[Characteristics and adaptation of seasonal drought in southern China under the background of climate change. III. Spatiotemporal characteristics of seasonal drought in southern China based on the percentage of precipitation anomalies].

To analyze the spatiotemporal characteristics and occurrence regularity of seasonal drought can provide theoretical basis for constituting the countermeasures of drought resistance and drought mitigation under the background of global climate change. Based on the 1959-2008 daily precipitation and atmospheric temperature data collected from the meteorological stations in 15 provinces (municipalities, and autonomous regions) of southern China, and using the percentages of precipitation anomalies (Pa) in the national standard "Meteorological Drought Classification", which were locally modified, the drought indices in southern China in 1959-2008 were calculated, and the spatial distribution characteristics of drought frequency in southern China in each year, each season, and each month, as well as the inter-annual changes of the drought intensity and the proportions of the stations with seasonal drought were analyzed. In the study period, the annual drought risk in southern China was generally low. There existed obvious seasonal differences in the spatial distribution characteristics of the drought. Autumn drought was most frequent and most intensive, mainly occurred in the middle and lower reaches of Yangtze River, South China and in the other major agricultural areas, winter drought was also frequent and intensive, mainly occurred in the west of Southwest China and the South China and other winter crop planting areas, while spring drought and summer drought were relatively less frequent or intensive. Spring drought mostly occurred in the southwest of Southwest China, the south of South China, and Huaibei area etc. , and summer drought mostly occurred in the middle and lower reaches of Yangtze River, southeastern coastal area of Fujian, and northeast of Southwest China. The area with drought frequently occurred showed an obvious monthly fluctuation and space transformation, which was decreased with time from November to next May, increased with time from May to November, in the smallest range from April to June, and in the widest range from November to December. The annual drought area showed a slight decrease while the drought intensity should a slight increase, but the situation differed with season, i. e. , spring drought area slightly decreased and the drought intensity weakened, summer drought area had an obvious decrease and the drought intensity weakened, autumn drought area increased obviously and the drought intensity increased, while winter drought area decreased and the drought intensity weakened.

[Characteristics and adaptation of seasonal drought in southern China under the background of climate change. V. Seasonal drought characteristics division and assessment in southern China].

Zoning seasonal drought based on the study of drought characteristics can provide theoretical basis for formulating drought mitigation plans and improving disaster reduction technologies in different arid zones under global climate change. Based on the National standard of meteorological drought indices and agricultural drought indices and the 1959-2008 meteorological data from 268 meteorological stations in southern China, this paper analyzed the climatic background and distribution characteristics of seasonal drought in southern China, and made a three-level division of seasonal drought in this region by the methods of combining comprehensive factors and main factors, stepwise screening indices, comprehensive disaster analysis, and clustering analysis. The first-level division was with the annual aridity index and seasonal aridity index as the main indices and with the precipitation during entire year and main crop growing season as the auxiliary indices, dividing the southern China into four primary zones, including semi-arid zone, sub-humid zone, humid zone, and super-humid zone. On this basis, the four primary zones were subdivided into nine second-level zones, including one semi-arid area-temperate-cold semi-arid hilly area in Sichuan-Yunnan Plateau, three sub-humid areas of warm sub-humid area in the north of the Yangtze River, warm-tropical sub-humid area in South China, and temperate-cold sub-humid plateau area in Southwest China, three humid areas of temperate-tropical humid area in the Yangtze River Basin, warm-tropical humid area in South China, and warm humid hilly area in Southwest China, and two super-humid areas of warm-tropical super-humid area in South China and temperate-cold super-humid hilly area in the south of the Yangtze River and Southwest China. According to the frequency and intensity of multiple drought indices, the second-level zones were further divided into 29 third-level zones. The distribution of each seasonal drought zone was illustrated, and the zonal drought characteristics and their impacts on the agricultural production were assessed. Accordingly, the drought prevention measures were proposed.

[Changes of China agricultural climate resources under the background of climate change. VIII. Change characteristics of heat resources during the growth period of double cropping rice in Jiangxi Province].

