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[aor-rtma] Inland lake temperature anomaly continues

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Thomas Turnage, modified 4 Years ago.

[aor-rtma] Inland lake temperature anomaly continues

Youngling Posts: 4 Join Date: 9/24/12 Recent Posts
Hi list, We continue to see questionable temperatures in the URMA with the same inland lake (Hamlin Lake) that has given us problems in the past. The attached image shows the 1/9/21 Min T analysis along with the observation points used for that analysis. It appears to me that the HRRR first guess might be dominating the signal, which would be surprising given that the recent upgrade to HRRRv4 was supposed to address these types of inland lake issues. Curious to know whether others are seeing similar inland lake temperature anomalies. Thanks, TJ @ GRR

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Matthew Morris, modified 4 Years ago.

RE: [aor-rtma] Inland lake temperature anomaly continues

Youngling Posts: 169 Join Date: 12/6/17 Recent Posts
Hi TJ,

The issue with the temperature analyses near Hamlin Lake is due to the downscaling procedure, specifically with the land/sea mask.  Please see the attached slide deck:

 Hamlin Lake Case Study: Min Temperature

Slides 3-6 show graphics for the 00Z URMA cycle on 9 January 2021.  [Recall that the background for min/maxT is derived from the min/max of the hourly background and analysis fields.]  Slides 3-4 show the first guess, analysis, and observations, slide 5 shows the HRRR and NAM Nest forecasted temperature (at native resolution of 3 km), and slide 6 shows the downscaled HRRR and NAM temperature output on the 2.5 km RTMA/URMA grid.  [Recall that the background for RTMA/URMA is a blend of the downscaled NAM Nest and HRRR output for temperature, moisture, and pressure.]  The warm pixels surrounding Hamlin Lake are present in the downscaled HRRR output, but not in the 3 km output.

Slide 7 shows the land/sea mask for the HRRR, while slide 8 shows the land/sea mask used when downscaling the HRRR and NAM Nest output. In the latter land/sea mask, there are several pixels near Hamlin Lake that are treated as water (white) rather than land (blue).  Given the proximity to Lake Michigan, the downscaling procedure is using water temperatures from Lake Michigan to adjust the temperature of the HRRR forecast over Hamlin Lake.

We will work to address this issue in the upcoming 3D-RTMA/URMA system, which is expected to be implemented operationally in ~FY2023.

Please let us know if you have any questions.

Thanks,
Matt

On Mon, Jan 11, 2021 at 12:16 PM VLab Notifications <VLab.Notifications@noaa.gov> wrote:
Hi list, We continue to see questionable temperatures in the URMA with the same inland lake (Hamlin Lake) that has given us problems in the past. The attached image shows the 1/9/21 Min T analysis along with the observation points used for that analysis. It appears to me that the HRRR first guess might be dominating the signal, which would be surprising given that the recent upgrade to HRRRv4 was supposed to address these types of inland lake issues. Curious to know whether others are seeing similar inland lake temperature anomalies. Thanks, TJ @ GRR
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Thomas Turnage RTMA/URMA Discussion Group Virtual Lab Forum http://vlab.noaa.gov/web/715073/home/-/message_boards/view_message/13295989 VLab.Notifications@noaa.gov