A Numerical Case Study of the Implications of Secondary Circulations to the Interpretation of Eddy-Covariance Measurements Over Small Lakes     

William T. Kenny  Gil Bohrer  Timothy H. Morin  Chris S. Vogel  Ashley M. Matheny  Ankur R. Desai 《Boundary-Layer Meteorology》2017,163(2):311-326

The CASES-99 experimental data are used to analyze turbulence behaviour under a range of stable conditions using an adaptive method based on Hilbert spectral analysis. The characteristic scales of intrinsic mode functions vary between different stratifications. The second-order Hilbert marginal spectra display clear separation between fine-scale turbulence and large-scale motions. After removing the large-scale motions, the statistical characteristics of the reconstructed signals confirm the distinction of different stratifications in the fine-scale range. The correlation coefficient analyses reveal that the Hilbert spectral analysis method separates turbulence from large-scale motions in the stable boundary layer.  相似文献   

Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model     

Ben Yang  Yun Qian  Larry K. Berg  Po-Lun Ma  Sonia Wharton  Vera Bulaevskaya  Huiping Yan  Zhangshuan Hou  William J. Shaw 《Boundary-Layer Meteorology》2017,162(1):117-142

We evaluate the sensitivity of simulated turbine-height wind speeds to 26 parameters within the Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height wind speeds. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. The parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height wind speeds. A larger Prandtl number results in smaller nighttime wind speeds. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of wind speed. All of the above parameters significantly affect the vertical profiles of wind speed and the magnitude of wind shear. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.  相似文献   

Trends in the seasonal length and opening dates of a winter road in the western James Bay region,Ontario, Canada     

Hori  Yukari  Gough  William A.  Butler  Ken  Tsuji  Leonard J.S. 《Theoretical and Applied Climatology》2017,129(3-4):1309-1320

Theoretical and Applied Climatology - In northern Canada, winter roads are essential for communities. The duration of the winter road season depends on particular meteorological conditions. In this...  相似文献   

Impact of early prehistoric farming on chironomid communities in northwest Ireland     

Karen J. Taylor  Aaron P. Potito  David W. Beilman  Beatrice Ghilardi  Michael O’Connell 《Journal of Paleolimnology》2017,57(3):227-244

This study explored the utility and performance of chironomid (Diptera: Chironomidae) autecology in the investigation of prehistoric farming impacts on freshwater lake systems. Chironomid subfossils, lake sediment geochemistry (δ¹³C, δ¹⁵N and C:N), pollen and macroscopic charcoal analyses were used in a comparative limnological assessment of three archaeologically rich study sites in northwest Ireland. At all three study sites, pastoral farming and its associated nutrient inputs, as represented by non-arboreal pollen indicative of grassland/pasture (NAPp) and lake sediment geochemistry, are concomitant with increases in eutrophic chironomid taxa. Redundancy analysis (RDA) and partial RDAs established that δ¹⁵N and NAPp were controlling factors of chironomid community compositional change during the Neolithic (4000–2500 BC) and Bronze Age (2500–600 BC). Bronze Age farming had a considerably greater impact on the lake systems than Neolithic farming, as indicated by a higher proportion of eutrophic taxa and increases in δ¹⁵N, C:N and δ¹³C values, consistent with increased erosion and agricultural inputs. Findings emphasise the importance of identifying the natural, pre-impacted state of a lake system to determine the extent of agricultural impact accurately. The timing and magnitude of change show that Neolithic and Bronze Age farming exhibited a strong control over chironomid communities at all three sites.  相似文献   

Holocene climate and environmental history of East Greenland inferred from lake sediments     

Amanda R. Lusas  Brenda L. Hall  Thomas V. Lowell  Meredith A. Kelly  Ole Bennike  Laura B. Levy  William Honsaker 《Journal of Paleolimnology》2017,57(4):321-341

Prediction of future Arctic climate and environmental changes, as well as associated ice-sheet behavior, requires placing present-day warming and reduced ice extent into a long-term context. Here we present a record of Holocene climate and glacier fluctuations inferred from the paleolimnology of small lakes near Istorvet ice cap in East Greenland. Calibrated radiocarbon dates of organic remains indicate deglaciation of the region before ~10,500 years BP, after which time the ice cap receded rapidly to a position similar to or less extensive than present, and lake sediments shifted from glacio-lacustrine clay to relatively organic-rich gyttja. The lack of glacio-lacustrine sediments throughout most of the record suggests that the ice cap was similar to or smaller than present throughout most of the Holocene. This restricted ice extent suggests that climate was similar to or warmer than present, in keeping with other records from Greenland that indicate a warm early and middle Holocene. Middle Holocene magnetic susceptibility oscillations, with a ~200-year frequency in one of the lakes, may relate to solar influence on local catchment processes. Following thousands of years of restricted extent, Istorvet ice cap advanced to within 365 m of its late Holocene limit at ~AD 1150. Variability in the timing of glacial and climate fluctuations, as well as of sediment organic content changes among East Greenland lacustrine records, may be a consequence of local factors, such as elevation, continentality, water depth, turbidity, and seabirds, and highlights the need for a detailed spatial array of datasets to address questions about Holocene climate change.  相似文献   

