scholarly journals Hurricane Sea Surface Inflow Angle and an Observation-Based Parametric Model

2012 ◽  
Vol 140 (11) ◽  
pp. 3587-3605 ◽  
Author(s):  
Jun A. Zhang ◽  
Eric W. Uhlhorn
Keyword(s):  
Ocean Circulation ◽  
Numerical Models ◽  
Surface Wind ◽  
Radial Distance ◽  
Parametric Model ◽  
Wind Vector ◽  
Near Surface ◽  
Storm Intensity ◽  
Significant Dependence ◽  
Motion Speed

Abstract This study presents an analysis of near-surface (10 m) inflow angles using wind vector data from over 1600 quality-controlled global positioning system dropwindsondes deployed by aircraft on 187 flights into 18 hurricanes. The mean inflow angle in hurricanes is found to be −22.6° ± 2.2° (95% confidence). Composite analysis results indicate little dependence of storm-relative axisymmetric inflow angle on local surface wind speed, and a weak but statistically significant dependence on the radial distance from the storm center. A small, but statistically significant dependence of the axisymmetric inflow angle on storm intensity is also found, especially well outside the eyewall. By compositing observations according to radial and azimuthal location relative to storm motion direction, significant inflow angle asymmetries are found to depend on storm motion speed, although a large amount of unexplained variability remains. Generally, the largest storm-relative inflow angles (<−50°) are found in the fastest-moving storms (>8 m s−1) at large radii (>8 times the radius of maximum wind) in the right-front storm quadrant, while the smallest inflow angles (>−10°) are found in the fastest-moving storms in the left-rear quadrant. Based on these observations, a parametric model of low-wavenumber inflow angle variability as a function of radius, azimuth, storm intensity, and motion speed is developed. This model can be applied for purposes of ocean surface remote sensing studies when wind direction is either unknown or ambiguous, for forcing storm surge, surface wave, and ocean circulation models that require a parametric surface wind vector field, and evaluating surface wind field structure in numerical models of tropical cyclones.

scholarly journals Modeling the Effect of Desert Urbanization on Local Climate and Natural Dust Generation: A Case Study for Erbil, Iraq

Urban Science ◽  
2020 ◽  
Vol 4 (4) ◽  
pp. 46
Author(s):  
Sherzad T. Tahir ◽  
Huei-Ping Huang
Keyword(s):  
Land Surface ◽  
Numerical Models ◽  
Surface Wind ◽  
Surface Fluxes ◽  
Slight Reduction ◽  
Rapid Urbanization ◽  
Near Surface ◽  
Local Climate ◽  
Surface Dust ◽  
Dust Generation

This study uses a suite of meteorological and land-surface models to quantify the changes in local climate and surface dust fluxes associated with desert urbanization. Formulas connecting friction velocity and soil moisture to dust generation are used to quantify surface fluxes for natural wind-blown dust. The models are used to conduct a series of simulations for the desert city of Erbil across a period of rapid urbanization. The results show significant nighttime warming and weak but robust daytime cooling associated with desert urbanization. A slight reduction in near-surface wind speed is also found in the areas undergoing urbanization. These findings are consistent with previous empirical and modeling studies on other desert cities. Numerical models and empirical formulas are used to produce climatological maps of surface dust fluxes as a function of season, and for the pre- and post-urbanization eras. This framework can potentially be used to bridge the gap in observation on the trends in local dust generation associated with land-use changes and urban expansions.

Assessment of energy resources of Polish Baltic Sea areas

2017 ◽  
Vol 32 (1) ◽  
pp. 93-102
Author(s):  
Maciej Kałas ◽  
Piotr Piotrowski
Keyword(s):  
Power Plants ◽  
Numerical Models ◽  
Wind Waves ◽  
Surface Wind ◽  
Sea Surface ◽  
Energy Resources ◽  
Near Surface ◽  
Sea Surface Wind ◽  
Physical Energy ◽  
Physical Phenomena

