Role of Asian and African orography in Indian summer monsoon

[1] Role of Asian and African orography in the Indian summer monsoon has been investigated using a general circulation model. Orography of Asian region west of 80degreesE appears to have more impact on the Indian summer monsoon rainfall than the orography to the east of 80degreesE. It has been found that removal of the African orography increases the seasonal precipitation over the Indian subcontinent by 28%, whereas removal of orography over the entire globe reduces it by 25%. Moreover, there was a substantial delay in all- India monsoon onset in the experiment in which mountains were removed globally, mainly due to the intrusion of midlatitude dry air west of 80degreesE. The increase in precipitation in which orography over Africa was removed was due to the positive feedback between the wind over the East African coast/ Arabian Sea and precipitation over Bay of Bengal, with the latter leading the former by about 2 days.