! Applicatin f a Cupled EnKF and 4DVar Data Assimilatin Methd in the Study f Trpical Cyclne Genesis Ashfrd Reyes, Gregry Jenkins, Jnathan PterJy and Fuqing Zhang Hward University Prgram fr Atmspheric Sciences, Washingtn DC Department f Meterlgy Pennsylvania State University, University The 6th EnKF Wrkshp May st 4
Intrductin This study makes use f a cupled EnKF-4DVar data assimilatin methd (knwn as E4DVar) t assimilate cnventinal and field campaign bservatins taken during NASA Genesis and Rapid Intensificatin Prcesses (GRIP) and NSF Pre-depressin Investigatin f Clud Systems in the Trpics (PREDICT) cnducted in summer f The bjective f bth GRIP and PREDICT was t cllect bservatins f trpical cyclnes in rder t test certain hypthesis fr genesis and rapid intensificatin Fr this study we will eamine and cmpare the genesis f hurricane Karl and trpical strm Mathew f the hurricane seasn
Case Studies UTC 8 Sept W W Hurricane Karl () 8 UTC 4 Sept 8 W 7 W Track trpical wave trpical depressin trpical strm hurricane UTC Sept 6 W Karl was a categry 3 hurricane with a minimum central pressure f 56 hpa and maimum sustained winds f knts Frmed at 8 N, 836 W n September 4th at 8Z 8 UTC 6 Sept W W Trpical Strm Mathew () 8 UTC 3 Sept Track trpical wave trpical depressin trpical strm hurricane UTC Sept Mathew had a minimum central pressure f 8 hpa and maimum sustained winds f 5 knts Frmed at 3 N, 76 W n September 3rd at 8Z 8 W 7 W 6 W
Observatins 3 N 3 N W Cnventinal Observatins + ++ + + + ++ + + + + + + + + + + + + + + ++ + + + + + + + + ++ + + + + + + + + + + + + + + + + + + UTC 8 Sept + + 8 UTC + 4 Sept UTC Sept + + W 8 W 7 W 6 W Track trpical wave trpical strm hurricane Observatins sat winds belw 5 mb sat winds abve 5 mb sundings + buys METARs 5 W Field Campaign Observatins Track trpical wave trpical strm hurricane Cnventinal bservatins were btained frm the Meterlgical Assimilatin Data Ingest System (MADIS) The assimilated data include cnventinal bservatins frm MADIS and drpsnde measurements cllected during PREDICT and GRIP field campaigns UTC 8 Sept 8 UTC 4 Sept PREDICT drpsndes Sept flight missins () Sept flight missin Sept flight missin 3 Sept flight missin 4 Sept flight missin GRIP drpsndes Sept flight missin 3 Sept flight missin 4 Sept flight missin 6 Sept flight missin 7 Sept flight missin UTC Sept W W 8 W 7 W 6 W 5 W
Cupled EnKF-4DVar Data Assimilatin Schematic Ensemble! Frecast! Separate ensemble int mean and perturbatins! Run 3D/4DVar and EnKF separately! 3D/4DVar analysis becmes psterir mean fr EnKF perturbatins! Ensemble! Analysis! f, f f,,,, N,,! f,! f f, f,,! N, 3D/4DVar! f - is used as first guess! -! f f f,,!,,,! N, are used in the cst functin! EnKF! f - is used as first guess! -! f f f,,!,,,! N, are used t estimate the cvariance! a,! a,! a,,,! a N, a,, a a,,, N, Zhang and Zhang (), Pterjy and Zhang (4)
EnKF, 4DVar and E4DVar Cmparisn
