Statistical downscaling of daily mean temperature, pan evaporation and precipitation for climate change scenarios in Haihe River, China

A statistical downscaling method (SDSM) was evaluated by simultaneously downscaling air temperature, evaporation, and precipitation in Haihe River basin, China. The data used for evaluation were large-scale atmospheric data encompassing daily NCEP/NCAR reanalysis data and the daily mean climate model results for scenarios A2 and B2 of the HadCM3 model. Selected as climate variables for downscaling were measured daily mean air temperature, pan evaporation, and precipitation data (1961–2000) from 11 weather stations in the Haihe River basin. The results obtained from SDSM showed that: (1) the pattern of change in and numerical values of the climate variables can be reasonably simulated, with the coefficients of determination between observed and downscaled mean temperature, pan evaporation, and precipitation being 99%, 93%, and 73%, respectively; (2) systematic errors existed in simulating extreme events, but the results were acceptable for practical applications; and (3) the mean air temperature would increase by about 0.7°C during 2011~2040; the total annual precipitation would decrease by about 7% in A2 scenario but increase by about 4% in B2 scenario; and there were no apparent changes in pan evaporation. It was concluded that in the next 30 years, climate would be warmer and drier, extreme events could be more intense, and autumn might be the most distinct season among all the changes.     

长江流域极端降水过程事件的年内分布特征

基于1960-2016年乌江流域41个气象站的逐日降水观测资料,利用线性倾向估计、滑动平均、累积距平等方法计算趋势系数和气候趋势,分析了研究时段内乌江流域年暴雨等级面雨量、年平均最大日降水量、年平均极端持续强降水次数和对应降水量的时空分布特征,分析表明：（1）乌江流域年暴雨等级面雨量和日数呈显著增加趋势（均通过α=0.05显著性水平检验）,而暴雨强度呈不显著性增加趋势;5-10月各旬暴雨等级面雨量及日数变化基本一致,5月中旬至8月上旬呈单峰型分布,暴雨强度呈波动增减分布。（2）近57 a乌江流域年平均最大日降水量年代际变化比较明显。（3）乌江流域发生极端持续强降水年平均次数呈不显著的减少趋势,但极端持续强降水量呈不显著的增加趋势。采用耿贝尔极值Ⅰ型分布法计算了乌江流域5个代表站不同重现期日最大降水量值,发现不同站点日极端最大降水量重现期水平差异明显,重现期时间尺度存在临界点,约为50 a。

     

Climate changes in the Amur River basin in the last 115 years

Tendencies in climate change in the Amur River basin are generally synchronous to the global ones. During the last century, the annual mean temperature of surface air increased by 1.3°C, minimum warming being observed in the east part of the basin (0.6°C) and maximum one in the west part (1.7–2.5°C). The largest impact on the annual mean temperature growth comes from winter and spring temperature increase (2–4°C/100 years). During the last 30 years, the warming rate in the basin was 2–3 times higher than during the whole period of 1891–2004. Simultaneously with warming in the Amur River basin, annual and warm-season precipitation totals increased by 8 and 6%, respectively, during the 115-year period. The highest increase in precipitation totals occurs in cold season (29% during 115 years). During the last 30 years, together with intense warming in the Amur River basin, the annual precipitation totals are found to decrease by an average of 2.1%/10 years.     

Variations in climatic and hydrological parameters in the Selenga River basin in the Russian Federation

The variations in average annual surface air temperature, precipitation, and runoff in the Selenga River basin (within Russia) are analyzed. It is demonstrated that the considerable increase in average annual temperature of surface air layers occurred in the 1980s-1990s. The decrease in peak water discharge in the rivers and the increase in the frequency of low-water periods were revealed in the forest-steppe and steppe zones of the Selenga River basin in 2001-2010. In the southwestern mountain regions (the Dzhida River basin) the river runoff increased during that period.     

