Application Of KF-Convection Scheme In 3-D Chemical Transport Model
EAS6410
Chun Zhao
4/20/2006 GA TECH - EAS6410 - Atmosphere Chemistry 2
Outline
Introduction
Application
Results and Discussion
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Introduction
3-D Chemistry Transport Model ( CTM)
Structure: Transport:1. Advection
2. Diffusion
3. Convection
Chemistry:1. Emission
2. Dry Deposition
3. Chemistry
Chemistry
Setup and Initial
Transport
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Grell-Convection Scheme
Structure:Cloud top
Cloud bottom
Ground surface
Downdraft original layer
Downdraft flux
Updraft flux
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KF-Convection Scheme
Structure:
Ground surface
Downdraft End layer
Downdraft Original layer
Cloud bottom
Cloud top
Updraft flux
entrainmentdetrainment
entrainment detrainment
Downdraft flux
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Convection Scheme Comparison
KF-Scheme1. Including the effects of
detrainment & entrainment;
2. Shallow (non precipitating) convection is allowed for any updraft that does not reach minimum cloud depth for precipitating clouds;
3. The downdraft end layer is dependent.
Grell-Scheme1. Without effects of
detrainment & entrainment;
2. Without shallow convection, using a separate shallow convection;
3. The downdraft end layer is surface.
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Application
Convection variables
1. Simulate the KF-Convection variables using WRF model.
2. Determine necessary variables for chemical transport model.
3. Develop an interface to output these necessary variables at the pacific time. In my case, I choose the first week in March.
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Convection Parameterization
1. Determine whether convection process occurs at a particular time (deep convection or shallow convection).
2. Do parameterization (deep and shallow)
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Mass Balance Control1. Doing subsiding and uplifting compensation to make mass
balance during convection;2. Set a maximum relative mass variance during convection ,
due to computation error.
Time Step Control1. Check negative concentration value after transport;2. Decrease time step, if there is any negative concentration
value after transport.
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Result
KF-Convection effect
The convection effect comparison between the two different schemes
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KF-Convection Effect Trend
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500hpa
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500hpa
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Convection Effect Comparison
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Summary
Convection effect in chemical transport process is very important;
Different convection schemes have different effect in transport;
There are still some problems to parameterize the convection very well in transport model. (i.e. time step control, mass balance)
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Question?