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PDSI Index (Palmer Drought Severity Index)
PDSI Index - Current situation - December 2021
According to the PDSI index, at the end of December the meteorological drought situation remains in almost the entire territory, with a slight decrease in the percentage of the territory in the severe drought class and an increase in the moderate drought class.
The percentage distribution by classes of the PDSI index in the territory is as follows:
- normal: 6.3%
- weak drought: 57.7%
- moderate drought: 27.3%
- severe drought: 8.7%
- extreme drought: 0%
Drought monitoring
- Summary and about
Legend
PDSI Index (Palmer Drought Severity Index) was developed by Palmer (1965) and implemented and calibrated for mainland Portugal (Pires, 2003).
> This index is based on the concept of the water balance taking into account data on the amount of precipitation, air temperature and available water capacity in the soil and allows the detection of periods of drought by classifying them in terms of intensity (weak, moderate, severe and extreme).
Table - Classification of the PDSI index for dry and rainy periods
Color legend
PDSI Classes
Description
greater than or equal to 4,0
Extreme rain
Extreme rain
3,00 to 3,99
Severe rain
Severe rain
2,00 to 2,99
Moderate rain
Moderate rain
1,00 to 1,99
Weak rain
Weak rain
-0,99 to 0,99
Normal
Normal
-1,99 to -1,0
Weak drought
Weak drought
-2,99 to -2,0
Moderate drought
Moderate drought
-3,99 to -3,0
Severe drought
Severe drought
less than or equal to -4,00
Extreme drought
Extreme drought
Last 12 month evolution
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Lisboa:
UTC:
Copyright © Portuguese Institute for Sea and Atmosphere 2022
