AIR MASS SOURCE REGIONS Form in Areas with light or no winds Quantico USMC 1

Conceptual Model 2

Midlatitude Cyclone Circulations: Patterns and Processes Figure from Global Atmospheric Circulations, by R. Grotjahn Note rotation about horizontal axis. Cold (warm) air sinking (rising) along isentropic surfaces  thermally direct circulation ( From Prof. Murphree Modern Climatology MR 3610) 4

(temperature advection occuring) Baroclinic Flow (temperature advection occuring) and Barotropic Flow (no temperature advection occuring) Baroclinic Flow alters height field at top of page 5

Veering and Backing Winds Thermal wind always points parallel to lines of constant thickness with lower thicknesses to the left Thermal wind always has the colder air to the left Veering winds turn clockwise with height and are associated with warm air advection (WAA) Backing winds turn counterclockwise with height and are associated with cold air advection (CAA) CAA WAA

8

9

May 15,2008 Jet Max Wind 04W Tropical Depression Matmo 10

Ageostrophic Winds wrt Curvature Supergeostrtophic Subgeostrophic Supergeostrophic The along-stream component of the ageostrophic wind produces patterns of divergence and convergence due to curvature in the flow. Thus, a short wavelength between an amplified trough and downstream ridge usually results in strong upper-level divergence and vertical motion. http://www.crh.noaa.gov/lmk/soo/presentations/atmos_processes.pdf WFO SOO T. Funk

With Jets and Curvature Ageostrophic, Divergent, and Vertical Motions Associated With Jets and Curvature

From Jet and curvature ageostrophic flows Low level convergence leads to upper level vorticity & Positive vorticity advection (PVA) 13

Developing Wave Cyclone Mid-latitude cyclones are "deep" pressure systems extending from the surface to tropopause level recall that they are an example of a "cold core low“ For the storm to develop and grow, it can NOT be vertically "stacked"

15

Life Cycle Birth Growth Mature Decay Examples Open Wave Occluded Cut-off and fill Examples 16

Recommended reading http://www. wpc. ncep. noaa

8. Look at low level (1000mb) relative vorticity to view the wind directional/speed change at a front. 18

19

typically less stable air warm front Forced Lifting – Frontal cold front steeper slope typically less stable air warm front more gradual slope typically more stable air DLA Fig. 5.23

0 C Conduction Convection Temperature Advection Latent Heating Adiabatic (heating-cooling) Radiative Heat Transfer 0 C 21

thermally direct circulation:  warm air rising/cold air sinking Ageostrophic, Divergent, and Vertical Motions Associated With Jets at jet entrance at jet exit thermally direct circulation:  warm air rising/cold air sinking  conversion of APE to KE thermally indirect circulation:  warm air sinking/cold air rising  conversion of KE to APE

vertical motion & diabatic processes layer perspective parcel perspective

Parcel does not exchange heat with its surroundings Conduction Convection Temperature Advection Latent Heating Adiabatic (heating-cooling) Radiative Heat Transfer Latent Heat release Atm Avg Lapse rate ~6.5 °C/km Expansion cooling  Compression warming Parcel does not exchange heat with its surroundings 24

change in mass distribution Big Six Equations of Atmospheric Dynamics These figures, which I call triangle diagrams, show schematically the highly complex, nonlinear relationships between energy, mass, and momentum in the climate system that are described by the big six equations. We usually think of these relationships in terms of T changes causing changes in mass distributions, which then cause changes in the winds. But the changes can also go in the other direction due to nonlinear feedbacks. For example, mass redistributions can cause T changes. And wind changes can advect mass and T, and thereby lead to T and mass changes. change in mass distribution = change in , p change in T change in wind = change in V T , p V (1-3) x, y, & z Momentum equations (parcels u,v,w) ( 4 ) Continuity equation (parcels Density) ( 5 ) Thermodynamic Energy Equation (parcels Temperature) ( 6 ) Equation of State (relates parcels T, Density, and Pressure) Slide From Prof Tom Murphree’s MR3610 Modern Climatology Course 25

26

http://www. newmediastudio http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Hurr_Structure_Energetics/Spiral_Winds/Spiral_Winds_fig05.jpg 27

Thickness (ΔZ) of a layer between 2 pressure surfaces is also proportional to the mean virtual temperature of that layer Cold air is more dense, therefore thinner Warm air is less dense, therefore thicker Temperature is the only factor that changes the thickness of a layer When you have a temperature contrast, you create height variations for a layer Height variation create a pressure gradient Pressure gradient creates a PGF The change in the Geostrophic Wind with height is directly proportional to the horizontal temperature gradient
This is the Thermal (temperature) Wind relationship

Hypsometric Equation Derived from the hydrostatic equation Implies that the thickness of a layer is directly proportional to the mean virtual temperature of the layer Write up hydrostatic equation and hypsometric equation. Discuss. Derivation below (DO NOT DERIVE in class, just for Ref.) Thickness calculation in most Met tools (eg. GARP) 29

Why Jet Streams Exist We have already qualitatively discussed how T / density / pressure /wind relationships can explain the presence of a jet stream  large horizontal temperature / density gradients produce large height and pressure gradients and, thus strong winds. We now have the tools to do so quantitatively: Hyspometric Equation: relates the mean T of a layer to the thickness and GPE. Helps to explain the creation of large height/pressure gradients in the upper-troposphere Thermal Wind Equation: relates the horizontal T structure to the vertical wind shear of the geostrophic wind. Helps to explain the increase in wind speed with height in the troposphere, the jet max at the tropopause, and the subsequent decrease above the tropopause Geostrophic Balance: relates the PGF to wind speed and direction. Helps to explain the jet max at tropopause level and the tendency for westerlies in the midlatitudes

Vg L H Hypsometric Eq. PGF T  Δp Thermal Wind Eq. Δp Why Jet Streams Exist Vg Hypsometric Eq. T  Δp PGF L H Thermal Wind Eq. Δp Geostrophic Balance PGF  Vg Δp Vg

Move into colder surface temperatures Shear off upper warm core Tropical Cyclone Cold Core Low Div Jet H Warm Core Low Move into colder surface temperatures Shear off upper warm core Halby Hints 32

Ageostrophic Winds wrt Jet Streaks ---300mb heights - - Isotachs The cross-stream component of the ageostrophic wind produces patterns of divergence and convergence due to accelerations (jet entrance regions) and decelerations (jet exit regions) in the flow. The stronger the along-stream wind variation in the flow, the greater the upper-level divergence due to this component. Superimposing jet streaks and curvature enhances upper-level divergence in right entrance and left exit regions. http://www.crh.noaa.gov/lmk/soo/presentations/atmos_processes.pdf WFO SOO T. Funk

Backing Cold advection Veering Warm Advection O O WAA CAA 850mb T