Twin Cyclone Research Articles

Influences of surface heat flux on twin cyclone structure during their explosive development over the East Asian marginal seas on 23 January 2008

The formation of explosively developing twin extratropical cyclones is investigated for background conditions involving a transition from double jets to a single jet. Upper-level double jets produced a latitudinally wide baroclinic zone before formation of the twin cyclones. In the early development stage, those double jets merged into the single jet with a strong potential vorticity (PV) streamer that moved to the Japan Sea and coupled with lower-level PV of the northernmost of the twin cyclones. Subsequently, the area of high PV associated with the single jet migrated to the northwestern Pacific, and the upper-level trough coupled with the southernmost of the twin cyclones. The northern low over the Japan Sea then merged with the developing southern low over the Pacific. For this case, sensitivity experiments suggest that sea surface turbulent heat flux before formation of the cyclones is crucial to formation of the twin cyclone structure, via development of a latitudinally elongated trough. Both Eady growth rate and water vapor mixing ratio near the surface were maintained by a strong sea surface turbulent heat flux and contributed to the development of the latitudinally elongated trough around Japan, where diabatic PV production strengthening the two lows separated into two distinct areas. The twin cyclone structure was formed when the lower-level trough extended from the humid Pacific region was developed by the surface turbulent heat flux. While the upper-level PV coupled with the northernmost low over the Japan Sea, the southernmost low developed independently in the lower-level Pacific region.

Investigating the Mechanisms Associated With the Evolutions of Twin Extratropical Cyclones Over the Northwest Pacific Ocean in Mid‐January 2011

AbstractTwin extratropical cyclones that appeared over the northwest Pacific Ocean in mid‐January 2011 experienced significantly different transitions: the northern cyclone dissipated rapidly, whereas the southern cyclone developed into an extreme example of an explosive (i.e., rapidly deepening) extratropical cyclone. This event was reasonably reproduced by the fifth‐generation Mesoscale Model, and its associated mechanisms were investigated using piecewise potential vorticity inversion and the Zwack‐Okossi vorticity budget. Main results are as follows. (i) The extratropical cyclone‐included twin cyclone event showed a Fujiwhara effect, during which the two cyclones orbited cyclonically about a midpoint, approached each other, and finally merged. The twin cyclone interactions enhanced the northern cyclone, but weakened the southern cyclone, by inducing warm advection and cold advection, respectively. (ii) Although upper level tropopause folding contributed the most to deepening of the twin cyclones, significant differences in their deepening rates were due predominantly to the contrast between lower level temperature advection and precipitation‐related latent heating. (iii) Stronger upper tropospheric positive absolute‐vorticity advection and warm advection associated with an upper level jet, and larger latent heating, made geostrophic vorticity of the southern cyclone increase more rapidly than that of the northern cyclone. (iv) Explosive deepening of the southern cyclone showed insensitive responses to its relative configuration with the upper level jet, whereas its rotation enhancement was faster when the cyclone was embedded within the upper level jet. (v) The upper level forcing had a greater influence on the large‐scale flow associated with the twin cyclones, whereas the middle‐level and lower level forcings were more dominant close to the cyclone core regions.

Twin tropical cyclones in the Indian Ocean: the role of equatorial waves

This study explores the background atmospheric conditions that led to the development of recent two sets of twin tropical cyclones in the Indian Ocean. One set of twins formed in late December 2011 (“pair A”) and other in May 2013 (“pair B”). An extensive area of active convection prevailing over wide-equatorial region and low-level westerly wind over near-equatorial region is major precursors to the two cases of twins. Convection and accompanying westerlies slowly strengthen, and the two sets of twins tend to emerge within it. The atmospheric equatorial convectively coupled Kelvin wave (CCKW) and convectively coupled equatorial Rossby (CCER) wave played key role in the formation of the two twins’ events. Wave-enhanced equatorial convection and low-level westerly anomalies produced by the combination of CCKW and CCER wave are crucial for the development of “pair A” twins. CCKW prior to “pair B” twins produced convection and westerly anomalies over equatorial region. The equatorial westerlies are further modulated by CCER wave favoring twins of “pair B.” Moreover, convection reinforced by CCER wave in OLR aided occurrence of Northern Hemispheric cyclone of “pair A” and Southern Hemispheric cyclone of “pair B.” While the CCKW and CCER wave appear to be associated with the formation of the two twin cyclone cases, more thorough understanding of the mechanisms involved needs considerable attention in forthcoming research.

