The utility of a drought index for assessing the drought hazard in Devon and Cornwall, South West England

Abstract

The utility of a drought severity index, based on accumulated monthly precipitation deficits and a three-monthly initiation and termination rule, for assessing the variability in the timing and severity of the drought hazard between four selected locations in Devon and Cornwall since 1957 is documented. The robustness of the drought events identified is then assessed by changing the index formulation rules. Results indicate that, using a six-monthly, rather than a three-monthly, rule, drought sequences are more difficult to initiate and terminate and are more persistent with a longer mean duration. The drought severity indices are then used to define a hierarchy of significant drought events, isolated in terms of the number of indices simultaneously exceeding an arbitrarily defined severity. Seven Class I droughts, regional in extent, are then discussed; and circulation contrasts between events highlighted using aggregated Lamb weather types. Two drought sub-types emerge, distinguishable according to whether the controlling anticyclone had a greater tendency to be located to the north and east of the UK or to the south and west. A comparative analysis of the ongoing 1995-drought, in terms of its persistence, and rapidity of onset and cessation, is also conducted.

The relationship between monthly and seasonal South‐west England rainfall anomalies and concurrent North Atlantic sea surface temperatures

“…No data were available at Chivenor from September 1974 to August 1980 or at Culdrose in 1994. Phillips and McGregor (1998) described the variations in meteorological drought severity at these four locations since 1950. The Princetown series was extended back, in terms of monthly totals, to January 1950 using data from the Monthly Weather Report (MWR) of the UK Meteorological Office (UKMO) and British Rainfall.…”

“…The homogeneity of the four monthly time series was confirmed by computing the non-parametric Kruskal-Wallis H statistic (Ebdon, 1985). Further details can be found in Phillips and McGregor (1998).…”

“…This precipitation resource also shows marked temporal variations: e.g. Devon and Cornwall have been affected by seven major meteorological drought events (winter 1962-63, 1964-65, 1975-76, late season 1978, 1983-84, 1991-92, 1995-97) since 1960(Phillips and McGregor, 1998.…”

“…The precipitation climatology of South-west England is characterized by its variability at a variety of temporal scales (Phillips and McGregor, 1998). Although attempts have been made at trying to understand this variability by considering atmospheric circulation variations (Phillips, 2000;Phillips and McGregor, 2001a,b), little work has been done on assessing the importance of other climate variables, such as sea surface temperature (SST).…”

Analysis of drought characteristics for improved understanding of a water resource system

“…Past research has been focused at European or national scales rather than at a regional scale, with large-scale studies often failing to capture the spatial variability that a smaller, regional study could provide (Hannaford et al 2010). Regional-scale studies are more beneficial for water resource management, as shown by Phillips andMcGregor (1998) andFowler andKilsby (2002) who use a regionalised approach to characterise drought events. Panu and Sharma (2002) identified several areas of future research focus within droughts; these included the importance of drought indices and recognition of regional variability.…”