Biondi, Riccardo

Neubert, Torsten

Peng Ho, Shu

Syndergaard, Stig

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 18, 2017Tropical cyclones detection using GPS radio occultation dataBiondi, Riccardo; Neubert, Torsten; Peng Ho, Shu; Syndergaard, StigPublication date:2011Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Biondi, R., Neubert, T., Peng Ho, S., & Syndergaard, S. (2011). Tropical cyclones detection using GPS radiooccultation data. Poster session presented at IUGG : Earth on the Edge: Science for a Sustainable Planet,Melbourne, Australia.RO coverageTropical cyclones detection using GPS radio occultation data Riccardo Biondi1, Torsten Neubert1, Shu Peng Ho2, Stig Syndergaard3 1DTU Space, Danish Space Institute, 2NCAR-UCAR/COSMIC , 3Danish Meteorological InstituteThe tropical deep convection usually redistributes the water vapor from troposphere to stratosphere and perturbs the thermal structure in the upper troposphere and lower stratosphere, which has noticeable impacts on the radiation balance of the atmosphere. Understanding the mechanisms that control these processes, will help for improving the cloud parameterization in the climate models and the severe weather forecasting schemes.The GPS radio occultation technique uses a GPS satellite transmitting the signal and a Low Earth Orbit (LEO) satellite receiving the signal to profile the atmospheric refractivity with high vertical resolution. Temperature, pressure and water vapour are derived via a one-dimensional variational (1Dvar) approach involving the refractivity and the ECMWF model.Bending angle anomaly profile shows a clear TC signature in the UTLSBending angle could be used as an indicator of TC top altitudeObjectiveCase selectionMethodologyDatasets & MethodsAnalyses – Krosa 2007We selected the tropical cyclone (TC) tracks and they were compared with GPS/MET, SAC-C, CHAMP, GRACE and COSMIC Radio Occultations (ROs). 1194 coincidences were found between ROs and TCs considering a time window of 3h and a space window of 300km from the eye of the TC, 77% of coincidences are coming from COSMIC project. Then we selected all the cases with available co-located radiosondes. GPSMET SACC CHAMP GRACE COSMIC Total1995 1 12001 13 9 222002 27 28 552003 29 292004 40 402005 33 332006 12 179 1912007 9 18 194 2212008 20 22 335 3772009 14 211 2251 40 180 54 919 1194CALIPSORadiosondeGPS ROCloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board of CALIPSO satellite is a two- wavelength (532 nm, 1064 nm) polarization-sensitive lidar that provides high-resolution vertical profiles of aerosols and clouds, with footprint of 100m, horizontal resolution of 333m and vertical resolution between 30m and 60m depending on the altitude. These measurements are used for the determination of the cloud top altitude.TC tracks The radiosondes (RAOBs) in FSL (Forecast System Laboratory) format, are part of the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA-ESRL) radiosonde database, and they are used as in situ validation of the temperature profiles, when close enough to the GPS RO. StatisticsUncertaintiesConclusionsNumber of coincidencesTropical cyclone Distance [km]Time distance [min]BasinRUMBIA 27 92 West PacificALBERTO 27 119 AtlanticKRISTY 18 96 East PacificPEIPAH 60 7 West PacificPABUK 15 52 West PacificMAN-YI 92 66 West PacificKROSA 18 39 West PacificPABUK 79 58 West PacificNAKRI 84 85 West PacificHANNA 58 37 AtlanticPHANFONE 20 88 West PacificELIDA 3 102 East PacificLOWELL 47 54 East Pacific5277.6 3.73 10p eNT T  limlim100 TC CanomalyC   lim( )anomaly TC CT T T atmPrf & wetPrfInterpolation Geo-location AverageAnomaly Computation6( 1) 10N n  2 21 ( )( ) exprp ppa ran r daa a      α: bending anglea: impact parameterrp : tangent radiusn: refractive indexN: refractivityp: pressureT: temperaturee: water vapor pressureαanomaly : bending angle anomaly αTC : TC bending angleαClim : climatological bending angleTanomaly : temperature anomalyTTC : TC temperatureTClim : climatological temperatureWe have found 13 ROs during TCs co-located with CALIPSO within a time window of 2 hours and a space window of 100 km. The bending angle anomaly spike is highly correlated to the maximum cloud top during the storm. The correlation is 0.98 and the rms is 365 meters. The correlation is still high (0.93) when we compare the bending angle anomaly spike with the averaged altitude of the storm, but a higher bias is evident in this case. The left panel shows the bending angle anomaly (together with the standard deviation of the mean) and the correspondent temperature anomaly in the range from 5 km below to 5 km above the top. Below the top, the troposphere is warmer than the climatology and the bending angle anomaly is negative, then, it rapidly increases, becoming positive and reaching the maximum amplitude exactly at the cloud top where the temperature is colder than the climatology. The right panel shows the same plot for 246 cases where the ROs are co-located with RAOBs.ROCALISPOThe water vapor Brightness Temperature (BT) from the  Geostationary Meteo Sat (GMS) at the same time and in the same location as the RO, was lower than 205K and the 11 microns BT was lower than 200K, suggesting an inversion due to the  convective clouds. During the TC in that area, more than 1500 strokes were detected from World Wide Lightning Location Network (WWLLN) in the same area of the RO.The bending angle anomaly (right panel) profile shows a double positive spike in the UTLS, the lower spike at 17.2 km of altitude, 600m above the lowest coldest point of 192K and another spike a couple of km above corresponding to a second temperature minimum of 199K. Comparing these profiles with the CALIOP total attenuated backscatter at 562 nm (right panel), it is clear how the altitude of the lowest bending angle spike almost corresponds to the maximum altitude of the cloud top which is 16.9 km. The tropopause from AIRS is located at 15.4 km of altitude which is more than 1 km below than the tropopause from the GPS RO climatology (16.7 km).Different perturbations act at the same time affecting the bending angleDifficult co-location between different instruments and TCsDifferent vertical resolutionsContact and ReferenceRiccardo Biondi DTU Space email: ribi@space.dtu.dkBiondi, R., Neubert, T., Syndergaard, S., Nielsen, J. K.: Radio occultation bending angle anomalies during tropical cyclones, Atmospheric Measurement Techniques, 4, 1053–1060, 2011, doi:10.5194/amt-4-1053-2011The climatological reference (Average) is a profile obtained averaging all the ROs within a 1 degree box (Geo- location) with a standard vertical resolution of 50 meters (Interpolation) applied to the Level 2 data (atmPrf&wetPrf)TClimαanomalyRAOB TanomalyαanomalyRO Tanomaly

Tropical cyclones detection using GPS radio occultation data

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Tropical cyclones detection using GPS radio occultation data

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