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JULES v4.6 details

Release Notes

The JULES vn4.6 release consists of 43 tickets from 22 authors across 52 commits.

Full details of the tickets committed for JULES vn4.6 can be found on the JULES shared repository Trac system.

Science changes

  • Multiple ice tiles in a gridbox to simulate snowpacks at different elevations
  • Snowpack physics for UKESM icesheet
  • Link whole plant maintenance respiration to soil moisture stress
  • Reading in clay content of soil for soil carbon decomposition model
  • Improved climate downscaling physics for ice elevation tiles
  • calculate FAO Penman-Monteith evapotranspiration for reference crop
  • Respiring Stem Fraction
  • Diagnostic Form Drag for Sea ice
  • Calculation of new sea ice variables required for CMIP6
  • Implement a canopy clumping factor
  • Allow for Non-istropic scattering in plant canopies
  • Investigate improvements to soil moisture stress on vegetation
  • Improve parametrisation of crop leaf senescence
  • Add new crop harvest diagnostics
  • FLake beneath multi-layer snow

Technical changes

  • JULES-C-1p1 Regression Tests
  • Remove the UM_FLAKE CPP macro
  • Move sorp and n_inorg_turnover to namelist to enable user input.
  • VM rose stem bug fixed.
  • Add support for rose-stem on MONSooN
  • Move some of the hard-wired crop parameters to JULES_CROPPARM
  • Remove UM descent.h include file and put values into JULES module descent.F90
  • Fix race conditions and improve OpenMP DEFAULTs
  • Modularise and header refactor science/snow

Bugs fixed

  • Fix GC3 tstar_sice bug
  • Correcting canopy nitrogen profiles
  • Reinstate missing veg parms, for trait initialisation.
  • Soil respiration bug resolved
  • Correct mistake in merging of crop PFT changes
  • N Diagnostic Bug fixed to avoid runtime crashes
  • Bug fix to calculation of dust deposition exchange coefficient
  • Bug Fix - CH4 wetland emission correction with TRIFFID on
  • Fix aerodynamic resistance diagnostic (UM diag)


Building and running JULES v4.6 is described in the JULES User Guide.

Technical documentation is provided by the model description papers referenced in the Publications section of this website.


Coding standards, and documentation can be viewed on the ‘github page <>_’.

Source code

We are in the process of transferring our JULES source code access to the Met Office Scientific Repository Service.The previous “tarball” method of delivery has been discontinued.

To request an account on the Repository Service please complete the online form and accept the JULES Terms and Conditions.