The new version of the R(A) method incorporates automatic tuning of α based on the rain type and the slope of the ZZDR dependency in a particular rain region. According to the new algorithm, precipitation region is first segregated into three rain categories: stratiform, convective, and tropical. For these regions, three values of α are calculated based on the Z-ZDR slopes in each of the three regions. The A field for an entire radar scan is first calculated using the optimal value of α obtained from the largest region. Then the values of A in the other two smaller regions are adjusted with a factor based on the estimated α to match their precipitation types. Rainfall rate for the scan is computed using adjusted A. The modified R(A) algorithm has been tested for light rain, flood, and hurricane precipitation events. Comparison with rain gauge measurements shows that the modified R(A) demonstrates better performance in terms of correlation coefficient, mean bias ratio, and the root mean square error than R(Z) and the original version of R(A) with fixed default value of the parameter α.