2008年10月的一次寒潮天气过程分析

文章选择常规天气以及物理量资料,利用天气学原理分析了2008年10月21—23日发生在包头地区的寒潮天气过程,从中寻求一些有物理意义的预报指标,为今后的预报提供可靠的预报依据。     

秸秆焚烧导致的江苏持续雾霾天气过程分析

利用常规观测资料和NCEP再分析资料,从污染情况、环流背景、地面气象要素特征、水汽、热力及动力条件等几个方面对江苏2012年6月中上旬持续雾霾天气进行了分析。结果表明:江苏及周边省市秸秆焚烧造成大量的气溶胶粒子悬浮于空中,是造成江苏出现持续不同程度的霾天气的主要原因,同时也为雾滴形成提供了丰富的凝结核;中高层冷空气强度未能完全破坏底层相对稳定的层结,较小的风速和较大的湿度有利于雾霾的发展,重度霾或雾风速多在3 m/s以下,且相对湿度在80%以上。频繁的弱降水过程对雾的形成和霾的加重起到了重要的作用;低层的逆温或近中性层结的维持,为雾霾持续存在提供了有利的层结条件,且浓雾形成主要有辐射贴地逆温和平流逆温两种形式;垂直上升运动与雾霾的发展之间有着互相影响的紧密联系,在具备一定的水汽条件时,底层弱的上升运动有利于雾体的向上发展从而促进雾的加浓。后向轨迹模拟雾霾相对较严重的6月10日污染轨迹表明沿江和苏南地区污染物浓度上升除了本地悬浮颗粒物外,安徽境内的污染物的输送也是一个重要因素,而北部地区更多还是本地的污染源。     

厦门空气污染指数与地面气象要素的关系分析

利用相关统计法分析2006—2008年厦门市地面气象要素对空气污染指数变化的影响规律。结果表明：风速、气温、降水、相对湿度和水汽压对空气污染指数有显著负效应作用,气压起显著正效应作用;风向影响较为复杂, NNW-N-E-ESE风起正效应作用, SE-S-W风起负效应作用,厦门风向总体不利于空气质量提高,全年仅夏季盛行SE-S-W风。API指数与风向、气温、降水、气压、相对湿度和水汽压的季节变化规律有高相关性。API指数与气象要素中的水汽压关系最相关,其次是气压。     

The Annual Characteristics of Rainwater HCHO in Guiyang City,Southwest of China

HCHO is ubiquitous and important chemical constitutes in the troposphere. The concentrations of the HCHO (aq) in the rainwater were measured in the Guiyang city, southeastern of China from May 2006 to April 2007 and 153 discrete samples were collected. Rainwater (N = 151) HCHO (aq) concentrations ranged from lower than method detection limit (MDL) to 40.2 µmol/L with a volume weighted mean value of 7.4 ± 8.8 µmol/L. The strong correlations between HCHO (aq) and HCOO^? (r = 0.69, n = 137), HCHO (aq) and nss‐ (r = 0.74, n = 137), HCHO (aq) and (r = 0.67, n = 137), HCHO (aq) and (r = 0.74, n = 133) suggest the significant influence of the anthropogenic input for the HCHO (aq) levels. The concentration levels of rainwater HCHO (aq) was inversely proportional to the amount of rainfall, indicating the below‐cloud process is the most important mechanism for rainwater HCHO (aq) scavenging processes. More than 70% of the HCHO (aq) wet deposition took place during the early stage of the rainfall. According to the air mass back‐trajectory analysis, the rainwater with industrial back‐trajectories coming from the north had the highest levels of HCHO (aq) while the rainwater with the green‐covered or marine back‐trajectories from the southeast had the lowest concentrations, and this indicate the HCHO (aq) originated from urban or industrial regions served as an important source of the rainwater. The annual HCHO (aq) wet deposition flux was calculated as 6.96 mmol/m² per year and the total deposition flux was estimated as 24.35 mmol/m² per year, 71.4% of which was dominated by dry deposition.     

邢台沙河市冬季大气污染特征与潜在源区分析

为了解邢台沙河市冬季大气污染特征,选取2017年12月至2018年2月沙河市区3个省控站点（司法局、市政府、宣传中心）的逐时监测数据,分析了沙河市主要污染物的时空分布特征和潜在源区。污染物浓度特征分析表明:整个冬季司法局、市政府和宣传中心站点的细颗粒物（PM2.5）平均浓度分别为118.0 μg/m3、121 μg/m3和135 μg/m3。在大气自然活动和人为污染排放的共同作用下,PM10、PM2.5、SO₂、NO₂和CO均有明显的日变化特征。整个冬季沙河市的ρ(PM2.5)/ρ(PM10)、ρ(SO₂)/ρ(NO₂)均值分别为0.57和1.05（ρ为各物质的浓度）。且随着污染加重,ρ(PM2.5)/ρ(PM10)、ρ(SO₂)/ρ(NO₂)均明显升高,表明燃煤贡献增加;污染物空间分布特征分析表明:位于3个站点东北处的玻璃企业产生的污染物可能对监测站点造成了一定影响。污染物空间差异分析表明,区域污染范围越大、强度越高,大气污染的空间差异性越小;潜在源分析表明:沙河市PM2.5的强潜在源区分布在其周边区域,随着PM2.5浓度增加,强潜在源区呈缩小趋势。沙河市东南部的本地源对PM2.5浓度有主要贡献,而此处正是玻璃企业的聚集地。     

