The Maproom explores historical rainy season length and total rainfall amount based on user-defined definition of onset. 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. Nov 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.
The default definition of the cessation date is the first date after April 1 st in 60 days when the soil water balance falls below 5mm for a period of 3 days.
Then the map shows yearly statistics of the rainy season length or total rainfall amount: 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 the rainy season length or total rainfall amount.
Note that if the criteria to define the onset or cessation date are not met within the search period, the analysis will return a missing value.
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.
Contact info@zmd.gov.zm with any technical questions or problems with this Maproom.