Thermodynamic control of hurricane intensity.

“SST also affects the development and evolution of tropical storms and hurricanes and is correlated with nutrient concentration [4], [5].”

“While several studies have been carried out on the thermodynamic properties of tropical cyclones (e.g., Emanuel, 1986, 1987, 1999, 2003; Bister and Emanuel, 1998), the thermal dissipation process seems to have been missing from the previous work.”

“The result of divergence is local upwelling, which will transport water from depth to the surface [1], [2].”

“Emanuel [31] used a simple numerical model to establish the progress of hurricane intensity.”

“The stress of the winds upon the sea surface generates divergent outward flow at the center of the hurricane, prompting entrainment (vertical mixing) and upwelling [9], [10].”

“Typhoon-forced SST cooling is generally thought to be a result of vertical entrainment of deep cold water into the surface mixed layer (ML), whereas direct air–sea heat exchanges are considered to play a relatively minor role (Price, 1981 ; Emanuel, 1999 ).”

“For example, the surface water temperature decreases by 1– 6°C in response to a hurricane passage [Price, 1981; Dickey et al., 1998; Emanuel, 1999 ].”

“The heat exchange of the upper ocean layer under the core of a hurricane was found to be a critical factor affecting the intensity of tropical cyclones ( Emanuel, 1999 ).”

“The expected influence of the hurricane to the ocean waters is the strong cold wake along the hurricane track (Fisher, 1958).”

“Studies have revealed the relationship between typhoon intensity and the SST: the higher the SST, the higher the intensity that typhoon can achieve (Price 1981; Emanuel 1999; Lin et al. 2005, 2008, 2009; Moon et al. 2007; Wu, Lee, and Lin 2007; Lin, Pun, and Wu 2009).”

“Even so, many scholars attempted to testify the relations between the TC activities and the climatic signals such as the ENSO (Chan and Liu, 2004; Camargo and Sobel, 2005) and other climatic factors (Emanuel, 1999; Tu et al., 2009).”

“There have also been theoretical and numerical modeling studies identifying SST as a factor in hurricane activity [e.g., Emanuel, 1986, 1999; Schade and Emanuel, 1999].”

“…shear (VWS), strong upper-level divergence, high mid-level humidity, and warm sea surface temperature (SST) and TC heat potential (TCHP), all experiencing the seasonal, interannual and interdecadal scale variabilities (Emanuel 1986, 1999; Mainelli et al. 2008; Wang et al. 2015; Wang and Liu 2016).”

“One reason why predicting TC intensity is difficult is because it is largely determined by far less predictable internal dynamics that is modulated by the large-scale environment [Holland, 1997; Emanuel, 1999].”

“THE ROLE of cyclones in inducing the phytoplankton blooms through entrainment (vertical mixing and upwelling) has been long studied [1], [2].”

“Likewise, tropical cyclones generate high wind speeds near the surface out of the condensational heating of moist air (e.g., Emanuel 1999).”

“This is because a TC’s self-induced cooling is smaller under a faster Uh [4] and more air–sea enthalpy fluxes [11] can be made available for TC intensification [14].”

“As we know, the intense TC wind inevitably mixes the colder subsurface water to the surface, thus cooling local SST (Price 1981; Price et al. 1994; Emanuel 1999; Bender and Ginis 2000; Emanuel et al. 2004; Cione and Uhlhorn 2003; Lin et al. 2013).”

“Cooling of SST of 2.5K near the core of a tropical cyclone can effectively shut down the energy production and either weakens or destroys it (Emanuel 1999).”

“The magnitude of the upper-level acceleration of about 60 m s21 day21 due to the eddies in Fig. 2a is of the same order as when symmetric friction and diabatic heating are included (Fig. 3b of MS02). The induced acceleration in the lower troposphere due to the eddies is, however, very much weaker than that due to the…”

“…entrains cooler deeper water into the surface mixed layer (D’Asaro et al., 2007; Price, 1981), a process that lowers SST and acts as a negative feedback on the storm's intensity (Bender & Ginis, 2000; Cione & Uhlhorn, 2003; K. Emanuel et al., 2004; K. A. Emanuel, 1999; Schade & Emanuel, 1999).”

“In general, a greater SSC led to a greater suppression of storm intensification, known as a negative feedback (Bender & Ginis, 2000; Emanuel, 1999).”

