intense surface cyclone activity in the arctic during the 2005 – 06 and 2006 – 07 cool seasons
DESCRIPTION
Intense Surface Cyclone Activity in the Arctic during the 2005 – 06 and 2006 – 07 Cool Seasons. Brian Silviotti, Lance F. Bosart, and Daniel Keyser Department of Earth and Atmospheric Sciences University at Albany, Albany, New York NSF Grant ATM-0434189 - PowerPoint PPT PresentationTRANSCRIPT
Intense Surface Cyclone Activity Intense Surface Cyclone Activity in the Arctic during the 2005in the Arctic during the 2005––06 06
and 2006and 2006––07 Cool Seasons07 Cool Seasons
Brian Silviotti, Lance F. Bosart, and Daniel KeyserBrian Silviotti, Lance F. Bosart, and Daniel Keyser Department of Earth and Atmospheric Sciences Department of Earth and Atmospheric Sciences
University at Albany, Albany, New YorkUniversity at Albany, Albany, New York
NSF Grant ATM-0434189NSF Grant ATM-0434189
1010thth Northeast Regional Operational Workshop Northeast Regional Operational Workshop 5 November 20085 November 2008
MotivationMotivation
Arctic cyclones not Arctic cyclones not extensively studiedextensively studied
Intense arctic cyclones Intense arctic cyclones
pose economic hazards, pose economic hazards,
especially to shippingespecially to shipping
Source: www.hofstra.edu
Major Arctic Shipping Routes
PurposePurpose
Establish a limited track climatology of Establish a limited track climatology of intense arctic surface cyclonesintense arctic surface cyclones
Relate track climatology to large-scale Relate track climatology to large-scale arctic flowarctic flow
Examine cyclone mergersExamine cyclone mergers
Perform a brief case study of a cyclone Perform a brief case study of a cyclone merger eventmerger event
DatasetsDatasets
GFS 0.5° analysisGFS 0.5° analysis• Storm-track climatology and case studyStorm-track climatology and case study
NCEP–NCAR ReanalysisNCEP–NCAR Reanalysis• Large-scale mean/anomaly computationsLarge-scale mean/anomaly computations
CPC daily teleconnection indicesCPC daily teleconnection indices• 1 Jan 1950 – 30 Jun 20081 Jan 1950 – 30 Jun 2008
SourcesSources• UAlbany DEAS data archiveUAlbany DEAS data archive• ESRLESRL• CPCCPC
MethodologyMethodology DefinitionsDefinitions
• Cool season: 1 Oct – 31 MarCool season: 1 Oct – 31 Mar• Arctic: poleward of 50°NArctic: poleward of 50°N• Intense cyclone: central MSLP ≤ 980 hPa Intense cyclone: central MSLP ≤ 980 hPa
Manually analyzed surface mapsManually analyzed surface maps
• Genesis/lysis timeGenesis/lysis time• Position and trackPosition and track• Central pressureCentral pressure• Merger/nonmergerMerger/nonmerger
Use teleconnection indices Use teleconnection indices
• Arctic Oscillation (AO) and North Atlantic Oscillation (NAO)Arctic Oscillation (AO) and North Atlantic Oscillation (NAO)
Normalize CPC datasetsNormalize CPC datasets
• Obtain a mean (Obtain a mean (μμ) of 0 and a standard deviation () of 0 and a standard deviation (σσ) of 1 ) of 1 for each index datasetfor each index dataset
Large-scale Arctic Flow RepresentationLarge-scale Arctic Flow Representation
PhasePhase σσ Ranges Ranges PercentilesPercentiles
NegativeNegative < −0.43 < −0.43 σσ 0 to 33.33%0 to 33.33%
NeutralNeutral −−0.43 to 0.43 0.43 to 0.43 σσ 33.34 to 66.67%33.34 to 66.67%
PositivePositive > 0.43 > 0.43 σσ 66.68 to 100%66.68 to 100%
Define regimesDefine regimes
• AO/NAO must remain in the positive or negative phase for at AO/NAO must remain in the positive or negative phase for at least five consecutive days for a time period to qualify as a least five consecutive days for a time period to qualify as a positive or negative regimepositive or negative regime
