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Sample records for eocene equatorial rain

  1. Survival probability of precipitations and rain attenuation in tropical and equatorial regions

    NASA Astrophysics Data System (ADS)

    Mohebbi Nia, Masoud; Din, Jafri; Panagopoulos, Athanasios D.; Lam, Hong Yin

    2015-08-01

    This contribution presents a stochastic model useful for the generation of a long-term tropospheric rain attenuation time series for Earth space or a terrestrial radio link in tropical and equatorial heavy rain regions based on the well-known Cox-Ingersoll-Ross model previously employed in research in the fields of finance and economics. This model assumes typical gamma distribution for rain attenuation in heavy rain climatic regions and utilises the temporal dynamic of precipitation collected in equatorial Johor, Malaysia. Different formations of survival probability are also discussed. Furthermore, the correlation between these probabilities and the Markov process is determined, and information on the variance and autocorrelation function of rain events with respect to the particular characteristics of precipitation in this area is presented. The proposed technique proved to preserve the peculiarities of precipitation for an equatorial region and reproduce fairly good statistics of the rain attenuation correlation function that could help to improve the prediction of dynamic characteristics of rain fade events.

  2. Characteristics of rainfall queues for rain attenuation studies over radio links at subtropical and equatorial Africa

    NASA Astrophysics Data System (ADS)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2014-08-01

    Attenuation due to precipitation remains an important design factor in the future deployment of terrestrial and earth-space communication radio links. Largely, there are concerted efforts to understand the dynamics of precipitation in attenuation occurrence at subtropical, tropical, and equatorial region of Africa. In this deliberate approach, rainfall spikes pertaining to rain cells are conceptualized as distinct rain spike traffic over radio links, by applying queueing theory concepts. The queue distributions at Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E)—respectively, of subtropical and equatorial climates—are investigated from distrometer measurements. The data sets at both sites are observed over four rain regimes: drizzle, widespread, shower, and thunderstorm. The queue parameters of service time and inter-arrival of rain spikes traffic at both regions are found to be Erlang-k distributed (Ek) and exponentially distributed (M), respectively. It is established that the appearance of rain rates over radio links invariably follows a First Come, First Served (FCFS), multi-server (s), infinite queue, and semi-Markovian process, designated as M/Ek/s/∞/FCFS discipline. Modeled queue parameters at both regions are found to vary significantly over different regimes. However, these queue parameters over the entire data set suggest similar queue patterns at both sites. More importantly, power law relationships describing other queue-related parameters are formulated. The paper concludes by demonstrating an application of queueing theory for rainfall synthesis. The proposed technique will provide an alternative method of estimating rain cell sizes and rain attenuation over satellite and terrestrial links.

  3. Neotropical eocene coastal floras and [sup 18]O/[sup 16]O-estimated warmer vs. cooler equatorial waters

    SciTech Connect

    Graham, A. )

    1994-03-01

    The history of the earth's sea-surface temperature (SST) in equatorial regions during the Tertiary is unsettled because of uncertainty as to the presence and extent of glaciers during the Paleogene. The [sup 16]O trapped in glaciers and subsequently released back to the ocean basins as meltwater during interglacials affects the [sup 18]O/[sup 16]O ratio of sea water, one of the variables that must be known for oxygen isotope paleotemperature analysis of calcareous fossils. Estimates of SST range from [approximately]18 to 20 C, assuming an ice-free earth, to [approximately]28 C assuming glaciers were present in the Paleogene. Low latitude SST presently averages 28C, so the former estimate gives a value 8 to 10 C cooler than present, while the latter gives a value as warm or slightly warmer than present. The figures are important for interpreting terrestrial vegetational history because the temperature differential between low and high latitudes is a major factor in determining global climates through the control of poleward transfer of heat. The middle( ) to late Eocene Gatuncillo Formation palynoflora of Panama was deposited at the ocean-continental interface at [approximately]9[degrees]N latitude. The individual components and paleocommunities are distinctly tropical and similar to the present vegetation along the Atlantic coast of southern Central America. This is consistent with data emerging from other recently studied tropical coastal biotas and represents a contribution from paleobiology toward eventually resolving the problem of Eocene equatorial marine environments. Collectively, the evidence is beginning to favor a model of Eocene SST near present values. 50 refs., 1 fig., 2 tabs.

  4. Assessment of prediction and predictability of short rains over equatorial East Africa using a multi-model ensemble

    NASA Astrophysics Data System (ADS)

    Bahaga, T. K.; Kucharski, F.; Tsidu, G. Mengistu; Yang, Hongwei

    2016-02-01

    In this study, the performance of dynamical seasonal forecast systems is evaluated for the prediction of short rain anomalies over equatorial East Africa. The evaluation is based on observational datasets and the Asia-Pacific Climate Center (APCC) Ocean-Atmosphere coupled multi-model ensemble (MME) retrospective forecasts (hindcasts). These forecast systems have different hindcast periods; here, we have selected common years from 1982 to 2005. The ensembles of individual models and their MME mean are evaluated. Hindcasts initialized on the 1st of August from each year alone are considered, as these are the most relevant to short rain predictions. The coupled climate model ensemble reproduces the spatial distribution of mean September-October-November (SON) rainfall and seasonal climate variations over equatorial East Africa with further improvement in MME mean. Individual coupled models and MME mean also show statistically significant skill in forecasting sea surface temperatures anomalies (SSTAs) over the western and eastern parts of the equatorial Indian Ocean, giving significant correlation at 99 % confidence level for Indian Ocean dipole (IOD). Moreover, five out of ten coupled models and MME mean show statistically significant skill in predicting equatorial East Africa short rains. The fidelity of hindcasts is further measured by anomaly correlation coefficient (ACC) and four models as well as MME mean show significant skill over East Africa. It is shown that the reproduction of the observed variability in the East African region is mainly due to a realistic relationship of East African rainfall with the Indian Ocean dipole. Overall, the skill of the dynamical models is attributed to the fact that slowly evolving SSTs are the primary source of predictability and to the fact that coupled climate models produce skillful predictions of SON SST anomalies over the tropical Indian Ocean. This information opens the possibility of using readily available seasonal

  5. Evidence for changes in subsurface circulation in the late Eocene equatorial Pacific from radiolarian-bound nitrogen isotope values

    NASA Astrophysics Data System (ADS)

    Robinson, Rebecca S.; Moore, Theodore C.; Erhardt, Andrea M.; Scher, Howie D.

    2015-07-01

    Microfossil-bound organic matter represents an important archive of surface ocean environmental information. Sedimentary nitrogen (N) isotope reconstructions of surface nitrate consumption and nitrogen source changes are made using fossil diatom (autotrophs) and planktic foraminiferal (heterotrophs)-bound organic matter with success. However, because diatoms and planktic foraminifera are poorly preserved and sedimentary organic matter content is near zero during the late Eocene, our ability to examine nutrient dynamics across this important climate transition is limited. Here we present new data exploring the use of N isotope records from radiolarian tests. A comparison of surface ocean nitrate and core top bulk and radiolarian N isotope values (as δ15N) from the equatorial Pacific indicates that radiolarian-N records δ15N variability with fidelity but that a significant offset exists between bulk sedimentary and diatom δ15N values and those measured from radiolarians (~7.1 ± 1.1‰). A downcore profile of radiolarian δ15N values is compared to siliceous microfossil assemblage changes across the Eocene-Oligocene boundary. Average of radiolarian-bound δ15N values is 0.5 ± 2.0‰, which, when corrected using the offset derived from the modern surface samples, suggests that the mean nitrogen isotopic composition of the early Cenozoic eastern Pacific was not significantly different from today. The overall trend, of decreasing δ15N values with decreasing export productivity, is consistent with either a regional decline in pelagic denitrification or a large-scale change in nutrient sources to the eastern equatorial Pacific (EEP), both linked to the cooling climate and changing intermediate water circulation. Decreasing/low δ15N values cooccur with high radiolarian species turnover at ~35.5 and 34 Ma, suggestive of a significant ecological change in the EEP, consistent with cooling and water mass distribution changes. The preliminary results suggest that

  6. Equatorial Pacific Reactive Phosphorus Accumulation Rates across the Eocene/Oligocene Transition

    NASA Astrophysics Data System (ADS)

    Faul, K. L.; Stewart, K. L.

    2007-12-01

    Paired benthic foraminiferal stable isotope and trace metal records from ODP Site 1218 in the equatorial Pacific have shown that the Eocence/Oligocene (E/O) transition (~34 Ma) represents a major increase in Antarctic ice accumulation and a rapid deepening of the global calcite compensation depth (CCD) occurring in two steps [e.g., Lear et al., 2000; Lear et al., 2004; Coxall et al., 2005; Palike et al., 2006]. Simultaneous increases in biogenic mass accumulation rates (MARs) around Australia and in the Atlantic Ocean have been interpreted as representing increased productivity and/or organic carbon (C) burial possibly linked to cooling and ice sheet growth [Diester-Hass and Zahn, 2001; Anderson and Delaney, 2005]. Because the global CCD deepens across the transition, there is a need to distinguish organic C burial changes from CCD changes. We are determining reactive phosphorus (P, micromol P cm-2 kyr-1) MARs as an indicator of organic C burial for Site 1218 to help constrain the relative role of productivity during the E/O climatic transition. Reactive phosphorus (the sum of oxide associated, authigenic, and organic P; sequentially extracted from bulk sediment), delivered to the sediment water interface with organic C, is well preserved in oxygenated sediments. Preliminary results show an order of magnitude decrease in reactive P concentrations (from ~100 to ~10 micromol P g-1) across the E/O boundary. This may indicate that absolute organic C burial as well as the ratio of organic C burial to calcite burial may have decreased across the E/O transition in the equatorial Pacific upwelling zone.

  7. Changes in opal flux and the rain ratio during the last 50,000 years in the equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Richaud, Mathieu; Loubere, Paul; Pichat, Sylvain; Francois, Roger

    2007-03-01

    Changes in the orgC/CaCO 3 ratio in particles sinking from the surface to the deep ocean have the potential to alter the atmospheric pCO 2 over the span of a glacial/interglacial cycle. Recent paleoceanographic and modern observational studies suggest that silica is a key factor in the global carbon biogeochemical cycle that can influence the flux ratio, especially at low latitudes, through "silicic acid leakage" [Brzezinski, M., Pride, C., Franck, M., Sigman, D., Sarmiento, J., Matsumoto, K., Gruber, N., Rau, R., Coale, K., 2002. A switch from Si(OH) 4 to NO3- depletion in the glacial Southern Ocean. Geophysical Research Letters 29, 5]. To test this hypothesis, we reconstruct biogenic fluxes of CaCO 3, orgC and Si for three equatorial Pacific cores. We find evidence that a floral shift from a SiO 2-based community to a CaCO 3-based occurred, starting in mid-marine isotope stage (MIS) 3 (24-59 cal. ka) and declining toward MIS 2 (19-24 cal. ka). This could reflect the connection of the Peru upwelling system to the subantarctic region, and we postulate that excess silica was transported from the subantarctic via the deep Equatorial Undercurrent to the eastern equatorial Pacific. In the eastern equatorial Pacific only, we document a significant decrease in rain ratio starting mid-MIS 3 toward MIS 2. This decrease is concomitant with a significant decrease in silica accumulation rates at the seabed. This pattern is not observed in the Pacific influenced by equatorial divergence and shallow upwelling, where all reconstructed fluxes (CaCO 3, orgC, and opal) increase during MIS 2. We conclude that the overall calcium carbonate pump weakened in the EEP under Peru upwelling influence.

  8. Dynamics above a dense equatorial rain forest from the surface boundary layer to the free atmosphere

    NASA Astrophysics Data System (ADS)

    Lyra, R.; Druilhet, A.; Benech, B.; Biona, C. Bouka

    1992-08-01

    During the Dynamique et Chimie de l'Atmosphère en Forêt Equatoriale (DECAFE) campaign, dynamical and thermodynamical measurements were made at Impfondo (1°37'N, 18°04'W), over the dense rain forest of northern Congo during the dry season (February 1988). During the measurement period the experimental site was located south of the intertropical convergence zone ground track which manages the dynamics of the large scale. Above the experimental site, the atmospheric low layers are supplied by monsoon air coming from the Guinean gulf; the upper layers (>1500 m) are supplied by warm and dry air (trade winds) coming from the northern desert region and the savanna. Our experimental approach consists of analyzing the heat and moisture content in the low troposphere from vertical soundings made by a tethered balloon (0-400 m) and an aircraft (0-4000 m). The analysis of the evolution of the observed planetary boundary layer (PBL) is made with a mixed layer one-dimensional model which is forced to represent correctly the observed PBL height growth. The simulated and observed budgets of the heat and moisture in the PBL are balanced by adding dry air to the simulated PBL in the afternoon. This drying out can be maintained only by high levels of entrainment flux at the PBL top. An entrainment velocity of 3 cm s-1 enables the balancing of the moisture budget. This entrainment velocity seems compatible with physicochemical transfers as those of methane and ozone.

  9. Potential Predictability of the Sea-Surface Temperature Forced Equatorial East Africa Short Rains Interannual Variability in the 20th Century

    NASA Astrophysics Data System (ADS)

    Bahaga, T. K.; Gizaw, G.; Kucharski, F.; Diro, G. T.

    2014-12-01

    In this article, the predictability of the 20th century sea-surface temperature (SST) forced East African short rains variability is analyzed using observational data and ensembles of long atmospheric general circulation model (AGCM) simulations. To our knowledge, such an analysis for the whole 20th century using a series of AGCM ensemble simulations is carried out here for the first time. The physical mechanisms that govern the influence of SST on East African short rains in the model are also investigated. It is found that there is substantial skill in reproducing the East African short rains variability, given that the SSTs are known. Consistent with previous recent studies, it is found that the Indian Ocean and in particular the western pole of the Indian Ocean dipole (IOD) play a dominant role for the prediction skill, whereas SSTs outside the Indian Ocean play a minor role. The physical mechanism for the influence of the western Indian Ocean on East African rainfall in the model is consistent with previous findings and consists of a gill-type response to a warm (cold) anomaly that induces a westerly(easterly) low-level flow anomaly over equatorial Africa and leads to moisture flux convergence (divergence) over East Africa. On the other hand, a positive El Nino-Southern Oscillation (ENSO) anomaly leads to a spatially non-coherent reducing effect over parts of East Africa, but the relationship is not strong enough to provide any predictive skill in our model. The East African short rains prediction skill is also analyzed within a model-derived potential predictability framework and it is shown that the actual prediction skill is broadly consistent with the model potential prediction skill. Low-frequency variations of the prediction skill are mostly related to SSTs outside the Indian Ocean region and are likely due to an increased interference of ENSO with the Indian Ocean influence on East African short rains after the mid-1970s climate shift.

  10. Eocene monsoons

    NASA Astrophysics Data System (ADS)

    Huber, Matthew; Goldner, Aaron

    2012-01-01

    A prominent example of climate-tectonic coupling is the Asian monsoon and the uplift of the Tibetan Plateau. Here we review some of what is known about the history of the monsoon, within a global context and present results from fully coupled Eocene simulations in which Tibetan Plateau height is varied. Peak elevations were doubled from 2000 m to 4000 m whereas mean elevations increased from 750 to 1500 m. The fully coupled Eocene simulations show that introducing a higher Tibetan Plateau into Asian topography intensifies rainfall over southwest Asia, but induces drying over and behind the Plateau. This atmospheric response is controlled by increases in heating over the Plateau region which drives increases in moisture convergence inducing shifts in lower level atmospheric moisture flux. With Eocene boundary conditions aspects of the canonical response from prior work remain the same: cooling over the uplifted region, a large stationary wave response emanating from the plateau and extending into North America, and a large increase in precipitation in summer in the regions with strongest relief, with a rain shadow behind it. But some important local responses are different from similar studies with modern boundary conditions, such as a warming behind the uplifted mountains, and southward advection of warm, moist air from Paratethys onto the Plateau. These results demonstrate that simulations with fully interactive ocean-atmosphere coupled models with a realistic history of paleogeographic boundary conditions will increase the realism of the resulting climatic simulations and increase the body of available proxy evidence for comparison. More generally we find that a global monsoon distribution of precipitation exists in the Eocene regardless of Tibetan Plateau height. Changing Plateau height has minor global impacts, which include a slight drying of midlatitude and cooling of the North Pacific. The results are robust to changes in climate model resolution and

  11. Response of CO2 and H2O fluxes of a mountainous tropical rain forest in equatorial Indonesia to El Niño events

    NASA Astrophysics Data System (ADS)

    Olchev, A.; Ibrom, A.; Panferov, O.; Gushchina, D.; Propastin, P.; Kreilein, H.; June, T.; Rauf, A.; Gravenhorst, G.; Knohl, A.

    2015-03-01

    The possible impact of El Niño-Southern Oscillation (ENSO) events on the main components of CO2 and H2O fluxes in a pristine mountainous tropical rainforest growing in Central Sulawesi in Indonesia is described. The fluxes were continuously measured using the eddy covariance method for the period from January 2004 to June 2008. During this period, two episodes of El Niño and one episode of La Niña were observed. All these ENSO episodes had moderate intensity and were of Central Pacific type. The temporal variability analysis of the main meteorological parameters and components of CO2 and H2O exchange showed a very high sensitivity of Evapotranspiration (ET) and Gross Primary Production (GPP) of the tropical rain forest to meteorological variations caused by both El Niño and La Niña episodes. Incoming solar radiation is the main governing factor that is responsible for ET and GPP variability. Ecosystem Respiration (RE) dynamics depend mainly on the air temperature changes and are almost insensitive to ENSO. Changes of precipitation due to moderate ENSO events did not cause any notable effect on ET and GPP, mainly because of sufficient soil moisture conditions even in periods of anomalous reduction of precipitation in the region.

  12. After the Rain: Rain.

    ERIC Educational Resources Information Center

    Old Elk, Arlene; Stoklas, Jackie

    The Heard Museum (Phoenix, Arizona) has developed and updated an integrated curriculum for use in grades K-3. The goals for this curriculum are to: (1) share museum resources with schools; (2) promote cross-cultural understanding through a focus on rain, a universal requirement for life; (3) help students understand that Native Americans are…

  13. Equatorial Guinea.

    PubMed

    1984-06-01

    Attention in this discussion of Equatorial Guinea is directed to the following: the people, history, geography, government, political conditions, the economy, foreign relations, and relations between the US and Equatorial Guinea. The population was estimated at 304,000 in 1983 and the annual growth rate was estimated in the range of 1.7-2.5. The infant mortality rate is 142.9/1000 with a life expectancy of 44.4 years for males and 47.6 years for females. The majority of the Equatoguinean people are of Bantu origin. The largest tribe, the Fang, is indigenous to the mainland, although many now also live on Bioko Island. Portuguese explorers found the island of Bioko in 1471, and the Portuguese retained control until 1778, when the island, adjacent islets, and the commercial rights to the mainland between the Niger and Ogooue Rivers were ceded to Spain. Spain lacked the wealth and the interest to develop an extensive economic infrastructure in Equatorial Guinea during the 1st half of this century, but the Spanish did help Equatorial Guinea achieve 1 of the highest literacy rates in Africa. They also founded a good network of health care facilities. In March 1968, under pressure from Guinean nationalists, Spain announced that it would grant independence to Equatorial Guinea as rapidly as possible. A referendum was held on August 11, 1968, and 63% of the electorate voted in favor of the constitution, which provided for a government with a general assembly and presidentially appointed judges in the Supreme Court. After the coup in August 1979, power was placed in the hands of a Supreme Military Council. A new constitution came into effect after a popular vote in August 1982, abolishing the Supreme Military Council. Under the terms of the constitution, the president was given extensive powers. By the end of 1983, a 60-member Chamber of Representatives of the people had been formed. The government, which is credited with restoring greater personal freedom, is regarded

  14. Radiolarian biostratigraphy of siliceous Eocene deposits in central California

    USGS Publications Warehouse

    Blueford, J.

    1988-01-01

    Abundant Eocene siliceous deposits in California are located in the San Joaquin and Sacramento valleys. The white shales to buff mudstones are characterized by radiolarians, diatoms, and silicoflagellates. Taxonomic descriptions and abundance data of key radiolarian species in existing monographs have limited biostratigraphic and paleoenvironmental interpretation. The California fauna is similar to faunas from the Norwegian Sea, Russian Platform, and southern oceans of Antarctica. Eocene faunas from the equatorial Pacific Ocean and Caribbean Sea differ considerably in diversity. In this study, the taxonomy and biostratigraphic information of species comprising more than 2% of the population are evaluated. Two radiolarian zones are erected for the middle Eocene of California, the Podocyrtis fasciata and Calocyclas semipolita Zones. Paleoenvironmental information suggests that some differences in the fauna may be environmentally controlled due to deposition in submarine canyons. -Authors

  15. Acid Rain.

    ERIC Educational Resources Information Center

    Openshaw, Peter

    1987-01-01

    Provides some background information on acid deposition. Includes a historical perspective, describes some effects of acid precipitation, and discusses acid rain in the United Kingdom. Contains several experiments that deal with the effects of acid rain on water quality and soil. (TW)

  16. Acid rain

    SciTech Connect

    Elsworth, S.

    1985-01-01

    This book was written in a concise and readable style for the lay public. It's purpose was to make the public aware of the damage caused by acid rain and to mobilize public opinion to favor the elimination of the causes of acid rain.

  17. Acid Rain

    MedlinePlus

    ... EPA Is Doing Acid Rain Program Cross-State Air Pollution Rule Progress Reports Educational Resources Kid's Site for ... Monitoring National Atmospheric Deposition Program (NADP) Exit Interstate Air Pollution Transport Contact Us to ask a question, provide ...

  18. Acid Rain

    USGS Publications Warehouse

    Bricker, Owen P.; Rice, Karen C.

    1995-01-01

    Although acid rain is fading as a political issue in the United States and funds for research in this area have largely disappeared, the acidity of rain in the Eastern United States has not changed significantly over the last decade, and it continues to be a serious environmental problem. Acid deposition (commonly called acid rain) is a term applied to all forms of atmospheric deposition of acidic substances - rain, snow, fog, acidic dry particulates, aerosols, and acid-forming gases. Water in the atmosphere reacts with certain atmospheric gases to become acidic. For example, water reacts with carbon dioxide in the atmosphere to produce a solution with a pH of about 5.6. Gases that produce acids in the presence of water in the atmosphere include carbon dioxide (which converts to carbonic acid), oxides of sulfur and nitrogen (which convert to sulfuric and nitric acids}, and hydrogen chloride (which converts to hydrochloric acid). These acid-producing gases are released to the atmosphere through natural processes, such as volcanic emissions, lightning, forest fires, and decay of organic matter. Accordingly, precipitation is slightly acidic, with a pH of 5.0 to 5.7 even in undeveloped areas. In industrialized areas, most of the acid-producing gases are released to the atmosphere from burning fossil fuels. Major emitters of acid-producing gases include power plants, industrial operations, and motor vehicles. Acid-producing gases can be transported through the atmosphere for hundreds of miles before being converted to acids and deposited as acid rain. Because acids tend to build up in the atmosphere between storms, the most acidic rain falls at the beginning of a storm, and as the rain continues, the acids "wash out" of the atmosphere.

  19. The effect of subtropical aerosol loading on equatorial precipitation

    NASA Astrophysics Data System (ADS)

    Dagan, G.; Chemke, R.

    2016-10-01

    Cloud-aerosol interactions are considered as one of the largest sources of uncertainties in the study of climate change. Here another possible cloud-aerosol effect on climate is proposed. A series of large eddy simulations (LES) with bin microphysics reveal a sensitivity of the total atmospheric water vapor amount to aerosol concentration. Under polluted conditions the rain is suppressed and the total amount of water vapor in the atmosphere increases with time compared to clean precipitating conditions. Theoretical examination of this aerosol effect on water vapor transport from the subtropics to the tropics, and hence on the equatorial rain and Hadley circulation, is conducted using an idealized general circulation model (GCM). It is shown that a reduction in the subtropical rain amount results in increased water vapor advection to the tropics and enhanced equatorial rain and Hadley circulation. This joins previously proposed mechanisms on the radiative aerosol effect on the general circulation.

  20. Aerosol Transport Over Equatorial Africa

    NASA Technical Reports Server (NTRS)

    Gatebe, C. K.; Tyson, P. D.; Annegarn, H. J.; Kinyua, A. M.; Piketh, S.; King, M.; Helas, G.

    1999-01-01

    Long-range and inter-hemispheric transport of atmospheric aerosols over equatorial Africa has received little attention so far. Most aerosol studies in the region have focussed on emissions from rain forest and savanna (both natural and biomass burning) and were carried out in the framework of programs such as DECAFE (Dynamique et Chimie Atmospherique en Foret Equatoriale) and FOS (Fires of Savanna). Considering the importance of this topic, aerosols samples were measured in different seasons at 4420 meters on Mt Kenya and on the equator. The study is based on continuous aerosol sampling on a two stage (fine and coarse) streaker sampler and elemental analysis by Particle Induced X-ray Emission. Continuous samples were collected for two seasons coinciding with late austral winter and early austral spring of 1997 and austral summer of 1998. Source area identification is by trajectory analysis and sources types by statistical techniques. Major meridional transports of material are observed with fine-fraction silicon (31 to 68 %) in aeolian dust and anthropogenic sulfur (9 to 18 %) being the major constituents of the total aerosol loading for the two seasons. Marine aerosol chlorine (4 to 6 %), potassium (3 to 5 %) and iron (1 to 2 %) make up the important components of the total material transport over Kenya. Minimum sulfur fluxes are associated with recirculation of sulfur-free air over equatorial Africa, while maximum sulfur concentrations are observed following passage over the industrial heartland of South Africa or transport over the Zambian/Congo Copperbelt. Chlorine is advected from the ocean and is accompanied by aeolian dust recirculating back to land from mid-oceanic regions. Biomass burning products are transported from the horn of Africa. Mineral dust from the Sahara is transported towards the Far East and then transported back within equatorial easterlies to Mt Kenya. This was observed during austral summer and coincided with the dying phase of 1997/98 El

  1. Estimating rainfall in the tropics using the fractional time raining

    NASA Technical Reports Server (NTRS)

    Morrissey, Mark L.; Krajewski, Witold F.; Mcphaden, Michael J.

    1994-01-01

    The relationship between the fractional time raining and tropical rainfall amount is investigated using raingage data and a point process model of tropical rainfall. Both the strength and the nature of the relationship are dependent upon the resolution of the data used to estimate the fractional time raining. It is found that highly accurate estimates of rainfall amounts over periods of one month or greater can be obtained from the fractional time raining so long as high-time-resolution data are used. It is demonstrated that the relationship between the fractional time raining and monthly atoll rainfall is quasi-homogeneous within the monsoon trough region of the equatorial western Pacific.

  2. Acid Rain

    USGS Publications Warehouse

    Bricker, Owen P.; Rice, Karen C.

    1993-01-01

    Acid deposition, or acid rain as it is more commonly referred to, has become a widely publicized environmental issue in the U.S. over the past decade. The term usually conjures up images of fish kills, dying forests, "dead" lakes, and damage to monuments and other historic artifacts. The primary cause of acid deposition is emission of S02 and NOx to the atmosphere during the combustion of fossil fuels. Oxidation of these compounds in the atmosphere forms strong acids - H2SO4 and HNO3 - which are returned to the Earth in rain, snow, fog, cloud water, and as dry deposition.Although acid deposition has only recently been recognized as an environmental problem in the U.S., it is not a new phenomenon (Cogbill & Likens 1974). As early as the middle of the 17th century in England, the deleterious effects of industrial emissions on plants, animals, and humans, and the atmospheric transport of pollutants between England and France had become issues of concern (Evelyn 1661, Graunt 1662). It is interesting that well over three hundred years ago in England, recommendations were made to move industry outside of towns and build higher chimneys to spread the pollution into "distant parts." Increasing the height of smokestacks has helped alleviate local problems, but has exacerbated others. In the U.S. the height of the tallest smokestack has more than doubled, and the average height of smokestacks has tripled since the 1950s (Patrick et al 1981). This trend occurred in most industrialized nations during the 20th century and has had the effect of transforming acid rain from a local urban problem into a problem of global scale.

  3. Acid Rain

    USGS Publications Warehouse

    Bricker, Owen P.; Rice, Karen C.; Dietrich, W.E.; Sposito, Garrison

    1997-01-01

    Acid deposition, or acid rain as it is more commonly referred to, has become a widely publicized environmental issue in the U.S. over the past decade. The term usually conjures up images of fish kills, dying forests, "dead" lakes, and damage to monuments and other historic artifacts. The primary cause of acid deposition is emission of S02 and NOx to the atmosphere during the combustion of fossil fuels. Oxidation of these compounds in the atmosphere forms strong acids - H2SO4 and HNO3 - which are returned to the Earth in rain, snow, fog, cloud water, and as dry deposition.Although acid deposition has only recently been recognized as an environmental problem in the U.S., it is not a new phenomenon (Cogbill & Likens 1974). As early as the middle of the 17th century in England, the deleterious effects of industrial emissions on plants, animals, and humans, and the atmospheric transport of pollutants between England and France had become issues of concern (Evelyn 1661, Graunt 1662). It is interesting that well over three hundred years ago in England, recommendations were made to move industry outside of towns and build higher chimneys to spread the pollution into "distant parts." Increasing the height of smokestacks has helped alleviate local problems, but has exacerbated others. In the U.S. the height of the tallest smokestack has more than doubled, and the average height of smokestacks has tripled since the 1950s (Patrick et al 1981). This trend occurred in most industrialized nations during the 20th century and has had the effect of transforming acid rain from a local urban problem into a problem of global scale.

  4. Eocene cooling linked to early flow across the Tasmanian Gateway.

    PubMed

    Bijl, Peter K; Bendle, James A P; Bohaty, Steven M; Pross, Jörg; Schouten, Stefan; Tauxe, Lisa; Stickley, Catherine E; McKay, Robert M; Röhl, Ursula; Olney, Matthew; Sluijs, Appy; Escutia, Carlota; Brinkhuis, Henk

    2013-06-11

    The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52-50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ~49-50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2-4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.

  5. Eocene cooling linked to early flow across the Tasmanian Gateway

    PubMed Central

    Bijl, Peter K.; Bendle, James A. P.; Bohaty, Steven M.; Pross, Jörg; Schouten, Stefan; Tauxe, Lisa; Stickley, Catherine E.; McKay, Robert M.; Röhl, Ursula; Olney, Matthew; Sluijs, Appy; Escutia, Carlota; Brinkhuis, Henk; Klaus, Adam; Fehr, Annick; Williams, Trevor; Carr, Stephanie A.; Dunbar, Robert B.; Gonzàlez, Jhon J.; Hayden, Travis G.; Iwai, Masao; Jimenez-Espejo, Francisco J.; Katsuki, Kota; Kong, Gee Soo; Nakai, Mutsumi; Passchier, Sandra; Pekar, Stephen F.; Riesselman, Christina; Sakai, Toyosaburo; Shrivastava, Prakash K.; Sugisaki, Saiko; Tuo, Shouting; van de Flierdt, Tina; Welsh, Kevin; Yamane, Masako

    2013-01-01

    The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52–50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ∼49–50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2–4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling. PMID:23720311

  6. Acid rain

    SciTech Connect

    Not Available

    1984-06-01

    An overview is presented of acid rain and the problems it causes to the environment worldwide. The acidification of lakes and streams is having a dramatic effect on aquatic life. Aluminum, present in virtually all forest soils, leaches out readily under acid conditions and interferes with the gills of all fish, some more seriously than others. There is evidence of major damage to forests in European countries. In the US, the most severe forest damage appears to be in New England, New York's Adirondacks, and the central Appalachians. This small region is part of a larger area of the Northeast and Canada that appears to have more acid rainfall than the rest of the country. It is downwind from major coal burning states, which produce about one quarter of US SO/sub 2/ emissions and one sixth of nitrogen oxide emissions. Uncertainties exist over the causes of forest damage and more research is needed before advocating expensive programs to reduce rain acidity. The President's current budget seeks an expansion of research funds from the current $30 million per year to $120 million.

  7. Acid rain

    SciTech Connect

    Boyle, R.H.; Boyle, R.A.

    1983-01-01

    Acid rain, says Boyle is a chemical leprosy eating into the face of North America and Europe, perhaps the major ecological problem of our time. Boyle describes the causes and scope of the phenomenon; the effects on man, wildlife, water, and our cultural heritage. He probes the delays of politicians and the frequent self-serving arguments advanced by industry in the face of what scientists have proved. The solutions he offers are to strengthen the Clean Air Act and require emission reductions that can be accomplished by establishing emission standards on a regional or bubble basis, burn low-sulfur coal, install scrubbers at critical plants, and invest in alternative energy sources. 73 references, 1 figure.

  8. Acid rain

    SciTech Connect

    Sweet, W.

    1980-06-20

    Acid precipitation includes not only rain but also acidified snow, hail and frost, as well as sulfur and nitrogen dust. The principal source of acid precipitation is pollution emitted by power plants and smelters. Sulfur and nitrogen compounds contained in the emissions combine with moisture to form droplets with a high acid content - sometimes as acidic as vinegar. When sufficiently concentrated, these acids can kill fish and damage material structures. Under certain circumstances they may reduce crop and forest yields and cause or aggravate respiratory diseases in humans. During the summer, especially, pollutants tend to collect over the Great Lakes in high pressure systems. Since winds typically are westerly and rotate clockwise around high pressure systems, the pollutants gradually are dispersed throughout the eastern part of the continent.

  9. Soak Up the Rain

    EPA Pesticide Factsheets

    Soak Up the Rain promotes green infrastructure practices such as rain barrels, rain gardens, permeable pavements and green roofs to reduce stormwater runoff and prevent water pollution while bringing about a broad range of community benefits.

  10. Equatorial convergence of India and early Cenozoic climate trends

    PubMed Central

    Kent, Dennis V.; Muttoni, Giovanni

    2008-01-01

    India's northward flight and collision with Asia was a major driver of global tectonics in the Cenozoic and, we argue, of atmospheric CO2 concentration (pCO2) and thus global climate. Subduction of Tethyan oceanic crust with a carpet of carbonate-rich pelagic sediments deposited during transit beneath the high-productivity equatorial belt resulted in a component flux of CO2 delivery to the atmosphere capable to maintain high pCO2 levels and warm climate conditions until the decarbonation factory shut down with the collision of Greater India with Asia at the Early Eocene climatic optimum at ≈50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO2 by efficient silicate weathering further perturbed the delicate equilibrium between CO2 input to and removal from the atmosphere toward progressively lower pCO2 levels, thus marking the onset of a cooling trend over the Middle and Late Eocene that some suggest triggered the rapid expansion of Antarctic ice sheets at around the Eocene-Oligocene boundary. PMID:18809910

  11. Equatorial convergence of India and early Cenozoic climate trends.

    PubMed

    Kent, Dennis V; Muttoni, Giovanni

    2008-10-21

    India's northward flight and collision with Asia was a major driver of global tectonics in the Cenozoic and, we argue, of atmospheric CO(2) concentration (pCO(2)) and thus global climate. Subduction of Tethyan oceanic crust with a carpet of carbonate-rich pelagic sediments deposited during transit beneath the high-productivity equatorial belt resulted in a component flux of CO(2) delivery to the atmosphere capable to maintain high pCO(2) levels and warm climate conditions until the decarbonation factory shut down with the collision of Greater India with Asia at the Early Eocene climatic optimum at approximately 50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO(2) by efficient silicate weathering further perturbed the delicate equilibrium between CO(2) input to and removal from the atmosphere toward progressively lower pCO(2) levels, thus marking the onset of a cooling trend over the Middle and Late Eocene that some suggest triggered the rapid expansion of Antarctic ice sheets at around the Eocene-Oligocene boundary.

  12. Extreme Seasonality During Early Eocene Hyperthermals

    NASA Astrophysics Data System (ADS)

    Plink-Bjorklund, P.; Birgenheier, L.

    2012-12-01

    intensification is seen as short intense rain seasons alternating with prolonged droughts. Such seasonality intensification had a profound effect on landscape morphology as well as on vegetation. River systems changed from braided streams to highly seasonal fluvial megafans with tens of meters deep channels. River channels staid dry through most of the prolonged droughts, as witnessed by intra-channel insect burrows and paleosols. The intense wet seasons caused extremely high water discharge in channels, resulting in high rates of erosion, sediment transport and deposition. As a result, the channels were filled locally by up to 10s of meters of sediment, causing rapid river course changes and terrestrial flooding. Particulate organic matter content is extremely low in these sediments. This is in contrast to river sediments that were deposited during less intense seasonality. The dataset was compared to other datasets from intermontane basins in the Western Interior and also Europe (Spain), where similar seasonality changes are indicated to have occurred during the PETM. This is in great contrast to intermontane Early Eocene river systems documented in Norwegian Arctic (e.g. Spitsbergen) and in tropics (e.g. Venezuela), where no seasonality intensification has been documented. Thus the seasonality intensification seems to have been confined to (northern) mid-latitudes and subtropics.

  13. Optical Rain Gauge Performance: Second Workshop on Optical Rain Gauge Measurements

    NASA Technical Reports Server (NTRS)

    Short, David A. (Editor); Thiele, Otto W. (Editor); Mcphaden, Michael J. (Editor)

    1994-01-01

    The primary focus of the workshop was on the performance and reliability of STi mini-Optical Rain Gauges in a number of environments, including deployments on ships and buoys in the western equatorial Pacific Ocean during the TOGA/COARE field experiment, deployments on buoys in U.S. coastal waters, and comparisons with other types of rain gauges on the Virginia coast and in Florida. The workshop was attended by 20 investigators, representing 10 different institutions, who gathered to present new results obtained since the first workshop (April 1993), to discuss problems, to consider solutions, and to chart future directions. Post-TOGA/COARE calibration studies were also presented.

  14. Quasar Rain

    NASA Astrophysics Data System (ADS)

    Elvis, Martin

    2015-01-01

    Velocity resolved reverberation mapping (VRRM) has shown clear evidence for inflows in the broad emission line (BEL) region of active galactic nuclei: redshifted BELs at zero lag (AGNs, e.g. Arp 151, Bentz et al. 2010; Grier et al. 2013). While radiative transfer in rotating disks can give shorter red side lags than blue, a zero lag has to be along our line of sight, so it is hard to escape infall. The BEL region is normally considered to be rotating or in outflow so this result is a surprise. Infalling BEL gas cannot fall far without the need to lose angular momentum for accreting gas producing an accretion disk.I suggest that quasar continuum irradiation induced cooling instabilities (Chakravorty et al 2009; Krolik, McKee & Tarter 1981) lead to dense BEL clouds condensing out of the semi-ubiquitous warm absorber (WA) outflows found in AGNs and that these clouds may produce a VRRM inflow signature.Unlike WA gas, dense high column density BEL clouds are hard to accelerate with radiation pressure (Risaliti & Elvis 2010; Mushotzky, Solomon & Strittmatter 1972). BEL clouds will thus stall in the outflow and begin to fall back toward the central black hole after a dynamical time, 'raining out' of the WA medium. If these BEL clouds condense out before these outflows reach escape velocity [v(esc)] then this inflow can potentially produce the observed VRRM signature. As the clouds fall back in they will be moving on elliptical orbits supersonically through the WA gas with Mach number ~(2000 km/s)/(100km/s) ~20. This will produce comet-like structures with narrow opening angles, as seen in asymmetric X-ray absorbing 'eclipses' (Maiolino et al. 2010). They will survive only a few months, as required to avoid forming a disk. For this picture to work the condensation time must be less than the acceleration time to v(esc) and the destruction time must be longer than the dynamical time.

  15. Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic

    NASA Astrophysics Data System (ADS)

    Tremblin, Maxime; Hermoso, Michaël; Minoletti, Fabrice

    2016-10-01

    Growth of the first permanent Antarctic ice sheets at the Eocene-Oligocene Transition (EOT), ˜33.7 million years ago, indicates a major climate shift within long-term Cenozoic cooling. The driving mechanisms that set the stage for this glaciation event are not well constrained, however, owing to large uncertainties in temperature reconstructions during the Eocene, especially at lower latitudes. To address this deficiency, we used recent developments in coccolith biogeochemistry to reconstruct equatorial Atlantic sea surface temperature (SST) and atmospheric pCO2 values from pelagic sequences preceding and spanning the EOT. We found significantly more variability in equatorial SSTs than previously reported, with pronounced cooling from the Early to Middle Eocene and subsequent warming during the Late Eocene. Thus, we show that the Antarctic glaciation at the Eocene-Oligocene boundary was preceded by a period of heat accumulation in the low latitudes, likely focused in a progressively contracting South Atlantic gyre, which contributed to cooling high-latitude austral regions. This prominent redistribution of heat corresponds to the emplacement of a strong meridional temperature gradient that typifies icehouse climate conditions. Our equatorial coccolith-derived geochemical record thus highlights an important period of global climatic and oceanic upheaval, which began 4 million years before the EOT and, superimposed on a long-term pCO2 decline, drove the Earth system toward a glacial tipping point in the Cenozoic.

  16. Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic.

    PubMed

    Tremblin, Maxime; Hermoso, Michaël; Minoletti, Fabrice

    2016-10-18

    Growth of the first permanent Antarctic ice sheets at the Eocene-Oligocene Transition (EOT), ∼33.7 million years ago, indicates a major climate shift within long-term Cenozoic cooling. The driving mechanisms that set the stage for this glaciation event are not well constrained, however, owing to large uncertainties in temperature reconstructions during the Eocene, especially at lower latitudes. To address this deficiency, we used recent developments in coccolith biogeochemistry to reconstruct equatorial Atlantic sea surface temperature (SST) and atmospheric pCO2 values from pelagic sequences preceding and spanning the EOT. We found significantly more variability in equatorial SSTs than previously reported, with pronounced cooling from the Early to Middle Eocene and subsequent warming during the Late Eocene. Thus, we show that the Antarctic glaciation at the Eocene-Oligocene boundary was preceded by a period of heat accumulation in the low latitudes, likely focused in a progressively contracting South Atlantic gyre, which contributed to cooling high-latitude austral regions. This prominent redistribution of heat corresponds to the emplacement of a strong meridional temperature gradient that typifies icehouse climate conditions. Our equatorial coccolith-derived geochemical record thus highlights an important period of global climatic and oceanic upheaval, which began 4 million years before the EOT and, superimposed on a long-term pCO2 decline, drove the Earth system toward a glacial tipping point in the Cenozoic.

  17. Arctic Climate during Eocene Hyperthermals: Wet Summers on Ellesmere Island?

    NASA Astrophysics Data System (ADS)

    Greenwood, D. R.; West, C. K.; Basinger, J. F.

    2012-12-01

    Previous work has shown that during the late Paleocene to middle Eocene, mesothermal conditions (i.e., MAT ~12-15° C) and high precipitation (MAP > 150cm/yr) characterized Arctic climates - an Arctic rain forest. Recent analyses of Arctic Eocene wood stable isotope chemistry are consistent with the annual and seasonal temperature estimates from leaf physiognomy and nearest living relative analogy from fossil plants, including the lack of freezing winters, but is interpreted as showing that there was a summer peak in precipitation - modern analogs are best sought on the summer-wet east coasts (e.g., China, Japan, South Korea) not the winter-wet west coasts of present-day northern temperate continents (e.g., Pacific northwest of North America). Highly seasonal 'monsoon-type' summer-wet precipitation regimes (i.e., summer precip./winter precip. > 3.0) seem to characterize Eocene hyperthermal conditions in several regions of the earth, including the Arctic and Antarctic, based on both climate model sensitivity experiments and the paleoclimate proxy evidence. The leaf physiognomy proxy previously applied to estimate Arctic Paleogene precipitation was leaf area analysis (LAA), a correlation between mean leaf size in woody dicot vegetation and annual precipitation. New data from modern monsoonal sites, however demonstrates that for deciduous-dicot dominated vegetation, summer precipitation determines mean leaf size, not annual totals, and therefore that under markedly seasonal precipitation and/or light regimes that summer precipitation is being estimated using LAA. Presented here is a new analysis of a leaf macrofloras from 3 separate florules of the Margaret Formation (Split Lake, Stenkul Fiord and Strathcona Fiord) from Ellesmere Island that are placed stratigraphically as early Eocene, and likely fall within Eocene thermal maximum 1 (ETM1; = the 'PETM') or ETM2. These floras are each characterized by a mix of large-leafed and small-leafed dicot taxa, with overall

  18. Understanding Acid Rain

    ERIC Educational Resources Information Center

    Damonte, Kathleen

    2004-01-01

    The term acid rain describes rain, snow, or fog that is more acidic than normal precipitation. To understand what acid rain is, it is first necessary to know what an acid is. Acids can be defined as substances that produce hydrogen ions (H+), when dissolved in water. Scientists indicate how acidic a substance is by a set of numbers called the pH…

  19. The Acid Rain Reader.

    ERIC Educational Resources Information Center

    Stubbs, Harriett S.; And Others

    A topic which is often not sufficiently dealt with in elementary school textbooks is acid rain. This student text is designed to supplement classroom materials on the topic. Discussed are: (1) "Rain"; (2) "Water Cycle"; (3) "Fossil Fuels"; (4) "Air Pollution"; (5) "Superstacks"; (6) "Acid/Neutral/Bases"; (7) "pH Scale"; (8) "Acid Rain"; (9)…

  20. No Rain, No Gain

    ERIC Educational Resources Information Center

    Perna, Mark C.

    2005-01-01

    Marketing is like the rain. Some people are quickly aware of it, while others take repeated and consistent drops for quite an extended period of time before they take action. Building on the marketing principles discussed in previous issues, the next key principle to smart marketing is the "Rain Effect." The Rain Effect is the use of consistent…

  1. Acid Rain Study Guide.

    ERIC Educational Resources Information Center

    Hunger, Carolyn; And Others

    Acid rain is a complex, worldwide environmental problem. This study guide is intended to aid teachers of grades 4-12 to help their students understand what acid rain is, why it is a problem, and what possible solutions exist. The document contains specific sections on: (1) the various terms used in conjunction with acid rain (such as acid…

  2. The Children's Rain Forest.

    ERIC Educational Resources Information Center

    Thornton, Carol A.; And Others

    1995-01-01

    Describes a unit on rain forests in which first graders studied about rain forests, built a classroom rain forest, and created a bulletin board. They also graphed rainfall, estimated body water, and estimated the number of newspapers that could be produced from one canopy tree. (MKR)

  3. Rain Gauges Handbook

    SciTech Connect

    Bartholomew, M. J.

    2016-01-01

    To improve the quantitative description of precipitation processes in climate models, the Atmospheric Radiation Measurement (ARM) Climate Research Facility deployed rain gauges located near disdrometers (DISD and VDIS data streams). This handbook deals specifically with the rain gauges that make the observations for the RAIN data stream. Other precipitation observations are made by the surface meteorology instrument suite (i.e., MET data stream).

  4. Study of equatorial scintillations

    NASA Technical Reports Server (NTRS)

    Pomalaza, J.; Woodman, R.; Tisnado, G.; Nakasone, E.

    1972-01-01

    Observations of the amplitude scintillations produced by the F-region in equatorial areas are presented. The equipment used for conducting the observations is described. The use of transmissions from the ATS-1, ATS-3, and ATS-5 for obtaining data is described. The two principal subjects discussed are: (1) correlation between satellite and incoherent radar observations of scintillations and (2) simultaneous observations of scintillations at 136 MHz and 1550 MHz.

  5. Integrated bio-magnetostratigraphy of ODP Site 709 (equatorial Indian Ocean).

    NASA Astrophysics Data System (ADS)

    Villa, Giuliana; Fioroni, Chiara; Florindo, Fabio

    2015-04-01

    Over the last decade, calcareous nannofossil biostratigraphy of the lower Eocene-Oligocene sediments has shown great potential, through identification of several new nannofossil species and bioevents (e.g. Fornaciari et al., 2010; Bown and Dunkley Jones, 2012; Toffanin et al., 2013). These studies formed the basis for higher biostratigraphic resolution leading to definition of a new nannofossil biozonation (Agnini et al., 2014). In this study, we investigate the middle Eocene-lower Oligocene sediments from ODP Hole 709C (ODP Leg 115) by means of calcareous nannofossils and magnetostratigraphy. Ocean Drilling Program (ODP) Site 709 was located in the equatorial Indian Ocean and biostratigraphy has been investigated in the nineties (Okada, 1990; Fornaciari et al., 1990) while paleomagnetic data from the Initial Report provided only a poorly constrained magnetostratigraphic interpretation, thus the cored succession was dated only by means of biostratigraphy. Our goal is to test the reliability in the Indian Ocean of the biohorizons recently identified at Site 711 (Fioroni et al., in press), by means of high resolution sampling, new taxonomic updates, quantitative analyses on calcareous nannofossils allowed to increase the number of useful bioevents and to compare their reliability and synchroneity. The new magnetostratigraphic analyses and integrated stratigraphy allow also to achieve an accurate biochronology of the time interval spanning Chrons C20 (middle Eocene) and C12 (early Oligocene). In addition, this equatorial site represents an opportunity to study the carbonate accumulation history and the large fluctuations of the carbonate compensation depth (CCD) during the Eocene (e.g. Pälike et al., 2012). The investigated interval encompasses the Middle Eocene Climatic Optimum (MECO), and the long cooling trend that leads to the Oligocene glacial state. By means of our new bio-magnetostratigraphic data and paleoecological results we provide further insights on

  6. Orbitally tuned timescale and astronomical forcing in the middle Eocene to early Oligocene

    NASA Astrophysics Data System (ADS)

    Westerhold, T.; Röhl, U.; Pälike, H.; Wilkens, R.; Wilson, P. A.; Acton, G.

    2014-05-01

    Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, a robust astronomically calibrated age model was constructed for the middle Eocene to early Oligocene interval (31-43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the middle Eocene climate optimum and the Eocene-Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new timescale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and 320-U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently orbital tuning of the records to the La2011 orbital solution was conducted. The resulting new timescale revises and refines the existing orbitally tuned age model and the geomagnetic polarity timescale from 31 to 43 Ma. The newly defined absolute age for the Eocene-Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano, Italy, global stratotype section and point. The compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during 2.4 myr eccentricity cycle minima around 35.5, 38.3, and 40.1 Ma.

  7. Orbitally tuned time scale and astronomical forcing in the middle Eocene to early Oligocene

    NASA Astrophysics Data System (ADS)

    Westerhold, T.; Röhl, U.; Pälike, H.; Wilkens, R.; Wilson, P. A.; Acton, G.

    2013-12-01

    Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, we construct a robust astronomically calibrated age model for the middle Eocene to early Oligocene interval (31-43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the Middle Eocene Climate Optimum and the Eocene/Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new time scale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and -U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently we applied orbital tuning of the records to the La2011 orbital solution. The resulting new time scale revises and refines the existing orbitally tuned age model and the Geomagnetic Polarity Time Scale from 31 to 43 Ma. Our newly defined absolute age for the Eocene/Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano (Italy) global stratotype section and point. Our compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during very long eccentricity cycle minima around 35.5, 38.3 and 40.1 Ma.

  8. ACTS Rain Fade Compensation

    NASA Technical Reports Server (NTRS)

    Coney, Thom A.

    1996-01-01

    Performance status of the Adaptive Rain Fade Compensation includes: (1) The rain fade protocol is functional detecting fades, providing an additional 10 dB of margin and seamless transitions to and from coded operation; (2) The stabilization of the link margins and the optimization of rain fade decision thresholds has resulted in improved BER performance; (3) Characterization of the fade compensation algorithm is ongoing.

  9. USGS Tracks Acid Rain

    USGS Publications Warehouse

    Gordon, John D.; Nilles, Mark A.; Schroder, LeRoy J.

    1995-01-01

    The U.S. Geological Survey (USGS) has been actively studying acid rain for the past 15 years. When scientists learned that acid rain could harm fish, fear of damage to our natural environment from acid rain concerned the American public. Research by USGS scientists and other groups began to show that the processes resulting in acid rain are very complex. Scientists were puzzled by the fact that in some cases it was difficult to demonstrate that the pollution from automobiles and factories was causing streams or lakes to become more acidic. Further experiments showed how the natural ability of many soils to neutralize acids would reduce the effects of acid rain in some locations--at least as long as the neutralizing ability lasted (Young, 1991). The USGS has played a key role in establishing and maintaining the only nationwide network of acid rain monitoring stations. This program is called the National Atmospheric Deposition Program/National Trends Network (NADP/NTN). Each week, at approximately 220 NADP/NTN sites across the country, rain and snow samples are collected for analysis. NADP/NTN site in Montana. The USGS supports about 72 of these sites. The information gained from monitoring the chemistry of our nation's rain and snow is important for testing the results of pollution control laws on acid rain.

  10. Modeling the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Stening, R. J.

    1985-02-01

    The equatorial electrojet is studied using a conductivity model with electron collision frequencies consistent with laboratory results. Electric fields and currents are calculated by an equivalent circuit method, and the results are compared with observations. Results are obtained for the electrojet height profile, the height and latitude of the cross-section profile, the height-integrated current density, the internal currents contribution, the scaling problem, the horizontal and vertical magnetic variation with latitude, and the effects of local winds in the F region.

  11. No extreme bipolar glaciation during the main Eocene calcite compensation shift.

    PubMed

    Edgar, Kirsty M; Wilson, Paul A; Sexton, Philip F; Suganuma, Yusuke

    2007-08-23

    Major ice sheets were permanently established on Antarctica approximately 34 million years ago, close to the Eocene/Oligocene boundary, at the same time as a permanent deepening of the calcite compensation depth in the world's oceans. Until recently, it was thought that Northern Hemisphere glaciation began much later, between 11 and 5 million years ago. This view has been challenged, however, by records of ice rafting at high northern latitudes during the Eocene epoch and by estimates of global ice volume that exceed the storage capacity of Antarctica at the same time as a temporary deepening of the calcite compensation depth approximately 41.6 million years ago. Here we test the hypothesis that large ice sheets were present in both hemispheres approximately 41.6 million years ago using marine sediment records of oxygen and carbon isotope values and of calcium carbonate content from the equatorial Atlantic Ocean. These records allow, at most, an ice budget that can easily be accommodated on Antarctica, indicating that large ice sheets were not present in the Northern Hemisphere. The records also reveal a brief interval shortly before the temporary deepening of the calcite compensation depth during which the calcite compensation depth shoaled, ocean temperatures increased and carbon isotope values decreased in the equatorial Atlantic. The nature of these changes around 41.6 million years ago implies common links, in terms of carbon cycling, with events at the Eocene/Oligocene boundary and with the 'hyperthermals' of the Early Eocene climate optimum. Our findings help to resolve the apparent discrepancy between the geological records of Northern Hemisphere glaciation and model results that indicate that the threshold for continental glaciation was crossed earlier in the Southern Hemisphere than in the Northern Hemisphere.

  12. What Is Acid Rain?

    ERIC Educational Resources Information Center

    Likens, Gene E.

    2004-01-01

    Acid rain is the collective term for any type of acidified precipitation: rain, snow, sleet, and hail, as well as the presence of acidifying gases, particles, cloud water, and fog in the atmosphere. The increased acidity, primarily from sulfuric and nitric acids, is generated as a by-product of the combustion of fossil fuels such as coal and oil.…

  13. Rain Forest Murals

    ERIC Educational Resources Information Center

    Kleiner, Cheryl

    2010-01-01

    The rain forest murals in the author's school began as a request from her principal to have students decorate the cafeteria with their own paintings. She decided to brainstorm ideas with her eighth-grade students. Taking into consideration the architectural space and the environmental concerns they wanted to convey, students chose the rain forest…

  14. Eocene prevalence of monsoon-like climate over eastern China reflected by hydrological dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Dehai; Lu, Shicong; Han, Shuang; Sun, Xiaoyan; Quan, Cheng

    2013-01-01

    Hydrological dynamics of sedimentary basins are essential for understanding regional climatic pattern in the geological past. In previous qualitative studies lithologically depending on the occurrence of featured sedimentary rocks, the Eocene climate of China had been subdivided into three latitudinal zones, with one subtropical high-controlled arid zone throughout middle China, and two humid zones respectively in the north and south. However, recent advances on mammalian fauna distribution, plant fossil-based quantitative paleoclimatic reconstruction, and modeling experiment jointly suggest that the relatively humid monsoonal climate might have prevailed over the territory. Here we examine and compare sedimentary sequences of 10 Eocene sections across eastern China, and hence the lake level fluctuations, to discuss the nature of climate type. Our results show that, instead of the categorically zonal pattern, the hydroclimate dynamics is intensified landward. This is demonstrated by the fact that, in contrast to the wide developed coal layers around the periphery, evaporites are growingly occurred endocentrically to the central part of middle China. However, although we have had assumed that all evaporites are indicator of extreme aridity, the highly oscillated climate in the central part of middle China was humid in the majority of the Eocene, distinct from permanent arid as seen in deserts or steppe along modern horse latitude. From the upcountry distribution pattern of the Eocene hydrological dynamics, it appears that the relatively dry climate in central China was caused by the impact of continentality or rain shadow effect under monsoonal, or monsoon-like climate.

  15. After the Rain: Using the Rain.

    ERIC Educational Resources Information Center

    Old Elk, Arlene; Stoklas, Jackie

    The Heard Museum (Phoenix, Arizona) has developed and updated an integrated curriculum for use in grades K-3. The goals for this curriculum are to: (1) share museum resources with schools; (2) promote cross-cultural understanding through a focus on rain, a universal requirement for life; (3) help students understand that Native Americans are…

  16. Equatorial MU Radar project

    NASA Astrophysics Data System (ADS)

    Yamamoto, Mamoru; Hashiguchi, H.; Tsuda, Toshitaka; Yamamoto, Masayuki

    Research Institute for Sustainable Humanosphere, Kyoto University (RISH) has been studying the atmosphere by using radars. The first big facility was the MU (Middle and Upper atmosphere) radar installed in Shiga, Japan in 1984. This is one of the most powerful and multi-functional radar, and is successful of revealing importance of atmospheric waves for the dynamical vertical coupling processes. The next big radar was the Equatorial Atmosphere Radar (EAR) installed at Kototabang, West Sumatra, Indonesia in 2001. The EAR was operated under close collaboration with LAPAN (Indonesia National Institute for Aeronautics and Space), and conducted the long-term continuous observations of the equatorial atmosphere/ionosphere for more than 10 years. The MU radar and the EAR are both utilized for inter-university and international collaborative research program for long time. National Institute for Polar Research (NIPR) joined EISCAT Scientific Association together with Nagoya University, and developed the PANSY radar at Syowa base in Antarctica as a joint project with University of Tokyo. These are the efforts of radar study of the atmosphere/ionosphere in the polar region. Now we can find that Japan holds a global network of big atmospheric/ionospheric radars. The EAR has the limitation of lower sensitivity compared with the other big radars shown above. RISH now proposes a plan of Equatorial MU Radar (EMU) that is to establish the MU-radar class radar next to the EAR. The EMU will have an active phased array antenna with the 163m diameter and 1055 cross-element Yagis. Total output power of the EMU will be more than 500kW. The EMU can detect turbulent echoes from the mesosphere (60-80km). In the ionosphere incoherent-scatter observations of plasma density, drift, and temperature would be possible. Multi-channel receivers will realize radar-imaging observations. The EMU is one of the key facilities in the project "Study of coupling processes in the solar-terrestrial system

  17. Life in Tropical Rain Forests.

    ERIC Educational Resources Information Center

    NatureScope, 1989

    1989-01-01

    Discusses the diversity of rain forest life, the adaptations of rain forest plants and animals, and ways these organisms interact. Includes activities on canopy critters with a copyable sheet, rain forest revue, design a plant, and jungle sleuths. (RT)

  18. Low-Latitude Ethane Rain on Titan

    NASA Technical Reports Server (NTRS)

    Dalba, Paul A.; Buratti, Bonnie J.; Brown, R. H.; Barnes, J. W.; Baines, K. H.; Sotin, C.; Clark, R. N.; Lawrence, K. J.; Nicholson, P. D.

    2012-01-01

    Cassini ISS observed multiple widespread changes in surface brightness in Titan's equatorial regions over the past three years. These brightness variations are attributed to rainfall from cloud systems that appear to form seasonally. Determining the composition of this rainfall is an important step in understanding the "methanological" cycle on Titan. I use data from Cassini VIMS to complete a spectroscopic investigation of multiple rain-wetted areas. I compute "before-and-after" spectral ratios of any areas that show either deposition or evaporation of rain. By comparing these spectral ratios to a model of liquid ethane, I find that the rain is most likely composed of liquid ethane. The spectrum of liquid ethane contains multiple absorption features that fall within the 2-micron and 5-micron spectral windows in Titan's atmosphere. I show that these features are visible in the spectra taken of Titan's surface and that they are characteristically different than those in the spectrum of liquid methane. Furthermore, just as ISS saw the surface brightness reverting to its original state after a period of time, I show that VIMS observations of later flybys show the surface composition in different stages of returning to its initial form.

  19. Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change

    PubMed Central

    Clarke, Julia A.; Ksepka, Daniel T.; Stucchi, Marcelo; Urbina, Mario; Giannini, Norberto; Bertelli, Sara; Narváez, Yanina; Boyd, Clint A.

    2007-01-01

    New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4–8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude ≈14°S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper. PMID:17601778

  20. Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change.

    PubMed

    Clarke, Julia A; Ksepka, Daniel T; Stucchi, Marcelo; Urbina, Mario; Giannini, Norberto; Bertelli, Sara; Narváez, Yanina; Boyd, Clint A

    2007-07-10

    New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4-8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude approximately 14 degrees S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper.

  1. An Early Cenozoic Ichthyolith Record from Demerara Rise (ODP Site 1258: Equatorial Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Bryant, R. M.; Sibert, E. C.; Norris, R. D.

    2014-12-01

    Peak global warmth during the early Eocene is a partial analog to the future structure of marine ecosystems in a high pCO2 world. Early Eocene oceans are generally regarded as supporting warmer oceans with lower overall productivity than today owing to the low concentrations of preserved organic matter in pelagic sediments. It has also been proposed that Eocene oceans were about as productive as now, but higher respiration rates in a warmer-than-modern ocean more efficiently recycled organic matter and nutrients. We investigated Eocene export productivity and its link to taxonomic diversity using the pelagic ichthyolith record. Ichthyoliths are calcium phosphate microfossils including fish teeth and shark denticles and their fragments, and are a unique paleoceanographic proxy because they represent a fossil record for marine vertebrates, a charismatic and tangible part of the ecosystem that generally goes unrepresented in the fossil record. Analysis of the ichthyolith record in Ocean Drilling Program Site 1258 (NE South America) shows a remarkable increase in accumulation rate of ichthyoliths from the Paleocene into the Eocene, suggesting that onset of the Early Eocene Climatic Optimum in the equatorial Atlantic was favorable to fish production. Our results suggest that, if anything, the early Eocene maintained higher productivity than in the late Paleocene. These results compare favorably with a record of ichthyolith accumulation in the South Pacific (DSDP 596), which also indicates unusually high rates of fish productivity in the peak of Eocene warm climates. Low resolution data sets from the Pacific suggest an explosion of morphotypes during the warm period associated with an increase in ichthyolith mass accumulation rates. Peak global warmth, therefore, appears to be associated with both higher fish production and higher taxonomic diversity than suggested by previous reconstructions of Eocene primary production. Increasing the amount of continuous records of

  2. Difficult Decisions: Acid Rain.

    ERIC Educational Resources Information Center

    Miller, John A.; Slesnick, Irwin L.

