scholarly journals 2-Day Westward-Propagating Inertio-Gravity Waves during GoAmazon

2021 ◽  
Author(s):  
Victor C. Mayta ◽  
Ángel F. Adames
Keyword(s):  
Gravity Waves ◽  
Linear Regression Analysis ◽  
Heat Fluxes ◽  
Mesoscale Convective Systems ◽  
Peak Activity ◽  
Propagation Characteristics ◽  
Shallow Water Theory ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Inertia Gravity Waves

AbstractThe dynamical and thermodynamical features of Amazonian 2-day westward-propagating inertia-gravity waves (WIG) are examined. On the basis of a linear regression analysis of satellite brightness temperature and data from the 2014-15 Observations and Modeling of the Green Ocean Amazon (GoAmazon) field campaign, it is shown that Amazonian WIG waves exhibit structure and propagation characteristics consistent with the n=1 WIG waves from shallow water theory. These WIG waves exhibit a pronounced seasonality, with peak activity occurring from March to May and a minimum occurring from June to September. Evidence is shown that mesoscale convective systems over the Amazon are frequently organized in 2-day WIG waves. Results suggest that many of the Amazonian WIG waves come from pre-existing 2-day waves over the Atlantic, which slow down when coupled with the deeper, more intense convection over tropical South America. In contrast to WIG waves that occur over the ocean, Amazonian 2-day WIG waves exhibit a pronounced signature in surface temperature, moisture, and heat fluxes.

Shear-Parallel Mesoscale Convective Systems in a Moist Low-Inhibition Mei-Yu Front Environment

2017 ◽  
Vol 74 (12) ◽  
pp. 4213-4228 ◽  
Author(s):  
Changhai Liu ◽  
Mitchell W. Moncrieff
Keyword(s):  
Gravity Waves ◽  
Asian Summer Monsoon ◽  
Momentum Transport ◽  
Mesoscale Convective Systems ◽  
Positive Sign ◽  
Cold Pool ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Convective Momentum Transport ◽  
Organized Convection

Abstract Numerical simulations are performed to investigate organized convection observed in the Asian summer monsoon and documented as a category of mesoscale convective systems (MCSs) over the U.S. continent during the warm season. In an idealized low-inhibition and unidirectional shear environment of the mei-yu moisture front, the structure of the simulated organized convection is distinct from that occurring in the classical quasi-two-dimensional, shear-perpendicular, and trailing stratiform (TS) MCS. Consisting of four airflow branches, a three-dimensional, eastward-propagating, downshear-tilted, shear-parallel MCS builds upshear by initiating new convection at its upstream end. The weak cold pool in the low-inhibition environment negligibly affects convection initiation, whereas convectively generated gravity waves are vital. Upstream-propagating gravity waves form a saturated or near-saturated moist tongue, and downstream-propagating waves control the initiation and growth of convection within a preexisting cloud layer. A sensitivity experiment wherein the weak cold pool is removed entirely intensifies the MCS and its interaction with the environment. The horizontal scale, rainfall rate, convective momentum transport, and transverse circulation are about double the respective value in the control simulation. The positive sign of the convective momentum transport contrasts with the negative sign for an eastward-propagating TS MCS. The structure of the simulated convective systems resembles shear-parallel organization in the intertropical convergence zone (ITCZ).

scholarly journals Long-Lived Mesoscale Systems in a Low–Convective Inhibition Environment. Part I: Upshear Propagation

2015 ◽  
Vol 72 (11) ◽  
pp. 4297-4318 ◽  
Author(s):  
Todd P. Lane ◽  
Mitchell W. Moncrieff
Keyword(s):  
Standard Model ◽  
Gravity Waves ◽  
Propagation Speed ◽  
Mesoscale Convective Systems ◽  
Dynamical Models ◽  
Convective Systems ◽  
The Standard Model ◽  
Mesoscale Convective ◽  
Convective Inhibition

Abstract Dynamical models of organized mesoscale convective systems have identified the important features that help maintain their overarching structure and longevity. The standard model is the trailing stratiform archetype, featuring a front-to-rear ascending circulation, a mesoscale downdraft circulation, and a cold pool/density current that affects the propagation speed and the maintenance of the system. However, this model does not represent all types of mesoscale convective systems, especially in moist environments where the evaporation-driven cold pools are weak and the convective inhibition is small. Moreover, questions remain about the role of gravity waves in creating and maintaining organized systems and affecting their propagation speed. This study presents simulations and dynamical models of self-organizing convection in a moist, low–convective inhibition environment and examines the long-lived convective regimes that emerge spontaneously. This paper, which is Part I of this study, specifically examines the structure, kinematics, and maintenance of long-lived, upshear-propagating convective systems that differ in important respects from the standard model of long-lived convective systems. Linear theory demonstrates the role of ducted gravity waves in maintaining the long-lived, upshear-propagating systems. A steady nonlinear model approximates the dynamics of upshear-propagating density currents that are key to the maintenance of the mesoscale convective system.

