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Abstract:
One of the generally accepted climatic effects of stratospheric
aerosol injection is the reduction of the global radiation in high
latitudes by an order of 57. at El Chichon type eruptions . It is
suggested that this‘radiation deficit is possible external forcing
factor for the above—mentioned climatic anomalies associated with
ENSO events. To test this hypothesis, the effect of high—latitude
radiational forcing was examined in a GCM experiment. The results
provide physically—consistent evidence in support of the basic
hypothesis. The main supporting factor is the creation of enhanced
snow cover in regions of Asia which are removed from the location
of the introduced radiation anomaly. The simulated results show
certain features, which are well known from observations in weak
monsoon years, i.e. the weakened easterly jet in the upper
troposphere over northern India, prolonged winter monsoon
conditions and prevailing anticyclonal vorticity anomalies over the
entire Indian summer monsoon region. Over the western Pacific at
the end of boreal winter (May), increased convective activity leads
to a negative Walker Circulation anomaly with westerly wind
anomalies near the surface and easterly anomalies in the upper
troposphere. This is known as one of the most important anomalies
at the beginning of an ENSO event.
