Evaluation of a Linear Phase Observation Operator with CHAMP Radio Occultation Data and High-Resolution Regional Analysis

Sokolovskiy, Sergey; Kuo, Ying‐Hwa; Wang, Wei

doi:10.1175/mwr3006.1

Cited by 25 publications

(17 citation statements)

References 22 publications

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“…The nonlocal op er a tor pro duces smaller er rors even at the low est height, and the er rors are gen er ally less than 1% at all the lev els and 0.5% above 6 km. Hence, the ob ser va tion er rors pro duced by the nonlocal op er a tor are about two times smaller than those by the lo cal op er a tor, which is in good agree ment with Sokolovskiy et al (2005b). With the sim i lar ob ser va tion errors as es ti mated from CHAMP and FORMOSAT-3/COS -MIC, we adopt the pro files of ob ser va tion er ror sta tis tics with a mod i fied curve in the low est level of 2 km for the nonlocal op er a tor.…”

Section: Ob Ser Va Tion Er Rorssupporting

confidence: 80%

supporting

confidence: 81%

“…In this study, the sta tis tics of ob ser va tion er rors us ing both lo cal and nonlocal op er a tors were es ti mated based on WRF sim u la tions. The ob ser va tion er rors produced by the nonlocal operator are about two times smaller than those generated by the local operator and in agreement with Sokolovskiy et al (2005b).Each of the three op er a tors is used to as sim i late GPS RO refractivity soundings from the FORMOSAT-3/COS MIC mis sion us ing the WRF 3DVAR sys tem. The WRF model then is ap plied to sim u late Ty phoons Kaemi (July 2006) which struck Tai wan with sig nif i cant tor ren tial rain fall.…”

supporting

confidence: 65%

“…For sim plic ity and ef fi ciency, the ray of the in te gra tion can be as sumed as a straight line (for de tails see Fig. 1 of Sokolovskiy et al 2005b). Such a forward model is the so-called nonlocal op er a tor as compared to the lo cal op er a tor us ing the point refractivity.…”

Section: Introductionmentioning

confidence: 99%

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Assimilation of GPS Refractivity from FORMOSAT-3/COSMIC Using a Nonlocal Operator with WRF 3DVAR and Its Impact on the Prediction of a Typhoon Event

Chen¹,

Huang²,

Kuo³

et al. 2009

Terr. Atmos. Ocean. Sci.

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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 al. (2005a) de vel oped a nonlocal ob ser va tion op er a tor, which would take into ac count the ef fects of hor i zon tal inhomogeneity on GPS RO mea sure ments. This nonlocal ob ser va tion op er a tor cal cu lates the in te grated amount of the model refractivity along the ray paths cen tered at the peri gee points. For com par a tive pur poses, the nonlocal ob ser va tion op er a tor can be sim pli fied by lim it ing the length of in te gra tion near the RO point. This is called the "lo cal op er a tor vari ant", which is equiv a lent to the orig i nal lo cal op er a tor ex cept that the orig i nal one is per formed with fixed tan gent points at ob ser va tion lev els. For com pu ta tional ef fi ciency, as sim i la tion us ing both the nonlocal op er a tor and lo cal op er a tor vari ant now is per formed with smear tan gent points at the mean height of each model ver ti cal level. In this study, the sta tis tics of ob ser va tion er rors us ing both lo cal and nonlocal op er a tors were es ti mated based on WRF sim u la tions. The ob ser va tion er rors produced by the nonlocal operator are about two times smaller than those generated by the local operator and in agreement with Sokolovskiy et al. (2005b).Each of the three op er a tors is used to as sim i late GPS RO refractivity soundings from the FORMOSAT-3/COS MIC mis sion us ing the WRF 3DVAR sys tem. The WRF model then is ap plied to sim u late Ty phoons Kaemi (July 2006) which struck Tai wan with sig nif i cant tor ren tial rain fall. The anal y sis in cre ments pro duced by the nonlocal op er a tor and lo cal op er a tor vari ant are quite sim i lar in hor i zon tal and ver ti cal dis tri bu tions; whereas, the for mer is slightly stretched along the ray's di rec tion, as a re sult of the lon ger in te gra tion length. The sim u lated ty phoon tracks prior to land fall are quite sim i lar for the three op er a tors. Both the nonlocal op er a tor and lo cal op er a tor vari ant im prove the de toured track af ter land fall as pre dicted by the lo cal op er a tor. The nonlocal op er a tor out per forms the two lo cal op er a tors in rain fall pre dic tion at later times. The per for mances of the nonlocal op er a tor in gen eral are promising and can replace the local operator at no marked cost of computational efficiency.Key words: FORMOSAT-3/COS MIC, Data as sim i la tion, Typhoon Ci ta tion: Chen, S. Y., C. Y. Huang, Y. H. Kuo, Y. R. Guo, and S. Sokolovskiy, 2009: As sim i la tion of GPS refractivity from FORM...

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Section: Ob Ser Va Tion Er Rorssupporting

confidence: 80%

supporting

confidence: 81%

supporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Assimilation of GPS Refractivity from FORMOSAT-3/COSMIC Using a Nonlocal Operator with WRF 3DVAR and Its Impact on the Prediction of a Typhoon Event

Chen¹,

Huang²,

Kuo³

et al. 2009

Terr. Atmos. Ocean. Sci.

