Journal of Atmospheric and Solar–Terrestrial Physics 211 (2020) 105452 Available online 10 October 2020 1364-6826/© 2020 Elsevier Ltd. All rights reserved. Atmospheric electric feld variations during fair weather and thunderstorms at different altitudes Hripsime Mkrtchyan a, * , Gayane Karapetyan a , Davit Aslanyan a a A.Alikhanyan National Science Laboratory, Armenia A R T I C L E INFO Keywords: Thunderstorm activity Fair weather Lightning activity Temperature Wind speed ABSTRACT Ground-based electric feld measurements during fair weather and thunderstorms are key parameters for Global Electric Circuit investigations and climate change assessment. We study the variations of near surface electric feld during fair weather and thunderstorms. In this work we present daily, monthly and yearly distribution of thunderstorm activity from 2012 to 2019 at different research stations of Cosmic Ray Division (CRD) of the A. Alikhanyan National Science Laboratory (Yerevan Physics Institute) which has been done the frst time for mentioned locations. The distribution of fair-weather days based on electric feld variation and meteorological parameters are also discussed. According to results, thunderstorm activity is very high from May to June and the most active part during the day is from 15:00 to 20:00 LT at three different altitudes. 1. Introduction Fair weather investigations show that a typical near surface electric feld at the ground is between 100 and 300 V/m Marshall et al. (1999). However, at the NASA Kennedy Space Center (at sea level) and U.S. Air Force Cape Canaveral Air Station the electric feld at the ground some- times reached 400–1200 V/m shortly after sunrise on days that other- wise seemed to be fair weather. Marshal T.C. et al. (1999) investigated this phenomenon and concluded that it is caused by solar heating after sunrise. Similar phenomenon was observed in mountainous regions of Armenia and Israel. Yaniv et al. (2017) suggested that as the sun rises charged particles accumulated near the surface due to the electrode effect rise up with evaporating dew and get blown uphill by intensifed surface winds. Yaniv et al. (2017), concluded that the main reason for the electric feld addition in the early morning are not charged particles themselves but the addition of aerosol concentrations (that also get carried by uphill winds), which results in lower conductivity. Past investigations have also revealed that thunderstorm activity is related to the fair weather through global electric circuits (Williams, 2009). Continuous measurements of electric felds have proven that there is not only an annual but also a daily variation of thunderstorm activity. Past investigations (Turman and Edgar, 1982, Whipple, 1929) have shown that thunderstorm activity by universal time has three maximums during each 24-h period, which correspond to the three tropical thunderstorm regions: Asia (at 09:00 UT), Africa (at 14:00 UT) and South America (at 20:00 UT) and a minimum (near 03:00 UT). It was suggested that each peak in the late afternoon hours (LT) is a result of solar heating of the surface during the day. The minimum is observed, when the sun is over the Pacifc Ocean. Ranalkar and Chaudhari (2019) discovered that May has the maximum frequency of lightning fashes and thunderstorm activity over the Indian subcontinent for 0–35N, 60E–100E. In the same work they also observed that thunderstorm activity during May occurs late at night and early in the morning hours (LT). Kumar, (2017) observed a good correlation of lightning activity with surface temperature and convec- tive available potential energy (CAPE). The main goal of this work is to investigate electric feld variations during fair weather and thunderstorms over different regions in Armenia during the year. Data obtained from our 4 stations (Dilijan station was only used for fair weather investigations, while Nor Amberd, Yerevan and Aragats stations for both fair weather and thunderstorm activity studies). In different locations are giving excellent opportunities to investigate daily and seasonal near surface electric feld disturbances, fuctuations of thunderstorms, and the relation of fuctuations with altitude. Moreover, studies of simultaneous measurements of electric feld and meteorological parameters correlations can reveal thunder- cloud electric structure, global and local electric circuit characteristics. Thunderstorm activity investigations can also be informative to farmers and provide data for crop protection. In this work we have taken Local Time which corresponds to UT +4 * Corresponding author. E-mail address: hripsime@yerphi.am (H. Mkrtchyan). Contents lists available at ScienceDirect Journal of Atmospheric and Solar-Terrestrial Physics journal homepage: www.elsevier.com/locate/jastp https://doi.org/10.1016/j.jastp.2020.105452 Received 26 March 2020; Received in revised form 5 September 2020; Accepted 8 September 2020