Radiation Scheme Research Articles

Stereotactic body radiation therapy for liver metastasis from colorectal cancer: size matters.

We analysed our initial experience with SBRT in liver metastasis from colorectal cancer at our institution. Between January/2014 and December/2017, 22 patients with 31 LMCCR were treated. Local control (LC) was assessed using the Kaplan-Meier and log-rank tests. We analysed potential prognostic factors for LC: sex, PTV size, number of LM and the radiation scheme. Median age: 69years. Prior chemotherapy or local liver treatments: 81.8% and 63.6% of patients, respectively. SBRT consisted of 3 × 20Gy (42.9%) and 3 × 15Gy (31.4%). There were 88.5% responses (57.1% CR and 31.4% PR). Median follow-up was 30months. LC per lesion at 12 and 24months was 85.3% and 61.8%, respectively. Tumour volumes > 30cc correlated with worsened 2-year-control rates (90% vs 34.5%) (p = 0.005). There was only a patient with CTC-grade 3 toxicity. LiverSBRTis a safe and effective treatment that achieves high local control rates. We found a significant correlation between larger LMCRC and worse local control.

A New k-Distribution Scheme for Clear-Sky Radiative Transfer Calculations in Earth’s Atmosphere. Part I: Thermal Infrared (Longwave) Radiation

Abstract A new k-distribution scheme of longwave radiation without the correlated-k-distribution assumption is developed. Grouping of spectral points is based on the line-by-line (LBL)-calculated absorption coefficient k at a few sets of reference pressure pr and temperature θr, where the cooling rate is substantial in a spectral band. In this new scheme, the range of k(pr, θr) of a band is divided into a number of equal intervals, or g groups, in log10(kr). A spectral point at the wavenumber ν is identified with one of the g groups according to its kν(pr, θr). For each g group, a Planck-weighted k-distribution function Hg and a nonlinearly averaged absorption coefficient k¯g⁡(p,θ) are derived. The function Hg and the absorption coefficient k¯g⁡(p,θ) constitute the new k-distribution scheme. In this k-distribution scheme, a spectral point can only be identified with a g group regardless of pressure and temperature, which is different from the correlated-k distribution scheme. The k-distribution scheme is applied to the H2O, CO2, O3, N2O, and CH4 absorption bands, and results are compared with LBL calculations. To balance between the accuracy and the computational economy, the number of g groups in a band of a given gas is chosen such that 1) the difference in cooling rate is <0.1 K day−1 in the troposphere and <1.0 K day−1 in the stratosphere and 2) the difference in fluxes is <0.5 W m−2 at both the top of the atmosphere and the surface. These differences are attained with 130 g groups, which is the sum of the g groups of all five gases.

Simulations of the reionization of the clumpy intergalactic medium with a novel particle-based two-moment radiative transfer scheme

AbstractThe progress of cosmic reionization depends on the presence of over-dense regions that act as photon sinks. Such sinks may slow down ionization fronts as compared to a uniform intergalactic medium (IGM) by increasing the clumping factor. We present simulations of reionization in a clumpy IGM resolving even the smallest sinks. The simulations use a novel, spatially adaptive and efficient radiative transfer implementation in the SWIFT SPH code, based on the two-moment method. We find that photon sinks can increase the clumping factor by a factor of ∼10 during the first ∼100 Myrs after the passage of an ionization front. After this time, the clumping factor decreases as the smaller sinks photoevaporate. Altogether, photon sinks increase the number of photons required to reionize the Universe by a factor of η ∼2, as compared to the homogeneous case. The value of η also depends on the emissivity of the ionizing sources.

