Preliminary study: testing the sensitivity of the model to simulate this CI case.
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Transcript of Preliminary study: testing the sensitivity of the model to simulate this CI case.
Numerical investigation of the multi-scale processes inducing convection initiation
for the 12 June 2002 IHOP case study
Preliminary study: testing the sensitivity of the model to simulate this CI case.
Sophie Bastin, Tammy Weckwerth, Fei Chen, Kevin Manning
NCAR
Acknowledgements: M. Weisman, S. Trier, M. Pagowsky, D. Posselt, D. Birkenheuer, and others (mesouser, …)
Motivations Better understanding of the influence of the processes at different
scales on the location and timing of convection
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Why did CI occur here?
Numerical simulations Control simulation
MM5 model version 3.71 domain, 4-km horizontal resolution44 vertical levels, about 20 half-sigma levels within the boundary layer Initialization at 12Z on June 12 (cold start), from NCEP Eta analyses (40 km resolution) Objective analysis and observations nudging (it’s not a forecast)Eta PBL parameterization, no cumulus scheme, Reisner2 microphysics scheme, Noah LSM
Sensitivity tests:Domain(s) sizeInitialization: time, 3D fields (NCEP ETA, RUC, LAPS, ECMWF), soil moisture and temperature fields (HRLDAS)Parameterizations: PBL processes, microphysics scheme, cumulus scheme
Control simulation (1)
Surface wind at 21 UTC (= initial time + 9h)
OK mesonet data
simulation
Control simulation (2)
Surface temperature at 21 UTC
OK mesonet data simulation
Control simulation (3)
Relative humidity at 21 UTC
OK mesonet data simulation
CONTROL simulation (4)
19 UTC
20 UTC
21 UTC
22 UTC
Column-integrated cloud water
Sensitivity study (1)
YES NO
3D initial conditions X (underway)
HRLDAS (surface conditions)
light
Domains X
Initial time X
PBL parameterization
X
Microphysics scheme
X
Convective scheme (with or without)
X
Sensitivity study (2)
CONTROL 2 domains Cold start at 00 UTC
dryline Good Good ~ good
Outflow boundary
Too weak Good (too strong?)
No
mesolow Good Too weak Larger scale circulation
Surface moisture values
Good Good around the dryline
~ good
Surface temperature
values
Good (except gradient at the outflow boun.)
same as CONTROL
~ good
CI along the dryline
Good but no CI at triple point
Too late Too early
Sensitivity to domainsSurf
ace
mix
ing r
ati
o
and w
ind a
t 2
1 U
TC
Colu
mn-i
nte
gra
ted
cloud w
ate
r at
21
U
TC
Control simulation 2 domains
Sensitivity study (2)
CONTROL 2 domains Cold start at 00 UTC
dryline Good Good ~ good
Outflow boundary
Too weak Good (too strong?)
No
mesolow Good Too weak Larger scale circulation
Surface moisture values
Good Good around the dryline
~ good
Surface temperature
values
Good (too hot western of dryline)
same as CONTROL
~ good
CI along the dryline
Good but no CI at triple point
Too late Too early
Sensitivity to initial time
Control simulation Initialization at 00 UTC
Reflectivity, potential temperature and surface wind at 16 UTC
Conclusion and future prospects
Main results:Current parameterizations do not guarantee high degree of accuracy in reproducing an outflow boundary.The number of factors involved in good simulations makes the success of high resolution simulations of thunderstorms a matter of …luck.
Future worksSensitivity to 3D fields initializationSimulation of gravity waves (GV) and horizontal convective rolls (HCR)
• sensitivity to the horizontal resolution (trying 2km)• WRF model
Analysis of the pre-storm environment in the different simulations to understand the physical processes affecting convection initiation (absence of GV and HCR = reasons of failure?)
Sensitivity study (2)
CONTROL 2 domains
Init. at 00Z MRF param.
dryline Good Good ~ good Good
Outflow boundary
Too weak Good (too strong?)
No Too weak
mesolow Good Too weak Larger scale circulation
Good
Surface moisture values
Good Good around the
dryline
~ good Too weak
Surface temperatur
e values
Good (too hot western of
dryline)
same as CONTROL
~ good Good
CI along the dryline
Good but no CI at triple
point
Too late Too early Good
Sensitivity to PBL parameterizationMRF PBL deeper, surface humidity weaker, moisture gradient at the dryline weaker
ETA Humidity more concentrated in the PBL and moisture gradient stronger, propitious to the development of convectionCI slightly delayed with the MRF parameterization
Control simulation
MRF param.