Water vapour and ozone profiles in the midlatitude upper troposphere

[摘要] We present an investigation of upper tropospheric humidity profiles measuredwith a standard radiosonde, the Vaisala RS80-A, and a commercial frost-pointhygrometer, the Snow White. Modifications to the Snow White, to enable themirror reflectivity and Peltier cooling current to be monitored duringflight, were found to be necessary to determine when the instrument wasfunctioning correctly; a further modification to prevent hydrometeorsentering the inlet was also implemented. From 23 combined flights of anozonesonde, radiosonde and Snow White between September 2001 and July 2002,clear agreement was found between the two humidity sensors, with a meandifference of <2% in relative humidity from 2 to 10km, and 2.2%between 10 and 13km. This agreement required a correction to the radiosondehumidity, as described by Miloshevich et al. (2001). Using this result, thedataset of 324 ozonesonde/RS80-A profiles measured from Aberystwyth between1991 and 2002 was examined to derive statistics for the distribution ofwater vapour and ozone. Supersaturation with respect to ice was frequentlyseen at the higher levels - 24% of the time in winter between 8 and 10km.The fairly uniform distribution of relative humidity persisted to120% in winter, but decreased rapidly above 100% in summer.

[学科分类] 大气科学