District
Sector
Search PeriodFrom Early Start date of and within the next days.
Wet Day definitionRainfall amount greater than mm
Onset Date definitionFirst window of days that totals mm or more and with at least wet days and that is not followed by a -day dry spell within the next days.
Cessation Date definitionFirst date after in days when the soil water balance falls below mm for a period of days.
Local Plots Range to days
Observations for
located in or near



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Historical Onset Dates
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Historical Cessation Dates

Historical Onset and Cessation Date

The Maproom explores historical rainy season onset and cessation dates based on user-defined definitions. The date when the rainy season starts is critical to agriculture planification, in particular for planting.

By enabling the exploration of the history of onset dates, the Maproom allows to understand the spatial and temporal variability of this phenomenon and therefore characterize the risk for a successful agricultural campaign associated with it.

The definition of the onset can be set up in the Control Bar at the top and is looking at a significantly wet event (e.g. 20mm in 3 days) that is not followed by a dry spell (e.g. 7-day dry spell in the following 21 days). The actual date is the first wet day of the wet event. The onset date is computed on-the-fly for each year according to the definition, and is expressed in days since an early start date (e.g. Feb. 1st). The search for the onset date is made from that early start date and for a certain number of following days (e.g. 60 days). The early start date serves as a reference and should be picked so that it is ahead of the expected onset date. Generally, two rainy seasons are expected in the region: Mar-May and Sep-Dec.

Then the map shows yearly statistics of the onset date: the mean (by default), standard deviation or probability of exceeding a chosen number of days. Clicking on the map will then produce a local yearly time series of onset dates, as well as a table with the actual date (as opposed to days since early start); and a probability of exceeding graph.

Note that if the criteria to define the onset date are not met within the search period, the analysis will return a missing value. And if the analysis returns 0 (days since the early start), it is likely that the early start date picked is within the rainy season.

Dataset Documentation

Reconstructed rainfall on a 0.0375˚ x 0.0375˚ lat/lon grid (about 4km) from Meteo Rwanda. The time series (1981 to 2021) were created by combining quality-controlled station observations in Meteo Rwanda’s archive with satellite rainfall estimates.

How to use this interactive map

ThePlots Range controls the range of the vertical axis of the time series and the horizontal axis of the probability of exceeding graph. Blanking the boxes will set the range to the extrema of graph in view.

Helpdesks

ContactMeteo Rwanda with any technical questions or problems with this Map Room.