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G. R. Halliwell Jr., L. K. Shay, J. K. Brewster, and W. J. Teague

from moored acoustic Doppler current profiler (ADCP) measurements. Unfortunately, targeted aircraft observations that could have provided simultaneous subsurface profiles of temperature, salinity, and currents before, during, and after Ivan were not available, thus limiting the extent of the evaluation that could be performed. Section 2 describes the ocean model, forcing fields, and observations. Section 3 summarizes the model experiments and analysis procedures. The evaluation and

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Laura Slivinski, Elaine Spiller, Amit Apte, and Björn Sandstede

Abstract

Lagrangian measurements from passive ocean instruments provide a useful source of data for estimating and forecasting the ocean’s state (velocity field, salinity field, etc.). However, trajectories from these instruments are often highly nonlinear, leading to difficulties with widely used data assimilation algorithms such as the ensemble Kalman filter (EnKF). Additionally, the velocity field is often modeled as a high-dimensional variable, which precludes the use of more accurate methods such as the particle filter (PF). Here, a hybrid particle–ensemble Kalman filter is developed that applies the EnKF update to the potentially high-dimensional velocity variables, and the PF update to the relatively low-dimensional, highly nonlinear drifter position variable. This algorithm is tested with twin experiments on the linear shallow water equations. In experiments with infrequent observations, the hybrid filter consistently outperformed the EnKF, both by better capturing the Bayesian posterior and by better tracking the truth.

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Yonghong Yin, Oscar Alves, and Peter R. Oke

, this approach has a detrimental effect on the salinity and velocity fields of the model. Troccoli et al. (2002) reported that the univariate assimilation of temperature profiles, without attempting to correct salinity, can induce spurious convection and result in errors in the subsurface temperature and salinity fields. Bell et al. (2004) found that assimilation of temperature data into an ocean model near the equator often results in a dynamically unbalanced state with unrealistically strong

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J. VON HANN

Newfoundland 6 anks icebergs were numerous, .1PRACTICAL APPLICATION OF THE ELECTRICALCON- DUCTIVITY METHOD OF MEASURING SEA-WATER SAL1 NITY.By A. L. THUEAB.[Reprinted from Jour. 1Wh. A d . Scima, vol. 11, no. 7, pp. l60-161.]Heretofore the only reliable method of measuring the total salt content of sea water has been by chemcally titrating for the amount of chlorine present. The rela- tion of chlorine to the total salts being a constant, ameasure of the salinity is thereby obtained. Salinity is defined as

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Newfoundland 6 anks icebergs were numerous, .1PRACTICAL APPLICATION OF THE ELECTRICALCON- DUCTIVITY METHOD OF MEASURING SEA-WATER SAL1 NITY.By A. L. THUEAB.[Reprinted from Jour. 1Wh. A d . Scima, vol. 11, no. 7, pp. l60-161.]Heretofore the only reliable method of measuring the total salt content of sea water has been by chemcally titrating for the amount of chlorine present. The rela- tion of chlorine to the total salts being a constant, ameasure of the salinity is thereby obtained. Salinity is defined as

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Hans Ngodock and Matthew Carrier

II field experiment was followed by reanalysis data experiments by several authors ( Haley et al. 2009 ; Chao et al. 2009 ; Shulman et al. 2009 ). The general conclusion from these experiments is that the reanalysis was in better agreement with both the assimilated and independent temperature and salinity observations after some model parameters were adjusted. The same fit was worse in the real-time support of the field experiment. Also, the surface velocity field derived from the reanalysis

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23 to ,I1lne 28 being de\.otedto special surrey work in the northeastern Indian Ocean 11s part of the I'nitetlStates Government's official participation in the Intern:~tion:~l Indinn 0cea11Expedit,ion. Temperat,ure, salinity, dissoll-ed oxygen, tlissolvetl silicate, ant1density distributions are shon-n for three north-south sections ilcI'oss the Equa-tor sout'h of the Hag of Bengal. Sediment antdyes are gij-ell for samples oh-tained from the St'rnit of Malacca, and the ,J:~v:l, Mindanao, antl

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Jeffrey S. Gall, William M. Frank, and Young Kwon

Abstract

Under high-wind conditions, breaking waves and whitecaps eject large numbers of sea spray droplets into the atmosphere. The spray droplets originate with the same temperature and salinity as the ocean surface and thus increase the effective surface area of the ocean in contact with the atmosphere. As a result, the spray alters the total sensible and latent heat fluxes in the near-surface layer. The spray drops in the near-surface layer also result in horizontal and vertical spray-drag effects. The mass of the spray introduces an additional drag in the vertical momentum equation and tends to stabilize the lower boundary layer (BL).

An initially axisymmetric control hurricane was created from the output of a real-data simulation of Hurricane Floyd (1999) using the nonhydrostatic fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5, version 3.4). The subsequent simulations, however, are not axisymmetric because the mass, wind, and spray fields are allowed to develop asymmetries. While such a design does not result in an axisymmetric simulation, the mass, wind, and spray fields develop more realistic structures than in an axisymmetric simulation. Simulations of the hurricane were conducted using a version of the Fairall et al. (1994) sea spray parameterization, which includes horizontal and vertical spray-drag effects. The simulations were run using varying spray-source function intensities and with and without horizontal and vertical spray-drag effects. At present, the relationship of spray production to surface wind speed is poorly known for hurricane-force wind regimes.

Results indicate that spray modifies the hurricane structure in important but complex ways. Spray moistens the near-surface layer through increased evaporation. The effect of spray on the near-surface temperature profile depends on the amount of spray and its location in the hurricane. For moderate spray amounts, the near-surface layer warms within the high-wind region of the hurricane and cools at larger radii. For larger spray amounts, the near-surface layer warms relative to the moderate spray case.

The moderate spray simulations (both with and without drag effects) have little net effect on the hurricane intensity. However, in the heavier spray runs, the total sensible heat flux is enhanced by 200 W m−2, while the total latent heat flux is enhanced by over 150 W m−2 in the high-wind region of the storm. Horizontal spray drag decreases wind speeds between 1 and 2 m s−1, and vertical spray drag increases the stability of the lower BL. In these heavy spray runs, the effect of the enhanced spray sensible and latent heat fluxes dominates the negative spray-drag effects, and as a result, the modeled storm intensity is upward of 10 mb stronger than the control run by the end of the simulation time. This study shows that spray has the capability of significantly affecting hurricane structure, but to do so, the amount of spray ejected into the BL of the hurricane would need to lie near the upper end of the currently hypothesized spray-source functions.

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David M. Holland and Adrian Jenkins

( Bleck and Boudra 1981 ; Bleck 1998 ): In these relations, v = ( u, υ ) is the horizontal velocity vector, p the pressure, C represents either one of the model's dynamically active tracers (i.e., potential temperature θ or salinity S ) as well as any passive tracers, ζ = ∂ υ /∂ x ξ − ∂ u /∂ y ξ the relative vorticity, α θ the specific volume, ϕ = gz the geopotential, g the gravitational acceleration, f the Coriolis parameter (spatially varying), k̂ the vertical unit vector

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Max Yaremchuk, Dmitri Nechaev, and Chudong Pan

; Brasseur and Verron 2006 ). They proved to be especially useful for monitoring comparatively large domains continuously covered by sea surface height/sea surface temperature (SSH/SST) observations at the surface with sporadic vertical temperature/salinity ( T / S ) soundings by Argo drifters and ships. The second type of assimilation algorithms employ steady-state covariances derived from long-term model integrations ( Yin et al. 2011 ) or heuristic Gaussian-shaped covariance operators with simple

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