scholarly journals A New Statistical Model for Predicting Seasonal North Atlantic Hurricane Activity

2015 ◽  
Vol 30 (3) ◽  
pp. 730-741 ◽  
Author(s):  
Kyle Davis ◽  
Xubin Zeng ◽  
Elizabeth A. Ritchie
Keyword(s):  
Statistical Model ◽  
North Atlantic ◽  
Decadal Variability ◽  
Poor Performance ◽  
Seasonal Prediction ◽  
Atlantic Multidecadal Oscillation ◽  
Hybrid Models ◽  
Colorado State University ◽  
Atlantic Hurricane ◽  
The North

Abstract Statistical, dynamical, and statistical–dynamical hybrid models have been developed in past decades for the seasonal prediction of North Atlantic hurricane numbers. These models’ prediction skills show considerable decadal variability, with particularly poor performance in the past few years. Here, environmental factors that affect hurricane activities are reevaluated to develop a new statistical model for seasonal prediction by 1 June of each year. The predictors include the April–May multivariate ENSO index (MEI) conditioned upon the Atlantic multidecadal oscillation (AMO) index, the power of the average zonal pseudo–wind stress across the North Atlantic in May, and the average March–May tropical Atlantic sea surface temperature. When compared to the actual number of hurricanes each year from 1950 to 2013, this model has a root-mean-square error (RMSE) of 1.91 with a correlation coefficient of 0.71. It shows a 39% improvement in RMSE over a no-skill metric (based on the 5-yr running mean of seasonal hurricane counts) for the period 2001–13. It also outperforms three statistical–dynamical hybrid models [CPC, Colorado State University (CSU), and Tropical Storm Risk (TSR)] by more than 25% for the same period. Furthermore, two approaches are developed to provide the uncertainty ranges around the predicted (deterministic) hurricane number per season that better encompass the range of uncertainty than does the standard method of adding/subtracting a standard deviation of the errors.

scholarly journals Seasonal Prediction of North Atlantic Accumulated Cyclone Energy and Major Hurricane Activity

2019 ◽  
Vol 34 (1) ◽  
pp. 221-232 ◽  
Author(s):  
Kyle Davis ◽  
Xubin Zeng
Keyword(s):  
North Atlantic ◽  
Seasonal Prediction ◽  
Absolute Error ◽  
Atlantic Multidecadal Oscillation ◽  
Active Season ◽  
The North ◽  
Major Hurricane ◽  
Multivariate Enso Index ◽  
Atlantic Multidecadal Oscillation Index ◽  
The North Atlantic

Abstract Building upon our previous seasonal hurricane prediction model, here we develop two statistical models to predict the number of major hurricanes (MHs) and accumulated cyclone energy (ACE) in the North Atlantic basin using monthly data from March to May for an early June forecast. The input data include zonal pseudo–wind stress to the 3/2 power, sea surface temperature in the North Atlantic, and, depending on the magnitude of the Atlantic multidecadal oscillation index, the multivariate ENSO index. From 1968 to 2017, these models have a mean absolute error of 0.96 storms for MHs and 30 units for ACE. When tested over an independent period from 1958 to 1967, the models show a 22% improvement for MHs and 16% for ACE over a no-skill metric based on a 5-yr running average. Both the MH and ACE results show consistent improvements over those produced by three other centers using statistical–dynamical hybrid models and a 5-yr running average prediction over the period 2000–17 for MHs (2003–17 for ACE) in a simulated real-time prediction. These improvements vary from 25% to 37% for MHs and from 15% to 37% for ACE. While most forecasting centers called for a slightly above-average hurricane season in May/June 2017, our models predicted in June 2017 a very active season, in much better agreement with observations.

scholarly journals Climate impacts on multidecadal <i>p</i>CO<sub>2</sub> variability in the North Atlantic: 1948–2009

2015 ◽  
Vol 12 (17) ◽  
pp. 15223-15244
Author(s):  
M. L. Breeden ◽  
G. A. McKinley
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Dissolved Inorganic Carbon ◽  
Atlantic Multidecadal Oscillation ◽  
Climate Impacts ◽  
Co2 Uptake ◽  
Subpolar Gyre ◽  
The North ◽  
The North Atlantic

