KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 天山北坡现代绿洲演变的气候与生态效应 | |
| Alternative Title | The Climatic and Ecological Effects of Modern Oasis Evolution in the North Tianshan Mountains |
| 蔡鹏 | |
| Subtype | 博士 |
| Thesis Advisor | 罗格平 ; Philippe De Maeyer ; Piet Termonia |
| 2020-06-30 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 理学博士 |
| Keyword | 山地-绿洲-荒漠系统 陆气相互作用 ALARO-SURFEX 生态系统碳水过程 AEM MODS Land Atmosphere Interaction ALARO-SURFEX Carbon and Water Cycle AEM |
| Abstract | 天山北坡位于欧亚大陆的内陆，远离海洋，是世界上最干旱的地区之一，属于典型的山地-绿洲-荒漠系统（MODS）。随着经济社会的发展和技术的进步，自1950s 以来，天山北坡的绿洲经历了快速的演变过程，导致自然生态系统被开垦为农田以及地表能量平衡过程发生变化。天山北坡的生态系统非常脆弱，对外部变化敏感。因此，研究绿洲的快速演变对区域生态系统和气候的影响，探索区域生态系统对未来气候变化的响应，对于天山北坡生态社会的可持续发展具有特别重要的意义。基于以上背景，本文旨在通过模型模拟来探讨绿洲演变的气候和生态效应。对于气候效应，我们主要通过区域气候模型 ALARO 耦合陆面过程模型 SURFEX来模拟分析 MODS 内的局地环流时空特征及其相互作用、 夏季降水对绿洲演变的响应。对于生态效应，我们通过运行干旱区生态系统模型（AEM）来研究区域生态系统对绿洲演变、 历史和未来气候变化的响应。论文的主要结果如下：首先，考虑到 ALARO-SURFEX 模型是首次被应用在天山北坡干旱区，我们使用课题组制作的土地覆被数据来改进 ECOCLIMAP 数据库中默认的土地覆被数据， 并利用分布在中国新疆境内的 53 个国家气象站和分布在天山北坡的 5 个自动气象站来评估 ALARO-SURFEX 的性能。验证结果表明，尽管该模型低估了日相对湿度和气温，但其可以较好地捕捉区域夏季气温和相对湿度的逐日和逐小时变化。然后，我们研究了在连续 4 日（2016 年 6 月 9 日至 12 日） 晴朗天气条件下绿洲环流（OBC）的动态变化及其与城市环流（UBC）的相互作用。观测和模拟结果均显示，在 19:00 - 21:00 时（北京时间， BJT），当山地-平原背景风系统较弱时，绿洲近地表出现了清晰的辐散系统。模型模拟结果表明，在 16:00-22:00BJT，绿洲环流与城市环流之间存在协同作用，且在 20:00BJT 时达到最大，此时绿洲上空的下沉气流（城市上空的上升气流） 速度增加 0.8（0.4） Pa/s。结果表明，绿洲扩张使乌鲁木齐市夜间城市热岛效应降低了 0.8°C，而城市扩张对绿洲冷岛的影响可以忽略不计。其次，通过实施是否有绿洲存在的两个敏感性试验，模拟 31 个夏季（1986-2016 年） 降水的时空变化， 并分析了 MODS 内绿洲扩张对区域夏季降水的影响及其机理过程。结果表明，绿洲的扩张主要影响山区的夏季降水，而不是绿洲区域。绿洲扩张在海拔低于 3100 m 的区域中对夏季降水起促进作用，而在海拔高于 4100 m 的区域中起抑制作用。绿洲扩张对山区夏季降水的促进作用可部分解释观测研究中发现的中山带变湿趋势，而其抑制作用则可能加速高山冰川萎缩。除了受影响最大的海拔范围和强度不同以外，绿洲扩张在 3 个 MODS（天山北坡、天山南坡和伊犁河流域）中对夏季降水影响的空间格局相似。这种空间格局主要是通过影响夏季午后对流性降水来实现的。 首先，山地-平原风系统中的平原风将绿洲的水汽输送到了山区。此外， 绿洲的扩张增加了低层大气的湿度，并降低了绿洲附近的地表温度， 引起下沉气流，进而降低了绿洲高空大气湿度，抑制了绿洲地区对流降水的形成。 并且，绿洲环流增强了平原风，从而促进了水汽从绿洲转移到山区， 湿气流受地形抬升后形成降水， 导致山区降水增加。但是，降水过后气流变干， 降低了高山地区的大气湿度并削弱了上升气流，导致降水减少。盛行风向的差异、绿洲规模和地形差异可解释 3 个 MODS 中绿洲扩张效应的空间格局差异。第三， 对 AEM 的灌溉模块进行了修改，以实现绿洲中不同的灌溉过程。然后，利用修改后的模型，模拟了 1971 年至 2013 年三工河流域绿洲和荒漠生态系统中 NPP 和 ET 在绿洲演变影响下的时空变化。研究结果表明，绿洲生态系统和荒漠生态系统对绿洲演变和气候变化有不同的响应。在整个研究期间，绿洲生态系统的NPP和ET均呈下降趋势，而荒漠生态系统的NPP和ET呈小幅上升趋势，且相对稳定。绿洲生态系统的 NPP 和 ET 的时间格局受绿洲演变的控制，而荒漠生态系统的 NPP 和 ET 的时间格局受气候变化的控制。气候变化对绿洲和荒漠生态系统均产生积极的影响，而绿洲演变对绿洲生态系统的年总 NPP 和耗水具有促进作用，而对荒漠生态系统具有抑制作用。绿洲演变决定了绿洲生态系统的年总 NPP 和总耗水量的变化，从第一阶段到第三阶段， 绿洲生态系统 NPP 增加169.4×109 g C，耗水量增加 127×106 m3。最后， 自 1971 年至 2013 年，在绿洲演变和气候变化的共同影响下，绿洲和荒漠生态系统的水分利用效率都增加了。最后，我们利用 AEM 模拟分析了 RCP2.6， RCP4.5 和 RCP8.5 情景下天山北坡各生态系统的 NPP 和 ET 动态变化。在各 RCP 情景下， 从 2006 年到 2055年，天山北坡的气候将经历一个暖湿化的趋势， 且在 RCP8.5 情景下暖湿化速度最快； 在空间上， 山区呈湿冷趋势， 荒漠区呈干热趋势。 在 RCP2.6， RCP4.5 和RCP8.5 情景下，随着气候和二氧化碳浓度的变化，区域年均 NPP 分别以 1.16、1.62 和 2.15 g C m-2 year-1 的速度增长。与区域年均 NPP 相似，区域年 ET 呈上升趋势，在 RCP2.6 下为 0.38 mm year-1，在 RCP4.5 下为 0.43 mm year-1，在RCP8.5 下为 0.52 mm year-1。因此，对于整个区域， 天山北坡将受益于2006-2055 年的气候变化与 CO2 浓度升高。不同 RCP 情景下区域年 NPP 差异的空间格局表明， NPP 的增加主要发生在农田广泛分布的中西部地区。在 RCP2.6情景下，区域年NPP的下降主要发生在东北部。区域ET差异的空间格局表明，ET 的增加主要发生在中西部地区，与 NPP 差异相似。但是，高山地区的 ET 下降主要是由于温度下降引起的。东北地区 ET 下降主要是由于 RCP2.6 情景下的降水下降。在各 RCP 情景下，天山北坡所有植被类型的 NPP 和 ET 均以不同的速率增加，且与其他植被类型相比， 非深根灌木， 深根灌木和草地对气候和CO2 浓度的变化更敏感，而温带落叶阔叶林和农田对这些变化的敏感性低于其他植被类型。在不同的研究时期和不同的 RCP 情景下，不同植被类型的敏感性会有所不同。但是，在所有 RCP 情景下，每种植被类型的水分利用效率都呈增加趋势。对于每种植被类型，由于暖湿化的气候变化趋势以及 CO2 浓度的增加，水分利用效率的增长率从 RCP2.6、 RCP4.5 到 RCP8.5 依次增加。 |
