BLANkET1 Technical Report 16
Smoke in south-eastern Tasmania, 15th March
2011
Air Section, EPA Division, May 2011
Context of the BLANkET reports
BLANkET (Base-Line Air Network of EPA Tasmania) reports are compiled
using BLANkET and other Tasmanian air quality data, as well as data from
other sources. The topics and events chosen for these reports are selected for
one or more of the following reasons: Scientific interest – for example if the event
demonstrates a principle or principles of general value in understanding smoke
movement and dispersal in the Tasmanian context; Well-documented events –
such as if the event is captured by two or more stations and hence provides
general information on smoke movement; General public interest – this includes
large–scale or other smoke events that have generated comment at the time or
are of intrinsic public interest for other reasons.
1 Base–Line
Air Network of EPA Tasmania
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Contents
1 Summary
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2 General
2.1 Public complaints . . . . . . . . . . . . .
2.2 Air Quality data . . . . . . . . . . . . .
2.3 Spatially–resolved view of the air quality
2.4 Bureau of Meteorology Synoptic charts .
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3 Known fires in southern Tasmania on the 15th of March 2011
3.1 Forest–Industry burns . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Data from the Tasmania Fire Service (TFS) . . . . . . . . . . . .
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4 Analysis
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4.1 Smoke concentrations at Dover and Cygnet . . . . . . . . . . . . 10
4.2 Order–of–magnitude calculations . . . . . . . . . . . . . . . . . . 14
4.3 Inferred source . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5 Conclusions
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6 Acknowledgements
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7 Appendix - spatial presentation of PM2.5 and wind data
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7.1 Schematic views from BLANkET network data alone . . . . . . . 24
7.2 Schematic views including Bureau of Meteorology wind data . . . 36
2
1
Summary
On the afternoon and the evening of the 15th of March the BLANkET air quality
stations in the Huon and Hobart recorded the northward movement of smoke.
The peak (instantaneous) concentrations were in the range of 40 to 60 µg m−3
in the Huon stations, and were near 20 µg m−3 at Hobart, for several hours.
The 24–hour average PM2.5 values were well below the Australian National
Environmental Protection Standards.
Three complaints were received from Dover and Cygnet (south of Hobart)
by the EPA Division relating to smoke levels on the afternoon of the 15th of
March. It seems likely that the smoke later measured in the Huon and Hobart
initially impacted at Dover and Cygnet. The most probable origin appears to
be from one or several of four forest–industry burns conducted in south–eastern
Tasmania on that day.
2
2.1
General
Public complaints
Three complaints were received from members of the public in the Dover and
Cygnet areas relating to smoke on the 15th of March 2011. These are summarised in Table 1. Note that not all detail received is listed here. Onset times
are given in EDT (subtract one hour for AEST to compare with the plots in
Figure 1). The common threads are that the smoke moved in as a general
smokiness from the south or west, and was present for several hours.
Location
Dover
Onset time
17:00 EDT
Origin
Description
behind Dover
Black general cloud, dense smoke.
poss. Southport Cough, dry eyes and throat.
Smoke present for several hours.
Cygnet
18:00 EDT
Not known.
Smoke from S and W, not a plume,
a blanket. Breathing difficulties.
8 km NE Dover 18:30 EDT
Not known.
General smokiness, S wind, light breeze.
Less annoying inside.
Table 1: Summary of public complaints, 15th March 2011.
2.2
Air Quality data
The PM2.5 levels measured at the Huon and Hobart BLANkET stations on
the 15th–16th of March 2011 are shown in Figure 1. The order of the plots
have been oriented to approximately match the south–to–north locations of the
stations. Also shown are proxy PM2.5 data from a particle counter in operation
3
at Howden, some 16 km south of Hobart city centre. Smoke onset at the more
northerly stations occurred several hours after smoke was first measured in the
Huon region.