Based on the observation data from the meteorological stations and agricultural experimental stations in Jiangxi Province, this paper studied the change trend of the growth period of double cropping rice in the province, and, by using the indices growing degree-days (GDD), cool degree-days (CDD), and heat degree-days (HDD), the change trends of the heat resources at each growth stage of the double cropping rice in 1981-2007 were analyzed. Under the background of climate warming, the mean air temperature, mean minimum air temperature, mean maximum air temperature during the growth period of the double cropping rice all had an increasing trend, leading to the shortening of double cropping rice growth season, with the most obvious decrease of vegetative growth phase and the prolonged reproductive growth phase. In the vegetative growth phase, the GDD and HDD increased, while the CDD decreased. In 1981-2007, the effective heat resources of double cropping rice in Jiangxi Province increased, low temperature risk reduced, while high temperature risk increased. The increment of the effective heat resources for double cropping rice was higher in northeast Jiangxi than in southwest Jiangxi, low temperature risk was higher in south Jiangxi than that in north Jiangxi, and high temperature risk was the highest in middle Jiangxi.

[Changes of China agricultural climate resources under the background of climate change. II. Spatiotemporal change characteristics of agricultural climate resources in Southwest China].

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.

[Changes of China agricultural climate resources under the background of climate change: IX. Spatiotemporal change characteristics of China agricultural climate resources].

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.

[Spatiotemporal evolution characteristics of late spring cold in Guizhou Province under global climate change].

Based on the 1959-2007 observation data of daily mean temperature from 19 meteorological stations in Guizhou Province, and combining with the late spring cold (LSC) intensity index and disaster grade division standard, this paper analyzed the spatiotemporal evolution characteristics of LSC, including LSC occurrence frequency, ratio of LSC-occurring stations to all stations, decadal variation, abrupt climate change, and periodic variation, in the province. In 1959-2007, the occurrence frequency of no LSC in the province was the highest, followed by serious LSC, and that of medium and slight LSC was approximately the same. Under the background of global warming, the ratio of medium LSC-occurring stations to all stations had the most obvious variation, with the climatic trend reached 1.4% x (10 a)(-1), while the ratios of no LSC-, slight LSC-, and serious LSC- occurring stations all showed an appreciably decreasing trend. The LSC intensity in the province was the highest in the 1990s, followed by in the 1980s, 1960s, 1970s, and 2000-2007. In the province, the LSC intensity showed an increasing trend in west and northwest high altitude areas, central area, and north area, but an appreciably decreasing trend in east and south areas. In the west, northwest, north, and central areas of the province, LSC intensity had a mutation from low to high in 1975. The LSC in the province had an obvious periodical variation, with the inter-annual period being mainly 2-4 years, and the decadal periods being mainly 13 - 15 years and 27-29 years.

[Spatiotemporal change characteristics of agricultural climate resources in middle and lower reaches of Yangtze River].

The period 1961-2007 was divided into two by the time node of year 1981, and the change characteristics of the agricultural climate resources both in period I (1961-1980) and in period II (1981-2007) were analyzed and compared. The results showed that under the background of global warming, the average climatic trend rate of > or = 10 degrees C accumulated temperature in the middle and lower reaches of Yangtze River in temperature-defined growth season during 1961-2007 was 74 degrees C x d x 10 a(-1), and the > or =10 degrees C accumulated temperature in period II was 124 d higher than that in period I. Comparing with that in period I, the safe planting boundary of double cropping rice in period II moved 0.79 degrees northward. In 1961-2007, the precipitation in temperature-defined growth season had an overall increasing trend. Comparing with those in period I, the precipitation and the area of > or = 767 mm precipitation (water requirement for normal growth of double cropping rice) in period II were increased by 1.6% and 1.13 x 10(4) km2, respectively. The average sunshine hour in temperature-defined growth season in period II was reduced by 8.1%, comparing with that in period I. In recent 47 years, about 91.1% stations in the reaches showed a decreasing trend in sunshine hours. Comparing with that in period I, the reference crop evapotranspiration in temperature-defined growth season in period II showed a slightly decreasing trend, and its low value region expanded while its high value region narrowed. The beginning date of daily temperature over 10 degrees C was averagely 2 days earlier in period II than that in period I, while the ending date was in reverse. The ending date of daily temperature over 22 degrees C was almost the same in periods I and II.