diff --git a/src/data_handling/__init__.py b/src/data_handling/__init__.py
index 198147842dc3fe2a606d71bbbeed479148824124..cb5aa5db0f29cf51d32ed54e810fa9b363d80cc6 100644
--- a/src/data_handling/__init__.py
+++ b/src/data_handling/__init__.py
@@ -10,6 +10,6 @@ __date__ = '2020-04-17'
 
 
 from .bootstraps import BootStraps
-from .data_preparation_join import DataPrep
+from .data_preparation_join import DataPrepJoin
 from .data_generator import DataGenerator
 from .data_distributor import Distributor
diff --git a/src/data_handling/data_generator.py b/src/data_handling/data_generator.py
index 672ef8a1355441f2481bbf41a40cc951f334a30f..7b83b56f8c7f6b79f0f598d3f1b3d33c34df53bf 100644
--- a/src/data_handling/data_generator.py
+++ b/src/data_handling/data_generator.py
@@ -13,7 +13,7 @@ import keras
 import xarray as xr
 
 from src import helpers
-from src.data_handling.data_preparation_join import DataPrep
+from src.data_handling.data_preparation_join import DataPrepJoin
 from src.helpers.join import EmptyQueryResult
 
 number = Union[float, int]
@@ -210,8 +210,8 @@ class DataGenerator(keras.utils.Sequence):
         std = None
         for station in self.stations:
             try:
-                data = DataPrep(self.data_path, self.network, station, self.variables, station_type=self.station_type,
-                                **self.kwargs)
+                data = DataPrepJoin(self.data_path, self.network, station, self.variables, station_type=self.station_type,
+                                    **self.kwargs)
                 chunks = (1, 100, data.data.shape[2])
                 tmp.append(da.from_array(data.data.data, chunks=chunks))
             except EmptyQueryResult:
@@ -249,8 +249,8 @@ class DataGenerator(keras.utils.Sequence):
         std = xr.DataArray(data, coords=coords, dims=["variables", "Stations"])
         for station in self.stations:
             try:
-                data = DataPrep(self.data_path, self.network, station, self.variables, station_type=self.station_type,
-                                **self.kwargs)
+                data = DataPrepJoin(self.data_path, self.network, station, self.variables, station_type=self.station_type,
+                                    **self.kwargs)
                 data.transform("datetime", method=method)
                 mean = mean.combine_first(data.mean)
                 std = std.combine_first(data.std)
@@ -260,7 +260,7 @@ class DataGenerator(keras.utils.Sequence):
         return mean.mean("Stations") if mean.shape[1] > 0 else None, std.mean("Stations") if std.shape[1] > 0 else None
 
     def get_data_generator(self, key: Union[str, int] = None, load_local_tmp_storage: bool = True,
-                           save_local_tmp_storage: bool = True) -> DataPrep:
+                           save_local_tmp_storage: bool = True) -> DataPrepJoin:
         """
         Create DataPrep object and preprocess data for given key.
 
@@ -288,8 +288,8 @@ class DataGenerator(keras.utils.Sequence):
             data = self._load_pickle_data(station, self.variables)
         except FileNotFoundError:
             logging.debug(f"load not pickle data for {station}")
-            data = DataPrep(self.data_path, self.network, station, self.variables, station_type=self.station_type,
-                            **self.kwargs)
+            data = DataPrepJoin(self.data_path, self.network, station, self.variables, station_type=self.station_type,
+                                **self.kwargs)
             if self.transformation is not None:
                 data.transform("datetime", **helpers.remove_items(self.transformation, "scope"))
             data.interpolate(self.interpolate_dim, method=self.interpolate_method, limit=self.limit_nan_fill)
diff --git a/src/data_handling/data_preparation.py b/src/data_handling/data_preparation.py
index e85d8a3ac732a2ce70a715cc7d6e6e21eee6b32b..366cce7629c3c4070d05f0b91e3fbbf5d556184a 100644
--- a/src/data_handling/data_preparation.py
+++ b/src/data_handling/data_preparation.py
@@ -78,7 +78,7 @@ class AbstractDataPrep(object):
         else:
             raise NotImplementedError("Either select hourly data or provide statistics_per_var.")
 
-    def load_data(self):
+    def load_data(self, source_name=""):
         """
         Load data and meta data either from local disk (preferred) or download new data by using a custom download method.
 
