Table 2: Statistical comparison of algorithms using nonlinear regression with PR observations (validation data sets).

Algorithm applied No. of data points Correlation coefficients Root mean square error (RMSE) (mm/h) Bias (mm/h) Nonlinear regression using SI only 6842 0.722 3.186 2.171 Nonlinear regression using PCT only 6842 0.741 2.763 1.962 Nonlinear regression using both SI and PCT 6842 0.784 1.896 1.182