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Benjamin A. Schenkel (bschenkel@albany.edu), University at Albany, State University of New York,

Refining the Climate R ole of Tropical C yclones : Key Constituents of the Summer Hadley Cell ?. Benjamin A. Schenkel (bschenkel@albany.edu), University at Albany, State University of New York, and Robert E. Hart, The Florida State University

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Benjamin A. Schenkel (bschenkel@albany.edu), University at Albany, State University of New York,

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  1. Refining the Climate Role of Tropical Cyclones: Key Constituents of the Summer Hadley Cell? Benjamin A. Schenkel (bschenkel@albany.edu), University at Albany, State University of New York, and Robert E. Hart, The Florida State University 4th International Summit on Hurricanes and Climate Change Research Sponsored by NASA Earth and Space Science Fellowship and NSF Grant #ATM–0842618

  2. Results • Conclusions • Motivation • Background Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 2/19

  3. Results • Conclusions • Motivation • Background Motivation Are TCs, on average, responsible for significant energy transports? Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 2/19

  4. Results • Conclusions • Motivation • Background Outline • Background • Review of TC structure • Results: Cross-equatorial energy transports by TCs • Spatial structure of meridional energy transports • Processes responsible for meridional energy transport • Summary and conclusions Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 3/19

  5. Results • Conclusions • Motivation • Background Outline • Background • Review of TC structure • Results: Cross-equatorial energy transports by TCs • Spatial structure of meridional energy transports • Processes responsible for meridional energy transport • Summary and conclusions Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 4/19

  6. Results • Conclusions • Motivation • Background Review of the Secondary Circulation of a TC • Secondary circulation of a TC consists of: • Isothermal radial inflow • Moist adiabatic ascent and radial outflow • Descent caused by radiative cooling • Adiabatic descent outside storm core Vertical Cross Section of TC Secondary Circulation 16 14 12 10 8 Altitude (km) 6 4 2 0 0 100 200 300 400 500 Radius from TC Center (km) Credit: Emanuel (2006) Warmer colors: high potential temperature Colder colors: low potential temperature Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 5/19

  7. Results • Conclusions • Motivation • Background Review of the Secondary Circulation of a TC • Secondary circulation of a TC consists of: • Isothermal radial inflow • Moist adiabatic ascent and radial outflow • Descent caused by radiative cooling • Adiabatic descent outside storm core • Primary focus of this talk will be on impacts of radial outflow on the atmospheric environment of the TC Vertical Cross Section of TC Secondary Circulation 16 14 12 10 8 Altitude (km) 6 4 2 0 0 100 200 300 400 500 Radius from TC Center (km) Credit: Emanuel (2006) Warmer colors: high potential temperature Colder colors: low potential temperature Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 5/19

  8. Results • Conclusions • Motivation • Background Upper-Tropospheric TC Structure • Composite of 200 hPa wind speed (m s-1; contours)and streamlines for North Atlantic TCs • Clockwise flow aloft due to generation of anticyclone from convective heat release • Flow is divergent and asymmetric • Strongest divergence found in “outflow jet” to northeast of TC • Location of outflow jet can change depending on large-scale environmental flow (e.g., polar jet) North South Credit: Merrill (1988) Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 6/19

  9. Results • Conclusions • Motivation • Background Motivating Questions • Can a TC, on average, yield significant cross-equatorial energy transports in the western North Pacific? • How are TCs able to transport energy equatorward? • Which factors (e.g., TC intensity, TC size) do cross-equatorial TC energy transports show the most sensitivity to? • Do western North Pacific TCs play a salient role in aggregate meridional energy transports? Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 7/19

  10. Results • Conclusions • Motivation • Background Outline • Background • Review of TC structure • Results: Cross-equatorial energy transports by TCs • Spatial structure of meridional energy transports • Processes responsible for meridional energy transport • Summary and conclusions Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 8/19

