近30年来内蒙古地区气候干湿状况时空分布特征

根据内蒙古115个气象站1971～2000年气象资料,采用改进的Selianinov干燥度计算公式,研究了内蒙古地区气候干湿状况时空变化。结果表明:内蒙古干燥度空间分布具有明显地带性分布规律,即从西向东随经度增加干燥度逐渐变小,气候变得湿润。从年际变化的空间分布可以看出,30年来内蒙古地区气候变化大致分为两种类型:1)干湿交替型,位于西部的典型荒漠区和东北部的大兴安岭森林区。2)持续变干型,内蒙古中东北地区的半湿润区和半干旱区的分界线,30年来持续向东南方向推进,使得半湿润区面积缩小,半干旱区面积增加。从年际变化的时间分布来看,70年代,年平均干燥度呈现波动式下降,气候变化趋于湿润化;80年代,气候经历了先干后湿又干的变化过程,干燥度波动较大;90年代,气候经历了先湿润后急剧变干的变化过程,其中1995～2000年干燥度增幅为30年最快的时段。在六大生态类型分区中,典型荒漠区干燥度变化最为剧烈,且对内蒙古全区干燥度的贡献率最大,大兴安岭林区和草甸草原区的干燥度变化最小。从气候干湿状况的年代际变化可以看出,80年代是内蒙古全区气候干旱比较严重的年代。     

山西省近50年地表干燥度变化趋势分析

利用山西省39个气象站1960—2010年的气象资料,结合地形特征,将山西省分为6个气候敏感区,采用潜在蒸散量和降水量的比值来计算干燥度指数,在此基础上使用IDW插值法生成山西省干燥度的分布图,并分析了近50 a山西省地表干燥度变化趋势。研究结果显示：（1）山西省多年平均干燥度指数为2．21,属于半干旱区;干燥度空间分布与气候、地形等因素密切相关,南北差异显著。整体上山西省中北部地区较为干旱,干燥度指数为2．36,东部南部则较为湿润,干燥度指数为1．93;由于降水和蒸散都呈下降趋势,因此,近50 a山西省干燥度指数虽有所上升,但变化幅度仅为0．04·10a－1,干旱化趋势并不显著;（2）近50 a来,除山西省北部地区干旱状况有所缓解外,其它地区干旱状况均呈增加趋势;（3）干燥度季节性差异显著,冬春干燥异常,夏秋则较为湿润。总体而言,气候变暖虽未加剧山西省的干燥程度,但暖干化趋势应引起足够的重视。     

近40a中国北方降水量与蒸发量变化

利用我国北方1951-1990年年降水量、年蒸发量、年平均风速和太阳辐射等资料,计算了干燥度指数,并据其将我国划分为干旱区(D<0.20),半干旱区(0.20～0.50),湿润区(D>0.50)。近40a我国半干旱区降水量和蒸发量发生了巨大变化,区域差异显著,年代际特征明显。东北区和华北区降水量具有减少趋势,西北东部和西南区有增加趋势。至于蒸发量的变化,东北区具有增加趋势,华北区、西北东部和西南区有减少趋势。近40a我国干旱半干旱区降水量与蒸发量均在减小,但降水量的减小速度大于蒸发量,气候在变干。我国气候的干湿变化主要取决于降水量的变化。     

21世纪中蒙干旱-半干旱地区干旱化趋势的模拟研究

利用区域气候模式RegCM3与公用气候系统模式CCSM3单向嵌套技术,进行未来不同情景下（高排放SRES A2、中等排放SRES A1B和低排放SRES B1）高分辨率数值试验,分析21世纪中国和蒙古国干旱-半干旱地区干旱化特征及其可能发展趋势。结果表明：不同排放情景下,未来中蒙干旱-半干旱地区降水量均呈增加趋势,地表温度也持续增加。仅从降水变化来看,未来干旱-半干旱地区干旱化程度变化不大,甚至有所减弱。但综合考虑降水和温度计算的Palmer干旱指数（PDSI）来看,研究区内干旱地区面积均持续扩张。极端、严重及中等干旱面积比例扩张趋势明显,达到95%显著性水平。相对21世纪中期、后期极端干旱面积在3种情景下均将扩张3%以上。相对21世纪中期和当代,21世纪后期A2情景下总的干旱面积分别将增加8%和11.51%,A1B情景下12.48%和18.34%,B1情景下9.73%和10.82%。对比降水与PDSI可见,在进行干旱-半干旱区气候变化预估研究中,必须综合考虑降水和温度的变化,才能更准确地反映干旱-半干旱地区干旱化特征及其干旱化趋势。     

