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在进入冬半年后,海口市受弱冷空气或较强下沉气流控制时,易出现污染天气,对2013—2015年当年10月至翌年1月的气团轨迹进行了聚类分析、潜在源贡献因子分析(Potential Source Contribution Function,PSCF)和重轨迹分析(Concentration Weighted trajectory,CWT),结果表明:在污染时段内,海口大多受到来自中国华南和华东的东北向气流影响。PSCF和CWT分析表明,广东、福建、江西的大部分地区,以及湖南东部、广西东部等地区,是对海口地区污染天气污染物浓度的潜在贡献大值区。在进行预报时,可参考主要天气影响系统,和一些关键区域的外源影响以及本地污染的堆积情况。 相似文献
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为提高连续小波变换识别位场场源准确度,研究噪声对场源识别结果的影响和尺度因子优选方法问题。根据连续小波变换识别位场场源的基本原理,用该方法对不同噪声水平的合成数据进行场源识别,分析噪声对于场源识别结果的影响,研究小波变换的尺度因子对噪声压制的效果,讨论连续小波变换进行场源识别时尺度因子的选取方法。理论模型和实测资料场源识别结果表明,噪声会降低连续小波变换场源识别结果的准确度,笔者提出的尺度因子优选方法能有效压制噪声干扰,提高场源识别结果的准确度。 相似文献
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Planetary boundary layer height (PBLH) is an important input parameter for any boundary layer study or model, either climate or atmospheric. The variation of the PBLH is also of great significance to the physical processes of numerical prediction, diagnosis of weather forecasting and monitoring urban pollutants. However, effective ways to monitor the PBLH continuously are lack. Wind profilers are commonly used in monitoring PBLH continuously because of its high temporal and spatial resolution, coupled with capability of continuous detection. In this paper, the covariance wavelet transform (CWT) is used to analyze the range-corrected signal-to-noise ratio (SNR) of the wind profiler to determine the PBLH, which is then compared with the results measured by the gradient method and the radiosonde. The conclusions are as follows: (1) The scaling parameter a and translation parameter b of the wavelet are critical in determination of the PBLH by applying the CWT as different values may get completely different results, which requires to select appropriate values in the calculation carefully. (2) Quality control is crucial in determining the PBLH because good quality control can help remove mutation points, which makes the determined PBLH more consistent with the actual situation. (3) In clear-air, the gradient method is not applicable if the boundary layer turbulence is inhomogeneous and the impact of noise is large for that it is easy to be impacted by the mutation of SNR caused by the atmosphere turbulence instability and other factors, which will cause large errors, while the CWT method as an improvement of the gradient method can determine the PBLH quite well. (4) Through quality control, the PBLHs determined by the CWT are consistent with those of radiosonde, and the correlation coefficient between them is 0.87. 相似文献
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利用HYSPLIT(Hybrid Single Particle Lagrangian Integrated Trajectory)模型和ERA_INTERIM数据,计算2013—2017年北京奥林匹克体育中心(以下简称奥体中心)2月期间抵达的72 h后向轨迹,并结合聚类分析方法和污染物浓度数据,分析2月不同轨迹对奥体中心污染物浓度的影响,采用四种不同的轨迹分析方法分析奥体中心污染物来源特征,并通过实例分析了不同轨迹分析方法的优缺点和适用性。结果表明:奥体中心2月主导气流明显,为西北路径,出现概率为55.85%;清洁通道为北向气流,污染来源为南向路径和偏东路径,对应颗粒物浓度最高;通过轨迹统计方法得到奥体中心2月颗粒物主要污染来源为河北地区、山东半岛、黄渤海区域、新疆北部与河西走廊。此外,研究发现潜在源贡献函数和浓度权重轨迹方法适用于近距离污染源的识别;停留时间浓度加权方法采用确定性办法通过迭代可以精准识别出北京奥体中心主要污染物来源;定量传输偏差分析方法引入不确定性概念,适用于大范围确定性污染源识别,但同时会产生虚假的污染物来源。不过,采用RTWC方法和QTBA方法相结合可消除QTBA方法带来的虚假污染源。 相似文献
