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1

Tropical cyclone formation  

SciTech Connect

The physics of tropical cyclone formation is not well understood, and more is known about the mature hurricane than the formative mechanisms that produce it. It is believed part of the reason for this can be traced to insufficient upper-level atmospheric data. Recent observations suggest that tropical cyclones are initiated by asymmetric interactions associated with migratory upper-level potential vorticity disturbances and low-level disturbances. Favored theories of cyclones formation, however, focus on internal processes associated with cumulus convection and/or air-sea interaction. This work focuses on external mechanisms of cyclone formation and, using both a two- and three-dimensional moist geostrophic momentum model, investigates the role of upper-level potential vorticity disturbances on the formation process. A conceptual model of tropical cyclone formation is proposed, and implications of the theory are discussed. 71 refs., 5 figs., 1 tab.

Montgomery, M.T.; Farrell, B.F. (Harvard Univ., Cambridge, MA (United States))

1993-01-15

2

Exploring Tropical Cyclones  

NSDL National Science Digital Library

This website offers an overview and sample of the Exploring Tropical Cyclones module (the actual module must be purchased). The module introduces students to the dynamic forces generating cyclones by using geographic information system (GIS) software to analyze data sets. Students explore the global distribution of cyclones, then focus in on U.S. hurricane hazards. They complete the module with an investigation of hurricanes in New York City.

3

Predicting tropical cyclone activity  

NASA Astrophysics Data System (ADS)

Tropical cyclones rank as the costliest natural disaster in the United States. They are also the most expensive and deadly natural catastrophe affecting much of southeast Asia. Skilful seasonal and intraseasonal forecasts of tropical cyclone activity can benefit society, business and government by reducing - through the available lead-time - the risk, uncertainty and financial volatility associated with varying active and inactive storm seasons. We review the extended-range prediction of seasonal tropical cyclone activity in the North Atlantic and Northwest Pacific. A number of groups and ventures now issue such forecasts. We compare the methodology and performance of these different models. In particular we examine how they performed in 2002 and, where possible, assess their independent hindcast skill over the period 1987-2001 at monthly leads out to 9 months. We consider the potential for (1) forecasting seasonal tropical cyclone landfalling activity and financial loss for the US, Caribbean Lesser Antilles and southeast Asia, (2) intraseasonal tropical cyclone forecasts. We provide the latest outlooks for tropical cyclone activity in 2003.

Saunders, M. A.

2003-04-01

4

The formation of tropical cyclones  

Microsoft Academic Search

Summary This paper attempts a synthesis of new observations and new concepts on how tropical cyclone formation occurs. Despite many worthy observational and numerical modeling studies in recent decades, our understanding of the detailed physical processes associated with the early stages of tropical cyclone formation is still inadequate; operational forecast skill is not very high. Although theoretical ideas cover a

W. M. Gray

1998-01-01

5

Structure of Developing Tropical Cyclones  

Microsoft Academic Search

Considerable progress has been made in the numerical modeling of tropical cyclones. The very high resolution now routinely used in research models allows realistic simulation of eyewall structure and breakdown, vortex Rossby waves, and numerous other processes that were beyond the capability of previous generations of models. At least one aspect of tropical cyclones, however, has not been reproduced in

J. E. Molinari

2006-01-01

6

Tropical Cyclones 1990-Central North Pacific.  

National Technical Information Service (NTIS)

Contents: Central North Pacific Tropical Cyclone Data, 1990; Tropical Storm AKA; Tropical Storm AKA - 24 Hour Forecast Verification; Tropical Storm AKA - 36 Hour Forecast Verification; Tropical Storm AKA - 48 Hour Forecast Verification; Tropical Storm AKA...

A. K. T. Chun R. T. Martin H. E. Rosendal

1991-01-01

7

Eastern North Pacific Tropical Cyclones, 1972.  

National Technical Information Service (NTIS)

The 1972 tropical cyclone season began in the eastern North Pacific Ocean on May 31 and continued through November 15. Twelve named tropical cyclones developed of which four reached tropical storm intensity and eight reached hurricane strength. A comparis...

1973-01-01

8

Cloudsat tropical cyclone database  

NASA Astrophysics Data System (ADS)

CloudSat (CS), the first 94 GHz spaceborne cloud profiling radar (CPR), launched in 2006 to study the vertical distribution of clouds. Not only are CS observations revealing inner vertical cloud details of water and ice globally but CS overpasses of tropical cyclones (TC's) are providing a new and exciting opportunity to study the vertical structure of these storm systems. CS TC observations are providing first time vertical views of TC's and demonstrate a unique way to observe TC structure remotely from space. Since December 2009, CS has intersected every globally named TC (within 1000 km of storm center) for a total of 5,278 unique overpasses of tropical systems (disturbance, tropical depression, tropical storm and hurricane/typhoon/cyclone (HTC)). In conjunction with the Naval Research Laboratory (NRL), each CS TC overpass is processed into a data file containing observational data from the afternoon constellation of satellites (A-TRAIN), Navy's Operational Global Atmospheric Prediction System Model (NOGAPS), European Center for Medium range Weather Forecasting (ECMWF) model and best track storm data. This study will describe the components and statistics of the CS TC database, present case studies of CS TC overpasses with complementary A-TRAIN observations and compare average reflectivity stratifications of TC's across different atmospheric regimes (wind shear, SST, latitude, maximum wind speed and basin). Average reflectivity stratifications reveal that characteristics in each basin vary from year to year and are dependent upon eye overpasses of HTC strength storms and ENSO phase. West Pacific (WPAC) basin storms are generally larger in size (horizontally and vertically) and have greater values of reflectivity at a predefined height than all other basins. Storm structure at higher latitudes expands horizontally. Higher vertical wind shear (? 9.5 m/s) reduces cloud top height (CTH) and the intensity of precipitation cores, especially in HTC strength storms. Average zero and ten dBZ height thresholds confirm WPAC storms loft precipitation sized particles higher into the atmosphere than in other basins. Two CS eye overpasses (32 hours apart) of a weakening Typhoon Nida in 2009 reveal the collapse of precipitation cores, warm core anomaly and upper tropospheric ice water content (IWC) under steady moderate shear conditions.

Tourville, Natalie D.

9

Observing Guidance for Tropical Cyclones.  

National Technical Information Service (NTIS)

Tropical cyclones (TCs), including hurricanes in the Atlantic and typhoons in the Western Pacific, are of great military and civilian interest around the world. In order to improve the prediction of TC intensity, structure, and track, THe Observing-system...

C. Amerault C. A. Reynolds H. Jin J. D. Doyle

2009-01-01

10

Tropical Cyclones of the North Atlantic Ocean, 1971-1980.  

National Technical Information Service (NTIS)

Contents: Characteristics of tropical cyclones; Classification of Atlantic Tropical Cyclones; Data sources; Accuracy of tracks and intensity classifications; North Atlantic Tropical Cyclone tracks; Frequency of North Atlantic Tropical Cyclones.

C. J. Neumann G. W. Cry E. L. Caso B. R. Jarvinen

1981-01-01

11

North Atlantic Tropical Cyclones, 1972.  

National Technical Information Service (NTIS)

There were just four tropical cyclones in 1972 in the North Atlantic--the lowest total in the past 30 yr. Three of those storms reached hurricane intensity. Agnes, of little concern to mariners, became the most destructive storm in U.S. history. There wer...

R. M. DeAngelis

1973-01-01

12

Digitized Atlantic Tropical Cyclone Tracks.  

National Technical Information Service (NTIS)

A series of 138 maps and diagrams shows both the source regions and eventual disposition of all tropical cyclones passing through unit 2-1/2 degrees latitude-longitude boxes during the 84-year period of record, 1886-1969. Also included are the mean vector...

J. R. Hope C. J. Neumann

1971-01-01

13

Tropical Cyclone Ensemble Data Assimilation.  

National Technical Information Service (NTIS)

The ultimate goal of this project is to demonstrate that in the presence of tropical cyclones (TCs), a multi-scale approach for data assimilation can significantly enhance the analyses and the ensuing forecasts. Our multiscale approach is based on couplin...

I. Szunyogh

2012-01-01

14

Vorticity balance in East Pacific tropical cyclones  

Microsoft Academic Search

There are still questions about how a tropical cyclone develops out of an unorganized region of convection over the tropical oceans. In this study we investigate the evolution of a few cyclones that developed in the East Pacific during the EPIC2001 and IFEX2005 projects. We have analyzed in those cyclones the relative importance of the terms derived from the vorticity

J. Marin; D. J. Raymond; G. B. Raga

2007-01-01

15

Observational Analysis of Tropical Cyclone Formation.  

National Technical Information Service (NTIS)

This study investigates the genesis of tropical cyclones through a combination of the compositing approach and the case study approach. Twelve composite data sets are analyzed from the tropical Northwest Pacific and tropical Northwest Atlantic Oceans. Eac...

J. L. McBride W. M. Gray

1979-01-01

16

Tropical cyclone statistics in the Northeastern Pacific  

Microsoft Academic Search

The principal area of tropical cyclogenesis in the tropical eastern Pacific Ocean is offshore in the Gulf of Tehuantepec, between 8 and 15° N, and most of these cyclones move towards the west and northwest during their initial phase. Historical analysis of tropical cyclone data in the Northeastern (NE) Pacific over the last 38 years (from 1966 to 2004) shows

E. ROMERO-VADILLO; O. ZAYTSEV

2007-01-01

17

Tropical Cyclones 1989 - Central North Pacific.  

National Technical Information Service (NTIS)

Contents: Central north pacific tropical cyclone data 1989; Tropical depression FOUR-E and FIVE-E; Hurricane Dalilia; Hurricane Dalilia - actual vs best track error; Hurricane Dalilia - 24 hour forecast verification; Hurricane Dalilia - 36 hour forecast v...

A. K. T. Chun R. T. Martin H. E. Rosendal

1990-01-01

18

Eastern North Pacific Tropical Cyclones, 1973.  

National Technical Information Service (NTIS)

Tropical cyclone activity in the eastern North Pacific Ocean began June 1 and continued through October 9. It was one of the least active seasons since information from operational satellites, which completely cover the tropical areas, became available to...

1974-01-01

19

Tropical cyclone energy dispersion under vertical shears  

Microsoft Academic Search

Tropical cyclone Rossby wave energy dispersion under easterly and westerly vertical shears is investigated in a baroclinic model. In a resting environment, the model simulates a Rossby wave train that has a baroclinic structure with alternating cyclonic-anticyclonic-cyclonic (anticyclonic-cyclonic-anticyclonic) circulations in the lower (upper) troposphere. A significant asymmetry appears in the wave train development under easterly and westerly vertical shears, that

Xuyang Ge; Tim Li; Xiaqiong Zhou

2007-01-01

20

A View on Tropical Cyclones as CISK  

Microsoft Academic Search

The author's view on tropical cyclones as the conditional instability of the second kind (CISK) is presented. Many theoretical and numerical studies of tropical cyclones have discussed the original CISK of Ooyama (1964, 1969) and Charney and Eliassen (1964) in which frictional convergence plays an important role. In this paper, the author emphasizes that this CISK is applied primarily to

Masanori YAMASAKI

2007-01-01

21

Tropical Cyclones: Central North Pacific, 1994.  

National Technical Information Service (NTIS)

The 1994 Central Pacific tropical cyclone season was a near record year for the Central Pacific Hurricane Center (CPHC). A total of 11 tropical cyclones were observed in the Central Pacific. This total included five hurricanes (Emilia, Gilma, Li, John, an...

A. L. Garza G. H. Trapp B. Hablutzel H. E. Rosendal R. Farrell R. Matsuda J. Hoag

1995-01-01

22

Global trends in tropical cyclone risk  

NASA Astrophysics Data System (ADS)

The impact of tropical cyclones on humans depends on the number of people exposed and their vulnerability, as well as the frequency and intensity of storms. How will the cumulative effects of climate change, demography and vulnerability affect risk? Conventionally, reports assessing tropical cyclone risk trends are based on reported losses, but these figures are biased by improvements to information access. Here we present a new methodology based on thousands of physically observed events and related contextual parameters. We show that mortality risk depends on tropical cyclone intensity, exposure, levels of poverty and governance. Despite the projected reduction in the frequency of tropical cyclones, projected increases in both demographic pressure and tropical cyclone intensity over the next 20 years can be expected to greatly increase the number of people exposed per year and exacerbate disaster risk, despite potential progression in development and governance.

Peduzzi, P.; Chatenoux, B.; Dao, H.; de Bono, A.; Herold, C.; Kossin, J.; Mouton, F.; Nordbeck, O.

2012-04-01

23

Source of microbaroms from tropical cyclone waves  

NASA Astrophysics Data System (ADS)

Microbaroms are continuous infrasonic signals with a dominant frequency around 0.2 Hz produced by ocean surface waves. Monitoring stations around the globe routinely detect strong microbaroms in the lee of tropical cyclones. We utilize a parametric wind model and a spectral wave model to construct the tropical cyclone wave field and a theoretical acoustic source model to describe the intensity, spatial distribution, and dynamics of microbarom sources. This approach excludes ambient wave conditions and facilitates a parametric analysis to elucidate the source mechanism within the storm. A stationary tropical cyclone produces the strongest microbarom signals at the center, where the waves generated by the cyclonic winds converge. As the tropical cyclone moves forward, the converging wave field becomes less coherent and lags and expands behind the storm center. The models predict a direct relation between the storm forward speed and the location of maximum microbarom source intensity consistent with the infrasonic observations from Hurricane Felicia 2009 in the North Central Pacific.

Stopa, Justin E.; Cheung, Kwok Fai; GarcéS, Milton A.; Fee, David

2011-03-01

24

How can tropical cyclones survive?  

NASA Astrophysics Data System (ADS)

How can tropical cyclones survive? It is important for understanding the development of tropical cyclones to be able to quantify the exchange of enthalpy and momentum between air and water. Air-sea fluxes are often formulated as drag CD and enthalpy CK exchange coefficients. Emanuel, 1986, derived an expression for potential intensity that depends on local environment parameters and is proportional to the ratio of enthalpy and drag coefficients. This ratio should be larger than 0.75 for a cyclone to develop. There are no direct surface measurements of CK/ CD under hurricane conditions and extrapolation from most open-ocean measurements at 25 m/s gives values of CK/ CD< 0.75 and in that case no cyclone could survive and Emanuel's theory must be wrong. However there are measurements of CK taken over the Baltic Sea and Lake Ontario showing increasing values of CK up to 2.5 for wind speeds around 12 m/s. If this can be implemented for hurricane conditions the ratio CK/ CD>0.75 is in accordance with Emanuel's prediction. The high CK values are observed during situations when there is a regime shift of the structure of turbulence in the boundary layer. From spectral analysis it was found that as the boundary layer approaches neutral stratification, smaller-scale eddies become increasingly important in the turbulent transport of humidity and sensible heat and thus enhance the exchange coefficient CK. This turbulence regime is called the UVCN regime and require high wind speed, small temperature difference between air and water, sufficiently strong wind gradients and growing sea condition ( Smedman et al., 2007, Sahlee et al., 2008). What is the difference between world oceans and enclosed seas? The answer is the waves. The wave field over the open oceans is swell dominated but in enclosed seas and coastal areas swell is restricted mainly to low wind speed conditions, and swell is short lived because of short distances to the shores. When swell is present the MABL will be dominated by large eddies of zi size creating weak gradients of wind, temperature and humidity and thus small scale eddies cannot be formed leading to reduced CK-values. However, during hurricane condition the waves are expected to be young, stratification is close to neutral and gradients are sufficiently large to generate UVCN condition and thus increased CK values. References: K. A. Emanuel, 1986: An air-sea interaction theory for tropical cyclones, part I: Steady-state maintenance, J. Atmos. Sci., 43,585-604 E. Sahlee et al., 2008: Reevaluation of bulk exchange coefficient for humiditu at sea during unstable and neutral conditions, DOI:10.1175/2007JPO3754.1 A. Smedman, 2007: Heat/mass transfer in the slightly unstable atmospheric surface layer,Quart. J. Meteorol. Soc., 133, 37-51

Smedman, Ann-Sofi

2013-04-01

25

Diagnosis of the interaction of tropical cyclones  

Microsoft Academic Search

At present the mutual influence of tropical cyclones (TCs) has been investigated to a much lesser extent than the cyclones\\u000a themselves. Most frequently, such investigations are restricted to the study of the influence of the interaction of two TCs\\u000a on their motion. However, actually, the mutual influence of TCs is much more diverse. For example, each cyclone alters the\\u000a state

M. I. Yaroshevich; L. Kh. Ingel’

2006-01-01

26

NOAA Paper: Tropical Cyclone Heat Potential  

NSDL National Science Digital Library

At this website, NOAA's Physical Oceanography Division illustrates its research dealing with the predictions of sudden tropical cyclone intensification through the monitoring of the upper ocean thermal structure. Students can learn about the utilization of a two-layer reduced gravity ocean model to determine the relationship between the dynamic height and the mass field of the ocean. Scientists can find out how, through the examination of seven tropical cyclone basins, the division found in an association between the tropical cyclone intensity and a raise in the value of tropical cyclone heat potentials (TCHP). After viewing the examples of the intensification for three hurricanes and one typhoon, users can find daily maps of the latest TCHP, sea surface temperatures, sea height anomalies, and more. Scientists looking for long term statistics can find weekly maps and data from October 1992 to the present.

27

Typhoon Vamei: An equatorial tropical cyclone formation  

NASA Astrophysics Data System (ADS)

Due to the diminishing Coriolis effect, the belt 300 km either side of the equator has been considered tropical cyclone-free. Typhoon Vamei, which developed near Singapore on 27 December 2001, was the first recorded tropical cyclone formation within 1.5 degrees of the equator. The development was the result of two interacting systems, a weak Borneo vortex that drifted into the southern tip of the South China Sea and remained there for four days, and a strong and persistent cold surge that created the large background cyclonic vorticity at the equator. The probability of a similar equatorial development is estimated to be once every 100-400 years.

Chang, C.-P.; Liu, Ching-Hwang; Kuo, Hung-Chi

2003-02-01

28

Tropical Cyclones, Sea Surface Temperature, and Beyond  

NSDL National Science Digital Library

Part 1 The SAGUARO Exploring GIS Investigations for Earth Science curriculum requries the use of ESRI's ArcViewà GIS software version 3.0 for Macintosh or 3.2 and higher for PC. Use ArcGIS and data files from the SAGUARO Project's (http://www.scieds.com/saguaro/etc.html) Exploring Tropical Cyclones investigations. After the students are introduced to the program they are asked to determine what criteria are required for the formation of tropical cyclones. Exploring Tropical Cyclones Unit 1 has a great deal of data for the students to use. The data is presented as layers on a world map. Different features can be turned on and off at will, and layers can be brought in from other units if desired. Features they can work with are: August SST February SST tropical cyclone tracks locations of tropical cyclone formation for Jun-Sep locations of tropical cyclone formation for Dec-Mar Part 2 Students are divided into small groups (3-4 students works well) where they compare their findings (including what evidence they used) with the findings of the other group members. Each group is then asked to determine the threshold temperature for tropical cyclone formation as well as to calculate the area of the ocean that has SST equal to or above this threshold temperature (you can have them calculate this for each season, or as a total area including both February and August data). Part 3 Class discussion of what they have found so far. Introduce them to model predictions of SST for different atmospheric CO2 levels. Propose a 2 degree C increase in tropical SST and ask what they think that will mean. What other factors might influence the formation of tropical cyclones? Part 4 Assign an article or two (ideally a published peer reviewed article - to introduce them to this type of scientific writing - that is if you can find one that you consider appropriate for your students) that introduces them to other factors required for tropical cyclone formation and predictions of how climate change might affect them. For example an article that discusses the role of wind speed near the surface of the ocean, or vertical wind shear, or one that shows that the threshold temperature is actually predicted to increase by the same magnitude as the SST increase. Have them write a report that summaries the criteria for cyclogenesis as well as explaining how they would go about predicting where tropical cyclones will form as a result of an increased SST. They do not need to perform all of the tests they propose! They should state what sort of information they would like to obtain and why.

Schmitt, Danielle

29

Classifying dynamical forcing mechanisms using a climatology of extratropical cyclones  

NASA Astrophysics Data System (ADS)

A climatology of almost 700 extratropical cyclones is compiled by applying an automated feature-tracking algorithm to a database of objectively identified cyclonic features. Cyclones are classified according to the relative contributions to the midlevel vertical motion of the forcing from upper and lower levels averaged over the cyclone intensification period (average U/L ratio) and also by the horizontal separation between their upper-level trough and low-level cyclone (tilt).The frequency distribution of the average U/L ratio of the cyclones contains two significant peaks and a long tail at high U/L ratio. Although discrete categories of cyclones have not been identified, the cyclones comprising the peaks and tail have characteristics that have been shown to be consistent with the type A, B and C cyclones of the threefold classification scheme. Using the thresholds in average U/L ratio determined from the frequency distribution, type A, B and C cyclones account for 30%, 38% and 32% of the total number of cyclones respectively. Cyclones with small average U/L ratio are more likely to be developing cyclones (attain a relative vorticity ?1.2 × 10-4s-1) whereas cyclones with large average U/L ratio are more likely to be non-developing cyclones (60% of type A cyclones develop whereas 31% of type C cyclones develop). Type A cyclogenesis dominates in the development region east of the Rockies and over the Gulf Stream, type B cyclogenesis dominates in the region off the east coast of the USA, and type C cyclogenesis is more common over the oceans in regions of weaker low-level baroclinicity.

Gray, S. L.; Dacre, H. F.

2006-04-01

30

Potential Vorticity Analysis of Tropical Cyclone Intensification  

Microsoft Academic Search

The interaction of marginal Tropical Storm Danny (1985) with an upper-tropospheric positive potential vorticity anomaly was examined. The intensification mechanism proposed earlier for mature Hurricane Elena appears to be valid for Danny as well, despite significant differences in the synoptic-scale environment and in the stage of the tropical cyclone prior to the interaction. Both storms experienced rapid pressure falls as

John Molinari; Steven Skubis; David Vollaro; Frank Alsheimer; Hugh E. Willoughby

1998-01-01

31

DETAIL OF CYCLONE CLASSIFIER, WITH MARCY NO. 86 BALL MILL ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

DETAIL OF CYCLONE CLASSIFIER, WITH MARCY NO. 86 BALL MILL BELOW AND BEHIND IT. STRAIGHT HORIZONTAL PIPE IS SLIME FEED FROM ROD MILL. PIPE OUT TOP OF CYCLONE AND CURVING AT LOWER RIGHT CARRIED FINELY GROUND SLIME TO FLOTATION CONDITIONER TANK. PIPE NOT VISIBLE OUT BOTTOM OF CYCLONE CONVEYED COARSER SLIME TO BALL MILL. - Shenandoah-Dives Mill, 135 County Road 2, Silverton, San Juan County, CO

32

LANDFALLING TROPICAL CYCLONES NEAR HONG KONG IN 1999 AND 2000  

Microsoft Academic Search

The major challenge in predicting landfalling tropical cyclones lies in forecasting their intensity change, landing location and the rainfall they bring. To enable weather forecasters to provide timely warnings for these tropical cyclones, instrument observations and numerical weather prediction products are indispensable. In 1999, a total of four tropical cyclones, three of them of typhoon strength, directly hit Hong Kong.

C. M. Cheng; K. C. Tsui; B. Y. Lee

33

Wind speeds in tropical cyclones and associated insurance losses  

Microsoft Academic Search

This paper reviews the characteristics of wind speeds in tropical cyclones revealed by data from modern automatic weather stations, dropwindsondes, and Doppler radar in the United States. In general winds in tropical cyclones are found to possess the same relationships between surface and gradient speeds as extra-tropical cyclones and the same level of gustiness. Relationships between wind speeds and insurance

P. R. Sparks

2003-01-01

34

Raindrop Size Distribution Measurements in Tropical Cyclones  

NASA Astrophysics Data System (ADS)

Measurements of the raindrop size distribution (RSD) have been collected in tropical cyclones and hurricanes with an impact type disdrometer during the past three Atlantic hurricane seasons. The measurements were taken at Wallops Island, Virginia, Lafayette, Louisiana, and Orlando, Florida. The RSDs from the remnants of tropical cyclones or hurricanes at 40 dBZ agreed well with each other where the mean mass diameter was 1.65-1.7 mm, and the total concentration had a range of 600 to 800 drops/m3. Assuming the normalized gamma size distribution, the shape parameter will be 5-8 to satisfy the observed rain rate of 18-20 mm/hr. If the observations were taken during the extratropical phase of the storm where the tropical cyclone merges with a frontal system, the composite spectra at 40 dBZ include more large drops and less small to mid-size drops, typical for continental thunderstorms. Thus, the mean mass diameter was larger, while total concentration, and rain rate was less in extratropical cyclones than in tropical cyclones.

Tokay, A.; Bashor, P. G.; Habib, E.; Kasparis, T. C.

2006-12-01

35

Real-time superensemble tropical cyclone prediction  

Microsoft Academic Search

This study addresses the improvement of forecasting tropical cyclones (TCs) using ensemble forecasting techniques. The methodology for these forecasts is called the multi-model superensemble. This statistical method makes use of the real-time forecasts provided by a number of operational and research models to construct the superensemble forecasts. This method divides the forecast time line into two phases: a training phase

Charles Eric Williford

2002-01-01

36

Tropical Cyclones, Central North Pacific, 1992.  

National Technical Information Service (NTIS)

The Central Pacific Hurricane Center had one of its most active seasons in 1992, working a total of 11 tropical cyclones. Three of the systems became full blown hurricanes in or prior to entering the central Pacific. The season started on January 28 with ...

A. K. T. Chun R. T. Martin H. E. Rosendal G. H. Trapp

1993-01-01

37

Nuclear power plant risk from tropical cyclones  

SciTech Connect

Tropical cyclones are considered to have a potential for contributing to the overall core-melt frequency at Turkey Point. A tropical cyclone is known to have the four main hazards associated with it: wind, tidal surge, wind-generated missiles, and precipitation. To understand the contribution to overall core-melt risk at Turkey Point, it is essential to understand the mechanisms of these hazards and their relative importance. The results are bounded by the hurricane surge scenario, where the frequency of core melt is equal to the frequency of the surge reaching 19 ft NGVD (National Geographic Vertical Datum). This could be mitigated by potential recovery actions for the tropical cyclone scenario. The probability of the storm surge reaching 19 ft NVGD is estimated to be 1 x 10{sup {minus}4}. The data associated with the tropical cyclones as discussed in detail in the body of this paper are lacking in quantity and quality. By taking the conservative approach in creating the wind/frequency, wind/surge, and surge/frequency relationships, the conclusion that the results are worst case is reasonable. With this in mind, it is logical to conclude that the value of further hazard analysis to narrow down the built-in conservative margin using the existing data and technology is doubtful. Thus, a recovery approach to driving the risk level down is the most pragmatic step to be taken.

Gilmore, T.F. (Florida Power and Light Co., Juno Beach (United States))

1991-01-01

38

South Indian Tropical Cyclone Vector Mean Charts.  

National Technical Information Service (NTIS)

The paper presents resultant directions and distances for tropical cyclone movements in the South Indian Ocean. Charts present the movements for separate five-degree latitude-longitude areas, for five seasons and for six time intervals. In addition, the c...

H. L. Crutcher M. L. Nicodemus

1973-01-01

39

Hydrological Budgets of Landfalling Tropical Cyclones  

Microsoft Academic Search

Floods are among the most destructive forces of nature, costing human lives and property. In order to study the causes and effects of flooding, characteristics of meteorology and hydrology must be combined. The purpose of this study is to examine tropical cyclone-induced flooding and simulate river characteristics to aid in flood forecasting. The Florida State University Global Spectral Model (FSUGSM)

Tamara Ann Lyttek

2004-01-01

40

Tropical Cyclones (1980) - Central Pacific.  

National Technical Information Service (NTIS)

Tropical Storm Carmen and Hurricane Kay are described and their tracks are charted. Tropical Storm Carmen began as an active cluster of convective activity centered near 04N 178W on April 3, 1980. It became a Tropical Depression as it showed a drift towar...

A. K. T. Chun

1981-01-01

41

Tornadoes Associated with Cyclones of Tropical Origin-Practical Features  

Microsoft Academic Search

The frequency of reports of tornadoes associated with tropical cyclones is shown to have increased during the past decade to a level worthy of professional attention.Tornado incidence is demonstrated to be related to the direction of movement of the tropical cyclone, and to the intensity of the cyclone as it approaches the coast. A heading slightly cast of north is

E. L. Hill; William Malkin; W. A. Schulz Jr.

1966-01-01

42

Tropical Cyclones: Hurricane Mitch Fact Sheet  

NSDL National Science Digital Library

Hurricane Mitch developed in the Caribbean Sea in October 1998 and became one of the strongest and deadliest Atlantic hurricanes ever recorded. Some of the details of the hurricane and its effects are summarized including its origin, life cycle, records, and cost. Links lead to five images, including a distant view on 26 October 1998, a close up on 26 October 1998, a movie loop from tropical wave to extra-tropical storm (19 October to 07 November), the observed track from 23 October to 06 November and the observed tracks of all Atlantic tropical cyclones in 1998. Additional links lead to sites for more meteorological and humanitarian information.

43

Some interrelations between the stages of development of tropical cyclones  

Microsoft Academic Search

Energy interdependence between groups of tropical cyclones separated by time intervals of cyclonic “calm” is investigated.\\u000a A linear negative interrelation between the total powers of such groups is revealed. The groups consist of real tropical cyclones\\u000a that occurred within the active cyclonic zone in the northwestern Pacific. The corresponding regression relationships are\\u000a obtained. Interrelation between the stages of development of

M. I. Yaroshevich

2007-01-01

44

Tropical Cyclones - Central Pacific (1981).  

National Technical Information Service (NTIS)

Brief descriptions are given of Tropical Storm Greg (August 20-22, 1981) and Tropical Storm Jova (September 18-20, 1981) which took place in the Central Pacific. Verification statistics show that the 24-hour Central Pacific Hurricane Center (CPHC) forecas...

A. K. T. Chun

1982-01-01

45

Ocean barrier layers' effect on tropical cyclone intensification  

PubMed Central

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.

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

2012-01-01

46

On some interrelations in the dynamics of tropical cyclonic activity  

Microsoft Academic Search

A chronological series of tropical cyclones is a flow of cyclonic activity where the bursts and calms of cyclonic activity\\u000a alternate. Some interrelations between the stages of cyclonic activity have been studied. We derive the dependence that the\\u000a length of the time interval between two consecutive of bursts of cyclonic activity have on a number of parameters of the first

M. I. Yaroshevich

2011-01-01

47

Wind, terrain and structural damping characteristics under tropical cyclone conditions  

Microsoft Academic Search

A large number of buildings and structures, including some well-engineered structures, have been reported to be damaged during tropical cyclones. This stresses the need to study the various characteristics of tropical cyclone winds. A full-scale field experiment on a 52 m tall steel lattice tower has been undertaken to study the wind, terrain and structural characteristics under normal and tropical

J. Shanmugasundaram; P. Harikrishna; S. Gomathinayagam; N. Lakshmanan

1999-01-01

48

Sensitivity of Tropical-Cyclone Models to the Surface Drag Coefficient.  

National Technical Information Service (NTIS)

Motivated by recent developments in tropical-cyclone dynamics, this paper reexamines a basic aspect of tropical-cyclone behaviour, namely, the sensitivity of tropical-cyclone models to the surface drag coefficient. Previous theoretical and numerical studi...

M. T. Montgomery R. K. Smith S. V. Nguyen

2010-01-01

49

Tropical Cyclones and the Carbon Cycle  

NASA Astrophysics Data System (ADS)

The relationship between tropical cyclones and the carbon cycle poses an interesting question: tropical surface waters are generally quite warm and poor in nutrients, but the mixing in tropical cyclones entrains potentially large amounts of cold, nutrient-rich water. As the cold anomaly warms, there is a tendency toward over-saturation of carbon dioxide, and thus a net outgassing from the ocean to the atmosphere, but because nutrients are mixed into the photic zone, there is a simultaneous phytoplankton bloom which removes carbon from the mixed layer. The amount of carbon taken up into biota by the induced biological activity can in some cases create a net undersaturation of carbon dioxide in spite of the warming of entrained cold water, and therefore cause a net ingassing of carbon in the wake of a tropical cyclone. This is, however, only a short-term effect. Phytoplankton have a short life cycle, and the detritus they leave behind sinks and remineralizes; that which remineralizes below the climatological mixed layer represents a long-term sink of carbon from the atmosphere to the mixed layer, but the remainder will quickly return to the atmosphere. Both the warming of the mixed layer and the induced phytoplankton bloom are easily observable, but neither the sign nor the magnitude of the net effect is intuitive. To illuminate the question, a simple one-dimensional model is formulated which simulates the behavior of the upper few hundred meters of the ocean in response to tropical cyclone-induced mixing. Phytoplankton (and its remains), Nitrate, and Dissolved Inorganic Carbon are tracked, and the model is both initialized and forced with the best possible approximation to real chemical concentrations, winds, and heat fluxes, and the effect of the storm is estimated by comparing model behavior with the storm included and with the storm removed from observations. It is shown that the model performs acceptably well compared to such observations as exist. The model is then used to estimate the net flux of carbon between the deep ocean and the atmosphere for a large number of tropical cyclones around the world over the period 1999-2007. It is found that while in a few cases there is a large flux of carbon from the atmosphere to the deep ocean due biological sinking, for a large majority of storms the effect is quite small. For storms to cause a large carbon sink, they must be rather strong, and they must pass over a region of ocean with a both shallow nutricline and a relatively low stratification. While Typhoon Chanchu, which passed through the South China Sea in 2006, caused a large and well-studied sink of carbon that gave some initial cause for optimism that tropical cyclones might in general cause a similar effect, it now appears that such events are both too infrequent and cover too small an area to be a critical part of the carbon cycle in the current climate. It is reasoned that this may not necessarily be the case for previous climates with many more and stronger tropical cyclones, e.g. the early Pliocene.

Zimmerman, N. L.; Emanuel, K.

2010-12-01

50

Ocean Barrier Layers’ Effect on Tropical Cyclone Intensification  

SciTech Connect

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.

Balaguru, Karthik; Chang, P.; Saravanan, R.; Leung, Lai-Yung R.; Xu, Zhao; Li, M.; Hsieh, J.

2012-09-04

51

Effect of Ocean Barrier Layers on Tropical Cyclone Intensification  

NASA Astrophysics Data System (ADS)

Improving tropical cyclone forecasts and mitigating its destructive potential require the knowledge of various environmental factors that influence the cyclone's path and intensity. While information of upper ocean thermal structure has been shown to augment the intensity forecast, the idea that upper ocean salinity can also play a role has been hitherto untested at a global scale. Here, using a variety 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 reduces the storm induced vertical mixing and sea surface temperature cooling. This causes an increase in enthalpy heat flux from the ocean to the atmosphere and consequently an intensification of tropical cyclones. On average, tropical cyclone intensification rate is nearly five times higher over regions with Barrier Layers, as compared to regions without. Our finding underscores the importance of observing not only the upper ocean thermal but also the salinity structure in the regions of deep tropical Barrier Layers, in order to improve ocean state estimates and modeling of Barrier Layer processes, which may prove to be important keys to more skillful prediction of tropical cyclone intensities. As the hydrological cycle may change under global warming, associated Barrier Layer changes need to be considered in projecting future tropical cyclone activity.

Balaguru, K.; Chang, P.; Saravanan, R.; Leung, L. R.; Xu, Z.; Li, M.; Hsieh, J.-S.

2012-04-01

52

Tropical Cyclones of the North Atlantic Ocean, 1871 - 1977.  

National Technical Information Service (NTIS)

Over the 107-year period 1871 through 1977, a total of 850 tropical cyclones (tropical storms and hurricanes) of various intensities have been recorded over the North Atlantic area. The information given in this edition consists of the following: charater...

C. J. Neumann G. W. Cry E. L. Caso B. R. Jarvinen

1978-01-01

53

A Climatology of the Extratropical Transition of Atlantic Tropical Cyclones  

Microsoft Academic Search

A comprehensive climatology of extratropically transitioning tropical cyclones in the Atlantic basin is pre- sented. Storm tracks and intensities over a period from 1899 to 1996 are examined. More detailed statistics are presented only for the most reliable period of record, beginning in 1950. Since 1950, 46% of Atlantic tropical cyclones transitioned to the extratropical phase. The coastal Atlantic areas

Robert E. Hart; Jenni L. Evans

2001-01-01

54

An Evaluation of the Precipitation Distribution in Landfalling Tropical Cyclones  

Microsoft Academic Search

Often, precipitation forecasts associated with landfalling tropical cyclones are based on a simple algorithm where the maximum 24-h precipitation (in inches) is forecast by 100\\/v, where v (in m.p.h.) is the translational speed of the cyclone. This algorithm, however, provides little insight as to the precipitation distribution and intensity that can be expected in a landfalling tropical cyclone. Furthermore, several

Eyad H. Atallah; Lance F. Bosart

2004-01-01

55

Tropical Cyclone Boura on November 17, 2002  

NSDL National Science Digital Library

Tropical Cyclone Boura approaches Madagascar on November 17, 2002. The storm has intensified over night. The rain structure is depicted with 5 different isosurfaces. The first isosurface is grey and depicts areas with 0.5 inches of rain per hour. The second is light blue and reflects 1.0 inches of rain per hour. THe third is green and shows 1.7 inches of rain per hour. The forth is yellow and represents 2.0 inches of rain per hour. The last isosurface is red and shows 2.2 inches or more of rain per hour.

Perkins, Lori; Halverson, Jeff

2002-11-21

56

Tropical cyclone effects on Arctic Sea ice variability  

NASA Astrophysics Data System (ADS)

In recent years increasing interest has been put on the role that intense Tropical Cyclones can play in the climate system. The following study is aimed at highlighting the effects of strong Tropical Cyclones over the Tropical Atlantic on the mean climate. Their composite effect on the surface winds is made apparent by a wide cyclonic perturbation that affects a large portion of the Atlantic tropical Ocean. Teleconnection patterns, which are visible in the Sea Level Pressure anomalies associated with this Tropical Composite Cyclone, appear to link the activity of the hurricanes to the Arctic Ocean. A significant negative correlation between the energy dissipated by hurricanes in the Tropical atmosphere and the sea ice cover along the Transpolar Drift Stream path, has also been found.

Scoccimarro, Enrico; Gualdi, Silvio; Navarra, Antonio

2012-09-01

57

Tropical Cyclone Structure and Intensity Change.  

NASA Astrophysics Data System (ADS)

This paper is concerned with two basic areas in the study of tropical cyclones: (a)structure and (b)genesis and intensity change. Utilizing the compositing approach, fourteen years (1961-1974) of northwest Atlantic rawinsonde soundings are analyzed to obtain the basic thermodynamic and wind fields of the hurricane. A comparison is undertaken of the basic structure of the composited west Atlantic hurricane and the west Pacific typhoon as reported by Frank (1977a, b). Similarities and differences are discussed. In order to investigate differences which lead to tropical cyclone genesis and intensification, eighteen Atlantic and Pacific data sets are also composited and divided into two groups: (a)deepening and (b)filling/steady systems. Deepening systems are found to have supergradient winds in the lower troposphere and less subgradient winds in the upper levels than filling/steady disturbances. The thermal wind equation indicates that an imbalance exists such that deepening systems have larger vertical tangential wind shear (WS) than baroclinicity. The opposite is true of filling systems. A genesis and intensification mechanism is proposed based on the adjustment of the baroclinicity to the imbalance in the vertical shear of the tangential wind. This mechanism agrees with the work of Silva Dias and Schubert (1979) and Schubert et al. (1980) which shows that in the tropics --where the Rossby radius of deformation is large--the temperature field adjusts to the wind field. It is suggested that the initial imbalance results from alterations of the disturbance's rotational part of the wind caused by the large-scale flow. Cumulus clouds and vertical mass recycling occurring in this favorable initial vertical shear are thought to maintain and increase the original imbalance. The system tries to reach a balanced state by increasing the baroclinicity (B) in order to balance the larger vertical wind shear (WS). Intensification is produced as the inner area of the disturbance warms. Intensification continues as long as the imbalance is maintained. Under unfavorable vertical shears, cumulus activity acts to reduce vertical wind shear causing a decrease in the baroclinicity and weakening. A primary finding of this research is the documentation of the important role of cumulus convection in the rearrangement of horizontal momentum. This rearrangement of momentum in the radial and tangential direction is estimated to be of fundamental importance to an understanding of tropical cyclone structure, genesis, and intensification. Qualitative arguments are employed to show how cumulus updraft and downdraft action can produce such momentum alteration.

Nunez, Edwin

58

On the Wavelength of the Rossby Waves Radiated by Tropical Cyclones  

Microsoft Academic Search

The authors present a theory for the zonal wavelength of tropical depression-type disturbances, which occur as a result of Rossby wave radiation from a preexisting tropical cyclone (TC). In some cases, such disturbances undergo tropical cyclogenesis, resulting in a pair of tropical cyclones; the theory then predicts the zonal separation distance of such tropical cyclone pairs. Numerical experiments are presented

Kyle D. Krouse; Adam H. Sobel; Lorenzo M. Polvani

2008-01-01

59

Tropical Cyclone Crystal on December 25, 2002  

NSDL National Science Digital Library

Tropical Cyclone Crystal approaches the island of Mauritius in the Indian Ocean. The storm packed sustained winds of 80 miles per hour with gusts up to 96 miles per hour. Mauritius is situated east of Madagascar off of the Africas southeastern coast. This animation shows the storms rain structure with 5 different isosurfaces. The first isosurface is grey and depicts areas with 0.5 inches of rain per hour. The second is light blue and reflects 1.0 inches of rain per hour. The third is green and shows 1.7 inches of rain per hour. The forth is yellow and represents 2.0 inches of rain per hour. The last isosurface is red and shows 2.2 inches or more of rain.

Perkins, Lori; Halverson, Jeff

2002-12-30

60

Tropical cyclones as a possible factor affecting seismic activity in the cyclonic zone of the northwestern Pacific  

Microsoft Academic Search

A possible influence of tropical cyclones on seismic activity in the cyclonic zone of the northwestern Pacific is considered.\\u000a There is no direct and sufficiently reliable method for calculating the degree of impact of tropical cyclones on the Earth’s\\u000a crust. Therefore, a sort of inverse problem is solved in the investigation: a possible qualitative influence of tropical cyclones\\u000a on seismic

M. I. Yaroshevich

2011-01-01

61

Guidelines for Disaster Prevention and Preparedness in Tropical Cyclone Areas.  

National Technical Information Service (NTIS)

Following a general introduction and background information, forecasts and warnings of tropical cyclones, river floods, and storm surges are reviewed. The role of disaster prevention in national planning is discussed together with legislation for disaster...

1977-01-01

62

Sea Surface Signature of Tropical Cyclones Using Microwave Remote Sensing.  

National Technical Information Service (NTIS)

Measuring the sea surface during tropical cyclones (TC) is challenging due to severe weather conditions that prevent shipboard measurements and clouds which mask the sea surface for visible satellite sensors. However, sea surface emission in the microwave...

B. Kil D. Burrage J. Wesson S. Howden

2013-01-01

63

Extra-tropical cyclone and climate (Alfred Wegener Medal lecture)  

NASA Astrophysics Data System (ADS)

Extra-tropical cyclones play a key role in the climate system in effectively transporting heat, water vapour and momentum towards higher latitudes. The main energy source of extra-tropical cyclones is the available potential energy of the atmosphere first recognized by Max Margules in the beginning of the last century but clarified much later in a series of papers by Edward Lorenz. With the assumption that the initial state is well determined present weather prediction models are able to predict the development of extra-tropical systems several days in advance and this is one of the reasons to the large improvement in weather forecasting in recent years. Whilst our knowledge of extra-tropical cyclones has continued to improve several questions requires a better scientific understanding. One of these is the mutual interaction between transient cyclones and the large-scale quasi-stationary pattern of the atmospheric circulation such as blocking. Another important issue is the possible change in extra-tropical cyclones in a warmer climate. This might come about through changes in the storm tracks or in changes in extreme cyclones. In my presentation I will present some recent results based on the assessment of storm tracks and the evolution of cyclones in high-resolution global models in the present and future climate using a Lagrangean approach.

Bengtsson, L.

2009-04-01

64

Sensitivity of tropical cyclone models to the surface exchange coefficients  

Microsoft Academic Search

Motivated by recent developments in tropical cyclone dynamics, this paper examines the sensitivity of tropical-cyclone models to the surface exchange coefficients of momentum and heat (enthalpy) in a three-dimensional, non-hydrostatic, and cloud-representing context. Previous theoretical and numerical studies of the sensitivity in axisymmetric models have found that the intensity decreases markedly with increasing drag coefficient. Contrary to prior theoretical studies

Michael T. Montgomery; Roger K. Smith; Sang V. Nguyen

65

Relationship between Tropical Atlantic sea surface temperature variability and southern Indian Ocean tropical cyclones  

NASA Astrophysics Data System (ADS)

Recent studies have found that tropical Atlantic sea surface temperature (SST) variability may be influencing tropical Indian Ocean climate. Due to the economic and social impact of tropical cyclones, it is important to investigate how an Atlantic-Indian Ocean connection may be affecting tropical cyclone behavior in the southern Indian Ocean. In this study, the International Best Track Archive for Climate Stewardship (IBTrAC) tropical cyclone database is used to derive metrics of tropical cyclone behavior, which are then compared with an index of tropical Atlantic SST variability. Changes in tropical Atlantic SSTs are found to coincide with significant differences in tropical cyclone activity for portions of the southern Indian Ocean. In addition, for these same regions, tropical Atlantic SST variability is associated with changes in large-scale atmospheric conditions, including wind shear, low-level vorticity, and humidity, typically associated with tropical cyclogenesis. These findings indicate a possible link between tropical Atlantic conditions and cyclone activity in the Indian Ocean mediated through a teleconnection between tropical Atlantic SSTs and large scale atmospheric conditions over the southern Indian Ocean. The nature of this teleconnection and the mechanisms driving it are being further explored with model experiments.

DeBlander, E.; Shaman, J. L.

2011-12-01

66

Tropical cyclone motion and recurvature in TCM-90. Master's thesis  

SciTech Connect

Rawinsonde and satellite data collected during the Tropical Cyclone Motion (TCM90) experiment, which was conducted during the summer of 1990 in the Western North pacific, is used to examine tropical cyclone steering motion and recurvature. TCM-90 composite results are compared with those found in a composite study using twenty-one years (1957-77) of Western North Pacific rawinsonde data during the same August-September period and also for all months during this same 21-year period. Both data sets indicate that the composite deep-layer-mean (850-300 mb) winds 5-7 deg from the cyclone center provide an important component of the steering flow for tropical cyclones. However, despite the rawinsonde data enhancements of the TCM-90 experiment, data limitations prevented an accurate observation of steering flow conditions at individual time periods or for the average of only 5-10 time periods when composited together.

Fitzpatrick, M.E.

1992-01-01

67

Influence of Greenhouse Warming on Tropical Cyclone Frequency  

Microsoft Academic Search

Influences of sea surface temperature (SST) spatial patterns and cumulus parameterizations on trop- ical cyclone (TC) frequency, in the context of global warming impacts, are investigated using an atmo- spheric general circulation model at T106 horizontal resolution. Simulated TCs in this high-resolution model are categorized into tropical storms (TSs) and tropical depressions (TDs). Model TSs are defined as TCs with

Jun YOSHIMURA; Masato SUGI; Akira NODA

2006-01-01

68

Cloud Condensation Nuclei Measurements in Tropical Cyclones  

NASA Astrophysics Data System (ADS)

The first measurements of cloud condensation nuclei (CCN) within and around tropical cyclones were made with the Desert Research Institute (DRI) CCN spectrometer (Hudson 1989) from a NOAA P-3 Hurricane Hunter aircraft throughout the 2001 season. Two penetrations of the closed eye of Hurricane Erin off the northeast US coast on Sept. 10 showed concentrations consistently well in excess of 1000 per cubic cm at approximately 1.4% supersaturation. Simultaneous condensation nuclei (CN--total particle) concentrations were consistently well in excess of 2000 per cubic cm throughout these closed eye penetrations. These within eye measurements at 4 km altitude far exceeded CCN and CN measurements just outside of the storm at similar altitudes--300 and 600 per cubic cm respectively. These CCN and CN concentrations within this closed eye were far above concentrations in maritime air masses; they are characteristic of continental or polluted air masses. Although there was a possibility that Saharan dust may have gotten into this storm these sub tenth micrometer particles are much too small and much too numerous to be dust. Such high concentrations may have originated from European air pollution, which may have been transported by similar airflow patterns to those that carry Saharan dust across the Atlantic. These high concentrations may be a manifestation of descending air that brings higher concentrations that are often characteristic of the upper troposphere (Clarke and Kapustin 2002). Later in the month measurements in Humberto showed highly variable CCN and CN concentrations that ranged from less than 5 per cubic cm to more than 1000 per cubic cm over km scale distances within and around the open eye of this tropical storm/hurricane. These very low concentrations suggest strong cloud scavenging. Clarke, A.D. and V.N. Kapustin, J. Atmos. Sci., 59, 363-382, 2002. Hudson, J.G., J. Atmos. & Ocean. Tech., 6, 1055-1065, 1989.

Hudson, J. G.; Simpson, J.

2002-05-01

69

Global climate change and tropical cyclones  

SciTech Connect

This paper offers an overview of the authors's studies during a specialized international symposium where they aimed at making an objective assessment of whether climate changes, consequent on an expected doubling of atmospheric CO[sub 2] in the next six or seven decades, are likely to increase significantly the frequency or intensity of tropical cyclones (TC). Out of three methodologies available for addressing the question they employ two, discarding the third for reasons set out in the appendix. In the first methodology, the authors enumerate reasons why, in tropical oceans, the increase in sea surface temperature (SST) suggested by climate change models might be expected to affect either (i) TC frequency, because a well-established set of six conditions for TC formation include a condition that SST should exceed 26[degrees]C, or (ii) TC intensity, because this is indicated by thermodynamic analysis to depend critically on the temperature at which energy transfer to air near the sea surface takes place. But careful study of both suggestions indicates that the expected effects of increased SST would be largely self-limiting (i) because the other five conditions strictly control how far the band of latitudes for TC formation can be further widened, and (ii) because intense winds at the sea surface may receive their energy input at a temperature significantly depressed by evaporation of spray, and possibly through sea surface cooling. In the second methodology, the authors study available historical records that have very large year-to-year variability in TC statistics. They find practically no consistent statistical relationships with temperature anomalies; also, a thorough analysis of how the El Nino-Southern Oscillation cycle influences the frequency and distribution of TCs shows any direct effects of local SST changes to be negligible. 28 refs., 4 figs.

Lighthill, J. (Univ. College London (United Kingdom)); Holland, G. (Bureau of Meteorology Research Center, Melbourne (Australia)); Gray, W.; Landsea, C. (Colorado State Univ., Fort Collins, CO (United States)); Craig, G. (Univ. of Reading (United Kingdom)); Evans, J. (Pennsylvania State Univ., College Park, PA (United States)); Kurihara, Yoshio (Princeton Univ., NJ (United States)); Guard, C. (Univ. of Guam, Mangilao (Guam))

1994-11-01

70

The Navy's Analog Scheme for Forecasting Tropical Cyclone Motion over the Northeastern Pacific Ocean.  

National Technical Information Service (NTIS)

The Navy's EPANALOG (Northeastern Pacific Analog Tropical Cyclone Tracker) forecast program is introduced. EPANALOG selects analog tropical cyclones from a 25-year Northeastern Pacific Ocean history. The selected analog tracks, statistically adjusted for ...

J. D. Jarrell C. J. Mauck R. J. Renard

1975-01-01

71

Seasonal dynamics of total intensities of tropical cyclones  

Microsoft Academic Search

In this work, some features of the dynamics of seasonal cyclonic activity are shown. Seasonal values of the total intensity of tropical cyclones (TC) in the northwestern and northeastern Pacific (1950?2004 and 1971?2004) and the northwestern Atlantic (1941? 2005) are calculated. Smoothed values of these indicators over six years reveal a 24-yr-periodicity for regions of the Pacific. Such empirical regularity

M. I. Yaroshevich

2007-01-01

72

Temporal clustering of tropical cyclones and its ecosystem impacts.  

PubMed

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

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

2011-10-17

73

Temporal clustering of tropical cyclones and its ecosystem impacts  

PubMed Central

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.

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

2011-01-01

74

Damage Costs of Climate Change through Intensification of Tropical Cyclone Activities: An Application of FUND  

Microsoft Academic Search

Climate change may intensify tropical cyclone activities and amplify their negative economic effects. We simulate the direct economic impact of tropical cyclones enhanced by climate change with the integrated assessment model FUND 3.4. The results show that in the base case, the direct economic damage of tropical cyclones ascribed to the effect of climate change amounts to $19 billion globally

Richard S. J. Tol; Daiju Narita; David Anthoff

2008-01-01

75

The effects of the Southwest Indian Ocean tropical cyclones on Ethiopian drought  

Microsoft Academic Search

Tropical cyclones are one of the prominent weather systems that are generated over the tropical oceans. The cyclones that develop in the Southwest Indian Ocean (SWIO) usually travel west then southwest and finally recurve to southeast, generally before reaching the East African coast. However, it is shown in this study how SWIO-tropical cyclones\\/depressions can indirectly affect Ethiopian weather. Using correlation

Dula Shanko; Pierre Camberlin

1998-01-01

76

The impact of climate change on global tropical cyclone damage  

NASA Astrophysics Data System (ADS)

One potential impact from greenhouse-gas emissions is increasing damage from extreme events. Here, we quantify how climate change may affect tropical cyclone damage. We find that future increases in income are likely to double tropical cyclone damage even without climate change. Climate change is predicted to increase the frequency of high-intensity storms in selected ocean basins depending on the climate model. Climate change doubles economic damage, but the result depends on the parameters of the damage function. Almost all of the tropical cyclone damage from climate change tends to be concentrated in North America, East Asia and the Caribbean-Central American region. This paper provides a framework to combine atmospheric science and economics, but some effects are not yet modelled, including sea-level rise and adaptation.

Mendelsohn, Robert; Emanuel, Kerry; Chonabayashi, Shun; Bakkensen, Laura

2012-03-01

77

Maintenance of Tropical Cyclone Bill (1988) after landfall  

NASA Astrophysics Data System (ADS)

The mechanism for the maintenance of Tropical Cyclone Bill (1988) after landfall is investigated through a numerical simulation. The role of the large-scale environmental flow is examined using a scale separation technique, which isolates the tropical cyclone from the environmental flow. The results show that Bill was embedded in a deep easterly-southeasterly environmental flow to the north-northeast of a large-scale depression and to the southwest of the western Pacific subtropical high. The depression had a quasibarotropic structure in the mid-lower troposphere and propagated northwestward with a speed similar to the northwestward movement of Bill. The moisture budgets associated with both the large-scale and the tropical cyclone scale motions indicate that persistent low-level easterly-southeasterly flow transported moisture into the inner core of the tropical cyclone. The low-level circulation of the tropical cyclone transported moisture into the eyewall to support eyewall convection, providing sufficient latent heating to counteract energy loss due to surface friction and causing the storm to weaken relatively slowly after landfall. Warming and a westward extension of the upper-level easterly flow led to westward propagation of the environmental flow in the mid-lower troposphere. As a result, Bill was persistently embedded in an environment of deep easterly flow with high humidity, weak vertical wind shear, convergence in the lower troposphere, and divergence in the upper troposphere. These conditions are favorable for both significant intensification prior to landfall and maintenance of the tropical cyclone after landfall.

Xu, Yamei

2013-08-01

78

Real-time superensemble tropical cyclone prediction  

NASA Astrophysics Data System (ADS)

This study addresses the improvement of forecasting tropical cyclones (TCs) using ensemble forecasting techniques. The methodology for these forecasts is called the multi-model superensemble. This statistical method makes use of the real-time forecasts provided by a number of operational and research models to construct the superensemble forecasts. This method divides the forecast time line into two phases: a training phase and a forecast computing phase. The training phase includes an inventory of past applicable hurricane forecasts, each by the multi-models. The model biases of position and intensity errors of past forecasts are summarized via a simple linear multiple regression of these forecasts against the best-observed estimates of position and intensity. The analysis of this technique and its usage requires a review of the real-time Atlantic TC superensemble forecasts for the years 1999 to 2001. The training and statistics for the 1998 Atlantic season were used and passed on to future forecasts of the multi-models in order to forecast the hurricanes of 1999. This method was first tested for the hurricanes of 1998 with considerable success and those statistics were refined for the 1999 Atlantic season. Overall, the main result of the seasonal summary is that the errors for the multi-model superensemble are generally less than those of all of the participating models during 1 to 5 day real-time forecasts. Some of the major storms of the Atlantic 1999 season, such as Dennis, Floyd, Irene and Lenny, were extremely well handled by this superensemble approach. Due to significant model changes prior to the 2000 and 2001 hurricane seasons, many of the TCs in 2000 and 2001 were not as well handled compared to the 1999 cases. These significant changes to the models are key reasons for this reduced operational performance. In order to enhance the superensemble's capabilities in TC prediction, this research describes an optimized, objective technique for real-time superensemble forecasting. This research validates that it is a viable technique to construct improved real-time forecasts of TC positions and intensity and details the drawbacks and possible improvements of using this TC forecasting technique for both research and operational prediction.

Williford, Charles Eric

79

Validation of models and algorithms for microwave radiometric investigations of tropical cyclones  

Microsoft Academic Search

The applicability of standard passive microwave data interpreting techniques to observing tropical cyclones is studied basing on the SSM\\/I observations of tropical cyclones in July-September 1994. It is shown that spatial distributions of wind speed retrieved from the SSM\\/I data provide a good description of tropical cyclones structure at distances of 200-300 km from the cyclone center including some quantitative

B. Z. Petrenko; A. F. Nerushev; L. I. Milekhin; G. K. Zagorin

1997-01-01

80

Tropical Cyclone Genesis: A Dynamician's Point of View  

NASA Astrophysics Data System (ADS)

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.

Bouali, Safieddine; Leys, Jos

81

Tropical-cyclone intensification and predictability in three dimensions  

Microsoft Academic Search

ABSTRACT: We present numerical-model,experiments,to investigate the dynamics,of tropical-cyclone amplification and its predictability in three dimensions. For the prototype amplification problem,beginning with a weak-tropical-storm-strength vortex, the emergent flow becomes highly asymmetric and dominated by deep convective vortex structures, even though the problem,as posed is essentially axisymmetric. The asymmetries,that develop,are highly sensitive to the boundary- layer moisture distribution. When a small random

Nguyen Van Sang; Roger K. Smith; Michael T. Montgomery

2008-01-01

82

Long-Term Natural Variability of Tropical Cyclones in Australia  

Microsoft Academic Search

Numerous late Holocene records of tropical cyclones have been collected from tropical northern Australia. They are in the\\u000a form of multiple shore parallel sedimentary ridges deposited over the past 6,000 years and an 800 year long annual resolution\\u000a oxygen isotope record from a calcium carbonate cave stalagmite. The sedimentary ridges are composed of coral fragments, or\\u000a shell and sand or

Jonathan Nott

83

On Estimates of Historical North Atlantic Tropical Cyclone Activity  

Microsoft Academic Search

In this study, an estimate of the expected number of Atlantic tropical cyclones (TCs) that were missed by the observing system in the presatellite era (between 1878 and 1965) is developed. The significance of trends in both number and duration since 1878 is assessed and these results are related to estimated changes in sea surface temperature (SST) over the \\

Gabriel A. Vecchi; Thomas R. Knutson

2007-01-01

84

WIND WAVES GENERATED BY TROPICAL CYCLONES AND HURRICANES  

Microsoft Academic Search

Tropical cyclone wave spectra in deep water have been put in a universal form similar to the JONSWAP spectra. Average spectral shape parameters were defined from values obtained in the open literature. Spectral level, peak frequency and significant wave height correlations with dimensionless fetch were obtained from Gulf of Mexico hurricanes Camille 1969, Eloise 1975, Edith 1971 and Felice 1970

Y. Keen Lee

1983-01-01

85

Atlantic Sea Surface Temperatures and Tropical Cyclone Formation  

Microsoft Academic Search

It has long been accepted that interannual fluctuations in sea surface temperature (SST) in the Atlantic are associated with fluctuations in seasonal Atlantic basin tropical cyclone frequency. To isolate the physical mech- anism responsible for this relationship, a singular value decomposition (SVD) is used to establish the dominant covarying modes of tropospheric wind shear and SST as well as horizontal

Lloyd J. Shapiro; Stanley B. Goldenberg

1998-01-01

86

Ocean Spray Modelling for Tropical Cyclone Wind Speeds  

Microsoft Academic Search

Because of the potentially important influence of ‘spray cooling’ on the thermodynamics of Tropical Cyclones, there is a need for estimates of ocean spray distribution at extreme wind speeds, at least twice those for which detailed spray observations have been made. To assist in such extrapolation, a simplified probabilistic model is developed, with the three main effects (gusts, gravity, evaporation)

James Lighthill

1997-01-01

87

APPLICATIONS OF LIGHTNING OBSERVATIONS TO TROPICAL CYCLONE INTENSITY FORECASTING  

Microsoft Academic Search

The next generation geostationary satellite system starting with GOES-R will include a geostationary lightning mapper (GLM). The GLM will provide nearly continuous times and locations of total lightning with an accuracy of about 10 km over most of the field of view of GOES-east and -west. This coverage will include nearly all of the regions where tropical cyclones occur in

Mark DeMaria; Robert T. DeMaria

2009-01-01

88

Rapid Development of the Tropical Cyclone Warm Core  

Microsoft Academic Search

This paper presents a simple theoretical argument to isolate the conditions under which a tropical cyclone can rapidly develop a warm-core thermal structure and subsequently approach a steady state. The theoretical argument is based on the balanced vortex model and, in particular, on the associated transverse circulation equation and the geopotential tendency equation. These second-order partial differential equations contain the

Jonathan L. Vigh; Wayne H. Schubert

2009-01-01

89

Have tropical cyclones been feeding more extreme rainfall?  

Microsoft Academic Search

We have conducted a study of the relationship between tropical cyclone (TC) and extreme rain events using GPCP and TRMM rainfall data, and storm track data for July through November (JASON) in the North Atlantic (NAT) and the western North Pacific (WNP). Extreme rain events are defined in terms of percentile rainrate, and TC-rain by rainfall associated with a named

K.-M. Lau; Y. P. Zhou; H.-T. Wu

2008-01-01

90

Australian region tropical cyclones: Influence of environment at different scales  

Microsoft Academic Search

This dissertation explores the influence of environmental factors on a variety of spatial and temporal scales on tropical cyclones (TCs) in the Australian region. Chapter 1 provides the motivation for the work presented, and leads into a discussion on the current state of knowledge of large-scale factors affecting the interannual variability of TCs in each of the seven global TC

Hamish Andrew Ramsay

2008-01-01

91

Observation, Analysis and Prediction of Atlantic tropical Cyclone Formation (Invited)  

NASA Astrophysics Data System (ADS)

During the 2010 Atlantic hurricane season, significant observational and prediction resources were used to study the process of tropical cyclone formation and its predictability. Observations, in addition to those routinely available from satellites, were provided by aircraft from NOAA, NASA and NSF participating jointly in an effort to understand tropical cyclone formation and the sometimes rapid transformation of a weak cyclone into a strong tropical cyclone. The NSF-sponsored PRE-Depression Investigation of Cloud-systems in the Tropics (PREDICT) is focused on tropical (easterly) waves over the Atlantic and seeks observations of the general wave trough region to distinguish characteristics of waves that develop into tropical cyclones from those that do not. Among the PREDICT hypotheses is that recirculation regions, defined by closed lower-tropospheric cyclonic circulations in a frame of reference moving with the wave, allow air parcels to be isolated from dry air, thus increasing their humidity over time. Deep moist convection in air with high humidity through a deep layer of the troposphere, in a region of strong rotation, produces comparatively weak or more localized downdrafts and tends to favor inflow and spinup of cyclonic circulation. Observations from dropsondes and an array of other instruments on the NSF/NCAR G-V aircraft sampled air inside and outside the recirculation regions as well as other structural characteristics of several tropical waves. These observations are synthesized to evaluate the central PREDICT hypotheses. One of the sub-hypotheses of PREDICT is that these recirculation regions, or their boundaries, can be the source of significant initial condition error, which limits the predictability of these disturbances. Moreover, it is also possible that uncertainties outside the recirculation region could have large impact on forecasts. We explore these possibilities using an ensemble Kalman filter analysis and forecasting system that is run with and without special field observations to understand inherited uncertainty in the background, how much this uncertainty can be reduced by observations in location where the forecast is sensitive to the initial conditions, particularly in the wave trough region, and how these initial condition uncertainties manifest themselves in forecasts. Finally, results from high-resolution forecasts used to predict formation and early intensification stages of Atlantic storms during the 2010 season will be highlighted.

Davis, C. A.; Torn, R. D.

2010-12-01

92

Decadal Variations of Tropical Cyclone Activity over the Central North Pacific  

Microsoft Academic Search

Tropical cyclone activity (tropical depressions, tropical storms, and hurricanes combined) in the central North Pacific has been found to be on the rise and this increase amounts to about 3.2 cyclones over the last 32 years (1966-97). An examination of time series of tropical storms and hurricanes and hurricane records alone also reveals an increasing trend in both series since

Pao-Shin Chu; James D. Clark

1999-01-01

93

Tropical Cyclone Structure Analysis: A Multi-Sensor Approach  

NASA Astrophysics Data System (ADS)

Tropical cyclones include many scales, ranging from the individual convective elements (1-10 km) to the upper level outflow that can extend to more than 1000 km from the storm center. At the present time there is no individual sensor that can measure all aspects of tropical cyclones. In this study, a multi-sensor method for diagnosing the tropical cyclone wind field is described. GOES visible and IR data are used to estimate the maximum surface wind using the traditional Dvorak technique. A new method to use GOES IR data to map the low-level inner core wind field out to 200 km is also described. Active and passive scatterometer data (QuikSCAT and WindSat) provide surface winds away from the inner core region, and GOES feature-track winds provide winds at larger distances from the storm. A method that uses hydrostatic and balance constraints from microwave and IR temperature retrievals (from AMSU and AIRS) provides the three dimensional wind structure away from the storm inner core. The AMSU data can also be used to estimate the maximum wind. An objective analysis system is described that can combine these data sources to provide an estimate of the complete low-level wind field. The multi-sensor wind analyses and aircraft reconnaissance data are used to illustrate the large variability in tropical cyclone wind structure. For example, tropical cyclones of similar intensity can be of much different sizes. The typical evolution of storm intensity and size is described, as well as factors that can lead to the structure variability. Results show that both inner core processes and external forcing can influence storm structure changes.

Demaria, M.; Maclay, K. S.; Knaff, J. A.

2006-12-01

94

Tropical Cyclones, Central North Pacific, 1993.  

National Technical Information Service (NTIS)

There were two tropical depressions, one tropical storm, and two hurricanes that affected the Honolulu Central Pacific Hurricane Center's (CPHC) area of responsibility in 1993 (all of which occurred during the months of July and August). All of these trop...

G. H. Trapp A. L. Garza H. E. Rosendal B. Hablutzel A. K. T. Chun

1994-01-01

95

Tropical Cyclones, 1987 - Central North Pacific.  

National Technical Information Service (NTIS)

Tropical Storm FERNANDA crossed 140W and into the Central Pacific Hurricane Center's area of responsibility on July 26 at 0000 UTC. FERNANDA developed about 48 hours earlier near 11N 130W as Tropical Depression NINE-E and subsequently attained tropical st...

W. Au A. Chun H. Rosendal

1988-01-01

96

Vulnerability of bangladesh to climate change and sea level rise through tropical cyclones and storm surges  

Microsoft Academic Search

Bangladesh is frequently visited by natural disasters such as tropical cyclones, storm surges, floods, droughts, tornadoes, and “norwesters.” Of these, tropical cyclones originating in the Bay of Bengal and associated storm surges are the most disastrous. There are various reasons for the disastrous effects of cyclones and storm surges in Bangladesh. Superimposed on these disastrous effects, climate change and any

A. Ali

1996-01-01

97

Effect of remote sea surface temperature change on tropical cyclone potential intensity  

Microsoft Academic Search

The response of tropical cyclone activity to global warming is widely debated. It is often assumed that warmer sea surface temperatures provide a more favourable environment for the development and intensification of tropical cyclones, but cyclone genesis and intensity are also affected by the vertical thermodynamic properties of the atmosphere. Here we use climate models and observational reconstructions to explore

Gabriel A. Vecchi; Brian J. Soden

2007-01-01

98

Stalagmite stable isotope record of recent tropical cyclone events  

NASA Astrophysics Data System (ADS)

We present a 23 yr stalagmite record (1977 2000) of oxygen isotope variation, associated with 11 tropical cyclones (TCs), from Actun Tunichil Muknal cave in central Belize. High-resolution microsampling yielded a record of monthly to weekly temporal resolution that contains abrupt decreases (negative excursions) in calcite ?18O values that correspond with recent TC rain events nearby. A logistic discriminant model reliably identified TC proxy signals using the measurable parameters ?18O and ?13C values, and single point changes in ?18O value. The logistic model correctly identified 80% of excursions as TC events and incorrectly classified only 1 of nearly 1200 nonstorm sampling points. In addition to enabling high-resolution TC frequency reconstruction, this geologic proxy also provides information about the intensity of individual TCs. A multiple regression predicted TC intensity (R2 = 0.465, p = 0.034) using sampling frequency and excursion amplitude. Consistent with previous low-resolution studies, we found that the decadal average ?18O value was lower during the 1990s when several TCs produced rainfall in the area, but higher during the 1980s when only one TC struck. Longer, accurately dated, high-resolution speleothem stable isotope records may be a useful new tool for paleotempestology, to clarify associations between highly variable TC activity and the dynamic range of Quaternary climate.

Benoit Frappier, Amy; Sahagian, Dork; Carpenter, Scott J.; González, Luis A.; Frappier, Brian R.

2007-02-01

99

An Evaluation of the Precipitation Distribution in Landfalling Tropical Cyclones  

NASA Astrophysics Data System (ADS)

Often, precipitation forecasts associated with landfalling tropical cyclones are based on a simple algorithm where the maximum 24-h precipitation (in inches) is forecast by 100/v, where v (in m.p.h.) is the translational speed of the cyclone. This algorithm, however, provides little insight as to the precipitation distribution and intensity that can be expected in a landfalling tropical cyclone. Furthermore, several recent cases (Danny 1997, Dennis, Floyd, and Irene 1999) show that precipitation distribution and intensity can be drastically altered by interactions with mid-latitude troughs and jet streaks, which often result in extratropical transitions. Occasionally, these interactions produce catastrophic rainfalls as illustrated by hurricane Floyd in September 1999. This talk will present diagnostics of results from composites of several storms from a Quasi-Geostrophic potential vorticity (PV) perspective, designed to elucidate the important dynamics responsible for the modulation of the precipitation distribution and intensity. Results indicate that precipitation distribution in landfalling tropical systems may be characterized in the following ways: 1) Precipitation is heaviest along/very near the track of a storm when there is no significant interaction with a midlatitude trough, 2) Precipitation distribution is heaviest to the right of the track of the storm when downstream intensification of the ridge is important, and 3) Precipitation distribution is heaviest to the left of the storm track in a transitioning storm. Without large scale forcing for vertical motion associated with a midlatitude trough in situation 1, most of the greater vertical velocities remain near the storm core in the region of greatest diabatic heating and maximum wind speeds. In situation 2, the intensification of the downstream ridge ahead of a weak midlatitude trough can accentuate the PV gradient between the tropical system and the downstream ridge, enhancing the cyclonic PV advection (implied ascent). In a transitioning cyclone (situation 3), a midlatitude trough approaching the tropical cyclone from the northwest often results in a strong baroclinic between the two systems. Once the tropical cyclone interacts with the baroclinic zone, a large region of precipitation develops in the left front quadrant of the storm in a region of strong warm air advection. Furthermore, diabatic heating from the resulting precipitation can re-distribute PV in the midlatitude trough creating a more dynamically active system with a negative tilt.

Atallah, E.; Bosart, L.

2004-05-01

100

Tree-ring isotope records of tropical cyclone activity  

PubMed Central

The destruction wrought by North Atlantic hurricanes in 2004 and 2005 dramatically emphasizes the need for better understanding of tropical cyclone activity apart from the records provided by meteorological data and historical documentation. We present a 220-year record of oxygen isotope values of ?-cellulose in longleaf pine tree rings that preserves anomalously low isotope values in the latewood portion of the ring in years corresponding with known 19th and 20th century landfalling/near-coastal tropical storms and hurricanes. Our results suggest the potential for a tree-ring oxygen isotope proxy record of tropical cyclone occurrence extending back many centuries based on remnant pine wood from protected areas in the southeastern U.S.

Miller, Dana L.; Mora, Claudia I.; Grissino-Mayer, Henri D.; Mock, Cary J.; Uhle, Maria E.; Sharp, Zachary

2006-01-01

101

Genesis of tropical cyclone Nargis revealed by multiple satellite observations  

NASA Astrophysics Data System (ADS)

Tropical cyclone (TC) Nargis recently battered Myanmar on May 2 2008 is one of the most deadly tropical storms in history. Nargis was initiated by an abnormally strong intraseasonal westerly event associated with Madden-Julian oscillation (MJO) in the eastern Indian Ocean. An incipient cyclonic disturbance emerged as an emanation of Rossby wave-induced vortex when the intraseasonal convective anomaly reached the Maritime Continent. The northeastward movement of MJO convection facilitated further development of the disturbance. The incipient disturbance became a tropical disturbance (TD) with a central warm-core structure on April 26. The further development from the TD to TC formation on April 28 is characterized by two distinctive stages: a radial contraction followed by a rapid intensification. The processes responsible for contraction and rapid intensification are discussed by diagnosis of multiple satellite data. This proposed new scenario is instrumental for understanding how a major TC develops in the northern Indian Ocean.

Kikuchi, Kazuyoshi; Wang, Bin; Fudeyasu, Hironori

2009-03-01

102

TRMM Flyby of Tropical Cyclone Narelle  

NASA Video Gallery

This animated, 3-D flyby of Major Cyclone Narelle was created using data on Jan. 11, from NASA's TRMM satellite. Narelle's wind speeds were near 132 mph. A few thunderstorm towers in Narelle's eye extend to about 16km (9.9 miles) high (in red). Credit: NASA/SSAI, Hal Pierce

Lynn Jenner

2013-01-11

103

Growth and Decay of an Extra-Tropical Cyclone’s PV-Tower  

Microsoft Academic Search

Summary   The surface low of a mature extra-tropical cyclone is often surmounted by a troposphere-spanning column of anomalously high\\u000a potential vorticity (PV). In this study the growth and decay of such a PV-tower is traced for one major North Atlantic frontal-wave\\u000a cyclone using the ECMWF analysis fields and adopting both Eulerian and Lagrangian frameworks.\\u000a \\u000a A tower’s structure and composition relates

A. M. Rossa; H. Wernli; H. C. Davies

2000-01-01

104

Surface-based Rain, Wind, and Pressure Fields in Tropical Cyclones over North Carolina Since 1989.  

National Technical Information Service (NTIS)

During the recent 12-year span of hurricane seasons (1989-2000), several major hurricanes, tropical storms, and tropical depressions affected North Carolina. These tropical cyclones included: 1989, Hurricane Hugo; 1995, the remnants of Hurricane Allison a...

J. Cline

2002-01-01

105

Clustering of tropical cyclones in the North Atlantic  

NASA Astrophysics Data System (ADS)

We investigate the spatial dependence of and the large-scale atmospheric and climatic effects on the clustering of tropical cyclones in the North Atlantic Ocean. Tropical cyclone tracks from the HURDAT database are examined. We study the transit of tropical cyclones near points belonging to a grid covering the North Atlantic Ocean. Clustering is characterized by the dispersion (ratio of the variance and the mean) of the yearly counts of cyclone transits at distance less than a radius R from the gridpoints. Coherent patches of overdispersion are found for large radii (R>=300km) in the main development region, in the central North Atlantic, off the Mexican coast in the Gulf of Mexico and in the Caribbean sea. Transits of tropical cyclones with intense windspeeds (>60kt) are overdispersed in smaller regions. Patches of overdispersion occur in the central North Atlantic and in a region surrounding the souther coast of Florida, the western coast of Cuba and the coast of Belize. The influence of large-scale atmospheric and climatic processes is analysed by Poisson regression with a time-varying rate that depends on indices for the Atlantic Multidecadal Oscillation (AMO), the North Atlantic Oscillation (NAO) and the Southern Oscillation (SO). A clear-cut signal is found at the largest spatial scales (R>=300km). The AMO has positive effects on the local transit rate in a very large region of the North Atlantic, around the main development region and Caribbean Sea. Positive effects are found for the NAO around Cuba and the Caribbean. Negative (though small) effects are found for the SOI in the Caribbean and the Gulf of Mexico.

Vitolo, Renato; Stephenson, David; Cook, Ian

2010-05-01

106

Tropical Cyclone Report: Tropical Storm Jerry (AL112007), September 23-24, 2007.  

National Technical Information Service (NTIS)

Jerry was a short-lived tropical cyclone over the far northeastern Atlantic. A non-tropical low formed in the central North Atlantic on 21 September and meandered for a few days, while gradually developing deep convection. The thunderstorm activity became...

L. A. Avila

2007-01-01

107

The Tropical Cyclone Modeling Team (TCMT): Evaluation of Experimental Models for Tropical Cyclone Forecasting in Support of the NOAA Hurricane Forecast Improvement Project (HFIP)  

Microsoft Academic Search

In 2009, the National Center for Atmospheric Science (NCAR)\\/Research Applications Laboratory's (RALs) Joint Numerical Testbed (JNT) Program formed a new entity called the Tropical Cyclone Modeling Team (TCMT). The focus of this team is testing and evaluation of experimental models with the goal of improving tropical cyclone forecasts. Much of this effort is sponsored by NOAA's Hurricane Forecast Improvement Project

P. A. Kucera; B. Brown; L. B. Nance; K. M. Crosby; C. Williams; T. Jensen

2010-01-01

108

Recent Advances in Understanding Tropical Cyclone-Climate Interactions Using Climate Models of Varying Complexity  

NASA Astrophysics Data System (ADS)

Understanding potential feedbacks associated with tropical cyclones in the coupled ocean-atmosphere system is important within the context of climate change. Here we present results from recent ocean/atmosphere modeling studies addressing the role of tropical cyclones within the climate system. We use multiple models featuring varying levels of complexity, and we simulate the effects of tropical cyclones in several ways. This includes modifying the ocean's vertical mixing budget and surface wind fields to reflect conditions consistent with present-day tropical cyclone activity, as well as for altered climate states. We find tropical cyclones can significantly alter the thermal structure of the upper ocean in the tropical and subtropical latitudes, and these changes affect the dynamics of the subtropical overturning circulation. Effects are enhanced for climate scenarios with amplified tropical cyclone activity. Furthermore, altered sea surface temperatures directly impact the strength and spatial extent of large scale atmospheric circulations such as the Hadley and Walker cells. We find tropical cyclones do not significantly influence the equator to pole oceanic heat transport for present-day conditions. Results point to the possibility of tropical cyclone-induced climate feedbacks, however, these feedbacks are significant only for scenarios with increased tropical cyclone activity compared to the current climatology.

Sriver, R. L.; Goes, M. P.; Mann, M. E.; Huber, M.; Keller, K.

2010-12-01

109

A cloud-resolving regional simulation of tropical cyclone formation  

NASA Astrophysics Data System (ADS)

The development of Tropical Cyclone Diana (1984) is simulated with a mesoscale model using 1.2 km grid spacing over a regional-scale (>1000 km) domain in the first known experiment of this kind. With only a synoptic-scale disturbance in the initial conditions, the model first develops a mesoscale convective system along a remnant frontal zone, which yields a mesoscale vortex. After a period of quiescence, banded convection organizes about the vortex from isolated, grid-resolved cells, with the system becoming warm-core and intensifying into Tropical Storm Diana.

Powers, Jordan G.; Davis, Christopher A.

2002-01-01

110

The Extratropical Transition of Tropical Cyclones: Forecast Challenges, Current Understanding, and Future Directions  

Microsoft Academic Search

A significant number of tropical cyclones move into the midlatitudes and transform into extratropical cyclones. This process is generally referred to as extratropical transition (ET). During ET a cyclone frequently produces intense rainfall and strong winds and has increased forward motion, so that such systems pose a serious threat to land and maritime activities. Changes in the structure of a

Sarah C. Jones; Patrick A. Harr; Jim Abraham; Lance F. Bosart; Peter J. Bowyer; Jenni L. Evans; Deborah E. Hanley; Barry N. Hanstrum; Robert E. Hart; François Lalaurette; Mark R. Sinclair; Roger K. Smith; Chris Thorncroft

2003-01-01

111

Tropical Cyclones of the North Atlantic Ocean, 1871-1980 (With Storm Track Maps Updated Through 1984).  

National Technical Information Service (NTIS)

The report presents North Atlantic tropical cyclone tracks and certain basic statistical summaries. A detailed analysis of the tracks was not attempted. Despite the availability of studies dealing with the climatology of tropical cyclones, many of the hun...

C. J. Neumann G. W. Cry E. L. Caso B. R. Jarvinen

1985-01-01

112

Disaster triggers disaster: Earthquake triggering by tropical cyclones  

NASA Astrophysics Data System (ADS)

Three recent devastating earthquakes, the 1999 M=7.6 Chi-Chi (Taiwan), 2010 M=7.0 Leogane (Haiti), 2010 M=6.4 Kaohsiung (Taiwan), and additional three moderate size earthquakes (6tropical mountainous areas shortly after very wet tropical cyclones (hurricane or typhoon) hit the very same area. The most familiar example is Haiti, which was hit during the late summer of 2008 by two hurricanes and two tropical storms (Fay, Gustav, Hanna and Ike) within 25 days. A year an a half after this very wet hurricane season, the 2010 Leogane earthquake occurred in the mountainous Haiti's southern peninsula and caused the death of more than 300,000 people. The other cases are from Taiwan, which is characterized by a high seismicity level and frequent typhoon landfall. The three wettest typhoons in Taiwan's past 50 years were Morakot (in 2009, with 2885 mm or rain), Flossie (1969, 2162 mm) and Herb (1996, 1987 mm)[Lin et al., 2010]. Each of this three very wet storms was followed by one or two main-shock M>6 earthquake that occurred in the central mountainous area of Taiwan within three years after the typhoon. The 2009 Morakot typhoon was followed by 2009 M=6.2 Nantou and 2010 M=6.4 Kaohsiung earthquakes; the 1969 Flossie typhoon was followed by an M=6.3 earthquake in 1972; and the 1996 Herb typhoon by the 1998 M=6.2 Rueyli and 1999 M=7.6 Chi-Chi earthquakes. The earthquake catalog of Taiwan lists only two other M>6 main-shocks that occurred in Taiwan's central mountainous belt, one of them was in 1964 only four months after the wet Typhoon Gloria poured heavy rain in the same area. We suggest that the close proximity in time and space between wet tropical cyclones and earthquakes reflects a physical link between the two hazard types in which these earthquakes were triggered by rapid erosion induced by tropical cyclone's heavy rain. Based on remote sensing observations, meshfree finite element modeling, and Coulomb failure stress analysis, we show that the erosion induced by very wet cyclones increased the failure stresses at the hypocenters' depth by 300-1500 Pa, which ultimately triggered these earthquakes. Our findings are supported by a statistical analysis indicating a very low probability (1-5%) for a random earthquake occurrence process to form the observed typhoon-earthquake temporal distribution.

Wdowinski, S.; Tsukanov, I.

2011-12-01

113

Measurement and modelling of tropical cyclone waves in the Great Barrier Reef  

Microsoft Academic Search

Recorded wave data from four wave measuring instruments located at various points within a section of the Great Barrier Reef during the passage of a tropical cyclone are presented. A spectral wave prediction model is used as an aid to the interpretation of the data. The tropical cyclone generated significant wave heights of approximately 10 m seaward of the reef

I. R. Young; T. A. Hardy

1993-01-01

114

Analysis of North Atlantic tropical cyclone intensify change using data mining  

Microsoft Academic Search

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 study aims to tackle two factors that account for the underperformance of current TC

Jiang Tang

2010-01-01

115

On the role of tropical cyclones in ocean heat transport (Invited)  

Microsoft Academic Search

It has been suggested that the enhanced mixing caused by tropical cyclones might contribute significantly to the ocean heat transport, causing an additional heat uptake in the low latitudes of about 0.5 to 1.5 PW. These results, however, were based on the assumption that all heat pumped below the mixed layer by tropical cyclones is finally released in higher latitudes.

M. F. Jansen; R. M. Ferrari

2010-01-01

116

Analysis of North Atlantic Tropical Cyclone Intensify Change Using Data Mining  

ERIC Educational Resources Information Center

|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…

Tang, Jiang

2010-01-01

117

Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment  

Microsoft Academic Search

The very limited instrumental record makes extensive analyses of the natural variability of global tropical cyclone activities difficult in most of the tropical cyclone basins. However, in the two regions where reasonably reliable records exist (the North Atlantic and the western North Pacific), substantial multidecadal variability (particularly for intense Atlantic hurricanes) is found, but there is no clear evidence of

A. Henderson-Sellers; H. Zhang; G. Berz; K. Emanuel; W. Gray; C. Landsea; G. Holland; J. Lighthill; S.-L. Shieh; P. Webster; K. McGuffie

1998-01-01

118

Wind Speed Retrievals from MultiSensor Satellite Data from Hurricanes and Tropical Cyclones  

Microsoft Academic Search

It is well known that tropical cyclones (TCs) pose an increasingly serious threat to coastal areas, for example in China and USA. Millions of people live and vacation along the coastline and the rate of construction of homes and businesses in coastal areas continues to increase. The accuracy and lead-time for forecasts of tropical cyclone tracks and intensities must improve

Yijun He; Biao Zhang; Hui Shen; William Perrie

2008-01-01

119

Simulations of stratospheric to tropospheric transport during the tropical cyclone Marlene event  

Microsoft Academic Search

Enhanced ozone values observed in the upper troposphere near intense tropical cyclones have raised the question of the role of stratospheric–tropospheric exchange. The dynamical mechanisms involved in the enhanced ozone values of 6 April 1995 observed at Reunion and associated with the tropical cyclone Marlene could not be explained by ECMWF meteorological analysis with 1.125° horizontal resolution. A previous study

J. Leclair De Bellevue; J. L. Baray; S. Baldy; G. Ancellet; R. Diab; F. Ravetta

2007-01-01

120

Impact of tropical cyclones on aerosol properties over urban region of Hyderabad, India  

Microsoft Academic Search

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

Shailesh Kumar Kharol; K. V. S. Badarinath; Anu Rani Sharma; V. Krishna Prasad; Dimitrios G. Kaskaoutis; Panagiotis T. Nastos; Harry D. Kambezidis

2010-01-01

121

Contribution of Tropical Cyclones to the Interannual Variability of Baiu Precipitation  

NASA Astrophysics Data System (ADS)

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.

Yamaura, T.; Tomita, T.

2011-12-01

122

Tropical Cyclone Winds Retrieved from Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

Within this paper we will introduce and validate our methodologies to retrieve high-resolution wind fields from synthetic aperture radar (SAR) with particular focus on tropical cyclones. SAR wind directions are extracted from the orientation of wind induced streaks, which are visible in the SAR images and that in general are well aligned with the mean surface wind direction. Wind speeds are retrieved from the measured normalized radar cross section (NRCS) from the ocean surface under consideration on the SAR derived wind direction and imaging geometry. Depending on the frequency as well as the SAR polarization for transmit and receive different geophysical model functions (GMF) have to be considered. In case of SAR data acquired at C-band with co-polarization using vertical (V) polarization in transmit and receive we use the well-known C-band model CMOD5n. For horizontal polarization in transmit and receive (HH-polarization) the CMOD5n model is extended by a function that describes the ratio of V to H polarization. For images acquired at H-polarization for transmit and V-polarization for receive (cross pol) or vice versa, we have developed our own GMF. We have investigated a large data set of SAR data acquired under tropical cyclone conditions and compared our retrieved wind fields to scatterometer winds, GPS drope sonde surface wind vectors and SFMR wind speeds acquired during the storms. The results show the quality of the SAR-retrieved wind fields from co-pol and, in particular, cross-pol winds., The later have an rms error similar to the SFMR measurements, which up to date is one of the best accepted wind measurement sources for tropical cyclone winds.

Horstmann, Jochen; Wackerman, Chris; Foster, Ralph; Caruso, Michael; Graber, Hans

2013-04-01

123

A note concerning the Lighthill "sandwich model" of tropical cyclones  

PubMed Central

The basic element of Lighthill's “sandwich model” of tropical cyclones is the existence of “ocean spray,” a layer intermediate between air and sea made up of a cloud of droplets that can be viewed as a “third fluid.” We propose a mathematical model of the flow in the ocean spray based on a semiempirical turbulence theory and demonstrate that the availability of the ocean spray over the waves in the ocean can explain the tremendous acceleration of the wind as a consequence of the reduction of the turbulence intensity by droplets. This explanation complements the thermodynamic arguments proposed by Lighthill.

Barenblatt, G. I.; Chorin, A. J.; Prostokishin, V. M.

2005-01-01

124

Relationship of maximum tropical cyclone intensity to sea surface temperature and tropical cyclone heat potential in the North Pacific Ocean  

NASA Astrophysics Data System (ADS)

We investigated whether the maximum intensity of tropical cyclones (TC) in the North Pacific Ocean depends on sea surface temperature (SST) and tropical cyclone heat potential (TCHP). The study used reanalysis data sets for both the oceans and atmosphere: daily, 10-day, and monthly oceanic data sets; six-hour and monthly atmospheric data sets; and a daily satellite SST data set, for the July-to-October season from 2002 to 2005. For each TC, we summed TCHP from the time of genesis to the time of first reaching a minimum central pressure (MCP), to obtain an accumulated TCHP. In a linear regression analysis, the relationship between maximum TC intensity and accumulated TCHP differed between the eastern and western Pacific: high values of accumulated TCHP were needed before a TC attained a certain MCP in the western Pacific. In addition, the background convective available potential energy (CAPE) value was nearly four times larger in the western Pacific than in the eastern Pacific. The static stability was also 6.5% lower, the inertial stability 29.7% higher, and the size of tropical cyclones 38.2% larger in the western Pacific than in the eastern Pacific. The result indicated a deeper Rossby penetration depth and stronger TC in the western Pacific. Finally, we validated the TCHP values derived from three oceanic reanalysis data sets by using Argo profiling float observations. We found that use of only the daily data can reproduce the cooling effect of a passage of a TC, which caused a decrease in the TCHP values.

Wada, Akiyoshi; Usui, Norihisa; Sato, Kanako

2012-06-01

125

Sea surface signature of tropical cyclones using microwave remote sensing  

NASA Astrophysics Data System (ADS)

Measuring the sea surface during tropical cyclones (TC) is challenging due to severe weather conditions that prevent shipboard measurements and clouds which mask the sea surface for visible satellite sensors. However, sea surface emission in the microwave L-band can penetrate rain and clouds and be measured from space. The European Space Agency (ESA) MIRAS L-band radiometer on the Soil Moisture and Ocean Salinity (SMOS) satellite enables a view of the sea surface from which the effects of tropical cyclones on sea surface emissivity can be measured. The emissivity at these frequencies is a function of sea surface salinity (SSS), sea surface temperature (SST), sea surface roughness, polarization, and angle of emission. If the latter four variables can be estimated, then models of the sea surface emissivity can be used to invert SSS from measured brightness temperature (TB). Actual measured TB from space also has affects due to the ionosphere and troposphere, which have to be compensated for, and components due to the galactic and cosmic background radiation those have to be removed. In this research, we study the relationships between retrieved SSS from MIRAS, and SST and precipitation collected by the NASA TMI sensor from the Tropical Rainfall Measuring Mission (TRMM) satellite during Hurricane Isaac, in August 2012. During the slower movement of the storm, just before landfall on the vicinity of the Louisiana Shelf, higher precipitation amounts were associated with lower SSS and slightly increased SST. This increased trend of SST and lower SSS under regions of high precipitation are indicative of inhibited vertical mixing. The SMOS Level 2 SSS were filtered by a stepwise process with removal of high uncertainty in TB under conditions of strong surface roughness which are known to create noise. The signature of increased SST associated with increasing precipitation was associated with decreased SSS during the storm. Although further research is required, this study shows that there is a TB signal from the sea surface beneath a tropical cyclone that provides information on roughness and salinity.

Kil, Bumjun; Burrage, Derek; Wesson, Joel; Howden, Stephan

2013-06-01

126

Indications of the influence of the force of gravity on tropical cyclones in the northwestern part of the Pacific Ocean  

Microsoft Academic Search

Peculiarities of the spatial distribution of the begin? nings and the most intense stages of tropical cyclones in the northwestern part of the Pacific Ocean are dem? onstrated in this paper in comparison with the values of the gravity force anomalies in the cyclone zone. Relations are distinguished in which some group char? acteristics of the tropical cyclones and the

M. I. Yaroshevich

2011-01-01

127

Global Losses and Declining Vulnerability to Tropical Cyclones  

NASA Astrophysics Data System (ADS)

Approach An extreme environmental event may generate different losses for different societies. If the physical exposure to an event is held fixed, then the magnitude of a society's loss defines its vulnerability to that event. Competing hypotheses suggest that social and economic developments could make vulnerability rise or fall over time, but previous studies have been unable to reject either hypothesis because they lacked accurate data on societies' physical exposure to extreme events. We address this problem for a specific type of event by reconstructing the exposure of 233 countries to every tropical cyclone (TC) on the planet between 1950 and 2008 in making use of the Limited Information Cyclone Reconstruction and Integration for Climate and Economics (LICRICE) model [Hsiang, 2010]. By filling a critical data gap, this reconstruction enables us to compare how revenue losses, damages, and deaths from physically similar events change over time. Our approach contrasts with a large literature, which relies almost exclusively on self-reporting data of TC damages compiled by the Emergency Events Database (EM-DAT)[OFDA/CRED, 2009]. Results On a global scale, we find that populations rapidly mitigate certain TC risks, reducing their reported damages from a TC of low intensity by a remarkable 9.4% yr-1 and death rates by 5.1% yr-1 (Figure 1). However, these rapid reductions in vulnerability are not evident for the highest intensity TCs and lost agricultural revenues, which are more difficult to observe than deaths or damages, exhibit non-declining vulnerability for events of all intensities. Because the vulnerability of agriculture has remained high while vulnerability to damages has declined rapidly, our results indicate that lost agricultural revenues have dominated TC losses ever since ˜1990. References Hsiang, S. M. (2010). Temperatures and cyclones strongly associated with economic production in the Caribbean and Central America. Proceedings of the National Academy of Sciences, 107(35):15367-15372. OFDA/CRED (2009). The International Disaster Database.

Narita, D.; Hsiang, S. M.

2011-12-01

128

The impact of limiting ocean roughness on GEOS-5 AGCM tropical cyclone forecasts  

NASA Astrophysics Data System (ADS)

Global climate models have been shown to simulate tropical cyclone-like behavior even at relatively coarse resolution, and recent higher resolution simulations more accurately capture the intensity, structure, and interannual variability. Even the highest resolution global models, however, continue to underestimate the intensity of the strongest tropical cyclones. The simulated cyclone intensity has been shown by many studies to be greatly influenced by the fluxes at the air-sea interface. A simple modification has been implemented in the GEOS-5 atmospheric general circulation model (AGCM) based on existing theory and laboratory experiments, which demonstrated that the ocean roughness does not increase with surface stress beyond some threshold. A series of strong tropical cyclone simulations were performed with the GEOS-5 AGCM to evaluate the impact of imposing a limit on ocean surface roughness at high wind speeds. The results demonstrated clear improvements in cyclone intensity and structure in the simulations with limited ocean roughness.

Molod, Andrea; Suarez, Max; Partyka, Gary

2013-01-01

129

Spectra of The Stratospheric GWs Induced by A Tropical Cyclone  

NASA Astrophysics Data System (ADS)

Source spectra of Gravity Waves GWs are prerequisite for gravity-wave-drag parameterization schemes GWD In this presentation an unique spectra of the GWs induced by a tropical cyclone TC will be introduced The spectra was derived from a numerical simulation with a North-Western Pacific typhoon The simulation revealed that pronounced stratospheric GWs with distinct appearance for example spiral wave fronts seen at 20 km altitude were generated during a typhoon passage TC-GWs With conducting spectral analysis with model output spectra of the TC-GWs were found to be also distinctive The salient feature was that predominant GW components exhibited persistent oscillation with time periods around 14-hr In general the shape of momentum flux spectra with respect to horizontal wave-number and frequency was different to those having been already presented in the previous studies where corresponding mechanisms responsible for the respective GW generation have also been proposed such as thermal forcing mechanism mechanical oscillator effect and moving mountain effect The singular momentum flux spectra of the TC-GWs suggests that TC-GWs were triggered by an independent mechanism Extensive investigation on the primary circulation of the TC i e the vorticity in mid-troposphere was conducted with using the empirical orthogonal function EOF method Significant oscillation was seen in the leading EOF vectors representing the evolution of the main body of the cyclone Concurrently the TC related circulation in the mid- to upper troposphere was

Chen, Z.; Lu, D.; Preusse, P.; Ern, M.

130

Tropical cyclone intensification trends during satellite era (1986-2010)  

NASA Astrophysics Data System (ADS)

Using International Best Track Archive for Climate Stewardship (IBTrACS, version v03r03) analysis during satellite era (1986-2010) we determined the trends of intensification of tropical cyclones (TC) over all the global basins, except the North Indian Ocean. Over all the basins, the rate of TC intensification from 64 kt to first peak of intensity maxima (global average value = 104 kt) was found to be positive. The above trends were significant for 4 out of 5 basins, except the North West Pacific. The trends indicate that the TCs now intensify from 64 kt to 104 kt nearly 9 hours earlier than they did 25 years back. The maximum reduction in intensification time is noticed over the North Atlantic Ocean where the average time needed for TC to intensify from 64 kt to 112 kt has reduced by nearly 20 hours during the past 25-year period.

Kishtawal, C. M.; Jaiswal, Neeru; Singh, Randhir; Niyogi, D.

2012-05-01

131

The genesis of tropical cyclone Bilis (2000) associated with cross-equatorial surges  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to explore how a tropical cyclone forms from a pre-existing large-scale depression which has been observed and associated with cross-equatorial surges in the western North Pacific. Tropical cyclone Bilis (2000) was selected as the case to study. The research data used are from the results of the non-hydrostatic mesoscale model (MM5), which has successfully simulated the transformation of a pre-existing weak large-scale tropical depression into a strong tropical storm. The scale separation technique is used to separate the synoptic-scale and sub-synoptic-scale fields from the model output fields. The scale-separated fields show that the pre-existing synoptic-scale tropical depression and the subsynoptic scale tropical cyclone formed later were different scale systems from beginning to end. It is also shown that the pre-existing synoptic-scale tropical depression did not contract to become the tropical cyclone. A series of weak, sub-synoptic-scale low and high pressure systems appeared and disappeared in the synopticscale depression, with one of the low systems near the center of the synoptic-scale depression having deepened to become the tropical cyclone. The roles of the synoptic-scale flow and the sub-synoptic scale disturbances in the formation of the tropical cyclone are investigated by diagnoses of the scale-separated vertical vorticity equation. The results show that the early development of the sub-synoptic scale vortex was fundamentally dependent on the strengthening synoptic-scale environmental depression. The depression was strengthened by cross-equatorial surges, which increased the convergence of the synoptic-scale depression at low levels and triggered the formation of the tropical cyclone.

Xu, Yamei

2011-05-01

132

Atlantic Tropical Cyclones Variability and Time Series Analysis  

NASA Astrophysics Data System (ADS)

Formation and evolution of Atlantic tropical cyclones (ATC) is typically investigated using: 1) short-term forecasting of the track and intensity of storms based on high resolution mesoscale models, and 2) statistical forecast of seasonal storm activity. The underlying assumption of statistical methods is that physical precursors in the ocean-atmosphere system determine the probability of genesis and development of ATC. Recently, low- resolution climate models have been used to investigate the seasonal genesis and evolution of ATC. The skill in forecasting the seasonal or inter-annual ATC activity with dynamical models is still limited, due to rapid decay of predictability in such models. Nonetheless, these models can provide a qualitative understanding of the link between various major physical perturbations in the ocean-atmosphere system and ATC activity. Such factors, extensively reported in literature, are: Sea surface temperature (SST) anomalies, El Nino-Southern Oscillation (ENSO), Vertical wind shear, West African Rainfall, Quasi-biennial oscillation (QBO), Atlantic Multidecadal Oscillation, etc. If these factors predetermine or are significantly correlated with ATC activity, then, past ocean- atmosphere observations might provide further understanding of the relationships between climatic anomalies (for example SST anomalies) and the ATC activity (such as number of hurricanes per year). We use time series of data accumulated over the past half century to get insight into the general features of the system. Power spectrum density analysis of time series of annual ATC numbers shows quasi-periods similar to those found in annual SST anomaly, between latitudes of 30 S and 30 N, and of the annual CAR Index (the SST anomaly in the Caribbean region). The analysis suggests that part of ATC inter-annual variability can be directly linked to SST variations in the same region. The study underlines the potential role of time-series analysis to complement other statistical and climate dynamic methods used in the description and forecasting of tropical cyclones.

Andronache, C.; Phillips, V.

2008-05-01

133

Is there any long-term memory effect in the tropical cyclones?  

NASA Astrophysics Data System (ADS)

The investigation of the intrinsic properties of the annual tropical cyclone count over Atlantic, during 1870-2006, is herewith attempted. The motivation behind this exploration is to contribute to the current understanding about the dynamics of these disastrous events, as tropical cyclones create destructive impacts for people living around tropical areas. The analytical tool used is the detrended fluctuation analysis, and the exponent obtained reveals that the time series of the annual tropical cyclone count over Atlantic obeys the classical random walk (white noise). In other words, the number of tropical cyclones seems to exhibit neither persistent nor antipersistent behavior. The reliability of the lack of scaling dependence in the time series of the annual tropical cyclone count is confirmed, by applying error bounds statistics and studying the decay of the autocorrelation function (i.e., not rejected exponential decay) and the variability of local slopes (i.e., lack of constancy in a sufficient range). In addition, the fact that the series used is fractional Gaussian noise depicts that the results obtained are reliable, despite the fact that the available data set is still limited. The indication of a nearly white noise signal in the tropical cyclone count fluctuations does not suggest that the climate change phenomenon does not exist.

Varotsos, Costas A.; Efstathiou, Maria N.

2013-03-01

134

Heightened Tropical Cyclone Activity in the North Atlantic: Natural Variability or Climate Trend?  

Microsoft Academic Search

We find that long-period variations tropical cyclone and hurricane frequency over the past century has occurred as three, relatively stable regimes separated by sharp transitions. Each regime has seen 50 percent more cyclones and hurricanes than the previous one and is associated with a distinct range in eastern Atlantic sea surface temperatures (SSTs). The end result has been a substantial,

G. J. Holland; P. J. Webster

2006-01-01

135

Correcting for Precipitation Effects in Satellite-Based Passive Microwave Tropical Cyclone Intensity Estimates.  

National Technical Information Service (NTIS)

Accurate tropical cyclone (TC) intensity estimates are best achieved from satellite observations. The Advanced Microwave Sounding Unit (AMSU) has operated since 1998 on polar-orbiting environmental satellites and is able to measure the warm temperature an...

R. S. Wacker

2005-01-01

136

Forecasting Tropical Cyclone Recurvature Using an Empirical Orthogonal Function Representation of the Synoptic Forcing.  

National Technical Information Service (NTIS)

Empirical Orthogonal Function (EOF) representation of the synoptic forcing is combined with past meridional and zonal displacements (persistence) to forecast tropical cyclone recurvature at 36, 54 and 72 h. Recurvature is defined following Leftwich (1978,...

T. D. Lage

1982-01-01

137

Forecasting of Tropical Cyclone Motion Using an EOF (Empirical Orthogonal Function) Representation of Wind Forcing.  

National Technical Information Service (NTIS)

Empirical Orthogonal Function (EOF) analysis is used to represent the environmental wind forcing of selected western North Pacific tropical cyclone tracks from 1979-1983. The EOF analysis is applied separately to the zonal and meridional wind components a...

