diff --git a/modules/util/util.py b/modules/util/util.py
index 726644216aa4f352b3549ee5ea5064a3d3fc5149..ed605e94abb2ae3a9b9a54bd2c51817d5b231376 100644
--- a/modules/util/util.py
+++ b/modules/util/util.py
@@ -185,6 +185,23 @@ def value_to_index(nda, value):
     return idx
 
 
+def find_bin_index(nda, value):
+    idxs = np.arange(nda.shape[0])
+
+    above = nda >= value
+    if not above.any():
+        return -1
+
+    below = nda < value
+    if not below.any():
+        return -1
+
+    iL = idxs[above].max()
+
+    return iL
+
+
+
 # array solzen must be degrees, missing values must NaN. For small roughly 50x50km regions only
 def is_day(solzen, test_angle=80.0):
     solzen = solzen.flatten()