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Sample records for mid-latitude continental convective

  1. The Mid-latitude Continental Convective Clouds (MC3E) Experiment Final Campaign Report

    SciTech Connect

    Jensen, Michael; Kollias, Pavlos; Giangrande, Scott

    2014-04-01

    The Mid-latitude Continental Convective Clouds Experiment (MC3E) took place from April 22 through June 6, 2011, centered at the ARM Southern Great Plains site (http://www.arm.gov/sites/sgp) in northcentral Oklahoma. MC3E was a collaborative effort between the ARM Climate Research Facility and the National Aeronautics and Space Administration’s (NASA’s) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The campaign leveraged the largest ground-based observing infrastructure available in the central United States, including recent upgrades through the American Recovery and Reinvestment Act of 2009, combined with an extensive sounding array, remote sensing and in situ aircraft observations, and additional radar and in situ precipitation instrumentation. The overarching goal of the campaign was to provide a three-dimensional characterization of convective clouds and precipitation for the purpose of improving the representation of convective lifecycle in atmospheric models and the reliability of satellite-based retrievals of precipitation.

  2. The Mid-Latitude Continental Convective Clouds Experiment (MC3E)

    SciTech Connect

    Petersen,W.; Jensen,M.; Genio, A. D.; Giangrande, S.; Heymsfield, A.; Heymsfield, G.; Hou, A.; Kollias, P.; Orr, B.; Rutledge, S.; Schwaller, M.; Zipser, E.

    2010-03-15

    The Midlatitude Continental Convective Cloud Experiment (MC3E) will take place in central Oklahoma during the April-May 2011 period. The experiment is a collaborative effort between the U.S. Department of Energy Atmospheric Radition Measurement Program and the National Aeronautics and Space Administration's (NASA) Global Precipitation Measurement (GPM) mission Ground Validation program. The Intensive Observation Period leverages the unprecedented observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors and new ARM instrumentation purchased with American Recovery and Reinvestment Act funding. The overarching goal is to provide the most complete characterization of convective cloud systems, precipitation and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall observations over land that have never before been available. Several different components of convective processes tangible to the convective parameterization problem are targeted such as, pre-convective environment and convective initiation, updraft / downdraft dynamics, condensate transport and detrainment, precipitation and cloud microphysics, influence on the environment and radiation and a detailed description of the large-scale forcing. MC3E will use a new multi-scale observing strategy with the participation of a network of distributed sensors (both passive and active). The approach is to document in 3-D not only the full spectrum of precipitation rates, but also clouds, winds and moisture in an attempt to provide a holistic view of convective clouds and their feedback with the environment. A goal is to measure cloud and precipitation transitions and environmental quantities that are important for satellite retrieval algorithms, convective parameterization in large-scale models

  3. On the synoptic and mesoscale organization of mid-latitude, continental convective snow events

    NASA Astrophysics Data System (ADS)

    Melick, Christopher J.

    An ingredients-based methodology was pursued in order to evaluate the likelihood of thunderstorms occurring in the presence of snowfall (i.e. thundersnow; TSSN) by validating the collective presence of forcing, moisture, and instability in the atmosphere. Since the latter factor has been cited as crucial in distinguishing from typical snowstorms (i.e. non-TSSN), the detailed examination focused on stability characteristics of wintertime convection across the central United States immediately leading up to the onset of the event. Although results from several commonly employed techniques performed successfully, the research primarily analyzed the value of the seldom applied growth rate parameter through initial output fields of the 40-km Rapid Update Cycle model. The current work substantiated the premise that atmospheres were more unstable in episodes of convective snow. The analyses revealed pronounced forcing mechanisms and greater susceptibility to the produced upward vertical motions, thus, illustrating the positive feedback and strong, crucial connection between the two ingredients. The development of TSSN and any associated banding was correctly and most accurately predicted from trends in plots of the growth rate parameter analyzed at the level at which the highest significant growth rates occurred. An outlook for elevated, cold-season thunderstorms can be more accurately issued by identifying regions where reduced values of equivalent potential vorticity (i.e. small symmetric stability or instability) are collocated with estimates of high growth rates (i.e. where small-scale slantwise perturbations will grow). Given the overall success, it is hoped that some of the conclusions established will be implemented routinely in an operational environment and provide forecasters an additional, essential tool in dealing with nowcasting situations of hazardous winter weather events.

  4. Integrated framework for retrievals in a networked radar environment: Application to the Mid-latitude Continental Convective Clouds Experiment

    NASA Astrophysics Data System (ADS)

    Hardin, J. C.; Chandrasekar, C. V.; Yoshikawa, E.; Ushio, T.

    2012-12-01

    The Mid-Latitude Continental Convective Clouds Experiment (MC3E), was a joint DOE Atmospheric Radiation Measurement (ARM) and NASA Global Precipitation Measurements (GPM) field campaign that took place from April - June 2011 in Central Oklahoma centered at the ARM Southern Great Plains site. The experiment was a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign involved a large suite of observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors, and new ARM instrumentation. The overarching goal was to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that had never before been available. The experiment consisted of a large number of ground radars, including NASA scanning dual-polarization radar systems (NPOL) at S-band, wind profilers, and a dense network of surface disdrometers. In addition to these special MC3E instruments, there were three networked scanning X-band radar systems, four wind profilers, a C-band scanning radar, a dual-wavelength (Ka/W) scanning cloud radar. There is extensive literature on the retrieval algorithms for precipitation and cloud parameters from single frequency, dual-polarization radar systems. With the cost of instruments such as radars becoming more affordable, multiple radar deployments are becoming more common in special programs, and the MC3E is a text book example of such a deployment. Networked deployments are becoming more common popularized by the

  5. Spectral characteristics of mid-latitude continental convection from a global variable-resolution Voronoi-mesh atmospheric model

    NASA Astrophysics Data System (ADS)

    Wong, M.; Skamarock, W. C.

    2015-12-01

    Global numerical weather forecast tests were performed using the global nonhydrostatic atmospheric model, Model for Prediction Across Scales (MPAS), for the NOAA Storm Prediction Center 2015 Spring Forecast Experiment (May 2015) and the Plains Elevated Convection at Night (PECAN) field campaign (June to mid-July 2015). These two sets of forecasts were performed on 50-to-3 km and 15-to-3 km smoothly-varying horizontal meshes, respectively. Both variable-resolution meshes have nominal convection-permitting 3-km grid spacing over the entire continental US. Here we evaluate the limited-area (vs. global) spectra from these NWP simulations. We will show the simulated spectral characteristics of total kinetic energy, vertical velocity variance, and precipitation during these spring and summer periods when diurnal continental convection is most active over central US. Spectral characteristics of a high-resolution global 3-km simulation (essentially no nesting) from the 20 May 2013 Moore, OK tornado case are also shown. These characteristics include spectral scaling, shape, and anisotropy, as well as the effective resolution of continental convection representation in MPAS.

  6. Physical Validation of GPM Retrieval Algorithms Over Land: An Overview of the Mid-Latitude Continental Convective Clouds Experiment (MC3E)

    NASA Technical Reports Server (NTRS)

    Petersen, Walter A.; Jensen, Michael P.

    2011-01-01

    The joint NASA Global Precipitation Measurement (GPM) -- DOE Atmospheric Radiation Measurement (ARM) Midlatitude Continental Convective Clouds Experiment (MC3E) was conducted from April 22-June 6, 2011, centered on the DOE-ARM Southern Great Plains Central Facility site in northern Oklahoma. GPM field campaign objectives focused on the collection of airborne and ground-based measurements of warm-season continental precipitation processes to support refinement of GPM retrieval algorithm physics over land, and to improve the fidelity of coupled cloud resolving and land-surface satellite simulator models. DOE ARM objectives were synergistically focused on relating observations of cloud microphysics and the surrounding environment to feedbacks on convective system dynamics, an effort driven by the need to better represent those interactions in numerical modeling frameworks. More specific topics addressed by MC3E include ice processes and ice characteristics as coupled to precipitation at the surface and radiometer signals measured in space, the correlation properties of rainfall and drop size distributions and impacts on dual-frequency radar retrieval algorithms, the transition of cloud water to rain water (e.g., autoconversion processes) and the vertical distribution of cloud water in precipitating clouds, and vertical draft structure statistics in cumulus convection. The MC3E observational strategy relied on NASA ER-2 high-altitude airborne multi-frequency radar (HIWRAP Ka-Ku band) and radiometer (AMPR, CoSMIR; 10-183 GHz) sampling (a GPM "proxy") over an atmospheric column being simultaneously profiled in situ by the University of North Dakota Citation microphysics aircraft, an array of ground-based multi-frequency scanning polarimetric radars (DOE Ka-W, X and C-band; NASA D3R Ka-Ku and NPOL S-bands) and wind-profilers (S/UHF bands), supported by a dense network of over 20 disdrometers and rain gauges, all nested in the coverage of a six-station mesoscale rawinsonde

  7. Tropical and mid-latitude forcing of continental Antarctic temperatures

    NASA Astrophysics Data System (ADS)

    Turney, C. S. M.; Fogwill, C. J.; Klekociuk, A. R.; van Ommen, T. D.; Curran, M. A. J.; Moy, A. D.; Palmer, J. G.

    2015-12-01

    Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid-latitudes to high latitudes of the Southern Hemisphere (SH), which over the last few decades have experienced extreme and regionally variable trends in precipitation, ocean circulation and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually resolved record of δD - a proxy for temperature - from the geographic South Pole where we find a significant influence from extratropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a significant influence on mid- to high-latitude SH climate, modulated by the tropical Pacific Ocean. This work adds to a growing body of literature confirming the important roles of tropical and mid-latitude atmospheric circulation variability on Antarctic temperatures. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.

  8. A comparison of the microphysical and kinematic characteristics of mid-latitude and tropical convective updrafts and downdrafts

    NASA Astrophysics Data System (ADS)

    Stith, J. L.; Haggerty, J.; Grainger, C.; Detwiler, A.

    2006-11-01

    Airborne measurements of updraft speeds, liquid water content and other microphysical parameters were measured in convective storms during two mid-latitude summers in North Dakota, USA, and in two tropical locations (the continental Amazon region in tropical South America and Kwajalein in the tropical central Pacific Ocean). Data representing 0.5 km averages of data collected from a large number of clouds sampled during the field seasons are examined. In the North Dakota clouds, updraft values of a given magnitude were found about as often as downdrafts of similar magnitude in midlevels of the clouds, while lower levels favored downdrafts and upper levels favored updrafts. Drafts in tropical clouds were much weaker and favored updrafts in mid to upper regions of the clouds (the lower levels were not sampled). In two temperature regions (- 5 to - 12 °C and - 12 to - 20 °C), there was little difference in the frequency of occurrence of liquid water content values in the North Dakota clouds, while in the tropical clouds, higher liquid water contents were less likely to be found in the colder temperature intervals. The particle concentrations measured by FSSP instruments were similar in lower and midlevels of the North Dakota clouds, and decreased in upper levels. In the tropical clouds, the concentrations were similar in the mid and upper regions of the clouds. These results are discussed in terms of previous measurements of midlatitude and tropical clouds.

  9. Tracing troposphere-to-stratosphere transport above a mid-latitude deep convective system

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Brunner, D.; Wernli, H.; Schwierz, C.; Martius, O.; Hoor, P.; Fischer, H.; Parchatka, U.; Spelten, N.; Schiller, C.; Krebsbach, M.; Weers, U.; Staehelin, J.; Peter, Th.

    2004-05-01

    this level. Elevated H2O mixing ratios in the ECMWF and HRM model are seen only up to about tropopause height at 340 hPa and 270hPa, respectively, well below flight altitude of about 200 hPa. However, forward tracing of the convective influence as identified by satellite brightness temperature measurements and counts of lightning strokes shows that during this part of the flight the aircraft was closely following the border of an air mass which was heavily impacted by convective activity over Spain and Algeria. This is evidence that deep convection at mid-latitudes may have a large impact on the tracer distribution of the lowermost stratosphere reaching well above the thunderstorms anvils as claimed by recent studies using cloud-resolving models.

  10. Tracing troposphere-to-stratosphere transport above a mid-latitude deep convective system

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Brunner, D.; Wernli, H.; Schwierz, C.; Martius, O.; Hoor, P.; Fischer, H.; Spelten, N.; Schiller, C.; Krebsbach, M.; Parchatka, U.; Weers, U.; Staehelin, J.; Peter, Th.

    2004-01-01

    this level. Elevated H2O mixing ratios in the ECMWF and HRM model are seen only up to about tropopause height at 340 hPa and 270hPa, respectively, well below flight altitude of about 200 hPa. However, forward tracing of the convective influence as identified by satellite brightness temperature measurements and counts of lightning strokes shows that during this part of the flight the aircraft was closely following the border of an air mass which was heavily impacted by convective activity over Spain and Algeria. This is evidence that deep convection at mid-latitudes may have a large impact on the tracer distribution of the lowermost stratosphere reaching well above the thunderstorms anvils as claimed by recent studies using cloud-resolving models.

  11. New SuperDARN Radar Capabilities for Observing Ionospheric Plasma Convection and ITM Coupling in the Mid-Latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Baker, J. B.; Greenwald, R. A.; Clausen, L. B.; Shepherd, S. G.; Bristow, W. A.; Talaat, E. R.; Barnes, R. J.

    2010-12-01

    Within the past year the first pair of SuperDARN radars funded under the NSF MSI program has become operational at a site near Hays, Kansas. The fields of view of the co-located radars are oriented to provide common-volume observations with two existing radars in Virginia (Wallops, Blackstone) and two MSI radars under construction in Oregon (Christmas Valley). The emerging mid-latitude radar chain will complement the existing SuperDARN coverage at polar cap and auroral latitudes within North America. The mid-latitude radars observe the expansion of auroral effects during disturbed periods, subauroral polarization streams, and small-scale ionospheric irregularities on the nightside that open a window on the plasma drifts and electric fields of the quiet-time subauroral ionosphere. They also measure neutral winds at mesospheric heights and the propagation of ionospheric disturbances due to the passage of atmospheric gravity waves. The new radar capabilities provide unprecedented views of ITM processes in the subauroral ionosphere with applications to studies of ionospheric electric fields, ion-neutral coupling, atmospheric tides and planetary waves, ionospheric plasma structuring and plasma instability. In this talk we describe the new capabilities and the potential for providing large-scale context for related ITM measurements over North America. We present the first high-resolution two-dimensional maps of ionospheric plasma convection at mid-latitudes as generated from common-volume observations with the Hays and Blackstone radars.

  12. Bulk Hydrometeor Types of Mid-Latitude Convective Systems from Bin-Resolving Cloud Simulations and Dual-Polarimetric Scanning Radar Retrieval

    NASA Astrophysics Data System (ADS)

    Matsui, T.; Iguchi, T.; Tao, W. K.; Dolan, B.; Rutledge, S. A.

    2014-12-01

    Robust hydrometeor identification (HID) algorithm has emerged through the use of multi-wavelength polarimetric weather radars [Dolan et al. 2013]. This presentation provides a simple yet useful method to evaluate simulated hydrometeor profiles against the polarimetric radar-retrieved HID data in the specific case study of the Mid-latitude Continental Convective Cloud Experiment (MC3E). The MC3E is the joint NASA-DOE-funded field campaign over the DOE Southern Great Plains (SGP) site, Oklahoma, USA in Spring 2011. We focus on the April 25 case, which observed a strong deep convective system propagating over the SGP site. Colorado State University (CSU) multi-wavelength HID algorithm revealed instantaneous HID profiles and also time-integrated HID diagram separately for shallow, deep stratiform, and deep convective columns. These retrievals are used to evaluate the Weather Research Forecasting model with Spectra-Bin Microphysics (WRF-SBM) [Iguchi et al. 2013]. For this, we have developed a simple emulator of the CSU HID algorithm to consider similar hydrometeor assumptions between the WRF-SBM and CSU HID algorithm. Initial evaluation appears to be reasonable in profiles of shallow and deep stratiform columns between WRF-SBM and CSU HID retrievals, while there is apparent discrepancy in deep convective columns, which is further related to an intuitive assumption in the CSU HID algorithm. Finally feasibility and uncertainties of this approach are discussed.

  13. Modeling Convective Injection of Water Vapor into the Lower Stratosphere in the Mid-Latitudes over North America

    NASA Astrophysics Data System (ADS)

    Clapp, C.; Leroy, S. S.; Anderson, J. G.

    2015-12-01

    Water vapor in the upper troposphere and lower stratosphere (UTLS) from the tropics to the poles is important both radiatively and chemically. Water vapor is the most important greenhouse gas, and increases in water vapor concentrations in the UTLS lead to cooling at these levels and induce warming at the surface [Forster and Shine, 1999; 2002;Solomon et al., 2010]. Water vapor is also integral to stratospheric chemistry. It is the dominant source of OH in the lower stratosphere [ Hanisco et al. , 2001], and increases in water vapor concentrations promote stratospheric ozone loss by raising the reactivity of several key heterogeneous reactions as well as by promoting the growth of reactive surface area [Anderson et al., 2012; Carslaw et al., 1995; Carslaw et al., 1997; Drdla and Muller , 2012; Kirk-Davidoff et al., 1999; Shi et al., 2001]. However, the processes that control the distribution and phase of water in this region of the atmosphere are not well understood. This is especially true at mid-latitudes where several different dynamical mechanisms are capable of influencing UTLS water vapor concentrations. The contribution by deep convective storm systems that penetrate into the lower stratosphere is the least well understood and the least well represented in global models because of the small spatial scales and short time scales over which convection occurs. To address this issue, we have begun a modeling study to investigate the convective injection of water vapor from the troposphere into the stratosphere in the mid-latitudes. Fine-scale models have been previously used to simulate convection from the troposphere to the stratosphere [e.g., Homeyer et al., 2014]. Here we employ the Advanced Research Weather and Research Forecasting model (ARW) at 3-km resolution to resolve convection over the eastern United States during August of 2007 and August of 2013. We conduct a comparison of MERRA, the reanalysis used to initialize ARW, and the model output to assess

  14. Enhanced antisunward convection and F region scintillations at mid-latitudes during storm onset

    SciTech Connect

    Foster, J.C. ); Aarons, J. )

    1988-10-01

    Millstone Hill radar observations over a wide span of latitudes detail the onset of 300 m/s antisunward (westward) convection at mid and low latitudes in the morning sector as a region of storm-enhanced sunward convection retreats poleward. Ring current observations reported by Lui et al. (1987) suggest that the magnetospheric shielding layer was coincident with the observed reversal between sunward and antisunward convection. A strong southward component of the F region neutral wind is observed at latitudes equatorward of the convection reversal. These observations are in agreement with the model of Spiro et al. (1988), who find that storm-enhanced neutrral winds at latitudes equatorward of the shielding layer can generate a long-lived perturbation electric field in the inner magnetosphere. The observations show the growth of the subauroral electric field as the shielding boundary moves poleward. They observe 136-MHz scintillations in both the auroral sunwarrd convection region and the region of subauroral antisunward convection when the convection electric fields exceed 5 mV/m.

  15. The mesoscale precipitation distribution in mid-latitude continental regions: observational uncertainty and evaluation of 25-km global model simulations.

    NASA Astrophysics Data System (ADS)

    Vidale, P. L.; Schiemann, R.; Demory, M. E.; Roberts, C. J.

    2014-12-01

    Mid-latitude precipitation over land exhibits a high degree of variability due to the complex interaction of governing atmospheric processes with coastlines, the heterogeneous land surface, and orography. General circulation models (GCMs) have traditionally shown limited ability in capturing variability in the mesoscale range (here ~50-500 km), due to their low resolution. Recent advances in resolution have provided ensembles of multidecadal climate simulations with GCMs using ~25 km grid spacing. Here, we assess this class of GCM simulations, from the UPSCALE (UK on PrACE - weather-resolving Simulations of Climate for globAL Environmental risk) campaign. Increased model resolution also poses new challenges to the observational datasets used to evaluate models. Global gridded data products (e.g. from the Global Precipitation Climatology Project, GPCP) are invaluable for assessing large-scale precipitation features, but may not sufficiently resolve mesoscale structures. In the absence of alternative estimates, the intercomparison of specialised, regional observational datasets may be the only way to gain insight into the uncertainties associated with these observations. We focus on three mid-latitude continental regions where gridded precipitation observations based on higher-density gauge networks are available, complementing the global data sets: Europe (with a particular emphasis on the Alps), South and East Asia, and the continental US. Additional motivation, and opportunity, arises from continuing efforts to quantify the components of the global radiation budget and water cycle. Recent estimates based on radiation measurements suggest that the global mean precipitation/evaporation may be up to 10 Wm-2 (about 0.35 mm day-1) larger than the estimate obtained from GPCP. While the main part of this discrepancy is thought to be due to the underestimation of remotely-sensed ocean precipitation, there is also considerable uncertainty about 'unobserved' precipitation

  16. Convective transport of reactive constituents to the tropical and mid-latitude tropopause region: I. Observations

    NASA Technical Reports Server (NTRS)

    Ridley, B.; Atlas, E.; Selkirk, H.; Pfister, L.; Montzka, D.; Walega, J.; Donnelly, S.; Stroud, V.; Richard, E.; Kelly, K.

    2004-01-01

    Measurements of ozone, reactive carbon and nitrogen, and other trace constituents from flights of the NASA WB-57F aircraft in the upper troposphere and lower stratosphere reveal that convection in the tropics can present a complex mix of surface-emitted constituents right up to the altitude of the lapse rate tropopause. At higher latitudes over the southern US, the strongest transport signal, in terms of constituent mixing ratios, occurred in the potential temperature range of 340-350K or approximately over the altitude range of 9-11km. Weaker convective signals were also seen up to near the tropopause. There was no evidence of convective transport directly into the lower stratosphere from these flights. $CPY 2003 Elsevier Ltd. All rights reserved.

  17. Isotopic evidence for continental ice sheet in mid-latitude region in the supergreenhouse Early Cretaceous

    PubMed Central

    Yang, Wu-Bin; Niu, He-Cai; Sun, Wei-Dong; Shan, Qiang; Zheng, Yong-Fei; Li, Ning-Bo; Li, Cong-Ying; Arndt, Nicholas T.; Xu, Xing; Jiang, Yu-Hang; Yu, Xue-Yuan

    2013-01-01

    Cretaceous represents one of the hottest greenhouse periods in the Earth's history, but some recent studies suggest that small ice caps might be present in non-polar regions during certain periods in the Early Cretaceous. Here we report extremely negative δ18O values of −18.12‰ to −13.19‰ for early Aptian hydrothermal zircon from an A-type granite at Baerzhe in northeastern China. Given that A-type granite is anhydrous and that magmatic zircon of the Baerzhe granite has δ18O value close to mantle values, the extremely negative δ18O values for hydrothermal zircon are attributed to addition of meteoric water with extremely low δ18O, mostly likely transported by glaciers. Considering the paleoaltitude of the region, continental glaciation is suggested to occur in the early Aptian, indicating much larger temperature fluctuations than previously thought during the supergreenhouse Cretaceous. This may have impact on the evolution of major organism in the Jehol Group during this period. PMID:24061068

  18. Isotopic evidence for continental ice sheet in mid-latitude region in the supergreenhouse Early Cretaceous.

    PubMed

    Yang, Wu-Bin; Niu, He-Cai; Sun, Wei-Dong; Shan, Qiang; Zheng, Yong-Fei; Li, Ning-Bo; Li, Cong-Ying; Arndt, Nicholas T; Xu, Xing; Jiang, Yu-Hang; Yu, Xue-Yuan

    2013-01-01

    Cretaceous represents one of the hottest greenhouse periods in the Earth's history, but some recent studies suggest that small ice caps might be present in non-polar regions during certain periods in the Early Cretaceous. Here we report extremely negative δ(18)O values of -18.12‰ to -13.19‰ for early Aptian hydrothermal zircon from an A-type granite at Baerzhe in northeastern China. Given that A-type granite is anhydrous and that magmatic zircon of the Baerzhe granite has δ(18)O value close to mantle values, the extremely negative δ(18)O values for hydrothermal zircon are attributed to addition of meteoric water with extremely low δ(18)O, mostly likely transported by glaciers. Considering the paleoaltitude of the region, continental glaciation is suggested to occur in the early Aptian, indicating much larger temperature fluctuations than previously thought during the supergreenhouse Cretaceous. This may have impact on the evolution of major organism in the Jehol Group during this period. PMID:24061068

  19. An Aircraft And Radar Based Analysis Of Cloud And Precipitation Microphysics In Mid-Latitude Continental Clouds

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Kumjian, M.; Bansemer, A.; Giangrande, S. E.; Ryzhkov, A.; Toto, T.

    2014-12-01

    An observational analysis of precipitation microphysics was conducted using data obtained during the Midlatitude Continental Convective Clouds Experiment (MC3E) that took place around the Atmospheric Radiation Measurement (ARM) site in Lamont, Oklahoma from April 22- June 6, 2011. MC3E was a collaborative campaign led by the National Aeronautic and Space Administration's (NASA's) Global Precipitation Measurement (GPM) mission and the U.S. Department of Energy ARM program. MC3E provided a unique opportunity to compare in-situ data from aircraft based microphysical probes with data from polarimetric radars in the radar bright band region or melting layer. One of the primary objectives of this study was to understand how riming and aggregation affect polarimetric signatures. In depth case study analysis of cloud and precipitation microphysics was performed for two specific cases, April 27th, 2011 (A27) and May 20th, 2011 (M20). Both these cases provided coincident aircraft and radar data in extensive stratiform cloud regions. Measurements from the University of North Dakota (UND) Citation aircraft and polarimetric data from the ARM CSAPR data reveal interesting details of cloud scale processes. Observations based on data from cloud probes (2DC, CIP and HVPS) along with in-situ observations of environmental variables provide remarkable details of particle growth and cloud dynamics for both case studies. For the A27 case study, UND aircraft measurements from two successive spiral profiles through the stratiform cloud region showed a transition from a riming dominated region to an aggregation dominated region. This is supported by polarimetric data from the C-Band ARM Precipitation Radar (CSAPR ). An extensive region of trailing stratiform precipitation was sampled in the M20 case study, where the aggregation, melting, and evaporation processes were measured in detail with the in-situ microphysical instruments. Latest findings from MC3E based on this combined aircraft

  20. Submarine geomorphology of the Celtic Sea - new observations and hypotheses for the glaciation of a mid-latitude continental shelf

    NASA Astrophysics Data System (ADS)

    Praeg, Daniel; McCarron, Stephen; Dove, Dayton; Cofaigh, Colm Ó.; Monteys, Xavier; Coxon, Peter; Accettella, Daniella; Cova, Andrea; Facchin, Lorenzo; Romeo, Roberto; Scott, Gill

    2015-04-01

    The southern limit of glaciation of the European continental margin lies in the Celtic Sea, where the full extent and dynamics of the British-Irish Ice Sheet (BIIS) remain in question. This is in part because the broad continental shelf contains no obvious glacial geomorphological features, but is dominated by a system of shelf-crossing sediment ridges, up to 60 m high, 10 km wide and 300 km long, traditionally interpreted as moribund palaeo-tidal sand banks. Ice sheet extent has been constrained by samples of subglacial and glacimarine sediments recovered (in the 1970s) between the ridges, and in places on their flanks, used to propose a tidewater ice margin that advanced to a grounding line on the mid-shelf, overriding a precursor ridge system. New information on the glaciation of the Celtic Sea is available from geophysical and core data acquired during Italian- and Irish-led campaigns in 2009, 2012, and 2014, both from the mid- and outer shelf. On the mid-shelf, multibeam seabed imagery of a 25 x 100 km area reveal a distinctive rectilinear network of en echelon ridge segments giving way laterally and longitudinally to transverse ribs. Seismic correlation to glacigenic sediments previously cored on a ridge flank (at core site 49/-09/44) indicates the ribs to be composed in part of glacimarine sediments, above a till reflection that can be traced across the ridge crest. No change in seabed morphology is observed across the proposed grounding line. On the outer shelf, new cores of glacigenic sediments were obtained from the flank of a shelf-crossing ridge, and provide evidence of ice sheet advance to the shelf edge, 150 km beyond the proposed grounding line. The cores from outer Cockburn Bank contain facies interpreted to record subglacial deformation and glacimarine deposition from turbid meltwater plumes during withdrawal of a tidewater ice sheet margin from the shelf edge by 24,265 ± 195 cal BP. These sediments are inferred to form part of a sheet of

  1. Mid-latitude Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    7 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes on the floor of a southern mid-latitude impact crater. Craters are commonly the site of sand dunes, as sand may become trapped in these topographic depressions. In this case, the winds responsible for the dunes generally blew from the south/southeast (bottom/lower right),

    Location near: 51.8oS, 105.5oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  2. Mid-latitude Gullies

    NASA Technical Reports Server (NTRS)

    2005-01-01

    25 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of south mid-latitude gullies on a crater wall. Gullies such as these may have formed by runoff of liquid water.

    Location near: 38.0oS, 167.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  3. The continental drift convection cell

    NASA Astrophysics Data System (ADS)

    Whitehead, J. A.; Behn, Mark D.

    2015-06-01

    Continents on Earth periodically assemble to form supercontinents and then break up again into smaller continental blocks (the Wilson cycle). Previous highly developed numerical models incorporate fixed continents while others indicate that continent movement modulates flow. Our simplified numerical model suggests that continental drift is fundamental. A thermally insulating continent is anchored at its center to mantle flow on an otherwise stress-free surface for infinite Prandtl number cellular convection with constant material properties. Rayleigh numbers exceed 107, while continent widths and chamber lengths approach Earth's values. The Wilson cycle is reproduced by a unique, rugged monopolar "continental drift convection cell." Subduction occurs at the cell's upstream end with cold slabs dipping at an angle beneath the moving continent (as found in many continent/subduction regions on Earth). Drift enhances vertical heat transport up to 30%, especially at the core-mantle boundary, and greatly decreases lateral mantle temperature differences.

  4. South Mid-latitude Gullies

    NASA Technical Reports Server (NTRS)

    2005-01-01

    19 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows deep gullies cut into the wall of a south mid-latitude crater. Erosion has exposed layers in the upper wall of the crater; it is possible that groundwater seeping through a layer or layers in the wall led to the genesis of the gullies. The banked nature of the gully channels suggests that a liquid was involved.

    Location near: 35.5oS, 194.8oW Image width: width: 2 km (1.2 mi) Illumination from: upper left Season: Southern Spring

  5. Refining Isotopic Parameterization Choices Using Stable Water Isotope Profiles In Surface Layer And Soil To Improve Modeling Of Mid-Latitude Continental Moisture Cycling

    NASA Astrophysics Data System (ADS)

    Kaushik, A.; Berkelhammer, M. B.; O'Neill, M.; Noone, D. C.

    2015-12-01

    The moisture balance of the continental boundary layer plays an important role in regulating the exchange of water and energy between the land surface and atmosphere. The surface layer moisture balance is controlled by a number of factors including precipitation, infiltration, evaporation and transpiration. Measurements of stable isotope ratios in water can be exploited to better understand the mechanisms controlling atmosphere-land surface water fluxes. We present three years of in situ tower-based measurements of stable isotope ratios of water (δD and δ18O) in vapor, precipitation, vegetation and soil from the Boulder Atmospheric Observatory, a semi-arid 300 meter tall-tower site in Erie, Colorado. Co-located meteorological and disdrometer measurements at the surface and 300m allow us to explore key aspects of continental moisture cycling in a semi-arid environment such as the important contribution of sub-surface vapor diffusion to the surface water vapor budget and its implications for partitioning in dry ecosystems, and the role of rain evaporation during precipitation events on inter-event and seasonal time scales. We use our observations to constrain a Craig-Gordon evaporation model at the land surface to weight the contributions of rainfall, surface water vapor exchange and sub-surface vapor diffusion to soil water isotope values. A multi-season in situ time series of surface vapor isotope profiles in conjunction with soil and precipitation allows us to field-validate choices for parameters such as the kinetic fractionation factor for each process. This has implications both for modeling short-term gas exchange at the land surface in modern-day climate models as well as for refining paleoclimate interpretations of stable oxygen and hydrogen isotope-based proxies. Tall-tower precipitation and vapor isotope profile data can also be analyzed in conjunction with disdrometer data on inter-event and seasonal time scales to quantify the role of rain evaporation

  6. ARM - Midlatitude Continental Convective Clouds (jensen-sonde)

    DOE Data Explorer

    Jensen, Mike; Comstock, Jennifer; Genio, Anthony Del; Giangrande, Scott; Kollias, Pavlos

    2012-01-19

    A major component of the Mid-latitude Continental Convective Clouds Experiment (MC3E) field campaign was the deployment of an enhanced radiosonde array designed to capture the vertical profile of atmospheric state variables (pressure, temperature, humidity wind speed and wind direction) for the purpose of deriving the large-scale forcing for use in modeling studies. The radiosonde array included six sites (enhanced Central Facility [CF-1] plus five new sites) launching radiosondes at 3-6 hour sampling intervals. The network will cover an area of approximately (300)2 km2 with five outer sounding launch sites and one central launch location. The five outer sounding launch sites are: S01 Pratt, KS [ 37.7oN, 98.75oW]; S02 Chanute, KS [37.674, 95.488]; S03 Vici, Oklahoma [36.071, -99.204]; S04 Morris, Oklahoma [35.687, -95.856]; and S05 Purcell, Oklahoma [34.985, -97.522]. Soundings from the SGP Central Facility during MC3E can be retrieved from the regular ARM archive. During routine MC3E operations 4 radiosondes were launched from each of these sites (approx. 0130, 0730, 1330 and 1930 UTC). On days that were forecast to be convective up to four additional launches were launched at each site (approx. 0430, 1030, 1630, 2230 UTC). There were a total of approximately 14 of these high frequency launch days over the course of the experiment.

  7. Characterization of residuals from ice particles and droplets sampled in mid-latitude natural and aviation-influenced cirrus and in tropical deep convective cloud systems during ML-CIRRUS and ACRIDICON

    NASA Astrophysics Data System (ADS)

    Mertes, Stephan; Kästner, Udo; Schulz, Christiane; Klimach, Thomas; Krüger, Mira; Schneider, Johannes

    2015-04-01

    Airborne sampling of cloud particles inside different cirrus cloud types and inside deep convective clouds was conducted during the HALO missions ML-CIRRUS over Europe in March/April 2014 and ACRIDICON over Amazonia in September 2014. ML-CIRRUS aims at the investigation of the for-mation, evolution, microphysical state and radiative effects of different natural and aviation-induced cirrus clouds in the mid-latitudes. The main objectives of ACRIDICON are the microphysical vertical profiling, vertical aerosol transport and the cloud processing of aerosol particles (compari-son in- and outflow) of tropical deep convective cloud systems in clean and polluted air masses and over forested and deforested regions. The hydrometeors (drops and ice particles) are sampled by a counterflow virtual impactor (CVI) which has to be installed in the front part of the upper fuselage of the HALO aircraft. Such an intake position implies a size dependent abundance of cloud particles with respect to ambient conditions that was studied by particle trajectory simulations (Katrin Witte, HALO Technical Note 2008-003-A). On the other hand, this sampling location avoids that large ice crystals which could potentially bias the cloud particle sampling by shattering and break-up at the inlet shroud and tip enter the inlet. Both aspects as well as the flight conditions of HALO were taken into account for an optimized CVI design for HALO (HALO-CVI). Interstitial particles are pre-segregated and the condensed phase is evaporated/sublimated by the CVI, such that the residuals from cloud droplets and ice particles (CDR and IPR) can be microphysically and chemically analyzed by respective aerosol sensors located in the cabin. Although an even more comprehensive characterization of CDR and IPR was carried out, we like to report on the following measurements of certain aerosol properties. Particle number concentra-tion and size distribution are measured by a condensation particle counter (CPC) and an

  8. Biomass Smoke Influences on Deep Convection during the 2011 Midlatitude Continental Convective Clouds Experiment (MC3E)

    NASA Astrophysics Data System (ADS)

    Dong, X.; Logan, T.; Xi, B.

    2015-12-01

    Three deep convective cloud cases were selected during the 2011 Mid-Latitude Continental Convective Clouds Experiment (MC3E). Although biomass burning smoke advected from Mexico and Central America was the dominant source of cloud condensation nuclei (CCN) for deep convective cloud formation, the 11 May, 20 May, and 23 May cases exhibited different convective characteristics. The convection in the 11 May and 23 May cases formed in smoke laden environments in the presence of convective available potential energy (CAPE) values exceeding 1000 m2 s-2 and 3000 m2 s-2 along with low-level (0-1 km) shear of 10.3 m s-1 and 5.1 m s-1, respectively. The 11 May case had linear convection while the 23 May case featured discrete supercells. The 20 May case featured elevated linear convection that formed in a more moist environment with cleaner aerosol conditions, weak CAPE (<50 m2 s-2), and stronger low-level shear (25.6 m s-1). Though the 20 May case had the highest precipitation amount and duration, the 23 May case had the highest ice water content (IWC) in the upper levels of the convection (>9 km) suggesting a warm rain suppression mechanism caused by a combination of strong aerosol loading, large CAPE, and weak low-level wind shear. The observed results for the 20 May and 23 May cases agree well with recent modeling studies that simulated the convection and precipitation in these cases. Furthermore, the modeling of the 11 May case is suggested since the abundant amount of smoke CCN did not greatly enhance the overall precipitation amount and could be a possible aerosol-induced precipitation suppression case.

  9. Simulating deep convection with a shallow convection scheme

    NASA Astrophysics Data System (ADS)

    Hohenegger, C.; Bretherton, C. S.

    2011-10-01

    Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES) as a benchmark to test and refine a unified convection scheme implemented in the Single-column Community Atmosphere Model (SCAM). Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle. Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and mid-latitude continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas.

  10. ARM - Midlatitude Continental Convective Clouds

    DOE Data Explorer

    Jensen, Mike; Bartholomew, Mary Jane; Genio, Anthony Del; Giangrande, Scott; Kollias, Pavlos

    2012-01-19

    Convective processes play a critical role in the Earth's energy balance through the redistribution of heat and moisture in the atmosphere and their link to the hydrological cycle. Accurate representation of convective processes in numerical models is vital towards improving current and future simulations of Earths climate system. Despite improvements in computing power, current operational weather and global climate models are unable to resolve the natural temporal and spatial scales important to convective processes and therefore must turn to parameterization schemes to represent these processes. In turn, parameterization schemes in cloud-resolving models need to be evaluated for their generality and application to a variety of atmospheric conditions. Data from field campaigns with appropriate forcing descriptors have been traditionally used by modelers for evaluating and improving parameterization schemes.

