Comparison of extrapolation and interpolation methods for estimating daily photosynthetically active radiation (PAR)

Measurements of photosynthetically active radiation (PAR), which are indispensable for simulating plant growth and productivity, are generally very scarce. This study aimed to compare two extrapolation and one interpolation methods for estimating daily PAR reaching the earth surface within the Poyang Lake national nature reserve, China. The daily global solar radiation records at Nanchang meteorological station and daily sunshine duration measurements at nine meteorological stations around Poyang Lake were obtained to achieve the objective. Two extrapolation methods of PARs using recorded and estimated global solar radiation at Nanchang station and three stations (Yongxiu, Xingzi and Duchang) near the nature reserve were carried out, respectively, and a spatial interpolation method combining triangulated irregular network (TIN) and inverse distance weighting (IDW) was implemented to estimate daily PAR. The performance evaluation of the three methods using the PARs measured at Dahuchi Conservation Station (day number of measurement = 105 days) revealed that: (1) the spatial interpolation method achieved the best PAR estimation (R ₂ = 0.89, s.e. = 0.99, F = 830.02, P < 0.001); (2) the extrapolation method from Nanchang station obtained an unbiased result (R ₂ = 0.88, s.e. = 0.99, F = 745.29, P < 0.001); however, (3) the extrapolation methods from Yongxiu, Xingzi and Duchang stations were not suitable for this specific site for their biased estimations. Considering the assumptions and principles supporting the extrapolation and interpolation methods, the authors conclude that the spatial interpolation method produces more reliable results than the extrapolation methods and holds the greatest potential in all tested methods, and more PAR measurements should be recorded to evaluate the seasonal, yearly and spatial stabilities of these models for their application to the whole nature reserve of Poyang Lake.     

Comparison of Extrapolation and Interpolation Methods for Estimating Daily Photosynthetically Active Radiation(PAR)——A Case Study of the Poyang Lake National Nature Reserve,China

Measurements of photosynthetically active radiation(PAR),which are indispensable for simulating plant growth and productivity,are generally very scarce.This study aimed to compare two extrapolation and one interpolation methods for estimating daily PAR reaching the earth surface within the Poyang Lake national nature reserve,China.The daily global solar radiation records at Nanchang meteorological station and daily sunshine duration measurements at nine meteorological stations around Poyang Lake were obtain...     

Observations of Minor Planets

Es werden 151 Positionen von 32 Planetoiden gegeben, die auf Platten des 400/1950 mm-Astrographen der Sonneberger Sternwarte aus den Jahren 1979 bis 1983 gefunden wurden.     

The analysis of oil trapped during secondary migration

During secondary migration, there is an opportunity for oil to be trapped as fluid inclusions (FIs) within framework grains such as quartz and within diagenetic cements that have a crystalline structure. Oil saturation on migration pathways remains relatively low, so typically fewer oil inclusions get trapped compared with samples from an oil column. Geochemical analysis of the much smaller amounts of inclusion oil present in samples from interpreted oil migration pathways has been attempted for two samples from the Champagny-1 and Delamere-1 wells in the Vulcan Sub-Basin, northern offshore Australia. A combination of petrographic analysis, bulk geochemical inclusion analysis and log evaluation confirmed that both samples were from oil migration pathways. Despite the small number of oil inclusions, reliable geochemical data were acquired from both samples that were significantly above the levels detected for the system and outside-rinse blanks. The FI oil trapped on the interpreted oil migration pathway in Champagny-1 was generated from clay-rich marine source rock with little terrigenous organic matter input. It was generated at peak oil window maturity and correlates best with oils derived from the Late Jurassic Lower Vulcan Formation. In contrast, the Delamere-1 FI oil contains evidence of greater input of terrigenous organic matter and was generated at early oil window maturity. This FI oil also contains a signature of a biodegraded component, which could have been generated either from the Middle Jurassic Plover Formation, or from an older source rock. These data indicate that it is feasible to geochemically map migration pathways across prospects or basins, and to analyse palaeo-oil compositions in oil zones where the few inclusions get trapped. This also suggests that the few oil inclusions that sometimes occur in Proterozoic or Archaean rocks may be analysable in the future, which would provide relatively pristine and robust data on the composition and diversity of Earth’s early biosphere.     

Modeling climate change and biophysical impacts of crop production in the Austrian Marchfeld Region

Climate change affects major biophysical processes in agricultural crop production (e.g. evaporation of plants and soils, nutrient cycles, and growth of plants). This analysis aims to assess some of these effects by simulating regional climate projections that are integrated in the biophysical process model EPIC (Environmental Policy Integrated Climate). Statistical climate models have been developed for six weather parameters based on daily weather records of a weather station in the Austrian Marchfeld region from 1975 to 2006. These models have been used to estimate daily weather parameters for the period 2007–2038. The resulting projections have been compared to climate scenarios provided from the TYNDALL Centre for Climate Change Research, which are based on General Circulation Models (GCMs). The comparison indicates some differences, namely a smaller temperature increase and a higher precipitation amount in the TYNDALL data. Both climate datasets have been used to simulate impacts of climate change on crop yields, topsoil organic carbon content, and nitrate leaching with EPIC and thus to perform a sensitivity analysis of EPIC. Yield impacts have been assessed for four simulated crops, i.e. 6.2?t/ha for winter wheat for statistical climate projections compared to 5.7?t/ha for TYNDALL scenarios, 10.6?t/ha for corn compared to 10.5?t/ha, 3.9?t/ha for sunflower compared to 3.7?t/ha, and 4.5?t/ha for spring barley compared to 4.3?t/ha—all values as an average over the period 2007–2038. Smaller differences have been simulated for topsoil organic carbon content i.e. 55.1?t/ha for the statistical climate projections compared to 55.3?t/ha for the TYNDALL scenarios and nitrate leaching i.e. 7.1?kg/ha compared to 11.1?kg/ha. All crop yields as well as topsoil organic carbon content and nitrate leaching show highest sensitivity to temperature and solar radiation.     

