Complex network analysis of climate change in the Tarim River Basin, Northwest China

The complex network theory provides an approach for understanding the complexity of climate change from a new perspective.In this study,we used the coarse graining process to convert the data series of daily mean temperature and daily precipitation from 1961 to 2011 into symbol sequences consisting of five characteristic symbols(i.e.,R,r,e,d and D),and created the temperature fluctuation network(TFN)and precipitation fluctuation network(PFN)to discover the complex network characteristics of climate change in the Tarim River Basin of Northwest China.The results show that TFN and PEN both present characteristics of scale-free network and small-world network with short average path length and high clustering coefficient.The nodes with high degree in TFN are RRR,d RR and Re R while the nodes with high degree in PFN are rre,rrr,eee and err,which indicates that climate change modes represented by these nodes have large probability of occurrence.Symbol R and r are mostly included in the important nodes of TFN and PFN,which indicate that the fluctuating variation in temperature and precipitation in the Tarim River Basin mainly are rising over the past 50 years.The nodes RRR,DDD,Re R,RRd,DDd and Ree are the hub nodes in TFN,which undertake 19.71%betweenness centrality of the network.The nodes rre,rrr,eee and err are the hub nodes in PFN,which undertake 13.64%betweenness centrality of the network.

Climate change regionalization in China(1961–2010)

Since climatic condition is the important foundation for human subsistence and development and the key factor in sustainable development of economy and society, climate change has been a global issue attracting great attentions of politicians, scientists, governments, and the public alike throughout the world. Existing climate regionalization in China aims to characterize the regional differences in climate based on years of the mean value of different climate indexes. However, with the accelerating climate change nowadays, existing climate regionalization cannot represent the regional difference of climate change, nor can it reflect the disasters and environmental risks incurred from climate changes. This paper utilizes the tendency value and fluctuation value of temperature and precipitation from 1961 to 2010 to identify the climate change quantitatively, and completes the climate change regionalization in China(1961–2010) with county administrative regionalization as the unit in combination with China's terrain feature. Level-I regionalization divides China's climate change(1961–2010) into five tendency zones based on the tendency of temperature and precipitation, which are respectively Northeast China-North China warm-dry trend zone, East China-Central China wet-warm trend zone, Southwest China-South China dry-warm trend zone, Southeast Tibet-Southwest China wet-warm trend zone, and Northwest China-Qinghai-Tibet Plateau warm-wet trend zone; level-II regionalization refers to fourteen fluctuation regions based on level-I regionalization according to the fluctuation of temperature and precipitation.

World Regionalization of Climate Change(1961–2010)

Traditional climate classification or regionalization characterizes the mean state of climate condition, which cannot meet the demand of addressing climate change currently. We have developed a climate change classification method, as well as the fundamental principles, an indicator system, and mapping techniques of climate change regionalization. This study used annual mean temperature and total precipitation as climatic indices, and linear trend and variation change as change indices to characterize climate change quantitatively. The study has proposed a scheme for world climate change regionalization based on a half century of climate data(1961–2010). Level-I regionalization divides the world into 12 tendency zones based on the linear trend of climate, level-II regionalization resulted in 28 fluctuation regions based on the variation change of climate. Climate change regionalization provides a scientific basis for countries and regions to develop plans for adapting to climate change, especially for managing climate-related disaster or environmental risks.

Recent Climate Trends on the Northern Slopes of the Tianshan Mountains, Xinjiang, China

In arid regions, mountains fulfill important ecological and economic functions for the surrounding lowlands. In the scenario of global warming, mountain ecosystems change rapidly, especially in the arid region of northwestern China. This paper provides an assessment of the changes in temperature and precipitation in the historical records of climate on the northern slopes of the eastern Tianshan Mountains. A Mann-Kendall nonparametric trend and Sen's tests are employed to analyze the interannual changes and innerannual variability in temperature and precipitation in the regions of low to high altitude. The present study finds that the largest increases in annual temperature are observed at stations in the low altitude regions. The significant increasing trends in temperature tend to occur mainly in late winter and early spring at stations from middle to high altitude, but in summer and autumn at stations of low altitudes. The increasing trends in annual precipitation are found from the middle to high altitude areas, but decreasing trends are found in the low altitude areas. The significant increasing trends in precipitation occur mostly in winter and earlier spring at stations from the middle to high altitudes, while the increasing and decreasing trend coexists at stations of low altitude with most of the significant trend changes occurring in March, June and August.

