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1.
Precipitation and Temperature Estimation Error at Alpine Treeline Ecotones Using the Mountain Climate Simulator Model (MT-CLIM) 总被引：1，自引：1，他引：0
《自然地理学》2013,34(4):285-307
In order to improve modeling of alpine treeline responses to climate change, estimations of snowfall at treeline sites are needed. The MT-CLIM climate model was evaluated for this purpose by extrapolating precipitation and temperature from standard weather stations at lower elevations to 30 alpine SNOTEL study sites across the western United States. Quantification of the topography between the base stations and the SNOTEL sites was used in inverse distance weighting and compared to straight-line weighting. The predicted temperature and precipitation under different weighting methods were compared to observed data over three months during the winter of 2006-2007. The errors were mapped and their spatial pattern analyzed. Error patterns indicate strong gradients, particularly in the Pacific Northwest, that are suggestive of areas where additional characteristics of atmosphere-land interactions and boundary layer climatology need to be considered in modeling applications. 相似文献
2.
Woonsup Choi Hi-Ryong Byun Claudio Cassardo Jinmu Choi 《The Professional geographer》2018,70(3):463-475
This study examined meteorological and streamflow droughts for the period from 1951 to 2006 using the Milwaukee River basin in Wisconsin as the study area in an effort to improve the understanding of drought propagation. Specifically, this study aimed to answer the following research questions: (1) What are the temporal trends of meteorological and streamflow droughts identified by drought indicators? (2) How do the drought indicators manifest drought propagation? Meteorological droughts were identified using the Effective Drought Index (EDI), and streamflow droughts were identified using a threshold-level approach. The intensity and duration of both types of drought were found to have decreased over time, most likely due to increasing precipitation. Therefore, in the study area, and likely in the larger region, drought has become of less concern. The propagation of meteorological drought into streamflow drought was detected generally after moderate and severe sequences of negative EDI that eventually led to extreme meteorological drought events. The study finds that both EDI and the threshold-level approach are effective in diagnosing meteorological and streamflow drought events of all durations. 相似文献
3.
This paper has studied the change of streamflow and the impact of climatic vari-ability conditions on regional hydrological cycle in the headwater of the Tarim River Basin. This study investigates possible causes of observed trends in streamflow in an environment which is highly variable in terms of atmospheric conditions, and where snow and ice melt play an important role in the natural hydrological regime. The discharge trends of three head streams have a significant increase trend from 1957 to 2002 with the Mann–Kendall test. Complex time-frequency distributions in the streamflow regime are demonstrated especially by Morlet wavelet analysis over 40 years. The purpose is to ascertain the nature of climatic factors spatial and temporal distribution, involved the use of EOF (Empirical Orthogonal Function) to compare the dominant temperature, precipitation and evaporation patterns from normally climatic records over the Tarim’s headwater basin. It shows that the first principal component was dominated since the 1990s for temperature and precipitation, which identifies the significant ascending trend of spatial and temporal pattern characteristics under the con-dition of the global warming. An exponential correlation is highlighted between surface air temperature and mean river discharge monthly, so the regional runoff increases by 10%–16% when surface air temperature rises by 1℃. Results suggest that headwater basins are the most vulnerable environments from the point of view of climate change, because their wa-tershed properties promote runoff feeding by glacier and snow melt water and their funda-mental vulnerability to temperature changes affects rainfall, snowfall, and glacier and ice melt. 相似文献
4.
额济纳旗近100 a来胡杨年表的建立与响应分析 总被引：6，自引：3，他引：6
在野外采样、室内预处理、交叉定年的基础上,建立了近一百年来额济纳旗胡杨树木年轮年表,并将标准年表的树轮指数与采样点附近额济纳旗气象站的气温、降水及黑河中游正义峡水文站的径流量进行了相关分析。结果表明,年轮宽度指数与春季3~5月径流量和年径流量呈显著负相关,相关系数为-0.642和-0.525。由于该地区降水量为37.9mm,对树木生长的意义不大,径流量则成为胡杨生长的限制因子。正义峡径流量冷季大,暖季小,与该区胡杨的生长季不相吻合。春季树木生长开始,需要一定的水分供给,虽然该区春季径流量仅占全年径流量的16.42%,但是,采样点距离河床较近,地下水位较高,可以满足根系对水分的需要,有利于胡杨生长,因而该相关具有明确的生物学意义。进一步进行响应函数分析的结果表明,重建序列与实测序列较为相近,采用的回归方程比较稳定可信。 相似文献
5.
