def clear_data(self) -> None:
        """Delete the data and reset the last loaded day"""
        logger.debug("clearing data")
        if self._has_data_loaded:
            if self._file:
                self._file.close()

        self._has_data_loaded = False  # grids are "loaded" ? (netCDF files are opened)
        self._file = None
        self._day_idx = 0
        self._timestamp = None
        self._zeta = None
        self._siglay = None
        self._h = None
        self._lats = None
        self._lons = None
        self._lat = None
        self._lon = None
        self._loc_idx = None
        self._d = None
        self._temp = None
        self._sal = None