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[资源共享]JMA氣象研究部論文:海燕登陸前強度及內核的雷達分析

楼主#
更多 发布于:2017-12-13 12:47
Intensity and Inner-core Structure of Typhoon Haiyan (2013) Near Landfall: Doppler Radar Analysis
http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-17-0120.1

The intensity and inner-core structure of an extremely intense tropical cyclone, Typhoon Haiyan (2013), were examined using real-time ground-based Doppler radar products from the Guiuan radar over the period of about 2.5 h immediately before the storm approached Guiuan in Eastern Samar, Philippines. Haiyan’s wind fields from 2- to 6-km altitude were retrieved by the ground-based velocity track display (GBVTD) technique from the Doppler velocity data. The GBVTD-retrieved maximum wind speed reached 101 m s–1 at 4-km altitude on the right side of the track. The relatively fast forward speed of Haiyan, about 11 m s–1, increased maximum wind speed on the right hand side of the storm. Azimuthal mean tangential wind increased with height from 2 to 5 km, and a local maximum of 86 m s–1 occurred at 5-km altitude. The central pressure was estimated as 906 hPa with an uncertainty of ±4 hPa by using the GBVTD-retrieved tangential wind and by assuming gradient wind balance. The radius of maximum radar reflectivity was about 23 km from the center, a few kilometers inside the radius of maximum wind. The reflectivity structure was highly asymmetric at and above 3-km altitude, and was more symmetric below 3-km altitude in the presence of relatively weak vertical shear (~4 m s–1). The center of the eyewall ring was tilted slightly downshear with height.

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[新细明体于2017-12-13 14:03编辑了帖子]
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meow
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1楼#
发布于:2017-12-13 13:29
说“强度再分析”歧义太大,应该直接说雷达加速度分析,以前我也发过类似报告。

http://bbs.typhoon.org.cn/read.php?tid=76588&fid=10
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  • 新细明体
    金钱 0.0
    and MRI is under JMA so there shouldn't be any further problem.
    2017-12-13 13:45
  • 新细明体
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    Edited and please note that this is the full paper.
    2017-12-13 13:43
Meow, a sex-starved pussy, gets aroused when everyone at the pool stares at her white and soaked up swimsuit turning see-through and exposing her tempting body.
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2楼#
发布于:2017-12-13 14:45
最后总结比较多风迷关注的内容,推算一分钟持续风速在每秒81到91米之间,和JTWC评价相当;推算登陆前最低气压906百帕,稍高于JMA评价。

We examined the intensity and inner-core structure of a very intense TC, Typhoon Haiyan (2013), by using Doppler velocity and radar reflectivity data observed by the Guiuan radar over a period of about 2.5 h immediately before the storm approached Guiuan in Eastern Samar, Philippines. The Doppler velocity data used in this study suffered from serious issues associated with Doppler aliasing and spatial smoothing. The spatial smoothing of the Doppler velocity data with a local nine-point filter made it impossible to dealias Doppler velocities in some areas. We managed, however, to remove outliers by using threshold values to dealias Doppler velocities.

The maximum wind speed at 4-km altitude retrieved by the GBVTD technique was up to 101 m s –1 on the right side of the track. The relatively fast forward speed of Haiyan, about 11 m s –1 , increased maximum wind speed on the right hand side of the storm. By applying reduction factors (Franklin et al. 2003) to the 3- and 2-km maximum wind speeds, we estimated the surface 1-min sustained wind speed to be 81–91 m s –1 . This estimate is consistent with the maximum 1-min sustained wind speed of 170 kt (~88 m s –1 ) in JTWC’s best-track data, and it is also consistent with the lifetime maximum intensity of 176 kt (~91 m s –1 ) estimated by Velden et al. (2017). The MSLP of Haiyan was estimated to be 906 hPa with an uncertainty of ±4 hPa by using the GBVTD-retrieved tangential wind and the assumption of gradient wind balance. The estimated MSLP is slightly higher than that of RSMC Tokyo’s best track data.

