Surface Altitude Research Articles

Control of cave levels in Kanaan, Kassarat and Jeita karst systems (Central Mount Lebanon, Lebanon)

Mount Lebanon is a mountainous Mediterranean karst ridge, consisting of high plateaus reaching 3,088 m altitude and entrenched by deep valleys. Fluvial drainage systems run on a steep gradient and reach the Mediterranean Sea coast in less than 30 km distance. In Central Mount Lebanon, the downstream parts of Antelias and Kalb valleys host the Kanaan cave (160 m), the Kassarat cave (4.6 km) and the Jeita cave (10.05 km), whose subterranean rivers are connected to the karst springs located close to the contact between the Cretaceous aqui- clude and the Jurassic karst aquifer. The area thus comprises a dammed Jurassic aquifer in which all the studied cave levels developed at certain altitudes. A geomorphological study performed by speleological and geomorphological surveys and completed by analyses of cave sediments allowed the formulation of a first evolutionary framework of the karst system. Several features suggest a long-term and multi-stage evolution of the karst in both Antelias and Kalb valleys. The horizontal caves develop between 60 and 160 m a. s. l. and constitute water table caves in a steeply dipping structure (Mount Lebanon's western fold). These cave levels are part of an ancient system that developed near the water table controlled by the position of the aquiclude and correspond to the base level of a past fluvial network. An important phase of base level cave development is documented in the relict passages above 90 m a. s. l. Speleogenetic features between 90 and 160 m developed in a phreatic environment where paragenesis or per ascensum erosion processes occurred during base level rise. Epiphreatic features were identified at 60–70 m in Kassarat and Jeita caves. Typical morphological features such as horizontal solution passages and solution notches suggest a phase of stillstand of the base-level. The evolution of the water table level from a paragenetic rise above 90 m to a continuous lowering below 90 m and with a temporary stillstand phase at 70–60 m, is related to the fluvial base-level evolution. Preliminar chronological constraints for the evolution of the karst system are discussed based on U/Th dating of speleothems and cave levels (90–160 and 60–70 m) and their relationship with the altitude of the low-gradient surfaces. The cave levels between 90 and 160 m are related to a water table rise that caused an alluviation process at the river's mouth probably during the Pliocene transgression phase of the Mediterranean Sea (PHS). Abandoning of the upper cave levels (90–160 and 60–70 m) is the result of a continuous lowering of the water table related to fluvial incision. The lowering of the water table level below 90 m is mainly related to the fluvial incision of the acquiclude in a high geodynamic context (Mount Lebanon uplift) during the Pleistocene.

Spectral dependence on the correction factor of erythemal UV for cloud, aerosol, total ozone, and surface properties: A modeling study

Radiative transfer model simulations were used to investigate the erythemal ultraviolet (EUV) correction factors by separating the UV-A and UV-B spectral ranges. The correction factor was defined as the ratio of EUV caused by changing the amounts and characteristics of the extinction and scattering materials. The EUV correction factors (CFEUV) for UV-A [CFEUV(A)] and UV-B [CFEUV(B)] were affected by changes in the total ozone, optical depths of aerosol and cloud, and the solar zenith angle. The differences between CFEUV(A) and CFEUV(B) were also estimated as a function of solar zenith angle, the optical depths of aerosol and cloud, and total ozone. The differences between CFEUV(A) and CFEUV(B) ranged from −5.0% to 25.0% for aerosols, and from −9.5% to 2.0% for clouds in all simulations for different solar zenith angles and optical depths of aerosol and cloud. The rate of decline of CFEUV per unit optical depth between UV-A and UV-B differed by up to 20% for the same aerosol and cloud conditions. For total ozone, the variation in CFEUV(A) was negligible compared with that in CFEUV(B) because of the effective spectral range of the ozone absorption band. In addition, the sensitivity of the CFEUVs due to changes in surface conditions (i.e., surface albedo and surface altitude) was also estimated by using the model in this study. For changes in surface albedo, the sensitivity of the CFEUVs was 2.9%–4.1% per 0.1 albedo change, depending on the amount of aerosols or clouds. For changes in surface altitude, the sensitivity of CFEUV(B) was twice that of CFEUV(A), because the Rayleigh optical depth increased significantly at shorter wavelengths.

