Surface Altitude Research Articles

Hypsometric assessment of the pre-last Glaciation (Late Saalian) topography, the south-east Lithuania

The article deals with the hypsometric assessment of the pre-last Glaciation (Late Saalian) topography which represents a glaciogenic landforms of the Medininkai stadial in south-east Lithuania. The study area belongs to two elevations as orographic units: the Lyda Plateau and the Ašmena Upland. Cartometric topography analysis has been performed in nine reference areas based on large-scale (1:25 000) cartographic maps. The topographic relative height varies from 11.8 m to 30.6 m and depends on the surface altitude (correlation coefficient R = 0.85). The correlation links between the base and top surfaces (R = 0.74–0.92), concave-convex graph of hypsometric curves and value of hypsographic integrals (0.45–0.58) indicate that in general pre-last Glaciation topography of south-east Lithuania at the present stays in equilibrium conditions.

Observer Based Dynamic Surface Control of A Hypersonic Flight Vehicle

Abstract This paper describes the design and analysis of a proportional integral air speed controller and a nonlinear adaptive dynamic surface altitude controller for the longitudinal dynamics of a generic hypersonic flight vehicle. The uncertain nonlinear functions in the pure feedback flight vehicle model are approximated by using radial basis function neural networks. For the controller design, the complete states are assumed to be available for measurement, then a sliding mode observer is incorporated to estimate the states which are difficult to measure in practice. A detailed stability analysis of the designed altitude controller shows that all the signals of the closed loop system are uniformly ultimately bounded. The robustness and performance of the designed controllers, with and without the observer are verified through numerical simulations of the flight vehicle model for trimmed cruise conditions of 110,000 ft and Mach 15.

Influences of landform as a confounding variable on SOM-NDVI association in semiarid Ordos Plateau

Soil organic matter (SOM) plays an important role in maintaining vegetation cover and thus mitigating land erosion of fragile terrestrial ecosystems such as in the Northern Ordos Plateau of China (NOPC). However, little information is available on whether and how SOM varies spatially as an intrinsic characteristic of landform in NOPC. The objective of this study was to examine the spatial associations of SOM with landform and vegetation cover. The study was conducted in a 23,000-km 2 area within NOPC because this area has landforms of mobile dunes (MD), flat dunes (FD), grassy sandy land (GSL), flat sandy bedrocks (FSB), and swamps and salt lakes (SW), which are typical landforms in semiarid ecosystems. SOM was determined using a standard laboratory analysis method for 5 cm topsoil samples collected at 72 locations across the study area. In addition, the 250 m Multitem- poral Moderate Resolution Imaging Spectroradiometer (MODIS) imageries taken in the period from August 2006 to August 2010 were used to extract Normalized Difference Vegetation Index (NDVI) which in turn was used as the surrogate of vegetation cover. Classic and geostatistical methods were used to compare SOM concentration across different landforms. The results indicated that an area with a greater value for NDVI (i.e. better vegetation cover) tended to have a higher SOM concentration regardless of the landform types. However, the association between SOM and NDVI varied from one landform to another. The SW and GSL had a highest SOM concentration, while MD had a lowest concentration. For the study area as a whole and the FD, GSL, and MD, SOM was found to be the sole function of NDVI, whereas, for the FSB, SOM was influenced by several intrinsic variables, namely ground surface altitude, slope, and aspect, as well as NDVI. SOM for the SW landform was found to be a function of NDVI. Furthermore, SOM and NDVI exhibited a consistent spatial pattern of increasing from north to south and from west to east. The highest SOM concentration of 3.5% occurred along an east-westward belt, which is adjacent to water pathways, in the mid part of the study area.

