NOOS sea level error statistics, 2008-2012

Data handling

We process five calendar years of tide gauge data and modelled sea level: 2008-2012.

Tide gauge data is retrieved thru the DMI MySQL data base. Data is collected in real time.

Model data is retrieved from DMIs NOOS Exchange Archive. Partners issue forecasts on an N= 6-, 12-, or 24 hour schedule. We establish one-year time series by concatenating all forecasts, using only the part ranging from analysis time and N hours ahead. If a forecast is missing, N more hours of the previous forecast is used to bridge the gap. If two or more consecutive forecasts are missing, this is repeated if possible.

All data, tide gauge and model, is interpolated or sampled onto 10-minute series.


Tide gauge data QC checks for large jumps and spurious zeroes. frc-obs difference time series and scatter diagrams are inspected visually, in order to get rid of any remaining suspicious data.

Forecasts are QC'ed for utter crap. (This happens). Files with format overflow or wrong time stamps are discarded.

Error measures

We examine For peaks, we use the using 10 highest observed, with a minimum time separation of 12 hours. Forecasted peak must lie within -/+ 6 hours from the time of the observed peak.


Skewness, peaks, hit rate, peak hit rate and worst case are examined twice: when the bias for the year/station in question is subtracted.

Bias may appear either as a general off-set, or by different representation of low waters only. The latter happens typically when tide gauge data is skewed. In that case, unbiasing will not lead to a better forecast.

Average statistics for all stations

All stations

Pick an error measure

data coverage mean sea level range skewness variance peaks hit rate peak hit rate worst case

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TorsmindeKyst Esbjerg Vidaa Wick Aberdeen Immingham Lowestoft NorthShields Sheerness Helgoland Cuxhaven Borkum Bremerhaven Husum HoekVanHolland Vlissingen RoompotBuiten IJmuiden DenHelder Delfzijl Tregde Stavanger Oostende