Distribution, trends and drivers of flash droughts in the United Kingdom

Noguera, Iván ORCID: https://orcid.org/0000-0002-0696-9504; Hannaford, Jamie ORCID: https://orcid.org/0000-0002-5256-3310; Tanguy, Maliko ORCID: https://orcid.org/0000-0002-1516-6834. 2024 Distribution, trends and drivers of flash droughts in the United Kingdom. Egusphere, egusphere-2024-1969. 10.5194/egusphere-2024-1969

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Abstract/Summary

Flash droughts have been the subject of a great deal of scientific attention in the last 16 decade, but the greatest emphasis has been on relatively dry climates. Here, we 17 characterised the occurrence of this type of rapid-onset drought events in a more humid 18 setting, the United Kingdom (UK), for the period 1969-2021. Our results show that flash 19 droughts affected both the wetter regions of north-west and the drier regions of south-east 20 in every season over the last five decades. However, the spatiotemporal distribution of 21 flash droughts is highly variable in UK, with important regional and seasonal contrasts. 22 Central and northern regions were generally the most frequently affected by flash 23 droughts in comparison to southeastern region. Overall, there are non-significant trends 24 in flash drought frequencies in winter, summer, and autumn. Nevertheless, we found a 25 significant and notable increase in the number of flash droughts recorded in spring 26 months. In the UK, flash drought occurrence responds primarily to precipitation 27 variability in all seasons, and particularly in winter and autumn. In spring and summer, 28 the atmospheric evaporative demand (AED) is important as a secondary driver for 29 triggering flash droughts, especially in the drier regions of the southeastern UK. 30 Moreover, our findings evidenced that this relevance is rising significantly in spring and 31 summer in the southeast, over the study period. The atmospheric and oceanic conditions 32 controlling these anomalies in precipitation and AED that drive flash droughts were also 33 https://doi.org/10.5194/egusphere-2024-1969 Preprint.Discussionstarted:9July2024 cAuthor(s)2024.CCBY4.0License.2 analyzed. Remarkable anomalies in sea level pressure and 500 hPa geopotential height 34 associated with the presence of high-pressure systems were noted over UK during the 35 development of the most severe flash droughts in all seasons. Likewise, flash drought 36 development typically occurred under negative phase of North Atlantic Oscillation phase 37 in winter and autumn, while in summer and spring positive phase is dominant. We also 38 found positive anomalies in sea surface temperature during the development of flash 39 droughts in spring and summer, while mixed anomalies were reported in winter and 40 autumn. This study presents a detailed characterisation of flash drought phenomenon in 41 UK, providing useful information for drought assessment and management, and a 42 climatology of flash droughts that can be used as a baseline against which future changes 43 in flash drought occurrence can be assessed.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.5194/egusphere-2024-1969
UKCEH and CEH Sections/Science Areas:	Water Resources (Science Area 2017-)
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	flash drought, precipitation deficit, atmospheric evaporative demand (AED), Standardized Precipitation Evapotranspiration Index (SPEI), ocean-atmospheric conditions, North Atlantic Oscillation (NAO), United Kingdom
NORA Subject Terms:	Hydrology Meteorology and Climatology
Related URLs:	Dataset Dataset Dataset
Date made live:	12 Jul 2024 11:19 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/537704

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