In the absence of photochemical reactions, nocturnal ozone (O3) variation was found to be caused by boundary layer meteorological processes. In addition to low-level jet (LLJ) and convective storm (CS) events, cold front and foehn processes also cause nocturnal O3 increases (NOIs). The subsidence warming effect (Subsi.) caused by weak cold front and foehn processes cause the nocturnal surface temperature and O3 to increase. Statistical analysis revealed that NOI days accounted for 39.4 +/- 6.4% of the total number of days per year in Beijing, and the average occurrence frequency decreased by 1.7%/year over a recent five-year period (2018-2022). The LLJ process is the primary factor causing NOIs, and the average annual contributions of the LLJ, CS and Subsi. processes to NOIs were approximately 32.2 +/- 10.5%, 11.7 +/- 2.3% and 8.0 +/- 3.0%, respectively. From a seasonal point of view, the most NOI events occurred in summer, and the least occurred in autumn. LLJs contributed the most to the NOIs in each season, and the CS contribution was almost equal to that of LLJs in summer. LLJs that occurred near 00:00 LT and 04:00 LT had a greater probability of causing NOI events. Most of the nocturnal CS events occurred during 22:00 LT-02:00 LT (next day), and the contribution of CSs to NOIs fluctuated around 10.0%. More than half (68.0%) of the Subsi. events occurred during 23:00 LT-03:00 LT (next day). Subsi. events occurred during this period contributed more to NOIs than other periods. Meteorological processes more easily caused NOI events in the urban, Daxing and Tongzhou districts than other areas. The average surface O3 concentration during the early morning hours (04:00-06:00 LT) on NOI days was 8.8 +/- 3.2 mu g/m3 higher than that on non-NOI days, suggesting that NOIs can elevate the base O3 concentration during the following day.

This study analyzes the visibility characteristics in Beijing from 2015 to 2020 using the 10-min average horizonal visibility hourly data from 20 national meteorological stations (NMSs). We examine the visibility trends on different time and space scales, including year, month, day. Our findings reveal that the visibility of the Beijing area shows a noticeable change trend year by year. Overall, the number of days with high visibility (visibility ≥10 ​km) has increased, and the number of hours with low visibility (visibility < 1 ​km) has decreased. Low visibility in Beijing mainly occurs during winter, whereas high visibility occurs throughout the year. On a daily scale, low visibility mainly occurs around 6 a.m. and 8 p.m. Furthermore, the spatial distribution of high and low visibility in Beijing correlates with the topographic boundary between plains and mountains. We observed that mountainous areas have more days with increased visibility and fewer hours with low visibility, while plain areas have fewer days with high visibility and more hours with high visibility. These findings have implications for understanding the environmental hazards caused by poor visibility in Beijing, such as impaired air quality, increased traffic accidents, and reduced human mobility. By identifying the temporal and spatial patterns of visibility, this study provides valuable information that can be used to improve hazard mitigation strategies and promote public safety.

文章对北京市的气象低速回路风洞检定结果的测量不确定度进行了分析与研究.首先阐述了测量不确定度的定义和低速回路风洞的工作原理,然后通过建立风洞检定结果的数学模型,以及确定标准皮托管、温度传感器、湿度传感器、气压传感器和数字微压计分量的测量不确定度,得到气象低速回路风洞检定结果的扩展不确定度.由分析结果可以得出,要想提高风洞检定结果准确度,除了保证检定技术水平以外,还要进一步减少或消除仪器及仪器安装、人工读数、实验环境等影响因素带入的误差.

降雨的微观结构观测对于降水的精确预报以及人工影响天气至关重要,但受到非降水因素、湍流和雨滴重叠等因素影响,雨滴谱的观测数据存在一定的误差和错误.选取北京市9个国家级地面气象观测站在2017年4—10月期间的雨滴谱仪观测数据,结合翻斗雨量计观测资料和人工记录天气现象,研究雨滴谱观测数据质量控制方法.结果表明:错误的雨滴谱观测数据主要由霾、沙尘天气及昆虫活动引起,粒子速度主要在5 m·s-1以下,粒子大小分布较为分散.建立了速度、数量的双阈值质量控制方法,可以有效剔除错误雨滴谱观测数据,当速度、数量阈值系数分别为0.4和0.7时,TS评分最优,达到0.92;雨滴谱仪与翻斗雨量计观测降雨量的决定系数从0.757提高到0.985.该方法可以更有效地利用降雨观测资料,充分发挥新型探测设备建设效益.

