Download Wind Scent Transport - K9 ALERT Search and Rescue Dogs, Inc.

Weather, Wind and
Scent Transport
And the effect this has on
searching
10/17/03
Jeff Orrock, NWS
C. Louis, WCSAR
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What causes air movement..
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What creates the air movements
Temperature differences
Pressure differences
Atmospheric stability
Prevailing, general winds
Topography
Scent ‘pooling’
Scent plume patterns
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What causes the air to move?
 Differences in air pressure!!
– High pressure: clear skies. Air moves clockwise
and downward and is warmed with high
pressure.
– Low pressure: clouds and precipitation. Air
moves counterclockwise, upward, and is cooled
around low pressure.
 Prevailing winds (Jet Stream)
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Temperature, Pressure and Winds
The temperature differences cause pressure
differences in the atmosphere. Wind blows in
an attempt to equalize temperature differences
and to balance the pressure differences
between denser and lighter air. This creates
winds that blow from areas with higher
pressure to those with lower pressure.
When pressure changes rapidly between two
areas, we say that there is a "tight pressure
gradient." The tighter the pressure gradient, the
stronger the.
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Highs and Lows
Lines around the highs and lows, called "isobars,"
connect pressure observations that are the same.
Lows
Center of pressure surrounded on
all sides by higher pressure
Highs
Center of pressure surrounded on
all sides by lower pressure
Air moves counterclockwise
(cyclonically) around the center
Air moves clockwise (anticyclonically) around the center
Area of rising air
Often produces cloudy skies and
precipitation
Area of sinking air
Often suppresses clouds and
precipitation
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Pressure Differences Create
Wind
Higher pressure pushes air toward lower pressure
A half pound per square inch pressure difference between places 500
miles apart will accelerate still air to an 80 mph wind In three hours.
Increase the distance to 1000 mile, and the wind would be only 40 mph after three
hours. These speeds don’t factor in the effects of friction and other forces.
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Copyright 1992, USA TODAY. Reprinted with permission.
Jet streams
 Major influences in regional weather
 Moves from West to East starting at the
northwest of the continent, swooping
southerly, then a northerly swoop towards
the northeast of the continent.
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Jet Stream - Positions
Summer
In summer, jet stream
weakens and is
farther north
Winter
In winter, with greater
temperature
contrasts, jet streams
are stronger and
farther south
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Copyright 1992, USA TODAY. Reprinted with permission.
Jet Stream - Wind Speeds
more than 170 mph
150 mph to 170 mph
125 mph to 150 mph
100 mph to 125 mph
80 mph to 100 mph
The greater the temperature contrasts, the stronger the pressure differences
between warm and cold air. Stronger pressure differences create stronger winds.
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Copyright 1992, USA TODAY. Reprinted with permission.
Upper Air Patterns
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Air streams converging.
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Air streams diverging.
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Air piles up; pressure increasing.
High pressure
area growing;air
flowing out
clockwise.
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Pressure decreasing; air rising
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Low pressure
area growing;air
flowing
counterclockwise
.
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Copyright 1992, USA TODAY. Reprinted with permission.
Cold Fronts
The boundaries between different air masses
are called fronts. Across a front (which extends
vertically as well as horizontally), temperature,
humidity, pressure, and/or wind often change
rapidly over short distances.
•Fast moving with potential of storms
•Winds shift from SW to NW or NE
A cold front is the leading edge of an advancing cold air mass. At the surface, these
fronts mark where cold air overtakes and replaces warmer air. During the spring and
summer, cold fronts often initiate thunderstorms and other severe weather. In cold
weather, they produce hazardous winter conditions. Because the slope of the cold air
mass is steep, temperature, pressure, and weather tend to change dramatically near the
front.
