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

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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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Accepted Answer

Image Analyst
Image Analyst on 7 Aug 2020
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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Siân Chilcott
Siân Chilcott on 11 Aug 2020
I want to fit the polynomial to T_s. When I run it for 1 year it looks like the figure below (i've enforced it at 0 for melt reasons). I receive the error I explained earlier when I try and run it for more than one year. I would just like to know why it produces no real roots on day 615.
Image Analyst
Image Analyst on 11 Aug 2020
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.

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More Answers (1)

Sudheer Bhimireddy
Sudheer Bhimireddy on 7 Aug 2020
As soon as you estimated hsnow, force all/any negative values to 0


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