Copernicus Marine Service
OC-TAC - Quality Control and Validation


The objective of the Ocean Monitoring Indicators (OMIs) is to highlight specific events/trends updated in NRT.

It is linked to the contribution of the OCTAC to the Ocean State Report .

At present, there are on-going effort to define new metrics at CMEMS level. In a first step, experimental OMIs are provided by ACRI-ST and are based on the GlobColour-Copernicus Global Chlorophyll products distributed with CMEMS (dataset OCEANCOLOUR_GLO_CHL_L3_NRT_OBSERVATIONS_009_032 and OCEANCOLOUR_GLO_CHL_L3_REP_OBSERVATIONS_009_085).

In the future OMIs will be also provided for the regional areas provided by the OCTAC (Atlantic, Mediterranean, Arctic, BlackSea and Baltic)

The Chlorophyll products (S1) are inter-compared to a monthly climatology (S2) based on the period 1998-2014. Three experimental indicators are computed:

  • Absolute difference: S1 – S2
  • Relative difference: (S1 – S2) / S2
  • Relative difference ponderated by the climatology standard deviation: (S1 – S2) / sigma(S2)

For each indicator, the result is a monthly map which can be displayed from the OMIs/Anomalies tab:

  • The indicator is the difference of a monthly observation product with a monthly climatology observation
  • The indicator is updated on a daily basis based on a sliding monthly product (last 30 days observations compared to a climatology based on the same period).
  • The indicator is based on based on NRT products (available one day after satellite acquisition) and refreshed with consolidated products (available one month after satellite acquisition using better atmospheric inputs). See the OCTAC Product User Manual for more details.

From these maps, a times series covering the period [1998-present] is daily updated for each indicator:

  • It is based on the median and percentile 16 and 84 of the maps (considering a sinusoidal projection to avoid an over-estimation of high latitude.

These time-series are completed by a plot showing S1 and S2 on the same plot.