简评碳气溶胶观测研究中的不确定性

大气碳气溶胶具有重要的气候效应,但其观测研究中的不确定性还很大。作者对目前应用较广泛的气溶胶有机碳(OC)和元素碳(EC)采样观测和分析方法(包括光学法、热学法、热光学法及光学和热学实时在线观测方法)进行了评述。石英滤膜采集和实验室热光学分析方法应用较多,但在升温程序设置、OC/EC的划分和裂解碳校正方面还存在问题,而且需要准确评价样品采集过程中有机气体吸附和滤膜上已采集颗粒物挥发导致的采样偏差。光学和热学在线观测方法有助于避免采样和后期处理过程对颗粒物性质的改变,有利于反映颗粒物在大气中的初始特性,但此类方法尚需改进。对二次有机碳(SOC)的估算,采用将源直接排放的OC进一步划分为燃烧源排放和非燃烧源排放的方案可能更为准确。关于有机物质质量(OM)的估算,尚需开展相关研究以确定适合我国不同环境气溶胶特点的OM/OC估算因子。我国科学家应在碳气溶胶观测方法的改进和完善中做出应有的贡献,努力建立适合我国气溶胶特点的碳气溶胶观测方案和规范。     

季节冻土区保温隔水路基防冻胀效果研究

基于冻土路基温度场数值模型,结合室内模型试验,对保温隔水路基进行热-应力耦合计算,并用试验结果验证计算模型,旨在研究普通路基与保温隔水路基在环境温度变化时路基温度场和位移场的变化规律,对比评价保温隔水路基防冻胀效果。结果表明：相比普通路基,保温隔水路基保温效果明显,其冻结时间推迟约22%,冻胀速率减小60%,冻胀量减小35%~60%。此外,保温隔水路基竖向变形相对较小,变形过渡平缓,横向变形显著减小,由变形引起的破坏作用减弱,说明保温隔水路基是一种较好的防冻胀路基结构。     

基于氚同位素的安阳河中下游流域地下水更新能力研究

利用水中氚值与地下水年龄分布特征和多年平均更新速率,分析安阳河中下游流域地下水更新能力。应用MGMTP重建研究区1953—2016年大气降水氚值,应用集中参数模型(LPMs)计算地下水年龄,采用Le Gal La Shalle等提出的方法估算潜水与泉水多年平均更新速率。研究结果表明:(1)潜水与泉水由近20多年来大气降水补给。潜水样点受局部水文地质条件控制,补给径流条件差异明显。(2)小南海泉平均滞留时间23 a,多年平均更新速率3.6%,水量呈不断衰减趋势。(3)安阳河冲洪积扇扇后缘为补给区,受地表水渗漏与大气降水入渗补给,更新能力较强。扇中部至京港澳高速路地带为现代地下水,年龄40~60 a。扇前缘为现代与次现代地下水的混合水,年龄大于60 a,更新能力较弱。(4)剥蚀岗丘与冲洪积平原深层承压水为较老地下水,更新能力极弱。因此,对小南海泉域的保护需要加强,并在短时期内能取得明显成效。受南水北调中线水源补给及限量地下水开采影响,安阳市区地下水降落漏斗大幅度缩减。     

基于FY-4A卫星遥感数据分析2021年3次沙尘暴特征

FY 4A上搭载的多通道扫描成像辐射计（AGRI）无论是时间分辨率还是空间分辨率与我国第一代静止气象卫星风云二号上搭载的扫描辐射计（VISSR）相比都有了明显的改进。本文基于FY 4A AGRI成像仪IDDI(红外差值沙尘指数)和新的昼夜沙尘遥感改进算法开展2021年中国北方沙尘过程连续遥感监测处理,并系统分析了2021年3个典型个例的沙尘暴特征和影响区域。结果表明：① 3次典型沙尘过程对我国北方各省份的影响面积总计最低达到260万km2以上,最高达到300万km2以上,4月14—17日的沙尘暴影响面积最大。②2021年沙尘高发区在新疆南部、甘肃河西走廊以北以及内蒙古西部。与2019、2020年同期相比,2021年我国北方沙尘发生频次更高、影响范围更大。③新一代FY 4A静止卫星对我国沙尘过程年际变化具备更加完整的监测能力。     

等值线相关算法类库的开发与应用

介绍用VB.NET独立开发的等值线算法类库wContour.dll,包括离散数据网格化、基于网格数据的等值线追踪、平滑、裁剪及填充功能。该类库的算法经过随机生成数据的严格测试,能够灵活、有效地用于软件开发中等值线功能的实现。区域填充算法是基于拓扑关系的,能够生成多边形矢量图形。wContour.dll可以免费下载、使用。     

