A jump in irrig_c4per in UofMD-landState-h-3-1-1 multiple-management

[priyapattancheri]

Dataset source ID(s)

Dataset source ID(s): UofMD-landState-h-3-1-1
variable_id = "multiple-management"

Describe the issue

A spurious jump in irrig_c4per in multiple management for Scenario-h around 2024. The variable irrig_c3per also shows jumps, while irrig_c3ann and irrig_c3per are showing a smooth transition from Historical to Scenario. Figure attached. Is this expected ?

Expected data

Expecting a smooth transition from Hist to Scenario-h for irrig_c4per.

Screenshots

Additional context

[lchini]

Thanks for flagging this issue. I’ve tried to reproduce the problem and it looks like you’re probably plotting a time-series of:
sum(sum( irrig_c4per * cellarea ))
Is that correct?
Although this variable does show a sudden jump in values, in reality the irrig_c4per variable is intended to be used with the c4per variable to give the total irrigated area of c4per crops, rather than being used alone. If you want to plot the global fraction of c4per crops that is irrigated I would recommend:
sum(sum( irrig_c4per * c4per * cellar )) / sum(sum( c4per * cellarea ))
instead of just summing the irrigated fractions directly. There are also some sudden changes in values for the global c4per area and global c4per irrigated area, but those changes happen over a few years rather than in a single year and they are due to the underlying quick changes in the IAM data.

[priyapattancheri]

Thanks for your reply. Yes, I was just summing up all the grids and I also agree that it is not for a single year.

My intention is to make a LULC transition for scenarioMIP. For that purpose I am using irrigated fractions of respective crops functional types. This quick change in irr_c4per is getting reflected in transitioned LULC for scenario-h.

[lchini]

Can you give an example of what you are trying to compute and how you're computing it?
If you want to look at the irrigated area of a crop type that transitions to another land-use type, I would recommend using irrig_c4per * c4per to get the actual area of c4per that is irrigated, rather than just using irrig_c4per on its own. But perhaps I'm not quite understanding the issue that you're encountering.