diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index 5d9e5aa..be0e3e8 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -4,8 +4,7 @@ from typing import Callable
 
 from xmet.series import Series
 
-LAPSE_RATE_DRY   = 9.8 / 1000 # degrees C per km
-LAPSE_RATE_MOIST = 4.0 / 1000
+LAPSE_RATE_DRY = 9.8 / 1000 # degrees C per km
 
 PRESSURE_MAX  = 1050 # millibar
 PRESSURE_MSL  = 1013.25