On the Identification of Rainfall Variability in the Subequatorial Zone Case of Rainfall Observed in the Ngandajika Region in the South-Central Congo Basin in the Democratic Republic of Congo

Alphonse Kambi Dibaya Okito

  1. Institut Supérieur Pédagogique de Mbujimayi, DR Congo

  Open Access - Under a Creative Commons license

Abstract

In the intertropical region, precipitation varies from one year to another. The annual series of these precipitations is a chronological series. To identify the variability of this series, it is recommended to use rigid statistical tests. The precipitation series observed at the INERA-Ngandajika station from 1940 to 2006 being a chronological series, to identify its variability, four tests were used. The Nicholson index was used to calculate annual rainfall indices. The second-order Hanning low-pass filter method eliminated seasonal variations in the time series. The Tyson equation was used to calculate weighted rainfall totals and these totals were centered and reduced to visualize periods of rainfall surplus and deficit.

The Pettitt test made it possible to detect breaks in the rainfall series. These breaks are then, according to Pettitt, attributable to possible disturbances or changes. The presence of a break in a rainfall series means that there has been a variation in the level of rainfall over time and that this variation may or may not be significant. All these tests made it possible to calculate the average rainfall index. This index made it possible to analyze the temporal variability of precipitation in Ngandajika and to observe an abnormal period between 1940 and 2006 characterized by an interannual average of 1427.9 mm and a standard deviation of 198.6 mm. An abnormal period is defined as a period where the average annual rainfall does not tend towards the average total rainfall.


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