The El Niño-Southern Oscillation (ENSO) is the strongest signal of interannual change of short-term climate, and it has an important impact on global short-term climate change. Although ENSO occurs in the tropical Pacific region, its effects are felt world⁃wide. For example, during the El Niño event, the Panama region is prone to drought, which will have a significant impact on shipping on the Panama Canal. Recent reports show that the Panama Canal region has been affected by drought since the spring of 2023, resulting in an abnormally low water level in the canal and the worst blockage in nearly 8 years. In view of this extreme phenomenon, the standardized precipitation-evapotranspiration index (SPEI) is used to analyze the drought conditions in the Panama Canal region, and the

Based on dynamic downscaling simulation data of temperature and precipitation by the regional climate model version 4 (RegCM4) from National Climate Center under the representative concentration pathways 4.5 (RCP4.5) and RCP8.5 scenarios, the simulation ability of RegCM4 was tested in baseline period (1986-2005). And on this basis, the climate change was analyzed in North China in future of the 21st century. The results show that RegCM4 had a better performance in simulating air temperature and precipitation in North China in baseline period. The change of surface air temperature, precipitation, consecutive dry days (CDD) and strong precipitation (R95p) under RCP4.5 and RCP8.5 scenarios will increase gradually in North China in future of the 21st century, but their changes under RCP4.5 scenario will be obviously less than those under RCP8.5 scenario. Under the higher emission scenario of RCP8.5, the annual mean air temperature will rise 1.77, 3.44 and 5.82 ℃ in near term (2021-2035), medium term (2046-2065) and long term (2080-2098) of the 21st century, the annual mean precipitation will increase 8.1%, 14% and 19.3%, CDD will reduce 3, 3 and 12 d, and R95p will increase 30.8%, 41.9% and 69.8%, respectively. In space, the mean air temperature in the whole year, winter and summer in North China will rise consistently in future of the 21st century, and the warming in summer will be the most, while the mean precipitation in the whole year, winter and summer will increase in most regions, and the increase of precipitation in winter will be the most. Meanwhile, CDD will decrease except in Shanxi and Beijing-Tianjin-Hebei areas in near term and medium term, while R95p will increase, which indicated that the drought events will reduce and the extreme precipitation will increase in the 21st century.

In recent years, agriculture and animal husbandry production in the western Sichuan plateau was greatly affected by drought, therefore, it was necessary to study the applicability of remote sensing drought comprehensive index in the grassland area of the western Sichuan plateau. In this study, the vegetation condition index (VCI), the temperature condition index (TCI) and precipitation condition index (PCI) were selected to construct the scaled drought condition index (SDCI), which was suitable for the combination of the regional weight of grassland in the western Sichuan plateau, the index monitoring results were verified by standardized precipitation evapotranspiration index (SPEI) during the same period, the characteristics of summer drought from June to August during 2000-2018 were analyzed after the suitable drought grades in the study area were divided. The results show that: (1) The drought judgment index SDCI highlighted the cumulative effect of precipitation and had high monitoring accuracy. It was basically consistent with the monitoring results of SPEI on the drought events in 2006. Only in some places, the scope and intensity of the drought were slightly different from the actual situation. (2) The location of the month-scale drought was mostly distributed in the west and south of Ganzi Prefecture and the south of Aba Prefecture, and in the northeast of Zoige there was mostly no drought in summer during 2000-2018. The degree of drought was stronger in June and August, it was mainly mild to moderate drought, and in July there was mostly mild drought and no drought. (3) The frequency of drought was high and the range was wide in June and August during 2000-2018. In July, the frequency of mild drought was 60.66% in the whole region, and the frequency of drought above mild level was higher (more than 40%) in the southwest, northwest, north and east of Ganzi Prefecture, while the drought frequency in northern Aba Prefecture was lower (less than 40%). The research showed that the SDCI with prominent precipitation effect had the ability to respond to extreme drought events, it could objectively and effectively monitor the drought status of grassland in the western Sichuan plateau.

