The Greater Khingan Mountains (Daxinganling) are China's important ecological protective screen and also the region most sensitive to climate changes. To gain an in-depth understanding and reveal the climate change characteristic in this high-latitude, cold and data-insufficient region is of great importance to maintaining ecological safety and corresponding to global climate changes. In this article, the annual average temperature, precipitation and sunshine duration series were firstly constructed using tree-ring data and the meteorological observation data. Then, using the climate tendency rate method, moving-t-testing method, Yamamoto method and wavelet analysis method, we have investigated the climate changes in the region during the past 307 years. Results indicate that, since 1707, the annual average temperature increased significantly, the precipitation increased slightly and the sunshine duration decreased, with the tendency rates of 0.06℃/10a, 0.79 mm/10a and-5.15 h/10a, respectively (P≤0.01). Since the 21st century, the period with the greatest increase of the annual average temperature (also with the greatest increase of precipitation) corresponds to the period with greatest decrease of sunshine duration. Three sudden changes of the annual average temperature and sunshine duration occurred in this period while two sudden changes of precipitation occurred. The strong sudden-change years of precipitation and sunshine duration are basically consistent with the sudden-change years of annual average temperature, suggesting that in the mid-1860s, the climatic sudden change or transition really existed in this region. In the time domain, the climatic series of this region exhibit obvious local variation characteristics. The annual average temperature and sunshine duration exhibit the periodic variations of 25 years while the precipitation exhibits a periodic variation of 20 years. Based on these periodic characteristics, one can infer that in the period from 2013 to 2030, the temperature will be at a high-temperature stage, the precipitation will be at an abundant-precipitation stage and the sunshine duration will be at an less-sunshine stage. In terms of spatial distribution, the leading distribution type of the annual average temperature in this region shows integrity, i.e., it is easily higher or lower in the whole region; and the second distribution type is more (or less) in the southwest parts and less (or more) in the northeast parts. Precipitation and sunshine duration exhibit complex spatial distribution and include four Keywords: climate change; temporal and spatial characteristics; northern Greater Khingan Mountains; sudden change test; period analysis

No abstract

No abstract

No abstract

Basing on 30 years’ historical image data sources of Sanshan Lake between 1986 and 2017, this paper proposes a water body tracking and recognition algorithm according to the complex water area features of the lake and its branches to conduct the extraction of the historical water surface area and analysis on influence factors of Sanshan Lake. Comparing to conventional image extraction methods such as the region growing algorithm and the two-pass scanning method, this method shows its advantage of being fast and accurate. By analysing the water surface variation law of Sanshan Lake in 30 years and the influence factors, the area of Sanshan Lake is found to show a significant attenuation trend with the annual average attenuation rate reaches 0.98%; the water surface area weakly correlated with the precipitation change; the lake shore waterline line retreated 0.3- 10 meters in the 30 years; the pond and farmland area increased by 133%, indicating that the regulation of the lake water body is more affected by the lake shoreline dike and the Regulating capacity of gate pump.