Air-Sea Interaction

Ocean eddies and fronts affect surface stress via two mechanisms: (1) ocean surface currents altering the relative motion between air and sea and, hence, the stress fields and (2) ocean sea surface temperature (SST) gradients forcing changes in stability and nearsurface winds. In this paper, we quantify the first effect and how it impacts Tropical Instability Waves (TIW) in the eastern Pacific. High-resolution satellite data and a regional coupled model are used to distinguish between stress changes due to the surface currents and those due to the changes in stability and near-surface winds. It is found that both mechanisms affect the surface stress curl, but they do so at different latitudes, allowing for their effect on Ekman pumping to be distinguished. The Ekman pumping due to the surface current effect alone, leads to significant damping of the TIWs. In terms of the eddy kinetic energy, the inclusion of surface current in the stress leads to decay with an e-folding time comparable with the period of the TIWs. It is, thus, an important damping mechanism to be included in ocean and coupled ocean-atmosphere models.

A series of experiments were conducted at University of Delaware's Air-Sea Interaction Laboratory to examine the combined effects of rain and wind on air-water gas exchange. During this study, ASIL WRX I, a combination of 3 rain rates and 4 wind speeds were used, for a total of 12 different environmental conditions. The SF 6 evasion method was used to determine the bulk gas transfer velocities, and airside profiles of wind and CO 2 were used to estimate flux-profiles of momentum and carbon dioxide. In addition to measurements of fluxes with and without rain in a wind-wave boundary layer, measurements of wave properties were also obtained. Rain is shown to alter the wind profile in the flume, and dampen surface waves. Also, SF 6 evasion indicates that with the present experimental setup, for most of the experimental conditions, rain and wind combine linearly to influence air-water gas exchange. Flux-profile relationships for marine atmospheric boundary layers, which were performed to scale up to field measurements, were explored by a comparison between SF 6 -derived bulk fluxes and airside CO 2 profile measurements.

The problem of the world greatest lake, the Caspian Sea, level changes attracts the increased attention due to its environmental consequences and unique natural characteristics. Despite the huge number of studies aimed to explain the reasons of the sea level variations the underlying mechanism has not yet been clarified. The important question is to what extent the CSL variability is linked to changes in the global climate system and to what extent it can be explained by internal natural variations in the Caspian regional hydrological system. In this study an evidence of a link between the El Niño/Southern Oscillation phenomenon and changes of the Caspian Sea level is presented. This link was also found to be dominating in numerical experiments with the ECHAM4 atmospheric general circulation model on the 20th century climate.

The analysis of the ECMWF re-analysis surface meteorological fields (wind velocity, air temperature, relative humidity and cloud cover) is conducted on the Mediterranean basin and in its four small areas, mainly focusing on the interannual fluctuations of these data. This analysis (times series of surface integrals and EOF) shows an outstanding interannual signal in all data. In general, sporadic anomalous events in wind speed can occur during the winter months, while those in air temperature can occur during the summer months. Then, by comparing to COADS, a general underestimation of the wind speed and a good agreement in the air temperature are found.

The surface heat balance is analyzed in all its components to assess the most commonly used heat flux bulk formulas applied to the Mediterranean basin and to provide simulations of better air-sea interaction boundary conditions for Ž . Ž . Mediterranean OGCMs Ocean General Circulation Models . A 9-year data set 1980-1988 from 12 hourly NMC atmospheric analysis combined with Reynolds SST and COADS cloud coverage is used. The surface heat balance of the Mediterranean, including the ocean heat advection through the Strait of Gibraltar and the water budget of the basin, is computed using the NMC data at monthly and 12-hourly frequency. The 12-hourly NMC data yield the correct heat loss in Ž . the basin. This analysis identifies a set of heat flux bulk formulas 'the calibrated set' which represent best the heat balance of the Mediterranean Basin with our available data sets. The calibrated set of bulk formulas, used as heat flux boundary condition for the OGCM, is capable to improve the representation of the water masses in the Mediterranean basin and to reduce the model climatic drift.

Daily variations of vertical velocity at the bottom of surface mixed layer at the centres of two stationary polygons and zonal wind stress component over Arabian Sea during MONEX 1979 are studied using marine meteorological parameters obtained from Monex data set. The values of zooaI wind stress are in agreement with earlier reports, although some values observed in polygon II exceed the normal. This is attributed to the intensification of low level wind field prior to the onset vortex. Values of Ekman pumping velocity at the centre of polygon I differ from previous results. The strong positive values observed during onset phase (polygon II) are in fair agreement with the earlier reports and this can be attributed to the presence of strong monsoon westerlies over the Arabian Sea during this p'hase.

Infrastructure for Training and Partnerships - California Water and ... Principal Investigator: Co-Principal Investigators: David A. Siegel Jeffrey Dozier, Catherine Gautier, Frank Davis, Tommy Dickey, Thomas Dunne, James Frew, Arturo Keller, Sally MacIntyre, John Melack, Leal Mertes, Dar Roberts, Raymond Smith, Zhengming Wan, and Libe Washburn ... Institute for Computational Earth Systems Science (ICESS) ... Donald Bren School of Environmental Science & Mgmt. ... University of California, Santa Barbara 6832 Ellison Hall Santa Barbara, California 93106- ...

