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days over the middle and lower reaches of the Yangtze River （MLRYR） in the winter of 1670 were extracted from Chinese historical documents.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 （compare...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days over the middle and lower reaches of the Yangtze River （MLRYR） in the winter of 1670 were extracted from Chinese historical documents.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.展开更多
We initially estimated the cropland area at county level using local historical documents for the Songnen Plain （SNP） in the 1910s and 1930s.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area to grid cells with a size of 1 km &#...We initially estimated the cropland area at county level using local historical documents for the Songnen Plain （SNP） in the 1910s and 1930s.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.展开更多
基金supported by grants to the Institute of Geographic Sciences and Natural Resources Research (IGSNRR) from the Chinese Academy of Sciences (No. XDA05080100)the Ministry of Science and Technology of the People’s Republic of China (No. 2010CB950101)+1 种基金the Basic Research Project of the Ministry of Science and Technology (No. 2011FY120300)the National Natural Science Foundation of China (Nos. 41271124, 41071029)
文摘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.
基金National Natural Science Foundation of China, No.42171217, No.41471171 Doctorial Innovation Fund, No.HSDBSCX 2015-12
文摘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.
