Paths to accuracy for radiation parameterizations in atmospheric models

Pincus, Robert; Stevens, Björn

doi:10.1002/jame.20027

Cited by 85 publications

(80 citation statements)

References 51 publications

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“…In ECHAM6.3, to reduce marine stratocumulus biases (Stevens et al, ), a modification of the treatment of subgrid‐scale cloudiness has been introduced. In addition, the radiation scheme PSrad (Pincus & Stevens, ) is implemented to ECHAM6.3. A major change in ECHAM6.3 compared to previous versions represents the treatment of radiative effects of anthropogenic aerosol in the shortwave radiation calculation.…”

Section: Models Experiments and Datamentioning

confidence: 99%

ICON‐A, The Atmosphere Component of the ICON Earth System Model: II. Model Evaluation

Crueger

Giorgetta

Brokopf

et al. 2018

J Adv Model Earth Syst

101

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We evaluate the new icosahedral nonhydrostatic atmospheric (ICON‐A) general circulation model of the Max Planck Institute for Meteorology that is flexible to be run at grid spacings from a few tens of meters to hundreds of kilometers. A simulation with ICON‐A at a low resolution (160 km) is compared to a not‐tuned fourfold higher‐resolution simulation (40 km). Simulations using the last release of the ECHAM climate model (ECHAM6.3) are also presented at two different resolutions. The ICON‐A simulations provide a compelling representation of the climate and its variability. The climate of the low‐resolution ICON‐A is even slightly better than that of ECHAM6.3. Improvements are obtained in aspects that are sensitive to the representation of orography, including the representation of cloud fields over eastern‐boundary currents, the latitudinal distribution of cloud top heights, and the spatial distribution of convection over the Indian Ocean and the Maritime Continent. Precipitation over land is enhanced, in particular at high‐resolution ICON‐A. The response of precipitation to El Niño sea surface temperature variability is close to observations, particularly over the eastern Indian Ocean. Some parameterization changes lead to improvements, for example, with respect to rain intensities and the representation of equatorial waves, but also imply a warmer troposphere, which we suggest leads to an unrealistic poleward mass shift. Many biases familiar to ECHAM6.3 are also evident in ICON‐A, namely, a too zonal SPCZ, an inadequate representation of north hemispheric blocking, and a relatively poor representation of tropical intraseasonal variability.

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Section: Models Experiments and Datamentioning

confidence: 99%

ICON‐A, The Atmosphere Component of the ICON Earth System Model: II. Model Evaluation

Crueger

Giorgetta

Brokopf

et al. 2018

J Adv Model Earth Syst

101

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“…The coupling of the TenStream solver to the UCLA-LES follows the description in Jakub and Mayer (2016). One exception is the Monte Carlo spectral integration (Pincus and Stevens, 2009), which we do not use because of limitations with regards to computations involving interactive surface models (Pincus and Stevens, 2013).…”

Section: Les Modelmentioning

confidence: 99%

The role of 1-D and 3-D radiative heating in the organization of shallow cumulus convection and the formation of cloud streets

Jakub

Mayer

2017

Atmos. Chem. Phys.

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Abstract. The formation of shallow cumulus cloud streets was historically attributed primarily to dynamics. Here, we focus on the interaction between radiatively induced surface heterogeneities and the resulting patterns in the flow. Our results suggest that solar radiative heating has the potential to organize clouds perpendicular to the sun's incidence angle.To quantify the extent of organization, we performed a high-resolution large-eddy simulation (LES) parameter study. We varied the horizontal wind speed, the surface heat capacity, the solar zenith and azimuth angles, and radiative transfer parameterizations (1-D and 3-D). As a quantitative measure we introduce a simple algorithm that provides a scalar quantity for the degree of organization and the alignment. We find that, even in the absence of a horizontal wind, 3-D radiative transfer produces cloud streets perpendicular to the sun's incident direction, whereas the 1-D approximation or constant surface fluxes produce randomly positioned circular clouds. Our reasoning for the enhancement or reduction of organization is the geometric position of the cloud's shadow and its corresponding surface fluxes. Furthermore, when increasing horizontal wind speeds to 5 or 10 m s −1 , we observe the development of dynamically induced cloud streets. If, in addition, solar radiation illuminates the surface beneath the cloud, i.e., when the sun is positioned orthogonally to the mean wind field and the solar zenith angle is larger than 20 • , the cloud-radiative feedback has the potential to significantly enhance the tendency to organize in cloud streets. In contrast, in the case of the 1-D approximation (or overhead sun), the tendency to organize is weaker or even prohibited because the shadow is cast directly beneath the cloud. In a land-surface-type situation, we find the organization of convection happening on a timescale of half an hour. The radiative feedback, which creates surface heterogeneities, is generally diminished for large surface heat capacities. We therefore expect radiative feedbacks to be strongest over land surfaces and weaker over the ocean. Given the results of this study we expect that simulations including shallow cumulus convection will have difficulties producing cloud streets if they employ 1-D radiative transfer solvers or may need unrealistically high wind speeds to excite cloud street organization.

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“…DG Kernel is described in Section 2. Taumol03 kernel is extracted from PSRad [13]. PSrad is a new radiation package designed for use in models of the atmosphere.…”

Section: Resultsmentioning

confidence: 99%

Performance search engine driven by prior knowledge of optimization

Kim

Černý

Dennis

2015

Proceedings of the 2nd ACM SIGPLAN International Workshop on Libraries, Languages, and Compilers for Array Programming

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For scientific array-based programs, optimization for a particular target platform is a hard problem. There are many optimization techniques such as (semantics-preserving) source code transformations, compiler directives, environment variables, and compiler flags that influence performance. Moreover, the performance impact of (combinations of) these factors is unpredictable. This paper focuses on providing a platform for automatically searching through search space consisting of such optimization techniques. We provide (i) a search-space description language, which enables the user to describe optimization options to be used; (ii) search engine that enables testing the performance impact of optimization options by executing optimized programs and checking their results; and (iii) an interface for implementing various search algorithms. We evaluate our platform by using two simple search algorithms -a random search and a casetree search that heuristically learns from the already examined parts of the search space. We show that such algorithms are easily implementable in our platform, and we empirically find that the framework can be used to find useful optimized algorithms.

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Paths to accuracy for radiation parameterizations in atmospheric models

Cited by 85 publications

References 51 publications

ICON‐A, The Atmosphere Component of the ICON Earth System Model: II. Model Evaluation

ICON‐A, The Atmosphere Component of the ICON Earth System Model: II. Model Evaluation

The role of 1-D and 3-D radiative heating in the organization of shallow cumulus convection and the formation of cloud streets

Performance search engine driven by prior knowledge of optimization

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