300 



200 



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 300 



200 



J FMAM J J A S O N D J J FMAM J J A SONDJ J FMAMJ J ASONDJ J FMAM J JA SONDJ 



I I I I I I I I I I I I I I I I I I I I I I I I I I I I I [ I I I I I I I I I I I I I I I I I I I I I I 



50° N 40° N 34° N 27° N 



E 



» 100 



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J FMAM J J AS N D J J F M A M J J A S O N D J J F M A M J J A S O N D J J F M A M J J A S O N D J 



M ill I I I I I I I I 



34° N 

 128°W 



300 



200 



--100 



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I I I I I I I I I I I I I 



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J FMAM J J A S ON D J J F M A M J J A S N D J J F M A M J J A S N D J J F M A M J J A S O N D J 



Figure 19.— Mean annual cycles of heat exchange processes for the 1° squares at lat. 50°N, 40°N, 34°N, and 27°N near the coast and 10° offshore. The u 

 displays 1 ° square values at the coast and the lower row displays the offshore exchange processes. I denotes values of Q s ; 2 denotes Q s - Q B ; 3 denotes Q S ~Q B - Ue< 

 the heavy line denotes Q N = Q s -Q b -Qe~ Qc- The hatched regions between 1 and 2 denote the magnitude of Q B and the stippled regions between 2 and 3 indicate 

 magnitude of Q E . The annual mean net heat exchange ((? v ) is indicated for each location. Units are VV/m-. 



upper row 



Q E , and 



the 



tion of solar radiation at the coastal square at lat. 27°N with the 

 minimum value of 1 3 1 W/m- in December and the maximum value 

 of290W/m : inJune. 



The annual range of monthly Q, values is larger in the coastal 

 •upwelling areas off northern California and Oregon than in the cor- 

 responding squares offshore, which primarily reflects the effect of 

 relatively low cloud cover in summer when the input of solar radia- 

 tion is the highest. The range is largest near the coast at lat. 40°N 

 and 50°N where values range from <50 W/m ; in winter (Chart 12) 

 to more than 200 W/m 2 in summer (Chart 6). The lack of well- 

 defined maximum in solar radiation in the offshore squares at lat. 

 27 °N and 34 °N is indicative of the extensive area of low-level stra- 

 tocumulus clouds previously discussed. 



The hatched areas between the two topmost curves for each loca- 

 tion in Figure 19 indicate the annual cycles of heat loss due to effec- 

 tive back radiation. Q B . This term shows little seasonal or 

 latitudinal variation over the entire California Current region. 

 However, there is a tendency for lower values in summer (Chart 1 8) 

 than in winter (Chart 24). except near the coast between San Fran- 

 cisco (lat. 38°N) and Vancouver Island (lat. 50°N). The principal 

 gradients in the distributions of Q„ are zonal and reflect the sharp 

 increase in mean cloudiness from the coast toward midocean. The 

 higher mean cloud cover offshore reduces the magnitude of the net 

 long-wave flux emitted from the sea surface to approximately 20 

 \Y in ' . Near the coast the estimated heat loss exceeds 50 W/m : . The 

 effects of horizontal variations in cloud cover on Q B are enhanced, 

 but to a lesser extent, by corresponding increases in atmospheric 

 vapor pressure in the offshore direction, and moderated by warmer 



sea surface temperatures offshore with respect to conditions near 

 the coast. 



The annual cycles of latent heat flux from ocean to atmosphere 

 are shown in Figure 19 by the stippled regions between curves 2 

 and 3. Variations in the latent heat flux are related to fluctuations in 

 windspeed and sea-air vapor pressure differences. The principal 

 seasonal variations in Q E occur in the nearshore areas particularly 

 between Cape Mendocino and the Columbia River. In this region, 

 the presence of cold upwelled water at the sea surface in summer 

 cools the air. lowers the vapor pressure of the air close to the satura- 

 tion vapor pressure at the sea surface temperature, and effectively 

 suppresses latent heat flux. This effect is noted by minimum values 

 of latent heat flux in a narrow coastal zone from Cape Mendocino 

 to Vancouver Island during June, July, August, and September 

 (Charts 30-33). In this region the latent heat flux is lowered to val- 

 ues of < 5 to 20 W/m 2 . In certain locations the turbulent flux may 

 actually be from atmosphere to ocean (i.e., condensation). The 

 nearshore areas south of lat. 40°N are characterized by relatively 

 constant values of Q E , about 50 to 70 W/m 2 . except in the upwelling 

 regions south of Punta Baja (lat. 30°N) and south of Punta Eugenia 

 (lat. 27°N) in spring and summer. Latent heat flux decreases to val- 

 ues of 30 to 40 W/m : at these locations due to the depression of the 

 sea-air vapor pressure difference. 



Seasonal variations in Q E are less pronounced in the offshore 

 regions. Higher mean windspeeds and larger sea-air vapor pressure 

 differences contribute to evaporative fluxes which are 30 to 100% 

 greater in winter (Chart 36) than in summer (Chart 30). Horizontal 

 gradients of Q E lie in a southwest-northeast direction and values of 



26 