  11. Tropical influence on boreal summer mid-latitude stationary waves

    NASA Astrophysics Data System (ADS)

    Douville, Hervé; Bielli, S.; Cassou, C.; Déqué, M.; Hall, N. M. J.; Tyteca, S.; Voldoire, A.

    2011-11-01

    While organized tropical convection is a well-known source of extratropical planetary waves, state-of-the-art climate models still show serious deficiencies in simulating accurately the atmospheric response to tropical sea surface temperature (SST) anomalies and the associated teleconnections. In the present study, the remote influence of the tropical atmospheric circulation is evaluated in ensembles of global boreal summer simulations in which the Arpege-Climat atmospheric General Circulation Model (GCM) is nudged towards 6-h reanalyses. The nudging is applied either in the whole tropical band or in a regional summer monsoon domain. Sensitivity tests to the experimental design are first conducted using prescribed climatological SST. They show that the tropical relaxation does not improve the zonal mean extratropical climatology but does lead to a significantly improved representation of the mid-latitude stationary waves in both hemispheres. Low-pass filtering of the relaxation fields has no major effect on the model response, suggesting that high-frequency tropical variability is not responsible for extratropical biases. Dividing the nudging strength by a factor 10 only decreases the magnitude of the response. Model errors in each monsoon domain contribute to deficiencies in the model's mid-latitude climatology, although an exaggerated large-scale subsidence in the central equatorial Pacific appears as the main source of errors for the representation of stationary waves in the Arpege-Climat model. Case studies are then conducted using either climatological or observed SST. The focus is first on summer 2003 characterized by a strong and persistent anticyclonic anomaly over western Europe. This pattern is more realistic in nudging experiments than in simulations only driven by observed SST, especially when the nudging domain is centred over Central America. Other case studies also show a significant tropical forcing of the summer mid-latitude stationary waves and

  12. Impact of Activation Treatment and CCN/IN Concentrations on Simulations of A Continental Convective System

    NASA Astrophysics Data System (ADS)

    Rothenberg, D. A.; Wang, C.

    2014-12-01

    Aerosol play an important role in mediating cloud microphysics by serving as both cloud condensation and ice nuclei (CCN and IN). In mixed-phase, deep convective clouds, these CCN and IN can alter physical processes related to droplet activation and heterogeneous freezing, affecting the dynamics, microphysics, and ultimately evolution of the cloud. However, modifying the CCN and IN budget entrained into a cloud eventually leads to many simultaneous, competing microphysical processes which make it difficult to precisely predict how cloud properties will change. Here, we study the sensitivity of a continental convective system observed during the Mid-latitude Airborne Cirrus Properties Experiment (MACPEX) in 2011 to changes in CCN and IN burden with the help of 2D and 3D cloud-resolving model simulations. We explore how the potential for convective invigoration is sensitive to the treatment of droplet activation at the cloud base by adopting an emulator of an adiabatic parcel model to parameterize the activation calculation. Furthermore, we study how changes in the IN budget can enhance the role of heterogeneous freezing and diminish the efficacy of homogeneous freezing above the -40C isotherm within the cloud. Since anvil ice is typically produced homogeneously, we also study how this shift in freezing mechanisms affects the size distributions and properties of the system's anvil cirrus. The in situ observations of anvil ice obtained during MACPEX and the ice nuclei residuals are used as a reference to constrain the simulations.

  13. Storm time heavy ion outflow at mid-latitudes

    SciTech Connect

    Yeh, H.C.; Foster, J.C. )

    1990-06-01

    Local ionospheric observations with the Millstone Hill incoherent scatterradar reveal an upward ion bulk velocity in excess of 3 km s{sup {minus} 1} at 1,000 km altitude during the very large magnetic storm on February 8, 1986. The upward flux of O{sup +} ions exceeded 3 {times} 10{sup 9} cm{sup {minus}2} s{sup {minus}1} at 42{degree} geodetic latitude (55{degree} {Lambda}) for a 3-hour period around 18 MLT during the event. Frictinal ion heating with ion temperatures in excess of 4,000 K at 500 km altitude was observed by the radar in the vicinity of the ion outflow event. Satellite observations place the ion outflow event within a region of intense ion and electron precipitation on field lines associated with the storm-perturbed ring current. For a one-dimensional analysis of the observed plasma profiles, continuity considerations indicate a region of intense O{sup +} production (200 cm{sup {minus}3} s{sup {minus}1}) as well as significant upward acceleration (5-10 m s{sup {minus}2}) in the region between 600 km and 800 km altitude where the outflow approaches supersonic speed. Ionizing collisions involving fast backsplash neutral O atoms (Torr et al., 1974) produced by ring current heavy ion precipitation can provide sufficient upward momentum to account for the acceleration in the observed outflowing thermal O{sup +} fluxes. Alternatively, the outflow event can be explained in terms of a time-dependent diffusion process triggered by a sudden change in the frictional heating rate in the collision-dominated F region (St.-Maurice, 1989). The concurrence of rapid ion convection and energetic ring current precipitation is unique at mid-latitudes during intense magnetic storms. Under these conditions, the observations indicate that the mid-latitude ionosphere constitutes a significant source of upflowing thermal O{sup +} fluxes to the overlying magnetosphere.

  14. Relative humidities in mid-latitude contrails

    NASA Astrophysics Data System (ADS)

    Krämer, M.; Kübbeler, M.; Meyer, J.; Schiller, C.; Gayet, J.-F.; Fiebig, M.; Hamburger, Th.; Petzold, A. Minikin (4), A.; Schlager, H.; Voigt, Ch.

    2009-04-01

    Aircraft contrails frequently occur in the upper troposphere. They consist of ice particles having the potential to directly affect the Earth's climate. The frequency, life time, ice crystal size spectra and thus radiative properties of contrails depend strongly on the ambient distribution of the relative humidity with respect to ice (RHi). In air with RHi below 100% contrails are believed to be short-lived, while persistent contrails require an ambient RHi of at least 100% (Gao et al., 2006, Atmospheric Environment). During the mid-latitude aircraft experiments CONCERT 2008 (CONtrail and Cirrus ExpeRimenT, 6 flights), CIRRUS 2006 (1 flight) and PAZI 2003 ('PArtikel und ZIrren', 2 flights), RHi inside of contrails were measured using the high precision Fast In-situ Stratospheric lyman-alpha Hygrometer FISH. We present results from about 1 hour of observation time in 52 contrails during the 9 flights. The peak of the RHi frequency distribution is around 90%, i.e. most of the contrails are observed in subsaturated air. There is indication that the age of the contrails is much larger than expected, implying that, to date, the lifetime of contrails below 100% RHi is underestimated. Further analysis of the observations is needed to confirm/explain these results.

  15. Recent Advances in Mid-latitude Ionosphere/Thermosphere Science

    NASA Astrophysics Data System (ADS)

    Kelley, Michael

    One of the original reasons for building a National Ionospheric Observatory (now the National Astronomy and Ionospheric Center or NAIC) near Arecibo, Puerto Rico was the location, which is in the best behaved region of the ionosphere. At 30° magnetic latitude and 19° geographic latitude, it is well equatorward of the auroral and sub-auroral zones and poleward of the equatorial anomalies most of the time. The island thus has some of the best weather and space weather on the planet. However, similar to an occasional hurricane striking the island, the ionosphere overhead has occasional ionospheric and thermospheric disturbances. Some of these space weather phenomena, e.g., mesoscale TIDs and unstable sporadic E layers, are endemic to the region and, prior to the advent of airglow imagers and GPS networks, were difficult to visualize using radiowave data alone. Other weather events are caused by infringement on this zone from processes in more active weather regions. For example, neutral waves launched from the auroral oval (large scale TIDs) pass through the region; electric fields penetrate from the solar wind and create both plasma uplifts, causing positive ionospheric storms, and stormenhanced density plumes, coursing through the region. From the south, convective equatorial ionospheric storms create plasma bubbles that can reach mid-latitudes. Examples of data obtained during these phenomena, and possibly more, will be presented and discussed in light of our present understanding.

  16. Simulating deep convection with a shallow convection scheme

    NASA Astrophysics Data System (ADS)

    Hohenegger, C.; Bretherton, C. S.

    2011-03-01

    Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES) as a benchmark to test and refine a unified convection scheme implemented in the Single-Column Community Atmosphere Model (SCAM). Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle. Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas.

  17. Geomorphological studies along a transect from the taiga to the desert in Central Mongolia—evolution of landforms in the mid-latitude continental interior as a function of climate and vegetation

    NASA Astrophysics Data System (ADS)

    Dill, H. G.; Khishigsuren, S.; Majigsuren, Yo.; Myagmarsuren, S.; Bulgamaa, J.

    2006-07-01

    Variations of drainage systems in the central Mongolian steppe was investigated along a N-S transect covering all zones of vegetation and precipitation from the taiga to the outer reaches of the Gobi Desert. Geomorphological studies supplemented by sedimentological, mineralogical (heavy minerals, lithoclasts) and chemical analyses (arenaceous deposits) resulted in the delineation of five lithological groups which were subdivided into 23 rock types using rock strength, geomorphological forms/geometry, lithology, clast size, sorting, stratification, rock contacts and grain shape. To demonstrate the relationship between landforms and the climatic as well as morphological processes, a process-product approach was taken and eight rock type associations were established. The transport regime along the slopes is characterized by mass flows that pass upslope into solifluction/gelifluction sheets and soil creep. Towards the thalweg, mass flows grade into coarse-grained gravel deposition of highly sinuous and braided fluvial streams. On vegetated high-altitude peneplains and mid-slopes, as well as scarcely vegetated desert steppe plains, unconfined flow prevails over confined flow. Arenaceous deposits of aeolian origin gave rise to dune fields and sand sheets. Chemical weathering is moderate in the steppe of the continental interior and the pH value of meteoric fluids is straddling around neutral. Due to the intermediate position of the steppe between polar and warm deserts, salt efflorescence and calcretes came into being. The major characteristics of the steppe depositional environments will be discussed and summarized in order to provide a key for the interpretation of paleosteppe settings in the ancient sedimentary record.

  18. Tropical and mid-latitude forcing of continental Antarctic temperatures

    NASA Astrophysics Data System (ADS)

    Turney, C. S. M.; Fogwill, C. J.; Klekociuk, A.; van Ommen, T. D.; Curran, M. A. J.; Moy, A. D.; Palmer, J. G.

    2015-07-01

    Future changes in atmospheric circulation and associated modes of variability are a major source of uncertainty in climate projections. Nowhere is this issue more acute than across the mid- to high-latitudes of the Southern Hemisphere (SH) which over the last few decades has experienced extreme and regional variable trends in precipitation, ocean circulation, and temperature, with major implications for Antarctic ice melt and surface mass balance. Unfortunately there is a relative dearth of observational data, limiting our understanding of the driving mechanism(s). Here we report a new 130-year annually-resolved record of δ D - a proxy for temperature - from the South Geographic Pole where we find a significant influence from extra-tropical pressure anomalies which act as "gatekeepers" to the meridional exchange of air masses. Reanalysis of global atmospheric circulation suggests these pressure anomalies play a considerably larger influence on mid- to high-latitude SH climate than hitherto believed, modulated by the tropical Pacific Ocean. Our findings suggest that future increasing tropical warmth will strengthen meridional circulation, exaggerating current trends, with potentially significant impacts on Antarctic surface mass balance.

  19. Giant Raindrops in Mid-latitude Cumuli

    NASA Astrophysics Data System (ADS)

    French, Jeffrey; Leon, David; Lasher-Trapp, Sonia; Moser, Daniel; Blyth, Alan; Bennett, Lindsay; Brown, Phil; Korolev, Alexei

    2014-05-01

    The Convective Precipitation Experiment (COPE) took place during the summer months of 2013 in SW England. Among the objectives of COPE was to better understand the interplay between warm rain and ice processes, particularly secondary ice production, and their relative importance in producing heavy convective rainfall. Implicit in this objective is to be able to describe the production of warm rain prior to the initiation of ice. For this reason, aircraft observations were focused on obtaining measurements near tops of clouds as they penetrated through levels from 0 to -12 deg C. On several days, observations from optical array probes onboard the University of Wyoming King Air research aircraft reveal ~3 mm drops in the core of updrafts at temperatures colder than -7 deg C. On one day, observations of drops 8 mm in diameter, equal to the largest ever reported, were found in similar regions. These observations are unique for a number of reasons. All previous observations of such large drops were obtained in tropical conditions near or below cloud base. The observations in COPE were several km above cloud base, in the middle and upper portions of cloud. The largest drops in COPE were located within the high vertical velocity core (15 m s-1) in regions of liquid water content greater than 2 g m-3, and were collocated with polarimetric ground-based radar measurements. In this study we investigate the conditions that led to the development of very large raindrops in the updraft cores compared to the much more common observations of moderate sized raindrops (3 mm) in the same general cloud regions and conditions. Further, we investigate the development of elevated high reflectivity cores and high-ZDR 'columns' from the ground-based radar in context with the in situ observations and calculations from a 1D warm rain model. Finally, we consider that the conditions that lead to the production of giant drops may necessarily result from warm processes only.

  20. MID-LATITUDE NORTHERN HEMISPHERE BACKGROUND SULFATE CONCENTRATION IN RAINWATER

    EPA Science Inventory

    The pH is not sufficient to characterize the acidity of precipitation, but rather its acid-base components must be described. he chemistry of natural emission sources as well as the mechanism of precipitation formation determine the chemistry of precipitation at mid-latitude, Nor...

  1. Impacts of microphysics, radiation and environmental winds in mid-latitude and tropical squall-line systems, and their climatic implications

    SciTech Connect

    Chin, Hung-Neng

    1994-08-01

    Cloud-radiation feedback has been identified as the most important factor limiting general circulation models (GCMS) to further progress in climate change research (Cess et al., 1989). It is also regarded as a major uncertainty in estimating the impact of greenhouse gases on climate simulations. As a result, many GCMs showed high sensitivity to the treatment of clouds and cloud radiative properties. Therefore, a better understanding of cloud-radiation feedback on the large-scale environment is absolutely essential to improve the representation of cloud processes in GCMS. To this end, a cloud model with enhanced model physics is used to study the impact of cloud-radiation interactions on mesoscale convective systems (MCSs). Case studies representing a variety of convective systems are important to generalize the overall effects of anvil clouds on the large-scale environment. Our primary interesting is limited to the MCSs in an environment with substantial wind shear, such as squall-line systems, because they have longer lifetime and wider coverage to impact the earth radiation budget and climate. The objective of this study is to investigate the impacts of microphysics, radiation and environmental winds on mid-latitude continental and tropical oceanic squall-line systems. Comparisons between these two systems are presented. Recent studies indicated that the vertical shear of the environmental wind plays an important role in the formation of the anvil cloud through the tilting of MCSS. However, this process has not been represented in GCMS. A detailed investigation on the formation of anvil clouds and their relationship to cumulus portions of MCSs would help develop a better cloud parameterization for use in GCMS. Two important issues are addressed through these comparisons. First, what factors cause the differences between mid-latitude and tropical anvil clouds? Second, do these differences have climatic implications to improve our climate forecasting ability?

  2. The influence of mid-latitude storm tracks on hot, cold, dry and wet extremes

    NASA Astrophysics Data System (ADS)

    Lehmann, Jascha; Coumou, Dim

    2015-12-01

    Changes in mid-latitude circulation can strongly affect the number and intensity of extreme weather events. In particular, high-amplitude quasi-stationary planetary waves have been linked to prolonged weather extremes at the surface. In contrast, analyses of fast-traveling synoptic-scale waves and their direct influence on heat and cold extremes are scarce though changes in such waves have been detected and are projected for the 21st century. Here we apply regression analyses of synoptic activity with surface temperature and precipitation in monthly gridded observational data. We show that over large parts of mid-latitude continental regions, summer heat extremes are associated with low storm track activity. In winter, the occurrence of cold spells is related to low storm track activity over parts of eastern North America, Europe, and central- to eastern Asia. Storm tracks thus have a moderating effect on continental temperatures. Pronounced storm track activity favors monthly rainfall extremes throughout the year, whereas dry spells are associated with a lack thereof. Trend analyses reveal significant regional changes in recent decades favoring the occurrence of cold spells in the eastern US, droughts in California and heat extremes over Eurasia.

  3. The influence of mid-latitude storm tracks on hot, cold, dry and wet extremes

    PubMed Central

    Lehmann, Jascha; Coumou, Dim

    2015-01-01

    Changes in mid-latitude circulation can strongly affect the number and intensity of extreme weather events. In particular, high-amplitude quasi-stationary planetary waves have been linked to prolonged weather extremes at the surface. In contrast, analyses of fast-traveling synoptic-scale waves and their direct influence on heat and cold extremes are scarce though changes in such waves have been detected and are projected for the 21st century. Here we apply regression analyses of synoptic activity with surface temperature and precipitation in monthly gridded observational data. We show that over large parts of mid-latitude continental regions, summer heat extremes are associated with low storm track activity. In winter, the occurrence of cold spells is related to low storm track activity over parts of eastern North America, Europe, and central- to eastern Asia. Storm tracks thus have a moderating effect on continental temperatures. Pronounced storm track activity favors monthly rainfall extremes throughout the year, whereas dry spells are associated with a lack thereof. Trend analyses reveal significant regional changes in recent decades favoring the occurrence of cold spells in the eastern US, droughts in California and heat extremes over Eurasia. PMID:26657163

  4. The influence of mid-latitude storm tracks on hot, cold, dry and wet extremes.

    PubMed

    Lehmann, Jascha; Coumou, Dim

    2015-01-01

    Changes in mid-latitude circulation can strongly affect the number and intensity of extreme weather events. In particular, high-amplitude quasi-stationary planetary waves have been linked to prolonged weather extremes at the surface. In contrast, analyses of fast-traveling synoptic-scale waves and their direct influence on heat and cold extremes are scarce though changes in such waves have been detected and are projected for the 21st century. Here we apply regression analyses of synoptic activity with surface temperature and precipitation in monthly gridded observational data. We show that over large parts of mid-latitude continental regions, summer heat extremes are associated with low storm track activity. In winter, the occurrence of cold spells is related to low storm track activity over parts of eastern North America, Europe, and central- to eastern Asia. Storm tracks thus have a moderating effect on continental temperatures. Pronounced storm track activity favors monthly rainfall extremes throughout the year, whereas dry spells are associated with a lack thereof. Trend analyses reveal significant regional changes in recent decades favoring the occurrence of cold spells in the eastern US, droughts in California and heat extremes over Eurasia. PMID:26657163

  5. Electron temperature measurements in mid-latitude sporadic E layers

    NASA Technical Reports Server (NTRS)

    Schutz, S. R.; Smith, L. G.

    1976-01-01

    By using rocket-borne Langmuir probes, electron temperature profiles have been obtained in five mid-latitude sporadic E layers. The data show the electron temperature within the layers to be lower than the electron temperature at the adjacent altitudes. This is consistent with the layers' being maintained by a vertical redistribution of ionization. The magnitude of the observed electron temperature variation is, however, larger than expected.

  6. Mid-latitude afforestation shifts general circulation and tropical precipitation

    PubMed Central

    Swann, Abigail L. S.; Fung, Inez Y.; Chiang, John C. H.

    2012-01-01

    We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO2, but regional heating from the increase in forest cover is capable of driving unintended changes in circulation and precipitation. The ability of vegetation to affect remote circulation has implications for strategies for climate mitigation. PMID:22190490

  7. Mid-latitude afforestation shifts general circulation and tropical precipitation.

    PubMed

    Swann, Abigail L S; Fung, Inez Y; Chiang, John C H

    2012-01-17

    We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO(2), but regional heating from the increase in forest cover is capable of driving unintended changes in circulation and precipitation. The ability of vegetation to affect remote circulation has implications for strategies for climate mitigation. PMID:22190490

  8. Microphysical Ice Crystal Properties in Mid-Latitude Frontal Cirrus

    NASA Astrophysics Data System (ADS)

    Schlage, Romy; Jurkat, Tina; Voigt, Christiane; Minikin, Andreas; Weigel, Ralf; Molleker, Sergej; Klingebiel, Marcus; Borrmann, Stephan; Luebke, Anna; Krämer, Martina; Kaufmann, Stefan; Schäfler, Andreas

    2015-04-01

    Cirrus clouds modulate the climate by reflection of shortwave solar radiation and trapping of longwave terrestrial radiation. Their net radiative effect can be positive or negative depending on atmospheric and cloud parameters including ice crystal number density, size and shape. Latter microphysical ice crystal properties have been measured during the mid-latitude cirrus mission ML-CIRRUS with a set of cloud instruments on the new research aircraft HALO. The mission took place in March/April 2014 with 16 flights in cirrus formed above Europe and the Atlantic. The ice clouds were encountered at altitudes from 7 to 14 km in the typical mid-latitude temperature range. A focus of the mission was the detection of frontal cirrus linked to warm conveyor belts (WCBs). Within WCBs, water vapor is transported in the warm sector of an extra-tropical cyclone from the humid boundary layer to the upper troposphere. Cirrus cloud formation can be triggered in the WCB outflow region at moderate updraft velocities and additionally at low updrafts within the high pressure system linked to the WCB. Due to their frequent occurrence, WCBs represent a major source for regions of ice supersaturation and cirrus formation in the mid-latitudes. Here, we use data from the Cloud and Aerosol Spectrometer with detection for POLarization (CAS-POL) and the Cloud Combination Probe (CCP), combining a Cloud Droplet Probe (CDP) and a greyscale Cloud Imaging Probe (CIPgs) to investigate the ice crystal distribution in the size range from 0.5 µm to 1 mm. We derive microphysical cirrus properties in mid-latitude warm front cirrus. Further, we investigate their variability and their dependence on temperature and relative humidity. Finally, we compare the microphysical properties of these frontal cirrus to cirrus clouds that formed at low updrafts within high pressure systems or at high updraft velocities in lee waves. We quantify statistically significant differences in cirrus properties formed in these

  9. Insights into mid-latitude storm track dynamics from simulations with an idealized dry GCM

    NASA Astrophysics Data System (ADS)

    Mbengue, C. O.; Schneider, T.

    2012-12-01

    The mid-latitude storm tracks play an important role in balancing the earth's heat and momentum budget. They have a significant human impact through precipitation and adverse weather conditions; thus, the storm track response to changing climatic conditions is of great interest. In this study, we investigate the climatological response of the mid-latitude storm tracks to varying mean global temperature and convective static stability, using an idealized dry GCM. We demonstrate storm track migration in response to changes in global-mean surface temperatures without modifying the surface pole-equator temperature contrast or including moisture-related effects. The results help interpret the findings of previous global warming studies in which the mid-latitude storm tracks migrate poleward with increasing mean global temperatures. In our study, the storm track position is found to be particularly sensitive to changes in tropical static stability and tropopause height and their effect on the Hadley circulation. The mechanisms driving the dynamics of the mid-latitude storm tracks have been elusive. However, making use of the simplified framework employed in this study, which lends itself to dynamical decompositions, we have been able to improve upon some existing theories on storm track dynamics in dry atmospheres, as well as make additional observations. Previous studies into dry atmospheric dynamics have shown a linear scaling between eddy kinetic energy, a robust measure of the level of storminess, and the mean available potential energy (MAPE). This scaling is utilized in a decomposition that shows that the dominant quantity in storm track dynamics is the meridional gradient of the potential temperature—a measure of baroclinicity. This observation leads us to look for dynamical mechanisms that, on average, dictate the location of regions of elevated baroclinicity. Some credible explanations include the effects on mid-latitude isentropic slopes through a raising or

  10. Precipitation classification at mid-latitudes in terms of drop size distribution parameters

    NASA Astrophysics Data System (ADS)

    Caracciolo, C.; Porcã¹, F.; Prodi, F.

    2008-04-01

    The drop size distribution (DSD) is a fundamental property of rainfall because the shape of the distribution reflects the physics of rain formation processes. Given the lack of studies on the DSD at mid-latitudes, the present work focuses on the microphysical characterization of precipitation events occurring in Italy, using two different types of disdrometer. A large number of different rain events was collected: they underwent microphysical analysis by computing the Z-R relationships, observing the average DSDs and DSD parameters, fitting the real distribution for different rainfall rate categories and applying convective (C) - stratiform (S) discrimination algorithms. A general agreement with past works at mid-latitudes is found both in the Z-R relationship and in DSD parameters. The rain distribution is well described by a gamma DSD and only in some cases (especially the light rain events) by an exponential DSD. Marked differences are observed in DSD parameters and Z-R relationships between C and S episodes. The use of disdrometers for areas covered by multiparametric radar is suggested and will be performed in the near future.

  11. ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, Parcivel Disdrometer (williams-disdro)

    DOE Data Explorer

    Williams, Christopher; Jensen, Mike

    2012-11-06

    This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

  12. ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, Surface Meteorology (williams-surfmet)

    DOE Data Explorer

    Williams, Christopher; Jensen, Mike

    2012-11-06

    This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

  13. ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, 449 MHz Profiler(williams-449_prof)

    DOE Data Explorer

    Williams, Christopher; Jensen, Mike

    2012-11-06

    This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

  14. ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, Vertical Air Motion (williams-vertair)

    DOE Data Explorer

    Williams, Christopher; Jensen, Mike

    2012-11-06

    This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

  15. Arctic Amplification and Potential Mid-Latitude Weather Linkages

    NASA Astrophysics Data System (ADS)

    Overland, J. E.

    2014-12-01

    Increasing temperatures and other changes continued in the Arctic over the last decade, even though the rate of global warming has decreased in part due to a cool Pacific Ocean. Thus Arctic temperatures have increased at least 3 times the rate of mid-latitude temperatures. Credibility for persistent Arctic change comes from multiple indicators which are now available for multiple decades. Further, the spatial pattern of Arctic Amplification differs from patterns of natural variability. The role of the Arctic in the global climate system is based on multiple interacting feedbacks represented by these indicators as a causal basis for Arctic Amplification driven by modest global change. Many of these processes act on a regional basis and their non-linear interactions are not well captured by climate models. For example, future loss of sea ice due to increases in CO2 are demonstrated by these models but the rates of loss appear slow. It is reasonable to suspect that Arctic change which can produce the largest temperature anomalies on the planet and demonstrate recent extremes in the polar vortex could be linked to mid-latitude weather, especially as Arctic change will continue over the next decades. The meteorological community remains skeptical, however, in the sense of "not proven." Natural variability in chaotic atmospheric flow remains the main dynamic process, and it is difficult to determine whether Arctic forcing of a north-south linkage is emerging from the most recent period of Arctic change since 2007. Nonetheless, such a hypothesis is worthy of investigation, given the need to further understand Arctic dynamic atmospheric processes, and the potential for improving mid-latitude seasonal forecasts base on high-latitude forcing. Several AGU sessions and other forums over the next year (WWRP, IASC,CliC) address this issue, but the topic is not ready for a firm answer. The very level of controversy indicates the state of the science.

  16. ARM - Midlatitude Continental Convective Clouds Microwave Radiometer Profiler (jensen-mwr)

    DOE Data Explorer

    Jensen, Mike

    2012-02-01

    A major component of the Mid-latitude Continental Convective Clouds Experiment (MC3E) field campaign was the deployment of an enhanced radiosonde array designed to capture the vertical profile of atmospheric state variables (pressure, temperature, humidity wind speed and wind direction) for the purpose of deriving the large-scale forcing for use in modeling studies. The radiosonde array included six sites (enhanced Central Facility [CF-1] plus five new sites) launching radiosondes at 3-6 hour sampling intervals. The network will cover an area of approximately (300)2 km2 with five outer sounding launch sites and one central launch location. The five outer sounding launch sites are: S01 Pratt, KS [ 37.7oN, 98.75oW]; S02 Chanute, KS [37.674, 95.488]; S03 Vici, Oklahoma [36.071, -99.204]; S04 Morris, Oklahoma [35.687, -95.856]; and S05 Purcell, Oklahoma [34.985, -97.522]. Soundings from the SGP Central Facility during MC3E can be retrieved from the regular ARM archive. During routine MC3E operations 4 radiosondes were launched from each of these sites (approx. 0130, 0730, 1330 and 1930 UTC). On days that were forecast to be convective up to four additional launches were launched at each site (approx. 0430, 1030, 1630, 2230 UTC). There were a total of approximately 14 of these high frequency launch days over the course of the experiment. These files contain brightness temperatures observed at Purcell during MC3E. The measurements were made with a 5 channel (22.235, 23.035, 23.835, 26.235, 30.000GHz) microwave radiometer at one minute intervals. The results have been separated into daily files and the day of observations is indicated in the file name. All observations were zenith pointing. Included in the files are the time variables base_time and time_offset. These follow the ARM time conventions. Base_time is the number seconds since January 1, 1970 at 00:00:00 for the first data point of the file and time_offset is the offset in seconds from base_time.

  17. ARM - Midlatitude Continental Convective Clouds - Ultra High Sensitivity Aerosol Spectrometer(tomlinson-uhsas)

    DOE Data Explorer

    Tomlinson, Jason; Jensen, Mike

    2012-02-28

    Ultra High Sensitivity Aerosol Spectrometer (UHSASA) A major component of the Mid-latitude Continental Convective Clouds Experiment (MC3E) field campaign was the deployment of an enhanced radiosonde array designed to capture the vertical profile of atmospheric state variables (pressure, temperature, humidity wind speed and wind direction) for the purpose of deriving the large-scale forcing for use in modeling studies. The radiosonde array included six sites (enhanced Central Facility [CF-1] plus five new sites) launching radiosondes at 3-6 hour sampling intervals. The network will cover an area of approximately (300)2 km2 with five outer sounding launch sites and one central launch location. The five outer sounding launch sites are: S01 Pratt, KS [ 37.7oN, 98.75oW]; S02 Chanute, KS [37.674, 95.488]; S03 Vici, Oklahoma [36.071, -99.204]; S04 Morris, Oklahoma [35.687, -95.856]; and S05 Purcell, Oklahoma [34.985, -97.522]. Soundings from the SGP Central Facility during MC3E can be retrieved from the regular ARM archive. During routine MC3E operations 4 radiosondes were launched from each of these sites (approx. 0130, 0730, 1330 and 1930 UTC). On days that were forecast to be convective up to four additional launches were launched at each site (approx. 0430, 1030, 1630, 2230 UTC). There were a total of approximately 14 of these high frequency launch days over the course of the experiment. These files contain brightness temperatures observed at Purcell during MC3E. The measurements were made with a 5 channel (22.235, 23.035, 23.835, 26.235, 30.000GHz) microwave radiometer at one minute intervals. The results have been separated into daily files and the day of observations is indicated in the file name. All observations were zenith pointing. Included in the files are the time variables base_time and time_offset. These follow the ARM time conventions. Base_time is the number seconds since January 1, 1970 at 00:00:00 for the first data point of the file and time_offset is

  18. Map of Martian Potassium at Mid-Latitudes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma-rays from the element potassium. Potassium, having the chemical symbol K, is a naturally radioactive element and is a minor constituent of rocks on the surface of both Mars and Earth. The region of highest potassium content, shown in red, is concentrated in the northern part of Acidalia Planitia (centered near 55 degrees N, -30 degrees). Several areas of low potassium content, shown in blue, are distributed across the mid-latitudes, with two significant low concentrations, one associated with the Hellas Basin (centered near 35 degrees S, 70 degrees) and the other lying southeast of Elysium Mons (centered near 10 degrees N, 160 degrees). Contours of constant surface elevation are also shown. The long continuous line running from east to west marks the approximate separation of the younger lowlands in the north from the older highlands in the south.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The gamma ray spectrometer was provided by the University of Arizona, Tucson. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  19. Mid-latitude lidar observations of large sporadic sodium layers

    SciTech Connect

    Senft, D.C.; Collins, R.L.; Gardner, C.S. )

    1989-07-01

    During the early morning of October 31, 1988 two large sporadic Na (Na{sub s}) layers were observed near the mesopause above Urbana, IL (40{degree}N, 88{degree}W) with a Na lidar system. The layers began forming near 102 km at 0026 LST and 0110 LST and moved downward with vertical velocities as high as 4 ms{sup {minus}1} before dissipating between 94 and 96 km. The duration of each layer was approximately 80 min. The layers were narrow ({approximately} 1 km FWHM) and dense with maximum densities approaching 7,800 cm{sup {minus}3}. The characteristics of these two Na{sub s} layers are very similar to those of similar phenomena observed recently at Andoya, Norway and Mauna Kea, Hawaii. Lidar observations of the mesospheric Na layer have been conducted routinely by several groups at mid-latitudes for almost 20 years. Although large Na{sub s} layers now appear to be relatively common at low- and high-latitudes, to our knowledge the two layers described in this letter are only the second observation of this puzzling phenomenon at mid-latitudes.

  20. The Ionospheric Mid-Latitude Summer Nighttime Anomaly

    NASA Astrophysics Data System (ADS)

    Lin, C.; Chen, C.; Hsu, M.; Liu, C. H.; Liu, J. G.; Burns, A. G.; Wang, W.

    2009-12-01

    This paper presents monthly variations of the mid-latitude summer nighttime anomaly (MSNA) of the ionosphere for the first time by using global observations of the FORMOSAT-3/COSMIC (F3/C), NASA TIMED-GUVI, ground-based radars and GPS receiver network. The MSNA is characterized by greater nighttime (19:00 LT - 24:00 LT, or period of larger solar zenith angles) ionospheric electron density than that during daytime (08:00 - 18:00 LT, or period of smaller solar zenith angles) at middle latitudes during solstices. The anomaly shown in the southern hemisphere during December solstice was previously known as the Weddell Sea Anomaly (WSA) occurring around the Antarctica and the nearby Pacific Ocean, while a WSA-like electron density structure also occurs in the northern hemisphere around June solstice. This study demonstrates that the anomalies occurred in both the northern and southern hemispheres share similar character of greater nighttime density. Moreover, the latitude-altitude cross-section plots of the electron density structure show very similar time-varying electron density evolutions of the MSNA. In both hemispheres, the anomalies with similar electron density characteristics and variations caused by the similar mechanism prompts us to name this phenomenon the mid-latitude summer nighttime anomaly.

  1. Geographic control of Titan's mid-latitude clouds

    NASA Astrophysics Data System (ADS)

    Roe, H. G.; Brown, M. E.; Schaller, E. L.; Bouchez, A. H.; Trujillo, C. A.

    2005-08-01

    Observations of tropospheric clouds (1-6) and the recent Huygens images of channels show that Titan has an active methane hydrological cycle. Titan's south polar clouds are now well known (3-5) and thought to be driven by small seasonal variations in surface temperature (3). The recent discovery (6) and continued observations (7) of significant cloud activity at 40oS latitude led to the suggestion that these mid-latitude clouds are the result of either seasonally evolving global circulation or surface geography (6). We report here further observations of Titan that clearly link the formation of the mid-latitude clouds to a region of Titan's surface centered at ˜350oW longitude, ˜40oS latitude. Analysis of the complete dataset does not support the earlier suggestion (6) that these clouds are a new phenomenon related to seasonal change. The strong link between geographic location and cloud formation along with the lack of evidence for seasonal change in the mid-latitude clouds leads to the conclusion that a geological mechanism is responsible for the formation of these clouds. We propose that geysers or cryovolcanism are sporadically active near ˜350oW longitude, ˜40oS latitude. The implied rate of volatile release would easily supply enough methane to balance the loss to photolytic chemistry in the upper atmosphere. 1. Griffith, C.A., Owen, T., Miller, G.A., Geballe, T., Nature 395, 575-578 (1998). 2. Griffith, C.A., Hall, J.L., Geballe, T.R., Science 290, 509-513 (2000). 3. Brown, M.E., Bouchez, A.H., Griffith, C.A., Nature 420, 795-797 (2002). 4. Roe, H.G., de Pater, I., Macintosh, B.A., McKay, C.P., ApJ 581, 1399-1406 (2002). 5. Bouchez, A.H., Brown, M.E., ApJ 618, L53-L56 (2005). 6. Roe, H.G., Bouchez, A.H., Trujillo, C.A., Schaller, E.L., Brown, M.E., ApJ 618, L49-L52 (2005). 7. Porco, C.C., et al., Nature 434, 159-168 (2005). HGR is supported by an NSF Astronomy & Astrophysics Postdoctoral Fellowship (NSF AST-0401559). ELS is supported by an NSF Graduate

  2. Mesoscale variability in marine winds at mid-latitude

    NASA Astrophysics Data System (ADS)

    Overland, James E.; Wilson, Judith G.

    1984-11-01

    Wind data were collected by the National Oceanic and Atmospheric Administration WP-3D aircraft on low-level (50 and 90 m) crosswind and along-mean-wind tracks of approximately 350 km during the Storm Transfer and Response Experiment in November and December 1980. Observed mesoscale variations in the marine wind fields are characterized by the velocity correlation tensor for three atmospheric regimes: cloud streets, open and closed cellular convection, and prefrontal warm air advection. The dominant scale of mesoscale variation in the offshore wind field normal to the mean wind direction in the case of old continental air flowing over a warmer ocean, producing cloud streets, was 27 km. For this case, the standard deviation in momentum transfer, which was calculated from 2-km subsets of the flight track by the bulk aerodynamic method assuming a constant drag coefficient, was 13% of the synoptic scale (330km) mean. The dominant scale of mesoscale variation for open cellular convection was 62km, and the dominant scale for closed cellular convection was 90 km. The standard deviation of mesoscale momentum transfer (scales greater than 2 km; constant drag coefficient) for a 345-km flight track containing both cell types was 26% of the synoptic scale mean. The warm air advection case had no measurable mesoscale variability. For each regime a model of the horizontal velocity correlation tensor, which can be used to estimate a mesoscale variability, is fitted to the observed velocity correlation tensor with velocity component and weather regime dependent coefficients. This general model is consistent with an interpretation of the mesoscale wind field as an ensemble of coherent structures, associated with cloud type, in which the spatial variability of the wind field in each weather regime is associated with physically determined dominant length scales (i.e., cells or rolls), as contrasted with a continuum interpretation of two-dimensional turbulence. To accurately describe

  3. Midlatitude Continental Convective Clouds Experiment (MC3E)

    SciTech Connect

    Jensen, MP; Petersen, WA; Del Genio, AD; Giangrande, SE; Heymsfield, A; Heymsfield, G; Hou, AY; Kollias, P; Orr, B; Rutledge, SA; Schwaller, MR; Zipser, E

    2010-04-10

    The Midlatitude Continental Convective Clouds Experiment (MC3E) will take place in central Oklahoma during the April–May 2011 period. The experiment is a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration’s (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign leverages the unprecedented observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors, and new ARM instrumentation purchased with American Recovery and Reinvestment Act funding. The overarching goal is to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that have never before been available.