Randomized controlled trial to identify the optimal radiotherapy scheme for palliative treatment of incurable head and neck squamous cell carcinoma

BackgroundNo randomized controlled trials (RCT) have yet identified the optimal palliative radiotherapy scheme in patients with incurable head and neck squamous cell carcinoma (HNSCC). We conducted RCT to compare two radiation schemes in terms of efficacy, toxicity and quality-of-life (QoL). Materials and methodsPatients with locally-advanced HNSCC who were ineligible for radical treatment and those with limited metastatic disease were randomly assigned in 1:1 ratio to arm 1 (36 Gy in 6 fractions, twice a week) or arm 2 (50 Gy in 16 fractions, four times a week). ResultsThe trial was discontinued early because of slow accrual (34 patients enrolled). Objective response rates were 38.9% and 57.1% for arm 1 and 2 respectively (p = 0.476). The median time to loco-regional progression was not reached. The loco-regional control rates at 1 year was 57.4% and 69.3% in arm 1 and 2 (p = 0.450, HR = 0.56, 95%CI 0.12–2.58). One-year overall survival was 33.3% and 57.1%, with medians of 35.4 and 59.5 weeks, respectively (p = 0.215, HR = 0.55, 95%CI 0.21–1.43). Acute grade ≥3 toxicity was lower in arm 1 (16.7% versus 57.1%, p = 0.027), with the largest difference in grade 3 mucositis (5.6% versus 42.9%, p = 0.027). However, no significant deterioration in any of the patient-reported QoL-scales was found. ConclusionNo solid conclusion could be made on this incomplete study which is closed early. Long-course radiotherapy did not show significantly better oncologic outcomes, but was associated with more acute grade 3 mucositis. No meaningful differences in QoL-scores were found. Therefore, the shorter schedule might be carefully advocated. However, this recommendation should be interpreted with great caution because of the inadequate statistical power.

Impacts of spectrally resolved irradiance on photolysis frequency calculations within a forest canopy

Although photolysis frequencies are wavelength-dependent and the dependence varies among chemical species, previous canopy radiative transfer models did not consider more than three broad bands (ultraviolet, photosynthetically active radiation (PAR), and near-infrared). In this study, high spectral resolution and wavelength-dependent idealized leaf optical properties allow us to determine the disposition of the light spectrum within a mixed deciduous forest canopy. Four radiative transfer approaches of varying complexity are applied to obtain vertical profiles of spectral actinic flux. Broad-band radiation measurements made above and below a mixed deciduous forest provide the necessary information to verify the fidelity of each radiative transfer approach. Model comparison results indicate that the Beer–Lambert scheme gives less total actinic flux, while the other three schemes give similar actinic flux profiles. Spectral actinic flux profiles are used to calculate in-canopy photolysis for different chemical species and to assess the importance of in-canopy photochemistry in modifying biogenic volatile organic compounds transported to the overlying atmospheric boundary layer. We find that, depending on the time of day and chemical species, percent errors in photolysis frequencies incurred by using a common in-canopy approximation based on weighting by relative PAR profiles can be as high as ± 50% in lower regions of the canopy, or 10–20% in daily canopy integrated photolysis frequency. Results obtained using a one-dimensional photochemical model suggest that choice of canopy radiative transfer scheme can have substantial impacts on in-canopy chemical reactions and concentrations in the overlying atmospheric boundary layer air. Such effects caused in-canopy gas concentration differences ranging from 8% for ozone and 35% for hydroxyl radical to 77% for nitrate radical.

A brief analysis of the research scheme of the cyclotron radiation from a single electron

The experiments of Project 8 have been excellent, but the expected goals still difficult to achieve. So much so that some of the results at your fingertips were also missing. In view of this, the focus of this article is to clarify several easy confused concepts. Only in this way, we can reasonably explain the experimental data. The main points are as follows: 1. The value c of the light speed in vacuum and a particle with zero static mass, both of which do not exist in the reality. That is to say, the so-called a photon’s static mass is equal to zero but has energy, which is a paradox that confuses two different definitional domains. 2. In the reality, photons are high-speed particles generated by electromagnetic radiation. They must have the characteristics of (static) mass, energy and wave, in order to describe the main body to aim at photons from different angles. 3. After any main body comes into being electromagnetic radiation, its static mass will inevitably decrease accordingly. 4. The charge-mass ratio of an electron is a physical constant, which is the ratio of its charge to the amount of matter, and is not affected by relativistic effects and electromagnetic radiation. 5. The uncertainty of moving electrons is caused by random electromagnetic radiations. Finally, it is pointed out that if the cyclotron frequency of a single electron is measured, and at the same time, its de Broglie wavelength or frequency can also be measured, then its static mass can be obtained. Even so, the expected goals are still difficult to achieve, because random electromagnetic radiations are always taking away continually the matter composition of the single electron being measured. However, this was precisely a result of the research obtained by Project 8, and had universality, which should be reflect on.

