近50年玛纳斯河流域径流变化规律研究

玛纳斯河流域上游山区形成的径流是供给中下游平原区和玛纳斯绿洲的重要水源.文中利用玛纳斯河上游2个水文站和4个雨量站1956～2006年系列径流和降水资料,利用多种指标和小波分析法分析径流年内、年际变化特征.结果表明:玛纳斯河上游流域径流年内分配不均匀,主要集中在6～8月份,占多年平均流量的66.9%～70.3%;径流年...     

Monthly and seasonal streamflow forecasting of large dryland catchments in Brazil

Streamflow forecasting in drylands is challenging.Data are scarce,catchments are highly humanmodified and streamflow exhibits strong nonlinear responses to rainfall.The goal of this study was to evaluate the monthly and seasonal streamflow forecasting in two large catchments in the Jaguaribe River Basin in the Brazilian semi-arid area.We adopted four different lead times:one month ahead for monthly scale and two,three and four months ahead for seasonal scale.The gaps of the historic streamflow series were filled up by using rainfall-runoff modelling.Then,time series model techniques were applied,i.e.,the locally constant,the locally averaged,the k-nearest-neighbours algorithm(k-NN)and the autoregressive(AR)model.The criterion of reliability of the validation results is that the forecast is more skillful than streamflow climatology.Our approach outperformed the streamflow climatology for all monthly streamflows.On average,the former was 25%better than the latter.The seasonal streamflow forecasting(SSF)was also reliable(on average,20%better than the climatology),failing slightly only for the high flow season of one catchment(6%worse than the climatology).Considering an uncertainty envelope(probabilistic forecasting),which was considerably narrower than the data standard deviation,the streamflow forecasting performance increased by about 50%at both scales.The forecast errors were mainly driven by the streamflow intra-seasonality at monthly scale,while they were by the forecast lead time at seasonal scale.The best-fit and worst-fit time series model were the k-NN approach and the AR model,respectively.The rainfall-runoff modelling outputs played an important role in improving streamflow forecasting for one streamgauge that showed 35%of data gaps.The developed data-driven approach is mathematical and computationally very simple,demands few resources to accomplish its operational implementation and is applicable to other dryland watersheds.Our findings may be part of drought forecasting systems and potentially help allocating water months in advance.Moreover,the developed strategy can serve as a baseline for more complex streamflow forecast systems.     

新疆哈密石城子河流域水文水资源分析

不同地区的自然地理环境塑造了不同特征的河流,同时,河流的活动也在不断改变着与自身有关的自然环境。我国暖温带干旱区除塔里木河流域的水文特征、水资源及其合理利用有较多的研究外,其余中小河流的研究甚少。哈密石城子河的水文特征基本反映了我国暖温带干旱区众多中小河流域的水文特征。利用石城子河流域水文气象站1956-2001年资料,对该流域径流形成、洪水、泥沙、水质等进行分析,以揭示我国暖温带干旱区中小河流域的基本特征,为科学利用该地带中小河流域水资源提供理论依据。     

Climate change impacts on the streamflow of Zarrineh River,Iran

Zarrineh River is located in the northwest of Iran, providing more than 40% of the total inflow into the Lake Urmia that is one of the largest saltwater lakes on the earth. Lake Urmia is a highly endangered ecosystem on the brink of desiccation. This paper studied the impacts of climate change on the streamflow of Zarrineh River. The streamflow was simulated and projected for the period 1992-2050 through seven CMIP5 (coupled model intercomparison project phase 5) data series (namely, BCC-CSM1-1, BNU-ESM, CSIRO-Mk3-6-0, GFDL-ESM2G, IPSL-CM5A-LR, MIROC-ESM and MIROC-ESM-CHEM) under RCP2.6 (RCP, representative concentration pathways) and RCP8.5. The model data series were statistically downscaled and bias corrected using an artificial neural network (ANN) technique and a Gamma based quantile mapping bias correction method. The best model (CSIRO-Mk3-6-0) was chosen by the TOPSIS (technique for order of preference by similarity to ideal solution) method from seven CMIP5 models based on statistical indices. For simulation of streamflow, a rainfall-runoff model, the hydrologiska byrans vattenavdelning (HBV-Light) model, was utilized. Results on hydro-climatological changes in Zarrineh River basin showed that the mean daily precipitation is expected to decrease from 0.94 and 0.96 mm in 2015 to 0.65 and 0.68 mm in 2050 under RCP2.6 and RCP8.5, respectively. In the case of temperature, the numbers change from 12.33°C and 12.37°C in 2015 to 14.28°C and 14.32°C in 2050. Corresponding to these climate scenarios, this study projected a decrease of the annual streamflow of Zarrineh River by half from 2015 to 2050 as the results of climatic changes will lead to a decrease in the annual streamflow of Zarrineh River from 59.49 m³/s in 2015 to 22.61 and 23.19 m³/s in 2050. The finding is of important meaning for water resources planning purposes, management programs and strategies of the Lake's endangered ecosystem.     

