Using TIGGE Data to Diagnose Initial Perturbations and Their Growth for Tropical Cyclone Ensemble Forecasts

Abstract Ensemble initial perturbations around Typhoon Sinlaku (2008) produced by ECMWF, NCEP, and the Japan Meteorological Agency (JMA) ensembles are compared using The Observing System Research and Predictability Experiment (THORPEX) Interactive Grand Global Ensemble (TIGGE) data, and the dynamical mechanisms of perturbation growth associated with the tropical cyclone (TC) motion are investigated for the ECMWF and NCEP ensembles. In the comparison, it is found that the vertical and horizontal distributions of initial perturbations as well as the amplitude are quite different among the three NWP centers before, during, and after the recurvature of Sinlaku. In addition, it turns out that those variations cause a difference in the TC motion not only at the initial time but also during the subsequent forecast period. The ECMWF ensemble exhibits relatively large perturbation growth, which results from 1) the baroclinic energy conversion in a vortex, 2) the baroclinic energy conversion associated with the midlatitude waves, and 3) the barotropic energy conversion in a vortex. Those features are less distinctive in the NCEP ensemble. A statistical verification shows that the ensemble spread of TC track predictions in NCEP (ECMWF) is larger than ECMWF (NCEP) for 1- (3-) day forecasts on average. It can be inferred that while the ECMWF ensemble starts from a relatively small amplitude of initial perturbations, the growth of the perturbations helps to amplify the ensemble spread of tracks. On the other hand, a relatively large amplitude of initial perturbations seems to play a role in producing the ensemble spread of tracks in the NCEP ensemble.

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Transient eddy kinetic energetics on Mars in three reanalysis datasets

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-21-0038.1 ◽

2021 ◽

Author(s):

J. Michael Battalio

Keyword(s):

Kinetic Energy ◽

Energy Conversion ◽

Northern Hemisphere ◽

Thermal Emission ◽

Ensemble Member ◽

Eddy Kinetic Energy ◽

Mean Flow ◽

Short Period ◽

Barotropic Energy Conversion ◽

Baroclinic Energy Conversion

AbstractThe ability of Martian reanalysis datasets to represent the growth and decay of short-period (1.5 < P < 8 sol) transient eddies is compared across the Mars Analysis Correction Data Assimilation (MACDA), Open access to Mars Assimilated Remote Soundings (OpenMARS), and Ensemble Mars Reanalysis System (EMARS). Short-period eddies are predominantly surface-based, have the largest amplitudes in the northern hemisphere, and are found, in order of decreasing eddy kinetic energy amplitude, in Utopia, Acidalia, and Arcadia Planitae in the northern hemisphere, and south of the Tharsis Plateau and between Argyre and Hellas Basins in the southern hemisphere. Short-period eddies grow on the upstream (western) sides of basins via baroclinic energy conversion and by extracting energy from the mean flow and long-period (P > 8 sol) eddies when interacting with high relief. Overall, the combined impact of barotropic energy conversion is a net loss of eddy kinetic energy, which rectifies previous conflicting results. When Thermal Emission Spectrometer observations are assimilated (Mars years 24–27), all three reanalyses agree on eddy amplitude and timing, but during the Mars Climate Sounder (MCS) observational era (Mars years 28–33), eddies are less constrained. The EMARS ensemble member has considerably higher eddy generation than the ensemble mean, and bulk eddy amplitudes in the deterministic OpenMARS reanalysis agree with the EMARS ensemble rather than the EMARS member. Thus, analysis of individual eddies during the MCS era should only be performed when eddy amplitudes are large and when there is agreement across reanalyses.

