A comparison of the new filter ozonometer MICROTOPS II with Dobson and Brewer spectrometers at Hohenpeissenberg

The recently developed filter ozonometer MICROTOPS II No. 3128 (MTops 3128) was purchased in October 1996. Almost two years of intensive comparative m easurements with the regular spectrometers Dobson No. 104 (D104) and Brewer No. 10 (BR10) and intercomparison with the standard Dobsons No. 065 (D065) and 064 (D064) on selected days confirmed that the handy MTops 3128 is abl e to yield good total ozone measurements. The differences between the vario us instruments are mostly less than +/-2%, increasing at air masses higher than 3.5 or at hazy sky conditions. Both instrumental types contribute to t his increase with opposite effects. The handling during observation and dat a processing turned out to be easy with only few minor shortcomings. Replac ement of the quartz cover didn't change the original MTops calibration sign ificantly. Adverse effects of the filter aging or a calibration drift could not be detected over this 21-months period.