Benjamin A. Schenkel University at Albany, State University of New York, and Robert E. Hart, The Florida State University 38 th Northeastern Storms Conference On the Impacts of Western North Pacific Tropical Cyclones on the Moisture Content of Their Large Scale Tropical Atmospheric Environment Research Sponsored by NASA Earth and Space Science Fellowship and NSF Grant #ATM–

Outline Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 2/16 Motivation and previous research – Overview of tropical cyclone (TC) structure Motivation Results – Spatial scales of anomalous drying caused by TCs – Processes responsible for drying of environment by TCs Summary and conclusions BackgroundResultsConclusionsMotivation

Motivation and previous research – Overview of tropical cyclone (TC) structure Motivation 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 2/16 BackgroundResultsConclusionsMotivation

Primary Circulation of TC 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 3/16 BackgroundResultsConclusionsMotivation Horizontal winds of the TC constitute the “primary circulation” of the TC Lower tropospheric winds are cyclonic with the strongest winds generally found in the eyewall at the TC center Credit: Thomson Higher Education

Primary Circulation of TC 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 3/16 BackgroundResultsConclusionsMotivation Wind field of TC is approximately in gradient wind balance TC is a warm core cyclone meaning that cyclonic winds of TC weaken with height and become anticyclonic in the upper troposphere Credit: Thomson Higher Education

Secondary Circulation of a TC 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 4/16 BackgroundResultsConclusionsMotivation TC also contains a “secondary circulation” consisting of: 1.Lower tropospheric inflow towards low pressure at TC center 2.Ascent in the eyewall 3.Upper tropospheric outflow away from the anticyclone at the TC center 4.Adiabatic descent outside the TC circulation Credit:

Secondary Circulation of a TC 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 4/16 BackgroundResultsConclusionsMotivation If the TC is sufficiently strong, some of air that ascends in the eyewall will adiabatically descend in the TC eye serving to lower the pressure of the TC Secondary circulation results from surface friction which causes air to converge towards TC center primarily in the lower troposphere Credit:

Secondary Circulation of a TC 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 4/16 BackgroundResultsConclusionsMotivation Credit: Secondary circulation is significantly weaker than the primary circulation of the TC

Asymmetric Structure of TCs 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 5/16 BackgroundResultsConclusionsMotivation Credit: CIMMS-UWM TC structure can be very asymmetric particularly in the upper troposphere Both the magnitude and direction of the radial outflow vary significantly in Hurricane Sandy Middle-to-Upper Tropospheric Water Vapor Imagery and Satellite Derived Winds (kt) for Hurricane Sandy at 1500 UTC 25 October 2012 Dry Mois t

Dry Mois t Asymmetric Structure of TCs 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 5/16 BackgroundResultsConclusionsMotivation Credit: CIMMS-UWM TC structure can be very asymmetric particularly in the upper troposphere Both the magnitude and direction of the radial outflow vary significantly in Hurricane Sandy Subtropical jet to the north enhances outflow on northern side of storm with winds exceeding 120 kts! Middle-to-Upper Tropospheric Water Vapor Imagery and Satellite Derived Winds (kt) for Hurricane Sandy at 1500 UTC 25 October 2012 Focus of the results of this talk will be on the impacts of the asymmetric upper tropospheric structure of TCs on its atmospheric environment

Motivation and previous research – Overview of tropical cyclone (TC) structure Motivation 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 6/16 BackgroundResultsConclusionsMotivation

Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 7/16 BackgroundResultsConclusionsMotivation km

Motivation Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 7/16 BackgroundResultsConclusionsMotivation km km

Motivation Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 7/16 BackgroundResultsConclusionsMotivation km km km

Credit: COMET/UCAR Motivation Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 8/ UTC 29 August 1995 BackgroundResultsConclusionsMotivation

Motivating Questions Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 9/16 What is the role of TCs in the tropics? How do TCs impact their tropical atmospheric environment? What are the spatial scales over which TCs impact the tropical atmosphere? Can the impact of TCs upon their tropical atmospheric environment on the aggregate help explain the annual number of TCs? BackgroundResultsConclusionsMotivation

Outline Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 10/16 Motivation and previous research – Overview of tropical cyclone (TC) structure Motivation Results – Spatial scales of anomalous drying caused by TCs – Processes responsible for drying of environment by TCs Summary and conclusions BackgroundResultsConclusionsMotivation

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 will occur using 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 winds  64 kt) in the Western North Pacific equatorward of 36°N from 1982 to 2009 (N = 477 TCs) Reanalysis: A past model simulation that assimilates historical observations providing the most likely atmospheric state at a given time (Thorne and Vose 2010) Impact of TCs on Environmental Moisture Content Benjamin A. Schenkel University at Albany, SUNY 11/16 BackgroundResultsConclusionsMotivation

