diff --git a/modules/util/util.py b/modules/util/util.py
index 7c4c2d696f2d2c3b1fa7e5eb0fa1e583ae8ea550..1040a030443f32283d2092e0f27ff328c7a06638 100644
--- a/modules/util/util.py
+++ b/modules/util/util.py
@@ -87,7 +87,7 @@ def pressure_to_altitude(pres, temp, prof_pres, prof_temp, sfc_pres=None, sfc_te
         prof_temp = np.array(temp_s)
         i_bot = prof_pres.shape[0] - 1
 
-        if sfc_pres > prof_pres[i_bot]:
+        if sfc_pres > prof_pres[i_bot]:  # surface below profile bottom
             pres_s = pres_s + [sfc_pres]
             temp_s = temp_s + [sfc_temp]
         else: