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WRF-CLM land use and landcover change simulations


New member
Hi all,

I'm employing WRF-CLM (v3.81, sf_surface_physics = 5) to examine the impacts of land use and land cover change on regional climate. The control simulation uses the default land use, and the land use frictions (LANDUSEF) and dominant index (LU_INDEX) of future ones are modified following SSP scenarios. However, several problems occur while comparing the historical and future runs.

1. I know that in WRF-Noah, only the changes in dominant land use (LU_INDEX) will impact surface properties and local climate unless the mosaic option is turned on. Meanwhile, CLM's manual says that there are five land units within each grid; thus, I assume changes in LANDUSEF will always alter the regional climate, even if the dominant land use is consistent. However, in my simulations, significant warming will only occur when the dominant land use changes to urban. For example, if the historical LU_INDEX is already urban, the impacts would be negligible even if the urban LANDUSEF increases from 0.5 to 0.9. It seems WRF-CLM uses a dominant land use scheme similar to WRF-Noah instead of five land units.

2. In WRF-CLM, there are three 4-dimensional (XTIME, subgrid_stag, south_north, west_east) latent heat component variables (LHSOI, LHVEG, and LHTRAN). I'm curious what does the subgrid_stag mean here? I assumed it indicates the soil layer as both have ten layers; however, the sum of these three variables is about 20% larger than the latent heat output on average.

3. In the lookup table, the albedo of urban and crop are 0.15 and 0.18, respectively. Thus, I presume the albedo will decrease when the cropland changes to urban land in the future, causing the warming effect. However, the ALBEDO variable shows the albedo will increase by about 0.12, and the magnitude of ALBEDO (~0.6) is much larger than the values in the lookup table.

4. I assume that the downwelling shortwave radiation (SWDOWN and SWDNB) will not be impacted by land use change; however, both values are changed, thus confusing me.

I really appreciate it if anyone could help me with them. Thanks for your time!

I have been reviewing the manuals of WRF and CLM but cannot figure them out. Could anyone help me with it?