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maximum difference in sensible and latent heat fluxes can be about 30 W/m 2 , the mean values for latent heat fluxes are 22.27 W/m 2 for January and 5.40 W/m 2 for July. For sensible heat, they are 2.82 W/m 2 for January and 5.64 W/m 2 for July. We show that the maximum difference in net radiative fluxes can be as high as 55 W/m 2 , for January, the mean difference in net SW is 6.31 W/m 2 and in net LW it is 12.14 W/m 2 . For July, the respective differences are 29.99 W/m 2 for the SW and 14.31 W/m 2 for the LW. Relationships between the fluxes and satellite derived surface wind speed, total precipitable water, and cloud cover provide insight on the dominant processes that control the net heat flux. This study is intended to present an estimate of uncertainties that still exist in the net heat flux at the ocean-atmosphere interface.

Over the last 100 years, boundary layer meteorology grew from the subject of mostly near-surface observations to a field encompassing diverse atmospheric boundary layers (ABLs) around the world. From the start, researchers drew from an ever-expanding set of disciplines—thermodynamics, soil and plant studies, fluid dynamics and turbulence, cloud microphysics, and aerosol studies. Research expanded upward to include the entire ABL in response to the need to know how particles and trace gases dispersed, and later how to represent the ABL in numerical models of weather and climate (starting in the 1970s–80s); taking advantage of the opportunities afforded by the development of large-eddy simulations (1970s), direct numerical simulations (1990s), and a host of instruments to sample the boundary layer in situ and remotely from the surface, the air, and space. Near-surface flux-profile relationships were developed rapidly between the 1940s and 1970s, when rapid progress shifted to the fair-weather convective boundary layer (CBL), though tropical CBL studies date back to the 1940s. In the 1980s, ABL research began to include the interaction of the ABL with the surface and clouds, the first ABL parameterization schemes emerged; and land surface and ocean surface model development blossomed. Research in subsequent decades has focused on more complex ABLs, often identified by shortcomings or uncertainties in weather and climate models, including the stable boundary layer, the Arctic boundary layer, cloudy boundary layers, and ABLs over heterogeneous surfaces (including cities). The paper closes with a brief summary, some lessons learned, and a look to the future.

Boundary-layer secondary circulations or ‘roll vortices’ can have a significant influence on the turbulent exchange of momentum, sensible heat and moisture throughout the hurricane boundary layer. In this study, analyses of data from a WP-3D aircraft of the National Oceanic and Atmospheric Administration (NOAA) are presented. As part of the Coupled Boundary Layer Air-Sea Transfer (CBLAST)-hurricane experiment sponsored through the Office of Naval Research and NOAA’s annual hurricane research program, flights were conducted to investigate energy exchange across the air–sea interface. We present the first in-situ aircraft-based observations of rolls in the hurricane boundary layer and investigate their influence on energy and momentum exchange. The rolls detected in Hurricane Isidore (year 2002) have a characteristic wavelength of about 900 m, in good agreement with analyses of data from a synthetic aperture radar image captured by the Canadian Space Agency’s RADARSAT satellite in the same storm. Our analyses of the airborne data suggest that roll vortices may be a significant factor modulating the air–sea momentum exchange.

Consideration of the dependence of various components of the sea-surface heat and momentum fluxes on sea surface temperature (SST) leads to an explanation for the observed reduction in the horizontal temperature gradients in the uppermost layer of the ocean (a few to 10 m in depth). Horizontal temperature gradients within the mixed layer can be masked by a near-surface layer of warm water. This camouflage of horizontal temperature gradients has importance for the remote sensing of SST used by the fishing industry, for the estimation of acoustic transmission, and for the forecasting of hurricane development, among many uses of SST data. Diurnal warming conditions in the Straits of Florida are examined by a simulation calculation and by analysis of observations obtained on moorings deployed on the south-east Florida shelf. When there is net heating (i.e., the solar input is stronger than the combined latent, sensible and longwave radiative heat losses) the originally warmer water experiences less heating than the colder water, leading to a weakening of the horizontal SST gradients as seen by surface buoys or satellites. The warmer water also experiences more mixing and therefore less increase in temperature. The strongest effect of the diurnal heating on wind stress occurs when the SST starts out cooler than the air temperature and the atmosphere is stably stratified. Diurnal warming can then rapidly increase the SST above the air temperature because of reduced wind stress and reduced upper-ocean mixing. After that the wind stress increases as convectively driven turbulence contributes to the atmospheric exchange.

Sea surface temperature (SST) is a result of multiple interactions in air-sea processes. During days with strong insolation and low wind speed, there may be uneven net heating of the water layer near the surface of the ocean, when there are horizontal temperature gradients at the sea surface. Cooling of the water caused by evaporation, sensible, or longwave radiative, heat loss would be greater from warm water compared to that from relatively cold water. As a result, under low wind speed conditions and clear skies, the horizontal SST discontinuities, occurring at fronts, eddies, or in storm wakes, may diminish or even vanish. This phenomenon is illustrated here with some field and modelling results. The dependence on latitude and mean environmental conditions of the difference in warming on the cold and warm side of SST discontinuities is explored. The time dependence is important for the impact on remote sensing of SST, and it is found to be short enough that substantial masking of SST gradients can occur during the first six hours of the diurnal heating cycle, but the effect would continue to grow if calm and solar heating persist for several subsequent days. An integrated effect of this uneven net heating is seen in the seasonal masking of subsurface temperature gradients in the Gulf of Mexico and Florida Straits.

Surface fluxes of momentum, freshwater, and energy across the air–sea interface determine oceanic circulation and its variability at all timescales. The goal of this paper is to estimate and examine some ocean surface flux variables using satellite measurements. The remotely sensed data come from the European Remote Sensing (ERS) satellite scatterometer on ERS-2, NASA scatterometer (NSCAT), and several Defense Meteorological Satellite Program (DMSP) radiometers [Special Sensor Microwave Imager (SSM/I)] on board the satellites F10–F14. The sea surface temperature comes from daily analysis calculated from Advanced Very High Resolution Radiometer (AVHRR) measurements. This study focuses on the 9-month period (October 1996–June 1997) of the NSCAT mission. To ensure high quality of the merged surface parameter fields, comparisons between different satellite estimates for the same variable have been performed, and bias corrections have been applied so that they are compatible with each other. The satel...

