kh fix. add **3

obl_legacy.f90

@@ -301,7 +301,7 @@ module obl_legacy
 
     do k = 2, nz
       if (rit(k) >= 0.0) then
-        kh(k) = kh_0 / (1.0 + 5.0 * rit(k)) + kh_b(k)
+        kh(k) = kh_0 / (1.0 + 5.0 * rit(k))**3 + kh_b(k)
       else
         kh(k) = unstable
       end if