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 atthe 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 andoutgoing longwave radiation observations are also used to relate cloudinessvariations to regional features of the general circulations such asprecipitation zones, persistent cloudiness, and areas of subsidence. Amethod requiring only measurements of outgoing long wave radiationand planetary albedo is applied to evaluate the relative importance ofthe albedo and long wave radiation on the atmospheric circulation. Theapproach of studying these observations in time and space is also usedto examine the radiative energy budget of different geographic locationssuch as deserts, high land, and coastal areas. The results indicatethat there are clear relationships between the variability in outgoinglongwave radiation, albedo, and features of the atmospheric circulation,which appear to be linked to changes in cloudiness. In addition, the effectof geographical variations of Saudi Arabia on cloud is analyzedand related to circulation features. The longwave mean ranges from257.1 Wm.2 to 307.7 Wm.2, and the longwave standard deviation rangesfrom 10.6 Wm.2 to 27.9 Wm.2 over the region. The albedo meanranges from 20.9% to 30.6%, and the albedo standard deviation rangesfrom 5.5% to 8.7% over the region. The longwave cloud forcing at thetop 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 acloud free atmosphere, the January mean cloudiness, as it was present,reduces the outgoing longwave radiation for the total earth-atmospheresystem 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%. Forclear sky desert conditions, a weak relationship (R^2 = 0.38) between thealbedo and outgoing longwave radiation was found at some locationsover the Kingdom. Whereas the relationship between all sky albedoand all sky outgoing longwave radiation results in a strong relationship(R2 = 0.80) at some locations.