Figure 1: PM2.5 data from the BLANkET air stations in the Huon and Hobart
areas and from a particle counter at Howden, 16 km south of Hobart. The
station data are shown from top to bottom are shown in their approximate
south–to–north order.
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Figure 2: Two–minute PM10 , PM2.5 data (upper panel) and 10–minute meterological data (lower panel) from the BLANkET air station at Geeveston,
for the 15th of March 2011. Smoke onset at 17 h AEST corresponds to the
commencement of a light easterly breeze.
5
Two–minute PM10 , PM2.5 data (upper panel) and 10–minute meteorological data (lower panel) from the BLANkET air at Geeveston, the southernmost station, for the 15th of March 2011 are shown in Figure 2 as an example
of the smoke event. Smoke onset at Geeveston commenced at 17:00 AEST
(18:00 EDT), when a light easterly wind set in, with a rise from a low, ‘clean–
air’ background level of a few µg m−3 to near 10 µg m−3 over approximately
half an hour. This was followed by a steep rise commencing about 17:30 AEST
(18:30 EDT) to a peak over 60 µg m−3 . The steep rise commenced approximately 30 minutes after smoke was reported at Cygnet, some 12 km (in an
air–line) to the west of Geeveston.
2.3
Spatially–resolved view of the air quality data
Figures 15 to 25 in the Appendix provide a spatial–schematic illustration of
the smoke movement through the Huon to Hobart on the 15th of March. This
provides a means of visualising the interrelationship between the wind changes
and smoke levels. In general, these figures show that smoke onset at each
station is generally preceded by an interval of southerly wind – an exception is
Geeveston where the smoke onset is preceded by a wind change from westerly
to easterly. The following gives an outline of the 15th March smoke event as
measured at the Huon and Hobart stations. References are to the figures in the
appendix.
At midday on the 15th (Figure 15) the measured wind was generally north to
north–easterly at the stations, and PM2.5 levels were low. By 16:00 (Figure 18)
the wind was southerly at Clearys Gates, Judbury and Huonville, and south–
westerly at Geeveston. Smoke was reported in Dover, approximately 18 km
south of Geeveston, at this time (17:00 EDT = 16:00 AEST).
At 17:00 (Figure 19) Geeveston was under a light easterly breeze (i.e. from
the direction of the Huon River river). Smoke onset at Geeveston commenced
immediately after 17:00 (see Figure 2), also under an easterly wind. Smoke was
reported at Cygnet at 17:00 AEST (=18:00 EDT), and from a location 8 km
north–east of Dover approximately 30 minutes after this.
At 18:00 (Figure 20) Geeveston showed the presence of smoke and a north–
easterly wind. As noted smoke levels had been rising at Geeveston from immediately after 17:00. The wind was easterly at Geeeveston from 17:00 until just
before 18:00. Smoke onset had just commenced at Judbury and Huonville at
18:00.
By 19:00 (Figure 21) there were elevated levels of smoke at all three Huon
region stations. Smoke levels started rising at Howden (21 km east of Huonville
and 18 km south of Clearys Gates) just after 19:00 (see Figure 1).
At 20:00 (Figure 22) the situation was similar to one hour earlier. By 21:00
(Figure 23) smoke has reached Clearys Gates and New Town. The shorter
duration of the smoke at Judbury (as is also seen in Figure 1) was due to the
onset of a north–westerly wind at Judbury soon after 20:00. The north–westerly
wind did not extend to Huonville, 8 km downriver from Judbury.
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Smoke levels dropped at all other stations over the next few hours, clearing
at the Hobart stations early on the 16th of March.
