Variability of Updraft and Downdraft Characteristics in a Large Parameter Space Study of Convective Storms

2009 ◽  
Vol 137 (5) ◽  
pp. 1550-1561 ◽  
Author(s):  
Cody Kirkpatrick ◽  
Eugene W. McCaul ◽  
Charles Cohen
Keyword(s):  
Vertical Distribution ◽  
Wind Shear ◽  
Convective Available Potential Energy ◽  
Environmental Parameters ◽  
Cloud Base ◽  
Convective Storm ◽  
Convective Storms ◽  
Regression Methods ◽  
The Vertical Distribution ◽  
Large Parameter Space

Abstract Over 200 convective storm simulations are analyzed to examine the variability in storm vertical velocity and updraft area characteristics as a function of basic environmental parameters. While it is known that bulk properties of the troposphere such as convective available potential energy (CAPE) and deep-layer wind shear exert significant influence over updraft intensity and area, additional parameters such as the temperature at the cloud base, the height of the level of free convection (LFC), and the vertical distribution of buoyancy also have an effect. For example, at low CAPE, updraft strength is strongly related to the vertical distribution of buoyancy, and also to the bulk environmental wind shear. More generally, updraft area and its temporal variability both tend to increase in environments where the LFC is raised. Additionally, in environments with persistent storms, downdraft strength is sensitive to the bulk shear, environmental temperature, and LFC height. Using multiple linear regression methods, the best combinations of environmental parameters explain up to 81% of the interexperiment variance in second-hour mean peak updraft velocity, 74% for midlevel updraft area, and 64% for downdraft velocity. Downdraft variability is explained even less well (49%) when only persistent storms are considered. These idealized simulation results show that it is easier to predict storm updraft characteristics than those of the downdraft.

The Motion of Simulated Convective Storms as a Function of Basic Environmental Parameters

2007 ◽  
Vol 135 (9) ◽  
pp. 3033-3051 ◽  
Author(s):  
J. Cody Kirkpatrick ◽  
Eugene W. McCaul ◽  
Charles Cohen
Keyword(s):  
Vertical Distribution ◽  
Temporal Variability ◽  
Convective Available Potential Energy ◽  
Environmental Parameters ◽  
Vertical Shear ◽  
Cloud Base ◽  
Base Temperature ◽  
Storm Evolution ◽  
The Mean ◽  
The Vertical Distribution

Abstract Based on results from a three-dimensional cloud-resolving model, it is shown that simulated convective storm motions are affected by thermodynamic as well as kinematic properties of the environment. In addition to the mean wind and its vertical shear, the effect on isolated storm motion of parameters such as bulk convective available potential energy (CAPE), the vertical distribution of buoyancy in the profile, the heights of the lifting condensation level (LCL) and level of free convection (LFC), and cloud-base temperature is considered. Storm motions show at least some sensitivity to all input parameters. Consistent with previous studies, hodograph radius has the most pronounced effect, but the vertical distribution of shear (which also influences the mean wind) affects storm evolution and propagation, even when the effective hodograph radius is unchanged. Among the thermodynamic parameters, the most significant variations occur when the LCL–LFC configuration is modified or when cloud-base temperature is changed. The effects of increases in bulk CAPE act mainly to increase the temporal variability of storm motions. This temporal variability is found to consist both of oscillations about a mean state and trends (accelerations) and is related to increases in the complexity of storm evolution with increasing CAPE. The results point to the importance of environmental factors that enhance storm intensity and rotation, which play a key role in determining storm deviate motion.

scholarly journals Ambient conditions prevailing during hail events in central Europe

2020 ◽  
Author(s):  
Michael Kunz ◽  
Jan Wandel ◽  
Elody Fluck ◽  
Sven Baumstark ◽  
Susanna Mohr ◽  
...  
Keyword(s):  
Wind Shear ◽  
Deep Layer ◽  
Lapse Rate ◽  
Synoptic Scale ◽  
Ambient Conditions ◽  
Convective Storm ◽  
Convective Storms ◽  
Investigation Area ◽  
Severe Thunderstorms ◽  
Eyewitness Reports

Abstract. Around 26 000 severe convective storm tracks between 2005 and 2014 have been estimated from 2D radar reflectivity for parts of Europe, including Germany, France, Belgium, and Luxembourg. This event-set was further combined with eyewitness reports, convection-related parameters from ERA-Interim reanalysis and synoptic-scale fronts based on the same reanalysis. Our analyses reveal that about a quarter of all severe thunderstorms in the investigation area were associated with a front. Over complex terrains, such as in southern Germany, the proportion of frontal convective storms is around 10–15 %, while over flat terrain half of the events require a front to trigger convection. Frontal hailstorms on average produce larger hailstones and have a longer track. These events usually develop in a high-shear environment. Using composites of environmental conditions centered around the hailstorm tracks, we found that dynamical proxies such as deep-layer shear or storm-relative helicity become important when separating hail diameters and, in particular, their lengths; 0–3 km helicity as a dynamical proxy performs better compared to wind shear for the separation. In contrast, thermodynamical proxies such as Lifted Index or lapse rate show only small differences between the different intensity classes.

