{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T07:26:45Z","timestamp":1767857205545,"version":"3.49.0"},"reference-count":40,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2021,6,5]],"date-time":"2021-06-05T00:00:00Z","timestamp":1622851200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Because of its clear physical meaning, physical methods are more often used for space-borne microwave radiometers to retrieve the rain rate, but they are rarely used for ground-based microwave radiometers that are very sensitive to rainfall. In this article, an opacity physical retrieval method is implemented to retrieve the rain rate (denoted as Opa-RR) using ground-based microwave radiometer data (21.4 and 31.5 GHz) of the tropospheric water radiometer (TROWARA) at Bern, Switzerland from 2005 to 2019. The Opa-RR firstly establishes a direct connection between the rain rate and the enhanced atmospheric opacity during rain, then iteratively adjusts the rain effective temperature to determine the rain opacity, based on the radiative transfer equation, and finally estimates the rain rate. These estimations are compared with the available simultaneous rain rate derived from rain gauge data and reanalysis data (ERA5). The results and the intercomparison demonstrate that during moderate rains and at the 31 GHz channel, the Opa-RR method was close to the actual situation and capable of the rain rate estimation. In addition, the Opa-RR method can well derive the changes in cumulative rain over time (day, month, and year), and the monthly rain rate estimation is superior, with the rain gauge validated R2 and the root-mean-square error value of 0.77 and 22.46 mm\/month, respectively. Compared with ERA5, Opa-RR at 31GHz achieves a competitive performance.<\/jats:p>","DOI":"10.3390\/rs13112217","type":"journal-article","created":{"date-parts":[[2021,6,7]],"date-time":"2021-06-07T01:56:40Z","timestamp":1623031000000},"page":"2217","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Physical Retrieval of Rain Rate from Ground-Based Microwave Radiometry"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8251-2514","authenticated-orcid":false,"given":"Wenyue","family":"Wang","sequence":"first","affiliation":[{"name":"Institute of Applied Physics, University of Bern, CH-3012 Bern, Switzerland"},{"name":"Oeschger Centre for Climate Change Research, University of Bern, CH-3012 Bern, Switzerland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2178-9920","authenticated-orcid":false,"given":"Klemens","family":"Hocke","sequence":"additional","affiliation":[{"name":"Institute of Applied Physics, University of Bern, CH-3012 Bern, Switzerland"},{"name":"Oeschger Centre for Climate Change Research, University of Bern, CH-3012 Bern, Switzerland"}]},{"given":"Christian","family":"M\u00e4tzler","sequence":"additional","affiliation":[{"name":"Institute of Applied Physics, University of Bern, CH-3012 Bern, Switzerland"},{"name":"Oeschger Centre for Climate Change Research, University of Bern, CH-3012 Bern, Switzerland"}]}],"member":"1968","published-online":{"date-parts":[[2021,6,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1016\/j.jhydrol.2003.11.039","article-title":"Rainfall assimilation in RAMS by means of the Kuo parameterisation inversion: Method and preliminary results","volume":"288","author":"Orlandi","year":"2004","journal-title":"J. Hydrol."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Wang, J., Xu, Y., Yang, L., Wang, Q., Yuan, J., and Wang, Y. (2020). Data assimilation of high-resolution satellite rainfall product improves rainfall simulation associated with landfalling tropical cyclones in the Yangtze river Delta. Remote Sens., 12.","DOI":"10.3390\/rs12020276"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"742","DOI":"10.1109\/TGRS.2002.1006317","article-title":"Ground-based multifrequency microwave radiometry for rainfall remote sensing","volume":"40","author":"Marzano","year":"2002","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1485","DOI":"10.5194\/amt-13-1485-2020","article-title":"Ground-based observations of cloud and drizzle liquid water path in stratocumulus clouds","volume":"13","author":"Cadeddu","year":"2020","journal-title":"Atmos. Meas. Tech."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"6468","DOI":"10.1109\/TGRS.2017.2728699","article-title":"Microwave passive ground-based retrievals of cloud and rain liquid water path in drizzling clouds: Challenges and possibilities","volume":"55","author":"Cadeddu","year":"2017","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"394","DOI":"10.1175\/2009JAMC2340.1","article-title":"Characterization of precipitating clouds by ground-based measurements with the triple-frequency polarized microwave radiometer ADMIRARI","volume":"49","author":"Battaglia","year":"2010","journal-title":"J. Appl. Meteorol. Climatol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"259","DOI":"10.5194\/adgeo-2-259-2005","article-title":"Monitoring of rainfall by ground-based passive microwave systems: Models, measurements and applications","volume":"2","author":"Marzano","year":"2005","journal-title":"Adv. Geosci."