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Dorman, CE, Mejia J, Koracin D, McEvoy D.  2019.  World marine fog analysis based on 58-years of ship observations. International Journal of Climatology.   10.1002/joc.6200   AbstractWebsite

This study presents the first global-scale comprehensive climatology of marine fog and is based on ICOADS ship present weather observations for the period 1950-2007. In general, the median marine fog occurrence away from the polar oceans is low (0.2%). Substantially greater marine fog occurrences are limited to four regions, not including the polar region. Fog occurrence maxima along the western side of the sub-polar ocean gyre occur during the warm season and over the shelf, which includes one centred over the Northwest Pacific Kuril Islands (60%) and one over the Northwest Atlantic Grand Banks (45%), while a third lies over the Argentinean shelf break. Fog maxima over seven marginal seas occur over the Okhotsk Sea, Sea of Japan, Yellow Sea, South China Sea, Nova Scotia, North Sea, and Baltic Sea. Five wind-driven coastal upwelling zone maxima comprise the California-Oregon, Namibia-South Africa, Peru, Morocco and Arabian regions. Maximum upwelling fog occurrence during the warm season was found to be inversely proportional to the minimum sea surface temperature (SST). Most fog maximum occurrence locations lie over SST minima in shallow water during the warm season and are capped by a stable lower atmosphere. Positive correlations (up to 0.79) were found between 5-year moving averages of fog in the Kuril Islands and the North Pacific Oscillation. Five-year moving averages of fog in the Grand Banks were positively and significantly correlated (up to 0.56), with the North Atlantic Oscillation represented by the sea level pressure difference between Gibraltar and Reykjavik. In contrast, 5-year moving averages of fog in the Grand Banks and the Atlantic Multidecadal Oscillation index were negatively and significantly correlated (up to -0.75).

Dorman, CE.  2017.  Early and Recent Observational Techniques for Fog.. Marine Fog: Challenges and Advancements in Observations, Modeling, and Forecasting.. ( Koracin D, Dorman CE, Eds.)., Zurich: Springer International Publishing   10.1007/978-3-319-45229-6_3  
Dorman, CE.  2017.  Worldwide Marine Fog Occurrence and Climatology. Marine Fog: Challenges and Advancements in Observations, Modeling, and Forecasting. . ( Koracin D, Dorman CE, Eds.)., Zurich: Springer International Publishing   10.1007/978-3-319-45229-6_2  
Koracin, D., Dorman, C. E. (Eds.).  2017.  Marine Fog: Challenges and Advancements in Observations, Modeling, and Forecasting. Springer Atmospheric Sciences. :537.: Springer International Publishing   10.1007/978-3-319-45229-6   AbstractWebsite

This volume presents the history of marine fog research and applications, and discusses the physical processes leading to fog's formation, evolution, and dissipation. A special emphasis is on the challenges and advancements of fog observation and modeling as well as on efforts toward operational fog forecasting and linkages and feedbacks between marine fog and the environment.

Fewings, MR, Washburn L, Dorman CE, Gotschalk C, Lombardo K.  2016.  Synoptic forcing of wind relaxations at Pt. Conception, California. Journal of Geophysical Research-Oceans. 121:5711-5730.   10.1002/2016jc011699   AbstractWebsite

Over the California Current upwelling system in summer, the prevailing upwelling-favorable winds episodically weaken (relax) or reverse direction for a few days. Near Pt. Conception, California, the wind usually does not reverse, but wind relaxation allows poleward oceanic coastal flow with ecological consequences. To determine the offshore extent and synoptic forcing of these wind relaxations, we formed composite averages of wind stress from the QuikSCAT satellite and atmospheric pressure from the North American Regional Reanalysis (NARR) using 67 wind relaxations during summer 2000-2009. Wind relaxations at Pt. Conception are the third stage of an event sequence that repeatedly affects the west coast of North America in summer. First, 5-7 days before the wind weakens near Pt. Conception, the wind weakens or reverses off Oregon and northern California. Second, the upwelling-favorable wind intensifies along central California. Third, the wind relaxes at Pt. Conception, and the area of weakened winds extends poleward to northern California over 3-5 days. The NARR underestimates the wind stress within similar to 200 km of coastal capes by a factor of 2. Wind relaxations at Pt. Conception are caused by offshore extension of the desert heat low. This synoptic forcing is related to event cycles that cause wind reversal as in Halliwell and Allen (1987) and Mass and Bond (1996), but includes weaker events. The wind relaxations extend similar to 600 km offshore, similarly to the California-scale hydraulic expansion fan shaping the prevailing winds, and similar to 1000 km alongshore, limited by an opposing pressure gradient force at Cape Mendocino.