长江流域气候变化高分辨率模拟与RCP4.5情景下的预估

基于长江流域142个气象站1986—2005年月降水和气温数据,评估由MPI-ESM-LR模式驱动的CCLM区域气候模式对长江流域气温和降水的模拟能力,并采用EDCDF法对气温和降水预估数据进行偏差校正。结果表明：该区域气候模式能较好地模拟出长江流域平均气温的季节变化和空间分布特征,但模拟值无论在季节还是年际尺度上均高于观测值。对降水而言,该模式不能较好地模拟出降水的季节分布特征,导致春季、冬季及年模拟值高于观测值,而夏季和秋季模拟值低于观测值。总体而言,该模式对气温的模拟效果相对较好。偏差校正后的预估结果表明：在RCP4.5情景下,长江流域未来（2016—2035年）平均气温相对于基准期（1986—2005年）将升高0.66℃,年降水量将减少2.2%。     

近50年气候变化对滦河上游径流的影响

为了解近50年滦河上游气温和降水气候的变化特征、趋势及其对该流域径流量的影响,利用1956-2009年滦河上游的实测气温、降水量和径流深资料,分析了该流域气温、降水和径流深的年均和季度变化的时间序列,并建立了该流域气候变化对径流影响的复相关回归模型。结果表明,年径流深随着年降水量的减少而减少,随着年平均气温的升高而减少;春、夏和秋季的径流深随着同期降水量和气温的变化趋势与年际变化趋势基本一致,但冬季径流深则相反,而且其变化幅度非常小。     

Simulation of extreme precipitation indices in the Yangtze River basin by using statistical downscaling method (SDSM)

In this study, the applicability of the statistical downscaling model (SDSM) in modeling five extreme precipitation indices including R10 (no. of days with precipitation ≥10?mm?day^?1), SDI (simple daily intensity), CDD (maximum number of consecutive dry days), R1d (maximum 1-day precipitation total) and R5d (maximum 5-day precipitation total) in the Yangtze River basin, China was investigated. The investigation mainly includes the calibration and validation of SDSM model on downscaling daily precipitation, the validation of modeling extreme precipitation indices using independent period of the NCEP reanalysis data, and the projection of future regional scenarios of extreme precipitation indices. The results showed that: (1) there existed good relationship between the observed and simulated extreme precipitation indices during validation period of 1991–2000, the amount and the change pattern of extreme precipitation indices could be reasonably simulated by SDSM. (2) Under both scenarios A2 and B2, during the projection period of 2010–2099, the changes of annual mean extreme precipitation indices in the Yangtze River basin would be not obvious in 2020s; while slightly increase in the 2050s; and significant increase in the 2080s as compared to the mean values of the base period. The summer might be the more distinct season with more projected increase of each extreme precipitation indices than in other seasons. And (3) there would be distinctive spatial distribution differences for the change of annual mean extreme precipitation indices in the river basin, but the most of Yangtze River basin would be dominated by the increasing trend.     

博斯腾湖流域气候变化对开都河径流量的影响

利用线性回归分析法、突变检验法等分析博斯腾湖流域1980～2018年的年均气温、年降水量、年蒸发量等气候因子变化趋势和突变现象及其对开都河径流量的影响.结果表明:1980～2018年博斯腾湖流域年均气温呈波动中上升趋势,其变化速率为0.15℃(10a)-1,年降水量则以0.765mm(10a)-1的速率增加,而年蒸发量...     

作物生长对流域水文过程与区域气候的影响

利用区域气候模式RegCM3以及考虑作物生长过程的耦合模式RegCM3_CERES对东亚区域进行20年模拟,研究作物生长对流域水文过程与区域气候的影响。结果表明：考虑作物生长过程的耦合模式模拟海河流域、松花江流域、珠江流域多年平均降水效果明显改进,在除黑河流域外的各流域模拟的温度负偏差有所减小,其中在海河流域、淮河流域的夏季改进尤为明显。各流域夏季（6、7、8月）月蒸散量最高,其中长江流域、海河流域、淮河流域、珠江流域的夏季月蒸散量基本上在100 mm左右,并且七大流域蒸散发的季节变化趋势跟总降水基本一致。多数流域考虑作物生长过程的耦合模式模拟得出蒸散发减少且进入的水汽增加,导致局地水循环率减小;黑河流域与黄河流域降水有所增加,其他流域均有不同程度的减小。针对长江流域,比较耦合模式RegCM3_CERES与模式RegCM3模拟结果显示,叶面积指数减少1.20 m²/m²,根区土壤湿度增加0.01 m³/m³,进而导致潜热通量下降1.34 W/m²（其中在四川盆地地区减少16.00 W/m²左右）,感热通量增加2.04 W/m²,从而影响到降水和气温。     

