PART IV — DYNAMICS OF THE ATMOSPHERE-OCEAN SYSTEM 



raincoats, farm implements), fuel and 

 power companies, agriculturalists, 

 construction companies, and com- 

 modity market men, to say nothing 

 of vacationers. Aside from this, long- 

 range forecasting, by setting the cli- 

 matic background peculiar to a given 

 month or season, is of distinct value 

 to the short-range forecaster. For ex- 

 ample, it can alert him to the likeli- 

 hood of certain types of severe 

 storms, including hurricanes, intense 

 extratropical cyclones, and even broad 

 areas most frequently vulnerable to 

 tornadoes. 



Most of the needs of these groups 

 for long-range forecasts cannot pres- 

 ently be met, however, because of the 

 low skill level of predictions or the 

 inability to predict anomalous weather 

 at ranges beyond a month or season. 

 Why is the problem so intractable? 



The General Problem 



In the first place, long-range fore- 

 casting requires routine observations 

 of natural phenomena over vast areas 

 — and by vast we mean at least 

 hemisphere-wide coverage in three 

 dimensions. More probably, the en- 

 tire world's atmosphere, its oceans 

 and its continents, must be surveyed 

 because of large-scale interactions 

 within a fluid that has no lateral 

 boundaries but surrounds the entire 

 earth. In contrast to the physicist, 

 the meteorologist has no adequate 

 laboratory in which to perform con- 

 trolled experiments on this scale, al- 

 though some recent work with elec- 

 tronic computers holds out hope for 

 useful simulation. 



Inadequate Observational Net- 

 works — When the immense scale of 

 the atmosphere is realized, it becomes 

 clear that the present network of 

 meteorological and oceanographic ob- 

 servations is woefully inadequate. 

 Even in temperate latitudes of the 

 northern hemisphere, relatively well 

 covered by surface and upper-air re- 

 ports, there are "blind" areas of a 

 size greater than that of the United 



States. The tropics are only sparsely 

 covered by reports, and the data cov- 

 erage in the southern hemisphere is 

 poorer still. 



In the southern hemisphere, a moat 

 thousands of miles in diameter sepa- 

 rates the data-rich antarctic continent 

 from the temperate latitudes, making 

 it virtually impossible to get a coor- 

 dinated picture of what is occurring 

 now, let alone what may occur in the 

 future. The "secrets of long-range 

 forecasting locked in Antarctica" — a 

 cliche often found in press articles — 

 are indeed securely locked. Of course, 

 cloud and radiation observations from 

 satellites are assisting to an ever in- 

 creasing degree, but better methods 

 of determining the atmosphere's pres- 

 sure, wind, and temperature distribu- 

 tion from satellite and other types of 

 observations are urgently needed. 



Inadequate Understanding — Even 

 if every cubic mile of the atmosphere 

 up to a height of 20 kilometers were 

 continuously surveyed, however (and 

 there are 2,500 million such volumes), 

 reliable long-range forecasts would 

 still not be realizable. Regardless of 

 their frequency and density, observa- 

 tions are not forecasts; they merely 

 provide "input data" for extended 

 forecasting. Meteorologists have yet 

 to develop a sufficient understanding 

 of the physics of the atmosphere and 

 the ocean to use these input data 

 effectively in long-range forecasting, 

 although this understanding is un- 

 likely to come about in the absence 

 of such data. 



The Present Situation 



The Data Base — Today the data 

 and facilities for making long-range 

 forecasts, inadequate as they may be, 

 are far better than ever. In addition 

 to about 25,000 surface weather re- 

 ports (22,000 over land and 3,000 

 over sea) available each day at a 

 center like Washington, there are 900 

 balloon observations of wind direc- 

 tion and speed, and 1,500 radiosonde 

 observations of upper air pressure, 



temperature, and humidity and, fre- 

 quently, wind. In the same 24-hour 

 period about 1,300 aircraft reports, 

 dozens of indirect soundings of up- 

 per air temperatures made by the 

 Nimbus-SIRS satellite system, and 

 hundreds of satellite cloud photo- 

 graphs are received. 



While these figures are impressive 

 they are inadequate, especially be- 

 cause they represent a most tineven 

 geographical array of observations 

 and neglect proper surveillance of the 

 ocean. The vast blind areas are, un- 

 fortunately, located in important wind 

 and weather system-generating areas, 

 like the northern Pacific Ocean, the 

 tropics, and parts of the southern 

 hemisphere. These systems, once 

 generated, soon influence weather in 

 distant areas around the world, their 

 complex effects often traveling faster 

 than the storms themselves. Hence, 

 if an area is especially storm-prone 

 during a particular winter, the storms 

 will persistently influence other areas 

 thousands of miles distant, sometimes 

 leading to floods or droughts. Obvi- 

 ously, if the wind and weather char- 

 acteristics in the primary generating 

 area are imperfectly observed one 

 cannot hope to predict the distant 

 responses. 



As pointed out earlier, data alone, 

 regardless of how extensive in space 

 and how frequent in time, are not 

 sufficient to insure reliable long-range 

 forecasts. It does appear, however, 

 that more data of special kind and 

 accuracy are required if a successful 

 solution is to be obtained. The kinds 

 of data required and a rough estimate 

 of the density will be discussed later. 



State of the Art — Forecasts can be 

 made for future days by using elabo- 

 rate numerico-dynamical methods and 

 high-speed computers. In these meth- 

 ods, one predicts various meteoro- 

 logical elements at many levels for 

 successive time-steps. The approach 

 always begins with the initial condi- 

 tions observed at many levels at a 

 certain time over a large area like the 

 northern hemisphere and forecasts 



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