High‐resolution monthly precipitation climatologies over Norway (1981–2010): Joining numerical model data sets and in situ observations

The 1981-2010 monthly precipitation climatologies for Norway at 1 km resolution are presented. They are computed by an interpolation procedure (HCLIM+RK) combining the output from a numerical model with the in situ observations. Specifically, the regional climate model data set HCLIM-AROME, based on the dynamical downscaling of the global ERA-Interim reanalysis onto 2.5 km resolution, is considered together with 2009 rain-gauges located within the model domain. The precipitation climatologies are defined by superimposing the grid of 1981-2010 monthly normals from the numerical model and the kriging interpolation of station residuals. The combined approach aims at improving the quality of gridded climatologies and at providing reliable precipitation gradients also over those remote Norwegian regions not covered by observations, especially over the northernmost mountainous areas. The integration of rain-gauge data greatly reduces the original HCLIM-AROME biases. The HCLIM+RK errors obtained from the leave-one-out station validation turn out to be lower than those provided by two considered interpolation schemes based on observations only: a multi-linear local regression kriging (MLRK) and a local weighted linear regression (LWLR). As average over all months, the mean absolute (percentage) error is 10.0 mm (11%) for HCLIM+RK, and 11.4 (12%) and 11.6 mm (12%) for MLRK and LWLR, respectively. In addition, by comparing the results at both station and grid cell level, the accuracy of MLRK and LWLR is more sensitive to the spatial variability of station distribution over the domain and their interpolated fields are more affected by discontinuities and outliers, especially over those areas not covered by the rain-gauge network. The obtained HCLIM+RK climatologies clearly depict the main west-to-east gradient occurring from the orographic precipitation regime of the coast to the more continental climate of the inland and it allows to point out the features of the climatic subzones of Norway

Market-driven Derivation of Field Performance Requirements for Conceptual Aircraft Design

An approach to derive a take-off field length for the initial specification of a new aircraft design is introduced in this paper. Based on a passenger demand forecast the runway lengths of the origin and destination airports are analyzed. The physical lengths of the runways are corrected by airports’ elevation and reference temperatures. The approach to derive airport reference temperatures on air transport system level is described in more detail. For an exemplary range of flight distances and the corresponding market, runway lengths are determined and corrected. Consequently the percentage of passenger demand can be described as a function of runway lengths. The example illustrates that airports’ elevation and reference temperature significantly affect the percentage of passenger demand that can be accommodated by an aircraft design for a given take-off field length

Norway spruce physiological and anatomical predisposition to dieback.

Top dieback on Norway spruce has frequently occurred in stands of southern Norway and it is a serious threat to the productivity and stability of economically important spruce stands. The underlying dieback mechanisms are unclear; often the whole stand is not affected, but only individual trees. Drought stress is hypothesized as a crucial trigger for the onset of symptoms; therefore, we studied the response-effect relationships of water limitation and tree specific traits. We analyzed year ring anatomy, i.e. wood density, as an estimate of drought vulnerability, and carbon and oxygen isotope composition of the year rings as an estimate of leaf physiology. At two sites in SE Norway, we grouped declining and symptomless trees in direct vicinity of each other into pairs for comparison of anatomical and physiological traits. For one site, we observed a distinct lower wood density and higher radial growth of declining trees in comparison with the healthy trees over several years. We identified high vulnerability to cavitation due to lower wood density as a trait of individuals prone to dieback. We observed lower intrinsic water-use efficiency (WUEi) associated with increased stomatal conductance. The healthy trees had lower stomatal conductance, which most likely prevented water losses during dry periods. Within a population, we observed a trade-off between long-term growth performance under “average” conditions and a different response for “extreme” events. These resource strategies will be important for Norway spruce management, especially for regions facing an increase in the frequency of drought events