Estimation Of Atmospheric Water Vapour Flux Profiles In The Nocturnal Unstable Urban Boundary Layer With Doppler Sodar And Raman Lidar |
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| Authors: | MP Rao S Casadio G Fiocco M Cacciani A Di Sarra D Fuá P Castracane |
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| Institution: | (1) Department of Physics, Andhra University, Visakhapatnam, 530003, India;(2) Department of Physics, University of Rome  La Sapienza , I-00185 Rome, Italy;(3) AMB/ENEA, I-00060 S. Maria di Galeria, Italy |
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| Abstract: | The vertical wind profiles determined by Doppler sodar and the water vapourmixing ratio profiles obtained by Raman lidar are used to estimate the atmosphericwater vapour flux profiles in the nocturnal urban boundary layer under unstableconditions. The experiment was conducted for several nights in the central areaof Rome under a variety of moisture conditions and different urban boundary-layerflow regimes. Despite some scatter in the profiles, the latent heat flux is found tobe positive throughout the depth of the nocturnal urban boundary-layer. Thelayer-averaged flux shows a variation between -4 to +40 W m-2, whileindividual values of flux in excess of +150 W m-2 pertain to a case offree convection during cold air advection caused by the sea breeze. The qualityof flux estimates is found to be highly limited by the low sampling rates employedin the experiment resulting in errors to the order of 60%. Therefore, the results mustbe viewed as estimates rather than precise measurements. The skewness profiles ofthe turbulent fluctuations of vertical velocity and water vapour mixing ratio are alsopositive. |
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| Keywords: | Latent heat Lidar Moisture flux Sodar Urban boundary layer Water vapour |
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