@@ -86,31 +86,33 @@ class AbstractDataPrep(object):
         cases, downloaded data is only stored locally if store_data_locally is not disabled. If this parameter is not
         set, it is assumed, that data should be saved locally.
         """
+        source_name = source_name if len(source_name) == 0 else f" from {source_name}"
         check_path_and_create(self.path)
         file_name = self._set_file_name()
         meta_file = self._set_meta_file_name()
         if self.kwargs.get('overwrite_local_data', False):
-            logging.debug(f"overwrite_local_data is true, therefore reload {file_name} from JOIN")
+            logging.debug(f"overwrite_local_data is true, therefore reload {file_name}{source_name}")
             if os.path.exists(file_name):
                 os.remove(file_name)
             if os.path.exists(meta_file):
                 os.remove(meta_file)
-            self.download_data(file_name, meta_file)
-            logging.debug("loaded new data from JOIN")
+            data, self.meta = self.download_data(file_name, meta_file)
+            logging.debug(f"loaded new data{source_name}")
         else:
             try:
                 logging.debug(f"try to load local data from: {file_name}")
                 data = xr.open_dataarray(file_name)
                 self.meta = pd.read_csv(meta_file, index_col=0)
+                self.check_station_meta()
                 logging.debug("loading finished")
             except FileNotFoundError as e:
                 logging.debug(e)
-                logging.debug("load new data from JOIN")
+                logging.debug(f"load new data{source_name}")
                 data, self.meta = self.download_data(file_name, meta_file)
                 logging.debug("loading finished")
-            # create slices and check for negative concentration.
-            data = self._slice_prep(data)
-            self.data = self.check_for_negative_concentrations(data)
+        # create slices and check for negative concentration.
+        data = self._slice_prep(data)
+        self.data = self.check_for_negative_concentrations(data)
 
     def download_data(self, file_name, meta_file) -> [xr.DataArray, pd.DataFrame]:
         """
@@ -121,6 +123,14 @@ class AbstractDataPrep(object):
         """
         raise NotImplementedError
 
+    def check_station_meta(self):
+        """
+        Placeholder function to implement some additional station meta data check if desired.
+
+        Ideally, this method should raise a FileNotFoundError if a value mismatch to load fresh data from a source.
+        """
+        pass
+
     def _set_file_name(self):
         all_vars = sorted(self.statistics_per_var.keys())
         return os.path.join(self.path, f"{''.join(self.station)}_{'_'.join(all_vars)}.nc")
diff --git a/src/data_handling/data_preparation_join.py b/src/data_handling/data_preparation_join.py
index 4313891131ddbc4699de6de499c1c3512e2a21dd..1c6593d65b5bdb4484bdf468c176c1becfba3981 100644
--- a/src/data_handling/data_preparation_join.py
+++ b/src/data_handling/data_preparation_join.py
@@ -4,6 +4,7 @@ __author__ = 'Felix Kleinert, Lukas Leufen'
 __date__ = '2019-10-16'
 
 import datetime as dt
+import inspect
 import logging
 import os
 from functools import reduce
@@ -16,6 +17,7 @@ import xarray as xr
 from src.configuration import check_path_and_create
 from src import helpers
 from src.helpers import join, statistics
+from src.data_handling.data_preparation import AbstractDataPrep
 
 # define a more general date type for type hinting
 date = Union[dt.date, dt.datetime]
@@ -25,7 +27,7 @@ num_or_list = Union[number, List[number]]
 data_or_none = Union[xr.DataArray, None]
 
 
-class DataPrep(object):
+class DataPrepJoin(AbstractDataPrep):
     """
     This class prepares data to be used in neural networks.
 
@@ -57,65 +59,11 @@ class DataPrep(object):
 
