Abstract:

Guangdong Province is situated in the coastal area of South China and belongs to the subtropical monsoon climate zone. Though precipitation is abundant, its spatial and temporal distribution is uneven. Drought is one of the major natural disasters in Guangdong Province. As global warming continues, droughts occur more frequently in Guangdong Province. Based on the monthly precipitation and temperature data of 36 meteorological stations in Guangdong Province during 1960-2015, the occurrence of drought in Guangdong Province was identified by standardized precipitation evapotranspiration index (SPEI), and drought variation trends and their spatial distributions were analyzed in this work. Crop (especially rice) drought disaster is of the widest area and greatest impact in Guangdong Province. Thus, the water demanding period of crops was used as a drought stage to identify drought years in this study. The spring drought period from February to April was defined as early spring drought, while the one from March to May late spring drought, which were identified by April SPEI3 and May SPEI3s, respectively. Similarly, September and October SPEI3s were used to identify early autumn drought and late autumn drought, respectively. April and May SPEI6s were used to identify droughts occurring from early and late winter to the next spring, respectively. The results show that drought disaster occurred every 3 to 4 years from 1960 to 2015 on average, and the identified drought years are basically consistent with drought disaster statistics. The drought changing tendency in Guangdong Province was analyzed by linear function fitting of the mean SPEI sequences. The fitted linear slope of the October SPEI3 sequence was -0.011, which passed the significance test of 0.1. However, the fitted linear slopes of the other SPEI sequences didn’t pass the significance test of 0.1. It means that the overall occurrence of drought did not significantly increase or reduce in spring or from winter to the next spring. However, occurrence of late autumn drought displayed a tendency to increase. Finally, the slopes of the linear functions fitting the SPEI sequences were spatially interpolated to demonstrate the spatial distribution of drought changing tendency in Guangdong. A significant tendency of alleviation of late spring drought was found for Shaoguan and Guangzhou, but a significant tendency of exacerbation of winter to the next spring drought for the Leizhou Peninsula. In most parts of the province, autumn drought mainly showed a tendency of intensification.

Key words: SPEI, drought identification, drought trend, Guangdong Province