Postcode forecasting

Postcode forecasting

Evaluation of a numerical model of the British–Irish ice sheet using relative sea‐level data: implications for the interpretation of trimline observations

AbstractThe glacial isostatic adjustment (GIA) of the British Isles is complex due to the interplay between local and non‐local signals. A number of recent studies have modelled the GIA response of the British Isles using relative sea‐level data. This study extends these previous analyses by using output from a numerical glaciological model as input to a GIA model. This is a necessary step towards more realistic GIA models, and although there have been similar studies for the major late Pleistocene ice sheets, this is the first study to do so for the British Isles. We test three reconstructions, classed as ‘minimal’, ‘median’ and ‘maximal’ in terms of their volume at maximum extent, and find it is possible to obtain good data–model fits. The minimal reconstruction is clearly preferred by the sea‐level data. The ice reconstructions tested were not constrained by geomorphological information of past ice extent (lateral and vertical). As a consequence, the reconstructions extend further than much of this information suggests, particularly in terms of ice thickness. It is notable, however, that the reconstructions produce good fits to many sea‐level data from central, mountainous regions (e.g. Scottish highlands), which lends support to the suggestion that trimlines, often used as an constraint on the palaeo ice surface location, are in fact features formed at the transition from warm‐ to cold‐based ice and so mark a minimum constraint on the ice surface altitude. Based on data–model misfits, suggestions are made for improving the ice model reconstructions. However, in many locations, the cause of the misfit could be due to non‐local, predominantly Fennoscandian ice and so interpretation is not straightforward. As a result, we suggest that future analyses of this type consider models and observations for both Fennoscandia and the British Isles. Copyright © 2012 John Wiley & Sons, Ltd.

Contribution of ground surface altitude difference to thermal anomaly detection using satellite images: Application to volcanic/geothermal complexes in the Andes of Central Chile

Detection of thermal anomalies in volcanic-geothermal areas using remote sensing methodologies requires the subtraction of temperatures, not provided by geothermal manifestations (e.g. hot springs, fumaroles, active craters), from satellite image kinetic temperature, which is assumed to correspond to the ground surface temperature. Temperatures that have been subtracted in current models include those derived from the atmospheric transmittance, reflectance of the Earth's surface (albedo), topography effect, thermal inertia and geographic position effect. We propose a model that includes a new parameter (K) that accounts for the variation of temperature with ground surface altitude difference in areas where steep relief exists. The proposed model was developed and applied, using ASTER satellite images, in two Andean volcanic/geothermal complexes (Descabezado Grande-Cerro Azul Volcanic Complex and Planchón-Peteroa-Azufre Volcanic Complex) where field data of atmosphere and ground surface temperature as well as radiation for albedo calibration were obtained in 10 selected sites. The study area was divided into three zones (Northern, Central and Southern zones) where the thermal anomalies were obtained independently. K value calculated for night images of the three zones are better constrained and resulted to be very similar to the Environmental Lapse Rate (ELR) determined for a stable atmosphere (ELR>7°C/km). Using the proposed model, numerous thermal anomalies in areas of ≥90m×90m were identified that were successfully cross-checked in the field. Night images provide more reliable information for thermal anomaly detection than day images because they record higher temperature contrast between geothermal areas and its surroundings and correspond to more stable atmospheric condition at the time of image acquisition.

Hybrid dimension based modeling of part surface topography and identification of its characteristic parameters

Since the complete description of complex part surface is difficult to achieve using the existing integral dimensional or fractal dimensional approaches, the novel concept of hybrid dimension and its modeling method of part surface topography are proposed in this paper. The hybrid dimensional model of part surface topography is established based on the deflection method of surface correlation coefficient, which associates the integral dimensional and fractal dimensional surface topographies. Superimposing the normalized fractal dimensional surface altitude field on the B-spline surface, the hybrid dimensional model can express the integral dimensional information of part surface in macro level, and the fractal dimensional detail in micro level. And the correlation of part surface topographies among different scales and different dimensions is established by the Hybrid Dimensional Surface Correlation Coefficient. Moreover, the characteristic parameter identification method for the hybrid dimensional model of part surface topography is proposed. The component information of integral dimension and fractal dimension is separated and extracted by wavelet analysis, and hybrid dimensional characteristic parameters are identified by the generalized surface structure function method and the roughness mapping method. Finally, the proposed method is applied to design and manufacture of turbo expander.

