Five year ahead prediction of Sea Surface Temperature in the Tropical Atlantic: a comparison between IPCC climate models and simple statistical methods
There is a clear positive correlation between boreal summer tropical Atlantic sea-surface temperature and annual hurricane numbers. This motivates the idea of trying to predict the sea-surface temperature in order to be able to predict future hurricane activity. In previous work we have used simple statistical methods to make 5 year predictions of tropical Atlantic sea surface temperatures for this purpose. We now compare these statistical SST predictions with SST predictions made by an ensemble mean of IPCC climate models.
One possible method for the year-ahead prediction of hurricane numbers would be to make a year-ahead prediction of sea surface temperature (SST), and then to apply relationships that link SST to hurricane numbers. As a first step towards setting up such a system this article compares three simple statistical methods for the year-ahead prediction of the relevant SSTs.
This study assesses the ability of six European seasonal forecast models to simulate the observed teleconnection between ENSO and tropical cyclones (TCs) over the North Atlantic. While the models generally capture the basin-wide observed link, its magnitude is overestimated in all forecast models compared to reanalysis. Furthermore, the ENSO - TC relationship in the Caribbean is poorly simulated. It is shown that incorrect forecasting of wind shear appears to affect the representation of the teleconnection in some models, however it is not a completely sufficient explanation for the overestima…
We are developing schemes that predict future hurricane numbers by first predicting future sea surface temperatures (SSTs), and then apply the observed statistical relationship between SST and hurricane numbers. As part of this overall goal, in this study we compare the historical performance of three simple statistical methods for making five-year SST forecasts. We also present SST forecasts for 2006-2010 using these methods and compare them to forecasts made from two structural time series models.
Tropical cyclones that evolve from a non-tropical origin may pose a special challenge for predictions, as they often emerge at the end of a multi-scale cascade of atmospheric processes. Climatological studies have shown that the 'tropical transition' (TT) pathway plays a prominent role in cyclogenesis, in particular over the North Atlantic Ocean. Here we use operational European Centre for Medium-Range Weather Forecasts ensemble predictions to investigate the TT of North Atlantic Hurricane Chris (2012), whose formation was preceded by the merger of two potential vorticity (PV) maxima, eventual…
Bayesian statistical models were developed for the number of tropical cyclones and the rate at which these cyclones became hurricanes in the North Atlantic. We find that, controlling for the cold tongue index and the North Atlantic oscillation index, there is high probability that the number of cyclones has increased in the past thirty years; but the rate at which these storms become hurricanes appears to be constant. We also investigate storm intensity by measuring the distribution of individual storm lifetime in days, storm track length, and Emanuel's power dissiptation index. We find little…
Consistent with satellite-tracked trajectories of drogued drifters, but at odds with Eulerian assessment of satellite-altimetry measurements of sea-surface height, we show that North Brazil Currents Rings (NBCRs) are incapable of bypassing the Lesser Antilles as structures that coherently transport material. The nature of the inability of the de-facto oceanographic Eulerian, streamline-based eddy detection technique to produce a correct assessment is rooted in its lack of objectivity. We arrive at this conclusion by applying \emph{geodesic eddy detection} on the altimetric dataset over nearly …
We employ a statistical model of North Atlantic tropical cyclone (TC) tracks to investigate the relationship between sea-surface temperature (SST) and North American TC landfall rates. The track model is conditioned on summer SST in the tropical North Atlantic being in either the 19 hottest or the 19 coldest years in the period 1950-2005. For each conditioning many synthetic TCs are generated and landfall rates computed. Compared to direct analysis of historical landfall, the track model reduces the sampling error by projecting information from the entire basin onto the coast. There are 46% mo…
Previous studies have shown that wind-forced baroclinic Rossby waves can capture a large portion of low-frequency steric SSH variations in the North Atlantic. In this paper, we extend the classical wind-driven Rossby wave model derived in a 1.5 layer ocean to include surface buoyancy forcing, and then use it to assess the contribution from buoyancy-forced Rossby waves to low-frequency North Atlantic steric SSH variations. In the tropical-to-mid-latitude North Atlantic we find that wind-driven Rossby waves are dominant, however, in the eastern subpolar North Atlantic their contribution is rough…
We study the specific influence of African dust on each one of the categories of Atlantic hurricanes. By applying wavelet analysis, we find a strong decadal modulation of African dust on Category 5 hurricanes and an annual modulation on all other categories of hurricanes. We identify the formation of Category 5 hurricanes occurring mainly around the decadal minimum variation of African dust and in deep water areas of the Atlantic Ocean, where hurricane eyes have the lowest pressure. According to our results, future tropical cyclones will not evolve to Category 5 until the next decadal minimum …
