Region
Spatially Average Over
Analysis

Merged Station-Satellite Rainfall for


a)
b)
c)
d)


a) Dekadal (i.e., ~10-daily) rainfall for the selected region over the last 3 years.

b) Dekadal rainfall differences (from 1991-2020 mean) for the selected region over the last 3 years.

c) Smoothed dekadal rainfall for the current year (thick black line) compared to previous years (blue-1 yr from present; pink- 2 yrs from present; grey-3 yrs from present).

d) Cumulative dekadal rainfall (solid blue line) and the cumulative long-term average rainfall (solid black line) from user-chosen calendar day in the selected region. The grey plume indicates the range of the 5th and 95th cumulative rainfall percentiles.

image

Dekadal Rainfall

Rainfall

This Analysis tool allows users to view different presentations of the the most recent dekad.

The default map on this page displays dekadal (approximately 10-day) rainfall amounts over the country. The default map shows rainfall totals for the most recently available dekad, but totals for previous dekads can be displayed as well. By clicking a location on the map, the user can generate four time series graphs that provide analyses of recent rainfall averaged over an administrative district, with respect to that of recent years and the long-term mean.

Rainfall Anomaly

The rainfall anomalies map displays the difference between the most recent dekadal rainfall and the long-term average (1991-2020). Positive (negative) values indicate dekadal rainfall that are above (below) the long-term mean or climatology.

Rainfall Anomaly in Percent

The rainfall anomalies in percent map displays the difference between the most recent dekadal rainfall and the long-term average (1991-2020) expressed as a percentage of the climatology. Positive (negative) values indicate dekadal rainfall that are above (below) the long-term mean or climatology.

Cumulative Rainfall

The cumulative rainfall map displays the accumulated rainfall from a user selected day.

Cumulative Anomaly

The cumulative anomaly map displays the difference between the accumulated rainfall from a user selected day and the long-term average (1991-2020) for the same period. Positive (negative) values indicate accumulated rainfall that are above (below) the long-term mean or climatology.

Cumulative Anomaly in Percent

The cumulative anomaly map displays the difference between the accumulated rainfall from a user selected day and the long-term average (1991-2020) for the same period expressed as a percentage of the climatology. Positive (negative) values indicate accumulated rainfall that are above (below) the long-term mean or climatology.

Standard Precipitation Index (SPI)

The SPI map displays the standard rainfall index of the most recent dekadal rainfall (using 1991 to the latest complete year as base period). The SPI (McKee 1993) is the number of standard deviations that observed cumulative rainfall deviates from the climatological average. To compute the index, a long-term time series of rainfall accumulations over dekads are used to estimate an appropriate probability density function. The analyses shown here are based on the Pearson Type III distribution (i.e., 3-parameter gamma) as suggested by Guttman (1999). The associated cumulative probability distribution is then estimated and subsequently transformed to a normal distribution. The result is the SPI, which can be interpreted as a probability using the standard normal distribution (i.e., users can expect the SPI be within one standard deviation about 68% of the time, two standard deviations about 95% of the time, etc.) The analyses shown here utilize the FORTRAN code made available by Guttman (1999). Places where the dekadal climatology is less than 2 mm are masked out. 


                           

                              

                                 
                                    
    

                                    		
                                      SPI Values     
                                        Category       
                              

                              

                                 
                                    

                                    		
                                 ≥ 2.00
                                 Extremely Wet
                              

                              

                                 
                                    

                                    		
                                 1.50 to 1.99
                                 Severely Wet
                              

                              

                                 
                                    

                                    		
                                 1.00 to 1.49
                                 Moderately Wet
                              

                              

                                 
                                    

                                    		
                                 -0.99 to 0.99
                                 Near Normal
                              

                              

                                 
                                    

                                    		
                                 -1.00 to -1.49
                                 Moderately Dry
                              

                              

                                 
                                    

                                    		
                                  -1.50 to -1.99
                                 Severely Dry
                              

                              

                                 
                                    

                                    		
                                 ≤ -2.00
                                 Extremely Dry
                              

                           

                           
                        

                        
                     		
                  

                  

                     
                        
                        

                           

                              
                                 
                                 
Table adapted from McKeeet al. (1993)

                                 
                              		
                           

                        

                        
                     		
                  

               

               
            

            
         


         
         

            
            
Dataset Documentation

            
            
Reconstructed rainfall over land areas on a 0.05 x 0.05 lat/lon grid (about 4km).
               The rainfall times series (1981 to present) were created by combining quality-controlled
               observations from stations with satellite rainfall estimates.
            

            
         

         
         

            
            
How to use this interactive map

            
            

               
               

               
            

            
         

         
         

            
            
Helpdesk

            
            
Contactwebadmin@meteo.go.ke with any technical questions or problems with this Map Room.