Long-term projection of main parameters of regional climate till the year 3000

The methods are considered to solve the problem of secure isolation of radioactive waste containing long-lived products of nuclear fuel processing with a half-life of tens of thousands years (plutonium etc.). The methodology of long-term projection of average annual surface air temperature and total precipitation is proposed. Taking into account the possible scenarios of the development of the global socioeconomic system, variations due to the anthropogenic impact in average annual temperature at the Northern Hemisphere mid-latitudes for the period till 2300 are estimated. Based on paleoclimatic data, projections of natural trends in global average annual temperature and total precipitation till the year 3000 are developed. Taking into account the anthropogenic component, the projective ranges of these climatic parameters in the Vyatka River basin in 2100-3000 are evaluated.     

45年来塔里木河流域气候变化对径流量的影响研究

根据塔里木河流域40个气象站1961-2005年的降水、 气温资料及源区内7个水文站1957-2005年年径流量资料, 利用Mann-Kendall检验, 分析了近45年来塔里木河流域的气候变化的特征, 探讨了气候变化对塔里木河流域水资源的影响。结果表明： 整个流域除个别站点外, 塔里木河流域气温整体呈显著上升趋势, 且以秋季最显著, 降水增加以夏季最明显。特别是中天山南坡, 而流域西南部、 和田地区和巴州南部的降水量几乎没有增加。根据Mann-Kendall检验结果, 除阿克苏河年径流量呈显著增加趋势外, 其它3条源流（和田河、 叶尔羌河、 开都河）径流量近45年变化趋势均不显著。     

Evaluation of SDSM developed by annual and monthly sub-models for downscaling temperature and precipitation in the Jhelum basin, Pakistan and India

The study evaluates statistical downscaling model (SDSM) developed by annual and monthly sub-models for downscaling maximum temperature, minimum temperature, and precipitation, and assesses future changes in climate in the Jhelum River basin, Pakistan and India. Additionally, bias correction is applied on downscaled climate variables. The mean explained variances of 66, 76, and 11 % for max temperature, min temperature, and precipitation, respectively, are obtained during calibration of SDSM with NCEP predictors, which are selected through a quantitative procedure. During validation, average R ² values by the annual sub-model (SDSM-A)—followed by bias correction using NCEP, H3A2, and H3B2—lie between 98.4 and 99.1 % for both max and min temperature, and 77 to 85 % for precipitation. As for the monthly sub-model (SDSM-M), followed by bias correction, average R ² values lie between 98.5 and 99.5 % for both max and min temperature and 75 to 83 % for precipitation. These results indicate a good applicability of SDSM-A and SDSM-M for downscaling max temperature, min temperature, and precipitation under H3A2 and H3B2 scenarios for future periods of the 2020s, 2050s, and 2080s in this basin. Both sub-models show a mean annual increase in max temperature, min temperature, and precipitation. Under H3A2, and according to both sub-models, changes in max temperature, min temperature, and precipitation are projected as 0.91–3.15 °C, 0.93–2.63 °C, and 6–12 %, and under H3B2, the values of change are 0.69–1.92 °C, 0.56–1.63 °C, and 8–14 % in 2020s, 2050s, and 2080s. These results show that the climate of the basin will be warmer and wetter relative to the baseline period. SDSM-A, most of the time, projects higher changes in climate than SDSM-M. It can also be concluded that although SDSM-A performed well in predicting mean annual values, it cannot be used with regard to monthly and seasonal variations, especially in the case of precipitation unless correction is applied.     