Bayesian statistical models were developed for the number of tropical cyclones and the rate at which these cyclones became hurricanes in the North Atlantic, North and South Indian, and East and West Pacific Oceans. We find that there is small probability that the number of cyclones has increased in the past thirty years. The rate at which these storms become hurricanes appears to be constant. The rate at which hurricanes evolve into category 4 and higher major storms does appear to have increased. We also investigate storm intensity by measuring the distribution of individual storm lifetime in…
Persistence without Multifractality in Tropical Atlantic SST Indices: Scaling-Range Artefacts and a Reappraisal of the ENSO Association
Comisión Nacional de Energía Atómica（国家原子能委员会）；Instituto Sábato（萨巴托研究所）；Department of Mathematical Sciences, University of Texas at El Paso（德克萨斯大学埃尔帕索分校数学科学系）
Dynamics of East Atlantic seed vortex populations in global km-scale models
University of Leeds（利兹大学）；University of Oxford（牛津大学）；Met Office（英国气象局）；National Centre for Atmospheric Science (NCAS), University of Reading（雷丁大学国家大气科学中心）；Department of Meteorology, University of Reading（雷丁大学气象系）
The teleconnection between European climate and Atlantic Multidecadal Variability (AMV) remains difficult to isolate in observations because of internal variability and anthropogenically-forced signals. Using model sensitivity experiments proposed within the CMIP6/DCPP-C framework, the wintertime AMV/Europe teleconnection is investigated in large ensembles of pacemaker-type simulations in the CNRM-CM5 global circulation model. To evaluate the sensitivity of the model response to the AMV amplitude, experiments with AMV-forcing pattern multiplied by 2 and 3 (hereafter 2xAMV and 3xAMV, respective…
Recent US major landfalling hurricanes Katrina and Rita and last year's four U.S. landfalling major hurricanes have spawned an abundance of questions concerning the role that global warming might be playing in these events. This idea has been given added credence by the September 2005 Science paper of Webster, Holland, Curry and Chang (Vol. 304, pp. 1844-1846) showing that the global number of Category 4-5 hurricanes have increased in the last 15 years (1990-2004) in comparison with the prior 15-year period of 1975-1989. They report 171 Category 4-5 hurricanes in the earlier 15-year period vs.…
Kilometer-Scale AI Downscaling of Atlantic Hurricanes with Generative Ensembles
Research Applications Laboratory（研究应用实验室）；NSF National Center for Atmospheric Research（美国国家科学基金会国家大气研究中心）；Department of Mathematics, Emory University（埃默里大学数学系）
The proposition that the tropical cyclogenesis increases with the size of the warm pool, the area enclosed by the 26C SST isotherm, is tested by comparing the seasonal variation of the warm pool area with the seasonality of the number of tropical cyclones. A non-linear relationship of high statistical significance is found between the area and the number of cyclones, which may explain both why there is no linear trend in the number of cyclones over time and the recent upturn in the number of Atlantic hurricanes.
This study presents the first systematic comparison of the (thermo-)dynamics associated with all major tropical wave types causing rainfall modulation over northern tropical Africa: Madden Julian Oscillation (MJO), Equatorial Rossby waves (ERs), mixed Rossby-gravity waves (MRGs), Kelvin waves, tropical disturbances (TDs, including African Easterly Waves), and eastward inertio-gravity waves (EIGs). Reanalysis and radiosonde data were analyzed for the period 1981--2013 based on space-time filtering of outgoing longwave radiation. The identified circulation patterns are largely consistent with th…
Knowledge of ocean surface dynamics is crucial for oceanographic and climate research. The satellite-tracked movements of hundreds of drifters deployed by research and voluntary observing vessels provide high-frequency and high-resolution information on near-surface currents around the globe. Consequently, they constitute a major component of the Global Ocean Observing System (GOOS). However, maintaining this array is costly and in some oceanic regions such as the tropics, spatio-temporal coverage is limited. Here, we demonstrate that the GPS-buoy equipped fish aggregating devices (FADs) used …
The relatively warm climate found in the North- Western Europe is due to the gulf stream that circulates warm saline water from southern latitudes to Europe. In North Atlantic ocean the stream gives out a large amount of heat, cools down and sinks to the bottom to complete the Thermohaline circulation. There is considerable debate on the stability of the stream to inputs of fresh water from the melting ice in Greenland and Arctic. The circulation, being switched off, will have massive impact on the climate of Europe. Intergovernmental panel on climate change (IPCC) has warned of this danger in…
Advancing Seasonal Prediction of Tropical Cyclone Activity with a Hybrid AI-Physics Climate Model
University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；Google Research（谷歌研究院）；Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration（美国国家海洋和大气管理局地球流体动力学实验室）
A Spatial Persistence Gradient in European Warming Consistent with North Atlantic Cold-Blob Influence
Research Center on Sustainability and Strategic Resource Management (CISGER)（可持续性与战略资源管理研究中心（CISGER））；Faculty of Engineering, Universidad del Desarrollo（发展大学工程学院）
African dust exhibits strong variability on a range of time scales. Here we show that the interhemispheric contrast in Atlantic SST (ICAS) drives African dust variability on interannual, multidecadal, and millennial timescales, and a strong anthropogenic decline of African dust in the future can be expected due to the projected increase of the ICAS. During the recent past, the ICAS is found to significantly correlate with various dust observations and proxies that extend as far back as 1851. Physically, positive ICAS anomalies induce large-scale circulation changes that push the Intertropical …