A topographic parameter inversion method based on laser altimetry

A topographic parameter inversion method based on laser altimetry is developed in this paper, which can be used to deduce the surface vertical profile and retrieve the topographic parameters within the laser footprints by analyzing and simulating return waveforms. This method comprises three steps. The first step is to build the numerical models for the whole measuring procedure of laser altimetry, construct digital elevation models for surfaces with different topographic parameters, and calculate return waveforms. The second step is to analyze the simulated return waveforms to obtain their characteristics parameters, summarize the effects of the topographic parameter variations on the characteristic parameters of simulated return waveforms, and analyze the observed return waveforms of laser altimeters to acquire their characteristic parameters at the same time. The last step is to match the characteristic parameters of the simulated and observed return waveforms, and deduce the topographic parameters within the laser footprint. This method can be used to retrieve the topographic parameters within the laser footprint from the observed return waveforms of spaceborne laser altimeters and to get knowledge about the surface altitude distribution within the laser footprint other than only getting the height of the surface encountered firstly by the laser beam, which extends laser altimeters’ function and makes them more like radars.

Middle‐Late Pleistocene Glacial Lakes in the Grand Canyon of the Tsangpo River, Tibet

Abstract:Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers formed during Quaternary glacial epoch demonstrate lakes were created by damming of the river. Research was conducted on the geological environment, contained sediments, spatial distribution, timing, and formation and destruction of these paleolakes. The lacustrine sediments 14C (10537±268 aBP at Linzhi Brick and Tile Factory, 22510±580 aBP and 13925±204 aBP at Bengga, 21096±1466 aBP at Yusong) and a series of ESR (electron spin resonance) ages at Linzhi town and previous data by other experts, paleolakes persisted for 691∼505 kaBP middle Pleistocene ice age, 75–40 kaBP the early stage of last glacier, 27–8 kaBP Last Glacier Maximum (LGM), existence time of lakes gradually shorten represents glacial scale and dam moraine supply potential gradually cut down, paleolakes and dam scale also gradually diminished. This article calculated the average lacustrine sedimentary rate of Gega paleolake in LGM was 12.5 mm/a, demonstrates Mount Namjagbarwa uplifted strongly at the same time, the sedimentary rate of Gega paleolake is more larger than that of enclosed lakes of plateau inland shows the climatic variation of Mount Namjagbarwa is more larger and plateau margin uplifted more quicker than plateau inland. This article analyzed formation and decay cause about the Zelunglung glacier on the west flank of Mount Namjagbarwa got into the Tsangpo River valley and blocked it for tectonic and climatic factors. There is a site of blocking the valley from Gega to Chibai. This article according to moraines and lacustrine sediments yielded paleolakes scale: the lowest lake base altitude 2850 m, the highest lake surface altitude 3585 m, 3240 m and 3180 m, area 2885 km2, 820 km2 and 810 km2, lake maximum depth of 735 m, 390 m and 330 m. We disclose the reason that previous experts discovered there were different age moraines dividing line of altitude 3180 m at the entrance of the Tsangpo Grand Canyon is dammed lake erosive decay under altitude 3180 m moraines in the last glacier era covering moraines in the early ice age of late Pleistocene, top 3180 m in the last glacier moraine remained because ancient dammed lakes didn't erode it under 3180 m moraines in the early ice age of late Pleistocene exposed. The reason of the top elevation 3585 m moraines in the middle Pleistocene ice age likes that of altitude 3180 m. There were three times dammed lakes by glacier blocking the Tsangpo River during Quaternary glacial period. During other glacial and interglacial period the Zelunglung glacier often extended the valley but moraine supplemental speed of the dam was smaller than that of fluvial erosion and moraine movement, dam quickly disappeared and didn't form stable lake.

The Evaluation of MODIS Data and Geographic Data for Estimating Near Surface Air Temperature

The main objective of this study is to discuss the feasibility of predicting near-surface air temperature using MODIS products.Principal component analysis of land surface temperature(LST),ALBEDO,vegetation index(NDVI),altitude(ALT) and latitude(LAT) was employed,with some principal components of the cumulative variance in the front of these principal components as independent variables.Multiple linear relationships between independent variables and meteorological observation temperatures were established.The results show that the range of RMSE is between 0.5 and 2.3.Most of RMSE vary greatly in winter months but are relatively stable in summer months.Compared with Aqua/MODIS,Terra/MODIS can get better results.RMSE of Tmin modeled by Terra nighttime MODIS is lower,and so are Tmax and T14 modeled by Terra daytime MODIS.LST is the most powerful predictor,followed by ALT,LAT,NDVI and ALBEDO.The MODIS products can therefore monitor the spatial distribution of near-surface air temperature at different times,with the optimal products selections being different.

