Search

The northern edge of the East Asian monsoon region is also a transition zone of temperate continental and monsoon climate, which is a sensitive zone of global climate and ecological environment change. It is an urgent problem to find out the long-term climate change rules of this region. Using 101 tree core samples obtained from 54 trees, a 343-year tree-ring width chronology of the Platycladus orientalis (L.) Franco (1673–2016) in the Wula Mountains, Inner Mongolia, China was established. The analysis shows that the radial growth of P. orientalis is closely related to hydrothermal conditions, the average minimum temperature and relative humidity are the main factors that determine the growth of P. orientalis. Based on the strong correlation between the tree-ring indices and the annual average minimum temperature (r = −0.870, p < 0.001), we reconstructed an average annual minimum temperature series from 1673 to 2016 using a linear regression equation, and the reconstructed equation can explain 75.724% of the variance, respectively. According to the data from the past 343 years, the changes in the annual average minimum temperature series had the cycles of 58.6-, 7.7-, 3.4-, 3.1-, 2.2-, and 2.1-years; the series showed three warm periods (1824–1830, 1909–1922, and 1986–2011) and 4 cold periods (1703–1712, 1731–1738, 1754–1763, and 1937–1951). The low temperature periods recorded in the reconstructed series for the 17th and 18th centuries are consistent with the Little Ice Age that occurred in the northern hemisphere, and the heating rate significantly increased at the end of the 20th century. In addition, the cold and warm periods recorded by the reconstruction result is basically consistent with the extreme climate events recorded in the historical documents of the region and the reconstruction results in other regions. In this paper, the world's first chronology of P. orientalis tree ring width was established. A historical sequence of annual average minimum temperature of 343 years was reconstructed in a typical region of the East Asian monsoon climate. It fills in the blank of reconstruction sequence and variation characteristics of mean minimum temperature in the northern edge of East Asian monsoon and transition zone of temperate continental and monsoon climate in recent four centuries. [ABSTRACT FROM AUTHOR]

Based on the data of five observed meteorological elements (temperature, precipitation, wind speed, sunshine duration, and relative humidity) from 22 stations, the paper investigated the climate variations in northern Xinjiang over the past 50 years. The analytical results showed that both the temperature and the precipitation have increased significantly (0.35 °C/10 y, 11.2 mm/10 y) during the period of 1960–2011. An abrupt change was detected to have occurred in 1986 for temperature and in 1987 for precipitation. Autumn was the season when the temperature increased most dramatically, and winter and autumn were the seasons when the precipitation increased most dramatically. The twenty years after 1990 were the warmest and wettest two decades of the past ∼50 years, but the warming and wetting paces have slowed down during the same period. The results also showed that the mean annual minimum temperature increased more dramatically than the mean annual maximum temperature, resulting in a greatly reduced diurnal range. The reasons or mechanisms for rising trend of temperature during the past 50 years and also for the faster rising rate of the temperature in northern Xinjiang and the adjacent areas have been reasonably explored in published literature. However, the reasons or mechanisms for the rising trend of the past 50-year precipitation in northern Xinjiang and the adjacent areas have not been reasonably explored. This wetting trend has not extended further to the surrounding areas including Republic of Mongolia, major part of North China, and five republics of the former Soviet Union, and the need is thus pressing to explore the reasons or mechanisms behind this relatively “localized” wetting trend. [ABSTRACT FROM AUTHOR]

Abstract: Changes on water resources volume of 1960–2007 in the Upper Reaches of the Yangtze River are discussed in this paper. A time series (1960–2007) and its spatial patterns of actual evapotranspiration (ETa) estimation are analyzed based on Advection-Aridity model (A–A model) with selected parameters for 72 meteorological stations in the upper reaches of the Yangtze River Basin. The result indicates that average ETa of the basin changed in stages: slight increases in the first decade; a drop followed by fluctuations and lower increases in the next ten years; and then a dramatic decline in the latest decade, with three abrupt change years detected in the early 1970s, 1990s, and 2000s. ETa increases from mountainous northwest areas to plains in eastern areas, with significant decreases in plain regions and increases in the mountain region. ETa in the Sichuan Basin is found to decrease at the most rapid rate, and ETa in the sub-area to the south of the upland mountain region is increasing significantly. Such patterns of spatial trend in ETa result in reductions in regional variation, both annually and in all seasons. The change in ETa of this area is believed to be related to local water resource changes, and is impacted by the changes in climate factors. Temperature of this area has increased, and sunshine duration hours have shortened, leading to a reduction in net radiation. Relative humidity also has decreased. Comprehensively, reduction in both energy and moisture supply for evapotranspiration result in an increasing ETa. Moreover, a sharp drop of ETa occurred in the early 2000s, and meteorological factors including wind speed also show abrupt change to different extents. The impact of ETa on regional water balance at both inter-annual and intra-annual scales is also discussed in this study. [Copyright &y& Elsevier]