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Warm Fronts
•Rain may be a day away
(slower moving storms)
•Wind shift from SE to SW
The edge of an advancing warm air mass is a warm front. At the frontal
boundary, warmer air overtakes and replaces colder air. Warm fronts generally
bring light or moderate, but steady, precipitation. Notice the slope of the warm
air mass is relatively gentle. Consequently, warm fronts are seldom as distinct
on the surface as cold fronts, and they usually move much more slowly.
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Weather Map
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Localized Weather
•Pressure, temperature, and moisture influence weather. On the small
local scale, patterns and changes in these variables overlay the larger
weather patterns, modifying local weather.
•As a result you might have warmer and drier conditions in the open
and cooler and more humid conditions in a wooded area with wet
ground.
•Small-scale changes in pressure, temperature, and moisture can occur for many
reasons. Topography plays an important role. Smaller sources of moisture also
affect the weather.
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Atmospheric Stability
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Lapse rates
Concentration/exposure
Inversions
Humidity
Scent plume patterns
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Lapse rates
 The amount by which atmospheric temperature
decreases over each unit of vertical distance is
called the environmental lapse rate. It is a
measurement of how rapidly the temperature of
the atmosphere decreases with altitude at any
particular moment in time. It varies from place to
place and time to time. (On the long-term, global
average, dry air, it is about 6.5°C per kilometer, or
3.5°F per 1,000 ft.)
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Lapse Rates
 Explains also how the atmosphere cools as you
rise in altitude.
 Put very simply: heated air moves faster into a
cooler atmosphere
 If rising air remains warmer than surrounding air,
the resulting air is unstable:
– The cooling rate is slowed to 3.3 degrees F. with
saturated air.
– Air is more likely to continue to rise, and with humidity
clouds will form.
– Puffy cumulous clouds will result, supplying the energy
for storms.
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Lift and Atmospheric Instability
An unstable environment is one in which air parcels continue to rise, even
after the lifting forces stop. Instability is important because rising air creates
vertical cloud development that can result in severe storms.
This diagram shows an unstable environment.
The temperature of an air parcel (orange balloon)
starts out at the same temperature as its
surroundings (white line). As it rises, the parcel
cools (yellow line). In this case, the environment
at 10,000 ft is only 20°F compared to the parcel's
temperature of 23°F (temperatures and heights
are chosen only as an example). Because it is
warmer than its environment, the parcel will
continue to rise until it is no longer warmer (at
20,000 ft in this case).
Before a mission: check forecast air stability or instability.
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Lift and Atmospheric Stability
In a stable environment, air parcels that are forced
upward are colder than their surroundings and tend to
sink or spread out. Because the air resists being
moved upward, few clouds may form, and those that
do will be more horizontal than the one shown in the
unstable case. In the example to the right, a parcel
lifted to either 10,000 ft or 20,000 ft would be colder
than the surroundings, and would not rise further.
The temperature inversion is a layer of warmer air on
top of colder air. Inversions inhibit vertical motions
because, a parcel that reaches the inversion layer is
cooling while the environment is warming. Inversions are
key factors in air pollution and fog events because they
act like lids, trapping air. They are common early in the
day, but if the atmosphere heats up enough, the inversion
can be destroyed and the fog (scent) will dissipate and
disperse.
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Stable & Unstable Air
Altitude
Temperature of
surrounding air
Stable air
Unstable air
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Copyright 1992, USA TODAY. Reprinted with permission.
Concentration/exposure
Wind inversely proportional to concentration:
•stronger the wind, lower the concentration
•weaker the wind, higher the concentration
The NWS can help with two important variables
critical for concentrations/exposure to help gauge ideal
SAR condition:
Wind & Stability
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Stability – the downwind plume from an event will be
extremely dependent on the structure of the temperature
profile in the vertical (the stability)
Stable atmosphere
stays very confined
In the vertical
Unstable atmosphere
over stable
stays confined above
surface, but expands
aloft
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Unstable atmosphere
spreads vertically with
time and distance
Very unstable atmosphere
spreads very widely over
the vertical
Stable atmosphere
over unstable
Starts with little vertical
Extent, but with mixing
Expands greatly
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Lifting Mechanisms (thermals)
As the sun heats the earth’s surface, parcels of air
rise like bubbles. These are called “thermals”. As the
air rises and cools, it can produce clouds if it becomes
saturated.
