Massive-Parallel Trajectory Calculations (MPTRAC) is a Lagrangian particle dispersion model for the analysis of atmospheric transport processes in the free troposphere and stratosphere. Changes in this release Documentation & Metadata Updated README, documentation, mkdocs manual, model-physics.md, references, CITATION.cff, and DEPENDENCIES.md. Added quick-start README and links to the MPTRAC Web Runner. Fixed Doxygen documentation and script descriptions. Build System, Dependencies & CI/CD Updated build scripts, requirements, dependencies, and compilation conditionals. Fixed MPI, OpenMP, OpenACC, CPU, and GPU compilation issues. Added and updated CI tests (Fortran wrapper, GRIB, ZFP, ZSTD, GPU). Fixed eccodes, SZ3, ZFP installation paths. Removed obsolete dependencies (CUDA runtime for Thrust, curl). Ignored HDF5 build check failures where appropriate. Code Quality & Refactoring General code cleanup, formatting, const qualifiers, and style fixes. Unified error handling and revised logging/info messages. Removed unused variables, imports, deprecated types (e.g. bool), and excessive debugging code. Improved memory handling and cleanup routines. Domain Decomposition (DD) Major redesign and stabilization of domain decomposition Introduced dd_t, ctl->dd, dd_init(), and module_dd. Refactored MPI communication, requests, sorting buffers, halos, and periodic boundaries. Fixed DD bugs (poles, halos, memory handling, CPU/GPU builds). Added conditional compilation, DD tests, and Makefile targets. Improved initialization, logging, and neighbor handling. Physics, Numerics & Algorithms Revised advection schemes (etadot/zetadot), interpolation, eta-level handling, and time-step computation. Improved NRMSE calculation and compression-rate metrics. Added fast pressure-to-eta conversion. Updated diffusivity control parameters and vertical coordinate determination. Fixed geopotential and other physics routines. I/O, Data Handling & Formats Added netCDF parallel I/O with additional I/O timing. Improved GRIB and netCDF readers (date/time handling, flexible vertical levels). Updated CSI writing and merged ensemble/non-ensemble routines. Improved working-directory cleanup and periodic maintenance. Compression Revised CMS, SZ3, ZSTD, and ZFP compression code. Added SZ3 compression for meteorological data. Added new ZFP control parameters and fixed compression-ratio calculations. GPU & Performance Ported core routines to GPUs (particles↔atmosphere, DD, advection). Added GPU-compatible DD (initial working version). Improved OpenMP scheduling, sorting fallbacks (GSL/Thrust), and performance logging. Added experimental GPU pragmas and alternative communication paths. Tests & Examples Added and updated tests for DD, GPU, GRIB, meteo data, and trajectories. Updated examples, simulation settings, plots, and visualization options. Added quick-look plots and parallelized their generation. Web Runner & User Interface Updated input forms, plot settings, defaults, and output options. Added play/stop controls, sliders, runtime warnings, and contact buttons. Added and updated support for ECMWF (IFS, AIFS), NCEP GFS, ERA5, JRA-3Q, and JRA-55. Fixed dataset paths, disabled unsupported reanalyses, and improved data retrieval scripts.

If you use this software, please cite it using the metadata from the CITATION.cff file.