diff --git a/PyStemmusScope/bmi/variable_reference.py b/PyStemmusScope/bmi/variable_reference.py
index 622bbeb..b245689 100644
--- a/PyStemmusScope/bmi/variable_reference.py
+++ b/PyStemmusScope/bmi/variable_reference.py
@@ -44,6 +44,7 @@ class BmiVariable:
         units="cm s-1",
         grid=0,
         keys=["Trap"],
+        all_timesteps=True,    
     ),
     # soil vars:
     BmiVariable(