Price James F.

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Potential vorticity constraint on the flow between two basins

(American Meteorological Society, 2007-09) Yang, Jiayan ; Price, James F.

This paper examines the role of potential vorticity (PV) balance in source- and sink-driven flows between two basins. As shown in previous studies, PV advection into a basin, say a positive PV advection, requires a negative frictional torque to maintain a steady PV balance. This sense of torque may be provided by a cyclonic boundary current within the basin. The PV advection through a channel is due almost entirely to advection of planetary PV, f/H, where f is the Coriolis parameter and H is the column thickness. Therefore a localized change of depth, and thus H in the channel, directly affects the PV transport and will result in a basinwide change of the circulation pattern. For example, if the channel depth is made shallower while holding the transport fixed, the PV advection is then increased and the result may be a strong recirculation within the basin, as much as two orders of magnitude greater than the transport through the channel. When the basins are connected by two channels at different latitudes or with different sill depths, the throughflow is found to be divided between the two channels in a way that satisfies the integral constraint for flow around an island. The partition of the flow between two channels appears to be such as to minimize the net frictional torque. In still another set of experiments, the large-scale pressure difference (layer thickness) between the basins is specified and held fixed, while the throughflow is allowed to vary in response to changes in the frictional torque. The interbasin transport is strongly influenced by the length of the boundary or the magnitude of the viscosity in the sense that a greater PV frictional torque allows a greater PV transport and vice versa. This result is counterintuitive, if it is assumed that the throughflow is determined by viscous drag within the channel but is a straightforward consequence of the basin-scale PV balance. Thus, the important frictional effect in these experiments is on the basin-scale flow and not on the channel scale.
Upper-ocean response to Hurricane Frances (2004) observed by Profiling EM-APEX floats

(American Meteorological Society, 2011-06) Sanford, Thomas B. ; Price, James F. ; Girton, James B.

Three autonomous profiling Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats were air deployed one day in advance of the passage of Hurricane Frances (2004) as part of the Coupled Boundary Layer Air–Sea Transfer (CBLAST)-High field experiment. The floats were deliberately deployed at locations on the hurricane track, 55 km to the right of the track, and 110 km to the right of the track. These floats provided profile measurements between 30 and 200 m of in situ temperature, salinity, and horizontal velocity every half hour during the hurricane passage and for several weeks afterward. Some aspects of the observed response were similar at the three locations—the dominance of near-inertial horizontal currents and the phase of these currents—whereas other aspects were different. The largest-amplitude inertial currents were observed at the 55-km site, where SST cooled the most, by about 2.2°C, as the surface mixed layer deepened by about 80 m. Based on the time–depth evolution of the Richardson number and comparisons with a numerical ocean model, it is concluded that SST cooled primarily because of shear-induced vertical mixing that served to bring deeper, cooler water into the surface layer. Surface gravity waves, estimated from the observed high-frequency velocity, reached an estimated 12-m significant wave height at the 55-km site. Along the track, there was lesser amplitude inertial motion and SST cooling, only about 1.2°C, though there was greater upwelling, about 25-m amplitude, and inertial pumping, also about 25-m amplitude. Previously reported numerical simulations of the upper-ocean response are in reasonable agreement with these EM-APEX observations provided that a high wind speed–saturated drag coefficient is used to estimate the wind stress. A direct inference of the drag coefficient CD is drawn from the momentum budget. For wind speeds of 32–47 m s−1, CD ~ 1.4 × 10−3.
SOFAR float Mediterranean outflow experiment : summary and data from 1986-88

(Woods Hole Oceanographic Institution, 1990-01) Zemanovic, Marguerite E. ; Richardson, Philip L. ; Price, James F.

