Evaluating the ability of a microwave radiometer and wrf to detect and simulate in-cloud icing conditions
Authors: Sanchez Jose Luis , Melcon Pablo , Merida Guillermo , Merino Andres , Garcia-Ortega Eduardo , Marcos Jose Luis , Lopez Laura , Sanchez-Muñoz Laura , Valero Francisco , Fernandez Javier , Bolgiani Pedro , Martin Maria Luisa , Fernandez-Gonzalez Sergio , Navarro Andres 
Published: March 2020

&lt;p&gt;Icing occurs when an unheated solid structure is exposed to liquid cloud droplets at temperatures below the freezing point. Supercooled liquid water (SLW) in the atmosphere can persist in a physically metastable state until coming into contact with a solid object &amp;#8220;In-cloud icing&amp;#8221; occurs when super cooled liquid droplets (SLD) like clouds collide with a structure or object and freezes.&lt;/p&gt;&lt;p&gt;Atmospheric icing prediction has gain attention in the last years. Despite the progress made in meteorology, both weather forecasting modelling and atmospheric observations through advanced experimental technologies, there are still limitations in the accurate forecast and detection of icing conditions. The GFA&amp;#8208;ULE group has carried out some NWPs. In a previous work, we investigated the capability of the Weather Research and Forecasting model to detect regions containing supercooled cloud drops, proposing a multiphysics ensemble approach. Four microphysics and two planetary boundary layer schemes were used. Morrison and Goddard parameterizations with the YSU scheme, yielded superior results in evaluating the presence of liquid water content.&lt;/p&gt;&lt;p&gt;Concerning the remote detection of icing conditions, some European research centres (i.e. DLR, CIRA, ONERA, INCAS) as well as University of Leon (GFA-ULE) already have nowcasting or forecasting activities for detection of clouds and icing conditions. In this work a multichannel, microwave radiometer (MMWR) was used to detect the appearance of SLW. Consequently, we present both comparison between indirect detection of SLW and the output obtained by WRF with the two combination of parametrizations selected.&lt;/p&gt;&lt;p&gt;In our work we have taken into account:&lt;/p&gt;&lt;ol&gt;&lt;li&gt;The comparison has been made at different levels, from the ground up to 5000 meters high&lt;/li&gt;
&lt;li&gt;We have taken different thresholds of the SLW: 0.05, 0.1, 0.15, 0.20, 0.25 and 0.30 g m&lt;sup&gt;-3&lt;/sup&gt; because of the flight campaigns carried out previously, which revealed that the presence of low concentrations of SLW could lead to the appearance of aircraft icing.&lt;/li&gt;
&lt;/ol&gt;&lt;p&gt;The results show a good concordance between the number of events found by the MMWR and the result of the two numerical modeling performed. Therefore, everything seems to indicate that indirect detection by MMWR can be an accurate technology to detect the appearance of SLW and that the models can be qualitatively validated.&lt;/p&gt;&lt;p&gt;Acknowledgments: Data support came from the Atmospheric Physics Group, IMA, University of Le&amp;#243;n, Spain, and the National Institute of &amp;#160;Aerospace Technology (INTA). This research was carried out in the framework of the SAFEFLIGHT project, financed by MINECO (CGL2016&amp;#8208;78702) and LE240P18 project (Junta de Castilla y Le&amp;#243;n). We also thank R. Weigand for computer support.&lt;/p&gt;