Self-Calibrated Palmer Drought Severity Index (sc-PDSI)

Self-Calibrated Palmer Drought Severity Index (sc-PDSI)


Index name: Self-Calibrated Palmer Drought Severity Index (sc-PDSI).

Ease of use: Yellow.

Origins: Initial work was conducted at the University of Nebraska-Lincoln by Wells et al. in the early 2000s.

Characteristics: Accounts for all the constants contained in the PDSI and includes a methodology in which the constants are calculated dynamically based upon the characteristics present at each station location. The self-calibrating nature of sc-PDSI is developed for each station and changes based upon the climate regime of the location. It has wet and dry scales.

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

Applications: Can be applied to meteorological, agricultural and hydrological drought situations. With the results being tied directly to station location, extreme events are rare, as they are related directly to that station’s information and not a constant.

Strengths: With the calculations for sc-PDSI accounting for each individual location, the index reflects what is happening at each site and allows for more accurate comparisons between regions. Different time steps can be calculated.

Weaknesses: As the methodology is not significantly different from PDSI, it has the same issues in terms of time lag and frozen precipitation and frozen soils.

Resources: The code can be obtained from the National Drought Mitigation Center (NDMC). The National Center for Atmospheric Research (NCAR) has developed the CRU SC-PDSI (Self-Calibrating PDSI) over Europe & North America tool.

Reference: Wells, N., S. Goddard and M.J. Hayes, 2004: A self-calibrating Palmer Drought Severity Index. Journal of Climate, 17: 2335–2351. DOI: 10.1175/1520-0442(2004)017<2335:ASPDSI>2.0.CO;2.

17 Responses

    1. Dear Gaye

      Thank you for your question. The development of the PDSI is explained in the following publication:

      There are R packages available to calculate PDSI, for example this one:

      You can find some more information on the PDSI and its usage here:–PDSI%20and%20scPDSI.pdf

      Best regards
      IDMP TSU

  1. Let me ask you: what’s the unit of the Available Water Capacity, what’s the meaning of the unit and how to convert volume percentage to it? Thanks

    1. Dear Veromca Roy

      Available water capacity is the water held in soil between its field capacity and permanent wilting point. Water capacity is usually expressed as a volume fraction or percentage, or as a depth (in or cm). It is dependent on soil texture, as different particle distributions in a soil will lead to different soil porosity. In order to convert from volume percentage to mm, the total soil depth needs to be known. Please find an example of unit conversion here:

      Best regards
      IDMP TSU

  2. Dear Nkem Ekpeni

    In order to provide you with more information, could you please be more specific on what these variable names stand for and which tool you used to generate the PHDI values?

    Best regards
    IDMP team

  3. Dear Nkem Ekpeni

    The Palmer Hydrological Drought index (PHDI) is a modification of the PDSI to take into account longer-term dryness. You can find more information on it here:
    The Modified or Weighted Palmer Drought Severity Index (WPLM) is obtained from the sum of the wet and dry terms weighted by probability values. The WPLM has the same value as the PDSI during established dry or wet spells but can be different during transition periods.

    Best regards
    IDMP team

    Here is

  4. I want to compute self-calibrated Palmer drought severity index over Congo Basin (Central Africa). It is possible for me to have the parameters. How can I consider inputs file. Please I need your support

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