To monitor changes in surface conditions from space requires information on the state of the atmosphere to correct for atmospheric effects in the remotely sensed signal. The least observed and most variable atmospheric parameters are aerosols. Of particular interest are changes of surface conditions in areas where desert encroachment is of concern. An effort was initiated at one of such locations to monitor atmospheric conditions from the ground and surface conditions from space. In this paper we present results only on the ground observations of the aerosol optical depths, in particular their annual and diurnal variations, in the context of prevailing synoptic conditions.¿ 1997 American Geophysical Union