Long-term variations in runoff of the Syr Darya River Basin under climate change and human activities

In this study,we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930–2015 to investigate variations in river runoff and the impacts of climate change and human activities on river runoff.The Syr Darya River,which is supplied by snow and glacier meltwater upstream,is an important freshwater source for Central Asia,as nearly half of the population is concentrated in this area.River runoff in this arid region is sensitive to climate change and human activities.Therefore,estimation of the climatic and hydrological changes and the quantification of the impacts of climate change and human activities on river runoff are of great concern and important for regional water resources management.The long-term trends of hydrological time series from the selected 11 hydrological stations in the Syr Darya River Basin were examined by non-parametric methods,including the Pettitt change point test and Mann-Kendall trend tests.It was found that 8 out of 11 hydrological stations showed significant downward trends in river runof f.Change of river runoff variations occurred in the year around 1960.Moreover,during the study period(1930–2015),annual mean temperature,annual precipitation,and annual potential evapotranspiration in the river basin increased substantially.We employed hydrological sensitivity method to evaluate the impacts of climate change and human activities on river runoff based on precipitation and potential evapotranspiration.It was estimated that human activities accounted for over 82.6%–98.7%of the reduction in river runoff,mainly owing to water withdrawal for irrigation purpose.The observed variations in river runoff can subsequently lead to adverse ecological consequences from an ecological and regional water resources management perspective.     

图们江干流区间流域径流变化特征

以图们江干流区间为研究对象，应用Mann-Kendall非参数检验法分析干流区间4个水文站点径流年际与年内变化趋势。在此基础上，采用R/S分析方法分析年径流、季节径流和月径流变化趋势在未来的可持续性，利用Mann-Kendall突变检验方法分析各水文站点年径流、季节径流和月径流发生突变的年份。结果表明：图们江干流区间各水文站径流年际和年内变化趋势均与干流径流变化趋势一致，呈下降趋势，非汛期径流下降的贡献主要来自春季和冬季径流的下降；Hurst指数表明，上游径流变化趋势的持续性最强，下游的持续性相对较弱；1985年是图们江干流区间年径流发生突变的年份，且降水量也发生了变化，可以推测降水量可能是径流不断减少的重要因素。     

Impacts of temperature and precipitation on runoff in the Tarim River during the past 50 years

The relationship between climate change and water resources in the Tarim River was analyzed by combining the temperature,precipitation and streamflow data from 1957 to 2007 from the four headstreams of the Tarim River (Aksu,Hotan,Yarkant and Kaidu rivers) in the study area.The long-term trend of the hydrological time series including temperature,precipitation and streamflow were studied using correlation analysis and partial correlations analysis.Holt double exponential smoothing was used to fit the trends between streamflow and the two climatic factors of Aksu River,Hotan River and Yarkant River.The streamflow of the main stream was forecasted by Autoregressive Integrated Moving Average Model (ARIMA) modeling by the method of time series analysis.The results show that the temperature experienced a trend of monotonic rising.The precipitation and runoff of the four headstreams of the Tarim River increased,while the inflow to the headstreams increased and the inflow into the Tarim River decreased.Changes of temperature and precipitation had a significant impact on runoff into the four headstreams of the Tarim River: the precipitation had a positive impact on water flow in the Aksu River,Hotan River and Kaidu River,while the temperature had a positive impact on water flow in the Yarkant River.The results of Holt double exponential smoothing showed that the correlation between the independent variable and dependent variable was relatively close after the model was fitted to the headstreams,of which only the runoff and temperature values of Hotan River showed a significant negative correlation.The forecasts by the ARIMA model for 50 years of annual runoff at the Allar station followed the pattern of the measured data for the same years.The short-term forecasts beyond the observed series adequately captured the pattern in the data and showed a decreasing tendency in the Tarim River flow of 3.07% every ten years.The results showed that global warming accelerated the water recharge process of the headstreams.The special hydrological characteristics of the arid area determined the significant association between streamflow and the two climatic factors studied.Strong glacier retreat is likely to bring a series of flood disasters within the study area.     

