Abstract's details
Using radiosonde networks to assess short scale Wet Tropospheric Correction retrieval improvement: illustration with SARAL/AltiKa mission.
CoAuthors
Event: 2018 Ocean Surface Topography Science Team Meeting
Session: Instrument Processing: Propagation, Wind Speed and Sea State Bias
Presentation type: Type Oral
Contribution: not provided
Abstract:
The wet tropospheric correction (WTC) is a major source of uncertainty in altimetry budget error, due to its large spatial and temporal variability.
During the nominal history of a mission, successive and improved versions of the retrieval algorithm are proposed. The current metric used to quantify the improvement is the well-known reduction of the variance of the Sea Surface Height at cross-overs.
The goal here, is to propose the quantification of the improvement of the budget error specific to the wet tropospheric correction, based on a comparison of the radiometer WTC to radiosonde.
The latest published similar comparison was performed by Shannon Brown et al. in 2004 [1] for the JMR on-board Jason-1. Using a set of radiosonde stations, Brown estimated an uncertainty on JMR WTC by extrapolation at 0 km of the difference between JMR WTC and radiosonde WTC against distance between the measurements. Assumptions were made on the error on radiosonde to retrieve the uncertainty on JMR WTC.
We propose to adapt this approach using an updated methodology and an updated error estimation on radiosonde, based on the work of Brogniez et al. 2015 [2] on the uncertainty of SAPHIR humidity measurements.
This approach is illustrated by the WTC of the SARAL/AltiKa mission through the comparison of the relative performance of the 4 different versions of the retrieval algorithm.
[1] S. Brown, C. Ruf, S. Keihm, and A. Kitiyakara, “Jason Microwave Radiometer Performance and On-Orbit Calibration,” Mar. Geod., vol. 27, no. February 2015, pp. 199–220, 2004.
[2] H. Brogniez, G. Clain, and R. Roca, “Validation of upper-tropospheric humidity from SAPHIR on board Megha-Tropiques using tropical soundings,” J. Appl. Meteorol. Climatol., vol. 54, no. 4, pp. 896–908, 2015.
During the nominal history of a mission, successive and improved versions of the retrieval algorithm are proposed. The current metric used to quantify the improvement is the well-known reduction of the variance of the Sea Surface Height at cross-overs.
The goal here, is to propose the quantification of the improvement of the budget error specific to the wet tropospheric correction, based on a comparison of the radiometer WTC to radiosonde.
The latest published similar comparison was performed by Shannon Brown et al. in 2004 [1] for the JMR on-board Jason-1. Using a set of radiosonde stations, Brown estimated an uncertainty on JMR WTC by extrapolation at 0 km of the difference between JMR WTC and radiosonde WTC against distance between the measurements. Assumptions were made on the error on radiosonde to retrieve the uncertainty on JMR WTC.
We propose to adapt this approach using an updated methodology and an updated error estimation on radiosonde, based on the work of Brogniez et al. 2015 [2] on the uncertainty of SAPHIR humidity measurements.
This approach is illustrated by the WTC of the SARAL/AltiKa mission through the comparison of the relative performance of the 4 different versions of the retrieval algorithm.
[1] S. Brown, C. Ruf, S. Keihm, and A. Kitiyakara, “Jason Microwave Radiometer Performance and On-Orbit Calibration,” Mar. Geod., vol. 27, no. February 2015, pp. 199–220, 2004.
[2] H. Brogniez, G. Clain, and R. Roca, “Validation of upper-tropospheric humidity from SAPHIR on board Megha-Tropiques using tropical soundings,” J. Appl. Meteorol. Climatol., vol. 54, no. 4, pp. 896–908, 2015.