Building a traceable climate model hierarchy with multi-level emulators
To study climate change on multi-millennial timescales or to explore a model's parameter space, efficient models with simplified and parameterised processes are required. However, the reduction in explicitly modelled processes can lead to underestimation of some atmospheric responses that are e...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-04-01
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| Series: | Advances in Statistical Climatology, Meteorology and Oceanography |
| Online Access: | http://www.adv-stat-clim-meteorol-oceanogr.net/2/17/2016/ascmo-2-17-2016.pdf |
| Summary: | To study climate change on multi-millennial timescales or to explore a
model's parameter space, efficient models with simplified and parameterised
processes are required. However, the reduction in explicitly modelled
processes can lead to underestimation of some atmospheric responses that are
essential to the understanding of the climate system. While more complex
general circulations are available and capable of simulating a more realistic
climate, they are too computationally intensive for these purposes. In this
work, we propose a multi-level Gaussian emulation technique to efficiently
estimate the outputs of steady-state simulations of an expensive atmospheric
model in response to changes in boundary forcing. The link between a
computationally expensive atmospheric model, PLASIM (Planet Simulator), and a cheaper model,
EMBM (energy–moisture balance model), is established through the common boundary condition specified by an
ocean model, allowing for information to be propagated from one to the other.
This technique allows PLASIM emulators to be built at a low cost. The method
is first demonstrated by emulating a scalar summary quantity, the global mean
surface air temperature. It is then employed to emulate the dimensionally
reduced 2-D surface air temperature field. Even though the two atmospheric
models chosen are structurally unrelated, Gaussian process emulators of
PLASIM atmospheric variables are successfully constructed using EMBM as a
fast approximation. With the extra information gained from the cheap model,
the multi-level emulator of PLASIM's 2-D surface air temperature field is
built using only one-third the amount of expensive data required by the
normal single-level technique. The constructed emulator is shown to capture
93.2 % of the variance across the validation ensemble, with the averaged RMSE
of 1.33 °C. Using the method proposed, quantities from PLASIM
can be constructed and used to study the effects introduced by PLASIM's
atmosphere. |
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| ISSN: | 2364-3579 2364-3587 |