View full text Add to dashboard Cite

show abstract

“…To re duce the er rors of rep re sen ta tive ness, they sug gest use of the in te grated amount of refractivity along the ray path, namely the ex cess phase (EPH), as the new ob serv able for as sim i la tion. This new operator as sim i lat ing ex cess phase is the so-called nonlocal operator since it takes into ac count the nonlocal ef fect of hor i zon tal gra di ents along the en tire path within the model depth (Sokolovskiy et al 2005b). As found, the nonlocal operator pro duces con sid er ably smaller frac tional er rors than the lo cal op er a tor us ing the point refractivity.…”

Section: Introductionmentioning

confidence: 87%

Impact of GPS Radio Occultation Refractivity Soundings on a Simulation of Typhoon Bilis (2006) upon Landfall

Kueh¹,

Huang²,

Chen³

et al. 2009

Terr. Atmos. Ocean. Sci.

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AB STRACTTy phoon Bilis which struck Tai wan in July 2006 was cho sen to as sess the po ten tial im pact of GPS ra dio occultation (RO) refractivity soundings on nu mer i cal sim u la tion us ing the WRF model. We found that this case elu ci dates the im pact of the lim ited GPS RO soundings on ty phoon pre dic tion due to their fa vor able lo ca tions. In ad di tion, on top of avail able precipitable wa ter (PW) and near-sur face wind speed from SSM/I data, we have also ex plored their com bined impacts on model prediction.The two GPS RO soundings avail able from FORMOSAT-3 near the model ini tial time are as sim i lated us ing the nonlocal op er a tor in WRF 3DVAR. More con tri bu tions af ter the as sim i la tion are found in the mois ture in cre ments (up to -1.2 g kg -1 ) sur round ing the cor re spond ing occultation po si tions to the east of the ty phoon vor tex and south west of the sub trop i cal high, with dry ness oc cur ring in the lower tro po sphere. The as sim i la tion of PW in duces much larger and wider mois ture in cre ments to the west of the ty phoon cen ter. The in ges tion of near-sur face wind speeds pro duces more pro nounced temperature and wind increments at lower levels. The SSM/I data im prove the pre dic tions of ty phoon in ten sity and in tense rain fall over Tai wan, es pe cially for the later sim u la tion time, but gen er ally have a less im pact on track pre dic tion as com pared to the GPS RO data. As sim i la tion of the two GPS RO soundings leads to a marked im prove ment on the track that oth er wise will be south ward bi ased prior to land fall and also en hances the pos i tive im pact when the SSM/I data have been as sim i lated as well. An im prove ment us ing the GPS RO data is also found for daily rain fall but only for larger thresh olds at later times when the bias in track in the con trol ex per i ment is rem e died. In gen eral, the com bined as sim i la tion of both GPS RO and SSM/I data has shown the most prom is ing per for mances. Fi nally, the sen si tiv ity tests in di cate that the closer GPS RO sound ing to the east of the ty phoon plays a more crucial role in the positive impact on track prediction.

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Airborne GPS radio occultation refractivity profiles observed in tropical storm environments

et al. 2015

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Airborne GPS radio occultation (ARO) data have been collected during the 2010 PRE-Depression Investigation of Cloud systems in the Tropics (PREDICT) experiment. GPS signals received by the airborne Global Navigation Satellite System Instrument System for Multistatic and Occultation Sensing (GISMOS) are used to retrieve vertical profiles of refractivity in the neutral atmosphere. The system includes a conventional geodetic GPS receiver component for straightforward validation of the analysis method in the middle to upper troposphere, and a high-sample rate (10 MHz) GPS recorder for postprocessing complex signals that probe the lower troposphere. The results from the geodetic receivers are presented here. The retrieved ARO profiles consistently agree within~2% of refractivity profiles calculated from the European Center for Medium-Range Weather Forecasting model Interim reanalyses as well as from nearby dropsondes and radiosondes. Changes in refractivity obtained from ARO data over the 5 days leading to the genesis of tropical storm Karl are consistent with moistening in the vicinity of the storm center. An open-loop tracking method was implemented in a test case to analyze GPS signals from the GISMOS 10 MHz recording system for comparison with geodetic receiver data. The open-loop mode successfully tracked~2 km deeper into the troposphere than the conventional receiver and can also track rising occultations, illustrating the benefit from the high-rate recording system. Accurate refractivity retrievals are an important first step toward the future goal of assimilating moisture profiles to improve forecasting of developing storms using this new GPS occultation technique.

show abstract

Evaluation of a Linear Phase Observation Operator with CHAMP Radio Occultation Data and High-Resolution Regional Analysis

Cited by 25 publications

References 22 publications

Assimilation of GPS Refractivity from FORMOSAT-3/COSMIC Using a Nonlocal Operator with WRF 3DVAR and Its Impact on the Prediction of a Typhoon Event

Assimilation of GPS Refractivity from FORMOSAT-3/COSMIC Using a Nonlocal Operator with WRF 3DVAR and Its Impact on the Prediction of a Typhoon Event

Impact of GPS Radio Occultation Refractivity Soundings on a Simulation of Typhoon Bilis (2006) upon Landfall

Airborne GPS radio occultation refractivity profiles observed in tropical storm environments

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