HDR Photography

I've been toying with HDR photography for some time, but I could never quite get it to work. Recently I found some new software and have had some spectacular results. This is just the tip of the iceberg.

This coming season I plan to do more HDR photography and perhaps some time lapse HDR work.

Terrain Following Coordinates

In previous posts I have mentioned a density current simulation. I have modified the code substantially, and have begun introducing terrain following coordinates. In the video you should see the cool bubble (this time red) fall because of its over density. Once reaching the surface it spreads out and a density current begins to travel along the surface. Notice how the density current slows before cresting the hill. This is the same reason a ball rolling up a surface would slow down. As the current comes down the other side of the mountain hill you can see it accelerates and produces additional sheer with the atmosphere above.

Why terrain following coordinates? Weather models don't like coordinates that don't follow terrain. They can produces waves/modes in the model that are hard to damp. Terrain also influences the atmosphere significantly. My research mainly focuses on the ability of terrain to produce waves. While storm chasing terrain can influence the generation of a thunder storm by lifting air, or can induce 'mesoscale' circulations (like the infamous palmer divide).

Wind Storms in the News

Wind storms in California have produced damage, and recently have made headlines:

Link to Article in LA Times
Link to Article in SF Chronicle

In New Mexico we're also experiencing some strong winds. While not exactly analogous to this event, it reminded me of other wind storm events in the lee of the Organ Mountains, which are to the east of Las Cruces.

While many factors helped to bring about these mountain winds, a factor that can often assist in the strengthening of mountain winds, is the reflection of internal buoyancy waves. Internal buoyancy waves occur in regions of connectively stable air, and arise because vertically displaced (i.e. moved) air parcels will 'feel' a buoyancy force against this displacement. This force will cause air to oscillate vertically about this displacement. Mountains can produce this vertical displacement of air, and thus can induce internal buoyancy waves.

Certain changes in the background wind profile or temperature structure can result in reflections of these waves. Changes in the temperature structure can act like walls and reflect waves, similar to how sound reflects at boundaries. Below is an image of a model I produced, showing how air traveling over the Organ mountains will be vertically displaced (assuming the air is traveling left to right in the image). Notice how the lines become 'bunched' together in the lee of the ridge, this 'bunching' of the lines essentially means its windier on that side of the mountain. The model assumes a change in the vertical temperature structure a few kilometers above the surface. Notice the repeated oscillation of the lines (the little waves in the lines) in the lee of the mountain, this can only arise in this model because of reflecting buoyancy waves. Certain changes in the temperature structure can amplify this effect and strengthen the wind in the lee of the ridge.

Fun with Lagrangian Vortex Modeling

Lagrangian vortex modeling is essentially a method where the model follows the fluid. I've been playing with vortex models attempting to arrive at a 'stable' configuration with a multivortex tornado. This is like in the 2d applet on the right, except this is in 3d. A large issue I'm running into is that when the vortex lines become concentrated, that is when the vortex strengthens, this causes the lines of vorticity to tilt above. The tilt induces a down draft which eventually dissipates the strengthening at the surface. The tilt I believe is similar to the complex affect of vortex break down. For example, in dust devils it is sometimes observed that there is a down draft at the top of the dust devil where the concentrated rotation dissipates.

Below are some examples of simulations I have produced. The lines represent locations where vorticity is concentrated.

Back to Modeling

I have been back to modeling again. I'm using Ames Mars General Circulation Model (GCM) computational model to research a possible connection to gravity waves either triggering or assisting in the development of global dust storms. Below is a movie showing the average temperature from this model through the course of a few years. The y-axis can generally be thought of pressure decreasing upwards, the x-axis is latitude. Red is warmer, blue is colder, and the "blank blue" region at the bottom are pressures not reached by the surface. Notice how the surface pressure changes through the year. Mars transfers mass between the polar icecaps and results in meridional flow unique when compared to Earth.

In future posts I will likely be sharing some video of a 3d model recently developed from the past 2d model presented previously here. I am also working on adding some terrain following coordinates for the code (will explain more later). For fun I also added a magnetic field to one version of the code, and I am exploring some "wacky" behavior caused by magnetohydrodynamics!

New Mexico Monsoon Begins

The New Mexico monsoon season is about to begin. While these storms are not tornadic (due to the lack of dynamics), they can be quite beautiful on their own. Photographed above was a weak storm over the Chama, NM valley. While I was not chasing, I thought it would still be nice to share here. I will be keeping my eye out for a short fall season this year. As noted in the blog last year, as the jetstream begins to work back south, New Mexico can occasionally produce a few tornado warned storms in the October timeframe. However, these would not be during the "monsoon season" specifically.

Composite Photo of Tornado

This is a composite photograph I made in photoshop over the weekend of the Mule Creek Junction, WY tornado. Click on the photo to see the the version with times listed for each funnel/tornado.