Tropical cyclones are affected by a large number of climatic factors, which translates into complex patterns of occurrence. The variability of annual metrics of tropical-cyclone activity has been intensively studied, in particular since the sudden activation of the N Atl in the mid 1990's. We provide first a swift overview on previous work by diverse authors about these annual metrics for the NAtl basin, where the natural variability of the phenomenon, the existence of trends, the drawbacks of the records, and the influence of global warming have been the subject of interesting debates. Next, …
Building on recent research for prediction of hurricane trajectories using recurrent neural networks (RNNs), we have developed improved methods and generalized the approach to predict Bayesian intervals in addition to simple point estimates. Tropical storms are capable of causing severe damage, so accurately predicting their trajectories can bring significant benefits to cities and lives, especially as they grow more intense due to climate change effects. By implementing the Bayesian interval using dropout in an RNN, we improve the actionability of the predictions, for example by estimating th…
CNN-based forecasting of early winter NAO using sea surface temperature
UMR LOCEAN, IPSL, Sorbonne Université, IRD, CNRS, MNHN（洛里昂海洋与气候研究所，法国国家科学研究中心，索邦大学）；Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Université de Bordeaux（波尔多大学）
Here we report a modelling study of the spring ozone maximum and its interhemispheric asymmetry in the remote marine boundary layer (MBL). The modelled results are examined at the surface and on a series of time-height cross sections at several locations spread over the Atlantic, the Indian, and the Pacific Oceans. Comparison of model with surface measurements at remote MBL stations indicate a close agreement. The most striking feature of the hemispheric spring ozone maximum in the MBL can be most easily identified at the NH sites of Westman Island, Bermuda, and Mauna Loa, and at the SH site o…
This paper develops a novel method to detect cold pools from atmospheric soundings over tropical oceans and applies it to sounding data from the EUREC4A field campaign, which took place south and east of Barbados in January-February 2020. The proposed method exploits the fact that the air in a cold pool is denser than the air above it. It leads us to define cold pool soundings as those for which the mixed-layer height is smaller than 400 m. We first test this criterion by verifying its consistency with surface temperature and precipitation in a realistic high-resolution simulation over the wes…
Trend-Run model was performed to estimate the trend in surface temperatures recorded at 12 sites in Guinea from 1960 to 2016 and to examine the contribution of each climate forcing. The coefficient of determination (R 2) calculated varies between 0.60 and 0.90, it provides total information about the simulation capability of the model. The decadal trend values also calculated show an upward trend (between 0.04 {\textdegree}C $\pm$ 0.06 {\textdegree}C decade --1 and 0.21 {\textdegree}C $\pm$ 0.06 {\textdegree}C decade --1). In addition, forcings' contributions were quantified, and the annual os…
Evidence is provided that the global distribution of tropical hurricanes is principally determined by a universal function H of a single variable z that in turn is expressible in terms of the local sea surface temperature and latitude. The data-driven model presented here carries stark implications for the large increased numbers of hurricanes which it predicts for a warmer world. Moreover, the rise in recent decades in the numbers of hurricanes in the Atlantic, but not the Pacific basin, is shown to have a simple explanation in terms of the specific form of H(z), which yields larger percentag…
Can AI weather models predict out-of-distribution gray swan tropical cyclones?
University of Chicago, Department of the Geophysical Sciences（芝加哥大学地质科学系）；University of Chicago, Committee on Computational and Applied Mathematics（芝加哥大学计算与应用数学委员会）；University of Chicago, Research Computing Center（芝加哥大学研究计算中心）；University of California, Department of Applied Mathematics（加州大学应用数学系）；New York University, Courant Institute of Mathematical Sciences（纽约大学Courant数学科学研究所）
This paper demonstrates how principle component analysis can be used to determine the distinct factors that house the terms that explain the variance among the co-dependent variables and how non-response analysis can be applied to model the non-functional relationship that exist in a dynamic system. Moreover, the analysis indicates that there are pumping actions or ebb and flow between the pressure and the water temperature readings near the surface of the water days before a tropical storm forms in the Atlantic Basin and that there is a high correlation between storm conditions and buoy condi…
How strong are quantitative contributions of the key natural modes of climate variability and the anthropogenic factor characterized by the changes of the radiative forcing of greenhouse gases in the atmosphere to the trends of the surface air temperature at different latitudes of the Northern and Southern Hemispheres on various time intervals? Such contributions to trends are estimated here from observation data with the simplest empirical models. Trivariate autoregressive models are fitted to the data since the 19th century and used to assess the impact of the anthropogenic forcing together …
Massachusetts Institute of Technology（麻省理工学院）；Harvard University（哈佛大学）
This paper describes a novel machine learning (ML) framework for tropical cyclone intensity and track forecasting, combining multiple ML techniques and utilizing diverse data sources. Our multimodal framework, called Hurricast, efficiently combines spatial-temporal data with statistical data by extracting features with deep-learning encoder-decoder architectures and predicting with gradient-boosted trees. We evaluate our models in the North Atlantic and Eastern Pacific basins on 2016-2019 for 24-hour lead time track and intensity forecasts and show they achieve comparable mean absolute error a…
