Midterm Exam 2006
A. Main Themes: Thunderstorms. Tools. General Meteorology.
1. Thunderstorms
Characteristics: appearance, associated clouds, cells & evolution, movement, climatology
Thunderstorm types & organization:
- Basic storms: air-mass storms, multicell storms, orographic storms,
- Mesoscale convective system: MCS, squall line, bow echo, MCC, MCV
- Supercells: LP, classic, HP
Key altitudes: zi (ML) , LCL, LFC, EL. Also determination of tropopause depth (Ch 6)
Conditions needed for Tstorm convection
- High humidity in the ABL
- Nonlocal Instability and CAPE (SBCAPE, MLCAPE, MUCAPE, nCAPE, etc.)
- Wind shear in the Environment: shear vector, mean shear, total shear, mean wind (storm motion), supercell storm motion (right and left-moving storms), bulk Richardson number
- Triggering mechanisms vs. convective inhibition CIN
Tstorm hazards
- Heavy rain
- Hail: nomenclature, sizes, formation, forecasting, damage, locations, mitigation, BWER
- Downbursts: characteristics, forces, precipitation drag, evaporative cooling, DCAPE, pressure perturbation, microbursts, affect on aircraft
- Outflow winds & gust fronts: characteristics and forcings, haboob, arc cloud
- Lightning: electrical charge formation, behavior, appearance, detection, hazards, safety
- Thunder: shock front, sound wave, ray paths, audibility distance
- Tornadoes: tangential velocity (Rankine combined vortex), core pressure deficit, Fujita scale, TORRO scale, tornado components, types of tornadoes and vortices, outbreaks, storm-relative winds, vorticity (both Ch 12 & 16), mesocyclones & helicity, storm-relative helicity, swirl ratio & multi-vortex tornadoes
Tstorm forecasting
- Outlooks, watches, warnings
- Stability indices for Tstorms: new, old
- Storm chasing, photography, and safety
2. Meteorological Tools (covered in Labs, Tutorials, and Stull course pack):
hodographs (basics: p29-42; tornadoes: 87-88, 90-94) - be able to plot and use hodograph
weather radar
- fundamentals (wavelengths, operations, scans, displays, beam propagation,
- Reflectivity: dBZ, radar equation, bright band, how to interpret radar images, storm tracking
- Doppler velocity: radial velocities, VAD, max range & velocity, tornado & downburst signatures
Polarimetric: uses
soundings/thermo diagrams (all except q-z) - be able to plot soundings and use thermo diagrams
3. General Meteorology
Atmosphere Basics
- meteorological conventions, earth frameworks & time zones, processes.
Thermodynamic state (P, T, r), structure/layers,
Equations: Ideal gas law, hydrostatic, hypsometric
Radiation
- orbital factors, seasonal effects, daily effects,
- Radiation principles: propagation, emission, distribution, absorption, reflection, transmission, Beer's law,
- Surface radiation budget: solar, IR, net.
- Actinometers (radiometers)
Heat
- Sensible and latent
- Lagrangian heat budget for unsaturated air (from Ch 3): air parcels, first law thermo, adiabatic processes,
dry lapse rate, potential temp.
- Lagrangian heat budget for saturated air (from Ch5): moist lapse rate, liquid-water pot. temp,
equiv. pot. temp, wet-bulb pot. temp.
- Eulerian heat budget: advection, conduction, turbulence, radiation, body sources, net budget
- Surface heat budget, Bowen ratio
Moisture
- saturation
- Variables: vapour pressure, mixing ratio, specific humidity, absolute humidity, relative humidity,
- dew-point, LCL, wet-bulb temperature,
- Total mixing ratio
- Lagrangian water budget: conservation of rT on thermo diagram
- Eulerian water budget: advection, precipitation, surface fluxes, turbulent transport
Static Stability –
- Thermo diagrams: components, pseudoadiabatic assumption, identification of diagram type.
- Thermo diagram types: emagram, Stuve, Skew-T, Tephigram
- Thermo diagram applications: state, processes (dry, moist), precipitation, radiative heating/cooling
- Parcels vs. environment: soundings, buoyancy, Brunt-Vaisala freq.
- Flow stability vs. turbulence: parcel method, layer method,
extension of nonlocal parcel method for Tstorms (Ch 16).
Dynamics
- Newton’s 2nd law, Lagrangian momentum budget
Eulerian momentum budget, eq. of motion
- - Forces: advection, pressure gradient, centrifugal, Coriolis, Turb. Drag
- - Winds: geostrophic, gradient, boundary-layer, BL-Gradient, cyclostrophic
- Mass conservation, continuity, incompressible assumption, boundary-layer pumping
- Measuring winds.
