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The Need For Geophysical Corrections
The Need For Geophysical Corrections
There are several types of corrections that are applied to the 'orbit minus range' equation in order to obtain a true surface height. These are introduced on the page on Sea Level Measurements, and covered in detail on the individual pages linked below.
Reason for Correction
Reason for Correction
Method of Calculation
Method of Calculation
Due to refractive index of free electrons in the upper atmosphere, which is proportional to the inverse square of the radar frequency.
Calculated by comparing the range measured for different bands on the altimeter (on Sentinel-6, the C and Ku bands)
Due to refractive index of atmospheric water vapour (and liquid water).
Calculated from the measurements of the microwave radiometer which is sensitive to water absorption features.
Due to refractive index of all other atmospheric gases.
Calculated from reanalysis / forecast modelled values of atmospheric pressure at sea level and local gravitational field.
Due to changes in sea level based on changes in atmospheric pressure pushing down the water.
Calculated from reanalysis / forecast modelled values of atmospheric pressure at sea level and local gravitational field.
Due to Moon and Sun tides in the oceans (and to a lesser extent land).
Calculated from tidal models.
Due to biases in how the radar pulse interacts with the ocean waves, and their skewness.
Currently calculated from empirical modelling based on altimetry observations.
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