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Abstract: In this paper, the spatio-temporal variation and trend of daily actual evapotranspiration (ETa) are calculated for the Haihe River Basin from 1961 to 2010. The methodology is based on the complementary relationship approach, i.e. the advection–aridity (AA) model with parameter validation from 1961 to 2010, which allows the determination of ETa that cannot be instrumentally measured. Daily data on mean/maximum/minimum temperature, air pressure, actual water vapor pressure, sunshine hours, wind speed, sunshine duration and cloud cover from 31 meteorological stations from 1961 to 2010 are used in order to identify the main drivers of changes in evapotranspiration. The trend tests applied in this study are the linear regression method and the nonparametric Mann–Kendall test (MKtest). The results show: 1) the Haihe River Basin has an annual ETa at about 484 mm/yr. The highest ETa occurs in summer, followed by autumn. From 1961 to 2010, the annual ETa, the ETa in summer and the ETa in autumn show a significant negative trend in the Haihe River Basin. The ETa varies insignificantly in spring and winter; 2) the ETa shows distinct spatial variability in the Haihe River Basin. It closely follows the topography and increases with greater distance from the sea, but varies significantly during the seasons; 3) the central plain area of the Basin around the capital city of Beijing shows the highest occurrence of negative trends of ETa with a decrease of ETa of 40 mm for the time series. 4) negative trends of ETa in summer are related to multiple factors: decreasing relative humidity and decreasing reduced sunshine duration under increasing surface temperatures in summer. Increases in surface temperature include the mean, maximum and minimum daily temperature. The decline of ETa in autumn can be explained by a negative trend of relative humidity. The decreasing ETa suggests a reduction in water availability and cycle in seasons with highest water demand. [Copyright &y& Elsevier]

The projected changes of precipitation and temperature in the Yangtze River Basin in the 20th Century from 20 models of the CMIP3 (phase 3 of the Coupled Model Inter-comparison Project) dataset are analyzed based on the observed precipitation and temperature data of 147 meteorological stations in the Yangtze River Basin. The results show that all models tend to underestimate the annual mean temperature over the Yangtze River Basin, and to overestimate the annual mean precipitation. The temporal changes of simulated annual mean precipitation and temperature are broadly comparable with the observations, but with large variability among the results of the models. Most of the models can reproduce maximum precipitation during the monsoon season, while all models tend to underestimate the mean temperature of each month over the Yangtze River Basin. The Taylor diagram shows that the differences between modeled and observed temperature are relatively smaller as compared to differences in precipitation. For a detailed investigation of regional characteristics of climate change in the Yangtze River Basin during 2011-2050, the multi-model ensembles produced by an upgraded REA method are carried out for more reliable projections. The projected precipitation and temperature show large spatial variability in the Yangtze River Basin. Mean precipitation will increase under the A1B and B1 scenarios and decrease under the A2 scenario, with linear trends ranging from −21 to 28.5 mm/decade. Increasing mean temperature can be found in all scenarios with linear trends ranging from 0.15 to 0.48°C/decade. Grids in the head region of the Jingshajiang catchment show distinct increasing trends for all scenarios. Some physical processes associated with precipitation are not well represented in the models. [ABSTRACT FROM AUTHOR]

In this paper, change-points in time series of annual extremes in temperature and precipitation in the Zhujiang River Basin are analyzed with the CUSUM test. The data cover the period 1961-2007 for 192 meteorological stations. Annual indicators are analyzed: mean temperature, maximum temperature, warm days, total precipitation, 5-day maximum precipitation, and dry days. Significant change-points (1986/87, 1997/98, 1968/69, and 2003/04) are detected in the time series of most of the indicators. The change-point in 1986/87 is investigated in more detail. Most stations with this change-point in temperature indicators are located in the eastern and coastal areas of the basin. Stations with this change-point in dry days are located in the western area. The means and trends of the temperature indicators increase in the entire basin after 1986/87. The highest magnitudes can be found at the coast and delta. Decreasing (increasing) tendencies in total and 5-day maximum precipitation (dry days) are mostly observed in the western and central regions. The detected change-points can be explained by changes in the indices of the Western Pacific subtropical high and the East Asian summer monsoon as well as by change-points in wind directions. In years when the indices simultaneously increase and decrease (indices taking reverse directions to negative and positive) higher annual temperatures and lower annual precipitation occur in the Zhujiang River Basin. The high station density and data quality are very useful for spatially assessing change-points of climatic extreme events. The relation of the change points to large-scale oscillation can provide valuable data for planning adaptation measures against climate risks, e.g. for flood control, disaster preparedness, and water resource management. [ABSTRACT FROM AUTHOR]

