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<br />is usually taken after obserwlQ cloud echoes <br />on TIT AN and the echo development trend <br />SometImes an operatIOn IS launched after <br />watching clouds grow visually or by observing <br />the surface temperature reach a threShold <br />when convection is expected 10 inrtiate or <br />intensify. referred to as the convectlve <br />temperature. For an operation 'Nith good <br />timing, decision time should be preceded by <br />qualificalJOn <br /> <br />3) Qualification is when a cloud becomes <br />seedable. This decision can be made visually <br />by the pilot observing a doud before It is <br />detected by radar. Most frequenUy, a cloud is <br />observed on radar before seeding OCCUr3. In <br />the SOAR target area, a seedable cloud echo <br />usually reaches a Vll of 10 kglm2 and <br />continues rising The volume of the cloud echo <br />should be in the order of 200km3 with cloud <br />tops above 8 km. The development trend of <br />other clouds outside the target area is usually <br />observed to determine the growth <br />characteristics and the lifetime of the clouds A <br />short lifetime does not allow much opportunity <br />for seeding On TITAN, a seedable cloud <br />usually shows a pocket of about 15% of the <br />echo volume with a higher reflectivity at or <br />slightly above 40 dBZ reflectivity at an altitude <br />ranging from 6 to 10 km. This is characteristic <br />of a doud with weak coalescence and 'Nith a <br />loading of supercooled liquid water above the <br />freezing level early in its lifetime. Such a case <br />is shown in Figure 12. <br /> <br />4) Treatment is the time after initial seeding <br />Occasionally, treatment may be preceded by <br />qualification in isolated cases. In most cases, <br />however, a cloud qualifies as seedable and the <br />meteorologist instructs the pilot 10 start <br />seeding The seeding starts when the pilot <br />encounter3, locates or is directed to the updraft <br />portion of the cloud where the agent is <br />released. The ulXiraft usually has to exceed <br />200 feet per minute. <br /> <br />5) Maintenance is when a constant rate of <br />seeding is established 'Nith continued <br />observations of growth in the echoing volume <br />During this period the cloud echo has not <br />reached it's half-life time. Careful analysis of <br />the dynamic variables of the cloud echo and <br />their trend is necessary to define the half.life of <br />the cloud. The pilot usually continues to <br />experience updrafts and the meteorologist is <br /> <br />able to locate areas of new growth 'Nithin the <br />doud structure. <br /> <br />6) Termination IS when seeding IS stopped. A <br />seeding operation is usually lenninated either <br />due to the absence of updrafts and/or due to <br />the doud echo exceeding its half..llfe time. <br />When the National Weather Service issues a <br />warning on the seeded cloud. the seeding is <br />terminated. <br /> <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />l <br />4 <br />4 <br />4 <br />4 <br />l <br />l <br />l <br />l <br />l <br />l <br />4 <br />4 <br />4 <br />4 <br />4 <br />4 <br />4 <br />4 <br />4 <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br /> <br />FIQure12 <br /> <br />F'9ure13 <br /> <br /> <br />F'9ure 14 <br /> <br />FlQures 12, 13 and 14 show- a seedable dood very early <br />In the stages of development on the 23m June 2003- <br />Fl9Ure 12 sha-Ns a region of high reflecllvity (A). FIQlJfe <br />14 ~ this region (C) to be alan altltude of6 km <br />Ideflbfying a s1rcf1g verbcaI grad~llfl refiectivity. ~ not <br />seeded, this cloud 'M)U\d retain the water above the 6 <br />km level and would be available to nucleate at CXlIder <br />terJl)efaltres and form hail, The lighter tones in Figure <br />13 ~ a large area of inflow (S}wtlefe the seeding <br />aJrl)'aftISPos:tloned <br /> <br />21 <br />