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首页> 外文期刊>Pure and Applied Geophysics >Analysis of Dynamical and Thermal Processes Driving Fog and Quasi-Fog Life Cycles Using the 2010-2013 ParisFog Dataset
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Analysis of Dynamical and Thermal Processes Driving Fog and Quasi-Fog Life Cycles Using the 2010-2013 ParisFog Dataset

机译：使用2010-2013 ParisFog数据集分析驱动雾和准雾生命周期的动力和热过程

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摘要

The data from suite of in situ sensors, passive and active remote sensing instruments dedicated to document simultaneously radiative and thermo-dynamical processes driving the fog life cycle at the SIRTA Observatory (instrumented site for atmospheric remote sensing research) near Paris during two periods of 6 months are analysed. The study focuses on the analysis of the relative role of key physical processes and their interactions during fog formation, development and dissipation phases. This work presents, from analysis of detailed observations, the range of values that critical parameters have to take for fog and quasi-fog formation. In our study, we consider fog (horizontal visibility lower than 1 km, a dataset of 300 h) and quasi-fog (horizontal visibility ranging from 1 to 2 km, a dataset of 400 h) events induced by radiative cooling (53 events) and stratus lowering (64 events). For the radiative fog events, (with radiative cooling during prefog conditions), we note that the longwave net radiative flux (around -60 +/- A 5 W/m(2)) induces a cooling of the surface layer. The vertical structure of this cooling is controlled by dynamics, that is, wind shear and horizontal and vertical velocities. In case of very low mixing (wind speed below 0.6 m/s), the thermal stability is very strong with a temperature inversion around 3.5 A degrees C for 10 m and a humidity gradient reaching 10 % preventing vertical development of the fog layer. For stratus-lowering fog events, the altitude of the stratus layer, the vertical mixing and the absolute value of humidity are driving parameters of the fog formation. Our statistical analysis shows that a stratus cloud with a cloud base around 170 m and with a small cloud-base subsidence rate of 50 m/h leads to fog, whereas a stratus cloud with a base around 800 m agl, with a larger cloud-base subsidence rate of 190 m/h conducts to quasi-fog situations with an important increase of the stratus liquid water path.
机译：来自一组原位传感器，被动和主动遥感仪器的数据，专用于同时记录辐射和热力学过程，这些过程驱动巴黎附近的SIRTA天文台（用于大气遥感研究的仪器站点）在两个6个周期内的雾气生命周期分析了几个月。该研究的重点是分析关键物理过程的相对作用及其在雾形成，发展和消散阶段的相互作用。通过对详细观测结果的分析，这项工作提出了雾和准雾形成关键参数所必须采用的取值范围。在我们的研究中，我们考虑了辐射冷却引起的雾（水平能见度低于1 km，数据集为300小时）和准雾（水平能见度为1至2 km，数据集为400 h）事件（53个事件）和地层下降（64个事件）。对于辐射雾事件（在预雾条件下进行辐射冷却），我们注意到长波净辐射通量（约-60 +/- A 5 W / m（2））引起表面层的冷却。这种冷却的垂直结构由动力学控制，即风切变以及水平和垂直速度。在非常低的混合（风速低于0.6 m / s）的情况下，热稳定性非常强，温度反转约为3.5 A达10 m，湿度梯度达到10％，可防止雾层垂直发展。对于降低地层的雾事件，地层的高度，垂直混合和湿度的绝对值是雾形成的驱动参数。我们的统计分析表明，云量约为170 m的云层，且云层下沉速率为50 m / h时会导致雾化，而云雾量为800 m agl的云层，则云量较大。基本沉降速度为190 m / h时，随着层状液态水路径的显着增加而发生准雾情况。

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