12th%20AMS%20Mountain%20Meteorology%20Conference

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Atmospheric Transport and Dispersion of the
Mountain Pine Beetle in British Columbia

• Peter L. Jackson
• Yuanqiao Wen
• Brendan Murphy
• Brenda Moore
• University of Northern British Columbia
• Funded by NRCan/CFS Mountain Pine Beetle
  Initiative

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• Mountain Pine Beetle (MPB) infestation
• has reached epidemic proportions in central BC
  affecting more than 7 million ha and 280 million
  m3 of timber (2004 red attack)

a)
d)

• successful reproduction requires
• mass attack to overwhelm tree

c)
b)
Photo credits (clockwise from top) a)
http//www.ecoforestry.ca/jrnl_artilces/images/17-
1-Partridge-Reuters.jpg bc) http//www.sparwood.b
c.ca/forest/untreated.htm d) http//www.pfc.fores
try.ca/entomology/mpb/management/
silviculture/images/valley_lrg.jpg
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So, what do beetles have to do with mountain
meteorology?

• Besides the name (Mountain Pine Beetle),
  meteorological issues are
• Do MPB utilize winds in the ABL to aid their
  movement?, and if so
• Are they able make the jump across the Rockies
  from the beetle infested area in the BC central
  interior to the Jack Pine stands to the east?

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MPB Behaviour

• behaviour to a large extent is meteorologically
  controlled
• Emergence and flight in summer after 3 days of
  Tmax gt 18 ºC but lt 30C
• Peak emergence for successful mass-attack occurs
  when Tmax gt 25 ºC

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• Dispersion is
• active by flight over short distances / light
  wind
• (local scale within stand over a few km)
• passive advection due to winds and turbulence
  above and within canopy (landscape scale between
  stands perhaps 10-100 km)
• Passive transport may allow epidemic to spread
  rapidly over great distances ? little is known
  about passive transport and this is the focus of
  our work

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MPB Spread in BC 1959-2002

• animation based on annual aerial survey of MPB
  reds (last years attack)

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MPB Infestation 2005

• eastward movement of the front
• spread of MPB limited by the -40 ºC annual
  minimum isotherm
• climate change moves -40 ºC northeastward
• concern over MPB crossing the Rocky Mountains
  and affecting the Jack Pine stands of Northern
  Canada

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Methods

• Assume that passive transport of MPB is similar
  to transport and dispersion of air pollutants
• CSU Regional Atmospheric Modeling System (RAMS)
  to simulate the conditions during MPB flight
• The meteorological fields from RAMS are used to
  calculate trajectories

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• The Synoptic weather pattern determines the
  atmospheric background conditions in which MPB
  emerge and move.
• Average weather pattern(s) associated with MPB
  flight are found using compositing
• This leads to an understanding of regional wind
  patterns during flight

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Synoptic Climatology

• It is likely that passive transport will be most
  important when peak emergence is occurring
• Peak emergence is associated with higher
  temperatures
• Define HC2 as days with Tmax gt 25 C, but lt 30 C

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composite
2002
Evolution of HC2 composite 500 hPa and Lifted
Index (shaded) based on NCEP Reanalysis data as
upper ridge passes atmosphere becomes moderately
unstable (Lifted index negative) resulting in
thermals convecting MPB into the ABL
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Realistic event Simulation
Prince George
Infestation East of Rockies initiated in 2002
Hourly output from RAMS simulation at model level
2 (40 m AGL), from grid 4 at 3 km horizontal
resolution (only every 2nd wind vector shown)
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Back Trajectories ending at 00Z 24 July 2002
(1700 PDT)

• issue is how high do they fly?
• entomologists dont know
• weather radar offers promise

105m
1100m
14

• July 25/26 2005 event similar to synoptic
  climatology
• Warm
• MSLP falling
• Preceded by passage of upper ridge

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• MPB flux in ABL 42 million beetles per hour
  crossing a 1 km line

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Conclusions and Future Work

• MPB emergence, flight, mortality determined by
  weather
• Potential for long-range transport in ABL seen on
  radar and verified by in-situ capture
• Trajectory analysis indicates movement across
  Rockies likely explanation for start of
  infestation to the east
• We have simulated over 60 MPB flight days and
  will be producing ensemble trajectory estimates
  of MPB long-range movement for input into
  Decision Support models used by forest managers

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The End
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Future Work

• Continue idealized simulations in relation to
  terrain
• rules of thumb for beetle spread on the
  landscape
• Continue simulation / validation of case studies
  to predict where beetles go from one year to the
  next.
• used in real time for planning beetle control
  strategies
• Ensemble trajectories created for each grid point
  in the landscape, based on a runs of a large
  number of past peak emergence heating cycle
  events.
• used as input to beetle spread scenarios models
  for forest managers to assess the impact of
  silvicultural and management practices

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Idealized Simulations

• goal is to understand how atmospheric flows in
  complex terrain might affect MPB transport
• Idealized (sinusoidal) terrain inserted into RAMS
• Under light synoptic conditions generate anabatic
  (upslope) flows by day
• Intent is to insert particles into the flow
  field and see how they are dispersed

• N-S vertical cross section with ridges running
  W-E in afternoon
• Contours Temperature