Koracin, D, Dorman CE, Lewis JM, Hudson JG, Wilcox EM, Torregrosa A.  2014.  Marine fog: A review. Atmospheric Research. 143:142-175.   10.1016/j.atmosres.2013.12.012   AbstractWebsite

The objective of this review is to discuss physical processes over a wide range of spatial scales that govern the formation, evolution, and dissipation of marine fog. We consider marine fog as the collective combination of fog over the open sea along with coastal sea fog and coastal land fog. The review includes a history of sea fog research, field programs, forecasting methods, and detection of sea fog via satellite observations where similarity in radiative properties of fog top and the underlying sea induce further complexity. The main thrust of the study is to provide insight into causality of fog including its initiation, maintenance, and destruction. The interplay between the various physical processes behind the several stages of marine fog is among the most challenging aspects of the problem. An effort is made to identify this interplay between processes that include the microphysics of fog formation and maintenance, the influence of large-scale circulations and precipitation/clouds, radiation, turbulence (air-sea interaction), and advection. The environmental impact of marine fog is also addressed. The study concludes with an assessment of our current knowledge of the phenomenon, our principal areas of ignorance, and future lines of research that hold promise for advances in our understanding. (C) 2013 Published by Elsevier B.V.

Dorman, CE, Mejia JF, Koračin D.  2013.  Impact of U.S. west coastline inhomogeneity and synoptic forcing on winds, wind stress, and wind stress curl during upwelling season. Journal of Geophysical Research: Oceans. :n/a-n/a.   10.1002/jgrc.20282   AbstractWebsite

Although buoy and aircraft measurements, as well as numerical simulations, have shown intense over-shelf and slope dynamics of the west coast of the United States in the summer upwelling season, satellite footprint limitations of approximately 25 km resolution have thus far precluded long term, spatially extended monitoring of the near-coastline dynamics. However, recent advancements in satellite data processing have allowed a finer footprint, of approximately 12 km resolution, to investigate further the properties of coastal winds and consequent upwelling. This improved satellite data analysis has confirmed the intense coastal winds over the shelf and slope and revealed their spatial extensions and inhomogeneities on event and multiday scales. The inhomogeneities are dominated by the along-coast pressure gradient modulated by the synoptic effects and topographical forcing of the five major capes, which also generate upwelling wind stress and curl pattern inhomogeneities. Synoptic forcing of the coastal flow was evidenced by high correlation coefficients, in excess of 0.8, between the buoy-measured pressure differences and wind speeds; wind speeds greater than 11 m s−1 occurred only when the along-coast pressure gradient was greater than 0.8 hPa/100 km. Based on Bernoulli flow principles, the observed upper limit of the wind speed on the downwind sides of the major capes is explained by using characteristic values of atmospheric marine layer parameters. Numerical simulations at a similar resolution (12 km) as the new satellite data footprint for June 2001, completed as part of multiyear regional climate modeling efforts, were able to reproduce the main characteristics of the flow.

Seo, H, Brink KH, Dorman CE, Koracin D, Edwards CA.  2012.  What determines the spatial pattern in summer upwelling trends on the US West Coast? Journal of Geophysical Research-Oceans. 117   10.1029/2012jc008016   AbstractWebsite

Analysis of sea surface temperature (SST) from coastal buoys suggests that the summertime over-shelf water temperature off the U. S. West Coast has been declining during the past 30 years at an average rate of -0.19 degrees C decade(-1). This cooling trend manifests itself more strongly off south-central California than off Oregon and northern California. The variability and trend in the upwelling north of off San Francisco are positively correlated with those of the equatorward wind, indicating a role of offshore Ekman transport in the north. In contrast, Ekman pumping associated with wind stress curls better explains the stronger and statistically more significant cooling trend in the south. While the coast-wide variability and trend in SST are strongly correlated with those of large-scale modes of climate variability, they in general fail to explain the southward intensification of the trend in SST and wind stress curl. This result suggests that the local wind stress curl, often topographically forced, may have played a role in the upwelling trend pattern.

