Genesis of Typhoon Chanchu (2006) from a Westerly Wind Burst Associated with the MJO. Part I: Evolution of a Vertically Tilted Precursor Vortex

2010 ◽  
Vol 67 (12) ◽  
pp. 3774-3792 ◽  
Author(s):  
Wallace Hogsett ◽  
Da-Lin Zhang
Keyword(s):  
Deep Convection ◽  
Final Analysis ◽  
Forecast Model ◽  
Tropical Cyclogenesis ◽  
Westerly Wind ◽  
Kelvin Wave ◽  
The Pacific ◽  
Westerly Wind Burst ◽  
The Indian Ocean ◽  
The Right

Abstract Although previous studies have shown the relationship between the Madden–Julian oscillation (MJO) and tropical cyclogenesis (TCG), many scale-interactive processes leading to TCG still remain mysterious. In this study, the larger-scale flow structures and evolution during the pregenesis, genesis, and intensification of Typhoon Chanchu (2006) near the equator are analyzed using NCEP’s final analysis, satellite observations, and 11-day nested numerical simulations with the Advanced Research Weather Research and Forecast model (ARW-WRF). Results show that the model could reproduce the structures and evolution of a synoptic westerly wind burst (WWB) associated with the MJO during the genesis of Chanchu, including the eastward progression of a WWB from the Indian Ocean into the Pacific Ocean, the modulation of the associated quasi-symmetric vortices, the initial slow spinup of a northern (pre-Chanchu) disturbance at the northeastern periphery of the WWB, and its general track and intensification. It is found that the MJO, likely together with a convectively coupled Kelvin wave, provides the necessary low-level convergence and rotation for the development of the pre-Chanchu disturbance, particularly through the eastward-propagating WWB. The incipient vortex evolves slowly westward, like a mixed Rossby–gravity wave, on the northern flank of the WWB, exhibits a vertically westward-tilted circulation structure, and eventually moves northward off of the equator. Results show that the interaction of the tilted vortex with moist easterly flows assists in the downtilt-right (i.e., to the right of the upward tilt) organization of deep convection, which in turn forces the tilted vortex to move toward the area of ongoing deep convection, thereby helping to partly decrease the vertical tilt with time. It is shown that despite several days of continuous convective overturning, sustained surface intensification does not commence until the vortex becomes upright in the vertical. A conceptual model is finally presented, relating the decreasing vortex tilt to convective development, storm movement, TCG, and surface intensification.

Global Survey of Precipitation Properties Observed during Tropical Cyclogenesis and Their Differences Compared to Nondeveloping Disturbances

2020 ◽  
Vol 148 (4) ◽  
pp. 1585-1606
Author(s):  
Jonathan Zawislak
Keyword(s):  
Brightness Temperature ◽  
North Pacific ◽  
Deep Convection ◽  
Passive Microwave ◽  
Tropical Cyclogenesis ◽  
Global Database ◽  
Areal Coverage ◽  
The Pacific ◽  
Rain Rates ◽  
The Western Pacific

Abstract This study evaluates precipitation properties involved in tropical cyclogenesis by analyzing a multiyear, global database of passive microwave overpasses of the pregenesis stage of developing disturbances and nondeveloping disturbances. Precipitation statistics are quantified using brightness temperature proxies from the 85–91-GHz channels of multiple spaceborne sensors, as well as retrieved rain rates. Proxies focus on the overall raining area, areal coverage of deep convection, and the proximity of precipitation to the disturbance center. Of interest are the differences in those proxies for developing versus nondeveloping disturbances, how the properties evolve during the pregenesis stage, and how they differ globally. The results indicate that, of all of the proxies examined, the total raining area and rain volume near the circulation center are the most useful precipitation-related predictors for genesis. The areal coverage of deep convection also differentiates developing from nondeveloping disturbances and, similar to the total raining area, generally also increases during the pregenesis stage, particularly within a day of genesis. As the threshold convective intensity is increased, pregenesis cases are less distinguishable from nondeveloping disturbances. Relative to the western Pacific and Indian Oceans, the Atlantic and eastern North Pacific Oceans have less precipitation and deep convection observed during genesis and the smallest differences between developing and nondeveloping disturbances. This suggests that the total raining area and areal coverage of deep convection associated with tropical disturbances are better predictors of tropical cyclogenesis fate in the Pacific and Indian Oceans than in the Atlantic and eastern North Pacific.