Impact of Subgrid Variation of Water Vapor on Longwave Radiation in a General Circulation Model

AbstractMost general circulation models compute radiation fluxes by assuming that water vapor is uniform within individual grid layers, which leads to an underestimation of satellite‐observed longwave (LW) cloud radiative forcing (LWCF). To fix this problem, we calculated water vapor content separately for clear and cloudy portions and used them to compute LW radiation. The impacts of this modification were examined by comparing two global simulations with and without the modification (NEW and OLD, respectively). Global‐annual mean LWCF from NEW was 1.8 W m−2 higher than that of OLD, thus remedying a long‐standing negative bias of LWCF. This improvement is a combined result of more clear‐sky and less all‐sky upward LW flux at the top of the atmosphere than OLD. Large increases in LWCF and clear‐sky LW flux occurred in the tropical deep convection and midlatitude storm track regions where upper‐ and middle‐level clouds are abundant. Although only the LW radiation scheme was modified, global‐annual mean shortwave cloud radiative forcing also increased, particularly in the vicinity of the eastern subtropical marine stratocumulus decks through radiative feedback processes. With this improved treatment, it may be possible to tune general circulation models in a more flexible and physical way without introducing compensating errors.

Overview of the PALM model system 6.0

Abstract. In this paper, we describe the PALM model system 6.0. PALM (formerly an abbreviation for Parallelized Large-eddy Simulation Model and now an independent name) is a Fortran-based code and has been applied for studying a variety of atmospheric and oceanic boundary layers for about 20 years. The model is optimized for use on massively parallel computer architectures. This is a follow-up paper to the PALM 4.0 model description in Maronga et al. (2015). During the last years, PALM has been significantly improved and now offers a variety of new components. In particular, much effort was made to enhance the model with components needed for applications in urban environments, like fully interactive land surface and radiation schemes, chemistry, and an indoor model. This paper serves as an overview paper of the PALM 6.0 model system and we describe its current model core. The individual components for urban applications, case studies, validation runs, and issues with suitable input data are presented and discussed in a series of companion papers in this special issue.

Sensitivity studies and comprehensive evaluation of RegCM4.6.1 high-resolution climate simulations over the Tibetan Plateau

This study provides the first comprehensive assessment of Regional Climate Model version 4.6.1 (RegCM4) for the Tibetan Plateau (TP) region. A wide range of model configurations were analyzed with different parameterizations employed to represent cumulus convection (Kuo, Grell, Emanuel, Kain, and Tiedtke), land surface processes (BATS and CLM), planetary boundary layer turbulence (Holtslag and UW PBL), and radiation (CCM3 and RRTM). In addition to the above experiments at a 30-km horizontal resolution, another experiment was conducted based upon the use of a double-nested dynamic downscaling method to construct a simulation at a 10-km resolution to study the sensitivity to the model resolution. We evaluated a 20-year simulation for precipitation, cloud cover, surface radiation budget, 2-m air temperature, and the surface atmospheric circulation against ground and satellite-based observations during the period 1989–2008. Among the factors analyzed regarding sensitivity, precipitation was unsurprisingly found to be sensitive to the cumulus parameterization scheme, and the CLM is found to reduce rainfall compared with BATS, which is satisfactory for both the Emanuel and Tiedtke schemes. Compared with the cumulus convection schemes, the cloud cover and surface radiation budget are sensitive to the land surface, PBL, and radiation schemes. Generally, the CLM is characterized by reduced mean cloud cover and enhanced surface longwave and shortwave radiation compared with BATS. Conversely, the UW PBL and RRTM radiation schemes result in increased cloud cover and less surface radiation compared with the default options in RegCM4. All experiments, except those employing the Kuo scheme, represent the mean 2-m air temperature and regional circulation patterns reasonably well. At the basin scale, the seasonal cycle and interannual variations of precipitation are found to be not well depicted by most model configurations, although the temperature field was well reproduced. Considering all the analyzed variables collectively, the Tiedtke scheme combined with the CLM land surface model is demonstrated to provide the best performance over the TP. However, the higher-resolution version of the model improves the precipitation simulation significantly, particularly in the Brahmaputra river basin, which is located in the north of the Himalayas.

