The Role of Environmental Shear and Thermodynamic condition in Determining the Structure and Evolution of Mesoscale Convective Systems during TOGA COARE Mon. Wea. Rev. 1998 M. A. LeMone, E. J. Zipser and S. B. Trier Today’s contents 1 線状MCSの論文のレビュー (Histrocal Reviews of line-shaped MCS ) 2 LeMoneの論文紹介 （Introduction of LeMone’s paper） 3 自分の研究との関わり合い (Future work of my study) 発表者： 清水 慎吾 Shingo SHIMIZU はじめに Characteristic of linear MCS 線状メソ対流系の特徴 •２～１０個の対流セルがある決まった方向に並んだ強い雨域 （convective line） •１０４ｋｍ２以上の広い面積をもつ弱い雨域（stratiform region） stratiform region Large area of Weak rain region convective line Area of several Convective cells (Houze,1990) 線状MCS全体としての研究課題 (common subject) •三次元構造（対流域と層状域）、気流構造の解明 ① •発生・発達・組織化・維持のmechanismの解明 ② •より大きな場との相互作用（環境場、大きな場へのフィードバック） ③ （運動量輸送、熱輸送、放射特性） 線状MCSの研究年表 ① structure ② mechanism ③ environment 観測解析 数値実験 数値実験 二次元モデル Newton 1950 ① 線状MCSの内部構造（Reflectivity） Moncrieff 1976,78,81 ②② 鉛直シアーとcold poolの関係（対流性と層状性の雨域の特徴） Moncrieff 1976,78,81 Zipser 1977 ① （上昇流の維持過程） Thorpe 1982 ③ Thorpe 1982 Barns 1984 線状MCSと環境風の関係 ②② Rottuno 1985,88 Rottuno 1985,88 Bluestein 1985,87 ③ （下層、中層鉛直シアー） Weisman 1986,92,93 三次元モデル Houze 1990 ③ Weisman 1986,92,93 移動方向、走向、組織化過程 鉛直シアーとcold poolの関係 Fovell 1988 ② （上昇流の維持過程） Fovell 1988 Smull 1985,87a,87b ① 線状MCSの気流構造 ② 上昇流の維持過程 Biggerstaff 1991 ① 二次元モデル Wang 1990 鉛直シアーとcold poolの関係 Keenan 1992 ① ③ 線状MCSの地域特性 （組織化過程） Alexander 1992 Schiesser 1995 LeMene 1998 ③ 地域特性の比較 線状MCSと環境場（UV,T,RH） Main theme 1 環境風に対して、ライン状対流域がどのような走向をもつのか？ (the relation between environmental wind and line orientation) Barnes and Sieckman(1984) ～ Review of past studies ～ GATEの観測結果から ９００～５００hPaの ラインに直交shear ： 大 → fast-moving 小 → slow-moving (ただし、ライン平行shear：中) (more or less than 7 m/s ) Alexander and Young(1992) ９５０～７５０hPaに５ｍ/ｓ以上の風速差 EMEXの観測結果から YES→ shear直交型(shear-perpendicular) NO→ shear平行型（parallel to 800～400 hPa shear ） TOGA-COAREの観測概要と観測領域 Toropical Ocean Global Atmosphere(TOGA)Coupled Atmosphere-Ocean Response Experiment(COARE) (1992-1993年) TOGA-COAREのHPより Five category (Lemone,98) slow-moving Fast-moving ①shear直交型 ②shear平行型 ③小規模scale対流群 ④shear無縁型 ⑤非組織化型 ①shear直交型 下層（１０００～８００hPa） shearに直交 ② shear平行型 中層（８００～４００hPa） shearに平行 ① ② 混合型は？ ⑤ ① ② ①② 目的 (objective) ①環境風に対して、ライン状対流域がどのような走向をもつのか？ （The relation between environmental vertical wind shear and convective line orientation） ②ライン状対流域が維持に、重要な環境場の熱力学パラメータ は？ （What environmental thermodynamical factor determines the maintenance of convective line ?） ～ 観測計画間の比較（GATE,EMEXとの比較） ～ データ(data) 飛行機搭載radarによる反射強度分布データ （radar reflectivity observed by three airplanes.) (20 cases during 1992 – 1993 in TOGA-COARE) 3台の飛行機による (three airplane observation) •直接観測(potential theta, specific humidity,winds) •飛行機からのドロップゾンデ(dropsonde) ゾンデデータ(radiosonde) データ（analysis method） 走向の評価 飛行機による radar観測 環境場の評価 Radiosonde （6km～） dropsonde （1km～6km） In situ measurement （1km～6km） (30m～1km) Definition of “inflow environment” storm-relative inflow の風上150 km ×150 kmの領域において •高度300m以下で混合層がよく発達した場 （qv,θ一様場） •高度400m以下で降水がない (no liquid water) 目的１ Objective 1 環境風に対して、ライン状対流域がどのような走向をもつのか？ The relation between environmental vertical wind shear And Orientaion of Line-shaped MCS データ（Case selection） 20 cases of line-MCS Each case studies were reported by (Observation) Jorgensen(97) Lewis(98) (Numerical simulation) Trier(96,98) Reflectivity and hodograph ①Shear直交型 下層（１０００～８００hPa） shearに直交 高度３００ｍの ラインの走向 と 移動速度の 走向に直交する 成分 １５ dBZがoutline ２５ dBZがshade low-level shear : Large Definition of “Large shear” 2 (1.25) m/s per 100 hPa 4 m/s (1000-800 hPa) 5 m/s (800-400 hPa) Fast-moving (7 m/s) (perpendicular to convective line) CAPE Reflectivity and hodograph ②Shear平行型 中層shearに平行 low-level shear : Small mid-level shear : Strong Slow-moving (almost stationary) ２０ dBZがoutline ３０ dBZがshade Reflectivity and hodograph ①②混合型 下層shearに直交 中層shearに平行 low-level shear : Strong mid-level shear : Strong Fast-moving Secondary band ２０ dBZがoutline ３０ dBZがshade Time evolution of orientation ３０分後 After 30 min ２０ dBZがoutline ３０ dBZがshade Reflectivity and hodograph ①②混合型 下層shearに直交 中層shearに平行 low-level shear : Strong mid-level shear : Strong Fast-moving (except for 6 Feb) ２０ dBZがoutline ３０ dBZがshade Reflectivity and hodograph ①②混合型 下層shearに直交 中層shearに平行 low-level shear : Strong mid-level shear : Strong Fast-moving ２０ dBZがoutline ３０ dBZがshade Summary of objective 1 The relation between vertical shear and Line orientation １）If strong low-level shear exists, → shear-perpendicular type 2）If strong mid-level shear exists without strong low-level shear, → shear-parallel type 3）If strong both low- and midlevel shear exists, → primary bands first form perpendicular to low-level shear →After that, secondary bands form trailing or leading primary band parallel to mid-level shear 目的２ Objective 2 ライン状対流域が維持に重要な 環境場の熱力学パラメータは？ What environmental thermodynamical parameter determines the maintenance of line-shaped MCS ? Comparison of “convective line” lifetime between GATE and COARE In a strong low-level vertical shear environment, Convective line tends to be long-lived (Rottuno,1988) In this study, the impact of thermodynamical parameters on the lifetime. Slow-moving lines are focused. (they forms in a weak low-level vertical shear) slow-moving line in GATE •Typical lifetime of convective line is 4-5 hours •Continuous propagation slow-moving line in COARE •Longest lifetime was 3 hours (2/17 case), the others was < 2 hours •Discontinuously propagation (except for 2/17) The comparison of RH profiles between GATE and COARE Mid-level RH (top of BL and 500 hPa) is higher in slow-moving GATE than that of COARE The lifetime of Slow-moving lines in GATE is longer than those in COARE Strength of cold pool Evaluated by the deficit of temperature Cold pool was weaker in both GATE and COARE than that of midlatitude Cold pool of 2/17 is weaker than that of 2/18 Lifetime of line on 2/17 Is longer than that on 2/18 The vertical