Annex III. Remarks concerning data transmission and suggestions for improvement

Annex III

REMARKS CONCERNING DATA TRANSMISSION AND SUGGESTIONS FOR IMPROVEMENT.

During the preparation of this report several 'problems' were encountered while processing the data. These problems and other remarks concerning data transmission are summarized below.

• The definition of exceedance is ambiguous: seven countries reported an exceedance when the ozone concentration equals the threshold value, the other countries indicated only when concentrations are greater than the threshold value. The latter definition is preferred.
• From the available information it is not always clear whether no exceedances have been observed at a station. In order to estimate the size of attainment areas, it is recommended to report (in computer readable form) explicitly results from stations where no exceedances are observed.
• Information on data coverage (fraction of time with valid measurements) is presented for hourly values and for the moving eight hourly values; it is recommended to give it also on a daily basis. Criteria for the calculation of valid eight hourly and daily values should be given. Following the criteria for the validity of the calculation of percentile values (see Annex III of the Ozone Directive), it could be considered that at least 6 and 18 valid hourly values, distributed uniformly throughout the period in question, should be available for calculating of a valid eight hourly or daily average value, respectively.
• For feedback on possible errors encountered during the processing of the data it is recommended to identify a contact person at the national institute responsible for data submissions.
• the code for erroneous or missing data for the station elevation (- 1) is confusing as an elevation below sea level (small negative values) may occur. It is recommended to use the error code - 999.
• VOC data has been submitted by 2 Member States only. According to the proposed format Italy submitted statistical information on daily average concentrations of total Non Methane Hydro Carbons (NMHC) at two stations; for one staion averaging time was 1 hour. The Netherlands submitted data (for 8 stations yearly averaged values based on an averaging time of one week) of 47 individual organic compounds using a different format. A further harmonization on VOC-data transmission is to be discussed.
• In the reporting of NOx concentrations there is confusion about the units. It is recommended to report NOx concentrations (defined as the sum of NO and NO₂ concentrations) in ppb-units and NO₂ in µg/m³.