Atmospheric Corrections in Coastal Altimetry
Abstract
The range measurements from the altimeter are associated with a large number of geophysical corrections which needs special attention near coasts and the shallow water regions. The corrections due to ionosphere, dry and wet troposphere and that due to sea state are of primary importance in altimetry. Water vapor dominates the wet tropospheric corrections by several factors which is more complex with higher spatio-temporal variations and thus needs a careful attention near coasts. In addition to this rain is one of the major atmospheric phenomena which attenuate the backscatter altimeter measurements which in turn affect the altimeter derived wind and wave measurements. Thus during rain events utmost care should be taken while deriving the altimeter wind speeds and wave heights. The first objective of the present study involves the comparison of the water vapor corrections estimated from radiosonde measurements near the coastal regions with the model estimated corrections applied in the altimeter range measurements. Analysis has been performed for the Coastal Altimeter products provided by the PISTACH to observe these corrections. The second objective is to estimate the rain rate using altimeter backscatter measurements. The differential attenuation of KU band over C band due to rain has been utilized to identify the rain events and to estimate the amount of rain fall. JASON-2 altimeter data during two tropical cyclonic events over Bay of Bengal have been used for this purpose. An attempt is made to compare the estimated rain rate from altimeter measurements with the other available collocated satellite observations like KALPANA and TRMM-TMI. The results are encouraging and can be used to provide valid rain flags in the altimeter products in addition to the radiometer rain flags.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39...50A