diff --git a/modules/aeolus/aeolus_amv.py b/modules/aeolus/aeolus_amv.py
index 6a28b4dc69c47a1ffa516f873529d4332719415d..d947a46ed21a5bc691e8928624df7b72d7d1ea0c 100644
--- a/modules/aeolus/aeolus_amv.py
+++ b/modules/aeolus/aeolus_amv.py
@@ -92,6 +92,8 @@ def match_amvs_to_raobs(raob_dict, raob_time, amv_ds, time_window=10, filepath=N
         cc = nc4f[amv_ds.elem_name][:].data
         ll = nc4f[amv_ds.line_name][:].data
 
+    num_amvs = amv_lons.shape[0]
+
     param_s = []
     param_s.append(amv_lons)
     param_s.append(amv_lats)
@@ -110,6 +112,7 @@ def match_amvs_to_raobs(raob_dict, raob_time, amv_ds, time_window=10, filepath=N
             param_s.append(data.data[1])
         else:
             param_s.append(data.data)
+    param_s.append(np.arange(num_amvs))  # The absolute dataset index of amvs
 
     # filter
     qc_name = amv_ds.get_qc_params()
@@ -144,8 +147,7 @@ def match_amvs_to_raobs(raob_dict, raob_time, amv_ds, time_window=10, filepath=N
         in_ll = np.logical_and(ll > l_rng[0], ll < l_rng[1])
         in_box = np.logical_and(in_cc, in_ll)
 
-        num_amvs = np.sum(in_box)
-        if num_amvs == 0:
+        if np.sum(in_box) == 0:
             continue
         match_dict[key] = param_nd[:, in_box]