Equatorial belt vapour measurements in the upper TTL under superpressure balloon during STRATEOLE 2 pre-campaign: tape recorder effect, role of waves and deep convection.

2021 ◽  
Author(s):  
Emmanuel Riviere ◽  
Mélanie Ghysels ◽  
Georges Durry ◽  
Jérémie Burgalat ◽  
Nadir Amarouche ◽  
...  
Keyword(s):  
Water Vapour ◽  
Lower Stratosphere ◽  
Deep Convection ◽  
Tape Recorder ◽  
Kelvin Wave ◽  
Water Vapour Content ◽  
The Pacific ◽  
Equatorial Belt ◽  
Local Water ◽  
Constant Altitude

<p>STRATEOLE 2 is a French-American project based on superpressure balloon borne measurements to study dynamics and processes in the TTL and the lower stratosphere of equatorial regions. One single flight of these balloons (of a duration of about 80 days) can make several turns of the Earth.</p><p>Here we present water vapour measurements by the Pico-SDLA infrared laser spectrometer on-board the TTL 2 gondola. The float altitude was of about 19 km during the technical campaign of STRATEOLE 2, providing measurements at the top of the TTL or the lower stratosphere. In this presentation, we analyse the tape recorder signal at a constant altitude during the 80 days of flight. We compute an anomaly of the <em>in situ</em> water vapour measurements with respect to a regional/temporal satellite-borne mean climatology from Aura MLS. It allows to analyse the local measurements by Pico-SDLA with respect to what is expected at a given position and a given time. The obtained contrast allows the positioning of observations with respect to local climatology and therefore, the identification of singular events responsible for modulation of the local water vapour content. Our analysis shows that a long wet anomaly above the Pacific Ocean is explained by the balloon “surfing” on a warm perturbation of a Kelvin wave. Concurrently, a dry anomaly is put to the fore over the Indian Ocean, associated to a packet of gravity waves cold perturbations. The balloon has flown twice above the Maritime Continent. For each passage, a short scale succession of dry and wet anomalies is shown, indicating a possible influence of local deep convection. This influence is studied further using satellite borne cloud top data.</p>

scholarly journals Variations in the Flow of the Global Atmosphere Associated with a Composite Convectively Coupled Oceanic Kelvin Wave

2010 ◽  
Vol 23 (15) ◽  
pp. 4192-4201 ◽  
Author(s):  
Paul E. Roundy ◽  
Lynn M. Gribble-Verhagen
Keyword(s):  
Southern Oscillation ◽  
Deep Convection ◽  
Composite Analysis ◽  
High Latitudes ◽  
Madden Julian Oscillation ◽  
Global Flow ◽  
Kelvin Wave ◽  
Coupled Mode ◽  
The Pacific ◽  
The Pacific Ocean

Abstract Kelvin waves in the Pacific Ocean occasionally develop and propagate eastward together with anomalies of deep convection and low-level westerly wind. This pattern suggests coupling between the oceanic waves and atmospheric convection. A simple composite analysis based on observed coupled events from October through April demonstrates that this apparent coupled mode is associated with significant large anomalies in the global flow that extend to high latitudes. These high-latitude anomalies are significantly larger than those that are linearly associated with the El Niño–Southern Oscillation (ENSO), and they evolve on time scales between those of the Madden–Julian oscillation and ENSO, potentially providing an opportunity for enhanced subseasonal predictability in the flow of the global atmosphere.

scholarly journals Examining Tropical Cyclone–Kelvin Wave Interactions Using Adjoint Diagnostics

2016 ◽  
Vol 144 (11) ◽  
pp. 4421-4439 ◽  
Author(s):  
Carolyn A. Reynolds ◽  
James D. Doyle ◽  
Xiaodong Hong
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Static Stability ◽  
Kelvin Wave ◽  
Initial State ◽  
Wave Interactions ◽  
Low Level ◽  
Westerly Wind Burst ◽  
The Indian Ocean ◽  
Far Eastern

