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SUMMARY:Energetic signatures of tropical rainband biases &amp\; shifts in 
 CMIP6 - Ruth Geen\, U of Birmingham
DTSTART:20241204T130000Z
DTEND:20241204T140000Z
UID:TALK225250@talks.cam.ac.uk
CONTACT:Alison Ming
DESCRIPTION:Tropical and subtropical precipitation impact millions of peop
 le via agriculture and rainfall-driven disasters\, driving interest in the
 ir potential future change. CMIP6 simulations broadly predict an increase 
 in global monsoon precipitation. However\, regional projections from indiv
 idual models vary in magnitude and sign\, and projected changes by the end
  of the century are often small compared with model biases. This motivates
  an interest in understanding model biases\, and how to interpret the futu
 re shifts in rainfall.\n\n\nThe Hadley and Walker circulations transport M
 oist Static Energy (MSE\, the combination of the parcels enthalpy\, potent
 ial energy and latent heat content) in the direction of their upper branch
 es\, so that the change in sign of MSE transport acts as a proxy for mass 
 convergence in the tropical rainband. MSE transport can then be interprete
 d in terms of top-of-atmosphere and surface energy fluxes using the column
  energy budget. \n\n \n\nRecent work attributes contributions to annual- a
 nd zonal-mean divergent MSE transport to radiative fluxes\, evaporative fl
 uxes and sensible heat\, and suggests that evaporative fluxes are key in s
 etting the spatial structure of MSE transport. Here we extend this approac
 h to regional and seasonal scales\, and explore inter-model differences in
  CMIP6 historical simulations\, and projected changes under SSP585. \n\n \
 n\nMSE transport attributed to evaporative and radiative fluxes dominate t
 he regional JJA & DJF transport. Empirical Orthogonal Functions (EOFs) are
  used to express historical intermodel differences in MSE transport in a 2
 -dimensional space of leading EOFs linked to land-sea thermal contrast (38
 .2% of variance) and interhemispheric thermal contrast (30.1% of variance)
 . The contributions from the different fluxes to intermodel MSE difference
 s and changes under SSP585 are then projected into this space. This reveal
 s energetic signatures of model bias and future change\, that illustrate h
 ow different processes contribute to the overall differences in energy tra
 nsport. \n\n \n\nShared energetic signatures of bias are predominantly see
 n within model families. In contrast\, shared signatures of future change 
 emerge across (and differ within) model families\, with a shared bias sign
 ature not implying a shared change signature. This suggests a set coherent
  but differing pathways through which climate change affects the energy bu
 dget and associated tropical rainfall in particular groups of models.
LOCATION:MR15\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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