中国20世纪干旱化趋势分析

采用东安格利亚大学气候研究中心的时间序列2.0气象数据集,利用Holdridge可能蒸散率干燥度计算方法,分析20世纪我国干燥度的动态变化。用GIS软件对其结果进行插值计算,并做出干燥度分布的数字化地图。分析结果表明：20世纪我国的湿润气候区面积减少严重,半湿润气候区面积有较大增加,干旱气候区面积增加也较显著,干旱化趋势明显。温度升高和降水量的减少导致了地表水分收支减小,不利于陆地表面的水分累积,是产生和加剧干旱的一个重要因素。     

西北干旱区大气水分循环要素变化研究进展

西北干旱区是对全球气候变化响应最敏感的地区之一。全球变暖加剧水循环,引起大气水分循环要素发生明显变化。借助最新资料对过去50 a西北干旱区大气水分循环要素变化特征和相关科学问题进行了梳理总结,其主要结论:(1)西北干旱区水汽和降水量有一致性变化趋势,在20世纪80年代中后期突变型增多,21世纪初有微弱的减小态势。受季风强度减弱的影响,西北东部地区水汽和降水量减小明显。(2)降水量增加站点占到95.9%,形成了天山、祁连山等增湿中心,具有明显的增湿海拔依赖性特征。(3)实际蒸散发量呈微弱的减小趋势,天山山区明显减少,而祁连山地区明显增加。(4)干旱区西部夏季降水以西风带水汽输送为主,但大尺度大降水过程发生时,低纬水汽输送尤为重要。全球气候变暖在影响着大气水分循环要素明显变化的同时,也加剧了干旱区水循环过程和水资源的不确定性。     

内蒙古中部地区近40年来降水时空变化

内蒙古中部呼和浩特市、包头市、乌兰察布市、鄂尔多斯市、巴彦淖尔市和乌海市是半干旱区向干旱区的生态地理过渡地带。利用该区45个气象站点1961-2003年逐日降水数据,借助小波分析、地统计学分析研究了该区43年来降水量的时空变化特征。结果表明:研究区降水量年际波动大,总体呈现略微增加的趋势;降水量变化的周期性比较明显,存在3～4年、6～7年和14～15年尺度的周期。降水年内分配呈现单峰型模式。在空间上,多年平均降水量呈现由东南向西北逐渐递减的趋势,年降水变化的趋势和波动性区域差异显著。另外发现,作为重要地理分界线的200mm等降水量线空间分布在43年中处于波动之中,对草原和荒漠生态系统产生了直接影响。对该区降水时空变化的探讨,有助于理解水资源的时空分异,同时为全球变化的区域响应提供科学依据。     

我国北方半干旱区草地水分供需状况研究

利用半干旱区181个站点40a的气象资料,依据伊万诺夫湿润系数对半干旱区草地进行气候分区,采用计算精度较高的FAO Penman-Monteith方法(1998)计算可能蒸散。在计算不同草地类型草地蒸散系数的基础上,计算半干旱区草地实际蒸散量,通过水分盈亏和水分订正系数等来分析评价不同草地类型的水分供需状况。结果表明:不同草地类型的蒸散系数也不同,草甸草原的蒸散系数最大,荒漠的蒸散系数最小;不同草地类型的实际需水量也不同:草甸草原>典型草原>荒漠化草原>草原化荒漠>荒漠;在半干旱地区实施退耕还草有利于水资源的可持续利用和生态环境的改善。     