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 A Case Study on the Far-Field Properties of Propagating Tropospheric Gravity Waves

2016 ◽  
Vol 144 (8) ◽  
pp. 2947-2961 ◽  
Author(s):  
Claudia C. Stephan ◽  
M. Joan Alexander ◽  
Michael Hedlin ◽  
Catherine D. de Groot-Hedlin ◽  
Lars Hoffmann
Keyword(s):  
Great Plains ◽  
Gravity Waves ◽  
Three Dimensional ◽  
Ground Level ◽  
The United States ◽  
Latent Heating ◽  
Propagation Characteristics ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
The Waves

Abstract Mesoscale gravity waves were observed by barometers deployed as part of the USArray Transportable Array on 29 June 2011 near two mesoscale convective systems in the Great Plains region of the United States. Simultaneously, AIRS satellite data indicated stratospheric gravity waves propagating away from the location of active convection. Peak perturbation pressure values associated with waves propagating outside of regions where there was precipitation reached amplitudes close to 400 Pa at the surface. Here the origins of the waves and their relationship to observed precipitation are investigated with a specialized model study. Simulations with a 4-km resolution dry numerical model reproduce the propagation characteristics and amplitudes of the observed waves with a high degree of quantitative similarity despite the absence of any boundary layer processes, surface topography, or moist physics in the model. The model is forced with a three-dimensional, time-dependent latent heating/cooling field that mimics the latent heating inside the precipitation systems. The heating is derived from the network of weather radar precipitation observations. This shows that deep, intense latent heat release within the precipitation systems is the key forcing mechanism for the waves observed at ground level by the USArray. Furthermore, the model simulations allow for a more detailed investigation of the vertical structure and propagation characteristics of the waves. It is found that the stratospheric and tropospheric waves are triggered by the same sources, but have different spectral properties. Results also suggest that the propagating tropospheric waves may potentially remotely interact with and enhance active precipitation.

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

scholarly journals An Observational Study of Mesoscale Convective Systems with Heavy Rainfall over the Korean Peninsula

2006 ◽  
Vol 21 (2) ◽  
pp. 125-148 ◽  
Author(s):  
Hyung Woo Kim ◽  
Dong Kyou Lee
Keyword(s):  
Observational Study ◽  
Korean Peninsula ◽  
Wind Shear ◽  
Heavy Rainfall ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Mesoscale Convective Systems ◽  
Low Level ◽  
Convective Systems ◽  
Mesoscale Convective

Abstract A heavy rainfall event induced by mesoscale convective systems (MCSs) occurred over the middle Korean Peninsula from 25 to 27 July 1996. This heavy rainfall caused a large loss of life and property damage as a result of flash floods and landslides. An observational study was conducted using Weather Surveillance Radar-1988 Doppler (WSR-88D) data from 0930 UTC 26 July to 0303 UTC 27 July 1996. Dominant synoptic features in this case had many similarities to those in previous studies, such as the presence of a quasi-stationary frontal system, a weak upper-level trough, sufficient moisture transportation by a low-level jet from a tropical storm landfall, strong potential and convective instability, and strong vertical wind shear. The thermodynamic characteristics and wind shear presented favorable conditions for a heavy rainfall occurrence. The early convective cells in the MCSs initiated over the coastal area, facilitated by the mesoscale boundaries of the land–sea contrast, rain–no rain regions, saturated–unsaturated soils, and steep horizontal pressure and thermal gradients. Two MCSs passed through the heavy rainfall regions during the investigation period. The first MCS initiated at 1000 UTC 26 July and had the characteristics of a supercell storm with small amounts of precipitation, the appearance of a mesocyclone with tilting storm, a rear-inflow jet at the midlevel of the storm, and fast forward propagation. The second MCS initiated over the upstream area of the first MCS at 1800 UTC 26 July and had the characteristics of a multicell storm, such as a broken areal-type squall line, slow or quasi-stationary backward propagation, heavy rainfall in a concentrated area due to the merging of the convective storms, and a stagnated cluster system. These systems merged and stagnated because their movement was blocked by the Taebaek Mountain Range, and they continued to develop because of the vertical wind shear resulting from a low-level easterly inflow.

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