6.
David Changnon 《自然地理学》2013,34(1):29-46
Hydroclimatic parameters were examined to identify spatial variability among 19 Midwestern basins during the 1950–1990 period. The magnitude of annual streamflow variability values increased westward across the Midwest and appeared to be associated with a similar pattern in annual precipitation variability. Basin seasonal streamflow values were analyzed to determine the occurrence of hydrologic drought. A criterion that combined duration and severity of low-flow characteristics was used to determine hydrologic droughts. Sixteen of the 19 basins experienced between one and four hydrologic droughts, whereas 3 experienced none. The temporal distribution and spatial extent of the 45 hydrologic droughts indicated that there were two classifications of Midwestern hydrologic drought during this period. The first type–“long-term” hydrologic drought–occurred over: (1) a period of 12 or more consecutive seasons and (2) a broad latitudinal belt across the Midwest. Long-term hydrologic droughts occurred during the period from the early 1950s through the late 1960s. Since 1970, hydrologic droughts can be described as “short-term” and are characterized as having occurred over: (1) periods generally less than two years and (2) a smaller region. This information could assist hydrologists and water managers in understanding the more precise nature of temporal and spatial differences that exist in Midwestern hydrologic drought. [Key words: hydrologic drought, hydroclimatic variability, Midwest United States.] 相似文献
7.
Accuracy evaluation of two precipitation datasets over upper reach of Heihe River Basin, northwestern China 总被引：1，自引：0，他引：1
As an important forcing data for hydrologic models, precipitation has significant effects on model simulation. The China Meteorological Forcing Dataset (ITP) and Global Land Data Assimilation System (G... 相似文献
8.
J.D. Miranda C. Armas F.M. Padilla F.I. Pugnaire 《Journal of Arid Environments》2011,75(12):1302-1309
The structure and functioning of semi-arid ecosystems are strongly influenced by precipitation patterns. Water availability in such environments is highly pulsed, and discrete rainfall events interspersed with drought periods are important components of the annual water supply. Plant communities do not only respond to rainfall quantity, but also to variations in time, so that relatively small changes in rainfall frequency (i.e., pulsed inputs) may have strong effects on communities. Within the Mediterranean basin, climate change models forecast a decrease in mean annual precipitation and more extreme events (i.e., less rainy days and longer drought periods between events), along with seasonal changes. However, little is known on the consequences of these future precipitation changes on plant communities, especially in semi-arid environments. Here, we summarize the few experiments that have manipulated rainfall patterns in arid and semi-arid areas worldwide, and introduce the first results of a pioneer, long-term rainfall exclusion in the semi-arid southeast region of the Iberian Peninsula. The experiment is not only manipulating the amount of rainfall, but also its frequency and seasonal distribution in a grassland-shrubland in the Tabernas desert (Almería, Spain). This work monitored the effect of precipitation changes on different ecosystem processes for five years, at the species and community level, concluding that this plant community (as other communities studied in the same area) exhibited great resilience to changes in rainfall availability, likely caused by plant adaptation to large intra- and inter-annual precipitation variability. 相似文献
9.
塔里木河流域径流变化趋势及其对气候变化的响应 总被引：7，自引：0，他引：7
This paper has studied the change of streamflow and the impact of climatic variability conditions on regional hydrological cycle in the headwater of the Tarim River Basin. This study investigates possible causes of observed trends in streamflow in an environment which is highly variable in terms of atmospheric conditions, and where snow and ice melt play an important role in the natural hydrological regime. The discharge trends of three head streams have a significant increase trend from 1957 to 2002 with the Mann-Kendall test. Complex time-frequency distributions in the streamflow regime are demonstrated especially by Morlet wavelet analysis over 40 years. The purpose is to ascertain the nature of climatic factors spatial and temporal distribution, involved the use of EOF （Empirical Orthogonal Function） to compare the dominant temperature, precipitation and evaporation patterns from normally climatic records over the Tarim＇s headwater basin. It shows that the first principal component was dominated since the 1990s for temperature and precipitation, which identifies the significant ascending trend of spatial and temporal pattern characteristics under the condition of the global warming. An exponential correlation is highlighted between surface air temperature and mean river discharge monthly, so the regional runoff increases by 10%-16% when surface air temperature rises by 1 ℃. Results suggest that headwater basins are the most vulnerable environments from the point of view of climate change, because their watershed properties promote runoff feeding by glacier and snow melt water and their fundamental vulnerability to temperature changes affects rainfall, snowfall, and glacier and ice melt. 相似文献
10.