Corrigendum to “Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit”

A recent paper published in Life Sciences in Space Research (El-Jaby and Richardson, 2015) presented estimates of the secondary neutron ambient and effective dose equivalent rates, in air, from surface altitudes up to suborbital altitudes and low Earth orbit. These estimates were based on MCNPX (LANL, 2011) (Monte Carlo N-Particle eXtended) radiation transport simulations of galactic cosmic radiation passing through Earth's atmosphere. During a recent review of the input decks used for these simulations, a systematic error was discovered that is addressed here. After reassessment, the neutron ambient and effective dose equivalent rates estimated are found to be 10 to 15% different, though, the essence of the conclusions drawn remains unchanged.

HYPSOGRAPHIC CURVE OF THE EARTH’S SURFACE WITH ICE AND WATER DELETED

The distribution curve of the heights and hypsographic curve of the Earth were compiled on the basis of the current data on the surface elevation and the bedrock topography of our planet. The dataset included the satellite data, bathymetry data for the World Ocean and the bedrock topography of Greenland and Antarctica – the most important glaciers of our planet. The results show that taking into account the ice cover has a significant impact on the shape of the curves The greatest differences are in the ranges of heights between 1500 and 4000 m and between –1000 and –200 m. According to calculations, the average altitude of the land surface and the stone surface is 800 m and 605 m, respectively.

The Vérard et al. (2015) method for 3D palaeogeographic reconstructions: How solid is its base?

Veacute;rard and co-workers proposed in an earlier issue of this journal a method to reconstruct the 3D palaeogeography “anywhere in the world at any time”. The present contribution is a discussion of some of the assumptions on which the method of Veacute;rard et al. is based. The reason for this discussion is that the method will give, at least seemingly, illogical outcomes for numerous situations. Moreover, some assumptions used by Veacute;rard and his team pose theoretical problems. It is deduced that the method developed by Veacute;rard and co-workers may occasionally help, indeed, to obtain a rough picture of the altitude of the sedimentary surface on the continents and of the depth of the sedimentary surface in the oceans in the geological past. The outcomes should, however, be treated with utmost care as several of the assumptions on which the interpretative 3D method is based have no solid basis, so that even the rough outcomes of the method must be considered questionable.

Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit

Occupational exposures from ionizing radiation are currently regulated for airline travel (<20 km) and for missions to low-Earth orbit (∼300–400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit.

Assessing the possibilities of sensing CH4 and CO2 greenhouse gases above the underlying surface with satellite-based IPDA lidar

The IPDA method is used to analyze the possible uncertainties of CH4 and CO2 measurements in the troposphere in the presence of clouds. The choice of wavelengths is substantiated. A software system written for simulating the radiative transfer in satellite sensing is briefly described. It is shown that multiple scattering under cloudy conditions can influence the power of the received signal at a single wavelength; at the same time, the use of a differential scheme mitigates this effect for closely lying wavelengths. We calculate the uncertainties versus underlying surface altitudes and the presence of clouds.

Spatial variation of stress orientations in NE Japan revealed by dense seismic observations

In order to investigate the spatial distribution of the crustal stress state across NE Japan, we determined 1370 focal mechanisms by picking P-wave polarities from seismograms observed by temporary and permanent seismic networks densely deployed in this area. We applied stress tensor inversions to these data, plus to those routinely determined. The results show that the stress state in NE Japan is heterogeneous in space, which is different from previous results that showed that the NE Japan arc is characterized by margin normal compression. The orientations of the maximum compressional stress (σ1.) axes are significantly different with 95% confidence limits between the arc–backarc region and the forearc region. The arc–backarc region is characterized by spatially uniform margin normal compression. However, the north and south parts of the forearc region have the σ1 axis oriented nearly N–S and vertical, respectively. The region in between has a similar stress orientation to the arc–backarc region. Moreover, the stress regime in the arc–backarc region varies spatially in response to change in the surface altitude. Beneath regions of relatively low altitudes, a reverse faulting stress regime is dominant. However, regions of higher altitudes are characterized by a strike–slip faulting stress regime. Numerical model calculations, in which gravitational and buoyancy forces caused by topography are incorporated, show that differential stresses of about 15–25MPa are needed to explain the lateral variation of the stress regime observed in the arc–backarc region. This suggests that the background deviatoric stress magnitude in NE Japan is very low.

