Photo by Michael Marston - Department of Emergency Services ...

Photos by Mark Cross
Research uncovers
dry slot phenomena
By Femke Mason
This year’s bushfire season is already
well underway and the ongoing
drought and subsequent high fuel load
are presenting a huge challenge for the
State’s fire service.
With these realities facing firefighters,
the availability of research that may
provide an insight into the behaviour of
bushfires comes at a crucial time.
After several years of studying weather
and fire patterns, Bureau of Meteorology
Research Centre and Bushfire
Cooperative Research Centre (CRC)
scientist, Dr Graham Mills, has revealed
that fire behaviour may be affected by
what he refers to as ‘dry slots’.
The dry slot phenomena, as described
in an article produced by the CRC in
conjunction with Dr Mills, consists of
columns of super-dry air that descend to
the earth’s surface from high altitudes.
When this air reaches the surface, a
rapid loss of humidity occurs and causes
extreme drying of fuel on the ground,
often increasing fire activity.
“I’m a meteorologist, not a fire behaviour
scientist, but I understand that fine fuel
moisture content will respond to changes
of atmospheric moisture within an hour,
so these extreme drying events will
affect fine fuel moisture,” Dr Mills said.
“It is known that fire activity increases as
the fuel dries, so there is a potential link.
“To what degree this occurs is hard to
say, but these processes have been
observed for Canberra and one or two
other major fires, so it would seem to
be worth making a careful study of this
phenomenon.”
Dr Mills said that while these dry slots
occurred in the upper levels virtually on
a daily basis throughout the country, and
could be monitored using specialised
satellite imagery, it is the processes that
lead to this air reaching the surface that
formed the basis of his current research.
Preliminary results revealed that this is
more likely to occur in the afternoon,
particularly if the day is hot.
In addition, it would appear that
mountains and wind changes could
also enhance the likelihood of dry slots
affecting fire behaviour.
QFRS Assistant Commissioner Rural
Operations, Steve Rothwell, said the
information revealed from the research
would be useful during the bushfire
season.
“This kind of research is very important
in our planning for the bushfire season,”
Steve said.
“While unfortunately it’s unlikely we’ll
ever be able to predict fire behaviour,
the knowledge that these kinds of
phenomena are more likely to occur in
the afternoon and in geographically
diverse areas, means we can increase
firefighter awareness and safety.
“We now have the knowledge that in areas
surrounded by mountains, and particularly
in the afternoon of a dry and hot day, we
will need to be aware of this possibility.
“With the Bureau of Meteorology’s
support, this information will further
assist with firefighter safety by providing
us with at least some warning of
potential changes to the fire.”
Both Steve and Dr Mills agreed that
while it would be impossible to completely
control the way a fire behaves, the more
research and understanding that can be
undertaken, the better.
“While mother nature is always going to
be too determined when it comes to fire,
if we can get a better handle on these
types of phenomena and provide at
least a few hours of warning, then a
hope might be that we can keep
firefighters even safer,” Dr Mills said.
10 EMERGENCY October 2006 www.emergency.qld.gov.au