},{"key":"ref_8","first-page":"55","article-title":"An application of brightness temperature received from a ground-based microwave radiometer to estimation of precipitation occurrences and rainfall Intensity","volume":"45","author":"Won","year":"2009","journal-title":"Asia-Pac. J. Atmos. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.atmosres.2014.01.021","article-title":"Effect of off-zenith observations on reducing the impact of precipitation on ground-based microwave radiometer measurement accuracy","volume":"140\u2013141","author":"Xu","year":"2014","journal-title":"Atmos. Res."},{"key":"ref_10","unstructured":"M\u00e4tzler, C., and Morland, J. (2014). Advances in Surface-Based Radiometry of Atmospheric Water, Institut f\u00fcr Angewandte Physik, Universit\u00e4t Bern. IAP Research Report 2008-02-MW."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Hocke, K., Navas-Guzm\u00e1n, F., Moreira, L., Bernet, L., and M\u00e4tzler, C. (2017). Diurnal cycle in atmospheric water over switzerland. Remote Sens., 9.","DOI":"10.3390\/rs9090909"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"12083","DOI":"10.5194\/acp-19-12083-2019","article-title":"Diurnal cycle of short-term fluctuations of integrated water vapour above Switzerland","volume":"19","author":"Hocke","year":"2019","journal-title":"Atmos. Chem. Phys."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"905","DOI":"10.1029\/98RS01000","article-title":"Weighted mean tropospheric temperature and transmittance determination at millimeter-wave frequencies for ground-based applications","volume":"33","author":"Ingold","year":"1998","journal-title":"Radio Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1585","DOI":"10.1109\/TGRS.2008.2006984","article-title":"Refined physical retrieval of integrated water vapor and cloud liquid for microwave radiometer data","volume":"47","author":"Morland","year":"2009","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_15","first-page":"431","article-title":"Dielectric properties of natural media","volume":"Volume 52","year":"2006","journal-title":"Thermal Microwave Radiation: Applications for Remote Sensing"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"18173","DOI":"10.1029\/92JD01717","article-title":"Radiometric determination of water vapor and liquid water and its validation with other techniques","volume":"97","author":"Peter","year":"1992","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_17","unstructured":"Morland, J. (2002). TROWARA\u2013Tropospheric Water Vapour Radiometer: Radiometer Review and New Calibration Model, Institut f\u00fcr Angewandte Physik, Universit\u00e4t Bern. IAP Research Report 2002-15."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1000","DOI":"10.1109\/TGRS.2004.839595","article-title":"Modeling and measurement of rainfall by ground-based multispectral microwave radiometry","volume":"43","author":"Marzano","year":"2005","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"919","DOI":"10.1029\/98RS01182","article-title":"Water vapor microwave continuum absorption: A comparison of measurements and models","volume":"33","author":"Rosenkranz","year":"1998","journal-title":"Radio Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"125084","DOI":"10.1016\/j.jhydrol.2020.125084","article-title":"Comparison of methods to estimate areal means of short duration rainfalls in small catchments, using rain gauge and radar data","volume":"588","author":"Hwang","year":"2020","journal-title":"J. Hydrol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"497","DOI":"10.1175\/JHM431.1","article-title":"Intercomparison of rain gauge, radar, and satellite-based precipitation estimates with emphasis on hydrologic forecasting","volume":"6","author":"Yilmaz","year":"2005","journal-title":"J. Hydrometeorol."},{"key":"ref_22","unstructured":"Donald Ahrens, C., and Henson, R. (2009). Meteorology Today: An Introduction to Weather, Climate and the Environment, Cengage Learning. [9th ed.]."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1","DOI":"10.5194\/esd-12-1-2021","article-title":"Evaluating the dependence structure of compound precipitation and wind speed extremes","volume":"12","author":"Zscheischler","year":"2021","journal-title":"Earth Syst. Dynam."},{"key":"ref_24","unstructured":"Hersbach, H., De Rosnay, P., Bell, B., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Balmaseda, A., Balsamo, G., and Bechtold, P. (2018). Operational Global Reanalysis: Progress, Future Directions and Synergies with NWP, ERA Report Series 27, European Centre for Medium RangeWeather Forecasts."