Peer review report 2 on âSpace-time Trends in U.S. Meteorological Droughtsâ

This well motivated and generally well-written paper evaluates variability and trends in drought severity, duration and frequency, as well as the space-time variability, of meteorological droughts, defined in terms of precipitation deficits over the multiple regions in CONUS as constrained by the Standard Precipitation Index (SPI).While in other studies other drought attributes exhibit different or insignificant trends depending on the data and metrics, this study identifies for the first time an increasing trend in the spatial coverage of drought over CONUS.Attractive aspects of this study is the great care taken to delineate trends and patterns unaffected by choice of data they used or statistical method, and the focus on the influence of extreme drought years on the results.The authors used different datasets for SPI: USHCN V2.5 monthly data (1926-2013, subset of 616 stations selected, referred to as "D1-out"); the same dataset, but from 1950-2009 and without outlying drought years (referred to as D1-No-out); and NCDC DSI 3240 daily data (aggregated to monthly totals from 1950-2009; subset of 1023 stations selected, referred to as "D2-No-out"), which also excludes extreme drought years.The study addresses the relation between drought attributes (severity, duration, frequency and spatial coverage) and how interdependencies between these attributes impact design curves?The authors also used a copula-based approach to generate drought severity-duration-frequency (SDF) curves that explicit consider nonlinearities in the interdependency of drought attributes.These SDF curves are similar to intensity-durationfrequency curves for precipitation extremes, and can inform monitoring, attribution, early warning, resources planning, and infrastructure resilience.Lines 25-42-This is an important paper, so I feel that the Abstract should be much tighter and more focused.As currently written, it tends to wander a bit.Line 33-Here, in the Abstract, the statement is made that the coverage of extreme meteorological droughts over the last half decade exceeds that of the dust bowl era [Dust Bowl should be capitalized, by the way].In Line 554-556, the authors state that recent droughts have more spatial coverage than the 1930's and 1950's.Maybe the statement in the Abstract should state that, "Since the 1970's, and especially post-2010, the spatial coverage of extreme meteorological droughts across CONUS exceeds that of the 1930's and 1950s.Line 167-(Andreadis et at al., 2005) should be Andreadis et al. (2005) Line 269-Even time series splits are made for the three datasets (44-yr split, 1926-1969 vs. 1970-2013, for D1-out; 30-yr split, 1950-1979 for D1-No-out and D2-No-out), and these splits are justified by the fact that most of the anthropogenic warming has occurred since 1970.I think this is fine, but since the analysis emphasizes precipitation, it may help to mention

Abstract licence: CC BY-NC

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