Fifty years of studying the Medvezhiy Glacier (West Pamirs) by the Institute of Geography, RAS

Overview of researches conducted over 50 years (1963–2012) by Institute of Geography RAS on the surging glacier Medvezhiy, the West Pamirs is given. Ground investigations (changes of its surface altitude, ice movement velocity, ablation, ice thickness, temperature and others) made after surge 1963 allowed finding the basic features of this glacier regime and calculating the mass balance of its surging part for the whole cycle from the recovery phase up to a surge. Using the results a quality model for prediction of rapid motions of surging glaciers had been developed. Forecast of the next surge of the Medvezhiy Glacier made for 1973 on the basis of this model had been justified. As a result of the aerial and topographic monitoring (1989–1991) the glacier surge was quantitatively followed for the first time over its whole cycle, i.e. from a surge up to a next stage of its recovery. Results of our researches allowed formulating the foundations of the space monitoring of surging glaciers. In 2001 and 2011 surges of the glacier were detected and traced using the satellite imagery (MIR, ISS). In total for 50 years, five surges of this glacier and two full cycles of its life were investigated by various methods in different details.

Application of a global-to-beam irradiance model to the NASA GEWEX SRB dataset: An extension of the NASA Surface meteorology and Solar Energy datasets

The DIRINDEX model was designed to estimate hourly solar beam irradiances from hourly global horizontal irradiances. This model was applied to the NASA GEWEX SRB (Rel. 3.0) 3-hourly global horizontal irradiance data to derive 3-hourly global maps of beam, or direct normal, irradiance for the period from January 2000 to December 2005. The DIRINDEX model is a combination of the DIRINT model, a quasi-physical global-to-beam irradiance model based on regression of hourly observed data, and a broadband simplified version of the SOLIS clear-sky beam irradiance model. In this study, the input variables of the DIRINDEX model are 3-hourly global horizontal irradiance, solar zenith angle, dew-point temperature, surface altitude, surface pressure, sea-level pressure, aerosol optical depth at 700nm, and atmospheric column water vapor. The resulting values of the 3-hourly direct normal irradiance are then used to compute daily and monthly means. The results are validated against the ground-based BSRN data. The monthly means show better agreement with the BSRN data than the results from an earlier endeavor which empirically derived the monthly mean direct normal irradiance from the GEWEX SRB monthly mean global horizontal irradiance. To assimilate the observed information into the final results, the direct normal fluxes from the DIRINDEX model are adjusted according to the comparison statistics in the latitude–longitude–cosine of solar zenith angle phase space, in which the inverse-distance interpolation is used for the adjustment. Since the NASA Surface meteorology and Solar Energy derives its data from the GEWEX SRB datasets, the results discussed herein will serve to extend the former.

The CO2 continuum absorption in the 1.10- and 1.18-μm windows on Venus from Maxwell Montes transits by SPICAV IR onboard Venus express

One of the difficulties in modeling Venus’ nightside atmospheric windows is the need to apply CO2 continuum opacity due to collision-induced CO2 bands and/or extreme far wings of strong allowed CO2 bands. Characterizing the CO2 continuum absorption at near-IR wavelengths as well as searching for a possible vertical gradient of minor species near the surface require observations over different surface elevations. The largest change in altitude occurs during a passage above Maxwell Montes at high northern latitudes. In 2011, 2012 and 2013 the SPICAV instrument aboard the Venus Express satellite performed three sets of observations over Maxwell Montes with variation of surface altitude from −2 to 9km in the 1.10, 1.18 and 1.28-μm windows. The retrieved CO2 continuum absorption for the 1.10- and 1.18-μm windows varies from 0.29 to 0.66×10−9cm−1amagat−2 and from 0.30 to 0.78×10−9cm−1amagat−2, respectively, depending on the assumed input parameters. The retrieval is sensitive to possible variations of the surface emissivity. Our values fall between the results of Bézard et al., (2009, 2011) based on VIRTIS-M observations and laboratory measurements by Snels et al. (2014). We can also conclude that the continuum absorption at 1.28μm can be constrained below 2.0×10−9cm−1amagat−2. Based on the 1.18μm window the constant H2O mixing ratio varying from 25.7+1.4–1.2ppm to 29.4+1.6–1.4ppm has been retrieved assuming the surface emissivity of 0.95 and 0.6, respectively. No firm conclusion from SPICAV data about the vertical gradient of water vapor content at 10–20km altitude could be drawn because of low signal-to-noise ratio and uncertainties in the surface emissivity.