嫩江是东北地区最重要的河流之一,了解嫩江长期水文变化规律,对嫩江流域林业、农牧业生产具有重要意义。通过对嫩江上游4个地点兴安落叶松（Larix gmelinii）树轮年表与气候水文数据分析,发现4个地点的平均年表与1~3月平均径流量有着极显著关系。因此,基于树轮宽度重建了嫩江上游1804年以来1~3月平均径流量,重建方程解释了43.9%的径流变异,经检验证明重建结果可靠。重建嫩江径流变化表明：1804年以来,嫩江流域上游1~3月份径流经历了6个偏枯和7个偏丰阶段。同时,嫩江上游径流量存在60、4.3~4.0、3.4~3.2、3.1~2.9和2.3 a的变化周期。在19世纪初至20世纪初嫩江1~3月流量的变化幅度较小,而20世纪中后期变化幅度较大。另外,重建结果与黑龙江省历史记载的旱涝时期比较吻合。 相似文献
11.
黄河中游多沙粗沙区水沙变化趋势及其主控因素的贡献率 总被引：5，自引：0，他引：5
随着气候变化和人类活动影响加剧,黄河中游多沙粗沙区的水沙变化剧烈,因此研究影响黄河中游多沙粗沙区径流量和输沙量的驱动因素对预测未来水沙变化具有重要意义。本文选取Mann-Kendall趋势检验法,Pettitt突变点检验法,位置、尺度、形状的广义可加模型以及累积量斜率变化率比较法对黄河中游多沙粗沙区15个水文站控制流域1956-2010年的年降水量、年径流量以及年输沙量变化特征及其贡献率进行分析,确定影响黄河中游多沙粗沙区径流量和输沙量变化的主要原因。结果表明：① Mann-Kendall趋势检验在5%的显著性水平下,表明降水量虽呈减少趋势但并不显著,径流量和输沙量则有显著的减少趋势;② Pettitt突变点检验得出所研究区域径流量和输沙量的突变年份在1972年、1985年以及1996年左右;③ GAMLSS模型分析结果同样表明降水的均值不随时间发生变化,但降水的方差有减小的趋势;④ 通过累积量斜率变化率比较法得出,人类活动对窟野河流域径流输沙的影响大于无定河流域。通过分析黄河中游多沙粗沙区径流量和输沙量变化的原因,可为黄河中游多沙粗沙区水资源合理分配提供一定的理论支持。 相似文献
12.
Samuel Ogunjo Adeyemi Olusola Olufemi Durowoju 《Singapore journal of tropical geography》2023,44(3):479-498
Droughts affect human well-being and the economy of countries across the world. Understanding the long-term evolution of droughts within a particular region will help in drought mitigation and adaptation plans, thereby reducing drought impact on the environment. This study examined the multidecadal trends in hydrological droughts at two stations along River Niger using 3-month, 6-month, and annual time scales. Hydrological drought events were identified using the streamflow drought index (SDI) between 1915 and 1990 based on the Theil-Sen slope and Mann-Kendall approaches. Across the timescales, extreme and severe droughts occurred in 1982/84 and 1983/84 with -2 ≤ Sd < -1.5. On an annual scale, the results from the annual SDI further showed that the 7th and 8th decades (1971−1990) recorded more drought events of varying degrees ranging from mild to extreme drought in both stations than in other decades. The last two decades (7th and 8th) further revealed the most extended hydrological drought duration from 1974/75 to 1988/89 for Baro and from 1979/80 to 1988/89 for Lokoja. The highest severity recorded at Baro was -15.56 and -14.26 at Lokoja. The prolonged duration of drought events across the stations and their associated yearly intensities suggests that more proactive measures are needed to ameliorate the hydrological drought impact in the study area. 相似文献
13.