2.4
Bureau of Meteorology Synoptic charts
The Bureau of Meteorology (BOM) surface pressure charts for 10, 16 and 22 h
AEST on the 15th of March are shown in Figures 3, 4 and 5. The main feature
of this day is the approach and crossing of Tasmania of a cold front initially in
the Southern Ocean to the west of Tasmania. The situaiton at 22:00 (Figure 5)
would at face value suggest south–westerly winds in the south–east of Tasmania. The measurements from the Huon and Hobart BLANkET stations is that
the wind, particularly near the coast, was more southerly than south–westerly,
although further inland a more northerly wind persists until at least 23:00 (e.g.
see Figures 23 to 25. It is likely that this is due to, effectively, frictional drag
along the coast of Tasmania, which slews the frontal winds from south–westerly
flow to a more southerly flow in consequence. Discussions with the Tasmanian
Office of the BOM confirmed that this was a reasonably common effect. The
wind deflection is generally limited to the near–surface layers of the atmosphere.
Figure 3: Bureau of Meteorology surface pressure chart for 10:00 AEST
(11:00 EDT), 15th March 2011.
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Figure 4: Bureau of Meteorology surface pressure chart for 16:00 AEST
(17:00 EDT)), 15th March 2011.
The Tasmanian Office of the BOM supplied wind data from automatic
weather stations (AWS) at Tasman Island, Cape Bruny, Hartz Mountains,
Warra, and Grove. These data are included in the schematic figures showing BLANkET data in Figures 26, 27, 28 and 29 in the appendix. In general,
the more–inland, higher–altitude station and Hartz Mountains shows less of a
southerly component in the wind at this site. Cape Bruny AWS shows a strong
southerly wind change near 13:00 AEST, well before the southerly wind was
seen at the Huon and Hobart BLANkET stations. The general view is consistent with a slewing of the near–surface coastal winds to a southerly than
south–westerly direction.
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3.1
Known fires in southern Tasmania on the 15th
of March 2011
Forest–Industry burns
Forest–industry burns are recorded under the Coordinated Smoke Management Strategy (CSMS) operated by the Forest Practices Authority. The CSMS
database lists four burns for the far south of Tasmania for the 15th of March
2011. These were conducted by Forestry Tasmania (see also Figure 30 in the
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Figure 5: Bureau of Meteorology surface pressure chart for 22:00 AEST
(23:00 EDT)), 15th March 2011.
appendix). The burn details are listed in Table 2.
ID
1
2
3
4
Ignition time
13:37 EDT
14:53 EDT
15:51 EDT
16:15 EDT
Origin (UTM grid)
487000 5174000
490000 5180000
487000 5190000
493000 5210000
Approx. Fuel Weight (tonnes)
20,400
31,600
9,200
3,200
Table 2: CSMS recorded burns, far southern Tasmania, 15th March 2011. The
ID number is purely for the purposes of this report and has no other significance.
The fuel weight is an estimate only.
3.2
Data from the Tasmania Fire Service (TFS)
The Tasmania fire permit period was in operation on the 15th of March 2011.
All open air burns are required to have a permit issued by the TFS before
burning can occur. The CSMS burns noted above therefore also required a
TFS–issued permit. The TFS provided data on vegetation burns as recorded in
their permit database for the 15th of March. These are shown in Figure 6 by
the circle symbols. Where given in the database the areas (in hectares) are also
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shown. An area of 0 means the burn area was not recorded. This may mean the
burn was small, below 1 ha, but also may just mean that the details were not
recorded. Also shown are the locations on the Huon and Hobart air stations,
as well as the locations of Kingston (Ki), Cygnet (Cy) and Dover (Do) for
reference. There are six burns running nearly in a line due south of Geeveston.
As noted, only burns were listed in the CSMS database.
Comparing the TFS and CSMS records and obtaining further details from
Forestry Tasmania provided some clarification to this plot. The four CSMS–
recorded burns listed in Table 2 were the burns carried out by Forestry Tasmania
on the 15th of March in the Huon region. In summary:
• 1) The southernmost 51 ha burn in Figure 6 corresponds to CSMS burn
ID 1.
• 2) The third southernmost burn (with an area of zero in Figure 6) corresponds to CSMS burn ID 2, and was of 79 ha in size. Originally a
different coupe (shown as the 55 ha burn, second southernmost in in Figure 6) was planned to be burnt instead, but the change was made due to
local conditions on the day.
