Results of Outgoing Longwave Radiation and Albedo over Saudi Arabia from Earth Radiation Budget Experiment (ERBE) Data

Changes in the albedo and outgoing longwave radiation at the top of the atmosphere derived from Earth Radiation Budget Experiment (ERBE) are specified as a function of atmospheric (all sky conditions) and surface properties (clear sky conditions). Albedo and outgoing longwave radiation observations are also used to relate cloudiness variations to regional features of the general circulations such as precipitation zones, persistent cloudiness, and areas of subsidence. A method requiring only measurements of outgoing long wave radiation and planetary albedo is applied to evaluate the relative importance of the albedo and long wave radiation on the atmospheric circulation. The approach of studying these observations in time and space is also used to examine the radiative energy budget of different geographic locations such as deserts, high land, and coastal areas. The results indicate that there are clear relationships between the variability in outgoing longwave radiation, albedo, and features of the atmospheric circulation, which appear to be linked to changes in cloudiness. In addition, the effect of geographical variations of Saudi Arabia on cloud is analyzed and related to circulation features. The longwave mean ranges from 257.1 Wm.2 to 307.7 Wm.2, and the longwave standard deviation ranges from 10.6 Wm.2 to 27.9 Wm.2 over the region. The albedo mean ranges from 20.9% to 30.6%, and the albedo standard deviation ranges from 5.5% to 8.7% over the region. The longwave cloud forcing at the top of the atmosphere equals 15 Wm.2 for January, 22 Wm.2 for April, 14 Wm.2 for July, and 10 Wm.2 for October 1989. Thus compared to a cloud free atmosphere, the January mean cloudiness, as it was present, reduces the outgoing longwave radiation for the total earth-atmosphere system by about 6%, for the month of April by about 8%, for the month of July by about 5%, and for the month of October by about 3%. For clear sky desert conditions, a weak relationship (R2 = 0.38) between the albedo and outgoing longwave radiation was found at some locations over the Kingdom. Whereas the relationship between all sky albedo and all sky outgoing longwave radiation results in a strong relationship (R2 = 0.80) at some locations.