W. E. Wilson

1984-01-01

138

Extended Forecast of the Frequencies of North Atlantic Basin Tropical Cyclone Activity for 2009.  

National Technical Information Service (NTIS)

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 a...

R. M. Wilson

2009-01-01

139

Is cumulus convection the concertmaster of tropical cyclone activity in the Atlantic?  

NASA Astrophysics Data System (ADS)

The influence of the cloud representation in global climate models on the accuracy of the North Atlantic tropical cyclone simulations is investigated. The North Atlantic tropical cyclone activity is simulated with a standard climate model, CCSM. The conventional parameterization of cloud processes in CCSM is replaced by the “super-parameterization” and the simulation is run again. The comparison of tropical cyclone statistics reveals that the model with explicit representation of cloud processes produces a larger number of events, with stronger intensity and longer life-cycle. The results show that clouds have a significant impact on the mechanisms associated with tropical cyclone activity such as surface temperature and ocean subsurface processes, vertical wind shear, and the transport of moisture in the lower troposphere.

Stan, Cristiana

2012-10-01

140

Consistent Tropical Cyclone Wind and Wave Forecasts for the U.S. Navy.  

National Technical Information Service (NTIS)

A new algorithm to generate wave heights consistent with tropical cyclone official forecasts from the Joint Typhoon Warning Center (JTWC) has been developed. The process involves generating synthetic observations from the forecast track and the 34-, 50-, ...

C. R. Sampson H. L. Tolman P. A. Wittmann

2010-01-01

141

Large-Scale Characteristics of Rapidly Intensifying Tropical Cyclones in the North Atlantic Basin  

Microsoft Academic Search

The National Hurricane Center (NHC) and Statistical Hurricane Intensity Prediction Scheme (SHIPS) databases are employed to examine the large-scale characteristics of rapidly intensifying Atlantic basin tropical cyclones. In this study, rapid intensification (RI) is defined as approximately the 95th percentile of over-water 24-h intensity changes of Atlantic basin tropical cyclones that developed from 1989 to 2000. This equates to a

John Kaplan; Mark Demaria

2003-01-01

142

On the Influences of Vertical Wind Shear on Symmetric Tropical Cyclone Structure Derived from AMSU  

Microsoft Academic Search

Axisymmetric temperatures and gradient-balanced winds associated with tropical cyclones derived from the Advanced Microwave Sounding Unit are stratified by the 24-h averaged vector difference of the horizontal wind between 200 and 850 hPa (or vertical wind shear). Using 186 total cases that are limited to tropical cyclones with intensities greater than 33 m s 21 (or mature) and are located

John A. Knaff; Stacey A. Seseske; Mark DeMaria; Julie L. Demuth

2004-01-01

143

Sensitivity of high-resolution tropical cyclone intensity forecasts to surface flux parameterization  

Microsoft Academic Search

Surface flux parameterization schemes used in current dynamic models are primarily based upon measurements at low and moderate\\u000a wind speeds. Recent studies show that these parameterization schemes may be incorrect at high wind speeds (e.g., tropical\\u000a cyclone forecasts). Five high-resolution numerical model experiments are designed to assess the sensitivity of tropical cyclone\\u000a intensity forecasts to changes in the surface flux

Chi-Sann Liou

2007-01-01

144

The genesis of tropical cyclone Bilis (2000) associated with cross-equatorial surges  

Microsoft Academic Search

The purpose of this paper is to explore how a tropical cyclone forms from a pre-existing large-scale depression which has\\u000a been observed and associated with cross-equatorial surges in the western North Pacific. Tropical cyclone Bilis (2000) was\\u000a selected as the case to study. The research data used are from the results of the non-hydrostatic mesoscale model (MM5), which\\u000a has successfully

Yamei Xu

2011-01-01

145

Simulated tropical cyclones using the National Center for Atmospheric Research community climate model  

Microsoft Academic Search

The possibility of simulating tropical cyclones (TCs) using the National Center for Atmospheric Research community climate model (CCM2) is explored. Daily outputs from two long-term simulation runs using the standard T42 resolution CCM2 are examined to identify simulated tropical cyclones (STCs) using a search scheme that selects qualified STCs resembling observed TCs. The two simulation cases are a 20-year run

Jun-ichi Tsutsui; Akira Kasahara

1996-01-01

146

Analysis of the influence of Saharan air layer on tropical cyclone intensity using AIRS/Aqua data  

NASA Astrophysics Data System (ADS)

How the Saharan air layer(SAL) affects tropical cyclone intensity in the North Atlantic Ocean is an issue in debate. A composite study of 274 cases from 37 named tropical cyclones that formed during the period 2005-2007 is conducted using AIRS relative humidity between 600-700 hPa. Typically the dry SAL air is first observed within 1000 km north of the tropical cyclone center and then intrudes southward and towards the inner region of tropical cyclones along the cyclonic flow. This study provides evidence that the SAL can affect tropical cyclone intensity in both favorably and unfavorably manners by intensifying tropical cyclones when it is first found mostly in the northwest quadrant and then weakening tropical cyclones when its dry air intrudes within 360 km of the tropical cyclone center, mostly in the southwest and southeast quadrants. It appears that the SAL is favorable for the initial development of tropical cyclones but unfavorable for their subsequent intensification.Average characteristics of the SAL dry air intrusion for intensifying and weakening cases, respectively with bold numbers indicating that the differences between the two cases are statistically significant at 99% level

Shu, S.; Wu, L.

2010-12-01

147

Climate-driven changes in tropical cyclone intensity shape dune activity on Earth's largest sand island  

NASA Astrophysics Data System (ADS)

I use historical aerial photos and detailed climatic time series to show the geomorphological consequences of a dramatic decrease in tropical cyclone frequency and intensity in eastern Australia since the early 1980s, leading to rapid dune stabilization on the Earth's largest sand island and a World Heritage Site, Fraser Island, Australia. Climate warming is generally expected to increase the intensity of tropical cyclones. However, some models predict that tropical cyclones' frequency will decrease in a warmer world. Here, I show that tropical cyclone frequency and intensity significantly declined in eastern Australia (south of 20°S) since the early 1980s, corresponding with the shift to a positive phase of the Inter-decadal Pacific Oscillation (in 1977) and an increased frequency of El-Niño events since 1982-83. Using remote sensing techniques I show that most of Fraser Island's sand blows were advancing inland in the period between 1948-1982, and that tropical cyclones in that period were strong enough to initiate small sand blows (< 1 ha). However, the decline in wind power since 1982 resulted in the contraction of Fraser Island's sand blows' area size, at an average rate of 0.5% of their area per year. This study demonstrates the importance of global changes in wind power, in addition to studied effects of changes in temperature, rainfall and sea level. In areas where tropical cyclones frequency and intensity are increasing, dune activation may be expected.

Levin, Noam

2010-05-01

148

Advances in research and forecasting of tropical cyclones from 1963-2013  

NASA Astrophysics Data System (ADS)

A review of progress over the past 50 years in observing and forecasting of tropical cyclones is presented. Tremendous progress has been made in track forecasting in the past 20 years with the improvement in numerical model guidance and the use of consensus forecasting, and this has contributed to a number of warning centers now issuing five-day track forecasts that are as accurate as three-day forecasts of a decade ago. Techniques are now available to specify the track forecast uncertainty for assessing the risk of a tropical cyclone. With the advent of five-day forecasts, a focus on improved understanding of formation has led to two field experiments. A recent advance has been in extended-range (5-30 days) forecasts of tropical cyclone events (formations and tracks) in the western North Pacific from the ECMWF 32-day ensemble predictions. This advance is a contribution to a goal of seamless forecasting from one day to a season for tropical cyclones. Little progress has been made in intensity forecasting, although the Hurricane Forecast Improvement Project in the United States and recent field experiments may offer some future advances. Some advances in forecasting tropical cyclone impacts such as storm surge, surface waves, and precipitation have been achieved. Future opportunities for continued advances are possible such that improved warnings can lead to reductions in losses of lives and minimizing damages from tropical cyclones.

Elsberry, Russell L.

2013-09-01

149

Observed recent trends in tropical cyclone rainfall over the North Atlantic and the North Pacific  

NASA Astrophysics Data System (ADS)

In this study, we use Tropical Rainfall Measurement Mission and Global Precipitation Climatology Project rainfall data together with historical storm track records to examine the trend of tropical cyclone (TC) rainfall in the North Atlantic and the northeast and northwest Pacific during two recent decades (1988-1997 and 1998-2007). We find that there is an approximate linear relationship between TC rain (defined as accumulated total rainfall along storm tracks) and storm intensity as classified by the Saffir-Simpson scheme. During the data period, total TC rain has trended upward at a rate of 23.8% ± 23.5% per decade over the North Atlantic but downward with a rate of 25.1% ± 19.7% per decade over the northeast Pacific. Over the northwest Pacific, there is a reduction in TC rain of approximately 20.9% ± 13.5% per decade, possibly associated with a strong interdecadal-scale oscillation. Storm characteristics such as duration and TC rain energy per storm (EPS) remain unchanged for the North Atlantic and the northeast Pacific. For the northwest Pacific, a 28% ± 18% reduction in EPS from the first decade (1988-1997) to the second decade (1998-2007) is found with the track data from the Joint Typhoon Warning Center. Analyses of the probability distribution function of TC rain show that there is an overall increase in TC frequency across the entire TC rainfall spectrum over the North Atlantic but an overall decrease for the northeast Pacific. In the northwest Pacific, we find a redistribution in EPS with decreased frequency in heavy-rain storms and increased frequency in light-rain storms. Overall, trends in TC rain in the different ocean basins are consistent with long-term relative changes in the ambient large-scale sea surface temperature and vertical wind shear and, to a lesser extent, tropical cyclone Maximum Potential Intensity.

Lau, William K. M.; Zhou, Y. P.

2012-02-01

150

A 320-year AMM+SOI Index Reconstruction from Historical Atlantic Tropical Cyclone Records  

NASA Astrophysics Data System (ADS)

Trends in the frequency of North Atlantic tropical cyclones, including major hurricanes, are dominated by those originating in the deep tropics. In addition, these tropical cyclones are stronger when making landfall and their total power dissipation is higher than storms forming elsewhere in the Atlantic basin. Both the Atlantic Meridional Mode (AMM) and El Nino-Southern Oscillation (ENSO) are the leading modes of coupled air-sea interaction in the Atlantic and Pacific, respectively, and have well-established relationships with Atlantic hurricane variability. Here we use a 320-year record of tropical cyclone activity in the Lesser Antilles region of the North Atlantic from historical manuscript and newspaper records to reconstruct a normalized seasonal (July-October) index combining the Southern Oscillation Index (SOI) and AMM employing both the modern analog technique and back-propagation artificial neural networks. Our results indicate that the AMM+SOI index since 1690 shows no long-term trend but is dominated by both short-term (<10 years) and long-term (quasi-decadal to bi-decadal) variations. The decadal-scale variation is consistent with both instrumental and proxy records elsewhere from the global tropics. Distinct periods of high and low index values, corresponding to high and low tropical cyclone frequency, are regularly-appearing features in the record and provides further evidence that natural decadal -scale variability in Atlantic tropical cyclone frequency must be accounted for when determining trends in records and attribution of climate change.

Chenoweth, M.; Divine, D.

2010-12-01

151

Tree-ring Oxygen Isotope Records of Climate Modes Influencing North Atlantic Tropical Cyclone Activity  

NASA Astrophysics Data System (ADS)

The relatively short instrumental record hinders our ability to discern the linkages between low frequency modes of climate variability and tropical cyclone activity and to differentiate natural versus anthropogenic components of these trends. The development of biological proxies for tropical cyclone activity and climate provides a basis for evaluation of these linkages over much longer time frames. The oxygen isotope composition of tree-ring cellulose, sampled at high resolution (seasonal or better), provides a new proxy for tropical cyclone activity that preserves a concurrent isotope time series reflecting the influence of climate variability. This proxy archive potentially extends many centuries beyond the instrumental and historical (documentary) record of climate and tropical cyclone activity. Isotope time series for longleaf pines (Pinus palustris Mill.) in southern Georgia and South Carolina preserve distinct tropical cyclone histories, yet similar, long term trends in cellulose ? 18O compositions. The isotope time series correlate to various climate modes proposed to impact hurricane formation and frequency. Tree-ring cellulose ? 18O values at the Georgia study site show a significant negative correlation with AMO indices from 1875 to about 1950, and a weaker, positive correlation from about 1965 to 1990. The "crossover" parallels a change in the predominant ontogeny of North Atlantic tropical cyclones from tropical-only to baroclinically-enhanced hurricanes. The intervening 1950s is marked by greater correspondence to ENSO indices. Reduced seasonality in the isotope record (i.e., the difference between earlywood and latewood ? 18O values) corresponds to warm phases of the PDO. An isotope series for 1580 to 1650 suggests little tropical cyclone activity coinciding with a period (1560-1625) of severe drought in the African Sahel. Although preliminary, these results suggest that tree-ring oxygen isotope compositions are sensitive to changes in climate modes that affect hurricane frequency and may ultimately yield a long, rich archive of climate information.

Mora, C. I.; Miller, D. L.; Grissino-Mayer, H. D.; Kocis, W. N.; Lewis, D. B.

2006-12-01

152

Modeling the Effects of Climate Variability and Change on Tropical Cyclone Activity  

NASA Astrophysics Data System (ADS)

Potential changes in future tropical cyclone activity arising from climate variability and change are hotly debated and are of critical importance to society. This paper describes results of high-resolution simulations together with statistical downscaling techniques to assess future changes in tropical cyclone activity in the North Atlantic basin. The global Community Climate System Model, one of the standard models used by the IPCC, is used to drive regional climate simulations using the NCAR Nested Regional Climate Model (NRCM) for three time-slices of 1995-2005, 2020-2030 and 2045-2055 at sufficient resolution to generate and sustain tropical storms and intense hurricanes. Bias in the global model climate is shown to feed down into the NRCM resulting in poor reproduction of current climate tropical cyclone activity. A method to remove bias from the global model data is presented and, when used to drive the NRCM, results in a good simulation of tropical cyclone activity in current climate. Changes in tropical cyclone activity over the next 50 years are presented using both dynamical and statistical downscaling techniques from the bias-corrected global climate data.

Done, J.; Bruyere, C.; Holland, G. J.; Suzuki-Parker, A.

2009-12-01

153

Isotopic spikes from tropical cyclones in surface waters: Opportunities in hydrology and paleoclimatology  

Microsoft Academic Search

The stable isotopic ratio of precipitation from tropical cyclones is very low compared to that of normal summer precipitation (Lawrence and Gedzelman, 1996). Tropical Storms Allison and Chantal made landfall in southeast Texas in the summer of 1989 and dumped large amounts of rain. Isotope ratios of surface waters measured at five different sites decreased markedly after the passage and

James R Lawrence

1998-01-01

154

An inverse relationship between aggregate northern hemisphere tropical cyclone activity and subsequent winter climate  

Microsoft Academic Search

Our understanding of the climate role of tropical cyclones (TCs) remains incomplete despite increasing efforts to quantify it. TCs cool the sea surface over a large area, transport heat vertically and meridionally, and dry the tropical atmosphere. Following an anomalous TC season, when TCs have done an anomalous share of energy transport, there may be alterations of other climate mechanisms.

Robert E. Hart

2011-01-01

155

Objective Estimation of the 24-h Probability of Tropical Cyclone Formation  

Microsoft Academic Search

A new product for estimating the 24-h probability of TC formation in individual 5 83 58 subregions of the North Atlantic, eastern North Pacific, and western North Pacific tropical basins is developed. This product uses environmental and convective parameters computed from best-track tropical cyclone (TC) positions, National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) analysis fields, and water

Andrea B. Schumacher; Mark DeMaria; John A. Knaff

2009-01-01

156

Comment--An Interpretation of Kurihara and Kawase's Two-Dimensional Tropical-Cyclone Development Model  

Microsoft Academic Search

This comment presents a detailed examination of the published model results of Kurihara and Kawase in an attempt to clarify the role of wave-CISK in the development of tropical cyclones. Kurihara and Kawase's model simulates the development of a tropical depression, although the vertical structure differs significantly from observations. The physical roles of vertical shear and nonlinear dynamics in the

John L. McBride; Hugh E. Willoughby

1986-01-01

157

Trends in Tropical Cyclone Impact: A Study in Andhra Pradesh, India.  

NASA Astrophysics Data System (ADS)

Contrary to the common perception that tropical cyclones are on the increase, due perhaps to global warming, studies all over the world show that, although there are decadal variations, there is no definite long-term trend in the frequency or intensity of tropical cyclones over the period of about a century for which data are available. There is, nevertheless, a sharp increase in the socio-economic impact of tropical cyclones in the form of increasing property damage. An analysis of cyclones affecting the state of Andhra Pradesh, India, in the last quarter century by normalizing cyclone damage for economic and demographic factors shows that here, as elsewhere, the greater vulnerability is attributable mainly to these factors and not to any increase in frequency or intensity of cyclones. The decrease of alertness in disaster management that often occurs after a few years' lull in occurrence of cyclones, known as the "fading memory syndrome," also contributes to increases in loss of lives and property damage. This distinction between meteorological and socio-economic causes for the increased impact is important to avoid a tendency for political and administrative decision makers to blame natural causes. They have to take these realities into account, not just in developing a vigilant disaster management system, but in land-use planning, development of coastal districts, and insurance measures.

Raghavan, S.; Rajesh, S.

2003-05-01

158

Pollution and dust aerosols modulating tropical cyclones intensities  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TC) are propelled mostly by realization of latent heat that is stored in vapor coming off warm sea surfaces. The heating occurs when the vapor condenses into cloud drops. Re-evaporation of the cloud water takes back the released heat, whereas precipitation of the water as rain fixates the heat in the air. Therefore, it is expected that TC intensities would be sensitive to precipitation forming processes that affect the amount and distribution of latent heat release. This has been simulated by numerical models, which showed that cloud condensation nuclei (CCN) aerosols weaken the storms apparently by slowing the conversion of cloud drops into precipitation. If so, we should expect that storm predictions that do not take this aerosol effect into account would over-predict TC intensities. Here we show that increased aerosols quantities in a TC periphery can explain about 8% of the forecast errors of the TC. Indeed, actual intensities of polluted TCs were found to be on average lower than their predicted values, providing supporting observational evidence to the hypothesis. It was also found that TC intensity might be more susceptible to the impacts of aerosols during their developing stages and less in the TC mature and dissipating stages.

Rosenfeld, Daniel; Clavner, Michal; Nirel, Ronit

2011-10-01

159

Tropical cyclones in enhanced resolution CMIP5 experiments  

NASA Astrophysics Data System (ADS)

This study investigates the possible effects of global warming on tropical cyclone (TC) activity. The study is conducted using the coupled ocean-atmosphere global climate model EC-Earth configured at a relatively high resolution (T159 with 62 vertical levels), which is integrated following the CMIP5 protocol. By considering the late twentieth century (1979-2009) in the historical simulation and the twenty-first century end (2070-2100) in the RCP4.5 and RCP8.5 scenarios, significant future annual mean frequency decreases are found globally and in both hemispheres, accompanied by significant mean lifetime decreases and significant intensity increases, the latter being found through several different measures (but with caveats). In addition, the relatively novel aspect of simulating TCs of the past (1900-1930) is studied to further assess the robustness of the climate change results. These results suggest that TCs in the early twentieth century were more frequent in the southern hemisphere and dissipated more energy in the southern hemisphere and the South Indian Ocean. Although some model biases are present and the coarse model resolution prevents intense TCs in being simulated, reasonable TC simulation skill for other metrics (e.g., TC genesis, frequency of occurrence) is found when validated against present day observations. Thus the model displays an acceptable ability to connect TC climatology with the larger scale circulation.

Rathmann, Nicholas Mossor; Yang, Shuting; Kaas, Eigil

2013-06-01

160

Impacts of tropical cyclones on hydrochemistry of a subtropical forest  

NASA Astrophysics Data System (ADS)

Tropical cyclones (typhoons/hurricanes) have major impacts on the biogeochemistry of forest ecosystems, but the stochastic nature and the long intervals between storms means that there are limited data on their effects. We characterised the impacts of 14 typhoons over six years on hydrochemistry of a subtropical forest plantation in Taiwan, a region experiencing frequent typhoons. Typhoons contributed 1/3 of the annual rainfall on average, but ranged from 4 to 55%. The stochastic nature of annual typhoon related precipitation poses a challenge with respect to managing the impacts of these extreme events. This challenge is exacerbated by the fact that typhoon-related rainfall is not significantly correlated with wind velocity, the current focus of weather forecasts. Thus, little advance warning is provided for the hydrological impacts of these storms. The typhoons we studied contributed approximately one third of the annual input and output of most nutrients (except nitrogen) during an average 9.5 day yr-1 period, resulting in nutrient input/output rates an order of magnitude greater than during non-typhoon months. Nitrate output balanced input during the non-typhoon period, but during the typhoon period an average of 10 kg ha-1 yr-1 nitrate was lost. Streamwater chemistry exhibited similarly high variability during typhoon and non-typhoon periods and returned to pre-typhoon levels one to three weeks following each typhoon. The streamwater chemistry appears to be very resilient in response to typhoons, resulting in minimal loss of nutrients.

Chang, C. T.; Hamburg, S. P.; Hwong, J. L.; Lin, N. H.; Hsueh, M. L.; Chen, M. C.; Lin, T. C.

2013-10-01

161

Convective asymmetries associated with tropical cyclone landfall: ?-plane simulations  

NASA Astrophysics Data System (ADS)

The physical processes associated with changes in the convective structure of an idealized tropical cyclone (TC) during landfall on a beta-plane were studied using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model, version 3 (MM5). The simulation results suggested that the suppression of moisture supply and increased friction acted to enhance the convection from the left and front quadrants of the TC to the front and right of the TC during different periods of landfall. When surface moisture flux was turned off, convection in other parts of the quadrant was clearly suppressed and the total rainfall was reduced. When surface friction was increased, precipitation showed a marked increase after the TC made landfall. Wetter air at low and intermediate levels, and drier air at high levels around the onshore side of the coastline led to a high value of convective available potential energy (CAPE). Consequently, convection was enhanced immediately downstream of this area when the surface moisture flux was cut off. When surface friction was increased, the physical process was similar prior to landfall. After landfall, increased convergence at the onshore side of the land resulted in enhanced convection in front of the TC. Consistent with previous findings, our results suggest that during landfall the TC structure changes from one of thermodynamic symmetry to asymmetry due to differential moisture flux between the land and sea surface. The asymmetry of the thermodynamic structure, which can be explained by the distribution of CAPE, causes an asymmetric rainfall structure.

Huang, Wei; Liang, Xudong

2010-07-01

162

Variations in tropical cyclone precipitation in Texas (1950 to 2009)  

NASA Astrophysics Data System (ADS)

and temporal variations of tropical cyclone precipitation (TCP) in Texas are examined using 60 years of precipitation data from Cooperative Observing Network gages (1950 to 2009). An automated extraction method is used to identify TCP. Texas receives an average of 123.5 mm of TCP/year, which is ~13% of the state's mean annual precipitation. September is the month with the most TCP with an average of 18.5 mm. As expected, TCP generally deceases as you move inland. Long-term trends (>50 years) in TCP are evident at some locations, but there are no statistically significant long-term trends in aggregated annual TCP metrics for Texas. Despite the lack of long-term trends, TCP metrics show some spectral power at periodicities of ~2-3 years, ~5-8 years, and >10 years. Areas within 400 km of the coast have higher risk of extreme daily TCP (>100 mm), but inland Texas can also occasionally experience extreme TCP. In some areas in southeastern Texas the probability of receiving >100 mm of daily TCP in any given year is ~0.30 (i.e., daily TCP exceeds 100 mm, on average, 1 out every 3 years).

Zhu, Laiyin; Quiring, Steven M.

2013-04-01

163

The impact of tropical sea surface temperatures on various measures of Atlantic tropical cyclone activity  

NASA Astrophysics Data System (ADS)

Since 1995 there has been a resurgence of Atlantic hurricane activity, with 2005 being the most active and destructive hurricane season on record. The influence of sea surface temperatures (SSTs) upon trends in Atlantic hurricane activity is investigated by considering SSTs in the southern tropical North Atlantic, an area known as the main development region (MDR). Significant differences in hurricane activity are observed when comparing the ten coolest and ten warmest years of SSTs in the MDR for the period spanning from 1941 to 2006, with increasing MDR SSTs linked to the increased duration and frequency of tropical cyclones. It is concluded that future increases in SSTs, as climate models project, could result in increased Atlantic basin hurricane activity. Understanding how oceanic processes affecting the MDR may change with climate change could therefore help increase the predictive capability for hurricane activity.

Steenhof, P. A.; Gough, W. A.

2008-05-01

164

Numerical diagnosis of a small, quasi-tropical cyclone over the western Mediterranean: Dynamical vs. boundary factors  

Microsoft Academic Search

SUMMARY A small, quasi-tropical cyclone occurred on 12 September 1996 over the western Mediterranean. Intense convective activity over the region during this period also produced a tornado outbreak in the Balearic Islands and torrential precipitation over eastern mainland Spain. Mesoscale model runs properly simulate the cyclone formation and show convection and heavy precipitation following the cyclone trajectory during its eastward

V. Homar; R. Romero; D. J. Stensrud; C. Ramis; S. Alonso

2003-01-01

165

Effect of remote sea surface temperature change on tropical cyclone potential intensity.  

PubMed

The response of tropical cyclone activity to global warming is widely debated. It is often assumed that warmer sea surface temperatures provide a more favourable environment for the development and intensification of tropical cyclones, but cyclone genesis and intensity are also affected by the vertical thermodynamic properties of the atmosphere. Here we use climate models and observational reconstructions to explore the relationship between changes in sea surface temperature and tropical cyclone 'potential intensity'--a measure that provides an upper bound on cyclone intensity and can also reflect the likelihood of cyclone development. We find that changes in local sea surface temperature are inadequate for characterizing even the sign of changes in potential intensity, but that long-term changes in potential intensity are closely related to the regional structure of warming; regions that warm more than the tropical average are characterized by increased potential intensity, and vice versa. We use this relationship to reconstruct changes in potential intensity over the twentieth century from observational reconstructions of sea surface temperature. We find that, even though tropical Atlantic sea surface temperatures are currently at a historical high, Atlantic potential intensity probably peaked in the 1930s and 1950s, and recent values are near the historical average. Our results indicate that--per unit local sea surface temperature change--the response of tropical cyclone activity to natural climate variations, which tend to involve localized changes in sea surface temperature, may be larger than the response to the more uniform patterns of greenhouse-gas-induced warming. PMID:18075590

Vecchi, Gabriel A; Soden, Brian J

2007-12-13

166

Tropical cyclones in the Bay of Bengal and deterministic methods for prediction of their trajectories  

Microsoft Academic Search

Based on information about tropical storms and depressions in the Bay of Bengal over a 100-year period (1877–1976), certain\\u000a climatic characteristics of tropical cyclones are examined. A brief description of climatic parameters, notably the region\\u000a of their development, direction and nature of movement and percentage of disturbances intensified into severe tropical storms\\u000a in different seasons of the year, which are

U C Mohanty

1994-01-01

167

Comparative analysis of TEC disturbances over tropical cyclone zones in the North–West Pacific Ocean  

NASA Astrophysics Data System (ADS)

In this paper, we study ionospheric total electron content (TEC) disturbances associated with tropical cyclones (TCs). The study relies on the statistical analysis of six cyclones of different intensity which occurred in the North-West Pacific Ocean in September-November 2005. We have used TEC data from the international network of two-frequency ground-based GPS receivers and NCEP/NCAR meteorological archive. TEC variations of different period ranges (02-20 and 20-60 min) are shown to be more intense during TC peaks under quiet geomagnetic conditions. The highest TEC variation amplitudes are registered when the wind speed in the cyclone and the TC area are maximum. The intensification of TEC disturbances is more pronounced when several cyclones occur simultaneously. We have revealed that the ionospheric response to TC can be observed only after the cyclone has reached typhoon intensity. The ionospheric response is more pronounced at low satellite elevation angles.

Polyakova, A. S.; Perevalova, N. P.

2013-10-01

168

Trends and interannual variability of extra-tropical cyclones derived from different diagnostic methods  

NASA Astrophysics Data System (ADS)

One central effort of the IMILAST (Intercomparison of Mid Latitude Storm Diagnostics) project is to assess diagnostic method-induced differences with respect to basic scientific investigations on extra-tropical cyclone characteristics, like trends and variability. Will answers to scientific questions relevant to cyclone studies be sensitive to the specific identification and tracking method applied? Due to differences in the cyclone diagnostic methods used, one would not expect a one-to-one overlap for the identified cyclones. The inter-methods differences could also vary from one cyclone characteristic to another, or for a particular subset of cyclones. For example, the differences in absolute trends in cyclone statistics could be larger than relative measures, and bigger for weak-moderate cyclone statistics than for strong cyclone statistics, etc. and the multi-method spread could be dependent on the intensity of the subset of cyclones investigated. This presentation focuses on basic trend behaviour and interannual variability of cyclones as diagnosed by different methods. In order to concentrate on inter-method differences, all participating methods have been applied to the same data set, the ERA-Interim reanalysis data for the period 1989-2008. Although a 20-yr period is too short to assess long term (e.g. anthropogenic) trends in cyclone activity, it is useful to see how different/similar the interannual variability and trends in cyclone activity are. Although trends in different cyclone parameters might be small for the period analyzed, an overall agreement of the trends and interannual variability diagnosed by the different methods would strengthen the applicability of those methods for addressing scientific questions. The inter-comparison of trends and variability will be presented for the northern and southern hemispheres, separately. In general, the inter-methods differences are much less notable in the trend estimates than in the absolute values of cyclone statistics. It is also noted that the methods perform more similarly for the subset of strong cyclones than for weak-moderate cyclones. Discrepancies between the methods are smallest in the regions of identified significant trends, revealing that the basic findings remain robust between the methods. Similar results are achieved with respect to the capability of the methods to identify coherent patterns of the interannual variability.

Leckebusch, G. C.; Wang, X. L.; Kew, S. F.; Grieger, J.; Schuster, M.; Ulbrich, U.; Gulev, S.; Imilast Team

2012-04-01

169

Tropical cyclones and reproductive ecology of Crocodylus acutus Cuvier, 1807 (Reptilia: Crocodilia: Crocodylidae) on a Caribbean atoll in Mexico  

Microsoft Academic Search

Crocodylus acutus, a coastal species nesting in sand beaches, could be affected by increasing tropical cyclone frequency. We studied key characteristics of C. acutus reproductive ecology on Banco Chinchorro atoll from 2006 to 2009, including the impact of two tropical cyclones. Hurricanes increased canopy openness causing earlier nesting the following year. Crocodiles nested at the beginning of the wet season

Pierre Charruau; John B. Thorbjarnarson; Yann Hénaut

2010-01-01

170

Cost-benefit analysis of a green electricity system in Japan considering the indirect economic impacts of tropical cyclones  

Microsoft Academic Search

Global warming is likely to profoundly influence future weather patterns, and one consequence of this is the likelihood of an increase in tropical cyclone intensity. The present paper presents a cost-benefit analysis of introducing significant amounts of green energy in the electricity system in Japan in the light of the economic damage that an increase in tropical cyclone intensity could

Miguel Esteban; Qi Zhang; Gorka Longarte-Galnares

2012-01-01

171

Vortex Rossby Waves in a Numerically Simulated Tropical Cyclone. Part I: Overall Structure, Potential Vorticity, and Kinetic Energy Budgets  

Microsoft Academic Search

The asymmetric structure in the inner core of a numerically simulated tropical cyclone is analyzed in this study. The simulated tropical cyclone is found to be highly asymmetric in the inner core. In the mid-lower troposphere, the asymmetry in the core is dominated by azimuthal wavenumber-1 and wavenumber-2 vortex Rossby waves. These waves propagate azimuthally upwind against the azimuthal mean

Yuqing Wang

2002-01-01

172

Atlantic tropical cyclones in the twentieth century: natural variability and secular change in cyclone count  

NASA Astrophysics Data System (ADS)

The twentieth century record of the annual count of Atlantic tropical cyclones (TCs) is analyzed to develop consistent estimates of its natural variability and secular change components. The analysis scheme permits development of multidecadal trends from natural variability alone, reducing aliasing of the variability and change components. The scheme is rooted in recurrent variability modes of the influential SST field and cognizant of Pacific-Atlantic links. The origin of increased cyclone counts in the early 1930s, suppressed counts in 1950-1960s, and the recent increase (since 1990s) is investigated using the count data set developed by Landsea et al. (J Clim 23: 2508-2519, 2010). We show that annual TC counts can be more closely reconstructed from Pacific and Atlantic SSTs than SST of the main development region (MDR) of Atlantic TCs; the former accounting for ~60% of the decadal count variance as opposed to ~30% for MDR SST. Atlantic Multidecadal Oscillation (AMO) dominates the reconstruction, accounting for ~55% of the natural decadal count variance, followed by the ENSO Non-Canonical and Pan-Pacific decadal variability contributions. We argue for an expansive view of the domain of influential SSTs—extending much beyond the MDR. The additional accounting of count variance by SSTs outside the MDR suggests a role for remotely-forced influences over the tropical Atlantic: the Pan-Pacific decadal mode is linked with decreased westerly wind shear (200-850 hPa) in its warm phase, much as the AMO impact itself. Non-canonical ENSO variability, in contrast, exerts little influence on decadal timescales. Interestingly, the secular but non-uniform warming of the oceans is linked with increased westerly shear, leading to off-setting dynamical and thermodynamical impacts on TC activity! The early-1930s increase in smoothed counts can be partially (~50%) reconstructed from SST natural variability. The 1950-1960s decrease, in contrast, could not be reconstructed at all, leading, deductively, to the hypothesis that it results from increased aerosols in this period. The early-1990s increase is shown to arise both from the abatement of count suppression maintained by SST natural variability and the increasing SST secular trend contribution; the abatement is related to the AMO phase-change in early-1990s. Were it not for this suppression, TC counts would have risen since the early 1970s itself, tracking the secular change contribution. The analysis suggests that when SST natural variability begins to significantly augment counts in the post-1990 period—some evidence for which is present in the preceding decade—Atlantic TC counts could increase rapidly on decadal timescales unless offset by SST-unrelated effects which apparently account for a non-trivial amount (~40%) of the decadal count variance.

Nigam, Sumant; Guan, Bin

2011-06-01

173

Development of a tropical cyclone tracker and applications to tropical cyclones occurred in 2008 in North Western Pacific  

NASA Astrophysics Data System (ADS)

To investigate whether tropical cyclones (TCs) are simulated correctly and verify forecast skill for TCs in numerical weather prediction models, it is necessary to derive trajectories of TCs from model output data and compare them with TC best track information. Because TC tracks are not model output variables, they can be diagnosed from basic variables as pressure, wind, and temperature of a model. A method to decide the TC center is to find out the center manually by looking at the weather charts. However, this manual method is not efficient and sometimes impossible to pinpoint the TC center. Furthermore, determining TC center manually from ensemble prediction results becomes increasingly inefficient. Thus an objective analysis of TC center and trajectory becomes an indispensable work. In this study, a TC tracker that has been developed (hereafter YSU TC tracker) for various model output format including netCDF used in WRF, binary data used in MM5, and GRIB used in GFS and ECMWF YOTC, with various projection including Lambert conformal and cylindrical equidistant (lat/lon) grid is applied for the model output to investigate the performance of the tracker. In detecting step, YSU TC tracker used mean sea level pressure, vorticity and geopotential height at 700 and 850hPa. In tracking step, a search area of next forecast time is determined with specified radius around TC center position of the next forecast time, guessed by using thresholds of cyclone movement such as direction, range of angle, and search radius based on TC speed between two consecutive analyses. The YSU TC tracker developed above was applied on the TCs occurred in 2008 in North Western Pacific. As a forecast data, 0.5° by 0.5° resolution NCEP GFS and ECMWF YOTC data on cylindrical equidistant grid were used. To investigate the performance of the YSU TC tracker, the YSU TC tracker was applied to the GFS data and the results are compared with those from the NCEP tracker. Average track positional errors from the best track data were similar for both trackers, implying that the YSU TC tracker performs as well as the NCEP tracker. To investigate the average forecast skill of the NCEP GFS and ECMWF YOTC data, the YSU TC tracker was applied on both data. The average track positional errors for both data were similar at the initial time, but the average track positional error of the NCEP GFS becomes larger than that of ECMWF YOTC data as the forecast time increases. More comprehensive results will be presented in the meeting.

Kim, J.; Kim, H.; Atmospheirc Predictability; Data Assimilation Laboratory

2010-12-01

174

Proxies of Tropical Cyclone Isotope Spikes in Precipitation: Landfall Site Selection  

NASA Astrophysics Data System (ADS)

The human experience of climate change is not one of gradual changes in seasonal or yearly changes in temperature or rainfall. Despite that most paleoclimatic reconstructions attempt to provide just such information. Humans experience climate change on much shorter time scales. We remember hurricanes, weeks of drought or overwhelming rainy periods. Tropical cyclones produce very low isotope ratios in both rainfall and in atmospheric water vapor. Thus, climate proxies that potentially record these low isotope ratios offer the most concrete record of climate change to which humans can relate. The oxygen isotopic composition of tropical cyclone rainfall has the potential to be recorded in fresh water carbonate fossil material, cave deposits and corals. The hydrogen isotopic composition of tropical cyclone rainfall has the potential to be recorded in tree ring cellulose and organic matter in fresh water bodies. The Class of carbonate organisms known as Ostracoda form their carapaces very rapidly. Thus fresh water ephemeral ponds in the subtropics are ideal locations for isotopic studies because they commonly are totally dry when tropical cyclones make landfall. The other proxies suffer primarily from a dilution effect. The water from tropical cyclones is mixed with pre-existing water. In cave deposits tropical cyclone rains mix with soil and ground waters. In the near shore coral environment the rain mixes with seawater. For tree rings there are three sources of water: soil water, atmospheric water vapor that exchanges with leaf water and tropical cyclone rain. In lakes because of their large size rainfall runoff mixes with ground water and preexisting water in the lake. A region that shows considerable promise is Texas / Northeast Mexico. In a study of surface waters that developed from the passage of Tropical Storm Allison (2001) in SE Texas both the pond water and Ostracoda that bloomed recorded the low oxygen isotope signal of that storm (Lawrence et al, 2008). In 2010 rain from Hurricane Alex, Tropical Depression 2 and Tropical Storm Hermine flooded ephemeral ponds in south Texas. Isotopic analysis of water and fossil Ostracoda from ephemeral ponds in south Texas is planned. Cores (50 cm in length) were taken in one of these ponds where living Ostracoda were found and collected.

Lawrence, J. R.; Maddocks, R.

2011-12-01

175

Improving the behavior of the cumulus parameterization for tropical cyclone prediction: Convection trigger  

NASA Astrophysics Data System (ADS)

Numerical studies have consistently shown the importance of moist convection in the evolution of tropical cyclones. However, a systematic evaluation of cumulus parameterization in the simulation of tropical cyclone is rare. The objective of this study is to 1) assess the performance of various subgrid-scale cumulus parameterization schemes in the simulation of tropical cyclones. Emphasis is placed on the intensity, distribution, and character of precipitation and on the forecast location and intensity of tropical cyclones; 2) improve the behavior of one of the cumulus parameterization schemes by modifying the parameterization, the weakness of which is identified in 1). The distribution and intensity of precipitation, its partitioning into grid-resolvable and subgrid-scale portions, the location and intensity of tropical cyclone were extremely sensitive to the choice of cumulus parameterization scheme. The scheme developed by Betts and Miller [Betts, A.K., Miller, M.J., 1993. The Betts-Miller scheme. In:Emanuel, K.A., Raymond, D.J. (Eds.), The Representation of Cumulus Convection in Numerical Models. Amer. Meteor. Soc., 246 pp] reproduced most of the features of rainfall distribution over the land, it tends to overestimate the rainfall coverage and make false alarm of intense rainfall. The mass flux scheme developed by Kain and Fritsch [Kain, J.S., Fritsch, J.M., 1993. Convective parameterization for mesoscale models: the Kain-Fritsch scheme. The Representation of Cumulus Convection in Numerical Models, Meteor. Monogr., No. 46, Amer. Meteor. Soc., 165-170] gave the best simulation of tropical cyclone on the 15 km grids, while the quasi-equilibrium scheme proposed by Grell [Grell, G., 1993. Prognostic evaluation of assumptions used by cumulus parameterization. Mon. Weather Rev., 121, 764-787] tended to underestimate sub-grid scale rainfall due to its deficiency in removing instability. Finally, it is also suggested that the Kain-Fritsch scheme can be improved for the case of weak synoptic forcing. In particular, the parameterization of the convective parcel's temperature perturbation by the environmental vertical velocity in the convective trigger function seems not quite robust. To improve this deficiency for our application, the effect of moisture advection is taken into account in determining the convective parcel's temperature perturbation. Preliminary results show that, the modified scheme can eliminate reasonably well the convective instability under weak synoptic forcing, change the response of the disturbance in the lower troposphere disturbance to environmental humidity and in favor of simulation of tropical cyclone. The results of this study should be of potential use for improving the performance of operational tropical cyclone prediction.

Ma, Lei-Ming; Tan, Zhe-Min

2009-04-01

176

Tropical cyclone induced physical and biogeochemical response in the Arabian Sea  

NASA Astrophysics Data System (ADS)

Tropical cyclone moving over a warm ocean is a manifestation of intense air-sea interaction process. Though the destructive power associated with the landfall of a cyclone is well known, its role in enhancing the biological production, and associated biogeochemical fluxes is least understood. In the Arabian Sea, located in the western part of the north Indian Ocean, tropical cyclones occurs regularly during spring (April-May) and fall (October-November) intermonsoons. In this presentation the life cycle of a tropical cyclone Phyan, which occurred during 9-11 November 2009 in the Arabian Sea is analyzed to understand the quantitative response in sea surface temperature (SST), chlorophyll concentration, net primary production (NPP) and CO2 out-gassing using a variety of remotely sensed as well as in situ data. Associated with the passage of cyclone, SST showed a rapid cooling of 2oC. The cooling was in response to the strong cyclonic wind stress curl and associated upward Ekman-pumping. The chlorophyll biomass as well as net primary productivity showed a 2-fold increase. The biological response mediated by the upward Ekman pumping-driven vertical transport of subsurface nutrient showed a time lag of 3-4 days. During the period of cyclone development, entrainment of CO2 into the surface ocean by turbulent mixing and Ekman-pumping enhanced the out-gassing from the ocean, which was 0.123 Tg C. This accounted for ~85% of the total out-gassing from the eastern Arabian Sea during November. Thus, if the frequency and intensity of the cyclone increases in future due to warming, the Arabian Sea would become more productive, and also release more CO2 to the atmosphere than the present. In addition, increased productivity, in turn, will exert increased demand on mid-depth oxygen exerting additional stress on already existing oxygen minimum zone (OMZ).

Kumar, Prasanna; Bhaskar, Byju

2013-04-01

177

Tropical cyclones in a T159 resolution global climate model: comparison with observations and re-analyses  

NASA Astrophysics Data System (ADS)

Tropical cyclones have been investigated in a T159 version of the MPI ECHAM5 climate model using a novel technique to diagnose the evolution of the three-dimensional vorticity structure of tropical cyclones, including their full life cycle from weak initial vortices to their possible extra-tropical transition. Results have been compared with re-analyses [the European Centre for Medium-Range Weather Forecasts (ECMWF) 40-yr Re-analysis (ERA40) and Japanese 25 yr re-analysis (JRA25)] and observed tropical storms during the period 1978-1999 for the Northern Hemisphere. There is no indication of any trend in the number or intensity of tropical storms during this period in ECHAM5 or in re-analyses but there are distinct inter-annual variations. The storms simulated by ECHAM5 are realistic both in space and time, but the model and even more so the re-analyses, underestimate the intensities of the most intense storms (in terms of their maximum wind speeds). There is an indication of a response to El Niño-Southern Oscillation (ENSO) with a smaller number of Atlantic storms during El Niño in agreement with previous studies. The global divergence circulation responds to El Niño by setting up a large-scale convergence flow, with the centre over the central Pacific with enhanced subsidence over the tropical Atlantic. At the same time there is an increase in the vertical wind shear in the region of the tropical Atlantic where tropical storms normally develop. There is a good correspondence between the model and ERA40 except that the divergence circulation is somewhat stronger in the model. The model underestimates storms in the Atlantic but tends to overestimate them in the Western Pacific and in the North Indian Ocean. It is suggested that the overestimation of storms in the Pacific by the model is related to an overly strong response to the tropical Pacific sea surface temperature (SST) anomalies. The overestimation in the North Indian Ocean is likely to be due to an over prediction in the intensity of monsoon depressions, which are then classified as intense tropical storms. Nevertheless, overall results are encouraging and will further contribute to increased confidence in simulating intense tropical storms with high-resolution climate models.

Bengtsson, L.; Hodges, K. I.; Esch, M.

2007-08-01

178

Potential indirect effects of aerosol on tropical cyclone development  

NASA Astrophysics Data System (ADS)

Observational and model evidence suggest that a 2008 Western Pacific typhoon (NURI) came into contact with and ingested elevated concentrations of aerosol as it neared the Chinese coast. This study uses a regional model with two-moment bin emulating microphysics to simulate the typhoon as it enters the field of elevated aerosol concentration. A continental field of cloud condensation nuclei (CCN) was prescribed based on satellite and global aerosol model output, then increased for further sensitivity tests. The typhoon was simulated for 96 hours beginning 17 August 2008, the final 60 of which were under varying CCN concentrations as it neared the Philippines and coastal China. The model was initialized with both global reanalysis model data and irregularly spaced dropsonde data from a 2008 observational campaign using an objective analysis routine. At 36 hours, the internal nudging of the model was switched off and allowed to evolve on its own. As the typhoon entered the field of elevated CCN in the sensitivity tests, the presence of additional CCN resulted in a significant perturbation of windspeed, convective fluxes, and hydrometeor species behavior. Initially ingested in the outer rainbands of the storm, the additional CCN resulted in an initial damping and subsequent invigoration of convection. The increase in convective fluxes strongly lag-correlates with increased amounts of supercooled liquid water within the storm domain. As the convection intensified in the outer rainbands the storm drifted over the developing cold-pools, affecting the inflow of air into the convective towers of the typhoon. Changes in the timing and amount of rain produced in each simulation resulted in differing cold-pool strengths and size. The presence of additional CCN increased resulted in an amplification of convection within the storm, except for the extremely high CCN concentration simulation, which showed a damped convection due to the advection of pristine ice away from the storm. This study examines the physical mechanisms that could potentially alter a tropical cyclone (TC) in intensity and dynamics upon ingesting elevated levels of CCN.

Krall, Geoffrey

179

Coastal boundary layer transition within tropical cyclones at landfall  

NASA Astrophysics Data System (ADS)

Hurricanes pose a great risk to life and property with their high winds, excessive rainfall, wave action, and storm surge. Predicting changes within hurricanes at and near the time of landfall requires an understanding of the dynamics that drive the boundary layer flow. Forecasters predict the timing, duration, and effects of the intense winds associated with a hurricane when it comes ashore, while emergency management officials call for public evacuations based upon these forecasts. One region where understanding the magnitude and structure of the wind is critical is within the surface layer just downstream of the coastline in the onshore flow. Within this region the flow begins to adjust to changes in surface triggered by its passage from the shallow coastal waters to the less homogeneous and rougher land. This adjustment may include a slowing of the mean wind with an increase in turbulence, both resulting from the increased friction of the man-made and natural terrain. Hurricane observing programs consisting of portable and mobile equipment and regional coastal mesoscale observing networks are leading to a better understanding of the processes involved with these flow modifications. The Texas Tech University Wind Engineering Mobile Instrumented Tower Experiment (WEMITE) continues to play a leading role in the observation and analysis of the boundary layer of tropical cyclones at landfall. In order to gain further insight into the characteristics of this coastal transition zone, experiments were planned utilizing portable in-situ and remote measuring devices to be placed within the onshore flow at landfall. Experiment plan designs along with results from these experiments are discussed, including the analysis of a dataset collected by multiple institutions during the landfall of Hurricane Lili (2002) along the south-central Louisiana coast. Investigation reveals the existence of frictionally-induced changes in the boundary layer downwind of the coastline within the right semicircle with respect to Lili's forward motion. In the outer reaches of Lili, these transitions appear similar to internal boundary layers produced by flow moving over an abrupt change in surface. The impact on the magnitude of the wind within this near-shore region is a reduction of 4--10% per 10 km distance from the coast up to 50 km inland for open terrain. Results of the study show this reduction to be an exponential function of distance from the coast, which is dependent upon surface roughness. This rate of wind decay slows with farther progression inland and appears to be much faster than the rate found in some modeling studies. In contrast, near Lili's circulation center, little or no decrease in the magnitude of the mean wind was found for distances of up to 20 km inland.

Howard, James Robert

180

Landfalling Tropical Cyclones: Forecast Problems and Associated Research Opportunities  

USGS Publications Warehouse

The Fifth Prospectus Development Team of the U.S. Weather Research Program was charged to identify and delineate emerging research opportunities relevant to the prediction of local weather, flooding, and coastal ocean currents associated with landfalling U.S. hurricanes specifically, and tropical cyclones in general. Central to this theme are basic and applied research topics, including rapid intensity change, initialization of and parameterization in dynamical models, coupling of atmospheric and oceanic models, quantitative use of satellite information, and mobile observing strategies to acquire observations to evaluate and validate predictive models. To improve the necessary understanding of physical processes and provide the initial conditions for realistic predictions, a focused, comprehensive mobile observing system in a translating storm-coordinate system is required. Given the development of proven instrumentation and improvement of existing systems, three-dimensional atmospheric and oceanic datasets need to be acquired whenever major hurricanes threaten the United States. The spatial context of these focused three-dimensional datasets over the storm scales is provided by satellites, aircraft, expendable probes released from aircraft, and coastal (both fixed and mobile), moored, and drifting surface platforms. To take full advantage of these new observations, techniques need to be developed to objectively analyze these observations, and initialize models aimed at improving prediction of hurricane track and intensity from global-scale to mesoscale dynamical models. Multinested models allow prediction of all scales from the global, which determine long- term hurricane motion to the convective scale, which affect intensity. Development of an integrated analysis and model forecast system optimizing the use of three-dimensional observations and providing the necessary forecast skill on all relevant spatial scales is required. Detailed diagnostic analyses of these datasets will lead to improved understanding of the physical processes of hurricane motion, intensity change, the atmospheric and oceanic boundary layers, and the air- sea coupling mechanisms. The ultimate aim of this effort is the construction of real-time analyses of storm surge, winds, and rain, prior to and during landfall, to improve warnings and provide local officials with the comprehensive information required for recovery efforts in the hardest hit areas as quickly as possible.

Marks, F. D.; Shay, L. K.; Barnes, G.; Black, P.; Demaria, M.; McCaul, B.; Mounari, J.; Montgomery, M.; Powell, M.; Smith, J. D.; Tuleya, B.; Tripoli, G.; Xie, L.; Zehr, R.

1998-01-01

181

Dynamical simulation of tropical cyclones in high-resolution GCMs (Invited)  

NASA Astrophysics Data System (ADS)

Dynamical simulation of extreme events, such as tropical cyclones, in a global climate context is increasingly possible with improved general circulation model (GCM) resolution, physics, and simulation length. High-resolution GCMs - such as the HiGEM and NUGAM models, developed through the UK High Resolution Global Environmental Modelling (HiGEM) project and the UK Japan Climate Collaboration (UJCC) - now resolve sufficient detail to be able to simulate important aspects of tropical cyclone activity. Using a feature-tracking algorithm, developed at the University of Reading, applied to several hundred years of climate simulations, storms are located and tracked through their lifetime. These simulations have the potential to improve our understanding of the impact of natural variability and change on extreme weather events. We use a hierarchy of GCM resolutions to investigate the role of resolution in the simulation of tropical cyclone activity, in terms of storm location, frequency, structure, intensity, and hence risk. Our results reveal that resolution is not so crucial for the simulating the geographical location of the tropical cyclones, but becomes increasingly crucial for the simulation of storm frequency. Fully simulating storm structure the distribution of storm intensities requires a resolution much higher than is currently possible with GCMs. Assessment of tropical cyclones in a global context using the global modelling approach, although restrictive in terms of horizontal resolution, allows us to: 1. Build a long-term, globally consistent source of dynamically simulated tropical storms under current state of the atmosphere/climate; this reduces reliance on limited and/or inconsistent historical data and provides a much larger storm sample size; 2. Investigate how large scale natural climate variability may influence regional tropical cyclone activity on interannual to multidecadal time scales, and assess how this may alter risk; 3. Analyse of correlated weather events though teleconnections, and hence potential accumulation of seemingly unrelated risk; 4. Undertake future climate scenario runs, and assess how climate change may affect tropical cyclone risk in the future. This is important research from a scientific point of view, but also has significant implications for risk assessment and the insurance industry. Through a long-term collaboration with the insurance industry, via the Willis Research Network (WRN), we are working to integrate our findings and dynamical modelling approach into the risk assessment process to assist risk analysts in the evaluation climate-related risk.

