Question

which estimate the amount of rainfall based on wetness of soil after rain

Answer 1

There is no direct relationship between soil moisture content and rainfall, soil moisture content depends up on a lot of factors like atmospheric pressure, humidity, and type of soil and depth of soil.

There is however relationship between soil saturation and annual rainfall, as per current research in this field at MIT say that relationship between rainfall and soil moisture content is there in certain months of April, May, June, July and August which show a linear correlation between the rainfall and soil saturation but for other months of the year no such significant relationship exists indicating in other months soil moisture is unrelated to rainfall.