2007 Performance Metrics
Each year, the ARM Program must submit to DOE an overall performance measure related to scientific achievement. The overall performance measure includes specific metrics for reporting progress each quarter. This reporting process includes support documentation (usually a report or data file) appropriate for the metric.
Overall Performance Measure
Improve Climate Models
Provide new mixed-phase cloud parameterization for incorporation in atmospheric Global Climate Models (GCMs) and evaluate extent of agreement between climate model simulations and observations for cloud properties in the Arctic.
1st Quarter Metric—Completed
Provide and implement into a climate model a mixed-phase cloud parameterization.
Product Definition/Description – Introduce and implement treatments of ice nucleation and crystal growth by vapor deposition in a climate model, the NCAR Community Atmospheric Model version 3 (CAM3). Document and evaluate ice water content simulated by CAM3 using ARM and NASA Aura satellite data.
Product Documentation/Deliverables – The implementation of the cloud parameterization, initial testing of model, and some preliminary tests have been completed. The results of this development are documented in a short report (see below).
Result – More realistic parameterization for mixed-phase clouds has been implemented in a climate model (CAM3) and its configuration was successfully tested. The new parameterization can be used to determine aerosol effects on mixed-phase clouds. To learn more, read Mixed-Phase Cloud Microphysics for Global Climate Models.
2nd Quarter Metric—Completed
Document the performance of the mixed-phase cloud parameterization against ARM observations using a single-column model approach.
Product Definition/Description – The parameterization will be implemented into a single column model version of a GCM and numerical experiments will be performed. Model simulations using the existing and the new parameterization will be intercompared against the ARM data to evaluate model improvement.
Product Documentation/Deliverables – Testing of the cloud parameterization in the single column version of CAM3 (SCAM) and intercomparison of results obtained from using the old scheme with the new scheme and ARM observations has been completed. These results are documented in a short report (see below).
Result – SCAM with the modified microphysics have a more realistic prediction of the cloud phase structure and liquid water fraction against observations than the standard SCAM. These results can have important implications for the cloud radiative properties, surface radiation budget, precipitation and cloud lifetime as simulated in climate models. For more information, read Evaluation of Mixed-Phase Cloud Microphysics Parameterizations with the NCAR Single Column Climate Model (SCAM) and ARM Observations.
3rd Quarter Metric—Completed
Evaluate the performance of the mixed-phase cloud parameterization on timescales of 1-4 day periods using an initial condition model testbed.
Product Definition/Description – Comparison between the existing and the new parameterization using short-range forecasts of the National Center for Atmospheric Research (NCAR) CAM3 and the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 climate models and ARM measurements will be performed. The examination periods will be dependent on the availability of ARM data and other data needed for initial forecasts of the climate model.
Product Documentation/Deliverables – Evaluation of the model has been completed. These results are documented in a short report (see below).
Result – The simulation of the mixed-phase clouds and their microphysical properties is considerably improved in CAM3 when the new physically based cloud microphysical scheme is used. The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes in CAM3. In contrast, AM2 reasonably reproduces the observed boundary layer clouds while its clouds contain much less cloud condensate than CAM3 and the observations. For more information, read Evaluation of Mixed-Phase Cloud Parameterizations in Short-Range Weather Forecasts with CAM3 and AM2 for Mixed-Phase Arctic Cloud Experiment.
4th Quarter Metric—Completed
Evaluate the extent of agreement between climate models simulations and ARM measurements of mixed-phase clouds.
Product Definition/Description – Comparison between ARM measurements and climate model simulations based on the new parameterization will be completed.
Product Documentation/Deliverables – Comparison between ARM measurements and climate model simulations based on the new parameterization has been completed. These results are documented in a short report (see below).
Result – The new cloud microphysics scheme is further tested in CAM3 climate simulations and results are evaluated using the ARM measurements. The new scheme leads to the improvement of the cloud fraction and reduction of temperature bias in the tropical tropopause. The predicted ice water content in the CAM3 with the new scheme is in better agreement with the ARM observation at the SGP site for the mixed-phase clouds and with the Aura MLS data than that in the standard CAM3. For more information, read Evaluation of a New Mixed-Phase Cloud Microphsysics Parameterization with the NCAR Climate Atmospheric Model (CAM3) and ARM Measurements.