Making a Cultural Landscape: The Case of Dongshan River Basin,Taiwan     

Shu-Chun Lucy Huang  William P. Stewart  Pao-Ning Yin 《社会与自然资源》2017,30(12):1507-1522

Developing a cultural landscape establishes a regional identity, creates value for residents, and has potential to diversify a community’s economic base due to tourism development. Changes in local landscape morphology lead to multidimensional challenges in terms of the environmental consciousness and cultural identity of residents. The study examined residents’ perception of changes in their local landscape regarding its visual form, the meanings they constructed with the landscape, and their functional experience of living and working in it. Findings revealed that in its agricultural era, the visual landscape, meanings, and experience consisted mainly of physical elements connected with residents’ small-scale agricultural and fishery production. In the tourism era, the visual landscape, meanings, and experience were connected to recreational settings and iconic landmarks associated with the tourism industry. Both agricultural and tourism development occurred in ways that complemented each other and built a cultural landscape that connected the past with the present.  相似文献   

Remote Sensing of Three-dimensional Winds with Elastic Lidar: Explanation of Maximum Cross-correlation Method     

William T. Buttler  Cecilia Soriano  Jose M. Baldasano  George H. Nickel 《Boundary-Layer Meteorology》2001,101(3):305-327

Maximum cross-correlation provides a method toremotely de-ter-mine high-lyre-solved three-dimensional fields of horizontalwinds with e-las-tic li-darthrough-out large volumes of the planetaryboundary layer (PBL). This paperdetails the technique and shows comparisonsbetween elastic lidar winds, remotelysensed laser Doppler velocimeter (LDV) windprofiles, and radiosonde winds.Radiosonde wind data were acquired at Barcelona,Spain, during the BarcelonaAir-Quality Initiative (1992), and the LDVwind data were acquired at SunlandPark, New Mexico during the 1994 Border AreaAir-Quality Study. Comparisonsshow good agreement between the differentinstruments, and demonstrate the methoduseful for air pollution management at thelocal/regional scale. Elastic lidar windscould thus offer insight into aerosol andpollution transport within the PBL. Lidarwind fields might also be used to nudge orimprove initialization and evaluation ofatmospheric meteorological models.  相似文献   

Circulatory Patterns of Air Pollutants within the Barcelona Air Basin in a Summertime situation: Lidar and Numerical Approaches     

Cecilia Soriano  José M. Baldasano  William T. Buttler  Kurt R. Moore 《Boundary-Layer Meteorology》2001,98(1):33-55

This work examines circulatory patterns of airpollutants in the area of Barcelona (Spain), a regionwith strong coastal and orographic influences. Thiswas achieved through exploitation ofelastic-backscatter lidar data and by numericalsimulation of the atmosphere with a meteorologicalmesoscale model (MEMO). Lidar data were acquired inJuly 1992 during a collaborative campaign between LosAlamos National Laboratory (LANL) and the PolytechnicUniversity of Catalonia (UPC). The lidar providedinformation about the distribution of aerosols and theprevailing winds, determined by application of amaximum cross-correlation algorithm toelastic-backscatter lidar data. Lidar winds are usedto evaluate high altitude winds simulated by themodel. This study showed that circulatory patterns inBarcelona are correlated with daytime convectivevertical mixing, sea-breeze circulations, and verticalforcing caused by mountain thermal and mechanicaleffects.  相似文献   

Below-Ground Processes in Gap Models for Simulating Forest Response to Global Change   总被引：4，自引：0，他引：4  

Stan D. Wullschleger  Robert B. Jackson  William S. Currie  Andrew D. Friend  Yiqi Luo  Florent Mouillot  Yude Pan  Guofan Shao 《Climatic change》2001,51(3-4):449-473

  相似文献   

Feedback Mechanisms For The Atmosphere And Ocean Surface   总被引：4，自引：0，他引：4  

Yaocun Zhang  William Perrie 《Boundary-Layer Meteorology》2001,100(2):321-348

Two kinds of feedback mechanisms in the coupling process between the atmosphere and ocean surface are identified in this paper. One is a negative feedback mechanism, which is effective in the dynamic interaction processes through momentum flux exchange. In this mechanism,the ocean extracts momentum from the atmosphere as a forcing field to generate waves, which decelerates atmospheric motions, lessening the intensity of synoptic systems. The second is a positive feedback mechanism, which is effective in the thermal interaction processes through heat flux exchange. This is a mechanism that is effective in the transport of sensible and latent heat fluxes to the atmosphere from the underlyingocean surface. As a result, the atmosphere obtains energy from the ocean, which intensifies atmospheric motions. For storm conditions typical of North Atlantic mid-latitudes, we consider these thermal and dynamical nteractions, the dominance of one over the other, and related implications for storm intensification.  相似文献