In this talk, we will present our work of coupling the Julia runtime with E3SM, an advanced earth system simulation application for supercomputers, and running E3SM with swappable in-situ Julia modules at large scale. The talk includes (1) the Julia runtime coupling with legacy High-Performance Computing (HPC) applications (i.e., E3SM), (2) the design of two in-situ data analysis modules in Julia, and (3) the communication design for E3SM and the in-situ Julia modules.