乌兰布和沙漠东北部不同下垫面的小气候变化特征

研究沙区不同下垫面小气候特征对充分利用气候资源及保证林业和农业的正常发展具有实践意义。该研究基于内蒙古磴口荒漠生态系统国家定位观测研究站2018年1-12月监测的荒漠区、荒漠-绿洲过渡带和绿洲内部的气温、相对湿度、风速和风向等气象资料,研究了3种下垫面的小气候特征并探讨了产生差异的原因。结果表明:1)荒漠区、荒漠-绿洲过渡带和绿洲内均为白天气温差异较小,夜间相差较大;由于近地层(0~50m)具有明显的逆温现象,使得植被在气温较高季节发挥降温增湿作用,而冬季发挥保温作用;2)绿洲使年均相对湿度增加1.31~2.57个百分点;就季节而言,夏、秋季,绿洲内的相对湿度较荒漠区和过渡带分别高4.04~6.17和0.93~1.94个百分点,春、冬季,由于近地层(0~50 m)存在明显的逆湿现象,因此绿洲内的相对湿度较荒漠区和过渡带分别低0.37~1.41和6.55~8.71个百分点;3)荒漠区、过渡带和绿洲内风向年变化特征均为以偏西风(W,WSW,SW,SSW)为主,荒漠区和过渡带的风向多变,绿洲内风向相对较为集中,绿洲能够使年均风速降低32.99%~37.05%。乌兰布和沙漠东北部过渡带植被和绿洲防护林体系对小气候具有很好的调节作用(降温、增湿、削减风速),研究区局地小气候主要体现在风速和夏秋季湿度上,而气温和冬春季湿度分别主要受逆温和逆湿的影响。

Microclimate variations of different underlying surfaces in Northeastern Ulan Buh Desert in Inner Mongolia of China

Microclimate characteristics of different underlying surfaces can pose a practical challenge to utilize climate resources for the normal growth of crops in desert areas.In this study,the microclimate differences were systematically analyzed in the three typical underlying surfaces.The data,including the air temperature,relative humidity(RH),wind speed and wind direction in desert area,desert-oasis ecotone and oasis in the northeastern of Ulan Buh Desert,were collected in synchronous observation from the“National Observation Station of Inner Mongolia Dengkou Desert Ecosystem”during January to December,2018.The results showed that there were significantly different effects of the properties of underlying surface on microclimate characteristics.1)The annual temperatures in desert area,desert-oasis ecotone and oasis were 9.66,9.38 and 9.14℃,respectively.There were few differences in daytime between the three underlying surfaces,but great differences in night.There was obviously inversion phenomenon within 50 m above the ground,where the vegetation has the function of cooling and humidification in the high temperature season,whereas,it has a heat preservation effect in winter.The temperatures of the desert-oasis ecotone and the oasis increased by 0.05 and 0.18℃,compared with that of the desert area in the winter,while those decreased by 0.38-1.50℃and 0.22-2.58℃,respectively,in spring,summer and autumn.2)The annual and diurnal variations of relative humidity remained consistent in desert area,desert-oasis ecotone and oasis.The annual average relative humidity in the oasis increased by 1.31 to 2.57 percentage points,compared with that in the desert-oasis ecotone and desert area.In terms of seasons,the relative humidity in the oasis was 4.04-6.17,0.93-1.94 percentage points higher than that in the desert area and the desert-oasis ecotone in summer and autumn.The relative humidity inside the oasis was 0.37-1.41percentage points,6.55-8.71 percentage points lower than that in the desert area and the desert-oasis ecotone.The reason can be that the humidity inversion phenomenon occurred within 50 m above the ground.3)The annual variations of wind direction were similar in the desert area and desert-oasis ecotone,where the main directions were the westerly winds(SW,WSW,W,WNW).The wind direction was changeable in the desert area and desert-oasis ecotone,whereas that relatively concentrated in the oasis.The average annual wind speed was reduced by 32.99%-37.05%in the oasis,compared with that in the desert-oasis ecotone and the desert area,indicating that the vegetation can effectively decrease the wind speed.Comprehensive analysis showed that the vegetation and oasis shelter forest systems in the transition zone of the northeastern of Ulan Buh Desert posed a good regulation effect on microclimates,such as cooling,humidifying,and reducing wind.The local microclimate in the study area demonstrated that the wind speed and humidity in summer and autumn,while,the temperature and humidity of spring and winter were mainly affected by inverse temperature and humidity.This finding can provide a theoretical basis to explore the microclimate ecological characteristics in arid areas,as well ecological protection and reasonable construction of oasis in desert areas.