Changes

Code changes to implement modificiations on wp3 clippings
This commit contains code changes to implement modifications of skewness
clippings on wp3 in src/CLUBB_core/clip_explicit.F90. The default method attempts
to apply smaller (larger) clippings below (above) 100m AGL level, which
can cause a discontinuities around 100m AGL level. This clippings is
found to trigger sawthooth oscillations in wp3 when linear diffusion is
used. Such swathooth oscillations are eleminated if a smoothed Heaviside
function is introduced to obtain a smooth transition of clippings at
around 100m AGL level. The changes is necessary to obtain the first
order convergence in CLUBB-SCM when lienar diffusion is used.

Previously committed by Shixuan.

Code changes to implement modificiations on wp3 clippings
This commit contains code changes to implement modifications of skewness
clippings on wp3 in src/CLUBB_core/clip_explicit.F90. The default method attempts
to apply smaller (larger) clippings below (above) 100m AGL level, which
can cause a discontinuities around 100m AGL level. This clippings is
found to trigger sawthooth oscillations in wp3 when linear diffusion is
used. Such swathooth oscillations are eleminated if a smoothed Heaviside
function is introduced to obtain a smooth transition of clippings at
around 100m AGL level. The changes is necessary to obtain the first
order convergence in CLUBB-SCM when lienar diffusion is used.

Previously committed by Shixuan.