Convectively Driven Mesoscale Weather Systems Aloft. Part II: Numerical Simulations

J. M. Fritsch NOAA, Environmental Research Laboratories, Office of Weather Research and Modification, Boulder, CO 80303

Search for other papers by J. M. Fritsch in
Current site
Google Scholar
PubMed
Close
and
R. A. Maddox NOAA, Environmental Research Laboratories, Office of Weather Research and Modification, Boulder, CO 80303

Search for other papers by R. A. Maddox in
Current site
Google Scholar
PubMed
Close
Full access

Abstract

A fine-mesh, 20-level, primitive equation model is used to study the generation of convectively driven weather systems in the vicinity of the tropopause. In a test simulation, a high-level (∼200 mb) mesoscale high pressure system forms in conjunction with the development of a convective complex. In response to this high-level mesohigh, winds aloft rapidly decelerate as they approach the convective complex. On the other hand, downstream of the convective system the mesoscale pressure gradient accelerates the wind to generate a jet maximum which is stronger than any wind speed prior to the development of the convection.

The formation of the high-level mesohigh appears to be linked to the convectively forced production of a layer of cold air above the tropopause. The cold layer of air is generated by cloud-scale cooling from overshooting tops and from adiabatic cooling by strong (∼0.5 m s−1) mesoscale lifting in response to the convective cloud warming below the tropopause.

The model-generated high-level convective system is compared to observed systems and briefly discussed in light of the interaction of these systems with their larger scale environment.

Abstract

A fine-mesh, 20-level, primitive equation model is used to study the generation of convectively driven weather systems in the vicinity of the tropopause. In a test simulation, a high-level (∼200 mb) mesoscale high pressure system forms in conjunction with the development of a convective complex. In response to this high-level mesohigh, winds aloft rapidly decelerate as they approach the convective complex. On the other hand, downstream of the convective system the mesoscale pressure gradient accelerates the wind to generate a jet maximum which is stronger than any wind speed prior to the development of the convection.

The formation of the high-level mesohigh appears to be linked to the convectively forced production of a layer of cold air above the tropopause. The cold layer of air is generated by cloud-scale cooling from overshooting tops and from adiabatic cooling by strong (∼0.5 m s−1) mesoscale lifting in response to the convective cloud warming below the tropopause.

The model-generated high-level convective system is compared to observed systems and briefly discussed in light of the interaction of these systems with their larger scale environment.

Save