GPS RO refractivity is typically modeled at the ray perigee point by a “local refractivity operator” in a data assimilation system. The Global Positioning System (GPS) radio occultation (RO) technique is becoming a robust global observing system. (c),(d) As in (a),(b), but for the estimated (dots) and fitted (red lines) observational errors in the summer month. The estimated (dashed lines) and fitted (solid lines) fractional standard deviations of the observational errors stratified in different latitudinal bins for (a) linear excess phase and (b) refractivity in the winter month. (c),(d) As in (a),(b), respectively, but for the standard deviation of the forecast errors (24-h forecast minus 12-h forecast). The monthly zonally averaged specific humidity of 12-h WRF forecasts in different latitudinal bins (color lines) in the (a) winter and (b) summer months. The counts of GPS RO soundings are presented by circles.įractional standard deviations of the observation errors of linear excess phase (solid lines) and refractivity (dashed lines) to the south (thin lines) and to the north (thick lines) of 30°N in the (a) winter and (b) summer months.įractional standard deviations of the observational errors stratified in different latitudinal bins (color lines) for (a),(c) linear excess phase and (b),(d) refractivity for the (a),(b) winter and (c),(d) summer months.Īs in Fig. The data before and after the criterion check are shown by the black lines and red lines, respectively.įractional standard deviations of the apparent error (thick solid lines), forecast error (dotted lines), and observational error (thin solid lines) for (a),(c) linear excess phase and (b),(d) refractivity in the (a),(b) winter and (c),(d) summer months. Angle brackets (〈 〉) indicate the mean of the observations at each model mean height. The model grid indices are also shown at the left and bottom sides of the figure.įractional differences between the observations ( S obs or N obs) and model forecasts ( S fst or N fst) at each model level for (a),(c) linear excess phase and (b),(d) refractivity in the (a),(b) winter and (c),(d) summer month. The geographical distributions of 2999 GPS RO soundings from COSMIC within the WRF model domain in the winter month (15 Jan–).