First insight into thermodynamic profiles, IWV and LWP from ground-based microwave radiometers during MOSAiC
Authors: Walbröl Andreas , Konjari Patrick , Engelmann Ronny , Griesche Hannes , Radenz Martin , Hofer Julian , Althausen Dietrich , Crewell Susanne , Ebell Kerstin 
Published: March 2021

&lt;p&gt;The Arctic is currently experiencing a more rapid warming compared to the rest of the&lt;br&gt;world. This phenomenon, known as Arctic Amplification, is the result of several processes.&lt;br&gt;Within the Collaborative Research Centre on Arctic Amplification: Climate Relevant Atmospheric&lt;br&gt;and Surface Processes and Feedback Mechanisms (AC)3, our research focuses&lt;br&gt;on the influence of water vapour, the strongest greenhouse gas. The collection of data&lt;br&gt;about water vapour is essential to understand its impact on Arctic Amplification. Over&lt;br&gt;the past decades, a positive trend in integrated water vapour in the Arctic has been&lt;br&gt;identified using radiosondes and reanalyses for certain regions and seasons. However, inconsistent&lt;br&gt;magnitudes of the moistening trend in the reanalyses cause the need of a more&lt;br&gt;thorough investigation. While radiosondes offer precise measurements of thermodynamic&lt;br&gt;(temperature and humidity) profiles, they fail to capture the variability of water vapour&lt;br&gt;because of the low sampling rate (two to four sondes per day) and spatial coverage. To&lt;br&gt;obtain a more complete picture of water vapour variability, remote sensing instruments&lt;br&gt;(satellite- and ground-based) are used. Microwave radiometers (MWRs) onboard polar&lt;br&gt;orbiting satellites allow the coverage of the entire Arctic but suffer from uncertainties&lt;br&gt;related to surface emission. Observations at the surface gathered during the Multidisciplinary&lt;br&gt;drifting Observatory for the Study of Arctic Climate (MOSAiC) campaign can&lt;br&gt;serve as reference measurements in the central Arctic for the assessment of water vapour&lt;br&gt;products from reanalyses, models and satellite retrievals.&lt;br&gt;&lt;br&gt;In this study, we give a first insight into the variability of integrated water vapour (IWV),&lt;br&gt;liquid water path (LWP) and thermodynamic profiles retrieved from two ground-based&lt;br&gt;MWRs onboard the research vessel Polarstern throughout the MOSAiC campaign. The&lt;br&gt;first radiometer is a standard low frequency HATPRO system and the other one is the&lt;br&gt;high-frequency MiRAC-P, which is particularly suited for low water vapour contents. The&lt;br&gt;retrieved quantities are compared with radiosonde measurements. A first analysis reveals&lt;br&gt;that the IWV is very well captured by the MWR measurements. Over the observation&lt;br&gt;period (October 2019 - October 2020), a large variety of meteorological conditions occurred.&lt;br&gt;Besides the considerable seasonal cycle, which is especially interesting because of&lt;br&gt;the contrast between polar night and polar day, several synoptic events contribute to the&lt;br&gt;variety of conditions, which will be highlighted as well.&lt;/p&gt;&lt;p&gt;&lt;br&gt;We gratefully acknowledge the funding by the Deutsche Forschungsgemeinschaft (DFG, German Research&lt;br&gt;Foundation) &amp;#8212; Project 268020496 &amp;#8212; TRR 172, within the Transregional Collaborative Research Center&lt;br&gt;&quot;Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms&lt;br&gt;(AC)3&quot;. Data used in this manuscript was produced as part of the international Multidisciplinary drifting&lt;br&gt;Observatory for the Study of the Arctic Climate (MOSAiC) with the tag MOSAiC20192020 and the&lt;br&gt;Polarstern expedition AWI_PS122_00.&lt;/p&gt;