A new geographic record of the oomycete Olpidiopsis feldmanni infecting the tetrasporophytic stage of the red alga Asparagopsis sp. from the Adriatic Sea, confirmed through morphological identification, allowed us to expand previous observations of this organism. Ultrastructural investigations of environmental material showed a large central vacuole and a cell wall thicker than previously reported from other basal oomycete pathogens of algae. Phylogenetic analysis closely associates O. feldmanni to O. bostrychiae concurrent with structural observations. This constitutes the first genetic characterisation of an Olpidiopsis species that was initially described before 1960, adding to the genetic data of 3 other marine Olpidiopsis species established and genetically characterised in the last 2 decades. The paper discusses concurrences of the ultrastructural observations made here and in previous studies of the marine Olpidiopsis species with those made on the freshwater species. © The authors 2015.

Far from land and surface ship observations, most tropical depressions are identified by examining images from geostationary satellites for the presence of rotation of the convective cloud masses. During the 1999 hurricane season, surface wind vectors obtained by the SeaWinds scatterometer on the QuikSCAT satellite for the tropical Atlantic and Caribbean Sea were examined to test the hypothesis that developing tropical depressions (TDs) could be observed with this satellite sensor, before identification by the traditional means. QuikSCAT was able to detect the presence of closed circulation in the surface winds before the systems were designated as depressions. The satellite's unprecedented large swath width of 1800 km allows twice a day observation of most of the tropical oceans. SeaWinds data can, therefore, provide valuable guidance that are an important addition to the tools available to the tropical cyclone forecasting community.

New results from turbulent flux measurements made over Lake Washington include the following: 1) The only direct measure of the vertical transport of the horizontal momentum, heat, and matter in the surface boundary layer is the so-called eddy correlation method. However, even if the measurement errors are negligible, the results obtained from point observations may show large scatter due to lack of stationarity and horizontal homogeneity in the turbulent field and to the sampling variability. Scatter may be greatly reduced by spatial averaging. In this study, such an effect is achieved by determining the surface roughness length, hence the neutral drag coefficient, from the measured wave height spectrum, which reflects the atmospheric input integrated over the fetch. Applicability and usefulness of the approach for general field measurements and remote sensing is discussed. 2) The evolution of the wave field observed on Lake Washington agrees in peak frequency and the slope of the equilibrium ra...

Two major campaigns (Surface of the Oceans, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE)) devoted to the study of ocean-atmosphere interaction were conducted in 1992 and 1993, respectively, in the Azores region. Among the various platforms deployed, instrumented aircraft and ship allowed the measurement of the turbulent flux of sensible heat, latent heat, and momentum. From coordinated missions we can evaluate the sea surface fluxes from (1) bulk relations and mean measurements performed aboard the ship in the atmospheric surface layer and (2) turbulence measurements aboard aircraft, which allowed the flux profiles to be estimated through the whole atmospheric boundary layer and therefore to be extrapolated toward the sea surface level. Continuous ship fluxes were calculated with bulk coefficients deduced from inertial-dissipation measurements in the same experiments, whereas aircraft fluxes were calculated with eddy-correlation technique. We present a comparison between these two estimations. Although momentum flux agrees quite well, aircraft estimations of sensible and latent heat flux are lower than those of the ship. This result is surprising, since aircraft momentum flux estimates are often considered as much less accurate than scalar flux estimates. The various sources of errors on the aircraft and ship flux estimates are discussed. For sensible and latent heat flux, random errors on aircraft estimates, as well as variability of ship flux estimates, are lower than the discrepancy between the two platforms, whereas the momentum flux estimates cannot be considered as significantly different. Furthermore, the consequence of the high-pass filtering of the aircraft signals on the flux values is analyzed; it is weak at the lowest altitudes flown and cannot therefore explain the discrepancies between the two platforms but becomes considerable at upper levels in the boundary layer. From arguments linked to the imbalance of the surface energy budget, established during previous campaigns performed over land surfaces with aircraft, we conclude that aircraft heat fluxes are probably also underestimated over the sea.

Unprecedented views of surface wind fields in tropical cyclones thereafter TCs) are provided by the European Remote Sensing Satellite (ERS) C band scatterometer. Scatterometer measurements at C band are able to penetrate convective storms clouds, observing the surface wind fields with good accuracy. However the resolution of the measurements (50x50 km(2)) limits the interpretation of the scatterometer signals in such mesoscale events. The strong gradients of the surface wind existing at scales of a few kms are smoothed in the measured features such as the intensity and location of the wind maxima, and the position of the center. Beyond the ERS systems, the scatterometers on-board the ADEOS and METOP satellites, designed by the Jet Propulsion Laboratory and by the European Space Agency, respectively, will be able to produce measurements of the backscattering coefficient at about 25x25 km(2) resolution. A few sets of ERS-1 orbits sampling TC events were produced with an experimental 25x25 km(2) resolution. Enhancing the resolution by a factor of 2 allows location of the wind maxima and minima in a TC with a much better accuracy than at 50 km resolution. In addition, a better resolution reduces the geophysical noise (variability of wind speed within the cell and effect of rain) that dominates the radiometric noise and hence improves the definition of the backscattering measurements. A comprehensive analysis of the backscattering measurements in the case of high winds and high sea states obtained within TCs is proposed in order to refine the interpretation of the wind vector derived from a backscattering model that is currently only calibrated up to moderate winds (< 20 m/s) in neutral conditions. Observations of the TOPEX-POSEIDON dual-frequency altimeter are also used for that purpose. Patterns of the surface winds in TCs are described and characteristic features concerning asymmetries in the maximum winds and in the divergence field are discussed.

During the Surface Wave Dynamics Experiment, direct measurements of momentum, heat, and water vapor fluxes were obtained from a mast on the foredeck of a SWATH (small water-plane area, twin hull) ship in deep water off the state of Virginia. Directional wave spectra were obtained simultaneously from a 6- or 3-wire wave-staff array mounted at the bow of the ship. One hundred and twenty-six 17-minute runs of flux and wave data obtained with the ship steaming slowly into the wind are examined for the effects of the relative direction of the wind sea and background swell on the momentum transfer. The adequacy of the inertial dissipation method, which depends on the high-frequency turbulent fluctuations for evaluating the wind stress, is also examined for any effects of swell. The results show that the presence of counter- and cross-swells can result in drag coefficients that are much larger than the value for a pure wind sea. The eddy correlation and inertial dissipation methods for measuring wind st...