Paklar, GB, Koracin D, Dorman C.  2009.  Wind-induced ocean circulation along California and Baja California coasts in June 1999. Atmospheric Research. 94:106-133.   10.1016/J.Atmosres.2009.01.019   AbstractWebsite

The circulation along the California Coast in June 1999 was influenced by strong upwelling-favourable winds. To study the ocean circulation and upwelling variability, the Princeton Ocean Model (POM) was setup for the California and Baja California coasts and it was forced with interactively computed wind stress and surface heat fluxes. Atmospheric fields used in the surface flux estimates during the POM runs were obtained from Mesoscale Model 5 (MM5) outputs, while the sea surface temperatures (SST) were prescribed by the ocean model. One-way coupled air-sea modelling was used in the process-oriented approach to asses the influence of the wind stress, wind stress curl, initial density gradients, and nesting procedure with global model for the predicted circulation and accompanied upwelling. Hourly SSTs measured at twelve buoys operated by the National Data Buoy Center (NDBC) were used to evaluate sensitivity modelling studies via root-mean-squared-errors (RMSE). Low-pass filtered currents measured at 15 stations along central and southern Californian coast were also used in the ocean model evaluation procedures.In order to resolve the particular roles and importance of the wind stress vs. wind stress curl in driving coastal upwelling, besides baseline experiment we performed a numerical experiment with curl-free wind forcing. Modelled surface currents obtained in the baseline experiment indicate southward and southwestward flow in the deep ocean areas and alternating equatorward and poleward current near the shore. Wind stress curl appeared to be crucial both for the current field structure and SST distribution. The inshore poleward current obtained in the baseline experiment and evidenced by direct measurements was replaced with an equatorward current in the curl-free experiment. Furthermore, a significant temperature drop occurred along the entire coast in the curl-free experiment, whereas in the baseline the areas of maximum upwelling were confined to the regions with the wind maxima. Climatological temperature profile integrated with the satellite SST appeared to be superior for initialization of the ocean model in comparison with Levitus climatology. Due to too high temperatures predicted by HYbrid Coordinate Ocean Model (HYCOM) along the West Coast, expected improvement of the baseline experiment was not achieved by nesting POM with the Pacific-scale HYCOM. Additionally, a selection of a drag coefficient parameterization appears to have a significant impact on the upwelling evolution. (C) 2009 Elsevier B.V. All rights reserved.

Dorman, CE, Koračin D.  2008.  Response of the Summer Marine Layer Flow to an Extreme California Coastal Bend. Monthly Weather Review. 136:2894-2992.: American Meteorological Society   10.1175/2007MWR2336.1   AbstractWebsite

A summer wind speed maximum extending more than 200 km occurs over water around Point Conception, California, the most extreme bend along the U.S. West Coast. The following several causes were investigated for this wind speed maximum: 1) synoptic conditions, 2) marine layer hydraulic flow effects, 3) diurnal variations, 4) mountain leeside downslope flow, 5) sea surface temperature structure, and 6) island influence. Synoptic conditions set the general wind speed around Point Conception, and these winds are classified as strong, moderate, or weak. The strong wind condition extends about Point Conception, reaching well offshore toward the southwest, and the highest speeds are within 20 km to the south. Moderate wind cases do not extend as far offshore, and they have a moderate maximum wind speed that occurs over a smaller area in the western mouth of the Santa Barbara Channel. The weak wind speed case consists of light and variable winds about Point Conception. Each category occurs about one-third of the time. Atmospheric marine layer hydraulic dynamics dominate the situation after the synoptic condition is set. This includes an expansion fan on the south side of the point and a compression bulge on the north side. The expansion fan significantly increases the wind speeds over a large area that extends to the southwest, south, and east of Point Conception, and the maximum wind speed is increased for the strong and moderate synoptic cases as well. The horizontal sea surface temperature pattern contributes to the sea surface wind maximum through the Froude number, which links the potential temperature difference between the sea surface temperature and the capping inversion temperature with marine layer acceleration in an expansion fan. A greater potential temperature difference across the top of the marine layer also causes more energy to be trapped in the marine layer, instead of escaping upward. The thermally driven flow resulting from differential heating over land in the greater Los Angeles, California, coastal and elevated area to the east is not directly related to the wind speed maximum, either in the Santa Barbara Channel or in the open ocean extending farther offshore. The effects of the thermally driven flow extend only to the east of the Santa Barbara Channel. The downslope flow on the south side of the Santa Ynez Mountains that is generated by winds crossing the Santa Ynez Mountain ridge contributes neither to the high-speed wind maximum in the Santa Barbara channel nor to that extending farther offshore. Fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) simulations do support a weak leeside flow in the upper portions of the Santa Ynez Mountains. The larger Channel Islands have a significant effect on the marine layer flow and the overwater wind structure. One major effect of the Santa Barbara Channel Islands is the extension of the zone of high-speed winds farther to the south than would otherwise be the case.

