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the cloud IR emissivity, with values between 0 and 1, with a global average around 0.7; the effective cloud amount, the cloud amount weighted by the cloud IR emissivity, with a global average of 0.5; the cloud (visible) optical depth varies within a range of 4 and 10. the cloud water path for the liquid and solid (ice) phases of the cloud particles
Under dry, cloud-free conditions, water vapor in atmosphere contributes 67% of the greenhouse effect on Earth. When there is enough moisture to form typical cloud cover, the greenhouse effect from "free" water vapor goes down to 50%, but water vapor which is now inside the clouds amounts to 25%, and the net greenhouse effect is at 75%. [21]
Clouds that have low densities, such as cirrus clouds, contain very little water, thus resulting in relatively low liquid water content values of around .03 g/m 3.Clouds that have high densities, like cumulonimbus clouds, have much higher liquid water content values that are around 1-3 g/m 3, as more liquid is present in the same amount of space.
Higher liquid water and ice content in a cloud increases its albedo, which is the dominant factor in determining the cloud's reflectivity. [ 6 ] [ 7 ] The change in albedo is greater for clouds with less water content to start with and larger clouds begin to receive diminishing returns with increased content.
Fog is commonly considered a surface-based cloud layer. [21] The fog may form at surface level in clear air or it may be the result of a very low stratus cloud subsiding to ground or sea level. Conversely, low stratiform clouds result when advection fog is lifted above surface level during breezy conditions.
Hurricanes are mixed-phase clouds, meaning that liquid and solid water (ice) are both present in the cloud. Typically, liquid water dominates at altitudes lower than the freezing level and solid water at altitudes where the temperature is colder than -40 °C. Between 0 °C and -40 °C water can exists in both phases simultaneously.
It marks where the cloud base begins when air is heated from below to the convective temperature, without mechanical lift. [ 1 ] Once the CCL is determined, the surface temperature necessary to raise a mass of air to that height can be found by using the Dry Adiabatic Lapse Rate (DALR) to determine the potential temperature.
A typical raindrop is about 2 mm in diameter, a typical cloud droplet is on the order of 0.02 mm, and a typical cloud condensation nucleus is on the order of 0.0001 mm or 0.1 μm or greater in diameter. [1] The number of cloud condensation nuclei in the air can be measured at ranges between around 100 to 1000 per cm 3. [1]