Radiation Weakens Idealized Midlatitude Cyclones

2018 ◽  
Vol 45 (6) ◽  
pp. 2833-2841 ◽  
Author(s):  
Sophia A. K. Schäfer ◽  
Aiko Voigt
Keyword(s):  
Midlatitude Cyclones

Midlatitude Cyclone Compositing to Constrain Climate Model Behavior Using Satellite Observations

2008 ◽  
Vol 21 (22) ◽  
pp. 5887-5903 ◽  
Author(s):  
P. R. Field ◽  
A. Gettelman ◽  
R. B. Neale ◽  
R. Wood ◽  
P. J. Rasch ◽  
...  
Keyword(s):  
Climate Model ◽  
Model Output ◽  
Liquid Water Path ◽  
Temperature Dependent ◽  
Community Atmosphere Model ◽  
Mean Wind Speed ◽  
Mean Fields ◽  
Microphysical Processes ◽  
Midlatitude Cyclones

Abstract Identical composite analysis of midlatitude cyclones over oceanic regions has been carried out on both output from the NCAR Community Atmosphere Model, version 3 (CAM3) and multisensor satellite data. By focusing on mean fields associated with a single phenomenon, the ability of the CAM3 to reproduce realistic midlatitude cyclones is critically appraised. A number of perturbations to the control model were tested against observations, including a candidate new microphysics package for the CAM. The new microphysics removes the temperature-dependent phase determination of the old scheme and introduces representations of microphysical processes to convert from one phase to another and from cloud to precipitation species. By subsampling composite cyclones based on systemwide mean strength (mean wind speed) and systemwide mean moisture the authors believe they are able to make meaningful like-with-like comparisons between observations and model output. All variations of the CAM tested overestimate the optical thickness of high-topped clouds in regions of precipitation. Over a system as a whole, the model can both over- and underestimate total high-topped cloud amounts. However, systemwide mean rainfall rates and composite structure appear to be in broad agreement with satellite estimates. When cyclone strength is taken into account, changes in moisture and rainfall rates from both satellite-derived observations and model output as a function of changes in sea surface temperature are in accordance with the Clausius–Clapeyron equation. The authors find that the proposed new microphysics package shows improvement to composite liquid water path fields and cloud amounts.

scholarly journals On the Relationship between Inertial Instability, Poleward Momentum Surges, and Jet Intensifications near Midlatitude Cyclones

2016 ◽  
Vol 73 (6) ◽  
pp. 2299-2315 ◽  
Author(s):  
Shellie M. Rowe ◽  
Matthew H. Hitchman
Keyword(s):  
Angular Momentum ◽  
Pressure Gradient ◽  
Zonal Wind ◽  
Momentum Conservation ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Wind Maximum ◽  
Stable Conditions ◽  
Inertial Instability ◽  
Midlatitude Cyclones

Abstract This study explores the role of inertial instability in poleward momentum surges and “flare ups” of the subpolar jet near midlatitude cyclones. Two cases are simulated with the University of Wisconsin Nonhydrostatic Modeling System to investigate the mechanisms involved in jet accelerations downstream of quasi-stationary “digging troughs.” Deep convection along the cold front leads to regions of inertial instability in the upper troposphere, which are intimately linked to jet accelerations. Terms in the zonal and meridional wind equations following the motion are evaluated for a selected air parcel within the inertially unstable region. A two-stage synoptic evolution is diagnosed, which is a characteristic signature of inertial instability. First, meridional flow accelerates following the motion, because of the subgeostrophic zonal flow and strong northward pressure gradient force (a statement of inertial instability). Second, supergeostrophic poleward flow leads to zonal acceleration and a jet flare-up. Inertial instability thus effectively displaces a westerly jet maximum poleward relative to inertially stable conditions. The structure of the poleward surge involves a distinctive “head” of high angular momentum, with the region of inertial instability enclosing the jet maximum and a core of strongly negative potential vorticity inside the surge. Departures from angular momentum–conserving profiles during meridional displacement are interpreted in terms of the pressure gradient force and degree of inertial stability. Inertial instability reduces the resulting zonal wind profile relative to angular momentum conservation but provides a significant poleward displacement of the resulting zonal wind maximum.

Atmospheric forcing of the Eastern Mediterranean Transient by midlatitude cyclones

2012 ◽  
Vol 39 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Joy Romanski ◽  
Anastasia Romanou ◽  
Michael Bauer ◽  
George Tselioudis
Keyword(s):  
Eastern Mediterranean ◽  
Atmospheric Forcing ◽  
Midlatitude Cyclones
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