ICOADS Web information page (Monday, 28-Apr-2014 17:39:41 UTC):

Release 1 NCDC Landlocked and Limits: GrADS Files

The NCDC quality control ("NCDC-QC") processing step was originally described in supp. J of COADS Release 1 (Slutz et al., 1985) as:

"...an important part of the duplicate elimination program (described in supp. K) because it provides a measure, in the form of a quality code, to judge which report among duplicates is retained. The quality code assigned to each report is the sum of the weights associated with the 14 flags given by Table J0-1, where the weight and the general meaning of each possible flag value is given by Table J0-2."
For this NCDC-QC step, which remains an important part of ICOADS processing, an "NCDC Landlocked and Limits" file (supplied by NCDC in 1981) provided the 5°x5° box long-term monthly means and standard deviations needed to assign L (suspect) and Q (erroneous) flags, on the condition that number of observations per box is at least 25.

For easier use, we reformatted the limits part of the NCDC Landlocked and Limits file into data (and control; ctl) files in the Grid Analysis and Display System (GrADS) format. The 1° landmask (LNDLMT) part of this file can be viewed and accessed on this separate webpage.

1. GrADS files

The first part of each file name indicates the variable:

air air temperature
dpt dew point temperature
slp sea level pressure
sst sea surface temperature
wbt wet bulb temperature

and the second part of the file name indicates the statistic:

mean mean
nobs number of observations
stddev standard deviation

Following are links to the GrADS data (compressed) and control files:

air.mean.ctl air.mean.dat.gz air.nobs.ctl air.nobs.dat.gz air.stddev.ctl air.stddev.dat.gz
dpt.mean.ctl dpt.mean.dat.gz dpt.nobs.ctl dpt.nobs.dat.gz dpt.stddev.ctl dpt.stddev.dat.gz
slp.mean.ctl slp.mean.dat.gz slp.nobs.ctl slp.nobs.dat.gz slp.stddev.ctl slp.stddev.dat.gz
sst.mean.ctl sst.mean.dat.gz sst.nobs.ctl sst.nobs.dat.gz sst.stddev.ctl sst.stddev.dat.gz
wbt.mean.ctl wbt.mean.dat.gz wbt.nobs.ctl wbt.nobs.dat.gz wbt.stddev.ctl wbt.stddev.dat.gz

2. Sample plots

JAN slp mean JAN slp nobs JAN slp stddev
JAN air mean JAN air nobs JAN air stddev
JAN wbt mean JAN wbt nobs JAN wbt stddev
JAN dpt mean JAN dpt nobs JAN dpt stddev
JAN sst mean JAN sst nobs JAN sst stddev
Figure 1. January values, including all extant 5°x5° boxes (i.e. >0 nobs), for sea level pressure (slp), air temperature (air), web bulb temperature (wbt), dew point temperature (dpt), and sea surface temperature (sst). The values are plotted separately for the three statistics mean, number of observations (nobs), and standard deviation (stddev) from left to right.

JAN 25 slp mean JAN 25 slp nobs JAN 25 slp stddev
JAN 25 air mean JAN 25 air nobs JAN 25 air stddev
JAN 25 wbt mean JAN 25 wbt nobs JAN 25 wbt stddev
JAN 25 dpt mean JAN 25 dpt nobs JAN 25 dpt stddev
JAN 25 sst mean JAN 25 sst nobs JAN 25 sst stddev
Figure 2. January values, including only 5°x5° boxes with at least 25 nobs, for sea level pressure (slp), air temperature (air), web bulb temperature (wbt), dew point temperature (dpt), and sea surface temperature (sst). The values are plotted separately for the three statistics mean, number of observations (nobs), and standard deviation (stddev) from left to right.

JUL slp mean JUL slp nobs JUL slp stddev
JUL air mean JUL air nobs JUL air stddev
JUL wbt mean JUL wbt nobs JUL wbt stddev
JUL dpt mean JUL dpt nobs JUL dpt stddev
JUL sst mean JUL sst nobs JUL sst stddev
Figure 3. As for Figure 1, but for July.

JUL 25 slp mean JUL 25 slp nobs JUL 25 slp stddev
JUL 25 air mean JUL 25 air nobs JUL 25 air stddev
JUL 25 wbt mean JUL 25 wbt nobs JUL 25 wbt stddev
JUL 25 dpt mean JUL 25 dpt nobs JUL 25 dpt stddev
JUL 25 sst mean JUL 25 sst nobs JUL 25 sst stddev
Figure 4. As for Figure 2, but for July.

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Updated: Apr 28, 2014 17:39:41 UTC
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