Potential Evapotranspiration Reduction and Its Influence on Crop Yield in the North China Plain in 1961–2014

Table 2

Humidity index (K).

Humidity index	Climate region
K < 0.03	Extremely arid climate region
0.03K < 0.2	Arid climate region
0.2K < 0.5	Semiarid climate region
0.5K < 1.0	Semihumid climate region
K > 1.0	Humid climate region