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D. Resio and W. Perrie

Abstract

The existence of an f −5 equilibrium range was hypothesized for middle to high frequencies for a well-developed sea generated by the physical parameters of gross sea state in the pioneering work of Phillips. Various experimental studies since then, notably JONSWAP, have shown that if the power law is −5, then the proportionality constant is frequency dependent. Recent Lake Ontario data has shown an f −4 variation, which agrees with models of the equilibrium range as a Kolmogorov cascade. From this, the JONSWAP fetch relation and appropriate Assumptions about momentum transfer are shown to imply an important new spectra form for energy transfer from wind to wave, which differs slightly from other recent attempts. With suitable parameter relations, the midrange spectral energy can be shown to be essentially the same as its well known f −5 counterpart.

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D. W. Perrie

A Microwave Early Warning Radar was operated at Clinton, Ontario from March until October, 1945, for the purpose of studying radar echoes from rain. The principal contribution from this operation has been a direct determination of the amount of rain (measured both by gauge and by drop measurements) required to produce an echo at a given range.

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W. Perrie and B. Toulany

Abstract

A model for the response of waves to turning wind was recently derived from the growth–fetch relations for developing waves. An essential part of the model involves the drag coefficient C d. Recently, the ERS-1 Grand Banks (GB) Wave Validation Experiment of 1991 measured wind speed and wave parameters at an open ocean position about 205 km from land. The GB experiment also measured C d and therefore provides the first complete verification of the model in open ocean conditions.

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W. Perrie and Y. Hu

Abstract

The energy exchange between ocean surface waves and ice floes in the marginal ice zone (MIZ) involves the scattering and attenuation of wave energy and the excitation of oscillation modes of the ice floes, as open ocean waves propagate into the MIZ. Heave, pitch, and roll modes of oscillation are linked to estimation of wave scattering and attenuation. A model is presented for wave attenuation and compared to measurements from the Marginal Ice Zone Experiments in the Greenland Sea, as reported by Wadhams et al.

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R. Padilla-Hernández, W. Perrie, B. Toulany, and P. C. Smith

Abstract

In this study, three state-of-the-art operational forecast wave models are implemented on nested grids in order to achieve fine-resolution wave simulations (0.1°) in the Gulf of Maine and related northwest Atlantic waters. These models are the Simulating Waves Nearshore (SWAN) model, the Wave Action Model (WAM), and WAVEWATCH-III (hereafter WW3). Model performance is evaluated through comparisons with field measurements. Four composite model systems are compared: WAM and WW3 implemented on three nested domains, SWAN nested within WAM, and SWAN nested within WW3. Storm case studies include two intense midlatitude winter storms from January 2000 and January 2002. Although the models are comparable in terms of their overall performance and skill, it is found that WW3 provides a better statistical fit to the observed wave data compared with the other models, and that SWAN gives slightly better results if nested within WW3, rather than within WAM.

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Z. Long, W. Perrie, J. Gyakum, D. Caya, and R. Laprise

Abstract

It is well known that large lakes can perturb local weather and climate through mesoscale circulations, for example, lake effects on storms and lake breezes, and the impacts on fluxes of heat, moisture, and momentum. However, for both large and small lakes, the importance of atmosphere–lake interactions in northern Canada is largely unknown. Here, the Canadian Regional Climate Model (CRCM) is used to simulate seasonal time scales for the Mackenzie River basin and northwest region of Canada, coupled to simulations of Great Bear and Great Slave Lakes using the Princeton Ocean Model (POM) to examine the interactions between large northern lakes and the atmosphere. The authors consider the lake impacts on the local water and energy cycles and on regional seasonal climate. Verification of model results is achieved with atmospheric sounding and surface flux data collected during the Canadian Global Energy and Water Cycle Experiment (GEWEX) program. The coupled atmosphere–lake model is shown to be able to successfully simulate the variation of surface heat fluxes and surface water temperatures and to give a good representation of the vertical profiles of water temperatures, the warming and cooling processes, and the lake responses to the seasonal and interannual variation of surface heat fluxes. These northern lakes can significantly influence the local water and energy cycles.

