I am trying to understand the basic dynamics of MJO, where I find several studies which relate it to the initiation of equatorial Rossby and Kelvin waves. Though MJO is an eastward propagating wave, I can relate it to the existence of Kelvin waves during that time but I am not getting any insight about the initiation of a westward wave. I think that the westward motion could be possible only due to the reflection of easterly wave through a boundary. Please correct me with the actual fact and its underlying mechanism.
I am mentioning some of the online sources which inform about the above mentioned fact but I am not getting the answers from any research papers
Actually I could not find the detailed study for source 1 but I found similar statements (Kelvin-Rossby relation) in other studies that made me more confused. The second mention raises this issue, they talk about Matsuno-Gill theory and the usage of equatorial waves in it but I am unable to get any understanding of their model about how it emerged from (A description is attached here).