Abstract
A melting layer detection algorithm is developed for the NCAR 94 GHz airborne cloud radar (HIAPER CloudRadar, HCR). The detection method is based on maxima in the linear depolarization ratio and a discontinuity in the radial velocity field. A melting layer field is added to the radar data, which provides detected, interpolated, and estimated altitudes of the melting layer and the altitude of the 0 °C isotherm detected in model temperature data. The icing level is defined as the lowest melting layer, and the cloud data are flagged as either above (cold) or below (warm) the icing level. Analysis of the detected melting layer shows that the offset between the 0 °C isotherm and the actual melting layer varies with cloud type: in heavy convection sampled in the tropics, the melting layer is found up to 500 m below the 0 °C isotherm, while in shallow clouds, the offset is much smaller or sometimes vanishes completely. A relationship between the offset and the particle fall speed both above and below the melting layer is established. Special phenomena, such as a lowering of the melting layer towards the center of storms or split melting layers, were observed.
Highlights
Layer Detection and ObservationThe mission of the Earth Observing Laboratory (EOL) at the National Center for Atmospheric Research (NCAR) is to develop and deploy observing facilities and provide expertise and data services to aid the scientific community in observational field campaigns.One of the instruments deployed by EOL on the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Gulfstream V aircraft is the HIAPER Cloud Radar (HCR, [1]), a 94 GHz W-band radar
Because it takes some time for the melting process to take effect once a frozen particle reaches positive temperatures on its downward trajectory, the melting layer is generally found below the 0 ◦ C isotherm
It is important to note that the melting layer altitudes detected in VEL are sometimes somewhat lower than those detected in linear depolarization ratio (LDR), as has been observed in previous studies, e.g., [22], but the difference was not significant, i.e., less than the overall noise, and merging them into the same data field seemed justified
Summary
The mission of the Earth Observing Laboratory (EOL) at the National Center for Atmospheric Research (NCAR) is to develop and deploy observing facilities and provide expertise and data services to aid the scientific community in observational field campaigns. The HCR team is committed to developing new data products to assist scientists in accomplishing their research goals and to increase the benefit of HCR data to the scientific community. One of these data products is a recently developed estimate of the altitude of the melting layer. The primary goal of the proposed melting layer data product is to allow users to distinguish between warm and cold clouds below and above the melting layer It is not aimed at studies of the melting layer itself and is not intended to distinguish between the top and the bottom of the melting layer as is the case with other more specialized algorithms, e.g., [9]. Noteworthy observations of special melting layer features are highlighted and discussed
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