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Climatology of High Lapse Rates and Associated Synoptic-Scale Flow Patterns over North America and the Northeast US(1974 2007). Title. Jason M. Cordeira*, Thomas J. Galarneau, Jr., and Lance F. Bosart. Dept. of Earth and Atmospheric Sciences University at Albany/SUNY. NROW X

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  1. Climatology of High Lapse Rates and Associated Synoptic-Scale Flow Patterns over North America and the Northeast US(19742007) Title Jason M. Cordeira*, Thomas J. Galarneau, Jr., and Lance F. Bosart Dept. of Earth and Atmospheric Sciences University at Albany/SUNY NROW X 6 November 2008 Albany, NY Cordeira@atmos.albany.edu Research funded by the National Science Foundation #ATM-0304254 and #ATM-0553017

  2. Motivation Motivation -The influence of high lapse rates on severe weather 12Z 6  00Z 9 June 2007 Eastern extent of 700500-hPa Lapse Rate Contour (8.0 K km1)SPC event archive / RUC analyses 00Z/9 12Z/8 12Z/7 00Z/8 00Z/7 12Z/6 700500-hPa Flow 00Z/7 H7-H5  Hail (168/8) Wind (473/5) Tornado (22) 06Z/7 00Z/8 06Z/8 00Z/9

  3. Objective Objective Using the North American radiosonde network: Part I: • Establish an annual and monthly climatology of high lapse rates over North America Part II: • Examine seasonal and intraseasonal variability of high lapse rates over regions of North America Part III: • Synoptic-scale flow patterns associated with high lapse rates over the Northeast US

  4. Methodology Methodology (1/2) 1. Establish which stations to use in climatology: Filters: 19742007 / 12Z (1014Z) Accounted for “station advection” Normalized to tmax = 12,418(34 years * 365 days + leap = 12,418) Stations with <6,209 radiosonde observations not used(0.5 * tmax) 118 stations

  5. Methodology Methodology (2/2) 2. Data acquisition: [NCDC] Integrated Global Radiosonde Archive (IGRA) ftp://ftp.ncdc.noaa.gov/pub/data/igra/data-por/ 72518 00-06-10  3. Station data: • 700-hPa T,Z • 500-hPa T,Z • 4. Calculated: • Lapse Rate () • Threshold of 8.0 K km1 • Potential Temperature 72429 90-08-28 

  6. Annual Part I: Results - cumulative frequency distribution Maxima centered on: • Elevated terrain • Warm-season phenomenon • Gulf of Alaska • Cold-season phenomenon Variability: • How do these maxima evolve with time? • What are the physical processes associated with each? 1525days/yr 5070 days/yr 13 days/yr 19742007 Shading represents 0.5 Barnes analysis of the station data

  7. Jan Part I: Results - monthly frequency distributions Jan Apr 5 Jul January 19742007 Oct

  8. Apr Part I: Results - monthly frequency distributions Jan Apr 10 Jul April 19742007 Oct

  9. July Part I: Results - monthly frequency distributions Jan Apr 1 Jul July 19742007 Oct

  10. Oct Part I: Results - monthly frequency distributions Jan Apr 1 Jul October 19742007 Oct

  11. Month Sum Part I: Summary - annual and monthly distributions • Cold-season maximum over Gulf of Alaska • Spring-time maximum over Mexico and southern Texas • Translated northwest over the Intermountain West from MayJune • Expansion of Intermountain maximum toward the California coast and Northern Plains JulyAugust Part II: • Examine seasonal and intraseasonal variability of high lapse rates over regions of North America

  12. SCP Part II: Results - regional histograms South Central Plains (SCP) South Central Plains Regional Monthly Frequency Regional Frequency Month

  13. IMW Part II: Results - regional histograms SCP Intermountain West (IMW) Intermountain West Regional Monthly Frequency Regional Frequency Month Note: y-axis scale has changed!

  14. NW Part II: Results - regional histograms IMW Northwest (NW) Northwest Regional Monthly Frequency Regional Frequency Similar for Upper-Midwest Month Note: y-axis scale has changed!

  15. CW Part II: Results - regional histograms Canada West (CW) Canada West Regional Monthly Frequency NW Regional Frequency Month Note: y-axis scale has changed!

  16. NE Part II: Results - regional histograms Northeast (NE) Northeast Regional Monthly Frequency CW Regional Frequency Month Note: y-axis scale has changed!

  17. SSV N Part II: Results - sub-seasonal variability 700500-hPa Lapse Rate Hovmöller 1995 • ‘Transitory’ • Cold season • Synoptic-scale periodicity 1 Jan 1 Mar 1 May 1 Jul 1 Sep 1 Nov 1 Jan 180 165W 105W 150W 135W 120W 90W 5565N Hovmöller Band 9.00 8.50 8.00 7.50 7.00 K km1 2.5 ECMWF Reanalysis 5 latitude of seasonal maximum

  18. SSV S Part II: Results - sub-seasonal variability 700500-hPa Lapse Rate Hovmöller 1995 • ‘Transitory’ • Cold season • Synoptic-scale periodicity • ‘Stationary’ • Warm season • Synoptic-Planetary-scale periodicity 1 Jan ~Albany 1 Mar 1 May 1 Jul 1 Sep 1 Nov 1 Jan 120W 105W 45W 90W 75W 60W 30W 3545N Hovmöller Band 9.00 8.50 8.00 7.50 7.00 K km1 2.5 ECMWF Reanalysis 5 latitude of seasonal maximum

  19. Pot_dist Part II: Results - mean potential temperature N=52,402 700-500-hPa -mean bin [C]

  20. Pot_dist Part II: Results - mean potential temperature Albany Albany ONDJFM Albany (year) Albany AMJJAS N=42 1 700-500-hPa -mean bin [C]

  21. Pot strat Part II: Results - potential temperature stratification Cold-season phenomenon Characteristics: Lower tropospheric warm advection Moist troposphere Low tropopause (~500 hPa) Likely dynamically-driven associated with cold upper-level troughs Intraseasonal movement related to fluctuations in the time-mean storm track 28

  22. Cold_strat Part II: Results - ‘cold season’ flow pattern composite N=28 K/km 48 h 72 h    24 h 0 h        500-hPa Height / Wind and 700-500-hPa Lapse Anomaly

  23. Pot strat Part II: Results - potential temperature stratification Warm-season phenomenon Characteristics: Originated as surface-based mixed layers over elevated terrain High tropopause (~200 hPa) Likely associated with strong surface sensible heating over elevated terrain Intraseasonal movement related to synoptic-scale activity and critical to severe weather (EMLs) 14

  24. Warm_strat Part II: Results - ‘warm season’ flow pattern composite N=14 K/km 48 h 72 h    24 h 0 h        500-hPa Height / Wind and 700-500-hPa Lapse Anomaly

  25. Summary Summary • Two maxima in high lapse rates over North America • Cold season - Gulf of Alaska (5565N) • Warm season - Intermountain West (3545N) • Seasonal variations likely associated with • Fluctuations in the “time-mean storm track” • Surface-based sensible heating over elevated terrain • A blend of the two (especially at middle latitudes) • Intraseasonal variations likely associated with • Synoptic-scale variability (flow patterns, disturbances, etc.) • Albany composite analyses suggest • Cold (warm) season occurrences of high lapse rates originate in Alberta (Colorado) in conjunction with Alberta storm track (eastward advection of high lapse rates) cordeira@atmos.albany.edu

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