潮白河流域气象水文干旱特征及其响应关系

利用潮白河流域7个气象站1960-2011年逐月降水以及密云水库同时期入库流量数据,分别以SPI和SDI两个干旱指标表征气象、水文干旱,采用游程理论、M-K检验、滑动t-检验、Spearman秩相关检验等方法研究了该流域气象水文干旱特征,并探求水文、气象干旱的响应关系。结果表明：研究期内潮白河流域气象干旱多以短历时干旱事件为主,历时1-2个月的干旱事件达研究期内气象干旱事件总次数的67.18%;但是气象干旱的年干旱烈度及其历时未通过MK趋势显著性检验,其线性斜率值仅为-0.025和-0.005,变化趋势不明显。而水文干旱存在极长历时重烈度干旱事件,历时达4个月以上的干旱事件达研究期内水文干旱事件总次数的46.54%,最长干旱历时达45个月;且研究期内水文干旱的年干旱烈度及其历时均通过显著性检验,线性斜率值达-0.419和0.228,变化显著;二者均在1980年和1998年出现突变现象。自20世纪90年代末以来,潮白河流域水文干旱频繁发生,且多为长历时连续干旱。研究期内水文干旱滞后气象干旱约1个月。     

Flow regime changes in three catchments with different landforms following ecological restoration in the Chinese Loess Plateau

The Chinese Loess Plateau is known as one of the most severe soil erosion regions in the world.Two ecological restoration projects,i.e.,the integrated soil conservation project since the 1970s and the'Grain for Green'project since 1999,have been progressively implemented to control the soil erosion in this area.Ecological restoration has greatly changed flow regime over the past five decades.However,the mechanism of how flow regime responds to ecological restoration among landforms remains poorly understood.In this study,we investigated the temporal dynamics of flow regime in three catchments,i.e.,Wuqi,Honghe and Huangling hydrological stations,respectively representing the loess hilly-gully,loess table-gully and rocky mountain(covered by secondary forest)areas in the Chinese Loess Plateau,using daily hydrological data during the 1960s–2010s.The nonparametric Mann-Kendall test,Pettitt's test and daily flow series were used to investigate the changes of flow regime.Significantly negative trends of annual streamflow were detected at the Wuqi and Honghe stations,except for the Huangling station.The annual baseflow at the Wuqi station showed a significantly positive trend whereas a significantly negative trend was observed at the Honghe station,and there was no significant trend at the Huangling station.It was interesting that baseflow index significantly increased during the whole period in all catchments.However,the trends and change points of daily flow series derived by different percentages of exceedance and extreme series in different consecutive days varied among individuals.Based on the change points analysis of annual streamflow,we divided data series into three periods,i.e.,the baseline period(from 1959 and 1963 to 1979,PI),the integrated soil conservation period(1980–1999,PII)and the'Grain for Green'period(2000–2011,PIII).We found that streamflow decreased due to the reduction of high streamflow(exceeding 5%of time within a year)and median streamflow(50%)in PII and PIII at the Wuqi and Honghe stations.However,low flow(95%)increased in PII and PIII at the Wuqi station while decreased at the Honghe station.Streamflow change at the Huangling station was more stable,thus potentially resulting in much less soil erosion in the forestry area than in the other areas.The great improvement in ecological environment on the Chinese Loess Plateau revealed the advantages of ecological restoration in reducing flood amount and compensating streamflow at a regional scale.     

气候变化与人类活动对共和盆地生态环境的影响

利用共和盆地共和、贵南2个气象站1961～2006年46年逐月平均气温和降水量资料,分析了年和四季的气候特征及气候变化趋势,并对气候突变进行了检验.结果表明:近46年来共和盆地表现出气温升高、降水量呈微弱增加、地表蒸发量增大的变化趋势,并且在20世纪90年代后期变化趋势更加明显.这种气候变化趋势加速了共和盆地草地退化和沙化,同时人类活动又加剧了共和盆地草地的退化和沙化趋势.     