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A teleconnection pattern of 10-30-day atmospheric oscilations over North Pacific during summer: Chracteristics and maintainance mechanism

10.5194/egusphere-egu2020-3187 ◽

2020 ◽

Author(s):

Lei Du ◽

Riyu Lu

Keyword(s):

Energy Conversion ◽

North Pacific ◽

Phase Locking ◽

Teleconnection Pattern ◽

Zonal Wavenumber ◽

Meridional Winds ◽

Gain Energy ◽

Barotropic Energy Conversion ◽

Baroclinic Energy Conversion ◽

Main Component

<p>The present study investigates the intraseasonal variations of meridional winds over North Pacific during summer based on reanalysis datasets. It is shown that the band of 10-30 days is the main component of total intraseasonal varaitions. We identified a teleconnection pattern over North Pacific at this band . This teleconnection pattern is characterized by a zonally-oriented wave-like structure with a zonal wavenumber 5, and does not show a phase-locking feature. In addition, the anomalies associated with the teleconnection pattern exhibit a roughly baratropic structure. Further analyses suggest that the teleconnection pattern can gain energy from the basic flow through the baroclinic energy conversion, while the barotropic energy conversion plays a trivial role.</p>

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Seasonality of Tropical Instability Waves and Its Feedback to the Seasonal Cycle in the Tropical Eastern Pacific

The Scientific World JOURNAL ◽

10.1100/2012/612048 ◽

2012 ◽

Vol 2012 ◽

pp. 1-11 ◽

Cited By ~ 7

Author(s):

Seul-Hee Im ◽

Soon-Il An ◽

Matthieu Lengaigne ◽

Yign Noh

Keyword(s):

Energy Conversion ◽

Seasonal Cycle ◽

Ocean Model ◽

Eastern Pacific ◽

Tropical Eastern Pacific ◽

Instability Waves ◽

Tropical Instability Waves ◽

Barotropic Energy Conversion ◽

Baroclinic Energy Conversion ◽

One Year

This study investigated the seasonality of tropical instability waves (TIWs) and its feedback to the seasonal cycle in the tropical eastern Pacific using a high-resolution ocean model covering 1958–2007. The climatological mean of the TIWs featured intraseasonal fluctuations, implying that TIWs are not occurring randomly, but their amplitude is partly in phase from one year to another. This seasonality of TIW activity is attributed to their dependency on the seasonal mean variation of current and temperature. Energy conversion analysis confirmed that the strong variability of TIWs near 4°N was due to the barotropic energy conversion associated with the large meridional shear of NECC and SEC and that at another pole near 2°N was due to the baroclinic energy conversion associated with the temperature front in the mixed layer. The former and latter poles are somehow largely responsible for amplifying the dynamic and thermal eddies of TIWs, respectively. The intensified TIWs during a boreal fall increase the tropical eastern Pacific SST by associating the warm thermal advection by anomalous currents, with a rate of up to 1°C/month in September. Therefore, this leads to interactive feedback between seasonal and intraseasonal variations, that is, TIWs in the tropical eastern Pacific.

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The Application of Nonlinear Local Lyapunov Vectors to Ensemble Predictions in Lorenz Systems

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-13-0270.1 ◽

2014 ◽

Vol 71 (9) ◽

pp. 3554-3567 ◽

Cited By ~ 22

Author(s):

Jie Feng ◽

Ruiqiang Ding ◽

Deqiang Liu ◽

Jianping Li

Keyword(s):

Nonlinear Models ◽

Random Perturbation ◽

Brier Score ◽

Ensemble Spread ◽

Ensemble Forecasts ◽

Ensemble Mean ◽

Improved Performance ◽

Analysis Errors ◽

Better Than ◽

Perturbation Growth

Abstract Nonlinear local Lyapunov vectors (NLLVs) are developed to indicate orthogonal directions in phase space with different perturbation growth rates. In particular, the first few NLLVs are considered to be an appropriate orthogonal basis for the fast-growing subspace. In this paper, the NLLV method is used to generate initial perturbations and implement ensemble forecasts in simple nonlinear models (the Lorenz63 and Lorenz96 models) to explore the validity of the NLLV method. The performance of the NLLV method is compared comprehensively and systematically with other methods such as the bred vector (BV) and the random perturbation (Monte Carlo) methods. In experiments using the Lorenz63 model, the leading NLLV (LNLLV) captured a more precise direction, and with a faster growth rate, than any individual bred vector. It may be the larger projection on fastest-growing analysis errors that causes the improved performance of the new method. Regarding the Lorenz96 model, two practical measures—namely the spread–skill relationship and the Brier score—were used to assess the reliability and resolution of these ensemble schemes. Overall, the ensemble spread of NLLVs is more consistent with the errors of the ensemble mean, which indicates the better performance of NLLVs in simulating the evolution of analysis errors. In addition, the NLLVs perform significantly better than the BVs in terms of reliability and the random perturbations in resolution.

