共查询到20条相似文献，搜索用时 593 毫秒
1.
大气、湖泊的边界层是大气边界层和湖泊边界层两部分组成的，它们之间通过湍流交换连接在一起，形成一整体系统。经过分界面的动量通量是连续的，热量是守恒的。基于此，本文在近几年工作的基础上，建立了大气边界层与水动力学模式的耦合模型，并对日本琵琶湖进行了实验研究，获得了一些比正压和均匀风场模式更符合观测实际的结论：（１）无论夏季（ＳＳＷ）和冬季（ＮＮＥ）作用下，湖面均可形成正的风涡度场；（２）夏季时，风的正涡度场对形成琵琶湖中观测到的环流特征起着十分重要的作用，而且还构造出与环流相匹配的深水区低、浅水区高的温度场；（３）夏季时，初始温度场的水平分布特征对模式结果的影响很小；（４）冬季时，湖中无明显水平环流生成。 相似文献
2.
Aaron P. Potito Craig A. Woodward Michelle McKeown David W. Beilman 《Journal of Paleolimnology》2014,52(4):385-404
Ireland provides a unique setting for the study of past climates, as its climate is dominated by westerly airflow from the North Atlantic and readily responsive to changes in North Atlantic circulation patterns. Although there has been substantial research on Ireland’s past environments, quantitative palaeolimnological research, especially chironomid-based research, has been lacking. In order to further develop chironomid-based palaeolimnological investigations, a calibration set was constructed to determine the dominant environmental controls on modern chironomids in western Ireland. Chironomid subfossils were collected from surface sediments of 50 lakes. The lakes were characterised with 36 environmental variables, including physical attributes, lake water characteristics, lake sediment characteristics and land cover within each catchment. In this exploratory study, no specific environmental variable was targeted and lakes were chosen to span gradients of latitude, elevation, depth and trophic status. Redundancy analysis showed that six environmental variables—mean July air temperature, lake depth, dissolved organic carbon, and percentage catchment land cover of agriculture, peat bog and scrubland—captured a large and statistically significant portion of the variance in the chironomid data. July temperature and agricultural land cover were the most dominant environmental variables, with July temperature proving the most suitable for inference model development. A classical weighted-averaging model was developed to estimate July air temperature, with a coefficient of determination (r jack 2 ) of 0.60 and root mean square error of prediction (RMSEP) of 0.57 °C. Results suggest that summer temperature is the dominant influence on chironomid distribution across a wide variety of lake types, and the relatively small RMSEP should allow for more accurate reconstructions of Ireland’s relatively subdued Holocene temperature fluctuations. 相似文献
3.
Climate records during the last millennium are essential in placing recent anthropogenic-induced climate change into the context of natural climatic variability. However, detailed records are still sparse in Alaska, and these records would help elucidate climate patterns and possible forcing mechanisms. Here we present a multiple-proxy sedimentary record from Kepler Lake in south-central Alaska to reconstruct climatic and environmental changes over the last 800?years. Two short cores (85 and 101?cm long) from this groundwater-fed marl lake provide a detailed stable isotope and sediment lithological record with chronology based on four AMS 14C dates on terrestrial macrofossils and 210Pb analysis. The ??18O values of inorganic calcite (CaCO3) range from ?17.0 to ?15.7???, with the highest values during the period of 1450?C1850 AD, coeval with the well-documented Little Ice Age (LIA) cold interval in Alaska. The high ??18O values during the cold LIA are interpreted as reflecting shifts in atmospheric circulation. A weakening of the wintertime Aleutian low pressure system residing over the Gulf of Alaska during the LIA would have resulted in 18O-enriched winter precipitation as well as a colder and possibly drier winter climate in south-central Alaska. Also, elevated calcite contents of >80?% during the LIA reflect a lowering of lake level and/or enhanced seasonality (warmer summer and colder winter), as calcite precipitation in freshwater lakes is primarily a function of peak summer temperature and water depth. This interpretation is also supported by high ??13C values, likely reflecting high aquatic productivity or increased residence times of the lake water during lower lake levels. The lower lake levels and warmer summers would have increased evaporative enrichment in 18O, also contributing to the high ??18O values during the LIA. Our results indicate that changes in atmospheric circulation were an important component of climate change during the last millennium, exerting strong influence on regional climate in Alaska and the Arctic. 相似文献
4.
