Knowledge Resource Center for Ecological Environment in Arid Area
| 全球变暖背景下青藏高原植被变化对中国降水影响的研究 | |
| 其他题名 | Influence of Vegetation Change over the Tibetan Platean on Precipitation of China under Global Warming |
| 张少波 | |
| 出版年 | 2015 |
| 学位类型 | 博士 |
| 导师 | 吕世华 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 全球变暖对全球范围内的植被变化产生了巨大影响，而在生态脆弱的高原地区，这一特征更为明显。最近几十年高原植被发生的剧烈变化，会对区域气候产生怎样的影响？21世纪高原植被的进一步变化又会对区域气候产生怎样的影响？这都是需要我们关注的关键问题，对于指导我们保护高原生态环境，应对全球变暖有积极的指导意义。基于此，本论文使用多种观测资料、CMIP5模式结果以及区域气候模式RegCM研究全球变暖背景下高原植被变化对我国降水的影响。在研究过程中，首先基于多元一次回归方法探讨了多个气象因素对降水的影响，之后在对区域气候模式RegCM的模拟性能进行评估后，设置高原植被改善的敏感性试验，研究高原植被变化对我国降水的影响，最后使用CMIP5的模式结果驱动RegCM模式，研究未来高原植被变化对我国降水的影响。通过研究，论文主要得到以下结论 （1）在21世纪，高原热力作用对降水的贡献会随着RCP情景的增加而增加。在全球变暖背景下，我国南方降水增加而北方的广大地区降水减少，使得我国的“南涝北旱”局势更为严重,各个分区的降水和叶面积指数均存在明显的升高趋势，且降水的变化特征较植被变化更为明显，但全球变暖也使得降水和叶面积指数波动更为剧烈，使得极端事件更容易发生。在21世纪中后期，高原热力作用对降水的贡献会随着RCP情景的增加而增加，但受模式中各种反馈机制的制约，其贡献在RCP4.5和RCP8.5的21世纪后期小于21世纪中期，但在RCP2.6高原热力作用对我国降水和我国东部将水的贡献则随时间增加。 （2）使用Tiedtke积云参数化方案的RegCM模式对于中国降水的空间分布及时间变化特征模拟具有一定优势。具体来讲，Kuo，Grell，Emanuel和Tiedtke均模拟出中国多年降水从东南向西北减少的分布特征，整体表现为江淮以南降水偏少，以北降水偏多。其中，Emanuel存在全国性的降水偏多，使得全国平均降水偏多87%，不同于其他方案的南方偏少而其他地区降水偏多。四个方案中，Tiedtke的降水偏差在各地普遍较小，能够更好地模拟出年降水空间分布特征。此外，各个方案均可模拟出中国降水的年内变化特征，其中Tiedtke方案对降水年内变化特征的模拟最为准确。而对于降水的年际变化特征，所有方案可以模拟出沿海的降水年际变化大于内陆的特征。Tiedtke方案模拟的东亚季风指数与再分析资料的偏差和均方根偏差最小，也表明该方案对东亚环流基本特征模拟最为准确，使得该方案的降水与观测结果偏差最小。 （3）高原植被变化后，高原感热通量和潜热通量的变化使得高原上空的温度场和位势高度场发生变化，通过影响高原上空南亚高压的位置和强度，进而对区域气候产生影响。理想试验结果表明，高原植被变化后，受对流层低层增强的水汽辐合和上升运动影响，长江流域降水增加0.25 mm day-1,而我国华南和黄河流域存在的异常水汽辐散和下沉运动也使得这些地区降水减少，且黄河流域降水减少更为明显，达到1mm day-1以上。半理想试验的结果与理想试验结果类似，高原植被改善后，高原地区感热通量和潜热通量的变化主要位于高原东部，高原热源的变化使得从高原到我国的东南沿海存在明显的降水增加区域。和理想试验相比，半理想试验降水变化的位置整体偏北，且降水的变化幅度小于理想试验。 （4）在21世纪，全球变暖会使得雨带北移，从而有利于北方的半干旱地区降水增多，高原的植被改善会使得长江流域降水增多而华南和黄河流域降水减少。和历史时期相比，RCP4.5情景下21世纪我国的新疆和内蒙等半干旱区域降水增加而长江流域降水减少，使得雨带北移。在RCP4.5情景下的21世纪中期，受高原植被改善影响，偏弱的夏季风使得我国东部存在东北向的异常水汽输送，从而减弱了对流层低层的水汽输送强度。受此影响，我国南方的广大地区出现了降水增加，长江中下游降水增加1 mm day-1以上，而黄河下游地区降水减少。21世纪后期与21世纪中期类似，长江流域的异常水汽辐合和偏强的上升运动也使得该地区降水增加明显，而华南和黄河流域的异常水汽辐散和异常的下沉运动也使得这些地区降水减少，部分地区降水减少1 mm day-1以上。 |
| 英文摘要 | Vegetation has been affected deeply by global warming on a global scale and this characteristic is more obvious in the Tibetan Plateau (TP), which is thought as an ecologically vulnerable area. What is the influence of vegetation change of the TP to the climate, and what may be the further influence if the changing continue in the coming 21 century? These issues should be concerned seriously, which is helpful to protect the environment of the TP and is consequential to research global warming. Based on this consideration, we have used several observation records, the models of CMIP5 and the Regional Climate Model (RegCM) to research the influence of vegetation change of the TP. During the research, we firstly discussed the influence of several meteorological factors to precipitation. Then, a performance evaluation of the RegCM was done using different cumulus parameter schemes (CPSs). By using a series of sensitivity test for the vegetation change of the TP, we researched the influence of vegetation change of the TP to the precipitation of China. Finally, the RegCM was driven by a model chosen from CMIP5 to study the further influence of vegetation change of the TP during the 21 century. From these research, we have got the following conclusions: (1) The contribution of the TP thermal action to the precipitation would be increased with the representative concentration pathways (RCP) changed from RCP2.6, RCP4.5 to RCP8.5 during the 21 century. Under global warming, the precipitation of Southern China increased while that of Northern China decreased, leading to a more serious precipitation pattern of “south flood north drought”. The trend of precipitation and leaf area index (LAI) for each area, especially the trend of precipitation, was increasing obviously. However, the deviation of precipitation and LAI also increased, meaning that extreme events would happen more frequently under global warming. Multi-model results from CMIP5 showed that the percentage of contribution of the TP thermal action would increased with the RCP scenario from RCP2.5, RCP4.5 to RCP8.5. However, the contribution percentage decreased in the later period of 21 century under RCP4.5 and RCP8.5 when compared with that in the middle