    1989-01-01

    Discusses some of the contributing factors and chemical reactions involved in the production of acid rain, its effects, and political issues pertaining to who should pay for the clean up. Supplies questions for consideration and discussion. (RT)

  3. Thinking in the Rain.

    ERIC Educational Resources Information Center

    Bartlett, Albert A.

    1989-01-01

    Four questions related to rain concerning aerodynamic drag force, pressure from the impact of raindrops, impact of wind on the pressure, and stopping force extended on the car by the water are proposed. (YP)

  4. The emergence of modern type rain forests and mangroves and their traces in the palaeobotanical record during the Late Cretaceous and early Tertiary

    NASA Astrophysics Data System (ADS)

    Mohr, Barbara; Coiffard, Clément

    2014-05-01

    The origin of modern rain forests is still very poorly known. This ecosystem could have potentially fully evolved only after the development of relatively high numbers of flowering plant families adapted to rain forest conditions. During the early phase of angiosperm evolution in the early Cretaceous the palaeo-equatorial region was located in a seasonally dry climatic belt, so that during this phase, flowering plants often show adaptations to drought, rather than to continuously wet climate conditions. Therefore it is not surprising that except for the Nymphaeales, the most basal members of extant angiosperm families have members that do not necessarily occur in the continuously wet tropics today. However, during the late Early Cretaceous several clades emerged that later would give rise to families that are typically found today mostly in (shady) moist places in warmer regions. This is especially seen among the monocotyledons, a group of the mesangiosperms, that developed in many cases large leaves often with very specific venation patterns that make these leaves very unique and well recognizable. Especially members of three groups are here of interest: the arum family (Araceae), the palms (Arecaceae) and the Ginger and allies (Zingiberales). The earliest fossil of Araceae are restricted to low latitudes during the lower Cretaceous. Arecaceae and Zingiberales do not appear in the fossil record before the early late Cretaceous and occur at mid latitudes. During the Late Cretaceous, Araceae are represented at mid latitudes by non-tropical early diverging members and at low latitudes by derived rainforest members. Palms became widespread during the Late Cretataceous and also Nypa, a typical element of tropical to subtropical mangrove environments evolved during this time period. During the Paleocene Arecaceae appear to be restricted to lower latitudes as well as Zingiberales. All three groups are again widespread during the Eocene, reaching higher latitudes and

  5. A Cenozoic record of the equatorial Pacific carbonate compensation depth.

    PubMed

    Pälike, Heiko; Lyle, Mitchell W; Nishi, Hiroshi; Raffi, Isabella; Ridgwell, Andy; Gamage, Kusali; Klaus, Adam; Acton, Gary; Anderson, Louise; Backman, Jan; Baldauf, Jack; Beltran, Catherine; Bohaty, Steven M; Bown, Paul; Busch, William; Channell, Jim E T; Chun, Cecily O J; Delaney, Margaret; Dewangan, Pawan; Dunkley Jones, Tom; Edgar, Kirsty M; Evans, Helen; Fitch, Peter; Foster, Gavin L; Gussone, Nikolaus; Hasegawa, Hitoshi; Hathorne, Ed C; Hayashi, Hiroki; Herrle, Jens O; Holbourn, Ann; Hovan, Steve; Hyeong, Kiseong; Iijima, Koichi; Ito, Takashi; Kamikuri, Shin-ichi; Kimoto, Katsunori; Kuroda, Junichiro; Leon-Rodriguez, Lizette; Malinverno, Alberto; Moore, Ted C; Murphy, Brandon H; Murphy, Daniel P; Nakamura, Hideto; Ogane, Kaoru; Ohneiser, Christian; Richter, Carl; Robinson, Rebecca; Rohling, Eelco J; Romero, Oscar; Sawada, Ken; Scher, Howie; Schneider, Leah; Sluijs, Appy; Takata, Hiroyuki; Tian, Jun; Tsujimoto, Akira; Wade, Bridget S; Westerhold, Thomas; Wilkens, Roy; Williams, Trevor; Wilson, Paul A; Yamamoto, Yuhji; Yamamoto, Shinya; Yamazaki, Toshitsugu; Zeebe, Richard E

    2012-08-30

    Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.

  6. The demise of the early Eocene greenhouse - Decoupled deep and surface water cooling in the eastern North Atlantic

    NASA Astrophysics Data System (ADS)

    Bornemann, André; D'haenens, Simon; Norris, Richard D.; Speijer, Robert P.

    2016-10-01

    Early Paleogene greenhouse climate culminated during the early Eocene Climatic Optimum (EECO, 50 to 53 Ma). This episode of global warmth is subsequently followed by an almost 20 million year-long cooling trend leading to the Eocene-Oligocene glaciation of Antarctica. Here we present the first detailed planktic and benthic foraminiferal isotope single site record (δ13C, δ18O) of late Paleocene to middle Eocene age from the North Atlantic (Deep Sea Drilling Project Site 401, Bay of Biscay). Good core recovery in combination with well preserved foraminifera makes this site suitable for correlations and comparison with previously published long-term records from the Pacific Ocean (e.g. Allison Guyot, Shatsky Rise), the Southern Ocean (Maud Rise) and the equatorial Atlantic (Demerara Rise). Whereas our North Atlantic benthic foraminiferal δ18O and δ13C data agree with the global trend showing the long-term shift toward heavier δ18O values, we only observe minor surface water δ18O changes during the middle Eocene (if at all) in planktic foraminiferal data. Apparently, the surface North Atlantic did not cool substantially during the middle Eocene. Thus, the North Atlantic appears to have had a different surface ocean cooling history during the middle Eocene than the southern hemisphere, whereas cooler deep-water masses were comparatively well mixed. Our results are in agreement with previously published findings from Tanzania, which also support the idea of a muted post-EECO surface-water cooling outside the southern high-latitudes.

  7. Rain radar instrument definition

    NASA Astrophysics Data System (ADS)

    Vincent, Nicolas; Chenebault, J.; Suinot, Noel; Mancini, Paolo L.

    1996-12-01

    As a result of a pre-phase a study, founded by ESA, this paper presents the definition of a spaceborne Rain Radar, candidate instrument for earth explorer precipitation mission. Based upon the description of user requirements for such a dedicated mission, a mission analysis defines the most suitable space segment. At system level, a parametric analysis compares pros and cons of instrument concepts associated with rain rate retrieval algorithms in order to select the most performing one. Several trade-off analysis at subsystem level leads then to the definition of the proposed design. In particular, as pulse compression is implemented in order to increase the radar sensitivity, the selected method to achieve a pulse response with a side-lobe level below--60 dB is presented. Antenna is another critical rain radar subsystem and several designs are com pared: direct radiating array, single or dual reflector illuminated by single or dual feed arrays. At least, feasibility of centralized amplification using TWTA is compared with criticality of Tx/Rx modules for distributed amplification. Mass and power budgets of the designed instrument are summarized as well as standard deviations and bias of simulated rain rate retrieval profiles. The feasibility of a compliant rain radar instrument is therefore demonstrated.

  8. Estimating Rain Rates from Tipping-Bucket Rain Gauge Measurements

    NASA Technical Reports Server (NTRS)

    Wang, Jianxin; Fisher, Brad L.; Wolff, David B.

    2007-01-01

    This paper describes the cubic spline based operational system for the generation of the TRMM one-minute rain rate product 2A-56 from Tipping Bucket (TB) gauge measurements. Methodological issues associated with applying the cubic spline to the TB gauge rain rate estimation are closely examined. A simulated TB gauge from a Joss-Waldvogel (JW) disdrometer is employed to evaluate effects of time scales and rain event definitions on errors of the rain rate estimation. The comparison between rain rates measured from the JW disdrometer and those estimated from the simulated TB gauge shows good overall agreement; however, the TB gauge suffers sampling problems, resulting in errors in the rain rate estimation. These errors are very sensitive to the time scale of rain rates. One-minute rain rates suffer substantial errors, especially at low rain rates. When one minute rain rates are averaged to 4-7 minute or longer time scales, the errors dramatically reduce. The rain event duration is very sensitive to the event definition but the event rain total is rather insensitive, provided that the events with less than 1 millimeter rain totals are excluded. Estimated lower rain rates are sensitive to the event definition whereas the higher rates are not. The median relative absolute errors are about 22% and 32% for 1-minute TB rain rates higher and lower than 3 mm per hour, respectively. These errors decrease to 5% and 14% when TB rain rates are used at 7-minute scale. The radar reflectivity-rainrate (Ze-R) distributions drawn from large amount of 7-minute TB rain rates and radar reflectivity data are mostly insensitive to the event definition.

  9. Rain sampling device

    DOEpatents

    Nelson, Danny A.; Tomich, Stanley D.; Glover, Donald W.; Allen, Errol V.; Hales, Jeremy M.; Dana, Marshall T.

    1991-01-01

    The present invention constitutes a rain sampling device adapted for independent operation at locations remote from the user which allows rainfall to be sampled in accordance with any schedule desired by the user. The rain sampling device includes a mechanism for directing wet precipitation into a chamber, a chamber for temporarily holding the precipitation during the process of collection, a valve mechanism for controllably releasing samples of said precipitation from said chamber, a means for distributing the samples released from the holding chamber into vessels adapted for permanently retaining these samples, and an electrical mechanism for regulating the operation of the device.

  10. Rain sampling device

    DOEpatents

    Nelson, D.A.; Tomich, S.D.; Glover, D.W.; Allen, E.V.; Hales, J.M.; Dana, M.T.

    1991-05-14

    The present invention constitutes a rain sampling device adapted for independent operation at locations remote from the user which allows rainfall to be sampled in accordance with any schedule desired by the user. The rain sampling device includes a mechanism for directing wet precipitation into a chamber, a chamber for temporarily holding the precipitation during the process of collection, a valve mechanism for controllably releasing samples of the precipitation from the chamber, a means for distributing the samples released from the holding chamber into vessels adapted for permanently retaining these samples, and an electrical mechanism for regulating the operation of the device. 11 figures.

  11. Formerly emerging crustal blocks in the equatorial Atlantic

    NASA Astrophysics Data System (ADS)

    Bonatti, Enrico; Chermak, Andy

    1981-02-01

    Anomalous crustal topographic highs, exceeding the level predicted by the thermal contraction model by up to 2-3 km, are observed along the Romanche Transform Zone in the equatorial Atlantic. Previous studies of shallow-water reef limestones recovered from one of the shallowest sites on these crustal highs indicated that this site was at or above sea level 5 million years ago and subsided since at an average rate one order of magnitude faster than the subsidence estimated by thermal contraction of the crust. Seismic reflection profiles obtained across the Romanche Transform Zone suggest that the anomalous highs are capped by reef limestones not only where limestones were actually sampled, but also at other locations. These findings support the idea that long segments of crust reached close to sea level in the past along the Romanche Transform Zone. The vertical crustal motions are probably caused by tectonism typical of long-offset transforms. Inasmuch as the Romanche has been a ridge—ridge transform since the earliest stages of the opening of the equatorial Atlantic, it is likely that intense vertical tectonic motions occurred along it throughout the evolution of the Atlantic. Support for this hypothesis is provided by the recovery during DSDP Leg 4 of shallow water reef limestone of the Eocene Age from the summit of the North Brazilian Ridge along the western extension of the Romanche Fracture Zone. The presence of shallow or emergent crust across the equatorial zone during the early stages of opening had probably important consequences upon the water circulation between the North and the South Atlantic, and may even have provided "land bridges" for faunal migrations between Africa and South America in early Cenozoic times after the two continents had already separated.

  12. Rain Forests: Tropical Treasures.

    ERIC Educational Resources Information Center

    Braus, Judy, Ed.

    1989-01-01

    Ranger Rick's NatureScope is a creative education series dedicated to inspiring in children an understanding and appreciation of the natural world while developing the skills they will need to make responsible decisions about the environment. The topic of this issue is "Rain Forests: Tropical Treasures." Contents are organized into the…

  13. The Acid Rain Debate.

    ERIC Educational Resources Information Center

    Oates-Bockenstedt, Catherine

    1997-01-01

    Details an activity designed to motivate students by incorporating science-related issues into a classroom debate. Includes "The Acid Rain Bill" and "Position Guides" for student roles as committee members, consumers, governors, industry owners, tourism professionals, senators, and debate directors. (DKM)

  14. Acid Rain Investigations.

    ERIC Educational Resources Information Center

    Hugo, John C.

    1992-01-01

    Presents an activity in which students investigate the formation of solid ammonium chloride aerosol particles to help students better understand the concept of acid rain. Provides activity objectives, procedures, sample data, clean-up instructions, and questions and answers to help interpret the data. (MDH)

  15. The Acid Rain Game.

    ERIC Educational Resources Information Center

    Rakow, Steven J.; Glenn, Allen

    1982-01-01

    Provides rationale for and description of an acid rain game (designed for two players), a problem-solving model for elementary students. Although complete instructions are provided, including a copy of the game board, the game is also available for Apple II microcomputers. Information for the computer program is available from the author.…

  16. Acid Rain Classroom Projects.

    ERIC Educational Resources Information Center

    Demchik, Michael J.

    2000-01-01

    Describes a curriculum plan in which students learn about acid rain through instructional media, research and class presentations, lab activities, simulations, design, and design implementation. Describes the simulation activity in detail and includes materials, procedures, instructions, examples, results, and discussion sections. (SAH)

  17. The Acid Rain Debate.

    ERIC Educational Resources Information Center

    Bybee, Rodger; And Others

    1984-01-01

    Describes an activity which provides opportunities for role-playing as industrialists, ecologists, and government officials. The activity involves forming an international commission on acid rain, taking testimony, and, based on the testimony, making recommendations to governments on specific ways to solve the problem. Includes suggestions for…

  18. Acid rain bibliography

    SciTech Connect

    Sayers, C.S.

    1983-09-01

    This bibliography identifies 900 citations on various aspects of Acid Rain, covering published bibliographies, books, reports, conference and symposium proceedings, audio visual materials, pamphlets and newsletters. It includes five sections: citations index (complete record of author, title, source, order number); KWIC index; title index; author index; and source index. 900 references.

  19. Rain Forest Dance Residency.

    ERIC Educational Resources Information Center

    Watson, Dawn

    1997-01-01

    Outlines the author's experience as a dancer and choreographer artist-in-residence with third graders at a public elementary school, providing a cultural arts experience to tie in with a theme study of the rain forest. Details the residency and the insights she gained working with students, teachers, and theme. (SR)

  20. Slouching in the Rain

    ERIC Educational Resources Information Center

    Bailey, Herb

    2013-01-01

    A number of papers find the velocity that minimizes the wetness of a traveler caught in the rain. In this capsule we determine, in addition, the necessary amount of forward bend (slouching) so that the traveler stays as dry as possible.

  1. Acid rain sourcebook

    SciTech Connect

    Elliott, T.C.; Schwieger, R.G.

    1984-01-01

    Discusses the problem of acid rain and how it can be controlled. The book is divided into seven key sections: the problem and the legislative solutions; international mitigation programs; planning the US program; emissions reduction-before combustion; emissions/reduction-during combustion; emissions reduction-after combustion and engineering solutions under development. 13 papers have been abstracted separately.

  2. The acid rain sourcebook

    SciTech Connect

    Elliott, T.C.; Schwieger, R.G.

    1985-01-01

    A reference collection of specialized information discussions on areas critical to the acid rain issue: problem definition, impact of legislation, emissions standards, international perspective, cost scenarios, and engineering solutions. The text is reinforced with 130 illustrations and about 50 tables. Contents: International mitigation programs. Emissions reduction: before combustion; during combustion; after combustion. Engineering solutions under development.

  3. After the Rain: Clouds.

    ERIC Educational Resources Information Center

    Old Elk, Arlene; Stoklas, Jackie

    The Heard Museum (Phoenix, Arizona) has developed and updated an integrated curriculum for use in grades K-3. The goals for this curriculum are to: (1) share museum resources with schools; (2) promote cross-cultural understanding through a focus on rain, a universal requirement for life; (3) help students understand that Native Americans are…

  4. After the Rain: Rainbows.

    ERIC Educational Resources Information Center

    Old Elk, Arlene; Stoklas, Jackie

    The Heard Museum (Phoenix, Arizona) has developed and updated an integrated curriculum for use in grades K-3. The goals for this curriculum are to: (1) share museum resources with schools; (2) promote cross-cultural understanding through a focus on rain, a universal requirement for life; (3) help students understand that Native Americans are…

  5. After the Rain: Dryspell.

    ERIC Educational Resources Information Center

    Old Elk, Arlene; Stoklas, Jackie

    The Heard Museum (Phoenix, Arizona) has developed and updated an integrated curriculum for use in grades K-3. The goals for this curriculum are to: (1) share museum resources with schools; (2) promote cross-cultural understanding through a focus on rain, a universal requirement for life; (3) help students understand that Native Americans are…

  6. After the Rain: Animals.

    ERIC Educational Resources Information Center

    Old Elk, Arlene; Stoklas, Jackie

    The Heard Museum (Phoenix, Arizona) has developed and updated an integrated curriculum for use in grades K-3. The goals for this curriculum are to: (1) share museum resources with schools; (2) promote cross-cultural understanding through a focus on rain, a universal requirement for life; (3) help students understand that Native Americans are…

  7. Rain Drop Charge Sensor

    NASA Astrophysics Data System (ADS)

    S, Sreekanth T.

    begin{center} Large Large Rain Drop Charge Sensor Sreekanth T S*, Suby Symon*, G. Mohan Kumar (1) , S. Murali Das (2) *Atmospheric Sciences Division, Centre for Earth Science Studies, Thiruvananthapuram 695011 (1) D-330, Swathi Nagar, West Fort, Thiruvananthapuram 695023 (2) Kavyam, Manacaud, Thiruvananthapuram 695009 begin{center} ABSTRACT To study the inter-relations with precipitation electricity and precipitation microphysical parameters a rain drop charge sensor was designed and developed at CESS Electronics & Instrumentation Laboratory. Simultaneous measurement of electric charge and fall speed of rain drops could be done using this charge sensor. A cylindrical metal tube (sensor tube) of 30 cm length is placed inside another thick metal cover opened at top and bottom for electromagnetic shielding. Mouth of the sensor tube is exposed and bottom part is covered with metal net in the shielding cover. The instrument is designed in such a way that rain drops can pass only through unhindered inside the sensor tube. When electrically charged rain drops pass through the sensor tube, it is charged to the same magnitude of drop charge but with opposite polarity. The sensor tube is electrically connected the inverted input of a current to voltage converter operational amplifier using op-amp AD549. Since the sensor is electrically connected to the virtual ground of the op-amp, the charge flows to the ground and the generated current is converted to amplified voltage. This output voltage is recorded using a high frequency (1kHz) voltage recorder. From the recorded pulse, charge magnitude, polarity and fall speed of rain drop are calculated. From the fall speed drop diameter also can be calculated. The prototype is now under test running at CESS campus. As the magnitude of charge in rain drops is an indication of accumulated charge in clouds in lightning, this instrument has potential application in the field of risk and disaster management. By knowing the charge

  8. Torrential Rain in China

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Concentric ovals of red, orange, yellow, and green are draped over southern China, showing rainfall totals for the week of June 4 through June 11, 2007. The rainfall totals are from the Goddard Space Flight Center Multi-satellite Precipitation Analysis, which is based on rainfall measurements taken by the Tropical Rainfall Measuring Mission (TRMM) satellite. Though seasonal rains are not unexpected in the area, the rain that fell during the week was torrential and relentless. As the image shows, a broad stretch of China received up to 200 millimeters (8 inches) of rain, and some areas were inundated with up to 500 millimeters (20 inches). Floods and landslides resulted, destroying crops and forcing some 643,000 people from their homes, reported the Xinhua News Agency on ReliefWeb. As of June 11, 71 people had died and 13 were missing. The most affected area was the southern coast, where rainfall totals are highest in this image. Heavy tropical rains combined with steep mountains make southeastern China prone to devastating landslides. Monitoring landslide-producing conditions typically requires extensive networks of ground-based rain gauges and weather instruments. But many developing countries in high-risk areas lack the resources to maintain such systems; heavy rains and flooding often wash away ground-based instruments. Robert Adler, a senior scientist in the Laboratory for Atmospheres at Goddard Space Flight Center, and Yang Hong, a research scientist at Goddard Earth Sciences Technology Center, are confronting the problem by developing a satellite-based system for predicting landslides. The system relies on TRMM data to predict when rainfall in different areas has reached a landslide-triggering threshold. The system makes data available on the Internet just a few hours after the satellite makes its observations. To read more about the landslide-monitoring system, please read the feature article Satellite Monitors Rains That Trigger Landslides, http

  9. Early Eocene climate warming increased petroleum production

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-04-01

    From the late Paleocene, about 58 million years ago, to the early Eocene, about 51 million years ago, Earth's surface temperatures warmed by about 5°-10°C. Also in the early Eocene, there was an increase of carbon-13-depleted carbon in the oceans that cannot be accounted for by changes in carbon cycling at the surface. To better understand the source of that carbon, Kroeger and Funnell modeled the thermal evolution of four sedimentary basins in the southwestern Pacific Ocean. The authors show that the rising surface temperatures of the early Eocene eventually led to warming of the sedimentary beds deep beneath the surface. Petroleum can be produced at only a certain range of temperatures; rising temperatures at greater depths would bring more potential source rocks into temperature conditions under which oil and gas can be produced and released.

  10. Low-Latitude Ethane Rain on Titan

    NASA Astrophysics Data System (ADS)

    Dalba, Paul; Buratti, B. J.; Brown, R. H.; Barnes, J. W.; Baines, K. H.; Sotin, C.; Clark, R. N.; Lawrence, K. J.; Nicholson, P. D.

    2012-10-01

    Cassini ISS observed multiple widespread changes in surface brightness in Titan's equatorial regions over the past three years (Barnes, J. W. et al. 2012, Icarus, submitted). These brightness variations are attributed to rainfall from cloud systems that appear to form seasonally (Turtle, E. P. et al. 2011, Science, 331, 1414-1417). Determining the composition of this rainfall is an important step in understanding the “methanological” cycle that dominates Titan's surface and atmosphere. In this study, we use data from Cassini VIMS to complete a thorough spectroscopic investigation of rain-wetted areas near Yalaing Terra, Hetpet Regio and central Adiri on Titan. We compute “before-and-after” spectral ratios of any areas that show either deposition or evaporation of rain at any point in the time span of August 2009 to January 2012. By comparing these spectral ratios to a model of liquid ethane that was calculated to match the resolution and sampling interval of VIMS (Brown, R. H. et al. 2008, Nature, 454, 607-610), we find that the rain is most likely composed of liquid ethane. The spectrum of liquid ethane contains multiple absorption features that fortunately fall within the 2-micron and 5-micron spectral windows in Titan's atmosphere. We show that these features are visible in the spectra taken of Titan's surface and that they are characteristically different than those in the spectrum of liquid methane. Furthermore, just as ISS saw the surface brightness reverting to its original state after a period of time, we show that VIMS observations of later flybys show the surface composition in different stages of returning to its initial form as well. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology under contract to the National Aeronautics and Space Administration. Copyright 2012. All rights reserved.

  11. Low-latitude ethane rain on Titan

    NASA Astrophysics Data System (ADS)

    Dalba, P. A.; Buratti, B. J.; Brown, R. H.; Barnes, J. W.; Baines, K. H.; Sotin, C.; Clark, R. N.; Lawrence, K. J.; Nicholson, P. D.

    2012-12-01

    Cassini ISS observed multiple widespread changes in surface brightness in Titan's equatorial regions over the past three years (Barnes, J. W. et al. 2012, Icarus, submitted). These brightness variations are attributed to rainfall from cloud systems that appear to form seasonally (Turtle, E. P. et al. 2011, Science, 331, 1414-1417). Determining the composition of this rainfall is an important step in understanding the "methanological" cycle that dominates Titan's surface and atmosphere. In this study, we use data from Cassini VIMS to complete a thorough spectroscopic investigation of rain-wetted areas near Yalaing Terra, Hetpet Regio and central Adiri on Titan. We compute "before-and-after" spectral ratios of any areas that show either deposition or evaporation of rain at any point in the time span of August 2009 to January 2012. By comparing these spectral ratios to a model of liquid ethane that was calculated to match the resolution and sampling interval of VIMS (Brown, R. H. et al. 2008, Nature, 454, 607-610), we find that the rain is most likely composed of liquid ethane. The spectrum of liquid ethane contains multiple absorption features that fortunately fall within the 2-micron and 5-micron spectral windows in Titan's atmosphere. We show that these features are visible in the spectra taken of Titan's surface and that they are characteristically different than those in the spectrum of liquid methane. Furthermore, just as ISS saw the surface brightness reverting to its original state after a period of time, we show that VIMS observations of later flybys show the surface composition in different stages of returning to its initial form as well. Funded by NASA.

  12. When It Rains, It Pours

    ERIC Educational Resources Information Center

    Mills, Linda

    2012-01-01

    "It's raining, it's pouring, the old man is snoring!" "The itsy, bitsy spider crawled up the waterspout, down came the rain and washed the spider out. Out came the sun and dried up all the rain, and the itsy, bitsy spider went up the spout again." What do children's nursery rhymes have to do with the school library? The author begins by telling a…

  13. Lessons from the Rain Forest.

    ERIC Educational Resources Information Center

    Phillips, Shelley

    2002-01-01

    Presents a first-grade art project after students learned about the rain forest and heard the story, "The Great Kapok Tree: A Tale of the Amazon Rain Forest" (Lynn Cherry). Explains that the students created pictures of the rain forest. (CMK)

  14. The politics of acid rain

    SciTech Connect

    Wilcher, M.E. )

    1989-01-01

    This work examines and compares the acid rain policies through the different political systems of Canada, Great Britain and the United States. Because the flow of acid rain can transcend national boundaries, acid rain has become a crucial international problem. According to the author, because of differences in governmental institutions and structure, the extent of governmental intervention in the industrial economy, the degree of reliance on coal for power generation, and the extent of acid rain damage, national responses to the acid rain problem have varied.

  15. Tectonic and climatic significance of a late Eocene low-relief, high-level geomorphic surface, Colorado

    NASA Technical Reports Server (NTRS)

    Gregory, Kathryn M.; Chase, Clement G

    1994-01-01

    New paleobotanical data suggest that in the late Eocene the erosion surface which capped the Front Range, Colorado was 2.2-2.3 km in elevation, which is similar to the 2.5-km present elevation of surface remnants. This estimated elevation casts doubt on the conventional belief that the low-relief geomorphic surface was formed by lateral planation of streams to a base level not much higher than sea level and that the present deeply incised canyons must represent Neogene uplift of Colorado. Description of the surface, calculations of sediment volume, and isostatic balance and fluvial landsculpting models demonstrate that while the high elevation of the erosion surface was due to tectonic forces, its smoothness was mostly a result of climatic factors. A sediment balance calculated for the Front Range suggests that from 2 to 4 km of material were eroded by the late Eocene, consistent with fission track ages. This amount of erosion would remove a significant portionof the 7 km of Laramide upper crustal thickening. Isostatic modeling implies that the 2.2-3.3 km elevation was most likely created by lower crustal thickening during the Laramide. A numerical model of fluvial erosion and deposition suggests a way that a late Eocene surface could have formed at this high elevation without incision. A humid climate with a preponderance of small storm events will diffusively smooth topography and is a possible mechanism for formation oflow-relief, high-level surfaces. Paleoclimate models suggest a lack of large strom events in the late Eocene because of cool sea surface temperatures in the equatorial region. Return to a drier but stormier climate post-Eocene could have caused the incision of the surface by young canyons. By this interpretation, regional erosion surfaces may represent regional climatic rather than tectonic conditions.

  16. Slant path rain attenuation comparison of prediction models for satellite applications in Malaysia

    NASA Astrophysics Data System (ADS)

    Mandeep, J. S.

    2009-09-01

    A 2-year campaign of slant path rain attenuation measurements has been carried out in Malaysia using the Superbird-C satellite beacon at 12.255 GHz. The rain intensity time series have been recorded with a conventional tipping-bucket rain gauge located at the station, during a continuous observation period spanning the same 2 years of the beacon measurements. The experimental cumulative distributions of rainfall rate and rain attenuation are presented. Two years of rain attenuation measurements at 12.255 GHz shows high values that have been detected for small percentage of time; for example, the attenuation exceeded 25 dB for 0.01% of time. The rainfall rate is compared with International Telecommunications Union-Radiocommunication (ITU-R) maps, and the measured rain rate distribution is close to that derived from the ITU-R maps. Measured rain attenuation values are compared with several prediction models. A good agreement has been found in the comparison of the experimental distribution with some prediction models (Ramachandran, Bryant, Matricciani, and Exponential Cell (EXCELL) with percentage errors below 11%) calculated using the measured rainfall rate distribution. The lack of rain measurement data from equatorial and tropical regions for verification causes predictions obtained from existing models to deviate from direct measurements.

  17. Equatorial Pacific ``stable isotope reference curve'' for the Oligocene

    NASA Astrophysics Data System (ADS)

    Pälike, H.; Norris, R.; Herle, J. O.; Wilson, P. A.; Lear, C. H.; Coxall, H. K.; Tripati, A. K.

    2005-12-01

    We present an uninterrupted chronology of climate and ocean carbon chemistry from ODP Site 1218 recovered in the equatorial Pacific, from the Eocene / Oligocene to the Oligocene / Miocene boundary, ~34 to 23 Ma. Using astronomically age calibrated data we find a strong imprint of the 405, 127 and 96-thousand-year (kyr) Earth's eccentricity as well as a dominant influence of the 1.2 million year (Myr) obliquity amplitude modulation cycles on periodically re-occurring Oligocene glacial and carbon cycle events. In combination, these astronomical modulations act as the ``heartbeat'' of the Oligocene climate system. The response of the climate system to intricate orbital variations is striking and suggests a fundamental role of the carbon cycle in the interaction between solar forcing and climate. Our record provides a new high-resolution view of the Oligocene climate system, prompts a re-evaluation of the previously hypothesised late Oligocene deglaciation, and sheds new light on Oligocene inter-ocean isotope gradients. Salient observations include foraminiferal benthic stable oxygen and carbon isotopes that co-vary, a phase lag of δ13C w.r.t. δ18O for the 405 kyr cycle, preferential filtering of longer orbital periods in δ13C, presumably due to σCO2 reservoir buffering. We then use simple orbitally forced carbon cycle box models and manage to re-create the patterns observed in our data, including the overall strong amplitude of 405 kyr cycles in δ13C. Depending on ice-sheet presence and pCO2 concentrations, our model predicts re-occurring conditions favouring glaciations every 2.4 Myr, including the Eocene/Oligocene transition.

  18. How did the equatorial ridge on Saturn's moon Iapetus form?

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-04-01

    Saturn's moon Iapetus is one of the most unusual moons in our solar system. Perhaps the most bizarre feature of Iapetus is its equatorial ridge, a 20-kilometer-high, 200-kilometer-wide mountain range that runs exactly along the equator, circling more than 75% of the moon. No other body in the solar system exhibits such a feature; as Dombard et al. show, previous models have been unable to adequately explain how the ridge formed. The authors propose that the ridge formed from an ancient giant impact that produced a subsatellite around Iapetus. Tidal interactions with Iapetus ultimately led to orbital decay, eventually bringing the subsatellite close enough that the same forces tore it apart, forming a debris ring around Iapetus. Material from this debris ring then rained down on Iapetus, the researchers say, creating the mountain ring along the equator. (Journal of Geophysical Research-Planets, doi:10.1029/2011JE004010, 2012)

  19. A Robust, Microwave Rain Gauge

    NASA Astrophysics Data System (ADS)

    Mansheim, T. J.; Niemeier, J. J.; Kruger, A.

    2008-12-01

    Researchers at The University of Iowa have developed an all-electronic rain gauge that uses microwave sensors operating at either 10 GHz or 23 GHz, and measures the Doppler shift caused by falling raindrops. It is straightforward to interface these sensors with conventional data loggers, or integrate them into a wireless sensor network. A disadvantage of these microwave rain gauges is that they consume significant power when they are operating. However, this may be partially negated by using data loggers' or sensors networks' sleep-wake-sleep mechanism. Advantages of the microwave rain gauges are that one can make them very robust, they cannot clog, they don't have mechanical parts that wear out, and they don't have to be perfectly level. Prototype microwave rain gauges were collocated with tipping-bucket rain gauges, and data were collected for two seasons. At higher rain rates, microwave rain gauge measurements compare well with tipping-bucket measurements. At lower rain rates, the microwave rain gauges provide more detailed information than tipping buckets, which quantize measurement typically in 1 tip per 0.01 inch, or 1 tip per mm of rainfall.

  20. More rain compensation results

    NASA Technical Reports Server (NTRS)

    Sworder, D. D.; Vojak, R.

    1992-01-01

    To reduce the impact of rain-induced attenuation in the 20/30 GHz band, the attenuation at a specified signal frequency must be estimated and extrapolated forward in time on the basis of a noisy beacon measurement. Several studies have used model based procedures for solving this problem in statistical inference. Perhaps the most widely used model-based paradigm leads to the Kalman filter and its lineal variants. In this formulation, the dynamic features of the attenuation are represented by a state process (x(sub t)). The observation process (y(sub t)) is derived from beacon measurements. Some ideas relating to the signal processing problems related to uplink power control are presented. It is shown that some easily implemented algorithms hold promise for use in estimating rain induced fades. The algorithms were applied to actual data generated at the Virginia Polytechnic Institute and State University (VPI) test facility. Because only one such event was studied, it is not clear that the algorithms will have the same effectiveness when a wide range of events are studied.

  1. The influence of extraterrestrial material on the late Eocene marine Os isotope record

    NASA Astrophysics Data System (ADS)

    Paquay, François S.; Ravizza, Greg; Coccioni, Rodolfo

    2014-11-01

    A reconstruction of seawater 187Os/188Os ratios during the late Eocene (∼36-34 Ma), based upon bulk sediment analyses from the sub-Antarctic Southern Atlantic Ocean (Ocean Drilling Program (ODP) Site 1090), Eastern Equatorial Pacific Ocean (ODP Sites 1218 and 1219) and the uplifted (land-based) Tethyan section (Massignano, Italy), confirms that the previously reported abrupt shift to lower 187Os/188Os is a unique global feature of the marine Os isotope record that occurs in magnetochron C16n.1n. This feature is interpreted to represent the change in seawater 187Os/188Os caused by the Popigai impact event. Higher in the Massignano section, two other iridium anomalies previously proposed to represent additional impact events do not show a comparable excursion to low 187Os/188Os, suggesting that these horizons do not record multiple large impacts. Comparison of records from three different ocean basins indicates that seawater 187Os/188Os begins to decline in advance of the Popigai impact event. At Massignano this decline coincides with a previously reported episode of elevated 3He flux, suggesting that increased influx of interplanetary dust particles (IDPs) contributed to the pre-impact shift in 187Os/188Os and not to the longer-term latest Eocene 187Os/188Os decline that occurred ∼1 million year after the Popigai impact event.

  2. Geochronology of Early Eocene strata, Baja California

    SciTech Connect

    Flynn, J.J.; Cipolletti, R.M.

    1985-01-01

    Recent discoveries clearly indicate a Wasatchian (Early Eocene) land mammal age for fossil vertebrates from the Punta Prieta area, Baja California North, Mexico. This fauna provides a rare test for discriminating the temporal significance of mammalian faunas over a broad geographic area. The authors sampled intertonguing, fossiliferous terrestrial and marine strata for paleomagnetic and biostratigraphic analyses to provide an independent age determination for the Punta Prieta area mammal fauna. The marine macroinvertebrate assemblage is most likely upper Meganos to lower Capay West Coast Molluscan Stage based on the temporal ranges of all the taxa; also, none of the taxa occur in pre-Meganos stages. Two genera of planktonic forams indicate a probably Eocene age. They sampled seventeen paleomagnetic sites over 50 meters in the terrestrial mammal-bearing section, and thirteen sites over 25 meters in the marine section. The entire terrestrial sequence is reversely magnetized; initial results indicate the marine sequence probably also is reversely magnetized. Based on all the available biochronologic evidence this reversed sequence most likely should be correlated with the long reversed polarity Chron C24R. Clarkforkian to Early Wasatchian faunas in Wyoming also are associated with Chron C24R. All the available biostratigraphic and magnetostratigraphic evidence strongly supports an Early Eocene age for the Punta Prieta mammalian fauna and temporal equivalence of the Punta Prieta Wasatchian fauna with Wasatchian faunas from the Western United States. Land mammal ages are synchronous and applicable across broad geographic areas.

  3. Interplay Between the Equatorial Geophysical Processes

    NASA Astrophysics Data System (ADS)

    Sridharan, R.

    2006-11-01

    r_sridharanspl@yahoo.com With the sun as the main driving force, the Equatorial Ionosphere- thermosphere system supports a variety of Geophysical phenomena, essentially controlled by the neutral dynamical and electro dynamical processes that are peculiar to this region. All the neutral atmospheric parameters and the ionospheric parameters show a large variability like the diurnal, seasonal semi annual, annual, solar activity and those that are geomagnetic activity dependent. In addition, there is interplay between the ionized and the neutral atmospheric constituents. They manifest themselves as the Equatorial Electrojet (EEJ), Equatorial Ionization Anomaly (EIA), Equatorial Spread F (ESF), Equatorial Temperature and Wind Anomaly (ETWA). Recent studies have revealed that these phenomena, though apparently might show up as independent ones, are in reality interlinked. The interplay between these equatorial processes forms the theme for the present talk.

  4. Seismostratigraphy of the Ceará Plateau: clues to decipher the Cenozoic evolution of Brazilian Equatorial Margin

    NASA Astrophysics Data System (ADS)

    Jovane, Luigi; Figueiredo, Jorge; Alves, Daniel; Iacopini, David; Giorgioni, Martino; Vannucchi, Paola; de Moura, Denise; Bezerra, Francisco; Vital, Helenice; Rios, Isabella; Molina, Eder

    2016-10-01

    The Ceará Plateau offshore Fortaleza holds some particular characteristics when compared to the other seamounts of the Brazilian Equatorial Margin (BEM). Not only it is the largest and the closest to the continent, it is also located at the boundary between the continental and the oceanic crusts, while all the others seamounts along the BEM are located on oceanic crust. Seismic imaging of the Ceará Plateau shows a “disorganized” interior, probably of volcanic origin, overlain by a series of horizontal seismic reflectors that can be interpreted as pelagic/hemipelagic sediments. As large uncertainties exist about the age of the initial formation of this seamount, three scenarios must be considered. If the age of the volcanic edifice is Coniacian (1), then the overlying pelagic/hemipelagic sedimentary succession can include an almost continuous record of the last 90 Ma at the Equatorial Atlantic Ocean. In the case that the volcanic edifice is Eocene in age (2), the sedimentary sequence would still encompass the upper Paleogene and all the Neogene. There is also the possibility that the volcanic edifice was built during multiple magmatic events (3). In this case, it is likely that the sediments are interfingered with volcanic rocks at the edge of the structure. Although the age estimation (between Coniacian and Eocene) has an uncertainty of more than 40 Myr, the current interpretation is that it developed initially as a volcanic edifice, formed by a series of magmatic events that occurred between the Santonian and the Eocene. Since then, the topography has been leveled by pelagic/hemipelagic sedimentation. Whichever was the initial age, a continuous and constant sequence of sediments deposited onto the Ceará Plateau, at the same latitude, and thus under the same oceanographic conditions, for the last several tens of million years. This represents a unique opportunity to record a long-term history of the Atlantic Equatorial Margin.

  5. Possible methane-induced polar warming in the early Eocene

    NASA Astrophysics Data System (ADS)

    Sloan, L. C.; Walker, James C. G.; Moore, T. C., Jr.; Rea, David K.; Zachos, James C.

    1992-05-01

    Estimates of Eocene wetland areas are considered and it is suggested that the flux of methane may have been substantially greater during the Eocene than at present. Elevated methane concentrations would have enhanced early Eocene global warming and also might have prevented severe winter cooling of polar regions because of the potential of atmospheric methane to promote the formation of optically thick polar stratospheric ice clouds.

  6. A local index of Maritime Continent intraseasonal variability based on rain rates over the land and sea

    NASA Astrophysics Data System (ADS)

    Vincent, C. L.; Lane, T. P.; Wheeler, M. C.

    2016-09-01

    A local index for describing intraseasonal variability over the Maritime Continent is developed. The index is based on the ratio of area-averaged rain rate over the land to that over the sea. It takes advantage of the fact that the main convective envelope of intraseasonal variability events tends to modulate the diurnal precipitation cycle over the land over the entire Maritime Continent. Lagged analysis is used to create composite intraseasonal variability events, where "day 0" is chosen according to when the normalized rain rate over the sea becomes greater than that over the land. The index identifies intraseasonal variability events associated with the Madden Julian Oscillation as well as equatorial Kelvin waves and westward propagating equatorial Rossby waves. The results suggest a similar local impact of all such events in suppressing the rain rate over land relative to that over the sea when the main convective envelope approaches.

  7. Equatorial refuge amid tropical warming

    NASA Astrophysics Data System (ADS)

    Karnauskas, Kristopher B.; Cohen, Anne L.

    2012-07-01

    Upwelling across the tropical Pacific Ocean is projected to weaken in accordance with a reduction of the atmospheric overturning circulation, enhancing the increase in sea surface temperature relative to other regions in response to greenhouse-gas forcing. In the central Pacific, home to one of the largest marine protected areas and fishery regions in the global tropics, sea surface temperatures are projected to increase by 2.8°C by the end of this century. Of critical concern is that marine protected areas may not provide refuge from the anticipated rate of large-scale warming, which could exceed the evolutionary capacity of coral and their symbionts to adapt. Combining high-resolution satellite measurements, an ensemble of global climate models and an eddy-resolving regional ocean circulation model, we show that warming and productivity decline around select Pacific islands will be mitigated by enhanced upwelling associated with a strengthening of the equatorial undercurrent. Enhanced topographic upwelling will act as a negative feedback, locally mitigating the surface warming. At the Gilbert Islands, the rate of warming will be reduced by 0.7+/-0.3°C or 25+/-9% per century, or an overall cooling effect comparable to the local anomaly for a typical El Niño, by the end of this century. As the equatorial undercurrent is dynamically constrained to the Equator, only a handful of coral reefs stand to benefit from this equatorial island effect. Nevertheless, those that do face a lower rate of warming, conferring a significant advantage over neighbouring reef systems. If realized, these predictions help to identify potential refuges for coral reef communities from anticipated climate changes of the twenty-first century.

  8. A Demonstration of Acid Rain

    ERIC Educational Resources Information Center

    Fong, Man Wai

    2004-01-01

    A demonstration showing acid rain formation is described. Oxides of sulfur and nitrogen that result from the burning of fossil fuels are the major pollutants of acid rain. In this demonstration, SO[subscript 2] gas is produced by the burning of matches. An acid-base indicator will show that the dissolved gas turns an aqueous solution acidic.

  9. Acid Rain: What's the Forecast?

    ERIC Educational Resources Information Center

    Bybee, Rodger

    1984-01-01

    Discusses various types of acid rain, considered to be a century-old problem. Topics include: wet and dry deposition, effects on a variety of environments, ecosystems subject to detrimental effects, and possible solutions to the problem. A list of recommended resources on acid rain is provided. (BC)

  10. Acid Rain: An Educational Opportunity?

    ERIC Educational Resources Information Center

    Marion, James I.

    1984-01-01

    Deals with how educators can handle the subject of acid rain; illustrates suggestions with experiences of grade nine students visiting Frost Valley Environmental Education Center (Oliverea, New York) to learn scientific concepts through observation of outdoor phenomena, including a stream; and discusses acid rain, pH levels, and pollution control…

  11. Acid rain & electric utilities II

    SciTech Connect

    1997-12-31

    This document presents reports which were presented at the Acid Rain and Electric Utilities Conference. Topics include environmental issues and electric utilities; acid rain program overview; global climate change and carbon dioxide; emissions data management; compliance; emissions control; allowance and trading; nitrogen oxides; and assessment. Individual reports have been processed separately for the United States Department of Energy databases.

  12. Acid Rain: The Scientific Challenge.

    ERIC Educational Resources Information Center

    Godfrey, Paul J.

    1991-01-01

    Documents the workings and findings of the Massachusetts Acid Rain Monitoring Project, which has pooled the volunteer efforts of more than 1,000 amateur and professional scientists since 1983. Reports on the origins of air pollution, the prediction of acid rain, and its effects on both water life and land resources. (JJK)

  13. An Umbrella for Acid Rain.

    ERIC Educational Resources Information Center

    Randal, Judith

    1979-01-01

    The Environmental Protection Agency has awarded several grants to study effects of and possible solutions to the problem of "acid rain"; pollution from atmospheric nitric and sulfuric acids. The research program is administered through North Carolina State University at Raleigh and will focus on biological effects of acid rain. (JMF)

  14. Rain Gardens: Stormwater Infiltrating Systems

    EPA Science Inventory

    The hydrological dynamics and changes in stormwater nutrient concentrations within rain gardens were studied by introducing captured stormwater runoff to rain gardens at EPA’s Urban Water Research Facility in Edison, New Jersey. The runoff used in these experiments was collected...

  15. Radio wave scintillations at equatorial regions

    NASA Technical Reports Server (NTRS)

    Poularikas, A. D.

    1972-01-01

    Radio waves, passing through the atmosphere, experience amplitude and phase fluctuations know as scintillations. A characterization of equatorial scintillation, which has resulted from studies of data recorded primarily in South America and equatorial Africa, is presented. Equatorial scintillation phenomena are complex because they appear to vary with time of day (pre-and postmidnight), season (equinoxes), and magnetic activity. A wider and more systematic geographical coverage is needed for both scientific and engineering purposes; therefore, it is recommended that more observations should be made at earth stations (at low-geomagnetic latitudes) to record equatorial scintillation phenomena.

  16. Acid rain in Asia

    NASA Astrophysics Data System (ADS)

    Bhatti, Neeloo; Streets, David G.; Foell, Wesley K.

    1992-07-01

    Acid rain has been an issue of great concern in North America and Europe during the past several decades. However, due to the passage of a number of recent regulations, most notably the Clean Air Act in the United States in 1990, there is an emerging perception that the problem in these Western nations is nearing solution. The situation in the developing world, particularly in Asia, is much bleaker. Given the policies of many Asian nations to achieve levels of development comparable with the industrialized world—which necessitate a significant expansion of energy consumption (most derived from indigenous coal reserves)—the potential for the formation of, and damage from, acid deposition in these developing countries is very high. This article delineates and assesses the emissions patterns, meteorology, physical geology, and biological and cultural resources present in various Asian nations. Based on this analysis and the risk factors to acidification, it is concluded that a number of areas in Asia are currently vulnerable to acid rain. These regions include Japan, North and South Korea, southern China, and the mountainous portions of Southeast Asia and southwestern India. Furthermore, with accelerated development (and its attendant increase in energy use and production of emissions of acid deposition precursors) in many nations of Asia, it is likely that other regions will also be affected by acidification in the near future. Based on the results of this overview, it is clear that acid deposition has significant potential to impact the Asian region. However, empirical evidence is urgently needed to confirm this and to provide early warning of increases in the magnitude and spread of acid deposition and its effects throughout this part of the world.

  17. Ozone measurements in the troposphere of an Amazonian rain forest environment

    NASA Technical Reports Server (NTRS)

    Kirchhoff, V. W. J. H.; Browell, E. V.; Gregory, G. L.

    1988-01-01

    Ozone concentration profiles from the ground to above the stratospheric peak were obtained in an equatorial rain forest environment near Manaus in the Amazon Basin between July and August of 1985. The peak ozone concentration (4.4 x 10 to the 22 molecules/cu cm) was found at 20 mbar (26.6 km). A major pollution (biomass-burning) event which occurred near the end of the experiment was responsible for large changes in ozone concentration.

  18. Central Equatorial Pacific Experiment (CEPEX)

    SciTech Connect

    Not Available

    1993-01-01

    The Earth's climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27[degree]C, but never 31[degree]C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  19. Micro-halocline enabled nutrient recycling may explain extreme Azolla event in the Eocene Arctic Ocean.

    PubMed

    van Kempen, Monique M L; Smolders, Alfons J P; Lamers, Leon P M; Roelofs, Jan G M

    2012-01-01

    In order to understand the physicochemical mechanisms that could explain the massive growth of Azolla arctica in the Eocene Arctic Ocean, we carried out a laboratory experiment in which we studied the interacting effects of rain and wind on the development of salinity stratification, both in the presence and in the absence of a dense Azolla cover. Additionally, we carried out a mesocosm experiment to get a better understanding of the nutrient cycling within and beneath a dense Azolla cover in both freshwater and brackish water environments. Here we show that Azolla is able to create a windproof, small-scale salinity gradient in brackish waters, which allows for efficient recycling of nutrients. We suggest that this mechanism ensures the maintenance of a large standing biomass in which additional input of nutrients ultimately result in a further expansion of an Azolla cover. As such, it may not only explain the extent of the Azolla event during the Eocene, but also the absence of intact vegetative Azolla remains and the relatively low burial efficiency of organic carbon during this interval.

  20. A "tropical" Early Eocene marine environment on the Antarctic margin: TEX86 results from IODP expedition 318

    NASA Astrophysics Data System (ADS)

    Bendle, J. A.; Bijl, P.; Toney, J. L.; Pross, J.; Contreras, L.; Schouten, S.; Roehl, U.; Tauxe, L.; Huber, M.; Brinkhuis, H.; Scientific Team of IODP Drilling Leg 318

    2011-12-01

    The early Eocene was characterised by high pCO2 (ca.1,000 to more than 2,000ppm) and mean global temperatures that reached a long-term maximum. Relative to the present day, meridional temperature gradients were unusually low, with warmer equatorial regions and much warmer subtropical Arctic and mid-latitude climates. Yet global climatic conditions during this pre-glacial interval have remained poorly constrained, as only a few temperature records are available portraying the Cenozoic climatic evolution of the high southern latitudes. Here we present dinoflagellate cyst assemblages and organic geochemical tetraether based sea-surface temperature estimates from IODP expedition 318, extracted from bio- and magnetostratigraphically dated, late early to early middle Eocene sediments recovered at Site U1356. For the first time, we reconstruct marine temperatures and ecological conditions from the Eocene Greenhouse world in direct proximity to the Antarctic continent. Early Eocene dinocyst assemblages are dominated by tropical dinocyst genus Apectodinium, whilst TEX86 results indicate persistent and remarkable warmth, with the magnitude of the reconstructed SSTs dependent on the applied calibration: TEX86-L = 20 - 26°C (Av. 23°C); TEX86-H = 27 - 33°C (Av. 32°C). Our marine based proxies are just several strands from multiple independent lines of evidence emerging from the Early Eocene of the Wilkes Land Antarctic margin, including: pollen, terrestrial biomarkers (e.g. MBT/CBT-MAT estimates of 22 - 27°C , Av. 26°C), compound specific plant wax D/H measurements and clay minerals. Taken together, this evidence of very high temperatures, thermophilic fauna, an invigorated hydrological cycle, chemically weathered soils and well developed wetlands gives a very compelling picture of environmental conditions comparable to the modern tropics. These results confirm that exceptionally warm polar-regions are a feature common to reconstructed Greenhouse periods. Such

  1. Acidification and Acid Rain

    NASA Astrophysics Data System (ADS)

    Norton, S. A.; Veselã½, J.

    2003-12-01

    endangers the existing biota. Concerns about acid (or acidic) rain in its modern sense were publicized by the Swedish soil scientist Svante Odén (1968). He argued, initially in the Swedish press, that long-term increases in the atmospheric deposition of acid could lower the pH of surface waters, cause a decline in fish stocks, deplete soils of nutrients, and accelerate damage to materials. By the 1970s, acidification of surface waters was reported in many countries in Europe as well as in North America. The late twentieth-century rush to understand the impact of acid rain was driven by: (i) reports of damaged or threatened freshwater fisheries and (ii) damaged forests. Perhaps the earliest linkage between acidic surface water and damage to fish was made by Dahl (1921) in southern Norway. There, spring runoff was sufficiently acidic to kill trout. It was not until the 1970s that a strong link was established between depressed pH, mobilization of aluminum from soil, and fish status ( Schofield and Trojnar,1980). The relationship between acidification of soils and forest health started with hypotheses in the 1960s and has slowly developed. Acid rain enhances the availability of some nutrients (e.g., nitrogen), and may either enhance or diminish the availability of others (e.g., calcium, magnesium, potassium, and phosphorus). Damage to anthropogenic structures, human health, and visibility have also raised concerns. The history of these early developments was summarized by Cowling (1982). Since the 1970s, sulfur and nitrogen emissions to the atmosphere have been reduced by 50-85% and 0-30%, respectively, both in North America and Europe. The emission reductions have occurred as a consequence of knowledge gained and economic factors. While recovery of water quality is underway in some areas, problems of acidification persist, and are now complicated by the effects of climate change ( Schindler, 1997).

  2. Seven Guideposts for Tropical Rain Forest Education.

    ERIC Educational Resources Information Center

    Rillero, Peter

    1999-01-01

    Identifies seven guideposts for tropical rain forest education. Aids teachers in finding structure and creating educational experiences that promote more complete understanding of tropical rain forests. (CCM)

  3. Instability of some equatorially trapped waves

    PubMed Central

    Constantin, Adrian; Germain, Pierre

    2013-01-01

    [1] A high-frequency asymptotics approach within the Lagrangian framework shows that some exact equatorially trapped three-dimensional waves are linearly unstable when their steepness exceeds a specific threshold. Citation: Constantin, A., and P. Germain (2013), Instability of some equatorially trapped waves, J. Geophys. Res. Oceans, 118, 2802–2810, doi:10.1002/jgrc.20219. PMID:26213669

  4. Equatorial potassium currents in lenses.

    PubMed

    Wind, B E; Walsh, S; Patterson, J W

    1988-02-01

    Earlier work with the vibrating probe demonstrated the existence of outward potassium currents at the equator and inward sodium currents at the optical poles of the lens. By adding microelectrodes to the system, it is possible to relate steady currents (J) to the potential difference (PD) measured with a microelectrode. By injecting an outward current (I), it is possible to determine resistances and also the PD at which the steady outward potassium current becomes zero (PDJ = 0). At this PD the concentration gradient for potassium efflux and the electrical gradient for potassium influx are balanced so that there is no net flow of potassium across the membranes associated with the production of J. The PDJ = 0 for 18 rat lenses was 86 mV and that for 12 frogs lenses was -95 mV. This agrees with the potassium equilibrium potential and provides strong evidence to support the view that the outward equatorial current, J, is a potassium current. With the injection of outward current, I, the PD becomes more negative, the outward equatorial current, J, decreases, and the inward current at the optical poles increases. This suggests that there are separate electrical loops for K+ and Na+ that are partially linked by the Na, K-pump. Using Ohm's law, it is possible to calculate the input resistance (R = delta PD/I), the resistance related to the production of J (RJ = delta PD/delta J), and the effect of the combined resistances (delta J/I). The driving force for J can be estimated (PDJ = 0-PD). The relationships among currents, voltages and resistance can be used to determine the characteristics of the membranes that are associated with the outward potassium current observed at the equator. The effects of graded deformation of the lens were determined. The effects were reversible. The sites of inward and outward currents were not altered. Following deformation, the equatorial current, J, increased, and the PD became less negative. The PDJ = 0 remains the same so the ratio of K

  5. Possible role of oceanic heat transport in Early Eocene climate

    NASA Astrophysics Data System (ADS)

    Sloan, L. Cirbus; Walker, James C. G.; Moore, T. C.

    1995-04-01

    Increased oceanic heat transport has often been cited as a means of maintaining warm high-latitude surface temperatures in many intervals of the geologic past, including the early Eocene. Although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically, determining how additional oceanic heat transport would take place has yet to be accomplished. That the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked. Using early Eocene climate as an example, we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early Eocene conditions. Our interpolation of early Eocene paleotemperature data indicate that an ˜30% increase in poleward heat transport would be required to maintain Eocene high-latitude temperatures. This increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early Eocene rates. Either oceanic processes were very different from those of the present to produce the early Eocene climate conditions or oceanic heat transport was not the primary cause of that climate. We believe that atmospheric processes, with contributions from other factors, such as clouds, were the most likely primary cause of early Eocene climate.

  6. Possible role of oceanic heat transport in early Eocene climate.

    PubMed

    Sloan, L C; Walker, J C; Moore, T C

    1995-04-01

    Increased oceanic heat transport has often been cited as a means of maintaining warm high-latitude surface temperatures in many intervals of the geologic past, including the early Eocene. Although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically, determining how additional oceanic heat transport would take place has yet to be accomplished. That the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked. Using early Eocene climate as an example, we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early Eocene conditions. Our interpolation of early Eocene paleotemperature data indicate that an approximately 30% increase in poleward heat transport would be required to maintain Eocene high-latitude temperatures. This increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early Eocene rates. Either oceanic processes were very different from those of the present to produce the early Eocene climate conditions or oceanic heat transport was not the primary cause of that climate. We believe that atmospheric processes, with contributions from other factors, such as clouds, were the most likely primary cause of early Eocene climate.

  7. Structural characteristics of rain fields

    NASA Astrophysics Data System (ADS)

    Mesnard, FréDéRic; Sauvageot, Henri

    2003-07-01

    This paper analyzes the shape of rain area size distributions (RASDs) observed by radar in tropical and midlatitude regions. The rain area is defined, with respect to a rain threshold τ, as the area, inside a contour, where the rain rate is higher than τ. The size considered is the diameter of the equivalent circular area D. The reflectivity peaks inside the rain areas are numbered and the rain areas put together by classes having the same peak number. The size distributions of the rain areas containing the same number of peaks p are well fitted by lognormal functions, the parameters of which, μp and σp, are weakly dependent on the conditions of the peak determination. The parameters μp and σp are found to be linked by a power relation. For D < 6 km most of the rain areas are single peaked. The RASD without peak number distinction is a lognormal mixture. Using the relations obtained for μp, σp, and the rain area number as functions of p enables one to simulate RASDs with results in good agreement with the observations. Because of the limitation in the radar sampling at both ends of the RASD and the decrease of area number with increasing size, the radar-observed RASDs are severely truncated. The possibility of an approximate fitting of the truncated RASD with diverse functions is discussed. At the intermediary values of the threshold, i.e., for τ ranging between 3 and 12 mm h-1, where the RASD is easiest to compute, the slope of these truncated distributions is not strongly dependent on the threshold. This slope appears not to be very sensitive to the minimum and maximum distances bounding the domain where the rain field is observed. The RASD is found to be sloping more over sea than over land. The slope of the RASDs shows a small diurnal variation but no significant annual variation. The "perimeter to area" (fractal) dimension of the rain area for the sample without peak number distinction is around 1.35. Single-peaked and multipeaked rain areas have

  8. Be an acid rain detective

    SciTech Connect

    Atwill, L.

    1982-07-01

    Acid rain is discussed in a question and answer format. The article is aimed at educating sport fishermen on the subject, and also to encourage them to write their congressmen, senators, and the President about the acid rain problem. The article also announces the availability of an acid rain test kit available through the magazine, ''Sports Afield.'' The kit consists of pH-test paper that turns different shades of pink and blue according to the pH of the water tested. The color of the test paper is then compared to a color chart furnished in the kit and an approximate pH can be determined.

  9. Can crops tolerate acid rain

    SciTech Connect

    Kaplan, J.K.

    1989-11-01

    This brief article describes work by scientists at the ARS Air Quality-Plant Growth and Development Laboratory in Raleigh, North Carolina, that indicates little damage to crops as a result of acid rain. In studies with simulated acid rain and 216 exposed varieties of 18 crops, there were no significant injuries nor was there reduced growth in most species. Results of chronic and acute exposures were correlated in sensitive tomato and soybean plants and in tolerant winter wheat and lettuce plants. These results suggest that 1-hour exposures could be used in the future to screen varieties for sensitivity to acid rain.

  10. Rain rate distributions for China from hourly rain gauge data

    NASA Astrophysics Data System (ADS)

    Li, Li; Zhu, Yuan-Jing; Zhao, Bolin

    1998-05-01

    Rain rate cumulative lognormal and Gamma distributions are calculated from hourly rain gauge data collected in 1991 at 333 locations in China. The Gamma distribution better represents the statistical rain rate distribution. So 1-min cumulative distribution to every gauge station is derived from the piecewise regression results of Gamma distribution through half-empirical conversion coefficients. We suggest the following actions: (1) In south China, there should be an approximately 9°E×5°N area of rain climatic zone K centered at about 112°E, 26°N inside International Telecommunication Union(ITU)-R designed zone M. (2) A geostationary communication satellite for China should be placed over eastern China (between 100°E and 125°E) in order to generally reduce the rain attenuation of Earth-satellite links all over China, based on rain rate distributions characteristic of China. Our data treatment procedure and results presented in this paper may be practical and useful in engineering design.

  11. Rain Rate Statistics in Southern New Mexico

    NASA Technical Reports Server (NTRS)

    Paulic, Frank J., Jr.; Horan, Stephen

    1997-01-01

    The methodology used in determining empirical rain-rate distributions for Southern New Mexico in the vicinity of White Sands APT site is discussed. The hardware and the software developed to extract rain rate from the rain accumulation data collected at White Sands APT site are described. The accuracy of Crane's Global Model for rain rate predictions is analyzed.

  12. EQUATORIAL SUPERROTATION ON TIDALLY LOCKED EXOPLANETS

    SciTech Connect

    Showman, Adam P.; Polvani, Lorenzo M.

    2011-09-01

    The increasing richness of exoplanet observations has motivated a variety of three-dimensional (3D) atmospheric circulation models of these planets. Under strongly irradiated conditions, models of tidally locked, short-period planets (both hot Jupiters and terrestrial planets) tend to exhibit a circulation dominated by a fast eastward, or 'superrotating', jet stream at the equator. When the radiative and advection timescales are comparable, this phenomenon can cause the hottest regions to be displaced eastward from the substellar point by tens of degrees longitude. Such an offset has been subsequently observed on HD 189733b, supporting the possibility of equatorial jets on short-period exoplanets. Despite its relevance, however, the dynamical mechanisms responsible for generating the equatorial superrotation in such models have not been identified. Here, we show that the equatorial jet results from the interaction of the mean flow with standing Rossby waves induced by the day-night thermal forcing. The strong longitudinal variations in radiative heating-namely intense dayside heating and nightside cooling-trigger the formation of standing, planetary-scale equatorial Rossby and Kelvin waves. The Rossby waves develop phase tilts that pump eastward momentum from high latitudes to the equator, thereby inducing equatorial superrotation. We present an analytic theory demonstrating this mechanism and explore its properties in a hierarchy of one-layer (shallow-water) calculations and fully 3D models. The wave-mean-flow interaction produces an equatorial jet whose latitudinal width is comparable to that of the Rossby waves, namely the equatorial Rossby deformation radius modified by radiative and frictional effects. For conditions typical of synchronously rotating hot Jupiters, this length is comparable to a planetary radius, explaining the broad scale of the equatorial jet obtained in most hot-Jupiter models. Our theory illuminates the dependence of the equatorial jet

  13. On the modelling of equatorial waves

    NASA Astrophysics Data System (ADS)

    Constantin, A.