  4. Midlatitude Continental Convective Clouds Experiment (MC3E)

    SciTech Connect

    Jensen, MP; Petersen, WA; Del Genio, AD; Giangrande, SE; Heymsfield, A; Heymsfield, G; Hou, AY; Kollias, P; Orr, B; Rutledge, SA; Schwaller, MR; Zipser, E

    2010-04-01

    Convective processes play a critical role in the Earth’s energy balance through the redistribution of heat and moisture in the atmosphere and subsequent impacts on the hydrologic cycle. Global observation and accurate representation of these processes in numerical models is vital to improving our current understanding and future simulations of Earth’s climate system. Despite improvements in computing power, current operational weather and global climate models are unable to resolve the natural temporal and spatial scales that are associated with convective and stratiform precipitation processes; therefore, they must turn to parameterization schemes to represent these processes. In turn, the physical basis for these parameterization schemes needs to be evaluated for general application under a variety of atmospheric conditions. Analogously, space-based remote sensing algorithms designed to retrieve related cloud and precipitation information for use in hydrological, climate, and numerical weather prediction applications often rely on physical “parameterizations” that reliably translate indirectly related instrument measurements to the physical quantity of interest (e.g., precipitation rate). Importantly, both spaceborne retrieval algorithms and model convective parameterization schemes traditionally rely on field campaign data sets as a basis for evaluating and improving the physics of their respective approaches. The Midlatitude Continental Convective Clouds Experiment (MC3E) will take place in central Oklahoma during the April–May 2011 period. The experiment is a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration’s (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign leverages the unprecedented observing infrastructure currently available in the central United States

  5. Map of Martian Silicon at Mid-Latitudes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma-rays from the element silicon. Silicon is one of the most abundant elements on the surface of both Mars and Earth (second only to oxygen). The most extensive region of highest silicon content, shown in red, is located in the high latitudes north of Tharsis (centered near 45 degrees latitude, -120 degrees longitude). The area of lowest silicon content, shown in blue, lies just to the east of the Hellas Basin (-45 degrees latitude, 90 degrees longitude). Contours of constant surface elevation are also shown. The long continuous contour line running from east to west marks the approximate separation of the younger lowlands in the north from the older highlands in the south.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The gamma ray spectrometer was provided by the University of Arizona, Tucson. Lockheed Martin Astronautics, Denver, Colo., is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  6. Habitable periglacial landscapes in martian mid-latitudes

    NASA Astrophysics Data System (ADS)

    Ulrich, M.; Wagner, D.; Hauber, E.; de Vera, J.-P.; Schirrmeister, L.

    2012-05-01

    Subsurface permafrost environments on Mars are considered to be zones where extant life could have survived. For the identification of possible habitats it is important to understand periglacial landscape evolution and related subsurface and environmental conditions. Many landforms that are interpreted to be related to ground ice are located in the martian mid-latitudinal belts. This paper summarizes the insights gained from studies of terrestrial analogs to permafrost landforms on Mars. The potential habitability of martian mid-latitude periglacial landscapes is exemplarily deduced for one such landscape, that of Utopia Planitia, by a review and discussion of environmental conditions influencing periglacial landscape evolution. Based on recent calculations of the astronomical forcing of climate changes, specific climate periods are identified within the last 10 Ma when thaw processes and liquid water were probably important for the development of permafrost geomorphology. No periods could be identified within the last 4 Ma which met the suggested threshold criteria for liquid water and habitable conditions. Implications of past and present environmental conditions such as temperature variations, ground-ice conditions, and liquid water activity are discussed with respect to the potential survival of highly-specialized microorganisms known from terrestrial permafrost. We conclude that possible habitable subsurface niches might have been developed in close relation to specific permafrost landform morphology on Mars. These would have probably been dominated by lithoautotrophic microorganisms (i.e. methanogenic archaea).

  7. Comparing ionospheric models with mid-latitude ionosonde observations

    NASA Astrophysics Data System (ADS)

    Al-Ubaidi, Najat M. R.

    2009-06-01

    The purpose of this research work is to validate the ionospheric models (IRI and CHIU) to assess its suitability and usefulness as an operational tool. The ionospheric model is a computer model designed to predict the state of the global ionosphere for 24 h. The scope was limited to conduct comparisons between the predicted F2 layer critical frequencies (f0F2) against observed ionosonde data. The ionospheric prediction model (IPM) was designed to predict by using monthly median sunspot number, while the observation data are taken from two digital ionospheric sounding stations (Okinawa, 26.28N, 127.8E and Wakkanai, 45.38N, 141.66E) which lies within the mid-latitude region of the globe. Analysis of the f0F2 data from stations for year (2001) with high solar activity and year (2004) with low solar activity, four months (March, June, September and December) chosen based primarily on data availability. From results it seen that the ratio between monthly median predicted and observed f0F2 values for each model used in this research work and for the chosen months was nonlinear with local time, so the empirical formula for applying correction factors were determined, these formula can be used to correct the error occurred in predicted f0F2 value.

  8. Map of Martian Thorium at Mid-Latitudes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma-rays from the element thorium. Thorium is a naturally radioactive element that exists in rocks and soils in extremely small amounts. The region of highest thorium content, shown in red, is found in the northern part of Acidalia Planitia (50 degrees latitude, -30 degrees longitude). Areas of low thorium content, shown in blue, are spread widely across the planet with significant low abundances located to the north of Olympus Mons (near 55 degrees latitude, -155 degrees longitude), to the east of the Tharsis volcanoes (-10 degrees latitude, -80 degrees longitude) and to the south and east of Elysium Mons (20 degrees latitude, 160 degrees longitude). Contours of constant surface elevation are also shown. The long continuous contour line running from east to west marks the approximate separation of the younger lowlands in the north from the older highlands in the south.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The gamma ray spectrometer was provided by the University of Arizona, Tucson. Lockheed Martin Astronautics, Denver, Colo., is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. The Midlatitude Continental Convective Clouds Experiment (MC3E)

    DOE PAGESBeta

    Jensen, M. P.; Petersen, W. A.; Bansemer, A.; Bharadwaj, N.; Carey, L. D.; Cecil, D. J.; Collis, S. M.; DelGenio, A. D.; Dolan, B.; Gerlach, J.; et al

    2015-12-18

    The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deepmore » convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms-1 supported growth of hail and large rain drops. As a result, data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.« less

  10. The Midlatitude Continental Convective Clouds Experiment (MC3E)

    SciTech Connect

    Jensen, M. P.; Petersen, W. A.; Bansemer, A.; Bharadwaj, N.; Carey, L. D.; Cecil, D. J.; Collis, S. M.; DelGenio, A. D.; Dolan, B.; Gerlach, J.; Giangrande, S. E.; Heymsfield, A.; Heymsfield, G.; Kollias, P.; Lang, T. J.; Nesbitt, S. W.; Neumann, A.; Poellot, M.; Rutledge, S. A.; Schwaller, M.; Tokay, A.; Williams, C. R.; Wolff, D. B.; Xie, S.; Zipser, E. J.

    2015-12-18

    The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deep convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms-1 supported growth of hail and large rain drops. As a result, data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.

  11. Airborne Measurements of Methane Fluxes over Mid-Latitude and Sub-Arctic Wetlands

    NASA Astrophysics Data System (ADS)

    Hartmann, J.; Sachs, T.

    2012-04-01

    For a quantification of the natural GHG budget of the atmosphere the emission of methane from the vast arctic wetlands need to be assessed accurately. The conventional methods of flux measurements made by closed chambers and eddy towers need to be upscaled, introducing a potentially large source of uncertainty, due to the heterogeneity of the emitting sources at the surface. In order to obtain a large area coverage and thus a higher spacial representativeness we performed airborne measurements of methane fluxes over mid-latitude and sub-arctic wetlands, for flight legs of tens of kilometres length. We installed a fast trace gas analyser, a Los Gatos RMT200, in the research aircraft Polar 5, together with the noseboom mounted turbulence sensor package. Measurement flights have been carried out in June 2011 over wetlands in Germany and in northern Finland in a convectively mixed boundary layer. Reference data have been optained at the surface by tower mounted eddy correlation measurements. A spectral analysis of the first measurements shows that the system is well suitable to measure the vertical flux of methane from natural surfaces transported by the dominating eddies in the convective boundary layer. Our flux measurements compare well to those obtained at the surface. On the high-frequency end of the spectrum the measurement accuracy is not sufficient to resolve the inertial subrange.

  12. Interactions between tropical cyclones and mid-latitude systems in the Northeastern Pacific

    NASA Astrophysics Data System (ADS)

    Lugo, A.; Abarca, S. F.; Raga, G. B.; Vargas, D. C.

    2014-12-01

    Major challenges in tropical meteorology include the short-term forecast of tropical cyclone (TC) intensity, which is defined as the maximum tangential wind. Several efforts have been made in order to reach this goal over the last decade: Among these efforts, the study of lightning in the TC inner core (the region inside a disc of 100 km radius from the center) as a proxy to deep convection, has the potential to be used as a predictor to forecast intensity (DeMaria et al, 2012, Mon. Wea. Rev., 140, 1828-1842).While most studies focus their objectives in studying the lightning flash density in the inner core, we study the probability of flash occurrence for intensifying and weakening cyclones. We have analyzed the trajectories of the observed 62 tropical cyclones that developed in the basin from 2006 to 2009, and classified them into separate clusters according to their trajectories. These clusters can broadly be described as having trajectories mostly oriented: East-West, towards the central Pacific, NW far from the Mexican coast, parallel to the Mexican coast and recurving towards the Mexican coast.We estimate that probability of inner core lightning occurrence increases as cyclones intensify but the probability rapidly decrease as the systems weaken. This is valid for cyclones in most of the clusters. However, the cyclones that exhibit trajectories that recurve towards the Mexican coast, do not present the same relationship between intensity and inner-core lightning probability, these cyclones show little or no decrease in the lightning occurrence probability as they weaken.We hypothesize that one of the reasons for this anomalous behavior is likely the fact that these cyclones interact with mid-latitude systems. Mid-latitude systems are important in determining the recurving trajectory but they may also influence the TC by advecting mid-level moisture towards the TC inner core. This additional supply of moisture as the system is approaching land may enhance deep

  13. Equatorial to Mid-Latitude Connections in Eastern Boundary Currents

    NASA Astrophysics Data System (ADS)

    Strub, T.

    2002-12-01

    Over twenty years ago, Enfield and Allen (1980, J. Phys. Oceaogr., 10, 557-578) used tide-gauge sea level height data to show the connection between the equator and the mid-latitude coastal ocean in the eastern Pacific. Careful selection of tide gauges and quality control of the data allowed both seasonal and interannual time scales to be examined over a period of 24 years. Today, 10 years of TOPEX/POSEIDON altimeter data allow us to re-examine the seasonal and non-seasonal connections between the equator and higher latitudes in the eastern boundary currents (EBC's) along the coasts of the Pacific and Atlantic Oceans. We present the seasonal progressions in both basins and hemispheres, showing the low-to-high latitude development of the seasonal cycle and also the offshore propagation of annual Rossby waves. This brings out several general tendencies: 1) The signals are stronger in the Northern Hemisphere basins, due to the fact that the ITCZ is located north of the equator in both basins; 2) The signals are stronger in the NE Pacific than in any of the other basins; and 3) There is an annual signal of high sea surface height that propagates down both Southern Hemisphere EBC's in austral spring (September-November) as the SW trade winds weaken along the equator and the equatorial cold tongue collapses. This last feature is somewhat like an annual "El Ni¤o" effect and acts to suppress the onset of wind driven upwelling in the Peru-Chile and Benguela Current Systems.

  14. Variability of Winter Air Temperature in Mid-Latitude Europe

    NASA Technical Reports Server (NTRS)

    Otterman, J.; Ardizzone, J.; Atlas, R.; Bungato, D.; Cierniewski, J.; Jusem, J. C.; Przybylak, R.; Schubert, S.; Starr, D.; Walczewski, J.

    2002-01-01

    The aim of this paper is to report extreme winter/early-spring air temperature (hereinafter temperature) anomalies in mid-latitude Europe, and to discuss the underlying forcing to these interannual fluctuations. Warm advection from the North Atlantic in late winter controls the surface-air temperature, as indicated by the substantial correlation between the speed of the surface southwesterlies over the eastern North Atlantic (quantified by a specific Index Ina) and the 2-meter level air temperatures (hereinafter Ts) over Europe, 45-60 deg N, in winter. In mid-March and subsequently, the correlation drops drastically (quite often it is negative). This change in the relationship between Ts and Ina marks a transition in the control of the surface-air temperature: absorption of insolation replaces the warm advection as the dominant control. This forcing by maritime-air advection in winter was demonstrated in a previous publication, and is re-examined here in conjunction with extreme fluctuations of temperatures in Europe. We analyze here the interannual variability at its extreme by comparing warm-winter/early-spring of 1989/90 with the opposite scenario in 1995/96. For these two December-to-March periods the differences in the monthly mean temperature in Warsaw and Torun, Poland, range above 10 C. Short-term (shorter than a month) fluctuations of the temperature are likewise very strong. We conduct pentad-by-pentad analysis of the surface-maximum air temperature (hereinafter Tmax), in a selected location, examining the dependence on Ina. The increased cloudiness and higher amounts of total precipitable water, corollary effects to the warm low-level advection. in the 1989/90 winter, enhance the positive temperature anomalies. The analysis of the ocean surface winds is based on the Special Sensor Microwave/Imager (SSM/I) dataset; ascent rates, and over land wind data are from the European Centre for Medium-Range Weather Forecasts (ECMWF); maps of 2-m temperature, cloud

  15. Source effects in mid-latitude geomagnetic transfer functions

    NASA Astrophysics Data System (ADS)

    Araya Vargas, Jaime; Ritter, Oliver

    2016-01-01

    Analysis of more than 10 yr of vertical magnetic transfer function (VTF) estimates obtained at 12 mid-latitude sites, located in different continents and tectonic settings, reveals significant temporal variations for a period range between approximately 250 and 2000 s. The most ubiquitous pattern is a seasonal modulation of the VTF element that relates the vertical to the horizontal north-south magnetic components (Tx), which shows a high peak around the June solstice (and a low peak around the December solstice) regardless of the location of the site. To quantify the influence of this source effect on the amplitude of VTFs, we modelled the temporal variations of VTFs using a function with dependence on season and magnetic activity indexes. The model shows that differences between VTF estimates obtained at seasonal peaks can reach 0.08 of Tx absolute values and that the effect increases with latitude and period. Seasonal variations are observed also in the VTF component relating vertical to horizontal east-west magnetic components (Ty), but here the pattern with respect to the geographic distribution is less clear. In addition to seasonal trends, we observe long-term modulations correlating with the 11-yr solar cycle at some sites. The influence of these external source effects should be taken into account, before attempting a geological interpretation of the VTFs. It can be misleading, for example, to combine or compare VTFs obtained from long-period geomagnetic data acquired at different seasons or years. An effective method to estimate and remove these source effects from VTFs is by comparison with temporal variations of VTFs from synchronously recorded data at sites located at similar latitude (<5° of difference) and longitude (<10° of difference). Source effects in temporal variations of VTFs can be identified as those patterns that exhibit similar amplitudes and significant correlation with the geomagnetic activity at all compared sites. We also provide a

  16. Ionospheric vertical drift response at a mid-latitude station

    NASA Astrophysics Data System (ADS)

    Kouba, Daniel; Koucká Knížová, Petra

    2016-07-01

    Vertical plasma drift data measured at a mid-latitude ionospheric station Pruhonice (50.0 ° N, 14.6 ° E) were collected and analysed for the year 2006, a year of low solar and geomagnetic activity. Hence these data provide insight into the drift behaviour during quiet conditions. The following typical diurnal trend is evident: a significant decay to negative values (downward peak) at dawn; generally less pronounced downward peak at dusk hours. Magnitude of the downward drift varies during the year. Typically it reaches values about 20 ms-1 at dawn hours and 10 ms-1 at dusk hours. Maximum dawn magnitude of about 40 ms-1 has been detected in August. During daytime the vertical drifts increases from the initial small downward drifts to zero drift around noon and to small upward drifts in the afternoon. Night-time drift values display large variability around a near zero vertical drift average. There is a significant trend to larger downward drift values near dawn and a less pronounced decrease of the afternoon upward vertical drifts near sunset. Two regular downward peaks of the drift associated with the dawn and dusk are general characteristics of the analysed data throughout the year 2006. Their seasonal course corresponds to the seasonal course of the sunrise and sunset. The duration of prevailing negative drift velocities forming these peaks and thus the influence of the dawn/dusk on the drift velocity is mostly 1.5-3 h. The dawn effect on vertical drift tends to be larger than the effect of the dusk. The observed magnitude of the sunrise and sunset peaks show significant annual course. The highest variability of the magnitude is seen during winter. High variability is detected till March equinox and again after September equinox. Around solstice, both peaks reaches lowest values. After that, the magnitudes of the drift velocity increase smoothly till maxima in summer (August). The vertical drift velocity course is smooth between June solstice and September

  17. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2014-05-01

    The analysis of the occurrence of mid-latitude storms is of great socio-economical interest due to their vast and destructive impacts. However, a unique definition of cyclones is missing as they are complex systems which may have very diverse characteristics. Thus, the definition of what a cyclone is as well as quantifying its strength contains subjective choices. Existing automatic cyclone identification and tracking algorithms are based on different definitions and use diverse characteristics. These methods generally differ in the following aspects: data transformation (e.g., grid transformation, smoothing, etc.), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (e.g. near neighborhood search), and elimination criteria (e.g., requiring a certain pressure minimum or minimum life time). The different choices made in these algorithms can lead to substantial differences in cyclone climatologies, temporal trends of the frequency, strength, or other characteristics of cyclones. These differences render the interpretation and comparison of cyclone studies rather difficult. The project IMILAST systematically compares different cyclone detection and tracking methods (currently 15 different algorithms), with the aim to comprehensively assess systematic uncertainties in mid-latitudinal storm identification and tracking. As a common data basis the ERA-interim reanalysis data set is used in all IMILAST studies. A first study presented a general overview of differences between the methods with respect to number, track density, life cycle characteristics, and trend patterns for a 20 year period of ERA-Interim. In a second study, potential differences of the long-term climate change signal of cyclonic activity between the methods were assessed. Currently, the intercomparison is extended to a 30 year period from 1979 to 2009 and focuses on more specific aspects, such as parameter

  18. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2013-04-01

    The detection of the occurrence of mid-latitude storms, which are of high societal interest due to their impacts, is less straightforward than it might seem. Since cyclones are complex systems with very diverse characteristics, the definition of what a cyclone is and what should be considered as describing the strength of a cyclone contains subjective choices. Thus, existing analysis methods, especially automatic algorithms, are based on different definitions and use diverse identification and tracking (i.e. detecting the path of an individual cyclone over time) methodologies. The different choices made in different cyclone identification and tracking algorithms can lead to critical differences in temporal trends of the frequency, strength or life cycle of cyclones. These differences render the interpretation and comparison of cyclone trend studies difficult. The project IMILAST performs a systematic intercomparison of different existing cyclone detection and tracking methods (currently 15 different algorithms), with the aim of a comprehensive assessment of methodological uncertainties in mid-latitudinal storm tracking and an overview of advantages and restrictions of different schemes. As input data all calculations used the same ERA-interim reanalysis data set. The methods generally differ in the following aspects: data transformation (e.g. grid transformation, smoothing), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (how to combine the cyclone centers at different times to a track), and elimination criteria (e.g. requiring a certain pressure minimum or minimum life time). After a first experiment comparing cyclone tracks for a 20 year test period for both the northern and southern hemispheres, now the detection of a set of 22 individual extreme storms by the different methods has been analysed. In addition, more specific analysis, as for example the influence of

  19. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, U.

    2012-04-01

    The detection of the occurrence of mid-latitude storms, which are of high societal interest due to their impacts, is less straightforward than it might seem. Since cyclones are complex systems with very diverse characteristics, the definition of what a cyclone is and what should be considered as describing the strength of a cyclone contains subjective choices. Thus, existing analysis methods, especially automatic algorithms, are based on different definitions and use diverse identification and tracking (i.e. detecting the path of an individual cyclone over time) methodologies. The different choices made in different cyclone identification and tracking algorithms can lead to critical differences in temporal trends of the frequency, strength or life cycle of cyclones. These differences render the interpretation and comparison of cyclone trend studies difficult. The project IMILAST performs a systematic intercomparison of different existing cyclone detection and tracking methods, with the aim of a comprehensive assessment of methodological uncertainties in mid-latitudinal storm tracking and an overview of advantages and restrictions of different schemes. The intensive discussions of first results have already pointed out a number of important issues that have to be carefully considered, and where some harmonization might make sense, like e.g. the arbitrary choice of thresholds like minimum life time or the elimination of cyclone tracks over high terrain. Currently, cyclone tracks for a 20 year test period for both the northern and southern hemispheres have been calculated with 15 different methodologies. As input data all calculations used the same ERA-interim reanalysis data set. The methods generally differ in the following aspects: data transformation (e.g. grid transformation, smoothing), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (how to combine the cyclone centers

  20. Exposed Ice in the Northern Mid-Latitudes of Mars

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.

    2007-01-01

    Ice-Rich Layer: Polygonal features with dimensions of approximately 100 meters, bounded by cracks, are commonly observed on the martian northern plains. These features are generally attributed to thermal cracking of ice-rich sediments, in direct analogy to polygons in terrestrial polar regions. We mapped polygons in the northern mid-latitudes (30 to 65 N) using MOC and HiRISE images. Polygons are scattered across the northern plains, with a particular concentration in western Utopia Planitia. This region largely overlaps the Late Amazonian Astapus Colles unit, characterized by polygonal terrain and nested pits consistent with periglacial and thermokarst origins. Bright and Dark Polygonal Cracks: An examination of all MOC images (1997 through 2003) covering the study area demonstrated that, at latitudes of 55 to 65 N, most of the imaged polygons show bright bounding cracks. We interpret these bright cracks as exposed ice. Between 40 and 55 N, most of the imaged polygons show dark bounding cracks. These are interpreted as polygons from which the exposed ice has been removed by sublimation. The long-term stability limit for exposed ice, even in deep cracks, apparently lies near 55 N. Bright and Dark Spots: Many HiRISE and MOC frames showing polygons in the northern plains also show small numbers of bright and dark spots, particularly in western Utopia Planitia. Many of the spots are closely associated with collapse features suggestive of thermokarst. The spots range from tens to approximately 100 meters in diameter. The bright spots are interpreted as exposed ice, due to their prevalence on terrain mapped as ice rich. The dark spots are interpreted as former bright spots, which have darkened as the exposed ice is lost by sublimation. The bright spots may be the martian equivalents of pingos, ice-cored mounds found in periglacial regions on Earth. Terrestrial pingos from which the ice core has melted often collapse to form depressions similar to the martian dark spots

  1. Intercomparison of mid latitude storm diagnostics (IMILAST) - project update

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2015-04-01

    The analysis of the occurrence of mid-latitude storms is of great socio-economical interest due to their vast and destructive impacts. However, a unique definition of cyclones is missing, and therefore the definition of what a cyclone is as well as quantifying its strength contains subjective choices. Existing automatic cyclone identification and tracking algorithms are based on different definitions and use diverse characteristics. These methods generally differ in the following aspects: data transformation (e.g., grid transformation, smoothing, etc.), metrics used for cyclone identification (e.g. sea level pressure or vorticity), cyclone identification procedures, different tracking methods (e.g. near neighborhood search), and elimination criteria (e.g., requiring a certain pressure minimum or minimum life time). The different choices made in these algorithms can lead to substantial differences in cyclone climatologies, temporal trends of the frequency, strength, or other characteristics of cyclones. The project IMILAST systematically compares different cyclone detection and tracking methods (currently 15 different algorithms), with the aim to comprehensively assess systematic uncertainties in mid-latitudinal storm identification and tracking. IMILAST uses the ERA-interim reanalysis data set as a common data basis in all studies. The first two intercomparison experiments focused on differences between the methods with respect to number, track density, life cycle characteristics, and trend patterns on the one hand and potential differences of the long-term climate change signal of cyclonic activity between the methods on the other hand. For current analysis activities, the intercomparison period is extended to a 30 year period from 1979 to 2009 and focuses on more specific aspects, such as parameter sensitivities, the comparison of automated to manual tracking sets, regional analysis (regional trends, Arctic and Antarctic cyclones, cyclones in the Mediterranean

  2. New Findings on Ice Nucleation in Mid-latitude Cirrus

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Mitchell, D. L.; Lawson, P.; Baker, B. A.

    2011-12-01

    Recent GCM simulations (CESM1) show a global aerosol indirect effect of -1.39 W m-2 with -2.02 W m-2 from shortwave and +0.63 W m-2 from longwave cloud forcing, the longwave being due to homogeneous nucleation of ice crystals. However, the extent of homogeneous nucleation in ice clouds is poorly understood. This study uses results from a recent field campaign, SPARTICUS (Small PARTicles In CirrUS), to evaluate the impact of homogeneous nucleation on the ice particle size distribution (PSD) shape, as well as ice particle concentration, shape, PSD effective size and fall speed. While earlier measurements were difficult to evaluate for ice nucleation effects due to the problem of ice particle shattering, recent in-situ measurements using the 2 dimensional-stereo (2D-S) probe have greatly reduced this problem resulting in provocative findings for both synoptic and anvil cirrus sampled during SPARTICUS. For mid-latitude synoptic and anvil cirrus around -40°C, these new measurements show that clear changes in the ice PSD and its properties occur regarding (1) PSD shape, (2) total number concentration-to-ice water content ratio (N/IWC), (3) PSD mean size, (4) PSD mean area ratio and (5) the mass-weighted fall velocity (Vm). These changes are consistent with a change in ice nucleation mechanism, with heterogeneous nucleation processes active at temperatures warmer than -40°C and homogeneous freezing nucleation at temperatures colder than -40°C. The change in Vm implies that cirrus colder than -40°C will have longer lifetimes and greater cloud coverage than warmer cirrus clouds, all other relevant factors remaining equal. The increase in N/IWC with colder temperatures (T < -40°C) appears consistent with homogeneous nucleation theory. Figure 1 shows normalized frequency distribution of PSD area ratios for temperatures above and below -40°C. Area ratios (ice particle projected area/area of circle defined by particle maximum dimension) are a measure of ice particle shape

  3. ML-CIRRUS - the HALO mission on mid latitude cirrus clouds

    NASA Astrophysics Data System (ADS)

    Voigt, Christiane; Minikin, Andreas; Schumann, Ulrich

    2015-04-01

    Clouds are a major source of uncertainty in current climate predictions. In particular, the observation of cirrus cloud variability and the classification of cirrus cloud properties in distinct meteorological regimes are prone to substantial ambiguities. Here we present results of the ML-CIRRUS mission with the German atmospheric science community high altitude long range aircraft HALO. The first in-situ cloud mission with the new research aircraft combined a state-of-the-art clould instrumentation consisting of 9 wing station probes with a novel aerosol, trace gas and radiation instrumentation and a high spectral resolution LIDAR inside the cabin. Further, a newly designed counter flow virtual impactor system allowed for the detection of ice residuals. In addition, models were specifically developed to support flight planning by forecasts of the occurrence and properties of natural cirrus (CLAMS, ECMWF) and frontal cirrus (WCB-ETH), as well as of aircraft induced clouds (CoCiP). In March and April 2014, the HALO research aircraft performed 16 flights (88 flight hours) in mid-latitude cirrus clouds and contrail cirrus at longitudes from 15 deg W to 15 deg E and latitudes from 36 to 58 deg N. Cirrus clouds with an ice water content < 0.5 mg m-3 were encountered up to 14 km altitude over a wide range of temperatures down to 204 K. More than 22 hours of in-situ observations in cirrus clouds plus remote sensing with the radiation instruments and the LIDAR onboard HALO allow to derive statistically significant data sets on microphysical and optical properties of mid latitude cirrus clouds. The clouds were observed in different meteorological regimes including jet stream cirrus, lee wave cirrus and convective clouds - with a strong focus on frontal cirrus. Besides natural cirrus, aircraft induced contrail cirrus were probed during 4 flights and an interesting contrail cirrus outbreak situation was encountered over the Atlantic. Here we present an overview and first

  4. ARM - Midlatitude Continental Convective Clouds Experiment (MC3E): Multi-Frequency Profilers, S-band Radar (williams-s_band)

    DOE Data Explorer

    Williams, Christopher

    2012-11-06

    This data was collected by the NOAA 449-MHz and 2.8-GHz profilers in support of the Department of Energy (DOE) and NASA sponsored Mid-latitude Continental Convective Cloud Experiment (MC3E). The profiling radars were deployed in Northern Oklahoma at the DOE Atmospheric Radiation Mission (ARM) Southern Great Plans (SGP) Central Facility from 22 April through 6 June 2011. NOAA deployed three instruments: a Parsivel disdrometer, a 2.8-GHz profiler, and a 449-MHz profiler. The parasivel provided surface estimates of the raindrop size distribution and is the reference used to absolutely calibrate the 2.8 GHz profiler. The 2.8-GHz profiler provided unattenuated reflectivity profiles of the precipitation. The 449-MHz profiler provided estimates of the vertical air motion during precipitation from near the surface to just below the freezing level. By using the combination of 2.8-GHz and 449-MHz profiler observations, vertical profiles of raindrop size distributions can be retrieved. The profilers are often reference by their frequency band: the 2.8-GHz profiler operates in the S-band and the 449-MHz profiler operates in the UHF band. The raw observations are available as well as calibrated spectra and moments. This document describes how the instruments were deployed, how the data was collected, and the format of the archived data.

  5. Exposed Ice in the Northern Mid-Latitudes of Mars

    NASA Astrophysics Data System (ADS)

    Allen, C. C.

    2007-12-01

    Ice-Rich Layer: Polygonal features with dimensions of approximately 100 meters, bounded by cracks, are commonly observed on the martian northern plains. These features are generally attributed to thermal cracking of ice-rich sediments, in direct analogy to polygons in terrestrial polar regions [1,2]. We mapped polygons in the northern mid-latitudes (30 to 65 N) using MOC and HiRISE images [3]. Polygons are scattered across the northern plains, with a particular concentration in western Utopia Planitia. This region largely overlaps the Late Amazonian Astapus Colles unit, characterized by polygonal terrain and nested pits consistent with periglacial and thermokarst origins [4]. Bright and Dark Polygonal Cracks: An examination of all MOC images (1997 through 2003) covering the study area demonstrated that, at latitudes of 55 to 65 N, most of the imaged polygons show bright bounding cracks. We interpret these bright cracks as exposed ice. Between 40 and 55 N, most of the imaged polygons show dark bounding cracks [5]. These are interpreted as polygons from which the exposed ice has been removed by sublimation. The long-term stability limit for exposed ice, even in deep cracks, apparently lies near 55 N. Bright and Dark Spots: Many HiRISE and MOC frames showing polygons in the northern plains also show small numbers of bright and dark spots, particularly in western Utopia Planitia. Many of the spots are closely associated with collapse features suggestive of thermokarst. The spots range from tens to approximately 100 meters in diameter. The bright spots are interpreted as exposed ice, due to their prevalence on terrain mapped as ice rich. The dark spots are interpreted as former bright spots, which have darkened as the exposed ice is lost by sublimation. The bright spots may be the martian equivalents of pingos, ice-cored mounds found in periglacial regions on Earth [6,7,8,9, 10]. Terrestrial pingos from which the ice core has melted often collapse to form depressions

  6. Ionospheric plasma drift and structure studies at high and mid-latitudes. Volume 1. Final report, October 1990-October 1993

    SciTech Connect

    Reinisch, B.W.; Scali, J.L.; Dozois, C.; Crowley, G.

    1993-12-01

    Ground-based observations of the high latitude ionosphere with Digisonde sounders at Quaanaaq, Sondrestrom, Goose Bay, Argentina and Millstone Hill provide a description of the patch structure and the convection pattern in the polar cap. Correlation analysis of observed F-region plasma drifts with the orientation of the interplanetary magnetic field (measured by IMP8) lead to a new technique of deducing the signs of Bz and By from the measured drifts. Real time calculation of the plasma drift was successfully introduced at one of the Digisonde stations (Sondrestrom) providing the possibility of determining the IMF components in real time. Analysis of mid-latitude trough observation shows large westward velocities in the trough region. Digisonde data from Quaanaaq and DMSP F8 and F9 satellite data showed the development of the ionospheric polar hole.

  7. Aerosol optical depth derived from solar radiometry observations at northern mid-latitude sites

    SciTech Connect

    Laulainen, N.S.; Larson, N.R.; Michalsky, J.J.; Harrison, L.C.

    1994-01-01

    Routine, automated solar radiometry observations began with the development of the Mobile Automated Scanning Photometer (MASP) and its installation at the Rattlesnake Mountain Observatory (RMO). We have introduced a microprocessor controlled rotating shadowband radiometer (RSR), both the single detector and the multi-filter/detector (MFRSR) versions to replace the MASP. The operational mode of the RSRs is substantially different than the MASP or other traditional sun-tracking radiometers, because, by virtue of the automated rotating shadowband, the total and diffuse irradiance on a horizontal plane are measured and the direct-normal component deduced through computation from the total and diffuse components by the self-contained microprocessor. Because the three irradiance components are measured using the same detector for a given wavelength, the calibration coefficients are identical for each component, thus reducing errors when comparing them. The MFRSR is the primary radiometric instrument in the nine-station Quantitative Links Network (QLN) established in the eastern United States in late 1991. Data from this network are being used to investigate how cloud- and aerosol-induced radiative effects vary in time and with cloud structure and type over a mid-latitude continental region. This work supports the DOE Quantitative Links Program to quantify linkages between changes in atmospheric composition and climate forcing. In this paper we describe the setup of the QLN and present aerosol optical depth results from the on-going measurements at PNL/RMO, as well as preliminary results from the QLN. From the time-series of data at each site, we compare seasonal variability and geographical differences, as well as the effect of the perturbation to the stratosphere by Mt. Pinatubo. Analysis of the wavelength dependence of optical depth also provides information on the evolution and changes in the size distribution of the aerosols.

  8. Trends toward an earlier peak of the growing season in Northern Hemisphere mid-latitudes.

    PubMed

    Xu, Chongyang; Liu, Hongyan; Williams, A Park; Yin, Yi; Wu, Xiuchen

    2016-08-01

    Changes in peak photosynthesis timing (PPT) could substantially change the seasonality of the terrestrial carbon cycle. Spring PPT in dry regions has been documented for some individual plant species on a stand scale, but both the spatio-temporal pattern of shifting PPT on a continental scale and its determinants remain unclear. Here, we use satellite measurements of vegetation greenness to find that the majority of Northern Hemisphere, mid-latitude vegetated area experienced a trend toward earlier PPT during 1982-2012, with significant trends of an average of 0.61 day yr(-1) across 19.4% of areas. These shifts correspond to increased annual accumulation of growing degree days (GDD) due to warming and are most highly concentrated in the eastern United States and Europe. Earlier mean PPT is generally a trait common among areas with summer temperatures higher than 27.6 ± 2.9 °C, summer precipitation lower than 84.2 ± 41.5 mm, and fraction of cold season precipitation greater than 89.2 ± 1.5%. The trends toward earlier PPT discovered here have co-occurred with overall increases in vegetation greenness throughout the growing season, suggesting that summer drought is not a dominant driver of these trends. These results imply that continued warming may facilitate continued shifts toward earlier PPT and cause these trends to become more pervasive, with important implications for terrestrial carbon, water, nutrient, and energy budgets. PMID:26752300

  9. Intermediate time error growth and predictability: tropics versus mid-latitudes

    NASA Astrophysics Data System (ADS)

    Straus, David M.; Paolino, Dan

    2009-10-01

    The evolution of identical twin errors from an atmospheric general circulation model is studied in the linear range (small errors) through intermediate times and the approach to saturation. Between forecast day 1 and 7, the normalized error variance in the tropics is similar to that at higher latitudes. After that, tropical errors grow more slowly. The predictability time τ taken for tropical errors to reach half their saturation values is larger than that for mid-latitudes, especially for the planetary waves, thus implying greater potential predictability in the tropics. The discrepancy between mid-latitude and tropical τ is more pronounced at 850 hPa than at 200 hPa, is largest for the planetary waves, and is more pronounced for errors arising from wave phase differences (than from wave amplitude differences). The spectra of the error in 200 hPa zonal wind show that for forecast times up to about 5 d, the tropical error peaks at much shorter scales than the mid-latitude errors, but that subsequently tropical and mid-latitude error spectra look increasingly similar. The difference between upper and lower level tropical τ may be due to the greater influence of mid-latitudes at the upper levels.

  10. Investigations of the Martian mid-latitudes: Implications for ground ice

    NASA Astrophysics Data System (ADS)

    Dundas, Colin Morrisey

    2009-06-01

    This dissertation examines several questions in Martian surface processes relating to water or ice using a combination of geomorphology and modeling. I first examine sublimation of ice from new small mid-latitude craters with freshly exposed ice imaged by the High Resolution Imaging Science Experiment (HiRISE) camera. I discuss the theory of sublimation by free convection and describe a model that improves on the standard version used in the Mars literature. This model shows some differences from experimental data, but this appears to be because experimental conditions do not accurately capture the sublimation regime appropriate to the Martian surface. I use this sublimation model in concert with a thermal model and calculate sublimation rates at the sites of freshly exposed ice. Calculated sublimated thicknesses of one or more millimeters during the period when HiRISE images show ice imply that this ice is relatively pure, not pore-filling. The ice table thus revealed appears consistent with a model of the Martian subsurface in which relatively clean ice overlies pore-filling ice. Pingos are hills with cores of ice formed by freezing of liquid water under pressure. Possible pingos on Mars have been much discussed because they would have significant implications for Martian hydrological processes. I surveyed HiRISE images across a broad portion of the Martian surface searching for fractured mounds. Such features are candidate pingos, since pingos often develop surface fractures as they grow. A small number of Martian landforms, not previously identified, are morphologically consistent with pingos; however, landforms that appear related to these do show morphological differences from pingos. Other origins are possible, particularly since it is difficult to produce the requisite hydrologic conditions for pingo formation. Previously proposed pingos on Mars lack surface fracturing and are unlikely to be pingos.

  11. The evolution of Titan's mid-latitude clouds

    USGS Publications Warehouse

    Griffith, C.A.; Penteado, P.; Baines, K.; Drossart, P.; Barnes, J.; Bellucci, G.; Bibring, J.; Brown, R.; Buratti, B.; Capaccioni, F.; Cerroni, P.; Clark, R.; Combes, M.; Coradini, A.; Cruikshank, D.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D.; McCord, T.; Mennella, V.; Nelson, R.; Nicholson, P.; Sicardy, B.; Sotin, C.; Soderblom, L.A.; Kursinski, R.