MODELING PHASE-ALIGNED GAMMA-RAY AND RADIO MILLISECOND PULSAR LIGHT CURVES

Since the discovery of the first eight gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope, this population has been steadily expanding. Four of the more recent detections, PSR J00340534, PSR J1939+2134 (B1937+21; the first MSP ever discovered), PSR J1959+2048 (B1957+20; the first discovery of a black widow system), and PSR J2214+3000, exhibit a phenomenon not present in the original discoveries: nearly phase-aligned radio and gamma-ray light curves (LCs). To account for the phase alignment, we explore models where both the radio and gamma-ray emission originate either in the outer magnetosphere near the light cylinder or near the polar caps. Using a Markov Chain Monte Carlo technique to search for best-fit model parameters, we obtain reasonable LC fits for the first three of these MSPs in the context of altitude-limited outer gap (alOG) and two-pole caustic (alTPC) geometries (for both gamma-ray and radio emission). These models differ from the standard outer gap (OG)/two-pole caustic (TPC) models in two respects: the radio emission originates in caustics at relatively high altitudes compared to the usual conal radio beams, and we allow both the minimum and maximum altitudes of the gamma-ray and radio emission regions to vary within a limited range (excluding the minimum gamma-ray altitude of the alTPC model, which is kept constant at the stellar radius, and that of the alOG model, which is set to the position-dependent null charge surface altitude). Alternatively, phase-aligned solutions also exist for emission originating near the stellar surface in a slot gap scenario (low-altitude slot gap (laSG) models). We find that the alTPC models provide slightly better LC fits than the alOG models, and both of these give better fits than the laSG models (for the limited range of parameters considered in the case of the laSG models). Thus, our fits imply that the phase-aligned LCs are likely of caustic origin, produced in the outer magnetosphere, and that the radio emission for these pulsars may come from close to the light cylinder. In addition, we were able to constrain the minimum and maximum emission altitudes with typical uncertainties of 30% of the light cylinder radius. Our results therefore describe a third gamma-ray MSP subclass, in addition to the two previously found by Venter et al.: those with LCs fit by standard OG/TPC models and those with LCs fit by pair-starved polar cap models.

Monitoring freshwater fish in Florida lakes using electrofishing: Lessons learned

Electrofishing was used in 30 Florida lakes to monitor fish communities over an 8-year period. Six 10-minute electrofishing transects were used annually per lake to estimate the catch per unit effort (CPUE, gm/hr) total fish, sport fish, and each individual fish species. A variance components analysis using CPUE as the dependent variable and lake, year within lake, and transect within year and lake as independent variables showed that in almost every case transect accounted for more than 50% of the variance in CPUE. The estimated variance from this sampling effort showed that the average number of electrofishing transects needed to estimate total fish and sport fish CPUE within 20% of the mean at a confidence of 95% would have to double and triple current effort, respectively. Lake trophic status, estimated with chlorophyll concentrations, was also monitored and showed a direct positive relation with total fish and sport fish, even with low sampling effort, providing a general ability to estimate CPUE in Florida lakes. After accounting for lake trophic status, estimates of aquatic plant abundance did not account for more variance in CPUE estimates because the sampling effort was not rigorous enough for multivariate analyses. Eight years of repeated sampling yielded an asymptote for cumulative species richness. Lake surface area and altitude were directly and inversely related to species richness, respectively, together accounting for 43% of the variance in species richness. Lake managers interested in monitoring fish populations should conduct a pilot study to estimate sampling frequency needed to answer stated objectives.

ГЕОДИНАМІКА

The study of Black Sea and Mediterranean Sea surface altitudes was carried out based on satellite altimetry data. The model of the Black Sea and Mediterranean Sea surface topography (SST) was build. The comparison of received results with the European quasigeoid was done.