Ammonium (NH 4 + ) concentration was measured at 15 stations in the NE Atlantic during the declining phase of the spring diatom bloom as part of the FISHES 2001 cruise. The NE Atlantic temperate spring bloom is one of the largest seasonal events in the oceanic cycle of primary productivity and represents the conversion of large amounts of oxidized nitrogen to organic (reduced) nitrogen by planktonic photosynthesis, much of which is recycled by heterotrophs as reduced N (DON and ammonium). We might expect recycled ammonium to be rapidly re-used by photosynthesizers. However, during the FISHES cruise the decline of the bloom was accompanied by a substantial buildup of dissolved ammonium (from ∼ 100 nM to >500 nM near the sea surface) caused by a temporary imbalance in production and consumption processes. Calculations of air-sea ammonia (NH 3 ) flux under assumed 'normal' 'peak bloom' and 'post-diatom-bloom' conditions are presented and these demonstrate that over a wide range of temperatures, post-bloom accumulation of ammonium will lead to changes in the magnitude and direction of air-sea ammonia flux. If our results are generally applicable then the seasonal succession of plankton communities may be accompanied by periods of anomalously high ammonium concentration and hence be disproportionately important for air-sea ammonia flux. Once in the atmosphere, ammonia neutralizes acidity and in doing so plays a potentially significant role in climate forcing via aerosol formation.

There are non zero correlations, with distinct geographical patterns, between SWH and SSH-<SSH>, where <> is a two year mean (fig. ). Correlations between SWH2-SWH1 and SSH2-SSH1 (1 and 2 indicating differences in time) show no regional correlations (fig. ). This raises the question, when using SSH-<SSH> to calculate SSB, does this method affect the results?

An Urban Planning Research Workshop (UPL 681) project by Areej Alkandari, Inshirah Shublaq, Israa El Shaarani, Joud Razzaz, and Lamees Hamid entitled, &quot;Project Final Report&quot;, submitted in Spring 2016. Project supervisor is Prof. Rafael Pizarro.

This article is the second part of a modeling study of upper ocean mesoscale physical processes in an area of the northeast Atlantic that was extensively sampled during the Programme Oce ´an Multidisciplinaire Me ´so-Echelle (POMME experiment, October 2000. The model is a high-resolution regional version of the ocean general circulation model OPA integrated from February to May 2001. The mesoscale upper ocean dynamics has been carefully validated in a first paper . In the present article, the simulation is used to analyze the contribution of mesoscale eddies to the mixed layer processes during the period that controls the annual subduction rate and the characteristics of the subducted water. Mesoscale eddies account for a significant part of the mixed layer heat, salt, and water budgets through mesoscale and submesoscale structures acting on the horizontal advective terms. They represent respectively 52% and 66% of the horizontal advection of temperature and salinity and 70% of the lateral induction. They also induce an earlier and more intense restratification. The domain-averaged detrainment appears to be reduced by more than 15% by mesoscale eddies and reaches about 0.8 Sv. However, these eddies increase the density of the detrained water. Some dense water, likely to be involved in the formation of subpolar mode water, is detrained by them in a way that maximizes its chance to be effectively subducted in the area.

The formation of the Atlantic cold tongue (ACT) is the dominant seasonal sea surface temperature signal in the eastern equatorial Atlantic (EEA). A comprehensive analysis of variability in its spatial extent, temperature, and onset is presented. Then, the physical mechanisms which initiate ACT onset, as well as the feedbacks from the ACT to the maritime boundary layer, and how the ACT influences the onset of the West African monsoon (WAM) are discussed. We argue that in the EEA, the air-sea coupling between the ACT and WAM occurs in two phases. From March to mid-June, the ACT results from the intensification of the southeastern trades associated with the St. Helena anticyclone. Steering of surface winds by the basin shape of the EEA imparts optimal wind stress for generating the maximum upwelling south of the equator. During the second phase (mid-June-August), wind speeds north of the equator increase as a result of the northward progression of the intensifying trades and as a result of significant surface heat flux gradients produced by the differential cooling between the ACT and the tropical waters circulating in the Gulf of Guinea (GG). It is anticipated that the atmospheric divergence induced at low levels north of the equator reduces convection over the GG and that increased northward winds shift convection over land. Correlations between the ACT and the WAM onset dates over the last 26 years measure as much as 0.8. This suggests that the ACT plays a key role in the WAM onset.

A modeling study of physical processes occurring in an area of the northeast Atlantic (21.33°-15.33°W, 38.00°-45.00°N) that was extensively sampled during the Programme Oce ´an Multidisciplinaire Me ´so Echelle (POMME) (October 2000-September 2001) is carried out. The model is a mesoscale version of the ocean general circulation model OPA developed at the Laboratoire d'Oce ´anographie Dynamique et de Climatologie in Paris. It is used in a three-dimensional limited area domain with a high-resolution grid (approximately 5 km horizontal spacing, 69 vertical levels) and realistic boundary conditions (initial state, air-sea fluxes, open boundary fluxes, and bottom topography). The objectives of the study are to properly simulate the upper ocean dynamics, particularly mesoscale activity and mixed layer evolution, during a key period (restratification) of the POMME experiment (POMME 1 and POMME 2, from February to May 2001) and to compare model results with oceanographic observations collected during the experiment in order to establish confidence in the model. Some results provided by the high-resolution simulation, in particular features related to mixed layer depth and vertical velocities, are also presented. There is no pronounced north-south mixed layer depth gradient, but strong filament-shaped structures associated with stirring at the periphery of eddies are present. Mixed layer restratification is simulated. It is associated with submesoscale mixed layer depth structures and intense vertical velocity filaments in the upper ocean correlated with the relative vorticity gradient field.