• 3) CSMS burn ID 3 is fourth southernmost burn in Figure 6, of size 23 ha.
• 4) CSMS burn ID 4 is to the immediate north–west of Dover in Figure 6,
and was of area 8 ha. Originally the burn to the immediate south–west
of Geeveston (of zero listed area in Figure 6) was planned by Forestry
Tasmania instead, but again the change was made on the day to suit local
conditions.
Hence, for the 15th of March, of the known burns that were conducted to
the south of Geeveston and Dover all were carried out by Forestry Tasmania.
4
4.1
Analysis
Smoke concentrations at Dover and Cygnet
There is currently no air quality monitoring in the Dover or Cygnet areas. Only
an estimate can be obtained of the smoke concentrations at these locations on
the 15th of March 2011 from the reports received from members of the public.
At Cygnet some photographs are also available. One is shown in Figure 7 which
shows part of the photographic image2 along with a similar simulated view as
obtained using Google Earth.
No photographs are to hand from Dover for this day. The initial report from
the member of the public at Dover reported visibility was 500 metres during
the smoke event. Subsequent discussion with the complainant determined that
2 Features that may identify the exact location and hence the identity of the photographer
have been omitted.
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Figure 6: Permit burns carried out in southern Tasmania on the 15th of March
2011, as recorded by the Tasmania Fire Service. The burn locations are shown
by the circular symbols. Where given the areas (in hectares) are also shown. An
area of 0 means the burn area was not recorded. The BLANkET air monitoring
stations are shown: GV=Geeveston; HV=Huonville; JB=Judbury; NT=New
Town (Hobart), as well as the two middle Derwent stations of Gretna (GR) and
Bryn Estyn (BE). Also marked are the towns of Kingston (Ki), Dover (Do) and
Cygnet (Cy) to aid in orientation.
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Figure 7: Comparison of a photographic view near Cygnet and the same view
seen in Google Earth. The photo was obtained on the 15th of March 2011 and
shows a degradation of distant visibility due the presence of smoke.
this referred to the height of the thickest part of the plume above the observer.
Local concentrations were lower: smoke was smelt and seen at ground level, but
ground–level visibility appears to have been at least several kilometres.
Estimating particulate concentrations from visibility measurements or estimates is intrinsically difficult. The visibility range is defined as the distance at
which objects, normally visible from a particular location, just become undetectable. A visibility estimate of smoke concentration will be influenced by the
local relative humidity, time of day, look–direction relative to the sun, cloudiness, presence of other aerosols (e.g. dust), and the extent and uniformity of
the smoke, as well as the need for landmarks at known distances to provide a
limiting visual–range estimate. Additionally, and importantly, it needs to be
borne in mind that a local mass concentration (as produced by the BLANkET
dustrak particle counters) and a visibility range (determined by eye or from a
photographic image) are measurements of intrinsically different quantities. A
mass concentration is, as implied by the name, a measure of particle mass per
volume. A visibility range is a measure of the total number of particles in a
viewing column – i.e. an ‘optical depth’. To explicitly consider this further,
consider a uniform smoke plume that covers a wide area. The mass concentration of this uniform plume is the same everywhere, but the number of particles
in a viewing column depends on the length of the column under consideration.
The longer the column (that is, the further one looks) the more particles one
looks through. A particle counter, such as a dustrak as used in the BLANkET
stations, would measure the same mass concentration everywhere in the column,
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Figure 8: A log–log plot of data from the Fairbanks–North Star Borough,
Alaska, of estimated visibility versus PM2.5 concentration.
no matter what length of column is considered, as long as the smoke remained
uniform throughout.
These differences are important, and ultimately limit the validity of deriving
a mass concentration from visibility (range) estimates.
