Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay     

Jérôme Harlay  Caroline De Bodt  Anja Engel  Sandra Jansen  Quentin d’Hoop  Judith Piontek  Nicolas Van Oostende  Steve Groom  Koen Sabbe  Lei Chou 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(8):1251-1265

The distribution of transparent exopolymer particles (TEP) was investigated during a coccolithophorid bloom in the northern Bay of Biscay (North Atlantic Ocean) in early June 2006. MODIS chlorophyll-a (Chl-a) and reflectance images before and during the cruise were used to localize areas of important biological activity and high reflectance (HR). TEP profiles along the continental margin, determined using microscopic (TEP_micro) and colorimetric (TEP_color) methods, showed abundant (6.1×10⁶–4.4×10⁷ L^?1) and relatively small (0.5–20 μm) particles, leading to a low total volume fraction (0.05–2.2 ppm) of TEP_micro and similar vertical profiles of TEP_color. Estimates of carbon content in TEP (TEP-C) derived from the microscopic approach yielded surface concentration of 1.50 μmol C L^?1. The contribution of TEP-C to particulate organic carbon (POC) was estimated to be 12% (molar C ratio) during this survey. Our results suggest that TEP formation is a probable first step to rapid and efficient export of C during declining coccolithophorid blooms.  相似文献   

Further observations of Hipparcos red stars and standards for  UBV(RI)_C  photometry     

D. Kilkenny  C. Koen  F. van Wyk  F. Marang  D. Cooper 《Monthly notices of the Royal Astronomical Society》2007,380(3):1261-1270

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The analysis of indexed astronomical time series – IX. A period change test     

Chris Koen  Fred Lombard 《Monthly notices of the Royal Astronomical Society》2004,353(1):98-104

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Quantitative estimation of skin soil moisture with the Special Sensor Microwave/Imager   总被引：1，自引：0，他引：1  

Koen De Ridder 《Boundary-Layer Meteorology》2000,96(3):421-432

A physically based retrieval scheme is described toinfer near surface moisture content of bare soilpatches from time series of the Special SensorMicrowave/Imager (SSM/I) Polarisation DifferenceTemperature (PDT) at 19.35 GHz. The PDT is modelled asa function of soil moisture using Fresnel's relationsfor specular reflection at the air-soil boundary,together with a dielectric mixing model for themoisture-dependent soil dielectric constant. Theproblem of the specification of parameters describingatmospheric and soil roughness effects is avoided byconsidering temporal variations of the PDT. Theretrieval method is applied to the FIFE site for atwo-week period in summer, during which heavy rainfalloccurred on a dry upper soil. Although differences insensing depths made a rigorous validation impossible,remotely sensed soil moisture showed a high degree ofconsistency with ground measurements. An erroranalysis shows that the method is capable of providingan accuracy of approximately 20% of moisture contentat field capacity. Finally, it is demonstrated thatthe method is relatively insensitive to soil texturalcharacteristics when moisture content is scaled withfield capacity.  相似文献   

The Urban Heat Island Intensity of Paris: A Case Study Based on a Simple Urban Surface Parametrization   总被引：1，自引：0，他引：1  

Abhijit Sarkar  Koen De Ridder 《Boundary-Layer Meteorology》2011,138(3):511-520

We explore the ability of a simple urban surface parametrization, embedded in a mesoscale meteorological model, to correctly reproduce observed values of the urban heat island (UHI) intensity, which is defined as the urban-rural surface air temperature difference. To do so, a simple urban scheme was incorporated into the Advanced Regional Prediction System (ARPS). Subsequently, a simulation was performed with the coupled model over the wider area of Paris, for a 12-day period in June 2006 that was characterised by conditions prone to UHI development. Simulated 2-m air temperature was compared with observed values for urban and rural stations, yielding mean errors of 1.4 and 1.5 K, respectively. More importantly, it was found that the model also displayed an overall good capability of reproducing the observed temperature differences. In particular, the magnitude (up to 6 K) and timing of the diurnal cycle of the UHI intensity was simulated well, the model exhibiting a mean error of 1.15 K. As a result, our conclusion is that the ARPS model, extended with simple urban surface physics, is able to capture observed urban-rural air temperature differences well, at least for the domain and period studied.  相似文献   

On the hydrodynamics of accretion discs     

Chris Koen 《Astrophysics and Space Science》1988,141(2):347-351

The widely used boundary condition on the tangential stress in accretion discs is discussed and found wanting on a number of counts. In particular, it is shown that the value of the viscous energy dissipation calculated from it is unphysical. An alternative boundary condition is suggested. Using this, it is found that the energy balance in the disc places certain restrictions on the rotational velocity in the disc. It seems unlikely that the latter could be of the Keplerian form.  相似文献   

The DA+dMe eclipsing binary EC13471–1258: its cup runneth over … just     

D. O'Donoghue  C. Koen  D. Kilkenny  R. S. Stobie  D. Koester  M. S. Bessell  N. Hambly  H. MacGillivray 《Monthly notices of the Royal Astronomical Society》2003,345(2):506-528

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The analysis of indexed astronomical time-series – VIII. Cross-correlating noisy autoregressive series     

Chris Koen 《Monthly notices of the Royal Astronomical Society》2003,344(3):798-808

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The analysis of indexed astronomical time series – X. Significance testing of O−C data     

Chris Koen 《Monthly notices of the Royal Astronomical Society》2006,365(2):489-495

It is assumed that   O − C   ('observed minus calculated') values of periodic variable stars are determined by three processes, namely measurement errors, random cycle-to-cycle jitter in the period, and possibly long-term changes in the mean period. By modelling the latter as a random walk, the covariances of all   O − C   values can be calculated. The covariances can then be used to estimate unknown model parameters, and to choose between alternative models. Pseudo-residuals which could be used in model fit assessment are also defined. The theory is illustrated by four applications to spotted stars in eclipsing binaries.  相似文献   

A search for short time-scale JHK variability in ultracool dwarfs     

C. Koen  N. Matsunaga  J. Menzies 《Monthly notices of the Royal Astronomical Society》2004,354(2):466-476

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