Mathematical consultation required - interpretation of dispersion plot

Appeal

Colleagues, if suddenly a mathematician who has extra free time reads the article, please help with the interpretation of the results of processing experimental data.

Experiment data

Experimental data is collected, then for each point t the sample variance is calculated for the input values (sample deviation squared) for the period [ t ; t-60 минут].

As a result, there are 2 graphs:

Fig.1. Graph of dispersion values for experimental site No. 1

Fig.2. Graph of dispersion values for experimental site No. 2.

Questions

1.How can you interpret a tangent graph? Those. the fact that one curve is steeper?

2.How can we interpret the fact that there is a break point in the graph? Has the spread of values increased sharply and the results of the experiment will be more approximate?