However, for the purposes of completeness, the photograph from Cygnet and
the reported ‘several kilometre’ visibility from Dover will be used to obtain a very
rough estimate of particle concentration. This is derived from data obtained at
Fairbanks, Alaska, of smoke concentrations and visibility.3
Figure 8 shows a log–log plot of PM2.5 data and visibility (in km) derived
from data collected at Fairbanks4 . The dotted line represents a linear fit to the
data. The validity of this line, and, in particular, the validity of extrapolating
this line to higher and lower ranges, is limited, hence the following should be
interpreted cautiously.
Inspection of Figure 7 indicates the visibility range was at least 5 km at the
3 Fairbanks is located in interior Alaska, where summer temperatures can exceed 30 C.
Annual rainfall is low in the Alaskan interior, with much of the precipitation coming as winter
snow rather than as rain. In late summer thunderstorms can start fires in the extensive boreal
forests (principally spruce and birch) that surround Fairbanks. In consequence Fairbanks
often experiences a number of days of high particle levels in late summer.
4 www.co.fairbanks.ak.us/airquality/Docs/ParticulateLevels.pdf
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time of the photograph. Figure 8 suggests this corresponds to an upper limit
near 80 µg m−3 . The peak PM2.5 level measured at Geeveston, approximately
12 km west of Cygnet, at 18:00 AEST was just over 60 µg m−3 . It is possible
then that peak smoke levels at Cygnet were comparable to those at Geeveston.
The reported ‘several kilometre’ visibility at Dover also appears consistent
with a local concentration near 50 to 80 µg m−3 , based on Figure 8.
4.2
Order–of–magnitude calculations
Near 20:00 AEST smoke was measured at Geeveston, Huonville, Judbury, and
Howden (Figure 1). The reports from the public indicated some smoke had not
obviously cleared at Dover and Cygnet. This defines a roughly 40×20 km area
of smoke. For the purposes of an exploratory calculation, it is assumed that
the smoke extends to 500 m altitude. It is further assumed the average smoke
concentration in this volume is near 40 µg m−3 , based on the data in the above
figure. This leads to a total tonnage of particles in this volume near 16 tonnes.
For a particle production rate of 1.5% (i.e. 1.5% of the total fuel consumed is
converted to particles) this implies a fuel tonnage near 1,000 tonnes. A heavy
fuel burn has a loading near 400 t ha−1 , indicating a heavy fuel burn of 2.5 ha
would produce enough smoke to account for the observations. A very–light
fuel burn may have a loading from around 5 t ha−1 (e.g. grass) up to around
50 t ha−1 (scrub, forest–floor fuels), implying a burn in the range of 20–200 ha
would be needed to produce the required particle tonnage. These burn areas
may be lower limits, as the smoke could have extended to areas where there
were no monitoring stations and hence could have filled a greater volume than
assumed here.
The TFS has no record of any large non–forestry burns south of Geeveston
or Dover on the 15th of March 2011.
4.3
Inferred source
The above analysis leads to identifying one or more of the four recorded forest–
industry burns as the likely source of the smoke in the Huon, Channel, and
Hobart areas on the 15th of March.
The MODIS Aqua image for southern Tasmania for 15:00 AEST (16:00 EDT)
for the 15th of March is shown in Figure 9. The locations of the BLANkET
stations are marked with red balloon symbols. Also shown is the location of the
particle counter at Howden (HD), and the location of Southport. The locations
of the four forestry burns are marked by the fire icons, along with the fuel–index
value (effectively the fuel tonnage divided by 10) and ignition times in EDT.
The locations and smoke onset times of the public complaints are also marked
with the ‘smoke’ icons.
A large smoke plume extends eastwards from the far south of Tasmania. As
this image was obtained prior to ignition of the two northernmost burns the
plume must have originated from one of the two earlier burns – judging from
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the appearance of the plume it is probably from the southernmost (and earliest)
burn, ignited at 13:37 EDT.