近50年来西北半干旱区气候变化特征

选用西北半干旱区33个气象站1951-2004年温度、降水、相对湿度、风速、蒸发量等气象观测资料,分析主要气候要素变化规律,揭示了近50年来西北半干旱区气候变化的一些新特征。结果表明,西北半干旱区降水量近50年来年际变化趋势除个别地方外绝大多数地区呈下降趋势,降水量变化曲线线性拟合倾向率在-59.168～-1.143 mm/10 a之间,秋季降水量减少最多,春季次之,而夏季部分地区和冬季大部分地区降水量呈略增趋势。降水量存在3年、6～8年的周期振荡特征,3年周期振荡在1962-1966年为中心的局部时段内最强,之后逐渐减弱。6～8年振荡在1980-1985年为中心的局部时段内最强。气温距平呈上升趋势,气温距平变化曲线线性拟合倾向率在0.074～0.507℃/10 a之间,大部分地区呈先降后升型,转型时间为20世纪60年代后期至70年代前期。冬季气温增高最多,秋季、春季次之,夏季陕、甘、宁交界区及陇中地区气温增高而其余地区气温距平略呈下降趋势。相对湿度近50年来年呈波动变化。平均风速近50年来年际变化趋势除个别地方略增外,其余各地均呈下降趋势。蒸发量近50年来年际变化趋势除个别地方呈上升趋势外,其余各地蒸发量呈下降趋势。

西北干旱区近50年气候变化特征与趋势

20世纪后期全球增暖趋势越来越明显,受全球增暖的影响,西北地区的气候也将受到不同程度的影响。选取了西北干旱区1951～2000年的21个代表站点气温、降水量资料,采用趋势系数法对西北干旱区近50年气温和降水变化进行分析,找出各分区的变化趋势。结果表明:近50年西北干旱区气温呈上升趋势(0.22℃/10 a),1986年后气温明显升高;柴达木盆地和新疆北部升温较大;各季都有增温趋势,贡献最大的是秋冬两季。降水变化有增加的趋势(3.2 mm/10 a),年降水量贡献最大的是夏季;各区降水都有增加,其中新疆北部降水增加最多。西北干旱区近50年气温升高趋势是南北高,中间低;降水量增加趋势从东南向西北呈现递增的格局。

中国北方中部地区近五十年气温和降水的变化趋势

基于中国北方中部地区150个气象站点的气象数据,对该地区近50年来气温和降水量的倾向率及其空间分布运用线性趋势分析和空间插值等方法进行分析.结果表明：该地区气温在近50年呈现出整体上升趋势,且2月份的升温最为显著;气温变化趋势的分布格局上,东南部升温速率较西北部低;平均最低气温上升趋势明显,对气温升高的贡献率较大;降水量呈下降趋势,下降区域主要集中在35~40°N之间,且主要与7、8月份降水量减少有关.

全球气候变化背景下中国敏感区区域响应比较

近50年来全球气候变化研究已经是当今自然科学重大课题之一,中国的区域响应也日渐引人关注。依据黑龙江、新疆、西藏三省区93个国家基准或基本气象站1961—2008年间的日气温和降水数据,就中国气候变化敏感区气温和降水变化过程和特征进行对比分析。①气温变化方面,三省区均呈明显升温趋势,研究时段内黑龙江、新疆、西藏增温幅度分别为1.71℃,1.20℃,1.15℃,且都通过了α=0.01的统计检验;②不同季节增温幅度上,黑龙江省以冬春增幅最大,而新疆和西藏则均以秋冬两季增温最强;③降水量变化方面,黑龙江年降水量有所减少,新疆和西藏则有所增多,但趋势都不十分明朗;④黑龙江年降水量的减少主要体现在夏秋两季,特别是夏季;⑤无论年降水总量还是不同季节降水量的年际波动量值均以新疆和黑龙江明显、西藏相对平稳为特征。

西北极端干旱区近54年降水量和温度变化趋势

利用西北极端干旱区32个气象站点1960—2013年的月均气温和降水资料,采用线性倾向率法、累积距平法和Mann-Kendall法,研究西北极端干旱区近54年降水量和温度的变化趋势。结果表明:1)54年来,西北极端干旱区平均气温9.3℃,30站表现为显著上升趋势,上升倾向率达到0.034℃/a(P<0.01),且冬季和春季增温幅度大于夏季和秋季,在空间上,西部塔里木盆地为高值区,东南部为低值区;2)西北极端干旱区平均年降水量55.35 mm,29站表现为增加趋势,其中11站通过了0.01水平的显著性检验,倾向率为0.346 mm/a(P<0.01),夏季增加幅度最大,春季最小,在空间上,西北部和东部为高值区、南部为低值区。研究结果表明,近54年西北极端干旱区总体气候呈现明显的暖湿化趋势。

黄河三角洲近四十年的气候变化特征

采用了惠民、滨洲和垦利三站平均的1957—1996年冬季平均气温（T）、春季平均风速（V）和夏季降水量（R），表征黄河三角洲的气候变化状态。分析结果显示，近40年来，该地区的气候变化具有以下特征；（1）长期变化趋势为，冬季T呈明显的增高；春季V则呈明显的减小；夏季R变化趋势不显著。（2）冬季T、春季V和夏季R变化存在着转折和跃变。跃变年份是1986年（T）和1975年（V）；转折年份是1972年（T）和1978年、1989年（R）。（3）冬季T、春季V和夏季R都存在着3．6—4．5年周期；此外，后两者还分别存在着约18年和6年周期。