ctsm5.3 landuse_timeseries PCT_* variables

[Fuhow]

Hi, I am now using CTSM5.3 and trying to modify landuse data in the IHIST case's Landuse_timeseries file.

I found that the PCT_* variables are different from those of CLM5.

In CLM5, surfdata requires that the sum of all PCT_* variables (should) be 100. But I didn't find any requirement about the Landuse_timeseries file, and the same applies to CTSM5.3.

So, my question is, is there a principle about PCT_* variables in the landuse_timeseries file?

Since I plotted the sum of some PCT_* variables, the results seem not to be equal to 100.


Besides, there is no PCT_NATVEG in landuse_timeseries file, should it be the sum of PCT_NAT_PFT?

 

[Yuan Sun]

Hi, I am now using CTSM5.3 and trying to modify landuse data in the IHIST case's Landuse_timeseries file.

I found that the PCT_* variables are different from those of CLM5.

In CLM5, surfdata requires that the sum of all PCT_* variables (should) be 100. But I didn't find any requirement about the Landuse_timeseries file, and the same applies to CTSM5.3.

So, my question is, is there a principle about PCT_* variables in the landuse_timeseries file?

Since I plotted the sum of some PCT_* variables, the results seem not to be equal to 100.

View attachment 6501
Besides, there is no PCT_NATVEG in landuse_timeseries file, should it be the sum of PCT_NAT_PFT?

Hi,

landuse_timeseries data is for transient landunit. The rest is counted as the percentage of natural vegetation (PCT_NATVEG).

Best,
Yuan

 

[Fuhow]

Hi,

landuse_timeseries data is for transient landunit. The rest is counted as the percentage of natural vegetation (PCT_NATVEG).

Best,
Yuan

Hi, Yuan

Many thanks for your response. It's very helpful to me.

I found that the document stated that PCT_CROP comes from the landuse.timeseries file, and PCT_GLACIER comes from the ice sheet model. Then, if the total land unit area of glaciers and crops is changed, the other land cover types will change by the same quantity in a specific order until the total percentage is once again 100%. The order is: natveg, crop, urban medium density, urban high density, urban tall building district, wetland, lake.

The document didn't mention anything about natveg. So, according to your specification, among the remaining types such as urban, crop, lake, wetland (zero), and glacier, the rest is natveg. Therefore, the proportion of glaciers and natveg can not be replace by modifying the landuse.timeseries , which should be the fluctuating data generated within a model.

As I want to use my higher-resolution land cover data to run an IHIST case, I was considering using all the land cover data to calculate the percentage of each land cover type. Then, replacing the PCT_* data of lake, crop, and urban with calculated percentage, and leave the data for glacier and natveg as they are. This is because PCT_GLACIER is from cism and PCT_NATVEG is calculated from the rest of the land cover types.

This is my idea about using my own land cover data for running an IHIST case. If possible, could you help me evaluate the scientific validity of this idea?

Thank you again for your response.

Best regards,
Fu Hao