Analyzing the evolution of dry and wet in Guangdong Province is of great significance for strengthening water resource utilization and maintaining ecological environment stability. Based on evapotranspiration product of MODIS (Moderate Resolution Imaging Spectroradiometer) and meteorological observation stations data, choosing CWSI (Crop Water Stress Index) as the index of drought, Mann-Kendall (M-K) trend analysis and contribution methods were adopted to spatial-temporal distribution characteristics of CWSI as well as dominant meteorological factors. The results were indicated as follows: the annual CWSI indicated a downward trend through M-K trend test (-2.8×10^-3 per year), season in year with the most significant downward trend was in winter (-7.0×10^-3 per year), followed by autumn and spring, and the weakest was in summer. The annual CWSI was characterized by high (dry) in the southeast and low (wet) in the northwest. The CWSI in northern Guangdong, Pearl River Delta, and some areas in western Guangdong were at a lower degree of variation, while in Zhaoqing and the eastern coastal areas of Guangdong were relatively high. The CWSI in western Guangdong were all located at a lower degree of variation during the four seasons. The change of relative humidity was the overall dominant factor in the trend change of CWSI in Guangdong region, with spatial relative humidity being the dominant factor at 44.19% stations in Guangdong, followed by wind speed (22.09%), temperature (18.61%), and sunshine duration (15.11%).

Based on observation data of temperature and precipitation in Tianjin region during 1921-2016, the precipitation from the Global Precipitation Climatology Centre (GPCC-P) and the temperature from the Climate Research Unit (CRU-T) were evaluated and it was found that they performed well. On the basis of these results, the standardized precipitation evapotranspiration index (SPEI) was further used to analyze the temporal-spatial evolution characteristics of drought for almost a century in Tianjin region and its change trend in the future was estimated. The results are as follows: (1) Drought mainly occurred in the early 1940s, late 1990s and early 2000s, and it was dominated by mild drought and moderate drought in four seasons, and its high frequency season evolved from autumn, winter to spring and summer. (2) During six periods, climate tendency of SPEI showed “increasing and decreasing” in other seasons, but it showed “increasing, decreasing and increasing” in autumn, moreover the decreasing tendency in summer was most significant with a climate tendency of -0.3 per decade at Ninghe station during 1961-2010. (3) During 1921-1970, 1931-1980, 1941-1990, it was found that precipitation was dominating factor for the wet tendency in spring and winter, while temperature and precipitation were factors in summer and autumn; during 1951-2000, 1961-2010, 1971-2016, drought tendency in spring was affected mainly by temperature, in summer and winter it was synergistically affected by temperature and precipitation. (4) There was a negative correlation between SPEI and PDO in four seasons during 1921-2016 in Tianjin region, the correlation in spring and summer decreased from northwest to southeast, while that decreased from southeast to northwest in autumn and winter. (5) In the future, it will present drought trendency in summer in the whole region and in winter in the southwestern region, while drought trendency in spring and wet trendency in autumn will not significant.