h9 



linear decrease of the effective back radiation with cloudiness while this 

 decrease goes with the cube in the case of the incoming short-wave radiation-- 

 This example throws some light on the most difficult problem we are faced 

 with: to develop formulae for the different components of the radiation 

 balance in which the influence of cloudiness is adequately assessed. There 

 may be some doubt about whether this will ever be possible with the present 

 system of estimating only the amount and kind of clouds and the altitude of 

 their base. In any case, much more routine measurements of the different 

 components of radiation are urgently needed at sea. 



Since more than 15 years ago a remarkable network of ocean weather ships 

 has been working continuously and at fixed positions in the North Atlantic 

 and the North Pacific Oceans • Thes e stations have assembled an amount of 

 meteorological data which are uniqu.= in marine meteorology. Unfortunately, 

 radiation measurements have been included in the observational program of 

 some of those stations but during the last years, practically since the 

 International Geophysical Year (IGY). Now some relevant publications have 

 come up. I would like to mention that of Ashbum (1963) which presents 

 daily and mean monthly data on total incoming radiation from sun and sky for 

 2 years at the North Pacific ocean station "Papa" as well as some values of 

 net radiation. With regard to the influence of cloudiness a new formula 

 ( the 11th as far as I can see) is offered which seems to represent the 

 measured data better than the other ones. This is but a beginning. Many 

 additional measurements will be necessary to determine the precision of the 

 measui^ments sxid to develop an equation expressing the total incoming radia- 

 tion received at the ocean surface as a function of the known physical 

 variables such as cloud types, cloud thickness, solar zenith distance and 

 albedo of the sea surface . 



A more sophisticated approach regarding the influence of cloudiness 

 was made by Lumb {l96h) . Using radiation measurements made on British 

 ocean weather ships he suggested a relationship for the total incoming 

 radiation during short periods (l hour) depending on different cloud 

 categories and the average solar altitude during that period. 



These first results should be warmly welcomed but much more radiation 

 measuring must be done on the oceans - both close to the sea surface and 

 also at upper levels - before we will have sufficient evidence about the 

 contribution of radiative fliixes to the energy balance of the atmosphere 

 and the ocean surface and before we will arrive at a marine climatology of 

 radiation which is based on really measured values. Certainly, the 

 instrumental and operational difficulties are great but not insurmountable 

 if scientists and engineers would recognize the challenge of this task. 

 Substantial progress could then be achieved. In addition to radiometers 

 installed on ships and buoys, such instruments could be carried by planes 

 and satellites and thus fill the gaps between the necessarily wide network 

 of radiation measuring stations in the marine boundary layer. Relevant 

 investigations have already been made . I would like to refer to Clarke 

 (1963) who presented observations of the long- wave radiative flux in the 