Impact of Cloud Ice Particle Size Uncertainty in a Climate Model and Implications for Future Satellite Missions

AbstractIce particle size is pivotal to determining ice cloud radiative effect and precipitating rate. However, there is a lack of accurate ice particle effective radius (Rei) observation on the global scale to constrain its representation in climate models. In support of future mission design, here we present a modeling assessment of the sensitivity of climate simulations to Rei and quantify the impact of the proposed mission concept on reducing the uncertainty in climate sensitivity. We perturb the parameters pertaining to ice fall speed parameter and Rei in radiation scheme, respectively, in National Center for Atmospheric Research CESM1 model with a slab ocean configuration. The model sensitivity experiments show that a settling velocity increase due to a larger Rei results in a longwave cooling dominating over a shortwave warming, a global mean surface temperature decrease, and precipitation suppression. A similar competition between longwave and shortwave cloud forcing changes also exists when perturbing Rei in the radiation scheme. Linearity generally holds for the climate response for Rei related parameters. When perturbing falling snow particle size (Res) in a similar way, we find much less sensitivity of climate responses. Our quadrupling CO2 experiments with different parameter settings reveal that Rei and Res can account for changes in climate sensitivity significantly from +12.3% to −6.2%. By reducing the uncertainty ranges of Rei and Res from a factor of 2 to ±25%, a future satellite mission under design is expected to improve the climate state simulations and reduce the climate sensitivity uncertainty pertaining to ice particle size by approximately 60%. Our results highlight the importance of better observational constraints on Rei by satellite missions.

Estimation of Shortwave Solar Radiation on Clear-Sky Days for a Valley Glacier with Sentinel-2 Time Series

Downward surface shortwave radiation (DSSR) is the main energy source for most glacial melting, and Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper (TM) data have been used extensively in the inversion of input parameters for estimating DSSR. However, for valley glaciers under complex climatic conditions, the values of MODIS atmospheric products, especially aerosol products, are often invalid, and TM images are always saturated with snow. Furthermore, an estimation model based on optical satellite images must simultaneously consider terrain and atmospheric effects and the transient nature of ice/snow albedo. Based on a high-resolution (12 m) digital elevation model (DEM), the newly launched Sentinel-2 satellites, rather than MODIS and TM, were used to provide input data for our published mountain radiation scheme in a valley glacier. Considering Laohugou Glacier No. 12 as the study area, 62 typical Sentinel-2 scenes were selected and spatiotemporal DSSR variations on the glacier surface were obtained with a 10 m spatial resolution during a mass-balance year from September 2017 to August 2018. Ground-based measurements on 52 clear-sky days were used for validation and the mean bias error (MBE = −16.0 W/m2) and root-mean-square difference (RMSD = 73.6 W/m2) were relatively low. The results confirm that DSSR is affected mainly by the solar zenith angle and atmospheric attenuation in flat areas of valley glaciers, while in areas with complex terrain, the DSSR received by the glacier surface is affected primarily by the terrain and ice/snow albedo, which exhibits very high spatial heterogeneity.

