## 5 Discussion  
Although EMMA is a very effective grain-size research tool [39; 53; 54; 55; 56], through the result, the end-member model cannot effectively extract the grain size components affected by a single geological action (Figure 4). The grain size of the lake sediments was affected by the combined effects  
Figure 5: Grain size distribution and nonlinear trend fitting in sediment core TLC01 from Lake Ta-Lung-Chi. The blue triangles for the change points with the method of Piecewise linear fitting and trend changing points [51; 52]. of multiple external stresses, or the strength of the same force has large fluctuations. Although the end member model has wide applicability [57, 58], it is not an effective method to conduct research in this region. Existing studies have shown that the size characteristics of lake sediments are sensitive to the regional climatic environment [59, 60, 61]. In humid-semi-humid regions, on inter-annual and 10-year scales, coarse-grained sediments indicate wet years with heavy rainfall while fine-grained sediments indicate dry years with low rainfall [60]. During the process of lake sedimentation, changes in rainfall affecting the intensity of surface runoff can also determine to a considerable extent the amounts of coarse and terrigenous elastic materials entering the lake. In years with heavy rainfall, the capacity of surface runoff for erosion and transport is enhanced, and the sediment particle size in the runoff is increased; in dry years with low rainfall, surface runoff is low, making it difficult to transport coarse particulate matter to the lake, and the sediment particle size in the runoff decreases [62, 63]. In arid and semi-arid regions, during humid periods, precipitation is high, lake water levels are high, and the sediment particles are coarse [64]. In summary, grain size of lake sediments can provide environmental information about lake runoff, which indirectly reflected the variation in the regional climate [61]. Studies on grain size in arid regions can also reveal the frequency and intensity of sandstroms that have occurred in the past [65, 66], e.g., lakes in the Tibetan Plateau [59], Lake Chaiwopu, Xinjiang Province, China [67], Lop Nur, Tarim Basin, northwestern China [68], San Juan Mountains, Colorado [69], and Lake Hongjiannao, Shaanxi Province, China [70], all of which indicate that the debris transported by wind in arid areas is also a source of sediments to lakes. Through this research on Lake Ta-Lung-Chi in the Tian Shan, it was found that lake sediment size data can reflect regional climate change information. Because the CRU data are based on data from existing meteorological monitoring stations, it was possible to reconstruct a complete set of high-resolution, monthly average surface climate data for the period 1901 to 2019 covering an area of 0.25\({}^{\circ}\)\(\times\) 0.25\({}^{\circ}\) that includes all land types [22]. The weather station serving the area where Lak Ta-Lung-Chi is located in the middle of the Tian Shan is shown in Figure 1[22]. The earliest record of meteorological stations in China related to the study of Lake Ta-Lung-Chi is from 1951. Therefore, it is necessary to verify whether the CRU precipitation data from before 1951 [22] are credible. Through this study, it was found that the three-point moving average curve of the silty fraction content (16-32 um) was significantly consistent with the curve of total precipitation from April to September since 1950 (Figure 6). The results suggested that the grain size of Lake Ta-Lung-Chi in the Tianshan Mountains sensitively recorded the information of precipitation changes. The proxies that are sensitive to precipitation changes in lake sediments are different in different regions, for example, biomarker compounds [34, 71, 72], Rb/Sr ratios [73], and magnetic susceptibility [74] are sensitive to changes in precipitation in some regions.