Transcript Meteorological Evolution and Model Performance for Fire Threat Days Over the Northeast U.S. Joe Pollina1,2, Brian A.

Meteorological Evolution and
Model Performance for Fire Threat
Days Over the Northeast U.S.
Joe Pollina1,2, Brian A. Colle1, Mike Erickson1
1School
of Marine and Atmospheric Sciences
Stony Brook University – SUNY
2National
Weather Service, New York City
and
and Joseph Charney
USDA Forest Service, East Lansing, MI
1995 “Sunrise Fire”
Westhampton, NY
Image taken from
the Cutchogue Fire
Department web
site at
www.cutchoguefiredept.org
1999-Sep 2009 Fire Events (>
100 Acres) Over the Northeast
U.S. (excluding PA and ME).
106 events total from the
Northeast Interagency
Coordination Center
Motivational Questions
• What is climatology of fire-threat days over
the Northeast U.S.? No formal studies have
been done for the entire Northeast.
• What are the large-scale flow patterns
associated with fire threat days across the
Northeast, and how do they evolve?
• What are the important physical processes
that lead to the fire threat?
• How well do mesoscale models predict these
fire threat conditions?
Data and Methods (Climatology)
• Data (Jan. 1998-mid Sep. 2009)
– Obtained 97 “fire threat” days which the National Fire
Danger Rating System (NFDRS) indicates that the fire danger
was “high, very high, or extreme”. This was obtained
through the Wildland Fire Assessment System (WFAS)
website:
http://www.wfas.net/component/option,com_wrapper/Ite
mid,92/
• Methods
– Monthly climatology of Fire Threat Days
– Synoptic Flow Classification
• Based on Yarnal (1993)
– Large scale flow composite of the “fire threat” days
• Used daily North American Regional Reanalysis (NARR)
(Mesinger et al. 2006)
Monthly Climatology of Fire Threat Days
60
PERCENTAGE
50
Normalized Difference
Vegetation Index
for 2008 Apr 14
40
30
20
10
0
Jan
Feb
Mar
Apr
May
Jun
Jul
MONTH
Aug
Sep
Oct
Nov
Dec
Classification of Synoptic Weather
Regimes
• Used Yarnal (1993) classification system that was
developed to describe the different types of surface
pressure patterns associated with West Virginia fire
events.
• Applied 8 different types of weather patterns:
– Pre-high (PH)
– Back of high (BH)
– Extended high (EH)
– High pressure cell to the south (HS)
– High pressure cell to the north (HN)
– Cyclonic conditions with rain (RC)
– Cold front passage (CF)
– Elongated low (EL)
H
H
L
H
H
H
Pre-high
Back of high
Extended high
L
H
High to the south
H
L
High to the north
Distribution of Fire Threat Days For Each
Yarnal Synoptic Type
45
PH=pre-high
EH=extended high
BH=back of high
CF=cold front
HS=high to south
HN=high to north
40
PERCENTAGE
35
30
25
20
15
10
5
0
PH
EH
BH
CF
YARNAL CLASSIFICATION
HS
HN
Distribution of Synoptic Type By Month
20
PH
18
EH (extended high)
16
BH (back of high)
14
Percentage
(pre-high)
CF
(cold front)
12
HS
(high to the south)
10
HN
(high to the north)
8
6
4
2
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Month
Aug
Sep
Oct
Dec
Overall:
PH: 39.2%
EH: 29.9%
BH: 20.6%
CF: 5.2%
HS: 3.1%
HN: 2.1%
NARR Composite of All Fire Threat Days
SLP
500Z
48 hours prior to
events
24 hours prior to
events
Day of the events
NARR Composite of All Fire Threat Days
Relatively dry and Deep PBL (Well-Mixed)
Composite PBL Height (m)
850-mb Relative Humidity (%)
NARR Composite of All Fire Threat Days
Additional Subsidence from Terrain
Composite 900 mb Wind Vector
Composite 2m RH
15-17 April 2008 Overlooks (NY) Fire Event
Overlooks
Fire
04/15/12z
04/15/12z
04/16/12z
04/16/12z
04/17/12z
04/17/12z
Drying and Warming at Albany, NY (4/14-4/17)
1200 UTC 14 April 2008
Surface RH
and wind
observations
for central
and southern
NY
Origin of the Dry Air
4/5 00 UTC
4/6
4/7
4/8
4/12
4/9
4/10
4/11
4/13
4/14
4/15
4/17 12 UTC
4/16 00 UTC
4/17 12 UTC
4/16
4/17
Backward trajectory (every 24 h)
starting at 12 UTC 17 April 2008
Using Hybrid Single-Particle
Lagrangian Integrated
Trajectory (HYSPLIT) program
(Draxler and
Rolph 2003). This
shows where the dry air
was 315 hours prior to
the event, and the path
it took up to the time of
the event.
