Experimental and numerical study on a model of offshore vertical axis wind turbine with pitching blades

International audienc

Cirene : air-sea iInteractions in the Seychelles-Chagos thermocline ridge region

Author Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 90 (2009): 1337-1350, doi:10.1175/2008BAMS2499.1.The Vasco—Cirene program ex-plores how strong air—sea inter-actions promoted by the shallow thermocline and high sea surface temperature in the Seychelles—Chagos thermocline ridge results in marked variability at synoptic, intraseasonal, and interannual time scales. The Cirene oceano-graphic cruise collected oceanic, atmospheric, and air—sea flux observations in this region in Jan-uary—February 2007. The contem-poraneous Vasco field experiment complemented these measure-ments with balloon deployments from the Seychelles. Cirene also contributed to the development of the Indian Ocean observing system via deployment of a moor-ing and 12 Argo profilers. Unusual conditions prevailed in the Indian Ocean during Janu-ary and February 2007, following the Indian Ocean dipole climate anomaly of late 2006. Cirene measurements show that the Seychelles—Chagos thermocline ridge had higher-than-usual heat content with subsurface anomalies up to 7°C. The ocean surface was warmer and fresher than average, and unusual eastward currents prevailed down to 800 m. These anomalous conditions had a major impact on tuna fishing in early 2007. Our dataset also sampled the genesis and maturation of Tropical Cyclone Dora, including high surface temperatures and a strong diurnal cycle before the cyclone, followed by a 1.5°C cool-ing over 10 days. Balloonborne instruments sampled the surface and boundary layer dynamics of Dora. We observed small-scale structures like dry-air layers in the atmosphere and diurnal warm layers in the near-surface ocean. The Cirene data will quantify the impact of these finescale features on the upper-ocean heat budget and atmospheric deep convection.CNES funded the Vasco part of the experiment; INSU funded the Cirene part. R/V Suroît is an Ifremer ship. The contributions from ODU, WHOI, and FOI (Sweden) are supported by the National Science Foundation under Grant Number 0525657. The participation of the University of Miami group was funded though NASA (NNG04HZ33C). PMEL participation was supported through NOAA’s Office of Climate Observation

Comparison of Five Satellite Derived Latent Heat Flux Products to Moored Buoy Data

Five satellite products of latent heat flux at the sea surface were compared to bulk fluxes calculated with data from 75 moored buoys, on almost 36 successive months from 1998 to 2000. The five products compared are the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Dataset (HOAPS-2), the Japanese Ocean Flux Datasets with Use of Remote Sensing Observations (J-OFURO), the Jones dataset, the Goddard Satellite-Based Surface Turbulent Fluxes, version 2 (GSSTF-2), and the Bourras–Eymard–Liu dataset (BEL). The comparisons were performed under tropical and midlatitude environmental conditions, with three datasets based on 66 Tropical Atmosphere–Ocean array (TAO) buoys in the tropical Pacific, nine National Data Buoy Center (NDBC) buoys off the U.S. coasts, and four Met Office/Météo-France (UK–MF) moorings west of the United Kingdom and France, respectively. The satellite products did not all compare well to surface data. However, for each in situ dataset (TAO, NDBC, or UK–MF) at least one satellite product was found that had a good fit to surface data, that is, an rms deviation of 15–30 W m2. It was found that HOAPS-2, J-OFURO, GSSTF-2, and BEL satellite products had moderate systematic errors with respect to surface data, from 13 to 26 W m2, and small biases at midlatitudes (6–8 W m2). Most of the satellite products were able to render the seasonal cycle of the latent heat flux calculated with surface data. The estimation of near-surface specific humidity was found to be problematic in most products, but it was best estimated in the HOAPS-2 product. GSSTF-2 and J-OFURO strongly overestimated the surface flux variations in time and space compared to surface data and to a flux climatology. With respect to TAO data, Jones fluxes yielded good results in terms of rms deviation (27 W m2) but also presented a large systematic deviation. Overall, for application of the satellite fluxes to the world oceans, it was found that HOAPS-2 was the most appropriate product, whereas for application to the Tropics, BEL fluxes had the best performance in rms with respect to TAO data (24 W m2)

Caractéristiques et résultats issus des données de la plateforme OCARINA

International audienc

Comparison of ECMWF-ERA5 turbulent Air-Sea Fluxes and related environmental variables to data from to the OCARINA wave following platforms

International audienceThe ECMWF-ERA5 reanalysis is amongst the best products to access the hourly state and trend of the global Atmosphere, Wave field, and Ocean over several decades, for many scientists and in many studies. In the proposed presentation, we will compare the turbulent momentum and heat exchange flux values output from the reanalysis to corresponding estimates that were not assimilated in the model. Those estimates were computed from data collected with a wave following platform that was deployed in several basins since 2012, including the Chile-Peru upwelling region in 2014. Not only the fluxes and the bulk variables will be statistically compared, but the focus will also be laid on the sensitivity of the results to the surface current, to the proximity of coast and, where it applies, to the direction of the wind (onshore, offshore and parallel to the coast)

