noah lsm cold bias during night

[nzWRF19+]

Hello,

WRF3.9.1 with NOAH lsm for New Zealand gives us very bad results in terms of 2m temperature and 2m dewpoint(as you can see in the attached verification) compared to SLAB - what surprisises me. The temperature during nighttime is completely off(massive cold bias), but recovers during the day and is even outperforming the other lsm-wrf-configurations. For me it looks like that there is something not going well with the heat capacity, as the changes are happening so fast.

I checked all the input data like vegfrac, lai, lu, soil moisture and soil types. All looks fine/reasonable to me. I also made tests with different PBL and RAD schemes - unrealistic decline of temperature still happens. I was not able to find something obviously wrong, so I wanted to ask, if you you have an idea why this is happing.

Thank you
Johannes Rausch

[emaiorana]

Hi, which PBL are you using? I'm struggling with a huge cold bias using noah lsm with ACM2 PBL on a very complex terrain like the Italian Alps. When i switch to Noah-MP lsm, the cold bias on the snow covered areas disappears.

[Ming Chen]

Cold T2 bias is a common feature in Noah LSM. We haven't come up with a solution to fix this problem.
If possible, please switch to noahMP.