  11. Results • Conclusions • Motivation • Background Methodology: Quantifying Cross-Equatorial Energy Transports by TCs • Objective: To quantify the mean cross-equatorial energy transports from a single TC in the western North Pacific • Evaluation of mean meridional energy transports by TCs utilizes three-dimensional storm-relative composites of atmospheric reanalysis data • Composites are constructed using the NCEP Climate Forecast System Reanalysis (Saha et al. 2010) for TCs (maximum 10-m wind speed ≥ 34 kt) in the western North Pacific equatorward of 21°N from 1982 to 2009 (N = 589 TCs) Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 9/19

  12. Results • Conclusions • Motivation • Background Methodology: Quantifying Cross-Equatorial Energy Transports by TCs • Meridional energy transports will be calculated to quantify the role of TCs in transporting energy out of the tropics: • Term 1: Meridional kinetic energy transports • Term 2: Meridional latent energy transports • Term 3: Meridional potential energy transports • Term 4: Meridional sensible heat transports • Any future reference to meridional energy transports will be referring to meridional transports of TOTAL energy • Total Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 9/19

  13. Results • Conclusions • Motivation • Background Lower-Tropospheric Structure of TC and the Environment • Cyclonic circulation of TC is dominant feature in lower and middle troposphere within composites TC large-scale response of environment to TC passage similar to TC Yuri Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 10/19

  14. Results • Conclusions • Motivation • Background Lower-Tropospheric Transports due to TC and the Environment • Transports by cyclonic circulation largely cancel each other out at a given latitude band • Transports at 925 hPa typify transports in the lower andmiddletroposphere Blue - Southward transport Red - Northward transport large-scale response of environment to TC passage similar to TC Yuri Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 11/19

  15. Results • Conclusions • Conclusions • Motivation • Background Upper-Tropospheric Structure of TC and the Environment • Convective heat release yields anticyclonic circulation in upper troposphere • Equatorward outflow jet found on southeastern flank of upper-tropospheric anticyclone H Outflow Jet large-scale response of environment to TC passage similar to TC Yuri Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 12/19

  16. Results • Conclusions • Motivation • Background Upper-Tropospheric Transports due to TC and the Environment • Equatorward energy transports by TC outflow jet are the dominant feature in deep tropics • Equatorward outflow jet of TC, on average, results in southward transport of energy into Southern Hemisphere Blue - Southward transport Red - Northward transport H large-scale response of environment to TC passage similar to TC Yuri • Next, we will vertically integrate the meridional energy transport anomalies from the surface to 50 hPa to obtain the net contribution of TCs in the troposphere… Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 13/19

  17. Results • Conclusions • Motivation • Background Vertically Integrated Meridional Energy Transports due to TCs • Meridional energy transports by TC are caused by three features: Blue/Dashed - Southward transport Red/Solid - Northward transport Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19

  18. Results • Conclusions • Motivation • Background Vertically Integrated Meridional Energy Transports due to TCs • Meridional energy transports by TC are caused by three features: • Cyclonic circulation of TC Blue/Dashed - Southward transport Red/Solid - Northward transport Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19

  19. Results • Conclusions • Motivation • Background Vertically Integrated Meridional Energy Transports due to TCs • Meridional energy transports by TC are caused by three features: • Cyclonic circulation of TC • Upper-tropospheric anticyclone of TC and equatorward outflow jet Blue/Dashed - Southward transport Red/Solid - Northward transport H Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19

  20. Results • Conclusions • Motivation • Background Vertically Integrated Meridional Energy Transports due to TCs • Meridional energy transports by TC are caused by three features: • Cyclonic circulation of TC • Upper-tropospheric anticyclone of TC and equatorward outflow jet • Extratropical cyclone triggered by interaction of TC with mid-latitudes Blue/Dashed - Southward transport Red/Solid - Northward transport L H Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19

  21. Results • Conclusions • Motivation • Background Vertically Integrated Meridional Energy Transports due to TCs • Meridional energy transports by TC are caused by three features: • Cyclonic circulation of TC • Upper-tropospheric anticyclone of TC and equatorward outflow jet • Extratropical cyclone triggered by interaction of TC with mid-latitudes • Outflow jet will be primary focus of the remainder of the study Blue/Dashed - Southward transport Red/Solid - Northward transport • Next, we will zonally integrate the meridional energy transports across the shaded region to determine the net transports due to TCs across each latitude band… Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19

