Abstract
In this study, the impact of soil freezing–thawing processes on August
rainfall in southern China (SC) during 1979–2008 and related physical
mechanisms are investigated using the Grid-Point Atmospheric Model
version 2.0 (GAMIL2.0). This model with considering the supercooled
water in soil freezing-thawing scheme reproduces the climatology and
trends of August precipitation in the SC region. Moisture-budget
analysis is employed to quantity the contributions of different factors
to the change of precipitation in SC. The results indicate that
evaporation contributes significantly to the climatologically August
rainfall in SC. The dynamic component of vertical moisture advection,
which is related to changes in atmospheric circulation, plays an
important role in August precipitation trends. The possible physical
mechanism is that the GAMIL2.0 considering the supercooled water
simulated much higher soil/air temperature on August especially in the
north of 40°N, weakened the meridional thermal contrast, decreased the
200hpa zonal winds, strengthened 850hpa northerly wind, which is more
benificial to the convergence in SC and lead to the precipitation
increased. This study provides a new interpretation of the ‘southern
flooding’ during 1979–2008 from the point of frozen soil changing.