diff --git a/mlair/plotting/data_insight_plotting.py b/mlair/plotting/data_insight_plotting.py
index cc8ba279d556726ef82ac13e0287077215d6b4d6..dcaf077b94ac20807ede909ef6f0c54e704b40ef 100644
--- a/mlair/plotting/data_insight_plotting.py
+++ b/mlair/plotting/data_insight_plotting.py
@@ -831,7 +831,7 @@ class PlotPeriodogram(AbstractPlotClass):  # pragma: no cover
 def f_proc(var, d_var):  # pragma: no cover
     var_str = str(var)
     t = (d_var.datetime - d_var.datetime[0]).astype("timedelta64[h]").values / np.timedelta64(1, "D")
-    f, pgram = LombScargle(t, d_var.values.flatten(), nterms=1).autopower()
+    f, pgram = LombScargle(t, d_var.values.flatten(), nterms=1, normalization="psd").autopower()
     return var_str, f, pgram