An extreme Arctic cyclone in August 2016 and its predictability on medium-range timescales

NASA Astrophysics Data System (ADS)

Yamagami, Akio; Matsueda, Mio; Tanaka, Hiroshi

2017-04-01

An extremely strong Arctic cyclone (AC) developed in August 2016. The AC exhibited a minimum sea level pressure (SLP) of 967.2 hPa and covered the entire Pacific sector of the Arctic Ocean at 0000UTC on 16 August. At this time the AC was comparable to the strong AC observed in August 2012, in terms of horizontal extent, position, and intensity as measured by SLP. Two processes contributed to the explosive development of the AC: growth due to baroclinic instability, similar to extratropical cyclones, during the early part of the development stage, and later nonlinear development via the merging of upper warm cores. The AC was maintained for more than one month through multiple mergings with cyclones both generated in the Arctic and migrating northward from lower latitudes, as a result of the high cyclone activity in summer 2016. This study also investigated the predictability of the AC using operational medium-range ensemble forecasts: CMC (Canada), ECMWF (EU), JMA (Japan), NCEP (USA), and UKMO (UK), available at the The Interactive Grand Global Ensemble (TIGGE) database. The minimum SLP of the AC at 0000UTC on 16 August was well predicted by ECMWF 6-day, NCEP and UKMO 5-day, CMC 4-day, and JMA 3-day in advance. The predictability of the minimum SLP of the AC in August 2016 was much higher than that of the AC in 2012 August. Whereas most of the members well predicted the cyclogenesis of the AC, the growth due to baroclinic instability was weaker in some members. Even if the baroclinic growth was predicted well, predicted AC did not develop when the nonlinear development via the merging was not predict accurately. The accurate prediction of the processes in both early and later parts of the development stage was important for the accurate prediction of the development of the AC.

An analysis of simulated and observed storm characteristics

NASA Astrophysics Data System (ADS)

Benestad, R. E.

2010-09-01

A calculus-based cyclone identification (CCI) method has been applied to the most recent re-analysis (ERAINT) from the European Centre for Medium-range Weather Forecasts and results from regional climate model (RCM) simulations. The storm frequency for events with central pressure below a threshold value of 960-990hPa were examined, and the gradient wind from the simulated storm systems were compared with corresponding estimates from the re-analysis. The analysis also yielded estimates for the spatial extent of the storm systems, which was also included in the regional climate model cyclone evaluation. A comparison is presented between a number of RCMs and the ERAINT re-analysis in terms of their description of the gradient winds, number of cyclones, and spatial extent. Furthermore, a comparison between geostrophic wind estimated though triangules of interpolated or station measurements of SLP is presented. Wind still represents one of the more challenging variables to model realistically.

A Green Method for Processing Polymers using Dense Gas Technology

PubMed Central

Yoganathan, Roshan B.; Mammucari, Raffaella; Foster, Neil R.

2010-01-01

Dense CO2 can be used as an environmentally-benign polymer processing medium because of its liquid-like densities and gas-like mass transfer properties.In this work, polymer bio-blends of polycarbonate (PC), a biocompatible polymer, and polycaprolactone (PCL), a biodegradable polymer were prepared. Dense CO2 was used as a reaction medium for the melt-phase PC polymerization in the presence of dense CO2-swollen PCL particles and this method was used to prepare porous PC/PCL blends. To extend the applicability of dense CO2 to the biomedical industry and polymer blend processing, the impregnation of ibuprofen into the blend was conducted and subsequent dissolution characteristics were observed.

Convection in Extratropical Cyclones: Analysis of GPM, NexRAD, GCMs and Re-Analysis

NASA Astrophysics Data System (ADS)

Jeyaratnam, J.; Booth, J. F.; Naud, C. M.; Luo, J.

2017-12-01

Extratropical Cyclones (ETCs) are the most common cause of extreme precipitation in mid-latitudes and are important in the general atmospheric circulation as they redistribute moisture and heat. Isentropic lifting, upright convection, and slantwise convection are mechanisms of vertical motion within an ETC, which deliver different rain rates and might respond differently to global warming. In this study we compare different metrics for identifying convection within the ETC's and calculate the relative contribution of convection to total ETC precipitation. We determine if convection occurs preferentially in specific regions of the storm and decide how to best utilize GPM retrievals covering other parts of the mid-latitudes. Additionally, mid-latitude cyclones are tracked and composites of these tracked cyclones are compared amongst multiple versions of Global Circulation Models (GCMs) from Coupled Model Intercomparison Project Phase 6 (CMIP6) prototype models and re-analysis data; Model Diagnostic Task Force (MDTF) Geophysical Fluid Dynamics Laboratory (GFDL) using a two-plume convection scheme, MDTF GFDL using the Donner convection scheme, Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2), and European Reanalysis produced by the European Center for Medium-Range Weather Forecasts (ECMWF).

Plastic scintillators in coincidence for the study of multi-particle production of sea level cosmic rays in dense medium

NASA Technical Reports Server (NTRS)

Chuang, L. S.; Chan, K. W.; Wada, M.

1985-01-01

Cosmic ray particles at sea level penetrate a thick layer of dense medium without appreciable interaction. These penetrating particles are identified with muons. The only appreciable interaction of muons are by knock on processes. A muon may have single, double or any number of knock on with atoms of the material so that one, two, three or more particles will come out from the medium in which the knock on processes occur. The probability of multiparticle production is expected to decrease with the increase of multiplicity. Measurements of the single, double, and triple particles generated in a dense medium (Fe and Al) by sea level cosmic rays at 22.42 N. Lat. and 114.20 E. Long. (Hong Kong) are presented using a detector composed of two plastic scintillators connected in coincidence.

Nonlinear dynamics of drift structures in a magnetized dissipative plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aburjania, G. D.; Rogava, D. L.; Kharshiladze, O. A.

2011-06-15

A study is made of the nonlinear dynamics of solitary vortex structures in an inhomogeneous magnetized dissipative plasma. A nonlinear transport equation for long-wavelength drift wave structures is derived with allowance for the nonuniformity of the plasma density and temperature equilibria, as well as the magnetic and collisional viscosity of the medium and its friction. The dynamic equation describes two types of nonlinearity: scalar (due to the temperature inhomogeneity) and vector (due to the convectively polarized motion of the particles of the medium). The equation is fourth order in the spatial derivatives, in contrast to the second-order Hasegawa-Mima equations. Anmore » analytic steady solution to the nonlinear equation is obtained that describes a new type of solitary dipole vortex. The nonlinear dynamic equation is integrated numerically. A new algorithm and a new finite difference scheme for solving the equation are proposed, and it is proved that the solution so obtained is unique. The equation is used to investigate how the initially steady dipole vortex constructed here behaves unsteadily under the action of the factors just mentioned. Numerical simulations revealed that the role of the vector nonlinearity is twofold: it helps the dispersion or the scalar nonlinearity (depending on their magnitude) to ensure the mutual equilibrium and, thereby, promote self-organization of the vortical structures. It is shown that dispersion breaks the initial dipole vortex into a set of tightly packed, smaller scale, less intense monopole vortices-alternating cyclones and anticyclones. When the dispersion of the evolving initial dipole vortex is weak, the scalar nonlinearity symmetrically breaks a cyclone-anticyclone pair into a cyclone and an anticyclone, which are independent of one another and have essentially the same intensity, shape, and size. The stronger the dispersion, the more anisotropic the process whereby the structures break: the anticyclone is more intense and localized, while the cyclone is less intense and has a larger size. In the course of further evolution, the cyclone persists for a relatively longer time, while the anticyclone breaks into small-scale vortices and dissipation hastens this process. It is found that the relaxation of the vortex by viscous dissipation differs in character from that by the frictional force. The time scale on which the vortex is damped depends strongly on its typical size: larger scale vortices are longer lived structures. It is shown that, as the instability develops, the initial vortex is amplified and the lifetime of the dipole pair components-cyclone and anticyclone-becomes longer. As time elapses, small-scale noise is generated in the system, and the spatial structure of the perturbation potential becomes irregular. The pattern of interaction of solitary vortex structures among themselves and with the medium shows that they can take part in strong drift turbulence and anomalous transport of heat and matter in an inhomogeneous magnetized plasma.« less

Study of the impact of cyclogenesis at the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Ribo, M.; Llasat, C.

2009-09-01

The Mediterranean Basin is usually affected by high impact weather events, generating high impacts in all Mediterranean countries and causing important damages. This basin is surrounded by mountains and arid regions, and the interaction of the air flow with the orography barriers produces many effects, the most important is the formation of low pressure centers. This is one of the reasons why the Mediterranean Sea is considered to be the most cyclogenetic area in the world (Jansà, 1997). Floods are also one of the most important natural hazards in the Mediterranean Basin. Flood events occur when soil absorption, runoff or drainage cannot adequately disperse intense rainfall from quasi-stationary or stationary weather systems in short time periods. In some occasions these floods produce high social impact in the affected areas. Our work presents the study of the relationship between the flood episodes and the presence of cyclones in the Mediterranean Basin during those episodes, between 1990 and 2004. Information about social impact of each event has also been considered. To do these analyses the MEDEX database (MEDiterranean EXperiment on cyclones that produce high impact weather in the Mediterranean) has been improved in the frame work of the European FLASH project, and information about cyclones and rainfall has been extracted from the MEDEX cyclones database. A total of 217 flood events had been identified. Once the presence of one or more cyclones during each flood episode has been identified, temporal and regional analyses were made to determine the distribution of the cyclonic centers and to study the evolution of the events. Mediterranean cyclogenesis is leaded by influence of external systems (along the African coast, from the Atlantic Ocean, and from the west of Europe), although the majority of the cyclones (87% of the studied cases) are generated in the Mediterranean Basin, under influence of preexistent systems. There are different Mediterranean cyclones, from weak mesoscale depressions to strong, intense and more extensive depressions, and are classified using different criteria. In our study each cyclone identified was characterized using two dynamic criteria: vertical structure and geostrophic circulation. The first characterization is based on the vertical profiles of the laplacian of temperature, depending on which atmospheric level is reached by the cyclone. The second characterization is based on the geostrophic circulation, defined with the geostrophic vorticity in the cyclone domain. From these two characterizations, we have classified the cyclonic centers into six different types: deep, medium and shallow; strong, moderate and weak cyclones. Results show that between 1990 and 2004, 25% of the days in this time period have recorded a flood event in the Mediterranean Basin, and 90.7% of these flood events were related to a cyclonic center. 57% of these events had been located at the western Mediterranean part, although some flood prone areas can be identified in all the Mediterranean Basin; Eastern Spain and Balearic Islands, northern of Italy (gulf of Genève), north of Africa (Sahara) and Cyprus and Turkey. Cyclones related with floods in the western part are mainly superficial cyclones. An important nucleus of deep cyclones related with floods can be found near Cyprus. The spatial distribution of cyclones related with floods, for the period from 1990 to 2004, is coherent with the general distribution of cyclones showed by Gil et al. 2002. There is a general tendency of increase of detected flood events with cyclonic center in the vicinity in the time period analyzed. A total of 4724 victims where counted during flood episodes. Results of the relationship between flood episodes and cyclonic centers show that 40% of the flood episodes with higher damages were related to weak cyclones.

Frequently Asked Questions - Naval Oceanography Portal

Science.gov Websites

high confidence. Circular TCFA areas are issued when a developing cyclone's speed and direction of ;, "Medium", and "High" mean on the ABIO and ABPW messages? What is a "Tropical rectangle? When does JTWC initiate warnings on tropical disturbances? How often are warnings updated by JTWC

Storm-Tracks in ERA-40 and ERA-Interim Reanalyses

NASA Astrophysics Data System (ADS)

Liberato, M. L. R.; Trigo, I. F.; Trigo, R. M.

2009-04-01

Extratropical cyclones, their dominant paths, frequency and intensity have long been the object of climatological studies. The analysis of cyclone characteristics for the Euro-Atlantic sector (85°W-70°E; 20°N-75°N) presented here is based on the cyclone detecting and tracking algorithm first developed for the Mediterranean region (Trigo et al., 1999, 2002) and recently extended to a larger Euro-Atlantic region (Trigo, 2006). The objective methodology, which identifies and follows individual lows (Trigo et al. 1999), is applied to 6-hourly geopotential data at 1000-hPa from two reanalyses datasets provided by the European Centre for Medium-Range Weather Forecasts (ECMWF): ERA-40 and ERA-Interim reanalyses. Two storm-track databases are built over the Northern Atlantic European area, spanning the common available extended winter seasons from October 1989 to March 2002. Although relatively short, this common period allows a comparison of systems represented in reanalyses datasets with distinct horizontal resolutions (T106 and T255, respectively). This exercise is mostly focused on the key areas of cyclone formation and dissipation and main cyclone characteristics for the Euro-Atlantic sector. Trigo, I. F., T. D. Davies, and G. R. Bigg, 1999: Objective climatology of cyclones in the Mediterranean region. J. Climate, 12, 1685-1696. Trigo I. F., G. R. Bigg and T. D. Davies, 2002: Climatology of Cyclogenesis Mechanisms in the Mediterranean. Mon. Weather Rev. 130, 549-569. Trigo, I. F. 2006: Climatology and Interannual Variability of Storm-Tracks in the Euro-Atlantic sector: a comparison between ERA-40 and NCEP/NCAR Reanalyses. Clim. Dyn. DOI 10.1007/s00382-005-0065-9.

Wave ensemble forecast system for tropical cyclones in the Australian region

NASA Astrophysics Data System (ADS)

Zieger, Stefan; Greenslade, Diana; Kepert, Jeffrey D.

2018-05-01

Forecasting of waves under extreme conditions such as tropical cyclones is vitally important for many offshore industries, but there remain many challenges. For Northwest Western Australia (NW WA), wave forecasts issued by the Australian Bureau of Meteorology have previously been limited to products from deterministic operational wave models forced by deterministic atmospheric models. The wave models are run over global (resolution 1/4∘) and regional (resolution 1/10∘) domains with forecast ranges of + 7 and + 3 day respectively. Because of this relatively coarse resolution (both in the wave models and in the forcing fields), the accuracy of these products is limited under tropical cyclone conditions. Given this limited accuracy, a new ensemble-based wave forecasting system for the NW WA region has been developed. To achieve this, a new dedicated 8-km resolution grid was nested in the global wave model. Over this grid, the wave model is forced with winds from a bias-corrected European Centre for Medium Range Weather Forecast atmospheric ensemble that comprises 51 ensemble members to take into account the uncertainties in location, intensity and structure of a tropical cyclone system. A unique technique is used to select restart files for each wave ensemble member. The system is designed to operate in real time during the cyclone season providing + 10-day forecasts. This paper will describe the wave forecast components of this system and present the verification metrics and skill for specific events.

Tropical Cyclone Wind Probability Forecasting (WINDP).

DTIC Science & Technology

1981-04-01

llq. h. ,c ilrac (t’ small probabilities (below 107c) is limited II(t’h, numb(r o!, significant digits given: therefore 1t( huld lU r~ruidvd as being...APPLIED SCI. CORP. ENGLAMD ;7MOS. SCIENCES OEPT., LIBRARY ATTN: LIBARY , SUITE 500 400 WASHINGTON AVE. 6811 KENILWORTH AVE. EUROPEAN CENTRE FOR MEDIUM

Hydrostatic and non-hydrostatic simulations of dense waters cascading off a shelf: The East Greenland case

NASA Astrophysics Data System (ADS)

Magaldi, Marcello G.; Haine, Thomas W. N.

2015-02-01

The cascade of dense waters of the Southeast Greenland shelf during summer 2003 is investigated with two very high-resolution (0.5-km) simulations. The first simulation is non-hydrostatic. The second simulation is hydrostatic and about 3.75 times less expensive. Both simulations are compared to a 2-km hydrostatic run, about 31 times less expensive than the 0.5 km non-hydrostatic case. Time-averaged volume transport values for deep waters are insensitive to the changes in horizontal resolution and vertical momentum dynamics. By this metric, both lateral stirring and vertical shear instabilities associated with the cascading process are accurately parameterized by the turbulent schemes used at 2-km horizontal resolution. All runs compare well with observations and confirm that the cascade is mainly driven by cyclones which are linked to dense overflow boluses at depth. The passage of the cyclones is also associated with the generation of internal gravity waves (IGWs) near the shelf. Surface fields and kinetic energy spectra do not differ significantly between the runs for horizontal scales L > 30 km. Complex structures emerge and the spectra flatten at scales L < 30 km in the 0.5-km runs. In the non-hydrostatic case, additional energy is found in the vertical kinetic energy spectra at depth in the 2 km < L < 10 km range and with frequencies around 7 times the inertial frequency. This enhancement is missing in both hydrostatic runs and is here argued to be due to the different IGW evolution and propagation offshore. The different IGW behavior in the non-hydrostatic case has strong implications for the energetics: compared to the 2-km case, the baroclinic conversion term and vertical kinetic energy are about 1.4 and at least 34 times larger, respectively. This indicates that the energy transfer from the geostrophic eddy field to IGWs and their propagation away from the continental slope is not properly represented in the hydrostatic runs.

Dense Medium Ore Concentrates of Bois-Noirs; MINERAIS DES BOIS NOIRS CONCENTRES DE MILIEU DENSE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Bris, J.; Leduc, M.

1959-01-01

The chemical treatment of uranium concentrates of BoisNoirs ore obtained by heavy medium are discussed. The first part deals with sulfuric acid attack on the concentrate, and the second part with the separation of the solution from residues by filtration. A third part deals with this separation by decantation. The fourth part deals with the carbonation of the pickling solutions obtained. (auth)

Expectations and Outcomes of Reserve Network Performance following Re-zoning of the Great Barrier Reef Marine Park.

PubMed

Emslie, Michael J; Logan, Murray; Williamson, David H; Ayling, Anthony M; MacNeil, M Aaron; Ceccarelli, Daniela; Cheal, Alistair J; Evans, Richard D; Johns, Kerryn A; Jonker, Michelle J; Miller, Ian R; Osborne, Kate; Russ, Garry R; Sweatman, Hugh P A

2015-04-20

Networks of no-take marine reserves (NTMRs) are widely advocated for preserving exploited fish stocks and for conserving biodiversity. We used underwater visual surveys of coral reef fish and benthic communities to quantify the short- to medium-term (5 to 30 years) ecological effects of the establishment of NTMRs within the Great Barrier Reef Marine Park (GBRMP). The density, mean length, and biomass of principal fishery species, coral trout (Plectropomus spp., Variola spp.), were consistently greater in NTMRs than on fished reefs over both the short and medium term. However, there were no clear or consistent differences in the structure of fish or benthic assemblages, non-target fish density, fish species richness, or coral cover between NTMR and fished reefs. There was no indication that the displacement and concentration of fishing effort reduced coral trout populations on fished reefs. A severe tropical cyclone impacted many survey reefs during the study, causing similar declines in coral cover and fish density on both NTMR and fished reefs. However, coral trout biomass declined only on fished reefs after the cyclone. The GBRMP is performing as expected in terms of the protection of fished stocks and biodiversity for a developed country in which fishing is not excessive and targets a narrow range of species. NTMRs cannot protect coral reefs directly from acute regional-scale disturbance but, after a strong tropical cyclone, impacted NTMR reefs supported higher biomass of key fishery-targeted species and so should provide valuable sources of larvae to enhance population recovery and long-term persistence. Copyright © 2015 Elsevier Ltd. All rights reserved.

Using CloudSat and the A-Train to Estimate Tropical Cyclone Intensity in the Western North Pacific

DTIC Science & Technology

2014-09-01

CloudSat System Data Flow (from Cooperative Institute for Research in the Atmosphere 2008...radar Department of Defense Data Processing Center European Centre for Medium-Range Weather Forecasts Earth observing system Earth observing... system data and information system Earth sciences systems pathfinder hierarchical data format moderate resolution imaging spectroradiometer moist

Cyclone Nargis survey in Myanmar's Ayeyarwady River delta

NASA Astrophysics Data System (ADS)

Fritz, H. M.; Blount, C.; Thwin, S.; Thu, M. K.; Chan, N.

2008-12-01

Tropical cyclone Nargis (Cat. 4) made landfall on May 2, 2008, causing the worst natural disaster in Myanmar's recorded history. Official death toll estimates exceed 130,000 fatalities making it the 7th deadliest cyclone ever recorded worldwide. Nargis took a rare nearly eastern track over the Bay of Bengal while developing sustained winds over 210 km/h with gusts up to 260 km/h hours prior to landfall in Myanmar at untypically low latitude near 16°N. It then proceeded northeast and approximately 12 hours later weakened to a Category 1 storm with sustained wind speeds of 130 km/h as it passed over Yangon. The first independent storm surge reconnaissance team was deployed to Myanmar from 9 to 23 August 2008. Cyclone Nargis struck low-lying coastal plains particularly vulnerable to storm surge flooding due to the lack of effective barriers. The team surveyed coastal and inland villages from Pyapon to Purian Point, encompassing the Bogale and Ayeyarwady River mouths. The survey by boat spanned more than 150 km parallel to the cyclone track between Pyapon and Pyinkhayan encompassing 20 hardest hit settlements such as Pyinsalu. More than 1m vertical erosion and 150 m land loss were measured at various coastal locations such as Aya. Massive deforestation of mangroves and land use were documented. Maximum storm surge elevations and overland flow depths were measured based on water marks on buildings, scars on trees, and rafted debris. The storm surge peaked in the landfall area south of Pyinkhayan and eastwards in Pyinsalu exceeding 5m. Storm waves more than 2m high were superimposed on the storm surge level in most areas according to eyewitnesses. Inundation distances reached beyond 50 km inland. Catastrophic peak fatality rates exceeded 80% in hardest hit villages with the majority being children and women. The high water marks and fatality rates significantly exceeded corresponding 2004 Indian Ocean tsunami values at every location. Eyewitnesses were interviewed to document the time history of the event, survival strategies, cyclone awareness and evacuation. At the end of the 3 month relief operations survivors were left drinking from rice paddies with contaminated wells and no source of safe drinking water besides rain water. Storm surge simulations can be benchmarked against the measured cyclone Nargis storm surge and inundation to perform vulnerability analysis. Unfortunately, the widely deforested, low lying and densely populated Ayeyarwady delta remains extremely vulnerable to future storm surge flooding or potential sea level rise.

Flash photoionization of gamma-ray burst environments

NASA Technical Reports Server (NTRS)

Band, David L.; Hartmann, Dieter H.

1992-01-01

The H-alpha line emission that a flash-photoionized region emits is calculated. Archival transients, as well as various theoretical predictions, suggest that there may be significant ionizing flux. The limits on the line flux which might be observable indicate that the density must be fairly high for the recombination radiation to be observable. The intense burst radiation is insufficient to melt the dust which will be present in such a dense medium. This dust may attenuate the observable line emission, but does not attenuate the ionizing radiation before it ionizes the neutral medium surrounding the burst source. The dust can also produce a light echo. If there are indeed gamma-ray bursts in dense clouds, then it is possible that the burst was triggered by Bondi-Hoyle accretion from the dense medium, although it is unlikely on statistical grounds that all bursts occur in clouds.

Elasticity-induced force reversal between active spinning particles in dense passive media

PubMed Central

Aragones, J. L.; Steimel, J. P.; Alexander-Katz, A.

2016-01-01

The self-organization of active particles is governed by their dynamic effective interactions. Such interactions are controlled by the medium in which such active agents reside. Here we study the interactions between active agents in a dense non-active medium. Our system consists of actuated, spinning, active particles embedded in a dense monolayer of passive, or non-active, particles. We demonstrate that the presence of the passive monolayer alters markedly the properties of the system and results in a reversal of the forces between active spinning particles from repulsive to attractive. The origin of such reversal is due to the coupling between the active stresses and elasticity of the system. This discovery provides a mechanism for the interaction between active agents in complex and structured media, opening up opportunities to tune the interaction range and directionality via the mechanical properties of the medium. PMID:27112961

Analysis of dense-medium light scattering with applications to corneal tissue: experiments and Monte Carlo simulations.

PubMed

Kim, K B; Shanyfelt, L M; Hahn, D W

2006-01-01

Dense-medium scattering is explored in the context of providing a quantitative measurement of turbidity, with specific application to corneal haze. A multiple-wavelength scattering technique is proposed to make use of two-color scattering response ratios, thereby providing a means for data normalization. A combination of measurements and simulations are reported to assess this technique, including light-scattering experiments for a range of polystyrene suspensions. Monte Carlo (MC) simulations were performed using a multiple-scattering algorithm based on full Mie scattering theory. The simulations were in excellent agreement with the polystyrene suspension experiments, thereby validating the MC model. The MC model was then used to simulate multiwavelength scattering in a corneal tissue model. Overall, the proposed multiwavelength scattering technique appears to be a feasible approach to quantify dense-medium scattering such as the manifestation of corneal haze, although more complex modeling of keratocyte scattering, and animal studies, are necessary.

The Influence of the North Atlantic Oscillation on Tropospheric Distributions of Ozone and Carbon Monoxide.

NASA Astrophysics Data System (ADS)

Knowland, K. E.; Doherty, R. M.; Hodges, K.

2015-12-01

The influence of the North Atlantic Oscillation (NAO) on the tropospheric distributions of ozone (O3) and carbon monoxide (CO) has been quantified. The Monitoring Atmospheric Composition and Climate (MACC) Reanalysis, a combined meteorology and composition dataset for the period 2003-2012 (Innes et al., 2013), is used to investigate the composition of the troposphere and lower stratosphere in relation to the location of the storm track as well as other meteorological parameters over the North Atlantic associated with the different NAO phases. Cyclone tracks in the MACC Reanalysis compare well to the cyclone tracks in the widely-used ERA-Interim Reanalysis for the same 10-year period (cyclone tracking performed using the tracking algorithm of Hodges (1995, 1999)), as both are based on the European Centre for Medium-Range Weather Forecasts' (ECMWF) Integrated Forecast System (IFS). A seasonal analysis is performed whereby the MACC reanalysis meteorological fields, O3 and CO mixing ratios are weighted by the monthly NAO index values. The location of the main storm track, which tilts towards high latitudes (toward the Arctic) during positive NAO phases to a more zonal location in the mid-latitudes (toward Europe) during negative NAO phases, impacts the location of both horizontal and vertical transport across the North Atlantic and into the Arctic. During positive NAO seasons, the persistence of cyclones over the North Atlantic coupled with a stronger Azores High promotes strong horizontal transport across the North Atlantic throughout the troposphere. In all seasons, significantly more intense cyclones occur at higher latitudes (north of ~50°C) during the positive phase of the NAO and in the southern mid-latitudes during the negative NAO phase. This impacts the location of stratospheric intrusions within the descending dry airstream behind the associated cold front of the extratropical cyclone and the venting of low-level pollution up into the free troposphere within the warm conveyor belt airstream which rises ahead of the cold front.

The use of a calculus-based cyclone identification method for generating storm statistics

NASA Astrophysics Data System (ADS)

Benestad, R. E.; Chen, D.

2006-08-01

Maps of 12 hr sea-level pressure (SLP) from the former National Meteotrological Center (NMC) and 24 hr SLP maps from the European Centre for Medium-range Weather Forecasts (ECMWF) 40 yr re-analysis (ERA40) were used to identify extratropical cyclones in the North Atlantic region. A calculus-based cyclone identification (CCI) method is introduced and evaluated, where a multiple regression against a truncated series of sinusoids was used to obtain a Fourier approximation of the north-south and east-west SLP profiles, providing a basis for analytical expressions of the derivatives. Local SLP minima were found from the zero-crossing points of the first-order derivatives for the SLP gradients where the second-order derivatives were greater than zero. Evaluation of cyclone counts indicates a good correspondence with storm track maps and independent monthly large-scale SLP anomalies. The results derived from ERA40 also revealed that the central storm pressure sometimes could be extremely deep in the re-analysis product, and it is not clear whether such outliers are truly representative of the actual events. The position and the depth of the cyclones were subjects for a study of long-term trends in cyclone number for various regions around the North Atlantic. Noting that the re-analyses may contain time-dependent biases due to changes in the observing practises, a tentative positive linear trend, statistically significant at the 10% level, was found in the number of intense storms over the Nordic countries over the period 1955-1994 in both the NMC and the ERA40 data. However, there was no significant trend in the western parts of the North Atlantic where trend analysis derived from NMC and ERA40 yielded different results. The choice of data set had a stronger influence on the results than choices such as the number of harmonics to include or spatial resolution of interpolation.

Dust emission and transport associated with a Saharan depression: The February 2007 case

NASA Astrophysics Data System (ADS)

Karam, Diana Bou; Flamant, Cyrille; Cuesta, Juan; Pelon, Jacques; Williams, Earle

2010-05-01

The dust activity over North Africa associated with the Saharan depression event in February 2007 is investigated by mean of spaceborne observations, ground based measurements and mesoscale simulation with Meso-NH. The main characteristics of the cyclone as well as the meteorological conditions during this event are described using the European Centre for Medium-range Weather Forecasts (ECMWF). The dust storm and cloud cover over North Africa is thoroughly described combining for the first time Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) images for the spatio-temporal evolution and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat observations for the vertical distribution. The Saharan depression formed over Algeria in the lee of the Atlas Mountain on the afternoon of February 20 in response to midlatitude trough intrusion. It migrated eastward with a speed of 11 m s-1 and reached Libya on February 22 before exiting the African continent toward the Mediterranean Sea on February 23. The horizontal scale of the cyclone at the surface varied between 800 km and 1000 km during its lifetime. On the vertical the cyclone extended over 8 km and a potential vorticity of 2 PVU was reported on its centre at 3 km in altitude. The cyclone was characterised by a surface pressure anomaly of about 9 hPa with respect to the environment, a warm front typified at the surface by an increase in surface temperature of 5°C, and a sharp cold front characterized by a drop in surface temperature of 8°C and an increase in 10 m wind speed of 15 m s-1. The cyclone provided a dynamical forcing that led to strong near-surface winds and produced a major dust storm over North Africa. The dust was transported all around the cyclone leaving a clear eye on its centre and was accompanied by a deep cloud band along the northwestern edge of the cyclone. On the vertical, slanted dust layers were consistently observed during the event over North Africa. Furthermore, the dust was lofted to altitudes as high as 7 km, becoming subject to long range transport. The model was able to reproduce reasonably the structure, the lifetime and the trajectory of the cyclone. Also comparison with MODIS deep blue AODs and CALIPSO/CloudSat observations suggests that the model can be used reliably to quantify the dust emissions associated with this event. The mean daily dust loads over the area influenced by the cyclone were simulated to range between 2 and 8 Tg during the lifetime of the Sharav cyclone (i.e. 5 days). This study suggests that dust emissions linked with Saharan cyclones may contribute significantly to the total dust load over West and North Africa observed annually.

Dust emission and transport associated with a Saharan depression: February 2007 case

NASA Astrophysics Data System (ADS)

Bou Karam, Diana; Flamant, Cyrille; Cuesta, Juan; Pelon, Jacques; Williams, Earle

2010-01-01

The dust activity over North Africa associated with the Saharan depression event in February 2007 is investigated by mean of spaceborne observations, ground-based measurements, and mesoscale simulation with Meso-NH. The main characteristics of the cyclone as well as the meteorological conditions during this event are described using the European Centre for Medium-Range Weather Forecasts (ECMWF). The dust storm and cloud cover over North Africa is thoroughly described combining for the first time Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) images for the spatiotemporal evolution and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat observations for the vertical distribution. The Saharan depression formed over Algeria in the lee of the Atlas Mountains on the afternoon of 20 February in response to midlatitude trough intrusion. It migrated eastward with a speed of 11 m s-1 and reached Libya on 22 February before exiting the African continent toward the Mediterranean Sea on 23 February. The horizontal scale of the cyclone at the surface varied between 800 and 1000 km during its lifetime. On the vertical the cyclone extended over 8 km, and a potential vorticity of 2 potential vorticity units (PVU) was reported at its center at 3 km in altitude. The cyclone was characterized by a surface pressure anomaly of about 9 hPa with respect to the environment, a warm front typified at the surface by an increase in surface temperature of 5°C, and a sharp cold front characterized by a drop in surface temperature of 8°C and an increase in 10 m wind speed of 15 m s-1. The cyclone provided dynamical forcing that led to strong near-surface winds and produced a major dust storm over North Africa. The dust was transported all around the cyclone leaving a clear eye at its center and was accompanied by a deep cloud band along the northwestern edge of the cyclone. On the vertical, slanted dust layers were consistently observed during the event over North Africa. Furthermore, the dust was lofted to altitudes as high as 7 km, becoming subject to long-range transport. The model was able to reasonably reproduce the structure, lifetime, and trajectory of the cyclone. Also, comparison with Moderate Resolution Imaging Spectrometer (MODIS) deep blue aerosol optical depths and CALIPSO-CloudSat observations suggests that the model can be reliably used to quantify the dust emissions associated with this event. The mean daily dust loads over the area influenced by the cyclone were simulated to range between 2 and 8 Tg during the lifetime of the Sharav cyclone (i.e., 5 days). This study suggests that dust emissions linked with Saharan cyclones may contribute significantly to the total dust load over West and North Africa observed annually.

Diamonds in dense molecular clouds - A challenge to the standard interstellar medium paradigm

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Sandford, S. A.; Tielens, A. G. G. M.; Herbst, T. M.

1993-01-01

Observations of a newly discovered infrared C-H stretching band indicate that interstellar diamond-like material appears to be characteristic of dense clouds. In sharp contrast, the spectral signature of dust in the diffuse interstellar medium is dominated by -CH2- and -CH3 groups. This dichotomy in the aliphatic organic component between the dense and diffuse media challenges standard assumptions about the processes occurring in, and interactions between, these two media. The ubiquity of this interstellar diamond-like material rules out models for meteoritic diamond formation in unusual circumstellar environments and implies that the formation of the diamond-like material is associated with common interstellar processes or stellar types.

Sedimentary record of Tropical Cyclone Pam from Vanuatu: implications for long-term event records in the tropical South Pacific

NASA Astrophysics Data System (ADS)

Pilarczyk, Jessica; Kosciuch, Thomas; Hong, Isabel; Fritz, Hermann; Horton, Benjamin; Wallace, Davin; Dike, Clayton; Rarai, Allan; Harrison, Morris; Jockley, Fred

2017-04-01

Vanuatu has a history of tropical cyclones impacting its coastlines, including Tropical Cyclone (TC) Pam, a rare Category 5 event that made landfall in March 2015. Reliable records of tropical cyclones impacting Vanuatu are limited to the last several decades, with only fragmentary evidence of events extending as far back as the 1890's. Geological investigations are a means for expanding the short historical record of tropical cyclones by hundreds to thousands of years, permitting the study of even the rare, but intense events. However, geological records of past tropical cyclones are limited in their ability to quantify the intensity of past events. Modern analogues of landfalling tropical cyclones present an opportunity to characterize overwash sediments deposited by a storm of known intensity. In this study, we document the sedimentological and micropaleontological characteristics of sediments deposited by TC Pam in order to assess sediment provenance associated with a landfalling Category 5 storm. Within three months of TC Pam making landfall on Vanuatu we surveyed high-water marks associated with the storm surge and documented the foraminiferal assemblages and grain size distributions contained within the overwash sediments from Manuro (mixed-carbonate site on Efate Island) and Port Resolution Bay (volcaniclastic site on Tanna Island). The combined use of foraminiferal taxonomy and taphonomy (surface condition of foraminifera) was most useful in distinguishing the TC Pam sediments from the underlying layer. TC Pam sediments were characterized by an influx of calcareous marine foraminifera that were dominantly unaltered relative to those that were abraded and fragmented. Similar to studies that use mollusk taphonomy to identify overwash deposits, we found that TC Pam sediments were associated with an influx of angular fragments that were broken during transport by the storm surge. A statistical comparison of foraminifera from six modern environments on Efate Island (open bay, forereef, reef crest, reef flat, mangrove, and beach) with TC Pam sediments revealed a shallow nearshore to supratidal (reef crest to beach) source, spanning depths ranging from 1.3 to -4.9 m above MSL. On Efate Island, the TC Pam sediments consisted of a medium-grained (1.20Φ), moderately well-sorted (0.55Φ), mixed-carbonate sand. At this location, the sand extended 130 m inland, where it abruptly transitioned to a pumice layer that extended 400 m inland. In contrast, TC Pam deposited a medium-grained (1.81Φ), moderately well-sorted volcanic sand at Port Resolution Bay, where the sand extended up to 320 m inland. We used a combination of measured flow heights obtained at the Port Resolution Bay site and laboratory derived grain size settling velocities to calculate the distance of sediment transport caused by TC Pam's storm surge. Based on the distribution of settling velocities from our samples, transport distances for material deposited in the trench suggests a source for the overwash sand ranging from the supratidal berm to 290 m seaward in the nearshore at Port Resolution Bay.

Effect of temperature on the shape of spatial quasi-periodic oscillations of the refractive index of alkali atoms in an optically dense medium with a closed excitation contour of Δ type

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barantsev, K A; Litvinov, A N

2014-10-31

A theory of a closed excitation contour (Δ system) of a three-level atom in an optically dense medium is constructed with allowance for temperature. The spatial quasi-periodic oscillations of the refractive index in the system under study are shown to damp with increasing temperature. The range of temperatures at which these oscillations are most pronounced is found. (quantum optics)

Satellite views of hurricane Camille

NASA Technical Reports Server (NTRS)

Shenk, W. E.; Rodgers, E. B.

1974-01-01

Three periods within the life cycle of Hurricane Camille (1969) are studied with radiometric and camera measurements from Nimbus-3 and camera information from ATS-3 in conjunction with conventional information. These periods are the deepening phase, the interaction of Camille with midlatitude westerlies, and the excessive rain producing period when the cyclone was over the central Appalachian Mountain. Just prior to significant deepening, the Nimbus-3 Medium Resolution Infrared Radiometer (MRIR) showed that a pronounced feeder band had formed southeast of the center which was associated with the rapid transport of moisture into the storm circulation. During the rapid deepening phase the MRIR measurements indicated the development of large scale subsidence throughout the troposphere northwest of the center. When Camille was over the lower Mississippi Valley it acted as an obstruction to the envrionmental wind. A region of widespread subsidence was created west and north of the cyclone center. Increased cloud-top elevations, back to the levels reached when Camille was an intense cyclone over the Gulf of Mexico, were estimated from the Nimbus-3 High Resolution Infrared Radiometer (HRIR) measurements on August 20, 1969, when Camille produced rains of major flood proportions near the east slopes of the Appalachians in central Virginia.

Advanced coal cleaning meets acid rain emission limits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boron, D.J.; Matoney, J.P.; Albrecht, M.C.

1987-03-01

The following processes were selected for study: fine-coal, heavy-medium cyclone separation/flotation, advanced flotation, Dow true heavy liquid separation, Advanced Energy Dynamics (AED) electrostatic separation, and National Research Council of Canada oil agglomeration. Advanced coal cleaning technology was done for the state of New York to investigate methods to use high sulfur coal in view of anticipated lower SO/sub 2/ emission limits.

Water security and societal impacts of tropical cyclones in northwestern Mexico, 1970-2010

NASA Astrophysics Data System (ADS)

Scott, C. A.; Farfan, L.

2012-12-01

Hydroclimatic variability is one of several potential threats to water security, defined as sustainable quantities and qualities of water for resilient societies and ecosystems in the face of uncertain global environmental change. Other threats can stem from human dimensions of global change, e.g., long-distance trade of water-intensive agricultural commodities or pollution resulting from industrial production and mining in response to rising global market demand. Drought and water scarcity are considered the principal, chronic, hydroclimatic drivers of water insecurity in arid and semi-arid regions. In these conditions, however, rainfall is both the water-supply lifeline and, in extreme events, the cause of flood hazard. In this study, we consider the monsoon-dominated Pacific coast of Mexico and assess the human impacts from tropical cyclone landfall over the past four decades (1970-2010). Storm data from the U.S. National Hurricane Center, rainfall reports from Mexico's National Meteorological Service, and indicators from an international disaster database at Belgium's Université Catholique de Louvain are used to assess the impacts of more than 30 landfall events. For the ten events with the greatest population impact, between 20,000 to 800,000 people were affected by each landfalling cyclone. Strong winds and heavy rainfall, particularly when sustained over periods of 1-3 days, result in significant property damage and loss of life. Results indicate that, in densely populated areas, excessive rainfall accumulations and high daily rates are important causes of cyclone disasters. Strengthening water security associated with extreme events requires planning via structured exchanges between scientists and decision-makers. Adaptive management that accounts for uncertainties, initiates responses, and iteratively assesses outcomes is the thrust of an emerging water-security initiative for the arid Americas that seeks to strengthen water security in northwestern Mexico.Norbert Impacts in Alamos, Sonora, 12 Oct. 2008

Invited Article: Refractive index matched scanning of dense granular materials

NASA Astrophysics Data System (ADS)

Dijksman, Joshua A.; Rietz, Frank; Lőrincz, Kinga A.; van Hecke, Martin; Losert, Wolfgang

2012-01-01

We review an experimental method that allows to probe the time-dependent structure of fully three-dimensional densely packed granular materials and suspensions by means of particle recognition. The method relies on submersing a granular medium in a refractive index matched fluid. This makes the resulting suspension transparent. The granular medium is then visualized by exciting, layer by layer, the fluorescent dye in the fluid phase. We collect references and unreported experimental know-how to provide a solid background for future development of the technique, both for new and experienced users.

Storm-tracks interannual variability and large-scale climate modes

NASA Astrophysics Data System (ADS)

Liberato, Margarida L. R.; Trigo, Isabel F.; Trigo, Ricardo M.

2013-04-01

In this study we focus on the interannual variability and observed changes in northern hemisphere mid-latitude storm-tracks and relate them to large scale atmospheric circulation variability modes. Extratropical storminess, cyclones dominant paths, frequency and intensity have long been the object of climatological studies. The analysis of storm characteristics and historical trends presented here is based on the cyclone detecting and tracking algorithm first developed for the Mediterranean region (Trigo et al. 1999) and recently extended to a larger Euro-Atlantic region (Trigo 2006). The objective methodology, which identifies and follows individual lows as minima in SLP fields, fulfilling a set of conditions regarding the central pressure and the pressure gradient, is applied to the northern hemisphere 6-hourly geopotential data at 1000 hPa from the 20th Century Reanalyses (20CRv2) project and from reanalyses datasets provided by the European Centre for Medium-Range Weather Forecasts (ECMWF): ERA-40 and ERA Interim reanalyses. First, we assess the interannual variability and cyclone frequency trends for each of the datasets, for the 20th century and for the period between 1958 and 2002 using the highest spatial resolution available (1.125° x 1.125°) from the ERA-40 data. Results show that winter variability of storm paths, cyclone frequency and travel times is in agreement with the reported variability in a number of large-scale climate patterns (including the North Atlantic Oscillation, the East Atlantic Pattern and the Scandinavian Pattern). In addition, three storm-track databases are built spanning the common available extended winter seasons from October 1979 to March 2002. Although relatively short, this common period allows a comparison of systems represented in reanalyses datasets with distinct horizontal resolutions. This exercise is mostly focused on the key areas of cyclogenesis and cyclolysis and main cyclone characteristics over the northern hemisphere. Trigo IF., TD Davies, GR Bigg (1999) Objective climatology of cyclones in the Mediterranean region. J. Climate 12: 1685-1696. Trigo IF (2006) Climatology and interannual variability of storm-tracks in the Euro-Atlantic sector: a comparison between ERA-40 and NCEP/NCAR reanalyses. Clim. Dyn. 26: 127-143.

Convectively-coupled Kelvin waves over the tropical Atlantic and African regions and their influence on Atlantic tropical cyclogenesis

NASA Astrophysics Data System (ADS)

Ventrice, Michael J.

High-amplitude convectively coupled atmospheric Kelvin waves (CCKWs) are explored over the tropical Atlantic during the boreal summer. Atlantic tropical cyclogenesis is found to be more frequent during the passage of the convectively active phase of the CCKW, and most frequent two days after its passage. CCKWs impact convection within the mean latitude of the inter-tropical convergence zone over the northern tropical Atlantic. In addition to convection, CCKWs also impact the large scale environment that favors Atlantic tropical cyclogenesis (i.e., deep vertical wind shear, moisture, and low-level relative vorticity). African easterly waves (AEWs) are known to be the main precursors for Atlantic tropical cyclones. Therefore, the relationship between CCKWs and AEW activity during boreal summer is explored. AEW activity is found to increase over the Guinea Highlands and Darfur Mountains during and after the passage of the convectively active phase of the CCKW. First, CCKWs increase the number of convective triggers for AEW genesis. Secondly, the associated zonal wind structure of the CCKW is found to affect the horizontal shear on the equatorward side of the African easterly jet (AEJ), such that the jet becomes more unstable during and after the passage of the convectively active phase of the CCKW. The more unstable AEJ is assumed to play a role with increased AEW growth. Through the increased number of AEWs propagating over the tropical Atlantic, as well as from the direct impact on convection and the large-scale environment over the tropical Atlantic, CCKWs are recommended to be used as a means for medium-range predictability of Atlantic tropical cyclones. In addition to modulating tropical cyclone activity over the tropical Atlantic, CCKWs might impact the intensification processes of tropical cyclones. A case study highlighting two August 2010 tropical cyclones (Danielle and Earl) is explored for potential CCKW-tropical cyclone interactions. While predicted to intensify by most model guidance, both Danielle and Earl struggled to do so. It is shown that Danielle and Earl interacted with the convectively suppressed phase of an eastward propagating CCKW during the time they were predicted to intensify. Composite analysis shows that during and after the passage of the convectively suppressed phase of the CCKW over the Atlantic, large-scale vertical wind shear increases as a result of anomalous upper-level westerlies collocated with anomalous lower-level easterlies. Large-scale subsidence associated with the convectively suppressed phase of the CCKW causes the atmosphere to dry. Further, when the upper-level westerly wind anomalies associated with the CCKW are located over the equatorial Atlantic, a tropical upper-tropospheric trough (TUTT) develops over the northern tropical Atlantic. TUTTs are upper-level disturbances known to negatively impact the intensity of tropical cyclones. CCKWs over the tropical Atlantic tend to occur during preferable locations of the Madden-Julian Oscillation (MJO). Results show that the MJO significantly modulates Atlantic tropical cyclogenesis using real-time multivariate MJO indices. Like CCKWs, AEW activity is found to vary coherently with MJO passages. Furthermore, the MJO also impacts the large-scale environment that favors for Atlantic tropical cyclogenesis. Therefore in addition to CCKWs, the state of the MJO should be used for Atlantic tropical cyclogenesis medium-range predictability.

Characteristic Paths of Extratropical Cyclones that Cause High Wind Events in the Northeast United States

NASA Astrophysics Data System (ADS)

Booth, J. F.; Rieder, H. E.; Lee, D.; Kushnir, Y.

2014-12-01

This study analyzes the association between wintertime high wind events (HWEs) in the northeast United States US and extratropical cyclones. Sustained wind maxima in the Daily Summary Data from the National Climatic Data Center's Integrated Surface Database are analyzed for 1979-2012. For each station, a Generalized Pareto Distribution (GPD) is fit to the upper tail of the daily maximum wind speed data, and probabilistic return levels at intervals of 1, 3 and 5-years are derived from the GPD fit. At each interval, wind events meeting the return level criteria are termed HWEs. The HWEs occurring on the same day are grouped into multi-station events allowing the association with extratropical cyclones, which are tracked in the European Center for Medium-Range Weather Forecast ERA-Interim reanalysis. Using hierarchical clustering analysis, this study finds that the HWEs are most often associated with cyclones travelling from southwest to northeast, usually originating west of the Appalachian Mountains. The results show that a storm approaching from the southwest is four times more likely to cause strong surface winds than a Nor'easter. A series of sensitivity analyses confirms the robustness of this result. Next, the relationship between the strength of the wind events and the corresponding storm minimum sea level pressure is analyzed. No robust relationship between these quantities is found for strong wind events. Nevertheless, subsequent analysis shows that a relationship between deeper storms and stronger winds emerges if the analysis is extended to the entire set of wintertime storms.

Optical tomography of fluorophores in dense scattering media based on ultrasound-enhanced chemiluminescence

NASA Astrophysics Data System (ADS)

Kobayashi, Masaki; Kikuchi, Naoto; Sato, Akihiro

2015-01-01

This letter proposes and demonstrates ultrasound-combined optical imaging in dense scattering media. A peroxyoxalate chemiluminescence system that includes fluorophores to chemically excite the pigment is stimulated by ultrasound irradiation with power of less than 0.14 W/cm2. Using focused ultrasound, the chemiluminescence is selectively spatially enhanced, which leads to imaging of the pigment when embedded in a light-scattering medium via scanning of the focal point. The ultrasonically enhanced intensity of the chemiluminescence depends on the base intensity of the chemiluminescence without the applied ultrasound irradiation, which thereby enables quantitative determination of the fluorophore concentration. The authors demonstrate the potential of this method to resolve chemiluminescent targets in a dense scattering medium that is comparable to biological tissue. An image was acquired of a chemiluminescent target that included indocyanine green as the fluorophore embedded at a depth of 20 mm in an Intralipid-10% 200 ml/l solution scattering medium (the reduced scattering coefficient was estimated to be approximately 1.3 mm-1), indicating the potential for expansion of this technique for use in biological applications.

Evaluation of Pump Pulsation in Respirable Size-Selective Sampling: Part II. Changes in Sampling Efficiency

PubMed Central

Lee, Eun Gyung; Lee, Taekhee; Kim, Seung Won; Lee, Larry; Flemmer, Michael M.; Harper, Martin

2015-01-01

This second, and concluding, part of this study evaluated changes in sampling efficiency of respirable size-selective samplers due to air pulsations generated by the selected personal sampling pumps characterized in Part I (Lee E, Lee L, Möhlmann C et al. Evaluation of pump pulsation in respirable size-selective sampling: Part I. Pulsation measurements. Ann Occup Hyg 2013). Nine particle sizes of monodisperse ammonium fluorescein (from 1 to 9 μm mass median aerodynamic diameter) were generated individually by a vibrating orifice aerosol generator from dilute solutions of fluorescein in aqueous ammonia and then injected into an environmental chamber. To collect these particles, 10-mm nylon cyclones, also known as Dorr-Oliver (DO) cyclones, were used with five medium volumetric flow rate pumps. Those were the Apex IS, HFS513, GilAir5, Elite5, and Basic5 pumps, which were found in Part I to generate pulsations of 5% (the lowest), 25%, 30%, 56%, and 70% (the highest), respectively. GK2.69 cyclones were used with the Legacy [pump pulsation (PP) = 15%] and Elite12 (PP = 41%) pumps for collection at high flows. The DO cyclone was also used to evaluate changes in sampling efficiency due to pulse shape. The HFS513 pump, which generates a more complex pulse shape, was compared to a single sine wave fluctuation generated by a piston. The luminescent intensity of the fluorescein extracted from each sample was measured with a luminescence spectrometer. Sampling efficiencies were obtained by dividing the intensity of the fluorescein extracted from the filter placed in a cyclone with the intensity obtained from the filter used with a sharp-edged reference sampler. Then, sampling efficiency curves were generated using a sigmoid function with three parameters and each sampling efficiency curve was compared to that of the reference cyclone by constructing bias maps. In general, no change in sampling efficiency (bias under ±10%) was observed until pulsations exceeded 25% for the DO cyclone. However, for three models of pumps producing 30%, 56%, and 70% pulsations, substantial changes were confirmed. The GK2.69 cyclone showed a similar pattern to that of the DO cyclone, i.e. no change in sampling efficiency for the Legacy producing 15% pulsation and a substantial change for the Elite12 producing 41% pulsation. Pulse shape did not cause any change in sampling efficiency when compared to the single sine wave. The findings suggest that 25% pulsation at the inlet of the cyclone as measured by this test can be acceptable for the respirable particle collection. If this test is used in place of that currently in European standards (EN 1232–1997 and EN 12919-1999) or is used in any International Organization for Standardization standard, then a 25% pulsation criterion could be adopted. This work suggests that a 10% criterion as currently specified in the European standards for testing may be overly restrictive and not able to be met by many pumps on the market. Further work is recommended to determine which criterion would be applicable to this test if it is to be retained in its current form. PMID:24064963

Evaluation of pump pulsation in respirable size-selective sampling: part II. Changes in sampling efficiency.

PubMed

Lee, Eun Gyung; Lee, Taekhee; Kim, Seung Won; Lee, Larry; Flemmer, Michael M; Harper, Martin

2014-01-01

This second, and concluding, part of this study evaluated changes in sampling efficiency of respirable size-selective samplers due to air pulsations generated by the selected personal sampling pumps characterized in Part I (Lee E, Lee L, Möhlmann C et al. Evaluation of pump pulsation in respirable size-selective sampling: Part I. Pulsation measurements. Ann Occup Hyg 2013). Nine particle sizes of monodisperse ammonium fluorescein (from 1 to 9 μm mass median aerodynamic diameter) were generated individually by a vibrating orifice aerosol generator from dilute solutions of fluorescein in aqueous ammonia and then injected into an environmental chamber. To collect these particles, 10-mm nylon cyclones, also known as Dorr-Oliver (DO) cyclones, were used with five medium volumetric flow rate pumps. Those were the Apex IS, HFS513, GilAir5, Elite5, and Basic5 pumps, which were found in Part I to generate pulsations of 5% (the lowest), 25%, 30%, 56%, and 70% (the highest), respectively. GK2.69 cyclones were used with the Legacy [pump pulsation (PP) = 15%] and Elite12 (PP = 41%) pumps for collection at high flows. The DO cyclone was also used to evaluate changes in sampling efficiency due to pulse shape. The HFS513 pump, which generates a more complex pulse shape, was compared to a single sine wave fluctuation generated by a piston. The luminescent intensity of the fluorescein extracted from each sample was measured with a luminescence spectrometer. Sampling efficiencies were obtained by dividing the intensity of the fluorescein extracted from the filter placed in a cyclone with the intensity obtained from the filter used with a sharp-edged reference sampler. Then, sampling efficiency curves were generated using a sigmoid function with three parameters and each sampling efficiency curve was compared to that of the reference cyclone by constructing bias maps. In general, no change in sampling efficiency (bias under ±10%) was observed until pulsations exceeded 25% for the DO cyclone. However, for three models of pumps producing 30%, 56%, and 70% pulsations, substantial changes were confirmed. The GK2.69 cyclone showed a similar pattern to that of the DO cyclone, i.e. no change in sampling efficiency for the Legacy producing 15% pulsation and a substantial change for the Elite12 producing 41% pulsation. Pulse shape did not cause any change in sampling efficiency when compared to the single sine wave. The findings suggest that 25% pulsation at the inlet of the cyclone as measured by this test can be acceptable for the respirable particle collection. If this test is used in place of that currently in European standards (EN 1232-1997 and EN 12919-1999) or is used in any International Organization for Standardization standard, then a 25% pulsation criterion could be adopted. This work suggests that a 10% criterion as currently specified in the European standards for testing may be overly restrictive and not able to be met by many pumps on the market. Further work is recommended to determine which criterion would be applicable to this test if it is to be retained in its current form.

On the Nature of the Mesoscale Variability in Denmark Strait

NASA Astrophysics Data System (ADS)

Pickart, Robert; von Appen, Wilken; Mastropole, Dana; Valdimarsson, Hedinn; Vage, Kjetil; Jonsson, Steingriumur; Jochumsen, Kerstin; Girton, James

2017-04-01

The dense overflow through Denmark Strait is the largest contributor to the lower limb of the Atlantic Meridional Overturning Circulation. As such, it is important to understand the sources of water feeding the overflow and how the water negotiates the sill as it passes into the Irminger Sea. Here we use a large collection of shipboard hydrographic transects occupied across the strait, together with 6-years of mooring data from the sill, to investigate the water masses and mesoscale variability of the overflow water. Two dominant types of mesoscale features were identified, referred to as a "bolus" and a "pulse". The former is a large lens of weakly stratified water corresponding to a slight increase in along-strait velocity. The latter is a thin layer with greater stratification and strongly enhanced along-strait flow. The boluses, which are often noted in the historical literature, are associated with cyclonic circulation, while pulses, which have not been previously identified, are associated with anti-cyclonic circulation. Both features result in increased transport of overflow water. It is argued that these fluctuations at the sill trigger energetic variability downstream in the Deep Western Boundary Current.

The environmental influence on tropical cyclone precipitation

NASA Technical Reports Server (NTRS)

Rodgers, Edward B.; Baik, Jong-Jin; Pierce, Harold F.

1994-01-01

The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were (1) mean climatological sea surface temperatures, (2) vertical wind shear, (3) environmental tropospheric water vapor flux, and (4) upper-tropospheric eddy relative angular momentum flux convergence. The analyses revealed that (1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; (2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; (3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; (4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; (5) in regions with the combined warm sea surface temperatures (above 26 C) and low vertical wind shear (less than 5 m/s), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence.

The Environmental Influence on Tropical Cyclone Precipitation.

NASA Astrophysics Data System (ADS)

Rodgers, Edward B.; Baik, Jong-Jin; Pierce, Harold F.

1994-05-01

The intensity, spatial, and temporal changes in precipitation were examined in three North Atlantic hurricanes during 1989 (Dean, Gabrielle, and Hugo) using precipitation estimates made from Special Sensor Microwave/Imager (SSM/I) measurements. In addition, analyses from a barotropic hurricane forecast model and the European Centre for Medium-Range Weather Forecast model were used to examine the relationship between the evolution of the precipitation in these tropical cyclones and external forcing. The external forcing parameters examined were 1) mean climatological sea surface temperatures, 2) vertical wind shear, 3) environmental tropospheric water vapor flux, and 4) upper-tropospheric eddy relative angular momentum flux convergence.The analyses revealed that 1) the SSM/I precipitation estimates were able to delineate and monitor convective ring cycles similar to those observed with land-based and aircraft radar and in situ measurements; 2) tropical cyclone intensification was observed to occur when these convective rings propagated into the inner core of these systems (within 111 km of the center) and when the precipitation rates increased; 3) tropical cyclone weakening was observed to occur when these inner-core convective rings dissipated; 4) the inward propagation of the outer convective rings coincided with the dissipation of the inner convective rings when they came within 55 km of each other; 5) in regions with the combined warm sea surface temperatures (above 26°C) and low vertical wind shear (less than 5 m s1), convective rings outside the region of strong lower-tropospheric inertial stability could be initiated by strong surges of tropospheric moisture, while convective rings inside the region of strong lower-tropospheric inertial stability could be enhanced by upper-tropospheric eddy relative angular momentum flux convergence.

Influence of the finite linewidth of the laser radiation spectrum on the shape of the coherent population trapping resonance line in an optically dense medium with a buffer gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barantsev, K. A., E-mail: kostmann@yandex.ru; Popov, E. N.; Litvinov, A. N., E-mail: andrey.litvinov@mail.ru

2015-11-15

The theory of coherent population trapping resonance is developed for the finite linewidth of the laser radiation spectrum in an optically dense medium of Λ atoms in a cell with a buffer gas. Equations are derived for the atomic density matrix and laser emission spectrum transfer in a cell with working and buffer gases at a finite temperature. The dependence of the quality factor of coherent population trapping resonance on the linewidth of the laser radiation spectrum is studied by measuring transmitted radiation and fluorescence signals.

On the Structure of the Mixing Zone at an Unstable Contact Boundary

NASA Astrophysics Data System (ADS)

Meshkov, E. E.

2018-01-01

The interface between two media of different densities (contact boundary) moving with an acceleration directed from the less dense medium to the more dense one is unstable (Rayleigh-Taylor instability) [1, 2]. The initial perturbations of the interface grow indefinitely and, as a result, a medium mixing zone growing with time is formed at the interface. The structure of such a mixing zone at gas-gas and gas-liquid interfaces is discussed on the basis of laboratory experiments on shock tubes of various types. It is concluded that the regions of turbulent and laminar flows are combined in the mixing zone.

Optical tomography of fluorophores in dense scattering media based on ultrasound-enhanced chemiluminescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Masaki, E-mail: masaki@tohtech.ac.jp; Kikuchi, Naoto; Sato, Akihiro

This letter proposes and demonstrates ultrasound-combined optical imaging in dense scattering media. A peroxyoxalate chemiluminescence system that includes fluorophores to chemically excite the pigment is stimulated by ultrasound irradiation with power of less than 0.14 W/cm{sup 2}. Using focused ultrasound, the chemiluminescence is selectively spatially enhanced, which leads to imaging of the pigment when embedded in a light-scattering medium via scanning of the focal point. The ultrasonically enhanced intensity of the chemiluminescence depends on the base intensity of the chemiluminescence without the applied ultrasound irradiation, which thereby enables quantitative determination of the fluorophore concentration. The authors demonstrate the potential of thismore » method to resolve chemiluminescent targets in a dense scattering medium that is comparable to biological tissue. An image was acquired of a chemiluminescent target that included indocyanine green as the fluorophore embedded at a depth of 20 mm in an Intralipid-10% 200 ml/l solution scattering medium (the reduced scattering coefficient was estimated to be approximately 1.3 mm{sup −1}), indicating the potential for expansion of this technique for use in biological applications.« less

The Relationship Between Extratropical Cyclone Steering and Blocking Along the North American East Coast

NASA Astrophysics Data System (ADS)

Booth, James F.; Dunn-Sigouin, Etienne; Pfahl, Stephan

2017-12-01

The path and speed of extratropical cyclones along the east coast of North America influence their societal impact. This work characterizes the climatological relationship between cyclone track path and speed, and blocking and the North Atlantic Oscillation (NAO). An analysis of Lagrangian cyclone track propagation speed and angle shows that the percentage of cyclones with blocks is larger for cyclones that propagate northward or southeastward, as is the size of the blocked region near the cyclone. Cyclone-centered composites show that propagation of cyclones relative to blocks is consistent with steering by the block: northward tracks more often have a block east/northeast of the cyclone; slow tracks tend to have blocks due north of the cyclone. Comparison with the NAO shows that to first-order blocking and the NAO steer cyclones in a similar manner. However, blocked cyclones are more likely to propagate northward, increasing the likelihood of cyclone related impacts.

Dynamic Hurricane Data Analysis Tool

NASA Technical Reports Server (NTRS)

Knosp, Brian W.; Li, Peggy; Vu, Quoc A.

2009-01-01

A dynamic hurricane data analysis tool allows users of the JPL Tropical Cyclone Information System (TCIS) to analyze data over a Web medium. The TCIS software is described in the previous article, Tropical Cyclone Information System (TCIS) (NPO-45748). This tool interfaces with the TCIS database to pull in data from several different atmospheric and oceanic data sets, both observed by instruments. Users can use this information to generate histograms, maps, and profile plots for specific storms. The tool also displays statistical values for the user-selected parameter for the mean, standard deviation, median, minimum, and maximum values. There is little wait time, allowing for fast data plots over date and spatial ranges. Users may also zoom-in for a closer look at a particular spatial range. This is version 1 of the software. Researchers will use the data and tools on the TCIS to understand hurricane processes, improve hurricane forecast models and identify what types of measurements the next generation of instruments will need to collect.

Observed ocean waves by tropical cyclones

NASA Astrophysics Data System (ADS)

Zhang, Lin; Oey, Leo

2017-04-01

Ocean waves produced by tropical cyclones (TC) modify air-sea fluxes which in turn are crucial to the storms' intensity and development, yet they are poorly understood. Here we use 24 years (1992-2015) of observed waves, winds and TC-track information to stratify storm-centered composite maps of waves and winds according to TC intensities and translation speeds (Uh). While the wind field is rightward-asymmetric independent of Uh, the wave field is rightward-symmetric in concert with the wind for slow-translating TCs (Uh ≤ 3 m s-1), but right-rear asymmetric with strongest waves in the 4th quadrant for medium to fast-translating TCs (3 < Uh ≤ 7 m s-1), especially for the very fast storms (Uh > 7 m s-1), all independent of TC-intensity. The dominance of the right-rear asymmetry for fast-translating TCs appears to be related to the development of cross swells as the storms move faster, but further research using models are needed to understand the physical mechanisms.

The spatial distribution and evolution characteristics of North Atlantic cyclones

NASA Astrophysics Data System (ADS)

Dacre, H.; Gray, S.

2009-09-01

Mid-latitude cyclones play a large role in determining the day-to-day weather conditions in western Europe through their associated wind and precipitation patterns. Thus, their typical spatial and evolution characteristics are of great interest to meteorologists, insurance and risk management companies. In this study a feature tracking algorithm is applied to a cyclone database produced using the Hewson-method of cyclone identification, based on low-level gradients of wet-bulb potential temperature, to produce a climatology of mid-latitude cyclones. The aim of this work is to compare the cyclone track and density statistics found in this study with previous climatologies and to determine reasons for any differences. This method is found to compare well with other cyclone identification methods; the north Atlantic storm track is reproduced along with the major regions of genesis. Differences are attributed to cyclone lifetime and strength thresholds, dataset resolution and cyclone identification and tracking methods. Previous work on cyclone development has been largely limited to case studies as opposed to analysis of climatological data, and does not distinguish between the different stages of cyclone evolution. The cyclone database used in this study allows cyclone characteristics to be tracked throughout the cyclone lifecycle. This enables the evaluation of the characteristics of cyclone evolution for systems forming in different genesis regions and a calculation of the spatial distribution and evolution of these characteristics in composite cyclones. It was found that most of the cyclones that cross western Europe originate in the east Atlantic where the baroclinicity and sea surface temperature gradients are weak compared to the west Atlantic. East Atlantic cyclones also have higher low-level relative vorticity and lower mean sea level pressure at their genesis point than west Atlantic cyclones. This is consistent with the hypothesis that they are secondary cyclones developing on the trailing fronts of pre-existing 'parent' cyclones. Furthermore, it was found that a higher proportion of east Atlantic cyclones are type C cyclones with strong upper-level forcing but weak low-level forcing suggesting that latent energy plays a more important role in their intensification than for west Atlantic cyclones.

The spatial distribution and evolution characteristics of North Atlantic cyclones

NASA Astrophysics Data System (ADS)

Dacre, H.; Gray, S.

2009-04-01

Mid-latitude cyclones play a large role in determining the day-to-day weather conditions in western Europe through their associated wind and precipitation patterns. Thus, their typical spatial and evolution characteristics are of great interest to meteorologists, insurance and risk management companies. In this study a feature tracking algorithm is applied to a cyclone database produced using the Hewson-method of cyclone identification, based on low-level gradients of wet-bulb potential temperature, to produce a climatology of mid-latitude cyclones. The aim of this work is to compare the cyclone track and density statistics found in this study with previous climatologies. This method is found to compare well with other cyclone identification methods; the north Atlantic storm track is reproduced along with the major regions of genesis. Differences are attributed to cyclone lifetime and strength thresholds, dataset resolution and cyclone identification and tracking methods. Previous work on cyclone development has been largely limited to case studies as opposed to analysis of climatological data, and does not distinguish between the different stages of cyclone evolution. The cyclone database used in this study allows cyclone characteristics to be tracked throughout the cyclone lifecycle. This enables the evaluation of the characteristics of cyclone evolution for systems forming in different genesis regions and a calculation of the spatial distribution and evolution of these characteristics in composite cyclones. It was found that most of the cyclones that cross western Europe originate in the east Atlantic where the baroclinicity and sea surface temperature gradients are weak compared to the west Atlantic. East Atlantic cyclones also have higher low-level relative vorticity and lower mean sea level pressure at their genesis point than west Atlantic cyclones. This is consistent with the hypothesis that they are secondary cyclones developing on the trailing fronts of pre-existing 'parent' cyclones. Furthermore, it was found that a higher proportion of east Atlantic cyclones are type C cyclones with strong upper-level forcing but weak low-level forcing suggesting that latent energy plays a more important role in their intensification than for west Atlantic cyclones.

Cyclone: java-based querying and computing with Pathway/Genome databases.

PubMed

Le Fèvre, François; Smidtas, Serge; Schächter, Vincent

2007-05-15

Cyclone aims at facilitating the use of BioCyc, a collection of Pathway/Genome Databases (PGDBs). Cyclone provides a fully extensible Java Object API to analyze and visualize these data. Cyclone can read and write PGDBs, and can write its own data in the CycloneML format. This format is automatically generated from the BioCyc ontology by Cyclone itself, ensuring continued compatibility. Cyclone objects can also be stored in a relational database CycloneDB. Queries can be written in SQL, and in an intuitive and concise object-oriented query language, Hibernate Query Language (HQL). In addition, Cyclone interfaces easily with Java software including the Eclipse IDE for HQL edition, the Jung API for graph algorithms or Cytoscape for graph visualization. Cyclone is freely available under an open source license at: http://sourceforge.net/projects/nemo-cyclone. For download and installation instructions, tutorials, use cases and examples, see http://nemo-cyclone.sourceforge.net.

Timing of floods in southeastern China: Seasonal properties and potential causes

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Gu, Xihui; Singh, Vijay P.; Shi, Peijun; Luo, Ming

2017-09-01

Flood hazards and flood risks in southeastern China have been causing increasing concerns due to dense population and highly-developed economy. This study attempted to address changes of seasonality, timing of peak floods and variability of occurrence date of peak floods using circular statistical methods and the modified Mann-Kendall trend detection method. The causes of peak flood changes were also investigated. Results indicated that: (1) floods were subject to more seasonality and temporal clustering when compared to precipitation extremes. However, seasonality of floods and extreme precipitation was subject to spatial heterogeneity in northern Guangdong. Similar changing patterns of peak floods and extreme precipitation were found in coastal regions; (2) significant increasing/decreasing seasonality, but no confirmed spatial patterns, were observed for peak floods and extreme precipitation. Peak floods in northern Guangdong province had decreasing variability, but had larger variability in coastal regions; (3) tropical cyclones had remarkable impacts on extreme precipitation changes in coastal regions of southeastern China, and peak floods as well. The landfalling of tropical cyclones was decreasing and concentrated during June-September; this is the major reason for earlier but enhanced seasonality of peak floods in coastal regions. This study sheds new light on flood behavior in coastal regions in a changing environment.

How will precipitation change in extratropical cyclones as the planet warms? Insights from a large initial condition climate model ensemble

NASA Astrophysics Data System (ADS)

Yettella, Vineel; Kay, Jennifer E.

2017-09-01

The extratropical precipitation response to global warming is investigated within a 30-member initial condition climate model ensemble. As in observations, modeled cyclonic precipitation contributes a large fraction of extratropical precipitation, especially over the ocean and in the winter hemisphere. When compared to present day, the ensemble projects increased cyclone-associated precipitation under twenty-first century business-as-usual greenhouse gas forcing. While the cyclone-associated precipitation response is weaker in the near-future (2016-2035) than in the far-future (2081-2100), both future periods have similar patterns of response. Though cyclone frequency changes are important regionally, most of the increased cyclone-associated precipitation results from increased within-cyclone precipitation. Consistent with this result, cyclone-centric composites show statistically significant precipitation increases in all cyclone sectors. Decomposition into thermodynamic (mean cyclone water vapor path) and dynamic (mean cyclone wind speed) contributions shows that thermodynamics explains 92 and 95% of the near-future and far-future within-cyclone precipitation increases respectively. Surprisingly, the influence of dynamics on future cyclonic precipitation changes is negligible. In addition, the forced response exceeds internal variability in both future time periods. Overall, this work suggests that future cyclonic precipitation changes will result primarily from increased moisture availability in a warmer world, with secondary contributions from changes in cyclone frequency and cyclone dynamics.

Dependent scattering and absorption by densely packed discrete spherical particles: Effects of complex refractive index

NASA Astrophysics Data System (ADS)

Ma, L. X.; Tan, J. Y.; Zhao, J. M.; Wang, F. Q.; Wang, C. A.; Wang, Y. Y.

2017-07-01

Due to the dependent scattering and absorption effects, the radiative transfer equation (RTE) may not be suitable for dealing with radiative transfer in dense discrete random media. This paper continues previous research on multiple and dependent scattering in densely packed discrete particle systems, and puts emphasis on the effects of particle complex refractive index. The Mueller matrix elements of the scattering system with different complex refractive indexes are obtained by both electromagnetic method and radiative transfer method. The Maxwell equations are directly solved based on the superposition T-matrix method, while the RTE is solved by the Monte Carlo method combined with the hard sphere model in the Percus-Yevick approximation (HSPYA) to consider the dependent scattering effects. The results show that for densely packed discrete random media composed of medium size parameter particles (equals 6.964 in this study), the demarcation line between independent and dependent scattering has remarkable connections with the particle complex refractive index. With the particle volume fraction increase to a certain value, densely packed discrete particles with higher refractive index contrasts between the particles and host medium and higher particle absorption indexes are more likely to show stronger dependent characteristics. Due to the failure of the extended Rayleigh-Debye scattering condition, the HSPYA has weak effect on the dependent scattering correction at large phase shift parameters.

Research on acting mechanism and behavior of a gas bubble in the air dense medium fluidized bed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, X.; Chen, Q.; Yang, Y.

1996-12-31

Coal dry beneficiation with air-dense medium fluidized bed has now been established as a high efficiency dry separation technology, it is the application of fluidization technology to the coal preparation field. The tiny particle media forms an uniform and stable fluidized bed with a density acted by airflow, which is used to separate 80{micro}m to {approximately}6mm size coal. This technology has achieved satisfied industrialization results, and attracted the expert`s attention in the field. In fluidized bed, the interaction between gas and solid was mainly decided by the existence state of heavy media particles mass (position and distance) relative velocity ofmore » gas-solid two phase, as well turbulent action. A change of vertical gas-solid fluidizing state essentially is the one of a energy transforming process. For a coal separating process with air-dense medium fluidized bed, the gas bubble, producing a turbulent and stirring action in the bed, leads to two effects. It can promote a uniform distribution of heavy media particles, and a uniform and stability of a bed density. Otherwise it will decrease effective contacts between gas-solids two phases, producing a bigger gas bubble. Therefore controlling a gas bubble size in bed should be optimized. This paper analyzes mutual movement between gas-solid, and studies the gas bubble behavior in the bed. A mechanic mode and a separating process of coal in the bed is discussed. It aims to research the coal separating mechanism with air-dense fluidized bed.« less

Multiple scattering in planetary regoliths using first-order incoherent interactions

NASA Astrophysics Data System (ADS)

Muinonen, Karri; Markkanen, Johannes; Väisänen, Timo; Penttilä, Antti

2017-10-01

We consider scattering of light by a planetary regolith modeled using discrete random media of spherical particles. The size of the random medium can range from microscopic sizes of a few wavelengths to macroscopic sizes approaching infinity. The size of the particles is assumed to be of the order of the wavelength. We extend the numerical Monte Carlo method of radiative transfer and coherent backscattering (RT-CB) to the case of dense packing of particles. We adopt the ensemble-averaged first-order incoherent extinction, scattering, and absorption characteristics of a volume element of particles as input for the RT-CB. The volume element must be larger than the wavelength but smaller than the mean free path length of incoherent extinction. In the radiative transfer part, at each absorption and scattering process, we account for absorption with the help of the single-scattering albedo and peel off the Stokes parameters of radiation emerging from the medium in predefined scattering angles. We then generate a new scattering direction using the joint probability density for the local polar and azimuthal scattering angles. In the coherent backscattering part, we utilize amplitude scattering matrices along the radiative-transfer path and the reciprocal path, and utilize the reciprocity of electromagnetic waves to verify the computation. We illustrate the incoherent volume-element scattering characteristics and compare the dense-medium RT-CB to asymptotically exact results computed using the Superposition T-matrix method (STMM). We show that the dense-medium RT-CB compares favorably to the STMM results for the current cases of sparse and dense discrete random media studied. The novel method can be applied in modeling light scattering by the surfaces of asteroids and other airless solar system objects, including UV-Vis-NIR spectroscopy, photometry, polarimetry, and radar scattering problems.Acknowledgments. Research supported by European Research Council with Advanced Grant No. 320773 SAEMPL, Scattering and Absorption of ElectroMagnetic waves in ParticuLate media. Computational resources provided by CSC - IT Centre for Science Ltd, Finland.

Microwave Signatures of Melting/Refreezing Snow: Observations and Modeling Using Dense Medium Radiative Transfer Theory

NASA Technical Reports Server (NTRS)

Tedesco, Marco; Kim, Edward J.; England, Anthony; deRoo, Roger; Hardy, Janet

2005-01-01

Microwave brightness temperatures of snow covered terrains can be modeled by means of the Dense Radiative Transfer Medium Theory (DMRT). In a dense medium, such as snow, the assumption of independent scattering is no longer valid and the scattering of correlated scatterers must be considered. In the DMRT, this is done considering a pair distribution function of the particles position. In the electromagnetic model, the snowpack is simulated as a homogeneous layer having effective permittivity and albedo calculated through the DMRT. In order to account for clustering of snow crystals, a model of cohesive particles can be applied, where the cohesion between the particles is described by means of a dimensionless parameters called stickiness (z), representing a measure of the inversion of the attraction of the particles. The lower the z the higher the stickiness. In this study, microwave signatures of melting and refreezing cycles of seasonal snowpacks at high altitudes are studied by means of both experimental and modeling tools. Radiometric data were collected 24 hours per day by the University of Michigan Tower Mounted Radiometer System (TMRS). The brightness temperatures collected by means of the TMRS are simulated by means of a multi-layer electromagnetic model based on the dense medium theory with the inputs to the model derived from the data collected at the snow pits and from the meteorological station. The paper is structured as follows: in the first Section the temperature profiles recorded by the meteorological station and the snow pit data are presented and analyzed; in the second Section, the characteristics of the radiometric system used to collect the brightness temperatures are reported together with the temporal behavior of the recorded brightness temperatures; in the successive Section the multi-layer DMRT-based electromagnetic model is described; in the fourth Section the comparison between modeled and measured brightness temperatures is discussed. We dedicate the last Section to the conclusions and future works.

Characteristics of the internal and external sources of the Mediterranean synoptic cyclones for the period 1956-2013

NASA Astrophysics Data System (ADS)

Almazroui, Mansour; Awad, Adel M.; Nazrul Islam, M.

