1. Atmospheric pressure is the pressure exerted by the weight of the earth's atmosphere. It is measured in hectopascals (hPa), with 1 hPa equal to 1 millibar. 2. Pressure gradient refers to the rate of change of pressure over distance and indicates how strongly winds will blow between areas of high and low pressure. 3. Dew point temperature is the temperature at which air becomes saturated with water vapor and fog can form. It is an important measurement for mariners to consider when deciding whether to ventilate cargo holds.