Abstract The initial-state sensitivity and interactions between a tropical cyclone and atmospheric equatorial Kelvin waves associated with the Madden–Julian oscillation (MJO) during the DYNAMO field campaign are explored using adjoint-based tools from the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS). The development of Tropical Cyclone 5 (TC05) coincided with the passage of an equatorial Kelvin wave (KW) and westerly wind burst associated with an MJO that developed in the Indian Ocean in late November 2011. COAMPS 18-h adjoint sensitivities of low-level kinetic energy to changes in initial state winds, temperature, and water vapor are analyzed for both TC05 and the KW to document when the evolution of each system is sensitive to the other. Time series of sensitivity patterns confirm that TC05 and the KW low-level westerlies are sensitive to each other when the KW is to the southwest and south of TC05. While TC05 is not sensitive to the KW after this, the KW low-level westerlies remain sensitive to TC05 until it enters the far eastern Indian Ocean. Vertical profiles of both TC05 and KW sensitivity indicate lower-tropospheric maxima in temperature, wind, and moisture, with KW sensitivity typically 20% smaller than TC05 sensitivity. The magnitude of the sensitivity for both systems is greatest just prior to, and during, their closest proximity. A case study examination reveals that adjoint-based optimal perturbations grow and expand quickly through a dynamic response to decreased static stability. The evolution of moist-only and dry-only initial perturbations illustrates that the moist component is primarily responsible for the initial rapid growth, but that subsequent growth rates are similar.

scholarly journals Analysis of Apparent Coupling between an Oceanic Kelvin Wave and Atmospheric Convection during the Winter of 1986/87

2010 ◽  
Vol 23 (23) ◽  
pp. 6352-6364 ◽  
Author(s):  
Lynn Gribble-Verhagen ◽  
Paul E. Roundy
Keyword(s):  
Deep Convection ◽  
High Amplitude ◽  
Sea Surface ◽  
Madden Julian Oscillation ◽  
Kelvin Wave ◽  
Atmospheric Convection ◽  
Convective Envelope ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Wind Bursts

Abstract This study analyzes the apparent coupling between an intraseasonal oceanic Kelvin wave in the Pacific Ocean and atmospheric moist deep convection for a particularly high-amplitude event during the winter of 1986/87. This wave was initiated initially by westerly wind bursts that developed in association with the Madden–Julian oscillation (MJO). After initiation by the MJO, the active convective anomaly slowed to roughly 1.5 m s−1, suggesting that the event became distinct from the MJO, which usually propagates at roughly 5–7 m s−1. This study demonstrates how surface winds, currents, SST anomalies, fluxes of sensible and latent heat across the sea surface, and atmospheric convection evolve throughout the event. Results suggest that the convective envelope and oceanic Kelvin wave are mutually beneficial and serve to prolong and enhance each other.

scholarly journals Atlantic Tropical Cyclogenesis: A Three-Way Interaction between an African Easterly Wave, Diurnally Varying Convection, and a Convectively Coupled Atmospheric Kelvin Wave

2012 ◽  
Vol 140 (4) ◽  
pp. 1108-1124 ◽  
Author(s):  
Michael J. Ventrice ◽  
Christopher D. Thorncroft ◽  
Matthew A. Janiga
Keyword(s):  
West Africa ◽  
Diurnal Cycle ◽  
Deep Convection ◽  
Active Phase ◽  
Boreal Summer ◽  
Tropical Cyclogenesis ◽  
Tropical Atlantic ◽  
Kelvin Wave ◽  
African Easterly Wave ◽  
Easterly Wave

This paper explores a three-way interaction between an African easterly wave (AEW), the diurnal cycle of convection over the Guinea Highlands (GHs), and a convectively coupled atmospheric equatorial Kelvin wave (CCKW). These interactions resulted in the genesis of Tropical Storm Debby over the eastern tropical Atlantic during late August 2006. The diurnal cycle of convection downstream of the GHs during the month of August is explored. Convection associated with the coherent diurnal cycle is observed off the coast of West Africa during the morning. Later, convection initiates over and downstream of the GHs during the afternoon. These convective features were pronounced during the passage of the pre-Debby AEW. The superposition between the convectively active phase of a strong CCKW and the pre-Debby AEW occurred shortly after merging with the diurnally varying convection downstream of the GHs. The CCKW–AEW interaction preceded tropical cyclogenesis by 18 h. The CCKW provided a favorable environment for deep convection. An analysis of high-amplitude CCKWs over the tropical Atlantic and West Africa during the Northern Hemisphere boreal summer (1979–2009) highlights a robust relationship between CCKWs and the frequency of tropical cyclogenesis. Tropical cyclogenesis is found to be less frequent immediately prior to the passage of the convectively active phase of the CCKW, more frequent during the passage, and most frequent just after the passage.

