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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]

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: 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]

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]