4/16 00 UTC
4/17 12 UTC
Short-Range Ensemble Systems
Stony Brook Univ. 13 Member Ensemble (00 UTC)
- 7 MM5, 6 WRFv2.2 members at 12 km grid spacing (NAM soil moisture and SST).
- IC: NAM, GFS, CMC and NOGAPS.
- CP: Grell, KF and Betts-Miller.
- PBL MM5: Blackadar, MRF, MY
- PBL WRF: MYJ and YSU.
- MP MM5: Sice, Reis2
- MP WRF: Ferrier, WSM3.
NCEP SREF 21 Member (21 UTC)
- 10 ETA members at 32 km grid spacing.
- 5 with BMJ CP and Ferrier MP.
- 5 with KF CP and Ferrier MP.
- 5 RSM members at 45 km grid spacing.
- 3 with SAS CP and Zhou GFS MP.
- 2 with RAS CP and Zhou GFS MP.
- 3 WRF-NMM members at 40 km grid spacing.
- 3 WRF-ARW members at 45 km grid spacing.
- IC's are perturbed using a breeding technique.
Verification of surface parameters (e.g.,
2-m temp and 10-m wsp) for 109 NWS
stations over NE for March-Sept 20062009

Surface Temperature Mean Error (12-36h) by Member
for Stony Brook and SREF Ensembles
NCEP SREF
(oC)
(oC)
SBU 12-km Ensemble
MYJ
MM5
WRF
SREF sub-group averages
Impact of Using Previous 5 Fire Threat Days
for Bias Correction of Surface Temperature (12-36 h avg)
NCEP SREF
(oC)
(oC)
SBU 12-km Ensemble
MM5
WRF
Note: MAE for SBU+SREF ens mean is 1.84 K (~0.10 K less than best
member, but comparable to SBU mean).
NARR Composite of Top 10 Largest and Smallest Cool Bias on Fire Threat Days
Sea-level
pressure (Pa)
Small T Bias
Large T Bias
Cloud Fraction
(%): Cool bias
associated with
partly cloudy
fire threat days
– model too
Small T Bias
Large T Bias
cloudy??.
Conclusions
• Peak fire threat over the Northeast U.S. occurs during the climatological
spring (~52% of events in April). This is the pre green-up period.
• Fire threat days were classified by synoptic type. Pre-high (39%), extended
high (30%), and back of high (21%) are the major synoptic patterns
associated with a high fire threat.
• NARR composites illustrate high pressure moving south from Canada to
the Northeast U.S., with a corresponding ridge at 500 mb approaching the
Great Lakes.
• Downsloping from northwesterly flow, subsidence from high pressure, and
mixing from large PBL heights are all likely important in bringing in
warmer, drier air to the surface.
• Ensembles have relatively large (cool) biases for fire threat days over the
Northeast U.S., which are larger than the average warm season biases.
• A standard 14-day bias correction (used by many studies) does not work
that well for fire threat days (since weather is more anomalous). A bias
correction using last 5 fire threat days removes most of ensemble bias.