Thermodynamic control of hurricane intensity.

“[4] The notion that the strong wind associated with tropical cyclones causes entrainment (vertical mixing) and upwelling [Price, 1981; Emanuel, 1999] in the tropical and subtropical oceans - whereby deep-layer cold, nutrient-rich water is brought to the light-replete euphotic zone to fuel…”

“Forecasts of TC motion have improved steadily over the last three decades, mostly due to a combination of better observations, especially the satellite (Soden et al, 2001) and dropsonde (Burpee et al, 1996; Tuleya and Lord, 1997; Aberson and Franklin, 1999) data; improvements in dynamical models (Kurihara et al, 1998)…”

“…condition for intensification, because such cooling would be sufficient to shut down the entire energy production of a storm (Gallacher et al. 1989; Emanuel 1999; Emanuel 3 Note: QH cp n i 1 T(x, y, zi, t) Z, where cp is the capacity heat of the seawater at constant pressure taken as 4178 J kg 1…”

“Since the ocean feedback on tropical cyclone intensity varies nearly as the square of the unperturbed ocean mixed-layer depth (Schade and Emanuel 1999), a unit decrease in ambient mixed-layer depth exerts more influence on storm intensity than a unit increase does.”

“The depth of these layers is directly related to global climate sensitivity (Hasselmann, 1976) and affects weather predictions (Emanuel, 1999).”

“Since storms are fueled by moisture convergence, storm-related extremes are expected to increase in a moister atmosphere (Emanuel 1999; Trenberth et al. 2003).”

“However, since the energy source (i.e., air-sea fluxes) for intensification comes from the ocean, i.e., ocean is a necessary condition in intensification [ Emanuel, 1999 ].”

“…fifth-generation Pennsylvania State University–National Center for Atmospheric Research (Penn State–NCAR) Mesoscale Model (MM5; Grell et al. 1994), Frank and Ritchie (1999) produced a behavior similar to that shown by Jones (1995) in environmental shears ranging between 5 and 15 m s21 between…”

“In terms of TC intensity, Evans (1993) found no statistically significant relationship between SST and the average intensity of TCs, although she did find that individual TCs were generally more intense over waters of higher temperature.”

“Scalar transport is important in the mixed layer, especially so for OBLs under high wind conditions since entrainment cooling can alter the development of tropical cyclones (e.g. Emanuel 1999, 2004).”

“…difficult to predict in reality ( 6 ) because of various internal and environmental factors involved in the evolution of TC intensity ( 7 , 8 ), such as vertical shear of horizontal winds in the troposphere ( 9 ) and interaction of the TC with the ocean ( 8 , 10 – 14 ) The challenge…”

“Historical oceanographic observations and satellite imagery show that an intense, slowly moving hurricane may cool the sea surface by 28–68C, which is comparable to the typical air– sea temperature difference (Price 1981; Emanuel 1999; Zedler et al. 2002).”

“…that PI (measured by maximum surface wind) has an explicit dependence on sea surface temperature (SST), air temperature of the outflow layer in the upper troposphere, the ratio of the exchange coefficient to the drag coefficient at the air sea interface (Ck/CD), and maximum entropy…”

“Warmer SST tends to create a favorable thermodynamic condition for tropical cyclones through the air‐sea heat flux exchange ( Emanuel 1999 ).”

“…topic because intensifica-tion is a complex process involving multiple interactions among the cyclone, ocean, and atmosphere (Gray 1977; Merrill 1988; Emanuel 1995, 1997, 1999, 2005; Shay et al. 2000; Frank and Ritchie 2001; Emanuel et al. 2004; Lin et al. 2005, 2008, 2009; Trenberth 2005;…”

“…derived for a given atmospheric thermodynamical profile and sea surface temperature (SST) [ Emanuel , 1988; Holland , 1997], but many internal and environmental processes can significantly limit the actual achievement of this maximum value [ Merrill , 1988; Emanuel , 1999; Emanuel et al. , 2004].”

“The dissipation rate per unit area is the MF times the wind speed (Emanuel 1999).”

“[3] Uncertainties in TC intensity forecasts are mainly related to three key factors: storm inner core dynamics, structure of the atmospheric synoptic scale environment, and interactions with upper-ocean layers [Emanuel, 1999; Marks and Shay, 1998].”

