30 January 2023
29 October 2018
The purpose of this study is to evaluate the suitability of cold target regions (Antarctic ice sheet) for a cross-validation of scatterometer data from different instruments and assess the long term stability of instrument calibration.
Objectives
The objective of this short study is the preparation of the validation of the upcoming ASCAT instrument on Metop-C, by developing a suitable cross-validation method to evaluate the radiometric properties (stability, relative accuracy) of the ASCAT instruments on Metop-A and -B.
Overview
A statistical analysis of the ASCAT time series from Metop-A and -B over a well-selected area in Antarctica will be performed using a 3-year period of data. ASCAT-A/B data variations will be explored with season, meteorological conditions and surface variations, with the help of auxiliary data from the global Numerical Weather Prediction model ARPEGE. Based on the results, a stable target region will be selected and the ASCAT backscatter signal will be evaluated with respect to the meteorological and surface conditions. The multi-year database of CNRM (Centre National de Recherches Météorologiques) surface emissivities will be used for preliminary statistical and quantitative analysis of microwave emissivities versus ASCAT backscatter over our target region in Antarctica to examine the backscatter variability with season and surface type. The potential of combining active and passive microwave data to explore new perspectives for inter-calibration of instruments will be investigated. The feasibility of using stable natural targets will be evaluated, aiming to propose a methodology to combine relevant measurements from passive and active instruments in order to perform cross-calibration of present and future microwave instruments.