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W. Perrie, C. L. Tang, Y. Hu, and B. M. DeTracy

Abstract

Ocean models usually estimate surface currents without explicit modeling of the ocean waves. To consider the impact of waves on surface currents, here a wave model is used in a modified Ekman layer model, which is imbedded in a diagnostic ocean model. Thus wave effects, for example, Stokes drift and wave-breaking dissipation, are explicitly considered in conjunction with the Ekman current, mean currents, and wind-driven pressure gradient currents. It is shown that the wave effect on currents is largest in rapidly developing intense storms, when wave-modified currents can exceed the usual Ekman currents by as much as 40%. A large part of this increase in velocity can be attributed to the Stokes drift. Reductions in momentum transfer to the ocean due to wind input to waves and enhancements due to wave dissipation are each of the order 20%–30%. Model results are compared with measurements from the Labrador Sea Deep Convection Experiment of 1997.

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Will Perrie, Weiqing Zhang, Mark Bourassa, Hui Shen, and Paris W. Vachon

Abstract

A variational data assimilation method is applied to remotely sensed wind data from Hurricanes Gustav (2002) and Isabel (2003) to produce enhanced marine wind estimates. The variational method utilizes constraints to ensure that an optimum combination of winds is determined, in the sense of minimization of a cost function measuring the misfit between observations and background input field data and constraining nongeophysical features in the spatial derivatives. Constraints are multiplied by weights, which are objectively determined by cross validation. Verification is obtained by comparison with available operational in situ buoy observations and analyses winds. It is shown that the newly constructed midlatitude wind fields represent an improvement relative to background wind field estimates and also relative to Quick Scatterometer–National Centers for Environmental Prediction reanalysis blended winds, and that the new winds have an impact on simulations of waves and upper-ocean currents.

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Biao Zhang, William Perrie, Jun A. Zhang, Eric W. Uhlhorn, and Yijun He

Abstract

This study presents a new approach for retrieving hurricane surface wind vectors utilizing C-band dual-polarization (VV, VH) synthetic aperture radar (SAR) observations. The copolarized geophysical model function [C-band model 5.N (CMOD5.N)] and a new cross-polarized wind speed retrieval model for dual polarization [C-band cross-polarized ocean surface wind retrieval model for dual-polarization SAR (C-2POD)] are employed to construct a cost function. Minimization of the cost function allows optimum estimates for the wind speeds and directions. The wind direction ambiguities are removed using a parametric two-dimensional sea surface inflow angle model. To evaluate the accuracy of the proposed method, two RADARSAT-2 SAR images of Hurricanes Bill and Bertha are analyzed. The retrieved wind speeds and directions are compared with collocated Quick Scatterometer (QuikSCAT) winds, showing good consistency. Results suggest that the proposed method has good potential to retrieve hurricane surface wind vectors from dual-polarization SAR observations.

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Z. Long, W. Perrie, C. L. Tang, E. Dunlap, and J. Wang

Abstract

The authors investigate the interannual variations of freshwater content (FWC) and sea surface height (SSH) in the Beaufort Sea, particularly their increases during 2004–09, using a coupled ice–ocean model (CIOM), adapted for the Arctic Ocean to simulate the interannual variations. The CIOM simulation exhibits a (relative) salinity minimum in the Beaufort Sea and a warm Atlantic water layer in the Arctic Ocean, which is similar to the Polar Hydrographic Climatology (PHC), and captures the observed FWC maximum in the central Beaufort Sea, and the observed variation and rapid decline of total ice concentration, over the last 30 years. The model simulations of SSH and FWC suggest a significant increase in the central Beaufort Sea during 2004–09. The simulated SSH increase is about 8 cm, while the FWC increase is about 2.5 m, with most of these increases occurring in the center of the Beaufort gyre. The authors show that these increases are due to an increased surface wind stress curl during 2004–09, which increased the FWC in the Beaufort Sea by about 0.63 m yr−1 through Ekman pumping. Moreover, the increased surface wind is related to the interannual variation of the Arctic polar vortex at 500 hPa. During 2004–09, the polar vortex had significant weakness, which enhanced the Beaufort Sea high by affecting the frequency of synoptic weather systems in the region. In addition to the impacts of the polar vortex, enhanced melting of sea ice also contributes to the FWC increase by about 0.3 m yr−1 during 2004–09.

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