Summary of Abstract Submission

Abstract Submission No. IO50-05-0004PresentationOral

INFLUENCE OF LAND SURFACE ALBEDO ON THE INDIAN SUMMER MONSOON IN A COUPLED OCEAN-ATMOSPHERE TROPICAL-CHANNEL MODEL

Guillaume Samson1, Sebastien Masson2, Fabien Durand**1, Pascal Terray2

1 LEGOS-Toulouse, France
2 LOCEAN-Paris, France

ABSTRACT :

We present the Indian Summer Monsoon (ISM) simulated with a 0.75 coupled ocean-atmosphere tropical-channel model over the 1989-2009 period. The model biases are comparable to those commonly found in global coupled models: the Findlater jet is too weak, precipitations are underestimated over India while they are overestimated over South East Asia and the Maritime Continent. We show that land surface temperature biases are the major source of the monsoon circulation biases in our model: a cold bias over the Middle-East region weakens the Findlater jet while a warm bias over India strengthens the monsoon circulation in the Bay of Bengal. A surface radiative heat budget analysis reveals that the cold bias is due to an overestimated albedo in this desert region. A new simulation with a satellite-observed land albedo shows a large improvement in terms of monsoon circulation and precipitations. The ISM onset is also shifted back almost one month in agreement with observations. These results highlight the strong sensitivity of the ISM and its onset to the land heating pattern and amplitude, especially in the Middle-East region