In October, 1984, the Woods Hole Oceanographic Institution SOFAR float group began a three and a half year field program to measure the velocity field of the Mediterranean water in the eastern North Atlantic. The principal scientific goal was to learn how the Mediterranean salt tongue is produced by the general circulation and the eddy diffusion of the Canary Basin. Thirty-two floats were launched at depths near 1100 m: 14 in a cluster centered on 32°N, 24°W, with nearest neighbors at 20 km spacing, 10 at much wider spacing to explore regional variations of first order flow statistics, and 8 in three different Meddies (Mediterranean water eddies) in collaboration with investigators from Scripps Institution of Oceanography and the University of Rhode Island. The floats were launched in 1984 and 1985, and tracked with U.S. and French ALSs (moored listening stations) from October 1984 to June 1988. This report includes a summary of the whole three and a half year experiment, the final year and a half of data processed from the third ALS setting (October 1986-June 1988), and the first deep sea test of Bobber EB014 in the eastern subtropical North Atlantic (May 1986-May 1988). Approximately 60 years of float trajectories were produced during the three and a half years of the experiment.
Intelligent chilled mirror humidity sensor

(Woods Hole Oceanographic Institution, 1988-12) Hosom, David S. ; Winget, Clifford L. ; Weisman, Sumner ; Doucet, Donald P. ; Price, James F.

A new, intelligent, chilled mirror humidity instrument has been designed for use on buoys and ships. The design goal is to make high quality dew point temperature measurements for a period of up to one year from an unattended platform, while consuming as little power as possible. Nominal system accuracy is 0.3°C, and a measure of data quality is provided to indicate possible drift in calibration. Energy consumption is typically 800 Joules per measurement; standby power consumption is 0.05 watts. Control of the instrument is managed by an onboard central processing unit which is programmable in BASIC, and communication to an external data logger is provided through an RS232 compatible interface. This report describes the preliminary sensor tests that led to this new design and provides the complete technical description required for fabrication.
An ocean coupling potential intensity index for tropical cyclones

(John Wiley & Sons, 2013-05-15) Lin, I.-I. ; Black, Peter G. ; Price, James F. ; Yang, C.-Y. ; Chen, Shuyi S. ; Lien, Chun-Chi ; Harr, Patrick ; Chi, N.-H. ; Wu, C.-C. ; D'Asaro, Eric A.

Timely and accurate forecasts of tropical cyclones (TCs, i.e., hurricanes and typhoons) are of great importance for risk mitigation. Although in the past two decades there has been steady improvement in track prediction, improvement on intensity prediction is still highly challenging. Cooling of the upper ocean by TC-induced mixing is an important process that impacts TC intensity. Based on detail in situ air-deployed ocean and atmospheric measurement pairs collected during the Impact of Typhoons on the Ocean in the Pacific (ITOP) field campaign, we modify the widely used Sea Surface Temperature Potential Intensity (SST_PI) index by including information from the subsurface ocean temperature profile to form a new Ocean coupling Potential Intensity (OC_PI) index. Using OC_PI as a TC maximum intensity predictor and applied to a 14 year (1998–2011) western North Pacific TC archive, OC_PI reduces SST_PI-based overestimation of archived maximum intensity by more than 50% and increases the correlation of maximum intensity estimation from r2 = 0.08 to 0.31. For slow-moving TCs that cause the greatest cooling, r2 increases to 0.56 and the root-mean square error in maximum intensity is 11 m s−1. As OC_PI can more realistically characterize the ocean contribution to TC intensity, it thus serves as an effective new index to improve estimation and prediction of TC maximum intensity.
Site L SOFAR float experiment, 1982-1985

(Woods Hole Oceanographic Institution, 1987-12) Price, James F. ; McKee, Theresa K. ; Owens, W. Brechner ; Valdes, James R.

Lagrangian measurements of low frequency currents in the vicinity of the Gulf Stream and its recirculation region in the western Sargasso Sea were made by tracking SOFAR floats. These floats were tracked using acoustic time of arrival information from an array of five Autonomous Listening Stations {ALSs) which were moored in the western Sargasso Sea. The ALSs performed almost flawlessly, returning over 90 percent of the possible data. Floats were released in three deployments of seven floats each in November 1982, February 1983, and June 1983. The floats were launched in initially coherent arrays (approximately 20 km spacing) at 34°N, 70°W, Site "L", and were ballasted for 700 m depth. The SOFAR floats themselves functioned with somewhat less than expected reliability; four floats failed fairly soon after launch, and several other floats suffered failures of their temperature and pressure telemetry. The majority of the SOFAR floats launched in this program produced long, and interesting trajectories. These new data will be valuable for estimating first order flow statistics in the dynamically important recirculation region, for visualizing interactions between the Gulf Stream and the New England Seamount Chain, and for estimating one and two particle diffusivities in a region of very high eddy energy.
Moored current meter data from the Canary Basin near 32°N, 24°W (1984-1986) Volume XL

(Woods Hole Oceanographic Institution, 1987-05) Tarbell, Susan A. ; Richardson, Philip L. ; Price, James F.