LAN Yongchao ZHAO Guohui ZHANG Yaonan WEN Jun HU Xinglin LIU Jinqi GU Minglin CHANG Junjie MA Jianhua 《地理学报》2010,20(6):848-860
Response of the runoff in the headwater region of the Yellow River to climate change and its sensibility are analyzed based on the measured data at the four hydrological stations and ten weather stations during the period 1959-2008. The result indicates that change of temperature in the region has an obvious corresponding relationship with global warming and the changes of annual average temperature in each subregion in the region have been presenting a fluctuant and rising state in the past 50 years. However the change of precipitation is more intricate than the change of temperature in the region because of the influences of the different geographical positions and environments in various areas, and the change of annual precipitation in the main runoff-producing area has been presenting a fluctuant and decreasing state in the past 50 years. And there is a remarkable nonlinear correlativity between runoff and precipitation and temperature in the region. The runoff in the region has been decreasing continuously since 1990 because the precipitation in the main runoff- producing area obviously decreases and the annual average temperature continuously rises. As a whole, the runoff in each subregion of the headwater region of the Yellow River is quite sensitive to precipitation change, while the runoff in the subregion above Jimai is more sensitive to temperature change than that in the others in the region, correspondingly. 相似文献
14.
15.
黄河源区径流对气候变化的响应及敏感性分析(英文) 总被引：4，自引：1，他引：3
Response of the runoff in the headwater region of the Yellow River to climate change and its sensibility are analyzed based
on the measured data at the four hydrological stations and ten weather stations during the period 1959–2008. The result indicates
that change of temperature in the region has an obvious corresponding relationship with global warming and the changes of
annual average temperature in each subregion in the region have been presenting a fluctuant and rising state in the past 50
years. However the change of precipitation is more intricate than the change of temperature in the region because of the influences
of the different geographical positions and environments in various areas, and the change of annual precipitation in the main
runoff-producing area has been presenting a fluctuant and decreasing state in the past 50 years. And there is a remarkable
nonlinear correlativity between runoff and precipitation and temperature in the region. The runoff in the region has been
decreasing continuously since 1990 because the precipitation in the main runoff-producing area obviously decreases and the
annual average temperature continuously rises. As a whole, the runoff in each subregion of the headwater region of the Yellow
River is quite sensitive to precipitation change, while the runoff in the subregion above Jimai is more sensitive to temperature
change than that in the others in the region, correspondingly. 相似文献
16.
The southeastern United States, including Florida, has been identified as a region of homogeneous response to the El Niño/Southern Oscillation (ENSO) climatic anomaly, in which mean monthly precipitation and discharge during winter is above or below normal following the onset of the warm (El Niño) or cold (La Niña) phase of ENSO, respectively. However, this understanding of the response is expanded through a study of the effects of the ENSO phenomenon on the probability distributions of mean monthly streamflows of the Santa Fe river. The Santa Fe river basin is situated between one region, which experiences the greatest proportion of annual streamflow during winter, and another where the largest percentage of annual flow occurs during late summer. The basin experiences both winter and summer peaks in precipitation and (subsequent) streamflow and may therefore display responses to ENSO during each season. A two-parameter lognormal distribution is employed to model these streamflows during warm and cold phases of ENSO. Increases in both the mean and the variance detected during warm phase winters are compatible with previous observations. Increases in variance apparent during cold phase summers have not been previously identified. These results, which have considerable bearing upon predictions of high and low flow probabilities during the year, suggest that the response in streamflow is not spatially homogeneous across the state. 相似文献
17.
基于印度河流域及周围54个地面气象站气温、降水资料，结合CRU气温和GPCC降水全球格点化陆面再分析资料，通过插值构建了一套0.5°×0.5°分辨率1980—2016年逐月格点数据集。采用Thornthwaite方法计算了潜在蒸散发，基于标准化降水蒸散指数（SPEI），探讨了印度河流域气候变化及干旱演变特征。结果表明：（1）1980—2016年，印度河流域年平均气温以0.30℃·（10 a）-1的速率呈显著上升趋势，21世纪初增温幅度最大；干季（11月~次年4月）升温速率较快，达0.36℃·（10 a）-1，湿季（5~10月）增速0.25℃·（10 a）-1。年降水量呈现少雨—多雨—少雨—多雨年代际振荡。伴随着持续升温，年和各季的潜在蒸发量增加显著。干季干旱频率较多，但湿季干旱强度高，各季干旱频率与降水呈现较一致的年代际波动；干旱的影响面积在干季呈现微弱地增加趋势，湿季却略有减少趋势。（2）空间上，除西北局部，流域其他区域的年和季平均气温、潜在蒸发量增加趋势显著，均达到95%置信水平。其中南部平原和东北山区升温幅度较高，南部平原区潜在蒸发量增加也较大。新德里到喀布尔的东南至西北带状区域的年和湿季降水量，以及喀布尔周围地区的干季降水量呈显著增加趋势。东南平原区和东北局部山区的干季，以及东北和西南局部山区的湿季呈现显著的干旱化态势，需要加强防灾减灾的意识并采取相应措施，以规避干旱增多带来的不利影响。 相似文献
18.
