noah lsm cold bias during night

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New member

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


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New member
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

Staff member
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.