利用北京国家基本气象站内多普勒测风激光雷达和L波段探空系统在2020年1月1日至5月31日期间进行了同步观测试验,在经过观测数据时间和空间匹配的基础上,以后者测风数据为参照标准,从探测风廓线的高度、风向和风速三个方面的一致性分析了激光雷达的测风数据质量.结果显示:在观测试验期间,激光雷达56.5％的观测时间里最大探测高度不低于2000 m,2.9％的观测时间最大探测高度不足1000 m;激光雷达探测获取的水平风向、风速与L波段探空系统具有较好的一致性,针对匹配得到的8491组对比观测数据,其风向和风速数据拟合总相关系数分别为0.965和0.986;总体风向、风速的平均偏差和均方根误差分别为?1.3°和16.1°、0.21 m·s?1和1.06 m·s?1;在2000 m以上高度,由于激光雷达观测数据的信噪比偏弱,获得可信的观测数据量减少,会对风向、风速一致性比对造成不利影响.

在湿度传感器检定过程中,除露点仪和温湿度箱引起检定结果的不确定度外,检定条件、操作不规范也会给检定结果带来附加误差.本文通过对标准器的各湿度点测得值标准偏差、露点仪工作时的热效应、掠过露点传感器的流量变化、露点仪最佳工作环境等进行了实际测试,结合湿度传感器测试历史资料,进行了综合分析.结果表明:①露点仪露点传感器的过流孔正对气流方向时,同温度下露点温度测得值偏高,露点仪测量的相对湿度偏小,否则会偏大.②在环境温度为20℃时,露点仪在各个湿度点上的n次测量值的标准偏差(离散性)最小.③露点仪的温度传感器在吸入式温湿度箱中,安装于露点传感器前端4 cm和后端4 cm时,其后端测得值比安装在前端测得值的最大值偏高0.45℃,相对湿度偏高0.5％.④各湿度点上的稳定时间(当箱内湿度达到设定值并趋于稳定后)应大于或等于20 s时,露点仪和被检湿度传感器采集到的标准值和测量值才真实.

文章根据活动保障和服务需求,在活动前期开展了多种表面温度观测,并与百叶箱气温、太阳辐射等进行对比与相关分析.结果 表明:各项观测温度的日最大值均出现在正午前后,常与太阳辐射辐照度同步达到日最大值.日变化最大的观测项目为人造假发温度,其次是柏油路面温度、塑料椅面温度和百叶箱外气温,日变化最小的观测项目为百叶箱内气温;采用人造假发放置地表的观测方法所得数据的误差较大,增加真发碎发、真发发套温度观测使数据更具代表性;塑料椅面与人造假发升温和降温较快;温度较高时,柏油路面温度较其他观测项目表面高温持续时间长.

文章介绍了一种新型湿度检定箱,其温度控制采用高效气液换热,湿度控制采用干湿气混合法反馈控制原理,湿度测量采用红外激光吸收式湿度传感器.通过实验测试,新型湿度检定箱的温度、湿度均匀度和波动度都优于目前计量测试部门使用的所有湿度检定箱,且测试室容积大,可对毛发湿度表(计)、干湿表等大型测试仪表和湿度传感器等进行检定测试,还可同时进行温度校准,具有很好地推广应用价值.

利用2016年10月-2017年2月大兴站CL51激光云高仪资料,分析霾、雾、轻霾、轻雾和晴空等天气后向散射强度廓线特征和日变化,统计各高度层后向散射强度、后向散射强度垂直梯度的概率分布.结果 表明:霾天气后向散射强度日变化不明显,雾和轻雾一般发生在夜间,清晨和傍晚.雾天气后向散射强度较霾天气大,雾厚度一般不超过300 m.霾天气后向散射强度随着高度的增加减小缓慢,霾的厚度＞500 m.与雾和轻雾相比,霾和轻霾天气垂直梯度绝对值取小值的概率较大.雾和轻雾天气400 m高度以上垂直梯度绝对值较小,400 m高度以下数值较大.由于霾区内粒子分布较均匀,雾区粒子分布起伏明显,所以雾天气垂直梯度绝对值出现大值的概率较霾天气高.

