An evaluation of the statistical homogeneity of the Twentieth Century Reanalysis

The Twentieth Century Reanalysis (20CR) holds the distinction of having the longest record length (140-year; 1871–2010) of any existing global atmospheric reanalysis. If the record can be shown to be homogenous, then it would be the first reanalysis suitable for long-term trend assessments, including those of the regional hydrologic cycle. On the other hand, if discontinuities exist, then their detection and attribution—either to artificial observational shocks or climate change—is critical to their proper treatment. Previous research suggested that the quintupling of 20CR’s assimilated observation counts over the central United States was the primary cause of inhomogeneities for that region. The same work also revealed that, depending on the season, the complete record could be considered homogenous. In this study, we apply the Bai-Perron structural change point test to extend these analyses globally. A rigorous evaluation of 20CR’s (in)homogeneity is performed, composed of detailed quantitative analyses on regional, seasonal, inter-variable, and intra-ensemble bases. The 20CR record is shown to be homogenous (natural) for 69 (89) years at 50 % of land grids, based on analysis of the July 2 m air temperature. On average 54 % (41 %) of the grids between 60°S and 60°N are free from artificial inhomogenetites in their February (July) time series. Of the more than 853,376 abrupt shifts detected in 26 variable fields over two monthly time series, approximately 72 % are non-climate in origin; 25 % exceed 1.8 standard deviations of the preceding time series. The knock-on effect of inhomogeneities in 20CR’s boundary forcing and surface pressure data inputs to its surface analysis fields is implicated. In the future, reassessing these inhomogeneities will be imperative to achieving a more definitive attribution of 20CR’s abrupt shifts.     

Laboratory Generation of Solitary Waves: An Inversion Technique to Improve Available Methods简

Solitary waves are often used in laboratory experiments to study tsunamis propagation and interaction with coasts. However, the experimental shape of the waves may differ from the theoretical one. In this paper, a correction technique aiming at minimizing the discrepancies between the two profiles is presented. Laboratory experiments reveal their effectiveness in correcting the experimental shape of solitary waves, mainly for low nonlinearities.     

Effect of a cement-lignin agent on the shear behavior of Shanghai dredged marine soils

With the rapid urbanization in Shanghai, China, suitable fill materials have been reported to be in great shortage in recent years. A prospective solution to these issues is to convert the huge amount of existing dredged marine soils to construction materials via solidification. However, there have been no studies on the shear behavior of solidified dredged materials from Shanghai region so far, while it has been reported by various researchers that the available data obtained from certain types of clay cannot be confidently and readily applied to other types of soils. To address this challenging issue, in this article, samples of Shanghai marine dredged soils were retrieved from the world’s largest reclamation project in Shanghai Lin-gang New City. A series of laboratory tests have been conducted to investigate the shear behavior of Shanghai dredged marine soils solidified using a new composite curing agent made of cement and lignin. The test results and the effect of this cement–lignin agent on the shear behavior of Shanghai marine soils, including the stress–strain behavior, shear strength properties, and failure characteristics are presented and discussed, which can provide valuable reference for the use of dredged soils as construction materials in the Shanghai region.     

Vegetation-based bioindication of humus forms in coniferous mountain forests

Humus forms, especially the occurrence and the thickness of the horizon of humified residues(OH), provide valuable information on site conditions.In mountain forest soils, humus forms show a high spatial variability and data on their spatial patterns is often scarce. Our aim was to test the applicability of various vegetation features as proxy for OH thickness.Subalpine coniferous forests dominated by Picea abies(L.) H. Karst. and Larix decidua Mill. were studied in the Province of Trento, Italian Alps,between ca. 900 and 2200 m a.s.l. Braun-Blanquet vegetation relevés and OH thickness were recorded at152 plots. The vegetation parameters, tested for their suitability as indicators of OH thickness,encompassed mean Landolt indicator values of the herb layer(both unweighted and cover-weighted means) as well as parameters of vegetation structure(cover values of plant species groups) calculated from the relevés. To our knowledge, the predictive power of Landolt indicator values(LIVs) for humus forms had not been tested before. Correlations between OH thickness and mean LIVs were strongest for the soil reaction value, but indicator values for humus,nutrients, temperature and light were also significantly correlated with OH thickness. Generally,weighting with species cover reduced the indicator quality of mean LIVs for OH thickness. The strongest relationships between OH thickness and vegetation structure existed in the following indicators: the cover of forbs(excluding graminoids and ferns) and the cover of Ericaceae in the herb layer. Regression models predicting OH thickness based on vegetation structure had almost as much predictive power as models based on LIVs. We conclude that LIVs analysis can produce fairly reliable information regarding the thickness of the OH horizon and, thus,the humus form. If no relevé data are readily available,a field estimation of the cover values of certain easily distinguishable herb layer species groups is much faster than a vegetation survey with consecutive indicator value analysis, and might be a feasible way of quickly indicating the humus form.