Data are shown from a two-year current meter mooring in the Canary Basin near 32°N, 24°W. Current meters were located at depths of 470 m, 970 m, 1070 m and 2970 m during the period October 19, 1984 to October 4, 1986. The mooring deployment is part of an 1984-1988 experiment to measure features of advection and diffusion of Mediterranean outflow water with neutrally buoyant SOFAR floats.
Highly resolved observations and simulations of the ocean response to a hurricane

(American Geophysical Union, 2007-07-07) Sanford, Thomas B. ; Price, James F. ; Girton, James B. ; Webb, Douglas C.

An autonomous, profiling float called EM-APEX was developed to provide a quantitative and comprehensive description of the ocean side of hurricane-ocean interaction. EM-APEX measures temperature, salinity and pressure to CTD quality and relative horizontal velocity with an electric field sensor. Three prototype floats were air-deployed into the upper ocean ahead of Hurricane Frances (2004). All worked properly and returned a highly resolved description of the upper ocean response to a category 4 hurricane. At a float launched 55 km to the right of the track, the hurricane generated large amplitude, inertially rotating velocity in the upper 120 m of the water column. Coincident with the hurricane passage there was intense vertical mixing that cooled the near surface layer by about 2.2°C. We find consistent model simulations of this event provided the wind stress is computed from the observed winds using a high wind-speed saturated drag coefficient.
Improving oceanic overflow representation in climate models : the Gravity Current Entrainment Climate Process Team

(American Meteorological Society, 2009-05) Legg, Sonya ; Ezer, Tal ; Jackson, Laura ; Briegleb, Bruce P. ; Danabasoglu, Gokhan ; Large, William G. ; Wu, Wanli ; Chang, Yeon ; Ozgokmen, Tamay M. ; Peters, Hartmut ; Xu, Xiaobiao ; Chassignet, Eric P. ; Gordon, Arnold L. ; Griffies, Stephen M. ; Hallberg, Robert ; Price, James F. ; Riemenschneider, Ulrike ; Yang, Jiayan

Oceanic overflows are bottom-trapped density currents originating in semienclosed basins, such as the Nordic seas, or on continental shelves, such as the Antarctic shelf. Overflows are the source of most of the abyssal waters, and therefore play an important role in the large-scale ocean circulation, forming a component of the sinking branch of the thermohaline circulation. As they descend the continental slope, overflows mix vigorously with the surrounding oceanic waters, changing their density and transport significantly. These mixing processes occur on spatial scales well below the resolution of ocean climate models, with the result that deep waters and deep western boundary currents are simulated poorly. The Gravity Current Entrainment Climate Process Team was established by the U.S. Climate Variability and Prediction (CLIVAR) Program to accelerate the development and implementation of improved representations of overflows within large-scale climate models, bringing together climate model developers with those conducting observational, numerical, and laboratory process studies of overflows. Here, the organization of the Climate Process Team is described, and a few of the successes and lessons learned during this collaboration are highlighted, with some emphasis on the well-observed Mediterranean overflow. The Climate Process Team has developed several different overflow parameterizations, which are examined in a hierarchy of ocean models, from comparatively well-resolved regional models to the largest-scale global climate models.
SOFAR float Mediterranean outflow experiment data from the second year, 1985-86

(Woods Hole Oceanographic Institution, 1988-09) Zemanovic, Marguerite E. ; Richardson, Philip L. ; Valdes, James R. ; Price, James F. ; Armi, Laurence

