The novel coronavirus, since its first outbreak in December, has, up till now, affected approximately 114,542 people across 115 countries. Many international agencies are devoting efforts to enhance the understanding of the evolving COVID-19 outbreak on an international level, its influences, and preparedness. At present, COVID-19 appears to affect individuals through person-toperson means, like other commonly found cold or influenza viruses. It is widely known and acknowledged that viruses causing influenza peak during cold temperatures and gradually subside in the warmer temperature, owing to their seasonality. Thus, COVID-19, due to its regular flu-like symptoms, is also expected to show similar seasonality and subside as the global temperatures rise in the northern hemisphere with the onset of spring. Despite these speculations, however, the systematic analysis in the global perspective of the relation between COVID-19 spread and meteorological parameters is unavailable. Here, by analyzing the region-and city-specific affected global data and corresponding meteorological parameters, we show that there is an optimum range of temperature and UV index strongly affecting the spread and survival of the virus, whereas precipitation, relative humidity, cloud cover, etc. have no effect on the virus. Unavailability of pharmaceutical interventions would require greater preparedness and alert for the effective control of COVID-19. Under these conditions, the information provided here could be very helpful for the global community struggling to fight this global crisis. It is, however, important to note that the information presented here clearly lacks any physiological evidences, which may merit further investigation. Thus, any attempt for management, implementation, and evaluation strategies responding to the crisis arising due to the COVID-19 outbreak must not consider the evaluation presented here as the foremost factor.

Coronaviruses are single stranded RNA viruses usually present in bats (reservoir hosts), and are generally lethal, highly transmissible, and pathogenic viruses causing sever morbidity and mortality rates in human. Several animals including civets, camels, etc. have been identified as intermediate hosts enabling effective recombination of these viruses to emerge as new virulent and pathogenic strains. Among the seven known human coronaviruses SARS-CoV, MERS-CoV, and SARS-CoV-2 (2019-nCoV) have evolved as severe pathogenic forms infecting the human respiratory tract. About 8096 cases and 774 deaths were reported worldwide with the SARS-CoV infection during year 2002; 2229 cases and 791 deaths were reported for the MERS-CoV that emerged during 2012. Recently ~ 33,849,737 cases and 1,012,742 deaths (data as on 30 Sep 2020) were reported from the recent evolver SARS-CoV-2 infection. Studies on epidemiology and pathogenicity have shown that the viral spread was potentially caused by the contact route especially through the droplets, aerosols, and contaminated fomites. Genomic studies have confirmed the role of the viral spike protein in virulence and pathogenicity. They target the respiratory tract of the human causing severe progressive pneumonia affecting other organs like central nervous system in case of SARS-CoV, severe renal failure in MERS-CoV, and multi-organ failure in SARS-CoV-2. Herein, with respect to current awareness and role of coronaviruses in global public health, we review the various factors involving the origin, evolution, and transmission including the genetic variations observed, epidemiology, and pathogenicity of the three potential coronaviruses variants SARS-CoV, MERS-CoV, and 2019-nCoV. Electronic supplementary material The online version of this article (10.1007/s13337-020-00632-9) contains supplementary material, which is available to authorized users.

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The COVID lockdown presented a unique opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event showing rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions over India provides important new clues to delineate contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing.

Covid lockdown presented an important opportunity to study relatively cleaner conditions in India. The complex factors of power production, industry, and transportation could be more carefully dissected because of the extreme reduction in the influence of the latter two emission sources. Measurements of cloud condensation nuclei (CCN) activity and other chemical properties of atmospheric aerosols showed that newly formed aerosol particles were produced in the SO 2 plume from a large coal-fired power plant, contrary to normal conditions of heavy pollution. The sulfate-rich particles had high CCN activity and

The COVID lockdown presented an interesting opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event resulting from distinct meteorological conditions. This event was marked by rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant in Southern India. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions provides important new clues to delineate the contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing.

Abstract. The Arctic is a unique part of the Earth system that is currently undergoing a warming phase called the Arctic Amplification (AA). Changes in aerosol abundance and composition are under the influence of the AA and may be, in turn, important drivers to the AA. However, their ground and space observations are particularly difficult and spatio-temporally sparse in this region, limiting the knowledge and ability to model their variability. In this study, we have used the total aerosol optical depth (AOD) determined by the AEROSNOW algorithm using data from the AATSR satellite instrument over snow- and ice-covered regions of the Arctic. This data is then used to evaluate the global GEOS-Chem 3D chemical transport model for the period 2003–2011. Thus, the main drivers of monthly and seasonal variations in spaceborne AOD were determined by using the GEOS-Chem model-simulated aerosol components. By comparing these two AOD datasets, we examined the spring and summer AOD over Arctic snow and ice for the period of space-borne observations. The space-borne and modelled AOD show consistent spatio-temporal distributions in both seasons, with a pronounced chemical speciation in GEOS-Chem. This behaviour is attributed to the different seasonal sources of AOD. In spring, Arctic aerosols originate from long-range pollution transport from low and mid-latitudes as well as from local sources, whereas in summer natural local sources within the Arctic Circle (here defined as > 60° N) dominate. Arctic AOD is generally highest in spring and lowest in summer due to wet scavenging. In addition, carbonaceous aerosols (black carbon, BC, and organic carbon, OC) are an increasingly important contributor to total AOD over Arctic sea ice in summer due to the expected increase in boreal forest fires. The relative contribution of sulfate to total AOD over Arctic sea ice decreases while that of carbonaceous aerosols increases during the spring-summer transition. This suggests that boreal wildfires are penetrating more deeply into Arctic sea ice at higher latitudes during this study period. GEOS-Chem showed a systematically smaller AOD value compared to AEROSNOW over the Arctic sea ice region in summer. The promising results of AEROSNOW could also serve as the baseline for the evaluation and improvement of aerosol forecasts for various chemical transport models, especially over Arctic sea ice.

Abstract. The Arctic climate has changed significantly over the past two to three decades. Aerosols play various roles in the radiative forcing in the Arctic, both directly and indirectly, depending on the changes in loading and composition. However, their observation from the ground or with airborne instruments is challenging and thus measurements are sparse. In this study, total Aerosol Optical Depth (AOD) is determined from top-of-atmosphere reflectance measurements by the Advanced Along-Track Scanning Radiometer (AATSR) aboard ENVISAT over snow and ice in the Arctic using a retrieval called AEROSNOW for the period 2003 to 2011. We use the dual-viewing capability of the AATSR instrument to reduce the impact of surface reflectance on the accuracy of AOD. The AOD is retrieved assuming that the surface reflectance observed by the satellite can be well-parametrized by a bidirectional snow reflectance distribution function, BRDF. The spatial distribution of AODs shows that high values in spring (March, April, May) and lower AOD values in summer (June, July, August) are well captured. Spaceborne AOD values are consistent with colocated AERONET measurements, with no systematic bias as a function of time. The AEROSNOW AOD in the high Arctic ( ≥ 72° N) was validated by comparison with ground-based measurements at the PEARL, OPAL, Hornsund, and Thule stations. The AEROSNOW AOD value is less than 0.15 on average and the regression to AERONET yields a slope of 0.98, a Pearson correlation coefficient of R = 0.86, and an RMSE = 0.01 at a monthly scale, both in spring and summer. These AOD results provide, for the first time, observational insights into the central Arctic with significant spatial and temporal coverage.