A Numerical Study of the Stratiform Region of a Fast-Moving Squall Line. Part II: Relationship between Mass, Pressure, and Momentum Fields

1995 ◽  
Vol 52 (3) ◽  
pp. 331-352 ◽  
Author(s):  
G. Caniaux ◽  
J-P. Lafore ◽  
J-L. Redelsperger
Keyword(s):  
Fast Moving ◽  
Numerical Study ◽  
Squall Line ◽  
Stratiform Region ◽  
Line Part

scholarly journals Sensitivity of a Cloud-Resolving Model to Bulk and Explicit Bin Microphysical Schemes. Part I: Comparisons

2009 ◽  
Vol 66 (1) ◽  
pp. 3-21 ◽  
Author(s):  
Xiaowen Li ◽  
Wei-Kuo Tao ◽  
Alexander P. Khain ◽  
Joanne Simpson ◽  
Daniel E. Johnson
Keyword(s):  
Cloud Microphysics ◽  
Squall Line ◽  
Mature Stage ◽  
High Temporal Resolution ◽  
Stratiform Region ◽  
Storm Flow ◽  
Cloud Resolving Model ◽  
Storm Dynamics ◽  
Convective Cells ◽  
Heating Profiles

Abstract A two-dimensional cloud-resolving model is used to study the sensitivities of two microphysical schemes, a bulk scheme and an explicit spectral bin scheme, in simulating a midlatitude summertime squall line [Preliminary Regional Experiment for Storm-Scale Operational and Research Meteorology (PRE-STORM), 10–11 June 1985]. In this first part of a two-part paper, the developing and mature stages of simulated storms are compared in detail. Some variables observed during the field campaign are also presented for validation. It is found that both schemes agree well with each other, and also with published observations and retrievals, in terms of storm structures and evolution, average storm flow patterns, pressure and temperature perturbations, and total heating profiles. The bin scheme is able to produce a much more extensive and homogeneous stratiform region, which compares better with observations. However, instantaneous fields and high temporal resolution analyses show distinct characteristics in the two simulations. During the mature stage, the bulk simulation produces a multicell storm with convective cells embedded in its stratiform region. Its leading convection also shows a distinct life cycle (strong evolution). In contrast, the bin simulation produces a unicell storm with little temporal variation in its leading cell regeneration (weak evolution). More detailed, high-resolution observations are needed to validate and, perhaps, generalize these model results. Interactions between the cloud microphysics and storm dynamics that produce the sensitivities described here are discussed in detail in Part II of this paper.

Observations of a Squall Line and Its Near Environment Using High-Frequency Rawinsonde Launches during VORTEX2

2010 ◽  
Vol 138 (11) ◽  
pp. 4076-4097 ◽  
Author(s):  
George H. Bryan ◽  
Matthew D. Parker
Keyword(s):  
Wind Shear ◽  
Deep Layer ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Squall Line ◽  
Cold Pool ◽  
Low Level ◽  
Stratiform Region ◽  
Gust Front

Abstract Rawinsonde data were collected before and during passage of a squall line in Oklahoma on 15 May 2009 during the Second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2). Nine soundings were released within 3 h, allowing for unprecedented analysis of the squall line’s internal structure and nearby environment. Four soundings were released in the prestorm environment and they document the following features: low-level cooling associated with the reduction of solar isolation by a cirrus anvil; abrupt warming (1.5 K in 30 min) above the boundary layer, which is probably attributable to a gravity wave; increases in both low-level and deep-layer vertical wind shear within 100 km of the squall line; and evidence of ascent extending at least 75 km ahead of the squall line. The next sounding was released ∼5 km ahead of the squall line’s gust front; it documented a moist absolutely unstable layer within a 2-km-deep layer of ascent, with vertical air velocity of approximately 6 m s−1. Another sounding was released after the gust front passed but before precipitation began; this sounding showed the cold pool to be ∼4 km deep, with a cold pool intensity C ≈ 35 m s−1, even though this sounding was located only 8 km behind the surface gust front. The final three soundings were released in the trailing stratiform region of the squall line, and they showed typical features such as: “onion”-shaped soundings, nearly uniform equivalent potential temperature over a deep layer, and an elevated rear inflow jet. The cold pool was 4.7 km deep in the trailing stratiform region, and extended ∼1 km above the melting level, suggesting that sublimation was a contributor to cold pool development. A mesoscale analysis of the sounding data shows an upshear tilt to the squall line, which is consistent with the cold pool intensity C being much larger than a measure of environmental vertical wind shear ΔU. This dataset should be useful for evaluating cloud-scale numerical model simulations and analytic theory, but the authors argue that additional observations of this type should be collected in future field projects.

scholarly journals Incorporating Diagnosed Intercept Parameters and the Graupel Category within the ARPS Cloud Analysis System for the Initialization of Double-Moment Microphysics: Testing with a Squall Line over South China

