Approximate solutions of non-linear circular orbit relative motion in curvilinear coordinates

A compact, time-explicit, approximate solution of the highly non-linear relative motion in curvilinear coordinates is provided under the assumption of circular orbit for the chief spacecraft. The rather compact, three-dimensional solution is obtained by algebraic manipulation of the individual Keplerian motions in curvilinear, rather than Cartesian coordinates, and provides analytical expressions for the secular, constant and periodic terms of each coordinate as a function of the initial relative motion conditions or relative orbital elements. Numerical test cases are conducted to show that the approximate solution can be effectively employed to extend the classical linear Clohessy–Wiltshire solution to include non-linear relative motion without significant loss of accuracy up to a limit of 0.4–0.45 in eccentricity and 40–45\(^\circ \) in relative inclination for the follower. A very simple, quadratic extension of the classical Clohessy–Wiltshire solution in curvilinear coordinates is also presented.     

A simple hydrologic framework for simulating wetlands in climate and earth system models

Wetlands are ecosystems of important functions in the earth??s climate system. Through relatively high evapotranspiration, they affect surface water and energy exchange with the atmosphere directly influencing the physical climate. Through CH₄, CO₂ and N₂O fluxes, they regulate the biogeochemical cycles, indirectly influencing the physical climate. However, current models do not explicitly include the water table, present under all large and stable wetlands; model wetlands are identified as flat land with wet soil resulting from precipitation events. That is, the wetlands are only ??wetted?? from above but not from below by the high water table. Furthermore, without the knowledge of the water table position, estimates of CH₄ and other gases (e.g., CO₂ and N₂O) are poorly constrained. We present a simple hydrologic framework for simulating wetlands based on water table depth. A synthesis of hydrologic controls on wetlands highlights the key role that groundwater plays. It directly feeds wetlands, supports surface-water fed wetlands by maintaining a saturated substrate, and links land drainage to sea level by impeding drainage in lowlands. Forced by routine climate model output (precipitation?Cevapotranspiration-surface runoff), land topography, and sea level, we simulate the present-day water table in North America at the 1?km scale. We validate the simulation with water table observations and compare regions of shallow water table to mapped wetlands. Our results show that the framework captures the salient features of wetland distribution and extent at regional and continental scales, a direct result of large-scale groundwater convergence that nourishes the lowlands even in arid climates. The low requirement of forcing and computation make the framework easy to adopt in climate and earth system models for simulating wetland responses to climate and sea level change for the present, paleo reconstructions, and future projections.     

Cytological and Population Genetic Changes in Northwestern Iberian Mussels After the Prestige Oil Spill

The ecological catastrophe produced by the Prestige oil spill (November 2002) caused severe damage in both North Spanish and French coastal communities. Wild mussel populations of Mytilus galloprovincialis in a zone with marginal introgression of Mytilus edulis were affected at all levels, from high DNA damage to increased polycyclic aromatic hydrocarbon content in tissues. In this article, we describe cytological and population genetic changes of wild mussel populations from the northwestern Iberian coast following the catastrophe. The micronucleus test was employed as an indicator of cytological damage, and the Barcoding mitochondrial cytochrome oxidase I (COI) and the nuclear Glu-5′ genes were analyzed for determining the species and assessing population genetic diversity. Immediate increase of micronuclei counts after the oil spill was found, with a further decrease in consecutive months although the counts did not recover pre-Prestige levels. Reduced variation at mitochondrial sequences in the most exposed areas and reduction of M. edulis traces in the regional genetic pool also suggest long-term impact that may result in evolutionary changes. These results highlight the need of adopting more strict measures in order to prevent this type of accidents and avoid long-term effects on wild populations.     

Coastal inundation under concurrent mean and extreme sea-level rise in Coral Gables,Florida, USA

Natural Hazards - Southeast Florida (SF) is among the most vulnerable regions to sea-level rise in the United States of America. The consequences associated with sea-level rise (SLR) are already...     