In October, 1984, the Woods Hole Oceanographic Institution SOFAR float group began a three-year-long field program to observe the low frequency currents in the Canary Basin. The principal scientific goal was to learn how advection and diffusion by these currents determine the shape and amplitude of the Mediterranean salt tongue. Fourteen floats were launched at a depth of 1100 min a cluster centered on 32°N, 24°W, and seven other floats were launched incoherently along a north/south line from 24°N to 37°N. At the same time investigators from Scripps Institution of Oceanography and the University of Rhode Island used four other SOFAR floats to tag a Meddy, a submesoscale lens of Mediterranean water. In October, 1985, seven additional floats were launched, four in three different Meddies, one of which was tracked during year 1. This report describes the second year of the floats launched in 1984 and the first year of the ones launched in 1985. Approximately 41 years of float trajectories were produced during the first two years of the experiment. One of the striking accomplishments is the successful tracking of one Meddy over two full years plus the tracking of two other Meddies during the second year.
A regional modeling study of the entraining Mediterranean outflow

(American Geophysical Union, 2007-12-12) Xu, X. ; Chassignet, Eric P. ; Price, James F. ; Ozgokmen, Tamay M. ; Peters, Hartmut

We have evaluated a regional-scale simulation of the Mediterranean outflow by comparison with field data obtained in the 1988 Gulf of Cádiz Expedition. Our ocean model is based upon the Hybrid Coordinate Ocean Model (HYCOM) and includes the Richardson number–dependent entrainment parameterization of Xu et al. (2006). Given realistic topography and sufficient resolution, the model reproduces naturally the major, observed features of the Mediterranean outflow in the Gulf of Cádiz: the downstream evolution of temperature, salinity, and velocity profiles, the mean path and the spreading of the outflow plume, and most importantly, the localized, strong entrainment that has been observed to occur just west of the Strait of Gibraltar. As in all numerical solutions, there is some sensitivity to horizontal and vertical resolution. When the resolution is made coarser, the simulated currents are less vigorous and there is consequently less entrainment. Our Richardson number–dependent entrainment parameterization is therefore not recommended for direct application in coarse-resolution climate models. We have used the high-resolution regional model to investigate the response of the Mediterranean outflow to a change in the freshwater balance over the Mediterranean basin. The results are found in close agreement with the marginal sea boundary condition (MSBC): A more saline and dense Mediterranean deep water generates a significantly greater volume transport of the Mediterranean product water having only very slightly greater salinity.
Metrics of hurricane-ocean interaction : vertically-integrated or vertically-averaged ocean temperature?

(Copernicus Publications on behalf of the European Geosciences Union, 2009-05-05) Price, James F.

The ocean thermal field is often represented in hurricane-ocean interaction by a metric termed upper Ocean Heat Content (OHC), the vertical integral of ocean temperature in excess of 26°C. High values of OHC have proven useful for identifying ocean regions that are especially favorable for hurricane intensification. Nevertheless, it is argued here that a more direct and robust metric of the ocean thermal field may be afforded by a vertical average of temperature. In the simplest version, dubbed T100, the averaging is from the surface to 100 m, a typical depth of vertical mixing by a category 3 hurricane. OHC and T100 are well correlated over the deep open ocean in the high range of OHC, ≥75 kJ cm−2. They are poorly correlated in the low range of OHC, ≤50 kJ cm−2, in part because OHC is degenerate when evaluated on cool ocean regions, ≤26°C. OHC and T100 can be qualitatively different also over shallow continental shelves: OHC will generally indicate comparatively low values regardless of the ocean temperature, while T100 will take on high values over a shelf that is warm and upwelling neutral or negative. In so far as the ocean thermal field alone is concerned, these warm, shallow continental shelves would appear to be as favorable for hurricane intensification as are warm, deep ocean regions.
Data tabulations and analysis of diurnal sea surface temperature variability observed at LOTUS

(Woods Hole Oceanographic Institution, 1986-02) Bowers, Clarke M. ; Price, James F. ; Weller, Robert A. ; Briscoe, Melbourne G.