The transfer coefficients for momentum and heat have been determined for 10 m neutral wind speeds (U-10n) between 0 and 12 m/s using data from the Surface of the Ocean, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiments. The inertial dissipation method was applied to wind and pseudo virtual temperature spectra from a sonic anemometer, mounted on a platform (ship) which was moving through the turbulence held. Under unstable conditions the assumptions concerning the turbulent kinetic energy (TKE) budget appeared incorrect. Using a bulk estimate for the stability parameter, Z/L (where Z is the height and L is the Obukhov length), this resulted in anomalously low drag coefficients compared to neutral conditions. Determining Z/L iteratively, a low rate of convergence was achieved. It was concluded that the divergence of the turbulent transport of TKE was not negligible under unstable conditions. By minimizing the dependence of the calculated neutral drag coefficient on stability, this term was estimated at about -0.65Z/L. The resulting turbulent fluxes were then in close agreement with other studies at moderate wind speed. The drag and exchange coefficients for low wind speeds were found to be C-en x 10(3) = 2.79U(10n)(-1) + 0.66 (U-10n < 5.2 m/s), C-en x 10(3) = C-hn x 10(3) = 1.2 (U-10n greater than or equal to 5.2 m/s), and C-dn x 10(3) = 11.7U(10n)(-2) + 0.668 (U-10n < 5.5 m/s), which imply a rapid increase of the coefficient values as the wind decreased within the smooth flow regime. The frozen turbulence hypothesis and the assumptions of isotropy and an inertial subrange were found to remain valid at these low wind speeds for these shipboard measurements. Incorporation of a free convection parameterization had little effect.

The TOPEX/POSEIDON mission offers the first opportunity to observe rain cells over the ocean by a dual-frequency radar altimeter (TOPEX) and simultaneously observe their natural radiative properties by a three-frequency radiometer (TOPEX microwave radiometer (TMR)). This work is a feasibility study aimed at understanding the capability and potential of the active/passive TOPEX/TMR system for oceanic rainfall detection. On the basis of past experiences in rain flagging, a joint TOPEX/TMR rain probability index is proposed. This index integrates several advantages of the two sensors and provides a more reliable rain estimate than the radiometer alone. One year's TOPEX/TMR TMR data are used to test the performance of the index. The resulting rain frequency statistics show quantitative agreement with those obtained from the Comprehensive Ocean-Atmosphere Data Set (COADS) in the Intertropical Convergence Zone (ITCZ), while qualitative agreement is found for other regions of the world ocean. A recent finding that the latitudinal frequency of precipitation over the Southern Ocean increases steadily toward the Antarctic continent is confirmed by our result. Annual and seasonal precipitation maps are derived from the index. Notable features revealed include an overall similarity in rainfall pattern from the Pacific, the Atlantic, and the Indian Oceans and a general phase reversal between the two hemispheres, as well as a number of regional anomalies in terms of rain intensity. Comparisons with simultaneous Global Precipitation Climatology Project (GPCP) multisatellite precipitation rate and COADS rain climatology suggest that systematic differences also exist. One example is that the maximum rainfall in the ITCZ of the Indian Ocean appears to be more intensive and concentrated in our result compared to that of the GPCP. Another example is that the annual precipitation produced by TOPEX/TMR is constantly higher than those from GPCP and COADS in the extratropical regions of the northern hemisphere, especially in the northwest Pacific Ocean. Analyses of the seasonal variations of prominent rainy and dry zones in the tropics and subtropics show various behaviors such as systematic migration, expansion and contraction, merging and breakup, and pure intensity variations, The seasonality of regional features is largely influenced by local atmospheric events such as monsoon, storm, or snow activities. The results of this study suggest that TOPEX and its follow-on may serve as a complementary sensor to the special sensor microwave/imager in observing global oceanic precipitation.

A new method is developed to estimate daily turbulent airsea fluxes over the global ocean on a 0.25 degrees grid. The required surface wind speed (w(10)) and specific air humidity (q(10)) at 10m height are both estimated from remotely sensed measurements. w(10) is obtained from the SeaWinds scatterometer on board the QuikSCAT satellite. A new empirical model relating brightness temperatures (T-b) from the Special Sensor Microwave Imager (SSM/I) and q(10) is developed. It is an extension of the author's previous q(10) model. In addition to T-b, the empirical model includes sea surface temperature (SST) and airsea temperature difference data. The calibration of the new empirical q(10) model utilizes q(10) from the latest version of the National Oceanography Centre airsea interaction gridded data set (NOCS2.0). Compared with mooring data, the new satellite q(10) exhibits better statistical results than previous estimates. For instance, the bias, the root mean square (RMS), and the correlation coefficient values estimated from comparisons between satellite and moorings in the northeast Atlantic and the Mediterranean Sea are 0.04gkg(1), 0.87gkg(1), and 0.95, respectively. The new satellite q(10) is used in combination with the newly reprocessed QuikSCAT V3, the latest version of SST analyses provided by the National Climatic Data Center (NCDC), and 10m air temperature estimated from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalyses (ERA-Interim), to determine three daily gridded turbulent quantities at 0.25 degrees spatial resolution: surface wind stress, latent heat flux (LHF), and sensible heat flux (SHF). Validation of the resulting fields is performed through a comprehensive comparison with daily, in situ values of LHF and SHF from buoys. In the northeast Atlantic basin, the satellite-derived daily LHF has bias, RMS, and correlation of 5Wm(2), 27Wm(2), and 0.89, respectively. For SHF, the statistical parameters are 2Wm(2), 10Wm(2), and 0.94, respectively. At global scale, the new satellite LHF and SHF are compared to NOCS2.0 daily estimates. Both daily fluxes exhibit similar spatial and seasonal variability. The main departures are found at latitudes south of 40 degrees S, where satellite latent and sensible heat fluxes are generally larger.

