1. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation of an IHOP Convective Initiation Case for GIFTS Preparation Derek J. Posselt 1, Erik Olson 1, Wayne F. Feltz 1, Russ Dengel 1, Gail Dengel 1, John R. Mecikalski 1, Robert Aune 1, Brian Osborne 1, Robert O. Knuteson 1, and William L. Smith 2 1 Cooperative Institute for Meteorological Satellite Studies, Space Science and Engineering Center, University of Wisconsin–Madison 2 NASA Langley Research Center

2. D. PosseltIHOP Spring Workshop24-26 March 2003 Objective Produce a realistic simulation of a CI event to simulate future high spectral resolution infrared satellite output Evaluate NWP model output using GOES-11 five minute imagery Generate high spectral resolution infrared spectra through forward model calculations performed on the NWP temperature and moisture fields Objectives: –Using a simulated CI event, determine GIFTS potential to observe moisture convergence prior to convective initiation –Demonstrate future uses of GIFTS observations and retrievals

3. D. PosseltIHOP Spring Workshop24-26 March 2003 Outline Introduction to GIFTS Choice of case: 12 June 2002 Evaluation of CI simulation GIFTS simulated radiances Uses of simulated radiances and retrievals Future Work

4. D. PosseltIHOP Spring Workshop24-26 March 2003 Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) GIFTS Details: Next generation geostationary imager/sounder with launch as early as 2006 Spectral resolution as high as 0.625 cm -1 Designed for horizontal resolution of 4 km, vertical resolution of 1-2 km, and maximum temporal resolution of 11 seconds Potential for much more rapid and high-resolution retrievals of temperature, moisture, and wind than are available with any current geostationary instrument. Pre-Launch Tasks: Produce simulations of several different atmospheric cases Use simulated atmosphere in the GIFTS forward radiative transfer model to obtain top of the atmosphere radiances Retrieve temperature, water vapor and winds from these radiances, and compare them with the original simulated atmosphere to assess retrieval accuracy Develop uses for radiance observations and retrieved quantities in advance of launch

5. D. PosseltIHOP Spring Workshop24-26 March 2003 Waveband (cm -1 )Wavelength (um) Unapodized spectral resolution (cm -1 ) 650 – 1200 15.38 – 8.33 0.625 1650 – 2250 6.06 – 4.44 0.625 GIFTS Spectral Range and Resolution H2OH2OH2OH2O O3O3 H2OH2O CO 2

6. D. PosseltIHOP Spring Workshop24-26 March 2003 GIFTS Measurements GIFTS Primary Advantage over GOES: High Spectral Resolution GIFTS Short-wave Band: 1650 - 2250 cm -1 GOES Water Vapor Mixing Ratio Weighting Functions: 18 Channels GIFTS Water Vapor Mixing Ratio Weighting Functions: > 1600 Channels

7. D. PosseltIHOP Spring Workshop24-26 March 2003 GIFTS LW 650 - 1200 cm -1

8. D. PosseltIHOP Spring Workshop24-26 March 2003 ABS’ LW 650 - 1200 cm -1

9. D. PosseltIHOP Spring Workshop24-26 March 2003

10. D. PosseltIHOP Spring Workshop24-26 March 2003 GIFTS IHOP 2002 CI Objectives IHOP Case Objectives: Produce simulated atmosphere to be used for GIFTS preparation Demonstrate GIFTS potential to observe moisture convergence prior to convective initiation Demonstrate GIFTS usefulness for observation of fine-scale rapidly- evolving water vapor structures Develop GIFTS data analysis techniques for CI applications GIFTS high spatial and temporal resolution water vapor measurements indicate vast potential for early detection and diagnosis of CI

11. D. PosseltIHOP Spring Workshop24-26 March 2003 Case: 12 June 2002 Convective initiation occurred at approximately 2100 UTC along a weak low-level trough stretching southwest to northeast through the Oklahoma panhandle Case Specifics for GIFTS Simulation: Environment mostly clear preceding convection CI occurred associated with strong, but small- scale water vapor gradient CI well-predicted and well-forced, leading to relative ease of simulation Occurred during a day specifically targeted for study of convective initiation during IHOP 2002 King Air Proteus P3

12. D. PosseltIHOP Spring Workshop24-26 March 2003

13. D. PosseltIHOP Spring Workshop24-26 March 2003 GOES-11 Imagery 10-minute (approximate) 10.7 micron GOES-11 imagery clearly depicting wind-shift boundary and CI

14. D. PosseltIHOP Spring Workshop24-26 March 2003 MM5 Configuration Configuration details: 4 km grid spacing, 60 vertical levels Initialized 0600 UTC, 24-hour duration Goddard microphysics MRF boundary layer No cumulus parameterization RRTM radiation OSU-Land surface model Nudged toward RUC analyses during 6-hour spin-up period Simulated atmospheric fields generated using the 5 th generation Penn State/NCAR Mesoscale Modeling system (MM5) initialized from 10 km RUC analyses

15. D. PosseltIHOP Spring Workshop24-26 March 2003 Use of AVHRR Vegetation Differences between climatological vegetation fraction (MM5 default) and vegetation fraction derived from the AVHRR NDVI. Values are shaded in units of percent green vegetation.

16. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results Simulated GOES-11 imagery for the full simulation domain

17. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results Cloud and water vapor features Color-shaded plot depicts 2- meter mixing ratio White iso-surfaces encompass cloud boundaries Wind vectors valid at 1.5 km height

18. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results Observed GOES-11 imagerySimulated GOES-11 imagery 1900 UTC

19. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results Observed GOES-11 imagerySimulated GOES-11 imagery 2000 UTC

20. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results Observed GOES-11 imagerySimulated GOES-11 imagery 2100 UTC

21. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results Observed GOES-11 imagerySimulated GOES-11 imagery 2200 UTC

22. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results Observed GOES-11 imagerySimulated GOES-11 imagery 2300 UTC

23. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulation Results MM5 vs. AERI Homestead time-height

24. D. PosseltIHOP Spring Workshop24-26 March 2003 GIFTS Simulated Radiances and Retrievals Procedure Generate simulated atmospheric fields representative of desired case Using GIFTS forward radiative transfer model, produce top of atmosphere radiances from simulated atmospheric fields Retrieve temperature and water vapor from top of atmosphere radiances Compare retrievals with “truth” atmosphere to assess accuracy of retrieval method Develop applications based on simulated radiances and retrievals Forward Model Radiances Model Atmosphere

25. D. PosseltIHOP Spring Workshop24-26 March 2003 Top of Atmosphere Brightness Temperatures Output from GIFTS forward radiative transfer model: 10.7 micron brightness temperatures 10-min time resolution 1800-2200 UTC

26. D. PosseltIHOP Spring Workshop24-26 March 2003 Top of Atmosphere Brightness Temperatures Output from GIFTS forward radiative transfer model: 5.88 micron brightness temperatures

27. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulated vs. Retrieved Water Vapor: 700 hPa “True” mixing ratio: 1800 UTCRetrieved mixing ratio: 1800 UTC

28. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulated vs. Retrieved Water Vapor: 700 hPa “True” mixing ratio: 1830 UTCRetrieved mixing ratio: 1830 UTC

29. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulated vs. Retrieved Water Vapor: 700 hPa “True” mixing ratio: 1900 UTCRetrieved mixing ratio: 1900 UTC

30. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulated vs. Retrieved Water Vapor: 700 hPa “True” mixing ratio: 1930 UTCRetrieved mixing ratio: 1930 UTC

31. D. PosseltIHOP Spring Workshop24-26 March 2003 Simulated vs. Retrieved Water Vapor: 700 hPa “True” mixing ratio: 2000 UTCRetrieved mixing ratio: 2000 UTC

32. D. PosseltIHOP Spring Workshop24-26 March 2003 Uses of Simulated Data Band differencing for CI detection –John Mecikalski and Kris Bedka –Subtraction of one spectral band from another to detect features associated with CI Wind retrievals –Chris Velden, Dave Stettner, Russ Dengel, Gail Dengel –Tracking retrieved water vapor gradients to produce derived winds

33. D. PosseltIHOP Spring Workshop24-26 March 2003 Band Differencing: 5.9-11 micron 5.9 micron weighting function peaks in upper troposphere (~300 mb) 11 micron window channel much less sensitive to water vapor absorption Details: Low clouds or clear scene: brightness temperature difference usually << 0 High, cold clouds: difference = 0 Cloud top at or above tropopause: difference may be > 0 Has been used to locate overshooting tops in geostationary satellite imagery and to monitor temporal trends in cloud top height Large temporal change in this band difference often an indicator of CI 1800-2200 UTC

34. D. PosseltIHOP Spring Workshop24-26 March 2003 Band Differencing: 8.5-11 micron Key: Differences in real and imaginary indices of refraction for liquid vs. ice Very small difference at 8.5 microns Maximum difference at 11 microns Band combination used in MODIS cloud phase product Details: Ice clouds: positive difference Water clouds: slightly negative difference Mixed phase: values near zero Clear sky: strongly negative differences, due to contribution of terrestrial radiation at 11 microns Band combination also highly dependent on effective radius of the size distribution Ice clouds with smaller particles: greater (positive) differences. 1800-2200 UTC

35. D. PosseltIHOP Spring Workshop24-26 March 2003 Winds From GIFTS Simulated Retrievals Using existing techniques, simulated water vapor retrievals are being used to obtain water vapor gradient-track winds 700 hPa500 hPa streamlines Mixing ratio (gray shaded), model winds (streamlines), and retrieved winds (barbs)

36. D. PosseltIHOP Spring Workshop24-26 March 2003 Future Work Rerun initializing from IHOP reanalyses Continued assessment of GIFTS utility for CI detection Rerun GIFTS forward model with improved cloud microphysics (improved scattering, multiple ice habits) Develop derived products from simulated data (stability, etc) Simulation of other cases (THORPEX)