大型人工湖气候效应观测研究——以密云水库为例 总被引：2，自引：1，他引：1
应用近5 a自动气象站观测资料,分析了华北地区最大人工湖——密云水库的局地气候效应。结果表明：① 密云水库库区相比于附近平原地带具有气温偏低、湿度偏高、风速偏弱、降水量偏大等特点。水库对区域气候的影响范围约在10 km内,离水库越近的地方,受影响越大。② 密云水库的气候效应主要体现在夏半年,尤以气温和降水最为明显。③ 水库南、北两侧受到的局地环流的影响具有明显的差异,库区东西方向的年平均局地风速约为0.14 m/s,南北方向约为 0.10 m/s。下垫面属性的热力差异及特殊地形条件使得密云水库附近同时存在山谷风和湖陆风现象,其叠加效应是导致区域内不同位置间气象要素出现季节性及日变化差异的主要原因。 相似文献
5.
青海湖是国内最大的内陆湖泊,位于青藏高原东北缘,因其处在东亚夏季风、印度季风和西风带的交替控制区域,对气候变化十分敏感,成为古环境变化研究的热点地区。有关青海湖的形成演化、环境变化和水文变化的研究也存在多种观点。本研究再分析了青海湖已报道的古环境指标和气候模式模拟的夏季、冬季温度和降水变化,力图更加全面地理解青海湖全新世以来的古环境变化。研究发现早全新世11~8 ka夏季降水量和表面蒸发量较大,冬季降水稀少,湖泊水位只有十余米深,使得青海湖周边风沙活动频繁。并且,早全新世的气候不稳定,经历了频繁和较大幅度的波动。全新世气候适宜期出现在8~6 ka,古环境指标指示这一时期为温暖湿润的气候环境,湖盆内植被以森林草原为主,湖泊水位不断上升。青海湖地区的夏季降水自6 ka开始减少,然而冬季降水增加,同时夏季温度和蒸发量减少,使得湖区植被组成由森林草原向高山草甸转变,湖区大范围形成古土壤。湖区古环境条件在晚全新世距今1.5 ka开始恶化,冬季和夏季降水同时减少,湖泊水位下降,风沙活动再次加强。 相似文献
6.
巴丹吉林沙漠典型湖泊湖气界面水一热交换特征 总被引：1，自引：0，他引：1
利用2012年8月-2013年7月在巴丹吉林沙漠腹地典型湖泊上用涡动相关系统观测的湍流资料,分析了湍流方差统计特征、微气象特征,计算了湍流热通量和湖泊蒸发量,初步结论为：①湖面上局地环流复杂,湍流三维风速的标准差与稳定度(Z/L)之间满足1/3次律。②湖面辐射分量具有明显季节变化和日变化特征,结冰期和非结冰期能量分配不同,冬季湖泊将储存的能量向大气传递;潜热通量和感热通量季节变化存在差异,但均有明显的昼夜变化特征。③湖气界面的感热通量在不同的月份也存在差异,感热以湖泊向大气传递为主;潜热通量夏半年远大于冬半年,在一天中6:00-8:00时处于最低值,15:00-16:00时达到峰值,在冬季会出现潜热向下输送现象。感热通量和潜热通量日变化呈负相关,湖面有效能量主要分配给潜热,湖泊同周围环境以水汽交换为主。④湖面平均蒸发速率为3.97 mm/d,累计蒸发量为1450±10 mm/a,同期的蒸发量是降水量的20多倍,湖泊主要靠地下水补给。这些结论可为进一步研究巴丹吉林沙漠腹地湖泊群的水循环及补给来源提供参考。 相似文献
7.
8.
9.
In pal\sgmaelig;olimnological studies, inference models based on aquatic organisms are frequently used to estimate summer lake surface water temperatures. However, the calibration of such models is often unsatisfactory because of the sparseness of measured water temperature data. This study investigates the feasibility of using air temperature data, usually available at much higher resolution, to calibrate such models by comparing regional air temperatures with surface water temperatures in 17 lakes on the Swiss Plateau. Results show that altitude-corrected air temperatures are sufficiently uniform over the entire Swiss Plateau to allow local air temperatures at any particular lake site to be adequately estimated from standard composite air temperature series. In early summer, day-to-day variability in air temperature is reflected extremely well in the temperature of the uppermost metre of the water column, while monthly mean air temperatures correspond well, with respect to both absolute value and interannual variations, with water temperatures in most of the epilimnion. Standardised altitude-corrected air temperature series may therefore be a useful alternative to surface water temperatures for the purposes of calibrating lake temperature inference models. In Northern Hemisphere temperate regions, mean air and water temperatures are likely to correspond most closely in July, suggesting that calibration and reconstruction efforts be concentrated on this month. 相似文献
10.