海河流域1961～2010年干旱化特征及其变化趋势分析

利用1961～2010年海河流域内及其周边51个站的降水、气温、相对湿度、风速、日照时数等气候因子日数据,采用相对湿润度指数方法揭示了流域50年不同等级干旱的时空演变规律,并剖析干旱与气候变化的关系;再利用小波分析法研究流域相对湿润度指数距平的周期变化规律,预测海河流域未来的干旱化趋势。结果表明:时间上,流域轻旱频率最高,年代际变化上总体趋向干旱化;空间上,东北部为轻旱频发区;西北部的中旱频率较高;重旱主要集中于张家口、忻州、邢台等周边地区;流域降水量和蒸发量的年代/年代际变化呈双降趋势,且后者减小速率相对较小,区域整体干旱化有减弱趋势。流域相对湿润度指数距平的时间序列存在10年尺度的显著变化周期,预计到2017年间海河流域总体仍处于干旱化阶段。     

1961—2010年青藏高原—黄土高原过渡区可能蒸散率的变化特征

利用位于青藏高原—黄土高原过渡区内18个气象站1961—2010年的月平均气温、月降水量等地面气象观测资料，采用Holdridge可能蒸散率(PER)计算方法，对区域内近50a（1961—2010年）地表干燥度的变化趋势进行了分析。发现在区域内存在极湿润区、湿润区、亚湿润区和半干旱区四个不同的气候区，PER在空间分布上有明显的自南向北逐渐上升的特点。区域内极湿润区、湿润区、亚湿润区和半干旱区PER的年际变化趋势分别为0.01·10a^-1、0.04·10a^-1、0.06·10a^-1和-0.02·10a^-1，从20世纪80～90年代开始，在湿润区、亚湿润区大部分地方出现了明显的暖干化趋势，而在半干旱区有暖湿化的趋势。区域东部PER升高的主要原因是由于降水量的减少和气温上升，区域西部在降水量增加的情况下，PER仍出现上升的趋势，其主要原因是由于气温上升导致蒸散量增加，且蒸散量增加的幅度超过了降水量增加的幅度；而处于半干旱区的青海省循化县，由于可能蒸散量的上升趋势和降水量的增加趋势非常接近，故其变化最小，有暖湿化的趋势。暖干化已经对青藏高原—黄土高原过渡区内的生态环境、水资源和农牧业生产造成了严重影响。     

Spatial and temporal variability in vegetation cover of Mongolia and its implications

In this paper, we attempted to determine the most stable or unstable regions of vegetation cover in Mongolia and their spatio-temporal dynamics using Terra/MODIS Normalized Difference Vegetation Index(NDVI) dataset, which had a 250-m spatial resolution and comprised 6 periods of 16-day composited temporal resolution data(from 10 June to 13 September) for summer seasons from 2000 to 2012. We also used precipitation data as well as biomass data from 12 meteorological stations located in 4 largest natural zones of Mongolia. Our study showed that taiga and forest steppe zones had relatively stable vegetation cover because of forest characteristics and relatively high precipitation. The highest coefficient of variation(CV) of vegetation cover occurred frequently in the steppe and desert steppe zones, mainly depending on variation of precipitation. Our results showed that spatial and temporal variability in vegetation cover(NDVI or plant biomass) of Mongolia was highly dependent on the amount, distribution and CV of precipitation. This suggests that the lowest inter-annual CV of NDVI can occur during wet periods of growing season or in high precipitation regions, while the highest inter-annual CV of NDVI can occur during dry periods and in low precipitation regions. Although the desert zone received less precipitation than other natural zones of the country, it had relatively low variation compared to the steppe and desert steppe, which could be attributed to the very sparse vegetation in the desert.     

