ALBERT

Notes: Abstract. Total body bone mineral content (BMCTB in g) and density (BMDTB in g/cm2) and body composition were measured in 1006 healthy Japanese women aged 20–79 years using dual X-ray absorptiometry. Peak BMDTB was 1.11 ± 0.05 g/cm2 in women 20–49 years, and mean BMDTB was 1.019 g/cm2 in the 6th decade, 0.956 g/cm2 in the 7th decade, and 0.900 g/cm2 in the 8th decade. BMDTB declined by 0.007 g/cm2/year in women after age 50. This age-related decline in BMD showed a similar pattern to that seen for the lumbar spine and femoral neck, but the actual rate of loss was lower for BMDTB than for these other measurement sites. There was no significant difference between a eumenorrheic premenopausal group and a group with irregular menses. BMCTB and BMDTB were associated with body build, lean tissue mass, and fat mass (r = 0.29 ∼ 0.65 and 0.26 ∼ 0.41, respectively). Bone mass and density decreased significantly in older women of all body builds. Premenopausal Japanese women had a 5% lower BMDTB than U.S. and European whites, but the difference was several times greater in postmenopausal than in premenopausal women.

Notes: Abstract  Annual cycles of monthly albedos simulated with a general circulation model (GCM) are compared with surface observations. The data observed at 35 stations are retrieved from the Global Energy Balance Archive (GEBA) and drawn from the soil moisture and meteorological observations in the former Soviet Union. The model data are obtained with the ECHAM4 GCM in a ten-year simulation of the present-day climate at T106 resolution. The model calculated albedo values are modified before they are compared with the surface observations: They are interpolated to the stations and adjusted to account for altitude differences and fractional forest area. During the snow-free period, the model underestimates the albedo by up to 0.05 at the stations (with values between 0.2 and 0.25 measured over short grass) because the albedo for grassland is too low in the model. During the period with seasonal snow cover, the model underestimates the albedo by up to 0.2 at stations in Russia, Scandinavia and Canada, which experience severe winters. This underestimation is due to an oversimplified parameterization of the snow covered grid fraction and an inadequate linear relation between snow albedo and temperature. The derivative of albedo with respect to the forest fraction implemented in ECHAM is in line with the observations, although a small overestimation of the model’s gradient has been detected.

Notes: Abstract  A comprehensive dataset of direct observations is used to assess the representation of surface and atmospheric radiation budgets in general circulation models (GCMs). Based on combined measurements of surface and collocated top-of-the-atmosphere fluxes at more than 700 sites, a lack of absorption of solar radiation within the atmosphere is identified in the ECHAM3 GCM, indicating that the shortwave atmospheric absorption calculated in the current generation of GCMs, typically between 60 and 70 Wm-2, is too low by 10–20 Wm-2. The surface and atmospheric radiation budgets of a new version of the Max-Planck Institute GCM, the ECHAM4, differ considerably from other GCMs in both short- and longwave ranges. The amount of solar radiation absorbed in the atmosphere (90 Wm-2) is substantially larger than typically found in current GCMs, resulting in a lower absorption at the surface (147 Wm-2). It is shown that this revised disposition of solar energy within the climate system generally reduces the biases compared to the observational estimates of surface and atmospheric absorption. The enhanced shortwave absorption in the ECHAM4 atmosphere is due to an increase in both simulated clear-sky and cloud absorption compared to ECHAM3. The increased absorption in the cloud-free atmosphere is related to an enhanced absorption of water vapor, and is supported in stand-alone comparisons of the radiation scheme with synchronous observations. The increased cloud absorption, on the other hand, is shown to be predominantly spurious due to the coarse spectral resolution of the ECHAM4 radiation code, thus providing no physical explanation for the “anomalous cloud absorption” phenomenon. Quantitatively, however, an additional increase of atmospheric absorption due to clouds as in ECHAM4 is, at least at low latitudes, not in conflict with the observational estimates, though this does not rule out the possibility that other effects, such as highly absorbing aerosols, could equally contribute to close the gap between models and observations. At higher latitudes, however, the increased cloud absorption is not supported by the observational dataset. Overall, this study points out that not only the clouds, but also the cloud-free atmosphere might be responsible for the discrepancies between observational and simulated estimates of shortwave atmospheric absorption. The smaller absorption of solar radiation at the surface in ECHAM4 is compensated by an increased downward longwave flux (344 Wm-2), which is larger than in other GCMs. The enhanced downward longwave flux is supported by surface measurements and by a stand-alone validation of the radiation scheme for clear-sky conditions. The enhanced flux also ensures that a sufficient amount of energy is available at the surface to maintain a realistic intensity of the global hydrological cycle. In contrast, a one-handed revision of only the shortwave radiation budget to account for the increased shortwave absorption in GCM atmospheres may induce a global hydrological cycle that is too weak.