“…TC moves too slow, cooling induced by turbulent mixing generated by the surface wind stress curl under the TC will disrupt the intensification (Schade and Emanuel 1999; Schade 2000), while if it moves too fast the resulting asymmetric structure will also inhibit intensification (Peng et al. 1999).”

“Hurricanes draw energy from the ocean in the form of sensible and latent heat fluxes that result from very high wind speeds and a rather small temperature difference between the subtropical atmosphere and warmer sea surface, typically only a few C (Emanuel, 1999).”

“the generation and dissipation of atmospheric motion [12] and associated optimality [13–15], the intensity of hurricanes [16], hydrological processes at the land surface [17,18], the atmospheric branch of hydrologic cycle [19,20], ocean dynamics [21,22], and, obviously, geochemical transformations.”

“Most storms never reach their PI (Merrill 1988, figure 1; DeMaria & Kaplan 1994, figure 1; Emanuel 1999).”

“Although Rayleigh–Bénard convection is the best-known example, similar threshold phenomena give rise to vortices in Taylor–Couette flow (Koschmieder 1993) and occurs naturally under the form of tornadoes and hurricanes (Emanuel 1999).”

“Theory and numerical models predict that as SST rises, the maximum potential intensity that storms can reach will increase, enabling more powerful hurricanes (Emanuel, 1999; Elsner et al., 2008).”

“For example, a simple coupled model of an axisymmetric hurricane model and one-dimensional ocean model can significantly improve the intensity predictions if the negative feedback of the sea surface temperature to TCs is taken into account (Emanuel 1999).”

“PI (Emanuel, 1999) is a representation of the hurricane’s thermodynamic environment.”

“Consequentially, SST and hence energy supply (i.e., enthalpy (sensible + latent) heat fluxes) from ocean to TC reduces [Emanuel, 1999; Bender and Ginis, 2000; Emanuel et al., 2004; Lin et al., 2013a].”

“For instance, a modest 1 C cooling can lead to a 40% decrease in surface enthalpy fluxes [Cione and Uhlhorn, 2003], while a 2.5 C decrease seems sufficient to shut down energy production entirely [Emanuel, 1999].”

“As typhoons intensify by extracting energy from the warm ocean surface, the underlying sea surface temperatures (SSTs) are critical for their development 5 .”

“More importantly, this wake forms underneath the typhoon, decreasing the sea surface temperature, thereby reducing the energy supply to the storm and limiting its intensity (Emanuel, 1999; Lin et al., 2008, 2009).”

“D model are captured by a strictly AX model (Anthes et al., 1971; Emanuel, 1991, 1999; Bryan et al., 2010).”

“Typhoon-induced winds can cause entrainment, strong vertical mixing, and upwelling, as well as the cooling of near-surface water on the right-hand side of the storm track [ Hazelworth , 1968; Dickey and Simpson , 1983; Stramma et al. , 1986; Sanford et al. , 1987; Price , 1981; Emanuel , 1999].”

“10d), the cyclone-phase SST could drop to 24 C (black curve), a low SST unfavorable for intensification (Emanuel 1999; Emanuel et al. 2004; Lin et al. 2005, 2008).”

“2004]. Extrapolations of the current parameterizations to hurricane wind speeds are inconsistent with theoretical analyses of the potential strength of tropical cyclones [ Emanuel, 1995, 1999 ].”

“For instance, Emanuel [22] found that cyclones dissipate less rapidly above the swamps in Florida and this may be important also in other areas such as, e.”

“…indicate a leveling off of the surface drag coefficient between 28 and 33 m s 21 (Powell et al. 2003; Donelan et al. 2004; Shay and Jacob 2006; French et al. 2007; Jarosz et al. 2007; Sanford et al. 2007), and C K /C D becomes independent of wind speed (Black et al. 2007; Drennan et al. 2007;…”

“In particular, a large SSTC of greater than 2.5 °C is considered not conducive to typhoon strengthening (Emanuel, 1999) and may even lead to typhoon weakening (Lin et al., 2008; Schade & Emanuel, 1999).”

“The TC-induced instantaneous cooling is a negative feedback ontoTC intensity by reducing air–sea heat fluxes (e.g., Brand 1971; Emanuel 1999; Schade and Emanuel 1999; Bender and Ginis 2000; Cione and Uhlhorn 2003; Bell and Montgomery 2008; Mei et al. 2012; Vincent et al. 2014).”

