Online Drought Indicators and Indices

Palmer Drought Severity Index (PDSI)


Index name: Palmer Drought Severity Index (PDSI).

Ease of use: Yellow.

Origins: Developed in the 1960s as one of the first attempts to identify droughts using more than just precipitation data. Palmer was tasked with developing a method to incorporate temperature and precipitation data with water balance information to identify droughts in crop-producing regions of the United States. For many years, PDSI was the only operational drought index, and it is still very popular around the world.

Characteristics: Calculated using monthly temperature and precipitation data along with information on the water-holding capacity of soils. It takes into account moisture received (precipitation) as well as moisture stored in the soil, accounting for the potential loss of moisture due to temperature influences.

Input parameters: Monthly temperature and precipitation data. Information on the water-holding capacity of soils can be used, but defaults are also available. A serially complete record of temperature and precipitation is required.

Applications: Developed mainly as a way to identify droughts affecting agriculture, it has also been used for identifying and monitoring droughts associated with other types of impacts. With the longevity of PDSI, there are numerous examples of its use over the years.

Strengths: Used around the world, and the code and output are widely available. Scientific literature contains numerous papers related to PSDI. The use of soil data and a total water balance methodology makes it quite robust for identifying drought.

Weaknesses: The need for serially complete data may cause problems. PDSI has a timescale of approximately nine months, which leads to a lag in identifying drought conditions based upon simplification of the soil moisture component within the calculations. This lag may be up to several months, which is a drawback when trying to identify a rapidly emerging drought situation. Seasonal issues also exist, as the PDSI does not handle frozen precipitation or frozen soils well.

Resource: Global PDSI by the Terrestrial Hydrology Research Group of Princeton University.

Alley, W.M., 1984: The Palmer Drought Severity Index: limitations and assumptions. Journal of Climate and Applied Meteorology, 23: 1100–1109. DOI: 10.1175/1520-0450(1984)023<1100:TPDSIL>2.0.CO;2.

Palmer, W.C., 1965: Meteorological Drought. Research Paper No. 45, US Weather Bureau, Washington, DC.

Currently used by: Bosnia and Herzegovina, Brazil, Bulgaria, Canada, Greece, Macedonia, Peru, Trinidad and Tobago, Turkey, USA.

  1. yuanning
    May 25, 2021 Reply

    think you for your article,could i calculate the PDSI using a special R software package?i kindly want to it
    and looking forward to your early reply.

  2. sammy
    December 22, 2020 Reply

    i kindly request the equation for the PDSI

  3. […] new study, published in Nature, makes use of the Palmer drought severity index (PDSI), which considers how warming affects rainfall and evapotranspiration, as well as soil […]

  4. […] of the most common, for example, is the Palmer Drought Severity Index (PDSI). This uses monthly estimates of evapotranspiration (calculated largely as a function of […]

  5. […] of the most common, for example, is the Palmer Drought Severity Index (PDSI). This uses monthly estimates of evapotranspiration (calculated largely as a function of […]

  6. […] of the most common, for example, is the Palmer Drought Severity Index (PDSI). This uses monthly estimates of evapotranspiration (calculated largely as a function of […]

  7. Hemu
    November 1, 2017 Reply

    Could this method be useful for Nepal?

    1. Robert Stefanski
      December 20, 2017 Reply

      Dear Hemu,

      Thank you for your email. PDSI was developed in the USA for deep soils. The PDSI is also a bit difficult to program. The SPI is much simpler and user to use. However, the SPI only uses precipitation and the PDSI uses temperature. So the PDSI is better suited for climate change studies. What is the application that you are working on?


  8. M .kudrat
    May 15, 2017 Reply

    kindly send me fromula or equation of Palmer Drought Severity Index (PDSI)
    it will be appreciated.
    yours sincerely

    1. Robert Stefanski
      July 13, 2017 Reply

      Please see the original paper by Palmer:


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