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 12/16 Precipitable water: measure of depth of liquid water that would result if all the water vapor in the column fell as precipitation TCs primarily impact their atmospheric environment by anomalously drying within two distinct regions BackgroundResultsConclusionsMotivation

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 12/16 Precipitable water: measure of depth of liquid water that would result if all the water vapor in the column fell as precipitation TCs primarily impact their atmospheric environment by anomalously drying within two distinct regions West region: stronger drying with area approximately equal to TC BackgroundResultsConclusionsMotivation West region

West region Southwes t region 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 12/16 Precipitable water: measure of depth of liquid water that would result if all the water vapor in the column fell as precipitation 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 BackgroundResultsConclusionsMotivation

West region Southwes t region 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 12/16 Although the horizontal scales of the drying are large, the anomalies do not last long after TC passage BackgroundResultsConclusionsMotivation

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 12/16 BackgroundResultsConclusionsMotivation West region Southwes t region The remainder of this talk will focus on the processes responsible for dry anomalies to the southwest of the TC… Although the horizontal scales of the drying are large, the anomalies do not last long after TC passage

Physical Explanation of Drying 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 13/16 Outflow Jet TC Anticyclone of TC Outflow Jet BackgroundResultsConclusionsMotivation

Physical Explanation of Drying 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 13/16 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 BackgroundResultsConclusionsMotivation Outflow Jet TC Anticyclone of TC Outflow Jet

Physical Explanation of Drying 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 13/16 Anomalous dry air to the southwest of the TC is immediately downstream of the TC outflow jet Location of the anomalous drying suggests that the upper tropospheric convergence caused by the outflow jet is the cause of the drying BackgroundResultsConclusionsMotivation Outflow Jet TC Anticyclone of TC Outflow Jet Area of significant dry precipitable water anomalies

Review of Divergence Induced by Anticyclonically Curved Jet 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 14/16 Convergence downstream and to the right of the jet axis is due to acceleration associated with the jet streak and the curvature of the flow According to the four quadrant jet streak model, a jet streak is associated with the following divergence pattern due to acceleration of the flow Credit: Beebe and Bates (1965) Divergence due to jet streak Convergence due to jet streak Divergence due to jet streak BackgroundResultsConclusionsMotivation

Review of Divergence Induced by Anticyclonically Curved Jet 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 14/16 Curvature of the flow will also induce divergence upstream and convergence downstream of the anticyclonically curved jet Credit: Beebe and Bates (1965) Divergence due to jet streak Convergence due to jet streak Divergence due to jet streak BackgroundResultsConclusionsMotivation

Review of Divergence Induced by Anticyclonically Curved Jet 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 14/16 Curvature of the flow will also induce divergence upstream and convergence downstream of the anticyclonically curved jet Credit: Beebe and Bates (1965) Convergence due to flow curvature Divergence due to flow curvature BackgroundResultsConclusionsMotivation

Review of Divergence Induced by Anticyclonically Curved Jet 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 14/16 Curvature of the flow will also induce divergence upstream and convergence downstream of the anticyclonically curved jet Added together, the contributions from the jet streak and curvature of the flow lead to strong divergence and convergence to the right of the jet axis and cancel each other to the left of jet axis Credit: Beebe and Bates (1965) Convergence due to flow curvature Divergence due to flow curvature BackgroundResultsConclusionsMotivation

Review of Divergence Induced by Anticyclonically Curved Jet 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 14/16 Curvature of the flow will also induce divergence upstream and convergence downstream of the anticyclonically curved jet Added together, the contributions from the jet streak and curvature of the flow lead to strong divergence and convergence to the right of the jet axis and cancel each other to the left of jet axis Convergence Divergence Credit: Beebe and Bates (1965) BackgroundResultsConclusionsMotivation

Physical Explanation of Drying 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 15/16 BackgroundResultsConclusionsMotivation

Physical Explanation of Drying 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 15/16 Upper tropospheric convergence in right exit region of the equatorward outflow jet yields anomalous subsidence and drying throughout the column Equatorward outflow jet results from interaction of the TC with its environment BackgroundResultsConclusionsMotivation

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 16/16 BackgroundResultsConclusionsMotivation Longitude Height Latitude

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 16/16 BackgroundResultsConclusionsMotivation Longitude Height Latitude

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 16/16 Right exit region of TC outflow jet yields upper tropospheric convergence, subsidence, and lower tropospheric divergence to southwest of TC BackgroundResultsConclusionsMotivation Height Latitude Longitude

Height Latitude 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 16/16 TC outflow jet induces an anomalous drying BackgroundResultsConclusionsMotivation

Longitude Height Latitude 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 16/16 BackgroundResultsConclusionsMotivation The drying of the environment by Western North Pacific TCs may explain the 1700 km spacing between TCs during multiple TC events