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%).

To improve the forecast and early warning ability for the low visibility along the expressway, the hourly observation data of 10 traffic meteorological stations along Shaanxi section of the Lian-Huo expressway and the hourly reanalysis data of the European Center for Medium-Range Weather Forecasts are employed to analyze the distribution characteristics of low visibility and to explore the relationship of low visibility with other meteorological factors. The results show that along Shaanxi section of the Lian-Huo expressway, January has the most low visibility, while February has the least. During a day, the low visibility mostly happens from 00:00 to 10:00, and the low visibility of 0-50 m mainly occurs from 05:00 to 06:00. The low visibility duration is short with the majority of within 2 hours and the longest of 17 hours. The low visibility weathers occur frequently from Xingping to Changxing and Chencang section, where attention should be paid in daily traffic meteorological service. Accordingly to the analysis of the relationship between low visibility and other meteorological factors, the low visibility generally occurs under the conditions of air temperature from 0 to 5 ℃, relative humidity above 90%, wind speed less than 1.0 m·s^-1 and northeast to east winds. The low visibility weather in summer and winter is mostly associated with precipitation, which usually occurs during or after the precipitation and is accompanied by weather systems always. Compared with the low visibility caused by radiation cooling, the low visibility associated with precipitation exhibits longer duration and the wider range. The low visibility weathers occur at different relative humilities in different seasons, which in winter, summer and autumn are high, while in spring are relatively low.