The main cause of high relative rainfall variability (measured by the…

CONCEPT

Relative rainfall variability is measured with the coefficient of variation (CV): standard deviation divided by mean rainfall. It expresses fluctuations as a share of the mean, not as an absolute rainfall amount.

For a fixed absolute deviation, reducing the mean increases this ratio, while increasing the mean reduces it. This denominator effect does not require an assumption about the number of rain events.

APPLICATION

Northwestern Madhya Pradesh has lower mean rainfall than the wetter parts of the state. Comparable year-to-year departures are therefore a larger fraction of the local mean, producing a higher coefficient of variation.

CONTRAST

• High rainfall: A larger mean increases the denominator, so the same absolute departure forms a smaller share of the mean.

• Lack of rainfall: A lower mean shrinks the denominator, so the same absolute departure forms a larger share of the mean.

• Maximum temperature: This is a daily thermal extreme that affects evapotranspiration; it is not a component of the rainfall coefficient-of-variation ratio.

• Continuous rainfall: Precipitation distributed persistently through time makes the seasonal total less dependent on isolated events.

CROSS-CHECK

The regional pattern is consistent with the ratio: mean rainfall declines toward northwestern Madhya Pradesh while relative rainfall variability rises in that direction.

Therefore, among the offered choices, lack of rainfall is the best answer.