Breakout Summary Report
ARM/ASR User and PI Meeting
19 - 23 March 2018
Model Development and Evaluation on Clouds, Convection, and Precipitation
21 March 2018
1:30 PM - 3:30 PM
50
J. Fan, S. Xie, D. Mechem, M. Ahlgrimm, K. Lamer, V. Larson, X. Liu, J. Tian, E. Roesler, R. Jackson
21 March 2018
1:30 PM - 3:30 PM
50
J. Fan, S. Xie, D. Mechem, M. Ahlgrimm, K. Lamer, V. Larson, X. Liu, J. Tian, E. Roesler, R. Jackson
Breakout Description
Clouds and precipitation are the essential components of weather and climate; however, accurately simulating clouds, convection, and precipitation is challenging in numerical models across scales from cloud-resolving models (CRMs) to general circulation models (GCMs). It is also challenging to appropriately evaluate model simulated cloud and convective properties and precipitation with observational data from various platforms, especially at coarse grid spacings. This breakout session will summarize the current efforts in parameterization development and evaluation from CRMs to GCMs with the observational data, including DOE ARM-supported measurements. It will also showcase the novel approaches for fair comparison between simulations and observations, and facilitate collaborations between modelers and observationalists.Main Discussion
Our discussion focused on the following items:(a) new approaches and data used for model development and evaluation
(b) major challenges in model evaluation with data of different temporal and spatial scales
(c) important issues related to observational data
(d) key measurements and data products needed.
Key Findings
• Many new data sets and approaches developed under CMDV projects are very useful for GCM evaluation (e.g., 4-D ice cloud properties from NEXRED retrieval over a large region and long time period and LWC for stratiform, the new radar simulators, the new MCS tracking method, etc.).• Use simulators, realize observations uncertainties, and conduct ensemble runs.
Issues
(1) The main challenges for model development and evaluation include single-point data, very coarse temporal presentation of convective and cloud processes in global model, etc. Some useful data often had a short time period.(2) Need long-time support for key data, particularly some guest instruments. Aircraft data for vertical profile of cloud properties need decent sample sizes at each altitude (often only had extensive data at one or two altitudes, making it hard to get the profile properties)
(3) Lack of concurrent microphysical data for convective cores. Lack of measurements of microphysical properties in the mixed-phase regime hinders further understanding of causes of the underestimation of stratiform precipitation of convective systems by CRM/LAM.
(4) Evaluation often does not get to the point of the causes, which is not instructive for model developments.
Needs
(1) Concurrent measurements in dynamics, thermodynamics, and microphysics in convective cores (important for both understanding and parameter development).(2) Evaluation of evaporative fraction (from CAUSES project).
(3) Obtain reliable microphysical properties in the mixed-phase regimes (from the CRM Intercomparison project).