2016 ◽  
Vol 144 (1) ◽  
pp. 371-392 ◽  
Author(s):  
Yujie Pan ◽  
Ming Xue ◽  
Guoqing Ge
Keyword(s):  
Precipitation Forecast ◽  
Squall Line ◽  
Precipitation Region ◽  
Stratiform Region ◽  
Regional Prediction ◽  
Analysis Scheme ◽  
Stratiform Precipitation ◽  
Double Moment ◽  
Analysis System ◽  
Cloud Analysis

Abstract In this study, a new set of reflectivity equations are introduced into the Advanced Regional Prediction System (ARPS) cloud analysis system. This set of equations incorporates double-moment microphysics information in the analysis by adopting a set of diagnostic relationships between the intercept parameters and the corresponding mass mixing ratios. A reflectivity- and temperature-based graupel classification scheme is also implemented according to a hydrometeor identification (HID) diagram. A squall line that occurred on 23 April 2007 over southern China containing a pronounced trailing stratiform precipitation region is used as a test case to evaluate the impacts of the enhanced cloud analysis scheme. The results show that using the enhanced cloud analysis scheme is able to better capture the characteristics of the squall line in the forecast. The predicted squall line exhibits a wider stratiform region and a more clearly defined transition zone between the leading convection and the trailing stratiform precipitation region agreeing better with observations in general, when using the enhanced cloud analysis together with the two-moment microphysics scheme. The quantitative precipitation forecast skill score is also improved.

scholarly journals Effects of Under-Resolved Convective Dynamics on the Evolution of a Squall Line

2019 ◽  
Vol 148 (1) ◽  
pp. 289-311 ◽  
Author(s):  
Adam Varble ◽  
Hugh Morrison ◽  
Edward Zipser
Keyword(s):  
Early Stage ◽  
Deep Convection ◽  
Mesoscale Convective System ◽  
Squall Line ◽  
Cold Pool ◽  
Convective System ◽  
Stratiform Region ◽  
Mesoscale Convective ◽  
Upper Level ◽  
Resolution Simulation

Abstract Simulations of a squall line observed on 20 May 2011 during the Midlatitude Continental Convective Clouds Experiment (MC3E) using 750- and 250-m horizontal grid spacing are performed. The higher-resolution simulation has less upshear-tilted deep convection and a more elevated rear inflow jet than the coarser-resolution simulation in better agreement with radar observations. A stronger cold pool eventually develops in the 250-m run; however, the more elevated rear inflow counteracts the cold pool circulation to produce more upright convective cores relative to the 750-m run. The differing structure in the 750-m run produces excessive midlevel front-to-rear detrainment, reinforcing excessive latent cooling and rear inflow descent at the rear of the stratiform region in a positive feedback. The contrasting mesoscale circulations are connected to early stage deep convective draft differences in the two simulations. Convective downdraft condensate mass, latent cooling, and downward motion all increase with downdraft area similarly in both simulations. However, the 750-m run has a relatively greater number of wide and fewer narrow downdrafts than the 250-m run averaged to the same 750-m grid, a consequence of downdrafts being under-resolved in the 750-m run. Under-resolved downdrafts in the 750-m run are associated with under-resolved updrafts and transport mid–upper-level zonal momentum downward to low levels too efficiently in the early stage deep convection. These results imply that under-resolved convective drafts in simulations may vertically transport air too efficiently and too far vertically, potentially biasing buoyancy and momentum distributions that impact mesoscale convective system evolution.

scholarly journals A Numerical Study of the Beijing Extreme Rainfall of 21 July 2012 and the Impact of Topography

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Hongxiong Xu ◽  
Wenqing Yao
Keyword(s):  
Numerical Study ◽  
Deep Convection ◽  
Mesoscale Convective System ◽  
Extreme Rainfall ◽  
Convective System ◽  
Stratiform Region ◽  
Moist Environment ◽  
The Right ◽  
Convective Cells ◽  
The Impact

The extreme rainfall on 21 July 2012 is the heaviest rainfall that has occurred in Beijing since 1961. Observations and WRF (Weather Research and Forecasting) model are used to study the effect of MCS (mesoscale convective system) and topography on the rainfall. In this high-impact event, a quasi-stationary MCS developed in a favorable moist environment. The numerical simulation successfully reproduced the amount, location, and time evolution of the rainfall despite 4–6 h delay. In particular, the model reproduced the repeat passage of convective cells at the leading convergence line region along Taihang Mountains and the trailing stratiform region, producing the rainfall at nearly the right position. Results indicate the important roles of mesolow and low-level jet in maintaining the conditional instability that lifted the moist air to trigger deep convection and the repeated initiation and movement of the line shaped convective cells that produced the rainfall. The sensitive experiment was then further carried out to examine the effect of topography on this heavy rainfall. The reduction in model elevation field significantly influenced the above mesoscale systems, which lead to convective cells becoming less organized, and the peak rainfall amount in Beijing decreased by roughly 50%.

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