Furthermore,
Air Pressure and Humidity
Air pressure is the weight of the atmosphere pressing down on the earth. It is measured by a barometer in units called millibars. Most barometers use mercury in a glass column, like a thermometer, to measure the change in air pressure.
When the weather is calm the mercury in the barometer seldom moves more than half-an-inch below the 30-inch mark.
If a high pressure system is on its way, often you can expect cooler temperatures and clear skies. If a low pressure system is coming, then look for warmer weather, storms and rain.
The weight pressing down on a one square-inch sample of air at sea level is 14.7 pounds, which is equivalent to a column of mercury 29.92 inches in height (1,000 millibars).
Air pressure changes with altitude. When you move to a higher place, say a tall mountain, air pressure decreases because there are fewer air molecules as you move higher in the sky.
Relative humidity is the amount of moisture the air can hold before it rains. The most it can hold is 100 percent. Humidity is measured by a psychrometer, which indicates the amount of water in the air at any one temperature.


ab'solute humid'ity

the mass of water vapor present in a unit volume of moist air. Cf. dew point, mixing ratio, relative humidity, specific humidity.

air mass,
large body of air within the earth's atmosphere in which temperature and humidity, although varying at different heights, remain similar throughout the body at any one height. Air masses form over parts of the earth's surface called source regions, which are large bodies of water or landmasses with relatively uniform topography, often ranging hundreds of thousands of square miles in area. When a body of air remains over a source region for days or weeks, it reaches an equilibrium with the surface. Radiation and convection exchanges between the surface and the air determines the air mass characteristics. Air masses formed over oceans generally contain more moisture than continental ones; air masses formed in polar latitudes are colder than those from the tropics. As an air mass moves away from its source region, it brings its particular weather conditions to areas over which it travels. At the same time, its characteristic properties are slowly modified by exposure to new environments. The boundaries between air masses, called fronts, are, typically, zones of rapid transition from cold to warm or from dry to moist air. Turbulence at the boundary often breeds low-pressure storms.

SO CREATE A HIGH PRESSURE STORM IN YOUR GROW ROOM................

dew,

thin film of water that has condensed on the surface of objects near the ground. Dew forms when radiational cooling of these objects during the nighttime hours also cools the shallow layer of overlying air in contact with them, causing the condensation of some water vapor. This condensation occurs because the capacity of air to hold water vapor decreases as the air is cooled. The temperature at which condensation begins, for a sample of air with a given water vapor content, is termed the dew point. If a dew point temperature below 32°F (0°C) is reached, sublimation occurs, i.e., the water vapor converts directly to frost. Should the surface temperature drop below 32°F after the dew has already collected, the dew may freeze into so-called white dew. Most authorities account for the supply of water vapor as coming from the atmosphere, though some research suggests that it also diffuses up through the soil and then condenses on the ground surface if conditions are favorable. Dew forms most readily on those surfaces that lose heat through radiation most efficiently but are nevertheless insulated from external heat sources. Dew formation is favored by high humidity in the lowest layers of air, which either supplies the moisture or at least inhibits the evaporation of the dew already deposited.

Strong winds inhibit dew formation because they mix a larger layer of air, creating a more homogeneous distribution of heat and water vapor; under such circumstances it is unlikely that a sufficiently cool and damp layer of air can form near the ground.

Meaning lower RH in higher heat with cfm.......