High temperature weather occurs frequently in Shandong Province. Studying the variation law of different high temperature indexes and their circulation background is conducive to better defense against the adverse effects of high temperature weather. Based on the daily meteorological observation data of daily maximum temperature, daily minimum temperature and relative humidity of 122 national meteorological stations in Shandong Province from 1981 to 2022, the variation characteristics of high temperature weather in Shandong Province were studied by analyzing the annual maximum temperature, high temperature days, warm night days, and high temperature heat wave days, and the circulation situations of typical high temperature heat wave processes were analyzed. The results show that high temperature weather mainly occurs in the central and western regions of Shandong, and less in the peninsula area. The annual maximum temperature is higher in the west and lower in the east, and high temperature days, warm night days and high temperature heat wave days are characterize by the distribution of more in the west and less in the east. The annual maximum temperature, high temperature days, warm night days and high temperature heat wave days with different grades in Shandong Province show an increasing trend, and the increase range is larger in the west and smaller in the east. The increase range of annual high temperature heat wave days with different grades is mild, moderate and severe in descending order. The wet type high temperature heat wave weather is dominant and shows a significant increasing trend. When there is an obvious circulation situation of “two ridges and two troughs” or “two ridges and one trough” in the middle and high latitudes, it is prone to high temperature and heat wave weathers in Shandong Province, and the subtropical high pressure over the northwest Pacific Ocean is abnormally strong and northerly, and the downdraft under continuous fine weathers causes the temperature to rise and high temperature persist.

The mean daily temperature of 10 ℃ is the lower limit temperature for the suitable growth of thermophilic crop. The ≥10 ℃ active accumulated temperature (ATT₁₀) is one of the important indexes to measure the heat resources in the main agricultural regions of the Brahmaputra River and its two tributaries over Xizang (BRTX). Based on the daily average temperature data of 9 meteorological stations in BRTX from 1981 to 2022, the linear trend estimation, Pearson coefficient, Mann-Kendall test and R/S analysis method were used to analyze climate change characteristics of ≥10 ℃ boundary temperature (BT₁₀). The results are as follows: (1) With the increase of altitude, the BT₁₀ showed obvious vertical zonal characteristics in the main agricultural regions of BRTX, including the delay of initial date, the advance of the last day, the decrease of duration days and the ATT₁₀. (2) From 1981 to 2022, the initial date of BT₁₀ was advanced by -2.53 d·(10 a)^-1, and the final date delayed with a rate of 3.33 d·(10 a)^-1, the duration days and ATT₁₀ significantly increased with a rate of 5.87 d·(10 a)^-1 and 106.19 °C·d·(10 a)^-1, respectively. Compared with the Qinghai-Xizang Plateau, the magnitude of BT₁₀ change was significantly larger. (3) The 1980s was the decade with the latest initial date, the earliest final date, the shortest duration days and the lowest ATT₁₀ in the past 40 years, while the 21st century was the opposite. (4) The H indexes of the BT₁₀ were all greater than 0.65, indicating that in the future the BT₁₀ will maintain a strong persistence of earlier initial day, later final day, prolonged duration days and increased ATT₁₀. The mutation change of the initial date of BT₁₀ occurred in the early 1990s, while the abrupt change of the final date, duration days and ATT₁₀ occurred in the first decade of the 21st century.

Based on daily temperature data from 122 national meteorological stations in Shandong Province from 1961 to 2018, three extreme low temperature indices were calculated, and it was found that the occurrence frequency of extremely low temperature events defined by the scale of drop in daily minimum temperature in 24 hours could better reflect the characteristics of extremely low temperature in spring in Shandong. And on this basis, ERA-Interim monthly reanalysis data and Hadley sea surface temperature data were used to analyze the spatial and temporal distribution characteristics of occurrence frequency of extremely low temperature events in spring in Shandong and the anomalous characteristics of atmospheric circulation. The results are as follows: (1) The occurrence frequency of extremely low temperature events had multi-time scale variation characteristics in spring in Shandong. (2) The obvious wave train structure on 500 hPa geopotential height field was existed in mid-high latitudes in the typical extreme low temperature years in spring in Shandong. (3) The North Atlantic Ocean to the south of Greenland was a key area for vertical wave flux transmission. In this key area, the energy in the lower layer transmitted upward, and dispersed outward in the upper layer, which was beneficial to the maintenance and enhancement of the extremely low temperature in spring in Shandong. (4) The triple pole mode of sea surface temperature in the North Atlantic in the preceding winter had a significant positive correlation with the occurrence frequency of extremely low temperature events in spring in Shandong. The triple pole mode of sea surface temperature excited the Eurasian wave, which led to the deepening and strengthening of 500 hPa trough over the Lake Baikal area. Due to the influence of cold air behind the trough, the extremely low temperature events occurred frequently in spring in Shandong.

 Based on conventional meteorological observation data in Tianjin and the ECWMF ERAInterim reanalysis data (0.125°×0.125°), the transformation processes of raintosleet and then sleettosnow were analyzed from October to next April during 2000-2015 in Tianjin. The humidity and geopotential thickness during the transformation process of precipitation phases were analyzed, and 9 factors, namely temperature on 850 hPa, 925 hPa,1000 hPa and surface, thickness from 1000 to 850 hPa and from 850 to 700 hPa, 0 ℃ layer height, -4 ℃ layer height and 925 hPa relative humidity, were identified, which had close relationship with transformation process of precipitation phases. Further, their corresponding threshold indexes for different precipitation phases were given. And through the analysis of 3 weather cases, the usability of the indicators had been further verified. The discriminant equation for precipitation phases was established by using the 9 factors, it was found that the backtesting discriminant accuracy for rain and snow was higher than 80%.

Taken the complex topography with lake, plain and mountains in Poyang Lake and its surrounding as a test area, the near ground wind speed with high temporal and spatial resolution was simulated under two boundary layer parameterized schemes (MRF and MYJ) of WRF model in 2010, and combined the observation data from three wind towers, the prediction results were tested. The results show that the effect of wind speed prediction at 70 m height by WRF model under two boundary layer parameterized schemes was well in complex underlying of Poyang Lake, the temporal change of predicted wind speed was in good agreement with the observations, and the prediction of wind speed with boundary layer of MRF scheme was slightly better than that of MYJ scheme. The influence of terrain on near ground wind speed prediction was obvious in Poyang Lake area, and the prediction of wind speed at 70 m height in Jishan with flat terrain was the best, while that in Shizishan with the most complex terrain was poor relatively. The forecast effect of wind speed with different levels was different. The forecast effect of 5-25 m·s-1 wind speed section was better than that of 0-5 m·s-1 wind speed section. The contribution rate of phase deviation was 60% and above as the main source influencing the error of wind speed prediction near surface layer of Poyang Lake area, while that of system deviation and amplitude deviation was small, so the effect of wind speed prediction could be improved to some extent through linear correction to system deviation and amplitude deviation.

Abstract:According to the data of temperature，precipitation，the beginning of frost，the end of frost，frost－free period，≥0℃and　≥10℃accumulated temperature from Shuozhou Meteorological Bureau in Shanxi Province during the period of 1957－2009，the climate change in Shuozhou city was analyzed．The results showed that the precipitation in Shuozhou decreased，but the temperature increased．Along with annual mean temperature’s increase and precipitation’s remarkable reduction during 1998－2009，the date for the　beginning of frost was obviously postponed;and the date for the end of frost presented stable and early trend．The frost－free time presented prolonged tendency．The accumulated temperature of≥0℃and≥10℃presented increase trend．These changes will affect　layout and structure of the local agricultural production．Key words:climatic change;precipitation;temperature;the date of beginning and end of frost;frost－free eriod;accumulated temperature;Shuozhou

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．