Unreasonable precipitation response after land use change

[Yuanlin]

Hello, WRF team

I am using wps-4.1 and wrf-4.1.2 for a land use sensitivity experiments. Specifically, we compares the differences between A (no change) and B (only land use change).

Comparing the differences between A and B, we find that unreasonable precipitation changes occur in areas without land use change, especially at low elevations. The results are in the attachments ( the file 'The figures.docx')

Here are two questions:
(1) Why does the unreasonable precipitation change occur? How to avoid it?
(2) If it cannot be avoided, will the unreasonable precipitation changes affect the results in the boundary (high altitude areas)?

the namelist.wps and namelist.input are also in the attachments. There are also several typical wrfout in google drive (https://drive.google.com/file/d/1PsFBN_uzjGoioa_nredtqzid8yj0mU6r/view?usp=sharing).

Thanks!

Yuanlin

 

[Ming Chen]

I am thinking that with the radical landuse change, somehow the thermal dynamic structure of the atmosphere changes in response and these changes are not only locally, but also on regional scale. This is why precipitation changes occur in areas without land use change. Would you please clarify why you think the precipitation change is 'unreasonable'?
To answer your second question, precipitation change will affect the simulation at high altitude (upper model levels).

 

[Yuanlin]

Thank you very much for your reply！

Sorry I didn't explain clearly why I think the precipitation change is unreasonable. In my point of view, the precipitation changes at a distance area should lag behind local changes and not particularly strong intensity. But at the start of the simulations, the precipitation changed immediately at a distance area (Figure 4 in 'The figures .docx'). This may be related to atmospheric changes as you say, but we are not sure if the precipitation changes are due to the model structure, especially in the high altitude area with complex terrain.

Furthermore, this means that land use changes lead to climate changes at a distance area and the changes at the distance area can affect the whole domain again?

Thanks!

Yuanlin

 

[Ming Chen]

Yuanlin,
Would you please double check your Figure 1 and Figure 2? They look the same.
This case is over the Tibetan Plateau, where topography has significant impact on precipitation. I am not sure how sensitive the model is to land use change in this area. It is possible that a slight change in vapor flux and surface heating might trigger large response. However, more detailed analysis is necessary before we can explain the phenomenon shown in your case.

 

[Yuanlin]

Thanks for your replay!

There are only lake grids have been changed, which are the yellow grids in Figure 1 and Figure 2.

It seems that the precipitation in Tibetan Plateau has a high sensitivity to land use change. However, the precipitation changes at lower altitudes seems irregular and looks like noise.

 

[Ming Chen]

Hi Yuanlin,
I cannot find large, systematic changes in landuse between your Fig. A and B. if only lake points are changed, and if there are not many lake points in the domain you illustrated, then I wouldn't expect significant precipitation changes. There might be some reasons behind what you have seen in your results, although I don't have an immediate answer to this issue. Please l=keep me updated if you find a reasonable explanation. Thanks in advance.