Overview of solar eclipse of 21st June 2020 and its impact on solar irradiance, surface ozone and different meteorological parameters over eight cities of India

Highlights

• First time study of annular solar eclipse effect simultaneously at eight stations of India.

• Stations are located nearly perpendicular to the eclipse axis with magnitude 98.6% to 77.2%.

• Substantial reduction in solar radiation, surface ozone & temperature is evident.

• Atmospheric cooling from eclipse induced dynamical changes to the meteorological parameters.

Abstract

The present study is aimed to investigate the variation in solar radiance, surface ozone, temperature, relative humidity and wind velocity during the most recent and one of the most significant annular solar eclipses of 21st June 2020. Effects of solar eclipse have been analyzed first time at eight different cities of India located nearly perpendicular to the eclipse axis having an eclipse magnitude from 98.6 % to 77.2 %. Significant reductions in solar irradiance at different stations were found during the maximum phase of the solar eclipse due to the occultation of the Sun by the Moon. With the progression of the solar eclipse, surface ozone concentrations were also found to be decreasing and reached to its minimum value during the maximum phase of eclipse and then after the end of the eclipse started regaining their original behavior. Overall, the change in ozone was found to be proportional to eclipse magnitude. A decrease of ozone levels ranged from 30 % to 65 % over all the stations. In addition to the above, atmospheric cooling from the solar eclipse of 21st June 2020 induced dynamical changes to the meteorological parameters (temperature, relative humidity and wind speed) with the change being most prominent during the maximum phase of the solar eclipse.

Introduction

The phenomena like solar eclipse have always been very interesting to different researchers to assess their impact on our surroundings (Gogosheva et al., 2002, Tzanis, 2005, Varotsos, 2002, Varotsos, 2004, Varotsos et al., 2005, Tzanis et al., 2008, Peñaloza-Murillo and Pasachoff, 2018). It is found that in a total solar eclipse event the value of solar irradiance decreases to zero whereas in a partial solar eclipse it does not decrease to zero (Aplin et al., 2016). Although a solar eclipse is primarily of astronomical interest, meteorological changes also result from the abrupt change in isolation, causing cooling in the atmospheric surface layers (Aplin and Harrison, 2003). In many studies, transient changes in meteorological parameters (temperature, relative humidity and wind velocity) solar radiance and surface ozone have been reported (Eliot, 1990, Zerefos et al., 2007, Tzanis et al., 2008, Hanna, 2000, Hanna et al., 2016, Hanna, 2018, Subrahmanyam et al., 2013, Dolas et al., 2002). During the partial phases of solar eclipse relatively gradual change in the value of different meteorological parameters is observed but at the time of totality, the changes are quite rapid. Many researchers have reported the effect of the solar eclipse on earth's environment viz. variation in ozone, wind speed, relative humidity and short time disturbance in Solar irradiance and in consequence thermal balance of the atmosphere (Srivastava et al., 1982, Fernandez et al., 1993, Zerefos et al., 2001, Tzanis, 2005, Kolev et al., 2005; Gerasopoulos et al., 2008; Chakrabarty et al., 1997, Niranjan et al., 1997, Girach et al., 2012, Dutta et al., 1999, Naja and Lal, 1997). Eliot (1990) reported the observations of air temperature, barometric pressure, relative humidity, cloud and rainfall at all one hundred and fifty-four meteorological stations in India and solar radiation observations at six stations during the solar eclipse of January 22, 1898. He further reported that the air temperature diminished in proportion to the obscuration and the maximum reduction of temperature was 12 °C at Karwar and there was a steady increase of pressure proceeding at a nearly uniform rate during the eclipse. Chakrabarty et al. (1997) reported a sharp decrease in the ozone column from its normal value 15 min before the maximum obscuration of the Sun, followed by a sharp rise 10 min after the maximum obscuration during the solar eclipse of October 24, 1995 over Ahmedabad. A substantial decrease in ozone concentration is reported by Zerefos et al. (2001) at Thessaloniki, Greece during the solar eclipse event of 11 August 1999. Atmospheric ozone production is a photochemical phenomenon, ozone decreases because of lack of solar irradiation (during the eclipse event) in the UV range (Jain et al., 2020). Decrease in temperature during solar eclipse also causes reduction in ozone formation in the lower atmosphere (Zerefos et al., 2007, Reid et al., 1994, Chimonas and Hines, 1971). Tzanis et al. (2008) reported a reduction of solar irradiance up to 97% over Greece, Athens. They further reported an increase in relative humidity as well as decrease in wind velocity. Several other workers have also reported changes in different meteorological parameters during the solar eclipse period (e.g. Fernandez et al., 1993, Fernandez et al., 1996, Anderson, 1999, Aplin and Harrison, 2003, Krishnan et al., 2004). Krishnan et al. (2004) reported a decrease of 0.5 °C in temperature and decrease in wind speed also, while the variation in relative humidity was reported within the natural variability of the day during a total solar eclipse effect of August 11, 1999 over Ahmadabad, India.

Despite various studies of the solar eclipse effect on solar irradiance, surface ozone and meteorological parameters at individual places, a complete study of all the above parameters simultaneous at different places having different magnitudes of a solar eclipse is lacking. To complete this gap, the present study has been initiated during the most recent annular solar eclipse of 21st June 2020 at eight different cities of India having different eclipse magnitudes.

The recent solar eclipse of 21st June 2020 provided us a unique opportunity to study changes in solar radiance, surface ozone and different meteorological parameters at different places in India. The annular solar eclipse was seen in the Indian states of Uttarakhand, Rajasthan and Haryana in the morning hours whereas partial solar eclipses were seen in the different other parts of the country. The eclipse magnitude ranged from 77.2% to 98.6% at different stations included in the present study. In the present work, we have selected different cities from the northern part of the country viz. Kurukshetra and Sirsa from Haryana state, Jaipur from Rajasthan, Amritsar and Jalandhar from Punjab, Varanasi from Uttar Pradesh, Chandigarh the union territory and Delhi the capital of India has been taken into consideration to study the environmental effects of the solar eclipse. An overview of variation in different meteorological parameters (temperature, relative humidity and wind speed) and also observed change in solar irradiance and ozone concentrations have been analyzed. The results obtained are compared with previously reported results during the solar eclipse in different parts of the world.