A spherical harmonic model of the lithospheric magnetic field of Mars

AbstractWe present a model of the lithospheric magnetic field of Mars which is based on Mars Global Surveyor orbiting satellite data and represented by an expansion of spherical harmonic (SH) functions up to degree and order 110. Several techniques were applied in order to obtain a reliable and well‐resolved model of the Martian lithospheric magnetic field: A modified Huber‐Norm was used to properly treat data outliers, the mapping phase orbit data was weighted based on an a priori analysis of the data, and static external fields were treated by a joint inversion of external and internal fields. Further, temporal variabilities in the data which lead to unrealistically strong anomalies were considered as noise and handled by additionally minimizing a measure of the horizontal gradient of the vertically down internal field component at surface altitude. Here we use an iteratively reweighted least squares algorithm to approach an absolute measure (L1 norm), allowing for a better representation of strong localized magnetic anomalies as compared to the conventional least squares measure (L2 norm). The resulting model reproduces all known characteristics of the Martian lithospheric field and shows a rich level of detail. It is characterized by a low level of noise and robust when downward continued to the surface. We show how these properties can help to improve the knowledge of the Martian past and present magnetic field by investigating magnetic signatures associated with impacts and volcanoes. Additionally, we present some previously undescribed isolated anomalies, which can be used to determine paleopole positions and magnetization strengths.

A Method to Linearly Evaluate Rainfall Frequency–Intensity Distribution

AbstractThis study presents a method to linearly evaluate the rainfall frequency–intensity distribution, which is an important component of climatological rainfall characteristics. To grasp and represent the key information of the rainfall frequency distribution by intensity, a two-parameter double exponential function is formulated and fitted to the hourly rainfall observation at each station. The values of the two parameters are estimated by transforming the distribution to a linear pattern. The two parameters determine the location and shape of the fitted distribution curve, and they have different modulating effects in different intensity categories, one governing the low-intensity section and the other dominating the intense rainfall. Through analysis of the estimated parameters, essential features of rainfall distribution can be obtained and assessed. The proposed method is applied to analyze the climatology and long-term variation of the late-summer rainfall in China. It is found that topography and monsoon circulation are two major factors controlling the rainfall frequency–intensity distribution. At stations with high surface altitudes and complex orography, the frequency of light rain is extremely high and the number of intense rainfall events is relatively small. In the plain areas of eastern China, especially those influenced by the main monsoon rain belt, heavy rainfall is more frequent. By tracking the displacement of the parameter pairs, the decadal changes in rainfall frequency–intensity distribution can be clearly visualized and evaluated on a plane constructed by the two parameters. The southern flooding and northern drought pattern can be attributed to the changes in light and moderate rainfall, while the intense rainfall exhibits opposite trends.

Little Ice Age and contemporary glacier extent in the Western and South-Western Piedmont Alps (North-Western Italy)

Glaciers are widely recognized as the best terrestrial indicators of climate change. Nevertheless, changes that have occurred since the end of the Little Ice Age (LIA) are often poorly understood. In Italy, glacier front variations in the last 100 years have been well documented, thanks to the efforts of the Italian Glaciological Committee (Comitato Glaciologico Italiano, CGI), which coordinates annual surveys on all glaciers, since 1927, in order to measure their front positions. However, although front variations are the easiest measurements to take in the field, they only partially describe changes that occur on the entire glacial mass. Moreover, the last national glacier inventory dates back to 1957–1958, which was promoted by the CGI on the occasion of the International Geophysical Year. Authors of the present work herein provide an updated inventory of present-day (2006) glaciers in the Western and South-Western Piedmont Alps (situated in the provinces of Turin and Cuneo). Along with the present-day glacial outlines, the map also includes a reconstruction of the extent of the glaciers during the Little Ice Age, inferred from morphological features such as LIA and post-LIA moraine ridges as well as the aid of historical archive data. Some basic glacier morphometric parameters (surface, length, width, mean slope, highest and lowest altitude, exposure) were computed for the two specified time periods (LIA and 2006). This study was carried out under the framework of the project ‘GlaRiskAlp – Glacial Risks in Western Alps’, project n.° 56 under the 2007–2013 ALCoTra programs.