A camada limite planetária (CLP) na região de Iperó-SP é estudada através de simulações numéricas utilizando um modelo unidimensional com fechamento de segunda ordem. Os resultados indicam que os fluxos verticais turbulentos, em resposta ao aquecimento solar, de calor sensível e latente têm valores máximos próximo à superfície decrescendo linearmente com a altura, favorecendo assim os transportes de calor e umidade para os níveis mais altos da atmosfera. No período noturno a turbulência térmica praticamente cessa e consequentemente os fluxos turbulentos são pequenos em toda extensão vertical da CLP. Em resposta a isto, os perfis verticais médios de temperatura e umidade são melhor simulados durante o dia. Por outro lado, os fluxos em superfície e o saldo de radiação simulados estão em quase perfeita concordância com os observados durante todo o período, e o ciclo diurno da temperatura do ar próximo à superfície é satisfatoriamente simulado.

Long-term observations of the marine atmospheric boundary layer were performed by an eddy correlation system, which was set-up on a platform in the Baltic Sea. In this experiment the three-dimensional wind vector and the turbulent fluxes of momentum, sensible and latent heat and CO 2 were measured for one and a half years. Simultaneously the CO 2 partial pressure p CO 2 in surface water was measured by a submersible autonomous moored instrument for CO 2 at the platform in 7-m depth. The high-resolution eddy correlation measurements of the atmospheric CO 2 flux F CO 2 , together with the measurements of the CO 2 partial pressure differences between air and sea Δp CO 2 led to a long-term data set which provided the possibility to investigate the parameterization of the CO 2 transfer velocity k as a function of 10-m wind speed u in a statistical manner. From half-hour mean CO 2 fluxes and CO 2 partial pressure differences, k was calculated using k = F CO 2 / (K 0 Δp CO 2 ), with K 0 the CO 2 solubility. The half-hour mean data points, used for the determination of the k-u parameterization, show large scatter. However, assuming a linear, quadratic dependency the analysis yields: k 660 = 0.365u 2 + 0.46u (k at 20 °C and salinity 35 psu) with a correlation coefficient of r 2 = 0.81. The large scatter indicates that the kinetics of the air-sea CO 2 transfer velocity is not only a function of the wind speed alone, but might also be controlled by other environmental parameters and mechanisms, such as sea state and surface coverage with surfactants.

Infrastructure for Training and Partnerships - California Water and ... Principal Investigator: Co-Principal Investigators: David A. Siegel Jeffrey Dozier, Catherine Gautier, Frank Davis, Tommy Dickey, Thomas Dunne, James Frew, Arturo Keller, Sally MacIntyre, John Melack, Leal Mertes, Dar Roberts, Raymond Smith, Zhengming Wan, and Libe Washburn ... Institute for Computational Earth Systems Science (ICESS) ... Donald Bren School of Environmental Science & Mgmt. ... University of California, Santa Barbara 6832 Ellison Hall Santa Barbara, California 93106- ...

The surface mooring component of the CLIVAR Long Term Evolution and Coupling of the Boundary Layers in the Stratus Deck Regions study (STRATUS) took place from October 2000 in the eastern tropical Pacific. As part of the Eastern Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC), STRATUS is a CLIVAR study with the goal of investigating links between sea surface temperature variability in the eastern tropical Pacific and climate over the American continents. This study started a three-year occupation off Chili in order to collect accurate time series of surface forcing and upper ocean variability. The Upper Ocean Processes (UOP) Group at WHOI deployed one fully instrumented surface mooring near 20°S 85°W in October 2000, at the western edge of the stratocumulus cloud deck found west of Peru and Chile, to achieve a good understanding of the role of clouds in the eastern Pacific in modulating atmosphere-ocean coupling. Data from the moorings will improve our understanding of the air-sea fluxes and be used to examine the processes that control sea surface temperature in the cold tongue/intertropical convergence zone (ITCZ) and in the stratus deck region. G 5/8" CHAIN SHACKLE, 7/8" ENDLINK, 7/8" ANCHOR SHACKLE H 100 M 3/8" WIRE 100 M 3/8" WIRE 500 M 3/8" WIRE 500 M. 7/8" NYLON HARDWARE REQUIRED (INCLUDES APPROX. 20% SPARES) 1" CHAIN SHACKLES 2 1" ANCHOR SHACKLES 2 1" WELDLESS END LINK 2 7/8" ANCHOR SHACKLES 4 7/8" CHAIN SHACKLES 2 7/8" WELDLESS LINKS 120 3/4" CHAIN SHACKLES 163 3/4" ANCHOR SHACKLES 11 5/8" CHAIN SHACKLES 60 MAXIMUM DIAMETER OF BUOY WATCH CIRCLE = 3.72 N. MILES T-POD w/ Load Bar 3.77 M. 3/4" PROOF COIL CHAIN 47.5 70 T-POD w/ Load Bar 6.2 M. 7/16" WIRE T-POD w/ Load Bar 3.43 M. 3/4" PROOF COIL CHAIN T-POD w/ Load Bar MicroCat 40 30 62.5 6.2 M. 7/16" WIRE 6.2 M. 7/16" WIRE First Deployment 0.96 M. 3/4" PROOF COIL CHAIN (14 Links) 0.48 M. 3/4" PROOF COIL CHAIN (7 Links) * Note: No adjustment required if the water depth is within plus or minus 100 Meters. * SEACAT SEACAT 2.74 M. 3/4" PROOF COIL CHAIN 6.2 M. 7/16" WIRE MicroCat T-POD w/ Load Bar T-POD w/ Load Bar 6.2 M. 7/16" WIRE 6.2 M. 7/16" WIRE 9.4 M. 7/16" WIRE

