scholarly journals Total Lightning Signatures of Thunderstorm Intensity over North Texas. Part II: Mesoscale Convective Systems

2007 ◽  
Vol 135 (10) ◽  
pp. 3303-3324 ◽  
Author(s):  
Scott M. Steiger ◽  
Richard E. Orville ◽  
Lawrence D. Carey
Keyword(s):  
Mesoscale Convective Systems ◽  
Research Network ◽  
Fort Worth ◽  
Convective Systems ◽  
Source Density ◽  
Stratiform Region ◽  
Straight Line ◽  
Lightning Detection ◽  
Mesoscale Convective ◽  
Total Lightning

Abstract Total lightning data from the Lightning Detection and Ranging (LDAR II) research network in addition to cloud-to-ground flash data from the National Lightning Detection Network (NLDN) and data from the Dallas–Fort Worth, Texas, Weather Surveillance Radar-1988 Doppler (WSR-88D) station (KFWS) were examined from individual cells within mesoscale convective systems that crossed the Dallas–Fort Worth region on 13 October 2001, 27 May 2002, and 16 June 2002. LDAR II source density contours were comma shaped, in association with severe wind events within mesoscale convective systems (MCSs) on 13 October 2001 and 27 May 2002. This signature is similar to the radar reflectivity bow echo. The source density comma shape was apparent 15 min prior to a severe wind report and lasted more than 20 min during the 13 October storm. Consistent relationships between severe straight-line winds, radar, and lightning storm cell characteristics (e.g., lightning heights) were not found for cells within MCSs as was the case for severe weather in supercells in Part I of this study. Cell interactions within MCSs are believed to weaken these relationships as reflectivity and lightning from nearby storms contaminate the cells of interest. Another hypothesis for these weak relations is that system, not individual cell, processes are responsible for severe straight-line winds at the surface. Analysis of the total lightning structure of the 13 October 2001 MCS showed downward-sloping source density contours behind the main convective line into the stratiform region. This further supports a charge advection mechanism in developing the stratiform charge structure. Bimodal vertical source density distributions were observed within MCS convection close to the center of the LDAR II network, while the lower mode was not detected at increasing range.

scholarly journals Total Lightning Characteristics Relative to Radar and Satellite Observations of Oklahoma Mesoscale Convective Systems

2013 ◽  
Vol 141 (5) ◽  
pp. 1593-1611 ◽  
Author(s):  
Jeffrey A. Makowski ◽  
Donald R. MacGorman ◽  
Michael I. Biggerstaff ◽  
William H. Beasley
Keyword(s):  
Early Morning ◽  
Mesoscale Convective Systems ◽  
Very High Frequency ◽  
Maximum Area ◽  
Convective Systems ◽  
Lightning Detection ◽  
Mesoscale Convective ◽  
Total Lightning ◽  
Cloud Tops ◽  
Mapping Arrays

Abstract The advent of regional very high frequency (VHF) Lightning Mapping Arrays (LMAs) makes it possible to begin analyzing trends in total lightning characteristics in ensembles of mesoscale convective systems (MCSs). Flash initiations observed by the Oklahoma LMA and ground strikes observed by the National Lightning Detection Network were surveyed relative to infrared satellite and base-scan radar reflectivity imagery for 30 mesoscale convective systems occurring over a 7-yr period. Total lightning data were available for only part of the life cycle of most MCSs, but well-defined peaks in flash rates were usually observed for MCSs having longer periods of data. The mean of the maximum 10-min flash rates for the ensemble of MCSs was 203 min−1 for total flashes and 41 min−1 for cloud-to-ground flashes (CGs). In total, 21% of flashes were CGs and 13% of CGs lowered positive charge to ground. MCSs with the largest maximum flash rates entered Oklahoma in the evening before midnight. All three MCSs entering Oklahoma in early morning after sunrise had among the smallest maximum flash rates. Flash initiations were concentrated in or near regions of larger reflectivity and colder cloud tops. The CG flash rates and total flash rates frequently evolved similarly, although the fraction of flashes striking ground usually increased as an MCS decayed. Total flash rates tended to peak approximately 90 min before the maximum area of the −52°C cloud shield, but closer in time to the maximum area of colder cloud shields. MCSs whose −52°C cloud shield grew faster tended to have larger flash rates.