Deterministic Track and Intensity Frecasts 4 N EnKF 4 N 4DVar 4 N E4DVar N N N 8 N 6 N 4 N 8 N 6 N 4 N 8 N 6 N 4 N N a) W 5 W W 85 W 8 W 75 W 7 W 65 W N b) W 5 W W 85 W 8 W 75 W 7 W 65 W N c) W 5 W W 85 W 8 W 75 W 7 W 65 W Ma wind speed (m s ) 5 4 3 d) Analysis time 6 UTC Sept UTC Sept 8 UTC Sept UTC 3 Sept 6 UTC 3 Sept UTC 3 Sept Sept 4 Sept 6 Sept 8 Sept 5 4 3 e) Sept 4 Sept 6 Sept 8 Sept 5 4 3 f) Sept 4 Sept 6 Sept 8 Sept Karl s frecasts initialized 3 6 h befre genesis and run t UTC Sept 8th Pterjy and Zhang (4)
Deterministic Track and Intensity Frecasts 4 N EnKF 4 N 4DVar 4 N E4DVar N N N 8 N 6 N 8 N 6 N 8 N 6 N 4 N 4 N 4 N N a) W 5 W W 85 W 8 W 75 W 7 W 65 W N b) W 5 W W 85 W 8 W 75 W 7 W 65 W N c) W 5 W W 85 W 8 W 75 W 7 W 65 W Ma wind speed (m s ) 5 4 3 d) Analysis time 8 UTC 3 Sept UTC 4 Sept 6 UTC 4 Sept UTC 4 Sept 8 UTC 4 Sept UTC 5 Sept Sept 4 Sept 6 Sept 8 Sept 5 4 3 e) Sept 4 Sept 6 Sept 8 Sept 5 4 3 f) Sept 4 Sept 6 Sept 8 Sept Karl s frecasts initialized within 48 h befre genesis and run t UTC Sept 8th Pterjy and Zhang (4)
EnKF, 4DVar and E4DVar Analyses 6 5 4 3 6 5 4 3 6 5 4 3 8 6 4 5 85 8 a) 5 mb ( 5 s ) b) 5 mb ( 5 s ) c) Tilt (km) d) Shear (m s ) e) Clumn RH (%) Analyses are cmpared between UTC Sept th and UTC Sept 8th Vrticity and 5-5 mb clumn relative humidity are averaged within 3 degrees f the strm center 5-5 mb vertical shear and vrte tilt are estimated using winds within 3 degrees f the strm center E4DVar analyses have smaller 5-5 mb vrte displacements and much higher clumn relative humidity 75 7 65 EnKF 4DVar E4DVar Sept Sept 3 Sept 4 Sept 5 Sept 6 Sept 7 Sept 8 Sept Pterjy and Zhang (4)
E4DVar
Eperimental Design 6 ensemble members Lcalizatin f km in the hrizntal & 5 levels in the vertical Relaatin cefficient f 8 Tw way cupling between EnKF and 4DVar 4DVar uses ensemble mean first guess and ensemble perturbatins EnKF update the ensemble members Hybrid 4DVar analysis replaces the EnKF analysis 8% f the increment cmes frm the ensemble perturbatins during the hybrid minimizatin Assimilatin perfrmed n 35-km grid spacing with 35 vertical levels and a 45-km tw-way nested frecast Eperiments were initialized frm GFS/GDAS analysis and cycled every 6 hurs
Deterministic Track and Intensity Frecasts 4 N 6 N Karl 4 4 N 4 N 6 6 N 6 N Mathew N N N N 8 N 8 8 N 8 N 6 N 4 N N W 5 W W 85 W 8 W 75 W 7 W 65 W 6 W 55 W 6 6 N 6 N 4 4 N 4 N N N N W W 5 5 W 5 W W 85 85 W 8 8 W W 85 W 8 W 75 75 W 7 7 7 W W 65 65 65 W W 6 W 6 6 W 55 W 55 55 W Ma wind speed (m s ) 6 5 4 3 Analysis time 8 UTC Sept UTC 3 Sept 6 UTC 3 Sept UTC 3 Sept 8 UTC 3 Sept UTC 4 Sept Ma Ma wind wind speed speed (m (m s ) 4 6 5 3 3 4 3 Analysis time 8 8 UTC Sept UTC Sept 6 6 UTC Sept UTC Sept 8 8 UTC Sept UTC 3 3 Sept Sept 4 Sept 6 Sept 8 Sept Sept Sept 4 Sept 4 Sept 6 Sept 6 Sept Frecasts initialized within 48-8 h befre genesis
