1. ATS/ESS 452: Synoptic Meteorology Friday 08 January 2016 Review Material Overview of Maps Equations of Motion Advection Continuity

2. What is Synoptic Meteorology? Definition: Synoptic meteorology is the study of the structure and evolution of weather systems on spatial scales of order 1000+ km Synoptic means “view together” or “view at a common point.” In this course, you’ll learn to view different parameters of the atmosphere together in order to examine/analyze the weather. What do YOU expect to get out of this course? This course will help you to begin thinking like a meteorologist. BUT…this is not a weather forecasting course…instead you’ll begin to learn how the weather “works.”

3. Quick Map Introduction & What’s Down the Road

4. What is this? What type of map is this? What important information is shown? Notice how the winds flow with respect to the isoheights.

5. What happened here?

9. Heavy rain is forecasted for the TN Valley Relate the location of the upper-level low and it’s associated vorticity to our forecast. Much more goes into making a local forecast, but what’s happening at 500 mb can tell you a lot and is very important on the synoptic scale!

10. Corresponding 60-hour 300mb forecast chart. What does this chart show? The information on this chart (jet level dynamics) will later be important for the ageostrophic wind equation. In general, lift/vertical motion is enhanced in the right-rear and left-front quadrants of jets Notice in this case, the upper-level low is vertically stacked. This isn’t always the case, and in fact, is not good for a developing cyclone. Want to see a westward tilt with height for a developing cyclone – more on this later

11. Later forecast… the previous shortwave that was affecting us is forecasted to move into New England Highly amplified trough pattern has developed over the mid-US Check out the air pouring out of Canada  POLAR air mass What do would you expect after the trough passes the TN Valley?

13. Now… notice how there is a westward tilt with height of the cyclone Also, very strong cold air advection.

15. Scales of Motion ScaleApproximate Length Scale Approximate Time Scale Types of Phenomena Planetary> ~ 6000 km> 1 week Synoptic Scale 1000 – 6000 km1 day – 1 week Mesoscale1 – 1000 km1 hour – 1 day Microscale< 1 km< 1 hour This information is important for simplifying the equations that describe our atmosphere through a process known as scale analysis **Determine which physical processes are most important and which can you neglect. Jet Stream, Trade Winds, Longwave pattern Shortwaves, Fronts, Jet Streaks Thunderstorms, Sea Breezes Turbulence, Boundary Layer Phenomena

16. Variables, Coordinates, & Units Cartesian coordinate system (x, y, z) is the most typical coordinate system used in meteorology -x: zonal (East-West) direction; positive towards the east -y: meridional (North-South) direction; positive to the north -z: vertical (up-dpwn) direction; positive upward What other coordinate system do you think we will use? - Pressure coordinates QuantityUnitSI units and notation LengthMeterM TimeSecondS MassKilogramKg TemperatureKelvinK VelocityMeter/Secondm s -1 ForceNewtonN (kg m s -2 ) Pressure (force/area)PascalPa (N m -2 or kg m -1 s -2 ) Energy or workJouleJ (N m or kg m 2 s -2 )

17. Variables, Coordinates, & Units

18. Synoptic Scale Governing Equations Frames of reference: Eulerian – object is fixed in space; it doesn’t move; changes due to air moving through the object; Referred to as the local derivative in equations Lagrangian – object is allowed to move with the air; Referred to as the total derivative in equations What is cold air advection (CAA)? What is warm air advection (WAA)? Cold air advection is the process in which the wind blows from a region of cold air to a region of warmer air Warm air advection is the process in which the wind blows from a region of warm air to a region of cooler air

19. CAAWAA

20. Temperature Advection

22. Where’s the Temp Advection?

24. Geostrophic Wind **A scale analysis of the *horizontal* governing equations reveals that only the pressure gradient force and Coriolis are important on the synoptic scale The resulting balance between these terms is called geostrophic balance, which yields the geostrophic wind **At the synoptic scale, in the Northern hemisphere, the geostrophic wind blows parallel to isobars (isoheights) with low pressure (low heights) to the left. Geostrophic balance allows the governing equations to be simplified considerably and allows the development of quasi-geostrophic theory (chapter 2)

25. Notice how wind in this 500mb map is flowing west to east, generally paralleling the isoheights  geostrophic balance

26. Geostrophic balance does not always apply  surface

27. Vertical Momentum Equation Which terms are left if you perform a scale analysis on this equation? All that remain are the vertical PGF and gravity. The balance between these two terms is called hydrostatic balance. **Synoptic scale motions are largely in hydrostatic balance in the vertical direction If we are to assume hydrostatic balance, then are we assuming no vertical air motion (i.e. no vertical acceleration)? NO… they’re just very small compared to the vertical PGF and gravity Vertical acceleration Vertical PGF Coriolis gravity friction

28. Continuity Equation This relation is based on the conservation of mass (in a closed system, mass will not change). The kinematic method uses the continuity equation to estimate vertical motion -Not very accurate -Errors in actual wind observations will lead to very large errors in the vertical motion estimate Convergence of winds at the surface leads to vertical motion What do you think convergence aloft leads to? Divergence of winds aloft? (sinking air)(rising air) Being able to correctly diagnose and forecast divergence and convergence aloft is an important component of this course

29. Most 700mb charts show negative values of “omega”…. Realize the differences between w and ω