Integration of a relocatable ocean model in the Mediterranean Forecasting System

International audienceThe MFS (Mediterranean Forecasting System) project and its follower MFSTEP (Mediterranean ocean Forecasting System?Towards Environmental Prediction) are being covering the Mediterranean Sea with operational Ocean General Circulation Models (OGCMs) at horizontal resolution varying from about 12 km till 2005 to 6.5 km in 2006 (reaching 3 km with some regional models and 1.5 km for few shelf models). Heat, water and momentum fluxes through the air-sea interface are derived from the European Center for Medium-range Weather Forecast (ECMWF) output at 0.5° horizontal resolution. Such horizontal resolutions could be not able to provide the needed forecast accuracy in some cases (localized emergencies at sea, e.g. oil spill; need for high resolution current forecasts, e.g. offshore works). A solution to this problem is represented by relocatable models able to be rapidly deployed and to produce forecasts starting from the MFS products. The Harvard Ocean Prediction System (HOPS) has been chosen as base of the relocatable model and it has been interfaced with the MFSTEP OGCM and one regional model. The relocatable model has demonstrated capability to produce forecasts within 2-3 days in many cases, and more rapid implementation may be obtained

Frequency-noise measurements of optical frequency combs by multiple fringe-side discriminator

open5noThe frequency noise of an optical frequency comb is routinely measured through the hetherodyne beat of one comb tooth against a stable continuous-wave laser. After frequency-to-voltage conversion, the beatnote is sent to a spectrum analyzer to retrive the power spectral density of the frequency noise. Because narrow-linewidth continuous-wave lasers are available only at certain wavelengths, heterodyning the comb tooth can be challenging. We present a new technique for direct characterization of the frequency noise of an optical frequency comb, requiring no supplementary reference lasers and easily applicable in all spectral regions from the terahertz to the ultraviolet. The technique is based on the combination of a low finesse Fabry-Perot resonator and the so-called "fringe-side locking" method, usually adopted to characterize the spectral purity of single-frequency lasers, here generalized to optical frequency combs. The effectiveness of this technique is demonstrated with an Er-fiber comb source across the wavelength range from 1 to 2 μm.Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, GianlucaColuccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluc

47-fs Kerr-lens mode-locked Cr:ZnSe laser with high spectral purity

We report on a room-temperature Kerr-lens mode-locked Cr:ZnSe femtosecond laser operating at around 2.4 µm emission wavelength. Self-starting nearly transform-limited pulse trains with a minimum duration of 47 fs, corresponding to six optical cycles, and average output power of 0.25 W are obtained with repetition frequencies in the range from 140 to 300 MHz. The femtosecond pulse train is characterized by high-spectral purity and low time jitter

The optical frequency comb fibre spectrometer

Optical frequency comb sources provide thousands of precise and accurate optical lines in a single device enabling the broadband and high-speed detection required in many applications. A main challenge is to parallelize the detection over the widest possible band while bringing the resolution to the single comb-line level. Here we propose a solution based on the combination of a frequency comb source and a fibre spectrometer, exploiting all-fibre technology. Our system allows for simultaneous measurement of 500 isolated comb lines over a span of 0.12 THz in a single acquisition; arbitrarily larger span are demonstrated (3,500 comb lines over 0.85 THz) by doing sequential acquisitions. The potential for precision measurements is proved by spectroscopy of acetylene at 1.53 μm. Being based on all-fibre technology, our system is inherently low-cost, lightweight and may lead to the development of a new class of broadband high-resolution spectrometers

Diode-pumped passively mode-locked Yb:YLF laser.

We demonstrate passive mode-locking by means of a semiconductor saturable-absorber mirror in a diode-pumped Yb:YLF laser. We present crystal growth process, spectroscopic measurements, and investigation of mode-locking performance. Pulse trains with minimum duration of 196 fs, average power of 54 mW and a repetition rate of 55 MHz were obtained. The optical spectrum, centered at 1028 nm, has a 7.1-nm bandwidth leading to nearly transform-limited pulses. (C) 2008 Optical Society of America

S1 stanica, rijeka Po: rukovanje podacima i prikaz podataka

The technical setting of the mete-oceanographic buoy at site S1 south of the Po River delta is presented. The station was deployed by Istituto di Scienze Marine (ISMAR) of CNR of Bologna, in cooperation with the local Regional Government and Environmental Agencies (ARPA) of E. Romagna, and ADRICOSM. The buoy mooring and data flow architecture is discussed, with some emphasis on the WWW data presentation. The possible integration with other remote stations, data and mete-oceanographic operational activities is also proposed.U radu je predstavljen tehnički postav meteorološko-oceanografske plutače na položaju S1 južno od delte rijeke Po. Stanicu su postavili ISMAR CNR iz Bolonje, u suradnji s lokalnom agencijom za zaštitu okoliša (ARPA) iz pokrajine Emilia-Romagna i ADRICOSM-om. Diskutirana su sama struktura plutače i arhitektura tijeka podataka s naglaskom na prikaz podataka na web-u. Predložena je, također, i moguća integracija s ostalim postajama, izvorima podataka i ostalim operativnim meteorološko-oceanografskim aktivnostima

