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County-level drought indices The Palmer Drought Severity Index(PDSI)and Palmer Hydrological Drought Index(PHDI)


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Bushra N., and Rohli R.V., 2017, County-level drought indices The Palmer Drought Severity Index(PDSI)and Palmer Hydrological Drought Index(PHDI):


Drought is a natural hazard that inflicts costly damage to the environment and human communities. Although ample literature exists on the climatological aspects of drought, little is known on whether existing drought indices can predict the damages and how different human communities respond and adapt to the hazard. This project examines (1) whether existing drought indices can predict the occurrence of drought events and their actual damages; (2) how the adaptive capacity (i.e., resilience) varies across space; and (3) what public outreach and engagement effort would be most effective for mitigation of risk and impacts. The study region includes all 503 counties in Arkansas, Louisiana, New Mexico, Oklahoma, and Texas. This data set [...]


Originator :
Nazla Bushra, Robert V. Rohli
Metadata Contact :
Nina Lam
Distributor :
U.S. Geological Survey - ScienceBase

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The Palmer Drought Severity Index (PDSI) and Palmer Hydrological Drought Index (PHDI) are publicly available data, collected from Midwestern Regional Climate Center (MRCC), which mainly originate from National Oceanic and Atmospheric Administration (NOAA). The PDSI and PHDI are published weekly and aggregated into a monthly dataset by NOAA, at the climate divisional level. Although several drought indices are available; which captures somewhat different aspects of drought conditions (Heim 2000), the Palmer Drought Severity Index (PDSI; Palmer 1965) and Palmer Hydrological Drought Index (PHDI; Karl 1986) are commonly used, highly regarded, and readily available metrics. The PDSI, a weekly index of long-term moisture conditions, is produced by NOAA’s Climate Prediction Center and is calibrated to ‘‘normal’’ conditions for its own subset of a state known as a climate division, with 0.0 representing average soil moisture conditions at that climate division for that time of year. Positive values represent above-normal moisture conditions for that location and negative values suggest below-normal soil moisture. Because the water balance calculations for PDSI include lags to take into account deep soil moisture conditions, PDSI is often considered in many applications a reasonable and versatile index of medium-term moisture. For evaluating longer-term hydrological conditions, the PHDI may prove more useful, because it's even longer-lagged response to changes in moisture conditions may better reflect the changes in groundwater availability and reservoir supplies that would be characteristic of drought impacts on communities’ long-term water supply and demand (Guttman 1991). These two indices remain the most widely used and cited measures of drought. The versatility and availability of the PDSI and PHDI on a near-real-time basis make these two indices most desirable for use by environmental planners. For the study, these monthly data are extracted for the 45 climate divisions in the five-state region over the 1975-2010 period.



  • National and Regional Climate Adaptation Science Centers
  • South Central CASC

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