    2005-01-01

    Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal that the horizontal structure, height, and optical depth of Titan's clouds are highly, dynamic. Vigorous cloud centers are seen to rise from the middle to the upper troposphere within 30 minutes and dissipate within the next hour. Their development indicates that Titan's clouds evolve convectively; dissipate through rain; and, over the next several hours, waft downwind to achieve their great longitude extents. These and other characteristics suggest that temperate clouds originate from circulation-induced convergence, in addition to a forcing at the surface associated with Saturn's tides, geology, and/or surface composition.

  12. Quantifying Transport Between the Tropical and Mid-Latitude Lower Stratosphere

    PubMed

    Volk; Elkins; Fahey; Salawitch; Dutton; Gilligan; Proffitt; Loewenstein; Podolske; Minschwaner; Margitan; Chan

    1996-06-21

    Airborne in situ observations of molecules with a wide range of lifetimes (methane, nitrous oxide, reactive nitrogen, ozone, chlorinated halocarbons, and halon-1211), used in a tropical tracer model, show that mid-latitude air is entrained into the tropical lower stratosphere within about 13.5 months; transport is faster in the reverse direction. Because exchange with the tropics is slower than global photochemical models generally assume, ozone at mid-latitudes appears to be more sensitive to elevated levels of industrial chlorine than is currently predicted. Nevertheless, about 45 percent of air in the tropical ascent region at 21 kilometers is of mid-latitude origin, implying that emissions from supersonic aircraft could reach the middle stratosphere. PMID:8662478

  13. Quantifying transport between the tropical and mid-latitude lower stratosphere

    SciTech Connect

    Volk, C.M.; Dutton, G.S.; Gilligan, J.M.

    1996-06-21

    Airborne in situ observations of molecules with a wide range of lifetimes (methane, nitrous oxide, reactive nitrogen, ozone, chlorinated halocarbons, and halon-1211), used in a tropical tracer model, show that mid-latitude air is entrained into the tropical lower stratosphere within about 13.5 months; transport is faster in the reverse direction. Because exchange with the tropics is slower than global photochemical models generally assume, ozone at mid-latitudes appears to be more sensitive to elevated levels of industrial chlorine than is currently predicted. Nevertheless, about 45 percent of air in the tropical ascent region at 21 kilometers is of mid-latitude origin, implying that emissions from supersonic aircraft could reach the middle stratosphere. 49 refs., 5 figs.

  14. Storm time electric field penetration observed at mid-latitude

    SciTech Connect

    Yeh, H.C.; Foster, J.C. ); Rich, F.J.; Swider, W. )

    1991-04-01

    During the height of the February 8-9, 1986, magnetic storm the Millstone Hill radar was in the evening local time sector (1600-2200 MLT). Radar observations indicate that high speed (>1,000 m s{sup {minus}1}) westward ion flow penetrated deeply below 50{degree} invariant latitude ({Lambda}) and persisted for 6 hours between 2100 UT on February 8 and 0300 UT on February 9. The double-peaked ion convection feature was pronounced throughout the period, and the separation in the dual maxima ranged from 4{degree} to 10{degree}. The latitude positions of the high-latitude ion drift peak and the convection reversal varied in unison. The low-latitude ion drift peak ({approximately}49{degree}{Lambda} or L =2.3) did not show significant universal time/magnetic local time (UT/MLT) variation in its latitude location but showed a decrease in magnitude during the initial recovery phase of the storm. Using simultaneous particle (30 eV-30 keV) precipitation data from the DMSP F6 and F7 satellites, the authors find the high-latitude ion drift peak to coincide with the boundary plasma sheet/central plasma sheet transition in the high ionospheric conductivity (>15 mho) region. The low-latitude ion drift peak lay between the equatorward edges of the electron and soft (< 1 keV) ion precipitation in the low conductivity region ({approximately}1 mho). A comparison between the low-altitude observations and simultaneous ring current observations from the high-altitude AMPTE satellite further suggests that the low-altitude ion drift peak is closely related to the maximum of the O{sup +} dominated ring current energy density in magnetic latitude. The low-latitude ion drift peak is the low-altitude signature of the electric field shielding effect associated with ring current penetration into the outer layer of the storm time plasmasphere.

  15. A mid-latitude ozone model for the US standard atmosphere, 1975 (summary)

    NASA Technical Reports Server (NTRS)

    Krueger, A. J.; Minzner, R. A.

    1974-01-01

    A mid-latitude, Northern-Hemisphere model of the daytime ozone distribution in the troposphere, stratosphere, and lower mesosphere was constructed. Data from rocket soundings in the latitude range 45 deg N + or - 15 deg, results of balloon soundings at altitudes from 41 to 47 deg N, and latitude gradients from satellite ozone observations were combined to produce estimates of the annual mean ozone concentration and its variability at heights to 72 km for an effective latitude of 45 deg N. The model is a revision, for heights above 26 km, of the tentative Mid-Latitude Ozone Model.

  16. Wintertime response of mid-latitude atmospheric circulation to heat anomalies in the Barents Sea in recent decades

    NASA Astrophysics Data System (ADS)

    Schlichtholz, Pawel

    2015-04-01

    Prospects for seasonal prediction of climate variability depend on the strength of feedbacks between different components of the climate system. Sources for seasonal predictability of surface atmospheric anomalies in middle latitudes have been previously sought in teleconnections to the tropical phenomenon of El-Niño-Southern Oscillation and among various extratropical drivers including sea surface temperature anomalies, Arctic sea ice cover extremes, continental snow variability and tropospheric-stratospheric interactions. However, impacts of extratropical subsurface ocean variability on atmospheric teleconnections are poorly known. Here we use a lagged regression analysis between an index of the observed summertime Atlantic water temperature (AWT) anomalies at the entrance to the Barents Sea in the period 1982-2005 and the corresponding year-round data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis to show that subsurface oceanic heat anomalies heading the Arctic Ocean are significant precursors of wintertime atmospheric anomalies over mid-latitude Eurasia and North Pacific. In particular, warm AWT anomalies precede an Arctic warming accompanied by a cooling over Eurasia. The summertime oceanic anomalies explain about 40% of the variance in the surface air temperature averaged over entire Eurasia from 35° to 45° N and 50% of the variance in surface winds over the Far East Asia in the following winter. We find that the remote tropospheric response arises from modification of planetary waves and interaction of mean winds with synoptic eddies leading to a reorganization of the mid-latitude storm tracks. The AWT anomalies explain about 60% of the variance in the upper-tropospheric storm track activity averaged over the Pacific and Eurasia from 35° to 55° N and in the lower-tropospheric poleward transient eddy heat flux over western Eurasia. Finally, we show that the tropospheric response to

  17. LOCATION AND MAGNETOSPHERIC MAPPING OF SATURN'S MID-LATITUDE INFRARED AURORAL OVAL

    SciTech Connect

    Stallard, Tom; Melin, Henrik; Cowley, Stanley W. H.; Miller, Steve; Lystrup, Makenzie B.

    2010-10-10

    Previous observations of Saturn's infrared aurorae have shown that a mid-latitude aurora exists significantly equatorward of the main auroral oval. Here, we present new results using data from four separate observing runs in 1998, 2003, 2008, and 2010. When combined, these provide a view of the mid-latitude aurora under a considerable range of viewing conditions, allowing the first calculation of the latitudinal position of this aurora to be made. This has shown that the mid-latitude aurora is located at the magnetic footprint of the region within the magnetosphere where the initial breakdown in corotation occurs, between 3 R {sub S} and the orbit of Enceladus ({approx}3.95 R {sub S}). We also confirm that this aurora is a continuous stable feature over a period of more than a decade and that an oval morphology is likely. When combined, these results indicate that the mid-latitude auroral oval is formed by currents driven by the breakdown process within the magnetosphere, in turn caused by mass loading from the torus of Enceladus, analogous with the volcanic moon Io's dominant role in the formation of Jupiter's main auroral oval.

  18. Spectroscopic Detection of COCLF in the Tropical and Mid-Latitude Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Nassar, Ray; Boone, Chris D.; Bernath, Peter; Chiou, Linda; Weisenstein, Debra K.; Mahieu, Emmanuel; Zander, Rodolphe

    2006-01-01

    We report retrievals of COClF (carbonyl chlorofluoride) based on atmospheric chemistry experiment (ACE) solar occultation spectra recorded at tropical and mid-latitudes during 2004-2005. The COClF molecule is a temporary reservoir of both chlorine and fluorine and has not been measured previously by remote sensing. A maximum COClF mixing ratio of 99.7+/- 48.0 pptv per unit volume, (10 (exp -12)I sigma) is measured at 28km for tropical and subtropical occultations (latitudes below 20 degrees in both hemispheres) with lower mixing ratios at both higher and lower altitudes. Northern hemisphere mid-latitude mixing ratios (30-50 degrees N) resulted in an average profile with a peak mixing ratio of 51.7 +/1 32.1 pptv, 1 sigma, at 27 km, also decreasing above and below that altitude. We compare the measured average profiles with the one reported set of in situ lower stratospheric mid-latitude measurements from 1986 and 1987, a previous two-dimensional (2-D) model calculation for 1987 and 1993, and a 2-D-model prediction for 2004. The measured average tropical profile is in close agreement with the model prediction; the northern mid-latitude profile is also consistent, although the peak in the measured profile occurs at a higher altitude (2.5-4.5km offset) than in the model prediction. Seasonal average 2-D-model predictions of the COClF stratospheric distribution for 2004 are also reported.

  19. Mid-latitude scintillation model. Technical report, 1 November 1985-31 October 1986

    SciTech Connect

    Robins, R.E.; Secan, J.A.; Fremouw, E.J.

    1986-10-31

    Radiowave scintillation in the presence of ionospheric disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report describes development of a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed mid-latitude F layer. The model will be incorporated into Program WBMOD, which includes subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. Earlier versions of WBMOD, were based on extensive analysis of scintillation data collected in the auroral and equatorial zones in Wideband Satellite Mission. The model described herein is based on similarly extensive analysis of Wideband data from one mid latitude station and of data collected from HiLat satellite at another mid latitude station. The model describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 10 along the field and whose one-dimensional spatial power spectrum obeys a single regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function apex latitude of the point. The report highlights a disagreement by a factor of approximately three between irregularity strength inferred from the two satellites in a region of overlap between the two mid-latitude stations.

  20. Spectroscopic Detection of COClF in the Tropical and Mid-Latitude Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Nassar, Ray; Boone, Chris D.; Bernath, Peter; Chiou, Linda; Weisenstein, Debra K.; Mahieu, Emmanuel; Zander, Rodolphe

    2007-01-01

    We report retrievals of COClF (carbonyl chlorofluoride) based on atmospheric chemistry experiment (ACE) solar occultation spectra recorded at tropical and mid-latitudes during 2004-2005. The COClF molecule is a temporary reservoir of both chlorine and fluorine and has not been measured previously by remote sensing. A maximum COClF mixing ratio of 99.7+/-48.0 pptv (10(exp -12) per unit volume, 1 sigma) is measured at 28km for tropical and subtropical occultations (latitudes below 20deg in both hemispheres) with lower mixing ratios at both higher and lower altitudes. Northern hemisphere mid-latitude mixing ratios (30-50degN) resulted in an average profile with a peak mixing ratio of 51.7+/-32.1 pptv, 1 sigma, at 27 km, also decreasing above and below that altitude. We compare the measured average profiles with the one reported set of in situ lower stratospheric mid-latitude measurements from 1986 and 1987, a previous two-dimensional (2-D) model calculation for 1987 and 1993, and a 2-D-model prediction for 2004. The measured average tropical profile is in close agreement with the model prediction; the northern mid-latitude profile is also consistent, although the peak in the measured profile occurs at a higher altitude (2.5-4.5km offset) than in the model prediction. Seasonal average 2-D-model predictions of the COClF stratospheric distribution for 2004 are also reported.

  1. Interaction of mid-latitude air masses with the polar dome area during RACEPAC and NETCARE

    NASA Astrophysics Data System (ADS)

    Bozem, Heiko; Hoor, Peter; Koellner, Franziska; Kunkel, Daniel; Schneider, Johannes; Schulz, Christiane; Herber, Andreas; Borrmann, Stephan; Wendisch, Manfred; Ehrlich, Andre; Leaitch, Richard; Willis, Megan; Burkart, Julia; Thomas, Jennie; Abbatt, Jon

    2016-04-01

    We present aircraft based trace gas measurements in the Arctic during RACEPAC (2014) and NETCARE (2014 and 2015) with the Polar 6 aircraft of Alfred Wegener Institute (AWI) covering an area from 134°W to 17°W and 68°N to 83°N. We focus on cloud, aerosol and general transport processes of polluted air masses into the high Arctic. Based on CO and CO2 measurements and kinematic 10-day back trajectories as well as Flexpart particle dispersion modeling we analyze the transport regimes of mid-latitude air masses traveling to the high Arctic prevalent during spring (RACEPAC 2014, NETCARE 2015) and summer (NETCARE 2014). In general more northern parts of the high Arctic (Lat > 75°N) were relatively unaffected from mid-latitude air masses. In contrast, regions further south are influenced by air masses from Asia and Russia (eastern part of Canadian Arctic and European Arctic) as well as from North America (central and western parts of Canadian Arctic). The transition between the mostly isolated high Arctic and more southern regions indicated by tracer gradients is remarkably sharp. This allows for a chemical definition of the Polar dome based on the variability of CO and CO2 as a marker. Isentropic surfaces that slope from the surface to higher altitudes in the high Arctic form the polar dome that represents a transport barrier for mid-latitude air masses to enter the lower troposphere in the high Arctic. Synoptic-scale weather systems frequently disturb this transport barrier and foster the exchange between air masses from the mid-latitudes and polar regions. This can finally lead to enhanced pollution levels in the lower polar troposphere. Mid-latitude pollution plumes from biomass burning or flaring entering the polar dome area lead to an enhancement of 30% of the observed CO mixing ratio within the polar dome area.

  2. Export of Ozone-Poor Air from the Lower Tropical Stratosphere to Mid-latitudes

    NASA Astrophysics Data System (ADS)

    Spackman, J. R.; Weinstock, E. M.; Anderson, J. G.

    2002-05-01

    Analysis of ozonesonde profiles shows a decline in ozone of 7 to 9%/decade during the past 20 to 30 years in the northern mid-latitude lower stratosphere [Logan et al., 1999], exposing the large population at these latitudes to increased health risks. Heterogeneous processing leading to halogen-catalyzed ozone loss is not expected to occur in the mid-latitude lower stratosphere because in situ measurements indicate the air is consistently undersaturated and low in ClO in this region [Smith et al., 2001]. Furthermore, in situ measurements acquired aboard the NASA ER-2 aircraft during SOLVE (SAGE III Ozone Loss and Validation Experiment) suggest that equatorward mixing of ozone-depleted air from the Arctic vortex does not contribute significantly to declines in mid-latitude lower stratospheric ozone. Instead, tracer-tracer correlations from SOLVE indicate that rapid isentropic transport from the lower tropical stratosphere coupled with diabatic descent in mid-latitudes delivers very young, ozone-poor air to the lowermost stratosphere (θ < 380 K) during northern winter. Given this result, we hypothesize that the seasonal and interannual variability in the strength of this transport from the lower tropical stratosphere modulates mid-latitude lower stratospheric ozone. We investigate methods of using in situ observations to test this hypothesis. Logan, J.A., et al., Trends in the vertical distribution of ozone: A comparison of two analyses of ozonesonde data, Journal of Geophysical Research, 104, 26373-26399, 1999. Smith, J.B., et al., Mechanisms for midlatitude ozone loss: Heterogeneous chemistry in the lowermost stratosphere?, Journal of Geophysical Research, 106, 1297-1309, 2001.

  3. ARM - Midlatitude Continental Convective Clouds (comstock-hvps)

    DOE Data Explorer

    Jensen, Mike; Comstock, Jennifer; Genio, Anthony Del; Giangrande, Scott; Kollias, Pavlos

    2012-01-06

    Convective processes play a critical role in the Earth's energy balance through the redistribution of heat and moisture in the atmosphere and their link to the hydrological cycle. Accurate representation of convective processes in numerical models is vital towards improving current and future simulations of Earths climate system. Despite improvements in computing power, current operational weather and global climate models are unable to resolve the natural temporal and spatial scales important to convective processes and therefore must turn to parameterization schemes to represent these processes. In turn, parameterization schemes in cloud-resolving models need to be evaluated for their generality and application to a variety of atmospheric conditions. Data from field campaigns with appropriate forcing descriptors have been traditionally used by modelers for evaluating and improving parameterization schemes.

  4. Ionospheric F2 layer responses to total solar eclipses at low and mid-latitude

    NASA Astrophysics Data System (ADS)

    Adekoya, B. J.; Chukwuma, V. U.

    2016-02-01

    In this article, we presented ionospheric F2 responses to total solar eclipses on the basis of the data obtained from five (5) equatorial/low-latitude and twenty-seven (27) mid-latitude ionosonde stations, which are within the obscuration percentage of 50-100% of the path of the total solar eclipses progression. Statistically, the diurnal changes in the F2 layer peak height hmF2 and electron density NmF2, as well as the latitudinal and hemispheric dependence and the contribution of both magnetic and solar activities during the eclipse window were investigated. The estimation of the solar ionizing radiation that remains unmasked during the eclipse window was as well carried out. Plasma diffusion processes dominate the F2 region plasma, and determine the height at which the F2 peak formed at mid-latitude. The electron density decreased during the eclipse window, closely following the variation in the local solar radiation at the mid-latitude. However, at equatorial/low-latitude, the plasma distribution during total solar eclipse depends on combine effect of solar radiation and the background nighttime ionospheric irregularities mechanism. The uncertainty level of the estimated solar ionizing radiation was <±0.3 at mid-latitude and greater±0.3 at equatorial/low-latitude. Their correlation ranges from (0.42-0.99). The ionospheric F2 layer eclipse effect is latitudinal and hemispheric dependent. The effect is largest at mid-latitude and relatively small at equatorial/low-latitudes. It is more pronounced at the equator, and decreases toward the equatorial ionospheric anomaly (EIA) region. The better correlation of 0.5840 and 0.6435 between geographic latitude and E(t) and electron density justifies the latitudinal relationship. The increase in percentage deviation of electron density increases with latitude and delay time (∆T) in the northern hemisphere of the mid-latitude. Conversely, in the southern hemisphere the percentage deviation decreases with an increase in

  5. Convective Removal of Continental Margin Lithosphere at the Edges of Subducting Oceanic Plates

    NASA Astrophysics Data System (ADS)

    Levander, A.; Bezada, M. J.; Palomeras, I.; Masy, J.; Humphreys, E.; Niu, F.

    2013-12-01

    Although oceanic lithosphere is continuously recycled to the deeper mantle by subduction, the rates and manner in which different types of continental lithospheric mantle are recycled is unclear. Cratonic mantle can be chemically reworked and essentially decratonized, although the frequency of decratonization is unclear. Lithospheric mantle under or adjacent to orogenic belts can be lost to the deeper mantle by convective downwellings and delamination phenomena. Here we describe how subduction related processes at the edges of oceanic plates adjacent to passive continental margins removes the mantle lithosphere from beneath the margin and from the continental interior. This appears to be a widespread means of recycling non-cratonic continental mantle. Lithospheric removal requires the edge of a subducting oceanic plate to be at a relatively high angle to an adjacent passive continental margin. From Rayleigh wave and body wave tomography, and receiver function images from the BOLIVAR and PICASSO experiments, we infer large-scale removal of continental margin lithospheric mantle from beneath 1) the northern South American plate margin due to Atlantic subduction, and 2) the Iberian and North African margins due to Alboran plate subduction. In both cases lithospheric mantle appears to have been removed several hundred kilometers inland from the subduction zones. This type of ';plate-edge' tectonics either accompanies or pre-conditions continental margins for orogenic activity by thinning and weakening the lithosphere. These processes show the importance of relatively small convective structures, i.e. small subducting plates, in formation of orogenic belts.

  6. Ionospheric scintillation modeling for high- and mid-latitude using B-spline technique

    NASA Astrophysics Data System (ADS)

    Priyadarshi, S.

    2015-09-01

    Ionospheric scintillation is a significant component of space-weather studies and serves as an estimate for the level of perturbation in the satellite radio wave signal caused due to small-scale ionospheric irregularities. B-spline functions are used on the GPS ground based data collected during the year 2007-2012 for modeling high- and mid-latitude ionospheric scintillation. Proposed model is for Hornsund, Svalbard and Warsaw, Poland. The input data used in this model were recorded by GSV 4004b receivers. For validation, results of this model are compared with the observation and other existing models. Physical behavior of the ionospheric scintillation during different seasons and geomagnetic conditions are discussed well. Model is found in good coherence with the ionospheric scintillation theory as well as to the accepted scintillation mechanism for high- and mid-latitude.

  7. Modeling study of the mid-latitude ionospheric nighttime electron density enhancement by SAMI3

    NASA Astrophysics Data System (ADS)

    Chen, C.; Huba, J. D.; Saito, A.; Lin, C.; Liu, J. G.; Chang, L. C.

    2012-12-01

    The mid-latitude summer nighttime anomaly (MSNA) is a feature that the nighttime electron density is larger than in the daytime around the mid-latitude ionosphere. This anomaly was first detected in the southern hemisphere five decades ago and reported in the northern hemisphere recently. Previous studies presented the electron density structure of MSNA by satellite observation data and found that MSNA is clearly seen at 300 km altitude during local summer around South American, European, and Northeast Asian regions. A three-dimensional self-consistent model, SAMI3 (Sami3 is Also a Model of the Ionosphere), with inputting neutral wind data from TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) model is used to simulate the MSNA feature and further discuss its mechanisms. The comparisons between observation data and the model simulation results suggest that the equatorial neutral winds play the most important role in the formation of MSNA.

  8. An assessment of the Jenkinson and Collison synoptic classification to a continental mid-latitude location

    NASA Astrophysics Data System (ADS)

    Spellman, Greg

    2016-01-01

    A weather-type catalogue based on the Jenkinson and Collison method was developed for an area in south-west Russia for the period 1961-2010. Gridded sea level pressure data was obtained from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The resulting catalogue was analysed for frequency of individual types and groups of weather types to characterise long-term atmospheric circulation in this region. Overall, the most frequent type is anticyclonic (A) (23.3 %) followed by cyclonic (C) (11.9 %); however, there are some key seasonal patterns with westerly circulation being significantly more common in winter than summer. The utility of this synoptic classification is evaluated by modelling daily rainfall amounts. A low level of error is found using a simple model based on the prevailing weather type. Finally, characteristics of the circulation classification are compared to those for the original JC British Isles catalogue and a much more equal distribution of flow types is seen in the former classification.

  9. The response of the mid-latitude thermospheric wind to magnetic activity

    NASA Astrophysics Data System (ADS)

    Yagi, T.; Dyson, P. L.

    1985-04-01

    Observations of the thermospheric wind at mid-latitude have been carried out using a Febry-Perot interferometer to measure the Doppler shift of the night-time OI emission at a wavelength of 630 nm. Results are presented for 12 different summer nights which show that the zonal wind has a distinct feature associated with magnetic activity. The influence of magnetic activity on the maximum strength, and duration of both the eastward and westward versions of the thermospheric wind, is discussed.

  10. An analysis on the mid-latitude scintillation and coherence frequency bandwidth using transionospheric VHF signals

    SciTech Connect

    Juang, Zhen; Roussel-dupre, Robert

    2008-01-01

    An analysis was perfonned on the mid-latitude scintillation and coherence frequency bandwidth (Fcoh) using transionospheric VHF signal data. The data include 1062 events spanning from November 1997 to June 2002. Each event records FORTE satellite received VHF signals from LAPP located at Los Alamos, New Mexico. Fcohs were derived to study scintillation characteristics on diurnal and seasonal variations, as well as changes due to solar and geomagnetic activities. Comparisons to the VHFIUHF coherence frequency bandwidth studies previously reported at equatorial and mid-latitude regions are made using a 4th power frequency dependence relationship. Furthennore, a wideband ionospheric scintillation model, WBMOD, was used to estimate Fcohs and compared with our VHF Fcoh values. Our analysis indicates mid-latitude scintillation characteristics that are not previously revealed. At the VHF bottom frequency range (3035 MHz), distinguished smaller Fcohs are found in time period from sunset to midnight, in wann season from May to August, and in low solar activity years. The effects of geomagnetic storm activity on Fcoh are characterized by a sudden transition at a Kp index of 50-60. Comparisons with median Fcohs estimated from other studies validated our VHF Fcohs for daytime while an order of magnitude larger Fcohs are found for nighttime, implying a time-dependent issue in applying the 4th order power relationship. Furthermore, comparisons with WBMOD-estimated Fcohs indicated generally matched median scintillation level estimates while differences do exist for those events undergoing high geomagnetic stonn activity which may imply underestimates of scintillation level by the WBMOD in the mid-latitude regions.

  11. Water Vapor Turbulence Profiles in Stationary Continental Convective Mixed Layers

    SciTech Connect

    Turner, D. D.; Wulfmeyer, Volker; Berg, Larry K.; Schween, Jan

    2014-10-08

    The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program’s Raman lidar at the ARM Southern Great Plains (SGP) site in north-central Oklahoma has collected water vapor mixing ratio (q) profile data more than 90% of the time since October 2004. Three hundred (300) cases were identified where the convective boundary layer was quasi-stationary and well-mixed for a 2-hour period, and q mean, variance, third order moment, and skewness profiles were derived from the 10-s, 75-m resolution data. These cases span the entire calendar year, and demonstrate that the q variance profiles at the mixed layer (ML) top changes seasonally, but is more related to the gradient of q across the interfacial layer. The q variance at the top of the ML shows only weak correlations (r < 0.3) with sensible heat flux, Deardorff convective velocity scale, and turbulence kinetic energy measured at the surface. The median q skewness profile is most negative at 0.85 zi, zero at approximately zi, and positive above zi, where zi is the depth of the convective ML. The spread in the q skewness profiles is smallest between 0.95 zi and zi. The q skewness at altitudes between 0.6 zi and 1.2 zi is correlated with the magnitude of the q variance at zi, with increasingly negative values of skewness observed lower down in the ML as the variance at zi increases, suggesting that in cases with larger variance at zi there is deeper penetration of the warm, dry free tropospheric air into the ML.

  12. Low- to Mid-Latitude X-Ray Emission from Jupiter

    NASA Technical Reports Server (NTRS)

    Bhardwaj, Anil; Elsner, Ronald F.; Gladstone, G. Randall; Waite, J. Hunter, Jr.; Branduardi-Raymont, Graziella; Cravens, Thomas E.; Ford, Peter

    2006-01-01

    The Chandra X-ray Observatory (CXO) observed Jupiter during the period 2003 February 24-26 for approx.40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each approx.8.5 hr long, were separated by an HRC-I exposure of approx.20 hr. The low- to mid-latitude non-auroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low- to mid-latitude X-ray count rate shows a small but statistically significant hour angle dependence, and is higher in regions of relatively low surface magnetic field strength, confirming ROSAT results. In addition, the spectrum from the low surface field region shows an enhancement in the energy band 1.14- 1.38 keV, perhaps partly due to line emission from that region. Correlation of surface magnetic field strength with count rate is not found for the 2000 December HRC-I data, at a time when solar activity was high. The low- to mid-latitude disk X-ray count rate observed by the HRC-I in the 2003 February observation is about 50% of that observed in 2000 December, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low- to mid-latitude X-ray emission does not show any oscillations similar to the -45 minute oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's non-auroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2 keV low- to mid-latitude X-ray spectra are harder than the auroral spectrum, and are different from each other at energies above 0.7 keV, showing variability in Jupiter s non-auroral X-ray emission on a time scale of a day. The 0.3-2.0 keV X-ray power emitted at low- to mid-latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures

  13. Experimental investigation of mechanisms of mid-latitude ionosphere and geophysical fields perturbation

    NASA Astrophysics Data System (ADS)

    Gavrilov, Boris; Zetzer, Julius; Egorov, Dmitry

    The investigations are carried out to study mechanisms and channels of the mid-latitude ionosphere, near-Earth electric field and current perturbations, and their connection to high-latitude and magnetospheric events. The basis of these investigations is a measurement of the geophysical fields in the Geophysical Observatory Mikhnevo (54.9 N, 37,8 E) of the Institute of Geospheres Dynamics RAS situated at 80 km to the south from Moscow. The observatory includes a set of measuring complexes for radiophysics, magnetic, electrical, optic, infrasound, seismic, and other investigations. All of them are controlled by the united computer centre in the common scale of time. Our approach bases on well known conception that the main reasons of the mid-latitude perturbations are the processes in the auroral regions. But auroral phenomena impact on mid-latitudes by means of different physical mechanisms and agents of disturbances. Fortunately, they differ from each other in the time of their generation and velocities of their propagation. For example, the typical velocity of propagation of thermosphere winds is about 100 m/s, the acoustic gravity wave propagate with a velocity of about 400 m/s, and a prompt penetration of the magnetospheric electric field affects the mid-latitude practically instantly. If we can determine a time lag between the action of the perturbation source and mid-latitude ionosphere response, we can determine the velocity of perturbation propagation and recognize the dominating mechanisms and channels of disturbances. The important requirements for the organization of such investigation is a positioning of different measuring facilities in one place and organization of coordinated and synchronous registration of the ionosphere parameters and geophysical fields variations with high temporal resolution. The Mikhnevo observatory gives us such ability. As an indicator and marker of high latitude events (magnetic storms and substorms) we use AE-index. The

  14. The oldest hominin butchery in European mid-latitudes at the Jaramillo site of Untermassfeld (Thuringia, Germany).

    PubMed

    Landeck, Günter; Garcia Garriga, Joan

    2016-05-01

    The late Early Pleistocene site of Untermassfeld, dated to the Jaramillo subchron (ca. 1.07 millions of years ago), is well known for its rich Epivillafranchian fauna. It has also recently yielded stone artefacts attesting hominin occupation. Now, we report here, for the first time, evidence of hominin butchery such as cut marks and intentional hammerstone-related bone breakage. This probable subsistence behaviour was detected in a small faunal subsample recovered from levels with Mode 1 stone tools. The butchered faunal assemblage was found during fieldwork and surveying in fluvial riverbanks (Lower Fluviatile Sands) and channel erosion sediments (Upper Fluviatile Sands). The frequent occurrence of butchery traces on bones of large-sized herd animals (i.e., Bison) may imply a greater need for meat in seasonal habitats characterised by a depletion of nutritive plants in winter. Early access to carcasses, before their consumption by carnivores, provided hominins with sufficient quantities of meat. This access was acquired with a Mode 1 lithic industry, to ensure food procurement and survival at high latitudes in Europe. Stone tools and faunal remains with signs of anthropic intervention recovered at Untermassfeld are evidence of the oldest hominin settlement at continental mid-latitudes (50° N). PMID:27178458

  15. Characteristics of winter precipitation systems over the mid-latitude North Pacific as analyzed from TRMM PR and VIRS data

    NASA Astrophysics Data System (ADS)

    Shimizu, H.; Masunaga, H.; Yamamoto, M. K.; Higuchi, A.

    2011-12-01

    Winter precipitation systems over the mid-latitude North Pacific are investigated using multiple sensors on board the Tropical Rainfall Measuring Mission (TRMM) satellite. The present study is focused on the vertical structure of precipitation in 11 winters. The vertical structure is diagnosed with echo-top height from the Precipitation Radar (PR) and the equivalent cloud-top height from the Visible Infrared and Scanner (VIRS) and Japanese 25-year Reanalysis (JRA-25). Precipitation systems are classified into three categories based on their vertical structure: Shallow Cumulus (SCu), Middle Systems (MdS), and Deep Convection (DpC). This categorization method is found to clearly delineate a systematic difference in precipitation between the east and west Pacific. To further explore the nature of precipitation systems, Cold Outbreak (CO), Extra-tropical Cyclone (EC), Front (F), and Sub tropical Cyclone (ST) patterns are identified by infrared imagery and upper level pressure. The zonal gradient across the Pacific in the vertical structure of precipitation may be interpreted in terms of these synoptic-scale disturbances superposed with different proportions.

  16. Inorganic bromine and iodine in the TTL and in the mid-latitude lower stratosphere

    NASA Astrophysics Data System (ADS)

    Volkamer, Rainer; Apel, Eric; Atlas, Elliot; Bowdalo, Dene; Bresch, Jim; Dix, Barbara; Eloranta, Ed; Evans, Matthew; Gao, Ru-Shan; Jacob, Daniel; Kinnison, Doug; Koenig, Theodore; Lamarque, Jean-Francois; Morley, Bruce; Pierce, Brad; Saiz-Lopez, Alfonso; Salawitch, Ross; Schmidt, Johan; Wang, Siyuan

    2015-04-01

    TTL over the tEPO, where elevated BrO correlates with stratospheric tracers (low H2O/O3 ratio). BrO in the lower stratosphere at mid-latitudes (Southern hemisphere) is found to be in closer agreement with models, and is only slightly higher than predicted. We constrain a box-model with observations from TORERO to estimate BrY in the TTL, assess the stratospheric BrY boundary condition in GEOS-Chem, and assess sensitivities in BrY partitioning to variations in the heterogeneous bromine recycling on aerosol/ice surfaces.

  17. Tropical Continental Convection (Amazonia and the North American Monsoon): Unique Observations from GPS Meteorological Networks

    NASA Astrophysics Data System (ADS)

    Adams, D. K.

    2015-12-01

    The complex interactions/feedbacks between water vapor fields and deep atmospheric convection remain one of the outstanding problems in Tropical Meteorology. The lack of high spatial/temporal resolution, all-weather observations in the Tropics has hampered progress. In this talk, we present results employing GPS meteorology from two topographically/climatologically unique Tropical Continental regimes: Central Amazonia and the Sierra Madre Occidental of Mexico. Specifically, we presents results on the shallow-to-deep convective transition from both regimes in addition to employing water vapor convergence as a proxy variable for convective intensity. Results from both convective regimes reveal an approximately 4-hour timescale of intense water vapor convergence associated with the transition from shallow to deep precipitating convection. This water vapor convergence time scale provides a useful metric for both high resolution and global climate models to replicate. Furthermore, we examime convective intensity from both regimes (defined utilizing lightning data, cloud top temperature or precipitation), which is also characterized by the time-rate-of-change of precipitable water vapor. The relationship between the time-rate-of-change of precipitable water vapor and convective intensity is positive, however, with a large amount spread in the data and some dependence on the regime and topography.

  18. Fractal and wavelet analysis evaluation of the mid latitude ionospheric disturbances associated with major geomagnetic storms

    NASA Astrophysics Data System (ADS)

    López-Montes, Rebeca; Pérez-Enríquez, Román; Araujo-Pradere, Eduardo A.; López Cruz-Abeyro, Jose Antonio

    2015-01-01

    Variations of the total electron content (TEC) of the ionosphere are mainly associated with major geomagnetic storms occurring with the arrival of coronal mass ejections (CMEs) to the Earth environment. The purpose of this paper is to show results of the analysis we made of the impact of all major geomagnetic storms (Dst < - 200 nT) on the ionosphere at mid latitudes, which have occurred since 2000. The analysis consists in the calculation of TEC of the ionosphere using data from several Mexican GPS stations, with the purpose of quantifying the impact into the ionosphere to these latitudes, through the variations in amplitude, Hurst index, that is roughness, and wavelet transform of the time series of TEC. Indeed, during the geomagnetic storms of April 7, 2000, July 16, 2000, October 30, 2003, November 20, 2003 and November 8, 2004, major ionospheric disturbances at mid latitudes took place with changes in amplitude of TEC going from 3.29 to 8.82 sigmas. These ionospheric disturbances were probably associated with prompt penetration electric fields (PPEFs) and equatorward neutral winds. On the other hand, during four geomagnetic storms (August 12, 2000, March 31, 2001, April 11, 2001 and May 15, 2005), there were negative ionospheric storms that pushed the TEC to significantly lower values. This has been interpreted as the presence of regions in which the neutral composition is changed. Also, in some cases during the disturbed days, the Hurst values were smaller than during the undisturbed days, i.e. during these geomagnetic storms, the roughness of the time series of TEC increased. The wavelet analysis showed a strong influence of the diurnal variation on TEC values (periodicities of 12 h), and periodicities characteristics of ionospheric disturbances of 1-8 h. It is found that large geomagnetic storms produce significant ionospheric disturbances at mid latitudes, as shown by the wavelet analysis and, in some cases, changes in the roughness of the time series of

  19. Greenland Blocking As a Mechanism for Recent Arctic/Mid-Latitude Weather Linkages

    NASA Astrophysics Data System (ADS)

    Overland, J. E.; Hanna, E.; Wang, M.

    2014-12-01

    High-latitude blocking (HLB) located near and west of Greenland and in northeastern Siberia is a process that links Arctic processes to mid-latitude weather. HLB lies north of the jet stream and tends to bifurcate or divert the jet stream southward, rather than providing a complete block to the westerly flow. It is differentiated from mid-latitude blocking located in the central Atlantic to Europe and the western Pacific along eddy-driven jet streams. It is important to identify and understand an increase in recent HLB in early winter during the last five years relative to time series since 1948, even though this length is too short to robustly distinguish the influence of Arctic forcing from random events. In the last five early winters (December-January 2009-10 through 2013-14), two record and four other negative Arctic Oscillation atmospheric circulation index events have been observed, with positive Greenland Blocking Indices (GBI, greater 500 hPa geopotential heights) and increased geopotential thickness west of Greenland. Cold air penetrated into the southeastern United States in December 2009 and 2010 and January 2014 related to amplification in the long-wave upper-level atmospheric wind pattern. Northward air flow over Davis Strait acts as a positive feedback to maintain the Greenland air temperature anomalies. Extreme negative GBI were observed in December 2011-January 2012. Increased thickness associated with positive GBI can be a response to external (local sea ice loss, Greenland surface warming, or even equatorial teleconnections) or internal (advection and orientation of the long wave patterns) processes. A similar blocking feature is observed in Siberia/eastern Asia. A Bayesian approach to an Arctic/mid-latitude weather linkage emphasizes the nearly irresolvable uncertainty surrounding causation of recent major weather events; yet it drives scientific understanding of linkages and potential impacts on seasonal forecasting.

