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Historical Precipitation Characteristics

The Maproom explores historical daily precipitation by calculating simple seasonal statistics.

Many options can be specified to produce yearly time series of a chosen seasonal diagnostic of the daily precipitation data. The user can then choose to map the mean, standard deviation, probability of exceeding a chosen threshold, over years, coefficient of variation in percentage or percentile of historical distribution; clicking on the map will then produce a local yearly time series of the chosen diagnostic.


Years and Season: Specify the range of years over which to perform the analysis, and choose the start and end dates of the season over which the diagnostics are to be performed.

Wet/Dry Day/Spell Definitions: These define the amount in millimeters (non inclusive) above which a day is considered to be a wet day (as opposed to dry), and the minimum number (inclusive) of consecutive wet (dry) days to define a wet (dry) spell.

Seasonal daily statistics: Choose the seasonal diagnostic quantity (i.e the statistic of the daily data) to be computed for each season, from the following choices.

Total Rainfall: total cumulative precipitation (in mm) falling over the season.

Number of Wet Days: the number of wet days (as defined above) during the season.

Rainfall Intensity:the average daily precipitation over the season considering only wet days.

Number of Wet (Dry) Spells: the number of wet (dry) spells during the season according to the definitions in the Options section. For example, if a wet spell is defined as 5 contiguous wet days, 10 contiguous wet days are counted as 1 wet spell. Note that a spell, according to the definitions above, that is overlapping the start or end of the season will be counted only if the part of the spell that falls within the season reaches the minimal length of consecutive days.

Percentage of Data Available: the percentage of days with non missing values within the season.

Yearly seasonal statistics: a choice of yearly statistics over the chosen season of the selected range of years to produce the map among: the mean, the standard deviation, the probability of exceeding a user specified threshold, the coefficient of variation (ratio of standard deviation to the mean) in percentage, and percentile of historical distribution (e.g., 0.1, 0.25, 0.5, 0.75 and 0.9).

Spatial Resolution: The analysis can performed and map at each grid point for both 0.25˚ and 0.05˚ resolution CHIRPS products. Additionally it is possible to average the results of the analysis over the 0.25˚ grid points falling within administrative boundaries for the time series graph.

Dataset Documentation

Data: Daily CHIRPS data with improved temporal downscaling procedure here.

How to use this interactive map


Contact help@iri.columbia.edu with any technical questions or problems with this Map Room.