Ages and genesis of terrace flights in the middle reaches of the Yarlung Zangbo River, Tibetan Plateau, China

Field investigation has shown that the middle reaches of the Yarlung Zangbo River, in Tibet (known as the Bhramaputra River in reaches downstream) has 11 terraces. The ages of these terraces were determined as follows: T11&gt;2000 ka, T10 = 1783 ka, T9 = 1238 ka, T8 = 683 ka, T7 = 382 ka, T6 = 150 ka, T5 = 82 ka, T4 = 67 ka, T3 = 43 ka, T2 = 28 ka and T1 = 10 ka. These terraces formed during several stages of the Quaternary when the Tibetan Plateau was uplifting, recording tectonic–climatic cycles or subcycles of 1.2, 0.4, 0.1, 0.04 and 0.02 million years duration. The tectonic–climatic cycles identified by this study are correlated with red soil and palaeosol records. The preservation of the Oligocene to Early Miocene conglomeratic Dazhuka Formation, close to the present altitude of the main planation surface of the Tibetan Plateau and occurring only in the Yarlung Zangbo valley, suggests that this river has existed since at least 7 Ma. Discoveries of old and thick fluvial gravel layers extending to within 630 m of the valley floor show that the Yarlung Zangbo River was already incised by 2000 m or more below the surface of the Tibetan Plateau, that much of the incision from plateau to valley floor had been accomplished and that the plateau was already substantially uplifted prior to the Quaternary. In addition to its importance for understanding the evolution of the Tibetan Plateau, this study documents the impact of varying rates of tectonic uplift on river development.

The Deformational Response of a Viscoelastic Solid Earth Model Coupled to a Thermomechanical Ice Sheet Model

We apply a coupled thermomechanical ice sheet—self-gravitating viscoelastic solid Earth model (SGVEM), allowing for the dynamic exchange of ice thickness and bedrock deformation, in order to investigate the effect of viscoelastic deformation on ice dynamics and vice versa. In a synthetic glaciation scenario, we investigate the interaction between the ice sheet and the solid Earth deformation, the glacial-isostatic adjustment (GIA), accounting for an atmospheric forcing depending on the ice sheet surface altitude. We compare the results from the coupled model to runs with the common elastic lithosphere/relaxing asthenosphere (ELRA) model, where the lithosphere is represented by a thin plate and the mantle relaxes with one characteristic relaxation time, as well as to a rigid Earth without any deformation. We find that the deformational behaviour of the SGVEM on ice dynamics (i.e. stored ice volume, ice thickness and velocity field) is comparable to the ELRA for an optimal choice of the parameters in steady state, but exhibits differences in the transient behaviour. Beyond the ice sheet, in the region of peripheral forebulge, the differences in the transient surface deformation between ELRA and SGVEM are substantial, demonstrating the inadequacy of the ELRA model for interpreting constraints on GIA in the periphery of the ice sheet, such as sea-level indicators and GPS uplift rates.

Impact of bedrock surface topography on spatial distribution of Quaternary sediments and on the flow pattern of late Weichselian glaciers on the East European Craton (Russian Plain)

This paper presents the first high quality maps of the bedrock surface topography and the Quaternary sediment distribution for the Late Weichselian glaciation area on the East European Craton (EEC) and the reasoning behind the estimated sediment distribution. Geographic information system (GIS)-based three-dimensional model of the bedrock surface topography, the current digital terrain model (DTM), and the ice flow pattern of the last glaciation provided the main source data for the analyses and interpretations. In the current continental area of the western EEC, which was covered by the last Scandinavian Ice Sheet (SIS), the bedrock lies overwhelmingly (85%) above the contemporary sea level, with an average altitude of ~54m above sea level. The topography of the bedrock surface is very well reflected in the current topography, and an 80-m difference in the ice bed surface altitudes results in the topographic focusing of the ice flow, and thus all late Weichselian ice streams were accommodated to the depressions in the subglacial surface. Such depressions are characterised by a thin (<10-m) layer of sediment with one till bed. Just 50m upslope from the bottom of the depressions, the thickness of the sediment increases two- to threefold and comprises five or more till layers, indicating relief enhancement through subsequent glaciations. The average calculated thickness of the Quaternary deposits in the study area was ~49m, and the total volume of sediments was ~20,280km3.

