Project Deliverable D50 Report on Best Practices ... - ESONET NoE

Common topics on time series analysis (Henry Ruhl)
•Common issues to consider when analysing time-series data include comparing results from
studies that look at different scales (e.g. seasonal versus interannual); secular trends and
detrending time series; trends over sub-sections of time series; aliasing such as when data is
unevenly distributed across time; gap filling; empirical, dynamical, hindcasting, forecasting,
and jackknife modelling techniques; correcting for calibration; serial autocorrelation; nonlinear
vs. linear behaviour in observations; parametric and non-parametric assumptions;
multidimensional analysis; and understanding the spatial applicability of times-series data
from one or a network of instruments (e.g. Sokal and Rohlf 1981, Hurlbert 1984, Heikkilai
1988, Clarke 1993, Pyper and Peterman 1998, Clarke Warwick 2001, Perry and Liebhold
2002, Quinn and Keough 2002, Buckland et al. 2007)
An example of gap filling can be found in Smith et al. (2009). The figure 2 below illustrates
particulate organic carbon flux measured using sediment traps (food supply for benthic
community) in the northeast Pacific where black, green, orange, and blue time-series lines
representing a composite of POCF estimates from 50 mab (black) and 600 mab (green)
sediment traps, as well as model-estimated flux combining climate indicators, the Laws
(2004) export flux model and the vertically generalized production model (Behrenfeld and
Falkowski 1997) (orange) and the carbon-based production model (Behrenfeld et al. 2006)
(blue) where possible. The red dashed line is model data that is unincorporated into the
composite (sensu Smith et al. 2006). The difference between the red dashed line and the black
line indicates how well the model estimates correspond to measured POC flux values at 50
mab, thus are an indicator of gap filling quality.
Examples of data acquired on mooring (bottom fixed platform)
Author: Ingrid Puillat (IFREMER)
Full version in Annex F1
Abstract: The example of ELISA one-year sub surface mooring data is presented. This
mooring fixed on the bottom was reaching the surface layer near 20m depths. Four
autonomous CTD + fluorimeter and a current-meter acquired data during one year between
the surface and ~100m. The time series were interrupted several times due to 2 mooring
<strong>Deliverable</strong> #50 - update October 2010 21