On Estimates of Historical North Atlantic Tropical Cyclone Activity*

2008 ◽  
Vol 21 (14) ◽  
pp. 3580-3600 ◽  
Author(s):  
Gabriel A. Vecchi ◽  
Thomas R. Knutson
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Linear Trend ◽  
Annual Number ◽  
Base Case ◽  
Expected Number ◽  
Storm Activity ◽  
Main Development ◽  
Development Region ◽  
The Relationship

Abstract 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 “main development region” (“MDR”). The sensitivity of the estimate of missed TCs to underlying assumptions is examined. According to the base case adjustment used in this study, the annual number of TCs has exhibited multidecadal variability that has strongly covaried with multidecadal variations in MDR SST, as has been noted previously. However, the linear trend in TC counts (1878–2006) is notably smaller than the linear trend in MDR SST, when both time series are normalized to have the same variance in their 5-yr running mean series. Using the base case adjustment for missed TCs leads to an 1878–2006 trend in the number of TCs that is weakly positive, though not statistically significant, with p ∼ 0.2. The estimated trend for 1900–2006 is highly significant (+∼4.2 storms century−1) according to the results of this study. The 1900–2006 trend is strongly influenced by a minimum in 1910–30, perhaps artificially enhancing significance, whereas the 1878–2006 trend depends critically on high values in the late 1800s, where uncertainties are larger than during the 1900s. The trend in average TC duration (1878–2006) is negative and highly significant. Thus, the evidence for a significant increase in Atlantic storm activity over the most recent 125 yr is mixed, even though MDR SST has warmed significantly. The decreasing duration result is unexpected and merits additional exploration; duration statistics are more uncertain than those of storm counts. As TC formation, development, and track depend on a number of environmental factors, of which regional SST is only one, much work remains to be done to clarify the relationship between anthropogenic climate warming, the large-scale tropical environment, and Atlantic TC activity.

Early Season Hurricane Risk Assessment: Climate-Conditioned HITS Simulation of North Atlantic Tropical Storm Tracks

2021 ◽  
Vol 60 (4) ◽  
pp. 559-575
Author(s):  
Jennifer Nakamura ◽  
Upmanu Lall ◽  
Yochanan Kushnir ◽  
Patrick A. Harr ◽  
Kyra McCreery
Keyword(s):  
Risk Assessment ◽  
North Atlantic ◽  
Large Scale ◽  
Assessment Model ◽  
Risk Modeling ◽  
Equatorial Pacific Ocean ◽  
Early Season ◽  
Main Development ◽  
Development Region ◽  
Hurricane Risk

AbstractWe present a hurricane risk assessment model that simulates North Atlantic Ocean tropical cyclone (TC) tracks and intensity, conditioned on the early season large-scale climate state. The model, Cluster-Based Climate-Conditioned Hurricane Intensity and Track Simulator (C3-HITS), extends a previous version of HITS. HITS is a nonparametric, spatial semi-Markov, stochastic model that generates TC tracks by conditionally simulating segments of randomly varying lengths from the TC tracks contained in NOAA’s Best Track Data, version 2, dataset. The distance to neighboring tracks, track direction, TC wind speed, and age are used as conditioning variables. C3-HITS adds conditioning on two early season, large-scale climate covariates to condition the track simulation: the Niño-3.4 index, representing the eastern equatorial Pacific Ocean sea surface temperature (SST) departure from climatology, and main development region, representing tropical North Atlantic SST departure from climatology in the North Atlantic TC main development region. A track clustering procedure is used to identify track families, and a Poisson regression model is used to model the probabilistic number of storms formed in each cluster, conditional on the two climate covariates. The HITS algorithm is then applied to evolve these tracks forward in time. The output of this two-step, climate-conditioned simulator is compared with an unconditional HITS application to illustrate its prognostic efficacy in simulating tracks during the subsequent season. As in the HITS model, each track retains information on velocity and other attributes that can be used for predictive coastal risk modeling for the upcoming TC season.

scholarly journals Revisiting the Relationship between Atlantic Dust and Tropical Cyclone Activity using Aerosol Optical Depth Reanalyses: 2003–2018

