diff --git a/src/pydartdiags/plots/plots.py b/src/pydartdiags/plots/plots.py
index 20406e8..a5ff2ad 100644
--- a/src/pydartdiags/plots/plots.py
+++ b/src/pydartdiags/plots/plots.py
@@ -62,54 +62,82 @@ def calculate_rank(df):
 
     return (rank, ens_size, result_df)
 
-def plot_profile(df, levels):
+def plot_profile(df, levels, verticalUnit = "pressure (Pa)"):
     """
-    Plots RMSE and Bias profiles for different observation types across specified pressure levels.
+    Plots RMSE, bias, and total spread profiles for different observation types across specified vertical levels.
 
     This function takes a DataFrame containing observational data and model predictions, categorizes
-    the data into specified pressure levels, and calculates the RMSE and Bias for each level and
-    observation type. It then plots two line charts: one for RMSE and another for Bias, both as functions
-    of pressure level. The pressure levels are plotted on the y-axis in reversed order to represent
-    the vertical profile in the atmosphere correctly.
+    the data into specified vertical levels, and calculates the RMSE, bias and total spread for each level and
+    observation type. It then plots three line charts: one for RMSE, one for bias, one for total spread,  as functions
+    of vertical level. The vertical levels are plotted on the y-axis in reversed order to represent
+    the vertical profile in the atmosphere correctly if the vertical units are pressure.
 
     Parameters:
-        df (pd.DataFrame): The input DataFrame containing at least the 'vertical' column for pressure levels,
-        and other columns required by the `rmse_bias` function for calculating RMSE and Bias.
-        levels (array-like): The bin edges for categorizing the 'vertical' column values into pressure levels.
+        df (pd.DataFrame): The input DataFrame containing at least the 'vertical' column for vertical levels,
+        the vert_unit column, and other columns required by the `rmse_bias` function for calculating RMSE and 
+        Bias.
+        levels (array-like): The bin edges for categorizing the 'vertical' column values into the desired 
+        vertical levels.
+        verticalUnit (string) (optional): The vertical unit to be used. Only observations in df which have this
+        string in the vert_unit column will be plotted. Defaults to 'pressure (Pa)'.
 
     Returns:
-        tuple: A tuple containing the DataFrame with RMSE and Bias calculations, the RMSE plot figure, and the
-        Bias plot figure. The DataFrame includes a 'plevels' column representing the categorized pressure levels
-        and 'hPa' column representing the midpoint of each pressure level bin.
+        tuple: A tuple containing the DataFrame with RMSE, bias and total spread calculations,
+        The DataFrame includes a 'vlevels' column representing the categorized vertical levels
+        and 'midpoint' column representing the midpoint of each vertical level bin. And the three figures.
 
     Raises:
         ValueError: If there are missing values in the 'vertical' column of the input DataFrame.
+        ValueError: If none of the input obs have 'verticalUnit' in the 'vert_unit' column of the input DataFrame.
 
     Note:
-        - The function modifies the input DataFrame by adding 'plevels' and 'hPa' columns.
-        - The 'hPa' values are calculated as half the midpoint of each pressure level bin, which may need
-          adjustment based on the specific requirements for pressure level representation.
+        - The function modifies the input DataFrame by adding 'vlevels' and 'midpoint' columns.
+        - The 'midpoint' values are calculated as half the midpoint of each vertical level bin, which may need
+          adjustment based on the specific requirements for vertical level representation.
         - The plots are generated using Plotly Express and are displayed inline. The y-axis of the plots is
-          reversed to align with standard atmospheric pressure level representation.
+          reversed to align with standard atmospheric pressure level representation if the vertical units
+          are atmospheric pressure.
     """
 