“The vertical zonal wind shear (VZWS) was defined as the difference of zonal winds between 200 and 850 hPa in this study, which is one of the major environmental factors affecting TC genesis over theWNP (e.g., Emanuel 1999;Wang and Chan 2002; Liu and Chan 2013; Zhan and Wang 2017).”

“Typhoon forced sea surface cooling is generally believed to be the results of vertical entrainment of the deep cold waters up to the upper ocean mixed layer [Price, 1981; Emanuel, 1999].”

“The potential intensity (PI), a theoretical limit to the maximum intensity that can be achieved by a TC, provides a framework to evaluate the ability of the ocean-atmosphere thermodynamic state to promote TC growth [Emanuel, 1999].”

“…(s−1), Vshear is the magnitude of the vertical wind shear (ms−1) between 850 hPa and 200 hPa, and Vpot is the maximum tropical cyclone potential intensity (PI) (ms−1) defined by Emanuel (1986, 1995, 1999) andmodified by Bister and Emanuel (1998, 2002) to take into account of dissipative heating.”

“This has been referred to as the SST feedback mechanism (Schade and Emanuel 1999).”

“…for RI, with a general consensus that TCs are likely to undergo RI when they form and develop over a region with large upper-ocean heat content (Emanuel 1986, 1999; Bender and Ginis 2000; Shay et al. 2000; Goni and Trinanes 2003; Lin et al. 2005, 2008, 2011; Black et al. 2007; Mainelli et al.…”

“Generally speaking, the TC-induced SST cooling plays a negative feedback role in TC intensification (e.g., Schade and Emanuel 1999; Cione and Uhlhorn 2003).”

“The hydrographical and biochemical responses to tropical typhoon in the upper ocean are mainly due to vertical turbulent mixing and upwelling by strong wind filed [Stramma et al., 1986; Emanuel, 1999 ].”

“…correlates with mean annual tropical temperature, thus this result is consistent with the hypothesis that tropical temperatures may directly regulate the integrated intensity of TCs. Citation: Sriver, R., and M. Huber (2006), Low frequency variability in globally integrated tropical cyclone…”

“…intensity is difficult to simulate correctly for a number of reasons related especially to initialization, feedbacks (e.g., from ocean and SST changes) and inner core dynamics [Emanuel, 1999], and these are documented and tested in detail for the WRF model in the work by Davis et al. [2007].”

“These air–sea fluxes are the primary contributors to the energy budget of a tropical cyclone and therefore greatly affect the storm intensity (see Emanuel 1991, 1999).”

“Tropical cyclones (TCs) intensify by convective release of latent heat drawn from the sea (e.g., Emanuel 1999).”

“As pointed out by Bender and Ginis [1], Emanuel [3], Emanuel et al. [4], and Shay et al. [32], this is not realistic because cyclones interact not only with the surface but also with the entire upper ocean column (typically down to 200 m).”

“The model simulations of Emanuel (1999) suggested that the evolution of the intensity of TCs is controlled mostly by their initial intensity along with the thermodynamic profile of the atmosphere and upper ocean through which they move.”

“required in order to obtain a better understanding of the intensification process (Emanuel 1999; Emanuel et al. 2004).”

“(1985), subgrid-scale cumulus convection parameterized with KUO’S (1974) scheme, a Newtonian cooling as used in the TC model by Rotunno and Emanuel(1987), and surface fluxes of momentum, sensible and latent heat calculated by the bulk aerodynamic method, in which the exchange coefficients are determined from the formu…”

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

“The SST reduction under an individual cyclone has been studied for its influence on later cyclones that cross its path (e.g., Brand 1971) or on the same one that itself induces the cooling (e.g., Schade and Emanuel 1999; Emanuel 1999 ).”

“Considering that air-sea coupling generates typically a negative feedback on the intensity of tropical cyclones, through vertical mixing of the oceanic column (Emanuel 1999), we could expect a similar intensity reduction on medicanes, at least for the most intense cyclones.”

“Thermodynamics has been used, for nstance, to expla n the intensity of hurricanes (Emanuel, 1999), or to describe hydrologic cycling in the context of vertical convection as a dehumidifier (Pauluis and Held, 2002a,b; Pauluis, 2011).”

“The most intense storm that can be sustained at a given place can be estimated from the PI value [Emanuel, 1999].”