scholarly journals Climate Changes of Atlantic Tropical Cyclone Formation Derived from Twentieth-Century Reanalysis

2013 ◽  
Vol 26 (22) ◽  
pp. 8995-9005 ◽  
Author(s):  
Ruifang Wang ◽  
Liguang Wu
Keyword(s):  
Global Warming ◽  
North Atlantic ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
The United States ◽  
Tropical Atlantic ◽  
The North ◽  
The Caribbean ◽  
The North Atlantic ◽  
Twentieth Century Reanalysis

Abstract Whereas some studies linked the enhanced tropical cyclone (TC) formation in the North Atlantic basin to the ongoing global warming, other studies attributed it to the warm phase of the Atlantic multidecadal oscillation (AMO). Using the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) Twentieth Century Reanalysis (20CR) dataset, the present study reveals the distinctive spatial patterns associated with the influences of the AMO and global warming on TC formation in the North Atlantic basin. Two leading empirical orthogonal function (EOF) patterns are identified in the climate change of TC formation on time scales longer than interannual. The first pattern is associated with the AMO and its spatial pattern shows the basin-scale enhancement of TC formation during the AMO positive phase. The second pattern is associated with global warming, showing enhanced TC formation in the east tropical Atlantic (5°–20°N, 15°–40°W) and reduced TC formation from the southeast coast of the United States extending southward to the Caribbean Sea. In the warm AMO phase, the basinwide decrease in vertical wind shear and increases in midlevel relative humidity and maximum potential intensity (MPI) favor the basinwide enhancement of TC formation. Global warming suppresses TC formation from the southeast coast of the United States extending southward to the Caribbean Sea through enhancing vertical wind shear and reducing midlevel relative humidity and MPI. The enhanced TC formation in the east tropical Atlantic is due mainly to a local increase in MPI or sea surface temperature (SST), leading to a close relationship between the Atlantic SST and TC activity over the past decades.

scholarly journals Climatology and Interannual Variability of North Atlantic Hurricane Tracks

2005 ◽  
Vol 18 (24) ◽  
pp. 5370-5381 ◽  
Author(s):  
Lian Xie ◽  
Tingzhuang Yan ◽  
Leonard J. Pietrafesa ◽  
John M. Morrison ◽  
Thomas Karl
Keyword(s):  
North Atlantic ◽  
The United States ◽  
Track Density ◽  
Spatial And Temporal Variability ◽  
Tropical Atlantic ◽  
Atlantic Hurricane ◽  
The North ◽  
Hurricane Track ◽  
The North Atlantic ◽  
Hurricane Tracks

Abstract The spatial and temporal variability of North Atlantic hurricane tracks and its possible association with the annual hurricane landfall frequency along the U.S. East Coast are studied using principal component analysis (PCA) of hurricane track density function (HTDF). The results show that, in addition to the well-documented effects of the El Niño–Southern Oscillation (ENSO) and vertical wind shear (VWS), North Atlantic HTDF is strongly modulated by the dipole mode (DM) of Atlantic sea surface temperature (SST) as well as the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). Specifically, it was found that Atlantic SST DM is the only index that is associated with all top three empirical orthogonal function (EOF) modes of the Atlantic HTDF. ENSO and tropical Atlantic VWS are significantly correlated with the first and the third EOF of the HTDF over the North Atlantic Ocean. The second EOF of North Atlantic HTDF, which represents the “zonal gradient” of North Atlantic hurricane track density, showed no significant correlation with ENSO or with tropical Atlantic VWS. Instead, it is associated with the Atlantic SST DM, and extratropical processes including NAO and AO. Since for a given hurricane season, the preferred hurricane track pattern, together with the overall basinwide hurricane activity, collectively determines the hurricane landfall frequency, the results provide a foundation for the construction of a statistical model that projects the annual number of hurricanes striking the eastern seaboard of the United States.

The Spatial Pattern of the Sun-Hurricane Connection across the North Atlantic

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Robert E. Hodges ◽  
James B. Elsner
Keyword(s):  
North Atlantic ◽  
Southern Oscillation ◽  
The United States ◽  
The Sun ◽  
Equal Area ◽  
The North ◽  
Spatial Response ◽  
The Caribbean ◽  
The North Atlantic ◽  
Eastern Seaboard

The authors define the spatial response of hurricanes to extremes in the solar cycle. Using an equal-area hexagon tessellation, regional hurricane counts are examined during the period 1851–2010. The response features fewer hurricanes across the Caribbean, Gulf of Mexico, and along the eastern seaboard of the United States when sunspots are numerous. In contrast fewer hurricanes are observed in the central North Atlantic when sunspots are few. The sun-hurricane connection is as important as the El Niño Southern Oscillation toward statistically explaining regional hurricane occurrences.

scholarly journals Lightning in Eastern North Pacific Tropical Cyclones: A Comparison to the North Atlantic

