Functions of Karez to Xinjiang Agriculture in the Qing Dynasty from the Perspective of Historical Documents

Desertification is increasingly serious in Xinjiang,and the construction of water conservancy is a precondition for the development of agriculture.The main project for the development of agriculture and water conservancy in Xinjiang is to build Karez,which played a vital role in the development of Xinjiang agriculture in the Qing Dynasty.It has been recorded many times in historical documents of the Qing Dynasty,such as Lin Zexu s Diary,Tao Baolian s Diary,Xinjiang Atlas and Zuo Zongtang s Memorial to the Emperor,etc.,which recorded the situation and historical origin of Karez.Karez made a significant contribution to the development of agriculture in the Qing Dynasty.It increased the cultivated land in Xinjiang at that time,and increased the types and yields of crops.It is conducive to the stability and development of Xinjiang s economy.Until today,Karez is still an important water source for agricultural irrigation in Xinjiang.

Variations in the Summer Monsoon Rainbands Across Eastern China over the Past 300 Years

Based on reconstructions of precipitation events from the rain and snowfall archives of the Qing Dynasty （1736-1911）, the drought/flood index data mainly derived from Chinese local gazettes from 1736-2000, and the observational data gathered since 1951, the spatial patterns of monsoon rainbands are analyzed at different time scales. Findings indicate that monsoon rainfall in northern China and the middle-lower reaches of the Yangtze River have significant inter-annual （e.g., 5-7-yr and 2-4-yr） as well as inter-decadal （e.g., 20-30-yr and quasi-10-yr） fluctuation signals. The spatial patterns in these areas also show significant cycles, such as on a 60-80-yr time scale, a reversal phase predominates the entire period from 1736-2000; on a quasi-30-yr time scale, a consistent phase was prevalent from 1736 to 2000; and on a 20-yr time scale, the summer monsoon rains show different spatial patterns before and after 1870.

An Integrated Analysis of Dry-Wet Variability in Western China for the Last 4-5 Centuries

The dry-wet variability in western China and its spatiotemporal structure during the last 4-5 centuries was examined using 24 climate proxies from sediments, ice cores, historical documents, and tree rings. Spatial patterns and temporal evolutions of dryness and wetness were not only extracted from the proxy data using rotated empirical orthogonal function （REOF） analysis for the last 4 centuries, but also for instrumental data in the last 40 years. The leading five REOF modes indicate that 5 dry-wet variation centers exist in western China. Moreover, long-term variability in dryness and wetness is seen on long （centennial） to short （inter-decadal） timescales. An out-of-phase relationship for the inter-decadal variation was observed between the Hetao-upper Yangtze River region and north Xinjiang, indicating influences on dry-wet variations of the East Asian summer monsoon and the westerly winds over the two regions, respectively. A particularly long dry spell was found in the central Tibetan Plateau in the 19th century. A predominance of wet decades in the last 4 centuries was found in the arid and Hetao regions. Three regional dry-wet series with annual resolution in north Xinjiang, the upper Yellow River valley, and the Hetao area were constructed for analyses of the last 500 years. Dry-wet oscillations with periodicities of 16, 50, and 150 years in north Xinjiang, 50 years in the upper Yellow River valley, and 70-80 years in the Hetao region were identified by wavelet analysis. In general, these periods correspond to large-scale oscillations found in the climate system, are mainly related to ocean-atmosphere interaction.

Study on the extremely cold winter of 1670 over the middle and lower reaches of the Yangtze River

The snow-cover days over the middle and lower reaches of the Yangtze River （MLRYR） in the winter of 1670 were extracted from Chinese historical documents. By these records, the winter temperature anomalies （compared to the mean of 1961-1990） recorded at seven meteorological stations and the regional mean winter temperature were estimated. The results show that： （1） There was an average of about 30 snow-cover days over the MLRYR region in 1670, ranging from 11-20 days in Shanghai and eastern Zhejiang to 5140 days in eastern Hunan Province. The snow-cover days averaged about 40 days in Anqing and Nan- cheng, and ranged from 30 to 40 days in Quzhou, Jingdezhen, and Nanchang; and （2） the regional mean winter temperature in 1670 was estimated to be approximately 4.0 ℃ lower than that of 1961-1990. The maximum negative anomaly of 5.6℃ occurred in Nanchang and the minimum anomaly of-2.8 ℃ was detected in Quzhou. Both of these were lower than that of the coldest winter during the instrumental observation period of 1951-2010. This research could not only provide a method to es- timate historical climate extremes, but also provide a background to understand the recent instrumentally climate extremes.

Text extraction method for historical Tibetan document images based on block projections

Text extraction is an important initial step in digitizing the historical documents. In this paper, we present a text extraction method for historical Tibetan document images based on block projections. The task of text extraction is considered as text area detection and location problem. The images are divided equally into blocks and the blocks are filtered by the information of the categories of connected components and corner point density. By analyzing the filtered blocks' projections, the approximate text areas can be located, and the text regions are extracted. Experiments on the dataset of historical Tibetan documents demonstrate the effectiveness of the proposed method.

Reconstruction of cropland spatial patterns and its spatiotemporal changes over the 20th century on the Songnen Plain, Northeast China

We initially estimated the cropland area at county level using local historical documents for the Songnen Plain （SNP） in the 1910s and 1930s. We then allocated this cropland area to grid cells with a size of 1 km ×1 km, using a range of cultivation possibilities from high to low; this was based on topography and minimum distances to rivers, settlements, and traffic lines. Cropland areas for the 1950s were obtained from the Land Use Map of Northeast China, and map vectorization was performed with ArcGIS technology. Cropland areas for the 1970s, 1980s, 1990s, 2000s, and 2010s were retrieved from Landsat images. We found that the cropland areas were 4.92 ×10^4 km^2 and 7.60 ×10^4 km^2, accounting for 22.8% and 35.2% of the total area of the SNP in the 1910s and 1930s, respectively, which increased to 13.14 × 10^4 km^2, accounting for 60.9% in the 2010s. The cropland increased at a rate of 1.18 ×10^4 km^2 per decade from the 1910s to 1970s while it was merely 0.285 ×10^4 km^2 per decade from the 1970s to 2010s. From the 1910s to 1930s, new cultivation mainly occurred in the central SNP while, from the 1930s to 1970s, it was mainly over the western and northern parts. This spatially explicit reconstruction could be offered as primary data for studying the effects of changes in human-induced land cover based on climate change over the last century.