title: How to remove a "redundant" dimension with CDO (climate data operators)?
body: <p>The ERA5 climate dataset is, in general, defined as a [lat, lon, time] matrix. Except for recent data, where it adds the <code>exp_ver</code> variable that indicate if the data is provisory (recent data, up to 3 months until the present, coded as &quot;05&quot;) or old (stable version, coded as &quot;01&quot;), so the matrix are defined [lat, lon, time, exp_ver] only for recent data.</p>
  <p>The exp_ver variable only has two values: &quot;01&quot; (old data) and &quot;05&quot; (recent data), and if there is data in &quot;01&quot; so the corresponding time has missing values in the &quot;05&quot; field, and viceversa. I'm looking for merge both &quot;01&quot; and &quot;05&quot; in a unique [lat, lon, time] matrix (so, remove the exp_ver variable), but I dont' know how to conduct this procedure. This is maybe an option:</p>
  <p>A. Split the file with <code>cdo splitlevel</code> obtaining the &quot;01&quot; and &quot;05&quot; exp_ver separate files.</p>
  <p>B. Remove the missing values segment, or only select the segment with data, from both files (I don't know how to to this!)</p>
  <p>C. Remove the redundant variable &quot;exp_ver&quot; from both files (with <code>cdo reduce_dim</code>)</p>
  <p>Any help with this? Thank you in advance!</p>
  <p>Diego</p>