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基于 WRF 气候模式的天山北坡山地 - 绿洲 - 荒漠系统水热格局与局地气候研究
Thesis Advisor罗格平 ; Philippe De Maeyer
Degree Grantor中国科学院大学
Place of Conferral新疆乌鲁木齐
Degree Discipline理学博士
Keyword气候模式 WRF 山体 - 绿洲 - 荒漠复合系统 灌溉绿洲效应 天山北坡 Climate model WRF Mountain - Oasis - Desert System Irrigated oasis effects The Northern Tianshan Mountains
Abstract天山北坡是亚洲中部干旱区气候与地形的缩影。该区域孕育了欧亚大陆腹地典型的山地 - 绿洲 - 荒漠复合生态系统(Mountain - Oasis - Desert System, MODS),地形复杂, 气候变化敏感, 近 60 年气温与降水呈现显著增长的趋势, 并且较其它亚洲干旱区域变化幅度更加剧烈。具体来说, 天山北坡降水呈现 11.3% 的增长趋势,增加幅度为 22% - 33%; 且温度以 0.8 ° C /10 年速率变暖, 而亚洲干旱区和全球陆地的变暖速率分别为 0.39 ° C/10 年和 0.27 - 0.31 °C/10 年。这个区域的人类活动主要表现为绿洲大规模的灌溉和快速的扩张。绿洲是这个区域的精华, 决定着这个区域人类生存与发展的命脉。这种发展于有限水土资源下和复杂山盆之间的灌溉绿洲及其扩张对区域气候的影响是怎样的还不清楚。从绿洲 - 荒漠交互和山盆之间交互的角度分析、 认识这个问题对干旱区人类活动与气候变化的相互作用机理具有重要的科学意义, 也对发展于有限水土资源下的绿洲稳定与可持续发展有着现实的指导意义。基于 Land Use/Cover Change(LUCC) 与气候变化关系的大科学问题背景, 本毕业设计通过使用区域气候模式 Weather Research and Forcasting(WRF) , 从能量、温度、湿度、降水、大气结构、风速与风向等要素分析复杂的天山北坡 MODS 的水热格局与局地气候特征, 重点从绿洲与荒漠交互作用, 山盆交互作用方面探讨灌溉绿洲对整个 MODS 的水热格局的影响及机制。研究内容主要包括以下几个方面:WRF 对陆面地理 - 生态参数的敏感性:由于 WRF 内嵌的基础地理数据集陈旧过时, 且在这种复杂缺资料区域利用真实遥感陆面参数替换所有内嵌地理数据耗时、耗力、不具操作性的问题, 我们探讨了 WRF 对于 Land Use(LU), Albedo, Leaf AreaIndex(LAI) 和 Green Vegetation Fraction(GVF) 的敏感性, 旨在寻找决定 WRF模拟局地/区域气候研究的关键参数。结果表明, WRF 对于真实的 GVF 陆面地理数据最为敏感, GVF 对模式模拟温度、湿度和潜热误差校正贡献率分别为 62%, 87%和 92%。 LU 数据作为模式一级参数对二级参数有决定作用, 在模拟过程中也不可忽视。耦合滴灌过程:针对 WRF 缺乏对干旱区典型的绿洲滴灌过程的有效表征, 限制了模式数值模拟客观反映绿洲的水热状态, 我们在前人研究基础上, 新发展一个符合干旱区灌溉模式的滴灌框架, 并将其与 WRF 耦合, 以提高模型对区域水热格局和局地气候的数值模拟精度。结果表明:改进的 WRF 现实地模拟了灌溉绿洲的水热状态, 模拟的灌溉量与区域灌溉定额和气候预测一致;并且结果表明: 灌溉不仅加强了灌溉季绿洲的冷湿岛效应和绿洲 - 荒漠局地环流, 也增加了上游山区高程大约为 1000 - 2000 米的降水量。绿洲效应, 与山盆交互作用的关系: MODS 的气温总体上呈现从山地到绿洲到荒漠条带性增长的格局, 而比湿在 1 km - 2 km 高程左右区域显著的高于同高度盆地区域, 10 - m 环流在盛行西风控制下, 展示了典型的区域山谷风格局。在这种水热格局特征下, 我们观测到北部绿洲 - 荒漠边界一条明显温湿梯度及白天绿洲上空气温(比湿)显著低于(高于)同高程的外围荒漠区域, 这是典型的绿洲冷湿岛效应特征, 这种效应强度在近地面可以达到−0.61 ° C(1.56 g kg−1) , 可以影响到绿洲上空大约 1.5 km 的高度。由于强劲山谷风的存在隐匿了由绿洲荒漠水热差异产生的绿洲 - 荒漠局地环流, 使得前人提出的理论―绿洲自我维持机制‖对天山北坡的绿洲的生态稳定不能发挥有效作用。而且, 白天谷风使得绿洲的冷湿气团向山区移动,在高程大约 1000 - 2000 米山区成云致雨;晚上, 山风将绿洲上空的冷湿气团携带进入部分荒漠区域, 有益于绿洲 - 荒漠过渡带的植被生长;但山谷风破坏了绿洲的自我维持机制, 使得其不能在当前 MODS 中发挥作用,并且加速了天山北坡内陆流域水文循环过程。
Other AbstractThe Northern Tianshan Mountains(NTM), which are located in the hinterland ofCentral Asia(CA), is a microcosm of the terrain and climate of CA and consists of a greatnumber of complex mountains and basins in the world. The NTM has been experiencingdistinct intense human activities in the recent 60 years. Based on limited runoff fromsnow - and glacial - melt in mountainous region and unrestrained extraction ofgroundwater for irrigation, oases with high primary productivity have developed betweenmountains and basins, thus the NTM can be consisting of mountain, oasis, and desertareas, named as Mountain - Oasis - Desert ecosystem (MODS) . The total area of oasishas expanded 4 times more than the original size. Meanwhile, recent studies indicate thatannual mean air temperature in the NTM has been increasing at an average rate of 0.8 ° Cdecade−1, which is far larger than the average rate for CA(i.e.,0.39 ° C decade−1 from 1979to 2011) and for global land areas (i.e.,0.27 - 0.31 ° C decade−1 from 1979 to 2005).Precipitation and frequency of extreme precipitation have an obvious increasing tendencyin NTM at an increase rate of 11.3%. How does the abnormal regional temperature andprecipitation change in NTM respond to irrigated oasis and its expansion in complexmountain and basin systems ? The answer is not yet clear. Answering the scientificquestion is essential, both theoretically and practically, to the sustainable developmentand ecological stability of oases and will provide useful information for furtherinvestigating the impact of oasis expansion on regional climate changes under globalwarming.In this study, the sensible heat, latent heat, temperature, humidity, atmosphericstructure and circulation patterns of the complex MODS in the NTM were simulatedusing the Weather