Peters, H, Lee CM, Orlic M, Dorman CE.  2007.  Turbulence in the wintertime northern Adriatic Sea under strong atmospheric forcing. Journal of Geophysical Research-Oceans. 112   10.1029/2006jc003634   AbstractWebsite

[1] In February 2003, we observed the response of the 40 to 50 m deep northern Adriatic Sea to strong surface forcing by 20 m s(-1) winds and 600 W m(-2) net upward heat flux resulting from cold bora winds blowing onto a relatively warm sea through gaps in the Croatian mountains. Ocean turbulence throughout the water column was observed with a microstructure profiler and a bottom-mounted, upward-looking, 5-beam, acoustic Doppler current profiler ( ADCP). Microstructure-based dissipation rates (epsilon) were close to similarity scaling of the surface wind stress. The surface buoyancy flux, related to the oceanic heat loss, contributed little energy to the turbulence, but led to sustained unstable stratification. The energy-containing range of the turbulence together with the upper end of the inertial subrange, with horizontal scales between a few hundred meters and about 10 m, contained coherent, anisotropic overturning motions aligned with the low-frequency, barotropic ocean currents which carried stress and showed an asymmetry between rare, narrow, faster downdrafts and diffuse, weak updrafts. These motions bear no similarity with Langmuir cells. The turbulence measurements were embedded in surveys of the mesoscale ocean variability. Part of the observations were set in a front a few hundred meters wide with little density contrast. As the bora wind relaxed, the front began to develop a highly stratified "foot'' undergoing intense mixing. The paper addresses problems of beam spreading and instrumental noise in ADCPs.

Pullen, J, Doyle JD, Haack T, Dorman C, Signell RP, Lee CM.  2007.  Bora event variability and the role of air-sea feedback. Journal of Geophysical Research-Oceans. 112   10.1029/2006jc003726   AbstractWebsite

A two-way interacting high resolution numerical simulation of the Adriatic Sea using the Navy Coastal Ocean Model (NCOM) and Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS(R)) was conducted to improve forecast momentum and heat flux fields, and to evaluate surface flux field differences for two consecutive bora events during February 2003. (COAMPS(R) is a registered trademark of the Naval Research Laboratory.) The strength, mean positions and extensions of the bora jets, and the atmospheric conditions driving them varied considerably between the two events. Bora 1 had 62% stronger heat flux and 51% larger momentum flux than bora 2. The latter displayed much greater diurnal variability characterized by inertial oscillations and the early morning strengthening of a west Adriatic barrier jet, beneath which a stronger west Adriatic ocean current developed. Elsewhere, surface ocean current differences between the two events were directly related to differences in wind stress curl generated by the position and strength of the individual bora jets. The mean heat flux bias was reduced by 72%, and heat flux RMSE reduced by 30% on average at four instrumented over-water sites in the two-way coupled simulation relative to the uncoupled control. Largest reductions in wind stress were found in the bora jets, while the biggest reductions in heat flux were found along the north and west coasts of the Adriatic. In bora 2, SST gradients impacted the wind stress curl along the north and west coasts, and in bora 1 wind stress curl was sensitive to the Istrian front position and strength. The two-way coupled simulation produced diminished surface current speeds of similar to 12% over the northern Adriatic during both bora compared with a one-way coupled simulation.