2015 ◽  
Vol 144 (1) ◽  
pp. 225-239 ◽  
Author(s):  
Stephanie N. Stevenson ◽  
Kristen L. Corbosiero ◽  
Sergio F. Abarca
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Pacific ◽  
Wind Shear ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Intensity Change ◽  
The North ◽  
The North Atlantic

Abstract As global lightning detection has become more reliable, many studies have analyzed the characteristics of lightning in tropical cyclones (TCs); however, very few studies have examined flashes in eastern North Pacific (ENP) basin TCs. This study uses lightning detected by the World Wide Lightning Location Network (WWLLN) to explore the relationship between lightning and sea surface temperatures (SSTs), the diurnal cycle, the storm motion and vertical wind shear vectors, and the 24-h intensity change in ENP TCs during 2006–14. The results are compared to storms in the North Atlantic (NA). Higher flash counts were found over warmer SSTs, with 28°–30°C SSTs experiencing the highest 6-hourly flash counts. Most TC lightning flashes occurred at night and during the early morning hours, with minimal activity after local noon. The ENP peak (0800 LST) was slightly earlier than the NA (0900–1100 LST). Despite similar storm motion directions and differing vertical wind shear directions in the two basins, shear dominated the overall azimuthal lightning distribution. Lightning was most often observed downshear left in the inner core (0–100 km) and downshear right in the outer rainbands (100–300 km). A caveat to these relationships were fast-moving ENP TCs with opposing shear and motion vectors, in which lightning peaked downmotion (upshear) instead. Finally, similar to previous studies, higher flash densities in the inner core (outer rainbands) were associated with nonintensifying (intensifying) TCs. This last result constitutes further evidence in the efforts to associate lightning activity to TC intensity forecasting.

scholarly journals Observation of Jet Stream Winds during NAWDEX and Characterization of Systematic Meteorological Analysis Errors

2020 ◽  
Vol 148 (7) ◽  
pp. 2889-2907 ◽  
Author(s):  
Andreas Schäfler ◽  
Ben Harvey ◽  
John Methven ◽  
James D. Doyle ◽  
Stephan Rahm ◽  
...  
Keyword(s):  
Wind Speed ◽  
North Atlantic ◽  
Wind Shear ◽  
Forecast Error ◽  
Vertical Wind Shear ◽  
Weather Forecast ◽  
Vertical Wind ◽  
Jet Stream ◽  
The North ◽  
The North Atlantic

Abstract Observations across the North Atlantic jet stream with high vertical resolution are used to explore the structure of the jet stream, including the sharpness of vertical wind shear changes across the tropopause and the wind speed. Data were obtained during the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) by an airborne Doppler wind lidar, dropsondes, and a ground-based stratosphere–troposphere radar. During the campaign, small wind speed biases throughout the troposphere and lower stratosphere of only −0.41 and −0.15 m s−1 are found, respectively, in the ECMWF and Met Office analyses and short-term forecasts. However, this study finds large and spatially coherent wind errors up to ±10 m s−1 for individual cases, with the strongest errors occurring above the tropopause in upper-level ridges. ECMWF and Met Office analyses indicate similar spatial structures in wind errors, even though their forecast models and data assimilation schemes differ greatly. The assimilation of operational observational data brings the analyses closer to the independent verifying observations, but it cannot fully compensate for the forecast error. Models tend to underestimate the peak jet stream wind, the vertical wind shear (by a factor of 2–5), and the abruptness of the change in wind shear across the tropopause, which is a major contribution to the meridional potential vorticity gradient. The differences are large enough to influence forecasts of Rossby wave disturbances to the jet stream with an anticipated effect on weather forecast skill even on large scales.

scholarly journals A Reanalysis of the 1911–20 Atlantic Hurricane Database

2008 ◽  
Vol 21 (10) ◽  
pp. 2138-2168 ◽  
Author(s):  
Christopher W. Landsea ◽  
David A. Glenn ◽  
William Bredemeyer ◽  
Michael Chenoweth ◽  
Ryan Ellis ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
The United States ◽  
Tropical Storm ◽  
Random Errors ◽  
The North ◽  
Systematic Biases ◽  
The Caribbean ◽  
The North Atlantic

Abstract A reanalysis of the Atlantic basin tropical storm and hurricane database (“best track”) for the period of 1911–20 has been completed. This reassessment of the main archive for tropical cyclones of the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico was necessary to correct systematic biases and random errors in the data as well as to search for previously unrecognized systems. A methodology for the reanalysis process for revising the track and intensity of tropical cyclone data is provided in detail. The dataset now includes several new tropical cyclones, excludes one system previously considered a tropical storm, makes generally large alterations in the intensity estimates of most tropical cyclones (both toward stronger and weaker intensities), and typically adjusts existing tracks with minor corrections. Average errors in intensity and track values are estimated for both open ocean conditions as well as for landfalling systems. Finally, highlights are given for changes to the more significant hurricanes to impact the United States, Central America, and the Caribbean for this decade.

