The Role of Cloud Microphysics Parameterization in the Simulation of Mesoscale Convective System Clouds and Precipitation in the Tropical Western Pacific

2013 ◽  
Vol 70 (4) ◽  
pp. 1104-1128 ◽  
Author(s):  
K. Van Weverberg ◽  
A. M. Vogelmann ◽  
W. Lin ◽  
E. P. Luke ◽  
A. Cialella ◽  
...  
Keyword(s):  
Mesoscale Convective System ◽  
Cloud Microphysics ◽  
Western Pacific ◽  
Convective System ◽  
Fall Velocity ◽  
Surface Precipitation ◽  
Cloud Systems ◽  
Tropical Western Pacific ◽  
Mesoscale Convective

Abstract This paper presents a detailed analysis of convection-permitting cloud simulations, aimed at increasing the understanding of the role of parameterized cloud microphysics in the simulation of mesoscale convective systems (MCSs) in the tropical western Pacific (TWP). Simulations with three commonly used bulk microphysics parameterizations with varying complexity have been compared against satellite-retrieved cloud properties. An MCS identification and tracking algorithm was applied to the observations and the simulations to evaluate the number, spatial extent, and microphysical properties of individual cloud systems. Different from many previous studies, these individual cloud systems could be tracked over larger distances because of the large TWP domain studied. The analysis demonstrates that the simulation of MCSs is very sensitive to the parameterization of microphysical processes. The most crucial element was found to be the fall velocity of frozen condensate. Differences in this fall velocity between the experiments were more related to differences in particle number concentrations than to fall speed parameterization. Microphysics schemes that exhibit slow sedimentation rates for ice aloft experience a larger buildup of condensate in the upper troposphere. This leads to more numerous and/or larger MCSs with larger anvils. Mean surface precipitation was found to be overestimated and insensitive to the microphysical schemes employed in this study. In terms of the investigated properties, the performances of complex two-moment schemes were not superior to the simpler one-moment schemes, since explicit prediction of number concentration does not necessarily improve processes such as ice nucleation, the aggregation of ice crystals into snowflakes, and their sedimentation characteristics.

Prediction of Graupel Density in a Bulk Microphysics Scheme

2013 ◽  
Vol 70 (2) ◽  
pp. 410-429 ◽  
Author(s):  
Jason A. Milbrandt ◽  
Hugh Morrison
Keyword(s):  
A Priori ◽  
Kinematic Model ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Atmospheric Conditions ◽  
Microphysics Scheme ◽  
Surface Precipitation ◽  
Convective Region ◽  
Wide Range ◽  
Mesoscale Convective

Abstract A method to predict the bulk density of graupel ρg has been added to the two-moment Milbrandt–Yau bulk microphysics scheme. The simulation of graupel using the modified scheme is illustrated through idealized simulations of a mesoscale convective system using a 2D kinematic model with a prescribed flow field and different peak updraft speeds. To examine the relative impact of the various approaches to represent rimed ice, simulations were run for various graupel-only and graupel-plus-hail configurations. Because of the direct feedback of ρg to terminal fall speeds, the modified scheme produces a much different spatial distribution of graupel, with more mass concentrated in the convective region resulting in changes to the surface precipitation at all locations. With a strong updraft, the model can now produce solid precipitation at the surface in the convective region without a separate hail category. It is shown that a single rimed-ice category is capable of representing a realistically wide range of graupel characteristics in various atmospheric conditions without the need for a priori parameter settings. Sensitivity tests were conducted to examine various aspects of the scheme that affect the simulated ρg. Specific parameterizations pertaining to other hydrometeor categories now have a direct impact on the simulation of graupel, including the assumed aerosol distribution for droplet nucleation, which affects the drop sizes of both cloud and rain, and the mass–size relation for snow, which affects its density and hence the embryo density of graupel converted from snow due to riming.

The Role of Momentum Transport in the Motion of a Quasi-Idealized Mesoscale Convective System

2009 ◽  
Vol 137 (10) ◽  
pp. 3316-3338 ◽  
Author(s):  
Kelly M. Mahoney ◽  
Gary M. Lackmann ◽  
Matthew D. Parker
Keyword(s):  
Wind Field ◽  
Mesoscale Convective System ◽  
Leading Edge ◽  
Propagation Speed ◽  
Momentum Transport ◽  
Cold Pool ◽  
Convective System ◽  
Vertical Advection ◽  
Mesoscale Convective

Abstract Momentum transport is examined in a simulated midlatitude mesoscale convective system (MCS) to investigate its contribution to MCS motion. Momentum budgets are computed using model output to quantify the role of specific processes in determining the low-level wind field in the system’s surface-based cold pool. Results show that toward the leading convective line of the MCS and near the leading edge of the cold pool, the momentum field is most strongly determined by the vertical advection of the storm-induced perturbation wind. Across the middle rear of the system, the wind field is largely a product of the pressure gradient acceleration and, to a lesser extent, the vertical advection of the background environmental (i.e., base state) wind. The relative magnitudes of the vertical advection terms in an Eulerian momentum budget suggest that, for gust-front-driven systems, downward momentum transport by the MCS is a significant driver of MCS motion and potentially severe surface winds. Results further illustrate that the contribution of momentum transport to MCS speed occurs mainly via the enhancement of the cold pool propagation speed as higher-momentum air from aloft is transported into the surface-based cold pool.