Strachan, J.; Vidale, P.; Hodges, K.; Roberts, M.

2010-12-01

182

Tropical Cyclone Impact on Ocean Heat Budget in the Southwest Pacific Ocean  

NASA Astrophysics Data System (ADS)

Tropical cyclones are the most extreme events of the tropical atmosphere and they induce intense ocean response along their propagation. Their role on the climatological heat budget of the ocean is under debate. The South Pacific experiences about 15% of the annual cyclones. In that region as in others, observational and coarse grid ocean modelling studies have suggested that these could contribute significantly to the climatological ocean heat transports. However, the actual amount of heat injected in the ocean and the pathways by which it may be transported remains unclear. Here we use a regional ocean model ROMS with 1/3° resolution for the Southwest Pacific forced by a regional atmospheric model WRF at 1/3° over the 1979-1986 time period. The atmospheric model produces a realistic South Pacific Convergence Zone (SPCZ) with adequate cyclone distribution and the ocean model, a realistic circulation. Together with the control run, an ocean model run where cyclone stress forcing is removed is analyzed. Along each cyclone trajectory, the ocean response with and without cyclone is analyzed. The terms balancing the temperature equation are computed and the processes affecting temperature are identified. Individual processes as well as composites along all trajectories are studied. Right under cyclones the wind-induced cooling reaches down to at least 500m, while it only affects the mixed layer to the cyclone sides, and preferentially to its left coherently with previous studies. Warming is observed on both sides in the thermocline. Despite some diversity in the ocean response, composites along cyclone tracks show that the SST cooling is mainly due to vertical mixing under the cyclone and to both vertical mixing and horizontal advections on the left side of the track. After the cyclone passing, SSTs are restored to pre-storm values by surface fluxes and horizontal advection. Under the mixed layer, deep cooling is driven by vertical advection under cyclones at least 30 days after the passing while both vertical mixing and total advection inject heat into the thermocline after 10 days to the cyclone sides. There, vertical advection heats while lateral advection cools in subtle balance. Thus, in addition to vertical mixing, it is important to consider lateral and vertical advection when studying heat redistribution in response to cyclones. The mix between deep cooling under cyclones and warming sideways leads to a complicated climatological picture. Due to cyclones, we show a maximum climatological warming of ~0.15°C in the 30-200 meters and a maximum cooling of ~0.1°C in the 200-500m under the thermocline. However these are inhomogeneously organized in the horizontal, in response to the complex zonal circulation, and in the vertical, so that heat content anomalies due to cyclones are locally positive or negative. Overall, integrating the whole water column in the domain, we find cyclone heat content anomalies to be close to zero that suggests internal heat redistribution within the domain rather than a coherent heat transport as previously suggested. Thus, previous estimates of cyclones subsurface heat injection may be overestimated.

Jullien, S.; Menkes, C.; Marchesiello, P.; Jourdain, N.; Lengaigne, M.; Lefevre, J.; Vincent, E. M.; Faure, V.; Koch-Larrouy, A.

2010-12-01

183

Tropical prediction using dynamical nudging, satellite-defined convective heat sources, and a cyclone bogus  

SciTech Connect

Some notable problems in tropical prediction have been (1) the sensitivity to, and inaccuracies in, the four-dimensional structure of parameterized convective heating, (2) the inability of conventional data networks to adequately define tropical cyclone structures, and (3) the so-called spinup problem of numerical models. To help overcome some of these deficiencies, a diabatic nudging scheme has been developed for the Bureau of Meteorology Research Center limited-area tropical prediction system. A target analysis for the nudging is first obtained from statistical interpolation of all observational data, using, as first-guess field, output from a global assimilation and prediction system. Tropical cyclones are optionally inserted via bogus wind observations. From 12 or 24 h prior to the base time of the forecast, the prediction model is nudged toward the target analysis. During nudging the 'observationally reliable' rotational wind component is preserved and the heating from the Kuo scheme is replaced by a heating function determined from 6-h satellite-observed cloud-top temperatures. The system introduces realistic tropical cyclone structures into the initial condition, defines a vertical-motion field consistent with the satellite cloud imagery, enhances rainfall rates during the early hours of the forecast, reduces the occurrence of spurious rainfall maxima, and improves mass-wind balance and retention of cyclone circulations during the model integration. Examples of system performance from enhanced observational datasets and from real-time forecasting are presented. Encouraging results for short-term prediction of both tropical cyclone behavior and rainfall events are documented. 29 refs.

Davidson, N.E.; Puri, K. (Research Centre, Melbourne (Australia))

1992-11-01

184

Effects of tropical cyclone waves on ecological and geomorphological structures on the Great Barrier Reef  

NASA Astrophysics Data System (ADS)

Damage to coral reefs caused by Tropical Cyclone Ivor (March 1990) on 46 sites over 150 km of the Great Barrier Reef was patchily distributed within 50 km of the path, while at distances 50km from the eye, it was uniformly low. These distances suggest that local wind-generated waves, not ocean swells, may be the major cause of destruction. Wind component incident on each site, UN, was therefore hindcast from tropical cyclone circulation models. The sum of hourly UN explained about 82% of the variance in an index of total damage and 90% of the destruction of a veneer of dense coral growth up to 1.5 m in thickness. This correlation is consistent with an “attrition” model, in which cyclone waves exfoliate reefs, chunk by chunk, over the period of storm waves.

Done, T. J.

1992-07-01

185

Warm ocean anomaly, air sea fluxes, and the rapid intensification of tropical cyclone Nargis (2008)  

NASA Astrophysics Data System (ADS)

On 2 May 2008, category-4 tropical cyclone Nargis devastated Myanmar. It was observed that just prior to its landfall, Nargis rapidly intensified from a weak category-1 storm to an intense category-4 storm within only 24 h. Using in situ ocean depth-temperature measurements and satellite altimetry, it is found that Nargis' rapid intensification took place on a pre-existing warm ocean anomaly in the Bay of Bengal. In the anomaly, the subsurface ocean is evidently warmer than climatology, as characterized by the depth of the 26°C isotherm of 73-101 m and the tropical cyclone heat potential of 77-105 kj cm-2. This pre-existing deep, warm subsurface layer leads to reduction in the cyclone-induced ocean cooling, as shown from the ocean mixed layer numerical experiments. As a result, there was a near 300% increase in the air-sea enthalpy flux to support Nargis' rapid intensification.

Lin, I.-I.; Chen, Chi-Hong; Pun, Iam-Fei; Liu, W. Timothy; Wu, Chun-Chieh

2009-02-01

186

Use of ECMWF operational analyses for studies of the tropical cyclone environment  

Microsoft Academic Search

Summary This study examined ECMWF operational analyses of the outflow layer of two tropical cyclones (Allen, 1980; Elena, 1985) during their passage across the Atlantic and Caribbean. Wind fields and related derived quantities were compared to those from objective analyses of specialized data sets. Errors in center position and storm motion from the ECMWF analyses were also evaluated.

J. Molinari; D. Vollaro; F. Robasky

1992-01-01

187

Understanding and Forecasting Tropical Cyclone Intensity Change with the Typhoon Intensity Prediction Scheme (TIPS)  

Microsoft Academic Search

A multiple regression scheme with tropical cyclone intensity change as the dependent variable has been developed. The new scheme is titled the Typhoon Intensity Prediction Scheme (TIPS) and is similar to one used operationally at the National Hurricane Center. However, TIPS contains two major differences: it is developed for the western North Pacific Ocean, and utilizes digitized satellite data; the

Patrick J. Fitzpatrick

1997-01-01

188

An explicit three-dimensional nonhydrostatic numerical simulation of a tropical cyclone  

Microsoft Academic Search

Summary A nonhydrostatic numerical simulation of a tropical cyclone is performed with explicit representation of cumulus on a meso-ß scale grid and for a brief period on a meso-? scale grid. Individual cumulus plumes are represented by a combination of explicit resolution and a 1.5 level closure predicting turbulent kinetic energy (TKE).

G. J. Tripoli

1992-01-01

189

Evolution of the Surface Wind Field in an Intensifying Tropical Cyclone  

Microsoft Academic Search

The surface wind field in a developing tropical cyclone (Agnes, 1972) was analyzed over a 1660 km radius for four days using conventional surface data, as the storm evolved from a disorganized depression to a hurricane. The transition to hurricane intensity was characterized by a wavelike disturbance propagating inward at 15 m s1 from the outermost radii to the storm

John Molinari; Steven Skubis

1985-01-01

190

Service Assessment. Hurricane/Post-Tropical Cyclone Sandy, October 22-29, 2012.  

National Technical Information Service (NTIS)

On October 22-29, 2012, Hurricane/Post-Tropical Cyclone Sandy moved from the Caribbean to the U.S. Eastern Seaboard, ultimately making landfall near Brigantine, NJ, around 7:30 p.m. on October 29. The storm resulted in an enormous impact to life and prope...

2013-01-01

191

Evaluating Environmental Favorableness for Tropical Cyclone Development with the Method of Point-Downscaling  

Microsoft Academic Search

A new method is presented to determine the favorableness for tropical cyclone development of an atmospheric environment, as represented by a mean sounding of temperature, humidity, and wind as a function of height. A mesoscale model with nested, moving grids is used to simulate the evolution of a weak, precursor vortex in a large domain with doubly periodic boundary conditions.

David S. Nolan

2011-01-01

192

The JPL Tropical Cyclone Information System: Data and Tools for Researchers  

Microsoft Academic Search

The JPL Tropical Cyclone Information System (TCIS) is now open to the public. This web portal is designed to assist researchers by providing a one-stop shop for hurricane related data and analysis tools. While there are currently many places that offer storm data, plots, and other information, none offer an extensive archive of data files and images in a common

B. W. Knosp; C. O. Ao; Y. Chao; V. Dang; M. Garay; Z. Haddad; S. Hristova-Veleva; B. Lambrigtsen; P. P. Li; W. L. Poulsen; M. A. Rosenman; H. Su; D. Vane; Q. A. Vu; J. K. Willis; D. Wu

2008-01-01

193

Atlantic Warm Pool acting as a link between Atlantic Multidecadal Oscillation and Atlantic tropical cyclone activity  

Microsoft Academic Search

Multidecadal variability of Atlantic tropical cyclone activity is observed to relate to the Atlantic Multidecadal Oscillation (AMO), a mode manifesting primarily in sea surface temperature (SST) in the high latitudes of the North Atlantic. In the low latitudes of the North Atlantic, a large body of warm water called the Atlantic Warm Pool (AWP) comprises the Gulf of Mexico, the

Chunzai Wang; Sang-Ki Lee; David B. Enfield

2008-01-01

194

Tropical Cyclone Intensity Increase near Australia as a Result of Climate Change  

Microsoft Academic Search

Idealized tropical cyclones are inserted into a regional climate model and the resulting intensity evolution of the storms is examined under current and enhanced greenhouse climates. The regional climate model is implemented over a model domain near Australia. In general, storm intensities increase under enhanced greenhouse conditions, although these increases are mostly not statistically significant. The simulated intensities are compared

Kevin J. E. Walsh; Brian F. Ryan

2000-01-01

195

Tropical Cyclone Intensity Increase near Australia as a Result of Climate Change  

Microsoft Academic Search

Idealized tropical cyclones are inserted into a regional climate model and the resulting intensity evolution of the storms is examined under current and enhanced greenhouse climates. The regional climate model is imple- mented over a model domain near Australia. In general, storm intensities increase under enhanced greenhouse conditions, although these increases are mostly not statistically significant. The simulated intensities are

Kevin J. E. Walsh; Brian F. Ryan

2000-01-01

196

Climate-driven changes in tropical cyclone intensity shape dune activity on Earth's largest sand island  

Microsoft Academic Search

I use historical aerial photos and detailed climatic time series to show the geomorphological consequences of a dramatic decrease in tropical cyclone frequency and intensity in eastern Australia since the early 1980s, leading to rapid dune stabilization on the Earth's largest sand island and a World Heritage Site, Fraser Island, Australia. Climate warming is generally expected to increase the intensity

Noam Levin

2010-01-01

197

A New Look at the Problem of Tropical Cyclones in Vertical Shear Flow: Vortex Resiliency  

Microsoft Academic Search

A new paradigm for the resiliency of tropical cyclone (TC) vortices in vertical shear flow is presented. To elucidate the basic dynamics, the authors follow previous work and consider initially barotropic vortices on an f plane. It is argued that the diabatically driven secondary circulation of the TC is not directly responsible for maintaining the vertical alignment of the vortex.

Paul D. Reasor; Michael T. Montgomery; Lewis D. Grasso

2004-01-01

198

Trends in tropical cyclones in the South Indian Ocean and the South Pacific Ocean  

Microsoft Academic Search

The statistical significance of trends in tropical cyclones (TCs) in the South Indian Ocean (SIO) and the South Pacific Ocean (SPO) has been examined. Calculation of significance is based on nonparametric Monte Carlo methods, and in addition we explore whether a constant model, a linear model, or a simple breakpoint model represents a best fit to the data. For the

Y. Kuleshov; R. Fawcett; L. Qi; B. Trewin; D. Jones; J. McBride; H. Ramsay

2010-01-01

199

Improvement of High-Resolution Tropical Cyclone Structure and Intensity Forecasts using COAMPS-TC.  

National Technical Information Service (NTIS)

The long-term goal of this project is to develop a robust and hardened high-resolution air-ocean coupled tropical cyclone (TC) data assimilation and prediction system that is able to assimilate the wide variety of available in-situ and remotely-sensed obs...

J. D. Doyle

2012-01-01

200

Tropical Cyclone Report: Hurricane Humberto (AL092007), September 12-14, 2007.  

National Technical Information Service (NTIS)

Humberto was a short-lived tropical cyclone that made landfall in extreme southeastern Texas as a strong category 1 hurricane (on the Saffir-Simpson Hurricane Scale). The hurricane is notable for its exceptionally rapid intensification near the coast of T...

E. S. Blake

2007-01-01

201

Decreasing Trend in Rainfall over Indochina during the Late Summer Monsoon: Impact of Tropical Cyclones  

Microsoft Academic Search

We examined the decreasing trend in rainfall during the late summer monsoon season (September) in Thailand from 1951 to 2000 and associated changes in tropical cyclone (TC) activity. Thailand receives significant rainfall from May to October and experiences two rainy peaks in late May to early June and in September. A previous study reported a decreasing trend in September rainfall

Hiroshi G. TAKAHASHI; Tetsuzo YASUNARI

2008-01-01

202

Numerical Experiment of Tropical Cyclone Formation in the Intertropical Convergence Zone  

Microsoft Academic Search

Employing an implicit representation scheme for cumulus convection (Yamasaki, 1986), numerical experiments are performed to study tropical cyclone formation in the intertropical convergence zone. Fine resolution grid of 40km is used in the tonal belt where the sea surface temperature is relatively high while two areas having a coarse grid resolution of 120km are located to the north and the

Masanori YAMASAKI

1989-01-01

203

Statistical Evaluations of Microphysics Fields From Observations and Simulations of Tropical Cyclones  

Microsoft Academic Search

There are many factors that determine tropical cyclone intensity and rainfall, such as the magnitude and direction of vertical shear of the environmental wind, upper oceanic temperature structure, and low- and mid- level environmental relative humidity. Ultimately, though, intensity and rainfall are dependent on the magnitude and distribution of the release of latent heat within the core of the storm.

R. Rogers; M. Black; S. Chen

2006-01-01

204

Explicit Three-Dimensional Nonhydrostatic Numerical Simulation of a Tropical Cyclone.  

National Technical Information Service (NTIS)

A nonhydrostatic numerical simulation of a tropical cyclone is performed with explicit representation of cumulus on a meso-beta scale grid and for a brief period on a meso-gamma scale grid. Individual cumulus plumes are represented by a combination of exp...

G. J. Tripoli

1992-01-01

205

Seasonal Atlantic tropical cyclone hindcasting\\/forecasting using two sea surface temperature datasets  

Microsoft Academic Search

Seasonal Atlantic basin tropical cyclone hindcasts are conducted from 1986–2005 using the Florida State University\\/Center for Ocean Atmospheric Prediction Studies atmospheric global spectral model and two sea surface temperature products. The two sea surface temperature products are: the National Oceanic and Atmospheric Administrations Climate Forecast System Model's 1 June forecast and the weekly observed sea surface temperatures. The hindcasts extend

Timothy E. LaRow; Lydia Stefanova; Dong-Wook Shin; Steven Cocke

2010-01-01

206

Seasonal Atlantic tropical cyclone hindcasting\\/forecasting using two sea surface temperature datasets  

Microsoft Academic Search

Seasonal Atlantic basin tropical cyclone hindcasts are conducted from 1986-2005 using the Florida State University\\/Center for Ocean Atmospheric Prediction Studies atmospheric global spectral model and two sea surface temperature products. The two sea surface temperature products are: the National Oceanic and Atmospheric Administrations Climate Forecast System Model's 1 June forecast and the weekly observed sea surface temperatures. The hindcasts extend

Timothy E. LaRow; Lydia Stefanova; Dong-Wook Shin; Steven Cocke

2010-01-01

207

Gust factors and surface-to-gradient wind-speed ratios in tropical cyclones  

Microsoft Academic Search

Digital wind-speed data from tropical cyclones that have impacted the United States during the last decade have been analysed. Using data from automatic weather stations, dropsondes, radiosondes, and Doppler radar, relationships between surface and gradient wind speeds have been determined. In addition, gust factors have been computed for offshore, coastal, and inland sites. It has been found that the wind-speed

P. R Sparks; Z Huang

2001-01-01

208

Tropical Cyclone Intensity Change from a Simple Ocean–Atmosphere Coupled Model  

Microsoft Academic Search

The interaction between a tropical cyclone (TC) and the underlying ocean is investigated using an atmosphere- ocean coupled model. The atmospheric model is developed from the Pennsylvania State University (Penn State)- National Center for Atmospheric Research (NCAR) mesoscale model version 4 MM4 and the ocean model consists of a mixed layer and an inactive stagnant layer beneath. Coupling between the

Johnny C. L. Chan; Yihong Duan; Lynn K. Shay

2001-01-01

209

Accuracy of United States Tropical Cyclone Landfall Forecasts in the Atlantic Basin (1976-2000)  

Microsoft Academic Search

About 13% of all Atlantic basin tropical cyclone forecasts issued from 1976 to 2000 are for landfalls along the United States coastline, and 2% more are for storms forecast to make landfall in the United States but that remain at sea. Landfall position and time forecasts are skillful at all forecast time periods and are more skillful than Atlantic basin

Mark D. Powell; Sim D. Aberson

2001-01-01

210

Historical Account of Tropical Cyclones That Have Impacted North Carolina Since 1586.  

National Technical Information Service (NTIS)

The report is a compilation of the tropical cyclones for which historical information could be found that have struck North Carolina, had any effect on the state, or passed close enough offshore to have been a serious threat to the coastal area. The decis...

J. D. Stevenson

1990-01-01

211

Mining Conditions in Rapid Intensifications of Tropical Cyclones ---A successful example of scientific data mining  

Microsoft Academic Search

Rapid intensification (RI) of tropical cyclones (TC) is a major error source in TC intensity forecasting. Unexpectedly strong storms can cause substantial damages and losses. In order to improve RI probability estimation, the association rule is used in this study in order to mine candidate sets of factors which have strong interactions with rapidly intensifying TCs. Our mining results identified

Jiang Tang; Ruixin Yang; Daniel Barbara; Menas Kafatos

212

Convection in tropical cyclones associated with vapor volume reduction - a new concept  

Microsoft Academic Search

Low pressure zone formation due to convection in a tropical cyclone is associated by a newly discovered phenomenon. The explanation is based on Avogadro's law. According to the law 18 grams (molecular weight expressed in grams) of water when evaporated occupies 22.414 litres of vapor at standard temperature and pressure (STP). Therefore, 1.0 gram of water in the vapor form

D. Mardhekar

2010-01-01

213

Variability in tornado frequency associated with U.S. landfalling tropical cyclones  

Microsoft Academic Search

A statistical model for tornado frequency from Gulf of Mexico landfalling tropical cyclones (TCs) is developed using TC size, intensity, recurvature, and mid-level specific humidity data. New datasets are assembled for tornado frequency and for TC size at landfall as measured by the radius of outer closed isobar and distance of tornado from the TC center. Owing to systematic undercounting

James I. Belanger; Judith A. Curry; Carlos D. Hoyos

2009-01-01

214

Estimation of Tropical Cyclone's Intensity Using TRMM\\/TMI Brightness Temperature Data  

Microsoft Academic Search

A new method for the estimation of tropical cyclone (TC) intensity utilizing 10, 19, 21, 37 and 85 GHz channel TRMM Microwave Imager (TMI) data from 1999 to 2003 is developed. As a first step, we investigated the relationship between the TRMM\\/TMI brightness temperature (TB) parameters, which are computed in concentric circles, or annuli of different radius in different TMI

Shunsuke HOSHINO; Tetsuo NAKAZAWA

2007-01-01

215

A Study of Long-lasting Rainbands Associated with Tropical Cyclones in the Western North Pacific  

NASA Astrophysics Data System (ADS)

Long-lasting rainbands might occur when tropical cyclones (TCs) interact with the environment, especially the southwest monsoon as in the cases of Typhoons Kalmeagi (2008), Morakot (2009) and Fanapi (2010) in the western North Pacific. These long-lasting rainbands are linear convective systems that have a large cold cloud shield, and last for more than six hours. They often pose great challenges to typhoon rainfall forecast when they interact with terrain to produce continuous torrential rain at remote region of TC. In this study, a total of 165 long-lasting rainbands that occurred to the south of TC centers during 1999-2009 are identified using infrared images and passive micro-wave images. Furthermore, these long-lasting rainbands are classified into two types: outer-MCS (85 cases) and enhanced-rainbands (80 cases), depending on the origin of these rainbands. A long-lasting rainband is classified as outer-MCS if it developed from a distant rainband of the TC. If the long-lasting rainband is a primary rainband, it is classified as enhanced-rainband. Results show that 31% of all TCs in the western North Pacific produce at least one long-lasting rainband during its life period. An outer-MCS generally occurs at area 200-700 km away from the TC center and moves usually outward with respect to the moving TC center. It often develops in the downshear right quadrant of a TC. On the other hand, an enhanced-rainband usually is distributed between 100- and 300-km radii of a TC and moves cyclonically. It often develops in the downshear left quadrant of a TC. The environmental conditions favorable for the development of long-lasting rainbands are identified, including low-level south-westerly flows, mid-level dry air associated with the subtropical high, and strong vertical wind shears. Results also show that impacts of outer-MCS and that of enhanced-rainbands on TC structure changes are quite different. When an enhanced-rainband occurs, the TC usually increases its size with a faster rate and the intensification rate remains the same. However, the increasing rate of size remains the same but the intensification rate becomes slower when an outer-MCS occurs.

Chen, Buo-Fu; Lee, Cheng-Shang

2013-04-01

216

The effect of translation speed upon the intensity of tropical cyclones over the tropical ocean  

NASA Astrophysics Data System (ADS)

During the past several decades operational forecasts of tropical cyclone (TC) tracks have improved steadily, but intensity forecast skills have experienced rather modest improvements. Here we use 40 years of TC track data to show that storm intensity correlates with translation speed, with hurricanes of category 5 moving on average 1 m s-1 faster than tropical storms. This correlation provides evidence that the translation speed of a storm can exert a significant control on the intensity of storms by modulating the strength of the negative effect of the storm-induced sea surface temperature (SST) reduction on the storm intensification (i.e., the SST feedback): Faster-moving storms tend to generate weaker sea surface cooling and have shorter exposure to the cooling, both of which tend to weaken the negative SST feedback. Consistently, there exists a minimum translation speed for intensification and its value grows with TC intensity, resulting in a minimum translation speed for the existence of a TC in each intensity category. Furthermore, a composite analysis of satellite-based SST measurements reveals that in the tropical region the average strength of the storm-induced sea surface cooling can be explained by the superposition of an effect due to the storm intensity and an effect associated with the translation speed, and implies that the variability of upper ocean stratification may not be an important factor in this region. Our results suggest that progress in the prediction of TC tracks, particularly in the translation speed of storms, should lead to improved storm intensity prediction.

Mei, Wei; Pasquero, Claudia; Primeau, François

2012-04-01

217

High-Resolution Paleotempestology: Proxy Models for Reconstructing Interannual-Decadal Variations in PreHistoric Tropical Cyclone Frequency and Intensity  

Microsoft Academic Search

Tropical cyclones (including hurricanes, typhoons, and cyclones) are among the most deadly and destructive natural hazards. As coastal populations and infrastructure in affected areas grow, the impact of these storms is sure to increase. On the other hand, the impact of global climate change on tropical cyclone activity remains uncertain and highly controversial. Recent research suggests that the destructive power

A. B. Frappier; D. Sahagian; S. J. Carpenter; B. R. Frappier

2005-01-01

218

Trend discrepancies among three best track data sets of western North Pacific tropical cyclones  

NASA Astrophysics Data System (ADS)

The hot debate over the influence of global warming on tropical cyclone (TC) activity in the western North Pacific over the past several decades is partly due to the diversity of TC data sets used in recent publications. This study investigates differences of track, intensity, frequency, and the associated long-term trends for those TCs that were simultaneously recorded by the best track data sets of the Joint Typhoon Warning Center (JTWC), the Regional Specialized Meteorological Center (RSMC) Tokyo, and the Shanghai Typhoon Institute (STI). Though the differences in TC tracks among these data sets are negligibly small, the JTWC data set tends to classify TCs of category 2-3 as category 4-5, leading to an upward trend in the annual frequency of category 4-5 TCs and the annual accumulated power dissipation index, as reported by Webster et al. (2005) and Emanuel (2005). This trend and potential destructiveness over the period 1977-2007 are found only with the JTWC data set, but downward trends are apparent in the RSMC and STI data sets. It is concluded that the different algorithms used in determining TC intensity may cause the trend discrepancies of TC activity in the western North Pacific.

Song, Jin-Jie; Wang, Yuan; Wu, Liguang

2010-06-01

219

Impact of a tropical cyclone on biogeochemistry of the central Arabian Sea  

NASA Astrophysics Data System (ADS)

Remotely sensed data are combined with shipboard measurements to investigate biogeochemical changes caused by a moderate tropical cyclone in the central Arabian Sea in December 1998. The sea surface temperature decreased by ˜4°C, whereas surface nitrate and chlorophyll concentrations increased by >5 ?M and up to 4 mg m-3, respectively, over a large area affected by the cyclone. Nutrient enrichment in the surface layer of the cyclone-affected zone is estimated to have supported a new production of ˜4.2 Tg C, approximately 5% of the annual organic carbon export to the deep sea (beyond the continental margin) for the entire Arabian Sea. Entrainment of nitrous oxide from the thermocline led to more than doubling of its concentration in the mixed layer. The cyclone also resulted in an increase in nitrous oxide inventory within the oxygen minimum zone. Our results imply that, should there be an increase in the frequency and intensity of tropical cyclones as a result of global warming, as projected in some recent reports, carbon production and respiration, and redox processes within the oxygen minimum zones, such as the production of nitrous oxide through nitrification/denitrification, and of molecular nitrogen through denitrification/anaerobic ammonium oxidation, may be significantly impacted.

Naik, Hema; Naqvi, S. W. A.; Suresh, T.; Narvekar, P. V.

2008-09-01

220

Vortex Rossby waves on smooth circular vortices Part II. Idealized numerical experiments for tropical cyclone and polar vortex interiors  

Microsoft Academic Search

Idealized linear and nonlinear numerical experiments are carried out to test the predictions of the theory developed in Brunet and Montgomery (Vortex Rossby Waves on Smooth Circular Vortices Part I: Theory (pages 153-177, this issue)). For a monopolar tropical cyclone-like vortex whose strength lies between a tropical depression and tropical storm, linear theory remains uniformly valid in time in the

Michael T. Montgomerya; Gilbert Brunet

221

Multi-year forecast of Atlantic tropical cyclone activity using EC-Earth  

NASA Astrophysics Data System (ADS)

Seasonal forecasts of Atlantic hurricane activity are now routinely performed by various groups and have become relatively successful at forecasting basin wide activity a few months before the official start of a hurricane season. Part of the skill in predicting the level of tropical cyclone activity for a given season comes from the ability to predict the behaviour of ENSO, which strongly impacts (through teleconnections) hurricane formation over the Atlantic. Over the same basin, the ~100 years of available hurricane records also show variations at the decadal timescale. This decadal fluctuation appears linked to an oscillation in North Atlantic sea surface temperatures (SSTs). Coined the Atlantic Multi-decadal Oscillation (AMO), a successful multi-year forecast of this oscillation offers the potential to produce a skillful multi-year forecast of hurricane activity. Such forecast could help mitigate against (potentially huge) hurricane-related losses through improved preparedness and improved insurance schemes. Using EC-Earth, a coupled global atmosphere-ocean model, we perform a series of ensemble decadal re-forecasts at 5 year intervals between the 1965-2005 period and investigate the ability of these re-forecasts at capturing observed variations in North Atlantic SSTs (in essence, the AMO) as well as other large-scale fields known to impact cyclogenesis. We also use an automated procedure to track the tropical cyclones produced in these re-forecasts, which then allows direct comparison with the actual number of tropical cyclones that formed over the equivalent period. Preliminary analysis shows that EC-Earth re-forecasts manage to capture variations in large-scale fields relatively well, especially variations in the AMO, which suggests a potential for skillful multi-year forecast of Atlantic tropical cyclones. However, direct comparison of simulated and observed TC numbers does not offer the same level of skill. Tropical cyclone numbers in the re-forecasts are biased low, and this appears to result not only from the low-resolution of the simulation (~1.125°), but also from a drift in simulated SSTs. This drift brings surface temperature below the 26°C threshold required for tropical cyclone formation, effectively shutting down storm formation over large parts of the tropical Atlantic. Potential solutions to circumvent these limitations are currently being considered and will be discussed.

Caron, L.-P.; Jones, C. G.; Doblas-Reyes, F. J.; Caian, M.

2012-04-01

222

meeting summary: Third COMPARE Workshop: A Model Intercomparison Experiment of Tropical Cyclone Intensity and Track Prediction.  

NASA Astrophysics Data System (ADS)

The Third Comparison of Mesoscale Prediction and Research Experiment (COMPARE) workshop was held in Tokyo, Japan, on 13-15 December 1999, cosponsored by the Japan Meteorological Agency (JMA), Japan Science and Technology Agency, and the World Meteorological Organization. The third case of COMPARE focuses on an event of explosive tropical cyclone [Typhoon Flo (9019)] development that occurred during the cooperative three field experiments, the Tropical Cyclone Motion experiment 1990, Special Experiment Concerning Recurvature and Unusual Motion, and TYPHOON-90, conducted in the western North Pacific in August and September 1990. Fourteen models from nine countries have participated in at least a part of a set of experiments using a combination of four initial conditions provided and three horizontal resolutions. The resultant forecasts were collected, processed, and verified with analyses and observational data at JMA. Archived datasets have been prepared to be distributed to participating members for use in further evaluation studies. In the workshop, preliminary conclusions from the evaluation study were presented and discussed in the light of initiatives of the experiment and from the viewpoints of tropical cyclone experts. Initial conditions, depending on both large-scale analyses and vortex bogusing, have a large impact on tropical cyclone intensity predictions. Some models succeeded in predicting the explosive deepening of the target typhoon at least qualitatively in terms of the time evolution of central pressure. Horizontal grid spacing has a very large impact on tropical cyclone intensity prediction, while the impact of vertical resolution is less clear, with some models being very sensitive and others less so. The structure of and processes in the eyewall clouds with subsidence inside as well as boundary layer and moist physical processes are considered important in the explosive development of tropical cyclones. Follow-up research activities in this case were proposed to examine possible working hypotheses related to the explosive development. New strategies for selection of future COMPARE cases were worked out, including seven suitability requirements to be met by candidate cases. The Vortex95 case was withdrawn as a candidate, and two other possible cases were presented and discussed.

Nagata, Masashi; Leslie, Lance; Kurihara, Yoshio; Elsberry, Russell L.; Yamasaki, Masanori; Kamahori, Hirotaka; Abbey, Robert, Jr.; Bessho, Kotaro; Calvo, Javier; Chan, Johnny C. L.; Clark, Peter; Desgagne, Michel; Hong, Song-You; Majewski, Detlev; Malguzzi, Piero; McGregor, John; Mino, Hiroshi; Murata, Akihiko; Nachamkin, Jason; Roch, Michel; Wilson, Clive

2001-09-01

223

The coincidence of daily rainfall events in Liberia, Costa Rica and tropical cyclones in the Caribbean basin  

Microsoft Academic Search

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

Peter R. Waylen; Michael Harrison

2005-01-01

224

Relating Convective and Microphysical Properties to Large-scale Dynamical and Thermodynamical processes within Tropical Cyclones  

NASA Astrophysics Data System (ADS)

It is well known that precipitating convection within tropical cyclones result from a complex interactions among large-scale, storm-scale, cloud-scale, and micro-scale processes. For improved representation of these processes within tropical cyclone models, it is crucial to first understand how micro-scale and cloud- scale properties within tropical cyclones are related to large-scale processes, one of the key objectives of the Year of Tropical Convection (YOTC) program. In this study, a combination of cloud resolving model (CRM) simulations, TRMM Microwave Imager (TMI) measurements, NOAA Optimum Interpolation sea surface temperatures (SST), and Global Forecasting System (GFS) analysis are used to address this issue. The University of Wisconsin Nonhydrostatic Modeling System (UWNMS), a CRM, is used to simulate hurricanes Dennis (9-10 July 2005), Katrina (29-30 2005), and Gustav (30-31 August 2008) at 2-km resolution, nested within 1ºx1º GFS analyses. The UWNMS-generated thermodynamic and hydrometeor profiles are used in a radiative transfer model to calculate brightness temperatures (Tbs) at TMI frequencies. The UWNMS-based Tbs and TRMM-based Tbs are compared to validate overall consistency of the CRM simulations. The cloud-scale profiles of hydrometeors, vertical wind, temperature, and wind shear from UWNMS are analyzed to study their characteristics as functions of SST and GFS-based large-scale regimes represented by parameters including horizontal moisture divergence, vertical moisture flux at 500 hPa, potential vorticity, large-scale wind shear, and Convective Available Potential Energy among others, throughout mature stage of these major hurricanes. Results of this study show how cloud-scale processes are related to large-scale processes within these tropical cyclones.

Mehta, A. V.; Smith, E. A.; Tripoli, G. J.

2008-12-01

225

Convective and rainfall properties of tropical cyclone inner cores and rainbands in relation to tropical cyclone intensity changes using eleven years of Tropical Rainfall Measuring Mission data  

NASA Astrophysics Data System (ADS)

Covering December 1997 through December 2008, over 13,000 tropical cyclone (TC) overpasses of 945 TCs by the Tropical Rainfall Measuring Mission (TRMM) satellite are used to document the observed passive microwave ice scattering magnitudes, radar reflectivity, IR cloud top height, total lightning, and derived rainfall parameters including rain rate, raining area, and volumetric rain. A semimanual method is used to divide TC raining area into inner core (IC), inner rainband (IB), and outer rainband (OB) regions. Precipitation features (PFs) within these regions are compared for their convective vigor and rainfall characteristics based on passive microwave, IR, radar, and lightning properties. These properties in the IC region are further examined in terms of different TC intensity and intensity change categories. TC intensity categories include tropical depressions (TDs), tropical storms (TSs), category 1-2 hurricanes (CAT12s), and category 3-5 hurricanes (CAT35s). The 24-h TC intensity change categories include weakening (W), neutral (N), slowly intensifying (SI), and rapidly intensifying (RI). The stronger tails of the convective intensity distributions are found to be similar for features in both the IC and OB regions, while the features in the IB region yield the weakest convective signatures. However, at the middle to weaker end of the convective spectrum, ice scattering signatures and reflectivity profiles are the strongest for features in the IC region, followed by those in the IB, then those in the OB. The same order is found for the whole distribution spectrum of feature conditional mean rain rates in these regions. The convective intensity of features in the IC region are found to increase as storm intensity increases, except at the strongest end of the spectrum, where ice scattering signatures and reflectivity profiles are stronger in features associated with TS and TD strength storms rather than those associated with hurricane strength storms. The IC conditional mean rain rate and volumetric rain increase as storm intensity increases. It is found that necessary conditions for RI are that the minimum 85 GHz PCT in the IC region must be less than 256 K and the minimum 37 GHz PCT must be less than 275 K. Over 98% of RI minimum 11im brightness temperatures in the IC region are less than 212 K. RI storms always have larger raining area and volumetric rain in the IC region than storms in other intensity change categories.

Ramirez, Ellen Michelle

226

Mesoscale Aspects of the Downshear Reformation of a Tropical Cyclone  

Microsoft Academic Search

The downshear reformation of Tropical Storm Gabrielle (2001) was investigated using radar reflectivity and lightning data that were nearly continuous in time, as well as frequent aircraft reconnaissance flights. Initially the storm was a marginal tropical storm in an environment with strong 850 200-hPa vertical wind shear of 12 13 m s-1 and an approaching upper tropospheric trough. Both the

John Molinari; Peter Dodge; David Vollaro; Kristen L. Corbosiero; Frank Marks Jr.

2006-01-01

227

Operational Evaluation of QuikSCAT Winds in Tropical Cyclones at the Tropical Prediction Center/National Hurricane Center  

NASA Astrophysics Data System (ADS)

Remotely sensed ocean surface vector winds from the QuikSCAT scatterometer aboard the NASA SeaWinds satellite are an important source of data at the Tropical Prediction Center (TPC)/National Hurricane Center (NHC). These data fill a large void in surface wind information over the open ocean portion of the NHC/TPC area of responsibility in the Eastern Pacific and Atlantic basins. QuikSCAT has been used at TPC/NHC to supplement other observations for estimation of tropical cyclone (TC) intensity and the radius of 34-kt and 50- kt winds. Both of these parameters are critical to the warning and forecast mission at TPC. In the TC environment, the quality of QuikSCAT winds is often degraded by rain contamination. However, the interpretation of the impact of rain on QuikSCAT winds is not straightforward, since no direct measurement of rain rate is co-located with the instrument, and the impact of rain varies with the rain rate and the actual near- surface wind speed. Examination of QuikSCAT wind data within the range of coastal radar and other rain rate estimates such as those from the Tropical Rainfall Measurement Mission (TRMM) have shown a strong relationship between high wind estimates from the scatterometer and rain rate. To quantify the accuracy of QuikSCAT winds in estimating TC intensity, maximum wind speeds from 25-km and 12.5-km near-real time QuikSCAT retrievals over classified TCs during the 2005 and 2006 Atlantic hurricane seasons are compared to the NHC best track intensity and Dvorak satellite intensity estimates. Results from 2005 indicate a positive bias in QuikSCAT maximum winds for tropical depressions and weak tropical storms due to rain enhancing backscatter to the instrument. A large negative bias of QuikSCAT intensity estimates was seen for hurricanes with maximum winds above 85 kt due to rain attenuation, resolution limitations, and signal saturation at high winds speed. QuikSCAT intensity estimates showed more skill in moderate to strong tropical storms and marginal hurricanes; although some of this reduced bias results from the cancellation of larger errors of opposite sign in this range of wind speeds. Estimates of outer wind radii have proven very useful, especially in major hurricanes where the maximum radius of 34 kt winds often extends outside the region of heavy rainfall near the TC center. These bulk statistical results indicate that QuikSCAT winds in the TC environment can provide valuable information, but must be carefully evaluated on a case-by-case basis. Results from 2006 will be evaluated and compared to those from 2005. Also, case examples comparing QuikSCAT winds to measurements from aircraft reconnaissance, the NOAA stepped-frequency microwave radiometer (SFMR), and ship and buoy observations will be presented. These examples will highlight the difficulty of interpreting QuikSCAT winds in an operational setting. Additionally, an evaluation of a new near-real time QuikSCAT retrieval algorithm developed by NASA and NOAA NESDIS may be possible prior to the end of the 2006 hurricane season. Finally, suggestions will be made for improvements to future ocean vector wind platforms necessary to support the operational mission at TPC.

Brennan, M. J.; Knabb, R.

2006-12-01

228

Operational Evaluation of QuikSCAT Winds in Tropical Cyclones at the Tropical Prediction Center/National Hurricane Center  

NASA Astrophysics Data System (ADS)

Remotely sensed ocean surface vector winds from the QuikSCAT scatterometer aboard the NASA SeaWinds satellite are an important source of data at the Tropical Prediction Center (TPC)/National Hurricane Center (NHC). These data fill a large void in surface wind information over the open ocean portion of the NHC/TPC area of responsibility in the Eastern Pacific and Atlantic basins. QuikSCAT has been used at TPC/NHC to supplement other observations for estimation of tropical cyclone (TC) intensity and the radius of 34-kt and 50- kt winds. Both of these parameters are critical to the warning and forecast mission at TPC. In the TC environment, the quality of QuikSCAT winds is often degraded by rain contamination. However, the interpretation of the impact of rain on QuikSCAT winds is not straightforward, since no direct measurement of rain rate is co-located with the instrument, and the impact of rain varies with the rain rate and the actual near- surface wind speed. Examination of QuikSCAT wind data within the range of coastal radar and other rain rate estimates such as those from the Tropical Rainfall Measurement Mission (TRMM) have shown a strong relationship between high wind estimates from the scatterometer and rain rate. To quantify the accuracy of QuikSCAT winds in estimating TC intensity, maximum wind speeds from 25-km and 12.5-km near-real time QuikSCAT retrievals over classified TCs during the 2005 and 2006 Atlantic hurricane seasons are compared to the NHC best track intensity and Dvorak satellite intensity estimates. Results from 2005 indicate a positive bias in QuikSCAT maximum winds for tropical depressions and weak tropical storms due to rain enhancing backscatter to the instrument. A large negative bias of QuikSCAT intensity estimates was seen for hurricanes with maximum winds above 85 kt due to rain attenuation, resolution limitations, and signal saturation at high winds speed. QuikSCAT intensity estimates showed more skill in moderate to strong tropical storms and marginal hurricanes; although some of this reduced bias results from the cancellation of larger errors of opposite sign in this range of wind speeds. Estimates of outer wind radii have proven very useful, especially in major hurricanes where the maximum radius of 34 kt winds often extends outside the region of heavy rainfall near the TC center. These bulk statistical results indicate that QuikSCAT winds in the TC environment can provide valuable information, but must be carefully evaluated on a case-by-case basis. Results from 2006 will be evaluated and compared to those from 2005. Also, case examples comparing QuikSCAT winds to measurements from aircraft reconnaissance, the NOAA stepped-frequency microwave radiometer (SFMR), and ship and buoy observations will be presented. These examples will highlight the difficulty of interpreting QuikSCAT winds in an operational setting. Additionally, an evaluation of a new near-real time QuikSCAT retrieval algorithm developed by NASA and NOAA NESDIS may be possible prior to the end of the 2006 hurricane season. Finally, suggestions will be made for improvements to future ocean vector wind platforms necessary to support the operational mission at TPC.

Sobolowski, S.; Frei, A.; Mahani, S.

2005-05-01

229

Characteristics of tropical cyclone precipitation features over the western Pacific warm pool  

NASA Astrophysics Data System (ADS)

In this study, ten years (1998-2007) of the Tropical Rainfall Measuring Mission (TRMM)-derivative radar precipitation feature (PF) product are analyzed in order to determine the differences between tropical cyclone-related precipitation characteristics compared with those of the tropical Pacific warm pool (10 to 30°N and 130 to 150°E) in general. The PF data, from the University of Utah's archive, are based on the TRMM precipitation radar's 2A25 product, where one PF consists of a single or group of contiguous pixels with near surface rainfall greater than zero. Using the PF database, the height and area of tropical background PFs versus those within 500 km of tropical cyclones (TCs) are compared. It is found that TC-related PFs are markedly more frequent from 5 to 10 km altitude than are background tropical PFs. The enhanced midlevel TC-related populations not only exist in stratiform precipitation around the melting level at 5.5 km, but also from 6 to 9 km in stratiform regions, in convective precipitation, and when culling the smallest features from the data set. This increase in congestus-like echoes in TC environments aligns well with observations regarding mesoscale convective systems (MCSs), in which the enhanced ice present in MCS (and TC) environments creates a stabilized melting layer through cooling immediately below 0°C. This stable layer appears to enhance the detrainment of convective PFs in our TC data set at and for a few kilometers above the melting level.

Thatcher, Levi; Takayabu, Yukari N.; Yokoyama, Chie; Pu, Zhaoxia

2012-08-01

230

Improved tropical cyclone forecasts over north Indian Ocean with direct assimilation of AMSU-A radiances  

NASA Astrophysics Data System (ADS)

The Weather Research and Forecasting (WRF-ARW) model and its three-dimensional variational data assimilation (3D-Var) system are used to investigate the impact of the Advanced Microwave Sounding Unit-A (AMSU-A) radiances on the prediction of Indian Ocean tropical cyclones. Three tropical cyclones are selected for this study: cyclone Mala (April 2006; Bay of Bengal), cyclone Gonu (June 2007; Arabian Sea), and cyclone Sidr (November 2007; Bay of Bengal). For each case, observing system experiments are designed, by producing two sets of analyses from which forecasts are initialized. Both sets of analyses contain all conventional and satellite observations operationally used, including, but not limited to, Quick Scatterometer (QuikSCAT) surface winds, Special Sensor Microwave/Imager (SSM/I) surface winds, Meteosat-derived atmospheric motion vectors (AMVs), and differ only in the exclusion (CNT) or inclusion (EXP) of AMSU-A radiances. Results show that the assimilation of AMSU-A radiances changes the large-scale thermodynamic structure of the atmosphere, and also produce a stronger warm core. These changes cause large forecast track improvements. In particular, without AMSU-A assimilation, most forecasts do not produce landfall. On the contrary, the forecasts initialized from improved EXP analyses in which AMSU-A data are included produce realistic landfall. In addition, intensity forecast is also improved. Even if the analyzed cyclone intensity is not affected by the assimilation of AMSU-A radiances, the predicted intensity improves substantially because of the development of warm cores which, through creation of stronger gradients, helps the model in producing intense low centre pressure.

Singh, Randhir; Kishtawal, C. M.; Pal, P. K.; Joshi, P. C.

2012-01-01

231

Predictability of tropical cyclone events on intraseasonal timescales with the ECMWF monthly forecast model  

NASA Astrophysics Data System (ADS)

The objective of this study is to provide evidence of predictability on intraseasonal time scales (10-30 days) for western North Pacific tropical cyclone formation and subsequent tracks using the 51-member ECMWF 32-day forecasts made once a week from 5 June through 25 December 2008. Ensemble storms are defined by grouping ensemble member vortices whose positions are within a specified separation distance that is equal to 180 n mi at the initial forecast time t and increases linearly to 420 n mi at Day 14 and then is constant. The 12-h track segments are calculated with a Weighted-Mean Vector Motion technique in which the weighting factor is inversely proportional to the distance from the endpoint of the previous 12-h motion vector. Seventy-six percent of the ensemble storms had five or fewer member vortices. On average, the ensemble storms begin 2.5 days before the first entry of the Joint Typhoon Warning Center (JTWC) best-track file, tend to translate too slowly in the deep tropics, and persist for longer periods over land. A strict objective matching technique with the JTWC storms is combined with a second subjective procedure that is then applied to identify nearby ensemble storms that would indicate a greater likelihood of a tropical cyclone developing in that region with that track orientation. The ensemble storms identified in the ECMWF 32-day forecasts provided guidance on intraseasonal timescales of the formations and tracks of the three strongest typhoons and two other typhoons, but not for two early season typhoons and the late season Dolphin. Four strong tropical storms were predicted consistently over Week-1 through Week-4, as was one weak tropical storm. Two other weak tropical storms, three tropical cyclones that developed from precursor baroclinic systems, and three other tropical depressions were not predicted on intraseasonal timescales. At least for the strongest tropical cyclones during the peak season, the ECMWF 32-day ensemble provides guidance of formation and tracks on 10-30 day timescales.

Elsberry, Russell L.; Jordan, Mary S.; Vitart, Frederic

2010-05-01

232

Recent increase in high tropical cyclone heat potential area in the Western North Pacific Ocean  

NASA Astrophysics Data System (ADS)

Main Development Region (MDR) for tropical cyclones (TCs) in the western North Pacific Ocean is the most active TC region in the world. Based on synergetic analyses of satellite altimetry and gravity observations, we found that the subsurface ocean conditions in the western North Pacific MDR has become even more favorable for the intensification of typhoons and supertyphoons. Compared to the early 1990s, a 10% increase in both the depth of the 26°C isotherm (D26) and Tropical Cyclone Heat Potential (TCHP) has occurred in the MDR. In addition, the areas of high TCHP (? 110 kJ cm-2) and large D26 (? 110 m) have 13% and 17% increases, respectively. Because these high TCHP and large D26 regions are often associated with intensification of the most intense TCs (i.e. supertyphoons), this recent warming requires close attention and monitoring.

Pun, Iam-Fei; Lin, I.-I.; Lo, Min-Hui

2013-09-01

233

Changes to environmental parameters that control tropical cyclone genesis under global warming  

NASA Astrophysics Data System (ADS)

This study uses the Meteorological Research Institute high-resolution Atmospheric Climate Model to determine whether environmental parameters that control tropical cyclone genesis in the Western North Pacific (WNP) and North Atlantic (NA) may differ in the global warming state. A box difference index was computed to quantitatively assess the role of environmental controlling parameters. The diagnosis of the model outputs shows that in the WNP, dynamic variables are of primary importance for separating developing and nondeveloping disturbances in the present-day climate, and such a relationship remains unchanged in a future warmer climate. This is in contrast to the NA, where box difference index increases for all dynamic variables investigated while it shows little change for thermodynamic variables. This implies that, when compared with the present-day climate in which thermodynamic variables have a major control on tropical cyclone genesis, dynamic and thermodynamic variables have equal control in the NA under the future warmer climate.

Murakami, Hiroyuki; Li, Tim; Peng, Melinda

2013-05-01

234

Xynthia: analysis of an exceptional extra-tropical cyclone  

NASA Astrophysics Data System (ADS)

Between end of February and early March, winter storm Xynthia has affected South Western Europe causing storm damage and flash floods along the Breton coast. The uniqueness of this storm refers to its path and the area of origin, being far southward of the usual North Atlantic storm track. In order to understand the course of the event, the storm development is first analysed by means of ERA-Interim data. An interesting feature is that Xynthia did not cross the polar jet. In fact, the existing split jet structure was responsible for enduring upper level divergence in the vicinity of the cyclone. The southerly area of origin (30N) raises the question to what extent latent heat release (LHR) contributes to the deepening and evolution of Xynthia. Therefore, sensitivity studies with the regional model COSMO-CLM have been carried to verify the amount LHR has on the cyclone development. First, a control simulation covering broad areas of the North Atlantic Ocean with a horizontal resolution of 0.22° shows the development of the storm in very good agreement with the development represented in the reanalysis data. In different sensitivity studies, the influence of LHR is examined. In a first approach, the sea surface temperature (SST) in the initial model fields was reduced in steps of 1K to a maximum decrease of 5K compared to the original SST field. The lowering of the SST was implemented only in the model area where Xynthia underwent massive deepening. The results show that the minimum core pressure remains about 10hPa higher than in the control simulation, while dynamical aspects like jet configuration did not change significantly. Another approach to quantify the amount of LHR on cyclone development is to disable the temperature increment due to latent heat effects. Finally, the energetics are examined to provide information about the environmental energy transfers being accountable for the evolution of the storm.

Ludwig, P.; Yuen, D.; Born, K.; Pinto, J. G.; Drinka, R.

