Effective Radius of Ice Cloud Particle Populations Derived from Aircraft Probes
Effective Radius of Ice Cloud Particle Populations Derived from Aircraft Probes
复制标题
飞机探测器产生的冰云粒子群的有效半径
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
D. Baumgardner
中科院分区：
文献类型：
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作者：
A. Heymsfield;C. Schmitt;A. Bansemer;G. V. Zadelhoff;M. McGill;C. Twohy;D. Baumgardner
有效半径（re）是大气环流模式中表示云层辐射特性的一个重要变量。该参数与冷凝水含量（CWC）除以消光率（）成正比。对于冰云层，re的参数化已经从飞机原位测量中发展出来：1）间接地，使用从粒子光谱仪探测器获得的数据以及关于粒子形状和质量的假设或观测来获得冰水含量（IWC）和要获得的面积，以及最近2）从探测器获得IWC和更直接地，称为直接方法，即使消光不是直接测量的。本研究比较了[IWC/]来自两种方法，使用从两个飞机上的可比仪器获得的数据集，一个采样云在中层，另一个在上层在卷云区域研究的热带铁砧和卷云层（CRYSTAL）佛罗里达地区卷云实验（FACE）现场计划在佛罗里达在2002年。一个渗透到一个寒冷的中纬度地形波云组成的小颗粒的飞机进一步评估。对于每个飞机数据集，以不同的方式对每种方法得出的和IWC进行比较和评估。直接测量值超过间接测量值2-2.5倍。IWC探头依赖于冰升华，除了当IWC很高或颗粒太大而不能在通过探头的短时间内完全升华时，IWC探头似乎可以准确测量。当直接测量可提供约束条件并在高IWC/大颗粒情况下提供有用信息时，从颗粒探针估计的IWC是准确的。由于直接法和间接法之间的估计值存在差异，两者之间的[IWC/]存在2-3倍的差异。虽然有显着的不确定性，在其使用中，与几个独立的数据来源的比较表明，间接方法是更准确的两种方法。然而，需要实验来解决差异的来源。
The effective radius (re) is a crucial variable in representing the radiative properties of cloud layers in general circulation models. This parameter is proportional to the condensed water content (CWC) divided by the extinction (). For ice cloud layers, parameterizations for re have been developed from aircraft in situ measurements 1) indirectly, using data obtained from particle spectrometer probes and assumptions or observations about particle shape and mass to get the ice water content (IWC) and area to get , and recently 2) from probes that derive IWC and more directly, referred to as the direct approach, even though the extinction is not measured directly. This study compares [IWC/] derived from the two methods using datasets acquired from comparable instruments on two aircraft, one sampling clouds at midlevels and the other at upper levels during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) field program in Florida in 2002. A penetration by one of the aircraft into a cold midlatitude orographic wave cloud composed of small particles is further evaluated. The and IWC derived by each method are compared and evaluated in different ways for each aircraft dataset. Direct measurements of exceed those derived indirectly by a factor of 2–2.5. The IWC probes, relying on ice sublimation, appear to measure accurately except when the IWC is high or the particles too large to sublimate completely during the short transit time through the probe. The IWC estimated from the particle probes are accurate when direct measurements are available to provide constraints and give useful information in high IWC/large particle situations. Because of the discrepancy in estimates between the direct and indirect approaches, there is a factor of 2–3 difference in [IWC/] between them. Although there are significant uncertainties involved in its use, comparisons with several independent data sources suggest that the indirect method is the more accurate of the two approaches. However, experiments are needed to resolve the source of the discrepancy in .