Estudios previos han demostrado que las temperaturas en la superficie del mar (SSTs) y las anomalías de temperatura de la superficie del mar (SST) en la región del Pacífico pueden clasificarse en siete patrones o conglomerados (A-G). Los conglomerados B y G (C, D y F) [A y E] son representativos de distribuciones SST en periodos de La Niña (El Niño) [neutral]. El análisis de patrones SST para el periodo 1955-1993 ha demostrado que los conglomerados A-D fueron predominantes en el primer periodo 1955-1977, mientras que los tipos E y F dominaron en el último periodo de estudio. Los conglomerados tipo G fueron poco frecuentes pero ocurrieron durante ambos periodos. Este cambio en la frecuencia de patrones durante 1977 corresponde a cambio de fase de la Oscilación Decadal del Pacífico (PDO). En este estudio se lleva a cabo un análisis similar extendido al periodo 1994-2005. Los resultados revelan un cambio en los patrones predominantes de SSTs asociado a un cambio simultáneo en la fase de la PDO durante 1999 y 2000. Los patrones SST evolucionaron desde unas anomalías predominantemente de tipo E y F en 1994 a anomalías de tipo A, B, D y G en 2005. Estos resultados sugieren que los conglomerados A-D (C, D y F) son característicos de fases negativas (positivas) de la PDO. Por otro lado, el empleo de una técnica modificada para generar diagramas de fase muestra la existencia de variaciones interanuales e interdecadales en la temperatura media mensual y en los registros de precipitación de la región central del Mississippi que pueden asociarse con ENSO y la PDO. Además, un análisis de la asociación estadística entre anomalías de temperatura y precipitación en la región central de Mississippi, y regímenes prolongados de SST revela que las anomalías B, D y G se asociaron con condiciones cálidas, mientras que las anomalías de tipo C y E lo hicieron con condiciones frías. Las anomalías C, D, F y G se asociaron con condiciones más secas de lo normal.

Lagged maximum covariance analysis (LMCA) is used to examine the intraseasonal variability of zonal wind, sea surface temperature (SST), and outgoing longwave radiation (OLR) in the northeastern tropical Pacific Ocean during Northern Hemisphere summertime. The analysis shows a strong temporal asymmetry in that wind and convection anomalies lead to SST anomalies, but SST anomalies are not followed by comparably strong wind and convection anomalies. This suggests that SST anomalies associated with the MJO in the northeastern tropical Pacific are largely subject to atmospheric variability. * Joint Institute for the Study of the Atmosphere and Ocean Contribution Number 999.

Infrastructure for Training and Partnerships - California Water and ... Principal Investigator: Co-Principal Investigators: David A. Siegel Jeffrey Dozier, Catherine Gautier, Frank Davis, Tommy Dickey, Thomas Dunne, James Frew, Arturo Keller, Sally MacIntyre, John Melack, Leal Mertes, Dar Roberts, Raymond Smith, Zhengming Wan, and Libe Washburn ... Institute for Computational Earth Systems Science (ICESS) ... Donald Bren School of Environmental Science & Mgmt. ... University of California, Santa Barbara 6832 Ellison Hall Santa Barbara, California 93106- ...

Plitkovodni gravitacijski val uzrokovan gibanjem atmosferskog poremecaja povecava svoju amplitudu kroz energetski transfer omogucen Proudmanovom rezonancijom. Nailaskom na lucki bazen oblika lijevka desava se dodatna amplificija valnog signala. Ukoliko valna grupa koja nailazi sadrži i frekvencije bliske luckim vlastitim frekvencijama moguca je i pojava rezonancije s daljnjim povecenjem valnih amplituda. Cjelokupna pojava naziva se meteocunami, a primjer te pojave desio se i 21.6.1978. u Veloj Luci, pri cemu su registrirane valne visine od 6 m. U radu je provedena numericka analiza dinamike morskih razi u krajnjoj tocki Vele Luke uslijed valne pobude s maksimalnim visinama od 0, 19 m ispred ulaza u zaljev Vela Luka. Kao odgovor na valnu pobudu u krajnjoj tocki luke dobivene su valne visine od 5, 5 m. Analiziran je utjecaj hipotetskih vertikalnih nepropusnih lukobrana, na valne visine u samoj Veloj luci. Koristene su dvije varijante pozicije ispred ulaza u Velu Luku. Modelski rezulta...

