The program ONLINE_BLANEY_CRIDDLE calculates reference crop evapotranspiration [ET]o and crop evapotranspiration [ET]c by the Blaney-Criddle method, given specified climatic conditions.

  1. The input is the following: Month [m], mean daily temperature for the given month [t oC], latitude [L] (degrees), hemisphere H (either North of South), actual insolation time i (either low, medium, or high), minimum relative humidity (either low, medium, or high), daytime wind speed (light, moderate, or strong), and type of crop (one of 30 types, including the reference crop).

  2. The actual insolation time [i] is characterized by the ratio (n/N) of actual and maximum possible bright sunshine hours, as follows: low (n/N < 0.6), medium (0.6 ≤ n/N ≤ 0.8) and high (n/N > 0.8).

  3. The relative humidity [RH] is characterized as follows: low (RH < 20%), medium (20% ≤ RH ≤ 50%) and high (RH > 50%).

  4. The daytime wind speed [w] is characterized as follows: Light (0 m/s ≤ w < 2 m/s), moderate (2 m/s ≤ w ≤ 5 m/s), strong (w > 5 m/s).

  5. The applicable crop coefficient [kc] for the chosen crop is taken as the midrange value of Table 2-5.

  6. The output is daily reference-crop and crop potential evapotranspiration, in mm, and monthly reference-crop and crop potential evapotranspiration, in mm/day.