Dorman, CE, Dever EP, Largier J, Koracin D.  2006.  Buoy measured wind, wind stress and wind stress curl over the shelf off Bodega Bay, California. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 53:2850-2864.   10.1016/J.Dsr2.2006.07.006   AbstractWebsite

An array of five buoys and three coastal stations is used to characterize the winds, stress, and curl of the wind stress over the shelf off Bodega Bay, California. The wind and wind stress are strong and persistent in the summer and weak in the winter. In the summer, wind and stress decrease strongly across the shelf, toward the coast. Combinations of buoys are used to compute the curl of the wind stress over different portions of the shelf. The mean summer 2001 curl of the wind stress over the array depends upon the area selected, varying between -1.32 x 10(-6) and +7.80 x 10(-6) Pa m(-1). The winter 2002 wind-stress curl also depends on location, varying from -2.06 x 10(-6) to + 2.78 x 10(-6) Pa m(-1). Mean monthly curl of the wind stress is a maximum in the summer and a minimum near zero in the winter. In both the summer and the winter, the correlation between the wind-stress curl for different portions of the shelf varies between moderate negative, though insignificance, to high positive. A wind measurement at a single point can be poorly related to the measured curl of the wind stress at other locations over the shelf. The measurements show that the use of one wind measurement to characterize the curl of the wind stress over the shelf without further investigation of the local wind-stress curl structure is risky. (c) 2006 Published by Elsevier Ltd.

Kochanski, A, Koracin D, Dorman CE.  2006.  Comparison of wind-stress algorithms and their influence on wind-stress curl using buoy measurements over the shelf off Bodega Bay, California. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 53:2865-2886.   10.1016/J.Dsr2.2006.07.008   AbstractWebsite

The main objectives of this study were to compare three wind-stress algorithms of varying intricacy and estimate the extent to which each method altered computed wind-stress curl. The algorithms included (1) a simple bulk formula for neutral conditions that is dependent only on wind velocity components; (2) a formula that in addition to dependence on wind components includes a simplified effect of thermal stability through differences in air and sea temperatures; and (3) an algorithm that includes full treatment of dynamics and atmospheric stability. Data for the analysis were from a field program that used a special buoy network off Bodega Bay during 28 June-4 August 2001.A diamond-shaped setup of five closely separated buoys in Bodega Bay allowed for one of the first attempts to compute wind-stress curl over the ocean using buoy measurements. Based on an analysis of the available dataset, the marine layer over Bodega Bay is characterized by positive wind-stress curl with a median value around 0.2 Pa (100 km)(-1) and maximum values reaching 2.5 Pa (100 km)(-1). Positive wind-stress curl was observed for all wind speed conditions, whereas negative wind-stress curl episodes were associated mostly with low-wind conditions.Comparison of wind-stress curl computed using the three algorithms showed that differences among them can be significant. The first and third algorithms indicated similar stress curl (difference around 10%), but the differences between these two and the second algorithm were much higher (approximately 40%). The reason for the difference is the stability correction, which in the third algorithm strongly decreases with an increase in wind speeds, but stays at a similar level for all wind speeds in the second algorithm. Consequently, for higher wind speeds the variability of wind stress calculated using the second algorithm is greater than for the other two algorithms, causing significant differences in computed wind-stress curl (root mean-square error equal to 0.19 Pa (100 km)(-1)).Despite the apparent biases in computed wind stress and wind-stress curl among the algorithms, all of them show a significant trend of decreasing sea-surface temperature (SST) with increasing wind-stress curl. The bootstrapping analysis has revealed that both the along-shore wind stress and wind-stress curl have noticeable correlation with the changes in the sea-surface temperature as an indirect indication of the upwelling. An additional analysis, based on the low-pass filtered data, showed also significant agreement between the measured divergence in the cross-shore surface transport and the wind-stress curl computed for all three algorithms. (c) 2006 Elsevier Ltd. All rights reserved.

Dorman, CE, Carniel S, Cavaleri L, Sclavo M, Chiggiato J, Doyle J, Haack T, Pullen J, Grbec B, Vilibić I, Janeković I, Lee C, Malačič V, Orlić M, Paschini E, Russo A, Signell RP.  2006.  February 2003 marine atmospheric conditions and the bora over the northern Adriatic. Journal of Geophysical Research: Oceans. 111:C03S03.   10.1029/2005JC003134   AbstractWebsite