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Singular Vectors for Tropical Cyclone–Like Vortices in a Nondivergent Barotropic Framework

Journal of the Atmospheric Sciences ◽

10.1175/2011jas3727.1 ◽

2011 ◽

Vol 68 (10) ◽

pp. 2273-2291 ◽

Cited By ~ 8

Author(s):

Munehiko Yamaguchi ◽

David S. Nolan ◽

Mohamed Iskandarani ◽

Sharanya J. Majumdar ◽

Melinda S. Peng ◽

...

Keyword(s):

Tropical Cyclone ◽

Japan Meteorological Agency ◽

Initial Time ◽

Ensemble Prediction ◽

Necessary Condition ◽

Initial Growth ◽

Barotropic Instability ◽

Ensemble Prediction System ◽

Singular Vectors ◽

Tangential Wind

Abstract In this study, singular vectors (SVs) are calculated for tropical cyclone (TC)–like vortices on an f plane and β plane using a barotropic model, and the structure and time evolution of the SVs are investigated. In the f-plane study, SVs are calculated for TC-like vortices that do and do not satisfy a necessary condition of barotropic instability of normal modes, in which the vorticity gradient changes sign. It is found that, in the case where the initial vortices do not meet the condition, 1) the SVs are tilted against the shear of the background angular velocity as found earlier by Nolan and Farrell, indicating the growth of SVs through the Orr mechanism; 2) the leading singular value increases with the maximum tangential wind speed Vmax and decreases with the radius of the maximum wind (RMW); and 3) the locations of SVs move outward with increasing RMW, Vmax, and the optimization time. In the case where the initial vortex allows for barotropic instability, the SV is initially tilted against the background shear and exhibits transient growth for a limited period. At a certain time during the initial growth, the SV “locks in” to a normal mode structure and remains in that structure so that it may grow exponentially with time. In contrast to the SVs on an f plane, the azimuthal distribution of the SVs on a β plane becomes more asymmetric, and the extent of the asymmetry increases as the strength of the beta gyres increases. On the β plane, all first and second SVs calculated in this study have an azimuthal wavenumber-1 structure at the optimization time, regardless of whether the vorticity gradient of initial TC-like vortices changes sign and the TC-like vortices include the beta gyres at initial time. It is found that when the first and second SVs are used as ensemble initial perturbations, the linear combination of the initial first and second SVs can shift the vortex toward any direction at the optimization time. This is true even when SVs with a low horizontal resolution are used as initial perturbations, as in the European Centre for Medium-Range Weather Forecasts (ECMWF) and Japan Meteorological Agency (JMA) ensemble prediction system. Such wavenumber-1 perturbations could be useful for generating sufficient spread among the tropical cyclone tracks in ensemble forecasts.

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Contributions of Barotropic Energy Conversion to Northwest Pacific Tropical Cyclone Activity during ENSO

Monthly Weather Review ◽

10.1175/mwr-d-12-00084.1 ◽

2013 ◽

Vol 141 (4) ◽

pp. 1337-1346 ◽

Cited By ~ 7

Author(s):

Yao Ha ◽

Zhong Zhong ◽

Yimin Zhu ◽

Yijia Hu

Keyword(s):