The article presents spatial characteristics of energy fluxes recorded in the area of the Polish Exclusive Economic Zone (EEZ) in the four-year period of 2013–16. Data presented in this work are based on results of forecast calculations with the application of numerical models of the atmosphere (HIRLAM) and sea (WAM and HIROMB). Conducted analyses were concerned with dynamics of physical phenomena above the sea surface (wind), on its surface (wind waves motion), and in its near-surface layer up to 4 m (seawater flows). Physical energy resources connected with these processes for subsequent four years were computed and compared with the amount of annual electricity output generated by conventional and renewable sources of energy. Such an analysis of estimated energy resources reveals that the resource is highly differentiated in terms of space and in individual years, and significantly exceed the annual production of Polish power plants.

scholarly journals A Statistical Analysis on the Dependence of Tropical Cyclone Intensification Rate on the Storm Intensity and Size in the North Atlantic

2015 ◽  
Vol 30 (3) ◽  
pp. 692-701 ◽  
Author(s):  
Jing Xu ◽  
Yuqing Wang
Keyword(s):  
Tropical Cyclone ◽  
North Atlantic ◽  
Turning Point ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Outer Core ◽  
Near Surface ◽  
Storm Intensity ◽  
The North ◽  
Intensity Prediction

Abstract The dependence of tropical cyclone (TC) intensification rate IR on storm intensity and size was statistically analyzed for North Atlantic TCs during 1988–2012. The results show that IR is positively (negatively) correlated with storm intensity (the maximum sustained near-surface wind speed Vmax) when Vmax is below (above) 70–80 knots (kt; 1 kt = 0.51 m s−1), and negatively correlated with storm size in terms of the radius of maximum wind (RMW), the average radius of gale-force wind (AR34), and the outer-core wind skirt parameter DR34 (=AR34 − RMW). The turning point for Vmax of 70–80 kt is explained as a balance between the potential intensification and the maximum potential intensity (MPI). The highest IR occurs for Vmax = 80 kt, RMW ≤ 40 km, and AR34 = DR34 = 150 km. The high frequency of occurrence of intensifying TCs occurs for Vmax ≤ 80 kt and RMW between 20 and 60 km, AR34 ≤ 200 km, and DR34 ≤ 150 km. Rapid intensification (RI) often occurs in a relatively narrow parameter space in storm intensity and both inner- and outer-core sizes. In addition, a theoretical basis for the intensity dependency has also been provided based on a previously constructed simplified dynamical system for TC intensity prediction.

Spray-Mediated Enthalpy Flux to the Atmosphere and Salt Flux to the Ocean in High Winds

2010 ◽  
Vol 40 (3) ◽  
pp. 608-619 ◽  
Author(s):  
Edgar L. Andreas
Keyword(s):  
Large Scale ◽  
Pure Water ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Salt Flux ◽  
Freshwater Flux ◽  
Near Surface ◽  
Storm Intensity ◽  
Spray Droplets ◽  
High Winds

Abstract Forecasts for the intensity and intensity changes of tropical cyclones have not improved as much as track forecasts. In high winds, two routes exist by which air and sea exchange heat and momentum: by spray-mediated processes and by interfacial transfer right at the air–sea interface, the only exchange route currently parameterized in most storm models. This manuscript quantifies two processes mediated by sea spray that could affect predictions of storm intensity when included in coupled ocean–atmosphere models. Because newly formed spray droplets cool rapidly to an equilibrium temperature that is lower than the air temperature, they cool the ocean when they reenter it, clearly transferring enthalpy from sea to air. These reentrant droplets proliferate in storm winds and are predicted to transfer enthalpy at a rate comparable to interfacial processes when the near-surface wind speed reaches 30 m s−1. Because reentrant spray droplets give up pure water to the atmosphere during their brief lifetime, they return to the sea saltier than the surface ocean water and thus also constitute an effective salt flux to the ocean (also related to a freshwater flux and a buoyancy flux). That is, reentrant spray droplets add enthalpy to the atmosphere to power storms and destabilize the ocean by increasing the salinity at the surface. Both processes can affect storm intensity. This manuscript demonstrates the magnitudes of the spray enthalpy and salt fluxes by combining a sophisticated microphysical model and data from the study of Humidity Exchange over the Sea (HEXOS) and the Fronts and Atlantic Storm-Tracks Experiment (FASTEX). It goes on to develop a fast algorithm for predicting these two fluxes in large-scale models.

