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ON

11. OUTPUT

PROCESSING

INSTRUCTIONS

wind vector

flirection

over an

output

interual.

Two differer*

calculations of wind

vector

direction

(and

standard deviation

of

wind

vector

direction) arg

available, one of

which is

weighted

foqwind speed.

When used

fvith

polar

sensors,

the

instruction

does

a mod{rlo

divide

by 360

on

wind

direction,

which allow{

the

wind

direction

(in

degrees) to

be

0 to 360,l0

to 540, less

than

0, or

greater

than 540.

Tfe ability to handle a

negative

reading

is u$eful

in

an example

where

a difficult

to

reach

wind vane

is

improperly oriented and

outputs

0 dQgrees at a true

reading of 340

outputs

0 dQgrees at a true

reading of 340

degrees.

Tl'fe simplest solution

is to enter

an

offset of

-20

in the instruction

measuring

the

wind vane,

vfhich results in the correct output

following

When a

speed

sample

is 0, the

instruction

uses 0 to scalar

or resultant

vector

wind speed

hnd

standard deviation,

but

the

sample

is n(t used in the

computation of wind

direction.

user may not

want a sample less

than the

threshold used

in the standard

deviation.

lff

this

is

the case

instruction 89 can

be used to

wind speed,

and if

less

than

the

Instruction 30 can

set the input

to

0.

Standard

deiviation can

be

processed

one of

two

ways:

1) using

every

sample taken during

by

from s

for

2).

Aveqaging

sub-interval

standard

ions

minimizes

the effects

of

69 WIND VECTOR

*'*

FUNCTION

Instruction 6p

processes

the

primary

variables

and direction

from either

polar

(wind

speedland

direction) or

orthogonal

(fixed

East and

propellers)

sensors.

lt

uses the

raw data

to

mean wind

the

mean wind speed, the

Standard deviation of

horizontal wind

fluctuations

from sub-intervals

is calculated

as

follows:

o(o)=[((oo1

)2+(c@2)2

...+1

oo*)2)/MJ1/2

where

o(@)

is

the

standard

deviation

over

the

output interual, and oO.t ...o@u

are sub-interval

standard deviations.

PARAM.

DATA

NUMBER TYPE DESCRIPTION

2 Repetitions

4 Samples

per

sub-interval

(number

of scans)

2 Sensor/Output

2 digits:

AB

A

Sensortype:

0

=

Speed

and

Direction

1

=

East and North

B

Output

option:

0 S,

@1,

o(@1)

1 S,01

2 S,

U, @u,

o(Ou)

04: 4

First

wind speed

input

location no.

(East

wind speed)

05: 4

First

wind direction

input

location no.

(North

wind speed)

Outputs Generated: 2-4

(depending

on output

option)

for each

repetition

A

sub-interval

is specified as a

number of

scans.

The

number of scans for a sub-interval

is

given

by:

Desired sub-interval

(secs)

/ scan

rate

(secs)

In

an example

where

the scan

rate is

1

second

and

the Output

Flag

is

set

every 60

minutes,

the

standard deviation

is

calculated

from all3600

scans when

the

sub-interval is 0. With a sub-

interval

of

900 scans

(15

minutes) the

standard

deviation is the average of the

four sub-interval

standard deviations. The last sub-interval

is

weighted

if

it

does

not

contain

the specified

number

of scans.

magnitude,

and the mean

standard deviations

processed

sub-intervals of the

output

period

01:

02:

03:

meander under

light wind conditions, and

it

provides

mQre complete

information

for

periods

of transition' .

'

EPA On-site

Meteorological

Program

Guidance

fdr Regulatory Modeling

Applications.

1 1-1

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