郭丽君,郭学良,栾天,吕恺. 2019. 云辐射效应在华北持续性大雾维持和发展中的作用[J]. 气象学报, 77(1):111-128, doi:10.11676/qxxb2018.041
云辐射效应在华北持续性大雾维持和发展中的作用
The role of cloud radiative effect in the maintenance and development of persistent heavy fog events in northern China
投稿时间:2017-12-06  修订日期:2018-05-10
DOI:10.11676/qxxb2018.041
中文关键词:  云辐射效应  持续性大雾  云-雾共存结构  数值模拟
英文关键词:Cloud radiative effect  Persistent fog events  Co-existing structure of clouds and fog  Numerical simulation
基金项目:国家自然科学基金项目(41605111、41675137)和中国气象科学研究院基本科研业务费专项(2016Z004)。
作者单位E-mail
郭丽君 中国气象科学研究院云雾物理环境重点实验室, 北京, 100081  
郭学良 中国气象科学研究院云雾物理环境重点实验室, 北京, 100081 guoxl@mail.iap.ac.cn 
栾天 中国气象科学研究院云雾物理环境重点实验室, 北京, 100081  
吕恺 美国怀俄明大学大气科学系, 拉勒米, 82071  
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中文摘要:
      观测研究发现华北地区的持续性大雾天气通常伴随高层云的存在,具有云-雾共存结构特征,为揭示云在持续性大雾维持和发展中的作用,利用中尺度数值模式WRF,结合华北雾霾观测试验期间的卫星、探空、地面观测、系留气艇、微波辐射计等观测资料,研究了2011年12月3—6日和2013年1月28—31日两次华北持续性大雾天气形成和发展演变过程。在模拟与观测对比检验研究的基础上,重点开展了云辐射效应在大雾维持和发展中作用的探讨。研究结果表明:两次大雾过程持续时间超过48 h,近地面具有偏南暖湿平流,在持续性大雾发展过程中,均出现了由单层雾发展为云-雾共存结构,一般是雾形成24 h以后有中高云移到雾层之上,云底高度在3 km以上,云厚超过3.5 km,云中以冰晶和雪晶为主。白天云-雾共存结构出现后,云-雾的反照率效应使地表接收的短波辐射减少71%—84%,地面增温效应显著减小,从而阻碍了大雾的消散过程,使大雾天气得以维持,同时由于云-雾产生的温室效应,湍流过程加强,使地面雾向上扩展,雾在稳定层内维持;夜晚云-雾共存时,由于云-雾温室效应使地表净长波辐射增大超过70 W/m2,导致地面长波辐射冷却过程减弱,并不利于雾的加强,但云对雾的增温效应有利于混合层内的湍流扩散过程,促使雾在更高的空间内得以维持。可见,在云-雾共存结构中,云辐射效应有利于低层大雾的长时间维持,对持续性大雾的形成和发展产生了重要作用。
英文摘要:
      Observations have shown that persistent heavy fog events in northern China are usually accompanied by the presence of clouds above the fog and characterized by co-existing clouds and fog. Combined with satellite, radiosonde and ground observations, tethered balloon soundings, and microwave radiometer data, the mesoscale model WRF is applied to investigate the role of cloud radiative effect in the maintenance and development of two persistent fog events occurred on 3-6 December 2011 and 28-31 January 2013, respectively. Horizontal distributions of fog and clouds as well as vertical profiles of temperature and relative humidity from the WRF simulations are compared with and verified against observations. The results indicate that the persistent fog processes lasted for more than 48 hours and accompanied by southward warm moist advection at lower levels near the ground. During the development of heavy fog events, the single-layer fog gradually developed into a cloud-fog coexisting state. The middle and high clouds with ice and snow particles covered the foggy area 24 hours after the fog formed. The cloud base was above 3 km height, and the cloud thickness was larger than 3.5 km. During the daytime, due to the co-existence of clouds and fog and enhanced solar radiation reflection by the clouds and fog, the solar radiation at the surface was greatly reduced by 71%-84%. This weakened the surface warming and prevented the fog from dissipating. Meanwhile, the greenhouse effect caused by the clouds and fog enhanced the turbulent mixing, which promoted the fog to extend upward and maintain in the stable layer. At the nighttime, longwave radiative cooling at the surface was reduced due to the greenhouse effect of the clouds and fog, and the surface net radiation increased by more than 70 W/m2. This was not conducive to further development of the fog event. However, the enhanced turbulent diffusion process due to the greenhouse effect of clouds and fog was favorable for the development of the fog event in the vertical direction. Thus, the presence of clouds above the fog plays an important role in the maintenance and development of the long-lasting fog event through cloud radiative effect.
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