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AOSC Seminar by Dr. Steve Koch, 10/13/2022

AOSC Seminar

Dr. Steve Koch

University of Arizona


Title: A Review of Mesoscale Gravity Waves and their relation to Spontaneous Balance Adjustment and Deep Convection


Gravity waves are ubiquitous entities in the atmosphere, being generated by topography, wind shear, latent heating, and flow imbalance associated with jets and fronts. Many of these waves display short wavelengths and have little bearing on the weather; however, mesoscale gravity waves (MGW), which have been found to be closely related to the existence of dynamical imbalance, can create coherent precipitation bands composed of ice pellets with lightning, blizzard conditions, or lines of severe convective storms.  The MGW sub-class of highly nonlinear waves can create damaging surface winds, disrupt aviation, and drive rapid changes of water level in both coastal and inland water bodies. These large-amplitude waves wreak havoc on local weather forecasts, being largely unanticipated and misunderstood.

Following a short review on the basics of gravity wave dynamics and terminology, this talk will emphasize the nature and diagnosis of unbalanced components of the mass and momentum adjustments leading to MGW generation and the importance this has on high-impact weather.  It will be shown that MGW genesis is favored as a jet streak propagates away from the upper-level trough axis and toward the inflection axis between the trough and downstream ridge, especially when the horizontal wavelength between this trough and ridge shortens with time, and the jet streak separates from its geostrophic component at the base of the trough and propagates toward the ridge. This evolution is favored when a synoptic cyclone and associated jet streak develop rapidly, especially when accompanied by latent heating.  Increasing separation between the geostrophic wind maximum and the actual jet streak is related to intensifying upper-level flow imbalance commonly associated with strong tropopause folding events, and leads to the repeated development of spontaneous, continuous emission of MGWs.  Convective latent heat release not only increases the flow imbalance, but it helps to maintain ducted MGWs, producing even greater imbalance and consequential increase of MGW emission – essentially, a positive feedback process.




University of Wisconsin – Madison                       Meteorology                          B.S., 1972

University of Wisconsin – Madison                       Meteorology                          M.S., 1974

University of Oklahoma – Norman                        Meteorology                          Ph.D., 1979

Employment and Distinguished Appointments

2021–       Research Professor and Instructor, University of Arizona

2019–       Adjunct Professor, Embry-Riddle Aeronautical University

2013–23  Affiliate Professor, University of Oklahoma

2011–19  Director, National Severe Storms Laboratory (retired)

2009–11  Adjunct External Examiner, North Carolina A&T University

2006–11  Director, Global Systems Division, NOAA/OAR/Earth Systems Research Lab

2004–11  Deputy Director, NOAA/NCAR Developmental Testbed Center

2000–05  Chief, Forecast Research Division, NOAA/OAR/Forecast Systems Laboratory

1993–00  Associate Professor (tenured), North Carolina State University

1980–93  Meteorologist, Lab for Atmospheres, NASA/Goddard Space Flight Center


Selected Honors, Distinctions, and Awards

Citations of refereed journal papers: 5,450, h-Index: 40 (as of 12 Sept 2022)

(based on Google Scholar Citation)

2019               Albert Nelson Marquis Lifetime Achievement honoree

2015               National Weather Association Larry R. Johnson Award recognizing extraordinary accomplishments which significantly contributed to operational meteorology

2008               Fellow, American Meteorological Society

1998               National Weather Association Research Achievement Award

1998               National Weather Service Award for Applied Research

1991               NASA/Goddard SFC Exceptional Achievement Award

Selected Community Service (since 2010)

2021 –       Editorial board member of MDPI journal Meteorology

2021 –       Copy Editor, Advances in Atmospheric Science, Institute of Atmospheric Physics, Chinese Academy of Sciences

2015–18    NOAA VORTEX-SE Program Manager and Executive Committee Chair

2015–17    Member, NOAA Storm Surge Roadmap Executive Steering Committee

2013–16    Member, Executive Committee, AMS Commission on Weather and Climate Enterprise Forecast Improvement Group

2012–        Fellow, Cooperative Institute for Mesoscale Meteorological Studies (CIMMS)

2012:          Executive Committee Chair for Weather Ready Nation Birmingham workshop

2012:          NSF Review Panel for National Center for Atmospheric Research

2012–18    External Advisory Panel, OU Center for Analysis and Prediction of Storms

2011–16    External Advisory Committee, NCAR Earth Observing Laboratory


Contact: Louis Uccellini

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AOSC Seminar

Pre-seminar refreshment: N/A
Seminar: 3:30-4:30pm, Room: ATL 2400(only when in-person)
Meet-the-Speaker: 4:30-5:00pm, Room: ATL 3400(only when in-person) [For AOSC Students only]

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