In this work, the diurnal evolution of the radiation balance components over the tropical Atlantic Ocean is described and analysed. The analysis is based on measurements carried out on board a Brazilian Navy ship during the observational campaign of the FluTuA Project (‘Fluxos Turbulentos sobre o Atlântico’), from 15 to 23 May 2002. The observations indicated that the albedo responds as expected to atmospheric attenuation effects with a diurnal evolution similar to the Fresnel albedo. In general, the observed longwave radiation values agreed better with the estimated values obtained without longwave reflection. In agreement with the literature, the average surface emissivity was around 0.97. The net radiation, estimated from published equations for albedo, atmospheric transmissivity and surface emissivity, agreed with the observations, indicating that these parameters are representative of the radiometric properties of the air‐sea interface in the region between Natal (6°S, 35.2°W) ...

This work aims to identify, by means of statistical analysis, the relationship between extreme precipitation events and SST anomalies (SSTA) in the municipalities surrounding the Ilha Grande (IGB) and Sepetiba (SB) bays in the state of Rio de Janeiro evaluating its annual distributions using measured data from rainfall stations and relating these events to potential SST anomalies found in this region. Data from 10 rainfall stations distributed around the bays and SST dataset obtained from the Multi-scale Ultra-high Resolution Sea Surface Temperature (MUR) from 2003 to 2014 were used. SSTA and their average were generated for each of the three subareas delimited in the study area. The obtained time series of each subarea define the thresholds for significant SSTA, based on their respective standard deviation. The number of days with SSTA were obtained from these significant anomaly values, and days with positive or negative SSTA, for each subarea, were computed. For SSTA analysis, on...

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The Northwest Tropical Atlantic Station (NTAS) was established to address the need for accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface temperature anomalies and the likelihood of significant local air-sea interaction on interannual to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 15°N, 51°W by successive mooring turnarounds. These observations will be used to investigate air-sea interaction processes related to climate variability. Deployment of the first (NTAS-1) and second (NTAS-2) moorings were documented in previous reports . This report documents recovery of the NTAS-2 mooring and deployment of the NTAS-3 mooring at the same site. Both moorings used 3-meter discus buoys as the surface element. These buoys were outfitted with two Air-Sea Interaction Meteorology (ASIMET) systems. Each system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air-sea fluxes of heat, moisture and momentum. The upper 150 m of the mooring line were outfitted with oceanographic sensors for the measurement of temperature and velocity. The mooring turnaround was done on the WHOI R/V Oceanus, Cruise OC-385-5, by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place between 12 and 23 February 2003. Deployment of the NTAS-3 mooring was on 15 February at approximately 14°49.5¢ N, 51°01.3¢ W in 4977 m of water. A 24hour intercomparison period followed, after which the NTAS-2 mooring was recovered. This report describes these operations, as well as some of the pre-cruise buoy preparations.

The surface current field of a mesoscale eddy in the East Sea (Sea of Japan) was derived from consecutive Geostationary Ocean Color Imager chlorophyll-a (chl-a) concentration images using the normalized maximum cross-correlation method. The estimated current field of the eddy exhibited anticyclonic structure demonstrated by the objective dynamic thresholds of correlation coefficients. The eddy periphery was defined by fitting an ellipse to subjectively selected points from the frontal map of chl-a concentration data. Radial distribution and hourly variation of the current speed around the eddy were presented. In terms of the magnitude and direction, the estimated current field was in good agreement with altimeter-based current field and current vectors from surface drifters. Diurnal variations in the current speeds of the mesoscale eddies showed a quadratic relation to the wind speed.

Satellite-borne scatterometer and infrared data collected over Gulf Stream warm and cold core rings are used to study the effect of the sea-air temperature difference on the wind speed over rings. The observed acceleration of the wind over and deceleration overis found to be consistent with that predicted by the planetary boundary layer model of . In addition it is shown that the distance over which the winds respond to an ocean surface temperature step is short ( 25km) while the distance over which the marine boundary layer responds to a surface temperature step is long (!175km).

• Lindzen and Nigam (1987) noted that air temperature anomalies were proportional to SST anomalies throughout the boundary layer in the tropics. • Ideal gas law and hydrostatic balance then implies that pressure gradients are negatively correlated with SST gradients. • Winds driven by pressure gradients lead to surface convergence and convection.

In this study, a reduced-gravity, primitive equation OGCM is used to investigate the seasonal variability of the bifurcation of the South Equatorial Current (SEC) into the Brazil Current (BC) to the south and the North Brazil Undercurrent/Current (NBUC/NBC) system to the north. Annual mean meridional velocity averaged within a 2°longitude band off the South American coast shows that the SEC bifurcation occurs at about 10°-14°S near the surface, shifting poleward with increasing depth, reaching 27°S at 1000 m, in both observations and model. The bifurcation latitude reaches its southernmost position in July (ϳ17°S in the top 200 m) and its northernmost position in November (ϳ13°S in the top 200 m). The model results show that most of the seasonal variability of the bifurcation latitude in the upper thermocline is associated with changes in the local wind stress curl due to the annual north-south excursion of the marine ITCZ complex. As the SEC bifurcation latitude moves south (north) the NBUC transport increases (decreases) and the BC transport decreases (increases). The remote forcing (i.e., westward propagation of anomalies) appears to have a smaller impact on the seasonal variability of the bifurcation in the upper thermocline.

