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Data Record
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0
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dsr_time
Nadir UTC time
in MJD format The
(nadir and forward view)
instrument data contributing
to a given cell or sub-cell
may cover a range of up to
150 seconds of
measurement times. It is
therefore not possible to
assign a unique time tag to
an AST record, and the time
tag is therefore
arbitrarily assigned as
follows. The
��nadir
time��
associated with a given AST
record represents the
scan time of a nadir pixel
contributing to the record.
In general this is the time
of the first filled pixel
encountered during
processing that falls within
the geometrical boundary of
the cell or sub-cell (see
link), although exception
cases may arise. Because
the cell boundaries bear no
clear geometrical
relationship to the AATSR
instrument scan it is not
possible to state in general
that this
corresponds to a particular
corner of the cell or
sub-cell. Note also that if
a cell is intersected by
coastline, so that it
contains both land and sea
pixels, the time tag of a
given record does not
necessarily correspond to a
pixel of the same surface type.
|
MJD |
1 |
mjd |
12 byte(s) |
|
1
|
quality_flag
Quality
Indicator (-1 for blank MDSR, 0
otherwise) This
field is set to -1 if all
the measurement values in
the record are invalid, and
is set to 0 otherwise.
|
flag |
1 |
BooleanFlag |
1 byte(s) |
|
2
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spare_1
Spare |
- |
1 |
SpareField |
3 byte(s) |
|
3
|
lat
Latitude of cell
The latitude of the lower
left-hand corner of the
cell, in units of
micro-degrees. The latitude
is defined in the range -90
degrees to +90 degrees. [If
the cell contains no valid
data, this field may be set
to the exceptional value
-399,999,999.?? This case
may not arise for the full cell.]
|
(1e-6) degrees |
1 |
GeoCoordinate |
4 byte(s) |
|
4
|
lon
Longitude of
cell The longitude
of the lower left-hand
corner of the cell, in units
of micro-degrees. The
longitude is defined in the
range -180 degrees
to +180 degrees.
|
(1e-6) degrees |
1 |
GeoCoordinate |
4 byte(s) |
|
5
|
m_actrk_pix_num
Mean
across-track pixel number
A weighted mean pixel
index of the nadir view
clear sea pixels that fall
within the cell and
contribute to the average.
This quantity is
derived by averaging the
mean across-track pixel
number (q.v.) over those
sub-cells which contain
sufficient valid pixels
to contribute to the
averaged SST in the cell.
|
- |
1 |
ss |
2 byte(s) |
|
6
|
m_nad
mean nadir-only
SST The mean sea
surface temperature (SST)
for the cell derived using
only data in the nadir view.
It is derived by averaging
the mean
nadir-only SST (q.v.) for
each of the (up to) 9
sub-cells that fall within
the cell and that contain
more than a minimum number
of valid clear sea
pixels. If none of the
contributing sub-cells
contains sufficient valid
pixels, the field is set to
the exceptional
value -1.
|
K/100 |
1 |
ss |
2 byte(s) |
|
7
|
sd_nad
standard
deviation of nadir-only SST
The standard deviation of
the mean nadir-only SST of
the contributing sub-cells.
|
K/100 |
1 |
ss |
2 byte(s) |
|
8
|
pix_nad
Number of pixels
in nadir-only average
The number of valid 11
and 12 micron pixels
contributing to the ABT
determination in the cell.
This will usually be the
same as the number
of valid 11 and 12 micron
pixels contributing to the
mean nadir-only SST
determination in the cell,
although if any
sub-cells contain too few
valid pixels to contribute
to the averaged SST, the
numbers may differ. In
general the numbers of valid
pixels in the 11 and 12
micron channels are expected
to be the same; if they
differ, the lower is given here.
|
- |
1 |
us |
2 byte(s) |
|
9
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m_dual_vw
mean dual-view
SST The mean sea
surface temperature (SST)
for the cell derived using
data from both nadir and
forward views. It is derived
by averaging the
mean dual view SST (q.v.)
for each of the (up to) 9
sub-cells that fall within
the cell and that contain
more than a
minimum number of valid
clear sea pixels. If none of
the contributing sub-cells
contains sufficient valid
pixels, the field is set to
the exceptional value -1.
|
K/100 |
1 |
ss |
2 byte(s) |
|
10
|
sd_dual_vw
standard
deviation of dual-view SST
The standard deviation of
the mean dual view SST of
the contributing sub-cells.
|
K/100 |
1 |
ss |
2 byte(s) |
|
11
|
pix_dual_vw
Number of pixels
in dual view average
The number of valid 11
and 12 micron pixels
contributing to the ABT
determination in the cell.
This will usually be the
same as the number
of valid 11 and 12 micron
pixels contributing to the
mean nadir-only SST
determination in the cell,
although if any
sub-cells contain too few
valid pixels to contribute
to the averaged SST, the
numbers may differ. The
numbers of valid pixels in
the different
channel and view
combinations are not
necessarily equal. When they
differ, the lowest is given here.
|
- |
1 |
us |
2 byte(s) |
|
12
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ast_conf_flags
AST confidence
word A 16-bit word
containing confidence flags
for the record. Bits 0 to 3
are set to indicate whether
or not 3.7 micron channel
data was used in
the SST retrieval, and
whether or not day-time data
contributes to the retrieved
temperatures. The detailed
interpretation of these bits
is defined in the table
below. Bits 4 to 31 are
currently unused.
|
flags |
2 |
us |
2*2 byte(s) |
|
13
|
cl_top_temp_nad
Cloud-top
temperature, nadir view
An estimate of the
cloud-top temperature in the
half-degree cell. This
estimate is derived by
generating a histogram of
the 11 micron
brightness temperatures of
cloudy sea pixels within the
cell in the nadir view, and
averaging the brightness
temperatures of
the lowest quartile. The
estimate is derived from sea
pixels only.
|
K/100 |
1 |
ss |
2 byte(s) |
|
14
|
perc_cl_cov_nad
Percentage
cloud-cover, nadir view
The fraction of nadir
view sea pixels within the
cell that are cloudy,
expressed as a percentage in
units of 0.01%.
|
%/100 |
1 |
ss |
2 byte(s) |
|
15
|
cl_top_temp_for
Cloud-top
temperature, forward view
An estimate of the
cloud-top temperature in the
half-degree cell. This
estimate is derived by
generating a histogram of
the 11 micron
brightness temperatures of
cloudy sea pixels within the
cell in the forward view,
and averaging the brightness
temperatures of
the lowest quartile. The
estimate is derived from sea
pixels only.
|
K/100 |
1 |
ss |
2 byte(s) |
|
16
|
perc_cl_cov_for
Percentage
cloud-cover, forward view
The fraction of forward
view sea pixels within the
cell that are cloudy,
expressed as a percentage in
units of 0.01%.
|
%/100 |
1 |
ss |
2 byte(s) |
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