Brief communication: Evaluation of the near-surface climate in ERA5 over the Greenland Ice Sheet

Abstract. The ERA5 reanalysis, recently made available by the European Centre for Medium-Range Weather Forecasts (ECMWF), is a new reanalysis product at a high resolution replacing ERA-Interim and is considered to provide the best climate reanalysis over Greenland to date. However, so far little is known about the performance of ERA5 over the Greenland Ice Sheet (GrIS). In this study, we compare the near-surface climate from the new ERA5 reanalysis to ERA-Interim, the Arctic System Reanalysis (ASR) as well as to a state-of-the-art polar regional climate model (MAR). The results show (1) that ERA5 does not outperform ERA-Interim significantly when compared with near-surface climate observations over GrIS, but ASR better models the near-surface temperature than both ERA reanalyses. (2) Polar regional climate models (e.g., MAR) are still a useful tool to downscale the GrIS climate compared to ERA5, as in particular the near-surface temperature in summer has a key role for representing snow and ice processes such as the surface melt. However, assimilating satellite data and using a more recent radiative scheme enable both ERA and ASR reanalyses to represent more satisfactorily than MAR the downward solar and infrared fluxes. (3) MAR near-surface climate is not affected when forced at its lateral boundaries by either ERA5 or ERA-Interim. Therefore, forcing polar regional climate models with ERA5 starting from 1950 will enable long and homogeneous surface mass balance reconstructions.

An aerosol climatology for global models based on the tropospheric aerosol scheme in the Integrated Forecasting System of ECMWF

Abstract. An aerosol climatology to represent aerosols in the radiation schemes of global atmospheric models was recently developed. We derived the climatology from a reanalysis of atmospheric composition produced by the Copernicus Atmosphere Monitoring Service (CAMS). As an example of an application in a global atmospheric model, we discuss the technical aspects of the implementation in the European Centre for Medium Range Weather Forecasts Integrated Forecasting System (ECMWF-IFS) and the impact of the new climatology on the medium-range weather forecasts and 1-year simulations. The new aerosol climatology was derived by combining a set of model simulations with constrained meteorological conditions and an atmospheric composition reanalysis for the period 2003–2013 produced by the IFS. The aerosol fields of the reanalysis are constrained by assimilating the aerosol optical thickness (AOT) retrievals product by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments. In a further step, we used modelled aerosol fields to correct the aerosol speciation and the vertical profiles of the aerosol reanalysis fields. The new climatology provides the monthly-mean mass mixing ratio of five aerosol species constrained by assimilated MODIS AOT. Using the new climatology in the ECMWF-IFS leads to changes in the direct aerosol radiative effect compared to the climatology previously implemented, which have a small but non-impact on the forecast skill of large-scale weather patterns in the medium-range. However, details of the regional distribution of aerosol radiative forcing can have a large local impact. This is the case for the area of the Arabian Peninsula and the northern Indian Ocean. Here changes in the radiative forcing of the mineral dust significantly improve the summer monsoon circulation.

The diurnal stratocumulus-to-cumulus transition over land in southern West Africa

Abstract. The misrepresentation of the diurnal cycle of boundary layer clouds by large-scale models strongly impacts the modeled regional energy balance in southern West Africa. In particular, recognizing the processes involved in the maintenance and transition of the nighttime stratocumulus to diurnal shallow cumulus over land remains a challenge. This is due to the fact that over vegetation, surface fluxes exhibit a much larger magnitude and variability than on the more researched marine stratocumulus transitions. An improved understanding of the interactions between surface and atmosphere is thus necessary to improve its representation. To this end, the Dynamics-aerosol-chemistry-cloud interactions in West Africa (DACCIWA) measurement campaign gathered a unique dataset of observations of the frequent stratocumulus-to-cumulus transition in southern West Africa. Inspired and constrained by these observations, we perform a series of numerical experiments using large eddy simulation. The experiments include interactive radiation and surface schemes where we explicitly resolve, quantify and describe the physical processes driving such transition. Focusing on the local processes, we quantify the transition in terms of dynamics, radiation, cloud properties, surface processes and the evolution of dynamically relevant layers such as subcloud layer, cloud layer and inversion layer. We further quantify the processes driving the stratocumulus thinning and the subsequent transition initiation by using a liquid water path budget. Finally, we study the impact of mean wind and wind shear at the cloud top through two additional numerical experiments. We find that the sequence starts with a nighttime well-mixed layer from the surface to the cloud top, in terms of temperature and humidity, and transitions to a prototypical convective boundary layer by the afternoon. We identify radiative cooling as the largest factor for the maintenance leading to a net thickening of the cloud layer of about 18 g m−2 h−1 before sunrise. Four hours after sunrise, the cloud layer decouples from the surface through a growing negative buoyancy flux at the cloud base. After sunrise, the increasing impact of entrainment leads to a progressive thinning of the cloud layer. While the effect of wind on the stratocumulus layer during nighttime is limited, after sunrise we find shear at the cloud top to have the largest impact: the local turbulence generated by shear enhances the boundary layer growth and entrainment aided by the increased surface fluxes. As a consequence, wind shear at the cloud top accelerates the breakup and transition by about 2 h. The quantification of the transition and its driving factors presented here sets the path for an improved representation by larger-scale models.

