Results of the TWP-ICE CRM Model Intercomparison: General Trends and Comparisons with Field Data

Ann Fridlind NASA - Goddard Institute for Space Studies
Andrew Ackerman NASA - Goddard Institute for Space Studies
Jean-Pierre Chaboureau University of Toulouse, France/CNRS
Jiwen Fan Pacific Northwest National Laboratory
Wojciech Grabowski NCAR
Adrian Hill UK Meteorological Office
Todd Jones Colorado State University
Hugh Morrison NCAR
Sunwook Park Iowa State University
Jean-Pierre Pinty University of Toulouse, France/CNRS
Xiaoqing Wu Iowa State University

Category: Cloud Properties

Working Group: Cloud Life Cycle

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Precipitation rate statistics at the surface and at 2.5 km elevation from eight cloud-resolving model simulations and four sensitivity tests are compared with the large-scale forcing data set, which is based on the scanning C-POL radar at Darwin, and with ECMWF re-analysis at three grid cells considered representative of local conditions. Mean value and standard deviations are listed, followed by percentage difference between forcing and C-POL data.

An idealized cloud-resolving model (CRM) intercomparison specification was based on observations obtained under active and suppressed monsoon conditions over 16 days during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE). Results of eight CRM simulations were submitted for the baseline case described in the specification. Sensitivity test results were also submitted for half of the eight models, wherein nudging to observed thermodynamic fields with a six-hour timescale was included. Results from the eight different models generally exhibit a wider spread than between baseline and sensitivity results from any single model. Considering all of the simulations together, predicted values of precipitation rate and liquid and ice water path, cloud optical thickness, and the ratio of upwelling over downwelling shortwave radiative flux all vary by about a factor of two. As a function of total predicted condensate path, liquid and ice water path and surface precipitation rate all tend to increase with a similar trend. While cloud optical thickness also exhibits the same general trend, scatter is much greater. By contrast, the ratio of upwelling to downwelling shortwave radiative flux at top of atmosphere is both widely scattered and poorly correlated with total condensate path, and instead closely correlated with the ratio of liquid water path to total condensate path, consistent with the dominant contribution of liquid to cloud optical thickness. We investigate the liquid water fraction and radiative flux differences in the context of simulated cloud macrophysical and microphysical structure. We present evidence that uncertainties in large-scale forcing fields are likely to produce differences in model results comparable to the spread in most reported values (e.g., precipitation rate), but can still identify various likely outlying simulation results through comparison of a wide range of reported diagnostics with disparate datastreams, such as cloud optical thickness range observed at the surface, upwelling longwave radiative flux range measured by satellite, and reflectivity fields measured by scanning precipitation radar.

http://science.arm.gov/wg/cpm/scm/scmic6/index.html

This poster will be displayed at ASR Science Team Meeting.

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