University of Alberta

The Atmosphere, EAS 372

Jan.-Apr., 2013

The Numerical Weather Prediction models solve more complete equation sets than those constituting any weather paradigm we may have studied, such as the quasi-geostrophic model. They do so with impressive spatial resolution, and starting from an enormous wealth of data regarding the initial state of the atmosphere. Therefore in this course we are not learning how to apply the equations of meteorology so as to predict weather: we are learning how to effectively interpret weather data, including NWP products. Sometimes our knowledge will allow us to see possibilities not mentioned in public forecasts; and it will usually equip us to comprehend how the weather is developing (or not developing).

The practical side of the course will aim cover the following topics (not necessarily in the order listed). After each has been covered, a checkmark (✔) will be addded:

Activity/Topic
Prepare a short range (e.g. 48-hr) weather forecast (repeating exercise)
Calculations using hydrostatic law, ideal gas law, sat.vap. press. tables
Compute geostrophic wind from height contour spacing
Compute rate of temperature advection
Plot a sounding
Use the skew-T chart to compute various properties (LCL, LFC, potential temperatures etc.)
Plot time series of thickness alongside time series of layer-mean temperature ✔Assig. 1
Write a program to compute saturation vapour pressure
Plot hodograph, infer thermal wind
Plot a cross-section from radiosonde data at stations along a transect
Analyses and forecasts of vertical motion available from NWP models
Compare NWP fields for divergence, thermal advection and vertical motion (context: QG paradigm)
Using GrADS (Grid Analysis and Display System) to display height field (using grib2 files from GEM prog)
Use GrADS to prepare a chart of the vertical vapour flux
Case study of frontogenesis in relation to deformation
Compute crop evapotranspiration (vertical eddy flux of water vapour) from time series of velocity and humidity
Plot diurnal cycle of components of the surface energy budget
Change in heat storage inferred from subsequent soundings. Implied 12-hr mean surface heat flux
Generate weather chart(s) for a past day from web-accessible archive (reanalysis)
Generate chart giving climatological isobaric height contours from web-accessible archive
Online computation/display of air parcel back-trajectories based on NWP wind fields
Compute a histogram and probability density function from given data ✔ Assig. 3
Calculating Heidke skill score ✔Assig. 2
Student weather briefings (teams of 2)

The following theory elements will be reviewed (most if not all should be familiar from pre-req classes), either by the instructor in class, or by assigned reading from the textbook. Topics will not necessarily be covered in the order listed; strike out will indicate material not covered:

Theme Activity/Topic
Vocabulary & meaning of equationsDerive statement of mass conservation in Cartesian coordinates. Express that equation in vector notation. Unit vectors. Meaning of grad operator
Lagrangian derivative. Conserved variables. Conservation of thermodynamic energy. Velocity divergence
The equations of motion in vector form; in component form relative to local rotating Cartesian coordinates
Atmospheric ParadigmsGeostrophic wind model
Continuity equation in isobaric coordinates. Height-integrated continuity equation. Relationship between horizontal divergence and vertical motion. Level(s) of non-divergence
Thermal wind
The quasi-geostrophic model. Vorticity equation. Omega equation. Significance of vorticity advection and thermal advection
Everyday toolsThermodynamic chart. Hodograph
Hypsometric equation. Dry adiabatic lapse rate. Natural coordinate system
Potential temperature. Thermodynamic chart. Energetics of vertical motion
Water vapour calculations. Dewpoint lapse rate. Mixing ratio lines on the thermodynamic chart
METARs, meteograms, TAF, PIREP, Graphical Area Forecast (GFA)
Vertical motion on the synoptic scale. Relationship with precipitation. Precipitable water. Vertical flux of water vapour
Further differential properties of the wind field: deformation
Satellite dataGOES, POES, and exotic meteorological satellites
Unresolved motionDecomposition into resolved/unresolved scales of motion. Fundamental view of friction. The closure problem. Eddy diffusion parameterization
Heat, mass and momentum exchange between the surface and the free troposphere. Unresolved ("turbulent") vertical fluxes in the atmospheric boundary layer. The surface layer ("constant flux layer"). The surface energy balance
Fronts & frontogenesis
NWPMSC's Global Environmental Multiscale model - model dynamics
MSC's GEM model - parameterizations
NCEP's NAM model
Re-analyses


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Last Modified: 26 Mar., 2013