黄淮海流域蒸发量的变化及其原因分析

利用研究区1956-2000年117个气象台站的小型蒸发皿观测资料,分析了黄淮海流域蒸发量的变化趋势及其可能原因。结果表明,近50年来本区蒸发量减少十分显著,其变化速率一般在-50 mm/10a,平原地区最大变化速率达到-80mm/10a以上。蒸发量下降最明显的季节是春季和夏季,其中春季减少最大区域主要在海河流域的东南部和黄河下游,而夏季的减少主要在淮河流域。造成蒸发量减少的直接气候原因可能是日照时数及太阳辐射的减少,平均风速和气温日较差的降低可能也起着重要的作用。     

藏北高原蒸发皿蒸发量及其影响因素的变化特征

采用气候倾向率方法,对藏北高原1971-2006年6个气象站年、季小型蒸发皿蒸发量及其影响气候因子的变化趋势进行了分析。结果表明:近36年藏北高原年蒸发皿蒸发量各站点均呈现显著的减少趋势,平均减少61.7mm/10a(通过99%显著性检验),以夏季减幅最明显。就地域分布而言,蒸发皿蒸发量的下降主要表现在藏北高原的中西部。蒸发量减少幅度随经度的增加减小,随海拔高度的升高而加大。影响蒸发皿蒸发量的主要气候因子日照时数、平均风速呈现显著下降趋势,平均相对湿度、降水量表现为显著增加,平均气温显著升高,平均最低气温的升温速率(0.54℃/10a)明显比平均最高气温的升温速率(0.17℃/10a)大,导致气温日较差的减小(-0.37℃/10a)。藏北高原平均气温日较差和日照时数的显著减小,以及平均相对湿度的明显增加可能是蒸发皿蒸发量显著下降的主要原因,降水量的增加和平均风速的明显减小在蒸发量减少趋势中的作用也不可忽视。     

1971—2006年珠穆朗玛峰地区蒸发皿蒸发量的变化及其影响因素

升温率略高于平均最高气温的升温率.珠峰地区日照时数和平均风速的显著下降,以及相对湿度的明显增加可能是蒸发皿蒸发量下降的主要原因.     

Estimation of potential evapotranspiration in Al-Hassa oasis,Saudi Arabia

An accurate estimation of the potential evapotranspiration can be achieved ba applying empirical evapotranspiration coefficients which are determined under Al-Hassa prevailing climatic conditions. Correlation coefficient results indicate that most of the climatological variables have a strong relationship with potential evapotranspiration except wind speed and precipition variables which have a weak relationship. Multiple regression results also indicate that there is a significant effect of some of the climatologiecal variables in the potential evatranspiration and there is no significant effect of the others at the significant level of 0.05. The results of the stepwise regression indicate that evaporation class “A” pan, air temperature, sunshine hours, radiation, relative humidity, and wind speed variables have a significant effect at the significant level of 0.05 on the overall mean monthly potential evapotranspiration of the Blaney-Criddle, Pan Evaporation, and Jensen-Haise, therefore, the equation which has developed for estimating potential evapotranspiration in Al-Hassa is based on these six variables (evaporation class “A” pan, air temperature, sunshine hours, radiation, relative humidity, and wind speed).     

气象极值变化及其导致的农业气象灾害趋势分析——以甘肃省为例

依据甘肃省62个气象站1960-2005年的地面气候资料, 分析农作物生育期(3-10月)内气象要素极值的变化趋势, 并用主成分分析方法研究了该变化对农业气象灾害发生趋势的影响.结果表明: 与温度相关的气象要素极值表现出了同平均气温类似的显著上升趋势,其中降水相关的气象要素极值变化说明甘肃省降水结构发生了改变, 极端性有所减弱;其他相关要素中, 最大风速存在明显下降趋势, 蒸发量呈下降趋势、日照时数呈上升趋势, 但都不够显著.大部分气象极值的变化与农业气象灾害的变化呈正相联系, 只有很少部分气象极值的变化与农业气象灾害的变化呈反相联系.综合分析这些气象极值在甘肃省范围内的变化趋势, 揭示出未来甘肃省干旱灾害倾向于加剧, 而洪涝灾害趋于减轻.     

