Global scale observation of cirrus, ozone and nitrogen dioxide variability in the tropical UTLS from circumnavigating infra-red montgolfier long duration balloons
Abstract
In preparation of a project for studying the impact of tropical convection on the stratosphere at global scale, three Infra-Red Montgolfier long duration balloons have been flown in February-March 2001 at 22^oS from Brazil. The balloons lasted in flight for respectively 34, 45 and 71 days, circumnavigating at almost constant latitude within two weeks. Among the three, one was carrying a SAOZ spectrometer from which ozone, NO_2 and clouds profiles were derived every morning and evening from 8 km (or cloud top) to 26 km. Most remarkable results of these flights, although not all fully understood yet, are: rightarrow the stability of ozone concentration in the lower stratosphere (i.e. <2% at 22 km) between 26 and 14^oS indicative of little impact of vertical and horizontal transport at these levels; rightarrow in contrast, its relatively large variability (30%) in the upper troposphere, shown to be mostly related to horizontal exchange and not to chemistry or convection; rightarrow an unexpected variability of NO_2 concentration in the lower stratosphere (25%), partly due to NO_y horizontal exchange but likely partly also to a NO_x production by electrical discharges between clouds and ionosphere or ionisation by particles precipitation in the South Atlantic anomaly; rightarrow an average NO_2 concentration and a diurnal variation in the lower stratosphere larger than that anticipated from photochemical models, suggestive of a still wrong representation of NO_x gas phase chemistry; rightarrow the frequent presence of sub-visual cirrus clouds at the altitude of the minimum temperature at the tropopause.
- Publication:
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EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....12860P