In this study, a reduced-gravity, primitive equation OGCM is used to investigate the seasonal variability of the bifurcation of the South Equatorial Current (SEC) into the Brazil Current (BC) to the south and the North Brazil Undercurrent/Current (NBUC/NBC) system to the north. Annual mean meridional velocity averaged within a 2° longitude band off the South American coast shows that the SEC bifurcation occurs at about 10°–14°S near the surface, shifting poleward with increasing depth, reaching 27°S at 1000 m, in both observations and model. The bifurcation latitude reaches its southernmost position in July (∼17°S in the top 200 m) and its northernmost position in November (∼13°S in the top 200 m). The model results show that most of the seasonal variability of the bifurcation latitude in the upper thermocline is associated with changes in the local wind stress curl due to the annual north–south excursion of the marine ITCZ complex. As the SEC bifurcation latitude moves south (north...

Numerical simulations of the local equatorial ocean response to idealized westerly wind burst (WWB) forcing are described. In particular, the authors examine the development and evolution of the subsurface westward jet (SSWJ) that has been observed to accompany these wind events. This westward current is interpreted as the signature of equatorial waves that accompany the downwelling and upwelling that occurs along the edges of the wind forcing region. Some important features of the SSWJ include maximum intensity toward the eastern edge of the forcing region, a time lag between the wind forcing and peak SSWJ development, and an eastward spreading of the SSWJ with time. The effect of wind burst zonal profile, magnitude, duration, and fetch on the SSWJ are explored. The response of an initially resting ocean to WWB forcing is compared with that for model oceans that are spun up with annual-mean surface fluxes and monthly varying fluxes. It is demonstrated that the gross features of the response for the spun up simulations can be well approximated by adding the background zonal current structure prior to the introduction of the wind burst to the initially resting ocean current response to the WWB. This result suggests that the zonal current structure that is present prior to the commencement of WWB forcing plays a key role in determining whether or not a SSWJ will develop.

North Pacific Subtropical Mode Water (NPSTMW) is an essential feature of the North Pacific subtropical gyre imparting significant influence on regional SST evolution on seasonal and longer time scales and, as such, is an important component of basin-scale North Pacific climate variability. This study examines the seasonal-to-interannual variability of NPSTMW, the physical processes responsible for this variability, and the connections between NPSTMW and basin-scale climate signals using an eddy-permitting 1979–2006 ocean simulation made available by the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2). The monthly mean seasonal cycle of NPSTMW in the simulation exhibits three distinct phases: (i) formation during November–March, (ii) isolation during March–June, and (iii) dissipation during June–November—each corresponding to significant changes in upper-ocean structure. An interannual signal is also evident in NPSTMW volume and other characteristic properties w...

Based on the NCEP ocean re-analysis data, the threedimensional co-evolution of the tropical Pacific climate system is examined to explain the onset of the 1991-92 E1 Nifio event. A logical sequence is discovered that links subsurface and surface temperature anomalies off and on the equator in the western and central Pacific. Along the North Equatorial Countercurrent (NECC) path, subsurface temperature anomalies propagated coherently eastward from the western boundary in mid-1989 to the date line in mid-1990, at a speed of about 10-20 cm -•. As the thermocline shoals eastward along the NECC, the subsurface anomalies outcropped in the regions near the date line, initiating warm sea surface temperature (SST) anomalies which further amplified while advectively extending into the equatorial wave guide. These subsurface-induced SST anomalies could then trigger local coupled air-sea interactions producing atmospheric-oceanic anomalies that developed and evolved in 1991, thus setting onset conditions for the 1991-92 E1 Nifio. These results differ markedly from the delayed oscillator physics in that a major role can be played by the eastward advection of off-equatorial subsurface thermal anomalies and their outcropping along the NECC subsurface pathways, not necessarily involving wave reflections along the western boundary for triggering E1 Ni•o. This mechanism explains well the observed, otherwise unaccounted for, surface warming near the date line during late 1989 and early 1990. Philander, 1992; Jin and Neelin, 1993). One popular E1 Ni•o cycle paradigm, called the delayed oscillator mechanism, has been proposed to explain its dynamics (Schopfand Suarez, 1988; Battisti and Hirst, 1989). This theory emphasizes equatorial wave processes; the phase transition can be explained as an equatorial Rossby wave which is generated midbasin at the height of the event that then propagates towards the western boundary, reflects and returns along the equator as an equatorial Kelvin wave. Kessler and McPhaden (1995a, KM thereafter) have systematically analyzed the evolution of the 1991-92 E1 Ni•o based on surface wind and temperature observations made by the 1Graduate School of Oceanography, University of Rhode Island 2Laboratory for Hydrospheric Processes, NASA/GSFC 3Atmospheric Sciences Research Center, SUNY at Albany ß

An upward-lookin g sonar instrument, the Ice Profiling Sonar (IPS), has been developed, and successfully used for obtaining time series measurements of ice keel depths over the continental shelves of the Arctic in support of scientific research. The IPS instrument capabilities have since been expanded to provide accurate measurement of ocean waves. This new instrument, the WaveSonar, uses a high frequency acoustic transducer (420 kHz), with a very narrow conical beam (2o width at -3 dB) to minimize the spatial smoothing of surface waves across the sonar footprint. With low power consumption, and large storage capacity (64 Mbytes flash EPROM), the instrument is capable of continuous measurements of wave amplitude at a sampling rate of 1 Hz over deployments of up to nine months. From March 4 to April 28 1998 an evaluation of the performance of this instrument, through intercomparison with a Waverider buoy, was conducted in open ocean conditions off the Pacific west coast. Instantaneou...

