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IHOP Workshop, Toulouse, June 14-18, 2004
MODELING OF A BORE OBSERVED ON MODELING OF A BORE OBSERVED ON JUNE 04 DURING IHOP 2002JUNE 04 DURING IHOP 2002
Mariusz PagowskiMariusz Pagowski NOAA Research - Forecast Systems Laboratory
CIRA, Colorado State University
Steven E. Koch
NOAA Research - Forecast Systems Laboratory
J.-W. Bao
NOAA Research - Environmental Technology Laboratory
Outline
Mesoscale Model Simulations
Comparison with Observations
Analysis
° Bore Origin
° Bore and the PBL
Conclusions
Model Setup
Nested MM5 model (18, 6, 2, 0.666 km) initialized at 00Z 4 June 02 Initial / boundary conditions from hourly RUC-20 km analyses 44 vertical levels (22 below 1500 m) Ensemble based convective parameterization (Grell and Devenyi 2002) in two lower resolution domains Different Mellor-Yamada based 1.5-order closures (Burk-Thompson 1989, Eta Janjic 1994, QL with prognostic mixing length Mellor and Yamada 1982) Reisner microphysics and Smirnova land-surface model
NWS Surface Reports and Model Results (6km)
0500 UTC
1000 UTC
S-POL Radar Reflectivity and Model Results (6km)
0500 UTC 0730 UTC
S-POL Radar Reflectivity and Model Results (2km)
Convergence / Divergence pattern
S-POL Radar Reflectivity and Model Results (2km)
Convergence / Divergence pattern
FM-CW, MAPR and Model Results (.6km)
Vertical velocity
Potential temperatureStructure function
Vertical velocity
Bore Origin
Divergence / convergence movie
Front-relative velocity / relative humidity movie
Bore Origin cont’d
Front-relative velocity
Relative humidity
Bore Origin cont’d
2 2
2 2
1N uS
u c zu c
Wave trapping when Scorer parameter decreases with height (lee waves, Holton 1992, Crook 1988)
Wave dispersion (Mahapatra et al. 1991)
Wave generation by pressure disturbances (Simpson 1987, Baines 1995)
Bore Origin cont’d
Vertical velocity / Scorer parameter movie
Bore and the PBL
TKE/Shear production movie
Bore and the PBL cont’d AERI Sounding and Model Results (.6km)
Potential temperature Mixing ratio
Bore and the PBL cont’d
Surface temperature Surface relative humidity / mixing ratio
Bore and the PBL cont’d
W-advection Turbulence
V-advectionU-advection
Conclusions
MM5 simulations show some realism in reproducing a second bore observed on June 4, 2002 during IHOP. Simulations show sensitivity to initial conditions and small sensitivity to TKE based PBL parameterizations.
Bore in the model is generated when wind/pressure perturbations induced by precipitation reach a surface front. This result cannot be verified since there are no observations.
The bore developed into a wave-train. Modeled wave amplitude and length is close to the observed. Origin of the wave-train is related to the nonhydrostatic (dynamic) pressure disturbances on the frontal head but cannot be verified.
Cooling and moistening of the mixed in the bore’s wake is reproduced by the model and can be easily explained. Surface warming and drying also occurs in the model due to advection. The warming is smaller than observed.