摘要
根据2007—2013年宁波市每日8次地面观测气象资料,运用罗氏法和统计分析法计算大气混合层高度,分析其在霾日和非霾日的不同日变化特征。结果表明宁波市霾日与非霾日混合层高度均呈白天高,夜晚低的日变化特征,夏季两者差值的日变化波动最明显,波峰时间比其他季节晚 3 h 。混合层高度日变化趋势与风速、气温、能见度趋于一致,霾等级越重,混合层高度越低。霾日与非霾日的气温差值除冬季呈正变温外,其他季节呈负变温,冬季14时差值最小,夜间加大,春夏季凌晨差值最小,14时最大,秋季波动不明显;风速差值除冬季夜间为正值外,其余季节为负值,秋冬季差值最小、夏季最大。大气处于不稳定状态时,混合层高度随着稳定度增加而逐渐处于稳定状态时,随着稳定度增加而降低,中性大气是宁波易致霾的大气层结。霾日与非霾日大气稳定度表现不一致,中午霾日中性大气占多数,非霾日则是不稳定大气;夜间霾日稳定—弱稳定大气和中性大气所占比例相当,非霾日稳定—弱稳定大气占多数。另外,PM 2.5 浓度在霾日和非霾日均为白天低、夜间高的日变化特征,但霾日波动大,波峰时间晚于非霾日 2 h ,峰值浓度也高于非霾日2.7倍;早晨或下午到上半夜是霾日的PM 2.5 浓度两个上升时段,上午为下降时段;非霾日的两个浓度缓升(降)时段分别出现凌晨和下午(上午和前半夜)。研究成果有助于预报员了解大气混合层高度及其对霾的可能影响,从而提高霾预报预警能力。
Based on meteorological observations of eight times a day in Ningbo from 2007 to 2013, the diurnal variations and characteristics at the Mixed Layer Height (MLH) in haze and non-haze days are calculated and analyzed by Roche method and statistics. The results show that the diurnal variations of MLH in haze and non-haze days in Ningbo are higher at daytime and lower at night. Summer witnesses the maximum fluctuation of difference values of diurnal variations between haze and non-haze days, and the peak time of fluctuation is three hours later than that in other seasons. The diurnal variations at MLH are consistent with wind speed, temperature and visibility;the worse the haze, the lower the MLH. Temperature difference between haze and non-haze days is negative in all seasons except winter. The temperature difference drops to the minimum at 14 ∶00 and increase at night in winter;the minimum difference occurs before dawn and increases to the maximum at 14 ∶00 in spring and summer;and the fluctuation is not obviously in autumn. Wind speed difference is negative in all seasons except at night in winter;the minimum occurs in autumn and winter, while the maximum in summer. The MLH gradually descends with the increasing degree of atmospheric instability when the atmosphere is unstable, and MLH experiences the same trend when the atmosphere is stable. Neutral atmosphere is easy to cause haze in Ningbo. Atmospheric stability is different in haze and non-haze days. Neutral atmosphere prevails in haze days and unstable atmosphere is the majority in non-haze days at noon. The ratio of stabile-weakly stable atmosphere is quite equal to that of neutral atmosphere in haze days at night, and stabile-weakly stable atmosphere prevails in non-haze days at night. In addition, the diurnal variations of PM 2.5 concentration in haze and non-haze days are lower at daytime and higher at night. But the fluctuation of PM 2.5 concentration in haze days is obvious, and the peak time of fluctuation in haze days is 2 h later than that in no
作者
俞科爱
陈磊
陈有利
张晶晶
朱佳敏
孙海波
YU Keai;CHEN Lei;CHEN Youli;ZHANG Jingjing;ZHU Jiamin;SUN Haibo(Beilun Meteorological Bureau, Zhejiang Ningbo 315826, China;Cixi Meteorological Bureau, Zhejiang Ningbo 315300,China;Ningbo Meteorology Observatory, Zhejiang Ningbo 315012,China)
出处
《气象科学》
北大核心
2019年第2期187-193,共7页
Journal of the Meteorological Sciences
基金
宁波市科技计划项目(2013C51013)
浙江省公益性技术应用研究计划社发项目(2015C33226)
浙江省气象科技计划项目(2018YB16)
