EPA/600/A-95/043
METEOROLOGICAL MEASUREMENTS IN THE VICINITY
OF A COAL BURNING POWER PLANT
Gennaro H. Crescenti'*
Atmospheric Sciences Modeling Division
Air Resources Laboratory
National Oceanic and Atmospheric Administration
Research Triangle Park, North Carolina
John E. Gaynor
Environmental Technology Laboratory
National Oceanic and Atmospheric Administration
Boulder, Colorado
1.	INTRODUCTION
High concentrations of sulfur dioxide (S02) are
commonly observed during the cool season (November to
February) in the vicinity of a coal burning power plant
located in the Mae Moh Valley of northern Thailand.
These high pollution fumigation events occur almost on a
daily basis, usually lasting for several hours between late
morning and early afternoon, One-hour average S02
concentrations are commonly observed in the range of
1000 to 2000 jig m"3. As a result, an increase in the
number of health complaints have been observed by local
clinics during this time of year.
In order to understand the atmospheric processes
which are responsible for these high pollution fumigation
events, meteorological data were acquired from a variety
of observing platforms during an intensive field study from
early December 1993 to mid-February 1994. Data were
acquired in the vicinity of the power plant from S02 gas
analyzers, in-situ sensors mounted on a 100-m tower, a
single-beam monostatic sodar, a three-axis monostatic
sodar, radar wind profiler, and a radio acoustic sounding
system (RASS). These data will also be used in the future
to initialize and verify dispersion models. This paper
briefly describes the meteorological measurements made
in the Mae Moh Valley during the winter of 1993/1994.
2.	DESCRIPTION OF THE PROBLEM
The power plant, operated by the Electric
Generating Authority of Thailand (EGAT), is located in
the Mae Moh Valley about 25 km east of the Changwat
Lampang Province in northern Thailand (Fig. 1). The
valley is about 15 to 20 km wide, 50 km long, and is
aligned from northeast to southwest. The valley floor is
relatively flat with an average elevation between 320 and
360 m above sea level (asl). Two ridges parallel the valley
on either side. To the northwest, the hills average 700 m
asl; to the southeast, 900 m asl. To the northeast, the
valley is also enclosed by hilly terrain. To the southwest,
the valley opens to the Changwat Lampang Province. The
valley is sparsely populated, with the largest concentration
of people living in several small villages south of the
power plant. The valley is primarily used for agriculture,
with the predominant crops being rice and sugar cane.
The coal burning power plant was constructed in
several phases over the last two decades in the center of
the valley to take advantage of a nearby lignite reservoir.
A total of eleven separate power generators in two
separate facilities produce approximately 2.025 GW of
power, supplying about a quarter of Thailand's electricity.
The three stacks of the first facility (Units 1,2, and 3) are
80 m high, while the eight stacks of second facility (Units
4 through 11) are 150 m high. The base of all eleven
stacks are 320 m asl. While electrostatic precipatators are
present in each unit to remove particulates, there are no
pollution controls (i.e., scrubbers) to remove S02. Since
there are no other major industrial activities in the Mae
Moh Valley, the power plant is the source for nearly all of
the observed S02 (Saengbangpla et al., 1981; 1982).
The number of health complaints have increased
during the cool season when high concentrations of S02
have been observed at numercws monitoring stations in the
vicinity of the power plant. These high pollution
fumigation events, which occur on almost on a daily basis,
last for no more than several hours, usually starting in the
late morning and ending by early afternoon.
'On assignment to the Atmospheric Research and Exposure Assessment Laboratory, U. S. Environmental Protection Agency.
"Corresponding author address: Gennaro H. Crescenti, U.S. EPA, AREAL, MD-56, Research Triangle Park, NC 27711.

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Height (m)
900
800
700
1600
1500

Longitude (°E)
Figure 1. Topographic map of the Mae Moh Valley. The power plant is represented as the two squares. S02 monitoring
stations are depicted by the circles. The unlabeled circle between the two squares is the 100-m tower located at the main
meteorological station (MMS).
3. MEASUREMENTS
S02 and meteorological data were acquired from
the beginning of December 1993 to mid-February 1994.
These data set are described below.
3.1 SO, Measurements
S02 measurements were acquired by Thermo
Environmental Instruments (model 43A) pulsed
fluorescent ambient air analyzers at seven surface
monitoring sites ranging from 1 to 8 km from the power
plant. These S02 sites were located at Ban Mae Chang
(BMC), Ban Sop Moh (BSM), Ban Sop Pad (BSP), main
meteorological station (MMS, 100-m tower), Ban Ko-Or
(BKO), Ban Huai Khing (BHK), and the Mae Moh
Government Center (MMG). These data were reported
through a radio telemetry link to a computer located in an
EGAT office near the power plant as ten-minute averages.
A typical fumigation event is depicted in Figure 2 for three
of the S02 monitoring stations.
3 .2 100-m Tower Instrumentation
An existing suite of Weathertronics (a division of
Qualimetrics) in-situ sensors were used to obtain
meteorological data from the 100-m tower for the field
study. Ambient air temperature was measured at 2,10, 50

