Cyclone Type Research Articles

A new objective procedure for classifying New Zealand synoptic weather types during 1958–2008

AbstractA set of 12 daily weather types has been obtained for the New Zealand region from the 51‐year NCAR/NCEP dataset by using a two‐stage classification procedure (rotated T‐mode principal component analysis followed by convergent K‐means clustering). Analysis of this classification confirms previous studies and provides further insight into the variation features of the regional synoptic weather on the seasonal, interannual and longer‐time scales.There are seasonal variations in both intensity and frequency of synoptic weather types. For example, southern highs are more frequent in summer and autumn, while troughs and lows occur more often in winter and secondarily spring. The high and low centres of weather types tend to be more intense in winter than summer.The frequency and lifetime of synoptic weather types fluctuate on the interannual and decadal scales; there exist significant correlations between frequencies of individual weather types and Southern Oscillation Index (SOI). In all seasons, the frequencies of weather types can change with phases of SOI. The most significant changes in weather type frequencies during the negative SOI phase occur in spring, and characterized by more frequent occurrence of weather types which provide prevailing southwesterly to westerly winds and reduced prominence of anticyclonic situations. The most significant changes in type frequencies during the positive SOI phase occur in summer, with more frequent anticyclonic types but less frequent cyclonic types. The frequency change in winter seems different from other seasons, although consistent with previous studies. In addition, the probability of extremely frequent occurrence or lack of occurrence of certain weather types during a month also varies significantly with SOI phases and with seasons, indicating that the chance for extreme weather conditions to occur is conditional on SOI.The results can be useful for climate forecasts, studies of climate extremes, air pollution, climatic impacts on human health and other environmental problems. Copyright © 2010 Royal Meteorological Society

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.

Numerical Simulation of the Two-Phase Flow in a New Type Cyclone

A new type cyclone with oblique top, transitional volute chamber, eccentric inner cylinders and sloping outlet were designed and manufactured by numerical analysis, which had been applied to the five-stage preheater in the cement plant with the capacity of 5000t/d. To simulate the gas flow field and particle trajectory in cyclone, the Fluent software was used, and the RNG k-ε model and discrete random walk model were proposed. The flow characteristics of gas-solid two-phase were analyzed. It is found that the strongly swirling flow occurs in the new type cyclone, and the particles of raw meal can be more efficiently separated from the gas.

The Research of Large-Diameter & Energy-Saving More Medium Supplied Gravity-Fed Three-Product Heavy Medium Cyclone

The characteristics and the development restrict factors in large-diameter area of the traditional three-product heavy medium cyclone are described. The paper mainly describes the structure and principles of large-diameter & energy-saving more medium supplied gravity-fed three-product heavy medium cyclone. The simulation analysis of this cyclone (DWP type) is presented. The results show that this type of more medium supplied cyclone is better than the one medium supplied cyclone for it has a faster separation speed, high processing ability and better separation efficiency. The applications in field of the 3SNWX1500/1100-Ⅳ type cyclone which using the new technology indicated that there have energy-saving, a high output, a stable separation efficiency, a high precision and a significant economic benefits.

Optimization of the recovery of plastics for recycling by density media separation cyclones

Material recovery processes are presented as the optimum option for recycling plastic wastes as a means of recovering hydrocarbon resources. There exist a large variety of automated material recovery processes for recycling of such wastes but each with significant limitations. Of these, the separation based on differences in densities is advocated as the optimum process either for producing recycled products or preparing wastes for subsequent recovery processing. Density separation processes based on cyclone type density media separation (DMS) is presented as an important, potential method for increasing plastics recycling process capacities. It is demonstrated to have the capacity to separate a significantly larger range of particle sizes than those presently processed industrially. The mathematical relationship for the prediction of quality of typical LARCODEMS type density media separations by particle size and density as expressed by the Ecart Probable is presented. A proposed device configuration is presented for density media separation to optimize the recovery and purity of both density fractions produced. It is also suggested that to be economically viable, a large scale of operation is required for industrial plastics recycling operations recovering and producing a number of different plastics with a purity to be used as a substitute for virgin material.

