Abstract

The construction of a LIDAR system for vertical profiling of tropospheric ozone is described. An overview of the first measurements of the system is given and the status of the system is discussed. The main conclusion are: - The construction of a laboratory version of the system is succesfully completed. - Since the beginning of April 1991 the system has been in use for routine measurements of ozone profiles from an altitude of about 600 m up to 5 km under clear weather conditions. The measurement range is limited to 5 km with analog detection. To achieve greater ranges photon couting is necessary. - It is expected that the system can be made operational in the Dutch TOR measurement network station Kollumerwaard. - Stimulated Raman Scattering (SRS), used for generation of the measurement wavelengths, has been investigated and shifting quantum efficiencies of up tp 77% in hydrogen and 45% for deuterium have been achieved. - The errors in the ozone profiles can be split in statistical errors (precision) and systematic errors. The error sources include differential aerosol backscattering and differential extinction by oxygen, sulphur dioxide, nitrogen dioxide, water vapour, molecules and aerosols. In the table below the present error situation is summarized for an averaging time of 100 seconds (1000 laser shots) and two measurement conditions: a clear, clean day, and a hazy, polluted day with enhanced loading of aerosols, SO2 and NO2. Water vapour is disregarded in the calculation in view of the very uncertain cross sections.- By applying corrective algorithms to the measurements and using longer averaging times the errors can be reduced. The table below gives the estimated situation after correction for systematic errors and 400 seconds averaging (4000 laser shots). - Further improvement of the statistical errors above circa 5 km altitude (i.e. the free troposphere) is possible with installation of photon counting.