In a sequence diagram, lifeline shows the existence or participation duration of an object during the interaction.

From the given figure, the increasing order of lifeline is from the object having the shortest lifeline to the object having the longest lifeline.

By observing the diagram:

Weather Data has the shortest lifeline.

Then comes Comms link.

Then comes Weather Station.

Sat Comms has the longest lifeline.

So, the increasing order is:

Weather Data $\rightarrow$ Comms link $\rightarrow$ Weather Station $\rightarrow$ Sat Comms