  20. Late Cenozoic fire enhancement response to aridification in mid-latitude Asia: Evidence from microcharcoal records

    NASA Astrophysics Data System (ADS)

    Miao, Yunfa; Fang, Xiaomin; Song, Chunhui; Yan, Xiaoli; Zhang, Ping; Meng, Qingquan; Li, Fang; Wu, Fuli; Yang, Shengli; Kang, Shuyuan; Wang, Yuanping

    2016-05-01

    Fire provides an important indicator of paleoclimatic change. However, little information relating to late Cenozoic fire history has been gathered in mid-latitude Asia (including Inner Asia and East Asia), a key region for understanding the development of the arid-monsoon climate system as well as the driving forces behind it. Here we first report the records of microcharcoal concentrations (MC) covering the Holocene (10-0 ka) and late Pleistocene (0.8-0 Ma), which we use to analyze the fire activity patterns at an orbital time scale; then we compile the late Cenozoic MC record to investigate the long-term fire history by analyzing four cores from the Yangtze River Delta (YRD) area, East Asia (representing 8-0 Ma) and three sites in Inner Asia (representing 18-2 Ma). The results show that the (i) MC remained higher during the relatively dry late Holocene/glacial stages than that during the humid middle Holocene/interglacial stages at individual sites; (ii) MC increased with time in both Inner Asia and East Asia after 18 and 8 Ma, respectively; and (iii) MC always remained higher in the dry Inner Asia than in the contemporaneous wet East Asia. All these characteristics imply that late Cenozoic fire occurrence in mid-latitude Asia experienced a gradual increasing trend along with the global temperature/ice volume change, and indicates a continuous aridification trend across mid-latitude Asia. The global cooling, rather than the Tibetan Plateau uplift, might have played a key role in this observed trend.

  1. Tracking Jupiter’s Quasi-Quadrennial Oscillation and Mid-Latitude Zonal Waves: Initial Results

    NASA Astrophysics Data System (ADS)

    Greathouse, Thomas K.; Orton, Glenn S.; Morales-Juberias, Raul; Fletcher, Leigh N.; DeWitt, Curtis N.; Cosentino, Rick; Richter, Matthew J.; Lacy, John H.

    2014-11-01

    We report on initial results of a long term observational study to track the temporal and 3-dimensional evolution of the Quasi-Quadrennial Oscillation (QQO) and the propagation and evolution of mid-latitude zonal waves in Jupiter’s stratosphere. These wave-driven phenomena affect variations in Jupiter’s vertical and horizontal temperature field, which can be inferred by measuring methane emission in the thermal infrared at 1245 cm-1. Using TEXES, the Texas Echelon cross-dispersed Echelle Spectrograph, mounted on the NASA Infrared Telescope Facility we observed high-spectral resolution (R=75,000) scan maps of Jupiter’s mid-latitudes in January and October 2012, February 2013, and February 2014. These initial datasets were taken using several different observing strategies in an attempt to optimize efficiency and mapping accuracy in preparation for our prime study period (2014-2019). We will present the zonally averaged inferred thermal structure over ±30° latitude and between 10 and 0.01 mbar, showing the QQO’s downward progression along with inferred 3-dimensional thermal maps (latitude, longitude, pressure) displaying a multitude of vertically isolated waves and eddies. These results set the stage for an unprecedented dataset that will: 1) significantly improve the determination of the period and vertical descent velocity of Jupiter’s QQO and map its 3-dimensional spatial structure; 2) measure the zonal wavenumbers, vertical wavelengths, zonal group velocities and lifetimes of transient mid-latitude waves that are impossible to obtain from historic mid-infrared imaging datasets due to their lack of vertical resolution; and 3) record the thermal state of Jupiter’s stratosphere in detail prior to, during, and after Juno’s prime mission to assist in analysis of Juno Mission observations from the Waves, JIRAM, and UVS instruments.

  2. Ion composition during the formation of a mid-latitude Es layer

    NASA Technical Reports Server (NTRS)

    Aikin, A. C.; Goldberg, R. A.; Azcarraga, A.

    1974-01-01

    The positive ion composition within a mid-latitude sporadic E layer has been measured with the aid of a rocketborne ion mass spectrometer launched from El Arenosillo, Spain on July 3, 1972 at 0743 LMT. Ionograms taken before and during the rocket flight showed a developing sporadic E layer near 114 km. Rocket data showed peaks in electron density and metallic ions at this same height. Both the maximum and total content of the metals are observed to be greater on the downleg than on the upleg measurement.

  3. The Influence of Arctic Amplification on Mid-Latitude Atmospheric Circulation and Extreme Weather Events

    NASA Astrophysics Data System (ADS)

    Vavrus, S. J.; Francis, J. A.

    2012-12-01

    We expand on our recent work that provided evidence for a mechanism linking Arctic Amplification to changes in mid-latitude circulation patterns that favor extreme weather events (Francis and Vavrus, 2012). Here we analyze greenhouse-forced projections from the Community Climate System Model (CCSM4) to assess the future evolution of Arctic change on Northern Hemisphere weather patterns. We hypothesize that remote impacts of changes in the energy budget of the Arctic surface will influence the atmospheric circulation in middle latitudes through changes in large-scale, deep-tropospheric, meridional thickness gradients that induce generally weaker zonal flow and higher amplitude large-scale waves aloft. Because such features are slow-moving and associated with persistent weather conditions, they favor more frequent and severe extreme weather episodes resulting from prolonged cold-air outbreaks, heat waves, droughts, and heavy precipitation. The primary physical mechanism driving this change is an enhanced and seasonally varying Arctic heating: in fall/winter it is ocean-based due to substantial sea ice loss, while in warmer months it is land-based due to earlier snow melt and reduced soil moisture. Simulations by CCSM4 support our hypothesized linkages, as the projected climate changes depict a seasonally varying circulation response hinging on the enhanced warming and resulting geopotential height increases aloft in the Arctic. During boreal autumn and winter, sea ice loss leads to upper-air height increases mainly over the Arctic Ocean with compensating decreases over mid-latitudes, which reduces the poleward gradient. During spring and summer, however, the band of maximum ridging shifts southward over high-latitude land. This behavior resembles the upper-air circulation changes induced by prescribed reductions in sea ice and snow cover in previous versions of the model. The associated seasonal changes in mid-tropospheric zonal winds exhibit a nearly symmetrical

  4. Present-day Exposures of Water Ice in the Northern Mid-latitudes of Mars

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.; Kanner, Lisa C.

    2007-01-01

    Water ice is exposed in the martian north polar cap, but is rarely exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60deg. We have examined mid-latitude areas of the northern plains displaying residual ice-rich layers, and report evidence of present-day surface exposures of water ice. These exposures, if confirmed, could con-strain the latitudinal and temporal stability of surface ice on Mars.

  5. Mid-Latitude Temperatures at 87 km: Results From Multi-Instrument Fourier Analysis

    NASA Technical Reports Server (NTRS)

    Drob, Douglas P.; Picone, J. M.; Eckermann, Stephen D.; She, C . Y.; Kafkalidis, J. F.; Ortland, D. A.; Niciejewski, R. J.; Killeen, T. L.

    2000-01-01

    Using a novel Fourier fitting method we combine two years of mid-latitude temperature measurements at 87 km from the High Resolution Doppler Imager, the Colorado State University lidar, and the Peach Mountain Interferometer. After accounting for calibration bias, significant local-time variations on the order of 10 K were observed. Stationary planetary waves with amplitudes up to 10 K were observed during winter, with weaker wave amplitudes occurring during other seasons. Because of calibration biases among these instruments, we could estimate the annual mean temperature to no better than 193.5 plus or minus 8.5 K.

  6. In situ measurements constraining the role of sulphate aerosols in mid-latitude ozone depletion

    NASA Technical Reports Server (NTRS)

    Fahey, D. W.; Kawa, S. R.; Woodbridge, E. L.; Tin, P.; Wilson, J. C.; Jonsson, H. H.; Dye, J. E.; Baumgardner, D.; Borrmann, S.; Toohey, D. W.

    1993-01-01

    In situ measurements of stratospheric sulphate aerosol, reactive nitrogen and chlorine concentrations at middle latitudes confirm the importance of aerosol surface reactions that convert active nitrogen to a less active, reservoir form. This makes mid-latitude stratospheric ozone less vulnerable to active nitrogen and more vulnerable to chlorine species. The effect of aerosol reactions on active nitrogen depends on gas phase reaction rates, so that increases in aerosol concentration following volcanic eruptions will have only a limited effect on ozone depletion at these latitudes.

  7. Evidence for Amazonian mid-latitude glaciation on Mars from impact crater asymmetry

    NASA Astrophysics Data System (ADS)

    Conway, Susan J.; Mangold, Nicolas

    2013-07-01

    We find that crater slopes in the mid-latitudes of Mars have a marked north-south asymmetry, with the pole-facing slopes being shallower. We mapped impact craters in two southern hemisphere sites (Terra Cimmeria and Noachis Terra) and one northern hemisphere site (Acidalia Planitia) and used elevation data from the High Resolution Stereo Camera (HRSC) onboard Mars Express to find the maximum slope of impact crater walls in the four cardinal directions. Kreslavsky and Head (Kreslavsky, M.A., Head, J.W. [2003]. Geophys. Res. Lett. 30), using Mars Orbiter Laser Altimeter (MOLA) track data, also found that, in general, conjugate slopes are shallower in the pole-facing direction, but over a narrower (˜10°) and more constrained latitude band. They linked the asymmetry to active-layer formation (thaw) at high obliquity. However, Parsons and Nimmo (Parsons, R.A., Nimmo, F. [2009]. J. Geophys. Res. 114) studied crater asymmetry using MOLA gridded data and found no evidence of a relationship between crater asymmetry and latitude. Our work supports the observations of Kreslavsky and Head (Kreslavsky, M.A., Head, J.W. [2003]. Geophys. Res. Lett. 30), and shows that asymmetry is also found on conjugate crater slopes below the resolution of MOLA, over a wider latitude band than found in their work. We do not systematically find a sudden transition to asymmetric craters with latitude as expected for thaw-related processes, such as solifluction, gelifluction, or gully formation. The formation of gullies should produce the opposite sense of asymmetry to our observations, so cannot explain them despite the mid-latitude location and pole-facing preferences of gullies. We instead link this asymmetry to the deposition of ice-rich crater deposits, where the base of pole-facing slopes receive ten to hundreds of meters of additional net deposition, compared to equator-facing ones over the mid-latitudes. In support of this hypothesis we found that craters in Terra Cimmeria that have

  8. Mid-latitude temperatures at 87 km: Results from multi-instrument Fourier analysis

    NASA Astrophysics Data System (ADS)

    Drob, Douglas P.; Picone, J. Michael; Eckermann, Stephen D.; She, C. Y.; Kafkalidis, J. F.; Ortland, D. A.; Niciejewski, R. J.; Killeen, T. L.

    2000-08-01

    Using a novel Fourier fitting method we combine two years of mid-latitude temperature measurements at 87 km from the High Resolution Doppler Imager, the Colorado State University lidar, and the Peach Mountain Interferometer. After accounting for calibration bias, significant local-time variations on the order of 10 K were observed. Stationary planetary waves with amplitudes up to 10 K were observed during winter, with weaker wave amplitudes occurring during other seasons. Because of calibration biases among these instruments, we could estimate the annual mean temperature to no better than 193.5±8.5 K.

  9. Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Willis, Emily M.; Parker, Linda Neergaard

    2014-01-01

    Spacecraft charging of the International Space Station (ISS) is dominated by the interaction of the high voltage US solar arrays with the F2-region ionospheric plasma environment. We are working to fully understand the charging behavior of the ISS solar arrays and determine how well future charging behavior can be predicted from in-situ measurements of plasma density and temperature. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that may be encountered at ISS orbital altitudes (approximately 400 km), the latitudes over which they occur, and the time periods for which the disturbances persist. We will present preliminary results from a study of ionospheric disturbances in the "mid-latitude" region defined as the approximately 30 - 60 degree extra-equatorial magnetic latitudes sampled by ISS. The study is focused on geomagnetic storm periods because they are well known drivers for disturbances in the high-latitude and mid-latitude ionospheric plasma. Changes in the F2 peak electron density obtained from ground based ionosonde records are compared to in-situ electron density and temperature measurements from the CHAMP and ISS spacecraft at altitudes near, or above, the F2 peak. Results from a number of geomagnetic storms will be presented and their potential impact on ISS charging will be discussed.

  10. Asian pollution climatically modulates mid-latitude cyclones following hierarchical modelling and observational analysis.

    PubMed

    Wang, Yuan; Zhang, Renyi; Saravanan, R

    2014-01-01

    Increasing levels of anthropogenic aerosols in Asia have raised considerable concern regarding its potential impact on the global atmosphere, but the magnitude of the associated climate forcing remains to be quantified. Here, using a novel hierarchical modelling approach and observational analysis, we demonstrate modulated mid-latitude cyclones by Asian pollution over the past three decades. Regional and seasonal simulations using a cloud-resolving model show that Asian pollution invigorates winter cyclones over the northwest Pacific, increasing precipitation by 7% and net cloud radiative forcing by 1.0 W m(-2) at the top of the atmosphere and by 1.7 W m(-2) at the Earth's surface. A global climate model incorporating the diabatic heating anomalies from Asian pollution produces a 9% enhanced transient eddy meridional heat flux and reconciles a decadal variation of mid-latitude cyclones derived from the Reanalysis data. Our results unambiguously reveal a large impact of the Asian pollutant outflows on the global general circulation and climate. PMID:24448316

  11. Ionospheric fluctuation study over mid-latitude during one large magnetic storm based on GPS observatio

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Li, Q.; Xiao, Z.

    Form Nov 5 to Nov 10 2004 a large number of solar events occurred that triggered many solar flares and CMEs These CMEs caused two large geomagnetic storms and continuous energy proton event During this period one large positive ionospheric storm happened over the East-Asian region on Nov 08 2004 On Nov 10 2004 a strong spread-F was observed by the ionosonda located in the mid-latitude region of East china and Japan and the ionospheric fluctuation over the ionosonda station derived from GPS observation was also obvious In this report the characteristics of the spatial distribution of the ionosphere fluctuation and its temporal evolution using the parameter of ROT derived from dual-frequency GPS measurement are studied It is found that the ionosphere over the mid-latitude region in southern and northern hemisphere between the longitude of 100 E and 180 E behaves strong fluctuating activity during the magnetic storm period on Nov 10 2004 a regular movement of the disturbing region is observed in the end the reason of the ionospheric fluctuation during this magnetic storm is analyzed

  12. Using Causal Effect Networks to analyze different Arctic drivers of mid-latitude winter circulation

    NASA Astrophysics Data System (ADS)

    Kretschmer, Marlene; Coumou, Dim; Donges, Jonathan; Runge, Jakob

    2016-04-01

    In the past years, the northern hemisphere mid-latitudes have suffered from severe winters like the extreme 2013/2014 winter in the eastern USA. These cold spells were linked to a meandering upper tropospheric jet stream pattern and a negative Arctic Oscillation Index (AO). However, the nature of the drivers behind these circulation patterns remains controversial. Various studies have proposed different mechanisms related to changes in the Arctic, most of them referring to a reduction in sea ice concentrations or increasing Eurasian snow cover. Here we introduce a novel type of time series analysis, called Causal Effect Networks (CEN) based on graphical models to assess causal relationships and their time-delays between different processes. We present the effect of different Arctic actors on winter circulation on weekly to monthly time-scales. Barents and Kara sea ice concentrations are detected to be important external drivers in the context of mid-latitude circulation, influencing winter AO via tropospheric mechanisms and through processes involving the Stratosphere. Eurasia snow cover is also detected to have a causal effect on sea level pressure in Asia, but its exact role on AO remains unclear. The CEN approach overcomes some difficulties in interpreting correlation analyses, complements model experiments for testing hypotheses involving teleconnections, and can be used to assess their validity.

  13. Ozone Depletion at Mid-Latitudes: Coupling of Volcanic Aerosols and Temperature Variability to Anthropogenic Chlorine

    NASA Technical Reports Server (NTRS)

    Solomon, S.; Portmann, R. W.; Garcia, R. R.; Randel, W.; Wu, F.; Nagatani, R.; Gleason, J.; Thomason, L.; Poole, L. R.; McCormick, M. P.

    1998-01-01

    Satellite observations of total ozone at 40-60 deg N are presented from a variety of instruments over the time period 1979-1997. These reveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical theories of ozone depletion. The observations are shown to be consistent with current understanding of the chemistry of ozone depletion when changes in reactive chlorine and stratospheric aerosol abundances are considered along with estimates of wave-driven fluctuations in stratospheric temperatures derived from global temperature analyses. Temperature fluctuations are shown to make significant contributions to model calculated northern mid-latitude ozone depletion due to heterogeneous chlorine activation on liquid sulfate aerosols at temperatures near 200-210 K (depending upon water vapor pressure), particularly after major volcanic eruptions. Future mid-latitude ozone recovery will hence depend not only on chlorine recovery but also on temperature trends and/or variability, volcanic activity, and any trends in stratospheric sulfate aerosol.

  14. Ionospheric response to magnetic activity at low and mid-latitude stations

    NASA Astrophysics Data System (ADS)

    Adebiyi, Shola; Adimula, Isaac; Oladipo, Olusola; Joshua, Benjamin; Adebesin, Babatunde; Ikubanni, Stephen

    2014-08-01

    The F2-layer response to the moderate storm of 5-7 April 2010 was investigated using data from two equatorial stations (Ilorin: lat. 8.5°N, 4.5°E; Kwajalein: lat. 9°N, long. 167.2°E) and mid-latitude (San Vito: lat. 40.6°N, long. 17.8°E; Pruhonice: lat. 50°N, long. 14.6°E). Before storm commencement, enhancement, and depletion of NmF2 values were observed in the equatorial and mid-latitude stations, respectively, indicating the latitudinal dependence of the pre-storm event. All the stations with the exception of Kwajalein show positive phase in NmF2 response at the storm onset stage. Positive phase in NmF2 continues over Ilorin and appears on the daytime ionosphere of Kwajalein on 6 April, whereas negative phase suppressed the positive feature in Pruhonice and San Vito until the recovery condition. The differences in the response of F2-layer to the storm for the two equatorial stations were attributed to their longitudinal differences. On the average, both the AE and D st indices revealed poor correlation relationship. More studies are required to ascertain this finding.

  15. Ionospheric TEC variations at mid-latitudes obsereved using SBAS L1/L5 signals.

    NASA Astrophysics Data System (ADS)

    Padokhin, A. M.; Kunitsyn, V.; Kurbatov, G.; Yasyukevich, Y.

    2014-12-01

    With the development of Satellite based augmentation systems (SBAS) the dual frequency L1/L5 observations from a number of geostationary satellites are now available. It provides the possibility to retrieve ionospheric total electron content (TEC) from these observations using the same approach as for dual frequency GPS/GLONASS observations. In this work we study L1/L5 signals of Indian GAGAN geostationary satellites observed with geodetic GNSS receivers at several stations at mid-latitudes and estimate corresponding geostationary TEC and errors of such estimations. TEC RMS was found to reach up to 1.5 TECU with typical values of 0.25-0.5 TECU which is several times greater than for common GPS/GLONASS observations. TEC RMS also manifests UT-dynamics which is specific for the chosen geostationary satellite and not relevant to the receiver site and signal paths. SBAS TEC was found to be in good agreement with the data of nearest ionosondes taking into account low elevation angles of SBAS satellites already at mid-latitudes and spatial gradients of electron density along the ray paths. We also present the wavelet analysis of geostationary TEC, providing typical periods of observed variations at different time scales (from tens of minutes to tens of days) and discuss the capabilities of SBAS TEC observations in connection with ionospheric effects of solar flares.

  16. Atmospheric Rivers in the Mid-latitudes: A Modeling Study for Current and Future Climates

    NASA Astrophysics Data System (ADS)

    Shields, C. A.; Kiehl, J. T.

    2015-12-01

    Atmospheric rivers (ARs) are dynamically-driven narrow intense bands of moisture that transport significant amounts of moisture from the tropics to mid-latitudes and are thus an important aspect the Earth's hydrological cycle. They are often associated with extratropical cyclones whose low level circulation is able to tap into tropical moisture and transport it northward. The "Pineapple Express" is an example of an AR that impacts the west coast of California predominately in the winter months and can produce heavy amounts of precipitation in a short period of time (hours up to several days). This work will focus on three mid-latitude AR regions including the west coast of California, the Pacific Northwest, and the United Kingdom as modeled by a suite of high-resolution CESM (Community Earth System Model) simulations for 20th century and RCP8.5 future climate scenarios. The CESM version employed utilizes half-degree resolution atmosphere/land components (~0.5o) coupled to the standard (1o) ocean/ice components. We use the high-resolution atmosphere because it is able to more accurately represent extreme, regional precipitation. CESM realistically captures ARs as spatial and temporal statistics show. Projections for future climate statistics for all three regions as well as analysis of the dynamical and thermodynamical mechanisms driving ARs, such as vorticity, jets and the steering flow, and water vapor transport, and will presented. Finally, teleconnections to climate variability processes, such as ENSO will be explored.

  17. Nonlinear characteristics of hydroclimate variability in the mid-latitude Asia over the past seven centuries

    NASA Astrophysics Data System (ADS)

    Zhou, Feifei; Fang, Keyan; Li, Yingjun; Chen, Qiuyan; Chen, Dan

    2015-07-01

    Hydroclimate variations in the mid-latitude Asia have received considerable attention due to its significance for the regional ecosystem and livelihood, while its nonlinear characteristics over the past centuries are not fully understood yet. Hydroclimate patterns for the mid-latitude Asia are classified into eastern and western modes based on a network of the reconstructed Palmer drought severity index (PDSI) of 197 grids spanning since 1300. The hydroclimate variations of western mode are more complex than that of eastern mode based on the Higuchi's fractal dimension (HFD) analysis, which may be related to the complex atmospheric circulation patterns that dominate them. The relationships of the hydroclimate variations between western and eastern modes at different time scales extracted by ensemble empirical mode decomposition method (EEMD) are detected. The anti-phase relationship of the hydroclimatic variations between western and eastern modes at the interdecadal variations occurs during the periods with the enhanced El Nino Southern Oscillation (ENSO) variance. Similarly, the multidecadal hydroclimate variations are anti-phase when the Pacific Decadal Oscillation (PDO) is in its warm phases. The inverse relationship between western and eastern modes is stable for the centennial scale.

  18. Mean annual temperatures of mid-latitude regions derived from stable hydrogen isotopes of wood lignin

    NASA Astrophysics Data System (ADS)

    Anhäuser, Tobias; Greule, Markus; Bowen, Gabriel J.; Keppler, Frank

    2016-04-01

    Tree rings are widely used climate archives providing annual resolutions on centennial to millennial timescales. Besides plant physiological parameters such as tree-ring width or maximum latewood density, stable isotope compositions (expressed as δ values) complement or even broaden the potential of the climate archive tree rings. A considerable wood constituent are ether-bonded methoxyl groups as part of lignin which can be used for stable hydrogen isotope studies. The δ²H value of the lignin methoxyl groups reflects the δ²H value of the tree source water as a result of a large uniform fractionation. Hence, this relation can be used to infer δ²H values of precipitation which are in temperate regions primarily controlled by temperature. Here, we measured δ²H values of lignin methoxyl groups (n = 111) of tree rings from various species collected along a ~3500 km north-south transect across Europe with mean annual temperatures (MAT) ranging from ‑4 to +17 °C. We found a significant linear correlation between δ²H values of the lignin methoxyl groups and MAT (R² = 0.81, p < 0.01). We used this relationship to predict MATs from randomly collected wood samples and found general agreement between predicted and observed MATs for the mid-latitudes on a global scale. Thus our results indicate that δ²H values of lignin methoxyl groups are a promising tool for mid-latitude temperature reconstruction of the Holocene.

  19. Total ozone patterns over the northern mid-latitudes: spatial correlations, extreme events and dynamical contributions

    NASA Astrophysics Data System (ADS)

    Rieder, H. E.; Staehelin, J.; Maeder, J. A.; Ribatet, M.; Bodeker, G. E.; Davison, A. C.

    2009-04-01

    Tools from geostatistics and extreme value theory are applied to analyze spatial correlations in total ozone for the northern mid-latitudes. The dataset used in this study is the NIWA combined total ozone dataset (Bodeker et al., 2001; Müller et al., 2008). New tools from extreme value theory (Coles, 2001; Ribatet, 2007) have recently been applied to the world's longest total ozone record from Arosa, Switzerland (e.g. Staehelin 1998a,b), in order to describe extreme events in low and high total ozone (Rieder et al., 200x). Within the current study, patterns in spatial correlation and frequency distributions of extreme events (e.g. ELOs and EHOs) are studied for the northern mid-latitudes. New insights in spatial patterns of total ozone for the northern mid-latitudes are presented. Koch et al. (2005) found that the increase in fast isentropic transport of tropical air to northern mid-latitudes contributed significantly to ozone changes between 1980 and 1989. Within this study the influence of changes in atmospheric dynamics (e.g. tropospheric and lower stratospheric pressure systems) on column ozone over the northern mid-latitudes is analyzed for the time period 1979-2007. References: Bodeker, G.E., J.C. Scott, K. Kreher, and R.L. McKenzie, Global ozone trends in potential vorticity coordinates using TOMS and GOME intercompared against the Dobson network: 1978-1998, J. Geophys. Res., 106 (D19), 23029-23042, 2001. Coles, S.: An Introduction to Statistical Modeling of Extreme Values, Springer Series in Statistics, ISBN:1852334592, Springer, Berlin, 2001. Koch, G., H. Wernli, C. Schwierz, J. Staehelin, and T. Peter (2005), A composite study on the structure and formation of ozone miniholes and minihighs over central Europe, Geophys. Res. Lett., 32, L12810, doi:10.1029/2004GL022062. Müller, R., Grooß, J.-U., Lemmen, C., Heinze, D., Dameris, M., and Bodeker, G.: Simple measures of ozone depletion in the polar stratosphere, Atmos. Chem. Phys., 8, 251-264, 2008. Ribatet

  20. The Midlatitude Continental Convective Clouds Experiment (MC3E) sounding network: operations, processing and analysis

    DOE PAGESBeta

    Jensen, M. P.; Toto, T.; Troyan, D.; Ciesielski, P. E.; Holdridge, D.; Kyrouac, J.; Schatz, J.

    2014-09-12

    The Midlatitude Continental Convective Clouds Experiment (MC3E) took place during the spring of 2011 centered in north-central Oklahoma, USA. The main goal of this field campaign was to capture the dynamical and microphysical characteristics of precipitating convective systems in the Central Plains. A major component of the campaign was a 6-site radiosonde array designed to capture the large-scale variability of the atmospheric state with the intent of deriving model forcing datasets. Over the course of the 46 day MC3E campaign, a total of 1362 radiosondes were launched from the enhanced sonde network. This manuscript describes the details of the instrumentationmore » used as part of the sounding array, the data processing activities including quality checks and humidity bias corrections and an analysis of the impacts of bias correction and algorithm assumptions on the determination of convective levels and indices. It is found that corrections for known radiosonde humidity biases and assumptions regarding the characteristics of the surface convective parcel result in significant differences in the derived values of convective levels and indices in many soundings.« less

  1. The Midlatitude Continental Convective Clouds Experiment (MC3E) sounding network: operations, processing and analysis

    DOE PAGESBeta

    Jensen, M. P.; Toto, T.; Troyan, D.; Ciesielski, P. E.; Holdridge, D.; Kyrouac, J.; Schatz, J.; Zhang, Y.; Xie, S.

    2015-01-27

    The Midlatitude Continental Convective Clouds Experiment (MC3E) took place during the spring of 2011 centered in north-central Oklahoma, USA. The main goal of this field campaign was to capture the dynamical and microphysical characteristics of precipitating convective systems in the US Central Plains. A major component of the campaign was a six-site radiosonde array designed to capture the large-scale variability of the atmospheric state with the intent of deriving model forcing data sets. Over the course of the 46-day MC3E campaign, a total of 1362 radiosondes were launched from the enhanced sonde network. This manuscript provides details on the instrumentationmore » used as part of the sounding array, the data processing activities including quality checks and humidity bias corrections and an analysis of the impacts of bias correction and algorithm assumptions on the determination of convective levels and indices. It is found that corrections for known radiosonde humidity biases and assumptions regarding the characteristics of the surface convective parcel result in significant differences in the derived values of convective levels and indices in many soundings. In addition, the impact of including the humidity corrections and quality controls on the thermodynamic profiles that are used in the derivation of a large-scale model forcing data set are investigated. The results show a significant impact on the derived large-scale vertical velocity field illustrating the importance of addressing these humidity biases.« less

  2. Nonstationary impact of the winter North Atlantic Oscillation and the response of mid-latitude Eurasian climate

    NASA Astrophysics Data System (ADS)

    Xu, Tingting; Shi, Zhengguo; Wang, Hongli; An, Zhisheng

    2016-04-01

    The North Atlantic Oscillation (NAO), although a local atmospheric mode over the North Atlantic Ocean, plays an important remote role in the Eurasian climate. However, the link between the NAO and Eurasian climate might be unstable. Here, we present a study on the relationship between the winter NAO and mid-latitude Eurasian climate, especially the mid-latitude East Asian precipitation, mainly based on meteorological data and output from an 1155-year-long coupled ocean-atmosphere model simulation. The results show that the winter NAO exerts a remarkable effect on the changes in mid-latitude Eurasian climate; however, the impact of the NAO is nonstationary. According to the model output, the impact of the NAO varies synchronously with the NAO variance with a period of around 150 years. During the high NAO variance period, the NAO has significant correlation with mid-latitude East Asian precipitation; low NAO variance periods do not. The variation of the NAO-precipitation teleconnection may arise from the changing influence of NAO on the local temperature. The NAO signal moves eastward by a zonally oriented wave train, where it modulates the atmospheric circulation structure, and thus results in the nonstationary relationship between the NAO and mid-latitude East Asian precipitation.

  3. Explaining darker deep convective clouds over the western Pacific than over tropical continental convective regions

    NASA Astrophysics Data System (ADS)

    Sohn, B.-J.; Choi, M.-J.; Ryu, J.

    2015-11-01

    This study attempted to explain why deep convective clouds (DCCs) over the western Pacific are generally darker than those found over tropical African and South American land regions. The western Pacific domain was further divided into its land and ocean regions to deduce the general differences in DCC characteristics between convectively active tropical land and ocean regions. DCC in this study is defined as a single-layer cloud whose thickness is greater than 15 km, and it is determined from CloudSat-measured reflectivity profiles. Corresponding MODIS-measured reflectivities at 0.645 μm were examined, along with the analysis of cloud products from Cloud Aerosol Lidar Infrared Pathfinder Satellite Observation (CALIPSO) measurements. From an analysis of the four January months of 2007-2010, a distinct difference in ice water path (IWP) between the ocean region of the western Pacific and the three tropical land regions was revealed. Distinct differences in the effective radius between land and ocean were also found. The findings lead to a conclusion that smaller IWP over the western Pacific ocean region than over the tropical land regions, which should be caused by different cloud microphysics between land and ocean, is the main cause of smaller reflectivity there.

  4. Classification of Arctic, Mid-Latitude and Tropical Clouds in the Mixed-Phase Temperature Regime

    NASA Astrophysics Data System (ADS)

    Costa, Anja; Afchine, Armin; Luebke, Anna; Meyer, Jessica; Dorsey, James R.; Gallagher, Martin W.; Ehrlich, André; Wendisch, Manfred; Krämer, Martina

    2016-04-01

    The degree of glaciation and the sizes and habits of ice particles formed in mixed-phase clouds remain not fully understood. However, these properties define the mixed clouds' radiative impact on the Earth's climate and thus a correct representation of this cloud type in global climate models is of importance for an improved certainty of climate predictions. This study focuses on the occurrence and characteristics of two types of clouds in the mixed-phase temperature regime (238-275K): coexistence clouds (Coex), in which both liquid drops and ice crystals exist, and fully glaciated clouds that develop in the Wegener-Bergeron-Findeisen regime (WBF clouds). We present an extensive dataset obtained by the Cloud and Aerosol Particle Spectrometer NIXE-CAPS, covering Arctic, mid-latitude and tropical regions. In total, we spent 45.2 hours within clouds in the mixed-phase temperature regime during five field campaigns (Arctic: VERDI, 2012 and RACEPAC, 2014 - Northern Canada; mid-latitude: COALESC, 2011 - UK and ML-Cirrus, 2014 - central Europe; tropics: ACRIDICON, 2014 - Brazil). We show that WBF and Coex clouds can be identified via cloud particle size distributions. The classified datasets are used to analyse temperature dependences of both cloud types as well as range and frequencies of cloud particle concentrations and sizes. One result is that Coex clouds containing supercooled liquid drops are found down to temperatures of -40 deg C only in tropical mixed clouds, while in the Arctic and mid-latitudes no liquid drops are observed below about -20 deg C. In addition, we show that the cloud particles' aspherical fractions - derived from polarization signatures of particles with diameters between 20 and 50 micrometers - differ significantly between WBF and Coex clouds. In Coex clouds, the aspherical fraction of cloud particles is generally very low, but increases with decreasing temperature. In WBF clouds, where all cloud particles are ice, about 20-40% of the cloud

  5. A mid-latitude space weather hazard driven directly by the magnetosphere

    NASA Astrophysics Data System (ADS)

    Sojka, J. J.; David, M.; Schunk, R. W.

    2002-03-01

    This study revisits and attempts to quantify the effects of high-latitude electric field penetration on the mid-latitude ionosphere. These penetration electric fields (PEFs) are strongest during geomagnetically dynamic and disturbed conditions. The consequences of PEFs arise principally from the induced vertical drift of the F-layer from the eastward electric field component. Both positive and negative storm phases are associated with the PEF. Although no readily available description of the PEF exists, observational and modeling results are combined to provide a crude model. The largest uncertainty arises from a lack of knowledge of whether PEFs are always short lived (less than 1h) or are a persisting feature of disturbed conditions. According to simulations with the Utah State University time dependent ionospheric model (TDIM), under Kp=3 conditions the PEF readily generates a factor of 2 increase in the pre-midnight ionosphere F-layer density (positive storm phase). For Kp=5 conditions this positive phase is further enhanced to produce almost an order of magnitude increase in F-region density. Negative storm phases, F-layer density decreases, are also present in the pre-dawn and pre-noon sectors. The pre-dawn negative storm phase can reach a factor of 10 for Kp=5 conditions while the pre-noon depletions are a few 10s of percent. These large density changes have operational impact on systems using coordinate registration based upon Global Positioning Satellite (GPS) measurements. GPS satellite-to-ground radio paths pass through the ionosphere at different angles relative to the zenith and hence have different propagation corrections dependent upon the paths total ionospheric electron content. Factors of 2 change in electron density corresponds to tens of centimeters to meters correction errors in coordinate registration position finding. Corrections this large are a potentially insurmountable obstacle for the GPS based wide area augmentation system (WAAS

  6. A case-study analysis of convectively sourced water vapor plumes in the overworld stratosphere over the continental U.S. observed in situ during the SEAC4RS mission

    NASA Astrophysics Data System (ADS)

    Smith, J. B.; Sargent, M. R.; Wilmouth, D. M.; Anderson, J. G.; Bedka, K. M.; Herman, R. L.; Pittman, J. V.; Jensen, E. J.

    2014-12-01

    Water vapor in the upper troposphere and lower stratosphere (UTLS) is important both radiatively and chemically. However, the processes that control the distribution and phase of water in this region of the atmosphere are not well understood. This is especially true at mid-latitudes where several different dynamical mechanisms are capable of influencing UTLS water vapor concentrations. Identifying and quantifying these mechanisms and understanding how these processes will change in response to anthropogenic climate forcing is a critical challenge facing the atmospheric chemistry and climate community. The Harvard Water Vapor (HWV) instrument has repeatedly observed moist layers in the summertime extra-tropical lower stratosphere, with some present well into the stratospheric overworld (potential temperature >380 K) over the continental U.S. Water vapor mixing ratios in these layers are elevated by several ppmv above the nominal background, with the magnitude of the enhancement diminishing with altitude. The present analysis utilizes high resolution in situ data acquired during the SEAC4RS mission in August of 2013, to describe encounters with elevated concentrations of water vapor in the overworld stratosphere over North America that show evidence of deep convection as their source. The plume observed over the Great Lakes on August 27, 2013, represents the largest enhancement (~10 ppmv) observed in situ between 400 K and 420 K. Trajectory calculations link these plumes to specific convective storms identified in NEXRAD radar data and in GOES satellite infrared imagery. It is theorized that ice lofted in summertime deep convective storm systems rapidly evaporates in the under-saturated stratosphere and provides a means of significantly elevating water vapor, with a minimal perturbation to other trace species. The in situ and remote data sets, in combination with trajectory analyses, are then used to describe in greater detail the spatial extent, water vapor content

  7. High and Mid-Latitude Wetlands, Climate Change, and Carbon Storage

    NASA Technical Reports Server (NTRS)

    Peteet, Dorothy

    2000-01-01

    Pollen and macrofossil stratigraphy from wetlands associated with AMS chronology provides a vegetational and climatic history over thousands of years. From these records we establish a record of climate change which can be compared with independent records of carbon accumulation rates in these same wetlands. In this way, inferences can be made concerning carbon storage during different climatic regimes. One focus of our research has been high-latitude regions such as Alaskan and Siberian tundra, from which we have paleorecords which span the last 10,000 years. We will present records from the Malaspina Glacier region, Alaska and the Pur-Taz region of Western Siberia. A second focus of our research is in mid-latitude eastern North America. We will present paleorecords from wetlands in Vermont, New York, and Virginia showing the relationship between carbon accumulation rates and climatic changes since the late Pleistocene.

  8. Comparison of high-latitude and mid-latitude ionospheric electric fields

    NASA Technical Reports Server (NTRS)

    Carpenter, L. A.; Kirchhoff, V. W. J. H.

    1975-01-01

    Simultaneous measurements of the F region electric field by the incoherent scatter technique have been made at Chatanika, Alaska (65.1 deg N, 147.5 deg W), and Millstone Hill, Massachusetts (42.6 deg N, 71.5 deg W), on July 18-19 and Aug. 7-8, 1973. Good correlation was observed in the time variation of the perpendicular electric field at the two stations. Magnetic conditions for these days were relatively quiet with some variations evident from the high-latitude magnetograms and the Chatanika radar, but no distinct effect appeared on the mid-latitude magnetograms. Since magnetospheric electric fields are thought to be the source of high-latitude electric fields such as those observed at Chatanika, the good correlation in the perpendicular electric field for the two stations indicates that the magnetospheric originated electric fields have an appreciable effect down to at least L equals 3.2.

