Thursday, October 23, 2014

New paper finds cooling, not warming, of mid- to upper troposphere increases likelihood of tropical cyclones

A paper published today in the Journal of Climate finds that cooling, not warming, of the mid- to upper troposphere increases the development of tropical cyclones. The mid- to upper troposphere mythical "hot spot" is predicted to warm the most from AGW, but despite millions of weather balloon and satellite measurements, has not been found in observations. Thus, if the mid- to upper troposphere missing "hot spot" ever does form, this paper implies that the probability of tropical cyclones would decrease, not increase as claimed by alarmists. 

In addition, global warming decreases the temperature gradients between the poles and the equator. Since temperature gradients drive all "extreme weather," global warming tends to decrease "extreme weather," not increase as claimed by alarmists.

The paper thus corroborates many others finding that if global warming resumes, it is expected to decrease tropical cyclones and hurricanes in the future. 

Note the paper refers to changing the "parameterized convection" in the climate model, which means that the model cannot directly simulate the physics of convection [due to low resolution] and thus uses fudge factors or "parameterizations" to simulate real convection, as do all IPCC climate models. Here's why and here.

Sensitivity of Tropical Cyclones to Parameterized Convection in the NASA GEOS5 Model

Young-Kwon Lim,1,2 Siegfried D. Schubert,1 Oreste Reale,1,3 Myong-In Lee,5 Andrea M. Molod,1,4 and Max J. Suarez1,3
1 Bldg. 33, code 610.1, 8800 Greenbelt Rd., Global Modeling and Assimilation Office, NASA/GSFC, Greenbelt, Maryland, 20771
2 Goddard Earth Sciences Technology and Research, I. M. Systems Group
3 Goddard Earth Sciences Technology and Research, Universities Space Research Association (USRA)
4 ESSIC, University of Maryland, College Park, Maryland
5 Ulsan Institute of Science and Technology (UNIST), Ulsan, South Korea
The sensitivity of tropical cyclones (TCs) to changes in parameterized convection is investigated to improve the simulation of TCs in the North Atlantic. Specifically, the impact of reducing the influence of the Relaxed Arakawa-Schubert (RAS) scheme-based parameterized convection is explored using the Goddard Earth Observing System version5 (GEOS5) model at 0.25° horizontal grid spacing. The years 2005 and 2006 characterized by very active and inactive hurricane seasons, respectively, are selected for simulation.
A reduction in parameterized deep convection results in an increase in TC activity (e.g., TC number and longer life cycle) to more realistic levels compared to the baseline control configuration. The vertical and horizontal structure of the strongest simulated hurricane shows the maximum wind speed greater than 60 ms-1 and the minimum sea level pressure reaching ~940mb, which are never achieved by the control configuration. The radius of the maximum wind of ~50km, the location of the warm core exceeding 10°C, and the horizontal compactness of the hurricane center are all quite realistic without any negatively affecting the atmospheric mean state.
This study reveals that an increase in the threshold of minimum entrainment suppresses parameterized deep convection by entraining more dry air into the typical plume. This leads to cooling and drying at the mid- to upper-troposphere, along with the positive latent heat flux and moistening in the lower-troposphere. The resulting increase in conditional instability provides an environment that is more conducive to TC vortex development and upward moisture flux convergence by dynamically resolved moist convection, thereby increasing TC activity.

Related: Why the AGW "Hot Spot" Won't Happen

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