Frank J La Fontaine 1 Robbie E Hood

Frank J. La. Fontaine 1, Robbie E. Hood 2, Courtney D. Radley 3, Daniel J. Cecil 4, and Gerald Heymsfield 5 Classification of Tropical Oceanic Precipitation using High-Altitude Aircraft Microwave and Electric Field Measurements Robbie E. Hood, Daniel J. Cecil, Frank J. La. Fontaine, Richard J. Blakeslee, Douglas M. Mach, Gerald M. Heymsfield, Frank D. Marks Jr. , Edward J. Zipser, and Michael Goodman (JAS 2006) The Advanced Microwave Precipitation Radiometer (AMPR) in Brief § Passive at 10. 7, 19. 35, 37. 1, and 85. 5 GHz § Scans + 45 degrees about nadir • 50 samples (pixels) per scan • Rotating polarization § Swath width 40 km at 20 km ER-2 altitude § Hot and cold load calibration loads • Hot load ~ 45 Celsius • Cold load ~ ambient air temperature § Scan rate is 3 seconds • 50 milliseconds per pixel • 0. 5 seconds to reposition mirror § Surface resolutions • • 2. 8 km at 10. 7 GHz 2. 8 km at 19. 35 GHz 1. 5 km at 37 GHz 0. 64 km at 85 GHz AMPR Precipitation Index (API) The AMPR Precipitation Index (API) characterizes the four independent brightness temperature data from AMPR into a simple index of qualitative amounts of rain water and ice. It was developed in part with use of EDOP (ER-2 Doppler Radar) data. 1 Raytheon Information Solutions, Huntsville, AL, 2 NASA Marshall Space Flight Center, Huntsville, AL, 3 Universities Space Research Association, Huntsville, AL, 4 University of Alabama in Huntsville, AL, 5 NASA Goddard Space Flight Center, Greenbelt, MD The Advanced Microwave Precipitation Radiometer was deployed on the NASA ER-2 for the Tropical Cloud Systems Processes experiment. AMPR provided high resolution imagery that is used for precipitation and land surface studies. API Samples from TSCP Flights Imagery shows the API for selected overpasses of tropical cyclones Dennis and Gert observed during TCSP. TD 4 (Dennis), 05 July TS Dennis, 06 July Preliminary Comparison of AMPR and EDOP Observations for Hurricane Emily The two direct ER-2 overpass legs of the eye of Hurricane Emily are plotted and displayed. AMPR and EDOP data were matched when the API indicated precipitation. The API and the two AMPR brightness temperature observations at nadir were averaged and compared with the time coincident EDOP maximum reflectivity and maximum velocity (updraft) between 1 – 13 kilometers altitude. (Note - the Doppler velocities are not yet corrected for fall speed. ) Hurricane Emily Eye Overpass 1 Hurricane Emily Eye Overpass 2 Hurricane Dennis, 09 July Index The API § 6 rain levels and 4 ice levels Ice Level 2 § LIP data used to correlate electric fields to API Ice Level 0 Ice Level 1 (No Ice or Undetectable Ice) “Moderate” Ice Content “High” Ice Content “Very High” Ice Content 85 GHz ice scattering 37 GHz ice scattering 19 GHz ice scattering High Ice Intensity Low No apparent 85 GHz ice scattering signal 3 6 11 Ice Level 3 4 7 12 § Qualitative measure of precipitation-sized rain and ice content The EDOP reflectivity with line plots of the AMPR 10. 7 and 85. 5 GHz brightness temperatures 5 8 13 9 14 16 Low § Developed with AMPR TBs and EDOP reflectivity data from CAMEX-3 and CAMEX-4 10 15 17 Rain Intensity TD 7 (Gert), 23 July TS Gert, 24 July 18 High The figure to the left represents horizontal mapping of the AMPR Precipitation Index (API) and projections of 3 D electric field and aircraft location onto (a) longitude–altitude plane, (b) latitude–altitude plane, and (c) longitude–latitude plane for Hurricane Bonnie in 1998. The “S” denotes start of aircraft track (1500 UTC), and the “e” denotes end of aircraft track (1600 UTC). API color scale is shown. Electric field and aircraft location are plotted as if projected onto three sides of a box. The projections of the electric field onto (a)–(c) are plotted as barbs originating at the aircraft location. A barb extending 2 km above the aircraft track denotes a +1 k. V m− 1 (positive charge below the aircraft) electric field. Note that the vertical component dominates the longitudinal and latitudinal components of electric field in (a) and (b). Barb lengths are scaled by a factor of 10 in (c) because the horizontal components of the electric field are so small. (Note, The EDOP data are missing in the eye region of overpass 1) The EDOP vertical velocity with line plots of the AMPR 10. 7 and 85. 5 GHz brightness temperatures Monitoring Surface Water and Flooding The table represents number of occurrences of weak, medium, and strong vertical electric fields as a function of the maximum API value in the vicinity. Taken from subjective analysis of 11 tropical cyclone and three non-cyclone aircraft missions. Analysis of electrification tends to be weak when the 37. 1 GHz channel is not scattered. There usually is significant electrification when the 37. 1 GHz channel is scattered and strong electrification when the 19. 35 GHz channel is scattered. AMPR 10. 7 GHz 05: 21: 22 - 05: 33: 17 UTC After landfall of Tropical Storm Gert on 25 July 2005, AMPR 10. 7 GHz brightness temperatures indicated areas of significant change in the microwave signals from the land surface. This could be an indication of standing water or flooding. Comparison with MODIS leaf area index and Shuttle Radar Topography Mission data are the next steps in the study. AMPR 10. 7 GHz 05: 53: 12 - 06: 04: 02 UTC An example of API with LIP electric fields and EDOP reflectivities for the first of two ER-2 overpasses of Hurricane Emily on 17 July 2005 (Halverson et al. , accepted by BAMS). AMPR 10. 7 GHz 06: 20: 36 - 06: 28: 32 UTC AMPR 10. 7 GHz 04: 55: 28 - 05: 09: 16 UTC The EDOP reflectivity maximum and API The EDOP updraft maximum and API The increases in the 10. 7 GHz rain and 85. 5 GHz ice scattering signals show good correlations with increasing radar reflectivity. AMPR 10. 7 GHz 06: 35: 44 - 06: 49: 24 UTC The maximum updraft velocities tend to have a fairly strong 10. 7 GHz rain signal and some 85. 5 GHz ice scattering.