Improved Atmospheric Modelling of the Oasis-Desert System in Central Asia Using WRF with Actual Satellite Products

Miao Zhang,Geping Luo,Peng Cai,Philippe De Maeyer,Alishir Kurban

doi:10.3390/rs9121273

Abstract

Because of the use of outdated terrestrial datasets, regional climate models (RCMs) have a limited ability to accurately simulate weather and climate conditions over heterogeneous oasis-desert systems, especially near large mountains. Using actual terrestrial datasets from satellite products for RCMs is the only possible solution to the limitation; however, it is impractical for long-period simulations due to the limited satellite products available before 2000 and the extremely time- and labor-consuming processes involved. In this study, we used the Weather Research and Forecasting (WRF) model with observed estimates of land use (LU), albedo, Leaf Area Index (LAI), and green Vegetation Fraction (VF) datasets from satellite products to examine which terrestrial datasets have a great impact on simulating water and heat conditions over heterogeneous oasis-desert systems in the northern Tianshan Mountains. Five simulations were conducted for 1–31 July in both 2010 and 2012. The decrease in the root mean squared error and increase in the coefficient of determination for the 2 m temperature (T2), humidity (RH), latent heat flux (LE), and wind speed (WS) suggest that these datasets improve the performance of WRF in both years; in particular, oasis effects are more realistically simulated. Using actual satellite-derived fractional vegetation coverage data has a much greater effect on the simulation of T2, RH, and LE than the other parameters, resulting in mean error correction values of 62%, 87%, and 92%, respectively. LU data is the primary parameter because it strongly influences other secondary land surface parameters, such as LAI and albedo. We conclude that actual LU and VF data should be used in the WRF for both weather and climate simulations.

Highlights

The arid region of Central Asia (CA), which includes Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, and the Xinjiang Province of China [1,2], is located deep inside the continent and has unique geomorphological characteristics, including mountain–basin systems
All of the simulations conducted in this study produce the characteristic of the “wet–cold” island effect over the oasis area, as reported previously [7,14,71,72], Weather Research and Forecasting (WRF) can more accurately reflect the intensity of the oasis cold–wet effects when using all actual land use (LU), albedo, Leaf Area Index (LAI), and Vegetation Fraction (VF) data
The current study used WRF with actual LU, albedo, LAI, and VF data derived from satellite products to improve the simulation of weather and climate conditions in the oasis–desert system of the northern Tianshan Mountains (NTM) in 2010 and 2012

Summary

Introduction

The arid region of Central Asia (CA), which includes Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, and the Xinjiang Province of China [1,2], is located deep inside the continent and has unique geomorphological characteristics, including mountain–basin systems In this area, elevations can increase dramatically, from a few hundred metres above sea level in the basin areas to over 5000 m above sea level in the mountainous areas, over a horizontal distance of less than 200 km; there is high heterogeneity in land cover types [3]. The geographical and ecological characteristics differ significantly between these oases and the surrounding deserts, causing significant differences in energy budgets, the exchange rate of momentum, and water vapor levels These differences produce typical oasis effects [13] such as the “cold–wet” island effects of oases (an oasis is a wet, cold island capped by warm–dry air), and the thermal differences between oases and the surrounding deserts result in oasis breeze circulation (OBC). CA, because of its large elevation differences and the importance of oases, can be divided into mountainous region, oases, and desert areas, often named the Mountain–Oasis–Desert System (MODS)

Objectives

Methods

Results

Discussion

Conclusion