Abstract. The North Atlantic is the most intense region of ocean CO2 uptake. Here, we investigate multidecadal timescale variability of the partial pressure CO2 (pCO2) that is due to the natural carbon cycle using a regional model forced with realistic climate and pre-industrial atmospheric pCO2 for 1948–2009. Large-scale patterns of natural pCO2 variability are primarily associated with basin-averaged sea surface temperature (SST) that, in turn, is composed of two parts: the Atlantic Multidecadal Oscillation (AMO) and a long-term positive SST trend. The North Atlantic Oscillation (NAO) drives a secondary mode of variability. For the primary mode, positive AMO and the SST trend modify pCO2 with different mechanisms and spatial patterns. Warming with the positive AMO increases subpolar gyre pCO2, but there is also a significant reduction of dissolved inorganic carbon (DIC) due primarily to reduced vertical mixing. The net impact of positive AMO is to reduce pCO2 in the subpolar gyre. Through direct impacts on SST, the net impacts of positive AMO is to increase pCO2 in the subtropical gyre. From 1980 to present, long-term SST warming has amplified AMO impacts on pCO2.

scholarly journals Euro-Atlantic Atmospheric Circulation during the Late Maunder Minimum

2018 ◽  
Vol 31 (10) ◽  
pp. 3849-3863 ◽  
Author(s):  
Javier Mellado-Cano ◽  
David Barriopedro ◽  
Ricardo García-Herrera ◽  
Ricardo M. Trigo ◽  
Mari Carmen Álvarez-Castro
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Decadal Variability ◽  
Complete Classification ◽  
Maunder Minimum ◽  
The North ◽  
Late Maunder Minimum ◽  
The North Atlantic Oscillation ◽  
Nao Pattern

Abstract This paper presents observational evidence of the atmospheric circulation during the Late Maunder Minimum (LMM, 1685–1715) based on daily wind direction observations from ships in the English Channel. Four wind directional indices and 8-point wind roses are derived at monthly scales to characterize the LMM. The results indicate that the LMM was characterized by a pronounced meridional circulation and a marked reduction in the frequency of westerly days all year round, as compared to the present (1981–2010). The winter circulation contributed the most to the cold conditions. Nevertheless, findings indicate that the LMM in Europe was more heterogeneous than previously thought, displaying contrasting spatial patterns in both circulation and temperature, as well as large decadal variability. In particular, there was an increase of northerly winds favoring colder winters in the first half of the LMM, but enhanced southerlies contributing to milder conditions in the second half of the LMM. The analysis of the atmospheric circulation yields a new and complete classification of LMM winters. The temperature inferred from the atmospheric circulation confirms the majority of extremely cold winters well documented in the literature, while uncovering other less documented cold and mild winters. The results also suggest a nonstationarity of the North Atlantic Oscillation (NAO) pattern within the LMM, with extremely cold winters being driven by negative phases of a “high zonal” NAO pattern and “low zonal” NAO patterns dominating during moderately cold winters.

Near-surface wind speeds in ERA5: Climatology, decadal variability and long-term trends

2021 ◽  
Author(s):  
Terhi K. Laurila ◽  
Victoria A. Sinclair ◽  
Hilppa Gregow
Keyword(s):  
Iberian Peninsula ◽  
North Atlantic ◽  
Decadal Variability ◽  
Surface Wind ◽  
Northern Europe ◽  
Near Surface ◽  
Wind Speeds ◽  
The North ◽  
The North Atlantic

&lt;p&gt;The knowledge of long-term climate and variability of near-surface wind speeds is essential and widely used among meteorologists, climate scientists and in industries such as wind energy and forestry. The new high-resolution ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) will likely be used as a reference in future climate projections and in many wind-related applications. Hence, it is important to know what is the mean climate and variability of wind speeds in ERA5.&lt;/p&gt;&lt;p&gt;We present the monthly 10-m wind speed climate and decadal variability in the North Atlantic and Europe during the 40-year period (1979-2018) based on ERA5. In addition, we examine temporal time series and possible trends in three locations: the central North Atlantic, Finland and Iberian Peninsula. Moreover, we investigate what are the physical reasons for the decadal changes in 10-m wind speeds.&lt;/p&gt;&lt;p&gt;The 40-year mean and the 98th percentile wind speeds show a distinct contrast between land and sea with the strongest winds over the ocean and a seasonal variation with the strongest winds during winter time. The winds have the highest values and variabilities associated with storm tracks and local wind phenomena such as the mistral. To investigate the extremeness of the winds, we defined an extreme find factor (EWF) which is the ratio between the 98th percentile and mean wind speeds. The EWF is higher in southern Europe than in northern Europe during all months. Mostly no statistically significant linear trends of 10-m wind speeds were found in the 40-year period in the three locations and the annual and decadal variability was large.&lt;/p&gt;&lt;p&gt;The windiest decade in northern Europe was the 1990s and in southern Europe the 1980s and 2010s. The decadal changes in 10-m wind speeds were largely explained by the position of the jet stream and storm tracks and the strength of the north-south pressure gradient over the North Atlantic. In addition, we investigated the correlation between the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO) in the three locations. The NAO has a positive correlation in the central North Atlantic and Finland and a negative correlation in Iberian Peninsula. The AMO correlates moderately with the winds in the central North Atlantic but no correlation was found in Finland or the Iberian Peninsula. Overall, our study highlights that rather than just using long-term linear trends in wind speeds it is more informative to consider inter-annual or decadal variability.&lt;/p&gt;

A global decadal mode in a high-end climate model and in observations: Any connection to the solar cycle?