Air/sea measurements from the Long-Term Upper Ocean Study (LOTUS) buoy in the Sargasso Sea are analyzed to learn how the diurnal response of sea surface temperature, ΔTs, is related to the surface heating, H, and the wind stress, S. Data are taken from the LOTUS-3 and LOTUS-5 records which span the summers of 1982 and 1983. The basic data are shown in monthly plots, and the analyzed daily values of ΔTs, H, and S are given in tables and in figures. Analyzed data show a clear trend of ΔTs increasing with H and decreasing with S. A best-fit, three-parameter, empirical function can account for 90 percent of the variance in a screened subset of the LOTUS data (172 days) and 81 percent of the variance of the full data set (361 days). The analyzed data are also compared with a theoretical model function now used for ocean predictions in the Diurnal Ocean Surface Layer model (DOSL) of Fleet Numerical Oceanography Center. The DOSL model function was derived from the assumption that wind-mixing occurs by a mechanism of shear flow instability. It is fully predictive and shows a parameter dependence consistent with the LOTUS data over a wide range of H and S. The DOSL model function can account for almost as much variance as the best-fit empirical function.
The upper-oceanic response to overflows : a mechanism for the Azores Current

(American Meteorological Society, 2008-04) Kida, Shinichiro ; Price, James F. ; Yang, Jiayan

The oceanic response to overflows is explored using a two-layer isopycnal model. Overflows enter the open ocean as dense gravity currents that flow along and down the continental slope. While descending the slope, overflows typically double their volume transport by entraining upper oceanic water. The upper oceanic layer must balance this loss of mass, and the resulting convergent flow produces significant vortex stretching. Overflows thus represent an intense and localized mass and vorticity forcing for the upper ocean. In this study, simulations show that the upper ocean responds to the overflow-induced forcing by establishing topographic β plumes that are aligned more or less along isobaths and that have a transport that is typically a few times larger than that of the overflows. For the topographic β plume driven by the Mediterranean overflow, the occurrence of eddies near Cape St. Vincent, Portugal, allows the topographic β plume to flow across isobaths. The modeled topographic β-plume circulation forms two transatlantic zonal jets that are analogous to the Azores Current and the Azores Countercurrent. In other cases (e.g., the Denmark Strait overflow), the same kind of circulation remains trapped along the western boundary and hence would not be readily detected.
A data archive from Discovery 247, a process study of the Faroe Bank Channel overflow

( 2006-05-23) Price, James F.

CTD, XCP and LADCP data acquired during the June 2000 Discovery cruise 247 to Faroe Bank Channel are provided in a data archive that may be accessed by Matlab 7.X.
A report of data and preliminary analysis from Discovery 247, a process study of the Faroe Bank Channel overflow

( 2006-05-23) Price, James F.

CTD, XCP and LADCP data acquired during the June 2000 Discovery cruise 247 to Faroe Bank Channel are shown in a variety of graphical forms. Most of the data were collected as part of 17 sections run in a direction mainly across the path of the Faroe Bank Channel overflow and comprising approximately 200 stations. These data have been used to estimate the transport of overflow water, approx 1.8 Sv on average, but fairly time-variable. The entrainment into the overflow as well as the bottom stress and vorticity are also analyzed.
Rapid intensification of Typhoon Hato (2017) over shallow water

(MDPI, 2019-07-06) Pun, Iam-Fei ; Chan, Johnny C. L. ; Lin, I.-I. ; Chan, Kelvin T. F. ; Price, James F. ; Ko, Dong S. ; Lien, Chun-Chi ; Wu, Yu-Lun ; Huang, Hsiao-Ching

On 23 August, 2017, Typhoon Hato rapidly intensified by 10 kt within 3 h just prior to landfall in the city of Macau along the South China coast. Hato’s surface winds in excess of 50 m s−1 devastated the city, causing unprecedented damage and social impact. This study reveals that anomalously warm ocean conditions in the nearshore shallow water (depth < 30 m) likely played a key role in Hato’s fast intensification. In particular, cooling of the sea surface temperature (SST) generated by Hato at the critical landfall point was estimated to be only 0.1–0.5 °C. The results from both a simple ocean mixing scheme and full dynamical ocean model indicate that SST cooling was minimized in the shallow coastal waters due to a lack of cool water at depth. Given the nearly invariant SST in the coastal waters, we estimate a large amount of heat flux, i.e., 1.9k W m−2, during the landfall period. Experiments indicate that in the absence of shallow bathymetry, and thus, if nominal cool water had been available for vertical mixing, the SST cooling would have been enhanced from 0.1 °C to 1.4 °C, and sea to air heat flux reduced by about a quarter. Numerical simulations with an atmospheric model suggest that the intensity of Hato was very sensitive to air-sea heat flux in the coastal region, indicating the critical importance of coastal ocean hydrography.
Argo array observation of ocean heat content changes induced by tropical cyclones in the north Pacific

(American Geophysical Union, 2011-12-16) Park, Jong Jin ; Kwon, Young-Oh ; Price, James F.