Predicting habitat to optimize sampling of Pacific sardine (Sardinops sagax)

AbstractZwolinski, J. P., Emmett, R. L., and Demer, D. A. 2011. Predicting habitat to optimize sampling of Pacific sardine (Sardinops sagax). – ICES Journal of Marine Science, 68: 867–879. More than 40 years after the collapse of the fishery for Pacific sardine, a renewed fishery has emerged off the west coasts of the United States and Canada. The daily egg production method (DEPM) and acoustic-trawl surveys are performed annually and, to minimize the uncertainties in the estimates, sampling effort needs to be allocated optimally. Here, based on a 12-year dataset including the presence/absence of sardine eggs and concomitant remotely sensed oceanographic variables, a probabilistic generalized additive model is developed to predict spatio-temporal distributions of habitat for the northern stock of Pacific sardine in the California Current. Significant relationships are identified between eggs and sea surface temperature, chlorophyll a concentration, and the gradient of sea surface altitude. The model accurately predicts the habitat and seasonal migration pattern of sardine, irrespective of spawning condition. The predictions of potential habitat are validated extensively by fishery landings and net-sample data from the northeast Pacific. The predicted habitat can be used to optimize the time and location of the DEPM, acoustic-trawl, and aerial surveys of sardine. The method developed and illustrated may be applicable too to studies of other stocks of sardine and other epipelagic fish in other eastern boundary, upwelling regions.

GAMMA-RAY EMISSION FROM THE VELA PULSAR MODELED WITH THE ANNULAR GAP AND THE CORE GAP

The Vela pulsar represents a distinct group of {\gamma}-ray pulsars. Fermi {\gamma}-ray observations reveal that it has two sharp peaks (P1 and P2) in the light curve with a phase separation of 0.42 and a third peak (P3) in the bridge. The location and intensity of P3 are energy-dependent. We use the 3D magnetospheric model for the annular gap and core gap to simulate the {\gamma}-ray light curves, phase-averaged and phase-resolved spectra. We found that the acceleration electric field along a field line in the annular gap region decreases with heights. The emission at high energy GeV band is originated from the curvature radiation of accelerated primary particles, while the synchrotron radiation from secondary particles have some contributions to low energy {\gamma}-ray band (0.1 - 0.3 GeV). The {\gamma}-ray light curve peaks P1 and P2 are generated in the annular gap region near the altitude of null charge surface, whereas P3 and the bridge emission is generated in the core gap region. The intensity and location of P3 at different energy bands depend on the emission altitudes. The radio emission from the Vela pulsar should be generated in a high-altitude narrow regions of the annular gap, which leads to a radio phase lag of ~ 0.13 prior to the first {\gamma}-ray peak.

Applied spatial analytic tools in orchards with special regard to agro-ecology

Our investigation was carried out in several orchards in Hungary. This study reviews applicability of the different spatial analytical techniques in orchard especially models based on surface relief, such as digital elevation model, digital terrain model, slope and aspect maps. In recent time, the generation of digital elevation model has become a popular examination method. However, the elevation models generated from contour lines or elevation points could be applied to evaluate agro- ecological potential of fruit orchards to some extent. The highest deficiency of these models is the fact that these show the altitude of soil surface only and do not demonstrate landmarks on the surface. Consequently, the calculation of the radiation value results data relating to soil surface. The terrain model generated and applied by our team demonstrates fine surface texture and the landmarks in the orchard, so it is suitable for further examination.

An algorithm for estimating downward shortwave radiation from GMS 5 visible imagery and its evaluation over China

