Variability of Rainfall in India

Rainfall Variability in India:

One defining characteristic of Indian rainfall is its notable variability. This variability is quantified using the following formula to calculate the coefficient of variation (C.V.):

C.V. = (Standard deviation) / Mean * 100

The coefficient of variation values illustrate the extent of departure from the mean rainfall values. In specific regions, actual rainfall can deviate by around 20-50 percent. These coefficient of variation values effectively depict the range of rainfall variability across India. Regions with a coefficient of variation under 25 percent include the western coasts, Western Ghats, northeastern Peninsula, the Ganga's eastern plains, northeastern India, Uttarakhand, Himachal Pradesh, and the southwestern part of Jammu and Kashmir. These areas witness an annual rainfall surpassing 100 cm. Conversely, regions with a coefficient of variation exceeding 50 percent are found in the western portion of Rajasthan, the northern part of Jammu and Kashmir, and the interior of the Deccan plateau. These regions experience annual rainfall amounts of less than 50 cm. The remainder of India exhibits a coefficient of variation ranging between 25 and 50 percent, with annual rainfall falling between 50 and 100 cm.

Rainfall Variability Levels in India:

Regions with Low Variability (Less than 25%): Such conditions are observed along the western coasts, the Western Ghats, northeastern Peninsula, eastern plains of the Ganga, northeastern India, Uttarakhand, Himachal Pradesh, and the southwestern part of Jammu and Kashmir. These geographical zones experience an annual rainfall exceeding 100 cm.

Regions with High Variability (Over 50%): This phenomenon is prominent in the western sector of Rajasthan, the northern segment of Jammu and Kashmir, and the interior regions of the Deccan plateau. These areas encounter annual rainfall amounts below 50 cm.

Intermediate Variability (25-50%): The remaining regions in India exhibit a variability range of 25 to 50 percent. These areas receive an annual rainfall ranging between 50 and 100 cm.

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