Pressureis measured in hecto-Pascals(hPa) or millibars.
-Standard pressure at sea level is defined as 1013hPa, but we can see large areas of either high or low pressure.
-Areas of high and low pressure are caused by ascending and descending air. As air warms, it ascends leading to low pressure at the surface. As air cools, it descends leading to high pressure at the surface.