2020 ◽  
Author(s):  
Peng Xian ◽  
Philip J. Klotzbach ◽  
Jason P. Dunion ◽  
Matthew A. Janiga ◽  
Jeffrey S. Reid ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
North Atlantic ◽  
Large Scale ◽  
Tropical Atlantic ◽  
African Dust ◽  
Tropical North Atlantic ◽  
June July ◽  
The Relationship

Abstract. Previous studies have noted a relationship between African dust and Atlantic tropical cyclone (TC) activity. However, due to the limitations of past dust analyses, the strength of this relationship remains uncertain. The emergence of aerosol reanalyses, including the Navy Aerosol Analysis and Prediction System (NAAPS) Aerosol Optical Depth (AOD) reanalysis, NASA Modern-Era Retrospective analysis for Research and Applications, Version-2 (MERRA-2) and ECMWF Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA) enable an investigation of the relationship between African dust and TC activity over the tropical Atlantic and Caribbean in a consistent temporal and spatial manner for 2003–2018. Although June-July-August (JJA) 550 nm dust AOD (DAOD) from all three reanalysis products correlate significantly over the tropical Atlantic and Caribbean, the difference in DAOD magnitude between products can be as large as 60 % over the Caribbean and 20 % over the tropical North Atlantic. Based on the three individual reanalyses, we have created an aerosol multi-reanalysis-consensus (MRC). The MRC presents overall better root mean square error over the tropical Atlantic and Caribbean compared to individual reanalyses when verified with ground-based AErosol RObotic NETwork (AERONET) AOD measurements. Each of the three individual reanalyses and the MRC have significant negative correlations between JJA Caribbean DAOD and seasonal Atlantic Accumulated Cyclone Energy (ACE), while the correlation between JJA tropical North Atlantic DAOD and seasonal ACE is weaker. Possible reasons for this regional difference are provided. A composite analysis of three high versus three low JJA Caribbean DAOD years reveals large differences in overall Atlantic TC activity. We also show that JJA Caribbean DAOD is significantly correlated with large-scale fields associated with variability in interannual Atlantic TC activity including zonal wind shear, mid-level moisture and SST, as well as ENSO and the Atlantic Meridional Mode (AMM), implying confounding effects of these factors on the dust-TC relationship. Further analysis indicates that seasonal Atlantic DAOD and the AMM, the leading mode of coupled Atlantic variability, are inversely related and intertwined in the dust-TC relationship.

scholarly journals The ability of general circulation models to simulate tropical cyclones and their precursors over the North Atlantic main development region

2012 ◽  
Vol 39 (7-8) ◽  
pp. 1559-1576 ◽  
Author(s):  
Anne Sophie Daloz ◽  
Fabrice Chauvin ◽  
Kevin Walsh ◽  
Sally Lavender ◽  
Deborah Abbs ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
General Circulation ◽  
General Circulation Models ◽  
The North ◽  
Main Development ◽  
Development Region ◽  
The North Atlantic

On vortices initiated over West Africa and their impact on North Atlantic tropical cyclones

2020 ◽  
Author(s):  
Jean Philippe Duvel
Keyword(s):  
West Africa ◽  
North Atlantic ◽  
The North ◽  
Potential Index ◽  
Main Development ◽  
Development Region ◽  
Vertical Development ◽  
Fouta Djallon ◽  
North And South ◽  
Seasonal And Interannual Variations

<p>Numerous low and mid-level vortices are initiated respectively north and south of 15°N in West Africa and enter the North Atlantic where they may trigger cyclogenesis. Applying an objective vortex tracking algorithm on 38 years of meteorological re-analysis, this work investigates the vortex origin and their role in cyclogenesis with an emphasis on: (i) orography, (ii) seasonal variations and, (iii) merge between low and mid-level vortex tracks. North path vortices are mostly initiated downstream of Hoggar Mountains (5°E, 24°N) and south path vortices are mostly initiated downstream of Fouta Djallon Mountains (15°W, 10°N). About 55% of cyclogeneses in the Main Development Region (MDR: east of 60°W; 5 to 20°N) is associated with vortices initiated on the continent east of 10°W. MDR cyclonic activity is governed by seasonal and interannual variations of the local Genesis Potential Index (maximal in August-September) and not by the number of vortices entering the Ocean. North path vortices, which are more numerous in July, are thus less cyclogenetic compared to south path vortices that are more numerous in August-September. Considering together vortices initiated on the continent and near the coast, about 20% of the cyclogeneses are associated with merge of north and south path vortices and about 14% with north path vortices only. The remaining part is mostly associated with south path vortices. In addition, south path vortices with greater intensity and vertical development between Greenwich and the coast are more cyclogenetic.</p>

