Zhi-Juan Liu

Based on the 1961-2007 ground surface meteorological data from 558 meteorological stations in China, this paper analyzed the differences of agricultural climate resources in China different regions, and compared the change characteristics of the agricultural climate resources in 1961-1980 (period I) and 1981-2007 (period II), taking the year 1981 as the time node. As compared with period I, the mean annual temperature in China in period II increased by 0.6 degrees C, and the > or = 0 degrees C active accumulated temperature in the growth periods of chimonophilous crops and the > or = 10 degrees C active accumulated temperature in the growth periods of thermophilic crops increased averagely by 123.3 degrees C x d and 125.9 degrees C x d, respectively. In 1961-2007, the mean annual temperature increased most in Northeast China, and the > or = 10 degrees C active accumulated temperature in the growth periods of thermophilic crops increased most in South China. The whole year sunshine hours and the sunshine hours in the growth periods of chimonophilous crops and of thermophilic crops in period II decreased by 125.7 h, 32.2 h, and 53.6 h, respectively, compared with those in period I. In 1961-2007, the annual sunshine hours decreased most in the middle and lower reaches of Yangtze River, while the sunshine hours in the growth periods of chimonophilous crops and of thermophilic crops decreased most in North China and South China, respectively. In the whole year and in the growth periods of chimonophilous and thermophilic crops, both the precipitation and the reference crop evapotranspiration in this country all showed a decreasing trend, with the largest decrement in the precipitation in the whole year and in the growth periods of chimonophilous and thermophilic crops in North China, the largest decrement in the reference crop evapotranspiration in the whole year and in the growth periods of thermophilic crops in the middle and lower reaches of Yangtze River, and the largest decrement in the reference crop evapotranspiration in the growth periods of chimonophilous crops in Northwest China. In 1961-2007, the climate in China in the whole year and in the growth periods of thermophilic crops showed an overall tendency of warm and dry, and the climate in the growth periods of thermophilic crops became warm and dry in Southwest China, North China, and Northeast China, but warm and wet in the middle and lower reaches of Yangtze River, Northwest China, and South China, whereas the climate in the growth periods of chimonophilous crops became warm and dry in North China, but became warm and wet in Northwest China.

Based on the 1959-2007 daily precipitation data and 1983-2007 spring maize phenologyical data, the thresholds of extreme precipitation at different places in Sanjiang Plain of Heilongjiang Province were calculated by percentile method, and, in combining with the indices involving the frequency and intensity of extreme precipitation, longest consecutive wet (dry) days, and contribution rate of extreme precipitation, the annual change characteristics of extreme precipitation, quantitative change of different grade precipitation, and distribution characteristics of extreme precipitation at each growth stage of spring maize were analyzed. In 1959-2007, the annual precipitation in Sanjiang Plain showed a slight decreasing trend, and the decreasing amplitude of precipitation days was much larger than that of precipitation. Accordingly, the annual distribution of precipitation tended to be more concentrated. The frequency and intensity of extreme precipitation declined, and the annual fluctuation of the frequency was bigger than that of the intensity. There was a slight decrease in the proportion of annual extreme precipitation to annual precipitation, but the decreasing tendency was not significant. The annual light rain days had a significant decreasing trend, but the annual moderate and heavy rain days didn't have. During spring maize growth season, the distribution ratio of extreme precipitation from high to low was reproductive growth stage, coexistence stage of vegetative growth and reproductive growth, vegetative growth stage, and premergence stage. There was a significant decrease in the proportion of the precipitation during spring maize growth season to annual precipitation, resulting in an increasing risk of precipitation scarcity during the growth season. The longest consecutive dry days during spring maize growth season showed a significant increasing trend, with the increment averaged 1.1 d x (10a)(-1), while the longest consecutive wet days showed a significant decreasing trend, with the decrement averaged 0.5 d x (10a)(-1). Under natural precipitation, the spring maize drought risk in the study region increased.

Based on the 1961-2007 observation data from 66 meteorological stations in the sub-humid and warm-temperate irrigated wheat-maize agricultural area of Huang-Huai-Hai Plain, this paper analyzed the spatiotemporal change characteristics of agro-climate resources for chimonophilous and thermophilic crops in the area in 1961-1980 and 1981-2007. The analyzed items included the length of temperature-defined growth season and the active accumulative temperature, sunshine hours, precipitation, reference evapotranspiration, and aridity index during the temperature-defined growth season. With climate warming, the length of temperature-defined growth season of chimonophilous and thermophilic crops in the area in 1981-2007 extended by 7. 4 d and 6. 9 d, and the > or = 0 degrees C and > or = 10 degrees C accumulative temperature increased at a rate of 4.0-137.0 and 1.0-142.0 degrees C d (10 a)(-1), respectively, compared with those in 1961-1980. The sunshine hours during the temperature-defined growth season of the crops decreased markedly; and the precipitation during the temperature-defined growing season decreased in most parts of the area, being obvious in Hebei and north Shandong Province, but increased in north Anhui and southeast Henan Province. In most parts of the area, the reference evapotranspiration of chimonophilous and thermophilic crops during their temperature-defined growth season decreased, and the aridity index increased.