We examine integrated water vapor fields and rain intensity patterns derived from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) for several rapidly deepening and non-rapidly deepening midlatitude cyclones in the North Atlantic. Our goal is to identify features in the satellite data unique to the rapidly deepening cases, and to explore how these data can potentially be used in the analysis and forecasting of these events.

Recent experiments measuring turbulence dissipation rates in the upper ocean can be divided into two types: those supporting an analogy between the upper ocean and lower atmosphere, with dissipation rates following wall layer behavior, and those finding oceanic dissipation rates to be much higher than wall layer predictions. In an attempt to reconcile these two diverse acts of observations, Terray et al. proposed a wave-dependent scaling of the dissipation rate based on the significant wave height and the rate of energy input from the wind to the waves. Their parameterization was derived from observations of strongly forced, fetch-limited waves, although they conjectured that it would apply in typical oceanic conditions as well. This paper reports new measurements of turbulent kinetic energy dissipation made in the North Atlantic Ocean from a SWATH ship during the recent Surface Waves Dynamics Experiments (SWADE).These data support the scaling of Terray et al., verifying its validity when applied...

In HEXOS, a programme of coordinated laboratory, field and model studies, an international group of participants has extended the range of measurements of evaporation from the sea and has investigated the role of droplets in the transfer of water to the atmosphere. Predictions of a rapid rise in the evaporation coefficient at wind speeds above 15 m s-1 have not been substantiated. Wind stress measurements showed a relationship with wave age. New methods were developed for coping with flow distortion.

Heat flux estimates obtained using the inertial dissipation method, and the profile method applied to radiosonde soundings, are assessed with emphasis on the parameterization of the roughness lengths for temperature and specific humidity. Results from the inertial dissipation method show a decrease of the temperature and humidity roughness lengths for increasing neutral wind speed, in agreement with previous studies. The sensible heat flux estimates were obtained using the temperature estimated from the speed of sound determined by a sonic anemometer. This method seems very attractive for estimating heat fluxes over the ocean. However allowance must be made in the inertial dissipation method for non-neutral stratification. The SOFIA/ASTEX and SEMAPHORE results show that, in unstable stratification, a term due to the transport terms in the turbulent kinetic energy budget, has to be included in order to determine the friction velocity with better accuracy. Using the profile method with radiosonde data, the roughness length values showed large scatter. A reliable estimate of the temperature roughness length could not be obtained. The humidity roughness length values were compatible with those found using the inertial dissipation method.

Accurate measurement of fluctuations in temperature and humidity are needed for determination of the surface evaporation rate and the air-sea sensible heat flux using either the eddy correlation or inertial dissipation method for flux calculations. These measurements are difficult to make over the ocean, and are subject to large errors when sensors are exposed to marine air containing spray droplets. All currently available commercial measurement devices for atmospheric humidity require frequent maintenance. Included in the objectives of the Humidity Exchange over the Sea program were testing and comparison of sensors used for measuring both the fluctuating and mean humidity in the marine atmosphere at high wind speeds and development of techniques for the protection of these sensors against contamination by oceanic aerosols. These sensors and droplet removal techniques are described and comparisons between measurements from several different systems are discussed in this paper. To accomplish these goals, participating groups devised and tested three methods of removing sea spray from the sample airstream. The best performance was given by a rotating semen device, the “spray Ringer.” Several high-frequency temperature and humidity instruments, based on different physical principles, were used in the collaborative field experiment. Temperature and humidity fluctuations were measured with sufficient accuracy inside the spray removal devices using Lyman-α hygrometers and a fast thermocouple psychrometer. Comparison of several types of psychrometers (using electric thermometers) and a Rotronic MP-100 humidity sensor for measuring the mean humidity illustrated the hysteresis of the Rotronic MP-100 device after periods of high relative humidity. Confidence in the readings of the electronic psychrometer was established by in situ calibration with repeated and careful readings of ordinary hand-held Assman psychrometers (based on mercury thermometers). Electronic psychrometer employing platinum resistance thermometers perform very well.

During the Surface Wave Dynamics Experiment (SWADE), the swath ship Frederick G. Creed was equipped with an array of wave staffs for the estimation of wave directional spectra. This paper reports on the first such estimates taken from a ship at sea. An algorithm for removing the effects of the ship motion, including those resulting from the Doppler shifting of observed frequencies, is presented along with some results from the SWADE experiment. A comparison with directional wave spectra taken from a nearby buoy shows the fidelity of the method.

Based on a geometric optics model and the assumption of an isotropic Gaussian surface slope distribution, the component of ocean surface microwave emissivity variation due to large-scale surface roughness is parameterized for the frequencies and approximate viewing angle of the Special Sensor Microwave/Imager. Independent geophysical variables in the parameterization are the effective (microwave frequency dependent) slope variance and the sea surface temperature. Using the same physical model, the change in the effective zenith angle of reflected sky radiation arising from large-scale roughness is also parameterized. Independent geophysical variables in this parameterization are the effective slope variance and the atmospheric optical depth at the frequency in question. Both of the above model-based parameterizations are intended for use in conjunction with empirical parameterizations relating effective slope variance and foam coverage to near-surface wind speed. These empirical parameterizations are the subject of a separate paper.

Several methods are examined for correction of turbulence and eddy fluxes in the atmospheric boundary layer, two of them based on a potential-flow approach initiated by Wyngaard. If the distorting object is cylindrical or if the distance to the sensor is much greater than the size of the body, the undisturbed wind stress can be calculated solely from measurements made by the sensor itself; no auxiliary measurements or lengthy model calculations are needed. A more general potential-flow correction has been developed in which distorting objects of complex shape are represented as a number of ellipsoidal elements. These models are applied to data from three turbulence anemometers with differing amounts of flow distortion, operated simultaneously in the Humidity Exchange over the Sea (HEXOS) Main Experiment. The results are compared with wind-stress estimates by the inertial-dissipation technique; these are much less sensitive to local flow distortion and are consistent with the corrected eddy correl...