2017-07-01

This paper investigates the main sources and features of the Mediterranean synoptic cyclones affecting the basin, using the cyclone tracks. The cyclones' tracks are identified using sea level pressure (SLP) from the NCEP/NCAR reanalysis data for the period 1956-2013. The identified cyclones are classified into two categories: basin affected and basin non-affected. Most of the basin-affected (non-affected) cyclones are internal (external), i.e., generated inside (outside) the Mediterranean basin. This study reveals four (five) main sources of internal (external) cyclones. These four (five) main sources generated about 63.76% (57.25%) of the internal (external) cyclones. Seasonal analysis shows that most of the basin-affected internal (external) cyclones were generated in the winter (spring) season. The lowest number of cyclones were found in the summer. Moreover, the synoptic study of the atmospheric systems accompanied the highest- and lowest-generated years demonstrates that the deepening of the north Europe cyclones and the relative positions of Azores- and Siberian-high systems represent the important factors that influence the number of internal cyclones. Essential factors influencing the external cyclones are the strength of the maximum upper wind, Azores high, Siberian high, and orientations of their ridges.

Cyclonic eddies identified in the Cape Basin of the South Atlantic Ocean

NASA Astrophysics Data System (ADS)

Hall, C.; Lutjeharms, J. R. E.

2011-03-01

Inter-ocean exchange south of Africa takes place largely through the movement of Agulhas Rings into the Cape Basin. Recent observations have shown that the highly energetic flow field in this basin consists of anti-cyclonic rings as well as cyclonic eddies. Very little is known of the characteristics of the cyclonic eddies. Using altimetric data, this study determines the location, frequency and seasonality of these cyclonic eddies their size, trajectories, life spans and their association with Agulhas Rings. Cyclonic eddies were seen to split, merge and link with other cyclonic eddies, where splitting events created child cyclonic eddies. The 105 parent and 157 child cyclonic eddies identified over a decade show that on average 11 parent and 17 child cyclonic eddies appear annually in AVISO merged absolute dynamic topography data along the continental slope. Thirty-two percent follow an overall west south-westward direction, with 27% going west north-westward. Average translocation speeds are 2.2 ± 0.1 km/day for parent and 3.0 ± 0.2 km/day for child cyclonic eddies. Parent cyclonic eddy lifespan averaged 250 ± 18 days; whereas child cyclonic eddies survived for only 118 ± 11 days. A significant difference in lifespan for parent and child cyclonic eddies identified in the north and south region of the study area was detected. Seventy-seven percent of the northern and 93% of the southern cyclonic eddies were first detected directly adjacent to passing Agulhas Rings, suggesting a vital interaction between these mesoscale eddies within the region. Topographical features appeared to affect the behaviour and lifespan of these deep cyclonic eddies.

Contributions of Tropical Cyclones to the North Atlantic Climatological Rainfall as Observed from Satellites

NASA Technical Reports Server (NTRS)

Rodgers, Edward B.; Adler, Robert F.; Pierce, Harold F.; Einaudi, Franco (Technical Monitor)

2000-01-01

The tropical cyclone rainfall climatology study that was performed for the North Pacific was extended to the North Atlantic. Similar to the North Pacific tropical cyclone study, mean monthly rainfall within 444 km of the center of the North Atlantic tropical cyclones (i.e., that reached storm stage and greater) was estimated from passive microwave satellite observations during, an eleven year period. These satellite-observed rainfall estimates were used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and inter-annual distribution of the North Atlantic total rainfall during, June-November when tropical cyclones were most abundant. The main results from this study indicate: 1) that tropical cyclones contribute, respectively, 4%, 3%, and 4% to the western, eastern, and entire North Atlantic; 2) similar to that observed in the North Pacific, the maximum in North Atlantic tropical cyclone rainfall is approximately 5 - 10 deg poleward (depending on longitude) of the maximum non-tropical cyclone rainfall; 3) tropical cyclones contribute regionally a maximum of 30% of the total rainfall 'northeast of Puerto Rico, within a region near 15 deg N 55 deg W, and off the west coast of Africa; 4) there is no lag between the months with maximum tropical cyclone rainfall and non-tropical cyclone rainfall in the western North Atlantic, while in the eastern North Atlantic, maximum tropical cyclone rainfall precedes maximum non-tropical cyclone rainfall; 5) like the North Pacific, North Atlantic tropical cyclones Of hurricane intensity generate the greatest amount of rainfall in the higher latitudes; and 6) warm ENSO events inhibit tropical cyclone rainfall.

Statistical characteristics of austral summer cyclones in Southern Ocean

NASA Astrophysics Data System (ADS)

Liu, Na; Fu, Gang; Kuo, Ying-Hwa

2012-06-01

Characteristics of cyclones and explosively developing cyclones (or `bombs') over the Southern Ocean in austral summer (December, January and February) from 2004 to 2008 are analyzed by using the Final Analysis (FNL) data produced by the National Centers for Environmental Prediction (NCEP) of the United States. Statistical results show that both cyclones and explosively developing cyclones frequently develop in January, and most of them occur within the latitudinal zone between 55°S and 70°S. These cyclones gradually approach the Antarctic Continent from December to February. Generally cyclones and bombs move east-southeastward with some exceptions of northeastward movement. The lifetime of cyclones is around 2-6 d, and the horizontal scale is about 1000 km. Explosive cyclones have the lifetime of about 1 week with the horizontal scale reaching up to 3000 km. Compared with cyclones developed in the Northern Hemisphere, cyclones over the southern ocean have much higher occurrence frequency, lower central pressure and larger horizontal scale, which may be caused by the unique geographical features of the Southern Hemisphere.

Automated Historical and Real-Time Cyclone Discovery With Multimodal Remote Satellite Measurements

NASA Astrophysics Data System (ADS)

Ho, S.; Talukder, A.; Liu, T.; Tang, W.; Bingham, A.

2008-12-01

Existing cyclone detection and tracking solutions involve extensive manual analysis of modeled-data and field campaign data by teams of experts. We have developed a novel automated global cyclone detection and tracking system by assimilating and sharing information from multiple remote satellites. This unprecedented solution of combining multiple remote satellite measurements in an autonomous manner allows leveraging off the strengths of each individual satellite. Use of multiple satellite data sources also results in significantly improved temporal tracking accuracy for cyclones. Our solution involves an automated feature extraction and machine learning technique based on an ensemble classifier and Kalman filter for cyclone detection and tracking from multiple heterogeneous satellite data sources. Our feature-based methodology that focuses on automated cyclone discovery is fundamentally different from, and actually complements, the well-known Dvorak technique for cyclone intensity estimation (that often relies on manual detection of cyclonic regions) from field and remote data. Our solution currently employs the QuikSCAT wind measurement and the merged level 3 TRMM precipitation data for automated cyclone discovery. Assimilation of other types of remote measurements is ongoing and planned in the near future. Experimental results of our automated solution on historical cyclone datasets demonstrate the superior performance of our automated approach compared to previous work. Performance of our detection solution compares favorably against the list of cyclones occurring in North Atlantic Ocean for the 2005 calendar year reported by the National Hurricane Center (NHC) in our initial analysis. We have also demonstrated the robustness of our cyclone tracking methodology in other regions over the world by using multiple heterogeneous satellite data for detection and tracking of three arbitrary historical cyclones in other regions. Our cyclone detection and tracking methodology can be applied to (i) historical data to support Earth scientists in climate modeling, cyclonic-climate interactions, and obtain a better understanding of the cause and effects of cyclone (e.g. cyclo-genesis), and (ii) automatic cyclone discovery in near real-time using streaming satellite to support and improve the planning of global cyclone field campaigns. Additional satellite data from GOES and other orbiting satellites can be easily assimilated and integrated into our automated cyclone detection and tracking module to improve the temporal tracking accuracy of cyclones down to ½ hr and reduce the incidence of false alarms.

Impact of potential large-scale and medium-scale irrigation on the West African Monsoon and its dependence on location of irrigated area

NASA Astrophysics Data System (ADS)

Eltahir, E. A. B.; IM, E. S.

2014-12-01

This study investigates the impact of potential large-scale (about 400,000 km2) and medium-scale (about 60,000 km2) irrigation on the climate of West Africa using the MIT Regional Climate Model. A new irrigation module is implemented to assess the impact of location and scheduling of irrigation on rainfall distribution over West Africa. A control simulation (without irrigation) and various sensitivity experiments (with irrigation) are performed and compared to discern the effects of irrigation location, size and scheduling. In general, the irrigation-induced surface cooling due to anomalously wet soil tends to suppress moist convection and rainfall, which in turn induces local subsidence and low level anti-cyclonic circulation. These local effects are dominated by a consistent reduction of local rainfall over the irrigated land, irrespective of its location. However, the remote response of rainfall distribution to irrigation exhibits a significant sensitivity to the latitudinal position of irrigation. The low-level northeasterly flow associated with anti-cyclonic circulation centered over the irrigation area can enhance the extent of low level convergence through interaction with the prevailing monsoon flow, leading to significant increase in rainfall. Despite much reduced forcing of irrigation water, the medium-scale irrigation seems to draw the same response as large-scale irrigation, which supports the robustness of the response to irrigation in our modeling system. Both large-scale and medium-scale irrigation experiments show that an optimal irrigation location and scheduling exists that would lead to a more efficient use of irrigation water. The approach of using a regional climate model to investigate the impact of location and size of irrigation schemes may be the first step in incorporating land-atmosphere interactions in the design of location and size of irrigation projects. However, this theoretical approach is still in early stages of development and further research is needed before any practical application in water resources planning. Acknowledgements.This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's Center for Environmental Sensing and Modeling interdisciplinary research program.

Flexible fiber in interaction with a dense granular flow close to the jamming transition

NASA Astrophysics Data System (ADS)

Algarra, Nicolas; Leang, Marguerite; Lazarus, Arnaud; Vandembroucq, Damien; Kolb, Evelyne

2017-06-01

We propose a new fluid/structure interaction in the unusual case of a dense granular medium flowing against an elastic fiber acting as a flexible intruder. We study experimentally the reconfiguration and the forces exerted on the flexible fiber produced by the flow at a constant and low velocity of a two-dimensional disordered packing of grains close but below the jamming transition.

Impulsivity and overeating in children in the absence and presence of hunger.

PubMed

Nederkoorn, Chantal; Dassen, Fania C M; Franken, Loes; Resch, Christine; Houben, Katrijn

2015-10-01

Overweight children appear to be more responsive to environmental, hedonic cues and easily overeat in the current obesogenic environment. They are also found to overeat in the absence of hunger, and this overeating seems related to impulsivity: impulsive participants are more prone to external eating. However, some studies showed that impulsive adults are also more prone to hunger cues: impulsive participants overate especially when feeling hungry. This would mean impulsive people are more reactive to both external and internal cues. The overeating was limited to palatable high energy-dense foods: hunger made them fancy a snack. In the current study, we wanted to test the interaction between impulsivity, hunger and consumption of food type in children. Impulsivity was measured in 88 children between the ages of 7 and 9. Next, half of the participants performed a taste test before their own regular lunch and half of the participants immediately after their lunch. During the taste test, low, medium and high energy-dense food items were presented. Results showed that impulsive children ate more high energy-dense foods than low impulsive children, both before and after their lunch. No differences were found on low or medium energy-dense foods. Impulsive children therefore showed normal sensitivity for internal hunger and satiety cues, but abnormal response to high energy-dense foods. This might render them vulnerable to tasty temptation in the environment and to weight gain in their future. Copyright © 2015 Elsevier Ltd. All rights reserved.

A climatology of extratropical cyclones over East Asia during 1958-2001

NASA Astrophysics Data System (ADS)

Zhang, Yingxian; Ding, Yihui; Li, Qiaoping

2012-06-01

A climatology of extratropical cyclones (ECs) over East Asia (20°-75°N, 60°-160°E) is analyzed by applying an improved objective detection and tracking algorithm to the 4-time daily sea level pressure fields from the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis data. A total of 12914 EC processes for the period of 1958-2001 are identified, with an EC database integrated and EC activities reanalyzed using the objective algorithm. The results reveal that there are three major cyclogenesis regions: West Siberian Plain, Mongolia (to the south of Lake Baikal), and the coastal region of East China; whereas significant cyclolysis regions are observed in Siberia north of 60°N, Northeast China, and Okhotsk Sea-Northwest Pacific. It is found that the EC lifetime is largely 1-7 days while winter ECs have the shortest lifespan. The ECs are the weakest in summer among the four seasons. Strong ECs often appear in West Siberia, Northeast China, and Okhotsk Sea-Northwest Pacific. Statistical analysis based on k-means clustering has identified 6 dominating trajectories in the area south of 55°N and east of 80°E, among which 4 tracks have important impacts on weather/climate in China. ECs occurring in spring (summer) tend to travel the longest (shortest). They move the fastest in winter, and the slowest in summer. In winter, cyclones move fast in Northeast China, some areas of the Yangtze-Huaihe River region, and the south of Japan, with speed greater than 15 m s-1. Explosively-deepening cyclones are found to occur frequently along the east coast of China, Japan, and Northwest Pacific, but very few storms occur over the inland area. Bombs prefer to occur in winter, spring, and autumn. Their annual number and intensity in 1990 and 1992 in East Asia (EA) are smaller and weaker than their counterparts in North America.

Cyclone tolerance in new world arecaceae: biogeographic variation and abiotic natural selection.

PubMed

Griffith, M Patrick; Noblick, Larry R; Dowe, John L; Husby, Chad E; Calonje, Michael A

2008-10-01

Consistent abiotic factors can affect directional selection; cyclones are abiotic phenomena with near-discrete geographic limits. The current study investigates selective pressure of cyclones on plants at the species level, testing for possible natural selection. New World Arecaceae (palms) are used as a model system, as plants with monopodial, unbranched arborescent form are most directly affected by the selective pressure of wind load. Living specimens of known provenance grown at a common site were affected by the same cyclone. Data on percentage mortality were compiled and analysed in biogeographic and phylogenetic contexts. Palms of cyclone-prone provenance exhibited a much lower (one order of magnitude) range in cyclone tolerance, and significantly lower (P < 0.001) mean percentage mortality than collections from cyclone-free areas. Palms of cyclone-free provenance had much greater variation in tolerance, and significantly greater mean percentage mortality. A test for serial independence recovered no significant phylogenetic autocorrelation of percentage mortality. Variation in cyclone tolerance in New World Arecaceae correlates with biogeography, and is not confounded with phylogeny. These results suggest natural selection of cyclone tolerance in cyclone-prone areas.

Demonstration of coal reburning for cyclone boiler NO{sub x} control. Appendix, Book 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

Based on the industry need for a pilot-scale cyclone boiler simulator, Babcock Wilcox (B&W) designed, fabricated, and installed such a facility at its Alliance Research Center (ARC) in 1985. The project involved conversion of an existing pulverized coal-fired facility to be cyclone-firing capable. Additionally, convective section tube banks were installed in the upper furnace in order to simulate a typical boiler convection pass. The small boiler simulator (SBS) is designed to simulate most fireside aspects of full-size utility boilers such as combustion and flue gas emissions characteristics, fireside deposition, etc. Prior to the design of the pilot-scale cyclone boiler simulator,more » the various cyclone boiler types were reviewed in order to identify the inherent cyclone boiler design characteristics which are applicable to the majority of these boilers. The cyclone boiler characteristics that were reviewed include NO{sub x} emissions, furnace exit gas temperature (FEGT) carbon loss, and total furnace residence time. Previous pilot-scale cyclone-fired furnace experience identified the following concerns: (1) Operability of a small cyclone furnace (e.g., continuous slag tapping capability). (2) The optimum cyclone(s) configuration for the pilot-scale unit. (3) Compatibility of NO{sub x} levels, carbon burnout, cyclone ash carryover to the convection pass, cyclone temperature, furnace residence time, and FEGT.« less

Temporal clustering of tropical cyclones on the Great Barrier Reef and its ecological importance

NASA Astrophysics Data System (ADS)

Wolff, Nicholas H.; Wong, Aaron; Vitolo, Renato; Stolberg, Kristin; Anthony, Kenneth R. N.; Mumby, Peter J.

2016-06-01

Tropical cyclones have been a major cause of reef coral decline during recent decades, including on the Great Barrier Reef (GBR). While cyclones are a natural element of the disturbance regime of coral reefs, the role of temporal clustering has previously been overlooked. Here, we examine the consequences of different types of cyclone temporal distributions (clustered, stochastic or regular) on reef ecosystems. We subdivided the GBR into 14 adjoining regions, each spanning roughly 300 km, and quantified both the rate and clustering of cyclones using dispersion statistics. To interpret the consequences of such cyclone variability for coral reef health, we used a model of observed coral population dynamics. Results showed that clustering occurs on the margins of the cyclone belt, being strongest in the southern reefs and the far northern GBR, which also has the lowest cyclone rate. In the central GBR, where rates were greatest, cyclones had a relatively regular temporal pattern. Modelled dynamics of the dominant coral genus, Acropora, suggest that the long-term average cover might be more than 13 % greater (in absolute cover units) under a clustered cyclone regime compared to stochastic or regular regimes. Thus, not only does cyclone clustering vary significantly along the GBR but such clustering is predicted to have a marked, and management-relevant, impact on the status of coral populations. Additionally, we use our regional clustering and rate results to sample from a library of over 7000 synthetic cyclone tracks for the GBR. This allowed us to provide robust reef-scale maps of annual cyclone frequency and cyclone impacts on Acropora. We conclude that assessments of coral reef vulnerability need to account for both spatial and temporal cyclone distributions.

The dynamical link between deep Atlantic extratropical cyclones and intense Mediterranean cyclones

NASA Astrophysics Data System (ADS)

Raveh-Rubin, Shira; Flaounas, Emmanouil

2017-04-01

Breaking of atmospheric Rossby waves has been previously shown to lead to intense Mediterranean cyclones, one of the most prominent environmental risks in the region. Wave breaking may be enhanced by warm conveyor belts (WCBs) associated with extratropical cyclones developing over the Atlantic Ocean. More precisely, WCBs supply the upper troposphere with air masses of low potential vorticity that, in turn, amplify ridges and thus favor Rossby wave breaking. This study identifies and validates the relevance of the mechanism that connects Atlantic cyclones and intense mature Mediterranean cyclones through ridge amplification by WCBs. Using ECMWF ERA-Interim reanalyses and a feature-based approach, we analyze the 200 most intense Mediterranean cyclones for the years 1989-2008 and show that their majority (181 cases) is indeed associated with this mechanism upstream. Results show that multiple Atlantic cyclones are associated with each case of intense Mediterranean cyclone downstream. Moreover, the associated Atlantic cyclones are particularly deep compared to climatology.

Large-scale dynamics associated with clustering of extratropical cyclones affecting Western Europe

NASA Astrophysics Data System (ADS)

Pinto, Joaquim G.; Gómara, Iñigo; Masato, Giacomo; Dacre, Helen F.; Woollings, Tim; Caballero, Rodrigo

2015-04-01

Some recent winters in Western Europe have been characterized by the occurrence of multiple extratropical cyclones following a similar path. The occurrence of such cyclone clusters leads to large socio-economic impacts due to damaging winds, storm surges, and floods. Recent studies have statistically characterized the clustering of extratropical cyclones over the North Atlantic and Europe and hypothesized potential physical mechanisms responsible for their formation. Here we analyze 4 months characterized by multiple cyclones over Western Europe (February 1990, January 1993, December 1999, and January 2007). The evolution of the eddy driven jet stream, Rossby wave-breaking, and upstream/downstream cyclone development are investigated to infer the role of the large-scale flow and to determine if clustered cyclones are related to each other. Results suggest that optimal conditions for the occurrence of cyclone clusters are provided by a recurrent extension of an intensified eddy driven jet toward Western Europe lasting at least 1 week. Multiple Rossby wave-breaking occurrences on both the poleward and equatorward flanks of the jet contribute to the development of these anomalous large-scale conditions. The analysis of the daily weather charts reveals that upstream cyclone development (secondary cyclogenesis, where new cyclones are generated on the trailing fronts of mature cyclones) is strongly related to cyclone clustering, with multiple cyclones developing on a single jet streak. The present analysis permits a deeper understanding of the physical reasons leading to the occurrence of cyclone families over the North Atlantic, enabling a better estimation of the associated cumulative risk over Europe.

Diabatic processes and the evolution of two contrasting extratropical cyclones

NASA Astrophysics Data System (ADS)

Methven, John; Martinez-Alvarado, Oscar; Gray, Suzanne

2017-04-01

Extratropical cyclones are typically weaker and less frequent in summer as a result of differences in the background state flow and diabatic processes with respect to other seasons. Two extratropical cyclones were observed in summer 2012 with a research aircraft during the DIAMET (DIAbatic influences on Mesoscale structure in ExTratropical storms) field campaign. The first cyclone deepened only down to 995 hPa; the second cyclone deepened down to 978 hPa and formed a potential vorticity (PV) tower, a frequent signature of intense cyclones. The cyclones were analyzed through numerical simulations incorporating tracers for the effects of diabatic processes on potential temperature and PV. It was found that the observed maximum vapor flux in the stronger cyclone was twice as strong as in the weaker cyclone; the water vapor mass flow along the warm conveyor belt of the stronger cyclone was over half that typical in winter even though the flow was weaker. Did the greater water transport and latent heat release associated with condensation result in the greater circulation in the PV tower case? A cyclone-centred integral framework is introduced relating the tracers with cross-isentropic mass transport and circulation around the cyclone. It is shown that the circulation increases much more slowly than the amplitude of the diabatically-generated PV tower at its centre. This effect is explained using the PV impermeability theorem and the influence of diabatic heating on circulation around a cyclone is shown to scale with Rossby number. The implication is that the stronger a cyclone becomes (larger Rossby number), the stronger the influence of latent heating on circulation.

Abnormal enhancement against interference inhibition for few-cycle pulses propagating in dense media

NASA Astrophysics Data System (ADS)

Chen, Yue-Yue; Feng, Xun-Li; Xu, Zhi-Zhan; Liu, Chengpu

2016-04-01

We numerically study the reflected spectrum of a few-cycle pulse propagating through an ultrathin resonant medium. According to the classical interference theory, a destructive interference dip is expected at the carrier frequency ωp for a half-wavelength medium. In contrast, an abnormal enhanced spike appears instead. The origin of such an abnormal enhancement is attributed to the coherent transient effects. In addition, its scaling laws versus medium length, pulse area and duration are obtained, which follow simple rules.

The dynamical structure of intense Mediterranean cyclones

NASA Astrophysics Data System (ADS)

Flaounas, Emmanouil; Raveh-Rubin, Shira; Wernli, Heini; Drobinski, Philippe; Bastin, Sophie

2015-05-01

This paper presents and analyzes the three-dimensional dynamical structure of intense Mediterranean cyclones. The analysis is based on a composite approach of the 200 most intense cyclones during the period 1989-2008 that have been identified and tracked using the output of a coupled ocean-atmosphere regional simulation with 20 km horizontal grid spacing and 3-hourly output. It is shown that the most intense Mediterranean cyclones have a common baroclinic life cycle with a potential vorticity (PV) streamer associated with an upper-level cyclonic Rossby wave breaking, which precedes cyclogenesis in the region and triggers baroclinic instability. It is argued that this common baroclinic life cycle is due to the strongly horizontally sheared environment in the Mediterranean basin, on the poleward flank of the quasi-persistent subtropical jet. The composite life cycle of the cyclones is further analyzed considering the evolution of key atmospheric elements as potential temperature and PV, as well as the cyclones' thermodynamic profiles and rainfall. It is shown that most intense Mediterranean cyclones are associated with warm conveyor belts and dry air intrusions, similar to those of other strong extratropical cyclones, but of rather small scale. Before cyclones reach their mature stage, the streamer's role is crucial to advect moist and warm air towards the cyclones center. These dynamical characteristics, typical for very intense extratropical cyclones in the main storm track regions, are also valid for these Mediterranean cases that have features that are visually similar to tropical cyclones.

Global Tropical Moisture Exports and their Influence on Extratropical Cyclone Activity

NASA Astrophysics Data System (ADS)

Knippertz, P.; Wernli, H.; Gläser, G.

2012-04-01

Many case studies have shown that heavy precipitation events and rapid cyclogenesis in the extratropics can be fuelled by moist and warm tropical air masses. Often the tropical moisture export (TME) occurs through a longitudinally confined region in the subtropics. Here a climatology of TMEs to both hemispheres is constructed on the basis of seven-day forward trajectories, which were started daily from the tropical lower troposphere and which were required to reach a water vapour flux of at least 100 g kg-1 m s-1 somewhere poleward of 35 degrees. For this analysis 6-hourly European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim re-analysis data have been used for the 32-year period 1979-2010. A comparison with a TME climatology based upon the older ERA-40 re-analysis shows little sensitivity. The results are then related to the deepening of objectively identified (extratropical) cyclones in both hemispheres. On average TME trajectories move upwards and eastwards on their way across the subtropics in both hemispheres and are associated with both moisture and meridional-wind anomalies. TME shows four main regions of activity in both hemispheres: In the northern hemisphere these are the eastern Pacific ("Pineapple Express" region) with a marked activity maximum in boreal winter, the West Pacific with maximum activity in summer and autumn associated with the Asian monsoon, the narrow Great Plains region with a maximum in spring and summer associated with the North American monsoon and the western Atlantic or Gulf Stream region with a rather flat seasonal cycle. In the southern hemisphere activity peaks over the central and eastern Pacific, eastern South America and the adjacent Atlantic, the western Indian Ocean, and western Australia. Southern hemisphere TME activity peaks in boreal winter, particularly over the Atlantic and Pacific Oceans, which suggests a significant influence of northern hemispheric Rossby wave energy propagation across the equator. The interannual variability in several regions is significantly modulated by El Niño. A detailed analysis of TME encounters along individual extratropical cyclone tracks reveals several extraordinary cyclone-deepening events associated with TME trajectories (e.g. storm "Klaus" in January 2009). A statistical analysis quantifies the fraction of explosively deepening cyclones that occur with and without a TME influence.

Micro-Fresnel Zone Plate Optical Devices Using Densely Accumulated Ray Points

NASA Technical Reports Server (NTRS)

Choi, Sang H. (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

2011-01-01

An embodiment generally relates to an optical device suitable for use with an optical medium for the storage and retrieval of data. The optical device includes an illumination means for providing a beam of optical radiation of wavelength .lamda. and an optical path that the beam of optical radiation follows. The optical device also includes a diffractive optical element defined by a plurality of annular sections. The plurality of annular sections having a first material alternately disposed with a plurality of annular sections comprising a second material. The diffractive optical element generates a plurality of focal points and densely accumulated ray points with phase contrast phenomena and the optical medium is positioned at a selected focal point or ray point of the diffractive optical element.

Retrieval of Dry Snow Parameters from Radiometric Data Using a Dense Medium Model and Genetic Algorithms

NASA Technical Reports Server (NTRS)

Tedesco, Marco; Kim, Edward J.

2005-01-01

In this paper, GA-based techniques are used to invert the equations of an electromagnetic model based on Dense Medium Radiative Transfer Theory (DMRT) under the Quasi Crystalline Approximation with Coherent Potential to retrieve snow depth, mean grain size and fractional volume from microwave brightness temperatures. The technique is initially tested on both noisy and not-noisy simulated data. During this phase, different configurations of genetic algorithm parameters are considered to quantify how their change can affect the algorithm performance. A configuration of GA parameters is then selected and the algorithm is applied to experimental data acquired during the NASA Cold Land Process Experiment. Snow parameters retrieved with the GA-DMRT technique are then compared with snow parameters measured on field.

Contribution of Tropical Cyclones to the North Pacific Climatological Rainfall as Observed from Satellites

NASA Technical Reports Server (NTRS)

Rodgers, Edward B.; Adler, Robert F.; Pierce, Harold F.

1997-01-01

Tropical cyclone monthly rainfall amounts are estimated from passive microwave satellite observations for an eleven year period. These satellite-derived rainfall amounts are used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and inter-annual distribution of the North Pacific Ocean total rainfall during June-November when tropical cyclones are most important. To estimate these tropical cyclone rainfall amounts, mean monthly rain rates are derived from passive microwave satellite observations within 444 km radius of the center of those North Pacific tropical cyclones that reached storm stage and greater. These rain rate observations are converted to monthly rainfall amounts and then compared to those for non-tropical cyclone systems. The main results of this study indicate that: 1) tropical cyclones contribute 7% of the rainfall to the entire domain of the North Pacific during the tropical cyclone season and 12%, 3%, and 4% when the study area is limited to, respectively, the western, central, and eastern third of the ocean; 2) the maxima in tropical cyclone rainfall are poleward (5 deg to 10 deg latitude depending on longitude) of the maxima in non-tropical cyclone rainfall; 3) tropical cyclones contribute a maximum of 30% northeast of the Philippine Islands and 40% of the lower Baja California coast; 4) in the western North Pacific, the tropical cyclone rainfall lags the total rainfall by approximately two months and shows seasonal latitudinal variation following the ITCZ; and 5) in general, tropical cyclone rainfall is enhanced during the El Nino years by warm SSTs in the eastern North Pacific and by the monsoon trough in the western and central North Pacific.

Contribution of Tropical Cyclones to the North Pacific Climatological Rainfall as Observed from Satellites.

NASA Astrophysics Data System (ADS)

Rodgers, Edward B.; Adler, Robert F.; Pierce, Harold F.

2000-10-01

Tropical cyclone monthly rainfall amounts are estimated from passive microwave satellite observations for an 11-yr period. These satellite-derived rainfall amounts are used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and interannual distribution of the North Pacific Ocean total rainfall during June-November when tropical cyclones are most important.To estimate these tropical cyclone rainfall amounts, mean monthly rain rates are derived from passive microwave satellite observations within 444-km radius of the center of those North Pacific tropical cyclones that reached storm stage and greater. These rain-rate observations are converted to monthly rainfall amounts and then compared with those for nontropical cyclone systems.The main results of this study indicate that 1) tropical cyclones contribute 7% of the rainfall to the entire domain of the North Pacific during the tropical cyclone season and 12%, 3%, and 4% when the study area is limited to, respectively, the western, central, and eastern third of the ocean; 2) the maximum tropical cyclone rainfall is poleward (5°-10° latitude depending on longitude) of the maximum nontropical cyclone rainfall; 3) tropical cyclones contribute a maximum of 30% northeast of the Philippine Islands and 40% off the lower Baja California coast; 4) in the western North Pacific, the tropical cyclone rainfall lags the total rainfall by approximately two months and shows seasonal latitudinal variation following the Intertropical Convergence Zone; and 5) in general, tropical cyclone rainfall is enhanced during the El Niño years by warm SSTs in the eastern North Pacific and by the monsoon trough in the western and central North Pacific.

Cyclone Activity in the Arctic From an Ensemble of Regional Climate Models (Arctic CORDEX)

NASA Astrophysics Data System (ADS)

Akperov, Mirseid; Rinke, Annette; Mokhov, Igor I.; Matthes, Heidrun; Semenov, Vladimir A.; Adakudlu, Muralidhar; Cassano, John; Christensen, Jens H.; Dembitskaya, Mariya A.; Dethloff, Klaus; Fettweis, Xavier; Glisan, Justin; Gutjahr, Oliver; Heinemann, Günther; Koenigk, Torben; Koldunov, Nikolay V.; Laprise, René; Mottram, Ruth; Nikiéma, Oumarou; Scinocca, John F.; Sein, Dmitry; Sobolowski, Stefan; Winger, Katja; Zhang, Wenxin

2018-03-01

The ability of state-of-the-art regional climate models to simulate cyclone activity in the Arctic is assessed based on an ensemble of 13 simulations from 11 models from the Arctic-CORDEX initiative. Some models employ large-scale spectral nudging techniques. Cyclone characteristics simulated by the ensemble are compared with the results forced by four reanalyses (ERA-Interim, National Centers for Environmental Prediction-Climate Forecast System Reanalysis, National Aeronautics and Space Administration-Modern-Era Retrospective analysis for Research and Applications Version 2, and Japan Meteorological Agency-Japanese 55-year reanalysis) in winter and summer for 1981-2010 period. In addition, we compare cyclone statistics between ERA-Interim and the Arctic System Reanalysis reanalyses for 2000-2010. Biases in cyclone frequency, intensity, and size over the Arctic are also quantified. Variations in cyclone frequency across the models are partly attributed to the differences in cyclone frequency over land. The variations across the models are largest for small and shallow cyclones for both seasons. A connection between biases in the zonal wind at 200 hPa and cyclone characteristics is found for both seasons. Most models underestimate zonal wind speed in both seasons, which likely leads to underestimation of cyclone mean depth and deep cyclone frequency in the Arctic. In general, the regional climate models are able to represent the spatial distribution of cyclone characteristics in the Arctic but models that employ large-scale spectral nudging show a better agreement with ERA-Interim reanalysis than the rest of the models. Trends also exhibit the benefits of nudging. Models with spectral nudging are able to reproduce the cyclone trends, whereas most of the nonnudged models fail to do so. However, the cyclone characteristics and trends are sensitive to the choice of nudged variables.

A Classification of Mediterranean Cyclones Based on Global Analyses

NASA Technical Reports Server (NTRS)

Reale, Oreste; Atlas, Robert

2003-01-01

The Mediterranean Sea region is dominated by baroclinic and orographic cyclogenesis. However, previous work has demonstrated the existence of rare but intense subsynoptic-scale cyclones displaying remarkable similarities to tropical cyclones and polar lows, including, but not limited to, an eye-like feature in the satellite imagery. The terms polar low and tropical cyclone have been often used interchangeably when referring to small-scale, convective Mediterranean vortices and no definitive statement has been made so far on their nature, be it sub-tropical or polar. Moreover, most of the classifications of Mediterranean cyclones have neglected the small-scale convective vortices, focusing only on the larger-scale and far more common baroclinic cyclones. A classification of all Mediterranean cyclones based on operational global analyses is proposed The classification is based on normalized horizontal shear, vertical shear, scale, low versus mid-level vorticity, low-level temperature gradients, and sea surface temperatures. In the classification system there is a continuum of possible events, according to the increasing role of barotropic instability and decreasing role of baroclinic instability. One of the main results is that the Mediterranean tropical cyclone-like vortices and the Mediterranean polar lows appear to be different types of events, in spite of the apparent similarity of their satellite imagery. A consistent terminology is adopted, stating that tropical cyclone- like vortices are the less baroclinic of all, followed by polar lows, cold small-scale cyclones and finally baroclinic lee cyclones. This classification is based on all the cyclones which occurred in a four-year period (between 1996 and 1999). Four cyclones, selected among all the ones which developed during this time-frame, are analyzed. Particularly, the classification allows to discriminate between two cyclones (occurred in October 1996 and in March 1999) which both display a very well-defined eye-like feature in the satellite imagery. According to our classification system, the two events are dynamically different and can be categorized as being respectively a tropical cyclone-like vortex and well-developed polar low.

Clusters of cyclones encircling Jupiter's poles.

PubMed

Adriani, A; Mura, A; Orton, G; Hansen, C; Altieri, F; Moriconi, M L; Rogers, J; Eichstädt, G; Momary, T; Ingersoll, A P; Filacchione, G; Sindoni, G; Tabataba-Vakili, F; Dinelli, B M; Fabiano, F; Bolton, S J; Connerney, J E P; Atreya, S K; Lunine, J I; Tosi, F; Migliorini, A; Grassi, D; Piccioni, G; Noschese, R; Cicchetti, A; Plainaki, C; Olivieri, A; O'Neill, M E; Turrini, D; Stefani, S; Sordini, R; Amoroso, M

2018-03-07

The familiar axisymmetric zones and belts that characterize Jupiter's weather system at lower latitudes give way to pervasive cyclonic activity at higher latitudes. Two-dimensional turbulence in combination with the Coriolis β-effect (that is, the large meridionally varying Coriolis force on the giant planets of the Solar System) produces alternating zonal flows. The zonal flows weaken with rising latitude so that a transition between equatorial jets and polar turbulence on Jupiter can occur. Simulations with shallow-water models of giant planets support this transition by producing both alternating flows near the equator and circumpolar cyclones near the poles. Jovian polar regions are not visible from Earth owing to Jupiter's low axial tilt, and were poorly characterized by previous missions because the trajectories of these missions did not venture far from Jupiter's equatorial plane. Here we report that visible and infrared images obtained from above each pole by the Juno spacecraft during its first five orbits reveal persistent polygonal patterns of large cyclones. In the north, eight circumpolar cyclones are observed about a single polar cyclone; in the south, one polar cyclone is encircled by five circumpolar cyclones. Cyclonic circulation is established via time-lapse imagery obtained over intervals ranging from 20 minutes to 4 hours. Although migration of cyclones towards the pole might be expected as a consequence of the Coriolis β-effect, by which cyclonic vortices naturally drift towards the rotational pole, the configuration of the cyclones is without precedent on other planets (including Saturn's polar hexagonal features). The manner in which the cyclones persist without merging and the process by which they evolve to their current configuration are unknown.

Extreme storm activity in North Atlantic and European region

NASA Astrophysics Data System (ADS)

Vyazilova, N.

2010-09-01

The extreme storm activity study over North Atlantic and Europe includes the analyses of extreme cyclone (track number, integral cyclonic intensity) and extreme storm (track number) during winter and summer seasons in the regions: 1) 55°N-80N, 50°W-70°E; 2) 30°N-55°N, 50°W-70°E. Extreme cyclones were selected based on cyclone centre pressure (P<=970 mbar). Extreme storms were selected from extreme cyclones based on wind velocity on 925 mbar. The Bofort scala was used for this goal. Integral cyclonic intensity (for region) includes the calculation cyclone centers number and sum of MSLP anomalies in cyclone centers. The analyses based on automated cyclone tracking algorithm, 6-hourly MSLP and wind data (u and v on 925 gPa) from the NCEP/NCAR reanalyses from January 1948 to March 2010. The comparision of mean, calculated for every ten years, had shown, that in polar region extreme cyclone and storm track number, and integral cyclonic intensity gradually increases and have maximum during last years (as for summer, as for winter season). Every ten years means for summer season are more then for winter season, as for polar, as for tropical region. Means (ten years) for tropical region are significance less then for polar region.

Quantitative observations on tropical cyclone tracks in the Arabian Sea

NASA Astrophysics Data System (ADS)

Terry, James P.; Gienko, Gennady

2018-03-01

The Arabian Sea basin represents a minor component of global total cyclones annually and has not featured so prominently in cyclone research compared with other basins where greater numbers of cyclones are registered each year. This paper presents the results of exploratory analysis of various features of cyclone tracks in the Arabian Sea, with a particular focus on examining their temporal and spatial patterns. Track morphometry also reveals further information on track shape. The study indicates how cyclones spawned during May in the early pre-monsoon period (often strong events) have a tendency to follow more sinuous tracks, whereas cyclones occurring in October in the post-monsoon period tend to follow straighter tracks. Track sinuosity is significantly related to other attributes, including cyclone longevity and intensity. Comparisons are also drawn between the general characteristics of cyclone tracks in the Arabian Sea and other ocean basins, suggesting how the size and geography of the Arabian Sea basin exert influences on these characteristics.

Impacts of tropical cyclones on Fiji and Samoa

NASA Astrophysics Data System (ADS)

Kuleshov, Yuriy; Prakash, Bipendra; Atalifo, Terry; Waqaicelua, Alipate; Seuseu, Sunny; Ausetalia Titimaea, Mulipola

2013-04-01

Weather and climate hazards have significant impacts on Pacific Island Countries. Costs of hazards such as tropical cyclones can be astronomical making enormous negative economic impacts on developing countries. We highlight examples of extreme weather events which have occurred in Fiji and Samoa in the last few decades and have caused major economic and social disruption in the countries. Destructive winds and torrential rain associated with tropical cyclones can bring the most damaging weather conditions to the region causing economic and social hardship, affecting agricultural productivity, infrastructure and economic development which can persist for many years after the initial impact. Analysing historical data, we describe the impacts of tropical cyclones Bebe and Kina on Fiji. Cyclone Bebe (October 1972) affected the whole Fiji especially the Yasawa Islands, Viti Levu and Kadavu where hurricane force winds have been recorded. Nineteen deaths were reported and damage costs caused by cyclone Bebe were estimated as exceeding F20 million (F 1972). Tropical cyclone Kina passed between Fiji's two main islands of Viti Levu and Vanua Levu, and directly over Levuka on the night of 2 January 1993 with hurricane force winds causing extensive damage. Twenty three deaths have been reported making Kina one of the deadliest hurricanes in Fiji's recent history. Severe flooding on Viti Levu, combined with high tide and heavy seas led to destruction of the Sigatoka and Ba bridges, as well as almost complete loss of crops in Sigatoka and Navua deltas. Overall, damage caused by cyclone Kina was estimated as F170 million. In Samoa, we describe devastation to the country caused by tropical cyclones Ofa (February 1990) and Val (December 1991) which were considered to be the worst cyclones to affect the Samoan islands since the 1889 Apia cyclone. In Samoa, seven people were killed due to cyclone Ofa, thousands of people were left homeless and entire villages were destroyed. Damage on Samoa totalled to US130 million. Cyclone Val caused damage and destruction to 95% of houses in Samoa and severe crop damage; total damage was estimated as US200 million. Recently, severe tropical cyclone Evan affected Samoa and Fiji (December 2012). Significant progress in operational tropical cyclone forecasting has been achieved over the past few decades which resulted in improving early warning system but death toll attributed to cyclones is still high - at least 14 deaths in Samoa are related to cyclone Evan (luckily, no death reports in Fiji). Cyclone-related economic losses also remain very high making significant negative impact on economies of the countries. Preliminary assessment of damage caused by cyclone Evan in Fiji indicates loses of about 75.29 million. By the end of this century projections suggest decreasing numbers of tropical cyclones but a possible shift towards more intense categories. In addition, geographic shifts in distribution of tropical cyclone occurrences caused by warming of the atmospheric and oceanic environment are possible. This should be taken in consideration by authorities of the Pacific Island Countries when developing adaptation strategies to increasing tropical cyclone risk due to climate change.

Contribution of Tropical Cyclones to the Interannual Variability of Baiu Precipitation

NASA Astrophysics Data System (ADS)

Yamaura, T.; Tomita, T.

2011-12-01

This work examines the contribution of tropical cyclones to the interannual variability of Baiu precipitation with the large-scale interannual variations in the tropics, that is, the El Niño/Southern Oscillation (ENSO) and the Tropospheric Biennial Oscillation (TBO) in the Asian monsoon. The data used are the Global Precipitation Climatology Project, the Japanese 25-year Reanalysis Project/Japan Meteorological Agency Climate Data Assimilation System, and the Joint Typhoon Warning Center. The diagnosed months and the time period are June and July, and 30 years from 1979 to 2008. When the negative precipitation anomalies appear in the entire Baiu front with the cold ENSO phase, the number of tropical cyclones increases around the northern part of the Philippines, and a larger-scale anomalous cyclone is formed there. Tropical cyclones contribute to strengthening the anomalous cyclone. Anomalous convective activity in the anomalous cyclone excites Rossby waves that propagate northward within the low-level jet and form an anomalous anticyclone around Japan. The anomalous anticyclone decreases the Baiu precipitation. On the other hand, the number of tropical cyclones decreases, and an anomalous anticyclone is set around the northern part of the Philippines, when the positive precipitation anomalies are observed in the Baiu front with the warm ENSO phase. The contribution of tropical cyclones is insignificant in this phase. The warm and cold TBO phases are judged from sea surface temperature (SST) anomalies in the equatorial central Pacific that is different from the region for ENSO. In the cold TBO phase with the negative SST anomalies, there appear the negative precipitation anomalies around Kyushu and the positive ones to the southeast of Japan. Concurrently, an anomalous cyclone appears, and the accumulated cyclone energy estimated from the tropical cyclones increases to the southeast of Japan. Tropical cyclones contribute to forming the anomalous cyclone, which shifts the axis of monsoon southwesterlies southward. Thus, the negative precipitation anomalies and the positive ones appear in Kyushu and to the southeast of Japan. In the opposite TBO phase, an anomalous anticyclone is set to the southeast of Japan and suppresses tropical cyclones there. The contribution of tropical cyclones is small in this case. As such, local tropical cyclones contribute to the interannual variation of the Baiu precipitation with larger atmospheric circulations in the western North Pacific.

An updated climatology of explosive cyclones using alternative measures of cyclone intensity

NASA Astrophysics Data System (ADS)

Hanley, J.; Caballero, R.

2009-04-01

Using a novel cyclone tracking and identification method, we compute a climatology of explosively intensifying cyclones or ‘bombs' using the ERA-40 and ERA-Interim datasets. Traditionally, ‘bombs' have been identified using a central pressure deepening rate criterion (Sanders and Gyakum, 1980). We investigate alternative methods of capturing such extreme cyclones. These methods include using the maximum wind contained within the cyclone, and using a potential vorticity column measure within such systems, as a measure of intensity. Using the different measures of cyclone intensity, we construct and intercompare maps of peak cyclone intensity. We also compute peak intensity probability distributions, and assess the evidence for the bi-modal distribution found by Roebber (1984). Finally, we address the question of the relationship between storm intensification rate and storm destructiveness: are ‘bombs' the most destructive storms?

Effect of Nock-Ten Tropical Cyclone on Atmospheric Condition and Distribution of Rainfall in Gorontalo, Ternate, and Sorong Regions

NASA Astrophysics Data System (ADS)

Lumbangaol, A.; Serhalawan, Y. R.; Endarwin

2017-12-01

Nock-Ten Tropical Cyclone is an atmospheric phenomenon that has claimed many lives in the Philippines. This super-typhoon cyclone grows in the Western Pacific Ocean, North of Papua. With the area directly contiguous to the trajectory of Nock-Ten Tropical Cyclone growth, it is necessary to study about the growth activity of this tropical cyclones in Indonesia, especially in 3 different areas, namely Gorontalo, Ternate, and Sorong. This study was able to determine the impact of Nock-Ten Tropical Cyclone on atmospheric dynamics and rainfall growth distribution based on the stages of tropical cyclone development. The data used in this study include Himawari-8 IR channel satellite data to see the development stage and movement track of Tropical Cyclone Nock-Ten, rainfall data from TRMM 3B42RT satellite product to know the rain distribution in Gorontalo, Ternate, and Sorong, and reanalysis data from ECMWF such as wind direction and speed, vertical velocity, and relative vorticity to determine atmospheric conditions at the time of development of the Nock-Ten Tropical Cyclone. The results of data analysis processed using GrADS application showed the development stage of Nock-Ten Tropical Cyclone has effect of changes in atmospheric dynamics condition and wind direction pattern. In addition, tropical cyclones also contribute to very light to moderate scale intensity during the cycle period of tropical cyclone development in all three regions.

In-Medium Parton Branching Beyond Eikonal Approximation

NASA Astrophysics Data System (ADS)

Apolinário, Liliana

2017-03-01

The description of the in-medium modifications of partonic showers has been at the forefront of current theoretical and experimental efforts in heavy-ion collisions. It provides a unique laboratory to extend our knowledge frontier of the theory of the strong interactions, and to assess the properties of the hot and dense medium (QGP) that is produced in ultra-relativistic heavy-ion collisions at RHIC and the LHC. The theory of jet quenching, a commonly used alias for the modifications of the parton branching resulting from the interactions with the QGP, has been significantly developed over the last years. Within a weak coupling approach, several elementary processes that build up the parton shower evolution, such as single gluon emissions, interference effects between successive emissions and corrections to radiative energy loss of massive quarks, have been addressed both at eikonal accuracy and beyond by taking into account the Brownian motion that high-energy particles experience when traversing a hot and dense medium. In this work, by using the setup of single gluon emission from a color correlated quark-antiquark pair in a singlet state (qbar{q} antenna), we calculate the in-medium gluon radiation spectrum beyond the eikonal approximation. The results show that we are able to factorize broadening effects from the modifications of the radiation process itself. This constitutes the final proof that a probabilistic picture of the parton shower evolution holds even in the presence of a QGP.

Clusters of cyclones encircling Jupiter’s poles

NASA Astrophysics Data System (ADS)

Adriani, A.; Mura, A.; Orton, G.; Hansen, C.; Altieri, F.; Moriconi, M. L.; Rogers, J.; Eichstädt, G.; Momary, T.; Ingersoll, A. P.; Filacchione, G.; Sindoni, G.; Tabataba-Vakili, F.; Dinelli, B. M.; Fabiano, F.; Bolton, S. J.; Connerney, J. E. P.; Atreya, S. K.; Lunine, J. I.; Tosi, F.; Migliorini, A.; Grassi, D.; Piccioni, G.; Noschese, R.; Cicchetti, A.; Plainaki, C.; Olivieri, A.; O’Neill, M. E.; Turrini, D.; Stefani, S.; Sordini, R.; Amoroso, M.

2018-03-01

The familiar axisymmetric zones and belts that characterize Jupiter’s weather system at lower latitudes give way to pervasive cyclonic activity at higher latitudes. Two-dimensional turbulence in combination with the Coriolis β-effect (that is, the large meridionally varying Coriolis force on the giant planets of the Solar System) produces alternating zonal flows. The zonal flows weaken with rising latitude so that a transition between equatorial jets and polar turbulence on Jupiter can occur. Simulations with shallow-water models of giant planets support this transition by producing both alternating flows near the equator and circumpolar cyclones near the poles. Jovian polar regions are not visible from Earth owing to Jupiter’s low axial tilt, and were poorly characterized by previous missions because the trajectories of these missions did not venture far from Jupiter’s equatorial plane. Here we report that visible and infrared images obtained from above each pole by the Juno spacecraft during its first five orbits reveal persistent polygonal patterns of large cyclones. In the north, eight circumpolar cyclones are observed about a single polar cyclone; in the south, one polar cyclone is encircled by five circumpolar cyclones. Cyclonic circulation is established via time-lapse imagery obtained over intervals ranging from 20 minutes to 4 hours. Although migration of cyclones towards the pole might be expected as a consequence of the Coriolis β-effect, by which cyclonic vortices naturally drift towards the rotational pole, the configuration of the cyclones is without precedent on other planets (including Saturn’s polar hexagonal features). The manner in which the cyclones persist without merging and the process by which they evolve to their current configuration are unknown.

Contrasting effects of tropical cyclones on the annual survival of a pelagic seabird in the Indian Ocean.

PubMed

Nicoll, Malcolm A C; Nevoux, Marie; Jones, Carl G; Ratcliffe, Norman; Ruhomaun, Kevin; Tatayah, Vikash; Norris, Ken

2017-02-01

Tropical cyclones are renowned for their destructive nature and are an important feature of marine and coastal tropical ecosystems. Over the last 40 years, their intensity, frequency and tracks have changed, partly in response to ocean warming, and future predictions indicate that these trends are likely to continue with potential consequences for human populations and coastal ecosystems. However, our understanding of how tropical cyclones currently affect marine biodiversity, and pelagic species in particular, is limited. For seabirds, the impacts of cyclones are known to be detrimental at breeding colonies, but impacts on the annual survival of pelagic adults and juveniles remain largely unexplored and no study has simultaneously explored the direct impacts of cyclones on different life-history stages across the annual life cycle. We used a 20-year data set on tropical cyclones in the Indian Ocean, tracking data from 122 Round Island petrels and long-term capture-mark-recapture data to explore the impacts of tropical cyclones on the survival of adult and juvenile (first year) petrels during both the breeding and migration periods. The tracking data showed that juvenile and adult Round Island petrels utilize the three cyclone regions of the Indian Ocean and were potentially exposed to cyclones for a substantial part of their annual cycle. However, only juvenile petrel survival was affected by cyclone activity; negatively by a strong cyclone in the vicinity of the breeding colony and positively by increasing cyclone activity in the Northern Indian Ocean where they spend the majority of their first year at sea. These contrasting effects raise the intriguing prospect that the projected changes in cyclones under current climate change scenarios may have positive as well as the more commonly perceived negative impacts on marine biodiversity. © 2016 John Wiley & Sons Ltd.

A Subtropical Cyclone in the Canary Islands: the October 2014 event

NASA Astrophysics Data System (ADS)

Quitian, Lara; Martin, Maria Luisa; Jesús González-Alemán, Juan; Santos-Muñoz, Daniel; Valero Rodríguez, Francisco

2016-04-01

Depending on the thermal structure and dynamics, there are different types of cyclones in the troposphere. Subtropical cyclones (STC) are low pressure systems that share tropical and extratropical characteristics, having hybrid thermal structures. In October 2014, a cyclonic system landfall the Canary Islands, causing widespread damages. The system began to develop in October 18 and its effects lasted until October 21. Here, the diagnosis and identification of such cyclone as STC is carried out, examining its dynamical and thermal evolution. Diverse fields have been obtained from three different numerical models, and several diagnostic tools and cyclone phase space diagrams have been used. The cyclone evolved from a typical extratropical cyclone, detached from the atmospheric circulation which was highly meridional and became a stationary cut-off low. The meridional intrusion of the trough as well as a low-level baroclinic zone favored the formation of a STC northwestern of the Canary Islands. Several cyclone phase space diagrams are used to classify the cyclone as a STC, highlighting a deep cold core in its early stages that develops into a shallow warm core. High potential vorticity areas associated with the cyclone promoted strong winds and precipitation over the Islands. Throughout the event, an increased conditional instability is observed in the different soundings, leading to strong vertical wind shear. Moreover, relatively warm sea surface temperature is obtained, establishing the conditions to favor the organization of long-lived convective structures.

The study of Merydunal and Zonal Index and its relationships with Cyclone Gonu

NASA Astrophysics Data System (ADS)

Ezzatian, Victoria

2010-05-01

Distinguish the integrated natural disaster management is basic, also there happens rarely during 100 years. Cyclone Gonu, an unusually strong tropical cyclone, developed in the eastern part of the Arabian Sea on June 1st. The cyclone made landfall in Oman on the 6th with maximum sustained winds near 148 km/hr. A few days prior to landfall, Gonu had intensified to a powerful super cyclonic storm with maximum sustained winds near 260 km/hr on the 5th, becoming the first documented super cyclone in the Arabian Sea and tied for the strongest cyclone in the North Indian Ocean. After making landfall in Oman, Gonu moved through the Gulf of Oman making a second landfall in Iran. Tropical Cyclone Gonu affected more than 20,000 people and was responsible for 49 fatalities and 27 missing people in Oman. Gonu brought heavy rainfall which caused floods and landslides. Meanwhile in Iran 5 fatalities were reported and 9 people remain missing. Tropical cyclones as strong as Gonu are rare in the Arabian Sea. Severe thunderstorms, associated with an outer band of the tropical cyclone Yemyin , produced heavy rains and winds during June 23-25. The storms produced heavy rains which caused floodings and destroyed thousands of homes .Tropical Cyclone Yemyin developed as a depression in the Bay of Bengal on the 21st and made landfall in India's southern state on the 22nd. Yemyin brought heavy rain in the southern parts of India, leaving over 254 mm of rain. After crossing over India, Yemyin moved into the Arabian Sea and began moving towards the northwest. On June 26, the cyclone intensified and maximum sustained winds reached 93 km/hr. The cyclone was responsible for at least 21 fatalities in the Baluchistan province. Meanwhile in Afghanistan, Yemyin produced heavy rainfall which prompted floods that were responsible for 56 deaths and left thousands of people homeless . Because of these happenings we decided surveying the synoptic patterns in this month. Key words: Tropical cyclones, Tropical Cyclone Gonu, merridional index, zonal index .

Installation of a stoker-coal preparation plant in Krakow, Poland. Technical progress report 11, October--December 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

This project is one of eight projects selected under the assessment program in the Support of Eastern Democracy (SEED) Act of 0989 by the federal government to reduce low-level emission sources in the Krakow area of Poland. The objective of this Cooperative Agreement is to demonstrate that the quality of stack gas emissions can be improved through the substitution of run-of-mine coal by washed coal. To this end, EFH Coal Company will design, build, and operate a 300-mtph (330 stph) preparation plant and produce a low ash, double-screened washed coal for burning in a traveling-grate stoker in one of themore » many water heating plants in the city of Krakow. By burning this prepared coal under proper combustion condition, combustion efficiency will be increased, stoker maintenance will be lowered and the amount of carbon monoxide, sulfur dioxide and particulates in the stack gases will be reduced significantly. Contracts to: provide the raw-coal feed to the plant; dispose of plant wastes; burn the clean coal in a demonstration water heating plant in Krakow; and to market any surplus production are in place. An international irrevocable purchase order has been let for the procurement of a customized modular 300 mtph (330 stph) dense medium cyclone preparation plant to wash the 20 mm ({approx} 3/4 in.) by 5 mm. ({approx} 1/4 in.) size fraction of raw coal produced by the Katowice Coal Holding Company. This plant will be fabricated and shipped from the United States to Poland as soon as the final land-us and construction permits are granted.« less

A multiple scattering theory for EM wave propagation in a dense random medium

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.; Wong, K. W.

1985-01-01

For a dense medium of randomly distributed scatterers an integral formulation for the total coherent field has been developed. This formulation accounts for the multiple scattering of electromagnetic waves including both the twoand three-particle terms. It is shown that under the Markovian assumption the total coherent field and the effective field have the same effective wave number. As an illustration of this theory, the effective wave number and the extinction coefficient are derived in terms of the polarizability tensor and the pair distribution function for randomly distributed small spherical scatterers. It is found that the contribution of the three-particle term increases with the particle size, the volume fraction, the frequency and the permittivity of the particle. This increase is more significant with frequency and particle size than with other parameters.

Dense Regions in Supersonic Isothermal Turbulence

NASA Astrophysics Data System (ADS)

Robertson, Brant; Goldreich, Peter

2018-02-01

The properties of supersonic isothermal turbulence influence a variety of astrophysical phenomena, including the structure and evolution of star-forming clouds. This work presents a simple model for the structure of dense regions in turbulence in which the density distribution behind isothermal shocks originates from rough hydrostatic balance between the pressure gradient behind the shock and its deceleration from ram pressure applied by the background fluid. Using simulations of supersonic isothermal turbulence and idealized waves moving through a background medium, we show that the structural properties of dense, shocked regions broadly agree with our analytical model. Our work provides a new conceptual picture for describing the dense regions, which complements theoretical efforts to understand the bulk statistical properties of turbulence and attempts to model the more complex features of star-forming clouds like magnetic fields, self-gravity, or radiative properties.

The Variation of Tropical Cyclone Rainfall within the North Atlantic and Pacific as Observed from Satellites

NASA Technical Reports Server (NTRS)

Rodgers, Edward; Pierce, Harold; Adler, Robert

1999-01-01

Tropical cyclone monthly rainfall amounts are estimated from passive microwave satellite observations in the North Atlantic and in three equal geographical regions of the North Pacific (i.e., Western, Central, and Eastern North Pacific). These satellite-derived rainfall amounts are used to assess the impact of tropical cyclone rainfall in altering the geographical, seasonal, and inter-annual distribution of the 1987-1989, 1991-1998 North Atlantic and Pacific rainfall during June-November when tropical cyclones are most abundant. To estimate these tropical cyclone rainfall amounts, mean monthly rain rates are derived from the Defence Meteorological Satellite Program (DMSP) Special Sensor Microwave/ Radiometer (SSM/I) observations within 444 km radius of the center of those North Atlantic and Pacific tropical cyclones that reached storm stage and greater. These rain rate observations are then multiplied by the number of hours in a given month. Mean monthly rainfall amounts are also constructed for all the other North Atlantic and Pacific raining systems during this eleven year period for the purpose of estimating the geographical distribution and intensity of rainfall contributed by non-tropical cyclone systems. Further, the combination of the non-tropical cyclone and tropical cyclone (i.e., total) rainfall is constructed to delineate the fractional amount that tropical cyclones contributed to the total North Pacific rainfall.

Groundnut shell gasification performance in a fluidized bed gasifier with bubbling air as gasification medium.

PubMed

Singh, Dharminder; Yadav, Sanjeev; Rajesh, V M; Mohanty, Pravakar

2018-05-24

This work was focused on finding the groundnut shell (GNS) gasification performance in a fluidized bed gasifier with bubbling air as gasification medium. GNS in powder form (a mixture of different particle size as given in table 8 in the article) was gasified using naturally available river sand as bed material, top of the bed feeding, conventional charcoal as bed heating medium, and two cyclones for proper cleaning and cooling the product gas. Experiments were performed using different operating conditions such as equivalence ratio (ER) between 0.29 and 0.33, bed temperature between 650°C and 800°C, and feedstock feeding rate between 36 and 31.7 kg/h. Different parameters were evaluated to study the gasifier performance such as gas yield, cold gas efficiency, carbon conversion efficiency (CCE), and high heating value. The most suitable ER value was found to be 0.31, giving the most stable bed temperature profile at 714.4°C with 5-10% fluctuation. Cold gas efficiency and CCE at optimal ER of 0.31 was found to be 71.8% and 91%, respectively.

Characterizing the Multi-Phase Origin of the [CII] Emission in M101 and NGC 6946

NASA Astrophysics Data System (ADS)

Tarantino, Elizabeth; Bolatto, Alberto; Herrera-Camus, Rodrigo

2018-01-01

The bright far-infrared line [CII] is a dominant cooling channel of the neutral interstellar medium (ISM) and is a tracer of star formation. However, [CII] can be excited in different environments of the ISM, such as in dense photodissociation regions (PDRs), the cold/warm neutral medium (CNM/WNM), and the warm ionized medium (WIM). Separating the [CII] emission into its multiple components is vital for understanding star formation and for using [CII] as a star formation tracer. We present spectrally resolved SOFIA/GREAT data of the 158 μm [CII] emission, as well as ancillary HI and CO 2-1 data, to disentangle the multiple phases of the ISM. We use 18 pointings that sample the range of different environments present in these galaxies, including star formation activity, metallicity, radiation field strength, and gas content. We find that on average the [CII] is more associated with the dense CO gas coming from PDRs than the neutral medium, consistent with other results in the literature. Additionally, the [CII] observations allow us to access the “CO-faint” molecular gas in regions that have too low of a metallicty to produce CO. This adds to the small number of studies that have explored this “CO-faint” regime.

Extinction measurement of dense media by an optical coherence tomography technique

NASA Astrophysics Data System (ADS)

Ago, Tomoki; Iwai, Toshiaki; Yokota, Ryoko

2016-10-01

The optical coherence tomography will make progress as the next stage toward a spectroscopic analysis technique. The spectroscopic analysis is based on the Beer-Lambert law. The absorption and scattering coefficients even for the dense medium can be measured by the Beer-Lambert law because the OCT can detect only the light keeping the coherency which propagated rectilinearly and retro-reflected from scatters. This study is concerned with the quantitative verification of Beer-Lambert law in the OCT imaging.

Intercomparison of mid latitude storm diagnostics (IMILAST) - synthesis of project results

NASA Astrophysics Data System (ADS)

Neu, Urs

2017-04-01

The analysis of the occurrence of mid-latitude storms is of great socio-economical interest due to their vast and destructive impacts. However, a unique definition of cyclones is missing, and therefore the definition of what a cyclone is as well as quantifying its strength contains subjective choices. Existing automatic cyclone identification and tracking algorithms are based on different definitions and use diverse characteristics, e.g. data transformation, metrics used for cyclone identification, cyclone identification procedures or tracking methods. The project IMILAST systematically compares different cyclone detection and tracking methods, with the aim to comprehensively assess the influence of different algorithms on cyclone climatologies, temporal trends of frequency, strength or other characteristics of cyclones and thus quantify systematic uncertainties in mid-latitudinal storm identification and tracking. The three main intercomparison experiments used the ERA-interim reanalysis as a common input data set and focused on differences between the methods with respect to number, track density, life cycle characteristics, and trend patterns on the one hand and potential differences of the long-term climate change signal of cyclonic activity between the methods on the other hand. For the third experiment, the intercomparison period has been extended to a 30 year period from 1979 to 2009 and focuses on more specific aspects, such as parameter sensitivities, the comparison of automated to manual tracking sets, regional analysis (regional trends, Arctic and Antarctic cyclones, cyclones in the Mediterranean) or specific phenomena like splitting and merging of cyclones. In addition, the representation of storms and their characteristics in reanalysis data sets is examined to further enhance the knowledge on uncertainties related to storm occurrence. This poster presents a synthesis of the main results from the intercomparison activities within IMILAST.

Ultrafast Outflows: Galaxy-scale Active Galactic Nucleus Feedback

NASA Astrophysics Data System (ADS)

Wagner, A. Y.; Umemura, M.; Bicknell, G. V.

2013-01-01

We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.

ULTRAFAST OUTFLOWS: GALAXY-SCALE ACTIVE GALACTIC NUCLEUS FEEDBACK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, A. Y.; Umemura, M.; Bicknell, G. V., E-mail: ayw@ccs.tsukuba.ac.jp

We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves inmore » the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.« less

Detection of centers of tropical cyclones using Communication, Ocean, and Meteorological Satellite data

NASA Astrophysics Data System (ADS)

Lee, Juhyun; Im, Jungho; Park, Seohui; Yoo, Cheolhee

2017-04-01

Tropical cyclones are one of major natural disasters, which results in huge damages to human and society. Analyzing behaviors and characteristics of tropical cyclones is essential for mitigating the damages by tropical cyclones. In particular, it is important to keep track of the centers of tropical cyclones. Cyclone center and track information (called Best Track) provided by Joint Typhoon Warning Center (JTWC) are widely used for the reference data of tropical cyclone centers. However, JTWC uses multiple resources including numerical modeling, geostationary satellite data, and in situ measurements to determine the best track in a subjective way and makes it available to the public 6 months later after an event occurred. Thus, the best track data cannot be operationally used to identify the centers of tropical cyclones in real time. In this study, we proposed an automated approach for identifying the centers of tropical cyclones using only Communication, Ocean, and Meteorological Satellite (COMS) Meteorological Imager (MI) sensor derived data. It contains 5 bands—VIS (0.67µm), SWIR (3.7µm), WV (6.7µm), IR1 (10.8µm), and IR2 (12.0µm). We used IR1 band images to extract brightness temperatures of cloud tops over Western North Pacific between 2011 and 2012. The Angle deviation between brightness temperature-based gradient direction in a moving window and the reference angle toward the center of the window was extracted. Then, a spatial analysis index called circular variance was adopted to identify the centers of tropical cyclones based on the angle deviation. Finally, the locations of the minimum circular variance indexes were identified as the centers of tropical cyclones. While the proposed method has comparable performance for detecting cyclone centers in case of organized cloud convections when compared with the best track data, it identified the cyclone centers distant ( 2 degrees) from the best track centers for unorganized convections.

Serial Clustering of North Atlantic Cyclones and Wind Storms: A New Identification Base and Sensitivity to Intensity and Intra-Seasonal Variability

NASA Astrophysics Data System (ADS)

Leckebusch, G. C.; Kirchner-Bossi, N. O.; Befort, D. J.; Ulbrich, U.

2015-12-01

Time-clustered mid-latitude winter storms are responsible for a large portion of the overall windstorm-related damage in Europe. Thus, its study entails a high meteorological interest, while its outcome can result in a crucial utility for the (re)insurance industry. In addition to existing cyclone-based studies, here we use an event identification approach based on surface near wind speeds only, to investigate windstorm clustering and compare it to cyclone clustering. Specifically, cyclone and windstorm tracks are identified for winter 1979-2013 (Oct-Mar), to perform two sensitivity analyses on event-clustering in the North Atlantic using ERA-Interim Reanalysis. First, the link between clustering and cyclone intensity is analysed and compared to windstorms. Secondly, the sensitivity of clustering on intra-seasonal time scales is investigated, for both cyclones and windstorms. The wind-based approach reveals additional regions of clustering over Western Europe, which could be related to extreme damages, showing the added value of investigating wind field derived tracks in addition to that of cyclone tracks. Previous studies indicate a higher degree of clustering for stronger cyclones. However, our results show that this assumption is not always met. Although a positive relationship is confirmed for the clustering centre located over Iceland, clustering off the coast of the Iberian Peninsula behaves opposite. Even though this region shows the highest clustering, most of its signal is due to cyclones with intensities below the 70th percentile of the Laplacian of MSLP. Results on the sensitivity of clustering to the time of the winter season (Oct-Mar) show a temporal evolution of the clustering patterns, for both windstorms and cyclones. Compared to all cyclones, clustering of windstorms and strongest cyclones culminate around February, while all cyclone clustering peak in December to January.

Diabatic processes and the evolution of two contrasting extratropical cyclones

NASA Astrophysics Data System (ADS)

Martinez-Alvarado, Oscar; Gray, Suzanne; Methven, John

2016-04-01

Two contrasting extratropical cyclones were observed over the United Kingdom during the summer 2012 field campaign of the DIAMET (DIAbatic influences on Mesoscale structures in ExtraTropical storms) project. The first cyclone, observed in July, was a shallow system typical of summer over west Europe while the second cyclone, observed in August, was a much deeper system which developed a potential vorticity (PV) tower. The evolution of these two cyclones was analysed and compared in terms of diabatic effects with respect to two aspects. The first aspect is the amount and distribution of heat produced during the development of each cyclone, measured by the cross-isentropic motion around the cyclone centre. The second aspect is the modification to the circulation around the cyclones' centres, measured by area-averaged isentropic vorticity. The contributions from individual diabatic processes, such as convection, cloud microphysics and radiation, to these two aspects is also considered. The cyclones were analysed via hindcast simulations with a research version of the Met Office Unified Model, enhanced with on-line tracers of diabatic changes of potential temperature and PV. A new methodology for the interpretation of these tracers was also implemented and used. The hindcast simulations were compared with the available dropsonde observations from the field campaign as well as operational analyses and radar rainfall rates. It is shown that, while boundary layer and turbulent mixing processes and cloud microphysics processes contributed to the development of both cyclones, the main differences between the cyclones in terms of diabatic effects could be attributed to differences in convective activity. It is also shown that the contribution from all these diabatic processes to changes in the circulation was modulated by the characteristics of advection around each cyclone in a highly nonlinear fashion. This research establishes a new framework for a systematic comparison of diabatic processes and their importance for the evolution of extratropical cyclones.

The threat to coral reefs from more intense cyclones under climate change.

PubMed

Cheal, Alistair J; MacNeil, M Aaron; Emslie, Michael J; Sweatman, Hugh

2017-04-01

Ocean warming under climate change threatens coral reefs directly, through fatal heat stress to corals and indirectly, by boosting the energy of cyclones that cause coral destruction and loss of associated organisms. Although cyclone frequency is unlikely to rise, cyclone intensity is predicted to increase globally, causing more frequent occurrences of the most destructive cyclones with potentially severe consequences for coral reef ecosystems. While increasing heat stress is considered a pervasive risk to coral reefs, quantitative estimates of threats from cyclone intensification are lacking due to limited data on cyclone impacts to inform projections. Here, using extensive data from Australia's Great Barrier Reef (GBR), we show that increases in cyclone intensity predicted for this century are sufficient to greatly accelerate coral reef degradation. Coral losses on the outer GBR were small, localized and offset by gains on undisturbed reefs for more than a decade, despite numerous cyclones and periods of record heat stress, until three unusually intense cyclones over 5 years drove coral cover to record lows over >1500 km. Ecological damage was particularly severe in the central-southern region where 68% of coral cover was destroyed over >1000 km, forcing record declines in the species richness and abundance of associated fish communities, with many local extirpations. Four years later, recovery of average coral cover was relatively slow and there were further declines in fish species richness and abundance. Slow recovery of community diversity appears likely from such a degraded starting point. Highly unusual characteristics of two of the cyclones, aside from high intensity, inflated the extent of severe ecological damage that would more typically have occurred over 100s of km. Modelling published predictions of future cyclone activity, the likelihood of more intense cyclones within time frames of coral recovery by mid-century poses a global threat to coral reefs and dependent societies. © 2017 John Wiley & Sons Ltd.

Tropical cyclones over the North Indian Ocean: experiments with the high-resolution global icosahedral grid point model GME

NASA Astrophysics Data System (ADS)

Kumkar, Yogesh V.; Sen, P. N.; Chaudhari, Hemankumar S.; Oh, Jai-Ho

2018-02-01

In this paper, an attempt has been made to conduct a numerical experiment with the high-resolution global model GME to predict the tropical storms in the North Indian Ocean during the year 2007. Numerical integrations using the icosahedral hexagonal grid point global model GME were performed to study the evolution of tropical cyclones, viz., Akash, Gonu, Yemyin and Sidr over North Indian Ocean during 2007. It has been seen that the GME model forecast underestimates cyclone's intensity, but the model can capture the evolution of cyclone's intensity especially its weakening during landfall, which is primarily due to the cutoff of the water vapor supply in the boundary layer as cyclones approach the coastal region. A series of numerical simulation of tropical cyclones have been performed with GME to examine model capability in prediction of intensity and track of the cyclones. The model performance is evaluated by calculating the root mean square errors as cyclone track errors.

Effects of cyclone-generated disturbance on a tropical reef foraminifera assemblage.

PubMed

Strotz, Luke C; Mamo, Briony L; Dominey-Howes, Dale

2016-04-29

The sedimentary record, and associated micropalaeontological proxies, is one tool that has been employed to quantify a region's tropical cyclone history. Doing so has largely relied on the identification of allochthonous deposits (sediments and microfossils), sourced from deeper water and entrained by tropical cyclone waves and currents, in a shallow-water or terrestrial setting. In this study, we examine microfossil assemblages before and after a known tropical cyclone event (Cyclone Hamish) with the aim to better resolve the characteristics of this known signal. Our results identify no allochthonous material associated with Cyclone Hamish. Instead, using a swathe of statistical tools typical of ecological studies but rarely employed in the geosciences, we identify new, previously unidentified, signal types. These signals include a homogenising effect, with the level of differentiation between sample sites greatly reduced immediately following Cyclone Hamish, and discernible shifts in assemblage diversity. In the subsequent years following Hamish, the surface assemblage returns to its pre-cyclone form, but results imply that it is unlikely the community ever reaches steady state.

A statistical analysis of the association between tropical cyclone intensity change and tornado frequency

NASA Astrophysics Data System (ADS)

Moore, Todd W.

2016-07-01

Tropical cyclones often produce tornadoes that have the potential to compound the injury and fatality counts and the economic losses associated with tropical cyclones. These tornadoes do not occur uniformly through time or across space. Multiple statistical methods were used in this study to analyze the association between tropical cyclone intensity change and tornado frequency. Results indicate that there is an association between the two and that tropical cyclones tend to produce more tornadoes when they are weakening, but the association is weak. Tropical cyclones can also produce a substantial number of tornadoes when they are relatively stable or strengthening.

Ocean barrier layers' effect on tropical cyclone intensification.

PubMed

Balaguru, Karthik; Chang, Ping; Saravanan, R; Leung, L Ruby; Xu, Zhao; Li, Mingkui; Hsieh, Jen-Shan

2012-09-04

Improving a tropical cyclone's forecast and mitigating its destructive potential requires knowledge of various environmental factors that influence the cyclone's path and intensity. Herein, using a combination of observations and model simulations, we systematically demonstrate that tropical cyclone intensification is significantly affected by salinity-induced barrier layers, which are "quasi-permanent" features in the upper tropical oceans. When tropical cyclones pass over regions with barrier layers, the increased stratification and stability within the layer reduce storm-induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, an intensification of tropical cyclones. On average, the tropical cyclone intensification rate is nearly 50% higher over regions with barrier layers, compared to regions without. Our finding, which underscores the importance of observing not only the upper-ocean thermal structure but also the salinity structure in deep tropical barrier layer regions, may be a key to more skillful predictions of tropical cyclone intensities through improved ocean state estimates and simulations of barrier layer processes. As the hydrological cycle responds to global warming, any associated changes in the barrier layer distribution must be considered in projecting future tropical cyclone activity.

Ocean Barrier Layers’ Effect on Tropical Cyclone Intensification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balaguru, Karthik; Chang, P.; Saravanan, R.

2012-09-04

Improving a tropical cyclone's forecast and mitigating its destructive potential requires knowledge of various environmental factors that influence the cyclone's path and intensity. Herein, using a combination of observations and model simulations, we systematically demonstrate that tropical cyclone intensification is significantly affected by salinity-induced barrier layers, which are 'quasi-permanent' features in the upper tropical oceans. When tropical cyclones pass over regions with barrier layers, the increased stratification and stability within the layer reduce storm-induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, an intensification of tropicalmore » cyclones. On average, the tropical cyclone intensification rate is nearly 50% higher over regions with barrier layers, compared to regions without. Our finding, which underscores the importance of observing not only the upper-ocean thermal structure but also the salinity structure in deep tropical barrier layer regions, may be a key to more skillful predictions of tropical cyclone intensities through improved ocean state estimates and simulations of barrier layer processes. As the hydrological cycle responds to global warming, any associated changes in the barrier layer distribution must be considered in projecting future tropical cyclone activity.« less

Positive predictive values by mammographic density and screening mode in the Norwegian Breast Cancer Screening Program.

