1. Benjamin A. Schenkel (bschenkel@albany.edu), University at Albany, State University of New York, and Robert E. Hart, The Florida State University 6th Northeast Tropical Workshop Impacts of Western North Pacific Tropical Cyclones on the Atmospheric Moisture Content of Their Large-Scale Environment Research Sponsored by NASA Earth and Space Science Fellowship and NSF Grant #ATM–0842618

2. Motivation Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 2/18 Backgroun d ResultsConclusion s - 1600 km Motivatio n

3. Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 2/18 - 1600 km - 1700 km Backgroun d ResultsConclusion s Motivatio n

4. Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 2/18 - 1600 km - 1700 km - 1800 km Backgroun d ResultsConclusion s Motivatio n

5. Credit: COMET/UCAR Motivation Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 3/18 1200 UTC 29 August 1995 Motivatio n Backgroun d ResultsConclusion s

6. Background and previous research – Overview of tropical cyclone (TC) structure Results – Spatial scales of anomalous drying caused by TCs – Processes responsible for drying of environment by TCs Summary and conclusions Outline Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 4/18 Motivation ResultsConclusion s Backgroun d

7. Background and previous research – Overview of tropical cyclone (TC) structure Results – Spatial scales of anomalous drying caused by TCs – Processes responsible for drying of environment by TCs Summary and conclusions Outline Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 4/18 Motivation ResultsConclusion s Backgroun d

8. Review of the Secondary Circulation of a TC Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 5/18 Credit: Emanuel (2006) Altitude (km) 0 10 16 8 12 6 4 2 14 0100200300400500 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 Motivation ResultsConclusion s Backgroun d

9. Review of the Secondary Circulation of a TC Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 5/18 Credit: Emanuel (2006) Altitude (km) 0 10 16 8 12 6 4 2 14 0100200300400500 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 Motivation ResultsConclusion s Backgroun d

10. Upper Level Structure of the TC Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 6/18 Credit: Merrill (1988) Clockwise flow aloft due to generation of anticyclone from convective heat release Composite of 200 hPa wind speed (m s -1 ; contours) and streamlines for North Atlantic TCs North South Motivation ResultsConclusion s Backgroun d TC

11. Upper Level Structure of the TC Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 6/18 Credit: Merrill (1988) Clockwise flow aloft due to generation of anticyclone from convective heat release Flow is divergent and generally very asymmetric Strongest divergence found in “outflow jet” well away from TC Location of outflow jet can change depending on large-scale environment (e.g., tropical upper- tropospheric troughs, subtropical jet) Composite of 200 hPa wind speed (m s -1 ; contours) and streamlines for North Atlantic TCs North South Motivation ResultsConclusion s Backgroun d TC

12. Motivating Questions Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 7/18 What impact do TCs have upon their large-scale tropical atmospheric environment? What are the spatial and temporal scales over which TCs alter their atmospheric environment? Is the response of the atmospheric environment sensitive to the size or intensity of the TC? Can the aggregate impact of TCs upon their atmospheric and oceanic environment help explain the annual number of TCs? MotivationBackgroun d ResultsConclusion s

13. Background and previous research – Overview of tropical cyclone (TC) structure Results – Spatial scales of anomalous drying caused by TCs – Processes responsible for drying of environment by TCs Summary and conclusions Outline Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 8/18 MotivationBackgroun d Conclusion s Results

14. Methodology: Quantifying the Large-Scale Response to TCs Objective: To examine how western North Pacific TCs impact the moisture content of their large-scale tropical atmospheric environment Evaluation of mean environmental response to TC passage will utilize three- dimensional storm-relative composites of normalized and raw anomalies Composites are constructed using the NCEP Climate Forecast System Reanalysis (Saha et al. 2010) for strong TCs (maximum 10-m wind speed ≥ 64 kt) in the western North Pacific equatorward of 36°N from 1982 to 2009 (N = 477 TCs) Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 9/18 MotivationBackgroun d ResultsConclusion s

15. Large-Scale Drying in the Tropics Following TC Passage Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 10/18 TCs primarily impact their atmospheric environment by anomalously drying within two distinct regions MotivationBackgroun d Conclusion s Results 0.1σ ≈ 1 kg m -2

16. Large-Scale Drying in the Tropics Following TC Passage Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 10/18 TCs primarily impact their atmospheric environment by anomalously drying within two distinct regions West region: stronger drying with area approximately equal to TC Southwest region: weaker drying in area over twice as large as TC Although the horizontal scales of the drying are large, the anomalies do not last long after TC passage West region MotivationBackgroun d Conclusion s Results Southwes t region 0.1σ ≈ 1 kg m -2

17. Large-Scale Drying in the Tropics Following TC Passage Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 10/18 TCs primarily impact their atmospheric environment by anomalously drying within two distinct regions West region: stronger drying with area approximately equal to TC Southwest region: weaker drying in area over twice as large as TC Although the horizontal scales of the drying are large, the anomalies do not last long after TC passage MotivationBackgroun d Conclusion s Results The remainder of this talk will focus on the processes responsible for dry anomalies to the southwest of the TC… 0.1σ ≈ 1 kg m -2 West region Southwes t region

18. Upper-Tropospheric Forcing of Dry Anomalies in the Southwest Region Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 11/18 Outflow Jet TC Anticyclone of TC Outflow Jet MotivationBackgroun d Conclusion s Results