Based on the 1961-2007 ground observation data from 88 meteorological stations in Southwest China, and by using statistical methods and GIS software, this paper analyzed the spatiotemporal change characteristics of agricultural climate resources in this region in the whole year and during temperature-defined growth period. In 1961-2007, the annual mean temperature in the region showed an increasing trend, with the increment averaged 0.18 degrees C x (10 a)(-1). The > or = 10 degrees C and > or = 15 degrees C accumulated temperature during temperature-defined growth period also showed an increasing trend, with the increment averaged 55.3 degrees C x d x (10 a)(-1) and 37 degrees C x d x (10 a)(-1), respectively. The annual sunshine hours decreased gradually from west to east, and the decreasing trend was more significant in eastern than in western region. The sunshine hours during temperature-defined growth period showed an overall increasing trend, and the spatial difference was great. The precipitation resource had an overall decrease, with the decrement in whole year and during temperature-defined growth period averaged 10 mm x (10 a)(-1) and 8 mm x (10 a)(-1), respectively. The annual reference crop evapotranspiration generally decreased, but the decrement was less than that of annual precipitation. The reference crop evapotranspiration during temperature-defined growth period within about 53% meteorological stations decreased.

By using the 1961-2007 daily weather data from 66 meteorological stations all over South China, this paper studied the spatiotemporal change characteristics of agricultural climate resources, including heat, light, and precipitation, in this region on the scales of whole year and temperature-defined growth season. In 1961-2007, the mean annual air temperature in this region tended to be increased by 0.20 degrees C x (10 a)(-1), and the climatic trend of > or = 10 degrees C accumulated temperature in temperature-defined growth season increased gradually from north to south, with an average of 98 degrees C x d x (10 a)(-1). Comparied with those in 1961-1980, the areas of the accumulated temperature zone of 6200-7500 degrees C x d and 7500-8000 degrees C x d in 1981-2007 increased by 1.5 x 10(4) and 4.7 x 10(4) km2, respectively. In 1961-2007, the sunshine hours on the scales of whole year and temperature-defined growth season decreased by -57 h x (10 a)(-1) and -38 h x (10 a)(-1), respectively, and the areas with sunshine hour > or = 1800 h on the two scales tended to be decreased, compared with those in 1961-1980. The precipitation on the two scales increased slightly, and the increment varied obviously in different parts of the region. There were 62% and 52% of the stations where the reference crop evapotranspiration on the scales of whole year and temperature-defined growth season was in negative, respectively. In 1981-2007, the high-value area of reference crop evapotranspiration decreased, while the low-value area increased, compared with those in 1961-1980. The mean climatic trend of annual humidity index was 0.01 x (10 a)(-1), and 70% of the stations showed an increasing trend. Comparing with that in 1961-1980, the humidity index on the scale of temperature-defined growth season in 1981-2007 was increased by 0. 02, with 53% of the stations showed positive. On the whole, the change characteristics of climate in South China in 1961-2007 showed a tendency of warming and wetting, which would impact the cropping system, yield, and agricultural structure in the region.

Based on the 1961-2007 weather data from 72 meteorological stations in three provinces of Northeast China, the change characteristics of agricultural climatic factors including yearly and temperature-defined growing season's mean air temperature, > or =10 degrees C accumulated temperature, precipitation, reference evapotranspiration, and sunshine hours were analyzed. In 1961-2007, the yearly mean air temperature in the three provinces had an increasing trend, with a rate of 0.38 degrees C x 10 a(-1). The > or =10 degrees C accumulated temperature in temperature-defined growing season also had an increasing trend, and the border of > or =10 degrees C accumulated temperature belt moved northward and eastward. The area of > or =3200 degrees C x d accumulated temperature increased by 2.2 x 10(4) km2. The belt of 2800-3200 degrees C x d moved northward about 0.85 degrees and eastward about 0.67 degrees, while that of 2400-2800 degrees C x d moved northward about 1.1 degrees. The sunshine hours decreased significantly, especially in the east part of Songnen Plain, central and west plains of Jilin Province, and west part of Liaohe River Plain. The area with sunshine hours > 2800 h decreased from 13.6 x 10(4) km2 to 4. 1 x 10(4) km2, and the zone with sunshine hours 2600-2800 h moved westward about 1.5 degrees. The average sunshine hour in temperature-defined growing season was 1174 h. Comparing with that in 1961-1980, the region with more sunshine hours in temperature-defined growing season in 1981-2007 narrowed significantly, and the zone with sunshine hours 1200-1400 h moved westward about 0.9 degrees. In 1961-2007, both the yearly and the temperature-defined growing season's precipitation decreased, and the yearly reference evapotranspiration increased in Heilongjiang Province and in the eastern mountain areas of Jilin Province but decreased in the central and west plains of Jilin Province and in Liaoning Province. Comparing with that in 1961-1980, the zone of reference evapotranspiration with the value of > or =900 mm in 1981-2007 moved westward about 1 degree, and the reference evapotranspiration in temperature-defined growing season increased in most regions of Heilongjiang and Jilin Province but decreased in a rate of 0-14 mm x 10 a(-1) in most regions of Liaoning Province.