PubMed

Moshina, Nataliia; Ursin, Giske; Roman, Marta; Sebuødegård, Sofie; Hofvind, Solveig

2016-01-01

To investigate the probability of breast cancer among women recalled due to abnormal findings on the screening mammograms (PPV-1) and among women who underwent an invasive procedure (PPV-2) by mammographic density (MD), screening mode and age. We used information about 28,826 recall examinations from 26,951 subsequently screened women in the Norwegian Breast Cancer Screening Program, 1996-2010. The radiologists who performed the recall examinations subjectively classified MD on the mammograms into three categories: fatty (<30% fibroglandular tissue); medium dense (30-70%) and dense (>70%). Screening mode was defined as screen-film mammography (SFM) and full-field digital mammography (FFDM). We examined trends of PPVs by MD, screening mode and age. We used logistic regression to estimate odds ratio (OR) of screen-detected breast cancer associated with MD among women recalled, adjusting for screening mode and age. PPV-1 and PPV-2 decreased by increasing MD, regardless of screening mode (p for trend <0.05 for both PPVs). PPV-1 and PPV-2 were statistically significantly higher for FFDM compared with SFM for women with fatty breasts. Among women recalled, the adjusted OR of breast cancer decreased with increasing MD. Compared with women with fatty breasts, the OR was 0.90 (95% CI: 0.84-0.96) for those with medium dense breasts and 0.85 (95% CI: 0.76-0.95) for those with dense breasts. PPVs decreased by increasing MD. Fewer women needed to be recalled or undergo an invasive procedure to detect one breast cancer among those with fatty versus dense breasts in the screening program in Norway, 1996-2010. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Do Tropical Cyclones Shape Shorebird Habitat Patterns? Biogeoclimatology of Snowy Plovers in Florida

PubMed Central

Convertino, Matteo; Elsner, James B.; Muñoz-Carpena, Rafael; Kiker, Gregory A.; Martinez, Christopher J.; Fischer, Richard A.; Linkov, Igor

2011-01-01

Background The Gulf coastal ecosystems in Florida are foci of the highest species richness of imperiled shoreline dependent birds in the USA. However environmental processes that affect their macroecological patterns, like occupancy and abundance, are not well unraveled. In Florida the Snowy Plover (Charadrius alexandrinus nivosus) is resident along northern and western white sandy estuarine/ocean beaches and is considered a state-threatened species. Methodology/Principal Findings Here we show that favorable nesting areas along the Florida Gulf coastline are located in regions impacted relatively more frequently by tropical cyclones. The odds of Snowy Plover nesting in these areas during the spring following a tropical cyclone impact are seven times higher compared to the odds during the spring following a season without a cyclone. The only intensity of a tropical cyclone does not appear to be a significant factor affecting breeding populations. Conclusions/Significance Nevertheless a future climate scenario featuring fewer, but more extreme cyclones could result in a decrease in the breeding Snowy Plover population and its breeding range. This is because the spatio-temporal frequency of cyclone events was found to significantly affect nest abundance. Due to the similar geographic range and habitat suitability, and no decrease in nest abundance of other shorebirds in Florida after the cyclone season, our results suggest a common bioclimatic feedback between shorebird abundance and tropical cyclones in breeding areas which are affected by cyclones. PMID:21264268

Objectively classifying Southern Hemisphere extratropical cyclones

NASA Astrophysics Data System (ADS)

Catto, Jennifer

2016-04-01

There has been a long tradition in attempting to separate extratropical cyclones into different classes depending on their cloud signatures, airflows, synoptic precursors, or upper-level flow features. Depending on these features, the cyclones may have different impacts, for example in their precipitation intensity. It is important, therefore, to understand how the distribution of different cyclone classes may change in the future. Many of the previous classifications have been performed manually. In order to be able to evaluate climate models and understand how extratropical cyclones might change in the future, we need to be able to use an automated method to classify cyclones. Extratropical cyclones have been identified in the Southern Hemisphere from the ERA-Interim reanalysis dataset with a commonly used identification and tracking algorithm that employs 850 hPa relative vorticity. A clustering method applied to large-scale fields from ERA-Interim at the time of cyclone genesis (when the cyclone is first detected), has been used to objectively classify identified cyclones. The results are compared to the manual classification of Sinclair and Revell (2000) and the four objectively identified classes shown in this presentation are found to match well. The relative importance of diabatic heating in the clusters is investigated, as well as the differing precipitation characteristics. The success of the objective classification shows its utility in climate model evaluation and climate change studies.

Scale-chiral symmetry, ω meson, and dense baryonic matter

NASA Astrophysics Data System (ADS)

Ma, Yong-Liang; Rho, Mannque

2018-05-01

It is shown that explicitly broken scale symmetry is essential for dense skyrmion matter in hidden local symmetry theory. Consistency with the vector manifestation fixed point for the hidden local symmetry of the lowest-lying vector mesons and the dilaton limit fixed point for scale symmetry in dense matter is found to require that the anomalous dimension (|γG2| ) of the gluon field strength tensor squared (G2 ) that represents the quantum trace anomaly should be 1.0 ≲|γG2|≲3.5 . The magnitude of |γG2| estimated here will be useful for studying hadron and nuclear physics based on the scale-chiral effective theory. More significantly, that the dilaton limit fixed point can be arrived at with γG2≠0 at some high density signals that scale symmetry can arise in dense medium as an "emergent" symmetry.

The interstellar N2 abundance towards HD 124314 from far-ultraviolet observations.

PubMed

Knauth, David C; Andersson, B-G; McCandliss, Stephan R; Moos, H Warren

2004-06-10

The abundance of interstellar molecular nitrogen (N2) is of considerable importance: models of steady-state gas-phase interstellar chemistry, together with millimetre-wavelength observations of interstellar N2H+ in dense molecular clouds predict that N2 should be the most abundant nitrogen-bearing molecule in the interstellar medium. Previous attempts to detect N2 absorption in the far-ultraviolet or infrared (ice features) have hitherto been unsuccessful. Here we report the detection of interstellar N2 at far-ultraviolet wavelengths towards the moderately reddened star HD 124314 in the constellation of Centaurus. The N2 column density is larger than expected from models of diffuse clouds and significantly smaller than expected for dense molecular clouds. Moreover, the N2 abundance does not explain the observed variations in the abundance of atomic nitrogen (N I) towards high-column-density sightlines, implying that the models of nitrogen chemistry in the interstellar medium are incomplete.

From ATLASGAL to SEDIGISM: Towards a Complete 3D View of the Dense Galactic Interstellar Medium

NASA Astrophysics Data System (ADS)

Schuller, F.; Urquhart, J.; Bronfman, L.; Csengeri, T.; Bontemps, S.; Duarte-Cabral, A.; Giannetti, A.; Ginsburg, A.; Henning, T.; Immer, K.; Leurini, S.; Mattern, M.; Menten, K.; Molinari, S.; Muller, E.; Sánchez-Monge, A.; Schisano, E.; Suri, S.; Testi, L.; Wang, K.; Wyrowski, F.; Zavagno, A.

2016-09-01

The ATLASGAL survey has provided the first unbiased view of the inner Galactic Plane at sub-millimetre wavelengths. This is the largest ground-based survey of its kind to date, covering 420 square degrees at a wavelength of 870 µm. The reduced data, consisting of images and a catalogue of > 104 compact sources, are available from the ESO Science Archive Facility through the Phase 3 infrastructure. The extremely rich statistics of this survey initiated several follow-up projects, including spectroscopic observations to explore molecular complexity and high angular resolution imaging with the Atacama Large Millimeter/submillimeter Array (ALMA), aimed at resolving individual protostars. The most extensive follow-up project is SEDIGISM, a 3D mapping of the dense interstellar medium over a large fraction of the inner Galaxy. Some notable results of these surveys are highlighted.

Environmental Forcing of Super Typhoon Paka's (1997) Latent Heat Structure

NASA Technical Reports Server (NTRS)

Rodgers, Edward B.; Olson, William; Halverson, Jeff; Simpson, Joanne; Pierce, Harold

1999-01-01

The distribution and intensity of total (i.e., combined stratified and convective processes) rainrate/latent heat release (LHR) were derived for tropical cyclone Paka during the period 9-21 December, 1997 from the F-10, F-11, F-13, and F-14 Defense Meteorological Satellite Special Sensor Microwave/Imager and the Tropical Rain Measurement Mission Microwave Imager observations. These observations were frequent enough to capture three episodes of inner core convective bursts that preceded periods of rapid intensification and a convective rainband (CRB) cycle. During these periods of convective bursts, satellite sensors revealed that the rainrates/LHR: 1) increased within the inner eye wall region; 2) were mainly convectively generated (nearly a 65% contribution), 3) propagated inwards; 4) extended upwards within the middle and upper-troposphere, and 5) became electrically charged. These factors may have caused the eye wall region to become more buoyant within the middle and upper-troposphere, creating greater cyclonic angular momentum, and, thereby, warming the center and intensifying the system. Radiosonde measurements from Kwajalein Atoll and Guam, sea surface temperature observations, and the European Center for Medium Range Forecast analyses were used to examine the necessary and sufficient condition for initiating and maintaining these inner core convective bursts. For example, the necessary conditions such as the atmospheric thermodynamics (i.e., cold tropopause temperatures, moist troposphere, and warm SSTs [greater than 26 deg]) suggested that the atmosphere was ideal for Paka's maximum potential intensity (MPI) to approach super-typhoon strength. Further, Paka encountered weak vertical wind shear (less than 15 m/s ) before interacting with the westerlies on 21 December. The sufficient conditions, on the other hand, appeared to have some influence on Paka's convective burst, but the horizontal moisture flux convergence values in the outer core were weaker than some of the previously examined tropical cyclones. Also, the upper tropospheric outflow generation of eddy relative angular momentum flux convergence was 4D much less than that found during moderate tropical cyclone/trough interaction. These results indicated how important the external necessary condition and the internal forcing (i.e., CRB cycle) were in generating Paka's convective bursts as compared to the external sufficient forcing mechanisms found in higher latitude tropical cyclones. Later, as Paka began to interact with the westerlies, both the necessary (i.e., strong vertical shear and colder SSTs) and sufficient (i.e., dry air intrusion) external forcing mechanisms helped to decrease Paka's rainrate.

Environmental Forcing of Supertyphoon Paka's (1997) Latent Heat Structure.

NASA Astrophysics Data System (ADS)

Rodgers, Edward; Olson, William; Halverson, Jeff; Simpson, Joanne; Pierce, Harold

2000-12-01

The distribution and intensity of total (i.e., combined stratified and convective processes) rain rate/latent heat release (LHR) were derived for Tropical Cyclone Paka during the period 9-21 December 1997 from the F-10, F-11, F-13, and F-14 Defense Meteorological Satellite Special Sensor Microwave Imager and the Tropical Rainfall Measuring Mission Microwave Imager observations. These observations were frequent enough to capture three episodes of inner-core convective bursts and a convective rainband cycle that preceded periods of rapid intensification. During these periods of convective bursts, satellite sensors revealed that the rain rates/LHR 1) increased within the inner-core region, 2) were mainly convectively generated (nearly a 65% contribution), 3) propagated inward, 4) extended upward within the mid- and upper troposphere, and 5) became electrically charged. These factors may have increased the areal mean ascending motion in the mid- and upper-troposphere eyewall region, creating greater cyclonic angular momentum, and, thereby, warming the center and intensifying the system.Radiosonde measurements from Kwajalein Atoll and Guam, sea surface temperature observations, and the European Centre for Medium-Range Forecasts analyses were used to examine the necessary and sufficient conditions for initiating and maintaining these inner-core convective bursts. For example, the necessary conditions such as the atmospheric thermodynamics [i.e., cold tropopause temperatures, moist troposphere, and warm SSTs (>26°C)] fulfill the necessary conditions and suggested that the atmosphere was ideally suited for Paka's maximum potential intensity to approach supertyphoon strength. Further, Paka encountered moderate vertical wind shear (<15 m s1) before interacting with the westerlies on 21 December. The sufficient conditions that include horizontal moisture and the upper-tropospheric eddy relative angular momentum fluxes, on the other hand, appeared to have some influence on Paka's convective burst. However, the horizontal moisture flux convergence values in the outer core were weaker than some of the previously examined tropical cyclones. Also, the upper-tropospheric outflow generation of eddy relative angular momentum flux convergence was much less than that found during moderate tropical cyclone-trough interaction. These results indicated how important the external necessary condition and the internal forcing (i.e., convective rainband cycle) were in generating Paka's convective bursts as compared with the external sufficient forcing mechanisms found in higher-latitude tropical cyclones. Later, as Paka began to interact with the westerlies, both the necessary (i.e., strong vertical wind shear and colder SSTs) and sufficient (i.e., dry air intrusion) external forcing mechanisms helped to decrease Paka's rain rate.

Kinematic reversal schemes for the geomagnetic dipole.

NASA Technical Reports Server (NTRS)

Levy, E. H.

1972-01-01

Fluctuations in the distribution of cyclonic convective cells, in the earth's core, can reverse the sign of the geomagnetic field. Two kinematic reversal schemes are discussed. In the first scheme, a field maintained by cyclones concentrated at low latitude is reversed by a burst of cyclones at high latitude. Conversely, in the second scheme, a field maintained predominantly by cyclones in high latitudes is reversed by a fluctuation consisting of a burst of cyclonic convection at low latitude. The precise fluid motions which produce the geomagnetic field are not known. However, it appears that, whatever the details are, a fluctuation in the distribution of cyclonic cells over latitude can cause a geomagnetic reversal.

Statistical Aspects of the North Atlantic Basin Tropical Cyclones: Trends, Natural Variability, and Global Warming

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2007-01-01

Statistical aspects of the North Atlantic basin tropical cyclones for the interval 1945- 2005 are examined, including the variation of the yearly frequency of occurrence for various subgroups of storms (all tropical cyclones, hurricanes, major hurricanes, U.S. landfalling hurricanes, and category 4/5 hurricanes); the yearly variation of the mean latitude and longitude (genesis location) of all tropical cyclones and hurricanes; and the yearly variation of the mean peak wind speeds, lowest pressures, and durations for all tropical cyclones, hurricanes, and major hurricanes. Also examined is the relationship between inferred trends found in the North Atlantic basin tropical cyclonic activity and natural variability and global warming, the latter described using surface air temperatures from the Armagh Observatory Armagh, Northern Ireland. Lastly, a simple statistical technique is employed to ascertain the expected level of North Atlantic basin tropical cyclonic activity for the upcoming 2007 season.

Tropical cyclone rainfall area controlled by relative sea surface temperature

PubMed Central

Lin, Yanluan; Zhao, Ming; Zhang, Minghua

2015-01-01

Tropical cyclone rainfall rates have been projected to increase in a warmer climate. The area coverage of tropical cyclones influences their impact on human lives, yet little is known about how tropical cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that tropical cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the tropical mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between tropical cyclone size and mid-tropospheric relative humidity. Global statistics of tropical cyclone rainfall area are not expected to change markedly under a warmer climate provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates. PMID:25761457

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foltz, Gregory R.; Balaguru, Karthik; Leung, Lai-Yung R.

The impact of tropical cyclones on surface chlorophyll concentration is assessed in the western subtropical North Atlantic Ocean during 1998–2011. Previous studies in this area focused on individual cyclones and gave mixed results regarding the importance of tropical cyclone-induced mixing for changes in surface chlorophyll. Using a more integrated and comprehensive approach that includes quantification of cyclone-induced changes in mixed layer depth, here it is shown that accumulated cyclone energy explains 22% of the interannual variability in seasonally-averaged (June–November) chlorophyll concentration in the western subtropical North Atlantic, after removing the influence of the North Atlantic Oscillation (NAO). The variance explainedmore » by tropical cyclones is thus about 70% of that explained by the NAO, which has well-known impacts in this region. It is therefore likely that tropical cyclones contribute significantly to interannual variations of primary productivity in the western subtropical North Atlantic during the hurricane season.« less

The role of latent heat in kinetic energy conversions of South Pacific cyclones

NASA Technical Reports Server (NTRS)

Kann, Deirdre M.; Vincent, Dayton G.

1986-01-01

The four-dimensional behavior of cyclone systems in the South Pacific Convergence Zone (SPCZ) is analyzed. Three cyclone systems, which occurred during the period from January 10-16, 1979, are examined using the data collected during the first special observing period of the FGGE. The effects of latent heating on the life cycles of the cyclones are investigated. Particular attention is given to the conversions of eddy available potential energy to eddy kinetic energy and of mean kinetic energy to eddy kinetic energy. The net radiation profile, sensible heat flux, total field of vertical motion, and latent heat component were computed. The life cycles of the cyclones are described. It is observed that the latent heating component accounts for nearly all the conversion in the three cyclones, and latent heating within the SPCZ is the major source of eddy kinetic energy for the cyclones.

Associating extreme precipitation events to parent cyclones in gridded data

NASA Astrophysics Data System (ADS)

Rhodes, Ruari; Shaffrey, Len; Gray, Sue

2015-04-01

When analysing the relationship of regional precipitation to its parent cyclone, it is insufficient to consider the cyclone's region of influence as a fixed radius from the centre due to the irregular shape of rain bands. A new method is therefore presented which allows the use of objective feature tracking data in the analysis of regional precipitation. Utilising the spatial extent of precipitation in gridded datasets, the most appropriate cyclone(s) may be associated with regional precipitation events. This method is applied in the context of an analysis of the influence of clustering and stalling of extra-tropical cyclones in the North Atlantic on total precipitation accumulations over England and Wales. Cyclone counts and residence times are presented for historical records (ERA-Interim) and future projections (HadGEM2-ES) of extreme (> 98th percentile) precipitation accumulations over England and Wales, for accumulation periods ranging from one day to one month.

Growing Land-Sea Temperature Contrast and the Intensification of Arctic Cyclones

NASA Astrophysics Data System (ADS)

Day, Jonathan J.; Hodges, Kevin I.

2018-04-01

Cyclones play an important role in the coupled dynamics of the Arctic climate system on a range of time scales. Modeling studies suggest that storminess will increase in Arctic summer due to enhanced land-sea thermal contrast along the Arctic coastline, in a region known as the Arctic Frontal Zone (AFZ). However, the climate models used in these studies are poor at reproducing the present-day Arctic summer cyclone climatology and so their projections of Arctic cyclones and related quantities, such as sea ice, may not be reliable. In this study we perform composite analysis of Arctic cyclone statistics using AFZ variability as an analog for climate change. High AFZ years are characterized both by increased cyclone frequency and dynamical intensity, compared to low years. Importantly, the size of the response in this analog suggests that General Circulation Models may underestimate the response of Arctic cyclones to climate change, given a similar change in baroclinicity.

Collective Lamb Shift of a Nanoscale Atomic Vapor Layer within a Sapphire Cavity

NASA Astrophysics Data System (ADS)

Peyrot, T.; Sortais, Y. R. P.; Browaeys, A.; Sargsyan, A.; Sarkisyan, D.; Keaveney, J.; Hughes, I. G.; Adams, C. S.

2018-06-01

We measure the near-resonant transmission of light through a dense medium of potassium vapor confined in a cell with nanometer thickness in order to investigate the origin and validity of the collective Lamb shift. A complete model including the multiple reflections in the nanocell reproduces accurately the observed line shape. It allows the extraction of a density-dependent shift and width of the bulk atomic medium resonance, deconvolved from the cavity effect. We observe an additional, unexpected dependence of the shift with the thickness of the medium. This extra dependence demands further experimental and theoretical investigations.

Sea surface height evidence for long-term warming effects of tropical cyclones on the ocean

PubMed Central

Mei, Wei; Primeau, François; McWilliams, James C.; Pasquero, Claudia

2013-01-01

Tropical cyclones have been hypothesized to influence climate by pumping heat into the ocean, but a direct measure of this warming effect is still lacking. We quantified cyclone-induced ocean warming by directly monitoring the thermal expansion of water in the wake of cyclones, using satellite-based sea surface height data that provide a unique way of tracking the changes in ocean heat content on seasonal and longer timescales. We find that the long-term effect of cyclones is to warm the ocean at a rate of 0.32 ± 0.15 PW between 1993 and 2009, i.e., ∼23 times more efficiently per unit area than the background equatorial warming, making cyclones potentially important modulators of the climate by affecting heat transport in the ocean–atmosphere system. Furthermore, our analysis reveals that the rate of warming increases with cyclone intensity. This, together with a predicted shift in the distribution of cyclones toward higher intensities as climate warms, suggests the ocean will get even warmer, possibly leading to a positive feedback. PMID:23922393

Sea surface height evidence for long-term warming effects of tropical cyclones on the ocean.

PubMed

Mei, Wei; Primeau, François; McWilliams, James C; Pasquero, Claudia

2013-09-17

Tropical cyclones have been hypothesized to influence climate by pumping heat into the ocean, but a direct measure of this warming effect is still lacking. We quantified cyclone-induced ocean warming by directly monitoring the thermal expansion of water in the wake of cyclones, using satellite-based sea surface height data that provide a unique way of tracking the changes in ocean heat content on seasonal and longer timescales. We find that the long-term effect of cyclones is to warm the ocean at a rate of 0.32 ± 0.15 PW between 1993 and 2009, i.e., ∼23 times more efficiently per unit area than the background equatorial warming, making cyclones potentially important modulators of the climate by affecting heat transport in the ocean-atmosphere system. Furthermore, our analysis reveals that the rate of warming increases with cyclone intensity. This, together with a predicted shift in the distribution of cyclones toward higher intensities as climate warms, suggests the ocean will get even warmer, possibly leading to a positive feedback.

Testing coral-based tropical cyclone reconstructions: An example from Puerto Rico

USGS Publications Warehouse

Kilbourne, K. Halimeda; Moyer, Ryan P.; Quinn, Terrence M.; Grottoli, Andrea G.

2011-01-01

Complimenting modern records of tropical cyclone activity with longer historical and paleoclimatological records would increase our understanding of natural tropical cyclone variability on decadal to centennial time scales. Tropical cyclones produce large amounts of precipitation with significantly lower δ18O values than normal precipitation, and hence may be geochemically identifiable as negative δ18O anomalies in marine carbonate δ18O records. This study investigates the usefulness of coral skeletal δ18O as a means of reconstructing past tropical cyclone events. Isotopic modeling of rainfall mixing with seawater shows that detecting an isotopic signal from a tropical cyclone in a coral requires a salinity of ~ 33 psu at the time of coral growth, but this threshold is dependent on the isotopic composition of both fresh and saline end-members. A comparison between coral δ18O and historical records of tropical cyclone activity, river discharge, and precipitation from multiple sites in Puerto Rico shows that tropical cyclones are not distinguishable in the coral record from normal rainfall using this approach at these sites.

Is the poleward migration of tropical cyclone maximum intensity associated with a poleward migration of tropical cyclone genesis?

NASA Astrophysics Data System (ADS)

Daloz, Anne Sophie; Camargo, Suzana J.

2018-01-01

A recent study showed that the global average latitude where tropical cyclones achieve their lifetime-maximum intensity has been migrating poleward at a rate of about one-half degree of latitude per decade over the last 30 years in each hemisphere. However, it does not answer a critical question: is the poleward migration of tropical cyclone lifetime-maximum intensity associated with a poleward migration of tropical cyclone genesis? In this study we will examine this question. First we analyze changes in the environmental variables associated with tropical cyclone genesis, namely entropy deficit, potential intensity, vertical wind shear, vorticity, skin temperature and specific humidity at 500 hPa in reanalysis datasets between 1980 and 2013. Then, a selection of these variables is combined into two tropical cyclone genesis indices that empirically relate tropical cyclone genesis to large-scale variables. We find a shift toward greater (smaller) average potential number of genesis at higher (lower) latitudes over most regions of the Pacific Ocean, which is consistent with a migration of tropical cyclone genesis towards higher latitudes. We then examine the global best track archive and find coherent and significant poleward shifts in mean genesis position over the Pacific Ocean basins.

Spatially-explicit valuation of coastal wetlands for cyclone mitigation in Australia and China.

PubMed

Ouyang, Xiaoguang; Lee, Shing Yip; Connolly, Rod M; Kainz, Martin J

2018-02-14

Coastal wetlands are increasingly recognised for their pivotal role in mitigating the growing threats from cyclones (including hurricanes) in a changing climate. There is, however, insufficient information about the economic value of coastal wetlands for cyclone mitigation, particularly at regional scales. Analysis of data from 1990-2012 shows that the variation of cyclone frequencies is related to EI Niño strength in the Pacific Ocean adjacent to Australia, but not China. Among the cyclones hitting the two countries, there are significant relationships between the ratio of total economic damage to gross domestic production (TD/GDP) and wetland area within cyclone swaths in Australia, and wetland area plus minimum cyclone pressure despite a weak relationship in China. The TD/GDP ratio is significantly higher in China than in Australia. Despite their extensive and growing occurrence, seawalls in China appear not to play a critical role in cyclone mitigation, and cannot replace coastal wetlands, which provide other efficient ecosystem services. The economic values of coastal wetlands in Australia and China are respectively estimated at US$52.88 billion and 198.67 billion yr -1 for cyclone mitigation, albeit with large within-country geographic variation. This study highlights the urgency to integrate this value into existing valuations of coastal wetlands.

Synoptic and climatological aspects of extra-tropical cyclones

NASA Astrophysics Data System (ADS)

Leckebusch, G. C.

2010-09-01

Mid-latitude cyclones are highly complex dynamical features embedded in the general atmospheric circulation of the extra-tropics. Although the basic mechanisms leading to the formation of cyclones are commonly understood, the specific conditions and physical reasons triggering extreme, partly explosive development, are still under investigation. This includes also the identification of processes which might modulate the frequency and intensity of cyclone systems on time scales from days to centennials. This overview presentation will thus focus on three main topics: Firstly, the dynamic-synoptic structures of cyclones, the possibility to objectively identify cyclones and wind storms, and actual statistical properties of cyclone occurrence under recent climate conditions are addressed. In a second part, aspects of the interannual variability and its causing mechanisms are related to the seasonal predictability of extreme cyclones producing severe storm events. Extending the time frame will mean to deduce information on decadal or even centennial time periods. Thus, actual work to decadal as well as climatological variability and changes will be presented. In the last part of the talk focus will be laid on potential socio-economical impacts of changed cyclone occurrence. By means of global and regional climate modeling, future damages in terms of insured losses will be investigated and measures of uncertainty estimated from a multi-model ensemble analysis will be presented.

Serial clustering of extratropical cyclones and relationship with NAO and jet intensity based on the IMILAST cyclone database

NASA Astrophysics Data System (ADS)

Ulbrich, Sven; Pinto, Joaquim G.; Economou, Theodoros; Stephenson, David B.; Karremann, Melanie K.; Shaffrey, Len C.

2017-04-01

Cyclone families are a frequent synoptic weather feature in the Euro-Atlantic area, particularly during wintertime. Given appropriate large-scale conditions, such series (clusters) of storms may cause large socio-economic impacts and cumulative losses. Recent studies analyzing reanalysis data using single cyclone tracking methods have shown that serial clustering of cyclones occurs on both flanks and downstream regions of the North Atlantic storm track. Based on winter (DJF) cyclone counts from the IMILAST cyclone database, we explore the representation of serial clustering in the ERA-Interim period and its relationship with the NAO-phase and jet intensity. With this aim, clustering is estimated by the dispersion of winter (DJF) cyclone passages for each grid point over the Euro-Atlantic area. Results indicate that clustering over the Eastern North Atlantic and Western Europe can be identified for all methods, although the exact location and the dispersion magnitude may vary. The relationship between clustering and (i) the NAO-phase and (ii) jet intensity over the North Atlantic is statistically evaluated. Results show that the NAO-index and the jet intensity show a strong contribution to clustering, even though some spread is found between methods. We conclude that the general features of clustering of extratropical cyclones over the North Atlantic and Western Europe are robust to the choice of tracking method. The same is true for the influence of the NAO and jet intensity on cyclone dispersion.

Identification of a subtropical cyclone in the proximity of the Canary Islands and its analysis by numerical modeling

NASA Astrophysics Data System (ADS)

Quitián-Hernández, L.; Martín, M. L.; González-Alemán, J. J.; Santos-Muñoz, D.; Valero, F.

2016-09-01

Subtropical cyclones (STC) are low-pressure systems that share tropical and extratropical characteristics. Because of the great economic and social damage, the study of these systems has recently grown. This paper analyzes the cyclone formed in October 2014 near the Canary Islands and diagnoses such a cyclone in order to identify its correspondence to an STC category, examining its dynamical and thermal evolution. Diverse fields have been obtained from three different numerical models, and several diagnostic tools and cyclone phase space diagrams have been used. An extratropical cyclone, in its early stage, experimented a process of cut-off and isolation from the midlatitude flow. The incursion of a trough in conjunction with a low-level baroclinic zone favored the formation of the STC northwestern of the Canary Islands. Streamers of high potential vorticity linked to the cyclone favored strong winds and precipitation in the study domain. Cyclone phase space diagrams are used to complement the synoptic analysis and the satellite images of the cyclone to categorize such system. The diagrams reveal the transition from extratropical cyclone to STC remaining for several days with a subtropical structure with a quite broad action radius. The study of the mesoscale environment parameters showed an enhanced conditional instability through a deep troposphere layer. It is shown that moderate to strong vertical wind shear together with relatively warm sea surface temperature determine conditions enabling the development of long-lived convective structures.

Frequency changes of tropical cyclones during the last century recorded in a canyon of the northern Bay of Bengal

NASA Astrophysics Data System (ADS)

Kudrass, Hermann; Machalett, Björn; Palamenghi, Luisa; Meyer, Inka

2017-04-01

Frequent cyclones originating in the Bay of Bengal and landfall to the southern delta of the Ganges and Brahmaputra are well recorded in sediment cores from a canyon which deeply incises into the shelf and ends at the foreset beds of the submarine Ganges Brahmaputra delta. The large sediment supply by the two rivers during the monsoonal floods forms temporary deposits on the inner shelf, which are mobilized by waves and currents during the passage of cyclones. The resulting sand-silt-clay suspension forms high-density water masses, which plunge from the inner shelf into the shelf canyon, where they deposit graded beds evenly draping the broad canyon floor. A simple model was used to rank the historical known cyclones according to their capacity to transfer sediment from the submarine delta into the canyon. In a 362 cm-long sediment core ranging from the year 1985 to 2006, 48 graded beds can be correlated with the observed 41 cyclones. The cyclonic impact on the sediment transport has decreased by a factor of three during the last decade. The highest cyclonic impact occurred during the seventies. Compared to the sediment transfer by cyclones, the input by tidal currents and monsoonal floods is negligible. Thus cyclones are the dominating process for mobilizing and distributing sediment on the Bangladesh shelf and probably also on all shelf areas, which lie in the track of tropical cyclones.

Analysis of Tropical Cyclone Tracks in the North Indian Ocean

NASA Astrophysics Data System (ADS)

Patwardhan, A.; Paliwal, M.; Mohapatra, M.

2011-12-01

Cyclones are regarded as one of the most dangerous meteorological phenomena of the tropical region. The probability of landfall of a tropical cyclone depends on its movement (trajectory). Analysis of trajectories of tropical cyclones could be useful for identifying potentially predictable characteristics. There is long history of analysis of tropical cyclones tracks. A common approach is using different clustering techniques to group the cyclone tracks on the basis of certain characteristics. Various clustering method have been used to study the tropical cyclones in different ocean basins like western North Pacific ocean (Elsner and Liu, 2003; Camargo et al., 2007), North Atlantic Ocean (Elsner, 2003; Gaffney et al. 2007; Nakamura et al., 2009). In this study, tropical cyclone tracks in the North Indian Ocean basin, for the period 1961-2010 have been analyzed and grouped into clusters based on their spatial characteristics. A tropical cyclone trajectory is approximated as an open curve and described by its first two moments. The resulting clusters have different centroid locations and also differently shaped variance ellipses. These track characteristics are then used in the standard clustering algorithms which allow the whole track shape, length, and location to be incorporated into the clustering methodology. The resulting clusters have different genesis locations and trajectory shapes. We have also examined characteristics such as life span, maximum sustained wind speed, landfall, seasonality, many of which are significantly different across the identified clusters. The clustering approach groups cyclones with higher maximum wind speed and longest life span in to one cluster. Another cluster includes short duration cyclonic events that are mostly deep depressions and significant for rainfall over Eastern and Central India. The clustering approach is likely to prove useful for analysis of events of significance with regard to impacts.

Southern Hemisphere Extratropical Cyclones and their Relationship with ENSO in springtime

NASA Astrophysics Data System (ADS)

Reboita, M. S.; Ambrizzi, T.; Da Rocha, R.

2013-05-01

Extratropical cyclones occurrence is associated with the teleconnection mechanisms that produce climate variability. Among these mechanisms we have El Niño-Southern Oscillation (ENSO). Some works have indicated that during the ENSO positive phase there are more cyclogenetic conditions in some parts of the globe as the southwest of South Atlantic Ocean. Therefore, the purpose of this study is to verify if the extratropical cyclones number and location are altered in the different ENSO phases in the austral spring over the Southern Hemisphere (SH). The Melbourne University automatic tracking scheme was used to determine the cyclone climatology from 1980 to 2012. All cyclones that appear with lifetime higher or equal to 24 hours in the sea level pressure data from National Centers for Environment Prediction reanalysis I were included in the climatology. El Niño (EN), La Niña (LN) and Neutral (N) years were identified through the Oceanic Niño Index (ONI) from Climate Prediction Center/NOAA. The average number of cyclones in the spring over the SH is similar in the EN (200), N (184) and LN (197) episodes. By latitude bands, during EN episodes the cyclones occurrence reduces in 16% between 70-60 degrees and increases in ~15% between 80-70 and 50-40 degrees. On the other hand, during the LN episodes, the cyclones are 17% more frequent in 50-60 degrees and 22% less frequent in 30-20 degrees. One more detailed analysis of the cyclones trajectory density (that is a statistic product of the tracking algorithm) shows that in the South Atlantic Ocean, near the southeast of South America, the number of cyclones in EN years is higher than in the neutral period and lower than in the LN years. In the Indian Ocean, the EN year is characterized by a cyclones reduction in the west and east sector, near the continents. In the Pacific Ocean, the region southward the New Zealand presents more cyclones occurrence in EN years.

The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves

PubMed Central

Zhang, Jinlun; Ashjian, Carin; Campbell, Robert; Hill, Victoria; Spitz, Yvette H; Steele, Michael

2014-01-01

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink. PMID:26213671

The great 2012 Arctic Ocean summer cyclone enhanced biological productivity on the shelves.

PubMed

Zhang, Jinlun; Ashjian, Carin; Campbell, Robert; Hill, Victoria; Spitz, Yvette H; Steele, Michael

2014-01-01

[1] A coupled biophysical model is used to examine the impact of the great Arctic cyclone of early August 2012 on the marine planktonic ecosystem in the Pacific sector of the Arctic Ocean (PSA). Model results indicate that the cyclone influences the marine planktonic ecosystem by enhancing productivity on the shelves of the Chukchi, East Siberian, and Laptev seas during the storm. Although the cyclone's passage in the PSA lasted only a few days, the simulated biological effects on the shelves last 1 month or longer. At some locations on the shelves, primary productivity (PP) increases by up to 90% and phytoplankton biomass by up to 40% in the wake of the cyclone. The increase in zooplankton biomass is up to 18% on 31 August and remains 10% on 15 September, more than 1 month after the storm. In the central PSA, however, model simulations indicate a decrease in PP and plankton biomass. The biological gain on the shelves and loss in the central PSA are linked to two factors. (1) The cyclone enhances mixing in the upper ocean, which increases nutrient availability in the surface waters of the shelves; enhanced mixing in the central PSA does not increase productivity because nutrients there are mostly depleted through summer draw down by the time of the cyclone's passage. (2) The cyclone also induces divergence, resulting from the cyclone's low-pressure system that drives cyclonic sea ice and upper ocean circulation, which transports more plankton biomass onto the shelves from the central PSA. The simulated biological gain on the shelves is greater than the loss in the central PSA, and therefore, the production on average over the entire PSA is increased by the cyclone. Because the gain on the shelves is offset by the loss in the central PSA, the average increase over the entire PSA is moderate and lasts only about 10 days. The generally positive impact of cyclones on the marine ecosystem in the Arctic, particularly on the shelves, is likely to grow with increasing summer cyclone activity if the Arctic continues to warm and the ice cover continues to shrink.

EFFECT OF ACTIVE ACCUMULATION OF CALCIUM AND PHOSPHATE IONS ON THE STRUCTURE OF RAT LIVER MITOCHONDRIA

PubMed Central

Greenawalt, John W.; Rossi, Carlo S.; Lehninger, Albert L.

1964-01-01

Rat liver mitochondria allowed to accumulate maximal amounts of Ca++ and HPO4 = ions from the suspending medium in vitro during respiration have a considerably higher specific gravity than normal mitochondria and may be easily separated from the latter by isopycnic centrifugation in density gradients of sucrose or cesium chloride. When the mitochondria are allowed to accumulate less than maximal amounts of Ca++ and HPO4 = from the medium, they have intermediate specific gravities which are roughly proportional to their content of calcium phosphate. Maximally "loaded" mitochondria are relatively homogeneous with respect to specific gravity. Correlated biochemical and electron microscopic studies show that Ca++-loaded mitochondria contain numerous dense granules, of which some 85 per cent are over 500 A in diameter. These granules are electron-opaque not only following fixation and staining with heavy metal reagents, but also following fixation with formaldehyde, demonstrating that the characteristic granules in Ca++-loaded mitochondria have intrinsic electron-opacity. The dense granules are almost always located within the inner compartment of the mitochondria and not in the space between the inner and outer membranes. They are frequently located at or near the cristae and they often show electron-transparent "cores." Such granules appear to be made up of clusters of smaller dense particles, but preliminary x-ray diffraction analysis and electron diffraction studies have revealed no evidence of crystallinity in the deposits. The electron-opaque granules decrease in number when the Ca++-loaded mitochondria are incubated with 2,4-dinitrophenol; simultaneously there is discharge of Ca++ and phosphate from the mitochondria into the medium. PMID:14228516

Holographic Imaging In Dense Artificial Fog

NASA Technical Reports Server (NTRS)

Liu, Hua-Kuang; Marzwell, Neville

1996-01-01

Artificial fog serves as volume-projection medium for display of three-dimensional image. Projection technique enables display of images for variety of purposes, possibly including entertainment, indoor and outdoor advertising, medical diagnostics and image representations for surgical procedures, and education.

40 CFR 63.11623 - What are the testing requirements?

Code of Federal Regulations, 2010 CFR

2010-07-01

...? (a) If you are demonstrating that the cyclone required by § 63.11621(e) is designed to reduce... A to part 60 to determine the particulate matter mass rate at the inlet and outlet of the cyclone. You must conduct at least three runs at the cyclone inlet and three runs at the cyclone outlet. Each...

40 CFR 63.11623 - What are the testing requirements?

Code of Federal Regulations, 2011 CFR

2011-07-01

...? (a) If you are demonstrating that the cyclone required by § 63.11621(e) is designed to reduce... A to part 60 to determine the particulate matter mass rate at the inlet and outlet of the cyclone. You must conduct at least three runs at the cyclone inlet and three runs at the cyclone outlet. Each...

Properties and circulation of Jupiter's circumpolar cyclones as measured by JunoCam

NASA Astrophysics Data System (ADS)

Orton, G. S.; Eichstaedt, G.; Rogers, J. H.; Hansen, C. J.; Caplinger, M.; Momary, T.; Tabataba-Vakili, F.; Intersoll, A. P.

2017-09-01

JunoCam has taken the first high-resolution visible images of Jupiter's poles, which show that each pole has a cluster of circumpolar cyclones, each one separated in longitude by roughly equal spacing. There are five at the south pole and eight at the north pole. These configurations, including their asymmetries and the characteristics of individual cyclones, have remained stable over 7 months from perijove 1 to perijove 5 as of this writing. Each cyclone has a circular outline with a prominent system of trailing spiral arms. In the north, the internal morphology of adjacent cyclones alternates from one to the next. Angular motions within each cyclone appear to be similar to each other but quite different from vortices at lower latitudes.

The Human Impact of Tropical Cyclones: a Historical Review of Events 1980-2009 and Systematic Literature Review

PubMed Central

Doocy, Shannon; Dick, Anna; Daniels, Amy; Kirsch, Thomas D.

2013-01-01

Background. Cyclones have significantly affected populations in Southeast Asia, the Western Pacific, and the Americas over the past quarter of a century. Future vulnerability to cyclones will increase due to factors including population growth, urbanization, increasing coastal settlement, and global warming. The objectives of this review were to describe the impact of cyclones on human populations in terms of mortality, injury, and displacement and, to the extent possible, identify risk factors associated with these outcomes. This is one of five reviews on the human impact of natural disasters. Methods. Data on the impact of cyclones were compiled using two methods, a historical review from 1980 to 2009 of cyclone events from multiple databases and a systematic literature review of publications ending in October 2012. Analysis included descriptive statistics and bivariate tests for associations between cyclone characteristics and mortality using Stata 11.0. Findings. There were 412,644 deaths, 290,654 injured, and 466.1 million people affected by cyclones between 1980 and 2009, and the mortality and injury burden was concentrated in less developed nations of Southeast Asia and the Western Pacific. Inconsistent reporting suggests this is an underestimate, particularly in terms of the injured and affected populations. The primary cause of cyclone-related mortality is drowning; in developed countries male gender was associated with increased mortality risk, whereas females experienced higher mortality in less developed countries. Conclusions. Additional attention to preparedness and early warning, particularly in Asia, can lessen the impact of future cyclones. PMID:23857074

Aerosol midlatitude cyclone indirect effects in observations and high-resolution simulations

NASA Astrophysics Data System (ADS)

McCoy, Daniel T.; Field, Paul R.; Schmidt, Anja; Grosvenor, Daniel P.; Bender, Frida A.-M.; Shipway, Ben J.; Hill, Adrian A.; Wilkinson, Jonathan M.; Elsaesser, Gregory S.

2018-04-01

Aerosol-cloud interactions are a major source of uncertainty in inferring the climate sensitivity from the observational record of temperature. The adjustment of clouds to aerosol is a poorly constrained aspect of these aerosol-cloud interactions. Here, we examine the response of midlatitude cyclone cloud properties to a change in cloud droplet number concentration (CDNC). Idealized experiments in high-resolution, convection-permitting global aquaplanet simulations with constant CDNC are compared to 13 years of remote-sensing observations. Observations and idealized aquaplanet simulations agree that increased warm conveyor belt (WCB) moisture flux into cyclones is consistent with higher cyclone liquid water path (CLWP). When CDNC is increased a larger LWP is needed to give the same rain rate. The LWP adjusts to allow the rain rate to be equal to the moisture flux into the cyclone along the WCB. This results in an increased CLWP for higher CDNC at a fixed WCB moisture flux in both observations and simulations. If observed cyclones in the top and bottom tercile of CDNC are contrasted it is found that they have not only higher CLWP but also cloud cover and albedo. The difference in cyclone albedo between the cyclones in the top and bottom third of CDNC is observed by CERES to be between 0.018 and 0.032, which is consistent with a 4.6-8.3 Wm-2 in-cyclone enhancement in upwelling shortwave when scaled by annual-mean insolation. Based on a regression model to observed cyclone properties, roughly 60 % of the observed variability in CLWP can be explained by CDNC and WCB moisture flux.

Hurricanes and Climate: The U.S. CLIVAR Working Group on Hurricanes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walsh, Kevin J. E.; Camargo, Suzana J.; Vecchi, Gabriel A.

While a quantitative climate theory of tropical cyclone formation remains elusive, considerable progress has been made recently in our ability to simulate tropical cyclone climatologies and to understand the relationship between climate and tropical cyclone formation. Climate models are now able to simulate a realistic rate of global tropical cyclone formation, although simulation of the Atlantic tropical cyclone climatology remains challenging unless horizontal resolutions finer than 50 km are employed. This article summarizes published research from the idealized experiments of the Hurricane Working Group of U.S. Climate and Ocean: Variability, Predictability and Change (CLIVAR). This work, combined with results frommore » other model simulations, has strengthened relationships between tropical cyclone formation rates and climate variables such as midtropospheric vertical velocity, with decreased climatological vertical velocities leading to decreased tropical cyclone formation. Systematic differences are shown between experiments in which only sea surface temperature is increased compared with experiments where only atmospheric carbon dioxide is increased. Experiments where only carbon dioxide is increased are more likely to demonstrate a decrease in tropical cyclone numbers, similar to the decreases simulated by many climate models for a future, warmer climate. Experiments where the two effects are combined also show decreases in numbers, but these tend to be less for models that demonstrate a strong tropical cyclone response to increased sea surface temperatures. Lastly, further experiments are proposed that may improve our understanding of the relationship between climate and tropical cyclone formation, including experiments with two-way interaction between the ocean and the atmosphere and variations in atmospheric aerosols.« less

Multiple Satellite Observations of Cloud Cover in Extratropical Cyclones

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Booth, James F.; Posselt, Derek J.; van den Heever, Susan C.

2013-01-01

Using cloud observations from NASA Moderate Resolution Imaging Spectroradiometer, Multiangle Imaging Spectroradiometer, and CloudSat-CALIPSO, composites of cloud fraction in southern and northern hemisphere extratropical cyclones are obtained for cold and warm seasons between 2006 and 2010, to assess differences between these three data sets, and between summer and winter cyclones. In both hemispheres and seasons, over the open ocean, the cyclone-centered cloud fraction composites agree within 5% across the three data sets, but behind the cold fronts, or over sea ice and land, the differences are much larger. To supplement the data set comparison and learn more about the cyclones, we also examine the differences in cloud fraction between cold and warm season for each data set. The difference in cloud fraction between cold and warm season southern hemisphere cyclones is small for all three data sets, but of the same order of magnitude as the differences between the data sets. The cold-warm season contrast in northern hemisphere cyclone cloud fractions is similar for all three data sets: in the warm sector, the cold season cloud fractions are lower close to the low, but larger on the equator edge than their warm season counterparts. This seasonal contrast in cloud fraction within the cyclones warm sector seems to be related to the seasonal differences in moisture flux within the cyclones. Our analysis suggests that the three different data sets can all be used confidently when studying the warm sector and warm frontal zone of extratropical cyclones but caution should be exerted when studying clouds in the cold sector.

Hurricanes and Climate: The U.S. CLIVAR Working Group on Hurricanes

DOE PAGES

Walsh, Kevin J. E.; Camargo, Suzana J.; Vecchi, Gabriel A.; ...

2015-06-01

While a quantitative climate theory of tropical cyclone formation remains elusive, considerable progress has been made recently in our ability to simulate tropical cyclone climatologies and to understand the relationship between climate and tropical cyclone formation. Climate models are now able to simulate a realistic rate of global tropical cyclone formation, although simulation of the Atlantic tropical cyclone climatology remains challenging unless horizontal resolutions finer than 50 km are employed. This article summarizes published research from the idealized experiments of the Hurricane Working Group of U.S. Climate and Ocean: Variability, Predictability and Change (CLIVAR). This work, combined with results frommore » other model simulations, has strengthened relationships between tropical cyclone formation rates and climate variables such as midtropospheric vertical velocity, with decreased climatological vertical velocities leading to decreased tropical cyclone formation. Systematic differences are shown between experiments in which only sea surface temperature is increased compared with experiments where only atmospheric carbon dioxide is increased. Experiments where only carbon dioxide is increased are more likely to demonstrate a decrease in tropical cyclone numbers, similar to the decreases simulated by many climate models for a future, warmer climate. Experiments where the two effects are combined also show decreases in numbers, but these tend to be less for models that demonstrate a strong tropical cyclone response to increased sea surface temperatures. Lastly, further experiments are proposed that may improve our understanding of the relationship between climate and tropical cyclone formation, including experiments with two-way interaction between the ocean and the atmosphere and variations in atmospheric aerosols.« less

A study on raindrop size distribution variability in before and after landfall precipitations of tropical cyclones observed over southern India

NASA Astrophysics Data System (ADS)

Janapati, Jayalakshmi; seela, Balaji Kumar; Reddy M., Venkatrami; Reddy K., Krishna; Lin, Pay-Liam; Rao T., Narayana; Liu, Chian-Yi

2017-06-01

Raindrop size distribution (RSD) characteristics in before landfall (BLF) and after landfall (ALF) of three tropical cyclones (JAL, THANE, and NILAM) induced precipitations are investigated by using a laser-based (PARticleSIze and VELocity - PARSIVEL) disdrometer at two different locations [Kadapa (14.47°N, 78.82°E) and Gadanki (13.5°N, 79.2°E)] in semi-arid region of southern India. In both BLF and ALF precipitations of these three cyclones, convective precipitations have higher mass weighted mean diameter (Dm) and lower normalized intercept parameter (log10Nw) values than stratiform precipitations. The radar reflectivity (Z) and rain rate (R) relations (Z=A*Rb) showed distinct variations in BLF and ALF precipitations of three cyclones. BLF precipitation of JAL cyclone has a higher Dm than ALF precipitation. Whereas, for THANE and NILAM cyclones ALF precipitations have higher Dm than BLF. The Dm values of three cyclones (both in BLF and ALF) are smaller than the Dm values of the other (Atlantic and Pacific) oceanic cyclones. Interaction of different regions (eyewall, inner rainbands, and outer rainbands) of cyclones with the environment and underlying surface led to RSD variations between BLF and ALF precipitations through different microphysical (collision-coalescence, breakup, evaporation, and riming) processes. The immediate significance of the present work is that (i) it contributes to our understanding of cyclone RSD in BLF and ALF precipitations, and (ii) it provides the useful information for quantitative estimation of rainfall from Doppler weather radar observations.

A satellite observational and numerical study of precipitation characteristics in western North Atlantic tropical cyclones

NASA Technical Reports Server (NTRS)

Rodgers, Edward B.; Chang, Simon W.; Pierce, Harold F.

1994-01-01

Special Sensor Microwave/Imager (SSM/I) observations were used to examine the spatial and temporal changes of the precipitation characteristics of tropical cyclones. SSM/I observations were also combined with the results of a tropical cyclone numerical model to examine the role of inner-core diabatic heating in subsequent intensity changes of tropical cyclones. Included in the SSM/I observations were rainfall characteristics of 18 named western North Atlantic tropical cyclones between 1987 and 1989. The SSM/I rain-rate algorithm that employed the 85-GHz channel provided an analysis of the rain-rate distribution in greater detail. However, the SSM/I algorithm underestimated the rain rates when compared to in situ techniques but appeared to be comparable to the rain rates obtained from other satellite-borne passive microwave radiometers. The analysis of SSM/I observations found that more intense systems had higher rain rates, more latent heat release, and a greater contribution from heavier rain to the total tropical cyclone rainfall. In addition, regions with the heaviest rain rates were found near the center of the most intense tropical cyclones. Observational analysis from SSM/I also revealed that the greatest rain rates in the inner-core regions were found in the right half of fast-moving cyclones, while the heaviest rain rates in slow-moving tropical cyclones were found in the forward half. The combination of SSM/I observations and an interpretation of numerical model simulations revealed that the correlation between changes in the inner core diabetic heating and the subsequent intensity became greater as the tropical cyclones became more intense.

Evaluation of Extratropical Cyclone Precipitation in the North Atlantic Basin: An analysis of ERA-Interim, WRF, and two CMIP5 models.

PubMed

Booth, James F; Naud, Catherine M; Willison, Jeff

2018-03-01

The representation of extratropical cyclones (ETCs) precipitation in general circulation models (GCMs) and a weather research and forecasting (WRF) model is analyzed. This work considers the link between ETC precipitation and dynamical strength and tests if parameterized convection affects this link for ETCs in the North Atlantic Basin. Lagrangian cyclone tracks of ETCs in ERA-Interim reanalysis (ERAI), the GISS and GFDL CMIP5 models, and WRF with two horizontal resolutions are utilized in a compositing analysis. The 20-km resolution WRF model generates stronger ETCs based on surface wind speed and cyclone precipitation. The GCMs and ERAI generate similar composite means and distributions for cyclone precipitation rates, but GCMs generate weaker cyclone surface winds than ERAI. The amount of cyclone precipitation generated by the convection scheme differs significantly across the datasets, with GISS generating the most, followed by ERAI and then GFDL. The models and reanalysis generate relatively more parameterized convective precipitation when the total cyclone-averaged precipitation is smaller. This is partially due to the contribution of parameterized convective precipitation occurring more often late in the ETC life cycle. For reanalysis and models, precipitation increases with both cyclone moisture and surface wind speed, and this is true if the contribution from the parameterized convection scheme is larger or not. This work shows that these different models generate similar total ETC precipitation despite large differences in the parameterized convection, and these differences do not cause unexpected behavior in ETC precipitation sensitivity to cyclone moisture or surface wind speed.

The contribution of sting-jet windstorms to extreme wind risk in the North Atlantic

NASA Astrophysics Data System (ADS)

Hart, Neil C.; Gray, Suzanne L.; Clark, Peter A.

2016-04-01

Windstorms are a major winter weather risk for many countries in Europe. These storms are predominantly associated with explosively-developing extratropical cyclones that track across the region. A substantial body of literature exists on the synoptic-scale dynamics, predictability and climatology of such storms. More recently, interest in the mesoscale variability of the most damaging winds has led to a focus on the role of sting jets in enhancing windstorm severity. We present a present-era climatology of North Atlantic cyclones that had potential to produce sting jets. Considering only explosively-developing cyclones, those with sting-jet potential are more likely to have higher relative vorticity and associated low-level wind maxima. Furthermore, the strongest winds for sting-jet cyclones are more often in the cool sector, behind the cold front, when compared with other explosively-developing cyclones which commonly have strong warm-sector winds too. The tracks of sting-jet cyclones, and explosively-developing cyclones in general, show little offset from the climatological storm track. While rare over Europe, sting-jet cyclones are relatively frequent within the main storm track with up to one third of extratropical cyclones exhibiting sting-jet potential. Thus, the rarity and, until recently, lack of description of sting-jet windstorms is more due to the climatological storm track location away from highly-populated land masses, than due to an actual rarity of such storms in nature.

Model finds bigger, stronger tropical cyclones with warming seas

NASA Astrophysics Data System (ADS)

Schultz, Colin

2014-03-01

In the wake of powerful tropical cyclones such as Hurricanes Sandy and Katrina and Typhoon Haiyan, questions about the likely effect of climate change on tropical cyclone activity are on the public's mind. The interactions between global warming and cyclone activity, however, are complex, with rising sea surface temperatures, changing energy distributions, and altered atmospheric dynamics all having some effect.

A Climatological Study of Hurricane Force Extratropical Cyclones

DTIC Science & Technology

2012-03-01

extratropical cyclone by months in the Pacific basin. Most of the storms occur from October through March...hurricane force extratropical cyclone. Starting from left to right; the first column is the storm name, second column is the year, month, day, hour (UTC...2000 through 2007 illustrates that the number of hurricane-force extratropical cyclones is quite significant: approximately 500 storms , nearly evenly

A Composite Diagnosis of Synoptic-Scale Extratropical Cyclone Development over the United States

NASA Technical Reports Server (NTRS)

Rolfson, Donald M.; Smith, Phillip J.

1996-01-01

This paper presents a composite diagnosis of synoptic-scale forcing mechanisms associated with extratropical cyclone evolution. Drawn from 12 cyclone cases that occurred over the continental United States during the cool season months, the diagnosis provides a 'climatology' of development mechanisms for difference categories of cyclone evolution ranging from cyclone weakening through three stages of cyclone intensification. Computational results were obtained using an 'extended' form of the Zwack-Okossi equation applied to routine upper-air and surface data analyzed on a 230 km x 230 km grid. Results show that cyclonic vorticity advection, which maximizes in the upper troposphere, was the primary contributor to cyclone development regardless of the stage of development. A second consistent contributor to development was latent heat release. Horizontal temperature advection, often acknowledged as a development mechanism, was found to contribute to development only during more intense stages. During weakening and weaker development stages, temperature advection opposed development, as the warm-air advection invariably found at upper levels was dominated by cold air advection in the lower half of the troposphere. In the more intense stages, development was moderated by dry-adiabatic cooling associated with the ascending vertical motions.

Scale-dependent cyclone-anticyclone asymmetry in a forced rotating turbulence experiment

NASA Astrophysics Data System (ADS)

Gallet, B.; Campagne, A.; Cortet, P.-P.; Moisy, F.

2014-03-01

We characterize the statistical and geometrical properties of the cyclone-anticyclone asymmetry in a statistically steady forced rotating turbulence experiment. Turbulence is generated by a set of vertical flaps which continuously inject velocity fluctuations towards the center of a tank mounted on a rotating platform. We first characterize the cyclone-anticyclone asymmetry from conventional single-point vorticity statistics. We propose a phenomenological model to explain the emergence of the asymmetry in the experiment, from which we predict scaling laws for the root-mean-square velocity in good agreement with the experimental data. We further quantify the cyclone-anticyclone asymmetry using a set of third-order two-point velocity correlations. We focus on the correlations which are nonzero only if the cyclone-anticyclone symmetry is broken. They offer two advantages over single-point vorticity statistics: first, they are defined from velocity measurements only, so an accurate resolution of the Kolmogorov scale is not required; second, they provide information on the scale-dependence of the cyclone-anticyclone asymmetry. We compute these correlation functions analytically for a random distribution of independent identical vortices. These model correlations describe well the experimental ones, indicating that the cyclone-anticyclone asymmetry is dominated by the large-scale long-lived cyclones.

The influence of local sea surface temperatures on Australian east coast cyclones

NASA Astrophysics Data System (ADS)

Pepler, Acacia S.; Alexander, Lisa V.; Evans, Jason P.; Sherwood, Steven C.

2016-11-01

Cyclones are a major cause of rainfall and extreme weather in the midlatitudes and have a preference for genesis and explosive development in areas where a warm western boundary current borders a continental landmass. While there is a growing body of work on how extratropical cyclones are influenced by the Gulf Stream and Kuroshio Current in the Northern Hemisphere, there is little understanding of similar regions in the Southern Hemisphere including the Australian east coast, where cyclones that develop close to the coast are the main cause of severe weather and coastal flooding. This paper quantifies the impact of east Australian sea surface temperatures (SSTs) on local cyclone activity and behavior, using three different sets of sea surface temperature boundary conditions during the period 2007-2008 in an ensemble of Weather Research and Forecasting Model physics parameterizations. Coastal sea surface temperatures are demonstrated to have a significant impact on the overall frequency of cyclones in this region, with warmer SSTs acting as a trigger for the intensification of weak or moderate cyclones, particularly those of a subtropical nature. However, sea surface temperatures play only a minor role in the most intense cyclones, which are dominated by atmospheric conditions.

Chemistry and Evolution of Interstellar Clouds

NASA Technical Reports Server (NTRS)

Wooden, D. H.; Charnley, S. B.; Ehrenfreund, P.

2003-01-01

In this chapter we describe how elements have been and are still being formed in the galaxy and how they are transformed into the reservoir of materials present at the time of formation of our protosolar nebula. We discuss the global cycle of matter, beginning at its formation site in stars, where it is ejected through winds and explosions into the diffuse interstellar medium. In the next stage of the global cycle occurs in cold, dense molecular clouds, where the complexity of molecules and ices increases relative to the diffuse ISM.. When a protostar forms in a dense core within a molecular cloud, it heats the surrounding infalling matter warms and releases molecules from the solid phase into the gas phase in a warm, dense core, sponsoring a rich gas-phase chemistry. Some material from the cold and warm regions within molecular clouds probably survives as interstellar matter in the protostellar disk. For the diffuse ISM, for cold, dense clouds, and for dense-warm cores, the physio-chemical processes that occur within the gas and solid phases are discussed in detail.

Buoyancy and shear characteristics of hurricane-tornado environments

NASA Technical Reports Server (NTRS)

Mccaul, Eugene W., Jr.

1991-01-01

This study presents detailed composite profiles of temperature, moisture, and wind constructed for tornado environments in tropical cyclones that affected the U.S. between 1948 and 1986. Winds are composited in components radial and tangential to the tropical cyclone center at observation time. Guided by observed patterns of tornado occurrence, composites are constructed for a variety of different stratifications of the data, including proximity to tornadoes, position relative to the cyclone center, time of day, time after cyclone landfall, cyclone translation speed, and landfall location. The composites are also compared to composite soundings from Great Plains tornado environments. A variety of sounding parameters are examined to see which are most closely related to the tornado distribution patterns. Lower-tropospheric vertical shears are found to be stronger in the tropical cyclone tornado environments than on the Great Plains. Buoyancy for the tropical cyclone tornado cases is much smaller than that seen with Great Plains tornado events and exhibits a weak negative correlation with tornado outbreak severity.

Observational study of upper ocean cooling due to Phet super cyclone in the Arabian Sea

NASA Astrophysics Data System (ADS)

Muni Krishna, K.

2016-05-01

Phet super cyclone (31 May-7 June 2010) was the most intense and also the rarest of the rare track in Arabian Sea as per the recorded history during 1877-2009. The present study focuses on the ocean physical responses to Phet cyclone using satellite and Argo observations. The sea surface temperature is decreased to 6 °C with an approximately 350 km long and 100 km width area in the Arabian Sea after the cyclone passage. The translation speed of cyclone is 3.86 m/s, the mixed layer is 79 m, and thermocline displacement is 13 m at the cooling area. With the relationship of wind stress curl and Ekman pumping velocity (EPV), the author found that the speed of EPV was increased after the passage of cyclone. So the extent of the SST drop was probably due to the moving speed of cyclone and the depth of the mixed layer.

Persistent northward North Atlantic tropical cyclone track migration over the past five centuries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baldini, Lisa M.; Baldini, James U. L.; McElwaine, Jim N.

Accurately predicting future tropical cyclone risk requires understanding the fundamental controls on tropical cyclone dynamics. Here we present an annually-resolved 450-year reconstruction of western Caribbean tropical cyclone activity developed using a new coupled carbon and oxygen isotope ratio technique in an exceptionally well-dated stalagmite from Belize. Western Caribbean tropical cyclone activity peaked at 1650 A.D., coincident with maximum Little Ice Age cooling, and decreased gradually until the end of the record in 1983. Considered with other reconstructions, the new record suggests that the mean track of Cape Verde tropical cyclones shifted gradually north-eastward from the western Caribbean toward the Northmore » American east coast over the last 450 years. Since ~1870 A.D., these shifts were largely driven by anthropogenic greenhouse gas and sulphate aerosol emissions. In conclusion, our results strongly suggest that future emission scenarios will result in more frequent tropical cyclone impacts on the financial and population centres of the northeastern United States.« less

Persistent northward North Atlantic tropical cyclone track migration over the past five centuries

NASA Astrophysics Data System (ADS)

Baldini, Lisa M.; Baldini, James U. L.; McElwaine, Jim N.; Frappier, Amy Benoit; Asmerom, Yemane; Liu, Kam-Biu; Prufer, Keith M.; Ridley, Harriet E.; Polyak, Victor; Kennett, Douglas J.; MacPherson, Colin G.; Aquino, Valorie V.; Awe, Jaime; Breitenbach, Sebastian F. M.

2016-11-01

Accurately predicting future tropical cyclone risk requires understanding the fundamental controls on tropical cyclone dynamics. Here we present an annually-resolved 450-year reconstruction of western Caribbean tropical cyclone activity developed using a new coupled carbon and oxygen isotope ratio technique in an exceptionally well-dated stalagmite from Belize. Western Caribbean tropical cyclone activity peaked at 1650 A.D., coincident with maximum Little Ice Age cooling, and decreased gradually until the end of the record in 1983. Considered with other reconstructions, the new record suggests that the mean track of Cape Verde tropical cyclones shifted gradually north-eastward from the western Caribbean toward the North American east coast over the last 450 years. Since ~1870 A.D., these shifts were largely driven by anthropogenic greenhouse gas and sulphate aerosol emissions. Our results strongly suggest that future emission scenarios will result in more frequent tropical cyclone impacts on the financial and population centres of the northeastern United States.

Persistent northward North Atlantic tropical cyclone track migration over the past five centuries

DOE PAGES

Baldini, Lisa M.; Baldini, James U. L.; McElwaine, Jim N.; ...

2016-11-23

Accurately predicting future tropical cyclone risk requires understanding the fundamental controls on tropical cyclone dynamics. Here we present an annually-resolved 450-year reconstruction of western Caribbean tropical cyclone activity developed using a new coupled carbon and oxygen isotope ratio technique in an exceptionally well-dated stalagmite from Belize. Western Caribbean tropical cyclone activity peaked at 1650 A.D., coincident with maximum Little Ice Age cooling, and decreased gradually until the end of the record in 1983. Considered with other reconstructions, the new record suggests that the mean track of Cape Verde tropical cyclones shifted gradually north-eastward from the western Caribbean toward the Northmore » American east coast over the last 450 years. Since ~1870 A.D., these shifts were largely driven by anthropogenic greenhouse gas and sulphate aerosol emissions. In conclusion, our results strongly suggest that future emission scenarios will result in more frequent tropical cyclone impacts on the financial and population centres of the northeastern United States.« less

Developing an enhanced tropical cyclone data portal for the Southern Hemisphere and the Western Pacific Ocean

NASA Astrophysics Data System (ADS)

Kuleshov, Yuriy; de Wit, Roald; Atalifo, Terry; Prakash, Bipendra; Waqaicelua, Alipate; Kunitsugu, Masashi; Caroff, Philippe; Chane-Ming, Fabrice

2013-04-01

Tropical cyclones are the most extreme weather phenomena which severely impact coastal communities and island nations. There is an ongoing research (i) on accurate analysis of observed trends in tropical cyclone occurrences, and (ii) how tropical cyclone frequency and intensity may change in the future as a result of climate change. Reliable historical records of cyclone activity are vital for this research. The Pacific Australia Climate Change Science and Adaptation Planning (PACCSAP) program is dedicated to help Pacific Island countries and Timor Leste gain a better understanding of how climate change will impact their regions. One of the key PACCSAP projects is focused on developing a tropical cyclone archive, climatology and seasonal prediction for the regions. As part of the project, historical tropical cyclone best track data have been examined and prepared to be subsequently displayed through the enhanced tropical cyclone data portal for the Southern Hemisphere and the Western Pacific Ocean. Data from the Regional Specialised Meteorological Centre (RSMC) Nadi, Fiji and Tropical Cyclone Warning Centres (TCWCs) in Brisbane, Darwin and Wellington for 1969-1970 to 2010-2011 tropical cyclone seasons have been carefully examined. Errors and inconsistencies which have been found during the quality control procedure have been corrected. To produce a consolidated data set for the South Pacific Ocean, best track data from these four centres have been used. Specifically, for 1969-1970 to 1994-1995 tropical cyclone seasons, data from TCWCs in Brisbane, Darwin and Wellington have been used. In 1995, RSMC Nadi, Fiji has been established with responsibilities for issuing tropical cyclone warnings and preparing best track data for the area south of the equator to 25°S, 160°E to 120°W. Consequently, data from RSMC Nadi have been used as a primary source for this area, starting from the 1995-1996 tropical cyclone season. These data have been combined with the data from TCWC Wellington for the area 25°S to 40°S, 160°E to 120°W and with the data from TCWCs in Brisbane and Darwin for the area south of the equator to 37°S, 135°E to 160°E. In addition, tropical cyclone best track data for the North-West Pacific for 1977-2011 seasons prepared at RSMC Tokyo and for the South Indian Ocean for 1969-2011 prepared at RSMC la Réunion have been added to the dataset. As a result, new design of the Southern Hemisphere/Pacific Tropical Cyclone Data Portal (http://www.bom.gov.au/cyclone/history/tracks/) incorporates best track data for the Western Pacific both south and north of the equator and for the South Indian Ocean. The portal has been developed using the OpenLayers web mapping library. Main features of the portal include dynamic map navigation, presenting detailed cyclone information for a selected region in the Southern Hemisphere and North-West Pacific and displaying changes in tropical cyclone intensity over the lifetime of a cyclone. One of the unique features of the portal is its enhanced functionality for spatial and temporal selection for cyclones in selected areas (e.g. economic exclusion zones of the countries). Acknowledgement The research discussed in this paper was conducted through the PACCSAP supported by the AusAID and the Department of Climate Change and Energy Efficiency and delivered by the Bureau of Meteorology and CSIRO. We acknowledge C. Shamsu, D. Duong, P. Lopatecki, W. Banerjee, P. He, P. Wickramasinghe and A. Bauers from the School of Computer Sciences and IT at the Royal Melbourne Institute of Technology (RMIT) University, Melbourne, Australia for their contribution to the development of the portal's functionality on spatial selection.

How ocean color can steer Pacific tropical cyclones

NASA Astrophysics Data System (ADS)

Gnanadesikan, Anand; Emanuel, Kerry; Vecchi, Gabriel A.; Anderson, Whit G.; Hallberg, Robert

2010-09-01

Because ocean color alters the absorption of sunlight, it can produce changes in sea surface temperatures with further impacts on atmospheric circulation. These changes can project onto fields previously recognized to alter the distribution of tropical cyclones. If the North Pacific subtropical gyre contained no absorbing and scattering materials, the result would be to reduce subtropical cyclone activity in the subtropical Northwest Pacific by 2/3, while concentrating cyclone tracks along the equator. Predicting tropical cyclone activity using coupled models may thus require consideration of the details of how heat moves into the upper thermocline as well as biogeochemical cycling.

The Life Cycles of Intense Cyclonic and Anticyclonic Circulation Systems Observed over Oceans

NASA Technical Reports Server (NTRS)

Smith, Phillip J.

1996-01-01

This report presents a summary of research accomplished over the past four years under the sponsorship of NASA grant #NAG8-915. Building on previously funded NASA grants, this part of the project focused on the following specific goals relative to cyclone/anticyclone systems: the jet streak link between block formation and upstream cyclone activity; the role of northward warm air advection in block formation; the importance of cooperative participation of several forcing mechanisms during explosive cyclone development; and the significance of the vertical distribution of forcing processes during cyclone/anticyclone development.

Synthesis and cytotoxicity evaluation of granular magnesium substituted β-tricalcium phosphate.

PubMed

Tavares, Débora dos Santos; Castro, Leticia de Oliveira; Soares, Gloria Dulce de Almeida; Alves, Gutemberg Gomes; Granjeiro, José Mauro

2013-01-01

The aim of this study was to produce dense granules of tricalcium phosphate (β-TCP) and magnesium (Mg) substituted β-TCP, also known as β-TCMP (Mg/Ca=0.15 mol), in order to evaluate the impact of Mg incorporation on the physicochemical parameters and in vitro biocompatibility of this novel material. The materials were characterized using X-ray diffraction (XRD), infrared spectroscopy (FTIR), electron microscopy and inductively coupled plasma (ICP). Biocompatibility was assayed according to ISO 10993-12:2007 and 7405:2008, by two different tests of cell survival and integrity (XTT and CVDE). The XRD profile presented the main peaks of β-TCP (JCPDS 090169) and β-TCMP (JCPDS 130404). The characteristic absorption bands of TCP were also identified by FTIR. The ICP results of β-TCMP granules extract showed a precipitation of calcium and release of Mg into the culture medium. Regarding the cytotoxicity assays, β-TCMP dense granules did not significantly affect the mitochondrial activity and relative cell density in relation to β-TCP dense granules, despite the release of Mg from granules into the cell culture medium. β-TCMP granules were successfully produced and were able to release Mg into media without cytotoxicity, indicating the suitability of this promising material for further biological studies on its adequacy for bone therapy.

Changes in Tropical Cyclone Intensity Over the Past 30 Years: A Global and Dynamic Perspective

NASA Technical Reports Server (NTRS)

Wu, Liguang; Wang, Bin; Braun, Scott A.

2006-01-01

The hurricane season of 2005 was the busiest on record and Hurricane Katrina (2005) is believed to be the costliest hurricane in U. S. history. There are growing concerns regarding whether this increased tropical cyclone activity is a result of global warming, as suggested by Emanuel(2005) and Webster et al. (2005), or just a natural oscillation (Goldenberg et al. 2001). This study examines the changes in tropical cyclone intensity to see what were really responsible for the changes in tropical cyclone activity over the past 30 years. Since the tropical sea surface temperature (SST) warming also leads to the response of atmospheric circulation, which is not solely determined by the local SST warming, this study suggests that it is better to take the tropical cyclone activities in the North Atlantic (NA), western North Pacific (WNP) and eastern North Pacific (ENP) basins as a whole when searching for the influence of the global-scale SST warming on tropical cyclone intensity. Over the past 30 years, as the tropical SST increased by about 0.5 C, the linear trends indicate 6%, 16% and 15% increases in the overall average intensity and lifetime and the annual frequency. Our analysis shows that the increased annual destructiveness of tropical cyclones reported by Emanuel(2005) resulted mainly from the increases in the average lifetime and annual frequency in the NA basin and from the increases in the average intensity and lifetime in the WNP basin, while the annual destructiveness in the ENP basin generally decreased over the past 30 years. The changes in the proportion of intense tropical cyclones reported by Webster et a1 (2005) were due mainly to the fact that increasing tropical cyclones took the tracks that favor for the development of intense tropical cyclones in the NA and WNP basins over the past 30 years. The dynamic influence associated with the tropical SST warming can lead to the impact of global warming on tropical cyclone intensity that may be very different from our current assessments, which were mainly based on the thermodynamic theory of tropical cyclone intensity.

Impacts of different grades of tropical cyclones on infectious diarrhea in Guangdong, 2005-2011.

PubMed

Kang, Ruihua; Xun, Huanmiao; Zhang, Ying; Wang, Wei; Wang, Xin; Jiang, Baofa; Ma, Wei

2015-01-01

Guangdong province is one of the most vulnerable provinces to tropical cyclones in China. Most prior studies concentrated on the relationship between tropical cyclones and injuries and mortality. This study aimed to explore the impacts of different grades of tropical cyclones on infectious diarrhea incidence in Guangdong province, from 2005 to 2011. Mann-Whitney U test was firstly used to examine if infectious diarrhea were sensitive to tropical cyclone. Then unidirectional 1:1 case-crossover design was performed to quantitatively evaluate the relationship between daily number of infectious diarrhea and tropical cyclone from 2005 to 2011 in Guangdong, China. Principal component analysis (PCA) was applied to eliminate multicollinearity. Multivariate logistic regression model was used to estimate the hazard ratios (HRs) and the 95% confidence intervals (CI). There were no significant relationships between tropical cyclone and bacillary dysentery, amebic dysentery, typhoid, and paratyphoid cases. Infectious diarrhea other than cholera, dysentery, typhoid and paratyphoid significantly increased after tropical cyclones. The strongest effect were shown on lag 1 day (HRs = 1.95, 95%CI = 1.22, 3.12) and no lagged effect was detected for tropical depression, tropical storm, severe tropical storm and typhoon, with the largest HRs (95%CI) of 2.16 (95%CI = 1.69, 2.76), 2.43 (95%CI = 1.65, 3.58) and 2.21 (95%CI = 1.65, 2.69), respectively. Among children below 5 years old, the impacts of all grades of tropical cyclones were strongest at lag 0 day. And HRs were 2.67 (95%CI = 1.10, 6.48), 2.49 (95%CI = 1.80, 3.44), 4.89 (95%CI = 2.37, 7.37) and 3.18 (95%CI = 2.10, 4.81), respectively. All grades of tropical cyclones could increase risk of other infectious diarrhea. Severe tropical storm has the strongest influence on other infectious diarrhea. The impacts of tropical cyclones on children under 5 years old were higher than total population.

Contrasting the projected change in extreme extratropical cyclones in the two hemispheres

NASA Astrophysics Data System (ADS)

Chang, E. K. M.

2017-12-01

Extratropical cyclones form an important part of the global circulation. They are responsible for much of the high impact weather in the mid-latitudes, including heavy precipitation, strong winds, and coastal storm surges. They are also the surface manifestation of baroclinic waves that are responsible for much of the transport of momentum, heat, and moisture across the mid-latitudes. Thus how these storms will change in the future is of much general interest. In particular, how the frequency of the extreme cyclones change are of most concern, since they are the ones that cause most damages. While the projection of a poleward shift of the Southern Hemisphere storm track and cyclone activity is widely accepted, together with a small decrease in the total number of extratropical cyclones, as discussed in the 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5), projected change in cyclone intensity is still rather uncertain. Several studies have suggested that cyclone intensity, in terms of absolute value of sea level pressure (SLP) minima or SLP perturbations, is projected to increase under global warming. However, other studies found no increase in wind speed around extratropical cyclones. In this study, CMIP5 multi-model projection of how the frequency of extreme cyclones in terms of near surface wind intensity may change under global warming has been examined. Results suggest significant increase in the occurrences of extreme cyclones in the Southern Hemisphere. In the Northern Hemisphere, CMIP5 models project a northeastward shift in extreme cyclone activity over the Pacific, and significant decrease over the Atlantic. Substantial differences are also found between projected changes in near surface wind intensity and wind intensity at 850 hPa, suggesting that wind change at 850 hPa is not a good proxy for change in surface wind intensity. Finally, projected changes in the large scale environment are examined to understand the dynamics behind these contrasting projected changes.

Impacts of Different Grades of Tropical Cyclones on Infectious Diarrhea in Guangdong, 2005-2011

PubMed Central

Zhang, Ying; Wang, Wei; Wang, Xin; Jiang, Baofa; Ma, Wei

2015-01-01

Objective Guangdong province is one of the most vulnerable provinces to tropical cyclones in China. Most prior studies concentrated on the relationship between tropical cyclones and injuries and mortality. This study aimed to explore the impacts of different grades of tropical cyclones on infectious diarrhea incidence in Guangdong province, from 2005 to 2011. Methods Mann-Whitney U test was firstly used to examine if infectious diarrhea were sensitive to tropical cyclone. Then unidirectional 1:1 case-crossover design was performed to quantitatively evaluate the relationship between daily number of infectious diarrhea and tropical cyclone from 2005 to 2011 in Guangdong, China. Principal component analysis (PCA) was applied to eliminate multicollinearity. Multivariate logistic regression model was used to estimate the hazard ratios (HRs) and the 95% confidence intervals (CI). Results There were no significant relationships between tropical cyclone and bacillary dysentery, amebic dysentery, typhoid, and paratyphoid cases. Infectious diarrhea other than cholera, dysentery, typhoid and paratyphoid significantly increased after tropical cyclones. The strongest effect were shown on lag 1 day (HRs = 1.95, 95%CI = 1.22, 3.12) and no lagged effect was detected for tropical depression, tropical storm, severe tropical storm and typhoon, with the largest HRs (95%CI) of 2.16 (95%CI = 1.69, 2.76), 2.43 (95%CI = 1.65, 3.58) and 2.21 (95%CI = 1.65, 2.69), respectively. Among children below 5 years old, the impacts of all grades of tropical cyclones were strongest at lag 0 day. And HRs were 2.67 (95%CI = 1.10, 6.48), 2.49 (95%CI = 1.80, 3.44), 4.89 (95%CI = 2.37, 7.37) and 3.18 (95%CI = 2.10, 4.81), respectively. Conclusion All grades of tropical cyclones could increase risk of other infectious diarrhea. Severe tropical storm has the strongest influence on other infectious diarrhea. The impacts of tropical cyclones on children under 5 years old were higher than total population. PMID:26106882

A global slowdown of tropical-cyclone translation speed.

