AgPaDS v1.0: a GPU-accelerated interactive Lagrangian atmospheric transport model with 3-D in situ visualization for simulating windborne dispersal of crop pathogens

Lagrangian models are widely adopted to study atmospheric transport processes, with applications in various domains, including the investigation of windborne crop diseases and epidemic risks in agriculture. Widely used Atmospheric Transport Modelling frameworks (ATMs) do not exploit the potential for performance gains and advanced computer graphics that Graphical Processing Units (GPUs) provide, and they impose limitations regarding customization for domain-specific applications in crop epidemiology and agrometeorology. The objective of this study is to contribute to addressing these gaps by developing and testing a new simulation model. We introduce AgPaDS, the Agricultural Pest and Disease Simulator, a GPU-accelerated stochastic Lagrangian model with an option for advanced interactive 3-D in-situ visualization of global-scale atmospheric transport simulations. The tool was developed with two main goals: (i) accelerate compute times through an efficient GPU implementation that enables exploratory visual analyses by means of interactive simulation setup in a graphical user interface with embedded 3-D in situ visualization; (ii) build a new atmospheric transport model dedicated to applications in crop epidemiology with model components not available in widely used ATMs and with flexibility for future domain-specific customizations. It is based on an optimized massively parallelized CUDA C++ and OpenGL implementation. We report on model formulation, technical implementation and testing, including a systematic comparison with HYSPLIT, one of the most widely used ATMs, and a case-evaluation with in-situ visualization of complex 3-D dynamics of simulated crop pathogen transport during the hurricane that has likely transmitted soybean rust into the USA in 2004. We show that AgPaDS produces atmospheric transport quantities broadly consistent with HYSPLIT across a set of test cases whilst providing substantial speedups for simulations with very large particle numbers (up to three orders of magnitude). The model can simulate the release of millions of Lagrangian particles from heterogeneous crop landscapes on global scales with live 3-D visualization of simulated windborne dispersal of crop pathogens. A set of supplementary videos illustrates interactive and in situ 3-D visualization methods. Examples of future use-cases include (i) exploratory 3-D visual analyses of atmospheric transport simulations, including interactions between meteorological and biological processes; (ii) assessment of global airborne connectivity of agricultural landscapes; (iii) efficient representation of wind dispersal in crop disease forecasting systems.