Naval Postgraduate School

About: Naval Postgraduate School is a education organization based out in Monterey, California, United States. It is known for research contribution in the topics: Tropical cyclone & Nonlinear system. The organization has 5246 authors who have published 11614 publications receiving 298300 citations. The organization is also known as: NPS & U.S. Naval Postgraduate School.

Sulphur hexafluoride as a tracer of biogeochemical and physical processes in an open-ocean iron fertilisation experiment

Abstract: The first open-ocean experiment to test the iron hypothesis in the equatorial Pacific was undertaken using the tracer gas sulphur hexafluoride (SF 6 ) to locate and track the fertilised surface water. Continuous surface measurements showed that the SF 6 patch spread rapidly in the first 24 h, from an initial release area of ∼64 km 2 to a total area of 214 km 2 , and remained relatively constant in size for the following three-day period. SF 6 data was mapped in a Lagrangian frame of reference by the use of a drogued GPS buoy released at the centre of the patch. The SF 6 patch remained coherent and exhibited a slow, anti-cyclonic oscillation during the first four days. The buoy was transported downwind of the patch in a northwesterly direction within two days, which has implications for the future use of buoys in surface-water advection studies. Following subduction below a low-salinity front 3–4 days after release, the patch centre was relocated by its SF 6 signal at a depth of 25–30 m to the east of the residual surface patch. The latter spread rapidly to the southwest during the remainder of the experiment, whilst the subducted patch remained relatively stationary. Density-corrected SF 6 profiles were used to calculate a mean vertical eddy diffusivity of 0.25 cm 2 /s across the thermocline following the subduction event. A vertical flux of nitrate of 2.5 mmol/m -2 d -1 into the mixed layer was estimated, which implied an f -ratio value of 0.4 on comparison with productivity data. The results demonstrate that SF 6 is a successful tracer of water masses, and emphasise the potential of this technique for the in situ measurement and manipulation of open-ocean processes.

Downstream development associated with the extratropical transition of tropical cyclones over the western North Pacific

Abstract: The movement of a tropical cyclone into the midlatitudes involves interactions among many complex physical processes over a variety of space and time scales. Furthermore, the extratropical transition (ET) of a tropical cyclone may also result in a high-amplitude Rossby wave response that can extend to near-hemispheric scales. After an ET event occurs over the western portion of a Northern Hemisphere ocean basin, the high-amplitude downstream response often forces anomalous midlatitude circulations for periods of days to a week. These circulations may then be related to high-impact weather events far downstream of the forcing by the ET event. In this study, downstream development following ET events over the western North Pacific Ocean is examined. Local eddy kinetic energy analyses are conducted on four cases of North Pacific tropical cyclones of varying characteristics during ET into varying midlatitude flow characteristics during 15 July–30 September 2005. The goal is to examine the impact of e...

Reexamining the Vertical Development of Tornadic Vortex Signatures in Supercells

Abstract: Observations from a hybrid phased-array Doppler radar, the Mobile Weather Radar, 2005 X-band, Phased Array (MWR-05XP), were used to investigate the vertical development of tornadic vortex signatures (TVSs) during supercell tornadogenesis. Data with volumetric update times of ∼10 s, an order of magnitude better than that of most other mobile Doppler radars, were obtained up to storm midlevels during the formation of three tornadoes. It is found that TVSs formed upward with time during tornadogenesis for two cases. In a third case, missing low-level data prevented a complete time–height analysis of TVS development; however, TVS formation occurred first near the ground and then at storm midlevels several minutes later. These results are consistent with the small number of volumetric mobile Doppler radar tornadogenesis cases from the past ∼10 years, but counter to studies prior to that, in which a descending TVS was observed in roughly half of tornado cases utilizing Weather Surveillance Radar-1988 Do...

A decision support system for purchasing management of large projects

Abstract: This paper describes a model based Decision Support System (DSS) for purchasing materials and components for large projects. The DSS may be used under two scenarios. Under the first scenario, we have a project to execute, and we are looking for a good way to manage the purchasing to minimize the expected costs. The decisions under our control are when and from whom to order each item. Under the other scenario, we are bidding for the project, and wish to assess the costs associated with the purchasing decisions which we should consider before making our bid. In both cases, we take into account expected out of pocket costs as well as lateness and/or expediting penalties. The DSS is designed to help choose the best supplier for each item and schedule the placement of the orders—decisions which are very difficult to make well without such a model based DSS.

Millimeter-Wave Fin-Line Characteristics

Abstract: This paper presents an analysis of the fin line. The spectral-domain technique is used to determine both wavelength and characteristic impedance. Numerical results are compared with known data for ridged waveguide slab-loaded waveguide, and slotline. Design curves are presented for practical millimeter-wave fin line structures.