Glacier mass balance and its impacts on streamflow in a typical inland river basin in the Tianshan Mountains,northwestern China

Glaciers are known as natural 'solid reservoirs', and they play a dual role between the composition of water resources and the river runoff regulation in arid and semi-arid areas of China. In this study, we used in situ observation data from Urumqi Glacier No. 1, Xinjiang Uygur Autonomous Region, in combination with meteorological data from stations and a digital elevation model, to develop a distributed degree-day model for glaciers in the Urumqi River Basin to simulate glacier mass balance processes and quantify their effect on streamflow during 1980-2020. The results indicate that the mass loss and the equilibrium line altitude (ELA) of glaciers in the last 41 years had an increasing trend, with the average mass balance and ELA being -0.85 (±0.32) m w.e./a (meter water-equivalent per year) and 4188 m a.s.l., respectively. The glacier mass loss has increased significantly during 1999-2020, mostly due to the increase in temperature and the extension of ablation season. During 1980-2011, the average annual glacier meltwater runoff in the Urumqi River Basin was 0.48×10⁸ m³, accounting for 18.56% of the total streamflow. We found that the annual streamflow in different catchments in the Urumqi River Basin had a strong response to the changes in glacier mass balance, especially from July to August, and the glacier meltwater runoff increased significantly. In summary, it is quite possible that the results of this research can provide a reference for the study of glacier water resources in glacier-recharged basins in arid and semi-arid areas.     

Hydrological response to land use and land cover changes in a sub-watershed of West Liaohe River Basin,China

In recent years, the streamflow of the Laohahe Basin in China showed a dramatic decrease during the rainy season as a result of climate change and/or human activities. The objective of this work was to document significant streamflow changes caused by land use and land cover （LULC） changes and to quantify the impacts of the observed changes in Laohahe Basin. in the study area, the observed streamflow has been influenced by LULC changes, dams, and irrigation from rivers, industry, livestock and human consumption. Most importantly, the growth of population and gross domestic product （GDP） accompanied by the growth in industrial and agricultural activities, which led to LULC changes with increased residential land and cropland and decreased grassland since 2000s. Statistical methods and Variable Infiltration Capacity （VIC） hydrological model were used to estimate the effects of climate change and LULC changes on streamflow and evaportranspiration lET）. First, the streamflow data of the study area were divided into three sub-periods according to the Pettitt test. The hydrological process was then simulated by VIC model from 1964 to 2009. Furthermore, we compared the simulated results based on land use scenarios in 1989, 1999 and 2007, respectively for exploring the effect of LULC changes on the spatio-temporal distribution of streamflow and ET in the Laohahe Basin. The results suggest that, accompanied with climate change, the LULC changes and human water consumption appeared to be the most likely factors contributing to the sig- nificant reduction in streamflow in the Laohahe Basin by 64% from1999 to 2009.     

近50年来喀什噶尔河流域气温、降水及径流的变化趋势

应用喀什噶尔河流域内7个气象站、3个水文站的观测资料,分析了全流域、平原区和帕米尔高原的气温、降水以及出山口控制站年径流量的变化特征.结果显示:①从20世纪90年代开始,喀什噶尔河全流域以及平原区和帕米尔高原的年以及冬、秋季明显增暖,近5年春季迅速增温.从90年代起,全流域与高原区的年降水量明显增加,近5年平原区也明显增加;自90年代起全流域的春季、夏季降水明显增加,而近5年秋、冬季增湿迅速;近5年平原区的秋、春季以及冬季降水增加明显,高原区却以夏、秋季增湿最明显.②喀什噶尔河全流域以及平原区和帕米尔高原的年气温与降水量都呈显著的线性增加趋势.平原区的秋、冬季气温显著上升,冬季最明显,夏季呈不显著的下降趋势;平原区的四季降水呈不显著的上升趋势.帕米尔高原的夏、秋、冬季气温呈显著的上升趋势,秋季最明显;帕米尔高原的四季降水呈上升趋势,只有夏季的增湿趋势较显著.③喀什噶尔河年径流量(3站合计)近47年来呈显著的线性上升趋势,以3.0%·(10 a)-1的速率增加.流域内3条河流情况有所不同,克孜河径流量的线性增加趋势最明显,而盖孜河呈不显著的下降趋势.     

