 |
| Titel |
Hydration of the lower stratosphere by ice crystal geysers over land convective systems |
| VerfasserIn |
S. Khaykin, J.-P. Pommereau, L. Korshunov, V. Yushkov, J. Nielsen, N. Larsen, T. Christensen, A. Garnier, A. Lukyanov, E. Williams |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 6 ; Nr. 9, no. 6 (2009-03-27), S.2275-2287 |
| Datensatznummer |
250007109
|
| Publikation (Nr.) |
 copernicus.org/acp-9-2275-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| The possible impact of deep convective overshooting over land has been
explored by six simultaneous soundings of water vapour, particles and ozone
in the lower stratosphere next to Mesoscale Convective Systems (MCSs) during
the monsoon season over West Africa in Niamey, Niger in August 2006. The
water vapour measurements were carried out using a fast response FLASH-B
Lyman-alpha hygrometer. The high vertical resolution observations of the
instrument show the presence of accumulation of enhanced water vapour layers
between the tropopause at 370 K and the 420 K level. Most of these moist
layers are shown connected with overshooting events occurring upwind as
identified from satellite IR images over which the air mass probed by the
sondes passed during the three previous days. In the case of a local
overshoot identified by echo top turrets above the tropopause by the MIT
C-band radar also in Niamey, tight coincidence was found between enhanced
water vapour, ice crystal and ozone dip layers indicative of fast uplift of
tropospheric air across the tropopause. The water vapour mixing ratio in the
enriched layers exceeds frequently by 1–3 ppmv the average 6 ppmv saturation
ratio at the tropopause and by up to 7 ppmv in the extreme case of local
storm in coincidence with the presence of ice crystals. The presence of such
layers strongly suggests hydration of the lower stratosphere by geyser-like
injection of ice particles over overshooting turrets. The pile-like increase
of water vapour up to 19 km seen by the high-resolution hygrometer during
the season of maximum temperature of the tropopause, suggests that the above
hydration mechanism may contribute to the summer maximum moisture in the
lower stratosphere. If this interpretation is correct, hydration by ice
geysers across the tropopause might be an important contributor to the
stratospheric water vapour budget. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|