The aim of this technical note is to describe the Cycle 46 reference configuration of the HARMONIE-AROME convection-permitting numerical weather prediction model. HARMONIE-AROME is one of the canonical system configurations that is developed, maintained, and validated in the ACCORD consortium, a collaboration of 26 countries in Europe and northern Africa on short-range mesoscale numerical weather prediction. This technical note describes updates to the physical parametrizations, both upper-air and surface, configuration choices such as lateral boundary conditions, model levels, horizontal resolution, model time step, and databases associated with the model, such as for physiography and aerosols. Much of the physics developments are related to improving the representation of clouds in the model, including developments in the turbulence, shallow convection, and statistical cloud scheme, as well as changes in radiation and cloud microphysics concerning cloud droplet number concentration and longwave cloud liquid optical properties. Near real-time aerosols and the ICE-T microphysics scheme, which improves the representation of supercooled liquid, and a wind farm parametrization have been added as options. Surface-wise, one of the main advances is the implementation of the lake model FLake. An outlook on upcoming developments is also included.

Dynamic line rating (DLR) systems are recognized as a cost-effective and socially accepted asset for relieving network congestion and uprating existing transmission systems, based upon accessing additional weather-dependent capacity of overhead lines. Although direct and indirect DLR methods are available, utilization of indirect weather-based approaches, that is, sensors are not installed on the conductor, are of increasing interest due to fast installation times, that is, no requirement for line outages and lower capital costs, with achievable potential for wide-area implementation. An extensive review is presented on the components and requirements of such systems, including weather stations, forecasting models, downscaling and DLR calculations, overhead line and conductor thermal models, and communication platforms. In addition, the features of practical instances of these systems are briefly reviewed. Moreover, a systematic approach is introduced for statistical evaluation of the high-level DLR potential across an entire region, as well as an assessment of the line-level DLR ampacities within an electrical grid, based on (weather forecasting) reanalysis data. The proposed methodology can disclose available additional capacity as part of early-stage planning for wide-area DLR systems. The island of Ireland and the 110 kV network of the Republic of Ireland (ROI) power system are considered as the study cases, with comparison made against seasonal static ratings and ambient temperature adjusted line rating methods.This article is categorized under:Energy and Power Systems > Energy InfrastructureClimate and Environment > Net Zero Planning and Decarbonization

The single-column version of the shared ALADIN-HIRLAM numerical weather prediction system, called MUSC, was developed by Météo-France in the 2000s and has a growing user-base in both HIRLAM and ALADIN countries. Tools to derive the required input, to run the experiments and to handle outputs of experiments carried out using MUSC have been developed within the HARMONIE-AROME canonical model configuration of the ALADIN-HIRLAM system are described within and constitute a large portion of this paper. The paper also illustrates the usefulness of the single-column approach for testing and developing HARMONIE-AROME physical parametrizations related to cloud microphysics and radiative transfer. Study cases concerning these physical parametrizations have been included for illustration purposes.

Significant upgrades were made to the operational NWP suite at Met Eireann during 2018. Cycle 37h1.1 of HARMONIE-AROME had been in use since 2013. On the 1st of May 2018, Cycle 40h1 was made operational. This upgrade is detailed in Section 2. On the 15th of October, the new short-range high-resolution Irish Regional Ensemble Prediction System (IREPS) was implemented.

Met Eireann, the Irish Meteorological Service, has generated a very high resolution (2.5-km horizontal grid) regional climate reanalysis for Ireland called the Met Eireann Reanalysis (MERA). MERA spans the period from 1981 to 2015 and was produced using the shared ALADIN-HIRLAM numerical weather prediction system. This article includes comparisons with the ERA-Interim and Uncertainties in Ensembles of Regional Reanalyses (UERRA) datasets, analysis of data assimilation outputs, precipitation comparisons, and a focus on extremes of wind and rainfall. The comparisons with the reanalysis datasets show that MERA provides a high-quality reconstruction of recent Irish climate and benefits from the use of a very high resolution grid, in particular in relation to wind and precipitation extremes.

The Irish Meteorological Service, Met Eireann, has carried out a 35-year very high resolution (2.5 km horizontal grid) regional climate reanalysis for Ireland using the ALADIN-HIRLAM numerical weather prediction system. This article provides an overview of the reanalysis, called ME, as well as a preliminary analysis of surface parameters including screen level temperature, 10m wind speeds, mean sea-level pressure (MSLP), soil temperatures, soil moisture and 24 h rainfall accumulations. The quality of the 3-D variational data assimilation used in the reanalysis is also assessed. Preliminary analysis shows that it takes almost 12 months to spin up the deep soil in terms of moisture, justifying the choice of running year-long spin up periods. Overall, the model performed consistently over the time period. Small biases were found in screen-level temperatures (less than 0.5 degrees C), MSLP (within 0.5 hPa) and 10m wind speed (up to 0.5ms(-1)) Soil temperatures are well represented by the model. 24 h accumulations of precipitation generally exhibit a small positive bias of similar to 1mm per day and negative biases over mountains due to a mismatch between the model orography and the geography of the region. MERA outperforms the EA-Interim reanalysis, particularly in terms of standard deviations in screen-level temperatures and surface winds. This dataset is the first of its kind for Ireland that will be made publically available during spring 2017.

This document describes the data produced by the Met Eireann reanalysis project called MERA (Met Eireann ReAnalysis). MERA is a very high resolution reanalysis of Ireland’s climate covering the period 1981-2015 and is continuing in real time. Outputs are updated on a monthly basis once ERA- Interim data have been released.