Design and Development of Exhaust Valves From the Perspective of Modern Thinking: Part 3: Reverse Engineering of American and British Sodium-Cooled Valves

Reverse engineering is a procedure normally used for producing close copies of engineering equipment made by an industrial competitor or in an enemy country. But it can be used by industrial historians to explain why components which were apparently doing similar jobs had a rather different configuration. In this case, the reasons behind the distinct differences between exhaust valves used in two American air-cooled radials, the Pratt and Whitney Double Wasp, the Curtis Wright Twin Cyclone and the Rolls-Royce liquid-cooled Merlin are explored. Comments are also made on the sleeve valve engines made by Bristol, intended to avoid the supposed problems of the hot poppet exhaust valve. Sodium cooling of the valves in all engines was needed because of the high rates of heat transfer. The American engines incorporated a hemispherical cylinder head incorporating two valves. Because of the size of valves, these had to be of the hollow head type. The Merlin engine, to minimise frontal area, opted for a pan shaped head, which forced the use of four valves per cylinder. Stem cooling in these valves was adequate.

A study on the optimal design of a cyclone system for vacuum cleaner with the consideration of house dust

Cyclone, a type of particle collector widely used in the field of ambient sampling and industrial particulate control, is the principal type of gas-solids separator that use a centrifugal force. The goal of this study is to transform conventional cyclone into a new type of cyclone that can be used for the household vacuum cleaners. To meet the goal, first, the analysis about local environment and dust is carried out. Second, it must have enough high-efficiency not to reduce suction power due to clogging of exhaust filter unit. Two single cyclones with central-hopper-dust-outlet and side-wall-dust-outlet and a twin cyclone are designed and fabricated to evaluate, and compare, their dust collection efficiencies and pressure drops. The measurements of separation efficiency for dust by using DMT test dust type 08 are carried out. House dust experiment is additionally performed to check the local matters applicability such as tissue papers, fur and hairs. The collection efficiency of the twin cyclone is found to be 3–6% greater than those of two single cyclones with the same body diameter, inlet and inner cylinder diameter. Twin cyclone with a large body diameter, a small inner cylinder diameter, a short inner cylinder, a narrow inlet has high separation efficiency. This result indicates the possibility of achieving higher collection efficiencies with a twin cyclone.

A climatological study on the role of the South China Sea monsoon onset in the development of the East Asian summer monsoon

The unique role of the South China Sea summer monsoon (SCSSM) onset process in the development of the East Asian summer monsoon (EASM) is demonstrated in this study. The SCSSM onset process is examined in terms of the vertical linkage between the Western Pacific subtropical high (WPSH) and the South Asian high (SAH). A composite analysis is performed in order to adequately describe the vertical linkage in a synoptic timescale. The South China Sea (SCS) is a key region for the seasonal migrations of the WPSH and the SAH, with the former retreating northeastward, the latter advancing northwestward, and both taking place over the SCS during the SCSSM onset period. The SCSSM onset process is characterized by a significant change in the relative configuration of the ridge lines of the WPSH and the SAH. Just prior to the onset period, the ridge lines intersect vertically over the SCS, thus prohibiting convective activities. During the onset period, the ridge line intersection moves away from the SCS due to the retreating WPSH and the northward shift of the SAH ridge line. This coincides with the emergence of monsoonal convective activities over the SCS and the establishment of a moisture channel from the tropics, which in turn provides favorable conditions for the development of deep convective activity. The northeastward intrusion of the lower level southwesterlies and the moisture supplying channel are closely related to the development of a preexisting twin cyclone in the Bay of Bengal. The northeastward lower level southwesterlies form a monsoonal ascending motion in the SCS, which further merges upward into the northeasterlies to the south of the SAH ridge line. This is a signature of the establishment of the local Hadley circulation, which marks the beginning of the EASM. The frontal system is the most frequent attendant synoptic event during the SCSSM onset. From the viewpoint of synoptic process, the SCSSM undergoes a two-stage onset process which is characterized by the southward intrusion of the frontal system in the earlier stage and the outbreak of the tropical convection in the later stage. The frontal system may act as a trigger for the outbreak of the tropical convection in the later stage. The burst out of the monsoonal convection over the SCS is essential for the breakdown of the vertical intersection between the WPSH and the SAH therein.

