Trace gas signatures of the transport sectors within a typical North Atlantic cyclone - Results from the NARE-97 aircraft intensive

The North Atlantic Regional Experiment (NARE) 1993 summertime intensive led to the development of a very simple conceptual model illustrating how cyclones transport pollutants to the western North Atlantic Ocean (WNAO). A current priority of NARE is to classify air masses sampled by aircraft, and subsequently discern the chemical characteristics of various cyclone sectors in the lower and mid-to-upper troposphere. Aircraft data from the autumn 1997 NARE intensive were analyzed with a variety of techniques to identify air masses within cyclones and track their development enroute to the WNAO. Remotely sensed GOES infra-red and water vapor imagery, in conjunction with gridded meteorological fields and aircraft meteorological data were used to identify air mass boundaries. The newly developed GOES specific humidity product proved extremely useful in tracking cyclone development, and back trajectories also aided in the identification of air mass origin. Stratosphere/troposphere exchange regions were specifically sampled during the campaign with ozonesondes launched from Sable Island. Remotely sensed total column ozone and the dynamic tracer, isentropic potential vorticity, were used in conjunction with the ozonesondes and aircraft measurements to discern the extent of the stratosphere/troposphere exchange regions. The results of such an extensive analysis are presented for an aircraft flight through a North Atlantic cyclone, during mid-September. Segregation of the flight data according to storm sector and air mass origin resulted in very different relationships between O3 and the following trace gases: CO, water vapor mixing ratio, NOx, NOy and NOz. These differences illustrate the typical chemical signatures of warm and cold conveyor belts. This information will be used with data from a number of other flights to expand the idealized cyclone conceptual model to include a description of chemistry.