scholarly journals Understanding the dynamic of poleward shifting of atmospheric and oceanic circulation using aqua-planet model simulations​

2021 ◽  
Author(s):  
Hu Yang ◽  
Jian Lu ◽  
Xiaoxu Shi ◽  
Qiang Wang ◽  
Gerrit Lohmann
Keyword(s):  
Atmospheric Circulation ◽  
Ocean Circulation ◽  
Surface Wind ◽  
Ocean Warming ◽  
Ocean Dynamics ◽  
Circulation System ◽  
Oceanic Circulation ◽  
Dynamical Mechanism ◽  
Near Surface ◽  
Poleward Shift

<p>Growing evidence suggests that the oceanic and atmospheric circulation experiences a systematic poleward shift under climate change. However, due to the complexity of climate system, such as, the coupling between the ocean and the atmosphere, natural climate variability and land-sea distribution, the dynamical mechanism of such shift is still not fully understood. Here, using an idealized partially coupled ocean and atmosphere aqua-planet model, we explore the mechanism of the shifting oceanic and atmospheric circulation. We find that, in contrast to the rising GHG concentration, the subtropical ocean warming plays a dominant role in driving the shift in the circulation system. More specifically, due to background ocean dynamics, a relatively faster warming over the subtropical ocean drives a poleward shift in the atmospheric circulation. The shift in the atmospheric circulation in turn drives a shift in the oceanic circulation. Our simulations, despite being idealized, capture the main features of observed climate changes, for example, the enhanced subtropical ocean warming, poleward shift of the patterns of near-surface wind, sea level pressure, cloud, precipitation, storm tracks and large-scale ocean circulation, implying that global warming not only raises the temperature, but also systematically shifts the climate zones.​</p>

scholarly journals Can Existing Theory Predict the Response of Tropical Cyclone Intensity to Idealized Landfall?

2021 ◽  
Author(s):  
Jie Chen ◽  
Daniel R. Chavas
Keyword(s):  
Tropical Cyclone ◽  
Transient Response ◽  
Surface Wind ◽  
Surface Roughening ◽  
Tropical Cyclone Intensity ◽  
Surface Drag ◽  
Near Surface ◽  
Cyclone Intensity ◽  
Storm Intensity ◽  
Theoretical Predictions

AbstractTropical cyclones cause significant inland hazards, including wind damage and freshwater flooding, that depend strongly on how storm intensity evolves after landfall. Existing theoretical predictions for storm intensification and equilibrium storm intensity have been tested over the open ocean but have not yet been applied to storms after landfall. Recent work examined the transient response of the tropical cyclone low-level wind field to instantaneous surface roughening or drying in idealized axisymmetric f -plane simulations. Here, experiments testing combined surface roughening and drying with varying magnitudes of each are used to test theoretical predictions for the intensity response. The transient response to combined surface forcings can be reproduced by the product of their individual responses, in line with traditional potential intensity theory. Existing intensification theory is generalized to weakening and found capable of reproducing the time-dependent inland intensity decay. The initial (0-10min) rapid decay of near-surface wind caused by surface roughening is not captured by existing theory but can be reproduced by a simple frictional spin-down model, where the decay rate is a function of surface drag coefficient. Finally, the theory is shown to compare well with the prevailing empirical decay model for real-world storms. Overall, results indicate the potential for existing theory to predict how tropical cyclone intensity evolves after landfall.

scholarly journals Decoding the dynamic of poleward shifting climate zones using aqua-planet model simulation

2021 ◽  
Author(s):  
Hu Yang ◽  
Jian Lu ◽  
Xiaoxu Shi ◽  
Qiang Wang ◽  
Gerrit Lohmann
Keyword(s):  
Atmospheric Circulation ◽  
Ocean Circulation ◽  
Model Simulation ◽  
Surface Wind ◽  
Ocean Warming ◽  
Ocean Dynamics ◽  
Causal Mechanism ◽  
Near Surface ◽  
Climate Zones ◽  
Poleward Shift

