Compared to inland areas, meteorological stations in the island regions appear scarce and unevenly distributed, which leads to noteworthy uncertainty in detailed characterisation of various meteorological elements. For the Zhoushan Islands, located in Southeast China, there exist many islands and islets, and the local terrain is quite complex. Therefore, different interpolation strategies usually generate diverse gridded results, which largely influence the reliability and accuracy of operational climate monitoring and diagnosing. Under the background of climate change, the Zhoushan region is frequently invaded by cold waves in recent years, so how to scientifically choose an interpolation scheme to reasonably represent spatial distribution characteristics of temperature becomes an important issue in local climate operations. To solve this problem, based on the index of root mean square error (RMSE), the interpolation effect of Ordinary Kriging (OK), Inverse Distance Weighting (IDW), and ANUSPLIN (ANU) are comparatively analysed for 8 cold wave processes influencing Zhoushan during 2014-2021. Two subdivided indices, i.e., temporal RMSE (TRMSE) and spatial RMSE (SRMSE) are further designed to evaluate the interpolation results on temporal and spatial dimensions respectively. Eleven stations are randomly selected from the total 53 meteorological observational stations to test the interpolation results of OK, IDW, and ANU for the minimum temperature, reduction of daily minimum temperature and daily-mean temperature in the 8 processes. It can be found that the bias in the ANU case is higher than that in the OK and IDW cases. To explain such a phenomenon, 3 interpolation experiments with dense surrounding stations, sparse surrounding stations, and specific distribution of examining stations (all the examining stations are not distributed in the main island of Zhoushan) are further designed. The results demonstrate that the performance of the ANU strategy is closely linked to the spread situation of peripheral stations. When the surrounding stations are concentrated, the interpolation bias of ANU is usually smaller than that of OK and IDW. However, if the surrounding stations appear sparse, the bias of ANU exhibits much larger. In the scenario of dense peripheral stations, regardless of the examining sites distributed over the main island or not, the ANU solution can always get the optimal interpolation results, which implies that the impact of topography on the performance of ANU in temperature interpolation is of less importance. Also, the influence of horizontal resolution for interpolation seems secondary. When the horizontal resolution for three interpolation schemes falls down to 1 km×1 km from 30 m×30 m, the change of RMSE is generally less than 0.1 ℃ for most circumstances, so the impact of interpolation resolution can be neglected.

利用常规资料、自动站加密资料、探空资料、ERA5再分析数据及多普勒天气雷达资料,对2021年4月30日影响浙北沿海的一次强对流天气过程进行分析.结果表明:①此次过程发生在高空冷涡及其槽后强劲的西北急流背景下,低空切变线和地面辐合线共同提供了抬升触发条件.②适当的对流抑制能量CIN、相对较低的自由对流高度LFC和较高的对流有效位能CAPE有利于形成上冷下暖的不稳定层结,深厚的垂直风切变配合中层干空气夹卷,使得强对流天气进一步发生、维持和发展.③此次阵风锋发展经历了 3个阶段,产生阵风锋的雷暴主体发展强烈并引起地面大风时,存在强回波中心高度快速下降、后侧中层强入流、径向速度辐散场及速度模糊等特征.④强冷空气堆下沉形成气压梯度密集区和风温湿切变易造成雷暴大风天气,负变温中心及正变压中心对强对流有一定指示性.⑤阵风锋过境时常出现气压陡升、风速加大、风向突变、温度骤降,由于雷达观测距离限制,预报员需前期分析潜势,结合自动站要素与雷达信息共同研判.

The CFSv2 forecast products have been widely used in climate prediction operation all over the world. Although the real-time forecast is able to basically capture large pattern of climate anomaly, there still exists obvious bias, which may have enormous impacts on predicted result and thus cannot be

利用NCEP等再分析资料,着重分析了2020年和2021年舟山地区大气环流形势的变化,得出以下结论:(1)2020年,全球受中部型厄尔尼诺事件的影响,副高总体偏弱,同时,西伯利亚长期存在的暖高压配合东北冷涡,使得北方的冷空气获得了足够抗衡副高推动雨带北移的能量,使副高难以在我国近海北抬,进而造成梅雨带在长江中下游地区和华东地区徘徊.孟加拉湾海域的特强气旋风暴"安攀"(超强台风级),驱动水汽通过其气旋性结构进入(逆时针旋转)其南侧形成西南风,获得足够多的动量和能量,使得西南风携带大量水汽涌入南海,加速了南海季风暴发.(2)2021年全球受弱的拉尼娜事件的影响,副高前期发展旺盛,同年西伯利亚中高纬度冷空气比较弱,无法与副高分庭抗礼,是造成2021年入梅早、出梅早,降水略超过常年的一个原因.后期副高迅速衰退到西太平洋,使得雨带在北方冷空气南下侵入,再次对舟山产生影响,产生了"倒黄梅"的降水现象.