Abstract: Most of China’s coastline is economically developing, densely populated, and frequently hit by landfalling Tropical Cyclones (TCs). Economic losses below province level have not been systematically analyzed due to lack of data. The objective of this paper is to conduct a TC loss assessment on county level in Fujian Province, coastal SE China, and to break down economic losses from province-scale to smaller administrative units. A unique loss database established by the China Meteorological Administration (CMA) and National Climate Center is used, and four entries at county-level are derived: location of losses due to TC, total economic losses per TC, start time of TC, and end time of TC. Tracks and intensities of TCs from 1949–2008 are derived from the CMA and Shanghai Typhoon Center annual typhoon yearbooks. Physical and economic data are overlaid in a Geographical information System. The landfall spots of TCs on China’s mainland coastline from 1949–2008 are determined by generating segments of 1° length. The result shows that Guangdong Province (South China) and Fujian Province (South-East China) host distinct hot spots where TCs make frequent landfall. All TCs making landfall in Central-North Fujian originated from the West North Pacific and none from the South China Sea. Direct economic losses in 25 counties along Fujian’s coastline due to TCs from 1984–2007 are analyzed and corrected with the Consumer Price Index. Some counties report losses frequently at low magnitude but seldom at high magnitude. Others like urban Fuzhou experience losses above 10 million CNY per TC, the most costly one 70 times higher. Other rural counties might experience economic losses far below 10 million CNY when being hit. Landfalling TCs in average cause economic losses of minimum 10 million CNY in 21 of 25 counties. In roughly one third of the counties, economic losses account for more than 30 million CNY when a TC has impact. The average economic losses per TC are 0.2–0.5% of the counties’ GDP (South and North of Fujian’s coastline) and even more than 0.5% of the GDP in North-East Fujian. The economic impacts of TCs are higher along the southern and northern coastline of Fujian Province where TC landfall activity is higher, but higher economic losses are triggered by higher GDP in these counties. The most costly TCs in Fujian had intensities of Severe Tropical Storm or Typhoon and occurred mostly in the 2000’s after making landfall in July. [Copyright &y& Elsevier]

Abstract: Spatial and temporal characteristics of temperature and precipitation in the Zhujiang River Basin, South China, are analysed in order to identify tendencies in dryness and wetness. Trend tests are applied to daily temperature and precipitation data from 1961 to 2007 of 192 weather stations. Nine indicators are applied in order to detect cycles of dryness and wetness and are compared with the drought indices Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI). Tendencies in temperature and precipitation characteristics can be observed. Significant positive trends (>90% confidence level) can be found for annual temperature, number of warm days, longest warm period, no rain days, and longest dry period. A significant increase in temperature by more than 0.7K from 1961 to 2007 can be observed in the entire basin and the coastal and far western areas in particular. Negative trends are observed for annual cool days, cool period, wet days, and wet period. Almost no significant trends in annual mean and extreme precipitation are detected. Rain days decreased, and a tendency to longer dry periods and shorter wet periods can be observed. The magnitude of indices describing dryness has increased in the Zhujiang River Basin, and dry periods have become longer while wet periods have shortened in time. Rainfall intensity has increased along the coastline and in the far west of the catchment. This tendency can be partially explained by the weakening of the East Asian Summer Monsoon. Regarding the high temperature increases, the influences of the urban heat island effect due to urbanization and industrialization, especially along the coast and at the delta, should be considered. The high station density and data quality are very useful for describing detailed changes in wetness and dryness in the Zhujiang River basin. [Copyright &y& Elsevier]