In situ observations from the autonomous Argo float array are used to assess the basin-averaged ocean heat content change driven by tropical cyclones (TCs) in the North Pacific for 2000–2008. A new statistical approach based on pairs of profiles before and after each TC event is employed here to estimate the near-surface and subsurface heat content changes. Previous studies have suggested a dominant role for vertical mixing in the SST cooling response during TC passages. The Argo float observations show that, under strong TCs (greater than or equal to category 4), the subsurface warming expected from vertical mixing occurs with comparable magnitude to near-surface cooling. However, when weak TCs (less than or equal to category 3, which are about 86% of the total of TCs) were also considered, the subsurface warming was not detectable in the Argo data set, while near-surface cooling was still significant. Therefore, these results suggest that air-sea heat exchange and (upward) vertical advection likely play a somewhat greater role in the case of weak TCs. Additionally, Argo observations suggest that the restoring time scale of the near-surface heat content is greater than 30 days, which may be compared with the approximately 10 day time scale for the restoration of sea surface temperature. The mixed layer temperature and mixed layer depth evolutions also estimated from Argo data support the notion that only a thin surface layer is restored quickly to pre-TC conditions, while the rest of the cooled near-surface layer retained the TC-induced response for a good deal longer.
Satellite-derived ocean thermal structure for the North Atlantic hurricane season

(American Meteorological Society, 2015-12-08) Pun, Iam-Fei ; Price, James F. ; Jayne, Steven R.

This paper describes a new model (method) called Satellite-derived North Atlantic Profiles (SNAP) that seeks to provide a high-resolution, near-real-time ocean thermal field to aid tropical cyclone (TC) forecasting. Using about 139 000 observed temperature profiles, a spatially dependent regression model is developed for the North Atlantic Ocean during hurricane season. A new step introduced in this work is that the daily mixed layer depth is derived from the output of a one-dimensional Price–Weller–Pinkel ocean mixed layer model with time-dependent surface forcing. The accuracy of SNAP is assessed by comparison to 19 076 independent Argo profiles from the hurricane seasons of 2011 and 2013. The rms differences of the SNAP-estimated isotherm depths are found to be 10–25 m for upper thermocline isotherms (29°–19°C), 35–55 m for middle isotherms (18°–7°C), and 60–100 m for lower isotherms (6°–4°C). The primary error sources include uncertainty of sea surface height anomaly (SSHA), high-frequency fluctuations of isotherm depths, salinity effects, and the barotropic component of SSHA. These account for roughly 29%, 25%, 19%, and 10% of the estimation error, respectively. The rms differences of TC-related ocean parameters, upper-ocean heat content, and averaged temperature of the upper 100 m, are ~10 kJ cm−2 and ~0.8°C, respectively, over the North Atlantic basin. These errors are typical also of the open ocean underlying the majority of TC tracks. Errors are somewhat larger over regions of greatest mesoscale variability (i.e., the Gulf Stream and the Loop Current within the Gulf of Mexico).
CTD sections from Discovery 247, a process study of the Faroe Bank Channel overflow

( 2006-05-23) Price, James F.

CTD sections acquired during the June 2000 Discovery cruise 247 to Faroe Bank Channel are plotted in section (depth and horizontal distance) format. In all there were 17 sections run in a direction mainly across the path of the Faroe Bank Channel overflow and comprising approximately 200 stations. The CTD data have been contoured and displayed in eps format. For each section, there are displays of potential temperature, salinity, potential density and dissolved oxygen concentration. There are also maps showing the location of each section. These figures are public domain.

Price James F.

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