区域性的湖泊水位能反映有效降水及气候变化,已成为重建第四纪降水和水量平衡最重要的指标。亚洲分布着几乎全球各种成因类型的湖泊,第四纪湖泊演化在全球第四纪研究中占有重要地位。多年来通过对地貌学、沉积学、生物地球化学和考古学的研究重建了各个区域的湖泊水位变化,并据此建立了湖泊演变数据库,作为研究第四纪亚洲区域气候变化的重要基础。本文介绍湖泊水位气候理论的发展历程,回顾晚第四纪亚洲湖泊水位研究的历史;分析晚第四纪亚洲从西到东不同区域湖泊水位变化历史和地域特征,并根据晚第四纪冰期和间冰期的两个特征期湖泊空间变化特征,从古气候模拟的角度探讨了气候驱动机制下湖泊水位变化的成因。 相似文献
11.
中国夏季高温日数时空变化及其环流背景 总被引：8，自引：1，他引：7
本研究利用1955~2005年全国193个气象站点夏季(5~9月)逐日最高气温资料,分析了我国东部地区夏季高温日数变化的空间分布特征和时间变化规律。经验正交函数分析结果显示高温日数的变化有明显的区域特征,第一模态表现为区域整体一致的异常,中心区位于长江中下游地区,第二模态表现为江淮流域与华南反向变化的特点,第三模态表现为东南部地区与西南、华北的反向变化。这些模态与高层大气环流的变化有关。分析表明ENSO(厄尔尼诺-南方涛动)、赤道印度洋和西太平洋暖池海温,可以通过影响西太平洋和东亚地区大气环流而影响我国夏季高温日数频次,其中ENSO和西太平洋暖池区海温对高温日数变化第一模态的相关比较明显;而热带印度洋海温对第二模态有显著影响。与前期海温的关系分析可知,第一模态与前期夏季的西太平洋暖池和前期冬季赤道东太平洋海温相关关系最好,第二模态则受热带印度洋前期冬季海温影响最大,这对高温预测具有指示意义。 相似文献
12.
北极阿拉斯加巴罗地区现代环境的地球化学特征研究* 总被引：2，自引：0，他引：2
本文以北极阿拉斯加巴罗地区样品分析为依据,研究泻湖、淡水湖、河流、沼泽、土壤等的环境地球化学特征。结果表明,巴罗地区融冻物理风化作用强烈,化学风化和生物地球化学作用较弱,物质以机械搬运为主,H+为地带性标型元素。地表水化学类型阴离子以Cl-为主,阳离子以K+Na+为主。现代沉积物、地表土壤、沼泽泥炭层有机质含量丰富,最高可达50.07%.大量元素SiO2含量极高,稀有稀土元素、微量元素含量偏低,但Hg、Cd、Cr的含量相对较高。 相似文献
13.
A survey of the modern physical setting of Lake El’gygytgyn, northeastern Siberia, is presented here to facilitate interpretation
of a 250,000-year climate record derived from sediment cores from the lake bottom. The lake lies inside a meteorite impact
crater that is approximately 18 km in diameter, with a total watershed area of 293 km2, 110 km2 of which is lake surface. The only surface water entering the lake comes from the approximately 50 streams draining from
within the crater rim; a numbering system for these inlet streams is adopted to facilitate scientific discussion. We created
a digital elevation model for the watershed and used it to create hypsometries, channel networks, and drainage area statistics
for each of the inlet streams. Many of the streams enter shallow lagoons dammed by gravel berms at the lakeshore; these lagoons
may play a significant role in the thermal and biological dynamics of the lake due to their higher water temperatures (>6°C).
The lake itself is approximately 12 km wide and 175 m deep, with a volume of 14.1 km3. Water temperature within a column of water near the center of this oligotrophic, monomictic lake never exceeded 4°C over
a 2.5 year record, though the shallow shelves (<10 m) surrounding the lake can reach 5°C in summer. Though thermally stratified
in winter, the water appears completely mixed shortly after lake ice breakup in July. Mean annual air temperature measured
about 200 m from the lake was −10.3°C in 2002, and an unshielded rain gage there recorded 70 mm of rain in summer of 2002.