为深入了解气象探测环境对气温观测数据的影响,利用2017年北京市观象台(54511)与南海子站(A1274)逐小时地面气象要素数据,分析两站气温差异以及因站点探测环境导致的日照、风速和降水对两站气温差异的影响.结果表明:2017年两站气温差异较明显,年平均气温54511站比A1274站高0.75℃;两站逐月平均气温54511站全年高于A1274站,两站差值7月最低为0.60℃,9月最高为1.09℃;两站平均日最高气温较接近,平均日最低气温差异较大,54511站较A1274站高1.24℃;两站气温的日变化特征相似,呈单峰分布,54511站气温日较差低于A1274站.两站小时气温差值随着日照时长和强度的增加而增加,短波辐射效应最强的10—14时和长波辐射效应最强的19—23时两站气温差值与当日白天直接辐射曝辐量的相关系数分别为0.459和0.601;水平风速对两站气温差值的影响较大.水平风速超过5 m·s-1时,两站气温差小于0.1℃;当水平风速不超过1 m·s-1时,两站观测气温差值达到1.28℃;降水天气下两站的气温差值小于非降水天气,出现降水时次54511站平均气温仅比A1274站高0.2℃.两站相距4.3 km,气候均一,测站周边2 km范围内建设用地占比54511站比A1274站高约30％,植被占比低28％,水体占比相差不大.另外,54511站附近的五环路具有低反射率和高热容的特征,白天能够吸收太阳辐射储存较多的热量,这些热量在夜间释放,可能是两站探测环境对太阳辐射吸收的差异决定了两站温差受太阳辐射和风速的影响较大,而受降水影响较小.

The computation of atmospheric boundary layer height (ABLH) using ceilometer is performed based on the data of Vaisala CL51 ceilometer observed in October 2016 by the Beijing Daxing station. Both the gradient method and the wavelet covariance method were adopted. Our results show that the boundary layer height has different characteristics under different weather conditions. We compared our calculated results by the above two methods and found that there is no significant difference in ABLH. In the case of haze pollution, due to the absorption and scattering of solar radiation by pollutants in the atmosphere, the solar radiation that reached earth's surface is less, the atmospheric turbulence is weak, the ABLH is lower, and there is no obvious daily variation in the ABLH. While on sunny days, because of the warming of the earth by solar radiation, the ABLH is higher than that of haze days, and the daily variation of ABLH is more obvious. We found that the mass concentrations are negatively correlated with ABLH, and the correlation is more obvious for PM2.5 than that for PM10. We also compared the ABLH of ceilometer observation with that of radiosonde observation, Our results show that the above two approaches have good consistency with difference less than 150 m, and the correlation coefficient between them is 0.67. In most cases, the result of radiosonde observation is higher than that of ceilometer observation.

风寒温度表征不同气温和风速组合对人体的冻伤风险与舒适状况,直接影响雪上运动安全性和体验感。针对2022年冬奥会气象服务需求,利用延庆地区21个气象站的冬季观测数据,研究分析风寒温度的时空变化特征。结果表明:（1）风寒温度高值区处于延庆盆地区域,低值区处于缙云山等高海拔地区,均存在中度冻伤风险;（2）佛爷顶站冬季平均风寒温度为-15. 1℃,极端风寒温度达到-49. 4℃,冻伤暴露风险等级为中度到严重;（3）风寒温度的日变化为单峰单谷型分布,月变化中风寒温度最低值出现在1月中下旬,最高值出现在2月下旬;（4）在2010年1月5日与2016年1月23日2次典型寒潮天气过程中,引起风寒温度极低值的原因存在明显差异,前者为温度主导,而后者为风速主导;（5） 1978—2016年,延庆站冬季由于增温显著,导致风寒温度有明显上升趋势,而佛爷顶站温度增幅较小但由于风速有显著减小趋势,风寒温度也存在明显上升趋势。

Based on minute rainfall data collected at 362 automatic weather stations from June to September between 2013 and 2015 in Beijing, the authors analyze the characteristics of short-period heavy rainfall in summer, and propose a blue rainstorm warning (BRW) index. The analysis suggests that: 1) The maximum rainfall intensities in 5 minutes and 10 minutes in BRW events (events that meet the BRW criterion) are about five times that in other events, and the rainfall intensity decreases significantly after reaching the BRW criterion. 2) 63.0% of the total BRW events that meet the criterion last no more than 60 min after the rain begins, and the BRW events that start during 1800 LST to 0100 LST count for 60% of the total BRW events. 3) High minute-rainfall intensity can be a good index for BRW. If a BRW is issued when 5-minute rainfall reaches 7.7 mm, the lead time will be 16.7 min and the HSS score can be up to 0.503.

