Based on the series of daily mean temperature,maximum temperature and minimum temperature in Xi'an observation station from 1971 to 2013,the interpolation experiments are carried out by using standard series method and multiple linear regression method,calculating the average error,average absolute error,root mean square error and the proportion of samples with the error between the interpolation value and the measured value within 0.5℃.The relative advantages and disadvantages of the two interpolation methods are compared and analyzed The experimental results show that the daily temperature series which obtained by the multiple linear regression method is better than the standard series method,and the characteristics of climate trend are more consistent with the actual observed data series.The t-test,the penalized maximal T test(PMTT)and the penalized maximal F test(PMFT)are used to test the homogeneity of the annual mean temperature series in Xi'an observation station from 1951 to 2020.The test results show that according to the t-test conducted on the historical evolution data of the station,only 2 of 6 times changes caused the discontinuity of the annual mean temperature and annual mean maximum temperature series,which were respectively caused by the increase of observation time and the change the instrument type.There were four discontinuities in the annual mean minimum temperature,which were caused by the relocation of stations,the increase of observation time,the replacement of instruments and the interpolation of missing measurement values.The four discontinuity points found in PMTT and PMFT detection are considered to be reasonable discontinuity points because there is no metadata support,and none of the two methods detected discontinuities caused by interpolation of missing measurement values,which indicates to a certain extent that the temperature series of Xi'an observation station from 1951 to 2020 obtained by the interpolation of missing measurement values with multiple linear regression method is relatively reasonable,and the temperature series have good homogeneity.
新疆东部黑戈壁气候恶劣、人迹罕至，是具有黑色砾石下垫面的生态脆弱区。利用东疆哈密戈壁陆气相互作用站2018年全年观测资料，给出该戈壁地表动力学与热力学粗糙度、比辐射率和地表反照率等陆面过程特征参数，并将这些参数代入Noah模式对该戈壁热通量、地表温度及土壤温湿度进行模拟。结果表明：（1）东疆黑戈壁下垫面动力学粗糙度为1.13×10-3 m，热力学粗糙度为0.32×10-3 m，比辐射率为0.905。（2）地表反照率日变化呈早晚高，中午低的“U”型曲线。12月因地面积雪，反照率最高，年内极大值出现在12月8日，为0.79，年均反照率为0.29。地表反照率关于太阳高度角的参数化方案为：α=0.78-0.47×(1-e^((-h)/1.12))，地表反照率关于5 cm土壤湿度的参数化方案为α=0.28-0.136w_s。（3）将改进后的陆面过程参数带入Noah模式，大大提高了模式在戈壁区域的模拟能力。
采用1961—2020年西北地区364站逐日降水观测数据，从降水量和降水日的角度对比研究了西北地区夏季降水趋势时空变化特征。结果表明：平均而言，西北地区夏季降水量占该地区全年总降水量的50%以上。整体上西北地区降水量呈现显著增多的线性趋势，但并非全区一致性增多。降水量增多（减少）的站数约占区域内总站数的57%（43%），降水日数呈现增多（减少）的站数约占总站数的43%（57%）。两者同时增加的站点主要位于南疆盆地、北疆西部及青海中部和北部等地，两者同时减少的站点主要位于甘肃东南部、宁夏、陕西中部偏东等地，而两者反相变化的站点主要位于新疆北疆地区、青海省西南部边缘地区和陕西南部。近60年西北地区极端降水量和降水日数也呈现出线性增加的趋势。西北地区各个区域降水量和降水日数除年际变化外，还存在年代际变化特征，但不同区域变化位相存在一定差异。
A wide-range low temperature rain and snow occurred in southern China at the end of 2018 and 2021 respectively,which made a severe damage to the life and production.As a result,it is of great significance to compare the formation factors of the two low temperature rain and snow weathers.The results show that:the northerly airflow in front of high pressure ridge lying the west side of the Lake Baikal accumulates at the rear of the downstream transverse trough which makes the Siberian high become stronger.The Rossby wave originating from the North Atlantic has energy dispersion in the blocking high regions,which is conducive to the weakening and collapse of blocking high.The cold air sweeps across China after the transverse trough turns to a meridional trough,resulting in strong cooling of the ground.At this time,the related strong cooling on the east and south sides of the Siberian high is controlled by the cold advection by low-frequency wind.The south branch trough in the low latitude is active,and the warm and wet air northward merges with the cold air from mid-high latitude,causing a wide range of rain,snow and freezing rain in southern China.However,compared with the process in 2018,the process in 2021 has shorter duration,smaller precipitation range and greater cooling amplitude in key regions.The reason is that Rossby wave energy disperses faster and the blocking high weakens more quickly which makes the cold air directly intrude China from mid-high latitude.While the cold air accumulates and transports westward near Lake Baikal,and then becomes weak when it penetrates southward in the 2018 process.
利用2017、2019年7月塔克拉玛干沙漠腹地GPS探空观测数据和地面观测资料，对比分析了沙漠腹地夏季晴天和沙尘暴天气大气边界层结构变化特征。结果表明：晴天和沙尘暴天气大气边界层结构显著不同，两者的位温、风速和比湿垂直分布规律差异较大。晴天大气边界层各气象要素垂直分布较为均一，形成深厚的对流边界层，高度可达5000m，夜间稳定边界层一般在500m左右。沙尘暴天气边界层内各气象要素垂直分布变化较大，白天对流边界层在1500m左右，而夜间稳定边界层在1000m左右。在陆面过程中，晴天净辐射强烈，地表增温迅速，近地层感热通量能量充足，为对流运动和湍流运动提供了热力条件，是形成深厚的对流边界层主要因素。而沙尘暴天气因云和沙尘颗粒的影响，阻挡了到达地表的辐射轻度，减弱了外部的热力条件，同时大尺度天气系统冷平流提供了充足的动力条件，迫使低空2000m高度范围的温度减小，风速增大，并携带大量的水汽，导致气象要素垂直分布特征改变，并最终形成了沙尘暴天气独特的大气边界层结构特征。