    2012-03-01

    The present theory of geophysical waves that either raise or lower the equatorial thermocline, based on the reduced-gravity shallow-water equations on the β-plane, ignores vertical variations of the flow. In particular, the vertical structure of the Equatorial Undercurrent is absent. As a remedy we propose a simple approach by modeling this geophysical process as a wave-current interaction in the f-plane approximation, the underlying current being of positive constant vorticity. The explicit dispersion relation allows us to conclude that, despite its simplicity, the proposed model captures to a reasonable extent essential features of equatorial waves.

  14. Ozone and Aitken nuclei over equatorial Africa - Airborne observations during DECAFE 88

    NASA Technical Reports Server (NTRS)

    Andreae, M. O.; Chapuis, A.; Cros, B.; Fontan, J.; Helas, G.; Justice, C.; Kaufman, Y. J.; Minga, A.; Nganga, D.

    1992-01-01

    Results of ozone and Aitken condensation nuclei measurements made over the rain forest in equatorial Africa during February 12-25, 1988 are presented. The results indicate the presence of a layer between 1 and 4 km altitude where these species are strongly enriched. Based on information derived from simultaneous measurements of other chemical and meteorological parameters, satellite imagery, and trajectory calculations, this enrichment is attributed to emissions from biomass burning in sub-Saharan Africa, from which ozone is formed by photochemical reactions.

  15. Tectonic control of Eocene arkosic sediment deposition, Oregon and Washington

    SciTech Connect

    Armentrout, J.M.; Ulrich, A.R.

    1983-03-01

    Chronostratigraphic and geographic studies of Eocene arkosic sandstones suggest deposition during a volcanically quiet interval resulting from the westward jump of the Farallon-Kula plate subduction zone in Oregon and Washington. The Eocene arkosic sandstones were deposited as part of a broad fluvial plain-coastal plain-shelf margin basin complex extending throughout Oregon and Washington between uplands of Mesozoic rocks. Feldspathic-quartzose sediments were transported from the east by river systems draining granitic terrains perhaps as far away as the Idaho Batholith. Chronostratigraphic correlations suggest that the arkosic sandstones were deposited along the margins of the depositional system during the early Eocene, prograded westward during the middle Eocene, and then regressed during the latest Eocene and Oligocene simultaneously with the influx of abundant pyroclastic debris. During the early Eocene, a northwest-southeast seamount chain was extruded on the Farallon and Kula plates west of an eastward-dipping subduction zone. Subduction of the oceanic plates moved the seamount chain obliquely toward the subduction zone. In middle Eocene time-49 to 40 m.y.b.p-the seamount chain reached the subduction zone creating instability in the subduction system and resulting in the westward jump of the underthrust boundary between the Farallon-Kula and North American plates. Coincident with and continuing after the subduction zone jump and seamount accretion, eastwardly derived arkosic sediments prograded across Oregon and Washington spilling into the new fore-arc basin and enveloping the seamounts.

  16. Seminal role of stratiform clouds in large-scale aggregation of tropical rain in boreal summer monsoon intraseasonal oscillations

    NASA Astrophysics Data System (ADS)

    Kumar, Siddharth; Arora, Anika; Chattopadhyay, R.; Hazra, Anupam; Rao, Suryachandra A.; Goswami, B. N.

    2016-04-01

    Modification of the vertical structure of non-adiabatic heating by significant abundance of the stratiform rain in the tropics has been known to influence the large-scale circulation. However, the role of the stratiform rain on the space-time evolution of the observed Boreal summer monsoon intraseasonal oscillations (MISO) has so far been ignored. In the present study, we unravel a feedback mechanism through which the stratiform component of the rain leads to aggregation (organization) of rain on the MISO scale, making it an indispensable component of the MISO evolution dynamics. Using TRMM 3A25 monthly mean data (between 1998 and 2013), the ratio between convective and stratiform rain (RCS) is shown to be strongly related to the total rainfall. Further, composites of rainfall and circulation anomalies corresponding to high (low) values of RCS over the Central India or over the Equatorial Indian Ocean show spatial structures remarkably similar to that associated with the MISOs. Analyzing lead-lag relationship between the convective rain, the stratiform rain and the large scale moisture convergence with respect to peak active (break) spells from daily modern era retrospective-analysis for research and applications data, we unravel that the initial isolated convective elements spawn the stratiform rain which in turn modifies the vertical distribution of heating and leads to stronger large scale moisture convergence thereby producing more convective elements and more stratiform rain ultimately leading to aggregation of rain on the MISO scale. Our finding indicates that large and persisting systematic biases in simulating the summer monsoon rainfall over the Asian monsoon region by climate models are likely to be related to the systematic biases in simulating the MISOs which in turn are related to the serious underestimation of stratiform rain in most climate models.

  17. Seminal role of stratiform clouds in large-scale aggregation of tropical rain in boreal summer monsoon intraseasonal oscillations

    NASA Astrophysics Data System (ADS)

    Kumar, Siddharth; Arora, Anika; Chattopadhyay, R.; Hazra, Anupam; Rao, Suryachandra A.; Goswami, B. N.

    2017-02-01

    Modification of the vertical structure of non-adiabatic heating by significant abundance of the stratiform rain in the tropics has been known to influence the large-scale circulation. However, the role of the stratiform rain on the space-time evolution of the observed Boreal summer monsoon intraseasonal oscillations (MISO) has so far been ignored. In the present study, we unravel a feedback mechanism through which the stratiform component of the rain leads to aggregation (organization) of rain on the MISO scale, making it an indispensable component of the MISO evolution dynamics. Using TRMM 3A25 monthly mean data (between 1998 and 2013), the ratio between convective and stratiform rain (RCS) is shown to be strongly related to the total rainfall. Further, composites of rainfall and circulation anomalies corresponding to high (low) values of RCS over the Central India or over the Equatorial Indian Ocean show spatial structures remarkably similar to that associated with the MISOs. Analyzing lead-lag relationship between the convective rain, the stratiform rain and the large scale moisture convergence with respect to peak active (break) spells from daily modern era retrospective-analysis for research and applications data, we unravel that the initial isolated convective elements spawn the stratiform rain which in turn modifies the vertical distribution of heating and leads to stronger large scale moisture convergence thereby producing more convective elements and more stratiform rain ultimately leading to aggregation of rain on the MISO scale. Our finding indicates that large and persisting systematic biases in simulating the summer monsoon rainfall over the Asian monsoon region by climate models are likely to be related to the systematic biases in simulating the MISOs which in turn are related to the serious underestimation of stratiform rain in most climate models.

  18. Longitudinal variations of the equatorial electojet

    NASA Astrophysics Data System (ADS)

    Shume, Esayas

    We have utilized a three dimensional electrostatic potential model to explain the longitudinal variations of the equatorial electrojet. The model runs were constrained by net H component magnetic field measurements from three equatorial stations, namely, Huancayo (Peru) 12.05 S, 284.67 E; Addis Ababa (Ethiopia) 9.8 N, 38.8 E; Tirunelveli (India) 8.42 N, 77.48 E. The model runs were done in an iterative fashion until the computed and measured H component magnetic field values come into a close agreement. The physical mechanisms for the longitudinal variations of the equatorial electrojet were inferred by comparing and contrasting the resulting computed vertical polarization electric field (which drives the equatorial electrojet), and zonal current density profiles for the three stations mentioned above.

  19. Equatorial thermosphere anomaly: Observations and simulations

    NASA Astrophysics Data System (ADS)

    Lei, J.; Thayer, J. P.; Wang, W.; Richmond, A. D.

    2011-12-01

    Several mechanisms including heat transport due to zonal winds, chemical heating and field-aligned ion drag have been proposed to explain the formation of the Equatorial Thermosphere Anomaly (ETA), but the real cause of the ETA formation in thermosphere temperature is still a mystery. Various observations of the ionosphere and thermosphere have been used to investigate the variations of equatorial anomalies in both the ETA and EIA, and their interactions. The similarities and differences between the ETA and the EIA can provide important insight to the physical connections of this ion-neutral coupling problem. Meanwhile, the combination of observations and theoretical models allows us to understand the fundamental physical and chemical ion-neutral processes in the equatorial F region. This talk will highlight the recent progress of the formation of the ETA associated with the ion-neutral coupling in the equatorial region.

  20. The Arctic Forest of the Middle Eocene

    NASA Astrophysics Data System (ADS)

    Jahren, A. Hope

    2007-05-01

    Lush forests, dominated by deciduous conifers, existed well north of the Arctic Circle during the middle Eocene (45 Ma). The Fossil Forest site, located on Axel Heiberg Island, Canada, has yielded a particularly rich assemblage of plant macro- and microfossils, as well as paleosols -- all exquisitely preserved. Methods ranging from classical paleobotany, to stable-isotope geochemistry, have been applied to materials excavated from the Fossil Forest and have revealed layers of diverse conifer forests with a rich angiosperm understory that successfully endured three months of continuous light and three months of continuous darkness. Paleoenvironmental reconstructions suggest a warm, ice-free environment, with high growing-season-relative humidity, and high rates of soil methanogenesis. Methods to evaluate intraseasonal variability highlight the switchover from stored to actively fixed carbon during the short annual growing season.

  1. Digital ionosonde observations during equatorial spread F-italic

    SciTech Connect

    Argo, P.E.; Kelley, M.C.

    1986-05-01

    In this paper we present and discuss equatorial spread F-italic data taken with a digital ionosonde/HF radar located at Huancayo, Peru. A modified phenomenology is developed which uses the system's ability to do echo location. The onset of irregularities is seen to occur in the east and to move westward, while inside this large-scale structure the plasma is found to drift eastward. A very curious difference has been identified between spread F-italic observations with the ionosonde and with the VHF radar at Jicamarca. At VHF, spread F-italic onset often occurs when the ionosphere is rising, whereas in all five examples presented here, the digital ionosonde detected onset when the apparent ionosphere motion was downward. The result even held on the one night of common data taking. The effect could be instrumental but may be related to the considerable orographic differences in the two sites. Isolated scattering patches are observed and are tentatively identified as detached or ''fossil'' plumes. At frequencies above the nominal f-italic/sub 0/F-italic/sub 2/ the system (and other ionosondes) may in fact function as a coherent radar. During one night, data were obtained simultaneously with the HF radar, a rocket, and the Jicamarca VHF radar. Comparisons of these data are discussed in detail. Finally, additional evidence is presented that acoustic gravity waves play a role in the development of equatorial spread F-italic and in the formation of detached plumes. To be self-consistent, the gravity waves must come from nearby sources such as the tropical rain forest to the east of Jicamarca.

  2. Planetary boundary layer dynamics over the Amazon rain forest

    NASA Astrophysics Data System (ADS)

    Pereiradeoliveira, Amauri

    Observations of the diurnal evolution of the planetary boundary layer (PBL) over the Amazon rain forest, in the area of the Amazon boundary layer experiment (ABLE) 2A and 2B experiments showed the existence of a low level circulation with low level nocturnal maxima winds. These circulations are shown to be induced by the thermal contrast between the river and the forest. A linear model was applied to identify the horizontal extent of these circulations and an associated perturbation pressure gradient consistent with the observations. A second order closure model was used to simulate changes in the PBL caused by the thermal circulation. Good agreement with the observations was obtained when the forcing was a horizontal pressure gradient equal to 0.5 mb/100km of limited vertical extent. The dynamics of the equatorial PBL was shown to be plausibly explained using a hypothesis of a river breeze circulation.

  3. Planetary Boundary Layer Dynamics Over the Amazon Rain Forest

    NASA Astrophysics Data System (ADS)

    Oliveira, Amauri Pereira De.

    1990-02-01

    Observations of the diurnal evolution of the Planetary Boundary Layer (PBL) over the Amazon rain forest, in the area of the ABLE 2A and 2B experiments showed the existence of a low level circulation with low level nocturnal maxima winds. These circulations are shown to be induced by the thermal contrast between the river and the forest. A linear model was applied to identify the horizontal extent of these circulations and an associated perturbation pressure gradient consistent with the observations. A second order closure model was used to simulate changes in the PBL caused by the thermal circulation. Good agreement with the observations was obtained when the forcing was a horizontal pressure gradient equal to 0.5 mb/100km of limited vertical extent. The dynamics of the equatorial PBL was shown to be plausibly explained using a hypothesis of a river breeze circulation.

  4. Understanding the Unique Equatorial Density Irregularities

    DTIC Science & Technology

    2015-04-01

    monitoring devices. In addition, the Low Earth Orbiting (LEO) satellites ion density observations show unique features for the African sector [Hei et al. 2005...installed in Africa [Amory-Mazaudier, et al. 2009] since 2007. Alongside this activity, universities in Africa (e.g. Bahir Dar Uni- versity, Ethiopia...African sector, show unique equatorial iono- spheric structure [Hei et al. 2005]. For example, this region equatorial plasma bubbles, which produce

  5. EQUATORIAL ZONAL JETS AND JUPITER's GRAVITY

    SciTech Connect

    Kong, D.; Liao, X.; Zhang, K.; Schubert, G.

    2014-08-20

    The depth of penetration of Jupiter's zonal winds into the planet's interior is unknown. A possible way to determine the depth is to measure the effects of the winds on the planet's high-order zonal gravitational coefficients, a task to be undertaken by the Juno spacecraft. It is shown here that the equatorial winds alone largely determine these coefficients which are nearly independent of the depth of the non-equatorial winds.

  6. Periodic Structures in the Equatorial Ionosphere (Postprint)

    DTIC Science & Technology

    2012-05-13

    AFRL-RV-PS- AFRL-RV-PS- TP-2012-0004 TP-2012-0004 PERIODIC STRUCTURES IN THE EQUATORIAL IONOSPHERE (POSTPRINT) Cheryl Y. Huang...in the Equatorial Ionosphere (Postprint) 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) 5d. PROJECT NUMBER 2301...International Reference Ionosphere model to remove variations in density due to changes in spacecraft altitude and latitude along the orbit. In this

  7. Was the Arctic Eocene 'rainforest' monsoonal? Estimates of seasonal precipitation from early Eocene megafloras from Ellesmere Island, Nunavut

    NASA Astrophysics Data System (ADS)

    West, Christopher K.; Greenwood, David R.; Basinger, James F.

    2015-10-01

    The early Eocene was the warmest interval of the Cenozoic, and included within it were several hyperthermal events, with the Paleocene-Eocene Thermal Maximum (PETM) the most pronounced of these. These globally warm climates extended into the Arctic and substantive paleobotanical evidence for high Arctic precipitation (MAP > 150 cm/yr) is indicative of an Arctic rainforest, which contradicts some climate models that show low Arctic precipitation. Prior studies of Arctic early Eocene wood stable-isotope chemistry, however, have shown a summer peak in precipitation, which suggests modern analogs are best sought on the summer-wet east coast of the Asia (e.g., China, Japan, South Korea), not the winter-wet west coasts of the Pacific Northwest of North America). Furthermore, some prior modeling data suggest that highly seasonal 'monsoon-type' summer-wet precipitation regimes (i.e., summer:MAP > 55%) characterized certain mid and lower latitude regions in the early to mid-Eocene. Presented here is a new analysis using leaf physiognomy of 3 leaf megafloras (Split Lake, Stenkul Fiord and Strathcona Fiord) and palynofloral Bioclimatic Analysis from the Margaret Formation from Ellesmere Island, placed stratigraphically as early Eocene, possibly occurring during or following one of the early Eocene hyperthermals. These new data indicate high summer precipitation in the Arctic during the early Eocene, which in part corroborates the results from Eocene wood chemistry. Nevertheless, in contradiction to the wood analysis, monsoonal conditions are not indicated by our analysis, consistent with current modeling studies. High summer (light season) and winter (dark season) precipitation in the Eocene Arctic during hyperthermals would have contributed to regional warmth.

  8. Dynamic, Large-Magnitude CCD Changes in the Atlantic During the Middle Eocene Climatic Optimum

    NASA Astrophysics Data System (ADS)

    Kordesch, W.; Bohaty, S. M.; Palike, H.; Wilson, P. A.; Edgar, K. M.; Agnini, C.; Westerhold, T.; Roehl, U.

    2015-12-01

    The Middle Eocene Climatic Optimum (MECO; ~40.1 Ma) is a transient global warming event that abruptly reversed the long-term Eocene cooling trend. The primary driving mechanism(s) must be linked to a CO2 increase; however, geochemical modeling experiments show that prevailing hypotheses are incompatible with the paleoclimate record. To further examine changes in deep-sea carbonate burial, we identify the MECO for the first time at ODP Site 929 (Equatorial Atlantic; ~3935 m paleodepth) and present new lithological and geochemical data for this site, including benthic foraminiferal stable isotopes (δ18O and δ13C), XRF scanning data, and an orbitally tuned age model. We combine these records with data from a suite of Atlantic sites to form a depth transect between ~2-4 km (DSDP Site 523, ODP Site 1260 and 1263, IODP Site U1404) representing the first detailed record of carbonate dissolution in the Atlantic spanning the MECO. This compilation reveals dissolution at water depths as shallow as ~2 km (>1 km shallower than previous estimates) with multiple and discrete short-lived (<100 kyr) phases of carbonate compensation depth (CCD) shoaling during and after the event. Careful reevaluation of the Pacific CCD records combined with new results suggests similar short-term variability and magnitude of shoaling globally. These data provide new constraints on carbon release history during the MECO and, potentially, the forcing mechanisms for warming. The transient CCD shoaling events indicate multiple pulses of carbon input and acidification decoupled from deep-sea δ18O and δ13C records, indicating that these events must not have been driven directly by changes in temperature or carbon burial/storage - potentially reconciling some of the data-model discrepancies.

  9. Atmospheric dust and acid rain

    SciTech Connect

    Hedin, L.O.; Likens, G.E.

    1996-12-01

    Why is acid rain still an environmental problem in Europe and North America despite antipollution reforms? The answer really is blowing in the wind: atmospheric dust. These airborne particles can help neutralize the acids falling on forests, but dust levels are unusually low these days. In the air dust particles can neutralize acid rain. What can we do about acid rain and atmospheric dust? Suggestions range from the improbable to the feasible. One reasonable suggestion is to reduce emissions of acidic pollutants to levels that can be buffered by natural quantities of basic compounds in the atmosphere; such a goal would mean continued reductions in sulfur dioxide and nitrogen oxides, perhaps even greater than those prescribed in the 1990 Amendments to the Clean Air Act in the U.S. 5 figs.

  10. The Terrestrial Eocene-Oligocene Transition in North America

    NASA Astrophysics Data System (ADS)

    Prothero, Donald R.; Emry, Robert J.

    1996-06-01

    The transition from the Eocene to the Oligocene epoch, occurring approximately 47 to 30 million years ago, was the most dramatic episode of climatic and biotic change since the demise of the dinosaurs. The mild tropical climates of the Paleocene and early Eocene were replaced by modern climatic conditions and extremes, including glacial ice in Antarctica. The first part of this book summarizes the latest information in the dating and correlation of the strata of late middle Eocene through early Oligocene age in North America. The second part reviews almost all the important terrestrial reptiles and mammals found near the Eocene-Oligocene boundary, in the White River Chronofauna--from the turtles, snakes and lizards to the common rodents, carnivores, oreodonts and deer of the Badlands. This is the first comprehensive treatment of these topics in over sixty years, and will be invaluable to vertebrate paleontologists, geologists, mammalogists and evolutionary biologists.

  11. Dissolution kinetics of calcium carbonate in equatorial Pacific sediments

    NASA Astrophysics Data System (ADS)

    Berelson, William M.; Hammond, Douglas E.; McManus, James; Kilgore, Tammy E.

    1994-06-01

    Benthic chambers were deployed in the equatorial eastern Pacific Ocean on a transect along the equator between 103°W and 140°W and on a transect across the equator at 140°W in order to establish the rate of calcium carbonate dissolution on the seafloor. Dissolution was determined from the rate of alkalinity increase within an incubation chamber, measured over an 80-120 hour incubation period. Dissolution rates were lowest at eastern Pacific sites (0.2-0.4 mmol CaCO3/m2/d) and highest at the equatorial, 140°W sites (0.5-0.7 mmol/m2/d). Both oxygen consumption rates and the degree of bottom water saturation govern dissolution rates. Measured dissolution and oxygen consumption rates are used with a numerical model to constrain the value of the dissolution rate constant k, formulated according to the equation developed by Keir [1980]: dissolution rate = kγ(1-Ω)n. The observed dissolution fluxes are predicted by the model when k = 5 to 100%/d and n = 4.5. This range of k values has important implications regarding the type of carbonate dissolving and its location within the sediment column. At low values of k, organic carbon rain rates to the seafloor become the dominant driving force of carbonate dissolution. At higher values of k, the degree of bottom water undersaturation becomes more important. Dissolution of carbonate within equatorial Pacific sediments can be adequately described with k = 20 ± 10%/d, a rate constant much lower than some previously used values. Dissolution rates do not vary significantly over chamber boundary layer thicknesses between 200 and 800 μm, indicating that dissolution is not controlled by hydrodynamic conditions. Chambers acidified with HCl yield very large dissolution rates, but for a given degree of acidification the dissolution rate was constant for sites ranging from water depths of 3300-4400 m. This implies that there are not more and less easily dissolved forms of CaCO3 arriving on the seafloor between these depths. A budget

  12. Latitudinal comparisons of equatorial Pacific zooplankton

    NASA Astrophysics Data System (ADS)

    Roman, M. R.; Dam, H. G.; Le Borgne, R.; Zhang, X.

    Zooplankton biomass and rates of ingestion, egestion and production in the equatorial Pacific Ocean along 140°W and 180° exhibit maximum values in the High-Nutrient Low-Chlorophyll (HNLC) zone associated with equatorial upwelling (5°S-5°N) as compared to the more oligotrophic regions to the north and south. Zooplankton biomass and rates are not usually highest on the equator, but increase "downstream" of the upwelling center as the zooplankton populations exhibit a delayed response to enhanced phytoplankton production. The vertical distribution of zooplankton biomass in the equatorial HNLC area tends to be concentrated in surface waters and is more uniform with depth in oligotrophic regions to the north and south of the equatorial upwelling zone. In general, the amount of mesozooplankton (>200 μm) carbon biomass is approximately 25% of estimated phytoplankton biomass and 30% of bacterial biomass in the HNLC area of the equatorial Pacific Ocean. Zooplankton grazing on phytoplankton is low in the equatorial Pacific Ocean, generally <5% of the total chlorophyll-a standing stock grazed per day. Based on estimates of metabolic demand, it is apparent that zooplankton in the equatorial Pacific Ocean are omnivores, consuming primarily microzooplankton and detritus. Estimated zooplankton growth rates in the warm waters of the HNLC equatorial Pacific Ocean are high, ranging from 0.58 d -1 for 64-200 μm zooplankton to 0.08 d -1 for 1000-2000 μm zooplankton. Thus, the numerical and functional response of equatorial zooplankton to increases in phytoplankton production are more rapid than normally occurs in sub-tropical and temperate waters. Potential zooplankton fecal pellet production, estimated from metabolic demand, is approximately 1.6 times the estimated gravitational carbon flux at 150 m in the zone of equatorial upwelling (5°S-5°N) and 1.1 times the export flux in the more oligotrophic regions to the north and south. The active flux of carbon by diel migrant

  13. Vegetable production after heavy rains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is not clear if extraordinary precipitation stored in the soil was able to support vegetable crops planted after rains events returned to normal levels. Cucumber and sweet corn were established from seed and non-pungent jalapeno peppers were established from 8-week old transplants on beds. Half...

  14. Voronoi Diagrams and Spring Rain

    ERIC Educational Resources Information Center

    Perham, Arnold E.; Perham, Faustine L.

    2011-01-01

    The goal of this geometry project is to use Voronoi diagrams, a powerful modeling tool across disciplines, and the integration of technology to analyze spring rainfall from rain gauge data over a region. In their investigation, students use familiar equipment from their mathematical toolbox: triangles and other polygons, circumcenters and…

  15. THE ACID RAIN NOX PROGRAM

    EPA Science Inventory

    Between 350,000 and 400,000 tons of annual NOx emissions have been eliminated as a result of Phase I of the Acid Rain NOx Program. As expected. the utilities have chosen emissions averaging as the primary compliance option. This reflects that, in general, NO x reductions have ...

  16. Transition to a climate state qualitatively different from modern in NCAR CCSM simulations of the Eocene

    NASA Astrophysics Data System (ADS)

    Caballero, R.; Huber, M.; Hanley, J.

    2012-04-01

    Recent paleoclimate proxy reconstructions indicate that global-mean surface temperatures in past warm climates may have been some 10-15°C higher than today. Little is known about atmospheric dynamics at temperatures this warm. In particular, is it possible that the general circulation may transition to a qualitatively different state at warm enough temperatures? We study this question in a set of simulations using NCAR's Community Climate System Model in both full- and slab-ocean configurations with a range of atmospheric CO2 concentrations extending from preindustrial values (280 ppm) up to 8960 ppm (5 doublings). We find that the simulation at 4480 ppm CO2 gives a remarkably good fit to recent surface temperature reconstructions of the early Eocene, and does not suffer from the classical 'low gradient' problem. We also find that the atmospheric general circulation in this and warmer simulations differs qualitatively from the modern regime in at least two major ways: 1) When equatorial surface temperatures exceed ~33°C, the model undergoes a transition to equatorial superrotation, a state with strong annual- and zonal-mean westerlies on the equator. The transition is driven by zonal momentum convergence due to large-amplitude transient eddies on the equator. These eddies have a structure similar to the observed Madden-Julian Oscillation (MJO). The model's MJO variability is weaker than observed when simulating the modern climate but increases sharply with temperature, coming to dominate the tropical variability and mean state of the warmest climates. 2) Poleward atmospheric moisture transport across midlatitudes decreases with increasing temperature, the opposite behaviour to that at temperatures close to modern. We account for this non-monotonic behaviour in terms of a simple diffusive model of the oceanic storm tracks which suggests that it is due mostly to the drop in mean eddy amplitudes as temperature increases.

  17. On-Disk Coronal Rain

    NASA Astrophysics Data System (ADS)

    Antolin, Patrick; Vissers, Gregal; Rouppe van der Voort, Luc

    2012-10-01

    Small and elongated, cool and dense blob-like structures are being reported with high resolution telescopes in physically different regions throughout the solar atmosphere. Their detection and the understanding of their formation, morphology, and thermodynamical characteristics can provide important information on their hosting environment, especially concerning the magnetic field, whose understanding constitutes a major problem in solar physics. An example of such blobs is coronal rain, a phenomenon of thermal non-equilibrium observed in active region loops, which consists of cool and dense chromospheric blobs falling along loop-like paths from coronal heights. So far, only off-limb coronal rain has been observed, and few reports on the phenomenon exist. In the present work, several data sets of on-disk Hα observations with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1- m Solar Telescope (SST) are analyzed. A special family of on-disk blobs is selected for each data set, and a statistical analysis is carried out on their dynamics, morphology, and temperature. All characteristics present distributions which are very similar to reported coronal rain statistics. We discuss possible interpretations considering other similar blob-like structures reported so far and show that a coronal rain interpretation is the most likely one. The chromospheric nature of the blobs and the projection effects (which eliminate all direct possibilities of height estimation) on one side, and their small sizes, fast dynamics, and especially their faint character (offering low contrast with the background intensity) on the other side, are found as the main causes for the absence until now of the detection of this on-disk coronal rain counterpart.

  18. Rain Hampers Tsunami Relief Efforts

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The cleanup and relief efforts from the recent tsunamis continue in coastal communities that were ravaged by the waves all across the Indian Ocean. Heavy rains have further complicated the matter and added to the misery in parts of eastern Sri Lanka. Between December 28, 2004, and January 5, 2005, up to 10 to 15 inches of rain may have fallen along the southeast coast of the island, and as much as 20 inches (red areas) fell just offshore. This rainfall map was created by the TRMM-based, near-real time Multi-satellite Precipitation Analysis (MPA) at the NASA Goddard Space Flight Center, which monitors rainfall over the global tropics. The map shows that many other regions around the Indian Ocean were also affected by the rains, including Malaysia and parts of Sumatra. The heaviest rains fell on December 31 and January 4. The rains were likely the result of a combination of the northeast monsoon interacting with the topography and an active phase of what is known as the Madden-Julian Oscillation (MJO) (or 30-60 day oscillation). The MJO is a large-scale disturbance that propagates eastward from the Indian Ocean into the West Pacific Ocean, bringing extended periods of unsettled weather with it. Individual convective complexes within the MJO can last on the order of a day. TRMM is a joint mission between NASA and the Japanese space agency JAXA. NASA image produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).

  19. Nature in the Classroom: Acid Rain.

    ERIC Educational Resources Information Center

    Doyle, Charles

    1982-01-01

    As a lesson topic, acid rain is defined, its chemistry given, and its development since the 1950s described. The worldwide effects of acid rain are discussed along with the available technology for controlling the problem. (CM)

  20. Acid Rain: The Silent Environmental Threat.

    ERIC Educational Resources Information Center

    Zmud, Mia

    1992-01-01

    Describes the silent environmental threat posed by acid rain. Caused mainly by manmade pollutants, acid rain damages water and trees, decreases visibility, corrodes monuments, and threatens public health. The article includes guidelines for action. (SM)

  1. Inter-comparison of automatic rain gauges

    NASA Technical Reports Server (NTRS)

    Nystuen, Jeffrey A.

    1994-01-01

    The Ocean Acoustics Division (OAD) of the Atlantic Oceanographic and Meteorological Laboratory (AOML), in cooperation with NOAA/NESDIS and NASA, has deployed six rain gauges for calibration and intercomparison purposes. These instruments include: (1) a weighing rain gauge, (2) a RM Young Model 50202 capacitance rain gauge, (3) a ScTI ORG-705 (long path) optical rain gauge, (4) a ScTI ORG-105 (mini-ORG) optical rain gauge, (5) a Belfort Model 382 tipping bucket rain gauge, and (6) a Distromet RD-69 disdrometer. The system has been running continuously since July 1993. During this time period, roughly 150 events with maximum rainfall rate over 10 mm/hr and 25 events with maximum rainfall rates over 100 mm/hr have been recorded. All rain gauge types have performed well, with intercorrelations 0.9 or higher. However, limitations for each type of rain gauge have been observed.

  2. Acid Rain Program Opt-in Factsheet

    EPA Pesticide Factsheets

    Learn about the Opt-in Program, which allows sources not required to participate in the Acid Rain Program the opportunity to enter the program on a voluntary basis and receive Acid Rain Program allowances.

  3. Fertilizing the Amazon and equatorial Atlantic with West African dust

    NASA Astrophysics Data System (ADS)

    Bristow, Charlie S.; Hudson-Edwards, Karen A.; Chappell, Adrian

    2010-07-01

    Atmospheric mineral dust plays a vital role in Earth's climate and biogeochemical cycles. The Bodélé Depression in Chad has been identified as the single biggest source of atmospheric mineral dust on Earth. Dust eroded from the Bodélé is blown across the Atlantic Ocean towards South America. The mineral dust contains micronutrients such as Fe and P that have the potential to act as a fertilizer, increasing primary productivity in the Amazon rain forest as well as the equatorial Atlantic Ocean, and thus leading to N2 fixation and CO2 drawdown. We present the results of chemical analysis of 28 dust samples collected from the source area, which indicate that up to 6.5 Tg of Fe and 0.12 Tg of P are exported from the Bodélé Depression every year. This suggests that the Bodélé may be a more significant micronutrient supplier than previously proposed.

  4. Acid rain control: the costs of compliance

    SciTech Connect

    Gilleland, D.S.; Swisher, J.H.

    1985-01-01

    This document is the proceedings from a conference sponsored by the Illinois Energy Resources Commission and the Coal Extraction and Utilization Research Center, Southern Illinois University at Carbondale and held in Carbondale on March 18, 1984. Topics addressed include: the sources and impacts of acid rain, the problems inherent in modeling the impacts of acid rain legislation, the effects of acid rain legislation on the socio-economic sector, compliance costs, and the impact of acid rain legislation on related industries (railroads).

  5. Acid Rain: What We Must Do.

    ERIC Educational Resources Information Center

    Gorham, Eville

    1983-01-01

    Addresses questions about the nature, source, and history of acid rain. In addition, discusses the questions: Why is acid rain a problem? Is acid rain getting worse? What is the threat of further problems? Concludes that it is time to act on the problem and recommends an appropriate course of action. (JN)

  6. Create a Rain Forest in the Gym.

    ERIC Educational Resources Information Center

    Kane, Karen

    1995-01-01

    Describes a creative interdisciplinary program for K-3 students that involves setting up a rain forest in the gymnasium to teach students gymnastic skills in the context of the Amazon rain forest. The paper describes how to set up the rain forest and teach a variety of classes. Rainforest resources are included. (SM)

  7. Rain, Snow, and Spring Runoff Revisited.

    ERIC Educational Resources Information Center

    Bohren, Craig F.

    1995-01-01

    Explores the theory behind the correlation between warm rain, rapid snowmelt, and the subsequent runoff using the concepts of enthalpy, thermal transfer, and energy transfer. Concludes that rapid runoff is not a consequence of rain per se but of the high humidities associated with the rain. (JRH)

  8. A Walk in the Rain Forest.

    ERIC Educational Resources Information Center

    Gustafson, Glenn

    2001-01-01

    Presents a learning project in which students prepare a guided, multisensory rain forest tour representing its ecology. Develops five stop points presenting a theme or an important aspect of the rain forest. Includes a list of selected resources for rain forest studies. (YDS)

  9. Rain, fog, and clouds for aircraft simulators

    NASA Technical Reports Server (NTRS)

    Chase, W. D.

    1981-01-01

    Environmental chamber creates realistic fog and rain effects in aircraft simulator. It reproduces clouds, homogeneous fog, patches of fog, rain and fog, and rain only. It is used with real time digital computer, color computer generated image display that simulates airport lights, or color television camera that produces moving display of airport runway as depicted on model terrain board.

  10. Eocene lizard from Germany reveals amphisbaenian origins.

    PubMed

    Müller, Johannes; Hipsley, Christy A; Head, Jason J; Kardjilov, Nikolay; Hilger, André; Wuttke, Michael; Reisz, Robert R

    2011-05-19

    Amphisbaenia is a speciose clade of fossorial lizards characterized by a snake-like body and a strongly reinforced skull adapted for head-first burrowing. The evolutionary origins of amphisbaenians are controversial, with molecular data uniting them with lacertids, a clade of Old World terrestrial lizards, whereas morphology supports a grouping with snakes and other limbless squamates. Reports of fossil stem amphisbaenians have been falsified, and no fossils have previously tested these competing phylogenetic hypotheses or shed light on ancestral amphisbaenian ecology. Here we report the discovery of a new lacertid-like lizard from the Eocene Messel locality of Germany that provides the first morphological evidence for lacertid-amphisbaenian monophyly on the basis of a reinforced, akinetic skull roof and braincase, supporting the view that body elongation and limblessness in amphisbaenians and snakes evolved independently. Morphometric analysis of body shape and ecology in squamates indicates that the postcranial anatomy of the new taxon is most consistent with opportunistically burrowing habits, which in combination with cranial reinforcement indicates that head-first burrowing evolved before body elongation and may have been a crucial first step in the evolution of amphisbaenian fossoriality.

  11. Widespread Antarctic glaciation during the Late Eocene

    NASA Astrophysics Data System (ADS)

    Carter, Andrew; Riley, Teal R.; Hillenbrand, Claus-Dieter; Rittner, Martin

    2017-01-01

    Marine sedimentary rocks drilled on the southeastern margin of the South Orkney microcontinent in Antarctica (Ocean Drilling Program Leg 113 Site 696) were deposited between ∼36.5 Ma to 33.6 Ma, across the Eocene-Oligocene climate transition. The recovered rocks contain abundant grains exhibiting mechanical features diagnostic of iceberg-rafted debris. Sand provenance based on a multi-proxy approach that included petrographic analysis of over 275,000 grains, detrital zircon geochronology and apatite thermochronometry rule out local sources (Antarctic Peninsula or the South Orkney Islands) for the material. Instead the ice-transported grains show a clear provenance from the southern Weddell Sea region, extending from the Ellsworth-Whitmore Mountains of West Antarctica to the coastal region of Dronning Maud Land in East Antarctica. This study provides the first evidence for a continuity of widespread glacier calving along the coastline of the southern Weddell Sea embayment at least 2.5 million yrs before the prominent oxygen isotope event at 34-33.5 Ma that is considered to mark the onset of widespread glaciation of the Antarctic continent.

  12. Paleoclimatic analyses of middle Eocene through Oligocene planktic foraminiferal faunas

    USGS Publications Warehouse

    Keller, G.

    1983-01-01

    Quantitative faunal analyses and oxygen isotope ranking of individual planktic foraminiferal species from deep sea sequences of three oceans are used to make paleoceanographic and paleoclimatic inferences. Species grouped into surface, intermediate and deep water categories based on ??18O values provide evidence of major changes in water-mass stratification, and individual species abundances indicate low frequency cool-warm oscillations. These data suggest that relatively stable climatic phases with minor cool-warm oscillations of ???0.5 m.y. frequency are separated by rapid cooling events during middle Eocene to early Oligocene time. Five major climatic phases are evident in the water-mass stratification between middle Eocene through Oligocene time. Phase changes occur at P14/P15, P15/P16, P20/P21 and P21/P22 Zone boundaries and are marked by major faunal turnovers, rapid cooling in the isotope record, hiatuses and changes in the eustatic sea level. A general cooling trend between middle Eocene to early late Oligocene is indicated by the successive replacement of warm middle Eocene surface water species by cooler late Eocene intermediate water species and still cooler Oligocene intermediate and deep water species. Increased water-mass stratification in the latest Eocene (P17), indicated by the coexistence of surface, intermediate and deep dwelling species groups, suggest that increased thermal gradients developed between the equator and poles nearly coincident with the development of the psychrosphere. This pattern may be related to significant ice accumulation between late Eocene and early late Oligocene time. ?? 1983.

  13. Palynostratigraphy and depositional environment of Vastan Lignite Mine (Early Eocene), Gujarat, western India

    NASA Astrophysics Data System (ADS)

    Rao, M. R.; Sahni, Ashok; Rana, R. S.; Verma, Poonam

    2013-04-01

    Early Eocene sedimentary successions of south Asia, are marked by the development of extensive fossil-bearing, lignite-rich sediments prior to the collision of India with Asia and provide data on contemporary equatorial faunal and vegetational assemblages. One such productive locality in western India is the Vastan Lignite Mine representing approximately a 54-52 Ma sequence dated by the presence of benthic zone marker species, Nummulites burdigalensis burdigalensis. The present study on Vastan Lignite Mine succession is based on the spore-pollen and dinoflagellate cyst assemblages and documents contemporary vegetational changes. 86 genera and 105 species belonging to algal remains (including dinoflagellate cysts), fungal remains, pteridophytic spores and angiospermous pollen grains have been recorded. On the basis of first appearance, acme and decline of palynotaxa, three cenozones have been recognized and broadly reflect changing palaeodepositional environments. These are in ascending stratigraphic order (i) Proxapertites Spp. Cenozone, (ii) Operculodinium centrocarpum Cenozone and (iii) Spinizonocolpites Spp. Cenozone. The basal sequence is lagoonal, palm-dominated and overlain by more open marine conditions with dinoflagellate cysts and at the top, mangrove elements are dominant. The succession has also provided a unique record of fish, lizards, snakes, and mammals.

  14. Rapid and sustained surface ocean acidification during the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Penman, Donald E.; Hönisch, Bärbel; Zeebe, Richard E.; Thomas, Ellen; Zachos, James C.

    2014-05-01

    The Paleocene-Eocene Thermal Maximum (PETM) has been associated with the release of several thousands of petagrams of carbon (Pg C) as methane and/or carbon dioxide into the ocean-atmosphere system within ~10 kyr, on the basis of the co-occurrence of a carbon isotope excursion (CIE), widespread dissolution of deep sea carbonates, and global warming. In theory, this rapid carbon release should have severely acidified the surface ocean, though no geochemical evidence has yet been presented. Using boron-based proxies for surface ocean carbonate chemistry, we present the first observational evidence for a drop in the pH of surface and thermocline seawater during the PETM. Planktic foraminifers from a drill site in the North Pacific (Ocean Drilling Program Site 1209) show a ~0.8‰ decrease in boron isotopic composition (δ11B) at the onset of the event, along with a 30-40% reduction in shell B/Ca. Similar trends in δ11B are present in two lower-resolution records from the South Atlantic and Equatorial Pacific. These observations are consistent with significant, global acidification of the surface ocean lasting at least 70 kyr and requiring sustained carbon release. The anomalies in the B records are consistent with an initial surface pH drop of ~0.3 units, at the upper range of model-based estimates of acidification.

  15. The rain-powered cart

    NASA Astrophysics Data System (ADS)

    Mungan, Carl E.; Lipscombe, Trevor C.

    2016-09-01

    A frictionless cart in the shape of a right triangle (with the vertical side forward) is elastically impacted by vertically falling raindrops. The speed of the cart as a function of time can be analytically deduced as an exercise in the use of trigonometric and hyperbolic functions. A characteristic time defines the approach to a terminal speed which is a sizeable fraction of the speed of the rain. The treatment is accessible to a student in a calculus-based mechanics course.

  16. Acid Rain: What It Is -- How You Can Help!

    ERIC Educational Resources Information Center

    National Wildlife Federation, Washington, DC.

    This publication discusses the nature and consequences of acid precipitation (commonly called acid rain). Topic areas include: (1) the chemical nature of acid rain; (2) sources of acid rain; (3) geographic areas where acid rain is a problem; (4) effects of acid rain on lakes; (5) effect of acid rain on vegetation; (6) possible effects of acid rain…

  17. Taxonomy, affinities, and paleobiology of the tiny metatherian mammal Minusculodelphis, from the early Eocene of South America.

    PubMed

    Oliveira, Édison Vicente; Zimicz, Natalia; Goin, Francisco J

    2016-02-01

    With less than 3 g of estimated body mass, the early Eocene Minusculodelphis minimus Paula Couto (Mammalia, Metatheria, Jaskhadelphyidae) is one of the smallest mammals, living or extinct. It has alternatively been regarded as a didelphid or a derorhynchid "ameridelphian," or even as an eometatherian marsupial. Here, we describe a new species of Minusculodelphis coming from the same locality (Itaboraí Quarry, Brazil) and age (Itaboraian age) of the type species of the genus. It differs from M. minimus in its larger size and several dental characters. The new species offers data on the upper dentition and femur, which are unknown in the type species. Compared to other Paleogene metatherians, Minusculodelphis shows closer relationships with Jaskhadelphys, from the early Paleocene of Tiupampa, Bolivia, as well as with Kiruwamaq, from the late Eocene-early Oligocene of Perú. A cladistic analysis places all three genera within the family Jaskhadelphyidae (Metatheria, Order indet.), which includes small to tiny, insectivorous-like metatherians. We argue that insectivory (soft insects) is the best-supported diet for both species of Minusculodelphis, and that the most probable microhabitat for them was the understorey or leaf litter of tropical, rain forested environments.

  18. Taxonomy, affinities, and paleobiology of the tiny metatherian mammal Minusculodelphis, from the early Eocene of South America

    NASA Astrophysics Data System (ADS)

    Oliveira, Édison Vicente; Zimicz, Natalia; Goin, Francisco J.

    2016-02-01

    With less than 3 g of estimated body mass, the early Eocene Minusculodelphis minimus Paula Couto (Mammalia, Metatheria, Jaskhadelphyidae) is one of the smallest mammals, living or extinct. It has alternatively been regarded as a didelphid or a derorhynchid "ameridelphian," or even as an eometatherian marsupial. Here, we describe a new species of Minusculodelphis coming from the same locality (Itaboraí Quarry, Brazil) and age (Itaboraian age) of the type species of the genus. It differs from M. minimus in its larger size and several dental characters. The new species offers data on the upper dentition and femur, which are unknown in the type species. Compared to other Paleogene metatherians, Minusculodelphis shows closer relationships with Jaskhadelphys, from the early Paleocene of Tiupampa, Bolivia, as well as with Kiruwamaq, from the late Eocene-early Oligocene of Perú. A cladistic analysis places all three genera within the family Jaskhadelphyidae (Metatheria, Order indet.), which includes small to tiny, insectivorous-like metatherians. We argue that insectivory (soft insects) is the best-supported diet for both species of Minusculodelphis, and that the most probable microhabitat for them was the understorey or leaf litter of tropical, rain forested environments.

  19. Constructing an Eocene Marine Ecosystem Sensitivity Scale

    NASA Astrophysics Data System (ADS)

    D'haenens, S.; Bornemann, A.; Speijer, R. P.; Hull, P. M.

    2014-12-01

    A key question in the face of current global environmental change is how marine ecosystems will respond and evolve in the future. To answer this, we first need to understand the relationship between environmental and ecosystem change - i.e., the ecosystem sensitivity. Addressing this question requires understanding of how biota respond to (a succession of) sudden environmental perturbations of varying sizes and durations in varying background conditions (i.e., climatic, oceanographic, biotic). Here, we compare new and published data from the Early to Middle Eocene greenhouse world to understand the sensitivity of marine ecosystems to background environmental change and hyperthermal events. This work focuses on the early Paleogene, because it is considered to be a good analog for a future high CO2 world. Newly generated high-resolution multiproxy datasets based on northern Atlantic DSDP Leg 48 and IODP Leg 342 material will allow us to compare the marine ecosystem responses (including bentho-pelagic systems) to abiotic drivers across climatic disruptions of differing magnitude. Initial results of a benthic foraminiferal community comparison including the PETM and ETM2 hyperthermals in the northeastern Atlantic DSDP sites 401 and 5501 suggest that benthic ecosystem sensitivity may actually be non-linearly linked to background climate states as reflected by a range of geochemical proxies (XRF, TOC, CaCO3, grain sizes, XRD clay mineralogy and foraminiferal δ18O, δ13C, Mg/Ca)2,3, in contrast to planktic communities4. Testing the type of scaling across different taxa, communities, initial background conditions and time scales may be the first big step to disentangle the often synergistic effects of environmental change on ecosystems5. References: 1D'haenens et al., 2012, in prep. 2Bornemann et al., 2014, EPSL 3D'haenens et al., 2014, PA 4Gibbs et al., 2012, Biogeosc. 5 Norris et al., 2013, Science

  20. The Dynamics of Equatorial F Layer Irregularities.

    DTIC Science & Technology

    2014-09-26

    RD-8158 650 THE DYNAMICS OF EQUATORIAL F LAYER IRREGULARITIE5(U) BOSTON UNIV MR DEPT OF ASTRONOMY J AARONS ET AL. 38 JUN 85 RCBU-6276-5 N88814-82-K...Jules Aarons and Michael Mendillo, Co-Principal Investigators Department of Astronomy Boston University Boston, MA 02215 BOSTON UNIVERSITY Thi doumnt

  1. Elevated Eocene atmospheric CO2 and its subsequent decline.

    PubMed

    Lowenstein, Tim K; Demicco, Robert V

    2006-09-29

    Quantification of the atmospheric concentration of CO2 ([CO2]atm) during warm periods of Earth's history is important because burning of fossil fuels may produce future [CO2]atm approaching 1000 parts per million by volume (ppm). The early Eocene (~56 to 49 million years ago) had the highest prolonged global temperatures of the past 65 million years. High Eocene [CO2]atm is established from sodium carbonate minerals formed in saline lakes and preserved in the Green River Formation, western United States. Coprecipitation of nahcolite (NaHCO3) and halite (NaCl) from surface waters in contact with the atmosphere indicates [CO2]atm > 1125 ppm (four times preindustrial concentrations), which confirms that high [CO2]atm coincided with Eocene warmth.

  2. Asian monsoons in a late Eocene greenhouse world

    NASA Astrophysics Data System (ADS)

    Licht, A.; van Cappelle, M.; Abels, H. A.; Ladant, J.-B.; Trabucho-Alexandre, J.; France-Lanord, C.; Donnadieu, Y.; Vandenberghe, J.; Rigaudier, T.; Lécuyer, C.; Terry, D., Jr.; Adriaens, R.; Boura, A.; Guo, Z.; Soe, Aung Naing; Quade, J.; Dupont-Nivet, G.; Jaeger, J.-J.

    2014-09-01

    The strong present-day Asian monsoons are thought to have originated between 25 and 22 million years (Myr) ago, driven by Tibetan-Himalayan uplift. However, the existence of older Asian monsoons and their response to enhanced greenhouse conditions such as those in the Eocene period (55-34 Myr ago) are unknown because of the paucity of well-dated records. Here we show late Eocene climate records revealing marked monsoon-like patterns in rainfall and wind south and north of the Tibetan-Himalayan orogen. This is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from Myanmar, and by aeolian dust deposition in northwest China. Our climate simulations support modern-like Eocene monsoonal rainfall and show that a reinforced hydrological cycle responding to enhanced greenhouse conditions counterbalanced the negative effect of lower Tibetan relief on precipitation. These strong monsoons later weakened with the global shift to icehouse conditions 34 Myr ago.

  3. Wave Forcing of Saturn's Equatorial Oscillation

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Schlinder, P. J.; Guerlet, S.; Fouchet, T.

    2011-01-01

    Ground-based measurements and Cassini data from CIRS thermal-infrared spectra and radio-occultation soundings have characterized the spatial structure and temporal behavior of a 15-year equatorial oscillation in Saturn's stratosphere. The equatorial region displays a vertical pattern of alternating warm and cold anomalies and, concomitantly, easterly and westerly winds relative to the cloud-top winds, with a peak-to-peak amplitude of 200 m/s. Comparison of the Cassini data over a four-year period has established that the pattern of mean zonal winds and temperatures descends at a rate of roughly I scale height over 4 years. This behavior is reminiscent of the equatorial oscillations in Earth's middle atmosphere. Here the zonal-mean spatial structure and descending pattern are driven by the absorption of vertically propagating waves. The maximum excursions in the pattern of easterly and westerly winds is determined by the limits of the zonal phase velocities of the waves. Here we report on the characterization of the waves seen in the temperature profiles retrieved from the Cassini radio-occultation soundings. The equatorial profiles exhibit a complex pattern of wavelike structure with dimensions one pressure scale height and smaller. We combine a spectral decomposition with a WKBJ analysis, where the vertical wavelength is assumed to vary slowly with the ambient static stability and doppler-shifted phase velocity of the wave. Use of the temperature and zonal wind maps from CIRS makes this approach viable. On Earth, the wave forcing associated with the equatorial oscillations generates secondary meridional circulations that affect the mean flow and planetary wave ducting well away from the equator. This may relate to the triggering of the recently reported mid-latitude storms on Saturn.

  4. Climate Sensitivity to Vegetation Distribution in the Early Eocene

    NASA Astrophysics Data System (ADS)

    Clifthorne, S. J.; Shellito, C. J.; Sloan, L. C.

    2004-12-01

    There are large uncertainties associated with the reconstructions of global vegetation distributions for past time periods in Earth history. In order to investigate the influence of the global distribution of vegetation on modeled early Eocene climate, we carried out two experiments with the National Center for Atmospheric Research Community Atmosphere Model (v.2.0.2.). Both experiments used an atmospheric CO2 level of 560 ppm and sea surface temperatures generated in a previous Eocene modeling study (Huber and Sloan, 2001). The experiments differed only in their prescribed vegetation distributions. The first experiment used output from an Eocene study with a dynamic global vegetation model (DGVM) (Shellito and Sloan, in preparation), while the second case used a vegetation scheme based on fossil flora (Sewall et al., 2000). In creating the Sewall et al. (2000) vegetation scheme, no specific atmospheric CO2 level was specified, whereas the DGVM in the study by Shellito and Sloan (in preparation) allowed the initial vegetation to reach equilibrium with a pCO2 level of 560 ppm. Two additional experiments were run with higher atmospheric CO2 concentrations of 1120 ppm; one used output from an Eocene DGVM study with a pCO2 of 1120 ppm (Shellito and Sloan, in preparation), while the second case used the Sewall et al. (2000) vegetation. Comparison of early Eocene climates resulting from each pair of pCO2 experiments allows us to assess the influence of prescribed vegetation upon climate. By evaluating these results at two different levels of atmospheric CO2, we can investigate the combined effects of pCO2 and vegetation upon the resulting early Eocene climate.

  5. High plant diversity in Eocene South America: evidence from Patagonia.

    PubMed

    Wilf, Peter; Cúneo, N Rubén; Johnson, Kirk R; Hicks, Jason F; Wing, Scott L; Obradovich, John D

    2003-04-04

    Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude approximately 47 degrees S, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.

  6. High plant diversity in Eocene South America: Evidence from Patagonia

    USGS Publications Warehouse

    Wilf, P.; Cuneo, N.R.; Johnson, K.R.; Hicks, J.F.; Wing, S.L.; Obradovich, J.D.

    2003-01-01

    Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude ~47oS, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.

  7. Rainfall time series synthesis from queue scheduling of rain event fractals over radio links

    NASA Astrophysics Data System (ADS)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2015-12-01

    Rainfall attenuation over wireless networks stems from random fluctuations in the natural process of arriving rainfall rates over radio links. This arrival process results in discernible rainfall traffic pattern which manifests as naturally scheduled and queue-generated rain spikes. Hence, the phenomenon of rainfall process can be approached as a semi-Markovian queueing process, with event characteristics dependent on queue parameters. However, a constraint to this approach is the knowledge of the physical characteristics of queue-generated rain spikes. Therefore, this paper explores the probability theory and descriptive mathematics of rain spikes in rainfall processes. This investigation presents the synthesis of rainfall queue with rain spikes at subtropical and equatorial locations of Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E), respectively. The resulting comparative analysis of rainfall distributions, using error analysis at both locations, reveals that queue-generated rainfall compares well with measured rainfall data set. This suggests that the time-varying process of rainfall, though stochastic, can be synthesized via queue scheduling with the application of relevant queue parameters at any location.

  8. Rain on small tropical islands

    NASA Astrophysics Data System (ADS)

    Sobel, A. H.; Burleyson, C. D.; Yuter, S. E.

    2011-04-01

    A high-resolution rainfall climatology based on observations from the Tropical Rainfall Measuring Mission's Precipitation Radar (PR) instrument is used to evaluate the influence of small tropical islands on climatological rainfall. Islands with areas between one hundred and several thousand km2 are considered in both the Indo-Pacific Maritime Continent and Caribbean regions. Annual mean climatological (1997-2007) rainfall over each island is compared with that over the surrounding ocean region, and the difference is expressed as a percentage. In addition to total rainfall, rain frequency and intensity are also analyzed. Results are stratified into two 12 h halves of the diurnal cycle as well as eight 3 h periods, and also by a measure of each island's topographic relief. In both regions, there is a clear difference between larger islands (areas of a few hundred km2 or greater) and smaller ones. Both rain frequency and total rainfall are significantly enhanced over larger islands compared to the surrounding ocean. For smaller islands the enhancement is either negligibly small, statistically insignificant, or, in the case of Caribbean rain frequency, negative. The enhancement in total rainfall over larger islands is partly attributable to greater frequency and partly to greater intensity. A diurnal cycle in island enhancement is evident in frequency but not intensity, except over small Caribbean islands where the converse is true. For the larger islands, higher orography is associated with greater rainfall enhancements. The orographic effect is larger (percentagewise) in the Caribbean than in the Maritime Continent. Orographic precipitation enhancement manifests more strongly as increased frequency of precipitation rather than increased intensity and is present at night as well as during the day. The lack of a clear diurnal cycle in orographic enhancement suggests that much of the orographic rainfall enhancement is attributable to mechanically forced upslope flow

  9. Large Variations in Ice Volume During the Middle Eocene "Doubthouse"

    NASA Astrophysics Data System (ADS)

    Dawber, C. F.; Tripati, A. K.

    2008-12-01

    The onset of glacial conditions in the Cenozoic is widely held to have begun ~34 million years ago, coincident with the Eocene-Oligocene boundary1. Warm and high pCO2 'greenhouse' intervals such as the Eocene are generally thought to be ice-free2. Yet the sequence stratigraphic record supports the occurrence of high-frequency sea-level change of tens of meters in the Middle and Late Eocene3, and large calcite and seawater δ18O excursions (~0.5-1.0 permil) have been reported in foraminifera from open ocean sediments4. As a result, the Middle Eocene is often considered the intermediary "doubthouse". The extent of continental ice during the 'doubthouse' is controversial, with estimates of glacioeustatic sea level fall ranging from 30 to 125m2,3,5. We present a new δ18Osw reconstruction for Ocean Drilling Project (ODP) Site 1209 in the tropical Pacific Ocean. It is the first continuous high-resolution record for an open-ocean site that is not directly influenced by changes in the carbonate compensation depth, which enables us to circumvent many of the limitations of existing records. Our record shows increases of 0.8 ± 0.2 (1 s.e) permil and 1.1 ± 0.2 permil at ~44-45 and ~42-41 Ma respectively, which suggests glacioeustatic sea level variations of ~90 m during the Middle Eocene. Modelling studies have shown that fully glaciating Antarctica during the Eocene should drive a change in seawater (δ18Osw) of 0.45 permil, and lower sea level by ~55 m6. Our results therefore support significant ice storage in both the Northern and Southern Hemisphere during the Middle Eocene 'doubthouse'. 1.Miller, Kenneth G. et al., 1990, Eocene-Oligocene sea-level changes in the New Jersey coastal plain linked to the deep-sea record. Geological Society of America Bulletin 102, 331-339 2.Pagani, M. et al., 2005, Marked decline in atmospheric carbon dioxide concentrations during the Paleogene. Science 309 (5734), 600-603. 3.Browning, J., Miller, K., and Pak, D., 1996, Global implications

  10. Acid rain. Rhetoric and reality

    SciTech Connect

    Park, C.

    1988-01-01

    The book examines the implications of recent scientific studies, and sets the political debate in the main 'polluting' countries--Britain and the United States--into its proper international context. It provides a wealth of U.S. data, including a history of the development of U.S. acid rain policy. The author presents a review of the evidence for damage and the statistics of change. Data is drawn from around the world, with particular emphasis on damage in Scandinavia and West Germany.

  11. Equatorial Pacific Productivity Events and Intervals in the Middle and late Miocene through XRF-Scanned Bulk Sediment Composition Data

    NASA Astrophysics Data System (ADS)

    Lyle, M. W.; Stepanova, A.; Wilson, J. K.; Marcantonio, F.

    2014-12-01

    The equatorial Pacific is the largest open ocean productivity center, responsible for nearly half of global marine new production and about 40% of CaCO3 burial. Understanding how the equatorial Pacific upwelling system has evolved over the Neogene is critical to understand the evolution of the global carbon cycle. We know from reconnaissance studies that productivity in equatorial Pacific surface waters as well as dissolution driven by deep waters have strongly affected the sediment record. We have used calibrated XRF scanning to capture anomalies in equatorial Pacific upwelling and productivity at Milankovitch-resolving resolution since the early Miocene. The 8 elements calibrated in the XRF scans can be used to distinguish intervals of high carbonate dissolution from those of high productivity. Carbonate dissolution intervals are recorded by a drop of CaCO3 relative to Aeolian clays, with little change in the ratio between estimated opal and clay (estimated by TiO2). In contrast, high production intervals have high opal/TiO2 and low CaCO3. Low CaCO3 contents are caused partly by dilution, since high production skews tropical particulate rain to be more opal-rich relative to carbonate, and additional C-org rain can help to increase CaCO3 dissolution within near-surface sediments. We observe long-lived high production anomalies modulated by orbitally-driven climate variability. Prominent intervals are found at the end of the Miocene climate optimum (~ 14 Ma), interspersed with dissolution intervals in the Carbonate Crash interval (~9-11 Ma), and in the Biogenic Bloom interval (8-4.5 Ma). Using relationships among biogenic fluxes in modern equatorial sediment trap studies, especially the positive correlations between biogenic Ba , C-org, and CaCO3 fluxes, we find that the highest production intervals have much higher opal/C-org in the particulate rain, implying an inefficient carbon pump to the deep ocean. If confirmed, productivity was not as strong a feedback to

  12. A probability distribution model for rain rate

    NASA Technical Reports Server (NTRS)

    Kedem, Benjamin; Pavlopoulos, Harry; Guan, Xiaodong; Short, David A.

    1994-01-01

    A systematic approach is suggested for modeling the probability distribution of rain rate. Rain rate, conditional on rain and averaged over a region, is modeled as a temporally homogeneous diffusion process with appropiate boundary conditions. The approach requires a drift coefficient-conditional average instantaneous rate of change of rain intensity-as well as a diffusion coefficient-the conditional average magnitude of the rate of growth and decay of rain rate about its drift. Under certain assumptions on the drift and diffusion coefficients compatible with rain rate, a new parametric family-containing the lognormal distribution-is obtained for the continuous part of the stationary limit probability distribution. The family is fitted to tropical rainfall from Darwin and Florida, and it is found that the lognormal distribution provides adequate fits as compared with other members of the family and also with the gamma distribution.

  13. Two groups challenge US acid rain efforts

    SciTech Connect

    Not Available

    1987-11-01

    In its report, Acid Rain Invades Our National Parks, the National Parks and Conservation Association (NPCA) says acid rain is being detected at all 27 national park monitoring sites. In 1980, 87 national parks expressed concern in a NPCA survey over acid rain. Repolled in 1986, more than half of the respondents reported that no research on acid rain was under way. The NPCA report concludes that the alarm that was sounded in 1980 fell largely on deaf ears, and calls for the structural and scientific reorganization of the National Park Service. The National Audubon Society shares NPCA's dissatisfaction with federal efforts to tackle the problem of acid rain and has taken testing into its own hands. Through its Citizens Acid Rain Monitoring Network, Audubon volunteers have collected readings of acidity at 64 monitoring stations in 31 states since July.

  14. Living on the edge: The oxygen isotope record of Eocene Basins at the margin of the Cenozoic North American plateau

    NASA Astrophysics Data System (ADS)

    Methner, Katharina; Mulch, Andreas; Chamberlain, Page

    2013-04-01

    the site or within close proximity. However, paleofloral data from e.g. the Chumstick basin to the E of the modern Cascades indicate moderate elevations and montane rain forest conditions during a warm (MAT = 14°C) and rather wet, seasonal Eocene climate. Therefore, we tentatively suggest that these basins were at moderate elevations, allowing dense vegetation and seasonal drying of soils, but were fed by isotopically highly 18O-depleted runoff and groundwater from elevated catchment areas in the vicinity of the basins. This requires Eocene highlands of the North American Cordillera to be laterally extensive already during the Eocene and places important constraints on the impact of the plateau region on atmospheric circulation patterns.

