Model Code
WRF 4.5.2
Noah-MP v4.5
Platform
Linux x86_64 INTEL (ftn/icc): Cray XC (dmpar)
Model Summary
4km SE USA
Restart run starting from Oct. 1974 through Dec. 2020
Forced with ERA5 from the Copernicus CDS via python API
Geogrid run with GEOGRID.TBL.ARW.noahmp
Notable modules:
Summary of Problem
Anomalously cold computed daily-maximum air temperature at ground level (T2)
Troubleshooting Actions
All troubleshooting was conducted for the simulation period Feb. 11-19, 1984 when there was no anomaly at the beginning of the run and a small one develops after a few days. Feb. 11 coincides with the end of one restart run and the beginning of another allowing us to test whether the model state restart files were tainted. The only action that gave acceptable results was using the Noah LSM instead of Noah-MP.
Discussion
Hi all,
I have a 4km model that spans the SE USA that I'm running for the period 1974-2020. In post-processing output I've computed daily maximum surface temperature from T2 (adjusting -5 hours from GMT to EST) and have found significant masses of anomalously cold air at ground level that extends across large swaths of the continental part of my domain and which can last for months on end. One such example begins with the settling of a cold front around the 3rd week of January, 1983 (fig. 1). Left panel shows Tmax from Daymet, middle panel shows calculated Tmax from WRF simulated output with red dots corresponding to GHCN station locations, and the right panel shows the GHCN station-level input observations for the day as published by Daymet (Daymet: Station-Level Inputs and Cross-Validation for North America, Version 4 R1, https://doi.org/10.3334/ORNLDAAC/2132). Model performance is decent enough.
Figure 1. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for January 20, 1983.
If we fast-forward to February 16, 1983 (fig. 2) we can see there is a massive amount of cold air (< 45 degrees F) across the northern half of the domain which has not cleared out since the front settled approximately 3 weeks prior. The maps of Tmax are visibly different and model performance is poor. Note the change in scale for temperature.
Figure 2. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for February 16, 1983.
Moving ahead in time to April 21, 1983 there are still large pockets of cold air, but we can see clearly that some of it is concentrated along the river valleys in the coastal plain of Georgia and the Carolinas (fig. 3).
Figure 3. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for April 21, 1983.
To cap off the demonstration of the extreme nature of the anomalously cold air here is a plot for August 15, 1983 (fig. 4) during which time there shouldn't be daily-max temperatures this low over such a large area of the southeastern US. It's notable that peninsular Florida is relatively unaffected in all of these plots.
Figure 4. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for August 15, 1983.
This particular event lasted through December when another front moves through and "resets" everything (fig. 5). Again, note the change in scale for temperature.
Figure 5. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for December 25, 1983.
WRF 4.5.2
Noah-MP v4.5
Platform
Linux x86_64 INTEL (ftn/icc): Cray XC (dmpar)
Model Summary
4km SE USA
Restart run starting from Oct. 1974 through Dec. 2020
Forced with ERA5 from the Copernicus CDS via python API
Geogrid run with GEOGRID.TBL.ARW.noahmp
Notable modules:
- Thompson MP
- CAM radiation physics
- Noah-MP
- Miguez-Macho & Fan runoff scheme
- BEM urban canopy model (sf_urban_physics = 3)
- FDDA on
Summary of Problem
Anomalously cold computed daily-maximum air temperature at ground level (T2)
Troubleshooting Actions
All troubleshooting was conducted for the simulation period Feb. 11-19, 1984 when there was no anomaly at the beginning of the run and a small one develops after a few days. Feb. 11 coincides with the end of one restart run and the beginning of another allowing us to test whether the model state restart files were tainted. The only action that gave acceptable results was using the Noah LSM instead of Noah-MP.
- run without warm-start from restart files
- Noah-MP: use free drainage and topmodel runoff schemes
- Noah-MP: adjust soiltstep
- Noah-MP: use opt_snf = 4 (wrf precip partitioning)
- Noah-MP: use opt_frz = 2 (Koren's iteration)
- Noah-MP: use opt_stc = 2 (full-implicit soil temp time scheme)
- Try updated code WRF 4.6.0 (solves bug in "GRDFLX" term: Bug fix for Noah-MP snow, vegetation and urban (#1929) · wrf-model/WRF@ce1069f)
- Use Noah LSM
Discussion
Hi all,
I have a 4km model that spans the SE USA that I'm running for the period 1974-2020. In post-processing output I've computed daily maximum surface temperature from T2 (adjusting -5 hours from GMT to EST) and have found significant masses of anomalously cold air at ground level that extends across large swaths of the continental part of my domain and which can last for months on end. One such example begins with the settling of a cold front around the 3rd week of January, 1983 (fig. 1). Left panel shows Tmax from Daymet, middle panel shows calculated Tmax from WRF simulated output with red dots corresponding to GHCN station locations, and the right panel shows the GHCN station-level input observations for the day as published by Daymet (Daymet: Station-Level Inputs and Cross-Validation for North America, Version 4 R1, https://doi.org/10.3334/ORNLDAAC/2132). Model performance is decent enough.
Figure 1. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for January 20, 1983.
If we fast-forward to February 16, 1983 (fig. 2) we can see there is a massive amount of cold air (< 45 degrees F) across the northern half of the domain which has not cleared out since the front settled approximately 3 weeks prior. The maps of Tmax are visibly different and model performance is poor. Note the change in scale for temperature.
Figure 2. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for February 16, 1983.
Moving ahead in time to April 21, 1983 there are still large pockets of cold air, but we can see clearly that some of it is concentrated along the river valleys in the coastal plain of Georgia and the Carolinas (fig. 3).
Figure 3. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for April 21, 1983.
To cap off the demonstration of the extreme nature of the anomalously cold air here is a plot for August 15, 1983 (fig. 4) during which time there shouldn't be daily-max temperatures this low over such a large area of the southeastern US. It's notable that peninsular Florida is relatively unaffected in all of these plots.
Figure 4. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for August 15, 1983.
This particular event lasted through December when another front moves through and "resets" everything (fig. 5). Again, note the change in scale for temperature.
Figure 5. Plots showing Daymet Tmax (left), computed Tmax from WRF simulated output (center), computed Tmax from WRF simulated output versus station-level inputs from GHCN for December 25, 1983.
Attachments
Last edited: