Modelling medium and long-range movement of MPB using atmospheric models

FERIC/FORREX: Mountain Pine Beetle Research Update An Operational Perspective January 25, 2005

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Modelling medium and long-range movement of MPB using

atmospheric modelsPeter L. Jackson

UNBC Environmental Science & EngineeringWith assistance from:

Brendan Murphy, Ben Burkholder, Brenda Moore, Vera Lindsay

Funded by: NRCan/CFS Mountain Pine Beetle Initiative grant awarded to Jackson, Lindgren and Ackerman


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Outline

1. Introduction / Motivation

2. Objectives / Outcomes

3. Methods

4. Synoptic Climatology Results Highlights

5. Atmospheric Modelling – Idealized Case

6. Atmospheric Modelling – Realistic Case

7. Information Needs…


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Introduction / Motivation

• MBP infestation has reached epidemic proportions in central BC affecting 4.2 million ha and 176 million m3 of timber

• Emergence and flight in summer after 3 days of Tmax > 18 ºC but < 30°C

• Peak emergence for successful mass-attack occurs when Tmax > 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 allows 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 fly on hot summer days

• Warmest conditions usually occur under slack synoptic weather conditions

terrain-induced thermal circulations (e.g. mountain/valley winds, anabatic/katabatic flows) and steering of winds by terrain should determine the above-canopy, and the within-canopy air flow


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Objectives

1. Identify synoptic weather patterns present during periods of MPB dispersal

2. Identify fundamental relationships between terrain features, atmospheric flows and MPB fallout zones

3. Assess potential for physics-based meteorological and dispersion models to estimate MPB dispersal from one year to the next


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Methods• Passive transport of MPB is similar to

transport and dispersion of air pollutants

• CSU Regional Atmospheric Modeling System (RAMS) to simulate the atmosphere (wind, temperature, humidity, pressure, etc. on a nested 3D grid)

• The meteorological fields from RAMS will be used to calculate trajectories


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• A basic step prior to modelling is to find the average environmental conditions present during MPB flight

• 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


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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 > 25 C, but < 30 C


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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”

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Relationships between topographic features and MPB: interaction with atmospheric flows

• Morice Lakes has detailed infestation inventory

• General pattern of spread is increasing elevation of new attack each year

• Will be simulating these cases in real terrain

• Also used as “ground truth” for idealized terrain simulations


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Idealized simulation• Vertical cross-section

over a series of hills• One day is simulated

from 5 am PDT to 4 am the next day, each frame is an hour

• Temperature (colour)• Winds (arrows)• Diurnal variation and

onset/collapse of up/downslope flows


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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)

Hasler

Bear Lake

Prince George


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Back Trajectories ending at 00Z 24 July 2002 (17:00 PDT)

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1100m


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Conclusions & Future Work• RAMS seems capable of representing the

conditions during MPB emergence and flight• Approaches to future atmospheric modelling:

1. Continue idealized simulations in relation to terrain– “rules of thumb” for beetle spread on the landscape

2. 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

3. 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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Information Needs

• Need beetle validation / initialization data:– More documented MPB flight / emergence

periods, ideally at daily resolution– More “case studies” of between stand

movement for validation (especially isolated populations)

– MPB time in flight, height of flight – how many fly above the canopy? – Prince George Doppler Radar holds intriguing promise…


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July 14-15, 2004 Peak emergence event


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Doppler radar image

“clear air” returns are some type of insect timing of appearance is consistent with peak emergence of MPB

0.5 degree PPI radar scan from 00Z 15 July 2004 (1700 PDT 14 July 2004)

Reflectivity < 0 DBZ

Echo tops 800 – 1500 m AGL


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The End

Modelling medium and long-range movement of MPB using atmospheric models

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