大气阻力引起卫星轨道衰减的数值模拟

本文以德国低轨道卫星CHAMP为例,联合考虑地球扁率和大气阻力摄动的影响,对相应摄动方程进行数值积分,计算轨道根数变化,并进而计算得到卫星空间位置,由此模拟考察大气阻力引起的轨道高度衰减.模拟中使用综合考虑了太阳辐射和磁暴等多种因素影响的最新国际大气标准JB2008模式来计算热层大气密度. 选取CHAMP卫星轨道高度自然衰减（无点火提升卫星高度操作）的2005全年进行模拟;为了考察不同年份阻力系数的可能变化,对2002年1—3月处在较大高度的轨道也进行了模拟.考虑到CHAMP卫星的特殊几何构形及飞行高度的热层温度条件,取阻力系数大于2.8,并在一定范围内变化,以求得模拟与实际轨道衰减符合较好.结果表明,对于2005年,阻力系数为2.91时模拟得到的轨道高度的衰减与实际轨道衰减符合得最好,模拟与实际轨道半长轴全年的标准偏差为81m;在卫星高度稍高的2002年,模拟的最佳阻力系数为3.0;模拟所得最佳阻力系数值比传统使用的值2.2大30%以上.由于在模拟中忽略了高阶保守力分量,所得近/远地点高度没有出现实际轨道所显示的周期性起伏.     

The Effects of Environmental Conditions on Concentration and Emission of Ammonia in Chicken Farms during Summer Season

This paper presents a field study conducted in northwest Turkey and characterizes the NH₃ concentration and emission measured in summer season from three chicken farms. The influence of environmental conditions on NH₃ concentration and emission was also investigated in this study. Ammonia concentration, temperature, relative humidity and airflow rate were continuously recorded for four sequential days. The environmental conditions were measured using a multifunction temperature and humidity‐meter with a hot wire probe. Portable multiple gas detectors with electro‐chemical sensors were used to measure NH₃ concentration. The NH₃ emission rates for houses were calculated by multiplying simultaneously measured NH₃ concentrations and air flow rates. The average daily mean (ADM) house concentrations of house 1 (H1), house 2 (H2), and house 3 (H3) were measured as 4.43, 3.71, and 6.20 ppm, respectively. NH₃ concentration was inversely proportional to temperature (r = ?0.279), relative humidity (r = ?0.063) and airflow rate (r = ?0.554) for all monitored houses. The ADM house NH₃ emission was 135 g/(h house) for H1, 255 g/(h house) for H2, and 117 g/(h house) for H3. The combined average emission rate in this study (0.26 g/(d bird)) was lower than the emission rate measured in chicken farms in the USA. However, our results were comparable to rates calculated in European studies because house design, ventilation system and bird diet applied in Turkish chicken farms are very similar to those employed in European countries. The NH₃ emissions were significantly correlated to NH₃ concentrations (r = 0.45, p ≤ 0.001) and airflow rates (r = 0.97, p ≤ 0.001). A clear diurnal pattern was obtained for NH₃ concentrations rather than NH₃ emissions at the end of the study.     

A Novel Concept for the Removal of Solvent Vapors from Exhaust Air

The emission of large amounts of solvent vapors with exhaust air from industrial production into the environment is a serious problem. In Germany, industry‐sector‐specific threshold values are applied and technical measures for pollution reduction are required. Different techniques for exhaust air cleaning are in use but still posing problems concerning costs and reliability. For these reasons, the development of processes for exhaust air treatment is the subject of the current research. A new concept for exhaust air cleaning is introduced that combines absorption of a solvent vapor by an organic fluid and a subsequent adsorption by a molecular sieve placed in the absorber. It was managed to close the loops of solvent recovery and sorbents regeneration. In laboratory‐scale experiments it was possible to reduce an initial ethylacetate pollution of 800 mg/m³ or 349 mg C/m³ below the limit value of 75 mg C/m³ over 60 h duration. Thermogravimetric measurements assisted to define optimum conditions for solvent recovery at 180°C from the molecular sieve. One unexpected positive finding was the considerable increase in the solvent release in the presence of the absorption fluid while adsorption isotherms revealed first insight into this process.     

长短期记忆神经网络(LSTM)模型在低能见度预报中的应用

利用浙江省义乌市2015—2019年逐小时气象观测数据(相对湿度、风速、地气温差、能见度)和空气质量指数(Air Quality Index, AQI)数据, 分析了义乌地区低能见度天气(观测能见度lt; 10 km)的分布特征和气象要素条件。利用长短期记忆神经网络(Long Short Term Memory Neural Network, LSTM)模型对逐小时能见度进行模拟, 分别对比了观测能见度作为输入变量与否的模拟效果; 根据义乌地区低能见度天气条件的特征, 将模拟时段分为三个时期(11月至翌年2月, 3—6月, 7—10月), 对比了分时期模拟的效果; 以及评估了模型的预报步长。结果表明: 高湿、高污染、气温高于地温和低风速是义乌地区低能见度天气的主要特征。LSTM模型对单站能见度有较好的模拟效果, 当输入参数中加入历史观测能见度时, 能大幅提高模拟准确度, 日均能见度模拟结果均方根误差RMSE=0.63 km, 平均绝对误差MAE=0.51 km, 拟合优度R²=0.99;分时期进行模拟能得到更精准的模拟结果。本研究中选用的输入要素在冬季(11月至翌年2月)模拟效果最好, RMSE=2.35 km, MAE=1.46 km, 低能见度均方根误差RMSE_10 km=1.81 km, 低能见度平均绝对误差MAE_10 km=1.13 km, R²=0.83; 3—6月的模拟中, 输入变量中不加AQI模拟效果更好, 这意味着3—6月义乌地区的低能见度天气以雾天气为主导, 加入过多变量并不一定能提高模型准确度; 随着预报步长增大, 模型预报效果变差, 预测步长等于3 h, R²=0.71, 预测结果已不具备实际应用意义。