First insight into thermodynamic profiles, IWV and LWP from ground-based microwave radiometers during MOSAiC

Abstract

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