Extracting vertical velocity variance (w′²) by KBLT option in HYSPLIT v5.4.2 (Linux / CentOS 8)

[min_k]

Hello,

I am running HYSPLIT v5.4.2 on CentOS Linux 8, using hycs_std in concentration mode.
My goal is to reproduce results similar to the developer paper figures, specifically the vertical velocity variance (w′²) or related vertical turbulent statistics as a function of height, in order to compare different KBLT vertical mixing options.


According to the documentation and developer papers, the KBLT option controls how vertical turbulent mixing is calculated, and the vertical velocity variance (or σw) is a key quantity representing vertical dispersion strength. However, I have not been able to find any existing output file or post-processing program in the Linux version of HYSPLIT that directly provides height-resolved vertical velocity variance.

Because of this, I attempted to extract the variable directly from the source code by adding WRITE statements in prfcom.f, where the KBLT-related calculations are performed. Despite successfully recompiling and running the model, the expected output file is not created, and I am unsure whether:

prfcom.f is the correct location to write out vertical velocity variance, the relevant variable is available at that stage of the code, or whether this quantity is intentionally not exposed in standard HYSPLIT outputs.

My questions are:

1. Is it currently possible to output vertical velocity variance (w′² or σw²) by height in HYSPLIT v5.4.2 on Linux without modifying the source code?

2. If source-code modification is required, is prfcom.f the appropriate place to extract this information during a concentration run (hycs_std)?

3. Are there recommended diagnostics or alternative variables that developers suggest for representing vertical turbulent mixing strength by KBLT option?

Any guidance or confirmation from the developers or experienced users would be greatly appreciated.

Thank you.


*Ngan, F., Loughner, C. P., & Stein, A. (2019).
The evaluation of mixing methods in HYSPLIT using measurements from controlled tracer experiments.
Atmospheric Environment, 219, 117043.