Cation ordering in BaAl2Ge2O8-feldspar: implications for the phase transition in anorthite

BaAl₂Ge₂O₈-Feldspar undergoes an order-disorder phase transition I2/c↔C2/m at T _tr ≈1690 K. The thermodynamics of the Al,Ge cation ordering process is described in terms of the compressible Ising model in mean field approximation. The mean field potential predicts a first order character of the phase transition. This is compared to antiferromagnetic ordering in a two-dimensional square Ising model with NN-pair interactions and four-spin interactions on alternating squares. Calculated order parameters and short range ordering are in good agreement with the corresponding properties observed in BaAl₂Ge₂O₈-feldspar by means of X-ray diffraction, hard mode infrared spectroscopy and TEM. Using known calorimetric data a similar model is postulated for Al,Si ordering in anorthite, CaAl₂Si₂O₈, for which the derived potential describes a transition with slightly stronger first order character at T _tr ≈1928 K. Received: 30 January 1998 / Revised, accepted: 29 August 1998     

Controls on channel deposits of highly variable rivers: Comparing hydrology and event deposits in the Burdekin River,Australia

Discharge event frequency, magnitude and duration all control river channel morphology and sedimentary architecture. Uncertainty persists as to whether alluvial deposits in the rock record are a time-averaged amalgam from all discharge events, or a biased record of larger events. This paper investigates the controls on channel deposit character and subsurface stratigraphic architecture in a river with seasonal discharge and very high inter-annual variability, the Burdekin River of north-east Australia. In such rivers, most sediment movement is restricted to a few days each year and at other times little sediment moves. However, the maximum discharge magnitude does not directly correlate with the amount of morphological change and some big events do not produce large deposits. The Burdekin channel deposits consist of five main depositional elements: (i) unit bars; (ii) vegetation-generated bars; (iii) gravel sheets and lags; (iv) antidune trains; and (v) sand sheets. The proportions of each depositional element preserved in the deposits depend on the history of successive large discharge events, their duration and the rate at which they wane. Events with similar peak magnitude but different rate of decline preserve different event deposits. The high intra-annual and inter-annual discharge variability and rapid rate of stage change make it likely that small to moderate-scale bed morphology will be in disequilibrium with flow conditions most of the time. Consequently, dune and unit bar size and cross-bed set thickness are not good indicators of event or channel size. Antidunes may be more useful as indicators of flow conditions at the time they formed. Rivers with very high coefficient of variance of maximum discharge, such as the Burdekin, form distinctive channel sediment bodies. However, the component parts are such that, if they are examined in isolation, they could lead to misleading interpretation of the nature of the depositional environment if conventional interpretations are used.     

Unit bar architecture in a highly-variable fluvial discharge regime: Examples from the Burdekin River,Australia

Unit bars are relatively large bedforms that develop in rivers over a wide range of climatic regimes. Unit bars formed within the highly-variable discharge Burdekin River in Queensland, Australia, were examined over three field campaigns between 2015 and 2017. These bars had complex internal structures, dominated by co-sets of cross-stratified and planar-stratified sets. The cross-stratified sets tended to down-climb. The development of complex internal structures was primarily a result of three processes: (i) superimposed bedforms reworking the unit bar avalanche face; (ii) variable discharge triggering reactivation surfaces; and (iii) changes in bar growth direction induced by stage change. Internal structures varied along the length and across the width of unit bars. For the former, down-climbing cross-stratified sets tended to pass into single planar cross-stratified deposits at the downstream end of emergent bars; such variation related to changes in fluvial conditions whilst bars were active. A hierarchy of six categories of fluvial unsteadiness is proposed, with these discussed in relation to their effects on unit bar (and dune) internal structure. Across-deposit variation was caused by changes in superimposed bedform and bar character along bar crests; such changes related to the three-dimensionality of the channel and bar geometry when bars were active. Variation in internal structure is likely to be more pronounced in unit bar deposits than in smaller bedform (for example, dune) deposits formed in the same river. This is because smaller bedforms are more easily washed out or modified by changing discharge conditions and their smaller dimensions restrict the variation in flow conditions that occur over their width. In regimes where unit bar deposits are well-preserved, their architectural variability is a potential aid to their identification. This complex architecture also allows greater resolution in interpreting the conditions before and during bar initiation and development.     

Performance of Landsat TM in ship detection in turbid waters

The visible and near infrared bands of Landsat have limitations for detecting ships in turbid water. The potential of TM middle infrared bands for ship detection has so far not been investigated. This study analyzed the performance of the six Landsat TM visible and infrared bands for detecting dredging ships in the turbid waters of the Poyang Lake, China. A colour composite of principal components analysis (PCA) components 3, 2 and 1 of a TM image was used to randomly select 81 dredging ships. The reflectance contrast between ships and adjacent water was calculated for each ship. A z-score and related p-value were used to assess the ship detection performance of the six Landsat TM bands. The reflectance contrast was related to water turbidity to analyze how water turbidity affected the capability of ship identification. The results revealed that the TM middle infrared bands 5 and 7 better discriminated vessels from surrounding waters than the visible and near infrared bands 1–4. A significant relation between reflectance contrast and water turbidity in bands 1–4 could explain the limitations of bands 1–4; while water turbidity has no a significant relation to the reflectance contrast of bands 5 and 7. This explains why bands 5 and 7 detect ships better than bands 1–4.