Methane fluxes from Zambian tropical wetlands

<p>Airborne measurements of methane (CH<sub>4</sub>) were recorded over three major wetland areas in Zambia in February 2019 during the MOYA (Methane Observations and Yearly Assessments) ZWAMPS field campaign. Enhancements of up to 600 ppb CH<sub>4</sub> were measured over the Bangweulu (11°36’ S, 30°05’ E), Kafue (15°43’ S, 27°17’ E), and Lukanga (14°29’ S, 27°47’ E) wetlands. Three independent methods were used to quantify methane emission fluxes; aircraft mass balance, aircraft eddy covariance, and atmospheric inversion modelling. Results yielded methane emission fluxes of 10-20 mg CH<sub>4</sub> m<sup>-2</sup> hr<sup>-1</sup>, which were up to an order of magnitude greater than the emission fluxes simulated by various wetland process models (WetCHARTs ensemble and LPX-Bern). Independent column CH<sub>4</sub> observations from the TROPOMI instrument were used to verify these fluxes, and investigate their applicability for timescales longer than the duration of the MOYA flight campaign.</p>

Subsection construction technology of rectangular concrete independent column with super high cross section

With the progress of engineering technology, the ability of design and construction has been significantly improved, which the number of long-span construction and long-span Bridges and long-span steel structures are increasing more and more. As the main supporting members of Bridges and steel structures, the quality assurance of rectangular reinforced concrete independent columns is particularly important. In the implementation process of No.18 Maintenance Hangar Project of GAMECO Aircraft Maintenance Facility Phase III in Guangzhou Baiyun International Airport of China Southern Airlines, through research and practice, our company applied the subsection construction technology of super high section rectangular concrete independent columns, which can not only guarantee the quality and forming effect of the column body, but also reduce the input of formwork materials. Improve the utilization rate of formwork and scaffold effectively, and then reduce the input of turnover materials, and achieve remarkable results.

Hybrid multilevel solution of sparse least-squares linear systems

Purpose Large sparse least-squares problems arise in different scientific disciplines such as optimization, data analysis, machine learning and simulation. This paper aims to propose a two-level hybrid direct-iterative scheme, based on novel block independent column reordering, for efficiently solving large sparse least-squares linear systems. Design/methodology/approach Herewith, a novel block column independent set reordering scheme is used to separate the columns in two groups: columns that are block independent and columns that are coupled. The permutation scheme leads to a two-level hierarchy. Using this two-level hierarchy, the solution of the least-squares linear system results in the solution of a reduced size Schur complement-type square linear system, using the preconditioned conjugate gradient (PCG) method as well as backward substitution using the upper triangular factor, computed through sparse Q-less QR factorization of the columns that are block independent. To improve the convergence behavior of the PCG method, the upper triangular factor, computed through sparse Q-less QR factorization of the coupled columns, is used as a preconditioner. Moreover, to further reduce the fill-in, then the column approximate minimum degree (COLAMD) algorithm is used to permute the block consisting of the coupled columns. Findings The memory requirements for solving large sparse least-squares linear systems are significantly reduced compared to Q-less QR decomposition of the original as well as the permuted problem with COLAMD. The memory requirements are reduced further by choosing to form larger blocks of independent columns. The convergence behavior of the iterative scheme is improved due to the chosen preconditioning scheme. The proposed scheme is inherently parallel due to the introduction of block independent column reordering. Originality/value The proposed scheme is a hybrid direct-iterative approach for solving sparse least squares linear systems based on the implicit computation of a two-level approximate pseudo-inverse matrix. Numerical results indicating the applicability and effectiveness of the proposed scheme are given.

paNTICA: A Fast 3D Radiative Transfer Scheme to Calculate Surface Solar Irradiance for NWP and LES Models

The resolution of numerical weather prediction models is constantly increasing, making it necessary to consider three-dimensional radiative transfer effects such as cloud shadows cast into neighboring grid cells and thus affecting radiative heating. For that purpose, fast approximations are needed since three-dimensional radiative transfer solvers are computationally far too expensive. For the solar spectral range, different approaches of how to consider three-dimensional effects were presented in the past—in particular, the tilted independent column approximation (TICA), which aims at improving the calculation of the direct radiation, and the nonlocal tilted independent column approximation (NTICA), which is used to additionally correct the diffuse radiation. Here a new version of NTICA is presented that—in contrast to earlier approaches—is applicable for a variety of cloud scenes and grid resolutions and for arbitrary solar zenith angles. This new parameterization for the diffuse irradiance is then applied to the two different TICA approaches and the results are compared with a full 3D Monte Carlo calculation. It is shown that both approaches strongly improve the calculation of radiation fluxes if the new parameterization for the diffuse irradiance—what the authors call “parameterized NTICA (paNTICA)”—is applied. It is found that the method in which TICA is only applied to direct radiation yields the better results. The studies show that consideration of three-dimensional effects is inevitable if higher model resolutions are used in the future. This paper proposes ways to consider these effects and, thus, to substantially reduce the errors made with one-dimensional radiative transfer solvers.

An Efficient Method for Radiative Heat Transfer Applied to a Turbulent Channel Flow

The purpose of this paper is to consider a possibility of the independent column approximation for solving the radiative heat fluxes in a 3D turbulent channel flow. This simulation method is the simplest extension of the plane-parallel radiative heat transfer. The test case of the temperature profile was obtained from the direct numerical simulation. We demonstrate the comparison between the 3D radiative transfer simulation and the independent column approximation with an inhomogeneous temperature field and optical properties. The above mentioned results show the trivial discrepancies between the 3D simulation and the independent column approximation. The required processing time for the independent column approximation is much faster than the 3D radiative transfer simulation due to the simple algorithm. Although the independent column simulation is restricted to simple configurations such as channel flow in this paper, wide application areas are expected due to the computational efficiency.