     def __init__(self, path: str, network: str, station: Union[str, List[str]], variables: List[str],
                  station_type: str = None, **kwargs):
-        """Construct instance."""
-        self.path = os.path.abspath(path)
         self.network = network
-        self.station = helpers.to_list(station)
-        self.variables = variables
         self.station_type = station_type
-        self.mean: data_or_none = None
-        self.std: data_or_none = None
-        self.history: data_or_none = None
-        self.label: data_or_none = None
-        self.observation: data_or_none = None
-        self.extremes_history: data_or_none = None
-        self.extremes_label: data_or_none = None
-        self.kwargs = kwargs
-        self.data = None
-        self.meta = None
-        self._transform_method = None
-        self.statistics_per_var = kwargs.get("statistics_per_var", None)
-        self.sampling = kwargs.get("sampling", "daily")
-        if self.statistics_per_var is not None or self.sampling == "hourly":
-            self.load_data()
-        else:
-            raise NotImplementedError("Either select hourly data or provide statistics_per_var.")
-
-    def load_data(self):
-        """
-        Load data and meta data either from local disk (preferred) or download new data from TOAR database.
-
-        Data is either downloaded, if no local data is available or parameter overwrite_local_data is true. In both
-        cases, downloaded data is only stored locally if store_data_locally is not disabled. If this parameter is not
-        set, it is assumed, that data should be saved locally.
-        """
-        check_path_and_create(self.path)
-        file_name = self._set_file_name()
-        meta_file = self._set_meta_file_name()
-        if self.kwargs.get('overwrite_local_data', False):
-            logging.debug(f"overwrite_local_data is true, therefore reload {file_name} from JOIN")
-            if os.path.exists(file_name):
-                os.remove(file_name)
-            if os.path.exists(meta_file):
-                os.remove(meta_file)
-            self.download_data(file_name, meta_file)
-            logging.debug("loaded new data from JOIN")
-        else:
-            try:
-                logging.debug(f"try to load local data from: {file_name}")
-                data = xr.open_dataarray(file_name)
-                self.meta = pd.read_csv(meta_file, index_col=0)
-                if self.station_type is not None:
-                    self.check_station_meta()
-                logging.debug("loading finished")
-            except FileNotFoundError as e:
-                logging.debug(e)
-                logging.debug("load new data from JOIN")
-                data, self.meta = self.download_data(file_name, meta_file)
-                logging.debug("loading finished")
-            # create slices and check for negative concentration.
-            data = self._slice_prep(data)
-            self.data = self.check_for_negative_concentrations(data)
+        params = helpers.remove_items(inspect.getfullargspec(AbstractDataPrep.__init__).args, "self")
+        kwargs = {**{k: v for k, v in locals().items() if k in params and v is not None}, **kwargs}
+        super().__init__(**kwargs)
 
     def download_data(self, file_name, meta_file):
         """
@@ -133,13 +81,14 @@ class DataPrep(object):
 
         Will raise a FileNotFoundError if the values mismatch.
         """
-        check_dict = {"station_type": self.station_type, "network_name": self.network}
-        for (k, v) in check_dict.items():
-            if self.meta.at[k, self.station[0]] != v:
-                logging.debug(f"meta data does not agree with given request for {k}: {v} (requested) != "
-                              f"{self.meta.at[k, self.station[0]]} (local). Raise FileNotFoundError to trigger new "
-                              f"grapping from web.")
-                raise FileNotFoundError
+        if self.station_type is not None:
+            check_dict = {"station_type": self.station_type, "network_name": self.network}
+            for (k, v) in check_dict.items():
+                if self.meta.at[k, self.station[0]] != v:
+                    logging.debug(f"meta data does not agree with given request for {k}: {v} (requested) != "
+                                  f"{self.meta.at[k, self.station[0]]} (local). Raise FileNotFoundError to trigger new "
+                                  f"grapping from web.")
+                    raise FileNotFoundError
 
     def download_data_from_join(self, file_name: str, meta_file: str) -> [xr.DataArray, pd.DataFrame]:
         """
@@ -166,426 +115,12 @@ class DataPrep(object):
             meta.to_csv(meta_file)
         return xarr, meta
 
-    def _set_file_name(self):
-        all_vars = sorted(self.statistics_per_var.keys())
-        return os.path.join(self.path, f"{''.join(self.station)}_{'_'.join(all_vars)}.nc")
-
-    def _set_meta_file_name(self):
-        all_vars = sorted(self.statistics_per_var.keys())
-        return os.path.join(self.path, f"{''.join(self.station)}_{'_'.join(all_vars)}_meta.csv")
-
     def __repr__(self):
         """Represent class attributes."""
         return f"Dataprep(path='{self.path}', network='{self.network}', station={self.station}, " \
                f"variables={self.variables}, station_type={self.station_type}, **{self.kwargs})"
 