Change trends of air temperature and precipitation over Shanxi Province, China

A dataset of air temperature and precipitation time series (1959?C2008) from 61 stations across Shanxi, China is used to analyze the climate change. The monotonic trends and step (abrupt) trends for annual and seasonal series data of mean air temperature and total precipitation are tested by using Mann?CKendall test and Mann?CWhitney test, respectively. The results show that annual mean air temperature has increased by 1.20°C during the past 50?years. Winter, spring, and autumn have experienced a significant increase in air temperature. The step trend for annual mean air temperature is different from, but closely related with, those for seasonal mean air temperature. Spatially, there is an enhanced warming trend from south to north in Shanxi, and the most remarkable warming occurs in northern Shanxi. Annual precipitation has decreased by 99.20?mm during the past half century. The decrease is mainly caused by precipitation decline in rainy season (June?CSeptember), though precipitation in post-rainy season (October?CNovember) also tended to decrease. An abrupt decrease in precipitation has occurred since late 1970s. Decrease in precipitation is highest in central Shanxi and in the area along the west fringe between Sanchuan River and Fenhe River in western Shanxi.     

Variation of atmospheric aerosol optical depth and its relationship with climate change in China east of 100°E over the last 50 years

Understanding the role of aerosols in global and regional climate change requires the long-term measurements of aerosol optical properties. We use an indirect method to infer aerosol optical depths (AODs) based on atmospheric visibility and water vapor pressure measured at 504 key climate stations in eastern China (east of 100° E) over 1951–2002. Inferred AODs are compared with the MODIS satellite measurements for year of 2002. Results show that AODs averaged over 1951–2000 exhibit large values in Sichuan Basin and Changjiang River Delta, and there are two belts of high AODs, one from Beijing to South China by the middle reaches of Changjiang River and the other from Beijing to Changjiang Delta. Inferred AODs in eastern China show the lowest value in 1960s, increase dramatically in 1980s, and reach maximum in 1990s. The ratios of the regional and decadal mean AOD in 1950s, 1960s, 1970s, 1980s, and 1990s to that in 1960s are 1.085, 1.0, 1.066, 1.195, and 1.22, respectively. Statistical analysis shows that variations in AODs correlate with the changes in precipitation and air temperature in eastern China over the past 50 years. Correlation coefficients between annual mean AOD and precipitation are 0.39, 0.37, and 0.57 in the upper (Sichuan Basin), middle, and lower reaches of the Changjiang River, respectively. In the Sichuan Basin, the increase in annual mean AOD correlates with the reduction in air temperature with a correlation coefficient of ?0.33 at 95% confidence level.     

1961—2009年辽河流域水文气象要素变化特征

依据1961—2009年辽河流域5个气象观测站点逐日降水和气温观测资料,运用非参数检验方法（Mann-Kendall法）,对辽河流域降水和气温的变化趋势进行了分析。利用2006—2010年夏季共162d降水日的铁岭站日降水量与铁岭水文站径流量资料,探讨了日降水量与径流量之间的相关关系。结果表明：辽河流域年降水量减少趋势明显,降水量偏少年份明显增加,其主要原因为占全年降水量65%的夏季降水以7.4 mm/10 a的气候趋势倾向率递减,呈现出明显的减少趋势;辽河流域的年平均气温是在波动中逐渐上升的,且升温趋势明显,春季呈明显的升温趋势,夏季略有下降,秋季变化不大,冬季是气温上升最明显的季节;日降水量与径流量存在正相关关系,且日降水量与降水第二日的径流量相关显著。     

Thermal interaction between near-water atmospheric layer and surface water layer on the northeastern shelf of the Black Sea

Thermal interaction between near-water atmospheric layer and surface water layer is considered within long-term, seasonal, synoptic, and mesoscale variability ranges from long-term air and water temperature measurement data. It is established that long-term mean monthly values of water temperature within annual cycle are greater than corresponding values of air temperature. Equations of relationships are obtained for long-term mean annual, mean seasonal, and mean monthly air and water temperature values.     

