Decide location of Roughnees change line from sea to land at seaside

[YOCUI]

Hi wasp expert,

i am comparing wasp predicted profile at mast location with measured profile at

several costal projects , to search for a rule of thumb to decide the location

of roughness change line from sea to land . i find six projects , all masts have

a distance to sea around hundrads of meters . all 6 sites with very flat

terrain , and roughness length change is low no forests , no obstacles. if i

locate the sea-land roughness line according to the reality,( means the mast is

located within land area about hundards meters away from sealand roughness

change line ) than all 6 six predicted profile is very bad , with only one

intersection point with the measured profile indicate only self point prediction

is ok .( mast measurement height 30m 50m 70m/80m use the highest level for

calculation full year data )but if i extend the sea-land roughness change line

to cover the mast ( mast within sea area hundards meters to the roughness change

line ) than all 6 predicted profile get a obivious improvement .(due to low

roughness length change from sea to land 0.00~0.0x , the effect of IBL model can

be neglect i think )measured and predict profile very alligned from 30~90m at

all masts .do we have any rule of thumb already for determine the sea land

roughness change line ?

Thanks in advance !