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JULY, 2009

The Mexico City 2006 Wind Direction States

A. T. CeladaA. T. Celada--Murillo, A.Murillo, A.SalcidoSalcido

Instituto de Investigaciones Elctricas

MEXICO

20 th IASTED International Conference on Modelling and Simulation 2009

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Motivation

The characterization of the wind circulation events and the recognition

of their main patterns constitute an important issue to understand how the

air pollutants will be spatially and temporally distributed by the winds on

the urban settlements.

Objetive

Identify, organize and classify the surface wind circulation events at the

Mexican City Metropolitan Area, in terms of a simple and discrete wind

direction state variable.

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Antecedents

Atmospheric emissions

High level atmospheric emissions

mobile sources Topography

Meteorology

Bad urbanization

Mexican City Metropolitan Area (MCMA) is one of the world

Megacities with strong air pollution problems.

80% vehicle emissions from a

fleet of 4 million cars

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Physiography

MCMA is a basin, with an average

altitude of 2240 masl, surrounded by

mountains on the W, S and E sides, with

a main opening at the N, and a gap at SE.

Chalco

The topographical and meteorological conditions here are two factors thatincrease the complexity and gravity of MCMA air pollution problem.

Low possibilities of air pollutant ventilation

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WIND DIRECTION STATES MODELWIND DIRECTION STATES MODEL

1

2

State 1377 = 767 (decimal)

43N

E

NE

SSW

W

NW

SE

Wind direction states

or

0 4095(decimal base)

0000 7777(octal base)

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The 4096 wind direction states can be organized in 81 groups

GROUPS

(, , )

sign of the vorticity of the state

Anticyclonic (A) : - 1

Null vorticity : 0

Cyclonic (C) : + 1

sign of the divergence of the state

Convergent winds (C) : - 1

Null divergent : 0 Divergent winds (D) : + 1

Wind direction sector of the average value of the

four mean wind directions of one quadrant

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Meteorological Data

6666 h

performance 100% simultaneously

1250 different wind direction states

5.33 % average occurrence for each state.

Year 2006

9 meteorological RAMA stations

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CC = 25.5 %

AC = 24.7 %

CD = 12.7 %

FLAT = 12.0 %

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AC = 12.3 %

CC = 10.2 %

CD = 7.1 %

FLAT = 7.2 %

Day

Night

CC = 15.3 %

AC = 12.4 %

CD = 5.6 %

FLAT = 4.8 %

Divergent winds: 18.9 %

Convergent winds: 25.2%

Divergent winds: 8.1 %

Convergent winds: 31.6%

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ConclusionsConclusions

We presented a model that represents complex wind circulation events

with a simplified and discrete wind direction state variable.

Wind circulation events can be represented only by 4096 states

These states, also, can be organized in 81 groups taking into accounttheir cyclonic or anticyclonic, divergent or convergent circulation

features.

These organization can help us in the search of the correlation withthe wind driving mechanisms in a study area.

Our results, at qualitatively level, show the effects of these differentwind driving forces in the simplified wind direction states.