1 / 32

準理想中尺度對流系統中的動量傳輸

準理想中尺度對流系統中的動量傳輸. Mahoney, K. M., G. M. Lackmann, and M. D. Parker, 2009: The role of momentum transport in the motion of a quasi-idealized mesoscale convective system. Mon. Wea. Rev. , 137 , 3316–3338. 前言 前人研究 模式設定 結果 結論. 大鋼. Radar reflectivity.

alta
Download Presentation

準理想中尺度對流系統中的動量傳輸

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 準理想中尺度對流系統中的動量傳輸 Mahoney, K. M., G. M. Lackmann, and M. D. Parker, 2009: The role of momentum transport in the motion of a quasi-idealized mesoscale convective system. Mon. Wea. Rev., 137, 3316–3338.

  2. 前言 • 前人研究 • 模式設定 • 結果 • 結論 大鋼

  3. Radar reflectivity Houze et al.(1989) → RIJ向下傳遞過程決定於MCS的對流區和層狀區的渦度平衡結果。Weisman (1992) RIJ與對流區的中尺度渦旋結合，會在近地面產生強風。Trapp and Weisman (2003) and Atkins andSt. Laurent (2009) C: 加速度 Cold pool 前言

  4. CPschemes中過於忽略或簡化MCS中的convective momentum transport (CMT) process 會影響正確的MCS運動的表現。 • 本篇主要探討驅使MCS移動的過程，特別是CMT過程。 前言

  5. 周圍環境的大尺度動量場中，MCS內CMT的影響。( e.g.,Houze 1973; Grubisˇic´ and Moncrieff 2000; Mechemet al. 2006) • 在熱帶MCSs的層狀區內和其下方的動量傳輸，影響低對流層的風場。Houze et al. (2000) andMechem et al. (2006) • 經由上層西風動量的向下傳輸，使得近地面的西風增強。Mechem et al. (2006) 前人研究

  6. 動量方程： (忽略摩擦項) • RIJ受到中尺度低壓的”擾動氣壓梯度力”的影響，產生加速度。 • 下降的RIJ，主要受到層狀區”負浮力”的影響。(融化、昇華、蒸發和雨水) • (e.g., Srivastava 1987; Braun and Houze 1997; Grimet al. 2009) MCS 動量傳輸

  7. RIJ將環境中的乾空氣引入層狀降水區，產生融化、蒸發或昇華，造成冷卻，使得RIJ有助於維持近地面冷池。RIJ將環境中的乾空氣引入層狀降水區，產生融化、蒸發或昇華，造成冷卻，使得RIJ有助於維持近地面冷池。 • RIJ將高層動量傳遞至低層，增加冷池內的風速。 (e.g., Smull and Houze 1987;Haertel and Johnson 2000; Houze et al. 2000; Mechemet al. 2006)

  8. 模式設定

  9. Initial background state (F00) Contours: 500-hPa geopotential heigh Shaded: wind (m/s) Solid contours: isentropes (K) Dash contours: isotachs (m/s) Shaded: CAPE (J/kg) Contours: CIN(J/kg) Weisman and Klemp (1982) Surface-base 35N，95W

  10. WRF modelV2.2 4-km 1800 km X 1800 km 1-km 676 km X 604 km

  11. u = uSR + Cx ; v = vSR +Cy 水平動量方程

  12. 結果

  13. Simulated composite reflectivity Cold pool: T’ = -2℃ dBz

  14. Contour:p’ (hPa) Shaded: cold pool Contour: total perturbation wind Gray dotted contour: reflectivity (℃)

  15. (k) (k) Shaded: T’ (k)at 2 m Blak contours : divergence at 10m (-5X10^-4 s-1) Dash : reflectivity

  16. Theoretical cold pool speed: Nicholls et al. (1988) and Trier et al. (2006)

  17. (3 km) (900-200 hPa)

  18. Shaded: totalwind speed (m/s) Contours: reflectivity(dBz)

  19. Blue contours : cold pool Shaded: downward momentum flux Black contours: reflectivity convergence Moment flux 800 m 800 m 2000 m 2000 m (m2/s2) (m/s2)

  20. F06 Shaded : reflectivity 800 m

  21. (TEN) F06 Shaded : u (m/s) Dotted contours: reflectivity (HAu’) (PGA) _ (VAu’) (VAu)

  22. Volume-averaged momentum budget Trailing: △x = 40-120km △z = 0-6km Leading: △x = 0-40km △z = 0-3km

  23. VOL-leading VOL-trailing

  24. RIJ~5 km

  25. 結論

  26. Rear-to-front wind

  27. 由高處向下傳輸的動量，增加冷池內的風速以及MCS本身的速度。由高處向下傳輸的動量，增加冷池內的風速以及MCS本身的速度。 • MCS的運動受到水平動量的垂直傳輸所影響。

  28. THE END

  29. CMT影響MCS運動的方式： • MCS運動中的平流項會經由高層部分的RIJ而增加。 • 向下的CMT增加冷池本身的速度，使得系統移速增加。

More Related