“The TC destructive potential is measured by the integrated power dissipation (IPD; Emanuel, 1999b), which can be written as IPD = ∫ S ρCDV(r)3dS , (10) where the drag coefficient, CD, is calculated with the wind speed (Large and Yeager, 2008); and S is the integral area with the radius of…”

“down the energy production entirely (Emanuel 1999; Emanuel 2003).”

“E-mail: mmali110@gmail.com Received: 17 February 2013 Revised: 30 April 2013 Accepted: 30 April 2013 Keywords: cyclone intensity prediction change; artificial neural network approach; ocean heat content”

“The intensity of a TC is controlled by its internal dynamics and external ocean and atmosphere conditions in which the TC is embedded 6 , including vertical wind shear 7,8 , mid-atmosphere relative humidity 9,10 , sea surface temperature 11 (SST), and potential intensity 12 .”

“The intensifiedmegaENSO produces anomalous low-level negative vorticity and increased VWS and SLP, all suppressing TC genesis and intensification in the EWNP.”

“Moreover, SST influences the development of extreme wind events such as hurricanes and tropical cyclones [3], [4].”

“In particular, large SSTC in excess of 2.5 °C was found to be unfavorable for typhoon intensification (Emanuel 1999), and can even cause typhoon weakening (Schade and Emanuel 1999; Lin et al. 2008).”

“Ocean heat content has a major role in the formation and intensification of the storms (Emanuel 1999).”

“The critical latitude is determined in part by a velocity scale that is estimated by the TC potential intensity (PI; K. A. Emanuel, 1999), which is the theoretical maximum intensity a TC can attain in a given environment.”

“Much of the issue with intensity forecasting skill can be attributed to complex interactions between internal dynamics, TC structure, and surrounding air-sea environments (Emanuel, 1999; Kaplan et al., 2015; Wang & Wu, 2004).”

“Severe typhoons were not only attracted by warmer land surface, they were also enhanced before landfalls by extracting energy from warmer ocean surface (Emanuel, 1999).”

“Next, we explore if and to what extent the configurations of the initial and boundary conditions for WRF affect the storm surge prediction. a. Sea surface temperature Previous studies have highlighted the crucial roles of SST in determining the storm intensity (Emanuel 1999; Zhu and Zhang 2006b).”

“A key difference compared to other recently published methods [e.g., Schade and Emanuel, 1999; Lin et al., 2013; Balaguru et al., 2013] is the ability to account for TC shape and size via a small set of parameters, most important being the radial decay parameter 𝛽 .”

“…evolution of a TC event, including its genesis and the change of intensity and track, is influenced by the surrounding environment, air-sea thermal conditions, upper and lower airflow movements (Gray 1968; Emanuel 1999; Emanuel and Sobel 2013; Schade and Emanuel 2001; Jaimes et al. 2015), etc.”

“Typhoons (or hurricanes, tropical cyclones), when passing over the ocean, have both local (entrainment, vertical mixing, and upwelling) and non-local (horizontal advection, horizontal mixing, and pressure gradients) impacts on the ocean (Price 1981, Stramma et al. 1986, Emanuel 1999).”

“The warm ocean is the energy source for TC development, and TCs draw energy and moisture from the ocean through the enthalpy fl ux at the air – sea interface (Emanuel 1999).”

“Moreover, the potential intensity (PI) is a known major factor controlling TC intensity evolution (Emanuel, 1999), which describes the thermodynamically based maximum TC intensity that the environment will support and thus connects closely to TC genesis and intensification.”

“Because the ocean surface and subsurface thermal conditions have an important influence on tropical cyclone intensity [Leipper and Volgenau, 1972; Emanuel, 1999; Shay et al., 2000; Lin et al., 2005, 2008, 2009; Goni et al., 2009; Wada, 2009; Moon and Kwon, 2012; Pun et al., 2013].”

“Franklin et al. (2003) demonstrated that peak winds in hurricanes exist closer to the surface than previously accepted with average peak horizontal winds only 500– 750 m AGL.”

“Emanuel K-A (1999) Thermodynamic control of hurricane intensity.”

“…to atmospheric motion, for instance approaches using the proposed principle of Maximum Entropy Production (Paltridge, 1978; Ozawa and Ohmura, 1997; Lorenz et al., 2001; Ozawa et al., 2003) or applications to hurricanes and atmospheric convection (Emanuel, 1999; Pauluis and Held, 2002a, b).”

