Validation of Refractivity Profiles Retrieved from FORMOSAT-3/COSMIC Radio Occultation Soundings: Preliminary Results of Statistical Comparisons Utilizing Balloon-Borne Observations

Abstract

AB STRACTThe GPS ra dio occultation (RO) soundings by the FORMOSAT-3/COS MIC (Tai wan's Formosa Sat el lite Misssion #3/Con stel la tion Ob serv ing Sys tem for Me te o rol ogy, Ion o sphere and Cli mate) sat el lites launched in mid-April 2006 are com pared with high-res o lu tion bal loon-borne (ra dio sonde and ozonesonde) ob ser va tions. This pa per pres ents pre lim i nary re sults of val i da tion of the COS MIC RO mea sure ments in terms of refractivity through the tro po sphere and lower strato sphere. With the use of COS MIC RO soundings within 2 hours and 300 km of sonde pro files, sta tis ti cal com par i sons be tween the col lo cated refractivity pro files are per formed for some trop i cal re gions (Ma lay sia and West ern Pa cific is lands) where mois ture-rich air is ex pected in the lower tro po sphere and for both north ern and south ern po lar ar eas with a very dry tro po sphere. The re sults of the com par i sons show good agree ment be tween COS MIC RO and sonde refractivity pro files through out the tro po sphere (1 -1.5% dif fer ence at most) with a pos i tive bias gen er ally be com ing larger at pro gres sively higher al ti tudes in the lower strato sphere (1 -2% dif fer ence around 25 km), and a very small stan dard de vi a tion (about 0.5% or less) for a few ki lo me ters be low the tropo pause level. A large stan dard de vi a tion of frac tional dif fer ences in the low er most tro po sphere, which reaches up to as much as 3.5 -5% at 3 km, is seen in the tropics while a much smaller standard deviation (1 -2% at most) is evident throughout the polar troposphere.

Strong Kelvin wave activity observed during the westerly phase of QBO – a case study

“…Between 30 and 40 km, a large difference of 8 K was found when compared to lidar observations. Hayashi et al (2009) also showed good comparisons between COSMIC RO and the radiosonde refractivity profiles with 1-2 % mean difference. Kishore et al (2009) performed a validation study using the operational stratospheric analyses including the National Centers for Environmental Prediction reanalysis (NCEP), the Japanese 25-year Reanalysis (JRA-25) and the United Kingdom Met Office (UKMO) datasets.…”

Investigation of Kelvin Waves in the Stratosphere Using FORMOSAT-3/COSMIC Temperature Data

“…Between 30 and 40 km, a large di¤erence of 8 K was found when compared with lidar observations. Hayashi et al (2009) also showed good comparisons between COSMIC RO and the radiosonde refractivity profiles with 1-2% mean di¤er-ence. Kishore et al (2009) performed a validation study using the operational stratospheric analyses including the National Centers for Environmental Prediction-Reanalysis (NCEP), the Japanese 25-year Reanalysis (JRA-25), and the United Kingdom Met O‰ce (UKMO) data sets.…”

COSMIC GPS Observations of Northern Hemisphere winter stratospheric gravity waves and comparisons with an atmospheric general circulation model

“…COSMIC refractivity precision is < 0.2% between 10–20 km and is 0.7% at 30 km [ Schreiner et al , 2007]. A positive bias of 1–2% between radiosondes and COSMIC was observed by Hayashi et al [2008]. The raw temperature profiles have an independent height resolution of about 1 km in the upper troposphere and lower stratosphere.…”