244 MALKUS [chap. 4 



(iv) Pressure field and the oceanic heat source 



As just demonstrated, pressures and pressure gradients of the moderate 

 hurricane model are similar to those observed in storms of medium intensity 

 such as Dais3% 1958. Outward of r = 90 km, where ps^ 996 mb, the pressure 

 field may be maintained by a mixture of air with the characteristics of the 

 average tropical atmosphere and varying amounts of sub-cloud air that have 

 ascended in cumulus towers. The admixture of low-level air must increase 

 inward so that, at r = 90 km, the vertical temperature distribution becomes 

 entirely contrclled by the moist adiabatic ascent. Inward of r~30 km or 

 ^s~966 mb. a sloping eye wall may possibly be called upon to compute the 

 excessive pressure drop often encountered just inside the eye boundary. 

 Neither of these solutions can account for the pressure drop of approximately 

 30 mb between r = 90 km and r = 30 km. This must be related to adiabatic 

 ascent at increasing values of Q, and we are now prepared to relate the heating 

 quantitatively to ocean input. We shall first do this following trajectories in a 

 new "Lagrangian" approach to exchange and then in the old-fashioned areal 

 manner, in terms of mass, heat and moisture budgets. 



We first take the radial pressure field of Table XVII and deduce from it the 

 low-level potential temperature, d, and specific humidity, q, as a function of 

 radius from Fig. 69. These are entered in Table XVIII. The condensation level 

 (LCL) was determined (roughly) from film measurements of cloud base in Daisy 

 and the surface relative humidity, rh, follows. Table XIX gives the trajectory 

 distances and travel time for air particles by radial interval computed from 

 the data of Table XVII, and the sensible and latent heat increments experienced 

 by these particles in calories /gram. 



Table XVIII 

 Thermodynamic Properties of the Moderate Hurricane Inflow Layer 



r, ps, 6, T, q, rh, LCL, 



km mb °A °C g/kg % m 



One should expect that, following a particle, the heat transfer from the 

 ocean will be governed only by the differences in temperature and vapor 

 pressure between sea and air and wind speed. The subscript p will denote 

 calculations performed with respect to the moving particle. Denoting sensible 

 and latent transfer by Qsp and Qep, we may postulate that 



Qsp = ksr,u{TQ-Ta) (61) 



and 



Qep = kepU{eo-ea). (62) 



