Past projects

CPT liaison

I was the NCAR liaison for the Climate Process Team (CPT) on Low-Latitude Cloud Feedbacks on Climate Sensitivity. This was a multi-institution NSF/NOAA-sponsored project (10/03-9/06)to try to better understand the differences in cloud feedbacks on climate sensitivity in three leading US climate models (NCAR, GFDL, and NASA-GMAO), and to use recent findings from observations and process models to reduce uncertainties in climate sensitivity by improving the representation of cloud microphysics, turbulence and moist convection, and radiative transfer in cloudy atmospheres in these models.

CPT columns

We provide one-year full-time resolution datasets of single-column outputs at 20 locations proposed by the CPT. The datasets are in NetCDF format and can be downloaded from this website. We also provide plots of key diagnostics.


• CAM3 column outputs (plots and datasets)
• Comparison CAM3/AM2 column outputs
• Virtual Field campaigns on deep tropical convection in climate models.
  by Brian E Mapes, Julio Bacmeister, Marat Khairoutdinov, Cécile Hannay, Ming Zhao
  To appear in J. Climate (revised 4/2008).

 

Comparison of the NCAR and GFDL models in subsidence regions

The focus of our research is on the role of low tropical clouds in affecting climate sensitivity. Comparison of climate simulations between the Community Atmosphere Model (CAM3) and the GFDL Atmospheric Model (AM2) indicates that these models have a very different response to a warming due to increased carbon dioxide. Low clouds in regions off the west coast of tropical continents play a particular important role in modulating sea surface temperatures in these regions. Stratiform cloud cover off the coasts of southern California, northern South America, north and south Africa reduce shortwave radiation reaching the sea surface by order 50 to 80 Wm-2.


• Project Description and results overview
• CAM3 and AM2 diagnostics
• Comparison of the NCAR and GFDL models versus observations and reanalysis I
• Comparison of the NCAR and GFDL models versus observations and reanalysis II

Subgrid scale cloud variability: subcolumn generator and McICA method implementation

To take into account the subgrid scale cloud variability in CAM, we have implemented a subcolumn column generator. The idea of the cloud generator is that the Subgrid scale cloud variability can be represented by a set of subcolumns that are generated randomly.
We are testing the subcolumn generator on radiation calculations using the Monte Carlo Independant Column Approximation (McICA). The McICA is a method developed to improve the treatment of cloud variability in climate models. This method is essentially a sampling strategy that yields unbiased estimates of heating rate profiles with respect to the full ICA, but that speeds the calculation up compared to the full ICA.


• Project description