Characteristics of agricultural climate factors during persistent droughts in North China

摘要

The spatio-temporal evolvements of effective rainfall, active accumulated temperature, and sunshine hours during drought periods in the North China were analyzed by using the methods of standardized precipitation index (SPI), Mann-Kendall (M-K), and ArcGIS, based on the daily climatic data of 93 meteorological stations from 1961 to 2010. The results were as follows: (1) The effective rainfall between the drought period in spring and summer and the multiyear showed no obvious differences, while it in crop growth period was less than the multiyear average, with the difference of 30 mm. The active accumulated temperature (= 0 degrees C) also displayed no difference, while in crop growth period it showed obvious differences, with the value as 70 degrees C and the maximum value up to 90 degrees C. The same rules were shown in the active accumulated temperature (= 0 degrees C) and in the active accumulated temperature (= 10 degrees C). Sunshine hours in drought periods showed less changes than average value in spring, summer, and growth period. (2) In the north-eastern Inner Mongolia, the effective rainfall in drought period in spring leveled with the average value. The difference of active accumulated temperature (= 0 degrees C) between spring, summer, in crop growth period, and multiyear reached 70 degrees C, 90 degrees C, and 50 degrees C, respectively. The active accumulated temperature (= 10 degrees C) showed the same rule with the active accumulated temperature (= 0 degrees C); In the central and northern Shanxi, the effective rainfall in drought period in spring and summer displayed less difference with the average value, while the difference in crop growth period was the most with the value of 65 mm; In Hebe, Beijing, and Tianjin, the variation of effective rainfall was not apparent in spring and summer, but there was a difference of 65 mm in the crop planting area. The active accumulated temperature (= 0 degrees C) in drought period in spring was higher than the average temperature for many years with the difference of 70 degrees C and in summer with the difference of 90 degrees C in the most severely affected areas.