Search results
Results from the WOW.Com Content Network
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
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.
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]
Water content and cloud thickness together make a cloud's liquid water path. This value also notably varies with changing cloud droplet size. [6] Liquid water path is typically measured in units of g/m 2 and in excess of 20 g/m 2 clouds typically will become opaque to long-wavelength light although this may not hold true with cirrus clouds. [7]
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.
Clouds form when the dew point temperature of water is reached in the presence of condensation nuclei in the troposphere. The atmosphere is a dynamic system, and the local conditions of turbulence, uplift, and other parameters give rise to many types of clouds. Various types of cloud occur frequently enough to have been categorized.
Normally, the sun heats the ground, which in turn heats the air just above it. Thermals form when this warm air rises into the cold air (warm air is less dense than cold air), a process called convection. A convective layer such as this has the potential for cloud formation, since condensation occurs as the warm air rises and cools.
Assuming no cloud cover, most of the surface emissions that reach space do so through the atmospheric window. The atmospheric window is a region of the electromagnetic wavelength spectrum between 8 and 11 μm where the atmosphere does not absorb longwave radiation (except for the ozone band between 9.6 and 9.8 μm). [19]