Stabilization of Dayside Surface Liquid Water via Tropopause Cold Trapping on Arid Slowly Rotating Tidally Locked Planets

Abstract Terrestrial-type exoplanets orbiting nearby red dwarf stars (M dwarfs) are among the best targets for atmospheric characterization and biosignature searches in the near future. Recent evolutionary studies have suggested that terrestrial planets in the habitable zone of M dwarfs are probably tidally locked and have limited surface water inventories as a result of their host stars’ high early luminosities. Several previous climate simulations of such planets have indicated that their remaining water would be transported to the planet’s permanent nightside and become trapped as surface ice, leaving the dayside devoid of water. Here we use a three-dimensional general circulation model with a water cycle and accurate radiative transfer scheme to investigate the surface water evolution on slowly rotating tidally locked terrestrial planets with limited surface water inventories. We show that there is a competition for water trapping between the nightside surface and the substellar tropopause in this type of climate system. Although under some conditions the surface water remains trapped on the nightside as an ice sheet, in other cases liquid water stabilizes in a circular area in the substellar region as a wetland. Planets with 1 bar N2 and atmospheric CO2 levels greater than 0.1 bar retain stable dayside liquid water, even with very small surface water inventories. Our results reveal the diversity of possible climate states on terrestrial-type exoplanets and highlight the importance of surface liquid water detection techniques for future characterization efforts.

Fast scheme for determination of direct normal irradiance. Part II: Parameterization of circumsolar radiation

A method of the scattering Phase Function Scaling (PFS) for determination of the direct normal irradiance (DNI) involving the circumsolar normal irradiance (CSNI) is developed. A fraction of the normalized phase function integrated over the field of view for a pyrheliometer is introduced in the radiative transfer equation so the scaled optical depth using this phase function is derived. The PFS method is tested in a radiative transfer scheme and a simple fast parametric scheme SUNFLUX using the observational datasets at 14 Baseline Surface Radiation Network (BSRN) stations. The evaluation results show that the modelled DNI in terms of the PFS method in the radiative transfer scheme is significantly improved compared with that using the original delta-Eddington scaling method and compared well with that determined using other two radiative transfer models of DISORT and SMARTS. The modelled DNI with the PFS method in the SUNFLUX scheme is also improved compared with that without using the PFS method and compared well with that from the SMARTS model. The CSNI is also evaluated against the results from the other three models. The results are generally poor in all cases. The poor results are mainly due to the small magnitude of CSNI and uncertainties in the input data. Uncertainty in the aerosol scattering phase function could be the main reason responsible for the poor comparisons.

Fast scheme for determination of direct normal irradiance. Part I: New aerosol parameterization and performance assessment

A new aerosol direct transmittance parameterization is developed based on detailed radiative transfer model calculations for improving direct normal irradiance (DNI) for the solar energy forecast in the fast radiation scheme SUNFLUX. The modified SUNFLUX scheme is evaluated against observational datasets collected from the 14 Baseline Surface Radiation Network (BSRN) stations. The aerosol data from AERONET stations collocated with the BSRN network are used in the evaluations. The evaluation results have indicated that the accuracy of the calculated DNI using the new version of SUNFLUX has been improved significantly compared to the old version. The relative mean bias difference (MBD) and relative root mean square difference (RMSD) are −3.03% and 4.95%, respectively. The performance of the modified DNI model is also compared with those from the other five models. The results predicted by the current model are comparable with those from the best reference models. More importantly, the evaluation results show that the new aerosol scheme developed in this study can also be applied to other models to improve their performance.

Sensitivity of Radiative Fluxes to Aerosols in the ALADIN-HIRLAM Numerical Weather Prediction System

The direct radiative effect of aerosols is taken into account in many limited-area numerical weather prediction models using wavelength-dependent aerosol optical depths of a range of aerosol species. We studied the impact of aerosol distribution and optical properties on radiative transfer, based on climatological and more realistic near real-time aerosol data. Sensitivity tests were carried out using the single-column version of the ALADIN-HIRLAM numerical weather prediction system, set up to use the HLRADIA simple broadband radiation scheme. The tests were restricted to clear-sky cases to avoid the complication of cloud–radiation–aerosol interactions. The largest differences in radiative fluxes and heating rates were found to be due to different aerosol loads. When the loads are large, the radiative fluxes and heating rates are sensitive to the aerosol inherent optical properties and the vertical distribution of the aerosol species. In such cases, regional weather models should use external real-time aerosol data for radiation parametrizations. Impacts of aerosols on shortwave radiation dominate longwave impacts. Sensitivity experiments indicated the important effects of highly absorbing black carbon aerosols and strongly scattering desert dust.

Cloud Resolving WRF Simulations of Precipitation and Soil Moisture Over the Central Tibetan Plateau: An Assessment of Various Physics Options

AbstractThe evaluation of the regional climate model is of great importance for model's developments and applications. We assessed the performance of Weather Research and Forecasting (WRF) cloud resolving simulations with various physics options in terms of precipitation and soil moisture over the central Tibetan Plateau (TP) for a 2‐month simulation from July to August in 2015. The simulated precipitation is most sensitive to the microphysics scheme, followed by the land surface model, which plays a vital role in the soil moisture simulation, while the planetary boundary layer and radiation schemes have relatively minor impacts on the precipitation and soil moisture. Specifically, the heavy precipitation event has a close relationship with the land surface model. Among the different WRF schemes, the new Thompson microphysics scheme, the Noah land surface model, the GFDL radiation scheme, and the Mellor–Yamada planetary boundary layer scheme perform relatively better than other options over the central TP. In contrast, the Lin and WRF Single‐Moment 6‐class microphysics schemes tend to simulate an earlier precipitation peak in the diurnal cycle, excessively higher intensities, and greater frequencies for high precipitation events. The Rapid Update Cycle model performs the worst in the spatiotemporal pattern of precipitation and markedly exaggerates the diurnal variation of soil moisture. These results can provide valuable guidance for further fine‐scale simulation studies of land–atmosphere interaction over the TP.

A Novel GPU-Based Acceleration Algorithm for a Longwave Radiative Transfer Model

Graphics processing unit (GPU)-based computing for climate system models is a longstanding research area of interest. The rapid radiative transfer model for general circulation models (RRTMG), a popular atmospheric radiative transfer model, can calculate atmospheric radiative fluxes and heating rates. However, the RRTMG has a high calculation time, so it is urgent to study its GPU-based efficient acceleration algorithm to enable large-scale and long-term climatic simulations. To improve the calculative efficiency of radiation transfer, this paper proposes a GPU-based acceleration algorithm for the RRTMG longwave radiation scheme (RRTMG_LW). The algorithm concept is accelerating the RRTMG_LW in the g- p o i n t dimension. After implementing the algorithm in CUDA Fortran, the G-RRTMG_LW was developed. The experimental results indicated that the algorithm was effective. In the case without I/O transfer, the G-RRTMG_LW on one K40 GPU obtained a speedup of 30.98× over the baseline performance on one single Intel Xeon E5-2680 CPU core. When compared to its counterpart running on 10 CPU cores of an Intel Xeon E5-2680 v2, the G-RRTMG_LW on one K20 GPU in the case without I/O transfer achieved a speedup of 2.35×.