热带气旋远距离暴雨(TRP)往往成为高影响天气,是业务预报难点.本文用地面、探空观测资料、雷达遥感资料以及NCEP一日四次0.5°×0.5°再分析资料,对2018年第22号台风"山竹"登陆广东期间在长江三角洲(简称长三角)地区引起的远距离暴雨过程进行分析.结果 表明:(1)这是一次发生在副热带高压(简称副高)控制范围内的热带气旋远距离暴雨,低层受台风倒槽影响.(2)这次过程第一阶段暴雨主要是在强的对流不稳定条件下,由对流层低层"山竹"倒槽中的辐合线触发对流产生,同时对流层高层"山竹"的极向流出汇入加大了中纬度西风风速,在长三角地区上空产生辐散,有利于上升运动的维持.第二阶段,对流不稳定条件有所减弱,但前一阶段强回波产生的低层偏北外出气流与东南风形成辐合线,辐合线上还有中γ尺度的涡旋产生,又促进了对流发展.850hPa台风倒槽北端形成一个低涡,500hPa副高边缘发展出一个短波槽,暴雨的动力条件更为有利.(3)长三角的3个强降水中心分别在长江口、杭州湾北岸的嘉兴沿海及宁波沿海,都是在水陆边界附近.(4)远距离暴雨区的涡度收支诊断发现:暴雨的初始扰动主要由近地层水平辐合辐散项提供,850hPa的水平辐合辐散项和扭曲项共同作用形成和加强低涡,并通过垂直运动上传使中层700～500hPa附近涡度增长,进而发展出500hPa短波槽.850 hPa涡度来自于台风倒槽和副高边缘的偏南急流.(5)在这次远距离暴雨过程中,台风"山竹"与海上西太平洋副高之间形成偏南低空急流,向长三角输送水汽,这与典型TRP事件相似.不同之处在于:典型TRP中暴雨的初始扰动一般由西风槽提供,而这次过程主要由低空台风倒槽和偏南急流提供,涡度上传形成高空短波槽,是不同于典型TRP事件的一个物理过程.

极端最高气温是日最高气温变化的上限.基于浙江省66个常规气象站的长序列气温观测资料,分析了浙江区域1973-2019年极端最高气温的时空演变特点,发现全省平均极端最高气温和最大极端最高气温均表现出明显的上升趋势,二者之间存在显著相关,前者在上世纪80年代末～90年代初发生了突变;在空间分布上,多年平均极端最高气温和最大极端最高气温大致呈现自内陆向沿海逐步递减的特征;浙江全省极端最高气温多出现在浙南的丽水市,但从上世纪90年代中后期开始出现在浙北地区(主要是杭州市、绍兴市和宁波市)的年份明显增多;2005年之前全省极端最高气温主要出现在浙西和浙中地区,之后出现在浙东地区的年份显著增多;极端最高气温最易出现在盛夏7～8月特别是7月下旬和8月上旬.在此基础上,进一步探讨了全省极端最高气温出现在浙北、浙中和浙南地区对应的大尺度环流特征以及ENSO不同位相与盛夏极端最高气温出现月份之间的关联,并对拓展研究区域、开展长三角和华东区域极端最高气温研究提出了展望.

Based on various statistical indices, the abilities of multi-generation reanalyses, namely the NCEP / NCAR Reanalysis 1 (R1), the NCEP-DOE Reanalysis 2 (R2) and the NCEP Climate Forecast System Reanalysis (CFSR), to reproduce the spatiotemporal characteristics of precipitation over Zhejiang Province are comprehensively compared. The mean absolute bias percentages for three reanalyses are 20% (R1), 10% (R2) and 37% (CFSR). R2 (R1) gives the best (worst) general depiction of the spatial characteristics of the observed precipitation climatology, whereas a significant wet bias is noticed in the CFSR. All reanalyses reasonably reproduce the interannual variability with the correlation coefficients of 0.72 (R1), 0.72 (R2) and 0.84 (CFSR). All reanalyses well represent the first two modes of the observed precipitation through Empirical Orthogonal Function analysis, with CFSR giving the best capture of the principal components. The root-mean-square error (RMSE) is the largest (smallest) in the CFSR (R2). The large RMSE of CFSR in summer (especially in June) contributes mostly to its systematic wet bias. After 2001, the wet bias of CFSR substantially weakens, probably attributed to increasing observations assimilated in the CFSR. On a monthly basis, the percentage of neutral bias cases are similar for all reanalyses, while the ratio of positive (negative) bias cases for CFSR is distinctly larger (smaller) than that of R1 and R2. The proportions of negative bias cases for R1 and R2 begin to increase after 2001 while keeping stable for CFSR. On a daily basis, all reanalyses give good performances of reproducing light rain; however, the reflection of moderate rain and heavier rain by the CFSR is better than R1 and R2. Overall, despite being a third-generation reanalysis product, the CRSR does not exhibit comprehensive superiorities over R1 and R2 in all aspects on a regional scale.