-    def interpolate(self, dim: str, method: str = 'linear', limit: int = None, use_coordinate: Union[bool, str] = True,
-                    **kwargs):
-        """
-        Interpolate values according to different methods.
-
-        (Copy paste from dataarray.interpolate_na)
-
-        :param dim:
-                Specifies the dimension along which to interpolate.
-        :param method:
-                {'linear', 'nearest', 'zero', 'slinear', 'quadratic', 'cubic',
-                          'polynomial', 'barycentric', 'krog', 'pchip',
-                          'spline', 'akima'}, optional
-                    String indicating which method to use for interpolation:
-
-                    - 'linear': linear interpolation (Default). Additional keyword
-                      arguments are passed to ``numpy.interp``
-                    - 'nearest', 'zero', 'slinear', 'quadratic', 'cubic',
-                      'polynomial': are passed to ``scipy.interpolate.interp1d``. If
-                      method=='polynomial', the ``order`` keyword argument must also be
-                      provided.
-                    - 'barycentric', 'krog', 'pchip', 'spline', and `akima`: use their
-                      respective``scipy.interpolate`` classes.
-        :param limit:
-                    default None
-                    Maximum number of consecutive NaNs to fill. Must be greater than 0
-                    or None for no limit.
-        :param use_coordinate:
-                default True
-                    Specifies which index to use as the x values in the interpolation
-                    formulated as `y = f(x)`. If False, values are treated as if
-                    eqaully-spaced along `dim`. If True, the IndexVariable `dim` is
-                    used. If use_coordinate is a string, it specifies the name of a
-                    coordinate variariable to use as the index.
-        :param kwargs:
-
-        :return: xarray.DataArray
-        """
-        self.data = self.data.interpolate_na(dim=dim, method=method, limit=limit, use_coordinate=use_coordinate,
-                                             **kwargs)
-
-    @staticmethod
-    def check_inverse_transform_params(mean: data_or_none, std: data_or_none, method: str) -> None:
-        """
-        Support inverse_transformation method.
-
-        Validate if all required statistics are available for given method. E.g. centering requires mean only, whereas
-        normalisation requires mean and standard deviation. Will raise an AttributeError on missing requirements.
-
-        :param mean: data with all mean values
-        :param std: data with all standard deviation values
-        :param method: name of transformation method
-        """
-        msg = ""
-        if method in ['standardise', 'centre'] and mean is None:
-            msg += "mean, "
-        if method == 'standardise' and std is None:
-            msg += "std, "
-        if len(msg) > 0:
-            raise AttributeError(f"Inverse transform {method} can not be executed because following is None: {msg}")
-
-    def inverse_transform(self) -> None:
-        """
-        Perform inverse transformation.
-
-        Will raise an AssertionError, if no transformation was performed before. Checks first, if all required
-        statistics are available for inverse transformation. Class attributes data, mean and std are overwritten by
-        new data afterwards. Thereby, mean, std, and the private transform method are set to None to indicate, that the
-        current data is not transformed.
-        """
-
-        def f_inverse(data, mean, std, method_inverse):
-            if method_inverse == 'standardise':
-                return statistics.standardise_inverse(data, mean, std), None, None
-            elif method_inverse == 'centre':
-                return statistics.centre_inverse(data, mean), None, None
-            elif method_inverse == 'normalise':
-                raise NotImplementedError
-            else:
-                raise NotImplementedError
-
-        if self._transform_method is None:
-            raise AssertionError("Inverse transformation method is not set. Data cannot be inverse transformed.")
-        self.check_inverse_transform_params(self.mean, self.std, self._transform_method)
-        self.data, self.mean, self.std = f_inverse(self.data, self.mean, self.std, self._transform_method)
-        self._transform_method = None
-
-    def transform(self, dim: Union[str, int] = 0, method: str = 'standardise', inverse: bool = False, mean=None,
-                  std=None) -> None:
-        """
-        Transform data according to given transformation settings.
-
-        This function transforms a xarray.dataarray (along dim) or pandas.DataFrame (along axis) either with mean=0
-        and std=1 (`method=standardise`) or centers the data with mean=0 and no change in data scale
-        (`method=centre`). Furthermore, this sets an internal instance attribute for later inverse transformation. This
-        method will raise an AssertionError if an internal transform method was already set ('inverse=False') or if the
-        internal transform method, internal mean and internal standard deviation weren't set ('inverse=True').
-
-        :param string/int dim: This param is not used for inverse transformation.
-                | for xarray.DataArray as string: name of dimension which should be standardised
-                | for pandas.DataFrame as int: axis of dimension which should be standardised
-        :param method: Choose the transformation method from 'standardise' and 'centre'. 'normalise' is not implemented
-                    yet. This param is not used for inverse transformation.
-        :param inverse: Switch between transformation and inverse transformation.
-
-        :return: xarray.DataArrays or pandas.DataFrames:
-                #. mean: Mean of data
-                #. std: Standard deviation of data
-                #. data: Standardised data
-        """
-
-        def f(data):
-            if method == 'standardise':
-                return statistics.standardise(data, dim)
-            elif method == 'centre':
-                return statistics.centre(data, dim)
-            elif method == 'normalise':
-                # use min/max of data or given min/max
-                raise NotImplementedError
-            else:
-                raise NotImplementedError
-
-        def f_apply(data):
-            if method == "standardise":
-                return mean, std, statistics.standardise_apply(data, mean, std)
-            elif method == "centre":
-                return mean, None, statistics.centre_apply(data, mean)
-            else:
-                raise NotImplementedError
-
-        if not inverse:
-            if self._transform_method is not None:
-                raise AssertionError(f"Transform method is already set. Therefore, data was already transformed with "
