Impacts of soil moisture content on simulated mesoscale circulations during the summer over eastern Spain

The Regional Atmospheric Modeling System (RAMS) version 6.0 has been used to investigate the impact and influence of initial soil moisture distributions on mesoscale circulations. To do this, two different events have been selected from the 2011 summer season: one at the beginning of the season (June) and the other one at the end of the season (August). For each of these mesoscale frameworks a total of five distinct simulations were performed varying the initial soil moisture content: a control run and four additional sensitivity tests. The control run, corresponding to a low soil moisture content, is the one used within the real-time weather forecasting system implemented in the Valencia Region. In the corresponding sensitivity simulations this low value has been progressively increased in different steps until the original soil moisture content doubled. It has been found that high soil moisture is associated with colder near-surface temperature, a moister relative humidity and a slightly lower near-surface wind speed, whereas a drier soil resulted in a dryer relative humidity, warmer temperature and a slight low-level wind. In general, the highest soil moisture contents are required to reproduce the near-surface daily cycles of temperature and relative humidity through higher values of latent heat flux and lower values of sensible heat flux. In this regard, moistening the soil improves the previous results obtained using the RAMS configuration used within the operational forecasting system. However, the wind speed is not quite sensitive to changes in the soil moisture content over flatter terrain. Finally, although a warming and dryer mixing layer is obtained with the lowest soil moisture content, the mixing layer height remains practically unchanged when using the distinct configurations over flat terrain. These differences are enhanced over more complex terrain.