Wind shear

About: Wind shear is a research topic. Over the lifetime, 8023 publications have been published within this topic receiving 185373 citations.

Heating, Moistening, and Rainfall over the Western Pacific Warm Pool during TOGA COARE

Abstract: Rawinsonde, surface, and satellite data collected from the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean Atmosphere Response Experiment (COARE) are used to investigate the distributions of beating, moistening, precipitation, and evaporation over the western Pacific warm pool. The behavior of the atmosphere and the response of the ocean surface before, during, and after the passages of westerly wind bursts are examined. The tropospheric vertical wind shear associated with tropical low-frequency oscillations strongly modulated convective beating and moistening. Heavy precipitation usually fell 1 to 3 weeks prior to the peak westerly wind bursts. SSTs reached their maximum during the undisturbed phase of the intraseasonal oscillations (ISOs), gradually decreased as convection intensified, and reached their minimum during the periods of peak westerly winds when deep convection was generally suppressed over the intensive flux array (IFA). Surface latent heat fluxes were positively correlated w...

Effects of Vertical Wind Shear on the Predictability of Tropical Cyclones

Abstract: Through cloud-resolving simulations, this study examines the effect of vertical wind shear and system-scale flow asymmetry on the predictability of tropical cyclone (TC) intensity during different stages of the TC life cycle. A series of ensemble experiments is performed with varying magnitudes of vertical wind shear, each initialized with an idealized weak TC-like vortex, with small-scale, small-amplitude random perturbations added to the initial conditions. It is found that the environmental shear can significantly affect the intrinsic predictability of tropical cyclones, especially during the formation and rapid intensification stage. The larger the vertical wind shear, the larger the uncertainty in the intensity forecast, primarily owing to the difference in the timing of rapid intensification.In the presence of environmental shear, initial random noise may result in changes in the timing of rapid intensification by as much as 1–2 days through the randomness (and chaotic nature) of moist conve...

Environmental Flow Impacts on Tropical Cyclone Structure Diagnosed from Airborne Doppler Radar Composites

Abstract: Following a recent demonstration of multicase compositing of axisymmetric tropical cyclone (TC) structure derived from airborne Doppler radar measurements, the authors extend the analysis to the asymmetric structure using an unprecedented database from 75 TC flights. In particular, they examine the precipitation and kinematic asymmetry forced by the TC's motion and interaction with vertical wind shear. For the first time they quantify the average magnitude and phase of the three-dimensional shear-relative kinematic asymmetry of observed TCs through a composite approach. The composite analysis confirms principal features of the shear-relative TC asymmetry documented in prior numerical and observational studies (e.g., downshear tilt, downshear-right convective initiation, and a downshear-left precipitation maximum). The statistical significance of the composite shear-relative structure is demonstrated through a stratification of cases by shear magnitude. The impact of storm motion on eyewall convect...

On the propagation of atmospheric gravity waves through regions of wind shear

Abstract: Removal of incident wave spectrum by background wind shears during atmospheric gravity waves propagation to ionosphere from lower regions

Minimal model for aeolian sand dunes.

Abstract: We present a minimal model for the formation and migration of aeolian sand dunes in unidirectional winds. It combines a perturbative description of the turbulent wind velocity field above the dune with a continuum saltation model that allows for saturation transients in the sand flux. The latter are shown to provide a characteristic length scale, called saturation length, which is distinct from the saltation length of the grains. The model admits two different classes of solutions for the steady-state profile along the wind direction: smooth heaps and dunes with slip face. We clarify the origin of the characteristic properties of these solutions and analyze their scaling behavior. We also investigate in some detail the dynamic evolution of heaps and dunes, including the steady-state migration velocity and transient shape relaxation. Although the minimal model employs nonlocal expressions for the wind shear stress as well as for the sand flux, it is simple enough to serve as a very efficient tool for analytical and numerical investigations and opens up the way to simulations of large scale desert topographies.