Benjamin A. Schenkel and Robert E. AMS Tropical Conference 2012 Department of Earth, Ocean, and Atmospheric Science The Florida State University Assessing the Climate Footprint of Tropical Cyclones: Pertinent Players or Irrelevant Pawns? Research Sponsored by NASA Earth and Space Science Fellowship and NSF Grant #ATM

Motivation Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 2/13 IntroductionMethodologyLarge Scale Impacts of TCs

Motivation Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 2/13 IntroductionMethodologyLarge Scale Impacts of TCs

Motivation ??? Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 3/13 IntroductionMethodologyLarge Scale Impacts of TCs

High Energy Atmospheric Response to TC Passage Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 4/ °N Sfc. Tropopause Does the tropical environmental response extend beyond the SST cold wake? Significant heat and moisture transports IntroductionMethodologyLarge Scale Impacts of TCs Low Energy Significant reduction in meridional energy gradient

Methodology: Quantifying the Large Scale Response to TC Passage Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 5/13 Objective: To analyze the response of the tropical atmospheric environment to TC passage Evaluation of mean environmental response will occur using four- dimensional storm-relative composites of normalized anomalies Composites are constructed using the NCEP Climate Forecast System Reanalysis (Saha et al. 2011) for category 3 to 5 Best-Track TCs in the Western North Pacific from (N=257 TCs) Space-time spectral analysis (Wheeler and Kiladis 1999) used to determine which equatorial waves are responsible for anomalies at tropical latitudes IntroductionMethodologyLarge Scale Impacts of TCs

Large Scale Pressure Anomalies in the Tropics Following TC Passage Large scale response of environment to TC passage similar to TC Yuri 8000 km by 2000 km response to TC passage Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 6/13 IntroductionMethodologyLarge Scale Impacts of TCs

Large Scale Pressure Anomalies in the Tropics Following TC Passage Large scale response of environment to TC passage similar to TC Yuri 8000 km by 2000 km response to TC passage Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 6/13 IntroductionMethodologyLarge Scale Impacts of TCs

Large scale response similar to TC Tip with significant anomalies through day 11 Anomalies are significant (  0.2σ) over an area extending over one-quarter of the circumference of the globe Reduced need for the Hadley cell to do work Large Scale Pressure Anomalies in the Tropics Following TC Passage Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 7/13 IntroductionMethodologyLarge Scale Impacts of TCs

Large Scale Pressure Anomalies in the Tropics Following TC Passage Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 7/13 IntroductionMethodologyLarge Scale Impacts of TCs Vertical cross-sections will be presented next through the domain center Large scale response similar to TC Tip with significant anomalies through day 11 Anomalies are significant (  0.2σ) over an area extending over one-quarter of the circumference of the globe Reduced need for the Hadley cell to do work

Physical Processes Responsible for Cooling and Drying of Equator Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 8/13 IntroductionMethodologyLarge Scale Impacts of TCs Weakening of Hadley cell following TC passage Convergence Divergence Subsidence NorthSouth

Physical Processes Responsible for Cooling and Drying of Equator Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 9/13 IntroductionMethodologyLarge Scale Impacts of TCs Weakening of zonal mean circulation following TC passage Cooling and drying in lower troposphere due to reduction in low level convergence of heat and moisture into ITCZ Anomalous diabatic cooling from reduction in deep convection NorthSouth Next, we will examine the role of equatorial waves in generating these anomalies

Attributing Physical Processes to Equatorial Waves Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 10/13 Normalized mean sea level pressure anomalies averaged for points within five degrees of the equator Negative sea level pressure anomaly associated with TC Positive sea level pressure anomaly at equator IntroductionMethodologyLarge Scale Impacts of TCs EastWest

Attributing Physical Processes to Equatorial Waves: MJO Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 11/13 Normalized mean sea level pressure anomalies averaged for points within five degrees of the equator Negative sea level pressure anomaly associated with TC Positive sea level pressure anomaly at equator Dashed black contours: convectively active MJO IntroductionMethodologyLarge Scale Impacts of TCs EastWest

Attributing Physical Processes to Equatorial Waves: MJO Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 11/13 Normalized mean sea level pressure anomalies averaged for points within five degrees of the equator Negative sea level pressure anomaly associated with TC Positive sea level pressure anomaly at equator Dashed black contours: convectively active MJO Solid black contours: convectively suppressed MJO IntroductionMethodologyLarge Scale Impacts of TCs EastWest

Attributing Physical Processes to Equatorial Waves: MJO Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 11/13 MJO amplitude is maximized at time of TC passage although its magnitude is not significant according to Wheeler and Hendon (2004) Magnitude and relative location of positive pressure anomalies is beyond what can be attributed solely to MJO suggesting that TCs may also have an impact IntroductionMethodologyLarge Scale Impacts of TCs EastWest

Attributing Physical Processes to Equatorial Waves: Kelvin Waves Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 12/13 Dashed orange contours: convectively active Kelvin wave IntroductionMethodologyLarge Scale Impacts of TCs EastWest

Attributing Physical Processes to Equatorial Waves: Kelvin Waves Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 12/13 Dashed orange contours: convectively active Kelvin wave Solid orange contours: convectively suppressed Kelvin wave Triggering of convectively suppressed Kelvin wave is stronger and further east than expected for MJO event IntroductionMethodologyLarge Scale Impacts of TCs EastWest

Attributing Physical Processes to Equatorial Waves: Kelvin Waves Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 12/13 Timing and magnitude of the anomalies may suggest that TCs modulate and possibly initiate Kelvin waves potentially due to the following processes: 1. Suppression of deep convection by the subsident secondary circulation outside the TC inner core 2. TCs “steal” heat and moisture rich air at low levels from their environment IntroductionMethodologyLarge Scale Impacts of TCs EastWest

Conclusion: A Conceptual Model Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 13/ °N Sfc. Tropopause IntroductionMethodologyLarge Scale Impacts of TCs

Conclusion: A Conceptual Model Large scale response of environment to TC passage similar to TC Yuri 0 45°N Sfc. Anomalous flux of heat and moisture converging into TC at expense of environment Tropopause Suppression of precipitation yields cold anomalies due to reduction in diabatic heat release Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 13/13 IntroductionMethodologyLarge Scale Impacts of TCs Significant positive pressure anomalies occur across the entire basin

Time Series of Sensible Heat Tendency Term Anomalies Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 30/13 Introduction MethodologyLarge Scale Impacts of TCs

Vertical Structure of Moisture Anomalies Large scale response of environment to TC passage similar to TC Yuri Assessing the TC Climate Footprint Benjamin A. Schenkel and Robert E. Hart The Florida State University 20/13 Moistening of upper troposphere due to TC Drying of boundary layer due to reduction in sea surface fluxes from cold SST wake from TC Anomalous drying of troposphere following TC passage in region in which TC did not directly pass through IntroductionMethodologyLarge Scale Impacts of TCs