SECT. 2] 



LARGE-SCALE INTERACTIONS 



173 



computations from actual Mind data (cf, Palmen, 1955; Palmen and Alaka, 

 1952; Palmen, Riehl and Vuorela, 1958). 



The Cn profile of Fig. 34 is now used to compute the lateral moisture inflow 

 by the mass circulation. The resulting import of 0.80 units exceeds the balance 

 requirement of 0.63 units found from Qe — LP. Although this discrepancy may 

 arise from uncertainties in any or all calculations (particularly the neglect of 

 Qvo, which if it were 20% Qc would exactly account for it), one would actually 

 expect poleward moisture export from the region by eddies. Observational 

 studies show significant correlation on the synoptic scale between high moisture 

 content and winds blowing out of the equatorial zone. Hence this difference of 

 0.17 units has been called "eddy moisture export". Fig. 35 summarizes the 



E 500 



RodiQlion -0.44 



1.29- 



mass outflow 



protected cores 



downdroft 2.41 



0.17 - 

 eddy 



Radiation -0.56 



0.38 0.93 



Distance (°lat.) from equatorial trough 



Fig. 35. Heat budget for winter side of equatorial trough zone. (After Riehl and Malkus, 

 1958, Fig. 18.) 



Fluxes in lO^^ cal/sec for 10" -latitude belt. Troposphere divided into two layers, 

 1000-500 mb and 500-125 mb. Vertical arrows through 500 mb surface denote fluxes 

 required for joint heat energy and mass balance in each layer, hypothesized due to 

 protected cumulonimbus cores partially compensated mass-wise by downdrafts. 



lateral fluxes oi Q = CpT + Agz + Lq in the layers 1000-500 mb and 500-100 mb. 

 These fluxes have been tabulated separately in 100-mb layers in the original 

 work by Riehl and Malkus (1958). In the lower layer, the mean circulation 

 import (solid arrow labelled "mass inflow") is 28% in the form of h (largely 

 CpT at low levels) and 72% in Lq or latent heat. The 34% larger upper export, 

 on the other hand, is 98% in the form of sensible heat and potential energy. 

 We shall now examine the combustion process within the "firebox" which 

 converts the moisture, thereby also providing the thermal distribution respon- 

 sible for the pressure head. 



