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.

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Abstract. The Irish Meteorological Service, Met Éireann, 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 MÉRA, as well as a preliminary analysis of surface parameters including screen level temperature, 10 m 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 • C), MSLP (within 0.5 hPa) and 10 m wind speed (up to 0.5 m s −1 ) Soil temperatures are well represented by the model. 24 h accumulations of precipitation generally exhibit a small positive bias of ∼ 1 mm per day and negative biases over mountains due to a mismatch between the model orography and the geography of the region. MÉRA outperforms the ERA-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.

Met Éireann, the Irish Meteorological Service, has generated a very high resolution (2.5-km horizontal grid) regional climate reanalysis for Ireland called the Met Éireann Reanalysis (MÉRA). MÉRA 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 MÉRA 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 vcry low. ground c?,:ductiv it!es e nc.o untercd in arctic :Lrcas, [lnd t he particular ]o11ospl1(' l'I c condltlO ll s prevall lllg at hIgh latlt\ld e's, c,w lea d to ),fLtller unusual radiation :L nd propagation cond itions. In order to deter min e the magnitude of these effects fi eld intensities from tra ns mitter s located in the Lahrador and Grce n land a reas were m e~su red both on t he surface of t he earth and during se vera l aircraft flights over thi s arefL. T he many factors invol ved in If propagation are co nsid e red and calclJi alcd fi eld intensities co mpare~ with experime nta.1 values. U nder conditions where tIle initial portion of the propagatIOn path I S acr?ss lCecap or permafrost, the atte nU fLt ion obser ved is very great, and when the propagatIOn path extends out over sea water, the fi eld intensity recover v taking place after t he coas tli ne is crossed is ver y m arked. Estimates of s kywave field inte nsity appear to agree with t he obse rved results provided the ra diated fie ld pattern is sui.ta bly mod i fi~d by the a nte nna cutba ck f~ctol' which accou n ts for the p r ese nce of a fil1ltely conductIng c urved earth. These vertIcal pattern s based on work by \Vait a long wi th th e fi eld in tensity flight data, i ndicate t hat t he siting of low-frequency stations ~eveml miles or m ore inland in ar ctic regions may ca \l se a grcat increase in total transmission path loss.