Estimations of the maximum tangential velocity V θm in the vortex core region and also the mean rotational velocity V oi near the concave wall surface in the returned flow type cyclone dust collector

There are many types of cyclone dust collectors for separating the fine solid and dust particles from gases in the various industries and also in the home used purposes. For estimating the power loss and the collection efficiency, one of the most important factors is the maximum tangential velocity Vθm in the vortex core region in the cyclone body. In order to determine Vθm by the simple method, it is useful to apply the mechanical balance of the angular momentum fluxes under the assumption of Ogawa combined vortex model which is composed of the quasi-forced vortex in the vortex core region and also the quasi-free vortex surrounded the vortex core region and also under the assumption of the introduction of equivalent length Heq corresponding to the cone spaces of the cyclone body and the dust bunker. On the other hand, the mean rotational velocity Voi near the concave wall surface is also estimated by the mechanical balance of angular momentum fluxes with the moment of viscous friction force. For confirming the general applications of the obtained equations, the returned flow types cyclones changed the throat diameter D3 are designed. The material of the cyclone is the transparent acrylic resin. Therefore the inner surface of the cyclone body can be regarded as smooth surface. The comparisons of the measured velocities Vθm and Voi by a cylindrical Pitot tube are shown in good agreement with those of the proposed equations. The above stated results are described in detail.

A link between reduced Barents‐Kara sea ice and cold winter extremes over northern continents

The recent overall Northern Hemisphere warming was accompanied by several severe northern continental winters, as for example, extremely cold winter 2005–2006 in Europe and northern Asia. Here we show that anomalous decrease of wintertime sea ice concentration in the Barents‐Kara (B‐K) seas could bring about extreme cold events like winter 2005–2006. Our simulations with the ECHAM5 general circulation model demonstrate that lower‐troposphere heating over the B‐K seas in the Eastern Arctic caused by the sea ice reduction may result in strong anticyclonic anomaly over the Polar Ocean and anomalous easterly advection over northern continents. This causes a continental‐scale winter cooling reaching −1.5°C, with more than 3 times increased probability of cold winter extremes over large areas including Europe. Our results imply that several recent severe winters do not conflict the global warming picture but rather supplement it, being in qualitative agreement with the simulated large‐scale atmospheric circulation realignment. Furthermore, our results suggest that high‐latitude atmospheric circulation response to the B‐K sea ice decrease is highly nonlinear and characterized by transition from anomalous cyclonic circulation to anticyclonic one and then back again to cyclonic type of circulation as the B‐K sea ice concentration gradually reduces from 100% to ice free conditions. We present a conceptual model that may explain the nonlinear local atmospheric response in the B‐K seas region by counter play between convection over the surface heat source and baroclinic effect due to modified temperature gradients in the vicinity of the heating area.

Design parameter studies on cyclone type mixers

The influence of different structural parameters on mixing in cyclone type mixers was investigated numerically and experimentally utilizing computational fluid dynamics (CFD) and the Iodide Iodate Reaction Method.The hydrodynamics of the mixing processes were investigated numerically. The results indicate the desired swirl motion in the mixing chamber as well as the occurrence of zones of complete recirculation (dead zones) and a zone with the occurrence of cavitation effects. The residence time distribution for a given mixer and mass flow was extracted from the data obtained from numerical simulations.Experimental and numerical results on pressure drop are in very good agreement.The length of the cyclone mixing chamber has only a minor influence on mixing, indicated by the triiodide concentrations of the resulting mixtures. The diameter of the cyclone mixing chamber had a severe effect on mixing. A cyclone mixing chamber with a diameter of 1mm yields a significantly reduced ‘mixing quality’ compared to a diameter of 500μm (‘standard design’). Experimental and numerical data describing mixing could be correlated for mixers with the same internal volume.

