“…Therefore, the CWDI can be regarded as a cumulative value to reflect the actual water deficit degree. When studying the crop water deficit during a certain 10 day period, it is often necessary to consider the impact of the previous four 10‐day water deficits on the current 10 day period, which can be determined as follows: where CWDI i is the crop cumulative water deficit index in time units (10 days), CWDI i , CWDI i −1 , CWDI i −2 , CWDI i −3 and CWDI i −4 are the crop water deficit index values in the i , i − 1, i − 2, i − 3, and i − 4 time units, respectively, a , b , c , d , and e are the cumulative weight coefficients of the corresponding time units, and the values are 0.3, 0.25, 0.2, 0.15 and 0.1, respectively 12,30,31 …”