Midlatitude ClO during the maximum atmospheric chlorine burden: in situ balloon measurements and model simulations

[摘要] Chlorine monoxide (ClO) plays a key role in stratospheric ozone lossprocesses at midlatitudes. We present two balloon-borne in situmeasurements of ClO conducted in northern hemisphere midlatitudesduringthe period of the maximum of total inorganic chlorine loadingin the atmosphere. Both ClO measurements were conducted on board theTRIPLE balloon payload, launched in November 1996 in León, Spain, andin May 1999 in Aire sur l'Adour, France. For both flights aClO daylight andnight-time vertical profile was derived over an altitude range ofapproximately 15-35 km. ClO mixing ratios are compared tomodel simulations performed with thephotochemical box model versionof the Chemical Lagrangian Model of the Stratosphere(CLaMS). Simulations along 24-hour backward trajectories wereperformed to study the diurnal variation of ClO in themidlatitudelower stratosphere.Model simulations for the flight launched inAire sur l'Adour 1999 show an excellent agreement with the ClO measurements.For the flight launched in León 1996, an overall good agreement isfound, whereas the flight is characterized by a more complex dynamicalsituation due to a possible mixture of vortex and non-vortex air. Wenote thatfor both flights at solar zenith angles greater than86°-87° simulated ClO mixing ratios arehigher than observed ClO mixing ratios. However, the presentfindings indicate that no substantial uncertainties exist inmidlatitude chlorine chemistry of the stratosphere.

[学科分类] 大气科学