In this paper, a cost-efficient sedimentation algorithm is described. The numerical resolution of the sedimentation equation is replaced by three probabilities of transfer associated with the ...following three types of precipitation: (i) precipitation present in the layer at the beginning of the time step; (ii) precipitation coming from the layer above and crossing the layer under consideration and (iii) precipitation produced locally during the time step. This scheme can be considered as a special case of the more general statistical approach where a simple step function is chosen as the basis for these probabilities. The main advantage is a near-perfect reproduction of advective (Eulerian or Lagrangian) classical sedimentation schemes at low computation cost. The practical use of the scheme in the operational models of M´et´eo-France is described. We believe that this approach can be used to compute sedimentation in any microphysical scheme. Moreover, the simplicity of the algorithm makes it possible to consider improvements which would have been complex to implement in the original schemes.
The Clouds Above the United States and Errors at the Surface (CAUSES) project is aimed at gaining a better understanding of the physical processes that are leading to the creation of warm ...screen-temperature biases over the American Midwest, which are seen in many numerical models. Here in Part 1, a series of 5-day hindcasts, each initialised from re-analyses and performed by 11 different models, are evaluated against screen-temperature observations. All the models have a warm bias over parts of the Midwest. Several ways of quantifying the impact of the initial conditions on the evolution of the simulations are presented, showing that within a day or so all models have produced a warm bias that is representative of their bias after 5 days, and not closely tied to the conditions at the initial time. Although the surface temperature biases sometimes coincide with locations where the re-analyses themselves have a bias, there are many regions in each of the models where biases grow over the course of 5 days or are larger than the biases present in the reanalyses. At the Southern Great Plains site, the model biases are shown to not be confined to the surface, but extend several kilometres into the atmosphere. In most of the models, there is a strong diurnal cycle in the screen-temperature bias and in some models the biases are largest around midday, while in the others it is largest during the night. While the different physical processes that are contributing to a given model having a screen-temperature error will be discussed in more detail in the companion papers (Parts 2 and 3) the fact that there is a spatial coherence in the phase of the diurnal cycle of the error across wide regions and that there are numerous locations across the Midwest where the diurnal cycle of the error is highly correlated with the diurnal cycle of the error at SGP suggest that the detailed evaluations of the role of different processes in contributing to errors at SGP will be representative of errors that are prevalent over a much larger spatial scale.
Intracellular microelectrode techniques were employed to study the effects of diphenylamine-2-carboxylate (DPC) on ion transport in Necturus gallbladder epithelium. Under control conditions, addition ...of DPC to the mucosal bathing solution caused a concentration-dependent, reversible hyperpolarization of both cell membranes with no measurable resistance changes. In addition, DPC caused the following effects, all consistent with inhibition of apical membrane Cl(-)-HCO3- exchange: fall in intracellular Cl- activity (aCli), increase in intracellular pH (pHi), reduction of the changes in aCli and pHi produced by lowering mucosal solution Cl-, and reduction of the change in pHi produced by lowering mucosal solution HCO3-. Similar studies in theophylline-treated preparations indicate that DPC also inhibits anion exchange under these conditions, but has no effect on the apical membrane electrodiffusive Cl- permeability induced by cyclic AMP. Under these conditions, DPC caused cell membrane hyperpolarization but had no effect on the apparent ratio of membrane resistances. In addition, DPC had no effects on the rapid changes in apical membrane voltage elicited by altering mucosal Cl-, but caused significant reductions of the slower, secondary voltage changes observed in response to changes in mucosal Cl-, and the changes in aCli and pHi produced by lowering mucosal Cl-. Because others have demonstrated that DPC blocks Cl- channels in other epithelia (Distefano, A., M. Wittner, E. Schlatter, H. J. Lang, H. Englert, and R. Greger. Diphenylamine-2-carboxylate, a blocker of the Cl(-)-conductive pathway in Cl(-)-transporting epithelia. Pfluegers++ Arch. 405: S95-S100, 1985), it is possible that the structures of those channels and that induced by cyclic AMP in Necturus gallbladder are different. Because of its relatively high affinity and rapid reversibility, DPC may become useful in studies of anion exchange in other cells.
Vernet J.-L., Bazile-Robert Evelyne, Evin Jacques. Coordination des analyses anthracologiques et des datations absolues sur charbon de bois. In: Bulletin de la Société préhistorique française, tome ...76, n°3, 1979. pp. 76-79.
To parameterize land surface processes in atmospheric models, surface schemes use primary parameters derived from soil and vegetation maps. Vegetation cover can be inferred from radiometric ...properties in the visible and near infrared wavelengths. For this purpose, NOAA/AVHRR channels 1 and 2 were processed over Europe. Forests over Europe are first identified by thresholding the synthesis of visible reflectances. Then, the other classes of vegetation are obtained from an automatic clustering method based on temporal profiles of NDVI, using the maximum value composite method. Surface parameters are derived for each vegetation class. The impact of the new vegetation database has been assessed for the French forecast models.
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