Guest Opinion by Dr. Tim Ball
Claims that weather forecasts are reasonably accurate up to 48 hours are based on measured results for fair weather. Results for severe weather, which are really what is important for people, are very poor. The Intergovernmental Panel on Climate Change (IPCC) has a worse record for both. Every prediction/projection since their first Report in 1990 has been wrong, with claims for more severe weather part of that failure. They fail because of fundamental errors in assumptions and mechanics.
Essex and McKitrick identified the challenge of turbulence in building climate models.
Climate research is anything but a routine application of classical theories like fluid mechanics, even though some may be tempted to think it is.
Furthermore, experiment and theory have been struggling since the 19th century, literally for generations, with a complicated behavior of fluids call turbulence.
The experiments are bedeviled by the fact that a turbulent fluid is active on scales smaller than the size of the finest experimental probes. Thus the measurements themselves are not of the actual variables but of some kind of unspecified, instrument-dependent average of the variables, and only one small region of the fluid.
They are talking about turbulence at all scales. Severe weather is large-scale turbulence with basic triggers that convert laminar flow to turbulent flow. This is caused, by the following, among other conditions,
1. Rough terrain, such as the effect of the Rocky Mountains or the Andes on the Westerlies.
2. Transition of surface, such as from land to ocean, like in the Cape Hatteras area.
3. Transition of surface, such as from cool to warm ocean – this is the major driving mechanism in transformation of equatorial depressions to Tropical storms to hurricanes.
4. Different temperatures between air masses.
5. Different convergence and divergence along a Frontal zone.
Figure 1 shows a cross-section of energy balance from Pole to Pole.
It illustrates the average condition at present. Salient features include the areas of surplus and deficit energy and the point of zero energy balance (ZEB). It is different between the Hemispheres, 38N and 40S, because of different land-water ratios. The ZEB is coincident with some important boundaries.
· The snowline (summer and winter).
· The pole ward limit of trees.
· The location of the Circumpolar Vortex (Jet Stream).
· The major air mass boundary – the Polar Front.
Figure 2 shows the Polar Front as a simple division of the atmosphere between cold polar and warm tropical air. The pattern is the same for the Southern Hemisphere. It shows the approximate juxtaposition of the Jet Stream and the Front.
Because of the temperature difference across the Front, sometimes called the Zonal Index, it marks the area of most severe weather. These take the form of mid-latitude cyclones, with associated tornados. Intensity of the storm is directly related to the temperature and moisture contrast across the Front.
The IPCC argue that global warming is inevitable because CO2 levels will continue to rise from human activity. They also claim, warming will be greater in the polar region. If true, then temperature contrast across the Polar Front is lower and energy potential for severe weather reduced.
Figure 1 shows the average position of the ZEB, while Figure 4 shows the average seasonal latitudinal shift in the northern hemisphere, between approximately 35N in winter, and 65°N in summer.
Changes in these latitudes trigger changes in the dynamics created by rotational forces and the area of the surface affected. This is reflected in the changes to the angle of solar incidence variation caused by changing obliquity of the ecliptic (tilt). The Arctic and Antarctic Circles are at 66.5° N and S, the point at which the sun’s rays are tangential at Equinox. But this is only if you accept the angle of tilt as 23.5°. Almanacs list it currently at 23.4° and decreasing at 0.47” per century. The mean position of the ZEB shifts more as the global energy balance changes.
The mid-latitude cyclones that form as wave like patterns and migrate along the Polar Front, are major storm systems that occur more frequently and can impact much larger areas than any other severe weather system. Figure 5 shows a comparison between a mid-latitude cyclone and a hurricane.
A large system can cover up to 5000 km, with damaging winds, heavy rain, snow and freezing rain. Historic records of damage from these storms, is well documented for the US by David Ludlum . Similarly, details of such extreme examples for Europe include the 1588 storm that destroyed the Spanish Armada, well documented by J.A. Kington, and the storm of 1703 that hit England and Europe. Daniel Defoe traveled around England recording the damage in his book The Storm.
Systems are also important in mixing air between the surplus and deficit energy sectors, horizontally and vertically. Intensity of these systems is also defined by the temperature contrast across the Front. In the list of triggers (above) item 5 lists divergence and convergence as mechanism for development. Figure 6 shows the relationship between these and the surface development of the cyclone. As the wave like system develops a low pressure center is formed and a rotational effect is generated. The cold air dictates its momentum, because it is denser and heavier than the warm air. The Warm Front is defined by cold air retreating, and the Cold Front by cold air advancing
The advancing Cold Front acts like a bulldozer pushing already unstable convective cells, cumulonimbus, into extreme instability creating conditions for spawning tornados. Since the cold air is dominant then any decrease in its temperature relative to the warm air is going to have an effect.
An indicator of the difficulty, with turbulence created phenomena, is what happens with mid-latitude cyclones. A full cycle involves four stages.
1. Cyclogenesis, initiation of the wave.
2. Mature Stage with maximum low pressure and wind speeds.
3. Occluded Stage when the Cold Front advances rapidly and lifts the Warm Front above the surface.
4. Frontolysis when a small pool of warm air is trapped above the surface and the surface low pressure dissipates.
Cyclogenesis occurs quite often, but few systems go through the few cycle. An important question is how do you model a system that starts out sub grid size, but may expand to over a few grids?
A shift from Zonal to Meridional Flow in the Rossby Wave pattern of the Circumpolar Vortex will affect all the factors listed (1-5) that trigger mid-latitude cyclones. Development, track and intensity of these cyclones in the North Atlantic was a major focus of H. H. Lamb’s research beginning with his 1950 paper, “Types and spells of weather around the year in the British Isles”. Lamb also knew that a latitudinal shift in the Polar Front results in a change in the Coriolis Effect (creating an apparent force), as it decreases from zero at the Equator to maximum at the Poles.
Essex and McKitrick identified turbulence as a serious challenge for understanding climatology. They spoke to the problem at all levels,
…experiment and theory have been struggling since the 19th century, literally for generations, with a complicated behavior of fluids called turbulence. When a fluid is turbulent, (nearly all fluids are), not only are we unable to provide solutions of Navier – Stokes to confirm the behaviour theoretically, but we are also unable to experimentally measure the conditions in the fluid in such a way that we can fully capture what is going on.
The major factors inducing turbulence in laminar flow, and thereby severe weather, are the rough surface and contact zones of hot and cold air and water. One of the largest contact zones is the Polar Front between cold polar air and warm tropical air. Intensity of severe weather along the Front is a function of the temperature difference between the air masses. The IPCC claim this will decrease with global warming as the polar air warms more than the tropical air. Theoretically this creates fewer storms, but the IPCC are predicting more. So far the evidence of less severe weather seems to support the basic concepts, not the IPCC.