Spatio-temporal variation of hydrological drought under climate change during the period 1960–2013 in the Hexi Corridor,China

In recent years, climate change has been aggravated in many regions of the world. The Hexi Corridor is located in the semiarid climate zone of Northwest China, which is particularly affected by climate change. Climate change has led to the spatial and temporal variations of temperature and precipitation, which may result in hydrological drought and water shortage. Thus, it is necessary to explore and assess the drought characteristics of river systems in this area. The patterns of hydrological drought in the Hexi Corridor were identified using the streamflow drought index(SDI) and standardized precipitation index at 12-month timescale(SPI12) from 1960 to 2013. The evolution of drought was obtained by the Mann–Kendall test and wavelet transform method. The results showed that both the mean annual SDI and SPI12 series in the Hexi Corridor exhibited an increasing trend during the study period. According to the results of wavelet analysis, we divided the study period into two segments, i.e. before and after 1990. Before 1990, the occurrence of droughts showing decreased SDI and SPI12 was concentrated in the northern part of the corridor and shifted to the eastern part of the corridor after 1990. The probability of drought after 1990 in Shule River basin decreased while increased in Shiyang River basin. The wavelet analysis results showed that Shiyang River basin will be the first area to go through the next drought period. Additionally, the relationships between drought pattern and climate indices were analyzed. The enhanced westerly winds and increased precipitation and glacier runoff were the main reasons of wet trend in the Hexi Corridor. However, the uneven spatial variations of precipitation, temperature and glacier runoff led to the difference of hydrological drought variations between the Shule, Heihe and Shiyang River basins.     

Impact of climate change on the streamflow in the glacierized Chu River Basin,Central Asia

Catchments dominated by meltwater runoff are sensitive to climate change as changes in precipitation and temperature inevitably affect the characteristics of glaciermelt/snowmelt, hydrologic circle and water resources. This study simulated the impact of climate change on the runoff generation and streamflow of Chu River Basin(CRB), a glacierized basin in Central Asia using the enhanced Soil and Water Assessment Tool(SWAT). The model was calibrated and validated using the measured monthly streamflow data from three discharge gauge stations in CRB for the period 1961–1985 and was subsequently driven by downscaled future climate projections of five Global Circulation Models(GCMs) in Coupled Model Inter-comparison Project Phase 5(CMIP5) under three radiative forcing scenarios(RCP2.6, RCP4.5 and RCP8.5). In this study, the period 1966–1995 was used as the baseline period, while 2016–2045 and 2066–2095 as the near-future and far-future period, respectively. As projected, the climate would become warmer and drier under all scenarios in the future, and the future climate would be characterized by larger seasonal and annual variations under higher RCP. A general decreasing trend was identified in the average annual runoff in glacier(–26.6% to –1.0%), snow(–21.4% to +1.1%) and streamflow(–27.7% to –6.6%) for most of the future scenario periods. The projected maximum streamflow in each of the two future scenarios occurred one month earlier than that in the baseline period because of the reduced streamflow in summer months. Results of this study are expected to arouse the serious concern about water resource availability in the headwater region of CRB under the continuously warming climate. Changes in simulated hydrologic outputs underscored the significance of lowering the uncertainties in temperature and precipitation projection.     

Reconstruction of hydrological changes based on tree-ring data of the Haba River,northwestern China

Reconstructing the hydrological change based on dendrohydrological data has important implications for understanding the dynamic distribution and evolution pattern of a given river. The widespread, long-living coniferous forests on the Altay Mountains provide a good example for carrying out the dendrohydrological studies. In this study, a regional composite tree-ring width chronology developed by Larix sibirica Ledeb. and Picea obovata Ledeb. was used to reconstruct a 301-year annual(from preceding July to succeeding June) streamflow for the Haba River, which originates in the southern Altay Mountains, Xinjiang, China. Results indicated that the reconstructed streamflow series and the observations were fitting well, and explained 47.5% of the variation in the observed streamflow of 1957–2008. Moreover, floods and droughts in 1949–2000 were precisely captured by the streamflow reconstruction. Based on the frequencies of the wettest/driest years and decades, we identified the 19 th century as the century with the largest occurrence of hydrological fluctuations for the last 300 years. After applying a 21-year moving average, we found five wet(1724–1758, 1780–1810, 1822–1853, 1931–1967, and 1986–2004) and four dry(1759–1779, 1811–1821, 1854–1930, and 1968–1985) periods in the streamflow reconstruction. Furthermore, four periods(1770–1796, 1816–1836, 1884–1949, and 1973–1997) identified by the streamflow series had an obvious increasing trend. The increasing trend of streamflow since the 1970s was the biggest in the last 300 years and coincided with the recent warming-wetting trend in northwestern China. A significant correlation between streamflow and precipitation in the Altay Mountains indicated that the streamflow reconstruction contained not only local, but also broad-scale, hydro-climatic signals. The 24-year, 12-year, and 2.2–4.5-year cycles of the reconstruction revealed that the streamflow variability of the Haba River may be influenced by solar activity and the atmosphere–ocean system.     