A winter oceanographic field experiment provided an opportunity to examine the atmospheric marine conditions over the northern Adriatic. Mean February winds are from a northeasterly direction over most of the Adriatic and a more northerly direction along the western coast. Wind speeds are fastest in jets over the NE coast during bora events and weakest in the mid-northwestern Adriatic. Diurnal air temperature cycles are smallest on the NE coast and largest in the midwestern Adriatic. The maximum sea-air difference is +10°C on the eastern coast and near zero on the midwestern Adriatic. Boras are northeasterly (from) wind events that sweep off Croatia and Slovenia, bringing slightly colder and drier air over the northern Adriatic. The main bora season is December to March. Winter 2002–2003 was normal for bora events. Synoptic-scale temporal variations are correlated over the northern Adriatic. Fastest Bora winds and highest wind stress over the northern Adriatic is concentrated in four topographically controlled jets. The strongest is the Senj Jet, while the Trieste Jet extends across the entire northern Adriatic. Between each two jets is a weak wind zone. The greatest mean net heat loss is in bora jets in the NE Adriatic, where it was −438 W m−2 and is weakest in the midwestern northern Adriatic, where it was near zero. Wind stress is concentrated over the NE half of Adriatic in four bora jets, while wind stress is weak in the NW Adriatic. There is significant variation in wind stress mean and standard deviation structure over the northern Adriatic with each bora event.

Dever, EP, Dorman CE, Largier JL.  2006.  Surface boundary-layer variability off Northern California, USA, during upwelling. Deep Sea Research Part II: Topical Studies in Oceanography. 53:2887-2905.   AbstractWebsite

A five-element mooring array is used to study surface boundary-layer transport over the Northern California shelf from May to August 2001. In this region, upwelling favorable winds increase in strength offshore, leading to a strong positive wind stress curl. We examine the cross-shelf variation in surface Ekman transport calculated from the wind stress and the actual surface boundary-layer transport estimated from oceanic observations. The two quantities are highly correlated with a regression slope near one. Both the Ekman transport and surface boundary layer transport imply curl-driven upwelling rates of about 3×10−4 m s−1 between the 40 and 90 m isobaths (1.5 and 11.0 km from the coast, respectively) and curl-driven upwelling rates about 1.5×10−4m s−1 between the 90 and 130 m isobaths (11.0 and 28.4 km from the coast, respectively). Thus curl-driven upwelling extends to at least 25 km from the coast. In contrast, upwelling driven by the adjustment to the coastal boundary condition occurs primarily inshore of the 40-m isobath. The upwelling rates implied by the differentiating the 40-m transport observations with the coastal boundary condition are up to 8×10−4 m s−1. The estimated upwelling rates and the temperature–nitrate relationship imply curl-driven vertical nitrate flux divergences are about half of those driven by coastal boundary upwelling.

Roughan, M, Garfield N, Largier J, Dever E, Dorman C, Peterson D, Dorman J.  2006.  Transport and retention in an upwelling region: The role of across-shelf structure. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 53:2931-2955.   10.1016/J.Dsr2.2006.07.015   AbstractWebsite

The paradox of upwelling is the relationship between strong wind forcing, nutrient enrichment, and shelf productivity. Here we investigate how across-shelf structure in velocity and hydrography plays a role in the retention (inshore) and export (offshore) of particles such as nutrients, plankton and larvae. We examine the spatial structure of the coastal currents during wind-driven upwelling and relaxation on the northern Californian Shelf. The field work was conducted as part of the Wind Events and Shelf Transport (WEST) project, a 5-year NSF/CoOP-funded study of the role of wind-driven transport in shelf productivity off Bodega Bay (northern California) from 2000 to 2003. We combine shipboard velocity profiles (ADCP) and water properties from hydrographic surveys during the upwelling season to examine the mean across-shelf structure of the hydrography and velocity fields during three contrasting upwelling seasons, and throughout the upwelling-relaxation cycle. We also present results from two winter seasons that serve as contrast to the upwelling seasons.During all three upwelling seasons clear spatial structure is evident in velocity and hydrography across the shelf, exemplified by current reversals inshore and the presence of a persistent upwelling jet at the shelf break. This jet feature changes in structure and distance from the coast under different wind forcing regimes. The jet also changes from the north of our region, where it is a single narrow jet, adjacent to the coast, and to the south of our region, where it broadens and at times two jets become evident. We present observations of the California Under Current, which was observed at the outer edge of our domain during all three upwelling seasons. The observed across-shelf structure could aid both in the retention of plankton inshore during periods of upwelling followed by relaxation and in the export of plankton offshore in the upwelling jet. (c) 2006 Elsevier Ltd. All rights reserved.

