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On the Conditions for Onset and Development of Fog Over New Delhi: An Observational Study from the WiFEX
Pure and Applied Geophysics ( IF 2 ) Pub Date : 2021-07-07 , DOI: 10.1007/s00024-021-02800-4
Narendra G. Dhangar 1, 2 , D. M. Lal 1 , Sachin D. Ghude 1 , Avinash N. Parde 1, 3 , Prakash Pithani 1 , Chinmay Jena 1 , Veeresh S. Sajjan 1 , Thara Prabhakaran 1 , K. Niranjan 2 , Dasari S. V. V. D. Prasad 2 , A. K. Karipot 3 , R. K. Jenamani 4 , Surender Singh 5 , Rachana Kulkarni 6 , M. Rajeevan 7
Affiliation  

Dense fog events and their micrometeorological characteristics and structural evolution at Indira Gandhi International Airport (IGIA), New Delhi, during the Winter Fog Experiment (WiFEX) are illustrated in this study. Four dense fog events that occurred in January 2016 for which visibility dropped below 200 m have been selected. Depending on the visibility and micrometeorological structure, the fog processes were classified into (i) an initial formation as a thermally stable optically thin fog and (ii) a subsequent mature, weakly unstable deep fog. Surface radiative cooling supported by a deep saturated layer in the nocturnal surface layer promotes the rapid development and intensification of the initial shallow fog into the extremely dense fog. Optically thin fog appeared to develop when a thin saturated layer of air formed near the ground under low-turbulence kinetic energy (< 0.1 m2/s2). The fog was sustained in the optically thin phase until the air at 20 m remained in a sub-saturated condition in the thermally stable surface layer. Furthermore, when the saturated layer near the surface progressively expanded upward as a result of sustained cooling inside the shallow fog, it rapidly transformed into an extremely dense fog. The threshold for transition from the optically thin phase to extremely dense phase appeared when the air at 20 m neared the saturation point. The dense fog observations for all cases indicate that when the saturated layer was deeper than 20 m, the fog was able to withstand larger turbulence intensity (TKE values between 0.4 m2/s2 and 0.5 m2/s2).



中文翻译:

新德里雾的发生和发展条件:来自WiFEX的观测研究

本研究阐述了新德里英迪拉甘地国际机场 (IGIA) 在冬季雾实验 (WiFEX) 期间的浓雾事件及其微气象特征和结构演变。选择了 2016 年 1 月发生的四次能见度低于 200 m 的浓雾事件。根据能见度和微气象结构,雾过程分为(i)初始形成的热稳定光学薄雾和(ii)随后成熟的、弱不稳定的深雾。夜间表层深饱和层支持的地表辐射冷却促进了最初的浅雾快速发展和增强为极浓雾。2 / 秒2 )。雾在光学薄相中持续,直到 20 m 处的空气在热稳定表面层中保持在亚饱和状态。并且,当浅雾内部持续冷却,靠近地表的饱和层逐渐向上膨胀时,迅速转变为极浓雾。当 20 m 处的空气接近饱和点时,出现了从光学薄相向极密相转变的阈值。对所有情况的浓雾观测表明,当饱和层深度超过20 m 时,雾能够承受更大的湍流强度(TKE 值在0.4 m 2 /s 2和0.5 m 2 /s 2 之间)。

更新日期:2021-07-07
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