  15. Acid rain information book. Draft final report

    SciTech Connect

    1980-12-01

    Acid rain is one of the most widely publicized environmental issues of the day. The potential consequences of increasingly widespread acid rain demand that this phenomenon be carefully evaluated. Reveiw of the literature shows a rapidly growing body of knowledge, but also reveals major gaps in understanding that need to be narrowed. This document discusses major aspects of the acid rain phenomenon, points out areas of uncertainty, and summarizes current and projected research by responsible government agencies and other concerned organizations.

  16. Rain Effects on Radio Frequency Propagation

    DTIC Science & Technology

    1986-03-31

    ABSTRACT (Continue on reverse if necessary and identify by block number) Rain is a principal cause of signal degradation in a terrestrial or satellite trans...Predicted Attenuation, dB AS = Specific Rain Attenuation, dB/km av = Vertical Polarized Value of a Anooi A at 0.01% B = Satellite Beacon b = Empirical...Isotherm Height Ho = Height above Mean Sea Level, km Hr = the Rain Height, km ITU = International Telecommunications Union IWP = International

  17. Extension of the prognostic model of sea surface temperature to rain-induced cool and fresh lenses

    NASA Astrophysics Data System (ADS)

    Bellenger, Hugo; Drushka, Kyla; Asher, William; Reverdin, Gilles; Katsumata, Masaki; Watanabe, Michio

    2017-01-01

    The Zeng and Beljaars (2005) sea surface temperature prognostic scheme, developed to represent diurnal warming, is extended to represent rain-induced freshening and cooling. Effects of rain on salinity and temperature in the molecular skin layer (first few hundred micrometers) and the near-surface turbulent layer (first few meters) are separately parameterized by taking into account rain-induced fluxes of sensible heat and freshwater, surface stress, and mixing induced by droplets penetrating the water surface. Numerical results from this scheme are compared to observational data from two field studies of near-surface ocean stratifications caused by rain, to surface drifter observations and to previous computations with an idealized ocean mixed layer model, demonstrating that the scheme produces temperature variations consistent with in situ observations and model results. It reproduces the dependency of salinity on wind and rainfall rate and the lifetime of fresh lenses. In addition, the scheme reproduces the observed lag between temperature and salinity minimum at low wind speed and is sensitive to the peak rain rate for a given amount of rain. Finally, a first assessment of the impact of these fresh lenses on ocean surface variability is given for the near-equatorial western Pacific. In particular, the variability due to the mean rain-induced cooling is comparable to the variability due to the diurnal warming so that they both impact large-scale horizontal surface temperature gradients. The present parameterization can be used in a variety of models to study the impact of rain-induced fresh and cool lenses at different spatial and temporal scales.

  18. Vibration (?) spikes during natural rain events

    NASA Technical Reports Server (NTRS)

    Short, David A.

    1994-01-01

    Limited analysis of optical rain gauge (ORG) data from shipboard and ground based sensors has shown the existence of spikes, possibly attributable to sensor vibration, while rain is occurring. An extreme example of this behavior was noted aboard the PRC#5 on the evening of December 24, 1992 as the ship began repositioning during a rain event in the TOGA/COARE IFA. The spikes are readily evident in the one-second resolution data, but may be indistinguishable from natural rain rate fluctuations in subsampled or averaged data. Such spikes result in increased rainfall totals.

  19. Soak Up the Rain: What's the Problem?

    EPA Pesticide Factsheets

    Why citizens and communities should soak up the rain with green infrastructure: to prevent water pollution, reduce flooding, protect water resources, beautify neighborhoods and other community benefits

  20. Acid rain threatens marine life

    SciTech Connect

    Not Available

    1988-09-01

    In freshwater, acid rain harms aquatic organisms because one of its components, sulfur dioxide, lowers the water's pH. In seawater, the damage comes from other components of acid precipitation: nitrogen oxides. Acting as a nutrient, nitrogen promotes excessive algal growth, which blocks sunlight and depletes dissolved oxygen, thereby suffocating other plants and animals. Known as eutrophication, this phenomenon has been increasing in both frequency and intensity on the Atlantic coast during the past few years. The New York City-based Environmental Defense Fund (EDF), study focused on the Chesapeake Bay, the nation's largest estuary and an important spawning ground for many species of economic importance. It has long been known that the bay is suffering from nitrogen pollution. Until now, it was assumed that most of the nitrogen was coming from sewage and agricultural runoff. However, based on data collected from both federal and state agencies, EDF scientists estimated that nitrates from acid rain are responsible for 25% of the nitrogen entering the bay. The report says that if present trends continue, airborne nitrates will contribute 42% of annual nitrogen deposits into the Chesapeake Bay by the year 2030.

  1. Rain from Tropical Storm Noel

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Though not the most powerful storm of the 2007 Atlantic Hurricane season, Tropical Storm Noel was among the most deadly. Only Category 5 Hurricane Felix and its associated flooding had a higher toll. The slow-moving Tropical Storm Noel inundated the Dominican Republic, Haiti, Jamaica, Cuba, and the Bahamas with heavy rain between October 28 and November 1, 2007. The resulting floods and mudslides left at least 115 dead and thousands homeless throughout the Caribbean, reported the Associated Press on November 2, 2007. This image shows the distribution of the rainfall that made Noel a deadly storm. The image shows rainfall totals as measured by the Multi-satellite Precipitation Analysis (MPA) at NASA Goddard Space Flight Center from October 26 through November 1, 2007. The analysis is based on measurements taken by the Tropical Rainfall Measuring Mission (TRMM) satellite. The heaviest rainfall fell in the Dominican Republic and the Bahamas, northeast of Noel's center. Areas of dark red show that rainfall totals over the south-central Dominican Republic and parts of the Bahamas were over 551 millimeters (21 inches). Much of eastern Hispaniola, including both the Dominican Republic and Haiti received at least 200 mm (about 8 inches) of rain, shown in yellow. Rainfall totals over Haiti and Cuba were less, with a range of at least 50 mm (2 inches) to over 200 mm (8 inches).

  2. Long waves in the equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Philander, George; Halpern, David; Hansen, Donald; Legeckis, Richard; Miller, Laury; Watts, Randolph; Wimbush, Mark; Paul, Carl; Watts, Randolph; Weisberg, Robert

    Westward traveling waves, with a period of 3 weeks and a wavelength of ˜1000 km, are observed intermittently in the central and eastern equatorial Pacific Ocean (see cover). The waves were first detected in 1975 in satellite measurements of the sea surface temperature [Legeckis, 1977]. Since then, additional measurements (under the auspices of the NOAA program Equatorial Pacific Ocean Climate Studies (EPOCS)) with a variety of instruments—drifting buoys, current meters and temperature sensors on moorings, and inverted echo sounders—have provided considerable information about these waves and have confirmed the hypothesis that they are caused by instabilities associated primarily with the latitudinal shear of the surface currents near the equator [Philander, 1978a; Cox, 1980].

  3. Effect of ouabain on lens equatorial currents.

    PubMed

    Wind, B E; Walsh, S; Patterson, J W

    1988-11-01

    The equatorial potassium current measured with the vibrating probe is a segment of the potassium electrical loop. The equatorial current, J, was measured simultaneously with the PD and with the response to an injected current, I. The injection of sufficient inward current, I, made the PD more negative and increased the electrical gradient so that the current J became zero. The PD at which this occurs (PDJ-0) is the reversal potential. Following treatment with ouabain, the PD and PDJ-0 both become less negative. Since the driving force for the current, J, is equal to the difference between PD and PDJ-0, J may increase, stay the same or decrease depending on the relative changes in PD and PDJ-0. In the presence of ouabain, the PDJ-0 changes in parallel with or more rapidly than the PD.

  4. Eocene Paleoclimate: Incredible or Uncredible? Model data syntheses raise questions.

    NASA Astrophysics Data System (ADS)

    Huber, M.

    2012-04-01

    Reconstructions of Eocene paleoclimate have pushed on the boundaries of climate dynamics theory for generations. While significant improvements in theory and models have brought them closer to the proxy data, the data themselves have shifted considerably. Tropical temperatures and greenhouse gas concentrations are now reconstructed to be higher than once thought--in agreement with models--but, many polar temperature reconstructions are even warmer than the eye popping numbers from only a decade ago. These interpretations of subtropical-to-tropical polar conditions once again challenge models and theory. But, the devil, is as always in the details and it is worthwhile to consider the range of potential uncertainties and biases in the paleoclimate record interpretations to evaluate the proposition that models and data may not materially disagree. It is necessary to ask whether current Eocene paleoclimate reconstructions are accurate enough to compellingly argue for a complete failure of climate models and theory. Careful consideration of Eocene model output and proxy data reveals that over most of the Earth the model agrees with the upper range of plausible tropical proxy data and the lower range of plausible high latitude proxy reconstructions. Implications for the sensitivity of global climate to greenhouse gas forcing are drawn for a range of potential Eocene climate scenarios ranging from a literal interpretation of one particular model to a literal interpretation of proxy data. Hope for a middle ground is found.

  5. Arctic plant diversity in the Early Eocene greenhouse

    PubMed Central

    Harrington, Guy J.; Eberle, Jaelyn; Le-Page, Ben A.; Dawson, Mary; Hutchison, J. Howard

    2012-01-01

    For the majority of the Early Caenozoic, a remarkable expanse of humid, mesothermal to temperate forests spread across Northern Polar regions that now contain specialized plant and animal communities adapted to life in extreme environments. Little is known on the taxonomic diversity of Arctic floras during greenhouse periods of the Caenozoic. We show for the first time that plant richness in the globally warm Early Eocene (approx. 55–52 Myr) in the Canadian High Arctic (76° N) is comparable with that approximately 3500 km further south at mid-latitudes in the US western interior (44–47° N). Arctic Eocene pollen floras are most comparable in richness with today's forests in the southeastern United States, some 5000 km further south of the Arctic. Nearly half of the Eocene, Arctic plant taxa are endemic and the richness of pollen floras implies significant patchiness to the vegetation type and clear regional richness of angiosperms. The reduced latitudinal diversity gradient in Early Eocene North American plant species demonstrates that extreme photoperiod in the Arctic did not limit taxonomic diversity of plants. PMID:22072610

  6. Arctic plant diversity in the Early Eocene greenhouse.

    PubMed

    Harrington, Guy J; Eberle, Jaelyn; Le-Page, Ben A; Dawson, Mary; Hutchison, J Howard

    2012-04-22

    For the majority of the Early Caenozoic, a remarkable expanse of humid, mesothermal to temperate forests spread across Northern Polar regions that now contain specialized plant and animal communities adapted to life in extreme environments. Little is known on the taxonomic diversity of Arctic floras during greenhouse periods of the Caenozoic. We show for the first time that plant richness in the globally warm Early Eocene (approx. 55-52 Myr) in the Canadian High Arctic (76° N) is comparable with that approximately 3500 km further south at mid-latitudes in the US western interior (44-47° N). Arctic Eocene pollen floras are most comparable in richness with today's forests in the southeastern United States, some 5000 km further south of the Arctic. Nearly half of the Eocene, Arctic plant taxa are endemic and the richness of pollen floras implies significant patchiness to the vegetation type and clear regional richness of angiosperms. The reduced latitudinal diversity gradient in Early Eocene North American plant species demonstrates that extreme photoperiod in the Arctic did not limit taxonomic diversity of plants.

  7. A new Late Eocene anthropoid primate from Thailand.

    PubMed

    Chaimanee, Y; Suteethorn, V; Jaeger, J J; Ducrocq, S

    1997-01-30

    The fossil record of anthropoid primates from the Middle Eocene of South Asia is so far restricted to two genera (Pondaungia cotteri Pilgrim, 1937 and Amphipithecus mogaungensis Colbert, 1937 from the Eocene Pondaung deposits of Burma) whose anthropoid status and phylogenetic position have long been under debate because they represent the oldest highly derived fossil primates of anthropoid grade. Moreover, several new African taxa, some of which are even older, have been recently included in the suborder Anthropoidea, suggesting an African origin for this group. Conversely, new fossil primates recently discovered in China (Eosimias) have been related to the most primitive representatives of Anthropoidea, alternatively suggesting an Asian origin and a probable Asian radiation centre. We report here the discovery of a new anthropoid from the Thai Late Eocene locality of Krabi, which displays several additional anthropoid characters with regard to those of the Eocene Burmese genera. This species, which is about the size of the Fayum Aegyptopithecus, can be related to the Burmese forms, and it further provides strong additional evidence for a southeast Asian evolutionary centre for anthropoids.

  8. Possible methane-induced polar warming in the early Eocene.

    PubMed

    Sloan, L C; Walker, J C; Moore, T C; Rea, D K; Zachos, J C

    1992-05-28

    Reconstructions of early Eocene climate depict a world in which the polar environments support mammals and reptiles, deciduous forests, warm oceans and rare frost conditions. At the same time, tropical sea surface temperatures are interpreted to have been the same as or slightly cooler than present values. The question of how to warm polar regions of Earth without noticeably warming the tropics remains unresolved; increased amounts of greenhouse gases would be expected to warm all latitudes equally. Oceanic heat transport has been postulated as a mechanism for heating high latitudes, but it is difficult to explain the dynamics that would achieve this. Here we consider estimates of Eocene wetland areas and suggest that the flux of methane, an important greenhouse gas, may have been substantially greater during the Eocene than at present. Elevated methane concentrations would have enhanced early Eocene global warming, and also might specifically have prevented severe winter cooling of polar regions because of the potential of atmospheric methane to promote the formation of optically thick, polar stratospheric ice clouds.

  9. The Rise of Flowering Plants and Land Surface Physics: The Cretaceous and Eocene Were Different

    NASA Astrophysics Data System (ADS)

    Upchurch, G. R.; Feild, T.

    2010-12-01

    The Cretaceous and Eocene have served as the poster children of past greenhouse climates. One difference between the two time periods is that angiosperms (flowering plants) underwent a major diversification and rise to dominance during the mid-Cretaceous to Paleocene. Flowering plants differ from all other living and fossil plants in having significantly higher rates of transpiration and photosynthesis, which in modern leaves correlate with the density of venation (Dv), a feature that can be measured directly from fossils. This increase in Dv, coupled with an increase in the abundance of angiosperms, is thought to have had major impact on the climate system. This is, in part, because transpiration plays an important role in determining the ratio of sensible to latent heat flux from the land surface and in determining precipitation rate in regions such as the equatorial rainforest. Analysis of Dv in fossil leaves indicates two phases of increase in transpiration rate for angiosperms during the Cretaceous-Paleocene. The oldest known angiosperms (Aptian-early Albian) have a low Dv characteristic of extant and fossil ferns and gymnosperms. At this time angiosperms are low-stature plants of minor importance in terms of relative abundance and diversity (<5%). The first phase of Dv increase occurs during the Late Albian to Cenomanian, where average Dv is 40% greater than that of conifers and ferns, and maximum Dv reaches levels characteristic of many trees from the temperate zone. This first phase coincides with the first local dominance of angiosperms, the first occurrence of moderate to large angiosperm trees (up to 1 m in diameter) , and the first common occurrence of angiosperms in the Arctic. The second phase of Dv increase occurs during the Maastrichtian to Paleocene, where average Dv reaches levels characteristic of modern tropical forests and maximum Dv reaches the level found in highly productive modern vegetation. This second phase coincides with the rise to

  10. Models of the Equatorial Ocean Circulation.

    DTIC Science & Technology

    1980-01-01

    doctoral committee for their encouragement and advice in the development of this work. I am especially indebted to Dr. Julian P. McCreary of Nova University...large scale wind fluctuations thousands of kilometers to the west in the Central Pacific ( McCreary , 1977). A better understanding of such events could...all equatorial oceans can be found in Knauss (1963); Philander (1973b); Leetmaa, McCreary and Moore (1980); Tsuchiya (1975); Cochrane et al. (1979) and

  11. Modeling carbon and silicon cycling in the equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Fujii, Masahiko; Chai, Fei

    2007-03-01

    The equatorial Pacific is a region of significant particulate inorganic carbon (PIC) and biogenic silica sedimentation, the majority of which is carried out by coccolithophorids and diatoms. We developed an ecosystem model that explicitly includes three phytoplankton functional groups (picoplankton, coccolithophorids, and diatoms), two zooplankton functional groups (microzooplankton and mesozooplankton), nutrients (nitrate NO 3, ammonium NH 4, and silicate Si(OH) 4), detritus (particulate organic matter, biogenic silica, and PIC), total alkalinity, total CO 2, and partial pressure of CO 2 at the surface water (pCO 2sea). The model is capable of reproducing many biogeochemical features for the region, such as high-nutrient low-chlorophyll condition, significant exposure of phytoplankton under grazing controls by zooplankton, and large CO 2 release to the atmosphere. The export ratio of PIC to particulate organic carbon (rain ratio) to the deep water was 0.16, higher than the global-mean values, implying predominant PIC sedimentation in the equatorial Pacific upwelling region. Comparison between calcification and no-calcification model results indicates that when coccolithophorids are present, the community interactions actually induce more diatom biomass, export fluxes of detritus, and CO 2 release to the atmosphere. The model results show remarkable calcification in the subsurface layers, which suggests more field data on calcification processes are needed. Increase of source (120 m depth) Si(OH) 4 concentration associated with the tropical instability waves lead to a linear increase in biogenic silica export. Higher Si(OH) 4 concentration stimulates diatom growth, which causes a decrease in picoplankton because feeding pressure by mesozooplankton switched from picoplankton's grazer, microzooplankton, to the abundant diatoms. Surface coccolithophorid biomass has its maximum at intermediate source Si(OH) 4 concentrations as a result of higher grazing pressure on

  12. Equatorial scintillations: advances since ISEA-6

    SciTech Connect

    Not Available

    1985-01-01

    Our understanding of the morphology of equatorial scintillations has advanced due to more intensive observations at the equatorial anomaly locations in the different longitude zones. The unmistakable effect of the sunspot cycle in controlling irregularity belt width and electron concentration responsible for strong scintillation in the controlling the magnitude of scintillations has been recognized by interpreting scintillation observations inthe light of realistic models of total electron content at various longitudes. A hypothesis based on the alignment of the solar terminator with the geomagnetic flux tubes as an indicator of enhanced scintillation occurrence and another based on the influence of a transequatorial thermospheric neutral wind have been postulated to describe the observed longitudinal variation. A distinct class of equatorial irregularities known as the bottomside sinusoidal (BSS) type was identified. These irregularities occur in very large patches, sometimes in excess of several thousand kilometers in the E-W direction and are associated with frequency spread on ionograms. Scintillations caused by such irregularities exist only in the VHF band, exhibit Fresnel oscillations in intensity spectra and are found to give rise to extremely long durations (approx. several hours) of uninterrrupted scintillations.

  13. Sunrise enhancement of equatorial vertical plasma drift

    NASA Astrophysics Data System (ADS)

    Liu, Libo; Zhang, Ruilong; Le, Huijun

    2016-04-01

    Sunrise enhancement in vertical plasma drift over equatorial regions is not discernible in the statistical picture compared with the significant enhancement during dusk hours. In this report, it is the first time to investigate the occurrence of the dawn enhancement in the equatorial ionospheric vertical plasma drift from ROCSAT-1 observations during geomagnetic quiet times. The dawn enhancements occur most frequently in June solstice and least frequently in December solstice. The statistical survey shows that the occurrence depends on the magnetic declination. The enhancement has the strongest amplitude in regions near 320° longitude and peaks during June solstice. The dawn enhancement reaches its peak after the sunrise in conjugated E regions. Furthermore, it is found that the dawn enhancement is closely related to the difference between the sunrise times in the conjugated E regions (sunrise time lag). The dawn enhancement occurs easily in regions with a large sunrise time lag. Moreover, we will report the effects of the sunrise enhancement of vertical plasma drift on the equatorial ionosphere as indicated from the observations and model simulations. We thanks National Central University of Taiwan providing the ROCSAT-1 data. The Ap and F107 indices are obtained from the National Geophysical Data Center (http://spidr.ngdc.noaa.gov/spidr/). This research is supported by National Natural Science Foundation of China (41231065), the Chinese Academy of Sciences project (KZZD-EW-01-3), National Key Basic Research Program of China (2012CB825604) and National Natural Science Foundation of China (41321003).

  14. Evaluation of TRMM Ground-Validation Radar-Rain Errors Using Rain Gauge Measurements

    NASA Technical Reports Server (NTRS)

    Wang, Jianxin; Wolff, David B.

    2009-01-01

    Ground-validation (GV) radar-rain products are often utilized for validation of the Tropical Rainfall Measuring Mission (TRMM) spaced-based rain estimates, and hence, quantitative evaluation of the GV radar-rain product error characteristics is vital. This study uses quality-controlled gauge data to compare with TRMM GV radar rain rates in an effort to provide such error characteristics. The results show that significant differences of concurrent radar-gauge rain rates exist at various time scales ranging from 5 min to 1 day, despite lower overall long-term bias. However, the differences between the radar area-averaged rain rates and gauge point rain rates cannot be explained as due to radar error only. The error variance separation method is adapted to partition the variance of radar-gauge differences into the gauge area-point error variance and radar rain estimation error variance. The results provide relatively reliable quantitative uncertainty evaluation of TRMM GV radar rain estimates at various times scales, and are helpful to better understand the differences between measured radar and gauge rain rates. It is envisaged that this study will contribute to better utilization of GV radar rain products to validate versatile spaced-based rain estimates from TRMM, as well as the proposed Global Precipitation Measurement, and other satellites.

  15. Seasonal variability in Arctic temperatures during early Eocene time

    NASA Astrophysics Data System (ADS)

    Eberle, Jaelyn J.; Fricke, Henry C.; Humphrey, John D.; Hackett, Logan; Newbrey, Michael G.; Hutchison, J. Howard

    2010-08-01

    As a deep time analog for today's rapidly warming Arctic region, early Eocene (52-53 Ma) rock on Ellesmere Island in Canada's High Arctic (˜ 79°N.) preserves evidence of lush swamp forests inhabited by turtles, alligators, primates, tapirs, and hippo-like Coryphodon. Although the rich flora and fauna of the early Eocene Arctic imply warmer, wetter conditions than at present, the quantification of Eocene Arctic climate has been more elusive. By analyzing oxygen isotope ratios of biogenic phosphate from mammal, fish, and turtle fossils from a single locality on central Ellesmere Island, we infer early Eocene Arctic temperatures, including mean annual temperature (MAT) of ˜ 8 °C, mean annual range in temperature of ˜ 16.5-19 °C, warm month mean temperature of 19-20 °C, and cold month mean temperature of 0-3.5 °C. Our seasonal range in temperature is similar to the range in estimated MAT obtained using different proxies. In particular, relatively high estimates of early Eocene Arctic MAT and SST by others that are based upon the distribution of branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in terrestrial soil bacteria and isoprenoid tetraether lipids in marine Crenarchaeota fall close to our warm month temperature, suggesting a bias towards summer values. From a paleontologic perspective, our temperature estimates verify that alligators and tortoises, by way of nearest living relative-based climatic inference, are viable paleoclimate proxies for mild, above-freezing year-round temperatures. Although for both of these reptilian groups, past temperature tolerances probably were greater than in living descendants.

  16. Seasonal variability in Arctic temperatures during the early Eocene

    NASA Astrophysics Data System (ADS)

    Eberle, J. J.; Fricke, H. C.; Humphrey, J.; Hackett, L.; Newbrey, M.; Hutchison, H.

    2009-12-01

    As a deep time analog for today’s rapidly warming Arctic region, early Eocene (~53 Ma) rocks on Ellesmere Island, Arctic Canada (~79° N.) preserve evidence of lush swamp forests inhabited by turtles, alligators, primates, tapirs, and hippo-like Coryphodon. Although the rich flora and fauna of the early Eocene Arctic imply warmer, wetter conditions that at present, quantitative estimates of Eocene Arctic climate are rare. By analyzing oxygen isotope ratios of biogenic phosphate from mammal, fish, and turtle fossils from a single locality on central Ellesmere Island, we provide estimates of early Eocene Arctic temperature, including mean annual temperature (MAT) of ~ 8° C, mean annual range in temperature (MART) of ~ 16.5° C, warm month mean temperature (WMMT) of 16 - 19° C, and cold month mean temperature (CMMT) of 0 - 1° C. Our seasonal range in temperature is similar to the range in estimated MAT obtained using different proxies. In particular, unusually high estimates of early Eocene Arctic MAT and sea surface temperature (SST) by others that are based upon the distribution of branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in terrestrial soil bacteria and marine Crenarchaeota fall within our range of WMMT, suggesting a bias towards summer values. Consequently, caution should be taken when using these methods to infer MAT and SST that, in turn, are used to constrain climate models. From a paleontologic perspective, our temperature estimates verify that alligators and tortoises, by way of nearest living relative-based climatic inference, are viable paleoclimate proxies for mild, above-freezing year-round temperatures. Although in both of these reptiles, past temperature tolerances were greater than in their living descendants.

  17. Rapid Middle Eocene temperature change in western North America

    NASA Astrophysics Data System (ADS)

    Methner, Katharina; Mulch, Andreas; Fiebig, Jens; Wacker, Ulrike; Gerdes, Axel; Graham, Stephan A.; Chamberlain, C. Page

    2016-09-01

    Eocene hyperthermals are among the most enigmatic phenomena of Cenozoic climate dynamics. These hyperthermals represent temperature extremes superimposed on an already warm Eocene climate and dramatically affected the marine and terrestrial biosphere, yet our knowledge of temperature and rainfall in continental interiors is still rather limited. We present stable isotope (δ18O) and clumped isotope temperature (Δ47) records from a middle Eocene (41 to 40 Ma) high-elevation mammal fossil locality in the North American continental interior (Montana, USA). Δ47 paleotemperatures of soil carbonates delineate a rapid +9/-11 °C temperature excursion in the paleosol record. Δ47 temperatures progressively increase from 23 °C ± 3 °C to peak temperatures of 32 °C ± 3 °C and subsequently drop by 11 °C. This hyperthermal event in the middle Eocene is accompanied by low δ18O values and reduced pedogenic carbonate concentrations in paleosols. Based on laser ablation U/Pb geochronology of paleosol carbonates in combination with magnetostratigraphy, biostratigraphy, stable isotope, and Δ47 evidence, we suggest that this pronounced warming event reflects the Middle Eocene Climatic Optimum (MECO) in western North America. The terrestrial expression of northern hemisphere MECO in western North America appears to be characterized by warmer and wetter (sub-humid) conditions, compared to the post-MECO phase. Large and rapid shifts in δ18O values of precipitation and pedogenic CaCO3 contents parallel temperature changes, indicating the profound impact of the MECO on atmospheric circulation and rainfall patterns in the western North American continental interior during this transient warming event.

  18. Pollen selection under acid rain stress

    SciTech Connect

    Zhang, Y.

    1994-01-01

    To investigate whether acid rain stress induces pollen selection in nature, three different approaches were used, based on the assumption that the response of pollen grains to acid rain is controlled by an acid sensitive gene product. Germination of pollen from homozygous and heterozygous individuals under acid rain stress was examined to detect any differences in rate of germination between populations of homogeneous and heterogeneous pollen grains. In vitro and in vivo bulked segregant analysis using RAPDs was used to search for differences in DNA constitution between the survivors of acid rain stressed and non-acid rain stressed pollen populations in vitro and between the progenies of acid rain stressed and non-acid rain stressed populations during pollination, respectively. No evidence for the pollen selection under acid rain stress was obtained in any of the test systems. Inhibition of protein synthesis using cycloheximide led to significant reduction of tube elongation at 4 hr and had no effect on pollen germination at any time interval tested. Total proteins extracted from control and acid rain stressed pollen grain populations exhibited no differences. The reduction of corn pollen germination in vitro under acid rain stress was mainly due to pollen rupture. The present data indicates the reduction of pollen germination and tube growth under acid rain stress may be a physiological response rather than a genetic response. A simple, nontoxic, and effective method to separate germinated from ungerminated pollen grains has been developed using pollen from corn (Zea mays, L. cv. Pioneer 3747). The separated germinated pollen grains retained viability and continued tube growth when placed in culture medium.

  19. Anomalous opening of the Equatorial Atlantic due to an equatorial mantle thermal minimum

    NASA Astrophysics Data System (ADS)

    Bonatti, Enrico

    1996-09-01

    The geology of the Equatorial Atlantic is dominated by a broad east-west megashear belt where a cluster of large fracture zones offsets anomalously deep segments of the Mid-Atlantic Ridge (MAR). The origin and evolution of this megashear region may lie ultimately in an equatorial mantle thermal minimum. The notion of a mantle thermal minimum in the Equatorial Atlantic is supported by an equatorial minimum of zero-age topography, a maximum in mantle shear waves seismic velocity and a minimum in the degree of melting, indicated by the chemistry of MAR basalts and peridotites. This thermal minimum has probably been a stable feature since before the Cretaceous separation of Africa from South America; it caused a pre-opening equatorial continental lithosphere thicker and colder than normal. The Cretaceous Benue Trough in western Africa and the Amazon depression in South America are interpreted as morphostructural depressions created or rejuvenated by strike-slip, transpressional and transtensional tectonics ducing extension of the cold/thick equatorial lithosphere. The oceanic rift propagating northward from the South Atlantic impinged against the equatorial thicker, colder and, therefore, stronger than normal continental, lithosphere that consequently acted as a 'locked zone'. This, and a low magmatic budget due to the cold upper mantle, caused a lower than normal rate of propagation of the oceanic rift into the equatorial belt, with diffuse deformation during mostly amagmatic extension. The thick/cold lithosphere prevented major Cretaceous igneous activity from the St. Helena plume. Eventually initial 'weak' isolated nuclei oceanic lithosphere were emplaced, separated by E-W continent/continent transforms. Opening occurred largely by strike-slip motion along these initial transforms. The consequences were that the Equatorial Atlantic opened prevalently along an E-W direction, in contrast to the N-S opening of the North and South Atlantic, and that sheared continental

  20. Desert Dust and Monsoon Rain

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, Kyu-Myong

    2014-01-01

    For centuries, inhabitants of the Indian subcontinent have know that heavy dust events brought on by strong winds occur frequently in the pre-monsoon season, before the onset of heavy rain. Yet scientists have never seriously considered the possibility that natural dust can affect monsoon rainfall. Up to now, most studies of the impacts of aerosols on Indian monsoon rainfall have focused on anthropogenic aerosols in the context of climate change. However, a few recent studies have show that aerosols from antropogenic and natural sources over the Indian subcontinent may affect the transition from break to active monsoon phases on short timescales of days to weeks. Writing in Nature Geoscience, Vinoj and colleagues describe how they have shown that desert dust aerosols over the Arabian Sea and West Asia can strenghten the summer monsoon over the Indial subcontinent in a matter of days.

  1. Rain underscores need for injection

    SciTech Connect

    Stelling, K.F.

    1996-01-01

    Since 1987, steam production totals at The Geysers Geothermal field have fallen and water injection totals have remained quite stable, except for the unusually dry winter months of 1994 when injection fell by a record amount. The heavy rainfall in the first half of 1995 altered the long-term production and injection patterns and underscored the need to increase injection in the field. From January to June 1995, steam production at The Geysers was reduced by 37 percent form the amount produced during the same period in 1994--because the rain increased availability of hydroelectric power. At the same time, water injection in the field rose by 25 percent because more rainwater was available for injection. Consequently, both reservoir pressure and available steam reserves grew, and most power plants that returned on line in the second half of the year produced more megawatts with less steam. This confirmed findings form several injection studies at The Geyser`s.

  2. Rain garden guidelines for southwest Ohio

    EPA Science Inventory

    Rain gardens are a unique and practical landscape feature that can enhance the beauty of home gardens. When properly installed, they are one method of limiting the negative effects of rainfall runoff in urban areas. Indeed, rain gardens turn a "negative" into a "positive" by capt...

  3. Rainy Day Fun: Rain-Inspired Activities.

    ERIC Educational Resources Information Center

    Stanger, Annie Moretz

    1999-01-01

    Rainy days are opportunities to teach campers about weather and to plan activities around a rain theme. Indoor and outdoor science-based activities concerned with rain, water, or water conservation are suggested for specific age groups from ages 5-7 through 11-14. Campers can also develop ideas for activities using questions provided. (CDS)

  4. Human Ecology: Acid Rain and Public Policy.

    ERIC Educational Resources Information Center

    Bybee, Rodger W.

    1983-01-01

    A connection between science and society can be seen in the human and ecological dimensions of one contemporary problem: acid rain. Introduces a human ecological theme and relationships between acid rain and public policy, considering scientific understanding and public awareness, scientific research and public policy, and national politics and…

  5. Acid Rain Students Do Original Research.

    ERIC Educational Resources Information Center

    Outdoor Communicator, 1984

    1984-01-01

    At Park Senior High School (Cottage Grove, Minnesota), 46 juniors and seniors planted 384 red pine seedlings in connection with their original research on acid rain, with advice from Dr. Harriet Stubbs, director of the Acid Precipitation Awareness Program (West Saint Paul), which has been developing acid rain teaching materials. (MH)

  6. Acid Rain. LC Science Tracer Bullet.

    ERIC Educational Resources Information Center

    Hollmann, Pauline, Comp.

    The term "acid rain," also called "acid precipitation," generally refers to any precipitation having a pH value of less than 5.6. This guide to the literature on acid rain in the collections of the Library of Congress is not necessarily intended to be a comprehensive bibliography. It is designed to provide the reader with a set…

  7. Acid Rain: Activities for Science Teachers.

    ERIC Educational Resources Information Center

    Johnson, Eric; And Others

    1983-01-01

    Seven complete secondary/college level acid rain activities are provided. Activities include overview; background information and societal implications; major concepts; student objectives; vocabulary/material lists; procedures; instructional strategies; and questions/discussion and extension suggestions. Activities consider effects of acid rain on…

  8. Acid Thunder: Acid Rain and Ancient Mesoamerica

    ERIC Educational Resources Information Center

    Kahl, Jonathan D. W.; Berg, Craig A.

    2006-01-01

    Much of Mesoamerica's rich cultural heritage is slowly eroding because of acid rain. Just as water dissolves an Alka-Seltzer tablet, acid rain erodes the limestone surfaces of Mexican archaeological sites at a rate of about one-half millimeter per century (Bravo et al. 2003). A half-millimeter may not seem like much, but at this pace, a few…

  9. Environmental Education about the Rain Forest.

    ERIC Educational Resources Information Center

    Berkmuller, Klaus

    Designed to help in the development of an educational program about the value of rain forests, this handbook presents a condensation of issues, facts, and concepts. The handbook is divided into three parts. Part one introduces the rain forest ecosystem and provides conceptual background material needed in the determination of problems, the…

  10. GREEN INFRASTRUCTURE RESEARCH PROGRAM: Rain Gardens

    EPA Science Inventory

    the National Risk Management Research Laboratory (NRMRL) rain garden evaluation is part of a larger collection of long-term research that evaluates a variety of stormwater management practices. The U.S. EPA recognizes the potential of rain gardens as a green infrastructure manag...

  11. Neogene and Quaternary development of the neotropical rain forest: the forest refugia hypothesis, and a literature overview

    NASA Astrophysics Data System (ADS)

    Hooghiemstra, Henry; van der Hammen, Thomas

    1998-09-01

    The upheaval of the northern Andes in Miocene and Pliocene time changed the drainage system in northern South America significantly and caused the present-day rain forest areas of Chocó and the Lower Magdalena Valley became separated from Amazonas. Plant diversity may have reached the highest level in the Miocene or Pliocene, and excessive present-day phytodiversity may be regarded as a legacy of the Tertiary, rather than an evolutionary product of the Quaternary. In the Quaternary strong temperature oscillations, related to the series of ice-ages, were superposed on the Late Tertiary forest dynamics, which included river displacement and latitudinal migrations of the equatorial rain belt (caloric equator) with the rhythm of the precession cycle of orbital climate forcing. The hypothesis that claims a permanent rain forest cover all over the Amazon basin during the last glacial is in contrast with the `forest refugia hypothesis', which accepts replacement of rain forest by savanna, or savanna forest, during dry climatic intervals. Both scenarios have been evidenced by pollen records. In this paper, it is suggested that both hypotheses are not necessarily conflicting and apparently did occur in different parts of the Amazon basin, and in different periods, depending on the climatological constraints. A compilation of the most important literature concerning the vegetational, climatic, and environmental history of the rain forest areas of Amazonas and Chocó, and surrounding dry ecosystems has been included.

  12. Sudden intrusion of corrosive bottom water into the South Atlantic during the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Meissner, K. J.; Alexander, K.; Bralower, T. J.

    2015-12-01

    The Paleocene-Eocene Thermal Maximum, ˜55 million years before present, was a period of rapid warming marked by a negative carbon isotope excursion and widespread dissolution of seafloor carbonate. These changes have been attributed to a massive release of carbon into the exogenic carbon cycle, and thus, the event provides an analog for future climate and environmental changes given the current anthropogenic CO2 emissions. Previous attempts to constrain the amount of carbon released have produced widely diverging results, between 2000 and 10,000 gigatons carbon (GtC). Sediment records indicate that acidification of deep waters was generally more extensive and severe in the Atlantic and Caribbean regions, with more modest changes in the Southern and Pacific Oceans. Here we compare simulations integrated with the UVic Earth System Climate Model with reconstructions of temperature and dissolution to present a mechanism that might explain the observed spatial differences and to constrain the total mass of carbon released. Due to the late Paleocene topography, highly corrosive waters accumulate in the deep North Atlantic before the PETM in our simulations. Several thousand years into the event, deep ocean warming destabilizes the North Atlantic water column and triggers deep water formation. This causes the corrosive bottom water to spill over an equatorial sill into the South Atlantic and through the Southern and Pacific Oceans, progressively gaining alkalinity. The simulated pattern of sediment dissolution along the path taken by this corrosive water is consistent with most dissolution estimates made from CaCO3 measurements in the Paleocene-Eocene sediment record. We find two scenarios that agree best with proxy data: a carbon release of 7000 GtC in combination with pre-event atmospheric carbon dioxide concentrations of 840 ppm and a carbon release of 7000-10,000 GtC with pre-event CO2 concentrations of 1680 ppm.

  13. Scale Dependence of Spatiotemporal Intermittence of Rain

    NASA Technical Reports Server (NTRS)

    Kundu, Prasun K.; Siddani, Ravi K.

    2011-01-01

    It is a common experience that rainfall is intermittent in space and time. This is reflected by the fact that the statistics of area- and/or time-averaged rain rate is described by a mixed distribution with a nonzero probability of having a sharp value zero. In this paper we have explored the dependence of the probability of zero rain on the averaging space and time scales in large multiyear data sets based on radar and rain gauge observations. A stretched exponential fannula fits the observed scale dependence of the zero-rain probability. The proposed formula makes it apparent that the space-time support of the rain field is not quite a set of measure zero as is sometimes supposed. We also give an ex.planation of the observed behavior in tenus of a simple probabilistic model based on the premise that rainfall process has an intrinsic memory.

  14. First fossil record of Discocephalinae (Insecta, Pentatomidae): a new genus from the middle Eocene of Río Pichileufú, Patagonia, Argentina

    PubMed Central

    Petrulevičius, Julián F.; Popov, Yuri A.

    2014-01-01

    Abstract A new genus and species of Discocephalini, Acanthocephalonotum martinsnetoi gen. n. et sp. n. is described from Río Pichileufú, middle Eocene of Patagonia, Argentina at palaeolatitude ~ 46°S. The new species is the first fossil representative of the Discocephalinae. This taxon is extant in equatorial to subtropical America, and some species reach warm temperate latitudes (Buenos Aires province). The new genus is distinguished from the other genera of Discocephalini by the combination of these characters: interocular width greater than head length; head massive and quadrangular with the anterior margin almost straight; juga touching each other; labrum thick and curved; triangular ante-ocular process extending beyond the eye; broad spine-like antero-lateral process of the pronotum; pronotum explanate and bean shaped; scutellum triangular with a circular tongue reaching the anterior side of abdominal segment 7; and wings well developed with membrane just surpassing end of abdomen. PMID:25061387

  15. Acid Rain: A Teaching Focus for the Intermediate Grades.

    ERIC Educational Resources Information Center

    Adams, Renee B.; Adams, Neil D.

    1992-01-01

    The study of acid rain provides ample opportunities for active, interdisciplinary learning. This article describes 12 hands-on activities designed to expand students' understanding of acid rain. Background information on acid rain is included. (LB)

  16. What You Can Do to Soak Up the Rain

    EPA Pesticide Factsheets

    Take steps around your home and community to reduce stormwater runoff. Use rain barrels, disconnect/redirect downspouts, plant trees and rain gardens, use drywells and permeable pavers, and plant green roofs. Take action to soak up the rain.

  17. Lunar influence on equatorial atmospheric angular momentum

    NASA Astrophysics Data System (ADS)

    Bizouard, Christian; Zotov, Leonid; Sidorenkov, Nikolay

    2014-11-01

    This study investigates the relationship between the equatorial atmospheric angular momentum oscillation in the nonrotating frame and the quasi-diurnal lunar tidal potential. Between 2 and 30 days, the corresponding equatorial component, called Celestial Atmospheric Angular Momentum (CEAM), is mostly constituted of prograde circular motions, especially of a harmonic at 13.66 days, a sidelobe at 13.63 days, and of a weekly broadband variation. A simple equilibrium tide model explains the 13.66 day pressure term as a result of the O1 lunar tide. The powerful episodic fluctuations between 5 and 8 days possibly reflect an atmospheric normal mode excited by the tidal waves Q1 (6.86 days) and σ1 (7.095 days). The lunar tidal influence on the spectral band from 2 to 30 days is confirmed by two specific features, not occurring for seasonal band dominated by the solar thermal effect. First, Northern and Southern Hemispheres contribute equally and synchronously to the CEAM wind term. Second, the pressure and wind terms are proportional, which follows from angular momentum budget considerations where the topographic and friction torques on the solid Earth are much smaller than the one resulting from the equatorial bulge. Such a configuration is expected for the case of tidally induced circulation, where the surface pressure variation is tesseral and cannot contribute to the topographic torque, and tidal winds blow only at high altitudes. The likely effects of the lunar-driven atmospheric circulation on Earth's nutation are estimated and discussed in light of the present-day capabilities of space geodetic techniques.

  18. Equatorial Oscillations in Jupiter's and Saturn's Atmospheres

    NASA Technical Reports Server (NTRS)

    Flasar, F. Michael; Guerlet, S.; Fouchet, T.; Schinder, P. J.

    2011-01-01

    Equatorial oscillations in the zonal-mean temperatures and zonal winds have been well documented in Earth's middle atmosphere. A growing body of evidence from ground-based and Cassini spacecraft observations indicates that such phenomena also occur in the stratospheres of Jupiter and Saturn. Earth-based midinfrared measurements spanning several decades have established that the equatorial stratospheric temperatures on Jupiter vary with a cycle of 4-5 years and on Saturn with a cycle of approximately 15 years. Spectra obtained by the Composite Infrared Spectrometer (CIRS) during the Cassini swingby at the end of 2000, with much better vertical resolution than the ground-based data, indicated a series of vertically stacked warm and cold anomalics at Jupiter's equator; a similar structurc was seen at Saturn's equator in CIRS limb measurements made in 2005, in the early phase of Cassini's orbital tour. The thermal wind equation implied similar patterns of mean zonal winds increasing and decreasing with altitude. On Saturn the peak-to-pcak amplitude of this variation was nearly 200 meters per second. The alternating vertical pattern of wanner and colder cquatorial tcmperatures and easterly and westerly tendencies of the zonal winds is seen in Earth's equatorial oscillations, where the pattern descends with time, The Cassini Jupiter and early Saturn observations were snapshots within a limited time interval, and they did not show the temporal evolution of the spatial patterns. However, more recent Saturn observations by CIRS (2010) and Cassini radio-occultation soundings (2009-2010) have provided an opportunity to follow the change of the temperature-zonal wind pattern, and they suggest there is descent, at a rate of roughly one scale height over four years. On Earth, the observed descent in the zonal-mean structure is associated with the absorption of a combination of vertically propagating waves with easlerly and westerly phase velocities. The peak-to-peak zonal wind

  19. The equatorial electrojet satellite and surface comparison

    NASA Technical Reports Server (NTRS)

    Cain, J. C. (Editor); Sweeney, R. E. (Editor)

    1972-01-01

    The OGO 4 and 6 (POGO) magnetic field results for the equatorial electrojet indicate that while the present models are approximately correct, the possibility of a westward component must be incorporated. The scatter diagrams of POGO amplitudes and surface data show a correlation. The ratios between the amplitudes estimated from surface data and those at 400 km altitude are as follows: India 5 to 8, East Africa (Addis Ababa) 4, Central Africa 3, West Africa (Nigeria) 3, South America (Huancayo) 5, and Philippines 5. The variation in the ratio is due to the conductivity structure of the earth in various zones.

  20. Response of the Pacific inter-tropical convergence zone to global cooling and initiation of Antarctic glaciation across the Eocene Oligocene Transition.

    PubMed

    Hyeong, Kiseong; Kuroda, Junichiro; Seo, Inah; Wilson, Paul A

    2016-08-10

    Approximately 34 million years ago across the Eocene-Oligocene transition (EOT), Earth's climate tipped from a largely unglaciated state into one that sustained large ice sheets on Antarctica. Antarctic glaciation is attributed to a threshold response to slow decline in atmospheric CO2 but our understanding of the feedback processes triggered and of climate change on the other contents is limited. Here we present new geochemical records of terrigenous dust accumulating on the sea floor across the EOT from a site in the central equatorial Pacific. We report a change in dust chemistry from an Asian affinity to a Central-South American provenance that occurs geologically synchronously with the initiation of stepwise global cooling, glaciation of Antarctica and aridification on the northern continents. We infer that the inter-tropical convergence zone of intense precipitation extended to our site during late Eocene, at least four degrees latitude further south than today, but that it migrated northwards in step with global cooling and initiation of Antarctic glaciation. Our findings point to an atmospheric teleconnection between extratropical cooling and rainfall climate in the tropics and the mid-latitude belt of the westerlies operating across the most pivotal transition in climate state of the Cenozoic Era.

  1. Cretaceous and Eocene lignite deposits, Jackson Purchase, Kentucky

    USGS Publications Warehouse

    Hower, J.C.; Rich, F.J.; Williams, D.A.; Bland, A.E.; Fiene, F.L.

    1990-01-01

    Lignites occur in the Cretaceous McNairy Formation and the Eocene Claiborne Formation in the Jackson Purchase region of western Kentucky. The lone Cretaceous lignite sample has over 18 percent inertodetrinite and 32 percent humodetrinite which, along with the abundant mineral matter, suggests a possible allochthonous origin for the deposit. The Claiborne Formation lignites have higher humic maceral contents than the Cretaceous lignites. Palynology suggests that there was considerable variation in the plant communities responsible for the Claiborne deposits. Differences in the preservation of the various plants is also seen in the variations between the humic types, particularly in the ulminite and humodetrinite contents. Potter and Dilcher (1980) suggested that the Claiborne lignites in the Jackson Purchase and west Tennessee developed in the abandoned oxbows of Eocene rivers. Significant short-distance changes in the peat thickness, flora, and other depositional elements should be expected in such an environment and could easily account for the observed variations in composition. ?? 1990.

  2. Impact ejecta at the Paleocene-Eocene boundary.

    PubMed

    Schaller, Morgan F; Fung, Megan K; Wright, James D; Katz, Miriam E; Kent, Dennis V

    2016-10-14

    Extraterrestrial impacts have left a substantial imprint on the climate and evolutionary history of Earth. A rapid carbon cycle perturbation and global warming event about 56 million years ago at the Paleocene-Eocene (P-E) boundary (the Paleocene-Eocene Thermal Maximum) was accompanied by rapid expansions of mammals and terrestrial plants and extinctions of deep-sea benthic organisms. Here, we report the discovery of silicate glass spherules in a discrete stratigraphic layer from three marine P-E boundary sections on the Atlantic margin. Distinct characteristics identify the spherules as microtektites and microkrystites, indicating that an extraterrestrial impact occurred during the carbon isotope excursion at the P-E boundary.

  3. The Middle Eocene flora of Csordakút (N Hungary)

    NASA Astrophysics Data System (ADS)

    Erdei, Boglárka; Rákosi, László

    2009-02-01

    The Middle Eocene fossil plant assemblage from Csordakút (N Hungary) comprises plant remains preserved exclusively as impressions. Algae are represented by abundant remains of Characeae, including both vegetative fragments and gyrogonites. Remains of angiosperms comprise Lauraceae (Daphnogene sp.), Fagaceae (cf. Eotrigonobalanus furcinervis), Ulmaceae (Cedrelospermum div. sp.), Myricaceae (Myrica sp., Comptonia div. sp.), Leguminosae (leaves and fruit), Rhamnaceae (?Zizyphus zizyphoides), Elaeocarpaceae (Sloanea nimrodi, Sloanea sp. fruit), Smilacaceae (Smilax div. sp.). The absence of gymnosperms is indicative of a floristic similarity to the coeval floras of Tatabánya (N Hungary) and Girbou in Romania. Sloanea nimrodi (Ettingshausen) Kvaček & Hably, a new element for the Hungarian fossil record indicates a floristic relation to the Late Eocene flora of Kučlin (Bohemia).

  4. Late Eocene impact microspherules - Stratigraphy, age and geochemistry

    NASA Astrophysics Data System (ADS)

    Keller, G.; D'Hondt, S. L.; Orth, C. J.; Gilmore, J. S.; Oliver, P. Q.; Shoemaker, E. M.; Molina, E.

    1987-03-01

    The stratigraphy, faunal changes, and geochemistry of deep-sea sediments associated with late Eocene microtektite and microspherule layers are reported. Microprobe analyses of major element compositions of microspherules show that, although there is some compositional overlap in all three late Eocene layers as well as with the Pleistocene Australasian and Ivory Coast microtektites, each microspherule population has characteristic compositional features. All three microspherule layers are associated with decreased carbonate, possibly due to a sudden productivity change, increased dissolution as a result of sea-level and climate fluctuations, or impact events. A discovery of microtektites in the Gl. cerroazulensis Zone off the New Jersey coast extends the North American strewn field from the Caribbean to the northwest Atlantic.

  5. Impact ejecta at the Paleocene-Eocene boundary

    NASA Astrophysics Data System (ADS)

    Schaller, Morgan F.; Fung, Megan K.; Wright, James D.; Katz, Miriam E.; Kent, Dennis V.

    2016-10-01

    Extraterrestrial impacts have left a substantial imprint on the climate and evolutionary history of Earth. A rapid carbon cycle perturbation and global warming event about 56 million years ago at the Paleocene-Eocene (P-E) boundary (the Paleocene-Eocene Thermal Maximum) was accompanied by rapid expansions of mammals and terrestrial plants and extinctions of deep-sea benthic organisms. Here, we report the discovery of silicate glass spherules in a discrete stratigraphic layer from three marine P-E boundary sections on the Atlantic margin. Distinct characteristics identify the spherules as microtektites and microkrystites, indicating that an extraterrestrial impact occurred during the carbon isotope excursion at the P-E boundary.

  6. Kinematics of coronal rain in a transversely oscillating loop: Ponderomotive force and rain-excited oscillations

    NASA Astrophysics Data System (ADS)

    Verwichte, E.; Antolin, P.; Rowlands, G.; Kohutova, P.; Neukirch, T.

    2017-01-01

    Context. Coronal rain is composed of cool dense blobs that form in solar coronal loops and are a manifestation of catastrophic cooling linked to thermal instability. Once formed, rain falls towards the solar surface at sub-ballistic speeds, which is not well understood. Pressure forces seem to be the prime candidate to explain this. In many observations rain is accompanied by transverse oscillations and the interaction between rain and these oscillations needs to be explored. Aims: Therefore, an alternative kinematic model for coronal rain kinematics in transversely oscillating loops is developed to understand the physical nature of the observed sub-ballistic falling motion of rain. This model explicitly explores the role of the ponderomotive force arising from the transverse oscillation on the rain motion and the capacity of rain to excite wave motion. Methods: An analytical model is presented that describes a rain blob guided by the coronal magnetic field supporting a one-dimensional shear Alfvén wave as a point mass on an oscillating string. The model includes gravity and the ponderomotive force from the oscillation acting on the mass and the inertia of the mass acting on the oscillation. Results: The kinematics of rain in the limit of negligible rain mass are explored and falling and trapped regimes are found, depending on wave amplitude. In the trapped regime for the fundamental mode, the rain blob bounces back and forth around the loop top at a long period that is inversely proportional to the oscillation amplitude. The model is compared with several observational rain studies, including one in-depth comparison with an observation that shows rain with up-and-down bobbing motion. The role of rain inertia in exciting transverse oscillations is explored in inclined loops. Conclusions: It is found that the model requires displacement amplitudes of the transverse oscillation that are typically an order of magnitude larger than observed to explain the measured sub

  7. Modulation of Cenozoic climate by weathering of large igneous provinces on continents drifting through equatorial humid belt

    NASA Astrophysics Data System (ADS)

    Muttoni, G.; Kent, D. V.

    2011-12-01

    The small reservoir of CO2 in the atmosphere (pCO2) that modulates climate through the greenhouse effect is a delicate balance between large fluxes of sources and sinks. The major long-term source of CO2 is global degassing from sea-floor spreading, subduction, hotspot activity, and metamorphism; the ultimate sink is through weathering of continental silicates. Most carbon cycle models are driven by changes in the source flux, in particular, variable rates of ocean floor production (and concomitant subduction) but the area/age versus age distribution of the modern ocean is compatible with a steady rate since 180 Ma (Rowley, 2002 GSA Bulletin). We previously suggested (2008 PNAS) that evidence of high pCO2 and warm climates in the Cretaceous-early Cenozoic could be explained by the subduction of Tethyan ocean crust loaded with equatorial carbonate-rich pelagic (more readily subductable) sediments since the onset of India's northward flight at ~120 Ma up until the CO2-producing decarbonation factory slowed down with collision of India and Asia at the Early Eocene Climate Optimum at 50 Ma. At about this time, the India continent and the highly weatherable Deccan Traps drifted into the equatorial humid belt where uptake of CO2 by efficient silicate weathering would further lower the level of pCO2. Continued weathering uptake was influenced by the southerly extrusion of SE Asia in response to the Indian indentor starting at ~40 Ma (Molnar & Tapponnier, 1975 Science) as well as the emplacement of the Ethiopian traps near the Equator at 30 Ma. The ongoing impingement of India into Asia and resultant southerly tectonic extrusion of SE Asia (Replumaz & Tapponnier, 2003 JGR) makes it the dominant new area in the equatorial humid belt. Moreover, SE Asia presently accounts for 25% of CO2 consumption of all basaltic provinces, which account for ~1/3 of the total consumption by continental silicate weathering (Dessert et al., 2003 Chemical Geology) that is within the range of

  8. Early Eocene's climate and ocean circulation from coupled model simulations

    NASA Astrophysics Data System (ADS)

    Weber, Tobias; Thomas, Maik

    2014-05-01

    While proxy data provide a snapshot of climate conditions at a specific location, coupled atmosphere-ocean models are able to expand this knowledge over the globe. Therefore, they are indispensable tools for understanding past climate conditions. We model the dynamical state of atmosphere and ocean during the Early Eocene and pre-industrial times, using the coupled atmosphere-ocean model ECHAM5/MPIOM with realistic reconstructions of vegetation and CO2. The resulting simulated climate variables are compared to terrestrial and oceanic proxies. The Early Eocene climate is in the global mean warmer (~13°C) and wetter (~1 mm/d) than in pre-industrial times. Especially temperatures in the Southern Ocean, the Greenland Sea and Arctic Ocean raise by up to 25K, being in accordance with surface temperature estimates from terrestrial and marine proxy data. The oceans are hereby rendered ice-free, leading to a decrease of polar albedo and thereby facilitating polar warming. This leads to a by 5K diminished equator-to-pole temperature gradient. Warmer temperatures as well as changed bathymetry have an effect on ocean dynamics in the Early Eocene. Although deep-water formation can be found in the Greenland Sea, Weddell Sea, and Tethys Sea, it is weaker than in the pre-industrial run and the resulting circulation is shallower. This is not only visible in water transport through sea gates but also in the Atlantic Meridional Overturning Circulation (AMOC), adopting its maximum at 700m depths in the Early Eocene, while maximum transport is reached in the pre-industrial control run at 1200m. Albeit a shallow and weak thermohaline circulation, a global ocean conveyor belt is being triggered, causing a transport from the areas of subduction through the Atlantic and Southern Oceans into the Indian and Pacific Oceans.

  9. A New Eocene Casquehead Lizard (Reptilia, Corytophanidae) from North America.

    PubMed

    Conrad, Jack L

    2015-01-01

    A new fossil showing affinities with extant Laemanctus offers the first clear evidence for a casquehead lizard (Corytophanidae) from the Eocene of North America. Along with Geiseltaliellus from roughly coeval rocks in central Europe, the new find further documents the tropical fauna present during greenhouse conditions in the northern mid-latitudes approximately 50 million years ago (Ma). Modern Corytophanidae is a neotropical clade of iguanian lizards ranging from southern Mexico to northern South America.

  10. Asian Eocene monsoons as revealed by leaf architectural signatures

    NASA Astrophysics Data System (ADS)

    Spicer, Robert A.; Yang, Jian; Herman, Alexei B.; Kodrul, Tatiana; Maslova, Natalia; Spicer, Teresa E. V.; Aleksandrova, Galina; Jin, Jianhua

    2016-09-01

    The onset and development of the Asian monsoon systems is a topic that has attracted considerable research effort but proxy data limitations, coupled with a diversity of definitions and metrics characterizing monsoon phenomena, have generated much debate. Failure of geological proxies to yield metrics capable of distinguishing between rainfall seasonality induced by migrations of the Inter-tropical Convergence Zone (ITCZ) from that attributable to topographically modified seasonal pressure reversals has frustrated attempts to understand mechanisms underpinning monsoon development and dynamics. Here we circumvent the use of such single climate parameter metrics in favor of detecting directly the distinctive attributes of different monsoon regimes encoded in leaf fossils. Leaf form adapts to the prevailing climate, particularly under the extreme seasonal stresses imposed by monsoons, so it is likely that fossil leaves carry a unique signature of past monsoon regimes. Leaf form trait spectra obtained from fossils from Eocene basins in southern China were compared with those seen in modern leaves growing under known climate regimes. The fossil leaf trait spectra, including those derived from previously published fossil floras from northwestern India, were most similar to those found in vegetation exposed to the modern Indonesia-Australia Monsoon (I-AM), which is largely a product of seasonal migrations of the ITCZ. The presence of this distinctive leaf physiognomic signature suggests that although a monsoon climate existed in Eocene time across southern Asia the characteristics of the modern topographically-enhanced South Asia Monsoon had yet to develop. By the Eocene leaves in South Asia had become well adapted to an I-AM type regime across many taxa and points to the existence of a pervasive monsoon climate prior to the Eocene. No fossil trait spectra typical of exposure to the modern East Asia monsoon were seen, suggesting the effects of this system in southern

  11. A New Eocene Casquehead Lizard (Reptilia, Corytophanidae) from North America

    PubMed Central

    Conrad, Jack L.

    2015-01-01

    A new fossil showing affinities with extant Laemanctus offers the first clear evidence for a casquehead lizard (Corytophanidae) from the Eocene of North America. Along with Geiseltaliellus from roughly coeval rocks in central Europe, the new find further documents the tropical fauna present during greenhouse conditions in the northern mid-latitudes approximately 50 million years ago (Ma). Modern Corytophanidae is a neotropical clade of iguanian lizards ranging from southern Mexico to northern South America. PMID:26131767

  12. Webspinners in Early Eocene amber from western India (Insecta, Embiodea)

    PubMed Central

    Engel, Michael S.; Grimaldi, David A.; Singh, Hukam; Nascimbene, Paul C.

    2011-01-01

    Abstract The family Scelembiidae (Neoembiodea: Embiomorpha: Archembioidea) is recorded from Asia for the first time, based on two individuals preserved in Early Eocene amber from the Cambay Basin, western India. Kumarembia hurleyi Engel & Grimaldi, gen. n. et sp. n., is described, figured, and distinguished from other archembioid genera. The genus shares male genitalic features with scelembiids, otherwise known from South America and Africa. PMID:22287898

  13. Hydrocarbon potential of Middle Eocene carbonates, Sirt Basin, Libya

    NASA Astrophysics Data System (ADS)

    Swei, Giuma H.; Tucker, Maurice E.

    2015-11-01

    Deposition of Middle Eocene carbonates in the Sirt Basin in Libya has been the subject of considerable study in recent years because of the importance of sediments of this age as hydrocarbon reservoirs. The Gialo Formation is an important gas-producing reservoir in the Assumood, Sahl and other nearby fields. The gas which is generated from the gas-prone Sirt Shale source rock of the northern Ajdabiya Trough probably migrated in to the Assumood Ridge from the northeast through late Cretaceous, Paleocene and early Eocene carbonates, before being trapped beneath the Augila Shale (Upper Eocene) which is the principal regional seal in the area. This integrated study has enhanced our understanding of reservoir heterogeneity and hydrocarbon potential of the Gialo carbonates and should lead to improved exploration in the future. Reservoir quality in the Gialo Formation is a function of grain types, pore types, grain size, sorting, cementation and compaction, and predicting areas of high reservoir quality has proved difficult; exploration should be oriented to positioning wells into the main trend of the mid-ramp, nummulite accumulation. Different nummulite facies can be reservoirs depending on their diagenetic history. A diagenetic reduction in porosity must be distinguished from a lack of porosity resulting from an unfavourable depositional environment, so that exploration alternatives can be assessed. This integrated study has demonstrated the presence of suitable reservoir rocks, hydrocarbon traps and the close proximity of potential source rocks. These features should encourage further hydrocarbon exploration in the area.

  14. Eocene tidal deposits, northern San Diego County, California

    SciTech Connect

    Eisenberg, L.I.; Abbott, P.L.

    1985-02-01

    A transgressive-regressive sedimentation sequence is recorded in a band of middle Eocene strata a few miles wide. An abundance of primary sedimentary structures, along with interfingering relationships and paleontology, define 12 lithofacies representing depositional environments including nearshore shelf, outer and inner barrier island, tidal flats and channels, lagoon and lagoonal delta. Tide-influenced sedimentary features are well defined and include meandering and abandoned tidal channels, oppositely inclined superimposed cross-strata, interlaminated mud and sand along the basal and lateral accretion surfaces of migrating tidal channels, flaser and wavy bedding, and storm-deposited strata. The first sedimentary half cycle was transgressive and documents the compression of dominantly tidal-flat and lagoonal environments against a steep, hilly coastline by the overall rising sea level of early and medial middle Eocene time. The inboard tidal-flat and lagoonal mudstones (Delmar and Friars Formations) and outboard tidal flat, channel and bar sandstones (Torrey Sandstone and Scripps Formation) interfinger in a landward-climbing, 3-dimensional sedimentary mass that parallels and meets the basement with a pronounced unconformity. The second half cycle was regressive and occurred in the medial and late middle Eocene. It formed due to the influx of coarser, more angular sediment from the adjacent basement into the narrowed paralic zone. This westward (seaward) progradation of lagoonal delta and inner tidal-flat sandy sediments occurred despite the still-rising sea level.

