Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

A dynamical basis is established for understanding the structure and transport properties of organized convection and for expediting its parametrization in large-scale models. A two-dimensional model provides an exact theory of the momentum transport by mesoscale convective systems and similar phenomena. the system-scale dynamics are supposed to dominate local processes and are modelled by a stationary triple-branch airflow regime consisting of a double-branch updraught and a downdraught. It is argued that a jump updraught is essential and has a fundamental effect on the momentum transport. the triple-branch model degenerates into a form of conservative density current; another limiting case consists of a propagating positive pressure jump of maximum amplitude-an overturning updraught but no downdraught. the functional relationship among dynamical parameters is determined by a characteristic regime equation derived from elementary nonlinear Lagrangian conservation properties and the volume integral of the horizontal-momentum equation.

The inflow to the archetypal jump updraught is constant. an example shows that the inclusion of shear in this region alters the detailed shape of the momentum flux profile but its fundamental character, namely the negative values of momentum flux for a system travelling in the positive x-direction, is retained. This result, together with recent numerical simulations, implies that low-level shear directly influences the initiation and evolution of convective elements, whereas the mature-state fluxes for which the system-scale flow organization and tilt is paramount is a product of the distribution of heat sources/sinks and deep tropospheric shear. the universal nature of the momentum flux profiles is explained in elementary terms by appealing to dynamical theory.

The physical basis of the model and the momentum flux profiles are validated by using published results. the archetype emulates the basic character of the mass and momentum fluxes by mesoscale convective systems. For example an upper-tropospheric flow deceleration is consistent with the observed effect of tropical cloud clusters on the mean flow but is distinct from the balanced response due to diabatic heating.

The theory is used to develop a dynamical approach to the parametrization of organized convective processes that have hitherto been neglected in global models. Mass and momentum fluxes are obtained from the archetypal model in an approach that is fundamentally different from the statistical or averaging approximations that characterize present techniques. the activation of the parametrization scheme is also studied. Mass-flux criteria are used to define an amplitude function for the mesoscale flux divergence to incorporate the flux laws into the large-scale equations. the work can be extended to include thermodynamic fluxes by using generalized conservation properties.

Organized convective systems : archetypal dynamical models, mass and momentum flux theory, and parametrization

A commonly employed explanation for single- and multiple-banded clouds and precipitation in the extratropics is slantwise convection due to the release of moist symmetric instability (MSI), of which one type is conditional symmetric instability (CSI). This article presents a review of CSI with the intent of synthesizing the results from previous observational, theoretical, and modeling studies. This review contends that CSI as a diagnostic tool to assess slantwise convection has been, and continues to be, misused and overused. Drawing parallels to an ingredients-based methodology for forecasting deep, moist convection that requires the simultaneous presence of instability, moisture, and lift, some of the misapplications of CSI can be clarified. Many of these pitfalls have been noted by earlier authors, but are, nevertheless, often understated, misinterpreted, or neglected by later researchers and forecasters. Topics include the evaluation of the potential for slantwise convection, the relationship between frontogenesis and MSI, the coexistence of moist gravitational instability and MSI, the nature of banding associated with slantwise convection, and the diagnosis of slantwise convection using mesoscale numerical models. The review concludes with suggested directions for future observational, theoretical, and diagnostic investigation.

REVIEW The Use and Misuse of Conditional Symmetric Instability

Although considerable progress has been made in understanding the development of hurricanes, our knowledge of their three-dimensional structures of latent heat release and inner-core thermodynamics remains limited. In this study, the inner-core budgets of potential temperature (θ), moisture (q), and equivalent potential temperature (θe) are examined using a high-resolution (Δx = 6 km), nonhydrostatic, fully explicit simulation of Hurricane Andrew (1992) during its mature or intensifying stage. It is found that the heat energy is dominated by latent heat release in the eyewall, sublimative–evaporative cooling near the eye–eyewall interface, and the upward surface fluxes of sensible and latent heat from the underlying warm ocean. The latent heating (θ) rates in the eyewall range from less than 10°C h–1 to greater than 100°C h–1, depending upon whether latent heat is released in radial inflow or outflow regions. The latent heating rates decrease inward in the inflow regions and become negative near ...

A Multiscale Numerical Study of Hurricane Andrew (1992). Part V: Inner-Core Thermodynamics

A commonly employed explanation for single- and multiple-banded clouds and precipitation in the extratropics is slantwise convection due to the release of moist symmetric instability (MSI), of which one type is conditional symmetric instability (CSI). This article presents a review of CSI with the intent of synthesizing the results from previous observational, theoretical, and modeling studies. This review contends that CSI as a diagnostic tool to assess slantwise convection has been, and continues to be, misused and overused. Drawing parallels to an ingredients-based methodology for forecasting deep, moist convection that requires the simultaneous presence of instability, moisture, and lift, some of the misapplications of CSI can be clarified. Many of these pitfalls have been noted by earlier authors, but are, nevertheless, often understated, misinterpreted, or neglected by later researchers and forecasters. Topics include the evaluation of the potential for slantwise convection, the relationshi...