| Other Abstract | Located in the inland of Eurasia and far away from oceans, the north TianshanMountains is one of the driest regions in the world and a typicalMountains-Oasis-Desert system (MODS). With the development of economy andtechnology, the oasis in the north Tianshan Mountains has experienced rapid evolutionprocesses since the 1950s, resulting in conversion from natural ecosystems to cropsand alteration in land surface balance. The ecosystems in north Tianshan Mountainsare fragile and sensitive to the ambient changes. Therefore, it is of particularimportance to investigate the effects of rapid oasis evolution on local ecosystems andclimate, and explore the responses of local ecosystems to future changes for thesustainable development of the north Tianshan Mountains.Based on the above background, this dissertation aims to explore the climatic andecological effects of oasis evolution by conducting model simulations. For theclimatic effects, we mainly focus on the special circulations and summer precipitationwithin the MODS by running regional climate model ALARO coupled with landsurface model SURFEX. For the ecological effects, we investigate the responses oflocal ecosystems to oasis evolution, historical and future climate change by runningthe arid ecosystem model (AEM). The main results of this dissertation are concludedas follows:Firstly, considering the fact that it is the first time for ALARO-SURFEX modelto be applied in the north Tianshan Mountains, we improve the default land cover dataof the ECOCLIMAP database using the land cover data that were generated by theXinjiang Institute of Ecology and Geography and evaluate the ALARO-SURFEXperformance with 53 national meteorological stations spread in the Xinjiang provinceof China and 5 automatic meteorological stations in the north Tianshan Mountainsarea. The validation results show that the model can capture correctly the daily andhourly variation of the 2 m temperature and relative humidity in summer, although itunderestimates the relative humidity and the daily 2 m temperature. Then, we studythe dynamic of oasis breeze circulation (OBC) and its interactions with urban breezecirculation (UBC) in the 4 clear sky days (9-12 June 2016). Observations andsimulations both show that a low level divergence over oasis appears between 19:00and 21:00 Beijing Time when the background mountain-plain wind system is weak.The model simulates a synergistic interaction between the oasis-desert breeze andurban-rural breeze from 16:00 until 22:00 with a maximum effect at 20:00 when thedowndraft over oasis (updraft over urban) areas increases by 0.8 (0.4) Pa/s. Theresults show that the oasis expansion decreases the nocturnal urban heat island in thecity of Urumqi by 0.8 °C, while the impact of urban expansion on the oasis coldisland is negligible.Secondly, the oasis expansion effects on regional summer precipitation withinthe MODS are investigated by running 2 sensitivity simulations with and withoutoases during the 31 summers (1986 - 2016). The results show that the oasis expansionmainly influences the summer precipitation in the mountainous area rather than theoasis area where the irrigation takes place. The oasis expansion plays positive effectsin the areas with an elevation lower than 3100 m and negative effects in the areas withan elevation higher than 4100 m. The oasis expansion positive effects in themountainous areas may partly explain the wet trend found in the observational studies,while its negative effects may contribute to the glaciers retreat in the high mountainregions. The oasis expansion effects spatial patterns are similar in the 3 MODSsexcept for the maximum elevation ranges and the magnitude. These patterns aremainly realized by affecting the summer convective precipitation. On one hand, theoasis expansion increases the low-level atmosphere humidity and cools down the nearsurface temperature over the oasis, inducing subsidence that decreases the humidity ofthe high-level atmosphere and suppresses precipitation over oasis area. On the otherhand, the oasis expansion enhances the mountain/plain circulation that transfers thewater vapor from the oasis to the mountain regions, increasing the precipitation in themountain regions. However, it reduces the atmospheric humidity and weakens theupward flow in the high mountain regions, resulting in a decrease in the precipitation.The differences in the prevailing wind direction, the scale of the oasis and theorography may explain the spatial pattern differences of the oasis expansion effect inthe 3 MODSs.Thirdly, the irrigation submodel of AEM is modified to realize different irrigationprocesses in the oasis. Then we evaluated the spatiotemporal NPP and ET dynamicsunder the impacts of oasis evolution in the Sangong river basin’s oasis and desertecosystem from 1971 to 2013 by the modified model. The results of this studyindicated that the oasis ecosystem and desert ecosystem have different responses tothe oasis evolution and climate change. During the whole study period, both the NPP and ET of oasis ecosystem present a downward trend while those of the desertecosystem present a slight upward trend and relatively stable, respectively. Thetemporal patterns of NPP and ET of the oasis ecosystem were controlled by the oasisevolution while that of desert ecosystem were controlled by climate change. Theclimate change played positive effects on both oasis and desert ecosystems whileoasis evolution played positive effects on total annual NPP and water consumption ofoasis ecosystem and negative effects on that of desert ecosystem. The