  15. Eocene diversification of crown group rails (Aves: Gruiformes: Rallidae).

    PubMed

    García-R, Juan C; Gibb, Gillian C; Trewick, Steve A

    2014-01-01

    Central to our understanding of the timing of bird evolution is debate about an apparent conflict between fossil and molecular data. A deep age for higher level taxa within Neoaves is evident from molecular analyses but much remains to be learned about the age of diversification in modern bird families and their evolutionary ecology. In order to better understand the timing and pattern of diversification within the family Rallidae we used a relaxed molecular clock, fossil calibrations, and complete mitochondrial genomes from a range of rallid species analysed in a Bayesian framework. The estimated time of origin of Rallidae is Eocene, about 40.5 Mya, with evidence of intrafamiliar diversification from the Late Eocene to the Miocene. This timing is older than previously suggested for crown group Rallidae, but fossil calibrations, extent of taxon sampling and substantial sequence data give it credence. We note that fossils of Eocene age tentatively assigned to Rallidae are consistent with our findings. Compared to available studies of other bird lineages, the rail clade is old and supports an inference of deep ancestry of ground-dwelling habits among Neoaves.

  16. Eocene Diversification of Crown Group Rails (Aves: Gruiformes: Rallidae)

    PubMed Central

    García–R, Juan C.; Gibb, Gillian C.; Trewick, Steve A.

    2014-01-01

    Central to our understanding of the timing of bird evolution is debate about an apparent conflict between fossil and molecular data. A deep age for higher level taxa within Neoaves is evident from molecular analyses but much remains to be learned about the age of diversification in modern bird families and their evolutionary ecology. In order to better understand the timing and pattern of diversification within the family Rallidae we used a relaxed molecular clock, fossil calibrations, and complete mitochondrial genomes from a range of rallid species analysed in a Bayesian framework. The estimated time of origin of Rallidae is Eocene, about 40.5 Mya, with evidence of intrafamiliar diversification from the Late Eocene to the Miocene. This timing is older than previously suggested for crown group Rallidae, but fossil calibrations, extent of taxon sampling and substantial sequence data give it credence. We note that fossils of Eocene age tentatively assigned to Rallidae are consistent with our findings. Compared to available studies of other bird lineages, the rail clade is old and supports an inference of deep ancestry of ground-dwelling habits among Neoaves. PMID:25291147

  17. Late Eocene white pines (Pinus subgenus Strobus) from southern China

    PubMed Central

    Xu, Qingqing; Zhou, Wenjun; Kodrul, Tatiana M.; Naugolnykh, Serge V.; Jin, Jianhua

    2015-01-01

    Fossil records indicate that the genus Pinus L. split into two subgenera by the Late Cretaceous, although subgenus Strobus (D. Don) Lemmon is less well documented than subgenus Pinus L., especially in eastern Asia. In this paper, Pinus maomingensis sp. nov. is established based on a compressed seed cone from the upper Eocene of the Maoming Basin of southern China. This species is attributed to genus Pinus, subgenus Strobus, section Quinquefoliae Duhamel, subsection Strobus Loudon based on the combination of morphological characters obtained from the cone scales, specifically from the terminal umbo, rhombic apophysis, and cuticle structure. Associated fascicles of needle leaves with deciduous sheaths and bulbous bases are recognized as Pinus sp. and also represent Pinus subgenus Strobus. This new discovery from the Maoming Basin constitutes the first megafossil record of subgenus Strobus from southern China and implies that the members of this subgenus arrived in the southern region of China by the late Eocene. The extant species of subgenus Strobus are mainly distributed in northern temperate and tropical to subtropical mountainous regions. We propose that the Maoming Basin was adjacent to a mountainous region during the late Eocene. PMID:26548658

  18. Ultimate Eocene (Priabonian) Chondrichthyans (Holocephali, Elasmobranchii) of Antarctica

    PubMed Central

    Kriwet, Jürgen; Engelbrecht, Andrea; Mörs, Thomas; Reguero, Marcelo; Pfaff, Cathrin

    2017-01-01

    The Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula, is known for its remarkable wealth of fossil remains of chondrichthyans and teleosts. Chondrichthyans seemingly were dominant elements in the Antarctic Paleogene fish fauna, but decreased in abundance from middle to late Eocene, during which time remains of bony fishes increase. This decline of chondrichthyans at the end of the Eocene generally is related to sudden cooling of seawater, reduction in shelf area, and increasing shelf depth due to the onset of the Antarctic thermal isolation. The last chondrichthyan records known so far include a chimeroid tooth plate from TELM 6 (Lutetian) and a single pristiophorid rostral spine from TELM 7 (Priabonian). Here, we present new chondrichthyan records of Squalus, Squatina, Pristiophorus, Striatolamia, Palaeohypotodus, Carcharocles, and Ischyodus from the upper parts of TELM 7 (Priabonian), including the first record of Carcharocles sokolovi from Antarctica. This assemblage suggests that chondrichthyans persisted much longer in Antarctic waters despite rather cool sea surface temperatures of approximately 5°C. The final disappearance of chondrichthyans at the Eocene–Oligocene boundary concurs with abrupt ice sheet formation in Antarctica. Diversity patterns of chondrichthyans throughout the La Meseta Formation appear to be related to climatic conditions rather than plate tectonics. PMID:28298806

  19. Testing the Paleocene-Eocene Thermal Maximum Magnetofossil Spike Hypothesis

    NASA Astrophysics Data System (ADS)

    Tikoo, S. M.; Kopp, R. E.; Smirnov, A. V.; Raub, T. D.; Schumann, D.; Vali, H.; Kirschvink, J. L.

    2007-12-01

    Ferromagnetic resonance (FMR) spectroscopy detected a magnetofossil spike in Paleocene-Eocene Thermal Maximum (PETM) kaolinitic siltstone of New Jersey's Atlantic Coastal Plain, confirmed by two independent TEM studies and consistent with (but not required by) data from conventional rock magnetic analyses [1,2]. Applying first-order reversal curve (FORC) analysis to the same sediments demonstrates for the first time that ancient magnetofossils bear a FORC signature similar to that of both cultured and environmental magnetotactic bacteria. In order to test whether the observed PETM magnetofossil enrichment was a local or global phenomenon, we compare multi-proxy enviromagnetic profiles through the Atlantic Coastal Plain clay and present new FMR and rock-magnetic stratigraphies through other Paleocene-Eocene boundary sections. Our analyses of samples from the Paleocene-Eocene GSSP at Dababiya, Egypt, indicate the presence of a positive anisotropic, medium- to-high coercivity ferromagnetic component with FMR signatures similar to transitional signatures immediately preceding and following the magnetofossil spike in New Jersey. References: [1] R. E. Kopp,T. D. Raub, D. Schumann, H. Vali, A. V. Smirnov, and J. L. Kirschvink, 2007. Paleoceanography (in press). [2] P. C. Lippert and J. C. Zachos, 2007. Paleoceanography (in press).

  20. Continental temperature change during Early Eocene hyperthermal events

    NASA Astrophysics Data System (ADS)

    Ziegler, Martin; Abels, Hemmo; de Winter, Nils; Gingerich, Philip; Bernasconi, Stefano

    2015-04-01

    Carbonate clumped isotope thermometry has great potential for solving long-standing questions in paleoclimatology as it provides temperature estimates that are independent from assumptions regarding the isotopic or elemental composition of water from which the carbonate precipitated. The clumped isotope group at ETH has worked towards decreasing the sample size requirements and derived new calibrations for the Kiel method based on synthetic and natural calcites. Here we present results of clumped isotope based continental temperatures across the Paleocene-Eocene Thermal Maximum (PETM). The Bighorn Basin of northwestern Wyoming provides hundreds of meters of excellently exposed river floodplain strata of Paleocene and early Eocene age. Records of the the largest greenhouse-warming episode in this interval of time, were recovered soon after their discovery in deep marine sediments. This has allowed intensive study of the major impact this greenhouse warming event had on continental interior climate. Recently, records of four successive, smaller, transient greenhouse warming events in the early Eocene - ETM2/H1/Elmo, H2, I1, and I2 - were located in the fluvial rock record of the basin. We show that the (summer) temperature excursions during hyperthermal events in continental mid-latitudes were amplified compared to marine temperatures and proportional to the size of associated carbon isotope excursions.

  1. Tectonic model for Eocene Formation of the Columbia basin

    SciTech Connect

    Fisk, L.H. ); Fritts, S.G. )

    1990-05-01

    Evidence suggests that a major sedimentary basin underlies the Columbia plateau in Oregon and Washington; however, the Miocene Columbia River Basalts conceal critical structural relationships between adjacent exotic terranes. To date, no interpretations have been published that adequately address the three related questions of the architecture, age, and mechanism of formation of the Columbia basin. The authors interpret residual gravity and aerial photographic data to show, within the basin, a pattern of deep fault architecture consistent with northwest-southeast-oriented rifting. Paleotectonic reconstructions for the Pacific Northwest suggest that rifting may have begun during the Cretaceous, as interpreted previously, but stratigraphic, geophysical and well data point to an early Eocene age for initiation of dramatic rifting and basin subsidence resulting from oblique subduction of the Farallon plate. Their tectonic model for Eocene formation of rift basins underlying the Columbia River Basalt addresses important, previously unanswered questions regarding the tectonics of the Pacific Northwest and rationally relates tectonics and sedimentation over the full extent of the basin from north-central Washington to north-central Oregon. The rifting event(s) they propose explain that the formation of the Columbia basin is consistent in timing and geometry with tectonic events in areas adjacent to the Columbia basin, and thus is but a part of a much larger picture of dramatic extension affecting the entire Pacific Northwest in the Eocene.

  2. Late Eocene impact events recorded in deep-sea sediments

    NASA Technical Reports Server (NTRS)

    Glass, B. P.

    1988-01-01

    Raup and Sepkoski proposed that mass extinctions have occurred every 26 Myr during the last 250 Myr. In order to explain this 26 Myr periodicity, it was proposed that the mass extinctions were caused by periodic increases in cometary impacts. One method to test this hypothesis is to determine if there were periodic increases in impact events (based on crater ages) that correlate with mass extinctions. A way to test the hypothesis that mass extinctions were caused by periodic increases in impact cratering is to look for evidence of impact events in deep-sea deposits. This method allows direct observation of the temporal relationship between impact events and extinctions as recorded in the sedimentary record. There is evidence in the deep-sea record for two (possibly three) impact events in the late Eocene. The younger event, represented by the North American microtektite layer, is not associated with an Ir anomaly. The older event, defined by the cpx spherule layer, is associated with an Ir anomaly. However, neither of the two impact events recorded in late Eocene deposits appears to be associated with an unusual number of extinctions. Thus there is little evidence in the deep-sea record for an impact-related mass extinction in the late Eocene.

  3. The terminal eocene event and the polish connection

    USGS Publications Warehouse

    Van Couvering, J. A.; Aubry, M.-P.; Berggren, W.A.; Bujak, J.P.; Naeser, C.W.; Wieser, T.

    1981-01-01

    The Eocene/Oligocene boundary in Europe is marked by major discontinuities in all environments: the "Grande Coupure" in continental mammals; the elimination of semitropical elements from high-latitude floras; the virtually complete replacement of the shallow-marine malacofauna; and an extraordinary downslope excursion of carbonate deposition in deep-ocean basins (drop in the CCD). These phenomena collectively represent the "Terminal Eocene Event" (TEE). In the Carpathian Mountains, the TEE is manifested in the thin but regionally persistent Globigerina Marl, a calcareous unit containing abundant cool-water microplankton that occurs within very thick, siliceous, bathyal flysch sequences. In southern Poland, the marl is of very latest Eocene age, within planktonic foraminifera zone P17, calcareous nannoplankton zone NP19/20, and the zone of the dinoflagellate Rhomdodinium perforatum. Zircons from bentonites bracketing the marl are dated by fission-track analysis; at Polany, two underlying bentonites are 41.7 and 39.8 Ma, and at Znamirowice two overlying bentonites are 34.6 and 28.9 Ma, in sequence. This accords with glauconite K/Ar ages in Western Europe by which the Eo/Oligocene boundary age is estimated at 37-38 Ma. Global correlations indicate that the TEE corresponds to a major glacio-eustatic regression with a duration of about 0.5 Ma, in which a large Antarctic ice cap was formed, the ocean circulation was permanently changed to the psychrospheric condition, and world climate shifted irreversibly towards the modern state. ?? 1981.

  4. Late Eocene white pines (Pinus subgenus Strobus) from southern China.

    PubMed

    Xu, Qingqing; Zhou, Wenjun; Kodrul, Tatiana M; Naugolnykh, Serge V; Jin, Jianhua

    2015-11-09

    Fossil records indicate that the genus Pinus L. split into two subgenera by the Late Cretaceous, although subgenus Strobus (D. Don) Lemmon is less well documented than subgenus Pinus L., especially in eastern Asia. In this paper, Pinus maomingensis sp. nov. is established based on a compressed seed cone from the upper Eocene of the Maoming Basin of southern China. This species is attributed to genus Pinus, subgenus Strobus, section Quinquefoliae Duhamel, subsection Strobus Loudon based on the combination of morphological characters obtained from the cone scales, specifically from the terminal umbo, rhombic apophysis, and cuticle structure. Associated fascicles of needle leaves with deciduous sheaths and bulbous bases are recognized as Pinus sp. and also represent Pinus subgenus Strobus. This new discovery from the Maoming Basin constitutes the first megafossil record of subgenus Strobus from southern China and implies that the members of this subgenus arrived in the southern region of China by the late Eocene. The extant species of subgenus Strobus are mainly distributed in northern temperate and tropical to subtropical mountainous regions. We propose that the Maoming Basin was adjacent to a mountainous region during the late Eocene.

  5. Asian monsoons in a late Eocene greenhouse world.

    PubMed

    Licht, A; van Cappelle, M; Abels, H A; Ladant, J-B; Trabucho-Alexandre, J; France-Lanord, C; Donnadieu, Y; Vandenberghe, J; Rigaudier, T; Lécuyer, C; Terry, D; Adriaens, R; Boura, A; Guo, Z; Soe, Aung Naing; Quade, J; Dupont-Nivet, G; Jaeger, J-J

    2014-09-25

    The strong present-day Asian monsoons are thought to have originated between 25 and 22 million years (Myr) ago, driven by Tibetan-Himalayan uplift. However, the existence of older Asian monsoons and their response to enhanced greenhouse conditions such as those in the Eocene period (55-34 Myr ago) are unknown because of the paucity of well-dated records. Here we show late Eocene climate records revealing marked monsoon-like patterns in rainfall and wind south and north of the Tibetan-Himalayan orogen. This is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from Myanmar, and by aeolian dust deposition in northwest China. Our climate simulations support modern-like Eocene monsoonal rainfall and show that a reinforced hydrological cycle responding to enhanced greenhouse conditions counterbalanced the negative effect of lower Tibetan relief on precipitation. These strong monsoons later weakened with the global shift to icehouse conditions 34 Myr ago.

  6. Nighttime ionospheric D region: Equatorial and nonequatorial

    NASA Astrophysics Data System (ADS)

    Thomson, Neil R.; McRae, Wayne M.

    2009-08-01

    Nighttime ionospheric D region parameters are found to be generally well modeled by the traditional H‧ and β as used by Wait and by the U.S. Navy in their Earth-ionosphere VLF radio waveguide programs. New comparisons with nonequatorial, mainly all-sea VLF path observations reported over several decades are shown to be consistent with the previously determined height H‧ ˜ 85.0 km and sharpness β ˜ 0.63 km-1. These paths include NPM (Hawaii) to Washington, D. C., Omega Hawaii and NLK (Seattle) to Japan, NWC (N.W. Australia) to Madagascar, and NBA (Panama) to Colorado. In marked contrast, transequatorial path observations (even when nearly all-sea) are found to be often not well modeled: for example, for Omega Japan and JJI (Japan) to Dunedin, New Zealand, the observed amplitudes are markedly lower than those which would be expected from H‧ ˜ 85.0 km and β ˜ 0.63 km-1, or any other realistic values of H‧ and β. Other transequatorial observations compared with modeling include NWC to Japan, Omega Hawaii to Dunedin, and NPM (Hawaii) to Dunedin. It is suggested that the effects of irregularities in the equatorial electrojet may extend down into the nighttime D region and so account for the observed equatorial VLF perturbations through scattering or mode conversion.

  7. Central Equatorial Pacific Experiment (CEPEX). Design document

    SciTech Connect

    Not Available

    1993-04-01

    The Earth`s climate has varied significantly in the past, yet climate records reveal that in the tropics, sea surface temperatures seem to have been remarkably stable, varying by less than a few degrees Celsius over geologic time. Today, the large warm pool of the western Pacific shows similar characteristics. Its surface temperature always exceeds 27{degree}C, but never 31{degree}C. Heightened interest in this observation has been stimulated by questions of global climate change and the exploration of stabilizing climate feedback processes. Efforts to understand the observed weak sensitivity of tropical sea surface temperatures to climate forcing has led to a number of competing ideas about the nature of this apparent thermostat. Although there remains disagreement on the processes that regulate tropical sea surface temperature, most agree that further progress in resolving these differences requires comprehensive field observations of three-dimensional water vapor concentrations, solar and infrared radiative fluxes, surface fluxes of heat and water vapor, and cloud microphysical properties. This document describes the Central Equatorial Pacific Experiment (CEPEX) plan to collect such observations over the central equatorial Pacific Ocean during March of 1993.

  8. Midday reversal of equatorial ionospheric electric field

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1997-10-01

    A comparative study of the geomagnetic and ionospheric data at equatorial and low-latitude stations in India over the 20 year period 1956-1975 is described. The reversal of the electric field in the ionosphere over the magnetic equator during the midday hours indicated by the disappearance of the equatorial sporadic E region echoes on the ionograms is a rare phenomenon occurring on about 1% of time. Most of these events are associated with geomagnetically active periods. By comparing the simultaneous geomagnetic H field at Kodaikanal and at Alibag during the geomagnetic storms it is shown that ring current decreases are observed at both stations. However, an additional westward electric field is superimposed in the ionosphere during the main phase of the storm which can be strong enough to temporarily reverse the normally eastward electric field in the dayside ionosphere. It is suggested that these electric fields associated with the V×Bz electric fields originate at the magnetopause due to the interaction of the solar wind and the interplanetary magnetic field.

  9. LF radio wave propagation at equatorial regions

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Y.; Sawas, Sami; Galopeau, Patrick H. M.; Eichelberger, Hans; Schwingenschuh, Konrad

    2016-04-01

    We analyse night-side electric field observations recorded by the ICE experiment onboard the DEMETER micro-satellite. We show the presence of multiple spaced frequency bands between 30 kHz and 500 kHz, and sometimes in the range 3 MHz - 3.5 MHz, the upper frequency of the instrument. The frequency bandwidth is found to be less than 5 kHz and the time duration about several minutes. The frequency bands are recorded close to the equatorial plane, when the satellite latitudes extend between -05° and +05°. Particular enhancements occur at two geographical longitudes: 130°E and 160°W. Those LF radio waves may be associated to density irregularities in the equatorial region. These irregularities are occurring along the ray path between the emission source region and the satellite. We discuss in this study the locations where such frequency bands are generated, and we show that the observed spectral features may be comparable to the kilometric continuum radiation which is considered as a non-thermal radio emission.

  10. Fading of Jupiter's South Equatorial Belt

    NASA Technical Reports Server (NTRS)

    Sola, Michael A.; Orton, Glenn; Baines, Kevin; Yanamandra-Fisher, Padma

    2011-01-01

    One of Jupiter's most dominant features, the South Equatorial Belt, has historically gone through a "fading" cycle. The usual dark, brownish clouds turn white, and after a period of time, the region returns to its normal color. Understanding this phenomenon, the latest occurring in 2010, will increase our knowledge of planetary atmospheres. Using the near infrared camera, NSFCAM2, at NASA's Infrared Telescope Facility in Hawaii, images were taken of Jupiter accompanied by data describing the circumstances of each observation. These images are then processed and reduced through an IDL program. By scanning the central meridian of the planet, graphs were produced plotting the average values across the central meridian, which are used to find variations in the region of interest. Calculations using Albert4, a FORTRAN program that calculates the upwelling reflected sunlight from a designated cloud model, can be used to determine the effects of a model atmosphere due to various absorption, scattering, and emission processes. Spectra that were produced show ammonia bands in the South Equatorial Belt. So far, we can deduce from this information that an upwelling of ammonia particles caused a cloud layer to cover up the region. Further investigations using Albert4 and other models will help us to constrain better the chemical make up of the cloud and its location in the atmosphere.

  11. Topside sounder observations of equatorial bubbles

    NASA Technical Reports Server (NTRS)

    Dyson, P. L.; Benson, R. F.

    1978-01-01

    Large scale regions of depleted equatorial ionospheric plasma, called equatorial bubbles, are investigated using topside sounder data. The sounder's unique remote measuring capability enables the magnetic field-aligned nature of the bubbles to be investigated. A search of all available Alouette 2 and ISIS 1 ionograms during nighttime perigee passes near the magnetic equator has revealed a variety of echo signatures associated with bubbles. In addition to a sudden drop in electron density, these signatures usually include in situ spread F and ducted traces. The ducted traces have been used to determine the electron density distribution and to infer changes in ion composition along the magnetic field line within the duct associated with the bubble. In some cases it can be determined that the bubble is asymmetric with respect to the magnetic equator. Even though such features require 3 dimensional models for their explanation, the great field-aligned extent of the bubbles (relative to their cross section) suggests that current theories, which ignore variations along the magnetic field, are still applicable.

  12. Gravity Wave Seeding of Equatorial Plasma Bubbles

    NASA Technical Reports Server (NTRS)

    Singh, Sardul; Johnson, F. S.; Power, R. A.

    1997-01-01

    Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 km, in one example it was about 3000 km. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger scale wavelengths. In the multiple bubble patches, intrabubble spacings vaned from 55 km to 140 km. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

  13. New palynology-based astronomical and revised 40Ar/39Ar ages for the Eocene maar lake of Messel (Germany)

    NASA Astrophysics Data System (ADS)

    Lenz, Olaf K.; Wilde, Volker; Mertz, Dieter F.; Riegel, Walter

    2015-04-01

    The annually laminated oil shale from the Eocene maar lake at Messel (Federal State of Hessen, Germany) provides unique paleoenvironmental data for a time interval of ~640 ka during the Paleogene greenhouse phase. As a consequence of orbitally controlled changes in the vegetation in the vicinity of the lake, the lacustrine laminites can now be astronomically tuned. Dating is based on the short eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical La2010a/La2010d solutions in combination with a revised 40Ar/39Ar age of a basalt fragment from a lapilli tuff section below the first lacustrine sediments. Depending on different newly suggested ages for the Fish Canyon sanidine used as monitor for neutron irradiation, the age for the eruption at Messel is between 48.27 ± 0.22 and 48.11 ± 0.22 Ma. This allows for the first time the exact correlation of a Paleogene lacustrine sequence to the marine record in Central Europe. The Messel oil shale becomes now slightly older than previously assumed and includes the Ypresian/Lutetian boundary that moves the base of the European Land Mammal Age Geiseltalian (MP 11) into the Lower Eocene. This opens a window for establishing an independent chronostratigraphic framework for Paleogene terrestrial records and their correlation to the marine realm. Furthermore, the study reveals that higher amounts of pollen from "wet" and thermophilous plants indicate less seasonal and more balanced precipitation and slightly higher temperatures during a well-expressed eccentricity minimum.

  14. Iridium and Spherules in Late Eocene Impact Deposits

    NASA Technical Reports Server (NTRS)

    Kyte, F. T.; Liu, S.

    2002-01-01

    We have been independently examining the Ir (FTK) and spherule (SL) contents of recently discovered late Eocene impact deposits from the south Atlantic and western Indian oceans. These include ODP Sites 1090 [14,15], 709 [lo], and 699 [Liu in prep.]. Iridium abundances at these sites are within the typical range reported for late Eocene deposits, with peak concentrations between 100 and 1000 pg/g. In Table 1 we present estimated net Ir fluences (in ng Ir/cm ) for these and nine other sites. Although there are fewer sites than the K/T boundary, the average of 9 ng Ir/cm2 is probably a good estimate of the late Eocene global flux. This is enough Ir for a 6 km comet (assuming 250 ng/g Ir, p=1.5), is sufficient to produce the Popigai or Chesapeake Bay structures, and is 16% of the flux estimated for the K/T boundary (55 ng/cm2 [ 161). Figure 1 shows the relative abundances of Ir, glassy microtektites and cpx-bearing spherules in sediments from Sites 699 and 1090, which are separated by only 3100 km. Although these two sites have similar Ir anomalies, the abundances of spherules are quite different. Site 1090 has well-defined peaks for both types of spherules, with a peak of 562 cpx spheruledg, while Site 699 contains only a few glassy microtektites and no cpx spherules. While the different abundances of spherules may reflect a heterogeneous distribution of spherules on the Earth s surface, an equally likely cause of this difference may be differential preservation of spherules in the sediment. recovered are only a trace residue of the initial impact deposit. Earlier work found 0.22 ng/g Ir in glassy microtektites from Site 689 [17], an insufficient concentration to support 0.16 ng/g in the bulk sediment at this site. We measured 15 ng/g Ir in a group of 95 cpx spherules from Site 1090 with sizes from 63 to -200 pm, a set typical of the size distribution at this site. Although this is a significant concentration it also cannot support the Ir peak. We presently lack

  15. New Eocene damselflies and first Cenozoic damsel-dragonfly of the isophlebiopteran lineage (Insecta: Odonata).

    PubMed

    Garrouste, Romain; Nel, André

    2015-10-09

    The study of a new specimen of Petrolestes hendersoni from the Eocene Green Formation allows a more precise description of the enigmatic damselfly and the diagnosis of the Petrolestini. Petrolestes messelensis sp. nov. is described from the Eocene Messel Formation in Germany, extending the distribution of the Petrolestini to the European Eocene. The new damsel-dragonfly family Pseudostenolestidae is described for the new genus and species Pseudostenolestes bechlyi, from the Eocene Messel Formation. It is the first Cenozoic representative of the Mesozoic clade Isophlebioptera.

  16. Palaeotectonic implications of increased late Eocene-early Oligocene volcanism from South Pacific DSDP sites

    USGS Publications Warehouse

    Kennett, J.P.; Von Der Borch, C.; Baker, P.A.; Barton, C.E.; Boersma, A.; Cauler, J.P.; Dudley, W.C.; Gardner, J.V.; Jenkins, D.G.; Lohman, W.H.; Martini, E.; Merrill, R.B.; Morin, R.; Nelson, Campbell S.; Robert, C.; Srinivasan, M.S.; Stein, R.; Takeuchi, A.; Murphy, M.G.

    1985-01-01

    Late Eocene-early Oligocene (42-35 Myr) sediments cored at two DSDP sites in the south-west Pacific contain evidence of a pronounced increase in local volcanic activity, particularly in close association with the Eocene-Oligocene boundary. This pulse of volcanism is coeval with that in New Zealand and resulted from the development of an Indo- Australian / Pacific Plate boundary through the region during the late Eocene. The late Eocene / earliest Oligocene was marked by widespread volcanism and tectonism throughout the Pacific and elsewhere, and by one of the most important episodes of Cenozoic climatic cooling. ?? 1985 Nature Publishing Group.

  17. Discovery of an embrithopod mammal (Arsinoitherium?) in the late Eocene of Tunisia

    NASA Astrophysics Data System (ADS)

    Vialle, Nicolas; Merzeraud, Gilles; Delmer, Cyrille; Feist, Monique; Jiquel, Suzanne; Marivaux, Laurent; Ramdarshan, Anusha; Vianey-Liaud, Monique; Essid, El Mabrouk; Marzougui, Wissem; Ammar, Hayet Khayati; Tabuce, Rodolphe

    2013-11-01

    Dental and postcranial remains (an atlas, carpus and metacarpus elements, and a part of the pelvic girdle) of an embrithopod mammal are described from Bir Om Ali, Tunisia, a new late Eocene locality. The enamel microstructure of a tooth fragment found in association shows 'arsinoitheriid radial enamel', an enamel condition which is characteristic of Arsinoitherium (Arsinoitheriidae, Embrithopoda). Although the postcranial elements slightly differ in size and morphology from those of Arsinoitherium zitteli (late Eocene to early Oligocene), we tentatively refer this new Eocene Tunisian material to that genus. These fossils represent the first known embrithopod from the Eocene of Tunisia.

  18. Eocene to Miocene biostratigraphy of New Jersey core ACGS #4; implications for regional stratigraphy

    USGS Publications Warehouse

    Poore, Richard Z.; Bybell, Laurel M.

    1988-01-01

    A time versus depth plot controlled primarily by nannofossil zone boundaries shows that sediment accumulation rates during the early and middle Eocene were in the range of 6 to 15 feet per million years. During the late Eocene, accumulation rates were much higher, perhaps exceeding 70 feet per million years. The only clear hiatus detected in the Paleogene part of ACGS #4 on the basis of microfossils is between the early and (?)late Oligocene. However, hiatuses are suspected at the early-middle Eocene boundary and within the late Eocene. Occurrences of calcareous nannofossils and planktic foraminifers are documented, and a number of key taxa are illustrated.

  19. TECHNOLOGICAL OPTIONS FOR ACID RAIN CONTROL

    EPA Science Inventory

    Discussed are acid rain control options available to the electric utility industry. They include coal switching, flue gas desulfurization, and such emerging lower cost technologies as Limestone Injection Multistage Burners (LIMB) and Advanced Silicate (ADVACATE), both developed ...

  20. Soak Up the Rain Customizable Outreach Tools

    EPA Pesticide Factsheets

    Get customizable Soak Up the Rain business card, posters, & a banner that can be downloaded & copied for use by citizens, municipalities, watershed & planning organizations & others in their stormwater/green infrastructure education & outreach efforts.

  1. NASA's DC-8 With Rain Mapping Radar

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In a joint venture between NASA and Japan's NASDA, scientists have been using satellites, airplanes, and boats to measure rain physics in and under thunderstorms over open water. This Quick Time movie shows NASA's DC-8 jet with the instruments like the airborne rain mapping radar, i.e., the Advanced Microwave Precipitation Radiometer (AMPR) and a lightening imaging sensor. Earth science and weather studies are an important ongoing function of NASA and its affiliates.

  2. Raine syndrome: expanding the radiological spectrum.

    PubMed

    Koob, Mériam; Doray, Bérénice; Fradin, Mélanie; Astruc, Dominique; Dietemann, Jean-Louis

    2011-03-01

    We describe ante- and postnatal imaging of a 1-year-old otherwise healthy girl with Raine syndrome. She presented with neonatal respiratory distress related to a pyriform aperture stenosis, which was diagnosed on CT. Signs of chondrodysplasia punctata, sagittal vertebral clefting and intervertebral disc and renal calcifications were also found on imaging. This new case confirms that Raine syndrome is not always lethal. The overlapping imaging signs with chondrodysplasia punctata and the disseminated calcifications give new insights into its pathophysiology.

  3. Theoretical Analysis of Rain Attenuation Probability

    NASA Astrophysics Data System (ADS)

    Roy, Surendra Kr.; Jha, Santosh Kr.; Jha, Lallan

    2007-07-01

    Satellite communication technologies are now highly developed and high quality, distance-independent services have expanded over a very wide area. As for the system design of the Hokkaido integrated telecommunications(HIT) network, it must first overcome outages of satellite links due to rain attenuation in ka frequency bands. In this paper theoretical analysis of rain attenuation probability on a slant path has been made. The formula proposed is based Weibull distribution and incorporates recent ITU-R recommendations concerning the necessary rain rates and rain heights inputs. The error behaviour of the model was tested with the loading rain attenuation prediction model recommended by ITU-R for large number of experiments at different probability levels. The novel slant path rain attenuastion prediction model compared to the ITU-R one exhibits a similar behaviour at low time percentages and a better root-mean-square error performance for probability levels above 0.02%. The set of presented models exhibits the advantage of implementation with little complexity and is considered useful for educational and back of the envelope computations.

  4. Effects of acid rain on grapevines

    SciTech Connect

    Forsline, P.L.; Musselman, R.C.; Dee, R.J.; Kender, W.J.

    1983-01-01

    Mature vineyard-growing Concord grapevines were sprayed with simulated acid rain solutions ranging from pH 2.5 to 5.5 both as acute treatments at anthesis and chronically throughout the season in 1980 and 1981. In 1981, 8 additional varieties were also treated with simulated acid rain solutions at pH 2.75 and 3.25. With Concord in 1981, few foliar lesions on leaves were visible at pH 2.75. In contrast, many leaf lesions with decreased fruit soluble solids were observed at pH 2.5 in 1980. The relationship between acid-rain and oxidant stipple, chlorosis, and soluble solids in the absence of acid rain leaf lesions at pH>2.5 remains unclear. Acute sprays (pH2.75) at anthesis reduced pollen germination in four grape cultivars. However, fruit set was reduced in only one of these. Grape yields were not influenced by acid rain treatments. There was no evidence that acid-rain at ambient pH levels had negative effects on grape production or fruit quality.

  5. Effects of acid rain on grapevines

    SciTech Connect

    Forsline, P.L.; Musselman, R.C.; Dee, R.J.; Kender, W.J.

    1983-01-01

    Mature vineyard-growing Concord grapevines (Vitis labrusca, Bailey) were sprayed with simulated acid rain solutions ranging from pH 2.5 to pH 5.5 both as acute treatments at anthesis and chronically throughout the season in 1980 and 1981. In 1981, eight additional varieties were also treated with simulated acid rain solutions at pH 2.75 and pH 3.25. With Concord in 1981, few foliar lesions on leaves were visible at pH 2.75. In contrast, many leaf lesions with decreased fruit soluble solids in the absence of acid rain leaf lesions at pH>2.5 remains unclear. Acute sprays (pH 2.75) at anthesis reduced pollen germination in four grape cultivars. However, fruit set was reduced in only one of these. Only the cultivars de Chaunac and Ives had reduced berry soluble solids with chronic weekly sprays at pH 2.75. Reduction in soluble solids was not associated with increased oxidant stipple (ozone injury) in Concord and de Chaunac cultivars, but this association was observed in Ives. There was no evidence that acid rain in combination with ozone increased oxidant stipple as occurs when ozone and SO/sub 2/ are combined. Grape yields were not influenced by acid rain treatments. There was no evidence that acid rain at ambient pH levels had negative effects on grape production or fruit quality.

  6. Presenting the Rain-Sea Interaction Facility

    NASA Technical Reports Server (NTRS)

    Bliven, Larry F.; Elfouhaily, Tonas M.

    1993-01-01

    The new Rain-Sea Interaction Facility (RSIF) was established at GSFC/WFF and the first finds are presented. The unique feature of this laboratory is the ability to systematically study microwave scattering from a water surface roughened by artificial rain, for which the droplets are at terminal velocity. The fundamental instruments and systems (e.g., the rain simulator, scatterometers, and surface elevation probes) were installed and evaluated during these first experiments - so the majority of the data were obtained with the rain simulator at 1 m above the water tank. From these initial experiments, three new models were proposed: the square-root function for NCS vs. R, the log Gaussian model for ring-wave elevation frequency spectrum, and the Erland probability density distribution for back scattered power. Rain rate is the main input for these models, although the coefficients may be dependent upon other factors (drop-size distribution, fall velocity, radar configuration, etc.). The facility is functional and we foresee collaborative studies with investigators who are engaged in measuring and modeling rain-sea interaction processes.

  7. Electromagnetic and Stress Analyses of the ITER Equatorial Thermal Shield

    NASA Astrophysics Data System (ADS)

    Lei, Mingzhun; Song, Yuntao; Wang, Songke; Wang, Xianwei

    2013-08-01

    The ITER equatorial thermal shield is located inside the cryostat and outside the vacuum vessel, and its purpose is to provide a thermal shield from hot components to the superconducting magnets. Electromagnetic analysis of the equatorial thermal shield was performed using the ANSYS code, because electromagnetic load was one of the main loads. The 40° sector finite element model was established including the vacuum vessel, equatorial thermal shield, and superconducting magnets. The main purpose of this analysis was to investigate the eddy current and electromagnetic force in the equatorial thermal shield during plasma disruption. Stress analysis was implemented under the electromagnetic load. The results show that the equatorial thermal shield can accommodate the calculated electromagnetic loads.

  8. Extreme warmth and heat-stressed plankton in the tropics during the Paleocene-Eocene Thermal Maximum

    PubMed Central

    Frieling, Joost; Gebhardt, Holger; Huber, Matthew; Adekeye, Olabisi A.; Akande, Samuel O.; Reichart, Gert-Jan; Middelburg, Jack J.; Schouten, Stefan; Sluijs, Appy

    2017-01-01

    Global ocean temperatures rapidly warmed by ~5°C during the Paleocene-Eocene Thermal Maximum (PETM; ~56 million years ago). Extratropical sea surface temperatures (SSTs) met or exceeded modern subtropical values. With these warm extratropical temperatures, climate models predict tropical SSTs >35°C—near upper physiological temperature limits for many organisms. However, few data are available to test these projected extreme tropical temperatures or their potential lethality. We identify the PETM in a shallow marine sedimentary section deposited in Nigeria. On the basis of planktonic foraminiferal Mg/Ca and oxygen isotope ratios and the molecular proxy TEX86H, latest Paleocene equatorial SSTs were ~33°C, and TEX86H indicates that SSTs rose to >36°C during the PETM. This confirms model predictions on the magnitude of polar amplification and refutes the tropical thermostat theory. We attribute a massive drop in dinoflagellate abundance and diversity at peak warmth to thermal stress, showing that the base of tropical food webs is vulnerable to rapid warming. PMID:28275727

  9. Extreme warmth and heat-stressed plankton in the tropics during the Paleocene-Eocene Thermal Maximum.

    PubMed

    Frieling, Joost; Gebhardt, Holger; Huber, Matthew; Adekeye, Olabisi A; Akande, Samuel O; Reichart, Gert-Jan; Middelburg, Jack J; Schouten, Stefan; Sluijs, Appy

    2017-03-01

    Global ocean temperatures rapidly warmed by ~5°C during the Paleocene-Eocene Thermal Maximum (PETM; ~56 million years ago). Extratropical sea surface temperatures (SSTs) met or exceeded modern subtropical values. With these warm extratropical temperatures, climate models predict tropical SSTs >35°C-near upper physiological temperature limits for many organisms. However, few data are available to test these projected extreme tropical temperatures or their potential lethality. We identify the PETM in a shallow marine sedimentary section deposited in Nigeria. On the basis of planktonic foraminiferal Mg/Ca and oxygen isotope ratios and the molecular proxy [Formula: see text], latest Paleocene equatorial SSTs were ~33°C, and [Formula: see text] indicates that SSTs rose to >36°C during the PETM. This confirms model predictions on the magnitude of polar amplification and refutes the tropical thermostat theory. We attribute a massive drop in dinoflagellate abundance and diversity at peak warmth to thermal stress, showing that the base of tropical food webs is vulnerable to rapid warming.

  10. Formation of Jets and Equatorial Superrotation on Jupiter

    NASA Astrophysics Data System (ADS)

    Liu, Junjun; Schneider, T.

    2008-09-01

    The zonal flow in Jupiter's upper troposphere is organized into alternating retrograde and prograde jets, with a prograde (superrotating) jet at the equator. Existing models posit as the driver of the flow either differential radiative heating of the atmosphere or intrinsic heat fluxes emanating from the deep interior; however, they do not reproduce all large-scale features of Jupiter's jets and thermal structure. Here it is shown that the difficulties in accounting for Jupiter's jets and thermal structure resolve if the effects of differential radiative heating and intrinsic heat fluxes are considered together and if upper-tropospheric dynamics are linked to a magnetohydrodynamic drag deep in the atmosphere. Baroclinic eddies generated by differential radiative heating can account for the off-equatorial jets; meridionally propagating equatorial Rossby waves generated by intrinsic convective heat fluxes can account for the equatorial superrotation. The zonal flow extends deeply into the atmosphere, with its speed changing with depth, up to depths at which the magnetohydrodynamic drag acts. The theory is supported by simulations with an energetically consistent general circulation model of Jupiter's outer atmosphere. A simulation that incorporates differential radiative heating and intrinsic heat fluxes reproduces Jupiter's observed jets and thermal structure. A control simulation that incorporates only differential radiative heating but no intrinsic heat fluxes produces off-equatorial jets but no equatorial superrotation; another control simulation that incorporates only intrinsic heat fluxes but no differential radiative heating produces equatorial superrotation but no off-equatorial jets. The proposed mechanisms act in the atmospheres of all giant planets. Saturn's prograde equatorial jet is wider and stronger than Jupiter's due to its larger tropospheric gravity wave speed and consequently greater equatorial Rossby radius. Uranus and Neptune do not exhibit

  11. The Eastern Equatorial Pacific Chlorophyll Dynamics: Update of the `Equatorial Box' Project

    NASA Astrophysics Data System (ADS)

    Westberry, T.; Wang, X.; Murtugudde, R.; Behrenfeld, M.; Roesler, C.

    2006-12-01

    The `Equatorial Box' Project utilizes the mooring observations along the 125 and 140 TAO lines to provide carbon component data, including chlorophyll, primary production, POC and DOC. These parameters together with other oceanographic properties can be used to validate ocean circulation-ecosystem models. In turn, a validated model can offer considerable promise for not only filling the gaps in the spatial and temporal coverage from the available observations, but also enhancing our understanding of the mechanisms underlying the variability. Here, we present both measured and simulated vertical-meridional chlorophyll distributions and primary production along 125W and 140W. While there is a permanent layer of deep chlorophyll maximum at 30-60 m, there is no deep maximum in phytoplankton carbon biomass or primary production. Our analyses focus on impact of nutrient stress and light conditions on chlorophyll dynamics in the eastern equatorial Pacific. We also compare modeled primary productivity with ocean color derived rates.

  12. Particle entry into the equatorial magnetosphere.

    NASA Technical Reports Server (NTRS)

    Fritz, T. A.; Barfield, J. N.; Smith, P. H.; Hoffman, R. A.; Konradi, A.

    1973-01-01

    Explorer-45 data are reviewed which concern the behavior and dynamics of protons associated with the storm-time and quiet-time extraterrestrial ring current at the equatorial plane. The quiet-time proton energy spectrum exhibits a peak in the interval between 100 and 200 keV. During storm conditions, the intensities of the higher energy protons decrease while the intensities of protons from 10 to 100 keV are greatly enhanced, making them the dominant contributor to the storm-time particle energy density. It is shown that during magnetic storms, the ratio of the particle energy density to the magnetic field energy density reaches values greater than unity, and that the plasmasphere has a strong influence on the characteristics of particle injection.

  13. Electric field observations of equatorial bubbles

    NASA Astrophysics Data System (ADS)

    Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

    1992-03-01

    Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

  14. Electric field observations of equatorial bubbles

    NASA Technical Reports Server (NTRS)

    Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

    1992-01-01

    Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

  15. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the west, from between the cloud layers and over the patchy white clouds to the east of the hotspot. This is probably an area where moist convection is occurring over large horizontal distances, similar to the atmosphere over the equatorial ocean on Earth. The clouds are high and thick, and are observed to change rapidly over short time scales.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756

  16. Ozone variability in the equatorial middle atmosphere

    SciTech Connect

    Sun, Chirong; Leovy, C. )

    1990-08-20

    Ozone variability in the equatorial middle atmosphere is investigated and related to temperature and zonal wind variations using data from the Nimbus 7 and Solar Mesosphere Explorer (SME) satellite. The dominant component of the seasonal variability at most levels from the middle stratosphere to the lower thermosphere is the semiannual oscillation (SAO) which has maxima near 10, 3, 0.07, 0.01 mbar, and near or above 0.0024 mbar. There is evidence that the 10-mbar peak is due to vertical advection of odd nitrogen (NO{sub y}) by the semiannually varying residual mean circulation, while temperature dependence of chemical reactions coupled with the thermal SAO near the stratopause and in the upper mesosphere is responsible for the peaks near 3 and 0.07 mbar. The seasonal dependence suggests a contribution from gravity wave modulated vertical mixing of water vapor near the 0.01 mbar level, and the authors speculate that semiannually modulated mixing of atomic oxygen by the (1,1) mode of the thermal tide contributes to the SAO ozone peak above 0.0024 mbar. The negative correlation between temperature and ozone is so strong in the 7- to 0.5-mbar layer that ozone is a useful proxy for temperature variability on time scales from a few days to many months. A preliminary look at annual and interannual variations shows that differing patterns of winter high latitude Rossby wave variability in the two hemispheres are reflected in the signatures of equatorial ozone and temperature in the same layer.

  17. Variation of slant path Ka/V-band rain attenuation over seven tropical locations in Nigeria using synthetic storm techniques

    NASA Astrophysics Data System (ADS)

    Ojo, J. S.; Adediji, A. T.; Mandeep, J. S.; Ismail, M.

    2016-04-01

    In this paper, rain characteristics and slant path rain attenuation at 30 and 40 GHz using synthetic storm techniques over seven tropical locations in Nigeria have been presented. The technique can be used to predict the local first-order statistical rain attenuation to mitigate the severe fade experienced at higher frequency bands by employing local rainfall rate statistics. Three years rain rate data at seven tropical and equatorial locations in Nigeria were utilized for the purpose of this work. The predicted statistics are in good agreement with those obtained from the propagation beacon measurement (EUTELSAT W4/W7 satellite-12.245 GHz) It could be observed that at 99.99 % link availability over these locations, the fade margin of higher dB (74 and 81 dB) are required at 30 and 40 GHz frequency bands, respectively. When diurnal variation was observed for four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00, and 18:00-24:00, there is a variation of the fade margin over the hours of the day. The overall results will be needed for an acceptable planning that can effectively reduce the fade margin to a very low value for an optimum data communication over the studied locations.

  18. Profundal sideritic mudstone from an Eocene lake in Alaska

    SciTech Connect

    Dickinson, K.A.

    1987-08-01

    Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual iron-meromictic Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Upper Cretaceous Darby pluton and on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the valley of the ancestral Tubutulik River in early Eocene time. The lake sediments included a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital grains, mostly quartz and clay minerals. Both lacustrine facies contain turbidites. The lacustrine rocks graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake occupied a small, deep basin in a tectonically active area of high relief. Meromixis was apparently stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixis decreased as the lake became shallower from sediment filling. The source of the dissolved iron in the monoimolimnion was probably the Eocene basalt. Carbon isotope analysis of the siderite suggests that the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature (delta/sup 13/C = +16.9) consistent with residual carbonate formed during methanogenic fermentation.

  19. Mass-movement deposits in the lacustrine Eocene Green River Formation, Piceance Basin, western Colorado

    USGS Publications Warehouse

    Johnson, Ronald C.; Birdwell, Justin E.; Brownfield, Michael E.; Mercier, Tracey J.

    2015-01-01

    The Eocene Green River Formation was deposited in two large Eocene saline lakes, Lake Uinta in the Uinta and Piceance Basins and Lake Gosiute in the Greater Green River Basin. Here we will discuss mass-movement deposits in just the Piceance Basin part of Lake Uinta.

  20. The oldest accurate record of Scenopinidae in the Lowermost Eocene amber of France (Diptera: Brachycera).

    PubMed

    Garrouste, Romain; Azar, Dany; Nel, Andre

    2016-03-22

    Eocenotrichia magnifica gen. et sp. nov. (Diptera: Scenopinidae: Metatrichini) is described and illustrated from the Lowermost Eocene amber of Oise (France) and represents the oldest definitive window fly fossil. The present discovery in the Earliest Eocene supports the Late Cretaceous-Paleocene age currently proposed for the emergence of Metatrichini.

  1. Exploring Terrestrial Temperature Changes during the Early Eocene Hyperthermals

    NASA Astrophysics Data System (ADS)

    Snell, K. E.; Clyde, W. C.; Fricke, H. C.; Eiler, J. M.

    2012-12-01

    The Early Eocene is marked by a number of rapid global warming events called hyperthermals. These hyperthermals are associated with negative carbon isotope excursions (CIE) in both marine and terrestrial records. Multiple theories exist to explain the connection of these hyperthermals with the CIEs and each theory predicts different responses by the climate system. Characterizing the timing, duration and magnitude of temperature change that is associated with these hyperthermals is important for determining whether the hyperthermals are all driven by the same underlying climate dynamics or perhaps differ from one another in cause and climatic consequences. In the simplest case, all share a common underlying mechanism; this predicts that the associated temperature changes scale in a predictable way with the magnitude of the CIE (and perhaps exhibit other similarities, such as the relative amplitudes of marine and terrestrial temperature change). To our knowledge, however, the only hyperthermal with paleotemperature data from land is the Paleocene-Eocene Thermal Maximum (PETM). Here we present preliminary carbonate clumped isotope paleotemperature estimates for Early Eocene hyperthermal ETM2/H2 from paleosol carbonates from the Bighorn Basin in Wyoming, USA. We compare the results to existing clumped isotope paleotemperature estimates for the PETM in the Bighorn Basin. Temperatures recorded by paleosol carbonates (which likely reflect near-peak summer ground temperatures) prior to each CIE are ~30°C and increase to ~40-43°C during the apex of each CIE. Following both CIEs, temperatures drop back to pre-CIE values. In the case of ETM2/H2, temperatures begin to rise again immediately, possibly in association with a later hyperthermal, though further work needs to be done to establish this with certainty. These preliminary data suggest that both the absolute values and the magnitudes of temperature changes associated with the PETM and ETM2/H2 are similar; the

  2. Comet or asteroid shower in the late Eocene?

    PubMed

    Tagle, Roald; Claeys, Philippe

    2004-07-23

    The passage of a comet shower approximately 35 million years ago is generally advocated to explain the coincidence during Earth's late Eocene of an unusually high flux of interplanetary dust particles and the formation of the two largest craters in the Cenozoic, Popigai and the Chesapeake Bay. However, new platinum-group element analyses indicate that Popigai was formed by the impact of an L-chondrite meteorite. Such an asteroidal projectile is difficult to reconcile with a cometary origin. Perhaps instead the higher delivery rate of extraterrestrial matter, dust, and large objects was caused by a major collision in the asteroid belt.

  3. Acid rain and its ecological consequences.

    PubMed

    Singh, Anita; Agrawal, Madhoolika

    2008-01-01

    Acidification of rain-water is identified as one of the most serious environmental problems of transboundary nature. Acid rain is mainly a mixture of sulphuric and nitric acids depending upon the relative quantities of oxides of sulphur and nitrogen emissions. Due to the interaction of these acids with other constituents of the atmosphere, protons are released causing increase in the soil acidity Lowering of soil pH mobilizes and leaches away nutrient cations and increases availability of toxic heavy metals. Such changes in the soil chemical characteristics reduce the soil fertility which ultimately causes the negative impact on growth and productivity of forest trees and crop plants. Acidification of water bodies causes large scale negative impact on aquatic organisms including fishes. Acidification has some indirect effects on human health also. Acid rain affects each and every components of ecosystem. Acid rain also damages man-made materials and structures. By reducing the emission of the precursors of acid rain and to some extent by liming, the problem of acidification of terrestrial and aquatic ecosystem has been reduced during last two decades.

  4. Implications for Coronal Heating from Coronal Rain

    NASA Astrophysics Data System (ADS)

    Antolin, P.; Shibata, K.; Carlsson, M.; van der Voort, L. R.; Vissers, G.; Hansteen, V.

    2012-08-01

    Coronal rain is a phenomenon above active regions in which cool plasma condensations fall down from coronal heights. Numerical simulations of loops have shown that such condensations can naturally form in the case of footpoint concentrated heating through the “catastrophic cooling” mechanism. In this work we analize high resolution limb observations in Ca II H and Hα of coronal rain performed by Hinode/SOT and by Crisp of SST and derive statistical properties. We further investigate the link between coronal rain and the coronal heating mechanisms by performing 1.5-D MHD simulations of a loop subject to footpoint heating and to Alfvén waves generated in the photosphere. It is found that if a loop is heated predominantly from Alfvén waves coronal rain is inhibited due to the characteristic uniform heating they produce. Hence coronal rain can point both to the spatial distribution of the heating and to the agent of the heating itself, thus acting as a marker for coronal heating mechanisms.

  5. MULTIDIMENSIONAL MODELING OF CORONAL RAIN DYNAMICS

    SciTech Connect

    Fang, X.; Xia, C.; Keppens, R.

    2013-07-10

    We present the first multidimensional, magnetohydrodynamic simulations that capture the initial formation and long-term sustainment of the enigmatic coronal rain phenomenon. We demonstrate how thermal instability can induce a spectacular display of in situ forming blob-like condensations which then start their intimate ballet on top of initially linear force-free arcades. Our magnetic arcades host a chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes of physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into V-shaped features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views of blobs that evaporate in situ or are siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys of coronal rain showers in true multidimensional settings to connect parameterized heating prescriptions with rain statistics, ultimately allowing us to quantify the coronal heating input.

  6. Multidimensional Modeling of Coronal Rain Dynamics

    NASA Astrophysics Data System (ADS)

    Fang, X.; Xia, C.; Keppens, R.

    2013-07-01

    We present the first multidimensional, magnetohydrodynamic simulations that capture the initial formation and long-term sustainment of the enigmatic coronal rain phenomenon. We demonstrate how thermal instability can induce a spectacular display of in situ forming blob-like condensations which then start their intimate ballet on top of initially linear force-free arcades. Our magnetic arcades host a chromospheric, transition region, and coronal plasma. Following coronal rain dynamics for over 80 minutes of physical time, we collect enough statistics to quantify blob widths, lengths, velocity distributions, and other characteristics which directly match modern observational knowledge. Our virtual coronal rain displays the deformation of blobs into V-shaped features, interactions of blobs due to mostly pressure-mediated levitations, and gives the first views of blobs that evaporate in situ or are siphoned over the apex of the background arcade. Our simulations pave the way for systematic surveys of coronal rain showers in true multidimensional settings to connect parameterized heating prescriptions with rain statistics, ultimately allowing us to quantify the coronal heating input.

  7. Rain-induced spring wheat harvest losses

    NASA Technical Reports Server (NTRS)

    Bauer, A.; Black, A. L. (Principal Investigator)

    1983-01-01

    When rain or a combination of rain and high humidity delay wheat harvest, losses can occur in grain yield and/or grain quality. Yield losses can result from shattering, from reduction in test weight, and in the case of windrowed grain, from rooting of sprouting grain at the soil: windrow contact. Losses in grain quality can result from reduction in test weight and from sprouting. Sprouting causes a degradation of grain proteins and starches, hence flour quality is reduced, and the grain price deteriorates to the value of feed grain. Although losses in grain yield and quality are rain-induced, these losses do not necessarily occur because a standing or windrowed crop is wetted by rain. Spike water concentration in hard red spring wheat must be increased to about 45-49% before sprouting is initiated in grain that has overcome dormancy. The time required to overcome this dormancy after the cultivar has dried to 12 to 14% water concentration differs with hard red spring cultivars. The effect of rain on threshing-ready standing and windrowed hard red spring wheat grain yeild and quality was evaluated. A goal was to develop the capability to forecast the extent of expected loss of grain yield and quality from specific climatic events that delay threshing.

  8. Lidar Observation of Tropopause Ozone Profiles in the Equatorial Region

    NASA Astrophysics Data System (ADS)

    Shibata, Yasukuni; Nagasawa, Chikao; Abo, Makoto

    2016-06-01

    Tropospheric ozone in the tropics zone is significant in terms of the oxidizing efficiency and greenhouse effect. However, in the upper troposphere, the ozone budget in the tropics has not been fully understood yet because of the sparsity of the range-resolved observations of vertical ozone concentration profiles. A DIAL (differential absorption lidar) system for vertical ozone profiles have been installed in the equatorial tropopause region over Kototabang, Indonesia (100.3E, 0.2S). We have observed large ozone enhancement in the upper troposphere, altitude of 13 - 17 km, concurring with a zonal wind oscillation associated with the equatorial Kelvin wave around the tropopause at equatorial region.

  9. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the southeast, from between the cloud layers and over the north center of the region. The tall white clouds in the lower cloud deck are probably much like large terrestrial thunderclouds. They may be regions where atmospheric water powers vertical convection over large horizontal distances.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on

  10. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The upper haze layer has some features that match the lower cloud, such as the bright streak in the foreground of the frame. These are probably thick clouds that span several tens of vertical kilometers.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly

  11. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from the southwest looking northeast, from an altitude just above the high haze layer. The streaks in the lower cloud leading towards the hotspot are visible. The upper haze layer is mostly flat, with notable small peaks that can be matched with features in the lower cloud. In reality, these areas may represent a continuous vertical cloud column.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756

  12. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view to the northeast, from between the cloud layers and above the streaks in the lower cloud leading towards the hotspot. The hotspot is clearly visible as a deep blue feature. The cloud streaks end near the hotspot, consistent with the idea that clouds traveling along these streak lines descend and evaporate as they approach the hotspot. The upper haze layer is slightly bowed upwards above the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional

  13. Three dimensional Visualization of Jupiter's Equatorial Region

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Frames from a three dimensional visualization of Jupiter's equatorial region. The images used cover an area of 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles) near an equatorial 'hotspot' similar to the site where the probe from NASA's Galileo spacecraft entered Jupiter's atmosphere on December 7th, 1995. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. The bright clouds to the right of the hotspot as well as the other bright features may be examples of upwelling of moist air and condensation.

    This frame is a view from above and to the south of the visualized area, showing the entire model. The entire region is overlain by a thin, transparent haze. In places the haze is high and thick, especially to the east (to the right of) the hotspot.

    Galileo is the first spacecraft to image Jupiter in near-infrared light (which is invisible to the human eye) using three filters at 727, 756, and 889 nanometers (nm). Because light at these three wavelengths is absorbed at different altitudes by atmospheric methane, a comparison of the resulting images reveals information about the heights of clouds in Jupiter's atmosphere. This information can be visualized by rendering cloud surfaces with the appropriate height variations.

    The visualization reduces Jupiter's true cloud structure to two layers. The height of a high haze layer is assumed to be proportional to the reflectivity of Jupiter at 889 nm. The height of a lower tropospheric cloud is assumed to be proportional to the reflectivity at 727 nm divided by that at 756 nm. This model is overly simplistic, but is based on more sophisticated studies of Jupiter's cloud structure. The upper

  14. Provenance of the Eocene Soebi Blanco formation, Bonaire, Leeward Antilles: Correlations with post-Eocene tectonic evolution of northern South America

    NASA Astrophysics Data System (ADS)

    Zapata, S.; Cardona, A.; Montes, C.; Valencia, V.; Vervoort, J.; Reiners, P.

    2014-07-01

    Middle to upper Eocene fluvial strata in the island of Bonaire contain detrital components that were tracked to Precambrian to Triassic massifs in northern Colombia and Venezuela. These detrital components confirm previous hypothesis suggesting that Bonaire and the Leeward Antilles were attached to South American basement massifs (SABM). These are composed of different fragmented South American blocks (Paraguana, Falcon, Maracaibo, Guajira, Perija, and Santa Marta) representing an Eocene, right-laterally displaced tectonic piercing point along the southern Caribbean plate margin. U-Pb LA-ICP-MS from the metamorphic boulders of the Soebi Blanco Formation in Bonaire yield Grenvillian peaks ages (1000-1200 Ma), while detrital zircons recovered from the sandy matrix of the conglomerates contain populations with peaks of 1000 Ma-1200 Ma, 750-950 Ma, and 200-300 Ma. These populations match with geochronological data reported for the northern South American massifs. Thermochronological results from the metamorphic clasts yield Paleocene-middle Eocene ages (65-50 Ma) that confirm a regional-scale cooling event in this time. These data imply a land connection between the SABM and the Leeward Antilles in late Eocene times, followed by a significant strike slip right-lateral displacement and transtensional basin opening starting in latest Eocene times. The succession of Eocene tectonic events recorded by the Soebi Blanco Formation and adjacent basins is a major tracer of the oblique convergence of the Caribbean plate against the South American margin.

  15. Equatorial cloud level convection on Venus

    NASA Astrophysics Data System (ADS)

    Lee, Yeon Joo; Imamura, Takeshi; Sugiyama, Koichiro; Sato, Takao M.; Maejima, Yasumitsu

    2016-10-01

    In the equatorial region on Venus, a clear cloud top morphology difference depending on solar local time has been observed through UV images. Laminar flow shaped clouds are shown on the morning side, and convective-like cells on the afternoon side (Titov et al. 2012). Baker et al. (1998) suggested that deep convective motions in the low-to-middle cloud layers at the 40-60 km range can explain cellular shapes. Imamura et al. (2014), however argued that this cannot be a reason, as convection in the low-to-middle cloud layers can be suppressed near sub solar regions due to a stabilizing effect by strong solar heating. We suggest that the observed feature may be related to strong solar heating at local noon time (Lee et al. 2015). Horizontal uneven distribution of an unknown UV absorber and/or cloud top structure may trigger horizontal convection (Toigo et al. 1994). In order to examine these possibilities, we processed 1-D radiative transfer model calculations from surface to 100 km altitude (SHDOM, Evans 1998), which includes clouds at 48-71 km altitudes (Crisp et al. 1986). The results on the equatorial thermal cooling and solar heating profiles were employed in a 2D fluid dynamic model calculation (CReSS, Tsuboki and Sakakibara 2007). The calculation covered an altitude range of 40-80 km and a 100-km horizontal distance. We compared three conditions; an 'effective' global circulation condition that cancels out unbalanced net radiative energy at equator, a condition without such global circulation effect, and the last condition assumed horizontally inhomogeneous unknown UV absorber distribution. Our results show that the local time dependence of lower level cloud convection is consistent with Imamura et al.'s result, and suggest a possible cloud top level convection caused by locally unbalanced net energy and/or horizontally uneven solar heating. This may be related to the observed cloud morphology in UV images. The effective global circulation condition, however

  16. A novel rain removal technology based on video image

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Piao, Yan

    2016-11-01

    Due to the effect of bad weather conditions, it often conducts visual distortions on images for outdoor vision systems. Rain is one specific example of bad weather. Generally, rain streak is small and falls at high velocity. Traditional rain removal methods often cause blued visual effect. In addition, there is high time complexity. Moreover, some rain streaks are still in the de-rained image. Based on the characteristics of rain streak, a novel rain removal technology is proposed. The proposed method is not only removing the rain streak effectively, but also retaining much detail information. The experiments show that the proposed method outperform traditional rain removal methods. It can be widely used in intelligent traffic, civilian surveillance and national security so on.

  17. Canada issues booklet describing acid rain

    NASA Astrophysics Data System (ADS)

    A booklet recently released by Environment Canada describes acid rain in terms easily understood by the general public. Although Acid Rain — The Facts tends somewhat to give the Canadian side of this intercountry controversial subject, it nevertheless presents some very interesting, simple statistics of interest to people in either the U.S. or Canada. Copies of the booklet can be obtained from Inquiry Environment Canada, Ottawa, Ontario K1A OH3, Canada, tel. 613-997-2800.The booklet points out that acid rain is caused by emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx). Once released into the atmosphere, these substances can be carried long distances by prevailing winds and return to Earth as acidic rain, snow, fog, or dust. The main sources of SO2 emissions in North America are coal-fired power generating stations and nonferrous ore smelters. The main sources of NOx emissions are vehicles and fuel combustion. From economical and environmental viewpoints, Canada believes acid rain is one of the most serious problems presently facing the country: increasing the acidity of more than 20% of Canada's 300,000 lakes to the point that aquatic life is depleted and acidity of soil water and shallow groundwater is increasing, causing decline in forest growth and water fowl populations, and eating away at buildings and monuments. Acid rain is endangering fisheries, tourism, agriculture, and forest resources in an area of 2.6 million km2 (one million square miles) of eastern Canada, about 8% of Canada's gross national product.

