The Understanding Severe Thunderstorms and Alberta Boundary Layers
The Understanding Severe Thunderstorms and Alberta Boundary Layers Experiment (UNSTABLE): Overview and Preliminary Results 24 th Conference on Severe Local Storms 31 October, Savannah, GA • Neil M. Taylor 1, D. Sills 2, J. Hanesiak 3, J. A. Milbrandt 4, C. D. Smith 5, G. Strong 6, • S. Skone 7, P. J. Mc. Carthy 8, and J. C. Brimelow 3 • • 1 Hydrometeorology and Arctic Lab, Environment Canada Physics and Severe Weather Research Section, Environment Canada 3 Centre for Earth Observation Science (CEOS), University of Manitoba 4 Recherche en Prévision Numérique [RPN] (Numerical Weather Prediction Research Section), Environment Canada 5 Climate Research Division, Environment Canada 6 Department of Earth and Atmospheric Sciences, University of Alberta (Adjunct) 7 Department of Geomatics Engineering, University of Calgary 8 Prairie and Arctic Storm Prediction Centre, Environment Canada 2 Cloud
UNSTABLE Rationale Existing real-time surface observations over a region of the AB foothills 27 -32 > 32 Canada’s Population Density (2006) 22 -26 24 th Conference on Severe Local Storms 31 October, Savannah, GA
Experimental Design UNSTABLE Goals • Improve understanding of ABL processes and CI • Improve accuracy and lead time for warnings • Assess utility of high-res NWP to resolve processes and provide guidance • Revise conceptual models for CI and severe wx Red Deer Secondary Domain Targeting Storm Evolution 15 km Spacing Primary Domain Targeting Storm Initiation 25 km Spacing 3 Main Science Areas 1. ABL moisture and convergence boundaries 2. Surface processes (heat flux) 3. High resolution NWP model forecasts of CI and severe weather 24 th Conference on Severe Local Storms 31 October, Savannah, GA Calgary
Special Instrumentation WMI aircraft w/ AIMMS-20 Instrument Package (T, P, RH, 3 -axis wind & acceleration) MARS Trailer (AERI, WV Radiometer, Radiosondes, Cloud Base Temp. ) CRD Mobile Radiosonde Trailer and Interior Tethersonde Balloon ATMOS (Automated Transportable Meteorological Observation System) AMMOS (Automated Mobile Meteorological Observation System) 24 th Conference on Severe Local Storms 31 October, Savannah, GA Tethersonde
Some (Very) Preliminary Results
Science Question 1 (Taylor and Sills) 2000 UTC 13 July 2008 Existing Stations Indications of moisture gradient and convergence Td (°C) 50 km 24 th Conference on Severe Local Storms 31 October, Savannah, GA
Science Question 1 2000 UTC 13 July 2008 Fixed Stations Indications of a convergence boundary with Td difference 8. 4 °C over 10. 3 km (0. 8 °C km-1) Td (°C) 50 km 24 th Conference on Severe Local Storms 31 October, Savannah, GA
Science Question 1 2000 UTC 13 July 2008 Mobile Stations • Delineation of the boundary enhanced by addition of mobile observations • From AMMOS overall moisture difference of 8. 7 °C over 0. 5 km (16. 8 °C km-1 or 7. 2 g kg-1 km -1) Td (°C) m k 40 • Aircraft and other data undergoing analysis 24 th Conference on Severe Local Storms 31 October, Savannah, GA
Science Question 1 20: 48: 02 Z to 20: 48: 38 Z AMMOS • Two-second sample • • • observations Transect nearly perpendicular to orientation of boundary Embedded dewpoint change of 4. 8 °C over 179 m (26. 9 °C km-1 or 11. 0 g kg-1 km-1) Boundary traversed by multiple vehicles with similar moisture gradients 6 6 7 6 8 5 4 8 3 2 7 1 6 518 m 0 24 th Conference on Severe Local Storms 31 October, Savannah, GA 6 Strongest Td change 4. 8 °C over 179 m (26. 9 °C km-1) 0 1 2 3 6 4 5
Science Question 1 00 UTC MB 1 and MB 2 Radiosondes Evidence of elevated residual layer of warm air from dry side of boundary ~ 3700 m AGL dry and warm ABL with westerly wind 00 Z MB 1 and MB 2 Soundings ~ 1400 m AGL moist and cool with veering winds and cap ~ 700 mb 24 th Conference on Severe Local Storms 31 October, Savannah, GA
Science Question 2 (Hanesiak) 20 July 2008 Crops vs. Forest 16 UTC Soundings - MB 1 and MB 2 Research Flight Tracks 20 July 2008 600 700 Crops Forest MB 2 750 800 850 MB 1 Potential Temperature and Mixing Ratio from Research Flight at ~ 1400 m ASL Forest Crops 24 th Conference on Severe Local Storms 31 October, Savannah, GA
Science Question 3 (Milbrandt) Nested 1 -km LAM Runs • Real-time 2. 5 -km limited-area forecast runs • are produced daily by Environment Canada Nested 1 -km runs were performed daily from June 1 – August 31, 2008 for a special grid over the UNSTABLE domains Td + WINDS Surface Dewpoint and Wind • Standard and experimental forecast fields • available via website each morning Images and model data archived for future analysis and comparison to data collected during the UNSTABLE IOP 24 th Conference on Severe Local Storms 31 October, Savannah, GA Synthetic Reflectivity
And Finally…. In Conclusion… 24 th Conference on Severe Local Storms 31 October, Savannah, GA
Thank You! 24 th Conference on Severe Local Storms 31 October, Savannah, GA Photo courtesy Heather Rombough
- Slides: 14