1.南京信息工程大学地理科学学院;2.海南省气象局 南海气象防灾减灾重点实验室/海南省气象台;3.南京信息工程大学 气象灾害教育部重点实验室/气象灾害预报预警与评估协同创新中心
广东珠江人才团队计划项目(2019ZT08G669), 国家自然科学基金资助项目(41875027 和4166144039)；江苏省2013年度普通高校研究生科研创新计划项目(省助)（CXZZ13_0524）
1.Nanjing University of Information Science &2.Technology;3.Hainan Meteorological Bureau, Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province;4.Key Laboratory of Meteorological Disaster, Ministry of Education (KLME), and Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology
Guangdong Pearl River Talents Team Project (2019ZT08G669); Projects funded by the National Natural Science Foundation of China (41875027 and 4166144039); Jiangsu Province 2013 Postgraduate Research and Innovation Program for Ordinary Universities (Provincial Grant) (CXZZ13_0524).
摘要：本文利用青海地区1982-2016年的归一化植被指数(NDVI)和气象数据，依据基于马尔科夫链蒙特卡罗（MCMC）的copula 函数理论，分析生长季时段内不同季节昼夜增温的不对称变化对植被活动的影响。主要结论为：(1)近35年来青海地区生长季内季节性昼夜增温趋势显著；昼夜增温速率具有不对称性，春季白天的增温速率快于夜间，夏、秋季则呈现相反规律。昼夜温差呈现出季节性差异，春、夏、秋三季的昼夜温差波动很大。春季的昼夜温差呈上升趋势，而夏季和秋季的昼夜温差则表现为相反的变化规律。(2) 青海三个季节昼夜增温对植被的影响在季节性上呈现出明显差异，昼夜增温在整体上对青海地区植被影响程度较强，尤其是秋季昼夜增温对NDVI影响最大，夏季次之，春季最小。昼夜增温对青海地区植被影响程度存在差异，白天增温影响强于夜间。(3)青海三个季节的昼夜增温与NDVI的联合概率分布函数均呈现：当昼夜增温一定，NDVI越大时，或者当NDVI一定，昼夜增温越大时，其联合概率越大，说明昼夜增温取极小值时对NDVI影响较小；昼夜增温取极大值时对NDVI的影响明显。（4）重现期越小，昼夜增温与NDVI的取值范围越大，这说明当昼夜增温一定时，NDVI 出现较小重现期的可能性更多。昼夜增温越大，则重现期越大，表明昼夜增温超过一定的阈值，植物生长受抑制现象出现的概率更大。本研究有助于加深对全球气候变化背景下季节性昼夜不对称增温对青海高寒区植被动态影响的认识，从而更好地解释了高原陆地生态系统对全球气候变化的响应和反馈。
Abstract: In this dissertation, the author adopted the normalized differential vegetation index (NDVI) and meteorological data sets of 1982-2016 from Qinghai province, China to analyze the effects of daytime and nighttime warming asymmetric changes in spring, summer and autumn on vegetation activities during the growing season period according to the copula function theory based on Markov Chain Monte Carlo (MCMC). The main conclusions were as follows: (1) in the past 35 years, the seasonal daytime and nighttime warming trend of Qinghai plateau was remarkable in the growing season. The rate of daytime and nighttime warming was asymmetric. In spring, the warming rate in the daytime was faster than that at nighttime. However, in summer and autumn, the warming rate at nighttime was greater than that in the daytime. The diurnal temperature difference shows seasonal differences, with large fluctuations in spring, summer and autumn. The diurnal temperature difference presents an upward trend in spring, while it displays the opposite rule in summer and autumn. (2) The asymmetry of daytime and nighttime warming had great influence on vegetation, showing a seasonal difference. And the diurnal and nocturnal warming had the greatest influence on vegetation in autumn, followed by summer and the smallest in spring. The influence of daytime warming on vegetation was stronger than that of nighttime warming. (3) The joint probability distribution functions of daytime and nighttime warming and NDVI on the three seasons of plateau showed certain laws. If the daytime and nighttime warming was constant, then the greater the NDVI, the greater the joint probability would be; or if the NDVI was fixed, the greater the daytime and nighttime warming, the greater the joint probability would be. These phenomena indicated that the daytime and nighttime warming would have little effect on NDVI when they reached their minimum values. However, when the daytime and nighttime warming reached their maximum values, they would have remarkable effect on NDVI. (4) The smaller the return period was, the larger the value range of the diurnal and nocturnal warming and the NDVI were. This phenomenon indicated that the NDVI would be more likely to have a smaller return period when the diurnal and nocturnal warming was constant. The larger the diurnal and nocturnal warming, the greater the return period was, which indicated that the inhibition phenomenon of plant growth would have a higher probability to happen when the diurnal and nocturnal warming exceeded a certain threshold. This research can be helpful to deeply understanding the effects of daytime and nighttime warming asymmetry on the vegetation dynamics in typical plateau climatic region under the background of global climate change, thus better explaining the response and feedback of plateau terrestrial ecosystems to global climate change.
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