Climate variability on decadal time scales is generally recognized to influence high-latitude marine populations. Our recent work in studying air-sea interactions in the Bering Sea suggests that interannual to decadal climate variability is important through its modulation of the frequencies and magnitudes of weather events on intraseasonal time scales. We hypothesize that it is these weather events that directly impact the marine ecosystem of the Bering Sea shelf. The linkages between the event-scale weather and the ecosystem are illustrated with three examples: walleye pollock (Theragra chalcogramma), Tanner crabs (Chionoecetes bairdi), and coccolithophorid phytoplankton (Emiliania huxleyi). We hypothesize that the strong recruitment of walleye pollock that occurred in 1978, 1982, and 1996 can be attributed in part due to the seasonably strong storms that occurred in the early summer of those years. These storms caused greater than normal mixing of nutrients into the euphotic zone which presumably led to sustained primary productivity after the spring bloom and, possibly, enhanced prey concentrations for pollock larvae and their competitors. Recruitment of Tanner crab was particularly strong for the 1981 and 1984 year-classes. These years had periods of prominent east wind anomalies along the Alaska Peninsula during the previous winter. Such winds promote flow through Unimak Pass, and hence an enhanced flux of nutrient-rich water onto the shelf. This mechanism may have ultimately resulted in favorable feeding conditions for Tanner crab larvae. Finally, an unprecedented coccolithophorid bloom occurred over the Bering Sea shelf in the summer of 1997. This summer featured lighter winds and greater insolation than usual after a spring that included a very strong May storm. This combination brought about a warm, nutrient-poor upper mixed layer by mid-summer. This provided a competitive advantage for coccolithophorid phytoplankton in 1997 and to a lesser extent in 1998. Unusually high concentrations of coccolithophores persisted for the following two years although physical environmental conditions did not remain favorable. While slow variations in the overall aspects of the physical environment may be important for setting the stage, we propose that the significant multi-year adjustments in the marine ecosystem of the Bering Sea shelf are more directly caused by major air-sea interaction events on intraseasonal time scales.

The Ocean Reference Station at 20°S, 85°W under the stratus clouds west of northern Chile is being maintained to provide ongoing, climate-quality records of surface meteorology, of air-sea fluxes of heat, freshwater, and momentum, and of upper ocean temperature, salinity, and velocity variability. The Stratus Ocean Reference Station (ORS Stratus) is supported by the National Oceanic and Atmospheric Administration's (NOAA) Climate Observation Program. It is recovered and redeployed annually, with cruises that have come between October and December. During the October 2006 cruise of NOAA's R/V Ronald H. Brown to the ORS Stratus site, the primary activities where recovery of the Stratus 6 WHOI surface mooring that had been deployed in October 2005, deployment of a new (Stratus 7) WHOI surface mooring at that site, in-situ calibration of the buoy meteorological sensors by comparison with instrumentation put on board by staff of the NOAA Earth System Research Laboratory (ESRL, formerly ETL), and observations of the stratus clouds and lower atmosphere by NOAA ESRL. A buoy for the Pacific tsunami warning system was also serviced in collaboration with the Hydrographic and Oceanographic Service of the Chilean Navy (SHOA). The old DART (Deep-Ocean Assessment and Reporting of Tsunami) buoy was recovered and a new one deployed which carried IMET sensors and subsurface oceanographic instruments. Argo floats and drifters were also launched and CTD casts carried out during the cruise. The ORS Stratus buoys are equipped with two Improved Meteorological (IMET) systems, which provide surface wind speed and direction, air temperature, relative humidity, barometric pressure, incoming shortwave radiation, incoming longwave radiation, precipitation rate, and sea surface temperature. The IMET data are made available in near real time using satellite telemetry. The mooring line carries instruments to measure ocean salinity, temperature, and currents. The ESRL instrumentation used during the 2006 cruise included cloud radar, radiosonde balloons, and sensors for mean and turbulent surface meteorology. Stratus 7 also received a new addition to its set of sensors: a partial CO2 detector from the Pacific Marine Environmental Laboratory (PMEL). Aerosol measurements were also carried out onboard RHB by personnel of the University of Hawaii. Finally, the cruise hosted a teacher participating in NOAA's Teacher at Sea Program.

Different effects of wind waves on the hydrodynamics in the North Sea are investigated using a coupled wave (WAM) and circulation (NEMO) model system. The terms accounting for the wave-current interaction are: the Stokes-Coriolis force, the sea-state dependent momentum and energy flux. The role of the different Stokes drift parameterizations is investigated using a particle-drift model. Those particles can be considered as simple representations of either oil fractions, or fish larvae. In the ocean circulation models the momentum flux from the atmosphere, which is related to the wind speed, is passed directly to the ocean and this is controlled by the drag coefficient. However, in the real ocean, the waves play also the role of a reservoir for momentum and energy because different amounts of the momentum flux from the atmosphere is taken up by the waves. In the coupled model system the momentum transferred into the ocean model is estimated as the fraction of the total flux that goes directly to the currents plus the momentum lost from wave dissipation. Additionally, we demonstrate that the wave-induced Stokes-Coriolis force leads to a deflection of the current. During the extreme events the Stokes velocity is comparable in magnitude to the current velocity. The resulting wave-induced drift is crucial for the transport of particles in the upper ocean. The performed sensitivity analyses demonstrate that the model skill depends on the chosen processes. The results are validated using surface drifters, ADCP, HF radar data and other in-situ measurements in different regions of the North Sea with a focus on the coastal areas. The using of a coupled model system reveals that the newly introduced wave effects are important for the drift-model performance, especially during extremes. Those effects cannot be neglected by search and rescue, oil-spill, transport of biological material, or larva drift modelling.

