Ping Huang, I-I Lin*, Chia Chou, Rong-Hui Huang Nature Communications, May 2015

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Price 1981 Uncoupled .vs. coupled Bender and Ginis 2000; Shay et al. 2000; Emanuel et al. 2004; Lin et al. 2005; 2013; 2014; Moon et al. 2007; 2008; Wada and Usui 2007; Wu et al. 2007; Goni et al. 2009; Balaguru et al. 2012; D’Asaro et al. 2014….. Price 1981 3

Assume Tair = 27℃, SST = 29℃, SLP =930mb, Qair = 20g kg-1 The effect of SST cooling in latent heat flux and sensible heat flux estimation transfer coefficients of CBLAST of Black et al., 2007. 4

Ocean coupling (cooling effect) Important: Ocean coupling (cooling effect) reduces air-sea latent and sensible heat fluxes

Q. SST warming and TC intensification, is it really that simple? Emanuel Nature 2005: uncoupled Vecchi and Soden Nature 2007: uncoupled Murakami et al. JC 2012; Sugi et al. GRL 2015: Uncoupled Emanuel et al. PNAS 2013: coupled but without updating the ocean subsurface field Knutson et al. JC 2001: Coupled, CMIP2 Bender et al. Science 2010: Coupled, CMIP3 mean profile, no ensemble spread Atlantic Knutson et al. JC 2015: Coupled, fixed future ocean mixed layer Huang, Lin et al. 2015: Coupled, CMIP5, 22 ensemble members with spread Emanuel JC 2015: Coupled, CMIP5, 7 ensemble members with spread 6

Huang, Lin et al. Nature Comm. 2015

Huang, Lin et al. Nature Comm. 2015 Emanuel JC 2015

Huang, Lin et al. Nature Comm. 2015

Emanuel 1988; Bister and Emanuel 1998 Intensity upper bound, but large error Emanuel 1988; Bister and Emanuel 1998 T_mix is determined by Pre-tc ocean profile, b. TC translation speed, c. TC size, d. wind speed. (Price 2009)

Vecchi and Soden Nature 2007

Huang, Lin et al. Nature Comm. 2015 Emanuel JC 2015

Summary ★ Under global warming, subsurface ocean warms SLOWER than surface ocean, thus ubsurface ocean temperature gradient sharpens (stratification increase), based on 22 CMIP5 Ocean models. This is found in both the main development regions (MDRs) of Western North Pacific and North Atlantic. ★ This sharpening increases tropical cyclone (TC) – ocean coupling (cooling) effect under global warming, thus is a previously undiscovered additional OFFSET to restrain TC intensification under global warming. ★ It appears the situation may not be as pessimistic, as predicted by the uncoupled projections.