  18. Scanning rain gauge based on photo electricity

    NASA Astrophysics Data System (ADS)

    Huang, Fei-long; Li, Yuan-hong

    2008-03-01

    A non-contact rain gauge with photo electricity technology is introduced in this paper. Dimensional distribution of rain inside a traditional rain gauge does not need to be changed, and the rainwater falls freely to the ground, so this new rain gauge doesn't need to be cleared as a traditional rain gauge does frequently. And then a capacitor is used as a switch that would drive LED light to scan and drive photo electricity inducing element Charge Coupled Device (CCD) to detect when it is induced by the falling drips. Light through a convex lens would scan the drips and project them on CCD across. Electrical signal is produced when CCD detects the shadow after another convex lens. The drips whose diameter is 0.3 millimeter can be distinguished and so as smaller drips of 0.1 millimeter if high-resolution CCD is used. After an amplifier the electrical signal would be transformed into digital signal and would be used to calculate the volume of rain. The Central Processing Unit on main control board gives commands to scanning trigger and controls interrupts from process of data acquisition and calculation. The non-contact photo electricity measurement can detect raindrops of different size. Parallel light projects every raindrop in space on CCD and tells its diameter exactly. So it gives satisfying precision and other useful data such as spectrum of raindrops. Further more, velocity of raindrop would be acquired according to its size. The system needs low cost with universal CCD and Single Chip Micyoco (SCM), and it is worth advocating.

  19. Rain in the U.S. Midwest

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The powerful storms that moved across the U.S. Midwest during the first week of May 2007 brought wind, hail, tornadoes, and drenching rain. This image shows rainfall totals over parts of Oklahoma, Kansas, and Nebraska between May 1 and May 8, based in part on measurements made by the Tropical Rainfall Measuring Mission (TRMM) satellite. More than 400 millimeters (15.7 inches) of rain fell over some regions, corresponding with locations where the National Weather Service reported severe weather. A wide swath of red and orange (between 240 and 400 millimeters of rain) arcs in a clockwise direction from western Oklahoma, through central Kansas, and into southeastern Nebraska. The reddish-orange bull's-eye over southeastern Louisiana is evidence of the torrential rains that pounded visitors to the annual New Orleans Jazz Festival. South-central Texas' Edward Plateau was soaked with more than 240 millimeters of rain during the period, as well. From May 4 to May 8, the National Weather Service received approximately 683 reports of severe weather, 140 of which were reports of tornadoes, including the massive F5 tornado that devastated the city of Greensburg, Kansas. Beyond the damaging winds and tornadoes, the torrential rain triggered extensive flooding throughout the Central Plains. On the evening of May 7, flood warnings were in effect from South Dakota to southern Texas, and by May 8, the Hydrologic Information Center reported moderate to major flooding at 53 stream gauge sites in South Dakota, Iowa, Kansas, Nebraska, Missouri, and Arkansas. The floods could be as severe as the 1993 flood, one of the costliest floods in U.S. history, reported the Associated Press.

  20. Episodic fresh surface waters in the Eocene Arctic Ocean.

    PubMed

    Brinkhuis, Henk; Schouten, Stefan; Collinson, Margaret E; Sluijs, Appy; Sinninghe Damsté, Jaap S; Dickens, Gerald R; Huber, Matthew; Cronin, Thomas M; Onodera, Jonaotaro; Takahashi, Kozo; Bujak, Jonathan P; Stein, Ruediger; van der Burgh, Johan; Eldrett, James S; Harding, Ian C; Lotter, André F; Sangiorgi, Francesca; van Konijnenburg-van Cittert, Han; de Leeuw, Jan W; Matthiessen, Jens; Backman, Jan; Moran, Kathryn

    2006-06-01

    It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions that characterized the early Palaeogene period (55-45 Myr ago) probably induced an intensified hydrological cycle with precipitation exceeding evaporation at high latitudes. Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (approximately 50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an approximately 800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea. The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from approximately 10 degrees C to 13 degrees C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas.

  1. Eocene paleosols of King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Spinola, Diogo; Portes, Raquel; Schaefer, Carlos; Kühn, Peter

    2016-04-01

    Red layers between lava flows on King George Island, Maritime Antarctica, were formed during the Eocene, which was one of the warmest periods on Earth in the Cenozoic. Our hypothesis is that these red layers are paleosols formed in periods of little or no volcanic activity. Therefore, our main objective was to identify the main pedogenic properties and features to distinguish these from diagenetic features formed after the lava emplacement. Additionally, we compared our results with volcanic soils formed under different climates to find the best present analogue. The macromorphological features indicate a pedogenic origin, because of the occurrence of well-defined horizons based on colour and structure. Micromorphological analyses showed that most important pedogenic features are the presence of biological channels, plant residues, anisotropic b-fabric, neoformed and illuvial clay and distinct soil microstructure. Although the paleosols are not strongly weathered, the geochemical data also support the pedogenic origin despite of diagenetic features as the partial induration of the profiles and zeolites filling nearly all voids in the horizons in contact with the overlying lava flow, indicating circulation of hydrothermal fluids. The macromorphological and micromorphological features of these paleosols are similar to the soils formed under seasonal climates. Thus, these paleosol features do not correspond to the other proxies (e.g. sediment, plant fossils), which indicate a wet, non-seasonal climate, as in Valdivian Forest, Chile, during the Eocene in King George Island

  2. Episodic fresh surface waters in the Eocene Arctic Ocean

    USGS Publications Warehouse

    Brinkhuis, H.; Schouten, S.; Collinson, M.E.; Sluijs, A.; Damste, J.S.S.; Dickens, G.R.; Huber, M.; Cronin, T. M.; Onodera, J.; Takahashi, K.; Bujak, J.P.; Stein, R.; Van Der Burgh, J.; Eldrett, J.S.; Harding, I.C.; Lotter, A.F.; Sangiorgi, F.; Cittert, H.V.K.V.; De Leeuw, J. W.; Matthiessen, J.; Backman, J.; Moran, K.

    2006-01-01

    It has been suggested, on the basis of modern hydrology and fully coupled palaeoclimate simulations, that the warm greenhouse conditions that characterized the early Palaeogene period (55-45 Myr ago) probably induced an intensified hydrological cycle with precipitation exceeding evaporation at high latitudes. Little field evidence, however, has been available to constrain oceanic conditions in the Arctic during this period. Here we analyse Palaeogene sediments obtained during the Arctic Coring Expedition, showing that large quantities of the free-floating fern Azolla grew and reproduced in the Arctic Ocean by the onset of the middle Eocene epoch (???50 Myr ago). The Azolla and accompanying abundant freshwater organic and siliceous microfossils indicate an episodic freshening of Arctic surface waters during an ???800,000-year interval. The abundant remains of Azolla that characterize basal middle Eocene marine deposits of all Nordic seas probably represent transported assemblages resulting from freshwater spills from the Arctic Ocean that reached as far south as the North Sea. The termination of the Azolla phase in the Arctic coincides with a local sea surface temperature rise from ???10??C to 13??C, pointing to simultaneous increases in salt and heat supply owing to the influx of waters from adjacent oceans. We suggest that onset and termination of the Azolla phase depended on the degree of oceanic exchange between Arctic Ocean and adjacent seas. ?? 2006 Nature Publishing Group.

  3. Sequence stratigraphy of the Misoa Formation (Eocene) Lake Maracaibo, Venezuela

    SciTech Connect

    Marais-Gilchrist, G.; Higgs, R. )

    1993-02-01

    A preliminary sequence analysis of the Misoa Formation has been done in the Maraven concession area, Lake Maracaibo, using well logs supported by palynological and seismic data. The Misoa Formation is interpreted to comprise a lower transgressive unit containing at least four third-order cycles (lithostratigraphic units C7 to C3, approximately), and an upper dominantly regressive unit consisting of six third-order cycles (approximately C2 to B1). A major flooding surface (gamma-ray log maximum) provides a marker near the top of the lower unit, almost coincident with the important N-M local pollen zone. A tentative correlation can be achieved with the Haq-Vail coastal onlap curves for the Tejas A 2.3 to 3.3 third-order cycles, 55 to 44 ma. The maximum flooding surface would correlate with the maximum Eocene onlap at 52.5 ma. These ages broadly agree with the local pollen zonation. Incised valley fill units interpreted on the basis of blocky log character in some wells could have accumulated during global Eocene sea level falls, particularly those between 55 and 54 ma. The sequences gradually onlap onto the Paleocene unconformity and converge in a southwestward (landward) direction. Although north-south-oriented high-angle sinusoidal events are evident on some seismic lines, these are thought to indicate rotated listric fault-bounded blocks formed during an extensional episode, possibly syn-Misoa. The study should aid exploration for stratigraphic traps in the lake area.

  4. Eocene Podocarpium (Leguminosae) from South China and its biogeographic implications

    PubMed Central

    Xu, Qingqing; Qiu, Jue; Zhou, Zhekun; Jin, Jianhua

    2015-01-01

    Podocarpium A. Braun ex Stizenberger is one of the most common legumes in the Neogene of Eurasia, including fossil fruits, seeds, leaves, and possible flower and pollen grains. This genus is not completely consistent with any extant genera according to gross morphological characters and poorly preserved cuticular structures reported in previous studies. The fossil pods collected from the coal-bearing series of the Changchang Basin of Hainan Island and Maoming Basin of Guangdong, South China, are examined by morphologically comparative work, with special reference to venation patterns and placental position. These distinctive features, as well as the ovule development of pods from different developmental stages and the epidermal structure of the pods, as distinguished from previous records lead to the conclusion that these fossils can be recognized as a new species of Podocarpium, P. eocenicum sp. nov. This new discovery indicates that Podocarpium had arrived in South China by the Eocene. Investigation on the fossil records of this extinct genus shows that P. eocenicum is the earliest and lowest latitude fossil data. The possible occurrence pattern of this genus is revealed as follows: Podocarpium had distributed in the South China at least in the middle Eocene, and then migrated to Europe during the Oligocene; in the Miocene this genus reached its peak in Eurasia, spreading extensively across subtropical areas to warm temperate areas; finally, Podocarpium shrank rapidly and became extinct in Eurasia during the Pliocene. PMID:26579179

  5. Eocene Arctic Ocean and earth's Early Cenozoic climate

    SciTech Connect

    Clark, D.L.

    1985-01-01

    Seasonal changes of the Arctic Ocean are an approximate microcosm of the present advanced interglacial climate of the Earth. A similar relationship has existed for several million years but was the Early Cenozoic Arctic Ocean an analog of Earth's climate, as well. Absence of polar ice during the Cretaceous is relatively well established. During the Cenozoic a worldwide decrease in mean annual ocean temperature resulted from such factors as altered oceanic circulation and lower atmospheric CO/sub 2/ levels. Limited Arctic Ocean data for the middle or late Eocene indicate the presence of upwelling conditions and accompanying high productivity of diatoms, ebridians, silicoflagellates and archaeomonads. During this interval, some seasonality is suggested from the varve-like nature of a single sediment core. However, the absence of drop stones or any ice-rafted sediment supports the idea of an open water, ice-free central Arctic Ocean during this time. Latest Cretaceous Arctic Ocean sediment is interpreted to represent approximately the same conditions as those suggested for the Eocene and together with that data suggest that the central Arctic Ocean was ice-free during part if not all of the first 20 my of the Cenozoic. Sediment representing the succeeding 30 my has not been recovered but by latest Miocene or earl Pliocene, ice-rafted sediment was accumulating, both pack ice and icebergs covered the Arctic Ocean reflecting cyclic glacial climate.

  6. Foraminiferal repopulation of the late Eocene Chesapeake Bay impact crater

    USGS Publications Warehouse

    Poag, C. Wylie

    2012-01-01

    The Chickahominy Formation is the initial postimpact deposit in the 85km-diameter Chesapeake Bay impact crater, which is centered under the town of Cape Charles, Virginia, USA. The formation comprises dominantly microfossil-rich, silty, marine clay, which accumulated during the final ~1.6myr of late Eocene time. At cored sites, the Chickahominy Formation is 16.8-93.7m thick, and fills a series of small troughs and subbasins, which subdivide the larger Chickahominy basin. Nine coreholes drilled through the Chickahominy Formation (five inside the crater, two near the crater margin, and two ~3km outside the crater) record the stratigraphic and paleoecologic succession of 301 indigenous species of benthic foraminifera, as well as associated planktonic foraminifera and bolboformids. Two hundred twenty of these benthic species are described herein, and illustrated with scanning electron photomicrographs. Absence of key planktonic foraminiferal and Bolboforma species in early Chickahominy sediments indicates that detrimental effects of the impact also disturbed the upper oceanic water column for at least 80-100kyr postimpact. After an average of ~73kyr of stressed, rapidly fluctuating paleoenvironments, which were destabilized by after-effects of the impact, most of the cored Chickahominy subbasins maintained stable, nutrient-rich, low-oxygen bottom waters and interstitial microhabitats for the remaining ~1.3myr of late Eocene time.

  7. Cretaceous to Eocene passive margin sedimentation in Northeastern Venezuela

    SciTech Connect

    Erikson, J.P. )

    1993-02-01

    Twenty two palinspastic paleogeographic maps are presented for the Cretaceous to Eocene strata of the Serrania del Interior of northeastern Venezuela. The mapped lithologies, environmental conditions, and evolving depositional systems record [approximately]90 m.y. of dominantly marine sedimentation on the only observable Mesozoic passive margin in the Western Hemisphere. The depositional systems of the passive margin are heterogeneous at lateral (i.e., along-margin) length scales greater than [approximately]40 km. The primary lateral heterogeneity is caused by a major Lower Cretaceous deltaic system that emanated southwest of the Serrania del Interior. All important intervals, such as the laterally variable Aptian-Albian El Cantil platform limestone and the hydrocarbon source rocks of the Upper Cretaceous Querecual and San Antonio formations, are related to probable causal mechanisms and environmental conditions. Stratigraphic events have been interpreted as of either local or regional extent; based on a combination of outcrop sedimentologic analyses and regional depositional systems interpretation. The 3-dimensional distribution of depositional systems and systems tracts reveals 4-6 regional sequence boundaries separated by 4-20 m.y. Subsidence analyses support the facies interpretation of a passive margin by showing continuous, thermally dominated subsidence during the Cretaceous to Eocene interval. Subsidence and accumulation rates increased and facies changed significantly in the Oligocene, indicating the end of passive margin sedimentation and the initiation of foredeep subsidence and accumulation associated with overthrusting the eastward-advancing Caribbean Plate.

  8. Continental ice in Greenland during the Eocene and Oligocene.

    PubMed

    Eldrett, James S; Harding, Ian C; Wilson, Paul A; Butler, Emily; Roberts, Andrew P

    2007-03-08

    The Eocene and Oligocene epochs (approximately 55 to 23 million years ago) comprise a critical phase in Earth history. An array of geological records supported by climate modelling indicates a profound shift in global climate during this interval, from a state that was largely free of polar ice caps to one in which ice sheets on Antarctica approached their modern size. However, the early glaciation history of the Northern Hemisphere is a subject of controversy. Here we report stratigraphically extensive ice-rafted debris, including macroscopic dropstones, in late Eocene to early Oligocene sediments from the Norwegian-Greenland Sea that were deposited between about 38 and 30 million years ago. Our data indicate sediment rafting by glacial ice, rather than sea ice, and point to East Greenland as the likely source. Records of this type from one site alone cannot be used to determine the extent of ice involved. However, our data suggest the existence of (at least) isolated glaciers on Greenland about 20 million years earlier than previously documented, at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher.

  9. Using fossil leaves as paleoprecipitation indicators: An Eocene example

    NASA Astrophysics Data System (ADS)

    Wilf, Peter; Wing, Scott L.; Greenwood, David R.; Greenwood, Cathy L.

    1998-03-01

    Estimates of past precipitation are of broad interest for many areas of inquiry, including reconstructions of past environments and topography, climate modeling, and ocean circulation studies. The shapes and sizes of living leaves are highly sensitive to moisture conditions, and assemblages of fossil leaves of flowering plants have great potential as paleoprecipitation indicators. Most quantitative estimates of paleoprecipitation have been based on a multivariate data set of morphological leaf characters measured from samples of living vegetation tied to climate stations. However, when tested on extant forests, this method has consistently overestimated precipitation. We present a simpler approach that uses only the mean leaf area of a vegetation sample as a predictor variable but incorporates a broad range of annual precipitation and geographic coverage into the predictor set. The significant relationship that results, in addition to having value for paleoclimatic reconstruction, refines understanding of the long-observed positive relationship between leaf area and precipitation. Seven precipitation estimates for the Eocene of the Western United States are revised as lower than previously published but remain far wetter than the same areas today. Abundant moisture may have been an important factor in maintaining warm, frost-free conditions in the Eocene because of the major role of water vapor in retaining and transporting atmospheric heat.

  10. Eocene Podocarpium (Leguminosae) from South China and its biogeographic implications.

    PubMed

    Xu, Qingqing; Qiu, Jue; Zhou, Zhekun; Jin, Jianhua

    2015-01-01

    Podocarpium A. Braun ex Stizenberger is one of the most common legumes in the Neogene of Eurasia, including fossil fruits, seeds, leaves, and possible flower and pollen grains. This genus is not completely consistent with any extant genera according to gross morphological characters and poorly preserved cuticular structures reported in previous studies. The fossil pods collected from the coal-bearing series of the Changchang Basin of Hainan Island and Maoming Basin of Guangdong, South China, are examined by morphologically comparative work, with special reference to venation patterns and placental position. These distinctive features, as well as the ovule development of pods from different developmental stages and the epidermal structure of the pods, as distinguished from previous records lead to the conclusion that these fossils can be recognized as a new species of Podocarpium, P. eocenicum sp. nov. This new discovery indicates that Podocarpium had arrived in South China by the Eocene. Investigation on the fossil records of this extinct genus shows that P. eocenicum is the earliest and lowest latitude fossil data. The possible occurrence pattern of this genus is revealed as follows: Podocarpium had distributed in the South China at least in the middle Eocene, and then migrated to Europe during the Oligocene; in the Miocene this genus reached its peak in Eurasia, spreading extensively across subtropical areas to warm temperate areas; finally, Podocarpium shrank rapidly and became extinct in Eurasia during the Pliocene.

  11. A Phororhacoid bird from the Eocene of Africa

    NASA Astrophysics Data System (ADS)

    Mourer-Chauviré, Cécile; Tabuce, Rodolphe; Mahboubi, M'hammed; Adaci, Mohammed; Bensalah, Mustapha

    2011-10-01

    The bird fossil record is globally scarce in Africa. The early Tertiary evolution of terrestrial birds is virtually unknown in that continent. Here, we report on a femur of a large terrestrial new genus discovered from the early or early middle Eocene (between ˜52 and 46 Ma) of south-western Algeria. This femur shows all the morphological features of the Phororhacoidea, the so-called Terror Birds. Most of the phororhacoids were indeed large, or even gigantic, flightless predators or scavengers with no close modern analogs. It is likely that this extinct group originated in South America, where they are known from the late Paleocene to the late Pleistocene (˜59 to 0.01 Ma). The presence of a phororhacoid bird in Africa cannot be explained by a vicariant mechanism because these birds first appeared in South America well after the onset of the mid-Cretaceous Gondwana break up (˜100 million years old). Here, we propose two hypotheses to account for this occurrence, either an early dispersal of small members of this group, which were still able of a limited flight, or a transoceanic migration of flightless birds from South America to Africa during the Paleocene or earliest Eocene. Paleogeographic reconstructions of the South Atlantic Ocean suggest the existence of several islands of considerable size between South America and Africa during the early Tertiary, which could have helped a transatlantic dispersal of phororhacoids.

  12. AN EQUATORIAL PACIFIC RAIN EVENT: INFLUENCE ON THE DISTRIBUTION OF IRON AND HYDROGEN PEROXIDE IN SURFACE WATERS

    EPA Science Inventory

    Methods are described for measuring changes in atmospheric O2 concentration with emphasis on gas handling procedures. Cryogenically dried air samples are collected in 5 L glass flasks at ambient pressure and analyzed against reference gases derived from high-pressure aluminum tan...

  13. Acid rain and electric utilities 2

    SciTech Connect

    1997-12-31

    This proceedings contains more than 100 technical presentations dealing with a variety of topics concerning the Title IV acid rain provisions of the Clean Air Act Amendments of 1990. Some of the major topics addressed include: emerging environmental issues impacting electric utilities (proposed revisions to the ozone and particulate matter NAAQS), acid rain program overview, continuous emissions monitoring rule revisions, global climate change and CO{sub 2}, emissions data management, Clean Air Power Initiative and regional issues, compliance/designated representative, flow monitoring, emissions control technology, allowance and trading, emission reductions, NO{sub x} control issues, hazardous air pollutants, and CEMS advances.

  14. Acid rain: Engineering solutions, regulatory aspects

    SciTech Connect

    Schwieger, R.G.; Elliott, T.C.

    1985-01-01

    Keeping up with efforts to control acid rain, this reference presents current scientific aspects associated with the problem of political and legislative concerns and ideas for developing effective mitigation programs at reasonable cost. The contributors are the authorities in attendance at the Second International Conference on Acid Rain - and this work represents the first time engineers and managers with firsthand knowledge of systems and equipment to reduce SO/sub 2/ and NO/sub x/ emissions gathered in one place. Throughout the book, some 200 tables, charts, diagrams, and photographs augment the textual material.

  15. Condor equatorial electrojet campaign: Radar results

    SciTech Connect

    Kudeki, E.; Fejer, B.G.; Farley, D.T.; Hanuise, C.

    1987-12-01

    A review of the experimental and theoretical background to the Condor equatorial electrojet compaign is followed by the presentation and discussion of VHF radar interferometer and HF radar backscatter data taken concurrently with two rocket in situ experiments reported in companion papers (Pfaff et al., this issue (a, b). Both experiments were conducted in strongly driven periods with the on-line radar interferometer displaying signatures of what has been interpreted in earlier radar work (Kudeki et al., 1982) as kilometer scale gradient drift waves. Low-frequency density fluctuations detected by in situ rocket sensors confirm the earlier interpretation. VHF radar/rocket data comparisons also indicate the existence of a turbulent layer in the upper portion of the daytime electrojet at about 108 km altitude driven purely by the two-stream instability. Nonlinear mode coupling of linearly growing two-stream waves to linearly damped 3-m vertical modes could account for the radar echoes scattered from this layer, which showed no indication of large-scale gradient drift waves. Nonlinear mode coupling may therefore compete with the wave-induced anomalous diffusion mechanism proposed recently by Sudan (1983) for the saturation of directly excited two-stream waves. Nighttime radar data show a bifurcated layer with the two parts having comparable echo strength but oppositely directed zonal drift velocities. The lower layer shows narrow backscatter spectra; the upper layer is characterized by kilometer scale waves and vertically propagating type 1 waves.

  16. Vertical motions in the equatorial middle atmosphere

    NASA Technical Reports Server (NTRS)

    Weisman, M. L.

    1979-01-01

    A single station vertical velocity equation which considers ageostrophic and diabatic effects derived from the first law of thermodynamics and a generalized thermal wind relation is presented. An analysis and verification procedure which accounts for measurement and calculation errors as well as time and space continuity arguments and theoretical predictions are described. Vertical velocities are calculated at every kilometer between 25 and 60 km and for approximately every three hours for the above diurnal period at Kourou (French Guiana), Fort Sherman (Panama Canal Zone), Ascension Island, Antigua (British West Indies) and Natal (Brazil). The results, plotted as time series cross sections, suggest vertical motions ranging in magnitude from 1 or 2 cm/sec at 30 km to as much as 15 cm/sec at 60 km. Many of the general features of the results agree well with atmospheric tidal predictions but many particular features suggest that both smaller time scale gravity waves (periods less than 6 hours) and synoptic type waves (periods greater than 1 day) may be interacting significantly with the tidal fields. The results suggest that vertical motions can be calculated for the equatorial middle atmosphere and must be considered a significant part of the motion for time scales from 8 to 24 hours.

  17. Catastrophic ape decline in western equatorial Africa.

    PubMed

    Walsh, Peter D; Abernethy, Kate A; Bermejo, Magdalena; Beyers, Rene; De Wachter, Pauwel; Akou, Marc Ella; Huijbregts, Bas; Mambounga, Daniel Idiata; Toham, Andre Kamdem; Kilbourn, Annelisa M; Lahm, Sally A; Latour, Stefanie; Maisels, Fiona; Mbina, Christian; Mihindou, Yves; Obiang, Sosthène Ndong; Effa, Ernestine Ntsame; Starkey, Malcolm P; Telfer, Paul; Thibault, Marc; Tutin, Caroline E G; White, Lee J T; Wilkie, David S

    2003-04-10

    Because rapidly expanding human populations have devastated gorilla (Gorilla gorilla) and common chimpanzee (Pan troglodytes) habitats in East and West Africa, the relatively intact forests of western equatorial Africa have been viewed as the last stronghold of African apes. Gabon and the Republic of Congo alone are thought to hold roughly 80% of the world's gorillas and most of the common chimpanzees. Here we present survey results conservatively indicating that ape populations in Gabon declined by more than half between 1983 and 2000. The primary cause of the decline in ape numbers during this period was commercial hunting, facilitated by the rapid expansion of mechanized logging. Furthermore, Ebola haemorrhagic fever is currently spreading through ape populations in Gabon and Congo and now rivals hunting as a threat to apes. Gorillas and common chimpanzees should be elevated immediately to 'critically endangered' status. Without aggressive investments in law enforcement, protected area management and Ebola prevention, the next decade will see our closest relatives pushed to the brink of extinction.

  18. Equatorial Staphyloma Associated with Neurofibromatosis Type 1

    PubMed Central

    Shimada, Yoshiaki; Horiguchi, Masayuki

    2016-01-01

    We report a case of a 38-year-old man who presented with a recently self-detected lump under his left eyebrow. Previous ophthalmological history was unremarkable except for unilateral high myopia (left eye) since childhood. The appearance of the left eye was seemingly normal; however, with the top lid pulled up on downward gaze, a dark brown bulge emerged. The bulge was 10 × 7 mm and approximately 4 mm in height, and was covered by the extended superior rectus muscle. The diagnosis of equatorial staphyloma was made after coronal T1-weighted magnetic resonance imaging of the orbit revealed the dilatation of the vitreous cavity. Ocular movements were fully maintained and visual acuity was largely spared: 20/15 in the right eye without correction and 20/25 in the left eye with −10.00 spheres and −4.00 × 80 degrees cylinders. His past and family histories were unremarkable; however, small neurofibromas and café au lait spots all over his body led to the diagnosis of neurofibromatosis type 1 (NF1). From this case, similar to previous reports, we suggest that manifestations of NF1 are extremely variable and unpredictable. PMID:27721788

  19. POGO observations of the equatorial electrojet

    NASA Technical Reports Server (NTRS)

    Cain, J. C.; Sweeney, R. E.

    1972-01-01

    During intervals in 1967 to 1970, the OGO-4 and 6 spacecraft made over 2000 traversals over the equatorial electrojet in the altitude range 400-800 km when local times were between 9 and 15 hours. These spacecraft carried total field magnetometers making measurements to an accuracy of 2 gamma with a sample rate greater than once a second. Delta F values, the deviations from these observations, were formed from an internal reference model. The results were plotted for a 30 deg band about the equator, and the characteristics of the electrojet effect in the data were investigated. This effect was characterized by a sharp negative V-signature of some 16-19 deg in width and a variable amplitude. The position of this minimum was found to lie within 0.5 deg of the dip equator. A slight northward shift was noted at the longitude of Huancayo. The jet amplitudes were normalized to 400 km amplitudes and observed to be highly variable in time. Amplitudes over the longitude range 50 to 90 deg W averaged 60% higher than elsewhere, as expected, due to the weaker main field. However, though the scatter of amplitudes is high, the expected minima in east Asia was not evident. It was speculated that this could be due to a less conducting upper mantle in this area.

  20. The formation of an equatorial coronal hole

    NASA Astrophysics Data System (ADS)

    Yang, Liheng; Jiang, Yunchun; Zhang, Jun

    2010-02-01

    The formation of an equatorial coronal hole (CH) from 2006 January 9 to 12 was simultaneously observed by GOES-12/SXI, SOHO/EIT and SOHO/MDI instruments. The varieties of soft X-ray and EUV brightness, coronal temperature, and total magnetic flux in the CH were examined and compared with that of a quiet-sun (QS) region nearby. The following results are obtained. (1) A preexisting dark lane appeared on the location of the followed CH and was reinforced by three enhanced networks. (2) The CH gradually formed in about 81 hours and was predominated by positive magnetic flux. (3) During the formation, the soft X-ray and EUV brightness, coronal temperature, and total magnetic flux obviously decreased in the CH, but were almost no change in the QS region. The decrease of the total magnetic flux may be the result of magnetic reconnection between the open and closed magnetic lines, probably indicating the physical mechanism for the birth of the CH.

  1. Periodic equatorial water flows from a Hamiltonian perspective

    NASA Astrophysics Data System (ADS)

    Ionescu-Kruse, Delia; Martin, Calin Iulian

    2017-04-01

    The main result of this paper is a Hamiltonian formulation of the nonlinear governing equations for geophysical periodic stratified water flows in the equatorial f-plane approximation allowing for piecewise constant vorticity.

  2. Photoelectron escape fluxes over the equatorial and midlatitude regions

    NASA Technical Reports Server (NTRS)

    Narasingarao, B. C.; Singh, R. N.; Maier, E. J.

    1972-01-01

    Satellite measurements of photoelectron escape flux around noontime made by Explorer 31 in 600-800 km altitude range are reported for the equatorial and midlatitude regions. The pitch angle distributions and the spectral distributions are derived from the data. Analyzed data show that the flux for equatorial regions is lower by a factor 2 to 3 in comparison to that of midlatitude regions. Theoretical calculations are also made to compare with observed escape fluxes.

  3. On Irrotational Flows Beneath Periodic Traveling Equatorial Waves

    NASA Astrophysics Data System (ADS)

    Quirchmayr, Ronald

    2016-08-01

    We discuss some aspects of the velocity field and particle trajectories beneath periodic traveling equatorial surface waves over a flat bed in a flow with uniform underlying currents. The system under study consists of the governing equations for equatorial ocean waves within a non-inertial frame of reference, where Euler's equation of motion has to be suitably adjusted, in order to account for the influence of the earth's rotation.

  4. Overview of the Equatorial Electrojet and Related Ionospheric Current Systems

    DTIC Science & Technology

    2007-11-02

    NUWC-NPT Technical Report 11,676 25 April 2005 Overview of the Equatorial Electrojet and Related Ionospheric Current Systems John P. Casey...Overview of the Equatorial Electrojet and Related Ionospheric Current Systems PR A590045 6. AUTHOR(S) John P. Casey 7. PERFORMING ORGANIZATION NAME(S) AND...that flows in the ionosphere in a narrow zone above the magnetic dip equator during the daytime. The electrojet current produces a large enhancement of

  5. Upper Eocene tektite and impact ejecta layer on the Continental Slope off New Jersey

    NASA Astrophysics Data System (ADS)

    Glass, B. P.; Koeberl, C.; Blum, J. D.; McHugh, C. M. G.

    1998-03-01

    During Leg 150 of the Ocean Drilling Project (ODP) two sites (903C and 904A) were cored which have sediments of the same biostratigraphic age as the upper Eocene tektite-bearing ejecta layer at Deep Sea Drilling Project (DSDP) Site 612. Core 45X from ODP Site 904A (~ 4 km north of Site 612) contains a 5-cm-thick tektite-bearing ejecta layer and Core 56 from Site 903C (~ 8 km north-northwest of Site 904) contains a 2-cm-thick layer of impact ejecta without any tektite or impact glass. Shocked quartz and feldspar grains, with multiple sets of planar deformation features, and abundant coesite-bearing grains are present at both sites. The major oxide contents, trace element compositions, and rare earth element patterns of the Site 904 tektites are similar to those of the Site 612 tektites and to North American tektites (especially bediasites). The Sr and Nd values for one composite tektite sample from Site 904 fall within the range previously obtained for the Site 612 tektites, which defines a linear trend that, if extrapolated, would intersect the values obtained for North American tektites. The water contents of eight tektite fragments from Site 904 range from 0.017 to 0.098 wt. %, and, thus, are somewhat higher than is typical for tektites. The heavy mineral assemblages of the 63 - 125 m size fractions from the ejecta layers at Sites 612, 903, and 904 are all similar. Therefore, we conclude that the ejecta layer at all three sites are from the same impact event and that the tektites at Sites 904 and 612 belong to the North American tektite strewn field. Clinopyroxene-bearing (cpx) spherules occur below, or in the lower part of, the main ejecta layer at all three sites. At all three sites the cpx spherules have been partly or completely replaced with pyrite which preserved the original crystalline textures. Site 612, 903, and 904 cpx spherules are similar to those found in the Caribbean Sea, Gulf of Mexico, central equatorial Pacific, western equatorial Pacific, and

  6. Influence of Assimilation of Subsurface Temperature Measurements on Simulations of Equatorial Undercurrent and South Equatorial Current Along the Pacific Equator

    NASA Technical Reports Server (NTRS)

    Halpern, David; Leetmaan, Ants; Reynolds, Richard W.; Ji, Ming

    1997-01-01

    Equatorial Pacific current and temperature fields were simulated with and without assimilation of subsurface temperature measurements for April 1992 - March 1995, and compared with moored bouy and research vessel current measurements.

  7. Effects of rain damage on wilting forages

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the most common problems faced by hay or silage producers is how to manage production schedules around unfavorable weather. Inevitably, some wilting forage crops are damaged by unexpected rainfall events each year, and producers often inquire about the effects of unexpected rain damage, and w...

  8. Acid Rain Program CEM audit program

    SciTech Connect

    Nguyen, K.O.T.; Alexander, T.H.; Dupree, J.C.

    1997-12-31

    This presentation will give an overview of the Acid Rain Program CEM Audit Program: electronic and field audits. The presentation will include the reasons for audits, field audit types and levels the steps used in develop in the audit program and the audit procedures.

  9. Acid Rain: A Description of Bilingual Friesland.

    ERIC Educational Resources Information Center

    Zondag, Koen

    1984-01-01

    Using acid rain as a metaphor, discusses the status of the Frisian language and culture as one which, though apparently thriving, is really threatened. Examines the sources of this threat, i.e., the education system, the church, mass communication and transportation, and the demise of the Frisian village community. (SED)

  10. Air quality monitor and acid rain networks

    NASA Technical Reports Server (NTRS)

    Rudolph, H.

    1980-01-01

    The air quality monitor program which consists of two permanent air monitor stations (PAMS's) and four mobile shuttle pollutant air monitor stations (SPAMS's) is evaluated. The PAMS measures SO sub X, NO sub X particulates, CO, O3, and nonmethane hydrocarbons. The SPAMS measures O3, SO2, HCl, and particulates. The collection and analysis of data in the rain monitor program are discussed.

  11. Acid Rain Materials for Classroom Use.

    ERIC Educational Resources Information Center

    Factor, Lance; Kooser, Robert G.

    This booklet contains three separate papers suitable for use in an advanced high school or college chemistry course. The first paper provides background information on acids and bases. The second paper provides additional background information, focusing on certain aspects of atmospheric chemistry as it relates to the acid rain problem. An attempt…

  12. TECHNOLOGICAL OPTIONS FOR ACID RAIN CONTROL

    EPA Science Inventory

    The paper discusses technological options for acid rain control. Compliance with Title IV of the Clean Air Act Amendments of 1990 will require careful scrutiny of a number of issues before selecting control options to reduce sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions...

  13. Acid Rain: A Student's First Sourcebook.

    ERIC Educational Resources Information Center

    Kyle, Beth Ann; And Others

    The purpose of this guide is to help students better understand the science, citizen action, and research issues that are part of the acid rain problem. The guide is designed for students in grades 4-8 and their teachers. Following an introduction, the first seven sections are informative in nature. They include: (1) "Observations about Acidity";…

  14. Acid Rain. Teacher's Guide. LHS GEMS.

    ERIC Educational Resources Information Center

    Hocking, Colin; Barber, Jacqueline; Coonrod, Jan

    This teacher's guide presents a unit on acid rain and introduces hands-on activities for sixth through eighth grade students. In each unit, students act as real scientists and gather evidence by using science process skills such as observing, measuring and recording data, classifying, role playing, problem solving, critical thinking, synthesizing…

  15. Acid Rain: Resource Materials for Schools.

    ERIC Educational Resources Information Center

    American Biology Teacher, 1983

    1983-01-01

    Provides listings of acid rain resource material groups under: (1) printed materials (pamphlets, books, articles); (2) audiovisuals (slide/tape presentations, tape, video-cassette); (3) miscellaneous (buttons, pocket lab, umbrella); (4) transparencies; (5) bibliographies; and (6) curriculum materials. Sources and prices (when applicable) are…

  16. Disdrometer and Tipping Bucket Rain Gauge Handbook

    SciTech Connect

    Bartholomew. MJ

    2009-12-01

    The Distromet disdrometer model RD-80 and NovaLynx tipping bucket rain gauge model 260-2500E-12 are two devices deployed a few meters apart to measure the character and amount of liquid precipitation. The main purpose of the disdrometer is to measure drop size distribution, which it does over 20 size classes from 0.3 mm to 5.4 mm. The data from both instruments can be used to determine rain rate. The disdrometer results can also be used to infer several properties including drop number density, radar reflectivity, liquid water content, and energy flux. Two coefficients, N0 and Λ, from an exponential fit between drop diameter and drop number density, are routinely calculated. Data are collected once a minute. The instruments make completely different kinds of measurements. Rain that falls on the disdrometer sensor moves a plunger on a vertical axis. The disdrometer transforms the plunger motion into electrical impulses whose strength is proportional to drop diameter. The rain gauge is the conventional tipping bucket type. Each tip collects an amount equivalent to 0.01 in. of water, and each tip is counted by a data acquisition system anchored by a Campbell CR1000 data logger.

  17. Remote sensing of rain over the ocean

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Computer models of the microwave emission from the earth's atmosphere were used to study the problem of retrieving meteorological information from the SMMR instrument that will be flown on NIMBUS-G. Methods for retrieving rain rate, wind speed, cloud height, and ocean temperature are described for the case when the satellite is over the ocean.

  18. Rain compensation algorithm for ACTS mobile terminal

    NASA Astrophysics Data System (ADS)

    Levitt, Barry K.

    1992-02-01

    The initial advanced communication technology satellite (ACTS) mobile terminal (AMT) demonstrations will involve two-way communications between the high-bit-rate link evaluation terminal (HBR-LET), which is a fixed terminal (FT), and a van-housed mobile terminal (MT). The HBR-LET has the capability of adjusting its transmitted uplink power over an approximately 10-dB range to compensate for forward uplink rain attenuation. However, because of size and weight limitations, the MT cannot use power control as a rain compensation technique. Consequently, the AMT rain compensation algorithm (RCA) is based on a formula for varying the transmitted data rate in either direction to maintain link performance within acceptable limits. The objective of the AMT RCA is to ensure reliable operation in both the forward and return directions despite the possibility of uplink or downlink fading due to rain events in the vicinity of the FT or MT. In particular, the RCA must maintain at least a 3-dB link margin at the highest possible transmission rate (AMT can operate at 9.6, 4.8, or 2.4 kb/s) permitted by the prevailing channel conditions. The 3-dB minimum link margin is a system design safety factor to accommodate conceivable implementation losses.

  19. Promoting nitrate removal in rain gardens

    EPA Science Inventory

    Rain gardens are vegetated surface depressions, often located at low points in landscapes, designed to receive stormwater runoff from roads, roofs, and parking lots. The gardens’ sandy soils allow stormwater to drain quickly to the native soils below and eventually to groundwate...

  20. Rain Barrels: A Catalyst for Change?

    ERIC Educational Resources Information Center

    Bakacs, Michele E.; Haberland, Mike; Mangiafico, Salvatore S.; Winquist, Aileen; Obropta, Christopher C.; Boyajian, Amy; Mellor, Sara

    2013-01-01

    Over the past 4 years, rain barrel programming for residents has been implemented in both Northern Virginia and New Jersey as a method for educating the public about stormwater management and water conservation. Program participants demonstrated a significant increase in knowledge of water resource issues. Follow-up surveys showed 58% of New…

  1. GPM Rain Rates in Tropical Cyclone Pam

    NASA Video Gallery

    NASA-JAXA's GPM Satellite Close-up of Cyclone Pam's Rainfall NASA-JAXA's GPM core satellite captured rain rates in Tropical Cyclone Pam at 03:51 UTC (2:51 p.m. local time) on March 14, 2015. Heavie...

  2. Eastward traverse of equatorial plasma plumes observed with the Equatorial Atmosphere Radar in Indonesia

    NASA Astrophysics Data System (ADS)

    Fukao, S.; Yokoyama, T.; Tayama, T.; Yamamoto, M.; Maruyama, T.; Saito, S.

    2006-07-01

    The zonal structure of radar backscatter plumes associated with Equatorial Spread F (ESF), probably modulated by atmospheric gravity waves, has been investigated with the Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (0.20° S, 100.32° E; dip latitude 10.1° S) and the FM-CW ionospheric sounders on the same magnetic meridian as the EAR. The occurrence locations and zonal distances of the ESF plumes were determined with multi-beam observations with the EAR. The ESF plumes drifted eastward while keeping distances of several hundred to a thousand kilometers. Comparing the occurrence of the plumes and the F-layer uplift measured by the FM-CW sounders, plumes were initiated within the scanned area around sunset only, when the F-layer altitude rapidly increased. Therefore, the PreReversal Enhancement (PRE) is considered as having a zonal variation with the scales mentioned above, and this variation causes day-to-day variability, which has been studied for a long time. Modulation of the underlying E-region conductivity by gravity waves, which causes inhomogeneous sporadic-E layers, for example, is a likely mechanism to determine the scale of the PRE.

  3. Formaldehyde in remote marine air and rain - Flux measurements and estimates

    NASA Astrophysics Data System (ADS)

    Zafiriou, O. C.; Alford, J.; Herrera, M.; Peltzer, E. T.; Gagosian, R. B.; Liu, S. C.

    1980-05-01

    The tropospheric trace constituent formaldehyde, HCHO, was measured in rain and in the gas phase during the wet season at Enewetak Atoll, a remote marine site in the central equatorial Pacific. Rainwater averaged 8 + or - 2 microgram/kg; the gas phase averaged 0.4 + or 0.2 ppbv (0.5 microgram/cu m). These values, especially the rain, are among the lowest reported to date. The formaldehyde flux to the sea by rainout and washout extrapolates to 0.010 g/sq m per year. The gaseous flux into the sea surface is estimated to be 0.05 g/sq m per year by an air-sea exchange calculation that takes into account enhanced uptake by hydroxide-catalyzed formaldehyde hydration. The measured mixing ratio is close to the 0.18 ppbv prediction of a tropospheric chemistry model calculation. The methane oxidation chain probably is the sole formaldehyde source in the Enewetak area. The total formaldehyde flux as carbon into the ocean is approximately 2% of the estimated total organic carbon from rainout and washout. About 2-4% of the calculated column formaldehyde production is removed from the atmosphere by these processes.

  4. Petrology of Eocene volcanic rocks of Moalleman Damghan area

    NASA Astrophysics Data System (ADS)

    Zolfaghari, Seddigheh; Kohansal, Reza; Hashem Emami, Mohammad

    2010-05-01

    The Moalleman area is situated to the south of Damghan City, in the central of Torud sheet (scale 1:250000). The area is part of central Iran structural zone. The oldest and the youngest rocks units of the area include schists and limestone ascribed to Silurian and Devonian periods, and the fluvial terraces of Quaternary periods. Most of the volcanic rocks of the area are respectively related to Lutetion stage till upper Eocene, and are exposed between the Torud Angilu faults. Following to the eruption of these rocks, during upper Eocene to Oligocene, subvolcanic cryptodomes, hypoabyssal plutons and several dikes have intruded into this volcanic sequence. Igneous rocks of the study area may be classified into three main groups: Lavas, Pyroclastics and subvolcanic. Lavas include basalts, andesite, dacitic andesites and quartztrachyandesite, Trachyandesites form the major volume of these volcanic rocks with in the study. Pyroclastic rocks mainly consist of cryptallic tuff (with an andesitic to trachyandesitic composition) and crystal tuff. (With an andesitic to dacitic composition). The Major volume of volcanic rocks of study area have suffered alterations which gave rise to the formation of secondary minerals such as calcite, chlorite, sericite, epidote, serpentine, and iddingsite. It appears that the faults and fractures with in these rocks have facilitated the transition of hydrothermal solutions and the subsequent alteration. Microscopic evidences of magmatic contamination in lavas include phenomena such as resorption, formations of sieve texture, and osciliatory zoning in plagioclases, corrosion of pyroxenes and plagioclases, and two types of altered and unaltered plagioclases concurrence. According to the geochemical diagrams, the rocks of the study area of the alkaline and calc-alkaline types and have a tendency to potassium enrichment (probably related to contamination of their magma). Geochemical evidences such as great scatter in the diagrams and showing no

  5. First Record of Eocene Bony Fishes and Crocodyliforms from Canada’s Western Arctic

    PubMed Central

    Eberle, Jaelyn J.; Gottfried, Michael D.; Hutchison, J. Howard; Brochu, Christopher A.

    2014-01-01

    Background Discovery of Eocene non-marine vertebrates, including crocodylians, turtles, bony fishes, and mammals in Canada’s High Arctic was a critical paleontological contribution of the last century because it indicated that this region of the Arctic had been mild, temperate, and ice-free during the early – middle Eocene (∼53–50 Ma), despite being well above the Arctic Circle. To date, these discoveries have been restricted to Canada’s easternmost Arctic – Ellesmere and Axel Heiberg Islands (Nunavut). Although temporally correlative strata crop out over 1,000 km west, on Canada’s westernmost Arctic Island – Banks Island, Northwest Territories – they have been interpreted as predominantly marine. We document the first Eocene bony fish and crocodyliform fossils from Banks Island. Principal Findings We describe fossils of bony fishes, including lepisosteid (Atractosteus), esocid (pike), and amiid, and a crocodyliform, from lower – middle Eocene strata of the Cyclic Member, Eureka Sound Formation within Aulavik National Park (∼76°N. paleolat.). Palynology suggests the sediments are late early to middle Eocene in age, and likely spanned the Early Eocene Climatic Optimum (EECO). Conclusions/Significance These fossils extend the geographic range of Eocene Arctic lepisosteids, esocids, amiids, and crocodyliforms west by approximately 40° of longitude or ∼1100 km. The low diversity bony fish fauna, at least at the family level, is essentially identical on Ellesmere and Banks Islands, suggesting a pan-High Arctic bony fish fauna of relatively basal groups around the margin of the Eocene Arctic Ocean. From a paleoclimatic perspective, presence of a crocodyliform, gar and amiid fishes on northern Banks provides further evidence that mild, year-round temperatures extended across the Canadian Arctic during early – middle Eocene time. Additionally, the Banks Island crocodyliform is consistent with the phylogenetic hypothesis of a Paleogene divergence

  6. Radiative forcing by forest and subsequent feedbacks in the early Eocene climate

    NASA Astrophysics Data System (ADS)

    Port, U.; Claussen, M.; Brovkin, V.

    2015-03-01

    Using the Max Planck Institute for Meteorology Earth System Model, we investigate the forcing of forests and the feedback triggered by forests in the pre-industrial climate and in the early Eocene climate (about 54 to 52 million years ago). Other than the interglacial, pre-industrial climate, the early Eocene climate was characterised by high temperatures which led to almost ice-free poles. We compare simulations in which all continents are covered either by dense forest or by bare soil. To isolate the effect of soil albedo, we choose either bright soils or dark soils, respectively. Considering bright soil, forests warm in both, the early Eocene climate and the current climate, but the warming differs due to differences in climate feedbacks. The lapse-rate and water-vapour feedback is stronger in early Eocene climate than in current climate, but strong and negative cloud feedbacks and cloud masking in the early Eocene climate outweigh the stronger positive lapse-rate and water-vapour feedback. In the sum, global mean warming is weaker in the early Eocene climate. Sea-ice related feedbacks are weak in the almost ice-free climate of the early Eocene leading to a weak polar amplification. Considering dark soil, our results change. Forests cools stronger in the early Eocene climate than in the current climate because the lapse-rate and water-vapour feedback is stronger in the early Eocene climate while cloud feedbacks and cloud masking are equally strong in both climates. The different temperature change by forest in both climates highlights the state-dependency of vegetation's impact on climate.

  7. Isostatic compensation of equatorial highlands on Venus

    NASA Technical Reports Server (NTRS)

    Kucinskas, Algis B.; Turcotte, Donald L.

    1994-01-01

    Spherical harmonic models for Venus' global topography and gravity incorporating Magellan data are used to test isostatic compensation models in five 30 deg x 30 deg regions representative of the main classes of equatorial highlands. The power spectral density for the harmonic models obeys a power-law scaling with spectral slope Beta approximately 2 (Brown noise) for the topography and Beta approximately 3 (Kaula's law) for the geoid, similar to what is observed for Earth. The Venus topography spectrum has lower amplitudes than Earth's which reflects the dominant lowland topography on Venus. Observed degree geoid to topography ratios (GTRs) on Venus are significantly smaller than degree GTRs for uncompensated topography, indicative of substantial compensation. Assuming a global Airy compensation, most of the topography is compensated at depths greater than 100 km, suggesting a thick lithosphere on Venus. For each region considered we obtain a regional degree of compensation C from a linear regression of Bouguer anomaly versus Bouguer gravity data. Geoid anomaly (N) versus topography variation (h) data for each sample were compared, in the least-squares sense, to theoretical correlations for Pratt, Airy, and thermal thinning isostasy models yielding regional GTR, zero-elevation crustal thickness (H), and zero elevation thermal lithosphere thickness (y(sub L(sub 0)), respectively. We find the regional compensation to be substantial (C approximately 52-80%), and the h, N data correlations in the chosen areas can be explained by isostasy models applicable on the Earth and involving variations in crustal thickness (Airy) and/or lithospheric (thermal thinning) thickness. However, a thick crust and lithosphere (y(sub L(sub 0)) approximately 300 km) must be assumed for Venus.

  8. Equatorial Kelvin Waves: A UARS MLS View.

    NASA Astrophysics Data System (ADS)

    Canziani, Pablo O.; Holton, James R.; Fishbein, Evan; Froidevaux, Lucien; Waters, Joe W.

    1994-10-01

    Data from the Microwave Limb Sounder instrument on the Upper Atmosphere Research Satellite are used to compare two periods of Kelvin wave activity during different stages of the equatorial quasi-biennial oscillation. The analysis is carried out using an asynoptic mapping technique. A wide bandpass filter is used to isolate the frequency bands where Kelvin waves have been identified in previous studies. Time-height and time-latitude plots of the bandpassed data are used to identify Kelvin wave activity in the temperature and ozone fields. Frequency spectra of temperature and ozone amplitudes are constructed to further analyze the latitudinal and meridional distribution of Kelvin wave activity in zonal wavenumbers 1 and 2. The characteristics identified in these plots agree well with theoretical predictions and previous observations of middle atmosphere Kelvin waves.The time-height and time-latitude plots support the existence of Kelvin waves in discrete frequency bands; the slow, fast, and ultrafast Kelvin modes are all identified in the data. The characteristics of these modes do not vary much despite different mean flow conditions in the two periods examined.For the Kelvin wave-induced perturbations in ozone, the change from a transport-dominated regime below 10 hPa to a photochemically controlled regime above 10 hPa is clearly apparent in the height dependence of the phase difference between temperature and ozone. The ratios of the ozone perturbation amplitude to the temperature perturbation amplitude for the various observed Kelvin wave modes are in agreement with model estimates and LIMS (Limb Infrared Monitor of the Stratosphere) observations in the lower half of the region sampled but appear to be too large in the upper stratosphere and lower mesosphere.

  9. Equatorial Kelvin waves: A UARS MLS view

    NASA Technical Reports Server (NTRS)

    Canziani, Pablo O.; Holton, James R.; Fishbein, Evan; Froidevaux, Lucien; Waters, Joe W.

    1994-01-01

    Data from the Microwave Limb Sounder (MLS) instrument on the Upper Atmosphere Research Satellite (UARS) are used to compare two periods of Kelvin wave activity during different stages of the equatorial quasi-biennial oscillation. The analysis is carried out using an asynoptic mapping technique. A wide bandpass filter is used to isolate the frequency bands where Kelvin waves have been identified in previous studies. Time-height and time-latitude plots of the bandpassed data are used to identify Kelvin wave activity in the temperature and ozone fields. Frequency spectra of temperature and ozone amplitudes are constructed to further analyze the latitudinal and meridional distribution of Kelvin wave activity in zonal wavenumbers 1 and 2. The characteristics identified in these plots agree well with theoretical predictions and previous observations of middle atmosphere Kelvin waves. The time-height and time-latitude plots support the existence of Kelvin waves in discrete frequency bands; the slow, fast, and ultrafast Kelvin modes are all identified in the data. The characteristics of these modes do not vary much despite different mean flow conditions in the two periods examined. For the Kelvin wave-induced perturbations in ozone, the change from a transport-dominated regime below 10 hPa to a photochemically controlled regime above 10 hPa is clearly apparent in the height dependence of the phase difference between temperature and ozone. The ratios of the ozone perturbation amplitude to the temperature perturbation amplitude for the various observed Kelvin wave modes are in agreement with model estimates and LIMS (Limb Infrared Monitor of the Stratosphere) observations in the lower half of the region sampled but appear to be too large in the upper stratosphere and lower mesosphere.

  10. Climatology of equatorial stratosphere over Lagos, Nigeria

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi Samuel

    We have used 12 complete calendar years (January 1993-December 2004) of monthly averages of measurements made by the Dobson spectrophotometer instrument over an urban site, Lagos (6.6oN, 3.3oE), southwest Nigeria, to study equatorial stratospheric column ozone variations and trends. Our results indicate that the time-averaged total column ozone has a seasonal cy-cle, which maximizes in June and July with a value of 259 Dobson units (DU) and minimizes in February with a magnitude of 250 DU. Statistical analysis of the climatological mean monthly total Dobson O3 record for 1993-2004 show that the local trend is approximately +0.041±0.0011 DU/year (+0.49±0.013% per decade). Spectral analysis was applied to the monthly averages series. The significant periodicity at 95% confidence level demonstrate prominent spectra peaks near 1.9 and 3.6 years, representative of quasi-biennial oscillation (QBO) and quasi-triennial oscillation (QTO), respectively. Signal due to semiannual variation is also identified at Lagos sounding site. Comparison with the ozone observations from Total Ozone Mapping Spectrom-eter (TOMS) on board the Earth-Probe (EP) satellite for the period from 1997 to 2002 reveal that EP/TOMS instrument consistently larger than the ground-based measurement from Dob-son station. Percentage mean relative disparity ranges from -11% to 15%. The root mean square error (RMSE) between satellite and ground-based observations over Lagos ranges be-tween ˜35-83 DU with largest and lowest variability occurring during the ascending phase of solar activity (1999, 10.7 cm radio flux, F10.7 equals 154 flux units) and during the peak phase of solar activity (2001, F10.7 equals 181), respectively.

  11. Rain-rate data base development and rain-rate climate analysis

    NASA Technical Reports Server (NTRS)

    Crane, Robert K.

    1993-01-01

    The single-year rain-rate distribution data available within the archives of Consultative Committee for International Radio (CCIR) Study Group 5 were compiled into a data base for use in rain-rate climate modeling and for the preparation of predictions of attenuation statistics. The four year set of tip-time sequences provided by J. Goldhirsh for locations near Wallops Island were processed to compile monthly and annual distributions of rain rate and of event durations for intervals above and below preset thresholds. A four-year data set of tropical rain-rate tip-time sequences were acquired from the NASA TRMM program for 30 gauges near Darwin, Australia. They were also processed for inclusion in the CCIR data base and the expanded data base for monthly observations at the University of Oklahoma. The empirical rain-rate distributions (edfs) accepted for inclusion in the CCIR data base were used to estimate parameters for several rain-rate distribution models: the lognormal model, the Crane two-component model, and the three parameter model proposed by Moupfuma. The intent of this segment of the study is to obtain a limited set of parameters that can be mapped globally for use in rain attenuation predictions. If the form of the distribution can be established, then perhaps available climatological data can be used to estimate the parameters rather than requiring years of rain-rate observations to set the parameters. The two-component model provided the best fit to the Wallops Island data but the Moupfuma model provided the best fit to the Darwin data.

  12. Biochronology and paleoclimatic implications of Middle Eocene to Oligocene planktic foraminiferal faunas

    USGS Publications Warehouse

    Keller, G.

    1983-01-01

    Planktic foraminiferal assemblages have been analyzed quantitatively in six DSDP sites in the Atlantic (Site 363), Pacific (Sites 292, 77B, 277), and Indian Ocean (Sites 219, 253) in order to determine the nature of the faunal turnover during Middle Eocene to Oligocene time. Biostratigraphic ranges of taxa and abundance distributions of dominant species are presented and illustrate striking similarities in faunal assemblages of low latitude regions in the Atlantic, Pacific and Indian oceans. A high resolution biochronology, based on dominant faunal characteristics and 55 datum events, permits correlation between all three oceans with a high degree of precision. Population studies provide a view of the global impact of the paleoclimatic and paleoceanographic changes occurring during Middle Eocene to Oligocene time. Planktic foraminiferal assemblage changes indicate a general cooling trend between Middle Eocene to Oligocene time, consistent with previously published oxygen isotope data. Major faunal changes, indicating cooling episodes, occur, however, at discrete intervals: in the Middle Eocene 44-43 Ma (P13), the Middle/Late Eocene boundary 41-40 Ma ( P14 P15), the Late Eocene 39-38 Ma ( P15 P16), the Eocene/Oligocene boundary 37-36 Ma (P18), and the Late Oligocene 31-29 Ma ( P20 P21). With the exception of the E 0 boundary, faunal changes occur abruptly during short stratigraphic intervals, and are characterized by major species extinctions and first appearances. The Eocene/Oligocene boundary cooling is marked primarily by increasing abundances of cool water species. This suggests that the E 0 boundary cooling, which marks a major event in the oxygen isotope record affected planktic faunas less than during other cooling episodes. Planktic foraminiferal faunas indicate that the E 0 boundary event is part of a continued cooling trend which began during the Middle Eocene. Two hiatus intervals are recognized in low and high latitude sections at the Middle/Late Eocene

  13. Eocene oceanic responses to orbital forcing on precessional time scales

    NASA Astrophysics Data System (ADS)

    Sloan, L. Cirbus; Huber, Matthew

    2001-02-01

    The goal of our study was to gain an estimate of the variability of ocean-related climate processes driven by insolation forcing over a realistic precessional cycle in an Eocene greenhouse world. Between endmembers of a precessional cycle mean annual sea surface temperatures (SSTs) vary by up to 5°C at high northern latitudes, with minimal tropical SST response. Extratropical regions of the Pacific, Atlantic, and Tethys Oceans show up to a two-fold variation in upwelling strength, while oceanic regions adjacent to northwestern Africa, India, and South America exhibit little oceanic upweliing variability. The response of ocean surface moisture balance to the forcing is greatest in the tropics, varying by as much as 60%. Continental runoff varies by up to a factor of two in some regions. These results may be useful in identifying locations with maximum likelihood of future recovery of orbital cyclicity in deep-sea sediments.

  14. Identification of Late Eocene Impact Deposits at ODP Site 1090

    NASA Technical Reports Server (NTRS)

    Kyte, Frank T.

    2001-01-01

    Anomalous concentrations of Ir have been found in upper Eocene sediments from Ocean Drilling Program (ODP) Hole 1090B. Clear and dark-colored spherules that are believed to be microtektites and clinopyroxene- bearing microkrystites, respectively, were found in the samples with highest Ir. The peak Ir concentration in Sample 177- 1090B-30X-5,105-106 cm (954 pg/g) and the net Ir fluence (14 ng/cm2) at this site are higher that at most other localities except for Caribbean site RC9-58. The Ir anomaly and impact debris are probably correlative with similar deposits found at ODP Site 689 on the Maude Rise and at other localities around the world.

  15. High latitude hydrological changes during the Eocene Thermal Maximum 2

    NASA Astrophysics Data System (ADS)

    Krishnan, Srinath; Pagani, Mark; Huber, Matthew; Sluijs, Appy

    2014-10-01

    The Eocene hyperthermals, including the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM2), represent extreme global warming events ∼56 and 54 million years ago associated with rapid increases in atmospheric greenhouse gas concentrations. An initial study on PETM characteristics in the Arctic region argued for intensification of the hydrological cycle and a substantial increase in poleward moisture transport during global warming based on compound-specific carbon and hydrogen isotopic (2H/1H) records from sedimentary leaf-wax lipids. In this study, we apply this isotopic and hydrological approach on sediments deposited during ETM2 from the Lomonosov Ridge (Integrated Ocean Drilling Program Expedition 302). Our results show similar 2H/1H changes during ETM2 as during the PETM, with a period of 2H-enrichment (∼20‰) relative to “pre-event” values just prior to the negative carbon isotope shift (CIE) that is often taken as the onset of the hyperthermal, and more negative lipid δ2H values (∼-15‰) during peak warming. Notably, lipid 2H-enrichment at the base of the event is coeval with colder TEX86H temperatures. If 2H/1H values of leaf waxes primarily reflect the hydrogen isotopic composition of precipitation, the observed local relationship between temperature and 2H/1H values for the body of ETM2 is precisely the opposite of what would be predicted using a simple Rayleigh isotope distillation model, assuming a meridional vapor trajectory and a reduction in equator-pole temperature gradients. Overall, a negative correlation exists between the average chain length of n-alkanes and 2H/1H suggesting that local changes in ecology could have impacted the hydrogen isotopic compositions of leaf waxes. The negative correlation falls across three separate intervals - the base of the event, the initial CIE, and during the H2 hyperthermal (of which the assignment is not fully certain). Three possible mechanisms potentially explain 2H

  16. Geochemical evidence for a comet shower in the late Eocene.

    PubMed

    Farley, K A; Montanari, A; Shoemaker, E M; Shoemaker, C S

    1998-05-22

    Analyses of pelagic limestones indicate that the flux of extraterrestrial helium-3 to Earth was increased for a 2.5-million year (My) period in the late Eocene. The enhancement began approximately 1 My before and ended approximately 1.5 My after the major impact events that produced the large Popigai and Chesapeake Bay craters approximately 36 million years ago. The correlation between increased concentrations of helium-3, a tracer of fine-grained interplanetary dust, and large impacts indicates that the abundance of Earth-crossing objects and dustiness in the inner solar system were simultaneously but only briefly enhanced. These observations provide evidence for a comet shower triggered by an impulsive perturbation of the Oort cloud.

