National Ocean Service

About: National Ocean Service is a government organization based out in Silver Spring, Maryland, United States. It is known for research contribution in the topics: Algal bloom & Population. The organization has 500 authors who have published 643 publications receiving 46096 citations.

Annual patterns, distribution and long-term trends of Pseudo-nitzschia species in the northern Benguela upwelling system

Abstract: Phytoplankton data obtained from a 14-year data set off the coast of Namibia were analysed. The temporal distribution of species belonging to the diatom genus, Pseudo-nitzschia, was examined using samples collected quasi-monthly at onshore and offshore locations. This data set revealed that Pseudo-nitzschia blooms occurred sporadically along the central coast of Namibia, and cell concentrations frequently exceeded 200 000 cells L−1, with levels close to or exceeding 1 000 000 cells L−1 noted occasionally. Two relatively cold years (2005 and 2010) and three relatively warm years (2001, 2003 and 2011) were found to be exceptional for high biomass Pseudo-nitzschia blooms, so possible drivers (wind, temperature and nutrients) were evaluated. Pseudo-nitzschia species abundance was associated with moderate temperature (13–16°C) and nutrient conditions. Climatology showed an increase in Pseudo-nitzschia blooms during austral summer, reaching a maximum in May, June or July. These blooms seem to initiate following periods of high total phytoplankton concentrations. Wind was determined to play an important role in controlling these blooms. Low biomass Pseudo-nitzschia blooms were observed during months with high or irregular winds that coincided with periods of upwelling, whereas high biomass blooms were associated with the decrease of wind after the main wind peak at the end of summer.

Evaluating the accuracy and uncertainty of atmospheric and wave model hindcasts during severe events using model ensembles

Abstract: Various uncertainties exist in a hindcast due to the inabilities of numerical models to resolve all the complicated atmosphere-sea interactions, and the lack of certain ground truth observations. Here, a comprehensive analysis of an atmospheric model performance in hindcast mode (Hurricane Weather and Research Forecasting model—HWRF) and its 40 ensembles during severe events is conducted, evaluating the model accuracy and uncertainty for hurricane track parameters, and wind speed collected along satellite altimeter tracks and at stationary source point observations. Subsequently, the downstream spectral wave model WAVEWATCH III is forced by two sets of wind field data, each includes 40 members. The first ones are randomly extracted from original HWRF simulations and the second ones are based on spread of best track parameters. The atmospheric model spread and wave model error along satellite altimeters tracks and at stationary source point observations are estimated. The study on Hurricane Irma reveals that wind and wave observations during this extreme event are within ensemble spreads. While both Models have wide spreads over areas with landmass, maximum uncertainty in the atmospheric model is at hurricane eye in contrast to the wave model.