scholarly journals The Role of Gravity Wave Breaking in a Case of Upper-Level Near-Cloud Turbulence

2019 ◽  
Vol 147 (12) ◽  
pp. 4567-4588 ◽  
Author(s):  
Dragana Zovko-Rajak ◽  
Todd P. Lane ◽  
Robert D. Sharman ◽  
Stanley B. Trier
Keyword(s):  
High Resolution ◽  
Gravity Wave ◽  
Mesoscale Convective System ◽  
Environmental Flow ◽  
Vertical Shear ◽  
Convective System ◽  
South Side ◽  
Mesoscale Convective ◽  
Upper Level

Abstract An observed turbulence encounter that occurred outside a mesoscale convective system over the central United States on 3 June 2005 is investigated using observations and high-resolution numerical modeling. Here, the mechanisms associated with the observed moderate-to-severe turbulence during the evolution of this convective system are examined. Comparison between aircraft-observed eddy dissipation rate data with satellite and radar shows that a majority of turbulence reports are located on the south side and outside of a nocturnal mesoscale convective system (MCS), relatively large distances from the active convective regions. Simulations show that divergent storm-induced upper-level outflow reduces the environmental flow on the south side of the MCS, while on the north and northwest side it enhances the environmental flow. This upper-level storm outflow enhances the vertical shear near the flight levels and contributes to mesoscale reductions in Richardson number to values that support turbulence. In addition to the role of the MCS-induced outflow, high-resolution simulations (1.1-km horizontal grid spacing) show that turbulence is largely associated with a large-amplitude gravity wave generated by the convective system, which propagates away from it. As the wave propagates in the region with enhanced vertical shear caused by the storm-induced upper-level outflow, it amplifies, overturns, and breaks down into turbulence. The location of the simulated turbulence relative to the storm agrees with the observations and the analysis herein provides insight into the key processes underlying this event.

Investigation of cloud-to-ground flashes in the Non-Precipitating Stratiform Region of a Mesoscale Convective System on 20 August 2019 and Implications for Decision Support Services

2021 ◽  
Author(s):  
CHRISTOPHER J. SCHULTZ ◽  
ROGER E. ALLEN ◽  
KELLEY M. MURPHY ◽  
BENJAMIN S. HERZOG ◽  
STEPHANIE A. WEISS ◽  
...  
Keyword(s):  
Decision Support ◽  
Support Services ◽  
Risk Model ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Surface Precipitation ◽  
Stratiform Region ◽  
Mesoscale Convective ◽  
Average Size ◽  
Differential Reflectivity

AbstractInfrequent lightning flashes occurring outside of surface precipitation pose challenges to Impact-based Decision Support Services (IDSS) for outdoor activities. This paper examines the remote sensing observations from an event on 20 August 2019 where multiple cloud-to-ground flashes occurred over 10 km outside surface precipitation (lowest radar tilt reflectivity <10 dBZ and no evidence of surface precipitation) in a trailing stratiform region of a mesoscale convective system. The goal is to demonstrate the fusion of radar with multiple lightning observations and a lightning risk model to demonstrate how reflectivity and differential reflectivity combined provided the best indicator for the potential of lightning where all of the other lightning safety methods failed.Thirteen lightning flashes were observed by the Geostationary Lightning Mapper (GLM) within the trailing stratiform region between 2100 and 2300 UTC. The average size of the thirteen lightning flashes was 3184 km2, with an average total optical energy of 7734 fJ. Seventy-five NLDN flash locations were coincident with the thirteen GLM flashes, resulting in an average of 5.8 NLDN flashes (in-cloud (IC) and cloud-to-ground (CG)) per 37 GLM flash. Five of the GLM flashes contained at least one positive cloud-to-ground flash (+CG) flash identified by the NLDN, with peak amplitudes ranging between 66 and 136 kA. All eight CG flashes identified by the NLDN were located more than 10 km outside surface precipitation. The only indication of the potential of these infrequently large flashes was the presence of depolarization streaks in differential reflectivity (ZDR) and enhanced reflectivity near the melting layer.

scholarly journals Effects of Urban Plume Aerosols on a Mesoscale Convective System

2016 ◽  
Vol 73 (12) ◽  
pp. 4641-4660 ◽  
Author(s):  
Stacey Kawecki ◽  
Geoffrey M. Henebry ◽  
Allison L. Steiner
Keyword(s):  
Phase I ◽  
Phase Ii ◽  
Kansas City ◽  
Mesoscale Convective System ◽  
Cloud Microphysics ◽  
Squall Line ◽  
Convective System ◽  
Mesoscale Convective ◽  
Urban Emissions ◽  
The Impact

