Changes to dust emissions when Leung_2024 method is being used.

Tuning was needed since we saw some high biases in dust over semiarid
regions given all the updates in CTSM and CAM. The biggest
changes in CTSM that affects dust is an increase in friction velocity
(ustar; fv in CTSM) over vegetated, semiarid regions, mainly
due to a switch in the roughness scheme from 'ZengWang2007' to
'Meier2022'. Since dust emission is very sensitive to ustar, the dust
emission scheme magnifies this increase and caused strong high biases
over semiarid regions, including Australia and Patagonia (see
plots in issue #2732). To enhance the robustness of Leung_2023 and
reduce the likelihood to see huge changes in answers in the
future, we tried to limit the sensitivity of dust emissions to ustar. We
also tried different methods (see specific notes below) to
reduce dust emissions from semiarid regions given the high biases over
there.