There has been a lot of discussion recently about the polar vortex and severe weather that is supposed to be as a result of global warming — particularly because of what Jennifer A. Francis and Stephen J. Vavrus contend is the result of “arctic amplification” or the greater warming rate of the arctic vs. the mid latitudes that occurred between 1977-1998. (Read their paper in Geophysical Research Letters, vol. 39 from March 17, 2012.)
Francis and Vavrus are claiming that this arctic amplification has lead to the presence of increased long waves (big loops in the jet stream) that become stationary — thus persistent at mid latitudes and are causing more severe weather in the USA and other mid latitude locations. The authors invoke the Rossby wave theory to conclude what they did in their peer reviewed paper by the Geophysical Research Letters.
The problem is that their claims actually contradict the theory of Rossby waves as derived in the literature by Rossby himself. In their paper, Francis and Vavrus claim that because there was arctic warming that occurred at a faster rate than the mid latitudes from 1977-1998, that this warming weakened the jet stream winds at high latitudes. Thus, according to Rossby wave theory, this has allowed these waves to amplify and become more persistent around the earth as full latitude waves — creating bigger storms and more severe weather at mid latitudes. The implication is that severe snowstorms, thunderstorms, and tornadoes are a result of this arctic amplification.
The problem is, again, that this contradicts the physics of Rossby waves — as every meteorologist is required to understand — because the waves actually do the opposite of what is claimed in their paper. If it is true that the jet stream winds have decreased as claimed by the “reanalysis” of the upper level winds, it is also true that as you move to higher latitude, Rosssby waves can develop with a lessened wind speed and achieve a standing or stationary status. But this is less than half of the physics involved. The problem is that this is not true to obtain full latitude waves as discussed in their paper. For that to happen, winds must increase — as the amplitude of these waves is dependent upon the speed of the jet stream winds which must increase at lower latitudes, consistent with a greater difference in temperature across the latitude lines. This is the opposite of what they claim in their paper.
It is not possible for full latitude waves to develop based upon a weakening westerly jet stream as they claim. If their claims were true, the correct Rossby wave physics tells us that such waves would shorten in both amplitude and wave length and migrate further north — thus not affecting mid latitude locations in the USA as claimed that produce severe weather.
The fact that we have had persistent long waves this winter causing severe snow and cold in the USA is actually an indication of the opposite of what the authors claim. It is a fact that the North American continent has cooled over the last 10 years, while the global oceans have retained a lot of their heat energy as the higher specific heats have allowed thermal inertia to be a factor in global ocean temperatures with the declining solar magnetic. In terms of the near future, this could easily spell trouble for the USA’s Midwestern states this spring — as the severe cold and deep snow in the north will cause a slower warming rate of these areas vs. the more rapid warming of the southern latitudes that is always associated with the climbing sun angle of late winter and spring.
It is the difference in temperature across the latitude lines that liberates potential energy and creates storms and because there is no global warming present yet the likelihood that these temperature gradients will develop at mid latitudes during the next 4 months and be greater than average, that the severe weather season at mid latitude and in particular in the Midwest USA has the potential to be bad this year with a lot of severe thunderstorms and tornadoes.
Francis and Vavrus claim the severe weather is caused by arctic warming, but this contradicts all of the founding literature in atmospheric science as I pointed out to these authors including their claims about Rossby waves. Neither author has answered my concerns and questions.