Back to main menu  /   Help and usage   /  Use the clickable blipmaps on the right to get the name (mouse over) or the aerological profile (click on) of the place indicated by a black small star. Surface parameters: mslp / sfc temperature / sfc dew point / sunshine / snow cover   /  Wind parameters  /  thermal parameters  /  clouds parameters Quick help: This macroscale snow cover chart is showed in order to explain (warn) a potential limitation of RASP. Purple areas mean the ground surface is simply covered with snow without taking account of the thickness of snow. Blue areas mean region without snow. The forecast problem can be traced to input from the driving global GFS model, with too large snow region over the mountains at macroscale (GFS model view). Naturally if RASP is told there is snow cover it is going to under-evaluate BL, ground heating and thermals, and other predictions which depend upon surface heating will also be incorrect. The probable reason for the anomalously-and too coarsely predicted snow is that GFS uses "envelope topography" which for terrain values uses the maximum elevation in a grid cell, which would produce a large area of higher-than-actual elevations and hence more snow than is actually the case. Because the grid cell of macroscale GFS is around 50km, any such anomaly is spread over many points in the RASP grid. It is an example of a case in which RASP forecasts can be invalid due to its dependence upon forecasts from the global model. To alleviate this anomaly I "tell" to my Alps RASP model before it runs that there no snow in winter and in the beginning of spring when there has been no new snow fall for a few day, because in this case I empirically notice that probably the heating effect of snow-free alpine pine forest is not negligible in the alpine valley. Aide rapide: Cette carte de la couverture neigeuse montre les zones o la prvision des thermiques peut tre sous-estime. Les aires violettes signifient que RASP considre qu'elles sont couvertes de neige (quelque soit l'paisseur du manteau neigeux) alors que les aires bleues sont considres comme libre de neige. Ceci est d au fait que RASP n'est pas encore capable de calcul la couverture neigeuse en fonction de son relief ou du relief rel. Il fait donc ses calculs en prenant compte la couverture neigeuse du modle de base macrochelle (GFS) qui ne voit que grossirement celle-ci. Par exemple les valles profondes (non vue par GFS) dans une zone violette sont considres comme couvertes de neige alors qu'en ralit elles ne le sont pas. Pour palier cette anomalie, je dclenche dans le programme la prise en compte de la couverture nuageuse, lorsque j'observe peu de neige, notamment sur les forts de conifres, dans les valles, en particulier la fin de l'hiver et au dbut du printemps.