Evidence of change after 2001 in the seasonal behaviour of the mesopause region from airglow data at El Leoncito

J. SCHEER; E.R. REISIN

Montreal, Canadá

Congreso; 37th COSPAR Scientific Assembly; 2008

International Council of Science

at El Leoncito (31.8oS 69.3oW) provide good annual coverage in 1998 to 2002, 2006, and 2007, with between 192 and 311 nights of observation per year. These data can therefore be used to derive the seasonal variations during each of these seven years, in airglow brightness and temperatures at altitudes of 87 and 95 km. From 1998 to 2001, seasonal variations are so similar that they are well represented by a mean climatology, for each parameter. On the other hand, these climatologies do not agree with what is usually observed at other sites, maybe due to the particular orographic conditions at El Leoncito. With respect to the last three documented years (2002, 2006, and 2007), the similarity from year to year breaks down, and there are marked differences in the seasonal behaviour, more or less in all the parameters.The differences include, e.g., maxima occurring earlier or later than ”normal”, by one or two months. All this may suggest a sudden build-up of a new regime of intraseasonal variability. We look for a possible relationship to corresponding changes in wave activity.oS 69.3oW) provide good annual coverage in 1998 to 2002, 2006, and 2007, with between 192 and 311 nights of observation per year. These data can therefore be used to derive the seasonal variations during each of these seven years, in airglow brightness and temperatures at altitudes of 87 and 95 km. From 1998 to 2001, seasonal variations are so similar that they are well represented by a mean climatology, for each parameter. On the other hand, these climatologies do not agree with what is usually observed at other sites, maybe due to the particular orographic conditions at El Leoncito. With respect to the last three documented years (2002, 2006, and 2007), the similarity from year to year breaks down, and there are marked differences in the seasonal behaviour, more or less in all the parameters.The differences include, e.g., maxima occurring earlier or later than ”normal”, by one or two months. All this may suggest a sudden build-up of a new regime of intraseasonal variability. We look for a possible relationship to corresponding changes in wave activity.