Mixing Height Over Water And Its Role On The Correlation Between Temperature And Humidity Fluctuations In The Unstable Surface Layer |
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| Authors: | Anna Maria Sempreviva Sven-Erik Gryning |
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| Institution: | (1) Instituto di Fisica dell'Atmosfera, C.N.R., Rome, Italy;(2) Risø National Laboratory, DK-4000 Roskilde, Denmark |
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| Abstract: | Results from an experimental investigation of themixing height over inner Danish waters carriedout from September 1990 to October 1992, are discussed.The statistical analysis of the mixed-layer height (zi)over the sea does not exhibit the dailyvariation that is characteristic of the mixed layerover land, but it is nearly constant over a24-hour cycle. During summer, the mixed layer ishigher than during winter. A second inversionwas often observed.A case study of the development of the mixed layerover the sea under near-neutral and unstableatmospheric conditions during six consecutivedays is presented. A zero-order mixed-layer heightmodel is applied. In addition to momentum and heatfluxes the effect of subsidence was found to be importantfor the evolution of the mixed layer over the sea. Themodelled evolution of zi compared successfullywith measurements.We have investigated the influence of themixed-layer height on the correlation coefficient RqTbetween temperature and humidity fluctuations usingthe values obtained with the model.We found that the evolution of RqT follows theevolution of the mixing height. An empirical modellinking the surface values of RqT to zi and the Obukhov scaling length L has been suggested. The modelreproduces the experimental features. |
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| Keywords: | Marine surface layer Mixed-layer height Scalar correlation coefficient |
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