Precipitation charge and size measurements in the stratiform region of two mesoscale convective systems

1995 ◽  
Vol 100 (D8) ◽  
pp. 16341 ◽  
Author(s):  
Monte G. Bateman ◽  
W. David Rust ◽  
Bradley F. Smull ◽  
Thomas C. Marshall
Keyword(s):  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Stratiform Region ◽  
Mesoscale Convective

Impact of Convectively Generated Low-Frequency Gravity Waves on Evolution of Mesoscale Convective Systems

2020 ◽  
Vol 77 (10) ◽  
pp. 3441-3460
Author(s):  
Rebecca D. Adams-Selin
Keyword(s):  
Gravity Waves ◽  
Low Frequency ◽  
Mesoscale Convective Systems ◽  
Cloud Base ◽  
Mature Stage ◽  
First Order ◽  
Convective Systems ◽  
Stratiform Region ◽  
Mesoscale Convective ◽  
Wave Modes

AbstractIdealized numerical simulations of mesoscale convective systems (MCSs) over a range of instabilities and shears were conducted to examine low-frequency gravity waves generated during initial and mature stages of convection. In all simulations, at initial updraft development a first-order wave was generated by heating extending through the depth of the troposphere. Additional first-order wave modes were generated each time the convective updraft reintensified. Each of these waves stabilized the environment in advance of the system. As precipitation descended below cloud base, and as a stratiform precipitation region developed, second-order wave modes were generated by cooling extending from the midlevels to the surface. These waves destabilized the environment ahead of the system but weakened the 0–5 km shear. Third-order wave modes could be generated by midlevel cooling caused by rear inflow intensification; these wave modes cooled the midlevels destabilizing the environment. The developing stage of each MCS was characterized by a cyclical process: developing updraft, generation of n = 1 wave, increase in precipitation, generation of n = 2 wave, and subsequent environmental destabilization reinvigorating the updraft. After rearward expansion of the stratiform region, the MCSs entered their mature stage and the method of updraft reinvigoration shifted to absorbing discrete convective cells produced in advance of each system. Higher-order wave modes destabilized the environment, making it more favorable to development of these cells and maintenance of the MCS. As initial simulation shear or instability increased, the transition from cyclical wave/updraft development to discrete cell/updraft development occurred more quickly.

scholarly journals Microphysical and Thermodynamic Structure and Evolution of the Trailing Stratiform Regions of Mesoscale Convective Systems during BAMEX. Part II: Column Model Simulations

2009 ◽  
Vol 137 (4) ◽  
pp. 1186-1205 ◽  
Author(s):  
Joseph A. Grim ◽  
Greg M. McFarquhar ◽  
Robert M. Rauber ◽  
Andrea M. Smith ◽  
Brian F. Jewett
Keyword(s):  
Mesoscale Convective Systems ◽  
Sharp Change ◽  
Melting Layer ◽  
Thermodynamic Structure ◽  
Column Model ◽  
Convective Systems ◽  
Stratiform Region ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Microphysical Processes

Abstract This study employed a nondynamic microphysical column model to evaluate the degree to which the microphysical processes of sublimation, melting, and evaporation alone can explain the evolution of the relative humidity (RH) and latent cooling profiles within the trailing stratiform region of mesoscale convective systems observed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). Simulations revealed that observations of a sharp change in the profile of RH, from saturated air with respect to ice above the melting layer to subsaturated air with respect to water below, developed in response to the rapid increase in hydrometeor fall speeds from 1–2 m s−1 for ice to 2–11 m s−1 for rain. However, at certain times and locations, such as the first spiral descent on 29 June 2003 within the notch of lower reflectivity, the air may remain subsaturated for temperatures (T) < 0°C. Sufficiently strong downdrafts above the melting level, such as the 1–3 m s−1 downdrafts observed in the notch of lower reflectivity on 29 June, could enable this state of sustained subsaturation. Sensitivity tests, where the hydrometeor size distributions and upstream RH profiles were varied within the range of BAMEX observations, revealed that the sharp contrast in the RH field across the melting layer always developed. The simulations also revealed that latent cooling from sublimation and melting resulted in the strongest cooling at altitudes within and above the melting layer for locations where hydrometeors did not reach the ground, such as within the rear anvil region, and where sustained subsaturated air is present for T < 0°C, such as is observed within downdrafts. Within the enhanced stratiform rain region, the air is typically at or near saturation for T < 0°C, whereas it is typically subsaturated for T > 0°C; thus, evaporation and melting result in the primary cooling in this region. The implications of these results for the descent of the rear inflow jet across the trailing stratiform region are discussed.

scholarly journals Modeling the Flash Rate of Thunderstorms. Part I: Framework

2011 ◽  
Vol 139 (10) ◽  
pp. 3093-3111 ◽  
Author(s):  
Johannes M. L. Dahl ◽  
Hartmut Höller ◽  
Ulrich Schumann
Keyword(s):  
Radar Data ◽  
Mesoscale Convective Systems ◽  
New Approach ◽  
Flash Rate ◽  
Convective Systems ◽  
Cloud Properties ◽  
Lightning Detection ◽  
Mesoscale Convective ◽  
Lightning Discharges ◽  
New Framework