Based on the daily minimum temperature observation data in southeast of Gansu Province during 1969-2018, the variation of extreme low temperature events was analyzed, then 74 circulation characteristic quantities from National Climate Center were used to research the circulation system affecting the extreme low temperature events. The results are as follows: (1) The frequency of annual extreme low temperature events in southeast of Gansu Province reduced obviously with a rate of 2.3 d·(10 a)-1 in the last 50 years, and the reduction was most significant in summer and slowest in winter. There was an abrupt change of extreme low temperature days in 1987, after the abrupt change, the frequency of extreme low temperature events was relatively lower. (2) Compared with the climatic mean, the intensity of extreme low temperature events tended to increase, before 1987, the low temperature intensity anomaly increased with a rate of 0.2 ℃·(10 a)-1, while after 1987, the extrem low temperature intensity anomaly increased with a rate of 1.2 ℃·(10 a)-1. (3) The intensity of extreme low temperature in spring, summer, autumn and winter mainly ranged from -5.0～5.0 ℃, 10.0～15.0 ℃, -5.0～10.0 ℃, -20.0～-10.0 ℃, and the occurrence frequencies were 61.9%, 90.1%, 73.4% and 73.1%, respectively. (4) There was a positive correlation between extreme low temperature events and Eurasian meridional circulation in southeast of Gansu Province. The extreme low temperature events was related with cold air, the area index of western Pacific subtropical high and the intensity of polar vorticity center in the northern hemisphere in winter, while it was related with subtropical high northern boundary of South China sea, subtropical high northern boundary of the western Pacific and polar vorticity intensity of the Pacific in spring. The composited analysis of geopotential height fields indicated that Mongolia was a cold high pressure center on ground, and polar vorticity center was located in the eastern hemisphere from 500 hPa to 100 hPa, the westerly belt prevailed meridional circulation, and east Asian large trough in the westerly belt was deep and westward, the region of southeast of Gansu was controlled by strong northwest airflow after the trough, which was favourable to forming extreme low temperature events.

 Based on the information of wind disaster accidents in Jiangsu section of the Yangtze River waterway and observations of automatic meteorological stations along the Yangtze River during 2015-2017, this paper analyzed the relationship between wind disaster accidents and strong breeze, strong crosswind. And combined the geographical environment and atmospheric background, a reasonable gale evaluation index was established. The results are as follows: (1) Wind disaster accidents occurred most in spring, which was related to high frequency of strong breeze and strong crosswind in this period. (2) The high occurrence period of wind disaster accidents and strong breeze was during 14:00-15:00 in a day, which was related to increase of convective wind in the afternoon. (3) The frequency of strong breeze and strong crosswind was directly affected by the difference of geographical environment in Jiangsu section of the Yangtze River waterway and indirectly affected the amount of wind disaster accidents. (4) A wind pressure early warning system had been established, when wind pressure was above 40 N·m-2, the risk was higher. (5) The enhancement of instantaneous wind had a great influence on navigation of ships. The WFI was more reasonable to evaluate the risk of strong wind. (6) By calculating the variability of air flow through water surface, the maximum wind force that may be suffered by ships on the river surface in winter and summer was estimated again, it verified that the current wind warning index was reasonable.

Based on observations of sunshine hours，cloud amount，wind speed and other meteorological elements during 1961－2009 in Shuozhou，the annual，seasonal and monthly variation of sunshine hours and its influencing factors were analyzed in this paper．The results indicated that the annual sunshine hours presented obvious ecreasing trend with－118．1 h/10 a tendency rate，and this phenomena started in 1980 and after 1990 it was more obvious．The seasonal sunshine hours also presented decrease trend，especially in summer．And monthly variation of sunshine hours also decreased especially in May．The annual wind speed in Shuozhou also reduced in recent 50 years especially after 1990．The air pollution increased after 1990 and annual wind speed reduction in Shuozhou may be the important reason for sunshine hours reduction in these years．