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断层等不连续性结构的检测在地震勘探中具有重要的意义.本文简单介绍了高维连续小波变换的基本理论,包括:高维连续小波变换的定义、高维小波变换系数的切片以及快速实现方法等,利用典型的合成信号说明了高维连续小波变换具有更好的方向选择性(相比于常用的高维张量积小波变换),将高维连续小波变换引入地震资料不连续性检测,并提出了利用小尺度高维连续小波变换系数检测地震资料不连续性的方法,同时给出了方法的实现流程.合成信号以及实际三维地震数据处理效果验证了本文所提方法的有效性. 相似文献
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利用全国空气质量指数(Air Quality Index,AQI)、PM_(2.5)地面观测数据、全球数据同化系统GDAS数据和FNL再分析气象资料,研究了2015/2016年冬季南京北郊空气质量变化特征以及环境输送条件和污染物源区。结果表明:以AQI为代表的冬季江淮地区污染程度存在3种典型的污染物跨区域输送路径—西北路径、北方路径和西南路径。西北路径通常发生在蒙古高压较强,且处于平均位置时刻,南京北郊上空有冷平流,不利于污染物扩散;北方路径对应蒙古高压弱,东北附近为弱高压控制,偏北气流将污染物带至南京北郊,如跨海洋,则污染减弱;西南路径对应南京北郊为边界层内反气旋式环流中心,下沉气流十分不利于污染物扩散。影响南京北郊污染的潜在源区主要分布在河北南部、山东西部、河南南部、安徽东部和湖北西部。河北省是重要的污染源区,河北南部和山东西部污染物通过北方路径输送至南京北郊,因此北方路径虽发生污染概率少于其他两种,却是形成南京北郊严重污染的重要路径。河南南部污染物通过西北路径输送。安徽和湖北污染物通过西南路径输送。定量分析表明,平流输送是南京北郊重度污染的重要原因,近地层风速对AQI的平流输送占AQI变化的贡献率超过70%,甚至可达85%。 相似文献
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The Continuous Wavelet Transform was recently proposed for the interpretation of gravity and magnetic potential data. We utilize the Continuous Wavelet Transform of gravity and magnetic data to address one of the most common issues in exploration geophysics: mapping of sub‐basaltic sedimentary strata. We observe that the magnetic response of the basaltic layer is dominant in a three‐layer case of a basalt‐sediment‐basement, whereas the gravity signal is dominated by the base of the sediment. Thus the Continuous Wavelet Transform of the magnetic data is related to the thickness of the basalt and the Continuous Wavelet Transform of the gravity data is related mostly to the bottom of the sediment. These observations are demonstrated with a synthetic model and a few field examples. Derived depths using Continuous Wavelet Transform are in good agreement with known vertical cross‐sections. Therefore, Continuous Wavelet Transform analysis of both gravity and magnetic data offers a possibility for primary information of sub‐basaltic sediment thickness, which can provide a basis for further detailed modelling. 相似文献
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Based on meteorological and pollution data from January 2017 to December 2019, in this paper the long-term distribution of surface aerosol particles, and the interaction between aerosol pollution and meteorological factors in four cities of the Yangtze River Delta (YRD) region is investigated. The long-term observation shows the law of typical aerosol pollution characteristics. Meteorological factors are significantly different during aerosol-polluted and nonpolluted days. The effect of each meteorological factor on aerosol pollution may vary by different seasons and cities. The changes in meteorological factors are not completely consistent during aerosol fine-mode and coarse-mode polluted days. To distinguish the possible sources of surface aerosol particles, the potential source contribution function and concentration-weighted trajectory models are applied to study transport sources. Based on the detailed analyses, this study will provide a reliable basis for further pollution control in the YRD. 相似文献
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