Latitude 4DVar 84 e) 835 83 85 855 8 Vma = 65 m s Deterministic Frecasts 85 845 84 87 865 86 855 85 88 875 87 865 Lngitude Lngitude Lngitude f) g) h) 85 85 85 85 8 8 8 8 75 75 75 UTC 8 UTC 4 UTC 5 5 UTC 5 6 75 V m s ma = 85 m Vma = 8 ms s Vma = 4 Vma = 6 m s 845 84 83 a) 84 b) c) d) 835 85 855 85 87 86 855 85 88 875 87 865 UTC 865 UTC 4 6 4 UTC 4 8 UTC 4 5 5 8 85 i) j) k) l) 85 8 85 a) b) c) d) 85 85 85 75 8 8 85 85 75 8 8 8 8 85 85 7 75 8 8 75 7 75 75 75 75 8 8 65 Vma = s V ma = 5 s V ma = 7 s Vma = 65 m s m m 75 7 m 7 75 65 855 85 7 845 835 85 855 85 845 84 865 88 875 87 865 83 84 87 86 7 Vma s m s = 6 m s V ma = 8 m s V ma = 7 m V ma 7 = 44 Lngitude Lngitude Lngitude Lngitude 75 ma = ma Vma = 4 =ms Vma = 5 s m s m s V 6 V m 84 f) g) h) 845e) 84 835 83 85 855 85 845 87 865 86 855 85 885 88 875 87 865 85 75 7 785 78 8 85 8 75 85 8 83 8 85 84 835 Lngitude Lngitude Lngitude Lngitude 85 85 85 85 4 4 4 7 5 7 5 4 7 5 4 4 7 5 4 4 8 8 8 8 75 75 75 75 Vma = Vma = 8 m s Vma m s 6 m s Vma = 85 m s = 4 Lngitude Karl Latitude Latitude Latitude E4DVar 845 Latitude 4DVar Vma = m s 7 85 Mathew 84 835 83 85 855 85 845 84 87 865 86 855 85 88 875 87 865 8 UTC 3 6 UTC 3 UTC 3 UTC 5 3 i) j) k) l) 45 b) c) a) 4 45 d) 85 4 85 4 85 35 4 8 85 35 35 8 8 3 35 75 8 3 3 75 75 5 s 3 Vma = 44 7 Vma = 6 m s V ma = 8 m s V ma = 7 m m s 75 5 V ma = Vma = 4 m s 8 ma = 73 m s Vma = 7 m s V s m 84 87 845 84 835 83 85 855 85 845 87 865 86 855 85 885 88 875 865 Frecasts initialized 8 h prir t genesis Dashed: 5 mb strm-relative streamlines Shaded: 5 mb relative vrticity (4 4s ) Checkered: 5-5 mb clumn RH (> %) Latitude Latitude E4DVar 8 75 75 Vma = 5 m s Vma = 7 m s 7 75 75 7 75 7 75 735 73 Lngitude 7 5 75 7 75 745 Lngitude 4 4 7 5 74 735 765 76 Lngitude 4 4 7 5 755 75 Lngitude 4 4 7 5 4 4
85 mb Divergence/Cnvergence Field UTC 4 6 UTC 4 Karl UTC 4 8 UTC 4 Latitude 8 75 7 a) 8 75 7 b) 85 8 75 c) 85 8 d) Frecasts initialized 8 h prir t genesis 65 Latitude 65 75 7 6 75 7 785 78 8 85 8 75 83 85 8 85 8 84 835 83 85 Lngitude Lngitude Lngitude Lngitude 3 3 3 3 3 3 3 3 4 35 3 5 5 7 75 7 75 Lngitude Mathew UTC 3 6 UTC 3 UTC 3 8 UTC 3 a) b) c) d) 4 4 4 35 35 35 3 3 5 735 73 75 7 Lngitude 3 5 75 745 74 735 765 76 755 75 Lngitude Lngitude 3 3 3 3 3 3 3 3 Dashed: 85 mb strm-relative streamlines Shaded: 85 mb divergence ( 4 s ) Grid centered ver lw-level vrticity maimum
UTC 4 8 6 UTC 4 a) UTC 4 b) 8 8 UTC 4 c) d) 85 Latitude 75 8 UTC 4 6 UTC 5 Dashed: mb strm-relative streamlines Shaded: mb divergence ( 4s ) Grid centered ver lw-level vrticity maimum 8 UTC 5 7 a) 8 6 UTC 4 8 Frecasts initialized 8 h prir t genesis 85 75 7 b) 8 75 8 c) d) 65 75 Latitude 7 7 6 7 785 78 8 85 Lngitude 6 75 65 7 8 75 83 Lngitude 85 8 85 8 84 835 Lngitude 8 83 85 Lngitude 6 3 5 3 3 3 7 3 3 3 5 3 8 6 4 8 8 e) 4 8 7 78 84 83 f) UTC 3 8 8 a) Mathew 8 8 87 g) 6 UTC 3 b) 4 7 Latitude E4Dvar MADIS Karl 35 Latitude E4Dvar GRIP mb Divergence/Cnvergence Field 86 85 84 8 h) UTC 3 c) 35 8 7 6 3 3 5 5 5 8 UTC 3 d) 35 6 3 86 4 4 35 87 8 7 88 3 5 5 8 7 3 8 75 8 7 Lngitude Lngitude 7 5 7 75 735 4 7 6 3 3 84 73 83 75 8 7 8 75 87 Lngitude Lngitude 7 5 5 4 3 3 86 745 74 85 84 735 Lngitude Lngitude 7 5 765 8 4 3 3 76 88 755 87 Lngitude Lngitude 7 5 75 86 4 3
