Implementation of slope irradiance in Mesoscale Model version 5 and its effect on temperature and wind fields during the breakup of a temperature inversion

Abstract

[1] The atmospheric mesoscale model MM5 has been used at high horizontal resolution to simulate the breakup of a temperature inversion in complex topography. To improve the surface parameterizations during daytime, slope and orientation of the terrain have been taken into account in the calculation of short wave radiation at the surface. As the model resolution becomes higher, slope irradiance becomes increasingly important at high latitude. To evalute MM5 and slope irradiance's effect on the wind and temperature, a situation from 21 September 1994 is chosen. The situation is dominated by high pressure and no clouds, which gives the possibility of investigating the topography's effect on the radiation in greater detail. Compared to observations, results show improvement in both temperature and wind fields after the implementation of slope irradiances in MM5. The breakup period of the temperature inversion is also simulated more correctly. The RMS error is reduced by 35% for wind speed and 13% for temperature. This suggests that the influence of slope irradiance is larger for wind than for temperature in this situation.

A High-Resolution Topographic Correction Method for Clear-Sky Solar Irradiance Derived with a Numerical Weather Prediction Model

“…These results are in agreement with those reported by Hauge and Hole (2003) using the MM5 model at Norway with a horizontal spatial resolution of 500 m. We have found a larger change in the minimum and maximum values, however, that is likely explained by the higher spatial resolution that we are using (100 m).…”

“…Hauge and Hole (2003) included the effects of surface slope and orientation on ground level shortwave radiation within the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5). Hauge and Hole (2003) included the effects of surface slope and orientation on ground level shortwave radiation within the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5).…”

Wintertime Subkilometer Numerical Forecasts of Near-Surface Variables in the Canadian Rocky Mountains

“…An additional simulation at 250-m grid spacing (simulation RAD0p25; Table 3) considers the effects of slope angle and slope aspect on incoming solar radiation (self-shading) using a parameterization developed for the 2010 Vancouver Olympic and Paralympic Games. It follows the approach of Hauge and Hole (2003) and accounts for the effect of slopes on direct and diffuse shortwave radiation and for the reflection of total solar radiation from the surrounding terrain. Shadowing effects from neighboring orography and corrections of longwave incoming radiation are not included in this parameterization.…”

Current Challenges in Understanding and Predicting Transport and Exchange in the Atmosphere over Mountainous Terrain

“…Radiation parameterization: Parameterizing shortwave and longwave radiation fluxes in mountainous terrain poses additional challenges compared to flat terrain. The effects of slope angle and orientation on incoming solar radiation, as well as shading effects by the surrounding terrain are now increasingly represented in models and their positive effects on simulation results have been shown in multiple studies (e.g., [161,173,174]). Topography, however, also induces three-dimensional effects in the local radiation budget, which are typically not captured by traditional one-dimensional (column) radiation parameterizations.…”