• All other time periods qualify as neutral regimes All other time periods qualify as neutral regimes
Large-scale Arctic Flow RepresentationLarge-scale Arctic Flow Representation
2005–06 Cool-season AO/NAO Time Series2005–06 Cool-season AO/NAO Time Series
AO NAO
Red shading: positive regime
Blue shading: negative regime
2006–07 Cool-season AO/NAO Time Series2006–07 Cool-season AO/NAO Time Series
Red shading: positive regime
Blue shading: negative regime
AO NAO
2005–06 Cool-season 300 hPa 2005–06 Cool-season 300 hPa Height Anomaly and Wind SpeedHeight Anomaly and Wind Speed
Source: www.esrl.noaa.gov
CI = 2.5 m s−1
Wind Speed
CI = 10 m
Height Anomaly
μAO
μNAO
= −0.35= −0.22
Source: www.esrl.noaa.gov
Wind Speed
2006–07 Cool-season 300 hPa 2006–07 Cool-season 300 hPa Height Anomaly and Wind SpeedHeight Anomaly and Wind Speed
CI = 2.5 m s−1CI = 10 m
Height Anomaly
μAO
μNAO
= 0.52= 0.13
Large-scale Arctic Flow SummaryLarge-scale Arctic Flow Summary
2005–06 Cool Season2005–06 Cool Season• Mainly negative AO/NAO patternMainly negative AO/NAO pattern• Weakened polar jetWeakened polar jet
2006–07 Cool Season2006–07 Cool Season• Mainly positive AO/NAO patternMainly positive AO/NAO pattern• Strengthened polar jetStrengthened polar jet
2005–06 Cool-season Storm Tracks2005–06 Cool-season Storm Tracks
Oct–Nov
Dec–Jan
Feb–Mar
50 Storms• Oct–Nov: 20
• Dec–Jan: 21
• Feb–Mar: 9
2006–07 Cool-season Storm Tracks2006–07 Cool-season Storm Tracks
Oct–Nov
Dec–Jan
Feb–Mar
Case Study
95 Storms• Oct–Nov: 25
• Dec–Jan: 46
• Feb–Mar: 24
Cyclogenesis Events vs. AO/NAO Regime (2005–07)Cyclogenesis Events vs. AO/NAO Regime (2005–07)
Arctic more Arctic more active during neutral to positive AO/NAO regimes (strengthened polar jet)
Merger Locations by Month (2005–07)Merger Locations by Month (2005–07)Oct–Nov
Dec–Jan
Feb–Mar
Case Study
39 Mergers• Oct–Nov: 11
• Dec–Jan: 17
• Feb–Mar: 11
Arctic–Arctic Mergers
21
Arctic–Midlatitude Mergers
18
Merger Locations by Strength (2005–07)Merger Locations by Strength (2005–07)970–980 hPa
960–969 hPa
950–959 hPa
< 950 hPa
39 Mergers• 970–980 hPa: 15
• 960–969 hPa: 13
• 950–959 hPa: 9
• < 950 hPa: 2
Case Study
Arctic–Arctic Mergers
Arctic–Midlatitude Mergers
Case StudyCase Study
Example of an arctic–midlatitude cyclone merger Example of an arctic–midlatitude cyclone merger eventevent
Occurred over the North Atlantic southeast of Occurred over the North Atlantic southeast of Greenland during 7–11 Dec 2006Greenland during 7–11 Dec 2006
Two surface cyclones and three positive potential Two surface cyclones and three positive potential vorticity (PV) anomalies mergedvorticity (PV) anomalies merged
Surface Low Tracks and 500 hPa Mean HeightSurface Low Tracks and 500 hPa Mean Height
500 hPa mean height (dam) for 6–12 Dec 2006
MSLP Time SeriesMSLP Time Series
• Well-developed, rapidly strengthening midlatitude cyclone absorbs arctic cyclone
• System deepens 53 hPa in 24 h (1800 UTC 8 Dec – 1800 UTC 9 Dec)
• Merged cyclone reaches lowest MSLP value of 928 hPa on 1200 UTC 10 Dec
PV Anomaly Tracks PV Anomaly Tracks
• PV anomaly “A” breaks off high PV reservoir over Siberia (21 Nov)
• PV anomalies “C” and “D” break off high PV reservoir over North Pole (3–4 Dec)
• PV anomaly “B” breaks off PV anomaly “A” over Labrador Sea (6 Dec)
• PV anomalies “B,” “C,” and “D” merge over North Atlantic (10 Dec)
Surface Lows and PV AnomaliesSurface Lows and PV Anomalies
• PV anomaly “B” induces arctic cyclone on 0000 UTC 7 Dec
• PV anomaly “D” induces midlatitude cyclone on 0000 UTC 8 Dec