Effects of climate change on phenology and primary productivity in the desert steppe of Inner Mongolia

 Variations in temperature and precipitation affect local ecosystems. Considerable spatial and temporal heterogeneity exists in arid ecosystems such as desert steppes. We analyzed the spatiotemporal dynamics of climate and vegetation phenology in the desert steppe of Inner Mongolia, China, using meteorological data from 11 stations (1961–2010) and phenology data from 6 ecological stations (2004–2012). We also estimated the gross primary production for the period of 1982–2009 and found that the annual mean temperature increased at a rate of 0.47ºC/decade during 1961–2010, with the last 10 years being consistently warmer than the 50-year mean. The most significant warming occurred in winters. Annual precipitation slightly decreased during the 50-year period, with summer precipitation experiencing the highest drop in the last 10 years, and spring precipitation, a rise. Spatially, annual precipitation increased significantly in the northeast and eastern central area of the region next to the typical steppe. From 2004 to 2012, vegetation green-up and senescence date advanced in the area, shortening the growing season. Consequently, the primary productivity of the desert steppe decreased along precipitation gradient from southeast to northwest. Temporally, productivity increased during the period of 1982–1999 and significantly decreased after 2000. Overall, the last decade witnessed the most dramatic climatic changes that were likely to negatively affect the desert steppe ecosystem. The decreased primary productivity, in particular, decreases ecosystem resilience and impairs the livelihood of local farmers and herdsmen.     

近40 a内蒙古正蓝旗气候变化特征

气候变化特征对于当地适应气候变化政策及制定相应的管理对策具有重要意义,利用内蒙古锡林郭勒盟正蓝旗1970-2009年气温和降水资料,结合回归分析对该旗气候变化的主要特征进行了分析。结果表明：内蒙古正蓝旗气温呈明显的上升趋势,变化倾向率为0.57 ℃·（10a)^-1,40 a平均气温为2.26 ℃,其中21世纪初前10 a上升幅度最大,其年代平均气温攀升至峰值,达到3.07 ℃;降水量也呈上升趋势,其变化倾向率为4.85 mm·（10a）^-1,40 a平均降水量为352.31 mm,其中20世纪90年代降水量最高,达到398.74 mm,而21世纪初前10 a降水量迅速下降,成为近40 a降水量最低点,低于多年平均降水量19.62 mm。总体而言,正蓝旗20世纪70年代趋于相对干冷,80年代则由相对干冷向暖湿发展的过渡期,而90年代正蓝旗呈相对明显的暖湿化趋势,21世纪前10 a降水量减少和气温继续升高,出现暖干化趋势。     

Distribution pattern of Caragana species under the influence of climate gradient in the Inner Mongolia region,China

There is a strong climate gradient in the Inner Mongolia region, China, with solar radiation and air temperature increasing but precipitation decreasing gradually from the northeast to the southwest. Sixteen Cara- gana species exist in the Inner Mongolia region. These Caragana species exhibit a distribution pattern across moisture zones and form a geographical replacement series. In order to examine the mechanisms responsible for Caragana species distribution pattern, we selected 12 Caragana species that exhibit a distinct distribution pattern across multiple moisture zones in the Inner Mongolia region, and determined the relationships between the leaf ecological and physiological traits of these Caragana species and the aridity index and solar radiation. Along with the climatic drought gradient and the solar radiation intensification from the northeast to the southwest, leaf eco- logical characteristics of Caragana species changed drastically, i.e. the leaf shape gradually turned from flat into tegular or tubbish; the leaf hair became denser, longer and lighter in color; the leaf area, leaf biomass and specific leaf area(SLA) decreased significantly; the leaf thickness and the ratio of leaf thickness to leaf area increased sig- nificantly; and the leaf chlorophyll content decreased significantly. As the climatic drought stress increased, osmotic potentials of the main osmotic adjustment substances and the cytoplasmic ion concentration of Caragana species increased significantly. Meanwhile, the total and free water contents and water potential of leaves decreased sig- nificantly; the ratio of bound to free water increased significantly; the stomatal conductance and transpiration rate reduced significantly; and the water use efficiency(WUE) increased significantly. In addition, with the intensification of climatic drought stress, peroxidase(POD) and superoxide dismutase(SOD) activities in leaves increased sig- nificantly. As a result, the malondialdehyde(MDA) content increased while the oxygen free radical content decreased. Our results showed that most of the leaf ecological and physiological traits of the 12 Caragana species varied in ac- cordance with the climatic drought gradient in the Inner Mongolia region, which reflected the adaptation of the Cara- gana species to the local climate conditions. With relatively more active metabolism and faster growth, the Caragana species in the northeast had strong competitive abilities; on the other hand, with stronger resistance to climatic drought stress, the Caragana species in the southwest could survive in harsh environments. Based on our results, we con- cluded that both the environmental gradients and the adaptive responses of Caragana species to their environments played important roles in the formation of the Caragana species distribution pattern across the Inner Mongolia region.     

