Triple annual maximum series in wave climate analyses

A recurring problem in wave climate analyses is the need to predict long term events from short duration records. The relative sparsity of the observational record is enhanced by judicious recognition of near-maximum events, in addition to the annual maximum events. This paper pursues the application of triple annual maximum series. Given any extreme value distribution, the theoretical distributions for the annual second largest monthly wave and the annual third largest monthly wave are established. A maximum likelihood method is proposed to fit these simultaneous distributions to the triple annual maximum series. An application of the method to the historical record at the Farallon Is. off San Francisco adopts several of the more common extreme value distributions and demonstrates the potential of triple annual maximum series in enhancing the reliability of distribution fits. Nevertheless, the common practice of extrapolating short duration records to long term events remains precarious.     

Seasonal and interannual variation of the phytoplankton and copepod dynamics in Liverpool Bay

The seasonal and interannual variability in the phytoplankton community in Liverpool Bay between 2003 and 2009 has been examined using results from high frequency, in situ measurements combined with discrete samples collected at one location in the bay. The spring phytoplankton bloom (up to 29.4 mg chlorophyll m⁻³) is an annual feature at the study site and its timing may vary by up to 50 days between years. The variability in the underwater light climate and turbulent mixing are identified as key factors controlling the timing of phytoplankton blooms. Modelled average annual gross and net production are estimated to be 223 and 56 g C m⁻² year⁻¹, respectively. Light microscope counts showed that the phytoplankton community is dominated by diatoms, with dinoflagellates appearing annually for short periods of time between July and October. The zooplankton community at the study site is dominated by copepods and use of a fine mesh (80 μm) resulted in higher abundances of copepods determined (up to 2.5 × 10⁶ ind. m⁻²) than has previously reported for this location. There is a strong seasonal cycle in copepod biomass and copepods greater than 270 μm contribute less than 10% of the total biomass. Seasonal trends in copepod biomass lag those in the phytoplankton community with a delay of 3 to 4 months between the maximum phytoplankton biomass and the maximum copepod biomass. Grazing by copepods exceeds net primary production at the site and indicates that an additional advective supply of carbon is required to support the copepod community.