地理小知识（Little knowledge of Geography）.doc

地理小知识（Little knowledge of Geography） salinity The highest salinity waters in the world: Red Sea, salinity between 3.6 ~ 3.8%; the lowest salinity waters: Baltic Sea, salinity is only 7 ~ 8 per thousand. The latitude and latitude of 30~40 are the highest in the world and lower in the equator. Because the amount of evaporation in the middle latitude is greater than that of precipitation, the equatorial region, although affected by the equatorial low pressure, has higher temperature, but the precipitation is large, so the salinity is low. The polar region is frozen, the water can not evaporate, there is not much rainfall, so the salinity is high. Density flow Ocean currents due to the uneven distribution of the horizontal direction of the sea water density, resulting from the inclination of isobaric surfaces, are called density currents. In other words, the density stream is the difference in the horizontal distribution of the water itself. The density of the sea depends on the temperature, salinity, and pressure of the sea, and varies horizontally. For example, the sea due to the heat of the sun and accept the temperature, volume expansion, density becomes small, the surface (isobaric) slightly increased; in another area of the sun in less heat, the relative density is bigger, the water temperature is low, the volume is reduced, and the sea (isobaric) relatively low. The pressure surface between the two sea areas and the sea surface and the following layers has different degrees of tilt, that is, any horizontal plane (i.e., equipotential surface) in the sea water has different pressures. Under the influence of horizontal pressure gradient force, sea water flows from a place of great pressure to a region of low pressure. Once water starts to flow, Coriolis force occurs immediately, this should be along the flow direction of the sea level pressure gradient force pull to the right (northern hemisphere), until the Coriolis force and the horizontal pressure gradient force