SLIDE 3 Meteorology. Downwind expsoure rate contours were estimated hy several groups (Armed Forces Special Weapons Project, Rand Corporation, Naval Radiological Defense Laboratory) for the BRAVO detonation (Ha79). These contours were - based on observations of BRAVO cloud dimensions and hodographs for 3 hours, 6 hours and 9 hours post detonation. These contours do not all agree but are within a factor of two for any specific location at Rongelap and Utirik Atolls. Significant departure in exposure rate contours occurs 32 to 190 km (20 to 120 miles) north of Rongelap Atoll out to a distance of 480 km (300 miles) east of the detonation site. Kendall Peterson estimated downwind exposures using the MATHEW-ADPIC modified code suite (Pe81). ditiogally, .Petergqn develo instantaneous activity concentrations for 1280 134; 1353 137C6. and Po for Ailingnae Atoll and the southeastern part of Rongelap Atoll in proximity to Rongelap Island. The computer codes were developed for the Atmospheric Release Advisory Capability of the Department of Energy. They were modified to include a large number of upper-air wind levels which was thought by Peterson to be important. Additional modification included a turbulent wake correction to large granules falling from the stratosphere. Parameters for a tropical atmosphere were incorporated into granule fall velocity calculations. An assumption that the activity per granule increased as the cube of granule radius was made. Further description of the analytical approach has heen given by Peterson (Pe8l1). METEOROLOGY 47.5 $2.5 42.5 37.5 375 37.5 32.5 32.5 32.5