period of 21 century, the reason could be summarized as the feedback of climate system. (2) When using the Tiedtke CPS, the RegCM showed a better representation of the pattern and time variation of the precipitation in China. In detail, the annual precipitation distribution of China, decreasing from Southeastern to Northwestern was well simulated by all the CPSs. However, the Emanuel scheme produced an overestimate of annual precipitation, with a bias ratio of 87%, while the other three CPSs had only overestimated the annual precipitation over northern and northwestern China but underestimated it over southern China. Among the four CPSs, the Tiedtke scheme exhibited the smallest overestimate of precipitation in winter and summer, indicating its advantage in simulating precipitation over China. All the CPSs were able to better simulate seasonal than interannual variance of precipitation. The Tiedtke scheme produced the best seasonal variation in precipitation. For interannual variance, all the CPSs captured the larger interannual variation of precipitation along the southeastern coastal areas of China where abundant precipitation occurs than in inland areas. The Tiedtke scheme produced the smallest bias in the strength of EASMI, suggesting that it may better simulate the atmosphere circulation and hence lead to a better precipitation result. (3) When the TP vegetation changed better, the changes of sensible heat flux and latent heat flux would lead to a broader change of temperature and geopotential height above the TP. By affecting the position and strength of the South Asia High (SAH), the vegetation change of TP would have a deep influence on the regional climate. The results of ideal experiments showed that, when vegetation of the TP changed better, the precipitation of Yangtze river basin increased 0.25 mm day-1 because of the abnormally strong water vapour convergence and ascending motion. However, the precipitation of South China and Yellow river basin decreased, especially the Yellow river basin, because of the abnormally strong water vapour divergence and sinking motion. The half ideal experiments showed the similar results with the ideal experiments. When vegetation of the TP changed better, the changes of sensible heat flux and latent heat flux mainly appeared in the east part of TP and there was a broad area with precipitation increasing from the TP to East China. Compared with the results of the ideal experiments, those of the half ideal experiments showed a more north pattern with smaller precipitation change. (4) The rain band was likely to move north in the 21 century under global warming, leading to more precipitation in the semiarid area of China. When the vegetation of TP changed in the 21 century, the precipitation of Yangtze river basin increased while those of South China and Yellow river basin decreased. Compared with the historical simulation results, the precipitation of the semiarid area, such as Sinkiang and Inner Mongolia, increased while that of Yangtze river basin decreased, meaning that the rain band was likely to move north in the 21 century under RCP4.5. Under the middle period of 21 century in RCP4.5, when vegetation of the TP changed better, the abnormally northeast water vapour transport would decrease the strength of water vapour transport of the lower troposphere. The precipitation of south China, especially the Yangtze river basin, increased while that of Yellow river basin decreased. Under the latter period of 21 century in RCP4.5, the change of precipitation showed similar pattern with that of the the middle period of 21 century. The precipitation of Yangtze river basin increased because of the abnormally strong water vapour convergence and ascending motion while the precipitation of South China and Yellow river basin decreased because of the abnormally strong water vapour divergence and sinking motion. |
| 中文关键词 | 青藏高原 ; 植被变化 ; 降水 ; 全球变暖 ; RegCM |
| 英文关键词 | Tibetan Plateau vegetation change precipitation global warming RegCM |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 大气物理学与大气环境 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287553 |
| 推荐引用方式 GB/T 7714 | 张少波. 全球变暖背景下青藏高原植被变化对中国降水影响的研究[D]. 中国科学院大学,2015. |
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