Summary: The characteristics of hydro-climatic changes in the Tarim River Basin were analysed based on data collected at 39 weather stations and 29hydrological stations for the period 1961–2008 and 1952–2008, respectively. A non-parametric trend test on basin scale for annual data shows an increasing trend of precipitation, relative humidity, vapour pressure, and the aridity index since 1986. Surface temperature started increasing in 1996. A decreasing trend of sunshine started in 1990. The potential evapotranspiration (ET) is calculated by the Penman–Monteith equation, and points out decreasing trend of potential evapotranspiration since 1985. This negative trend can also be detected for wind speed in both the same time scale and spatial extent. The stations with significant increasing trends in annual streamflow are mainly distributed at the southern slope of Tianshan Mountain, which can only be explained by climatic changes. The detected negative runoff trend of the main stream of the Tarim River can be explained by anthropogenic activities (such as irrigation and domestic water use) and climatic changes. A quantitative assessment reveals that local human activities since the 1970s led to a decrease of the water volume diverted into the main stream of the Tarim River Basin, which has been aggravated in the 2000s. [ABSTRACT FROM AUTHOR]

Spatial and temporal characteristics of precipitation trends in the Zhujiang River basin, South China, are analyzed. Nonparametric trend tests are applied to daily precipitation data from 192 weather stations between 1961 and 2007 for the following indices: annual, monthly, and daily precipitation; annual and monthly number of rain days and precipitation intensity; annual and monthly maximum precipitation; 5-day maximum precipitation, number of rainstorms with >50 mm day−−1, and peaks over thresholds (90th, 95th, and 99th percentile). The results show that few stations experienced trends in the precipitation indices on an annual basis. On a monthly basis, significant positive and negative trends above the 90%% confidence level appear in all months except December. Trends in the indices of monthly precipitation, rain intensity, rain days, and monthly maximum precipitation show very similar characteristics. They experience the most distinct negative (positive) trends in October (January). A change of the mean wind direction by 50°° from east-southeast to east-northeast explains the downward trend in precipitation in October. Dry October months (months with low precipitation indices) can be observed when the mean wind direction is east-northeast (arid) instead of the prevailing mean wind direction, east-southeast (moist). The former is typical for the East Asian winter monsoon (EAWM). Nearly 90%% of the driest October months can be explained by wind directions typical for the EAWM. The upward trend in precipitation indices in January cannot be explained by changes in large-scale circulation. The analysis of the precipitation indices delivers more detailed information on observed changes than other studies in the same area. This can be attributed to the higher station density, the quality of daily data, and the focus on monthly trends in the current study. [ABSTRACT FROM AUTHOR]

Abstract: Tropical cyclones (TCs) are historically documented along the coastline of China. They can have negative impacts on society and damages are reported annually. This paper examines to what extent TCs are responsible for heavy rain days (precipitation > 100 mm/d) in coastal Fujian Province. The average deviation of TCs making landfall in China is 25%, and they occur more reliably than TCs in the west North Pacific. A distinct typhoon season between July and September/October was detected and can be explained by low interannual variability during these months. The annual number of TCs is below average (above average) during El Niño (La Niña) years, but the intensity of TCs is higher during El Niño years. From 1960 to 2007, 41% of heavy rain days (precipitation > 100 mm/d) at all 66 weather stations in Fujian Province were triggered by TCs. The number of heavy rain days is higher during El Niño years, although the number of TCs affecting Fujian in general is higher during La Niña years. For the coastal weather stations in east Fujian, 57% (45%) of the heavy rain days are triggered by TCs during El Niño (La Niña) years. In the research area, more than 50% of annual heavy rain days can be explained by TCs, and the ratio reaches 85% in the northern part bordering Zhejiang Province. More TCs impact Fujian during La Niña years, but more TCs cause heavy precipitation days during El Niño years. The number of heavy rain days fluctuates in line with the interannual variability of TCs making landfall. [ABSTRACT FROM AUTHOR]

