Stochastic Aspects of Physical and Radar Meteorology

这项研究寻求在云物理、降水物理、雷达气象学和云中的辐射传输方面的基本理解。为此，研究人员与研究生合作，计划进行理论研究，进行数值实验，分析来自各种传感器的数据，并提出新的实验建议。具体目标如下：1.雨的物理学：所有的雨滴都以终极速度落下吗？将对视频圆盘测量仪和多普勒雷达的数据进行理论研究和分析，重点是雨滴下降速度的波动和偏离终端速度的情况。这项研究将对剖面仪、多普勒雷达和视盘测量仪的反演产生影响。雷达气象学：这项研究将在新的理论分析基础上寻找相干的后向散射数据。将进行短脉冲雷达的数据分析和探索性信号处理。这项研究将对最近在雷达偏振测量中发现的雨滴表面张力的波动产生影响。还将研究雷达回波的非瑞利信号统计特性和异质目标的同相/正交特征。云物理：云冰是不是“草率”的？将研究过冷水滴的冻结和由此产生的“伤痕”冰，并从理论上研究冰中缺陷数密度与过冷度的关系。将研究云滴的扩散增长，重点是混合相云中的准稳态近似和相关的松弛时间。云中的辐射传输：将研究表面活性剂引起的光学性质的变化以及云反照率中高光谱特征的可能性。此外，对云和降水中波动的基础研究可能会对降水介质的结构、云中的基本过程、雷达信号的分析和解释以及非均质材料中的光衰减产生深刻的影响。它将改善降雨空间结构的特征，以便更好地利用天气雷达估计降雨量，以及云的辐射特性。此外，由于过冷水是一种亚稳态液体，与之相关的不可逆相变在材料科学中引起了广泛的兴趣。因此，对由此产生的缺陷--千疮百孔的冰--的研究可能会对固体物理学和物理气象学做出贡献。

The research seeks fundamental understanding in cloud physics, precipitation physics, radar meteorology, and radiative transfer through clouds. To that end, the researcher, in collaboration with graduate students, plans to conduct theoretical investigations, perform numerical experiments, analyze data from a variety of sensors, and suggest novel experiments. The specific objectives are following.1. Physics of rain: do all raindrops fall at terminal speed? Theoretical investigation and analysis of data from video disdrometers and Doppler radars will be conducted, with emphasis on fluctuations of raindrop fall velocities and deviations from a terminal speed. This study will have implications for retrieval by profilers, Doppler radars and disdrometers.2. Radar meteorology: the research will search for coherent backscatter data based on new theoretical analyses. Data analysis from short pulse radars, and exploratory signal processing will be conducted. This study will have implications of recently discovered fluctuations in raindrop surface tension in radar polarimetry. Non-Rayleigh signal statistics of radar echoes and in-phase/quadrature signatures of heterogeneous targets will also be investigated.3. Cloud physics: Is cloud ice "sloppy"? Study of freezing of supercooled water droplets and the resulting "scarred" ice and theoretical investigation of defect number density in ice versus the degree of supercooling will be carried out. Investigation of diffusional growth of cloud droplets with emphasis on the quasi-steady approximation and associated relaxation times in mixed-phase clouds will be conducted.4. Radiative transfer through clouds: surfactant-caused change in optical properties and the possibility of hyperspectral signatures in cloud albedo will be investigated.Intellectual merits:The questions above have not been fully addressed previously. Furthermore, fundamental studies of fluctuations in clouds and precipitation are likely to yield insights into the structure of precipitation media, fundamental processes in clouds, radar signal analysis and interpretation, and light attenuation in heterogeneous materials.Broader impacts:This research is also likely to have broad impacts on cloud physics and development of precipitation. It will improve characterization of rainfall spatial structure for better rainfall estimation with weather radar, and radiative properties of clouds. In addition, insofar as supercooled water is a metastable liquid, the associated irreversible phase transition is of wide interest in material science. Hence, study of the resulting defect riddled ice is likely to contribute to solid state physics as well as to physical meteorology.