  17. Geochemical evidence for a comet shower in the late Eocene

    USGS Publications Warehouse

    Farley, K.A.; Montanari, A.; Shoemaker, E.M.; Shoemaker, C.S.

    1998-01-01

    Analyses of pelagic limestones indicate that the flux of extraterrestrial helium-3 to Earth was increased for a 2.5-million year (My) period in the late Eocene. The enhancement began ~1 My before and ended ~1.5 My after the major impact events that produced the large Popigai and Chesapeake Bay craters ~36 million years ago. The correlation between increased concentrations of helium-3, a tracer of fine-grained interplanetary dust, and large impacts indicates that the abundance of Earth-crossing objects and dustiness in the inner solar system were simultaneously but only briefly enhanced. These observations provide evidence for a comet shower triggered by an impulsive perturbation of the Oort cloud.

  18. Cretaceous and Eocene poroid hymenophores from Vancouver Island, British Columbia.

    PubMed

    Smith, Selena Y; Currah, Randolph S; Stockey, Ruth A

    2004-01-01

    Two fossil poroid hymenophore fragments, one from the Cretaceous Period and the other from the Eocene Epoch, are described. The permineralized specimens were obtained from marine calcareous concretions on Vancouver Island, British Columbia, Canada, and were studied using the cellulose acetate peel technique. Size and distribution of pores in the hymenophores, as well as the hyphal anatomy of the dissepiments and some hymenial elements, were examined. In the Cretaceous specimen, Quatsinoporites cranhamii sp. nov., pores are round to elliptical, three per mm, and 130-540 μm diam. Dissepiments consist of narrow, simple septate, hyphae. Neither basidia nor basidiospores are present, but acuminate hymenial cystidia, up to 54 μm in length, are common. The Eocene specimen, Appianoporites vancouverensis sp. nov., has a pore density of six per mm and pores are 130-163 μm in diam. Dissepiments consist of narrow, simple septate, thin-walled hyphae. Neither basidia nor basidiospores are present, but acuminate, thick-walled hymenial cystidia, up to 32 μm in length, are common. The poroid hymenophore is a characteristic of a number of extant basidiomycete taxa, including the Boletales, Polyporales and Hymenochaetales. It is unlikely that the fleshy, ephemeral, terrestrial basidiomata of the Boletales would be preserved in a marine environment, and thus the specimens are interpreted as belonging to basidiomycete lineages, with persistent, leathery or corky basidiomata. The simple septate hyphae, the minute pores and presence of cystidia most closely resemble taxa of the Hymenochaetales. These fossils unequivocally push back the minimum age of homobasidiomycetes and extend their paleogeographical range.

  19. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 16 2011-07-01 2011-07-01 false General Acid Rain Program provisions. 76.3 Section 76.3 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program...

  20. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false General Acid Rain Program provisions. 76.3 Section 76.3 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program...

  1. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 17 2013-07-01 2013-07-01 false General Acid Rain Program provisions. 76.3 Section 76.3 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program...

  2. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 17 2014-07-01 2014-07-01 false General Acid Rain Program provisions. 76.3 Section 76.3 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program...

  3. 40 CFR 76.3 - General Acid Rain Program provisions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 17 2012-07-01 2012-07-01 false General Acid Rain Program provisions. 76.3 Section 76.3 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) ACID RAIN NITROGEN OXIDES EMISSION REDUCTION PROGRAM § 76.3 General Acid Rain Program...

  4. Effects of acid rain on crops and trees

    SciTech Connect

    Cowling, E.B.; Dochinger, L.S.

    1984-01-01

    A general treatment of the subject of acid rain and its effets are discussed along with sources of acid rain and its near-term (the last couple of decades). The effects of acid rain on terrestrial ecosystems are treated in some detail. Some treatment is given of the ecosystem-level effects of acid precipitation.

  5. 14 CFR 33.78 - Rain and hail ingestion.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Rain and hail ingestion. 33.78 Section 33... AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.78 Rain and... rain and hail, as defined in appendix B to this part. Acceptable engine operation precludes...

  6. 14 CFR 33.78 - Rain and hail ingestion.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rain and hail ingestion. 33.78 Section 33... AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.78 Rain and... rain and hail, as defined in appendix B to this part. Acceptable engine operation precludes...

  7. 14 CFR 33.78 - Rain and hail ingestion.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Rain and hail ingestion. 33.78 Section 33... AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.78 Rain and... rain and hail, as defined in appendix B to this part. Acceptable engine operation precludes...

  8. 14 CFR 33.78 - Rain and hail ingestion.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Rain and hail ingestion. 33.78 Section 33... AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.78 Rain and... rain and hail, as defined in appendix B to this part. Acceptable engine operation precludes...

  9. 14 CFR 33.78 - Rain and hail ingestion.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Rain and hail ingestion. 33.78 Section 33... AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.78 Rain and... rain and hail, as defined in appendix B to this part. Acceptable engine operation precludes...

  10. The Effects of Rain Garden Size on Performance

    EPA Science Inventory

    The presentation discusses the effect of rain garden size on the hydrologic and pollutant removal performance of rain garden systems. The slides will summarize data from both the full-scale rain garden project associated with the permeable pavement parking lot as well as the pilo...

  11. More on accreting black hole spacetime in equatorial plane

    NASA Astrophysics Data System (ADS)

    Salahshoor, K.; Nozari, K.; Khesali, A. R.

    2017-02-01

    Spacetime around an accreting black hole is an interesting issue to study. The metric of an isolated black hole (rotating or non-rotating) spacetime has been well-known for decades. Although metrics of some spacetimes containing accreting black holes are known in some situations, the issue has some faces that are not well-known yet and need further investigation. In this paper, we construct a new form of metric which the effect of accretion disk on black hole spacetime is taken into account in the equatorial plane. We study motion and trajectories of massive particles and also photons falling from infinity towards black hole in equatorial plane around the black hole. We use an exponential form for the density profile of the accretion disk in equatorial plane as ρ =ρ0e^{-α r}. We show that with this density profile, the disk is radially stable if α ≤ 3 × 10^{-3} (in units of length inverse). In order to study some important quantities related to the accretion disks such as locations of marginally stable circular orbits (r_{ms} or r_{ISCO}), marginally bounded circular orbits (r_{mb}), and also photon orbits in equatorial plane, we use the effective potential approach. We show that in this spacetime metric the innermost stable circular orbit in equatorial plane is given by r_{ISCO}=4.03 μ (where μ =MG/c 2) which is different, but comparable, with the Schwarzschild spacetime result, r^{(Sch)}_{ISCO}=6 μ . We show that the maximum radiation efficiency of the accretion disk, η , in equatorial plane is 8.6 percent which is greater than the corresponding value for Schwarzschild spacetime. Finally, we show that in this setup photons can have stable circular orbits in equatorial plane unlike the Schwarzschild spacetime.

  12. Polar and equatorial ionosphere interaction during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Biktash, L.

    The solar wind-magnetosphere-ionosphere coupling as applied to the polar and equatorial ionosphere dynamics is examined. To do this simultaneous observations of the IMF, ground-based measurements of the ionospheric parameters and geomagnetic field variations from the high latitudes to the equator are used during magnetic storms. It is shown that the auroral electric fields during magnetically disturbed conditions by the magnetospheric current systems can play a dominant role in the equatorial ionosphere processes. During magnetic storms the equatorial ionosphere parameters h'F, foF2 and etc. widely deviated from quiet day conditions and different kinds of ionospheric irregularities are formed. The equatorial ionospheric irregularities manifest as spread F in ionograms, reversals of drift velocities, scintillation of radio transmissions through the ionosphere, etc. These phenomena can interpret as the result of direct penetration of electric fields from the high latitude field-aligned currents (FAC) to the equatorial ionosphere. Model of direct penetration of FAC electric field of Polar Regions 1 and Region 2, which are controlled by the solar wind, to the equatorial ionosphere is presented. From this model the solar wind electric field through the FAC is likely to the factor wich generate or inhibit the equatorward penetration of the high latitude electric field. We demonstrate that the model is suitable to explain h'F, foF2 variations and scintillation activity during geomagnetic storms. Taking into account of the equatorial and auroral electric fields coupling, relationship, between these regions can be useful to study difficult auroral conditions during magnetic storms.

  13. Late Cretaceous-Early Eocene Climate Change Linked to Tectonic Eevolution of Neo-Tethyan Subduction Systems

    NASA Astrophysics Data System (ADS)

    Jagoutz, O. E.; Royden, L.; Macdonald, F. A.

    2015-12-01

    In this presentation we demonstrate that the two tectonic events in the late Cretaceous-Early Tertiary triggered the two distinct cooling events that followed the Cretaceous Thermal Maximum (CTM). During much of the Cretaceous time, the northern Neo Tethyan ocean was dominated by two east-west striking subduction system. Subduction underneath Eurasia formed a continental arc on the southern margin of Eurasia and intra oceanic subduction in the equatorial region of the Neo Tethys formed and intra oceanic arc. Beginning at ~85-90 Ma the western part of the TTSS collided southward with the Afro-Arabian continental margin, terminating subduction. This resulted in southward obduction of the peri-Arabian ophiolite belt, which extends for ~4000 km along strike and includes the Cypus, Semail and Zagros ophiolites. At the same time also the eastern part of the TTS collided northwards wit Eurasia. After this collisional event, only the central part of the subduction system remained active until it collided with the northern margin of the Indian continent at ~50-55 Ma. The collision of the arc with the Indian margin, over a length of ~3000 km, also resulted in the obduction of arc material and ophiolitic rocks. Remnants of these rocks are preserved today as the Kohistan-Ladakh arc and ophiolites of the Indus-Tsangpo suture zone of the Himalayas. Both of these collision events occurred in the equatorial region, near or within the ITCZ, where chemical weathering rates are high and are contemporaneous with the onset of the global cooling events that mark the end of the CTM and the EECO. The tectonic collision events resulted in a shut down of subduction zone magmatism, a major CO2 source and emplacement of highly weatherable basaltic rocks within the ITCZ (CO2 sink). In order to explore the effect of the events in the TTSS on atmospheric CO2, we model the potential contribution of subduction zone volcanism (source) and ophiolite obduction (sink) to the global atmospheric CO2

  14. The geography of diversification in mutualistic ants: a gene's-eye view into the Neogene history of Sundaland rain forests.

    PubMed

    Quek, S-P; Davies, S J; Ashton, P S; Itino, T; Pierce, N E

    2007-05-01

    We investigate the geographical and historical context of diversification in a complex of mutualistic Crematogaster ants living in Macaranga trees in the equatorial rain forests of Southeast Asia. Using mitochondrial DNA from 433 ant colonies collected from 32 locations spanning Borneo, Malaya and Sumatra, we infer branching relationships, patterns of genetic diversity and population history. We reconstruct a time frame for the ants' diversification and demographic expansions, and identify areas that might have been refugia or centres of diversification. Seventeen operational lineages are identified, most of which can be distinguished by host preference and geographical range. The ants first diversified 16-20 Ma, not long after the onset of the everwet forests in Sundaland, and achieved most of their taxonomic diversity during the Pliocene. Pleistocene demographic expansions are inferred for several of the younger lineages. Phylogenetic relationships suggest a Bornean cradle and major axis of diversification. Taxonomic diversity tends to be associated with mountain ranges; in Borneo, it is greatest in the Crocker Range of Sabah and concentrated also in other parts of the northern northwest coast. Within-lineage genetic diversity in Malaya and Sumatra tends to also coincide with mountain ranges. A series of disjunct and restricted distributions spanning northern northwest Borneo and the major mountain ranges of Malaya and Sumatra, seen in three pairs of sister lineages, further suggests that these regions were rain-forest refuges during drier climatic phases of the Pleistocene. Results are discussed in the context of the history of Sundaland's rain forests.

  15. Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America

    NASA Astrophysics Data System (ADS)

    Münnich, M.; Neelin, J. D.

    2005-11-01

    In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

  16. Differing Eocene floral histories in southeastern North America and Western Europe: influence of paleogeography

    USGS Publications Warehouse

    Frederiksen, N.O.

    1995-01-01

    Pollen data show that in southeastern North America, the Eocene angiosperm flora attained its maximum relative diversity some 8 m.y. after the late early Eocene to earliest middle Eocene to earliest middle Eocene climatic maximum. Increasing diversity resulted in part from the flora's position on a large continent which allowed easy migration. In western Europe, the floral diversity began decreasing even before the climatic maximum. Paleogeography played large roles in this diversity decrease. In western Europe, terrestrial floras were on islands and peninsulas in the sea, so that the floras underwent increasing isolation and partial local extermination. Temperate plants generally did not migrate to western Europe, because of a lack of nearby uplands, lack of northern terrestrial source areas for these plants, and presence of the Turgai Straights barrier. -from Authors

  17. Microfloral diversity patterns of the late Paleocene Eocene interval in Colombia, northern South America

    NASA Astrophysics Data System (ADS)

    Jaramillo, Carlos A.; Dilcher, David L.

    2000-09-01

    The late Paleocene early Eocene interval was characterized by a long period of global warming that culminated with the highest temperatures of the Tertiary. This interval was also associated with plant extinctions and a subsequent increase in plant diversity in temperate latitudes. However, tropical regions remain largely unknown. We compare the microfloral diversity of the late Paleocene with the late early to middle Eocene in flood plain, coastal plain, and estuarine facies of a section in the Colombian eastern Andes. Several techniques such as range-through method, rarefaction, bootstrap, detrended correspondence analysis, and Simpson index were used to assess the significance of the diversity pattern observed throughout the section. The microfloral record indicates a distinct, diverse Paleocene flora declining toward the end of the Paleocene, being replaced by a different and much more diverse Eocene flora. It is uncertain, however, how these floral changes correlate with the latest Paleocene thermal maximum and Eocene thermal maximum events.

  18. Sources of variability in equatorial topside ionospheric and plasmaspheric temperatures

    NASA Astrophysics Data System (ADS)

    Varney, Roger H.; Hysell, David L.; Huba, J. D.

    2013-10-01

    Jicamarca measurements of electron temperatures at high altitudes (500-1500km) from the last solar minimum routinely show variations of hundreds of Kelvin from day-to-day. Possible sources of these variations are explored using the SAMI2-PE is another model of the ionosphere including photoelectron transport (SAMI2-PE) model, which includes a multistream photoelectron transport model. Changes to the electric fields, meridional winds, and thermospheric densities can all change the electron densities and temperatures at high altitudes. The high altitude electron temperatures are primarily determined by a balance between heating from photoelectrons which travel up the field lines and thermal diffusion which carries heat back down the field lines. The winds and electric fields will change the altitude and densities of the off-equatorial F-region peaks, especially on the field lines connected to the equatorial arcs. The densities and temperatures in the plasmasphere will self consistently adjust themselves to achieve diffusive equilibrium with the off-equatorial F-regions. Furthermore, decreases in the density and/or altitude of the F-region makes it easier for photoelectrons to escape to high altitudes. These connections between the equatorial plasmasphere, the off-equatorial F-regions, and the neutral thermosphere suggest that high altitude measurements at Jicamarca could be used to study thermospheric variability.

  19. Equatorial Winds on Saturn and the Stratospheric Oscillation

    NASA Technical Reports Server (NTRS)

    Li, Liming; Jian, Xun; Ingersoll, Andrew P.; DelGenio, Anthony D.; Porco, Carolyn C.; West, Robert A.; Vasavada, Ashwin R.; Ewald, Shawn P.; Conrath, Barney J.; Gierasch, Peter J.; Simon-Miller, Amy A.; Nixon, Conor A.; Achterberg, Richard K.; Orton, Glenn S.; Fletcher, Leigh N.; Baines, Kevin H.

    2011-01-01

    The zonal jets on the giant planets are generally thought to be stable with time. Recently, there are still some debates about the general thought. Here, we report a significant temporal variation of the equatorial jet at high-altitude on Saturn. Long-term (2004-2009) observations by Cassini reveal that wind speed at the 60-mbar level increased from 270 m/s in 2004 to 290 m/s in 2008, while the wind speed has been mostly constant over time at the 500-mbar level in the southern equatorial region. The Cassini observations further reveal that the equatorial jet intensified approximately 60 m/s in the stratosphere (1-5 mbar) from 2005 to 2008. The fact that the wind acceleration is weaker at the 60-mbar level (approximately 20 m/s) than at the 1-mbar level (approximately 60 m/s) demonstrates that the equatorial oscillation is damped when it propagates downwards to the tropopause around 60 mbar. The direct measurement of the varying equatorial jet around the tropopause also serves as a key boundary condition when deriving the thermal wind fields in the stratosphere.

  20. Meridional equatorial electrojet current in the American sector

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1999-02-01

    Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H) is associated with a simultaneous increase of eastward geomagnetic field (Y). It is shown that during the counter electrojet period when H is negative, Y also becomes negative. Thus, the diurnal variation of Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej). At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej), a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.

  1. Equatorial Mountain Torques and Cold Surges in a GCM

    NASA Astrophysics Data System (ADS)

    Lott, Francois; Mailler, Sylvain

    2014-05-01

    The dynamical relations between the equatorial atmospheric angular momentum, the equatorial mountain torque and the cold surges are analysed in a General Circultaion Model (GCM). First we show that the global equatorial atmospheric momentum budget is very well closed in the model which is a clear benefit when we compare with results from the NCEP reanalysis. We then confirm that the equatorial torques due to the Tibetan plateau, the Rockies and the Andes are well related to the cold surges developping over South Eastern China, North America, and the Southern South America respectively. For all these mountains, a peack in the Equatorial mountain torque component that points locally toward the pole preceeds by few days the development of the cold surges, yielding a predictive interest to our results. We also analyse the contributions to the torques of the parameterized mountain stresses and find that they contribute substantially. In experiments without the parameterized stresses, we also find that the explicit terms partly compensate the parameterized contributions to the torque, and the cold surges are not much affected. This shows that the cold surges can be well captured by models, providing that the synoptic conditions prior to their onset are well represented. The compensation between torques is nevertheless not complete and some weekening of the cold surges is found when the mountain forcings are reduced. This illustrates how the exact torques are needed at a given time to produce the correct synoptic scale dynamics at a later stage.

  2. Variability in climate and productivity during the Paleocene-Eocene Thermal Maximum in the western Tethys (Forada section)

    NASA Astrophysics Data System (ADS)

    Giusberti, L.; Boscolo Galazzo, F.; Thomas, E.

    2016-02-01

    arid climate, characterized by strong winds and intense upwelling, and an overall humid climate, with abundant rains and high sediment delivery (including refractory organic carbon) from land. Precessionally paced marl-limestone couplets occur throughout the recovery interval of the carbon isotope excursion (CIE) and up to 10 m above it, suggesting that these wet-dry cycles persisted, though at declining intensity, after the peak PETM. Enhanced climate extremes at mid-latitudes might have been a direct response to the massive CO2 input in the ocean atmosphere system at the Paleocene-Eocene transition, and may have had a primary role in restoring the Earth system to steady state.

  3. Benthic foraminifera at the Paleocene/Eocene thermal maximum in the western Tethys (Forada section): variability in climate and productivity

    NASA Astrophysics Data System (ADS)

    Giusberti, L.; Boscolo Galazzo, F.; Thomas, E.

    2015-09-01

    overall arid climate, characterized by strong winds and intense upwelling, with an overall humid climate, with abundant rains and high sediment delivery (including refractory organic carbon) from land. Precessionally paced marl-limestone couplets occur throughout the recovery interval of the CIE and up to ten meters above it, suggesting that these wet-dry cycles persisted, though at declining intensity, after the peak PETM. Enhanced climate extremes at mid-latitudes might have been a direct response to the massive CO2 input in the ocean atmosphere system at the Paleocene-Eocene transition, and may have had a primary role in restoring the Earth system to steady state.

  4. Inter- annual variability of water vapor over an equatorial coastal station using Microwave Radiometer observations.

    NASA Astrophysics Data System (ADS)

    Renju, Ramachandran Pillai; Uma, K. N.; Krishna Moorthy, K.; Mathew, Nizy; Raju C, Suresh

    The south-western region of the Indian peninsula is the gateway of Indian summer monsoon. This region experiences continuous monsoon rain for a longer period of about six months from June to November. The amount of water vapor variability is one of the important parameters to study the onset, active and break phases of the monsoon. Keeping this in view, a multi-frequency Microwave Radiometer Profiler (MRP) has been made operational for continuous measurements of water vapor over an equatorial coastal station Thiruvananthapuram (8.5(°) N, 76.9(°) E) since April 2010. The MRP estimated precipitable water vapor (PWV) for different seasons including monsoon periods have been evaluated by comparing with the collocated GPS derived water vapor and radiosonde measurements. The diurnal, seasonal and inter annual variation of water vapor has been studied for the last four years (2010-2013) over this station. The significant diurnal variability of water vapor is found only during the winter and pre-monsoon periods (Dec -April). The vertical distribution of water vapour is studied in order to understand its variability especially during the onset of monsoon. During the building up of south-west monsoon, the specific humidity increases to ˜ 10g/kg in the altitude range of 4-6 km and consistently maintained it throughout the active spells and reduces to below 2g/kg during break spells of monsoon. The instrument details and the results will be presented.

  5. State acid rain permitting programs: A report from EPA

    SciTech Connect

    Miller, R.L.

    1995-12-31

    States and EPA are laying the groundwork for state acid rain permitting in Phase 2 of the Acid Rain Program. Early indications suggest a high degree of state compliance with the acid rain permitting requirements of the Acid Rain Program. Phase 2 acid rain permitting forms have been revised and are available on EPA`s Technology Transfer Network. EPA has developed a policy and rationale concerning submission of Phase 2 permit applications, as well as suggested state timing and methodology regarding adoption of 40 CFR Part 76, the NO{sub x} regulation.

  6. The Acid Rain Program: Monitoring the future

    SciTech Connect

    Bloomer, B.J.

    1995-12-31

    This paper presents a summary of the development of the Acid Rain Program`s approach to Continuous Emissions Monitoring Systems (CEMS) and their use in the market based pollution control program of Title IV of the Clean Air Act Amendments of 1990. The roles of the regulatory agencies are discussed and projections are put forward as to how the roles will evolve over time. In addition a discussion of the activities the regulated community is expected to focus on is presented. Finally, a discussion occurs about the requirements that new technologies and instrument providers and purchasers should keep in mind about the Acid Rain Program`s monitoring requirements as they attempt to bring new products into this market.

  7. Climatology tuned reflectivity-rain rate relations

    NASA Technical Reports Server (NTRS)

    Short, David A.; Rosenfeld, Daniel; Atlas, David

    1989-01-01

    The climatologically-tuned relationships between reflectivity, Z, and rain rate, R, are examined. A method is presented which selects the Z-R relation that assures that the values of R are weighted according to their climatological frequency of occurrence. The method is an extension of the approach suggested by Calheiros and Zawadski (1987). Also, consideration is given to the method of optimizing Z-R relations by matching hourly gage and radar-deduced rain amounts proposed by Smith et al. (1975). These two methods are described and applied to data from Germany and from the GARP Atlantic Tropical Experiment. The differences in the Z-R relations obtained using the two approaches are discussed.

  8. Fraud in the acid rain debate

    SciTech Connect

    Bagge, C.

    1984-06-01

    Electric utility executives, according to the author, and millions of other Americans are the victims of a gigantic fraud being carried on in the name of controlling acid rain. This fraud, states the author, involves the distorted, dire image of acidity in nature being created by environmental groups, politicians and others - to gain public sympathy for their legislative goals. The alleged fraud involves the very nature of the legislation being promoted as a low-cost cure for acid rain. On the basis of scientific evidence to date there is no assurance it will reduce acidity by any appreciable amount, but on the other hand it most certainly will cost users of electricity hundreds of billions of dollars in new costs. What has already happened to the nuclear industry is also meant for coal.

  9. A scattering model for rain depolarization

    NASA Technical Reports Server (NTRS)

    Wiley, P. H.; Stutzman, W. L.; Bostian, C. W.

    1973-01-01

    A method is presented for calculating the amount of depolarization caused by precipitation for a propagation path. In the model the effects of each scatterer and their interactions are accounted for by using a series of simplifying steps. It is necessary only to know the forward scattering properties of a single scatterer. For the case of rain the results of this model for attenuation, differential phase shift, and cross polarization agree very well with the results of the only other model available, that of differential attenuation and differential phase shift. Calculations presented here show that horizontal polarization is more sensitive to depolarization than is vertical polarization for small rain drop canting angle changes. This effect increases with increasing path length.

  10. NASA's DC-8 With Rain Mapping Radar

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In a joint venture between NASA and Japan's NASDA, scientists have been using satellites, airplanes, and boats to measure rain physics in and under thunderstorms over open water. This Quick Time movie shows the ER-2, a high altitude reconnaissance aircraft equipped with 8 lightening detectors and other instruments used to study hurricanes and thunderstorms. Earth science and weather studies are an important ongoing function of NASA and its affiliates.

  11. Simulator Of Rain In Flowing Air

    NASA Technical Reports Server (NTRS)

    Clayton, Richard M.; Cho, Young I.; Shakkottai, Parthasarathy; Back, Lloyd H.

    1989-01-01

    Report describes relatively inexpensive apparatus that creates simulated precipitation from drizzle to heavy rain in flowing air. Small, positive-displacement pump and water-injecting device positioned at low-airspeed end of converging section of wind tunnel 10 in. in diameter. Drops injected by array entrained in flow of air as it accelerates toward narrower outlet, 15 in. downstream. Outlet 5 in. in diameter.

  12. Acid rain in Shenandoah National Park, Virginia

    USGS Publications Warehouse

    Rice, Karen C.; Deviney, Frank A.; Olson, Gordon

    2007-01-01

    Visitors to Shenandoah National Park (SNP) enjoy the animal and plant life and the scenery but may not realize how vulnerable these features are to various threats, such as invasion of exotic plants and insects, improper use of park resources by humans, and air and water pollution. The National Park Service strives to protect natural resources from such threats to ensure that the resources will be available for enjoyment now and in the future. Because SNP has limited influence over the air pollution that envelops the region, acidic deposition--commonly known as acid rain--is one of the more challenging threats facing park managers. With the help of U.S. Geological Survey (USGS) scientists, park managers can understand how acid rain interacts with ground- and surface-water resources, which enables them to explain why reductions in air pollution can help preserve park resources. Such understanding also provides essential insight into ecosystem processes, as managers strive to unravel and resolve other environmental problems that are interrelated to acid rain.

  13. Energetic photoelectrons and the polar rain

    NASA Technical Reports Server (NTRS)

    Decker, Dwight T.; Jasperse, J. R.; Winningham, J. D.

    1990-01-01

    In the daytime midlatitudes, the Low Altitude Plasma Instrument (LAPI) on board the Dynamics Explorer 2 satellite has observed photoelectrons with energies as high as 850 eV. These energetic photoelectrons are an extension of the 'classical' photoelectrons (less than 60 eV) and result from photoionization of neutrals by soft solar X-rays. Since these photoelectrons are produced wherever the solar flux is incident on the earth's atmosphere, they should be present in sunlit polar cap. But in the polar cap, over these same energies, there is a well-known electron population: the polar rain, a low intensity electron flux of magnetospheric origin. Thus, in the sunlit polar cap, an energetic population of electrons should consist of both an ionospheric (photoelectron) and a magnetospheric (polar rain) component. Using numerical solutions of an electron transport equation with appropriate boundary conditions and sunlit polar cap LAPI data, it is shown that the two populations (photoelectron and polar rain) are indeed present and are both needed to explain polar cap observations.

  14. The palaeobiology of high latitude birds from the early Eocene greenhouse of Ellesmere Island, Arctic Canada

    PubMed Central

    Stidham, Thomas A.; Eberle, Jaelyn J.

    2016-01-01

    Fossils attributable to the extinct waterfowl clade Presbyornithidae and the large flightless Gastornithidae from the early Eocene (~52–53 Ma) of Ellesmere Island, in northernmost Canada are the oldest Cenozoic avian fossils from the Arctic. Except for its slightly larger size, the Arctic presbyornithid humerus is not distinguishable from fossils of Presbyornis pervetus from the western United States, and the Gastornis phalanx is within the known size range of mid-latitude individuals. The occurrence of Presbyornis above the Arctic Circle in the Eocene could be the result of annual migration like that of its living duck and geese relatives, or it may have been a year-round resident similar to some Eocene mammals on Ellesmere and some extant species of sea ducks. Gastornis, along with some of the mammalian and reptilian members of the Eocene Arctic fauna, likely over-wintered in the Arctic. Despite the milder (above freezing) Eocene climate on Ellesmere Island, prolonged periods of darkness occurred during the winter. Presence of these extinct birds at both mid and high latitudes on the northern continents provides evidence that future increases in climatic warming (closer to Eocene levels) could lead to the establishment of new migratory or resident populations within the Arctic Circle. PMID:26867798

  15. Planktic foraminiferal biostratigraphy, paleoecology and chronostratigraphy across the Eocene/Oligocene boundary in northern Tunisia

    NASA Astrophysics Data System (ADS)

    Karoui-Yaakoub, Narjess; Grira, Chaima; Mtimet, Moncef Saïd; Negra, Mohamed Hédi; Molina, Eustoquio

    2017-01-01

    The biostratigraphic analysis of the Eocene-Oligocene transition of the Menzel Bou Zelfa and Jhaff sections in northeastern Tunisia (Cap Bon peninsula) allows us to identify a continuous planktic foraminiferal biozonation. The following biozones were recognized: Globigerinatheka semiinvoluta Zone (E14), Globigerinatheka index Zone (E15), (Hantkenina alabamensis Zone (E16) of the upper Eocene and Pseudohastigerina naguewichiensis Zone (O1) of the lower Oligocene. A rapid mass extinction event in planktic foraminifera occurred at the Eocene-Oligocene transition, including the extinction of the turborotalids (Turborotalia cerroazulensis, Turborotalia cocoaensis and Turborotalia cunialensis) followed by a significant size reduction of the genus Pseudohastigerina and the extinction of the hantkeninids (Hantkenina alabamensis, Hantkenina brevispina, Hantkenina nanggulanensis and Cribrohantkenina lazzarii), which mark the Eocene/Oligocene boundary. These species were tropical and subtropical surface and intermediate dwellers, with distinctive morphologies (carinate turborotalids and spinose hantkeninids), which were well adapted species of k-strategy. The surviving planktic foraminifera species were quite similar in morphology with globular chambers (globigerinids) and small planispiral (pseudohastigerinids), which were opportunistic species of r-strategy. The recognition of a 4 m thick interval, between the extinction of turborotalids and hantkeninids, indicates that the section is continuous and one of the most expanded throughout the Eocene-Oligocene transition. This section could serve as an auxiliary section (hypostratotype) for the complete definition of the Global Stratotype Section and Point for the Eocene/Oligocene boundary, which mark the base of the Rupelian Stage.

  16. The palaeobiology of high latitude birds from the early Eocene greenhouse of Ellesmere Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Stidham, Thomas A.; Eberle, Jaelyn J.

    2016-02-01

    Fossils attributable to the extinct waterfowl clade Presbyornithidae and the large flightless Gastornithidae from the early Eocene (~52–53 Ma) of Ellesmere Island, in northernmost Canada are the oldest Cenozoic avian fossils from the Arctic. Except for its slightly larger size, the Arctic presbyornithid humerus is not distinguishable from fossils of Presbyornis pervetus from the western United States, and the Gastornis phalanx is within the known size range of mid-latitude individuals. The occurrence of Presbyornis above the Arctic Circle in the Eocene could be the result of annual migration like that of its living duck and geese relatives, or it may have been a year-round resident similar to some Eocene mammals on Ellesmere and some extant species of sea ducks. Gastornis, along with some of the mammalian and reptilian members of the Eocene Arctic fauna, likely over-wintered in the Arctic. Despite the milder (above freezing) Eocene climate on Ellesmere Island, prolonged periods of darkness occurred during the winter. Presence of these extinct birds at both mid and high latitudes on the northern continents provides evidence that future increases in climatic warming (closer to Eocene levels) could lead to the establishment of new migratory or resident populations within the Arctic Circle.

  17. Propagation of VLF waves through the equatorial anomaly

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Cairo, L.

    1980-12-01

    The propagation characteristics of artificial VLF waves (NBA, 24.0 kHz) through the equatorial ionosphere have been studied by means of data obtained onboard the FR-1 satellite at 750 km altitude over Latin America. Large latitudinal variations of the vertical component of the wave normal generally appear in the evening at geomagnetic latitudes of 10 to 15 deg, and they also appear on most of the passes examined at night at latitudes of 5 to 10 deg. Ray and wave normal directions of the VLF waves are computed in various models of field-aligned equatorial anomaly. The latitudinal variations in the evening are due to large negative latitudinal gradients of electron density associated with the equatorial anomaly, and the latitudinal variations at night are due to relatively small density gradients.

  18. The Equatorial Ridges of Pan and Atlas: Terminal Accretionary Ornaments?

    NASA Astrophysics Data System (ADS)

    Charnoz, Sébastien; Brahic, André; Thomas, Peter C.; Porco, Carolyn C.

    2007-12-01

    In the outer regions of Saturn’s main rings, strong tidal forces balance gravitational accretion processes. Thus, unusual phenomena may be expected there. The Cassini spacecraft has recently revealed the strange “flying saucer” shape of two small satellites, Pan and Atlas, located in this region, showing prominent equatorial ridges. The accretion of ring particles onto the equatorial surfaces of already-formed bodies embedded in the rings may explain the formation of the ridges. This ridge formation process is in good agreement with detailed Cassini images showing differences between rough polar and smooth equatorial terrains. We propose that Pan and Atlas ridges are kilometers-thick “ring-particle piles” formed after the satellites themselves and after the flattening of the rings but before the complete depletion of ring material from their surroundings.

  19. Bistability between equatorial and axial dipoles during magnetic field reversals.

    PubMed

    Gissinger, Christophe; Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel

    2012-06-08

    Numerical simulations of the geodynamo in the presence of heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m=0 axial dipolar field is replaced by a hemispherical magnetic field, dominated by an oscillating m=1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of Earth's dynamo.

  20. Iron sources and pathways into the Pacific Equatorial Undercurrent

    NASA Astrophysics Data System (ADS)

    Qin, Xuerong; Menviel, Laurie; Sen Gupta, Alex; Sebille, Erik

    2016-09-01

    Using a novel observationally constrained Lagrangian iron model forced by outputs from an eddy-resolving biogeochemical ocean model, we examine the sensitivity of the Equatorial Undercurrent (EUC) iron distribution to EUC source region iron concentrations. We find that elevated iron concentrations derived from New Guinea Coastal Undercurrent (NGCU) alone is insufficient to explain the high concentrations observed in the EUC. In addition, due to the spread in transit times, interannual NGCU iron pulses are scavenged, diluted, or eroded, before reaching the eastern equatorial Pacific. With an additional iron source from the nearby New Ireland Coastal Undercurrent, EUC iron concentrations become consistent with observations. Furthermore, as both the New Guinea and New Ireland Coastal Undercurrents strengthen during El Niño, increased iron input into the EUC can enhance the iron supply into the eastern equatorial Pacific. Notably, during the 1997/1998 El Niño, this causes a simulated 30% iron increase at a 13 month lag.

  1. The effect of islands on low frequency equatorial motions

    NASA Technical Reports Server (NTRS)

    Cane, M. A.; Du Penhoat, Y.

    1982-01-01

    A complete analytic solution is presented for the influence of equatorial islands on steady low-frequency waves. If the island is small (the meridional extent is much less than the equatorial radius of deformation, R), the waves pass it almost undisturbed, with the mass flux incident on the upstream side flowing around it nearly equally to the north and to the south and continuing on downstream in the lee of the island. For large islands (comparable in extent with R or larger), the principal response is organized as it would be if the island barrier were meridionally infinite. An incident Kelvin wave is largely reflected as long Rossby waves; symmetric long Rossby waves are reflected as equatorial Kelvin waves, while antisymmetric ones stop at the island barrier. In all cases, a boundary current composed of short Rossby waves forms at the eastern side of the island and accomplishes the required meridional redistribution of the zonal mass flux.

  2. A recent, equatorial, periglacial environment on Mars

    NASA Astrophysics Data System (ADS)

    Balme, M. R.; Gallagher, C.; Murray, J. B.; Muller, J.-P.

    2009-04-01

    During the Viking era, Mars' recent climatic history was held to be cold and dry with little evidence for long-lived liquid water near the surface; signs of a past wetter, warmer climate were confined to ancient Noachian or Hesperian-aged terrains. Recent missions have revealed contemporary near-surface water-ice to be abundant at high latitudes, and a population of mid-latitude fluvial-like gullies that appear to have formed by transient melting of ice or snow. Thus today's view of Mars' recent surface evolution is one of global permafrost existing within a framework of climate change, the timescales of which are governed by obliquity cycles with periods of tens to hundreds of thousands of years. However, in recent mapping work of the equatorial Elysium Planitia region using the latest very high resolution images of Mars (HiRISE; 25cm/pixel) we have found evidence for longer-lived, geologically recent liquid water at the martian surface. This suggests that there was a recent period when the climate was warmer than current obliquity cycle-based models predict. The Elysium Planitia region of Mars is both geologically young (late Amazonian period; <100 Ma) and hosts a variety of landforms that are morphologically similar to those of periglacial and permafrost environments on Earth. The region was exposed to massive flooding from deep underground sources during the late Amazonian, as demonstrated by the distinctive fluvial morphologies seen in the outflow channel Athabasca Vallis. These floods would have provided both the source of ice and particulate material required for a periglacial or permafrost landscape and there was probably a long-lived, but slowly freezing, lake or sea in the downstream Elysium basin. However, the provenance of the materials and landforms of this region is disputed: many authors still regard the Athabasca Vallis and Elysium basin as being flood lava provinces, with effusive volcanic materials reoccupying earlier flood landscapes (a classic

  3. The crazy hollow formation (Eocene) of central Utah

    USGS Publications Warehouse

    Weiss, M.P.; Warner, K.N.

    2001-01-01

    The Late Eocene Crazy Hollow Formation is a fluviatile and lacustrine unit that was deposited locally in the southwest arm of Lake Uinta during and after the last stages of the lake the deposited the Green River Formation. Most exposures of the Crazy Hollow are located in Sanpete and Sevier Counties. The unit is characterized by a large variety of rock types, rapid facies changes within fairly short distances, and different lithofacies in the several areas where outcrops of the remnants of the formation are concentrated. Mudstone is dominant, volumetrically, but siltstone, shale, sandstone, conglomerate and several varieties of limestone are also present. The fine-grained rocks are mostly highly colored, especially in shades of yellow, orange and red. Sand grains, pebbles and small cobbles of well-rounded black chert are widespread, and "salt-and-pepper sandstone" is the conspicuous characteristic of the Crazy Hollow. The salt-and-pepper sandstone consists of grains of black chert, white chert, quartz and minor feldspar. The limestone beds and lenses are paludal and lacustrine in origin; some are fossiliferous, and contain the same fauna found in the Green River Formation. With trivial exceptions, the Crazy Hollow Formation lies on the upper, limestone member of the Green River Formation, and the beds of the two units are always accordant in attitude. The nature of the contact differs locally: at some sites there is gradation from the Green River to the Crazy Hollow; at others, rocks typical of the two units intertongue; elsewhere there is a disconformity between the two. A variety of bedrock units overlie the Crazy Hollow at different sites. In the southeasternmost districts it is overlain by the late Eocene formation of Aurora; in western Sevier County it is overlain by the Miocene-Pliocene Sevier River Formation; in northernmost Sanpete County it is overlain by the Oligocene volcanics of the Moroni Formation. At many sites bordering Sanpete and Sevier Valleys

  4. Equatorial Atmospheric and Ionospheric Modeling for Space Surveillance

    DTIC Science & Technology

    2010-11-04

    170 Longitude (deg E) 30 15 -15 0 La tit ud e (d eg N ) Equatorial Anomaly SMH 11/24/99 Equatorial Spread-F A l t i t u d e ( k m ) Local Time...Operation T E C ( 1 0 1 6 e l e c t r o n s m - 2 ) Model Integration and Test SMH 11/24/99 Two Frequency Radar vs IECM TEC -6.5 6.50 E l e v a t i o n

  5. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    NASA Technical Reports Server (NTRS)

    Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

  6. Optimal joint remote state preparation of equatorial states

    NASA Astrophysics Data System (ADS)

    Li, Xihan; Ghose, Shohini

    2015-12-01

    We present a scheme for optimal joint remote state preparation of two-qubit equatorial states. Our protocol improves on a previous scheme (Choudhury and Dhara in Quantum Inf Process 14:373-379, 2015) that had a success probability of 25 %, which increased to 50 % when extra classical information is sent to the receiver. We show that using our modified scheme, the desired state can be prepared deterministically with the same quantum channel. Moreover, we generalize the scheme to prepare N-qubit equatorial states in which the receiver can reconstruct the original state with 100 % success probability.

  7. Convective Draft Structure and Transport Over the Amazonian Rain Forest

    NASA Astrophysics Data System (ADS)

    Scala, John Richard

    1990-01-01

    Field observations acquired during two expeditions to the Amazon rain forest of Brazil (ABLE-2A, ABLE-2B), and two-dimensional moist cloud model simulations are used to determine: (1) the vertical structure of convective up- and downdrafts, (2) the major levels of entrainment and detrainment, and (3) the role of temperature and moisture in convective scale transport over the continental tropics. The thermodynamic and kinematic structure of the convective troposphere is obtained from aircraft surveys flown during the dry season and a surface-based network triangle designed for wet season multi-instrumental sampling. Dry season deep convection develops in an environment marked by a mid-tropospheric minimum in equivalent potential temperature. The available supply of cool, dry air supports penetrating downdrafts which feed propagating gust fronts at the surface. Model results indicate the existence of organized cloud fields characterized by multiple updraft cores. The upward vertical transport of air from the subcloud layer to a broad anvil is accomplished without extensive mid-level detrainment. Undilute cores are required to perform the vertical exchange in the presence of mid-tropospheric heat and moisture sinks. Marked moisture gradients are absent in the well -mixed environment of the wet season. Model predicted column heating budgets suggest the evaporation of rainwater into a rear inflow is insufficient to sustain strong downdrafts or an extensive surface cool pool. Complex mid-tropospheric circulations, particularly the existence of a rotor, account for the observed redistribution of a conservative tracer. Undilute transport of boundary layer air to the upper troposphere is markedly reduced by multiple levels of detrainment. In one case, greater than 50% of the air transported to the anvil region originated at or above 6 km rather than directly from the boundary layer. The vertical distribution of boundary layer aerosols in the presence of convection is

  8. Paleohydrology of the eocene ballena gravels, San Diego County, California

    NASA Astrophysics Data System (ADS)

    Steer, Bradley L.; Abbott, Patrick L.

    1984-03-01

    The Ballena Gravels are remnants of a river system that flowed westward across the ancestral Peninsular Ranges during medial and late Eocene time. The Gravels (actually conglomerate) are channelized fluvial deposits that built westward as alluvial fan (Poway Group), submarine canyon (Scripps Formation) and submarine fan (Jolla Vieja Formation) depositional systems. Because the integrated sedimentary system contains distinctive Poway rhyolite clasts of limited geographic and temporal extent the now separated component formations are recognizable on the San Diego coastal plain and on the Channel Islands. Paleogeographic reconstructions suggest a transport distance of about 315 km. Multiple techniques analysis suggests the channel gradient in the San Diego area was 12-18 m km -1. Stream velocity, based on a competent particle size of 52 cm, ranges from 2.5 to 4 m s -1. Eight equations based on slope and velocity generated estimates of channel depth at food stage that vary from 2.5 to 4.5 m. Paleodischarge can be estimated from regime-type engineering equations that are based on gradient, depth, and grain size. Paleodischarge also is calculated using a technique based on stream length and drainage area. Values generated by multiple techniques suggest 2.33-yr flood discharges of about 275 m 3 s -1. Extrapolation based on a logarithmic curve indicates 100-yr flood discharges around 27,500 m 3 s -1. Channel-width estimates for 1 to 2.33 yr floods range from 25 to 75 m. Calculations of seasonally dominant rainfall, based on runoff and temperature, vary between 50-75 cm annually. Runoff is estimated from discharge values and paleotemperatures are based on caliche type, salt-fractured clasts, and the immature clay mineral suite. The Nueces River of Texas shares some of the same characteristics of the Eocene Ballena river. The Nueces has a highly varied discharge due to seasonally intense rainfall similar to that interpreted for the Ballena river. Several rivers flowing to

  9. Was the Eocene Arctic a Source Area for Exotic Plants and Mammals? (Invited)

    NASA Astrophysics Data System (ADS)

    Eberle, J. J.; Harrington, G. J.; Fricke, H. C.; Humphrey, J.; Hackett, L.; Newbrey, M.; Hutchison, J. H.

    2010-12-01

    Today’s High Arctic is undergoing rapid warming, but the impact on its animal and plant communities is not clear. As a deep time analog to better understand and predict the impacts of global warming on the Arctic biota, early Eocene (52-53 Ma) rocks on Ellesmere Island, Nunavut in Canada’s High Arctic (~79°N latitude) preserve evidence of diverse terrestrial ecosystems that supported dense forests inhabited by turtles, alligators, snakes, primates, tapirs, brontotheres, and hippo-like Coryphodon. The fossil localities were just a few degrees further south and still well above the Arctic Circle during the early Eocene; consequently, the biota experienced months of continuous sunlight as well as darkness, the Arctic summer and winter, respectively. The flora and fauna of the early Eocene Arctic imply warmer, wetter conditions than at present, and recently published analyses of biogenic phosphate from fossil fish, turtle, and mammal estimate warm summers (19 - 20 C) and mild, above-freezing winters. In general, temperature estimates for the early Eocene Arctic can be compared to those found today in temperate rainforests in the Pacific Northwest of the United States. The early Eocene Arctic mammalian fauna shares most genera with coeval mid-latitude faunas thousands of kilometers to the south in the US Western Interior, and several genera also are shared with Europe and Asia. Recent analyses suggest that the large herbivores such as hippo-like Coryphodon were year-round inhabitants in the Eocene Arctic forests. Although several of the Eocene Arctic mammalian taxa are hypothesized to have originated in either mid-latitude North America or Asia, the earlier occurrence of certain clades (e.g., tapirs) in the Arctic raises the possibility of a northern high-latitude origin. Analysis of the early Eocene Arctic palynoflora indicates comparable richness to early Eocene plant communities in the US Western Interior, but nearly 50% of its species (mostly angiosperms) are

  10. Principal modes of variation of rain-rate probability distributions

    NASA Technical Reports Server (NTRS)

    Bell, Thomas L.; Suhasini, R.

    1994-01-01

    Radar or satellite observations of an area generate sequences of rain-rate maps. From a gridded map a histogram of rain rates can be obtained representing the relative areas occupied by rain rates of various strengths. The histograms vary with time as precipitating systems in the area evolve and decay and amounts of convective and stratiform rain in the area change. A method of decomposing the histograms into linear combinations of a few empirical distributions with time-dependent coefficients is developed, using principal component analysis as a starting point. When applied to a tropical Atlantic dataset (GATE), two distributions emerge naturally from the analysis, resembling stratiform and convective rain-rate distributions in that they peak at low and high rain rates, respectively. The two 'modes' have different timescales and only the high-rain-rate mode has a statistically significant diurnal cycle. The ability of just two modes to describe rain variabiltiy over an area can explain why methods of estimating area-averaged rain rate from the area covered by rain rates above a certain threshold are so successful.

  11. Mesozoic and Eocene ductile deformation of western Central Iran: from Cimmerian collisional orogeny to Eocene extension and exhumation

    NASA Astrophysics Data System (ADS)

    Kargaranbafghi, Fariba; Neubauer, Franz; Genser, Johann

    2010-05-01

    To advance our understanding of the Mesozoic to Eocene tectonics and kinematics of basement units exposed in the south-western Central Iran plateau, this paper presents new structural and thermochronological data from the Chapedony metamorphic core complex and hangingwall units, particularly from the Posht-e-Badam complex. The overall Paleogene structural characteristics of the area are related to an oblique convergent zone. The Saghand area represent part of a deformation zone between the Arabia and Eurasia plates, and can be interpreted as a product of the Central Iran intracontinental deformation as a weak zone during Mesozoic to Paleogene times. Field and microstructural evidence reveals that the metamorphic and igneous rocks in the study area suffered a ductile shear deformation including mylonitization at the hangingwall boundary of the Eocene Chapedony metamorphic core complex. The shear zone is subhorizontal low-angle normal fault and the shear direction of the hangingwall unit is towards NE, based on the attitude of foliation and lineation of ductility deformed rocks and shear sense indicators. Comparison of deformation features in the described mylonites and other structural features within the footwall unit lead to the conclusion that the mylonites were formed in a subhorizontal shear zone by NE-SW stretching in the extension tectonics during Middle to Late Eocene. The Chapedony metamorphic core complex is characterized by amphibolite-facies metamorphism and development of S and S-L tectonic fabrics. The Posht-e-Badam complex is deformed by two stages during Cimmerian tectonic processes forming the Paleo-Tethyan suture. The Posht-e-Badam complex is overprinted by two stages of metamorphism. White mica ages at 203 and 181 Ma are related to cooling after medium-grade metamorphism respectively ductile shearing. These ages are variably overprinted by low-grade metamorphism also affecting Jurassic metasediments in the Polo area. Consequently, these are

  12. Eocene bipolar glaciation associated with global carbon cycle changes.

    PubMed

    Tripati, Aradhna; Backman, Jan; Elderfield, Henry; Ferretti, Patrizia

    2005-07-21

    The transition from the extreme global warmth of the early Eocene 'greenhouse' climate approximately 55 million years ago to the present glaciated state is one of the most prominent changes in Earth's climatic evolution. It is widely accepted that large ice sheets first appeared on Antarctica approximately 34 million years ago, coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world's oceans, and that glaciation in the Northern Hemisphere began much later, between 10 and 6 million years ago. Here we present records of sediment and foraminiferal geochemistry covering the greenhouse-icehouse climate transition. We report evidence for synchronous deepening and subsequent oscillations in the calcite compensation depth in the tropical Pacific and South Atlantic oceans from approximately 42 million years ago, with a permanent deepening 34 million years ago. The most prominent variations in the calcite compensation depth coincide with changes in seawater oxygen isotope ratios of up to 1.5 per mil, suggesting a lowering of global sea level through significant storage of ice in both hemispheres by at least 100 to 125 metres. Variations in benthic carbon isotope ratios of up to approximately 1.4 per mil occurred at the same time, indicating large changes in carbon cycling. We suggest that the greenhouse-icehouse transition was closely coupled to the evolution of atmospheric carbon dioxide, and that negative carbon cycle feedbacks may have prevented the permanent establishment of large ice sheets earlier than 34 million years ago.

  13. Paleoecology of Early eocene strata near Buffalo, Wyoming

    SciTech Connect

    Durkin, T.V.; Rich, F.J.

    1986-08-01

    Palynological investigation has helped illustrate the paleoecology of a vertical section of strata from the Wasatch Formation between the Healy and Walters coal burns near Buffalo, Wyoming. Numerous silicified logs and stumps of cypress and sequoia have been preserved at the site and drew initial attention to it. Flood-basin deposits enclose the trees and include sandstones, siltstones, shale, and coal beds that accumulated as channel, levee, crevasse-splay, and swamp/marsh sediments. Detrital sediments were probably derived from the Bighorn Mountains and accumulated as they were carried into the Powder River basin fluvial system. One hundred five polynomorph taxa have been distinguished, as well as 10 types of fungal spores. Platycarya, Tilia, Sparganium, and Platanus pollen indicate an early Eocene age for the strata. Other pollen, as well as the genera of trees and megafossil remains from a clinker bed several miles from the study area, reinforce the interpretation of a warm-temperature or subtropical climate at the time of deposition. The megafossil assemblage includes pinnae of the aquatic fern Marsilea, never before described from the fossil record. Variations in the species composition of the polynomorph assemblages show that several plant communities existed in succession at the site. These varied from pond or marsh types to mature forests.

  14. Continental warming preceding the Palaeocene-Eocene thermal maximum.

    PubMed

    Secord, Ross; Gingerich, Philip D; Lohmann, Kyger C; Macleod, Kenneth G

    2010-10-21

    Marine and continental records show an abrupt negative shift in carbon isotope values at ∼55.8 Myr ago. This carbon isotope excursion (CIE) is consistent with the release of a massive amount of isotopically light carbon into the atmosphere and was associated with a dramatic rise in global temperatures termed the Palaeocene-Eocene thermal maximum (PETM). Greenhouse gases released during the CIE, probably including methane, have often been considered the main cause of PETM warming. However, some evidence from the marine record suggests that warming directly preceded the CIE, raising the possibility that the CIE and PETM may have been linked to earlier warming with different origins. Yet pre-CIE warming is still uncertain. Disentangling the sequence of events before and during the CIE and PETM is important for understanding the causes of, and Earth system responses to, abrupt climate change. Here we show that continental warming of about 5 °C preceded the CIE in the Bighorn Basin, Wyoming. Our evidence, based on oxygen isotopes in mammal teeth (which reflect temperature-sensitive fractionation processes) and other proxies, reveals a marked temperature increase directly below the CIE, and again in the CIE. Pre-CIE warming is also supported by a negative amplification of δ(13)C values in soil carbonates below the CIE. Our results suggest that at least two sources of warming-the earlier of which is unlikely to have been methane-contributed to the PETM.

  15. Seawater calcium isotopic ratios across the Eocene-Oligocene Transition

    NASA Astrophysics Data System (ADS)

    Griffith, E. M.; Paytan, A.

    2009-12-01

    We reconstructed the evolution of the seawater calcium (Ca) isotopic ratio from marine (pelagic) barite and bulk calcium carbonate over the Eocene-Oligocene Transition (EOT), a period of extreme and rapid change in the global calcite compensation depth (CCD) (Lyle et al., 2008). The CCD is controlled by the balance between calcium carbonate deposition and dissolution in deep sea sediments. Large fluctuations in the CCD may cause changes in the concentration of dissolved Ca in seawater and its isotopic composition if accompanied by imbalances in marine Ca sources and sinks (De La Rocha and DePaolo, 2000). Our results show that the permanent deepening of the CCD during the EOT, which coincided with the major Cenozoic glaciation around 34 million years ago (Zachos et al., 2001), was not accompanied by a significant long-term change in the isotopic ratio of Ca in seawater or its sink (calcium carbonate). A simple isotopic mass balance model is constructed to compare predicted and observed isotopic fluctuations. References: Lyle, M. et al. Pacific Ocean and Cenozoic evolution of climate. Rev. Geophys. 46, 1-47 (2008). De La Rocha, C. L. & DePaolo, D. J. Isotopic evidence for variations in the marine calcium cycle over the Cenozoic. Science 289, 1176-1178 (2000). Zachos, J., Pagani, M., Sloan, L., Thomas, E. & Billups, K. Trends, rhythms, and aberrations in global climate 65 ma to present. Science 292, 686-693 (2001).

  16. Middle Eocene seagrass facies from Apennine carbonate platforms (Italy)

    NASA Astrophysics Data System (ADS)

    Tomassetti, Laura; Benedetti, Andrea; Brandano, Marco

    2016-04-01

    Two stratigraphic sections located in the Latium-Abruzzi (Monte Porchio, Central Apennines, Central Italy) and in the Apulian carbonate platform (S. Cesarea-Torre Tiggiano, Salento, Southern Italy) were measured and sampled to document the sedimentological characteristic and the faunistic assemblages of Middle Eocene seagrass deposits. The faunistic assemblages are dominated by porcellaneous foraminifera Orbitolites, Alveolina, Idalina, Spiroloculina, Quinqueloculina, Triloculina and abundant hooked-shaped gypsinids, associated with hooked red algae and green algae Halimeda. Fabiania, rotaliids and textulariids as well as nummulitids are subordinated. The samples were assigned to Lutetian (SBZ13-16) according to the occurrence of Nummulites cf. lehneri, Alveolina ex. gr. elliptica, Idalina berthelini, Orbitolites complanatus, Slovenites decastroi and Medocia blayensis. At Santa Cesarea reticulate nummulites occur in association with Alveolina spp. and Halkyardia minima marking the lower Bartonian (SBZ17). Three main facies associations have been recognised: I) larger porcellaneous foraminiferal grainstones with orbitolitids and alveolinids deposited into high-energy shallow-water settings influenced by wave processes that reworked the sediments associated with a seagrass; II) grainstone to packstone with small porcellaneous foraminifera and abundant permanently-attached gypsinids deposited in a more protected (e.g., small embayment) in situ vegetated environment; III) bioclastic packstone with parautochthonous material reworked from the seagrass by rip currents and accumulated into rip channels in a slightly deeper environment. The biotic assemblages suggest that the depositional environment is consistent with tropical to subtropical vegetated environments within oligotrophic conditions.

  17. Is the Eocene's climate affected by ocean tides?

    NASA Astrophysics Data System (ADS)

    Weber, Tobias; Thomas, Maik

    2014-05-01

    Global ocean models can generally be divided into Ocean General Circulation and tidal models. Paleoclimate simulations consider dynamics due to the ocean's general, i.e., thermohaline, wind and pressure driven circulation, while tidal dynamics most commonly are neglected due to their strict periodicity and high frequencies. Nevertheless, it could be demonstrated that transport ellipses and energy fluxes are being deformed over shelf areas due to tidal induced friction thus altering ocean circulation and energy fluxes on longer timescales. This makes tides not only an interesting subject of investigation of present-day dynamics, but also of paleo time slices, when both different celestial constellations and geometric shapes of ocean basins affected tidal waves. Using the coupled atmosphere-ocean general circulation model ECHAM5/MPIOM with an integrated tidal module based on luni-solar ephemerides, we simultaneously simulate circulation and tidal dynamics for the Early Eocene (50Ma) and a pre-industrial control run. Major changes in ocean circulation cannot only be observed in shelf areas, but also in the open ocean, for example the Indian and North Atlantic Oceans. Especially the opening of the Tethys Sea alters ocean basin geometry and hereby the dissipation of tidal waves. The southern position of Australia allows resonance between the Indian and Pacific Ocean and leads to high amplitudes in the M2 tide that dominate the Western Pacific and Eastern Indian Oceans. Including tidal dynamics in the ocean model also affects climate by decreasing global mean temperature.

  18. Primate postcrania from the late middle Eocene of Myanmar

    PubMed Central

    Ciochon, Russell L.; Gingerich, Philip D.; Gunnell, Gregg F.; Simons, Elwyn L.

    2001-01-01

    Fossil primates have been known from the late middle to late Eocene Pondaung Formation of Myanmar since the description of Pondaungia cotteri in 1927. Three additional primate taxa, Amphipithecus mogaungensis, Bahinia pondaungensis and Myanmarpithecus yarshensis, were subsequently described. These primates are represented mostly by fragmentary dental and cranial remains. Here we describe the first primate postcrania from Myanmar, including a complete left humerus, a fragmentary right humerus, parts of left and right ulnae, and the distal half of a left calcaneum, all representing one individual. We assign this specimen to a large species of Pondaungia based on body size and the known geographic distribution and diversity of Myanmar primates. Body weight estimates of Pondaungia range from 4,000 to 9,000 g, based on humeral length, humeral midshaft diameter, and tooth area by using extant primate regressions. The humerus and ulna indicate that Pondaungia was capable of a wide variety of forelimb movements, with great mobility at the shoulder joint. Morphology of the distal calcaneus indicates that the hind feet were mobile at the transverse tarsal joint. Postcrania of Pondaungia present a mosaic of features, some shared in common with notharctine and adapine adapiforms, some shared with extant lorises and cebids, some shared with fossil anthropoids, and some unique. Overall, Pondaungia humeral and calcaneal morphology is most consistent with that of other known adapiforms. It does not support the inclusion of Pondaungia in Anthropoidea. PMID:11438722

  19. Anthropoid humeri from the late Eocene of Egypt

    PubMed Central

    Seiffert, Erik R.; Simons, Elwyn L.; Fleagle, John G.

    2000-01-01

    A number of recent studies have, by necessity, placed a great deal of emphasis on the dental evidence for Paleogene anthropoid interrelationships, but cladistic analyses of these data have led to the erection of phylogenetic hypotheses that appear to be at odds with biogeographic and stratigraphic considerations. Additional morphological data from the cranium and postcranium of certain poorly understood Paleogene primates are clearly needed to help test whether such hypotheses are tenable. Here we describe humeri attributable to Proteopithecus sylviae and Catopithecus browni, two anthropoids from late Eocene sediments of the Fayum Depression in Egypt. Qualitative and morphometric analyses of these elements indicate that humeri of the oligopithecine Catopithecus are more similar to early Oligocene propliopithecines than they are to any other Paleogene anthropoid taxon, and that Proteopithecus exhibits humeral similarities to parapithecids that may be symplesiomorphies of extant (or “crown”) Anthropoidea. The humeral morphology of Catopithecus is consistent with certain narrowly distributed dental apomorphies—such as the loss of the upper and lower second premolar and the development of a honing blade for the upper canine on the lower third premolar—which suggest that oligopithecines constitute the sister group of a clade containing propliopithecines and Miocene-Recent catarrhines and are not most closely related to Proteopithecus as has recently been proposed. PMID:10963669

  20. Seawater calcium isotope ratios across the Eocene-Oligocene transition

    USGS Publications Warehouse

    Griffith, E.M.; Paytan, A.; Eisenhauer, A.; Bullen, T.D.; Thomas, E.

    2011-01-01

    During the Eocene-Oligocene transition (EOT, ca. 34 Ma), Earth's climate cooled significantly from a greenhouse to an icehouse climate, while the calcite (CaCO3) compensation depth (CCD) in the Pacific Ocean increased rapidly. Fluctuations in the CCD could result from various processes that create an imbalance between calcium (Ca) sources to, and sinks from, the ocean (e.g., weathering and CaCO3 deposition), with different effects on the isotopic composition of dissolved Ca in the oceans due to differences in the Ca isotopic composition of various inputs and outputs. We used Ca isotope ratios (??44/40Ca) of coeval pelagic marine barite and bulk carbonate to evaluate changes in the marine Ca cycle across the EOT. We show that the permanent deepening of the CCD was not accompanied by a pronounced change in seawater ??44/40Ca, whereas time intervals in the Neogene with smaller carbonate depositional changes are characterized by seawater ??44/40Ca shifts. This suggests that the response of seawater ??44/40Ca to changes in weathering fluxes and to imbalances in the oceanic alkalinity budget depends on the chemical composition of seawater. A minor and transient fluctuation in the Ca isotope ratio of bulk carbonate may reflect a change in isotopic fractionation associated with CaCO3 precipitation from seawater due to a combination of factors, including changes in temperature and/or in the assemblages of calcifying organisms. ?? 2011 Geological Society of America.

  1. Do Sverdrup transports account for the Pacific North Equatorial Countercurrent

    SciTech Connect

    Meyers, G.

    1980-02-20

    Poleward and equatorward geostrophic transports calculated from density are nearly equal to Sverdrup transports calculated from the curl of the wind stress in the North and South Pacific subtropical gyres. But the Sverdrup transports do not account for the Pacific North Equatorial Countercurrent.