Climate projections for the Huaihe River Basin, China, for the years 2001–2100 are derived from the ECHAM5/MPI-OM model based on observed precipitation and temperature data covering 1964–2007. Streamflow for the Huaihe River under three emission scenarios (SRES-A2, A1B, B1) from 2010 to 2100 is then projected by applying artificial neural networks (ANN). The results show that annual streamflow will change significantly under the three scenarios from 2010 to 2100. The interannual fluctuations cover a significant increasing streamflow trend under the SRES-A2 scenario (2051–2085). The streamflow trend declines gradually under the SRES-A1B scenario (2024–2037), and shows no obvious trend under the SRES-B1 scenario. From 2010 to 2100, the correlation coefficient between the observed and modeled streamflow in SRES-A2 scenario is the best of the three scenarios. Combining SRES-A2 scenario of the ECHAM5 model and ANN might therefore be the best approach for assessing and projecting future water resources in the Huaihe basin and other catchments. Compared to the observed period of streamflows, the projected periodicity of streamflows shows significant changes under different emission scenarios. Under A2 scenario and A1B scenario, the period would delay to about 32–33a and 27–28a, respectively, but under B1 scenario, the period would not change, as it is about 5–6a and the observed period is about 7–8a. All this might affect drought/flood management, water supply and irrigation projects in the Huaihe River basin. [ABSTRACT FROM AUTHOR]

Abstract: The present study examines the spatial and temporal variation of extreme precipitation over the Yangtze River Basin based on meteorological data for 1960–2004. From 147 stations, regional characteristics of extreme precipitation are analyzed using a rotated empirical orthogonal function (REOF). Non-parametric trend analysis and wavelet transformation analysis are applied to analyze the temporal variation of extreme precipitation. The results show that (1) 6 leading modes of extreme precipitation exist in the following area: east/north-eastern Yangtze, north/central Yangtze, south-eastern Yangtze, north-western Yangtze, western Yangtze and south/south-western Yangtze; (2) significant positive changes can be found for extreme precipitation averaged for the east/north-eastern Yangtze and the western Yangtze basin, and statistically significant abruption is detected in year 1986 for both regions; (3) significant negative trends can be detected over the north-western Yangtze basin with abruption in the years 1968 and 1990; and (4) long-term trends and inter-decadal oscillations of extreme precipitation can be found for 6 mode domains, but not constant periodicity. The increase in heavy precipitation in the middle-lower reaches can partly explain the frequent occurrence of floods in the 1990s. It is difficult to predict the trends of heavy precipitation for future years, but possible alternating of high-frequency extreme precipitation in the middle and lower reaches indicates flood disaster might be aggravated in the incoming decade of the 21st century in the Yangtze River Basin. [Copyright &y& Elsevier]

Abstract: The present study examines the spatial and temporal trends of precipitation, flood/drought, runoff, high and low river flow during flood season (May–October) for the Yangtze River Basin. Analyses are based on daily meteorological data for 137 stations from 1960 to 2004, daily hydrological data for two discharge-measuring stations at the Yangtze River and monthly hydrological data for one station for the same reference period. Flood/drought examination was done for the western, middle, and lower Yangtze River Basin. Significant precipitation changes can be detected for June and July during 1960–2004. The strongest precipitation increase was detected in the lower Yangtze region. A statistically significant negative trend can be found in September over the Yangtze River Basin, especially at the middle region. Changes of the precipitation extremes from May to October are of direct importance to the occurrences of high and low river flow. The main increase of flooding events can be detected for July in the lower Yangtze region, together with significant upward trends both for the monthly runoff and for the high river water stage. Drought frequency increased in the middle Yangtze River Basin in May, September and October, where downward trends for the monthly runoff and low river flow especially in May. During these months, flood and drought hazards in the Yangtze River Basin have been aggravated. [Copyright &y& Elsevier]