  9. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars

    USGS Publications Warehouse

    Head, J.W.; Neukum, G.; Jaumann, R.; Hiesinger, H.; Hauber, E.; Carr, M.; Masson, P.; Foing, B.; Hoffmann, H.; Kreslavsky, M.; Werner, S.; Milkovich, S.; Van Gasselt, S.

    2005-01-01

    Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the base of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice-rich glacier-like viscous flow and sublimation. Together with new evidence for recent ice-rich rock glaciers at the base of the Olympus Mons scarp superposed on larger Late Amazonian debris-covered piedmont glaciers, we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid-latitude regions of Mars during periods of increased spin-axis obliquity when polar ice was mobilized and redeposited in microenvironments at lower latitudes. The data indicate that abundant residual ice probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration.

  10. Distribution of mid-latitude ground ice on Mars from new impact craters.

    PubMed

    Byrne, Shane; Dundas, Colin M; Kennedy, Megan R; Mellon, Michael T; McEwen, Alfred S; Cull, Selby C; Daubar, Ingrid J; Shean, David E; Seelos, Kimberly D; Murchie, Scott L; Cantor, Bruce A; Arvidson, Raymond E; Edgett, Kenneth S; Reufer, Andreas; Thomas, Nicolas; Harrison, Tanya N; Posiolova, Liliya V; Seelos, Frank P

    2009-09-25

    New impact craters at five sites in the martian mid-latitudes excavated material from depths of decimeters that has a brightness and color indicative of water ice. Near-infrared spectra of the largest example confirm this composition, and repeated imaging showed fading over several months, as expected for sublimating ice. Thermal models of one site show that millimeters of sublimation occurred during this fading period, indicating clean ice rather than ice in soil pores. Our derived ice-table depths are consistent with models using higher long-term average atmospheric water vapor content than present values. Craters at most of these sites may have excavated completely through this clean ice, probing the ice table to previously unsampled depths of meters and revealing substantial heterogeneity in the vertical distribution of the ice itself. PMID:19779195

  11. Mid-latitude Ionospheric HF Channel Reciprocity: Evidence from the Ionospheric Oblique Incidence Sounding Experiments

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Zhao, Zhengyu; Zhang, Yuannong

    The mid-latitude ionospheric HF channel reciprocity is studied in this paper through theoret-ical considerations and ionospheric oblique incidence sounding experiments. The reciprocity of ionospheric HF channel experiments were carried out by using two identical Wuhan Iono-spheric Oblique Incidence Sounding Systems (WIOISS) located in Wuhan (30° 32N, 114° 21E) and Wanning (18° 58N, 110° 31E) respectively. The comparisons of group distance and Doppler shift between Wuhan-Wanning and Wanning-Wuhan HF ionospheric propagation paths show that the reciprocity of ionospheric HF channel is satisfied to some extent. The group dis-tances of two paths are calculated by a 3-D ray tracing simulation as well. The theoretical and experimental results could be widely used for HF communication systems and sky wave over-the-horizon radar.

  12. Observation of drift compressional waves with a mid-latitude decameter coherent radar

    NASA Astrophysics Data System (ADS)

    Chelpanov, Maksim; Mager, Pavel; Klimushkin, Dmitriy; Berngardt, Oleg; Mager, Olga

    2016-06-01

    Magnetospheric Pc5 pulsations observed on December 26, 2014 are analyzed. They were recorded in the nightside magnetosphere with a mid-latitude coherent decameter radar located near Ekaterinburg. It registers velocity variations in electric drift of ionospheric plasma caused by ULF waves in the magnetosphere. The westward direction of azimuthal propagation of wave coincides with the direction of magnetic drift of protons. A cross-wavelet analysis reveals that the frequency of oscillations depends on the wave number m, and the correlation between them is 0.90. The frequency increase from 2.5 to 5 mHz was followed by an increase in the absolute value m from 20 to 80. These features of the wave under study testify that it should be classified as a drift compressional mode which is typical for the ULF mode in kinetics. Existence conditions for it are the terminal pressure of plasma and its inhomogeneity across magnetic shells.

  13. Measured and modeled HOCl profiles in the mid-latitude stratosphere : implication for ozone loss

    NASA Technical Reports Server (NTRS)

    Kovalenko, L. J.; Salawitch, R. J.; Blavier, J. -F.; Sen, B.; Toon, G. C.; Jucks, K. W.; Johnson, D. G.; Stachnik, R. A.; Margitan, J. J.

    2004-01-01

    The HOCl catalytic cycle is an efficient ozone loss mechanism in the lower mid-latitude stratosphere. We use a diurnal steady-state photochemical model to calculate profiles of HOCl for conditions encountered by a number of high-altitude balloon flights. To assess how well this model represents ozone loss by the HOCl cycle, we compare our calculations of HOCl and its precursors Cl0 and HO2 with measurements obtained by an FTIR solar absorption spectrometer (MkIV), a far-infrared emission spectrometer (FIRS-2), and a submillimetenvave limb sounder (SLS). We then evaluate these comparisons in light of a number of recent laboratory studies of the main formation mechanism of HOCl, the reaction of Cl0 + HO2. Those studies measured both the reaction rate constant and the quantum yield for a second product pathway, formation of HCl.

  14. The weakening summer circulation in the Northern Hemisphere mid-latitudes

    NASA Astrophysics Data System (ADS)

    Coumou, Dim; Lehmann, Jascha; Beckmann, Johanna

    2015-04-01

    Rapid warming in the Arctic could influence mid-latitude circulation by reducing the poleward temperature gradient. The largest changes are generally expected in autumn or winter, but whether significant changes have occurred is debated. Here we report significant weakening of summer circulation detected in three key dynamical quantities: (i) the zonal-mean zonal wind, (ii) the eddy kinetic energy (EKE), and (iii) the amplitude of fast-moving Rossby waves. Weakening of the zonal wind is explained by a reduction in the poleward temperature gradient. Changes in Rossby waves and EKE are consistent with regression analyses of climate model projections and changes over the seasonal cycle. Monthly heat extremes are associated with low EKE, and thus the observed weakening might have contributed to more persistent heat waves in recent summers.

  15. A study of the conditions necessary for the onset of mid-latitude spread F

    NASA Technical Reports Server (NTRS)

    Zinchenko, G. N.

    1976-01-01

    Ionospheric conditions associated with the initiation of spread F in the mid-latitude ionosphere were observed. The morphology of spread F at Puerto Rico was investigated. Data from 7 nights was examined for Arecibo, five with spread F and two without. The relative height of the F layer maximum and the vertically integreted Pedersen conductivity, the relation between E and F region conductivities, the coupling lengths between the E and F regions, and vertical and horizontal gradients of electron density were examined. At Millstone Hill 13 nights were examined for all of which spread F was observed. The EW and NS velocities and the vertical velocities and the electric ion temperature ratio were examined.

  16. Importance of E-F Region Coupling on Low and Mid-Latitude Ionospheric Irregularities

    NASA Astrophysics Data System (ADS)

    Yokoyama, T.

    2014-12-01

    It is well known that ionospheric conductivity has a strong anisotropy so that even a relatively small-scale electrostatic polarization electric field can be easily mapped along geomagnetic field lines. As well as the conjugate characteristics between the northern and southern henmispheres, the electrodynamical coupling between the E and F region plays an important role in the formation of the ionospheric irregularities in low and mid-latitude: equatorial plasma bubbles (EPBs) and medium-scale traveling ionospheric disturbances (MSTIDs). Although they are characterized as the F-region plasma density irregularities, they are substantially controlled by the E-region effect such as the conductivity gradient in the evening and patchy sporadic-E layers. Recent observations and numerical studies of EPBs and MSTIDs will be presented.

  17. Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Willis, Emily M.; Neergaard Parker, Linda

    2014-01-01

    Spacecraft charging of the International Space Station (ISS) is dominated by interaction of the US high voltage solar arrays with the F2-region ionosphere plasma environment. ISS solar array charging is enhanced in a high electron density environment due to the increased thermal electron currents to the edges of the solar cells. High electron temperature environments suppress charging due to formation of barrier potentials on the charged solar cell cover glass that restrict the charging currents to the cell edge [Mandell et al., 2003]. Environments responsible for strong solar array charging are therefore characterized by high electron densities and low electron temperatures. In support of the ISS space environmental effects engineering community, we are working to understand a number of features of solar array charging and to determine how well future charging behavior can be predicted from in-situ plasma density and temperature measurements. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that occur at ISS orbital altitudes (approximately 400 km) over time scales of days, the latitudes over which significant variations occur, and the time periods over which the disturbances persist once they start. This presentation provides examples of mid-latitude electron density and temperature disturbances at altitudes relevant to ISS using data sets and tools developed for our ISS plasma environment study. "Mid-latitude" is defined as the extra-tropical region between approx. 30 degrees to approx. 60 degrees magnetic latitude sampled by ISS over its 51.6 degree inclination orbit. We focus on geomagnetic storm periods because storms are well known drivers for disturbances in the ionospheric plasma environment.

  18. Mid-latitude field-aligned ionospheric irregularities and its impact on GPS

    NASA Astrophysics Data System (ADS)

    Yasyukevich, Yury; Afraimovich, Edward; Ishin, Artem; Tinin, Mikhail

    2010-05-01

    Strong scintillations of amplitude and phase of transionospheric radio signals occur due to signal scattering on intensive small scale irregularities. Scintillation can have an adverse effect on GPS signals and cause a GPS receiver to lose lock on the signal in some extreme cases. Although the plasma bubble is a common phenomenon and it has been studied for years, precise observed data of ionospheric scintillations and loss of lock to GPS receivers due to plasma bubble at mid-latitude are still limited. In most papers there are no data regarding the space geometry of field-aligned irregularities. For the first time, we propose a GPS method to detect mid-latitude field-aligned irregularities (FAIs) by line-of-sight angular scanning regarding the local magnetic field vector. We show that total GPS L2 phase slips over Japan during the recovery phase of the 12 February, 2000 geomagnetic storm (Ma and Maruyama, 2006, doi:10.1029/2006GL027512) were caused by GPS signal scattering on FAIs for the line-of-sight of both aligned to magnetic field line (the field of aligned scattering, FALS), and across it or at large angles to magnetic field line (the field of across scattering, FACS). Our FALS results confirm well with data of investigation of magnetic field orientation control of GPS occultation observations of equatorial scintillation during detailed LEO CHAMP, SAC-C and PICOSat measurements, realized by Anderson and Strauss (2005, doi:10.1029/2005GL023781). The role of large-angle scattering almost along the normal to the magnetic field line in GPS scintillation is determined by attenuation of the irregularity anisotropy factor as compared with the other factors. The work was supported by the Fundamental Research Program of RAS Physical Science Department (Project IV.12 "Modern problems of radiophysics").

  19. Water-bearing minerals on mars: source of observed mid-latitude water?

    SciTech Connect

    Bish, D. L.; Carey, J. W.; Fialips, C. I.

    2003-01-01

    The Odyssey spacecraft documented the existence of heterogeneously distributed hydrogen at martian mid-latitudes, suggesting that large areas of the near-equatorial highlands contain near-surface deposits of 'chemically and/or physically bound H20 and/or OH' in amounts up to 3 .8% equivalent H20. Shallow occurrences of water ice are not stable near the martian equator, making the hydrogen deposits at these latitudes somewhat enigmatic. Clay minerals and zeolites have both been proposed as possible water-bearing constituents on Mars, and both are common terrestrial alteration products of hydrovolcanic basaltic ashes and palagonitic material comparable to those that may be widespread on Mars. Smectites within martian meteorites, attributed to hydrous alteration on Mars rather than on Earth, provide direct evidence of clay minerals from Mars. In addition, new thermal emission spectrometer (TES) data provide good evidence for unspecified zeolites in martian surface dust [6] . The nature of the hydrogen-containing material observed in the equatorial martian regolith is of particular importance to the question of whether hydrous minerals have formed in the past on Mars. Also, whether these minerals exist in a hydrated (i .e., containing H2O molecules in their structures) or dehydrated state is a crucial question . The existence of hydrous minerals is also important in connection with their possible role in affecting the diurnal variation of the martian atmosphere, in their potential role in unraveling the paleohydrology and paleobiology of Mars, and in their possible use as a water resource to support exploration of the martian mid-latitudes.

  20. The structure of temperature changes across mid-latitude North America over the Holocene

    NASA Astrophysics Data System (ADS)

    Marsicek, J.; Brewer, S.; Foster, D. R.; Oswald, W.; Shuman, B. N.

    2013-12-01

    Lake-level, isotope, and fossil pollen data highlight abrupt changes during the Holocene in mid-latitude North America, but associated temperature changes in this region have not been well constrained. Here we generate a new summer temperature reconstruction by applying the modern analog technique to a transect of 16 highly-resolved fossil pollen records from North Dakota to Maine. We infer pronounced cooling of ~0.4°C in the regional mean temperature history at ca. 5.8-5.0 ka coincident with millennial-scale effective-moisture anomalies indicated by aeolian-activity and lake-level changes. Individual temperature reconstructions and sub-regional averages reveal that the changes span multiple biomes (pollen assemblages) with more pronounced cooling in the west (Minnesota, Iowa) than at sites in the northeastern U.S. (Massachusetts). At 5.0 ka, inferred temperature gradients rapidly shifted in response to warming of >0.7°C at sites from Ontario, New York, and inland Massachusetts, and cooling of 0.2-2.7°C along the northeast coast and west of the Great Lakes. Insolation, the area of the Laurentide Ice sheet, and a record of North Atlantic Deep Water production explain 77% of the variance in the mean reconstruction, and indicate that dynamical linkages between the continent and North Atlantic may underlie the reconstructed abrupt changes. Overall, the temperature inferences highlight the importance of abrupt centennial and millennial-scale changes even after the end of major ice-meltwater-ocean interactions at ca. 8.2 ka, and indicate that other external forcing or intrinsic climate variability also shaped mid-latitude Holocene climate history.

  1. A potential vorticity perspective on the motion of a mid-latitude winter storm

    NASA Astrophysics Data System (ADS)

    Rivière, G.; Arbogast, P.; Lapeyre, G.; Maynard, K.

    2012-06-01

    The motion of mid-latitude surface cyclones relative to the jet streams is of particular interest because of the commonly observed strong and rapid deepening they undergo when they cross the upper-level jet axis. The purpose of the present study is to validate a recent theory that may explain this motion which is a generalization of the so-called beta drift in the mid-latitude baroclinic context. According to this theory, the key parameter controlling the movement of a surface cyclone across the mean tropospheric jet is the vertically averaged potential vorticity (PV) gradient associated with the jet. To test this theoretical result, numerical sensitivity experiments are performed using the Météo-France global operational forecast model ARPEGE-IFS for the particular case of the storm Xynthia (26-28 February 2010). The control forecast, starting from the operational analysis almost 2 days before the storm hit France, represents the trajectory of the storm quite well, together with the deepening during the crossing of the upper-level jet axis. A PV-inversion tool is used to modify the vertically averaged PV gradient of the initial state. As expected from the theory, when the PV gradient is intensified, there is a quicker displacement of the surface cyclone toward the jet axis and the jet-crossing phase occurs earlier than in the control forecast. The opposite occurs for a reduced PV gradient. The interpretation is that an enhanced PV gradient reinforces the dipolar PV anomaly located at upper levels which, in turn, advects the surface cyclone faster towards the jet axis.

  2. Total ozone patterns over the southern mid-latitudes: spatial correlations, extreme events and dynamical contributions

    NASA Astrophysics Data System (ADS)

    Rieder, Harald E.; di Rocco, Stefania; Staehelin, Johannes; Maeder, Jörg A.; Ribatet, Mathieu; Peter, Thomas; Davison, Anthony C.

    2010-05-01

    Tools from geostatistics and extreme value theory are applied to analyze spatial correlations in total ozone for the southern mid-latitudes. The dataset used in this study is the NIWA-assimilated total ozone dataset (Bodeker et al., 2001; Müller et al., 2008). Recently new tools from extreme value theory (Coles, 2001; Ribatet, 2007) have been applied to the world's longest total ozone record from Arosa, Switzerland (e.g. Staehelin 1998a,b) and 5 other long-term ground based stations to describe extreme events in low and high total ozone (Rieder et al., 2010a,b,c). Excursions in the frequency of extreme events reveal "fingerprints" of dynamical factors such as ENSO or NAO, and chemical factors, such as cold Arctic vortex ozone losses, as well as major volcanic eruptions of the 20th century (e.g. Gunung Agung, El Chichón, Mt. Pinatubo). Furthermore, atmospheric loading in ozone depleting substances lead to a continuous modification of column ozone in the northern hemisphere also with respect to extreme values (partly again in connection with polar vortex contributions). It is shown that application of extreme value theory allows the identification of many more of such fingerprints than conventional time series analysis on basis of annual and seasonal mean values. Especially, the analysis shows the strong influence of dynamics, revealing that even moderate ENSO and NAO events have a discernible effect on total ozone (Rieder et al., 2010b,c). Within the current study patterns in spatial correlation and frequency distributions of extreme events (e.g. ELOs and EHOs) are studied for the southern mid-latitudes. It is analyzed if "fingerprints"found for features in the northern hemisphere occur also in the southern mid-latitudes. New insights in spatial patterns of total ozone for the southern mid-latitudes are presented. Within this study the influence of changes in atmospheric dynamics (e.g. tropospheric and lower stratospheric pressure systems, ENSO) as well as

  3. ARM - Midlatitude Continental Convective Clouds - Single Column Model Forcing (xie-scm_forcing)

    DOE Data Explorer

    Xie, Shaocheng; McCoy, Renata; Zhang, Yunyan

    2012-10-25

    The constrained variational objective analysis approach described in Zhang and Lin [1997] and Zhang et al. [2001]was used to derive the large-scale single-column/cloud resolving model forcing and evaluation data set from the observational data collected during Midlatitude Continental Convective Clouds Experiment (MC3E), which was conducted during April to June 2011 near the ARM Southern Great Plains (SGP) site. The analysis data cover the period from 00Z 22 April - 21Z 6 June 2011. The forcing data represent an average over the 3 different analysis domains centered at central facility with a diameter of 300 km (standard SGP forcing domain size), 150 km and 75 km, as shown in Figure 1. This is to support modeling studies on various-scale convective systems.

  4. Redistribution of Lunar Polar Water to Mid-latitudes and Its Role in Forming an OH Veneer

    NASA Technical Reports Server (NTRS)

    Farrell, William M.; Hurley, D. M.; Hodges, R. R.; Killen, R. M.; Halekas, J. S.; Zimmerman, M. I.; Delory, G. T.

    2013-01-01

    We suggest that energization processes like ion sputtering and impact vaporization can eject/release polar water molecules residing within cold trapped regions with sufficient velocity to allow their redistribution to mid-latitudes. We consider the possibility that these polar-ejected molecules can contribution to the water/OH veneer observed as a 3 micrometer IR absorption feature at mid-latitudes by Chandrayaan-1, Cassini, and EPOXI. We find this source cannot fully account for the observed IR feature, but could be a low intensity additional source.

  5. Impact of rising greenhouse gases on mid-latitude storm tracks and associated hydroclimate variability and change

    SciTech Connect

    Seager, Richard

    2014-12-08

    Project Summary This project aimed to advance physical understanding of how and why the mid-latitude jet streams and storm tracks shift in intensity and latitude in response to changes in radiative forcing with an especial focus on rising greenhouse gases. The motivation, and much of the work, stemmed from the importance that these mean and transient atmospheric circulation systems have for hydroclimate. In particular drying and expansion of the subtropical dry zones has been related to a poleward shift of the mid-latitude jets and storm tracks. The work involved integrated assessment of observation and model projections as well as targeted model simulations.

  6. Late Quaternary environmental change in the African sector of Southern Hemisphere mid-latitudes: trends and teleconnections. (Invited)

    NASA Astrophysics Data System (ADS)

    Chase, B. M.

    2013-12-01

    At the northern boundary of the Southern Hemisphere westerly wind belt, and the northern limit of the related frontal systems, SW African environments are particularly sensitive to variations in mid-latitude oceanic and atmospheric circulation systems. It has long been postulated that during relatively cold periods of the late Quaternary, SW Africa - if not much of southern Africa - has experienced an increase in the precipitation linked to phenomena related to an equatorward shift/expansion of the westerly storm track (for review see Chase and Meadows, 2007, Earth-Science Reviews). However, a reliable chain of evidence to support this hypothesis has been elusive, and studies from both the data and modelling communities have yet to resolve the debate. This paper will present the state-of the-art in our understanding of how environments in SW Africa have changed during the course of the last glacial-interglacial cycle. New evidence from both the marine and terrestrial realms, particularly in the form of high resolution stable isotope and pollen records obtained from fossilised rock hyrax middens (Chase et al., 2012, Quaternary Science Reviews; www.hyrax.univ-montp2.fr), is providing a detailed, and coherent, but complex picture of climate dynamics and forcing mechanisms along the northern boundary of westerly influence. While records from the continental interior remain rare, and thus the degree to which an expansion of the westerlies may have influenced southern Africa as a whole remains to be adequately resolved, sites from the SW continental margin do appear to indicate that shifts of the oceanic Subtropical Front and westerly storm track strongly affect the amount of precipitation the region receives. The dynamics of this system, however, do not operate in isolation, and conditions north of the Subtropical Front are very sensitive to variations in the position and intensity of the South Atlantic Anticyclone, which appears to be most responsive to changes in

  7. Redistribution of Lunar Polar Water to Mid-latitudes and its Role in Forming an OH veneer - Revisited

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Killen, R. M.; Hurley, D. M.; Hodges, R. R.; Halekas, J. S.; Delory, G. T.

    2012-01-01

    We suggest that energization processes like ion sputtering and impact vaporization can eject/release polar water molecules residing within lunar cold trapped regions with sufficient velocity to allow their redistribution to mid-latitudes. We consider the possibility that these polar-ejected molecules can be an additional (but not dominant) contribution to the water/OH veneer observed as a 3 micron absorption feature at mid-latitudes by Chandrayaan-I, Cassini, and EPOXI. Taking the conservative case that polar water is ejected only from the floor of polar craters with an 0.1 % icy regolith then overall source rates are near 10(exp 18) H20s/s. This outflow amounts to approx 10(exp -7) kg/s of water to be ejected from each pole and is a water source rate that is 10(exp .5 lower than the overall exospheric source rate for all species. Hence, the out-flowing polar water is a perturbation in the overall exosphere composition & dynamics. This polar water 'fountain' model may not fully account for the relatively high concentrations in the mid-latitude water veneer observed in the IR (approx 10-1000 ppm). However, it may account for some part of the veneer. We note that the polar water fountain source rates scale linearly with ice concentration, and larger mass fractions of polar crater water should provide correspondingly larger fractions of water emission out of the poles which then 'spills' on to mid-latitude surfaces.

  8. Interactions Between Vestige Atlantic Tropical Cyclones and Mid-Latitude Storms Over Mediterranean Basin

    NASA Technical Reports Server (NTRS)

    Smith, Eric A.; Mehta, Amita; Mugnai, Alberto; Tripoli, Gregory J.

    2007-01-01

    One of the more interesting tropical-mid-latitude interactions is one that has important effects on precipitation within the Mediterranean basin. This interaction consists of an Atlantic tropical cyclone vestige whose original disturbance travels eastward and northward across Atlantic basin, eventually intermingling with a mid-latitude cyclone entering southern Europe and/or the \\bestern Mediterranean Sea. The period for these interactions is from mid-September through November. If the tropical cyclone and its vestige is able to make the eastward Atlantic transit within the low to mid-levels, or if an upper level potential vorticity perturbation Cjet streak) emitted by a Hurricane in its latter stages within the central Atlantic is able to propagate into and along the longwave pattern affecting the western Mediterranean Sea (MED), then there is the prospect for the tropical cyclone remnant to produce a major modification of the mid-latitude storm system preparing to affect the MED region. For such an occurrence to take place, it is necessary for an amplifying baroclinic perturbation to be already situated to the rear of a longwave trough, or to be excited by the emitted jet streak to the rear of a longwave trough -- in either case, preparing to affect the western MED. The Algiers City flood of 9-10 November 2001, which killed some 700 people, was produced by a Mediterranean cyclone that had been influenced by two vestige Atlantic tropical cyclones, 1,orenzo and Noel. A published modeling study involving various of this study's authors has already described the dynamical development of the Algiers storm as it amplified from a developing baroclinic disturbance in the Rossby wave train, into a northern Africa hazardous flood system, then lingered in the western MED as a semi-intense warm core cyclone. In our new modeling experiments, we investigate the impact of what might have happened in the eventual precipitation field. had the main features of the tropical

  9. Mantle convection with continental drift and heat source around the mantle transition zone

    NASA Astrophysics Data System (ADS)

    Ichikawa, H.; Kameyama, M.; Kawai, K.

    2012-12-01

    Geological studies have suggested that significant amount of granitic crustal materials have been lost from the surface by the delamination (~1.1 km^3/yr) [1], continental collision (~0.4-0.7 km^3/yr) [1, 2], and subduction at ocean-margin (~2.5-3 km^3/yr) [1, 2]. At ocean-margin subduction zones, most of the granitic materials subducted from the surface are expected to be conveyed through subduction channels by viscous drag to 270km depth [Ichikawa el al., in revision]. If so, then the subducted crustal materials might be expected to be trapped in the mid-mantle owing to the density difference from peridotitic materials induced by the phase transition from coesite to stishovite at 270km depth. In other words, strong heat source materials are most likely to be accumulated around the mantle transition zone, at least, near the plate subduction zones. In this study, we conducted two-dimensional numerical experiments of mantle convection with continental drift and a heat source placed around the mantle transition zone, in order to study the effect of the subducted granitic materials drifting around the mantle transition zone. The simulations deal with a time-dependent convection of fluid under the extended Boussinesq approximation in a model of a two-dimensional rectangular box of 2900km height and 11600km width, where a continent and heat source is imposed. We found that the addition of the heat source considerably reduces the time scale of continental drift. In the absence of the heat source, the resulting time scale is too long compared with that of the so-called supercontinent cycle, where the breakup is induced from a plume generated by an insulating effect of the continent. The heat source also causes massive mechanical mixing especially on the upper mantle. The result suggests that the heat source drifting around mantle transition zone can be a possible candidate inducing the supercontinent cycle in an appropriate time scale. [1] Clift, P. D., P. Vannucchi, and

  10. Continental radiative-convective equilibrium experiments in a single column model (LMDZ5B GCM)

    NASA Astrophysics Data System (ADS)

    Rochetin, N.; Gentine, P.; Lintner, B. R.; Sobel, A. H.; Findell, K. L.

    2013-12-01

    The radiative-convective instability results both from (i) the average net cooling experienced by the Earth's atmosphere (~ 110 W/m?) and (ii) from the equivalent warming of the Earth's surface. Ultimately, this drives the Earth atmosphere to a radiative-convective equilibrium (RCE) state, in a sense that, at the global scale, surface fluxes and radiative cooling compensate each other. Since the convection time scale (i.e. some hours) is much shorter than the radiation one (i.e. about 40 days), the resulting global temperature lapse rate is generally closer to the moist adiabat than to the dry adiabat. This is especially true over the tropics, where moist convection is in near-equilibrium. The RCE is then often used as a common approximation of the tropical mean state. It has been extensively used over oceans in SCMs (Single Column Models), as well as in CRMs (Cloud Resolving Models), to investigate the tropical moist convection sensitivity (i) to boundary conditions (e.g. SST, surface wind, drag coefficient, etc...) and (ii) to atmospheric conditions (e.g. radiative cooling, wind shear, tropospheric humidity, etc...). Nevertheless, to our knowledge the present study is the first one investigating the RCE over a continental surface. Indeed, in the present study, the single column version of the LMDZ GCM (LMDZ5B, from the Laboratoire de Meteorologie Dynamique) is ran to RCE, with a coupled land surface both in terms of temperature and moisture. This continental RCE demonstrates very different sensitivity compared to its oceanic counterpart in particular because of the large- amplitude heat flux diurnal cycle, which is shown to strongly impact the equilibrium state. Sensitivity studies (i) to solar forcing (latitude) (ii) to total water content, and (iii) to the initial conditions are performed to study the different equilibrium states, with a particular focus on the role of clouds. We also performed a bifurcation diagram. Low-level clouds and fog are shown to be key

  11. Surface wind modification near mid-latitude ocean fronts: Observational and dynamical analysis

    NASA Astrophysics Data System (ADS)

    O'Neill, Larry W.

    Interactions between surface winds and meanders in mid-latitude sea surface temperature (SST) fronts with horizontal length scales of 100-1000 km are investigated from satellite observations and numerical simulations. Observations from the Sea-Winds scatterometer on the QuikSCAT satellite show that the magnitude, direction, curl, and divergence of the surface wind stress and 10-m winds are well correlated with small-scale SST structures associated with large-scale ocean currents. Detailed analysis of the response of the surface winds to SST fronts from these satellite observations exposed shortcomings in previous conceptual hypotheses governing the relationships between surface winds and SST. To gain understanding of the physical mechanism needed to explain the satellite wind observations, we performed a numerical experiment simulating the atmospheric flow over meandering SST fronts. Based on these results, a new conceptual model is constructed to explain the dynamical response of the surface winds consistent with the satellite observations and numerical simulation analysis. Of particular importance was the finding that the wind stress curl and divergence fields observed from QuikSCAT are linearly related to the crosswind and downwind components of the SST gradient, respectively. This relationship was generally thought to result from modification of the vertical turbulent mixing of momentum within the atmospheric boundary layer (ABL). We show that this mechanism is overly simplistic; nearly all of the terms in the momentum budget are needed to explain these observed statistical relationships, consistent with recent work. SST-induced surface wind changes are a manifestation of more complicated changes to the vertical structure of the dynamic forces within the ABL. Among the most significant of several new findings presented here concerns the influence of SST on the meridional wind field. Since winds are generally westerly at mid-latitudes, SST-induced changes in

  12. Contributions from Different Current Systems to Sym and Asy Mid-Latitude Indices

    NASA Astrophysics Data System (ADS)

    Ganushkina, N. Y.; Dubyagin, S.

    2014-12-01

    Separating the contributions from different current systems from point magnetic field measurements and interpreting them is very difficult, and caution must be used when deciphering near-Earth currents from either data or modeling results. At the same time, there are other continuously measured quantities, which can provide, though indirectly, information about the dynamics of the magnetospheric current systems. The SYM-H and ASY-H indices, computed from the observations of magnetic field at low latitude ground-based stations, contain contributions from major magnetospheric current systems, such as the symmetric and asymmetric ring current, tail current, magnetopause currents and field-aligned currents. Highly distorted magnetospheric magnetic field during storm times due to disturbances in the current systems is reflected in the SYM-H and ASY-H observed variations.Using empirical magnetospheric models we study the relative contribution from different current systems to the SYM and ASY mid-latitude indices. It was found that the models can reproduce ground based mid-latitude indices rather well. The good agreement between the indices computed using magnetospheric models and real ones indicates that purely ionospheric current systems, on average, give modest contribution to these indices. The superposed epoch analysis of the indices computed using the models shows that the cross-tail current gives dominant contribution to SYM-H index during the main phase though this contribution can not be separated from FAC region 2 and partial ring current contributions since these systems are overlapped. The relative contribution from symmetric ring current to SYM-H starts to increase a bit prior or just after SYM-H minimum and attains its maximum during recovery phase. The ASY-H and ASY-D indices are controlled by interplay between three current systems which close via the ionosphere. The region 1 FAC gives the largest contribution to ASY-H and ASY-D indices during the main

  13. Magnetospheric current systems as inferred from SYM and ASY mid-latitude indices

    NASA Astrophysics Data System (ADS)

    Ganushkina, Natalia; Dubyagin, Stepan

    2015-04-01

    Separating the contributions from different current systems from point magnetic field measurements and interpreting them as belonging to one system or another is very difficult, and caution must be used when deciphering near-Earth currents from either data or modeling results. At the same time, there are other continuously measured quantities, which can provide, though indirectly, information about the dynamics of the magnetospheric current systems. The SYM-H and ASY-H indices, computed from the observations of magnetic field at low latitude ground-based stations, contain contributions from major magnetospheric current systems, such as the symmetric and asymmetric ring current, tail current, magnetopause currents and field-aligned currents. Highly distorted magnetospheric magnetic field during storm times due to disturbances in the current systems is reflected in the SYM-H and ASY-H observed variations. Using empirical magnetospheric models we study the relative contribution from different current systems to the SYM and ASY mid-latitude indices. It was found that the models can reproduce ground based mid-latitude indices rather well. The good agreement between the indices computed using magnetospheric models and real ones indicates that purely ionospheric current systems, on average, give modest contribution to these indices. The superposed epoch analysis of the indices computed using the models shows that the cross-tail current gives dominant contribution to SYM-H index during the main phase though this contribution can not be separated from FAC region 2 and partial ring current contributions since these systems are overlapped. The relative contribution from symmetric ring current to SYM-H starts to increase a bit prior or just after SYM-H minimum and attains its maximum during recovery phase. The ASY-H and ASY-D indices are controlled by interplay between three current systems which close via the ionosphere. The region 1 FAC gives the largest contribution to ASY

  14. Identification of bomb-produced chlorine-36 in mid-latitude glacial ice of North America

    USGS Publications Warehouse

    DeWayne, Cecil L.; Vogt, S.

    1997-01-01

    In 1991, the U.S. Geological Survey collected a 160-meter (m) ice core from the Upper Fremont Glacier (43??07???N, 109??36???W) in the Wind River Mountain Range of Wyoming in the western United States [1]. In 1994-95, ice from this core was processed at the National Ice Core Laboratory in Denver, Colorado, and analyzed for chlorine-36 (36Cl) by accelerator mass spectrometry at PRIME Laboratory, Purdue University. A tritium bomb peak identified in the work by [1] was used as a marker to estimate the depth of bomb-produced 36Cl. Tritium concentrations ranged from 0 tritium units (TU) for older ice to more than 300 TU at 29 m below the surface of the glacier, a depth that includes ice that was deposited as snow during nuclear-weapons tests through the early 1960's. Maximum 36Cl production during nuclear-weapons tests was in the late 1950's; therefore, the analyses were performed on ice from a depth of 29.8 to 32 m. Calculated flux for 36Cl in ice deposited in the late 1950's ranged from 1.2 ?? 0.1 ?? 10-1 atoms/cm2 s for ice from 29.8 to 30.4 m, to 2.9 ?? 0.1 ?? 10-1 atoms/cm2 s for ice from 31.5 to 32.0 m. Ice samples from a depth of 104.7 to 106.3 m were selected to represent pre-weapons tests 36Cl flux. Calculated flux for 36Cl in this deeper ice was 4.6 ?? 0.8 ?? 10-3 atoms/cm2 s for ice from 104.7 to 105.5 m and 2.0 ?? 0.2 ?? 10-2 atoms/cm2 s for ice from 105.5 to 106.3 m. These flux calculations from the Upper Fremont Glacier analyses are the first for bomb-produced 36Cl in ice from a mid-latitude glacier in North America. It may now be possible to fully quantify the flux of 36Cl from nuclear-weapons tests archived in mid-latitude glacial ice and to gain a better understanding of the distribution of 36Cl and other cosmogenic nuclides.

  15. Evolution of the exposed ice in a fresh mid-latitude crater on Mars

    NASA Astrophysics Data System (ADS)

    Kossacki, Konrad; Portyankina, Ganna; Thomas, Nicolas

    Recent observations of the surface of Mars have shown several fresh mid-latitude craters. Sur-prisingly, some of these craters show exposed ice Byrne et al (2009). In some craters albedo of ice slowly decreases, while in other remains nearly constant. We attempt to determine influence of the regolith structure on the rate of sublimation of ice. We have investigated the evolution of exposed ice patch inside fresh crater formed at northern mid-latitude plains. We considered situation, when the floor of the model crater is covered by a thin, up to 1 cm, uniform layer of clean water ice. The problem has multiple free parameters which are not or weakly constrained by observational data. Influence of wind speed, albedo change model, time of crater formation, volumetric fraction of the ice in the subsurface, model crater depth and thickness of the ice layer were evaluated. Some of them (the way albedo reacts to the change in ice cover, depth of model crater) are shown to be negligible. Contrary, other parameters are appeared to be critical. The strongest influence on sublimation rates comes however from subsurface volumetric fraction of water ice. We have found, that the observed darkening of an ice patch on the crater floor can be sufficient to determine volume fraction of ice in the regolith beneath the crater. However, this can be possible only when the ice layer is initially few millimeters thick, or when the wind speed is high. Otherwise, the calculated albedo of the crater floor remains nearly constant. Thus, visibility of a darkening should indicate small thickness of the ice layer, and allow to determine at least approximate concentration of ice beneath the crater. The amount of ice in subsurface is important for understanding formation processes of many periglacial features observed in northern plains. Our calculations indicate that subsurface is not ice free, otherwise the ice patches must have disappeared faster than observed. When the ice layer is initially 5

  16. Does Temperature (Rather than Precipitation) Dictate the Geomorphic Legacy of Glacial Intervals in Unglaciated Mid-Latitude Terrains?

    NASA Astrophysics Data System (ADS)

    Marshall, J. A.; Roering, J. J.; Bartlein, P. J.; Praskievicz, S. J.; Gavin, D. G.; Hales, T. C.; Granger, D. E.

