Transcript Modeling of a Bore Observed on June 04 during IHOP_2002 (Pagowski)

MODELING OF A BORE OBSERVED ON
JUNE 04 DURING IHOP 2002
Mariusz 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
IHOP Workshop, Toulouse, June 14-18, 2004
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)
Structure function
Potential temperature
Vertical velocity
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

Wave trapping when Scorer parameter decreases with height
(lee waves, Holton 1992, Crook 1988)
S


N2
u  c 
2
1  2u

 u  c  z 2
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
U-advection
V-advection
W-advection
Turbulence
Conclusions

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
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.