Marine Boundary-Layer Variability Over The Indian Ocean During Indoex (1998) |
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| Authors: | Vijayakumar Manghnani Sethu Raman Devdutta S Niyogi Vinayaka Parameswara John M Morrison S V Ramana J V S S Raju |
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| Institution: | (1) Department of Marine, Earth and Atmospheric Sciences, NCSU, Box 8208, Raleigh, NC, 27695, U.S.A.;(2) Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum, India;(3) Center for Atmospheric and Ocean Sciences, Indian Institute of Sciences, Bangalore, India |
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| Abstract: | The variability in boundary-layerstructure over the Indian Ocean during a north-eastmonsoon and the factors influencing it areinvestigated. This study was made possible as acomponent of the Indian Ocean Experiment (INDOEX),conducted from February 19 to March 30, 1998. The dataused are, surface-layer mean and turbulencemeasurements of temperature, humidity and wind, andvertical soundings of temperature and humidity.Significant spatio-temporal variability was observedin the boundary-layer structure throughout the cruise.The ITCZ was characterized as the region withstrongest winds and maximum surface turbulent fluxesof momentum and heat. One of the important findingsfrom this study was a strong influence of continentalair masses on the boundary-layer structure in theNorthern Hemisphere, even at a distance of 600 km offthe Indian coast. This was generally evident in theform of an elevated plume of dry continental airbetween altitudes of 1500 m and 2700 m. Advection ofcontinental aerosols in this layer presents potentialfor significant entrainment into shallow clouds inthis region, which eventually feed deeper clouds atthe ITCZ. This finding provides an explanation foranomalous higher aerosol concentrations found duringprevious studies. The structure of the marineboundary layer was influenced by various factors suchas proximity to land, an anomalous warm pool in theocean and the ITCZ. In the southern hemisphere, theboundary-layer height was primarily governed bysurface-layer sensible heat flux and was found to behighest in the vicinity of the ITCZ. North of theequator it was strongly influenced by land-air-seainteractions. In addition to this synoptic modulation,there was also a significant diurnal variability inthe boundary-layer height. |
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| Keywords: | Indian Ocean INDOEX ITCZ Marine boundary layer North-east monsoon |
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