There are still large areas not covered by the AERONET network. One of these large gaps is located in Northern South America (Tropical Andes). This gap is ~27° latitudinal when one specifically looks at the Andes (11° N – 16° S). We propose to seasonally (6 months/year) monitor and retrieve aerosol properties and Total Precipitable Water (TPW) at carefully selected sites in Colombia using an automatic sunphotometer provided by NASA/GSFC. The sunphotometer will be evenly shared with the Lasers and Spectroscopy Group (GLEO) of Universidad Nacional de Colombia at Medellin. The seasonal operation of the sunphotomer will allow us to measure, retrieve and calculate, for the first time in Colombia, a significant number of aerosol and meteorological parameters over several scientifically promising monitoring sites. The atmospheric measurements and retrieved properties, along with back trajectory calculations, will provide new information on the aerosol load, evolution and transport over regionally representative locations, and eventually on aerosol pollution events (e.g. from biomass burning and volcano activity) over Colombia. The quasi-climatological dataset built over time will allow us to develop a comprehensive picture of the regional aerosol behavior over Colombia. The dataset will also contribute to satellite measurement validation.