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2250
O)
o
O
CO
100 m Tower
-- Ban Huai Khing
Ban Mae Chang
1500 —!
750 —
500
250 —
— ll' 11 ^
12	15
Time (LST)
Figure 2.
Chang.
S02 concentrations (jig m"3) observed on 1 January 1994 at the 100-m tower, Ban Huai Khing, and Ban Mae
and 100 m by a thermistor (model 4480). This sensor was
housed inside an aspirated radiation shield to minimize the
measurement errors associated with solar heating.
Horizontal wind speed and direction were measured at 10,
50, and 100 m by a cup anemometer (model 2030) and
vane (model 2020), respectively. Vertical wind velocity
was measured at 10, 50, and 100 m by a propeller
anemometer (model 2070). These data were acquired by
a Sum-X data logger as one-hour averages.
A new suite of in-situ meteorological sensors
were installed on the 100-m tower for the field study.
Ambient air temperature and relative humidity were
measured at 2, 10, 50 and 100 m by an R. M. Young
Company (model 43372C) relative humidity/temperature
probe. This dual sensor was housed inside an R. M.
Young (model 43408) Gill aspirated radiation shield.
Horizontal and vertical wind velocity were measured by an
R. M. Young (model 27005) Gill UVW propeller
anemometer at 10, 50, and 100 m. Global solar radiation
was measured near the surface by an Eppley Laboratory
Precision Spectral Pyranometer (model PSP). These data
were acquired by a Campbell Scientific (model CR-10)
data logger over 15-minute intervals.
Wind velocity and turbulent flux measurements
were obtained by an Applied Technologies sonic
anemometer (model SWS-211/3K). The sonic
anemometer was mounted at 10 m on the 100-m tower. A
program written in BASIC on a 386 PC was used to
interrogate the sonic anemometer at 10 Hz and average
those data over 15 minute intervals. These data included
the mean of the three component wind velocity (U, V, W)
and virtual air temperature (T„); standard deviation of the
three component wind velocity (ou, ov, o») and virtual air
temperature (oT), resultant mean wind speed and wind
direction (WS, WD); and covariances of U and V, U and
W, V and W, U and T, V and T, W and T. A one-week
time series of some 10-m in-situ data are shown (Fig. 3).
3 3 Single-Beam Monostotic Sodar
A 2 KHz single-beam monostatic sodar (NOAA
designed and built) was located about 3 km to the west of
the 100-m tower and about 1 km to the northwest of Ban
Ko-Or, This remote profiler continuously recorded the
thermal structure of the atmosphere from the surface up to
a height of 700 m. Data were recorded on tabulating
computer papa by a dot matrix printer. Figure 4 shows an
example of a hour sodar plot

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1—i—!—i—i—i—r
t~i—i—r
i-94 3-Jan-94 4-Jan-94 5-Jan-94 6-Jan-94 7^1an-94 8-Jan-94 9-Jan-94
eries of in-situ meteorological data obtained at 10 m from 2 January to 9 January 1994. From top-to-
wind velocity, northward wind velocity, vertical wind velocity, air temperature, relative humidity, solar
triance of W and T (sensible heat flux).