During winters, the northern Adriatic Sea experiences frequent, intense cold-air outbreaks that drive oceanic heat loss and imprint complex but predictable patterns in the underlying waters. This strong, reliable forcing makes this region an excellent laboratory for observational and numerical investigations of air-sea interaction, sediment and biological transport, and mesoscale wind-driven fl ow. Narrow sea surface wind jets, commonly known as "bora, " occur when cold, dry air spills through gaps in the Dinaric Alps (the mountain range situated along the Adriatic's eastern shore). Horizontal variations in these winds drive a mosaic of oceanic cyclonic and anticyclonic cells that draw coastal waters far into the middle basin. The winds also drive intense cooling and overturning, producing a sharp front between dense, vertically homogenous waters (North Adriatic Dense Water, or NAdDW) in the north and the lighter (colder, fresher), stratifi ed waters of the Po River plume. Once subducted at the front, the NAdDW fl ows southward in a narrow vein following the isobaths (contours of constant depth) of the Italian coast. In addition to governing the basin's general circulation, these processes also infl uence sediment transport and modulate biological and optical variability.

In this paper we explore onset ald duration of several severe B;ra events, focusing on the circulation tlat such events impose in the greater Kvamer regiol. Three periods, better documented me:eorologically and/or oceanographically, were selected for modelling and analysis: 5-9 November 1999, 8-15 February 2A03, and, 12-16 November 2004. In the performed simulations the wind emerged as the dominant driving force with important coastal and bathymetric constrains. The modelled baro*opic response to the selected Bura events is characterized by a multitude of cyclonic and anticyclonic circulation cells, strongly controlled by the rich insular topology, lateral geometry, and bottom topography. The high resolutiol finite-element mesh of the model has aUowed for the fixt time to resolve the intricacies of numerous sub-basins and chanaels, and to elucidate the interplay of laterally heterogeneous wind stress and bottom topography. The important aspect ofthe heat loss and surfuce cooting triggered by Bura episodes has been also addressed to the extent the model and data limitations allowed.

A new reduced gravity, primitive equation model of the upper equatorial ocean has been developed by It has been configured to simulate the annual cycle in the tropical Pacific Ocean. It is forced by the monthly winds from Rasmusson and Carpenter (1982) and a new heat flux formulation from Seager et al. (1988). The coefficients of vertical eddy viscosity and conductivity depend upon the Richardson number of the flow. With this mixing a deep warm pool forms in the Western Pacific, increasing the west-east gradient of the thermocline and equatorial undercurrent. The model has been diagnosed as to what factors maintain this deep warm pool. 1. Heat flux parameterization. Heat Flux =Incoming Solar -Latent -(Sensible + Longwave) * Incoming Solar Flux =(1 -A) (1 -0.62 C + 0.(0198) Q o A is albedo, C is % cloud cover, 8 is solar altitude, Q o is clear sky flux * Latent Heat Flux = P a C E L [u] (1-8) qs(SST) [u] is wind speed with minimum of 4 m s', q (SST) is saturation humidity, and humidity factor 8 is related to relative humidity, 8 rh , 8 qs(SST) =8 rh qs(Ta) * Sensible + Longwave Flux =Cl (SST -T*) [A =0.06,8 =0.78, Cl =1.8 m s', 1'* =2.8°C] 2. Vertical mixing coefficients. * Diffusivity: v = 1()3 (1+lORJ2 + VB * Conductivity: K = 1()3 (1+lORJ3 + KB ~B (z) varies between 1 and 2 cms-l K B (z) varies between 1/2 and 1 cm 2 s-l In the COARE volume, Ri is nearly always> 3, so that the vertical mixing is done solely by the background values VB and K B • Sections of average temperature and zonal velocity in January along the equator down to 400 m and along 160°E down to 500 m are shown in Figures .

This paper extends the work of our previous study, which showed the potential of using precipitation in the eastern Indian Ocean to predict when an El Nino would begin. The paper begins by showing the successful prediction of the 2002-03 El Nino. However, precipitation is really used as a substitute for wind (storms are usually accompanied by heavy wind), because a popular hypothesis is that winds (especially % winds out of the West) stir up the ocean surface in the western Pacific sending currents of warm waters to the east Pacific where El Ninos form. This paper shows that it is typical for storms that produce strong winds in the western Pacific to have traveled from the Indian Ocean. We begin in the Indian Ocean looking at strong bursts of wind over several days. The number of windy days seems to increase in the months prior to El Nino. We examined these relationships in detail for November 2001 to April 2002, before the recent El Nino, using NASA&#39;s TRMM and QuikSCAT data. We...