Preprints
https://doi.org/10.5194/amt-2021-415
https://doi.org/10.5194/amt-2021-415
11 Jan 2022
 | 11 Jan 2022
Status: this preprint was under review for the journal AMT but the revision was not accepted.

Retrieval of the land-sea contrast of cloud liquid water path by applying a physical inversion algorithm to combined zenith and off-zenith ground-based microwave measurements

Vladimir Kostsov, Dmitry Ionov, and Anke Kniffka

Abstract. Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide an opportunity to study horizontal inhomogeneities of the humidity field in the troposphere and of the cloud liquid water path (LWP) spatial distribution. However, practical applications are difficult and require thorough analysis of the information content of measurements, assessment of errors of data processing algorithm and the development of the quality control procedures. In this study we analyse the application of our LWP retrieval algorithm based on the inversion of the radiative transfer equation to the problem of detection of the LWP horizontal inhomogeneities by means of ground-based microwave observations in the vicinity of a coastline of a water object of medium size. The study is based on data acquired by the microwave radiometer RPG-HATPRO which is located in the suburbs of St.Petersburg, Russia, at 2.5 km distance from the coastline of the Neva Bay (the Gulf of Finland) and is operating in angular scanning mode in the vertical plane. The retrieval setup is organised in such a way that zenith and off-zenith measurements provide equal sensitivity to atmospheric parameters. The optimal elevation angles for off-zenith observations are selected. The possibility to detect LWP horizontal inhomogeneity, namely the LWP land-sea contrast, for different measurement geometries (elevation angles) and values of cloud base height is analysed. It is shown that ground-based microwave observations in the vicinity of a coastline can be a valuable tool for validation of the space-borne measurements of the LWP land-sea contrast if three principal requirements are met: (a) the multi-parameter physical inversion method is used for retrieving LWP; (b) rigorous bias correction and quality control procedures are applied to the retrieval results; (c) the information on the cloud base height is available. As a result of processing the microwave measurements at the observational site of St.Petersburg State University, the monthly-averaged values of the LWP land-sea difference have been obtained for summer months within the period 2013–2021. For 24 out of 25 months of high quality observations, the LWP land-sea monthly difference is positive (larger values over land and smaller values over water) and can reach 0.06–0.07 kg m−2. The estimations of the LWP land-sea contrast obtained from the ground-based microwave measurements at the observational site of St.Petersburg University are in very good agreement with the values of the LWP land-sea contrast obtained from the multi-year space-borne measurements by the SEVIRI instrument (Spinning Enhanced Visible and InfraRed Imager) in the region of the Neva Bay (the Gulf of Finland) in June and July. For August, the so-called “August anomaly” detected by space-borne observations is not confirmed by the ground-based measurements.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Vladimir Kostsov, Dmitry Ionov, and Anke Kniffka

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-415', Anonymous Referee #1, 25 Feb 2022
  • RC2: 'Comment on amt-2021-415', Anonymous Referee #2, 13 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-415', Anonymous Referee #1, 25 Feb 2022
  • RC2: 'Comment on amt-2021-415', Anonymous Referee #2, 13 Mar 2022
Vladimir Kostsov, Dmitry Ionov, and Anke Kniffka
Vladimir Kostsov, Dmitry Ionov, and Anke Kniffka

Viewed

Total article views: 1,200 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
997 159 44 1,200 36 27
  • HTML: 997
  • PDF: 159
  • XML: 44
  • Total: 1,200
  • BibTeX: 36
  • EndNote: 27
Views and downloads (calculated since 11 Jan 2022)
Cumulative views and downloads (calculated since 11 Jan 2022)

Viewed (geographical distribution)

Total article views: 1,157 (including HTML, PDF, and XML) Thereof 1,157 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 12 Jun 2024
Download
Short summary
Combined zenith and off-zenith ground-based observations by modern microwave radiometers provide an opportunity to study horizontal inhomogeneities of cloud cover. However, practical applications are difficult and require thorough analysis due to large variability of cloud parameters and specific observation geometry. We show principal requirements which should be met in order that the land-sea contrast of the cloud liquid water path could be successfully derived from microwave observations.