光谱学与光谱分析, 2018, 38 (12): 3653, 网络出版: 2018-12-16  

基于光谱分析的大气混合层高度测量研究

Study of the Estimation of Atmospheric Mixing Layer Height Using Spectral Analysis Technology
项雅静 1,*王珊珊 1,2周斌 1,2,3
作者单位
1 上海市大气颗粒物污染防治重点实验室, 复旦大学环境科学与工程系, 上海 200438
2 上海崇明生态研究院, 上海 202151
3 复旦大学大气科学研究院, 上海 200438
摘要
基于地基主动和被动差分光学吸收光谱(DOAS)分析方法, 在2015年5月至2016年5月期间对上海近地面NO2浓度(cNO2)及对流层NO2的垂直柱浓度(NO2 VCDtrop)进行了观测。 主动长光程差分光学吸收光谱系统(long-path DOAS, LP-DOAS)观测得的cNO2小时均值与上海市全市空气质量cNO2小时均值呈正相关, 相关系数为0.81。 被动多轴差分光学吸收光谱系统(multi-axis DOAS, MAX-DOAS)观测得的NO2 VCDtrop与GOME-2和OMI卫星传感器测得的NO2 VCDtrop也均呈正相关, 相关系数分别为0.89和0.88。 大气污染物的输送、 扩散、 稀释和沉降等过程主要发生在边界层中, 白天混合层占到边界层的大部分, 混合层高度(MLH)以上的自由对流层中污染物浓度较小, 混合层内NO2接近均匀混合时, 利用地基主、 被动DOAS观测得到的NO2数据可以快速计算大气混合层高度。 计算得的MLH与GDAS气象数据库中的边界层高度(PBLH)明显相关, 相关系数达0.93, 二者结果大小均在0.1~2 km之间。 实验观测期间, MLH与PBLH日变化趋势均呈单峰形, MLH高值出现在12:00—15:00, 由于PBLH时间分辨率低, 最高值出现在14:00, 同时二者月均变化趋势一致, 2015年9月和2016年2月数值较高, 2015年7月和2016年3月数值较低, 另外求得MLH约为PBLH的0.98±0.59倍, 符合狭义MLH与PBLH的关系。 计算得的MLH与同点位激光雷达测得的PBLHLidar也具有较高的相关性, 相关系数达0.75, PBLHLidar略大于MLH, 但是二者在早晨5和6时和下午5和6时大小趋于相同, 符合大气发展规律。 说明该算法具有较高的可行性。
Abstract
The ground surface NO2 concentration (cNO2) and tropospheric NO2 vertical column density (NO2 VCDtrop) in Shanghai area were measured by ground-based active and passive DOAS methods from May 2015 to May 2016. The hourly cNO2 measured by LP-DOAS was positively associated with Air Quality monitoring data (r=0.81), while the NO2 VCDtrop retrieved form MAX-DOAS measurements agreed well with GOME-2 and OMI satellite observations (r=0.89, 0.88). The results of both active and passive DOAS were reliable. In daytime, Mixing Layer takes up a majority of Planetary Boundary Layer, where most of the air pollutants’ transportation, dispersion, dilution and deposition occur. The concentration of pollutants such as NO2 mixes well within the Mixing Layer and reduces nearly to zero in free troposphere above the Mixing Layer. A new method was proposed to estimate the Mixing Layer Height (MLH) by combining the active and passive DOAS observations. The feasibility of this method was discussed in details in this paper. The calculated MLH was significantly correlated to Planet Boundary Layer Height (PBLH) deduced from GDAS meteorology database (r=0.93). Both MLH and PBLH ranged from 0.1 to 2 km. The diurnal variation showed a single peak. The MLH reached the maximum during 12:00 to 15:00, whereas the PBLH peaked at 14:00 due to the lower temporal resolution. The monthly averaged MLH and PBLH had similar seasonal variation, which were higher in Sept. 2015 and Feb. 2016, and lower in July 2015 and March 2016. The ratio of MLH and PBLH was 0.98±0.59, which was consisted with the relationship between them. The deduced MLH was also highly correlated with PBLHLidar obtained from the co-located Lidar results (r=0.75). PBLHLidar value was slightly higher than MLH, but they tended to be the same at the beginning and end of daytime. The validations with other methodologies suggested that this method was evidently reliable.

项雅静, 王珊珊, 周斌. 基于光谱分析的大气混合层高度测量研究[J]. 光谱学与光谱分析, 2018, 38(12): 3653. XIANG Ya-jing, WANG Shan-shan, ZHOU Bin. Study of the Estimation of Atmospheric Mixing Layer Height Using Spectral Analysis Technology[J]. Spectroscopy and Spectral Analysis, 2018, 38(12): 3653.

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