/pdf/the-use-and-misuse-of-conditional-symmetric-instability-yoanrgyzwi.pdf

The use and misuse of conditional symmetric instability

This paper presents evidence on the development of negative moist potential vorticity (MPV) or moist symmetric instability (MSI) in the stratiform region of a midlatitude squall line, based on a three-dimensional (3D) numerical simulation of a case that occurred on 10–11 June 1985 during the Preliminary Regional Experiment for STORM-Central (PRE-STORM). The results show that the stratiform region, though convectively stable to pure vertical displacement, is considerably unstable to slantwise displacement along the system's broad front-to-rear (FTR) saturated ascending flow. It is found that this instability evolves from boundary-layer convective instability that has previously been removed by upright convection over the leading portion of the squall system. The negative MPV in the stratiform region is mainly the result of upward and rearward transport of the low-level convectively unstable air along the sloping FTR ascending flow and of processes that reverse the signs of both the convective stab...

The development of negative moist potential vorticity in the stratiform region of a simulated squall line

A mesoβ-scale momentum budget and its effect on larger-scale mean flow in a midlatitude mesoscale convective system are investigated using a numerical simulation of an intense squall line that occurred during 10–11 June 1985 PRE-STORM. It is found that the momentum generation normal to the line associated with the latent heating and cooling contributes most significantly to the momentum budget and determines the mesoβ-scale internal structure and evolution of the squall line. The momentum generation along the line contributes to the initial development of a mesovortex but has little effect on the final vertical structure of the along-line flow. Both vertical and horizontal momentum advection have significant contributions, particularly to the vertical mixing of the along-line flow; and this component of the horizontal momentum is locally transported down-gradient. It is also found that for midlatitude convective systems, convectively generated downdrafts can play as prominent a role as updrafts i...

Mesoscale Momentum Budget in a Midlatitude Squall Line: A Numerical Case Study

The structure and evolution of frontal rainbands in relation to conditional symmetric instability (CSI) are presented with a high-resolution, three-dimensional (3-D) simulation of an Eady wave. This work extends an earlier 2-D study of Knight and Hobbs by use of the same mesoscale model and similar initial conditions. The model simulates numerous updraft bands that correspond to the warm-sector (WSF), the surface cold frontal (SCF), the wide cold frontal (WCF) and the post-frontal (PCF) bands as observed. It is shown that the WSF band develops in a convectively near-neutral environment, while the WCF band forms under a convectively stable but slantwisely unstable condition and it interacts closely with the PCF and SCF bands. It is found that the present 3-D results conform in many respects to CSI theory and support the earlier 2-D interpretations of the rainbands. However, some differences exist, which include the development of deep and intense rainbands without downshear tilt, the deviation of the rainbands from the direction of thermal winds, strong low-level jets and intense across-frontal thermal gradients. By introducing the third spatial dimension, the model appears to show better the relationships between these rainbands and their environments, thus providing more realistic representation of the mesoscale structure and evolution of the rainbands. The importance of some physical parameters in determining the formation of various rainbands is examined. It is found that the surface friction, ice microphysics, static stability, baroclinicity and the magnitude of centrifugal forces all have important contributions to the formation, structure and dynamics of the frontal rainbands. DOI: 10.1034/j.1600-0870.1995.00003.x

Three-dimensional simulation of frontal rainbands and conditional symmetric instability in the Eady-wave model

The dynamic effects of a cumulus ensemble on a quasi-geostrophic weather system in the midlatitude region are examined, in addition to the heating due to release of latent heat. It has been found that the effects of the eddy vertical advection of momentum, and the eddy dynamic pressure due to the eddy kinetic energy associated with cumulus clouds are rather small. The only important dynamic effect comes from the ability of clouds to produce a horizontal eddy flux of vertical vorticity. In the momentum equation, this effect appears in the form of an eddy Coriolis force, which may be obtained from the horizontal eddy vorticity flux by rotating it by 90° clockwise. In the vorticity equation, it appears in the form of generation of positive vorticity by convective elements in the lower levels, and generation of negative vorticity in the upper levels. Using Ekman-layer pumping theory as the closure condition, the effects of cumulus convection on baroclinic instability are investigated. It has been found that the growth rate of a baroclinically unstable wave is increased appreciably by the cloud scale processes. DOI: 10.1111/j.2153-3490.1982.tb01793.x

Dynamics of quasi-geostrophic systems with cumulus convection

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Han-Ru Cho

Author Tools

Chat about Author

Papers

The development of negative moist potential vorticity in the stratiform region of a simulated squall line

Mesoscale Momentum Budget in a Midlatitude Squall Line: A Numerical Case Study

Three-dimensional simulation of frontal rainbands and conditional symmetric instability in the Eady-wave model

Dynamics of quasi-geostrophic systems with cumulus convection