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Effects of Temperature Anomalies on the Palmer
Drought Severity Index in the Central United States

Qi Hu and Gary D. Willson

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Abstract: The purpose of this study is to improve our understanding of temperature and precipitation effects on the Palmer Drought Severity Index (PDSI). Both theoretical and observational analyses were applied to separate and compare temperature and precipitation effects on PDSI. The results showed that because of the dependence of PDSI on the 'climatologically appropriate rainfall', which is a function of time and varies with surface air temperature, the PDSI can be equally affected by temperature and precipitation, when both have similar magnitudes of anomalies. Calculations using observational data further illustrated the temperature influence on PDSI in different climate regions in the central United States. The temperature effect on PDSI complicates the usage of the index in interpreting precipitation anomalies and its application in inferring precipitation variations, particularly from reconstructed PDSI.

Key Words: central United States; interpreting reconstructed PDSI; observation; Palmer Drought Severity Index; precipitation; temperature; theoretical analysis

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This resource is based on the following source (Northern Prairie Publication 1118):

Hu, Qi, and Gary D. Willson.  2000.  Effects of temperature anomalies 
     on the Palmer Drought Severity Index in the central United States.  
     International Journal of Climatology 20:1899-1911.

This resource should be cited as:

Hu, Qi, and Gary D. Willson.  2000.  Effects of temperature anomalies 
     on the Palmer Drought Severity Index in the central United States.  
     International Journal of Climatology 20:1899-1911.  Jamestown, 
     ND: Northern Prairie Wildlife Research Center Online.  
     http://www.npwrc.usgs.gov/resource/habitat/tempanom/index.htm  
     (Version 20AUG2001).

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Table of Contents

• Introduction
• A Theoretical Analysis
• An Observational Analysis
• Concluding Remarks
• Acknowledgments
• References

Figures

• Figure 1 -- The geographical location of the study areas.
• Figure 2 -- Response of Z-index to temperature and precipitation perturbations for June in Region 2.
• Figure 3 -- Correlations of PDSI versus regional average precipitation, temperature and correlation of regional average precipitation versus temperature for Region 1.
• Figure 4 -- Correlations of PDSI versus regional average precipitation, temperature and correlation of regional average precipitation versus temperature for Region 2.
• Figure 5 -- Variations of monthly precipitation anomaly, temperature anomaly and corresponding PDSI for 1977-1979 at Auburn, NE.
• Figure 6 -- Variations of July normalized precipitation, temperature and PDSI for Region 1.

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Qi Hu, School of Natural Resource Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
Correspondence to: School of Natural Resource Sciences, 237 L.W. Chase Hall, University of Nebraska-Lincoln (UNL), Lincoln, NE 68583-0728, USA; e-mail: qhu2@unl.edu.
Gary D. Willson, Northern Prairie Wildlife Research Center, USGS, and Department of Soil and Atmospheric Sciences, University of Missouri-Columbia, Columbia, MO, USA

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