-                                     f"{self._transform_method}. Please perform inverse transformation of data first.")
-            self.mean, self.std, self.data = locals()["f" if mean is None else "f_apply"](self.data)
-            self._transform_method = method
-        else:
-            self.inverse_transform()
-
-    def get_transformation_information(self, variable: str) -> Tuple[data_or_none, data_or_none, str]:
-        """
-        Extract transformation statistics and method.
-
-        Get mean and standard deviation for given variable and the transformation method if set. If a transformation
-        depends only on particular statistics (e.g. only mean is required for centering), the remaining statistics are
-        returned with None as fill value.
-
-        :param variable: Variable for which the information on transformation is requested.
-
-        :return: mean, standard deviation and transformation method
-        """
-        try:
-            mean = self.mean.sel({'variables': variable}).values
-        except AttributeError:
-            mean = None
-        try:
-            std = self.std.sel({'variables': variable}).values
-        except AttributeError:
-            std = None
-        return mean, std, self._transform_method
-
-    def make_history_window(self, dim_name_of_inputs: str, window: int, dim_name_of_shift: str) -> None:
-        """
-        Create a xr.DataArray containing history data.
-
-        Shift the data window+1 times and return a xarray which has a new dimension 'window' containing the shifted
-        data. This is used to represent history in the data. Results are stored in history attribute.
-
-        :param dim_name_of_inputs: Name of dimension which contains the input variables
-        :param window: number of time steps to look back in history
-                Note: window will be treated as negative value. This should be in agreement with looking back on
-                a time line. Nonetheless positive values are allowed but they are converted to its negative
-                expression
-        :param dim_name_of_shift: Dimension along shift will be applied
-        """
-        window = -abs(window)
-        self.history = self.shift(dim_name_of_shift, window).sel({dim_name_of_inputs: self.variables})
-
-    def shift(self, dim: str, window: int) -> xr.DataArray:
-        """
-        Shift data multiple times to represent history (if window <= 0) or lead time (if window > 0).
-
-        :param dim: dimension along shift is applied
-        :param window: number of steps to shift (corresponds to the window length)
-
-        :return: shifted data
-        """
-        start = 1
-        end = 1
-        if window <= 0:
-            start = window
-        else:
-            end = window + 1
-        res = []
-        for w in range(start, end):
-            res.append(self.data.shift({dim: -w}))
-        window_array = self.create_index_array('window', range(start, end))
-        res = xr.concat(res, dim=window_array)
-        return res
-
-    def make_labels(self, dim_name_of_target: str, target_var: str_or_list, dim_name_of_shift: str,
-                    window: int) -> None:
-        """
-        Create a xr.DataArray containing labels.
-
-        Labels are defined as the consecutive target values (t+1, ...t+n) following the current time step t. Set label
-        attribute.
-
-        :param dim_name_of_target: Name of dimension which contains the target variable
-        :param target_var: Name of target variable in 'dimension'
-        :param dim_name_of_shift: Name of dimension on which xarray.DataArray.shift will be applied
-        :param window: lead time of label
-        """
-        window = abs(window)
-        self.label = self.shift(dim_name_of_shift, window).sel({dim_name_of_target: target_var})
-
-    def make_observation(self, dim_name_of_target: str, target_var: str_or_list, dim_name_of_shift: str) -> None:
-        """
-        Create a xr.DataArray containing observations.
-
-        Observations are defined as value of the current time step t. Set observation attribute.
-
-        :param dim_name_of_target: Name of dimension which contains the observation variable
-        :param target_var: Name of observation variable(s) in 'dimension'
-        :param dim_name_of_shift: Name of dimension on which xarray.DataArray.shift will be applied
-        """
-        self.observation = self.shift(dim_name_of_shift, 0).sel({dim_name_of_target: target_var})
-
-    def remove_nan(self, dim: str) -> None:
-        """
-        Remove all NAs slices along dim which contain nans in history, label and observation.
-
-        This is done to present only a full matrix to keras.fit. Update history, label, and observation attribute.
-
-        :param dim: dimension along the remove is performed.
-        """
-        intersect = []
-        if (self.history is not None) and (self.label is not None):
-            non_nan_history = self.history.dropna(dim=dim)
-            non_nan_label = self.label.dropna(dim=dim)
-            non_nan_observation = self.observation.dropna(dim=dim)
-            intersect = reduce(np.intersect1d, (non_nan_history.coords[dim].values, non_nan_label.coords[dim].values,
-                                                non_nan_observation.coords[dim].values))
-
-        min_length = self.kwargs.get("min_length", 0)
-        if len(intersect) < max(min_length, 1):
-            self.history = None
-            self.label = None
-            self.observation = None
-        else:
-            self.history = self.history.sel({dim: intersect})
-            self.label = self.label.sel({dim: intersect})
-            self.observation = self.observation.sel({dim: intersect})
-
-    @staticmethod
-    def create_index_array(index_name: str, index_value: Iterable[int]) -> xr.DataArray:
-        """
-        Create an 1D xr.DataArray with given index name and value.
-
-        :param index_name: name of dimension
-        :param index_value: values of this dimension
-
-        :return: this array
-        """
-        ind = pd.DataFrame({'val': index_value}, index=index_value)
-        res = xr.Dataset.from_dataframe(ind).to_array().rename({'index': index_name}).squeeze(dim='variable', drop=True)
-        res.name = index_name
-        return res
-
-    def _slice_prep(self, data: xr.DataArray, coord: str = 'datetime') -> xr.DataArray:
-        """
-        Set start and end date for slicing and execute self._slice().
-
-        :param data: data to slice
-        :param coord: name of axis to slice
-
-        :return: sliced data
-        """
-        start = self.kwargs.get('start', data.coords[coord][0].values)
-        end = self.kwargs.get('end', data.coords[coord][-1].values)
-        return self._slice(data, start, end, coord)
-
-    @staticmethod
-    def _slice(data: xr.DataArray, start: Union[date, str], end: Union[date, str], coord: str) -> xr.DataArray:
-        """
