Tropical cyclones cause significant inland hazards, including wind damage and freshwater flooding, that depend strongly on how storm intensity evolves at and after landfall. Existing theoretical predictions for the time-dependent and equilibrium response of storm intensity have been tested over the open ocean but not yet to be applied to storms after landfall. Recent work examined the transient response of the tropical cyclone low-level wind field to instantaneous surface roughening or drying in idealized axisymmetric f-plane simulations. Here, experiments testing combined surface roughening and drying with varying magnitudes of each are used to test theoretical predictions for the intensity response. The transient response to combined surface forcings can be reproduced by the product of their individual responses, in line with traditional potential intensity theory. Existing intensification theory is generalized to weakening and found capable of reproducing the time-dependent inland intensity decay. The initial (0-10min) rapid decay of near-surface wind caused by surface roughening is not captured by existing theory but can be reproduced by a simple frictional spin-down model, where the decay rate is a function of surface roughness. Finally, the theory is shown to compare well with the prevailing empirical decay model for real-world storms. Overall, results indicate the potential for existing theory to predict how tropical cyclone intensity evolves after landfall.
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…
Inland tropical cyclone (TC) impacts due to high winds and rainfall-induced flooding depend strongly on the evolution of the wind field and precipitation distribution after landfall. However, research has yet to test the detailed response of a mature TC and its hazards to changes in surface forcing in idealized settings. This work tests the transient response of an idealized hurricane to instantaneous transitions in two key surface properties associated with landfall: surface roughening and drying. Simplified axisymmetric experiments are performed in CM1 where surface drag coefficient and evap…
Water level measurements from 15 tide gauges in the coastal zone of Bangladesh are analyzed in conjunction with cyclone tracks and wind speed data for 54 cyclones between 1977 and 2010. Storm surge magnitude is inferred from residual water levels computed by subtracting modeled astronomical tides from observed water levels at each station. Observed residual water levels are generally smaller than reported storm surge levels for cyclones where both are available, and many cyclones produce no obvious residual at all. Both maximum and minimum residual water levels are higher for west-landing cycl…
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.…
Cyclone Amphan, a super cyclone in the Bay of Bengal after 21 years, intensified from a cyclonic storm (CAT 1) to a super cyclone (CAT 5) in less than 36 hours. It went on to make landfall over West Bengal as a Very Severe Cyclonic Storm (VSCS) with winds close to 155 kmph. Here, we analyze the dynamics that led to its rapid intensification, given that the system struggled to develop initially despite the presence of ripe conditions like high Sea Surface Temperature (SST) in the Bay. Our analysis clearly reveals that a Convectively Coupled Kelvin Wave (CCKW) from upper troposphere might have i…
Rapid intensification (RI) is likely the most crucial contributor to the development of strong tropical cyclones and the largest source of prediction error resulting in great threats to life and property, which can become more threatening with proximity to landfall. While enormous efforts have been devoted to studying the basin-wide fluctuation, temporal-spatial variations of global RI events remain uncertain. Here, we show that, compared with open oceans where the annual RI counts do not show any significant change, the coastal offshore regions within 400 km from the coastline host significan…
The Geostationary Operational Environmental Satellite (GOES) sounder-derived Wet Microburst Severity Index (WMSI) was originally developed and implemented to assess the potential magnitude of convective downbursts over the central and eastern continental United States. The WMSI algorithm incorporates convective available potential energy (CAPE), to parameterize static instability, as well as the vertical theta-e (equivalent potential temperature) difference (TeD) between the surface and mid-troposphere to infer the presence of a mid-level dry air layer. It has been noted with two recent landfa…