珠峰地区天气气候特征分析

利用珠穆朗玛峰地区北部定日站和西部聂拉木站1971-2009年的月平均气温、月平均最高、最低气温、月降水量、月蒸发量资料,对珠峰地区1971-2009年近39a来气候变化的时空分布特征进行了分析.同时,利用该区域5个自动气象观测站2009年的资料进行了温、压、湿、风等分析.结果表明:1971-2009年珠峰地区气温呈现出明显的上升趋势,尤其是进入21世纪后,增温更为显著,高于同期全球平均温度变化幅度;定日站增幅较聂拉木站明显,且以冬、春两季的气温增长幅度大.位于珠峰的西边略偏北的聂拉木站,迎向暖湿气流,降水丰富,但季节差异很小;定日站的年降水量不到聂拉木站的一半,且夏季降水占到了全年的85%;定日站的年降水量略微呈上升状态,蒸发量下降,两者的变化趋势都不是太明显;聂拉木站的降水量下降趋势比定日站明显,蒸发量略显上升.2009年资料显示,珠峰地区5个站的气温、气压、相对湿度、风速各异,温度、气压与各站的海拔密切相关.     

Temporal variations of reference evapotranspiration and controlling factors: Implications for climatic drought in karst areas

Variations in reference evapotranspiration (ET₀) and drought characteristics play a key role in the effect of climate change on water cycle and associated ecohydrological patterns. The accurate estimation of ET₀ is still a challenge due to the lack of meteorological data and the heterogeneity of hydrological system. Although there is an increasing trend in extreme drought events with global climate change, the relationship between ET₀ and aridity index in karst areas has been poorly studied. In this study, we used the Penman–Monteith method based on a long time series of meteorological data from 1951 to 2015 to calculate ET₀ in a typical karst area, Guilin, Southwest China. The temporal variations in climate variables, ET₀ and aridity index (AI) were analyzed with the Mann–Kendall trend test and linear regression to determine the climatic characteristics, associated controlling factors of ET₀ variations, and further to estimate the relationship between ET₀ and AI. We found that the mean, maximum and minimum temperatures had increased significantly during the 65-year study period, while sunshine duration, wind speed and relative humidity exhibited significant decreasing trends. The annual ET₀ showed a significant decreasing trend at the rate of ?8.02 mm/10a. However, significant increase in air temperature should have contributed to the enhancement of ET₀, indicating an “evaporation paradox”. In comparison, AI showed a slightly declining trend of ?0.0005/a during 1951–2015. The change in sunshine duration was the major factor causing the decrease in ET₀, followed by wind speed. AI had a higher correlation with precipitation amount, indicating that the variations of AI was more dependent on precipitation, but not substantially dependent on the ET₀. Although AI was not directly related to ET₀, ET₀ had a major contribution to seasonal AI changes. The seasonal variations of ET₀ played a critical role in dryness/wetness changes to regulate water and energy supply, which can lead to seasonal droughts or water shortages in karst areas. Overall, these findings provide an important reference for the management of agricultural production and water resources, and have an important implication for drought in karst regions of China.     

Analysis of long-term ozone trend over Delhi and its meteorological adjustment

Present study deals with the statistical analysis of long-term ground level ozone (O₃) trend and the influence of meteorological variables on its variation over Delhi, India. Daily mean and maximum of O₃ and meteorological data, obtained from India Meteorological Department, were arranged for the period of 9 years (1998–2006). Based on the preliminary correlation study of all the data with O₃, six variables viz. daily maximum temperature, daily average relative humidity, dew point, wind speed, visibility, and total sunshine were selected. Classical additive time series decomposition technique was used to obtain seasonally adjusted long-term trend. To analyze the masking effect of meteorology, adjustment was made using Kolmogorov–Zurbenko filters followed by stepwise regression analysis to the smoothed series of O₃ maximum and meteorological variables, which showed that long-term trend was independent of sunshine duration. Results indicate a significant increasing trend with annual increase of 1.13 % for O₃ mean and 3 % for O₃ maximum. Annual deseasonalized trend for seasonal cycle shows bimodal oscillations. About 43 % of O₃ variation was explained by the selected meteorological factors and rest of variation attributed to factors like emission of precursor gases, pollutant transport, policy changes, etc. Among the three tested regression models, performance of Model 2 with variable temperature, wind speed, and visibility was found to be best that resulted in lowering of O₃ trend. Large variability (23 %) was explained by the variable visibility depicted that the emission of primary pollutants not only provides the precursor gases but also control the local photochemical reactions.     

The relation of seasonal pattern in stable carbon compositions to meteorological variables in the leaves of <Emphasis Type="Italic">Sabina</Emphasis><Emphasis Type="Italic">przewalskii</Emphasis> Kom. and <Emphasis Type="Italic">Sabina chinensis</Emphasis> (Lin.) Ant.

