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821.
Summary It is investigated how long-term UV trends can be assessed by analysing the longest time series of measured spectral UV irradiance in Europe, which have been started in the early 1990s in Thessaloniki, Greece and Sodankylä, Finland. It can be concluded that both time series do not yet show an unambiguous yearly trend in UV irradiance. The regression lines show no uniform behaviour and vary irregularly in strength and from one solar zenith angle to the next if all sky conditions are analysed. It is emphasised that these findings do not disagree with previous studies, that significant changes in UV irradiance have been observed over Europe especially in spring.Our study introduces a new method to estimate the required time series length for trend detection using the measured time series in combination with model calculations. At Sodankylä, a reduction of the total ozone column of –5.7% per decade has been observed from 1979 to 1998. A positive UV trend due to such conditions may be detected after 12 years at the earliest. For Thessalonki, a decrease in total ozone of –4.5% per decade has been observed. A corresponding increase of UV irradiance should be detectable after 15 years. It should be noted that a constant ozone trend over the whole period had to be assumed for this analysis.Since 1990 there has been a considerable variability of total ozone, but no steady decrease could be observed. Consequently, no general UV increase could be expected due to ozone changes. Even if there was a constant ozone trend over that period it is shown that even the longest European time series of UV irradiance are still too short to show distinct trends. However, this does not imply that no changes have occurred, it only shows that the large natural variability of UV irradiance has so far hindered the identification of unambiguous trends. The only way to find significant and consistent UV trends is the continuation of high-quality long-term measurements of spectral UV irradiance. 相似文献
822.
Presented are the explanations of reasons for the anomalous heat in summer of 2010 in the central area of the European part of Russia. It is demonstrated that this event occurred due to the beating of the solar annual (365 days) and lunar annual (355 days) fluctuations of air temperature. To substantiate this conclusion, the data are given on the synchronization of changes in atmospheric processes with the tidal variations of the Earth??s rotation velocity and on the nature of lunar cycles. Illustrated are the evidences of their existence in air temperature fluctuations. Revealed is the sequence of anomalously hot summer seasons in 1901, 1936 (1938), 1972, and 2010 corroborating the existence of the 35-year period of air temperature beats. Proposed is a mechanism of the impact of luni-solar tides on the air temperature based on the interaction between the gravitational luni-solar tides and the radiation conditions in the atmosphere (caused by the cloudiness amount variations). 相似文献
823.
V. V. Efimov V. N. Belokopytov A. E. Anisimov 《Russian Meteorology and Hydrology》2012,37(11-12):769-774
Presented are the estimates of precipitation amount and evaporation for the Black Sea basin based on the data of numerical regional reanalysis. The spatial distribution of considered variables is compared with the results obtained before using the method of extrapolation of measurements at the coastal meteorological stations. The computed water balance components of the Black Sea compared with the available literature data are used for obtaining the estimate of the mean water discharge in the Bosphorus. 相似文献
824.
A. E. Efimov 《Russian Meteorology and Hydrology》2010,35(9):641-649
The method is proposed to determine the main fluxes characterizing the surface stratified layer of plants’ habitat using the
Monin-Obukhov length scale. The gradient measurements of the profiles of wind flow speed, relative humidity, and air temperature
are carried out. The experimental data are obtained using the mobile automated system. The wavelet analysis of time series
is carried out. The nonlinear equation system is numerically solved to determine the heat, moisture, and momentum fluxes which
can be used for the optimum control of the plant moisture supply in the agricultural field. 相似文献
825.
Sampling efforts are constrained by limited availability of resources. Therefore, methods to reduce the number of samples, while still achieving reasonable accuracy are needed. Land-surface segmentation (LSS) has proven a powerful technique to partition digital elevation models (DEMs) and their derivatives into relatively homogeneous areas, which can be further employed as support in soil sampling. Though topography is one of the main soil forming factors, a robust assessment of the potential of this technique to digital soil mapping (DSM) is still missing. In this study, we aimed at evaluating the potential of LSS in stratifying a landscape into relatively homogeneous areas, which can be used as strata for guiding the selection of sampling points in DSM. The experiments were carried out in two study areas where soil samples were available. Land-surface derivatives were derived from DEMs and segmented with a tool based on the multiresolution segmentation algorithm, into objects considered as homogeneous soil-landscape divisions. Thus, one sample was randomly selected within each segment from the existing sample data, based on which predictions of soil classes/sub-orders and properties, i.e. soil texture and A-horizon thickness, were made. Results were compared with predictions based on simple random sampling (SRS) and conditioned Latin hypercube (cLHS). The segmentation-based sampling (SBS) scheme performed better than SRS and cLHS schemes in predicting the A-horizon thickness, soil texture fractions and soil classes, showing a high potential of LSS in stratifying a landscape for the purposes of DSM. The novelty of this study is in the way strata are constructed, rather than in the sampling design itself. Further research is needed to demonstrate the value of a SBS design for practical use. The analyses presented here further highlight the importance of considering locally adaptive techniques in optimization of sampling schemes and predictions of soil properties. 相似文献
826.
827.
828.
Pollen collected from snow samples on the Quelccaya Ice Cap in 2000 and 2001 reveals significant interannual variability in pollen assemblage, concentration, and provenance. Samples from 2000, a La Niña year, contain high pollen concentrations and resemble samples from the Andean forests (Yungas) to the east. Samples from 2001, an El Niño year, contain fewer pollen and resemble those from the Altiplano. We suggest that varying wind patterns under different El Niño/Southern Oscillation (ENSO) conditions may affect the processes of pollen transport over the Altiplano and on the ice cap, although confounding variables such as flowering phenology and sublimation should also be considered 相似文献
829.
830.
The relationship between depth, age and gravity in the oceans 总被引:2,自引:0,他引:2