Monitoring Agricultural Drought in Mainland Portugal - Monitoring and Predicting Agricultural Drought: A Global Study - page 188

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Figure 14.3 Time series of Palmer drought severity index for Lisbon, Evora, and Beja stations
in southern Portugal (from Pires, 2003).

extreme droughts, as expected due to the consequences on agricultural pro-
duction.
The next step to improve agricultural drought monitoring is to imple-
ment the crop moisture index (CMI), an index also developed by Palmer
(1968) and based on PDSI procedures. Whereas the PDSI monitors long-
term meteorological wet and dry spells, the CMI was designed to evalu-
ate short-term moisture, as it is based on the mean temperature and total
precipitation for each week and also for the CMI value from the previous
week. The CMI responds rapidly to changing conditions and, like PDSI, it is
weighted by location and time, allowing the preparation of maps covering
moisture conditions at different locations (Hayes, 2002).