The cloud cover and cloud water content obtained from integration of a limited area mesoscale prediction model are compared with the corresponding quantities derived from AVHRR and SSM/I satellite data. The model has an elaborate condensation-cloud parameterization scheme, in which cloud water is a prognostic variable. From AVHRR data, both cloud cover and liquid water content are retrieved by utilization of radiances from the visible, near infrared and infrared channels. From the 37GHz polarization difference in the microwave data obtained from SSM/I measurements, liquid water content is interpreted; this is only possible over the sea. An important feature of this comparison exercise is that the retrieved data are distributed on the same grid as the model. The difference between the simulation and the analysed cloud fields can thus easily be quantified and exhibited on the model domain. It is demonstrated that this type of retrieved meteorological parameters constitutes potentially useful data samples for quantitative verification of model simulations. There are some weaknesses in the retrieval methods that have to be removed before we can have sufficient confidence in the data to make quantitative verification meaningful. Furthermore, calibration against cloud parameters obtained through other measurements is necessary, although the three data sets show a remarkably good agreement in pattern and range of magnitude in the liquid water content. Even if improvements are needed, the present study has made it possible to make inferences about some deficiencies in the parameterization scheme of the model. DOI: 10.1034/j.1600-0870.1991.t01-3-00006.x

Uncertainties in turbulent ocean-atmosphere heat flux estimates, both among the estimates and between them and ground truth, suggest that further comparisons are needed. We analyze estimates from the French Research Institute for Exploitation of the Sea (IFREMER) and the Woods Hole Oceanographic Institution's Objectively Analyzed air-sea Fluxes (WHOI OAFlux). The IFREMER products are based on satellite observations and the WHOI OAFlux ones on data from satellites, buoys, and ships assimilated into numerical analyses. We focus on the Atlantic sector (70 degrees W-30 degrees E, 45 degrees S-45 degrees N) during 1996-2005, where the variables that enter the bulk formulae for computing fluxes (wind speed, sea surface and air temperature, and specific humidity) can be evaluated against buoys in the Prediction and Research Moored Array in the Atlantic (PIRATA). Since WHOI assimilates PIRATA observations, we have added two independent buoy data sets: FETCH and ROMEO. To examine how each variable contributes to the difference between estimated and buoy fluxes, the method of Bourras (2006) is applied. His so-called Q terms showed that specific air humidity and air temperature contributed the most to the biases of IFREMER latent and sensible heat fluxes, respectively, at both independent buoys. For WHOI OAFlux products, deviations from FETCH values were mainly due to wind speed and sea surface temperature differences, while in comparison with ROMEO fluxes, WHOI OAFlux biases were primarily due to specific humidity and sea surface temperature estimates. Modified estimates of turbulent fluxes with the IFREMER approach using the 10 m specific humidity and air temperature products of Jackson et al. (2009) show significant improvement in three test cases at PIRATA buoys.

This chapter addresses the estimation of global surface winds, surface wind stress, latent heat flux, and sensible heat flux over the oceans with high spatial and temporal resolution using satellite radar and radiometer measurements. An overview of the physics of remotely sensed data, of methods and algorithms used to retrieve surface fluxes is provided. The retrievals are used to estimate regular in space and time surface parameters, requested for oceanic forcing function, over global ocean. The characteristics of the former are investigated at global and regional scales.

A detailed parameterization is developed for the contribution of the nonprecipitating atmosphere to the microwave brightness temperatures observed by the Special Sensor Microwave/Imager (SSM/I). The atmospheric variables considered include the viewing angle, the integrated water vapor amount and scale height, the effective tropospheric lapse rate and near-surface temperature, the total cloud liquid water, the effective cloud height, and the surface pressure. The dependence of the radiative variables on meteorological variables is determined for each of the SSM/I frequencies 19.35, 22.235, 37.0, and 85.5 GHz, based on the values computed from 16,893 maritime temperature and humidity profiles representing all latitude belts and all seasons. A comparison of the predicted brightness temperatures with brightness temperatures obtained by direct numerical integration of the radiative transfer equation for the radiosonde-profile dataset yielded rms differences well below 1 K for all four SSM/I frequencies.

Atmospheric and surface parameters retrieved from observations by satellites in the TIROS-N/NOAA series provide valuable information for meteorological investigations in the data-sparse polar regions. A pattern-recognition method for processing these observations, the Improved Initialization Inversion (3I) system, has been developed at Laboratoire de Meteorologie Dynamique (LMD). This technique has been applied to several satellite passes, and the capability of the TIROS-N Operational Vertical Sounder (TOVS) to provide a description of mesoscale atmospheric phenomena has been demonstrated. In addition, the Special Sensor Microwave/Imager (SSM/I) launched in June 1987 on a satellite in the United States Defense Meteorological Satellite Program (DMSP) allows a new insight into the mesoscale structures of cyclones over the ocean by providing estimates of atmospheric water vapor, cloud water and surface winds. TOVS and SSM/I-inferred parameters are presented and discussed for several cases, including polar lows, and the mutual contribution of these two types of satellite data is shown.

The aim of this article is to estimate surface latent heat fluxes in the vicinity of a rapidly deepening cyclone before and during its period of most rapid intensification. This is done with a bulk parameterization scheme and remotely sensed input data. A method for estimating the difference in specific humidity between the surface and a 10-m height is investigated using the Special Sensor Microwave/Imager-observed integrated water vapor field and a sea surface temperature analysis. The surface latent heat flux fields generally have estimated errors below 40 percent south of 40 deg N and outside the region of high integrated water vapor values associated with frontal bands. The method of estimating surface latent heat fluxes for the case study was found to be usable in most regions of the northwest Atlantic Ocean except for those locations directly adjacent to coastlines in instances of offshore flow and in the vicinity of surface fronts.