泰山PM10及其中化学成分变化特征

为研究华北平原区域背景气溶胶成分及其变化特征,2010年6月至2011年7月在泰山顶采集了64个PM10滤膜样品,分析了样品的PM10及其中无机盐离子和有机碳（OC）、元素碳（EC）的质量浓度,并对各成分相关性等进行了分析。泰山PM10年均质量浓度约为68.4 mg/m³,其中无机盐离子约占总质量的64.8%,碳气溶胶约占17.4%。无机盐离子的质量浓度从春季逐渐增大,夏季达到峰值,秋季下降,冬季最小;OC质量浓度从春季至秋季逐渐增高,冬季最低,EC变化类似,但夏秋两季差别不大。二次有机碳（SOC）与OC的比值四季均在50%以上,年均值约为58.5%。通过后向轨迹聚类分析发现,在经过城市的较短轨迹以及南方较短混合轨迹的影响下,泰山PM10质量浓度较高,而西北长距离传输气团PM10浓度均较低。     

Optical and radiative properties of aerosols during a severe haze episode over the North China Plain in December 2016

The optical and radiative properties of aerosols during a severe haze episode from 15 to 22 December 2016 over Beijing, Shijiazhuang, and Jiaozuo in the North China Plain were analyzed based on the ground-based and satellite data, meteorological observations, and atmospheric environmental monitoring data. The aerosol optical depth at 500 nm was < 0.30 and increased to > 1.4 as the haze pollution developed. The Ångström exponent was > 0.80 for most of the study period. The daily single-scattering albedo was > 0.85 over all of the North China Plain on the most polluted days and was > 0.97 on some particular days. The volumes of fine and coarse mode particles during the haze event were approximately 0.05–0.21 and 0.01–0.43 μm³, respectively—that is, larger than those in the time without haze. The daily absorption aerosol optical depth was about 0.01–0.11 in Beijing, 0.01–0.13 in Shijiazhuang, and 0.01–0.04 in Jiaozuo, and the average absorption Ångström exponent varied between 0.6 and 2.0. The aerosol radiative forcing at the bottom of the atmosphere varied from –23 to –227,–34 to –199, and –29 to –191 W m^–2 for the whole haze period, while the aerosol radiative forcing at the top of the atmosphere varied from –4 to –98, –10 to –51, and –21 to –143 W m^–2 in Beijing, Shijiazhuang, and Jiaozuo, respectively. Satellite observations showed that smoke, polluted dust, and polluted continental components of aerosols may aggravate air pollution during haze episodes. The analysis of the potential source contribution function and concentration-weighted trajectory showed that the contribution from local emissions and pollutants transport from upstream areas were 190–450 and 100–410 μg m^–3, respectively.     

Integration of Multi-source Measurements to Monitor Dust over North China：A Case Study

The aerosol optical depth （AOD） data from the Moderate Resolution Imaging Spectroradiometer （MODIS） aboard Satellite Aqua, along with the altitude-resolved aerosol subtypes product from the Cloud-Aerosol LIdar with Orthogonal Polarization （CALIOP）, as well as surface PM 10 measurements, were utilized to investigate the dust activities common in springtime of northern China. Specifically, a dust storm episode that occurred over the North China Plain （NCP） during 17-21 March 2010 was identified. The PM 10 concentration at Beijing （39.8 °N, 116.47 °E） reached the peak value of 283 μgm -3 on 20 March 2010 from the background value of 15 μg m-3 measured on 17 March 2010, then dropped to 176 μgm-3 on 21 March 2010. Analysis of the CALIOP aerosol subtypes product showed that numerous large dust plumes floated over northern China, downwind of main desert source regions, and were lifted to altitudes as high as 3.5 km during this time period. The MODIS AOD data provided spatial distributions of dust load, broadly consistent with ground-level PM 10 , especially in cloud free areas. However, inconsistency between the MODIS AOD and surface PM 10 measurements under cloudy conditions did exist, further highlighting the unique capability of the CALIOP lidar. CALIOP can penetrate the cloud layer to give unambiguous and altitude-resolved dust measurements, albeit a relatively long revisit period （16 days） and narrower swath （90 m）. A back trajectory simulation using the Hybrid Single-Particle Lagrangian Integrated Trajectory （HYSPLIT） model was performed, and it was found that the sand-dust storm originated from the Gobi Desert on 18 March 2010 travelled approxi-mately 1200-1500 km day-1 eastward and passed over the NCP on 19 March 2010, in good agreement with previous findings. In addition, the multi-sensor measurements integrated with the HYSPLIT model output formed a three-dimensional view of the transport pathway for this dust episode, indicating that this episode was largely associated with the desert source regions to the northwest of the NCP. The results imply the importance of integration of multi-sensor measurements for clarifying the overall structure of dust events over northern China.     

MODFLOW不同算法及参数设定对计算精度的影响

为了提高MODFLOW中模型计算的精确度,减少不收敛情况的发生,通过建立数值模型算例,分析了不同解算器对计算精度的影响差异、主要参数值的设定对计算精度产生的影响以及收敛指标与迭代次数的定量关系。结果表明,PCG、SAMG和GMG计算精度较高,WHS和SOR计算精度较低。PCG算法中,低收敛指标使得计算精度有所提高,但稳定性却明显降低;计算精度对PCG算法中的阻尼因子的敏感性比对SIP算法中的加速因子敏感性低,二者的减小均导致计算精度降低;SIP算法中,计算过程中的迭代次数、运行时间与水头变化的收敛指标值呈明显的反比关系。当收敛指标设定小于一定值时,迭代次数和收敛指标的对数值呈现明显的线性关系。