scholarly journals Climatology of persistent deep stable layers in Utah's Salt Lake Valley, USA

2011 ◽  
Vol 6 (1) ◽  
pp. 59-62 ◽  
Author(s):  
S. Zhong ◽  
X. Xu ◽  
X. Bian ◽  
W. Lu
Keyword(s):  
Interannual Variability ◽  
Large Scale ◽  
Salt Lake ◽  
Linear Trend ◽  
Winter Season ◽  
Salt Lake Valley ◽  
Data Analyses ◽  
The Relationship

Abstract. The characteristics of winter season persistent deep stable layers (PDSLs) over Utah's Salt Lake Valley are examined using 30-year twice daily rawinsonde soundings. The results highlight the basic climatological characteristics of the PDSLs, including the strengths of the inversion, the frequency of the occurrence, and the duration of the events. The data analyses also reveal linear trend, interannual variability, as well as the relationship between the interannual variability of PDSLs and the variability of large-scale circulations. Finally, the study investigates the large-scale atmosphere conditions accompanying the formation and destruction of the PDSL episodes.

scholarly journals The Influence of Depth-Dependent Seasonal Temperature Variability on Growth Signal in Arctica islandica

2021 ◽  
Vol 8 ◽  
Author(s):  
Diana E. Caldarescu ◽  
Thomas Brey ◽  
Doris Abele ◽  
Lars Beierlein ◽  
Gerrit Lohmann ◽  
...  
Keyword(s):  
Water Depth ◽  
North Atlantic ◽  
Large Scale ◽  
Seasonal Temperature ◽  
North Atlantic Current ◽  
Arctica Islandica ◽  
Atlantic Sector ◽  
The North ◽  
The North Atlantic ◽  
The Relationship

Bivalve sclerochronological records with annually resolved growth bands are applicable proxies in reconstructing features of the hydro-climate system. Here we evaluate the relationship between growth indices of A. islandica, previously collected at approximately 82 m depth in the North Atlantic, and seasonal subsurface temperature at various depths for the 1900–2005 period. Correlations with sea surface temperature at the collection site are not significant during winter and weak for the remaining seasons. The strongest in-phase correlations persist for summer and autumn below 56 m water depth, whereas weaker correlations are lagged by one or two years. We also observe similarities with distant water bodies in the North Atlantic sector, and a corresponding large-scale oceanographic pattern that increases significantly with water depth along the trajectory of the North Atlantic Current. We suggest that by investigating the relationship with the temperature signal at various depths locally and at large-scale increases the reliability and application of bivalve shells as marine archives.

scholarly journals The Relationship between Tropical Cyclones at Genesis and Their Maximum Attained Intensity

2017 ◽  
Vol 30 (13) ◽  
pp. 4897-4913 ◽  
Author(s):  
Sarah D. Ditchek ◽  
T. Connor Nelson ◽  
Michaela Rosenmayer ◽  
Kristen L. Corbosiero
Keyword(s):  
Tropical Cyclone ◽  
Regression Coefficients ◽  
Tropical Cyclone Intensity ◽  
Cyclone Intensity ◽  
Compact Region ◽  
Multiple Parameter ◽  
Main Development ◽  
Development Region ◽  
Tropical Depressions ◽  
The Relationship

