cpt.UCLA

This joint initiative between NSF and NOAA seeks to improve the representation of low clouds in climate models. Disparities in the representation of low cloud fields is one of the leading causes of uncertainty in predictions of climate change from increases in greenhouse gases.

I. Mixed layer theory as a representation of marine stratocumulus

In this project we evaluate the ability of mixed layer theory to represent the climatology of marine stratocumulus clouds. To evaluate the theory, it is applied using (i) observed conditions near 30 N, 120 W from the DYCOMS-II field campaign and (ii) the global climatology from the ERA-40 reanalysis. The qualitative agreement between mixed layer theory and observations allows us to explore the factors responsible for seasonal variations in stratocumulus-topped boundary layers, such as advection, radiative forcing, lower-tropospheric stability, and divergence.
Yunyan Zhang

II. Low-cloud feedbacks on climate

General circulation models (GCMs) give our best representations of future and past climates, but the simulated climate is limited by current understanding of cloud feedbacks. In this project, we employ a sophisticated GCM to investigate the effects of low clouds on climate. The model is run with highly simplified geography to isolate the cloud effects. By using the idealized configuration and running a suite of climate change experiments, we are able to explore the role that low clouds play in different climates and the influence they have on climate sensitivity. These experiments can be compared with more realistic ones to explore, e.g., the applicability of zonally symmetric theories for cloud feedbacks.
Brian Medeiros
[pdf of presentation]