2018年5月浙江省出现历史罕见的极端高温热浪,全省大部极端最高气温达36℃以上,局部地区超过40℃,多站高温日数和极端最高气温破历史同期纪录;高温累积站次和有效积温均居历史第一位.利用浙江省66个常规气象站的逐日观测资料、NCEP/NCAR再分析资料以及国家气候中心西太副高环流特征量指数资料等对此次高温过程的环流特征进行诊断分析,结果表明:西太平洋副热带高压偏强、偏西、偏北是造成极端高温热浪的直接原因,副高的"西伸"与南亚高压的"东进"相向而行;在副高控制下,850 hPa中国东南部至西北太平洋区域形成强大的反气旋式风场异常,浙江地区盛行下沉气流;5月14—18日强高温过程期间,短波辐射通量表现为正距平,"辐射增温"与"下沉增温"的叠加效应进一步加剧了高温的极端性.副高强度和位置的变化与热带和中纬度环流关系密切.海洋性大陆对流活动增强、热带中太平洋和北印度洋对流异常旺盛、南海地区对流减弱、西太平洋无台风生成均是副高增强的有利因素;200 hPa西风急流轴偏北,利于西太副高的稳定维持.

运用天气学和动力诊断方法,结合卫星云图,分析了1211号台风“海葵”在浙江近海移向突然变化、强度爆发性增强的原因.结果发现:大陆暖高东移过程中脊线的转变,西太平洋副高西伸加强北抬,并与大陆暖高合并是促使“海葵”移向转变、移速加快的关键因素.“海葵”进入浙江近海时,弱的环境风垂直切变、强烈的低层辐合和高层辐散、东风急流和西南气流水汽输送的加强、低层正涡度的输入是其得以爆发性增强的主要原因.台风爆发性增强时,卫星云图上表现为:台风环流螺旋度迅速加大,结构密实,有完整清晰的台风眼形成,眼区范围缩小,南北两条水汽输送通道建立,水汽输入云带发展强烈,以及台风水平尺度发展到最大等特征.

By using four meteorological stations' data in Zhoushan from 1962 to 2015,the hourly automatic weather observation data and buoy station data from 2014 to 2015,the features of the sea fogs over Zhoushan sea area were statistically analyzed.Results show that the sea fog usually comes with the large scale background condition and a certain hydrographic characteristics.It shows that they come frequently in spring and less in autumn;however,they usually happen in the nighttime and early morning,while the time between midnight and early morning is the most frequently,and the fogs won't lift until 11:00.The sea fogs can be divided into four types on the basis of weather situations,while it has lots of differences for the seasons' changes and diurnal variations.This is the element characteristic of the heavy fog:the air temperature in the range of 5-27 ℃,the sea surface temperature in the range of 9-27 ℃,the depression of dew point in the range of 0-4 ℃.About 90％ heavy fogs happen when the relative humidity (2 m highly) ≥95％ and air-sea temperature difference in the range of-3.7-3.2 ℃,and the wind direction of the heavy fogs usually land between southeasterly and southerly winds,while the average wind speed in the range of 1-5 gale.By using the element threshold to show the revision of WRF visibility mode,it can obviously improve the accuracy of the qualitative forecasting for the heavy sea fogs.

本文选取定海站2016年6月—2017年6月的日均相对湿度、日均气温、日均风速和天气状况作为预报因子,建立起鱼鲞晾晒风干气象指数预报方程,对鱼鲞晾晒风干气象指数等级进行划分,得出晾晒风干指数等级和相应对策,为舟山渔农企业等从事鱼鲞风干晾晒加工工作的单位和个人做指导预报.

采用建立隶属度函数模型的方法,综合考虑了风、能见度和降水3个主要的气象因子,研发了对渔场捕捞适宜程度进行分级评价的气象指数产品—渔场捕捞安全气象指数,对政府部门应急决策和指导渔民安全生产具有重要意义.