Tropical Cyclone Intensity Estimation in the North Atlantic Basin Using an Improved Deviation Angle Variance Technique

2012 ◽  
Vol 27 (5) ◽  
pp. 1264-1277 ◽  
Author(s):  
Elizabeth A. Ritchie ◽  
Genevieve Valliere-Kelley ◽  
Miguel F. Piñeros ◽  
J. Scott Tyo
Keyword(s):  
Root Mean Square ◽  
North Atlantic ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Mean Square ◽  
Deviation Angle ◽  
The North ◽  
Variance Technique ◽  
The North Atlantic

Abstract This paper describes results from an improvement to the objective deviation angle variance technique to estimate the intensity of tropical cyclones from satellite infrared imagery in the North Atlantic basin. The technique quantifies the level of organization of the infrared cloud signature of a tropical cyclone as an indirect measurement of its maximum wind speed. The major change described here is to use the National Hurricane Center’s best-track database to constrain the technique. Results are shown for the 2004–10 North Atlantic hurricane seasons and include an overall root-mean-square intensity error of 12.9 kt (6.6 m s−1, where 1 kt = 0.514 m s−1) and annual root-mean-square intensity errors ranging from 10.3 to 14.1 kt. A direct comparison between the previous version and the one reported here shows root-mean-square intensity error improvements in all years with a best improvement in 2009 from 17.9 to 10.6 kt and an overall improvement from 14.8 to 12.9 kt. In addition, samples from the 7-yr period are binned based on level of intensity and on the strength of environmental vertical wind shear as extracted from Statistical Hurricane Intensity Prediction Scheme (SHIPS) data. Preliminary results suggest that the deviation angle variance technique performs best at the weakest intensity categories of tropical storm through hurricane category 3, representing 90% of the samples, and then degrades in performance for hurricane categories 4 and 5. For environmental vertical wind shear, there is far less spread in the results with the technique performing better with increasing vertical wind shear.

Allied High Commission for Germany

1951 ◽  
Vol 5 (4) ◽  
pp. 825-832
Keyword(s):  
United States ◽  
North Atlantic ◽  
Foreign Minister ◽  
The United States ◽  
Scrap Metal ◽  
German Federal Republic ◽  
The North ◽  
The United Kingdom ◽  
The North Atlantic ◽  
Contractual Agreements

With the development of certain administrative frictions (concerning coal quotas, occupation costs, and the scrap metal treaty) between the western occupying powers and the German Federal Republic, early indications were that if the talk of “contractual agreements” did materialize it would reserve, for the occupying powers, wide controls over important areas of west Germany's internal and external affairs. In Washington, however, a general modification of approach was noted during the September discussions between the United States Secretary of State (Acheson), the United Kingdom Foreign Secretary (Morrison), and the French Foreign Minister (Schuman), preparatory to the Ottawa meetings of the North Atlantic Council.

Strategy and the Atlantic Alliance

1963 ◽  
Vol 17 (3) ◽  
pp. 709-732 ◽  
Author(s):  
Robert R. Bowie
Keyword(s):  
United States ◽  
North Atlantic ◽  
North Atlantic Treaty Organization ◽  
The United States ◽  
The North ◽  
Nuclear Control ◽  
The North Atlantic ◽  
The Military

The debate over strategy, forces, and nuclear control, which now divides the North Atlantic Treaty Organization (NATO), is framed largely in military terms: what is the best way to protect the NATO area and its members from aggression? The military aspects are complex in themselves, but the import of these issues extends far beyond defense. Their handling will greatly affect prospects for a partnership between the United States and a strong, united Europe

Shaping the postwar balance of power: multilateralism in NATO

1992 ◽  
Vol 46 (3) ◽  
pp. 633-680 ◽  
Author(s):  
Steve Weber
Keyword(s):  
United States ◽  
Soviet Union ◽  
North Atlantic ◽  
Balance Of Power ◽  
The United States ◽  
The North ◽  
The Soviet Union ◽  
The North Atlantic ◽  
Multilateral Organization ◽  
John Ruggie

At the end of the 1940s, the United States and several West European states allied to defend themselves against invasion by the Soviet Union. Balance-ofpower theory predicts the recurrent formation of such balances among states. But it says little about the precise nature of the balance, the principles on which it will be constructed, or its institutional manifestations. The North Atlantic Treaty Organization (NATO) has been a peculiar mix. As a formal institution, NATO has through most of its history been distinctly nonmultilateral, with the United States commanding most decision-making power and responsibility. At the same time, NATO provided security to its member states in a way that strongly reflected multilateral principles. Within NATO, security was indivisible. It was based on a general organizing principle, the principle that the external boundaries of alliance territory were completely inviolable and that an attack on any border was an attack on all. Diffuse reciprocity was the norm. In the terms set out by John Ruggie, NATO has generally scored low as a multilateral organization but high as an institution of multilateralism.

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