ESS124
Prof.
Jin-Yi Yu
Drought Index
TABLE
26.1
Categories
of Palmer Drought Severity Index
•Because the normal values of precipitation and temperature vary regionally and seasonally, it is difficult to quantify
drought in term of
actual temperature and precipitation.
•Standardized measurements have come into use.
•One of the most widely used indices is the Palmer Drought Severity Index (PDSI).
•This Palmer Index is a measure of moisture deficiency standardized to local climate conditions.
•It is based on a groundwater balance that includes the supply of water by
precipitation and
stored water, and the depletion of water by temperature-depedent evaporation, recharge of subsurface water and runoff.