total annualNPP and total water consumption of oasis ecosystem were dominated by the oasisevolution effect, which resulted in 169.4×109 g C carbon sequestration and 127×106m3 water consumption from the first stage to the third stage. Finally, the WUE of boththe oasis and desert ecosystem increased under the influence of oasis evolution andclimate change from 1971 to 2013.Finally, we explored the NPP and ET dynamics of the arid ecosystem in TianshanNorth Slope under RCP2.6, RCP4.5, and RCP8.5 by using AEM. The climate inTianshan North Slope will experience a wetter and warming trend from 2006 to 2055under each RCP scenario. In response to the changes in climate and CO2concentration, the regional mean annual NPP increases by a rate of 1.16, 1.62, and2.15 g C m−2 year−1 under RCP2.6, RCP4.5, and RCP8.5, respectively. Similar to theregional mean annual NPP, the regional annual ET presents an increasing trend withthe rate of 0.38 mm year−1 under RCP2.6, 0.43 mm year−1 under RCP4.5, and 0.52mm year−1 under RCP8.5. Hence, for the entire region, the Tianshan North Slope willbenefit from the changes from 2006–2055. The spatial patterns of regional annualNPP differences under different RCP scenarios show that the increase of NPP mainlyoccurs in the central and western parts where the CRP is abundant. The decline inregional annual NPP mainly occurs in the northeastern part under RCP2.6. The spatialpatterns of regional ET differences indicate that the increase of ET mainly occurs inthe central and western parts, which is similar to those of the NPP difference.However, the ET decreases in the high mountains, which is mainly caused by thedecline in temperature. The decline of ET in the northeast part is mainly induced bythe decline in precipitation under the RCP2.6 scenario. Different vegetation typesrespond differently to the changes in climate and CO2 concentration under differentRCP scenarios. All vegetation types in Tianshan North Slope experience increasedNPP and ET with various rates under each RCP scenario. Under each RCP, the NPS,PS, and GRS are more sensitive to the changes in climate and CO2 concentration compared to the other vegetation types, while those of the TBF and CRP are lesssensitive to the changes. The sensitivity of the different vegetation types varies duringdifferent study periods and under different RCP scenarios. However, the WUE of eachvegetation type shows an increasing trend under all RCP scenarios. For eachvegetation type, the increasing rate of WUE increases from RCP2.6 to RCP8.5,resulting from the warm and wet climate change and increasing CO2 concentration. |
| Subject Area | 地图学与地理信息系统 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/15404 |
| Collection | 中国科学院新疆生态与地理研究所 研究系统 |
| Affiliation | 中国科学院新疆生态与地理研究所 |
| First Author Affilication | 中国科学院新疆生态与地理研究所 |
| Recommended Citation GB/T 7714 | 蔡鹏. 天山北坡现代绿洲演变的气候与生态效应[D]. 北京. 中国科学院大学,2020. |
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