scholarly journals Pengaruh Mesoscale Convective System terhadap Hujan Ekstrem Pesisir Barat Sumatra

2021 ◽  
Vol 35 (1) ◽  
pp. 9
Author(s):  
Achmad Fahruddin Rais ◽  
Rezky Yunita ◽  
Tri Setyo Hananto
Keyword(s):  
Indian Ocean ◽  
Mesoscale Convective System ◽  
Extreme Rainfall ◽  
Convective System ◽  
Westerly Wind ◽  
The West ◽  
Trade Winds ◽  
Mesoscale Convective ◽  
Westerly Wind Burst ◽  
The Indian Ocean

Tulisan ini merupakan studi awal yang membuktikan pengaruh Mesoscale Convective System (MCS) terhadap curah hujan (CH) ekstrem di pesisir barat Sumatra dengan menggunakan citra rapidscan 10 menit Himawari-8 kanal IR1. Untuk mendapatkan data yang berkualitas, penulis melakukan koreksi data CH penakar Hellman terhadap data standar CH di Moelaboh (MLH), Sibolga (SBG), Teluk Bayur (TBR) dan Bengkulu (BKL) serta koreksi paralaks data citra Himawari-8. Dalam mengidentifikasi MCS, penulis menggunakan kriteria brightness temperature (BT) ≤ 221 derajat kelvin (K), luasan BT ≥ 10.000 km2 dan durasi ≥ 3 jam. Hasil penelitian mengindikasikan bahwa CH ekstrem bersamaan dengan keberadaaan MCS yang membuktikan bahwa CH ekstrem diakibatkan oleh MCS di MLB, SBG, TBR dan BKL. MCS tersebut sangat dipengaruhi oleh kemunculan Westerly Wind Burst (WWB) yang terhalangi oleh Bukit Barisan untuk kasus CH ekstrem di SBG dan TBR atau berinteraksi dengan angin pasat tenggara dari Samudra Hindia sebelah barat daya Sumatra untuk kasus CH ekstrem di BKL. Untuk kaus CH ekstrem di MLB, MCS terbentuk akibat interaksi angin pasat di Samudra Hindia sebelah barat Sumatra dan aliran siklonik sebelah barat MLB. This paper was a preliminary study that proved the impact of the mesoscale convective system (MCS) on extreme rainfall on the west coast of Sumatra using rapid scan imagery of 10 minutes Himawari-8 channel IR1. To get qualified data, we conducted the correction of rainfall data of Hellman gauge to the rainfall standard data in Moelaboh (MLH), Sibolga (SBG), Teluk Bayur (TBR), and Bengkulu (BKL) and the parallax correction to Himawari-8 imagery data. To identify MCS, we used brightness temperature (BT) ≤ 221 K, BT area ≥ 10.000 km2 and duration ≥ 3 hours as the criteria. The results indicated that extreme rainfall occured simultaneously with MCS proved that the extreme rainfall caused by MCS in MLB, SBG, TBR, and BKL. The MCS was greatly influenced by the appearance of westerly wind burst (WWB) which was blocked by Bukit Barisan for extreme rainfall cases in SBG and TBR or interacted with the southeast trade winds of the Indian Ocean in the southwest of Sumatra for extreme rainfall case in BKL. For extreme rainfall case in MLB, MCS was formed due to the interaction of trade winds of the Indian Ocean in the west of Sumatra and cyclonic flow in the west of MLB.  

scholarly journals Diagnosing ISO Forecast from GloSea5 Using Dynamic-Oriented ISO Theory

