On the variability of near-surface screen temperature anomalies in the 20 March 2015 solar eclipse

Abstract

Near-surface air temperature (NSAT) anomalies during the 20 March 2015 solar eclipse are investigated at 266UK sites, using operational data. The high density of observing sites, together with the wide range of ambient meteorological conditions, provided an unprecedented opportunity for analysis of the spatial variability of NSAT anomalies under relatively uniform eclipse conditions. Anomalies ranged from -0.03°C to -4.23°C (median -1.02°C). The maximum (negative) anomaly lagged the maximum obscuration by 15 min on average. Cloud cover impacted strongly on NSAT anomalies, with larger anomalies in clearsky situations (p<0.0001). Weaker, but statistically significant, correlations were found with wind speed (larger anomalies inweaker winds), proximity to coast (larger anomalies at inland sites), topography (larger anomalies in topographical low points) and land cover (larger anomalies over vegetated surfaces). In this mid-morning eclipse, the topographical influences on NSAT anomalies were apparently dominated by variations in residual nocturnal inversion strength, as suggested by significant correlations between postsunrise temperature and NSAT anomaly at clear-sky sites (larger negative anomalies with lower postsunrise temperatures). The largest NSAT anomaly occurred at a coastal site where flow transitioned from onshore to offshore during the eclipse, in a situation with large coastal temperature gradients associated with antecedent nocturnal cooling. This article is part of the themed issue Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse.