Kinematic Vertical Motion and Relative Vorticity Profiles in a Long-Lived Midlatitude Convective System

1986 ◽  
Vol 43 (12) ◽  
pp. 1297-1299 ◽  
Author(s):  
Lance F. Bosart
Keyword(s):  
Vertical Motion ◽  
Relative Vorticity ◽  
Convective System

scholarly journals Comparison between Low-Flash and Non-Lightning-Producing Convective Areas within a Mature Mesoscale Convective System

2011 ◽  
Vol 26 (4) ◽  
pp. 468-486 ◽  
Author(s):  
Jennifer L. Palucki ◽  
Michael I. Biggerstaff ◽  
Donald R. MacGorman ◽  
Terry Schuur
Keyword(s):  
Vertical Motion ◽  
Mesoscale Convective System ◽  
Phase Region ◽  
Life Cycles ◽  
Radar Reflectivity ◽  
Mixed Phase ◽  
Convective System ◽  
Lightning Flash ◽  
Mesoscale Convective ◽  
Mixed Phase Region

Abstract Two small multicellular convective areas within a larger mesoscale convective system that occurred on 20 June 2004 were examined to assess vertical motion, radar reflectivity, and dual-polarimetric signatures between flash and non-flash-producing convection. Both of the convective areas had similar life cycles and general structures. Yet, one case produced two flashes, one of which may have been a cloud-to-ground flash, while the other convective area produced no flashes. The non-lightning-producing case had a higher peak reflectivity up to 6 km. Hence, if a reflectivity-based threshold were used as a precursor to lightning, it would have yielded misleading results. The peak upward motion in the mixed-phase region for both cases was 8 m s−1 or less. However, the lightning-producing storm contained a wider region where the updraft exceeded 5 m s−1. Consistent with the broader updraft region, the lightning-producing case exhibited a distinct graupel signature over a broader region than the non-lightning-producing convection. Slight differences in vertical velocity affected the quantity of graupel present in the mixed-phase region, thereby providing the subtle differences in polarimetric signatures that were associated with lightning activity. If the results here are generally applicable, then graupel volume may be a better precursor to a lightning flash than radar reflectivity. With the dual-polarimetric upgrade to the national observing radar network, it should be possible to better distinguish between lightning- and non-lightning-producing areas in weak convective systems that pose a potential safety hazard to the public.

scholarly journals Synoptic and dynamic characteristics of selected deep depressions over Cyprus

2006 ◽  
Vol 7 ◽  
pp. 175-180 ◽  
Author(s):  
K. A. Nicolaides ◽  
S. C. Michalelides ◽  
T. Karacostas
Keyword(s):  
Dynamic Characteristics ◽  
Vertical Motion ◽  
Static Stability ◽  
Relative Vorticity ◽  
Stability Parameter ◽  
Cold Period ◽  
Spatial And Temporal Distributions ◽  
Selection Of

Abstract. In this study, the spatial and temporal distributions of dynamic and synoptic characteristics of a selection of 32 deep baroclinic depressions have been investigated. The study covers the cold period months of November till March, in the period from 1 November 1986 to 31 March 2003. For the needs of the study, several synoptic characteristics of these depressions have been extracted. Also, several dynamic characteristics during the evolution of the depressions were studied: relative vorticity, divergence, vertical motion and a static stability parameter. The results are presented in the form of isobaric distributions over, three tropospheric isobaric levels, namely the lower 850 hPa, the middle 500 hPa and the upper 300 hPa.

Growth of Mesoscale Convective Systems in Observations and a Seasonal Convection-Permitting Simulation over Argentina

2021 ◽  
Vol 149 (10) ◽  
pp. 3469-3490
Author(s):  
Zhixiao Zhang ◽  
Adam Varble ◽  
Zhe Feng ◽  
Joseph Hardin ◽  
Edward Zipser
Keyword(s):  
Growth Rate ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Vertical Motion ◽  
Rain Gauge ◽  
Convective System ◽  
Low Level ◽  
Environmental Controls ◽  
Mesoscale Convective ◽  
Rain Rates

AbstractA 6.5-month, convection-permitting simulation is conducted over Argentina covering the Remote Sensing of Electrification, Lightning, And Mesoscale/Microscale Processes with Adaptive Ground Observations and Clouds, Aerosols, and Complex Terrain Interactions (RELAMPAGO-CACTI) field campaign and is compared with observations to evaluate mesoscale convective system (MCS) growth prediction. Observed and simulated MCSs are consistently identified, tracked, and separated into growth, mature, and decay stages using top-of-the-atmosphere infrared brightness temperature and surface rainfall. Simulated MCS number, lifetime, seasonal and diurnal cycles, and various cloud-shield characteristics including growth rate are similar to those observed. However, the simulation produces smaller rainfall areas, greater proportions of heavy rainfall, and faster system propagations. Rainfall area is significantly underestimated for long-lived MCSs but not for shorter-lived MCSs, and rain rates are always overestimated. These differences result from a combination of model and satellite retrieval biases, in which simulated MCS rain rates are shifted from light to heavy, while satellite-retrieved rainfall is too frequent relative to rain gauge estimates. However, the simulation reproduces satellite-retrieved MCS cloud-shield evolution well, supporting its usage to examine environmental controls on MCS growth. MCS initiation locations are associated with removal of convective inhibition more than maximized low-level moisture convergence or instability. Rapid growth is associated with a stronger upper-level jet (ULJ) and a deeper northwestern Argentinean low that causes a stronger northerly low-level jet (LLJ), increasing heat and moisture fluxes, low-level vertical wind shear, baroclinicity, and instability. Sustained growth corresponds to similar LLJ, baroclinicity, and instability conditions but is less sensitive to the ULJ, large-scale vertical motion, or low-level shear. Growth sustenance controls MCS maximum extent more than growth rate.

scholarly journals Deep-convective influence on the upper troposphere–lower stratosphere composition in the Asian monsoon anticyclone region: 2017 StratoClim campaign results

2020 ◽  
Vol 20 (20) ◽  
pp. 12193-12210
Author(s):  
Silvia Bucci ◽  
Bernard Legras ◽  
Pasquale Sellitto ◽  
Francesco D'Amato ◽  
Silvia Viciani ◽  
...  
Keyword(s):  
Asian Monsoon ◽  
Lower Stratosphere ◽  
Trace Gases ◽  
Vertical Motion ◽  
Back Trajectory ◽  
Convective System ◽  
Small Contribution ◽  
Back Trajectories ◽  
Air Masses ◽  
Upper Troposphere

Abstract. The StratoClim stratospheric aircraft campaign took place in summer 2017 in Nepal (27 July–10 August) and provided for the first time a wide dataset of observations of air composition inside the Asian monsoon anticyclone (AMA). In the framework of this project, with the purpose of modelling the injection of pollutants and natural compounds into the stratosphere, we performed a series of diffusive back trajectory runs along the flights' tracks. The availability of in situ measurements of trace gases has been exploited to evaluate the capability of the trajectory system to reproduce the transport in the upper troposphere–lower stratosphere (UTLS) region. The diagnostics of the convective sources and mixing in the air parcel samples have been derived by integrating the trajectory output with high-resolution observations of cloud tops from the Meteosat Second Generation (MSG1) and Himawari geostationary satellites. Back trajectories have been calculated using meteorological fields from European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-Interim and ERA5) at 3 and 1 h resolution, using both kinematic and diabatic vertical motion. The comparison among the different trajectory runs shows, in general, a higher consistency with observed data as well as a better agreement between the diabatic and kinematic version when using ERA5-based runs with respect to ERA-Interim. Overall, a better capacity in reproducing the pollution features is finally found in the diabatic version of the ERA5 runs. We therefore adopt this setting to analyse the convective influence in the UTLS starting from the StratoClim observations. A large variety of transport conditions have been individuated during the eight flights of the campaign. The larger influence by convective injections is found from the continental sources of China and India. Only a small contribution appears to be originated from maritime regions, in particular the South Pacific and the Bay of Bengal, which, unexpectedly, was not particularly active during the period of the campaign. In addition, a mass of clean air injected from a typhoon has also been detected at around 18 km. Thin filamentary structures of polluted air, characterized by peaks in CO, are observed, mostly associated with young convective air (age less than a few days) and with a predominant South China origin. The analysis revealed a case of direct injection of highly polluted air close to the level of the tropopause (anomalies of around 80 ppbv injected at 16 km) that then kept rising inside the anticyclonic circulation. Due to the location of the campaign, air from continental India, in contrast, has been only observed to be linked to air masses that recirculated within the anticyclone for 10 to 20 d, resulting in a lower concentration of the trace gas. The analysis of a flight overpassing an intense convective system close to the southern Nepalese border revealed the injection of very young air (few hours of age) directly in the tropopause region (∼18 km), visible in the trace gases as an enhancement in CO and a depletion in the O3 one. From the whole campaign, a vertical stratification in the age of air is observed: up to 15 km, the age is less than 3 d, and these fresh air masses constitute almost the totality of the air composition. A transition layer is then individuated between 15 and 17 km, where the convective contribution is still dominant, and the ages vary between 1 and 2 weeks. Above this level, the mean age of the air sampled by the aircraft is estimated to be 20 d. There, the convective contribution rapidly decreases with height and finally becomes negligible around 20 km.

scholarly journals Connection between Two Leading Modes of Autumn Rainfall Interannual Variability in Southeast China and Two Types of ENSO-Like SSTA

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Kui Liu ◽  
Jilong Chen ◽  
Ruowen Yang
Keyword(s):  
Interannual Variability ◽  
Vertical Motion ◽  
Walker Circulation ◽  
Meridional Wind ◽  
Relative Vorticity ◽  
Northwest Pacific ◽  
Positive Anomaly ◽  
Dipole Mode ◽  
Good Correspondence ◽  
Southeast China

The interannual variability of autumn rainfall in Southeast China (SEC) is significant, with two major modes, namely, monopole and dipole modes. It is found that the monopole mode is closely related to EP ENSO-like sea surface temperature anomaly (SSTA), and the dipole mode is related to CP ENSO-like SSTA. During the warm phase of EP ENSO-like SSTA, an anomalous anti-Walker circulation emerges in the tropical Pacific, with an anomalous subsiding during 110°E–120°E and an anomalous ascending branch in SEC. These two branches of anomalous current are in the same longitude and form a closed meridional circulation. Besides, there also exists an anticyclone anomaly in the Northwest Pacific (NWP), transporting water vapor into SEC. These circulation configurations induced by the warm phase of EP ENSO-like SSTA are consistent with those of monopole mode positive anomaly year. The good correspondence between EP ENSO warm event and the positive monopole mode also helps to support the corresponding relationship between the EP ENSO-like SSTA and monopole mode of SEC autumn rainfall. After the diagnosis of the perturbation omega equation, the anomalous subsiding branch over SEC, as the key link of EP ENSO-like warm phase SSTA exerting impact on the monopole mode during positive anomaly year, is mainly related with the anomalous relative vorticity advection transported by basic zonal wind and temperature advection transported by meridional wind anomaly. As for the dipole mode, it is related to the CP ENSO-like SSTA, but the corresponding relationship is weaker than that of the monopole mode and EP ENSO-like SSTA. In special, during the warm phase of CP ENSO-like SSTA, an anomalous cyclone appears in the NWP and prevailing sinking motion over SEC, both of which favors the appearance of positive anomaly of the dipole mode. Specially, the local anomalous vertical motion mainly depends on anomalous relative vorticity transported by basic meridional wind. Generally speaking, the monopole (dipole) mode is closely associated with the EP (CP) ENSO-like SSTA, demonstrating some correspondence.

scholarly journals Genesis of an East Pacific Easterly Wave from a Panama Bight MCS: A Case Study Analysis from June 2012

2020 ◽  
Vol 77 (10) ◽  
pp. 3567-3584
Author(s):  
Justin W. Whitaker ◽  
Eric D. Maloney
Keyword(s):  
Vertical Structure ◽  
Model Simulation ◽  
Vertical Motion ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Easterly Wave ◽  
Budget Analysis ◽  
East Pacific ◽  
Vorticity Budget ◽  
Mesoscale Convective

AbstractThis study investigates the transition of a Panama Bight mesoscale convective system (MCS) into the easterly wave (EW) that became Hurricane Carlotta (2012). Reanalysis, observations, and a convective-permitting Weather Research and Forecasting (WRF) Model simulation are used to analyze the processes contributing to EW genesis. A vorticity budget analysis shows that convective coupling and vortex stretching are very important to the transition in this case, while horizontal advection is mostly responsible for the propagation of the system. In the model, the disturbance is dominated by stratiform vertical motion profiles and a midlevel vortex, while the system is less top-heavy and is characterized by more prominent low-level vorticity later in the transition in reanalysis. The developing disturbance starts its evolution as a mesoscale convective system in the Bight of Panama. Leading up to MCS formation the Chocó jet intensifies, and during the MCS-to-EW transition the Papagayo jet strengthens. Differences in the vertical structure of the system between reanalysis and the model suggest that the relatively more bottom-heavy disturbance in reanalysis may have stronger interactions with the Papagayo jet. Field observations like those collected during the Organization of Tropical East Pacific Convection (OTREC) campaign are needed to further our understanding of this east Pacific EW genesis pathway and the factors that influence it, including the important role for the vertical structure of the developing disturbances in the context of the vorticity budget.

scholarly journals Biophysical Submesoscale Processes in the Wake of Hurricane Ivan: Simulations and Satellite Observations

2019 ◽  
Vol 7 (11) ◽  
pp. 378 ◽  
Author(s):  
Smith ◽  
Jolliff ◽  
Walker ◽  
Anderson
Keyword(s):  
Tropical Cyclone ◽  
Chlorophyll A ◽  
Vertical Motion ◽  
Mechanistic Explanation ◽  
Relative Vorticity ◽  
Lateral Strain ◽  
Phytoplankton Productivity ◽  
Fully Integrated ◽  
Hurricane Ivan ◽  
Submesoscale Processes

Tropical cyclone induced phytoplankton productivity is examined using a tropical cyclone version of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®). A four-component Nutrient–Phytoplankton–Detritus biological model is integrated into COAMPS to create a fully integrated air-ocean-wave-biology model. This study investigates the upper ocean physical and biological states before and after Hurricane Ivan traversed the central Gulf of Mexico, in mid-September 2004. Elevated concentrations of surface chlorophyll-a appear in the simulation two days after the passage of the tropical cyclone, and these results are spatially and temporally coherent with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data for this time period. Model results reveal enhancement of chlorophyll-a in submesoscale filaments on the periphery of a warm-core eddy that are dominated by large values of lateral strain and relative vorticity at the surface. The vertical circulation of the filament, with its associated upward vertical motion, permits surface ventilation of cold, nitrogen-rich water and subsequent stimulation of primary biological production. Here, we show for the first time that coupled biological-physical submesoscale processes may be simulated via a fully integrated air-sea-wave-biology tropical cyclone model that provides a mechanistic explanation of the conspicuous features revealed in satellite ocean color imagery following Ivan.

scholarly journals The Different Impact of Positive-Neutral and Negative-Neutral ENSO Regimes on Australian Tropical Cyclones

2013 ◽  
Vol 26 (20) ◽  
pp. 8008-8016 ◽  
Author(s):  
Savin S. Chand ◽  
Kevin J. Tory ◽  
John L. McBride ◽  
Matthew C. Wheeler ◽  
Richard A. Dare ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Vertical Motion ◽  
Relative Vorticity ◽  
La Niña ◽  
Sea Level Pressure ◽  
Australian Region ◽  
La Nina ◽  
Significant Difference ◽  
The Difference

Abstract The number of tropical cyclones (TCs) in the Australian region exhibits a large variation between different ENSO regimes. While the difference in TC numbers and spatial distribution of genesis locations between the canonical El Niño and La Niña regimes is well known, the authors demonstrate that a statistically significant difference in TC numbers also exists between the recently identified negative-neutral and positive-neutral regimes. Compared to the negative-neutral and La Niña regimes, significantly fewer TCs form in the Australian region during the positive-neutral regime, particularly in the eastern subregion. This difference is attributed to concomitant changes in various large-scale environmental conditions such as sea level pressure, relative vorticity, vertical motion, and sea surface temperature.

South-westward Propagating Quasi-biweekly Oscillation over South-western Indian Ocean during Boreal Winter

2020 ◽  
Author(s):  
Sambrita Ghatak ◽  
Jai Sukhatme
Keyword(s):  
Indian Ocean ◽  
Wave Train ◽  
Phase Speed ◽  
Vertical Motion ◽  
Longwave Radiation ◽  
Western Indian Ocean ◽  
Relative Vorticity ◽  
Boreal Winter ◽  
Horizontal Structure ◽  
Tightly Coupled

<div>The Quasi-Biweekly Oscillation (QBWO), with a period between the synoptic scale and the Madden Julian Oscillation (MJO), is an important component of tropical intraseasonal variability (ISV). While this mode has received a lot of attention over India (during the summer monsoon) and South China sea region, less attention has been paid on South-western Indian Ocean (SWIO). Apart from improving our understanding of ISV, this mode is important in the SWIO during boreal winter as this is an active basin for tropical cyclones (TC), and the QBWO significantly influences TCs. Here we study details of the genesis of the QBWO, its propagation, vertical structure and evolution. The data used comprises of NCEP-NCAR and ERA-interim reanalysis and NOAA outgoing longwave radiation (OLR) from 2000-2010. A composite analysis based on 10-30 day filtered data during the boreal winter reveals a well-organized convectively-coupled wave-train pattern, namely the QBWO, over the SWIO. It emerges from south of the equator (5S), between 50-80E, and then propagates south-westward. The horizontal structure exhibits a slight southwest-northeast tilt, but mainly longitudinal elongation. After arriving Madagascar, the system shows more pronounced southward migration. Further, negative (positive) OLR anomalies are tightly coupled with a cyclonic  (anticyclonic) circulation at 850 hPa. In the end, the QBWO with associated anomalous convection dies down near 40S, between 40-70E. Overall, over this oceanic basin, the QBWO has a period of approximately 18 days, wavelength of about 5000-6000 km, a southward (westward) phase speed of 1.9 (2.7)°/day and a near zero group velocity. Near equator, the system emerges with an equivalent barotropic structure. When mature with strongest convection around 10-20S, the system becomes weakly baroclinic, with relative vorticity anomaly changing sign near 400 hPa, and in the dying phase after 30S, the QBWO becomes equivalent barotropic again. Finally, the centres of relative vorticity and vertical motion near the equator are consistent with the characteristics of equatorial Rossby waves, whereas the cyclonic circulation is tightly coupled with anomalous convection as the wave moves away from the equator.</div>

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