Convective-storm environments in subtropical South America from high-frequency soundings during RELAMPAGO-CACTI

2021 ◽  
Author(s):  
Russ S. Schumacher ◽  
Deanna A. Hence ◽  
Stephen W. Nesbitt ◽  
Robert J. Trapp ◽  
Karen A. Kosiba ◽  
...  
Keyword(s):  
South America ◽  
High Frequency ◽  
Wind Shear ◽  
Field Experiments ◽  
Deep Convection ◽  
Convective Available Potential Energy ◽  
Vertical Wind Shear ◽  
Mobile Platforms ◽  
Convective Storms ◽  
Low Level

AbstractDuring the RELAMPAGO-CACTI field experiments in 2018-19, an unprecedented number of balloon-borne soundings were collected in Argentina. Radiosondes were launched from both fixed and mobile platforms, yielding 2712 soundings during the period 15 October 2018-30 April 2019. Approximately 20% of these soundings were collected by highly mobile platforms, strategically positioned for each intensive observing period, and launching approximately once per hour. The combination of fixed and mobile soundings capture both the overall conditions characterizing the RELAMPAGO-CACTI campaign, as well as the detailed evolution of environments supporting the initiation and upscale growth of deep convective storms, including some that produced hazardous hail and heavy rainfall. Episodes of frequent convection were characterized by sufficient quantities of moisture and instability for deep convection, along with deep-layer vertical wind shear supportive of organized or rotating storms. Eleven soundings showed most-unstable convective available potential energy (MUCAPE) exceeding 6000 J kg−1, comparable to the extreme instability observed in other parts of the world with intense deep convection. Parameters used to diagnose severe-storm potential showed that conditions were often favorable for supercells and severe hail, but not for tornadoes, primarily owing to insufficient low-level wind shear. High-frequency soundings also revealed the structure and evolution of the boundary layer leading up to convection initiation, convectively generated cold pools, the South American Low-Level Jet (SALLJ), and elevated nocturnal convection. This sounding dataset will enable improved understanding and prediction of convective storms and their surroundings in subtropical South America, as well as comparisons with other heavily studied regions such as the central United States that have not previously been possible.

scholarly journals Severe Convective Storm Environments in Turkey

2017 ◽  
Vol 145 (12) ◽  
pp. 4711-4725 ◽  
Author(s):  
Abdullah Kahraman ◽  
Mikdat Kadioglu ◽  
Paul M. Markowski
Keyword(s):  
Wind Shear ◽  
Convective Available Potential Energy ◽  
Vertical Wind Shear ◽  
The United States ◽  
Reanalysis Data ◽  
Severe Weather ◽  
Vertical Wind ◽  
Severe Storm ◽  
Convective Storms ◽  
Ecmwf Reanalysis

Severe convective storms occasionally result in loss of life and property in Turkey, a country not known for its severe convective weather. However, relatively little is known about the characteristics of Turkish severe weather environments. This paper documents these characteristics using European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data on tornado and severe hail days in Turkey from 1979 to 2013. Severe storm environments are characterized by larger convective available potential energy (CAPE) in Turkey compared to the rest of Europe, but the CAPE values are less than those in typical U.S. severe storm environments. Severe hail is associated with large CAPE and vertical wind shear. Nonmesocyclonic tornadoes are associated with less CAPE compared with the other forms of severe weather. Deep-layer vertical wind shear is slightly weaker in Turkish supercell environments than in U.S. supercell environments, and Turkish tornadic supercell environments are characterized by much weaker low-level shear than in the United States and Europe, at least in the ECMWF reanalysis data. Composite parameters such as the supercell composite parameter (SCP) and energy–helicity index (EHI) can discriminate between very large hail and large hail environments.

scholarly journals Vertical and seasonal distribution of eight Clausocalanus species (Copepoda: Calanoida) in oligotrophic waters

2004 ◽  
Vol 61 (4) ◽  
pp. 645-653 ◽  
Author(s):  
Àurea Peralba ◽  
Maria Grazia Mazzocchi
Keyword(s):  
Vertical Distribution ◽  
Quantitative Data ◽  
Environmental Parameters ◽  
Seasonal Distribution ◽  
Ecological Niches ◽  
Seasonal Cycles ◽  
Tyrrhenian Sea ◽  
Gulf Of Naples ◽  
Offshore Station ◽  
The Vertical Distribution

Abstract Copepods of the genus Clausocalanus Giesbrecht, 1888 are among the most abundant calanoids in the Mediterranean Sea, both in coastal and offshore regions. The vertical distribution of C. arcuicornis, C. furcatus, C. jobei, C. lividus, C. mastigophorus, C. parapergens, C. paululus, and C. pergens, which co-occur in the upper 200 m in the Gulf of Naples (Tyrrhenian Sea), was investigated during an annual sampling cycle conducted at an offshore station in 2002. The quantitative data on distribution of each species were analysed in relation to the environmental parameters. The patterns that we observed in the seasonal cycles and vertical distribution provided insights on the ecological niches of the eight Clausocalanus species.

History of Convective Storm Science

2016 ◽  
Author(s):  
Charles A. Doswell
Keyword(s):  
United States ◽  
World War Ii ◽  
Convective Available Potential Energy ◽  
Vertical Wind Shear ◽  
The United States ◽  
World War ◽  
Convective Storm ◽  
Severe Storms ◽  
Convective Storms ◽  
Modern Era

Convective storms are the result of a disequilibrium created by solar heating in the presence of abundant low-level moisture, resulting in the development of buoyancy in ascending air. Buoyancy typically is measured by the Convective Available Potential Energy (CAPE) associated with air parcels. When CAPE is present in an environment with strong vertical wind shear (winds changing speed and/or direction with height), convective storms become increasingly organized and more likely to produce hazardous weather: strong winds, large hail, heavy precipitation, and tornadoes. Because of their associated hazards and their impact on society, in some nations (notably, the United States), there arose a need to have forecasts of convective storms. Pre-20th-century efforts to forecast the weather were hampered by a lack of timely weather observations and by the mathematical impossibility of direct solution of the equations governing the weather. The first severe convective storm forecaster was J. P. Finley, who was an Army officer, and he was ordered to cease his efforts at forecasting in 1887. Some Europeans like Alfred Wegener studied tornadoes as a research topic, but there was no effort to develop convective storm forecasting. World War II aircraft observations led to the recognition of limited storm science in the topic of convective storms, leading to a research program called the Thunderstorm Product that concentrated diverse observing systems to learn more about the structure and evolution of convective storms. Two Air Force officers, E. J. Fawbush and R. C. Miller, issued the first tornado forecasts in the modern era, and by 1953 the U.S. Weather Bureau formed a Severe Local Storms forecasting unit (SELS, now designated the Storm Prediction Center of the National Weather Service). From the outset of the forecasting efforts, it was evident that more convective storm research was needed. SELS had an affiliated research unit called the National Severe Storms Project, which became the National Severe Storms Laboratory in 1963. Thus, research and operational forecasting have been partners from the outset of the forecasting efforts in the United States—with major scientific contributions from the late T. T. Fujita (originally from Japan), K. A. Browning (from the United Kingdom), R. A. Maddox, J. M. Fritsch, C. F. Chappell, J. B. Klemp, L. R. Lemon, R. B. Wilhelmson, R. Rotunno, M. Weisman, and numerous others. This has resulted in the growth of considerable scientific understanding about convective storms, feeding back into the improvement in convective storm forecasting since it began in the modern era. In Europe, interest in both convective storm forecasting and research has produced a European Severe Storms Laboratory and an experimental severe convective storm forecasting group. The development of computers in World War II created the ability to make numerical simulations of convective storms and numerical weather forecast models. These have been major elements in the growth of both understanding and forecast accuracy. This will continue indefinitely.

scholarly journals Climatology of Convective Storms in Estonia from Radar Data and Severe Convective Environments

2021 ◽  
Vol 13 (11) ◽  
pp. 2178
Author(s):  
Tanel Voormansik ◽  
Tuule Müürsepp ◽  
Piia Post
Keyword(s):  
Convective Available Potential Energy ◽  
Grid Cell ◽  
Radar Data ◽  
Detection Algorithm ◽  
Radar Reflectivity ◽  
Convective Storm ◽  
Convective Storms ◽  
Base Level ◽  
Circulation Types ◽  
System Data