19. Upper-Tropospheric Forcing of Dry Anomalies in the Southwest Region Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 11/18 To the north and east of TC, air is forced to rotate clockwise around TC’s anticyclone Parcels eventually pass through anticyclonically curved outflow jet to the southeast of the TC Upon exiting the jet, these parcels will converge and subside… MotivationBackgroun d Conclusion s Results Outflow Jet TC Anticyclone of TC Outflow Jet

20. Upper-Tropospheric Forcing of Dry Anomalies in the Southwest Region Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 11/18 Anomalous dry air to the southwest of the TC is immediately downstream of the TC outflow jet Area of statistically significant dry precipitable water anomalies MotivationBackgroun d Conclusion s Results Outflow Jet TC Anticyclone of TC Outflow Jet

21. Linking the TC Outflow Jet to the Dry Anomalies Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 12/18 MotivationBackgroun d Conclusion s Results Adapted from Beebe and Bates (1955) JET MAX Location of dry anomalies relative to the anticyclonically curved jet can vary with latitude

22. Linking the TC Outflow Jet to the Dry Anomalies Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 12/18 MotivationBackgroun d Conclusion s Results Adapted from Beebe and Bates (1955) JET MAX Convergence Divergence Location of dry anomalies relative to the anticyclonically curved jet can vary with latitude TC outflow jet in tropical latitudes has convergence throughout exit region Divergence patterns induced by acceleration/deceleration of flow in presence of weak Coriolis and pressure gradient forces Tropical Environment

23. JET MAX Linking the TC Outflow Jet to the Dry Anomalies Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 13/18 MotivationBackgroun d Conclusion s Results Adapted from Beebe and Bates (1955) Subtropical Environment Divergence pattern induced by two factors: 1.Ageostrophic wind due to change in pressure gradient relative to Coriolis force as parcels move through jet (four quadrant model) Convergence Divergence Convergence Divergence

24. JET MAX Linking the TC Outflow Jet to the Dry Anomalies Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 13/18 MotivationBackgroun d Conclusion s Results Adapted from Beebe and Bates (1955) Subtropical Environment Divergence pattern induced by two factors: 1.Ageostrophic wind due to change in pressure gradient relative to Coriolis force as parcels move through jet (four quadrant model) 2.Ageostrophic wind due to curvature of the flow Convergence Divergence Convergence Divergence Convergence Divergence

25. JET MAX Linking the TC Outflow Jet to the Dry Anomalies Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 13/18 MotivationBackgroun d Conclusion s Results Adapted from Beebe and Bates (1955) Convergence Divergence Subtropical Environment Divergence pattern induced by two factors: 1.Ageostrophic wind due to change in pressure gradient relative to Coriolis force as parcels move through jet (four quadrant model) 2.Ageostrophic wind due to curvature of the flow Net impact of two factors yields convergence in right exit region of TC outflow jet

26. Linking the TC Outflow Jet to the Dry Anomalies Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 14/18 MotivationBackgroun d Conclusion s Results JET MAX Conv. Div. Subtropical Environment JET MAX Conv. Div. Tropical Environment Upper-tropospheric convergence in jet exit region is hybrid of tropical and subtropical environment in composites due to varying latitude of TCs

27. Linking the TC Outflow Jet to the Dry Anomalies Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 15/18 MotivationBackgroun d Conclusion s Results Composite TC Outflow Jet JET MAX Conv. Div. Upper-tropospheric convergence in jet exit region is hybrid of tropical and subtropical environment in composites due to varying latitude of TCs

28. Location of Upper-Tropospheric Convergence Relative to Outflow Jet in Composites Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 16/18 MotivationBackgroun d Conclusion s Results

29. Location of Upper-Tropospheric Convergence Relative to Outflow Jet in Composites Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 16/18 Upper tropospheric convergence in exit region of the equatorward outflow jet yields anomalous subsidence and dry anomalies Upper-tropospheric convergence favored slightly to right of jet axis MotivationBackgroun d Conclusion s Results

30. Conceptual Model of Drying Induced by TCs 0 45°N Sfc. Tropopause Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 17/18 Longitude Height Latitude MotivationBackgroun d ResultsConclusion s

31. Conceptual Model of Drying Induced by TCs 0 45°N Sfc. Tropopause Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 17/18 Longitude Height Latitude MotivationBackgroun d ResultsConclusion s

32. Conceptual Model of Drying Induced by TCs 0 45°N Sfc. Tropopause Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 17/18 Longitude Height Latitude MotivationBackgroun d ResultsConclusion s Dry anomalies located to the west and southwest of TC

33. Longitude Conceptual Model of Drying Induced by TCs 0 45°N Sfc. Tropopause Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 17/18 Exit region of TC outflow jet yields upper-tropospheric convergence, subsidence, and lower-tropospheric divergence to southwest of TC Height Latitude MotivationBackgroun d ResultsConclusion s

34. Longitude Conceptual Model of Drying Induced by TCs 0 45°N Sfc. Tropopause Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 17/18 Height Latitude MotivationBackgroun d ResultsConclusion s Why do we observe approximately 1700 km spacing between WPAC TCs?

35. Large-Scale response of environment to TC passage similar to TC Yuri Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 18/18 Concluding Thoughts MotivationBackgroun d ResultsConclusion s ~1800 km ~2000 km 1800 km Perhaps TCs may control the spacing between TCs during multiple TC events… Anomalous vertical wind shear Anomalous drying ~3800 km TC?