Nov , /24 An Evaluation of the Practicability of Current Mapping Functions using Ray-traced Delays from JMA Mesoscale Numerical Weather Data (1) Ichikawa R., (1) T. Hobiger, (1) Koyama Y., and (1), (2) Kondo T. (1) Koyama Y., and (1), (2) Kondo T. (1) National Institute of Information and Communications Technology (NICT), Japan (2) Ajou University, Republic of Korea

Nov , /24 Content 1.Motivation 2.KARAT 3.Mapping Functions 4.Position Error Simulation 5.PPP Analysis Results 6.Summary and Outlook

Nov , /24 Motivation VLBI GNSS Atmosphere Analysis DATA Result

Nov , /24 Motivation (cont’d)  Estimation of Atmospheric Path Delay by Ray Tracing Technique through Numerical Weather Models Mitigation of Atmospheric Path Delay ErrorMitigation of Atmospheric Path Delay Error  GNSS, VLBI, In-SAR, …etc. Understanding of Position Error Behavior due to Atmospheric Path DelayUnderstanding of Position Error Behavior due to Atmospheric Path Delay

Nov , /24 KARAT KAshima RAy-tracing Tool through Numerical Weather Models Kashima We are here

Nov , /24 Numerical Weather Model Numerical Weather Model

Nov , /24 NWM from JMA  Japan Meteorological Agency (JMA) provides information about Pressure (P), temperature (T), rel. humidity (which allows to calculate partial pressure of water vapour – P v )Pressure (P), temperature (T), rel. humidity (which allows to calculate partial pressure of water vapour – P v ) Refractivity N can be used to compute troposphere delayRefractivity N can be used to compute troposphere delay  Mesoscale Analysis Data (MANAL data) Raster width 10km (≈ 0.1 deg)Raster width 10km (≈ 0.1 deg) 21 pressure levels up to 10hPa 21 pressure levels up to 10hPa Time resolution: 3 hrsTime resolution: 3 hrs

Nov , /24 Covered region of JMA MANAL data Boundaries =[107˚,157˚]  = [19˚,49 ˚ ] Countries covered: - Japan (100%) - Korea (100%) - Taiwan (100%) - China (partly)

Nov , /24 Estimated Zenith Total Delay using KARAT 1 st -31 st of July, 2006 Epoch: 1hr

Nov , /24 Mapping Functions e

Nov , /24 a, b, and c are determined by NWM NMFNiell[1996] lat, doy, hgt [none] IMF Niell et al.[2001] NWMNCEP GMF Boehm et al.[2006] lat, lon, doy, hgt (indirect use of NWM) ECMWF VMF Boehm and Schuh[2004] NWMECMWF Typical Mapping Functions

Nov , /24 Comparison of Mapping Functions (Example) Accuracy: VMF < GMF << NMF (Boehm and Schuh[2004]) Kashima

Nov , /24 Position Error Simulation using KARAT  Position Error Behavior  Evaluation of Mapping Functions

Nov , /24 NWM misfit residual misfit residual misfit residual misfit residual Estimated ZWD gradient vector position error Position Error Simulation using KARAT water vapor water vapor water vapor water vapor KARAT slant delay Slant delay calculated by MF

Nov , /24 Simulated Position Error due to the Neglection of Atmospheric Asymmetry IR Images by GMS

Nov , /24 Simulated Position Error: Comparison at Uchinoura GMF onlyGMF with gradient 2007

Nov , /24 PPP Analysis  Period: July 1 st – August 31 st, 2007  Whole GEONET Stations (~1350 stations)  GPSTools Ver (Takasu and Kasai, 2005)  Comparison of Atmospheric Delay Corrections 1.KARAT reduced RINEX 2.GMF with horizontal gradient 3.GMF w/o horizontal gradient

Nov , /24 Meteorological Condition (JMA,2007) Total Precipitation during 2 nd – 17 th of July, 2007 Typhoon #4 (MAN-YI) (JMA,2007) Heavy Rain Fall

Nov , /24 North-South Repeatability during 2 Months GMF with gradient < KARAT < GMF only

Nov , /24 East-West Repeatability during 2 Months GMF with gradient < KARAT < GMF only

Nov , /24 Station Height Repeatability during 2 Months GMF with gradient ≤ KARAT < GMF only

Nov , /24 Concluding Remarks  Position error simulation is available. large position errors during heavy rain fall eventslarge position errors during heavy rain fall events  Ex. EW: ~15mm, NS: ~20mm, UD: ~35mm  KARAT performance for atmospheric path delay correction in PPP analysis is evaluated. GMF with gradient ≤ KARAT < GMF onlyGMF with gradient ≤ KARAT < GMF only

Nov , /24 Outlook  High Spatial and Temporal Resolution Numerical weather prediction data with more fine meshNumerical weather prediction data with more fine mesh  Ex. JMA 5km MANAL Improvement of time interpolation between two NWM epochsImprovement of time interpolation between two NWM epochs  ex. To use numerical weather model such as MM5 is one possibility

Nov , /24 Thank you for your attention

Nov , /24

Nov , /24 Result

Nov , /24 Ray-tracing  Once the data slices have been prepared ray-tracing can be carried out very efficiently using analytical expressions for the calculation of 3D - intersection points3D - intersection points with the slices with the slices Delay inside the segmentsDelay inside the segments Bending angle due toBending angle due to refractivity gradients  Output of total delay, bending angle and ground refractivity