How do people changing fields after PhD overcome competition with "locals"? There are a number of questions here about changing-fields.  Those are mostly about how common it is, how it affects future career, or whether a move from X to Y is feasible (example 1, 2, 3).  At any rate, it does happen — I have come across people with background in particle physics, astrophysics, or space science, who were all in postdocs in atmospheric science.  A frequent motivation may be to resolve the two body problem.  And some fields have a higher ratio of jobs to PhD graduates than others.

But if someone with a PhD in particle physics, astrophysics, or space science, applies for a post-doc in atmospheric science, how do they overcome the competition with candidates who do have PhDs specialising in (the right subfield of) atmospheric science?  Wouldn't a potential host quickly dismiss candidates who show neither experience nor interest in the relevant field, even if they have spoken the person, when other applicants are pre-trained "locals"?
Some of my best hires have had virtually no direct or recent experience in HPC, but have demonstrated a number of other extremely desirable features including:


A passion for learning and doing
A clear track record of success in their related area (including publishing, mentoring, grant-writing, etc.).
An strong awareness of their own limitations in the field and a plan for dealing with them
A strong understanding of our needs based on researching our mission, goals, website, etc. and a plan for how they fit into that.


Based on this, I've taken a flyer on a researcher or two who wasn't a perfect fit but was too passionate, engaging, and obviously successful to pass up. A ridiculously strong reference is also helpful.