Wind shear

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

Parameterizations and Algorithms for Oceanic Whitecap Coverage

Abstract: Shipboard measurements of fractional whitecap coverage W and wind speed at 10-m height, obtained during the 2006 Marine Aerosol Production (MAP) campaign, have been combined with ECMWF wave model and Quick Scatterometer (QuikSCAT) satellite wind speed data for assessment of existing W parameterizations. The wind history trend found in an earlier study of the MAP data could be associated with wave development on whitecapping, as previously postulated. Whitecapping was shown to be mainly wind driven; for high wind speeds (>9 m s−1), a minor reduction in the scatter of in situ W data points could be achieved by including sea state conditions or by using parameters related to wave breaking. The W values were slightly larger for decreasing wind/developed waves than for increasing wind/developing waves, whereas cross-swell conditions (deflection angle between wind and swell waves between ±45° and ±135°) appeared to dampen whitecapping. Tabulated curve fitting results of the different parameterizations s...

Projection of changes in tropical cyclone activity and cloud height due to greenhouse warming: Global cloud‐system‐resolving approach

Abstract: [1] Tropical cyclone (TC) activity change due to global warming (GW) has been investigated using general circulation models. However, they involve uncertainty in treating the ensemble effects of deep convections. Here we sidestep such uncertainty by using a global cloud-system-resolving model (GCRM) and assess TC changes with a time-slice experiment for the present-day and future GW experiments spanning 5 months each. The results support the Intergovernmental Panel on Climate Change Fourth Assessment Report; reduction in global frequency but increase in more intense TCs. Consistent with recent studies, frequency is reduced over the North Atlantic due to intensified vertical wind shear. Over the Pacific, frequency is almost unchanged and the genesis location shifts eastward under the prescribed El-Nino like sea surface temperature change. With the GCRM's advantage of representing mesoscale properties, we find that the cloud height becomes taller for more intense TCs and that this relationship is strengthened with GW.

Long-wavelength turbulence and the heating of the solar wind.

Abstract: Solar wind model for studying long wavelength turbulence as heat source for alpha particles and protons in solar plasma

Tropical Cyclogenesis within an Equatorial Rossby Wave Packet

Abstract: A packet of equatorial Rossby (ER) waves that lasted 2.5 months is identified in the lower troposphere of the northwest Pacific. Waves within the packet had a period of 22 days, a wavelength of 3600 km, a westward phase speed of 1.9 m s−1, and a near-zero group speed. The wave properties followed the ER wave dispersion relation with an equivalent depth near 25 m. The packet was associated with the development of at least 8 of the 13 tropical cyclones that formed during the period. A composite was constructed around the genesis locations. Tropical cyclones formed east of the center of the composite ER wave low in a region of strong convection and a separate 850-hPa vorticity maximum. The background flow during the life of the packet was characterized by 850-hPa zonal wind convergence and easterly vertical wind shear. Wave amplitude peaked at the west end of the convergent region, suggesting that wave accumulation played a significant role in the growth of the packet. The presence of easterly verti...

Is the poleward migration of tropical cyclone maximum intensity associated with a poleward migration of tropical cyclone genesis

Abstract: A recent study showed that the global average latitude where tropical cyclones achieve their lifetime-maximum intensity has been migrating poleward at a rate of about one-half degree of latitude per decade over the last 30 years in each hemisphere. However, it does not answer a critical question: is the poleward migration of tropical cyclone lifetime-maximum intensity associated with a poleward migration of tropical cyclone genesis? In this study we will examine this question. First we analyze changes in the environmental variables associated with tropical cyclone genesis, namely entropy deficit, potential intensity, vertical wind shear, vorticity, skin temperature and specific humidity at 500 hPa in reanalysis datasets between 1980 and 2013. Then, a selection of these variables is combined into two tropical cyclone genesis indices that empirically relate tropical cyclone genesis to large-scale variables. We find a shift toward greater (smaller) average potential number of genesis at higher (lower) latitudes over most regions of the Pacific Ocean, which is consistent with a migration of tropical cyclone genesis towards higher latitudes. We then examine the global best track archive and find coherent and significant poleward shifts in mean genesis position over the Pacific Ocean basins.