Shortwave radiation balance at the wall missing reflected direct and diffuse radiation reflection from the wall terms.

[joshi994]

Shortwave radiation_Single Layer.pdf

@cenlinhe

In this pull request, we corrected the shortwave radiation balance at the wall, particularly the reflected direct and diffuse radiation reaching the wall. A couple of terms that represent contribution from the reflected radiation from walls were absent in the code. We followed the formulations (equation 8 from Kusaka at. al. (2001))and corrected the shortwave radiation balance.

TYPE: Bug fix

KEYWORDS: Shortwave radiation balance, reflected radiation, shadowing effect, single-layer urban canopy model (SLUCM), direct and diffuse radiation.

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

DESCRIPTION OF CHANGES:
 Problem:
The single-layer urban canopy model missed a couple of terms that represent the direct and diffuse radiation reaching at a wall reflected from the other wall. It leads to an inaccurate calculation of the shortwave radiation at the walls.

Solution:
Mathematical formulation by Kusaka et. al. (2001) was followed to verify the equations used in the SLUCM module in WRF. The equations are corrected.

ISSUE: For use when this PR closes an issue.
Fixes #123

LIST OF MODIFIED FILES: module_sf_urban.F

TESTS CONDUCTED:

1. No tests has been conducted yet.

RELEASE NOTE: Contribution from the reflected direct and diffuse shortwave radiation from the wall was missing in the code. Present pull request fix the error which leads to underestimation of SWR at the wall.