Abstract: Reconstructed historical temperature and flood/drought variations based on historical records for the Yangtze Delta are analyzed with the help of power spectral and continuous wavelet analyses. Three distinct climate periods can be identified in the Yangtze Delta: Warm Medieval Period (AD 1000–1400), Little Ice Age (AD 1400–1920), and the ongoing well-established Global Warming Period (AD 1920–present). The variability of temperature is of great magnitude, and periods dominated by warm/cold temperature are usually interrupted by cold/warm periods. A comparison of flood/drought variations and temperature variations indicates that there are obviously no fixed modes of climate changes such as warm-wet, cold-wet, warm-dry or cold-dry. However, the results demonstrate that large-magnitude temperature variations usually lead to a higher frequency of flood/drought hazards in the Yangtze Delta. Furthermore, the frequency of flood/drought events usually increased in the transition periods from one climate state to another. The ongoing period of climate change is another transition from cold temperatures during the Little Ice Age to increasing temperatures and variability. This might increase the probability and reoccurrence of flood/drought events and other extreme climate events in the Yangtze Delta. [Copyright &y& Elsevier]

Precipitation trends in the Yangtze River catchment (PR China) have been analyzed for the past 50 years by applying the Mann-Kendall trend test and geospatial analyses. Monthly precipitation trends of 36 stations have been calculated. Significant positive trends at many stations can be observed for the summer months, which naturally show precipitation maxima. They were preceded and/or followed by negative trends. This observation points towards a concentration of summer precipitation within a shorter period of time. The analysis of a second data set on a gridded basis with 0.5° resolution reveals trends with distinct spatial patterns. The combination of classic trend tests and spatially interpolated precipitation data sets allows the spatiotemporal visualization of detected trends. Months with positive trends emphasize the aggravation of severe situation in a region, which is particularly prone to flood disasters during summer. Reasons for the observed trends were found in variations in the meridional wind pattern at the 850 hPa level, which account for an increased transport of warm moist air to the Yangtze River catchment during the summer months. [ABSTRACT FROM AUTHOR]

The simulation results of CMIP5 (Coupled Model Inter-comparison Project phase 5) multi-model ensemble in the Indus River Basin (IRB) are compared with the CRU (Climatic Research Unit) and APHRODITE (Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation) datasets. The systematic bias between simulations and observations is corrected by applying the equidistant Cumulative Distribution Functions matching method (EDCDFm) and high-resolution simulations are statistically downscaled. Then precipitation and temperature are projected for the IRB for the mid-21st century (2046–2065) and late 21st century (2081–2100). The results show that the CMIP5 ensemble captures the dominant features of annual and monthly mean temperature and precipitation in the IRB. Based on the downscaling results, it is projected that the annual mean temperature will increase over the entire basin, relative to the 1986–2005 reference period, with greatest changes in the Upper Indus Basin (UIB). Heat waves are more likely to occur. An increase in summer temperature is projected, particularly for regions of higher altitudes in the UIB. The persistent increase of summer temperature might accelerate the melting of glaciers, and has negative impact on the local freshwater availability. Projections under all RCP scenarios show an increase in monsoon precipitation, which will increase the possibility of flood disaster. A decreasing trend in winter and spring precipitation in the IRB is projected except for the RCP2.6 scenario which will cause a lower contribution of winter and spring precipitation to water resources in the mid and high altitude areas of the IRB. [ABSTRACT FROM AUTHOR]

In this paper, precipitation concentrations across the Pearl River basin and the associated spatial patterns are analyzed based on daily precipitation data of 42 rain gauging stations during the period 1960–2005. Regions characterized by the different changing properties of precipitation concentration index (CI) are identified. The southwest and northeast parts of the Pearl River basin are characterized by lower and decreasing precipitation CI; the northwest and south parts of the study river basin show higher and increasing precipitation CI. Higher but decreasing precipitations CI are found in the West and East River basin. Comparison of precipitation CI trends before and after 1990 shows that most parts of the Pearl River basin are characterized by increasing precipitation CI after 1990. Decreasing precipitation CI after 1990 (compared to precipitation CI changes before 1990) is observed only in a few stations located in the lower Gui River and the lower Yu River. Significant increasing precipitation CI after 1990 is detected in the West River, lower North River and upper Beipan River. These changes of precipitation CI in the Pearl River basin are likely to be associated with the consequences of the well-evidenced global warming. These findings can contribute to basin-scale water resource management and conservation of ecological environment in the Pearl River basin. [ABSTRACT FROM AUTHOR]

