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Correcting the equation that calculates the net longwave fluxes in single layer UCM. #2016

Closed joshi994 closed 3 months ago

joshi994 commented 4 months ago

To correct for the underestimation of net longwave flux absorbed by the building wall, RB2, in module_sf_urban.F

TYPE: Bug fix

KEYWORDS: Longwave flux, radiation/energy balance, Surface temperature, Urban climate, SLUCM

SOURCE: Parag Joshi (Brookhaven National Lab), Katia Lamer (Brookhaven National Lab)

DESCRIPTION OF CHANGES: Problem: The net long wave fluxes absorbed by the building walls is being underestimated due to multiplication of the emissivity twice in the equation. The command/lines that evaluate RB2 in the module_sf_urban.F (Lines 1300 and 1419 of WRF version-4.5.2) reflect the net long wave fluxes absorbed by building walls.

Solution: The code has been corrected by referring to the equation A9 of in the article, Kusaka & Kimora 2004, Journal of Applied Meteorology.

ISSUE: For use when this PR closes an issue. Fixes #2011

LIST OF MODIFIED FILES: module_sf_urban.F

TESTS CONDUCTED:

  1. The test can be conducted by running WRF with SLUCM with and without corrected module and quantify the values of RB2.
  2. It passed Jenkins tests.

RELEASE NOTE: Correcting the net long wave fluxes for application in modeling urban climate using Single Layer Urban Canopy Model (SLUCM). It slightly improved 2-m temperature in urban area.

weiwangncar commented 4 months ago

@joshi994 Thanks for this PR. Can you describe how big the impact is? If you have plots to show, that is good too.

weiwangncar commented 4 months ago

The regression test results:

Test Type              | Expected  | Received |  Failed
= = = = = = = = = = = = = = = = = = = = = = = =  = = = =
Number of Tests        : 23           24
Number of Builds       : 60           56
Number of Simulations  : 158           150        0
Number of Comparisons  : 95           86        0

Failed Simulations are: 
None
Which comparisons are not bit-for-bit: 
None
weiwangncar commented 4 months ago

@cenlinhe Can you review this PR?

cenlinhe commented 4 months ago

@cenlinhe Can you review this PR?

I will review this in the next few days.

cenlinhe commented 4 months ago

this bug is described in this issue in more detail: https://github.com/wrf-model/WRF/issues/2011 This is indeed a bug and the fix in this PR looks good to me.

cenlinhe commented 4 months ago

@joshi994 Do you have a figure showing the difference in temperature or outgoing LW due to this bug fix?

joshi994 commented 4 months ago

@joshi994 Do you have a figure showing the difference in temperature or outgoing LW due to this bug fix?

@cenlinhe No, I don't have figures showing the difference in temperature or the LW flux as I am lacking computational resources to quantify the impact.

cenlinhe commented 4 months ago

Our group has done a test for this bug fix, which slightly improves urban 2-m temperature. Please see here: https://github.com/NCAR/hrldas/pull/167#issuecomment-1987061648

weiwangncar commented 3 months ago

@cenlinhe Thanks for your group's test. Would you like to approve this PR?

cenlinhe commented 3 months ago

@cenlinhe Thanks for your group's test. Would you like to approve this PR?

Yes, I approve this PR.