为了解决对湿度快速测量的需要,基于水汽分子对特定红外波长的吸收随其浓度变化的原理,文章通过对水汽分子吸收光谱的分析,设计了一种实用的湿度测量传感器,对其测量原理、技术实现及实际应用情况进行了介绍,实现了对水汽浓度的快速检测.该传感器在较宽的温度范围内,相对湿度测量准确度优于±1％RH,同时具有测量时间短、响应速度快等特点,在各种湿度测量、检定等场合具有广泛的应用前景.

The weighing gauges have been widely used nationwide in ground observing stations,undertaking the observation task of winter precipitation and providing observation data for winter precipitation forecast and service.Currently,126 sets of weighing gauges have been put to use by the Beijing Meteorological Service,of which 90％ are DSC2 weighing gauges.This paper focuses on the introduction of basic principles and the data quality control algorithm of DSC2 weighing gauges,and then two kinds of typical common faults are analyzed to propose the corresponding judgment methods and solutions.Finally,several precautions of daily maintenance for DSC2 weighing gauges are put forward to reduce related equipment failures.

To continuously improve the technology content and informationalized level of meteorological detection equipment management,it is urgent to establish efficient and timely relevant management platforms.Based on the actual situation of meteorological equipment management and relevant demands in Beijing,in this paper,we propose a design of the dynamic information management platform based on RFID (Radio Frequency Identification) for meteorological detection equipments.We expatiate the design of system structure,focus on RFID technology information transmission and detailed functions,and also put forward some thoughts and prospects for platform construction.

为更有效地利用降雨观测数据,充分发挥新型探测设备建设效益,文章对DSC2型称重降水传感器的测雨性能进行分析评估,选取北京市13个国家级地面气象观测站在2013年4-10月,称重式降水传感器与人工、翻斗观测降雨量的业务观测资料,分析称重与人工和翻斗观测在降雨总量、日降雨量等方面的差异.结果表明:在选取样本中,12个台站的总降雨量误差符合现行业务要求,三种测量在日降雨量等级判断方面基本一致.称重比人工观测的日降雨量平均偏小0.13 mm,日降雨量相关系数为0.9968,对应地,称重比翻斗观测的结果平均偏小0.17 mm,日降雨量相关系数为0.9983.

为掌握称重式降水传感器的仪器性能,分析称重式降水传感器在业务应用中存在的问题,提高称重式降水传感器数据可用性,选取北京地区38个台站称重降水传感器的异常降水观测进行统计分析,依照产生原因对异常降水记录开展归纳分类,将其总结为4个类型,即电源干扰型、温度敏感型、滞后型和融冻型,并分别对各类型异常降水记录的产生原因与误报特征进行分析,最后提出增加直流稳压模块、加强温度系数测定、改进设备结构或工艺、规范维护操作等多方面的对应解决思路.

为了更好地使用降水观测数据,对引起称重观测和人工观测的差异原因进行分析,选取北京市15个国家级地面观测站2012年11月-2014年1月称重式降水传感器与人工观测降水量业务资料,探讨称重观测与人工观测累积降水量的差异,并细化为对固态降水和液态降水两种降水类型进行相关性研究.结果表明:称重观测与人工观测日降水量相关系数为0.9990,88.0％的对比次数中,两者日降水量差值满足业务要求;在出现固态降水时,称重观测较人工观测降水量偏大,在出现液态降水时,称重观测较人工观测降水量偏小;两者在日降水量等级判断差异较小,小量降水时称重观测的能力较优;防风圈可显著提高称重观测固态降水的捕捉率,而称重观测内筒蒸发对夏季降水测量有一定影响.