-        Slice through a given data_item (for example select only values of 2011).
-
-        :param data: data to slice
-        :param start: start date of slice
-        :param end: end date of slice
-        :param coord: name of axis to slice
-
-        :return: sliced data
-        """
-        return data.loc[{coord: slice(str(start), str(end))}]
-
-    def check_for_negative_concentrations(self, data: xr.DataArray, minimum: int = 0) -> xr.DataArray:
-        """
-        Set all negative concentrations to zero.
-
-        Names of all concentrations are extracted from https://join.fz-juelich.de/services/rest/surfacedata/
-        #2.1 Parameters. Currently, this check is applied on "benzene", "ch4", "co", "ethane", "no", "no2", "nox",
-        "o3", "ox", "pm1", "pm10", "pm2p5", "propane", "so2", and "toluene".
-
-        :param data: data array containing variables to check
-        :param minimum: minimum value, by default this should be 0
-
-        :return: corrected data
-        """
-        chem_vars = ["benzene", "ch4", "co", "ethane", "no", "no2", "nox", "o3", "ox", "pm1", "pm10", "pm2p5",
-                     "propane", "so2", "toluene"]
-        used_chem_vars = list(set(chem_vars) & set(self.variables))
-        data.loc[..., used_chem_vars] = data.loc[..., used_chem_vars].clip(min=minimum)
-        return data
-
-    def get_transposed_history(self) -> xr.DataArray:
-        """Return history.
-
-        :return: history with dimensions datetime, window, Stations, variables.
-        """
-        return self.history.transpose("datetime", "window", "Stations", "variables").copy()
-
-    def get_transposed_label(self) -> xr.DataArray:
-        """Return label.
-
-        :return: label with dimensions datetime, window, Stations, variables.
-        """
-        return self.label.squeeze("Stations").transpose("datetime", "window").copy()
-
-    def get_extremes_history(self) -> xr.DataArray:
-        """Return extremes history.
-
-        :return: extremes history with dimensions datetime, window, Stations, variables.
-        """
-        return self.extremes_history.transpose("datetime", "window", "Stations", "variables").copy()
-
-    def get_extremes_label(self) -> xr.DataArray:
-        """Return extremes label.
-
-        :return: extremes label with dimensions datetime, window, Stations, variables.
-        """
-        return self.extremes_label.squeeze("Stations").transpose("datetime", "window").copy()
-
-    def multiply_extremes(self, extreme_values: num_or_list = 1., extremes_on_right_tail_only: bool = False,
-                          timedelta: Tuple[int, str] = (1, 'm')):
-        """
-        Multiply extremes.
-
-        This method extracts extreme values from self.labels which are defined in the argument extreme_values. One can
-        also decide only to extract extremes on the right tail of the distribution. When extreme_values is a list of
-        floats/ints all values larger (and smaller than negative extreme_values; extraction is performed in standardised
-        space) than are extracted iteratively. If for example extreme_values = [1.,2.] then a value of 1.5 would be
-        extracted once (for 0th entry in list), while a 2.5 would be extracted twice (once for each entry). Timedelta is
-        used to mark those extracted values by adding one min to each timestamp. As TOAR Data are hourly one can
-        identify those "artificial" data points later easily. Extreme inputs and labels are stored in
-        self.extremes_history and self.extreme_labels, respectively.
-
-        :param extreme_values: user definition of extreme
-        :param extremes_on_right_tail_only: if False also multiply values which are smaller then -extreme_values,
-            if True only extract values larger than extreme_values
-        :param timedelta: used as arguments for np.timedelta in order to mark extreme values on datetime
-        """
-        # check if labels or history is None
-        if (self.label is None) or (self.history is None):
-            logging.debug(f"{self.station} has `None' labels, skip multiply extremes")
-            return
-
-        # check type if inputs
-        extreme_values = helpers.to_list(extreme_values)
-        for i in extreme_values:
-            if not isinstance(i, number.__args__):
-                raise TypeError(f"Elements of list extreme_values have to be {number.__args__}, but at least element "
-                                f"{i} is type {type(i)}")
-
-        for extr_val in sorted(extreme_values):
-            # check if some extreme values are already extracted
-            if (self.extremes_label is None) or (self.extremes_history is None):
-                # extract extremes based on occurance in labels
-                if extremes_on_right_tail_only:
-                    extreme_label_idx = (self.label > extr_val).any(axis=0).values.reshape(-1, )
-                else:
-                    extreme_label_idx = np.concatenate(((self.label < -extr_val).any(axis=0).values.reshape(-1, 1),
-                                                        (self.label > extr_val).any(axis=0).values.reshape(-1, 1)),
-                                                       axis=1).any(axis=1)
-                extremes_label = self.label[..., extreme_label_idx]
-                extremes_history = self.history[..., extreme_label_idx, :]
-                extremes_label.datetime.values += np.timedelta64(*timedelta)
-                extremes_history.datetime.values += np.timedelta64(*timedelta)
-                self.extremes_label = extremes_label  # .squeeze('Stations').transpose('datetime', 'window')
-                self.extremes_history = extremes_history  # .transpose('datetime', 'window', 'Stations', 'variables')
-            else:  # one extr value iteration is done already: self.extremes_label is NOT None...
-                if extremes_on_right_tail_only:
-                    extreme_label_idx = (self.extremes_label > extr_val).any(axis=0).values.reshape(-1, )
-                else:
-                    extreme_label_idx = np.concatenate(
-                        ((self.extremes_label < -extr_val).any(axis=0).values.reshape(-1, 1),
-                         (self.extremes_label > extr_val).any(axis=0).values.reshape(-1, 1)
-                         ), axis=1).any(axis=1)
-                # check on existing extracted extremes to minimise computational costs for comparison
-                extremes_label = self.extremes_label[..., extreme_label_idx]
-                extremes_history = self.extremes_history[..., extreme_label_idx, :]
-                extremes_label.datetime.values += np.timedelta64(*timedelta)
-                extremes_history.datetime.values += np.timedelta64(*timedelta)
-                self.extremes_label = xr.concat([self.extremes_label, extremes_label], dim='datetime')
-                self.extremes_history = xr.concat([self.extremes_history, extremes_history], dim='datetime')
-
 