At the time the MODIS image was obtained a southerly wind was present
at Huonville and Clearys Gates, and had been southerly to south–westerly at
Cape Bruny for an hour and a half. It seems likely that smoke from the two
later burns would have, at some time after ignition, moved north or north–
north–easterly towards the Huon, Channel, and Hobart areas, rather than due
eastwards as occurred earlier in the day prior to the arrival of the wind change.
At low altitudes the wind change may have had a stronger northerly–directed
component than at higher–latitudes, probably due to the interaction of the
surface wind with the southern Tasmanian coastline.
Smoke arrival at Dover at 17:00 EDT was noted in the report from the
member of the public to have arrived in the town largely from the direction of
the hills behind the school, although some smoke coming from the Southport
area was also indicated. Figure 10 shows an oblique view from Google Earth
of south–eastern Tasmania, with the 15th March burns and smoke complaint
locations marked. Also marked are the towns of Dover and Southport. The
white line running westward from Dover is the reported approximate smoke
arrival direction at Dover at 17:00 EDT on the 15th. The report from Dover
also reports ash falling from the plume over the town. The arrival direction and
the presence of ash (indicating the burn was probably relatively local) suggests
that CSM burn 4 (ignited at 16:15 EDT) was the likely source of most of the
smoke that reach Dover at this time, indicating a general westerly wind was
present, at least locally.
It is possible that smoke from earlier burns may have combined with smoke
from the 16:15 burn and joined the general northward movement up the coast
to the Huon and Hobart later on this day. The Bureau of Meteorology carried
out on request a trajectory analysis (which trace the paths of air parcels under the forecast and derived meteorological fields) which is of use for obtaining
more understanding of conditions on the day. The trajectory analysis is however
only a guide as to air parcel movement – it does not explicitly model air movement around small–scale, complex topography, as is present in south–eastern
Tasmania.
The resulting trajectories for an origin at 16:00 AEST are shown in Figures 11 to 14. These show respectively the trajectory paths for CSMS burns 1
to 4, from Table2. The main features are:
• Burn 1: Air parcels originating at ground–level and at 200 m at the location of this burn move towards the Dover and lower Huon River area,
arriving soon after 17:00, and remaining in this locality for several hours
before moving eastwards over Bruny Island.
• Burn 2: Air parcels originating at ground–level and at 200 m at the
location of this burn move north–eastward into the Channel then turn
northerly, arriving at North Bruny Island and Tinderbox around 22:00 AEST.
• Burn 3: Air parcels from this burn, the westernmost (furtherest inland)
15
Figure 9: MODIS Aqua image from 16:00 EDT for the 15th of March 2011.
The location of the four burns, with fuel-indices and ignition times, are shown
as fire icons. The locations and smoke onset times of the three public complaints
relating to the 15th of March are also indicated. The BLANkET air monitoring
stations are shown as the red balloon symbols: GV=Geeveston; HV=Huonville;
JB=Judbury; CG=Clearys Gates; NT=New Town (Hobart). Also marked is
the location of a particle counter at Howden (HD), and the town of Southport
(S’port).
16
Figure 10: Oblique view from Google Earth of south–eastern Tasmania, with
the 15th March burns and smoke complaint locations marked. Also marked are
the towns of Dover and Southport. The white line running westward from Dover
is the reported approximate smoke arrival direction at Dover at 17:00 EDT on
the 15th.
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of the three southern burns, move generally eastwards, with almost no
variation in trajectory with height.
• Burn 4: The ground level air parcel has nearly a 10–hour residency in the
Dover area before moving northwards towards Hobart. The 400 m parcel
moves eastwards.