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Figure 4. Monostatic sodar plot for 1 January 1994.
Horizontal axis is time (positive from left to right) from
1100 to 1200 LST. Vertical axis is height from 0-700 m.
3.4	Three-Axis Monostatic Sodar
A Remtech three-axis monostatic sodar system
(model AO), collocated with the monostatic sodar, was
used to acquire detailed wind profiles in the lowest several
hundred meters of the atmospheric boundary layer. The
sodar system was modified in which the Remtech data
acquisition system was removed and replaced by Radian
Corporation electronics. The antenna array remain
unchanged. Profiles of horizontal and vertical wind
velocity were obtained as 15-minute averages from 50 m
to about 500 m over 25 m intervals.
3.5	Radar Wind Profiler and RASS
A 915 MHz radar wind profiler (NOAA
designed and built), collocated with the sodars, was used
to acquire profiles of horizontal and vertical wind velocity.
The output frequency of the remote sensor was readjusted
to 924 MHz to insure that Thai mobile telephone
communication frequencies of 900 to 915 MHz would not
interfere with operation of the profiler. A radio acoustic
sounding system (RASS) was used in conjunction with the
wind profiler to obtain profiles of virtual air temperature.
Three 15-minute wind profiles were acquired each hour by
the wind profiler while three 5-minute temperature profiles
were acquired each hour by the RASS. The three wind
profiles were then combined to create a one-hour average.
The same was done for the temperature profiles. Wind
data were collected from about 140 m up to about 2500 m
over 60 m intervals. Temperature data were collected
from about 125 m up to about 1300 m over 60 m intervals.
Figures 5 and 6 display one day profile plots of the
horizontal wind velocity and virtual air temperature,
respectively.
4.	SUMMARY
Various sensors were used to acquire air
pollution and meteorological data in the vicinity of the
EGAT coal burning power plant located in the Mae Moh
Valley of northern Thailand. These data have been briefly
described in this report. They include S02 data from seven
surface monitoring stations, in-situ meteorological data
taken from a 100-m tower, and remotely sensed data from
two sodars, a radar wind profiler, and RASS. When all of
these data are combined into one unifying database, a
detailed picture of the atmospheric boundary layer is
created in time and vertically in space. This data will be
useful in examining the atmospheric processes which are
responsible for the high pollution fumigation events in the
vicinity of the power plant during the cool seasoa In
addition, these data will be very useful for initializing and
verifying dispersion models which will attempt to
numerically reproduce these events.
5.	ACKNOWLEDGEMENTS
The authors wish to thank the many members of
the Royal Thai government, the Pollution Control
Department, and the Electric Generating Authority of
Thailand for their help with the Mae Moh air pollution
field study. The authors give sincere thanks to Scott
Abbott, Cat Russell, Jim Jordon, Cathy Sharp, and
Dominique Ruffieux for all their help in preparing, setting
up, and tearing down the NOAA sodar and radar profiling
equipment used in the study.
6.	DISCLAIMER
This document has been reviewed in accordance
with U. S. Environmental Protection Agency policy and
approved for publication. Mention of trade names or
commercial products does not constitute endorsement or
recommendation for use.
7.	REFERENCES
Saengbangpla, S, T. Sumitra, V. Chongvisal, W.
Limpaseni, and C. Benyajati, 1981: Air
Pollution Study of Mae Moh Power Plant
Project. Chuan Printing Press, Bangkok, 144
PP-
Saengbangpla, S., T. Sumitra, V. Chongvisal, P.
Karasuddhi, W. Limpaseni, and N. Chankow,
1982: Plume Dispersion Study for Mae Moh
Power Plant Units ] to 9. Chuan Printing Press,
Bangkok, 240 pp.

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0	3	6	9	12	15	18	21
Time (LST)
Figure 5. Wind profile data obtained by the NOAA 915 MHz radar on 1 January 1994.
Time (LST)
Figure 6. Virtual air temperature profile based on tower and RASS measurements for 1 January 1994.

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TECHNICAL REPORT DATA
1. REPORT NO.
EPA/600/A-95/Q43
4. TITLE AND SUBTITLE
Meteorological Measurements in the Vicinity of a
Coal Burning Power Plant
5.REPORT DATE
6.PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Gennaro H. Crescenti and John E. Gaynor
8.PERFORMING ORGANIZATION REPORT NO.
PERFORMING ORGANIZATION NAME AND ADDRESS
1C.PROGRAM ELEMENT NO.
U.S. Environmental Protection Agency
Atmospheric Research and Exposure Assessment Lab.
ERC Annex, MD-56
Research Triangle Park, NC 27711
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Atmospheric Research and Exposure Assessment Lab.
ERC Annex, MD-56
Research Triangle Park, NC 27711
13.TYPE CF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT	> r
c	, i
High concentrations of sulfur dioxide (S02) are commonly observed during the
cool season in the vicinity of a 2.5 GW coal burning power plant located in the Mae
Moh Valley of northern Thailand. The power plant is the source for nearly all of
the observed S02 since there are no other major industrial activities in this
region. These high pollution fumigation events occur almost on a daily basis,
usually lasting for several hours between late morning and early afternoon. One-
hour average S02 • concentrations commonly exceed 1000 /zg m"
As a result, an
increase in the number of respiratory type health complaints have been observed by
local clinics during this time of year.
Meteorological data were acquired from a variety of observing platforms during
an intensive field study from December 1993 to February 1994.- A 2 KHz single-beam
monostatic sodar, located about 3 km to the west of the power plant, was used to
record the thermal structure of the atmosphere. A 915 MHz radar wind profiler and
radio acoustic sounding system (RASS), collocated with the sodar, were used to
collect wind and temperature profiles. In-situ meteorological measurements were
made from a 100 m tower located near the power plant. <' Those: measurements included
horizontal and vertical wind velocity, air temperature, relative humidity, and solar
radiation. In addition, turbulent flux measurements were acquired by a sonic
anemometer. S02 measurements were made at seven monitoring sites scattered
throughout the valley. These data were used to examine the atmospheric processes
which are responsible for these high pollution fumigation events. ^ .
17 .
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