South of Bordeaux city, here is an area where the meso climate is strongly affected by the thermic shock caused by the Cerons joining the Gironde. The cold and faster flowing tributary hits the shallow and warmer river and creates fog that promotes the formation of Botrytis Cinerea (noble rot) which is a characteristic of these wines. All Barsac is Sauternes, since it is a sub region and has the reputation of being more delicate and fine than the wines from the area surrounding it. Dry whites can be made but even they are often affected by rot. (CW 11/01/12)