  22. Results • Conclusions • Motivation • Background Climatological Meridional Energy Transports • Climatology consists of transports due to all phenomena (e.g., Hadley cell, Asian monsoon, TCs) primarily during the summer and fall • Energy is exported out of the Northern Hemisphere tropics • Energy is imported into the Southern Hemisphere tropics, Northern Hemisphere subtropics, and mid-latitudes • Energy Convergence • Energy Divergence large-scale response of environment to TC passage similar to TC Yuri • Energy Convergence Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 15/19

  23. Results • Conclusions • Motivation • Background Comparison of Transports at Time of TC Passage Versus Climatology • Blue line comprised of meridional transports by all phenomena (e.g., TCs, Hadley cell, MJO) at time of TC passage • TCs generally strengthen Hadley cell circulation • Peak transports in the tropics are highly anomalous compared to the subtropics and mid-latitudes • Increased northward transports • Increased southward transports large-scale response of environment to TC passage similar to TC Yuri Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 16/19

  24. Results • Conclusions • Motivation • Background Comparison of Transports at Time of TC Passage Versus Climatology • Southward transports of energy from the Northern Hemisphere tropics to the Southern Hemisphere tropics are primarily due to equatorwardTC outflow jet large-scale response of environment to TC passage similar to TC Yuri Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 16/19

  25. Results • Conclusions • Motivation • Background Outline • Background • Review of TC structure • Results: Cross-equatorial energy transports by TCs • Spatial structure of meridional energy transports • Processes responsible for meridional energy transport • Summary and conclusions Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 17/19

  26. Results • Conclusions • Motivation • Background Conceptual Model of TC Impacts on Meridional Energy Transports Late Summer Western Pacific Hadley Cell Hadley cell Hadley cell Adapted from Waliser et al. (1999) p 30°S 15°S 0 15°N 30°N Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

  27. Results • Conclusions • Motivation • Background Conceptual Model of TC Impacts on Meridional Energy Transports Late Summer Western Pacific Hadley Cell with a Low-Latitude TC TC Hadley cell Hadley cell Adapted from Waliser et al. (1999) p 30°S 15°S 0 15°N 30°N Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

  28. Results • Conclusions • Motivation • Background Conceptual Model of TC Impacts on Meridional Energy Transports Late Summer Western Pacific Hadley Cell with a Low-Latitude TC TC Hadley cell Hadley cell Adapted from Waliser et al. (1999) p Heat and Moisture 30°S 15°S 0 15°N 30°N • TCs are associated with anomalous lower-tropospheric imports of heat and moisture from Southern Hemisphere into Northern Hemisphere Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

  29. Results • Conclusions • Motivation • Background Conceptual Model of TC Impacts on Meridional Energy Transports Late Summer Western Pacific Hadley Cell with a Low-Latitude TC TC Heat and Potential Energy Hadley cell Hadley cell Adapted from Waliser et al. (1999) p Heat and Moisture 30°S 15°S 0 15°N 30°N • TC are also responsible for anomalous upper-tropospheric imports of heat and potential energy from Northern Hemisphere into Southern Hemisphere Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

  30. Results • Conclusions • Motivation • Background Conceptual Model of TC Impacts on Meridional Energy Transports Late Summer Western Pacific Hadley Cell with a Low-Latitude TC TC Heat and Potential Energy Hadley cell Hadley cell Adapted from Waliser et al. (1999) p Heat and Moisture 30°S 15°S 0 15°N 30°N • Net transport of energy from Northern Hemisphere to Southern Hemisphere suggests that TCs may be responsible for locally accelerating the Hadley cell Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

  31. Results • Conclusions • Motivation • Background Questions Raised • Can the average annual frequency of western North Pacific TCs be partially explained by the role of TCs in transporting energy from the Northern Hemisphere into the Southern Hemisphere during the late summer and early fall? • Can cross-equatorial energy transports by TCs help explain the inter-compensation in TC activity that exists between some basins (e.g., North Atlantic and eastern North Pacific; Maue 2009)? • Is the fidelity of general circulation model simulations of future climates potentially impacted if the model is unable to reasonably simulate cross-equatorial energy transports associated with TCs? Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 19/19

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