RKOT. 2] LAROK-SCALE INTKRAOTIONS 151 



Tlie solution from (1) for the sum Qs + Qe was carried out, using climatological 

 data, for each month of the year, althougli the meteorological study was 

 restricted to two particular winter months. The Caribbean Sea is particularly 

 suited for this purpose. A small, nearly enclosed water body, it contains one 

 well-defined sea current with entrance in the Lesser Antilles and exit in the 

 Yucatan Channel (see Fig. 25). Plentiful oceanographic data permit direct 

 estimates of Qro and iS in (1) and their seasonal march, as we shall see. 



The computation of the radiation balance R of the ocean surface is sum- 

 marized in the first eight entries of Table XI. Monthly values of the incoming 

 radiation at the top of the atmosphere for the latitude belt 10°-20°N were 

 adopted from the Smithsonian Tables (List, 1951). Monthly values of atmos- 

 pheric transmissivity were adjusted from London's (1957) seasonal results, 

 ignoring local departures from the latitudinal average water-vapor, ozone and 

 cloudiness structure. The insolation reaching the earth's surface was then 

 entered in line 3, Table XI. Absorption by the sea (line 4) was calculated using 

 a constant 6% albedo throughout the year. 



The net long-wave radiation loss by the sea surface was obtained for cloudless 

 conditions from Sverdrup's (1942) graph, which gives Qbo as a function of water 

 temperature and relative humidity at ship's deck level. The magnitudes of the 

 actual Qb for cloudy skies were obtained from equation (5a) and London's 

 monthly values of cloudiness in the belt 10°-20°N (line 6, Table XI). Qb appears 

 in line 7, Table XI, and the final result for R, the radiation balance of the 

 Caribbean Sea surface, in line 8. 



The absorbed short-wave radiation (line 4, Table XI) is greatest in April and 

 May and least in December, with a range about 30% of the annual mean. 

 Seasonal differences result mainly from variations in solar altitude and mean 

 cloudiness ; the latter is especially important in the warm season. During June, 

 July and August, the sun's height is about the same as in April and May but 

 the cloudiness is much greater. Since Qb changes little (slight opposite seasonal 

 march to that of cloudiness), the radiation balance varies in phase with the 

 short-wave absorption. It decreases from a maximum of about 10.2 kg cal cm~2 

 per month ( ~ 340 cal cm~2 day~"i) in May to a minimum of 6.3 kg cal cm~2 per 

 month (210 cal cm~2 day^i) in December, a range 42% of the annual mean. 



Fig. 26. Meteorological conditions over the Caribbean region in December, 1956, typical of 

 winter season. (After Colon, 1960, Figs. 3, 4 and 7.) 



(a) The low-level flow patterns at the 850 mb (~ 5000 ft) pressure surface. Stream- 

 lines are solid lines with arrow-heads. Isotachs (knots) are dashed lines. Min. denotes 

 regions of low windspeed ; Max. denotes regions of high windspeed. 



(b) The high-level (upper troposphere) flow patterns at the 200 mb (~ 40,000 ft) 

 pressure surface. Streamlines are solid lines with arrowheads. Isotachs (knots) are 

 dashed lines. 



(c) Typical vertical wind-profile with height. Station depicted is Guantanamo at 

 the southeastern tip of Cuba. Wind-speed profile solid line ; wind-direction profile 

 dashed line. Vertical co-ordinate is pressure in lOO's of millibars. 



(d) Vertical profile of directional wind steadiness in per cent. Ordinate is pressure in 

 lOO's of millibars. 