“Via air-sea enthalpy fluxes, the ocean provides an important energy source for TC’s strengthening [Emanuel, 1986, 1999; Shay et al., 2000; Black et al., 2007; Lin et al., 2008, 2009a, 2013a, 2013b].”

“Emanuel (1999) indicated that the heat exchange with the upper layer of the ocean under the core of the hurricane was one of the factors that determined the evolution of the TC’s intensity.”

“Emanuel (1999) concluded that after a storm reaches tropical-storm strength the intensity is dependent on the thermodynamics of the upper ocean layer and of the atmosphere Tellus 62A (2010), 5 along with other factors which are different for different basins and exhibits spatial and temporal…”

“As storms pass over the ocean, they entrain a great deal of heat from the upper warm water layer and induce vertical mixing of the seawater, causing upwelling, which decreases the SST and weakens the storms (Emanuel 1999).”

“Here we use the widely accepted PI estimate based on SST (SST_PI, Emanuel 1999) but also adapt it to create an average ocean temperature PI index based on initial ocean temperature through the top 50 m layer, to estimate TC T50m_PI.”

“The strong winds associated with typhoons cause vertical mixing and upwelling in the tropical and subtropical regions, which in turn cool the sea surface and deepen the ocean mixed layer along the storm track [5,6].”

“, Term2 = [ max ( V PI − 35 ) , 0 ]2 , Term3 = −4 3 , and Term4 = ( 25 + V sh )−4 , is the absolute vorticity at 850 hPa, VPI is the maximum tropical cyclone potential intensity (PI) defined by Emanuel (1999).”

“The evolution of TC intensity depends mainly on three factors: its initial intensity, dynamic and thermodynamic state of the atmosphere, and heat exchange with the upper ocean (Emanuel, 1988, 1999, 2005; Lin et al., 2013; Mei et al., 2015).”

“This coupling is vital for tropical cyclone (Sutyrin and Khain 1984; Bender et al. 1993; Emanuel 1999; Warner et al. 2010; Olabarrieta et al. 2012) and coastal, midlatitude cyclone (Anthes et al. 1983; Kuo et al. 1991; Ren et al. 2004; Eckhardt and Stohl 2004; Knippertz and Wernli 2010) simulations…”

“It should be noted that climate change has likely influenced the vulnerability of estuaries to eutrophication in several ways, including changes in mixing characteristics caused by alternations in freshwater runoff and changes in temperature, sea level, and exchange with the coastal ocean (Kennedy 1990; Peterson et al…”

“Observational (Gallina and Velden, 2002) and model studies (Frank and Ritchie, 2001) have identified an essentially linear relationship between lower (higher) magnitudes of VWS and intensification (dissipation) of TCs. Zehr (1992) observed that VWS above a threshold value of 12.5 m s−1 between 200…”

“0094-8276/12/2012GL053974 GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L22603, doi:10.1029/2012GL053974, 2012 L22603 1 of 6 deeper thermocline (Figure 1) which favours cyclogenesis [Emanuel, 1999; Ali et al., 2007].”

“Many studies found that high 850–200-hPa VWS, low RHUM and descent motion (Omega) limit the intensification of TCs (Emanuel 1999; Webster et al.”

“Consequently, the cold surface temperature modifies the typhoon intensity by blocking the following typhoons from gaining energy from the warm ocean surface [6,7].”

“SST cooling of about 2.5 °C under the typhoon core is found to be sufficient to shut down its energy production (Emanuel 1999).”

“Previous studies have shown that the relationship between SST and MPI is not perfect [29] and that the sensitivity of hurricane intensity to changes in SST varies across space [3, 30].”

“The SST cooling depends on many factors, such as the mixed layer depth, the thermocline depth and the air-sea heat fluxes (Emanuel, 1999; Lee and Niller, 2003).”

“It is dissipative in that its motion acts to dissipate or reduce the heat gradient between the upper and lower atmosphere, in the process exporting entropy to the surrounding air mass (see, e.g., the discussion of the thermodynamics of hurricane behavior in Emanuel 1999).”

“Initial temperature profile was taken typical of hurricane season (Emanuel, 1999; Jordan, 1958).”

“Higher SSTs translate to a higher maximum Potential Intensity for a hurricane [ Emanuel , 1999], suggesting that the anomalous warmth during October 2015 may have fueled Patricia’s extraordinary strengthening.”