3.21 VARIATION IN ANNUAL RAINFALL

Data ID

Description:

Rainfall variation calculated as the standard deviation of annual totals as a percentage of average annual rainfall

Chapter:

3 Climate

File name:

Variation in annual rainfall

File type:

ArcView shapefile

Geographical area:

Namibia

Keywords:

rainfall

annual

variation

Notes on data, analysis and

Rainfall variation calculated as the standard deviation of annual totals as a percentage of average annual rainfall. To

compilation:

illustrate the co-efficient of variation, consider the following example: Take a location (station) with an average rainfall

of 400 mm per year and a co-efficient of variation of 40%. A value of 40% means that the standard deviation is 160

mm (40% = (160/400)*100), and that area would see annual rainfall totals of between 240 and 540 mm in two-thirds of

all years. In the remaining third of all years, annual rainfall totals would be below 240 or above 540 mm.

This shapefile was created from the Arcview grid file. This grid file was created from data for almost 300 stations and

came from the following report:

Namibia Resource Consultants. 1999. Rainfall distribution in Namibia: Data analysis and mapping of spatial, temporal,

and Southern Oscillation Index aspects. Windhoek: Ministry of Agriculture, Water and Rural Development. See Fig 3.18

Average and Median annual rainfall for source data

Data quality and organisation

Positional Accuracy:

Created from a grid interpolated from points - accuracy will be reasonable in areas with clusters of stations and low in

areas with few stations

Vector/Raster:

Vector

Spatial reference

Projection:

Geographic

Fields

Field name

Field description

PERCENT

variation in ranfall in10 percent intervals ranging from less than

30% to more than 100%

VALUE

Numerical rank of classes

Source/Distribution

Data Source:

Namibia Resource Consultants. 1999. Rainfall distribution in Namibia: Data analysis and mapping of spatial, temporal,

and Southern Oscillation Index aspects. Windhoek: Ministry of Agriculture, Water and Rural Development.

Distribution notes:

Unrestricted