Finer climate change information on spatial scale is required for impact studies than that presently provided by global or regional climate models. It is especially true for regions like South Asia with complex topography, coastal or island locations, and the areas of highly heterogeneous land-cover. To deal with the situation, an inexpensive method (statistical downscaling) has been adopted. Statistical DownScaling Model (SDSM) employed for downscaling of daily minimum and maximum temperature data of 44 national stations for base time (1961-1990) and then the future scenarios generated up to 2099. Observed as well as Predictors (product of National Oceanic and Atmospheric Administration) data were calibrated and tested on individual/multiple basis through linear regression. Future scenario was generated based on HadCM3 daily data for A2 and B2 story lines. The downscaled data has been tested, and it has shown a relatively strong relationship with the observed in comparison to ECHAM5 data. Generally, the southern half of the country is considered vulnerable in terms of increasing temperatures, but the results of this study projects that in future, the northern belt in particular would have a possible threat of increasing tendency in air temperature. Especially, the northern areas (hosting the third largest ice reserves after the Polar Regions), an important feeding source for Indus River, are projected to be vulnerable in terms of increasing temperatures. Consequently, not only the hydro-agricultural sector but also the environmental conditions in the area may be at risk, in future. [ABSTRACT FROM AUTHOR]

Actual evaporation in the Yangtze River basin is calculated by the complementary relationship approach-that is, the advection-aridity (AA) model with parameter validation from 1961 to 2007-and simulated by the general circulation model (GCM) ECHAM5-Max Planck Institute Ocean Model (MPI-OM) from 1961 to 2000. Trends of annual and seasonal estimated actual evaporation and air temperature, net radiation, saturation vapor pressure deficit, wind speed, and precipitation are examined by the linear regression method and nonparametric Mann-Kendall test. The stepwise regression method is used to analyze the significance to reference evapotranspiration of independent variables. Results show that a significant decreasing trend in annual reference evaporation is caused by a significant decline in wind speed. The annual actual evaporation decreases in the upper and midlower Yangtze reaches; more significantly in the AA model [-9.3 mm (10 yr)−1] than in the GCM [−3.6 mm (10 yr)−1]. Significant negative trends are found in spring and autumn, but they show reverse trends in summer and winter within the two methods, which is caused by the different contributors to the seasonal actual evaporation in the two methods. Decreasing net radiation is the main contributor to annual and spring actual evaporation in the two methods. Decreasing precipitation and net radiation are the main contributors to decreasing autumn actual evaporation in the AA model and the GCM. Increasing net radiation and decreasing precipitation are the main contributors to summer and winter actual evaporation in the GCM. Decreasing net radiation and increasing precipitation are the main contributors to decreasing summer and increasing winter actual evaporation in the AA model. [ABSTRACT FROM AUTHOR]

Abstract: A standard methodology is needed to recognize potentially suitable areas for sustainable bioenergy crop production. This facilitates better identification of promising crops and cropping systems, logistical and economic studies, and work needed to meet regulatory criteria. A possible approach is built upon three layers of internationally available spatial data: (1) degrading and abandoned areas, (2) potentially suitable land cover classes, (3) exclusion zones such as nature reserves and areas of high biodiversity. For China, areas identified as potentially suitable range from 1.2 to 6.0% of the national territory, depending on different levels of statistical confidence in degrading area status and allowable limits of terrestrial carbon. Verification on the ground showed that about 60% of points tested conformed to the remote suitability assessment in the scenario, which represents the results for the combination of all degrading areas and a terrestrial carbon stock limit of 200 t ha−1. A top-down approach is useful in framing potentially suitable locations, but a complementary bottom-up analysis is still required to ultimately identify areas for sustainable bio-fuel production. [Copyright &y& Elsevier]