profile of Relative Humidity (3 cases in COARE) The RH in mid-level (top of BL and 500 hPa) on 17 Feb was higher than that on 18 Feb A weaker cold pool on 2/17 Thermodynamical parameter Conclusion The relation between shear and orientation was confirmed and extended If strong both low- and mid-level shear exists, → primary band first forms perpendicular to low-level shear → After that, secondary convective line formed trailing or leading primary band parallel to mid-level shear Thermodynamical parameter to determine the lifetime of convective line In a weak low-level shear environment, Humidity between top of boundary layer and 500 hPa determines the lifetime of convective line (more than 1 hour longer). Convective inhibits in GATE and COARE (less than 10 J/kg) were smaller than those of midlatitude(60-100 J/kg) In small CIN, and high RH at mid-level environment, Convective line would be well-maintained. For my study・・・・ ① structure 観測解析 Newton 1950 ① Zipser 1977 ① ③ Barns 1984 Bluestein 1985,87 ③ Houze 1990 ③ Smull 1985,87a,87b ① Biggerstaff 1991 ① Wang 1990 Keenan 1992 ① ③ Alexander 1992 Schiesser 1995 LeMene 1998 ③ ② mechanism ③ environment 数値実験 Moncrieff 1976,78,81 ② Thorpe 1982 Rottuno 1985,88 Weisman 1986,92,93 ② Fovell 1988 ② •In various places, •Observational or Numerical Studies •Could be conducted in high-resolution For my study・・・・ ① structure Convective cell’s feature Bluestein 1985,87 ③ Fovell 1988 ② ② mechanism ③ environment Linear MCS’s feature Rottuno 1985,88 ② 環 境 場 の 特 性 LeMene 1998 ③ Barnes 1984 ③ Kato,1998 ① ② ③ Seko, 2002 ① ② ③ Yoshizaki,2000 ① ② ③ input (Environment) Instability Vertical shear Mid-level humidity dry Moist process (mechanism) output(structure) 対流セルとシステムの関係 •対流セル （対流セルの組織化過程） •ＭＣＳ の特徴 Composite profiles of θe, Obtained in GATE and COARE Equivalent PT of COARE is higher than that of GATE It depends on the difference of SST(1-2 K higher in COARE) The vertical gradient of EPT is Similar (17 K drop between 600 hPa and surface) Mean profiles of q,θ,θe within boundary layer Obtained in COARE Below 400 m, Mixing layer exists Qv,PT,EPT of COARE are higher (qv 18 g:PT: 301K:EPT : 355 K) （GATE : 17 g : 298.5 K :348 K） At surface Smaller scale convection (shallow convection and little stratiform region) ２０ dBZがoutline ３０ dBZがshade shear無縁型 （他のMCSの Outflowによるもの） ２０ dBZがoutline ３０ dBZがshade shear無縁型 ２０ dBZがoutline ３０ dBZがshade 非組織化型 鉛直シアーが 小さい ２０ dBZがoutline ３０ dBZがshade Orientation and wind shear 走向が鉛直シアーと３０°以内は太字 Discussion 1 Modification of wind by convective line Discussion 2 Frequency of linear MCS Frequency of organization to line-shape GATE : 90 % (Houze,96 ,Alkell 77) COARE: 66% (Rickenbanch , 1998) Frequency of slow or fast moving line GATE : mainly slow-moving (avarage speed 2.9 m/s) （slow moving : 80 cases, fast moving: 6 cases 7% ） COARE: more fast-moving can be observed relatively (fast moving : 30 % )
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