The seasonal variation of foliar δ¹³C values in Sabina przewalskii Kom. and Sabina chinensis (Lin.) Ant. was measured. The relationships between foliar δ¹³C values and branch δ¹³C values as well as environmental factors (monthly total precipitation, monthly average air temperature, monthly average soil temperature, monthly total solar duration, relative humidity, atmospheric pressure, vapor pressure, wind speed and potential evaporation) were investigated. The results showed that the foliar δ¹³C values were negatively correlated with air pressure, and positively correlated with air temperature, precipitation, vapor pressure, potential evaporation, solar duration, wind speed and soil temperature. No significant relationship between δ¹³C values and relative humidity was detected. This demonstrates that the foliar δ¹³C of Sabina is a successful empirical indictor of these meteorological factors within the usual range of C₃ whole-leaf δ¹³C values. Furthermore, the δ¹³C signature of leaf tissue is similar to that of wood tissue and the responses of δ¹³C values in S. przewalskii Kom. to environmental factors are also relatively stronger than that of S. chinensis (Lin.) Ant. These results provided strong evidence that it is feasible to extract climatic information from tree-ring δ¹³C series and S. przewalskii Kom. is a dendroclimatologically promising tree species.     

水面蒸发量与各气象因素关系的通径分析

从表面看,影响水面蒸发量的气象因素有日均气温、日最高气温、日最低气温和日均风速及日均相对湿度。通径分析表明,平均气温是水面蒸发量的主要的影响因素,其它气象因素大多通过平均气温对水面蒸发量起作用。与此同时,本文根据影响水面蒸发量的最主要因素,建立了相应的多元回归模型。结果表明,该模型具有较高精度和良好可靠性。     

新疆沙井子灌区各气象要素对水面蒸发量影响程度的灰色关联分析

根据新疆阿克苏市气象站1995～2003年E601蒸发皿蒸发量及相关常规气象观测资料,利用灰色关联度分析法分析了各气象要素对水面蒸发的影响程度,结果表明各气象要素对E601蒸发皿蒸发量的影响程度从大到小的排列顺序依次为温度〉日照时数〉风速〉相对湿度。建议在沙井子灌区水资源优化调度中,应当充分考虑湿度因素及日照时数对水资源的影响,合理配置水资源。     

近40a来江河源区生态环境变化的气候特征分析

利用月气象资料,对过去40a江河源气候变化特征进行分析,并与全球、全国、青藏高原进行了比较.结果表明:江河源区气温具有增暖趋势,近40a两地年平均气温分别增加约0.8℃和0.7℃,为高原异常变暖区.黄河源区变暖的主要特征是最低气温变暖,日照时数增加;最低、最高气温的显著变暖,以及较黄河源区增加更长的日照时数是长江源区变暖的主要特征.长江源区冬季变暖的作用不是主要的,春季、夏季和秋季的变暖作用比冬季还要大;黄河源区的变暖也并不主要是冬季变暖造成的,秋季变暖的作用与其相当,其它季节的变暖作用也不能忽视.近40a来江河源区降水量略有增加,主要体现在20世纪80年代中后期以来春季与冬季降水量的明显增加,夏季降水量虽然总体上没有明显变化,且局地夏季降水量呈持续减少趋势.与全球、全国以及高原区对比显示,江河源区对全球气候变暖的响应最敏感,变暖首先从长江源和整个高原发端,之后15a.黄河源和全国才进入显著温暖期.黄河源与长江源北部降水量的增加表明,气候变暖有利于高原增加降水量.     

Climate impacts of environmental degradation in Sudan

There exists an impressive amount of work for Sudan showing the anthropogenic degradation of natural vegetation cover. However, there are few examples of consequent climatic changes in literature. This work, thus, seeks to assess such effects of environmental forcing on various climatic patterns over the past few decades. Within the frame of the present analysis, the results are quite striking and are in concordance with scientific contentions that such land degradation could result in climatic modification. Higher temperature and less rainfall, sunshine duration and global radiation have been noticed. Evapotranspiration has responded more to the warming and drying conditions, thus showed signs of increasing rates, especially during the wet season. However, the extent of increase seems to have been suppressed by the decrease in sunshine duration and solar radiation as well as the inconsistent behaviour of wind speed. Changes in the variability of the within-year monthly observations have also occurred, thus suggesting an increase in the occurrence of extremes. The observed climatic modification in the country has exaggerated the insidious drought conditions. The present findings are hoped to contribute to our understanding of the effects of environmental problem and assist in considering policy responses. This revised version was published online in July 2006 with corrections to the Cover Date.     