Data from the C-band weather radar located in central Estonia in conjunction with the latest reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF), ERA5, and Nordic Lightning Information System (NORDLIS) lightning location system data are used to investigate the climatology of convective storms for nine summer periods (2010–2019, 2017 excluded). First, an automated 35-dBZ reflectivity threshold-based storm area detection algorithm is used to derive initial individual convective cells from the base level radar reflectivity. Those detected cells are used as a basis combined with convective available potential energy (CAPE) values from ERA5 reanalysis to find thresholds for a severe convective storm in Estonia. A severe convective storm is defined as an area with radar reflectivity at least 51 dBZ and CAPE at least 80 J/kg. Verification of those severe convective storm areas with lightning data reveals a good correlation on various temporal scales from hourly to yearly distributions. The probability of a severe convective storm day in the study area during the summer period is 45%, and the probability of a thunderstorm day is 54%. Jenkinson Collison’ circulation types are calculated from ERA5 reanalysis to find the probability of a severe convective storm depending on the circulation direction and the representativeness of the investigated period by comparing it against 1979–2019. The prevailing airflow direction is from SW and W, whereas the probability of the convective storm to be severe is in the case of SE and S airflow. Finally, the spatial distribution of the severe convective storms shows that the yearly mean number of severe convective days for the 100 km2 grid cell is mostly between 3 and 8 in the distance up to 150 km from radar. Severe convective storms are most frequent in W and SW parts of continental Estonia.

scholarly journals Environmental and Radar Characteristics of Gargantuan Hail-Producing Storms

2021 ◽  
Author(s):  
Rachel E. Gutierrez ◽  
Matthew R. Kumjian
Keyword(s):  
Wind Shear ◽  
Convective Available Potential Energy ◽  
Vertical Wind Shear ◽  
Environmental Parameters ◽  
Liquid Water Content ◽  
Growth Region ◽  
Maximum Dimension ◽  
Severe Storms ◽  
Slight Tendency ◽  
Extensive Damage

AbstractStorms that produce gargantuan hail (defined here as ≥ 6 inches or 15 cm in maximum dimension), although seemingly rare, can cause extensive damage to property and infrastructure, and cause injury or even death to humans and animals. Currently, we are limited in our ability to accurately predict gargantuan hail and detect gargantuan hail on radar. In this study, we analyze the environments and radar characteristics of gargantuan hail-producing storms to define the parameter space of environments in which gargantuan hail occurs, and compare environmental parameters and radar signatures in these storms to storms producing other sizes of hail. We find that traditionally used environmental parameters used for severe storms prediction, such as most unstable convective available potential energy (MUCAPE) and 0–6 km vertical wind shear, display considerable overlap between gargantuan hail-producing storm environments and those that produce smaller hail. There is a slight tendency for larger MUCAPE values for gargantuan hail cases, however. Additionally, gargantuan hail-producing storms seem to have larger low-level storm-relative winds and larger updraft widths than those storms producing smaller hail, implying updrafts less diluted by entrainment and perhaps maximizing the liquid water content available for hail growth. Moreover, radar reflectivity or products derived from it are not different from cases of smaller hail sizes. However, inferred mesocyclonic rotational velocities within the hail growth region of storms that produce gargantuan hail are significantly stronger than the rotational velocities found for smaller hail categories.

scholarly journals Forecasting Tornadic Thunderstorm Potential in Alberta Using Environmental Sounding Data. Part I: Wind Shear and Buoyancy

2006 ◽  
Vol 21 (3) ◽  
pp. 325-335 ◽  
Author(s):  
Max L. Dupilka ◽  
Gerhard W. Reuter
Keyword(s):  
Potential Energy ◽  
Wind Shear ◽  
Convective Available Potential Energy ◽  
Severe Storms ◽  
Convective Storms ◽  
Available Potential Energy ◽  
Observational Dataset ◽  
Severe Thunderstorms ◽  
Tornadic Storms

Abstract This study investigates, for Alberta, Canada, whether observed sounding parameters such as wind shear and buoyant energy can be used to help distinguish between thunderstorms with significant (F2–F5) tornadoes, thunderstorms with weak (F0–F1) tornadoes, and nontornadic severe thunderstorms. The observational dataset contains 87 severe convective storms, all of which occurred within 200 km of the upper-air site at Stony Plain, Alberta, Canada. Of these storms, 13 spawned significant (F2–F5) tornadoes, 61 spawned weak (F0–F1) tornadoes, and 13 had no reported tornadoes yet produced 3 cm or larger hailstones. The observations suggest that bulk shear contained information about the probability of tornado formation and the intensity of the tornado. Significant tornadic storms tended to have stronger shear values than weak tornadic or nontornadic severe storms. All significant tornado cases had a wind shear magnitude in the 900–500-mb layer exceeding 3 m s−1 km−1. Combining the 900–500-mb shear with the 900–800-mb shear increased the probabilistic guidance for the likelihood of significant tornado occurrence. The data suggest that buoyant energy alone (quantified by the most unstable convective available potential energy) provided no skill in discriminating between tornadic and nontornadic severe storms, or between significant and weak tornadoes.

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