Largier, JL, Lawrence CA, Roughan M, Kaplan DM, Dever EP, Dorman CE, Kudela RM, Bollens SM, Wilkerson FP, Dugdale RC, Botsford LW, Garfieldg N, Cervantes BK, Koracin D.  2006.  WEST: A northern California study of the role of wind-driven transport in the productivity of coastal plankton communities. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 53:2833-2849.   10.1016/J.Dsr2.2006.08.018   AbstractWebsite

The "Wind Events and Shelf Transport" (WEST) program was an interdisciplinary study of coastal upwelling off northern California in 2000-03. WEST was comprised of modeling and field observations. The primary goal of WEST was to better describe and understand the competing influences of wind forcing on planktonic productivity in coastal waters. While increased upwelling-favorable winds lead to increased nutrient supply, they also result in reduced light exposure due to deeper surface mixed layers and increased advective loss of plankton from coastal waters. The key to understanding high levels of productivity, amidst these competing responses to wind forcing, is the temporal and spatial structure of upwelling. Temporal fluctuations and spatial patterns allow strong upwelling that favors nutrient delivery to be juxtaposed with less energetic conditions that favor stratification and plankton blooms. Observations of winds, ocean circulation, nutrients, phytoplankton and zooplankton off Bodega Bay and Point Reyes (38 degrees N) were combined with model studies of winds, circulation and productivity. This overview of the WEST program provides an introduction to the WEST special issue of Deep-Sea Research, including the motivation for WEST, a summary of study components, an integrative synthesis of major research results to-date, and background on conditions during field studies in May-June 2001 (the upwelling period on which this special issue is focused). (c) 2006 Elsevier Ltd. All. rights reserved.

Dorman, CE, Friehe CA, Khelif D, Scotti A, Edson J, Beardsley C, Limeburner R, Chen SS.  2006.  Winter atmospheric conditions over the Japan/East Sea: The structure and impact of severe cold-air outbreaks. Oceanography. 19:96-109.   Abstract

The Japan/East Sea is a marginal sea strategically placed between the world's largest land mass and the world's largest ocean. The Eurasian land mass extending to high latitudes generates several unique winter synoptic weather features, the most notable being the vast Siberian Anticyclone that covers much of the northeast Asian land mass. The Japan/East Sea's very distinctive winter conditions result from being on the east side of the Eurasian landmass at mid-latitudes. The resulting winter atmospheric conditions over the Sea include the mean cold air flowing off Siberia that is occasionally spiked with severe very-cold-air outbreaks.

Koragin, D, Kochanski A, Dorman CE, Dever EP.  2005.  Wind stress curl and upwelling along the California coast. Bulletin of the American Meteorological Society. 86:629-630. AbstractWebsite
Koracin, D, Businger J, Dorman C, Lewis J.  2005.  Formation, evolution, and dissipation of coastal sea fog. Boundary-Layer Meteorology. 117:447-478.   10.1007/S10546-005-2772-5   AbstractWebsite

Evolution of sea fog has been investigated using three-dimensional Mesoscale Model 5 (MM5) simulations. The study focused on widespread fog-cloud layers advected along the California coastal waters during 14-16 April 1999. According to analysis of the simulated trajectories, the intensity of air mass modification during this advection significantly depended on whether there were clouds along the trajectories and whether the modification took place over the land or ocean. The air mass, with its trajectory endpoint in the area where the fog was observed and simulated, gradually cooled despite the gradual increase in sea-surface temperature along the trajectory. Modelling results identified cloud-top cooling as a major determinant of marine-layer cooling and turbulence generation along the trajectories. Scale analysis showed that the radiative cooling term in the thermodynamic equation overpowered surface sensible and latent heat fluxes, and entrainment terms in cases of the transformation of marine clouds along the trajectories. Transformation of air masses along the trajectories without clouds and associated cloud-top cooling led to fog-free conditions at the endpoints of the trajectories over the ocean. The final impact on cloud-fog transition was determined by the interaction of synoptic and boundary-layer processes. Dissipation of sea fog was a consequence of a complex interplay between advection, synoptic evolution, and development of local circulations. Movement of the high-pressure system over land induced weakening of the along-shore advection and synoptic-pressure gradients, and allowed development of offshore flows that facilitated fog dissipation.

