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

Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY2/19 Backgroun d ResultsConclusion s Motivatio n

Backgroun d ResultsConclusion s Motivatio n Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY2/19

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 Outline Backgroun d ResultsConclusion s Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY3/19

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 Outline Backgroun d ResultsConclusion s Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY4/19

Review of the Secondary Circulation of a TC Credit: Emanuel (2006) Altitude (km) Radius from TC Center (km) Vertical Cross Section of TC Secondary Circulation Secondary circulation of a TC consists of: 1.Isothermal radial inflow 2.Moist adiabatic ascent and radial outflow 3.Descent caused by radiative cooling 4.Adiabatic descent outside storm core Warmer colors: high potential temperature Colder colors: low potential temperature Backgroun d ResultsConclusion s Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY5/19

Review of the Secondary Circulation of a TC Credit: Emanuel (2006) Altitude (km) Radius from TC Center (km) Vertical Cross Section of TC Secondary Circulation Secondary circulation of a TC consists of: 1.Isothermal radial inflow 2.Moist adiabatic ascent and radial outflow 3.Descent caused by radiative cooling 4.Adiabatic descent outside storm core Primary focus of this talk will be on impacts of radial outflow on the atmospheric environment of the TC Warmer colors: high potential temperature Colder colors: low potential temperature Backgroun d ResultsConclusion s Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY5/19

Upper-Tropospheric TC Structure Credit: Merrill (1988) 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) Composite of 200 hPa wind speed (m s -1 ; contours) and streamlines for North Atlantic TCs North South Backgroun d ResultsConclusion s Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY6/19

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? Backgroun d ResultsConclusion s Motivation Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY7/19

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 Outline MotivationBackgroun d Conclusion s Results Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY8/19

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) MotivationBackgroun d Conclusion s Results Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY9/19

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 Methodology: Quantifying Cross-Equatorial Energy Transports by TCs Total MotivationBackgroun d Conclusion s Results Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY9/19

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

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

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

Upper-Tropospheric Transports due to TC and the Environment large-scale response of environment to TC passage similar to TC Yuri 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 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… MotivationBackgroun d Conclusion s Results Blue - Southward transport Red - Northward transport Blue - Southward transport Red - Northward transport Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 13/19

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

Vertically Integrated Meridional Energy Transports due to TCs MotivationBackgroun d Conclusion s Results Meridional energy transports by TC are caused by three features: 1.Cyclonic circulation of TC Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19 Blue/Dashed - Southward transport Red/Solid - Northward transport Blue/Dashed - Southward transport Red/Solid - Northward transport

Vertically Integrated Meridional Energy Transports due to TCs MotivationBackgroun d Conclusion s Results Meridional energy transports by TC are caused by three features: 1.Cyclonic circulation of TC 2.Upper-tropospheric anticyclone of TC and equatorward outflow jet Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19 Blue/Dashed - Southward transport Red/Solid - Northward transport Blue/Dashed - Southward transport Red/Solid - Northward transport

Vertically Integrated Meridional Energy Transports due to TCs MotivationBackgroun d Conclusion s Results Meridional energy transports by TC are caused by three features: 1.Cyclonic circulation of TC 2.Upper-tropospheric anticyclone of TC and equatorward outflow jet 3.Extratropical cyclone triggered by interaction of TC with mid-latitudes Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19 Blue/Dashed - Southward transport Red/Solid - Northward transport Blue/Dashed - Southward transport Red/Solid - Northward transport

Vertically Integrated Meridional Energy Transports due to TCs MotivationBackgroun d Conclusion s Results Meridional energy transports by TC are caused by three features: 1.Cyclonic circulation of TC 2.Upper-tropospheric anticyclone of TC and equatorward outflow jet 3.Extratropical cyclone triggered by interaction of TC with mid-latitudes Outflow jet will be primary focus of the remainder of the study 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… Blue/Dashed - Southward transport Red/Solid - Northward transport Blue/Dashed - Southward transport Red/Solid - Northward transport Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 14/19

Climatological Meridional Energy Transports large-scale response of environment to TC passage similar to TC Yuri Energy Divergence Energy Convergence 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 MotivationBackgroun d Conclusion s Results Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 15/19

Comparison of Transports at Time of TC Passage Versus Climatology large-scale response of environment to TC passage similar to TC Yuri 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 MotivationBackgroun d Conclusion s Results Increased northward transports Increased southward transports Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 16/19

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

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 Outline MotivationBackgroun d ResultsConclusion s Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 17/19

Conceptual Model of TC Impacts on Meridional Energy Transports Hadley cell p 30°N15°S015°N30°S Adapted from Waliser et al. (1999) Late Summer Western Pacific Hadley Cell MotivationBackgroun d ResultsConclusion s Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

Conceptual Model of TC Impacts on Meridional Energy Transports Late Summer Western Pacific Hadley Cell with a Low-Latitude TC Hadley cell p 30°N15°S0 TC 15°N30°S Adapted from Waliser et al. (1999) MotivationBackgroun d ResultsConclusion s Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

Conceptual Model of TC Impacts on Meridional Energy Transports Hadley cell p 30°N15°S015°N30°S Adapted from Waliser et al. (1999) TCs are associated with anomalous lower-tropospheric imports of heat and moisture from Southern Hemisphere into Northern Hemisphere MotivationBackgroun d ResultsConclusion s Late Summer Western Pacific Hadley Cell with a Low-Latitude TC Hadley cell TC Heat and Moisture Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 18/19

Conceptual Model of TC Impacts on Meridional Energy Transports Hadley cell p 30°N15°S015°N30°S Adapted from Waliser et al. (1999) MotivationBackgroun d ResultsConclusion s Late Summer Western Pacific Hadley Cell with a Low-Latitude TC Hadley cell TC Heat and Moisture Heat and Potential Energy 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

Conceptual Model of TC Impacts on Meridional Energy Transports Hadley cell p 30°N15°S015°N30°S Adapted from Waliser et al. (1999) MotivationBackgroun d ResultsConclusion s Late Summer Western Pacific Hadley Cell with a Low-Latitude TC Hadley cell TC Heat and Moisture Heat and Potential Energy 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

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? MotivationBackgroun d ResultsConclusion s Cross-Equatorial Energy Transports by TCs Benjamin A. Schenkel University at Albany, SUNY 19/19