PubMed

Kossin, James P

2018-06-01

As the Earth's atmosphere warms, the atmospheric circulation changes. These changes vary by region and time of year, but there is evidence that anthropogenic warming causes a general weakening of summertime tropical circulation 1-8 . Because tropical cyclones are carried along within their ambient environmental wind, there is a plausible a priori expectation that the translation speed of tropical cyclones has slowed with warming. In addition to circulation changes, anthropogenic warming causes increases in atmospheric water-vapour capacity, which are generally expected to increase precipitation rates 9 . Rain rates near the centres of tropical cyclones are also expected to increase with increasing global temperatures 10-12 . The amount of tropical-cyclone-related rainfall that any given local area will experience is proportional to the rain rates and inversely proportional to the translation speeds of tropical cyclones. Here I show that tropical-cyclone translation speed has decreased globally by 10 per cent over the period 1949-2016, which is very likely to have compounded, and possibly dominated, any increases in local rainfall totals that may have occurred as a result of increased tropical-cyclone rain rates. The magnitude of the slowdown varies substantially by region and by latitude, but is generally consistent with expected changes in atmospheric circulation forced by anthropogenic emissions. Of particular importance is the slowdown of 30 per cent and 20 per cent over land areas affected by western North Pacific and North Atlantic tropical cyclones, respectively, and the slowdown of 19 per cent over land areas in the Australian region. The unprecedented rainfall totals associated with the 'stall' of Hurricane Harvey 13-15 over Texas in 2017 provide a notable example of the relationship between regional rainfall amounts and tropical-cyclone translation speed. Any systematic past or future change in the translation speed of tropical cyclones, particularly over land, is therefore highly relevant when considering potential changes in local rainfall totals.

Observational evidence for cloud cover enhancement over western European forests.

PubMed

Teuling, Adriaan J; Taylor, Christopher M; Meirink, Jan Fokke; Melsen, Lieke A; Miralles, Diego G; van Heerwaarden, Chiel C; Vautard, Robert; Stegehuis, Annemiek I; Nabuurs, Gert-Jan; de Arellano, Jordi Vilà-Guerau

2017-01-11

Forests impact regional hydrology and climate directly by regulating water and heat fluxes. Indirect effects through cloud formation and precipitation can be important in facilitating continental-scale moisture recycling but are poorly understood at regional scales. In particular, the impact of temperate forest on clouds is largely unknown. Here we provide observational evidence for a strong increase in cloud cover over large forest regions in western Europe based on analysis of 10 years of 15 min resolution data from geostationary satellites. In addition, we show that widespread windthrow by cyclone Klaus in the Landes forest led to a significant decrease in local cloud cover in subsequent years. Strong cloud development along the downwind edges of larger forest areas are consistent with a forest-breeze mesoscale circulation. Our results highlight the need to include impacts on cloud formation when evaluating the water and climate services of temperate forests, in particular around densely populated areas.

Observational evidence for cloud cover enhancement over western European forests

PubMed Central

Teuling, Adriaan J.; Taylor, Christopher M.; Meirink, Jan Fokke; Melsen, Lieke A.; Miralles, Diego G.; van Heerwaarden, Chiel C.; Vautard, Robert; Stegehuis, Annemiek I.; Nabuurs, Gert-Jan; de Arellano, Jordi Vilà-Guerau

2017-01-01

Forests impact regional hydrology and climate directly by regulating water and heat fluxes. Indirect effects through cloud formation and precipitation can be important in facilitating continental-scale moisture recycling but are poorly understood at regional scales. In particular, the impact of temperate forest on clouds is largely unknown. Here we provide observational evidence for a strong increase in cloud cover over large forest regions in western Europe based on analysis of 10 years of 15 min resolution data from geostationary satellites. In addition, we show that widespread windthrow by cyclone Klaus in the Landes forest led to a significant decrease in local cloud cover in subsequent years. Strong cloud development along the downwind edges of larger forest areas are consistent with a forest-breeze mesoscale circulation. Our results highlight the need to include impacts on cloud formation when evaluating the water and climate services of temperate forests, in particular around densely populated areas. PMID:28074840

Sea turtle species vary in their susceptibility to tropical cyclones.

PubMed

Pike, David A; Stiner, John C

2007-08-01

Severe climatic events affect all species, but there is little quantitative knowledge of how sympatric species react to such situations. We compared the reproductive seasonality of sea turtles that nest sympatrically with their vulnerability to tropical cyclones (in this study, "tropical cyclone" refers to tropical storms and hurricanes), which are increasing in severity due to changes in global climate. Storm surges significantly decreased reproductive output by lowering the number of nests that hatched and the number of hatchlings that emerged from nests, but the severity of this effect varied by species. Leatherback turtles (Dermochelys coriacea) began nesting earliest and most offspring hatched before the tropical cyclone season arrived, resulting in little negative effect. Loggerhead turtles (Caretta caretta) nested intermediately, and only nests laid late in the season were inundated with seawater during storm surges. Green turtles (Chelonia mydas) nested last, and their entire nesting season occurred during the tropical cyclone season; this resulted in a majority (79%) of green turtle nests incubating in September, when tropical cyclones are most likely to occur. Since this timing overlaps considerably with the tropical cyclone season, the developing eggs and nests are extremely vulnerable to storm surges. Increases in the severity of tropical cyclones may cause green turtle nesting success to worsen in the future. However, published literature suggests that loggerhead turtles are nesting earlier in the season and shortening their nesting seasons in response to increasing sea surface temperatures caused by global climate change. This may cause loggerhead reproductive success to improve in the future because more nests will hatch before the onset of tropical cyclones. Our data clearly indicate that sympatric species using the same resources are affected differently by tropical cyclones due to slight variations in the seasonal timing of nesting, a key life history process.

Large‐scale heavy precipitation over central Europe and the role of atmospheric cyclone track types

PubMed Central

Lexer, Annemarie; Homann, Markus; Blöschl, Günter

2017-01-01

ABSTRACT Precipitation patterns over Europe are largely controlled by atmospheric cyclones embedded in the general circulation of the mid‐latitudes. This study evaluates the climatologic features of precipitation for selected regions in central Europe with respect to cyclone track types for 1959–2015, focusing on large‐scale heavy precipitation. The analysis suggests that each of the cyclone track types is connected to a specific pattern of the upper level atmospheric flow, usually characterized by a major trough located over Europe. A dominant upper level cut‐off low (COL) is found over Europe for strong continental (CON) and van Bebber's type (Vb) cyclones which move from the east and southeast into central Europe. Strong Vb cyclones revealed the longest residence times, mainly due to circular propagation paths. The central European cyclone precipitation climate can largely be explained by seasonal track‐type frequency and cyclone intensity; however, additional factors are needed to explain a secondary precipitation maximum in early autumn. The occurrence of large precipitation totals for track events is strongly related to the track type and the region, with the highest value of 45% of all Vb cyclones connected to heavy precipitation in summer over the Czech Republic and eastern Austria. In western Germany, Atlantic winter cyclones are most relevant for heavy precipitation. The analysis of the top 50 precipitation events revealed an outstanding heavy precipitation period from 2006 to 2011 in the Czech Republic, but no gradual long‐term change. The findings help better understand spatio‐temporal variability of heavy precipitation in the context of floods and may be used for evaluating climate models.

Extra-tropical Cyclones and Windstorms in Seasonal Forecasts

NASA Astrophysics Data System (ADS)

Leckebusch, Gregor C.; Befort, Daniel J.; Weisheimer, Antje; Knight, Jeff; Thornton, Hazel; Roberts, Julia; Hermanson, Leon

2015-04-01

Severe damages and large insured losses over Europe related to natural phenomena are mostly caused by extra-tropical cyclones and their related windstorm fields. Thus, an adequate representation of these events in seasonal prediction systems and reliable forecasts up to a season in advance would be of high value for society and economy. In this study, state-of-the-art seasonal forecast prediction systems are analysed (ECMWF, UK Met Office) regarding the general climatological representation and the seasonal prediction of extra-tropical cyclones and windstorms during the core winter season (DJF) with a lead time of up to four months. Two different algorithms are used to identify cyclones and windstorm events in these datasets. Firstly, we apply a cyclone identification and tracking algorithm based on the Laplacian of MSLP and secondly, we use an objective wind field tracking algorithm to identify and track continuous areas of extreme high wind speeds (cf. Leckebusch et al., 2008), which can be related to extra-tropical winter cyclones. Thus, for the first time, we can analyse the forecast of severe wind events near to the surface caused by extra-tropical cyclones. First results suggest a successful validation of the spatial climatological distributions of wind storm and cyclone occurrence in the seasonal forecast systems in comparison with reanalysis data (ECMWF-ERA40 & ERAInterim) in general. However, large biases are found for some areas. The skill of the seasonal forecast systems in simulating the year-to-year variability of the frequency of severe windstorm events and cyclones is investigated using the ranked probability skill score. Positive skill is found over large parts of the Northern Hemisphere as well as for the most intense extra-tropical cyclones and its related wind fields.

RegCM4-HadGEM2-ES simulated cyclone climatology (1979-2005) over the Southwestern South Atlantic Ocean

NASA Astrophysics Data System (ADS)

Porfírio da Rocha, Rosmeri; Simões Reboita, Michelle

2015-04-01

Cyclones over the Southwestern South Atlantic Ocean (SAO) are a subject of great interest once they modify the weather and control the climate near east coast of South America (SA). In this study we compare the cyclones climatology in the period 1979-2005 simulated by Regional Climate Model version 4 (RegCM4) with that from ERA-Interim reanalysis (ECMWF). RegCM4 was nested in HadGEM2-ES output and the simulation used the SA domain of CORDEX project, with a horizontal grid of 50 km and 18 sigma-pressure levels in the vertical. The RegCM4 simulation used the land surface Biosphere-Atmosphere Transfer Scheme (BATS) and the mixed convection Emanuel-Grell scheme configurations. This simulation is part of the CREMA (CORDEX REgCM4 hyper-MAtrix) experiment. The cyclones were identified using an automated tracking scheme based on minima (cyclonic in Southern Hemisphere) of relative vorticity from the wind at 925 hPa. The threshold of -1.5 x 10-5s-1 was used in the algorithm. All cyclones in RegCM4 and ERA-Interim with relative vorticity lower than this threshold and with lifetime higher or equal 24 hours were included in the climatology. ERA-Interim shows three main cyclogenetic regions near east coast of SA. In general, RegCM4 simulated these same regions but with an underestimation of the number of cyclones. In each of these regions, there is a different season of higher cyclones frequency. Over extreme south of southern Brazil and Uruguay the higher frequency of cyclones occurs in winter, while southeastern Brazil and southeastern Argentina cyclones are most frequent during summer. RegCM4 is able to simulate this observed seasonality.

Equatorial Mesosphere and Lower Thermosphere/Ionosphere (MLTI) Response to Severe Cyclonic Storm `Aila' and `Ward' observed over North Indian Ocean

NASA Astrophysics Data System (ADS)

G J, B.

2016-12-01

The present work investigates the Equatorial Mesosphere Lower Thermosphere/Ionosphere (MLTI) response to severe cyclonic storm `Aila (23-26 May 2009)' and `Ward (10-16 December 2009)' which were observed over north Indian Ocean during the extended solar minimum of the year 2009. This report reveals the coupling between Tropical Cyclone and MLTI region. Tropical cyclone track and data can be obtained from Indian Meteorological Department (IMD), New Delhi. Mesospheric and Ionospheric variation can be examined with the help of ground based Mesosphere Lower Thermosphere (MLT) radar and Digisonde located at equatorial low latitude station, Tirunelveli (8.7oN, 77.8oE). The Outgoing Long wave Radiation (OLR) data is used as a proxy for identifying the convective activity, which are retrieved from NOAA Climate Data Centre. It is observed that the tropical cyclone induced convection as the driving agent for the increased gravity wave activity in the lower atmosphere. These upward propagating gravity waves deposit their energy and momentum into the upper region of atmosphere as `Travelling Ionospheric Disturbances (TIDs). During the cyclonic storm periods, we found increased gravity wave amplitude with upward propagation in the MLT region. Ionospheric response to severe cyclonic storm is examined with the dynamical parameters, foF2, hmF2, h'F2 and Total Election Content (TEC). Significant increase of foF2 frequency is observed during `Ward' cyclonic storm. Drastic variation in foF2 and h'F2 is observed during Aila cyclonic storm than ward event. More statistical analysis has been done for finding the correlation between cyclonic storm and Ionospheric parameters. Detailed results will be presented in the meeting.

The short-term impacts of a cyclone on seagrass communities in Southwest Madagascar

NASA Astrophysics Data System (ADS)

Côté-Laurin, Marie-Claude; Benbow, Sophie; Erzini, Karim

2017-04-01

Cyclones are large-scale disturbances with highly destructive potential in coastal ecosystems. On February 22, 2013, a powerful tropical cyclone made landfall on the southwest coast of Madagascar, a region which is infrequently hit by such extreme weather events coming from the Mozambique Channel. Seagrass ecosystems, which provide valuable ecosystems services to local communities, are especially vulnerable because they thrive in shallow waters. The impact of Cyclone Haruna on seagrass diversity, height and coverage and associated fish diversity, abundance and biomass was assessed in 3 sites near Andavadoaka (22°07‧S, 43°23‧E) before and after the event using fish underwater visual census, video-transects, and seagrass quadrats. The cyclone caused a significant loss in seagrass cover at all 3 sites. Thalassia hemprichii and Syringodium isoetifolium were the most affected species. Andavadoaka beach, the most exposed site, which was also subject to human use and was most fragmented, suffered the largest negative effects of the cyclone. Cyclone Haruna was not found to significantly affect fish assemblages, which are highly mobile organisms able to use a diversity of niches and adjacent habitats after seagrass fragmentation. Extensive sampling and longer time-scale studies would be needed to fully evaluate the cyclone impact on communities of seagrass and fish, and track potential recovery in seagrass coverage. The intensity and destructive potential of cyclones is expected to increase with global warming, which is of concern for developing countries that encompass most of the world's seagrass beds. This study provided a unique and key opportunity to monitor immediate impacts of an extreme disturbance in a region where cyclones rarely hit coastal ecosystems and where local populations remain highly dependent on seagrass meadows.

Robustness of serial clustering of extra-tropical cyclones to the choice of tracking method

NASA Astrophysics Data System (ADS)

Pinto, Joaquim G.; Ulbrich, Sven; Karremann, Melanie K.; Stephenson, David B.; Economou, Theodoros; Shaffrey, Len C.

2016-04-01

Cyclone families are a frequent synoptic weather feature in the Euro-Atlantic area in winter. Given appropriate large-scale conditions, the occurrence of such series (clusters) of storms may lead to large socio-economic impacts and cumulative losses. Recent studies analyzing Reanalysis data using single cyclone tracking methods have shown that serial clustering of cyclones occurs on both flanks and downstream regions of the North Atlantic storm track. This study explores the sensitivity of serial clustering to the choice of tracking method. With this aim, the IMILAST cyclone track database based on ERA-interim data is analysed. Clustering is estimated by the dispersion (ratio of variance to mean) of winter (DJF) cyclones passages near each grid point over the Euro-Atlantic area. Results indicate that while the general pattern of clustering is identified for all methods, there are considerable differences in detail. This can primarily be attributed to the differences in the variance of cyclone counts between the methods, which range up to one order of magnitude. Nevertheless, clustering over the Eastern North Atlantic and Western Europe can be identified for all methods and can thus be generally considered as a robust feature. The statistical links between large-scale patterns like the NAO and clustering are obtained for all methods, though with different magnitudes. We conclude that the occurrence of cyclone clustering over the Eastern North Atlantic and Western Europe is largely independent from the choice of tracking method and hence from the definition of a cyclone.

Classic Maya civilization collapse associated with reduction in tropical cyclone activity

NASA Astrophysics Data System (ADS)

Medina, M. A.; Polanco-Martinez, J. M.; Lases-Hernández, F.; Bradley, R. S.; Burns, S. J.

2013-12-01

In light of the increased destructiveness of tropical cyclones observed over recent decades one might assume that an increase and not a decrease in tropical cyclone activity would lead to societal stress and perhaps collapse of ancient cultures. In this study we present evidence that a reduction in the frequency and intensity of tropical Atlantic cyclones could have contributed to the collapse of the Maya civilization during the Terminal Classic Period (TCP, AD. 800-950). Statistical comparisons of a quantitative precipitation record from the Yucatan Peninsula (YP) Maya lowlands, based on the stalagmite known as Chaac (after the Mayan God of rain and agriculture), relative to environmental proxy records of El Niño/Southern Oscillation (ENSO), tropical Atlantic sea surface temperatures (SSTs), and tropical Atlantic cyclone counts, suggest that these records share significant coherent variability during the TCP and that summer rainfall reductions between 30 and 50% in the Maya lowlands occurred in association with decreased Atlantic tropical cyclones. Analysis of modern instrumental hydrological data suggests cyclone rainfall contributions to the YP equivalent to the range of rainfall deficits associated with decreased tropical cyclone activity during the collapse of the Maya civilization. Cyclone driven precipitation variability during the TCP, implies that climate change may have triggered Maya civilization collapse via freshwater scarcity for domestic use without significant detriment to agriculture. Pyramid in Tikal, the most prominent Maya Kingdom that collapsed during the Terminal Classic Period (circa C.E. 800-950) Rainfall feeding stalagmites inside Rio Secreto cave system, Yucatan, Mexico.

Initial state nuclear effects for jet production measured in s=200GeV d+Au collisions by STAR

NASA Astrophysics Data System (ADS)

STAR Collaboration; Kapitán, Jan; STAR Collaboration

2009-11-01

Full jet reconstruction in heavy-ion collisions is a promising tool for quantitative study of properties of the dense medium produced at RHIC. Measurements of d+Au collisions are important to disentangle initial state nuclear effects from medium-induced k broadening and jet quenching. We report measurements of mid-rapidity (|η|<0.4|) di-jet correlations in d+Au using high-statistics run 8 RHIC data at s=200GeV.

Interstellar Dust: Contributed Papers

NASA Technical Reports Server (NTRS)

Tielens, Alexander G. G. M. (Editor); Allamandola, Louis J. (Editor)

1989-01-01

A coherent picture of the dust composition and its physical characteristics in the various phases of the interstellar medium was the central theme. Topics addressed included: dust in diffuse interstellar medium; overidentified infrared emission features; dust in dense clouds; dust in galaxies; optical properties of dust grains; interstellar dust models; interstellar dust and the solar system; dust formation and destruction; UV, visible, and IR observations of interstellar extinction; and quantum-statistical calculations of IR emission from highly vibrationally excited polycyclic aromatic hydrocarbon (PAH) molecules.

High-resolution imaging and target designation through clouds or smoke

DOEpatents

Perry, Michael D.

2003-01-01

A method and system of combining gated intensifiers and advances in solid-state, short-pulse laser technology, compact systems capable of producing high resolution (i.e., approximately less than 20 centimeters) optical images through a scattering medium such as dense clouds, fog, smoke, etc. may be achieved from air or ground based platforms. Laser target designation through a scattering medium is also enabled by utilizing a short pulse illumination laser and a relatively minor change to the detectors on laser guided munitions.

Promoting the confluence of tropical cyclone research.

PubMed

Marler, Thomas E

2015-01-01

Contributions of biologists to tropical cyclone research may improve by integrating concepts from other disciplines. Employing accumulated cyclone energy into protocols may foster greater integration of ecology and meteorology research. Considering experienced ecosystems as antifragile instead of just resilient may improve cross-referencing among ecological and social scientists. Quantifying ecosystem capital as distinct from ecosystem services may improve integration of tropical cyclone ecology research into the expansive global climate change research community.

Western North Pacific Tropical Cyclone Formation and Structure Change in TCS-08

DTIC Science & Technology

2012-09-30

cyclones often transition to a fast-moving and rapidly- developing extratropical cyclone that may contain gale-, storm -, or hurricane-force winds...there is a need to improve understanding and prediction of the extratropical transition phase of a decaying tropical cyclone. The structural evolution...of the transition from a tropical to an extratropical circulation involves rapid changes to the wind, cloud, and precipitation patterns that

Temporal clustering of tropical cyclones and its ecosystem impacts

PubMed Central

Mumby, Peter J.; Vitolo, Renato; Stephenson, David B.

2011-01-01

Tropical cyclones have massive economic, social, and ecological impacts, and models of their occurrence influence many planning activities from setting insurance premiums to conservation planning. Most impact models allow for geographically varying cyclone rates but assume that individual storm events occur randomly with constant rate in time. This study analyzes the statistical properties of Atlantic tropical cyclones and shows that local cyclone counts vary in time, with periods of elevated activity followed by relative quiescence. Such temporal clustering is particularly strong in the Caribbean Sea, along the coasts of Belize, Honduras, Costa Rica, Jamaica, the southwest of Haiti, and in the main hurricane development region in the North Atlantic between Africa and the Caribbean. Failing to recognize this natural nonstationarity in cyclone rates can give inaccurate impact predictions. We demonstrate this by exploring cyclone impacts on coral reefs. For a given cyclone rate, we find that clustered events have a less detrimental impact than independent random events. Predictions using a standard random hurricane model were overly pessimistic, predicting reef degradation more than a decade earlier than that expected under clustered disturbance. The presence of clustering allows coral reefs more time to recover to healthier states, but the impacts of clustering will vary from one ecosystem to another. PMID:22006300

Hurricanes and Climate: the U.S. CLIVAR Working Group on Hurricanes

NASA Technical Reports Server (NTRS)

Walsh, Kevin; Camargo, Suzana J.; Vecchi, Gabriel A.; Daloz, Anne Sophie; Elsner, James; Emanuel, Kerry; Horn, Michael; Lim, Young-Kwon; Roberts, Malcolm; Patricola, Christina;

Characterization of flash floods induced by tropical cyclones in Mexico

NASA Astrophysics Data System (ADS)

Real-Rangel, R. A.; Pedrozo-Acuña, A.

2015-12-01

This study investigates the role of tropical cyclones (hurricanes, tropical storms and depressions) in the generation of flash floods in Mexico. For this, a severity assessment during several cyclonic events for selected catchments was estimated through the evaluation of a flash flood index recently proposed by Kim and Kim (2014). This classification is revised, considering the forcing and areal extent of torrential rainfall generated by the incidence of tropical cyclones on the studied catchments, enabling the further study of the flood regime in catchments located in tropical regions. The analysis incorporates characteristics of the flood hydrographs such as the hydrograph shape (rising curve gradient, magnitude of the peak discharge and flood response time) in order to identify flash-flood prone areas. Results show the Qp-A scaling relationship in catchments that were impacted by tropical cyclones, enabling their comparison against floods generated by other meteorological events (e.g. convective and orographic storms). Results will inform on how peak flows relationships are modified by cyclonic events and highlighting the contribution of cyclonic precipitation to flash-flooding susceptibility.

Cyclonic circulation of Saturn's atmosphere due to tilted convection

NASA Astrophysics Data System (ADS)

Afanasyev, Y. D.; Zhang, Y.

2018-03-01

Saturn displays cyclonic vortices at its poles and the general atmospheric circulation at other latitudes is dominated by embedded zonal jets that display cyclonic circulation. The abundance of small-scale convective storms suggests that convection plays a role in producing and maintaining Saturn's atmospheric circulation. However, the dynamical influence of small-scale convection on Saturn's general circulation is not well understood. Here we present laboratory analogue experiments and propose that Saturn's cyclonic circulation can be explained by tilted convection in which buoyancy forces do not align with the planet's rotation axis. In our experiments—conducted with a cylindrical water tank that is heated at the bottom, cooled at the top and spun on a rotating table—warm rising plumes and cold sinking water generate small anticyclonic and cyclonic vortices that are qualitatively similar to Saturn's convective storms. Numerical simulations complement the experiments and show that this small-scale convection leads to large-scale cyclonic flow at the surface and anticyclonic circulation at the base of the fluid layer, with a polar vortex forming from the merging of smaller cyclonic storms that are driven polewards.

Monitoring tropical cyclone intensity using wind fields derived from short-interval satellite images

NASA Technical Reports Server (NTRS)

Rodgers, E. B.; Gentry, R. C.

1981-01-01

Rapid scan visible images from the Visible Infrared Spin Scan Radiometer sensor on board SMS-2 and GOES-1 were used to derive high resolution upper and lower tropospheric environmental wind fields around three western Atlantic tropical cyclones (1975-78). These wind fields were used to derive upper and lower tropospheric areal mean relative vorticity and their differences, the net relative angular momentum balance and upper tropospheric mass outflow. These kinematic parameters were shown by studies using composite rawinsonde data to be strongly related to tropical cyclone formation and intensity changes. Also, the role of forced synoptic scale subsidence in tropical cyclone formation was examined. The studies showed that satellite-derived lower and upper tropospheric wind fields can be used to monitor and possibly predict tropical cyclone formation and intensity changes. These kinematic analyses showed that future changes in tropical cyclone intensity are mainly related to the "spin-up" of the storms by the net horizontal transport of relative angular momentum caused by convergence of cyclonic vorticity in the lower troposphere and to a lesser extent the divergence of anticyclone vorticity in the upper troposphere.

PFB Coal Fired Combined Cycle Development Program. Advanced hot gas cleanup concept evaluation (Task 4. 3). Volume A. Aerodyne cyclone evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

This report summarizes the results of testing of a rotary flow cyclone, manufactured by Aerodyne Development Corporation under license by Siemens Kraftwerk Union. This cyclone was selected for evaluation due to the unusually high separative efficiencies claimed by the manufacturer (based on developer data), and relative lack of open literature data. The most significant finding of this work was the observation that electrostatic forces could enhance or, in fact, dominate the separation process. Separative efficiencies, with electrostatic forces present, were found to be substantially independent of flow rate and, by inference, could be independent of unit size. Hence this findingmore » offers a major hope that large cyclones employed in the hot gas cleanup train of the CFCC system may not suffer the performance degradation compared to small cyclones, as projected from conventional inertial theory. The separative efficiencies of the Aerodyne cyclone separator were found from both the cold flow and the hot flow tests to be disappointingly poorer than expectations (in agreement with Westinghouse results), and even poorer than conventional cyclones. (LTN)« less

Novel Descattering Approach for Stereo Vision in Dense Suspended Scatterer Environments

PubMed Central

Nguyen, Chanh D. Tr.; Park, Jihyuk; Cho, Kyeong-Yong; Kim, Kyung-Soo; Kim, Soohyun

2017-01-01

In this paper, we propose a model-based scattering removal method for stereo vision for robot manipulation in indoor scattering media where the commonly used ranging sensors are unable to work. Stereo vision is an inherently ill-posed and challenging problem. It is even more difficult in the case of images of dense fog or dense steam scenes illuminated by active light sources. Images taken in such environments suffer attenuation of object radiance and scattering of the active light sources. To solve this problem, we first derive the imaging model for images taken in a dense scattering medium with a single active illumination close to the cameras. Based on this physical model, the non-uniform backscattering signal is efficiently removed. The descattered images are then utilized as the input images of stereo vision. The performance of the method is evaluated based on the quality of the depth map from stereo vision. We also demonstrate the effectiveness of the proposed method by carrying out the real robot manipulation task. PMID:28629139

Electrostatic precipitator rapping with sonic horns at Atlantic Electric`s B.L. England Generating Station

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maziarz, M.; Gallo, F.

1995-12-31

B.L. England Generating Station (BLE) is located in Beesleys Point, NJ. Beesleys Point is on Great Egg Bay, which is 20 minutes south of Atlantic City and one hour east of Philadelphia. BLE has three generating units: No. 1 is a 120 Megawatt (MW) B&W cyclone boiler; No. 2 is a 160 MW B&W cyclone boiler; & No. 3 is a tangential fired Combustion Engineering boiler. Units 1 & 2 burn medium sulfur eastern bituminous coal. Unit 3 burns No. 6 oil. Units 1&2 are equipped with precipitators (ESPs). The two ESPs were manufactured by Environmental Elements Corp. (EEC) andmore » were placed in service in 1980. Units are dual chamber with each having four mechanical fields and eight electrical fields. Each field has two Transformer/Rectifier (T/R) sets for a total of sixteen per ESP. The ESPs are rigid frame design (Rigitrode by EEC) with hammer & anvil rapping. Ash reinjection systems permit direct or cross reinjection of fly ash. Both ESPs have perforated plates for inlet & outlet gas flow distribution. There are three inlet plates and one outlet plate. The first inlet plates and the outlets are cleaned via electric reciprocating vibrators. There was no means of cleaning the remaining plates provided.« less

Assessment of marine weather forecasts over the Indian sector of Southern Ocean

NASA Astrophysics Data System (ADS)

Gera, Anitha; Mahapatra, D. K.; Sharma, Kuldeep; Prakash, Satya; Mitra, A. K.; Iyengar, G. R.; Rajagopal, E. N.; Anilkumar, N.

2017-09-01

The Southern Ocean (SO) is one of the important regions where significant processes and feedbacks of the Earth's climate take place. Expeditions to the SO provide useful data for improving global weather/climate simulations and understanding many processes. Some of the uncertainties in these weather/climate models arise during the first few days of simulation/forecast and do not grow much further. NCMRWF issued real-time five day weather forecasts of mean sea level pressure, surface winds, winds at 500 hPa & 850 hPa and rainfall, daily to NCAOR to provide guidance for their expedition to Indian sector of SO during the austral summer of 2014-2015. Evaluation of the skill of these forecasts indicates possible error growth in the atmospheric model at shorter time scales. The error growth is assessed using the model analysis/reanalysis, satellite data and observations made during the expedition. The observed variability of sub-seasonal rainfall associated with mid-latitude systems is seen to exhibit eastward propagations and are well reproduced in the model forecasts. All cyclonic disturbances including the sub-polar lows and tropical cyclones that occurred during this period were well captured in the model forecasts. Overall, this model performs reasonably well over the Indian sector of the SO in medium range time scale.

Promoting the confluence of tropical cyclone research

PubMed Central

Marler, Thomas E

2015-01-01

Contributions of biologists to tropical cyclone research may improve by integrating concepts from other disciplines. Employing accumulated cyclone energy into protocols may foster greater integration of ecology and meteorology research. Considering experienced ecosystems as antifragile instead of just resilient may improve cross-referencing among ecological and social scientists. Quantifying ecosystem capital as distinct from ecosystem services may improve integration of tropical cyclone ecology research into the expansive global climate change research community. PMID:26480001

Vertical transport of ozone and CO during super cyclones in the Bay of Bengal as detected by Tropospheric Emission Spectrometer.

PubMed

Fadnavis, S; Beig, G; Buchunde, P; Ghude, Sachin D; Krishnamurti, T N

2011-02-01

Vertical profiles of carbon monoxide (CO) and ozone retrieved from Tropospheric Emission Spectrometer have been analyzed during two super cyclone systems Mala and Sidr. Super cyclones Mala and Sidr traversed the Bay of Bengal (BOB) region on April 24-29, 2006 and November 12-16, 2007 respectively. The CO and ozone plume is observed as a strong enhancement of these pollutants in the upper troposphere over the BOB, indicating deep convective transport. Longitude-height cross-section of these pollutants shows vertical transport to the upper troposphere. CO mixing ratio ~90 ppb is observed near the 146-mb level during the cyclone Mala and near 316 mb during the cyclone Sidr. Ozone mixing ratio ~60-100 ppb is observed near the 316-mb level during both the cyclones. Analysis of National Centers for Environmental Prediction (NCEP) reanalysis vertical winds (omega) confirms vertical transport in the BOB.

Tropical cyclone intensity change. A quantitative forecasting scheme

NASA Technical Reports Server (NTRS)

Dropco, K. M.; Gray, W. M.

1981-01-01

One to two day future tropical cyclone intensity change from both a composite and an individual case point-of-view are discussed. Tropical cyclones occurring in the Gulf of Mexico during the period 1957-1977 form the primary data source. Weather charts of the NW Atlantic were initially examined, but few differences were found between intensifying and non-intensifying cyclones. A rawinsonde composite analysis detected composite differences in the 200 mb height fields, the 850 mb temperature fields, the 200 mb zonal wind and the vertical shears of the zonal wind. The individual cyclones which make up the composite study were then separately examined using this composite case knowledge. Similar parameter differences were found in a majority of individual cases. A cyclone intensity change forecast scheme was tested against independent storm cases. Correct predictions of intensification or non-intensification could be made approximately 75% of the time.

Cretaceous polar climates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ziegler, A.M.; Horrell, M.A.; Lottes, A.L.

1988-02-01

The Cretaceous, like most Phanerozoic periods, was characterized by ice-free poles. Some still argue that the glaciers and sea ice were there, and that the tillites, etc, have been eroded or remain undiscovered. However, diverse floras, dense forests, and coal-forming cypress swamps, and dinosaurs, crocodilians, and lungfish are known from areas that were certainly at 75/degree/-80/degree/ north and south paleolatitude in the Cretaceous, implying that the coastal basins did not experience hard freezes. No deep marine connections to the North Pole existed in the Cretaceous, so oceanic polar heat transport can be discounted. However, the five north-south trending epeiric ormore » rift-related seaways that connected or nearly connected the Tethys to the Arctic would have dampened the seasonal temperature cycle, bring maritime climates deep into the North American and Eurasian continents and, more importantly, would have served as an energy source and channel for winter storms, much as the Gulf Stream does today. Cyclones have a natural tendency to move poleward, because of the increase in the Coriolis Parameter, and they transport both sensible and latent heat. The coastal regions of the relatively warm polar ocean in the Cretaceous would have received continuous precipitation during the winter because cyclones would be entering from as many as five directions. Coastal rainfall would also have been abundant in the summer but for a different reason; the land-sea temperature profile would reverse, with the warm land surface drawing in moisture, while clear ice-free conditions over the ocean would allow for solar warming.« less

Cretaceous polar climates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ziegler, A.M.; Horrell, M.A.; Lottes, A.L.

1988-01-01

The Cretaceous, like most Phanerozooic periods, was characterized by ice-free poles. Some still argue that the glacier and sea ice were there, and that the tillites, etc, have been eroded or remain undiscovered. However, diverse floras, dense forests, coal-forming cypress swamps, and dinosaurs, crocodilians, and lungfish are known from areas that were certainly at 75/sup 0/-80/sup 0/ north and south paleolatitude in the Cretaceous, implying that the coastal basins did not experience hard freezes. No deep marine connections to the North Pole existed in the Cretaceous, so oceanic polar heat transport can be discounted. However, the five north-south trending epeiricmore » or rift-related seaways that connected or nearly connected the Tethys to the Arctic would have dampened the seasonal temperature cycle, bringing maritime climates deep into the North American and Eurasian continents and, more importantly, would have served as an energy source and channel for winter storms, much as the Gulf Stream does today. Cyclones have a natural tendency to move poleward, because of the increase in the Coriolis Paramteter, and they transport both sensible and latent heat. The coastal regions of the relatively warm polar ocean in the Cretaceous would have received continuous precipitation during the winter because cyclones would be entering from as many as five directions. Coastal rainfall would also have been abundant in the summer but for a different reason; the land-sea temperature profile would reverse, with the warm land surface drawing in moisture, while clear ice-free conditions over the ocean would allow for solar warming.« less

Monitoring Coastal Embankment Subsidence and Relative Sea Level Rise in Coastal Bangladesh Using Satellite Geodetic Data

NASA Astrophysics Data System (ADS)

Guo, Q.; Shum, C. K.; Jia, Y.; Yi, Y.; Zhu, K.; Kuo, C. Y.; Liibusk, A.

2015-12-01

The Bangladesh Delta is located at the confluence of the mega Ganges, Brahmaputra and Meghan Rivers in the Bay of Bengal. It is home to over 160 million people and is one of the most densely populated countries in the world. It is prone to seasonal transboundary monsoonal flooding, potentially aggravated by more frequent and intensified cyclones resulting from anthropogenic climate change. Sea level rise, along with tectonic, sediment compaction/load and groundwater extraction induced land uplift/subsidence, have significantly exacerbated these risks and Bangladesh's coastal vulnerability. Bangladesh has built 123 coastal embankments or polders since the 1960's, to protect the coastal regions from cyclone/tidal flooding and to reduce salinity incursions. Since then, many coastal polders have suffered severe erosion and anthropogenic damage, and require repairs or rebuilding. However, the physical and anthropogenic processes governing the historic relative sea level rise and its future projection towards its quantification remain poorly understood or known, and at present not accurate enough or with an adequately fine local spatial scale for practical mitigation of coastal vulnerability or coastal resilience studies. This study reports on our work in progress to use satellite geodetic and remote sensing observations, including satellite radar altimetry/backscatter measurements over land and in coastal oceans, optical/infrared imageries, and SAR backscatter/InSAR data, to study the feasibility of coastal embankment/polder erosion monitoring, quantify seasonal polder water intrusions, observing polder subsidence, and finally, towards the goal of improving the relative sea level rise hazards assessment at the local scale in coastal Bangladesh.

The NASA EV-2 CYGNSS Small Satellite Constellation Mission

NASA Astrophysics Data System (ADS)

Ruf, C. S.; Gleason, S.; Jelenak, Z.; Katzberg, S. J.; Ridley, A. J.; Rose, R.; Scherrer, J.; Zavorotny, V.

2012-12-01

The NASA EV-2 Cyclone Global Navigation Satellite System (CYGNSS) is a spaceborne mission focused on tropical cyclone (TC) inner core process studies. CYGNSS attempts to resolve the principle deficiencies with current TC intensity forecasts, which lies in inadequate observations and modeling of the inner core. The inadequacy in observations results from two causes: 1) Much of the inner core ocean surface is obscured from conventional remote sensing instruments by intense precipitation in the eye wall and inner rain bands. 2) The rapidly evolving (genesis and intensification) stages of the TC life cycle are poorly sampled in time by conventional polar-orbiting, wide-swath surface wind imagers. CYGNSS is specifically designed to address these two limitations by combining the all-weather performance of GNSS bistatic ocean surface scatterometry with the sampling properties of a constellation of satellites. The use of a dense constellation of nanosatellite results in spatial and temporal sampling properties that are markedly different from conventional imagers. Simulation studies will be presented which examine the sampling as functions of various orbit parameters of the constellation. Historical records of actual TC storm tracks are overlaid onto a simulated time series of the surface wind sampling enabled by the constellation. For comparison purposes, a similar analysis is conducted using the sampling properties of several past and present conventional spaceborne ocean wind scatterometers. Differences in the ability of the sensors to resolve the evolution of the TC inner core are examined. The spacecraft and constellation mission are described. The signal-to-noise ratio of the measured scattered signal and the resulting uncertainty in retrieved surface wind speed are also examined.

Observational Analysis of Cloud and Precipitation in Midlatitude Cyclones: Northern Versus Southern Hemisphere Warm Fronts

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

2012-01-01

Extratropical cyclones are responsible for most of the precipitation and wind damage in the midlatitudes during the cold season, but there are still uncertainties on how they will change in a warming climate. An ubiquitous problem amongst General Circulation Models (GCMs) is a lack of cloudiness over the southern oceans that may be in part caused by a lack of clouds in cyclones. We analyze CloudSat, CALIPSO and AMSR-E observations for 3 austral and boreal cold seasons and composite cloud frequency of occurrence and precipitation at the warm fronts for northern and southern hemisphere oceanic cyclones. We find that cloud frequency of occurrence and precipitation rate are similar in the early stage of the cyclone life cycle in both northern and southern hemispheres. As cyclones evolve and reach their mature stage, cloudiness and precipitation at the warm front increase in the northern hemisphere but decrease in the southern hemisphere. This is partly caused by lower amounts of precipitable water being available to southern hemisphere cyclones, and smaller increases in wind speed as the cyclones evolve. Southern hemisphere cloud occurrence at the warm front is found to be more sensitive to the amount of moisture in the warm sector than to wind speeds. This suggests that cloudiness in southern hemisphere storms may be more susceptible to changes in atmospheric water vapor content, and thus to changes in surface temperature than their northern hemisphere counterparts. These differences between northern and southern hemisphere cyclones are statistically robust, indicating A-Train-based analyses as useful tools for evaluation of GCMs in the next IPCC report.

Effects of absorption on multiple scattering by random particulate media: exact results.

PubMed

Mishchenko, Michael I; Liu, Li; Hovenier, Joop W

2007-10-01

We employ the numerically exact superposition T-matrix method to perform extensive computations of elec nottromagnetic scattering by a volume of discrete random medium densely filled with increasingly absorbing as well as non-absorbing particles. Our numerical data demonstrate that increasing absorption diminishes and nearly extinguishes certain optical effects such as depolarization and coherent backscattering and increases the angular width of coherent backscattering patterns. This result corroborates the multiple-scattering origin of such effects and further demonstrates the heuristic value of the concept of multiple scattering even in application to densely packed particulate media.

Cyclone performance by velocity

USDA-ARS?s Scientific Manuscript database

Cyclones are used almost exclusively in the US cotton ginning industry for emission abatement on pneumatic conveying system exhausts because of their high efficiency, and low capital and operating cost.. Cyclone performance is improved by increasing collection effectiveness or decreasing energy cons...

Conceptual Models of Frontal Cyclones.

ERIC Educational Resources Information Center

Eagleman, Joe R.

1981-01-01

This discussion of weather models uses maps to illustrate the differences among three types of frontal cyclones (long wave, short wave, and troughs). Awareness of these cyclones can provide clues to atmospheric conditions which can lead toward accurate weather forecasting. (AM)

Rapid changes in synaptic vesicle cytochemistry after depolarization of cultured cholinergic sympathetic neurons

PubMed Central

1985-01-01

Sympathetic neurons taken from rat superior cervical ganglia and grown in culture acquire cholinergic function under certain conditions. These cholinergic sympathetic neurons, however, retain a number of adrenergic properties, including the enzymes involved in the synthesis of norepinephrine (NE) and the storage of measurable amounts of NE. These neurons also retain a high affinity uptake system for NE; despite this, the majority of the synaptic vesicles remain clear even after incubation in catecholamines. The present study shows, however, that if these neurons are depolarized before incubation in catecholamine, the synaptic vesicles acquire dense cores indicative of amine storage. These manipulations are successful when cholinergic function is induced with either a medium that contains human placental serum and embryo extract or with heart-conditioned medium, and when the catecholamine is either NE or 5-hydroxydopamine. In some experiments, neurons are grown at low densities and shown to have cholinergic function by electrophysiological criteria. After incubation in NE, only 6% of the synaptic vesicles have dense cores. In contrast, similar neurons depolarized (80 mM K+) before incubation in catecholamine contain 82% dense-cored vesicles. These results are confirmed in network cultures where the percentage of dense-cored vesicles is increased 2.5 to 6.5 times by depolarizing the neurons before incubation with catecholamine. In both single neurons and in network cultures, the vesicle reloading is inhibited by reducing vesicle release during depolarization with an increased Mg++/Ca++ ratio or by blocking NE uptake either at the plasma membrane (desipramine) or at the vesicle membrane (reserpine). In addition, choline appears to play a competitive role because its presence during incubation in NE or after reloading results in decreased numbers of dense-cored vesicles. We conclude that the depolarization step preceding catecholamine incubation acts to empty the vesicles of acetylcholine, thus allowing them to reload with catecholamine. These data also suggest that the same vesicles may contain both neurotransmitters simultaneously. PMID:4008529

Decay of Hurricanes Tracked by Dense Seismic Array

NASA Astrophysics Data System (ADS)

Lamontagne, A.; Tanimoto, T.

2014-12-01

Tropical cyclones (hurricanes and typhoons) are mostly atmospheric phenomena but they also generate significant ground motions in the solid earth when they become strong. If a dense seismological array existed along the path of a hurricane, we could learn about some processes near the hurricane eye and the change of its intensity through seismic data. We found a few cases of tropical cyclones that passed through the Transportable Array of Earthscope (TA) in the last four years. They provide some interesting time-evolving characteristics of hurricanes but in most cases seismic signals are too weak to gain any insight into the processes. The only exception we have found so far is Hurricane Isaac in 2012. Hurricane Isaac was mostly a tropical storm during its lifetime but it became a hurricane about 12 hours before the first landfall at the mouth of the Mississippi river at 0000 UTC August 29. The eye then went back over the ocean, but stayed near the coast, and made landfall again at 0800 UTC August 29. After this landfall, it went through the TA. This gave us an opportunity to study the decay of this hurricane based on seismic data. Our basic data are amplitude-distance plots for each 6-hour hurricane location. We confine our analysis to frequencies below 0.02 Hz because in higher frequency bands seismic waves were broader oceans, not necessarily near the hurricane eye. Right after the landfall, we found a sharp peak at about 75 km from the eye. This is most likely the location of the eyewall, where a strong ascending flow is known to exist. Over the next 12 hours, we see this peak deteriorate, which is undoubtedly related to the decay of the hurricane after landfall. The peak remained at the same location for these 12 hours and then in the following 18 hours started to move farther from the eye, to about 250 km. Therefore, we can monitor how the eyewall deteriorated over the 30 hours after landfall. The emphasis of this study will be on Hurricane Isaac but we will also report other cases for comparison and to clarify what we can learn about the processes near the hurricane eye by seismic data.

Trends in Northern Hemisphere surface cyclone frequency and intensity

USGS Publications Warehouse

McCabe, G.J.; Clark, M.P.; Serreze, Mark C.

2001-01-01

One of the hypothesized effects of global warming from increasing concentrations of greenhouse gases is a change in the frequency and/or intensity of extratropical cyclones. In this study, winter frequencies and intensities of extratropical cyclones in the Northern Hemisphere for the period 1959-97 are examined to determine if identifiable trends are occurring. Results indicate a statistically significant decrease in midlatitude cyclone frequency and a significant increase in high-latitude cyclone frequency. In addition, storm intensity has increased in both the high and midlatitudes. The changes in storm frequency correlate with changes in winter Northern Hemisphere temperature and support hypotheses that global warming may result in a northward shift of storm tracks in the Northern Hemisphere.

Sedimentological characteristics of the 2015 Tropical Cyclone Pam overwash deposits from Vanuatu, South Pacific

NASA Astrophysics Data System (ADS)

Hong, I.; Pilarczyk, J.; Horton, B.; Fritz, H. M.; Kosciuch, T. J.; Wallace, D. J.; Dike, C.; Rarai, A.; Harrison, M. J.; Jockley, F. R.

2016-12-01

Historical observations and overwash sediments deposited by prehistoric tropical cyclones (TC) enable the assessment of long-term patterns of tropical cyclone variability. Prehistoric TC reconstructions, however, are limited in their ability to quantify the intensity of past events. Modern analogues present an opportunity to characterize overwash sediments deposited by a TC of known intensity. On 13 March 2015, TC Pam made landfall on Vanuatu as a Category 5 storm with 10-minute sustained wind speeds as high as 250 km/h. Less than three months after landfall, we (1) measured the height and inland extent of TC Pam's storm surge; and (2) described the sedimentological characteristics of the TC Pam overwash deposits focusing on two of the hardest hit islands, Efate and Tanna. TC Pam's storm surge inundated Vanuatu with maximum high water marks of 5.6 m above mean sea level (MSL) on the island of Efate and 5.5 m above MSL on the island of Tanna. We measured surge heights of 4.2 m above MSL at our study area Manuro on Efate and 3.3 m above MSL at our study area Port Resolution Bay on Tanna. TC Pam deposited a medium-grained (mean: 1.20 Φ), moderately well-sorted (sorting: 0.55 Φ) mixed-carbonate sand with trace amounts of volcanic sediments and coral fragments at Manuro. The sand extends 130 m inland, abruptly transitioning into pumice that extends 400 m inland into Lake Otas. A sharp contact separates the base of the sand and the underlying organic-rich sand unit. In contrast, TC Pam deposited a medium-grained (mean: 1.81 Φ), moderately well-sorted (sorting: 0.67 Φ) volcanic sand at Port Resolution Bay. The sand extends up to 320 m inland. A sharp contact separates the base of the sand and the underlying rooted sandy soil. We found both a coarsening upward and fining upward sequences in trench M1 at Manuro and upward fining in trenches RB 3 and RB 2 at Port Resolution Bay. We used a combination of measured flow heights obtained at the Port Resolution Bay site and laboratory derived grain size settling velocities to calculate the distance of sediment transport caused by TC Pam's storm surge. Based on the distribution of settling velocities from our samples, transport distances for material deposited in the trench suggests a source for the overwash sand ranging from the supratidal berm to 290 m seaward in the nearshore at Port Resolution Bay.

Do Tropical Cyclones Shape Shorebird Habitat Patterns? Biogeoclimatology of Snowy Plovers in Florida

DTIC Science & Technology

2011-01-12

THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 coastal birds in north-west Europe . Using historical data...cyclone season begins in June and ends in November. A cyclone is classified as a tropical depression, tropical storm or hurricane depending on its lifetime...fledge before the storms arrive and subsequently are able to seek inland protection with the adults during the storms [26,27]. However, tropical cyclones

Proceedings of the 1998 Scientific Conference on Obscuration and Aerosol Research

DTIC Science & Technology

1999-10-01

water surroundings. Figure 2 exhibits minimal terrain effects upon the flow field as streamlines for this simple set of variable terrain for...Cyclone, where the cyclone is fitted with an upstream water spray for washing the cyclone wall. Sampling flow rate is 990 L/min and is controlled by a...990 L/min (35 cfm) and passes the air through a glass cyclone where aerosol particles with sufficient inertia are deposited. Water mist is introduced

Reduced death rates from cyclones in Bangladesh: what more needs to be done?

PubMed Central

Hashizume, Masahiro; Kolivras, Korine N; Overgaard, Hans J; Das, Bivash; Yamamoto, Taro

2012-01-01

Abstract Tropical storms, such as cyclones, hurricanes and typhoons, present major threats to coastal communities. Around two million people worldwide have died and millions have been injured over the past two centuries as a result of tropical storms. Bangladesh is especially vulnerable to tropical cyclones, with around 718 000 deaths from them in the past 50 years. However, cyclone-related mortality in Bangladesh has declined by more than 100-fold over the past 40 years, from 500 000 deaths in 1970 to 4234 in 2007. The main factors responsible for these reduced fatalities and injuries are improved defensive measures, including early warning systems, cyclone shelters, evacuation plans, coastal embankments, reforestation schemes and increased awareness and communication. Although warning systems have been improved, evacuation before a cyclone remains a challenge, with major problems caused by illiteracy, lack of awareness and poor communication. Despite the potential risks of climate change and tropical storms, little empirical knowledge exists on how to develop effective strategies to reduce or mitigate the effects of cyclones. This paper summarizes the most recent data and outlines the strategy adopted in Bangladesh. It offers guidance on how similar strategies can be adopted by other countries vulnerable to tropical storms. Further research is needed to enable countries to limit the risks that cyclones present to public health. PMID:22423166

Spherical Harmonic-based Random Fields Based on Real Particle 3D Data: Improved Numerical Algorithm and Quantitative Comparison to Real Particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

X Liu; E Garboczi; m Grigoriu

Many parameters affect the cyclone efficiency, and these parameters can have different effects in different flow regimes. Therefore the maximum-efficiency cyclone length is a function of the specific geometry and operating conditions in use. In this study, we obtained a relationship describing the minimum particle diameter or maximum cyclone efficiency by using a theoretical approach based on cyclone geometry and fluid properties. We have compared the empirical predictions with corresponding literature data and observed good agreement. The results address the importance of fluid properties. Inlet and vortex finder cross-sections, cone-apex diameter, inlet Reynolds number and surface roughness are found tomore » be the other important parameters affecting cyclone height. The surface friction coefficient, on the other hand, is difficult to employ in the calculations.We developed a theoretical approach to find the maximum-efficiency heights for cyclones with tangential inlet and we suggested a relation for this height as a function of cyclone geometry and operating parameters. In order to generalize use of the relation, two dimensionless parameters, namely for geometric and operational variables, we defined and results were presented in graphical form such that one can calculate and enter the values of these dimensionless parameters and then can find the maximum efficiency height of his own specific cyclone.« less

Statistical Detection of Anthropogenic Temporal Changes in the Distribution of Tropical Cyclones

NASA Astrophysics Data System (ADS)

Joannes-boyau, R.; Bodin, T.; Scheffers, A.; Sambridge, M.

2012-12-01

Recent studies highlighting the potential impact of climate change on tropical cyclones have added fuel to the already controversial debates. The link between climate change and tropical cyclone intensity and frequency has been disputed, as both appear to remain in the natural variability. The difficulty lies in our ability to distinguish natural changes from anthropogenic-induced anomalies. The increased anthropogenic atmospheric carbon dioxide leads to environmental changes such as warmer Sea Surface Temperatures (SST) and thus could impact tropical cyclones intensities and frequencies. However, recent studies show that, against an increasing SST, no global trend in respect to cyclone frequency has yet emerged. Scientists have warned to consider the heterogeneity of the existing dataset; especially since the historical tropical cyclone record is frequently accused to be incomplete. Given the abundance of cyclone record data and its likely sensitivity to a number of environmental factors, the real limitation comes from our ability to understand the record as a whole. Thus, strong arguments against the impartiality of proposed models are often debated. We will present an impartial and independent statistical tool applicable to a wide variety of physical and biological phenomena such as processes described by power laws, to observe temporal variations in the tropical cyclone track record from 1842 to 2010. This methodology allows us to observe the impact of anthropogenic-induced modifications on climatic events, without being clustered in subjective parameterised models.

PFB coal fired combined cycle development program. Advanced hot gas cleanup concept evaluation (Task 4. 3). Volume A. Aerodyne cyclone evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

This report summarizes the results of testing of a rotary flow cyclone, manufactured by Aerodyne Development Corporation under license by Siemens Kraftwerk Union. This cyclone was selected for evaluation due to the unusually high separative efficiencies claimed by the manufacturer (based on developer data), and relative lack of open literature data. The most significant finding of this work was the observation that electrostatic forces could enhance or, in fact, dominate the separation process. Separative efficiencies, with electrostatic forces present, were found to be substantially independent of flow rate and, by inference, could be independent of unit size. This finding suggestsmore » that large cyclones with natural or augmented electrostatic forces employed in the hot gas cleanup train of the CFCC system may not suffer the performance degradation compared to small cyclones, as projected from conventional inertial theory. This is of special importance since the use of many small cyclones in parallel, or multicyclones, commonly suffers from fouling and this approach is not recommended in the CFCC application. The original objective of this investigation was to assess the relative merits of the Aerodyne cyclone separator. It was found from both the cold flow and the hot flow tests that its separative efficiencies are disappointingly poorer than expectations (in agreement with Westinghouse results), and even poorer than conventional cyclones.« less

Heavy rainfall in Mediterranean cyclones. Part I: contribution of deep convection and warm conveyor belt

NASA Astrophysics Data System (ADS)

Flaounas, Emmanouil; Kotroni, Vassiliki; Lagouvardos, Konstantinos; Gray, Suzanne L.; Rysman, Jean-François; Claud, Chantal

2018-04-01

In this study, we provide an insight to the role of deep convection (DC) and the warm conveyor belt (WCB) as leading processes to Mediterranean cyclones' heavy rainfall. To this end, we use reanalysis data, lighting and satellite observations to quantify the relative contribution of DC and the WCB to cyclone rainfall, as well as to analyse the spatial and temporal variability of these processes with respect to the cyclone centre and life cycle. Results for the period 2005-2015 show that the relationship between cyclone rainfall and intensity has high variability and demonstrate that even intense cyclones may produce low rainfall amounts. However, when considering rainfall averages for cyclone intensity bins, a linear relationship was found. We focus on the 500 most intense tracked cyclones (responsible for about 40-50% of the total 11-year Mediterranean rainfall) and distinguish between the ones producing high and low rainfall amounts. DC and the WCB are found to be the main cause of rainfall for the former (producing up to 70% of cyclone rainfall), while, for the latter, DC and the WCB play a secondary role (producing up to 50% of rainfall). Further analysis showed that rainfall due to DC tends to occur close to the cyclones' centre and to their eastern sides, while the WCBs tend to produce rainfall towards the northeast. In fact, about 30% of rainfall produced by DC overlaps with rainfall produced by WCBs but this represents only about 8% of rainfall produced by WCBs. This suggests that a considerable percentage of DC is associated with embedded convection in WCBs. Finally, DC was found to be able to produce higher rain rates than WCBs, exceeding 50 mm in 3-h accumulated rainfall compared to a maximum of the order of 40 mm for WCBs. Our results demonstrate in a climatological framework the relationship between cyclone intensity and processes that lead to heavy rainfall, one of the most prominent environmental risks in the Mediterranean. Therefore, we set perspectives for a deeper analysis of the favourable atmospheric conditions that yield high impact weather.

The Sharav Cyclone: Observations and some theoretical considerations

NASA Astrophysics Data System (ADS)

Alpert, P.; Ziv, B.

1989-12-01

A special study of the Sharav Cyclones indicates that they are the result of large-scale weak baroclinicity, enhanced by vigorous boundary-layer baroclinicity between the North African coast and the Mediterranean. It is illustrated how the jet stream plays a major role in the vertical circulation in producing a complex cyclonic circulation dominated by at least three mechanisms: large-scale interior baroclinicity, boundary-layer baroclinicity, and jet stream related circulations. The main characteristics of the Sharav Cyclone (also called the Saharan Depression or Khamsin Depression) in the Mediterranean are reviewed. Unlike the cold winter cyclone, the Sharav Cyclone is a spring cyclone. Its tracks lie mainly along the North African coast and turn to the north near the southeastern Mediterranean. Its warm front is active and is sometimes associated with extremely high surface temperatures. Its cold front is shallow. The Sharav Cyclone moves eastward relatively fast, typically faster than 10 m s-1, and with a small speed variability. In general, there is an upper level trough to the west of the surface low and the surface horizontal scale is of the order of 500-1000 km. Finally, it is frequently associated with heavy dust/sand storms and low visibilities. Some of these features are illustrated in a case study of the April 28-30, 1986, cyclone. Vertical cross sections indicate a deep circulation associated with the exit region of an upper level jet. In addition to presenting evidence that the Sharav Cyclone is a deep tropospheric circulation, it is shown that the transverse indirect circulation at the exit region of the jet is a major component of its circulation. The classic two-level baroclinic model (Phillips, 1954) is applied. The effects of the major diabatic heating due to the sensible heat flux above the North African desert and the large north to south temperature gradients are incorporated through the thermal wind of the basic state. The model predicts the fast eastward motion, the relatively smaller horizontal scale and the fast growth rate. Furthermore, the model predicts an annual maximum growth rate in April and a secondary peak in October, which agrees with the frequency of occurrences of the Sharav Cyclones.

An important role of the moisture supply from the Kuroshio Current/Kuroshio Extension in the rapid development of an explosive cyclone

NASA Astrophysics Data System (ADS)

Hirata, H.; Kawamura, R.; Kato, M.; Shinoda, T.

2014-12-01

We investigated how the moisture supply from the Kuroshio Current/Kuroshio Extension affects the rapid intensification of an explosive cyclone using a couple atmosphere-ocean non-hydrostatic model, CReSS-NHOES. The Cloud-Resolving Storm Simulator (CReSS) and the Non-Hydrostatic Ocean model for the Earth Simulator (NHOES) have been developed by the Hydrospheric Atmospheric Research Center of Nagoya University and the Japan Agency for Marine-Earth Science and Technology, respectively. We performed a numerical simulation of an extratropical cyclone migrating along the southern periphery of the Kuroshio Current on January 14, 2013, that developed most rapidly in recent years in the vicinity of Japan. The evolutions of surface fronts related to the cyclone simulated by the CReSS-NHOES closely resemble Shapiro-Keyser model. In the lower troposphere, the cyclone's bent-back front and the associated frontal T-bone structure become evident with the cyclone development. Cold Conveyor Belt (CCB) is also well organized over the northern part of the cyclone. During its developing stage, since the CCB dominates just over the Kuroshio Current/Kuroshio Extension, a large amount of moisture is efficiently supplied from the warm current into the CCB. The vapor evaporated from the underlying warm current is transported into the bent-back front by the CCB and converges horizontally in the vicinity of the front. As a result, strong diabatic heating arises over the corresponding moisture convergence area in that vicinity, indicating that the abundant moisture due to the warm current plays a vital role in rapid development of the cyclone through latent heat release processes. Both processes of the moisture transport from the warm current into the cyclone system via the CCB and of the latent heat release around the bent-back front are also confirmed by trajectory analyses. The rapid SLP decrease of the cyclone center can in turn increase the moisture supply from the warm current through enhancement of the CCB. We anticipate that such a feedback process plays a key role in the rapid intensification of the cyclone highlighted in this study.

Comprehensive interpretation of thermal dileptons measured at the CERN super proton synchrotron.

PubMed

van Hees, Hendrik; Rapp, Ralf

2006-09-08

Employing thermal dilepton rates based on a medium-modified electromagnetic correlation function we show that recent dimuon spectra of the NA60 Collaboration in central In-In collisions at the CERN-SPS can be understood in terms of radiation from a hot and dense hadronic medium. Earlier calculated in-medium rho-meson spectral functions provide an accurate description of the data up to dimuon invariant masses of about M approximately or equal to 0.9 GeV, with good sensitivity to the predicted rho-meson line shape, identifying baryon-induced modifications as the prevalent ones. A reliable evaluation of the contribution enables the study of further medium effects: at masses M>0.9 GeV, 4-pion type annihilation accounts for the experimentally observed excess (possibly augmented by effects of "chiral mixing"), while predictions for thermal emission from in-medium omega and phi mesons may be tested in the future.

The Importance of Coral Larval Recruitment for the Recovery of Reefs Impacted by Cyclone Yasi in the Central Great Barrier Reef

PubMed Central

Lukoschek, Vimoksalehi; Cross, Peter; Torda, Gergely; Zimmerman, Rachel; Willis, Bette L.

2013-01-01

Cyclone Yasi, one of the most severe tropical storms on record, crossed the central Great Barrier Reef (GBR) in February 2011, bringing wind speeds of up to 285 km hr−1 and wave heights of at least 10 m, and causing massive destruction to exposed reefs in the Palm Island Group. Following the cyclone, mean (± S.E.) hard coral cover ranged from just 2.1 (0.2) % to 5.3 (0.4) % on exposed reefs and no reproductively mature colonies of any species of Acropora remained. Although no fragments of Acropora were found at impacted exposed sites following the cyclone, small juvenile colonies of Acropora (<10 cm diameter) were present, suggesting that their small size and compact morphologies enabled them to survive the cyclone. By contrast, sheltered reefs appeared to be unaffected by the cyclone. Mean (± S.E.) hard coral cover ranged from 18.2 (2.4) % to 30.0 (1.0) % and a large proportion of colonies of Acropora were reproductively mature. Macroalgae accounted for 8 to 16% of benthic cover at exposed sites impacted by cyclone Yasi but were absent at sheltered sites. Mean (± S.E.) recruitment of acroporids to settlement tiles declined from 25.3 (4.8) recruits tile−1 in the pre-cyclone spawning event (2010) to 15.4 (2.2) recruits tile−1 in the first post-cyclone spawning event (2011). Yet, post-cyclone recruitment did not differ between exposed (15.2±2.1 S.E.) and sheltered sites (15.6±2.2 S.E.), despite the loss of reproductive colonies at the exposed sites, indicating larval input from external sources. Spatial variation in impacts, the survival of small colonies, and larval replenishment to impacted reefs suggest that populations of Acropora have the potential to recover from this severe disturbance, provided that the Palm Islands are not impacted by acute disturbances or suffer additional chronic stressors in the near future. PMID:23755223

Extreme cyclone events in the Arctic: Wintertime variability and trends

NASA Astrophysics Data System (ADS)

Rinke, A.; Maturilli, M.; Graham, R. M.; Matthes, H.; Handorf, D.; Cohen, L.; Hudson, S. R.; Moore, J. C.

2017-12-01

Extreme cyclone events often occur during Arctic winters, and are of concern as they transport heat and moisture into the Arctic, which is associated with mixed-phase clouds and increased longwave downward radiation, and can cause temperatures to rise above freezing resulting in wintertime sea-ice melting or retarded sea-ice growth. With Arctic amplification and associated reduced sea-ice cover and warmer sea surface temperatures, the occurrence of extreme cyclones events could be a plausible scenario. We calculate the spatial patterns, and changes and trends of the number of extreme cyclone events in the Arctic based on ERA-Interim six-hourly sea level pressure (SLP) data for winter (November-February) 1979-2015. Further, we analyze the SLP data from the Ny-Ålesund station for the same 37 year period. We define an extreme cyclone event by an extreme low central pressure (SLP below 985 hPa, which is the 5th percentile of the Ny-Ålesund/N-ICE2015 SLP data). Typically 20-40 extreme cyclone events (sometimes called `weather bombs') occur in the Arctic North Atlantic per winter season, with an increasing trend of 6 events/decade, according to the Ny-Ålesund data. This increased frequency of extreme cyclones drive considerable warming in that region, consistent with the observed significant winter warming of 3 K/decade. The positive winter trend in extreme cyclones is dominated by a positive monthly trend of about 3-4 events/decade in November-December, due mainly to an increasing persistence of extreme cyclone events. A negative trend in January opposes this, while there is no significant trend in February. We relate the regional patterns of the trend in extreme cyclones to anomalously low sea-ice conditions in recent years, together with associated large-scale atmospheric circulation changes such as "blocking-like" circulation patterns (e.g. Scandinavian blocking in December and Ural blocking during January-February).

The importance of coral larval recruitment for the recovery of reefs impacted by cyclone Yasi in the central Great Barrier Reef.

PubMed

Lukoschek, Vimoksalehi; Cross, Peter; Torda, Gergely; Zimmerman, Rachel; Willis, Bette L

2013-01-01

Cyclone Yasi, one of the most severe tropical storms on record, crossed the central Great Barrier Reef (GBR) in February 2011, bringing wind speeds of up to 285 km hr⁻¹ and wave heights of at least 10 m, and causing massive destruction to exposed reefs in the Palm Island Group. Following the cyclone, mean (± S.E.) hard coral cover ranged from just 2.1 (0.2) % to 5.3 (0.4) % on exposed reefs and no reproductively mature colonies of any species of Acropora remained. Although no fragments of Acropora were found at impacted exposed sites following the cyclone, small juvenile colonies of Acropora (<10 cm diameter) were present, suggesting that their small size and compact morphologies enabled them to survive the cyclone. By contrast, sheltered reefs appeared to be unaffected by the cyclone. Mean (± S.E.) hard coral cover ranged from 18.2 (2.4) % to 30.0 (1.0) % and a large proportion of colonies of Acropora were reproductively mature. Macroalgae accounted for 8 to 16% of benthic cover at exposed sites impacted by cyclone Yasi but were absent at sheltered sites. Mean (± S.E.) recruitment of acroporids to settlement tiles declined from 25.3 (4.8) recruits tile⁻¹ in the pre-cyclone spawning event (2010) to 15.4 (2.2) recruits tile⁻¹ in the first post-cyclone spawning event (2011). Yet, post-cyclone recruitment did not differ between exposed (15.2±2.1 S.E.) and sheltered sites (15.6±2.2 S.E.), despite the loss of reproductive colonies at the exposed sites, indicating larval input from external sources. Spatial variation in impacts, the survival of small colonies, and larval replenishment to impacted reefs suggest that populations of Acropora have the potential to recover from this severe disturbance, provided that the Palm Islands are not impacted by acute disturbances or suffer additional chronic stressors in the near future.

Response of primary and secondary rainforest flowers and fruits to a cyclone, and implications for plant-servicing bats.

PubMed

Scanlon, Annette T; Petit, Sophie; Tuiwawa, Marika; Naikatini, Alivereti

2018-02-24

The response of primary (PF) and secondary (SF) rainforests to cyclones has broad implications for servicing fauna and the resilience of forest functions. We collected fine-scale data on the reproductive phenology of plant communities in Fijian PF and SF in 12 monthly surveys before and after Cyclone Tomas (2010). We generated a resource index from the reproductive loads of 2218 trees and 1150 non-trees (>190 species) and trunk and stem diameter to assess patterns in resource abundance for nectarivores and frugivores (hereafter NF resources). We aimed to determine (i) whether species richness of NF resources differed between forests; (ii) the patterns of resilience of NF resources at community level in both forests after a cyclone; and (iii) the effect of response on NF resources for plant-servicing bats (Pteropodidae). In 12 months preceding the cyclone, NF resources were greater in PF trees; non-tree resources fluctuated and were greater in SF. Lower species richness of NF resources in SF indicated that fewer opportunities exist there for exploitation by a diverse fauna. More resources were available for bats in PF. In 12 months following the cyclone, PF flowers and fruits, and SF fruits specifically used by pteropodid bats decreased for trees. Non-tree resources were especially susceptible to the cyclone. No universal pattern of decline was associated with the cyclone; instead, some NF resources declined and others were resilient or responded rapidly to a post-cyclone environment. Both PF and SF demonstrated resilience at the community level via increased flower survival (PF) and rapid flower production (SF). Reduced species richness of NF resources in SF will compromise future resilience and response to disturbance, including for threatened pteropodid bat species. These findings are critical for long-term management of forests, given predicted increases in cyclone frequency and intensity associated with anthropogenic climate change. © 2018 John Wiley & Sons Ltd.

Disaster, Deprivation and Death: Large but delayed infant mortality in the wake of Filipino tropical cyclones

NASA Astrophysics Data System (ADS)

Anttila-Hughes, J. K.; Hsiang, S. M.

2011-12-01

Tropical cyclones are some of the most disastrous and damaging of climate events, and estimates of their destructive potential abound in the natural and social sciences. Nonetheless, there have been few systematic estimates of cyclones' impact on children's health. This is concerning because cyclones leave in their wake a swath of asset losses and economic deprivation, both known to be strong drivers of poor health outcomes among children. In this paper we provide a household-level estimate of the effect of tropical cyclones on infant mortality in the Philippines, a country with one of the most active cyclone climatologies in the world. We reconstruct historical cyclones with detailed spatial and temporal resolution, allowing us to estimate the multi-year effects of cyclones on individuals living in specific locations. We combine the cyclone reconstruction with woman-level fertility and mortality data from four waves of the Filipino Demographic and Health Survey, providing birth histories for over 55,000 women. In multiple regressions that control for year and region fixed effects as well as intra-annual climate variation, we find that there is a pronounced and robust increase in female infant mortality among poor families in the 12-24 months after storms hit. The estimated mortality rate among this demographic subgroup is much larger than official mortality rates reported by the Filipino government immediately after storms, implying that much of a cyclone's human cost arrives well after the storm has passed. We find that high infant mortality rates are associated with declines in poor families' income and expenditures, including consumption of food and medical services, suggesting that the mechanism by which these deaths are effected may be economic deprivation. These results indicate that a major health and welfare impact of storms has been thus far overlooked, but may be easily prevented through appropriately targeted income support policies.

Role of the Southwest Tropical Indian Ocean on the Modulation of Tropical Cyclones

NASA Astrophysics Data System (ADS)

Burns, J. M.; Bulusu, S.

2016-02-01

The Seychelles-Chagos Thermocline Ridge (SCTR), located in the Indian Ocean and bound by 55°E-65°E and 5°S-12°S, is a key region for air-sea interaction. This feature inhabits one of the seven ocean basins where tropical cyclones regularly form and is unique in that the variability of the subsurface can influence cyclogenesis. Tropical cyclone days for this region span from November through April, with peaks in the months of January and February. The influence of thermocline variation is particularly strong during the months of December through May and it is known that a high correlation exists between the depth of the thermocline and sea surface temperature (key ingredient for cyclogenesis). Past research provides evidence that more tropical cyclone days are observed in Southwest Tropical Indian Ocean (SWTIO) during austral summers with a deep thermocline ridge than in austral summers when a shallow thermocline ridge exists. The formation and thickness of the Barrier layer (BL) have also been shown to impact tropical cyclones in this region. BL formation is an important parameter for surface heat exchange. The amount of salt in the boundary layer may also effect heat exchange and thus cyclones. Other ocean basins have verified that salt-stratified barrier layers influence the intensification of tropical cyclones, however, the role that salinity in SWTIO plays in the modulation of tropical cycles has still yet to be explored. This study further explores how the dynamic properties of the SCTR influence the modulation of cyclones. Primarily Argo observations of salinity and temperature along with Soil Moisture Ocean Salinity (SMOS) and Aquarius salinity, and Hybrid Coordinate Ocean Model (HYCOM) simulations are used to examine this influence of the BL and salinity on cyclone formation and intensity in this region. This study is progressed with a particular focus on the austral summer of 2012/2013 when seven tropical cyclones developed in the region.

Tropical Cyclone Signatures in Atmospheric Convective Available Potential Energy

NASA Astrophysics Data System (ADS)

Studholme, Joshua; Gulev, Sergey

2016-04-01

Tropical cyclones play an important role in the climate system providing transports of energy and water vapor, forcing the ocean, and also affecting mid-latitude circulation phenomena. Tropical cyclone tracks experience strong interannual variability and in addition, longer term trend-like changes in all ocean basins. Analysis of recent historical data reveal a poleward shift in the locations of tropical cyclone tracks in both the Northern and Southern Hemispheres (Kossin et al. 2014, Nature, 509, 349-352). The physical consequences of these alterations are largely unconstrained. For example, the increasing encroachment of tropical cyclone activity into the extra-tropical environment presents a novel and still poorly understood paradigm for tropical-extratropical interactions. In this respect, the role that the atmospheric convective available potential energy (CAPE) plays in the dynamics of tropical cyclones is highly interesting. The two characteristic global-scale spatial patterns in CAPE are identified using EOF analysis. The first pattern shows an abundance of CAPE in the centre of the Pacific and corresponds to the El Nino Southern Oscillation. The second one is capturing positive CAPE anomalies in the oceanic tropics and negative anomalies over equatorial Africa. Associated with these buoyancy patterns, alterations in tropical cyclone activity occur in all basins forming both zonal and meridional patterns. Atmospheric buoyancy is the trigger for deep convection, and subsequently cyclone genesis. This is the mechanism of impact upon location at the start of cyclone tracks. It is found to have less impact upon where cyclones subsequently move, whether or not they undergo extratropical transition and when and where they experience lysis. It is shown that CAPE plays a critical role in the general circulation in the tropics which in turn is the larger steering context for embedded systems within the Walker and Hadley cells. So this lack of `latter life' impact posits an interesting start for further theoretical and physical consideration.

Ocean barrier layers’ effect on tropical cyclone intensification

PubMed Central

Balaguru, Karthik; Chang, Ping; Saravanan, R.; Leung, L. Ruby; Xu, Zhao; Li, Mingkui; Hsieh, Jen-Shan

2012-01-01

Improving a tropical cyclone’s forecast and mitigating its destructive potential requires knowledge of various environmental factors that influence the cyclone’s path and intensity. Herein, using a combination of observations and model simulations, we systematically demonstrate that tropical cyclone intensification is significantly affected by salinity-induced barrier layers, which are “quasi-permanent” features in the upper tropical oceans. When tropical cyclones pass over regions with barrier layers, the increased stratification and stability within the layer reduce storm-induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy flux from the ocean to the atmosphere and, consequently, an intensification of tropical cyclones. On average, the tropical cyclone intensification rate is nearly 50% higher over regions with barrier layers, compared to regions without. Our finding, which underscores the importance of observing not only the upper-ocean thermal structure but also the salinity structure in deep tropical barrier layer regions, may be a key to more skillful predictions of tropical cyclone intensities through improved ocean state estimates and simulations of barrier layer processes. As the hydrological cycle responds to global warming, any associated changes in the barrier layer distribution must be considered in projecting future tropical cyclone activity. PMID:22891298

Predicting the trajectories and intensities of hurricanes by applying machine learning techniques

NASA Astrophysics Data System (ADS)

Sujithkumar, A.; King, A. W.; Kovilakam, M.; Graves, D.

2017-12-01

The world has witnessed an escalation of devastating hurricanes and tropical cyclones over the last three decades. Hurricanes and tropical cyclones of very high magnitude will likely be even more frequent in a warmer world. Thus, precise forecasting of the track and intensity of hurricane/tropical cyclones remains one of the meteorological community's top priorities. However, comprehensive prediction of hurricane/ tropical cyclone is a difficult problem due to the many complexities of underlying physical processes with many variables and complex relations. The availability of global meteorological and hurricane/tropical storm climatological data opens new opportunities for data-driven approaches to hurricane/tropical cyclone modeling. Here we report initial results from two data-driven machine learning techniques, specifically, random forest (RF) and Bayesian learning (BL) to predict the trajectory and intensity of hurricanes and tropical cyclones. We used International Best Track Archive for Climate Stewardship (IBTrACS) data along with weather data from NOAA in a 50 km buffer surrounding each of the reported hurricane and tropical cyclone tracts to train the model. Initial results reveal that both RF and BL are skillful in predicting storm intensity. We will also present results for the more complicated trajectory prediction.

Tropical Cyclone-Driven Sediment Dynamics Over the Australian North West Shelf

NASA Astrophysics Data System (ADS)

Dufois, François; Lowe, Ryan J.; Branson, Paul; Fearns, Peter

2017-12-01

Owing to their strong forcing at the air-sea interface, tropical cyclones are a major driver of hydrodynamics and sediment dynamics of continental shelves, strongly impacting marine habitats and offshore industries. Despite the North West Shelf of Australia being one of the most frequently impacted tropical cyclone regions worldwide, there is limited knowledge of how tropical cyclones influence the sediment dynamics of this shelf region, including the significance of these episodic extreme events to the normal background conditions that occur. Using an extensive 2 year data set of the in situ sediment dynamics and 14 yearlong calibrated satellite ocean-color data set, we demonstrate that alongshore propagating cyclones are responsible for simultaneously generating both strong wave-induced sediment resuspension events and significant southwestward subtidal currents. Over the 2 year study period, two particular cyclones (Iggy and Narelle) dominated the sediment fluxes resulting in a residual southwestward sediment transport over the southern part of the shelf. By analyzing results from a long-term (37 year) wind and wave hindcast, our results suggest that at least 16 tropical cyclones had a strong potential to contribute to that southwestward sediment pathway in a similar way to Iggy and Narelle.

Seasonal differences in the response of Arctic cyclones to climate change in CESM1

NASA Astrophysics Data System (ADS)

Day, Jonathan J.; Holland, Marika M.; Hodges, Kevin I.

2017-06-01

The dramatic warming of the Arctic over the last three decades has reduced both the thickness and extent of sea ice, opening opportunities for business in diverse sectors and increasing human exposure to meteorological hazards in the Arctic. It has been suggested that these changes in environmental conditions have led to an increase in extreme cyclones in the region, therefore increasing this hazard. In this study, we investigate the response of Arctic synoptic scale cyclones to climate change in a large initial value ensemble of future climate projections with the CESM1-CAM5 climate model (CESM-LE). We find that the response of Arctic cyclones in these simulations varies with season, with significant reductions in cyclone dynamic intensity across the Arctic basin in winter, but with contrasting increases in summer intensity within the region known as the Arctic Ocean cyclone maximum. There is also a significant reduction in winter cyclogenesis events within the Greenland-Iceland-Norwegian sea region. We conclude that these differences in the response of cyclone intensity and cyclogenesis, with season, appear to be closely linked to changes in surface temperature gradients in the high latitudes, with Arctic poleward temperature gradients increasing in summer, but decreasing in winter.