Lateral variation and frequency dependence of coda-Q in the southern part of Iberia

b
A method based on the coda attenuation law: Q = Q ₀( f/f ₀)^v leads to the determination of the lateral variation of coda- Q in the southern part of the Iberian Peninsula using seismograms belonging to the seismological network of the Cartuja Observatory, located in Granada. The lateral variation of Q ₀ ( Q value corresponding to a reference frequency f ₀ of 1 Hz) and its frequency dependence for the 1 to 5 Hz frequency range are, in general, in agreement with coda- Q values for frequencies less than about 1 Hz, previously determined in the region under study.
To determine the coda- Q values analytical functions have been used to fit the magnification curves of the vertical component short-period seismographs belonging to the Cartuja network. The problem is solved by using least-squares techniques and non-linear inversion. The determined coda- Q ₀ values and its frequency dependence correlate well with several known geophysical parameters in the southern part of the Iberian Peninsula.     

Nuclear magnitudes and the size distribution of Jupiter family comets

We present a new catalog of absolute nuclear magnitudes of Jupiter family (JF) comets, which is an updated version of our previous catalog [Tancredi, G., Fernández, J.A., Rickman, H., Licandro, J., 2000. Astron. Astrophys. Suppl. Ser. 146, 73-90]. From the new catalog we find a linear cumulative luminosity function (CLF) of slope 0.54±0.05 for JF comets with q?2.5 AU. By considering this CLF combined with the few measured geometric albedos with their respective uncertainties, and assuming a canonical albedo of 0.035±0.012 for those comets with undetermined albedos, we derive a cumulative size distribution that follows a power-law of index −2.7±0.3. The slope is similar to that derived from some theoretical collisional models and from some populations of Solar System bodies like the trans-neptunian objects. We also discuss and compare our size distribution with those by other authors that have recently appeared in the literature. Some striking differences in the computed slopes are explained in terms of biases in the studied samples, the different weights given to the brightest members of the samples, and discrepancies in the values of a few absolute nuclear magnitudes. We also compute sizes and fractions of active surface area of JF comets from their estimated absolute nuclear magnitudes and their water production rates. With the outgassing model that we use, about 60% of the computed fractions f of active surface area are found to be smaller than 0.2, with one case (28P/Neujmin 1) of no more than 0.001, which suggests that JF comets may transit through stages of very low activity, or even dormancy. There is an indication that JF comets with radii RN?3 km have active fractions f?0.01, which might be due to the rapid formation of insulating dust mantles on larger nuclei.     

Understanding precipitation recycling over the Tibetan Plateau using tracer analysis with WRF

The precipitation recycling (PR) ratio is an important indicator that quantifies the land-atmosphere interaction strength in the Earth system’s water cycle. To better understand how the heterogeneous land surface in the Tibetan Plateau (TP) contributes to precipitation, we used the water-vapor tracer (WVT) method coupled with the Weather Research and Forecasting (WRF) regional climate model. The goals were to quantify the PR ratio, in terms of annual mean, seasonal variability and diurnal cycle, and to address the relationships of the PR ratio with lake treatments and precipitation amount. Simulations showed that the PR ratio increases from 0.1 in winter to 0.4 in summer when averaged over the TP with the maxima centered at the headwaters of three major rivers (Yangtze, Yellow and Mekong). For the central TP, the highest PR ratio rose to over 0.8 in August, indicating that most of the precipitation was recycled via local evapotranspiration in summer. The larger daily mean and standard deviation of the PR ratio in summer suggested a stronger effect of land-atmosphere interactions on precipitation in summer than in winter. Despite the relatively small spatial extent of inland lakes, the treatment of lakes in WRF significantly impacted the calculation of the PR ratio over the TP, and correcting lake temperature substantially improved both precipitation and PR ratio simulations. There was no clear relationship between PR ratio and precipitation amount; however, a significant positive correlation between PR and convective precipitation was revealed. This study is beneficial for the understanding of land-atmosphere interaction over high mountain regions.