The data upon precipitation p and especially ablation a in glaciated regions have so far been rather poor. The parabola with a maximum in the height where the ablation is nearly zero is an approximation for the superposition p − a of the precipitation and ablation curves. This parabola has proved true to a certain extent in the Eastern Alps for precipitationReference Koch and Reichel
1
and also ablation measurements by our calculations of the height z
0 of the snow line. The method used by myself for fixing the height z
0 does not depend absolutely on this parabola as I have mentioned on page 310, Vol. 2, No. 15, of this Journal. But if it is possible to draw a parabola the calculation of the height of the snow line is very easy and quick.
2
It is certain that the shapes of the curves p − a for precipitation and ablation can vary in the way Lliboutry explains in his interesting letter. The shape can be a parabola as in Fig. 1 or nearly a straight line as in Fig. 2 or a curve of higher order. For fixing the height of snow line by the formula (5) on page 310 of my paper it is only necessary to shift the curve parallel to itself in the direction of the z-axis until Σf.a or in the writing of Lliboutry
, is zero. The fixing of the height
z
0 of the snow line becomes more accurate the larger is the angle by which the curve
p −
a cuts the
z-axis.
The method shown by Lliboutry in Fig. 3 for fixing z
0 is very interesting. By shifting the two curves p and a in the direction of the z-axis one can obtain equality in the two shaded areas. In practice it would be necessary to draw very accurately in order to obtain a sufficiently accurate result by this graphic method.
I agree with Lliboutry also with respect to his closing remark. It would be very useful to obtain more data about the variation of accumulation and ablation with height.
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The data upon precipitation p and especially ablation a in glaciated regions have so far been rather poor. The parabola with a maximum in the height where the ablation is nearly zero is an approximation for the superposition p − a of the precipitation and ablation curves. This parabola has proved true to a certain extent in the Eastern Alps for precipitationReference Koch and Reichel 1 and also ablation measurements by our calculations of the height z 0 of the snow line. The method used by myself for fixing the height z 0 does not depend absolutely on this parabola as I have mentioned on page 310, Vol. 2, No. 15, of this Journal. But if it is possible to draw a parabola the calculation of the height of the snow line is very easy and quick. 2
It is certain that the shapes of the curves p − a for precipitation and ablation can vary in the way Lliboutry explains in his interesting letter. The shape can be a parabola as in Fig. 1 or nearly a straight line as in Fig. 2 or a curve of higher order. For fixing the height of snow line by the formula (5) on page 310 of my paper it is only necessary to shift the curve parallel to itself in the direction of the z-axis until Σf.a or in the writing of Lliboutry
The method shown by Lliboutry in Fig. 3 for fixing z 0 is very interesting. By shifting the two curves p and a in the direction of the z-axis one can obtain equality in the two shaded areas. In practice it would be necessary to draw very accurately in order to obtain a sufficiently accurate result by this graphic method.
I agree with Lliboutry also with respect to his closing remark. It would be very useful to obtain more data about the variation of accumulation and ablation with height.