Cloud Resolving Model Studies of Tropical Deep Convection Observed During HIBISCUS 2004.

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Cloud Resolving Model Studies of Tropical Deep
Convection Observed During HIBISCUS 2004.
By Daniel Grosvenor, Thomas W. Choularton,
Hugh Coe - The University of Manchester, United
Kingdom With thanks to Gerhard Held - IPMET,
Brazil Jorge Gomes CPTEC, Brazil Andrew
Robinson UCAM, United Kingdom.
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Aims of Work

• To simulate transport of material from lower to
  upper troposphere by deep convective clouds
• Gases, aerosols, water vapour, ice hydrometeors
• Testing and improvement of model
• Comparisons to observations
• GCM parameterisations
• Data set for development and testing

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The LEM Model

• Cloud Resolving Model
• UK Met Office
• Bulk microphysics parameterisation
• 38 conversion processes between
• Vapour, liquid, rain, ice, snow, graupel.
• Double moment for ice hydrometeors
• Highly variable resolution-
• Boundary layer processes
• Deep convection
• Periodic boundary conditions

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24th February, 2004 Case Study

• Large squall line moving from north passes over
  Bauru.

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Model Initialisation

• One sounding for whole domain
• Time forcing possible
• Available soundings
• 0900 LT Campo Grande
• 1715 LT Bauru
• 2100 LT Sao Paulo
• Bauru sounding fairly stable - no deep
  convection produced by model
• Campo Grande sounding used and model forced
  towards Bauru sounding

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Model Initialisation

• Squall line initialised using a warm perturbation
• 2-D, 500km domain, 1km resolution
• Sensitivity to aerosol concentration tested
• Comparisons to radar statistics of echo tops and
  3.5km CAPPI data

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Timeseries of max 3.5km radar reflectivity
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Timeseries of 3.5km radar reflectivity modes
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Log-Normal Distribution of 3.5km dBZ from
1400-2300
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Timeseries of Max Echotops
-3
CCN 720cm
-3
CCN 240cm
Radar data
Maximum of 10dBZ radar echo tops (km)
Maximum of 10dBZ radar echo tops (km)
Local Time
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Timeseries of Echotop Modes
-3
CCN 720cm
-3
CCN 240cm
Radar data
Mode of 10dBZ radar echo tops (km)
Local Time
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Timeseries of Echotop Variances
)
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Variance of 10dBZ radar echo tops (km
Local Time
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Log-Normal Distribution of Echotops from
1400-2300
-0.5
-1
-1.5
-2
-2.5
Log10 of Normalised Distribution of Echo Tops
-3
-3.5
-4
-4.5
-5
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Max Tracer at each Height as Percentage of Max
Input
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CFC-11 tracer measurements from SF-4 (DIRAC, UCAM)
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Profile of Mean Liquid Water
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Conclusions

• Echotop agreement reasonable but lack of high
  echotops
• Simulated 3.5km dBZ generally too high related
  to above?
• 2-D simulations produce highly time variable
  statistics
• Mean values hard to compare with 2-D simulations
  slices through radar data should be better
• Tracer outflow height close to apparent outflow
  from observations

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Future Work

• Vertical radar slice comparisons (RHIs)
• ECMWF/Meso model for soundings and forcing
  comparisons to clouds obtained in these models
• Full double moment scheme
• Vertical aerosol transport
• EMM (Explicit Microphysics Model)