Effects of climatic change and climatic variability on the Thornthwaite moisture index in the Delaware River basin

The Thornthwaite moisture index is useful as an indicator of the supply of water in an area relative to the demand under prevailing climatic conditions. This study examines the effects of long-term changes in climate (temperature and precipitation) on the Thornthwaite moisture index in the Delaware River basin. Temperature and precipitation estimates for doubled-CO₂ conditions derived from three general circulation models (GCMs) are used to study the response of the moisture index for steady-state doubled-CO₂ conditions and for gradual changes from present to doubled-CO₂ conditions.Results of the study indicate that temperature and precipitation under doubled-CO₂ conditions will cause the Thornthwaite moisture index to decrease, implying significantly drier conditions in the Delaware River basin than currently exist. The amount of decrease depends, however, on the GCM climatic-change scenario used. The results also indicate that future changes in the moisture index will be partly masked by natural year-to-year variability in temperature and precipitation.     

车尔臣河流域1955-2010年气候变化特征分析

摘 要：利用车尔臣河流域1955-2010年气温、降水、云量、浮尘、沙尘暴和大风等气象资料,分析了近56a来流域气候变化特征。结果表明:(1)车尔臣河流域年、季平均气温均呈明显上升趋势,以冬季增暖最显著;且在1990年前后出现了冷暖突变,2001-2010年是近56a来最暖的时期。(2)年、季降水量呈小幅增加趋势,春季降水增加趋势达显著水平;降水在1962年出现干湿突变,而1980s后降水增加则趋于平稳。(3)年、季平均总云量呈增加趋势,其中夏季云量的增加最明显。(4)年浮尘、沙尘暴和大风日数呈显著减少趋势,但值得注意的是2005年以后沙尘日数不降反升。总体上看,近56a车尔臣河流域气候朝暖湿方向发展,生态环境明显改善。     

1961-2005年嫩江流域右岸气候变化及对水资源的影响

利用累积距平法和气候倾向率对1961－2005年嫩江流域右岸气温、降水量和径流量资料进行分析,研究嫩江流域右岸气候变化及其对水资源的影响。结果表明：近45 a来嫩江流域右岸气温显著增高,平均以0.52 ℃/10 a的速率上升,而且四季均为上升趋势, 不同季节增温幅度以冬、春、秋、夏季依次递减,1986年以来为气温升高最显著的时段;降水变化可分为3个阶段： 1961－1982年降水量呈减少趋势,1982－1998年处于增加时期,1998年以来降水量又呈现减少趋势。夏季降水量变化趋势与年降水量变化趋势趋于一致, 降水量总趋势是在波动中微弱上升;嫩江流域右岸主要控制站年径流量与年降水量保持同步变化。     

气候变化对长江上游径流影响预估

利用第五次国际耦合模式比较计划(CMIP5)中5个气候模式在3种典型浓度路径(RCPs)下的预估结果驱动SWAT水文模型,预估了21世纪气候变化对长江上游年径流量、季节分配以及极端径流的影响。结果表明：预估的长江上游平均气温呈显著上升趋势,21世纪末较当前(1986—2005年)升高1.5~5.5℃,降水总体呈增加趋势,在21世纪30年代后高于当前气候平均值,21世纪末相对于当前增加5%~15%。流域内气候变化存在明显空间差异,金沙江和岷沱江流域气温升高和降水增加幅度均大于流域平均值。预估的长江上游年径流量及各月平均径流均有增加趋势,在21世纪30年代后高于当前多年平均值,21世纪中期增加4%~8%,21世纪末增加10%~15%。预估的径流年内分布的均匀性有所增加,但年际变化明显增大,极端旱涝事件的频率和强度明显增加。预估的各子流域径流变化对气候变化的响应也存在差异,金沙江和岷沱江流域年径流量、年际变化和年内分布变化小,对气候变化的响应表现为低敏感;嘉陵江流域、乌江流域和长江上游干流径流增加幅度大,同时极端丰枯出现的频率和程度增加显著,是气候变化响应的敏感区域。