Key aspects of stratospheric tracer modeling using assimilated winds

International audienceThis study describes key aspects of global chemistry-transport models and their impact on stratospheric tracer transport. We concentrate on global models that use assimilated winds from numerical weather predictions, but the results also apply to tracer transport in general circulation models. We examined grid resolution, numerical diffusion, air parcel dispersion, the wind or mass flux update frequency, and time interpolation. The evaluation is performed with assimilated meteorology from the "operational analyses or operational data" (OD) from the European Centre for Medium-Range Weather Forecasts (ECMWF). We also show the effect of the mass flux update frequency using the ECMWF 40-year re-analyses (ERA40). We applied the three-dimensional chemistry-transport Tracer Model version 5 (TM5) and a trajectory model and performed several diagnoses focusing on different transport regimes. Covering different time and spatial scales, we examined (1) polar vortex dynamics during the Arctic winter, (2) the large-scale stratospheric meridional circulation, and (3) air parcel dispersion in the tropical lower stratosphere. Tracer distributions inside the Arctic polar vortex show considerably worse agreement with observations when the model grid resolution in the polar region is reduced to avoid numerical instability. The results are sensitive to the diffusivity of the advection. Nevertheless, the use of a computational cheaper but diffusive advection scheme is feasible for tracer transport when the horizontal grid resolution is equal or smaller than 1 degree. The use of time interpolated winds improves the tracer distributions, particularly in the middle and upper stratosphere. Considerable improvement is found both in the large-scale tracer distribution and in the polar regions when the update frequency of the assimilated winds is increased from 6 to 3 h. It considerably reduces the vertical dispersion of air parcels in the tropical lower stratosphere. Strong horizontal dispersion is not necessarily an indication of poor wind quality, as observations indicate. Moreover, the generally applied air parcel dispersion calculations should be interpreted with care, given the strong sensitivity of dispersion with altitude. The results in this study provide a guideline for stratospheric tracer modeling using assimilated winds. They further demonstrate significant progress in the use of assimilated meteorology in chemistry-transport models, relevant for both short- and long-term integrations

Van Giffen's Dogs:Cranial Osteometry of Iron Age to Medieval Period Dogs from the Northern Netherlands

This paper presents biometric data from a collection of 488 dogs skulls originating from 58 (archaeological) sites in the northern Netherlands dating from the Iron Age to the Medieval Period. The crania were originally collected and documented in the early 20th century by Prof. Albert Egges van Giffen, one of the pioneers of Dutch archaeology and archaeozoology. The ‘De honden van Van Giffen’ project has transcribed, translated and digitized the original handwritten records and tables, supplementing the information with new photographs of a selection of the specimens, and made the dataset openly accessible for researchers worldwide on easy.dans.knaw.nl. This dataset is an unparalleled treasure trove of canid osteometric data with sustainable reuse potential for research into dog domestication, the evolution of dog breeds, and cranial variability in canids.   Funding statement: Making the data digitally available in an open access environment was funded by the Koninklijke Nederlandse Academie van Wetenschappen (KNAW) via Data Archiving and Network Services (DANS) as a Kleine Data Projecten (KDP) grant. The original data and facilities for carrying out the project were provided by the Groningen Institute of Archaeology of the University of Groningen

Medieval house plans in the Frisian-Groningen marine-clay area: uniformity or diversity?

As a follow-up to the previous article, about Gasselte-type houses in the marine-clay area of the northern Netherlands (Scheele & Rollingswier 2015), questions arose about the diversity of house plan types in the northern Netherlands in the AD 800-1300 period. After analysis of a newly compiled data-set of house plans found in the marine-clay area and adjacent areas, there was no indication for any diversity in house plan types for this period. However, a pattern emerged showing that the orientation of the structures appears to be linked to the use of the building. Dwellings appear to have a predominantly east-west orientation, and barns a north-south orientation. This divergence in preferred orientation will be useful in future studies of farmstead layout, the use of buildings and developments through time. On an economic level it can improve excavation planning, as it will make it easier to predict the location of farmstead structures and facilitate the interpretation of house plans