Turbulent fluxes have been measured in the atmospheric surface layer from a boom extending upwind from the Dutch offshore research platform Meetpost Noordwijk (MPN) during HEXMAX (Humidity Exchange over the Sea Main Experiment) in October-November, 1986. We started out to study eddy flux of water vapour, but discrepancies among simultaneous measurements made with three different anemometers led us to develop methods to correct eddy correlation measurements of wind stress for flow distortion by nearby objects. We then found excellent agreement among the corrected wind stress data sets from the three anemometers on the MPN boom and with eddy correlation measurements from a mast on a tripod. Inertial-dissipation techniques gave reliable estimates of wind stress from turbulence spectra, both at MPN and at a nearby ship. The data cover a range of wave ages and the results yield new insights into the variation of sea surface wind stress with sea state; two alternative formulas are given for the nondimensional surface roughness as a function of wave age. ONR

Until recently, the scarcity of meteorological observations over polar areas has limited studies of high-latitude weather systems, but now data from polar orbiting satellites offer a new opportunity to observe and describe these systems. TOVS data have been used successfully for delineating synoptic and sub-synoptic systems, since they provide the vertical temperature structure of the atmosphere; SSM/I observations have proved valuable for analysing storms through water vapour and rain determinations. These positive results prompted us to analyze simultaneous TOVS and SSM/I observations obtained during a cold air outbreak over the Norwegian Sea. After a description of the instruments and the retrieval schemes, the mutually supporting information from these two independent instruments is discussed. Implications for the monitoring of polar lows are presented. DOI: 10.1034/j.1600-0870.1992.t01-1-00002.x

Studies of midlatitude and tropical cyclones and regional weather and climate analyses are examined. Consideration is also given to studies of long swell, sea ice, and continental ice sheets with Seasat data. Many of these results of the Seasat mission were serendipitous. In preparation for the major NASA initiative for the next decade, the Earth Observing Satellite program, it was thought timely to bring some of the Seasat experiences to the fore, since valuable lessons can be learned from the successes and the failures (or omissions) of the Seasat program. Data have been obtained about: (1) the synergistic value of integrated overlapping sampling by several instruments, (2) the invaluable contribution of carefully planned surface measurements, and (3) the importance of retaining flexibility in the system (enough data retention) to allow unexpected and innovative analysis techniques. 72 refs.

With the atmospheric water-vapor content information available from the SEASAT and Nimbus-7 Scanning Multichannel Microwave Radiometers (SMMR), differences in water-vapor distribution between cyclonic storms in different regions of the global ocean can be examined in more detail than previously possible from radiosondes. SMMR-derived integrated water vapor is a robust and dependable variable of the same accuracy as integrated radiosonde soundings. In this study, maximum and minimum water-vapor content in the vicinity of cold fronts of 80 storms that occurred in the North Atlantic, North Pacific and Southern oceans are compared. North Atlantic storms were found to have significantly higher maximum and minimum water-vapor content near cold fronts on average than North Pacific or Southern ocean storms for both the warm and cold seasons. These differences are attributed to warmer sea surface temperatures and air temperatures in the North Atlantic, and higher baroclinity and consequently stronger upwa...

Results are presented from calculations of radiation budgets for the sea-ice and the open-water regimes in the marginal ice zone (MIZ) of the Fram Strait, from measurements of surface irradiances and meteorological conditions made during the 1984 Marginal Ice Zone Experiment. Simultaneous measurements on either side of the ice edge allowed a comparison of the open-water and the sea-ice environments. The results show significant differences between the radiation budgets of the two regimes in the MIZ. The open water absorbed twice as much radiation as did the ice, and the mean cooling rate of the atmosphere over water was approximately 15 percent larger than that over ice. Calculated fluxes and atmospheric cooling rates were found to compare well with available literature data.

Based on an interpretation of a field experiment it is argued that, due to breaking of wind waves in deep water, the dissipation of energy is restricted to a range of frequencies ω > ωg, much higher than the frequency ωm of the dominant waves. In this dissipation range the spectrum has the form S(ω) = βg2ω−5 where g is the acceleration due to gravity and β = 0.025. For spectral wave components at ω ≤ ωg, only a local balance between energy input from the wind and the weak, third-order, nonlinear interaction is important. Asymptotically as ω ≫ ωm the wind input becomes unimportant, and the wave spectrum has the Kitaigorodskii form of a Kolgomorov analog S(ω) = 2aϵ0⅓ g4/3 ω−4 where ϵ0 is a constant flow of mean energy per unit surface area through the spectrum dissipated at high frequencies (when multiplied by g and water density ρw). From a method of M. S. Longuet-Higgins we estimate the magnitude of the dissipation (due to wave breaking) and find the Kolmogorov constant to be a ≈ 0.6. When a mode...

Humidity Exchange over the Sea (HEXOS) is an international program for the study of evaporation and spray droplet flux from sea to air. The program includes measurements in the field, simulation studies in wind tunnels, interpretive studies such as flow distortion modeling, boundary-layer modeling and development of parameterization for use in synoptic, and climatic models of the atmosphere and ocean. The HEXOS Main Experiment (HEXMAX) was carried out in October and November of 1986 at the Dutch offshore research platform Meetpost Noordwijk (MPN) and from ship, aircraft, and shore stations in the vicinity. Evaporation, wind stress, and heat flux were determined at all stations using combinations of eddy correlation, dissipation, and profile methods. Concurrent measurements of spray and aerosol distributions and other relevant parameters, and the regular occurence of favorable winds and weather make the HEXMAX dataset unique in its completeness and in the range of conditions covered. Some preliminary resul...

The organisation of the endoplasmic reticulum (ER) was examined in branching thallus cells and germinating cells derived from regenerated protoplasts (protoplast derived cells; PDCs) of Macrocystis pyrifera gametophytes by both immunofluorescent labelling of the HDEL sequence and vital staining with DiOC6(3), and in branching thallus cells of Splachnidium rugosum and Choristocarpus tenellus with DiOC6 (3) staining. In M. pyrifera and S. rugosum cells, distinctive cortical ER configurations with a clear radial arrangement were found at sites where a protrusion will emerge, while branching C. tenellus cells had a cortical ER patch from which a few linear ER elements expanded towards the rest of the cell. Examination of the organization of actin filaments (AFs) revealed similar radial AF structures at the site of the future protrusion, while the microtubule (Mt) organisation did not show any similar characteristic structure at the protrusion site. Latrunculin B inhibited germination in M. pyrifera PDCs, and the treated cells lacked radial ER or AF configurations. Treatment with taxol did not affect the germination process or the radial configurations. The structural similarity and the temporal and spatial coincidence of the ER and AF configurations combined with the inhibitor experiments lead to the hypothesis that ER, in conjunction with AFs, is implicated in the fixation of the polar axis in brown algal cells. The existence of characteristic ER and AF configurations in polarising cells of the three species suggests that they are a common characteristic of the brown algae. © 2007 British Phycological Society.

