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排序方式: 共有309条查询结果,搜索用时 15 毫秒
91.
92.
The study has been carried for visual discrimination of natural salt affected soils on FCC images of IRS 1 B in Pali district of Rajasthan. The salt affected soils show wide variations in salinity (EC2.53.7 to 28 dSm-1), alkalinity (pH 8.5-9.8), cover ofP. juliflora (10-90%), salt tolerant grasses (10–55%) and gravelly surface (20–35%). ThoughP. juliflora and grasses were present at most of the observation points their cover decreased with soil EC2.5 values more than 10 and 13 dSm-1, respectively. Five darkness categories derived as the result of visual interpretation of FCCs; and ground and laboratory studies revealed that the darkness category 1 represented fewer plant community with high salinity (EC 28.7 dSm-1) and gravelly surface, categories 2 and 3 were characterised by grass cover and moderate salt affected soils (EC 3-10 dSm-1) whereas category 4 was dominated by thicket ofP. juliflora. The derived numerical darkness categories of the FCC images were slightly low for February images. The darkness values of observation pixel on February images correlated positively withP. juliflora cover and negatively with grass cover and soil pH indicating that surface features on FCC were related with the immediate observation pixels. 相似文献
93.
Phenology: Its Importance to the Global Change Community 总被引:10,自引:0,他引:10
Annette Menzel 《Climatic change》2002,54(4):379-385
94.
Jose Henrique G. M. Alves Diana J. M. Greenslade Michael L. Banner 《Journal of Atmospheric & Ocean Science》2002,8(4):239-267
The impact of a modified parametric form of the dissipation source function S ds on the skill of an operational spectral wind-wave model is investigated. Numerical experiments are made with a version of the WAM model presently used operationally by the Australian Bureau of Meteorology to produce sea-state forecasts within the Australian region. Performances of wave hindcasts obtained using several alternative forms of this newly proposed dissipation source function are compared to those produced with forms of S ds commonly used operationally. A new ad hoc technique to compare modelled and observed wave spectra is introduced to assess the quality of calculated one-dimensional frequency spectra.
Our results indicate that wave model performance in terms of integral spectral parameters, such as the significant wave height H s , may benefit from improved parameterisations of the dissipation source term S ds . On the other hand, we also found that model performance was relatively poor in terms of predictions of the one-dimensional frequency spectrum, regardless of the chosen form of S ds . These results suggest that further refinements of the dissipation source term are strongly dependent on improved parametrisations of the nonlinear interactions source term S nl . 相似文献
Our results indicate that wave model performance in terms of integral spectral parameters, such as the significant wave height H s , may benefit from improved parameterisations of the dissipation source term S ds . On the other hand, we also found that model performance was relatively poor in terms of predictions of the one-dimensional frequency spectrum, regardless of the chosen form of S ds . These results suggest that further refinements of the dissipation source term are strongly dependent on improved parametrisations of the nonlinear interactions source term S nl . 相似文献
95.
Forecasting of waves under extreme conditions such as tropical cyclones is vitally important for many offshore industries, but there remain many challenges. For Northwest Western Australia (NW WA), wave forecasts issued by the Australian Bureau of Meteorology have previously been limited to products from deterministic operational wave models forced by deterministic atmospheric models. The wave models are run over global (resolution 1/4°) and regional (resolution 1/10°) domains with forecast ranges of +?7 and +?3 day respectively. Because of this relatively coarse resolution (both in the wave models and in the forcing fields), the accuracy of these products is limited under tropical cyclone conditions. Given this limited accuracy, a new ensemble-based wave forecasting system for the NW WA region has been developed. To achieve this, a new dedicated 8-km resolution grid was nested in the global wave model. Over this grid, the wave model is forced with winds from a bias-corrected European Centre for Medium Range Weather Forecast atmospheric ensemble that comprises 51 ensemble members to take into account the uncertainties in location, intensity and structure of a tropical cyclone system. A unique technique is used to select restart files for each wave ensemble member. The system is designed to operate in real time during the cyclone season providing +?10-day forecasts. This paper will describe the wave forecast components of this system and present the verification metrics and skill for specific events. 相似文献
96.