},{"key":"ref_25","first-page":"17","article-title":"Global reanalysis: Goodbye ERA-Interim, hello ERA5","volume":"159","author":"Hersbach","year":"2019","journal-title":"ECMWF Newsl."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"100608","DOI":"10.1016\/j.ejrh.2019.100608","article-title":"Evaluation of variability among different precipitation products in the Northern Great Plains","volume":"24","author":"Xu","year":"2019","journal-title":"J. Hydrol. Reg. Stud."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"124632","DOI":"10.1016\/j.jhydrol.2020.124632","article-title":"Inter-comparison of ERA-5, ERA-interim and GPCP rainfall over the last 40 years: Process-based analysis of systematic and random differences","volume":"583","author":"Nogueira","year":"2020","journal-title":"J. Hydrol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"124707","DOI":"10.1016\/j.jhydrol.2020.124707","article-title":"Performance evaluation of satellite- and model-based precipitation products over varying climate and complex topography","volume":"584","author":"Amjad","year":"2020","journal-title":"J. Hydrol."},{"key":"ref_29","unstructured":"M\u00e4tzler, C., and Martin, L. (2002). Effects of Rain on Propagation, Absorption and Scattering of Microwave Radiation Based on the Dielectric Model of Liebe, Institut f\u00fcr Angewandte Physik, Universit\u00e4t Bern. IAP Research Report 2002-10-MW."},{"key":"ref_30","unstructured":"Leuenberger, A. (2009). Precipitation Measurements with Microwave Sensors. [Master\u2019s Thesis, Philosophisch-Naturwissenschaftliche Fakult\u00e4t]."},{"key":"ref_31","first-page":"1","article-title":"Radiative transfer and microwave radiometry","volume":"Volume 52","year":"2006","journal-title":"Thermal Microwave Radiation: Applications for Remote Sensing"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1029\/91RS03052","article-title":"Ground-based observations of atmospheric radiation at 5, 10, 21, 35, and 94 GHz","volume":"27","year":"1992","journal-title":"Radio Sci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1007\/BF01030053","article-title":"Physical retrievals of over-ocean rain rate from multichannel microwave imagery. Part I: Theoretical characteristics of normalized polarization and scattering indices","volume":"54","author":"Petty","year":"1994","journal-title":"Meteorl. Atmos. Phys."},{"key":"ref_34","first-page":"437","article-title":"Wireless sensor network design for earthquake\u2019s and landslide\u2019s early warnings","volume":"11","author":"Latupapua","year":"2018","journal-title":"Indones. J. Electr. Eng. Comput. Sci."},{"key":"ref_35","unstructured":"M\u00e4tzler, C. (2002). Drop-Size Distributions and Mie Computations for Rain, Institut f\u00fcr Angewandte Physik, Universit\u00e4t Bern. IAP Research Report 2002-16-MW."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"465","DOI":"10.1002\/asl.583","article-title":"Atmospheric water parameters measured by a ground-based microwave radiometer and compared with the WRF model","volume":"16","author":"Cossu","year":"2015","journal-title":"Atmos. Sci. Lett."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1016\/j.jhydrol.2005.11.042","article-title":"Neural-network approach to ground-based passive microwave estimation of precipitation intensity and extinction","volume":"328","author":"Marzano","year":"2006","journal-title":"J. Hydrol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"354","DOI":"10.1109\/LGRS.2009.2013484","article-title":"Rain observations by a multifrequency dual-polarized radiometer","volume":"6","author":"Battaglia","year":"2009","journal-title":"IEEE Geosci. Remote. Sens. Lett."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"e2020JD032456","DOI":"10.1029\/2020JD032456","article-title":"Comparative study of cloud liquid water and rain liquid water obtained from microwave radiometer and micro rain radar observations over central China during the monsoon","volume":"125","author":"Zhang","year":"2020","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_40","unstructured":"(2014). Climate Normals Bern\/Zollikofen (Reference Period. 1981\u22122010), Swiss Federal Office of Metreology and Climatology, MeteoSwiss. Zurich-Airport."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/11\/2217\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:11:17Z","timestamp":1760163077000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/13\/11\/2217"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,6,5]]},"references-count":40,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2021,6]]}},"alternative-id":["rs13112217"],"URL":"https:\/\/doi.org\/10.3390\/rs13112217","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,6,5]]}}}