B. Textbook Readings (in numerical order)
1. Rauber, Walsh, & Charlevoix 2nd Edition Chapters:
- Ch 1. Atmosphere - all
- Ch 2. Measurements - all
- Ch 3. Vorticity - p54 (Focus box 3.1)
- Ch 6. Forces & Winds - p 115-124
- Ch 17. Thunderstorms - all
- Ch 18. Tornado - all
- Ch 19. Hail - all
- Ch 20. Lightning - all
- Ch 21. Downbursts - all
2. Stull Chapters (from Course Material Pack.):
- Ch 1. Atmosphere - all
- Ch 2. Radiation - all
- Ch 3. Heat - all except wind chill and heat indices
- Ch 5. Moisture - all
- Ch 6. Static Stability – (all except: q-z diagrams, dynamic stability)
- Ch 9. Weather Radar - 22-41
- Ch 10. Dynamics - all
- Ch 12. Vorticity - p233-234
- Ch 16. Thunderstorms - all
- Appendix A. Science - all
- Errata (from web page [home page/textbooks]) - all for the Chapts we covered
C. Friday Videos & DVDs
- Supercell storms, Tstorm types,
- Art of storm chasing
- Tornado Spotters Guide, Extreme tornadoes, Violent Prairie Tornadoes, Tornadoes 2002
- Multi-vortex tornadoes;
- Mesocyclones
- Hail
- Lightning
- Downbursts, gust fronts
(Comprehensive. But emphasizes material since previous midterm, as listed below.)
Items below in [square brackets] will have less emphasis on the final exam. These items were in the readings, but were not covered during lecture.
Main Themes:
Synoptics:
- Weather Maps - WMO, UTC, synoptic observations, synoptic weather maps, station plotting model, weather symbols, surface maps, upper-air constant-pressure maps, [typical maps used in operational meteorology, cross sections], map analysis, isoplething, identification of frontal zones.
- Air Masses and Fronts - anticyclones (highs), characteristics of highs (subsidence, fair weather, light winds), air mass types and formation, [air-mass modification], air-mass boundaries, frontal zones, surface fronts, horizontal and vertical structure (of cold and warm fronts), clouds and precip associated with fronts, mid-tropospheric fronts (occluded fronts), dry lines.
- Lows (Mid-latitude or extra-tropical cyclones) - Bergen cyclone model, formation, evolution, tracks, intensity, seasonality, lifetime, [characteristics (central pressure, vorticity, vertical motion, bad weather), case studies of cyclones in prairies,] cyclolysis, [lows over the NE Pacific Ocean (that approach BC), west-coast weather].
- Weather Forecasting - using local observations of clouds & barometer readings, operational NWP models, limitations of models, research models, useful forecasting interpretation of NWP maps.
Clouds - [processes causing saturation], cloud identification, [cloud classification], sky cover, [cloud sizes and shapes, fog].
Global Circulation - nomenclature, differential heating, meridional temperature gradient, net heat transport by atmosphere and ocean, thermal-wind relationship, thickness, baroclinicity, jet streams (polar and sub-tropical), jet streaks, Hadley cell, trade winds, 3-band general circulation.
Synoptic Dynamics:
- Rossby Waves - troughs and ridges, [beta plane], development of lows and highs, [barotropic and baroclinic instability], long and short Rossby waves, [planetary waves, Rossby radius of deformation, geostrophic adjustment]
- Cyclone Dynamics - cyclogenesis, lee cyclogenesis, conservation of potential vorticity, [spin-up (vorticity tendency, tilting, stretching, quasi-geostrophic approximation, application to idealized weather patterns), upward motion (omega, omega equation, continuity effects, jet stream curvature, jet streak divergence, ageostrophic wind), sea-level pressure tendency (mass budget, diabatic heating), iso-surfaces and their utility (isentropic, isobaric).]
NWP - [numerical approximations, parameterizations, grid points, finite-difference methods, numerical stability, data assimilation, balancing mass and flow fields, analysis, forecasts, post processing including forecast refinement (MOS, Kalman filtering), verification (accuracy, skill, anomaly correlation)], persistence, nonlinear dynamics and chaos (Lorenz strange attractor, butterfly effect), ensemble forecasting.
Hurricanes (Tropical Cyclones) - characteristics (spiral bands, eye, eye wall), Saffir-Simpson intensity scale, damage, tracks and steering winds, seasonality, favorable and unfavorable environments, sea-surface temperature, dynamics (triggering in easterly waves, spin-up and development), thermodynamics (warm core, [Carnot cycle]), central pressure vs max wind speed, hurricane structure (pressure, velocities, temperature, clouds), storm surge [(pressure head, Ekman transport, Kelvin wave), surface wind waves,] forecasting hurricanes, case studies, The Perfect Storm, hurricane safety.
Detailed List of Topics , in the Order Covered: see Syllabus (handout or on-line).
.
Textbook Readings (in numerical order)
Rauber, Walsh, & Charlevoix (2nd Ed.) Chapters :
...Synoptics :
- Ch 4. Forecasting - all
- Ch 7. Lows and Highs – all
- Ch 8. Air Masses and Fronts - all
- Ch 9. Lows forming east of Rockies - all
...Hurricanes :
.
Stull Chapters:
Misc :
- Ch 7. Clouds – all
- Ch 9. Satellites – p1-21.
Synoptics :
- Ch 12. Global Circulation - all
- Ch 13. Air Masses & Fronts - all
- Ch 14. Mid-Latitude Cyclones – all
- Ch 15. NWP – all
Hurricanes :
.
Labs/Tools :
- Lab 3: Weather Satellites - all
- Lab 4: NWP - all
.
Friday Video Themes :
- Perfect Storm & Storm of the Century
- [Hurricane videos.]
- UBC numerical weather forecast maps
.
Synthesis:
Have an ability to use weather maps, satellite loops, radar images, your own observations, and soundings in two ways:
(1) to forecast your local weather, and
(2) to interpret the dominant dynamics.
.
-end-
Roland Stull, UBC
Dec 2006
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