get the KL parcov scaling matrix attribute.  Create the attribute if
        it has not yet been created

        Returns
        -------
        fehalf : pyemu.Matrix

def fehalf(self):
        """get the KL parcov scaling matrix attribute.  Create the attribute if
        it has not yet been created

        Returns
        -------
        fehalf : pyemu.Matrix

        """
        if self.__fehalf != None:
            return self.__fehalf
        self.log("fehalf")
        self.__fehalf = self.parcov.u * (self.parcov.s ** (0.5))
        self.log("fehalf")
        return self.__fehalf