  2. The equatorial electrojet current modelling from SWARM satellite data

    NASA Astrophysics Data System (ADS)

    Benaissa, Mahfoud

    2016-07-01

    Equatorial ElectroJet (EEJ) is an intense eastward electric current circulating in the ionospheric magnetic equator band between 100 and 130 km of altitude in E region. These currents vary by day, by season, by solar activity, and also with the main magnetic field of internal origin. The irregularity of the ionosphere has a major impact on the performance of communication systems and navigation (GPS), industry.... Then it becomes necessary study the characteristics of EEJ. In this paper, we present a study of the equatorial electrojet (EEJ) phenomenon along one year (2014) period. In addition, the satellite data used in this study are obtained with SWARM satellite scalar magnetometer data respecting magnetically quiet days with KP < 2. In this paper, we process to separate and extract the electrojet intensity signal from other recorded signal-sources interfering with the main signal and reduce considerably the signal to noise ratio during the SWARM measurements. This pre-processing step allows removing all external contributions in regard to EEJ intensity value. Key words: Ionosphere (Equatorial ionosphere; Electric fields and currents; Equatorial electrojet (EEJ)); SWARM.

  3. Local Stability for an Exact Steady Purely Azimuthal Equatorial Flow

    NASA Astrophysics Data System (ADS)

    Ionescu-Kruse, Delia; Martin, Calin Iulian

    2016-12-01

    The aim of this paper is to present a short-wavelength stability analysis of an exact steady equatorial flow which does not vary in the azimuthal direction, but has an arbitrary variation with depth. We show that for some velocity profiles of the basic flow, this flow is locally stable to short-wavelength perturbations.

  4. Exact Nonlinear Internal Equatorial Waves in the f-plane

    NASA Astrophysics Data System (ADS)

    Hsu, Hung-Chu

    2016-07-01

    We present an explicit exact solution of the nonlinear governing equations for internal geophysical water waves propagating westward above the thermocline in the f-plane approximation near the equator. Moreover, the mass transport velocity induced by this internal equatorial wave is eastward and a westward current occurs in the transition zone between the great depth where the water is still and the thermocline.

  5. Equatorial decline of reef corals during the last Pleistocene interglacial

    NASA Astrophysics Data System (ADS)

    Kiessling, Wolfgang; Simpson, Carl; Beck, Brian; Mewis, Heike; Pandolfi, John M.

    2012-12-01

    The Last Interglacial (LIG; ca. 125,000 y ago) resulted from rapid global warming and reached global mean temperatures exceeding those of today. The LIG thus offers the opportunity to study how life may respond to future global warming. Using global occurrence databases and applying sampling-standardization, we compared reef coral diversity and distributions between the LIG and modern. Latitudinal diversity patterns are characterized by a tropical plateau today but were characterized by a pronounced equatorial trough during the LIG. This trough is governed by substantial range shifts away from the equator. Range shifts affected both leading and trailing edges of species range limits and were much more pronounced in the Northern Hemisphere than south of the equator. We argue that interglacial warming was responsible for the loss of equatorial diversity. Hemispheric differences in insolation during the LIG may explain the asymmetrical response. The equatorial retractions are surprisingly strong given that only small temperature changes have been reported in the LIG tropics. Our results suggest that the poleward range expansions of reef corals occurring with intensified global warming today may soon be followed by equatorial range retractions.

  6. Evolution of Ion Clouds in the Equatorial Ionosphere

    NASA Astrophysics Data System (ADS)

    Petrochuk, Yevgeny; Blaunstein, Nathan; Mishin, Evgeny; Pedersen, Todd; Caton, Ron; Viggiano, Al; Schuman, Nick

    2015-11-01

    We report on the results of 2- and 3-dimentional numerical investigations of the evolution of samarium ion clouds injected in the equatorial ionosphere, alike the recent MOSC experiments. The ambient conditions are described by a standard model of the quiet-time equatorial ionosphere from 90 to 350 km. The altitudinal distribution of the transport processes and ambient electric and magnetic fields is taken into account. The fast process of stratification of ion clouds and breaking into small plasmoids occur only during the late stage of the cloud evolution. The role of the background plasma and its depletion zones formed due to the short-circuiting currents is not as evident as in mid latitudes. It is also revealed that the altitudinal dependence of the diffusion and drift plays a minor role in the cloud evolution at the equator. Likewise, the cloud remains stable with respect to the Raleigh-Taylor and gradient-drift instabilities. These two features are defined by the equatorial near-horizontal magnetic field which leads to a strongly-elongated ellipsoid-like plasma cloud. The critical dip angle separating the stable (equatorial) and unstable (mid-latitude) cloud regimes will be defined in future simulation studies, as well as the dependence on the ambient electric field and neutral wind. 2Space Vehicles Directorate, Air Force Research Laboratory

  7. History of the Italian San Marco equatorial mobile range

    NASA Technical Reports Server (NTRS)

    Nesbitt, H. N.

    1971-01-01

    Events leading to the development of the San Marco Equatorial Range are presented. Included are background information leading to the cooperative space program between the United States and Italy, conceptual planning, training activities, equipment design and fabrication, and range utilization. The technical support provided the San Marco Program by Scout Project Office, and other NASA installations is described.

  8. Upwelling: a unit of disturbance in equatorial spread F

    NASA Astrophysics Data System (ADS)

    Tsunoda, Roland T.

    2015-12-01

    Plasma structure in the nighttime equatorial F layer, often referred to as equatorial spread F (ESF), is not uniformly distributed, either in time or in space. Observations indicate that ESF in the bottomside F layer takes the form of patches; plasma structure within the F layer takes the form of localized plasma depletions, called equatorial plasma bubbles (EPBs), which tend to occur in clusters. Another observed feature is an upwelling, which has been described as a localized, upward modulation of isodensity contours in the bottomside F layer. Interestingly, zonal widths of ESF patches, EPB clusters, and upwellings are similar. Moreover, all display an east-west asymmetry. The objective of this paper is to show, for the first time, that an ESF patch is the bottomside counterpart of an EPB cluster, and that both are products of the electrodynamical process that takes place within an upwelling. The process can be described as having three phases: (1) amplification of upwelling amplitude during the post-sunset rise of the F layer, (2) launching of the first EPB of the evening, from crest of the upwelling, and (3) structuring of plasma within the upwelling. Hence, an upwelling, whose presence is responsible for the formation of ESF patches and EPB clusters, can be envisioned as a unit of disturbance that occurs in the nighttime equatorial ionosphere.

  9. Commercial Logging and HIV Epidemic, Rural Equatorial Africa

    PubMed Central

    Bourgeois, Anke; Mpoudi, Mireille; Butel, Christelle; Peeters, Martine; Mpoudi-Ngolé, Eitel; Delaporte, Eric

    2004-01-01

    We found a high seroprevalence of HIV among young women in a commercial logging area in Cameroon. The vulnerability of these young women could be related to commercial logging and the social and economic networks it induces. The environmental changes related to this industry in Equatorial Africa may facilitate HIV dissemination. PMID:15550206

  10. Late Eocene stable isotope stratigraphy of North Atlantic IODP Site U1411: Orbitally paced climatic heartbeat at the close of the Eocene greenhouse

    NASA Astrophysics Data System (ADS)

    Coxall, Helen; Bohaty, Steve; Wilson, Paul; Liebrand, Diederik; Nyberg, Anna; Holmström, Max

    2016-04-01

    Integrated Ocean Drilling Program (IODP) Expedition 342 drilled sediment drifts on the Newfoundland margin to recover high-resolution records of North Atlantic ocean-climate history and track the evolution of the modern climate system through the Late Cretaceous and Early Cenozoic. An early Paleogene deep-sea benthic stable isotope composite record from multiple Exp. 342 sites is currently in development and will provide a key reference section for investigations of Atlantic and global climate dynamics. This study presents initial results for the late Eocene slice of the composite from Site U1411, located at mid depth (˜2850m Eocene paleodepth) on the Southeast Newfoundland Ridge. Stable oxygen (δ18O) and carbon (δ13C) isotope ratios were measured on 640 samples hosting exceptionally well-preserved epifaunal benthic foraminifera obtained from the microfossil-rich uppermost Eocene clays at 4cm spacing. Sedimentation rates average 2-3 cm/kyr through the late Eocene, such that our sampling resolution is sufficient to capture the dominant Milankovitch frequencies. Late Eocene Site U1411 benthic δ18O values (1.4 to 0.5‰ VPDB) are comparable to the Pacific and elsewhere in the Atlantic at similar depths; however, δ13C is lower by ˜0.5 ‰ with values intermediate between those of the Southern Labrador Sea to the north (-1 to 0) and mid latitude/South Atlantic (0.5 to 1.5) to the south, suggesting poorly ventilated bottom waters in the late Eocene North Atlantic and limited production of North Atlantic deep water. Applying the initial shipboard magneto-biostratigraphic age framework, the Site U1411 benthic δ13C and δ18O records display clear cyclicity on orbital timescales. Spectral analysis of the raw unfiltered datasets identifies eccentricity (400 and 100 kyr), obliquity (40 kyr) and precession (˜20 kyr) signals imprinted on our time series, revealing distinct climatic heart beats in the late Eocene prior to the transition into the 'ice house'.

  11. Technological options for acid rain control

    SciTech Connect

    Princiotta, F.T.; Sedman, C.B.

    1993-01-01

    The paper discusses technological options for acid rain control. Compliance with Title IV of the Clean Air Act Amendments of 1990 will require careful scrutiny of a number of issues before selecting control options to reduce sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions. One key consideration is the effect of fuel switching or control technology upon the existing dust collector, with additional air toxics legislation looming ahead. A number of likely SO2 and NOx retrofit technologies and estimated costs are presented, along with results of retrofit case studies. New hybrid particulate controls are also being developed to meet future requirements.

  12. Acid rain reduced in eastern United States

    SciTech Connect

    Bowersox, V.C.; Lynch, J.A.; Grimm, J.W.

    1997-12-31

    Sulfate and free hydrogen ion concentrations in precipitation decreased 10 to 25 percent over large areas of the eastern United States in 1995. The largest decreases in both ions occurred in and downwind of the Ohio River Valley, the same area where Phase I of the 1990 Clean Air Act Amendments set limitations, effective January 1, 1995, on sulfur dioxide emissions from affected coal-fired sources. Based on our analysis of precipitation chemistry and emissions data, we conclude that substantial declines in acid rain occurred in the eastern United States in 1995 because of large reductions in sulfur dioxide emissions in the same region.

  13. Monitoring Fires in Southwestern Amazonia Rain Forests

    NASA Astrophysics Data System (ADS)

    Brown, I. Foster; Schroeder, Wilfrid; Setzer, Alberto; de Los Rios Maldonado, Monica; Pantoja, Nara; Duarte, Alejandro; Marengo, Jose

    2006-06-01

    From mid-July to mid-October 2005, an environmental disaster unfolded in the trinational region of Madre de Dios, Peru; Acre, Brazil; and Pando, Bolivia (the MAP region), in southwestern Amazonia. A prolonged dry season and human-initiated fires resulted in smoke pollution affecting more than 400,000 persons, fire damage to over 300,000 hectares of rain forest, and over US$50 million of direct economic losses. Indicators suggest that anomalous drought conditions could occur again this year.

  14. The greenhouse effect and acid rain

    SciTech Connect

    Traeger, R.K.

    1990-01-01

    The concentrations of carbon dioxide, methane, sulfur dioxide, nitrous oxides and chlorofluorocarbons is increasing in the earth's atmosphere. Increased concentrations of these trace gases could lead to global warming, increased acid rain and increased UV radiation on the earth's surface; however, the actual impacts are still uncertain and are also the subject of great debate. Application of clean'' energy sources such as geothermal are obviously desirable for decreasing these effects and improving our overall general environment. This paper briefly summarizes the global environment concerns, providing a backdrop for the following papers which describe the geothermal role in future environmental considerations. 5 refs., 2 figs., 1 tab.

  15. Marine and terrestrial environmental changes in NW Europe preceding carbon release at the Paleocene-Eocene transition

    NASA Astrophysics Data System (ADS)

    Kender, Sev; Stephenson, Michael H.; Riding, James B.; Leng, Melanie J.; Knox, Robert W. O.'B.; Peck, Victoria L.; Kendrick, Christopher P.; Ellis, Michael A.; Vane, Christopher H.; Jamieson, Rachel

    2012-11-01

    Environmental changes associated with the Paleocene-Eocene thermal maximum (PETM, ∼56 Ma) have not yet been documented in detail from the North Sea Basin. Located within proximity to the North Atlantic igneous province (NAIP), the Kilda Basin, and the northern rain belt (paleolatitude 54 °N) during the PETM, this is a critical region for testing proposed triggers of atmospheric carbon release that may have caused the global negative carbon isotope excursion (CIE) in marine and terrestrial environments. The CIE onset is identified from organic matter δ13C in exceptional detail within a highly expanded sedimentary sequence. Pollen and spore assemblages analysed in the same samples for the first time allow a reconstruction of possible changes to vegetation on the surrounding landmass. Multiproxy palynological, geochemical, and sedimentologic records demonstrate enhanced halocline stratification and terrigenous deposition well before (103 yrs) the CIE, interpreted as due to either tectonic uplift possibly from a nearby magmatic intrusion, or increased precipitation and fluvial runoff possibly from an enhanced hydrologic cycle. Stratification and terrigenous deposition increased further at the onset and within the earliest CIE which, coupled with evidence for sea level rise, may be interpreted as resulting from an increase in precipitation over NW Europe consistent with an enhanced hydrologic cycle in response to global warming during the PETM. Palynological evidence indicates a flora dominated by pollen from coastal swamp conifers before the CIE was abruptly replaced with a more diverse assemblage of generalist species including pollen similar to modern alder, fern, and fungal spores. This may have resulted from flooding of coastal areas due to relative sea level rise, and/or ecologic changes forced by climate. A shift towards more diverse angiosperm and pteridophyte vegetation within the early CIE, including pollen similar to modern hickory, documents a long term

  16. Observations of ULF wave related equatorial electrojet and density fluctuations

    NASA Astrophysics Data System (ADS)

    Yizengaw, E.; Zesta, E.; Moldwin, M.; Damtie, B.; Mebrahtu, A.; Anad, F.; Pfaff, R. F.

    2011-12-01

    Global magnetospheric Ultra Low Frequency (ULF) pulsations with frequencies in the Pc 4-5 range (f = 1.0 - 8 mHz) have been observed for decades in space and on Earth. ULF pulsations contribute to magnetospheric particle transport and diffusion and play an important role in magnetospheric dynamics. However, only a few studies have been performed on ionospheric observations of ULF wave-related perturbations in the vicinity of the equatorial region. In this paper we report on Pc5 wave related electric field and thus vertical drift velocity oscillations at the equator as observed by ground magnetometers and radar. We show that the magnetometer estimated equatorial ExB drift oscillate with the same frequency as ULF Pc5 waves, creating significant ionospheric density fluctuations. For independent confirmation of the vertical drift velocity fluctuation, we used JULIA 150 km radar drift velocities and found similar fluctuation with the period of 8-10 minutes. We also show ionospheric density fluctuations during the period when we observed ULF wave activities. All these demonstrate that the Pc5 wave can penetrate to the equatorial ionosphere and modulate the equatorial electrodynamics. Finally, in order to detect the ULF activities both on the ground and in space, we use groundbased magnetometer data from African Meridian B-field Education and Research (AMBER) and the South American Meridional B-field Array (SAMBA). From space, we use magnetic field observations from the GOES 12 and the Communication/Navigation Outage and Forecast System (C/NOFS) satellites. Using the WIND spacecraft as the upstream solar wind monitor, we present direct evidence that solar wind number density and ram pressure fluctuations observed far upstream from the terrestrial magnetosphere are the main drivers of ULF wave activity inside the magnetosphere. Finally, we show that the ULF waves in the same frequency range are observed in the magnetosphere by the geosynchronous GOES spacecraft, in the

  17. Fog/cloud and rain chemistry in northern coastal California

    SciTech Connect

    Bicknell, S.H.; Lemcke, S.

    1987-07-01

    Fog, clouds and rain were sampled for 2 years at Redwood National Park (RNP) and one year at Arcata and Oakland. Fog and cloud water samples were more acidic and contained higher concentrations of Ca, Mg, K, Na, NH4, SO4, NO3 and Cl, than rain samples at all sites. Cloud/fog water and rain sample chemistry was not different for RNP and Arcata; but Oakland samples were significantly more acid and had higher concentrations of all elements. RNP and Arcata cloud/fog samples were more acid and contained higher elemental concentrations than expected under pristine conditions. Average pH's were: RNP cloud/fog - 4.12, RNP rain - 4.63, Arcata cloud/fog - 4.00, Arcata rain - 4.66, Oakland cloud/fog - 3.87, Oakland rain - 4.37.

  18. Post-midnight occurrence of equatorial plasma bubbles

    NASA Astrophysics Data System (ADS)

    Ajith, K. K.; Otsuka, Yuichi; Yamamoto, Mamoru; Yokoyama, Tatsuhiro; Tulasiram, S.

    2016-07-01

    The equatorial plasma bubbles (EPBs)/equatorial spread F (ESF) irregularities are an important topic of space weather interest because of their impact on transionospheric radio communications, satellite-based navigation and augmentation systems. This local plasma depleted structures develop at the bottom side F layer through Rayleigh-Taylor instability and rapidly grow to topside ionosphere via polarization electric fields within them. The steep vertical gradients due to quick loss of bottom side ionization and rapid uplift of equatorial F layer via prereversal enhancement (PRE) of zonal electric field makes the post-sunset hours as the most preferred local time for the formation of EPBs. However, there is a different class of irregularities that occurs during the post-midnight hours of June solstice reported by the previous studies. The occurrence of these post-midnight EPBs maximize during the low solar activity periods. The growth characteristics and the responsible mechanism for the formation of these post-midnight EPBs are not yet understood. Using the rapid beam steering ability of 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2°S geographic latitude, 100.3°E geographic longitude, and 10.4°S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. The responsible mechanism for the genesis of summer time post-midnight EPBs were discussed in light of growth rate of Rayleigh-Taylor instability using SAMI2 model.

  19. Lidar Observation of Ozone Profiles in the Equatorial Tropopause Region

    NASA Astrophysics Data System (ADS)

    Abo, M.; Shibata, Y.; Nagasawa, C.

    2014-12-01

    Tropospheric ozone in the tropics zone is significant in terms of the oxidizing efficiency and greenhouse effect. However, in the upper troposphere, the ozone budget in the tropics has not been fully understood yet because of the sparsity of the range-resolved observations of vertical ozone concentration profiles. We have constructed the lidar facility for survey of atmospheric structure over troposphere, stratosphere, mesosphere and low thermosphere over Kototabang (100.3E, 0.2S), Indonesia in the equatorial region. The lidar system consists of the Mie and Raman lidars for tropospheric aerosol, water vapor and cirrus cloud measurements, the Rayleigh lidar for stratospheric and mesospheric temperature measurements and the Resonance lidar for metallic species such as Na, Fe, Ca ion measurements and temperature measurements in the mesopause region. The lidar observations started from 2004, and routine observations of clouds and aerosol in the troposphere and stratosphere are continued now. We have installed DIAL (differential absorption lidar) system for high-resolution measurements of vertical ozone profiles in the equatorial tropopause region over Kototabang. There were many ozone DIAL systems in the world, but their systems are almost optimized for stratospheric ozone layer measurement or tropospheric ozone measurement. Because of deep ozone absorption in the UV region, the wavelength selection is important. Over the equatorial region, the tropopause height is almost 17km. So we use 305nm for on-line and 355nm for off-line using second harmonics of dye laser and third harmonics of Nd:YAG laser. We have observed large ozone enhancement in the upper troposphere, altitude of 13-17km in June 2014, concurring with a zonal wind oscillation associated with the equatorial Kelvin wave around the tropopause[1] at equatorial region. References Fujiwara, M. et al., JGR, 103, D15, 19,173-19,182, 1998.

  20. Response of the Pacific inter-tropical convergence zone to global cooling and initiation of Antarctic glaciation across the Eocene Oligocene Transition

    NASA Astrophysics Data System (ADS)

    Hyeong, Kiseong; Kuroda, Junichiro; Seo, Inah; Wilson, Paul A.

    2016-08-01

    Approximately 34 million years ago across the Eocene–Oligocene transition (EOT), Earth’s climate tipped from a largely unglaciated state into one that sustained large ice sheets on Antarctica. Antarctic glaciation is attributed to a threshold response to slow decline in atmospheric CO2 but our understanding of the feedback processes triggered and of climate change on the other contents is limited. Here we present new geochemical records of terrigenous dust accumulating on the sea floor across the EOT from a site in the central equatorial Pacific. We report a change in dust chemistry from an Asian affinity to a Central-South American provenance that occurs geologically synchronously with the initiation of stepwise global cooling, glaciation of Antarctica and aridification on the northern continents. We infer that the inter-tropical convergence zone of intense precipitation extended to our site during late Eocene, at least four degrees latitude further south than today, but that it migrated northwards in step with global cooling and initiation of Antarctic glaciation. Our findings point to an atmospheric teleconnection between extratropical cooling and rainfall climate in the tropics and the mid-latitude belt of the westerlies operating across the most pivotal transition in climate state of the Cenozoic Era.

  1. Response of the Pacific inter-tropical convergence zone to global cooling and initiation of Antarctic glaciation across the Eocene Oligocene Transition

    PubMed Central

    Hyeong, Kiseong; Kuroda, Junichiro; Seo, Inah; Wilson, Paul A.

    2016-01-01

    Approximately 34 million years ago across the Eocene–Oligocene transition (EOT), Earth’s climate tipped from a largely unglaciated state into one that sustained large ice sheets on Antarctica. Antarctic glaciation is attributed to a threshold response to slow decline in atmospheric CO2 but our understanding of the feedback processes triggered and of climate change on the other contents is limited. Here we present new geochemical records of terrigenous dust accumulating on the sea floor across the EOT from a site in the central equatorial Pacific. We report a change in dust chemistry from an Asian affinity to a Central-South American provenance that occurs geologically synchronously with the initiation of stepwise global cooling, glaciation of Antarctica and aridification on the northern continents. We infer that the inter-tropical convergence zone of intense precipitation extended to our site during late Eocene, at least four degrees latitude further south than today, but that it migrated northwards in step with global cooling and initiation of Antarctic glaciation. Our findings point to an atmospheric teleconnection between extratropical cooling and rainfall climate in the tropics and the mid-latitude belt of the westerlies operating across the most pivotal transition in climate state of the Cenozoic Era. PMID:27507793

  2. Geographical distribution and temporal variation of rain acidity over China

    SciTech Connect

    Wen-Xing Wang; Yan-Bo Pang; Guo-An Ding

    1996-12-31

    In recent decade, large areas of acid rain have appeared in China. With the increasing emission of SO{sub 2} and NO{sub x} year by year, the acidity of precipitation has increased, and the acid rain area is expanding. Presently, the acid rain in China has become the third largest area of acid rain in the world, next to Europe and North America. The Chinese government took action against acid rain and planned a five-year National Acid Deposition Research Project. The space-time distribution and variation of rain acidity described in this paper is a part of this project. China is a large country. The area is almost equal to that of Europe. Its climate varies greatly and spans the tropics, subtropics, temperate and frigid zone. There is a varied topography including mountain, hilly country, desert and plain, on the other hand the distribution of anthropogenic sources are not even. All of the human and natural factors caused different chemical composition in different parts of China, the acidity of precipitation varies also. The acidity of the precipitation is the most important parameter in the acid rain research. In order to obtain the regional representative distribution of rain acidity, National Acidic Deposition Research Monitoring Network with 261 monitoring sites was established in 1992. This paper summarizes the rain acidity of 21355 precipitation samples, and gave the annual, seasonal, and the monthly pH contours. Results show that the acid rain area has expanded from the south during winter. Regional differences of monthly acid precipitation exists, generally, the rain acidity level is higher during summer and fall and lower during winter and spring in the northern provinces. The 9 opposite is the case in the southern provinces. The central areas are in a transitional situation. The geographical distribution and temporal variation of rain acidity are quite different from North America and Europe.

  3. Response of soybean seed germination to cadmium and acid rain.

    PubMed

    Liu, Ting Ting; Wu, Peng; Wang, Li Hong; Zhou, Qing

    2011-12-01

    Cadmium (Cd) pollution and acid rain are the main environmental issues, and they often occur in the same agricultural region. Nevertheless, up to now, little information on the combined pollution of Cd(2+) and acid rain action on crops were presented. Here, we investigated the combined effect of Cd(2+) and acid rain on the seed germination of soybean. The results indicated that the single treatment with the low level of Cd(2+) (0.18, 1.0, 3.0 mg L(-1)) or acid rain (pH ≥3.0) could not affect the seed germination of soybean, which was resulted in the increased activities of peroxidase and catalase. The single treatment with the high concentration of Cd(2+) (>6 mg L(-1)) or acid rain at pH 2.5 decreased the activities of peroxidase and catalase, damaged the cell membrane and then decreased the seed germination of soybean. Meanwhile, the same toxic effect was observed in the combined treatment with Cd(2+) and acid rain, and the combined treatment had more toxic effect than the single treatment with Cd(2+) or acid rain. Thus, the combined pollution of Cd(2+) and acid rain had more potential threat to the seed germination of soybean than the single pollution of Cd(2+) or acid rain.

  4. New rain shed (Building No. 241) interior showing posts, braces, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    New rain shed (Building No. 241) interior showing posts, braces, and roof structure. - Hawaii Volcanoes National Park Water Collection System, Hawaii Volcanoes National Park, Volcano, Hawaii County, HI

  5. Rain erosion considerations for launch vehicle insulation systems

    NASA Technical Reports Server (NTRS)

    Daniels, D. J.; Sieker, W. D.

    1977-01-01

    In recent years the Delta launch vehicle has incorporated the capability to be launched through rain. This capability was developed to eliminate a design constraint which could result in a costly launch delay. This paper presents the methodology developed to implement rain erosion protection for the insulated exterior vehicle surfaces. The effect of the interaction between insulation material rain erosion resistance, rainstorm models, surface geometry and trajectory variations is examined. It is concluded that rain erosion can significantly impact the performance of launch vehicle insulation systems and should be considered in their design.

  6. Geochronology of upper Paleocene and lower Eocene strata, eastern Gulf Coastal Plain

    SciTech Connect

    Mancini, E.A.; Tew, B.H. Geological Survey of Alabama, Tuscaloosa, AL )

    1994-03-01

    Four samples of glauconitic sand from upper Paleocene and lower Eocene strata of the eastern Gulf Coastal Plain were analyzed for conventional potassium-argon (K-Ar) age determination. Results from these analyses are as follows: Coal Bluff Marl Member of the Naheola Formation of the Midway Group (58.2 [+-] 1.5 MA), Ostrea thirsae beds of the Nanafalia Formation of the Wilcox Group (56.3 [+-] 1.5 MA), upper Tuscahoma Sand of the Wilcox Group (54.5 [+-] 1.4 MA), and Bashi Marl Member of the Hatchetigbee Formation of the Wilcox Group (53.4 [+-] 1.4 MA). The Nanafalia Formation (Wilcox Group) disconformably overlies the Naheola Formation (Midway Group), and based on the data presented here, the age of this unconformity is bracketed between 59.7 and 54.8 MA. The Paleocene-Eocene Epoch boundary occurs in the Wilcox Group and coincides with the lithostratigraphic contact of the upper Paleocene Tuscahoma Sand with the lower eocene Hatchetigbee Formation. The age of this boundary, which is also an unconformity, can be placed between 55.9 and 52.0 MA. The K-Ar age dates for this boundary in the Gulf Coastal Plain compare favorably with the numerical limits placed on the Paleocene-Eocene boundary in the published literature. Generally, the Paleocene-Eocene Epoch boundary is reported as approximately 54 to 55 MA.

  7. Fossil plant stomata indicate decreasing atmospheric CO2 prior to the Eocene-Oligocene boundary

    NASA Astrophysics Data System (ADS)

    Steinthorsdottir, Margret; Porter, Amanda S.; Holohan, Aidan; Kunzmann, Lutz; Collinson, Margaret; McElwain, Jennifer C.

    2016-02-01

    A unique stratigraphic sequence of fossil leaves of Eotrigonobalanus furcinervis (extinct trees of the beech family, Fagaceae) from central Germany has been used to derive an atmospheric pCO2 record with multiple data points spanning the late middle to late Eocene, two sampling levels which may be earliest Oligocene, and two samples from later in the Oligocene. Using the inverse relationship between the density of stomata and pCO2, we show that pCO2 decreased continuously from the late middle to late Eocene, reaching a relatively stable low value before the end of the Eocene. Based on the subsequent records, pCO2 in parts of the Oligocene was similar to latest Eocene values. These results suggest that a decrease in pCO2 preceded the large shift in marine oxygen isotope records that characterizes the Eocene-Oligocene transition and that when a certain threshold of pCO2 change was crossed, the cumulative effects of this and other factors resulted in rapid temperature decline, ice build up on Antarctica and hence a change of climate mode.

  8. Fossil plant stomata indicate decreasing atmospheric CO2 prior to the Eocene-Oligocene boundary

    NASA Astrophysics Data System (ADS)

    Steinthorsdottir, M.; Porter, A. S.; Holohan, A.; Kunzmann, L.; Collinson, M.; McElwain, J. C.

    2015-10-01

    A unique stratigraphic sequence of fossil leaves of Eotrigonobalanus furcinervis (extinct trees of the beech family, Fagaceae) from central Germany has been used to derive an atmospheric pCO2 record with multiple data points spanning the late middle to late Eocene, two sampling levels which may be earliest Oligocene, and two samples from later in the Oligocene. Using the inverse relationship between the density of stomata and pCO2, we show that pCO2 decreased continuously from the late middle to late Eocene, reaching a relatively stable low value before the end of the Eocene. Based on the subsequent records, pCO2 in parts of the Oligocene was similar to latest Eocene values. These results show that a decrease in pCO2 preceded the large shift in marine oxygen isotope records that characterizes the Eocene-Oliogocene transition. This may be related to the "hysteresis effect" previously proposed - where a certain threshold of pCO2 change was crossed before the cumulative effects of this and other factors resulted in rapid temperature decline, ice build up on Antarctica and hence a change of climate mode.

  9. Multiple microtektite horizons in upper Eocene marine sediments: No evidence for mass extinctions

    USGS Publications Warehouse

    Keller, G.; D'Hondt, S.; Vallier, T.L.

    1983-01-01

    Microtektites have been recovered from three horizons in eight middle Eocene to middle Oligocene marine sediment sequences. Five of these occurrences are coeval and of latest Eocene age (37.5 to 38.0 million years ago); three are coeval and of early late Eocene age (38.5 to 39.5 million years ago); and three are of middle Oligocene age (31 to 32 million years ago). In addition, rare probable microtektites have been found in sediments with ages of about 36.0 to 36.5 million years. The microtektite horizon at 37.5 to 38.0 million years can be correlated with the North American tektite-strewn field, which has a fission track age (minimum) of 34 to 35 million years and a paleomagnetic age of 37.5 to 38.0 million years. There is no evidence for mass faunal extinctions at any of the microtektite horizons. Many of the distinct faunal changes that occurred in the middle Eocene to middle Oligocene can be related to the formation of the Antarctic ice sheet and the associated cooling phenomena and intensification of bottom currents that led to large-scale dissolution of calcium carbonate and erosion, which created areally extensive hiatuses in the deep-sea sediment records. The occurrence of microtektite horizons of several ages and the lack of evidence for faunal extinctions suggest that the effects of extraterrestrial bolide impacts may be unimportant in the biologic realm during middle Eocene to middle Oligocene time.

  10. Larger benthic foraminiferal turnover across the Eocene-Oligocene transition at Siwa Oasis, Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Orabi, H.; El Beshtawy, M.; Osman, R.; Gadallah, M.

    2015-05-01

    In the Eocene part of the Siwa Oasis, the larger foraminifera are represented by the genera Nummulites, Arxina, Operculina, Sphaerogypsina, Asterocyclina, Grzybowskia, Silvestriella, Gaziryina and Discocyclina in order of abundance. Operculina continues up to the early Oligocene as modern representatives in tropical regions, while the other genera became extinct. Nevertheless, the most common larger foraminiferal genus Lepidocyclina (Nephrolepidina) appears only in the lowermost Oligocene. In spite of the Eocene-Oligocene (E/O) transition is thought to have been attended by major continental cooling at northern middle and high latitudes, we discover that at the Siwa Oasis, there is a clear warming trend from the late Eocene (extinction level of Nummulites, Sphaerogypsina, Asterocyclina, Grzybowskia, Silvestriella and Discocyclina) to the early Oligocene is observed due to the high abundance of Operculina and occurrence of kaolinite and gypsiferous shale deposits in both Qatrani and El Qara formations (Oligocene) at this transition. The El Qara Formation is a new rock unit proposed herein for the Oligocene (Rupelian age) in the first time. Several episodes of volcanic activity occurred in Egypt during the Cenozoic. Mid Tertiary volcanicity was widespread and a number of successive volcanic pulses are starting in the late Eocene. The release of mantle CO2 from this very active volcanic episode may have in fact directly caused the warm Eocene-Oligocene greenhouse climate effect.

  11. Multiple microtektite horizons in upper eocene marine sediments: no evidence for mass extinctions.

    PubMed

    Keller, G; D'Hondt, S; Vallier, T L

    1983-07-08

    Microtektites have been recovered from three horizons in eight middle Eocene to middle Oligocene marine sediment sequences. Five of these occurrences are coeval and of latest Eocene age (37.5 to 38.0 million years ago); three are coeval and of early late Eocene age (38.5 to 39.5 million years ago); and three are of middle Oligocene age (31 to 32 million years ago). In addition, rare probable microtektites have been found in sediments with ages of about 36.0 to 36.5 million years. The microtektite horizon at 37.5 to 38.0 million years can be correlated with the North American tektite-strewn field, which has a fission track age (minimum) of 34 to 35 million years and a paleomagnetic age of 37.5 to 38.0 million years. There is no evidence for mass faunal extinctions at any of the microtektite horizons. Many of the distinct faunal changes that occurred in the middle Eocene to middle Oligocene can be related to the formation of the Antarctic ice sheet and the associated cooling phenomena and intensification of bottom currents that led to large-scale dissolution of calcium carbonate and erosion, which created areally extensive hiatuses in the deep-sea sediment records. The occurrence of microtektite horizons of several ages and the lack of evidence for faunal extinctions suggest that the effects of extraterrestrial bolide impacts may be unimportant in the biologic realm during middle Eocene to middle Oligocene time.

  12. The oldest African bat from the early Eocene of El Kohol (Algeria)

    NASA Astrophysics Data System (ADS)

    Ravel, Anthony; Marivaux, Laurent; Tabuce, Rodolphe; Adaci, Mohammed; Mahboubi, Mohammed; Mebrouk, Fateh; Bensalah, Mustapha

    2011-05-01

    The Afro-Arabian Paleogene fossil record of Chiroptera is very poor. In North Africa and Arabia, this record is limited, thus far, to a few localities mainly in Tunisia (Chambi, late early Eocene), Egypt (Fayum, late Eocene to early Oligocene), and Sultanate of Oman (Taqah, early Oligocene). It consists primarily of isolated teeth or mandible fragments. Interestingly, these African fossil bats document two modern groups (Vespertilionoidea and Rhinolophoidea) from the early Eocene, while the bat fossil record of the same epoch of North America, Eurasia, and Australia principally includes members of the "Eochiroptera." This paraphyletic group contains all primitive microbats excluding modern families. In Algeria, the region of Brezina, southeast of the Atlas Mountains, is famous for the early Eocene El Kohol Formation, which has yielded one of the earliest mammalian faunas of the African landmass. Recent fieldwork in the same area has led to the discovery of a new vertebrate locality, including isolated teeth of Chiroptera. These fossils represent the oldest occurrence of Chiroptera in Africa, thus extending back the record of the group to the middle early Eocene (Ypresian) on that continent. The material consists of an upper molar and two fragments of lower molars. The dental character association matches that of "Eochiroptera." As such, although very fragmentary, the material testifies to the first occurrence of "Eochiroptera" in Algeria, and by extension in Africa. This discovery demonstrates that this basal group of Chiroptera had a worldwide distribution during the early Paleogene.

  13. Invading Europe: did climate or geography trigger early Eocene primate dispersals?

    PubMed

    Soligo, Christophe

    2007-01-01

    The Palaeocene-Eocene transition is characterized by a significant turnover of mammalian taxa in the fossil record of the northern continents, and primates are among the groups that make their first appearance at this time. One of the many questions that remain to be answered with regard to the earliest evolution of primates is the reason for their sudden and virtually simultaneous appearance in the fossil records of Asia, Europe and North America. The most obvious environmental correlate of the Palaeocene-Eocene transition is a sharp but relatively short-lived warming event leading up to the Palaeocene-Eocene thermal maximum (PETM) and evidenced in the stratigraphic record by a negative delta(13)C excursion. It remains unclear, however, whether or how this warming event may have influenced Palaeocene-Eocene faunal turnovers. This paper explores the hypothesis that environmental changes associated with the PETM facilitated an invasion of Western Europe by primates by comparing the ecological structure of local mammalian fauna immediately before and following the Palaeocene-Eocene transition. The results suggest that changes to the ecological profile of local mammalian fauna were relatively small and did not favour an invasion by primates, although a major uncertainty remains with respect to the availability of arboreal niches. At present it seems more likely that the invasion of western Europe by primates was due to the breakdown of one or more dispersal barriers close to the end of the Palaeocene.

  14. Sonora, Mexico, source for the Eocene Poway Conglomerate of southern California

    NASA Astrophysics Data System (ADS)

    Abbott, Patrick L.; Smith, T. E.

    1989-04-01

    Alluvial-fan conglomerates of the Eocene Poway Group are composed largely of exotic rhyolite and dacite clasts derived from far to the east of their Eocene depositional site. Remnants of the Upper Jurassic bedrock source of the Poway rhyolite clasts may yet be exposed in hills in Sonora, Mexico. For this study, pieces of bedrock were taken from hills 13 km west of El Plomo in Sonora. Clasts texturally and mineralogically similar to the Sonoran bedrock were collected from the apex of the Eocene alluvial fan in San Diego County, California Nine couplets of bedrock and conglomerate clast samples (textural twins) were analyzed for 16 trace elements selected for their wide range of behaviors during magmatic and alteration processes. Statistical comparisons of the trace-element data, by using the standard error-of-the-difference method, show that there are no significant differences between the two populations. These data strongly suggest that the rhyolitic bedrock hills west of El Plomo were part of the source terrane for the Eocene conglomerate in San Diego. The latitudinal separation between bedrock source and the site of deposition is only the 2° created by the opening of the Gulf of California This implies that any boundary separating a paleomagnetically efined, Baja-Borderland terrane from the craton since Eocene time was at least 100 km east of the Gulf of California in northernmost Sonora.

  15. Characteristics of Foraminifera from Eocene Hyperthermal Events in Western India

    NASA Astrophysics Data System (ADS)

    Khanolkar, S.; Saraswati, P.

    2013-12-01

    The carbon isotope excursions (CIE) attributed to Early Eocene warming events were recently reported from low latitude, inner shelf to marginal marine sequences of Kutch and Vastan in western India. In this study we examine the response of foraminifera to the hyperthermal events demarcated in the two sections. The sections are biostratigraphically constrained by shallow benthic zones(SBZ). The PETM is demarcated in the SBZ 5/6 by a negative CIE of 2.1 ‰. The assemblage is characterized by low diversity and moderate abundance of dwarfed foraminifera. The planktic foraminifera consist of Chiloguembelina trinitatensis and Jenkinsina columbiana. Presence of benthic foraminifera like Nummulites, Rotalia, Rosalina, Cibicides, Pararotalia and Nonionella indicate deposition in brackish water, marginal marine to inner shelf conditions. Rectilinear benthic foraminifera (RBF), including the species of Bulimina and Praebulimina having large test pore size(~5μm), vary between 20-30% in the assemblage indicating low oxygen depositional conditions. The α-diversity varies from 2-3 during the event and reduces further to < 1 just after PETM but increases (α = 3-4) again prior to the next warming event. The ETM2 is marked by 1‰ negative shift in δ13C in SBZ 8. Planktic foraminifera J.columbiana, Acarinina esnanensis, C.crinita are found. The benthic foraminifera are dominated by Nummulites, Asterigerina, Cibicides, Pararotalia, Rotalia. RBF (Bulimina, Buliminella and Brizalina) varies between 30-40% indicating low oxygen depositional conditions. The abundance of triserial foraminifera Jenkinsina at certain levels indicates high run off and eutrophic conditions. The ETM3 is marked by a negative shift of 1‰ δ13C in undifferentiated SBZ 9-10. The SBZ 10 is marked by an increase in alpha diversity of foraminifera (α = 4-5) in Vastan. The dwarfed benthic foraminifera are dominated by RBF (Bulimina, Buliminella, Praebulimina) and brackish water, marginal marine foraminiferal

  16. Upper Eocene Spherules at ODP Site 1090B

    NASA Technical Reports Server (NTRS)

    Liu, S.; Kyte, F. T.; Glass, B. P.; Gersonde, R.

    2000-01-01

    Our two labs independently discovered upper Eocene microtektites and microkrystites at ODP Site 1090, a new South Atlantic locality near the Agulhus Ridge. This is a significant new data point for the strewn fields of these spherules, which were recently extended into the Atlantic sector of the Southern Ocean when they were reported at ODP Site 689 on the Maude Rise. The microtektites have been regarded as related to North American tektites and the microkrystites as belonging to the clinopyroxene-bearing (cpx) spherule strewn field. Initial reports indicate that Site 1090 contains a complete sequence of upper Eocene sediments composed of diatom and nannofossil oozes. The magneto- and bio-stratigraphy indicate that impact-age sediments should occur in core 30X of Hole 1090B. One of us (FTK) took 2 cc samples at 10 cm intervals over 600 cm of core for Ir analyses and the senior author (SL) took 3 cc samples at 20 cm intervals to search for spherules. Both studies proved successful and additional samples were obtained to confirm initial results and better define the Ir anomaly and spherule abundances. Peak Ir concentrations of 0.97 ng/g were found at 1090B-30X-5, 105-106cm and 0.78 ng/g at 115-116 cm. Anomalous Ir concentrations (greater than 0.1 ng/g) extend over about 100 cm of core. Preliminary results indicate that the excess Ir at this site is about 25 ng per sq cm. About 380 microtektites (>63 pm) and 2492 microkrystites (>63 pm) were recovered over a 1.8 m interval with a peak abundance of microtektites (106/gram) and microkrystites (562/gram) at 1090B-30X- 5, 114-115 cm. The largest microtektite is approximately 960 x 1140 micron in size. About 55 % are spherical, and the rest are disc, cylinder, dumbbell, teardrop, or fragments. Most of the microtektites are transparent colorless, but a few are transparent pale brown or green. Preliminary data indicate that the microtektites at Site 1090 have similar major oxide compositions to those at Site 689. About 50% of

  17. Atmospheric carbon dioxide through the Eocene-Oligocene climate transition.

    PubMed

    Pearson, Paul N; Foster, Gavin L; Wade, Bridget S

    2009-10-22

    Geological and geochemical evidence indicates that the Antarctic ice sheet formed during the Eocene-Oligocene transition, 33.5-34.0 million years ago. Modelling studies suggest that such ice-sheet formation might have been triggered when atmospheric carbon dioxide levels (pCO2atm) fell below a critical threshold of approximately 750 p.p.m.v., but the timing and magnitude of pCO2atm relative to the evolution of the ice sheet has remained unclear. Here we use the boron isotope pH proxy on exceptionally well-preserved carbonate microfossils from a recently discovered geological section in Tanzania to estimate pCO2atm before, during and after the climate transition. Our data suggest that are reduction in pCO2atm occurred before the main phase of ice growth,followed by a sharp recovery to pre-transition values and then a more gradual decline. During maximum ice-sheet growth, pCO2atm was between approximately 450 and approximately 1,500 p.p.m.v., with a central estimate of approximately 760 p.p.m.v. The ice cap survived the period of pCO2atm recovery,although possibly with some reduction in its volume, implying (as models predict) a nonlinear response to climate forcing during melting. Overall, our results confirm the central role of declining pCO2atm in the development of the Antarctic ice sheet (in broad agreement with carbon cycle modelling) and help to constrain mechanisms and feedbacks associated with the Earth's biggest climate switch of the past 65 Myr.

  18. Longitudinal Differences of Ionospheric Vertical Density Distribution and Equatorial Electrodynamics

    NASA Technical Reports Server (NTRS)

    Yizengaw, E.; Zesta, E.; Moldwin, M. B.; Damtie, B.; Mebrahtu, A.; Valledares, C.E.; Pfaff, R. F.

    2012-01-01

    Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian approx. 37 deg and 290 deg E, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation

  19. Cloud and rain liquid water statistics in the CHUVA campaign

    NASA Astrophysics Data System (ADS)

    Calheiros, Alan J. P.; Machado, Luiz A. T.

    2014-07-01

    The purpose of this study is to present statistics related to the integration of cloud and rain liquid water and the profiles for different cloud types and regimes. From 2010 to 2012, the CHUVA project collected information regarding cloud and rain characteristics in different precipitation regimes in Brazil. CHUVA had four field campaigns between 2010 and 2011, located in the North, Northeast and Southeast regions of Brazil, covering the semi-arid, Amazon, coastal and mountain regions. The synergy of several instruments allowed us to classify rain events and describe the cloud processes regionally. Microwave radiometers, LiDAR, radar, and disdrometers were employed in this study. The rain type classification was made using vertical profiles of reflectivity (VPR) and polarimetric variables from dual polarization radar (XPOL). The integrated liquid water (ILWC) for non-precipitating clouds was retrieved with a microwave ground-based radiometer using a neural network. For rainy conditions, the profiles from the rain liquid water content (LWCR) and their integrated (ILWR) properties were estimated by Micro Rain Radar (MRR) and XPOL VPRs. For non-precipitating clouds, the ILWC values were larger for the sites in tropical regions, in particular near the coast, than for Southeast Brazil. For rainy cases, distinct LWCR profiles were observed for different rain classifications and regions. The differences are small for low rain rates and a distinction between different rainfall regimes is more evident for high rain rates. Vale and Belém clouds present the deepest layers and largest convective rain rates. The clouds in the Southeast region of Brazil (Vale do Paraíba) and North region (Belém) showed the largest reflectivity in the mixed and glaciated layers, respectively. In contrast, the Northeast coastal site (e.g. Fortaleza) showed larger values in the warm part of the clouds. Several analyses are presented, describing the cloud processes and the differences among the

  20. Rain attenuation statistics over millimeter wave bands in South Korea

    NASA Astrophysics Data System (ADS)

    Shrestha, Sujan; Choi, Dong-You

    2017-01-01

    Rain induced degradations are significant for terrestrial microwave links operating at frequencies higher than 10 GHz. Paper presents analyses done on rain attenuation and rainfall data for three years between 2013 till 2015, in 3.2 km experimental link of 38 GHz and 0.1 km link at 75 GHz. The less link distance is maintained for 75 GHz operating frequency in order to have better recording of propagation effect as such attenuation induced by rain. OTT Parsivel is used for collection of rain rate database which show rain rate of about 50 mm/h and attenuation values of 20.89 and 28.55 dB are obtained at 0.01% of the time for vertical polarization under 38 and 75 GHz respectively. Prediction models, namely, ITU-R P. 530-16, Da Silva Mello, Moupfouma, Abdulrahman, Lin and differential equation approach are analyzed. This studies help to identify most suitable rain attenuation model for higher microwave bands. While applying ITU-R P. 530-16, the relative error margin of about 3%, 38% and 42% along with 80, 70, 61% were obtained in 0.1%, 0.01% and 0.001% of the time for vertical polarization under 38 and 75 GHz respectively. Interestingly, ITU-R P. 530-16 shows relatively closer estimation to measured rain attenuation at 75 GHz with relatively less error probabilities and additionally, Abdulrahman and ITU-R P. 530-16 results in better estimation to the measured rain attenuation at 38 GHz link. The performance of prominent rain attenuation models are judged with different error matrices as recommended by ITU-R P. 311-15. Furthermore, the efficacy of frequency scaling technique of rain attenuation between links distribution are also discussed. This study shall be useful for making good considerations in rain attenuation predictions for terrestrial link operating at higher frequencies.

  1. Latitudinal gradients in greenhouse seawater δ(18) O: evidence from Eocene sirenian tooth enamel.

    PubMed

    Clementz, Mark T; Sewall, Jacob O

    2011-04-22

    The Eocene greenhouse climate state has been linked to a more vigorous hydrologic cycle at mid- and high latitudes; similar information on precipitation levels at low latitudes is, however, limited. Oxygen isotopic fluxes track moisture fluxes and, thus, the δ(18)O values of ocean surface waters can provide insight into hydrologic cycle changes. The offset between tropical δ(18)O values from sampled Eocene sirenian tooth enamel and modern surface waters is greater than the expected 1.0 per mil increase due to increased continental ice volume. This increased offset could result from suppression of surface-water δ(18)O values by a tropical, annual moisture balance substantially wetter than that of today. Results from an atmospheric general circulation model support this interpretation and suggest that Eocene low latitudes were extremely wet.

  2. Post-Eocene movement on the Coast Range thrust, northern Sacramento Valley, California

    SciTech Connect

    Ramirez, V. )

    1990-05-01

    Subsurface structure mapping with more than 600 wells and 200 miles of seismic data in a portion of the northern Sacramento basin and surface geologic mapping in the Rumsey Hills area to the west indicates that Upper Cretaceous strata along the western edge of the basin are doubled in thickness along thrust faults. These east-dipping detachments are part of the Coast Range thrust fault system. Eocene strata crop out in the fault zone and indicate that considerable post-Eocene movement occurred. Cretaceous movement on these faults can be surmised but not proven from reconstructions. Similarly, analysis from five subsurface structure maps to the east shows that deformation there also is post-Eocene; only minor Upper Cretaceous deformation can be discerned. Underthrusting of Franciscan accretionary rocks best accounts for the development of these faults and a western high along the basin margin.

  3. Space Radar Image of Randonia Rain Cell

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This multi-frequency space radar image of a tropical rainforest in western Brazil shows rapidly changing land use patterns and it also demonstrates the capability of the different radar frequencies to detect and penetrate heavy rainstorms. This color image was created by combining the three separate radar frequencies into a composite image. The three black and white images below represent the individual frequencies. The lower left image, X-band vertically transmitted and received, is blue in the color image; the lower center image, C-band horizontally transmitted and vertically received is green; and the lower right image, L-band horizontally transmitted and vertically received is red. A heavy downpour in the lower center of the image appears as a black 'cloud' in the X-band image, the same area is shows up faintly in the C-band image, and is invisible in the L-band image. When combined in the color image, the rain cell appears red and yellow. Although radar can usually 'see' through clouds, short radar wavelengths (high frequency), such as X and C-band, can be changed by unusually heavy rain cells. L-band, at a 24 cm (9 inches) wavelength, is unaffected by such rain cells. By analyzing the way the radar changes, scientist can estimate rainfall rates. The area shown is in the state of Rondonia, in western Brazil. The pink areas are pristine tropical rainforest, and the blue and green patches are areas where the forest has been cleared for agriculture. Cleared areas are typically able to support intense farming for a only few years, before soil erosion renders the fields unusable. Radar imaging can be used to monitor not only the rainforest destruction, but also the rates of recovery of abandoned fields. This image is 35.2 kilometers by 21.3 kilometers (21.8 miles by 13.2 miles) and is centered at 11.2 degrees south latitude, 61.7 degrees west longitude. North is toward the upper left. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic

  4. Pronounced zonal heterogeneity in Eocene southern high-latitude sea surface temperatures

    PubMed Central

    Douglas, Peter M. J.; Affek, Hagit P.; Ivany, Linda C.; Houben, Alexander J. P.; Sijp, Willem P.; Sluijs, Appy; Schouten, Stefan; Pagani, Mark

    2014-01-01

    Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 °C in the southwest Pacific contrasting with SSTs between 5 and 15 °C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10–17 °C (1σ SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of ∼7 °C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 °C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The pronounced zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands. PMID:24753570

  5. Pronounced zonal heterogeneity in Eocene southern high-latitude sea surface temperatures.

    PubMed

    Douglas, Peter M J; Affek, Hagit P; Ivany, Linda C; Houben, Alexander J P; Sijp, Willem P; Sluijs, Appy; Schouten, Stefan; Pagani, Mark

    2014-05-06

    Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 °C in the southwest Pacific contrasting with SSTs between 5 and 15 °C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10-17 °C (1σ SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of ∼7 °C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 °C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The pronounced zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands.

  6. Fog and rain in the Amazon

    PubMed Central

    Anber, Usama; Gentine, Pierre; Wang, Shuguang; Sobel, Adam H.

    2015-01-01

    The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents. PMID:26324902

  7. Fog and rain in the Amazon

    NASA Astrophysics Data System (ADS)

    Anber, Usama; Gentine, Pierre; Wang, Shuguang; Sobel, Adam H.

    2015-09-01

    The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents.

  8. BOREAS HYD-9 Belfort Rain Gauge Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Kouwen, Nick; Soulis, Ric; Jenkinson, Wayne; Graham, Allyson; Knapp, David E. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-6 team collected several data sets related to the moisture content of soil and overlying humus layers. This data set contains water content measurements of the moss/humus layer, where it existed. These data were collected along various flight lines in the Southern Study Area (SSA) and Northern Study Area (NSA) during 1994. The data are available in tabular ASCII files. The HYD-9 Belfort rain gauge data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  9. Fog and rain in the Amazon.

    PubMed

    Anber, Usama; Gentine, Pierre; Wang, Shuguang; Sobel, Adam H

    2015-09-15

    The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents.

  10. The critical slope for orographic rain

    NASA Astrophysics Data System (ADS)

    Breidenthal, Robert; Zagar, Nedjeljka

    2013-11-01

    Krishnamurti has shown that orographic rain depends on the slope of the windward terrain rather than just the total elevation gain. A simple physical model is proposed to account for the effect of slope. Based on the inhibiting effect of vortex (rotational) acceleration on entrainment, a critical slope angle is derived. If the rate of orographic lifting is sufficiently large, the enhanced buoyancy from latent heat release increases the acceleration parameter. As a consequence, the entrainment rate of under-saturated air is reduced. The critical slope corresponds to the situation where the rate of condensation in a rising adiabatic parcel just equals the rate of evaporation due to the entrainment of under-saturated air. The model is also applied to the trigger conditions for towering cumulus in general.

  11. The critical slope angle for orographic rain

    NASA Astrophysics Data System (ADS)

    Breidenthal, R. E.; Zagar, N.

    2013-12-01

    Krishnamurti has shown that orographic rain depends on the slope of the windward terrain rather than just the total elevation gain. A simple physical model is proposed to account for the effect of slope. Based on the inhibiting effect of vortex (rotational) acceleration on entrainment, a critical slope angle is derived. If the rate of orographic lifting is sufficiently large, the enhanced buoyancy from latent heat release increases the acceleration parameter. As a consequence, the entrainment rate of under-saturated air is reduced. The critical slope corresponds to the situation where the rate of condensation in a rising adiabatic parcel just equals the rate of evaporation due to the entrainment of under-saturated air. The model is also applied to the trigger conditions for towering cumulus in general.

  12. Industrial concessions, fires and air pollution in Equatorial Asia

    NASA Astrophysics Data System (ADS)

    Spracklen, D. V.; Reddington, C. L.; Gaveau, D. L. A.

    2015-09-01

    Forest and peatland fires in Indonesia emit large quantities of smoke leading to poor air quality across Equatorial Asia. Marlier et al (2015 Environ. Res. Lett. 10 085005) explore the contribution of fires occurring on oil palm, timber (wood pulp and paper) and natural forest logging concessions to smoke emissions and exposure of human populations to the resulting air pollution. They find that one third of the population exposure to smoke across Equatorial Asia is caused by fires in oil palm and timber concessions in Sumatra and Kalimantan. Logging concessions have substantially lower fire emissions, and contribute less to air quality degradation. This represents a compelling justification to prevent reclassification of logging concessions into oil palm or timber concessions after logging. This can be achieved by including logged forests in the Indonesian moratorium on new plantations in forested areas.

  13. Bispectral analysis of equatorial spread F density irregularities

    NASA Technical Reports Server (NTRS)

    Labelle, J.; Lund, E. J.

    1992-01-01

    Bispectral analysis has been applied to density irregularities at frequencies 5-30 Hz observed with a sounding rocket launched from Peru in March 1983. Unlike the power spectrum, the bispectrum contains statistical information about the phase relations between the Fourier components which make up the waveform. In the case of spread F data from 475 km the 5-30 Hz portion of the spectrum displays overall enhanced bicoherence relative to that of the background instrumental noise and to that expected due to statistical considerations, implying that the observed f exp -2.5 power law spectrum has a significant non-Gaussian component. This is consistent with previous qualitative analyses. The bicoherence has also been calculated for simulated equatorial spread F density irregularities in approximately the same wavelength regime, and the resulting bispectrum has some features in common with that of the rocket data. The implications of this analysis for equatorial spread F are discussed, and some future investigations are suggested.

  14. Relationship between Fe /+/ ions and equatorial spread F.

    NASA Technical Reports Server (NTRS)

    Hanson, W. B.; Sanatani, S.

    1971-01-01

    Evaluation of observations from the retarding potential analyzer on Ogo 6 near the magnetic equator, demonstrating an intimate relationship between the presence of Fe(+) ions and irregularities in the total ion concentration. The ionospheric irregularities (or structure) are probably another manifestation of equatorial spread F, although this has not yet been verified. Nearly half the nighttime equatorial crossings below 700 km exhibit both Fe(+) and structure, but only 10% of the passes without Fe(+) have structure. Approximately one-third of the passes with Fe(+) are not structured, which indicates that Fe(+) may be a necessary but not sufficient condition for structure formation. The Atlantic region shows an extremely high and detailed correlation between Fe(+) ions and the irregularities.

  15. Small-Scale Magnetic Reconnection at Equatorial Coronal Hole Boundaries

    NASA Astrophysics Data System (ADS)

    Lamb, Derek; DeForest, C. E.

    2011-05-01

    Coronal holes have long been known to be the source of the fast solar wind at both high and low latitudes. The equatorial extensions of polar coronal holes have long been assumed to have substantial magnetic reconnection at their boundaries, because they rotate more rigidly than the underlying photosphere. However, evidence for this reconnection has been sparse until very recently. We present some evidence that reconnection due to the evolution of small-scale magnetic fields may be sufficient to drive coronal hole boundary evolution. We hypothesize that a bias in the direction of that reconnection is sufficient to give equatorial coronal holes their rigid rotation. We discuss the prospects for investigating this using FLUX, a reconnection-controlled coronal MHD simulation framework. This work was funded by the NASA SHP-GI program.

  16. Lunar-solar interactions in the equatorial electrojet

    NASA Astrophysics Data System (ADS)

    Gasperini, F.; Forbes, J. M.

    2014-05-01

    To first order the ground magnetic signature of the equatorial electrojet (EEJ) reflects the height integral of J = σE, where σis a conductivity and E represents some combination of the global dynamo-generated electric field and the electric field due to local winds. Day-to-day variations in the conductivity are strongly controlled by the solar flux, while E depends on solar and lunar tides, planetary waves, and the disturbance dynamo. In this study we demonstrate how complexity is introduced into the EEJ due to the interaction between lunar tide variability in the equatorial electric field and solar-driven variability in the E region conductivity. Toward this end, we analyze magnetometer data from the Huancayo observatory both in the time and frequency domain. We present results for the year 1990, and we show that 86% of the variance in the EEJ is due to the lunar-solar interaction.

  17. Bottomside sinusoidal irregularities in the equatorial F region

    NASA Technical Reports Server (NTRS)

    Valladares, C. E.; Hanson, W. B.; Mcclure, J. P.; Cragin, B. L.

    1983-01-01

    By using the Ogo 6 satellite, McClure and Hanson (1973) have discovered sinusoidal irregularities in the equatorial F region ion number density. In the present investigation, a description is provided of the properties of a distinct category of sinusoidal irregularities found in equatorial data from the AE-C and AE-E satellites. The observed scale sizes vary from about 300 m to 3 km in the direction perpendicular to B, overlapping with and extending the range observed by using Ogo 6. Attention is given to low and high resolution data, a comparison with Huancayo ionograms, the confinement of 'bottomside sinusoidal' (BSS) irregularities essentially to the bottomside of the F layer, spectral characteristics, and BSS, scintillation, and ionosonde observations.

  18. Modeling study of equatorial ionospheric height and spread F occurrence

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi

    1996-03-01

    In the ionospheric F region at equatorial latitudes, the strength of the zonal electric field in the evening hours is closely connected with the generation of equatorial spread F and plasma bubbles. Many researchers discuss the electric fields and dynamics of the ionosphere in terms of the time derivative of F layer virtual heights (dh'F/dt) scaled on the ionograms, and this paper examines the accuracy of zonal electric fields derived by such a method. Although the effect of transequatorial thermospheric wind had been thought to be negligible, model calculations of ion concentration show that this wind significantly changes ionospheric height in the evening hours. Further, the electric field strength is estimated based on observed dh'F/dt, considering the apparent vertical drift of the ionosphere due to the thermospheric wind effect. Rayleigh-Taylor growth rates calculated for those electric fields agree quantitatively with the spread F occurrence.

  19. Equatorial plasma bubbles/range spread firregularities and the QBO

    NASA Astrophysics Data System (ADS)

    Chen, Pei-Ren

    1993-11-01

    Investigation of the relationship between the percentage occurrence of equatorial plasma bubbles/range spread F irregularities (EPBRSI) and the Quasi-Biennial Oscillation (QBO) of the lower stratospheric mean zonal wind in the equatorial zone reveals a QBO-modulation effect on the percentage occurrence of the EPBRSI. A longitudinal dependence of this QBO-modulation effect has also been found: the percentage occurrence of EPBRSI increases (decreases) in the easterly phase of the QBO in the Indian-East African sector (in the American sector) and decreases (increases) in the westerly phase of the QBO in the Indian-East African sector (in the American sector). It is suggested that this represents new evidence that the low-latitude ionosphere is modulated by atmospheric planetary waves from below.

  20. Ongoing Analysis of Jupiter's Equatorial Hotspots and Plumes from Cassini

    NASA Technical Reports Server (NTRS)

    Choi, D. S.; Showmwn, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

    2012-01-01

    We present updated results from our ongoing analysis of Cassini observations of Jupiter's equatorial meteorology. For two months preceding the spacecraft's closest approach of the planet, the ISS instrument onboard Cassini regularly imaged the atmosphere of Jupiter. We created time-lapse movies from this period that show the complex activity and interactions of the equatorial atmosphere. During this period, hot spots exhibited significant variations in size and shape over timescales of days and weeks. Some of these changes appear to be a result of interactions with passing vortex systems in adjacent latitudes. Strong anticyclonic gyres to the southeast of the dark areas converge with flow from the west and appear to circulate into a hot spot at its southwestern corner.