1959-2008长江源被净初级生产力对气候变化的响应

基于长江源区1959-2008年月平均气温、最高气温、最低气温、相对湿度、降水量、风速和日照时数等气候要素资料,应用修订的Thornthwaite Memorial模型计算了50a被净初级生产力,分析其年际和年代际变化特征及其对气候变化的响应.结果表明：1959-2008年间,研究区年NPP变化呈显著上升趋势,NPP变...     

Impacts of climate change and human activities on the aboveground production in alpine grasslands: a case study of the source region of the Yellow River,China

Changes in aboveground net primary productivity (ANPP) in alpine grasslands are the consequence of climate change and human activities, but it is difficult to disentangle their relative contributions. Based on monthly remote-sensed vegetation index and meteorological data during the period 1982–2010, we analysed the long-term variation of annual ANPP in the source region of the Yellow River and quantified the effects of climate and human activities including grazing on ANPP variability, using the Carnegie–Ames–Stanford Approach (CASA) model and the ANPP-based residual trend analysis method. Our results suggested that ANPP increased in 80% of alpine grasslands. Areas with negative changes in ANPP were found mainly in the eastern portion of the region, accounting for 0.3% of alpine grasslands. ANPP was positively correlated with the monthly mean temperature from June to September and the sunshine duration in September at a regional scale. Moreover, ANPP was negatively correlated with the total livestock numbers. Using the residual trend analysis method, we demonstrated that climate and human activities accounted for 76.6 and 23.4%, respectively, of the variability in ANPP for the entire study region in 1982–2010. We concluded that climate change alleviated climatic constraints, in particular temperature limitations and sunshine duration, resulting in a significant increase in ANPP. Overgrazing was supposed to be the primary driver for grassland degradation in the eastern region. Our study has implications for grassland management and its sustainability to minimize the risk of grassland degradation and desertification processes in geo-ecologically and socially important regions such as the study region in China.     

Analysis of the Influence of Climate and Vegetation Change on Runoff in the Middle and Upper Reaches of the Pearl River Basin Based on Budyko Hypothesis*

Runoff, which is a key component in the hydrological cycle, is mainly controlled by climate factors and land-surface elements in non-humid regions. The impacts of climate and vegetation changes on runoff based on Budyko hypothesis in the middle and upper reaches of the Pearl River Basin was analyzed in this article. First, the temporal trend of variables in the study area during 1981-2013 was examined by using the Mann-Kendall trend test with trend-free pre-whitening. Second, the relationship of the parameter n in Fu's equation with factors of climate and vegetation coverage was built to reveal the time-variation process of n. Finally, the effects of climatic factors and vegetation coverage on runoff were assessed by analyzing the sensitivity of runoff to each variable. It is found that average temperature (T), maximum temperature (T_max) and minimum temperature (T_min) in the study area present an increasing trend while runoff (Q), precipitation (P), wind speed (u₂) and relative humid (RH) present decreasing trend. The parameter n in Fu's equation is significantly related to both climatic factors (including precipitation (P), average temperature (T), relative humid (RH), sunshine duration (S), wind speed (u₂)) and vegetation coverage index (NDVI). In terms of sensitivity of Runoff (Q) to the variation of each climatic factors and NDVI in the middle and upper reaches of the Pearl River Basin, precipitation (P) and NDVI have the highest sensitivity, followed by other climatic factors. Additionally, the precipitation (P) reduction is the main driving factor to the decline in runoff, while vegetation coverage is another important factor. In general, climate change affects runoff not only by changing the hydrological inputs (precipitation (P) and potential evaporation (PET) but also by altering the watershed characteristics as represented by the parameter n, while the impacts of vegetation coverage on runoff are exerted mainly through the alteration of the watershed characteristics.     

青藏高原那曲中部土壤温湿分布特征

青藏高原土壤水热状况对气候变化和植被退化方面的研究具有重要意义,土壤湿度的准确刻画还会影响到数值预报模式对当地及其下游地区降水的模拟能力。为此,采用中国科学院那曲高寒气候环境观测研究站安多观测点2014年1—12月的土壤温度、土壤湿度观测资料以及同期安多气象站观测数据,分析了青藏高原那曲中部不同深度土壤温湿度的分布特征及其与气温、降水量等气象要素的关系。结果表明：土壤温度在浅层为正弦曲线,随着土壤深度的增加,曲线逐渐接近直线。土壤升温迅速而降温过程缓慢。封冻和解冻日期随土壤深度的增加而推迟,封冻期逐渐缩短。不同层次土壤湿度日内变化较小。月变化呈单峰型结构,峰值和谷值基本出现在8月和12月。土壤湿度上升速率较下降速率缓慢。区域尺度上GLDAS-NOAH资料显示出类似的变化特征。土壤温湿度在一年中的变化不一致,但土壤温湿度呈显著正相关。浅层土壤的温度梯度明显大于深层;浅层土壤湿度最大,中间层较大,深层土壤湿度最小。随着干季向湿季的转换,由于太阳辐射的增加,非绝热加热呈增加的趋势。土壤湿度与气象要素在不同时段的相关性存在一些差异,但总体上土壤湿度与气温、降水量和相对湿度呈正相关,与风速、日照时数相关性不显著。     

