Characteristics of temperature evolution from 1960 to 2015 in the Three Rivers’ Headstream Region, Qinghai, China

Abstract

The cumulative anomaly analysis, the ensemble empirical mode decomposition (EEMD), the Bernaola Galvan heuristic segmentation algorithm (BGSA), the Le Page test, the moving t test at different sub-series scales, and the quasi-periodic oscillations (QPOs) were used to demonstrate the statistical characteristics of the temperature changes in the study area from 1960 to 2015. The results were as follows: the temperatures varied obviously among subregions and seasons and they generally increased; the climate tendency rates of autumn mean temperatures were higher than those of summer and spring; additionally, the temperatures in the three subregions of the Three Rivers’ Headstream Region (THRHR) were relatively low in the 1960s, especially in the early 1960s, followed by those in the 1970s, and the annual mean temperature has been increasing since the mid-late 1980s, especially in the middle 1990s. The results of EEMD showed that the QPOs of the annual mean temperature series in the study area were mainly quasi-3 years, quasi-5–8 years, quasi-12–15 years, and quasi-35–38 years. The results of the annual mean temperature series mutational sites showed that a significant warming mutation began in approximately 1997; and the mutational sites of seasonal mean temperature series in the three subregions of the THRHR all began in the middle and late 1990s. The prediction result of the temperature series trend based on multiple methods showed that the warming persistence of annual and seasonal mean temperature series would be stronger, and their seasonal and regional differences were obvious.

Intensified Moisture Sources of Heavy Precipitation Events Contributed to Interannual Trend in Precipitation Over the Three-Rivers-Headwater Region in China

“…Taking the TRHR as a whole region, the summer precipitation over the target region is increased due to the contribution from the northwestern part (as shown in Figure 1C, black dots). This interannual precipitation trend of the "south-drier and north-wetter" spatial pattern is consistent with the wetting trend in the TRHR, which have been demonstrated in previous studies, for example, by Yi et al (2013) and Liu et al (2019).…”

Analysis of runoff variation and driving mechanism in Huangfuchuan River Basin in the middle reaches of the Yellow River, China

“…On the contrary, the curve shows a downward trend. According to the slope change, obvious mutation points can be detected and the time of mutation of the data series can be judged (Liu et al 2020).…”

Characteristics and trends of grassland degradation research

“…Due to its particular geographical location, alpine grassland is characterized by specific factors such as high altitude, sensitivity to climate change (Chen et al 2013), fragile habitat, distinctive structure of husbandry, and limited livelihood of local people. In addition, the alpine grasslands have been subject to an overall "warm and humid" climatic trend in the Qinghai-Tibetan Plateau (Xu et al 2008;Chen et al 2013;Liu et al 2020b). These single or complex factors, directly and indirectly, lead to the spatial and temporal differences of degradation forms, degradation intensity, and restoration methods of alpine grassland (Chen et al 2013;Li et al 2013;McSherry and Ritchie 2013;Yan and Lu 2015;Cao et al 2019;Dong et al 2020;Fayiah et al 2020;Wang et al 2020).…”