data$assimila*on$of$satellite$ac*ve$ …math.ucdenver.edu/~jmandel/slides/coimbra2014jm.pdf ·...
TRANSCRIPT
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Data Assimila*on of Satellite Ac*ve Fire Detec*on in Coupled Atmosphere-‐
Fire Simula*on by WRF-‐SFIRE
Jan Mandel University of Colorado Denver
with Adam K. Kochanski, Martin Vejmelka, Jonathan D. Beezley,
and Sher Schranz University of Utah, Czech Acadeny of Sciences, Kitware,
Colorado State University/NOAA
Supported partially by NASA NNX13AH59G, NSF DMS-1216481, and Czech Science Foundation 13-34856S.
VII Interna)onal Conference on Forest Fire Research, Coimbra, Portugal, November 18, 2014
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!SFIRE
Atmosphere!model!WRF
Surface!fire!spread!model
Wind
Heat!and!vapor!fluxes
Fuel!moisture!model
Surface!air!temperature,!rela?ve!humidity,rain
Chemical!transport!model!WRFBChem
Fire!emissions!(smoke)
RAWS fuel moisture sta)ons VIIRS/MODIS fire detec)on
HRRR forecast
Data assimila)on
WRF-‐SFIRE components
Data assimila*on
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Satellite Fire Detec*on – 2010 Fourmile Canyon Fire, Boulder, CO
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MODIS/VIIRS Ac*ve Fire Detec*on Data
• MODIS instrument resolu)on 750m at nadir to 1.6km, geo-‐loca)on uncertainty up to 1.5km, VIIRS resolu)on 375m.
• MODIS processed to 1km detec)on squares available, VIIRS 750m. Research processing VIIRS to 375m polygons exists (Schroeder 2013). Much coarser scale than fire behavior models (10-‐100m)
• False nega*ves are common. 90% detec)on at best. 100m2 flaming fire has 50% detec)on probability (MODIS. VIIRS is be[er but nothing can be ever 100% accurate).
• No detec)on under cloud cover -‐ should not count
• Detec)on squares in arbitrary loca)ons -‐ fire sensed somewhere in the square, not that the whole square would be burning.
• No global, binary fire/no fire map.
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• Data assimila)on = data improve the model in a sta)s)cal sense.
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• Ac)ve Fire detec)on should be used to improve fire modeling in a sta)s)cal sense only, not as a direct input.
• Data assimila)on ≠ cyclic reini)aliza)on from new data.
Assimila*on of Ac*ve Fire detec*on data
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VIIRS Ac*ve Fire Detec*on for 2013 Barker Canyon fire
VIIRS fire detec)on squares
Simulated fire arrival )me Time
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MODIS ac*ve fires detec*on with simulated fire arrival *me
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A method for assimila*on of ac*ve fires detec*on data
• Modify the fire arrival 0me to simultaneously minimize the change and to maximize the likelihood of the observed fire detec;on.
• Inspired by computer vision in Microsoa Kinect, which modifies a model of human mo)on to simultaneously minimize the change and to maximize the likelihood of the observed images (A. Blake, Gibbs lecture at JMM 2014)
• Bayesian sta)s)cs view: maximum posterior likelihood, found by nonlinear least squares.
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Fit the fire arrival )me T to the forecast Tf and fire detec)on data , inspired by computer vision (Microsoa Kinect design, Blake 2014)
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Assimila*on of MODIS/VIIRS Ac*ve Fire detec*on
• Ts = satellite overpass )me • constraint C(T-Ts)=0 : no change of fire arrival )me at igni)on points • f(t,x,y) = likelihood of fire detec)on t hours aaer )me arrival • A =ellip)c differen)al operator to penalize non-‐smooth changes • smooth descent direc)on δ by solving the saddle point problem
J (T ) = ε
2T −T f
A
2− f (T S∫ −T ,x, y)dxdy → minC (T−T f )=0 ,
Aδ +Cλ = ∂
∂tf (T S −T ,x, y), CTδ = 0,
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f(t,x,y) : log of the likelihood of fire detec)on as a func)on of the )me t elapsed since the
fire arrival at the loca)on (x,y)
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Assimila*on of the VIIRS Fire Detec*on into the Fire Arrival Time for the 2012 Barker Fire
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Forecast Search direc)on
Analysis Fireline = contour of fire arrival )me
Decrease of the fire arrival )me
VIIRS fire detec)ons
Time
Forecast fire arrival )me
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But fire is coupled with the atmosphere
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Atmosphere
Heat release
Fire propaga)on
Wind Heat flux
• Heat flux from the fire changes the state of the atmosphere over )me.
• Then the fire model state changes by data assimila)on. • The atmospheric state is no longer compa)ble with the fire. • How to change the state of the atmosphere model in
response data assimila)on into the fire model? • And not break the atmospheric model.
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Spin up the atmospheric model aRer the fire model state is updated by data assimila*on
Fire arrival )me changed by data assimila)on
Ac*ve fire detec*on
Atmosphere out of sync with fire
Forecast fire simula)on
Coupled atmosphere-‐fire
Replay heat fluxes derived from the changed fire arrival *me
Rerun atmosphere model from an earlier *me
Con)nue coupled fire-‐atmosphere simula)on
Atmosphere and fire in sync again
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Conclusion • A simple and efficient method – implemented by FFT 2-‐3 itera)ons are sufficient to minimize the cost func)on numerically, 1 itera)on already pre[y good
• Pixels under cloud cover do not contribute to the cost func)on
• Standard bayesian data assimila)on framework Forecast + data = analysis
• Future: – Ac)ve fire detec)on likelihood from the physics and the instrument proper)es?
– Combina)on with standard data assimila)on into the atmospheric model, e.g. add 4DVAR cost func)on?
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