Drought Occurrences and Their Characteristics across Selected Spatial Scales in the Contiguous United States

Navaratnam Leelaruban,G Padmanabhan

doi:10.3390/geosciences7030059

Abstract

An understanding of drought occurrences and their characteristics such as intensity, duration, frequency, and areal coverage, and their variations on different spatial scales, is crucial to plan for droughts in different regions and in different sized areas. This study investigated the variations of spatio-temporal characteristics of droughts under selected spatial scales: National (Contiguous U.S.), regional (High Plains), state (North Dakota, ND), climatic division (South Central, ND), and county (Grant, ND). Weekly drought area coverage data for the period spanning the years 2000–2014 from the U.S. Drought Monitor of the National Drought Mitigation Center were used. The study captured the areal coverages and occurrence frequency of droughts with different intensity levels for the years 2000 to 2014 for the contiguous U.S. Year to year variability in spatial distribution of the areal coverages of droughts with different intensity levels were also analysed. The study further investigated how the weekly percentage area under different intensity categories varied along time, and extracted the spatio-temporal characteristics of different drought intensity categories at different spatial scales. The study identified areas that are frequently affected by droughts of different intensity categories in the U.S. at the national scale, and reported the spatial scale dependence of drought characteristics.

Highlights

Drought stands apart from other natural hazards in many ways, in that it is difficult to identify and predict its onset and termination [1,2,3,4]
The spatio-temporal characteristics of drought under different spatial scales show that the total duration, average percentage area, and maximum percentage areas are decreasing with increasing intensity for all spatial scales; and in the smaller spatial scale, the drought persists for a smaller duration compared to a larger spatial scale
This study quantitatively demonstrates that there is clear variation in the drought characteristics such as intensity coverage, duration, and occurrence at different spatial scales

Summary

Introduction

Drought stands apart from other natural hazards in many ways, in that it is difficult to identify and predict its onset and termination [1,2,3,4]. Droughts in general can be characterized based on severity, areal coverage, duration, and frequency. Drought indices are derived from meteorological variables (e.g., precipitation, temperature) and hydrological variables (e.g., stream flows, reservoir storage, soil moisture, groundwater levels) [7]. There are indices developed based on the eco-hydrological model to assess different types of droughts [8]. The most commonly used indices include: (1) The Palmer Drought Severity Index (PDSI) [9]; (2) the Standardized

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