Energy Source ◽

Tropical Cyclone ◽

Kinetic Energy ◽

Energy Conversion ◽

Large Scale ◽

Meridional Wind ◽

Eddy Kinetic Energy ◽

Northwest Pacific ◽

Enso Cycle ◽

Barotropic Energy Conversion

Abstract The contribution of barotropic energy conversion to tropical cyclone (TC) activity over the western North Pacific (WNP) during warm and cold phases of El Niño–Southern Oscillation (ENSO) is investigated by separating TC vortices from reanalysis data and using a linearized eddy kinetic energy tendency equation. By comparing the characteristics of TC disturbances with synoptic-scale disturbances, it is found that the modulation of ENSO on the WNP TC intensity is presented more objectively by using TC kinetic energy (EKETC) than eddy kinetic energy (EKE). Barotropic energy conversion (KmKe) into TC disturbances (KmKeTC) is an effective indicator in detecting the barotropic energy source of low-level cyclone genesis and maintenance during the ENSO cycle. However, its dynamical processes play different roles. Shear in large-scale zonal wind and convergence in large-scale meridional wind provide direct barotropic energy source for TC genesis, but make effects in different regions of the WNP. In contrast, convergence in large-scale zonal and shear in large-scale meridional wind exert little influence on TC genesis during ENSO.

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Energetics of Interactions between African Easterly Waves and Convectively Coupled Kelvin Waves

Monthly Weather Review ◽

10.1175/mwr-d-21-0003.1 ◽

2021 ◽

Vol 149 (11) ◽

pp. 3821-3835

Author(s):

Rama Sesha Sridhar Mantripragada ◽

C. J. Schreck III ◽

Anantha Aiyyer

Keyword(s):

Kinetic Energy ◽

Energy Conversion ◽

Kelvin Waves ◽

Energy Budgets ◽

African Easterly Waves ◽

Kelvin Wave ◽

Easterly Waves ◽

Available Energy ◽

Barotropic Energy Conversion ◽

Baroclinic Energy Conversion

Abstract Perturbation kinetic and available energy budgets are used to explore how convectively coupled equatorial Kelvin waves (KWs) impact African easterly wave (AEW) activity. The convective phase of the Kelvin wave increases the African easterly jet’s meridional shear, thus enhancing the barotropic energy conversions, leading to intensification of southern track AEWs perturbation kinetic energy. In contrast, the barotropic energy conversion is reduced in the suppressed phase of KW. Baroclinic energy conversion of the southern track AEWs is not significantly different between Kelvin waves’ convective and suppressed phases. AEWs in the convective phase of a Kelvin wave have stronger perturbation available potential energy generation by diabatic heating and stronger baroclinic overturning circulations than in the suppressed phase of a Kelvin wave. These differences suggest that southern track AEWs within the convective phase of Kelvin waves have more vigorous convection than in the suppressed phase of Kelvin waves. Barotropic energy conversion of the northern track AEWs is not significantly different between Kelvin waves’ convective and suppressed phases. The convective phase of the Kelvin wave increases the lower-tropospheric meridional temperature gradient north of the African easterly jet, thus enhancing the baroclinic energy conversion, leading to intensification of northern track AEWs perturbation kinetic energy. In contrast, the baroclinic energy conversion is reduced in the suppressed phase of KW. These results provide a physical basis for the modulation of AEWs by Kelvin waves arriving from upstream.

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Barotropic energetics analysis of tropical cyclone Khai Muk

MAUSAM ◽

10.54302/mausam.v64i1.654 ◽

2022 ◽

Vol 64 (1) ◽

pp. 49-58

Author(s):

S. BALACHANDRAN

Keyword(s):