As noted, the trajectory analysis should be taken as a guide only, particularly
when small–scale movement in region of complex topography is important as
in this case. However, the analysis as it stands suggests that any low–altitude
smoke from burn 1 that reached Dover and the lower Huon would have done so
at a time approximately consistent with the reports of smoke arrival received
from the public. The possibility is noted for completeness that any smoke from
this burn, once in the lower Huon after 17:00 AEST, could have moved further
up river than indicated by the trajectory analysis, reaching the BLANKET
stations at Geeveston, Huonville and Judbury – a strong southerly wind was
observed at Huonville at this time. Smoke at low altitude from burn 2 would
have moved up the Channel towards Tinderbox, with a calculated arrival time
of 2 or so hours after smoke onset was measured at Howden, with a possibility
of then continuing onto Hobart. Smoke from burn 3 is indicated by the analysis
as moving due east, and consequently would not have impacted in the Huon,
the Channel, or at Hobart. Any low–altitude smoke present from burn 4 is
indicated as having a long residency time in the Dover area.
The possibility, indicated from this analysis, that smoke arrived at Dover
from both burn 1 (south of Southport) and burn 4 (north–west of Dover) would
be consistent with the smoke arrival directions indicated from the first public
report listed in Table 1.
The time–profile of smoke concentrations at Howden (Figure 1) is potentially
of interest. The smoke concentrations initially increased from ∼19:00 AEST to
reach a peak near 30 µg m−3 soon after 20:00 AEST, followed by a slight decline.
(Peak concentrations at the two Hobart stations were comparable at around
25 µg m−3 , and were reached at 21:00 AEST.) Shortly before 21:00 AEST at
Howden smoke concentrations rose again, to reach near 50 µg m−3 , exhibiting a
plateau of 2 hours duration. Meteorological data are not available from Howden.
The double–peak in smoke concentrations at Howden may be evidence for two
separate smoke trajectories – one path being from the Channel (which may
have continued into Hobart), the other being from the Huon Valley. This issue
cannot be resolved at present, but is noted again for completeness.
5
Conclusions
An analysis of air quality and meteorological data, together with information
on known burns in far south–east Tasmania, indicates the likely source of the
smoke reported at Dover and Cygnet, and measured in the Huon, Channel, and
Hobart, on the 15th of March 2011 was one or more of four Forestry Tasmania
burns. The peak (instantaneous) PM2.5 concentrations measured at the air
18
Figure 11: BoM trajectory analysis for an origin at 16:00 AEST on the 15th of
March 2011, for the location of burn 1 (Table 2.) The red and the green lines
respectively represent the paths of air parcels originally at 0 and 200 metre
elevation.
19
Figure 12: BoM trajectory analysis for an origin at 16:00 AEST on the 15th of
March 2011, for the location of burn 2 (Table 2.) The red and the green lines
respectively represent the paths of air parcels originally at 0 and 200 metre
elevation.
20
Figure 13: BoM trajectory analysis for an origin at 16:00 AEST on the 15th of
March 2011, for the location of burn 3 (Table 2.) The red, the yellow and the
blue lines respectively represent the paths of air parcels originally at 0, 400, and
800 metre elevation.
21
Figure 14: BoM trajectory analysis for an origin at 16:00 AEST on the 15th of
March 2011, for the location of burn 4 (Table 2.) The red and the blue lines
respectively represent the paths of air parcels originally at 0 and 400 metre
elevation.
22
quality stations were in the range of 40 to 60 µg m−3 in the Huon, and were
near 20 µg m−3 at Hobart, for several hours. The 24–hour average PM2.5 values
were well below the Australian National Environmental Protection Standards.
Estimated concentrations at Dover and Cygnet (derived from photographic and
visibility estimates) appear to indicate comparable concentrations as seen in
the Huon. Trajectory analysis from the Bureau of Meteorology provides some
further insight into the sources, and also indicates the complexity and difficulty
of analysing (and by implication predicting), detailed air movement in regions
of complex topography.
6
Acknowledgements
The use of the NASA MODIS satellite images is acknowledged. The Tasmanian
office of the Bureau of Meteorology is thanked for providing Automatic Weather
Station data and for informative discussions. The Melbourne office of the Bureau of Meteorology carried out the trajectory analysis. The Tasmania Fire
Service provided information from their incident database. Forestry Tasmania provided details of their burns from the 15th of March. Other information
came from the CSMS database of the Tasmanian Forest Practices Authority.