2012-04-01

235

The Challenges of Interpreting Microwave-Sounded Height Registered Water near Tropical Cyclones  

Microsoft Academic Search

Satellite-derived coincident profiles of water, and liquid water (cloud properties) provide some of the best constraints on the energetics of tropical cyclones. The problem addressed is how accuracy depends on amount and distribution of cloud liquid water. We focus on products derived from the AMSU\\/MHS sounders using algorithms from the AIRS\\/AMSU\\/HSB investigations. We use error analysis and inter omparisons with

E. Fishbein; E. Fetzer; B. Kahn; B. Lambrightsen; J. Teixeira

2008-01-01

236

Scalability Improvements in the NASA Goddard Multiscale Modeling Framework for Tropical Cyclone Climate Studies  

Microsoft Academic Search

A current, challenging topic in tropical cyclone (TC)1 research is how to improve our understanding of TC inter-annual variability and the impact of climate change on TCs. Paired with the substantial computing power of the NASA Columbia supercomputer, the newly- developed multi-scale modeling framework (MMF) (1) shows potential for the related studies. The MMF consists of two NASA state-of-the-art modeling

Bo-Wen Shen; Wei-Kuo Tao; K. Palaniappan

2009-01-01

237

Lightning Observations During Tropical Cyclone Intensity Change: A Composite Study of Spatial and Temporal Relationships  

Microsoft Academic Search

Although tropical cyclone (TC) track forecasts have improved considerably in recent years, predicting their intensity continues to be a challenge for both meteorologists and numerical models. A storm’s path is primarily influenced greatly by large-scale atmospheric circulations; however, its strength appears to be dominated both by large scale influences and small-scale mechanisms within the storm itself. Most previous research on

Marcus Austin

2010-01-01

238

Predictability of tropical cyclone events on intraseasonal timescales with the ECMWF monthly forecast model  

Microsoft Academic Search

The objective of this study is to provide evidence of predictability on intraseasonal time scales (10–30 days) for western\\u000a North Pacific tropical cyclone formation and subsequent tracks using the 51-member ECMWF 32-day forecasts made once a week\\u000a from 5 June through 25 December 2008. Ensemble storms are defined by grouping ensemble member vortices whose positions are\\u000a within a specified separation

Russell L. Elsberry; Mary S. Jordan; Frederic Vitart

2010-01-01

239

Influence of the Global Warming on Tropical Cyclone Climatology: An Experiment with the JMA Global Model  

Microsoft Academic Search

The influence of the global warming on tropical cyclones has been examined using a high resolution AGCM. Two ten-year integrations were performed with the JMA global model at T106 horizontal resolu- tion. For the control experiment, the observed SST for the period 1979-1988 is prescribed, while for the doubling CO2 (2 ? CO2) experiment, SST anomaly due to the global

Masato SUGI; Akira NODA; Nobuo SATO

2002-01-01

240

On sea surface roughness parameterization and its effect on tropical cyclone structure and intensity  

Microsoft Academic Search

A new parameterization scheme of sea surface momentum roughness length for all wind regimes, including high winds, under tropical\\u000a cyclone (TC) conditions is constructed based on measurements from Global Positioning System (GPS) dropsonde. It reproduces\\u000a the observed regime transition, namely, an increase of the drag coefficient with an increase in wind speed up to 40 m s?1, followed by a

Zhihua Zeng; Yuqing Wang; Yihong Duan; Lianshou Chen; Zhiqiu Gao

2010-01-01

241

ENSO and Western North Pacific tropical cyclone activity simulated in a CGCM  

Microsoft Academic Search

A high-resolution (T213) coupled ocean–atmosphere general circulation model (CGCM) has been used to examine the relationship\\u000a between El Niño\\/Southern Oscillation (ENSO) and tropical cyclone (TC) activity over the western North Pacific (WNP). The model\\u000a simulates ENSO-like events similar to those observed, though the amplitude of the simulated Niño34 sea surface temperature\\u000a (SST) anomaly is twice as large as observed. In

Satoshi Iizuka; Tomonori Matsuura

2008-01-01

242

The temporal and spatial characteristics of surrogate tropical cyclones from a multi-millenial simulation  

Microsoft Academic Search

Output from a simulation with the CSIRO Mark 2 climatic model has been used to investigate the secular variability of tropical\\u000a cyclone formation over the globe using Gray’s Seasonal Genesis Parameter. This simulation differs from previous surrogate\\u000a studies in using a coupled atmospheric-oceanic model, instead of specified sea surface temperatures, as well as being of multi-millenial\\u000a duration, compared with decadal

B. G. Hunt; I. G. Watterson

2010-01-01

243

Influence of tropical cyclone landfalls on spatiotemporal variations in typhoon season rainfall over South China  

Microsoft Academic Search

This study examined the impact of tropical cyclone (TC) landfalls on the spatiotemporal variations in the rainfall over South\\u000a China for the period 1957–2005. The target region was selected to show the noteworthy contribution of TC landfalls to the\\u000a total rainfall during the typhoon season (July–October). Two prevailing spatial variations in the rainfall were obtained from\\u000a an EOF analysis. The

Min-Hee Lee; Chang-Hoi Ho; Joo-Hong Kim

2010-01-01

244

Interannual variability of the South Pacific Convergence Zone and implications for tropical cyclone genesis  

Microsoft Academic Search

The interannual variability of the South Pacific Convergence Zone (SPCZ) and its influence on tropical cyclone (TC) genesis\\u000a in the South Pacific are investigated using observations and ERA40 reanalysis over the 1979–2002 period. In austral summer,\\u000a the SPCZ displays four typical structures at interannual timescales. The first three are characterized by a diagonal orientation\\u000a of the SPCZ and account for

Emmanuel M. Vincent; Matthieu Lengaigne; Christophe E. Menkes; Nicolas C. Jourdain; Patrick Marchesiello; Gurvan Madec

2011-01-01

245

Analysis of tropical cyclone dynamics in two models of different complexity  

NASA Astrophysics Data System (ADS)

Tropical cyclone dynamics and its sensitivity to several climatological parameters is investigated within the axisymmetric high-resolution cloud model HURMOD on and by means of a conceptual tropical cyclone (TC) model. Within the conceptual model, the TC is divided into three regions, the eye, eyewall and ambient region. The conceptual model forms a low order dynamical system of three ordinary differential equations. These are based on entropy budget equations comprising processes of surface enthalpy transfer, entropy advection, convection and radiative cooling. For tropical ocean parameter settings, the system possesses four non-trivial steady state solutions when the sea surface temperature (SST) is above a critical value. Two steady states are unstable while the two remaining states are stable. Bifurcation diagrams provide an explanation why only finite-amplitude perturbations above a critical SST can transform into TCs. Besides SST, relative humidity of the ambient region forms an important model parameter as it highly affects the entrainment of low entropy air into the inflow region of the TC. The surfaces that describe equilibria as a function of SST and relative humidity reveal a cusp-catastrophe where the two non-trivial equilibria split into four. Within the model regime of four equilibria, cyclogenesis becomes very unlikely due to the repelling and attracting effects of the two additional equilibria. It is tested, whether the qualitative behaviour observed in the box-model simulations is reproducible in the axisymmetric cloud model HURMOD by variation of the initial vortex strength and climatological parameters in analogy to conceptual model experiments. It is shown that an attractor associated with a tropical cyclone exists in HURMOD when a warm-rain micro-physical scheme is applied. By varying SST, the reference temperature profile and relative humidity of the reference state, we find a tropical cyclone branch and a bifurcation in HURMOD similar to those detected in the low order box-model. The results evince the relevance of approaching the dynamics of tropical cyclone formation and its maximum potential intensity (MPI) using a hierarchy of models of different complexity.

Schönemann, D. B.; Frisius, T.

2012-04-01

246

Barotropic process contributing to the formation and growth of tropical cyclone Nargis  

NASA Astrophysics Data System (ADS)

This study reveals the barotropic dynamics associated with the formation and growth of tropical cyclone Nargis in 2008, during its formation stage. Strong equatorial westerlies occurred over the southern Bay of Bengal in association with the arrival of an intraseasonal westerly event during the period 22-24 April 2008. The westerlies, together with strong tropical-subtropical easterlies, constituted a large-scale horizontal shear flow, creating cyclonic vorticity and thereby promoting the incipient disturbance that eventually evolved into Nargis. This basic zonal flow in the lower troposphere was barotropically unstable, with the amplified disturbance gaining more kinetic energy from the easterly jet than from the westerly jet during 25-26 April. This finding suggests that more attention should be paid to the unstable easterly jet when monitoring and predicting the development of tropical cyclones. Energetics analyses reveal that barotropic energy conversion by the meridional gradient of the basic zonal flow was indeed an important energy source for the growth of Nargis.

Mao, Jiangyu; Wu, Guoxiong

2011-05-01

247

Impact of physical parameterizations on idealized tropical cyclones in the Community Atmosphere Model  

NASA Astrophysics Data System (ADS)

This paper explores the impact of the physical parameterization suite on the evolution of an idealized tropical cyclone within the National Center for Atmospheric Research's (NCAR) Community Atmosphere Model (CAM). The CAM versions 3.1 and 4 are used to study the development of an initially weak vortex in an idealized environment over a 10-day simulation period within an aqua-planet setup. The main distinction between CAM 3.1 and CAM 4 lies within the physical parameterization of deep convection. CAM 4 now includes a dilute plume Convective Available Potential Energy (CAPE) calculation and Convective Momentum Transport (CMT). The finite-volume dynamical core with 26 vertical levels in aqua-planet mode is used at horizontal grid spacings of 1.0°, 0.5° and 0.25°. It is revealed that CAM 4 produces stronger and larger tropical cyclones by day 10 at all resolutions, with a much earlier onset of intensification when compared to CAM 3.1. At the highest resolution CAM 4 also accounts for changes in the storm's vertical structure, such as an increased outward slope of the wind contours with height, when compared to CAM 3.1. An investigation concludes that the new dilute CAPE calculation in CAM 4 is largely responsible for the changes observed in the development, strength and structure of the tropical cyclone.

Reed, K. A.; Jablonowski, C.

2011-02-01

248

Influence of the Saharan Air Layer on Atlantic tropical cyclone formation during the period 1-12 September 2003  

NASA Astrophysics Data System (ADS)

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.

Pan, Weiyu; Wu, Liguang; Shie, Chung-Lin

2011-01-01

249

A Gcm Study of the Impact of Greenhouse Gas Increase on the Frequency of Occurrence of Tropical Cyclones  

Microsoft Academic Search

In order to make inferences on the possible future changes of tropical cyclogenesis frequency, we apply the diagnostic computation of the Yearly Genesis Parameter (YGP) proposed by Gray (1975) to the large-scale fields simulated by a GCM. The YGP is an empirical diagnostic of the frequency of Tropical Cyclones (TCs) based on six physical parameters computed from seasonal means of

J.-F. Royer; F. Chauvin; B. Timbal; P. Araspin; D. Grimal

1998-01-01

250

On the Asymmetric Structure of the Tropical Cyclone Outflow Layer.  

National Technical Information Service (NTIS)

ATS-III satellite data and conventional aerological data are used to construct detailed wind analyses of the outflow layer for four hurricanes and one tropical storm. Harmonic analysis of these data, and of the data for a mean Atlantic hurricane and a mea...

P. G. Black R. A. Anthes

1971-01-01

251

Processes setting the characteristics of sea surface cooling induced by tropical cyclones  

NASA Astrophysics Data System (ADS)

A 1/2° resolution global ocean general circulation model is used to investigate the processes controlling sea surface cooling in the wake of tropical cyclones (TCs). Wind forcing related to more than 3000 TCs occurring during the 1978-2007 period is blended with the CORE II interannual forcing, using an idealized TC wind pattern with observed magnitude and track. The amplitude and spatial characteristics of the TC-induced cooling are consistent with satellite observations, with an average cooling of ˜1°C that typically extends over 5 radii of maximum wind. A Wind power index (WPi) is used to discriminate cooling processes under TCs with high-energy transfer to the upper ocean (strong and/or slow cyclones) from the others (weak and/or fast cyclones). Surface heat fluxes contribute to ˜50 to 80% of the cooling for weak WPi as well as away from the cyclone track. Within 200 km of the track, mixing-induced cooling increases linearly with WPi, explaining ˜30% of the cooling for weak WPis and up to ˜80% for large ones. Mixing-induced cooling is strongly modulated by pre-storm oceanic conditions. For a given WPi, vertical processes can induce up to 8 times more cooling for shallow mixed layer and steep temperature stratification than for a deep mixed layer. Vertical mixing is the main source of rightward bias of the cold wake for weak and moderate WPi, but along-track advection becomes the main contributor to the asymmetry for the largest WPis.

Vincent, Emmanuel M.; Lengaigne, Matthieu; Madec, Gurvan; Vialard, JéRôMe; Samson, Guillaume; Jourdain, Nicolas C.; Menkes, Christophe E.; Jullien, Swen

2012-02-01

252

Climate-driven changes in tropical cyclone intensity shape dune activity on Earth's largest sand island  

NASA Astrophysics Data System (ADS)

In this study historical aerial photos and detailed climatic time series are used to show the geomorphological consequences of a significant decrease in tropical cyclone frequency and intensity in eastern Australia since the early 1980s, leading to rapid dune stabilization on Earth's largest sand island and a World Heritage Site, Fraser Island, Australia. It is shown that cyclone frequency and intensity significantly declined in eastern Australia (south of 20°S) since the early 1980s, corresponding with the shift to a positive phase of the Interdecadal Pacific Oscillation (in 1977) and an increased frequency of ENSO events since 1982-83. Using historical aerial photos and remote sensing techniques it is shown that most of Fraser Island's transgressive dune fields were advancing inland during the period between 1948 and 1982, and that tropical cyclones in that period were strong enough to initiate small blow outs (< 1 ha). However, the decline in sand drift potential by wind since 1982 resulted in the contraction of the area of Fraser Island's dune fields, at an average rate of 0.5% of their area per year.

Levin, Noam

2011-01-01

253

Structural variation in genesis and landfall locations of North Atlantic tropical cyclones related to SST  

NASA Astrophysics Data System (ADS)

The influence of sea surface temperature (SST) on the locations of the genesis and of landfall of tropical cyclones in the North Atlantic is analyzed. For that purpose, these locations are calculated from HURDAT and split into two disjoint subsets according to whether SST in the North Atlantic was above or below average in the year the corresponding storms occurred. Landfalls are investigated separately for the groups of cyclones categorized as tropical storms, minor hurricanes, or major hurricanes at the moment of landfall. The locations are considered realizations of inhomogeneous Poisson point processes, and the corresponding density functions are estimated with kernel estimation methods. In this way, any spatial structure inherent in the data is taken into account. These density functions are then compared with Monte Carlo methods from spatial statistics, which allows the detection of areas of statistically significant differences in the two sets with high and low SST, respectively. Results show many such areas, which is of relevance for the insurance industry and mathematical modelling of cyclones, as well as for decision support during the preparation for natural disasters.

Rumpf, Jonas; Weindl, Helga; Faust, Eberhard; Schmidt, Volker

2010-05-01

254

Study of tropical cyclone "Fanoos" using MM5 model - a case study  

NASA Astrophysics Data System (ADS)

Tropical cyclones are one of the most intense weather hazards over east coast of India and create a lot of devastation through gale winds and torrential floods while they cross the coast. So an attempt is made in this study to simulate track and intensity of tropical cyclone "Fanoos", which is formed over the Bay of Bengal during 5-10 December 2005 by using mesoscale model MM5. The simulated results are compared with the observed results of India Meteorological Department (IMD); results show that the cumulus parameterization scheme, Kain-Fritsch (KF) is more accurately simulated both in track and intensity than the other Betts-Miller (BM) and Grell Schemes. The reason for better performance of KF-1 scheme may be due to inclusion of updrafts and downdrafts. The model could predict the minimum Central Sea Level Pressure (CSLP) as 983 hPa as compared to the IMD reports of 984 hPa and the wind speed is simulated at maximum 63 m/s compared to the IMD estimates of 65 m/s. Secondly "Fanoos" development from the lagrangian stand point in terms of vertical distribution of Potential Vorticity (PV) is also carried out around cyclone centre.

Ramalingeswara Rao, S.; Muni Krishna, K.; Bhanu Kumar, O. S. R. U.

2009-01-01

255

Long-term rainfall risk from tropical cyclones in coastal areas  

NASA Astrophysics Data System (ADS)

We develop a methodology for the frequency of extreme rainfall intensities caused by tropical cyclones (TCs) in coastal areas. The model does not account for landfall effects. This makes the developed framework best suited for open water sites and coastal areas with flat topography. The mean rainfall field associated with a TC with maximum tangential wind speed Vmax, radius of maximum winds Rmax, and translation speed Vt is obtained using a physically based model, whereas rainfall variability at both large scales (from storm to storm) and small scales (due to rainbands and local convection) is modeled statistically. The statistical component is estimated using precipitation radar data from the Tropical Rainfall Measuring Mission. Taylor's hypothesis is used to convert spatial rainfall intensity fluctuations to temporal fluctuations at a given location A. The combined physical-statistical model gives the distribution of the maximum rainfall intensity at A during an averaging period D for a TC with characteristics (Vmax, Rmax, Vt) that passes at a given distance from A. To illustrate the use of the model for long-term rainfall risk analysis, we formulate a recurrence model for tropical cyclones in the Gulf of Mexico that make landfall between longitudes 85° and 95°W. We then use the rainfall and recurrence models to assess the rainfall risk for New Orleans. For return periods of 100 years or more and long averaging durations (D around 12-24 h), tropical cyclones dominate over other rainfall event types, whereas the reverse is true for shorter return periods or shorter averaging durations.

Langousis, Andreas; Veneziano, Daniele

2009-11-01

256

Global near-realtime monitoring of Tropical Cyclones Using Weather Satellites  

NASA Astrophysics Data System (ADS)

The Naval Research Laboratory maintains a satellite web portal that monitors global tropical cyclones in every basin on a continuing basis. The portal is used routinely by agencies around the world in forecasting operations and the issuance of warnings. Products from this site are widely redistributed and published frequently in journal articles, seasonal storm summaries, and ongoing World Wide Web discussions. Traditionally, weather satellite reconnaissance of tropical cyclones has depended on the interpretation of visible and infrared imagery. But such methods have limitations. Visible images are not available during the nighttime, and both kinds of imagery often fail to detect important structure, including storm eyes, which are vital for determining the strength and location of tropical systems. Thus, the portal supplements visible and infrared coverage with products from satellite microwave sensors. These sensors penetrate higher clouds to reveal important detail about low-level cloud and precipitation features. The first part of the talk will discuss how these various products can be used together for improved analysis. The second part of talk will present information about tropical cyclone structure. Surface winds from aircraft will be compared to features seen in passive microwave images. We see that low brightness temperature features on 85 GHz images often corresponding to wind maxima near the sea surface. We shall make some inferences about how the observation of specific structures in satellite images can help characterize the wind field when no aircraft data are available. Special attention will be paid to multiple eye walls apparent on satellite images. These are associated with very intense storms which undergo an evolutionary process not observed in weaker systems.

Lee, T.; Hawkins, J.; Turk, F.; Miller, S.; Sampson, C.; Kuciauskas, A.; Richardson, K.; Kent, J.

2006-12-01

257

Impacts of tropical cyclones on U.S. forest tree mortality and carbon flux from 1851 to 2000  

PubMed Central

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.

Zeng, Hongcheng; Chambers, Jeffrey Q.; Negron-Juarez, Robinson I.; Hurtt, George C.; Baker, David B.; Powell, Mark D.

2009-01-01

258

Impacts of tropical cyclones on U.S. forest tree mortality and carbon flux from 1851 to 2000.  

PubMed

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 CO(2) 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

Zeng, Hongcheng; Chambers, Jeffrey Q; Negrón-Juárez, Robinson I; Hurtt, George C; Baker, David B; Powell, Mark D

2009-04-27

259

A simple model for post-landfall intensity changes of tropical cyclone over India, Bangladesh and Myanmar coasts  

NASA Astrophysics Data System (ADS)

Using JTWC (Joint Typhoon Warning Center) best track analysis data for the Indian Ocean cyclones, we developed an empirical equation for prediction of maximum surface wind speed of tropical cyclones during first 6-12 hours of landfall along the coastline of Indian subcontinent. A non-linear data fitting approach, the Genetic Algorithm, has been used to develop the above empirical equation using data for 74 tropical cyclones that made landfall on the coasts of India, Bangladesh and Myanmar during the period 1978-2011. For an out of sample validation test, the mean absolute error of the prediction was found to be 5.2 kt, and a correlation of 0.97. Our analysis indicates that time-integration of land area intercepted by cyclones during the landfall is a better predictor of post-landfall intensity compared to post-landfall time span. This approach also helps to tackle the complexity of coastline geometry of Indian subcontinent area.

Kishtawal, C. M.; Shah, Shivani; Chaurasia, Sashmita; Jaiswal, Neeru

2013-08-01

260

Estimating present day extreme water level exceedance probabilities around the coastline of Australia: tropical cyclone-induced storm surges  

NASA Astrophysics Data System (ADS)

The incidence of major storm surges in the last decade have dramatically emphasized the immense destructive capabilities of extreme water level events, particularly when driven by severe tropical cyclones. Given this risk, it is vitally important that the exceedance probabilities of extreme water levels are accurately evaluated to inform risk-based flood and erosion management, engineering and for future land-use planning and to ensure the risk of catastrophic structural failures due to under-design or expensive wastes due to over-design are minimised. Australia has a long history of coastal flooding from tropical cyclones. Using a novel integration of two modeling techniques, this paper provides the first estimates of present day extreme water level exceedance probabilities around the whole coastline of Australia, and the first estimates that combine the influence of astronomical tides, storm surges generated by both extra-tropical and tropical cyclones, and seasonal and inter-annual variations in mean sea level. Initially, an analysis of tide gauge records has been used to assess the characteristics of tropical cyclone-induced surges around Australia. However, given the dearth (temporal and spatial) of information around much of the coastline, and therefore the inability of these gauge records to adequately describe the regional climatology, an observationally based stochastic tropical cyclone model has been developed to synthetically extend the tropical cyclone record to 10,000 years. Wind and pressure fields derived for these synthetically generated events have then been used to drive a hydrodynamic model of the Australian continental shelf region with annual maximum water levels extracted to estimate exceedance probabilities around the coastline. To validate this methodology, selected historic storm surge events have been simulated and resultant storm surges compared with gauge records. Tropical cyclone induced exceedance probabilities have been combined with estimates derived from a 61-year water level hindcast described in a companion paper to give a single estimate of present day extreme water level probabilities around the whole coastline of Australia. Results of this work are freely available to coastal engineers, managers and researchers via a web-based tool ( www.sealevelrise.info ). The described methodology could be applied to other regions of the world, like the US east coast, that are subject to both extra-tropical and tropical cyclones.

Haigh, Ivan D.; MacPherson, Leigh R.; Mason, Matthew S.; Wijeratne, E. M. S.; Pattiaratchi, Charitha B.; Crompton, Ryan P.; George, Steve

2013-02-01

261

Current Enhanced Atlantic Tropical Cyclone Frequency: A Climate-Change Impact?  

NASA Astrophysics Data System (ADS)

Previous studies of Atlantic tropical cyclone response to anthropogenic climate change have assumed that this has occurred as a quasi-linear trend from around the turn of the 20th century. However, comparison of Global Climate Model (GCM) simulations with and without forcing by anthropogenic gases indicates that the warming due to climate change component was indistinguishable from natural variability until the mid 20th century (Meehl et al 2004). The global change trend became distinct from the annual variability by ~1975. This analysis suggests that internal variability may not be a dominant contributor to the current record temperatures in the MDR, in disagreement with early studies that concluded it was entirely due to internal variability associated with the Atlantic Multidecadal Oscillation (AMO) or similar. Other studies have shown that the warming in the MDR could be explained by changes in both radiative forcing from anthropogenic considerations or by a combination of both radiative and internal effects. Here we adopt the working hypothesis that anthropogenic forcing of climate change moved above the natural climate variability noise level after 1960 and that the majority of the current record level of MDR SST is due to anthropogenic forcing (see Gillett et al for a summary). While this will undoubtedly be controversial, we provide evidence that it fits the available evidence far better than the century-long linear increase that has been assumed in previous studies. We are considering the impacts of this hypothesis on all aspects of Atlantic tropical cyclones; however this presentation will focus on frequency. We first discuss the potential impacts of data errors and shown that these are negligible over the period of interest. We next utilize the association between tropical cyclone frequency and the MDR SST, the MDR SST anomaly compared to the tropics as a whole, and a Genesis Parameter (GP) that incorporates a range of environmental parameters. We find that the current enhanced tropical cyclone frequency arises mainly from climate change with a minority contribution from internal variability. Gillett, N. P., P. A. Stott, and B. D. Santer (2008), Attribution of cyclogenesis region sea surface temperature change to anthropogenic influence, Geophys. Res. Lett., 35, L09707, doi:10.1029/2008GL033670. Meehl, Gerald A., Warren M. Washington, Caspar M. Ammann, Julie M. Arblaster, T. M. L. Wigley, Claudia Tebaldi, 2004: Combinations of Natural and Anthropogenic Forcings in Twentieth-Century Climate. J. Climate, 17, 3721-3727.

Holland, G. J.; Bruyere, C.

2010-12-01

262

The impact of assimilation of AMSU data for the prediction of a tropical cyclone over India using a mesoscale model  

Microsoft Academic Search

Tropical cyclones form over the seas: a typical data?sparse region for conventional observations. Therefore, satellites, especially with microwave sensors, are ideal for cyclone studies. The advanced microwave sounding unit (AMSU) , in addition to providing very valuable data over non?precipitating cloudy regions, can provide very high horizontal resolution of the temperature and humidity soundings. Such high?resolution microwave data can improve

S. Sandeep; A. Chandrasekar; D. Singh

2006-01-01

263

Sediment transport off Bangladesh: the power of tropical cyclones recorded in a submarine canyon  

NASA Astrophysics Data System (ADS)

Marine sediments offshore Bangladesh are mainly supplied by the Ganges-Brahmaputra river system and are accumulated on the shelf of Bangladesh. The average sediment discharge of the world's biggest river system is estimated to be 0.8-1 billion tons per year. The shallow shelf is cut by a steep and up to 1000 m deep anaerobic canyon, called the "Swatch of No Ground", which acts as a sediment trap. An extremely high annual sedimentation flux of 20-45 cm was determined for the last 50 years by 137Cs and 210Pb measurements. In order to investigate the sediment transport in the Bay of Bengal a marine sediment core was taken from the mid-part of the Swatch of No Ground (21°18N/89°34E) and analyzed for element composition and grain-size distributions. Results show a sequence of graded fine-sand-silt-clay layers. These sequences can be directly related to the historical record of tropical storms, which move across the northern Bay of Bengal during pre- and post-monsoon flood peak and mobilize huge amounts of the shallow marine and coastal sediments into turbid hyperpycnal water masses. Due to the anti-clockwise rotation of the cyclones and their northward path the main transport direction is westward. The coarse grained sediment, remobilized by storm waves, is supported by cyclone-induced currents toward the canyon while the fine grained fraction follows afterward supported by the storm swell plus the semi-diurnal tidal component. Despite the high riverine input the amount of sediment mobilized during normal weather conditions is minimal compared to the sediment mobilized by the cyclonic high-energy input. Similar cyclone-induced sediment transport probably also governs erosion and deposition in most tropical shelf areas affected by the monsoon regime.

Meyer, I.; Kudrass, H.; Palamenghi, L.

2011-12-01

264

Predicting tropical cyclogenesis with a global mesoscale model: Hierarchical multiscale interactions during the formation of tropical cyclone Nargis (2008)  

NASA Astrophysics Data System (ADS)

Very severe cyclonic storm Nargis devastated Burma (Myanmar) in May 2008, caused tremendous damage and numerous fatalities, and became one of the 10 deadliest tropical cyclones (TCs) of all time. To increase the warning time in order to save lives and reduce economic damage, it is important to extend the lead time in the prediction of TCs like Nargis. As recent advances in high-resolution global models and supercomputing technology have shown the potential for improving TC track and intensity forecasts, the ability of a global mesoscale model to predict TC genesis in the Indian Ocean is examined in this study with the aim of improving simulations of TC climate. High-resolution global simulations with real data show that the initial formation and intensity variations of TC Nargis can be realistically predicted up to 5 days in advance. Preliminary analysis suggests that improved representations of the following environmental conditions and their hierarchical multiscale interactions were the key to achieving this lead time: (1) a westerly wind burst and equatorial trough, (2) an enhanced monsoon circulation with a zero wind shear line, (3) good upper-level outflow with anti-cyclonic wind shear between 200 and 850 hPa, and (4) low-level moisture convergence.

Shen, B.-W.; Tao, W.-K.; Lau, W. K.; Atlas, R.

2010-07-01

265

Evaluation of the ECMWF 32-day ensemble predictions during 2009 season of western North Pacific tropical cyclone events on intraseasonal timescales  

Microsoft Academic Search

The performance of the ECMWF 32-day ensemble predictions of western North Pacific tropical cyclone events (formation plus track) made once a week during the 2009 season is evaluated with the same procedures as for the 2008 season. Seventeen of the 23 tropical cyclones during the 2009 season occurred during multiple storm scenarios that are more difficult to predict, and many

Russell L. Elsberry; Mary S. Jordan; Frederic Vitart

2011-01-01

266

Tropical Cyclones and Climate Controls in the Western Atlantic Basin during the First Half of the Nineteenth Century  

NASA Astrophysics Data System (ADS)

This study describes new comprehensive reconstructions of individual Western Atlantic Basin tropical cyclones for each year of the first half of the nineteenth century in the Western Atlantic Basin that are directly compatible and supplement the National Hurricane Center's HURDAT (Atlantic basin hurricane database). Data used for reconstructing tropical cyclones come from ship logbooks, ship protests, diaries, newspapers, and early instrumental records from more than 50 different archival repositories in the United States and the United Kingdom. Tropical cyclone strength was discriminated among tropical storms, hurricanes, major hurricanes, and non-tropical lows at least at tropical storm strength. The results detail the characteristics of several hundred storms, many of them being newly documented, and tracks for all storms were mapped. Overall, prominent active periods of tropical cyclones are evident along the western Atlantic Ocean in the 1830s but Caribbean and Gulf coasts exhibit active periods as being more evident in the 1810s and 1820s. Differences in decadal variations were even more pronounced when examining time series of activity at the statewide scale. High resolution paleoclimate and historical instrumental records of the AMO, NAO, ENSO, Atlantic SSTs, West African rainfall, and volcanic activity explain how different modes in these forcing mechanisms may explain some of the multidecadal and interannual variations. The early nineteenth century active hurricane activity appears to be particularly unique in corresponding with a low (negative index) AMO period, and as they relate to particular synoptic-scale patterns in the latter part of the Little Ice Age. Model simulations offer some hypotheses on such patterns, perhaps suggesting increased baroclinic-related storms and a slight later possible shift in the seasonal peak of tropical cyclones for some areas at times. Some years, such as 1806, 1837, 1838, 1842, and 1846 have particularly very active seasons, and we critically examined the synoptic-scale circulation responsible and also related some of the storms as they relate to potential modern analogs.

Mock, C. J.; Dodds, S. F.; Rodgers, M. D.; Patwardhan, A.

2008-12-01

267

Polar Satellite Products for the Operational Forecaster: Microwave Analysis of Tropical Cyclones  

NSDL National Science Digital Library

This module introduces forecasters to the use of microwave image products for observing and analyzing tropical cyclones. Microwave data from polar-orbiting satellites is crucial to operational forecasters, and particularly for those with maritime forecasting responsibilities where in situ observations are sparse. This module includes information on storm structure and techniques for improved storm positioning using the 37 and 85-91 GHz channels from several satellite sensors. Information on current sensors and on the product availability in the NPOESS era is also presented.

Spangler, Tim

2004-11-10

268

The Challenges of Interpreting Microwave-Sounded Height- Registered Water near Tropical Cyclones  

NASA Astrophysics Data System (ADS)

Satellite-derived coincident profiles of water, and liquid water (cloud properties) provide some of the best constraints on the energetics of tropical cyclones. The problem addressed is how accuracy depends on amount and distribution of cloud liquid water. We focus on products derived from the AMSU/MHS sounders using algorithms from the AIRS/AMSU/HSB investigations. We use error analysis and inter omparisons with total precipitable and liquid water from AMSR-E and MODIS. Accuracy degrades as cloud liquid water amount increases and the vertical distribution of water vapor depends on climatological constraints on either partitioning between phases or vertical correlation.

Fishbein, E.; Fetzer, E.; Kahn, B.; Lambrightsen, B.; Teixeira, J.

2008-12-01

269

Tropical Cyclone Zoe devastates South Pacific Islands on Sunday December 29, 2002.  

NSDL National Science Digital Library

Tropical Cyclone Zoe brought winds in excess of 300 km per hour (186 mph) and dangerous waves to the south pacific islands on December 29, 2002. The visualization zooms down to the storm and then shows the overall rain structure. Blue represents areas where at least 0.5 inches of rain fell per hour. Green shows at least 1.0 inch of rain. Yellow is 1.7 inches and red depicts more than 2.2 inches of rain per hour.

Perkins, Lori; Halverson, Jeff

2003-01-09

270

Idealized Tropical Cyclone Simulations of Intermediate Complexity: A Test Case for AGCMs  

NASA Astrophysics Data System (ADS)

The testing of atmospheric general circulation models (AGCMs) is an important component of continued model evaluation and improvement. These tests help reveal the impact of an individual AGCM's design on the representation of atmospheric circulation and climate. The hierarchy of test cases for AGCMs spans deterministic and statistical dry dynamical core tests, aqua-planet experiments with complex physical parameterizations, climate-like simulations with prescribed sea surface temperatures (SSTs) and sea ice, and fully-coupled atmosphere-ocean simulations. The increase in complexity helps support the systematic evaluation of the AGCM designs and their dynamical cores. However, there is a large gap in complexity between dry dynamical core and full-physics aqua-planet runs that makes it difficult to understand the causes and effects of model differences and the dynamics-physics interaction. We introduce a test case of intermediate complexity. Therein we suggest that an AGCM dynamical core be paired with simple moist physics to test the evolution of a single, idealized, initially weak vortex into a tropical cyclone over 10 simulation days. The initial conditions are based on an initial vortex seed that is in gradient-wind and hydrostatic balance. The simple physics consists of parameterizations of bulk surface fluxes for moisture, sensible heat and momentum, vertical diffusion in the boundary layer, and large-scale condensation. This simple-physics configuration thereby includes important driving mechanisms for tropical cyclones, and leads to a rapid intensification of the initial vortex over a forecast period of 10 days. The presentation pays special attention to the impact of the AGCM dynamical core on the evolution of the tropical cyclone. The dynamical core is the central component of every AGCM and determines the numerical methods, diffusion properties and computational mesh for the resolved fluid flow. In particular, we investigate four dynamical cores that are part of NCAR's hydrostatic Community Atmosphere Model CAM 5. The research reveals the influence of the numerical schemes on the evolution of the cyclone and comparisons to simulations with the CAM 5 full-physics package is presented. It is shown that the simple-physics simulations capture the dominant characteristics of the tropical storm. The setup is therefore recommended as a moist AGCM test case of intermediate complexity.

Reed, K. A.; Jablonowski, C.

2011-12-01

271

Idealized Tropical Cyclone Simulations of Intermediate Complexity: A Test Case for Atmospheric GCMs  

NASA Astrophysics Data System (ADS)

The hierarchy of test cases for atmospheric General Circulation Models (GCMs) spans deterministic and statistical dry dynamical core tests, aqua-planet experiments with complex physical parameterizations, climate-like simulations with prescribed sea surface temperatures (SSTs) and sea ice, and fully-coupled atmosphere-ocean simualtions. The increase in complexity helps support the systematic evaluation of the GCM designs and their dynamical cores. However, there is a big gap in complexity between dry dynamical core anf full-physics aqua-planet runs that makes it difficult to understand the causes and effects of model differences and the dynamics-physics interplay. We suggest closing this gap by introducing a new moist dynamical core test case of intermediate complexity. In particular, we present the design of an idealized tropical cyclone test case for high-resolution GCMs in an aqua-planet mode with constant SSTs. The initial conditions are based on an analytic initial vortex seed that is in gradient-wind and hydrostatic balance. Simplified physical parameterizations are suggested that only incorporate bulk surfcae fluxes for moisture, sensible heat and momentum, vertical diffusion in the boundary layer, and large-scale condensation. A simple Betts-Miller-type convection scheme is optional. This simple-physics configuration thereby includes some important driving mechanisms for tropical cyclones, and leads to a rapd intensification of the initial vortex over a forecast period of 10-12 days. The presentation pays special attention to the impact of the GCM dynamical core on the evolution of the tropical cyclone. In particular, we investigate four dynamical cores that are part of NCAR's hydrostatic Community Atmosphere Model CAM5. The research reveals the influence of the numerical schemes on the evolution of the cyclone. Selected comparisons to simulations with NCAR's full-physics package are presented. It is shown that the simple-physics simulations capture the dominant characteristics of the tropical storm and that the model differences seen in the simple-physics simulations resemble the differences of full-physics runs. The setup is therefore recommended as a moist GCM test case of intermediate complexity.

Jablonowski, C.; Reed, K. A.

2010-12-01

272

Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TCs) actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air-sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO) buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

Sriver, R. L.; Huber, M.; Chafik, L.

2012-09-01

273

Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TCs) actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air-sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO) buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

Sriver, R. L.; Huber, M.; Chafik, L.

2013-01-01

274

Spatial Heterogeneity In The Variability Of Tropical Cyclone Climatologies For The Caribbean Basin  

NASA Astrophysics Data System (ADS)

Historically, variations in MDR SST and ENSO have not been associated with spatially-uniform changes in topical cyclone climatologies in the Atlantic. The heterogeneous response in the Caribbean basin between 1950-2006 is examined. High-resolution estimates (1 x 1 km) of tropical cyclone climates are estimated using a novel "kernel," which takes into account several statistically parameterized structures of storms. Application of this kernel to historical data non-parametrically estimates cyclone climatologies for a number of measures and suggests a strong role for high-relief orography in setting storm climates over wide regions. Point-wise bivariate regressions of seasonal storm measures on seasonal MDR SST and annual ENSO 3.4 reveal a broadly positive influence of high MDR SST on storm intensity and frequency measures and a broadly negative influence of high ENSO 3.4 on the same measures. Bootstrapped resampling reveals regions exhibiting statistically significant associations between storm climates and these state variables. Rising MDR SST increases storm frequencies in a narrow band traversing the central basin but increases energy-release along a broader band and regions Northeast of the basin. Higher ENSO 3.4 suppresses storm frequencies and energy dissipation in the southwest of the basin, along the Central American coast and throughout the band of tracks north of the Greater Antilles. These results provide the tools for improved seasonal forecasts at sub-basin resolutions and highlight the importance of a considering spatially heterogenous responses of storm climatologies to anthropogenic climate forcing.

Hsiang, S. M.

2008-12-01

275

Relationship between the frequency of tropical cyclones in Taiwan and the Pacific/North American pattern  

NASA Astrophysics Data System (ADS)

The frequency of tropical cyclones (TCs) in Taiwan during June to October (JJASO) is found to have a strong negative correlation with the Pacific/North American (PNA) pattern in the preceding April. In the negative PNA phase, the anomalous cyclonic and the anomalous anticyclonic circulations are intensified at low latitudes and midlatitudes from East Asia to the North Atlantic, respectively, from April to JJASO. Particularly in East Asia, the anomalous southeasterly that converges between the anomalous anticyclone to the east of Japan and the anomalous cyclone to the east of Taiwan plays a decisive role in moving TCs not only to Taiwan, but also to the midlatitude coastal regions of East Asia as a result of the steering flow. In addition, a southwestward extension of a western North Pacific (WNP) high during the positive PNA phase also contributed to a frequent movement of TCs to southern China without traveling north toward the midlatitude regions of East Asia. Due to the difference in the typical tracks of the TC in the WNP according to the PNA phase, the intensity of the TC in the negative PNA phase is stronger than that in the positive PNA phase.

Choi, Ki-Seon; Moon, Il-Ju

276

Integrated impact of tropical cyclones on sea surface chlorophyll in the North Atlantic  

USGS Publications Warehouse

Past studies have shown that surface chlorophyll-a concentrations increase in the wake of hurricanes. Given the reported increase in the intensity of North Atlantic hurricanes in recent years, increasing chlorophyll-a concentrations, perhaps an indication of increasing biological productivity, would be an expected consequence. However, in order to understand the impact of variable hurricane activity on ocean biology, the magnitude of the hurricane-induced chlorophyll increase relative to other events that stir or mix the upper ocean must be assessed. This study investigates the upper ocean biological response to tropical cyclones in the North Atlantic from 1997-2005. Specifically, we quantitatively compare the anomalous chlorophyll-a concentrations created by cyclone activity to the total distribution of anomalies in the subtropical waters. We show that the cyclone-induced chlorophyll-a increase has minimal impact on the integrated biomass budget, a result that holds even when taking into consideration the lagged and asymmetrical response of ocean color. Copyright 2008 by the American Geophysical Union.

Hanshaw, M. N.; Lozier, M. S.; Palter, J. B.

2008-01-01

277

The evacuation of cairns hospitals due to severe tropical cyclone Yasi.  

PubMed

On February 2, 2011, Tropical Cyclone Yasi, the largest cyclone to cross the Australian coast and a system the size of Hurricane Katrina, threatened the city of Cairns. As a result, the Cairns Base Hospital (CBH) and Cairns Private Hospital (CPH) were both evacuated, the hospitals were closed, and an alternate emergency medical center was established in a sports stadium 15 km from the Cairns central business district. This article describes the events around the evacuation of 356 patients, staff, and relatives to Brisbane (approximately 1,700 km away by road), closure of the hospitals, and the provision of a temporary emergency medical center for 28 hours during the height of the cyclone. Our experience highlights the need for adequate and exercised hospital evacuation plans; the need for clear command and control with identified decision-makers; early decision-making on when to evacuate; having good communication systems with redundancy; ensuring that patients are adequately identified and tracked and have their medications and notes; ensuring adequate staff, medications, and oxygen for holding patients; and planning in detail the alternate medical facility safety and its role, function, and equipment. PMID:22978739

Little, Mark; Stone, Theona; Stone, Richard; Burns, Jan; Reeves, Jim; Cullen, Paul; Humble, Ian; Finn, Emmeline; Aitken, Peter; Elcock, Mark; Gillard, Noel

2012-09-01

278

Simulations of Severe Tropical Cyclone Nargis over the Bay of Bengal Using RIMES Operational System  

NASA Astrophysics Data System (ADS)

The Regional Integrated Multi-Hazard Early Warning System (RIMES), an international, intergovernmental organization based in Thailand is engaged in disaster risk reduction over the Asia-Pacific region through early warning information. In this paper, RIMES' customized Weather Research Forecast (WRF) model has been used to evaluate the simulations of cyclone Nargis which hit Myanmar on 2 May 2008, the most deadly severe weather event in the history of Myanmar. The model covers a domain of 35ºE to 145ºE in the east—west direction and 12ºS to 40ºN in the north—south direction in order to cover Asia and east Africa with a resolution of 9 km in the horizontal and 28 vertical levels. The initial and boundary conditions for the simulations were provided by the National Center for Environmental Prediction-Global Forecast System (NCEP-GFS) available at 1º lon/lat resolution. An attempt is being made to critically evaluate the simulation of cyclone Nargis by seven set of simulations in terms of track, intensity and landfall time of the cyclone. The seven sets of model simulations were initialized every 12 h starting from 0000 UTC 28 April to 01 May 2008. Tropical Rainfall Measurement Mission (TRMM) precipitation (mm) is used to evaluate the performance of the simulations of heavy rainfall associated with the tropical cyclone. The track and intensity of the simulated cyclone are compared by making use of Joint Typhoon Warning Center (JTWC) data sets. The results indicate that the landfall time, the distribution and intensity of the rainfall, pressure and wind field are well simulated as compared with the JTWC estimates. The average landfall track error for all seven simulations was 64 km with an average time error of about 5 h. The average intensity error of central pressure in all the simulations were found out to be approximately 6 hPa more than the JTWC estimates and in the case of wind, the simulations under predicted it by an average of 12 m s-1.

Raju, P. V. S.; Potty, Jayaraman; Mohanty, U. C.

2012-10-01

279

Impact of tropical cyclones on the intensity and phase propagation of fall Wyrtki jets  

NASA Astrophysics Data System (ADS)

Observations and model simulations are used to study the impact of tropical cyclones (TC) on the fall Wyrtki jets (WJ). These strong narrow equatorial currents peak during November and play a vital role in the energy and mass transport in the tropical Indian Ocean (TIO). Maximum number of TCs is observed over TIO during November with longer than normal life span (8-15 days). These TCs enhance equatorial westerly winds (surface) and amplify monthly mean WJs (both at surface and subsurface) by 0.4 ms-1 (anomalies exceed 0.7 ms-1 during TC), which is about half of the climatological amplitude. Intensified WJs increase the heat content of eastern TIO and modulate air-sea interaction. It is also shown that movement of TCs is mainly responsible for the westward phase propagation of WJs, a previously unexplored mechanism. These features are evident in ECCO2 simulations as well.

Sreenivas, P.; Chowdary, J. S.; Gnanaseelan, C.

2012-11-01

280

The Impact of Tropical Cyclones on Coral Bleaching and Coral Diseases  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TCs) impact coral reef ecology in various ways, they cool down ambient sea surface temperature (SST), damage coral reefs by wave action, decrease salinity, increase nutrients, and increase sedimentation rates on a reef. Here we present an investigation into the effect of TCs on coral bleaching and the effect TCs have on the occurrence of coral diseases. Coral bleaching, the condition where the symbiotic zooxanthellae leave the coral host, is one of the major threats to coral reefs. Bleaching occurs in anomalously warm waters, analysis of historical TC tracks show that TCs frequently occur near coral bleaching episodes. Intriguingly, TCs cool down sea surface temperature by vertical mixing and as SST is the most important factor in coral bleaching this phenomenon might have an impact on the duration, occurrence and the resulting coral mortality, of bleaching events. In recent literature a correlation has been seen in the power of tropical cyclones and average sea surface temperature, making the study of the effect of TCs on the ecology of reefs an urgent one. We will present case studies where a TCs occurred near bleaching episodes and a statistical analysis to quantify this effect. To do this we use historical cyclone track data, satellite SST data, and a dataset of reefs. But there are other TC effects on reefs that bear investigation. Because TCs occur near corals that experience thermal stress, the changes in the corals environment caused by TCs might be anomalously detrimental. For example, data suggests that corals, because they are stressed by increased sedimentation, are more vulnerable to disease and algal overgrowth after TC damage. Nutrients have been shown to increase the severity of coral diseases. With satellite data it can be shown that short-term events such as increased run-off due to tropical cyclones can be an important part of the distribution of pollutants and pathogens affecting reefs. Infectious diseases severely affect scleractinian corals. We compare a database of coral disease outbreaks and a database of historical hurricane tracks and quantify run-off using satellite data to investigate the hypothesis that TCs can contribute to the spread of coral diseases by run-off induced transport of sediment, nutrients, pollutants and pathogens to a reef.

van Hooidonk, R. J.; Huber, M.

2006-12-01

281

Punctuated global tropical cyclone activity over the past 5,000 years  

NASA Astrophysics Data System (ADS)

There are now a substantial number of millennial scale records of tropical cyclones from a variety of locations globally. Some of these, such as those in the Atlantic and Gulf of Mexico, show patterns of long-term, generally intense, tropical cyclone (TC) behaviour that have been suggested to be due to either variations in ENSO or shifts in the position of the Atlantic High pressure system and the jet stream. Comparisons are made here of the sedimentary overwash records from the Gulf of Mexico and Atlantic Ocean Basin with the overwash records from the north-west Pacific and beach ridge records from the south-west Pacific and south east Indian Ocean basins. There is a substantial degree of synchroneity in global intense TC behaviour over the past 3,000 to 5,000 years. One of the most striking aspects of these records is they all display extended alternating periods (centuries to millennia) of relative quiescence and heightened intense TC activity irrespective of both the resolution and type of long-term TC record. The cause(s) of this punctuated activity are at present difficult to identify but are likely exogenic in origin rather than due to an intrinsic aspect of the records or the methods used to derive them. The identification of punctuated global long-term TC behaviour is important for understanding future TC activity and for assessing risk to coastal communities.

Nott, Jonathan; Forsyth, Anthony

2012-07-01

282

Modeling High-Impact Weather and Climate: Lessons From a Tropical Cyclone Perspective  

SciTech Connect

Although the societal impact of a weather event increases with the rarity of the event, our current ability to assess extreme events and their impacts is limited by not only rarity but also by current model fidelity and a lack of understanding of the underlying physical processes. This challenge is driving fresh approaches to assess high-impact weather and climate. Recent lessons learned in modeling high-impact weather and climate are presented using the case of tropical cyclones as an illustrative example. Through examples using the Nested Regional Climate Model to dynamically downscale large-scale climate data the need to treat bias in the driving data is illustrated. Domain size, location, and resolution are also shown to be critical and should be guided by the need to: include relevant regional climate physical processes; resolve key impact parameters; and to accurately simulate the response to changes in external forcing. The notion of sufficient model resolution is introduced together with the added value in combining dynamical and statistical assessments to fill out the parent distribution of high-impact parameters. Finally, through the example of a tropical cyclone damage index, direct impact assessments are presented as powerful tools that distill complex datasets into concise statements on likely impact, and as highly effective communication devices. Capsule: "Combining dynamical modeling of high-impact weather using traditional regional climate models with statistical techniques allows for comprehensive sampling of the full distribution, uncertainty estimation, direct assessment of impacts, and increased confidence in future changes."

Done, James; Holland, Greg; Bruyere, Cindy; Leung, Lai-Yung R.; Suzuki-Parker, Asuka

2012-06-01

283

Application of scale-selective data assimilation to tropical cyclone track simulation  

NASA Astrophysics Data System (ADS)

Tropical cyclone track is strongly controlled by the large-scale environmental circulation. In limited-area models (LAMs) driven by global analyses or forecasts through a conventional lateral boundary nesting approach, the global analyses are often distorted by the use of "sponge zone" or interpolation when they are passed into the LAM. In this study, a dynamical downscaling approach based on scale-selective data assimilation (SSDA) is applied to a limited-area numerical weather prediction model with emphasis on tropical cyclone track simulation. The idea of the SSDA approach is to drive the LAM not only from the lateral boundary but also from the model domain interior. The large-scale flow from global analyses or forecasts is assimilated into the regional model using 3-D variational data assimilation. The large-scale features in the LAM are thus constrained to follow the global analyses while allowing the regional model itself to develop the regional and small-scale characteristics. The results from the case study of Hurricane Katrina (2005) show that both large- and small-scale flows in the regional model benefited from the SSDA approach, leading to an improvement in the accuracy of storm track simulation when provided with an accurate large-scale circulation from global analyses. In addition, the SSDA procedure is shown to be an effective method to construct a nested-grid regional modeling system that reduces model sensitivity to model domain geometry and location.

Xie, Lian; Liu, Bin; Peng, Shiqiu

2010-09-01

284

Rotational speed study of tropical cyclone spiral rainband by using geostationary satellite images  

NASA Astrophysics Data System (ADS)

The studies of tropical cyclone spiral rainband activities usually used radar-based observation when not landing. The rotational velocities were calculated by manually or automatically matching the movement of storm-scale reflectivity from two sequences of radar data. In this study, we used satellite-based infrared data as the search objects. The rotational speed of outer rainband and different annular radii was obtained by using rotational maximum cross-correlation (MCC) technique as matching approach. The benefit of this approach is the ability to get large scale movements of tropical cyclones and get better understanding the nature of revolving. We apply typhoon Nangka(2003), Soudelor(2003), Morakot(2003) and Dujuan(2003) for studying rotational speed. The results show that the average speed of all is 4.6 degree per hour and median value is 4 degree per hour. When comparing with typhoon strength, it shows that the stronger typhoons have bigger rotational speed. When considering different annular radii, we get different rotational speed and found that more near typhoon center have bigger rotational speed.

Chao, C.; Liu, G.; Liu, C.; Huang, S.

2006-12-01

285

Oscillation responses to tropical Cyclone Gonu in northern Arabian Sea from a moored observing system  

NASA Astrophysics Data System (ADS)

In June 2007, tropical Cyclone Gonu passed over an ocean observing system consisting of a deep autonomous mooring system in the northern Arabian Sea and a shallow cabled mooring system in the Sea of Oman. Gonu was the largest cyclone known to have occurred in the Arabian Sea and to strike the Arabian Peninsula. The instruments on the moorings continuously recorded water velocities, temperature, conductivity, pressure, dissolved oxygen (DO) and turbidity at multiple depths and at hourly intervals during the storm. Near-inertial oscillations at all moorings from thermocline to seafloor are coincident with the arrival of Gonu. Sub-inertial oscillations with periods of 2-10 day are recorded at the post-storm relaxation stage of Gonu, primarily in the thermocline of the deep array and at the onshore regions of the shallow array. These oscillations consist of warm, saline water masses, likely originating from the Persian Gulf. Prominent 12.7-day sub-inertial waves, measured at a station ˜300 km offshore, are bottom-intensified and have characteristics of baroclinic topographically trapped waves. Theoretical results from a topographically trapped wave model are in a good agreement with the observed 12.7-day waves at Murray Ridge. The wavelength of the 12.7-day waves is about 590 km calculated from the dispersion relationship. Further analysis suggests that a resonant standing wave is responsible for trapping the 12.7-day wave energy inside the Sea of Oman basin. The observational results reported here are the first measurements of deepwater responses to a tropical cyclone in the Sea of Oman/Arabian Sea. Our study demonstrates the utility of sustained monitoring for studying the impact of extreme weather events on the ocean.

Wang, Zhankun; DiMarco, Steven F.; Stössel, Marion M.; Zhang, Xiaoqian; Howard, Matthew K.; du Vall, Ken

2012-06-01

286

Investigation into impact of tropical cyclones on the ionosphere using GPS sounding and NCEP/NCAR Reanalysis data  

NASA Astrophysics Data System (ADS)

Spatial-temporal dynamics of Total Electron Content (TEC) disturbances over zones with higher cyclonic activity was investigated. The TEC data from the international network of two-frequency ground-based GPS receivers were used. An increase in intensity of wave TEC disturbances in two period ranges (2-20 min and 15-40 min) was registered under quiet geo-magnetic conditions during several tropical cyclones. We mapped the TEC variation intensity for strong tropical cyclones observed over the Northwest Atlantic Ocean in August-November 2005. It is shown that analysis of spatial distribution of ionospheric disturbances using TEC variation maps allows us to select disturbances most probably associated with cyclones. Com-parative analysis of TEC variations with changes in meteorological parameters was made. For this purpose we used the NCEP Reanalysis data provided by NOAA/OAR/ESRL PSD, Boul-der, Colorado, USA, from their website at http://www.esrl.noaa.gov/psd/. We also estimated influence of the wind atmospheric regime on appearance of ionospheric disturbances generated by tropical cyclones. This work was supported by the Russian Foundation for Basic Research (grant 08-05-00658).

Polyakova, Anna; Perevalova, Natalia

287

Extra-Tropical Cyclones in a Warming Climate: Observational Evidence of Trends in Frequencies and Intensities in the North Pacific, North Atlantic, and Great Lakes Regions  

Microsoft Academic Search

Extra-Tropical Cyclone (ETC) is a generic term for any non-tropical, synoptic-scale, low pressure storm system that develops along a boundary between warm and cold air masses. The extra- tropical types of cyclonic storms are baroclinic, in that they derive their energy from lateral gradients in temperature and pressure. They are the dominant weather phenomenon occurring in the mid- and high-

David H. Levinson; Peter D. Bromirski

2007-01-01

288

Analysis of tropical cyclone dynamics in a conceptual box-model and the axisymmetric cloud model HURMOD  

NASA Astrophysics Data System (ADS)

Tropical cyclone dynamics is investigated by means of a low order box-model and an axisymmetric high-resolution cloud model. Within the conceptual model the tropical cyclone is divided into three regions, namely the eye, the eyewall and the ambient region. It comprises the processes of surface evaporation, radial entropy advection, convection and radiative cooling. For typical tropical ocean parameter settings the system possesses three steady state solutions when the sea surface temperature (SST) is above a critical minimum value. One steady state is unstable while the two remaining states are stable. One of the stable solutions represents the atmosphere at rest and the other can be identified as a tropical cyclone at its maximum potential intensity (MPI). A saddle node bifurcation appears at a critical minimum temperature where two branches vanish. Below the critical temperature, only the atmosphere at rest represents a steady state solution in the system. A bifurcation diagram provides an explanation why only finite-amplitude perturbations above a critical SST can transform into tropical cyclones. Besides SST, relative humidity of the ambient region forms an important model parameter and the surfaces that describe equilibria as a function of SST and relative humidity reveal a cusp-catastrophe where the two non-trivial equilibria split up into four. Within the model regime of four equilibria, cyclogenesis becomes very unlikely due to the repulsing and attracting effects of the two additional equilibria. The results are in qualitative agreement with observations. Furthermore it is tested, whether the qualitative behaviour observed in the box-model simulations is reproducible in the axisymmetric cloud model HURMOD. It is shown that an attractor associated with a tropical cyclone exists in HURMOD when a simplified cloud physics is applied, so that condensate terminates immediately. By varying SST we find a tropical cyclone branch and a bifurcation in HURMOD similar to those detected in the low order box-model. The results evince the relevance of the simple model approach to the dynamics of tropical cyclone formation and its maximum potential intensity (MPI).

Schönemann, D.; Frisius, T.

2010-09-01

289

Influence of local and remote SST on North Atlantic tropical cyclone potential intensity  

NASA Astrophysics Data System (ADS)

We examine the role of local and remote sea surface temperature (SST) on the tropical cyclone potential intensity in the North Atlantic using a suite of model simulations, while separating the impact of anthropogenic (external) forcing and the internal influence of Atlantic Multidecadal Variability. To enable the separation by SST region of influence we use an ensemble of global atmospheric climate model simulations forced with historical, 1856-2006 full global SSTs, and compare the results to two other simulations with historical SSTs confined to the tropical Atlantic and to the tropical Indian Ocean and Pacific. The effects of anthropogenic plus other external forcing and that of internal variability are separated by using a linear, "signal-to-noise" maximizing EOF analysis and by projecting the three model ensemble outputs onto the respective external forcing and internal variability time series. Consistent with previous results indicating a tampering influence of global tropical warming on the Atlantic hurricane potential intensity, our results show that non-local SST tends to reduce potential intensity associated with locally forced warming through changing the upper level atmospheric temperatures. Our results further indicate that the late twentieth Century increase in North Atlantic potential intensity, may not have been dominated by anthropogenic influence but rather by internal variability.

Camargo, Suzana J.; Ting, Mingfang; Kushnir, Yochanan

2013-03-01

290

Evolution of the Surface Wind Field in an Intensifying Tropical Cyclone.  

NASA Astrophysics Data System (ADS)

The surface wind field in a developing tropical cyclone (Agnes, 1972) was analyzed over a 1660 km radius for four days using conventional surface data, as the storm evolved from a disorganized depression to a hurricane. The transition to hurricane intensity was characterized by a wavelike disturbance propagating inward at 15 m s1 from the outermost radii to the storm core over a 36-hour period. This propagating disturbance was clearly visible in the radial and vertical motion fields as a surge of inflow and upward motion. Rapid intensification of the storm began within hours after the leading edge of the surge reached the storm center. The analysis of consecutive 12-hour periods without compositing of data from nonsynoptic times was essential for identification of this feature.The surge had the same asymmetry as the upper-level outflow channel, indicating the possible involvement of the outflow layer in its initiation. No clear evidence of an external forcing mechanism for the surge, such as the passage of an easterly wave across the circulation, could be found. No instability theory could account for propagation of this feature across regions with such strongly varying dynamical properties. As a result, it remains uncertain whether the inflow surge represented an environmental trigger to hurricane formation or a manifestation of an internal instability.The boundary layer momentum budget was dominated by Coriolis torque and frictional dissipation. The sum of these two terms acted as a momentum source primarily during the passage of the inflow surge across each radial region. Inward lateral flux of momentum contributed significantly only within 440 km of the center.A distinct diurnal oscillation in pressure tendency occurred until hurricane strength was reached, with maximum deepening at 1200 local time, and minimum deepening at 0000 local time. Diurnal oscillations in other variables were more subtle and often at variance with those described in other tropical cyclones.Because the inflow surge developed at outer radii 36 hours prior to rapid deepening and had a clear signature in the time change of radial mass flux, it provides a potential tool for forecasting tropical cyclogenesis 24 hours or more in advance which requires only the use of conventional data. More study is needed to determine whether such an early warning signal frequently occurs in intensifying tropical cyclones.

Molinari, John; Skubis, Steven

1985-12-01

291

Analysis of Water Properties and Geostrophic Currents in FijiWaters Before and After Tropical Cyclone Gene  

Microsoft Academic Search

Problem statement: Water properties influence ocean primary productio n and drive the ocean food chain. This study depicts changes in tem perature and salinity and its effects on geostrophi c currents near Fiji before and after Tropical Cyclon e (TC) Gene. Approach: Available Argo float data from 6 January-4 February 2008 were used for analysis since TC Gene passed the

Shivneel Prasad; Than Aung; Awnesh Singh

2009-01-01

292

Evaluation of Experimental Models for Tropical Cyclone Forecasting in Support of the NOAA Hurricane Forecast Improvement Project (HFIP)  

NASA Astrophysics Data System (ADS)

The Tropical Cyclone Modeling Team (TCMT) in NCAR's Joint Numerical Testbed (JNT) Program focuses on the verification of experimental forecasts of tropical cyclones (TCs). Activities of the team include the development of new verification methods and tools for TC forecasts and the design and implementation of diagnostic verification experiments to evaluate the performance of tropical cyclone forecast models. For the Hurricane Forecast Improvement Project (HFIP), the TCMT has designed and conducted verification studies involving various regional and global forecast models that participate in the annual HFIP retrospective and real-time forecast demonstration studies. The TCMT has also developed new statistical approaches that provide statistically meaningful diagnostic evaluations of TC forecasts. These methods include new diagnostic tools to aid, for example, in the evaluation of track and intensity errors and ensemble forecasts. Recently, the TCMT conducted a retrospective evaluation of eight experimental tropical cyclone forecast models that ranged from deterministic to ensemble forecast systems. These models were evaluated for storms that occurred in the 2008-2010 hurricane seasons in the North Atlantic and Eastern Pacific Oceans. The forecasts from these models were also evaluated for the 2011 HFIP demonstration experiment. This presentation will provide an overview of the evaluation methodology including new methods along with a summary of key results from the 2011 HFIP retrospective and demonstration studies.

Kucera, P. A.; Brown, B. G.; Nance, L.; Williams, C.

2012-04-01

293

Orographic Effects on Rainfall Induced by the Passage of Tropical Cyclones over Mountainous Islands Part I: Control Experiment  

Microsoft Academic Search

The passage of a tropical cyclone (TC) over a mesoscale mountainous island, such as Puerto Rico, often brings heavy rainfall which produces flooding and landslides. Factors that affect quantities and distribution of this type of orographic rainfall in this region are not well understood. The numerical mesoscale Advanced Research Weather Research and Forecast (ARW) model was adopted to conduct a

I. C. Colon-Pagan; Y. Lin; Y. Kuo; W. S. Schreiner

2009-01-01

294

The influence of landfall variation on tropical cyclone losses in the United States as simulated by HAZUS  

Microsoft Academic Search

Tropical cyclone losses in the United States have shown an increasing trend since the beginning of the 20th century. This is mainly due to increased exposure along America's coast. The amount of coastal property at risk persistently increases due to inflation, wealth increase, and population growth. When researchers have normalized the loss record to remove the influence of exposure and

Kevin Joseph Sharp

2009-01-01

295

Restoration of a 132 kV over head transmission line affected by tropical cyclone Gonu in Oman  

Microsoft Academic Search

This paper presents a procedure for restoring a 132 kV transmission line subjected to the tropical cyclone Gonu which hit the Sultanate of Oman recently. Six steel towers have fallen due to massive water floods and strong winds in a valley called Wadi Adi, which resulted in line outage and interruption of the electricity supply to a remote substation. The

Omar H. Abdalla; Thani M. Alkhusaibi; Masoud Awlad-Thani; Mohammed N. Al-Mazrouey

2008-01-01

296

Satellite-based tropical cyclone intensity estimation using NOAA-KLM series advanced microwave sounding unit (AMSU) data  

Microsoft Academic Search

Satellite-borne passive microwave radiometers are well suited to monitor tropical cyclones (TCs) by virtue of their ability to assess changes in tropospheric warm core structure in the presence of clouds. The temporal variability in TC warm core size, structure, and magnitude provide vital information on changes in kinematic structure and minimum sea level pressure (MSLP) through implicit thermodynamic and dynamic

Kurt Frederick Brueske

2001-01-01

297

The Aeroclipper, a new device to explore tropical convective systems and cyclones  

NASA Astrophysics Data System (ADS)

The Aeroclipper is a new balloon device designed to perform relatively long flights (up to 30 days) in the surface layer (under 50 m) over remote ocean regions. The balloon carries a guide rope floating at the surface of the ocean. The Aeroclipper moves on quasi-Lagrangian trajectories, performing in situ measurements in the atmospheric surface layer and at the surface of the ocean. The Aeroclipper is able to measure low level dynamics and surface turbulent fluxes for several weeks over remote regions of the tropical oceans. Like superpressure balloons in the boundary layer, an Aeroclipper is attracted toward convective regions by the low-level wind convergence generated by the associated low surface pressure. Compared to Eulerian platforms (moored buoys) or to oceanographic ships, these balloons are thus expected to increase atmospheric boundary layer sampling in active convective systems. During the Validation of the Aeroclipper System under Convective Occurrences (VASCO) test experiment (Indian Ocean in January and February 2007), two Aeroclippers survived in tropical cyclone Dora, enduring wind speed larger than 40 ms-1 and giving continuous estimates of tangential and radial winds as a function of the distance from the eye during the convergence phase. The two Aeroclippers then stayed in the eye of Dora for more than a week and remained captured in the low-pressure center when Dora became an extra-tropical depression. Due to this success in mechanical design, and despite some deficiencies of the present system that require new developments, we think that such a device has a good potential for further use, especially for cyclone nowcasting. The scientific objectives of the Aeroclipper; its current design and instrumentation; some preliminary results of the VASCO test experiment; and future experiments will be presented.

Philippe, Duvel Jean

298

Seasonal tropical cyclone precipitation in Texas: A statistical modeling approach based on a 60 year climatology  

NASA Astrophysics Data System (ADS)

Sixty years of tropical cyclone precipitation (TCP) in Texas has been analyzed because of its importance in extreme hydrologic events and the hydrologic budget. We developed multiple linear regression models to provide seasonal forecasts for annual TCP, TCP's contribution (percentage) to total precipitation, and the number of TCP days in Texas. The regression models are based on three or fewer predictors with model fits ranging from 0.18 to 0.43 (R2) and cross-validation accuracy of 0.05-0.36 (R2). La Niña exhibits the most important control on TCP in Texas. It is the major driver in our models and acts to reduce the vertical shear in the Caribbean and the tropical Atlantic, thereby generating more precipitating storms in Texas. Lower maximum potential velocity, the theoretical maximum wind speed that storms can attain, in the Gulf of Mexico, and low-level vorticity in the Atlantic hurricane main development region increased the modeled R2 by 20% or more. Both variables have negative coefficients in the TCP models. Lower maximum potential velocity and vorticity are associated with tropical cyclones with lower maximum wind speed and slower translation speed. Such weak TCs produce the majority of TCP and extreme TCP events in Texas. The quartiles of the TCs with strongest maximum wind speed and fastest translation speed are not associated with the largest mean daily precipitation based on observations in Texas. We have also shown that sea level pressure in the Gulf of Mexico, sea surface temperature in the Caribbean, and the North Atlantic Oscillation are potentially important predictors of seasonal TCP in Texas.

Zhu, Laiyin; Frauenfeld, Oliver W.; Quiring, Steven M.

2013-08-01

299

Trends and low frequency variability of extra-tropical cyclone activity in the ensemble of twentieth century reanalysis  

NASA Astrophysics Data System (ADS)

An objective cyclone tracking algorithm is applied to twentieth century reanalysis (20CR) 6-hourly mean sea level pressure fields for the period 1871-2010 to infer historical trends and variability in extra-tropical cyclone activity. The tracking algorithm is applied both to the ensemble-mean analyses and to each of the 56 ensemble members individually. The ensemble-mean analyses are found to be unsuitable for accurately determining cyclone statistics. However, pooled cyclone statistics obtained by averaging statistics from individual members generally agree well with statistics from the NCEP-NCAR reanalyses for 1951-2010, although 20CR shows somewhat weaker cyclone activity over land and stronger activity over oceans. Both reanalyses show similar cyclone trend patterns in the northern hemisphere (NH) over 1951-2010. Homogenized pooled cyclone statistics are analyzed for trends and variability. Conclusions account for identified inhomogeneities, which occurred before 1949 in the NH and between 1951 and 1985 in the southern hemisphere (SH). Cyclone activity is estimated to have increased slightly over the period 1871-2010 in the NH. More substantial increases are seen in the SH. Notable regional and seasonal variations in trends are evident, as is profound decadal or longer scale variability. For example, the NH increases occur mainly in the mid-latitude Pacific and high-latitude Atlantic regions. For the North Atlantic-European region and southeast Australia, the 20CR cyclone trends are in agreement with trends in geostrophic wind extremes derived from in-situ surface pressure observations. European trends are also consistent with trends in the mean duration of wet spells derived from rain gauge data in Europe.

Wang, Xiaolan L.; Feng, Y.; Compo, G. P.; Swail, V. R.; Zwiers, F. W.; Allan, R. J.; Sardeshmukh, P. D.

2013-06-01

300

Formation and Quasi-Periodic Behavior of Outer Spiral Rainbands in a Numerically Simulated Tropical Cyclone  

NASA Astrophysics Data System (ADS)

The formation and quasi-periodic behavior of outer spiral rainbands in a tropical cyclone simulated in the cloud-resolving tropical cyclone model version 4 (TCM4) are analyzed. The outer spiral rainbands in the simulation are preferably initiated near the 60-km radius, or roughly about three times the radius of maximum wind (RMW). After initiation, they generally propagate radially outward with a mean speed of ~5 m s-1. They are reinitiated quasi-periodically with a period between 22 h and 26 h in the simulation. While the inner spiral rainbands, which form within a radius of about three times the RMW, are characterized by the convectively coupled vortex Rossby waves (VRWs), the formation of outer spiral rainbands, namely, rainbands formed outside a radius of about three times the RMW, is much more complicated. It is shown that outer spiral rainbands are triggered by the inner-rainband remnants immediately outside the rapid filamentation zone and inertial instability in the upper troposphere. The preferred radial location of initiation of outer spiral rainbands is understood as a balance between the suppression of deep convection by rapid filamentation and the favorable dynamical and thermodynamic conditions for initiation of deep convection. The quasi-periodic occurrence of outer spiral rainbands is found to be associated with the boundary layer recovery from the effect of convective downdrafts and the consumption of convective available potential energy (CAPE) by convection in the previous outer spiral rainbands. Specifically, once convection is initiated and organized in the form of outer spiral rainbands, it will produce strong downdrafts and consume CAPE. These effects weaken convection near its initiation location. As the rainband propagates outward further, the boundary layer air near the original location of convection initiation takes about 10 h to recover by extracting energy from the underlying ocean. Convection and thus new outer spiral rainbands will be initiated near a radius of about three times the RMW. This will be followed by a similar outward propagation and the subsequent boundary layer recovery, leading to a quasi-periodic occurrence of outer spiral rainbands. In response to the quasi-periodic appearance of outer spiral rainbands, the storm intensity experiences a similar quasi-periodic oscillation with its intensity or intensification rate starting to decrease after about 4 h of the initiation of an outer spiral rainband. The results provide an alternative explanation or one of the mechanisms that are responsible for the quasi-periodic (quasi-diurnal) variation in the intensity and in the area of outflow-layer cloud canopy of observed tropical cyclones.

Li, Q.; Wang, Y.

2012-04-01

301

The Effect of Tropical Cyclones on the Mixed-Layer Ocean Heat Content  

NASA Astrophysics Data System (ADS)

The effect of strong wind of two consecutive tropical cyclones (04B and 05B) in October and November, 1999 on mixed-layer ocean heat content (MOHC) of the Bay of Bengal (BOB) has been investigated. The HYbrid Coordinate Ocean Model (HYCOM) is driven by meteorological forcings from ERA interim reanalysis output with a) control wind field and b) experimental wind field in which 04B- and/or 05B-associated wind are filtered out. The simulations show anomalously large MOHC and cool sea surface temperature (SST) in northeastern BOB, caused by 05B. The importance of strong tropical cyclones is signified by the persistence of MOHC anomaly. The BOB mean MOHC anomaly of 04B in our control run lasts until 05B resets the thickness of the mixed layer, while that of 05B reaches its maximum during the tropical cyclone lifetime, diminishes for 10 days, and re-emerge through small-scaled features across BOB. The MOHC anomaly is mainly determined by the mixed-layer thickness, and the mixed layer deepens most to the right of 05B, partly due to stronger wind on the right and ocean counter flow on the left. The position of lowest SST coincides with the position of deepest mixed layer. Although the heat (sensible heat plus latent heat) exchange following the TCs is characterized by its strong wind effect, its BOB mean is similar in the control run and in the experimental runs, showing that energy extraction from the ocean is only significant within strong wind radius in our simulation. This reveals the importance of driving forces of the ocean model in the mesoscale when investigating air-sea feedbacks. The deepened mixed layer caused by the TCs in the control run increases the upper ocean heat capacity, which may expedite the heat transfer into BOB after the TC events in the long term. Therefore, the long term effect of large OHC anomaly caused by TCs on the climate needs further investigation.

Wang, J.; Han, W.

2010-12-01

302

A validation study for GPS radio occultation data with moist thermodynamic structure of tropical cyclones  

NASA Astrophysics Data System (ADS)

We exploit the cloud-penetrating capability and insensitivity to precipitation of the Global Positioning System radio occultation (GPSRO) technique to study the humidity environment of tropical cyclones (TCs). We focus in regions within and around the vicinity of TCs' eye, where infrared and microwave observations are difficult to acquire due to cloudiness and heavy precipitation. We use data from the National Hurricane Center TC Best Tracks to identify the location of North Atlantic TCs. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center provides concurrent refractivity, temperature, and humidity measurements from the Challenging Minisatellite Payload and COSMIC missions and the European Centre for Medium-Range Weather Forecasts (ECMWF). The distribution of GPSRO-derived humidity profiles as functions of altitude and distance from the storms' center identifies a pronounced low-level inflow, characteristic of mature TCs, at distances between 50 and 90 km, which coincide with the area where the eyewall of TCs forms. We also capture wavelike structures resembling spiral rainbands beyond the eyewall. The distribution of water vapor as functions of altitude and TC intensity shows a decrease at all altitudes when a tropical system matures from a tropical depression to a Category 1 (Cat 1) hurricane. The water vapor gradually increases from Cat 2 to Cat 5 hurricanes—a result that is also identified in ECMWF data sets and Atmospheric Infrared Sounder observations. We conclude that GPSRO data can contribute significantly to the understanding and modeling of the vertical structures of TCs.

Vergados, Panagiotis; Mannucci, Anthony J.; Su, Hui

2013-08-01

303

The use of reflected GPS signals to retrieve ocean surface wind speeds in tropical cyclones  

NASA Astrophysics Data System (ADS)

the first intentional acquisition of GPS signals reflected from water bodies, one of the objectives which has driven the research is to determine whether the acquired signal can provide useful geophysical information about the reflecting surface. One obvious condition of considerable interest is ocean surface wind speed. Theory suggested that the reflection technique, a form of bistatic RADAR, would be sensitive to surface roughness which in turn is driven by wind speed. This paper reports the results derived from data acquired over the past decade of applying the GPS reflection technique to ocean surface winds, particularly ocean surface winds in tropical cyclones. Examples of wind speed retrievals will be given for some illustrative cases of hurricanes and tropical storms. The results from several hurricanes and tropical storms on how the signal was calibrated will be presented. In addition, a quantitative comparison will be given between dropsondes deployed by NOAA during the storms and GPS reflection derived wind speeds taken at the same time. Conditions in which the GPS technique offers excellent comparisons as well as examples where the comparison is not so good will be presented. Suggestions will be given as to when the GPS technique can be used with confidence and when it is likely to be at variance with other methods.

Katzberg, Stephen J.; Dunion, Jason; Ganoe, George G.

2013-07-01

304

A weather analysis system for the Baja California peninsula: tropical cyclone season of 2007  

NASA Astrophysics Data System (ADS)

General characteristics of tropical weather systems were documented on a real-time basis. The geographical area of interest is the Baja California peninsula, located in northwestern Mexico. This study covers the warm season of 2007, from May through October, and includes observations derived from radar and satellite imagery as well as reports from a network of rain gauges. A set of graphical products were generated and they were available to the public through the internet. The analysis system has been in operation since the summer of 2005 and it is focused to document the development of tropical cyclones in eastern Pacific Ocean. During the season of 2007, this basin had a total of 11 tropical storms and four of them were within 800 km from the west coast of Mexico (Dalila, Ivo, Juliette and Kiko). Only one system made landfall in the area of interest: Hurricane Henriette which moved across Baja California, the Gulf of California and a portion of the state of Sonora. This presentation provides an overview of the graphical products along with lessons learned from the season studied, collaborations with local emergency managers and plans for the upcoming season of 2008.

Farfan, L. M.; Cosio, M. A.

2008-05-01

305

Analog ensemble forecasts of tropical cyclone tracks in the australian region  

NASA Astrophysics Data System (ADS)

A self-adapting analog forecast scheme has been developed for ensemble predictions of tropical cyclones tracks in the Australian region. Starting with the Euclidean metric and a given set of states defined by best track data, the model learns how to weight components of the predictor states by minimising forecast error. These weights, which result from the metric adaption, are an indication of the importance of corresponding components. They show that displacements and season are more important for analog search than cyclone positions. When comparing different analog models, it is shown that both ensemble forecasting and metric adaption lead to substantial forecast improvements. Comparison of the self-adapting analog ensemble forecasts with an Australian region CLIPER (CLImate PERsistence) reference shows different results for each of three regions of the Australian basin with positive (negative) skill in the eastern and western (northern) domain. Further comparison with NWP model forecasts of the British Meteorological Office and the official forecasts of the Australian Bureau of Meteorology demonstrates the good performance of the analog ensemble scheme in the average. Mean (and median) forecast errors in spread classes grow linearly with increasing ensemble spread. As this relation deteriorates with increasing lead time, it may qualify as a performance measure of ensemble predictions. Actual analog ensemble forecasts are provided via Internet (http://visibility.dkrz.de/TC).

Raible, C. C.; Fraedrich, K.; Sielmann, F.

2003-04-01

306

Influence of the Western Pacific teleconnection pattern on Western North Pacific tropical cyclone activity  

NASA Astrophysics Data System (ADS)

This study analyzes the characteristics of Western North Pacific (WNP) tropical cyclone (TC) activity and large-scale environments according to the Western Pacific (WP) teleconnection pattern in summer. In the positive WP phase, an anomalous cyclone and an anomalous anticyclone develop in the low and middle latitudes of the East Asia area, respectively. As a result, southeasterlies are reinforced in the northeast area of East Asia (including Korea and Japan), which facilitates the movement of TC to this area, whereas northwesterlies are reinforced in the southwest area of East Asia (including southern China and the Indochina Peninsula) which blocks the movement of TC to that area. Due to the spatial distribution of this reinforced pressure system, TCs that develop during the positive WP phase move and turn more to the northeast of the WNP than TCs which develop during the negative WP phase. The characteristics of this TC activity during the positive WP phase are associated with the upper tropospheric jet being located farther to the northeast. TCs during the negative WP phase mainly move to the west from the Philippines toward southern China and the Indochina Peninsula. Due to the terrain effect caused by the passage of TCs in mainland China, the intensity of TCs during the negative WP phase is weaker than those during the positive WP phase.

Choi, Ki-Seon; Moon, Il-Ju

2012-09-01

307

Predictability and prediction of tropical cyclones on daily to interannual time scales  

NASA Astrophysics Data System (ADS)

The spatial and temporal complexity of tropical cyclones (TCs) raises a number of scientific questions regarding their genesis, movement, intensification, and variability. In this dissertation, the principal goal is to determine the current state of predictability for each of these processes using global numerical prediction systems. The predictability findings are then used in conjunction with several new statistical calibration techniques to develop a proof-of-concept, operational forecast system for North Atlantic TCs on daily to intraseasonal time scales. To quantify the current extent of tropical cyclone predictability, we assess probabilistic forecasts from the most advanced global numerical weather prediction system to date, the ECMWF Variable Resolution Ensemble Prediction System (VarEPS; Hamill et al. 2008, Hagedorn et al. 2012). Using a new false alarm clustering technique to maximize the utility of the VarEPS, the ensemble system is shown to provide well-calibrated probabilistic forecasts for TC genesis through a lead-time of one week and pregenesis track forecasts with similar skill compared to the VarEPS's postgenesis track forecasts. These findings provide evidence that skillful real-time TC genesis predictions may be made in the North Indian Ocean—a region that even today has limited forecast warning windows for TCs relative to other ocean basins. To quantify the predictability of TCs on intraseasonal time scales, forecasts from the ECMWF Monthly Forecast System (ECMFS) are examined for the North Atlantic Ocean. From this assessment, dynamically based forecasts from the ECMFS provide forecast skill exceeding climatology out to weeks three and four for portions of the southern Gulf of Mexico, western Caribbean and the Main Development Region. Forecast skill in these regions is traced to the model's ability to capture correctly the variability in deep-layer vertical wind shear as well as the relative frequency of easterly waves moving through these regions. Following the TC predictability studies, a proof-of-concept operational forecast system for North Atlantic TCs is presented for daily to intraseasonal time scales. Findings from the predictability studies are used in conjunction with recently developed forecast calibration techniques to render the VarEPS and ECMFS forecasts more useful in an operational setting. The proposed combination of bias-calibrated regional probabilistic forecast guidance along with objectively-defined measures of confidence is a new way of providing TC forecasts on intraseasonal time scales. On interannual time scales, the predictability of TCs is examined by considering their relationship with tropical Atlantic easterly waves. First, a set of easterly wave climatologies for the Climate Forecast System-Reanalysis, ERA-Interim, ERA-40, and NCEP/NCAR Reanalysis are developed using a new easterly wave tracking algorithm based on 700 hPa curvature relative vorticity anomalies. From the reanalysis-derived easterly wave climatologies, a moderately positive and statistically significant relationship is seen with tropical Atlantic TCs, suggesting that approximately 20-30% of the total variance in the number of TCs on interannual time scales may be explained by the frequency of easterly waves. In relation to large-scale climate modes, the Atlantic Multidecadal Oscillation (AMO) and Atlantic Meridional Mode (AMM) exhibit the strongest positive covariability with Atlantic easterly wave frequency. Besides changes in the number of easterly waves, the intensification efficiency of easterly waves, which is the percentage of waves that induce North Atlantic TC formation, has also been evaluated. These findings offer a plausible physical explanation for the recent increase in the number of NATL TCs, as it has been concomitant with an increasing trend in both the number of tropical Atlantic easterly waves and intensification efficiency. In addition, the easterly wave-tropical cyclone pathway is likely an important mechanism governing how the AMO and AMM modulate North Atlantic TC frequency—more

Belanger, James Ian

308

Variability in tornado frequency associated with U.S. landfalling tropical cyclones  

NASA Astrophysics Data System (ADS)

A statistical model for tornado frequency from Gulf of Mexico landfalling tropical cyclones (TCs) is developed using TC size, intensity, recurvature, and mid-level specific humidity data. New datasets are assembled for tornado frequency and for TC size at landfall as measured by the radius of outer closed isobar and distance of tornado from the TC center. Owing to systematic undercounting of tornadoes, the model is used to reconstruct the TC tornado climatology back to 1948, and further back to 1920 using a modified model that does not include mid-level specific humidity. Relative to the previous active period for Gulf TC landfalls of 1948-1964, the active period since 1995 has seen a statistically significant increase (95% level) in median TC tornadoes and in the frequency of large TC tornado outbreaks. These changes are linked to an increase in the median size and frequency of large Gulf landfalling TCs.

Belanger, James I.; Curry, Judith A.; Hoyos, Carlos D.

2009-09-01

309

Tropical cyclone kinetic energy and structure evolution in the HWRFx model  

NASA Astrophysics Data System (ADS)

Tropical cyclones exhibit significant variability in their structure, especially in terms of size and asymmetric structures. The variations can influence subsequent evolution in the storm as well as its environmental impacts and play an important role in forecasting. This study uses the Hurricane Weather Research and Forecasting Experimental System (HWRFx) to investigate the horizontal and vertical structure of tropical cyclones. Five real data HWRFx model simulations from the 2005 Atlantic tropical cyclone season (two of Hurricanes Emily and Wilma, and one of Hurricane Katrina) are used. Horizontal structure is investigated via several methods: the decomposition of the integrated kinetic energy field into wavenumber space, composite analysis of the wind fields, and azimuthal wavenumber decomposition of the tangential wind field. Additionally, a spatial and temporal decomposition of the vorticity field to study the vortex Rossby wave contribution to storm asymmetries with an emphasis on azimuthal wavenumber-2 features is completed. Spectral decomposition shows that the average low level kinetic energy in azimuthal wavenumbers 0, 1 and 2 are 92%, 6%, and 1.5% of the total kinetic energy. The kinetic energy in higher wavenumbers is much smaller. Analysis also shows that the low level kinetic energy wavenumber 1 and 2 components can vary between 0.3--36.3% and 0.1--14.1% of the total kinetic energy, respectively. The asymmetries associated with storm motion, environmental shear, and the relative orientation of these vectors are examined. A composite analysis shows a dominant wavenumber-1 asymmetry associated with the storm motion and shear vectors. For storm motion the asymmetry is located in the right front quadrant relative to the motion vector with a magnitude exceeding 2.5 m/s, and for shear the asymmetry is located 90° left of the shear vector with a magnitude exceeding 5 m/s. The locations of these wavenumber-1 asymmetries are consistent with the findings of previous studies. Further composite analysis of the asymmetries associated with the relative orientation of the storm motion and shear vectors reveals that when the vectors are aligned versus opposed the wavenumber-1 asymmetries have roughly equivalent magnitude but very different azimuthal location (when aligned the maximum is located in the left front quadrant relative to the storm motion, and when opposed is located nearly 90° to the right of the storm motion). The magnitude of the wavenumber-2 asymmetries is much larger when the storm motion and shear vectors are aligned (exceeding 2.5 m/s) than when they are opposed (˜0.5 m/s). The results indicate that shear induced asymmetries extend more deeply through the troposphere than storm motion induced asymmetries. Furthermore, the vortex Rossby wave analysis provides compelling evidence to support their existence and their contribution to the wavenumber-2 asymmetries in the simulated storms. The vertical structure is studied in terms of the relationship between the size of the radius of maximum wind and its slope, and whether the radius of maximum wind is well approximated by a constant absolute angular momentum surface. The impacts of environmental shear on these relationships are specifically examined. While there is some evidence to suggest that moderate shear can have a constructive influence on the storm, the relationships between the radius of maximum wind and its slope, and the slopes of the radius of maximum wind and the constant absolute angular momentum surface deteriorate quickly with increasing shear. The vertical warm core structure of the tropical cyclones is investigated in terms of the height and magnitude of the primary and any possible secondary warm core features (as measured in terms of the temperature anomalies). The purpose of this analysis is to determine the general warm core structure and establish if there are any significant trends with respect to storm evolution, environmental shear, or storm intensity change. It is determined that there is often a dual warm core structure with a pri

Maclay, Katherine S.

310

Comparison and further development of parametric tropical cyclone models for storm surge modelling  

Microsoft Academic Search

Cyclone forced storm surges cause severe damage to coastal structures and loss of human lives and properties. In cyclone protection and warning it is important to be able to calculate the cyclone air pressure and wind field on the basis of rather limited information, such as cyclone position, pressure drop, maximum wind speed and radius to maximum wind speed. In

Flemming Jakobsen; Henrik Madsen

2004-01-01

311

Environmental modeling, technology, and communication for land falling tropical cyclone/hurricane prediction.  

PubMed

Katrina (a tropical cyclone/hurricane) began to strengthen reaching a Category 5 storm on 28th August, 2005 and its winds reached peak intensity of 175 mph and pressure levels as low as 902 mb. Katrina eventually weakened to a category 3 storm and made a landfall in Plaquemines Parish, Louisiana, Gulf of Mexico, south of Buras on 29th August 2005. We investigate the time series intensity change of the hurricane Katrina using environmental modeling and technology tools to develop an early and advanced warning and prediction system. Environmental Mesoscale Model (Weather Research Forecast, WRF) simulations are used for prediction of intensity change and track of the hurricane Katrina. The model is run on a doubly nested domain centered over the central Gulf of Mexico, with grid spacing of 90 km and 30 km for 6 h periods, from August 28th to August 30th. The model results are in good agreement with the observations suggesting that the model is capable of simulating the surface features, intensity change and track and precipitation associated with hurricane Katrina. We computed the maximum vertical velocities (W(max)) using Convective Available Kinetic Energy (CAPE) obtained at the equilibrium level (EL), from atmospheric soundings over the Gulf Coast stations during the hurricane land falling for the period August 21-30, 2005. The large vertical atmospheric motions associated with the land falling hurricane Katrina produced severe weather including thunderstorms and tornadoes 2-3 days before landfall. The environmental modeling simulations in combination with sounding data show that the tools may be used as an advanced prediction and communication system (APCS) for land falling tropical cyclones/hurricanes. PMID:20623002

Tuluri, Francis; Reddy, R Suseela; Anjaneyulu, Y; Colonias, John; Tchounwou, Paul

2010-04-28

312

Environmental Modeling, Technology, and Communication for Land Falling Tropical Cyclone/Hurricane Prediction  

PubMed Central

Katrina (a tropical cyclone/hurricane) began to strengthen reaching a Category 5 storm on 28th August, 2005 and its winds reached peak intensity of 175 mph and pressure levels as low as 902 mb. Katrina eventually weakened to a category 3 storm and made a landfall in Plaquemines Parish, Louisiana, Gulf of Mexico, south of Buras on 29th August 2005. We investigate the time series intensity change of the hurricane Katrina using environmental modeling and technology tools to develop an early and advanced warning and prediction system. Environmental Mesoscale Model (Weather Research Forecast, WRF) simulations are used for prediction of intensity change and track of the hurricane Katrina. The model is run on a doubly nested domain centered over the central Gulf of Mexico, with grid spacing of 90 km and 30 km for 6 h periods, from August 28th to August 30th. The model results are in good agreement with the observations suggesting that the model is capable of simulating the surface features, intensity change and track and precipitation associated with hurricane Katrina. We computed the maximum vertical velocities (Wmax) using Convective Available Kinetic Energy (CAPE) obtained at the equilibrium level (EL), from atmospheric soundings over the Gulf Coast stations during the hurricane land falling for the period August 21–30, 2005. The large vertical atmospheric motions associated with the land falling hurricane Katrina produced severe weather including thunderstorms and tornadoes 2–3 days before landfall. The environmental modeling simulations in combination with sounding data show that the tools may be used as an advanced prediction and communication system (APCS) for land falling tropical cyclones/hurricanes.

Tuluri, Francis; Reddy, R. Suseela; Anjaneyulu, Y.; Colonias, John; Tchounwou, Paul

2010-01-01

313

The role of ?-effect and a uniform current on tropical cyclone intensity  

NASA Astrophysics Data System (ADS)

A limited-area primitive equation model is used to study the role of the ?-effect and a uniform current on tropical cyclone (TC) intensity. It is found that TC intensity is reduced in a non-quiescent environment compared with the case of no uniform current. On an f-plane, the rate of intensification of a tropical cyclone is larger than that of the uniform flow. A TC on a ?-plane intensifies slower than one on an f-plane. The main physical characteristic that distinguishes the experiments is the asymmetric thermodynamic (including convective) and dynamic structures present when either a uniform flow or ?-effect is introduced. But a fairly symmetric TC structure is simulated on an f-plane. The magnitude of the warm core and the associated subsidence are found to be responsible for such simulated intensity changes. On an f-plane, the convection tends to be symmetric, which results in strong upper-level convergence near the center and hence strong forced subsidence and a very warm core. On the other hand, horizontal advection of temperature cancels part of the adiabatic heating and results in less warming of the core, and hence the TC is not as intense. This advective process is due to the tilt of the vortex as a result of the ?-effect. A similar situation occurs in the presence of a uniform flow. Thus, the asymmetric horizontal advection of temperature plays an important role in the temperature distribution. Dynamically, the asymmetric angular momentum (AM) flux is very small on an f-plane throughout the troposphere. However, the total AM exports at the upper levels for a TC either on a ?-plane or with a uniform flow environment are larger because of an increase of the asymmetric as well as symmetric AM export on the plane at radii >450 km, and hence there is a lesser intensification.

Duan, Yihong; Wu, Rongsheng; Yu, Hui; Liang, Xudong; Chan, Johnny C. L.

2004-02-01

314

Development of a geovisual analytics environment using parallel coordinates with applications to tropical cyclone trend analysis  

NASA Astrophysics Data System (ADS)

A global transformation is being fueled by unprecedented growth in the quality, quantity, and number of different parameters in environmental data through the convergence of several technological advances in data collection and modeling. Although these data hold great potential for helping us understand many complex and, in some cases, life-threatening environmental processes, our ability to generate such data is far outpacing our ability to analyze it. In particular, conventional environmental data analysis tools are inadequate for coping with the size and complexity of these data. As a result, users are forced to reduce the problem in order to adapt to the capabilities of the tools. To overcome these limitations, we must complement the power of computational methods with human knowledge, flexible thinking, imagination, and our capacity for insight by developing visual analysis tools that distill information into the actionable criteria needed for enhanced decision support. In light of said challenges, we have integrated automated statistical analysis capabilities with a highly interactive, multivariate visualization interface to produce a promising approach for visual environmental data analysis. By combining advanced interaction techniques such as dynamic axis scaling, conjunctive parallel coordinates, statistical indicators, and aerial perspective shading, we provide an enhanced variant of the classical parallel coordinates plot. Furthermore, the system facilitates statistical processes such as stepwise linear regression and correlation analysis to assist in the identification and quantification of the most significant predictors for a particular dependent variable. These capabilities are combined into a unique geovisual analytics system that is demonstrated via a pedagogical case study and three North Atlantic tropical cyclone climate studies using a systematic workflow. In addition to revealing several significant associations between environmental observations and tropical cyclone activity, this research corroborates the notion that enhanced parallel coordinates coupled with statistical analysis can be used for more effective knowledge discovery and confirmation in complex, real-world data sets.

Steed, Chad Allen

315

MID-LATITUDE CYCLONES WITH TROPICAL ORIGINS: lessons from two historical case studies.  

NASA Astrophysics Data System (ADS)

Interest in storm and hurricane activity has grown over recent years, their changing incidence being seen, rightly or wrongly, as a gauge of ‘global warming'. Yet such judgements can be confidently offered only on the basis of a reliable long period of record that provides more informative perspective on the events of the past few decades. This presentation is concerned with two examples of hurricane activity, both of which make valuable use of historical source material but provide different lessons for climatologists. The first example is from 1680 and demonstrates the value of historical source material in reconstructing events from the distant past and suggests a way forward in developing and improving the long-term storm chronologies. The other, based on the analogous events of 1842 and 2005, offers a convincing demonstration of the need to call upon such comprehensive long-term chronologies in order to avoid making mistaken and unintentionally ill-informed observations on the seeming idiosyncrasies of recent climatic variation. The first example, from August 1680, reconstructs the trajectory and development of an Atlantic tropical cyclone, and draws upon a notable variety of documentary sources ranging from ships' logbooks, official and unofficial correspondence and some early examples of instrumental data. It serves as a model of how such sources, which remain largely unexploited, can be called upon to provide important climatic information. It allows also for the reconstruction the tropical and extratropical phases of the cyclone's trajectory and its possible impact over the UK. The second example, which compares hurricane Vince (2005) with an earlier but overlooked analogue from 1842, demonstrates the caution with which recent events should be interpreted and the need to take as long-term view as possible. Hurricane Vince, which moved directly from the eastern Atlantic towards Iberia, was widely proclaimed as a unique event and a consequence of global warming. Yet a careful search of the historical record provided an almost perfect analogue from 1842 and in doing so offered a salutary warning of our need for caution and for a clearer picture of the past. This presentation reviews both examples and discusses their implications in terms of the possibility of improving the cyclone chronology and, thereby, of assisting in our understanding of present-day events. References Vaquero J.M., R. García-Herrera, D. Wheeler, M. Chenoweth and C. J. Mock, 2008: An historical analogue of 2005 hurricane Vince. Bulletin of the American Meteorological Society, 89, 191 - 201. WheelerD., R. García-Herrera, J.M.Vaquero, M. Chenoweth and C. J. Mock, 2009: Reconstructing the trajectory of the August 1680 Hurricane from contemporary records Bulletin of the American Meteorological Society,(accepted).

García-Herrera, R.; Vaquero, J. M.; Wheeler, D.

2009-04-01

316

Tropical Cyclone Activity and Climate Fluctuations Captured by Oxygen Isotopes in Tree-Ring Cellulose From the Southeastern US  

NASA Astrophysics Data System (ADS)

Tropical cyclone activity in the Atlantic Ocean and Gulf of Mexico fluctuates on seasonal to century scales. Large climate oscillations, such as the El Nino Southern Oscillation, Atlantic Multidecadal Oscillation, and the Pacific Decadal Oscillation may affect this tropical cyclone activity. To better discern and understand factors influencing long-term trends in hurricane occurrence, proxies are needed that extend the record beyond historical documents. Tree rings preserve excellent records of climate that can be tracked on an intra-annual scale. Two trees in southern Georgia, slash and longleaf pine, were collected and dated using dendrochronological techniques and a 156- year record (1840-1997) was examined. The tree rings were processed to alpha cellulose, with intra-annual resolution, for examination of oxygen isotopes from both earlywood (EW) and latewood (LW) growing seasons. In the southeastern U.S., temperature variation across the growing season for slash and longleaf pines is modest (27-33° C) and oxygen isotope compositions largely reflect the composition of precipitation. Tropical cyclones produce precipitation that is significantly depleted in 18O compared to average seasonal rainfall and generally occur during the LW growing season. The relatively depleted oxygen isotope ratios are incorporated into LW cellulose and thus the annual ring set is marked by a large difference between EW and LW ? 18O values. For years without a significant event, EW-LW differences are expected to be nominal. The 156-year long tree-ring oxygen isotope record of major hurricane occurrence corresponds well with known tropical cyclone occurrence in the study area. The record also captures evidence of EW drought. The tropical cyclone record appears to be overprinted upon a much larger climate oscillation that is characterized by periods of relative separation (i.e., apart from the larger differences due to hurricanes) vs. coincidence of the EW/LW oxygen isotope compositions. The frequency of tropical cyclones appears to be much greater during the EW/LW separation phase of this larger climate oscillation, in particular the decades of 1840 to mid-1920's and mid-1940 to mid-1970's.

Miller, D. L.; Mora, C. I.; Grissino-Mayer, H. D.; Mock, C. J.; Uhle, M. E.

2003-12-01

317

The JPL Tropical Cyclone Information System: Data and Tools for Researchers  

NASA Astrophysics Data System (ADS)

The JPL Tropical Cyclone Information System (TCIS) is now open to the public. This web portal is designed to assist researchers by providing a one-stop shop for hurricane related data and analysis tools. While there are currently many places that offer storm data, plots, and other information, none offer an extensive archive of data files and images in a common space. The JPL TCIS was created to fill this gap. As currently configured, the JPL Tropical Cyclone Portal has three main features for researchers. The first feature consists of storm-scale data and plots for both observed and modeled data. As of the TCIS' first release, the entire 2005 storm season has been populated with data and plots from AIRS, MLS, AMSU-A, QuikSCAT, Argo floats, WRF models, GPS, and others. Storm data is subsetted to a 1000x1000 km window around the hurricane track for all six oceanic cyclone basins, and all the available data during the life time of any storm can be downloaded with one mouse click. Users can also view pre-generated storm-scale plots from all these data sets that are all co-located to the same temporal and spatial parameters. Work is currently underway to backfill all storm seasons to 1998 with as many relevant data sets as possible. The second offering from this web portal are large-scale data sets and associated visualization tools powered by Google Maps. On this interactive map, researchers can view a particular storm's intensity and track. Users may also overlay large-scale data such as aerosol maps from MODIS and MISR, and a blended microwave sea-surface temperature (SST) to gain an understanding of the large-scale environment of the storm. For example, by using this map, the cold sea-surface temperature wake can be tracked as a storm passes by. The third feature of this portal deals with interactive model and data analysis. A single-parameter analysis tools has recently been developed and added to this portal where users can plot maps, profiles, and histograms of any given data set on this portal and also get several statistics, such as the mean, standard deviation, and median of the data they are viewing. Also available is the ability to compare and condition data sets with each other. For example, users can choose to view sea surface temperature when wind speed is X m/s. Additional data sets continue to be added to this tool and it will eventually expand to include multi- parameter analyses. In this presentation, we will describe the current configuration of the JPL Tropical Cyclone Portal and demonstrate how it will be an asset to researchers. Future plans for the site will also be discussed.

Knosp, B. W.; Ao, C. O.; Chao, Y.; Dang, V.; Garay, M.; Haddad, Z.; Hristova-Veleva, S.; Lambrigtsen, B.; Li, P. P.; Park, K.; Poulsen, W. L.; Rosenman, M. A.; Su, H.; Vane, D.; Vu, Q. A.; Willis, J. K.; Wu, D.

2008-12-01

318

A multitree perspective of the tree ring tropical cyclone record from longleaf pine (Pinus palustris Mill.), Big Thicket National Preserve, Texas, United States  

NASA Astrophysics Data System (ADS)

Tree rings afford the temporal resolution needed to characterize extreme weather events such as tropical cyclones, their frequency and variability. External factors such as soil water isotopic variability, soil heterogeneity, and/or stand disturbance affect the isotopic composition of individual trees in a stand, resulting in inaccuracies in the record. Single-tree isotope chronologies should be tested against multiple-tree chronologies to determine whether individual trees sufficiently characterize tropical cyclone variability. Eight individual trees from two sites in Big Thicket National Preserve were analyzed to evaluate whether they synchronously record tropical cyclone events. The ability of individual isotope models to capture an event was low (?50%), and individual trees did not always record similar events. A composite chronology from the Turkey Creek Unit identified 5 false positive years and missed five storms. The composite chronology from the Big Sandy Creek Unit identified 5 false positives and missed four storms. All but 3 false positive years were characterized by above average precipitation that followed below average precipitation in the previous year. This mimics the negative isotopic excursion expected from tropical cyclones. Another year (1991) was coincident with a strong El Niño event, resulting in a shift in the dominant moisture source for the Texas Gulf Coast. Drought conditions occurred in years where storms were missed, which dampened the 18O-depleted signal associated with tropical cyclones. These data show that the number of trees is critical for properly characterizing tropical cyclone frequency through time, especially for periods prior to reliable instrumental records.

Lewis, Daniel B.; Finkelstein, David B.; Grissino-Mayer, Henri D.; Mora, Claudia I.; Perfect, Edmund

2011-06-01

319

Tropical cyclone and extreme rainfall trends in East Asian summer monsoon since mid-20th century  

NASA Astrophysics Data System (ADS)

Proper interpretations of extreme rainfall trends in the Asian monsoon regions are complicated by tropical cyclones (TCs) from tropical oceans, whose rainfall trend may be different from the local monsoon (non-TC) rain. Here we show that the trends over the China summer monsoon region have been distorted by western North Pacific typhoons, which bring rainfall with decreasing frequency and increasing intensity. Typically the latter is not sufficient to overcome the former, so TC-related extreme rainfall trend is smaller than monsoon-related extreme rainfall. The net impact underestimates the increasing trend and overestimates the decreasing trend in monsoon extreme rainfall over most areas. The effect is minimal in the Meiyu rain belt region, but reaches 30% in northeastern and southern China. The largest distortions occur on offshore islands in the main TC paths that underwent significant decadal variations. In Hainan, the -3%/decade trend becomes +7%/decade if typhoon rainfall is removed. An opposite case occurs in Taiwan, where the extreme rainfall trend is hugely inflated by local increases in TC rainfall. These opposite effects emphasize the importance of considering the different mechanisms of rainfall systems in order to avoid mis-attribution of regional effects on extreme rainfall to thermodynamic consequences of global warming.

