Application Of KF-Convection Scheme In 3-D Chemical Transport Model

EAS6410

Chun Zhao

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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?