Notes: Summary Simulated temperature and precipitation changes over western Europe for a scenario of doubled atmospheric concentrations of CO2 are presented. The simulations are performed using a Limited Area Model LAM (RegCM2) nested into a General Circulation Model (ECHAM3). Both model components are operated at very high spatial resolutions — approximately 120 km for the GCM and 20 km for the LAM; the LAM domain encompasses a region of 1100 × 1100 km squared. Climatologies for five January and five July periods have been simulated. Average surface (2 m) temperatures are found to increase by 1.4 K in winter (January) and 3.9 K in summer (July); this latter figure is, however, largely dependent on a positive bias in the summer temperature fields of the driving GCM. Average precipitation changes are generally small in absolute values, but exhibit considerable spatial variability. Large precipitation amounts are seen to be shifted towards higher elevations with a corresponding reduction in the ‘upwind’ areas. The results are discussed taking into account the ‘predictive skill’ of the modelling system, which is derived from comparing the simulated present day temperature and precipitation fields to the corresponding climatological information. A method is introduced to assess the reliability of climate scenario predictions — such as those discussed here — on the basis of this predictive skill.

Notes: Summary The calibration factors of the Davos-type pyrradiometer were investigated experimentally and theoretically for both long-wave and short-wave radiation. The apparatus which was developed for calibrating pyrradiometers for long-wave radiation is illustrated. The calibration for long-wave radiation was made over melting ice and a heated water surface of 40°C with an instrument temperature of 20°C. The following characteristics were investigated: cosine and azimuth errors; the efficiency of the thermopile; the effects of ventilation, thermal stability of the air in the hemisphere and the overheating of the polyethylene hemisphere. The results are summarized in the form of ratios of calibration factors for long-wave radiation to those for short-wave radiation under various conditions. Improved methods of installing pyrradiometers and of evaluating the field data are recommended.

Notes: Summary High resolution January and July present day climatologies over the central-western Alpine region are simulated with a Regional Climate Model (RegCM) nested within a General Circulation Model (GCM). The RegCM was developed at the National Center for Atmospheric Research (NCAR) and is run at 20 km grid point spacing. The model is driven by output from a “present day” climate simulation performed with the GCM ECHAM3 of the Max Planck Institute for Meteorology (MPI) at T106 resolution (~ 120 km). Five January and July simulations are conducted with the nested RegCM and the results for surface air temperature and precipitation are compared with a gridded observed dataset and a dataset from 99 observing stations throughout the Swiss territory. The driving ECHAM3 simulation reproduces well the position of the northeastern Atlantic jet, but underestimates the jet intensity over the Mediterranean. Precipitation over the Alpine region in the ECHAM3 simulation is close to observed in January but lower than observed in July. Compared to the driving GCM, the nested RegCM produces more precipitation in both seasons, mostly as a result of the stronger model orographic forcing. Average RegCM temperature over the Swiss region is 2–3 degrees higher than observed, while average precipitation is within 30% of observed values. The spatial distribution of precipitation is in general agreement with available gridded observations and the model reproduces the observed elevation dependency of precipitation in the summer. In the winter the simulated elevation of maximum precipitation amounts is lower than observed. Precipitation frequencies are overestimated, while precipitation intensities show a reasonable agreement with observations, especially in the winter. Sensitivity experiments with different cumulus parameterizations, soil moisture initialization and model topography are discussed. Overall, the model performance at the high resolution used here did not deteriorate compared to previous lower resolution experiments.