End of winter snow water equivalent on the lake was approximately 110 mm in May 2002. Analysis of NCEP reanalysis air temperatures
(1948–2002) reveals that the 8 warmest years and 10 warmest winters have occurred since 1989, with the number of days below
−30°C dropping from a pre-1989 mean of 35 to near 0 in recent years. The crater region is windy as well as cold, with hourly
wind speeds exceeding 13.4 m s−1 (30 mph) typically at least once each month and 17.8 m s−1 (40 mph) in winter months, with only a few calm days per month; wind may also play an important role in controlling the modern
shape of the lake. Numerous lines of evidence suggest that the physical hydrology and limnology of the lake has changed substantially
over the past 3.6 million years, and some of the implications of these changes on paleoclimate reconstructions are discussed.
This is the second in a series of eleven papers published in this special issue dedicated to initial studies of El'gygytgyn Crater Lake and
its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue. 相似文献
14.
重建黄旗海水位、水化学和湖泊生物学变化历史可为研究我国夏季风边缘区冰后期气候变化提供重要环境记录。对该湖中央HQH4岩芯研究结果显示,末次冰期晚期沉积物中湖泊自生有机质烧失量和自生碳酸盐烧失量的平均值分别仅为全新世沉积物的1/13和1/5,造成这种结果的主导因素是夏季气温在全新世初显著升高和黄旗海从此进入稳定的湖泊环境。晚全新世自生碳酸盐烧失量平均值比早、中全新世低14%,其最大值也明显低于早、中全新世,这种情况很可能是因为晚全新世夏季温度略低于早、中全新世所致。自生有机质和碳酸盐烧失量是快速、经济地获取闭流型半咸水湖泊冰后期环境变化的有效代用指标。 相似文献
15.
1974—2009年西藏羊卓雍错湖泊水位变化分析 总被引：3，自引：0，他引：3
羊卓雍错(简称羊湖)是青藏高原南部最大的一个封闭型内陆湖泊,位于西藏自治区浪卡子县境内,与纳木错、玛旁雍错一起并列为西藏三大圣湖,是藏南地区重要的风景旅游区。始建于1989年的羊湖发电站于1997年正式投入运营,为世界上海拔最高的抽水蓄能电站。在全球气候变暖和人类活动的影响下,其湖面水位变化及其成因备受国内外关注。利用1974—2009年羊湖白地水文观测资料,分析了36年来羊湖水位年际、年内变化特征及其与自然要素(气温、降水和蒸发等)和人类活动之间的关系。结果表明,羊湖平均水位为19.06 m,历史最高值出现在1980年,为21.37 m,2009年水位降至17.08 m的历史最低值。自1974年有水位观测资料以来,羊湖水位呈波动式下降趋势,其中,1974—1977年水位表现为逐年下降,幅度为0.26 m/a;之后至1980年以0.4 m/a呈上升态势,1980年羊湖水位达到了历史最高值;此后,至1996年水位呈显著下降趋势,减少速率为2.08 m/(10 a),1996年是羊湖水位上升的一个转折点,至2004年水位在逐年上升;2004—2009年是一个水位显著下降的时段,速率为0.57 m/a,也是水位下降趋势最为显著的时段。羊湖水位下降年份占整个时段的56%,而44%的年份水位在上升。1974—1984年及2001—2005年水位高于多年平均值,而1985—2000年及2006年之后水位都低于多年平均值。羊湖水位的年内最低值一般出现在6月,最高值则在10月。羊湖年内水位变化对流域降水量的响应具有一定的滞后性,时间为2个月左右。羊湖水位变化主要是由降水波动、气温上升、蒸发的变化等自然因素共同作用的结果,特别是,流域年际降水量波动是湖面水位升降的主要影响因子,人为和工程的影响范围和程度均较小。自羊湖电站1997年运行以来,流域的环境在暖湿的气候大背景下有所改善,且对羊湖水位变化无明显影响。但如果电站不能蓄水与发电并举,达不到总体不消耗羊湖水量的设计目标和水量平衡,对羊湖水位的影响将不可忽视。 相似文献
16.