Pseudoscalar D and B mesons in the hot dense and nonstrange symmetric medium

NASA Astrophysics Data System (ADS)

Chhabra, Rahul; Kumar, Arvind

2017-01-01

We investigate the effect of temperature and density on the shift in the masses and decay constants of the pseudoscalar D and B mesons in the nonstrange symmetric medium. We use chiral SU(3) model to calculate the medium modified scalar and isoscalar fields σ, ζ, δ and χ. We use these modified fields to calculate the in-medium quark and gluon condensates by solving the coupled equations of motions in the chiral SU(3) model. We obtain the medium modified mass and decay constant through these medium modified condensates using the QCD sum rules. Further we use the 3P0 model by taking the internal structure of the mesons to calculate the in-medium decay width of the higher charmonium states χ(3556) , ψ(3686) and ψ(3770) to the D D pairs, through the in-medium mass of D meson and neglecting the mass modification of higher charmonium states. We also compare the present data with the previous results. These results of present investigation may be important to explain the possible outcomes of the experiments like CBM, Panda at GSI.

Developmental anatomy of blueberry (Vaccinium corymbosum L. ‘Aurora’) shoot regeneration

USDA-ARS?s Scientific Manuscript database

The culture of Vaccinium corymbosum L. ’Aurora’ leaves on regeneration medium results in the regeneration of adventitious shoots. We present anatomical evidence that these new shoot apices are directly regenerated from the cultured blades. Mounds of densely staining cells, which formed from epidermi...

A laboratory method for precisely determining the micro-volume-magnitudes of liquid efflux

NASA Technical Reports Server (NTRS)

Cloutier, R. L.

1969-01-01

Micro-volumetric quantities of ejected liquid are made to produce equal volumetric displacements of a more dense material. Weight measurements are obtained on the displaced heavier liquid and used to calculate volumes based upon the known density of the heavy medium.

How do beetle assemblages respond to cyclonic disturbance of a fragmented tropical rainforest landscape?

PubMed

Grimbacher, Peter S; Stork, Nigel E

2009-09-01

There are surprisingly few studies documenting effects of tropical cyclones (including hurricanes and typhoons) on rainforest animals, and especially insects, considering that many tropical forests are frequently affected by cyclonic disturbance. Consequently, we sampled a beetle assemblage inhabiting 18 upland rainforest sites in a fragmented landscape in north-eastern Queensland, Australia, using a standardised sampling protocol in 2002 and again 12 months after the passage of Severe Tropical Cyclone Larry (March 2006). The spatial configuration of sites allowed us to test if the effects of a cyclone and those from fragmentation interact. From all insect samples we extracted 12,568 beetles of 382 species from ten families. Beetle species composition was significantly different pre-and post-cyclone although the magnitude of faunal change was not large with 205 species, representing 96% of all individuals, present in both sampling events. Sites with the greatest changes to structure had the greatest changes in species composition. At the site level, increases in woody debris and wood-feeding beetle (Scolytinae) counts were significantly correlated but changes in the percent of ground vegetation were not mirrored by changes in the abundance of foliage-feeding beetles (Chrysomelidae). The overall direction of beetle assemblage change was consistent with increasing aridity, presumably caused by the loss of canopy cover. Sites with the greatest canopy loss had the strongest changes in the proportion of species previously identified in the pre-cyclone study as preferring arid or moist rainforest environments. The magnitude of fragmentation effects was virtually unaltered by the passage of Cyclone Larry. We postulate that in the short-term the effects of cyclonic disturbance and forest fragmentation both reduce the extent of moist, interior habitat.

Extratropical Transition and Re-Intensification of Typhoon Toraji (2001): Large-Scale Circulations, Structural Characteristics, and Mechanism Analysis

NASA Astrophysics Data System (ADS)

Zhu, Xiande; Wu, Lixin; Wang, Qi

2018-06-01

With the use of data from the National Centers for Environmental Prediction Climate Forecast System Reanalysis, the environment and structure of typhoon Toraji (2001) are investigated during the re-intensification (RI) stage of its extratropical transition (ET), a process in which a tropical cyclone transforms into an extratropical or mid-latitude cyclone. The results provide detailed insight into the ET system and identify the specific features of the system, including wind field, a cold and dry intrusion, and a frontal structure in the RI stage. The irrotational wind provides the values of upper-and lower-level jets within the transitioning tropical cyclone and the cyclone over Shandong Peninsula, accompanied with the reduced radius of maximum surface winds around the cyclone center in the lower troposphere. Simultaneously, dry air intrusion enhances the formation of fronts and leads to strong potential instability in the southwest and northeast quadrants. The distribution of frontogenesis shows that the tilting term associated with vertical motion dominates the positive frontogenesis surrounding the cyclone center, especially in the RI stage. The diagnostics of the kinetic energy budget suggest that the divergent kinetic energy generation whose time evolution corresponds well to that of cyclone center pressure is the primary factor for the development of Toraji in the lower troposphere. The ET of Toraji is a compound pattern that contains a development similar to that of a B-type extratropical cyclone within the maintaining phase and an A-type extratropical cyclone within the strengthening period, which corresponds to the distribution of the E-P fluxes with vertically downward propagation in the maintaining stage and upwards momentum in the strengthening phase.

Initial Assessment of Cyclone Global Navigation Satellite System (CYGNSS) Observations

NASA Astrophysics Data System (ADS)

McKague, D. S.; Ruf, C. S.

2017-12-01

The NASA Cyclone Global Navigation Satellite System (CYNSS) mission provides high temporal resolution observations of cyclones from a constellation of eight low-Earth orbiting satellites. Using the relatively new technique of Global Navigation Satellite System reflectometry (GNSS-R), all-weather observations are possible, penetrating even deep convection within hurricane eye walls. The compact nature of the GNSS-R receivers permits the use of small satellites, which in turn enables the launch of a constellation of satellites from a single launch vehicle. Launched in December of 2016, the eight CYGNSS satellites provide 25 km resolution observations of mean square slope (surface roughness) and surface winds with a 2.8 hour median revisit time from 38 S to 38 N degrees latitude. In addition to the calibration and validation of CYGNSS sea state observations, the CYGNSS science team is assessing the ability of the mission to provide estimates of cyclone size, intensity, and integrated kinetic energy. With its all-weather ability and high temporal resolution, the CYGNSS mission will add significantly to our ability to monitor cyclone genesis and intensification and will significantly reduce uncertainties in our ability to estimate cyclone intensity, a key variable in predicting its destructive potential. Members of the CYGNSS Science Team are also assessing the assimilation of CYGNSS data into hurricane forecast models to determine the impact of the data on forecast skill, using the data to study extra-tropical cyclones, and looking at connections between tropical cyclones and global scale weather, including the global hydrologic cycle. This presentation will focus on the assessment of early on-orbit observations of cyclones with respect to these various applications.

Interactions Between Vestige Atlantic Tropical Cyclones and Mid-Latitude Storms Over Mediterranean Basin

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Mehta, Amita; Mugnai, Alberto; Tripoli, Gregory J.

2007-01-01

One of the more interesting tropical-mid-latitude interactions is one that has important effects on precipitation within the Mediterranean basin. This interaction consists of an Atlantic tropical cyclone vestige whose original disturbance travels eastward and northward across Atlantic basin, eventually intermingling with a mid-latitude cyclone entering southern Europe and/or the \\bestern Mediterranean Sea. The period for these interactions is from mid-September through November. If the tropical cyclone and its vestige is able to make the eastward Atlantic transit within the low to mid-levels, or if an upper level potential vorticity perturbation Cjet streak) emitted by a Hurricane in its latter stages within the central Atlantic is able to propagate into and along the longwave pattern affecting the western Mediterranean Sea (MED), then there is the prospect for the tropical cyclone remnant to produce a major modification of the mid-latitude storm system preparing to affect the MED region. For such an occurrence to take place, it is necessary for an amplifying baroclinic perturbation to be already situated to the rear of a longwave trough, or to be excited by the emitted jet streak to the rear of a longwave trough -- in either case, preparing to affect the western MED. The Algiers City flood of 9-10 November 2001, which killed some 700 people, was produced by a Mediterranean cyclone that had been influenced by two vestige Atlantic tropical cyclones, 1,orenzo and Noel. A published modeling study involving various of this study's authors has already described the dynamical development of the Algiers storm as it amplified from a developing baroclinic disturbance in the Rossby wave train, into a northern Africa hazardous flood system, then lingered in the western MED as a semi-intense warm core cyclone. In our new modeling experiments, we investigate the impact of what might have happened in the eventual precipitation field. had the main features of the tropical cyclones NOT interacted with thc developing baroclinic disturbance as it penetrated the western MED. To do so, we first remove the moisture and dynamical features of the two vestigial tropical cyclones from the large scale meteorological fields used to initialize the Mediterranean cyclone simulation. This is done through depletion of the moisture front associated with the two tropical cyclones, accomplished by relaxation to the suppressed east Atlantic conditions. The dynamical effects are removed through energetic destruction of the latter stages of the eastward traveling tropical cyclones, accomplished by lowering the underlying sea surface temperatures. A precipitation-distribution impact experiment is then run by initializing with the customized large-scale fields. The final precipitation-impact field is described by differencing the "impact" run from the "control" run -- the latter defined as the original simulation which intrinsically includes the effects of the two vestigial tropical cyclones.

An evaluation of the real-time tropical cyclone forecast skill of the Navy Operational Global Atmospheric Prediction System in the western North Pacific

NASA Technical Reports Server (NTRS)

Fiorino, Michael; Goerss, James S.; Jensen, Jack J.; Harrison, Edward J., Jr.

1993-01-01

The paper evaluates the meteorological quality and operational utility of the Navy Operational Global Atmospheric Prediction System (NOGAPS) in forecasting tropical cyclones. It is shown that the model can provide useful predictions of motion and formation on a real-time basis in the western North Pacific. The meterological characteristics of the NOGAPS tropical cyclone predictions are evaluated by examining the formation of low-level cyclone systems in the tropics and vortex structure in the NOGAPS analysis and verifying 72-h forecasts. The adjusted NOGAPS track forecasts showed equitable skill to the baseline aid and the dynamical model. NOGAPS successfully predicted unusual equatorward turns for several straight-running cyclones.

Human Influence on Tropical Cyclone Intensity

NASA Technical Reports Server (NTRS)

Sobel, Adam H.; Camargo, Suzana J.; Hall, Timothy M.; Lee, Chia-Ying; Tippett, Michael K.; Wing, Allison A.

2016-01-01

Recent assessments agree that tropical cyclone intensity should increase as the climate warms. Less agreement exists on the detection of recent historical trends in tropical cyclone intensity.We interpret future and recent historical trends by using the theory of potential intensity, which predicts the maximum intensity achievable by a tropical cyclone in a given local environment. Although greenhouse gas-driven warming increases potential intensity, climate model simulations suggest that aerosol cooling has largely canceled that effect over the historical record. Large natural variability complicates analysis of trends, as do poleward shifts in the latitude of maximum intensity. In the absence of strong reductions in greenhouse gas emissions, future greenhouse gas forcing of potential intensity will increasingly dominate over aerosol forcing, leading to substantially larger increases in tropical cyclone intensities.

Numerical model-based diagnostic study of the rapid development phase of the Presidents' Day cyclone

NASA Technical Reports Server (NTRS)

Whitaker, Jeffrey S.; Uccellini, Louis W.; Brill, Keith F.

1988-01-01

A mesoscale model simulation of the Presidents' Day cyclone at 1200 GMT 18 February 1979 is presented which captures the upper-tropospheric intrusion of stratospheric air upstream of the East Coast and subsequent development of the surface cyclone. The model simulation is then used to examine the descent of the stratospheric air mass and the interaction of this air mass with a lower-tropospheric potential vorticity maximum associated with an inverted trough and coastal front along the East Coast. The model is also used to examine the processes that contribute to the rapid decrease of sea-level pressure and increase in lower-tropospheric cyclonic vorticity during the explosive development phase of the cyclone.

Suspension chemistry and electrophoretic deposition of zirconia electrolyte on conducting and non-conducting substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Debasish; Basu, Rajendra N., E-mail: rnbasu@cgcri.res.in

2013-09-01

Graphical abstract: - Highlights: • Stable suspension of yttria stabilized zirconia (YSZ) obtained in isopropanol medium. • Suspension chemistry and process parameters for electrophoretic deposition optimized. • Deposited film quality changed with iodine and water (dispersants) concentration. • Dense YSZ film (∼5 μm) fabricated onto non-conducting porous NiO-YSZ anode substrate. - Abstract: Suspensions of 8 mol% yttria stabilized zirconia (YSZ) particulates in isopropanol medium are prepared using acetylacetone, iodine and water as dispersants. The effect of dispersants concentration on suspension stability, particle size distribution, electrical conductivity and pH of the suspensions are studied in detail to optimize the suspension chemistry.more » Electrophoretic deposition (EPD) has been conducted to produce thin and dense YSZ electrolyte films. Deposition kinetics have been studied in depth and good quality films on conducting substrate are obtained at an applied voltage of 15 V for 3 min. YSZ films are also fabricated on non-conducting NiO-YSZ anode substrate using a steel plate on the reverse side of the substrate. Upon co-firing at 1400 °C for 6 h a dense YSZ film of thickness ∼5 μm is obtained. Such a half cell (anode + electrolyte) can be used to fabricate a solid oxide fuel cell on applying a suitable cathode layer.« less

Advances in dust cyclone research

USDA-ARS?s Scientific Manuscript database

Dust cyclones reduce particulate emissions but their operation consumes electrical energy. Response surface methodology was used to compare two strategies to reduce energy costs without increasing emissions. Cyclones of a standard design (1D3D) were operated singly and in series, as was an ‘Experi...

Economics of oversized cyclones in the cotton ginning industry

USDA-ARS?s Scientific Manuscript database

Cost of reducing pollution to meet increasingly stringent air quality standards particularly for the U.S. cotton ginning industry is rising overtime. Most industry participants use cyclones to control air pollutants. These cyclones have no moving parts and their initial investment costs are relative...

Risk factors for mortality in the Bangladesh cyclone of 1991.

PubMed

Bern, C; Sniezek, J; Mathbor, G M; Siddiqi, M S; Ronsmans, C; Chowdhury, A M; Choudhury, A E; Islam, K; Bennish, M; Noji, E

1993-01-01

Cyclones continue to pose a dangerous threat to the coastal populations of Bangladesh, despite improvements in disaster control procedures. After 138,000 persons died in the April 1991 cyclone, we carried out a rapid epidemiological assessment to determine factors associated with cyclone-related mortality and to identify prevention strategies. A nonrandom survey of 45 housing clusters comprising 1123 persons showed that mortality was greatest among under-10-year-olds (26%) and women older than 40 years (31%). Nearly 22% of persons who did not reach a concrete or brick structure died, whereas all persons who sought refuge in such structures survived. Future cyclone-associated mortality in Bangladesh could be prevented by more effective warnings leading to an earlier response, better access to designated cyclone shelters, and improved preparedness in high-risk communities. In particular, deaths among women and under-10-year-olds could be reduced by ensuring that they are given special attention by families, neighbours, local authorities, and especially those in charge of early warnings and emergency evacuation.

The impact of Cyclone Nargis on the Ayeyarwady (Irrawaddy) River delta shoreline and nearshore zone (Myanmar): Towards degraded delta resilience?

NASA Astrophysics Data System (ADS)

Besset, Manon; Anthony, Edward J.; Dussouillez, Philippe; Goichot, Marc

2017-10-01

The Ayeyarwady River delta (Myanmar) is exposed to tropical cyclones, of which the most devastating has been cyclone Nargis (2-4 May 2008). We analysed waves, flooded area, nearshore suspended sediments, and shoreline change from satellite images. Suspended sediment concentrations up to 40% above average during the cyclone may reflect fluvial mud supply following heavy rainfall and wave reworking of shoreface mud. Massive recession of the high-water line resulted from backshore flooding by cyclone surge. The shoreline showed a mean retreat of 47 m following Nargis. Erosion was stronger afterwards (-148 m between August 2008 and April 2010), largely exceeding rates prior to Nargis (2000-2005: -2.14 m/year) and over 41 years (1974-2015: -0.62 m/year). This implies that resilience was weak following cyclone impact. Consequently, the increasingly more populous Ayeyarwady delta, rendered more and more vulnerable by decreasing fluvial sediment supply, could, potentially, become more severely impacted by future high-energy events.

Citizen scientists analyzing tropical cyclone intensities

NASA Astrophysics Data System (ADS)

Hennon, Christopher C.

2012-10-01

A new crowd sourcing project called CycloneCenter enables the public to analyze historical global tropical cyclone (TC) intensities. The primary goal of CycloneCenter, which launched in mid-September, is to resolve discrepancies in the recent global TC record arising principally from inconsistent development of tropical cyclone intensity data. The historical TC record is composed of data sets called "best tracks," which contain a forecast agency's best assessment of TC tracks and intensities. Best track data have improved in quality since the beginning of the geostationary satellite era in the 1960s (because TCs could no longer disappear from sight). However, a global compilation of best track data (International Best Track Archive for Climate Stewardship (IBTrACS)) has brought to light large interagency differences between some TC best track intensities, even in the recent past [Knapp et al., 2010Knapp et al., 2010]. For example, maximum wind speed estimates for Tropical Cyclone Gay (1989) differed by as much as 70 knots as it was tracked by three different agencies.

Extreme cyclone events in the Arctic: Wintertime variability and trends

NASA Astrophysics Data System (ADS)

Rinke, A.; Maturilli, M.; Graham, R. M.; Matthes, H.; Handorf, D.; Cohen, L.; Hudson, S. R.; Moore, J. C.

2017-09-01

Typically 20-40 extreme cyclone events (sometimes called ‘weather bombs’) occur in the Arctic North Atlantic per winter season, with an increasing trend of 6 events/decade over 1979-2015, according to 6 hourly station data from Ny-Ålesund. This increased frequency of extreme cyclones is consistent with observed significant winter warming, indicating that the meridional heat and moisture transport they bring is a factor in rising temperatures in the region. The winter trend in extreme cyclones is dominated by a positive monthly trend of about 3-4 events/decade in November-December, due mainly to an increasing persistence of extreme cyclone events. A negative trend in January opposes this, while there is no significant trend in February. We relate the regional patterns of the trend in extreme cyclones to anomalously low sea-ice conditions in recent years, together with associated large-scale atmospheric circulation changes such as ‘blockinglike’ circulation patterns (e.g. Scandinavian blocking in December and Ural blocking during January-February).

Cyclone shelters and their locational suitability: an empirical analysis from coastal Bangladesh.

PubMed

Mallick, Bishawjit

2014-07-01

Bangladesh is one of the poorest and the most disaster-prone countries in Asia; it is important, therefore, to know how its disaster reduction strategies are organised and planned. Cyclone shelters comprise a widely acceptable form of infrastructural support for disaster management in Bangladesh. This paper attempts to analyse empirically their use during cyclones in a sample study area along the southwest coastal belt of the country. It shows how the location of a cyclone shelter can determine the social power structure in coastal Bangladesh. The results reveal that the establishment of cyclone shelters in the studied communities is determined by neither a right-based nor a demand-based planning approach; rather, their creation is dependent on the socio-political affluence of local-level decision-makers. The paper goes on to demonstrate that socially vulnerable households (defined, for example, by income or housing conditions) are afforded disproportionately less access to cyclone shelters as compared to less socially vulnerable households. © 2014 The Author(s). Disasters © Overseas Development Institute, 2014.

Accumulation in coastal West Antarctic ice core records and the role of cyclone activity

NASA Astrophysics Data System (ADS)

Hosking, J. Scott; Fogt, Ryan; Thomas, Elizabeth R.; Moosavi, Vahid; Phillips, Tony; Coggins, Jack; Reusch, David

2017-09-01

Cyclones are an important component of Antarctic climate variability, yet quantifying their impact on the polar environment is challenging. We assess how cyclones which pass through the Bellingshausen Sea affect accumulation over Ellsworth Land, West Antarctica, where we have two ice core records. We use self-organizing maps (SOMs), an unsupervised machine learning technique, to group cyclones into nine SOM nodes differing by their trajectories (1980-2015). The annual frequency of cyclones associated with the first SOM node (SOM1, which generally originate from lower latitudes over the South Pacific Ocean) is significantly (p < 0.001) correlated with annual accumulation, with the highest seasonal correlations (p < 0.001) found during autumn. While significant (p < 0.01) increases in vertically integrated water vapor over the South Pacific Ocean coincide with this same group of cyclones, we find no indication that this has led to an increase in moisture advection into, nor accumulation over, Ellsworth Land over this short time period.

Analysis of Storm Surge in Hong Kong

NASA Astrophysics Data System (ADS)

Kao, W. H.

2017-12-01

A storm surge is a type of coastal flood that is caused by low-pressure systems such as tropical cyclones. Storm surges caused by tropical cyclones can be very powerful and damaging, as they can flood coastal areas, and even destroy infrastructure in serious cases. Some serious cases of storm surges leading to more than thousands of deaths include Hurricane Katrina (2005) in New Orleans and Typhoon Haiyan (2013) in Philippines. Hong Kong is a coastal city that is prone to tropical cyclones, having an average of 5-6 tropical cyclones entering 500km range of Hong Kong per year. Storm surges have seriously damaged Hong Kong in the past, causing more than 100 deaths by Typhoon Wanda (1962), and leading to serious damage to Tai O and Cheung Chau by Typhoon Hagupit (2008). To prevent economic damage and casualties from storm surges, accurately predicting the height of storm surges and giving timely warnings to citizens is very important. In this project, I will be analyzing how different factors affect the height of storm surge, mainly using data from Hong Kong. These factors include the windspeed in Hong Kong, the atmospheric pressure in Hong Kong, the moon phase, the wind direction, the intensity of the tropical cyclone, distance between the tropical cyclone and Hong Kong, the direction of the tropical cyclone relative to Hong Kong, the speed of movement of the tropical cyclone and more. My findings will also be compared with cases from other places, to see if my findings also apply for other places.

Australian tropical cyclone activity lower than at any time over the past 550-1,500 years.

PubMed

Haig, Jordahna; Nott, Jonathan; Reichart, Gert-Jan

2014-01-30

The assessment of changes in tropical cyclone activity within the context of anthropogenically influenced climate change has been limited by the short temporal resolution of the instrumental tropical cyclone record (less than 50 years). Furthermore, controversy exists regarding the robustness of the observational record, especially before 1990. Here we show, on the basis of a new tropical cyclone activity index (CAI), that the present low levels of storm activity on the mid west and northeast coasts of Australia are unprecedented over the past 550 to 1,500 years. The CAI allows for a direct comparison between the modern instrumental record and long-term palaeotempest (prehistoric tropical cyclone) records derived from the (18)O/(16)O ratio of seasonally accreting carbonate layers of actively growing stalagmites. Our results reveal a repeated multicentennial cycle of tropical cyclone activity, the most recent of which commenced around AD 1700. The present cycle includes a sharp decrease in activity after 1960 in Western Australia. This is in contrast to the increasing frequency and destructiveness of Northern Hemisphere tropical cyclones since 1970 in the Atlantic Ocean and the western North Pacific Ocean. Other studies project a decrease in the frequency of tropical cyclones towards the end of the twenty-first century in the southwest Pacific, southern Indian and Australian regions. Our results, although based on a limited record, suggest that this may be occurring much earlier than expected.

Arabian Sea tropical cyclones intensified by emissions of black carbon and other aerosols.

PubMed

Evan, Amato T; Kossin, James P; Chung, Chul Eddy; Ramanathan, V

2011-11-02

Throughout the year, average sea surface temperatures in the Arabian Sea are warm enough to support the development of tropical cyclones, but the atmospheric monsoon circulation and associated strong vertical wind shear limits cyclone development and intensification, only permitting a pre-monsoon and post-monsoon period for cyclogenesis. Thus a recent increase in the intensity of tropical cyclones over the northern Indian Ocean is thought to be related to the weakening of the climatological vertical wind shear. At the same time, anthropogenic emissions of aerosols have increased sixfold since the 1930s, leading to a weakening of the southwesterly lower-level and easterly upper-level winds that define the monsoonal circulation over the Arabian Sea. In principle, this aerosol-driven circulation modification could affect tropical cyclone intensity over the Arabian Sea, but so far no such linkage has been shown. Here we report an increase in the intensity of pre-monsoon Arabian Sea tropical cyclones during the period 1979-2010, and show that this change in storm strength is a consequence of a simultaneous upward trend in anthropogenic black carbon and sulphate emissions. We use a combination of observational, reanalysis and model data to demonstrate that the anomalous circulation, which is radiatively forced by these anthropogenic aerosols, reduces the basin-wide vertical wind shear, creating an environment more favourable for tropical cyclone intensification. Because most Arabian Sea tropical cyclones make landfall, our results suggest an additional impact on human health from regional air pollution.

The impact of environmental inertial stability on the secondary circulation of axisymmetric tropical cyclones

NASA Astrophysics Data System (ADS)

O'Neill, M. E.; Chavas, D. R.

2017-12-01

In f-plane numerical simulations and analytical theory, tropical cyclones completely recycle their exhausted outflow air back into the boundary layer. This low-angular momentum air must experience cyclonic torque at the sea surface for cyclone to reach equilibrium. On Earth, however, it is not clear that tropical cyclones recycle all of the outflow air in a closed secondary circulation, and strong asymmetric outflow-jet interactions suggest that much of the air may be permanently evacuated from the storm over its lifetime. The fraction of outflow air that is returned to the near-storm boundary layer is in part a function of the environmental inertial stability, which controls the size and strength of the upper anticyclone. We run a suite of idealized axisymmetric tropical cyclone simulations at constant latitude while varying the outer domain's inertial stability profile. Fixing the latitude allows the gradient wind balance of the storm core to remain constant except for changes due to the far environment. By varying both the outer inertial stability and its location with respect to the Rossby radius of deformation, we show how the tropical cyclone's area-of-influence is controlled by the nature and strength of the upper anticyclone. Parcel tracking additionally demonstrates the likelihood of outflow air parcels to be quickly re-consumed by the secondary circulation as a function of inertial stability. These experiments demonstrate the sensitivity of the tropical cyclone's secondary circulation, typically assumed to be closed, to the dynamics of the far environment.

An Estimate of the North Atlantic Basin Tropical Cyclone Activity for the 2011 Hurricane Season

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2011-01-01

Estimates are presented for the expected level of tropical cyclone activity for the 2011 North Atlantic Basin hurricane season. It is anticipated that the frequency of tropical cyclones for the North Atlantic Basin during the 2011 hurricane season will be near to above the post-1995 means. Based on the Poisson distribution of tropical cyclone frequencies for the current more active interval 1995-2010, one computes P(r) = 63.7% for the expected frequency of the number of tropical cyclones during the 2011 hurricane season to be 14 plus or minus 3; P(r) = 62.4% for the expected frequency of the number of hurricanes to be 8 plus or minus 2; P(r) = 79.3% for the expected frequency of the number of major hurricanes to be 3 plus or minus 2; and P(r) = 72.5% for the expected frequency of the number of strikes by a hurricane along the coastline of the United States to be 1 plus or minus 1. Because El Nino is not expected to recur during the 2011 hurricane season, clearly, the possibility exists that these seasonal frequencies could easily be exceeded. Also examined are the effects of the El Nino-Southern Oscillation phase and climatic change (global warming) on tropical cyclone seasonal frequencies, the variation of the seasonal centroid (latitude and longitude) location of tropical cyclone onsets, and the variation of the seasonal peak wind speed and lowest pressure for tropical cyclones.

Efficient dye-sensitized solar cells from mesoporous zinc oxide nanostructures sensitized by N719 dye

NASA Astrophysics Data System (ADS)

Kumara, G. R. A.; Deshapriya, U.; Ranasinghe, C. S. K.; Jayaweera, E. N.; Rajapakse, R. M. G.

2018-03-01

Dye-sensitized solar cells (DSCs) have attracted a great deal of attention due to their low-cost and high power conversion efficiencies. They usually utilize an interconnected nanoparticle layer of TiO2 as the electron transport medium. From the fundamental point of view, faster mobility of electrons in ZnO is expected to contribute to better performance in DSCs than TiO2, though the actual practical situation is quite the opposite. In this research, we addressed this problem by first applying a dense layer of ZnO on FTO followed by a mesoporous layer of interconnected ZnO nanoparticle layer, both were prepared by spray pyrolysis technique. The best cell shows a power conversion efficiency of 5.2% when the mesoporous layer thickness is 14 μm and the concentration of the N719 dye in dye coating solution is 0.3 mM, while a cell without a dense layer shows 4.2% under identical conditions. The surface concentration of dye adsorbed in the cell with a dense layer and that without a dense layer are 5.00 × 10‑7 and 3.34 × 10‑7 mol/cm2, respectively. The cell with the dense layer has an electron lifetime of 54.81 ms whereas that without the dense layer is 11.08 ms. As such, the presence of the dense layer improves DSC characteristics of ZnO-based DSCs.

NOAA releases final report of Sandy service assessment

Science.gov Websites

released a report on the National Weather Service's performance during hurricane/post tropical cyclone Sandy. The report, Hurricane/Post Tropical Cyclone Sandy Service Assessment, reaffirms that the National warnings for dangerous storms like Sandy, even when they are expected to become post-tropical cyclones by

Novel cyclone empirical pressure drop and emissions with heterogeneous particulate

USDA-ARS?s Scientific Manuscript database

New cyclone designs equally effective at controlling emissions that have smaller pressure losses would reduce both the financial and the environmental cost of procuring electricity. Tests were conducted with novel and industry standard 30.5 cm diameter cyclones at inlet velocities from 8 to 18 m s-...

16 CFR Figure 2 to Subpart A of... - Cyclone Receiver Weldment

Code of Federal Regulations, 2010 CFR

2010-01-01

... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Cyclone Receiver Weldment 2 Figure 2 to Subpart A of Part 1209 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION CONSUMER PRODUCT SAFETY ACT... to Subpart A of Part 1209—Cyclone Receiver Weldment EC03OC91.032 ...

16 CFR Figure 2 to Subpart A of... - Cyclone Receiver Weldment

Code of Federal Regulations, 2011 CFR

2011-01-01

... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Cyclone Receiver Weldment 2 Figure 2 to Subpart A of Part 1209 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION CONSUMER PRODUCT SAFETY ACT... to Subpart A of Part 1209—Cyclone Receiver Weldment EC03OC91.032 ...

FORMAT OF TROPICAL CYCLONE RECORDS ("TCVITALS")

Science.gov Websites

FORMAT OF TROPICAL CYCLONE VITAL STATISTICS RECORDS ("TCVITALS") 8-16-2007 CHARACTER(S - These appear only in records that have been processed by the NCEP tropical cyclone quality control program SYNDAT_QCTROPCY. BOLDFACE - These appear only in NHC records. 1 - Prior to 1999, report date was

Analysis of North Atlantic Tropical Cyclone Intensify Change Using Data Mining

ERIC Educational Resources Information Center

Tang, Jiang

2010-01-01

Tropical cyclones (TC), especially when their intensity reaches hurricane scale, can become a costly natural hazard. Accurate prediction of tropical cyclone intensity is very difficult because of inadequate observations on TC structures, poor understanding of physical processes, coarse model resolution and inaccurate initial conditions, etc. This…

Evaluation of the Utility of Static and Adaptive Mesh Refinement for Idealized Tropical Cyclone Problems in a Spectral Element Shallow Water Model

DTIC Science & Technology

2015-04-09

where u is the zonal momentum per unit mass, v is the meridional momentum per unit mass, h is the fluid depth, and f is the Coriolis parameter. An...from each cyclone advects the other116 creating a net cyclonic motion (the Fujiwhara effect ; Fujiwhara 1921) (case 2 idealization).117 In Fig. 2c, the...the interaction of the two136 vortices cause a net cyclonic motion (the Fujiwhara effect ).137 The initial condition for the binary vortex interaction

Cyclone Chris Hits Australia

NASA Technical Reports Server (NTRS)

2002-01-01

This false-color image shows Cyclone Chris shortly after it hit Australia's northwestern coast on February 6, 2002. This scene was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite. (Please note that this scene has not been reprojected.) Cyclone Chris is one of the most powerful storms ever to hit Australia. Initially, the storm contained wind gusts of up to 200 km per hour (125 mph), but shortly after making landfall it weakened to a Category 4 storm. Meteorologists expect the cyclone to weaken quickly as it moves further inland.

A preliminary computer pattern analysis of satellite images of mature extratropical cyclones

NASA Technical Reports Server (NTRS)

Burfeind, Craig R.; Weinman, James A.; Barkstrom, Bruce R.

1987-01-01

This study has applied computerized pattern analysis techniques to the location and classification of features of several mature extratropical cyclones that were depicted in GOES satellite images. These features include the location of the center of the cyclone vortex core and the location of the associated occluded front. The cyclone type was classified in accord with the scheme of Troup and Streten. The present analysis was implemented on a personal computer; results were obtained within approximately one or two minutes without the intervention of an analyst.

Coal reburning for cyclone boiler NO{sub x} control demonstration. Quarterly report No. 6, July--September, 1991

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1991-12-31

It is the objective of the Coal Reburning for Cyclone Boiler NO{sub x} Control Project to fully establish that the cola reburning clean coal technology offers cost-effective alternatives to cyclone operating electric utilities for overall oxides of nitrogen control. The project will evaluate the applicability of the reburning technology for reducing NO{sub x} emissions in full scale cyclone-fired boilers which use coal as a primary fuel. The performance goals while burning coal are: (1) Greater than 50 percent reduction in NO{sub x} emissions, as referenced to the uncontrolled (baseline) conditions at full load. (2) No serious impact on cyclone combustormore » operation, boiler efficiency or boiler fireside performance (corrosion and deposition), or boiler ash removal system performance.« less

Coal reburning for cyclone boiler NO sub x control demonstration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1991-01-01

It is the objective of the Coal Reburning for Cyclone Boiler NO{sub x} Control Project to fully establish that the cola reburning clean coal technology offers cost-effective alternatives to cyclone operating electric utilities for overall oxides of nitrogen control. The project will evaluate the applicability of the reburning technology for reducing NO{sub x} emissions in full scale cyclone-fired boilers which use coal as a primary fuel. The performance goals while burning coal are: (1) Greater than 50 percent reduction in NO{sub x} emissions, as referenced to the uncontrolled (baseline) conditions at full load. (2) No serious impact on cyclone combustormore » operation, boiler efficiency or boiler fireside performance (corrosion and deposition), or boiler ash removal system performance.« less

The persistent signature of tropical cyclones in ambient seismic noise

NASA Astrophysics Data System (ADS)

Gualtieri, Lucia; Camargo, Suzana J.; Pascale, Salvatore; Pons, Flavio M. E.; Ekström, Göran

2018-02-01

The spectrum of ambient seismic noise shows strong signals associated with tropical cyclones, yet a detailed understanding of these signals and the relationship between them and the storms is currently lacking. Through the analysis of more than a decade of seismic data recorded at several stations located in and adjacent to the northwest Pacific Ocean, here we show that there is a persistent and frequency-dependent signature of tropical cyclones in ambient seismic noise that depends on characteristics of the storm and on the detailed location of the station relative to the storm. An adaptive statistical model shows that the spectral amplitude of ambient seismic noise, and notably of the short-period secondary microseisms, has a strong relationship with tropical cyclone intensity and can be employed to extract information on the tropical cyclones.

Public understanding of cyclone warning in India: Can wind be predicted?

PubMed

Dash, Biswanath

2015-11-01

In spite of meteorological warning, many human lives are lost every year to cyclone mainly because vulnerable populations were not evacuated on time to a safe shelter as per recommendation. It raises several questions, most prominently what explains people's behaviour in the face of such danger from a cyclonic storm? How do people view meteorological advisories issued for cyclone and what role they play in defining the threat? What shapes public response during such situation? This article based on an ethnographic study carried out in coastal state of Odisha, India, argues that local public recognising inherent limitations of meteorological warning, fall back on their own system of observation and forecasting. Not only are the contents of cyclone warning understood, its limitations are accommodated and explained. © The Author(s) 2014.

The kinetic and available potential energy budget of a winter extratropical cyclone system

NASA Technical Reports Server (NTRS)

Smith, P. J.; Dare, P. M.

1986-01-01

The energy budget of an extratropical cyclone system which traversed North America and intensified through the period January 9-11, 1975 is presented. The objectives of the study are: (1) to document the complete energy budget of a significant winter cyclone event, and (2) to comment on the significance of latent heat release (LHR) in the cyclone's evolution. Results reveal an overall increase in both kinetic (K) and available potential energy (A). K increases are accounted for by boundary flux convergence of K, while A increases are due to generation by LHR and K to A conversion. In addition, the general A increase is accompanied by a 24 h oscillation that is explained largely by the flux quantity in the A budget equation and is correlated with a similar fluctuation in the K to A conversion. LHR does not appear to be critical in the development of this cyclone system. Rather, LHR acts to increase the intensity of the event. It is hypothesized that the direct influence that LHR had on the deepening cyclone's reduced mass was augmented by an indirect influence, in which pre-existing dry dynamical forcing was enhanced by diabatic heating, thus leading to accelerated cyclone development at a later time.

Analysis of Impact of Tropical Cyclone Blance on Rainfall at Kupang Region Based on Atmospheric Condition and Satellite Imagery

NASA Astrophysics Data System (ADS)

Roguna, S.; Saragih, I. J. A.; Siregar, P. S.; Julius, A. M.

2018-04-01

The Tropical Depression previously identified on March 3, 2017, at Arafuru Sea has grown to Tropical Cyclone Blance on March 5, 2017. The existence of Tropical Cyclone Blance gave impacts like increasing rainfall for some regions in Indonesia until March 7, 2017, such as Kupang. The increase of rainfall cannot be separated from the atmospheric dynamics related to convection processes and the formation of clouds. Analysis of weather parameters is made such as vorticity to observe vertical motion over the study area, vertical velocity to see the speed of lift force in the atmosphere, wind to see patterns of air mass distribution and rainfall to see the increase of rainfall compared to several days before the cyclone. Analysis of satellite imagery data is used as supporting analysis to see clouds imagery and movement direction of the cyclone. The results of weather parameters analysis show strong vorticity and lift force of air mass support the growth of Cumulonimbus clouds, cyclonic patterns on wind streamline and significant increase of rainfall compared to previous days. The results of satellite imagery analysis show the convective clouds over Kupang and surrounding areas when this phenomena and cyclone pattern moved down from Arafuru Sea towards the western part of Australia.

Interactions between tropical cyclones and mid-latitude systems in the Northeastern Pacific

NASA Astrophysics Data System (ADS)

Lugo, A.; Abarca, S. F.; Raga, G. B.; Vargas, D. C.

2014-12-01

Major challenges in tropical meteorology include the short-term forecast of tropical cyclone (TC) intensity, which is defined as the maximum tangential wind. Several efforts have been made in order to reach this goal over the last decade: Among these efforts, the study of lightning in the TC inner core (the region inside a disc of 100 km radius from the center) as a proxy to deep convection, has the potential to be used as a predictor to forecast intensity (DeMaria et al, 2012, Mon. Wea. Rev., 140, 1828-1842).While most studies focus their objectives in studying the lightning flash density in the inner core, we study the probability of flash occurrence for intensifying and weakening cyclones. We have analyzed the trajectories of the observed 62 tropical cyclones that developed in the basin from 2006 to 2009, and classified them into separate clusters according to their trajectories. These clusters can broadly be described as having trajectories mostly oriented: East-West, towards the central Pacific, NW far from the Mexican coast, parallel to the Mexican coast and recurving towards the Mexican coast.We estimate that probability of inner core lightning occurrence increases as cyclones intensify but the probability rapidly decrease as the systems weaken. This is valid for cyclones in most of the clusters. However, the cyclones that exhibit trajectories that recurve towards the Mexican coast, do not present the same relationship between intensity and inner-core lightning probability, these cyclones show little or no decrease in the lightning occurrence probability as they weaken.We hypothesize that one of the reasons for this anomalous behavior is likely the fact that these cyclones interact with mid-latitude systems. Mid-latitude systems are important in determining the recurving trajectory but they may also influence the TC by advecting mid-level moisture towards the TC inner core. This additional supply of moisture as the system is approaching land may enhance deep convection in the inner core and result in increases of lightning probability even though the cyclones are weakening. We use a Lagrangian approach similar to the used by Rutherford and Montgomery (2012, Atmos. Chem. Phys., 12, 11355-11381, 2012), to study moisture fluxes between intensifying and weakening in recurving tropical cyclones.

The influence of an atmospheric Two-Way coupled model system on the predictability of extratropical cyclones

NASA Astrophysics Data System (ADS)

Schuster, Mareike; Thürkow, Markus; Weiher, Stefan; Kirchner, Ingo; Ulbrich, Uwe; Will, Andreas

2016-04-01

A general bias of global atmosphere ocean models, and also of the MPI-ESM, is an under-representation of the high latitude cyclone activity and an overestimation of the mid latitude cyclone activity in the North Atlantic, thus representing the extra-tropical storm track too zonal. We will show, that this effect can be antagonized by applying an atmospheric Two-Way Coupling (TWC). In this study we present a newly developed Two-Way Coupled model system, which is based on the MPI-ESM, and show that it is able to capture the mean storm track location more accurate. It also influences the sub-decadal deterministic predictability of extra-tropical cyclones and shows significantly enhanced skill compared to the "uncoupled" MPI-ESM standalone system. This study evaluates a set of hindcast experiments performed with said Two-Way Coupled model system. The regional model COSMO CLM is Two-Way Coupled to the atmosphere of the global Max-Plack-Institute Earth System Model (MPI-ESM) and therefore integrates and exchanges the state of the atmosphere every 10 minutes (MPI-TWC-ESM). In the coupled source region (North Atlantic), mesoscale processes which are relevant for the formation and early-stage development of cyclones are expected to be better represented, and therefore influence the large scale dynamics of the target region (Europe). The database covers 102 "uncoupled" years and 102 Two-Way Coupled years of the recent climate (1960-2010). Results are validated against the ERA-Interim reanalysis. Besides the climatological point of view, the design of this single model ensemble allows for an analysis of the predictability of the first and second leadyears of the hindcasts. As a first step to understand the improved predictability of cyclones, we will show a detailed analysis of climatologies for specific cyclone categories, sorted by season and region. Especially for cyclones affecting Europe, the TWC is capable to counteract the AOGCM's biases in the North Atlantic. Also, cyclones which are generated in the northern North Atlantic and the Labrador Sea are to an extraordinary extent underestimated in the "uncoupled" MPI-ESM - for the latter region the TWC can balance this shortcoming. In the Northern Hemisphere annual mean statistics the TWC does not change the distribution of the strength of cyclones, but it changes the distribution of the lifetime of cyclones.

Comparison of Mid-latitude Cyclones in Sea Level Pressure, Gepotential Height and Vorticity Fields

NASA Astrophysics Data System (ADS)

Raible, Christoph C.; Blender, Richard; Fraedrich, Klaus

2013-04-01

The mid-latitudes are dominated by diurnal variability, which is related to traveling high- and low-pressure systems. The lows or cyclones are a major source of natural hazards. This has led to growing interest in the scientific community to develop Eulerian and Lagrangian measures and to analyze the atmospheric high-frequency variability. One important issue is that there is no straight forward definition of cyclones resulting in a large variety of so-called cyclone detection and tracking methods. Each of these methods relies on different input fields which are related to specific features of a cyclone, e.g., sea level pressure (SLP), which specifically focuses on the mass aspect of the velocity field. Recently, the available methods have been compared with respect to climatology and life cycles using the ERA interim data set (Neu et al. 2013). Based on this study we investigate different fields as input for one specific method. We focus on the three mostly used input data, sea level pressure (SLP), 1000-hPa gepotential height (Z1000) and 850-hPa vorticity (850VOR). The cyclone detection and tracking method developed by Blender et al. (1997) is used and we apply it to ERA interim data in the 1.5 x 1.5 resolution. The method was mainly applied for Z1000 and the Northern Hemisphere (e.g., Blender et al. 1997; Raible et al. 2008). To compare the tracks and cyclone characteristics obtained from the different input data we need to adapt critical parameters of the method in such a way that comparable numbers of cyclone centers are identified in either field. The target is set to the number of cyclone centers in northern hemispheric winter. This enables us to assess the seasonal and hemispheric dependence. Preliminary results show that the agreement between cyclones based on SLP and Z1000 varies between roughly 70 to 80% depending on the season and the hemisphere. Spatially, most of the differences are found around orographic features like Greenland. An interesting finding is that the number of cyclones based on Z1000 is increased comparing the winter and summer season as the number of heat lows increases in summer. However, the behavior is vice versa for cyclones based on SLP. References: Blender R., K. Fraedrich, and F. Lunkeit, 1997: Identification of cyclone-track regimes in the North Atlantic. Quart. J. Roy. Meteor. Soc., 123, 727-741. Neu, U., M. G. Akperov, N. Bellenbaum, R. Benestad, R. Blender, R. Caballero, A. Cocozza, H. F. Dacre, Y. Feng, K. Fraedrich, J. Grieger, S. Gulev, J. Hanley, T. Hewson, M. Inatsu, K. Keay, S. F. Kew, I. Kindem, G. C. Leckebusch, M. L. R. Liberato, P. Lionello, I. I. Mokhov, J. G. Pinto, C. C. Raible, M. Reale, I. Rudeva, M. Schuster, I. Simmonds, M. Sinclair, M. Sprenger, N. D. Tilinina, I. F. Trigo, S. Ulbrich, U. Ulbrich, X. L. Wang, H. Wernli, 2012: IMILAST - a community effort to intercompare extratropical cyclone detection and tracking algorithms: assessing method-related uncertainties, Bulletin of the American Meteorological Society, in press. Raible, C. C., P. Della-Marta, C. Schwierz, H. Wernli, and R. Blender, 2008: Northern Hemisphere extratropical cyclones: A comparison of detection and tracking methods and different reanalyses, Mon. Wea. Rev., 136 880-897.

Fractional condensation of pyrolysis vapors produced from Nordic feedstocks in cyclone pyrolysis

DOE PAGES

Johansson, Ann-Christine; Lisa, Kristiina; Sandström, Linda; ...

2016-12-06

Pyrolysis oil is a complex mixture of different chemical compounds with a wide range of molecular weights and boiling points. Due to its complexity, an efficient fractionation of the oil may be a more promising approach of producing liquid fuels and chemicals than treating the whole oil. In this work a sampling system based on fractional condensation was attached to a cyclone pyrolysis pilot plant to enable separation of the produced pyrolysis vapors into five oil fractions. The sampling system was composed of cyclonic condensers and coalescing filters arranged in series. Our objective was to characterize the oil fractions producedmore » from three different Nordic feedstocks and suggest possible applications. The oil fractions were thoroughly characterized using several analytical techniques including water content; elemental composition; heating value, and chemical compound group analysis using solvent fractionation, quantitative 13C NMR and 1H NMR and GC x GC - TOFMS. The results show that the oil fractions significantly differ from each other both in chemical and physical properties. The first fractions and the fraction composed of aerosols were highly viscous and contained larger energy-rich compounds of mainly lignin-derived material. The middle fraction contained medium-size compounds with relatively high concentration of water, sugars, alcohols, hydrocarbonyls and acids and finally the last fraction contained smaller molecules such as water, aldehydes, ketones and acids. But, the properties of the respective fractions seem independent on the studied feedstock types, i.e. the respective fractions produced from different feedstock are rather similar. Furthermore, this promotes the possibility to vary the feedstock depending on availability while retaining the oil properties. Possible applications of the five fractions vary from oil for combustion and extraction of the pyrolytic lignin in the early fractions to extraction of sugars from the early and middle fractions, and extraction of acids and aldehydes in the later fractions.« less

Fractional condensation of pyrolysis vapors produced from Nordic feedstocks in cyclone pyrolysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johansson, Ann-Christine; Lisa, Kristiina; Sandström, Linda

Pyrolysis oil is a complex mixture of different chemical compounds with a wide range of molecular weights and boiling points. Due to its complexity, an efficient fractionation of the oil may be a more promising approach of producing liquid fuels and chemicals than treating the whole oil. In this work a sampling system based on fractional condensation was attached to a cyclone pyrolysis pilot plant to enable separation of the produced pyrolysis vapors into five oil fractions. The sampling system was composed of cyclonic condensers and coalescing filters arranged in series. Our objective was to characterize the oil fractions producedmore » from three different Nordic feedstocks and suggest possible applications. The oil fractions were thoroughly characterized using several analytical techniques including water content; elemental composition; heating value, and chemical compound group analysis using solvent fractionation, quantitative 13C NMR and 1H NMR and GC x GC - TOFMS. The results show that the oil fractions significantly differ from each other both in chemical and physical properties. The first fractions and the fraction composed of aerosols were highly viscous and contained larger energy-rich compounds of mainly lignin-derived material. The middle fraction contained medium-size compounds with relatively high concentration of water, sugars, alcohols, hydrocarbonyls and acids and finally the last fraction contained smaller molecules such as water, aldehydes, ketones and acids. But, the properties of the respective fractions seem independent on the studied feedstock types, i.e. the respective fractions produced from different feedstock are rather similar. Furthermore, this promotes the possibility to vary the feedstock depending on availability while retaining the oil properties. Possible applications of the five fractions vary from oil for combustion and extraction of the pyrolytic lignin in the early fractions to extraction of sugars from the early and middle fractions, and extraction of acids and aldehydes in the later fractions.« less

Medium-range Performance of the Global NWP Model

NASA Astrophysics Data System (ADS)

Kim, J.; Jang, T.; Kim, J.; Kim, Y.

2017-12-01

The medium-range performance of the global numerical weather prediction (NWP) model in the Korea Meteorological Administration (KMA) is investigated. The performance is based on the prediction of the extratropical circulation. The mean square error is expressed by sum of spatial variance of discrepancy between forecasts and observations and the square of the mean error (ME). Thus, it is important to investigate the ME effect in order to understand the model performance. The ME is expressed by the subtraction of an anomaly from forecast difference against the real climatology. It is found that the global model suffers from a severe systematic ME in medium-range forecasts. The systematic ME is dominant in the entire troposphere in all months. Such ME can explain at most 25% of root mean square error. We also compare the extratropical ME distribution with that from other NWP centers. NWP models exhibit similar spatial ME structure each other. It is found that the spatial ME pattern is highly correlated to that of an anomaly, implying that the ME varies with seasons. For example, the correlation coefficient between ME and anomaly ranges from -0.51 to -0.85 by months. The pattern of the extratropical circulation also has a high correlation to an anomaly. The global model has trouble in faithfully simulating extratropical cyclones and blockings in the medium-range forecast. In particular, the model has a hard to simulate an anomalous event in medium-range forecasts. If we choose an anomalous period for a test-bed experiment, we will suffer from a large error due to an anomaly.

The Intense Arctic Cyclone of Early August 2012: A Dynamically Driven Cyclogenesis Event

NASA Astrophysics Data System (ADS)

Bosart, L. F.; Turchioe, A.; Adamchcik, E.

2013-12-01

A series of surface cyclones formed along an anomalously strong northeast-southwest oriented baroclinic zone over north-central Russia on 1-3 August 2012. These cyclones moved northeastward, intensified slowly, and crossed the coast of Russia by 4 August. The last cyclone in the series strengthened rapidly as it moved poleward over the Arctic Ocean on 5-6 August, achieved a minimum sea level pressure of < 965 hPa by 6 August, and was arguably the most intense storm system to impact the Arctic Ocean in the modern data record going back to the International Geophysical Year in 1957-1958. The purpose of this presentation is to illustrate the structure and life cycle of this Arctic Ocean cyclone from a multiscale perspective. Anticyclonic wave breaking in the upper troposphere across Russia in late July and very early August 2012 created an anomalously strong baroclinic zone across northern Asia between 60-80°N. During 1-5 August, negative 850 hPa temperature anomalies between -2° and -4°C were found poleward of 70-75°N between 90°E and the Dateline over the Arctic Ocean while positive 850 hPa temperature anomalies of 8-9°C were found over eastern Russia near 60°N. The associated anomalously strong 850 hPa meridional temperature gradient of ~10°C (2000 km)-1 helped to sustain an anomalously strong (20-30 m s-1) 250 hPa jet along the coast of northeastern Russia. A local wind speed maximum (~50 m s-1 ) embedded in this 250 hPa jet corridor contributed to the extreme intensity of the trailing (last) surface cyclone in the series. Although the dominant surface cyclone in the series of surface cyclones intensified most rapidly over the relatively ice free Arctic Ocean, the impact of surface heat and moisture fluxes appeared to be secondary to jet-driven dynamical processes in the deepening process. Anomalously high observed 1000-500 hPa thickness values between 564-570 dam, precipitable water values between 30-40 mm, and CAPE values between 500-1000 J kg-1 in the warm sector of the developing cyclone over north-central Russia were indicative of the enhanced baroclinicity and instability in the cyclone warm sector and the ability of lower tropospheric warm-air advection to sustain deep ascent in the intensifying cyclone. The relative importance of dynamical versus thermodynamical forcing to the cyclogenesis process as well as the bulk upscale effects of the intense cyclone on the larger scale higher-latitude circulation and the distribution of sea ice will be discussed. A noteworthy aspect of the post-storm polar environment was the upscale growth of a midlevel cyclonic circulation to include most of the Arctic Ocean. The off-pole displacement of this midlevel cyclonic circulation toward northern Canada by mid-August may have contributed to the termination of the 2012 summer-long intensive heat wave over most of the continental United States.

How much does the MSW effect contribute to the reactor antineutrino anomaly?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdiviesso, G. A.

2015-05-15

It has been pointed out that there is a 5.7 ± 2.3 discrepancy between the predicted and the observed reactor antineutrino flux in very short baseline experiments. Several causes for this anomaly have been discussed, including a possible non-standard forth sterile neutrino. In order to quantify how much non-standard this anomaly really is, the standard MSW effect is reviewed. Knowing that reactor antineutrinos are produced in a dense medium (the nuclear fuel) and is usually detected in a less dense one (water, or scintillator), non-adiabatic effects are expected to happen, creating a difference between the creation and detection mixing angles.

Role of equatorial waves in tropical cyclogenesis

NASA Astrophysics Data System (ADS)

Schreck, Carl J., III

Tropical cyclones typically form within preexisting wavelike disturbances that couple with convection. Using Tropical Rainfall Measuring Mission (TRMM) multisatellite rainfall estimates, this study determines the relative number of tropical cyclones that can be attributed to various wave types, including the Madden--Julian oscillation (MJO), Kelvin waves, equatorial Rossby (ER) waves, mixed Rossby--gravity (MRG) waves, and tropical depression (TD)-type disturbances. Tropical cyclogenesis is attributed to an equatorial wave's convection when the filtered rainfall anomaly exceeds a threshold value at the genesis location. More storms are attributed to TD-type disturbances than to any other wave type in all of the Northern Hemisphere basins. In the Southern Hemisphere, however, ER waves and TD-type disturbances are equally important as precursors. Fewer storms are attributed to MRG waves, Kelvin waves, and the MJO in every basin. Although relatively few storms are attributed to the MJO, tropical cyclogenesis is 2.6 times more likely in its convective phase compared with its suppressed phase. This modulation arises in part because each equatorial wave type is amplified within MJO's convective phase. The amplification significantly increases the probability that these waves will act as tropical cyclone precursors. A case study from June 2002 illustrates the effects of a series of Kelvin waves on two tropical cyclone formations. These waves were embedded in the convective phase of the MJO. Together, the MJO and the Kelvin waves preconditioned the low-level environment for cyclogenesis. The first Kelvin wave weakened the trade easterlies, while the subsequent waves created monsoon westerlies near the equator. These westerlies provided the background cyclonic vorticity within which both storms developed. The effects of tropical cyclone-related rainfall anomalies are also investigated. In the wavenumber--frequency spectrum for rainfall, tropical cyclones can inflate the power for shorter wavelength westward propagating waves by up to 27%. This spectrum contains signals from all longitudes, but the greatest contamination occurs in regions like the Philippines where tropical cyclones are most frequent. Here, tropical cyclones contribute more than 40% of the rainfall variance in each filter band. To mitigate these effects, tropical cyclone-related anomalies were removed before filtering in this study.

Climate change impacts on tropical cyclones and extreme sea levels in the South Pacific — A regional assessment

NASA Astrophysics Data System (ADS)

Walsh, Kevin J. E.; McInnes, Kathleen L.; McBride, John L.

2012-01-01

This paper reviews the current understanding of the effect of climate change on extreme sea levels in the South Pacific region. This region contains many locations that are vulnerable to extreme sea levels in the current climate, and projections indicate that this vulnerability will increase in the future. The recent publication of authoritative statements on the relationship between global warming and global sea level rise, tropical cyclones and the El Niño-Southern Oscillation phenomenon has motivated this review. Confident predictions of global mean sea level rise are modified by regional differences in the steric (density-related) component of sea level rise and changing gravitational interactions between the ocean and the ice sheets which affect the regional distribution of the eustatic (mass-related) contribution to sea level rise. The most extreme sea levels in this region are generated by tropical cyclones. The intensity of the strongest tropical cyclones is likely to increase, but many climate models project a substantial decrease in tropical cyclone numbers in this region, which may lead to an overall decrease in the total number of intense tropical cyclones. This projection, however, needs to be better quantified using improved high-resolution climate model simulations of tropical cyclones. Future changes in ENSO may lead to large regional variations in tropical cyclone incidence and sea level rise, but these impacts are also not well constrained. While storm surges from tropical cyclones give the largest sea level extremes in the parts of this region where they occur, other more frequent high sea level events can arise from swell generated by distant storms. Changes in wave climate are projected for the tropical Pacific due to anthropogenically-forced changes in atmospheric circulation. Future changes in sea level extremes will be caused by a combination of changes in mean sea level, regional sea level trends, tropical cyclone incidence and wave climate. Recommendations are given for research to increase understanding of the response of these factors to climate change. Implications of the results for adaptation research are also discussed.

Locating sources within a dense sensor array using graph clustering

NASA Astrophysics Data System (ADS)

Gerstoft, P.; Riahi, N.

2017-12-01

We develop a model-free technique to identify weak sources within dense sensor arrays using graph clustering. No knowledge about the propagation medium is needed except that signal strengths decay to insignificant levels within a scale that is shorter than the aperture. We then reinterpret the spatial coherence matrix of a wave field as a matrix whose support is a connectivity matrix of a graph with sensors as vertices. In a dense network, well-separated sources induce clusters in this graph. The geographic spread of these clusters can serve to localize the sources. The support of the covariance matrix is estimated from limited-time data using a hypothesis test with a robust phase-only coherence test statistic combined with a physical distance criterion. The latter criterion ensures graph sparsity and thus prevents clusters from forming by chance. We verify the approach and quantify its reliability on a simulated dataset. The method is then applied to data from a dense 5200 element geophone array that blanketed of the city of Long Beach (CA). The analysis exposes a helicopter traversing the array and oil production facilities.

Stable Isotope Anatomy of Tropical Cyclone Ita, North-Eastern Australia, April 2014

PubMed Central

Munksgaard, Niels C.; Zwart, Costijn; Kurita, Naoyuki; Bass, Adrian; Nott, Jon; Bird, Michael I.

2015-01-01

The isotope signatures registered in speleothems during tropical cyclones (TC) provides information about the frequency and intensity of past TCs but the precise relationship between isotopic composition and the meteorology of TCs remain uncertain. Here we present continuous δ18O and δ2H data in rainfall and water vapour, as well as in discrete rainfall samples, during the passage of TC Ita and relate the evolution in isotopic compositions to local and synoptic scale meteorological observations. High-resolution data revealed a close relationship between isotopic compositions and cyclonic features such as spiral rainbands, periods of stratiform rainfall and the arrival of subtropical and tropical air masses with changing oceanic and continental moisture sources. The isotopic compositions in discrete rainfall samples were remarkably constant along the ~450 km overland path of the cyclone when taking into account the direction and distance to the eye of the cyclone at each sampling time. Near simultaneous variations in δ18O and δ2H values in rainfall and vapour and a near-equilibrium rainfall-vapour isotope fractionation indicates strong isotopic exchange between rainfall and surface inflow of vapour during the approach of the cyclone. In contrast, after the passage of spiral rainbands close to the eye of the cyclone, different moisture sources for rainfall and vapour are reflected in diverging d-excess values. High-resolution isotope studies of modern TCs refine the interpretation of stable isotope signatures found in speleothems and other paleo archives and should aim to further investigate the influence of cyclone intensity and longevity on the isotopic composition of associated rainfall. PMID:25742628

Borneo vortex and mesoscale convective rainfall

NASA Astrophysics Data System (ADS)

Koseki, S.; Koh, T.-Y.; Teo, C.-K.

2014-05-01

We have investigated how the Borneo vortex develops over the equatorial South China Sea under cold surge conditions in December during the Asian winter monsoon. Composite analysis using reanalysis and satellite data sets has revealed that absolute vorticity and water vapour are transported by strong cold surges from upstream of the South China Sea to around the Equator. Rainfall is correspondingly enhanced over the equatorial South China Sea. A semi-idealized experiment reproduced the Borneo vortex over the equatorial South China Sea during a "perpetual" cold surge. The Borneo vortex is manifested as a meso-α cyclone with a comma-shaped rainband in the northeast sector of the cyclone. Vorticity budget analysis showed that the growth/maintenance of the meso-α cyclone was achieved mainly by the vortex stretching. This vortex stretching is due to the upward motion forced by the latent heat release around the cyclone centre. The comma-shaped rainband consists of clusters of meso-β-scale rainfall cells. The intense rainfall in the comma head (comma tail) is generated by the confluence of the warmer and wetter cyclonic easterly flow (cyclonic southeasterly flow) and the cooler and drier northeasterly surge in the northwestern (northeastern) sector of the cyclone. Intense upward motion and heavy rainfall resulted due to the low-level convergence and the favourable thermodynamic profile at the confluence zone. In particular, the convergence in the northwestern sector is responsible for maintenance of the meso-α cyclone system. At both meso-α and meso-β scales, the convergence is ultimately caused by the deviatoric strain in the confluence wind pattern but is significantly self-enhanced by the nonlinear dynamics.

Attributing Tropical Cyclogenesis to Equatorial Waves in the Western North Pacific

NASA Technical Reports Server (NTRS)

Schreck, Carl J., III; Molinari, John; Mohr, Karen I.

2009-01-01

The direct influences of equatorial waves on the genesis of tropical cyclones are evaluated. Tropical cyclogenesis is attributed to an equatorial wave when the filtered rainfall anomaly exceeds a threshold value at the genesis location. For an attribution threshold of 3 mm/day, 51% of warm season western North Pacific tropical cyclones are attributed to tropical depression (TD)-type disturbances, 29% to equatorial Rossby waves, 26% to mixed Rossby-Gravity waves, 23% to Kelvin waves, 13% to the Madden-Julian oscillation (MJO), and 19% are not attributed to any equatorial wave. The fraction of tropical cyclones attributed to TD-type disturbances is consistent with previous findings. Past studies have also demonstrated that the MJO significantly modulates tropical cyclogenesis, but fewer storms are attributed to the MJO than any other wave type. This disparity arises from the difference between attribution and modulation. The MJO produces broad regions of favorable conditions for cyclogenesis, but the MJO alone might not determine when and where a storm will develop within these regions. Tropical cyclones contribute less than 17% of the power in any portion of the equatorial wave spectrum because tropical cyclones are relatively uncommon equatorward of 15deg latitude. In regions where they are active, however, tropical cyclones can contribute more than 20% of the warm season rainfall and up to 50% of the total variance. Tropical cyclone-related anomalies can significantly contaminate wave-filtered precipitation at the location of genesis. To mitigate this effect, the tropical cyclone-related rainfall anomalies were removed before filtering in this study.

Products and Services Notice - Naval Oceanography Portal

Science.gov Websites

Tropical Cyclone Formation Alert, Northwest Pacific Ocean Issued as required when tropical cyclone PGTW Tropical Cyclone Formation Alert, North Indian Ocean Issued as required when TC formation is , Southwest Pacific Ocean Issued as required when TC formation is expected in 12-24 hours WTPS31-35 PGTW

Improved design of a tangential entry cyclone separator for separation of particles from exhaust gas of diesel engine.

PubMed

Mukhopadhyay, N

2011-01-01

An effective design of cyclone separator with tangential inlet is developed applying an equation derived from the correlation of collection efficiency with maximum pressure drop components of the cyclone, which can efficiently remove the particles around 1microm of the exhaust gas of diesel engine.

Toward Clarity on Understanding Tropical Cyclone Intensification

DTIC Science & Technology

2015-08-01

forefront of tropical cyclone research for a number of years , espe- cially in the context of the rapid intensification or decay of storms. Rapid...67, 1817 – 1830, doi:10.1175/2010JAS3318.1. Vigh, J. L., and W. H. Schubert, 2009: Rapid development of the tropical cyclone warm core. J. Atmos

Global climatology of explosive cyclones

NASA Astrophysics Data System (ADS)

Balcerak, Ernie

2013-03-01

Explosive cyclones, which have rapidly intensifying winds and heavy rain, can seriously threaten life and property. These "meteorological bombs" are difficult to forecast, in part because scientists need a better understanding of the physical mechanisms by which they form. In particular, the large-scale circulation conditions that may contribute to explosive cyclone formation are not well understood.

The Structural Changes of Tropical Cyclones Upon Interaction with Vertical Wind Shear

NASA Technical Reports Server (NTRS)

Ritchie, Elizabeth A.

2003-01-01

The Fourth Convection and Moisture Experiment (CAMEX-4) provided a unique opportunity to observe the distributions and document the roles of important atmospheric factors that impact the development of the core asymmetries and core structural changes of tropical cyclones embedded in vertical wind shear. The state-of-the-art instruments flown on the NASA DC-8 and ER-2, in addition to those on the NOAA aircraft, provided a unique set of observations that documented the core structure throughout the depth of the tropical cyclone. These data have been used to conduct a combined observational and modeling study using a state-of-the-art, high- resolution mesoscale model to examine the role of the environmental vertical wind shear in producing tropical cyclone core asymmetries, and the effects on the structure and intensity of tropical cyclones.The scientific objectives of this study were to obtain in situ measurements that would allow documentation of the physical mechanisms that influence the development of the asymmetric convection and its effect on the core structure of the tropical cyclone.

Characteristics and development of European cyclones with tropical origin in reanalysis data

NASA Astrophysics Data System (ADS)

Dekker, Mark M.; Haarsma, Reindert J.; Vries, Hylke de; Baatsen, Michiel; Delden, Aarnout J. van

2018-01-01

Major storm systems over Europe frequently have a tropical origin. This paper analyses the characteristics and dynamics of such cyclones in the observational record, using MERRA reanalysis data for the period 1979-2013. By stratifying the cyclones along three key phases of their development (tropical phase, extratropical transition and final re-intensification), we identify four radically different life cycles: the tropical cyclone and extratropical cyclone life cycles, the classic extratropical transition and the warm seclusion life cycle. More than 50% of the storms reaching Europe from low latitudes follow the warm seclusion life cycle. It also contains the strongest cyclones. They are characterized by a warm core and a frontal T-bone structure, with a northwestward warm conveyor belt and the effects of dry intrusion. Rapid deepening occurs in the latest phase, around their arrival in Europe. Both baroclinic instability and release of latent heat contribute to the strong intensification. The pressure minimum occurs often a day after entering Europe, which enhances the potential threat of warm seclusion storms for Europe. The impact of a future warmer climate on the development of these storms is discussed.

Performance and Characteristics of a Cyclone Gasifier for Gasification of Sawdust

NASA Astrophysics Data System (ADS)

Azman Miskam, Muhamad; Zainal, Z. A.; Idroas, M. Y.

The performance and characteristics of a cyclone gasifier for gasification of sawdust has been studied and evaluated. The system applied a technique to gasify sawdust through the concept of cyclonic motion driven by air injected at atmospheric pressure. This study covers the results obtained for gasification of ground sawdust from local furniture industries with size distribution ranging from 0.25 to 1 mm. It was found that the typical wall temperature for initiating stable gasification process was about 400°C. The heating value of producer gas was about 3.9 MJ m-3 that is sufficient for stable combustion in a dual-fuel engine generator. The highest thermal output from the cyclone gasifier was 57.35 kWT. The highest value of mass conversion efficiency and enthalpy balance were 60 and 98.7%, respectively. The highest efficiency of the cyclone gasifier obtained was 73.4% and this compares well with other researchers. The study has identified the optimum operational condition for gasifying sawdust in a cyclone gasifier and made conclusions as to how the steady gasification process can be achieved.

The View from the Top: CALIOP Ice Water Content in the Uppermost Layer of Tropical Cyclones

NASA Technical Reports Server (NTRS)

Avery, Melody A.; Deng, Min; Garnier, Anne; Heymsfield, Andrew; Pelon, Jacques; Powell, Kathleen A.; Trepte, Charles R.; Vaughan, Mark A.; Winker, David M.; Young, Stuart

2012-01-01

NASA's CALIPSO satellite carries both the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP) and the Imaging Infrared Radiometer (IIR). The lidar is ideally suited to viewing the very top of tropical cyclones, and the IIR provides critical optical and microphysical information. The lidar and the IIR data work together to understand storm clouds since they are perfectly co-located, and big tropical cyclones provide an excellent complex target for comparing the observations. There is a lot of information from these case studies for understanding both the observations and the tropical cyclones, and we are just beginning to scratch the surface of what can be learned. Many tropical cyclone cloud particle measurements are focused on the middle and lower regions of storms, but characterization of cyclone interaction with the lowermost stratosphere at the upper storm boundary may be important for determining the total momentum and moisture transport budget, and perhaps for predicting storm intensity as well. A surprising amount of cloud ice is to be found at the very top of these big storms.

Cyclone-induced rapid creation of extreme Antarctic sea ice conditions

PubMed Central

Wang, Zhaomin; Turner, John; Sun, Bo; Li, Bingrui; Liu, Chengyan

2014-01-01

Two polar vessels, Akademik Shokalskiy and Xuelong, were trapped by thick sea ice in the Antarctic coastal region just to the west of 144°E and between 66.5°S and 67°S in late December 2013. This event demonstrated the rapid establishment of extreme Antarctic sea ice conditions on synoptic time scales. The event was associated with cyclones that developed at lower latitudes. Near the event site, cyclone-enhanced strong southeasterly katabatic winds drove large westward drifts of ice floes. In addition, the cyclones also gave southward ice drift. The arrival and grounding of Iceberg B9B in Commonwealth Bay in March 2011 led to the growth of fast ice around it, forming a northward protruding barrier. This barrier blocked the westward ice drift and hence aided sea ice consolidation on its eastern side. Similar cyclone-induced events have occurred at this site in the past after the grounding of Iceberg B9B. Future events may be predictable on synoptic time scales, if cyclone-induced strong wind events can be predicted. PMID:24937550

X-ray emission from SN 2012ca: A Type Ia-CSM supernova explosion in a dense surrounding medium

NASA Astrophysics Data System (ADS)

Bochenek, Christopher D.; Dwarkadas, Vikram V.; Silverman, Jeffrey M.; Fox, Ori D.; Chevalier, Roger A.; Smith, Nathan; Filippenko, Alexei V.

2018-01-01

X-ray emission is one of the signposts of circumstellar interaction in supernovae (SNe), but until now, it has been observed only in core-collapse SNe. The level of thermal X-ray emission is a direct measure of the density of the circumstellar medium (CSM), and the absence of X-ray emission from Type Ia SNe has been interpreted as a sign of a very low density CSM. In this paper, we report late-time (500-800 d after discovery) X-ray detections of SN 2012ca in Chandra data. The presence of hydrogen in the initial spectrum led to a classification of Type Ia-CSM, ostensibly making it the first SN Ia detected with X-rays. Our analysis of the X-ray data favours an asymmetric medium, with a high-density component which supplies the X-ray emission. The data suggest a number density >108 cm-3 in the higher density medium, which is consistent with the large observed Balmer decrement if it arises from collisional excitation. This is high compared to most core-collapse SNe, but it may be consistent with densities suggested for some Type IIn or superluminous SNe. If SN 2012ca is a thermonuclear SN, the large CSM density could imply clumps in the wind, or a dense torus or disc, consistent with the single-degenerate channel. A remote possibility for a core-degenerate channel involves a white dwarf merging with the degenerate core of an asymptotic giant branch star shortly before the explosion, leading to a common envelope around the SN.

A CFD Study on the Prediction of Cyclone Collection Efficiency

NASA Astrophysics Data System (ADS)

Gimbun, Jolius; Chuah, T. G.; Choong, Thomas S. Y.; Fakhru'L-Razi, A.

2005-09-01

This work presents a Computational Fluid Dynamics calculation to predict and to evaluate the effects of temperature, operating pressure and inlet velocity on the collection efficiency of gas cyclones. The numerical solutions were carried out using spreadsheet and commercial CFD code FLUENT 6.0. This paper also reviews four empirical models for the prediction of cyclone collection efficiency, namely Lapple [1], Koch and Licht [2], Li and Wang [3], and Iozia and Leith [4]. All the predictions proved to be satisfactory when compared with the presented experimental data. The CFD simulations predict the cyclone cut-off size for all operating conditions with a deviation of 3.7% from the experimental data. Specifically, results obtained from the computer modelling exercise have demonstrated that CFD model is the best method of modelling the cyclones collection efficiency.

Human influence on tropical cyclone intensity.

PubMed

Sobel, Adam H; Camargo, Suzana J; Hall, Timothy M; Lee, Chia-Ying; Tippett, Michael K; Wing, Allison A

2016-07-15

Recent assessments agree that tropical cyclone intensity should increase as the climate warms. Less agreement exists on the detection of recent historical trends in tropical cyclone intensity. We interpret future and recent historical trends by using the theory of potential intensity, which predicts the maximum intensity achievable by a tropical cyclone in a given local environment. Although greenhouse gas-driven warming increases potential intensity, climate model simulations suggest that aerosol cooling has largely canceled that effect over the historical record. Large natural variability complicates analysis of trends, as do poleward shifts in the latitude of maximum intensity. In the absence of strong reductions in greenhouse gas emissions, future greenhouse gas forcing of potential intensity will increasingly dominate over aerosol forcing, leading to substantially larger increases in tropical cyclone intensities. Copyright © 2016, American Association for the Advancement of Science.

Tropical Cyclone Genesis: A Dynamician's Point of View

NASA Astrophysics Data System (ADS)

Bouali, Safieddine; Leys, Jos

The paper focuses the route to the maturity of a cyclone as a twist process of the Hadley cell. The approach is qualified by a "dynamician's viewpoint" since the aerologic mechanism of the cyclone genesis is replicated without the classical tools of the meteorological fluid framework. Indeed, we introduce a pure dynamical model of a 2D vertical rotor of an airparcel to emulate the Hadley cell. Twisted by an appropriate feedback to inject geophysical forcing, the simulation displays two stretched solenoid rolls with clockwise and anticlockwise paths representing the Hadley belts wrapping the Earth. When the forcing parameter is higher, computations simulate overlapped whirlwind funnels revealing strong similarities with the structure of cyclones, hurricanes, and typhoons described in the atmospheric science literature. We conjecture that ocean-atmosphere interactions separate and convert a "slice" of the Hadley rotor into a fully tropical cyclone.

A climatological model of North Indian Ocean tropical cyclone genesis, tracks and landfall

NASA Astrophysics Data System (ADS)

Wahiduzzaman, Mohammad; Oliver, Eric C. J.; Wotherspoon, Simon J.; Holbrook, Neil J.

2017-10-01

Extensive damage and loss of life can be caused by tropical cyclones (TCs) that make landfall. Modelling of TC landfall probability is beneficial to insurance/re-insurance companies, decision makers, government policy and planning, and residents in coastal areas. In this study, we develop a climatological model of tropical cyclone genesis, tracks and landfall for North Indian Ocean (NIO) rim countries based on kernel density estimation, a generalised additive model (GAM) including an Euler integration step, and landfall detection using a country mask approach. Using a 35-year record (1979-2013) of tropical cyclone track observations from the Joint Typhoon Warning Centre (part of the International Best Track Archive Climate Stewardship Version 6), the GAM is fitted to the observed cyclone track velocities as a smooth function of location in each season. The distribution of cyclone genesis points is approximated by kernel density estimation. The model simulated TCs are randomly selected from the fitted kernel (TC genesis), and the cyclone paths (TC tracks), represented by the GAM together with the application of stochastic innovations at each step, are simulated to generate a suite of NIO rim landfall statistics. Three hindcast validation methods are applied to evaluate the integrity of the model. First, leave-one-out cross validation is applied whereby the country of landfall is determined by the majority vote (considering the location by only highest percentage of landfall) from the simulated tracks. Second, the probability distribution of simulated landfall is evaluated against the observed landfall. Third, the distances between the point of observed landfall and simulated landfall are compared and quantified. Overall, the model shows very good cross-validated hindcast skill of modelled landfalling cyclones against observations in each of the NIO tropical cyclone seasons and for most NIO rim countries, with only a relatively small difference in the percentage of predicted landfall locations compared with observations.

Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux Variability on Daily Through Decadal Time Scales

NASA Technical Reports Server (NTRS)

Romanski, Joy; Romanou, Anastasia; Bauer, Michael; Tselioudis, George

2013-01-01

We analyze daily wintertime cyclone variability in the central and eastern Mediterranean during 1958-2001, and identify four distinct cyclone states, corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc), and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux observations. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deep water formation was observed in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern (NCP), showing that the area of influence of large scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters.

Multi-hazard risk assessment of coastal vulnerability from tropical cyclones - A GIS based approach for the Odisha coast.