The near universal references to the above paper by most of the major US media outlets and blogs since Katrina and Rita made US landfall requires a response from a few of us who study hurricanes. Having been involved with hurricane research and forecasting for nearly 50 years, I feel I have an obligation to offer comments on this paper's findings which, in my view, are not valid. This paper concludes that global tropical cyclone net power dissipation (or friction times wind) taken to be proportional to the sum of each cyclone's individual 6-hour track period maximum wind speed (Vmax^3) has und…
Tropical Cyclone Viyaru, formerly known as Cyclonic Storm Mahasen was a rapidly intensifying, category 01B storm that made landfall in Chittagong, Bangladesh on the 16th of May, 2013. In this study, the sensitivity of numerical simulations of tropical cyclone to cumulus physics parametrization is carried out with a view to determine the best cumulus physics option for prediction of the cyclones track, timing, and central pressure evolution in the Bay of Bengal. For this purpose, the tropical cyclone Viyaru has been simulated by WRF ARW in a nested domain with NCEP Global Final Analysis(FNL) da…
A hidden Markov model is developed to simulate tropical cyclone intensity evolution dependent on the surrounding large-scale environment. The model considers three unobserved (hidden) discrete states of intensification and associates each state with a probability distribution of intensity change. The storm's transit from one state to another is described as a Markov chain. Both the intensity change and state transit components of the model are dependent on environmental variables including potential intensity, vertical wind shear, relative humidity, and ocean feedback. This Markov environment-…
Anomalous Diffusion of Tropical Cyclones Observed in Huge Ensembles of Hindcasts
NVIDIA Corporation（英伟达公司）；National Energy Research Scientific Computing Center (NERSC), LBNL（美国国家能源研究科学计算中心（NERSC）, 劳伦斯伯克利国家实验室）；Criteo AI Lab（Criteo人工智能实验室）；Earth and Environmental Sciences, Lawrence Berkeley National Laboratory (LBNL)（劳伦斯伯克利国家实验室（LBNL）地球与环境科学部）；The School of Environmental Sciences, University of East Anglia（东英吉利大学环境科学学院）；University of California, Berkeley（加州大学伯克利分校）；Department of Earth System Science, University of California, Irvine（加州大学尔湾分校地球系统科学系）
Recent work found evidence using aquaplanet experiments that tropical cyclone size on Earth is limited by the Rhines scale, which depends on the planetary vorticity gradient, $β$. This study aims to examine how the Rhines scale limits the size of an individual tropical cyclone. The traditional Rhines scale is first re-expressed as a vortex Rhines scale and Rhines speed to characterize how wave effects vary with radius in a vortex whose wind profile is known. Experiments are performed using a simple barotropic model on a $β$-plane initialized with a TC-like axisymmetric vortex defined using a r…
This paper presents numerical solutions and idealized analytical solutions of axisymmetric, $f$-plane models of the tropical cyclone boundary layer. In the numerical model, the boundary layer radial and tangential flow is forced by a specified pressure field, which can also be interpreted as a specified gradient balanced tangential wind field $v_{\rm gr}(r)$ or vorticity field $ζ_{\rm gr}(r)$. When the specified $ζ_{\rm gr}(r)$ field is changed from one that is radially concentrated in the inner core to one that is radially spread, the quasi-steady-state boundary layer flow transitions from a …
A 10,000-Year Global Stochastic Tropical Cyclone Catalog with Wind-Dependent Track Transitions (WHITS)
Lamont-Doherty Earth Observatory, Columbia University（哥伦比亚大学拉蒙特-多赫蒂地球观测站）；School of Complex Adaptive Systems, Arizona State University（亚利桑那州立大学复杂适应系统学院）；Earth and Environmental Engineering, Columbia University（哥伦比亚大学地球与环境工程系）
Potential Paradigm Shift in Hazard Risk Management: AI-Based Weather Forecast for Tropical Cyclone Hazards
Tongji University（同济大学）；Princeton University（普林斯顿大学）；The Hong Kong Polytechnic University（香港理工大学）；University of Wollongong（伍伦贡大学）；Nanjing University（南京大学）；Shanghai Jiao Tong University（上海交通大学）
The concept of Maximum Potential Intensity (MPI) is widely used in tropical cyclone research to estimate the minimum central pressure and the maximum velocity of tropical storms from environmental parameters. The MPI pressure derives from consideration of an idealized thermodynamic cycle, while the MPI velocity additionally requires information about real-time power and heat flows within the storm. Recently MPI velocity was proposed to be a substantial overestimate (by 10-30 percent) presumably neglecting the power needed to lift precipitating water (the gravitational power of precipitation). …
