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Last Updated: 3:02 PM GMT on October 24, 2009
— Last Comment: 4:13 PM GMT on December 31, 2009
FLUID DYNAMICS-DEFINITION
Fluid dynamics is a bit more advanced, and requires a deeper understanding of atmospheric physics. Fluid dynamics studies the motions of liquid. Our atmosphere is best modeled as a fluid. Fluids exhibit different properties, and thus act differently, just as our atmosphere has a broad composition of various gases. Fluids are assumed to follow modeled as the continuum assumption which states fluids are continuous, not discreet. This is best governed with fluids that are very dense. The perfect gas equation of state is as follows: P=(pRT)/M where P is pressure, p is density, R is the gas constant, M is molar mass, and T is temperature. We can simplify this equation like we did the ideal gas law, to derive relationships. See that explanation on the ideal gas law(in the first part of the tutorial) to formulate relationships using this equation. The atmosphere is approximately modeled as fluid. COMPRESSIBLE/INCOMPRESSIBLE FLOW Fluid flow can be described as either compressible, or incompressible. A compressible fluid will show a change in density as a result of changes in pressure and temperature. Compressibility is the measure of volume change in a fluid as a result of pressure changes. p=m/V where p is density, m is mass, and V is volume. This equation says that density is measured by how much mass there is per volume. While we do not need to memorize complex equations, it is important to learn many of the simpler ones to grasp fluid dynamics well. Incompressible flow assumes the fluid to have constant density as it moves. To model this, we will form a very scary derivative: Dp/Dt=0 The "D" means it is a derivative. The coupling "Dp" means this is a change in density. The "Dt" means a change in time. All this equals zero. What this means for an incompressible fluid, is that in time, density does not change(hence why this equals zero). When changes of pressure and temperature are sufficiently small, we can assume the flow incompressible. In other words, these variables become negligible. VISCOSITY Viscosity is a measure of resistance(fluid friction) that a fluid flows due to stresses. One can think of viscosity as meaning "thickness". For example, water is thinner than honey and flows more readily than honey. In other words, the less viscous a fluid is, the more readily it will flow. If you were to put honey in the microwave, it becomes less viscous, because heat was added(increasing molecular motions). In fluid dynamics, we cannot ignore viscosity near solid boundaries because of frictional effects. TURBULENT AND LAMINAR FLOW When fluids encounter regions of stresses which create eddies, random flow, etc...it is known as turbulent flow. Flow that is not turbulent is know as laminar flow. There are cases where eddies can be present within laminar flow, but this gets too complicated for this tutorial. Most of the atmosphere is not considered to be in laminar flow. Fluid that flows in parallel layers without disruption is laminar.  A good way to look at the atmosphere, is that of a fluid in motion. That is, visualize it as a stream. Watching a river will give you some ideas on how the atmosphere works. For instance, in a river with large rocks, watch the flow pattern around them and notice the "eddies" that form due to stresses on the fluid. These stresses can be modeled in our atmosphere, with pressure regions dictating wind patterns. Notice, when a stream has almost no obstacles in an area, the flow is more stable and straight. Also, notice how in general(especially true in large, deep areas of water) that temperature typically decreases with depth in water. Knowing that cold air is heavier than warm air, it sinks. Hence the reason why cold water pools at the bottom and warm water on top. A big difference between water and the atmosphere, is that water has a very high heat capacity(ability to store heat more efficiently) while the atmosphere in itself, is not as efficient. Of course, the atmosphere has certain gases which help store heat, or else the planet would be extremely cold. Another difference, is that the atmosphere is chiefly warmed from below, while water is warmed from above. Because water is warmed from above, it cannot "rise" as air does, and cannot sink(due to it being cooler below). This is how SST's can frequently be quite warm near the surface in a shallow layer, but not with depth. The area of integrating oceanic process with atmospheric processes is one of the most complex areas in meteorology, because there are many similarities between fluid dynamics and atmospheric processes, but lots of differences too.
Update*-I've added part 9 & appendix A to this hurricane forecasting tutorial!!Welcome fellow bloggers to this hurricane forecasting tutorial!I will be using this site along with other tools(such as Jeff Haby & WU graphics) and my knowledge to put this together....All sources will be properly shown or implied(quotations)......Some sites offer techniques that are too complex for the layman to understand, and I will attempt to make it clearer....This is ONLY meant to ...
This last part of the hurricane forecasting tutorial will explore hurricanes in light of global warming. Here is a graph depicting global temperatures(source, Dr Roy Spencer, phD climatologist):A common statement by proponents of AGW, is that hurricanes will increase in frequency and intensity due to increasing temperatures on the earth. First, as a meteorological analysis, this statement is severely flawed and misleading. To say that rising global temperatures(a gl...
Welcome fellow bloggers to this hurricane forecasting tutorial!I will be using this site along with other tools(such as Jeff Haby & WU graphics) and my knowledge to put this together....All sources will be properly shown or implied(quotations)......Some sites offer techniques that are too complex for the layman to understand, and I will attempt to make it clearer....This is ONLY meant to be a basic tutorial in which I will try and make my discussions as clear as pos...
When forecasting hurricanes, there will sometimes be cases where cyclones are not truly "tropical" entities...I will explain how to distinguish between extratropical, subtropical, and tropical cyclones......When you hear "warm core" cyclone, this is talking about the center of the cyclone being relatively warmer than its surrounding environment and vice versa for "cold core".Extratropical cyclones form with cold cored structures. They maintain themselves by defined ...
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