48 



NA TURE 



[NoVEMliER II, 1909 



•different lemperatures. The second is, of course, tlie more 

 desirable plan, but tlie difficulties involved in applying it 

 to the larger type of instrument are so considerable that 

 the former method is generally adopted where such instru- 

 ments are used. The simplicity of the smaller type of 

 instrument devised by Dines enables the second method to 

 be adopted in testing it, without elaborate and expensive 

 apparatus. 



Temperature records obtained simultaneously with 

 different instruments show differences which, in the mean, 

 do not exceed 1° C, and the temperatures may, in general, 

 hi taken to be correct to this degree of accuracy, but 

 lagging of the instruments makes it doubtful if in all 

 cases the recorded temperatures and heights actually 

 correspond. 



In dealing with the observations, it is found convenient 

 to express temperatures in degrees C. above the absolute 

 zero, —273° C. on the ordinary scale. Where necessary 

 the letter A is used to characterise this scale. Atmospheric 

 temperatures, both at the surface and in the upper air, lie 

 almost always between 200° A and 300° A, so that the 2 

 may be dropped without risk of confusion. Gradients of 

 temperature are expressed in degrees C. per km., and are 

 reckoned + when temperature decreases upwards. 

 . The mean value of the gradient up to 3 km. is as 

 follows ; — 



From the Berlin manned balloon ascents, i888-i8q7 5't 



,, ., ,. . 1897-1907 4'6 



,, [Berlin and Lindenbe'g kite ascents 47 



Calculated by Hann from mountain observations 57 



It follows from these results that the mountains are 

 colder than the free atmosphere at the same height, and 

 many observers have verified this fact by direct com- 

 parison. Shaw and Dines found that in July, 1902, the 

 temperature on Ben Nevis was 2-6° C. below that of the 

 free atmosphere at the same height to the west of the 

 mountain. Schmauss found that the temperature on 

 Zugspitze (nearly 3000 m.), which lies on the northern 

 edge of a mountainous region, was continually lower than 

 that of the free atmosphere, but was higher than that at 

 the same height on Sonnblick, which lies in the middle 

 of the Alps. 



It was pointed out by Von Bezold that increase of 

 temperature on a mountain is limited by convection, 

 whereas no immediate limit is set in this way to cooling. 

 There is a onc-sidedness in the heat exchange between 

 the mountain surface and the atmosphere which would 

 tend to produce the result found by observation. More- 

 over, convection always tends to raise the temperature of 

 the upper air above what it would be otherwise, and, in 

 addition, the cold of winter is, as it were, stored up in 

 the snow, while no such process holds for the warmth of 

 summer. Both conditions are probablv effective in increas- 

 ing the temperature difference. The most important 

 deduction to be made from the results is that the moun- 

 tains are not cold because the uoper air is cooled by con- 

 vection, but they are cooled by their radiation to space. 



The mean values of the gradients up to 15 km., found 

 from registering balloon ascents at ten European stations 

 and for St. Louis, U.S. .A., are given in the table : — 



Height o-t 1-2 2-3 3-4 4-5 q-6 5-7 7-8km. 



G™1ien.{|-£^„i- :■■ 3-6 4-, 5- 5-8 63 



HeiRht 



5 ■ 53 4'7 

 8~p 9-T0 10- 

 6-8 5-0 3 



7'8 87 

 13-14 i4-'5 kn 



The inaximum value occurs in the layer 7-8 km., and 

 its magnitude indicates that the effect of radiation is to 

 leave practically unchanged the natural gradient in air in 

 vertical motion. Gold showed that in the upper layers 

 absorption exceeded radiation, and in the lower layers 

 radiation exceeded absorption, and both processes would 

 diminish the temperature gradient. .At an intermediate 

 stage absorption and radiation must balance, and the 

 results indicate that this is the case at a height of 7-8 km. 

 The temperature at different heights up to 15 km. shows 

 practically no variation for the ten European stations 

 except in the case of Pavlovsk, where the temperature is 

 imiformly lower up to 10 kin. and higher above 10 km. 

