Drought index: Threshold Temporal Spatial information Di (Ds) information Di: Computed Computed on historical values Persistent for As a drought evolves with time it is using monthly or of the index. timescales longer than important to use preferably a GIS longer timescale It should provide a beyond a season. to: description: precipitation totals, which, values are statistically Record at station level 1. Calculate the area affected by the or in combination rare(*), or a certain threshold value information on the and at which magnitude or with other having potential negative impacts starting time, ending severity. variables such as on one or several application time and duration of evaporation, sectors. drought. Keep the Quantitative temperature and (*) The WMO Climatological information in a relative humidity. Standard normal should be used to database. the extent possible to define the base periods and departure from the average and percentiles. Magnitude Duration Extent of Di-Ds; or defined by a synthesized method. Computed at station The geographical area computed Event level which is the on multi-station data with number consecutive gridding when observing networks months, seasons, or are dense. Another option is to use yearssatisfying the remote sensing precipitation data characterizations: criteria. when only precipitation data is considered.
Quantitative description: Drought index: Di Threshold (Ds) Temporal information Spatial information Di: Computed using monthly or longer timescale precipitation totals, or in combination with other variables such as evaporation, temperature and relative humidity. Computed on historical values of the index. It should provide a beyond which, values are statistically rare(*), or a certain threshold value having potential negative impacts on one or several application sectors. (*) The WMO Climatological Standard normal should be used to the extent possible to define the base periods and departure from the average and percentiles. Persistent for timescales longer than a season. Record at station level information on the starting time, ending time and duration of drought. Keep the information in a database. As a drought evolves with time it is important to use preferably a GIS to: 1. Calculate the area affected by the and at which magnitude or severity. Event characterizations: Magnitude Duration Extent of Di-Ds; or defined by a synthesized method. Computed at station level which is the number consecutive months, seasons, or yearssatisfying the criteria. The geographical area computed on multi-station data with gridding when observing networks are dense. Another option is to use remote sensing precipitation data when only precipitation data is considered.
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