Based on radar data and intensive surface observations,combined with JMA reanalysis data,a typical case with three consecutive squall lines is analyzed,which occurred in the north part of Zhejiang Province on 2 July 2008.Corresponding atmospheric conditions are investigated in detail.Special emphasis is given on the relationship between convection current and underlying surface state such as temperature,humidity and convergence of wind,especially the impact of land-sea boundary on rebirth and strengthening of convection current.Besides,the forming processes of the third typical bow echo,including development,attenuation,effluent,inflow,rebirth and dissemination of convection cell are studied in horizontal and vertical direction.After that,favorable conditions for all evolutionary stages and interrelation of three squall lines are summarized.It shows that there are specific places where newly-born convections and convection reinforcements are likely to be found,such as high temperature region,high humidity region,frontal surface,convergence line and coastline.In general,it's favorable for convection when the ground temperature is more than 32℃,the dew point temperature is greater than 23℃,the ground temperature gradient is greater than 0.l℃/km,or the ground level wind shear is greater than 5 m/s.Severe convective systems also react on underlying surface,and then convective systems are influenced as well,severe thunderstorm causes strong divergent outflow and cool pool is formed on ground layer.Cold air in the front of thunderstorm diverges outwards and causes gust front,which lifts the pre-frontal warm and moist.New convective cells develop close to the gust front,so that convective systems can diffuse forward.The question about convective systems' change crossing coastlines is complex.If they move to the sea by day,the temperature of underlying surface will descend and system's intensity would be weaken easily,and the situation will become opposite by night.In addition,the convergence of wind and intensity of convective systems enhance over the sea on account of small frictional forces and strong wind speed.Severe thunderstorm generates and strengthens at coastlines frequently,and particularly at the junction between the gust front and the coastline due to convergence caused by wind discontinuity around coastlines.Finally,the convection weather concept model before the trough is summarized:The area is within the scope of subtropical high before the trough at 500 hPa.There is strong southwest jet and warm wet tongue at low level,which forms unstable stratification.There is a big wind belt at 500 hPa,which forms a larger vertical wind shear from 0 to 6 km level,adding to the potential instability,and a strong convection system is triggered if a cold front comes.

Based on environment field,satellite images and the data of insular AWS(Automatic Weather Station),the reason that No.1007 tropical cyclone "KOMPASU" keeping stable track under the influence of "three cyclones" and the strong Subtropical High is analyzed.It shows that the weaker Tropical Cyclone has little impact on the relatively violent typhoon;the inner force of eccentric typhoon has much relative relationship with its own structure;the warming of the right front of typhoon can provide guidance for the typhoon track.

In this paper,a strong cold air gale process in March 2010 was analyzed.The results showed that the strong cold air gale appeared in the typical synoptic situation of the horizontal trough before the ridge of Lake Baikal.The cold air breaked out from lower levels to higher levels because the upper lever trough changed from the horizontal direction to vertical direction.The main reason of this strong gale was the pressure gradient caused by the interaction of the cold air and the intense development of depression in the East China Sea,and the strong cold temperature advection in low and middle layer.In addition,the coupling of divergence with a negative(positive) value at upper(low) level and intense momentum transportation downward,caused by the dynamic forcing descending due to the upper frontal zone passage,further increased the ground wind speed.

The climatic characteristics of typhoon influenced Zhoushan over the past 50 years are analyzed.It is found that the typhoons show distinct annual and monthly variations.The typhoon impact is closely related to its moving track,intensity at landfall and duration time after landfall.Analysis also shows that heayy rain driven by typhoon occurred at the north/east of Zhoushan is less than that at the south/west,while the situation of disastrous gale is opposite to the heavy rain.Typhoons shifting to the offshore sea,landing on Zhejiang and Fujiang prov-ince are the main tracks which have correspondence with strong rainfall and disastrous gales.Finally,the serious impact of four typhoon storms and two wind circulation features of typhoon are concluded.

对舟山海域一次猛烈的低压大风过程进行了诊断分析。结果表明:地面气旋的强烈发展是由于其与高空疏散槽前的正涡度平流中心、辐散中心和暖平流中心在垂直方向紧密耦合的结果,高空急流的活动和加强进一步促进了地面气旋的发展,地面气旋发生发展在青藏高原上空西北急流出口区的左侧和日本海上空西南急流入口区的右侧。地面气旋的发展和冷空气共同作用造成的强气压梯度是引起海上强风的主要原因;高空西南急流轴附近激发出的次级环流下沉支中往南的非地转风,加大了地面风速;对流层中下层垂直环流由上升运动转为一致的下沉运动,引起动量下传进一步加大了地面风速。