Radial and vertical velocity field in a steady state symmetric tropical storm

ABSTRACT. A method to construct a consistent structure of steady state symmetric tropical storms from a few known values of temperature anomaly in the centre and around it has been developed. The role of kinematic eddy coefficient of viscosity in producing the transverse circulation in a tropical storm has been tested and discussed. The well known features and characteristics of a tropical storm, such as, eyewall, sinking motion, inside the eyewall, low-level radial inflow and high level outflow are well produced in the model. The computation shows that there is an increase of transverse circulation with increase of the magnitude of eddy coefficient. In the boundary layer, the vertical eddy coefficient plays more important role than the radial eddy coefficient; while in the upper layer the latter is much more important than the former. It has also been found that in absence of radial exchange coefficient, there can be no sinking motion in the central region of the storm. The magnitude of radial and vertical wind in the eye region is more sensitive to the variation of radial eddy coefficient. In addition to the eddy coefficients, transverse circulations also depend upon the tangential wind distribution above the boundary layer.

The Circulation Response of a Two-Dimensional Frontogenetic Model to Optimized Moisture Perturbations

An analysis of the influence and sensitivity of moisture in an idealized two-dimensional moist semigeostrophic frontogenesis model is presented. A comparison between a dry (relative humidity, RH=0%) and moist (RH=80%) version of the model demonstrates that the impact of moisture is to increase frontogenesis, strengthen the transverse circulation (??????,??), generate a low-level potential-vorticity anomaly and develop a low-level jet. The idealized model is compared to a real case simulated with the full-physics three-dimensional Coupled Ocean-Atmospheric Mesoscale Prediction System (COAMPS) model establishing good agreement and thereby confirming that the idealized model retains the essential physical processes relevant for improving understanding of midlatitude frontogenesis. Optimal perturbations of mixing ratio are calculated to quantify the circulation response of the model through the computation of singular vectors, which determines the fastest-growing modes of a linearized version of the idealized model. The vertical velocity is found to respond strongly to initial-condition mixing-ratio perturbations such that small changes in moisture lead to large changes in the ascent. The progression of physical processes responsible for this nonlinear growth is (in order): jet/front transverse circulation → moisture convergence ahead of the front → latent heating at mid-to-low elevations → reduction in static stability ahead of the front → strengthening of the transverse circulation, and the feedback cycle repeats. Together, these physical processes represent a pathway by which small perturbations of moisture can strongly impact a forecast involving midlatitude frontogenesis.

The critical role of cloud–infrared radiation feedback in tropical cyclone development

The tall clouds that comprise tropical storms, hurricanes, and typhoons—or more generally, tropical cyclones (TCs)—are highly effective at trapping the infrared radiation welling up from the surface. This cloud–infrared radiation feedback, referred to as the “cloud greenhouse effect,” locally warms the lower–middle troposphere relative to a TC’s surroundings through all stages of its life cycle. Here, we show that this effect is essential to promoting and accelerating TC development in the context of two archetypal storms—Super Typhoon Haiyan (2013) and Hurricane Maria (2017). Namely, this feedback strengthens the thermally direct transverse circulation of the developing storm, in turn both promoting saturation within its core and accelerating the spin-up of its surface tangential circulation through angular momentum convergence. This feedback therefore shortens the storm’s gestation period prior to its rapid intensification into a strong hurricane or typhoon. Further research into this subject holds the potential for key progress in TC prediction, which remains a critical societal challenge.

A Case Study of the Physical Processes Associated with the Atmospheric River Initial-Condition Sensitivity from an Adjoint Model

Analysis of a strong landfalling atmospheric river is presented that compares the evolution of a control simulation with that of an adjoint-derived perturbed simulation using the Coupled Ocean–Atmosphere Mesoscale Prediction System. The initial-condition sensitivities are optimized for all state variables to maximize the accumulated precipitation within the majority of California. The water vapor transport is found to be substantially enhanced at the California coast in the perturbed simulation during the time of peak precipitation, demonstrating a strengthened role of the orographic precipitation forcing. Similarly, moisture convergence and vertical velocities derived from the transverse circulation are found to be substantially enhanced during the time of peak precipitation, also demonstrating a strengthened role of the dynamic component of the precipitation. Importantly, both components of precipitation are associated with enhanced latent heating by which (i) a stronger diabatically driven low-level potential vorticity anomaly strengthens the low-level wind (and thereby the orographic precipitation forcing), and (ii) greater moist diabatic forcing enhances the Sawyer–Eliassen transverse circulation and thereby increases ascent and dynamic precipitation. A Lagrangian parcel trajectory analysis demonstrates that a positive moisture perturbation within the atmospheric river increases the moisture transport into the warm conveyor belt offshore, which enhances latent heating in the perturbed simulation. These results suggest that the precipitation forecast in this case is particularly sensitive to the initial moisture content within the atmospheric river due to its role in enhancing both the orographic precipitation forcing and the dynamic component of precipitation.