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 114
Author(s):  
Young-Min Yang ◽  
Taehyoun Shim ◽  
Ja-Yeon Moon ◽  
Ki-Young Kim ◽  
Yu-Kyung Hyun
Keyword(s):  
Indian Ocean ◽  
Deep Convection ◽  
Intraseasonal Oscillation ◽  
Lower Troposphere ◽  
Moisture Convergence ◽  
Lower Atmosphere ◽  
Vertical Shear ◽  
Boreal Summer ◽  
Kelvin Wave ◽  
The Indian Ocean

A Madden–Jillian oscillation (MJO) and boreal summer intraseasonal oscillation (BSISO) are important climate variabilities, which affect a forecast of weather and climate. In this study, the MJO and the BSISO hindcasts from the Global Seasonal Forecast System, version 5 (GS5) were diagnosed using dynamic-oriented theories. We additionally analyzed the GS5 climatological run to identify whether the weakness of the GS5 hindcast results from the model physics or initialization processes. The GS5 hindcast captures three-dimensional dynamics and thermodynamics structure of MJO eastward propagation well in the Indian Ocean. The model produces the boundary layer (BL) moisture convergence anomalies to the east of the MJO deep precipitation with easterly anomalies associated with the Kelvin wave. The enhanced BL moisture convergence increases upward transport of moisture from the surface to the lower troposphere, inducing the moist lower troposphere and the positive convective instability by destabilization of the lower atmosphere and, thus, generating the next convection to the east of MJO deep convection and promoting MJO eastward propagation. However, the signal for eastward propagation is relatively weak in the Maritime Continent (MC) and the Western Pacific (WP). To improve the MJO eastward propagation in the MC and WP, improved heating induced by shallow (or congestus) clouds interacting with enhanced BL dynamics may be required. On the other hand, the GS5 hindcast reproduces the BSISO northward propagation reasonably well in the Indian Ocean, which is attributed to positive vorticity anomalies induced by strong vertical shear.

scholarly journals Research Gap Analysis of Remote Sensing Application in Fisheries: Prospects for Achieving the Sustainable Development Goals

2021 ◽  
Vol 13 (5) ◽  
pp. 1013
Author(s):  
Kuo-Wei Yen ◽  
Chia-Hsiang Chen
Keyword(s):  
Sustainable Development ◽  
Indian Ocean ◽  
Atlantic Ocean ◽  
The Sustainable Development ◽  
The North ◽  
The Pacific ◽  
Development Goals ◽  
The Indian Ocean ◽  
The Pacific Ocean ◽  
Research Hotspots

Remote sensing (RS) technology, which can facilitate the sustainable management and development of fisheries, is easily accessible and exhibits high performance. It only requires the collection of sufficient information, establishment of databases and input of human and capital resources for analysis. However, many countries are unable to effectively ensure the sustainable development of marine fisheries due to technological limitations. The main challenge is the gap in the conditions for sustainable development between developed and developing countries. Therefore, this study applied the Web of Science database and geographic information systems to analyze the gaps in fisheries science in various countries over the past 10 years. Most studies have been conducted in the offshore marine areas of the northeastern United States of America. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. This study also found that research hotspots of satellite RS applications in fisheries were mainly conducted in (1) the northeastern sea area in the United States, (2) the high seas area of the North Atlantic Ocean, (3) the surrounding sea areas of France, Spain and Portugal, (4) the surrounding areas of the Indian Ocean and (5) the East China Sea, Yellow Sea and Bohai Bay sea areas to the north of Taiwan. A comparison of publications examining the three major oceans indicated that the Atlantic Ocean was the most extensively studied in terms of RS applications in fisheries, followed by the Indian Ocean, while the Pacific Ocean was less studied than the aforementioned two regions. In addition, all research hotspots were located in the Northern Hemisphere, indicating a lack of relevant studies from the Southern Hemisphere. The Atlantic Ocean and the Indian Ocean have been the subjects of many local in-depth studies; in the Pacific Ocean, the coastal areas have been abundantly investigated, while offshore local areas have only been sporadically addressed. Collaboration and partnership constitute an efficient approach for transferring skills and technology across countries. For the achievement of the sustainable development goals (SDGs) by 2030, research networks can be expanded to mitigate the research gaps and improve the sustainability of marine fisheries resources.

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