Abstract In this study a straightforward theoretical approach to determining the flash rate in thunderstorms is presented. A two-plate capacitor represents the basic dipole charge structure of a thunderstorm, which is charged by the generator current and discharged by lightning. If the geometry of the capacitor plates, the generator-current density, and the lightning charge are known, and if charging and discharging are in equilibrium, then the flash rate is uniquely determined. To diagnose the flash rate of real-world thunderstorms using this framework, estimates of the required relationships between the predictor variables and observable cloud properties are provided. With these estimates, the flash rate can be parameterized. In previous approaches, the lightning rate has been set linearly proportional to the electrification rate (such as the storm’s generator power or generator current), which implies a constant amount of neutralization by lightning discharges (such as lightning energy or lightning charge). This leads to inconsistencies between these approaches. Within the new framework proposed here, the discharge strength is allowed to vary with storm geometry, which remedies the physical inconsistencies of the previous approaches. The new parameterization is compared with observations using polarimetric radar data and measurements from the lightning detection network, LINET. The flash rates of a broad spectrum of discrete thunderstorm cells are accurately diagnosed by the new approach, while the flash rates of mesoscale convective systems are overestimated.

scholarly journals Thermodynamic Properties of Mesoscale Convective Systems Observed during BAMEX

2008 ◽  
Vol 136 (11) ◽  
pp. 4242-4271 ◽  
Author(s):  
James Correia ◽  
Raymond W. Arritt
Keyword(s):  
Potential Temperature ◽  
Mesoscale Convective Systems ◽  
Lapse Rate ◽  
Spatiotemporal Variability ◽  
Cold Pool ◽  
Convective Systems ◽  
Stratiform Region ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Lapse Rates

Abstract Dropsonde observations from the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) are used to document the spatiotemporal variability of temperature, moisture, and wind within mesoscale convective systems (MCSs). Onion-type sounding structures are found throughout the stratiform region of MCSs, but the temperature and moisture variability is large. Composite soundings were constructed and statistics of thermodynamic variability were generated within each subregion of the MCS. The calculated air vertical velocity helped identify subsaturated downdrafts. It was found that lapse rates within the cold pool varied markedly throughout the MCS. Layered wet-bulb potential temperature profiles seem to indicate that air within the lowest several kilometers comes from a variety of source regions. It was also found that lapse-rate transitions across the 0°C level were more common than isothermal, melting layers. The authors discuss the implications these findings have and how they can be used to validate future high-resolution numerical simulations of MCSs.

scholarly journals Correction of Radar QPE Errors for Nonuniform VPRs in Mesoscale Convective Systems Using TRMM Observations

2013 ◽  
Vol 14 (5) ◽  
pp. 1672-1682 ◽  
Author(s):  
Youcun Qi ◽  
Jian Zhang ◽  
Qing Cao ◽  
Yang Hong ◽  
Xiao-Ming Hu
Keyword(s):  
High Resolution ◽  
Vertical Direction ◽  
Tropical Rainfall Measuring Mission ◽  
The United States ◽  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Quantitative Precipitation Estimation ◽  
Stratiform Region ◽  
Precipitation Estimation ◽  
Mesoscale Convective

Abstract Mesoscale convective systems (MCSs) contain both regions of convective and stratiform precipitation, and a bright band (BB) is often found in the stratiform region. Inflated reflectivity intensities in the BB often cause positive biases in radar quantitative precipitation estimation (QPE). A vertical profile of reflectivity (VPR) correction is necessary to reduce such biases. However, existing VPR correction methods for ground-based radars often perform poorly for MCSs owing to their coarse resolution and poor coverage in the vertical direction, especially at far ranges. Spaceborne radars such as the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), on the other hand, can provide high resolution VPRs. The current study explores a new approach of incorporating the TRMM VPRs into the VPR correction for the Weather Surveillance Radar-1988 Doppler (WSR-88D) radar QPE. High-resolution VPRs derived from the Ku-band TRMM PR data are converted into equivalent S-band VPRs using an empirical technique. The equivalent S-band TRMM VPRs are resampled according to the WSR-88D beam resolution, and the resampled (apparent) VPRs are then used to correct for BB effects in the WSR-88D QPE when the ground radar VPR cannot accurately capture the BB bottom. The new scheme was tested on six MCSs from different regions in the United States and it was shown to provide effective mitigation of the radar QPE errors due to BB contamination.

A five-year climatological lightning characteristics of linear mesoscale convective systems over North China

2021 ◽  
Vol 256 ◽  
pp. 105580
Author(s):  
Dongxia Liu ◽  
Mengyu Sun ◽  
Debin Su ◽  
Wenjing Xu ◽  
Han Yu ◽  
...  
Keyword(s):  
North China ◽  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Mesoscale Convective
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