As the sun heats the land, thermals rise, lowering the
pressure. The air over the water is colder and denser,
and therefore is an area of relatively higher pressure.
As the air from the higher pressure flows toward the
lower pressure, it converges and rises.
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Sea Breeze
Land heats up
more quickly than
water
Cold air begins to
push inland
creating a breeze
off the ocean
Rising warm air
cools and moves
over the ocean to
replace cold air that
moved inland
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Copyright 1992, USA TODAY. Reprinted with permission.
Stable or Unstable??
Stable
 Clouds horizontal, no
vertical motion
 Stratus clouds
 Hazy or foggy
 Steady winds
Unstable
 Clouds are vertical,
cumulus
 Flagging tape goes
‘up’ and ‘down’
(upward and
downward currents)
 Gusty winds
 Great visibility
 Leaves spin in circles
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Inversions
 Happens when cold air underlies warmer air at
higher altitudes, causing stable air.
 Temperature inversion may occur during the
passage of a cold front or result from the invasion
of sea air by a cooler onshore breeze.
 Overnight radiating cooling of surface air often
results in a nocturnal temperature inversion which
dissipates after sunrise by the warming of air near
the ground. You will feel the temperature
difference as you move uphill
 An inversion breaks up after sunrise, and your
winds will be crazy
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Nighttime Inversion
(will usually mix out with daytime heating)
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Humidity
(Daily Fluctuation)
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The Explosive Nature of Water...
P Water is the only thing on earth that exists in all 3 phases...
Solid - Liquid - Gas
P Breaking the liquid bonds (vaporization) requires kinetic energy
(heat) which is lost from the environment (ocean)...the ocean cools!
P When water vapor condenses, those liquid bonds reform and heat is
released to the environment (air), where it exhausts upward.
Liquid Water -each
water molecule grips
and releases its
neighbors
6,000,000,000 times
per second
Like little Magnets
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Factors affecting wind strength
 Friction: an object causes the wind to slow
(e.g. a ‘catch’)
 Pressure Gradient force: the pressure
difference and the distance between high
pressure areas and low pressure areas.
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Topographic effects on winds
Slope and Valley winds
– Typically uphill/upslope/upvalley winds during
day, downhill/slope/valley winds at night.
– Up-valley winds begin late morning or early
afternoon, ending in the afternoon
– Down-valley winds begin gradually, ending with
a pooling of cool, heavy air in valley bottoms.
 Search UP in the morning, DOWN at night
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This slope aspect
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Affects humidity levels
Affects vegetation
Affects wind speed
transition times of slope winds.
Wind direction
shadows
sun
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In Hilly Terrain
With morning heating air rising up all slopes will influence the
wind speed you experience based on your location to the
prevailing wind and exposure
Where do you
put your K9s
team in this
example?
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Terrain Effect
Terrain can greatly influence wind direction as well as speed.
Wind channels in valleys and low lying areas. This produces a
wind direction which will vary significantly than the observed
wind measured over the larger area. In the case below the
general NE winds are being influenced by the terrain.
Those searching the low terrain are experiencing
more of a N wind than those elsewhere.
Place your K9
teams at night and
then at 10am the
following morning.
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Wind Flow and Terrain
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Wind Shadow behind Tree Line
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Combination of Terrain and Stability
on Wind Flow
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Terrain and Heating
As discussed before heating
over different terrain will
cause a thermal imbalance
thus generating wind.
In this example the wind is
being influenced by a large
Or other body of water.
The same holds true for
wooded versus open areas.
Place your
K9’s at in
each
example
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Less Friction Over Water
 Enhanced winds on downwind (lee) side of
the lake.