PubMed

Sahoo, Bishnupriya; Bhaskaran, Prasad K

2018-01-15

The coastal region bordering the East coast of India is a thickly populated belt exposed to high risk and vulnerability from natural hazards such as tropical cyclones. Tropical cyclone frequencies that develop over the Bay of Bengal (average of 5-6 per year) region are much higher as compared to the Arabian Sea thereby posing a high risk factor associated with storm surge, inland inundation, wind gust, intense rainfall, etc. The Odisha State in the East coast of India experiences the highest number of cyclone strikes as compared to West Bengal, Andhra Pradesh, and Tamil Nadu. To express the destructive potential resulting from tropical cyclones the Power Dissipation Index (PDI) is a widely used metric globally. A recent study indicates that PDI for cyclones in the present decade have increased about six times as compared to the past. Hence there is a need to precisely ascertain the coastal vulnerability and risk factors associated with high intense cyclones expected in a changing climate. As such there are no comprehensive studies attempted so far on the determination of Coastal Vulnerability Index (CVI) for Odisha coast that is highly prone to cyclone strikes. With this motivation, the present study makes an attempt to investigate the physical, environmental, social, and economic impacts on coastal vulnerability associated with tropical cyclones for the Odisha coast. The study also investigates the futuristic projection of coastal vulnerability over this region expected in a changing climate scenario. Eight fair weather parameters along with storm surge height and onshore inundation were used to estimate the Physical Vulnerability Index (PVI). Thereafter, the PVI along with social, economic, and environmental vulnerability was used to determine the overall CVI using the GIS based approach. The authors believe that the comprehensive nature of this study is expected to benefit coastal zone management authorities. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cyclone as a precleaner to ESP--a need for Indian coal based thermal power plants.

PubMed

George, K V; Manjunath, S; Rao, C V Chalapati; Bopche, A M

2003-11-01

Almost all coal based thermal power plants (CTPP) in India use electrostatic precipitator (ESP) for reduction of particulate matter (PM) in flue gas generated due to the combustion of Indian coal. This coal is characterized by high ash content, low calorific value and low sulfur content resulting in the generation of a very large amount of highly electrically-resistive fly-ash; thereby requiring a very large size ESP to minimize the fly-ash emissions. However, the flue-gas particle size distribution analysis showed that 60% of the particles are above 15 microm size, which can be conveniently removed using a low-cost inertial separator such as a cyclone separator. It is proposed that a cyclone be used, as a pre-cleaner to ESP so that the large size fraction of fly-ash can be removed in the pre-cleaning and the remaining flue-gas entering the ESP will then contain only small size particles with low dust loading, thereby requiring a small ESP, and improving overall efficiency of dust removal. A low efficiency (65%), high throughput cyclone is considered for pre-cleaning flue gas and the ESP is designed for removal of the remaining 35% fly-ash from the flue gas. It is observed that with 100% dust load, the ESP requires six fields per pass, whereas with cyclone as a pre-cleaner, it requires only five fields per pass. Introducing cyclone into the flue gas path results in additional head loss, which needs to be overcome by providing additional power to induced draft (ID) fan. The permissible head loss due to the cyclone is estimated by comparing the power requirement in the bag filter control unit and cyclone-ESP combined unit. It is estimated that a head loss of 10 cm of water can be permitted across the cyclone so as to design the same for 65% efficiency.

Tropical cyclone track Analysis over Indian Coast Using Spatio-Temporal data-mining

NASA Astrophysics Data System (ADS)

Mohapatra, Gyanendranath; Manjunath, Swetha; Behera, Sasmita; Mohanty, Pratap Kumar

2015-04-01

Tropical cyclones are a natural hazard which largely affects the lives and property with its destructive wind and heavy rainfall. Fluctuations in the frequency and intensity complicate the detection of long-term trends and play an important role in the global climate system; therefore understanding and predicting tropical cyclones track, intensity, and landfall location is of both societal and scientific significance. In this study a data-mining approach is being used to analyze the tropical cyclone track both in the temporal and spatial scale. Basically, the Indian coast line is divided into four zones viz. north east, south east in the eastern side adjoining Bay of Bengal and North west and south west in the western side adjoining Arabian sea as these coastal areas are very much vulnerable for disaster due to maximum number of landfall of Tropical Cyclones. The track and landfall associated with all the cyclones are clustered based on their intensity (Severe, moderate and low) and landfall location. The analyses are carried out for landfall location and the extent of track separately for the events happening in two seasons i.e. pre-monsoon and post-monsoon period. Along with categorization of intensity, trend analysis of track and the targeted zone of maximum damage also been studied. Algorithms are being developed for potential resilient and impact assessment of the parameters associated with cyclone disaster in the coastal region of India. One of the important objectives of this present work is also the identification of most disaster prone coastal area and becoming a part of the information support system during the cyclone period. Based on the statistics like mean, Standard Deviation, regression and correlation analysis, an index is developed which determines the level of damage and vulnerability along the coastal region. This index can be used for the early warning system of particular coastal areas for the preparedness and mitigation of future cyclone events.

The Galactic interstellar medium: foregrounds and star formation

NASA Astrophysics Data System (ADS)

Miville-Deschênes, Marc-Antoine

2018-05-01

This review presents briefly two aspects of Galactic interstellar medium science that seem relevant for studying EoR. First, we give some statistical properties of the Galactic foreground emission in the diffuse regions of the sky. The properties of the emission observed in projection on the plane of the sky are then related to how matter is organised along the line of sight. The diffuse atomic gas is multi-phase, with dense filamentary structures occupying only about 1% of the volume but contributing to about 50% of the emission. The second part of the review presents aspect of structure formation in the Galactic interstellar medium that could be relevant for the subgrid physics used to model the formation of the first stars.

Tropical cyclone Pam field survey in Vanuatu

NASA Astrophysics Data System (ADS)

Fritz, Hermann M.; Pilarczyk, Jessica E.; Kosciuch, Thomas; Hong, Isabel; Rarai, Allan; Harrison, Morris J.; Jockley, Fred R.; Horton, Benjamin P.

2016-04-01

Severe tropical cyclone Pam (Cat. 5, SSHS) crossed the Vanuatu archipelago with sustained winds of 270 km/h on March 13 and 14, 2015 and made landfall on Erromango. Pam is the most intense tropical cyclone to make landfall on Vanuatu since the advent of satellite imagery based intensity estimates in the 1970s. Pam caused one of the worst natural disaster in Vanuatu's recorded history. Eleven fatalities were directly attributed to cyclone Pam and mostly due to lack of shelter from airborne debris. On March 6 Pam formed east of the Santa Cruz Islands causing coastal inundation on Tuvalu's Vaitupu Island located some 1100 km east of the cyclone center. Pam intensified while tracking southward along Vanuatu severely affecting the Shefa and Tafea Provinces. An international storm surge reconnaissance team was deployed to Vanuatu from June 3 to 17, 2015 to complement earlier local surveys. Cyclone Pam struck a remote island archipelago particularly vulnerable to the combined cyclonic multi-hazards encompassing extreme wind gusts, massive rainfall and coastal flooding due to a combination of storm surge and storm wave impacts. The team surveyed coastal villages on Epi, the Shepherd Islands (Tongoa and Mataso), Efate (including Lelepa), Erromango, and Tanna. The survey spanned 320 km parallel to the cyclone track between Epi and Tanna encompassing more than 45 sites including the hardest hit settlements. Coastal flooding profiles were surveyed from the shoreline to the limit of inundation. Maximum coastal flood elevations and overland flow depths were measured based on water marks on buildings, scars on trees, rafted debris and corroborated with eyewitness accounts. We surveyed 91 high water marks with characteristic coastal flood levels in the 3 to 7 m range and composed of storm surge with superimposed storm waves. Inundation distances were mostly limited to a few hundred meters but reached 800 m on Epi Island. Wrack lines containing pumice perfectly delineated the inundation at many sites and were mapped as line features. Coral boulders of more than 1 m diameter were measured on Erromango. Along each island that was sampled, Cyclone Pam deposited a 1 - 20 cm thick sedimentary layer consisting of foraminfera-bearing sand and pumice cobbles. Infrastructure damage on traditional and modern structures was assessed. Eyewitnesses were interviewed at most sites to document the chronology of the wind and coastal flooding events, survival strategies, cyclone and tsunami awareness, evacuation procedures, shelter locations and ancestral knowledge. Field observations were compared with surveyed eyewitness accounts of historic events such as severe tropical cyclone Uma in 1987. The measured cyclone Pam high water marks will facilitate the interpretation of the collected sedimentary evidence and serve as benchmarks for modeling studies.

In-medium jet evolution: interplay between broadening and decoherence effects. The XXVth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

NASA Astrophysics Data System (ADS)

Apolinário, Liliana; Armesto, Néstor; Milhano, Guilherme; Salgado, Carlos A.

2016-12-01

The description of the modifications of the coherence pattern in a parton shower, in the presence of a QGP, has been actively addressed in recent studies. Among the several achievements, finite energy corrections, transverse momentum broadening due to medium interactions and interference effects between successive emissions have been extensively improved as they seem to be essential features for a correct description of the results obtained in heavy-ion collisions. In this work, based on the insights of our previous work [L. Apolinário, N. Armesto, J. G. Milhano, C. A. Salgado, Medium-induced gluon radiation and colour decoherence beyond the soft approximation, JHEP 1502 (2015) 119. arxiv:arXiv:1407.0599], we explore the physical interplay between broadening and decoherence, by generalising previous studies of medium-modifications of the antenna spectrum [Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, Antiangular Ordering of Gluon Radiation in QCD Media, Phys. Rev. Lett. 106 (2011) 122002. arxiv:arXiv:1009.2965, J. Casalderrey-Solana, E. Iancu, Interference effects in medium-induced gluon radiation, JHEP 08 (2011) 015. arxiv:arXiv:1105.1760, Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, The Radiation pattern of a QCD antenna in a dense medium, JHEP 10 (2012) 197. arxiv:arXiv:1205.5739] - so far restricted to the case where transverse motion is neglected. The result allow us to identify two quantities controlling the decoherence of a medium modified shower that can be used as building blocks for a successful future generation of jet quenching Monte Carlo simulators: a generalisation of the Δmed parameter of the works of [Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, Antiangular Ordering of Gluon Radiation in QCD Media, Phys. Rev. Lett. 106 (2011) 122002. arxiv:arXiv:1009.2965, Y. Mehtar-Tani, C. A. Salgado, K. Tywoniuk, The Radiation pattern of a QCD antenna in a dense medium, JHEP 10 (2012) 197. arxiv:arXiv:1205.5739] - that controls the interplay between the transverse scale of the hard probe and the transverse resolution of the medium - and of the Δcoh in [L. Apolinário, N. Armesto, J. G. Milhano, C. A. Salgado, Medium-induced gluon radiation and colour decoherence beyond the soft approximation, JHEP 1502 (2015) 119. arxiv:arXiv:1407.0599] - that dictates the interferences between two emitters as a function of the transverse momentum broadening acquired by multiple scatterings with the medium.

Rate of prescription of antidepressant and anxiolytic drugs after Cyclone Yasi in North Queensland.

PubMed

Usher, Kim; Brown, Lawrence H; Buettner, Petra; Glass, Beverley; Boon, Helen; West, Caryn; Grasso, Joseph; Chamberlain-Salaun, Jennifer; Woods, Cindy

2012-12-01

The need to manage psychological symptoms after disasters can result in an increase in the prescription of psychotropic drugs, including antidepressants and anxiolytics. Therefore, an increase in the prescription of antidepressants and anxiolytics could be an indicator of general psychological distress in the community. The purpose of this study was to determine if there was a change in the rate of prescription of antidepressant and anxiolytic drugs following Cyclone Yasi. A quantitative evaluation of new prescriptions of antidepressants and anxiolytics was conducted. The total number of new prescriptions for these drugs was calculated for the period six months after the cyclone and compared with the same six month period in the preceding year. Two control drugs were also included to rule out changes in the general rate of drug prescription in the affected communities. After Cyclone Yasi, there was an increase in the prescription of antidepressant drugs across all age and gender groups in the affected communities except for males 14-54 years of age. The prescription of anxiolytic drugs decreased immediately after the cyclone, but increased by the end of the six-month post-cyclone period. Control drug prescription did not change. There was a quantifiable increase in the prescription of antidepressant drugs following Cyclone Yasi that may indicate an increase in psychosocial distress in the community.

Effects of uniformities of deposition of respirable particles on filters on determining their quartz contents by using the direct on-filter X-ray diffraction (DOF XRD) method.

PubMed

Chen, Ching-Hwa; Tsaia, Perng-Jy; Lai, Chane-Yu; Peng, Ya-Lian; Soo, Jhy-Charm; Chen, Cheng-Yao; Shih, Tung-Sheng

2010-04-15

In this study, field samplings were conducted in three workplaces of a foundry plant, including the molding, demolding, and bead blasting, respectively. Three respirable aerosol samplers (including a 25-mm aluminum cyclone, nylon cyclone, and IOSH cyclone) were used side-by-side to collect samples from each selected workplace. For each collected sample, the uniformity of the deposition of respirable dusts on the filter was measured and its free silica content was determined by both the DOF XRD method and NIOSH 7500 XRD method (i.e., the reference method). A same trend in measured uniformities can be found in all selected workplaces: 25-mm aluminum cyclone>nylon cyclone>IOSH cyclone. Even for samples collected by the sampler with the highest uniformity (i.e., 25-mm aluminum cyclone), the use of the DOF XRD method would lead to the measured free silica concentrations 1.15-2.89 times in magnitude higher than that of the reference method. A new filter holder should be developed with the minimum uniformity comparable to that of NIOSH 7500 XRD method (=0.78) in the future. The use of conversion factors for correcting quartz concentrations obtained from the DOF XRD method based on the measured uniformities could be suitable for the foundry industry at this stage. 2009 Elsevier B.V. All rights reserved.

Extratropical Cyclones near Iceland

NASA Image and Video Library

2010-04-22

A cyclone is a low-pressure area of winds that spiral inwards. Although tropical storms most often come to mind, these spiraling storms can also form at mid- and high latitudes. Two such cyclones formed in tandem in November 2006. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying onboard NASA’s Terra satellite took this picture on November 20. This image shows the cyclones south of Iceland. Scotland appears in the lower right. The larger and perhaps stronger cyclone appears in the east, close to Scotland. Cyclones at high and mid-latitudes are actually fairly common, and they drive much of the Earth’s weather. In the Northern Hemisphere, cyclones move in a counter-clockwise direction, and both of the spiraling storms in this image curl upwards toward the northeast then the west. The eastern storm is fed by thick clouds from the north that swoop down toward the storm in a giant “V” shape on either side of Iceland. Skies over Iceland are relatively clear, allowing some of the island to show through. South of the storms, more diffuse cloud cover swirls toward the southeast. Credit: NASA NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe. Follow us on Twitter Join us on Facebook

Structures and Evolutions of Explosive Cyclones over the Northwestern and Northeastern Pacific

NASA Astrophysics Data System (ADS)

Zhang, Shuqin; Fu, Gang

2018-06-01

In this study, the structures and evolutions of moderate (MO) explosive cyclones (ECs) over the Northwestern Pacific (NWP) and Northeastern Pacific (NEP) are investigated and compared using composite analysis with cyclone-relative coordinates. Final Operational Global Analysis data gathered during the cold seasons (October-April) of the 15 years from 2000 to 2015 are used. The results indicate that MO NWP ECs have strong baroclinicity and abundant latent heat release at low levels and strong upper-level forcing, which favors explosive cyclogenesis. The rapid development of MO NEP ECs results from their interaction with a northern cyclone and a large middle-level advection of cyclonic vorticity. The structural differences between MO NWP ECs and MO NEP ECs are significant. This results from their specific large-scale atmospheric and oceanic environments. MO NWP ECs usually develop rapidly in the east and southeast of the Japan Islands; the intrusion of cold dry air from the East Asian continent leads to strong baroclinicity, and the Kuroshio/Kuroshio Extension provides abundant latent heat release at low levels. The East Asian subtropical westerly jet stream supplies strong upper-level forcing. While MO NEP ECs mainly occur over the NEP, the low-level baroclinicity, upper-level jet stream, and warm ocean currents are relatively weaker. The merged cyclone associated with a strong middle-level trough transports large cyclonic vorticity to MO NEP ECs, which favors their rapid development.

The impacts of tropical cyclones on the net carbon balance of eastern US forests (1851-2000)

NASA Astrophysics Data System (ADS)

Fisk, J. P.; Hurtt, G. C.; Chambers, J. Q.; Zeng, H.; Dolan, K. A.; Negrón-Juárez, R. I.

2013-12-01

In temperate forests of the eastern US, tropical cyclones are a principal agent of catastrophic wind damage, with dramatic impacts on the structure and functioning of forests. Substantial progress has been made to quantify forest damage and resulting gross carbon emissions from tropical cyclones. However, the net effect of storms on the carbon balance of forests depends not only on the biomass lost in single events, but also on the uptake during recovery from a mosaic of past events. This study estimates the net impacts of tropical cyclones on the carbon balance of US forests over the period 1851-2000. To track both disturbance and recovery and to isolate the effects of storms, a modeling framework is used combining gridded historical estimates of mortality and damage with a mechanistic model using an ensemble approach. The net effect of tropical cyclones on the carbon balance is shown to depend strongly on the spatial and temporal scales of analysis. On average, tropical cyclones contribute a net carbon source over latter half of the 19th century. However, throughout much of the 20th century a regional carbon sink is estimated resulting from periods of forest recovery exceeding damage. The large-scale net annual flux resulting from tropical cyclones varies by up to 50 Tg C yr-1, an amount equivalent to 17%-36% of the US forest carbon sink.

Tropical Cyclone Storm Surge Inundation and Velocity Hazard Mapping of the State of Andhra Pradesh (India) using ADCIRC

NASA Astrophysics Data System (ADS)

Brackins, J. T.; Kalyanapu, A. J.

2017-12-01

The Northern Indian Ocean Bay of Bengal region, including parts of India, Bangladesh, Myanmar, and Sri Lanka, is the largest bay in the world and is structured in such a manner as to produce the world's largest tropical cyclone (TC) storm surges (SS), with approximately five surge events greater than 5 meters in magnitude each decade. (Needham et al. 2015). Although some studies have been performed to attempt to capture the magnitude and location of historical surges (Shaji et al. 2014) and to model surges in the immediate sense, there is a notable lack of application to the effects on coastal infrastructure in these areas. Given that these areas are some of the most densely populated and least economically able to prepare and recover, it is important to consider the potential effects of storm surge to discover areas where improvements can be made with the limited resources available to these areas. To this end, an ADvanced-CIRCulation (ADCIRC) model (Luettich and Westerink 2004) was created for the Bay of Bengal, using the General Bathymetric Chart of the Oceans (GEBCO 2014) as bathymetric and topographic data, and a combination of the Joint Typhoon Warning Center (JTWC) and India Meteorological Department (IMD) records for storm tracks. For the state of Andhra Pradesh, several major TC events ranging from 1977 to 2014 were selected to be modeled with the goal of creating hazard maps of storm surge inundation and velocity for the state. These hazard maps would be used to identify high-vulnerability areas with the goal of implementing land-use planning and coastal development practices that will aid in ameliorating both the loss of life and economic damages sustained as a result of these TCs.

Monitoring crop and vegetation condition using the fused dense time-series landsat-like imagery

USDA-ARS?s Scientific Manuscript database

Since the launch of the first Landsat satellite in the early 1970s, Landsat has been widely used in many applications such as land cover and land use change monitoring, crop yield estimation, forest fire detection, and global ecosystem carbon cycle studies. Medium resolution sensors like Landsat hav...

SURFACTANT ENHANCED RECOVERY OF TETRACHLOROETHYLENE FROM A POROUS MEDIUM CONTAINING LOW PERMEABILITY LENSES. 1. EXPERIMENTAL STUDIES. (R825409)

EPA Science Inventory

Abstract

A matrix of batch, column and two-dimensional (2-D) box experiments was conducted to investigate the coupled effects of rate-limited solubilization and layering on the entrapment and subsequent recovery of a representative dense NAPL, tetrachloroethylene (PCE)...

The evaporation of dense sprays as a mixing process

NASA Astrophysics Data System (ADS)

de Rivas, Alois; Villermaux, Emmanuel

2014-11-01

A dense spray of micron-sized droplets (water or ethanol) is formed in air by a pneumatic atomizer in a closed chamber, and is then conveyed through a nozzle in ambient air, forming a plume whose extension depends on the relative humidity of the diluting medium. We focus on the dry ambient medium, and large plume Reynolds number limit. Standard shear instabilities develop at the plume edge, forming the stretched lamellar structures familiar with passive scalars, except that these vanish in a finite time, because individual droplets evaporate at their border. Experiments also demonstrate that the lifetime of an individual droplet embedded in a lamellae is much larger than expected from the usual d-square law for an isolated droplet. By analogy with the way mixing times are understood from the convection-diffusion equation for passive scalars, we show that the lifetime of a lamellae stretched at a rate γ is tv =1/γ ln (1/+ ϕ ϕ ) where ϕ is a parameter which incorporates the thermodynamic and diffusional properties of the vapor in the diluting phase. The droplets field thus behaves as a -non conserved- passive scalar.

Persistent X-Ray Emission from ASASSN-15lh: Massive Ejecta and Pre-SLSN Dense Wind?

NASA Astrophysics Data System (ADS)

Huang, Yan; Li, Zhuo

2018-06-01

The persistent soft X-ray emission from the location of the most luminous supernova (SN) so far, ASASSN-15lh (or SN 2015L), with L∼ {10}42 {erg} {{{s}}}-1, is puzzling. We show that it can be explained by radiation from electrons accelerated by the SN shock inverse-Compton scattering the intense UV photons. The non-detection in radio requires strong free–free absorption in the dense medium. In these interpretations, the circumstellar medium is derived to be a wind (n ∝ R ‑2) with mass-loss rate of \\dot{{M}}≳ 3× {10}-3{{M}}ȯ ({{v}}{{w}}/{10}3 {{k}}{{m}} {{{s}}}-1) {{{y}}{{r}}}-1, and the initial velocity of the bulk SN ejecta is ≲ 0.02c. These constraints imply a massive ejecta mass of ≳ 60({E}0/2× {10}52 {erg}){M}ȯ in ASASSN-15lh, and a strong wind ejected by the progenitor star within ∼ 8{({v}{{w}}/{10}3{km}{{{s}}}-1)}-1 yr before explosion.

Recycling of municipal solid waste incinerator fly ash by using hydrocyclone separation.

PubMed

Ko, Ming-Sheng; Chen, Ying-Liang; Wei, Pei-Shou

2013-03-01

The municipal solid waste incinerators (MSWIs) in Taiwan generate about 300,000 tons of fly ash annually, which is mainly composed of calcium and silicon compounds, and has the potential for recycling. However, some heavy metals are present in the MSWI fly ash, and before recycling, they need to be removed or reduced to make the fly ash non-hazardous. Accordingly, the purpose of this study was to use a hydrocyclone for the separation of the components of the MSWI fly ash in order to obtain the recyclable portion. The results show that chloride salts can be removed from the fly ash during the hydrocyclone separation process. The presence of a dense medium (quartz sand in this study) is not only helpful for the removal of the salts, but also for the separation of the fly ash particles. After the dense-medium hydrocyclone separation process, heavy metals including Pb and Zn were concentrated in the fine particles so that the rest of the fly ash contained less heavy metal and became both non-hazardous and recyclable. Copyright © 2012 Elsevier Ltd. All rights reserved.

The influence of the environment on the propagation of protostellar outflows

NASA Astrophysics Data System (ADS)

Moraghan, Anthony; Smith, Michael D.; Rosen, Alexander

2008-06-01

The properties of bipolar outflows depend on the structure in the environment as well as the nature of the jet. To help distinguish between the two, we investigate here the properties pertaining to the ambient medium. We execute axisymmetric hydrodynamic simulations, injecting continuous atomic jets into molecular media with density gradients (protostellar cores) and density discontinuities (thick swept-up sheets). We determine the distribution of outflowing mass with radial velocity (the mass spectrum) to quantify our approach and to compare to observationally determined values. We uncover a sequence from clump entrainment in the flanks to bow shock sweeping as the density profile steepens. We also find that the dense, highly supersonic outflows remain collimated but can become turbulent after passing through a shell. The mass spectra vary substantially in time, especially at radial speeds exceeding 15 kms-1. The mass spectra also vary according to the conditions: both envelope-type density distributions and the passage through dense sheets generate considerably steeper mass spectra than a uniform medium. The simulations suggest that observed outflows penetrate highly non-uniform media.

Sandy retired from list of Atlantic Basin tropical cyclone names

Science.gov Websites

2012 Atlantic hurricane season Media Contact Dennis Feltgen 305-229-4404 305-433-1933 (cellular) Share tropical cyclone names April 11, 2013 GOES East image of Hurricane Sandy, Oct. 29, 2012. This NOAA GOES-13 cyclone names by the World Meteorological Organization's hurricane committee because of the extreme

Cyclone energy: impact of inlet velocity and outlet évasé designs

USDA-ARS?s Scientific Manuscript database

Because electricity generation produces emissions, reducing cyclone pressure drop has the potential to benefit the environment. Enhanced 1D3D cyclones common in the cotton ginning industry were tested with various évasés, over a range of inlet velocities. With évasés it was possible to reduce the ...

30 CFR 71.204 - Approved sampling devices; maintenance and calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... voltage per cell value; (2) Examination of all components of the cyclone to assure that they are clean and free of dust and dirt; (3) Examination of the inner surface of the cyclone on the approved sampling... positioning of the cyclone body, vortex finder and cassette to assure that they are rigid, in alignment, and...

40 CFR 63.11621 - What are the standards for new and existing prepared feeds manufacturing facilities?

Code of Federal Regulations, 2010 CFR

2010-07-01

... emissions and route them to a cyclone designed to reduce emissions of particulate matter by 95 percent or...) You must demonstrate that the cyclone is designed to reduce emissions of particulate matter by 95... operation of the cyclone in accordance with the applicable requirement in paragraphs (e)(2)(i), (ii), or...

30 CFR 70.204 - Approved sampling devices; maintenance and calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... components of the cyclone to assure that they are clean and free of dust and dirt; (3) Examination of the inner surface of the cyclone on the approved sampling device to assure that it is free of scoring; (4... leaks, and; (5) Examination of the clamping and positioning of the cyclone body, vortex finder and...

30 CFR 90.204 - Approved sampling devices; maintenance and calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... voltage per cell value; (2) Examination of all components of the cyclone to assure that they are clean and free of dust and dirt; (3) Examination of the inner surface of the cyclone on the approved sampling... positioning of the cyclone body, vortex finder and cassette to assure that they are rigid, in alignment, and...

30 CFR 71.204 - Approved sampling devices; maintenance and calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... voltage per cell value; (2) Examination of all components of the cyclone to assure that they are clean and free of dust and dirt; (3) Examination of the inner surface of the cyclone on the approved sampling... positioning of the cyclone body, vortex finder and cassette to assure that they are rigid, in alignment, and...

Changes of Mediterranean cyclones in the future climate employing high resolution climate simulations

NASA Astrophysics Data System (ADS)

Hatzaki, M.; Flocas, H. A.; Kouroutzoglou, J.; Keay, K.; Simmonds, I.; Giannakopoulos, C. A.; Brikolas, V.

2011-12-01

A number of studies suggest that cyclone activity over both hemispheres has changed over the second half of the 20th century. The assessment of the future changes of the cyclonic activity as imposed by global warming conditions is very important since these cyclones can be associated with extreme precipitation conditions, severe storms and floods. This is more important for the Mediterranean that has been found to be more vulnerable to climate change. The main objective of the current study is to better understand and assess future changes in the main characteristics of Mediterranean cyclones, including temporal and spatial variations of frequency of cyclonic tracks, and dynamic and kinematic parameters, such as intensity, size, propagation velocity, as well as trend analysis. For this purpose, the MPI-HH regional coupled climate model of the Max Planck Institute for Meteorology is employed consisting of the REgional atmosphere MOdel (REMO), the Max-Planck-Institute for Meteorology ocean model (MPI-OM) and the Hydrological Discharge Model (HD Model). A 25 km resolution domain is established on a rotated latitude-longitude coordinate system, while the physical parameterizations are taken from the global climate model ECHAM-4. These model data became available through the EU Project CIRCE which aims to perform, for the first time, climate change projections with a realistic representation of the Mediterranean Sea. The model results for the present climate are evaluated against ERA-40 Reanalysis (available through ECMWF), for the period 1962-2001. The identification and tracking of cyclones is performed with the aid of the Melbourne University algorithm (MS algorithm), according to the Lagrangian perspective. MS algorithm characterizes a cyclone only if a vorticity maximum could be connected with a local pressure minimum. According to the results, a decrease of the storm number and a tendency towards deeper cyclones is expected in the future, in general agreement with the results of previous studies. However, new findings reveal with respect to the dynamic/kinematic characteristics of the cyclonic tracks. The model experiments verify that considerable inter-monthly variations of track density occur in the Mediterranean region. The study of the kinematic and dynamic parameters of the cyclonic tracks according to their origin domain show that the vast majority originate within the examined area itself. ACKNOWLEDGMENTS: M. Hatzaki would like to thank the Greek State Scholarships Foundation for financial support through the program of postdoctoral research. The support of EU-FP6 project CIRCE Integrated Project-Climate Change and Impact Research: the Mediterranean Environment (http://www.circeproject.eu) for climate model data provision is also greatly acknowledged.

The role of mid-level vortex in the intensification and weakening of tropical cyclones

NASA Astrophysics Data System (ADS)

Kutty, Govindan; Gohil, Kanishk

2017-10-01

The present study examines the dynamics of mid-tropospheric vortex during cyclogenesis and quantifies the importance of such vortex developments in the intensification of tropical cyclone. The genesis of tropical cyclones are investigated based on two most widely accepted theories that explain the mechanism of cyclone formation namely `top-down' and `bottom-up' dynamics. The Weather Research and Forecast model is employed to generate high resolution dataset required for analysis. The development of the mid-level vortex was analyzed with regard to the evolution of potential vorticity (PV), relative vorticity (RV) and vertical wind shear. Two tropical cyclones which include the developing cyclone, Hudhud and the non-developing cyclone, Helen are considered. Further, Hudhud and Helen, is compared to a deep depression formed over Bay of Bengal to highlight the significance of the mid-level vortex in the genesis of a tropical cyclone. Major results obtained are as follows: stronger positive PV anomalies are noticed over upper and lower levels of troposphere near the storm center for Hudhud as compared to Helen and the depression; Constructive interference in upper and lower level positive PV anomaly maxima resulted in the intensification of Hudhud. For Hudhud, the evolution of RV follows `top-down' dynamics, in which the growth starts from the middle troposphere and then progresses downwards. As for Helen, RV growth seems to follow `bottom-up' mechanism initiating growth from the lower troposphere. Though, the growth of RV for the depression initiates from mid-troposphere, rapid dissipation of mid-level vortex destabilizes the system. It is found that the formation mid-level vortex in the genesis phase is significantly important for the intensification of the storm.

Quality of cyclone early warning services: a case study in remote off-shore island in Bangladesh

NASA Astrophysics Data System (ADS)

Ashrafi, Z. M.; Mahmud, S.; Mahbub, A. Q. M.

2015-12-01

Geographic location, the unique natural setting of the country and its tropical monsoon climate modify and regulate the climatic condition, makes Bangladesh more vulnerable to cyclones and storm surges. Previous studies have showed that 80-90 % of global losses and 53 % of total cyclone-related deaths worldwide, occur in Bangladesh and out of which, 42% of cyclone-caused deaths were recorded in the last two centuries. The Cyclone Preparedness Program (CPP) is a unique joint program under the initiative of Government of Bangladesh and Bangladesh Red Crescent Society that provides a robust cyclone early warning (CEW) system for the 13 coastal districts in Bangladesh. CPP ensures rapid dissemination of official Bangladesh Meteorological Department's CEW signals to these communities. However, inconsistent CEW services are reported in several of these coastal communities. This study offered the quality assessment of CPP CEW services in Nijhum Island, a highly populated remotely located off-shore island in Bangladesh. Primary rural appraisal (household survey, focus group discussion and expert interview) were used for field data collection and Likert scale, for data analysis. Study revealed that cyclone early warning signal dissemination were restricted to small area covering only 35 percent of the total population. Moreover, local inhabitants had very poor understanding about disseminated CEW signals (flag signaling system, signal number & severity) although CPP initiated several training program to build and raise awareness. Consequently, people remained inactive during cyclone and reluctant to seek shelter which resulted in lack of proper post-disaster management. Moreover, local people had concern regarding accuracy of CEW signals disseminated by CPP. To ensure last mile connectivity of CEW services, it is highly recommended that local people should be given more training and awareness on CEW signals and how to respond to the same.

Quantitative and Qualitative Analyzes of the Explosive Cyclones that Reached the Antarctic Coast in the First Half of 2017

NASA Astrophysics Data System (ADS)

Pires, L. B. M.; Romao, M.; Freitas, A. C. V.

2017-12-01

An explosive cyclone is a kind of extratropical cyclone which shows a drop in pressure of at least 24 hPa in 24 hours. These are usually intense and they have rapid displacement which hinders their predictability. It is likely that climate change is causing an increase in this type of event in the Antarctic coast and, if this increase is confirmed, the regime of winds and temperatures may be changing. If there are more incidences of explosive cyclones, probably the Antarctic winds are becoming more intense and the temperatures in some places are becoming lower and in others are becoming higher. In the northern portion of the Antarctic Peninsula a decrease in temperature already has been recorded over the last 15 years, while a higher incidence of explosive cyclones over the region also has been found during this period. Studies also have suggested that the drop in temperatures in the Antarctic may be associated with the changes in wind direction, but the cause of these wind direction changes is unknown. Explosive cyclones, which change the wind patterns when they reach certain areas therefore may be contributing to this change in the Antarctic climate. This study is part of the "Explosive Cyclones on the Antarctic Coast" (EXCANC) Project conducted by the World Environmental Conservancy organization. This project analyzes data from meteorological stations strategically scattered throughout the coast and operated by various international Antarctic programs, and also utilizes satellite images. Results show that during the first half of 2017 the highest number of events were recorded at the Australian Casey station with 10 cases, followed by the French station of Dumont D'Urville with 7 cases. Halley's English station recorded its first explosive cyclone this year. Intensity analyzes also are shown.

Borneo Vortex and Meso-scale Convective Rainfall

NASA Astrophysics Data System (ADS)

Koh, T. Y.; Koseki, S.; Teo, C. K.

2014-12-01

We have investigated how the Borneo vortex develops over the equatorial South China Sea under cold surge conditions in December during the Asian winter monsoon. Composite analysis using reanalysis and satellite datasets has revealed that absolute vorticity and water vapour are transported by strong cold surges from upstream of the South China Sea to around the equator. Rainfall is correspondingly enhanced over the equatorial South China Sea. A semi-idealized experiment reproduced the Borneo vortex over the equatorial South China Sea during a perpetual cold surge. The Borneo vortex is manifested as a meso-alpha cyclone with a comma-shaped rainband in the northeast sector of the cyclone. Vorticity budget analysis showed that the growth/maintenance of the meso-alpha cyclone was achieved mainly by the vortex stretching. This vortex stretching is due to the upward motion forced by the latent heat release around the cyclone centre. The comma-shaped rainband consists of clusters of meso-beta scale rainfall cells. The intense rainfall in the comma-head (comma-tail) is generated by the confluence of the warmer and wetter cyclonic easterly flow (cyclonic southeasterly flow) and the cooler and drier northeasterly surge in the northwestern (northeastern) sector of the cyclone. Intense upward motion and heavy rainfall resulted due to the low-level convergence and the favourable thermodynamic profile at the confluence zone. In particular, the convergence in the northwestern sector is responsible for maintenance of the meso-alpha cyclone system. At both meso-alpha and meso-beta scales, the convergence is ultimately caused by the deviatoric strain in the confluence wind pattern but is significantly self-enhanced by the nonlinear dynamics. Reference: Koseki, S., T.-Y. Koh and C.-K. Teo (2014), Atmospheric Chemistry and Physics, 14, 4539-4562, doi:10.5194/acp-14-4539-2014, 2014.

Multiyear Composite View of Ozone Enhancements and Stratosphere-to-Troposphere Transport in Dry Intrusions of Northern Hemisphere Extratropical Cyclones

NASA Astrophysics Data System (ADS)

Jaeglé, Lyatt; Wood, Robert; Wargan, Krzysztof

2017-12-01

We examine the role of extratropical cyclones in stratosphere-to-troposphere (STT) exchange with cyclone-centric composites of O3 retrievals from the Microwave Limb Sounder (MLS) and the Tropospheric Emission Spectrometer (TES), contrasting them to composites obtained with the Modern-Era Retrospective-analysis for Research and Applications (MERRA and MERRA-2) reanalyses and the GEOS-Chem chemical transport model. We identify 15,978 extratropical cyclones in the northern hemisphere (NH) for 2005-2012. The lowermost stratosphere (261 hPa) and middle troposphere (424 hPa) composites feature a 1,000 km wide O3 enhancement in the dry intrusion (DI) airstream to the southwest of the cyclone center, coinciding with a lowered tropopause, enhanced potential vorticity, and decreased H2O. MLS composites at 261 hPa show that the DI O3 enhancements reach a 210 ppbv maximum in April. At 424 hPa, TES composites display maximum O3 enhancements of 27 ppbv in May. The magnitude and seasonality of these enhancements are captured by MERRA and MERRA-2, but GEOS-Chem is a factor of 2 too low. The MERRA-2 composites show that the O3-rich DI forms a vertically aligned structure between 300 and 800 hPa, wrapping cyclonically with the warm conveyor belt. In winter and spring DIs, O3 is enhanced by 100 ppbv or 100-130% at 300 hPa, with significant enhancements below 500 hPa (6-20 ppbv or 15-30%). We estimate that extratropical cyclones result in a STT flux of 119 ± 56 Tg O3 yr-1, accounting for 42 ± 20% of the NH extratropical O3 STT flux. The STT flux in cyclones displays a strong dependence on westerly 300 hPa wind speeds.

Synoptic regimes associated with the eastern Mediterranean wet season cyclone tracks

NASA Astrophysics Data System (ADS)

Almazroui, Mansour; Awad, Adel M.

2016-11-01

The main synoptic patterns associated with the wet season (October-May) eastern Mediterranean cyclones have been analyzed and described using NCEP/NCAR reanalysis datasets for the period 1958-2013. The cyclone tracks detected in the eastern Mediterranean are classified into two types based on their positions: the local tracks and the long tracks. The local tracks are either stationary or short tracks. The long tracks distinguished into eleven very closed and highly correlated clusters, which are presented into three regimes namely the northern, the southern and the eastern border Mediterranean regimes. Among the 940 (44.78% of a total of 2099) long tracks, the northern, southern, and eastern border regime contributes respectively about 53.62%, 41.81% and 5% of the long tracks. In addition, the distribution of the long tracks reveals that a larger proportion of the cyclones are generated at the northern coast during November and spring months, while few cyclones are developed over the eastern Mediterranean border in warm months (April and May). Further, their synoptic features show that the regimes are associated with the extension of Azores high, specifically for each regime, the cyclogenesis areas of its clusters are controlled by the intersection of low level (850 hPa) trough and the position of the upper level (250 hPa) maximum wind. Furthermore, the orientations of clusters are controlled by the extension of Siberian high and the shape of cyclonic trough at 850 hPa. In addition, the synoptic study shows that most of the southern cyclones generated externally by African and Red Sea troughs, while most of the northern and eastern border cyclones are generated internally.

Numerical investigation of the effect of number and shape of inlet of cyclone and particle size on particle separation

NASA Astrophysics Data System (ADS)

Khazaee, Iman

2017-06-01

Cyclones are one of the most common devices for removing particles from the gas stream and act as a filter. The mode of action of separating these particles, from mass gas flow, in this case, is that the inertia force exerted on the solid particles in the cyclone, several times greater than the force of inertia into the gas phase and so the particles are guided from the sides of the cyclone body to the bottom body but less power will be affected by the gas phase and from upper parts, solid particles, goes to the bottom chamber. Most of the attention has been focused on finding new methods to improve performance parameters. Recently, some studies were conducted to improve equipment performance by evaluating geometric effects on projects. In this work, the effect of cyclone geometry was studied through the creation of a symmetrical double and quad inlet and also studied cutting inlet geometry and their influence on separation efficiency. To assess the accuracy of modeling, selected model compared with the model Kim and Lee and the results were close to acceptable. The collection efficiency of the double inlet cyclone was found to be 20-25% greater than that of the single inlet cyclone and the collection efficiency of the quad inlet cyclone was found to be 40-45% greater than with the same inlet size. Also the collection efficiency of the rectangle inlet was found to be 4-6% greater than ellipse inlet and the collection efficiency of the ellipse inlet was found to be 30-35% greater than circle inlet.

Retrieval of spatially distributed hydrological properties from satellite observations for spatial evaluation of a national water resources model.

NASA Astrophysics Data System (ADS)

Mendiguren González, G.; Stisen, S.; Koch, J.

2016-12-01

The NASA Cyclone Global Navigation Satellite System (CYNSS) mission provides high temporal resolution observations of cyclones from a constellation of eight low-Earth orbiting satellites. Using the relatively new technique of Global Navigation Satellite System reflectometry (GNSS-R), all-weather observations are possible, penetrating even deep convection within hurricane eye walls. The compact nature of the GNSS-R receivers permits the use of small satellites, which in turn enables the launch of a constellation of satellites from a single launch vehicle. Launched in December of 2016, the eight CYGNSS satellites provide 25 km resolution observations of mean square slope (surface roughness) and surface winds with a 2.8 hour median revisit time from 38 S to 38 N degrees latitude. In addition to the calibration and validation of CYGNSS sea state observations, the CYGNSS science team is assessing the ability of the mission to provide estimates of cyclone size, intensity, and integrated kinetic energy. With its all-weather ability and high temporal resolution, the CYGNSS mission will add significantly to our ability to monitor cyclone genesis and intensification and will significantly reduce uncertainties in our ability to estimate cyclone intensity, a key variable in predicting its destructive potential. Members of the CYGNSS Science Team are also assessing the assimilation of CYGNSS data into hurricane forecast models to determine the impact of the data on forecast skill, using the data to study extra-tropical cyclones, and looking at connections between tropical cyclones and global scale weather, including the global hydrologic cycle. This presentation will focus on the assessment of early on-orbit observations of cyclones with respect to these various applications.

CYGNSS Surface Wind Observations and Surface Flux Estimates within Low-Latitude Extratropical Cyclones

NASA Astrophysics Data System (ADS)

Crespo, J.; Posselt, D. J.

2017-12-01

The Cyclone Global Navigation Satellite System (CYGNSS), launched in December 2016, aims to improve estimates of surface wind speeds over the tropical oceans. While CYGNSS's core mission is to provide better estimates of surface winds within the core of tropical cyclones, previous research has shown that the constellation, with its orbital inclination of 35°, also has the ability to observe numerous extratropical cyclones that form in the lower latitudes. Along with its high spatial and temporal resolution, CYGNSS can provide new insights into how extratropical cyclones develop and evolve, especially in the presence of thick clouds and precipitation. We will demonstrate this by presenting case studies of multiple extratropical cyclones observed by CYGNSS early on in its mission in both Northern and Southern Hemispheres. By using the improved estimates of surface wind speeds from CYGNSS, we can obtain better estimates of surface latent and sensible heat fluxes within and around extratropical cyclones. Surface heat fluxes, driven by surface winds and strong vertical gradients of water vapor and temperature, play a key role in marine cyclogenesis as they increase instability within the boundary layer and may contribute to extreme marine cyclogenesis. In the past, it has been difficult to estimate surface heat fluxes from space borne instruments, as these fluxes cannot be observed directly from space, and deficiencies in spatial coverage and attenuation from clouds and precipitation lead to inaccurate estimates of surface flux components, such as surface wind speeds. While CYGNSS only contributes estimates of surface wind speeds, we can combine this data with other reanalysis and satellite data to provide improved estimates of surface sensible and latent heat fluxes within and around extratropical cyclones and throughout the entire CYGNSS mission.

Local inertial oscillations in the surface ocean generated by time-varying winds

NASA Astrophysics Data System (ADS)

Chen, Shengli; Polton, Jeff A.; Hu, Jianyu; Xing, Jiuxing

2015-12-01

A new relationship is presented to give a review study on the evolution of inertial oscillations in the surface ocean locally generated by time-varying wind stress. The inertial oscillation is expressed as the superposition of a previous oscillation and a newly generated oscillation, which depends upon the time-varying wind stress. This relationship is employed to investigate some idealized wind change events. For a wind series varying temporally with different rates, the induced inertial oscillation is dominated by the wind with the greatest variation. The resonant wind, which rotates anti-cyclonically at the local inertial frequency with time, produces maximal amplitude of inertial oscillations, which grows monotonically. For the wind rotating at non-inertial frequencies, the responses vary periodically, with wind injecting inertial energy when it is in phase with the currents, but removing inertial energy when it is out of phase. The wind rotating anti-cyclonically with time is much more favorable to generate inertial oscillations than the cyclonic rotating wind. The wind with a frequency closer to the inertial frequency generates stronger inertial oscillations. For a diurnal wind, the induced inertial oscillation is dependent on latitude and is most significant at 30 °. This relationship is also applied to examine idealized moving cyclones. The inertial oscillation is much stronger on the right-hand side of the cyclone path than on the left-hand side (in the northern hemisphere). This is due to the wind being anti-cyclonic with time on the right-hand side, but cyclonic on the other side. The inertial oscillation varies with the cyclone translation speed. The optimal translation speed generating the greatest inertial oscillations is 2 m/s at the latitude of 10 ° and gradually increases to 6 m/s at the latitude of 30 °.

A study of formation and development of one kind of cyclone on the mei-yu (Baiu) front

NASA Astrophysics Data System (ADS)

Zhang, Feng; Zhao, Sixiong

2004-10-01

The paper presents one diagnosis of baroclinity and the coupling of jets during the developing process of a cyclone that occurred on the mei-yu (Baiu) front around the end of the second stage of the mei-yu (Baiu) in 1998. Results have shown that: (1) The advantageous changes of upper-level large-scale circulation caused the appearance and maintenance of the coupling between the upper-level jet (ULJ) and lower-level jet (LLJ) over the cyclone’s area. The coupling of jets in this case possesses some different characteristics from previous cases. Moreover, the coupling between the ULJ and LLJ caused the intensification of both lower-level convergence and upper-level divergence, which was favorable for the development of this cyclone. (2) From the analysis of the voricity budget, the role of lower-level convergence in the development of the cyclone was emphasized. Divergent wind in the lower troposphere was a direct contributor to the development of the cyclone. (3) During the development of the cyclone, cold air and warm air were active over the cyclone’s domain. Although this cyclone occurred at the mei-yu (Baiu) front, its development assumed baroclinity to a certain extent, which was just the main difference between this kind of cyclone and the first kind of low which is usually barotropic (or quasi-barotropic). (4) In recent years, studies on mei-yu front lows have paid more attention to the lower troposphere. In this paper, the analysis of the energy budget further supports this point: the certain effect of baroclinity forcing in the upper troposphere on mei-yu front lows cannot be ignored.

Model-Simulated Northern Winter Cyclone and Anticyclone Activity under a Greenhouse Warming Scenario.

NASA Astrophysics Data System (ADS)

Zhang, Yi; Wang, Wei-Chyung

1997-07-01

Two 100-yr equilibrium simulations from the NCAR Community Climate Model coupled to a nondynamic slab ocean are used to investigate the activity of northern winter extratropical cyclones and anticyclones under a greenhouse warming scenario. The first simulation uses the 1990 observed CO2, CH4, N2O, CFC-11, and CFC-12 concentrations, and the second adopts the year 2050 concentrations according to the Intergovernmental Panel on Climate Change business-as-usual scenario. Variables that describe the characteristic properties of the cyclone-scale eddies, such as surface cyclone and anticyclone frequency and the bandpassed root-mean-square of 500-hPa geopotential height, along with the Eady growth rate maximum, form a framework for the analysis of the cyclone and anticyclone activity.Objective criteria are developed for identifying cyclone and anticyclone occurrences based on the 1000-hPa geopotential height and vorticity fields and tested using ECMWF analyses. The potential changes of the eddy activity under the greenhouse warming climate are then examined. Results indicate that the activity of cyclone-scale eddies decreases under the greenhouse warming scenario. This is not only reflected in the surface cyclone and anticyclone frequency and in the bandpassed rms of 500-hPa geopotential height, but is also discerned from the Eady growth rate maximum. Based on the analysis, three different physical mechanisms responsible for the decreased eddy activity are discussed: 1) a decrease of the extratropical meridional temperature gradient from the surface to the midtroposphere, 2) a reduction in the land-sea thermal contrast in the east coastal regions of the Asian and North American continents, and 3) an increase in the eddy meridional latent heat fluxes. Uncertainties in the results related to the limitations of the model and the model equilibrium simulations are discussed.

Somatic embryogenesis and plant regeneration from cell suspension cultures of Cucumis sativus L.

PubMed

Chee, P P; Tricoli, D M

1988-06-01

A procedure for the regeneration of whole cucumber plants (Cucumis sativus L. cv. Poinsett 76) by embryogenesis from cell suspension cultures is described. Embryogenic callus was initiated from the primary leaves of 14-17 day old plants. Suspension cultures of embryogenic cells were grown in liquid Murashige and Skoog basal medium containing 5 uM 2,4,5-trichlorophenoxyacetic acid and 4 uM 6-benzylaminopurine. Suspension cultures were composed of a population of cells that were densely cytoplasmic and potentially embryogenic. Differentiation of embryos was enhanced by washing the suspension culture cells with MS basal medium containing 0.5% activated charcoal and twice with MS basal medium followed by liquid shake cultures in MS basal medium. Sixty to 70 percent of the embryos prewashed with activated charcoal germinated into plantlets with normal morphology. Embryos obtained from suspension cultured cells without prewashing with activated charcoal organized into plantlets with abnormal primary leaves. Morphologically normal plantlets were obtained by excising the shoot tips and transferring them to fresh medium.

Study of the Western Black Sea Storms with a Focus on the Storms Caused by Cyclones of North African Origin

NASA Astrophysics Data System (ADS)

Galabov, Vasko; Chervenkov, Hristo

2018-04-01

We present a study of the Black Sea storms, using a long hindcast of the western Black Sea wind waves. The goal of the work is to study the trends in the storminess indicators. We identify 238 storms with significant wave height above 4 m for the period 1900-2015. We study the cyclogenetic regions of the cyclones causing these storms and focus specifically on the Black Sea storms associated with cyclones originating over the Gulf of Sidra and the adjacent areas. We also identify which of these storms are associated with the so-called explosive cyclogenesis (with deepening rate above 1 Bergeron) and find that 3 out of 5 cases of severe Black Sea storms associated with explosive cyclones are caused by cyclones originating in the Gulf of Sidra. We find no evidence of steady trends in the western Black Sea storminess.

Westward migration of tropical cyclone rapid-intensification over the Northwestern Pacific during short duration El Niño.

PubMed

Guo, Yi-Peng; Tan, Zhe-Min

2018-04-17

The El Niño-Southern Oscillation (ENSO) can significantly affect the rapid intensification of tropical cyclones over the western North Pacific (WNP). However, ENSO events have various durations, which can lead to different atmospheric and oceanic conditions. Here we show that during short duration El Niño events, the WNP tropical cyclone rapid-intensification mean occurrence position migrates westward by ~8.0° longitude, which is caused by reduced vertical wind shear, increased mid-tropospheric humidity, and enhanced tropical cyclone heat potential over the westernmost WNP. The changes in these factors are caused by westward advected upper ocean heat during the decaying phase of a short duration El Niño. As super El Niño events tend to have short durations and their frequency is projected to increase under global warming, our findings have important implications for future projections of WNP tropical cyclone activity.

Aerosol Optical Depth Distribution in Extratropical Cyclones over the Northern Hemisphere Oceans

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

2016-01-01

Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database,the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere mid-latitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the post-cold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

Satellite Observations of Stratospheric Gravity Waves Associated With the Intensification of Tropical Cyclones

NASA Astrophysics Data System (ADS)

Hoffmann, Lars; Wu, Xue; Alexander, M. Joan

2018-02-01

Forecasting the intensity of tropical cyclones is a challenging problem. Rapid intensification is often preceded by the formation of "hot towers" near the eyewall. Driven by strong release of latent heat, hot towers are high-reaching tropical cumulonimbus clouds that penetrate the tropopause. Hot towers are a potentially important source of stratospheric gravity waves. Using 13.5 years (2002-2016) of Atmospheric Infrared Sounder observations of stratospheric gravity waves and tropical cyclone data from the International Best Track Archive for Climate Stewardship, we found empirical evidence that stratospheric gravity wave activity is associated with the intensification of tropical cyclones. The Atmospheric Infrared Sounder and International Best Track Archive for Climate Stewardship data showed that strong gravity wave events occurred about twice as often for tropical cyclone intensification compared to storm weakening. Observations of stratospheric gravity waves, which are not affected by obscuring tropospheric clouds, may become an important future indicator of storm intensification.

Statistical Aspects of Tropical Cyclone Activity in the North Atlantic Basin, 1945-2010

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2012-01-01

Examined are statistical aspects of the 715 tropical cyclones that formed in the North Atlantic basin during the interval 1945-2010. These 715 tropical cyclones include 306 storms that attained only tropical storm strength, 409 hurricanes, 179 major or intense hurricanes, and 108 storms that struck the US coastline as hurricanes. Comparisons made using 10-year moving average (10-yma) values between tropical cyclone parametric values and surface air and ENSO-related parametric values indicate strong correlations to exist, in particular, against the Armagh Observatory (Northern Ireland) surface air temperature, the Atlantic Multi-decadal Oscillation (AMO) index, the Atlantic Meridional Mode (AMM) index, and the North Atlantic Oscillation (NAO) index, in addition to the Oceanic Ni o index (ONI) and Quasi-Biennial Oscillation (QBO) indices. Also examined are the decadal variations of the tropical cyclone parametric values and a look ahead towards the 2012 hurricane season and beyond.

Exploring the feasibility of focusing CW light through a scattering medium into closely spaced twin peaks via numerical solutions of Maxwell’s equations

NASA Astrophysics Data System (ADS)

Tseng, Snow H.; Chang, Shih-Hui

2018-04-01

Here we present a numerical simulation to analyze the effect of scattering on focusing light into closely-spaced twin peaks. The pseudospectral time-domain (PSTD) is implemented to model continuous-wave (CW) light propagation through a scattering medium. Simulations show that CW light can propagate through a scattering medium and focus into closely-spaced twin peaks. CW light of various wavelengths focusing into twin peaks with sub-diffraction spacing is simulated. In advance, light propagation through scattering media of various number densities is simulated to decipher the dependence of CW light focusing phenomenon on the scattering medium. The reported simulations demonstrate the feasibility of focusing CW light into twin peaks with sub-diffraction dimensions. More importantly, based upon numerical solutions of Maxwell’s equations, research findings show that the sub-diffraction focusing phenomenon can be achieved with scarce or densely-packed scattering media.

A new numerical benchmark for variably saturated variable-density flow and transport in porous media

NASA Astrophysics Data System (ADS)

Guevara, Carlos; Graf, Thomas

2016-04-01

In subsurface hydrological systems, spatial and temporal variations in solute concentration and/or temperature may affect fluid density and viscosity. These variations could lead to potentially unstable situations, in which a dense fluid overlies a less dense fluid. These situations could produce instabilities that appear as dense plume fingers migrating downwards counteracted by vertical upwards flow of freshwater (Simmons et al., Transp. Porous Medium, 2002). As a result of unstable variable-density flow, solute transport rates are increased over large distances and times as compared to constant-density flow. The numerical simulation of variable-density flow in saturated and unsaturated media requires corresponding benchmark problems against which a computer model is validated (Diersch and Kolditz, Adv. Water Resour, 2002). Recorded data from a laboratory-scale experiment of variable-density flow and solute transport in saturated and unsaturated porous media (Simmons et al., Transp. Porous Medium, 2002) is used to define a new numerical benchmark. The HydroGeoSphere code (Therrien et al., 2004) coupled with PEST (www.pesthomepage.org) are used to obtain an optimized parameter set capable of adequately representing the data set by Simmons et al., (2002). Fingering in the numerical model is triggered using random hydraulic conductivity fields. Due to the inherent randomness, a large number of simulations were conducted in this study. The optimized benchmark model adequately predicts the plume behavior and the fate of solutes. This benchmark is useful for model verification of variable-density flow problems in saturated and/or unsaturated media.

Condition of Development of Channeled Flow in Analogue Partially Molten Medium

NASA Astrophysics Data System (ADS)

Takashima, S.; Kumagai, I.; Kurita, K.

2003-12-01

Melt migration in partially molten medium is conceptually classified into two contrasting models; homogeneous permeable flow and localized channeled flow. The transition from homogeneous flow to localized one is promoted with advance of melting and deformation of the medium, but the physics behind this transition is not yet clarified well. Here we show two kinds of experimental results which are mutually related. One is a development of the channeled flow in a so-called Rayleigh-Taylor Instability experiments. Dense viscous fluid is poured at the top of the matrix fluid; homogeneous mixture of soft transparent gel and viscous fluid having equal density. Liquid fraction is varied for this matrix fluid to see how the fraction controls the development. At the intermediate gel fraction (between70% to about 40%) the dense fluid at first migrates through the grain boundary as permeable flow. But local heterogeneity in the gel fraction induces relative movement of solid phase, which in turns enhances the localization of the flow and deformation. We measured the motion of fluid phase and solid phase separately by PIV/PTV methods. Estimated relative motion and divergence of velocity field of the solid phase show that the state in the relative movement of the solid phase could cause heterogeneous distribution of the solid fraction. The deformation-induced compaction plays an important role. The second experimental result is rheology of the dense suspension of soft gel and viscous fluid. Deformation experiment with concentric cylinders shows that the mixture system has yield strength at the intermediate gel fraction. In the stress state above the yield strength the region where deformation rate is large has low viscosity and its internal structure evolves to the state in heterogeneous distribution of viscosity. We would like to show that this nature is critical in the development of flow from homogeneous one to localized one.

Model simulations of dense bottom currents in the Western Baltic Sea

NASA Astrophysics Data System (ADS)

Burchard, Hans; Janssen, Frank; Bolding, Karsten; Umlauf, Lars; Rennau, Hannes

2009-01-01

Only recently, medium intensity inflow events into the Baltic Sea have gained more awareness because of their potential to ventilate intermediate layers in the Southern Baltic Sea basins. With the present high-resolution model study of the Western Baltic Sea a first attempt is made to obtain model based realistic estimates of turbulent mixing in this area where dense bottom currents resulting from medium intensity inflow events are weakened by turbulent entrainment. The numerical model simulation which is carried out using the General Estuarine Transport Model (GETM) during nine months in 2003 and 2004 is first validated by means of three automatic stations at the Drogden and Darss Sills and in the Arkona Sea. In order to obtain good agreement between observations and model results, the 0.5×0.5 nautical mile bathymetry had to be adjusted in order to account for the fact that even at that scale many relevant topographic features are not resolved. Current velocity, salinity and turbulence observations during a medium intensity inflow event through the Øresund are then compared to the model results. Given the general problems of point to point comparisons between observations and model simulations, the agreement is fairly good with the characteristic features of the inflow event well represented by the model simulations. Two different bulk measures for mixing activity are then introduced, the vertically integrated decay of salinity variance, which is equal to the production of micro-scale salinity variance, and the vertically integrated turbulent salt flux, which is related to an increase of potential energy due to vertical mixing of stably stratified flow. Both measures give qualitatively similar results and identify the Drogden and Darss Sills as well as the Bornholm Channel as mixing hot spots. Further regions of strong mixing are the dense bottom current pathways from these sills into the Arkona Sea, areas around Kriegers Flak (a shoal in the western Arkona Sea) and north-west of the island of Rügen.

Airships for transporting highly volatile commodities

NASA Technical Reports Server (NTRS)

Sonstegaard, M.

1975-01-01

Large airships may prove feasible as carriers of commodities that move as gases or cryogenic liquids; buoyant gaseous cargo could be ballasted with liquid cargo. Airships are compact in shape, operate in a rarified medium, and hence can be fast and perhaps economic carriers of costly cryogenic tanks. The high-pressure gas pipeline has excessive surface area when carrying hydrogen and excessive fluid density when carrying natural gas, while the cryogenic ocean tanker runs in a dense medium and makes gravity waves. But the airship, despite its fluid dynamic advantages, faces problems of safety, weather, and altitude control.

Toward Measuring Galactic Dense Molecular Gas Properties and 3D Distribution with Hi-GAL

NASA Astrophysics Data System (ADS)

Zetterlund, Erika; Glenn, Jason; Maloney, Phil

2016-01-01

The Herschel Space Observatory's submillimeter dust continuum survey Hi-GAL provides a powerful new dataset for characterizing the structure of the dense interstellar medium of the Milky Way. Hi-GAL observed a 2° wide strip covering the entire 360° of the Galactic plane in broad bands centered at 70, 160, 250, 350, and 500 μm, with angular resolution ranging from 10 to 40 arcseconds. We are adapting a molecular cloud clump-finding algorithm and a distance probability density function distance-determination method developed for the Bolocam Galactic Plane Survey (BGPS) to the Hi-GAL data. Using these methods we expect to generate a database of 105 cloud clumps, derive distance information for roughly half the clumps, and derive precise distances for approximately 20% of them. With five-color photometry and distances, we will measure the cloud clump properties, such as luminosities, physical sizes, and masses, and construct a three-dimensional map of the Milky Way's dense molecular gas distribution.The cloud clump properties and the dense gas distribution will provide critical ground truths for comparison to theoretical models of molecular cloud structure formation and galaxy evolution models that seek to emulate spiral galaxies. For example, such models cannot resolve star formation and use prescriptive recipes, such as converting a fixed fraction of interstellar gas to stars at a specified interstellar medium density threshold. The models should be compared to observed dense molecular gas properties and galactic distributions.As a pilot survey to refine the clump-finding and distance measurement algorithms developed for BGPS, we have identified molecular cloud clumps in six 2° × 2° patches of the Galactic plane, including one in the inner Galaxy along the line of sight through the Molecular Ring and the termination of the Galactic bar and one toward the outer Galaxy. Distances have been derived for the inner Galaxy clumps and compared to Bolocam Galactic Plane Survey results. We present the pilot survey clump catalog, distances, clump properties, and a comparison to BGPS.

40 CFR 63.11624 - What are the notification, reporting, and recordkeeping requirements?

Code of Federal Regulations, 2010 CFR

2010-07-01

... § 63.11621(e) to install and operate a cyclone to control emissions from pelleting operations, the... of the cyclone determined in accordance with § 63.11621(e)(2). (iv) If you own or operate an affected source that is not subject to the requirement in § 63.11621(e) to install and operate a cyclone to...

40 CFR 63.11624 - What are the notification, reporting, and recordkeeping requirements?

Code of Federal Regulations, 2011 CFR

2011-07-01

... § 63.11621(e) to install and operate a cyclone to control emissions from pelleting operations, the... of the cyclone determined in accordance with § 63.11621(e)(2). (iv) If you own or operate an affected source that is not subject to the requirement in § 63.11621(e) to install and operate a cyclone to...

North Atlantic Basin Tropical Cyclone Activity in Relation to Temperature and Decadal- Length Oscillation Patterns

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2009-01-01

Yearly frequencies of North Atlantic basin tropical cyclones, their locations of origin, peak wind speeds, average peak wind speeds, lowest pressures, and average lowest pressures for the interval 1950-2008 are examined. The effects of El Nino and La Nina on the tropical cyclone parametric values are investigated. Yearly and 10-year moving average (10-yma) values of tropical cyclone parameters are compared against those of temperature and decadal-length oscillation, employing both linear and bi-variate analysis, and first differences in the 10-yma are determined. Discussion of the 2009 North Atlantic basin hurricane season, updating earlier results, is given.

Cyclone: A close air support aircraft for tomorrow

NASA Technical Reports Server (NTRS)

Cox, George; Croulet, Donald; Dunn, James; Graham, Michael; Ip, Phillip; Low, Scott; Vance, Gregg; Volckaert, Eric

1991-01-01

To meet the threat of the battlefield of the future, the U.S. ground forces will require reliable air support. To provide this support, future aircrews demand a versatile close air support aircraft capable of delivering ordinance during the day, night, or in adverse weather with pin-point accuracy. The Cyclone aircraft meets these requirements, packing the 'punch' necessary to clear the way for effective ground operations. Possessing anti-armor, missile, and precision bombing capability, the Cyclone will counter the threat into the 21st Century. Here, it is shown that the Cyclone is a realistic, economical answer to the demand for a capable close air support aircraft.

Atmospheric water parameters in mid-latitude cyclones observed by microwave radiometry and compared to model calculations

NASA Technical Reports Server (NTRS)

Katsaros, Kristina B.; Hammarstrand, Ulla; Petty, Grant W.

1990-01-01

Existing and experimental algorithms for various parameters of atmospheric water content such as integrated water vapor, cloud water, precipitation, are used to examine the distribution of these quantities in mid latitude cyclones. The data was obtained from signals given by the special sensor microwave/imager (SSM/I) and compared with data from the nimbus scanning multichannel microwave radiometer (SMMR) for North Atlantic cyclones. The potential of microwave remote sensing for enhancing knowledge of the horizontal structure of these storms and to aid the development and testing of the cloud and precipitation aspects of limited area numerical models of cyclonic storms is investigated.

Downscaling CMIP5 climate models shows increased tropical cyclone activity over the 21st century

PubMed Central

Emanuel, Kerry A.

2013-01-01

A recently developed technique for simulating large [O(104)] numbers of tropical cyclones in climate states described by global gridded data is applied to simulations of historical and future climate states simulated by six Coupled Model Intercomparison Project 5 (CMIP5) global climate models. Tropical cyclones downscaled from the climate of the period 1950–2005 are compared with those of the 21st century in simulations that stipulate that the radiative forcing from greenhouse gases increases by over preindustrial values. In contrast to storms that appear explicitly in most global models, the frequency of downscaled tropical cyclones increases during the 21st century in most locations. The intensity of such storms, as measured by their maximum wind speeds, also increases, in agreement with previous results. Increases in tropical cyclone activity are most prominent in the western North Pacific, but are evident in other regions except for the southwestern Pacific. The increased frequency of events is consistent with increases in a genesis potential index based on monthly mean global model output. These results are compared and contrasted with other inferences concerning the effect of global warming on tropical cyclones. PMID:23836646

Analyzing the Response of Climate Perturbations to (Tropical) Cyclones using the WRF Model

NASA Astrophysics Data System (ADS)

Tewari, M.; Mittal, R.; Radhakrishnan, C.; Cipriani, J.; Watson, C.

2015-12-01

An analysis of global climate models shows considerable changes in the intensity and characteristics of future, warm climate cyclones. At regional scales, deviations in cyclone characteristics are often derived using idealized perturbations in the humidity, temperature and surface conditions. In this work, a more realistic approach is adopted by applying climate perturbations from the Community Climate System Model (CCSM4) to ERA-interim data to generate the initial and boundary conditions for future climate simulations. The climate signal perturbations are generated from the differences in 21 years of mean data from CCSM4 with representative concentration pathways (RCP8.5) for the periods: (a) 2070-2090 (future climate), (b) 2025-2045 (near-future climate) and (c) 1985-2005 (current climate). Four individual cyclone cases are simulated with and without climate perturbations using the Weather Research and Forecasting model with a nested configuration. Each cyclone is characterized by variations in intensity, landfall location, precipitation and societal damage. To calculate societal damage, we use the recently introduced Cyclone Damage Potential (CDP) index evolved from the Willis Hurricane Index (WHI). As CDP has been developed for general societal applications, this work should provide useful insights for resilience analyses and industry (e.g., re-insurance).

On the relationship between atmospheric water vapour transport and extra-tropical cyclones development

NASA Astrophysics Data System (ADS)

Ferreira, Juan A.; Liberato, Margarida L. R.; Ramos, Alexandre M.

2016-08-01

In this study we seek to investigate the role of atmospheric water vapour on the intensification of extra-tropical cyclones over the North Atlantic Ocean and more specifically to investigate the linkage between atmospheric rivers' conditions leading to the explosive development of extra-tropical cyclones. Several WRF-ARW simulations for three recent extra-tropical storms that had major negative socio-economic impacts in the Iberian Peninsula and south-western Europe (Klaus, 2009; Gong, 2013 and Stephanie, 2014) are performed in which the water vapour content of the initial and boundary conditions are tuned. Analyses of the vertically integrated vapour transport show the dependence of the storms' development on atmospheric water vapour. In addition, results also show changes in the shape of the jet stream resulting in a reduction of the upper wind divergence, which in turn affects the intensification of the extra-tropical cyclones studied. This study suggests that atmospheric rivers tend to favour the conditions for explosive extra-tropical storms' development in the three case studies, as simulations performed without the existence of atmospheric rivers produce shallow mid-latitude cyclones, that is, cyclones that are not so intense as those on the reference simulations.

Opposed-flow virtual cyclone for particle concentration

DOEpatents

Rader, Daniel J.; Torczynski, John R.

2000-12-05

An opposed-flow virtual cyclone for aerosol collation which can accurately collect, classify, and concentrate (enrich) particles in a specific size range. The opposed-flow virtual cyclone is a variation on the virtual cyclone and has its inherent advantages (no-impact particle separation in a simple geometry), while providing a more robust design for concentrating particles in a flow-through type system. The opposed-flow virtual cyclone consists of two geometrically similar virtual cyclones arranged such that their inlet jets are inwardly directed and symmetrically opposed relative to a plane of symmetry located between the two inlet slits. A top plate bounds both jets on the "top" side of the inlets, while the other or lower wall curves "down" and away from each inlet jet. Each inlet jet will follow the adjacent lower wall as it turns away, and that particles will be transferred away from the wall and towards the symmetry plane by centrifugal action. After turning, the two jets merge smoothly along the symmetry line and flow parallel to it through the throat. Particles are transferred from the main flows, across a dividing streamline, and into a central recirculating region, where particle concentrations become greatly increased relative to the main stream.

Acceleration of tropical cyclogenesis by self-aggregation feedbacks

NASA Astrophysics Data System (ADS)

Muller, Caroline J.; Romps, David M.

2018-03-01

Idealized simulations of tropical moist convection have revealed that clouds can spontaneously clump together in a process called self-aggregation. This results in a state where a moist cloudy region with intense deep convection is surrounded by extremely dry subsiding air devoid of deep convection. Because of the idealized settings of the simulations where it was discovered, the relevance of self-aggregation to the real world is still debated. Here, we show that self-aggregation feedbacks play a leading-order role in the spontaneous genesis of tropical cyclones in cloud-resolving simulations. Those feedbacks accelerate the cyclogenesis process by a factor of 2, and the feedbacks contributing to the cyclone formation show qualitative and quantitative agreement with the self-aggregation process. Once the cyclone is formed, wind-induced surface heat exchange (WISHE) effects dominate, although we find that self-aggregation feedbacks have a small but nonnegligible contribution to the maintenance of the mature cyclone. Our results suggest that self-aggregation, and the framework developed for its study, can help shed more light into the physical processes leading to cyclogenesis and cyclone intensification. In particular, our results point out the importance of the longwave radiative cooling outside the cyclone.

Examining South Atlantic Subtropical Cyclone Anita using the Satellite-Enhanced Regional Downscaling for Applied Studies Hourly Outputs

NASA Astrophysics Data System (ADS)

Vaicberg, H.; Palmeira, A. C. P. A.; Nunes, A.

2017-12-01

Studies on South Atlantic cyclones are mainly compromised by scarcity of observations. Therefore, remote sensing and global (re) analysis products are usually employed in investigations of their evolution. However, the frequent use of global reanalysis might difficult the assessment of the characteristics of the cyclones found in South Atlantic. In that regard, studies on "subtropical" cyclones have been performed using the 25-km resolution, Satellite-enhanced Regional Downscaling for Applied Studies (SRDAS), a product developed at the Federal University of Rio de Janeiro in Brazil. In SRDAS, the Regional Spectral Model assimilates precipitation estimates from environmental satellites, while dynamically downscaling a global reanalysis using the spectral nudging technique to maintain the large-scale features in agreement with the regional model solution. The use of regional models in the downscaling of general circulation models provides more detailed information on weather and climate. As a way of illustrating the usefulness of SRDAS in the study of the subtropical South Atlantic cyclones, the subtropical cyclone Anita was selected because of its intensity. Anita developed near Brazilian south/southeast coast, with damages to local communities. Comparisons with available observations demonstrated the skill of SRDAS in simulating such an extreme event.

Tropical cyclone induced asymmetry of sea level surge and fall and its presentation in a storm surge model with parametric wind fields

NASA Astrophysics Data System (ADS)

Peng, Machuan; Xie, Lian; Pietrafesa, Leonard J.

The asymmetry of tropical cyclone induced maximum coastal sea level rise (positive surge) and fall (negative surge) is studied using a three-dimensional storm surge model. It is found that the negative surge induced by offshore winds is more sensitive to wind speed and direction changes than the positive surge by onshore winds. As a result, negative surge is inherently more difficult to forecast than positive surge since there is uncertainty in tropical storm wind forecasts. The asymmetry of negative and positive surge under parametric wind forcing is more apparent in shallow water regions. For tropical cyclones with fixed central pressure, the surge asymmetry increases with decreasing storm translation speed. For those with the same translation speed, a weaker tropical cyclone is expected to gain a higher AI (asymmetry index) value though its induced maximum surge and fall are smaller. With fixed RMW (radius of maximum wind), the relationship between central pressure and AI is heterogeneous and depends on the value of RMW. Tropical cyclone's wind inflow angle can also affect surge asymmetry. A set of idealized cases as well as two historic tropical cyclones are used to illustrate the surge asymmetry.

Using Proxy Records to Document Gulf of Mexico Tropical Cyclones from 1820-1915

PubMed Central

Rohli, Robert V.; DeLong, Kristine L.; Harley, Grant L.; Trepanier, Jill C.

2016-01-01

Observations of pre-1950 tropical cyclones are sparse due to observational limitations; therefore, the hurricane database HURDAT2 (1851–present) maintained by the National Oceanic and Atmospheric Administration may be incomplete. Here we provide additional documentation for HURDAT2 from historical United States Army fort records (1820–1915) and other archived documents for 28 landfalling tropical cyclones, 20 of which are included in HURDAT2, along the northern Gulf of Mexico coast. One event that occurred in May 1863 is not currently documented in the HURDAT2 database but has been noted in other studies. We identify seven tropical cyclones that occurred before 1851, three of which are potential tropical cyclones. We corroborate the pre-HURDAT2 storms with a tree-ring reconstruction of hurricane impacts from the Florida Keys (1707–2009). Using this information, we suggest landfall locations for the July 1822 hurricane just west of Mobile, Alabama and 1831 hurricane near Last Island, Louisiana on 18 August. Furthermore, we model the probable track of the August 1831 hurricane using the weighted average distance grid method that incorporates historical tropical cyclone tracks to supplement report locations. PMID:27898726

Simulation of Extreme Arctic Cyclones in IPCC AR5 Experiments

NASA Astrophysics Data System (ADS)

Vavrus, S. J.

2012-12-01

Although impending Arctic climate change is widely recognized, a wild card in its expression is how extreme weather events in this region will respond to greenhouse warming. Intense polar cyclones represent one type of high-latitude phenomena falling into this category, including very deep synoptic-scale cyclones and mesoscale polar lows. These systems inflict damage through high winds, heavy precipitation, and wave action along coastlines, and their impact is expected to expand in the future, when reduced sea ice cover allows enhanced wave energy. The loss of a buffering ice pack could greatly increase the rate of coastal erosion, which has already been increasing in the Arctic. These and related threats may amplify if extreme Arctic cyclones become more frequent and/or intense in a warming climate with much more open water to fuel them. This possibility has merit on the basis of GCM experiments, which project that greenhouse forcing causes lower mean sea level pressure (SLP) in the Arctic and a strengthening of the deepest storms over boreal high latitudes. In this study, the latest Coupled Model Intercomparison Project (CMIP5) climate model output is used to investigate the following questions: (1) What are the spatial and seasonal characteristics of extreme Arctic cyclones? (2) How well do GCMs simulate these phenomena? (3) Are Arctic cyclones already showing the expected response to greenhouse warming in climate models? To address these questions, a retrospective analysis is conducted of the transient 20th century simulations among the CMIP5 GCMs (spanning years 1850-2005). The results demonstrate that GCMs are able to reasonably represent extreme Arctic cyclones and that the simulated characteristics do not depend significantly on model resolution. Consistent with observational evidence, climate models generate these storms primarily during winter and within the climatological Aleutian and Icelandic Low regions. Occasionally the cyclones remain very intense over the Arctic Ocean. The historical tendency in Arctic SLP varies considerably among the GCMs, but the intermodel average trend exhibits a lowering of mean-annual pressure over the Arctic during the past 150 years and an increase in extreme cyclones in the vicinity of the Aleutian and Icelandic Lows. However, only weak trends in extreme cyclones are simulated through 2005 over the Arctic Ocean, where simulations of future climate change produce the largest SLP falls.