 if __name__ == "__main__":
-    dp = DataPrep('data/', 'dummy', 'DEBW107', ['o3', 'temp'], statistics_per_var={'o3': 'dma8eu', 'temp': 'maximum'})
+    dp = DataPrepJoin('data/', 'dummy', 'DEBW107', ['o3', 'temp'], statistics_per_var={'o3': 'dma8eu', 'temp': 'maximum'})
     print(dp)
diff --git a/src/run_modules/post_processing.py b/src/run_modules/post_processing.py
index dedcda0a6a3ff8fb9246bc6efe097eeb6b463999..b97d28c1cf71d35526207450d6b0bb386ddefdb7 100644
--- a/src/run_modules/post_processing.py
+++ b/src/run_modules/post_processing.py
@@ -13,7 +13,7 @@ import numpy as np
 import pandas as pd
 import xarray as xr
 
-from src.data_handling import BootStraps, Distributor, DataGenerator, DataPrep
+from src.data_handling import BootStraps, Distributor, DataGenerator, DataPrepJoin
 from src.helpers.datastore import NameNotFoundInDataStore
 from src.helpers import TimeTracking, statistics
 from src.model_modules.linear_model import OrdinaryLeastSquaredModel
@@ -358,7 +358,7 @@ class PostProcessing(RunEnvironment):
         return getter.get(self._sampling, None)
 