Field Performance of the CATHIA-T Sampler and Two Cyclones against the Standard Cowled Sampler for Thoracic Fiber Concentrations

The performance of two thoracic samplers, the GK2.69 cyclone and the CATHIA-T sampler, and the GK3.51 cyclone was investigated in the field against the standard cowled sampler (current NIOSH 7400 method) to determine the effect of thoracic sampling. The CATHIA-T sampler and the GK2.69 cyclone were operated at 7 and 1.6 l min(-1), respectively. The GK3.51 sampler is related to the GK2.69 cyclone, but designed to give a thoracic cut at a flow rate of 3.2 l min(-1). A total of 136 area samples were obtained from a tremolitic talc processing mill and 148 area samples were obtained within a quarry in which metamorphosed volcanic rocks were being crushed for construction stone. Sample slides were prepared using the dimethyl formamide/Euparal technique and relocatable cover slips. NIOSH 7400 'A' counting rules were used to examine fibers. Additionally, counters were asked to record the number of fibers where a fiber meets the 'A' rules and is wider than 3-mum physical diameter in order to estimate the proportion of extra-thoracic fibers. A few slides from each sampler type were randomly selected and fiber widths for those fibers satisfying the counting rules were measured to determine median width ratios of each thoracic sampler to the cowled sampler. Overall, the combined results of this study and the previous study by the same authors (Lee et al., 2008) showed lower fiber concentrations for the CATHIA-T sampler and higher concentrations for the GK2.69 cyclone and the GK3.51 cyclone compared to the standard cowled sampler. The proportion of extra-thoracic fibers (>3-mum physical diameter) on the filters collected with each type of thoracic samplers was comparable to the proportion of such fibers collected with the cowled sampler. The most consistent result over this study and our previous study is that both cyclones gave higher fiber concentrations than the CATHIA-T sampler. However, the estimated width ratios of each cyclone type to the cowled sampler were similar to or equal to 1 indicating no separation of fiber bundles due to cyclone effects. An inverse relationship between the fiber concentration ratios of each thoracic sampler type to the cowled sampler and the relative sample loading rate compared to the cowled sampler was observed. The difference in fiber concentration ratios might be a function of sample loading rather than an effect of thoracic size selection. Therefore, it is not recommended that any of these samplers be used to replace the cowled sampler in measurements intended for comparison with limit values arising from risk assessments developed from cowled sampler measurements without considering this possible effect.

Potential of Industrial Solid Wastes as Energy Sources and Gaseous Emissions Evaluation in a Pilot Scale Burner (ES2008-54355)

Industrially, many solid wastes can be classified as biomass and their usage reduces disposal costs. In this work, seven wastes from textile and food industries were characterized chemically and physically and the gaseous emissions resulting from the combustion of three of them (textile residues 3, TR3; coffee grounds; and a mixture of meat processing industry wastewater sludge and saw dust (1:9) in weight, SS1) in a pilot scale cyclone type combustor were measured. Their potential for utilization as energy sources was assessed by comparing the emissions to current legislation. Chemical properties showed that the volatile matter values of all biomass were high, which indicate that the solids burn rapidly. Some biomass presented high levels of sulfur and consequently high levels of SO2 emission when burned. The lower heating values ranged from 6.44 MJ kg−1 (dry and ash free, daf) to 22.93 MJ kg−1 (daf) and thermogravimetric analysis of the biomasses showed ignition temperatures and maximum burning rates, which were compared with other papers’ data. Four combustion tests were carried out in a cyclone type combustor and CO, CO2, NOx, CxHy, and SO2 were measured. Moisture content and particulate matter were also measured during the combustion tests and showed effective combustion conditions. Volatile organic compounds were analyzed by gas chromatography-mass spectrometry and their content values were expressed as total organic carbon (TOC), being all TOC emissions below the limits imposed by the regulations taken as reference. Gaseous emissions were compared with limits imposed by Brazilian and international current legislations, what showed that the usage of these biomasses as energy sources is possible; however, gas treatment would be required, especially if the solid presents high levels of sulfur and chlorine.

