From 6bdf81bae326153a465d3ac1485b0628e29ec456 Mon Sep 17 00:00:00 2001
From: Thomas Rieutord <thomas.rieutord@gmail.com>
Date: Wed, 31 Jul 2024 13:03:38 +0100
Subject: [PATCH] Update bulk_richardson_number: fix null wind at bottom
 (comment #2 in PR #3572)

---
 src/metpy/calc/boundarylayer.py | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/metpy/calc/boundarylayer.py b/src/metpy/calc/boundarylayer.py
index 1d43ea0ebe..673b3f893e 100644
--- a/src/metpy/calc/boundarylayer.py
+++ b/src/metpy/calc/boundarylayer.py
@@ -93,13 +93,15 @@ def bulk_richardson_number(
     `pint.Quantity`
         Bulk Richardson number profile
     """
-
-    u[0] = 0 * units.meter_per_second
-    v[0] = 0 * units.meter_per_second
-
+    if idxfoot == 0:
+        # Force the ground level to have null wind
+        Du = u
+        Dv = v
+    else:
+        Du = u - u[idxfoot]
+        Dv = v - v[idxfoot]
+    
     Dtheta = potential_temperature - potential_temperature[idxfoot]
-    Du = u - u[idxfoot]
-    Dv = v - v[idxfoot]
     Dz = height - height[idxfoot]
 
     idx0 = Du**2 + Dv**2 + ustar**2 == 0