Generation of artificial transverse circulation in an open channel flow by submerged vanes

Introduction. In this article, we describe a method for sediment control in damless water intake hydraulic units consisting in artificial transverse circulation (ATC) generated by redistributing specific water flow rates in the cross-section of the supply channel. One of the simplest and most effective anti-sediment elements working according to this principle is the submerged vane (SV). The intensity of the ATC formed in the flow depends on the flow regime and the planned-geometric characteristics of the vanes. Available recommendations on the selection of the rational characteristics of SV under the conditions of river damless water intake appear to be contradictory, thus requiring clarification. This study is aimed at examining the interaction between SV and a model flow without water trapping under various planned-geometric characteristics of the vane and experimental hydraulic regimes of its work using a physical model of the errosion-resistant channel. In addition, we set out to assess the effect of essential parameters on the intensity of the ATC generated in the flow. Materials and methods. This research was based on physical modelling hydraulic studies and theoretical calculations. Five hydraulic modes of vane operation with different planned-geometric characteristics were studied using a physical model of the erosion-resistant channel. Multiple regression analysis of the obtained experimental data was carried out. Results. The results of laboratory hydraulic studies on the SV operating conditions are presented. Experimental dependencies characterising the intensity of the ATC generated in the flow are plotted. A multiple regression equation is derived for the amount of the data obtained. Conclusions. It is established that the relative height of the vane and its angle to the side of the flume (coastline) has a significant effect on the intensity of the generated ATC. It is experimentally confirmed for the first time that SV shows little efficiency in high water horizons in terms of in-flow ATC generation.

Reading Sideways

This book explores the pivotal role that various art forms played in American literary fiction in direct relation to the politics of gender and sexuality at the turn of the twentieth century. It tracks the transverse circulation of aesthetic ideas in fiction and argues that at stake in fin-de-siècle American writers’ aesthetic turn was not only the theorization of aesthetic experience, but also a fashioning forth of an understanding of aesthetic form in relation to political arguments and debates about available modes of sociability and cultural expression. To track these practices it performs an interpretive method Seitler calls “lateral reading,” a mode of interpretation that moves horizontally through various historical entanglements and across the fields of the arts to make sense of, and see in a new light, their connections, challenges, and productive frictions.

A mathematical model of the aerodynamics of drying chambers with vertical transverse circulation

In the article, from the standpoint of aerodynamics considered the concept of a mathematical model of the circulation channels marketing chambers of variable cross section with a vertically transverse circulation. Factors affecting the uniformity of the air flow in the pile of lumber. Developed analytical mathematical model of the motion of drying agent on the side channel of variable cross section. Revealed that the parameters of the lateral channel of the drying chamber of variable cross section does not depend on the temperature and humidity of the circulating air, and hence from the "rigidity" of the drying mode.

The Governing Dynamics of the Secondary Eyewall Formation of Typhoon Sinlaku (2008)

Through successful convection-permitting simulations of Typhoon Sinlaku (2008) using a high-resolution nonhydrostatic model, this study examines the role of peripheral convection in the storm's secondary eyewall formation (SEF) and its eyewall replacement cycle (ERC). The study demonstrates that before SEF the simulated storm intensifies via an expansion of the tangential winds and an increase in the boundary layer inflow, which are accompanied by peripheral convective cells outside the primary eyewall. These convective cells, which initially formed in the outer rainbands under favorable environmental conditions and move in an inward spiral, play a crucial role in the formation of the secondary eyewall. It is hypothesized that SEF and ERC ultimately arise from the convective heating released from the inward-moving rainbands, the balanced response in the transverse circulation, and the unbalanced dynamics in the atmospheric boundary layer, along with the positive feedback between these processes.

The Three-Dimensional Dynamic Characteristics on the South of Subei Radiation Shoal Waters

Based on the high precision terrain datas , high resolution FVCOM(Finite-Volume Coastal Ocean Model) numerical model was established to simulation for tide current and study three-dimensional dynamic characteristics of the south of Radiation shoal waters. Result show that transverse circulation was easy to produce in channel and groove. The vorticity and helicity computation method was applied in the area for the frist time. Transverse circulation and helical flow characteristics of typical sections were preliminary studied, and result show the quantitative evidence for the existence of the Spiral flow.Deep groove is not always appear double reverse spiral flow structure, it changes with the main flow velocity. Shoal grooves appear, a main spiral flow structure, and show great adaptability to the terrain, which is the reflection of the spiral flow to the terrain maintain mechanism .

The Roles of an Expanding Wind Field and Inertial Stability in Tropical Cyclone Secondary Eyewall Formation

The Weather and Research and Forecasting Model (WRF) is used to simulate secondary eyewall formation (SEF) in a tropical cyclone (TC) on the β plane. The simulated SEF process is accompanied by an outward expansion of kinetic energy and the TC warm core. An absolute angular momentum budget demonstrates that this outward expansion is predominantly a symmetric response to the azimuthal-mean and wavenumber-1 components of the transverse circulation. As the kinetic energy expands outward, the kinetic energy efficiency in which latent heating can be retained as local kinetic energy increases near the developing outer eyewall. The kinetic energy efficiency associated with SEF is examined further using a symmetric linearized, nonhydrostatic vortex model that is configured as a balanced vortex model. Given the symmetric tangential wind and temperature structure from WRF, which is close to a state of thermal wind balance above the boundary layer, the idealized model provides the transverse circulation associated with the symmetric latent heating and friction prescribed from WRF. In a number of ways, this vortex response matches the azimuthal-mean secondary circulation in WRF. These calculations suggest that sustained azimuthal-mean latent heating outside of the primary eyewall will eventually lead to SEF. Sensitivity experiments with the balanced vortex model show that, for a fixed amount of heating, SEF is facilitated by a broadening TC wind field.