scholarly journals Wet path delay and delay gradients inferred from microwave radiometer, GPS and VLBI observations

2000 ◽  
Vol 52 (10) ◽  
pp. 695-698 ◽  
Author(s):  
Lubomir P. Gradinarsky ◽  
Rüdiger Haas ◽  
Gunnar Elgered ◽  
Jan M. Johansson
Keyword(s):  
Microwave Radiometer ◽  
Path Delay ◽  
Vlbi Observations ◽  
Wet Path Delay

scholarly journals Sentinel-3 Microwave Radiometers: Instrument Description, Calibration and Geophysical Products Performances

2020 ◽  
Vol 12 (16) ◽  
pp. 2590 ◽  
Author(s):  
Marie-Laure Frery ◽  
Mathilde Siméon ◽  
Christophe Goldstein ◽  
Pierre Féménias ◽  
Franck Borde ◽  
...  
Keyword(s):  
Microwave Radiometer ◽  
Instrument Design ◽  
Sea Surface ◽  
Double Difference ◽  
Path Delay ◽  
Vicarious Calibration ◽  
Difference Methods ◽  
Two Parameters ◽  
Microwave Radiometers ◽  
Single Instrument

Copernicus Sentinel-3 Surface Topography Mission embarks a two-channel microwave radiometer combined with the altimeter in order to correct the altimeter range for the excess path delay resulting from the presence of water vapour in the troposphere. The in-flight calibration of a single instrument is the critical point to achieve the expected performances. In the context of a constellation, the inter-calibration is even more important. After a presentation of the instrument design, we present the diagnoses used for the calibration of Sentinel-3A, using vicarious calibration over specific areas and double difference methods. The inter-calibration of Sentinel-3B with Sentinel-3A is performed during the tandem phase, using the residual differences of co-located measurements. Finally performances are assessed at crossover points with two parameters, first the wet troposphere correction by comparison with Jason-3; secondly on the Sea Surface Height by difference of variance. Analysis results have shown that Sentinel-3A is well calibrated, consistent with other instruments, and that Sentinel-3B is calibrated within 0.4 K with Sentinel-3A as a reference. Performances and stability fulfill the requirements for both missions.

scholarly journals Modelling the Altitude Dependence of the Wet Path Delay for Coastal Altimetry Using 3-D Fields from ERA5

2019 ◽  
Vol 11 (24) ◽  
pp. 2973 ◽  
Author(s):  
Telmo Vieira ◽  
M. Joana Fernandes ◽  
Clara Lázaro
Keyword(s):  
Geographic Location ◽  
Global Navigation Satellite Systems ◽  
Path Delay ◽  
Satellite Systems ◽  
Altitude Dependence ◽  
External Sources ◽  
Maximum Root ◽  
Rms Error ◽  
Wet Path Delay ◽  
Global Navigation Satellite

Wet path delay (WPD) for satellite altimetry has been provided from external sources, raising the need of converting this value between different altitudes. The only expression available for this purpose considers the same altitude reduction, irrespective of geographic location and time. The focus of this study is the modelling of the WPD altitude dependence, aiming at developing improved expressions. Using ERA5 pressure level fields (2010–2013), WPD vertical profiles were computed globally. At each location and for each vertical profile, an exponential function was fitted using least squares, determining the corresponding decay coefficient. The time evolution of these coefficients reveals regions where they are highly variable, making this modelling more difficult, and regions where an annual signal exists. The output of this modelling consists of a set of so-called University of Porto (UP) coefficients, dependent on geographic location and time. An assessment with ERA5 data (2014) shows that for the location where the Kouba coefficient results in a maximum Root Mean Square (RMS) error of 3.2 cm, using UP coefficients this value is 1.2 cm. Independent comparisons with WPD derived from Global Navigation Satellite Systems and radiosondes show that the use of UP coefficients instead of Kouba’s leads to a decrease in the RMS error larger than 1 cm.

scholarly journals First Three Years of the Microwave Radiometer aboard Envisat: In-Flight Calibration, Processing, and Validation of the Geophysical Products

2006 ◽  
Vol 23 (6) ◽  
pp. 802-814 ◽  
Author(s):  
E. Obligis ◽  
L. Eymard ◽  
N. Tran ◽  
S. Labroue ◽  
P. Femenias
Keyword(s):  
Microwave Radiometer ◽  
Radiative Transfer Model ◽  
Altimeter Data ◽  
Transfer Model ◽  
Path Delay ◽  
Inversion Algorithm ◽  
Weather Forecasts ◽  
Brightness Temperatures ◽  
Medium Range ◽  
Satellite Altimeter Data

Abstract The Envisat microwave radiometer is designed to correct the satellite altimeter data for the excess path delay resulting from tropospheric humidity. Neural networks have been used to formulate the inversion algorithm to retrieve this quantity from the measured brightness temperatures. The learning database has been built with European Centre for Medium-Range Weather Forecasts (ECMWF) analyses and simulated brightness temperatures by a radiative transfer model. The in-flight calibration has been performed in a consistent way by adjusting measurements on simulated brightness temperatures. Finally, coincident radiosonde measurements are used to validate the Envisat wet-tropospheric correction, and this comparison shows the good performances of the method.

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