Modeling of intensity-modulated continuous-wave laser absorption spectrometer systems for atmospheric CO2 column measurements

The focus of this study is to model and validate the performance of intensity-modulated continuous-wave (IM-CW) CO(2) laser absorption spectrometer (LAS) systems and their CO(2) column measurements from airborne and satellite platforms. The model accounts for all fundamental physics of the instruments and their related CO(2) measurement environments, and the modeling results are presented statistically from simulation ensembles that include noise sources and uncertainties related to the LAS instruments and the measurement environments. The characteristics of simulated LAS systems are based on existing technologies and their implementation in existing systems. The modeled instruments are specifically assumed to be IM-CW LAS systems such as the Exelis' airborne multifunctional fiber laser lidar (MFLL) operating in the 1.57 μm CO(2) absorption band. Atmospheric effects due to variations in CO(2), solar radiation, and thin clouds, are also included in the model. Model results are shown to agree well with LAS atmospheric CO(2) measurement performance. For example, the relative bias errors of both MFLL simulated and measured CO(2) differential optical depths were found to agree to within a few tenths of a percent when compared to the in situ observations from the flight of 3 August 2011 over Railroad Valley (RRV), Nevada, during the summer 2011 flight campaign. In addition, the horizontal variations in the model CO(2) differential optical depths were also found to be consistent with those from MFLL measurements. In general, the modeled and measured signal-to-noise ratios (SNRs) of the CO(2) column differential optical depths (τd) agreed to within about 30%. Model simulations of a spaceborne IM-CW LAS system in a 390 km dawn/dusk orbit for CO(2) column measurements showed that with a total of 42 W of transmitted power for one offline and two different sideline channels (placed at different locations on the side of the CO(2) absorption line), the accuracy of the τd measurements for surfaces similar to the playa of RRV, Nevada, will be better than 0.1% for 10 s averages. For other types of surfaces such as low-reflectivity snow and ice surfaces, the precision and bias errors will be within 0.23% and 0.1%, respectively. Including thin clouds with optical depths up to 1, the SNR of the τd measurements with 0.1 s integration period for surfaces similar to the playa of RRV, Nevada, will be greater than 94 and 65 for sideline positions placed +3 and +10 pm, respectively, from the CO(2) line center at 1571.112 nm. The CO(2) column bias errors introduced by the thin clouds are ≤0.1% for cloud optical depth ≤0.4, but they could reach ∼0.5% for more optically thick clouds with optical depths up to 1. When the cloud and surface altitudes and scattering amplitudes are obtained from matched filter analysis, the cloud bias errors can be further reduced. These results indicate that the IM-CW LAS instrument approach when implemented in a dawn/dusk orbit can make accurate CO(2) column measurements from space with preferential weighting across the mid to lower troposphere in support of a future ASCENDS mission.

Using MATLAB for Processing RGPS Data to Determine the Altitude of Water Surface

The purpose of this study is to use the software of MATLAB for processing the direct and reflected signals of GPS to monitor altitude of water surface in the water flume, as well as to establish a practicable technique of measuring sea water level. It is because before determining water wave pattern, the feasibility and accuracy of reflected GPS method must be proved. Therefore, there was a field test in the Mid-size wave flume of the Tainan Hydraulics Laboratory, National Cheng Kung University. After improving RGPS positioning procedure, the tranquil water level and the steadily descending of water level observation for one hour were performed. In this research, an integrated GPS receiver that employed direct and reflected GPS signals for the measurement was introduced. Both RHCP and LHCP antennas were employed to simultaneously receive the L1 and L2 carrier phase of direct and reflected signals. After the data analysis of the GPS observation, the position of signal reflection and the water level of the wave were solved. The results of the RGPS, wave gauge, and staff meter were coincided within 0.5cm ~ 1.0 cm. The differences between the reflection heights of this GPS system and the record of wave gauge were almost identical within 90%. It is proved the reflected GPS technique is possible to monitor water surface altitude and determine water wave patterns.

Temperature effect correction for the cosmic ray muon data observed at the Brazilian Southern Space Observatory in São Martinho da Serra

The negative atmospheric temperature effect observed in the muon intensity measured by surface-level detectors is related to the atmospheric expansion during summer periods. According the first explanation given, the path of muons from the higher atmospheric level (where they are generated) to the ground becomes longer, and more muons decay, leading to a muon intensity decrease. A significant negative correlation, therefore, is expected between the altitude of the equi-pressure surface and the muon intensity. We compared measurements of the altitude of 100 hPa equi-pressure surface and data from the multidirectional muon detector installed at the Brazilian Southern Space Observatory in São Martinho da Serra, RS. Significant correlation coefficient were found (up to 0.95) when using data observed in 2008. For comparison, data from the multidirectional muon detector of Nagoya, located in the opposite hemisphere, is studied and an anti-phase in the cosmic ray variation related with the temperature effect is expected between data from detectors of Nagoya and São Martinho da Serra. The temperature influence is higher for the directional channels of Nagoya than for ones of São Martinho da Serra.