Modelling clouds, aerosols and atmospheric chemistry
Have you ever looked at the ocean and noticed that the sky above it appeared hazy? This is caused by the presence of tiny particles or droplets in the air. In remote, unpolluted regions such as the Southern Ocean, such “aerosols” form from natural sources, such as ocean waves breaking and releasing sea salt into the air.
Aerosols over the Southern Ocean are important because they influence cloud formation and play a role in the energy budget. However, the way aerosols behave in the atmosphere is complex, and it’s currently difficult to model them accurately. This may be one reason why contemporary climate models, including the NZ Earth System Model (NZESM), has difficulty simulating the energy budget over the Southern Ocean, which has flow-on implications for simulating New Zealand’s climate.
Clouds and aerosols are a leading source of errors in climate models, particularly over the Southern Ocean which plays a key role in determining New Zealand’s weather and climate. Throughout the Deep South National Science Challenge we have developed capacity in Earth System modelling, with considerable expertise in modelling clouds and aerosols.
- The introduction of a new functionality into the Global Coupled 5 (GC5) configuration of the Unified Model (the physical base model of NZESM and UKESM) to make dust particles freezing nuclei, meaning they can initiate the freezing of cloud droplets. This improvement has significantly improved the realism of the model simulations and will impact future climate models that are based on the Unified Model.
- We have worked with the Deep South observations team to improve marine aerosol fluxes, developed new aerosol chemistry schemes, and enhanced the ability of aerosols to interact with clouds, thus improving performance of the New Zealand Earth System Model in the Southern Ocean region.
- Updates to heterogeneous chemistry and inclusion of solar variability as a climate forcer resulted in more realistic simulations of the Antarctic ozone hole.
How this research is being used:
- We are involving MetOffice colleagues in this research who will be instrumental for making sure that our advances are lodged into the mainstream models in use at the UM Consortium.
- This research is working in close collaboration with the Observing Clouds and Aerosols projects to better understand the processes in relation to aerosols and cloud formation that are being modelled in the NZESM.
This project in the media:
- New Zealand’s Next Top Model, New Zealand Geographic
- Breaking the ice, NIWA
- Just the ticket! Not one, not two, but up to four “tickets” to improve the world’s centralised global climate model, Deep South Challenge news story
- Simulating Earth’s changing climate: why some models exaggerate future warming, The Conversation
- Climate Lessons: How clouds complicate climate models, Stuff
Abhi Ulayottil VenugopalUniversity of Canterbury
Laura RevellUniversity of Canterbury
Matthew WoodhouseCentre for Marine and Atmospheric Research
Jane MulcahyMet Office
Fraser DennisonUniversity of Canterbury, NIWA
Stefanie KremserBodeker Scientific
Greg BodekerBodeker Scientific, Victoria University of Wellington