The seasonal and anomaly variability of satellite-derived weekly latent heat fluxes occurring over the global oceans during a 3-yr period (January 1996–December 1998) is investigated using EOF and harmonic analyses. The seasonal cycle of latent heat flux is estimated by least squares fitting the first three (annual, semiannual, and 4 month) harmonics to the data. The spatial patterns of amplitudes of these harmonics agree well with the corresponding patterns for wind speed. The annual harmonic captures an oscillation that reflects high evaporation in late fall/early winter and low evaporation in late spring/early summer in both hemispheres, with larger amplitudes in the Northern Hemisphere over the western side of the oceans and significant phase differences within each hemisphere. The main feature of the semiannual harmonic is its large amplitude in the Asian monsoon region (e.g., in the Arabian Sea its amplitude is about 1.5 larger than the annual) and the out-of-phase relationship of this region with the high latitudes of the North Pacific, consistent with other studies. The third harmonic shows three main regions with relatively large amplitudes, one in the Arabian Sea and two out-of-phase regions in the central midlatitude North and South Pacific. After removing this estimate of the seasonal cycle from the data, the leading EOF of the anomalies isolates the 1997–98 El Niño signal, with enhanced evaporation in the eastern tropical Pacific, around the Maritime Continent, in the midlatitude North and South Pacific, and the equatorial Indian Ocean, and reduced evaporation elsewhere around the global ocean during April 1997–April 1998. This pattern is consistent with known patterns of ENSO variability and with the “atmospheric bridge” teleconnection concept. The current study illustrates the usefulness of satellite-derived latent heat fluxes for climatic applications.

The organization of actin filaments and their role in cytokinesis was studied in regenerating protoplasts and thallus cells of gametophytes of the brown alga Macrocystis pyrifera. Before the onset of cytokinesis, a ring of actin filaments appeared on the putative cytokinetic plane just under the plasmalemma. Light and electron microscopy of cytokinetic cells revealed that large vacuoles occupy the space between the daughter nuclei, which very often are eccentrically positioned at the cell cortex. By the progress of cytokinesis, actin filament bundles emanating from the cytokinetic ring tend to form an actin plate that enters cytoplasmic pockets in which the cytokinetic diaphragm develops. The mechanism of this cytokinetic pattern that has not been reported so far for brown algae is discussed. © Springer-Verlag 2005.

Scatterometers and radiometers on several polar-orbiting satellites routinely produce oceanic surface wind field data. For this study, we merged the NASA scatterometer (NSCAT) data with scatterometer data from the European Remote Sensing (ERS) satellite 2, and the wind speeds from two of the Special Sensor Microwave/Imagers (SSM/I) and produced daily 1° latitude by 1° longitude gridded wind fields over the global ocean for September 1996 through June 1997. This time period coincides with the lifetime of the NSCAT aboard ADEOS-1. We created these wind fields by utilizing the Kriging technique with its associated variograms, which consider both space and time wind vector structures. The resulting daily wind fields, when compared with moored-buoy wind speed and direction measurements, resulted in a root-mean-square (rms) difference of less than 1.5 m/s. No significant difference was found between statistical parameters estimated over the equatorial zone and middle latitudes. To investigate the global patterns of these new satellite wind fields, comparisons with the National Environmental Prediction Center's (NCEP) re-analysis products have been carried out. The satellite data and the NCEP products have a similar statistical error structure, but the merged wind fields provide complete coverage at much higher spatial resolution. Accurate surface wind speed estimates are an important factor in determining the velocity and magnitude of air-sea gas exchange.

The RADARSAT synthetic aperture radar (SAR) acquired C-band HH polarization images over four 1998 hurricanes: Bonnie, Danielle, Georges, and Mitch. The authors present the SAR images and discuss their quantitative use in understanding hurricane morphology. The SAR provides a complimentary "view from below" that is most beneficial when considered in the context of more conventional hurricane observations.

Review of several recent ocean surface wave models finds that while comprehensive in many regards, these spectral models do not satisfy certain additional, but fundamental, criteria. We propose that these criteria include the ability to properly describe diverse fetch conditions and to provide agreement with in situ observations of Cox and Munk [1954] and Jahne and Riemer [1990] and Hara et al. [1994] data in the high-wavenumber regime. Moreover, we find numerous analytically undesirable aspects such as discontinuities across wavenumber limits, nonphysical tuning or adjustment parameters, and noncentrosymmetric directional spreading functions. This paper describes a two-dimensional wavenumber spectrum valid over all wavenumbers and analytically amenable to usage in electromagnetic models. The two regime model is formulated based on the Joint North Sea Wave Project (JONSWAP) in the long-wave regime and on the work of Phillips [1985] and Kitaigorodskii [1973] at the high wavenumbers. The omnidirectional and wind-dependent spectrum is constructed to agree with past and recent observations including the criteria mentioned above. The key feature of this model is the similarity of description for the high- and low-wavenumber regimes; both forms are posed to stress that the air-sea interaction process of friction between wind and waves (i.e., generalized wave age, u/c) is occurring at all wavelengths simultaneously. This wave age parameterization is the unifying feature of the spectrum. The spectrum's directional spreading function is symmetric about the wind direction and has both wavenumber and wind speed dependence. A ratio method is described that enables comparison of this spreading function with previous noncentrosymmetric forms. Radar data are purposefully excluded from this spectral development. Finally, a test of the spectrum is made by deriving roughness length using the boundary layer model of Kitaigorodskii. Our inference of drag coefficient versus wind speed and wave age shows encouraging agreement with Humidity Exchange Over the Sea (HEXOS) campaign results.

