The option --alt-autoscale give me unfortunately not what I need.
The first image is made without the option alt-autoscale.
The second image is made with the option alt-autoscale.
The only difference is the position of 0 in the Y-axis.
Also the options alt-autoscale-min and alt-autoscale-max give me not what i need.
I want to see on the Y-axis only the part between 940 and 1040.

air_pressure_normal_scale.png
air_pressure_altautoscale.png