A study of the errors in the areal mean rainfall arising out of missing observations

Abstract

This is an experimental study of the mean errors in the areal rainfall in situations of missing observations. The area selected is Amravati district in Vidarbha having a very good network of raingauges and the periods considered are the months June to September and the monsoon season. Errors in the areal rainfall have been examined separately in each of the five situations when anyone, two, three, four or five stations are missing in each year, and histograms of the percentage relative error have been given, and extreme values of the percentage relative error have been brought out. Limits on the deciles of the error distribution have been obtained. Percentage Root Mean Square Error (RMSE) has also been computed for the typical monsoon month, July, and for the monsoon season for each of the situations of one, two, three, four and five stations missing randomly in space and time; the same for July is found to vary from 2.8 to 8.8 per cent as the number of missing observations varies from one to five, and for the season 2.2 to 7.0 per cent. Finally the percentage RMSE has been computed in a situation when the number of missing stations (zero to five) is random and the missing of stations is random in space and time; this error for the typical monsoon month, July, is 6.2 per cent and for the monsoon season, 5.6 per cent.