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DTSTAMP:20260421T090514Z
LOCATION:Bldg. 6 - Room 104
DTSTART;TZID=Europe/Stockholm:20260701T140000
DTEND;TZID=Europe/Stockholm:20260701T160000
UID:submissions.pasc-conference.org_PASC26_sess163@linklings.com
SUMMARY:MS5F - Single and Reduced Precision for Weather and Climate Models
DESCRIPTION:High-resolution weather and climate models are rapidly approac
 hing the long-standing goal of simulating one year per day at 1 km global 
 resolution, thanks to GPU-accelerated pre-Exascale and Exascale HPC system
 s. Achieving this performance sustainably, however, requires more than tra
 ditional code optimization - it demands HPC co-design, where scientific de
 velopers, numerical analysts, and computational experts collaborate to ret
 hink algorithms for modern hardware. One promising strategy is the use of 
 single- or reduced-precision arithmetic. Lower-precision computations impr
 ove memory bandwidth, cache efficiency, and energy usage, and enable explo
 itation of specialized GPU units optimized for fast, low-precision operati
 ons. At the same time, reducing precision raises important questions about
  scientific trust, numerical stability, and reproducibility, particularly 
 in chaotic, multi-scale Earth system models. This minisymposium will bring
  together experts from climate science, numerical modeling, and HPC to sha
 re experiences, challenges, and best practices in adopting lower-precision
  computations. Topics include algorithmic reformulation, precision-aware s
 oftware design, verification and validation strategies, and precision anal
 ysis tools. While focused on weather and climate models, the lessons learn
 ed are broadly applicable across computational science, offering guidance 
 for building performant, trustworthy, and future-ready models on next-gene
 ration HPC platforms.\n\nPerformance, Precision and Accuracy: Mixed-precis
 ion modelling for weather and climate applications at the MetOffice\n\nNum
 erical calculations using floating point numbers suffer from accumulated r
 ound-off error and moreover, they are not associative. This is problematic
  for  weather and climate applications as they rely on global sums in PDE 
 solvers and the numerical answer can then depend on the parallel decomposi
 t...\n\n\nChristopher Michael Maynard (Met Office)\n---------------------\
 nSingle Precision Trajectories in 4D‑Var Data Assimilation\n\nFour‑dimensi
 onal variational (4D‑Var) data assimilation is underpinning the generation
  of high‑quality initial conditions required for ECMWF’s weather forecasts
  and Destination Earth's (DestinE) Digital Twins. A major cost driver in t
 his system is the nonlinear (NL) model tra...\n\n\nJorge Bandeiras, Patric
 k Gillies, Balthasar Reuter, and Ioan Hadade (ECMWF)\n--------------------
 -\nDoes halving the precision yield twice the speed?\n\nModern GPU archite
 ctures offer substantially higher throughput for single-precision arithmet
 ic compared to double precision, making reduced-precision computation an a
 ttractive strategy for accelerating weather and climate models. In theory,
  halving the precision could yield up to twice the performan...\n\n\nDmitr
 y Alexeev (NVIDIA Inc.)\n---------------------\nReducing and Validating Pr
 ecision in the ICON model\n\nReducing model precision can significantly re
 duce the memory footprint of a model, and increase utilization on future A
 I-based hardware. However, identifying and validating single precision mod
 el components without compromising on the model accuracy of scientific exp
 eriments remains a key challenge....\n\n\nDylan Kierans (DKRZ)\n\nDomain: 
 Climate, Weather, and Earth Sciences\n\nSession Chairs: Balthasar Reuter (
 ECMWF) and Claudia Frauen (DKRZ)
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