Lee, CM, Askari F, Book J, Carniel S, Cushman-Roisin B, Dorman C, Doyle J, Flament P, Harris CK, Jones BH, Kuzmic M, Martin P, Ogston A, Orlic M, Perkins H, Poulain P-M, Pullen J, Russo A, Sherwood C, Signell RP, Thaler D.  2005.  Northern Adriatic response to a wintertime bora wind event. Eos, Transactions American Geophysical Union. 86:157-165.   10.1029/2005EO160001   AbstractWebsite

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 flow. 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), stratified waters of the Po River plume. Once subducted at the front, the NAdDW flows 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 influence sediment transport and modulate biological and optical variability

Dorman, CE, Beardsley RC, Limeburner R, Varlamov SM, Caruso M, Dashko NA.  2005.  Summer atmospheric conditions over the Japan/East sea. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 52:1393-1420.   10.1016/J.Dsr2.2004.09.033   AbstractWebsite

Atmospheric conditions over the Japan/East Sea (JES) during the 1999 warm season (May-August) were investigated using research vessel surface and sounding observations in conjunction with coastal station and moored buoy meteorological data. In the broad center of the sea, surface winds were weak and variable with a tendency to be northward in direction. Air temperatures were close to the sea-surface temperature but warmer on average. The lower atmospheric profiles were weakly unstable or stable with shallow inversions. The summer surface heat flux was dominated by radiation components. The large solar short-wave flux caused a large net gain of heat by the sea that was unchecked by the weaker, long-wave flux. Sensible and latent heat fluxes were both small due to modest air-sea temperature differences and weak winds. The surface wind stress was also weak.European Center for Medium-range Weather Forecasting (ECMWF) model surface fields compare favorably with our ship measurements in both summer of 1999 and the winter of 2000. The ECMWF model analysis followed the observed synoptic scale variations well but missed smaller scale variations. The ECMWF air temperature, dew point, pressure, wind speed, and wind direction were correlated with ship values at 0.8 or better. ECMWF forecasts and ship measurements of surface heat fluxes were well related. In the center of the JES, net fluxes in the winter and summer were correlated to 0.7-0.9, with winter the greater. ECMWF short-wave heat flux tended to exceed the ship-based values by 25-55 W/m(2). ECMWF wind stress magnitude was best correlated with winter ship measurements, with correlations that reached 0.76-0.89, while wind stress components were more poorly correlated. In both seasons, ECMWF underestimated the wind stress by 15-25%.Monthly mean climatologies of the JES surface heat flux and wind stress were computed using the 1991-2001 ECMWF surface flux time series. The annual heat flux cycle varies from a maximum heating of + 182 W/m(2) in June to a maximum cooling of -322 W/m(2) in December with the greatest loss at the SW edge of the sea. The annual-mcan flux is -48 W/m(2). The monthly mean wind stress in winter is nearly four times the mean summer value of 0.057 N/m(2), with the winter stress towards the S SE replaced by stress towards the N-NE in summer. The strongest stresses are over the North-central portion of the sea. Our ship/model comparisons suggest that the ECMWF heat flux is biased roughly 25-55 W/m(2) high due to systematic model short-wave flux overestimation and that the ECMWF wind stress is biased roughly 15-25% low due to model under-estimation of wind stress, (c) 2005 Published by Elsevier Ltd.

Koracin, D, Dorman CE, Dever EP.  2004.  Coastal perturbations of marine-layer winds, wind stress, and wind stress curl along California and Baja California in June 1999. Journal of Physical Oceanography. 34:1152-1173.   10.1175/1520-0485(2004)034<1152:Cpomww>2.0.Co;2   AbstractWebsite

Month-long simulations using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) with a horizontal resolution of 9 km have been used to investigate perturbations of topographically forced wind stress and wind stress curl during upwelling-favorable winds along the California and Baja California coasts during June 1999. The dominant spatial inhomogeneity of the wind stress and wind stress curl is near the coast. Wind and wind stress maxima are found in the lees of major capes near the coastline. Positive wind stress curl occurs in a narrow band near the coast, while the region farther offshore is characterized by a broad band of weak negative curl. Curvature of the coastline, such as along the Southern California Bight, forces the northerly flow toward the east and generates positive wind stress curl even if the magnitude of the stress is constant. The largest wind stress curl is simulated in the lees of Point Conception and the Santa Barbara Channel. The Baja California wind stress is upwelling favorable. Although the winds and wind stress exhibit great spatial variability in response to synoptic forcing, the wind stress curl has relatively small variation. The narrow band of positive wind stress curl along the coast adds about 5% to the coastal upwelling generated by adjustment to the coastal boundary condition. The larger area of positive wind stress curl in the lee of Point Conception may be of first-order importance to circulation in the Santa Barbara Channel and the Southern California Bight.