Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 428573
Title Some observational evidence for dry soils supporting cumulus onset
Author(s) Westra, D.; Steeneveld, G.J.; Holtslag, A.A.M.
Source In: Annual Meeting European Meteorological Society, 10-14 September 2012, Lodz, Poland. - EMS - p. EMS2012 - 1.
Event 12th EMS / 9th ECAC, 2012-09-10/2012-09-14
Department(s) Meteorology and Air Quality
Publication type Abstract in scientific journal or proceedings
Publication year 2012
Abstract The relative humidity tendency at the top of a clear convective boundary layer (RHtop) as indicator of cloud formation is studied over a semi-arid region within a conceptual framework introduced by Ek and Holtslag (2004). Their framework is based on a mixed layer model, coupled to the land surface via the surface energy budget. In a regime of relatively high soil moisture, the tendency of RHtop increases if the evaporative fraction at the land surface increases which supports boundary-layer moistening but only when boundary-layer growth is limited by atmospheric factors, such as dry air entrainment, boundary-layer growth and boundary-layer heating. This regime was confirmed earlier by Cabauw observations. Here we provide the first observational evidence that the tendency of RHtop can also increase as the surface becomes more dry, as consistent with a second regime of the conceptual framework. The observations used are from the AMMA intensive observational campaign near Niamey, Niger, June 20-25, 2006. In addition, we evaluate whether the WRF single-column model confirms the different regimes of the conceptual framework for a typical day in the AMMA campaign and it appears that the model confirms that dryer soils can support cloud formation.
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