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Definitions for global map plots
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Global plots of various diagnostics, for processed near-real time AATSR
data, are produced daily.
These global plots are produced by averaging the 10 arc minute data
to a 1 degree resolution. Global plots displaying
the averaged data over the previous month are also displayed. Only
SSTs
which pass certain quality control tests are included in these analyses:
they must be deemed to not be cloud contaminated, from threshold
tests
against the number of pixels contributing to each cell, and from threshold
tests against climate datasets. Checks are also performed to test
for
the presence of ice in the cell, with positive results rejected. Finally,
a mean global offset is added to the SST, differing for 2-channel
and 3-channel retrievals, to correct for mean biases observed between
the retrieval algorithms and against in situ SST data. Explanations
of the different plots produced are given below.
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The skin SST (the temperature of the ocean in the top couple of
millimetres) is estimated from AATSR brightness
temperatures. These skin SSTs are then used to estimate the bulk
(or sub-surface) SST at approximately one metre below the sea surface
using a skin effect model applied at the Met Office. Global maps
of these SSTs are displayed. Details of the form of the plotted
maps are listed:
- Bulk (sub-surface) SST originating from skin observations using
dual-view 2-channel retrieval algorithms (day & night).
- Bulk (sub-surface) SST originating from skin observations using
dual-view 3-channel retrieval algorithms (night only).
- Skin SST from dual-view, 2-channel retrieval algorithms (day
and night observations).
- Skin SST from dual-view, 3-channel retrieval algorithms (night
observations only).
In addition, global maps of the ESA supplied dual-view skin SST
are also plotted. Mean global offsets are not added to these SSTs.
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| Comparisons with HadISST1 |
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Global maps are produced where the bulk SST estimated
at the Met Office is compared against the 1
degree
HadISST1 dataset. Global maps of the means over each grid box
are displayed. Similar maps are produced for comparisons of
the
ESA supplied skin SST product against HadISST1.
The bulk SST field used within the comparisons is formed by combining
the day-time bulk SST 2-channel retrievals with the night-time
bulk
SST 3-channel retrievals, only when a good skin deltaT (the modelled
difference between the skin and bulk SSTs) has been calculated.
The HadISST1 dataset comprises both insitu and AVHRR observations
interpolated into 1 degree grid boxes and is supplied in monthly
files, with a month's delay. Follow this link
for more information on Met Office climate datasets.
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