than over the arid region R2, i.e., 740 days (1/5 of total days). Also, over the humid region R1, the highest lightning flash density was recorded as nearly 4.6 × 10 –4 flashes/km 2 /day observed for 18 days (1.5%); on the contrary, over the arid region R2, the maximum lightning flash density was observed to be 2.5 × 10 –4 flashes/km 2 /day and occurred for about 22 days (2.9%). The analysis shows that a nonlinear relationship exists between aerosol and lightning with a highly associated influence of relative humidity. A very significant positive and negative co-relation that varies with relative humidity has been observed between AOD and lightning for both humid and arid regions. This shows relative humidity is the key factor in determining the increase or decrease of lightning activity. This study also shows that the larger the cloud droplet size, the higher the relative humidity and vice versa. This study emphasizes that aerosol concentration in the atmosphere influences cloud microphysics by modulating the size of cloud droplets and thereby regulating the lightning frequency. The atmospheric humidity is the driving factor in deciding the positive or negative co-relationship between aerosol and lightning. Supplementary Information The online version contains supplementary material available at 10.1007/s00024-022-02981-6.

Lightning Development over the Distinct Climate Regions of Uttarakhand, India

“…None of the meteorological parameters follows the trend of the lightning flash count, which shows that contribution of meteorological parameters in the development of lightning activity over Uttarakhand is less. This clearly emphasizes the role of large-scale meteorological processes such as western disturbance (15) orographic convection and monsoon convection in the development of lightning activity in this region. The contribution of orographic convection over Uttarakhand is explained by Gautam in his recent publication in the year 2022 (22) .…”

“…Aerosol optical depth (AOD) of 550 nm with 1 • x1 • grid resolution data is retrieved from Moderate Resolution Imaging Spectroradiometer (MODIS)T(https://giovanni.gsfc.nasa.gov/giovanni)for the period 2018 -2021. More details of different region of India & World (13,15)…”

“…In the Himalayan region, CAPE and surface temperature are responsible for the instability (50-60 % relative humidity at 700 hpa) and lead to an ideal condition for intense lightning (14) . The satellite and model datasets are indicating that lightning activities are also governed by the aerosol concentration and it is increasing with the aerosol concentration (15,16) . The lightning activities also depend on elevation, the slope of mountains and vegetation over the Himalayan region.…”