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Motivation for TRMM-LBA

Characteristics of Convective Systems Observed During TRMM-LBA Rob Cifelli, Steve Nesbitt, and Steven A. Rutledge Colorado State University. Motivation for TRMM-LBA. • Amazon one of three primary regions of ascent in the Walker Circulation and an upward branch in the Hadley Circulation

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Motivation for TRMM-LBA

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  1. Characteristics of Convective Systems Observed During TRMM-LBARob Cifelli, Steve Nesbitt, and Steven A. RutledgeColorado State University

  2. Motivation for TRMM-LBA • Amazon one of three primary regions of ascent in the Walker Circulation and an upward branch in the Hadley Circulation • Copious precipitation/latent heat release, but relatively few detailed studies of deep convection

  3. TRMM-LBA • Joint with Large-scale Biosphere Atmosphere experiment (LBA) • Conducted in the State of Rondonia, Brazil (11oS, 62 W; SW corner of Amazon) during Jan.-Feb. 1999 • Goals: • Validation of TRMM satellite products • Validation of cloud models (e.g., GCEM) • Physics of convection and the processes driving convection • Instrumentation: • Ground radar: S-pol and TOGA radars (kinematics, microphysics, rainfall) • Aircraft: ER-2 (TRMM simulator) and UND Citation (microphysics) • Soundings (3-Tethersonde and 4-Radiosonde) • NASA MSFC Brazilian Lightning Detection Network • NOAA dual-frequency wind profiler • Four raingauge networks, 2DVD and JW disdrometers • Other platforms (e.g., CCN, fluxes, flat plate antennas etc.)

  4. Radars and Tethersonde

  5. TRMM-LBA Aircraft

  6. TRMM-LBA: Evidence of Convective Regimes • West U-wind= Low CI, moist troposphere; monsoon-like convection • Easterly U-wind= High CI, more dry troposphere; break-like convection

  7. East Regime Brazilian Lightning Detection Network (BLDN) • Oscillations apparent • • East (west) anomalies =more (less) lightning.

  8. Time series PDFs of TRMM precipitation feature 30 dBZ echo top heights (left) and minimum 85 GHz PCTDJFM 1998-1999 TRMM-LBA Radar Ops TRMM-LBA Radar Ops Petersen et al. (2002)

  9. Radar Observed Contrasts in TRMM-LBA Convection: Water Content Easterly Convection Westerly Convection Ice (gm m-3 - thin solid lines), liquid (gm m-3 - color contours), mean drop diameter (mm - heavy solid lines) • Active mixed phase microphysics • Copious ice in mid-upper troposphere • Paucity of ice in mid-upper troposphere • Significant differences in the vertical distribution of hydrometeors

  10. Easterly Westerly Easterly Westerly Mixed Phase Zone (4 - 8 km) Precipitation Ice and Rain Mass Frequency Distributions ICE RAIN Polarimetric radar analyses to identify microphysical differences Courtesy: Dr. Lawrence Carey, Texas A&M

  11. VERTICAL RADAR STRUCTURE EASTERLY REGIME WESTERLY REGIME 26 January 1999 2100 UTC X = 6 km 25 February 1999 2340 UTC Y = 67 km dBZ dBZ m s-1 m s-1 Height(km) Height (km) Distance N-S from S-POL (km) Distance E-W from S-POL (km)

  12. Easterly Convection Time (UTC) Westerly Convection Height (km) 109 kg s-1 Radar Observed Contrasts in TRMM-LBA Convection: Vertical Mass Transport Height (km) • Significant differences in intensity and lifecycle characteristics

  13. Profiler observations at Ji-Parana, Brazil 15 February 1999 (East) • Stratiform rain with embedded convective cells • Updrafts greater than 2 m/s above 6 km altitude Break period convective system viewed by profiler—C. Williams and K. Gage

  14. Relative Frequency Histograms of S-POL Radar Parameters 16 JAN 99 – 28 FEB 99 Zh D0 R Kdp

  15. Composite Q1 Profiles • ER Convective Q1 is broader due to importance of ice processes • Difference in total Q1’s largely due to WCSF

  16. PDFs of TRMM precipitation feature characteristics as a function of wind regime in RondôniaDJFM 1997-2000 PR echo top heights Higher radar tops TMI 85 & 37 GHz ice scattering PCTs Higher optical depths of ice Petersen et al. (2002)

  17. Comparisons of PR, Ground-Based and Airborne Radar Data in TRMM LBA Heymsfield et al. (2000)

  18. Model-Observations Comparison, Tao and Lang, GSFC Observed CAPPI reflectivity Simulated CAPPI reflectivity Observed CFAD reflectivity Simulated CFAD reflectivity Comparisons between model and observations have led to improved microphysical parameterizations and latent heating profiles

  19. Lessons Learned From TRMM-LBA • Integrated suite of measurements lead to identification of regimes in LBA • Dual polarimetric radar is key for characterizing microphysical variability within regimes • Gauge and disdrometer network important to evaluate errors in polarimetric rainfall measurements • TRMM-LBA ground network provided a template for GPM GV • More work is needed to understand the impact of regimes on satellite algorithms

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