AB STRACT A nonlocal ob ser va tion op er a tor has been de vel oped to as sim i late GPS
ra dio occultation (RO) refractivity with WRF 3DVAR. For sim plic ity, in the past GPS RO
refractivity was of ten as sim i lated us ing a lo cal ob ser va tion op er a tor with the as sump
tion that the GPS RO ob ser va tion was rep re sen ta tive of a model lo cal point. Such an op
er a tor did not take into ac count the ef fects of hor i zon tal inhomogeneity on the de rived
GPS RO refractivity. In or der to more ac cu rately model the observables, Sokolovskiy et …

A nonlocal observation operator has been developed to assimilate GPS radio occultation
(RO) refractivity with WRF 3DVAR. For simplicity, in the past GPS RO refractivity was often
assimilated using a local observation operator with the assumption that the GPS RO
observation was representative of a model local point. Such an operator did not take into
account the effects of horizontal inhomogeneity on the derived GPS RO refractivity. In order
to more accurately model the observables, Sokolovskiy et al.(2005a) developed a nonlocal …