Numerical simulation of flow field in three types of standard cyclone separators

The numerical simulation of the fluid flow and particle dynamics is presented by CFD techniques to characterize the performance of the three types of standard cyclones. The three types of cyclones named 1D3D, 2D2D and 1D2D. The length of cylindrical part of the body is equal to 1, 2 and 1 times of the body diameter, respectively; and the length of the conical part is 3, 2 and 2 times of the body diameter. The Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian–Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW ). The dependency of cyclone characteristics on its diameter is investigated and D 50 (Cut-Point) is calculated for different Particle Size Distributions (PSDs). The numerical results are compared with the experimental data and the theoretical model and good agreement is observed.

Relationships between occurrence of high precipitation and atmospheric circulation in Poland using different classifications of circulation types

The main objective of this study is to analyse the relationship between atmospheric circulation and high precipitation in Poland, using selected classifications of circulation types. Daily precipitation totals from 48 synoptic stations and three classifications of circulation types ( Litynski, 1969; Niedzwiedz, 1981, 2008; Ustrnul, 1997) were used. These classifications were described and compared. The relationships between high precipitation and atmospheric circulation were analysed by (i) determining those circulation types that favour the occurrence of high precipitation, (ii) analysing the spatial differentiation of the probability of high precipitation events for chosen cyclonic circulation types and (iii) the usefulness of the classifications to analyse relations between high precipitation in Poland and atmospheric circulation was assessed. Any study of relations between atmospheric circulation and climate elements demands a preceding detailed assessment of the usefulness of a given classification for a defined problem. The results for relations between high precipitation occurrence and circulation depend on the rules applied to classify circulation types. Ustrnul’s classification seems to be best suited to study the relationship between heavy precipitation and circulation in the southern part of Poland. This result is based on two methods, the range of probabilities for high precipitation in each circulation type of a given classification (Pr diff) and the Brier skill score (BSS). The Niedzwiedz classification mainly produces very good results in central southern Poland where its probability range is clearly wider than elsewhere. Both methods seem to be less useful to study the relationships between high precipitation and circulation in northern Poland. Litynski’s classification delivers a greater role of the cyclonic types in forming high precipitation, but no definite prevailing type can be identified at many of the stations. When analysing relations, regional classification of circulation should be applied rather than macro-scales ones.

Analysis of hourly precipitation characteristics in Kraków, southern Poland, using a classification of circulation types

This paper investigates the relationship between maximum precipitation in Kraków and types of atmospheric circulation in southern Poland, as classified by Niedźwiedź. Three characteristics were used to define this relationship: maximum precipitation (Pmax), its duration (d) and probability of exceedance (p). The input data came from Kraków's uniquely long and homogenous pluviographic record spanning the period 1886–2007. Hourly precipitation values for the maximum precipitation events were identified and arranged in 1–24 hour intervals. They were then processed using the generalized extreme value (GEV) distribution to produce quantiles of maximum precipitation totals in each of the intervals and broken down by the corresponding circulation type. Differences between the development mechanisms are manifested in relationships between precipitation characteristics and their measure of randomness, i.e. exceedance probability. This paper demonstrates that maximum precipitation events depend on their duration d and atmospheric circulation. The maximum short-duration (one-hour) events occur primarily in either of two circulation types: (i) cyclonic with advection from the east and from the southeast or (ii) low-pressure centre and cyclonic trough. Maximum long-duration precipitation events (24 hour), on the other hand, occur in the cyclonic type of circulation with advection from the north and from the northeast.

