How to prevent decrement (melting) past 0 until growth increases again?

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Siân Chilcott 2020-8-7

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评论： Siân Chilcott 2020-8-12

I am creating a snow and ice height time series. Once the snow (hsnow) has completely melted, the energy is used to melt ice (hice). I may be being stupid but I can't seem to find a way to prevent the snow height falling below 0 (as the energy that causes it to decrease past 0 would be used to decrease an ice layer).

Basically once the snow height falls below 0 I want to enforce it at 0 or prevent further decrement past 0, until the snowfall increases again.

hsnow(day+1) = hsnow(day) + snowfall(day) + dh_snow;
h_ice(day+1) = hice(day) + growth(day) + dh_ice;

(dh_snow and dh_ice are the amount of ice and snow melted per day based on the energy available.)

Thanks in advance for any help!

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Image Analyst 2020-8-7

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在 MATLAB Online 中打开

Another way, inside the loop, is to use the max() function:

hsnow(day+1) = max([0, hsnow(day) + snowfall(day) + dh_snow]);
h_ice(day+1) = max([0, hice(day) + growth(day) + dh_ice]);

If either one would be negative, like -5, then it will clip to 0 because the max of -5 and 0 is 0.

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Image Analyst 2020-8-11

Melt_test.m

For me it crashes at day 241. Try running the attached script.

Now let's say that I took the values of a, b, c, d, and e when it crashes and extend the days to 500. It would look like the plot in the lower left:

You can see that the 4th order equation has a min of 2.41 which means that it never crosses the x axis and has no real roots. So your code will just have to take that into account.

Siân Chilcott 2020-8-12