DOI: 10.1594/pangaea.968762
title: Relative humidity (rh) computed from radiosonde air pressure, retrieved temperature (temp) and specific humidity (q) during the MOSAiC expedition

description: This data set contains daily files of temperature (temp), specific humidity (q) and relative humidity (rh) profiles derived from combined measurements of the HATPRO and MiRAC-P microwave radiometers (see Walbröl et al. 2022, https://doi.org/10.1038/s41597-022-01504-1) operated aboard the Polarstern during cruise PS122 (MOSAiC expedition). The data covers the time range from 22 October 2019 until 02 October 2020 with a temporal resolution of about 1 second (except for temp_bl data, see below). Both microwave radiometers were mounted on top of the OCEANET-ATMOSPHERE container (Macke et al. 2010, https://doi.org/10.1051/epjconf/201009006; Engelmann et al. 2021, https://doi.org/10.5194/acp-21-13397-2021). HATPRO is a Humidity and Temperature Profiler (Rose et al. 2005, https://doi.org/10.1016/j.atmosres.2004.12.005) that measures atmospheric radiation emitted from water vapour along a rotational water vapour aborption line in the K-band (7 channels from 22.24 to 31.4 GHz) and from oxygen along the absorption complex in the V-band (7 channels from 51.26 to 58 GHz). The HATPRO measurements are also sensitive to radiation emitted from hydrometeors (cloud liquid water). MiRAC-P is a Low Humidity Profiler (LHUMPRO-243-340, Mech et al. 2019, https://doi.org/10.5194/amt-12-5019-2019), also known as the Microwave Radiometer for Arctic Clouds - Passive, that measures atmospheric radiation at higher frequencies along a strong water vapour absorption line in the G-band (6 channels from 183.31 +/- 0.6 to 183.31 +/- 7.5 GHz), and in the window channels (no distinct absorption lines) 243 and 340 GHz. We developed a Neural Network for each derived quantity. Because of the different water vapour sensitivities of the K-band and the G-band channels, the derived humidity profiles from combined HATPRO and MiRAC-P measurements were strongly improved compared to the HATPRO-only retrievals (see Walbröl et al. 2024; in preparation). Temperature profiles were retrieved from zenith observations using both HATPRO and MiRAC-P measurements (temp), and separately from boundary layer scans from HATPRO only (temp_bl), which were performed once every 30 minutes. Relative humidity (rh) was computed from retrieved q and temp profiles and combined with radiosonde air pressure measurements (Dahlke et al. 2023, https://doi.org/10.1594/PANGAEA.961881) that were interpolated onto the retrieval height grid and time axis. Specific humidity was retrieved until a height of 10000 m, while temperature and relative humidity profiles are limited to 0-8000 m because of the strong temperature gradient in the tropopause. Error estimates in terms of root mean squared error are provided within each file as variables (e.g., q_rmse for specific humidity). Quality flags of each instrument (flag_h for HATPRO and flag_m for MiRAC-P) are also included in each file and can be used to filter data with bad quality. The data has good quality when the flag values (flag_h and flag_m) are 0 or nan (depends on the importing routine). Additionally, data where flag_h is 32 can also be used with care.