Abstract. Observations collected during the SOuth west FOGs 3D experiment for processes study (SOFOG3D) field campaign are examined to document vertical profile of microphysical and thermodynamic properties of fog layers. In situ measurements collected under a tethered balloon provide 140 vertical profiles of liquid water content (LWC) from an adapted cloud droplet probe (CDP), which allow an exhaustive analysis of the life cycle of 8 thin fogs (thickness < 50 m) and 4 developed layers. We estimate thin-to-thick transition time from remote sensing instruments (microwave radiometer and Doppler cloud radar) and surface measurements, by using thresholds for longwave radiation flux, turbulent kinetic energy, vertical temperature gradient, fog top height and liquid water path (LWP) values. We found that a LWP threshold value of 15 g.m⁻² is more suited for the thick fogs sampled at the super-site. CDP data are used to compute the equivalent fog adiabaticity from closure (α^closure_eq) and compare to value derived from remote sensing instruments, 2-m height visibility, and an one-column conceptual model of adiabatic continental fog assuming that LWC linearly increases with height. The comparison of α^closure_eq shows a large variability that results mainly from the parameterization used to estimate LWC at ground, but their evolution as a function of the fog thickness follows the same trend. We found larger negative values of α^closure_eq for thin layers, associated to low LWP values. CDP data reveal that reverse trend of LWC profile (LWC being maximal at the ground and decreasing with altitude) are ubiquitous in optically thin fogs, while quasi-adiabatic features with increasing LWC values with altitude are mainly observed in well-mixed optically thick fogs. We investigate the actual fog adiabaticity and lapse rate fraction by using linear regressions to best fit the vertical profiles of LWC and temperature, respectively. This analysis highlights that reverse LWC profiles, when stable temperature conditions exist during the optically thin phase of fogs, evolve towards quasi-adiabatic features with slightly unstable temperature lapse rate, when fogs become optically thick. We also found that LWC at ground is higher during the thin phase and significantly decreases as the profile is changing from reverse to increasing with height. But this trend could be balanced when collision-coalescence and sedimentation processes redistribute the LWC through the fog layer from the top to the ground. This study provides new insights on the evolution of LWC profile during the fog life cycle, that would help to constrain numerical simulations.

中文翻译：

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SOFOG3D 实验期间雾层液态水含量的垂直剖面

摘要。对西南 FOG 过程研究 3D 实验 (SOFOG3D) 现场活动期间收集的观测结果进行了检查，以记录雾层微物理和热力学特性的垂直剖面。在系留气球下收集的原位测量结果可通过改装的云滴探测器 (CDP) 提供 140 个液态水含量 (LWC) 垂直剖面，从而可以对 8 个薄雾（厚度 < 50 m）和 4 个薄雾的生命周期进行详尽分析。发达的层次。我们通过使用长波辐射通量、湍流动能、垂直温度梯度、雾顶高度和液态水路径（LWP）的阈值，通过遥感仪器（微波辐射计和多普勒云雷达）和表面测量来估计从薄到厚的转变时间）值。我们发现15 gm ^-2的LWP阈值更适合在超级站点采样的浓雾。 CDP 数据用于计算闭合时的等效雾绝热性（α^闭合_eq），并与遥感仪器、2 米高度能见度和绝热大陆雾的单柱概念模型（假设 LWC 随时间线性增加）得出的值进行比较。高度。 α^闭合_eq的比较显示出很大的变异性，这主要是由于用于估计地面 LWC 的参数化造成的，但它们作为雾厚度函数的演变遵循相同的趋势。我们发现薄层的α^闭合_eq负值较大，与低 LWP 值相关。 CDP数据表明，在光学稀雾中，LWC剖面的反向趋势（LWC在地面最大，并随着高度的增加而减小）普遍存在，而LWC值随高度增加而增加的准绝热特征主要在混合良好的光学厚雾中观察到。我们通过使用线性回归分别最好地拟合 LWC 和温度的垂直剖面来研究实际的雾绝热性和递减率分数。该分析强调，当雾的光学稀相期间存在稳定的温度条件时，反向 LWC 剖面会在雾变得光学厚时演变成具有稍微不稳定的温度递减率的准绝热特征。我们还发现，在薄相阶段，地面的 LWC 较高，并且随着剖面从反向变为随高度增加而显着降低。但当碰撞聚结和沉积过程通过雾层从顶部到地面重新分配 LWC 时，这种趋势可能会得到平衡。这项研究提供了关于雾生命周期中 LWC 剖面演变的新见解，这将有助于限制数值模拟。