    2014-12-01

    Whereas glaciated landscapes record increased erosional efficiency through moraines and U-shaped valleys, unglaciated hillslopes and rivers lack a mechanistic theory for climate controls on their dynamics and form. Changes in precipitation and associated aggradation due to vegetation loss or incision due to increased river discharge are commonly invoked when considering the effect of glacial intervals on unglaciated terrains, but there is scant evidence supporting or discounting these hypotheses. Surprisingly, there is little consideration that temperature, rather than precipitation, may dictate the frequency, magnitude, or style of erosion in unglaciated landscapes during glacial intervals. Here, we present results combining a mechanistic frost-cracking model with downscaled general circulation model output to predict the extent and intensity of sediment production via frost processes across the unglaciated Oregon Coast Range (OCR) during the Last Glacial Maximum (LGM). Our results show that in this mid-latitude region, well south of the Cordilleran ice sheet, frost-driven processes likely shaped 90% of the present-day landmass during the LGM. A suite of geomorphic and vegetation data from a 50-ky sediment core from a paleo landslide-dammed lake in the OCR support our model results. Our study site, Little Lake, is located in the central portion of the OCR, over 400 m south of the maximum extent of the Cordilleran ice sheet. Based on 10Be-derived erosion rates, present-day catchment erosion rates average 0.07 ± 0.03 mm/yr (mean ± sd), while LGM erosion rates remained constant around 0.19 ± 0.01 mm/yr. These LGM values are nearly 3X greater than present-day erosion rates and coincide with high frost cracking intensity predicted by our model. We also observe a transition from finely laminated lacustrine clays and sands to coarse lacustrine blue-grey sands at ~ 28 ka, during the transition to the LGM. The presence of Picea sitchensis (Sitka spruce) and Abies

  17. Ion temperature of low-latitude and mid-latitude topside ionosphere for high solar activity

    NASA Astrophysics Data System (ADS)

    Cai, Lei; Zhang, Donghe; Hao, Yongqiang; Xiao, Zuo

    The International Reference Ionosphere (IRI) describes the day and night latitudinal variation of ion temperature at 430 km with two functions using AEROS satellite measurements. The ion temperature at this height as one of the boundary parameters is used to make the ion temperature profile represented by a Booker-function. Since the low-latitude and mid-latitude topside ionospheric ion temperature has been measured with the Ionopsheric Plasma and Elec-trodynamics Instrument (IPEI) onboard Rocsat-1 satellite at about 600 km during the high solar activity years from 2000 to 2002, a new boundary at 600 km can be set for the ion temperature modeling. The latitudinal variation of ion temperature could be approximated by Epstein family of functions for different local time sectors. Furthermore, the longitudinal and seasonal variations are also taken into account to decide the fitting parameters. Only the magnetic quiet time data (Kp <3) are used for the statistical study. The results are compared with IRI-2007 model. In addition, events when Kp >4 are also analyzed to feature the ion temperature characteristic during the magnetic disturbance time condition. Combined with the IPEI field-aligned ion flow velocities and the plasma temperatures measured by the Special Sensors-Ions, Electrons, and Scintillation (SSIES) thermal plasma analysis package on board the DMSP F13 and F15 satellites, several feasible ion heating and heat loss mechanisms are summarized to interpret the ion temperature crests and toughs for different local time sectors, seasonal and longitudinal variations.

  18. New Ionosonde Observations of Mid Latitude Spread-F at Wallops Island

    NASA Astrophysics Data System (ADS)

    Bullett, T.

    2008-12-01

    A new generation digital ionosonde, a Vertical Incidence Pulsed Ionospheric Radar (VIPIR) was installed at the NASA Wallops Island Flight Facility in Virginia and saw first operation in 2007. The VIPIR features dramatic improvements in ionosonde and radar system design, including multiple phase-coherent, fully digital receivers, improved antenna designs, and higher data resolution. This produces markedly improved ionograms. From the mid 1980's through today, NASA Wallops hosts a first generation digital ionosonde, a US Air Force Digital Ionospheric Sounding System or Digisonde 256. Phase coherent digital sampling of analog receiver output, digital data storage and automated real time ionogram scaling allowed spread-F quantification and use of the data for launch decisions. In the 1970's and early 1980's an analog ionosonde, at Wallops recorded data on photographic film. Hourly characteristics were later scaled by hand, with spread-F being qualitatively identified. Recently, select periods of film ionograms have been digitized by NOAA/NGDC and are available in electronic format. This presentation compares spread-F observations made with three generations of ionospheric sounding equipment operated at the NASA Wallops Island Flight Facility. Comparison of ionogram data from both VIPIR and Digisonde ionosondes during several different events reveals newly observed mid-latitude spread- F features.

  19. Mesospheric sodium airglow emission: Modeling and first results over a mid-latitude

    NASA Astrophysics Data System (ADS)

    Bag, Tikemani; Krishna, M. V. Sunil; Singh, Vir

    2016-07-01

    Atmospheric sodium plays a very important role in the mesospheric chemistry and dynamics. We have developed a comprehensive model for mesospheric/thermospheric sodium airglow emission by incorporating all the known reaction mechanisms. The latest reaction rate coefficients and the related cross sections are obtained from the theoretical studies and experimental observations. The continuity equations are explicitly solved for the major species. Similarly, the steady-state approximation has been used for the intermediate and short lived minor species. The number densities from in-situ observations, NRLMSISE-00, and IRI-2012 have been successfully implemented to calculate the vertical volume emission rate. The modeled results compared to a good agreement with the measured profiles of Na airglow emission. The mesospheric sodium density shows a large day-to-day variability. The observed variations in the mesospheric sodium layer have been incorporated to obtain the variations in the sodium airglow intensities. The nocturnal variation of sodium airglow emissions are presented over a mid latitude location using this model.

  20. A new source of horizontal electric fields in the mid-latitude stratosphere

    NASA Technical Reports Server (NTRS)

    Holzworth, R. H.

    1989-01-01

    Superpressure balloon-borne instruments that measure the vector stratospheric electric field at latitudes near 45 + or - 10 deg S reveal several features in fair weather that cannot be attributed to ionospheric, thunderstorm, or other known sources. Over 180 days of electric field, conductivity, and current density data have been taken at the constant altitude of 26 km, using long-duration balloon flights in the Southern Hemisphere. Throughout these data the fair-weather horizontal electric field has a magnitude (10-50 mV/m) that cannot be due to mid-latitude ionospheric dynamo action. Furthermore, the fields are highly variable in amplitude, almost turbulent in appearance, while the vector direction steadily rotates in a counterclockwise manner. The period of this rotation is close to the quasi-inertial wave period for the latitude of the balloon. For these flights, the electric field rotation period varies between 14 and 21 hours. Some possible causes that might explain the electric field and current measurements reported herein are discussed.

  1. Stratified verification of decadal mid-latitude cyclones and wind storms forecasts

    NASA Astrophysics Data System (ADS)

    Grieger, Jens; Kröner, Igor; Höschel, Ines; Rust, Henning W.; Ulbrich, Uwe

    2016-04-01

    This study investigates the decadal forecast skill of mid-latitude cyclones and wind storms dependent on low-frequency climate modes. Objective tracking methodologies are applied for the identification of cyclones and wind storms. The decadal prediction system of the German initiative on decadal predictions, MiKlip, is used to evaluate probabilistic prediction skills of windstorm densities. Initialized experiments are compared with climatological forecast as well as uninitialized historical simulations as reference whereas ERA reanalyses products are taken as observations. With respect to cyclone and windstorm track density the initialized experiments show a positive prediction skill over climatological forecast. For certain regions the hindcast experiments show also positive skill over uninitialized simulations. These are the entrance regions of the North Pacific and North Atlantic storm tracks as well as spots in the Eastern North Atlantic near the Iberian Peninsula. This contribution analyzes how far the skill of wind storms and cyclones depends on low-frequency climate modes, e.g. the Atlantic Multidecadal Variability (AMV). Stratifying verification along an AMV index it can be shown that skill is larger for negative than for positive phases, especially for the Eastern North Atlantic.

  2. Solar activity influence on climatic variations of stratosphere and mesosphere in mid-latitudes

    NASA Technical Reports Server (NTRS)

    Taubenheim, J.; Entzian, G.; Voncossart, G.

    1989-01-01

    The direct modulation of temperature of the mid-latitude mesosphere by the solar-cycle EUV variation, which leads to greater heat input at higher solar activity, is well established. Middle atmosphere temperature modulation by the solar cycle is independently confirmed by the variation of reflection heights of low frequency radio waves in the lower ionosphere, which are regularly monitored over about 30 years. As explained elsewhere in detail, these reflection heights depend on the geometric altitude of a certain isobaric surface (near 80 k), and on the solar ionizing Lyman-alpha radiation flux. Knowing the solar cycle variation of Lyman-alpha how much the measured reflection heights would be lowered with the transition from solar minimum to maximum can be calculated, if the vertical baric structure of the neutral atmosphere would remain unchanged. An discrepancy between expected and observed height change must be explained by an uplifting of the isobaric level from solar minimum to maximum, caused by the temperature rise in the mesosphere. By integrating the solar cycle temperature changes over the height region of the middle atmosphere, and assuming that the lower boundary (tropopause) has no solar cycle variation, the magnitude of this uplifting can be estimated. It is given for the Lidar-derived and for the rocket-measured temperature variations. Comparison suggests that the real amplitude of the solar cycle temperature variation in the mesosphere is underestimated when using the rocket data, but probably overestimated with the Lidar data.

  3. The missing aerosol response in twentieth-century mid-latitude precipitation observations

    NASA Astrophysics Data System (ADS)

    Osborne, Joe M.; Lambert, F. Hugo

    2014-05-01

    Regional temperature change over the twentieth century has been strongly influenced by aerosol forcing. The aerosol effect is also expected to be pronounced on regional precipitation change. Changes in historical precipitation--for the global mean and land mean of certain regions--should be more sensitive to spatially heterogeneous aerosol forcing than greenhouse gas forcing. Here, we investigate whether regional precipitation and temperature respond predictably to a significant strengthening in mid-twentieth-century Northern Hemisphere mid-latitude (NHML) aerosol forcing. Using the latest climate model experiments, we find that observed regional temperature changes and observed Northern Hemisphere tropical land precipitation changes are consistent with the IPCC Fifth Assessment Report aerosol forcing estimate, but observed NHML land precipitation changes show little evidence of an aerosol response. This may be a result of changes in precipitation measurement practice that increased observed precipitation totals at the same time that aerosol forcing was expected to reduce them. Investigating this inconsistency, we calculate the required increase in early-twentieth-century observed NHML land precipitation to bring this result in line with aerosol forcing. Biases greater than this calculated correction have been identified in countries within the NHML region previously, notably the former Soviet Union. These observations are frequently used as a metric for the quality of model-simulated precipitation. More homogeneity studies would be of huge benefit.

  4. Effects of clouds on the surface shortwave radiation at a rural inland mid-latitude site

    NASA Astrophysics Data System (ADS)

    Salgueiro, Vanda; Costa, Maria João; Silva, Ana Maria; Bortoli, Daniele

    2016-09-01

    Seven years (2003-2010) of measured shortwave (SW) irradiances were used to obtain estimates of the 10 min averaged effective cloud optical thickness (ECOT) and of the shortwave cloud radiative effect (CRESW) at the surface in a mid-latitude site (Évora - south of Portugal), and its seasonal variability is presented. The ECOT, obtained using transmittance measurements at 415 nm, was compared with the correspondent MODIS cloud optical thickness (MODIS COT) for non-precipitating water clouds and cloud fractions higher than 0.25. This comparison showed that the ECOT represents well the cloud optical thickness over the study area. The CRESW, determined for two SW broadband ranges (300-1100 nm; 285-2800 nm), was normalized (NCRESW) and related with the obtained ECOT. A logarithmic relation between NCRESW and ECOT was found for both SW ranges, presenting lower dispersion for overcast-sky situations than for partially cloudy-sky situations. The NCRESW efficiency (NCRESW per unit of ECOT) was also related with the ECOT for overcast-sky conditions. The relation found is parameterized by a power law function showing that NCRESW efficiency decreases as the ECOT increases, approaching one for ECOT values higher than about 50.

  5. Ecoclimate Teleconnections: The Large-Scale Impacts of Changes in Mid-Latitude Tree Cover

    NASA Astrophysics Data System (ADS)

    Swann, A. L. S.; Fung, I. Y.; Chiang, J. C. H.

    2014-12-01

    We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns both in the present day and the mid-Holocene. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We demonstrate that the remote and local forcing of atmospheric circulation by vegetation can lead to different dynamical patterns with consequences for precipitation across the globe. These ecoclimate teleconnections represent the linkages between the land surface in different regions of the globe and by inference show that proxy records of plant cover represent not only the response of vegetation to local climate but also that vegetation's influence on global climate patterns. The ability of vegetation to affect remote circulation also has implications for strategies for climate mitigation.

  6. Arctic sea ice melt, the Polar vortex, and mid-latitude weather: Are they connected?

    NASA Astrophysics Data System (ADS)

    Vihma, Timo; Overland, James; Francis, Jennifer; Hall, Richard; Hanna, Edward; Kim, Seong-Joong

    2015-04-01

    The potential of recent Arctic changes to influence broader hemispheric weather is a difficult and controversial topic with considerable skepticism, as time series of potential linkages are short (<10 years) and the signal-to-noise ratio relative to chaotic weather events is small. A way forward is through further understanding of potential atmospheric dynamic mechanisms. Although not definitive of change in a statistical or in a causality sense, the exceptionally warm Arctic winters since 2007 do contain increased variability according to some climate indices, with six negative (and two positive) Arctic Oscillation atmospheric circulation index events that created meridional flow reaching unusually far north and south. High pressure anomalies developed east of the Ural Mountains in Russia in response to sea-ice loss in the Barents/Kara Seas, which initiated eastward-propagating wave trains of high and low pressure that advected cold air over central and eastern Asia. Increased Greenland blocking and greater geopotential thickness related to low-level temperatures increases led to northerly meridional flow into eastern North America, inducing persistent cold periods. Arctic connections in Europe and western North America are less clear. The quantitative impact of potential Arctic change on mid-latitude weather will not be resolved within the foreseeable future, yet new approaches to high-latitude atmospheric dynamics can contribute to improved extended range forecasts as outlined by the WMO/Polar Prediction Program and other international activities.

  7. Characterization of different magnetospheric and ionospheric contributions at mid-latitude magnetic observatories

    NASA Astrophysics Data System (ADS)

    Castillo, Yvelice; Pais, Maria Alexandra; Fernandes, João; Ribeiro, Paulo; Morozova, Anna; Pinheiro, Fernando J. G.

    2016-04-01

    The main goal of space weather (SW) research is to produce reliable forecasts and nowcasts of the space environment and to evaluate the risks for technological infrastructures and human safety. Most of SW studies concern high and equatorial latitudes, because of well-known and significant effects of field-aligned currents and the equatorial electrojet at those latitudes. Less studies are made at mid-latitudes, resulting in an incomplete understanding of the local effect of magnetospheric and ionospheric currents. We compare the performance of global indices of geomagnetic activity such as Kp and Dst with simulations of the Tsyganenko semi-empirical model of storm-time geomagnetic field, in predicting the irregular geomagnetic activity observed at the Coimbra magnetic observatory (40.22 N, 351.58 E). At first we use principal component analysis to efficiently separate the geomagnetic daily variation. Then we identify the effect of different magnetospheric current systems and estimate their contributions. Finally, we discuss how ground observatory observations can benefit from semi-empirical models, but also contribute to improve their parameterization.

  8. Mid-latitude composition of mars from thermal and epithermal neutrons

    SciTech Connect

    Prettyman, T. H.; Feldman, W. C.; Elphic, R. C.; Boynton, W. V.; Bish, D. L.; Vaniman, D. T.; Funsten, H. O.; Lawrence, David J. ,; Maurice, S.; McKinney, G. W.; Moore, K. R.; Tokar, R. L.

    2003-01-01

    Epithermal neutron data acquired by Mars Odyssey have been analyzed to determine global maps of water-equivalent hydrogen abundance. By assuming that hydrogen was distributed uniformly with depth within the surface, a map of minimum water abundance was obtained. The addition of thermal neutrons to this analysis could provide information needed to determine water stratigraphy. For example, thermal and epithermal neutrons have been used together to determine the depth and abundance of waterequivalent hydrogen of a buried layer in the south polar region. Because the emission of thermal neutrons from the Martian surface is sensitive to absorption by elements other than hydrogen, analysis of stratigraphy requires that the abundance of these elements be known. For example, recently published studies of the south polar region assumed that the Mars Pathfinder mean soil composition is representative of the regional soil composition, This assumption is partially motivated by the fact that Mars appears to have a well-mixed global dust cover and that the Pathfinder soil composition is representative of the mean composition of the Martian surface. In this study, we have analyzed thermal and epithermal neutron data measured by the neutron spectrometer subsystem of the gamma ray spectrometer to determine the spatial distribution of the composition of elements other than hydrogen. We have restricted our analysis to mid-latitude regions for which we have corrected the neutron counting data for variations in atmospheric thickness.

  9. Can hydrous minerals account for the observed mid-latitude water on Mars?

    SciTech Connect

    Bish, D. L.; Vaniman, D. T.; Fialips, C. I.; Carey, J. W.; Feldman, W. C.

    2003-01-01

    Great interest was generated with the discovery by the Odyssey spacecraft OC heterogeneously distributed hydrogcn at martian mid-latitudes, suggesting that large areas of the near-equatorial highlands contain near-surface deposits of 'chemically and/or physically bound 1120 and/or OH' in amounts up to 3.8% equivalent H20. More recent interpretations of the Odyssey data using new calibrations suggest that some near-equatorial areas, such as Arabia Terra, contain up to 8.5f I .3% water-equivalent hydrogen. Such shallow occurrences (

  10. The structure of Holocene climate change in mid-latitude North America

    NASA Astrophysics Data System (ADS)

    Shuman, Bryan N.; Marsicek, Jeremiah

    2016-06-01

    A sequence of long-term and rapid changes during the Holocene appears in a network of 40 well-resolved paleoclimate datasets from mid-latitude North America, including records of pollen-inferred temperatures, alkenone-derived sea-surface temperatures (SSTs), lake-level changes, dust accumulation, and lake isotopes from Idaho to Maine. Statistical analyses reveal that changes in insolation and the Laurentide Ice Sheet explain 51.7% of the variance in the records, especially multi-millennial trends, but peak rates of change indicate additional rapid changes at ca. 10.8, 9.4, 8.3, 7.0, 5.5-5.2, 4.7, 2.1, and 0.9 ka. Step changes between 9.4 and 8.3 ka relate to ice sheet dynamics that warmed much of the region, and changes at 5.5 ka were the largest since the demise of the ice sheet. The shift at 5.5 ka initiated widespread cooling and increases in effective moisture, which culminated in the coolest, wettest millennia in most areas after 2.1 ka. Replicated evidence from multiple records also shows a spatially-varied set of multi-century fluctuations including 1) low temperatures and high effective moisture at 5.5-4.8 ka in the mid-continent and 2) repeated phases of low SSTs, cool summers, and drought superimposed upon long cooling, moistening trends in eastern North American since 5.5 ka.

  11. Investigation of TEC Variations over Mid-Latitude during Quit and Disturbed Days of March 2015

    NASA Astrophysics Data System (ADS)

    Atıcı, Ramazan; Saǧır, Selçuk; Güzel, Esat

    2016-07-01

    The variations during 09-14-March-2015 quit days and 15-20 March 2015 disturbed days of Total Electron Content (TEC) values (provided by IONOLAB group) obtained by analysis the data from Ankara Global Position System (GPS) station of Turkey located at mid-latitude, IRI -2012 model the and IRI-PLUS model are investigated. Also, the variations of the geomagnetic, interplanetary and solar wind parameters are examined. As a result of investigations, TEC values from all three models are not change too much at quit days. Unlike, at the disturbed days, although IRI-2012 and IRI-PLUS TEC values are not change too much, a noticeable change in GPS-TEC values is occurred. GPS-TEC values are rapidly increased on 17-March 2015 to be severe magnetic storm (Dst = -124 nT). Then, on following days it was observed to significantly decrease. Thus, it is said that GPS-TEC values are more sensitive than IRI-2012 and IRI-PLUS models to variations occurred on disturbed days.

  12. Evidence linking rapid Arctic warming to mid-latitude weather patterns

    PubMed Central

    Francis, Jennifer; Skific, Natasa

    2015-01-01

    The effects of rapid Arctic warming and ice loss on weather patterns in the Northern Hemisphere is a topic of active research, lively scientific debate and high societal impact. The emergence of Arctic amplification—the enhanced sensitivity of high-latitude temperature to global warming—in only the last 10–20 years presents a challenge to identifying statistically robust atmospheric responses using observations. Several recent studies have proposed and demonstrated new mechanisms by which the changing Arctic may be affecting weather patterns in mid-latitudes, and these linkages differ fundamentally from tropics/jet-stream interactions through the transfer of wave energy. In this study, new metrics and evidence are presented that suggest disproportionate Arctic warming—and resulting weakening of the poleward temperature gradient—is causing the Northern Hemisphere circulation to assume a more meridional character (i.e. wavier), although not uniformly in space or by season, and that highly amplified jet-stream patterns are occurring more frequently. Further analysis based on self-organizing maps supports this finding. These changes in circulation are expected to lead to persistent weather patterns that are known to cause extreme weather events. As emissions of greenhouse gases continue unabated, therefore, the continued amplification of Arctic warming should favour an increased occurrence of extreme events caused by prolonged weather conditions. PMID:26032322

  13. Tidal signature of the mid-latitude ionospheric nighttime anomaly using CHAMP and GRACE observations

    NASA Astrophysics Data System (ADS)

    Xiong, Chao; Lühr, Hermann

    2014-05-01

    This paper presents a study on the tidal signatures of the mid-latitude summer nighttime anomaly (MSNA), also known as Weddell Sea anomaly in the southern hemisphere. The electron density observations by CHAMP and GRACE show clear MSNA structures in both hemispheres during local summer nighttime. A linear least squares algorithm for extracting the solar tidal components is utilized to examine the major tidal components affecting the variation of the electron density. In the southern hemisphere, we find a prominent eastward propagating wave-1 of electron density in the local time frame, which could be explained by the symmetric diurnal wave (D0) and a stationary planetary wave (SPW1) component. Conversely, in the northern hemisphere during local summer, a prominent eastward wave-2 can be found, which could be attributed to the diurnal eastward propagating wave (DE1) and a stationary planetary wave (SPW2) component. We are going to offer some explanations that may be responsible for the different appearance of the wave structures in the two hemispheres.

  14. Observations and Modeling of the Nighttime Electron Density Enhancement in the Mid-latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Chen, C.; Saito, A.; Lin, C.; Huba, J. D.; Liu, J. G.

    2010-12-01

    In this study, we compare the observational data from FORMOSAT-3/COSMIC and theoretical model results performed by SAMI2 (Sami2 is Another Model of the Ionosphere) for studying the longitudinal structure of the Mid-latitude Summer Nighttime Anomaly (MSNA). In order to study the occurrence of the nighttime electron density enhancement, we defined MSNA index by the ratio of the difference of the nighttime and daytime electron densities. The observational results by the FORMOSAT-3/COSMIC satellites show that there are three obvious nighttime electron density enhancement areas around South American, European, and Northeast Asian regions during local summer. The SAMI2 model can also successfully reproduce the ionospheric MSNA structure during local summer on both hemispheres, except for Northeast Asian region. This difference between observation and model simulation may be caused by the difference between the neutral wind model and the real winds. The physical mechanisms for the longitudinal structure of the MSNA are investigated in the different model conditions. Results show that the equatorward meridional neutral winds can drive the electron density up to a higher altitude along the magnetic field lines and the longer plasma production rate by solar EUV at higher latitudes in the summer time can provide the electron density source in the nighttime ionosphere. We concluded that the combination effect by the neutral wind and the plasma production rate play the important role of the MSNA longitudinal structure.

  15. Mid-latitude Summer Nighttime Anomaly (MSNA) - observations and model simulations

    NASA Astrophysics Data System (ADS)

    Thampi, S. V.; Balan, N.; Lin, C.; Liu, H.; Yamamoto, M.

    2011-01-01

    In this paper, we present model simulations of the Mid-latitude Summer Nighttime Anomaly (MSNA) in the Northern Hemisphere, which is characterized by noon-time dip and evening maximum in the diurnal variation of the ionospheric density. The simulations are carried out using SUPIM (Sheffield University Plasmasphere Ionosphere Model) for solar minimum at 135° E longitude where MSNA is most pronounced in the Northern Hemisphere. The simulations are used to understand the relative importance of electric fields, and zonal and meridional winds in the formation of MSNA. The wind velocities measured by the Middle and Upper atmosphere radar (MU radar) and those obtained from the horizontal wind model (HWM93) are used. The results show that the formation of MSNA is closely related to the diurnal variation of the neutral winds with little contribution from the changes in the electric fields. The observed features of MSNA are better reproduced when MU radar winds are used as model input rather than HWM winds.

  16. Northern hemisphere mid-latitude geomagnetic anomaly revealed from Levantine Archaeomagnetic Compilation (LAC).

    NASA Astrophysics Data System (ADS)

    Shaar, R.; Tauxe, L.; Agnon, A.; Ben-Yosef, E.; Hassul, E.

    2015-12-01

    The rich archaeological heritage of Israel and nearby Levantine countries provides a unique opportunity for archaeomagnetic investigation in high resolution. Here we present a summary of our ongoing effort to reconstruct geomagnetic variations of the past several millennia in the Levant at decadal to millennial resolution. This effort at the Southern Levant, namely the "Levantine Archaeomagnetic Compilation" (LAC), presently consists of data from over 650 well-dated archaeological objects including pottery, slag, ovens, and furnaces. In this talk we review the methodological challenges in achieving a robust master secular variation curve with realistic error estimations from a large number of different datasets. We present the current status of the compilation, including the southern and western Levant LAC data (Israel, Cyprus, and Jordan) and other published north-eastern Levant data (Syria and southern Turkey), and outline the main findings emerging from these data. The main feature apparent from the new compilation is an extraordinary intensity high that developed over the Levant region during the first two millennia BCE. The climax of this event is a double peak intensity maximum starting at ca. 1000 BCE and ending at ca. 735 BCE, accompanied with at least two events of geomagnetic spikes. Paleomagnetic directions from this period demonstrate anomalies of up to 20 degrees far from the averaged GAD field. This leads us to postulate that the maximum in the intensity is a manifestation of an intense mid-latitude local positive geomagnetic anomaly that persisted for over two centuries.

  17. PCA Analysis of the Geomagnetic Field at Mid-Latitude Regions during High Solar Activity

    NASA Astrophysics Data System (ADS)

    Natali, Maria Paula; Meza, Amalia Margarita

    2016-07-01

    Our study is focused on the analysis of the geomagnetic variability of the H, D and Z components in the Northern hemisphere at mid-latitudes. We analyze two different local times, noon and night, recorded by 22 permanent observatories distributed over Europe and North America during a period of four years of high solar activity comprising 2000-2003. We used Principal Component Analysis (PCA) in order to identify the spatial and temporal variations of the geomagnetic field components. This technique produces a quite compact representation of the data by defining an orthonormal base derived from correlation within the data set. This helps us to identify possible causes of seasonal variations and anomalies, linking them with already observed currents. In fact, the analysis of PCA amplitudes and modes support our interpretation of the spectral and statistical features of the geomagnetic field. Using the first two modes we reconstruct more than 90% of the original signal for the European and North American region. The obtained results reconfirm the existence of a latitudinal dependence in the geomagnetic components during nighttime hours, associated with the ring current. During noon, the first mode represent the dominant component of the current originated by the ionosphere, while the second mode show the presence of a longitudinal variation at both sides of the longitudes with zero declination for Europe and North America.

  18. The behavior of the plasmapause at mid-latitudes: ISIS-1 Langmuir probe measurements

    NASA Technical Reports Server (NTRS)

    Brace, L. H.; Theis, R. F.

    1973-01-01

    Observations of the electron concentration, N sub e, and temperature, T sub e, from the electrostatic probes on the ISIS-1 satellite were used to examine the location and behavior of the plasmapause at about 3000 kilometers altitude in the vicinity of L = 4. At these altitudes, the N sub e measurements are equivalent to measurements of H(+) since the satellite is well into the protonosphere. The plasmapause as is evident as a sharp drop in N sub e by a factor of 10 to 100 as the satellite passes into the polar cap, and a corresponding increase is observed as it enters the plasmasphere on the opposite side of the Earth. An enhancement of T sub e is also observed at the plasmapause, an effect that is most visible at night when the temperatures at latitudes above and below the plasmapause are usually very low. The position of the plasmapause decreases with magnetic activity but is found to be somewhat less sensitive to K sub p than is the equatorial plasmapause. Also unlike its equatorial behavior, the mid-latitude plasmapause exhibits no detectable late afternoon bulge. These differences imply rather complex coupling of the thermal plasma along the field lines that link these two regions of the plasmasphere. An additional factor may be the recently observed axial asymmetry in the geomagnetic field at high altitudes.

  19. Mid-latitude ozone monitoring with the GOMOS-ENVISAT experiment version 5: the noise issue

    NASA Astrophysics Data System (ADS)

    Keckhut, P.; Hauchecorne, A.; Blanot, L.; Hocke, K.; Godin-Beekmann, S.; Bertaux, J.-L.; Barrot, G.; Kyrölä, E.; van Gijsel, J. A. E.; Pazmino, A.

    2010-12-01

    The GOMOS ozone profiles have been analysed to evaluate the GOMOS ability to capture the long-term ozone evolution at mid-latitudes during the expected recovery phase of the ozone layer. Version 5 of the operational GOMOS ozone data has been compared with data from two of the longest ground-based instruments based on different techniques and already involved with many other previous space instrument validations. Comparisons between ground-based and GOMOS data confirm the occurrence of spurious retrievals mainly occurring since 2006. Using a selected set of data it is shown that some bad retrievals are induced by the increasing dark charge of the detectors combined with an inadequate method for its correction. This effect does not only induce a continuous bias, but is rather exhibiting a bimodal distribution including the correct profiles and the bad retrievals. For long-term analyses it is recommended filtering the data according to background light conditions and star temperature (spectrum shape). The new method of the dark charge estimate proposed to be implemented in the version 6 of the ESA algorithm seems to significantly reduce the occurrence of such effects and should allow to monitor stratospheric ozone using GOMOS data with greater confidence.

  20. Confronting multi-year idealized LES with measurements at a mid-latitude meteorological site

    NASA Astrophysics Data System (ADS)

    Schemann, V.; Neggers, R.; Wegener, C.

    2015-12-01

    Long-term Large-Eddy Simulation (LES) at permanent meteorological sites is increasingly being used for the evaluation and improvement of parameterizations of fast boundary-layer physics for weather and climate models. Typically, idealized LES are generated that represent fine-scale downscalings of a large-scale model state at locations of interest, resolved at temporal and spatial resolutions at which turbulence and boundary layer clouds can be expected to be resolved. The setup relies on prescribed large-scale forings in combination with continuous nudging, at a time-scale large enough to allow the resolved fast physics to have enough freedom to establish their own, unique state. This study critically assesses the representativeness of such long-term LES, and asks to what degree the continuous nudging affects the budgets of thermodynamic state variables. To this purpose long-term, multi-year LES is confronted with relevant observations at a European midlatitude continental site. The large-scale advective forcings and surface properties used to drive the LES are derived from analyses of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). Evaluated aspects of the boundary layer include near-surface meteorology, vertical structure, and bulk properties including clouds. The evaluation focuses on the diurnal cycle, with the oservational datasets derived from state-of-the-art instrumentation at the Juelich Observatory for Cloud Evolution (JOYCE) in Germany. Conditional sampling is used to highlight results for regimes of interest, including the clear convective and shallow cumulus topped boundary layer. We find that the LES is able to reproduce the observed amplitude and time-variation of key boundary layer properties, including clouds. Budget studies of the thermodynamic state variables reveal that a rough balance exists between the prescribed larger-scale advection and the turbulence/convection as resolved by the

  1. Inferred Differences in Ice Crystal Nucleation Rates between Continental and Maritime Deep Convective Clouds

    NASA Astrophysics Data System (ADS)

    Mitchell, D. L.; Avery, M. A.; Garnier, A.

    2014-12-01

    We present in situ and remotely sensed evidence for the following working hypothesis: Heterogeneous nucleation dominates during deep continental convection until ice nuclei in the updraft cannot prevent supersaturation from increasing. As it increases, homogeneous nucleation eventually occurs near cloud top (T < -60°C), with much faster ice crystal production rates. This is not the case in maritime anvil cirrus, where updrafts associated with deep convection are slower, promoting heterogeneous nucleation. We hypothesize that differences in updraft velocities and their effect on supersaturation might create a difference in the N/IWC ratios. Based on In situ measurements of the ice particle size distribution (PSD) from two aircraft field campaigns (SPARTICUS & TC4) and MODIS satellite retrievals of the temperature dependence of the 12/11 μm effective absorption optical depth ratio or βeff, ice crystal nucleation rates appear to be anomalously high near the tops of continental thunderstorms relative to maritime thunderstorms. The ice crystal nucleation rate, having units of g-1 s-1, is more related to the ratio of ice particle number concentration/ice water content (or N/IWC, with units of g-1) than to N. A surprisingly tight relationship was discovered between βeff and N/IWC, allowing N/IWC to be estimated from satellite retrievals of βeff. These retrievals verified that deep convection during TC4 over water did not produce the much higher N/IWC ratios observed during SPARTICUS in continental anvil cirrus. The imaging infrared radiometer (IIR) aboard CALIPSO has channels at 8, 10 and 12 μm and provides a data record of βeff dating back to 2006, as well as vertical profiles of IWC, extinction, depolarization and 1064/532 nm backscatter ratio from the CALIOP lidar. We will compare the MODIS-derived βeff and N/IWC relationship with that derived using the IIR data. We will also investigate the relationship between N/IWC, βeff and the vertically-resolved lidar

  2. A Facies Model for Temperate Continental Glaciers.

    ERIC Educational Resources Information Center

    Ashley, Gail Mowry

    1987-01-01

    Discusses the presence and dynamics of continental glaciers in the domination of the physical processes of erosion and deposition in the mid-latitudes during the Pleistocene period. Describes the use of a sedimentary facies model as a guide to recognizing ancient temperate continental glacial deposits. (TW)

  3. The impact of atmosphere model resolution on mid-latitude storm track variability

    NASA Astrophysics Data System (ADS)

    Feng, X.; Huang, B.

    2014-12-01

    The impact of horizontal resolution in an atmospheric general circulation model (AGCM) on mid-latitude storm track simulation is investigated using the European Centre for Medium-Range Weather Forecasts' (ECMWF) Integrated Forecast System (IFS). In one set of experiments, the IFS is forced with prescribed monthly sea surface temperature (SST) observations for 1960-2007 at three resolutions with T159 (~126km), T511 (~39km) and T1279 (~16km). To assess the effect of air-sea feedback, we have also examined three seasonal hindcast experiments of 7-months long initialized in every May and November for 1982-2010. The hindcasts are conducted using the ECMWF seasonal prediction system with IFS as its atmospheric component, which is set at resolutions of T319 (~62km) T639 (~31km) and T1279 for the three hindcasts respectively. The climatologically annual cycle of the large-scale precipitation over the Kuroshio and Gulf Stream regions is well simulated by IFS. The mean precipitation is enhanced with increasing atmospheric resolution in both the AGCM and coupled runs. Monthly averaged variance of high-pass filtered daily 250hPa meridional wind is used as an indicator for storm track intensity. In comparison with ERA-40 reanalysis, all simulations overestimate the mean strength of the storm tracks in the North Hemisphere. An EOF analysis of the high-pass filtered variance fields further shows that the two leading modes of the T159 run are characterized by a simultaneous strengthening/weakening in both North Atlantic and Pacific and a seesaw between the two basins respectively, consistent with those from the ERA-40 reanalysis. As the resolution increases, however, the storm track variations in the two basins become more independent. Further analyses are being conducted to connect the storm track variability with the global and regional atmospheric and SST patterns in these simulations.

  4. Mid-latitude cirrus investigations at high-resolution through ground-based lidar measurements

    NASA Astrophysics Data System (ADS)

    Dionisi, Davide; Keckhut, Philippe; Hauchecorne, Alain; Gaudo, Thierry; Courcoux, Yann; Porteneuve, Jacques; Hoareau, Christophe; Congeduti, Fernando; Liberti, Gianluigi

    2013-04-01

    Although cirrus vertical distributions determine their local cooling or warming effects, one of the main missing information in Global Climate Models (GCMs) is the characterization of their vertical location and stratification. Lidar technique, in contrast, can detect cirrus with high spatial and temporal resolution, providing accurate information on their vertical distribution. In this work, the recent and on going studies about the the characterization of mid-latitude cirrus through lidar systems located at the Observatory of Haute Provence (OHP, 43.9 ° N, 5.7 ° E) in France and at Rome Tor Vergata (RTV, 41.8 ° N, 12.6 ° E) in Italy are presented. Cirrus have been firstly studied in terms of quasi-stationary periods regarding statistical variability. A clustering approach has been then adopted to derive cirrus classification (and climatology) over the period 1996-2007 for OHP lidar measurements and over 2007-2010 for RTV dataset. Three independent cirrus classes have been identified: I thin middle tropospheric cirrus, II thick upper tropospheric cirrus, III thin tropopause cirrus. The temporal variability of the optical properties of these classes has been then analyzed at lidar raw temporal sampling (180 sec). While advection dominates, at the first order, variability on timescale of minutes can be related to space fluctuations of cloud properties on typical scale of few kilometers. Lognormal distributions of the optical depth have been used to model variability of the cirrus optical depth as observed by lidars. Finally, the implementation of the OHP lidar system in terms of two analogic channels that collect the Rayleigh-Mie orthogonal and parallel component signals through an high-resolution acquisition chain (vertical and temporal sampling of 37.5 m and 1 sec, respectively) has been employed to investigate the high frequency cirrus variability in a recent campaign held at the OHP. The preliminary results of this campaign are also showed

  5. Land surface phenologies and seasonalities using cool earthlight in mid-latitude croplands

    NASA Astrophysics Data System (ADS)

    Alemu, W. G.; Henebry, G. M.

    2013-12-01

    Phenology deals with timing of biotic phenomena and seasonality concerns temporal patterns of abiotic variables. Studies of land surface phenology (LSP) and land surface seasonality (LSS) have long been limited to visible to near infrared (VNIR) wavelengths, despite degradation by atmospheric effects and solar illumination constraints. Enhanced land surface parameters derived from passive microwave data enable improved temporal monitoring of agricultural land surface dynamics compared to the vegetation index data available from VNIR data. LSPs and LSSs in grain growing regions of the Volga River Basin of Russia and the spring wheat belts of the USA and Canada were characterized using AMSR-E enhanced land surface parameters for the period from April through October for 2003 through 2010. Growing degree-days (GDDs) were calculated from AMSR-E air temperature retrievals using both ascending and descending passes with a base of 0 ° C and then accumulated (AGDD) with an annual restart each 1 April. Tracking the AMSR-E parameters as a function of AGDD revealed the expected seasonal pattern of thermal limitation in mid-latitude croplands. Vegetation optical depth (VOD), a microwave analog of a vegetation index, was modeled as a function of AGDD with the resulting fitted convex quadratic models yielding both high coefficients of determination (r2 > 0.90) and phenometrics that could characterize cropland differences between the Russian and North American sites. The AMSR-E data were also able to capture the effects of the 2010 heat wave that devastated grain production in European Russia. These results showed the potential of AMSR-E in monitoring and modeling cropland dynamics.