2021 ◽  
Author(s):  
Michael Ghil ◽  
Yizhak Feliks ◽  
Justin Small
Keyword(s):  
Solar Cycle ◽  
Sea Level ◽  
North Atlantic ◽  
Climate Model ◽  
Decadal Variability ◽  
Singular Spectrum Analysis ◽  
Coupled System ◽  
The North ◽  
Spatio Temporal ◽  
Decadal Mode

&lt;p&gt;The present work addresses two persistent quandaries of the climate sciences: (i) the existence of global oscillatory modes in the coupled ocean&amp;#8211;atmosphere system; and (ii) solar effects on this coupled system. Interannual oscillatory modes, atmospheric and oceanic, are present in several large regions of the globe. We examine here interannual-to-decadal variability over the entire globe in the Community Earth System Model (CESM) and in the NCEP-NCAR reanalysis, and apply multichannel singular spectrum analysis (MSSA) to these two datasets.&lt;/p&gt;&lt;p&gt;In the fully coupled CESM1.1 model, with its resolution of 0.1 &amp;#215; 0.1 degrees in the ocean and 0.25 &amp;#215; 0.25 degrees in the atmosphere, the &amp;#64257;elds analyzed are surface temperatures, sea level pressures and&amp;#160; the 200-hPa geopotential. The simulation is 100-yr long and the last 66 yr are used in the analysis. The two statistically signi&amp;#64257;cant periodicities in this IPCC-class model are 11 and 3.4 yr.&lt;/p&gt;&lt;p&gt;In the reanalysis, the &amp;#64257;elds of sea level pressure and of 200-hPa geopotential are analyzed at its resolution of 2.5 &amp;#215; 2.5 degrees over the 68-yr interval 1949&amp;#8211;2016. Oscillations with periods of 12 and 3.6 yr are found to be statistically signi&amp;#64257;cant in this dataset. The spatio-temporal patterns&amp;#160; of the oscillations in the two datasets are quite similar. The spatial pattern of these&amp;#160; global oscillations over the North Paci&amp;#64257;c and North Atlantic resemble the Paci&amp;#64257;c Decadal Oscillation and the interannual variability found in the western North Atlantic, respectively.&lt;/p&gt;&lt;p&gt;The two global modes, with their 11&amp;#8211;12-yr and 3.4&amp;#8211;3.6-yr periodicities, are quite robust, suggesting potential contributions of both to predictability at 1&amp;#8211;3-yr horizons. On the other hand, the CESM run has no year-to-year changes in the prescribed insolation, excluding any role of the solar cycle in the model&amp;#8217;s 11-yr mode. The solar cycle is present, however, in the reanalysis, since it is present in nature and hence it does affect the observations. We speculate, therefore, that regional oscillations &amp;#8212; with their distinct near-periodicities and spatial patterns &amp;#8212; are synchronized&amp;#160; over the globe, thus yielding both the global oscillatory modes found in CESM. In nature, the decadal mode could be further synchronized with the solar cycle, but that does not seem to be the case, given the slight difference in period &amp;#8212; 12 yr for the reanalysis and 11 yr for the solar cycle, which makes them drift in and out of phase.&lt;/p&gt;&lt;p&gt;The work&amp;#8217;s tentative conclusion is, therefore: (i) yes, there are global oscillatory modes in the climate system, especially a decadal mode; but (ii) no, this mode has little or nothing to do with the solar cycle.&lt;/p&gt;

The ability of the adjoint technique to recover decadal variability of the North Atlantic circulation

2013 ◽  
Vol 69 ◽  
pp. 166-180 ◽  
Author(s):  
Michael Brüdgam ◽  
Carsten Eden ◽  
Lars Czeschel ◽  
Johanna Baehr
Keyword(s):  
North Atlantic ◽  
Decadal Variability ◽  
The North ◽  
The North Atlantic

scholarly journals Reconciling two alternative mechanisms behind bi-decadal variability in the North Atlantic

2015 ◽  
Vol 137 ◽  
pp. 237-249 ◽  
Author(s):  
Pablo Ortega ◽  
Juliette Mignot ◽  
Didier Swingedouw ◽  
Florian Sévellec ◽  
Eric Guilyardi
Keyword(s):  
North Atlantic ◽  
Decadal Variability ◽  
The North ◽  
The North Atlantic

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.

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