Treatment of young thalli of Sphacelaria rigidula with 0.04 μg of nocodazole (Nz) per ml for up to 36 h affects microtubules (Mts) only slightly, but blocks a large number of mitotic cells in metaphase, without disruption of the metaphase plate. Higher concentrations of Nz (0.1 μg/ml) depolymerize interphase Mts. Only a few perinuclear and some short Mrs resist and remain associated with the centrosomes. Fragmented Mrs or groups of Mts sometimes remain in the apical dome. After treatment with 0.1 μg of Nz per ml, prometaphase cells are blocked at metaphase, while post-metaphase cells become binuclear, due to the failure of cytokinesis. With anticentrin immunofluorescence, a positive centrin signal is always observed in the centrosome area. Centrosome duplication is not affected by Nz, but separation is disturbed. After recovering for 2-4 h, most of the blocked metaphases proceed normally. In such cells duplicated centrosomes are seen in different stages of separation. In some cells independent aster-like microtubule configurations appear in the apical dome, occasionally displaying centrin at their centre. During recovery various configurations of bimitosis or multipolar mitosis were found. The multipolar spindles may share common centrosomes. Up to four centrosomes may accompany each nucleus. In some 24 h treated cells, as well as in cells recovering for 2 h, the centrin-positive structure is rod-like, extending in opposite directions from the usual position to the poles. Electron microscopical examination of thin sections revealed that the growth pattern of the apical cells is disrupted after Nz treatment. The observations show that: (a) the Mt cytoskeleton is involved in maintaining the polarity and growth pattern of apical cells, (b) mitosis is blocked by low concentrations of Nz without significant depolymerization of Mrs, (c) the centrosome cycle is independent of the nuclear cycle, (d) centrosome separation and differentiation are disturbed by Nz treatment, (e) during recovery from Nz treatment, centrosomal material that may have separated from the centrosomes, as well as Mt fragments that resisted depolymerization, may operate as Mt nucleation centres.

The SEMAPHORE (Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale) experiment has been conducted from June to November 1993 in the Northeast Atlantic between the Azores and Madeira. It was centered on the study of the mesoscale ocean circulation and air-sea interactions. The experimental investigation was achieved at the mesoscale using moorings, floats, and ship hydrological survey, and at a smaller scale by one dedicated ship, two instrumented aircraft, and surface drifting buoys, for one and a half month in October-November (IOP: intense observing period). Observations from meteorological operational satellites as well as spaceborne microwave sensors were used in complement. The main studies undertaken concern the mesoscale ocean, the upper ocean, the atmospheric boundary layer, and the sea surface, and first results are presented for the various topics. From data analysis and model simulations, the main characteristics of the ocean circulation were deduced, showing the close relationship between the Azores front meander and the occurrence of Mediterranean water lenses (meddies), and the shift between the Azores current frontal signature at the surface and within the thermocline. Using drifting buoys and ship data in the upper ocean, the gap between the scales of the atmospheric forcing and the oceanic variability was made evident. A 2 °C decrease and a 40-m deepening of the mixed layer were measured within the IOP, associated with a heating loss of about 100 W m-2. This evolution was shown to be strongly connected to the occurrence of storms at the beginning and the end of October. Above the surface, turbulent measurements from ship and aircraft were analyzed across the surface thermal front, showing a 30% difference in heat fluxes between both sides during a 4-day period, and the respective contributions of the wind and the surface temperature were evaluated. The classical momentum flux bulk parameterization was found to fail in low wind and unstable conditions. Finally, the sea surface was investigated using airborne and satellite radars and wave buoys. A wave model, operationally used, was found to get better results compared with radar and wave-buoy measurements, when initialized using an improved wind field, obtained by assimilating satellite and buoy wind data in a meteorological model. A detailed analysis of a 2-day period showed that the swell component, propagating from a far source area, is underestimated in the wave model. A data base has been created, containing all experimental measurements. It will allow us to pursue the interpretation of observations and to test model simulations in the ocean, at the surface and in the atmospheric boundary layer, and to investigate the ocean-atmosphere coupling at the local and mesoscales.

Incidence of wave breaking for pure wind driven waves has been studied on Lake Washington at wind speeds up to 8 m s−1. Video recordings were employed to identify and categorize the breaking events in terms of micro-scale, spilling and plunging breakers. These events were correlated with the magnitude of the wave spectrum measured with a resistance wire wave gauge and band pass filtered between 6 and 10 Hz. An equivalent percentage of breaking crests were found for spilling and plunging events.

Selected data obtained during the first year of operation of the scanning multichannel microwave radiometer (SMMR) on board the Nimbus 7 satellite (launched in late October 1978) have been used to calculate, on a global basis, various geophysical parameters over open oceans, polar regions, and terrain. Over open oceans these calculations have provided values for sea surface temperatures, near-surface winds, atmospheric water vapor in a column, and rainfall rates. In polar regions, sea ice concentration, multiyear ice fraction, and radiating temperatures have been obtained. Finally, the extent and water equivalence of snow cover over terrain have been calculated. These parameters have been compared with in situ measurements of the same geophysical parameters, where available, and the results of these comparisons are described. The self-consistency of the global displays of all the parameters is discussed along with the plans for archiving them for subsequent research purposes. A description of the SMMR calibration and data processing scheme is also given.

Near-surface data from ships, buoys, aircraft and a microwave remote-sensing satellite have been used to estimate the fluxes of momentum, heat and water vapour at the sea surface over a 200 km x 200 km area during the Joint Air-Sea Interaction Experiment of 1978. In particular, daily means of the surface heat balance and the wind stress are presented. Generally, the sensible heat flux was found to be less than 25 % of the latent heat flux. Over periods of a day the total upward heat flux was about a third of the net radiation, implying that a significant proportion of the available energy went into heating the ocean. The Ekman pumping accounted for most of the divergence in the atmospheric boundary layer but only 10 % at most of that in the upper ocean. Some case studies of the horizontal variation of the fluxes in relation to larger scales are also discussed and it is suggested that the fluxes are modulated by mesoscale patterns in sea-surface temperature.

Patterns in the horizontal distribution of integrated water vapor, integrated liquid water and rainfall rate derived from the Seasat Scanning Multichannel Microwave Radiometer (SMMR) during a September 10-12, 1978 North Pacific cyclone are studied. These patterns are compared with surface analyses, ship reports, radiosonde data, and GOES-West infrared satellite imagery. The SMMR data give a unique view of the large mesoscale structure of a midlatitude cyclone. The water vapor distribution is found to have characteristic patterns related to the location of the surface fronts throughout the development of the cyclone. An example is given to illustrate that SMMR data could significantly improve frontal analysis over data-sparse oceanic regions. The distribution of integrated liquid water agrees qualitatively well with corresponding cloud patterns in satellite imagery and appears to provide a means to distinguish where liquid water clouds exist under a cirrus shield. Ship reports of rainfall intensity agree qualitatively very well with SMMR-derived rainrates. Areas of mesoscale rainfall, on the order of 50 km x 50 km or greater are detected using SMMR derived rainrates.