E4DVar Analyses 6 a) 5 mb ( 5 s ) 4 6 4 b) 5 mb ( 5 s ) Karl s analyses frm UTC Sept th t UTC Sept 5th Mathew s analyses frm UTC Sept th t UTC Sept 4th 6 c) Tilt (km) 4 5 d) Shear (m s ) 5 Vrticity, Tilt, Shear and Clumn RH calculated within 3 degrees f the strm center Bth Karl and Mathew shwed relatively the same trend prir t and during genesis e) Clumn RH (%) 8 7 6 7 48 4 KARL MATHEW
Vrticity (ζ) Prfile Pressure (hpa) Pressure (hpa) 3 4 5 6 7 8 3 4 5 6 7 8 Karl Sept 3 Sept 4 Sept 5 Sept Mathew Sept Sept 3 Sept 4 Sept Karl analysis frm UTC Sept th t UTC Sept 5th Mathew analysis frm UTC Sept th t UTC Sept 4th Mean Vrticity ( 5 s ) calculated within 3 degrees f the strm center Mathew has a strnger mean mid-level vrticity prir t genesis in cmparisn t Karl 6 55 5 45 4 35 3 5 5 5 5 5 5 3 35 4 45 5 55 6
Perturbatin f Ptential Temperature (θ ) Prfile Pressure (hpa) Pressure (hpa) 3 4 5 6 7 8 3 4 5 6 7 8 Karl Sept 3 Sept 4 Sept 5 Sept Mathew Sept Sept 3 Sept 4 Sept 3 Sept 75 5 5 75 5 5 5 5 75 5 5 75 Karl analysis frm UTC Sept th t UTC Sept 5th Mathew analysis frm UTC Sept th t UTC Sept 4th Warming in the mid t upper levels prir t genesis Cling at the surface tgether with warming in the upper levels at time f genesis
Relative Humidity Prfile (3 Degree Avg) Pressure (hpa) Pressure (hpa) 3 4 5 6 7 8 3 4 5 6 7 8 Karl Sept 3 Sept 4 Sept 5 Sept Mathew Sept Sept 3 Sept 4 Sept Karl analysis frm UTC Sept th t UTC Sept 5th Mathew analysis frm UTC Sept th t UTC Sept 4th Mean Relative Humidity (%) calculated within 3 degrees f the strm center 4 45 5 55 6 65 7 75 8 85 5
Relative Humidity Prfile ( Degree Avg) Pressure (hpa) Pressure (hpa) 3 4 5 6 7 8 3 4 5 6 7 8 Karl Sept 3 Sept 4 Sept 5 Sept Mathew Sept Sept 3 Sept 4 Sept Karl analysis frm UTC Sept th t UTC Sept 5th Mathew analysis frm UTC Sept th t UTC Sept 4th Mean Relative Humidity (%) calculated within degrees f the strm center 4 45 5 55 6 65 7 75 8 85 5
Summary and Future Wrk E4DVar has shwn significant skill in the genesis f bth hurricane Karl and trpical strm Mathew E4DVar is able t accurately predict the genesis f Mathew 4 h in advance, which is a significant imprvement ver the NHC peratinal frecasts Add GRIP drpsndes and sunding bservatins t Karl PREDICT case with a 5-km tw way nested dmain Perfrm an independent quantitative verificatin using ECMWF analysis fr bth Karl and Mathew Cnduct ensemble sensitivity runs fr bth Karl and Mathew Analyze the 5-km simulatins t investigate the dynamics assciated with the genesis f Karl and Mathew
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