中空对柱状冰晶散射特征的影响.doc

 中空对柱状冰晶散射特征的影响 刘春雷 姚克亚 ( 地球和空间科学系 ,第三世界科学院中国科技大学地球科学和天文学高级研究中心) 摘要 使用光线跟踪法 ,对在二维平面和三维空间随机取向的中空六棱柱体的散射相函数进 行了计算. 三维模式结果显示 ,一般情况下 ,固体柱体和中空六棱柱体的散射相函数非常接近 , 仅当中空六棱柱体的柱壁非常薄时 ,会产生 120°峰值. 二维模式结果显示 ,中空六棱柱体产生 的 22°和 120°峰值随柱壁厚度不同而变化. 衍射计算结果表明 ,粒子内部结构对衍射影响不 大 ,衍射主要受粒子外形大小的影响. 关键词 柱状冰晶 ,中空影响 ,散射特征 中图法分类号 P422 . 31 第 2 6 卷 第 4 期 1 9 9 6 年 1 2 月 中 国 科 学 技 术 大 学 学 报 JO URNAL OF CHINA UNIVERSITY OF SCIENCE AND TECHNOLO GY Vol . 26 ,No . 4 Dec. 1996 The Holl o w Ef f ect on Col umnar Ice Crystal Sca tter ing Propert ies 3 Liu Chunlei Yao Keya (Dep t . of Eart h and Space Sciences ,Advanced Cent re for Eart h Sciences and Ast ro no my , U S TC , Third World Academy of Science) The p hase f unctio n p roperties were investigated fo r hollow column2like ice crys2 Abstract tals , using t he geo met rical ray t racing technique . The effect s of hollow cent res o n R EF ( re2 flectio n and ref ractio n) and diff ractio n of columnar crystals are investigated. The result s show t hat fo r ice crystals rando mly o riented in space , t here are small differences bet ween t he solid and hollow column p hase f unctio ns. Fo r instance , w hen t he side wall of t he hollow col2 umn is very t hin , t he intensit y of t he 22?halo will be decreased , and w hen t he hollow radius is aro und half of t he total column radius , t he weak 120?peak can be seen . Fo r ice crystals rando mly o riented in t he ho rizo ntal plane , t here are o bvio us differences bet ween t he solid and hollow ice crystals , t he 22?halo and 120?peak vary wit h t he t hickness of t he crystal side wall . So me of t hese scat tering feat ures are explained geo met rically. Key words columnar ice crystal , hollow effect , scat tering p roperties 1 Introduct ion Cirrus and ot her high altit ude clo uds w hich cover abo ut 20 % o r mo re of t he glo be were iden2 tified as o ne of t he majo r unsolved co mpo nent s in weat her and climate research1 . Due to t heir high altit ude , it is ve