 Ihan, at the other stations. The difference of temperature 

 between Strassburg and Pavlovsk, taken to represent 

 NO. 2089, VOL. 82] 



lat. 50° and lat. 60° respectively, is sufficient to produce 

 a gradient of pressure at a height of 10 km. which would 

 correspond to a steady west wind of about 24 m.p.s. 

 (54 miles per hour). The difference between Strassburg 

 and St. Louis (representing lat. 39°) would at the same 

 height correspond to a steady west wind of 15 m.p.s. in 

 intermediate latitudes. The observations are not suffici- 

 ently extensive to warrant much stress being laid on the 

 absolute values of these velocities, but it is of interest 

 to note that the approximate ratio of the west winds in 

 lats. 45°, 55°, deduced from Oberbeck's solution by a 

 purely theoretical treatment of the problem of the general 

 circulation, is 16/21 for the upper strata, a result in 

 tolerable agreement with the ratio 15/24 deduced from the 

 temperature observations. 



The problem of the vertical distribution of temperature 

 in cyclones and anticyclones depends for its solution on 

 upper-air observations. Hann deduced from the tempera- 

 tures at high-level observatories that cyclones were colder 

 than anticyclones, the mean difference of temperature up 

 to 3-5 km. being as much as 5° C. Grenander found 

 similar results by a consideration of the kite and balloon 

 ascents at Hald and Berlin, while Von Bezold deduced 

 from the Berlin manned balloon ascents that the relative 

 coldness of the cyclone was maintained even up to 8 km. 



The results in the present report, obtained by taking only 

 those cases in which the sea-level pressure exceeded 

 770 mm. or was less than 750 mm., and correcting the 

 observations for seasonal and local variations, showed that 

 the cyclone was colder than the anticyclone up to 9 km., 

 while at greater heights the conditions were reversed, and 

 the anticyclone became much colder than the cyclone ; 

 but the effect of the temoerature difference in the lower 

 layers on the pressure difference is so considerable that 

 even at 14 km. the pressure gradient is not reversed. In 

 these circumstances it is difficult to see how air can be 

 brought into the anticyclonic and out of the cyclonic 

 regions in the upper air. The cirrus observations imply 

 a definite outward motion over cyclonic regions, but a 

 rotation in the same direction as at the surface, which 

 can be the case only if the gradient of pressure is also 

 in the same direction its at the surface. I'hese results 

 imply that there is motion across the isobars from the 

 lower to the higher pressure. Now, although it is possible 

 for such motion to exist if the velocity in the cyclonic 

 region exceeds a certain value, or, in the anticvclonic 

 region, lies between certain limits, it is not possible lo 

 have steady motion of this type, and the effect of damn- 

 ing would be to make the motion from the higher to the 

 lower pressure. The evidence points to the conclusion 

 either (1) that cyclones and anticyclones arriving in the 

 Fiuropean area are in general dissipating systems which 

 are continually replaced by other systems arriving from 

 what inay be called productive regions, or (2) that there 

 is interchange of air with regions in which the surface 

 temperature or the temperature gradient differs sufficiently 

 to produce mean temperatures greater in low-pressure 

 areas and less in high-pressure areas than are found over 

 Europe. 



It is interesting in connection with this part of the 

 subject to note that Shaw and Lemofert deduced from a 

 discussion of surface air currents that the central areas 

 of anticyclones were not the regions of origin of currents, 

 and could not, therefore, be places where descent of air 

 was taking place, to any considerable extent. The 

 tf^mperature observations in the first 3- km. agree with 

 this conclusion, since they show that there is no approach 

 to a regular adiabatic gradient near the centres of anti- 

 cyclones. 



Perhaps the most remarkable phenomenon revealed by 

 the observations from registering balloons is the com- 

 paratively sudden cessation of the fall of temperature .at 

 a height which- varies from day to day. but is roughly 

 equal' to 10 km. Above this height, which mav be re- 

 garded as the height of an irregular, but roughly hori- 

 zontal, surface dividing the atmosphere into two regions, 

 the temperature at any time varies very little in a vertical 

 direction, showing, on the average, a slight tendency to 

 increase. The lower and upper regions are characterised 

 by the terms " convective " and " advective " respectively, 

 and the height and temperature of the dividing surface 