阿克苏地区库玛拉克河流域融雪洪水分型及成因

利用E0S/MODIS卫星资料和气象水文台站观测资料,对2002-2008年库玛拉克河流域融雪期的洪水成因、积雪变化与气象因子的相互关系以及混合型和融雪型洪水的天气特性等进行了分析.结果表明:①库玛拉克河7月中旬至8月中旬洪水的主要成因是高温融雪;②夏季0℃层高度的变化可作为融雪型洪水预测的较好指标;③盛夏库玛拉克河流...     

基于改进RVA法的黑河上游水文情势变化分析

客观地评价水文情势变化是进行河流生态修复和流域水资源综合管理的基础。改进RVA法将径流典型年份的变化纳入整体改变度的计算过程中,相对更全面地评价径流水文情势的变化。近几十年来黑河流域气候条件的发生显著变化,黑河上游河流水文情势的变化情况仍需进一步研究。以黑河上游为研究区域,应用M-K检验识别径流的突变年份,采用改进RVA法计算分析黑河上游河流水文情势变化。结果表明,黑河上游径流的突变年份为2002年,2002年前后分别以平水年和丰水年为主;采用RVA法计算的整体改变度为54.68%,而改进的RAV方法计算的整体改变度为74.62%,说明RVA法低估了黑河上游水文情势整体改变度;黑河上游径流水文情势变化主要包括:相比于1960—2002年,2003—2015年后各月平均流量均呈不同程度增加,但最小1日、3日、7日和最大7日流量减小,其余极端流量指标呈不同程度增加,高、低流量发生次数及历时变化微弱,流量平均增加率、减小率以及逆转次数均增加;采用改进的RVA法计算的黑河上游水文情势的整体改变度为74.62%,属于高度改变。气候变化是导致黑河上游水文情势高度改变的主要原因。     

基于ITPCAS再分析资料中国近地面风速时空变化特征

准确分析中国近地面风速时空变化规律对区域气候变化、蒸散发的估算、雾霾预报等研究具有重要意义。本文利用1979-2015年ITPCAS再分析资料的近地面风速(10 m)与中国110个气象站点的风速资料,分析该数据集在中国区域的适用性,并对2011-2012年风速数据进行修正,分析该区域近地面风速的时空变化特征。结果表明:①ITPCAS再分析数据集风速资料基本满足应用要求,但部分数据需修正。修正后的风速数据模拟精度得到较大提高,具有较好的应用前景,特别是在西北高寒、干旱地区;②1979-2015年中国62.12%的区域风速为下降趋势,全国平均风速每10 a变化速率为-0. 073 m·s^-1,其中东南诸河流域每10 a变化速率最大(-0.202 m·s^-1);③除珠江流域外,其他各流域风速均呈下降趋势。中国各月平均风速呈单峰形,最大值出现在4月,最小值出现在12月;④年平均风速变化主要表现在3-6月下降速率最大,风速变化趋势在各个流域、各月份保持不变。     

黑河流域近46年日照时数的气候变化特征及其影响因素

采用气候倾向率法,对黑河流域10个气象站1960-2005年逐月日照时数以及对日照有影响的总云量、低云量、水气压、降水量等资料进行了统计分析。结果表明:近46年黑河流域年日照时数平均每10年减少1.77 h,近26年来减少趋势更加明显。秋、冬季日照时数显著减少,但夏季呈明显上升趋势。20世纪60年代四季日照时数均为正距平;70年代除冬季外,春、夏、秋季日照均偏少;80年代夏、冬季为负距平,春、秋季日照充足;90年代春季为负距平,其他季节均日照充足。黑河流域年、秋季日照时数的减少与降水量和大气中水气压的增加呈负相关,夏季日照时数的增加主要是由于云量的减少引起。