Using Stochastically Generated Subcolumns to Represent Cloud Structure in a Large-Scale Model

Pincus, Robert; Hemler, Richard; Klein, Stephen A.
December 2006
Monthly Weather Review;Dec2006, Vol. 134 Issue 12, p3644
Academic Journal
A new method for representing subgrid-scale cloud structure in which each model column is decomposed into a set of subcolumns has been introduced into the Geophysical Fluid Dynamics Laboratory’s global atmospheric model AM2. Each subcolumn in the decomposition is homogeneous, but the ensemble reproduces the initial profiles of cloud properties including cloud fraction, internal variability (if any) in cloud condensate, and arbitrary overlap assumptions that describe vertical correlations. These subcolumns are used in radiation and diagnostic calculations and have allowed the introduction of more realistic overlap assumptions. This paper describes the impact of these new methods for representing cloud structure in instantaneous calculations and long-term integrations. Shortwave radiation computed using subcolumns and the random overlap assumption differs in the global annual average by more than 4 W m-2 from the operational radiation scheme in instantaneous calculations; much of this difference is counteracted by a change in the overlap assumption to one in which overlap varies continuously with the separation distance between layers. Internal variability in cloud condensate, diagnosed from the mean condensate amount and cloud fraction, has about the same effect on radiative fluxes as does the ad hoc tuning accounting for this effect in the operational radiation scheme. Long simulations with the new model configuration show little difference from the operational model configuration, while statistical tests indicate that the model does not respond systematically to the sampling noise introduced by the approximate radiative transfer techniques introduced to work with the subcolumns.


Related Articles

  • Precipitation Partitioning, Tropical Clouds, and Intraseasonal Variability in GFDL AM2. Lin, Yanluan; Zhao, Ming; Ming, Yi; Golaz, Jean-Christophe; Donner, Leo J.; Klein, Stephen A.; Ramaswamy, V.; Xie, Shaocheng // Journal of Climate;Aug2013, Vol. 26 Issue 15, p5453 

    A set of Geophysical Fluid Dynamics Laboratory (GFDL) Atmospheric Model version 2 (AM2) sensitivity simulations by varying an entrainment threshold rate to control deep convection occurrence are used to investigate how cumulus parameterization impacts tropical cloud and precipitation...

  • Precipitation Sensitivity to Surface Heat Fluxes over North America in Reanalysis and Model Data. Berg, Alexis; Findell, Kirsten; Lintner, Benjamin R.; Gentine, Pierre; Kerr, Christopher // Journal of Hydrometeorology;Jun2013, Vol. 14 Issue 3, p722 

    A new methodology for assessing the impact of surface heat fluxes on precipitation is applied to data from the North American Regional Reanalysis (NARR) and to output from the Geophysical Fluid Dynamics Laboratory's Atmospheric Model 2.1 (AM2.1). The method assesses the sensitivity of afternoon...

  • Frequency Domain Multimodel Analysis of the Response of Atlantic Meridional Overturning Circulation to Surface Forcing. MacMartin, Douglas G.; Tziperman, Eli; Zanna, Laure // Journal of Climate;Nov2013, Vol. 26 Issue 21, p8323 

    The dynamics of the Atlantic meridional overturning circulation (AMOC) vary considerably among different climate models; for example, some models show clear peaks in their power spectra while others do not. To elucidate these model differences, transfer functions are used to estimate the...

  • An assessment of oceanic variability for 1960-2010 from the GFDL ensemble coupled data assimilation. Chang, You-Soon; Zhang, Shaoqing; Rosati, Anthony; Delworth, Thomas; Stern, William // Climate Dynamics;Feb2013, Vol. 40 Issue 3/4, p775 

    The Geophysical Fluid Dynamics Laboratory has developed an ensemble coupled data assimilation (ECDA) system based on the fully coupled climate model, CM2.1, in order to provide reanalyzed coupled initial conditions that are balanced with the climate prediction model. Here, we conduct a...

  • Modulation of Tropical Cyclones over the Eastern Pacific by the Intraseasonal Variability Simulated in an AGCM. Jiang, Xianan; Zhao, Ming; Waliser, Duane E. // Journal of Climate;Oct2012, Vol. 25 Issue 19, p6524 

    This study illustrates that observed modulations of tropical cyclone (TC) genesis over the eastern Pacific (EPAC) by large-scale intraseasonal variability (ISV) are well represented in a recently developed high-resolution atmospheric model (HiRAM) at the NOAA/Geophysical Fluid Dynamics...

  • Response to CO2 Doubling of the Atlantic Hurricane Main Development Region in a High-Resolution Climate Model. DOI, TAKESHI; VECCHI, GABRIEL A.; ROSATI, ANTHONY J.; DELWORTH, THOMAS L. // Journal of Climate;6/15/2013, Vol. 26 Issue 12, p4322 

    Response of climate conditions in the Atlantic hurricane main development region (MDR) to doubling of atmospheric CO2 has been explored using the new high-resolution coupled climate model, version 2.5 (CM2.5), developed at the Geophysical Fluid Dynamics Laboratory (GFDL). In the annual mean, the...

  • The Pacific Meridional Mode and the Occurrence of Tropical Cyclones in the Western North Pacific. Zhang, W.; Vecchi, G. A.; Murakami, H.; Villarini, G.; Jia, L. // Journal of Climate;Jan2016, Vol. 29 Issue 1, p381 

    This study investigates the association between the Pacific meridional mode (PMM) and tropical cyclone (TC) activity in the western North Pacific (WNP). It is found that the positive PMM phase favors the occurrence of TCs in the WNP while the negative PMM phase inhibits the occurrence of TCs...

  • Evaluations of BDA Scheme Using the Advanced Research WRF (ARW) Model. Qingnong Xiao; Liqiang Chen; Xiaoyan Zhang // Journal of Applied Meteorology & Climatology;Mar2009, Vol. 48 Issue 3, p680 

    A tropical cyclone bogus data assimilation (BDA) scheme is built in the Weather Research and Forecasting three-dimensional variational data assimilation system (WRF 3D-VAR). Experiments were conducted (21 experiments with BDA in parallel with another 21 without BDA) to assess its impacts on the...

  • Toward Improving High-Resolution Numerical Hurricane Forecasting: Influence of Model Horizontal Grid Resolution, Initialization, and Physics. Gopalakrishnan, Sundararaman G.; Goldenberg, Stanley; Quirino, Thiago; Zhang, Xuejin; Marks, Frank; Yeh, Kao-San; Atlas, Robert; Tallapragada, Vijay // Weather & Forecasting;Jun2012, Vol. 27 Issue 3, p647 

    This paper provides an account of the performance of an experimental version of the Hurricane Weather Research and Forecasting system (HWRFX) for 87 cases of Atlantic tropical cyclones during the 2005, 2007, and 2009 hurricane seasons. The HWRFX system was used to study the influence of model...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics