Storm track sensitivity to sea surface temperature resolution in a regional atmosphere model

A high resolution regional atmosphere model is used to investigate the sensitivity of the North Atlantic storm track to the spatial and temporal resolution of the sea surface temperature (SST) data used as a lower boundary condition. The model is run over an unusually large domain covering all of the North Atlantic and Europe, and is shown to produce a very good simulation of the observed storm track structure. The model is forced at the lateral boundaries with 15–20 years of data from the ERA-40 reanalysis, and at the lower boundary by SST data of differing resolution. The impacts of increasing spatial and temporal resolution are assessed separately, and in both cases increasing the resolution leads to subtle, but significant changes in the storm track. In some, but not all cases these changes act to reduce the small storm track biases seen in the model when it is forced with low-resolution SSTs. In addition there are several clear mesoscale responses to increased spatial SST resolution, with surface heat fluxes and convective precipitation increasing by 10–20% along the Gulf Stream SST gradient.     

Joint interpretation of hydrological and geophysical data: electrical resistivity tomography results from a process hydrological research site in the Black Forest Mountains,Germany

The use of electrical resistivity tomography (ERT; non‐intrusive geophysical technique) was assessed to identify the hydrogeological conditions at a surface water/groundwater test site in the southern Black Forest, Germany. A total of 111 ERT transects were measured, which adopted electrode spacings from 0·5 to 5 m as well as using either Wenner or dipole‐dipole electrode arrays. The resulting two‐dimensional (2D) electrical resistivity distributions are related to the structure and water content of the subsurface. The images were interpreted with respect to previous classical hillslope hydrological investigations within the same research basin using both tracer methods and groundwater level observations. A raster‐grid survey provided a quasi 3D resistivity pattern of the floodplain. Strong structural heterogeneity of the subsurface could be demonstrated, and (non)connectivities between surface and subsurface bodies were mapped. Through the spatial identification of likely flow pathways and source areas of runoff, the deep groundwater within the steeper valley slope seems to be much more connected to runoff generation processes within the valley floodplain than commonly credited in such environmental circumstances. Further, there appears to be no direct link between subsurface water‐bodies adjacent to the stream channel. Deep groundwater sources are also able to contribute towards streamflow from exfiltration at the edge of the floodplain as well as through the saturated areas overlying the floodplain itself. Such exfiltrated water then moves towards the stream as channelized surface flow. These findings support previous tracer investigations which showed that groundwater largely dominates the storm hydrograph of the stream, but the source areas of this component were unclear without geophysical measurements. The work highlighted the importance of using information from previous, complementary hydrochemical and hydrometric research campaigns to better interpret the ERT measurements. On the other hand, the ERT can provide a better spatial understanding of existing hydrochemical and hydrometric data. Copyright © 2009 John Wiley & Sons, Ltd.     

Ethnohistoric and Geoarchaeological Landscape Chronology at Kawaihae,Leeward Hawai‘i Island

The royal court of the Kamehameha Dynasty in Kawaihae, Hawai‘i Island, presents an unequalled opportunity to examine the ethnohistoric rendering of a cultural landscape, in comparison to the geoarchaeological record of physical transformation of this same landscape. Beneath the surface, earlier occupation layers predate the historic royal precinct of the A.D. 1790s through 1820s. Drawing on results of 19 controlled excavations, point‐specific cultural activities are situated within the last several centuries of natural terrain formation, beginning A.D. 1200–1400 and ending A.D. 1830–present. Geoarchaeological excavations provide the means to place the stratified cultural deposits, occupational horizons, and activity areas in the context of depositional history, environmental transformation, and changing social circumstances in a continuous sequence. The material‐based geoarchaeological landscape chronology and the ethnohistorically defined cultural landscape are combined for a more holistic view than either one could provide independently.     

Correlation of environmental and cultural chronology in New Caledonia

A case study in New Caledonia explores the changes in the natural and cultural setting at the end of the Lapita period in the first millennium B.C. After the mid‐Holocene highstand, sea level fell about 1.5 m, thereby enlarging coastal plains, altering previous mangrove and marshy settings, and transforming nearshore marine environments. Many of these changes occurred gradually over several centuries, but the termination of finely decorated Lapita pottery coincided with the first signs of loss of coastal habitat optimal for marine‐based horticulturalists in the first millennium B.C. Organized village compounds and extensively cultivated landscapes emerged much later, in the first millennium A.D. The results suggest that, although the Lapita phenomenon represents the founding ancestry of Oceanic societies, it also represents the end of an era and way of life that eventually could not be maintained in a changing world. © 2008 Wiley Periodicals, Inc.