• PV anomaly “C” merges with “B” and “D,” helping merged cyclone intensify
1200 UTC 8 Dec 2006 Sounding for Upton, NY1200 UTC 8 Dec 2006 Sounding for Upton, NY
PV anomaly D
Dynamic Tropopause Height:
2630 m
QG Rossby Penetration Depth for PV anomaly “D”:
10320 m
0000 UTC 7 Dec 2006: 300 hPa Wind Speed (kt), 0000 UTC 7 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
1200 UTC 7 Dec 2006: 300 hPa Wind Speed (kt), 1200 UTC 7 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
0000 UTC 8 Dec 2006: 300 hPa Wind Speed (kt), 0000 UTC 8 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
1200 UTC 8 Dec 2006: 300 hPa Wind Speed (kt), 1200 UTC 8 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
0000 UTC 9 Dec 2006: 300 hPa Wind Speed (kt), 0000 UTC 9 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
1200 UTC 9 Dec 2006: 300 hPa Wind Speed (kt), 1200 UTC 9 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
0000 UTC 10 Dec 2006: 300 hPa Wind Speed (kt), 0000 UTC 10 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
1200 UTC 10 Dec 2006: 300 hPa Wind Speed (kt), 1200 UTC 10 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
0000 UTC 11 Dec 2006: 300 hPa Wind Speed (kt), 0000 UTC 11 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
1200 UTC 11 Dec 2006: 300 hPa Wind Speed (kt), 1200 UTC 11 Dec 2006: 300 hPa Wind Speed (kt),
1000–500 hPa Thickness (dam), MSLP (hPa)1000–500 hPa Thickness (dam), MSLP (hPa)
ConclusionsConclusions
145 intense arctic surface cyclones 145 intense arctic surface cyclones occurring over both cool seasons yielding occurring over both cool seasons yielding a frequency of 10–15 per montha frequency of 10–15 per month• High intraseasonal and interannual variabilityHigh intraseasonal and interannual variability
Arctic most active in neutral to positive Arctic most active in neutral to positive AO/NAO regimesAO/NAO regimes• Strengthened polar jet associated with higher Strengthened polar jet associated with higher
frequency of intense arctic stormsfrequency of intense arctic storms
ConclusionsConclusions
Storms most frequent over Gulf of Storms most frequent over Gulf of Alaska/Aleutians and North Atlantic/East Alaska/Aleutians and North Atlantic/East Arctic OceansArctic Oceans• Clustering near end of well-known storm tracksClustering near end of well-known storm tracks
Atlantic more active than the PacificAtlantic more active than the Pacific• More storms tend to form farther north in the AtlanticMore storms tend to form farther north in the Atlantic
ConclusionsConclusions
All mergers occur poleward of 50°NAll mergers occur poleward of 50°N• Storms stay or move into the arcticStorms stay or move into the arctic
Arctic–midlatitude mergers typically occur Arctic–midlatitude mergers typically occur when southern storm is well developedwhen southern storm is well developed• Arctic storm provides extra vorticity; expedites Arctic storm provides extra vorticity; expedites
vorticity growthvorticity growth
Further ResearchFurther Research
Use automated tracking program to include Use automated tracking program to include several more cool seasonsseveral more cool seasons
Other aspects of cyclones vs. regimesOther aspects of cyclones vs. regimes• IntensityIntensity• Mean locationMean location• Merger/nonmergerMerger/nonmerger
Merger BehaviorMerger Behavior• Strongest mergers southeast of GreenlandStrongest mergers southeast of Greenland• Arctic–arctic vs. arctic–midlatitude mergersArctic–arctic vs. arctic–midlatitude mergers
Questions/Comments?Questions/Comments?