Report
On the re-evaluation
of total ozone observations from
Performed during the WMO/CHMI Training of
Dobson Operators
Prepared by: Mr.
Mohamed Ferroudj NMOA
Mr.
Karel Vanicek CHMI
Mr.
Martin Stanek CHMI
Station: Tamanrasset
WOUDC station number 002
National
Meteorological Office of
Observations and
routine processing of data
− Monitoring of total ozone has been
performed at the station since May 1994 with the Dobson spectrophotometer D011.
− Observations are taken daily, 3 DS
GQP-AD or ZB/ZC-AD since May 1994
− Observations are performed by
meteorological observers from the station that are controlled by Mr.Mohamed
Mimouni the GAW Project Manager of RMDA and Mr. Lamine Boulkelia.
− Routine observations are processed
with the PC program developed at the station by Mr. Mohamed Mimouni since 1994 and
Mr. Lamine Boulkelia since 2000.
− Total ozone data are deposited
regularly into WOUDC by Lamine Boulkelia and Mr.
Mohamed Mimouni.
− The raw input data and calculated
total ozone values are recorded in ASCII electronic files for the whole period
of observations 1994-2004.
− As the ability of operators in
managing the English language has improved, the latest Windows version of the
Czech Dobson software can be used for processing of measurements
Calibration history of the D011 instrument
− D011 was installed at Tamanrasset
with calibration constants defined at IC Boulder, 1993
− Next calibrations of D011 were
performed at IC Pretoria-2000 and Dahab-2004
− The calibration documentation from
the above ICs is kept in files at Tamanrasset.
− Regular monthly Standard Lamp and
Mercury tests are performed on D011. Monthly corrections of N-Tables are
calculated, filed and applied in calculation of total ozone
− The calibration constants (Q-Tables,
N-Tables , RR-Readings) were used for operation of
D011 and processing the data in periods between particular ICs.
− Comparison with independent total
ozone data sets (TOMS-V7 and total ozone data series from
− The above shift was confirmed at IC
Pretoria-2000 [WMO/GAW Report No.138]
− A detailed investigation of the
long-term trends in XAD, XA, XD total ozone values has discovered a small shift
in XD in the beginning of 2001 that could originate a difference of about 1%
identified at IC Dahab-2000 (see the Report of DICE-2004).
Re-calculation of the total ozone data set, Tamanrasset,
V/1994-VIII/2004
−
The
raw data of individual observations of the period May/1994-August/2004 from
Tamanrasset were converted from the ASCII files into the DOBSON-VesrionXXX data
format
−
The
re-calculation of measurements was performed by the DOBSON-VXX software package
developed at SOO-HK taking into account recommendations of the reports from IC
Pretoria-2000 and Dahab-2004 as follows
− The period May/1994-March/2000:
·
N-Tables
and RR values dated
·
correction
of N-Tables by monthly SL tests
·
correction
of N-Tables by dNA = -3,3 and dND = -1,6 from the Initial IC,
− The period April/2000-January/2001:
·
N-Tables
and RR values dated
·
correction
of N-Tables by monthly SL tests
− The period February/2001-
February/2004:
·
N-Tables
and RR values dated
·
correction
of N-Tables by monthly SL tests
·
correction
of N-Tables by dNA = -0,6 and dND = -0,5 from the Initial IC, Dahab, 27
February 2004, as recommended in the DICE Report on D011
− The period March/2004 onwards (after
IC Dahab-2004) was not re-calculated at the training because these observations
will be processed at Tamanrasset by the DOBSON-V5 software package given to Mr.
Ferroudj.
− After all DS observations were
re-processed, new Zenith Polynomials have been developed for the Tamanrasset
station and used for re-calculation of all ZB/ZC measurements from the period
1994-2004. These polynomials will be used at the station for routine processing
of zenith observations onwards.
− Finally all DS and ZB/ZC
observations were checked individually to be prepared for re-deposition into WOUDC.
Recommendations
−
The
Windows version of the Czech software package DOBSON-V5 will be installed at
Tamanrasset and used for processing of total ozone observations and for
maintenance of the data base. The proper training of observers in use of this
software tool will be performed by Mr.Ferroudj.
−
The
re-evaluated data set of the period May/1994-February/2004 will be submitted
into WOUDC in extCSV formatted files together with this Report as a metadata
file under the auspices of the GAW manager of NMOA
−
It
has been found during the Training that the Q-Table of the D011 instrument
dated Dahab NNNN should be re-calculated by means of the updated HG temp. coefficient that seems to be
1,06 instead of the current value 1,20.