Here we study the balance of forces typical of atmospheric vortices and severe weather across scale, using the Rossby number as a guide. The activity parallels that taken in our ‘radial inflow’ laboratory experiment.
See the first Data class notes and slides.
Links to the notes and slides of the second Data class are given in the “Hurricane flow- balance of forces” section below.
Relevant theory and discussion of the balance of forces can be found in the reference materials.
Estimating the Rossby number as a function of scale
In the Project 1 intro class we estimated the Rossby number (by estimating time scales of rotation) of various vortices in the atmosphere in a manner which is analogous to that used in the laboratory experiments by tracking ‘virtual’particles in the evolving wind patterns using the EsGlobe – see EsGlobe.
Jet stream – geostrophic balance
In the first Data class, we will compare the distribution of climatology of zonal wind and north-south pressure gradient for zonal averages, using the EsGlobe, to verify that the jet stream is in geostrophic balance.
Hurricane flow – balance of forces
In the second Data class, we will analyze data from real hurricanes and compare them with the tank experiment. Check the second Data class slides and notes.
Choose a hurricane and plot the observed winds and Rossby Number in function of radius as described in the scatterometer-instructions page.
Discuss how the hurricane data compare and contrast with the radial inflow experiment.
List of interesting hurricane case studies is available here.
EXtra
Note that the surface wind tends to be cross isobaric. Read notes on the effect of friction on the geostrophic flow.