Parameterizing ice clouds using airborne observations and triple-frequency doppler radar data

冰云在大气中具有重要的作用，影响辐射传输和降水的形成。所有云类型对全球气候的影响估计为冷却效应。这种净冷却效应来自于液体云（通过将阳光反射回太空而冷却）和冰云（通过“温室”效应而变暖）的相反影响。不幸的是，由于冰粒子过程的复杂性以及大气运动、水蒸气和气溶胶粒子之间的相互作用，人们对冰云中发生的许多物理过程缺乏了解。这意味着冰云在气候模拟中是一个重要的不确定性来源，并可能导致天气预报的错误。由于缺乏对冰云特性的观测，确定哪种模式最准确仍然很困难。遥感技术（如雷达）可以提供对大面积冰云的连续观测，使其成为评估模型技能的理想方法。然而，这些技术通常不直接测量与大气有关的量（例如，一体积空气中冷凝水的质量），必须使用检索来获得可比数据。这些检索必须提出一些关于冰云性质的假设，而这些性质实际上是高度不确定的。我们提出了一个项目，利用研究飞机的现场观测数据收集一个新的数据集，直接观测冰云的性质。同时，在不同波长下工作的三种不同雷达将扫描相同的云层，从而开发和评估各种雷达检索。我们将在立交桥期间从各种不同的卫星上获得数据，这些卫星从太空观测冰云。这项工作将提高对冰云特性的基本理解，并导致改进的遥感检索，这两者都将导致提高模型精度和减少不确定性。

Ice clouds have an important role in the atmosphere, influencing radiative transfer and precipitation formation. The global climatic impact of all clouds types is estimated as a cooling effect. This net cooling effect results from the opposing impacts from liquid clouds (which cool by reflecting sunlight back into space) and ice clouds (which warm through a "greenhouse" effect). Unfortunately there is a lack of understanding of many of the physical processes occurring in ice clouds due to the complexity of ice particle processes and interactions between atmospheric motions, water vapour, and aerosol particles. This means ice clouds are a source of significant uncertainty in climate simulations, and can lead to errors in weather forecasts. Establishing which models are the most accurate remains difficult due to the lack of observations of ice cloud properties. Remote sensing techniques (e.g. radar) can provide observations of ice clouds over large areas on a continuous basis, making them ideal for assessing model skill. However, these techniques do not typically directly measure the atmospherically relevant quantity (e.g. mass of condensed water in a volume of air), and a retrieval must be used to obtain comparable data. These retrievals must invoke several assumptions about the properties of the ice clouds, properties which in reality are highly uncertain. We propose a project to collect a new dataset using in-situ observations from a research aircraft to directly observed ice cloud properties. At the same time, three different radars operating at difference wavelengths will scan the same clouds to allow a variety of radar retrievals to be developed and evaluated. We will obtain data during overpasses from a variety of different satellites which observe ice clouds from space. This work will improve fundamental understanding of ice cloud properties, and lead to improved remote sensing retrievals, both of which will lead to improved model accuracy and reduced uncertainty.