近60 a来内蒙古极端降水时空变化及其影响

基于内蒙古地区41个气象站点1958-2017年的逐日降水数据,采用世界气象组织等推荐的9个极端降水指数,运用线性趋势分析、克里金插值法、Mann-Kendall检验、Morlet小波分析和主成分分析等方法研究了内蒙古地区近60a来极端降水时空变化、周期规律和气象灾害效应。结果表明:内蒙古地区近60a来出现了干燥化趋势,即伴随着降水量的减少,各极端降水指数出现不同程度的下降趋势,以20世纪60年代和21世纪初下降最为明显。各极端降水指数倾向率在空间上大体呈现出从东西部向中部递减的规律,大都以集宁、呼和浩特、通辽和新巴尔虎右旗为低值中心。各极端降水指数的最大概率突变年为1995年,此后出现了不显著下降的趋势。各极端降水指数均存在3~5 a、14~17 a、20 a左右的周期变化。除连续无雨日数外,各极端降水指数与年降水量之间均存在较好的相关性。内蒙古极端降水变化导致该区旱灾与风灾增多加重,草原沙漠化加强,洪灾与低温冻害减少减轻,应有针对性地采取措施加强旱灾与风灾预防。     

西北干旱灾害及其气候趋势研究

利用西北五省1950～2000年降水、温度和农作物旱灾面积资料,用降水的Z指标法,农作物受旱成灾率确定了西北干旱指标和旱灾等级,分析了西北旱灾特征及气候变化趋势。表明西北农业旱灾以70、90年代最严重,而且呈增加趋势,气温在升高,降水在减少。根据预测21世纪前十年西北干旱有所减轻。     

Effects of grazing intensity on seed production of Caragana stenophylla along a climatic aridity gradient in the Inner Mongolia Steppe,China

As the increases of climatic aridity and grazing intensity,shrubs play an increasingly important role in grassland ecosystem in arid and semi-arid regions,and its abundance also generally increases.However,the effects of climatic aridity and grazing intensity on sexual reproduction of shrubs in grassland remain largely unclear.In order to understand the effects of grazing intensity and climatic drought stress,and their interaction on seed production of shrub species,we examined the seed number,seed weight and seed yield of Caragana stenophylla under three grazing intensities(fenced,mild grazing and severe grazing) across a climatic aridity gradient(semi-arid,arid,very arid and intensively arid zones) in the Inner Mongolia Steppe,northern China during 2012–2013.The seed number,seed weight and seed yield gradually increased from the semi-arid to the very arid zones,but decreased from the very arid to the intensively arid zones in fenced plots.The seed number and seed yield decreased from the semi-arid to the intensively arid zones in mild and severe grazing treatment plots,therefore,grazing enhanced the suppression effect of climatic aridity on seed production of C.stenophylla.The seed number and seed yield gradually decreased as grazing intensity increased.The seed weight was highest in severe grazing plots,followed by the mild grazing plots and then the fenced plots.Precipitation varied interannually during the study period.We observed that the seed number,seed weight and seed yield were lower in the low precipitation year(2013) than in the high precipitation year(2012).As climatic drought stress increased,the negative effects of grazing on seed production of C.stenophylla also gradually increased.Our results indicated that climatic drought stress may contribute to the encroachment of C.stenophylla shrub in arid zones by promoting its seed production.However,grazing had negative effects on sexual reproduction of C.stenophylla,and the combined effects of drought stress and grazing seriously suppressed sexual reproduction of C.stenophylla in the intensively arid zone.