Pressure, Temperature, and Wind in the Atmosphere. 39 



The following table, taken mainly from Hann, gives the 

 amplitudes a 2 and phases A 2 of the semi-diurnal temperature- 

 and pressure-waves at a number of places chiefly in low 

 latitudes : — 



Place. 



Barometer. Temperature. 



A, 



a 2 . A 2 '. a' 2 . 



A 2 -A 2 '. 



Equatorial j 



Ocean J 



Batavia 



Trevandrum 



Manila 



Madras 



i*San Jose 



158 



159 

 158 

 159 

 158 

 157 

 165 

 158 

 153 

 163 

 157 

 156 

 154 

 156 

 160 

 163 

 150 

 143 



mm. 

 •82 97 



•95 68 



1-08 85 

 •89 68 



1-11 7(5 

 •80 89 

 •84 (51 

 •71 87 

 •74 43 

 •88 80 



105 71 

 •98 8(5 

 •84 72 

 •91 90 

 •84 81 

 •89 57 



103 58 

 •23 58 



°C. 

 023 



0-83 

 0-75 

 0-75 

 0-98 

 1-38 

 074 

 0-86 

 066 

 110 

 0-87 

 1-05 

 05(5 

 095 

 113 

 1*58 

 0-88 

 058 



o 

 61 



91 

 73 

 91 

 82 

 68 



104 

 71 



110 

 83 

 86 

 70 

 82 

 66 

 79 

 96 

 92 

 85 

 95 

 76 



Juluit 



Ascension 



*St. Helena 



Port au Prince ... 



Am Gabun 



Singapore 



Loanda 



Dar-es-Salam ... 



*Bismarckburg ... 



Allahabad 



Greenwich 



Blue Hill 



Boston 



* Altitude above 500 in. 



The mean difference of phase is 83°, and is therefore in 

 full agreement with the theoretical result. 



The temperature amplitude corresponding to T,=280° A 

 ( = 7° C.) is, according to the theory, 1*5 e~&~ sin 3 </> degrees C. 

 The mean value of a' 2 for the equatorial stations is o, 9 C, 

 which is rather less than the theoretical value *. 



Many of the stations, however, are island or coast stations, 

 and it is probable that over the ocean the change in the 

 phase of the pressure variation with height would be less 

 than over the land. The value given by the formula for 

 Kew and Valencia is o, 4 C, and this is also the observed 

 value. For Ben Nevis the theoretical value is o, ll C, and 

 the observed value is o, 18 0. The difference of phase ought 

 to dimish only slowly with the height ; for lat. 45° the decrease 

 would only be 45° at a height of 10 km. 



The value of the temperature amplitude corresponding to 



* See, however, note above. 