近400年来新疆策勒红柳沙包稳定氧同位素与气候变化

建立红柳沙包沉积纹层年代序列和提取气候环境信息是高分辨率古气候环境变化研究的重要手段。利用策勒达玛沟红柳沙包高度约450 cm沉积纹层红柳落叶的稳定氧同位素数据,结合策勒气象站1960~2011年观测数据,运用移动平均法对稳定氧同位素和气象数据进行平滑处理后,运用相关分析及逐步回归法,定量重建了策勒地区近400年来的4月平均气温和3月降水量序列。研究结果表明:红柳落叶δ^18O平均值为33.96‰,波动范围为27.18‰~44.07‰,波动幅度为16.89‰,δ^18O变化受多个气候要素的综合影响。δ^18O与4月平均气温呈显著负相关,与2月和12月平均气温呈显著正相关;δ^18O与10月、4月、5月、9月、7月以及全年的空气相对湿度呈显著正相关;δ^18O与3月、9月和8月的降水量呈显著正相关,与2月降水量呈显著负相关;δ^18O与2月日照时数呈显著正相关,与9月和10月的日照时数呈显著负相关。策勒地区近400年来气候变化可划分4个阶段:1635~1725年为暖干期,1726~1792年为冷湿期,1793~1897年为暖干期,1898~2009年为冷湿期。     

1971-2010年内蒙古干湿变化特征及对水资源影响

利用1971-2010年内蒙古地区96个气象站的月降水量、月平均气温、月平均风速等气象资料,通过FAO Penman-Monteith 潜在蒸散量计算模型作为基础计算干湿指数,采用气候倾向率、滑动平均等数理统计方法,分析了1971-2010年内蒙古地区干湿指数的变化趋势及空间分布规律并划分出5 种干湿地区类型,探讨了干湿指数与降水量、日照时数、相对湿度等气象因子之间的关系。结果表明：近40a内蒙古地区年干湿指数呈略下降趋势,其变化倾向率为-0.003·（10a）^-1,20世纪90年代中期以来年干湿指数呈减少趋势。在地理分布上年干湿指数存在较大的差异性,自东向西逐渐递减,高值中心位于内蒙古大兴安岭东北部,低值中心在内蒙古巴丹吉林沙漠北部。在全球气候变暖的背景下,90年代后干湿指数下降明显,尤其是在内蒙古东部地区,干湿类型明显由湿向干转变,降水减少、区域增温是该地区干旱化的主要原因。内蒙古地区干湿变化主要的气候影响因子是降水量,相关系数在0.9以上,其次是日照时数、相对湿度、潜在蒸散量,相关系数在0.6~0.7之间。近10a来内蒙古地区水资源总量急剧下降,与近些年来地表干湿状况的变化有一定的关系。     

1961—2008年若尔盖高原湿地的气候变化和突变分析

利用1961—2008年若尔盖高原湿地境内的5个气象台站的逐月气象数据和玛曲水文站的径流数据,分析了近48a来若尔盖湿地的气候变化趋势,并应用M-K方法、累积距平和滑动t检验对年降水量和平均气温的气候突变进行了检测.结果表明:从1960年代的冷湿期,到1980年代中期到1990年代中后期的冷干期,再到1990年代末起增暖迅速进入暖干期,若尔盖湿地气候呈现较明显的暖干化趋势:一方面,总云量持续减少,日照时数上升,平均气温明显上升,气温日较差逐渐减小;另一方面,降水量、蒸发量、径流量总体都呈减少趋势,干燥指数也逐渐降低.秋季是若尔盖高原湿地气候发生暖干化最明显的季节,气候变暖主要是平均最低温度显著升高的贡献.日较差是蒸发量变化的最重要的影响因子,但低云量、气温、日照等的作用也不能忽视.年平均气温和降水量分别在1997年和1985年发生突变,分别转为迅速增暖和持续减少.