基于相对湿润度指数和非参数百分法,结合线性趋势法、Mann-Kendall非参数检验法和累积距平检验法,分析了1955-2015年内蒙古4个草原类型区（多伦、锡林浩特、海拉尔和四子王旗）温度和降水,以及极端气候事件变化特征。结果表明：（1）4个区域年平均气温均显著升高,升高速率约为0.40~0.47℃·（10 a）-1,气温变化存在非对称性升温特征,多伦、锡林浩特、海拉尔和四子王旗最低气温上升速率分别为最高气温上升速率的1.61倍、1.86倍、2.73倍和1.65倍,春冬季气温增加速率高于夏秋季。（2）多伦、海拉尔、四子王旗和锡林浩特年降水量分别为381.6 mm、350.5 mm、318.6 mm和283.6 mm;降水天数显著增加,而降水量无显著变化,但多伦和锡林浩特降水量呈现略微降低的趋势,其它两个区域呈现略微增加的趋势。（3）4个区域极端高温事件频率显著增加,突变点均出现在1990 s,极端低温事件频率显著减少,突变点均出现在1970s末。（4）4个区域均呈现暖干化的趋势,锡林浩特干旱事件发生最为突出,四子王旗以中度干旱为主,海拉尔和多伦以无旱为主,2000年后,4个区域干旱事件发生频率均明显增加。降水量变化不显著,而气温和潜在蒸散量显著升高可能是导致4个区域不断干旱化的主要原因。 相似文献
19.
松花江区气象水文干旱演变特征 总被引：3，自引：0，他引：3
采用标准化降水蒸散指数和径流干旱指数分析了1961~2010年研究区水文干旱和气象干旱时空演变特征,并探讨了水文干旱与气象干旱的关系。结果表明：① 1961~2010年松花江区呈总体干旱化且又有明显时段性的特征,其中1967~1983年和1996~2010年气象干旱频发、覆盖范围广、持续时间长且强度大;其它时段气象干旱少有发生。其次,气象干旱空间分布差异明显,东部的平均干旱频次和强度都大于西部地区,中部（嫩江流域中下游）平均干旱持续时间最长;但在嫩江流域和黑龙江上游地区干旱略有减弱趋势。② 松花江流域和挠力河流域水文干旱呈加剧的趋势,尤其是近15 a干旱化趋势明显;挠力河流域干旱频发、强度大且持续时间很长。松花江流域水文干旱程度弱于挠力河流域,但极端水文干旱事件频发。 ③ 松花江区气象干旱与水文干旱密切相关,嫩江流域水文干旱滞后于气象干旱2个月,而第二松花江流域和松花江流域水文干旱滞后于气象干旱3个月;挠力河流域水文干旱与气象干旱无明显的时滞相关性。 相似文献
20.
The regional spatial and inter-annual response of the Enhanced Vegetation Index (EVI, as a proxy for aboveground net primary production) to environmental controls was evaluated in drylands of SE Spain. By means of linear mixed-effects models we found that both the spatial patterns and inter-annual trends of the EVI annual mean were explained by climate variability but clearly modulated by lithology and vegetation. Along the spatial gradient, precipitation increased the EVI mean even compensating for the greater evapotranspiration of warmer sites. Limestones, with high available water content, showed the lowest dependence of EVI mean on precipitation. The greater capacity of scrublands to store and use soil moisture was only evident on marls sites. The observed 2001–2010 trends toward less stressful conditions (precipitation rises and temperature declines) led to EVI mean increases. This EVI mean response was steeper in grasslands, with shallow roots, and marls, with low available water content. The study revealed the importance of analyzing the seasonal timing of trends in Mediterranean drylands, where temperature and precipitation are out of phase. The observed earlier rain-arrival after summer drought and cooler early-autumn, caused very strong EVI increases at the beginning of the growing season that may favor the rest of the season. 相似文献