Comparison of aerosol optical depth from four solar radiometers during theFall 1997 ARM Intensive Observation Period

In the Fall of 1997 the Atmospheric Radiation Measurement (ARM) program con ducted an Intensive Observation Period (IOP) to study aerosols. Five sun-tr acking radiometers were present to measure the total column aerosol optical depth. This comparison performed on the Southern Great Plains (SGP) demons trates the capabilities and limitations of modern tracking sunphotometers a t a location typical of where aerosol measurements are required. The key re sult was agreement in aerosol optical depth measured by 4 of the 5 instrume nts within 0.015 (rms). The key to this level of agreement was meticulous c are in the calibrations of the instruments.