Benjamin Schenkel ([email protected]) and Robert Hart 2012 AMS Annual Meeting
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Transcript of Benjamin Schenkel ([email protected]) and Robert Hart 2012 AMS Annual Meeting
Benjamin Schenkel ([email protected]) and Robert Hart2012 AMS Annual Meeting
Department of Earth, Ocean, and Atmospheric ScienceThe Florida State University
Quantifying the Environmental Memory of Tropical Cyclones: Lingering Footprint
or Climate Amnesia?
Research Sponsored by NASA Earth and Space Science Fellowshipand NSF Grant #ATM–0842618
Motivation
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 2/9
Introduction Methodology Results
Motivation
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 2/9
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How does the poleward movement of tropical cyclones (TCs) impact the large scale circulation?
Introduction Methodology Results
Questions Raised
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 3/9
Credit: http://www.srh.noaa.gov/jetstream/global/images/jetstream3.jpg
• Do TCs transport significant quantities of moisture and heat polewards?
• Is the strength of the Hadley Cell substantially modulated by TCs?
• Do TCs significantly modulate the strength of the jet streams?
• Do the impacts of recurving TCs extend far beyond the time scales of the TC itself?
Cold/Dry: High Surface Pressure Warm/Moist: Low Surface Pressure
TC
Warm/Moist
TC
Warm/Moist
H L
51% of major TCs in the Western North Pacific recurve from the tropics into the mid-latitudes
Introduction Methodology Results
Methodology
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 4/9
• Objective: To analyze the response of the atmospheric environment to TC passage
• Evaluation of mean environmental response will occur using four-dimensional
storm-relative composites of raw variables, raw anomalies, and normalized
anomalies for 14 days prior to 14 days after TC passage at 6 hr intervals
• Reanalysis: A past model simulation that assimilates historical observations
providing the most likely atmospheric state at a given time (Thorne and Vose
2010)
• Composites are constructed using the NCEP Climate Forecast System Reanalysis
(Saha et al. 2011) for TCs in the historical record (e.g. best-track) with intensities
of Saffir-Simpson category 3-5 in the Western North Pacific basin from 1982-2009
(N=257 TCs)
Introduction Methodology Results
Evidence of Hadley Cell Modulation by TCs
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 5/9
Introduction Methodology Results
Evidence of Hadley Cell Modulation by TCs
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 5/9
Large scale response similar to TC Dale with significant anomalies through day 11
Statistically significant area 9000 km by 3000 km in composite domain
Reduced need for the Hadley cell to do work
Introduction Methodology Results
Modulation of Upper Level Jet Stream Circulations by TCs
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 6/9
Introduction Methodology Results
Anomalous heat and moisture of upper level anticyclone of TC pushes tropopause upwards
Modulation of Upper Level Jet Stream Circulations by TCs
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 6/9
Introduction Methodology Results
Strengthening and broadening of TEJ following TC passage
TEJ
Polar Jet
Modulation of Upper Level Jet Stream Circulations by TCs
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 6/9
Introduction Methodology Results
Anomalous westerlies occur in core of polar jet
TEJ
Polar Jet
Potential strengthening or weakening of jet streams depending on how far north TC moves
Quantifying Poleward Energy Transport by TCs
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 7/9
Upwards of 33% increase in peak northward energy transport due to TC at time when contribution from extratropical cyclones is relatively small
Strong increase in southward transport of energy away from tropics in region with relatively marginal climatological transport
Transport of energy away from tropics and into mid-latitudes yields a reduction of over 3% in the local meridional energy gradient for two weeks following TC passage
Introduction Methodology Results
Quantifying Poleward Energy Transport by TCs
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 8/9
Introduction Methodology Results
Majority of anomalous meridional energy transport is sensible heat and potential energy
0.1% 2.5%21.7%75.7%
Percentage of total energy anomaly
Broader Implications
Quantifying the Environmental Memory of TCs Benjamin Schenkel and Robert Hart The Florida State University 9/9
Cold/Dry: High Pressure Warm/Moist: Low Pressure
TCTC
Warmed/Moistened/Lower Pressure
Cooled/Dried/Higher Pressure
How long does the aggregate impact of all TCs from one season last? Weeks? Months?
H LLH
Introduction Methodology Results
Energy Divergence
Energy Convergence
Modulation of the jet streams