Overview of the South China sea monsoon experiment

The present paper gives an overview of the key project “ South China Sea Monsoon Experiment (SCSMEX)” operated by the Ministry of Science and Technology of China during the period of 1996–2001. The SCSMEX is a joint atmospheric and oceanic field experiment which aims to better understand the onset, maintenance, and variability of the summer monsoon over the South China Sea (SCS). It is a large-scale international effort with many participating countries and regions cooperatively involved in this experiment. With the field observation in May–August 1998, a large amount of meteorological and oceanic data was acquired, which provides excellent datasets for the study of the SCS monsoon and the East Asian monsoon and their interaction with the ocean. The preliminary research achievements are as follows. (1) The earliest onset of the Asian monsoon over the SCS and Indo-China Peninsula has been well documented. From the viewpoint of the synoptic process, its onset is closely related to the early rapid development of a twin cyclone to the east of Sri Lanka. The conceptual model of the SCS monsoon onset in 1998 was put forward. The 50-year time series of the SCS monsoon onset date was also made. (2) Two major modes, namely the 30–60-day and 10–20-day oscillations were ascertained. The influences of the abnormal SCS monsoon on the precipitation over eastern China and its modes were identified. A strong (weak) monsoon over the SCS usually leads to less (more) precipitation over the middle and lower reaches of the Yangtze River basin, and more (less) precipitation in North China. (3) During the monsoon onset over the SCS, a wide variety of organized mesoscale convective systems (MCSs) were observed by a Doppler radar array deployed over the northern SCS. The relationship between large-scale circulations and MCSs during the monsoon onset process in 1998 was clearly revealed. It was suggested that there is a kind of positive feedback mechanism between large-scale circulations and MCSs. (4) The SST over the SCS during the early period influences the timing of the monsoon onset date and the monsoon’s intensity. During the monsoon onset, the ocean undergoes a process of energy release through air-sea interaction. During the break phase of the SCS monsoon, the ocean demonstrates the process of energy re-accumulation. Obvious differences in the air-sea turbulent flux exchange between the southern and northern parts of the SCS due to different characteristic features of the atmosphere and sea structure were observed in those regions. (5) The verification of impact of intensive observations on the predictive performance is made by the use of regional models. The air-sea coupled regional climate model (CRCM) was also developed under the SCSMEX Project. The simulation of the oceanic circulation in 1998 produced with the model was well compared with the observations.

Onset and the evolution of the Summer Monsoon over the South China Sea during SCSMEX Field Experiment in 1998.

The South China Sea Monsoon Experiment (SCSMEX), which was carried out from 1 May to 31 August 1998, is a multi-endeavor that is closely linked to and coordinated with activities of national weather services and oceanographic bodies of different nations and regions. The scientific goal of the SCSMEX is to provide a better understanding of the key physical processes for the onset, maintenance and variability of the summer monsoon over Southeast Asia and the South China Sea (SCS), leading to improved predictions of monsoons. Based on the datasets obtained from the SCSMEX Intensive Observation Period (IOP), the characteristics of upper and low-level circulation, outgoing long-wave radiation (OLR) and precipitation patterns have been analyzed. The obtained results have shown that (1) the onset of the SCS summer monsoon consists of two stages: the first onset on the northern SCS and the full onset over the whole SCS. The summer monsoon onset over the northern part of the SCS occurred in the fourth pentad of May while for the whole area of the SCS the onset occurred in the fifth pentad of May. The date of the onset of the SCS summer monsoon for 1998 was overall about 1-2 pentads later than normal condition (May 15); (2) the monsoon onset over the northern part of the SCS was not a localized phenomenon. It broke out simultaneously with the monsoon over the Bay of Bengal and Indo-China Peninsula. From a viewpoint of synoptic process, its onset is related to the early rapid development of a twin cyclone to the east of Sri Lanka and subsequently a monsoon depression over the Bay of Bengal, two stepwise significant retreats of the subtropical high from the SCS and possible triggering effect of a strong cold wave from mid-latitude; (3) activities of the SCS monsoon were mainly affected by activities of the Indian monsoon, and its enhancement and northward advances were greatly influenced by acceleration and eastward extending of the near equatorial westerly wind from the Indian Ocean.

タワーミル粉砕機（ＫＤ−３型機）における微粒子実収率を高めるための捕集部と分級部の改良

In the previous studies on pulverization of limestone by a Tower Mill Pulverizer, a product containing particles finer than 10μm could be obtained using a newly developed Tower Mill KD-3. From now, the Tower Mill KD-3 needs a higher level of efficiency for its further development, that achieves a high recovery of fine particles from the pulverized products. With this purpose, a series of investigations have been carried out on different types of cyclones and classifiers to clarify the factors which could affect the recovery of pulverized particles: Single Cyclone with Spiral Ribbons (SCSR), Twin Cyclone (TC), Twin Cyclone with Spiral Ribbons (TCSR), Simple Classifying Part (SCP), Classifying Part with Inclined Sieves (CPIS).The results of these investigations can be summarized as follows:(1) An increase in the recovery of fine particles was recorded using a TCSR and a CPIS. In both cases the achieved performances are certainly due to the high air flow rate in the cyclone.(2) The relationships between the maximum particle diameters and the 50 % particle diameters of the products were approximately straight lines whatever cyclones and classifiers were used.

Collection and use of dry pollen for pollination of kiwifruit

Abstract Mechanical systems were developed and evaluated for the collection and application of dry kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) pollen to flowers on an extenslve basis. Pollen was collected by a twin cyclone operated from a tractor by one person. Collection rates were up to 140 g/h during both night and day. Purity and germination of the pollen was consistently acceptable. Application was by impaction of dry force-fed pollen onto a rotating velcro-covered wheel whlch was located in an airstream. The principle was simple and its inherent flexibility permitted the evaluation of various pollen rates, delivery airflows, and machine types. Acceptable fruit yields resulted.

1986-87エルニーニョ発生期における双子低気圧の発達と西風強化

1986-87エルニーニョ発生期における双子低気圧の発達と西風強化