Longitude

About: Longitude is a research topic. Over the lifetime, 2260 publications have been published within this topic receiving 54988 citations. The topic is also known as: angle of longitude.

A high-resolution satellite-derived sea surface temperature climatology for the western North Atlantic Ocean

Abstract: Long-term and high-resolution (∼1.2 km) satellite-derived sea surface temperature (SST) fields of a monthly mean time series for the 1985–1999 period, and a daily climatology have been calculated for the North West Atlantic Ocean. The SST fields extend from 78°W to 41°W in longitude, and 30°N to 56°N in latitude, encompassing the region off Cape Hatteras, North Carolina, to the southern Labrador Sea. The monthly mean time series, consists of 180 cloud-masked monthly mean SST fields, derived from a full-resolution NOAA/NASA Pathfinder SST data set for the 1985–1999 period. The satellite-derived monthly mean SST fields, as compared with in situ monthly mean near-surface ocean temperatures from buoys located in the western North Atlantic, yield an overall RMS difference of 1.15 °C. The daily climatology, which consists of 365 fields, was derived by applying a least-squares harmonic regression technique on the monthly mean SST time series for the full study period. The monthly mean and daily climatological SST fields will be useful for studying inter-annual variability related to climate variability of SST over the study domain.

Algorithm for Autonomous Longitude and Eccentricity Control for Geostationary Spacecraft

Abstract: To lower satellite orbital maintenance cost, spacecraft designers are seeking flight software that provides more autonomy. Longitude and eccentricity are good candidates for autonomous control of geostationary spacecraft.The algorithm presented couples longitude control with eccentricity control. Longitude drift is modeled as onedegree-of-freedom motion and controlled with a quadratic equation predicting the subspacecraft Earth reference longitude after a predetermined amount of time. After formulation of the basic longitude control algorithm, addition of a differential corrections scheme resulted in an improved longitude error of ′0.015° longitude. Finally, implementation of longitude control and two-part maneuvers for eccentricity control successfully met the desired mission constraints. The algorithms developed form the basis for preparation of flight software for a geostationary spacecraft scheduled to launch in the next few years.

Variability of the Pacific North Equatorial Current and its implications on Japanese eel (Anguilla japonica) larval migration

Abstract: The zonal velocity produced by a Regional Ocean Modeling System (ROMS)-based Pacific Ocean circulation model was validated against in situ measurements along the 137 degrees E longitude. The Pacific model successfully reproduced the position and the shape of the North Equatorial Current (NEC) as well as the latitude of maximum surface velocity in the NEC region (8-17 degrees N). The flow field produced by the Pacific model was then used to conduct numerical Lagrangian experiments, in which passive particles were released along a transect (142.5 degrees E, 12.5-17 degrees N) that traverses the known Japanese eel spawning area, and the effects of NEC strength and bifurcation latitude on the particle advection in the northwest Pacific were studied. Our results suggest that, in the 20-yr period (1993-2012), the variability of the currents alone can cause interannual variability of one order of magnitude in the Kuroshio Entrance (KE), the percentage of particles entering the Kuroshio, the range of which varies from 43% in 1997 to 6% in 2012. The yearly-averaged KE is not sensitive to the NEC bifurcation latitude. Instead, it is controlled by the average zonal velocity of a fixed domain (125-143 degrees E, 13.5-17 degrees N) and related to a recently-developed climate index, the Philippines-Taiwan Oscillation (PTO). During the positive phase of the PTO, the zonal velocity in the domain, hence the yearly-averaged KE, increases, and the opposite is true in the negative phase of the PTO. Considering only the trajectories, diel vertical migrations (DVM) in the top 400 m do not significantly affect Japanese eel larval transport, as incorporating DVM schemes does not increase the KE.

Seismic reflections from beneath the ocean floor

Abstract: Apparatus and procedures are described with which seismic reflections have been obtained from the ocean bottom and from deeper horizons. The area surveyed lies between Bermuda, the Greater Antilles, and the United States. All records obtained in an east-west strip, 70 to 80 mi wide, extending from 61° W longitude south of Bermuda to 71° W longitude and thence southward as a strip 200 to 300 mi wide to about 23° N latitude, show a single prominent reflecting horizon at depths exceeding 500 ft below the bottom (assuming the seismic velocity in the bottom sediment to be equal to or greater than that of sea water). In this area the bathymetric data indicate that the bottom is either flat or relatively smooth. The records from other parts of the area are, with few exceptions, more complicated, correlating with bathymetric evidence of a rougher bottom there. A system is outlined for classifying reflection records obtained in deep water with suggested geologic significance of the various record types.