A Mechanistic Investigation of the Oasis Effect in the Zhangye Cropland in Semiarid Western China

Abstract:

Providing mechanistic explanations for oasis cold island effect trends expands current understanding of how land use change affects local climate in semi-arid regions globally. Data from Zhangye, Gansu, China in 2013 were used to evaluate intrinsic biophysical mechanism (IBPM) theory's ability to model the oasis effect. The land-surface temperature oasis effect is observed most intensely in summer afternoon (average difference −12.66 ± 6.6 K at 13:30 between oasis and desert sites). Observed land-surface temperature oasis effects result from differences in surface albedo, Bowen ratio, soil heat flux and air temperature. The Bowen ratio change is the strongest predictor of land-surface temperature oasis effect, with a nearly 1:1 relationship to the observed land- surface oasis effect in summer (R2 = 0.6). The IBPM theory accurately predicts oasis effects for 66% of summer daylight hours, with an average RSME of 4.72 K. Correlation analysis is performed to evaluate the impacts of meteorological conditions on observed oasis effects, showing that higher windspeed and greater atmospheric clarity produce stronger land-surface temperature oasis effects. In summer, this relationship is strongest, with an R2 value of 0.65 and RSME of 3.77. This research has implications for evaluating temperature impacts of land use change in semi-arid regions globally.