Chang, Chih-Pei; Lei, Yonghui; Sui, Chung-Hisung; Lin, Xiaohong; Ren, Fumin

2012-09-01

320

Does the Asian monsoon modulate tropical cyclone activity over the South China Sea?  

NASA Astrophysics Data System (ADS)

To investigate whether the Asian monsoon influences tropical cyclone (TC) activity over the South China Sea (SCS), TCs (including tropical storms and typhoons) over the SCS are analyzed using the Joint Typhoon Warning Center dataset from 1945 to 2009. Results show an increasing trend in the frequencies of TC-all (all TCs over the SCS) and TY-all (all typhoons over the SCS), due mainly to an increase in the number of TCs moving into the SCS after development elsewhere. Little change is seen in the number of TCs that form in the SCS. The results of wavelet analysis indicate that the frequency of typhoons (TY) shows a similar oscillation as that of TCs, i.e., a dominant periodicity of 8-16 years around the 1970s for all TC activity, except for TC-mov (TCs that moved into the SCS from the western North Pacific). To examine the relationship between typhoon activity and the summer monsoon, a correlation analysis was performed that considered typhoons, TCs, and five monsoon indexes. The analysis reveals statistically significant negative correlation between the strength of the Southwest Asian summer monsoon and typhoon activity over the SCS, which likely reflects the effect of the monsoon on TC formation in the western North Pacific (WNP) and subsequent movement into the SCS. There is a statistically significant negative correlation between TY-loc (typhoons that developed from TCs formed over the SCS) and the South China Sea summer monsoon and Southeast Asian summer monsoon.

Huang, Qian; Guan, Yuping

2012-11-01

321

Climate impacts of intermittent upper ocean mixing induced by tropical cyclones  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TC) represent a powerful, albeit highly transient forcing able to redistribute ocean heat content locally. Recent studies suggest that TC-induced ocean mixing can have global climate impacts as well, including changes in poleward heat transport, ocean circulation, and thermal structure. In several previous modeling studies devoted to this problem, the TC mixing was treated as a permanent (constant in time) source of additional vertical diffusion in the upper ocean. In contrast, this study aims to explore the highly intermittent character of the mixing. We present results from a series of coupled climate experiments with different durations of the imposed intermittent mixing but where each has the same annual mean diffusivity. All simulations show robust changes in sea surface temperature and ocean subsurface temperature, independent of the duration of the mixing that varies between the experiments from a few days to a full year. Simulated temperature anomalies are characterized by a cooling in the subtropics, a moderate warming in middle to high latitudes, a pronounced warming of the equatorial cold tongue, and a deepening of the tropical thermocline. These effects are paralleled by substantial changes in ocean and atmosphere circulation and heat transports. While the general patterns of changes remain the same from one experiment to the next, their magnitude depends on the relative duration of the mixing. Stronger mixing, but of a shorter duration, has less of an impact. These results agree with a simple model of heat transfer for the upper ocean with a time-dependent vertical diffusivity.

Manucharyan, G. E.; Brierley, C. M.; Fedorov, A. V.

2011-11-01

322

Quantifying the contribution of tropical cyclones to extreme rainfall along the coastal southeastern United States  

NASA Astrophysics Data System (ADS)

Analysis of a unique satellite precipitation dataset coupled with an extensive database of storm tracks are used to develop a parameter called the ``millimeter-day (MD).'' MD analysis in 4 mini-basins near coastal southeastern United States reveals that September and October account for the largest number of extreme rainfall days (e.g. ``wet millimeter-days'' or MD > 0) during the 1998-2006 Atlantic hurricane seasons. Tropical cyclone (TC) days are more likely to produce ``wet millimeter days'' than non-TC days, and category 3-5 hurricane days (e.g., major hurricanes) produce the wet millimeter-days of largest magnitude. Major hurricanes produce the most extreme rainfall days, but tropical depression/storm days contribute most significantly to cumulative seasonal rainfall (8-17%, basin-dependent) due to frequency of occurrence. Thus, the influence of major hurricanes on rainfall may be most apparent in extreme daily events while weaker storms may be more critical for assessing trends in cumulative seasonal rainfall.

Shepherd, J. Marshall; Grundstein, Andrew; Mote, Thomas L.

2007-12-01

323

Concepts on tracking the impact of tropical cyclones through the coastal zone  

NASA Astrophysics Data System (ADS)

WAVEWATCH III™ (Tolman, 2009) models the evolution of wind wave spectra under influence of wind, breaking, nonlinear interactions, bottom interaction (including shoaling and refraction), currents, water level changes and ice concentrations. The NOAA/NCEP data system offers global estimates every 3 hr at 1° x 1.25° for wind speed and direction at 10m asl, wave direction, height, and period. These and other derived parameters are useful in characterizing wave conditions as tropical cyclones approach landfall. The Tropical Rainfall Measuring Mission or TRMM based precipitation estimates a global 0.25° x 0.25° grid between 50° N-S produced within ?7 hours of observation time. Estimates are derived from the Passive Microwave Radiometer, Precipitation Radar, and Visible-Infrared Scanner), plus data from: i) SSM/I ii) low-orbit GOES IR and TIROS Operational Vertical Sounder, iii) AMSR-E, iv) AMSU-B, and v) rain gauge data run through algorithm 3B-43. Data are served by the Goddard Distributed Active Archive Center. Evapotranspiration estimates are from the MODIS ET (MOD16) algorithm developed by Mu et al. (2007), based on the Penman-Monteith equation, modified with satellite information that uses: (1) vapor pressure deficit and minimum air temperature constraints on stomatal conductance; (2) leaf area index as a scalar for estimating canopy conductance; (3) the Enhanced Vegetation Index; and (4) a calculation of soil evaporation. TopoFlow is a spatially distributed hydrologic model able to ingest the TRMM and EV data through a suite of hydrologic processes (e.g. snowmelt, precipitation, evapotranspiration, infiltration, channel and overland flow, shallow subsurface flow, and flow diversions) to evolve in time in response to climatic forcings. Modeled or gauged discharge can then be coupled to sediment flux models to provide factor of 2 estimates of sediment flux (Syvitski et al. 2007, Kettner et al. 2008, Syvitski and Milliman 2007). The MODIS satellite constellation can track storm fronts and tropical cyclones and sense sediment discharged, resuspension of shoreline sediment, and be used to observe the dimensions and dynamics of delta flooding and delta-plain aggradation (Syvitski et al. 2009). An integrated workflow involving these models and data system will be presented outlining their use in characterizing sediment flux within the coastal zone.

Syvitski, J. P.; Hannon, M. T.; Kettner, A. J.; Bachman, S.

2009-12-01

324

The Role of “Vortical” Hot Towers in the Formation of Tropical Cyclone Diana (1984).  

NASA Astrophysics Data System (ADS)

A high-resolution (3-km horizontal grid spacing) near-cloud-resolving numerical simulation of the formation of Hurricane Diana (1984) is used to examine the contribution of deep convective processes to tropical cyclone formation. This study is focused on the 3-km horizontal grid spacing simulation because this simulation was previously found to furnish an accurate forecast of the later stages of the observed storm life cycle. The numerical simulation reveals the presence of vortical hot towers, or cores of deep cumulonimbus convection possessing strong vertical vorticity, that arise from buoyancy-induced stretching of local absolute vertical vorticity in a vorticity-rich prehurricane environment.At near-cloud-resolving scales, these vortical hot towers are the preferred mode of convection. They are demonstrated to be the most important influence to the formation of the tropical storm via a two-stage evolutionary process: (i) preconditioning of the local environment via diabatic production of multiple small-scale lower-tropospheric cyclonic potential vorticity (PV) anomalies, and (ii) multiple mergers and axisymmetrization of these low-level PV anomalies. The local warm-core formation and tangential momentum spinup are shown to be dominated by the organizational process of the diabatically generated PV anomalies; the former process being accomplished by the strong vertical vorticity in the hot tower cores, which effectively traps the latent heat from moist convection. In addition to the organizational process of the PV anomalies, the cyclogenesis is enhanced by the aggregate diabatic heating associated with the vortical hot towers, which produces a net influx of low-level mean angular momentum throughout the genesis.Simpler models are examined to elucidate the underlying dynamics of tropical cyclogenesis in this case study. Using the Sawyer Eliassen balanced vortex model to diagnose the macroscale evolution, the cyclogenesis of Diana is demonstrated to proceed in approximate gradient and hydrostatic balance at many instances, where local radial and vertical accelerations are small. Using a shallow water primitive equation model, a characteristic “moist” (diabatic) vortex merger in the cloud-resolving numerical simulation is captured in a large part by the barotropic model. Since a moist merger results in a stronger vortex and occurs twice as fast as a dry merger, it is inferred (consistent with related work) that a net low-level convergence can accelerate and intensify the merger process in the real atmosphere.Although the findings reported herein are based on a sole case study and thus cannot yet be generalized, it is believed the results are sufficiently interesting to warrant further idealized simulations of this nature.


Hendricks, Eric A.; Montgomery, Michael T.; Davis, Christopher A.

2004-06-01

325

An assessment of uncertainties and limitations in simulating tropical cyclone climatology and future changes  

NASA Astrophysics Data System (ADS)

The recent elevated North Atlantic hurricane activity has generated considerable interests in the interaction between tropical cyclones (TCs) and climate change. The possible connection between TCs and the changing climate has been indicated by observational studies based on historical TC records; they indicate emerging trends in TC frequency and intensity in some TC basins, but the detection of trends has been hotly debated due to TC track data issues. Dynamical climate modeling has also been applied to the problem, but brings its own set of limitations owing to limited model resolution and uncertainties. The final goal of this study is to project the future changes of North Atlantic TC behavior with global warming for the next 50 years using the Nested Regional Climate Model (NRCM). Throughout the course of reaching this goal, various uncertainties and limitations in simulating TCs by the NRCM are identified and explored. First we examine the TC tracking algorithm to detect and track simulated TCs from model output. The criteria and thresholds used in the tracking algorithm control the simulated TC climatology, making it difficult to objectively assess the model's ability in simulating TC climatology. Existing tracking algorithms used by previous studies are surveyed and it is found that the criteria and thresholds are very diverse. Sensitivity of varying criteria and thresholds in TC tracking algorithm to simulated TC climatology is very high, especially with the intensity and duration thresholds. It is found that the commonly used criteria may not be strict enough to filter out intense extratropical systems and hybrid systems. We propose that a better distinction between TCs and other low-pressure systems can be achieved by adding the Cyclone Phase technique. Two sets of NRCM simulations are presented in this dissertation: One in the hindcasting mode, and the other with forcing from the Community Climate System Model (CCSM) to project into the future with global warming. Both of these simulations are assessed using the tracking algorithm with cyclone phase technique. The NRCM is run in a hindcasting mode for the global tropics in order to assess its ability to simulate the current observed TC climatology. It is found that the NRCM is capable of capturing the general spatial and temporal distributions of TCs, but tends to overproduce TCs particularly in the Northwest Pacific. The overprediction of TCs is associated with the overall convective tendency in the model added with an outstanding theory of wave energy accumulation leading to TC genesis. On the other hand, TC frequency in the tropical North Atlantic is under predicted due to the lack of moist African Easterly Waves. The importance of high-resolution is shown with the additional simulation with two-way nesting. The NRCM is then forced by the CCSM to project the future changes in North Atlantic TCs. An El Nino-like SST bias in the CCSM induced a high vertical wind shear in tropical North Atlantic, preventing TCs from forming in this region. A simple bias correction method is applied to remove this bias. The model projected an increase both in TC frequency and intensity owing to enhanced TC genesis in the main development region, where the model projects an increased favorability of large-scale environment for TC genesis. However, the model is not capable of explicitly simulating intense (Category 3--5) storms due to the limited model resolution. To extrapolate the prediction to intense storms, we propose a hybrid approach that combines the model results and a statistical modeling using extreme value theory. Specifically, the current observed TC intensity is statistically modeled with the General Pareto distribution, and the simulated intensity changes from the NRCM are applied to the statistical model to project the changes in intense storms. The results suggest that the occurrence of Category 5 storms may be increased by approximately 50% by 2055.

Suzuki-Parker, Asuka

326

Safe-economical route and its assessment model of a ship to avoid tropical cyclones using dynamic forecast environment  

NASA Astrophysics Data System (ADS)

In heavy sea conditions related to tropical cyclones (TCs), losses to shipping caused by capsizing are greater than other kinds of accidents. Therefore, it is important to consider capsizing risk in the algorithms used to generate safe-economic routes that avoid tropical cyclones (RATC). A safe-economic routing and assessment model for RATC, based on a dynamic forecasting environment, is presented in this paper. In the proposed model, a ship's risk is quantified using its capsizing probability caused by heavy wave conditions. Forecasting errors in the numerical models are considered according to their distribution characteristics. A case study shows that: the economic cost of RATCs is associated not only to the ship's speed and the acceptable risk level, but also to the ship's wind and wave resistance. Case study results demonstrate that the optimal routes obtained from the model proposed in this paper are significantly superior to those produced by traditional methods.

Wu, L. C.; Wen, Y. Q.; Wu, D. Y.

2013-05-01

327

AIRS impact on precipitation analysis and forecast of tropical cyclones in a global data assimilation and forecast system  

NASA Astrophysics Data System (ADS)

The impact of assimilating quality-controlled Atmospheric Infrared Sounder (AIRS) temperature retrievals obtained from partially cloudy regions is assessed, with focus on precipitation produced by the GEOS-5 data assimilation and forecasting system, for three tropical cyclones: Nargis (April 27 - May 03, 2008) in the Indian Ocean, Wilma (October 15-26, 2005) and Helene (September 12-16, 2006) in the Atlantic. It is found that the precipitation analysis obtained when assimilating AIRS cloudy retrievals (AIRS) can capture regions of heavy precipitation associated with tropical cyclones much better than without AIRS data (CONTRL) or when using AIRS clear-sky radiances (RAD). The precipitation along the storm track shows that the AIRS assimilation produces larger mean values and more intense rain rates than the CONTRL and RAD assimilations. The corresponding precipitation forecasts initialized from AIRS analysis show reasonable prediction skill and better performance than forecasts initialized from CONTRL and RAD analyses up to day-2.

Zhou, Y. P.; Lau, K.-M.; Reale, O.; Rosenberg, R.

2010-01-01

328

Tropical cyclones and polar lows: Velocity, size, and energy scales, and relation to the 26°C cyclone origin criteria  

NASA Astrophysics Data System (ADS)

The goal of this paper is to quantitatively formulate some necessary conditions for the development of intense atmospheric vortices. Specifically, these criteria are discussed for tropical cyclones (TC) and polar lows (PL) by using bulk formulas for fluxes of momentum, sensible heating, and latent heating between the ocean and the atmosphere. The velocity scale is used in two forms: (1) as expressed through the buoyancy flux b and the Coriolis parameter l c for rotating fluids convection, and (2) as expressed with the cube of velocity times the drag coefficient through the formula for total kinetic energy dissipation in the atmospheric boundary layer. In the quasistationary case the dissipation equals the generation of the energy. In both cases the velocity scale can be expressed through temperature and humidity differences between the ocean and the atmosphere in terms of the reduced gravity, and both forms produce quite comparable velocity scales. Using parameters b and l c , we can form scales of the area and, by adding the mass of a unit air column, a scale of the total kinetic energy as well. These scales nicely explain the much smaller size of a PL, as compared to a TC, and the total kinetic energy of a TC is of the order 1018 - 1019 J. It will be shown that wind of 33 m s-1 is produced when the total enthalpy fluxes between the ocean and the atmosphere are about 700 W m-2 for a TC and 1700 W m-2 for a PL, in association with the much larger role of the latent heat in the first case and the stricter geostrophic constraints and larger static stability in the second case. This replaces the mystical role of 26°C as a criterion for TC origin. The buoyancy flux, a product of the reduced gravity and the wind speed, together with the atmospheric static stability, determines the rate of the penetrating convection. It is known from the observations that the formation time for a PL reaching an altitude of 5-6 km can be only a few hours, and a day, or even half a day, for a TC reaching 15-18 km. These two facts allow us to construct curves on the plane of T s and ? T = T s - T a to determine possibilities for forming an intense vortex. Here, T a is the atmospheric temperature at the height z = 10 m. A PL should have ? T > 20°C in accordance with the observations and numerical simulations. The conditions for a TC are not so straightforward but our diagram shows that the temperature difference of a few degrees, or possibly even a fraction of a degree, might be sufficient for TC development for a range of static stabilities and development times.

Golitsyn, G. S.

2009-05-01

329

Statistical features of tropical cyclones affecting China and its key economic zones  

NASA Astrophysics Data System (ADS)

Recent trends and variability in tropical cyclone (TC) frequency and intensity are examined for TCs that affected China, with particular focus on those TCs that affected China's key economic zones (e.g., the Yangtze River Delta, the Pearl River Delta, and the Beijing-Tianjin area). The results show that the frequency of TCs affecting China weakly declined during the 1980s and 2000s, followed by a slight increase. The time series of TC frequency shows insignificant variations at periods of 2-6 yr during the past 60 years; these variations are significantly correlated with ENSO activity. The frequency of TCs affecting the Pearl River Delta area is strongly correlated with the ENSO cycle while the frequency of TCs affecting the Yangtze River Delta is not. The TC frequency varies differently for TCs of different intensities. Tropical storms (TSs) affecting China were small in total number, but have clearly increased in frequency. The frequencies of severe tropical storm (STS), typhoon (TY), severe typhoon (STY), and super typhoon (super TY) affecting China declined significantly during the 1970s and 1980s, but the numbers of STY and super TY have increased over the 2000s. The typical intensity of TCs affecting China declined over the 60-yr timeframe, but increased over the most recent 10 years (2000-2010). This increase in the intensity of TCs has particularly impacted the Yangtze River Delta area, which has experienced increased numbers of STYs and super TYs. These tendencies are observed in changes of the maximum intensity of TCs affecting both China in general and the Yangtze River Delta in particular during both the full 60-yr analysis period and the latest 10-yr period; however, these tendencies are not observed in changes of the average intensity of TCs. By contrast, both the extreme intensity and the average intensity of TCs affecting the Pearl River Delta have decreased throughout the analysis period, including the most recent decade.

Chao, Qingchen; Chao, Jiping

2012-12-01

330

November 2009 tropical cyclone Phyan in the eastern Arabian Sea: Oceanic response along west India coast and Kavaratti lagoon  

Microsoft Academic Search

Spatial and temporal response of the coastal waters of eastern Arabian Sea (AS) and Kavaratti lagoon to the tropical cyclonic storm `Phyan', which developed in the southeastern AS and swept northward along the eastern AS during 9-12 November 2009 and finally made landfall at the northwest coast of India, is examined based on time-series measurements of sea-surface wind (U10), gust,

Antony Joseph; R. G. Prabhudesai; Prakash Mehra; Vijay Kumar; Yogesh Agarwadekar; Luis Ryan; Pradhan Rivankar; Blossom Viegas

2010-01-01

331

Influence of monsoon over the warm pool on interannual variation on tropical cyclone activity over the western North Pacific  

Microsoft Academic Search

The relationship between the interannual variation in tropical cyclone (TC) activity over the western North Pacific (WNP)\\u000a and the thermal state over the warm pool (WP) is examined in this paper. The results show that the subsurface temperature\\u000a in the WP is well correlated with TC geographical distribution and track type. Their relation is linked by the East Asian\\u000a monsoon

Guanghua Chen; Ronghui Huang

2008-01-01

332

Effects of Tropical Cyclones on Ocean Heat Transport as simulated by a High Resolution Coupled General Circulation Model  

Microsoft Academic Search

Tropical cyclones (TCs) activity and their relationship with the Northern hemispheric Ocean Heat Transport (OHT) is investigated. The analysis has been performed using 20C3M (20th Century) and A1B (21st Century) IPCC scenario climate simulations obtained running a state-of-the-art atmosphere-ocean-seaice coupled global model, with high-resolution in the atmosphere. The capability of the model to reproduce a realistic TC climatology has been

E. Scoccimarro; S. Gualdi; A. Bellucci; A. Sanna; M. Vichi; E. Manzini; P. Fogli; A. Navarra; P. Oddo

2010-01-01

333

Upper ocean variability in the Bay of Bengal during the tropical cyclones Nargis and Laila  

NASA Astrophysics Data System (ADS)

Upper ocean variability at different stages in the evolution of the tropical cyclones Nargis and Laila is evaluated over the Bay of Bengal (BoB) during May 2008 and May 2010 respectively. Nargis initially developed on 24 April 2008; intensified twice on 27-28 April and 1 May, and eventually made landfall at Myanmar on 2 May 2008. Laila developed over the western BoB in May 2010 and moved westward towards the east coast of India. Data from the Argo Profiling floats, the Research Moored Array for African-Asian-Australian Monsoon Analysis and prediction (RAMA), and various satellite products are analyzed to evaluate upper ocean variability due to Nargis and Laila. The analysis reveals pre-conditioning of the central BoB prior to Nargis with warm (>30 °C) Sea Surface Temperature (SST), low (<33 psu) Sea Surface Salinity (SSS) and shallow (<30 m) mixed layer depths during March-April 2008. Enhanced ocean response to the right of the storm track due to Nargis includes a large SST drop by ˜1.76 °C, SSS increase up to 0.74 psu, mixed layer deepening of 32 m, shoaling of the 26 °C isotherm by 36 m and high net heat loss at the sea surface. During Nargis, strong inertial currents (up to 0.9 ms-1) were generated to the right of storm track as measured at a RAMA buoy located at 15 °N, 90 °E, producing strong turbulent mixing that lead to the deepening of mixed layer. This mixing facilitated entrainment of cold waters from as deep as 75 m and, together with net heat loss at sea surface and cyclone-induced subsurface upwelling, contributed to the observed SST cooling in the wake of the storm. A similar upper ocean response occurs during Laila, though it was a significantly weaker storm than Nargis.

Maneesha, K.; Murty, V. S. N.; Ravichandran, M.; Lee, T.; Yu, Weidong; McPhaden, M. J.

2012-11-01

334

Observed near-surface flows under all tropical cyclone intensity levels using drifters in the northwestern Pacific  

NASA Astrophysics Data System (ADS)

Data from drifters of the surface velocity program and tropical cyclones (TCs) of the Joint Typhoon Warning Center during 1985-2009 were analyzed to demonstrate strong currents under various storm intensities such as category-4 to -5, category-2 to -3, and tropical storm to category-1 TCs in the northwestern Pacific. Current speeds over 2.0 m s-1 are observed under major TCs with the strongest mean currents to the right of the storm track. This study provides the characterization of the near-surface velocity response to all recorded TCs, and agrees roughly with Geisler's theory (1970). Our observations also verify earlier modeling results of Price (1983).

Chang, Yu-Chia; Chen, Guan-Yu; Tseng, Ruo-Shan; Centurioni, Luca R.; Chu, Peter C.

2013-05-01

335

Influence of a tropical cyclone on the upper ionosphere according to tomography sounding data over Sakhalin Island in November 2007  

NASA Astrophysics Data System (ADS)

Tomography sounding data for the first half of November 2007 are presented. The sounding was conducted over three points located at the same meridian—Yuzhno-Sakhalinsk (47° N, 143° E), Poronaisk (49° N, 143° E), and Nogliki (51° N, 143° E)—in order to find the possible influence of a tropical cyclone on the upper ionosphere. A change in the foF2 parameter by on average no more than 10-20% is a possible response of the upper ionosphere localized over the tropical cyclone (TC) zone (in the given case, 25°-30° northward and 5°-20° eastward) at a distance of approximately 3800-5500 km from it. A decrease or, vice versa, an increase in foF2 is related to the delay of the measurement moment relative to the beginning of the TC action. The complexity of a morphological analysis of the given event is that a tropical cyclone is a "wideband" (in the longitudinal and, to a lesser degree, in the latitudinal directions) and lasting disturbance source.

Vanina-Dart, L. B.; Romanov, A. A.; Sharkov, E. A.

2011-12-01

336

Large-scale influences on the pre-genesis of tropical cyclone Karl (2010)  

NASA Astrophysics Data System (ADS)

The genesis of Tropical Cyclone (TC) Karl (2010) in September 2010 provided a unique opportunity to examine the continuing problem of understanding tropical cyclogenesis. The precursor disturbance to Karl originated from a cluster of showers east of the Windward Islands and was well sampled by ongoing field campaigns, particularly the PRE-Depression Investigation of Cloud-systems in the Tropics (PREDICT), as the targeted disturbance progressed westward. While traditional genesis theories focusing on moisture and mass fields (e.g. top-down showerhead method) can explain the initial spin-up of the disturbance several days prior to its official genesis, additional perspectives are examined in concert with more traditional methods in order to provide a more complete analysis of the synoptic-scale patterns that influenced the pre-Karl disturbance. A surge of westerly winds from northern South America aids the initial spin-up of the pre-Karl disturbance on 8-9 September, leading to the formation of a nearly closed earth-relative circulation. It can be shown that these anomalous westerly winds are tied to the convectively active phase of a convectively coupled Kelvin wave (CCKW). The observed formation of the nearly closed circulation on 10 September is well timed with the passage of this convectively active phase, a relationship that has been shown to hold true in cases of CCKW-TC interactions around the globe. Physically, the CCKW increases deep convection and aids in the generation of low-level relative vorticity on the cyclonic shear side of the low-level westerly wind anomalies, both of which serve to help organize the pre-Karl disturbance. Finally, the passage of the CCKW coincides with an equatorward surge of cold air and southerly winds in the lee of the Andes, triggered by a passing mid-latitude disturbance on 31 August. As the surge passes the equator on 7 September, little temperature perturbation remains with the surge, but terrain-channeled low-level flow acts to turn southerly flow into westerly flow south of the pre-Karl disturbance. By 8-9 September, anomalous westerly winds with the surge merge with and enhance the anomalous westerly winds associated with the CCKW passage, strengthening the low-level vorticity generation in the cyclonic shear of the merged CCKW-wind surge on the pre-Karl disturbance. However, despite this increase in vorticity and convection, the environment surrounding the pre-Karl disturbance remained unfavorable for several more days, with increased vertical wind shear and the convectively suppressed phase of a CCKW inhibiting further development before TC genesis occurred on 14 September. Despite this delayed development, the interplay of both mid-latitude and equatorial wave precursors likely contributed to the eventual genesis of TC Karl.

Griffin, Kyle S.

337

Tropical cyclone inundation potential on the Hawaiian Islands of Oahu and Kauai  

NASA Astrophysics Data System (ADS)

The lack of a continental shelf in steep volcanic islands leads to significant changes in tropical cyclone inundation potential, with wave setup and runup increasing in importance and wind driven surge decreasing when compared to more gently-sloped mainland regions. This is illustrated through high resolution modeling of waves, surge, and runup on the Hawaiian Islands of Oahu and Kauai. A series of hurricane waves and water levels were computed using the SWAN + ADCIRC models for a suite of 643 synthetic storm scenarios, while local wave runup was evaluated along a series of 1D transects using the phase-resolving model Bouss1D. Waves are found to be an extremely important component of the inundation, both from breaking wave forced increases in storm surge and also from wave runup over the relatively steep topography. This is clear in comparisons with debris lines left by Hurricane Iniki on the Island of Kauai, where runup penetration is much greater than still water inundation in most instances. The difference between steeply-sloping and gently-sloping topographies was demonstrated by recomputing Iniki with the same landfall location as Hurricane Katrina in Louisiana. Surge was greatly increased for the mild-slope Iniki-in-Louisiana case, while pure wind surge for Iniki-in-Kauai was very small.For the entire suite of storms, maxima on Kauai show predicted inundation largely confined to a narrow coastal strip, with few locations showing more than a few hundred meters of flooding from the shoreline. As expected, maximum flooded areas for the 643 storms were somewhat greater than the Iniki inundation.Oahu has significantly more low-lying land compared to Kauai, and consequently hypothetical tropical cyclone landfalls show much more widespread inundation. Under direct impact scenarios, there is the potential for much of Honolulu and most of Waikiki to be inundated, with both still water surge and wave runup contributing. Other regions of Oahu show inundation confined to a more narrow coastal strip, although there is still much infrastructure at risk.Even for very strong storms in Oahu and Kauai, maximum still water surge is relatively small, and does not exceed 3 m in any storm modeled. In contrast, hurricane waves several kilometers from shore regularly exceed 10 m due to the lack of a continental shelf.

Kennedy, Andrew B.; Westerink, Joannes J.; Smith, Jane M.; Hope, Mark E.; Hartman, Michael; Taflanidis, Alexandros A.; Tanaka, Seizo; Westerink, Hans; Cheung, Kwok Fai; Smith, Tom; Hamann, Madeleine; Minamide, Masashi; Ota, Aina; Dawson, Clint

2012-08-01

338

Monitoring Tropical Cyclone Impacts on the Coastal Vegetation of the Southeastern USA in the First Decade of the 21st Century  

Microsoft Academic Search

Hurricanes and tropical storms are powerful and hazardous meteorological phenomena causing damages to natural and built areas all around the world. However, on the flip side, Tropical cyclones provide a significant influx of freshwater resources to surface and subsurface reservoirs during the warm season. Therefore it is important to understand ecosystem response to such extreme climatic events, especially in a

J. Brun; A. P. Barros

2010-01-01

339

A mechanism for long-term changes of Atlantic tropical cyclone intensity  

NASA Astrophysics Data System (ADS)

Although previous studies reported upward trends in the basin-wide average lifetime, annual frequency, proportion of intense hurricanes and annual accumulated power dissipation index of Atlantic tropical cyclones (TCs) over the past 30 years, the basin-wide intensity did not increase significantly with the rising sea surface temperature (SST). Observational analysis and numerical simulation conducted in this study suggest that Sahel rainfall is the key to understanding of the long-term change of Atlantic TC intensity. The long-term changes of the basin-wide TC intensity are generally associated with variations in Sahara air layer (SAL) activity and vertical wind shear in the main development region (MDR), both of which are highly correlated with Sahel rainfall. The drying Sahel corresponds to an equatorward shift in the African easterly jet and African easterly wave activity, introducing the SAL to lower latitudes and increasing the MDR vertical wind shear. As a result, Atlantic TCs are more vulnerable to the suppressing effects of the SAL and vertical wind shear. Since the SST warming, especially in the tropical Indian Ocean, is a dominant factor for the Sahel drying that occurred over the past 30 years, it is suggested that the remote effect of SST warming is important for the long-term change of Atlantic TC intensity. Although influence of the AMO warm phase that started in the early 1990s alone can provide a favorable condition for TC intensification, its influence may have been offset by the influence of the ongoing SST warming, particularly in the Indian Ocean. As a result, there was no significant trend observed in the basin-wide average and peak intensity of Atlantic TCs.

Wu, Liguang; Tao, Li

2011-05-01

340

Observations of Ocean surface response to Hurricane Igor: A Salty Tropical Cyclone Wake observed from Space  

NASA Astrophysics Data System (ADS)

The upper ocean response to a moving hurricane is studied using satellite and in situ observations. Sea surface salinity response is emphasized using Soil Moisture and Ocean Salinity Sensor data acquired before and after the passing of Igor, a category 5 hurricane that attained wind speeds of 136 knots in September 2010. Post minus pre-hurricane satellite estimates of sea surface salinity reveal a strong surface salinity enhancement of ~1 practical salinity unit over a ~89000 km2 ocean surface area located on the right-hand side quadrant of the storm as it passed over the Amazon and Orinoco freshwater plume. The presence of this salty wake is associated with the erosion of the freshwater plume by the hurricane-induced mixing. The strong surface layer erosion as detected from space on the right-hand side storm quadrant is confirmed by in situ observation from Argo float profilers. The thermal, density and ocean color wakes are also evaluated and exhibit very consistent patterns with the sea surface salinity wake. As Igor over passed the plume on its left-hand side quadrants, the presence of a thick barrier layer below the plume inhibited mixing and significantly reduced the surface cooling in the wake of the storm, which limited the surface cooling negative feedback on Igor intensification. With this demonstrative example, we show that the new sea surface salinity measurements from space can be very useful as a complementary dataset to help predicting Tropical cyclone intensification in thick barrier layer area, such as the western tropical Atlantic.

Reul, N.; Quilfen, Y.; Chapron, B.; Vialard, J.; Vincent, E.; Tenerelli, J.; Boyer de Montégut, C.; Vandemark, D.; Lengaigne, M.

2012-04-01

341

Long-term changes in rainfall and tropical cyclone activity over South and Southeast Asia  

NASA Astrophysics Data System (ADS)

Long-term changes in rainfall and associated tropical cyclone (TC) activity in transition seasons between the wet and dry seasons in South and Southeast Asia, namely boreal spring and fall, were examined, using gridded rainfall, TC tracks, and reanalysis datasets, the focus of discussion being the long-term changes in coastal regions. It was found that long-term changes in rainfall during the transition seasons in South and Southeast Asia were closely associated with those in TC activity over the north Indian Ocean and South China Sea. Rainfall in May increased in the last 40 years over and around Myanmar, which indicates an earlier monsoon onset over the western Indochina Peninsula. Rainfall over and around northern Vietnam also increased in the last 40 years during October, which is known as the monsoon retreat period. These increases were associated with the long-term changes in TC activity. Furthermore, although linear trends have been previously suggested, monotonically increasing or decreasing trends in these long-term changes were not found over the last 60 years.

Takahashi, H. G.

2011-05-01

342

Observational Rainfall change analysis of tropical cyclones making landfall in Zhejiang of China  

NASA Astrophysics Data System (ADS)

Being accompanied by torrential rains, tropical cyclones (TCs) are the most devastating natural disasters in Chinese coastal provinces, inflicting huge losses in property and human life. But most of these casualties occurred in Zhejiang and 140 people were killed in Zhejiang Province annually, even though the average number of TCs made landfall in Zhejiang is only 0.9 and it is much lower than that for Hainan, Guangdong and Fujian provinces. In other words, Zhejiang Provinces is more vulnerable to landfalling TCs than Fujian and Guangdong. Despite the significant impacts of torrential rainfall from TCs at landfall, predicting rainfall associated with TCs is a major operational challenge. Therefore, better understanding the rainfall change and the associated reasons during TCs landfall is an important step toward disaster prevention and mitigation. This study will examine the spatial distribution of TCs rainfall during making landfall in Zhejiang Province of China. We will use rainfall observations, vertical wind shear data, and TC motion data to examine the relationship between the storm motion, environmental vertical wind shear, and TC rainfall asymmetry. We will also investigate how these relationships vary for different stages when TCs made landfall in Zhejiang. Detailed advances will be shown in the oral presentation.

Yu, Z.

2012-04-01

343

Enhanced western North Pacific tropical cyclone activity in May in recent years  

NASA Astrophysics Data System (ADS)

The tropical cyclone (TC) power dissipation index (PDI) in May over the western North Pacific (WNP) region shows a remarkable increase from the pre-1999 years (1979-1999) to the post-1999 years (2000-2011). Both increased TC numbers and enhanced TC intensity contributed to the change in the PDI. The averaged TC number in May increased from 1.05 per year in the pre-1999 years to 1.75 per year in the post-1999 years. In particular, the number of intense typhoon goes up from 0.14 per year to 0.83 per year, implying a sharp increase of TC intensity. Examination of the large scale background circulation in May shows that the epochal increase of TC number is caused by a significant increase of the genesis potential index (GPI), which has increased by about 33 % from the first (1979-1998) to the second (1999-2011) epoch over the TC genesis region (110°E-160°E, 5°N-20°N). The higher TC intensity is related to the increased maximum potential intensity and reduced TC ambient vertical wind shear in the second epoch. These decadal changes in background conditions over the WNP are the results of the enhanced summer monsoon in May over the both South Asia and South China Sea.

Xu, Shibin; Wang, Bin

2013-09-01

344

Improvement of Advanced Microwave Sounding Unit Tropical Cyclone Intensity and Size Estimation Algorithms  

NASA Astrophysics Data System (ADS)

Previous work, in which Advanced Microwave Sounding Unit (AMSU) data from the Atlantic Ocean and east Pacific Ocean basins during 1999 2001 were used to provide objective estimates of 1-min maximum sustained surface winds, minimum sea level pressure, and the radii of 34-, 50-, and 64-kt (1 kt ? 0.5144 m s-1) winds in the northeast, southeast, southwest, and northwest quadrants of tropical cyclones, is updated to reflect larger datasets, improved statistical analysis techniques, and improved estimation through dependent variable transforms. A multiple regression approach, which utilizes best-subset predictor selection and cross validation, is employed to develop the estimation models, where the dependent data (i.e., maximum sustained winds, minimum pressure, wind radii) are from the extended best track and the independent data consist of AMSU-derived parameters that give information about retrieved pressure, winds, temperature, moisture, and satellite resolution. The developmental regression models result in mean absolute errors (MAE) of 10.8 kt and 7.8 hPa for estimating maximum winds and minimum pressure, respectively. The MAE for the 34-, 50-, and 64-kt azimuthally averaged wind radii are 16.9, 13.3, and 6.8 n mi (1 n mi ? 1852 m), respectively.

Demuth, Julie L.; Demaria, Mark; Knaff, John A.

2006-11-01

345

A new insight into the contribution of environmental conditions to tropical cyclone activities  

NASA Astrophysics Data System (ADS)

The changes of tropical cyclone (TC) activities in response to influencing environmental conditions have been paid more and more attention to in recent years. The potential contributions of single and multivariate environmental variables to annual TC frequency and intensity from 1970 to 2009 are investigated in this study. Instead of using correlation coefficient that assumes a set of samples satisfying the normal distribution, a quantitative measurement is formulated based on the information theory. The results show that dynamic environmental variables play an important role in variations of TC activities over the western North Pacific, North Atlantic, and eastern Pacific. These dynamic factors include wind shear between 850 and 200 hPa and 850-hPa relative vorticity. However, the effects of thermal factors on TC activities are distinct over different basins. The thermal environmental variables only have significant contributions to TC frequency and intensity over the eastern Pacific as well as to TC frequency over the North Atlantic. It is found that the primary factors influencing TC activities are indeed not the same over different basins because of the differences in atmospheric conditions and their changes across different areas. The effects of dynamic variables should be considered more in the regions such as the western North Pacific where the thermal conditions are always satisfied.

Wang, Yuan; Song, Jinjie; Wu, Rongsheng

2013-06-01

346

Tropical cyclone influence on the higher ionosphere from tomography sounding data over Sakhalin island  

NASA Astrophysics Data System (ADS)

In this paper the tomography sounding data (measured in 2007) are considered for the following 3 points: Uzhnosahalinsk (46°57'N, 142°44' E), Poronajsk (49°13' N, 143° 6' E) and Nogliki (51°49' N, 143°7'E). The aim of this research is to find the possible influence of a tropical cyclone (TC) on the higher ionosphere. The results demonstrate that values for critical frequency in the F2- layer (as measured at approximately 3000 km from the TC centre in a horizontal plane along the longitudinal direction) fall after several days. Also the foF2 values increased over a 1 or 2 day period near the TC active zone (in the longitudinal direction). Complexities of the morphological analysis of the given phenomenon arise because the TC is wide-spread (in a longitudinal direction, and to a much smaller degree in a horizontal direction) and a long-term source of disturbance. A major difficulty posed to our study is that the TC is wide-spread and long-lived.

Vanina-Dart, L. B.; Romanov, A. A.; Sharkov, E. A.

2010-09-01

347

Recent increases in U.S. heavy precipitation associated with tropical cyclones  

NASA Astrophysics Data System (ADS)

Precipitation time series for 935 long-term U.S. climate stations were analyzed to identify daily extreme events associated with tropical cyclones (TCs). Extremes were defined as daily amounts exceeding a threshold for a 1 in 5-yr occurrence. TCs account for 30% or more of all such extreme events at a number of stations and about 6% of the national annual total. During 1994-2008, the number of TC-associated events was more than double the long-term average while the total annual national number of events was about 25% above the long-term (1895-2008) average. Despite the limited spatial area and portion of the annual cycle affected by TCs, the anomalous number of events associated with TCs accounted for over one-third of the overall national anomaly for 1994-2008. While there has been a recent increase in the number of landfalling U.S. hurricances, the increase in TC-associated heavy events is much higher than would be expected from the pre-1994 association between the two.

Kunkel, Kenneth E.; Easterling, David R.; Kristovich, David A. R.; Gleason, Byron; Stoecker, Leslie; Smith, Rebecca

2010-12-01

348

Environmental influences on the intensity change of tropical cyclones in the western North Pacific  

NASA Astrophysics Data System (ADS)

The atmospheric and oceanic conditions are examined during different stages of the lifecycle of western North Pacific tropical cyclones (TCs), with the intention to understand how the environment affects the intensity change of TCs in this area. It is found that the intensification usually occurs when the underlying sea surface temperature (SST) is higher than 26°C. TCs usually experience a rapid intensification when the SST is higher than 27.5°C while lower than 29.5°C. However, TCs decay or only maintain its intensity when the SST is lower than 26°C. The intensifying TCs usually experience a low-to-moderate vertical wind shear (2-10 m s-1). The larger the vertical wind shear, the slower the TCs strengthen. In addition, the convective available potential energy (CAPE) is much smaller in the developing stage than in the formation stage of TCs. For the rapidly intensifying TCs, the changes of SST, CAPE, and vertical wind shear are usually small, indicating that the rapid intensification of TCs occurs when the evolution of the environment is relatively slow.

Chu, Huiyun; Wu, Rongsheng

2013-06-01

349

Ecosystem effects of a tropical cyclone on a network of lakes in northeastern North America.  

PubMed

Here we document the regional effects of Tropical Cyclone Irene on thermal structure and ecosystem metabolism in nine lakes and reservoirs in northeastern North America using a network of high-frequency, in situ, automated sensors. Thermal stability declined within hours in all systems following passage of Irene, and the magnitude of change was related to the volume of water falling on the lake and catchment relative to lake volume. Across systems, temperature change predicted the change in primary production, but changes in mixed-layer thickness did not affect metabolism. Instead, respiration became a driver of ecosystem metabolism that was decoupled from in-lake primary production, likely due to addition of terrestrially derived carbon. Regionally, energetic disturbance of thermal structure was shorter-lived than disturbance from inflows of terrestrial materials. Given predicted regional increases in intense rain events with climate change, the magnitude and longevity of ecological impacts of these storms will be greater in systems with large catchments relative to lake volume, particularly when significant material is available for transport from the catchment. This case illustrates the power of automated sensor networks and associated human networks in assessing both system response and the characteristics that mediate physical and ecological responses to extreme events. PMID:23016881

Klug, Jennifer L; Richardson, David C; Ewing, Holly A; Hargreaves, Bruce R; Samal, Nihar R; Vachon, Dominic; Pierson, Donald C; Lindsey, Amanda M; O'Donnell, David M; Effler, Steven W; Weathers, Kathleen C

2012-10-12

350

Terminal Doppler Weather Radar (TDWR) observation of atmospheric flow over complex terrain during tropical cyclone passages  

NASA Astrophysics Data System (ADS)

To facilitate warning of low-level wind shear associated with convective storms, a Terminal Doppler Weather Radar (TWDR) was installed about 12 km to the northeast of the Hong Kong International Airport (HKIA). The HKIA is located just off the northern shore of an island known as Lantau. The HKIA lies on the lee side of the complex terrain of Lantau when winds come from the east through the southwest. With the commissioning of the TDWR in 1997, interesting high-resolution radar data were collected in strong southerly flows during tropical cyclone passages. These data sets reveal the complex low-level atmospheric flow in the vicinity of the HKIA, including streaks of low-speed flow, reverse flows, small-scale vortices and high-speed gap flows. Animation sequences of the radar images suggest existence of von Karman vortex streets and vortex shedding in the wake regions. These phenomena could induce strong shear regions which led to significant low-level wind shear for landing/departing aircraft. Analysis of on-board flight data for a wind shear event experienced by a landing aircraft in strong southeasterly flow revealed that terrain- induced features with horizontal scale less than 1 km brought significant air speed changes to the aircraft over a short duration of time.

Shun, Chi M.; Lau, Sharon S.

2000-12-01

351

Terminal Doppler Weather Radar Observation of Atmospheric Flow over Complex Terrain during Tropical Cyclone Passages.  

NASA Astrophysics Data System (ADS)

A Terminal Doppler Weather Radar (TDWR) started operation in Hong Kong, China, in 1997 for monitoring wind shear associated with thunderstorms affecting the Hong Kong International Airport. The airport was built on land reclaimed from the sea and lies to the immediate north of the mountainous Lantau Island, which has hills rising to nearly 1000 m. Since 1997, the airport experienced a number of tropical cyclone passages, some bringing strong southerly winds across these hills. Under these conditions the TDWR captured interesting but complex flow patterns in the lower atmosphere. The TDWR Doppler velocity datasets reveal features not previously observed with conventional instruments. These include shear lines, reverse flow, small-scale vortices, streaks of low-speed flow set against a high-speed background, as well as gap-related downslope high-speed flow. Hovmöller diagrams constructed from the Doppler velocity data bring out in considerable detail periodic shedding of vortices and transient wind patterns in the wake of the hills.

Shun, C. M.; Lau, S. Y.; Lee, O. S. M.

2003-12-01

352

Predicting tropical cyclone rapid intensification using the 37 GHz ring pattern identified from passive microwave measurements  

NASA Astrophysics Data System (ADS)

A distinctive satellite-derived precipitative ring pattern around the tropical cyclone (TC) center is found to be related to rapid intensification (RI). The ring pattern appears on the Naval Research Laboratory (NRL) 37 GHz passive microwave composite color product as a cyan color ring. The probability of RI is evaluated for cases with this ring pattern by reviewing images of the NRL product for 84 TCs during 2003-2007 in the Atlantic basin using 6-hourly National Hurricane Center (NHC) best track data. It is found that when combining the ring criterion with the Statistical Hurricane Prediction Scheme (SHIPS) RI Index (RII), the probability of RI almost doubled, indicating that both the ring and SHIPS RII contain independent information for RI prediction. A subjective technique for predicting RI is proposed using both the 37 GHz ring and the SHIPS RII. Both the probability of detection (POD) and the false alarm ratio (FAR) for the combined ring+SHIPS RII are lower than those for SHIPS RII alone (POD, 24% versus 77%, and FAR, 26% versus 66%) when treating every 6-hr synoptic time as a separate case. Since the method was initially developed for RI event-based forecasts, statistics based on 2003-2007 Atlantic RI events, which consist of a contiguous period where any 24-hour subset shows at least a 30 kt intensity increase, are also generated. The method captures 21 out of these 28 events and produces 2 false alarms, producing a POD of 75% and a FAR of 9%.

Kieper, Margaret E.; Jiang, Haiyan

2012-07-01

353

Relationship of environmental relative humidity with North Atlantic tropical cyclone intensity and intensification rate  

NASA Astrophysics Data System (ADS)

Quantifying the relationship of large-scale environmental conditions such as relative humidity with hurricane intensity and intensity change is important for statistical hurricane intensity forecasts. Our composite analysis of 9 years of Atmospheric Infrared Sounder (AIRS) humidity data spanning 198 Atlantic tropical cyclones (TCs) shows that environmental relative humidity (ERH) above the boundary layer generally decreases with time as TCs evolve. Near the surface, ERH stays approximately constant. ERH generally increases with increasing TC intensity and intensification rate. Rapidly intensifying TCs are associated with free tropospheric ERH more than 10% (relative to the averaged ERH for all TCs) larger than that for weakening TCs. Substantial azimuthal asymmetry in ERH is also found, especially for the TCs attaining the highest intensities and largest intensification rates at distances greater than 400 km away from the TC center. In the front-right quadrant relative to TC motion, rapid intensification is associated with a sharp gradient of ERH in the upper troposphere, with a decrease from the near to the far environment between 400 hPa and 300 hPa. The ERH gradient weakens with the decrease of intensification rate. This radial ERH gradient might be a useful predictor for the statistical forecast of TC intensification.

Wu, Longtao; Su, Hui; Fovell, Robert G.; Wang, Bin; Shen, Janice T.; Kahn, Brian H.; Hristova-Veleva, Svetla M.; Lambrigtsen, Bjorn H.; Fetzer, Eric J.; Jiang, Jonathan H.

2012-10-01

354

Evaluation of TRMM 3B42 precipitation estimates of tropical cyclone rainfall using PACRAIN data  

NASA Astrophysics Data System (ADS)

This study evaluates the latest release TRMM 3B42 version 7 (V7) estimates of daily rainfall in tropical cyclones (TCs) using the Comprehensive Pacific Rainfall Database (PACRAIN) of 24 h rain gauge observations. The evaluation is performed on two different terrain types: low-lying atoll sites (assumed to represent open ocean conditions) and coastal and island sites (over land). The results show that TRMM 3B42 has good skill at detecting intense TC rainfall, with good correlation and pattern matching with PACRAIN observations. However, it tends to overestimate heavy rain frequency on atoll sites, but tends to underestimate heavy rain frequency on coastal and island sites. Overall, TRMM 3B42 is better able to estimate the intensity of TC heavy rain over ocean than over land. It is least skillful at coastal and island sites with high elevation, where it significantly underestimates TC heavy rainfall, suggesting that TRMM 3B42 is unable to capture orographic enhancement during TC landfall. Finally, results from V7 were compared with results from its predecessor, Version 6, showing that Version 7 of TRMM 3B42 has higher values on average for TC rain.

Chen, Yingjun; Ebert, Elizabeth E.; Walsh, Kevin J. E.; Davidson, Noel E.

2013-03-01

355

Landscape-Scale Analysis of Wetland Sediment Deposition from Four Tropical Cyclone Events  

PubMed Central

Hurricanes Katrina, Rita, Gustav, and Ike deposited large quantities of sediment on coastal wetlands after making landfall in the northern Gulf of Mexico. We sampled sediments deposited on the wetland surface throughout the entire Louisiana and Texas depositional surfaces of Hurricanes Katrina, Rita, Gustav, and the Louisiana portion of Hurricane Ike. We used spatial interpolation to model the total amount and spatial distribution of inorganic sediment deposition from each storm. The sediment deposition on coastal wetlands was an estimated 68, 48, and 21 million metric tons from Hurricanes Katrina, Rita, and Gustav, respectively. The spatial distribution decreased in a similar manner with distance from the coast for all hurricanes, but the relationship with distance from the storm track was more variable between events. The southeast-facing Breton Sound estuary had significant storm-derived sediment deposition west of the storm track, whereas sediment deposition along the south-facing coastline occurred primarily east of the storm track. Sediment organic content, bulk density, and grain size also decreased significantly with distance from the coast, but were also more variable with respect to distance from the track. On average, eighty percent of the mineral deposition occurred within 20 km from the coast, and 58% was within 50 km of the track. These results highlight an important link between tropical cyclone events and coastal wetland sedimentation, and are useful in identifying a more complete sediment budget for coastal wetland soils.

Tweel, Andrew W.; Turner, R. Eugene

2012-01-01

356

Does it make sense to modify tropical cyclones? A decision-analytic assessment.  

PubMed

Recent dramatic increases in damages caused by tropical cyclones (TCs) and improved understanding of TC physics have led DHS to fund research on intentional hurricane modification. We present a decision analytic assessment of whether it is potentially cost-effective to attempt to lower the wind speed of TCs approaching South Florida by reducing sea surface temperatures with wind-wave pumps. Using historical data on hurricanes approaching South Florida, we develop prior probabilities of how storms might evolve. The effects of modification are estimated using a modern TC model. The FEMA HAZUS-MH MR3 damage model and census data on the value of property at risk are used to estimate expected economic losses. We compare wind damages after storm modification with damages after implementing hardening strategies protecting buildings. We find that if it were feasible and properly implemented, modification could reduce net losses from an intense storm more than hardening structures. However, hardening provides "fail safe" protection for average storms that might not be achieved if the only option were modification. The effect of natural variability is larger than that of either strategy. Damage from storm surge is modest in the scenario studied but might be abated by modification. PMID:21506599

Klima, Kelly; Morgan, M Granger; Grossmann, Iris; Emanuel, Kerry

2011-04-20

357

A study of the connection between tropical cyclone track and intensity errors in the WRF model  

NASA Astrophysics Data System (ADS)

This study examines the dependence of the tropical cyclone (TC) intensity errors on the track errors in the Weather Research and Forecasting (WRF-ARW) model. By using the National Centers for Environmental Prediction global final analysis as the initial and boundary conditions for cloud-resolving simulations of TC cases that have small track errors, it is found that the 2- and 3-day intensity errors in the North Atlantic basin can be reduced to 15 and 19 % when the track errors decrease to 55 and 76 %, respectively, whereas the 1-day intensity error shows no significant reduction despite more than 30 % decrease of the 1-day track error. For the North-Western Pacific basin, the percentage of intensity reduction is somewhat similar with the 2- and 3-day intensity errors improved by about 15 and 19 %, respectively. This suggests that future improvement of the TC track forecast skill in the WRF-ARW model will be beneficial to the intensity forecast. However, the substantially smaller percentages of intensity improvement than those of the track error improvement indicate that ambient environment tends to play a less important role in determining the TC intensity as compared to other factors related to the vortex initialization or physics representations in the WRF-ARW model.