Despite recent improvements made to tropical cyclone intensity predictions, this study investigates a different approach than those attempted thus far. Here, the overall environmental setup at genesis is evaluated to determine whether it predisposes a storm to reach its future maximum intensity. Variables retrieved from ERA-Interim are used to generate storm-centered composites at the time of genesis for Atlantic basin, main development region TCs from 1979–2015. Composites are stratified by their maximum attained intensity: tropical depressions (GTD), tropical storms (GTS), minor hurricanes (GMN), or major hurricanes (GMJ). A multiple-parameter linear regression is then used to associate the eventual attained intensity of tropical cyclone to the obtained variables at genesis. The regression has an adjusted r2 of 0.39, which indicates that a statistical relationship is present. Regression coefficients, along with the spatial distribution of variables in the storm-centered composites, indicate that storms that reach higher intensities are associated at genesis with stronger, more compact, low-level vortices, better-defined outflow jets, a more compact region of high midlevel relative humidity, and higher atmospheric water vapor content.

scholarly journals The Seasonal Effects of ENSO on European Precipitation: Observational Analysis

2014 ◽  
Vol 27 (17) ◽  
pp. 6423-6438 ◽  
Author(s):  
Jeffrey Shaman
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Lower Troposphere ◽  
Seasonal Effects ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Atmospheric Conditions ◽  
Storm Activity ◽  
The North ◽  
The North Atlantic

Abstract An analysis and characterization of seasonal changes in the atmospheric teleconnection between ENSO and western European precipitation, as well as atmospheric conditions over the North Atlantic and Europe, are presented. Significant ENSO-associated changes in precipitation are evident during the boreal spring and fall seasons, marginal during boreal summer, and absent during boreal winter. The spring and fall precipitation anomalies are accompanied by statistically significant ENSO-related changes in large-scale fields over the North Atlantic and Europe. These seasonal teleconnections appear to be mediated by changes in upper tropospheric conditions along the coast of Europe that project down to the lower troposphere and produce onshore or offshore moisture flux anomalies, depending on the season. Some ENSO-related changes in storm activity are also evident during fall and winter. Analyses during boreal winter reveal little effect of coincident ENSO conditions on either European precipitation or upper tropospheric conditions over Europe.

scholarly journals On the Seasonal Cycles of Tropical Cyclone Potential Intensity

2017 ◽  
Vol 30 (16) ◽  
pp. 6085-6096 ◽  
Author(s):  
Daniel M. Gilford ◽  
Susan Solomon ◽  
Kerry A. Emanuel
Keyword(s):  
North Atlantic ◽  
Seasonal Cycle ◽  
Reanalysis Data ◽  
The Other ◽  
Thermodynamic Efficiency ◽  
Seasonal Cycles ◽  
Ambient Conditions ◽  
The North ◽  
Main Development ◽  
Development Region

Recent studies have investigated trends and interannual variability in the potential intensity (PI) of tropical cyclones (TCs), but relatively few have examined TC PI seasonality or its controlling factors. Potential intensity is a function of environmental conditions that influence thermodynamic atmosphere–ocean disequilibrium and the TC thermodynamic efficiency—primarily sea surface temperatures and the TC outflow temperatures—and therefore varies spatially across ocean basins with different ambient conditions. This study analyzes the seasonal cycles of TC PI in each main development region using reanalysis data from 1980 to 2013. TC outflow in the western North Pacific (WNP) region is found above the tropopause throughout the seasonal cycle. Consequently, WNP TC PI is strongly influenced by the seasonal cycle of lower-stratospheric temperatures, which act to damp its seasonal variability and thereby permit powerful TCs any time during the year. In contrast, the other main development regions (such as the North Atlantic) exhibit outflow levels in the troposphere through much of the year, except during their peak seasons. Mathematical decomposition of the TC PI metric shows that outflow temperatures damp WNP TC PI seasonality through thermodynamic efficiency by a quarter to a third, whereas disequilibrium between SSTs and the troposphere drives 72%–85% of the seasonal amplitude in the other ocean basins. Strong linkages between disequilibrium and TC PI seasonality in these basins result in thermodynamic support for powerful TCs only during their peak seasons. Decomposition also shows that the stratospheric influence on outflow temperatures in the WNP delays the peak month of TC PI by a month.

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