基于多源数据的夏威夷大气低层火山灾害影响分析

Analysis of the effects on low-level atmosphere by volcanic disasters in Hawaii based on multi-source data

自2018年5月3日起,位于美国夏威夷大岛上的Kilauea火山(19.41°N,155.28°W)开始了为期数月的剧烈喷发活动。为了探讨此次火山灾害活动对局地大气所造成的影响,综合利用地面环境监测站数据、MODIS Level 1B数据、GDAS再分析资料以及CALIPSO数据对此次火山活动期间的主要污染物浓度特征、火山灰气溶胶的水平分布特征及光学特性展开分析。结果表明,由于赤道东风带的存在,近地面火山口以西地区受喷发活动影响较大。在火山活动期间,西部沿海细粒子和SO 2浓度较3~4月明显上升,逐三小时SO 2浓度的中位数环比上升一个量级,PM 2.5浓度中位数则均达到前两个月数值水平3倍以上;利用MODIS和CALIPSO遥感数据分析得到,平均气溶胶光学厚度(Aerosol Optical Depth,AOD)的高值区总体上自夏威夷大岛往西呈现东北-西南向带状分布,西部沿海的部分区域平均AOD甚至超过1.6;此次火山活动过程中陆地部分的低层气溶胶类型以烟尘型为主,平均色比(Color Ratio,CR)达到1.2~1.5;平均粒子退偏振比(Particulate Depolarization Ratio,PDR)在2 km高度以上多分布在0~0.06范围内,以球形颗粒物居多,而在2 km以下区域则由非球形颗粒物占主导。研究显示,此次火山灾害事件中,夏威夷大岛以西地区在东风带输送下近地面污染物浓度剧烈上升,生成的颗粒物多为粒径较大且不规则的烟尘气溶胶。

Since May 3,2018,the Kilauea Volcano(19.41°N,155.28°W)on the Big Island of Hawaii has started a period of intense eruption for several months.In order to investigate the impact of the volcanic disaster on the local atmosphere,comprehensive use of ground environmental monitoring station data,MODIS L1B data,GDAS reanalysis data and CALIPSO data are made to analyze characteristics of main pollutant concentration,horizontal distribution and optical properties of ash aerosols during this volcanic activity.The results show that due to the existence of the equatorial easterly wind belt,the west of the near-surface crater is greatly affected by the eruption activity.During the volcanic activity,the concentration of fine particles and SO2 in the western coast increased significantly from March to April.The median of three-hour-mean SO2 concentration increased by an order of magnitude,and the median of PM2.5 concentration reached more than three times the level of that in the past two months.By using MODIS and CALIPSO remote sensing data,we find the high value area of the Aerosol Optical Depth(AOD)is generally distributed from the northeastern island of Hawaii to the northeast-southwest direction.The average AOD of some areas is even more than 1.6.The low-level aerosol type in the land part of the volcanic activity is dominated by smoke and dust,the average color ratio is 1.2~1.5.The average particle depolarization ratio over 2km is in the range of 0~0.06,most of the spherical particles are dominant in this altitude range,while those below 2km are dominated by non-spherical particles.According to the study,in the volcanic disaster,the concentration of near-surface pollutants in the west of the Big Island in Hawaii increased sharply because of the equatorial easterly wind belt,and particulate matter generated by volcanic activity were mostly smoke-dust particles with large size and regularity shape.