Abstract Growing evidence implies that the atmospheric and oceanic circulation experiences a systematic poleward shift in a warming climate. However, the complexity of climate system, including the coupling between the ocean and the atmosphere, natural climate variability and land-sea distribution, tends to obfuscate the causal mechanism underlying the circulation shift. Here, using an idealized coupled aqua-planet model, we explore the mechanism of the shifting circulation, by isolating the contributing factors from the direct CO2 forcing, the indirect ocean surface warming, and the wind-stress feedback from the ocean dynamics. We find that, in contrast to direct CO2 forcing, an enhanced subtropical ocean warming plays a leading role in driving the circulation shift. This enhanced subtropical ocean warming emerges from the background Ekman convergence of surface anomalous heat in the absence of the ocean dynamical change. It expands the tropical warm water zone, causes a poleward shift of the meridional temperature gradients, hence forces a corresponding shift in the atmospheric circulation. The shift in the atmospheric circulation in turn drives a shift in the ocean circulation. Our simulations, despite being idealized, capture the main features of observed climate changes, for example, the enhanced subtropical ocean warming, poleward shift of the patterns of near-surface wind, sea level pressure, storm tracks, precipitation and large-scale ocean circulation, implying that increase in greenhouse gas concentrations not only raises the temperature, but can also systematically shift the climate zones poleward.

scholarly journals Decoding the dynamics of poleward shifting climate zones using aqua-planet model simulations

2022 ◽  
Author(s):  
Hu Yang ◽  
Jian Lu ◽  
Qiang Wang ◽  
Xiaoxu Shi ◽  
Gerrit Lohmann
Keyword(s):  
Ocean Circulation ◽  
Surface Wind ◽  
Ocean Surface ◽  
Ocean Warming ◽  
Ocean Dynamics ◽  
Causal Mechanism ◽  
Near Surface ◽  
Climate Zones ◽  
Surface Warming ◽  
Poleward Shift

AbstractGrowing evidence indicates that the atmospheric and oceanic circulation experiences a systematic poleward shift in a warming climate. However, the complexity of the climate system, including the coupling between the ocean and the atmosphere, natural climate variability and land-sea distribution, tends to obfuscate the causal mechanism underlying the circulation shift. Here, using an idealised coupled aqua-planet model, we explore the mechanism of the shifting circulation, by isolating the contributing factors from the direct CO$$_2$$ 2 forcing, the indirect ocean surface warming, and the wind-stress feedback from the ocean dynamics. We find that, in contrast to the direct CO$$_2$$ 2 forcing, ocean surface warming, in particular an enhanced subtropical ocean warming, plays an important role in driving the circulation shift. This enhanced subtropical ocean warming emerges from the background Ekman convergence of surface anomalous heat in the absence of the ocean dynamical change. It expands the tropical warm water zone, causes a poleward shift of the mid-latitude temperature gradient, hence forces a corresponding shift in the atmospheric circulation and the associated wind pattern. The shift in wind, in turn drives a shift in the ocean circulation. Our simulations, despite being idealised, capture the main features of the observed climate changes, for example, the enhanced subtropical ocean warming, poleward shift of the patterns of near-surface wind, sea level pressure, storm tracks, precipitation and large-scale ocean circulation, implying that increase in greenhouse gas concentrations not only raises the temperature, but can also systematically shift the climate zones poleward.

Antarctic Climate History and Global Climate Changes

2017 ◽  
Author(s):  
Pontus Lurcock ◽  
Fabio Florindo
Keyword(s):  
Ocean Circulation ◽  
Climate Changes ◽  
Numerical Models ◽  
Global Climate ◽  
Sediment Cores ◽  
Ice Sheets ◽  
Global Ocean ◽  
Climate History ◽  
Global Climate Changes ◽  
Planetary Albedo

Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.

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