<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def update(self):
 """Update |RelSoilArea| based on |Area|, |ZoneArea|, and |ZoneType|. relsoilarea(0.3) """

        con = self.subpars.pars.control
        temp = con.zonearea.values.copy()
        temp[con.zonetype.values == GLACIER] = 0.
        temp[con.zonetype.values == ILAKE] = 0.
        self(numpy.sum(temp)/con.area)