This paper presents an operational scheme to estimate downward shortwave radiation (DSR) over China from the visible‐band top‐of‐atmosphere reflectance of the Geostationary Meteorological Satellite (GMS) 5 imagery. The proposed algorithm retrieves surface reflectance and atmospheric parameters directly from GMS 5 images by searching lookup tables, which are created by the radiative transfer model SBDART and consider the effects of water vapor absorption and surface altitude variations. Experiments show that the DSR retrieval is more sensitive to the selection of aerosol type and less to that of the cloud type. Uncertainty in the reflectance of a bright surface leads to a considerable DSR retrieval error (±(6–9%)). The instantaneous retrieved DSR is evaluated by field measurements on the Tibetan Plateau, and the daily retrieved DSR is compared with one year's ground‐based measurements at 96 stations in China. The results show that the estimated DSR is in good agreement with ground measurements with a correlation coefficient of ∼0.9 and a bias of 1.5%. Root‐mean square differences in the daily DSR are 17.7% for all‐sky and 13.1% for clear‐sky conditions. These results suggest that the proposed method applied to the GMS 5 satellite data can accurately estimate temporally and spatially continuous instantaneous and daily DSR. These DSR data sets will be useful for a wide range of applications.

An automatic evaluation method for the surface profile of a microlens array using an optical interferometric microscope

In this paper, an automatic evaluation method for the surface profile of a microlens array using an optical interferometric microscope is presented. For inspecting the microlens array, an XY-table is used to position it. With a He–Ne laser beam and optical fiber as a probing light, the measured image is sent to the computer to analyze the surface profile. By binary image slicing and area recognition, this study located the center of each ring and determined the substrate of the microlens array image through the background of the entire microlens array interference image. The maximum and minimum values of every segment brightness curve were determined corresponding to the change in the segment phase angle from 0° to 180°. According to the ratio of the actual ring area and the ideal ring area, the area ratio method was adopted to find the phase-angle variation of the interference ring. Based on the ratio of actual ring brightness and the ideal ring brightness, the brightness ratio method was used to determine the phase-angle variation of the interference ring fringe. The area ratio method and brightness ratio method are interchangeable in precisely determining the phase angles of the innermost and outermost rings of the interference fringe and obtaining different microlens surface altitudes of respective pixels in the segment, to greatly increase the microlens array surface profile inspection accuracy and quality.

High level shore features of Jersey (Channel Islands) and adjacent areas

Past marine surfaces occur between present low tide and 45 m mean sea level (msl) in the Channel Islands and along adjacent French coasts, particularly on Jersey. A detailed historical review of the early work concerned with the mapping of the range of marine surfaces is supported by detailed levelling surveys including a new one of the cove of Le Pulec in Jersey. The importance of the very large tidal ranges in parts of the area, that between Guernsey and the Baie du Mont-Saint-Michel being the largest in the world for relatively open sea, is shown to have an effect on the height range of present and former sea-levels. This information is applied to make estimates of past tidal ranges related to the outcrop evidence of the high marine surfaces. The survey results are applied to develop a sequence of high marine surfaces which differ in some important respects from those published to date for both the Channel Islands and adjacent French coasts. Discussion of the factors that may affect the altitude and age of the marine surfaces includes consideration of the current debates surrounding the origins of the uplift, whether of purely neotectonic or combined neotectonic and climatically induced factors.

Measuring volcanic degassing of SO 2 in the lower troposphere with ASTER band ratios

We present a new method for measuring SO 2 with the data from the ASTER (Advanced Spaceborne Thermal Emission and Reflectance radiometer) orbital sensor. The method consists of adjusting the SO 2 column amount until the ratios of radiance simulated on several ASTER bands match the observations. We present a sensitivity analysis for this method, and two case studies. The sensitivity analysis shows that the selected band ratios depend much less on atmospheric humidity, sulfate aerosols, surface altitude and emissivity than the raw radiances. Measurements with < 25% relative precision are achieved, but only when the thermal contrast between the plume and the underlying surface is higher than 10 K. For the case studies we focused on Miyakejima and Etna, two volcanoes where SO 2 is measured regularly by COSPEC or scanning DOAS. The SO 2 fluxes computed from a series of ten images of Miyakejima over the period 2000–2002 is in agreement with the long term trend of measurement for this volcano. On Etna, we compared SO 2 column amounts measured by ASTER with those acquired simultaneously by ground-based automated scanning DOAS. The column amounts compare quite well, providing a more rigorous validation of the method. The SO 2 maps retrieved with ASTER can provide quantitative insights into the 2D structure of non-eruptive volcanic plumes, their dispersion and their progressive depletion in SO 2.