Abstract This study examines the effects of urban aerosols on a mesoscale convective system (MCS) in the central Great Plains with the Weather Research and Forecasting Model coupled with chemistry (WRF-Chem). Urban emissions from Kansas City, Missouri, were scaled by factors of 0.5, 1.0, and 2.0 to investigate the impact of urban aerosol load on MCS propagation and strength. The first half of the storm development is characterized by a stationary front to the north of Kansas City (phase I; 1800 UTC 26 May–0600 UTC 27 May), which develops into a squall line south of the urban area (phase II; 0600–1800 UTC 27 May). During phase I, doubling urban emissions shifts the precipitation accumulation, with enhancement downwind of the storm propagation and suppression upwind. During phase II, a squall line develops in the baseline and doubled emissions scenarios but not when emissions are halved. These changes in MCS propagation and strength are a function of cold pool strength, which is determined by microphysical processes and directly influenced by aerosol load. Overall, changes in urban emissions drive changes in cloud microphysics, which trigger large-scale changes in storm morphology and precipitation patterns. These results show that urban emissions can play an important role in mesoscale weather systems.

Ensemble Probabilistic Prediction of a Mesoscale Convective System and Associated Polarimetric Radar Variables Using Single-Moment and Double-Moment Microphysics Schemes and EnKF Radar Data Assimilation

2017 ◽  
Vol 145 (6) ◽  
pp. 2257-2279 ◽  
Author(s):  
Bryan J. Putnam ◽  
Ming Xue ◽  
Youngsun Jung ◽  
Nathan A. Snook ◽  
Guifu Zhang
Keyword(s):  
Mesoscale Convective System ◽  
Radar Data ◽  
Convective Precipitation ◽  
Convective System ◽  
Ensemble Forecasts ◽  
Verification Methods ◽  
Probabilistic Forecasts ◽  
Mesoscale Convective ◽  
Single Moment ◽  
Double Moment

Abstract Ensemble-based probabilistic forecasts are performed for a mesoscale convective system (MCS) that occurred over Oklahoma on 8–9 May 2007, initialized from ensemble Kalman filter analyses using multinetwork radar data and different microphysics schemes. Two experiments are conducted, using either a single-moment or double-moment microphysics scheme during the 1-h-long assimilation period and in subsequent 3-h ensemble forecasts. Qualitative and quantitative verifications are performed on the ensemble forecasts, including probabilistic skill scores. The predicted dual-polarization (dual-pol) radar variables and their probabilistic forecasts are also evaluated against available dual-pol radar observations, and discussed in relation to predicted microphysical states and structures. Evaluation of predicted reflectivity (Z) fields shows that the double-moment ensemble predicts the precipitation coverage of the leading convective line and stratiform precipitation regions of the MCS with higher probabilities throughout the forecast period compared to the single-moment ensemble. In terms of the simulated differential reflectivity (ZDR) and specific differential phase (KDP) fields, the double-moment ensemble compares more realistically to the observations and better distinguishes the stratiform and convective precipitation regions. The ZDR from individual ensemble members indicates better raindrop size sorting along the leading convective line in the double-moment ensemble. Various commonly used ensemble forecast verification methods are examined for the prediction of dual-pol variables. The results demonstrate the challenges associated with verifying predicted dual-pol fields that can vary significantly in value over small distances. Several microphysics biases are noted with the help of simulated dual-pol variables, such as substantial overprediction of KDP values in the single-moment ensemble.

scholarly journals Comprehensive Analysis of a Coast Thunderstorm That Produced a Sprite over the Bohai Sea

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 718
Author(s):  
Cong Pan ◽  
Jing Yang ◽  
Kun Liu ◽  
Yu Wang
Keyword(s):  
Bohai Sea ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Return Stroke ◽  
Absolute Value ◽  
Transient Luminous Events ◽  
Stratiform Region ◽  
Before And After ◽  
Mesoscale Convective ◽  
Cloud To Ground Lightning

Sprites are transient luminous events (TLEs) that occur over thunderstorm clouds that represent the direct coupling relationship between the troposphere and the upper atmosphere. We report the evolution of a mesoscale convective system (MCS) that produced only one sprite event, and the characteristics of this thunderstorm and the related lightning activity are analyzed in detail. The results show that the parent flash of the sprite was positive cloud-to-ground lightning (+CG) with a single return stroke, which was located in the trailing stratiform region of the MCS with a radar reflectivity of 25 to 35 dBZ. The absolute value of the negative CG (−CG) peak current for half an hour before and after the occurrence of the sprite was less than 50 kA, which was not enough to produce the sprite. Sprites tend to be produced early in the maturity-to-dissipation stage of the MCS, with an increasing percentage of +CG to total CG (POP), indicating that the sprite production was the attenuation of the thunderstorm and the area of the stratiform region.

Sign in / Sign up

Export Citation Format

Share Document