A Nonlinear Statistical Model of Turbulent air-sea Fluxes

Most of the bulk algorithms used to calculate turbulent air-sea fluxes of momentum and heat are iterative algorithms whose convergence is slow and not always achieved. To avoid these drawbacks that are critical when large datasets must be processed, a statistical model of bulk air-sea fluxes based on artificial neural networks was developed. It was found that classical bulk algorithms were slower than the statistical model, by a factor of 1.75-7 depending on the bulk algorithm selected for the comparison. A set of 12 global analyses of an operational meteorological model as well as in situ data corresponding to equatorial and midlatitude conditions were used to assess the accuracy of the proposed model. The wind stress, latent, and sensible heat fluxes calculated with neural networks have acceptable biases with respect to bulk fluxes, between 0.4% and 1% depending on the flux magnitudes. Moreover, the rms deviation between bulk fluxes and neural network flux estimates is only 0.003 N m−2 for the momentum flux, 0.5 W m−2 for the sensible heat flux, and 1.8 W m−2 for the latent heat flux, at global scale, which is small compared with the natural variability of these quantities or the expected error

Expérience CAMPINTER: Résultats de l'analyse du réfractomètre

Note des activités instrumentales de l'IPS

Response of the atmospheric boundary layer to a mesoscale oceanic eddy in the northeast Atlantic

Fields of air-sea turbulent fluxes and bulk variables were derived from satellite sensor data from February to April 2001, over a region of the northeast Atlantic where a field experiment, Programme Oce´an Multidisciplinaire Meso Echelle (POMME), was conducted. The satellite products are in good agreement with in situ data in terms of heat fluxes, sea surface temperature, and wind speed. The central part of the experimental domain presented a cyclonic eddy in the ocean, which corresponded to a cold sea surface temperature (SST) anomaly. Winds were weaker within the eddy than outside of it, with lower latent and sensible heat loss. In order to analyze the relationship between the SST and wind anomalies, three numerical experiments were conducted with a regional atmospheric model. Three 3-month runs of the model were performed, using a realistic SST field, a smoothed SST field in which the cold SST was not present (reference run), and an SST field where the cold anomaly was increased by two degrees, successively. The fields simulated with the realistic SST were consistent with satellite sensor derived observations. In particular, the weak wind area over the cold SST anomaly was successfully rendered, whereas it was not present in the forcing fields. Taken individually, the three runs did not reveal the presence of secondary circulations. However, anomalous secondary circulations were clearly identified with respect to the reference run. The origin of the latter circulations was investigated with the Giordani and Planton generalization of the Sawyer-Eliassen equations. According to our results, differential heating induced by the cold SST anomaly mostly altered the vertical wind through the effect of friction and only marginally through pressure gradient forces. In the upper part of the boundary layer, the wind speed increased (decreased) over (downstream) the cold SST. We found that stability was the main factor that induced the simulated patterns of the friction term in the diagnostic equations. Therefore our results show that mesoscale wind patterns were significantly affected by SST gradients through the effect of stability, in a region of low oceanic eddy activity

Timbalès (Température et Imagerie. Mesures à profondeur Bulk par Avance en Ligne d’une Escadrille à Submeso-échelle)

National audienceNotre projet concerne le développement d’un jeu de dix drones de surface motorisés et coordonnés pour mesurer les variations spatiales de la température de surface de la mer, et fournir pour la première fois des champs de température superficielle de la mer à dix mètres de résolution sur une zone de 50 m x 50 m avec une précision de 0.002°C, et à 10 cm de profondeur, ce qui est sans précédent, au mieux de notre connaissance.On espère ainsi visualiser des variations spatiales de sub-submesoéchelle correspondant soit à des circulations de Langmuir sous l’effet de convergence-divergence du courant de surface généré par le vent, soit à des tourbillons en température, soit à des schémas spatiaux de température de surface correspondant à des risées, à des plumes ou thermiques (wind gustiness), ou à des phénomènes de circulation océanique de surface.Le projet est initié, un prototype a déjà été réalisé, un second prototype est en cours de réalisation, et la demande que nous soumettons ici à LEFE-IMAGO porte sur l’extension du projet à une flotte de dix drones.Référence : Puigserver Cécile, Denis Bourras, Luneau Christopher, Jean-Luc Fuda, Hubert Branger, et al.. Observation des variations spatiales de la SST à sub meso-échelle : quelle stratégie de mesure adopter ? AEI 2019, Atelier d’Expérimentation et d’Instrumentation de l’INSU, Jul 2019, Lille, France. ⟨hal-02373301