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Journal Article: BibTeX citation key:  Said2009
Saïd, F., Canut, G., Durand, P., Lohou, F. & Lothon, M. (2009) Seasonal evolution of the boundary-layer turbulence measured by aircraft during AMMA 2006 Special Observation Period. IN Quarterly Journal of the Royal Meteorological Society, 136. 47–65.
Added by: said frederique 2008-12-18 15:38:47    Last Edited by: Fanny Lefebvre 2010-11-24 15:01:40
Categories: Atmospheric processes, Monsoon system and its variability
Keywords: Atmospheric Boundary Layer, Seasonal cycle, SOP, Surface Flux
Creators: Canut, Durand, Lohou, Lothon, Saïd
Collection: Quarterly Journal of the Royal Meteorological Society
Bibliographies: Prior150410

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During AMMA, the ATR research aircraft made observations of fluxes and thermodynamics during three 15-days periods, which allowed to follow the seasonal evolution of the boundary-layer characteristics before and after the monsoon onset. As expected, temperature and humidity in the boundary-layer displayed an opposite trend from dry-warm conditions to moister-cooler conditions. The wind blew most of the time from north-westerly to south-westerly in the boundary-layer and from easterly in the free troposphere. Following rainfall events occuring in July and August, surface heat fluxes showed opposite behaviours : a decrease in sensible heat and an increase in moisture flux while the momentum flux remained large in the entire boundary-layer, whatever the period.
The aim of this paper is to characterize turbulence in terms of fluxes and lengthscales for boundary-layers that exhibit peculiar characteristics relative to i) the entrainment at the top, ii) the wind rotation at the top and iii) the seasonal variability. It is found that the turbulence measurements are more likely to be accurate during the monsoon period, when the evaporative fraction is high. During the driest period, when humidity transfers at the mixed-layer top prevail, all parameters strongly vary and measurements are critical. However, this period is crucial for gradually moistening the low troposphere.
Added by: said frederique    Last Edited by: Fanny Lefebvre