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

Abstract

Abstract. 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.

Cascading effects of drought in Xilin Gol temperate grassland, China

“…A relatively low ESI indicates water limitation to plants, and the actual rate is way below the PET. In contrast, a relatively high ESI indicates freely available water with the AET rate approaching or close to the PET 40 .The ESI is used to assess water stress using hydrological and ecological properties 41 . To compare different types of droughts, we used the standardized procedure for calculating SPEI to calculate the standardized drought index of ESI, i.e., the standardized evapotranspiration drought index (SEDI).…”

The Short-Term Effects of Heavy Thinning on Selected Soil Carbon Pools and Microbial Activity in a Young Aleppo Pine Forest

“…The average annual temperature is 14 • C, rainfall is irregular with annual values of 342 mm, and the average annual potential evapotranspiration is 837 mm [46]. The area is classified as semi-arid according to the aridity index climate classification [47,48]. Tree density and competition are high (overstocked), with aboveground biomass estimated from allometric equations at 47.3 Mg ha −1 (22.2 Mg C ha −1 ) [46].…”

Warming-induced vapor pressure deficit suppression of vegetation growth diminished in northern peatlands

“…Generally, higher SOC and lower BD indicated good soil hydraulic properties 32,33 . Climate water deficit (CWD) and available volumetric water content (VWC) were used to evaluate water availability [34][35][36] . A low CWD and a high VWC correspond to a wet environment.…”

“…The spatial distribution of the northern peatlands in this study was derived from PEATMAP 51 . The map is the result of a synthesized analysis of geospatial information from various sources at global, regional, and national scales 35 and has been used in a recent study 53 . The peatland extent in PEATMAP is extracted from Peat-ML, a map created using machine learning algorithms 52 .…”