scholarly journals Evaluation and Application of Conditional Symmetric Instability, Equivalent Potential Vorticity, and Frontogenetic Forcing in an Operational Forecast Environment

1998 ◽  
Vol 13 (1) ◽  
pp. 84-101 ◽  
Author(s):  
James L. Wiesmueller ◽  
Steven M. Zubrick
Keyword(s):  
Potential Vorticity ◽  
Operational Forecast ◽  
Equivalent Potential ◽  
Symmetric Instability ◽  
Conditional Symmetric Instability

Conditional symmetric instability in sting-jet storms

2011 ◽  
Vol 137 (659) ◽  
pp. 1482-1500 ◽  
Author(s):  
S. L. Gray ◽  
O. Martínez-Alvarado ◽  
L. H. Baker ◽  
P. A. Clark
Keyword(s):  
Symmetric Instability ◽  
Conditional Symmetric Instability

scholarly journals Numerical study of two-dimensional moist symmetric instability

2008 ◽  
Vol 17 ◽  
pp. 1-4 ◽  
Author(s):  
M. Fantini ◽  
P. Malguzzi
Keyword(s):  
Numerical Study ◽  
Finite Amplitude ◽  
Two Dimensional ◽  
Initial State ◽  
Linear Mode ◽  
Equivalent Potential ◽  
Start Up ◽  
Set Up ◽  
Symmetric Instability ◽  
Amplitude Evolution

Abstract. The 2-D version of the non-hydrostatic fully compressible model MOLOCH developed at ISAC-CNR was used in idealized set-up to study the start-up and finite amplitude evolution of symmetric instability. The unstable basic state was designed by numerical integration of the equation which defines saturated equivalent potential vorticity qe*. We present the structure and growth rates of the linear modes both for a supersaturated initial state ("super"-linear mode) and for a saturated one ("pseudo"-linear mode) and the modifications induced on the base state by their finite amplitude evolution.

Symmetric Instability in the Outflow Layer of a Major Hurricane

2014 ◽  
Vol 71 (10) ◽  
pp. 3739-3746 ◽  
Author(s):  
John Molinari ◽  
David Vollaro
Keyword(s):  
Potential Temperature ◽  
Outer Edge ◽  
Unstable State ◽  
Upper Troposphere ◽  
Hurricane Ivan ◽  
Equivalent Potential ◽  
Inertial Instability ◽  
Major Hurricane ◽  
Cloudy Region ◽  
Symmetric Instability

Abstract A set of 327 dropsondes from the NOAA G-IV aircraft was used to create a composite analysis of the azimuthally averaged absolute angular momentum in the outflow layer of major Hurricane Ivan (2004). Inertial instability existed over a narrow layer in the upper troposphere between the 350- and 450-km radii. Isolines of potential and equivalent potential temperature showed that the conditions for both dry and moist symmetric instability were satisfied in the same region, but over a deeper layer from 9 to 12 km. The radial flow maximized at the outer edge of the unstable region. The symmetrically unstable state existed above a region of outward decrease of temperature between the cirrus overcast of the storm and clear air outside. It is hypothesized that the temperature gradient was created as a result of longwave heating within the cirrus overcast and longwave cooling outside the cloudy region. This produced isentropes that sloped upward with radius in the same region that absolute momentum surfaces were flat or sloping downward, thus creating symmetric instability. Although this instability typically follows rather than precedes intensification, limited numerical evidence suggests that the reestablishment of a symmetrically neutral state might influence the length of the intensification period.

scholarly journals The Slope of Moist Symmetric Instability with Water Loading

2008 ◽  
Vol 65 (9) ◽  
pp. 2922-2935 ◽  
Author(s):  
Maurizio Fantini ◽  
Piero Malguzzi
Keyword(s):  
Potential Temperature ◽  
Normal Modes ◽  
Equivalent Potential Temperature ◽  
Neutral Buoyancy ◽  
Water Loading ◽  
Preferred Direction ◽  
Equivalent Potential ◽  
Condensed Water ◽  
Definition Of ◽  
Symmetric Instability

Abstract Idealized numerical experiments, supported by analytic considerations, are performed to determine the preferred direction of symmetric instability when water loading is considered. It is concluded that the most unstable direction is tangent to a surface of neutral buoyancy, which can be defined numerically from the water content of lifted air, and coincides with the tangent to saturated isentropes only when all condensed water is precipitated out, consistent with the thermodynamic approximations made in the definition of equivalent potential temperature. In more common situations, when part or all of the condensed water is retained in the cloud, the orientation of symmetrically unstable normal modes is much more slanted toward the horizontal, to the point that regions of the atmosphere, diagnosed as unstable from the consideration of equivalent potential temperature and vorticity, can in fact be stable.

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