     @staticmethod
-    def _create_observation(data: DataPrep, _, mean: xr.DataArray, std: xr.DataArray, transformation_method: str,
+    def _create_observation(data: DataPrepJoin, _, mean: xr.DataArray, std: xr.DataArray, transformation_method: str,
                             normalised: bool) -> xr.DataArray:
         """
         Create observation as ground truth from given data.
@@ -402,7 +402,7 @@ class PostProcessing(RunEnvironment):
         ols_prediction.values = np.swapaxes(tmp_ols, 2, 0) if target_shape != tmp_ols.shape else tmp_ols
         return ols_prediction
 
-    def _create_persistence_forecast(self, data: DataPrep, persistence_prediction: xr.DataArray, mean: xr.DataArray,
+    def _create_persistence_forecast(self, data: DataPrepJoin, persistence_prediction: xr.DataArray, mean: xr.DataArray,
                                      std: xr.DataArray, transformation_method: str, normalised: bool) -> xr.DataArray:
         """
         Create persistence forecast with given data.
diff --git a/test/test_data_handling/test_data_preparation.py b/test/test_data_handling/test_data_preparation.py
index a8ca555c9748f7656fefc007922ee0d7df1992fa..85c2b6a7c256deb6bfcfbf73483652031d034a27 100644
--- a/test/test_data_handling/test_data_preparation.py
+++ b/test/test_data_handling/test_data_preparation.py
@@ -8,7 +8,8 @@ import pandas as pd
 import pytest
 import xarray as xr
 
-from src.data_handling.data_preparation import DataPrep
+# from src.data_handling.data_preparation import DataPrep
+from src.data_handling.data_preparation_join import DataPrepJoin as DataPrep
 from src.helpers.join import EmptyQueryResult
 
 
@@ -52,8 +53,9 @@ class TestDataPrep:
         meta_file = data_prep_no_init._set_meta_file_name()
         data_prep_no_init.kwargs = {"store_data_locally": False}
         data_prep_no_init.statistics_per_var = {'o3': 'dma8eu', 'temp': 'maximum'}
-        data_prep_no_init.download_data(file_name, meta_file)
-        assert isinstance(data_prep_no_init.data, xr.DataArray)
+        data, meta = data_prep_no_init.download_data(file_name, meta_file)
+        assert isinstance(data, xr.DataArray)
+        assert isinstance(meta, pd.DataFrame)
 
     def test_download_data_from_join(self, data_prep_no_init):
         file_name = data_prep_no_init._set_file_name()
@@ -70,7 +72,8 @@ class TestDataPrep:
         meta_file = data_prep_no_init._set_meta_file_name()
         data_prep_no_init.kwargs = {"store_data_locally": False}
         data_prep_no_init.statistics_per_var = {'o3': 'dma8eu', 'temp': 'maximum'}
-        data_prep_no_init.download_data(file_name, meta_file)
+        _, meta = data_prep_no_init.download_data(file_name, meta_file)
+        data_prep_no_init.meta = meta
         assert data_prep_no_init.check_station_meta() is None
         data_prep_no_init.station_type = "traffic"
         with pytest.raises(FileNotFoundError) as e:
@@ -83,8 +86,8 @@ class TestDataPrep:
         data_prep_no_init.statistics_per_var = {'o3': 'dma8eu', 'temp': 'maximum'}
         file_path = data_prep_no_init._set_file_name()
         meta_file_path = data_prep_no_init._set_meta_file_name()
-        os.remove(file_path)
-        os.remove(meta_file_path)
+        os.remove(file_path) if os.path.exists(file_path) else None
+        os.remove(meta_file_path) if os.path.exists(meta_file_path) else None
         assert not os.path.exists(file_path)
         assert not os.path.exists(meta_file_path)
         data_prep_no_init.kwargs = {"overwrite_local_data": True}