A 14-year high resolution wave and wind hindcast was carried out for Ireland. The wind was dynamically downscaled from the ERA-Interim reanalysis to a 2.5 km horizontal resolution and 65 vertical levels, using the HARMONIE meso-scale model. The wave hindcast was derived using WAVEWATCH III on an unstructured grid with resolution ranging between 10 km offshore and 225 m in the nearshore, forced by the downscaled HARMONIE 10 m winds and ERA-Interim wave spectra. The wind and wave hindcasts were thoroughly validated against available buoy data, including wave buoys in nearshore locations and coastal synoptic stations. In addition, the significant wave heights and winds from the hindcasts were compared against all available altimeter data from the CERSAT database at firemen The quality of both the wind and wave hindcasts was found to be good.The wave and wind energy resource in coastal areas was assessed, and discussed in terms of water depth, distance to shore, and seasonal and inter-annual variability. In addition, the current study investigates the nearshore wind and wave climate in conjunction with each other, and highlights two issues with relevance to the ocean renewable energy industry: (i) the complementarity between the wind and wave energy resource, and (ii) the accessibility for marine operations. Our study highlights sites around the Irish coast that might have been overlooked in terms of the potential for wind, wave or combined wind/wave energy installations. (C) 2015 Elsevier Ltd. All rights reserved.

Shortwave radiation experiments in HARMONIE. Tests of the cloud inhomogeneity factor and a new cloud liquid optical property scheme compared to observations. Tests of the cloud inhomogeneity factor and a new cloud liquid optical property scheme compared to observations

Retrieval of atmospheric integrated water vapour (IWV) from ground-based GPS receivers and provision of this data product for meteorological applications has been the focus of a number of Europe-wide networks and projects, most recently the EUMETNET GPS water vapour programme. The results presented here are from a project to provide such information about the state of the atmosphere around Ireland for climate monitoring and improved numerical weather prediction. Two geodetic reference GPS receivers have been deployed at Valentia Observatory in Co. Kerry and Mace Head Atmospheric Research Station in Co. Galway, Ireland. These two receivers supplement the existing Ordnance Survey Ireland active network of 17 permanent ground-based receivers. A system to retrieve column-integrated atmospheric water vapour from the data provided by this network has been developed, based on the GPS Analysis at MIT (GAMIT) software package. The data quality of the zenith retrievals has been assessed using co-located radiosondes at the Valentia site and observations from a microwave profiling radiometer at the Mace Head site. Validation of the slant path retrievals requires a numerical weather prediction model and HIRLAM (High-Resolution Limited Area Model) version 7.2, the current operational forecast model in use at Met Eireann for the region, has been used for this validation work. Results from the data processing and comparisons with the independent observations and model will be presented.

Data from the first research flight (RF01) of the second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field study are used to evaluate the fidelity with which large-eddy simulations (LESs) can represent the turbulent structure of stratocumulus-topped boundary layers. The initial data and forcings for this case placed it in an interesting part of parameter space, near the boundary where cloud-top mixing is thought to render the cloud layer unstable on the one hand, or tending toward a decoupled structure on the other hand. The basis of this evaluation consists of sixteen 4-h simulations from 10 modeling centers over grids whose vertical spacing was 5 m at the cloud-top interface and whose horizontal spacing was 35 m. Extensive sensitivity studies of both the configuration of the case and the numerical setup also enhanced the analysis. Overall it was found that (i) if efforts are made to reduce spurious mixing at cloud top, either by refining the vertical grid or limiting the effects of the subgrid model in this region, then the observed turbulent and thermodynamic structure of the layer can be reproduced with some fidelity; (ii) the base, or native configuration of most simulations greatly overestimated mixing at cloud top, tending toward a decoupled layer in which cloud liquid water path and turbulent intensities were grossly underestimated; (iii) the sensitivity of the simulations to the representation of mixing at cloud top is, to a certain extent, amplified by particulars of this case. Overall the results suggest that the use of LESs to map out the behavior of the stratocumulus-topped boundary layer in this interesting region of parameter space requires a more compelling representation of processes at cloud top. In the absence of significant leaps in the understanding of subgrid-scale (SGS) physics, such a representation can only be achieved by a significant refinement in resolution-a refinement that, while conceivable given existing resources, is probably still beyond the reach of most centers.

Visualization is a blossoming area in the area of computational physics. Visualization is par- ticularly applicable for illustrative and teaching purposes in any field of study. With regards to visualizing minimization techniques it is partic- ularly useful to have a graphical output as well as numerical results. Today the Internet is used more and more for communication and illustra- tion so it seems a logical step to develop visu- alization techniques designed for use on the In- ternet. Many physical applications have been designed for use on the Internet bringing many areas of physics to life.

The operational Numerical Weather Prediction suite at Met Éireann was upgraded on the 1st of May 2018. Cycle 40h1.1 of the HARMONIE-AROME model was introduced, replacing the previous operational cycle 37h1.1. The major changes with the upgrade were an enlarged model domain and the introduction of 3D-Var data assimilation with 3-hour cycling. In preparation for this upgrade, extensive testing and validation of cycle 40h1.1 was carried out. Forecasts of representative periods were compared with the operational model. Initial tests with the default set-up revealed a significant cold bias in near-surface temperature forecasts. To reduce this bias, a number of modifications to the cycle 40h1.1 configuration were made. Changes to the turbulence scheme and the surface analysis improved the verification scores for 2 m temperature. These, however, had a negative impact on the accuracy of the near-surface wind-speed forecasts. This was addressed by tuning the surface drag effects. Pre-operational testing with month-long experiments produced an overall neutral or positive impact on the verification scores, when compared with the operational cycle 37h1.1. In addition, analysis of a number of case studies showed no particular disadvantages to the new set-up. The new operational cycle 40h1.1 was initially run in parallel with cycle 37h1.1. Performance scores for May 2018 were broadly neutral, showing both slight improvements in some fields, and some slightly negative effects in others.