DOI Page / Citation link:
https://doi.org/10.11588/diglit.20140#0164
140
DECREASE OP TEMPERATURE WITH HEIGHT IN THE TROPICS.
rapid, we ma}7 consider, I think, the circumstance that the elevation, though not very
considerable, extends with great uniformity over a large surface.
In the first and third group the values differ less from those in the Alps;
for all the Indian stations it is characteristic that the rainy season shows by far the
most rapid decrease. The principal cause of it is that at a certain elevation above
the general surface more heat than lower down becomes latent by the frequent dis-
solving of the clouds when sinking so far.1
In order to show simultaneously the variations of the decrease with the locality and
the seasons, I have drawn in the Atlas three topographical profiles,2 and have indicated for
each of the single seasons the difference of the respective decrease from its annual mean
value by drawing a dotted line in connexion with the topographical outline. Assam
and Bengal vary so little in the different seasons, that for them no special diagram
had to be drawn. The dotted line in these surfaces shows the contour which the
topographical section ought to have for the actual temperature of the season, sup-
posing the value of the decrease had remained the same throughout the year;
if, therefore, the decrease in the season is too slow, the new ideal position of the
station will be below the real topographical outline, on account of-the station having
a temperature as if it were in a less elevated situation; if, vice versa, the decrease is
more rapid than the annual mean, as we see it particularly to be the case in the
rainy season, the dotted line will show, for the same reason, a profile which is
higher than the topographical contour. For Ceylon I further added the point of its
highest peak, Peduru talla galle, 8,305 feet, for the sake of completing the general
topographical profile of the island, though I had no higher station for its mountainous
regions than Nurelia.
DECREASE IN THE FREE AIR.
What we can deduce from the comparison of stations of different elevation might
be interpreted wrongly if considered as the decrease of temperature in the free air.
The various bold explorations in balloon ascents have sufficiently shown how much
this varies with the atmospheric conditions, chiefly with the direction of the wind,
1 See "Moisture of the atmosphere and temperature of the rain" in Vol. V.
2 In Plate III. of the Illustrations of Indian Meteorology, "Isothermal lines of the seasons."
DECREASE OP TEMPERATURE WITH HEIGHT IN THE TROPICS.
rapid, we ma}7 consider, I think, the circumstance that the elevation, though not very
considerable, extends with great uniformity over a large surface.
In the first and third group the values differ less from those in the Alps;
for all the Indian stations it is characteristic that the rainy season shows by far the
most rapid decrease. The principal cause of it is that at a certain elevation above
the general surface more heat than lower down becomes latent by the frequent dis-
solving of the clouds when sinking so far.1
In order to show simultaneously the variations of the decrease with the locality and
the seasons, I have drawn in the Atlas three topographical profiles,2 and have indicated for
each of the single seasons the difference of the respective decrease from its annual mean
value by drawing a dotted line in connexion with the topographical outline. Assam
and Bengal vary so little in the different seasons, that for them no special diagram
had to be drawn. The dotted line in these surfaces shows the contour which the
topographical section ought to have for the actual temperature of the season, sup-
posing the value of the decrease had remained the same throughout the year;
if, therefore, the decrease in the season is too slow, the new ideal position of the
station will be below the real topographical outline, on account of-the station having
a temperature as if it were in a less elevated situation; if, vice versa, the decrease is
more rapid than the annual mean, as we see it particularly to be the case in the
rainy season, the dotted line will show, for the same reason, a profile which is
higher than the topographical contour. For Ceylon I further added the point of its
highest peak, Peduru talla galle, 8,305 feet, for the sake of completing the general
topographical profile of the island, though I had no higher station for its mountainous
regions than Nurelia.
DECREASE IN THE FREE AIR.
What we can deduce from the comparison of stations of different elevation might
be interpreted wrongly if considered as the decrease of temperature in the free air.
The various bold explorations in balloon ascents have sufficiently shown how much
this varies with the atmospheric conditions, chiefly with the direction of the wind,
1 See "Moisture of the atmosphere and temperature of the rain" in Vol. V.
2 In Plate III. of the Illustrations of Indian Meteorology, "Isothermal lines of the seasons."