ADRICOSM pilot projekt: Sustav predviđanja u obalnim područjima i riječnim bazenima Jadranskog mora

The ADRICOSM project was launched in October 2001, and ended in March 2005, with the main objective of demonstrating the feasibility of a near real time operational marine monitoring and forecasting system at the shelf and coastal scales, with connections to river basin runoff and coastal town sewer systems. The basic system consisted of an efficient network for the collection of marine data such as in situ temperature and salinity profiles and satellite sea surface temperature, a regional (AREG) and shelf scale modeling system, a data assimilation system and finally a coastal scale modeling system. Every week AREG releases 7 day marine forecasts at 5 km horizontal scales, which are used to nest other hydrodynamic models toward the coastal scale. Two shelf models (ASHELF-1 and ASHELF-2) at a 1.5 km horizontal scale were nested in AREG in order to simulate (and in the future to forecast) shelf scale oceanographic features. Another important aspect of ADRICOSM was the integration of the Cetina river (Croatia) and urban sewage monitoring/ modeling (Split, Croatia) systems with the shelf marine model. This integrated model system was used to simulate the dispersion of sewer discharges from the urban area in the coastal waters for water management performance studies. ADRICOSM is one of the first integrated land and marine waters operational oceanographic systems able to meet the urgent needs for reliable integrated coastal forecasts for the effective management of marine areas.Projekt ADRICOSM započeo je u listopadu 2001. i završio u ožujku 2005. godine. Glavni je cilj projekta bio pokazati mogućnosti operacionalizacije monitoringa i prognoze u skoro realnom vremenu na šelfu te u obalnim područjima koja su povezana s riječnim bazenima i gradskim otpadnim vodama. Sustav je bio opremljen efikasnom mrežom sakupljanja podataka izmjerenih u moru kao što su profili temperature i saliniteta te satelitske površinske temperature mora, regionalnim jadranskim modelom (AREG) i modelom na skali šelfa, sustavom asimilacije podataka te konačno, obalnim modelom. Svaki tjedan AREG je izrađivao 7-dnevnu oceanografsku prognozu na horizontalnoj skali od 5 km koja je upotrebljavana za gniježđenje drugih hidrodinamičkih modela duž obale. Dva modela na šelfu (ASHELF-1 i ASHELF-2) horizontalne rezolucije od 1.5 km ugniježđeni su u jadranski AREG model s ciljem simuliranja (te u budućnosti i prognoziranja) oceanografskih osobina šelfa. Drugi važan aspekt ADRICOSM projekta bio je integracija monitoringa i modeliranja dotoka rijekom Cetinom i sustavom otpadnih voda s oceanografskim modelom šelfa. Ovaj je integracijski sustav upotrebljen za simuliranje disperzije urbanih otpadnih voda u obalnom području. Projekt ADRICOSM je jedan od prvih integracijskih sustava kojim se za potrebe operativne oceanografije i prognoze ujedinjuju obalne vode s dotocima s kopna s ciljem efikasnog upravljanja obalnim područjima

250-MHz synchronously pumped optical parametric oscillator at 2.25-2.6 {\mu}m and 4.1-4.9 {\mu}m

A compact and versatile femtosecond mid-IR source is presented, based on an optical parametric oscillator (OPO) synchronously pumped by a commercial 250-MHz Er:fiber laser. The mid-IR spectrum can be tuned in the range 2.25-2.6 \mu m (signal) and 4.1-4.9 \mu m (idler), with average power from 20 to 60 mW. At 2.5 \mu m a minimum pulse duration of 110 fs and a power of 40 mW have been obtained. Active stabilization of the OPO cavity length has been achieved in the whole tuning range

Broadband Fourier-transform coherent Raman spectroscopy with an ytterbium fiber laser.

We demonstrate a Fourier transform (FT) coherent anti-Stokes Raman scattering (CARS) spectroscopy system based on fiber technology with ultra-broad spectral coverage and high-sensitivity. A femtosecond ytterbium fiber oscillator is amplified and spectrally broadened in a photonic crystal fiber to synthesize pulses with energy of 14 nJ at 1040 nm, that are compressed to durations below 20 fs. The resulting pulse train is coupled to a FT-CARS interferometer enabling measurement of high-quality CARS spectra with Raman shifts of ~3000 cm−1 and signal to noise ratio up to 240 and 690 with acetonitrile and polystyrene samples, respectively, for observation times of 160 µs; a detection limit of one part per thousand is demonstrated with a cyanide/water solution. The system has the potential to detect trace contaminants in water as well as other broadband high-sensitivity CARS spectroscopy applications

Passive mode locking of a Tm,Ho:KY(WO4)(2) laser around 2 μm

We report the first demonstration, to our knowledge, of passive mode locking in a Tm3+, Ho3+-codoped KYWO42 laser operating in the 2000-2060 nm spectral region. An InGaAsSb-based quantum well semiconductor saturable absorber mirror is used for the initiation and stabilization of the ultrashort pulse generation. Pulses as short as 3.3 ps were generated at 2057 nm with average output powers up to 315 mW at a pulse repetition frequency of 132 MHz for 1.15 W of absorbed pump power at 802 nm from a Ti:sapphire laser