Tropical Cyclone ◽

Kinetic Energy ◽

Energy Conversion ◽

Bay Of Bengal ◽

Zonal Flow ◽

Eddy Kinetic Energy ◽

Initial Growth ◽

Horizontal Shear ◽

Absolute Vorticity ◽

Barotropic Energy Conversion

bl 'kks/k i= esa 11&14 uoEcj 2008 ds nkSjku caxky dh [kkM+h esa cuus vkSj mlds vkxs c<+us okys m".kdfVca/kh; pØokr dSeqd dh xfrdh; fLFkfr;ksa ds fo’kys"k.k ij fopkj&foe’kZ fd;k x;k tks fupys Lrj ij ifjofrZr ok;qnkc&m".kdfVca/k ¼csjksVªkfid½ mtkZ ij dsfUnzr FkkA bl nkSjku ;g ik;k x;k fd if’peh iz’kkar egklkxj ls miks".kh; iwohZ gok;sa e/; caxky dh [kkM+h ds mRrj rd c<+h vkSj Åij m)`r vof/k esa Hkwe/;js[kh; if’peh gok;sa ¼iNok¡½ vkbZ-Vh-lh-tsM+- ds nf{k.k rd c<+h ftlds dkj.k {kSfrt; vi:i.k izokg vR;kf/kd ek=k esa cukA blls pØokrh vi:i.k Hkzfeyrk mRiUu gqbZ vkSj fo{kksHk cuk] tks ckn esa m".kdfVca/kh; pØokr dSeqd esa fodflr gks x;kA fupys {kksHkeaM+y esa ewyHkwr {ks=h; izokg ok;qnkcm".kdfVca/k :i ls vfLFkj Fkk ftls fujis{k Hkzfeyrk ds ;kE;ksrjh forj.k ds y{k.k ds ifjorZu }kjk crk;k x;k gS ftlls coaMj ds cuus esa xfrdh; ÅtkZ feyhA bl nkSjku fujis{k Hkzfeyrk ds ek/; {ks=h; izokg vkSj ;kE;ksrjh izo.krk ds chp ldkjkRed lglaca/k Fkk ftlls ok;qnkcm".kdfVca/k }kjk coaMj ek/; izokg dh vUrjfØ;kvksa ds }kjk coaM+j dh xfrdh; ÅtkZ esa o`f) gqbZA ÅtZLoh fo’ys"k.k ls irk pyk gS fd coaM+j okyh xfrdh; ÅtkZ ds ldkjkRed ifjorZu ds mPp nj ds {ks= ifjorhZ ok;qnkc m".kdfVca/k ds ldkjkRed {ks=ksa ls esy [kkrs gSa vkSj ifjorhZ m".kdfVca/k ds ifjek.k Hkzfey mRifRr okys {ks= ds vkl&ikl coaM+j okyh xfrdh; ÅtkZ ds ifjorZu ds LFkkuh; le; ds lkFk esy [kkrs gaSA ewyHkwr {ks=h; izokg ds ;kE;ksrjh vi:i.k }kjk ifjofrZr ok;qnkc m".kdfVca/k ÅtkZ m".kdfVca/kh; pØokr dSeqd ds cuus vkSj mlds vkxs c<+us okys ,d egRoiw.kZ ÅtkZ L=ksr FkkA Analysis of dynamical conditions in respect of formation and growth of tropical cyclone Khai Muk over the Bay of Bengal during 11-14 November 2008 is discussed with focus on barotropic energy conversion at lower level. It is observed that the extension of subtropical easterlies from the Western Pacific in to central Bay of Bengal to the north and equatorial westerlies to the south of ITCZ during the above period constituted a large scale horizontal shear flow. This led to generation of cyclonic shear vorticity and initiation of disturbance which later developed in to tropical cyclone Khai Muk. The basic zonal flow in the lower troposphere was barotropically unstable as depicted by change of sign of meridional distribution of absolute vorticity which provided the kinetic energy for the growth of eddy. There existed positive correlation between mean zonal flow and the meridional gradient of absolute vorticity which favoured increase of eddy kinetic energy through barotropic eddy-mean flow interactions. Energetic analysis indicated that areas of high rate of positive change of eddy kinetic energy coincided with positive areas of barotropic conversion and the magnitude of barotropic conversion matched with local rate of change of eddy kinetic energy around the area of vortex generation. Barotropic energy conversion by meridional shear of basic zonal flow was an important energy source for the formation and initial growth of tropical cyclone Khai Muk.

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