Topographic effects on polar low and tropical cyclone development in simple theoretical model

The polar low and tropical cyclone type vortices over topography are assumed to be the axisymmetrical and thermal-wind balanced systems, which are solved as an initial value problem of a linearized vortex equation set in cylindrical coordinates. The roles of the sensible and latent heating, friction, and topography in the structure and intensification of the polar low and tropical cyclone type vortices are analyzed. The radial velocity, vertical velocity, azimuthal velocity, and the unstable growth rate including the topography effects are obtained. It is shown that the interaction between the flow and the topography plays a significant role in the structure and intensification of the polar low and tropical cyclone system. The analysis of the topography term indicates that, in the up-slope side of the mountain, the radial inflow and the vertical ascent forced by the mountain can intensify the polar low and tropical cyclone type vortex and increase the unstable growth rate. However, in the lee side of the mountain, the radial inflow and the vertical descent forced by the mountain can weaken the polar low and tropical cyclone type vortex and decrease the unstable growth rate of the polar low and tropical cyclone system. In addition, the evolutionary process and the spatial structure of the polar low observed over the Japan Sea on 19 December 2003 are investigated with the observational data to verify this theoretical result.

Improvement of gas-cyclone performance by use of local fluid flow control method

The purpose of this paper is to study the effects of a secondary flow injection method on sub-micron particle separation in a new type of gas-cyclone. It was found that particle collection efficiency and classification accuracy of the improved type cyclone was higher than that of the original type cyclone. Three-dimensional simulation results of the improved type cyclone indicated increased fluid rotational velocity in the cylindrical part and increased downward velocity in the conical part compared to the original type cyclone. Experimental results qualitatively agree with the numerical simulation. In order to improve high particle separation performance of gas-cyclones, it is recommended to use both the secondary flow injection and inlet guide plate methods.

Ensemble sensitivities of the real atmosphere: application to Mediterranean intense cyclones

Ensemble sensitivity has been recently proposed as an alternative cheap approach to sensitivity analysis. We adapt it to compute climatological sensitivity estimates of intense Mediterranean cyclones using a climatology based of the ECMWF ERA-40 fields. A catalogue of 1202 events, objectively detected and classified in 25 clusters, is used in this study. Sensitivity fields are derived for each intense Mediterranean cyclone type by correlating the precursor conditions with the mature cyclones depths. Corrections to the raw sensitivity estimates are applied by means of the correlation coefficient. Further, a normalization based on the climatological spatial variability of the variance of the precursor conditions is used to derive the final sensitivity fields. The 24 h sensitivity information derived for each intense Mediterranean cyclone type is easily interpretable both in amplitude and distribution. A synthetic result combining the sensitivity fields for all 25 intense Mediterranean cyclone classes shows that the evolution of these high-impact systems 24 h prior to its maturity stage depends largely on structures located over Western Europe, the Northern African lands and parts of east North Atlantic. These results are in agreement and complement with previous results obtained with the expensive adjoint model, although further work is needed to objectively verify the results.

Atmospheric forcing of the Beaufort Sea ice gyre: Surface pressure climatology and sea ice motion

The Beaufort Gyre (BG) typically rotates anticyclonically and exerts an important control on Arctic Sea ice dynamics. Previous studies have shown reversals in the BG to rotate cyclonically during summer months and, in recent decades, throughout the annual cycle. In this investigation, we explore the synoptic climatology of atmospheric forcing and its relationship to sea ice motion and BG reversals. A catalog of daily synoptic weather types is generated for the Beaufort Sea Region covering the period 1979 to 2006 using NCEP/NCAR reanalysis mean sea level pressure data, principle components, and k‐means cluster analyses. Mean synoptic type frequency, persistence, and duration values are calculated for each synoptic type and contrasted between the summer and winter seasons. Daily synoptic types are linked to changes in sea ice vorticity by using correlation analysis on lagged sea ice vorticity data. Lag correlations are found between synoptic types and sea ice vorticity smoothed over a 12‐week running mean and show that cyclonic types, which promote southerly or easterly atmospheric circulation over the southern Beaufort Sea, commonly precede summer reversals. Furthermore, significant seasonal within‐type variability in sea ice vorticity is detected within the synoptic types illustrating the importance of seasonal variability on these processes.

