Dust and climate have mutual feedbacks. Although dust storms are due to large-scale and regional atmospheric circulation systems, but these systems will be affected by dust. In this study, these feedbacks will be investigated. The WRF-CHEM model and the GOCART aerospace scheme are used for the simulations. Investigation of the direct effects of dust in Mesopotamia and southwestern Iran shows that the occurrence of dust leads to increases the long-wave radiation and decreases the short-wave radiation, which decreases the rate of short-wave radiation much more than the amount of long-wave radiation at the surface. Therefore, the dust reduces the net radiation received at the surface. So dust leads to surface cooling over the study area. Dust also results in a weakening of the summer high pressure located in the eastern part of the Arabian Peninsula, which is one of the systems of pressure that influences the formation of sever summer wind in the Mesopotamia region. As the system weakens, the pressure difference between the eastern part of the Arabian Peninsula and the interior of Iran will decrease and such condition leads to decreases of wind speed. In the case study, the rate of wind speed reduction in the Gulf region and southern Iraq (at most) was -5 and -3 m/s respectively and the average rate of wind speed reduction in the region in this case was -2.3 m/s. Therefore, the presence of dust weakens the wind velocity, which results is weakening the diffusion of dust over the study area.