How can the types of clouds affect the radiative forcing

Clouds play an important role in the Earth’s energy balance and in particular in the natural greenhouse effect. Curiously enough, there are two aspects of clouds that derive their importance to the climate system:

(1) Clouds act like the greenhouse gases by absorbing and emitting infrared radiation and thus contribute to warming the Earth’s surface.

(2) At the same time; most clouds are bright reflectors of solar radiation and tend to cool the climate system. The net average effect of the Earth’s cloud cover in the present climate is known to be a slight cooling.

However, since there are so many types of clouds (i.e. cumuliform cloud, cirrostratus, cirrus… etc), their effects on climate may be highly variable depending on their types, height..Etc as we have learned in global environment class. For instance, the aviation-induced contrails which are a form of cirrus cloud are estimated to cause small positive radiative forcing while the impact of low-level cumulus clouds on SW (Shortwave flux) is thought to be much larger than that of cirrus clouds. So our team members wanted to know more how each type of clouds is formed and how this can affect on radiative forcing. Also we will study how this issue affects the climate change and how we could predict the climate change by predicting the clouds formation, if this is possible.

Our meteorology was

Firstly, we gathered information about cloud types such as cirrus, cirrostratus and study how they are formed. We think this was pretty easy since there were many studying materials and pictures showing various cloud types and their forming mechanisms on the internet.

Secondly, we researched papers related to our topic (mainly through http://scopus.com or some other paper researching websites), read and studied them together. Finally, we wrote up what we have studied and quantified the radiative effects of individual cloud type

Cloud affects the Earth's Climate

Clouds affect the earth’s climate by modulating the vertical and horizontal distributions of solar radiative heating, latent heating, and cooling by thermal radiation that drive the atmospheric circulation. Moreover, clouds alter moisture transports by forming precipitation that returns the evaporated water to the surface. The radiative effects of clouds have been studied for a long time, with observations or numerical models of the atmosphere; but most of these earlier studies have focused on the relationship between the earth radiation budget or surface radiation budget and total cloud cover, neglecting the effect of variations of other cloud properties (i.e., cloud types) due to the lack of global quantitative information on the properties of different cloud types.

Undoubtedly, this focus on the total cloud cover is an oversimplification because cloud-type variations (e.g., variations in cloud-top height and water content) may well affect both shortwave and longwave radiative fluxes as much as changes in total cloud cover and because the distribution and frequency of occurrence of different cloud types could change during climate variations providing another climate feedback. Considering the problem in terms of cloud types may also be necessary to establish an accurate quantitative connection between different kinds of atmospheric motions and cloud radiative properties in order to make reliable climate change predictions.

GE-5