Haiyan had an unusual vertical wind profile. The azimuthal mean tangential wind increased with height from 2 to 5 km and reached a maximum, 86 m s –1 , at 5-km altitude. The RMW sloped radially inward from 3- to 5-km altitude just below the wind maximum. The radius of maximum radar reflectivity (RMRR) was ~23 km from the center, a few kilometers inside the RMW. The strongest convection occurred in the downshear-left quadrant of the eyewall. The reflectivity structure of Haiyan was highly asymmetric at 3-km altitude and above, and more symmetric below 3-km altitude in the presence of a relatively weak vertical shear. We attributed the difference between reflectivity structures at low levels and mid to upper levels to the extremely strong wind speed and the relatively fast forward speed of Haiyan. The center was tilted slightly downshear with height. In addition, the time evolution of the tilt showed cyclonic rotation.

The results presented in this study could be used to study landfall effects of very intense TCs. If the quality of Doppler velocity data can be improved to retrieve wind speeds greater than 100 m s –1 without subjective quality control, it will be possible to retrieve TC wind fields in real time to monitor a landfalling TC. The analysis of Haiyan’s inner-core structure in this study was primarily done by using radar reflectivity data, except for the wind profile at 2020 UTC. To better understand the intensification and maintenance processes of very intense TCs, a more in-depth examination using wind field data is indispensable. In future studies, we plan to investigate other intense TCs observed by operational Doppler radars installed in the Philippines and to examine their dynamical processes.
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3楼#
发布于:2017-12-14 03:07
總結一下一些個人認為比較有趣的發現。

1. 海燕的垂直風力分佈中有兩個最大風速區:一個集中在低層並與邊界層相關,與一般颱風的結構也比較吻合,另一個集中在中高層。Dennis, Rita, Patricia等颶風亦出現過類似的垂直風力分佈。另外論文中使用了一般的換算因子推算風速,但按照Megi, Patricia等颱風的實測例子來看,飛行層面(~2km)換算因子可能比預期高,甚至接近1:1,所以論文中的推算也可能低估了強度。

图片:Screen Shot 2017-12-14 at 02.47.37.png



2. 海燕登陸前可能正準備開始眼壁置換

图片:Screen Shot 2017-12-14 at 02.49.22.png



3. 吉萬910hPa的數據可能是站壓,而本文亦因此進行了氣壓上的修正。翻查PAGASA的幾份報告,發現官方用詞一直也是‘pressure’和'station pressure',唯一指出此數據為海壓的好像只有iCyclone。再翻查吉萬站的國際報文,發現無論是站壓和海壓也不吻合。

图片:Screen Shot 2017-12-14 at 02.53.47.png


图片:Screen Shot 2017-12-14 at 02.53.00.png


图片:Screen Shot 2017-12-14 at 02.53.27.png


图片:Screen Shot 2017-12-14 at 02.53.58.png


(Reference: https://www.jst.go.jp/sicp/ws2015_j-rapid_result/pdf/1_Kubota_Cayanan_web.pdf & http://www.eumetrain.org/data/3/325/hiw_session_4.pdf)

基於菲國觀察和雷達資料上的質量問題,這項研究的強度推算結果還是有一定的不確定性的。當然,就內核分析而言,個人認為這份論文還是相當值得一看的。JMA也有打算用類似的方法推算其他菲國附近的頂級颱風,估計Meranti, Nock-ten等颱風之後也會有相關的分析。
[新细明体于2017-12-14 03:08编辑了帖子]
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  • 金杯
    威望 10
    好!
    2017-12-14 04:23
  • 颱風巨爵
    金钱 0.0
    被低估的例子,這和颶風在深厚高壓脊引導下高速西行似乎有一定關係。
    2017-12-14 03:51
  • 颱風巨爵
    金钱 0.0
    近表面風速等於甚至超過飛行層面,如Felix(2007)和Jose(2017)都是可能被低估的例子,
    2017-12-14 03:49
  • 颱風巨爵
    金钱 0.0
    關於(1)提及的換算因子,值得一提的是大西洋過去不少頂級颶風觀測出的近表面風速等於甚至超過飛行層面,
    2017-12-14 03:47
  • 颱風巨爵
    威望 5
    2017-12-14 03:25
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