为了更准确的掌握乌鲁木齐地区夏季气象干旱的变化特征并研究其成因,以乌鲁木齐地区5个站点的历史降水资料为基础,统计得到其1961-2015年夏季累积降水在100～250 mm范围内变化,并通过计算Z指数来表征干旱变化特征,利用Mann-Kendall检验和Morlet小波分析归纳了乌鲁木齐夏季气象干旱在1980年代中期的突变特征以及1986年以来12 a左右的周期性变化特征。在此基础上结合NCEP/NCAR再分析资料、JRA海表温度（SST）等数据,通过对比典型旱/涝年的异常特征,对夏季气象干旱发生的成因进行了分析,发现低纬东风输送强时水汽可由80°～90°E向北越过青藏高原影响新疆地区,反之则包括乌鲁木齐在内的天山以北地区可降水量都偏少,并且指出赤道东太平洋SST异常所导致的赤道纬向垂直环流异常是导致这一差异的可能成因。此外还对乌鲁木齐夏季气象干旱与大气环流指数存在的关联进行了讨论。这些结果为乌鲁木齐降水机理研究以及气候预报提供了重要依据,并为人工影响天气和抗旱减灾工作提供了有力支撑。 相似文献
17.
Martin Melles Julie Brigham-Grette Olga Yu. Glushkova Pavel S. Minyuk Norbert R. Nowaczyk Hans-W. Hubberten 《Journal of Paleolimnology》2007,37(1):89-104
The ca. 13 m long sediment core PG1351, recovered in 1998 from the central part of Lake El’gygytgyn, NE Siberia, was investigated
for lithostratigraphy, water content, dry bulk density (DBD), total organic carbon (TOC), total nitrogen (TN), total sulphur
(TS) and biogenic silica (opal) contents, and for TOC stable isotope ratios (δ13CTOC). The event stratigraphy recorded in major differences in sediment composition match variations in regional summer insolation,
thus confirming a new age model for this core, which suggests that it spans the last 250 ka BP. Four depositional units of
contrasting lithological and biogeochemical composition have been distinguished, reflecting past environmental conditions
associated with relatively warm, peak warm, cold and dry, and cold but more moist climate modes. A relatively warm climate,
resulting in complete summer melt of the lake ice cover and seasonal mixing of the water column, prevailed during the Holocene
and Marine Isotope Stages (MIS) 3, 5.1, 5.3, 6.1, 6.3, 6.5, 7.1–7.3, 7.5, 8.1 and 8.3. MIS 5.5 (Eemian) was characterized
by significantly enhanced aquatic primary production and organic matter supply from the catchment, indicating peak warm conditions.
During MIS 2, 5.2, 5.4, 6.2 and 6.4 the climate was cold and dry, leading to perennial lake ice cover, little regional snowfall,
and a stagnant water body. A cold but more moist climate during MIS 4, 6.6, 7.4, 8.2 and 8.4 is thought to have produced more
snow cover on␣the perennial ice, strongly reducing light penetration and biogenic primary production in␣the lake. While the
cold–warm pattern during␣the past three glacial–interglacial cycles is probably controlled by changes in regional summer insolation,
differences in the intensity of the warm phases and in the degree of aridity (changing snowfall) during cold phases likely
were due to changes in atmospheric circulation patterns.
This is the seventh in a series of eleven papers published in this special issue dedicated to initial studies of El'gygytgyn Crater Lake and
its catchment in NE Russia. JulieBrigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue. 相似文献
18.
末次冰盛期时吉兰泰盐湖的湖泊状态与古气候特征 总被引：1，自引：1，他引：0
通过现代季风边缘区的吉兰泰盐湖钻孔JLT11-A孔沉积岩芯的矿物分析,结合地层盘星藻的含量探讨末次冰盛期(LGM)时湖泊的状态和古气候特征。结果显示:在LGM时吉兰泰湖泊沉积矿物主要是石英、长石为主的碎屑岩沉积,含量在85%左右,显示出陆源碎屑矿物的高输入状态,可能指示区域寒冷干旱的环境;其次是以方解石为主的碳酸盐的沉积,含量约为10%;氯化物为主的石盐类矿物一般不足5%,但持续存在,指示湖泊仍然有较高的盐度,因此地层中的淡水藻类盘星藻可能是由河流输入。由于陆源碎屑矿物输入强烈,矿物组合可能难以直接指示吉兰泰盐湖湖水状态。区域的干冷的气候与大多数的古气候记录一致,而与新疆西部的冷湿的环境不同。对比邻近区域的古气候研究结果发现,本区域在LGM时段夏季降水相对于冰消期偏多,而相对于MIS3阶段晚期偏少,整体夏季风减弱。吉兰泰盐湖末次冰盛期到末次冰消期以来矿物组合的变化表明,湖泊环境可能受到夏季太阳辐射、全球与区域温度变化以及夏季风强弱变化的影响。 相似文献
19.
