Did anomalous atmospheric circulation favor the spread of COVID-19 in Europe?

The current pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is having negative health, social and economic consequences worldwide. In Europe, the pandemic started to develop strongly at the end of February and beginning of March 2020. Subsequently, it spread over the continent, with special virulence in northern Italy and inland Spain. In this study we show that an unusual persistent anticyclonic situation prevailing in southwestern Europe during February 2020 (i.e. anomalously strong positive phase of the North Atlantic and Arctic Oscillations) could have resulted in favorable conditions, e.g., in terms of air temperature and humidity among other factors, in Italy and Spain for a quicker spread of the virus compared with the rest of the European countries. It seems plausible that the strong atmospheric stability and associated dry conditions that dominated in these regions may have favored the virus propagation, both outdoors and especially indoors, by short-range droplet and aerosol (airborne) transmission, or/and by changing social contact patterns. Later recent atmospheric circulation conditions in Europe (July 2020) and the U.S. (October 2020) seem to support our hypothesis, although further research is needed in order to evaluate other confounding variables. Interestingly, the atmospheric conditions during the Spanish flu pandemic in 1918 seem to have resembled at some stage with the current COVID-19 pandemic.

Atmospheric circulation and mortality by unintentional drowning in Spain: from 1999 to 2018.

AIMS: Drowning deaths are a leading cause of unintentional deaths worldwide. Few studies have analysed the role of meteorology in drowning, and with inconclusive results. The aim of this work is to analyse the temporal and geographical distribution of deaths by accidental drowning and submersion in Spain over 20 years, and to assess the relationship between accidental drowning and main atmospheric circulation patterns. METHODS: An ecological study was performed, in which drowning and submersion mortality data from 1999 to 2018, considering demographic variables, were analysed. To study the association with atmospheric circulation we used an ERA5 reanalysis product over the whole European continent and the Climatic Research Unit Time Series (CRU TS) data set. RESULTS: The annual average rate of deaths by accidental drownings was 11.86 deaths per million of habitants in Spain. The incidence in males was four times higher than in females, and when comparing age groups, the rate in the eldest group was the highest. Unintentional drowning deaths were not equally distributed around the country; the provinces with the highest registered standardized drowning death rates were touristic waterfront provinces either in Eastern Spain or in one of the archipelagos. There was a significant relationship between accidental drowning and meteorological variables during summer months, and drowning deaths were spatially correlated with sea-level pressure over the Mediterranean basin. CONCLUSION: Although the mortality rate registered a statistically significant decreasing tendency over the studied period, our results must be taken into consideration to improve the prevention strategies in the country since most of these deaths are avoidable.

Coexisting oak species, including rear-edge populations, buffer climate stress through xylem adjustments.

The ability of trees to cope with climate change is a pivotal feature of forest ecosystems, especially for rear-edge populations facing warm and dry conditions. To evaluate current and future forests threats, a multi-proxy focus on the growth, anatomical and physiological responses to climate change is needed. We examined the long-term xylem adjustments to climate variability of the temperate Quercus robur L. at its rear edge and the sub-Mediterranean Quercus pyrenaica Willd. Both species coexist at a mesic (ME, humid and warmer) and a xeric (XE, dry and cooler) site in northern Spain, the latter experiencing increasing temperatures in recent decades. We compared xylem traits at each site and assessed their trends, relationships and responses to climate (1960-2008). Traits included basal area increment, earlywood vessel hydraulic diameter, density and theoretical-specific hydraulic conductivity together with latewood oxygen (δ18O) stable isotopes and δ13C-derived water-use efficiency (iWUE). Quercus robur showed the highest growth at ME, likely through enhanced cambial activity. Quercus pyrenaica had higher iWUE at XE compared with ME, but limited plasticity of anatomical xylem traits was found for the two oak species. Similar physiological performance was found for both species. The iWUE augmented in recent years especially at XE, likely explained by stomatal closure given the increasing δ18O signal in response to drier and sunnier growing seasons. Overall, traits were more correlated at XE than at ME. The iWUE improvements were linked to higher growth up to a threshold (~85 µmol mol-1) after which reduced growth was found at XE. Our results are consistent with Q. pyrenaica and Q. robur coexisting at the central and dry edge of the climatic species distribution, respectively, showing similar responses to buffer warmer conditions. In fact, the observed adjustments found for Q. robur point towards growth stability of similar rear-edge oak populations under warmer climate conditions.