Research and Forecasting (WRF) model. The main contents of thisstudy included the following:Because of the use of outdated terrestrial datasets, including Land Use (LU) , Albedo、Leaf Area Index(LAI)and Green Vegetation Fraction(GVF), the regional climate modelWRF has a limited ability to accurately simulate weather and climate conditions overheterogeneous MODS at such scale. Using actual terrestrial datasets from satelliteproducts is the only possible solution to the limitation; however, it is impractical for long- period simulations due to the extremely time - and labor - consuming processes involved.We used the WRF model with observed estimates of LU, albedo, LAI, and GVF datasetsfrom satellite products to examine which terrestrial datasets have a great impact onsimulating water and heat conditions over heterogeneous oasis - desert systems. Usingactual GVF data has a much greater effect on the simulation of T2, RH, and LE than theother parameters, accounting for mean error correction 62%, 87%, and 92%, respectively.LU data, which is the primary parameter and strongly influences other secondary landsurface parameters in the WRF, is also very important.The ability of WRF to accurately simulate water - heat conditions of irrigated oasisis limited due to lack of typical drip irrigation processes implemented. A drip irrigationscheme was incorporated into the WRF to realistically represent water - heat patterns ofoasis and to explore irrigation’s effects on local climate of complex MODS. Modelevaluation further reveals that the WRF coupled with the drip irrigation scheme cangenerate irrigation water amounts that are in close agreement with the observation.Irrigation strengthened cold - wet island effects of oasis and oasis breeze circulation(OBC) in the irrigation season, and increased precipitation amount in upwind mountainsareas with elevation approximately 1000 - 2000 m in daytime in the irrigation season.The air temperatures of MODS generally exhibit continuous stripe - like increasesfrom the mountainous areas to the oasis areas and to the desert areas, the specifichumidity in the mountainous area is higher than that over the basin area at the sameelevation; In the context of the prevailing westerly wind, a typical mountain-valley windis observed with wind direction of WNW at a wind speed of approximately 3 m/s occursduring the daytime, whereas a wind direction of SW with a wind speed of approximately4 m/s occurs at night. The typical ―cold - wet‖ island effects of the oasis and OBC arefully described within the context of the MODS, as evidence by an obvious temperature -humidity gradient line along the northern boundary of the oasis. The air temperature(pecific humidity) over the oasis during the day was significantly lower (higher) than theother areas at the same height. The intensity of such cold (wetting) island of the oasis isapproximately −0.61 ° C (1.56 g kg−1) at near surface, and extends to a height ofapproximately 1.5 km above the oasis surface. The OBC is counteracted by the strongerbackground circulation. Thus, the self - supporting mechanism of oases originating fromthe OBC plays a limited role in maintaining the ecological stability of oases MODS. Theairflow with increased moisture over irrigated oasis is brought to mountains areas by intense valley wind in daytime and forms precipitation with elevation approximately 1000- 2000 m due to adiabatic cooling and condensation in this region. Meanwhile intensemountain wind bring increased moisture over irrigated oasis to extend into thesurrounding desert area at night, which may produce wet conditions favorable for desertplants in the oasis - desert transition zone. These effects accelerated hydrological processin the NTM.
Subject Area地图学与地理信息系统
Document Type学位论文
Recommended Citation
GB/T 7714
张苗. 基于 WRF 气候模式的天山北坡山地 - 绿洲 - 荒漠系统水热格局与局地气候研究[D]. 新疆乌鲁木齐. 中国科学院大学,2018.
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