Mpo 551 asdasdasdradewinds

7/30/2019 Mpo 551 asdasdasdradewinds

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Vertical Structure of

the Atmospheric Boundary Layerin Trade Winds

Yumin Moon

MPO 551September 26, 2005


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Papers to Present

Riehl, H., Yeh T. C., Malkus J. S., and La Seur,N. E., 1951: The Northeast Trade of the PacificOcean. Quarterly Journal of the RoyalMeteorological Society. 77, 598-626.

Augstein E., Schmidt, H., and Ostapoff, F., 1974:The Vertical Structure of the Atmospheric

Planetary Boundary Layer in Undisturbed TradeWinds over the Atlantic Ocean. Boundary LayerMeteorology, 6, 129-150.


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Riehl 1951

Analyzed observations inthe Northeast Pacific

Ocean during the dry

season (July to October).

Three weather ships, PearlHarbor, Hickam Field, both

in Honolulu, HI.

Hourly surface

observations, two

radiosonde observations

per day.


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Riehl 1951

Wind Steadiness

Air above the

Inversion Top

Inversion Layer Cloud Layer

Subcloud layer

Vm = mean speed100mV

VS


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Riehl 1951

Vertical Cross-Section of Wind Speed Mean Vertical Distribution

of Wind Speed


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Riehl 1951

Vertical Distribution of Divergence

dzvs

dzwz

zz

)()(00

Equation of Continuity,

assuming steady state


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Riehl 1951

Whereas the inversionascends downstream,

individual columns

descend, shrink

vertically and spread

horizontally. Large

masses of air, located

above the inversion at

32N have become a

part of the cloud layerwhen they reach

Honolulu, HI.


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Riehl 1951

The air that has beenincorporated in the

inversion layer

The air that has been

incorporated in thecloud layer

The air that has been

below the inversion

throughout the journey

from 32N.


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Riehl 1951


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Riehl 1951


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Riehl 1951


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Riehl 1951

0)()()()( dsPELds

z

qA

zLdsqw

zLdsqv

sL

Equation of Continuity for Latent Heat in a layer of unit thickness and cross-section

and extending over the distance ds

VerticalHorizontal Turbulent

Exchange

Source/Sink

Steady-state is assumed.

Lateral mixing is neglected compared to vertical mixing.

The vertical coordinate is attached to the trajectory of the mean

motion

w vanishes everywhere thus the second term (vertical) isdropped out, except at the top where the boundary is a horizontal

surface.


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Riehl 1951


14/23

Riehl 1951 Rise of the inversion is

accomplished through the pickup oflatent heat by the trade in thecourse of its passage over thetropical ocean.

The bases of cumulus clouds are

nearly uniform height, but the topsare very irregular.

The tops of the cumulus cloudsbreak off and evaporate quickly.

Moisture is introduced into thelower portions of the inversion

layer. Then the air in the inversion layer

becomes gradually similar to thecharacteristics of the cloud layer.


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Riehl 1951

fsp

dtdv

1

fs

pvvdiv

t

v

)(

)(

dsdzfs

pdsdzvvdivvdsdz

t

)(

z

vz

f

0)()()(

dsz

v

z

vdzppvwdsvwdsvvdzvvdz btdu

btdu

Inflow term

upstream,

downstream

Inflow term

top, bottom

Pressure

Term

Turbulent term

top, bottom

Equation of momentum

Integrating over a volume bounded by ds, dz,

and of unit thickness in the direction normal to s


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Riehl 1951

Layer

(mb)

Inflow

Upstream

Outflow

Downstream

Net Inflow

Top

Outflow

Bottom

Net Pressure

Term

Turbulent

Term Bottom

Turbulent

Term Top

1020-

960

-0.3 -0.2 -0.1 0 0 0 -2.7 4.4 -1.6

960-

880

-0.4 -0.4 0 -0.1 0 -0.1 -2.6 1.6 1.1

880-

800

-0.4 -0.4 0 -0.1 -0.1 0 -1.2 -1.1 2.3

800-

720

-0.4 -0.3 -0.1 -0.1 -0.1 0 0 -2.3 2.4

In units of 10^8 G CM SEC^-2


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Augstein 1974

Analyzed observationscollected during the AtlanticExpedition 1965 Sep 12 toOct 11 and the Atlantic

Tradewind Experiment(ATEX) 1969 Feb 6-21.

Three ships, Planet at thenortheast, Discoverer atthe northwest, and Meteor

at the south. 8 radiosondes observations

per day, radar windmeasurements.


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Augstein 1974

Surface Layer adiabatic temperature gradient, decreaseof specific humidity with height, slight statical instability.

Mixed Layer adiabatic temperature lapse rate, nearly

constant vertical specific humidity.

Transition Layer nearly isothermal temperaturedistribution, strong upward decrease of moisture.

Cloud Layer temperature gradient slightly higher than the

moist adiabatic lapse rate, upward weak decrease of

specific humidity, conditionally unstable. Trade Inversion increasing temperature, steep decrease

of moisture.


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Augstein 1974


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Augstein 1974

Increasing cumulusconvection causes anincrease of downwardflux of inversion air intothe cloud layer, thus

pushing the inversionupward. This process iscombined with downwardheat flux which effects adiabatic warming of the

cloud layer.

Strong convective activitydestroys the tradeinversion; the organizedcloud circulation thentransports air parcels with

relatively low potentialtemperature upward andwith high potentialtemperature downward.This process results in a

diabatic warming of thelower part of the cloudregion and in a diabaticcooling of the upper part


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Augstein 1974


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Augstein 1974


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Augstein 1974

Mpo 551 asdasdasdradewinds

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