We participate in the Atmospheric Radiation Measurement (ARM) Program with two objectives: 1) to improve general circulation model (GCM) cloud/radiation treatment with focus on cloud vertical overlapping and layer cloud optical properties, and 2) to study the effects of cloud-radiation climate interaction on GCM climate simulations. This report summarizes the recent findings in sub-grid scale v...

[1] The interest in solar ultraviolet (UV) radiation from the scientific community and the general population has risen significantly in recent years because of the link between increased UV levels at the Earth’s surface and depletion of ozone in the stratosphere. As a consequence of recent research, UV radiation climatologies have been developed, and effects of some atmospheric constituents (s...

Various synoptic variables are related to satellite radiation data. It is shown that: (1) Vertical motion is related jointly to window radiation and water vapor radiation. (2) Surface relative humidity can be estimated from window radiation and cloud brightness. (3) Ceilings can be estimated from window radiation and cloud brightness.

The present study compared simple thermal indices and the indices derived from energy budget models in the northwest of Iran. For this purpose, the air temperature, solar radiation, relative humidity, cloud, cover and wind speed of 13 meteorological stations in the northwest of Iran during the  the period of 1986 to 2007 were selected for comparison. The results which were extracted using Biokl...

Atmospheric aerosols affect the radiation balance at the surface and at the top of the earth’s atmosphere. They directly scatter and absorb radiation, yet the aerosol particles indirectly affect the radiation budget because they act as cloud condensation nuclei (CCN). This changes the optical properties of the cloud. For example, an increase in aerosols increases the number of CCN. This may lea...

One of the three major goals of the Atmospheric Radiation Measurement (ARM) Program is to improve the quality of radiation models under clear sky, homogeneous cloud, and broken cloud conditions. This report is concerned with the development of the theory of radiation transfer in the broken clouds. Our approach is based on a stochastic description of the interaction between the radiation and clo...

Parameterization of cloud-radiation interactions in an atmospheric general circulation model using a stochastic approach allows for a statistical representation of cloud field geometry. Previous work indicates that the stochastic approach to cloud-radiation parameterization performs better than typical plane-parallel algorithms in situations where the horizontal cloud fraction is between 0.2 an...