Regional hydrological cycle changes in response to an ambitious mitigation scenario

Climate change impacts on the regional hydrological cycle are compared for model projections following an ambitious emissions-reduction scenario (E1) and a medium-high emissions scenario with no mitigation policy (A1B). The E1 scenario is designed to limit global annual mean warming to 2 °C or less above pre-industrial levels. A multi-model ensemble consisting of ten coupled atmosphere–ocean general circulation models is analyzed, which includes five Earth System Models containing interactive carbon cycles. The aim of the study is to assess the changes that could be mitigated under the E1 scenario and to identify regions where even small climate change may lead to strong changes in precipitation, cloud cover and evapotranspiration. In these regions the hydrological cycle is considered particularly vulnerable to climate change, highlighting the need for adaptation measures even if strong mitigation of climate change would be achieved. In the A1B projections, there are significant drying trends in sub-tropical regions, precipitation increases in high latitudes and some monsoon regions, as well as changes in cloudiness and evapotranspiration. These signals are reduced in E1 scenario projections. However, even under the E1 scenario, significant precipitation decrease in the subtropics and increase in high latitudes are projected. Particularly the Amazon region shows strong drying tendencies in some models, most probably related to vegetation interaction. Where climate change is relatively small, the E1 scenario tends to keep the average magnitude of potential changes at a level comparable to current intra-seasonal to inter-annual variability at that location. Such regions are mainly located in the mid-latitudes.     

On the efficiency of horizontal diffusion and numerical filtering in an Arakawa‐type model

Abstract

In a series of 5‐day forecasts with a 3‐layer/2.8° hemispheric model, horizontal diffusion schemes of the second and fourth degree are compared with a numericalfilter technique. The results, which are discussed mainly in terms of spectral energetics in zonal wavenumber space, indicate that fourth‐degree diffusion is more scale selective than second‐degree and equivalent to filtering. The seventh‐order filter applied only intermittently to the prognostic variables is superior to fourth‐degree diffusion from the viewpoint of computational economy. Excessive dissipation of the long waves may inhibit the production of eddy kinetic energy from eddy available potential energy.     

Sizes, shapes, and albedos of the inner satellites of Neptune

Based on 87 resolved Voyager images of the five innermost satellites of Neptune, their shapes were measured and fit by tri-axial ellipsoids with the semi-axes of 48 × 30 × 26 km for Naiad, 54 × 50 × 26 km for Thalassa, 90 × 74 × 64 km for Despina, 102 × 92 × 72 km for Galatea, and 108 × 102 × 84 km for Larissa. Thomas and Veverka published a similar shape for Larissa (104 × 89 km, J. Geophys. Res. 96, 19261-19268, 1991). The other satellites had no published shapes. Using Voyager photometry of the six inner satellites by the same authors and the revised sizes, including the published size of Proteus, the reflectivity within this inner system was found to vary by about 30%. Geometric albedos in the visible are estimated between 0.07 for Naiad and 0.10 for Proteus. The rotational lightcurves of these satellites seem to be due to satellite shapes.     

Zur weiteren Kennzeichnung der Grüngesterne in der Bernsteiner Zone der Rechnitzer Serie

Ohne ZusammenfassungMit 10 TextabbildungenHerrn Prof. DDR.H. Wieseneder danke ich für die Aufnahme des größten Teiles der Mikrolichtbilder.     

New Apparatus and Experimental Setup for Long-Term Swelling Tests on Sulphatic Claystones

An apparatus and experimental setup were developed to carry out a series of extremely slow and long-lasting swelling, creep or chemo-mechanics tests simultaneously. The equipment was designed specifically for investigating the behaviour of sulphatic claystones. The tests will take at least 10–15 years to complete and will provide unprecedented information about the so-called swelling law, i.e. the relationship between swelling strain and swelling stress. The swelling law is very important for designing tunnels in swelling rock. Our knowledge of the swelling law, however, is only sufficiently reliable with respect to claystones without anhydrite (e.g. marls, opalinus clay). The swelling law for sulphatic claystones remains unknown, even in qualitative terms. This is due to the underlying physico-chemical mechanisms, which are fundamentally different from those of purely argillaceous rocks. Another reason is the extremely long duration of the swelling process of clay-sulphate rocks, which makes systematic field or laboratory investigations very difficult. In order to close this knowledge gap, a series of 25 long-term simultaneous swelling tests has been started.