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<br />ATTACHMENT B <br /> <br />October 28, 1981 <br /> <br />SEEDING CRITERIA <br /> <br />The selection of suitable cloud systems for seeding operations will be <br />based on an evaluation of multiple meteorological and cloud physics <br />parameters. It is the understanding that the following criteria will be <br />adhered to: <br /> <br />a. Cloud base water - Natural Precipitation. Cloud systems <br />with a cloud base water content of 1.5 gms/kgm (North <br />Sector) to 1.8 gms/kgro (South Sector) or greater will be <br />considered as potentially seedab1e. In this consideration <br />a weather system will be evaluated for seeding potential if <br />it is determined that at least natural precipitation is <br />likely to occur. <br /> <br />b. Effective temperature Pre-trough or Pre-frontal. Cloud <br />systems with a 500 MB temperature of -27 degrees C or <br />warmer will be considered as potentially seedab1e. <br /> <br />c. Effective temperature Post-trough or Post-frontal. Cloud <br />systems with cloud top temperatures of -27 degrees C (North <br />Sector) to -30 degrees (South Sector) will be considered as <br />potentially seedab1e. <br /> <br />d. Barrier level winds. Wind speeds from favorable directions <br />at heights approximately 2,000 feet above the seeded <br />barrier of 30 knots or less for pre-trough cloud types and <br />up to 40 knots or less for post-trough clouds will be <br />considered as potentially favorable for seeding treatment. <br />Some adjustments are made to the acceptable wind velocity <br />ranges depending on the width of the barrier to be seeded. <br /> <br />e. Cloud base height. Cloud systems with bases less than <br />2,000 feet above the mean barrier height will be considered <br />as potentially seedab1e. <br /> <br />f. Additional weather system considerations. Additional <br />adjustments will be made on the seeding rate or the seeding <br />potential of a cloud system based upon the depth of the <br />cloud system to be seeded, whether the cloud system is <br />indicating redevelopment or is near its decaying stage and <br />whether the cloud system has a potential source of abundant <br />natural nuclei from higher cloud systems. <br /> <br />Once a weather system is considered seedab1e by evaluating <br />the above cloud and meteorological parameters, an <br />appropriate seed rate is calculated for the initial portion <br />of the weather system. As the forecast and observed <br />parameters of the weather system change, seeding rates are <br />re-evaluated and changed as is necessary for the new or <br />expected cloud conditions. <br />