Numerical Simulations of the Impacts of Mountain on Oasis Effects in Arid Central Asia

Miao Zhang,Alishir Kurban,Xinxin Wang,Rafiq Hamdi,Geping Luo,Philippe De Maeyer,Yuan Qiu

doi:10.3390/atmos8110212

Abstract

The oases in the mountain-basin systems of Central Asia are extremely fragile. Investigating oasis effects and oasis-desert interactions is important for understanding the ecological stability of oases. However, previous studies have been performed only in oasis-desert environments and have not considered the impacts of mountains. In this study, oasis effects were explored in the context of mountain effects in the northern Tianshan Mountains (NTM) using the Weather Research and Forecasting (WRF) model. Four numerical simulations are performed. The def simulation uses the default terrestrial datasets provided by the WRF model. The mod simulation uses actual terrestrial datasets from satellite products. The non-oasis simulation is a scenario simulation in which oasis areas are replaced by desert conditions, while all other conditions are the same as the mod simulation. Finally, the non-mountain simulation is a scenario simulation in which the elevation values of all grids are set to a constant value of 300 m, while all other conditions are the same as in the mod simulation. The mod simulation agrees well with near-surface measurements of temperature, relative humidity and latent heat flux. The Tianshan Mountains exert a cooling and wetting effects in the NTM region. The oasis breeze circulation (OBC) between oases and the deserts is counteracted by the stronger background circulation. Thus, the self-supporting mechanism of oases originating from the OBC plays a limited role in maintaining the ecological stability of oases in this mountain-basin system. However, the mountain wind causes the “cold-wet’’ island effects of the oases to extend into the oasis-desert transition zone at night, which is beneficial for plants in the transition region.

Highlights

Oases are common in the deserts of arid areas [1,2,3,4], especially in the hinterland of aridCentral Asia (CA)
Large urban areas and croplands in the Northern Tianshan Mountains (NTM) can be clearly observed in the actual land cover (LC) dataset (Figure 2b)—these features are absent in the default dataset (Figure 2a), which instead displays large areas of scrubland and grassland
The larger albedo values observed over the oasis areas in the actual dataset may be attributed to severe salinization [62,63] and considerable use of plastic-mulch [64], which have developed in the study area (Figure 2c,d).The differences in the leaf area index (LAI) and the green vegetation fraction (GVF) between the actual and the default datasets are shown in Figure 2e–h, respectively

Summary

Introduction

Oases are common in the deserts of arid areas [1,2,3,4], especially in the hinterland of arid. Atmosphere 2017, 8, 212 development in these mountain-basin systems [5]. Watersheds represent a basic unit in this mountain-oasis-desert system (MODS). The Northern Tianshan Mountains (NTM) is one of the typical geomorphic regions of CA and consists of a large number of complex MODSs. oases account for only a small proportion of the land surface (e.g., 4–5% in Xinjiang, a typical region in the hinterlands of Central Asia), more than 90% of the local population and >95% of the socioeconomic wealth are concentrated in oases [6]. Oases play a vital role in social and economic development

Methods

Results

Conclusion