Georg Schettler Qiang Liu Jens Mingram Jörg F. W. Negendank 《Journal of Paleolimnology》2006,35(2):239-270
The varved sediments of the dimictic Lake Sihailongwan (Long Gang mountain area, Jilin Province, Northeast China) represent
a palaeoclimatic archive which documents the local precipitation frequency during the summer monsoon, and variations in the
aeolian flux of dust with their remote sources in the arid and semi-arid regions of inner Asia. Based on a detailed discussion
of sediment genesis in Lake SHL, dust flux rates and palaeohydrological conditions were reconstructed on a decadal scale over
the past 220 years. The aeolian influx by dry and wet deposition was quantified and characterised in its chemical composition.
Photosynthetic production in the lake is positively correlated with the inflow of nutrient-rich groundwater. The groundwater
discharge largely reflects the strength of the summer monsoon. Net accumulation rates for biogenic silica were determined
for annually laminated sediments from the centre of the U-shaped lake basin based on sediment data. In a Si-balance model
of the modern lake, the depositional flux of biogenic silica could be independently quantified on the base of hydrochemical
monitoring data. Comparison of the both estimates allowed to asses the focussing of the particle flux in the lake. Though
water retention in Lake SHL is rather high (ca. 30 years), changes in the hydrological conditions are sensitively recorded
in the sediments because (i) nutrient-rich groundwater discharges into the productive zone of the lake, (ii) a substantial
proportion of the total dissolved Si-inventory of the mixed lake (ca. 30%) is annually consumed by diatom growth, and (3)
sediment accumulation is substantially focussed towards the flat bottom of the lake basin. The bulk siliciclastic sediment
fraction (ca. 75 wt.%) largely originates from influx of dust of remote provenance. In sediment thin-sections, the dry-deposited
dust fraction is microscopically identifiable as seasonal silt layer. Aeolian input by wet-deposition shows a distinctly higher
variability than the influx of dust by dry-deposition. As diatom production, wet-deposition of dust is positively correlated
with the rainfall during the summer monsoon. The inferred positive correlation between rainfall and dust flux during the summer
monsoon implies that dust deposition is determined by the out-wash efficiency of mineral particles for a permanent high atmospheric
dust concentration over Northeast China in the last 220 years. 相似文献
20.
西藏羊卓雍湖流域近45 年气温和降水的变化趋势 总被引：4，自引：0，他引：4
利用西藏羊卓雍湖流域气象、水文观测站1961-2005 年逐月的平均气温、降水量等资 料, 分析了近45 年流域气温、降水的年际和年代际变化特征和异常年份, 以及羊湖水位变化趋势及影响因子, 结果表明： 近45 年流域年平均气温以0.25 oC/10a 的速率显著升高, 增温主要表现在秋、冬季。近25 年, 流域平均降水量除冬季呈减少趋势外, 其他各季节表现为显 著的增加趋势, 增幅为11.4~30.0 mm/10a, 夏季增幅最大; 年降水量以54.2 mm/10a 的速率明显增加。20 世纪60 年代至90 年代, 除夏季外, 其他3 季表现为逐年代增温趋势。在夏季, 降水量除80 年代偏少外, 其他3 个年代偏多; 而冬季相反, 80 年代降水偏多, 其他3 个年代偏少。流域年平均气温异常偏高年出现过3 次, 且发生在20 世纪90 年代末至21 世纪初; 60 年代后期和70 年代初降水多异常年份。自1997 年发电以来, 降水量呈增加趋势, 流域平均降水量达409.7 mm, 明显高于平衡降水量, 水位呈较明显的上升趋势。降水增多、日照减少, 以及气温明显升高、冰雪融水增加是造成水位上升的主要原因。 相似文献