Diana Fuentes-Andino Keith Beven Anna Kauffeldt Chong-Yu Xu Sven Halldin Giuliano Di Baldassarre 《水文科学杂志》2017,62(2):232-245
Most conceptual rainfall–runoff models use as input spatially averaged rainfall fields which are typically associated with significant errors that affect the model outcome. In this study, it was hypothesised that a simple spatially and temporally averaged event-dependent rainfall multiplier can account for errors in the rainfall input. The potentials and limitations of this lumped multiplier approach were explored by evaluating the effects of multipliers on the accuracy and precision of the predictive distributions. Parameter sets found to be behavioural across a range of different flood events were assumed to be a good representation of the catchment dynamics and were used to identify rainfall multipliers for each of the individual events. An effect of the parameter sets on identified multipliers was found; however, it was small compared to the differences between events. Accounting for event-dependent multipliers improved the reliability of the predictions. At the cost of a small decrease in precision, the distribution of identified multipliers for past events can be used to account for possible rainfall errors when predicting future events. By using behavioural parameter sets to identify rainfall multipliers, the method offers a simple and computationally efficient way to address rainfall errors in hydrological modelling. 相似文献
97.
Diana Meilutytė-Lukauskienė Vytautas Akstinas Jūratė Kriaučiūnienė Diana Šarauskienė Aldona Jurgelėnaitė 《Acta Geophysica》2017,65(1):89-102
In this research, variability of spring (from 1 March to 30 May) and flash (from 1 June to 30 November) floods in rivers of different regions was analysed. The territory of Lithuania is divided into three regions according to hydrological regime of the rivers: Western, Central, and Southeastern. The maximum river discharge data of spring and flash floods [a total of 31 water gauging stations (WGS)] were analysed. Comparison of the data of four periods (1922–2013, 1941–2013, 1961–2013, and 1991–2013) with the data of the reference period (1961–1990) was performed. Analysis included the longest discharge data set of the Nemunas River at Smalininkai WGS (1812–2013) as well. Mixed patterns of flood changes in Lithuanian rivers were detected. The analysis of flood discharges of the Nemunas River indicated that both spring and flash floods in Lithuania were getting smaller. 相似文献
98.
Diana Petrova Kjurkchieva Velimir Angelov Popov Doroteya Lyubenova Vasileva Nikola Ivanov Petrov 《天文和天体物理学研究(英文版)》2018,(4)
Photometric observations in Sloan g′and i′ bands of W UMa binaries NSVS 4340949,T-Dra0–00959,GSC 03950–00707,NSVS 4665041,NSVS 4803568,MM Peg,MM Com and NSVS4751449 are presented.The light curve solutions revealed that the components of each target are of G and K spectral types.The binaries of the sample have middle-contact configurations whose fillout factors are within the range 0.2–0.4.The only exception is NSVS 4751449 which is in deeper contact(fillout factor of 0.55).It precisely obeys the relation between mass ratio and fillout factor for deep,low mass ratio overcontact binaries.One of the eclipses of almost all targets(except MM Peg)is an occultation and their photometric mass ratios and solutions could be accepted with confidence.We found that the target components have almost equal temperatures but differ considerably in size and mass.The components of the partially-eclipsed MM Peg have close parameters.Our solutions reveal that NSVS 4340949,T-Dra0–00959,NSVS 4803568 and MM Com are of W subtype while GSC 03950–00707,NSVS 4665041,MM Peg and NSVS 4751449 are of A subtype.This subclassification is well-determined for all totallyeclipsed binaries.The targets confirm the trends in which W-subtype systems have smaller periods and lower temperatures than A subtype binaries. 相似文献
99.
Menzel Peter Teichmann Jakob van den Boogaart Karl Gerald 《Mathematical Geosciences》2020,52(6):731-757
Mathematical Geosciences - Laguerre mosaics have been an important modeling approach in astronomy, physics, crystallography, geology and mathematics for several decades. In materials science, they... 相似文献
100.
Romo-Morales Diana Moreno-Rodríguez Verónica Molina-Freaner Francisco Valencia-Moreno Martín Ruiz Joaquín Minjárez-Osorio Christian Hernández-Mendiola Ernesto del Rio-Salas Rafael 《Natural Resources Research》2020,29(4):2773-2786
Natural Resources Research - Mining is an important activity in Mexico; however, despite its economic benefits, it carries potential environmental risks, including mine spills. On August 6,... 相似文献