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Picture: scent plume patterns
looping
Fanning
lofting
Fumigating
Evening
Sunrise
Search lower areas
Daytime
Sundown
Search ridges
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Clear weather scent plume patterns
 Looping –occurs in a high degree of
convective turbulence
 Coning – ideal scenting conditions
 Fanning – scent cone compression vertically
and spreads horizontally, usually caused by
an inversion
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Clear weather scent plume patterns
 Fumigating – stable air is above, unstable air at the
surface, allowing cooler air to diffuse down through
to the ground at daybreak. This happens at sunrise
in lower areas… Think of fishing on a lake with the
funny vertical ‘lake fog’. Search lower areas
 Lofting: think of this as the opposite of fumigating.
Happens after sunset on ridges. Occurs after the sun
sets and the ground is cooling. Try searching ridges
and higher slopes. This happens when you have
stable air at the surface, and unstable air on the
ridges.
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Scent Pooling
Occurs in
 Heavy brush: wax myrtles
 Porous rocks
 Depressions
 Moist areas
Pool of scent
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Pooling of cold air
Cold air is heavier and more
dense than warm air. On very
calm days in the woods and
especially on calm nights
colder air will settle into low
lying areas.
This results in higher
humidity values in low areas.
Where do you put your K9 team?
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What might
your K9 do
upon
reaching
this mossy
tree area if
the victim
was located
up the hill?
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What clues tell you when your dog
has or has lost scent?
 Dog’s tail suddenly down, ears suddenly back (whatever is
‘not’ your dogs normal search behavior!)
 Dog looks at you
 Dog stops moving, or blocks your path
 Dog sits
 Dog whines, clearly frustrated
 Dog ‘heals’
 Dog has more interest in food/water/critters
It is our job to determine why!!
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Why does the dog lose the alert?
 You have gone past the subject (Is the wind
at your back now? Could your dog be
interested in a ‘catch’ vs a subject?)
 Wind currents have changed due to
topography
 Wind currents have changed due to weather
changing
 Wind currents changed due to obstruction
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Obstructions
 Eddies: In heavy trees, wind is forced up
over the trees creating turbulence which
eddy on the leeward side of the trees.
 Obstacles: Depending on spacing between
obstacles you create gaps where the dog
can’t detect scent.
 Drainages: Wind velocity and size of dropoffs create scent ‘gaps’
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Chimney effect
 Beginner problem #1: Run into the trees and
hide. The victim sits next to a warm tree on
a sunny day.
 Problem: On hot days, trees heat up so
scent rises straight up into the air rather
than being carried by predominant winds.
 Results: your dog blows past the subject.
 Don’t fret: tell your victim to sit in the Shade!
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POD for dogs based on Air Stability
POD including factors such as
 Wind surface speed
 Stability of air
– Clear or cloud cover
– day or night searching
 For an example of this see POD based on
Graham, Hatch’s Probability of detection for
air-scenting dogs in wilderness searches
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So what creates the weather in my
search area?
The relationships among pressure, temperature, moisture, topography,
stability, and lifting mechanisms are very complex, and they are further
complicated by the interactions on all the scales we have discussed. It is
difficult to make generalizations.
The best advice is to understand the basics of meteorology and the
Current and forecast conditions for your search area.
* Check the weather and then talk to your NWS office about conditions
which might trouble you
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http://weather.gov/raleigh
Watch, Warning and
Advisory display. Shows
current products in effect.
Click on your LOCATION of
interest for best one stop
shopping! (This provides
you a POINT forecast…ie.
Durham)
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Point Forecast is generated
off a 5 km grid providing you
are forecast for more of a
specific location versus a
large area forecast.
Hourly graphs of weather
conditions through 48 hours.
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Detailed
Forecast
provides
weather type
and timing
Useful for
timing of
adverse
weather as well
as a first guess
for HAZMAT,
SAR and other
operations.
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How to get current
Conditions?
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