Abstract
Abstract. Both balloon-borne electrochemical ozonesondes and MOZAIC (measurements of ozone, water vapour, carbon monoxide and nitrogen oxides by in-service Airbus aircraft) provide very valuable data sets for ozone studies in the upper troposphere/lower stratosphere (UTLS). Although MOZAIC's highly accurate UV-photometers are regularly inspected and recalibrated annually, recent analyses cast some doubt on the long-term stability of their ozone analysers. To investigate this further, we perform a 16 yr comparison (1994–2009) of UTLS ozone measurements from balloon-borne ozonesondes and MOZAIC. The analysis uses fully three-dimensional trajectories computed from ERA-Interim (European Centre for Medium-Range Weather Forecasts Re-analysis) wind fields to find matches between the two measurement platforms. Although different sensor types (Brewer-Mast and Electrochemical Concentration Cell ozonesondes) were used, most of the 28 launch sites considered show considerable differences of up to 25% compared to MOZAIC in the mid-1990s, followed by a systematic tendency to smaller differences of around 5–10% in subsequent years. The reason for the difference before 1998 remains unclear, but observations from both sondes and MOZAIC require further examination to be reliable enough for use in robust long-term trend analyses starting before 1998. According to our analysis, ozonesonde measurements at tropopause altitudes appear to be rather insensitive to changing the type of the Electrochemical Concentration Cell ozonesonde, provided the cathode sensing solution strength remains unchanged. Scoresbysund (Greenland) showed systematically 5% higher readings after changing from Science Pump Corporation sondes to ENSCI Corporation sondes, while a 1.0% KI cathode electrolyte was retained.
Highlights
Over the last 40 yr electrochemical ozonesondes have been widely used for measuring ozone (O3) up to the burst of the balloon at altitudes of 30–35 km
Uccle and Payerne switched to ECC sondes (ES-Z type operated with 0.5 % KI half buffered sensing solution) in April 1997 and September 2002, respectively; Hohenpeißenberg (MOHp) still launches BM sondes, and is the only remaining BM station worldwide
Sonde–MOZAIC differences obtained from the unidirectional trajectories are negligibly small at all altitudes for both MOHP and Uccle, but range up to 5 % at Payerne, the differences in absolute concentrations are on the order of a few ppb in the troposphere
Summary
Over the last 40 yr electrochemical ozonesondes have been widely used for measuring ozone (O3) up to the burst of the balloon at altitudes of 30–35 km. Commercial airliners have been used to provide high-quality tropospheric and lower stratospheric O3 measurements, for example, as part of the MOZAIC aircraft program (Measurements of ozone, water vapour, carbon monoxide and nitrogen oxides by in-service Airbus aircraft, Marenco et al, 1998) or the Swiss NOXAR program (Nitrogen Oxides and Ozone along Air Routes, Brunner et al, 2001). For data in both programs, European long-range airliners are equipped with accurate UV photometers to measure O3 and other trace gases. The analysis of Staufer et al (2013) is extended to various other soundings sites in Europe, America, Japan, and Africa
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