Thunderstorm clouds may reach the lower stratosphere, affecting the exchange of greenhouse gases between the troposphere and stratosphere. This region of the atmosphere is difficult to access experimentally, and our knowledge of the processes taking place here is incomplete. We recently recorded color video footage of thunderstorms over the Bay of Bengal from the International Space Station. The observations show a multitude of blue, kilometer‐scale, discharges at the cloud top layer at ~18 km altitude and a pulsating blue discharge propagating into the stratosphere reaching ~40 km altitude. The emissions are related to the so‐called blue jets, blue starters, and possibly pixies. The observations are the first of their kind and give a new perspective on the electrical activity at the top of tropical thunderstorms; further, they underscore that thunderstorm discharges directly perturb the chemistry of the stratosphere with possible implications for the Earth's radiation balance.

Due to fast and deadly spread of corona virus (COVID-19), the Government of India implemented lockdown in the entire country from 25 April 2020. So, we studied the differences in the air quality index (AQI) of Delhi (DTU, Okhla and Patparganj), Haryana (Jind, Palwal and Hisar) and Uttar Pradesh (Agra, Kanpur and Greater Noida) from 17 February 2020 to 4 May 2020. The AQI was calculated by combination of individual sub-indices of seven pollutants, namely PM 2.5 , PM 10 , NO 2 , NH 3 , SO 2 , CO and O 3 , collected from the Central Pollution Control Board website. The AQI has improved by up to 30-46.67% after lockdown. The AQI slope values − 1.87, − 1.70 and − 1.35 were reported for Delhi, − 1.11, − 1.31 and − 1.04 were observed for Haryana and − 1.48, − 1.79 and − 1.78 were found for Uttar Pradesh (UP), which may be attributed to limited access of transportation and industrial facilities due to lockdown. The ozone (O 3) concentration was high at Delhi because of lesser greenery as compared to UP and Haryana, which provides higher atmospheric temperature favourable for O 3 formation. The air mass back trajectory (AMBT) analysis reveals the contribution of air mass from Europe, Africa and Gulf countries as well as local emissions from Indo-Gangetic Plain, Madhya Pradesh and Maharashtra states of India.

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Characteristics of small, intermediate and large ions and nanometre particles, and the influences of environmental conditions and local topography on the interactions of these ions and particles in the size range of 3.85-47.8 nm diameter are studied during new particle formation (NPF) events observed at Pune, India from 20 March to 23 May 2012. During the NPF events, the formation rate of 5 nm particles ranged from 3.5 to 13.9 cm −3 s −1 and growth rates of both positive and negative ions were greater than those of neutral particles. Total ion concentrations in this size range were approximately double on event days than on non-event days. The NPF events were generally preceded by 2-3 h periods of enhanced concentration of ions and aerosols (PECIA) which are associated with katabatic winds from the surrounding hill-slopes at our site. During PECIA, ions ≤8 nm diameter grew faster and attained mode diameters greater than those of neutral particles. PECIA provided the ions of sub-8 nm diameter and dramatically reduced the condensation sinks and thus contributed to the development of conditions conducive for NPF. During PECIA, total concentrations of the ions and particles become almost equal and the Boltzmann charge distribution breaks down. During NPF events, mode diameters of the ions and particles first steeply decreased accompanied by a steep increase in condensation sink but later gradually increased at identical rates.Observations of charging ratio of 3-4 nm particles being higher than the charge equilibrium value and non-observation of charge equilibrium for >5 nm ions and particles indicate occurrence of ion nucleation and/or advection during the PECIA.

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