On the dynamics of synoptic scale cyclones associated with flood events in Crete

NASA Astrophysics Data System (ADS)

Flocas, Helena; Katavoutas, George; Tsanis, Ioannis; Iordanidou, Vasiliki

2015-04-01

Flood events in the Mediterranean are frequently linked to synoptic scale cyclones, although topographical or anthropogenic factors can play important role. The knowledge of the vertical profile and dynamics of these cyclones can serve as a reliable early flood warning system that can further help in hazard mitigation and risk management planning. Crete is the second largest island in the eastern Mediterranean region, being characterized by high precipitation amounts during winter, frequently causing flood events. The objective of this study is to examine the dynamic and thermodynamic mechanisms at the upper and lower levels responsible for the generation of these events, according to their origin domain. The flooding events were recorded for a period of almost 20 years. The surface cyclones are identified with the aid of MS scheme that was appropriately modified and extensively employed in the Mediterranean region in previous studies. Then, the software VTS, specially developed for the Mediterranean cyclones, was employed to investigate the vertical extension, slope and dynamic/kinematic characteristics of the surface cyclones. Composite maps of dynamic/thermodynamic parameters, such as potential vorticity, temperature advection, divergence, surface fluxes were then constructed before and during the time of the flood. The dataset includes 6-hourly surface and isobaric analyses on a 0.5° x 0.5° regular latitude-longitude grid, as derived from the ERA-INTERIM Reanalysis of the ECMWF. It was found that cyclones associated with flood events in Crete mainly generate over northern Africa or southern eastern Mediterranean region and experience their minimum pressure over Crete or southwestern Greece. About 84% of the cyclones extend up to 500hPa, demonstrating that they are well vertically well-organized systems. The vast majority (almost 84%) of the surface cyclones attains their minimum pressure when their 500 hpa counterparts are located in the NW or SW, confirming that baroclinicity is one of the most important driving mechanisms for the cyclonic deepening over the examined region. The upper level dynamics acting well before the event and the low level diabatic processes over the Aegean or the Levantine sea contribute to the large amounts of precipitation. The research reported in this paper was fully supported by the "ARISTEIA II" Action ("REINFORCE" program) of the "Operational Education and Life Long Learning programme" and is co-funded by the European Social Fund (ESF) and National Resources.

Impact of tropical cyclones on aerosol properties over urban region of Hyderabad, India

NASA Astrophysics Data System (ADS)

Kharol, Shailesh Kumar; Badarinath, K. V. S.; Rani Sharma, Anu; Krishna Prasad, V.; Kaskaoutis, Dimitrios G.; Nastos, Panagiotis T.; Kambezidis, Harry D.

2010-05-01

Fierce tropical cyclones occur in India during the pre-monsoon (spring), early monsoon (early summer), or post-monsoon (fall) periods. Originating in both the Bay of Bengal and the Arabian Sea, tropical cyclones often attain velocities of more than 100 kmh-1 and are notorious for causing intense rain and tidal waves as they cross the Indian coast. Cyclones are associated with heavy rainfall, gusty winds, and sometimes, storm surges. In the present study, we have analyzed the changes in aerosol properties at Hyderabad, India, associated with very severe cyclonic storm "Mala" occurred during the last week of April, 2006 over the Central-Eastern part of the Bay of Bengal centered near Lat. 16.0 N and Long. 93.0 E, at 18:00 UTC on 28th April 2006, about 500 Km North of Portblair. This tropical cyclone, packing winds of 240 km/h, slammed into Myanmar on 28th April and 29th April destroying hundreds of houses, two beach resorts and at least five factories as per the reports of the Kyemon daily paper and the International Federation of the Red Cross. Cyclone "Mala" is described as the most severe cyclone in the Bay of Bengal after the 1999 Orissa Super Cyclone. The measurements for the case study were carried out in the premises of the National Remote Sensing Centre (NRSC) campus at Balanagar (17o.28' N and 78o.26' E) located within the Hyderabad urban center during cyclone period. Synchronous and continuous observations of columnar Aerosol Optical Depth (AOD) were carried out using a handheld multi-channel sun-photometer (Microtops-II, Solar Light Co., USA) at six wavelength bands centered around 380, 440, 500, 675, 870 and 1020 nm. Continuous measurements of particulate matter (PM) grain-size distribution were performed with the GRIMM aerosol spectrometer, model 1-108. The cyclone "Mala" over the Bay of Bengal occurred during 26-29 April, 2006, struck the coast of Myanmar with winds of 115 mph (185 kmh-1), causing severe damage and loss of human life on 29 April, 2006. Initially the depression was moving northwest and on 25 April it changed its direction and accelerated towards north and after northeast resulting in remarkable wind direction changes. As the cyclone moved towards the Myanmar coast on 29 and 30 April, the low-level convergence turned to northwesterly, pulling air from the northern Indian landscapes. This caused an increase in wind speed over the entire Bay of Bengal. The intensity of the cyclonic activity affected continental India on 28 and 29 April. On that day the wind field was dominated by a northwesterly flow from Indian continent towards the Bay of Bengal, which lifted a lot of mineral dust particles from the Indian arid landscapes. This is further confirmed from the analysis of Terra-MODIS image on 29 April, where the dust plumes over the Bay of Bengal can be clearly detected. The variation of the daily mean particulate-matter load measured by the GRIMM instrument showed nearly a two-fold increase in particulate-mass concentrations during the intense cyclone period (28th and 29th April). This is attributed to the increase in surface winds caused by the cyclonic activity, strongly associated with lifting of coarse-mode aerosols from the landscapes neighboring Hyderabad. Also, from the large standard deviations it is concluded that the diurnal pattern of the PMx concentrations are highly variable during the cyclonic activity, probably caused by the frequent and sharp changes in wind speed and direction accompanying it. The day-to-day variation of AOD500 and Ångström exponent α were also analysed. Contrary to the PMx concentrations, the AOD500 values showed remarkable decrease during the cyclone period. This decrease can be as high as 44% between the pre and during cyclone days (25th and 28th April), respectively and 41% between 28 and 30 April. These large variations in aerosol load are mainly attributed to the changes in wind speed and direction as well as the air mass trajectories, bringing marine air masses over the region on 28th April. Despite the uplifting of soil particles near the surface, the higher winds can act as a ventilation tool for the whole atmospheric column, thus resulting in lower AODs. Results are discussed in the paper.

Training on Eastern Pacific tropical cyclones for Latin American students

NASA Astrophysics Data System (ADS)

Farfán, L. M.; Raga, G. B.

2009-05-01

Tropical cyclones are one of the most impressive atmospheric phenomena and their development in the Atlantic and Eastern Pacific basins has potential to affect several Latin-American and Caribbean countries, where human resources are limited. As part of an international research project, we are offering short courses based on the current understanding of tropical cyclones in the Eastern Pacific basin. Our main goal is to train students from higher-education institutions from various countries in Latin America. Key aspects are tropical cyclone formation and evolution, with particular emphasis on their development off the west coast of Mexico. Our approach includes lectures on tropical cyclone climatology and formation, dynamic and thermodynamic models, air-sea interaction and oceanic response, ocean waves and coastal impacts as well as variability and climate-related predictions. In particular, we use a best-track dataset issued by the United States National Hurricane Center and satellite observations to analyze convective patterns for the period 1970-2006. Case studies that resulted in landfall over northwestern Mexico are analyzed in more detail; this includes systems that developed during the 2006, 2007 and 2008 seasons. Additionally, we have organized a human-dimensions symposium to discuss socio-economic issues that are associated with the landfall of tropical cyclones. This includes coastal zone impact and flooding, the link between cyclones and water resources, the flow of weather and climate information from scientists to policy- makers, the role of emergency managers and decision makers, impact over health issues and the viewpoint of the insurance industry.

Impacts of Particulate Matter on Gulf of Mexico Tropical Cyclones

NASA Astrophysics Data System (ADS)

Cao, W.; Rohli, R. V.

2017-12-01

The purpose of this project is to analyze the relationship between tropical cyclones of the Gulf of Mexico-Atlantic basin and fine particulate matter (PM2.5). The daily mean PM2.5 concentration values were collected from United States Environmental Protection Agency (EPA). Tropical cyclone data were collected from Tropical Prediction Center Best Track Reanalysis in Unisys Weather®. The GRIdded Binary (GRIB-formatted) data were downloaded from the Data Support Section of the Computational and Information Systems Laboratory at the National Center for Atmospheric Research (NCAR). Through ArcGIS®, the tropical cyclone tracks were compared with the interpolated daily mean PM2.5 concentration value. Results suggest that the tracks tend to avoid areas with higher PM2.5 concentrations, and the intensity was weakened significantly after passing the PM2.5-rich area. Through simulation using the Weather Research and Forecasting (WRF) model, the pressure and vertical structure of Hurricane Lili were weakened after passing the most PM2.5-rich area in Louisiana. Also, little evidence is found for the possibility of precipitation generated by the approaching tropical cyclone to cleanse the atmosphere of PM2.5 before storm passage. These results have important implications for tropical cyclone prediction as storms approach polluted areas or other places where PM2.5 particles are abundant, not only including urban environments but also in coastal areas where proscribed burns take place during tropical cyclone season, such as during sugarcane harvesting in southern Louisiana.

Vulnerability Factors and Effectiveness of Disaster Mitigation Measures in the Bangladesh Coast

NASA Astrophysics Data System (ADS)

Hossain, Md. Nazir; Paul, Shitangsu Kumar

2018-01-01

The major objective of this paper is to identify the vulnerability factors and examine the effectiveness of disaster mitigation measures undertaken by individuals, government and non-government organisations to mitigate the impacts of cyclones in the Bangladesh coast experiencing from Cyclone Aila. The primary data were collected from two villages of southwestern coastal areas of Bangladesh using questionnaire survey and interviews of the key informants. The data were analysed using the descriptive and inferential statistics. This paper reveals that the disaster management measures have a significant role to lessen the impacts of the cyclonic event, especially in pre-disaster preparedness, cyclone warning message dissemination, evacuation and post-disaster rehabilitation. The households, who have access to shelter, find weather forecast regularly and adopted pre-disaster awareness measures are relatively less susceptible to hazard's impacts. The disaster management measures undertaken by individuals and GOs and NGOs help coastal people to save their lives and property from the negative impacts of cyclones. The analysis shows that the NGOs' role is more effective and efficient than the GOs in cyclone disaster management. This paper identifies distance to shelter, participation in disaster training, efficient warning, etc. as the influential factors of vulnerability cyclones. The analysis finds the households as less affected who have adopted disaster preparedness measures. However, this paper concludes that the effective and proper disaster management and mitigation measures are very crucial to shield the lives and properties of the Bangladeshi coastal people.

Environmental Composites for Bomb Cyclones of the Western North Atlantic in Reanalysis, 1948-2016.

NASA Astrophysics Data System (ADS)

Adams, R.; Sheridan, S. C.

2017-12-01

"Bomb" cyclones represent a small subset of mid-latitude cyclones characterized by rapid intensification and frequently are associated with extreme weather conditions along the eastern coast of North America. Like other extreme phenomena, bomb cyclone predictions are prone to error leading to inadequate or untimely hazard warnings. The rare nature of bomb cyclones and the uniqueness of their evolutions has made it difficult for researchers to make meaningful generalizations on bomb cyclone events. This paper describes bomb cyclone climatology for the western North Atlantic, using data from the NCEP-NCAR Reanalysis for 1948-2016, and uses a synoptic climatological analysis to relate these bombs to their associated atmospheric environments. A self-organizing map (SOM) of 300-hPa geopotential height tendency is created to partition the regional atmospheric environment. Thermodynamic fields are contrasted by each 300-hPa geopotential height tendency pattern for both bomb and non-bomb events in composite difference maps. The SOM patterns most significantly associated with western North Atlantic bomb cyclogenesis are characterized by both strongly and weakly negative height tendencies along the eastern United States. In both cases, these patterns exhibit strong meridional flow, a distinction marked by the weakening and breaking down of the polar vortex in the boreal Winter. The composite maps for each pattern show the mean differences in low-mid level ascent and near surface thermodynamics for bomb environments contrasted with non-bomb environments, resulting in diverse spatiotemporal distributions of bombs in the western North Atlantic.

Vulnerability Factors and Effectiveness of Disaster Mitigation Measures in the Bangladesh Coast

NASA Astrophysics Data System (ADS)

Hossain, Md. Nazir; Paul, Shitangsu Kumar

2018-05-01

The major objective of this paper is to identify the vulnerability factors and examine the effectiveness of disaster mitigation measures undertaken by individuals, government and non-government organisations to mitigate the impacts of cyclones in the Bangladesh coast experiencing from Cyclone Aila. The primary data were collected from two villages of southwestern coastal areas of Bangladesh using questionnaire survey and interviews of the key informants. The data were analysed using the descriptive and inferential statistics. This paper reveals that the disaster management measures have a significant role to lessen the impacts of the cyclonic event, especially in pre-disaster preparedness, cyclone warning message dissemination, evacuation and post-disaster rehabilitation. The households, who have access to shelter, find weather forecast regularly and adopted pre-disaster awareness measures are relatively less susceptible to hazard's impacts. The disaster management measures undertaken by individuals and GOs and NGOs help coastal people to save their lives and property from the negative impacts of cyclones. The analysis shows that the NGOs' role is more effective and efficient than the GOs in cyclone disaster management. This paper identifies distance to shelter, participation in disaster training, efficient warning, etc. as the influential factors of vulnerability cyclones. The analysis finds the households as less affected who have adopted disaster preparedness measures. However, this paper concludes that the effective and proper disaster management and mitigation measures are very crucial to shield the lives and properties of the Bangladeshi coastal people.

Sensitivity of cyclone tracks to the initial moisture distribution: A moist potential vorticity perspective

NASA Astrophysics Data System (ADS)

Cao, Zuohao; Zhang, Da-Lin

2005-11-01

In this study, the characteristics of moist potential vorticity (MPV) in the vicinity of a surface cyclone center and their physical processes are investigated. A prognostic equation of surface absolute vorticity is then used to examine the relationship between the cyclone tracks and negative MPV (NMPV) using numerical simulations of the life cycle of an extratropical cyclone. It is shown that the MPV approach developed herein, i.e., by tracing the peak NMPV, can be used to help trace surface cyclones during their development and mature stages. Sensitivity experiments are conducted to investigate the impact of different initial moisture fields on the effectiveness of the MPV approach. It is found that the lifetime of NMPV depends mainly on the initial moisture field, the magnitude of condensational heating, and the advection of NMPV. When NMPV moves into a saturated environment at or near a cyclone center, it can trace better the evolution of the surface cyclone due to the conservative property of MPV. It is also shown that the NMPV generation is closely associated with the coupling of large potential temperature and moisture gradients as a result of frontogenesis processes. Analyses indicate that condensation, confluence and tilting play important but different roles in determining the NMPV generation. NMPV is generated mainly through the changes in the strength of baroclinicity and in the direction of the moisture gradient due to moist and/or dry air mass intrusion into the baroclinic zone.

Bomb Cyclones Of The Western North Atlantic

NASA Astrophysics Data System (ADS)

Adams, Ryan E.

"Bomb" cyclones represent a small subset of mid-latitude cyclones characterized by rapid intensification and frequently are associated with extreme weather conditions along the eastern coast of North America. Like other extreme phenomena, bomb cyclone predictions are prone to error leading to inadequate or untimely hazard warnings. The rare nature of bomb cyclones and the uniqueness of their evolutions has made it difficult for researchers to make meaningful generalizations on bomb cyclone events. This paper describes bomb cyclone climatology for the western North Atlantic, using data from the NCEP-NCAR Reanalysis for 1948-2016, and uses a synoptic climatological analysis to relate these bombs to their associated atmospheric environments. A self-organizing map (SOM) of 300-hPa geopotential height tendency is created to partition the regional atmospheric environment. Thermodynamic fields are contrasted by each 300-hPa geopotential height tendency pattern for both bomb and non-bomb events in composite difference maps. The SOM patterns most significantly associated with western North Atlantic bomb cyclogenesis are characterized by both strongly and weakly negative height tendencies along the eastern United States. In both cases, these patterns exhibit strong meridional flow, a distinction marked by the weakening and breaking down of the polar vortex in the boreal Winter. The composite maps for each pattern show the mean differences in low-mid level ascent and near surface thermodynamics for bomb environments contrasted with non-bomb environments, resulting in diverse spatiotemporal distributions of bombs in the western North Atlantic.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zardecki, A.

The effect of multiple scattering on the validity of the Beer-Lambert law is discussed for a wide range of particle-size parameters and optical depths. To predict the amount of received radiant power, appropriate correction terms are introduced. For particles larger than or comparable to the wavelength of radiation, the small-angle approximation is adequate; whereas for small densely packed particles, the diffusion theory is advantageously employed. These two approaches are used in the context of the problem of laser-beam propagation in a dense aerosol medium. In addition, preliminary results obtained by using a two-dimensional finite-element discrete-ordinates transport code are described. Multiple-scatteringmore » effects for laser propagation in fog, cloud, rain, and aerosol cloud are modeled.« less

Mather-type dense plasma focus as a new optical pump for short-wavelength high-power lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fanning, J.J.; Kim, K.

For the first time, a Mather-type dense plasma focus (MDPF) is successfully operated as an optical pump for lasers. Rhodamine-6G dye is optically pumped using the MDPF fluorescence, producing a laser pulse 1 ..mu..s in duration and more than 50 kW in output power. No optimization is attempted either of the laser cavity or of the lasing medium concentration and volume. A brief description of the experimental setup is presented, along with a summary and discussion of the results. The advantages of the present optical pump source and, in particular, their implications for the pumping of short-wavelength lasers are discussed.

Analysis of Wind and Sea State in SAR data of Hurricanes

NASA Astrophysics Data System (ADS)

Hoja, D.; Schulz-Stellenfleth, J.; Lehner, S.; Horstmann, J.

2003-04-01

Spaceborne synthetic aperture radar (SAR) is still the only instrument providing directional ocean wave and in addition surface wind information on a global and continuous basis. Operating in ASAR wave mode ENVISAT, launched in 2002, provides 10 km x 5 km SAR images every 100 km along the orbit. These SAR data continue and expand the SAR era of the European Remote Sensing satellites ERS-1 and ERS-2, which have acquired similar SAR data since 1991 on a global basis. To not only use the official ERS SAR wave mode product, which consists only of the SAR image power spectrum, but also the full SAR image information a subset of 27 days globally distributed ERS-2 SAR raw data were processed to single look complex SAR imagettes using the BSAR processor developed at the German Aerospace Center. These data have the same format as the official ESA product for ENVISAT ASAR wave mode data. This subset of 34,000 ERS-2 SAR imagettes was used to develop and validate algorithms for wind and wave retrieval, which are also applicable to ENVISAT ASAR wave mode data. The time frame of the dataset covers several tropical cyclones in the Atlantic Ocean of which hurricane Fran has been investigated in detail together with additional data available from scatterometers, buoys and weather centers. Hurricane Fran was active from August 23 to September 8, 1996. During this time, hurricane Fran developed near the African coast and progressed over the North Atlantic Ocean. Landfall occurred on September 5, 1996 at the coast of North Carolina, USA. Fran was part of a whole series of tropical cyclones travelling about the same course in a short time. The wind is extracted from SAR imagery and compared to results of the numerical model output provided by the European Center for Medium-Range Weather Forecast (ECMWF) and co-located ERS-2 scatterometer measurements. The Swell and wind sea systems generated by the tropical cyclones are measured using SAR cross spectra and a newly developed partitioning technique. For each component wave system (partition) spectral parameters like wavelength and wave propagation direction are calculated and compared to numerical model output provided by ECMWF. The progression of the tropical cyclones is presented and it is described, how the hurricanes are portrayed in the SAR data. The response of waves to fast turning winds is analyzed. Conclusions are drawn about the wave model forecast in hurricane situations using satellite wave mode data. Keywords: Hurricanes, SAR, ocean winds, ocean waves, wind sea and swell

Statistical Aspects of North Atlantic Basin Tropical Cyclones During the Weather Satellite Era, 1960-2013: Part 1

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2014-01-01

A tropical cyclone is described as a warm-core, nonfrontal, synoptic-scale system that originates over tropical or subtropical waters, having organized deep convection and closed surface wind circulation (counterclockwise in the Northern Hemisphere) about a well defined center. When its sustained wind speed equals 34-63 kt, it is called a tropical (or subtropical) storm and is given a name (i.e., alternating male and female names, beginning in 1979); when its sustained wind speed equals 64-95 kt, it is called a hurricane (at least in the Eastern Pacific and North Atlantic basin); and when its sustained wind speed equals 96 kt or higher, it is called an intense or major hurricane (i.e., categories 3-5 on the Saffir-Simpson Hurricane Wind Scale). Although tropical cyclones have been reported and described since the voyages of Columbus, a detailed record of their occurrences extends only from 1851 to the present, with the most reliable portion extending only from about 1945 to the present, owing to the use of near-continuous routine reconnaissance aircraft monitoring flights and the use of satellite imagery (beginning in 1960; see Davis). Even so, the record may still be incomplete, possibly missing at least one tropical cyclone per yearly hurricane season, especially prior to the use of continuous satellite monitoring. In fact, often an unnamed tropical cyclone is included in the year-end listing of events at the conclusion of the season, following post-season analysis (e.g., as happened in 2011 and 2013, each having one unnamed event). In this two-part Technical Publication (TP), statistical aspects of the North Atlantic basin tropical cyclones are examined for the interval 1960-2013, the weather satellite era. Part 1 examines some 25 parameters of tropical cyclones (e.g., frequencies, peak wind speed (PWS), accumulated cyclone energy (ACE), etc.), while part 2 examines the relationship of these parameters against specific climate-related factors. These studies are a continuation of nearly two decades of previous tropical cyclone-related investigations.

Multi-year composite view of ozone enhancements and stratosphere-to-troposphere transport in dry intrusions of northern hemisphere extratropical cyclones

NASA Astrophysics Data System (ADS)

Jaegle, L.; Wood, R.; Wargan, K.

2017-12-01

We examine the role of extratropical cyclones in stratosphere-to-troposphere (STT) exchange by using cyclone-centric composites of O3 retrievals from the Microwave Limb Sounder (MLS) and the Tropospheric Emission Spectrometer (TES) onboard the Aura satellite and contrasting them to composites obtained with Modern-Era Retrospective-analysis for Research and Applications (MERRA and MERRA-2) as well as with the GEOS-Chem chemical transport model. MERRA sea level pressure fields are used to identify 15,978 extratropical cyclones in the northern hemisphere (NH) between 2005 and 2012. The lowermost stratosphere (261 hPa) and middle troposphere (424 hPa) composites of these cyclones feature a distinct 1,000 km wide O3 enhancement in the dry intrusion to the southwest of the cyclone center, coinciding with a lowered tropopause, enhanced potential vorticity, and decreased water vapor. In the lowermost stratosphere, MLS composites show that the dry intrusion O3 enhancements reach a 210 ppbv maximum in April. In the middle troposphere, TES composites display dry intrusion maximum O3 enhancements of 27 ppbv in May. The magnitude and seasonality of these enhancements are captured by MERRA and MERRA-2, but GEOS-Chem is a factor of two too low. The MERRA-2 composites show that the O3-rich dry intrusion forms a coherent and vertically aligned structure between 300 and 800 hPa, wrapping cyclonically with the warm conveyor belt. In winter and spring dry intrusions, O3 is enhanced by 100 pbbv or 100-130% relative to background conditions at 300 hPa, with a significant contribution reaching pressure altitudes below 500 hPa (6-20 ppbv or 15-30% enhancement). We calculate that extratropical cyclones result in a STT flux of 119 Tg O3 yr-1, accounting for 42% of the annual NH O3 extratropical STT flux. The STT flux in cyclones is highest in spring and displays a strong dependence on westerly 300 hPa wind speeds.

Extreme cyclone events in the Arctic during wintertime: Variability and Trends

NASA Astrophysics Data System (ADS)

Rinke, Annette; Maturilli, Marion; Graham, Robert; Matthes, Heidrun; Handorf, Doerthe; Cohen, Lana; Hudson, Stephen; Moore, John

2017-04-01

Extreme cyclone events are of significant interest as they can transport much heat, moisture, and momentum poleward. Associated impacts are warming and sea-ice breakup. Recently, several examples of such extreme weather events occurred in winter (e.g. during the N-ICE2015 campaign north of Svalbard and the Frank North Atlantic storm during the end of December 2015). With Arctic amplification and associated reduced sea-ice cover and warmer sea surface temperatures, the occurrence of extreme cyclones events could be a plausible scenario. We calculate the spatial patterns, and changes and trends of the number of extreme cyclone events in the Arctic based on ERA-Interim six-hourly sea level pressure (SLP) data for winter (November-February) 1979-2015. Further, we analyze the SLP data from the Ny Alesund station for the same 37 year period. We define an extreme cyclone event by a extreme low central pressure (SLP below 985 hPa, which is the 5th percentile of the Ny Alesund/N-ICE2015 SLP data) and a deepening of at least 6 hPa/6 hours. Areas of highest frequency of occurrence of extreme cyclones are south/southeast of Greenland (corresponding to the Islandic low), between Norway and Svalbard and in the Barents/Kara Seas. The time series of the number of occurrence of extreme cyclone events for Ny Alesund/N-ICE show considerable interannual variability. The trend is not consistent through the winter, but we detect an increase in early winter and a slight decrease in late winter. The former is due to the increased occurrence of longer events at the expense of short events. Furthermore, the difference patterns of the frequency of events for months following the September with high and low Arctic sea-ice extent ("Low minus high sea ice") conforms with the change patterns of extreme cyclones numbers (frequency of events "2000-2015 minus 1979-1994") and with the trend patterns. This indicates that the changes in extreme cyclone occurrence in early winter are associated with sea-ice changes (regional feedback). In contrast, different mechanisms via large-scale circulation changes/teleconnections seem to play a role in late winter.

Health impact assessment of cyclone Bejisa in Reunion Island (France) using syndromic surveillance.

PubMed

Vilain, Pascal; Pagès, Frédéric; Combes, Xavier; Marianne Dit Cassou, Pierre-Jean; Mougin-Damour, Katia; Jacques-Antoine, Yves; Filleul, Laurent

2015-04-01

On January 2, 2014, Cyclone Bejisa struck Reunion Island (France). This storm led to major material damages, such as power outages, disturbance of drinking water systems, road closures, and the evacuation of residents. In this context, the Regional Office of French Institute for Public Health Surveillance in Indian Ocean (Cire OI) set up an epidemiological surveillance in order to describe short-term health effects of the cyclone. The assessment of the health impact was based mainly on a syndromic surveillance system, including the activity of all emergency departments (EDs) and the Emergency Medical Service (EMS) of the island. From these data, several health indicators were collected and analyzed daily and weekly. To complete this assessment, all medical charts recorded in the EDs of Reunion Island from January 2, 2014 through January 5, 2014 were reviewed in order to identify visits directly and indirectly related to the cyclone, and to determine mechanisms of injuries. The number of calls to the EMS peaked the day of the cyclone, and the number of ED visits increased markedly over the next two days. At the same time, a significant increase in visits for trauma, burns, and carbon monoxide poisoning was detected in all EDs. Among 1,748 medical records reviewed, eight visits were directly related to the cyclone and 208 were indirectly related. For trauma, the main mechanisms of injury were falls and injuries by machinery or tools during the clean-up and repair works. Due to prolonged power outages, several patients were hospitalized: some to assure continuity of care, others to take care of an exacerbation of a chronic disease. An increase in leptospirosis cases linked to post-cyclone clean-up was observed two weeks after the cyclone. Information based on the syndromic surveillance system allowed the authors to assess rapidly the health impact of Cyclone Bejisa in Reunion Island; however, an underestimation of this impact was still possible. In the near future, several lines of work will be planned by the authors in order to improve the assessment.

Analysis of moisture advection during explosive cyclogenesis over North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Ordóñez, Paulina; Liberato, Margarida L. R.; Pinto, Joaquim G.; Trigo, Ricardo M.

2013-04-01

The development of a mid-latitude cyclone may strongly be amplified by the presence of a very warm and moist air mass within its warm sector through enhanced latent heat release. In this work, a lagrangian approach is applied to examine the contribution of moisture advection to the deepening of cyclones over the North Atlantic Ocean. The warm sector is represented by a 5°x5° longitude/latitude moving box comprising the centre of the cyclone and its south-eastern area is defined for the tracks of different cyclones computed at 6-hourly intervals. Using the lagrangian particle model FLEXPART we evaluated the fresh water flux (E - P) along 2-days back-trajectories of the particles residing on the total column over the defined boxes for case studies occurring during winter months from 1980 to 2000. FLEXPART simulations were performed using one degree resolution and 60 model vertical levels available in ERA40 Reanalyses at 00, 06, 12, 18 UTC for each case. Sensitivity studies on the dimensions of the target area - chosen boxes representing the warm sector -, and on its relative position to the center, were performed. We have applied this methodology to several case studies of independent North Atlantic cyclones with notorious characteristics (e.g. deepening rate, wind speed, surface damages). Results indicate that the moisture transport is particularly relevant in what concerns the fast/explosive development stage of these extratropical cyclones. In particular, the advection of moist air from the subtropics towards the cyclone core is clearly associated with the warm conveyor belt of the cyclone. This methodology can be generalized to a much larger number of mid-latitude cyclones, providing a unique opportunity to analyze the moisture behavior associated with the explosive development. Acknowledgments: This work was partially supported by FEDER (Fundo Europeu de Desenvolvimento Regional) funds through the COMPETE (Programa Operacional Factores de Competitividade) Programme and by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) through project STORMEx FCOMP-01-0124-FEDER-019524 (PTDC/AAC-CLI/121339/2010).

Community-based assessment of human rights in a complex humanitarian emergency: the Emergency Assistance Teams-Burma and Cyclone Nargis

PubMed Central

2010-01-01

Introduction Cyclone Nargis hit Burma on May 2, 2008, killing over 138,000 and affecting at least 2.4 million people. The Burmese military junta, the State Peace and Development Council (SPDC), initially blocked international aid to storm victims, forcing community-based organizations such as the Emergency Assistance Teams-Burma (EAT) to fill the void, helping with cyclone relief and long-term reconstruction. Recognizing the need for independent monitoring of the human rights situation in cyclone-affected areas, particularly given censorship over storm relief coverage, EAT initiated such documentation efforts. Methods A human rights investigation was conducted to document selected human rights abuses that had initially been reported to volunteers providing relief services in cyclone affected areas. Using participatory research methods and qualitative, semi-structured interviews, EAT volunteers collected 103 testimonies from August 2008 to June 2009; 42 from relief workers and 61 from storm survivors. Results One year after the storm, basic necessities such as food, potable water, and shelter remained insufficient for many, a situation exacerbated by lack of support to help rebuild livelihoods and worsening household debt. This precluded many survivors from being able to access healthcare services, which were inadequate even before Cyclone Nargis. Aid efforts continued to be met with government restrictions and harassment, and relief workers continued to face threats and fear of arrest. Abuses, including land confiscation and misappropriation of aid, were reported during reconstruction, and tight government control over communication and information exchange continued. Conclusions Basic needs of many cyclone survivors in the Irrawaddy Delta remained unmet over a year following Cyclone Nargis. Official impediments to delivery of aid to storm survivors continued, including human rights abrogations experienced by civilians during reconstruction efforts. Such issues remain unaddressed in official assessments conducted in partnership with the SPDC. Private, community-based relief organizations like EAT are well positioned and able to independently assess human rights conditions in response to complex humanitarian emergencies such as Cyclone Nargis; efforts of this nature must be encouraged, particularly in settings where human rights abuses have been documented and censorship is widespread. PMID:20403200

Community-based assessment of human rights in a complex humanitarian emergency: the Emergency Assistance Teams-Burma and Cyclone Nargis.

PubMed

Suwanvanichkij, Voravit; Murakami, Noriyuki; Lee, Catherine I; Leigh, Jen; Wirtz, Andrea L; Daniels, Brock; Mahn, Mahn; Maung, Cynthia; Beyrer, Chris

2010-04-19

Cyclone Nargis hit Burma on May 2, 2008, killing over 138,000 and affecting at least 2.4 million people. The Burmese military junta, the State Peace and Development Council (SPDC), initially blocked international aid to storm victims, forcing community-based organizations such as the Emergency Assistance Teams-Burma (EAT) to fill the void, helping with cyclone relief and long-term reconstruction. Recognizing the need for independent monitoring of the human rights situation in cyclone-affected areas, particularly given censorship over storm relief coverage, EAT initiated such documentation efforts. A human rights investigation was conducted to document selected human rights abuses that had initially been reported to volunteers providing relief services in cyclone affected areas. Using participatory research methods and qualitative, semi-structured interviews, EAT volunteers collected 103 testimonies from August 2008 to June 2009; 42 from relief workers and 61 from storm survivors. One year after the storm, basic necessities such as food, potable water, and shelter remained insufficient for many, a situation exacerbated by lack of support to help rebuild livelihoods and worsening household debt. This precluded many survivors from being able to access healthcare services, which were inadequate even before Cyclone Nargis. Aid efforts continued to be met with government restrictions and harassment, and relief workers continued to face threats and fear of arrest. Abuses, including land confiscation and misappropriation of aid, were reported during reconstruction, and tight government control over communication and information exchange continued. Basic needs of many cyclone survivors in the Irrawaddy Delta remained unmet over a year following Cyclone Nargis. Official impediments to delivery of aid to storm survivors continued, including human rights abrogations experienced by civilians during reconstruction efforts. Such issues remain unaddressed in official assessments conducted in partnership with the SPDC. Private, community-based relief organizations like EAT are well positioned and able to independently assess human rights conditions in response to complex humanitarian emergencies such as Cyclone Nargis; efforts of this nature must be encouraged, particularly in settings where human rights abuses have been documented and censorship is widespread.

Extratropical Cyclones over Southwestern Atlantic Ocean: Present and Future Climates projected by RegCM4

NASA Astrophysics Data System (ADS)

Reboita, Michelle; Rodrigues, Marcelo; da Rocha, Rosmeri

2017-04-01

This study shows some of the climatological features of the extratropical cyclones in present and future climate over Southwestern Atlantic Ocean (SAO). The projections were carried out with Regional Climate Model (RegCM4) nested in HadGEM2-ES global model outputs and using representative concentration pathway 8.5 (RCP8.5) from the CMIP5. The simulations considered the South America domain suggested by CORDEX, horizontal grid spacing of 50 km, 18 sigma-pressure levels in the vertical. An objective tracking scheme based on cyclonic relative vorticity calculated using the wind at 925 hPa was used to identify the cyclones. All cyclones with relative vorticity lower than the -1.5 x 10-5 s-1 and with lifetime higher or equal 24 hours were included in the climatology. Considering the period from 1979 to 2098, RegCM4 and HadGEM2-ES project a negative trend in the frequency of the extratropical cyclones over SAO, with the biggest negative trend occuring in the latitudinal band between 40°S and 57.5°S. This result can be associated with the southward displacement of the baroclinic zone which contributes to the cyclones move to south leaving the region analyzed. The three subregions with largest cyclogenetic activity discussed in the literature (southeast coast of Brazil - RG1, coast of Uruguay and southern Brazil - RG2; east coast of Argentina - RG3) were better reproduced in RegCM4 than in HadGEM2-ES. Therefore, RegCM4 downscaling ads value in the HadGEM2-ES projections. The frequency of cyclones in present (1979-2005) and future climate (2070-2098) is higher in winter and lower in summer. Regarding the mean characteristics of the cyclones (life time, travel distance, velocity, initial relative vorticity and total average vorticity), both models successfully reproduced those obtained in the reanalysis (NCEP1, NCEP2, CFSR, ERA40 and ERA-Interim) and there are no significant differences in the future climate compared with the present.

Thermohaline variability in the Adriatic and Northern Ionian Seas observed from the Argo floats during 2010-2014

NASA Astrophysics Data System (ADS)

Kovačević, Vedrana; Ursella, Laura; Gačić, Miroslav; Notarstefano, Giulio; Menna, Milena; Bensi, Manuel; Civitarese, Giuseppe; Poulain, Pierre-Marie

2015-04-01

The Adriatic Sea is the northernmost basin of the Eastern Mediterranean Sea (EMed). At its southern end, the basin communicates with the adjacent Ionian Sea through the 80 km wide and 850 m deep Strait of Otranto. Due to the river discharge in the north and due to the strong winter cooling, the Adriatic is both a dilution basin and the dense water formation region. The basin-wide circulation is cyclonic. The circulation is however, energetic also at smaller spatial and temporal scales, and several circulation cells and mesoscale features are regularly observed equally along the littoral and in the open sea. The North Adriatic Dense Water (NAdDW) formed during winter is the densest water of the whole Mediterranean Sea (up to 1060 kg/m3). It flows as a density driven bottom current from the northern shelf toward south, filling the deep layers of the middle and southern Adriatic pits. The deep open-sea area of the South Adriatic Pit (SAP, 1200 m) feels the influence of a water mass exchange through the Strait of Otranto. Specifically, it receives salty and warm surface and Levantine Intermediate Waters from the Ionian Sea. Through the open-sea winter convection that homogenizes and ventilates 400-800 m thick upper water column, this salty water contributes to the formation of the Adriatic Deep Water (AdDW, 1029.17-1029.20 kg/m3), which is not as dense as the NAdDW. Both dense waters eventually mix and spill across the sill ventilating the deep and bottom layers of the Ionian Sea, and driving the deep thermohaline cell of the EMed. Thermohaline properties of the Adriatic Sea vary at wide spatial and temporal scales, and this in turn affects the properties of its dense waters. The long-term scales are of a particular interest, as they are often associated with the biogeochemical and biotic variability such as intrusion of alien species into the Adriatic Sea and interconnection with the adjacent Ionian basin. Due to the extremely variable meteo- and climatic conditions, the signal of the Adriatic dense waters can be fairly irregular and impulsive. Sporadic in-situ surveys by research vessels are not always sufficient to capture this irregularity and its consequences on the circulation. The Lagrangian platforms are disseminated within the whole Mediterranean through the international Argo program. They are a useful tool to assess some of the spatial and temporal variability in the two basins. Combining the information from the floats and in-situ CTD profiles from oceanographic campaigns, we picture the inter-annual variability of the thermohaline properties in general during 2010-2014. In addition, the peculiarities of the very dense water overflow that during 2012 spilled out form the Strait of Otranto into the Northern Ionian is evidenced. Also, by the remotely sensed sea surface topography, we depict the most prominent circulation features of the upper layer.

Building firelines with liquid explosive ... some preliminary results

Treesearch

John D. Dell; Franklin R. Ward

1970-01-01

Building firelines in logging slash or dense brush can be costly and hazardous. A new liquid explosive was tested in these and other forest fuel types, It proved effective in brush, understory vegetation, and light-medium slash, but was not effective in deep, heavy slash. Fireline construction by this technique shows promise, but will require more testing and...

Asymmetry in convection and restratification in the Nordic Seas: an idealized model study

NASA Astrophysics Data System (ADS)

Ypma, Stefanie L.; Brüggemann, Nils; Pietrzak, Julie D.; Katsman, Caroline A.

2017-04-01

The Nordic Seas are an important production region for dense water masses that feed the lower limb of the Atlantic Meridional Overturning Circulation. They display a pronounced hydrographic asymmetry, with a warm eastern basin, and a cold western basin. Previous studies have shown that this asymmetry is set by the interplay between large eddies shed near the coast of Norway where the continental slope steepens, and the Mohn-Knipovich ridge that separates the Lofoten Basin in the east from the Greenland Basin in the west. While it is known from earlier studies that eddies play a crucial role for the yearly cycle of wintertime convection and summertime restratification in marginal seas like the Labrador Sea, the situation in the Nordic Seas is different as the large eddies can only restratify the eastern part of the Nordic Seas due to the presence of the ridge. Possibly due to this asymmetry in eddy activity and a weaker stratification as a result, the western basin is more sensitive for intense deep convection. The question remains how this area is restratified after a deep convection event in the absence of large eddies and how the dense water is able to leave the basin. An high resolution, idealized model configuration of the MITgcm is used that reproduces the main characteristics of the Nordic Seas, including a warm cyclonic boundary current, a strong eddy field in the east and the hydrographic asymmetry between east and west. The idealized approach enables multiple sensitivity studies to changes in the eddy field and the boundary current and provides the possibility to investigate cause and effect, while keeping the set-up simple. We will present results of tracer studies where the sensitivity of the spreading and the restratification of dense water to the formation location in both basins is studied.

Epidemiology of injuries due to tropical cyclones in Hong Kong: a retrospective observational study.

PubMed

Rotheray, K R; Aitken, P; Goggins, W B; Rainer, T H; Graham, C A

2012-12-01

Tropical cyclones are huge circulating masses of wind which form over tropical and sub-tropical waters. They affect an average of 78 million people each year. Hong Kong is a large urban centre with a population of just over 7 million which is frequently affected by tropical cyclones. We aimed to describe the numbers and types of injuries due to tropical cyclones in Hong Kong, as well as their relation to tropical cyclone characteristics. The records of all patients presenting to Hong Kong's public hospital emergency departments from 1st January 2004 to 31st December 2009 with tropical cyclone related injuries were reviewed and information regarding patient and injury characteristics was collected. Meteorological records for the relevant periods were examined and data on wind speed, rainfall and timing of landfall and warning signals was recorded and compared with the timing of tropical cyclone related injuries. A total of 460 tropical cyclone related injuries and one fatality across 15 emergency departments were identified during the study period. The mean age of those injured was 48 years and 48% were female. 25.4% of injuries were work related. The head (33.5%) and upper limb (32.5%) were the most commonly injured regions, with contusions (48.6%) and lacerations (30.2%) being the most common injury types. Falls (42.6%) were the most common mechanism of injury, followed by being hit by a falling or flying object (22.0%). In univariable analysis the relative risk of injury increased with mean hourly wind speed and hourly maximum gust. Multivariable analysis, however, showed that relative risk of injury increased with maximum gust but not average wind speed, with relative risk of injury rising sharply above maximum gusts of greater than 20 m/s. Moderate wind speed with high gust (rather than high average and high gust) appears to be the most risky situation for injuries. Relative risk of injury was not associated with rainfall. The majority of injuries (56%) occurred in the 3h before and after a tropical cyclone's closest proximity to Hong Kong, with relative risk of injury being highest mid-morning. In tropical cyclone related injuries in Hong Kong the head and upper limb are the most commonly affected sites with falls and being hit by a falling or flying object being the most common mechanisms of injury. Hourly maximum gust appears to be more important that mean hourly wind speed in determining risk of injury. These findings have implications for injury prevention measures and emergency planning in Hong Kong and other regions effected by tropical cyclones. Copyright © 2011 Elsevier Ltd. All rights reserved.

Instability of supersonic cold streams feeding galaxies - I. Linear Kelvin-Helmholtz instability with body modes

NASA Astrophysics Data System (ADS)

Mandelker, Nir; Padnos, Dan; Dekel, Avishai; Birnboim, Yuval; Burkert, Andreas; Krumholz, Mark R.; Steinberg, Elad

2016-12-01

Massive galaxies at high redshift are predicted to be fed from the cosmic web by narrow, dense streams of cold gas that penetrate through the hot medium encompassed by a stable shock near the virial radius of the dark-matter halo. Our long-term goal is to explore the heating and dissipation rate of the streams and their fragmentation and possible breakup, in order to understand how galaxies are fed, and how this affects their star formation rate and morphology. We present here the first step, where we analyse the linear Kelvin-Helmholtz instability (KHI) of a cold, dense slab or cylinder in 3D flowing supersonically through a hot, dilute medium. The current analysis is limited to the adiabatic case with no gravity. By analytically solving the linear dispersion relation, we find a transition from a dominance of the familiar rapidly growing surface modes in the subsonic regime to more slowly growing body modes in the supersonic regime. The system is parametrized by three parameters: the density contrast between stream and medium, the Mach number of stream velocity with respect to the medium and the stream width with respect to the halo virial radius. A realistic choice for these parameters places the streams near the mode transition, with the KHI exponential-growth time in the range 0.01-10 virial crossing times for a perturbation wavelength comparable to the stream width. We confirm our analytic predictions with idealized hydrodynamical simulations. Our linear estimates thus indicate that KHI may be effective in the evolution of streams before they reach the galaxy. More definite conclusions await the extension of the analysis to the non-linear regime and the inclusion of cooling, thermal conduction, the halo potential well, self-gravity and magnetic fields.

Bottom-up determination of air-sea momentum exchange under a major tropical cyclone.

PubMed

Jarosz, Ewa; Mitchell, Douglas A; Wang, David W; Teague, William J

2007-03-23

As a result of increasing frequency and intensity of tropical cyclones, an accurate forecasting of cyclone evolution and ocean response is becoming even more important to reduce threats to lives and property in coastal regions. To improve predictions, accurate evaluation of the air-sea momentum exchange is required. Using current observations recorded during a major tropical cyclone, we have estimated this momentum transfer from the ocean side of the air-sea interface, and we discuss it in terms of the drag coefficient. For winds between 20 and 48 meters per second, this coefficient initially increases and peaks at winds of about 32 meters per second before decreasing.

Tropical cyclones in a stabilized 1.5 and 2 degree warmer world.

NASA Astrophysics Data System (ADS)

Wehner, M. F.; Stone, D. A.; Loring, B.; Krishnan, H.

2017-12-01

We present an ensemble of very high resolution global climate model simulations of a stabilized 1.5oC and 2oC warmer climate as envisioned by the Paris COP21 agreement. The resolution of this global climate model (25km) permits simulated tropical cyclones up to Category Five on the Saffir-Simpson scale Projected changes in tropical cyclones are significant. Tropical cyclones in the two stabilization scenarios are less frequent but more intense than in simulations of the present. Output data from these simulations is freely available to all interested parties and should prove a useful resource to those interested in studying the impacts of stabilized global warming.

Radio Transients and their Environments

NASA Astrophysics Data System (ADS)

Rajwade, Kaustubh

The interstellar medium is the principal ingredient for star formation and hence, it is necessary to study the properties of the interstellar medium. Radio sources in our Galaxy and beyond can be used as a probe of the intervening medium. In this dissertation, I present an attempt to use radio transients like pulsars and fast radio bursts and their interactions with the environment around them to study interstellar medium. We show that radio emission from pulsars is absorbed by dense ionized gas in their surroundings, causing a turnover in their flux density spectrum that can be used to reveal information about the absorbing medium. We carried out a multi-wavelength observation campaign of PSR B0611+22. The pulsar shows peculiar emission variability that is broadband in nature. Moreover, we show that the flux density spectrum of B0611+22 is unusual which can be attributed to the environment it lies in. We also present predictions of fast radio burst detections from upcoming low frequency surveys. We show that future surveys with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) will be able to detect 1 radio burst per hour even if the radio burst undergoes significant absorption and scattering. Finally, we present our results of pulsar population synthesis to understand the pulsar population in the Galactic Centre (GC) and place conservative upper limits on the GC pulsar population. We obtain an upper limit of 52 CPs and 10,000 MSPs in the GC. The dense, ionized environment of the GC gives us the opportunity to predict the probability of detection by considering scattering and absorption as the principle sources of flux mitigation. Our results suggest that the optimal frequency range for a pulsar survey in the GC is 9-14 GHz. A larger sample of absorbed spectrum pulsars and fast radio bursts will be beneficial not only for the study of emission processes but also for discerning the properties of the material permeating through space.

Evaluation of a Combined Cyclone and Gas Filtration System for Particulate Removal in the Gasification Process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rizzo, Jeffrey J.

2010-04-30

The Wabash gasification facility, owned and operated by sgSolutions LLC, is one of the largest single train solid fuel gasification facilities in the world capable of transforming 2,000 tons per day of petroleum coke or 2,600 tons per day of bituminous coal into synthetic gas for electrical power generation. The Wabash plant utilizes Phillips66 proprietary E-Gas (TM) Gasification Process to convert solid fuels such as petroleum coke or coal into synthetic gas that is fed to a combined cycle combustion turbine power generation facility. During plant startup in 1995, reliability issues were realized in the gas filtration portion of themore » gasification process. To address these issues, a slipstream test unit was constructed at the Wabash facility to test various filter designs, materials and process conditions for potential reliability improvement. The char filtration slipstream unit provided a way of testing new materials, maintenance procedures, and process changes without the risk of stopping commercial production in the facility. It also greatly reduced maintenance expenditures associated with full scale testing in the commercial plant. This char filtration slipstream unit was installed with assistance from the United States Department of Energy (built under DOE Contract No. DE-FC26-97FT34158) and began initial testing in November of 1997. It has proven to be extremely beneficial in the advancement of the E-Gas (TM) char removal technology by accurately predicting filter behavior and potential failure mechanisms that would occur in the commercial process. After completing four (4) years of testing various filter types and configurations on numerous gasification feed stocks, a decision was made to investigate the economic and reliability effects of using a particulate removal gas cyclone upstream of the current gas filtration unit. A paper study had indicated that there was a real potential to lower both installed capital and operating costs by implementing a char cyclonefiltration hybrid unit in the E-Gas (TM) gasification process. These reductions would help to keep the E-Gas (TM) technology competitive among other coal-fired power generation technologies. The Wabash combined cyclone and gas filtration slipstream test program was developed to provide design information, equipment specification and process control parameters of a hybrid cyclone and candle filter particulate removal system in the E-Gas (TM) gasification process that would provide the optimum performance and reliability for future commercial use. The test program objectives were as follows: 1. Evaluate the use of various cyclone materials of construction; 2. Establish the optimal cyclone efficiency that provides stable long term gas filter operation; 3. Determine the particle size distribution of the char separated by both the cyclone and candle filters. This will provide insight into cyclone efficiency and potential future plant design; 4. Determine the optimum filter media size requirements for the cyclone-filtration hybrid unit; 5. Determine the appropriate char transfer rates for both the cyclone and filtration portions of the hybrid unit; 6. Develop operating procedures for the cyclone-filtration hybrid unit; and, 7. Compare the installed capital cost of a scaled-up commercial cyclone-filtration hybrid unit to the current gas filtration design without a cyclone unit, such as currently exists at the Wabash facility.« less

Molecular gas in high-mass filament WB673

NASA Astrophysics Data System (ADS)

Kirsanova, Maria S.; Salii, Svetlana V.; Sobolev, Andrej M.; Olofsson, Anders Olof Henrik; Ladeyschikov, Dmitry A.; Thomasson, Magnus

2017-12-01

We studied the distribution of dense gas in a filamentary molecular cloud containing several dense clumps. The center of the filament is given by the dense clump WB673. The clumps are high-mass and intermediate-mass starforming regions. We observed CS (2-1), 13CO (1-0), C18O(1-0), and methanol lines at 96 GHz toward WB673 with the Onsala Space Observatory 20-m telescope. We found CS (2-1) emission in the inter-clump medium so the clumps are physically connected and the whole cloud is indeed a filament. Its total mass is 104 M⊙ and mass-to-length ratio is 360M⊙ pc-1 from 13CO (1-0) data. Mass-to-length ratio for the dense gas is 3.4 - 34M⊙ pc-1 from CS (2-1) data. The PV-diagram of the filament is V-shaped. We estimated physical conditions in the molecular gas using methanol lines. Location of the filament on the sky between extended shells suggests that it could be a good example to test theoretical models of formation of the filaments via multiple compression of interstellar gas by supersonic waves.

Utilization of satellite cloud information to diagnose the energy state and transformations in extratropical cyclones

NASA Technical Reports Server (NTRS)

Smith, P. J.

1984-01-01

A study of the contribution of latent heat release to the synoptic scale vertical motions in the Jan. 9-11, 1975 extratropical cyclone case study was completed. Results indicate that early cyclone development was dominated by dry dynamical forcing. However, as the cyclone matured, the influence of latent heating became more significant. This influence appeared to be of two types, (1) the direct impact of heating causing a lowering of surface pressures, and (2) an indirect role in which the heating altered thermal and vorticity gradients and lead to subsequent increases in dry dynamical forcing. The kinetic energy budget was completed and extended to include an available potential energy budget. Focusing on the eddy component of the budgets, results indicate that kinetic energy increased throughout the cyclone's development, with the increase being most pronounced after the onset of significant latent heat release. Latent heating played a strong role not only in generating available potential energy, but also in forcing baroclinic release of potential energy.

Extreme weather caused by concurrent cyclone, front and thunderstorm occurrences

PubMed Central

Dowdy, Andrew J.; Catto, Jennifer L.

2017-01-01

Phenomena such as cyclones, fronts and thunderstorms can cause extreme weather in various regions throughout the world. Although these phenomena have been examined in numerous studies, they have not all been systematically examined in combination with each other, including in relation to extreme precipitation and extreme winds throughout the world. Consequently, the combined influence of these phenomena represents a substantial gap in the current understanding of the causes of extreme weather events. Here we present a systematic analysis of cyclones, fronts and thunderstorms in combination with each other, as represented by seven different types of storm combinations. Our results highlight the storm combinations that most frequently cause extreme weather in various regions of the world. The highest risk of extreme precipitation and extreme wind speeds is found to be associated with a triple storm type characterized by concurrent cyclone, front and thunderstorm occurrences. Our findings reveal new insight on the relationships between cyclones, fronts and thunderstorms and clearly demonstrate the importance of concurrent phenomena in causing extreme weather. PMID:28074909

Study of Gas Solid Flow Characteristics in Cyclone Inlet Ducts of A300Mwe CFB Boiler

NASA Astrophysics Data System (ADS)

Tang, J. Y.; Lu, X. F.; Lai, J.; Liu, H. Z.

Gas solid flow characteristics in cyclone's inlet duct of a 300MW CFB boiler were studied in a cold circulating fluidized bed (CFB) experimental setup according to a 410t/h CFB boiler with a scale of 10∶1. Tracer particles were adopted in the experiment and their motion trajectories in the two kinds of cyclone's inlet ducts were photographed by a high-speed camera. By analyzing the motion trajectories of tracer particles, acceleration performance of particle phases in the two inlet ducts was obtained. Results indicate that the acceleration performance of particles in the long inlet duct is better than that in the short inlet duct, but the pressure drop of the long inlet duct is higher. Meanwhile, under the same operating conditions, both the separation efficiency and the pressure drop of the cyclone are higher when the cyclone is connected with the long inlet duct. Figs 11, Tabs 4 and refs 10.

Impact of surface coupling grids on tropical cyclone extremes in high-resolution atmospheric simulations

DOE PAGES

Zarzycki, Colin M.; Reed, Kevin A.; Bacmeister, Julio T.; ...

2016-02-25

This article discusses the sensitivity of tropical cyclone climatology to surface coupling strategy in high-resolution configurations of the Community Earth System Model. Using two supported model setups, we demonstrate that the choice of grid on which the lowest model level wind stress and surface fluxes are computed may lead to differences in cyclone strength in multi-decadal climate simulations, particularly for the most intense cyclones. Using a deterministic framework, we show that when these surface quantities are calculated on an ocean grid that is coarser than the atmosphere, the computed frictional stress is misaligned with wind vectors in individual atmospheric gridmore » cells. This reduces the effective surface drag, and results in more intense cyclones when compared to a model configuration where the ocean and atmosphere are of equivalent resolution. Our results demonstrate that the choice of computation grid for atmosphere–ocean interactions is non-negligible when considering climate extremes at high horizontal resolution, especially when model components are on highly disparate grids.« less

Western North Pacific Tropical Cyclone Formation and Structure Change in TCS-08

DTIC Science & Technology

2011-09-30

cyclones often transition to a fast-moving and rapidly- developing extratropical cyclone that may contain gale-, storm -, or hurricane-force winds... storm begins the process of extratropical transition have revealed the role of vertical wind shear in defining structural variations related to the...horizontal wind radii as the storm starts the process of extratropical transition. Elsberry et al. (2011) have extended the analysis of the

Western North Pacific Tropical Cyclone Formation and Structure Change in TCS08

DTIC Science & Technology

2013-09-30

transition to a fast-moving and rapidly- developing extratropical cyclone that may contain gale-, storm -, or hurricane-force winds, there is a need to...improve understanding and prediction of the extratropical transition phase of a decaying tropical cyclone. The structural evolution of the transition from...a tropical to an extratropical circulation involves rapid changes to the wind, cloud, and precipitation patterns that potentially impact maritime

Process Study of Oceanic Responses to Typhoons Using Arrays of EM-APEX Floats and Moorings

DTIC Science & Technology

2012-09-30

maximum potential intensity, structure , energy, trajectory, and dynamic evolution. The most energetic oceanic responses to tropical cyclone forcing are...during tropical cyclone passage will aid understanding of storm dynamics and structure . The ocean’s recovery after tropical cyclone passage depends...days). The wake was advected hundreds of kilometers from the storm track by a pre- existing mesoscale eddy. Its thermal structure could not be

An Extended Forecast of the Frequencies of North Atlantic Basin Tropical Cyclone Activity for 2009

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2009-01-01

An extended forecast of the frequencies for the 2009 North Atlantic basin hurricane season is presented. Continued increased activity during the 2009 season with numbers of tropical cyclones, hurricanes, and major hurricanes exceeding long-term averages are indicated. Poisson statistics for the combined high-activity intervals (1950-1965 and 1995-2008) give the central 50% intervals to be 9-14, 5-8, and 2-4, respectively, for the number of tropical cyclones, hurricanes, and major hurricanes, with a 23.4% chance of exceeding 14 tropical cyclones, a 28% chance of exceeding 8 hurricanes, and a 31.9% chance of exceeding 4 major hurricanes. Based strictly on the statistics of the current high-activity interval (1995-2008), the central 50% intervals for the numbers of tropical cyclones, hurricanes, and major hurricanes are 12-18, 6-10, and 3-5, respectively, with only a 5% chance of exceeding 23, 13, or 7 storms, respectively. Also examined are the first differences in 10-yr moving averages and the effects of global warming and decadal-length oscillations on the frequencies of occurrence for North Atlantic basin tropical cyclones. In particular, temperature now appears to be the principal driver of increased activity and storm strength during the current high-activity interval, with near-record values possible during the 2009 season.

Extreme waves from tropical cyclones and climate change in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Appendini, Christian M.; Pedrozo-Acuña, Adrian; Meza-Padilla, Rafael; Torres-Freyermuth, Alec; Cerezo-Mota, Ruth; López-González, José

2017-04-01

Tropical cyclones generate extreme waves that represent a risk to infrastructure and maritime activities. The projection of the tropical cyclones derived wave climate are challenged by the short historical record of tropical cyclones, their low occurrence, and the poor wind field resolution in General Circulation Models. In this study we use synthetic tropical cyclones to overcome such limitations and be able to characterize present and future wave climate associated with tropical cyclones in the Gulf of Mexico. Synthetic events derived from the NCEP/NCAR atmospheric reanalysis and the Coupled Model Intercomparison Project Phase 5 models NOAA/GFDL CM3 and UK Met Office HADGEM2-ES, were used to force a third generation wave model to characterize the present and future wave climate under RCP 4.5 and 8.5 escenarios. An increase in wave activity is projected for the future climate, particularly for the GFDL model that shows less bias in the present climate, although some areas are expected to decrease the wave energy. The practical implications of determining the future wave climate is exemplified by means of the 100-year design wave, where the use of the present climate may result in under/over design of structures, since the lifespan of a structure includes the future wave climate period.

Impact of tropical cyclone Matmo on mixed zone of the Yellow and Bohai seas

NASA Astrophysics Data System (ADS)

Guo, Jie; Ji, Diansheng; Hou, Chawei; Guo, Kai; Ji, Ling

2017-12-01

The Bohai Sea is a low-lying semi-enclosed sea area that is linked to the Yellow Sea via the Bohai straits (mixed zone). Its off shore seabed is shallow, which makes it vulnerable to serious marine meteorological disasters associated with the northward passage of Pacifi c tropical cyclones. Analyses on data of remote sensing and buoy of the mixed zone of the Yellow and Bohai seas indicate that all the wind speed, signifi cant wave height, and salinity (SAL) increased, sea surface temperature decreased, and wind energy density changed considerably during the passage of tropical cyclone Matmo on July 25, 2014. It was found that the SAL inversion layer in the mixed zone of the Yellow and Bohai Seas was caused by the tropical cyclone. Furthermore, it was found that the tropical cyclone transported the northern Yellow Sea cold water mass (NYSCWM) into the mixed zone of the Yellow and Bohai Seas. The NYSCWM has direct infl uence on both the aquaculture and the ecological environment of the region. Therefore, further research is needed to establish the mechanism behind the formation of the SAL inversion layer in the mixed zone, and to determine the infl uence of tropical cyclones on the NYSCWM.

Infectious Diseases and Tropical Cyclones in Southeast China.

PubMed

Zheng, Jietao; Han, Weixiao; Jiang, Baofa; Ma, Wei; Zhang, Ying

2017-05-07

Southeast China is frequently hit by tropical cyclones (TCs) with significant economic and health burdens each year. However, there is a lack of understanding of what infectious diseases could be affected by tropical cyclones. This study aimed to examine the impacts of tropical cyclones on notifiable infectious diseases in southeast China. Disease data between 2005 and 2011 from four coastal provinces in southeast China, including Guangdong, Hainan, Zhejiang, and Fujian province, were collected. Numbers of cases of 14 infectious diseases were compared between risk periods and reference periods for each tropical cyclone. Risk ratios (RR s ) were calculated to estimate the risks. TCs were more likely to increase the risk of bacillary dysentery, paratyphoid fever, dengue fever and acute hemorrhagic conjunctivitis ( ps < 0.05) than to decrease the risk, more likely to decrease the risk of measles, mumps, varicella and vivax malaria ( ps < 0.05) than to increase the risk. In conclusion, TCs have mixed effects on the risk of infectious diseases. TCs are more likely to increase the risk of intestinal and contact transmitted infectious diseases than to decrease the risk, and more likely to decrease the risk of respiratory infectious diseases than to increase the risk. Findings of this study would assist in developing public health strategies and interventions for the reduction of the adverse health impacts from tropical cyclones.

Impacts of tropical cyclones on U.S. forest tree mortality and carbon flux from 1851 to 2000

PubMed Central

Zeng, Hongcheng; Chambers, Jeffrey Q.; Negrón-Juárez, Robinson I.; Hurtt, George C.; Baker, David B.; Powell, Mark D.

2009-01-01

Tropical cyclones cause extensive tree mortality and damage to forested ecosystems. A number of patterns in tropical cyclone frequency and intensity have been identified. There exist, however, few studies on the dynamic impacts of historical tropical cyclones at a continental scale. Here, we synthesized field measurements, satellite image analyses, and empirical models to evaluate forest and carbon cycle impacts for historical tropical cyclones from 1851 to 2000 over the continental U.S. Results demonstrated an average of 97 million trees affected each year over the entire United States, with a 53-Tg annual biomass loss, and an average carbon release of 25 Tg y−1. Over the period 1980–1990, released CO2 potentially offset the carbon sink in forest trees by 9–18% over the entire United States. U.S. forests also experienced twice the impact before 1900 than after 1900 because of more active tropical cyclones and a larger extent of forested areas. Forest impacts were primarily located in Gulf Coast areas, particularly southern Texas and Louisiana and south Florida, while significant impacts also occurred in eastern North Carolina. Results serve as an important baseline for evaluating how potential future changes in hurricane frequency and intensity will impact forest tree mortality and carbon balance. PMID:19416842

Impact Factors and Risk Analysis of Tropical Cyclones on a Highway Network.

PubMed

Yang, Saini; Hu, Fuyu; Jaeger, Carlo

2016-02-01

Coastal areas typically have high social and economic development and are likely to suffer huge losses due to tropical cyclones. These cyclones have a great impact on the transportation network, but there have been a limited number of studies about tropical-cyclone-induced transportation network functional damages, especially in Asia. This study develops an innovative measurement and analytical tool for highway network functional damage and risk in the context of a tropical cyclone, with which we explored the critical spatial characteristics of tropical cyclones with regard to functional damage to a highway network by developing linear regression models to quantify their relationship. Furthermore, we assessed the network's functional risk and calculated the return periods under different damage levels. In our analyses, we consider the real-world highway network of Hainan province, China. Our results illustrate that the most important spatial characteristics were location (in particular, the midlands), travel distance, landfalling status, and origin coordinates. However, the trajectory direction did not obviously affect the results. Our analyses indicate that the highway network of Hainan province may suffer from a 90% functional damage scenario every 4.28 years. These results have critical policy implications for the transport sector in reference to emergency planning and disaster reduction. © 2015 Society for Risk Analysis.

The concurrence of atmospheric rivers and explosive cyclogenesis in the North Atlantic and North Pacific basins

NASA Astrophysics Data System (ADS)

Eiras-Barca, Jorge; Ramos, Alexandre M.; Pinto, Joaquim G.; Trigo, Ricardo M.; Liberato, Margarida L. R.; Miguez-Macho, Gonzalo

2018-01-01

The explosive cyclogenesis of extratropical cyclones and the occurrence of atmospheric rivers are characteristic features of a baroclinic atmosphere, and are both closely related to extreme hydrometeorological events in the mid-latitudes, particularly on coastal areas on the western side of the continents. The potential role of atmospheric rivers in the explosive cyclone deepening has been previously analysed for selected case studies, but a general assessment from the climatological perspective is still missing. Using ERA-Interim reanalysis data for 1979-2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific basins for the extended winter months (ONDJFM). Atmospheric rivers are identified for almost 80 % of explosive deepening cyclones. For non-explosive cyclones, atmospheric rivers are found only in roughly 40 % of the cases. The analysis of the time evolution of the high values of water vapour flux associated with the atmospheric river during the cyclone development phase leads us to hypothesize that the identified relationship is the fingerprint of a mechanism that raises the odds of an explosive cyclogenesis occurrence and not merely a statistical relationship. These new insights on the relationship between explosive cyclones and atmospheric rivers may be helpful to a better understanding of the associated high-impact weather events.

INFRARED SPECTROSCOPIC SURVEY OF THE QUIESCENT MEDIUM OF NEARBY CLOUDS. I. ICE FORMATION AND GRAIN GROWTH IN LUPUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boogert, A. C. A.; Chiar, J. E.; Knez, C.

2013-11-01

Infrared photometry and spectroscopy (1-25 μm) of background stars reddened by the Lupus molecular cloud complex are used to determine the properties of grains and the composition of ices before they are incorporated into circumstellar envelopes and disks. H{sub 2}O ices form at extinctions of A{sub K} = 0.25 ± 0.07 mag (A{sub V} = 2.1 ± 0.6). Such a low ice formation threshold is consistent with the absence of nearby hot stars. Overall, the Lupus clouds are in an early chemical phase. The abundance of H{sub 2}O ice (2.3 ± 0.1 × 10{sup –5} relative to N{sub H}) ismore » typical for quiescent regions, but lower by a factor of three to four compared to dense envelopes of young stellar objects. The low solid CH{sub 3}OH abundance (<3%-8% relative to H{sub 2}O) indicates a low gas phase H/CO ratio, which is consistent with the observed incomplete CO freeze out. Furthermore it is found that the grains in Lupus experienced growth by coagulation. The mid-infrared (>5 μm) continuum extinction relative to A{sub K} increases as a function of A{sub K}. Most Lupus lines of sight are well fitted with empirically derived extinction curves corresponding to R{sub V} ∼ 3.5 (A{sub K} = 0.71) and R{sub V} ∼ 5.0 (A{sub K} = 1.47). For lines of sight with A{sub K} > 1.0 mag, the τ{sub 9.7}/A{sub K} ratio is a factor of two lower compared to the diffuse medium. Below 1.0 mag, values scatter between the dense and diffuse medium ratios. The absence of a gradual transition between diffuse and dense medium-type dust indicates that local conditions matter in the process that sets the τ{sub 9.7}/A{sub K} ratio. This process is likely related to grain growth by coagulation, as traced by the A{sub 7.4}/A{sub K} continuum extinction ratio, but not to ice mantle formation. Conversely, grains acquire ice mantles before the process of coagulation starts.« less

Oceanic response to tropical cyclone `Phailin' in the Bay of Bengal

NASA Astrophysics Data System (ADS)

Pant, V.; Prakash, K. R.

2016-02-01

Vertical mixing largely explains surface cooling induced by Tropical Cyclones (TCs). However, TC-induced upwelling of deeper waters plays an important role as it partly balances the warming of subsurface waters induced by vertical mixing. Below 100 m, vertical advection results in cooling that persists for a few days after the storm. The present study investigates the integrated ocean response to tropical cyclone `Phaillin' (10-14 October 2013) in the Bay of Bengal (BoB) through both coupled and stand-alone ocean-atmosphere models. Two numerical experiments with different coupling configurations between Regional Ocean Modelling System (ROMS) and Weather Research and Forecasting (WRF) were performed to investigate the impact of Phailin cyclone on the surface and sub-surface oceanic parameters. In the first experiment, ocean circulation model ROMS observe surface wind forcing from a mesoscale atmospheric model (WRF with nested damin setup), while rest forcing parameters are supplied to ROMS from NCEP data. In the second experiment, all surface forcing data to ROMS directly comes from WRF. The modeling components and data fields exchanged between atmospheric and oceanic models are described. The coupled modeling system is used to identify model sensitivity by exchanging prognostic variable fields between the two model components during simulation of Phallin cyclone (10-14 October 2013) in the BoB.In general, the simulated Phailin cyclone track and intensities agree well with observations in WRF simulations. Further, the inter-comparison between stand-alone and coupled model simulations validated against observations highlights better performance of coupled modeling system in simulating the oceanic conditions during the Phailin cyclone event.

Analysis of ionospheric disturbances associated with powerful cyclones in East Asia and North America

NASA Astrophysics Data System (ADS)

Li, Wang; Yue, Jianping; Yang, Yang; Li, Zhen; Guo, Jinyun; Pan, Yi; Zhang, Kefei

2017-08-01

East Asia and North America are the regions most heavily affected by powerful cyclones. In this paper we investigate the morphological characteristics of ionospheric disturbances induced by cyclones in different continents. The global ionosphere map supplied by the Center for Orbit Determination in Europe (CODE), International Reference Ionosphere Model (IRI) 2012, and Wallops Island ionosonde station data are used to analyse the ionospheric variations during powerful typhoons/hurricanes in East Asia and North America, respectively. After eliminating the ionospheric anomalies due to the solar-terrestrial environment, the total electron content (TEC) time series over the point with maximum wind speed is detected by the sliding interquartile range method. The results indicate that significant ionospheric disturbances are observed during powerful tropical cyclones in East Asia and North America, respectively, and that all the ionospheric anomalies are positive. In addition, the extent and magnitude of travelling ionospheric disturbances are associated with the category of tropical cyclone, and the extent of TEC anomalies in longitude is more pronounced than that in latitude. Furthermore, the maximum ionospheric anomaly does not coincide with the eye of the storm, but appears in the region adjacent to the centre. This implies that ionospheric disturbances at the edges of cyclones are larger than those in the eye of the winds. The phenomenon may be associated with the gravity waves which are generated by strong convective cells that occur in the spiral arms of tropical cyclones. This comprehensive analysis suggests that the presence of powerful typhoons/hurricanes may be a possible source mechanism for ionospheric anomalies.

Tropical Cyclone Formation in 30-day Simulation Using Cloud-System-Resolving Global Nonhydrostatic Model (NICAM)

NASA Astrophysics Data System (ADS)

Yanase, W.; Satoh, M.; Iga, S.; Tomita, H.

2007-12-01

We are developing an icosahedral-grid non-hydrostatic AGCM, which can explicitly represent cumulus or meso-scale convection over the entire globe. We named the model NICAM (Nonhydrostatic ICosahedral Atmospheric Model). On 2005, we have performed a simulations with horizontal grid intervals of 14, 7 and 3.5 km using realistic topography and sea surface temperature in April 2004 (Miura et al., 2007; GRL). It simulated a typhoon Sudal that actually developed over the Northwestern Pacific in 2004. In the present study, the NICAM model with the horizontal grid interval of 14 km was used for perpetual July experiment with 30 forecasting days. In this simulation, several tropical cyclones formed over the wesetern and eastern North Pacific, althought the formation over the western North Pacific occured a little further north to the actually observed region. The mature tropical cyclones with intense wind speed had a structure of a cloud-free eye and eye wall. We have found that the enviromental parameters associated with the tropical cyclone genesis explain well the simulated region of tropical cyclone generation. Over the North Atlantic and eastern North Pacific, westward-moving disturbances like African wave are simulated, which seems to be related to the cyclone formation over the eastern North Pacific. On the other hand, the simulated tropical cyclones over the western North Pacifis seem to form by different factors as has been suggested by the previous studies based on observation. Although the model still has some problems and is under continuous improvement, we can discuss what dynamics is to be represented using a global high-resolution model.

Structure analyses of the explosive extratropical cyclone: A case study over the Northwestern Pacific in March 2007

NASA Astrophysics Data System (ADS)

Wang, Shuai; Fu, Gang; Pang, Huaji

2017-12-01

The synoptic situation and mesoscale structure of an explosive extratropical cyclone over the Northwestern Pacific in March 2007 are investigated through weather station observations and data reanalysis. The cyclone is located beneath the poleward side of the exit of a 200 hPa jet, which is a strong divergent region aloft. At mid-level, the cyclone lies on the downstream side of a well-developed trough, where a strong ascending motion frequently occurs. Cross-section analyses with weather station data show that the cyclone has a warm and moist core. A `nose' of the cold front, which is characterized by a low-level protruding structure in the equivalent potential temperature field, forms when the cyclone moves offshore. This `nose' structure is hypothesized to have been caused by the heating effect of the Kuroshio Current. Two low-level jet streams are also identified on the western and eastern sides of the cold front. The western jet conveys cold and dry air at 800-900 hPa. The wind in the northern part is northeasterly, and the wind in the southern part is northwesterly. By contrast, the eastern jet carries warm and moist air into the cyclone system, ascending northward from 900 hPa to 600-700 hPa. The southern part is dominated by the southerly wind, and the wind in the northern part is southwesterly. The eastern and western jets significantly increase the air temperature and moisture contrast in the vicinity of the cold front. This increase could play an important role in improving the rapid cyclogenesis process.

Role of extratropical cyclones in the recently observed increase in poleward moisture transport into the Arctic Ocean

NASA Astrophysics Data System (ADS)

Villamil-Otero, Gian A.; Zhang, Jing; He, Juanxiong; Zhang, Xiangdong

2018-01-01

Poleward atmospheric moisture transport (AMT) into the Arctic Ocean can change atmospheric moisture or water vapor content and cause cloud formation and redistribution, which may change downward longwave radiation and, in turn, surface energy budgets, air temperatures, and sea-ice production and melt. In this study, we found a consistently enhanced poleward AMT across 60°N since 1959 based on the NCAR-NCEP reanalysis. Regional analysis demonstrates that the poleward AMT predominantly occurs over the North Atlantic and North Pacific regions, contributing about 57% and 32%, respectively, to the total transport. To improve our understanding of the driving force for this enhanced poleward AMT, we explored the role that extratropical cyclone activity may play. Climatologically, about 207 extratropical cyclones move across 60°N into the Arctic Ocean each year, among which about 66 (32% of the total) and 47 (23%) originate from the North Atlantic and North Pacific Ocean, respectively. When analyzing the linear trends of the time series constructed by using a 20-year running window, we found a positive correlation of 0.70 between poleward yearly AMT and the integrated cyclone activity index (measurement of cyclone intensity, number, and duration). This shows the consistent multidecadal changes between these two parameters and may suggest cyclone activity plays a driving role in the enhanced poleward AMT. Furthermore, a composite analysis indicates that intensification and poleward extension of the Icelandic low and accompanying strengthened cyclone activity play an important role in enhancing poleward AMT over the North Atlantic region.

Variability in tropical cyclone heat potential over the Southwest Indian Ocean

NASA Astrophysics Data System (ADS)

Malan, N.; Reason, C. J. C.; Loveday, B. R.

2013-12-01

Tropical cyclone heat potential (TCHP) has been proposed as being important for hurricane and typhoon intensity. Here, a climatology of TCHP is developed for the Southwest Indian Ocean, a basin that experiences on average 11-12 tropical cyclones per year, many of which impact on Mauritius, Reunion and Madagascar, and Mozambique. SODA data and a regional ocean model forced with the GFDL-CORE v.2b reanalysis winds and heat fluxes are used to derive TCHP values during the 1948-2007 period. The results indicate that TCHP increases through the austral summer, peaking in March. Values of TCHP above 40 kJ cm-2, suggested as the minimum needed for tropical cyclone intensification, are still present in the northern Mozambique Channel in May. A time series of TCHP spatially averaged over the Seychelles-Chagos thermocline ridge (SCTR), an important area for tropical cyclones, is presented. The model time series, which agrees well with XBT-based observations (r = 0.82, p = 0.01), shows considerable interannual variability overlaying an upward tendency that matches with an observed increase in severe tropical cyclone days in the Southwest Indian Ocean. Although an increase in severe storms is seen during 1997-2007, the increasing TCHP tendency time series after 1997 coincides with a decrease in total cyclone numbers, a mismatch that is ascribed to increased atmospheric anticyclonicity over the basin. Seasons of increased (decreased) TCHP over the SCTR appear to be associated with dry (wet) conditions over certain areas of southern and East Africa and are linked with changes in zonal wind and vertical motion in the midtroposphere.

Variability of upper-ocean characteristics and tropical cyclones in the South West Indian Ocean

NASA Astrophysics Data System (ADS)

Mawren, D.; Reason, C. J. C.

2017-03-01

Track and intensity are key aspects of tropical cyclone behavior. Intensity may be impacted by the upper-ocean heat content relevant for TC intensification (known as Tdy) and barrier layer thickness (BLT). Here the variability of Tdy and BLT in the South West Indian Ocean and their relationships with tropical cyclones are investigated. It is shown that rapid cyclone intensification is influenced by large Tdy values, thick barrier layers and the presence of anticyclonic eddies. For TC generation in the South West Indian Ocean, the parameter Tdy was found to be important. Large BLT values overlay with large Tdy values during summer. Both fields are modulated by the westward propagation of Rossby waves, which are often associated with ENSO. For example, the 1997-1998 El Niño shows a strong signal in Tdy, SST, and BLT over the South West Indian Ocean. After this event, an increasing trend in Tdy occurred over most of the basin which may be associated with changes in atmospheric circulation. Increasing SST, Power Dissipation Index and frequency of Category 5 tropical cyclones also occurred from 1980 to 2010. To further examine the links between tropical cyclones, Tdy, and BLT, the ocean response to Category 5 Tropical Cyclone Bansi that developed near Madagascar during January 2015 was analyzed. Its unusual track was found to be linked with the strengthening of the monsoonal north westerlies while its rapid intensification from Category 2 to Category 4 was linked to a high-Tdy region, associated with a warm core eddy and large BLT.

