Skip to main content
U.S. flag

An official website of the United States government

Identifying a transition climate zone in an arid river basin using the evaporative stress index

Formally Refereed
Authors: Yongqiang Liu, Lu Hao, Decheng Zhou, Cen Pan, Peilong Liu, Zhe Xiong, Ge Sun
Year: 2019
Type: Scientific Journal
Station: Southern Research Station
Source: Natural Hazards and Earth System Sciences


Aridity indices have been widely used in climate classification. However, there is not enough evidence for
their ability in identifying the multiple climate types in areas with complex topography and landscape, especially in those
areas with a transition climate. This study compares a traditional meteorological aridity index (AI), defined as the ratio
of precipitation (P) to potential evapotranspiration (PET), with a hydrological aridity index, the evaporative stress index
(ESI) defined as the ratio of actual evapotranspiration (AET) to PET in the Heihe River Basin (HRB) of arid northwestern
China. PET was estimated using the Penman–Monteith and Hamon methods. The aridity indices were calculated using
the high-resolution climate data simulated with a regional climate model for the period of 1980–2010. The climate classified
by AI shows a climate type for the upper basin and a second type for the middle and lower basin, while three different
climate types are found using ESI, each for one river basin, indicating that only ESI is able to identify a transition climate
zone in the middle basin. The difference between the two indices is also seen in the interannual variability and extreme
dry/wet events. The magnitude of variability in the middle basin is close to that in the lower basin for AI, but different
for ESI. AI had a larger magnitude of the relative interannual variability and a greater decreasing rate from 1980 to 2010
than ESI, suggesting the role of local hydrological processes in moderating extreme climate events. Thus, the hydrological
aridity index is better than the meteorological aridity index for climate classification in the arid Heihe River Basin.


Liu, Yongqiang; Hao, Lu; Zhou, Decheng; Pan, Cen; Liu, Peilong; Xiong, Zhe; Sun, Ge. 2019. Identifying a transition climate zone in an arid river basin using the evaporative stress index. Natural Hazards and Earth System Sciences. 19(10): 2281-2294.