Evidence of long-term change in zonal wind in the tropical lower mesosphere: Observations and model simulations

In the present study, zonal wind observations between 70 and 80km over the Indian region provided by rocketsonde (1977-1991), HRDI/UARS (1991-1999), and MST radar (1995-2010) are used to construct a long-term data set from 1977 to 2010.

Using this unprecedented data set, a decreasing trend of 2m/s/yr is found, changing from strong eastward winds during the 1970s to weak westward winds in recent years. On the other hand, between 80 and 98km using medium frequency radar observations during 1993-2009, no perceptible trend is found. Simulations of NCAR TIME-GCM also showed a similar change in the circulation when CO2 in the atmosphere is doubled, suggesting role of anthropogenic changes in the dynamics of the mesosphere.