Ionospheric correction of GPS radio occultation data in the troposphere

摘要

For inversions of the GPS radio occultation (RO) data in theneutral atmosphere, this study investigates an optimal transition height forreplacing the standard ionospheric correction using the linear combinationof the L1 and L2 bending angles with the correction of the L1 bending angleby the L1–L2 bending angle extrapolated from above. The optimal transitionheight depends on the RO mission (i.e., the receiver and firmware) and isdifferent between rising and setting occultations and between L2P and L2CGPS signals. This height is within the range of approximately 10–20?km.One fixed transition height, which can be used for the processing ofcurrently available GPS RO data, can be set to 20?km. Analysis of the L1CAand the L2C bending angles shows that in some occultations the errors ofstandard ionospheric correction substantially increase around the stronginversion?layers (such as the top of the boundary?layer). This errorincrease is modeled and explained by the horizontal inhomogeneity of theionosphere.