     pd.options.mode.copy_on_write = True
     if df['vertical'].isnull().values.any(): # what about horizontal observations?
         raise ValueError("Missing values in 'vertical' column.")
+    elif verticalUnit not in df['vert_unit'].values:
+        raise ValueError("No obs with expected vertical unit '"+verticalUnit+"'.")
     else:
-        df.loc[:,'plevels'] = pd.cut(df['vertical'], levels)
-        df.loc[:,'hPa'] = df['plevels'].apply(lambda x: x.mid / 1000.) # HK todo units
-
-    df_profile = rmse_bias(df)
-    fig_rmse = px.line(df_profile, y='hPa', x='rmse', title='RMSE by Level', markers=True, color='type', width=800, height=800)
-    fig_rmse.update_yaxes(autorange="reversed")
+        df = df[df["vert_unit"].isin({verticalUnit})] # Subset to only rows with the correct vertical unit
+        df.loc[:,'vlevels'] = pd.cut(df['vertical'], levels)
+        if verticalUnit == "pressure (Pa)":
+            df.loc[:,'midpoint'] = df['vlevels'].apply(lambda x: x.mid / 100.) # HK todo units
+        else:
+            df.loc[:,'midpoint'] = df['vlevels'].apply(lambda x: x.mid)
+
+    # Calculations
+    df_profile = rmse_bias_totalspread(df)
+
+    # RMSE plot
+    fig_rmse = px.line(df_profile, y='midpoint', x='rmse', title='RMSE by Level', markers=True, color='type', width=800, height=800,
+                      labels={"midpoint": verticalUnit})
+    if verticalUnit == "pressure (Pa)":
+        fig_rmse.update_yaxes(autorange="reversed")
     fig_rmse.show()
 
-    fig_bias = px.line(df_profile, y='hPa', x='bias', title='Bias by Level', markers=True, color='type', width=800, height=800)
-    fig_bias.update_yaxes(autorange="reversed")
+    # totalspread plot
+    fig_ts = px.line(df_profile, y='midpoint', x='totalspread', title='Totalspread by Level', markers=True, color='type', width=800, height=800,
+                      labels={"midpoint": verticalUnit})
+    if verticalUnit == "pressure (Pa)":
+        fig_ts.update_yaxes(autorange="reversed")
+    fig_ts.show()
+
+    # bias plot
+    fig_bias = px.line(df_profile, y='midpoint', x='bias', title='Bias by Level', markers=True, color='type', width=800, height=800,
+                      labels={"midpoint": verticalUnit})
+    if verticalUnit == "pressure (Pa)":
+        fig_bias.update_yaxes(autorange="reversed")
     fig_bias.show()
+    
 
-    return df_profile, fig_rmse, fig_bias
+    return df_profile, fig_rmse, fig_ts, fig_bias
     
     
 def mean_then_sqrt(x):
@@ -130,12 +158,17 @@ def mean_then_sqrt(x):
         
     return np.sqrt(np.mean(x))
 
-def rmse_bias(df):
-    rmse_bias_df = df.groupby(['hPa', 'type']).agg({'sq_err':mean_then_sqrt, 'bias':'mean'}).reset_index()
-    rmse_bias_df.rename(columns={'sq_err':'rmse'}, inplace=True)
-    
-    return rmse_bias_df
+def rmse_bias_totalspread(df): 
+    rmse_bias_ts_df = df.groupby(['midpoint', 'type'], observed=False)
+    rmse_bias_ts_df = rmse_bias_ts_df.agg({'sq_err':mean_then_sqrt, 'bias':'mean', 'posterior_ensemble_spread':mean_then_sqrt, 'obs_err_var':mean_then_sqrt}).reset_index()
 
+    # Add column for totalspread
+    rmse_bias_ts_df['totalspread'] = np.sqrt(rmse_bias_ts_df['posterior_ensemble_spread']+rmse_bias_ts_df['obs_err_var'])
+
+    # Rename square error to root mean square error
+    rmse_bias_ts_df.rename(columns={'sq_err':'rmse'}, inplace=True)
+    
+    return rmse_bias_ts_df
 
 def rmse_bias_by_obs_type(df, obs_type):
     """
@@ -155,7 +188,7 @@ def rmse_bias_by_obs_type(df, obs_type):
         raise ValueError(f"Observation type '{obs_type}' not found in DataFrame.")
     else:
         obs_type_df = df[df['type'] == obs_type]
-        obs_type_agg = obs_type_df.groupby('plevels').agg({'sq_err':mean_then_sqrt, 'bias':'mean'}).reset_index()
+        obs_type_agg = obs_type_df.groupby('vlevels', observed=False).agg({'sq_err':mean_then_sqrt, 'bias':'mean'}).reset_index()
         obs_type_agg.rename(columns={'sq_err':'rmse'}, inplace=True)
         return obs_type_agg