Ensemble sensitivities of the real atmosphere: application to Mediterranean intense cyclones

Ensemble sensitivity has been recently proposed as an alternative cheap approach to sensitivity analysis. We adapt it to compute climatological sensitivity estimates of intense Mediterranean cyclones using a climatology based of the ECMWF ERA-40 fields. A catalogue of 1202 events, objectively detected and classified in 25 clusters, is used in this study. Sensitivity fields are derived for each intense Mediterranean cyclone type by correlating the precursor conditions with the mature cyclones depths. Corrections to the raw sensitivity estimates are applied by means of the correlation coefficient. Further, a normalization based on the climatological spatial variability of the variance of the precursor conditions is used to derive the final sensitivity fields. The 24 h sensitivity information derived for each intense Mediterranean cyclone type is easily interpretable both in amplitude and distribution. A synthetic result combining the sensitivity fields for all 25 intense Mediterranean cyclone classes shows that the evolution of these high-impact systems 24 h prior to its maturity stage depends largely on structures located over Western Europe, the Northern African lands and parts of east North Atlantic. These results are in agreement and complement with previous results obtained with the expensive adjoint model, although further work is needed to objectively verify the results.

Snowstorm over the southwestern coast of the Korean Peninsula associated with the development of mesocyclone over the Yellow Sea

This study investigates the characteristics of a heavy snowfall event over the southwestern part of the Korean Peninsula on 4 December 2005. The snowstorm was a type of mesoscale maritime cyclone which resulted from barotropic instability, and diabatic heating from the warm ocean in continental polar air masses.

Classification of Cyclone Tracks over the Apennines and the Adriatic Sea

Abstract Cyclones that appear in the Adriatic Sea basin strongly influence the climate and weather conditions in the area. In particular, apart from the usually mild climate, cyclone activity in the Adriatic and the central Mediterranean Sea provide both the main hydrological forcing and the trigger mechanisms for a range of extreme weather phenomena. Therefore, a basic understanding of the cyclogenesis over the Adriatic Sea is essential. In particular, the classification of different types of cyclogenesis in the area is fundamental because it will help the understanding and prediction of the relevant weather phenomena. In this study, based on the analysis of the 4-yr (2002–05) operational European Centre for Medium-Range Weather Forecasts T511 dataset, various types of cyclone tracks are classified and the mesocyclogenesis areas in the vicinity of the Adriatic Basin are isolated. This analysis indicates that the following four types of cyclogenesis over the Adriatic Sea can be identified: 1) type A: cyclones connected with preexisting Genoa cyclones [with two subcategories, (A-I) continuous track: Genoa cyclones crossing over the Apennines to the Adriatic Sea, and (A-II) discontinuous track: new surface cyclones generated over the Adriatic Sea under the influence of a parent cyclone generated in the Gulf of Genoa (Genoa cyclones) and moving toward the Adriatic but blocked by the Apennines]; 2) type B: cyclones developed in situ over the Adriatic Sea without any connections with other preexisting cyclones in the surrounding area; 3) type AB: mixed types A and B cyclones, including cases where two cyclones coexist and stride over the Apennines (twin or eyeglass cyclones); and 4) type C: cyclones moving from the Mediterranean Sea, but not from the Gulf of Genoa (non-Genoa cyclones) [with 2 subcategories: (C-I) continuous track: a non-Genoa cyclone is able to cross over the Apennines to the Adriatic Sea continuously, and (C-II) discontinuous track: a non-Genoa cyclone is blocked by the Apennines and a new surface cyclone is generated over the Adriatic Sea]. The relevant dynamics of the above types of cyclones are discussed along with characteristics of the cyclones and their synoptic situations at the lower and upper troposphere.