Tien, Du Duc; Ngo-Duc, Thanh; Mai, Hoang Thi; Kieu, Chanh

2013-10-01

358

Landscape-scale analysis of wetland sediment deposition from four tropical cyclone events.  

PubMed

Hurricanes Katrina, Rita, Gustav, and Ike deposited large quantities of sediment on coastal wetlands after making landfall in the northern Gulf of Mexico. We sampled sediments deposited on the wetland surface throughout the entire Louisiana and Texas depositional surfaces of Hurricanes Katrina, Rita, Gustav, and the Louisiana portion of Hurricane Ike. We used spatial interpolation to model the total amount and spatial distribution of inorganic sediment deposition from each storm. The sediment deposition on coastal wetlands was an estimated 68, 48, and 21 million metric tons from Hurricanes Katrina, Rita, and Gustav, respectively. The spatial distribution decreased in a similar manner with distance from the coast for all hurricanes, but the relationship with distance from the storm track was more variable between events. The southeast-facing Breton Sound estuary had significant storm-derived sediment deposition west of the storm track, whereas sediment deposition along the south-facing coastline occurred primarily east of the storm track. Sediment organic content, bulk density, and grain size also decreased significantly with distance from the coast, but were also more variable with respect to distance from the track. On average, eighty percent of the mineral deposition occurred within 20 km from the coast, and 58% was within 50 km of the track. These results highlight an important link between tropical cyclone events and coastal wetland sedimentation, and are useful in identifying a more complete sediment budget for coastal wetland soils. PMID:23185635

Tweel, Andrew W; Turner, R Eugene

2012-11-21

359

Reexamination of the influence of ENSO on landfalling tropical cyclones in Korea  

NASA Astrophysics Data System (ADS)

This study examines the influence of the El Niño-Southern Oscillation (ENSO) on the frequency of landfalling tropical cyclones (TCs) in the Korean Peninsula during the TC season, June through October, of the years 1951-2010. An ENSO year is defined when the seasonal mean of the NINO3.4 sea surface temperature (SST) anomalies is greater/less than the typical seasonal mean by 0.5°C. The overall results of this study support that ENSO does not affect the landfalling TCs in Korea; the mean frequencies of the TC landfalls (influences) during El Niño and La Niña calculated over the entire analysis period are 1.1 (3.3) and 1.2 (3.0), respectively. The variations in the basin-wide distribution of TCs show that the influence of ENSO on TC distribution is extended over southeastern Japan with no significant signals coming from over the Korean Peninsula and the East China Sea. The change in the intensity of the landfalling TCs in the Korean Peninsula due to ENSO leads to the same conclusion as that in the frequency of the landfalling TCs. In addition, the same conclusion is obtained when the TC season duration is expanded to include the entire year and when different definitions of the ENSO years (e.g., based on the preceding or following winter NINO3.4 SST anomalies) are selected for analysis.

Ho, Chang-Hoi; Kim, Hyeong-Seog

2011-11-01

360

Orographic Effects on Rainfall Induced by the Passage of Tropical Cyclones over Mountainous Islands Part I: Control Experiment  

NASA Astrophysics Data System (ADS)

The passage of a tropical cyclone (TC) over a mesoscale mountainous island, such as Puerto Rico, often brings heavy rainfall which produces flooding and landslides. Factors that affect quantities and distribution of this type of orographic rainfall in this region are not well understood. The numerical mesoscale Advanced Research Weather Research and Forecast (ARW) model was adopted to conduct a study of Hurricane Jeanne’s (2004) passage over the island. Four sensitivity experiments using microphysics (MP) schemes were performed. Each sensitivity experiment was represented by a single MP scheme, i.e.: WSM 5-Class (EXP1), Eta Ferrier Microphysics (EXP2), WSM 6-Class (EXP3), and the Thompson Graupel scheme (EXP4). In particular, we investigate the following scientific problem, what would be the impact of microphysics schemes in a tropical cyclone simulation using the ARW model? Results show strong consistency for the cyclonic track among all experiments with a significant landfall time difference of ~4 hours ahead of observations. Rainfall distribution was well represented, with maxima on the southeastern and higher regions. Only EXP3 reproduced acceptably both rainfall distribution and high peak locations. The cyclone’s wind intensity and minimum sea-level pressure at model landfall differ significantly from the reality. EXP2 and EXP3 produced a more realistic sea-level pressure between 988 and 992 hPa, and sustained winds of less than 87 mph, compared with 991 mbar and 60 mph, respectively. In conclusion, the WSM 6-Class scheme (EXP3) appears to be strongly comparable with observations and is more reliable for further investigations of the production of heavy orographic rainfall. Estimates of some control parameters and common ingredients, such as Convective Available Potential Energy (CAPE) and Precipitation Efficiency (E), respectively, and major sensitivity tests with mountain height variations, were performed to help understand the dynamical and physical processes in the production and modification by the orography. Hurricane Jeanne tropical cyclone track for both observations and 3km simulation starting on September 15th at 00Z for a 30-hour period. Also, the topography at the 3km resolution is plotted.

Colon-Pagan, I. C.; Lin, Y.; Kuo, Y.; Schreiner, W. S.

2009-12-01

361

Effects of Tropical Cyclones on Ocean Heat Transport as simulated by a High Resolution Coupled General Circulation Model  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TCs) activity and their relationship with the Northern hemispheric Ocean Heat Transport (OHT) is investigated. The analysis has been performed using 20C3M (20th Century) and A1B (21st Century) IPCC scenario climate simulations obtained running a state-of-the-art atmosphere-ocean-seaice coupled global model, with high-resolution in the atmosphere. The capability of the model to reproduce a realistic TC climatology has been assessed by comparing the model results from the simulation of the 20th Century with observations. The model is able to simulate tropical cyclone-like vortices with many features similar to the observed TCs. The simulated TC activity exhibits realistic structure, geographical distribution and interannual variability, indicating that the model is able to reproduce the major basic mechanisms that link the TC activity with the large scale circulation. The TC-induced ocean cooling is well represented and the TCs activity increases significantly the poleward OHT out of the tropics, but also increases the heat transport into the deep tropics. This effect, investigated looking at the 100 most intense Northern hemisphere TCs, is strongly correlated to the TC-induced momentum flux at the surface of the ocean. TCs frequency and intensity appear to be substantially stationary through the whole 1950- 2069 period. Also the effect of the TCs induced OHT) does not significantly change during the simulated period.

Scoccimarro, E.; Gualdi, S.; Bellucci, A.; Sanna, A.; Vichi, M.; Manzini, E.; Fogli, P.; Navarra, A.; Oddo, P.

2010-12-01

362

AIRS impact on the analysis and forecast track of tropical cyclone Nargis in a global data assimilation and forecasting system  

NASA Astrophysics Data System (ADS)

Tropical cyclones in the northern Indian Ocean pose serious challenges to operational weather forecasting systems, partly due to their shorter lifespan and more erratic track, compared to those in the Atlantic and the Pacific. Moreover, the automated analyses of cyclones over the northern Indian Ocean, produced by operational global data assimilation systems (DASs), are generally of inferior quality than in other basins, partly because of asymmetric data distribution and the absence of targeted observations inside cyclones. In this work it is shown that the assimilation of Atmospheric Infrared Sounder (AIRS) temperature retrievals under partial cloudy conditions can significantly impact the representation of the cyclone Nargis (which caused devastating loss of life in Myanmar in May 2008) in a global DAS. Forecasts produced from these improved analyses by a global model produce substantially smaller track errors. The impact of the assimilation of clear-sky radiances on the same DAS and forecasting system is positive, but smaller than the one obtained by ingestion of AIRS retrievals, probably due to poorer coverage.

Reale, O.; Lau, W. K.; Susskind, J.; Brin, E.; Liu, E.; Riishojgaard, L. P.; Fuentes, M.; Rosenberg, R.

2009-03-01

363

Evaluation of the ECMWF 32-day ensemble predictions during 2009 season of western North Pacific tropical cyclone events on intraseasonal timescales  

NASA Astrophysics Data System (ADS)

The performance of the ECMWF 32-day ensemble predictions of western North Pacific tropical cyclone events (formation plus track) made once a week during the 2009 season is evaluated with the same procedures as for the 2008 season. Seventeen of the 23 tropical cyclones during the 2009 season occurred during multiple storm scenarios that are more difficult to predict, and many of the deficient track predictions involved unusual and rapidly changing tracks that typically involve interactions with adjacent synoptic circulations that are not predictable on intraseasonal timescales (10-30 days). Such incorrect predictions of the duration and tracks of these multiple cyclones were found to degrade the performance in predicting subsequent tropical cyclone formations and tracks during the 32-day integration. Predominantly northward tracks throughout the life cycle tended to be less predictable on intraseasonal timescales. Given these caveats, the overall performance of the ECMWF ensemble for the 12 typhoons was more successful than during the 2008 season. However, the performance for three tropical storms during the 2009 season was less successful due to the difficult track forecast scenarios. A surprisingly good performance was found in predicting the formation location and early track segments of eight minimal tropical storms or tropical depressions. The less satisfactory aspect for many of the late season tropical depressions was that the ECMWF ensemble continued to predict member vortices for extended periods after the system had actually dissipated.

Elsberry, Russell L.; Jordan, Mary S.; Vitart, Frederic

2011-08-01

364

Tropical cyclone hazards and warning and disaster mitigation systems in India  

Microsoft Academic Search

The main features of a cyclone that cause death and destruction are: (1) Storm surge, a rapid increase in sea level along\\u000a the coast, primarily caused by the strong surface wind field of the cyclone as it approaches the coast, (2) the violent sustained\\u000a wind and wind gusts and cyclone-spawned tornadoes, and (3) the heavy rain and consequent flooding. The

Porathur V Joseph

1994-01-01

365

The effect of surface friction on the development of tropical cyclones  

NASA Astrophysics Data System (ADS)

When tropical cyclones (hereafter referred as TCs) are over the ocean, surface friction plays a dual role in the development of TCs. From the viewpoint of water vapor supply, frictional convergence and Ekman pumping provide a source of moisture for organized cumulus convection and is propitious to the spin-up of TCs. On the other hand, surface friction leads to a dissipation of kinetic energy that impedes the intensification of TCs. Which role is dominant in the developing stage of TCs is a controversial issue. In the present work, the influence of surface friction on the growth of TCs is re-examined in detail by conducting two sets of numerical experiments initialized with different cyclonic disturbances. Results indicate that, because of the inherent complexities of TCs, the impact of surface friction on the evolution of TCs can not be simply boiled down to being positive or negative. In the case that a TC starts from a low-level vortex with a warm core, surface friction and the resultant vertical motion makes an important contribution to the convection in the early developing stage of the TC by accelerating the build-up of convective available potential energy (CAPE) and ensuring moisture supply and the lifting of air parcels. This effect is so prominent that it dominates the friction-induced dissipation and makes surface friction a facilitative factor in the spin-up of the TC. However, for a TC formed from a mesoscale convective vortex (MCV) spawned in a long-lasting mesoscale convective system (MCS), the initial fields, and especially the low-level humidity and cold core, enable the prerequisites of convection (i.e., conditional instability, moisture, and lifting), to be easily achieved even without the help of boundary-layer pumping induced by surface friction. Accordingly, the reliance of the development of TCs on surface friction is not as heavy as that derived from a lowlevel vortex. The positive effect of surface friction on the development of TCs realized through facilitating favorable conditions for convection is nearly cancelled out by the friction-induced dissipation. However, as SST is enhanced in the latter case, the situation may be changed, and different development speeds may emerge between model TCs with and without surface friction considered. In short, owing to the fact that TC development is a complicated process affected by many factors such as initial perturbations, SST, etc., the importance of surface friction to the intensification of TCs may vary enormously from case to case.

Fang, Juan; Tang, Jianping; Wu, Rongsheng

2009-11-01

366

Stratosphere-troposphere exchange (STE) in the vicinity of (extra-tropical) cyclones  

NASA Astrophysics Data System (ADS)

The exchange of air masses across the tropopause plays an important role for the chemical composition of the stratosphere and troposphere. For instance, the injection of stratospheric air into the troposphere can enhance the ozone concentration significantly in the troposphere, even down to the boundary layer. On the other side, the amount of water vapor can be strongly increased when tropospheric air is transported into the stratosphere. Stratosphere-troposphere exchange (STE) occurs in different meteorological environments: e.g., near tropopause-level jet streams due to turbulent mixing, associated with the diabatic decay of upper-level cutoff lows, or in overshooting deep convective systems. In this study the importance of STE is quantified in the vicinity of (mainly extratropical) cyclones, based upon climatologies of cyclones and STE. Previous studies estimated the effects of STE in the vicinity of cyclones through case studies of single cyclones and extrapolated the results to the global scale. The caveat of this method is the uncertain representativeness of a single cyclone. Therefore, we use in this study 30 years of ERA-Interim data (1979-2011) to count all STE events in the vicinity of cyclones. A Lagrangian approach is used to identify STE events from the stratosphere to the troposphere and vice versa. The tropopause in this study is defined by the 2-pvu isosurface. A sophisticated cyclone identification and tracking tool determines the exact structure of a cyclone at each time step along its lifecycle. Therefore, an STE event can be clearly assigned to a specific cyclone. With this data set we build a climatology of STE events in the vicinity of cyclones and investigate their spatial and temporal distribution on a global scale and also within a cyclone life cycle. This enables us to study if STE events happen in preferred areas of a cyclone and during preferred phases of its lifecycle. Additionally, the climatology allows to determine if the mass flux through the troposphere is higher when a cyclone is present compared to the geographical mean. Furthermore, we address the question whether the intensity of STE is related to the minimum pressure of a cyclone, i.e., whether intense cyclones are associated with particularly intense cross-tropopause mass fluxes.

Reutter, P.; Skerlak, B.; Sprenger, M.; Wernli, H.

2012-04-01

367

Stratosphere-troposphere exchange (STE) in the vicinity of extra-tropical cyclones  

NASA Astrophysics Data System (ADS)

The exchange of air masses across the tropopause plays an important role for the chemical composition of the stratosphere and troposphere. For instance, the injection of stratospheric air into the troposphere can enhance the ozone concentration significantly in the troposphere, even down to the boundary layer. On the other side, the amount of water vapor can be strongly increased when tropospheric air is transported into the stratosphere. Stratosphere-troposphere exchange (STE) occurs in different meteorological environments: e.g., near tropopause-level jet streams due to turbulent mixing, associated with the diabatic decay of upper-level cutoff lows, or in overshooting deep convective systems. In this study the importance of STE is quantified in the vicinity of extratropical cyclones, based upon climatologies of cyclones and STE. Previous studies estimated the effects of STE in the vicinity of cyclones through case studies of single cyclones and extrapolated the results to the global scale. The caveat of this method is the uncertain representativeness of a single cyclone. Therefore, we use in this study 30 years of ERA-Interim data (1979-2011) to count all STE events in the vicinity of cyclones. A Lagrangian approach is used to identify STE events from the stratosphere to the troposphere and vice versa. The tropopause in this study is defined by the 2-pvu isosurface. A sophisticated cyclone identification and tracking tool determines the exact structure of a cyclone at each time step along its lifecycle. Therefore, an STE event can be clearly assigned to a specific cyclone. With this data set we build a climatology of STE events in the vicinity of cyclones and investigate their spatial and temporal distribution on a global scale and also within a cyclone life cycle. This enables us to study if STE events happen in preferred areas of a cyclone and during preferred phases of its lifecycle. Additionally, the climatology allows to determine if the mass flux through the troposphere is higher when a cyclone is present compared to the geographical mean. Furthermore, we address the question whether the intensity of STE is related to the minimum pressure of a cyclone, i.e., whether intense cyclones are associated with particularly intense cross-tropopause mass fluxes.

Reutter, Philipp; Skerlak, Bojan; Sprenger, Michael; Wernli, Heini

2013-04-01

368

Comparison of TRMM precipitation radar and microwave imager rainfall retrievals in tropical cyclone inner cores and rainbands  

NASA Astrophysics Data System (ADS)

Tropical Rainfall Measuring Mission (TRMM) rainfall retrieval algorithms are evaluated in tropical cyclone (TC) inner cores (IC), inner bands (IB), and outer rainbands (OB). In total, 1329 IC, 2149 IB, and 4627 OB storm regions are analyzed using data from a 12-year TRMM Tropical Cyclone Precipitation Feature (TCPF) database containing 1013 TCs viewed from December 1997 to December 2009. Attention is focused on the difference between the Precipitation Radar (PR) 2A25 and the TRMM Microwave Imager (TMI) 2A12 rainfall algorithms. The PR 2A25 produces larger mean rain rates than the TMI 2A12 in inner cores and inner bands, with the greatest difference occurring in hurricanes. This discrepancy is caused mostly by the TMI 2A12 significantly underestimating regions of moderate to heavy rain >15 mm hour-1 or when the PR reflectivity is greater than 30 dBZ. The TMI 2A12 rain rates are most closely related to the percentage coverage of 85 GHz polarization-corrected brightness temperature (PCT) <225 K in the IC and 85 GHz PCT <250 K in the IB and OB. These convective parameters are good predictors of the mean TMI 2A12 rain rate, but significant ice scattering is not always present in areas of heavy rain that are often widespread in TC inner regions. As a result, the TMI 2A12 algorithm may poorly measure the rain rate, particularly in the inner core of hurricanes.

Zagrodnik, Joseph P.; Jiang, Haiyan

2013-01-01

369

Modeling Tropical Cyclone Induced Inland Flooding at Tar Pamlico River Basin of North Carolina  

NASA Astrophysics Data System (ADS)

Landfalling tropical cyclones often produce heavy precipitation and result in river and flash floods. Such floods can not only cause loss of human lives and properties, but also lead to ecological disasters in the affected watershed areas, estuaries and coastal waters. In order to better understand and simulate large coastal watershed hydrology and hydro-meteorological processes associated with tropical cyclones (TC) - induced inland flooding, the Weather Research and Forecasting (WRF) model and the Annualized Agricultural Nonpoint Source Pollution Model (AnnAGNPS) have been employed in this study. The study focuses on four major hydro-meteorological identities and their interactions: 1) previous rainfall events, 2) synoptic atmospheric environment, 3) landfalling hurricane, and 4) surface and ground water hydrology. The research is divided into two parts. Part one focuses on the investigation of the impacts of previous rainfall events on watershed surface runoff while part two studies the impacts of the synoptic atmospheric environment on landfalling hurricanes and the resulting effect on surface runoff. Hurricane Floyd was chosen in this study as a special case because it produced massive flooding as a result of the combined effects of previous rainfall events from Hurricane Dennis and the synoptic atmospheric environment. The modeling results indicate that the AnnAGNPS model performs well in predicting the total amount of watershed runoff. However Muskingum channel routing is needed for AnnAGNPS to improve the hydrographs of flow discharge during hurricane events. Sensitivity analysis of soil saturated hydrological conductivity (Ks) indicates that both base flow and event total runoff are sensitive to Ks. Base flow increases as Ks increases when K s ?15 m/day, but slightly decreases when K s > 15 m/day which is out of assumption of linear relationship from Darcy's law. Peak runoff exponentially decreases as Ks increases. The results show that without the preceding Hurricane Dennis, the outlet discharge as a result of Hurricane Floyd would have been as much as 37% lower than that caused by the combined Dennis-Floyd effect. Precipitation during the landfall of Hurricane Floyd (1999) was simulated by using the WRF model with two-way nested domains. The horizontal grid spacing of the inner-most domain is 2 km. The WRF model could reproduce the northeast- southwest oriented narrow and intense band of precipitation that developed just inland of the coast over North Carolina. The distribution pattern of accumulated precipitation is consistent with the observed precipitation pattern. The magnitudes of the simulated precipitation are generally within 30% of the observed values at the weather stations in the study area. The effects of large-scale atmospheric environment on Hurricane Floyd - induced precipitation and flooding have also been investigated. Through a vortex removal technique, Hurricane Floyd vortex was mostly removed to obtain the large-scale atmospheric environmental field at the model initial time. It is shown that the environment-induced precipitation can be as high as 21.5% of total precipitation in domain 3 which covers most of the North Carolina and 7.3% in the focused hydrological study area. Idealized hydrological simulation results demonstrate that without large scale environmental impacts the discharge would have been as much as 10.4% lower at the Tarboro gauge station if assuming TC and synoptic environment interaction is linear. Using simulated precipitation from the WRF, AnnAGNPS model along with Muskingum routing was able to reproduce the hydrograph and total volume of surface runoff at the watershed outlet. This implies that with improved precipitation forecasts from numerical weather prediction models such as WRF, it is possible to make skillful river runoff forecasts using distributed hydrological models.

Tang, Qianhong

370

Influence of tropical cyclones on sea surface temperature seasonal cycle and ocean heat transport  

NASA Astrophysics Data System (ADS)

Recent studies suggested that tropical cyclones (TCs) contribute significantly to the meridional oceanic heat transport by injecting heat into the subsurface through mixing. Here, we estimate the long-term oceanic impact of TCs by inserting realistic wind vortices along observed TCs tracks in a 1/2° resolution ocean general circulation model over the 1978-2007 period. Warming of TCs' cold wakes results in a positive heat flux into the ocean (oceanic heat uptake; OHU) of ~480 TW, consistent with most recent estimates. However, ~2/5 of this OHU only compensates the heat extraction by the TCs winds during their passage. Another ~2/5 of this OHU is injected in the seasonal thermocline and hence released back to the atmosphere during the following winter. Because of zonal compensations and equatorward transport, only one-tenth of the OHU is actually exported poleward (46 TW), resulting in a marginal maximum contribution of TCs to the poleward ocean heat transport. Other usually neglected TC-related processes however impact the ocean mean state. The residual Ekman pumping associated with TCs results in a sea-level drop (rise) in the core (northern and southern flanks) of TC-basins that expand westward into the whole basin as a result of planetary wave propagation. More importantly, TC-induced mixing and air-sea fluxes cool the surface in TC-basins during summer, while the re-emergence of subsurface warm anomalies warms it during winter. This leads to a ~10 % reduction of the sea surface temperature seasonal cycle within TCs basins, which may impact the climate system.

Vincent, Emmanuel M.; Madec, Gurvan; Lengaigne, Matthieu; Vialard, Jérôme; Koch-Larrouy, Ariane

2013-10-01

371

Conditions under which CNOP Sensitivity Is Valid for Tropical Cyclone Adaptive Observations  

NASA Astrophysics Data System (ADS)

To determine whether significant improvements in tropical cyclone (TC) forecasting are achievable by deploying dropwindsondes according to conditional nonlinear optimal perturbation (CNOP) sensitivity, observing system simulated experiments (OSSEs) were conducted on 20 TCs that developed over the western North Pacific during 2010 using Mesoscale Model 5 and its 3DVar assimilation system. Of the 20 cases, 13 showed neutral or improved track forecasts of between 0% and 51.2%. Eliminating initial errors within the CNOP pattern, which are related to either the storm directly or the surrounding regimes indirectly, reduced the subsequent track forecast errors. The remaining seven TCs showed deterioration in the accuracy of the track forecasts over the 48 h forecast period. Accurate forecasts made without adaptive observations, a low sensitivity of forecast errors to initial errors, or major forecast errors associated with regimes other but TC, can lead to a decline in the accuracy of TC track forecasts. Following analysis of the potential causes of inaccuracy in the track forecasts, we find that TC cases with significant positive effects on track forecasts often satisfy following four conditions: i) an inaccurate initial forecast without additional observation data); ii) proper sensitivity of the forecast errors to the initial errors; iii) a large proportion of the forecast errors fall within the verification region; and iv) the TC system is the dominant regime in the verification region at verification time. Seven TCs satisfied these four conditions, and showed a mean reduction of 28.75% in track forecast errors over periods of 12 to 48 h. This result suggests that the TC cases satisfying these four conditions often show significant improvements on track forecast by dropwindsondes guided by CNOP sensitivity.

Qin, Xiaohao; Duan, Wansuo; Mu, Mu

2013-04-01

372

The effects of ocean feedback on tropical cyclone energetics under idealized air-sea interaction conditions  

NASA Astrophysics Data System (ADS)

effects of ocean feedback on the energetic characteristics of the tropical cyclone (TC) are investigated based on idealized TC-ocean coupling simulations. Results reveal notable impacts of ocean response on TC energetics. The ocean feedback reduces the latent energy of TCs, and consequently less latent heat is released in TC clouds, which leads to an evident decrease of the kinetic energy. A bulk equivalent potential temperature (?e) budget analysis demonstrates that the upward heat fluxes at the top of the boundary layer, of comparable magnitudes with the surface heat fluxes, are significantly diminished by the ocean feedback. A relatively higher portion of energy extracted from the ocean has been retained by the boundary layer under influences of the ocean feedback. The air parcels in contact with the cold wake possess evidently lowered moist static energy. To evaluate the evolution of moist static energy following these cooled air parcels, a three-dimensional Lagrangian analysis is conducted using a large sample of trajectory seeds. Statistical results indicate that there is a mixing process between the cooled and ambient air parcels that lasts mostly less than 240 min. Over 70% of the seeded air parcels approach to a radius of 30-90 km from the TC center before they obtain adequate energy from surrounding air to balance their negative asymmetric ?e. Most of the cooled air parcels are warmed up in the boundary layer, thereby producing impacts on TC energetics through changing directly the moist static energy of the boundary layer. More work of real case simulations is required to generalize the findings reported herein.

Ma, Zhanhong; Fei, Jianfang; Huang, Xiaogang; Cheng, Xiaoping

2013-09-01

373

Dynamical downscaling forecasts of Western North Pacific tropical cyclone genesis and landfall  

NASA Astrophysics Data System (ADS)

This study evaluates the potential use of the regional climate model version 3 (RegCM3) driven by (1) the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) data during 1982-2001 and (2) the NCEP Climate Forecast System Version 2 (CFS2) hindcast data during 2000-2010 in forecasting Western North Pacific (WNP) tropical cyclone (TC) activity. The first experiment is conducted to investigate the ability of the model in generating a good climatology of TC activity in spatial and temporal scales, so the model could be used in the second experiment to test its ability in forecasting TC genesis and landfall. Both experiments extend through the May to October WNP-TC season. Results show that the use of RegCM3 driven by the CFSR achieves a better simulation on the temporal and spatial variation of WNP-TC genesis during 1982-2001, as compared to previous studies using the same model but driven by the ERA40 reanalysis. In addition, diagnoses on the use of RegCM3 driven by the CFS2 point out that the 2000-2010 WNP-TC genesis locations and numbers from the model are very similar to those from the observations. The skill of RegCM3 in the forecasts of landfalling TCs is higher over the Southeast Asian region than over the other sub-regions of East Asia. Potential causes for such regional differences are discussed. Most importantly, statistical analyses show that the use of RegCM3 driven by the CFS2 gives a better forecast skill than the use of CFS2 alone for the prediction of WNP-TCs making landfall in East Asia. This indicates that the use of a dynamical downscaling method for the global forecast data would likely lead to a higher forecast skill of regional TC landfalls in most of the East Asian region.

Huang, Wan-Ru; Chan, Johnny C. L.

2013-04-01

374

Downscaling tropical cyclone activity using regional models: Impact of air-sea coupling on the frequency and intensity of Atlantic hurricanes Authors: Jen-shan Hsieh, Mingkui Li, R. Saravanan, and Ping Chang Texas A & M University, College Station, TX  

NASA Astrophysics Data System (ADS)

Tropical cyclones are an important component of climate variability in the tropics and the subtropics. Unfortunately, these cyclones are poorly represented in coarse-resolution global general circulation models. Fine-resolution regional atmospheric models can be used to better simulate the properties of tropical cyclones, typically using specified sea surface temperature as the lower boundary condition. Such a boundary condition cannot simulate the cold wake associated with a tropical cyclone, which arises due to the enhanced vertical mixing and entrainment below the oceanic mixed layer. This cold wake has potential implications for the intensity of the tropical cyclone itself, because it can act as a negative air-sea feedback and lead to a weakening of the storm. Therefore, proper representation of this air-sea feedback is important when assessing the sensitivity of tropical cyclone frequency and intensity to climate change. We address this issue using a coupled regional climate model, where a regional atmospheric model is coupled to a regional ocean model. The model domain encompasses the Atlantic Ocean and adjoining continental regions. The atmospheric component is the NCAR WRF model running at 30 km horizontal resolution. The oceanic component is the Regional Ocean Modeling System (ROMS) running at 0.25 degree resolution. The atmospheric and oceanic models exchange fluxes of momentum, heat, and freshwater. The control coupled integration using this model simulates fairly realistic tropical variability, including a number of hurricane-like tropical vortices. To assess the sensitivity of tropical cyclone activity to air-sea coupling, we have also carried out a companion uncoupled integration, where the time-evolving sea surface temperature from the control coupled integration is used as the lower boundary condition for the uncoupled atmospheric model. We analyze the frequency and intensity of the tropical cyclones, as well as the associated precipitation, in both the coupled and the uncoupled integrations. Preliminary results indicate that air-sea feedbacks can have a significant impact on tropical cyclone activity.

Hsieh, J.; Li, M.; Saravanan, R.; Chang, P.

2009-12-01

375

Decreasing trend in the strength of Tropical Easterly Jet during the Asian summer monsoon season and the number of tropical cyclonic systems over Bay of Bengal  

NASA Astrophysics Data System (ADS)

The NCEP/NCAR reanalysis data during the period 1958-1998 show a positive trend in the 100 hPa zonal wind, decrease in the strength of Tropical Easterly Jet (TEJ) during the summer monsoon period of June through September. This is confirmed by the Radiosonde data. The number of observed Tropical Cyclonic Systems (TCS) over Bay of Bengal during the same period shows a decreasing trend. There is a strong negative correlation (-0.549 for the period 1958-1998, 41 years, significant at 99.9% level by a two sided student t test) between the strength of TEJ and the number of Bay of Bengal TCS. This result has potential for long-range prediction of TCS, which is vital for the prediction of monsoon rainfall.

Rao, B. R. Srinivasa; Rao, D. V. Bhaskar; Rao, V. Brahmananda

2004-07-01

376

Sensitivity of physical parameterizations on prediction of tropical cyclone Nargis over the Bay of Bengal using WRF model  

NASA Astrophysics Data System (ADS)

Comprehensive sensitivity analyses on physical parameterization schemes of Weather Research Forecast (WRF-ARW core) model have been carried out for the prediction of track and intensity of tropical cyclones by taking the example of cyclone Nargis, which formed over the Bay of Bengal and hit Myanmar on 02 May 2008, causing widespread damages in terms of human and economic losses. The model performances are also evaluated with different initial conditions of 12 h intervals starting from the cyclogenesis to the near landfall time. The initial and boundary conditions for all the model simulations are drawn from the global operational analysis and forecast products of National Center for Environmental Prediction (NCEP-GFS) available for the public at 1° lon/lat resolution. The results of the sensitivity analyses indicate that a combination of non-local parabolic type exchange coefficient PBL scheme of Yonsei University (YSU), deep and shallow convection scheme with mass flux approach for cumulus parameterization (Kain-Fritsch), and NCEP operational cloud microphysics scheme with diagnostic mixed phase processes (Ferrier), predicts better track and intensity as compared against the Joint Typhoon Warning Center (JTWC) estimates. Further, the final choice of the physical parameterization schemes selected from the above sensitivity experiments is used for model integration with different initial conditions. The results reveal that the cyclone track, intensity and time of landfall are well simulated by the model with an average intensity error of about 8 hPa, maximum wind error of 12 m s-1and track error of 77 km. The simulations also show that the landfall time error and intensity error are decreasing with delayed initial condition, suggesting that the model forecast is more dependable when the cyclone approaches the coast. The distribution and intensity of rainfall are also well simulated by the model and comparable with the TRMM estimates.

Raju, P. V. S.; Potty, Jayaraman; Mohanty, U. C.

2011-09-01

377

Cyclone Susan  

NSDL National Science Digital Library

The Tropical Rainfall Measuring Mission (TRMM) satellite was launched in November 1997. An early TRMM observation was Cyclone Susan, which barreled through the South Pacific Ocean in the second week of January 1998. TRMM measured the storms rain height and coverage.

Shirah, Greg; Maher, Steve; Kummerow, Chris

1999-01-21

378

Natural hazards: causes and effects. Lesson 5--Tropical cyclones (hurricanes, typhoons, baguios, cordonazos, tainos).  

PubMed

The many conclusions drawn and lessons learned from past cyclones can be used to mitigate and better respond to future occurrences. Some of the most helpful are listed below: 1) Outbreaks of cholera do not follow cyclones. Cholera must be endemic previously to a community; 2) Waterborne diseases do not increase as a result of cyclones; 3) Massive food aid rarely is required after a cyclone; 4) Used clothing almost never is needed. It usually is culturally inappropriate. Though accepted by disaster victims, it almost never is worn; 5) Blankets can be useful, but if they are needed, they usually can be found locally and do not need to be imported; 6) Assistance by outsiders is most effective in the reconstruction period, not the emergency phase; 7) Most needs are met by the victims themselves or their local governments; 8) In general, victims do not respond to disasters with abnormal behavior. Cyclones do not incite panic, hysteria, or rioting; 9) Cyclone relief and reconstruction programs should be integrated with long-term development programs; 10) When properly executed, reconstruction assistance can provide a strong stimulus to recovery and a base for future development work; 11) Reconstruction programs should seek to reduce vulnerability to future disaster; 12) Re-establishment of the local economy, income security, and agriculture usually are more important to cyclone victims than is material assistance; and 13) Churches, schools, and other large buildings that often are designated as cyclone shelters usually are not safe. The number of deaths attributed to destroyed or flooded shelters is alarming. Most experts agree that the best alternative is adequate warning and evacuation of the threatened areas. PMID:10155431

Perez, E; Thompson, P

379

Using WWLLN and TRMM data to investigate lightning activity and convective parameters in 2005 - 2010 tropical cyclones  

NASA Astrophysics Data System (ADS)

The main objective of this research is to investigate the relationship between lightning activity in the inner core, intensity changes, and convective parameters in all tropical cyclones (TCs) that occurred between 2005 and 2010. The World Wide Lightning Location Network (WWLLN), a real-time network that covers the entire globe, is used to observe lightning activity during the evolution of TCs. The TCs intensification processes are quantified in terms of pressure and/or horizontal winds. Special attention is given to lightning activity accompanying intensity changes, since several previous works have identified peaks in lightning count in the inner core during intensification and weakening processes. The convective parameters are obtained from TRMM (Tropical Rainfall Measuring Mission) passive microwave radar data in the 37- and 85-GHz channels and TRMM-derived products (e.g., cloud liquid water, precipitable water, cloud ice, and precipitable ice). Several case studies are presented, including Cyclone Nargis in the North Indian Ocean, TCs near the Australian coast, and five intense Western North Pacific typhoons. Preliminary results indicate that lightning activity pinpoints the active convection areas in TCs, especially during intensity changes.

Solorzano, N. N.; Thomas, J. N.; Holzworth, R. H.

2010-12-01

380

Comparison of a regional tropical cyclone hindcast for Southeast Asia and western North Pacific with satellite- and reanalyses- based products  

NASA Astrophysics Data System (ADS)

The regional model COSMO-CLM abilities to dynamically downscale details of typhoons were taken under investigation. For this purpose derivation and comparison of typhoon statistics between different products has been made for the last decade. The study is considering mainly intensity, critical wind radius, life time and tracking methodologies. Numerous studies concerning tropical cyclone climatology use ‘Best Track' data which refers to the estimation of tropical cyclone location, maximum sustained wind and central pressure. Unfortunately data sets provided by various meteorological agencies are showing significant discrepancies. Therefore intercomparison is extended by satellite- , reanalyses, and merged two of a kind - based products: • Blended Sea Winds (NOAA's National Climatic Data Center ), • Blended Surface Winds (IFREMER/CERSAT - French ERS Processing and Archiving Facility), • ERA-Interim (European Centre for Medium-Range Weather Forecasts Reanalysis), • NCEP/NCAR reanalysis (National Centers for Environmental Prediction - National Center for Atmospheric Research) The methodology for typhoon events derivation is based on an automated lagrangean algorithm detecting and following individual cyclonic features. Alternative approaches assume that 'best track' data is providing the most accurate estimation of typhoon locations. Under this assumption comparison of statistics between different wind products on the locations provided by best track data was made. The comparison of modelled data with other products reveals small discrepancies in storm numbers and track locations beeing caused by unique for every product technique of derivation. These were also the reasons for differences between compared statistics. The satellite products concerning maximum intensity indicate strong agreement with regional model data. Analysed typhoon events simulated by the regional model are more representative for the satellite products than for best track data, concerning above-mentioned terms of statistics.

Barcikowska, M.; Feser, F.; von Storch, H.

2010-09-01

381

Improving the Detection and Tracking of Tropical Cyclones in Atmospheric General Circulation Models  

Microsoft Academic Search

Dynamical seasonal forecasts of tropical storm frequency require robust and efficient algorithms for detection and tracking of tropical storms in atmospheric general circulation models (AGCMs). Tropical storms are generally detected when dynamic and thermodynamic variables meet specified criteria. Here, it is shown that objectively defined model- and basin-dependent detection criteria improve simulations of tropical storm climatology and interannual variability in

Suzana J. Camargo; Stephen E. Zebiak

2002-01-01

382

Simple kinematic models for the environmental interaction of tropical cyclones in vertical wind shear  

NASA Astrophysics Data System (ADS)

A major impediment to the intensity forecast of tropical cyclones (TCs) is believed to be associated with the interaction of TCs with dry environmental air. However, the conditions under which pronounced TC-environment interaction takes place are not well understood. As a step towards improving our understanding of this problem, we analyze here the flow topology of a TC immersed in an environment of vertical wind shear in an idealized, three-dimensional, convection-permitting numerical experiment. A set of distinct streamlines, the so-called manifolds, can be identified under the assumptions of steady and layer-wise horizontal flow. The manifolds are shown to divide the flow around the TC into distinct regions. The manifold structure in our numerical experiment is more complex than the well-known manifold structure of a non-divergent point vortex in uniform background flow. In particular, one manifold spirals inwards and ends in a limit cycle, a meso-scale dividing streamline encompassing the eyewall above the layer of strong inflow associated with surface friction and below the outflow layer in the upper troposphere. From the perspective of a steady and layer-wise horizontal flow model, the eyewall is well protected from the intrusion of environmental air. In order for the environmental air to intrude into the inner-core convection, time-dependent and/or vertical motions, which are prevalent in the TC inner-core, are necessary. Air with the highest values of moist-entropy resides within the limit cycle. This "moist envelope" is distorted considerably by the imposed vertical wind shear, and the shape of the moist envelope is closely related to the shape of the limit cycle. In a first approximation, the distribution of high- and low-?e air around the TC at low to mid-levels is governed by the stirring of convectively modified air by the steady, horizontal flow. Motivated by the results from the idealized numerical experiment, an analogue model based on a weakly divergent point vortex in background flow is formulated. The simple kinematic model captures the essence of many salient features of the manifold structure in the numerical experiment. A regime diagram representing realistic values of TC intensity and vertical wind shear can be constructed for the point-vortex model. The results indicate distinct scenarios of environmental interaction depending on the ratio of storm intensity and vertical-shear magnitude. Further implications of the new results derived from the manifold analysis for TCs in the real atmosphere are discussed.

Riemer, M.; Montgomery, M. T.

2011-09-01

383

The impact of spaceborne Doppler radar observations on the simulation of a tropical cyclone  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TC) present a tremendous challenge for numerical weather prediction (NWP). Poorly specified initial conditions (i.e. model analyses) are one of the primary sources of forecast error, and high resolution observations are needed to rectify the problem. A geostationary Doppler radar instrument, NEXRAD-In-Space (NIS), has been proposed for this very purpose. A set of observing system simulation experiments (OSSE) is conducted to assess the potential role of data from NIS in improving prediction of TC via improved representation of the TC in the model analysis. Using the University of Wisconsin Nonhydrostatic Modeling System (UW-NMS) together with an ensemble Kalman filter (EnKF), it is demonstrated that, for a typical Atlantic basin TC, NIS-observed Doppler radial velocity ( VR) and equivalent reflectivity factor (Z e) are effective in significantly reducing analysis errors. When computed over the entire grid, the degree of improvement ranges from 20 to 80 percent relative to the control (CTL) simulation, while a more homogeneous degree of improvement (50 to 80 percent) is demonstrated at locations where observations have been assimilated. Furthermore, when examination of observation impact is restricted to those surface regions with significant weather (V surf > 34 kt and/or rain rate > 12.5 mm h-1), a nearly uniform improvement of 60 to 80 percent is apparent. In general, a four to six hour assimilation window is sufficient to achieve statistical convergence (i.e. produce errors that are asymptotic relative to control). In order to determine the degree to which the improved analysis leads to improved forecast results, a 48-hour integration is initialized from an analysis produced by assimilating both VR and Ze. Significant impact on both intensity and track are noted, with a 65 percent reduction in intensity error and 56 percent reduction in track error relative to CTL over the forecast period. In general, errors relating to surface wind are more effectively reduced than those relating to rain rate, as is evident from Brier Skill Scores (BSS) computed for a number of wind and rain rate thresholds.

Lewis, William E.

384

Cluster analysis of post-landfall tracks of landfalling tropical cyclones over China  

NASA Astrophysics Data System (ADS)

In this paper, we apply finite-mixture-model-based clustering algorithms to cluster post-landfall tracks of tropical cyclones (TCs) making landfall over China. Because existing studies find that landfall surfaces or elevations affect post-landfall TC movements, we also take account of elevations in addition to time orders in this model. Our study reveals three clusters, with cluster 1 making landfall in Hainan province and moving across the western coast of Guangdong province. Most of the TC tracks in cluster 1 move over the ocean and make secondary landfalls over Yunnan province of China and Vietnam. Cluster 1 finally dissipates inland and moves westward as a result of the westward-shift subtropical high, westward steering flow, easterly vertical wind shear and strong mountainous blocking. Cluster 2 makes landfall over Guangdong and Fujian provinces. TCs in cluster 2 subsequently move inland and disappear due largely to westward-shift subtropical high, easterly steering flow, easterly vertical wind shear and relatively strong mountainous blocking. Cluster 3 makes landfall along the Fujian and Zhejiang coast and sustains a long period of time, recurving mostly to the mid-latitude region owing to the surrounding eastward-shift subtropical high, westerly vertical wind shear, weak mountainous blocking and westerly steering flow. Because cluster 2 is significantly associated with La Niña events, TCs more likely make landfall over southeastern China coast and move westward or northwestward without recurving. Cluster 3 sustains a longer time than clusters 1 and 2 in spite of its weak horizontal and vertical water vapor supply. TCs in cluster 3 interact actively with westerlies during the post-landfall period. However, we cannot observe any analogous interactions with the mid-latitude westerlies in clusters 1 and 2. TCs of clusters 1 and 2 are influenced by summer monsoon flows. Moreover, summer monsoon exerts a greater influence on cluster 1 than cluster 2. The composite 200 hPa divergence of cluster 3 is stronger than that of clusters 1 and 2. This explains to some degree why cluster 3 sustains longer than clusters 1 and 2 after making landfall.

Zhang, Wei; Leung, Yee; Wang, Yuanfei

2013-03-01

385

Potential indirect effects of aerosol on tropical cyclone intensity: convective fluxes and cold-pool activity  

NASA Astrophysics Data System (ADS)

Observational and model evidence suggest that a 2008 Western Pacific typhoon (NURI) ingested elevated concentrations of aerosol as it neared the Chinese coast. This study uses a regional model with two-moment bin-emulating microphysics to simulate the typhoon as it enters the field of elevated aerosol concentrations. A clean maritime field of cloud condensation nuclei (CCN) was prescribed as marine background CCN concentrations and then based on satellite and global aerosol model output, increased to pollution levels and further enhanced in sensitivity tests. The typhoon was simulated for 96 h beginning 17 August 2008. During the final 60 h CCN concentrations were enhanced as it neared the Philippines and coastal China. The model was initialized with both global reanalysis model data and irregularly spaced dropsonde data from the 2008 T-PARC observational campaign using an objective analysis routine. At 36 h, the internal nudging of the model was switched off and allowed to freely evolve on its own. As the typhoon encountered the elevated CCN in the sensitivity tests, a significant perturbation of windspeed, convective fluxes, and hydrometeor species behavior was simulated. Early during the ingestion of enhanced CCN, precipitation was reduced due to suppressed collision and coalescence, and storm winds increased in strength. Subsequently, owing to reduced fall speeds of the smaller drops, greater amounts of condensate were thrust into supercooled levels where the drops froze releasing greater amounts of latent heat of freezing. Convection thereby intensified which resulted in enhanced rainfall and more vigorous convectively-produced downdrafts. As the convection intensified in the outer rainbands the storm drifted over the developing cold-pools. The enhanced cold-pools blocked the inflow of warm, moist air into the core of the typhoon which led to a weakening of the typhoon with significantly reduced low level wind speeds. The very high amounts of pollution aerosols resulted in large amounts of condensate being thrust into the storm anvil which weakened convective downdrafts and cold-pools, yet the system did show reductions in windspeed (although weaker) compared with the clean control run. This study suggests that ingestion of elevated amounts of CCN into a tropical cyclone (TC) can appreciably alter the intensity of the storm. This implies that intensity prediction of TCs would be improved by including indirect aerosol affects. However, the pollution aerosols have very little impact on the storm track.

Krall, G. M.; Cottom, W. R.

2012-01-01

386

The Effect of Regional Climate Model Domain Choice on the Simulation of Tropical Cyclone–Like Vortices in the Southwestern Indian Ocean  

Microsoft Academic Search

A regional climate model is tested for several domain configurations over the southwestern Indian Ocean to examine the ability of the model to reproduce observed cyclones and their landfalling tracks. The interaction between large-scale and local terrain forcing of tropical storms approaching and transiting the island landmass of Madagascar makes the southwestern Indian Ocean a unique and interesting study area.

Willem A. Landman; Anji Seth; Suzana J. Camargo

2005-01-01

387

The Evolution of Convective Structure in Tropical Cyclones Undergoing Rapid Intensification as Observed by Passive Microwave Sensors  

NASA Astrophysics Data System (ADS)

Documentation of improvements in tropical cyclone (TC) track forecasting by nearly 50% have been noted by the National Hurricane Center since 1990 however a concurrent lack of improvement has been noted in intensity forecasting. Particularly troubling to predict have been episodes of rapid intensification (RI) that are poorly anticipated by forecast models, possibly due to the influence of microphysical processes driving TC intensity change. Passive microwave sensors such as the Special Sensor Microwave Imager (SSM/I) and the Tropical Rainfall Measuring Mission Microwave Imager (TMI) are able to retrieve microphysical information about precipitation features through emission by liquid water at low frequency channels and ice-scattering at higher frequencies, which may detect key precursors to TC intensification. A dataset consisting of every SSM/I and TMI overpass of a tropical cyclone globally dating from the launch of each instrument through 2008 is used to examine the structural characteristics noted in storms undergoing varying degrees of intensity change. Composites of the RI class of storms show a distinct convective ring-like structure surrounding the system core not seen in the other classifications. In the 24-hour window after RI onset this ring shows a tendency to contract inwards towards the TC core and intensify. This methodology is also extended to 24 hours prior to the start of RI with an improvement in the convective organization seen as the vortex becomes increasingly axisymmetricized as the RI phase approaches. Potential asymmetric modes of RI are sought by stratifying the composites into classifications dependent on wind shear magnitude. The contribution and occurrence of convective bursts are also examined to evaluate whether they are typically a source or byproduct of the RI process.

Harnos, D. S.; Nesbitt, S. W.

2010-12-01

388

An assessment of the ECMWF tropical cyclone ensemble forecasting system and its use for insurance loss predictions  

NASA Astrophysics Data System (ADS)

Tropical cyclones (TC) are amongst the most impressive and destructive weather systems of Earth's atmosphere. The costs related to such intense natural disasters have been rising in recent years and may potentially continue to increase in the near future due to changes in magnitude, timing, duration or location of tropical storms. This is a challenging situation for numerical weather prediction, which should provide a decision basis for short term protective measures through high quality medium range forecasts on the one hand. On the other hand, the insurance system bears great responsibility in elaborating proactive plans in order to face these extreme events that individuals cannot manage independently. Real-time prediction and early warning systems are needed in the insurance sector in order to face an imminent hazard and minimise losses. Early loss estimates are important in order to allocate capital and to communicate to investors. The ECMWF TC identification algorithm delivers information on the track and intensity of storms based on the ensemble forecasting system. This provides a physically based framework to assess the uncertainty in the forecast of a specific event. The performance of the ECMWF TC ensemble forecasts is evaluated in terms of cyclone intensity and location in this study and the value of such a physically-based quantification of uncertainty in the meteorological forecast for the estimation of insurance losses is assessed. An evaluation of track and intensity forecasts of hurricanes in the North Atlantic during the years 2005 to 2009 is carried out. Various effects are studied like the differences in forecasts over land or sea, as well as links between storm intensity and forecast error statistics. The value of the ECMWF TC forecasting system for the global re-insurer Swiss Re was assessed by performing insurance loss predictions using their in-house loss model for several case studies of particularly devastating events. The generally known problem of the intensity bias in tropical cyclone forecasts is a very critical aspect, when using the meteorological forecasts for insurance loss prediction in such a chain modelling approach.

Aemisegger, F.; Martius, O.; Wüest, M.

2010-09-01

389

El Niño-Southern Oscillation, the Madden-Julian Oscillation and Atlantic basin tropical cyclone rapid intensification  

NASA Astrophysics Data System (ADS)

Both El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO) have previously been documented to impact Atlantic basin tropical cyclone (TC) activity through alterations in large-scale fields such as vertical wind shear, mid-level moisture, sea level pressure and sea surface temperature. Atlantic TC activity has been shown to be enhanced when La Niña conditions are present in the tropical Pacific, while activity is reduced when El Niño conditions occur. Atlantic TC activity is enhanced when the convectively active phase of the MJO is over Africa and the western Indian Ocean (Phases 1-2), while TC activity is suppressed when the convectively active phase of the MJO is over the tropical Pacific (Phases 6-7). These relationships are shown to extend to Atlantic basin rapid intensification (RI) events (typically defined as intensification of 30 knots or greater in 24 h), with nearly three times as many RI events in La Niña years when compared with El Niño years. In addition, approximately four times more RI episodes occur when the MJO exceeds one standard deviation in Phases 1-2 than when the MJO exceeds one standard deviation in Phases 6-7. Storms forming in Phases 1-2 are twice as likely to undergo at least one RI episode during their lifetime as storms forming in Phases 6-7. Even stronger relationships are seen when the MJO and ENSO are considered in combination.

Klotzbach, Philip J.

2012-07-01

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Tropical cyclone rainbands over land in South Florida: Multiwavelength radar observations and their educational applications  

NASA Astrophysics Data System (ADS)

This dissertation investigates the wind structure observed in outer rainbands of three tropical cyclones in August and September 2008 in South Florida. Average wind profiles during fourteen stratiform periods are evaluated using a velocity-azimuth display (VAD) technique applied to Level-2 Miami (KAMX) WSR-88D data to study wind structure in high vertical resolution from a height of 65 meters to 6550 meters above ground level. The maximum horizontal wind speed in the rainbands is typically observed between 1000-1500 meters in height, with occasional evidence of a secondary horizontal wind maximum near 3500-5000 meters. This secondary maximum is found to be stronger than the low-level maximum in four cases of stronger storms observed at further distances (425-450 km) from storm center. Storm-relative wind componen