We thank the members of the public who provided information on this event.
Report compiled by J. Innis.
23
7
7.1
Appendix - spatial presentation of PM2.5 and
wind data
Schematic views from BLANkET network data alone
A schematic illustration of the development of the smoke event of the 15th
of March is given in the following figures. Station locations are indicated
by the small upright crosses, and are labelled with the station abbreviation:
GV=Geeveston; JB=Judbury; Hv=Huonville; CG=Clearys Gates; NT=New
Town. The middle Derwent stations of Bryn Estyn (New Norfolk) and Gretna
(labelled BE and GR respectively) are also shown, as is the location of the particle counter at Howden (HD). The Howden data are not plotted on this or the
following figures. The wind direction is indicated by the arrow. The wind speed
is proportional to the arrow length. The scale is illustrated by the 15 km hr−1
wind vector shown and labelled at the left of the map. PM2.5 is indicated by
the colour and size of the diamond symbol at each station.
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Figure 15: Schematic of the smoke event on 15th March: view at 12:00 AEST.
The winds are generally north–easterly at this time.
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Figure 16: 15th March, 14:00 AEST. Geeveston shows a south–west wind. The
wind is southerly at Clearys Gates.
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Figure 17: 15th March, 15:00 AEST. The wind is southerly at Huonville.
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Figure 18: 15th March, 16:00 AEST. The wind remains south–west at Geeveston, and southerly at Clearys Gates. A light southerly is present at Huonville
and Judbury. Some unrelated smoke is seen in the middle Derwent.
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Figure 19: 15th March, 17:00 AEST. The wind is easterly at Geeveston. The
southerly wind is stronger at Huonville.
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Figure 20: 15th March, 18:00 AEST. The southerly wind is generally established
at Judbury, Huonville, and in the Derwent. At Geeveston wind is north–easterly:
smoke levels have risen here. Smoke has reached Judbury and Huonville.
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Figure 21: 15th March, 19:00 AEST. Smoke levels have risen at Huonville and
Judbury. Smoke levels also started rising at Howden (not shown on map) soon
after 19:00.
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Figure 22: 15th March, 20:00 AEST. Significant smoke remains present at Judbury, Huonville, as well and Geeveston.
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Figure 23: 15th March, 21:00 AEST. Smoke levels have dropped at Judbury
at the onset on a northerly wind but remain elevated at Huonville. Smoke has
reached Clearys Gates and New Town (obscured by the Clearys Gates symbol).
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Figure 24: 15th March, 22:00 AEST. Smoke levels have dropped, but smoke
remains present at Huonville, Clearys Gates and New Town.
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Figure 25: 15th March, 23:00 AEST. Smoke levels have dropped at Huonville,
Clearys Gates and New Town.
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7.2
Schematic views including Bureau of Meteorology wind
data
Figure 26: 15th March, 12:30 AEST. Schematic of 15th March 2011 including
data from the Bureau of Meteorology Automatic Weather Stations at Tasman
Island, Cape Bruny, Hartz Mountains, Warra, and Grove. The BOM data are
shown by the thicker arrows. The winds at Warra, Grove and Hartz Mountains
were west to north–westerly. The winds at Cape Bruny and Tasman Island were
northerly.
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Figure 27: 15th March, 13:00 AEST. At 13:00 AEST the winds at Cape Bruny
and Tasman Island were still northerly. A southerly wind was also present at
Grove, with south–westerly winds at Huonville and Warra.
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Figure 28: 15th March, 13:30 AEST. The wind at Cape Bruny has turned
southerly. The wind at Grove has strengthened and moved more southerly.
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Figure 29: 15th March, 19:00 AEST. An example of BOM and BLANkET
winds during the smoke interval at the Huon stations. The winds at Cape
Bruny, Warra and Hartz Mountains were south–westerly. The winds were more
southerly in the Huon Valley
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Figure 30: Extract from the on–line Mercury Newspaper, 15th March, 2011.
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