Influence of wintertime large-scale circulation on the explosively developing cyclones over the western North Pacific and their downstream effects

NASA Astrophysics Data System (ADS)

Yoshiike, Satoki; Kawamura, Ryuichi

2009-07-01

The relationships between large-scale wintertime circulation and extratropical cyclones that develop explosively (the so-called bomb cyclones) over the western North Pacific are investigated using Japanese long-term reanalysis project data. On a monthly basis, the East Asian winter monsoon variability strongly modulates the bomb cyclone activity in terms of its geographical distribution. When the monsoon is strong, the bomb cyclone activity tends to concentrate in the vicinity of the Kuroshio Current and the Kuroshio Extension near Japan, while when the monsoon is weak, it disperses over the broader areas. The enhancement of the monsoon increases the heat and moisture supply from warm currents, facilitating unstable conditions within the atmospheric boundary layer and intensifying baroclinicity in the lower troposphere. These factors are believed to play a role in inducing bomb cyclones, particularly along the warm currents. On submonthly timescales, the stationary Rossby wave propagation along the South Asian waveguide serves as a prominent trigger for the rapid reinforcement of synoptic-scale disturbances around Japan. When a pronounced bomb cyclone comes to its mature stage northeast of Japan, it is capable of exciting stationary Rossby waves downstream from the Asian jet exit region as vorticity forcing. The stationary wave packets developing southeastward across the North Pacific Ocean basin induce surface cyclogenesis in the vicinity of the Hawaiian Islands by leading to the equatorward advection of higher potential vorticity from the midlatitudes, bringing about the occurrence of kona storms, which cause weather hazards in Hawaii.

Assessing the influence of climate change on flooding hazards following tropical cyclone events in the Southeast United States

NASA Astrophysics Data System (ADS)

Stone, Monica Helen

Recent tropical cyclones, like Hurricane Katrina, have been some of the worst the United States has experienced. Tropical cyclones are expected to intensify, bringing about 20% more precipitation, in the near future in response to global climate warming. Further, global climate warming may extend the hurricane season. This study focuses on four major river basins (Neches, Pearl, Mobile, and Roanoke) in the Southeast United States that are frequently impacted by tropical cyclones. The Soil and Water Assessment Tool (SWAT) was used to model flow along these rivers from 1998-2014 with 20% more precipitation during tropical cyclones. The results of this study show that an increase in tropical cyclone precipitation due to future climate change may increase peak flows at the mouths of these Southeast rivers by ˜7-18%. Most tropical cyclones that impact these river basins occur during the low discharge season, and thus rarely produce flooding conditions at their mouths. An extension of the current hurricane season of June-November, due to global climate warming, could encroach upon the wet season in these basins and lead to increased flooding. On average, this analysis shows that an extension of the hurricane season to May-December increased flooding susceptibility by 63% for the rivers analyzed in this study. That is, 4-6 more days per year likely would have been above bankfull discharge if an average tropical cyclone had occurred any day (based on 1998-2014 data) in the months May-December than in the current hurricane season months of June-November. More research is needed on the mechanisms and processes involved in the water balance of the four rivers analyzed in this study, and others in the Southeast United States, and how this is likely to change in the near future with global climate warming.

South-Eastern Bay of Biscay eddy-induced anomalies and their effect on chlorophyll distribution

NASA Astrophysics Data System (ADS)

Caballero, Ainhoa; Rubio, Anna; Ruiz, Simón; Le Cann, Bernard; Testor, Pierre; Mader, Julien; Hernández, Carlos

2016-10-01

The analysis of deep-water glider hydrographic and fluorescence data, together with satellite measurements provides a new insight into eddy-induced anomalies within the South-Eastern Bay of Biscay, during summer. Two cyclonic eddies and a SWODDY have been observed in different glider transects and by means of different sources of satellite data. Vertical profiles reveal complex structures (characteristic of the second baroclinic mode): upward/downward displacement of the seasonal/permanent thermocline in the case of X13 and the opposite thermocline displacements in the case of the cyclones. This is a typical behaviour of mode-water and "cyclonic thinny" eddies. A qualitative analysis of the vertical velocities in the anticyclone indicates that though geostrophy dominates the main water column, depressing the isopycnals, near the sea-surface the eddy-wind interaction affects the vertical currents, favouring Ekman pumping and upwelling. The analysis of the Θ-S properties corroborates that inside cyclones and between the 26 and 27 isopycnals, net downwelling occurs. These two types of intra-thermocline lenses appear to deeply impact the Chl-a fluorescence profiles, since the maximum Chl-a fluorescence is located just below the seasonal thermocline. The mean Chl-a fluorescence was higher in the anticyclone than within the cyclones and the mean for the entire study period; the highest values were observed in the centre of the anticyclone. These results are in agreement with previous findings concerning the SWODDY F90 and surrounding cyclones, located in the South-Western Bay of Biscay. Significant differences in the Θ-S properties of the two cyclonic mesoscale structures have been observed: higher temperatures and lower salinity in the easternmost cyclone. Finally, time variation of the salinity content of the shallowest water masses of the anticyclone (salinity decreasing over time), probably indicates advective mixing processes occurred during the mission.

Bending transition in the penetration of a flexible intruder in a two-dimensional dense granular medium.

PubMed

Algarra, Nicolas; Karagiannopoulos, Panagiotis G; Lazarus, Arnaud; Vandembroucq, Damien; Kolb, Evelyne

2018-02-01

We study the quasistatic penetration of a flexible beam into a two-dimensional dense granular medium lying on a horizontal plate. Rather than a buckling-like behavior we observe a transition between a regime of crack-like penetration in which the fiber only shows small fluctuations around a stable straight geometry and a bending regime in which the fiber fully bends and advances through series of loading and unloading steps. We show that the shape reconfiguration of the fiber is controlled by a single nondimensional parameter L/L_{c}, which is the ratio of the length of the flexible beam L to L_{c}, a bending elastogranular length scale that depends on the rigidity of the fiber and on the departure from the jamming packing fraction of the granular medium. We show, moreover, that the dynamics of the bending transition in the course of the penetration experiment is gradual and is accompanied by a symmetry breaking of the granular packing fraction in the vicinity of the fiber. Together with the progressive bending of the fiber, a cavity grows downstream of the fiber and the accumulation of grains upstream of the fiber leads to the development of a jammed cluster of grains. We discuss our experimental results in the framework of a simple model of bending-induced compaction and we show that the rate of the bending transition only depends on the control parameter L/L_{c}.

Bending transition in the penetration of a flexible intruder in a two-dimensional dense granular medium

NASA Astrophysics Data System (ADS)

Algarra, Nicolas; Karagiannopoulos, Panagiotis G.; Lazarus, Arnaud; Vandembroucq, Damien; Kolb, Evelyne

2018-02-01

We study the quasistatic penetration of a flexible beam into a two-dimensional dense granular medium lying on a horizontal plate. Rather than a buckling-like behavior we observe a transition between a regime of crack-like penetration in which the fiber only shows small fluctuations around a stable straight geometry and a bending regime in which the fiber fully bends and advances through series of loading and unloading steps. We show that the shape reconfiguration of the fiber is controlled by a single nondimensional parameter L /Lc , which is the ratio of the length of the flexible beam L to Lc, a bending elastogranular length scale that depends on the rigidity of the fiber and on the departure from the jamming packing fraction of the granular medium. We show, moreover, that the dynamics of the bending transition in the course of the penetration experiment is gradual and is accompanied by a symmetry breaking of the granular packing fraction in the vicinity of the fiber. Together with the progressive bending of the fiber, a cavity grows downstream of the fiber and the accumulation of grains upstream of the fiber leads to the development of a jammed cluster of grains. We discuss our experimental results in the framework of a simple model of bending-induced compaction and we show that the rate of the bending transition only depends on the control parameter L /Lc .

Spectral softening in the X-RAY afterglow of GRB 130925A as predicted by the dust scattering model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Yi-Nan; Shao, Lang, E-mail: lshao@hebtu.edu.cn

2014-07-01

Gamma-ray bursts (GRBs) usually occur in a dense star-forming region with a massive circumburst medium. The small-angle scattering of intense prompt X-ray emission off the surrounding dust grains will have observable consequences and sometimes can dominate the X-ray afterglow. In most of the previous studies, only the Rayleigh-Gans (RG) approximation is employed for describing the scattering process, which works accurately for the typical size of grains (with radius of a ≤ 0.1 μm) in the diffuse interstellar medium. When the size of the grains may significantly increase, as in a more dense region where GRBs would occur, the RG approximationmore » may not be valid enough for modeling detailed observational data. In order to study the temporal and spectral properties of the scattered X-ray emission more accurately with potentially larger dust grains, we provide a practical approach using the series expansions of anomalous diffraction (AD) approximation based on the complicated Mie theory. We apply our calculations to understand the puzzling X-ray afterglow of recently observed GRB 130925A that showed a significant spectral softening. We find that the X-ray scattering scenarios with either AD or RG approximation adopted could well reproduce both the temporal and spectral profile simultaneously. Given the plateau present in the early X-ray light curve, a typical distribution of smaller grains as in the interstellar medium would be suggested for GRB 130925A.« less

Spectral Softening in the X-Ray Afterglow of GRB 130925A as Predicted by the Dust Scattering Model

NASA Astrophysics Data System (ADS)

Zhao, Yi-Nan; Shao, Lang

2014-07-01

Gamma-ray bursts (GRBs) usually occur in a dense star-forming region with a massive circumburst medium. The small-angle scattering of intense prompt X-ray emission off the surrounding dust grains will have observable consequences and sometimes can dominate the X-ray afterglow. In most of the previous studies, only the Rayleigh-Gans (RG) approximation is employed for describing the scattering process, which works accurately for the typical size of grains (with radius of a <= 0.1 μm) in the diffuse interstellar medium. When the size of the grains may significantly increase, as in a more dense region where GRBs would occur, the RG approximation may not be valid enough for modeling detailed observational data. In order to study the temporal and spectral properties of the scattered X-ray emission more accurately with potentially larger dust grains, we provide a practical approach using the series expansions of anomalous diffraction (AD) approximation based on the complicated Mie theory. We apply our calculations to understand the puzzling X-ray afterglow of recently observed GRB 130925A that showed a significant spectral softening. We find that the X-ray scattering scenarios with either AD or RG approximation adopted could well reproduce both the temporal and spectral profile simultaneously. Given the plateau present in the early X-ray light curve, a typical distribution of smaller grains as in the interstellar medium would be suggested for GRB 130925A.

New simple and low-cost methods for periodic checks of Cyclone® Plus Storage Phosphor System.

PubMed

Edalucci, Elisabetta; Maffione, Anna Margherita; Fornasier, Maria Rosa; De Denaro, Mario; Scian, Giovanni; Dore, Franca; Rubello, Domenico

2017-01-01

The recent large use of the Cyclone® Plus Storage Phosphor System, especially in European countries, as imaging system for quantification of radiochemical purity of radiopharmaceuticals raised the problem of setting the periodic controls as required by European Legislation. We described simple, low-cost methods for Cyclone® Plus quality controls, which can be useful to evaluate the performance measurement of this imaging system.

Simulation of Extreme Arctic Cyclones in IPCC AR5 Experiments

DTIC Science & Technology

2014-05-15

atmospheric fields, including sea level pressure ( SLP ), on daily and sub-daily time scales at 2° horizontal resolution. A higher-resolution and more...its 21st-century simulation. Extreme cyclones were defined as occurrences of daily mean SLP at least 40 hPa below the climatological annual-average... SLP at a grid point. As such, no cyclone-tracking algorithm was employed, because the purpose here is to identify instances of extremely strong

Tropical Cyclone Genesis and Sudden Changes of Track and Intensity in the Western Pacific

DTIC Science & Technology

2008-09-30

North Atlantic . (Published in 2008) Our work on the effect of internally generated inner-core asymmetries on tropical cyclone potential intensity has...of the atmospheric circulation in TC basins to the global warming is more critical than increasing SST to understanding the impacts of global warming...Japan and its adjacent seas is studied with WRF model. The results suggest that the northward moisture transport through the outer cyclonic circulation

On the Evolution of Precipitation Associated with a Wintertime East Coast Cyclone: A GALE Preliminary Study.

DTIC Science & Technology

1985-01-01

CYCLES (CYCLone Extratropical Storms project), a more elaborate study of precipitation structure, has been carried out by Hobbs and his collaborators...toward the heavily populated northeast portion of the country. The disruption of human activity caused by these often poorly forecast storms is...daily synoptic maps over a century ago permitted analysis of the structure and behavior of extratropical cyclones. Since then considerable literature

Ensemble Prediction of Tropical Cyclone Genesis

DTIC Science & Technology

2017-02-23

future changes in tropical cyclone (TC) activity around the Hawaiian Islands are investigated using the state-of-the-art climate models1–3. We find that...future warmer climate . This is in contrast to the NA, where BDI increases for all dynamic variables investigated while it shows little change for...Li, and A. Kitoh, 2013: Projected future increase in tropical cyclones near Hawaii. Nature Climate Change , 3, 749-754, doi:10.1038/nclimate1890

1994 Annual Tropical Cyclone Report

DTIC Science & Technology

1995-01-01

force winds exist near the center. . . . The NOGAPS model does not analyze Tropical Depression 20W as a distinct feature, nor does it develop the...NOGAPS model for very small westward-moving trop- ical cyclones (Figure 3-20-8). According to Carr, NOGAPS effective grid spacing is too large to properly...analyze a very small to small tropical cyclone. The bogus vortex inserted into the analysis starts out too large and usually expands if the model

Analysis of a Non-Developing Tropical Circulation System During the Tropical Cyclone Structure (TCS08) Field Experiment

DTIC Science & Technology

2009-12-01

Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaigns (T- PARC ). Aircraft dropwindsondes, special ELDORA radar observations...systems within TCS025 at 2030 UTC 24 August 2008. D. ELDORA BACKGROUND For the combined TCS08 and T- PARC field experiment, the ELDORA radar was...SUBJECT TERMS Electra Doppler Radar (ELDORA), Tropical Cyclone Structure (TCS08), TCS08, Tropical Cyclone Formation, Tropical Circulation System

The Navy’s Next-Generation Tropical Cyclone Model

DTIC Science & Technology

2009-09-30

when compared with the Doppler radar observations (Fig. 6c). An example of a real-time COAMPS-TC forecast during T- PARC /TCS-08 initialized on 26...prediction support for the THORPEX-Pacific Asian Campaign (T- PARC ) and the Tropical Cyclone Structure 2008 (TCS-08) (T- PARC /TCS-08) experiments...implemented from the CBLAST project. In support of the T- PARC /TCS-08 campaign, adaptive observing guidance for tropical cyclones has been provided

Tropical Cyclone Reconnaissance with the Global Hawk: Operational Thresholds and Characteristics of Convective Systems Over the Tropical Western North Pacific

DTIC Science & Technology

2013-12-01

Tropical cyclone research is an intense ongoing science that has acquired even greater importance in this era of global climate change . Increased study of...RECONNAISSANCE WITH THE GLOBAL HAWK: OPERATIONAL THRESHOLDS AND CHARACTERISTICS OF CONVECTIVE SYSTEMS OVER THE TROPICAL WESTERN NORTH PACIFIC by...TROPICAL CYCLONE RECONNAISSANCE WITH THE GLOBAL HAWK: OPERATIONAL THRESHOLDS AND CHARACTERISTICS OF CONVECTIVE SYSTEMS OVER THE TROPICAL WESTERN

A case study of GWE satellite data impact on GLA assimilation analyses of two ocean cyclones

NASA Technical Reports Server (NTRS)

Gallimore, R. G.; Johnson, D. R.

1986-01-01

The effects of the Global Weather Experiment (GWE) data obtained on January 18-20, 1979 on Goddard Laboratory for Atmospheres assimilation analyses of simultaneous cyclones in the western Pacific and Atlantic oceans are examined. The ability of satellite data within assimilation models to determine the baroclinic structures of developing extratropical cyclones is evaluated. The impact of the satellite data on the amplitude and phase of the temperature structure within the storm domain, potential energy, and baroclinic growth rate is studied. The GWE data are compared with Data Systems Test results. It is noted that it is necessary to characterize satellite effects on the baroclinic structure of cyclone waves which degrade numerical weather predictions of cyclogenesis.

Chronology of processes in high-gradient channels of medium-high mountains and their influence on the properties of alluvial fans

NASA Astrophysics Data System (ADS)

Šilhán, Karel

2014-02-01

High-gradient channels are the locations of the greatest geomorphological activity in medium-high mountains. The channels' frequency and character influence the contemporary morphology and morphometry of alluvial fans. There is currently no detailed information regarding the frequency of these processes in high-gradient channels and the evolution of alluvial fans in medium-high mountains in Central Europe. This study in the Moravskoslezské Beskydy Mts. analysed 22 alluvial fans (10 debris flow fans and 12 fluvial fans). The processes occurring on the fans were dated using dendrogeomorphological methods. A total of 748 increment cores were taken from 374 trees to reconstruct 153 geomorphological process events (60 debris flow and 93 floods). The frequency of the processes has been considerably increasing in the last four decades, which can be related to extensive tree cutting since the 1970s. Processes in high-gradient channels in the region (affecting the alluvial fans across the mountain range) are predominantly controlled by cyclonal activity during the warm periods of the year. Probable triggers of local events are heavy downpours in the summer. In addition, spring snowmelt has been identified as occasionally important. This study of the relations affecting the type and frequency of the processes and their effect on the properties of alluvial fans led to the creation of a universal framework for the medium-high flysch mountains of Central Europe. The framework particularly reflects the influence of the character of hydrometeorological extremes on the frequency and type of processes and their reflection in the properties of alluvial fans.

Remote sensing of Earth terrain

NASA Technical Reports Server (NTRS)

Kong, J. A.

1992-01-01

Research findings are summarized for projects dealing with the following: application of theoretical models to active and passive remote sensing of saline ice; radiative transfer theory for polarimetric remote sensing of pine forest; scattering of electromagnetic waves from a dense medium consisting of correlated Mie scatterers with size distribution and applications to dry snow; variance of phase fluctuations of waves propagating through a random medium; theoretical modeling for passive microwave remote sensing of earth terrain; polarimetric signatures of a canopy of dielectric cylinders based on first and second order vector radiative transfer theory; branching model for vegetation; polarimetric passive remote sensing of periodic surfaces; composite volume and surface scattering model; and radar image classification.

Studies of nuclei under the extreme conditions of density, temperature, isospin asymmetry and the phase diagram of hadronic matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mekjian, Aram

2016-10-18

The main emphasis of the entire project is on issues having to do with medium energy and ultra-relativistic energy and heavy ion collisions. A major goal of both theory and experiment is to study properties of hot dense nuclear matter under various extreme conditions and to map out the phase diagram in density or chemical potential and temperature. My studies in medium energy nuclear collisions focused on the liquid-gas phase transition and cluster yields from such transitions. Here I developed both the statistical model of nuclear multi-fragmentation and also a mean field theory.

Site characterization in densely fractured dolomite: Comparison of methods

USGS Publications Warehouse

Muldoon, M.; Bradbury, K.R.

2005-01-01

One of the challenges in characterizing fractured-rock aquifers is determining whether the equivalent porous medium approximation is valid at the problem scale. Detailed hydrogeologic characterization completed at a small study site in a densely fractured dolomite has yielded an extensive data set that was used to evaluate the utility of the continuum and discrete-fracture approaches to aquifer characterization. There are two near-vertical sets of fractures at the site; near-horizontal bedding-plane partings constitute a third fracture set. Eighteen boreholes, including five coreholes, were drilled to a depth of ???10.6 m. Borehole geophysical logs revealed several laterally extensive horizontal fractures and dissolution zones. Flowmeter and short-interval packer testing identified which of these features were hydraulically important. A monitoring system, consisting of short-interval piezometers and multilevel samplers, was designed to monitor four horizontal fractures and two dissolution zones. The resulting network consisted of >70 sampling points and allowed detailed monitoring of head distributions in three dimensions. Comparison of distributions of hydraulic head - and hydraulic conductivity determined by these two approaches suggests that even in a densely fractured-carbonate aquifer, a characterization approach using traditional long-interval monitoring wells is inadequate to characterize ground water movement for the purposes of regulatory monitoring or site remediation. In addition, traditional multiwell pumping tests yield an average or bulk hydraulic conductivity that is not adequate for predicting rapid ground water travel times through the fracture network, and the pumping test response does not appear to be an adequate tool for assessing whether the porous medium approximation is valid. Copyright ?? 2005 National Ground Water Association.

Prebiotic chemical evolution in the astrophysical context.

PubMed

Ziurys, L M; Adande, G R; Edwards, J L; Schmidt, D R; Halfen, D T; Woolf, N J

2015-06-01

An ever increasing amount of molecular material is being discovered in the interstellar medium, associated with the birth and death of stars and planetary systems. Radio and millimeter-wave astronomical observations, made possible by high-resolution laboratory spectroscopy, uniquely trace the history of gas-phase molecules with biogenic elements. Using a combination of both disciplines, the full extent of the cycling of molecular matter, from circumstellar ejecta of dying stars - objects which expel large amounts of carbon - to nascent solar systems, has been investigated. Such stellar ejecta have been found to exhibit a rich and varied chemical content. Observations demonstrate that this molecular material is passed onto planetary nebulae, the final phase of stellar evolution. Here the star sheds almost its entire original mass, becoming an ultraviolet-emitting white dwarf. Molecules such as H2CO, HCN, HCO(+), and CCH are present in significant concentrations across the entire age span of such nebulae. These data suggest that gas-phase polyatomic, carbon-containing molecules survive the planetary nebula phase and subsequently are transported into the interstellar medium, seeding the chemistry of diffuse and then dense clouds. The extent of the chemical complexity in dense clouds is unknown, hindered by the high spectral line density. Organic species such as acetamide and methyl amine are present in such objects, and NH2CHO has a wide Galactic distribution. However, organophosphorus compounds have not yet been detected in dense clouds. Based on carbon and nitrogen isotope ratios, molecular material from the ISM appears to become incorporated into solar system planetesimals. It is therefore likely that interstellar synthesis influences prebiotic chemistry on planet surfaces.

Soil resources, land cover changes and rural areas: towards a spatial mismatch?

PubMed

Ferrara, Agostino; Salvati, Luca; Sabbi, Alberto; Colantoni, Andrea

2014-04-15

The present study analyzes the impact of long-term urban expansion on soil depletion in Emilia-Romagna, an agricultural-specialized region of northern Italy. Using settlement density maps at three points in time (1945, 1971 and 2001) dense and diffused urbanization trends were assessed and correlated with soil quality. Non-urbanized land decreased from 11.8% in 1945 to 6.3% in 2001. Urbanization dynamics between 1945 and 1971 reflect the increase of dense settlements around pre-existing urban centers. To the contrary, a discontinuous, low- and medium-density urban expansion along the road network and in the most fertile lowland areas was observed between 1971 and 2001. Overall, urbanization consumed soils with progressively higher quality. However, a diverging trend was observed in the two investigated time intervals: soil with high quality was occupied by compact and dense settlements during 1945-1971 and by discontinuous, medium- and low-density settlements during 1971-2001. These findings document the polarization in areas with low and high soil capital and may reflect disparities in agricultural production and increasing environmental degradation. Moreover, the analysis shows a diverging trend between land and soil consumption patterns suggesting that the edification of pervious land is an unreliable indicator of soil quality depletion. Taken together, the results of this study illustrate the (increasing) spatial mismatch between agricultural land and high-quality soils as a consequence of urbanization-driven landscape transformations and may inform measures to contain soil depletion driven by economic growth. Copyright © 2014 Elsevier B.V. All rights reserved.

Site characterization in densely fractured dolomite: comparison of methods.

PubMed

Muldoon, Maureen; Bradbury, Ken R

2005-01-01

One of the challenges in characterizing fractured-rock aquifers is determining whether the equivalent porous medium approximation is valid at the problem scale. Detailed hydrogeologic characterization completed at a small study site in a densely fractured dolomite has yielded an extensive data set that was used to evaluate the utility of the continuum and discrete-fracture approaches to aquifer characterization. There are two near-vertical sets of fractures at the site; near-horizontal bedding-plane partings constitute a third fracture set. Eighteen boreholes, including five coreholes, were drilled to a depth of approximately 10.6 m. Borehole geophysical logs revealed several laterally extensive horizontal fractures and dissolution zones. Flowmeter and short-interval packer testing identified which of these features were hydraulically important. A monitoring system, consisting of short-interval piezometers and multilevel samplers, was designed to monitor four horizontal fractures and two dissolution zones. The resulting network consisted of >70 sampling points and allowed detailed monitoring of head distributions in three dimensions. Comparison of distributions of hydraulic head and hydraulic conductivity determined by these two approaches suggests that even in a densely fractured-carbonate aquifer, a characterization approach using traditional long-interval monitoring wells is inadequate to characterize ground water movement for the purposes of regulatory monitoring or site remediation. In addition, traditional multiwell pumping tests yield an average or bulk hydraulic conductivity that is not adequate for predicting rapid ground water travel times through the fracture network, and the pumping test response does not appear to be an adequate tool for assessing whether the porous medium approximation is valid.

Cornus sericea

Treesearch

Paula M. Pijut

2004-01-01

Redosier dogwood is a multistemmed, deciduous, stoloniferous shrub that grows 1 to 3 m tall and 3 m wide or more, often forming dense thickets. Leaves are opposite, simple, ovate to oblonglanceolate, acuminate, rounded at the base, 5 to 12 cm long, 2.5 to 6.4 cm wide, with petioles 1.3 to 2.5 cm long (Dirr 1998, Gleason and Cronquist 1991). Leaves are medium to dark...

Production and early field performance of RPM® seedlings in Missouri floodplains

Treesearch

Daniel C. Dey; Wayne Lovelace; John M. Kabrick; Michael A. Gold

2004-01-01

A new nursery culture process has been developed to produce large container RPM? seedlings in an effort to improve the success in artificially regenerating hardwoods. Major features of the process include air root pruning of seedlings grown in a well aerated soil medium to encourage a dense, fibrous root system. Production has focused on native bottomland tree, shrub,...

Enhancement of Feedback Efficiency by Active Galactic Nucleus Outflows via the Magnetic Tension Force in the Inhomogeneous Interstellar Medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asahina, Yuta; Ohsuga, Ken; Nomura, Mariko, E-mail: asahina@cfca.jp

By performing three-dimensional magnetohydrodynamics simulations of subrelativistic jets and disk winds propagating into the magnetized inhomogeneous interstellar medium (ISM), we investigate the magnetic effects on the active galactic nucleus feedback. Our simulations reveal that the magnetic tension force promotes the acceleration of the dense gas clouds, since the magnetic field lines, which are initially straight, bend around the gas clouds. In the jet models, the velocity dispersion of the clouds increases with an increase in the initial magnetic fields. The increment of the kinetic energy of the clouds is proportional to the initial magnetic fields, implying that the magnetic tensionmore » force increases the energy conversion efficiency from the jet to the gas clouds. Through simulations of the mildly collimated disk wind and the funnel-shaped disk wind, we confirm that such an enhancement of the energy conversion efficiency via the magnetic fields appears even if the energy is injected via the disk winds. The enhancement of the acceleration of the dense part of the magnetized ISM via the magnetic tension force will occur wherever the magnetized inhomogeneous matter is blown away.« less

Seismic gradiometry using ambient seismic noise in an anisotropic Earth

NASA Astrophysics Data System (ADS)

de Ridder, S. A. L.; Curtis, A.

2017-05-01

We introduce a wavefield gradiometry technique to estimate both isotropic and anisotropic local medium characteristics from short recordings of seismic signals by inverting a wave equation. The method exploits the information in the spatial gradients of a seismic wavefield that are calculated using dense deployments of seismic arrays. The application of the method uses the surface wave energy in the ambient seismic field. To estimate isotropic and anisotropic medium properties we invert an elliptically anisotropic wave equation. The spatial derivatives of the recorded wavefield are evaluated by calculating finite differences over nearby recordings, which introduces a systematic anisotropic error. A two-step approach corrects this error: finite difference stencils are first calibrated, then the output of the wave-equation inversion is corrected using the linearized impulse response to the inverted velocity anomaly. We test the procedure on ambient seismic noise recorded in a large and dense ocean bottom cable array installed over Ekofisk field. The estimated azimuthal anisotropy forms a circular geometry around the production-induced subsidence bowl. This conforms with results from studies employing controlled sources, and with interferometry correlating long records of seismic noise. Yet in this example, the results were obtained using only a few minutes of ambient seismic noise.

Rapid formation of large dust grains in the luminous supernova 2010jl.

PubMed

Gall, Christa; Hjorth, Jens; Watson, Darach; Dwek, Eli; Maund, Justyn R; Fox, Ori; Leloudas, Giorgos; Malesani, Daniele; Day-Jones, Avril C

2014-07-17

The origin of dust in galaxies is still a mystery. The majority of the refractory elements are produced in supernova explosions, but it is unclear how and where dust grains condense and grow, and how they avoid destruction in the harsh environments of star-forming galaxies. The recent detection of 0.1 to 0.5 solar masses of dust in nearby supernova remnants suggests in situ dust formation, while other observations reveal very little dust in supernovae in the first few years after explosion. Observations of the spectral evolution of the bright SN 2010jl have been interpreted as pre-existing dust, dust formation or no dust at all. Here we report the rapid (40 to 240 days) formation of dust in its dense circumstellar medium. The wavelength-dependent extinction of this dust reveals the presence of very large (exceeding one micrometre) grains, which resist destruction. At later times (500 to 900 days), the near-infrared thermal emission shows an accelerated growth in dust mass, marking the transition of the dust source from the circumstellar medium to the ejecta. This provides the link between the early and late dust mass evolution in supernovae with dense circumstellar media.

Comparison between the Coastal Impacts of Cyclone Nargis and the Indian Ocean Tsunami

NASA Astrophysics Data System (ADS)

Fritz, H. M.; Blount, C.

2009-12-01

On 26 December 2004 a great earthquake with a moment magnitude of 9.3 occurred off the North tip of Sumatra, Indonesia. The Indian Ocean tsunami claimed 230,000 lives making it the deadliest in recorded history. Less than 4 years later tropical cyclone Nargis (Cat. 4) made landfall in Myanmar’s Ayeyarwady delta on 2 May 2008 causing the worst natural disaster in Myanmar’s recorded history. Official death toll estimates exceed 138,000 fatalities making it the 7th deadliest cyclone ever recorded worldwide. The Bay of Bengal counts seven tropical cyclones with death tolls in excess of 100,000 striking India and Bangladesh in the past 425 years, which highlights the difference in return periods between extreme cyclones and tsunamis. Damage estimates at over $10 billion made Nargis the most damaging cyclone ever recorded in the Indian Ocean. Although the two natural disasters are completely different in their generation mechanisms they both share massive coastal inundations as primary damage and death cause. While the damage patterns exhibit similarities the forcing differs. The primary tsunami impact is dominated by the runup of a few main waves washing rapidly ashore and inducing high lateral forces. On the contrary the tropical cyclone storm surge damage is the result of numerous storm waves continuously hitting the flooded structures on the elevated storm tide level. While coastal vegetation such as mangroves may be effective at reducing superimposed storm waves they are limited at reducing storm surge. Unfortunately, mangroves have been significantly cut for charcoal and land use as rice paddies in Myanmar due to rapid population growth and economic reasons, thereby increasing coastal vulnerability and land loss due to erosion (Figure 1). The period of a storm surge is typically an order of magnitude longer than the period of a tsunami resulting in significantly larger inundation distances along coastal plains and river deltas. The storm surge of cyclone Nargis penetrated more than 50 km inland along the Ayeyarwady delta while the maximum inundation of the Indian Ocean tsunami was 7 km at Banda Aceh. The extent of affected coast lines differs with 2 m storm surge thresholds of cyclone Nargis spanning 200 km of coastline, whereas East Africa was severely affected by the Indian Ocean tsunami at 5000 km from the epicenter. The available time window for dissemination of warnings and evacuations are significantly shorter for tsunamis than cyclones. Coastal protection in the Indian Ocean must be approached with community-based planning, education and awareness programs suited for a multi-hazard perspective. Ayeyarwady delta in Myanmar after cyclone Nargis: (a) Deforestation of mangroves for use as charcoal and land use as rice paddies; (b) Drinking water wells scoured in surf zone at Aya highlighting more than 100 m land loss due to coastal erosion.

Enhancement of the Triple Alpha Rate in a Hot Dense Medium

NASA Astrophysics Data System (ADS)

Beard, Mary; Austin, Sam M.; Cyburt, Richard

2017-09-01

In a sufficiently hot and dense astrophysical environment the rate of the triple-alpha (3 α ) reaction can increase greatly over the value appropriate for helium burning stars owing to hadronically induced deexcitation of the Hoyle state. In this Letter we use a statistical model to evaluate the enhancement as a function of temperature and density. For a density of 106 g cm-3 enhancements can exceed a factor of 100. In high temperature or density situations, the enhanced 3 α rate is a better estimate of this rate and should be used in these circumstances. We then examine the effect of these enhancements on production of 12C in the neutrino wind following a supernova explosion and in an x-ray burster.

Dust coagulation. [in interstellar medium observed in stellar envelopes and planetary disks

NASA Technical Reports Server (NTRS)

Chokshi, Arati; Tielens, A. G. G. M.; Hollenbach, D.

1993-01-01

The microphysics of coagulation between two, colliding, smooth, spherical grains in the elastic limit is investigated, and the criteria for sticking as a function of particle sizes, collision velocities, elastic properties, and binding energy are calculated. Critical relative velocities for coagulation were evaluated as a function of grain sizes for solicate, icy, and carbonaceous grains. It is concluded that efficient coagulation requires coverage of grain cores by an icy grain mantle. In this case, coagulation leads to only a doubling of the mass of a large grain within a dense core lifetime. It is concluded that coagulation can have a dramatic effect on the visible and, particularly, the UV portion of the extinction curve in dense clouds and on their IR spectrum.

Structural Variability of Tropospheric Growth Factors Transforming Mid-latitude Cyclones to Severe Storms over the North Atlantic

NASA Astrophysics Data System (ADS)

Wild, Simon; Befort, Daniel J.; Leckebusch, Gregor C.

2015-04-01

The development of European surface wind storms out of normal mid-latitude cyclones is substantially influenced by upstream tropospheric growth factors over the Northern Atlantic. The main factors include divergence and vorticity advection in the upper troposphere, latent heat release and the presence of instabilities of short baroclinic waves of suitable wave lengths. In this study we examine a subset of these potential growth factors and their related influences on the transformation of extra-tropical cyclones into severe damage prone surface storm systems. Previous studies have shown links between specific growth factors and surface wind storms related to extreme cyclones. In our study we investigate in further detail spatial and temporal variability patterns of these upstream processes at different vertical levels of the troposphere. The analyses will comprise of the three growth factors baroclinicity, latent heat release and upper tropospheric divergence. Our definition of surface wind storms is based on the Storm Severity Index (SSI) alongside a wind tracking algorithm identifying areas of exceedances of the local 98th percentile of the 10m wind speed. We also make use of a well-established extra-tropical cyclone identification and tracking algorithm. These cyclone tracks form the base for a composite analysis of the aforementioned growth factors using ERA-Interim Reanalysis from 1979 - 2014 for the extended winter season (ONDJFM). Our composite analysis corroborates previous similar studies but extends them by using an impact based algorithm for the identification of strong wind systems. Based on this composite analysis we further identify variability patterns for each growth factor most important for the transformation of a cyclone into a surface wind storm. We thus also address the question whether the link between storm intensity and related growth factor anomaly taking into account its spatial variability is stable and can be quantified. While the robustness of our preliminary results is generally dependent on the growth factor investigated, some examples include i) the overall availability of latent heat seems to be less important than its spatial structure around the cyclone core and ii) the variability of upper-tropospheric baroclinicity appears to be highest north of the surface position of the cyclone, especially for those that transform into a surface storm.

Evolution of environmental factors affecting tropical cyclones from the LGM through the Holocene

NASA Astrophysics Data System (ADS)

Korty, R.

2010-12-01

The debate about whether and how tropical cyclones respond to warming climates has raised several interesting questions, but it has also revealed there is much we do not understand about controls on frequency and cumulative metrics of intensity and activity. In this work, I examine how the models used for anthropogenic climate predictions handle large-scale factors influencing tropical cyclone development in a different regime: the paleoclimate simulations of the LGM and Holocene. The models were forced under guidelines set forth by the second paleoclimate model intercomparison project (PMIP2), and produce equilibrium solutions for forcings far removed from small perturbations to the present-day world. (LGM has substantially lower CO2 and CH4 levels, while mid-Holocene cases have similar levels to today but different seasonal amplitudes from orbital variations.) The large-scale environmental factors that support tropical cyclones in today’s climate undergo complex and at times counter-intuitive changes in the colder simulations. The maximum potential intensity of tropical cyclones (MPI) is lower throughout the tropics in the mid-Holocene simulations, despite having SSTs very similar to today. MPI changes at LGM are more complex: lower in some regions but higher in much of the subtropics, while SSTs are uniformly lower than today. The water vapor deficits in the tropical midtroposphere change in such a way as to make tropical cyclone formation easier in the colder states; this is a counterintuitive result, but one consistent with the predictions of fewer storms in model simulations of a warmer climate by the end of the 21st century. I analyze the thermodynamic reasons behind the evolution in the large-scale environmental factors as well as relevant dynamic factors such as low-level vorticity and tropospheric wind shear. This analysis is the first part of a long-term project to analyze model prediction of tropical cyclone activity in the recent geologic past; the analysis provides a new line of evidence to compare with geologic proxies of tropical cyclone activity through the Holocene. Changes in midtropospheric entropy deficit from preindustrial (PI) climate to mid-Holocene (6ka) and LGM. Lower values indicate a smaller saturation deficit, which is conducive for tropical cyclone development.

Variability of cyclones over the North Atlantic and Europe since 1871

NASA Astrophysics Data System (ADS)

Welker, C.; Martius, O.

2012-04-01

The scarce availability of long-term atmospheric data series has so far limited the analysis of low-frequency activity and intensity changes of cyclones over the North Atlantic and Europe. A novel reanalysis product, the Twentieth Century Reanalysis (20CR; Compo et al., 2011), spanning 1871 to present, offers potentially a very valuable resource for the analysis of the decadal-scale variability of cyclones over the North Atlantic sector and Europe. In the 20CR, only observations of synoptic surface pressure were assimilated. Monthly sea surface temperature and sea ice distributions served as boundary conditions. An Ensemble Kalman Filter assimilation technique was applied. "First guess" fields were obtained from an ensemble (with 56 members) of short-range numerical weather prediction forecasts. We apply the cyclone identification algorithm of Wernli and Schwierz (2006) to this data set, i.e. to each individual ensemble member. This enables us to give an uncertainty estimation of our findings. We find that 20CR shows a temporally relatively homogeneous representation of cyclone activity over Europe and great parts of the North Atlantic. Pronounced decadal-scale variability is found both in the frequency and intensity of cyclones over the North Atlantic and Europe. The low-frequency variability is consistently represented in all ensemble members. Our analyses indicate that in the past approximately 140 years the variability of cyclone activity and intensity over the North Atlantic and Europe can principally be associated with the North Atlantic Oscillation and secondary with a pattern similar to the East Atlantic pattern. Regionally however, the correlation between cyclone activity and these dominant modes of variability changes over time. Compo, G. P., J. S. Whitaker, P. D. Sardeshmukh, N. Matsui, R. J. Allan, X. Yin, B. E. Gleason, R. S. Vose, G. Rutledge, P. Bessemoulin, S. Brönnimann, M. Brunet, R. I. Crouthamel, A. N. Grant, P. Y. Groisman, P. D. Jones, M. C. Kruk, A. C. Kruger, G. J. Marshall, M. Maugeri, H. Y. Mok, Ø. Nordli, T. F. Ross, R. M. Trigo, X. L. Wang, S. D. Woodruff, and S. J. Worley, 2011: The Twentieth Century Reanalysis project. Quarterly J. Roy. Meteorol. Soc., 137, 1-28. Wernli, H. and C. Schwierz, 2006: Surface cyclones in the ERA-40 dataset (1958-2001). Part I: Novel identification method and global climatology. J. Atmos. Sci., 63, 2486-2507.

The coincidence of daily rainfall events in Liberia, Costa Rica and tropical cyclones in the Caribbean basin

NASA Astrophysics Data System (ADS)

Waylen, Peter R.; Harrison, Michael

2005-10-01

The occurrence of tropical cyclones in the Caribbean and North Atlantic basins has been previously noted to have a significant effect both upon individual hydro-climatological events as well as on the quantity of annual precipitation experienced along the Pacific flank of Central America. A methodology for examining the so-called indirect effects of tropical cyclones (i.e. those effects resulting from a tropical cyclone at a considerable distance from the area of interest) on a daily rainfall record is established, which uses a variant of contingency table analysis. The method is tested using a single station on the Pacific slope of Costa Rica. Employing daily precipitation records from Liberia, north-western Costa Rica (1964-1995), and historic storm tracks of tropical cyclones in the North Atlantic, it is determined that precipitation falling in coincidence with the passage of tropical depressions, tropical storms, and hurricanes accounts for approximately 15% of average annual precipitation. The greatest effects are associated with storms passing within 1300 km of the precipitation station, and are most apparent in the increased frequency of daily rainfall totals in the range of 40-60 mm, rather than in the largest daily totals. The complexity and nonstationarity of factors affecting precipitation in this region are reflected in the decline in the number of tropical cyclones and their significance to annual precipitation totals after 1980, simultaneous to an increase in annual precipitation totals. The methodology employed in this study is shown to be a useful tool in illuminating the indirect effects of tropical cyclones in the region, with the potential for application in other areas.

Estimating the Risk of Tropical Cyclone Characteristics Along the United States Gulf of Mexico Coastline Using Different Statistical Approaches

NASA Astrophysics Data System (ADS)

Trepanier, J. C.; Ellis, K.; Jagger, T.; Needham, H.; Yuan, J.

2017-12-01

Tropical cyclones, with their high wind speeds, high rainfall totals and deep storm surges, frequently strike the United States Gulf of Mexico coastline influencing millions of people and disrupting off shore economic activities. Events, such as Hurricane Katrina in 2005 and Hurricane Isaac in 2012, can be physically different but still provide detrimental effects due to their locations of influence. There are a wide variety of ways to estimate the risk of occurrence of extreme tropical cyclones. Here, the combined risk of tropical cyclone storm surge and nearshore wind speed using a statistical copula is provided for 22 Gulf of Mexico coastal cities. Of the cities considered, Bay St. Louis, Mississippi has the shortest return period for a tropical cyclone with at least a 50 m s-1 nearshore wind speed and a three meter surge (19.5 years, 17.1-23.5). Additionally, a multivariate regression model is provided estimating the compound effects of tropical cyclone tracks, landfall central pressure, the amount of accumulated precipitation, and storm surge for five locations around Lake Pontchartrain in Louisiana. It is shown the most intense tropical cyclones typically approach from the south and a small change in the amount of rainfall or landfall central pressure leads to a large change in the final storm surge depth. Data are used from the National Hurricane Center, U-Surge, SURGEDAT, and Cooperative Observer Program. The differences in the two statistical approaches are discussed, along with the advantages and limitations to each. The goal of combining the results of the two studies is to gain a better understanding of the most appropriate risk estimation technique for a given area.

How Will Climate Change Affect Explosive Cyclones in the Extratropics of the Northern Hemisphere?

NASA Astrophysics Data System (ADS)

Seiler, C.; Zwiers, F. W.

2015-12-01

Explosive cyclones are rapidly intensifying low pressure systems generating severe wind speeds and heavy precipitation primarily in coastal and marine environments, such as the March 2014 nor'easter which developed along the United States coastline, with hurricane force winds in eastern Maine and the Maritimes. This study presents the first analysis on how explosive cyclones respond to climate change in the extratropics of the Northern Hemisphere. An objective-feature tracking algorithm is used to identify and track cyclones from 23 CMIP5 climate models for the recent past (1981-1999) and future (2081-2099). Explosive cyclones are projected to shift northwards by about 2.2° latitude on average in the northern Pacific, with fewer and weaker events south of 45°N, and more frequent and stronger events north of this latitude. This shift is correlated with a poleward shift of the jet stream in the inter-model spread (R = 0.56). In the Atlantic, the total number of explosive cyclones is projected to decrease by about 17% when averaging across models, with the largest changes occurring along North America's East Coast. This reduction is correlated with a decline in the lower-tropospheric Eady growth rate (R = 0.51), and is stronger for models with smaller frequency biases (R = -0.65). The same region is also projected to experience a small intensification of explosive cyclones, with larger vorticity values for models that predict stronger increases in the speed of the jet stream (R = 0.58). This strengthening of the jet stream is correlated with an enhanced sea surface temperature gradient in the North Atlantic (R = -0.63). The inverse relationship between model bias and projection, and the role of model resolution are discussed.

The Use of Red Green Blue Air Mass Imagery to Investigate the Role of Stratospheric Air in a Non-Convective Wind Event

NASA Technical Reports Server (NTRS)

Berndt, E. B.; Zavodsky, B. T.; Moltham, A. L.; Folmer, M. J.; Jedlovec, G. J.

2014-01-01

The investigation of non-convective winds associated with passing extratropical cyclones and the formation of the sting jet in North Atlantic cyclones that impact Europe has been gaining interest. Sting jet research has been limited to North Atlantic cyclones that impact Europe because it is known to occur in Shapiro-Keyser cyclones and theory suggests it does not occur in Norwegian type cyclones. The global distribution of sting jet cyclones is unknown and questions remain as to whether cyclones with Shapiro-Keyser characteristics that impact the United States develop features similar to the sting jet. Therefore unique National Aeronautics and Space Administration (NASA) products were used to analyze an event that impacted the Northeast United States on 09 February 2013. Moderate Resolution Imaging Spectroradiometer (MODIS) Red Green Blue (RGB) Air Mass imagery and Atmospheric Infrared Sounder (AIRS) ozone data were used in conjunction with NASA's global Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis and higher-resolution regional 13-km Rapid Refresh (RAP) data to analyze the role of stratospheric air in producing high winds. The RGB Air Mass imagery and a new AIRS ozone anomaly product were used to confirm the presence of stratospheric air. Plan view and cross sectional plots of wind, potential vorticity, relative humidity, omega, and frontogenesis were used to analyze the relationship between stratospheric air and high surface winds during the event. Additionally, the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to plot trajectories to determine the role of the conveyor belts in producing the high winds. Analyses of new satellite products, such as the RGB Air Mass imagery, show the utility of future GOES-R products in forecasting non-convective wind events.

Long-lived planetary vortices and their evolution: Conservative intermediate geostrophic model.

PubMed

Sutyrin, Georgi G.

1994-06-01

Large, long-lived vortices, surviving during many turnaround times and far longer than the dispersive linear Rossby wave packets, are abundant in planetary atmospheres and oceans. Nonlinear effects which prevent dispersive decay of intense cyclones and anticyclones and provide their self-propelling propagation are revised here using shallow water equations and their balanced approximations. The main physical mechanism allowing vortical structures to be long-lived in planetary fluid is the quick fluid rotation inside their cores which prevents growth in the amplitude of asymmetric circulation arising due to the beta-effect. Intense vortices of both signs survive essentially longer than the linear Rossby wave packet if their azimuthal velocity is much larger than the Rossby wave speed. However, in the long-time evolution, cyclonic and anticyclonic vortices behave essentially differently that is illustrated by the conservative intermediate geostrophic model. Asymmetric circulation governing vortex propagation is described by the azimuthal mode m=1 for the initial value problem as well as for steadily propagating solutions. Cyclonic vortices move west-poleward decaying gradually due to Rossby wave radiation while anticyclonic ones adjust to non-radiating solitary vortices. Slow weakening of an intense cyclone with decreasing of its size and shrinking of the core is described assuming zero azimuthal velocity outside the core while drifting poleward. The poleward tendency of the cyclone motion relative to the stirring flow corresponds to characteristic trajectories of tropical cyclones in the Earth's atmosphere. The asymmetry in dispersion-nonlinear properties of cyclones and anticyclones is thought to be one of the essential reasons for the observed predominance of anticyclones among long-lived vortices in the atmospheres of the giant planets and also among intrathermoclinic eddies in the ocean.

Fluvial sediment supply to a mega-delta reduced by shifting tropical-cyclone activity.

PubMed

Darby, Stephen E; Hackney, Christopher R; Leyland, Julian; Kummu, Matti; Lauri, Hannu; Parsons, Daniel R; Best, James L; Nicholas, Andrew P; Aalto, Rolf

2016-11-10

The world's rivers deliver 19 billion tonnes of sediment to the coastal zone annually, with a considerable fraction being sequestered in large deltas, home to over 500 million people. Most (more than 70 per cent) large deltas are under threat from a combination of rising sea levels, ground surface subsidence and anthropogenic sediment trapping, and a sustainable supply of fluvial sediment is therefore critical to prevent deltas being 'drowned' by rising relative sea levels. Here we combine suspended sediment load data from the Mekong River with hydrological model simulations to isolate the role of tropical cyclones in transmitting suspended sediment to one of the world's great deltas. We demonstrate that spatial variations in the Mekong's suspended sediment load are correlated (r = 0.765, P < 0.1) with observed variations in tropical-cyclone climatology, and that a substantial portion (32 per cent) of the suspended sediment load reaching the delta is delivered by runoff generated by rainfall associated with tropical cyclones. Furthermore, we estimate that the suspended load to the delta has declined by 52.6 ± 10.2 megatonnes over recent years (1981-2005), of which 33.0 ± 7.1 megatonnes is due to a shift in tropical-cyclone climatology. Consequently, tropical cyclones have a key role in controlling the magnitude of, and variability in, transmission of suspended sediment to the coast. It is likely that anthropogenic sediment trapping in upstream reservoirs is a dominant factor in explaining past, and anticipating future, declines in suspended sediment loads reaching the world's major deltas. However, our study shows that changes in tropical-cyclone climatology affect trends in fluvial suspended sediment loads and thus are also key to fully assessing the risk posed to vulnerable coastal systems.

Assessing the Importance of Atlantic Basin Tropical Cyclone Steering Currents in Anticipating Landfall Risk

NASA Astrophysics Data System (ADS)

Truchelut, R.; Hart, R. E.

2013-12-01

While a number of research groups offer quantitative pre-seasonal assessments of aggregate annual Atlantic Basin tropical cyclone activity, the literature is comparatively thin concerning methods to meaningfully quantify seasonal U.S. landfall risks. As the example of Hurricane Andrew impacting Southeast Florida in the otherwise quiet 1992 season demonstrates, an accurate probabilistic assessment of seasonal tropical cyclone threat levels would be of immense public utility and economic value; however, the methods used to predict annual activity demonstrate little skill for predicting annual count of landfalling systems of any intensity bin. Therefore, while current models are optimized to predict cumulative seasonal tropical cyclone activity, they are not ideal tools for assessing the potential for sensible impacts of storms on populated areas. This research aims to bridge the utility gap in seasonal tropical cyclone forecasting by shifting the focus of seasonal modelling to the parameters that are most closely linked to creating conditions favorable for U.S. landfalls, particularly those of destructive and costly intense hurricanes. As it is clear from the initial findings of this study that overall activity has a limited influence on sensible outcomes, this project concentrates on detecting predictability and trends in cyclogenesis location and upper-level wind steering patterns. These metrics are demonstrated to have a relationship with landfall activity in the Atlantic Basin climatological record. By aggregating historic seasonally-averaged steering patterns using newly-available reanalysis model datasets, some atmospheric and oceanic precursors to an elevated risk of North American tropical cyclone landfall have been identified. Work is ongoing to quantify the variance, persistence, and predictability of such patterns over seasonal timescales, with the aim of yielding tools that could be incorporated into tropical cyclone risk mitigation strategies.

Field theoretical prediction of a property of the tropical cyclone

NASA Astrophysics Data System (ADS)

Spineanu, F.; Vlad, M.

2014-01-01

The large scale atmospheric vortices (tropical cyclones, tornadoes) are complex physical systems combining thermodynamics and fluid-mechanical processes. The late phase of the evolution towards stationarity consists of the vorticity concentration, a well known tendency to self-organization , an universal property of the two-dimensional fluids. It may then be expected that the stationary state of the tropical cyclone has the same nature as the vortices of many other systems in nature: ideal (Euler) fluids, superconductors, Bose-Einsetin condensate, cosmic strings, etc. Indeed it was found that there is a description of the atmospheric vortex in terms of a classical field theory. It is compatible with the more conventional treatment based on conservation laws, but the field theoretical model reveals properties that are almost inaccessible to the conventional formulation: it identifies the stationary states as being close to self-duality. This is of highest importance: the self-duality is known to be the origin of all coherent structures known in natural systems. Therefore the field theoretical (FT) formulation finds that the cuasi-coherent form of the atmospheric vortex (tropical cyclone) at stationarity is an expression of this particular property. In the present work we examine a strong property of the tropical cyclone, which arises in the FT formulation in a natural way: the equality of the masses of the particles associated to the matter field and respectively to the gauge field in the FT model is translated into the equality between the maximum radial extension of the tropical cyclone and the Rossby radius. For the cases where the FT model is a good approximation we calculate characteristic quantities of the tropical cyclone and find good comparison with observational data.

Growth form-dependent response to physical disturbance and thermal stress in Acropora corals

NASA Astrophysics Data System (ADS)

Muko, S.; Arakaki, S.; Nagao, M.; Sakai, Kazuhiko

2013-03-01

To predict the community structure in response to changing environmental conditions, it is necessary to know the species-specific reaction and relative impact strength of each disturbance. We investigated the coral communities in two sites, an exposed and a protected site, at Iriomote Island, Japan, from 2005 to 2008. During the study period, a cyclone and thermal stress were observed. All Acropora colonies, classified into four morphologies (arborescent, tabular, corymbose, and digitate), were identified and tracked through time to calculate the annual mortality and growth rate. The mortality of all Acropora colonies in the protected site was lower than that in the exposed site during the period without disturbances. Extremely higher mortality due to bleaching was observed in tabular and corymbose Acropora, compared to other growth forms, at the protected sites after thermal stress. In contrast, physical disturbance by a tropical cyclone induced the highest mortality in arborescent and digitate corals at the exposed site. Moreover, arborescent corals exhibited a remarkable decline 1 year after the tropical cyclone at the exposed site. The growth of colonies that survived coral bleaching did not decrease in the following year compared to previous year for all growth forms, but the growth of arborescent and tabular remnant corals at the exposed site declined severely after the tropical cyclone compared to previous year. The delayed mortality and lowered growth rate after the tropical cyclone were probably due to the damage caused by the tropical cyclone. These results indicate that the cyclone had a greater impact on fragile corals than expected. This study provides useful information for the evaluation of Acropora coral response to progressing global warming conditions, which are predicted to increase in frequency and intensity in the near future.

Fuel for cyclones: The water vapor budget of a hurricane as dependent on its movement

NASA Astrophysics Data System (ADS)

Makarieva, Anastassia M.; Gorshkov, Victor G.; Nefiodov, Andrei V.; Chikunov, Alexander V.; Sheil, Douglas; Nobre, Antonio Donato; Li, Bai-Lian

2017-09-01

Despite the dangers associated with tropical cyclones and their rainfall, the origin of the moisture in these storms, which include destructive hurricanes and typhoons, remains surprisingly uncertain. Existing studies have focused on the region 40-400 km from a cyclone's center. It is known that the rainfall within this area cannot be explained by local processes alone but requires imported moisture. Nonetheless, the dynamics of this imported moisture appears unknown. Here, considering a region up to three thousand kilometers from cyclone center, we analyze precipitation, atmospheric moisture and movement velocities for severe tropical cyclones - North Atlantic hurricanes. Our findings indicate that even over such large areas a hurricane's rainfall cannot be accounted for by concurrent evaporation. We propose instead that a hurricane consumes pre-existing atmospheric water vapor as it moves. The propagation velocity of the cyclone, i.e. the difference between its movement velocity and the mean velocity of the surrounding air (steering flow), determines the water vapor budget. Water vapor available to the hurricane through its movement makes the hurricane self-sufficient at about 700 km from the hurricane center obviating the need to concentrate moisture from greater distances. Such hurricanes leave a dry wake, whereby rainfall is suppressed by up to 40% compared to the local long-term mean. The inner radius of this dry footprint approximately coincides with the hurricane's radius of water self-sufficiency. We discuss how Carnot efficiency considerations do not constrain the power of such open systems. Our findings emphasize the incompletely understood role and importance of atmospheric moisture stocks and dynamics in the behavior of severe tropical cyclones.

Influence of the Saharan Air Layer on Atlantic tropical cyclone formation during the period 1-12 September 2003

NASA Astrophysics Data System (ADS)

Pan, Weiyu; Wu, Liguang; Shie, Chung-Lin

2011-01-01

Atmospheric Infrared Sounder (AIRS) data show that the Saharan air layer (SAL) is a dry, warm, and well-mixed layer between 950 and 500 hPa over the tropical Atlantic, extending westward from the African coast to the Caribbean Sea. The formations of both Hurricane Isabel and Tropical Depression 14 (TD14) were accompanied with outbreaks of SAL air during the period 1-12 September 2003, although TD14 failed to develop into a named tropical cyclone. The influence of the SAL on their formations is investigated by examining data from satellite observations and numerical simulations, in which AIRS data are incorporated into the MM5 model through the nudging technique. Analyses of the AIRS and simulation data suggest that the SAL may have played two roles in the formation of tropical cyclones during the period 1-12 September 2003. First, the outbreaks of SAL air on 3 and 8 September enhanced the transverse-vertical circulation with the rising motion along the southern edge of the SAL and the sinking motion inside the SAL, triggering the development of two tropical disturbances associated with Hurricane Isabel and TD14. Second, in addition to the reduced environmental humidity and enhanced static stability in the lower troposphere, the SAL dry air intruded into the inner region of these tropical disturbances as their cyclonic flows became strong. This effect may have slowed down the formation of Isabel and inhibited TD14 becoming a named tropical cyclone, while the enhanced vertical shear contributed little to tropical cyclone formation during this period. The 48-h trajectory calculations confirm that the parcels from the SAL can be transported into the inner region of an incipient tropical cyclone.

Impacts of Tropical Cyclones and Accompanying Precipitation on Infectious Diarrhea in Cyclone Landing Areas of Zhejiang Province, China

PubMed Central

Deng, Zhengyi; Xun, Huanmiao; Zhou, Maigeng; Jiang, Baofa; Wang, Songwang; Guo, Qing; Wang, Wei; Kang, Ruihua; Wang, Xin; Marley, Gifty; Ma, Wei

2015-01-01

Background: Zhejiang Province, located in southeastern China, is frequently hit by tropical cyclones. This study quantified the associations between infectious diarrhea and the seven tropical cyclones that landed in Zhejiang from 2005–2011 to assess the impacts of the accompanying precipitation on the studied diseases. Method: A unidirectional case-crossover study design was used to evaluate the impacts of tropical storms and typhoons on infectious diarrhea. Principal component analysis (PCA) was applied to eliminate multicollinearity. A multivariate logistic regression model was used to estimate the odds ratios (ORs) and the 95% confidence intervals (CIs). Results: For all typhoons studied, the greatest impacts on bacillary dysentery and other infectious diarrhea were identified on lag 6 days (OR = 2.30, 95% CI: 1.81–2.93) and lag 5 days (OR = 3.56, 95% CI: 2.98–4.25), respectively. For all tropical storms, impacts on these diseases were highest on lag 2 days (OR = 2.47, 95% CI: 1.41–4.33) and lag 6 days (OR = 2.46, 95% CI: 1.69–3.56), respectively. The tropical cyclone precipitation was a risk factor for both bacillary dysentery and other infectious diarrhea when daily precipitation reached 25 mm and 50 mm with the largest OR = 3.25 (95% CI: 1.45–7.27) and OR = 3.05 (95% CI: 2.20–4.23), respectively. Conclusions: Both typhoons and tropical storms could contribute to an increase in risk of bacillary dysentery and other infectious diarrhea in Zhejiang. Tropical cyclone precipitation may also be a risk factor for these diseases when it reaches or is above 25 mm and 50 mm, respectively. Public health preventive and intervention measures should consider the adverse health impacts from tropical cyclones. PMID:25622139

A Long-lived Cyclone In Saturn's Atmosphere: Observations And Models

NASA Astrophysics Data System (ADS)

Del Rio Gaztelurrutia, Teresa; Legarreta, J.; Hueso, R.; Pérez-Hoyos, S.; Sánchez-Lavega, A.

2009-09-01

The atmospheres of the Giant Planets Jupiter and Saturn possess large numbers of atmospheric vortices. On Jupiter, anticyclones are generally long-lived structures while cyclones survive a much shorter time. A long term survey of images of Saturn atmosphere obtained by the Cassini ISS camera has revealed the presence of a long-lived cyclone in Saturn's southern hemisphere during at least four years, making this vortex the longest lived cyclone on either Jupiter or Saturn. We find that the vortex drifts following the wind profile, with changes in velocity following changes of latitude. During the four years of our survey its size remained essentially constant, and there was no other structure of comparable size at its latitude. Internal circulation is cyclonic, with a maximum velocity of 20±5 m/s and an average vorticity of 4·10-5 s-1, an order of magnitude lower than planetary vorticity, but only slightly higher than the ambient vorticity. Photometric analysis shows that the vortex is located at a slightly lower altitude than its surroundings, at an average of 10-20 mbar below adjacent clouds. Finally, EPIC simulations of the vortex that reproduce its behavior imply a Rossby deformation radius of 2000 km in the weather layer (1 - 10 bar), consistent with the size of the cyclone. The long-lifetime of this cyclonic spot is surprising in view of its low tangential velocity and it suggests that low dissipation conditions prevail at mid-latitudes in Saturn's upper troposphere. Acknowledgements This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07. RH acknowledges a "Ramón y Cajal” contract from MEC.

Fatty acid profiles of phyllosoma larvae of western rock lobster (Panulirus cygnus) in cyclonic and anticyclonic eddies of the Leeuwin Current off Western Australia

NASA Astrophysics Data System (ADS)

Wang, M.; O'Rorke, R.; Waite, A. M.; Beckley, L. E.; Thompson, P.; Jeffs, A. G.

2014-03-01

The recent dramatic decline in settlement in the population of the spiny lobster, Panulirus cygnus, may be due to changes in the oceanographic processes that operate offshore of Western Australia. It has been suggested that this decline could be related to poor nutritional condition of the post-larvae, especially lipid which is accumulated in large quantities during the preceding extensive pelagic larval stage. The current study focused on investigations into the lipid content and fatty acid (FA) profiles of lobster phyllosoma larvae from three mid to late stages of larval development (stages VI, VII, VIII) sampled from two cyclonic and two anticyclonic eddies of the Leeuwin Current off Western Australia. The results showed significant accumulation of lipid and energy storage FAs with larval development regardless of location of capture, however, larvae from cyclonic eddies had more lipid and FAs associated with energy storage than larvae from anticyclonic eddies. FA food chain markers from the larvae indicated significant differences in the food webs operating in the two types of eddy, with a higher level of FA markers for production from flagellates and a lower level from copepod grazing in cyclonic versus anticyclonic eddies. The results indicate that the microbial food web operating in cyclonic eddies provides better feeding conditions for lobster larvae despite anticyclonic eddies being generally more productive and containing greater abundances of zooplankton as potential prey for lobster larvae. Gelatinous zooplankton, such as siphonophores, may play an important role in cyclonic eddies by accumulating dispersed microbial nutrients and making them available as larger prey for phyllosoma. The markedly superior nutritional condition of lobster larvae feeding in the microbial food web found in cyclonic eddies, could greatly influence their subsequent settlement and recruitment to the coastal fishery.

Particulate Characterization and Control Evaluation for Carbon Fiber Composite Aircraft Crash Recovery Operations

DTIC Science & Technology

2010-03-01

Advanced Composite Office, Wright-Patterson BEE Flight, and USAFSAM for their help procuring the materials and supplies needed to perform this study...through the cyclone. (Cohen & Charles S . McCammonn, 2001) The major limitation of the cyclone is that the cut curve of the cyclone does not precisely...If the pump is not precisely calibrated to the specified flow the cut point will be altered. (Cohen & Charles S . McCammonn, 2001) Once the sample

Response of the South China Sea to Forcing by Tropical Cyclone Ernie (1996)

DTIC Science & Technology

1998-03-01

complicated. Wide continental shelves appear in the northwest and southwest of the basin and steep slopes in the central portion, framing a deep, bowl...bottom topography of the SCS basin provides a favorable condition for the formation of anticyclonic eddies in the central SCS during the spring. From...cyclone is produced. This cyclonic wind stress then generates Ekman upwelling in the central basin and the formation of a cold pool. Again, through

Tropical Cyclone Forecasters Reference Guide 2. Tropical Climatology

DTIC Science & Technology

1992-04-01

stratosphere and discovered three periods of oscillation: 1.3.3 1 Quasi-biennial Oscillation (OBO) The QBO in tropical stratospheric winds is defined as a...The QBO may be associated with the seasonal weather activities. Gray (1984a,b) has used the QBO at the 30-mb level as one of the indexes to predict the...yearly number of tropical cyclones in the Atlantic with some success. However, the physical links between cyclone activity and QBO are not clearly

An Interactive Parallel Coordinates Technique Applied to a Tropical Cyclone Climate Analysis

DTIC Science & Technology

2008-06-06

12). 3.4 Quasi-Biennial Oscillation Variable Research has also shown that the Quasi-Biennial Oscillation ( QBO ) is corre- lated to tropical cyclone...activity. The QBO is a stratospheric (16 to 35 km altitude) oscillation of equatorial east-west winds which vary with a period of about 26 to 30 months...again. The west phase of the QBO has been shown to provide favorable conditions for development of tropical cyclones, possibly because it reduces

The influence of an extended Atlantic hurricane season on inland flooding potential in the southeastern United States

NASA Astrophysics Data System (ADS)

Stone, Monica H.; Cohen, Sagy

2017-03-01

Recent tropical cyclones, like Hurricane Katrina, have been some of the worst the United States has experienced. Tropical cyclones are expected to intensify, bringing about 20 % more precipitation, in the near future in response to global climate warming. Further, global climate warming may extend the hurricane season. This study focuses on four major river basins (Neches, Pearl, Mobile, and Roanoke) in the southeastern United States that are frequently impacted by tropical cyclones. An analysis of the timing of tropical cyclones that impact these river basins found that most occur during the low-discharge season and thus rarely produce riverine flooding conditions. However, an extension of the current hurricane season of June-November could encroach upon the high-discharge seasons in these basins, increasing the susceptibility for riverine hurricane-induced flooding. Our results indicate that 28-180 % more days would be at risk of flooding from an average tropical cyclone with an extension of the hurricane season to May-December (just 2 months longer). Future research should aim to extend this analysis to all river basins in the United States that are impacted by tropical cyclones in order to provide a bigger picture of which areas are likely to experience the worst increases in flooding risk due to a probable extension of the hurricane season with expected global climate change in the near future.

Ship and satellite observations of chlorophyll stocks in interacting cyclone-anticyclone eddy pairs in the western Gulf of Mexico

NASA Technical Reports Server (NTRS)

Biggs, Douglas, C.; Mueller-Karger, Frank E.

1994-01-01

When anticyclonic eddies shed by the Loop Current of the Gulf of Mexico reach the western margin of the gulf, they influence the surface circulation over the continental slope and rise. Of particular interest is the generation of cyclone (cold-core)-anticyclone (warm-core) pairs when aging Loop Current eddies interact with the continental margin. In this paper we describe the physical and biological characteristics of these cyclone-anticyclone pairs. Our objective was to determine how eddy pairs affect the distribution of phytoplankton in the region and how satellite ocean color measurements are applicable to tracing of the eddies. We present shipboard data collected between 1980 and 1982 on the hydrography, chlorophyll stocks, and nutrient concentrations of eddy pairs in the western Gulf of Mexico and compare these data with coastal zone color scanner (CZCS) images collected during the time frame of the cruises. Surface pigment concentrations followed a seasonal cycle, with low concentrations (0.05-0.1 mg m(exp -3)) found within cyclones and anticyclones from April through early November and higher concentrations (greater than 0.1 mg(exp -3)) found in the winter. CZCS pigment concentrations were locally high in the flow confluence of cyclone-anticyclone pairs. The CZCS imagery shows that some cyclone-anticyclone geometries transport high-chlorophyll shelf water seaward at least 100-200 km off-shelf.

A simple method for simulating wind profiles in the boundary layer of tropical cyclones

DOE PAGES

Bryan, George H.; Worsnop, Rochelle P.; Lundquist, Julie K.; ...

2016-11-01

A method to simulate characteristics of wind speed in the boundary layer of tropical cyclones in an idealized manner is developed and evaluated. The method can be used in a single-column modelling set-up with a planetary boundary-layer parametrization, or within large-eddy simulations (LES). The key step is to include terms in the horizontal velocity equations representing advection and centrifugal acceleration in tropical cyclones that occurs on scales larger than the domain size. Compared to other recently developed methods, which require two input parameters (a reference wind speed, and radius from the centre of a tropical cyclone) this new method alsomore » requires a third input parameter: the radial gradient of reference wind speed. With the new method, simulated wind profiles are similar to composite profiles from dropsonde observations; in contrast, a classic Ekman-type method tends to overpredict inflow-layer depth and magnitude, and two recently developed methods for tropical cyclone environments tend to overpredict near-surface wind speed. When used in LES, the new technique produces vertical profiles of total turbulent stress and estimated eddy viscosity that are similar to values determined from low-level aircraft flights in tropical cyclones. Lastly, temporal spectra from LES produce an inertial subrange for frequencies ≳0.1 Hz, but only when the horizontal grid spacing ≲20 m.« less

A New Coupled Ocean-Waves-Atmosphere Model Designed for Tropical Storm Studies: Example of Tropical Cyclone Bejisa (2013-2014) in the South-West Indian Ocean

NASA Astrophysics Data System (ADS)

Pianezze, J.; Barthe, C.; Bielli, S.; Tulet, P.; Jullien, S.; Cambon, G.; Bousquet, O.; Claeys, M.; Cordier, E.

2018-03-01

Ocean-Waves-Atmosphere (OWA) exchanges are not well represented in current Numerical Weather Prediction (NWP) systems, which can lead to large uncertainties in tropical cyclone track and intensity forecasts. In order to explore and better understand the impact of OWA interactions on tropical cyclone modeling, a fully coupled OWA system based on the atmospheric model Meso-NH, the oceanic model CROCO, and the wave model WW3 and called MSWC was designed and applied to the case of tropical cyclone Bejisa (2013-2014). The fully coupled OWA simulation shows good agreement with the literature and available observations. In particular, simulated significant wave height is within 30 cm of measurements made with buoys and altimeters. Short-term (< 2 days) sensitivity experiments used to highlight the effect of oceanic waves coupling show limited impact on the track, the intensity evolution, and the turbulent surface fluxes of the tropical cyclone. However, it is also shown that using a fully coupled OWA system is essential to obtain consistent sea salt emissions. Spatial and temporal coherence of the sea state with the 10 m wind speed are necessary to produce sea salt aerosol emissions in the right place (in the eyewall of the tropical cyclone) and with the right size distribution, which is critical for cloud microphysics.

On the movement of tropical cyclone LEHAR

NASA Astrophysics Data System (ADS)

Dasari, Hari Prasad; V, Brahmananda Rao; SSVS, Ramakrishna; Gunta, Paparao; N, Nanaji Rao; P, Ramesh Kumar

2017-12-01

In this paper, an attempt has been made to delineate the physical processes which lead to the westward movement of the North Indian Ocean tropical cyclone LEHAR. The Advanced Weather Research and Forecasting (ARW) model is used to simulate LEHAR with 27 and 9 km resolutions. The results indicate that the model performed well in simulating the characteristics of cyclone compared with the Satellite and other observations. In addition to that all terms of the complete vorticity equation are computed to obtain the contribution of each term for the vorticity tendency. The vorticity tendency is calculated in four sectors, namely northwest, northeast, southwest and southeast and assumed that the cyclone moves from its existing location to the nearest point where the vortices tendency is maximum. It is noticed that the vorticity stretching term contributes most to the positive vorticity tendency. The second highest contribution is from the horizontal advection thus indicating the secondary importance of steering. The distribution of lightening flash rates also showing that the flash rates are higher in the SW and followed by NW sectors of the cyclone indicate more strong convective clouds are in SW sector. The equivalent potential temperatures ( θ e) at different stages of before, during and after the mature stage of the cyclone are also analysed and the analysis reveals that the wind-induced surface heat (WISH) exchange process is a plausible mechanism for the intensification of LEHAR.

Potential of a cyclone prototype spacer to improve in vitro dry powder delivery.

PubMed

Parisini, Irene; Cheng, Sean J; Symons, Digby D; Murnane, Darragh

2014-05-01

Low inspiratory force in patients with lung disease is associated with poor deagglomeration and high throat deposition when using dry powder inhalers (DPIs). The potential of two reverse flow cyclone prototypes as spacers for commercial carrier-based DPIs was investigated. Cyclohaler®, Accuhaler® and Easyhaler® were tested with and without the spacers between 30 and 60 Lmin−1. Deposition of particles in the next generation impactor and within the devices was determined by high performance liquid chromatography. Reduced induction port deposition of the emitted particles from the cyclones was observed due to the high retention of the drug within the spacers (e.g. salbutamol sulphate (SS): 67.89 ± 6.51% at 30 Lmin−1 in Cheng 1). Fine particle fractions of aerosol as emitted from the cyclones were substantially higher than the DPIs alone. Moreover, the aerodynamic diameters of particles emitted from the cyclones were halved compared to the DPIs alone (e.g. SS from the Cyclohaler® at 4 kPa: 1.08 ± 0.05 μm vs. 3.00 ± 0.12 μm, with and without Cheng 2, respectively) and unaltered with increased flow rates. This work has shown the potential of employing a cyclone spacer for commercial carrier-based DPIs to improve inhaled drug delivery.

Estimation of size of tropical cyclones in the North Indian Ocean using Oceansat-2 scatterometer high-resolution wind products

NASA Astrophysics Data System (ADS)

Jaiswal, Neeru; Ha, Doan Thi Thu; Kishtawal, C. M.

2018-03-01

Tropical cyclone (TC) is one of the most intense weather hazards, especially for the coastal regions, as it causes huge devastation through gale winds and torrential floods during landfall. Thus, accurate prediction of TC is of great importance to reduce the loss of life and damage to property. Most of the cyclone track prediction model requires size of TC as an important parameter in order to simulate the vortex. TC size is also required in the impact assessment of TC affected regions. In the present work, the size of TCs formed in the North Indian Ocean (NIO) has been estimated using the high resolution surface wind observations from oceansat-2 scatterometer. The estimated sizes of cyclones were compared to the radius of outermost closed isobar (ROCI) values provided by Joint Typhoon warning Center (JTWC) by plotting their histograms and computing the correlation and mean absolute error (MAE). The correlation and MAE between the OSCAT wind based TC size estimation and JTWC-ROCI values was found 0.69 and 33 km, respectively. The results show that the sizes of cyclones estimated by OSCAT winds are in close agreement to the JTWC-ROCI. The ROCI values of JTWC were analyzed to study the variations in the size of tropical cyclones in NIO during different time of the diurnal cycle and intensity stages.

A Simple Method for Simulating Wind Profiles in the Boundary Layer of Tropical Cyclones

NASA Astrophysics Data System (ADS)

Bryan, George H.; Worsnop, Rochelle P.; Lundquist, Julie K.; Zhang, Jun A.

2017-03-01

A method to simulate characteristics of wind speed in the boundary layer of tropical cyclones in an idealized manner is developed and evaluated. The method can be used in a single-column modelling set-up with a planetary boundary-layer parametrization, or within large-eddy simulations (LES). The key step is to include terms in the horizontal velocity equations representing advection and centrifugal acceleration in tropical cyclones that occurs on scales larger than the domain size. Compared to other recently developed methods, which require two input parameters (a reference wind speed, and radius from the centre of a tropical cyclone) this new method also requires a third input parameter: the radial gradient of reference wind speed. With the new method, simulated wind profiles are similar to composite profiles from dropsonde observations; in contrast, a classic Ekman-type method tends to overpredict inflow-layer depth and magnitude, and two recently developed methods for tropical cyclone environments tend to overpredict near-surface wind speed. When used in LES, the new technique produces vertical profiles of total turbulent stress and estimated eddy viscosity that are similar to values determined from low-level aircraft flights in tropical cyclones. Temporal spectra from LES produce an inertial subrange for frequencies ≳ 0.1 Hz, but only when the horizontal grid spacing ≲ 20 m.

An Estimate of North Atlantic Basin Tropical Cyclone Activity for 2008

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

2008-01-01

The statistics of North Atlantic basin tropical cyclones for the interval 1945-2007 are examined and estimates are given for the frequencies of occurrence of the number of tropical cyclones, number of hurricanes, number of major hurricanes, number of category 4/5 hurricanes, and number of U.S. land-falling hurricanes for the 2008 hurricane season. Also examined are the variations of peak wind speed, average peak wind speed per storm, lowest pressure, average lowest pressure per storm, recurrence rate and duration of extreme events (El Nino and La Nina), the variation of 10-yr moving averages of parametric first differences, and the association of decadal averages of frequencies of occurrence of North Atlantic basin tropical cyclones against decadal averages of Armagh Observatory, Northern Ireland, annual mean temperature (found to be extremely important for number of tropical cyclones and number of hurricanes). Because the 2008 hurricane season seems destined to be one that is non-El Nino-related and is a post-1995 season, estimates of the frequencies of occurrence for the various subsets of storms should be above long-term averages.

An atlas of 1977 and 1978 GEOS-3 radar altimeter data for tropical cyclone studies

NASA Technical Reports Server (NTRS)

Stanley, H. R.; Taylor, R. L.

1980-01-01

All of the GEOS 3 satellite altimeter schedule information were collected with all of the available 1977 and 1978 tropical cyclone positional information. The time period covers from March 23, 1977 through Nov. 23, 1978. The geographical region includes all ocean area north of the equator divided into the following operational areas: the Atlantic area (which includes the Caribbean and Gulf of Mexico); the eastern Pacific area; the central and western Pacific area; and the Indian Ocean area. All available source material concerning tropical cyclones was collected. The date/time/location information was extracted for each disturbance. This information was compared with the GEOS 3 altimeter ON/OFF history information to determine the existence of any altimeter data close enough in both time and location to make the data potentially useful for further study (the very liberal criteria used was time less than 24 hours and location within 25 degrees). Geographic plots (cyclone versus GEOS 3 orbit track) were produced for all of the events found showing the approximate location of the cyclone and the GEOS 3 orbit traces for the full day.