Observed Scaling in Clouds and Precipitation and Scale Incognizance in Regional to Global Atmospheric Models

O’Brien, T. A.; Li, Fuyu; Collins, William D.; Rauscher, Sara A.; Ringler, Todd D.; Taylor, Mark A.; Hagos, Samson; Leung, L. Ruby

doi:10.1175/jcli-d-13-00005.1

Cited by 49 publications

(60 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 4a compares the cloud fraction in the var-res simulation to the two uniform runs globally. The monotonic decrease of cloud fraction as horizontal resolution is increased is a troublesome but well-known issue with both the CAM3 and CAM4 physical parameterizations (e.g., Williamson 2008a,b;Rauscher et al 2013;Hagos et al 2013;O'Brien et al 2013). 12).…”

Section: Cam4 Climatologysupporting

confidence: 73%

Aquaplanet Experiments Using CAM’s Variable-Resolution Dynamical Core

et al. 2014

View full text Add to dashboard Cite

A variable-resolution option has been added within the spectral element (SE) dynamical core of the U.S. Department of Energy (DOE)-NCAR Community Atmosphere Model (CAM). CAM-SE allows for static refinement via conforming quadrilateral meshes on the cubed sphere. This paper investigates the effect of mesh refinement in a climate model by running variable-resolution (var-res) simulations on an aquaplanet. The variable-resolution grid is a 28 (;222 km) grid with a refined patch of 0.258 (;28 km) resolution centered at the equator. Climatology statistics from these simulations are compared to globally uniform runs of 28 and 0.258. A significant resolution dependence exists when using the CAM version 4 (CAM4) subgrid physical parameterization package across scales. Global cloud fraction decreases and equatorial precipitation increases with finer horizontal resolution, resulting in drastically different climates between the uniform grid runs and a physics-induced grid imprinting in the var-res simulation. Using CAM version 5 (CAM5) physics significantly improves cloud scaling at different grid resolutions. Additional precipitation at the equator in the highresolution mesh results in collocated zonally anomalous divergence in both var-res simulations, although this feature is much weaker in CAM5 than CAM4. The equilibrium solution at each grid spacing within the var-res simulations captures the majority of the resolution signal of the corresponding globally uniform grids. The var-res simulation exhibits good performance with respect to wave propagation, including equatorial regions where waves pass through grid transitions. In addition, the increased frequency of high-precipitation events in the refined 0.258 area within the var-res simulations matches that observed in the global 0.258 simulations.

show abstract

Section: Cam4 Climatologysupporting

confidence: 73%

Aquaplanet Experiments Using CAM’s Variable-Resolution Dynamical Core

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Additionally, analysis by Mishra [2015] on various regional climate models agrees with this conclusion. Although the height and geometry of the topography impact the flow over the terrain, we speculate that the production of excessive orographic diabatic heating in CAM is modulated by the adjustments in convective and large-scale parameterizations [O'Brien et al, 2013]. Additionally, the mediating role of moist static stability over the Himalayas may also explain some of the intermodel difference in monsoon behavior, since different physics schemes may change the degree of blocking and flow over topography.…”

Section: Discussionmentioning

confidence: 95%

The neglected Indo‐Gangetic Plains low‐level jet and its importance for moisture transport and precipitation during the peak summer monsoon

Acosta

Huber

2017

Geophysical Research Letters

View full text Add to dashboard Cite

Accurately simulating the Indo‐Asian monsoon (IAM) using atmospheric general circulation models (AGCMs) is challenging but crucial. This study uses reanalysis products European Centre of Medium‐Range Forecast Interim reanalysis, Japanese Reanalysis year 55, and High Asia Reanalysis to highlight an easterly, low‐level barrier jet along the Indo‐Gangetic Plain (referred from here as IG LLJ), which we identify as the primary moisture transport mechanism for the northeastern branch of the IAM. We show that the NCAR family of AGCMs (Community Atmospheric Model (CAM)) does not capture this circulation until 1/2° or greater spatial horizontal resolution is used. The IG LLJ develops due to a persistent low‐pressure system centered over the Ganges basin and is enhanced by the Himalayas. Using diabatic heating rates and the moist Froude number as diagnostics, we find that in CAM, this branch of the IAM displays two different dynamical regimes as a function of resolution. At low resolution, the atmosphere near the Himalayas is statically unstable, diabatic heating is strong, and the moisture flow is southwesterly from the Arabian Sea and moves over the terrain (unblocked). At high resolution, the moist static stability near the Himalayan Mountains is stable, diabatic heating is weak, and the flow primarily enters easterly from the Bay of Bengal and moves parallel to the terrain (blocked). During the summer season, the low‐resolution CAM is locked into the unblocked mode, which has serious implications for interpreting topography‐monsoon interactions. For a broader context, we demonstrate that more than half of the CMIP5 models do not capture the IG LLJ, which further highlights model‐data mismatch across the IAM region.

show abstract

“…Note that this switch, which also occurs in GCMs (e.g. Iorio et al 2004;Rauscher et al 2013), does not necessarily indicate an improvement in model performance: For model grid spacing coarser than approximately 10 km, the ratio of convective to non-convective precipitation should not change (Williamson 2008;O'Brien et al 2013). We return to the issue of resolvable-scale versus convective precipitation in Sect.…”

Section: K-s Statisticmentioning

confidence: 98%