Indian Monsoon, June 1988

From the GEOS-1 Multiyear Assimilation (Reanalysis)

The Figure shows a 3-D perspective of flow during the Indian Monsoon in June 1988. The fields are from the GEOS-1 data assimilation system. The view is from the South Indian Ocean looking north. The Indian subcontinent is in the center and Maylasia is to the right and Africa to the left. High topography is in brown and lower elevations are green. The arrows show near-surface winds. The strong winds blowing from Africa, south of Arabia and onto the western shore of Indian represent the Somali jet. This wind current brings moist sea air into the subcontinent. The yellow and blue ribbons are two air parcel trajectories. They show that air of maritime origin from the eastern Indian Ocean and western Pacific, as well as air descending over Arabia converge in the Somali jet. The white shows energy released as the air ascends and gives up its moisture to precipitation. The trajectories show a small event as they cross the Ghats Mountains on the west Indian coast. Later along the trajectory, over eastern India and Bangladesh, the trajectories are nearly vertical and move together to the top of the troposphere. The air then moves westward in the upper troposphere.

This picture was made with output from the GEOS-1 data assimilation system. GEOS-1 uses a general circulation model to produce a data constrained "movie" of the atmosphere. The data assimilation system uses the limited input data, dominated by temperature measurements, to generate less-observed or unobserved quantities such as ocean surface winds and energy release in clouds. Results from GEOS-1 show that interannual variability can be captured. In this case, comparisons of the 1987 and 1988 Indian monsoon show a clear link to the El Nino cycle.

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Data Assimilation Office / Code 910.3 / NASA - Goddard Space Flight Center

Office Head: Ricky Rood