  6. Hydrologic evaluation of satellite and reanalysis precipitation datasets over a mid-latitude basin

    NASA Astrophysics Data System (ADS)

    Seyyedi, Hojjat; Anagnostou, Emmanouil N.; Beighley, Edward; McCollum, Jeffrey

    2015-10-01

    Using precipitation data from satellite or global reanalysis products to force hydrologic models exhibits complex rainfall error and resolution effects in the simulation of streamflows. This study assesses the error propagation of two global (or near-global) precipitation datasets in terms of flood modeling for a range of basin scales (300-70,000 km2) focusing on multi-year (2002-2011) simulations over a mid-latitude basin (Susquehanna River Basin) in the Northeastern United States. These datasets are the TRMM Multi-satellite Precipitation Analysis 3B42V7 (TRMM3B42V7) research product and the Global Land Data Assimilation (GLDAS) reanalysis system precipitation dataset, which represent 3-hourly rainfall time series at 25-km and hourly time series at 100-km spatial grid resolutions, respectively. The precipitation products, aggregated to a common 3-hourly time resolution, are used to force a distributed hydrologic model (Hillslope River Routing - HRR) for moderate and heavy precipitation events over the basin. The NCEP multi-sensor precipitation analysis (Stage IV) is used as the reference rainfall field for the evaluation of the precipitation and hydrologic simulation errors. Results show that the satellite product exhibits significantly better error statistics compared to the GLDAS. Particularly for the simulated streamflow, GLDAS is shown to have up to 7 (3) times higher mean relative error compared to the corresponding TRMM3B42V7 error metric for moderate (extreme) streamflow values. This significant divergence in the runoff simulation error statistics is attributed to differences between the two precipitation products in terms of the propagation of their error properties from precipitation to simulated streamflow. Significant improvement of the statistical scores (up to 50%) with increasing basin size is shown for the satellite product; this basin scale effect is marginal for the GLDAS product.

  7. Sub-Auroral Ion Drifts as a Source of Mid-Latitude Plasma Density Irregularities

    NASA Astrophysics Data System (ADS)

    Sotnikov, V.; Kim, T.; Mishin, E.; Paraschiv, I.; Rose, D.

    Ionospheric irregularities cause scintillations of electromagnetic signals that can severely affect navigation and transionospheric communication, in particular during space storms. At midlatitudes, such space weather events are caused mainly by subauroral electric field structures (SAID/SAPS) [1, 2]. SAID/SAPS -related shear flows and plasma density troughs point to interchange and Kelvin-Helmholtz type instabilities as a possible source of plasma irregularities. A model of nonlinear development of these instabilities based on the two-fluid hydrodynamic description with inclusion of finite Larmor radius effects will be presented. A numerical code in C language to solve the derived nonlinear equations for analysis of interchange and flow velocity shear instabilities in the ionosphere was developed. This code was used to analyze competition between interchange and Kelvin Helmholtz instabilities in the equatorial region [3]. The high-resolution simulations with continuous density and velocity profiles will be driven by the ambient conditions corresponding to the in situ Defence Military Satellite Program (DMSP) satellite low-resolution data [2] during UHF/GPS L-band subauroral scintillation events. [1] Mishin, E. (2013), Interaction of substorm injections with the subauroral geospace: 1. Multispacecraft observations of SAID, J. Geophys. Res. Space Phys., 118, 5782-5796, doi:10.1002/jgra.50548. [2] Mishin, E., and N. Blaunstein (2008), Irregularities within subauroral polarization stream-related troughs and GPS radio interference at midlatitudes. In: T. Fuller-Rowell et al. (eds), AGU Geophysical Monograph 181, MidLatitude Ionospheric Dynamics and Disturbances, pp. 291-295, doi:10.1029/181GM26, Washington, DC, USA. [3] V. Sotnikov, T. Kim, E. Mishin, T. Genoni, D. Rose, I. Paraschiv, Development of a Flow Velocity Shear Instability in the Presence of Finite Larmor Radius Effects, AGU Fall Meeting, San Francisco, 15 - 19 December, 2014.

  8. Climatological study of ionospheric irregularities over the European mid-latitude sector with GPS

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Warnant, René

    2014-03-01

    High-frequency variability of the ionosphere, or irregularities, constitutes the main threat for real-time precise positioning techniques based on Global Navigation Satellite Systems (GNSS) measurements. Indeed, during periods of enhanced ionospheric variability, GNSS users in the field—who cannot verify the integrity of their measurements—will experience positioning errors that can reach several decimeters, while the nominal accuracy of the technique is cm-level. In the frame of this paper, a climatological analysis of irregularities over the European mid-latitude region is presented. Based on a 10 years GPS dataset over Belgium, the work analyzes the occurrence rate (as a function of the solar cycle, season and local time) as well as the amplitude of ionospheric irregularities observed at a single GPS station. The study covers irregularities either due to space weather events (solar origin) or of terrestrial origin. If space weather irregularities are responsible for the largest effects in terms of ionospheric error, their occurrence rate highly depends on solar activity. Indeed, the occurrence rate of ionospheric irregularities is about 9 % during solar maximum, whereas it drops to about 0 % during medium or low solar activity periods. Medium-scale ionospheric disturbances (MSTIDs) occurring during daytime in autumn/winter are the most recurrent pattern of the time series, with yearly proportions slightly varying with the solar cycle and an amplitude of about 10 % of the TEC background. Another recurrent irregularity type, though less frequent than MSTIDs, is the noise-like variability in TEC observed during summer nighttime, under quiet geomagnetic conditions. These summer nighttime irregularities exhibit amplitudes ranging between 8 and 15 % of the TEC background.

  9. A Comprehensive Assessment of Radio Occultation Ionospheric Measurements at Mid-Latitudes

    NASA Astrophysics Data System (ADS)

    Keele, C.; Brum, C. G. M.; Rodrigues, F. S.; Aponte, N.; Sulzer, M. P.

    2015-12-01

    The GPS radio occultation (RO) has become a widely used technique for global measurements of the ionospheric electron density (Ne). To advance our understanding of the accuracy of the RO profiles at mid latitudes, we performed a comprehensive comparison of RO measurements made by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites and observations of Ne profiles made by the Arecibo Observatory incoherent scatter radar (ISR). COSMIC is formed by six satellites in circular, 800 km altitude low-Earth orbit (LEO) at 72° inclination. The satellites orbit in their own plane, approximately 24° apart in ascending node. The satellites are equipped with dual-frequency GPS receivers capable of making measurements of the total electron content (TEC) along the signal path and, therefore, RO observations. The Arecibo ISR, located at(18.35°N, 66.75°W; ˜28.25°N dip latitude), operates at a frequency of 430 MHz with a maximum bandwidth of about 1 MHz. The large collecting area provided by the 300 m dish antenna combined with high peak power transmitters (2.0-2.5 MW) allows the radar to make accurate Ne measurements throughout the entire ionospheric F-region and topside heights. We analyzed 74 and 89 days of line feed and Gregorian data, respectively, collected between 2006 and 2014. There were 638 RO profiles measured within 10° of latitude and 20° of longitude from Arecibo Observatory and within ±10 minutes of the radar measurements. Preliminary analyses of the observations show patterns in the relationship between densities measured by the Arecibo ISR and densities estimated from the COSMIC ROs. We will present and discuss the behavior of the patterns. We will also present results of a numerical model representing the patterns and discuss the possibility of using this model to improve RO estimates of density profiles.

  10. Hesperian-Amazonian Transition Mid-Latitude Valleys: Markers of a Late Martian Climate Optima?

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey; Howard, A. D.; Parsons, Reid A.; Hobley, D. E.

    2012-01-01

    Recently the inventory of fluvial features that have been dated to the late Hesperian to early Amazonian epoch has increased dramatically, including a reassessment of the ages of the large alluvial fans and deltas (e.g., Eberswalde) to this time period. Mid-latitude Valleys (MLVs) are distinct from the older, more integrated Noachian-Hesperian Valley Networks which are deeply dissected, are generally of much larger spatial extent, and are more degraded. Although some MLVs involve rejuvenation of older Valley Networks, many MLVs are carved into smooth or rolling slopes and intercrater terrain. The MLVs range from a few meters to < 300 m in width, with nearly parallel valley walls and planforms that are locally sinuous. Although the MLVs in Newton and Gorgonum basins extend from the basin rims up to 75 km into the basin interior, most MLVs are shorter and often discontinuous. The occurrence of widespread MLVs suggest the possibility of their formation during one or perhaps more regional to global climatic episodes, possibly due to melting of seasonal to long-term accumulations of snow and ice. Temperatures warm enough to cause extensive melting may have occurred during optimal orbital and obliquity configurations, perhaps in conjunction with intensive volcanism releasing moisture and greenhouse gasses, or as a result of a brief episode of warming from a large impact. The concentration of MLVs to the northern and western basin slopes of Newton and Gorgonum basins suggests a possible aspect control to ice accumulation or melting. MLV activity occurred about at the same time as formation of the major outflow channels. A possible scenario is that delivery of water to the northern lowlands provided, through evaporation and sublimation, water that temporarily accumulated in the mid-southern latitudes as widespread ice deposits whose partial melting formed the MLVs and small, dominantly ice-covered lakes.

  11. Study of the mid-latitude ionospheric response to geomagnetic storms in the European region

    NASA Astrophysics Data System (ADS)

    Berényi, Kitti Alexandra; Barta, Veronika; Kis, Arpad

    2016-07-01

    Geomagnetic storms affect the ionospheric regions of the terrestrial upper atmosphere through different physical and atmospheric processes. The phenomena that can be regarded as a result of these processes, generally is named as "ionospheric storm". The processes depend on altitude, segment of the day, the geomagnetic latitude and longitude, strength of solar activity and the type of the geomagnetic storm. We examine the data of ground-based radio wave ionosphere sounding measurements of European ionospheric stations (mainly the data of Nagycenk Geophysical Observatory) in order to determine how and to what extent a geomagnetic disturbance of a certain strength affects the mid-latitude ionospheric regions in winter and in summer. For our analysis we used disturbed time periods between November 2012 and June 2015. Our results show significant changing of the ionospheric F2 layer parameters on strongly disturbed days compared to quiet ones. We show that the critical frequencies (foF2) increase compared to their quiet day value when the ionospheric storm was positive. On the other hand, the critical frequencies become lower, when the storm was negative. In our analysis we determined the magnitude of these changes on the chosen days. For a more complete analysis we compare also the evolution of the F2 layer parameters of the European ionosonde stations on a North-South geographic longitude during a full storm duration. The results present the evolution of an ionospheric storm over a geographic meridian. Furthermore, we compared the two type of geomagnetic storms, namely the CME caused geomagnetic storm - the so-called Sudden impulse (Si) storms- and the HSS (High Speed Solar Wind Streams) caused geomagnetic storms -the so-called Gradual storms (Gs)- impact on the ionospheric F2-layer (foF2 parameter). The results show a significant difference between the effect of Si and of the Gs storms on the ionospheric F2-layer.

  12. A statistical characterization of local mid-latitude total electron content

    SciTech Connect

    Gail, W.B.; Prag, A.B.; Coco, D.S.; Coker, C.

    1993-09-01

    The integrated line-of-slight electron density within the ionosphere, known as the total electron content (TEC), is commonly used to quantify ionospheric propagation effects. In order to extrapolate single-point measurements of TEC to other locations and times, some characterization of the TEC spatiotemporal variation must be available. Using a four-channel receiver tracking coded signals from the NAVSTAR Global Positioning System satellites, estimates of both the mean variation and correlation coefficient have been made for the approximately 1200-km or 1-hour local time radius ionospheric region within view of a mid-latitude station. Results were obtained for morning and midday over a 4-week period near the autumnal equinox in 1989. The derived mean variation was found to be well characterized by linear functions of the local time and latitude separation between the ground site and the ionospheric penetration point of the signal. The correlation coefficient during midday was found to decrease linearly with latitude, longitude, and time separation, with values of about 0.91 for a 1000-km separation and 0.98 for a 1-hour separation. During morning hours the longitude and time coefficients were similar to the midday values, but the latitude coefficient was found to have a nonlinear dependence, with values as small as 0.70. The combined results suggest that the decorrelation is due primarily to longer term TEC fluctuation, such as day-to-day variation in the TEC spatial dependence, rather than to transient effects such as traveling ionospheric disturbances. The analysis provides a spatiotemporal characterization of TEC that can be used to extrapolate TEC values from single-point measurements. 13 refs., 8 figs.

  13. Consequences of declining snow accumulation for water balance of mid-latitude dry regions

    USGS Publications Warehouse

    Schlaepfer, Daniel R.; Lauenroth, William K.; Bradford, John B.

    2012-01-01

    Widespread documentation of positive winter temperature anomalies, declining snowpack and earlier snow melt in the Northern Hemisphere have raised concerns about the consequences for regional water resources as well as wildfire. A topic that has not been addressed with respect to declining snowpack is effects on ecosystem water balance. Changes in water balance dynamics will be particularly pronounced at low elevations of mid-latitude dry regions because these areas will be the first to be affected by declining snow as a result of rising temperatures. As a model system, we used simulation experiments to investigate big sagebrush ecosystems that dominate a large fraction of the semiarid western United States. Our results suggest that effects on future ecosystem water balance will increase along a climatic gradient from dry, warm and snow-poor to wet, cold and snow-rich. Beyond a threshold within this climatic gradient, predicted consequences for vegetation switched from no change to increasing transpiration. Responses were sensitive to uncertainties in climatic prediction; particularly, a shift of precipitation to the colder season could reduce impacts of a warmer and snow-poorer future, depending on the degree to which ecosystem phenology tracks precipitation changes. Our results suggest that big sagebrush and other similar semiarid ecosystems could decrease in viability or disappear in dry to medium areas and likely increase only in the snow-richest areas, i.e. higher elevations and higher latitudes. Unlike cold locations at high elevations or in the arctic, ecosystems at low elevations respond in a different and complex way to future conditions because of opposing effects of increasing water-limitation and a longer snow-free season. Outcomes of such nonlinear interactions for future ecosystems will likely include changes in plant composition and productivity, dynamics of water balance, and availability of water resources.

  14. Study of TEC variations induced by powerful HF-heating in mid-latitude dayside ionosphere

    NASA Astrophysics Data System (ADS)

    Kunitsyn, Viacheslav; Padokhin, Artem; Frolov, Vladimir L.; Komrakov, G. P.

    In this work we report on the experimental evidences for the influence of the heating-induced electron density perturbations in the dayside mid-latitude ionosphere on the GNSS signals. We analyze the spectral characteristics of the observed perturbations for different heating regimes. The experiments were carried out at the Sura heating facility (Radio Physical Research Insti-tute, N. Novgorod). The inospheric heating was scheduled in such a way to provide crossing of the heated area by the ionospheric penetration points of several GPS-satellites during the ses-sions of heating with different time modulations of the effective radiated power of the O-mode pumping wave. Based on the studying of the variations in TEC (total electron content propor-tional to the reduced phases of the navigational signals), we show that in case of square-wave modulation of the effective radiated power (with periods of 1, 6, 10, and 15 minutes) of the heating wave, perturbations with periods of the main modulation of heating and its harmonics appear in the wavelet spectrum of TEC variations. Examples are presented of identification of the heating-induced variations in TEC, including the determination of amplitudes and time characteristics of these variations and estimation of electron density perturbations at the height of the heating wave reflection. The work was supported by the Russian Foundation for Basic Research (grants nos. 08-02-00171, 08-05-00676 and 10-05-01126). The authors are grateful to the staff of the Sura facility for their help in the experiments.

  15. Climate change in the mid-latitudes of North America during the marine isotope stage 11

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Rowe, H. D.; Wang, X.; Burnham, T. G.

    2008-12-01

    Orbital configurations during the Marine Isotope Stage (MIS) 11 are similar to those of today's interglacial period. Study on the climate of MIS 11 may provide information on the type and magnitude of modern climate variability that could be expected under non-anthropogenic conditions. We have obtained a high-resolution calcite speleothem record from Morril's Cave (aka Worley's Cave), eastern Tennessee. The chronology was determined by U-Th dates and stable isotopic analyses were done with a sampling interval of 0.5 mm. The sample was apparently deposited under equilibrium conditions. We thus interpret its stable isotope records, spanning continuously from ~400 ka to ~342 ka, in terms of climate and environmental changes at this mid-latitude location. The carbon isotope profile shows a step-wise increase of δ13C, shifting from approximately -12‰ in the middle of MIS 11 to -8‰ near the end of MIS 11 and then to -4‰ in MIS 10. This step-wise increase may indicate a wetting to drying climate shift near the end of MIS 11. In response to the climate change, it also suggests that C3 plants probably dominated in eastern Tennessee during MIS 11, while a major transition from C3 plants to C4 plants occurred in this region when the interglacial period terminated. The oxygen isotopic value gradually increases through the record, with oscillations following the local summer insolation. The record is consistent with marine and ice core records, but also featured with prominent millennial-scale variations, which suggests climate instability during the climate transition period.

  16. HiRISE Observations of Martian Mid-Latitude Fractured Mounds

    NASA Astrophysics Data System (ADS)

    Dundas, C. M.; Mellon, M. T.; McEwen, A. S.; Lefort, A.; Keszthelyi, L. P.; Thomas, N.; HiRISE Team

    2007-12-01

    The High Resolution Imaging Science Experiment (HiRISE) camera has now returned thousands of images of the Martian surface with pixel scale as small as 26 cm/pixel. These have revealed fractured mounds up to several hundred meters in diameter, bearing some morphological resemblance to terrestrial pingos (ice-cored hills formed by freezing groundwater). Pingos on Mars would be valuable indicators of ground ice and have been suggested at a number of sites, but in several cases reexamination has supported different origins. Some differences do exist between the fractured mounds and terrestrial pingos. In several instances, the mounds have roughly trapezoidal topographic profiles with flat, fractured summits. Other morphologies are also seen; we report on the range of morphologies observed so far by HiRISE and similarities and differences with pingos on Earth. The fractured mounds observed to date generally appear in the mid-latitudes, at a range of longitudes. Mars Orbiter Camera (MOC) images of flat-topped mounds in Utopia Planitia (including some previously proposed pingos) show a similar latitudinal dependence, generally occurring between 35-45° N. This supports a ground- ice related origin, particularly since the latitude range is close to the peak-abundance latitude of some other features likely related to water or ice, such as gullies. It is still uncertain whether the formation mechanism of the fractured mounds is the same as terrestrial pingos in detail. We discuss the distribution, properties and settings of fractured mounds observed planet-wide by HiRISE.

  17. An experimental manipulation of methane emissions in a mid-latitude prairie wetland

    SciTech Connect

    Valentine, D.W.; Pulliam, W.M.; Holland, E.A.

    1995-06-01

    Methane (CH{sub 4}) emissions from natural wetlands comprise about a quarter of the total annual atmospheric CH{sub 4} budget. Fluxes of CH{sub 4} from mid- latitude wetlands have received less attention than those from northern latitudes because of their relatively small surface areas and low carbon stores, and fluxes in prairie wetlands have never been measured. In order to do so, we developed a large (3m tall with 1m{sup 2} area), temperature controlled static chamber to assess fluxes of CH{sub 4} and CO{sub 2} in wetlands dominated by tall (3m) emergent plants such as Phragmites, Scirpus, and Typha. Based on previous work indicating that CH{sub 4} production and emission is limited by substrate quantity and quality, we set up a replicated, modified latin square design field experiment in which we added low quality C (C, as wheat straw) and high quality C (C+N, as wheat straw plus urea) to evaluate their importance in controlling CH{sub 4} emissions In Ballard`s Marsh In northern Nebraska. We measured very high CH{sub 4} emission rates (over 40 mg m{sup -2} h{sup -1}) in control plots, while disturbance associated with treatment plot establishment decreased emissions by half. Relative to the disturbance controls, the C addition lowered emissions slightly, the C+N additions increased emissions slightly, and both additions increased the proportion of CH{sub 4} emitted through bubbles. Emission rates of CH{sub 4} therefore appeared to be constrained more by N availability or substrate quality than by substrate quantity.

  18. Evidence linking Arctic amplification to fewer mid-latitude cold extremes

    NASA Astrophysics Data System (ADS)

    Screen, James

    2015-04-01

    In spite of mean climate warming, an ostensibly large number of high-impact cold extremes have occurred in the Northern Hemisphere mid-latitudes over the past decade. One explanation is that Arctic amplification -- the greater warming of the Arctic compared with lower latitudes associated with diminishing sea ice and snow cover -- is altering the polar jet stream and increasing temperature variability. Here we present evidence to the contrary, that in fact, temperature variability has decreased in the recent past and furthermore, that this decline is robustly projected to continue in the future. Observational evidence suggests that subseasonal cold-season temperature variability has significantly decreased over the mid- to high-latitude Northern Hemisphere in recent decades. This is partly because northerly winds and associated cold days are warming more rapidly than southerly winds and warm days, and so Arctic amplification acts to reduce subseasonal temperature variance. Similar changes are robustly projected by the CMIP5 models in response to increasing greenhouse gas concentrations, in AGCM simulations forced by solely Arctic sea ice loss, and in highly-idealised GCM experiments. Using as an illustrative example, the cold extremes experienced over North America in early January 2014, we show that projected Arctic sea ice loss alone reduces the odds of such an event by one quarter to one third by the mid twenty-first century, and to zero (or near-zero) by the late twenty-first century. Both projected mean warming and a decrease in winter temperature variability contribute to the reduced risk of daily cold extremes.

  19. Hydrological indications of aeolian salts in mid-latitude deserts of northwestern China

    NASA Astrophysics Data System (ADS)

    Zhu, Bing-Qi

    2016-06-01

    Large sandy deserts in middle latitude of northwestern China were studied on salt variations in modern and ancient aeolian sediments, aiming to explore their hydrological indications at the present and past. Globally, sulphate is rich in arid to semi-arid deserts, including the aeolian loess sediments in China and soils in low-latitude deserts, but is less common in the aeolian sediments from the mid-latitude deserts in this study. The compositional differences between aeolian salts and local natural waters is evident, indicating the chemistry of aeolian salts and the associated parent brines may be significantly different than that predicted for hydrologically closed systems. The formation of aeolian salts in the studied deserts is strongly controlled by earth surface processes in a large scale but not in a local scale. Vertical changes in facies and salinities are abrupt in the studied palaeo-aeolian sediment samples, which were interbedded by lacustrine/fluvial sediments with OSL and 14C ages ranging between 40 and 2 ka BP, reflecting rapid high-amplitude changes in hydrological settings during late Pleistocene to later Holocene in these ancient playa systems. A great difference in salt composition between aeolian and lacustrine sediments suggests that the inorganic salt is a latent geoproxy in revealing local hydrological variations and climate change in the desert areas. But the environmental indications could be amphibolous for the sedimentary sequences with dual/multiple depositional end-members; under this situation an increase in sequence salinity does not always represent an enhanced environmental aridity. Ancient playas are arid or humid at the same time based on several sporadic records is not a valid approach to correlation of salt deposits in adjacent saline playa basin in the studied areas. Effects of earth surface processes including erosion, deposition and other processes on sediment properties will bias the hydrological implications of sediment

  20. Mid-latitude storm track variability and its influence on atmospheric composition

    NASA Astrophysics Data System (ADS)

    Knowland, K. E.; Doherty, R. M.; Hodges, K.

    2013-12-01

    Using the storm tracking algorithm, TRACK (Hodges, 1994, 1995, 1999), we have studied the behaviour of storm tracks in the North Atlantic basin, using 850-hPa relative vorticity from the ERA-Interim Re-analysis (Dee et al., 2011). We have correlated surface ozone measurements at rural coastal sites in Europe to the storm track data to explore the role mid-latitude cyclones and their transport of pollutants play in determining surface air quality in Western Europe. To further investigate this relationship, we have used the Monitoring Atmospheric Composition Climate (MACC) Re-analysis dataset (Inness et al., 2013) in TRACK. The MACC Re-analysis is a 10-year dataset which couples a chemistry transport model (Mozart-3; Stein 2009, 2012) to an extended version of the European Centre for Medium-Range Weather Forecasts' (ECMWF) Integrated Forecast System (IFS). Storm tracks in the MACC Re-analysis compare well to the storm tracks using the ERA-Interim Re-analysis for the same 10-year period, as both are based on ECMWF IFSs. We also compare surface ozone values from MACC to surface ozone measurements previously studied. Using TRACK, we follow ozone (O3) and carbon monoxide (CO) through the life cycle of storms from North America to Western Europe. Along the storm tracks, we examine the distribution of CO and O3 within 6 degrees of the center of each storm and vertically at different pressure levels in the troposphere. We hope to better understand the mechanisms with which pollution is vented from the boundary layer to the free troposphere, as well as transport of pollutants to rural areas. Our hope is to give policy makers more detailed information on how climate variability associated with storm tracks between 1979-2013 may affect air quality in Northeast USA and Western Europe.

  1. TEC disturbances during major Sudden Stratospheric Warmings in the mid-latitude ionosphere.

    NASA Astrophysics Data System (ADS)

    Polyakova, Anna; Voeykov, Sergey; Chernigovskaya, Marina; Perevalova, Natalia

    Using total electron content (TEC) global ionospheric maps, dual-frequency GPS receivers TEC data and MLS (Microwave Limb Sounder, EOS Aura) atmospheric temperature data the ionospheric disturbances during the strong sudden stratospheric warmings (SSWs) of 2008/2009 and 2012/2013 winters are investigated in Russia's Asia region. It is established that during the SSW maximum the midday TEC decrease and the night/morning TEC increase compared to quiet days are observed in the mid-latitude ionosphere. As a result it caused the decrease of the diurnal TEC variations amplitude of about two times in comparison with the undisturbed level. The analysis of TEC deviations from the background level during the SSWs has shown that deviations dynamics vary depending on the observation point position. Negative deviations of TEC are registered in the ionosphere above the region of maximum stratosphere heating (the region of the stratospheric circulation change) as well as above the anticyclone. On the contrary, TEC values increase compared to the quiet day's values above the stratosphere cyclone. It is shown that during maximum phase of a warming, and within several days after it the amplification of wave TEC variations intensity with periods of up to 60 min is registered in ionosphere. The indicated effects may be attributed to the vertical transfer of molecular gas from a stratospheric heating region to the thermosphere as well as to the increase in activity of planetary and gravity waves which is usually observed during strong SSWs. The study is supported by the RF President Grant of Public Support for RF Leading Scientific Schools (NSh-2942.2014.5), the RF President Grant No. MK-3771.2012.5 and RFBR Grant No. 12-05-00865_а.

  2. First Tomographic Observations of the Mid-latitude Summer Nighttime Anomaly (MSNA) over Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, M.; Thampi, S.; Lin, C.; Liu, H.

    2009-12-01

    Recently, a chain of digital beacon receivers has been established over Japan, mainly for the tomographic imaging of the ionosphere. These receivers are installed at Shionomisaki (33.45°N, 135.8°E), Shigaraki (34.85°N, 136.1°E) and Fukui (36.06°N,136°E), which continuously track the Low Earth Orbiting Satellites (LEOS), and the simultaneous line-of-sight relative Total Electron Content (TEC) data are used for tomographic reconstruction. In the images obtained during July 2008, it is seen that the nighttime electron densities exceed the daytime values on almost all days over latitudes >33-34°N. On several days, these northern latitudes show enhanced electron densities compared to the low-latitude region during nighttime. These are the prominent features of the ‘Mid-latitude Summer Nighttime Anomaly (MSNA)’ that is recently observed in the northern hemisphere and is considered similar to the nighttime Weddell Sea Anomaly (WSA). This is the first study of the MSNA using tomographic technique, and found its significant day-to-day variability. The Formosat3/COSMIC occultation measurements, ionosonde data from Wakkanai (45.4°N, 141.7° E), ground-based GPS TEC observations using the GEONET, and CHAMP in situ electron density measurements are also used to confirm the presence of MSNA over this region and to examine its variability. It is seen that in general, during the local summer period, electron density over the northern latitudes is highest at ~2000-2100 LT and the latitudinal enhancement in electron density also begins to appear around the same time, which continues to exist even at later hours. This feature is explained by considering the neutral wind effect in the geomagnetic frame.

  3. The 17O Excess of Stratospheric Nitrous Oxide in Mid-latitude Air

    NASA Astrophysics Data System (ADS)

    Ridley, A.; Kaiser, J.; Laube, J. C.

    2015-12-01

    Tropospheric nitrous oxide (N2O) has a 17O excess of (0.9±0.1) ‰ relative to Vienna Standard Mean Ocean Water (VSMOW). The origin of this 17O excess is under debate: tropospheric and stratospheric in-situ sources as well as isotope fractionation and isotope exchange during biological N2O production are all considered to make a contribution, as might the stratospheric photolysis sink. To constrain the relative contributions of the different processes and to improve our understanding of the underlying atmospheric chemical and microbial processes, more measurements are required. We have measured the 17O excess of stratospheric samples from mid-latitudes, from altitudes between 8 and 26 km. N2O was extracted cryogenically, separated from CO2 and CHF3 by a PoraPlotQ pre-column and then thermally decomposed in a gold furnace at 900 ºC. The precision for the 17O excess of a single 5 nmol N2O aliquot was ±0.3 ‰. This dataset significantly enhances the limited range of oxygen triple isotope measurements in mostly lower stratospheric samples reported by Cliff et al. (1999). The average 17O excess of the stratospheric samples analysed was (-0.19 ±0.46) ‰ relative to tropospheric N2O. Since the 17O excess of the first measurements of stratospheric air is not significantly different to that in tropospheric air, this data suggests that the 17O excess is not of stratospheric origin. This confirms the idea that the origin of the 17O excess is not due to either stratospheric photolysis or reaction with electronically excited oxygen atoms. It suggests that the origin of the 17O excess may therefore be related to tropospheric in situ sources, e.g. NH2+NO2 as proposed by Röckmann et al., 2001, or to microbial nitrogen conversion reactions as suggested by Kaiser and Röckmann, 2005.

  4. Coherence of longterm stratospheric ozone time series for the study of ozone recovery in the northern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Nair, Prijitha J.; Godin-Beekmann, Sophie; Pazmino, Andrea

    2010-05-01

    Since mid-to late 1980s decreasing amounts of ozone concentration has been observed in northern mid-latitudes mainly due to the ozone depleting chlorofluorocarbon loading in the stratosphere. Recent works indicate the stabilization of ozone loss in the mid-latitudes, in the upper stratosphere in particular. In order to further investigate the evolution of ozone in the mid-latitudes, a coherent dataset is required. As a first step, we diagnose the long term evolution of ozone at Observatoire de Haute Provence (OHP - 43.93°N, 5.71°E), one of the northern mid-latitude stations. In this study, we present the inter comparison of ozone measurements from OHP LIDAR with collocated SBUV, SAGEII, HALOE, MLS and GOMOS satellite observations as well as the ground based Ozonesondes and Umkehr measurements. A detailed statistical study on the relative differences of the compared measurements is performed to check any specific drifts with time. In addition, the seasonal and annual averages of the relative deviations are also checked to quantify agreement among the data. On average, all instruments show their best agreement with LIDAR between 20 and 40 km, where the differences are within 5%. The agreement with SAGEII measurements are remarkably good since it falls within 1% at 17-41 km. A similar result is also found from the Ozonesondes comparison at 22-31 km. Most comparisons exhibit slightly larger deviations below 20 and above 42 km, of about 10%. The LIDAR masurements are also compared to Umkehr measurements by converting its ozone number density to Dobson units for each Umkehr layer. The analysis reveals a negative bias in Umkehr data within -10% except at layer 6 (around 30 km).

  5. Coupling between meridional wind nightly behavior and mid-latitude oxygen red 630.0 nm line intensity predawn enhancement

    NASA Astrophysics Data System (ADS)

    Didebulidze, Goderdzi; Gudadze, Nikoloz; Lomidze, Levan; Todua, Maya

    The coupling between meridional wind nightly behavior and winter time predawn enhancement (PE) in the mid-latitude oxygen red 630.0 nm line intensity at Abastumani (41.75 N, 42.82 E) is investigated. It is shown that red line intensity PE, which was considered as a result of increase in the photoelectron flux from magnetically conjugate regions, also can be caused by increase in the mid-latitude northward wind (or decrease in the southward one). In this case the observed mean monthly/seasonal nightly behavior of the red line intensity can be verified by the ionosphere F2 layer parameters observed at Tbilisi ionosphere station (41.65 N, 44.75 E -neighboring Abastumani) and the meridional component of the thermosphere wind given by Horizontal Wind Model 93 (HWM93). The estimation shows that the mean monthly/seasonal northward wind for 1957-1993 and the observed F2 layer peak density NmF2 and height hmF2 can be responsible for the PE in the red line intensity (LT 03 h-05 h), which is also noticeable in early spring and later fall. The observed seasonal midnight negative trend in the red line intensity is accompanied by its wintertime positive trend before morning twilight, which includes the PE and can be explained by long-term increase in the northward wind velocity. In these cases, the increase in the mid-latitude northward wind or decrease in the southward one following to the equatorial midnight temperature maximum (MTM) or similar phenomena could be important in the observed mid-latitude PE of the red line intensity.

  6. Horizontal Shapes of Daytime Mid-latitude Sporadic-E Imaged by GPS Total Electron Content Observations in Japan

    NASA Astrophysics Data System (ADS)

    Maeda, Jun; Heki, Kosuke

    2016-04-01

    Sporadic-E (Es) is a thin densely ionized plasma patch whose occurrence is highly unpredictable. Since the discovery of Es, its two-dimensional (2-D) horizontal shape has long remained ambiguous due to the lack of appropriate observation instruments. Here in our study, 2-D imaging of mid-latitude sporadic-E (Es) is performed by using a dense array of Global Navigation Satellite System (GNSS) receivers in Japan. We used Global Positioning System (GPS) satellites and the densely distributed GNSS receiver network to conduct GPS total electron content (TEC) observations and mapped positive TEC anomalies caused by Es. We analyzed over 70 Es occurrences over Japan to reveal morphological characteristics of daytime mid-latitude Es. Their horizontal shapes are characterized by frontal structure typically elongated in the east-west (E-W) direction by ~100 km with the north-south (N-S) width of 10-30 km. Frontal structures are often found to include smaller-scale structures, which are quasi-periodically located plasma patches. These small-scale patches indicate the operation of shear instability, e.g., Kelvin-Helmholtz (K-H) instability, in the horizontal structuring of daytime mid-latitude Es. In addition, frontal structures are observed to migrate mainly northward in the morning and southward in the afternoon with speeds of 30-100 m/s, which may reflect the directions and velocities of neutral winds controlled by the atmospheric tides.

  7. Titan's mid-latitude surface regions with Cassini VIMS and SAR

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Drossart, Pierre; Brown, Robert H.; Sohl, Frank; Stephan, Katrin; Jaumann, Ralf; Rodriguez, Sebastien; Bratsolis, Emmanuel; Schmitt, Bernard; Le Gall, Alice; Lopes, Rosaly; Malaska, Michael; Janssen, Michael; Maltagliati, Luca; Villanueva, Edward; Matsoukas, Christos

    2016-07-01

    We investigate the surface of Saturn's moon Titan by means of two Cassini instruments used in synergy. We apply a radiative transfer code to VIMS hyperspectral data to correct the strong atmospheric contribution and extract information on surface composition (Hirtzig et al. 2014; Solomonidou et al. 2014; 2015). We then put this in the context of terrain morphology by use of denoised Synthetic Aperture Radar (SAR) images (Bratsolis et al. 2012). We examine here the mid-latitude zones extending from 50ºN to 50ºS, which includes key geological features identified in Lopes et al. (2010, 2015) and Malaska et al. (2015): mountains, plains, labyrinths, dune fields, and possible cryovolcanic and/or evaporitic deposits. We find that many of the different units show compositional variations while units of significant geomorphological differences seem to consist of very similar material mixtures. The Huygens landing site and the candidate evaporitic regions are compositionally similar to the variable plains. We also find that temporal variations of surface albedo exist for two of the candidate cryovolcanic regions Tui Regio and Sotra Patera, suggesting the presence of surface activity, while a number of other regions such as Hotei Regio and the undifferentiated plains remain unchanged (Solomonidou et al. 2015). The surface albedo variations, together with the presence of volcanic-like morphological features, suggest that the active regions are possibly related to the deep interior, possibly via cryovolcanic processes (with important implications for the satellite's astrobiological potential) as also indicated by recent interior structure models of Titan and corresponding calculations of the spatial pattern of maximum tidal stresses (Sohl et al. 2014). In previous studies (Lopes et al. 2015; Solomonidou et al. 2015) we showed that a variety of surface processes could be linked to the formation of the various geomorphological units (aeolian, fluvial, sedimentary, lacustrine

  8. Absence of seasonal patterns in MBT-CBT indices in mid-latitude soils

    NASA Astrophysics Data System (ADS)

    Weijers, Johan W. H.; Bernhardt, Beth; Peterse, Francien; Werne, Josef P.; Dungait, Jennifer A. J.; Schouten, Stefan; Sinninghe Damsté, Jaap S.

    2011-06-01

    The degree of methylation and cyclization of bacteria-derived branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in soils depends on temperature and soil pH. Expressed in the methylation index of branched tetraethers (MBT) and cyclization ratio of branched tetraethers (CBT), these relationships are used to reconstruct past annual mean air temperature (MAT) based on the distribution of branched GDGTs in ancient sediments; the MBT-CBT proxy. Although it was shown that the best correlation of this proxy is with annual MAT, it remains unknown whether a seasonal bias in temperature reconstructions could occur, such as towards a seasonal period of 'optimal growth' of the, as yet, unidentified soil bacteria which produce branched GDGTs. To investigate this possibility, soils were sampled from eight different plots in the USA (Minnesota and Ohio), The Netherlands (Texel) and the UK (Devon) in time series over 1 year and analyzed for their branched GDGT content. Further analyses of the branched GDGTs present as core lipids (CLs; the presumed fossil pool) and intact polar lipids (IPLs; the presumed extant pool) were undertaken for two of the investigated soil plots. The amount of IPL-derived branched GDGTs is low relative to the branched GDGT CLs, i.e. only 6-9% of the total branched GDGT pool. In all soils, no clear change was apparent in the distribution of branched GDGT lipids (either core or IPL-derived) with seasonal temperature change; the MBT-CBT temperature proxy gave similar temperature estimates year-round, which generally matched the mean annual soil temperature. In addition to a lack of coherent changes in relative distributions, concentrations of the branched GDGTs did not show clear changes over the seasons. For IPL-derived GDGTs these results suggest that their turnover time in soils is in the order of 1 year or more. Thus, our study does not provide evidence for seasonal effects on the distribution of branched GDGTs in soils, at least at mid-latitudes

  9. Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill

    NASA Astrophysics Data System (ADS)

    Foster, J. C.; Holt, J. M.; Lanzerotti, L. J.

    2000-01-01

    Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor sim2) near the 320 km Shuttle orbital altitude persisted for sim35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of sim6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a sim80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar sim80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (sim95 s period) accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID) launched by the enhanced auroral activity. The most reasonable conclusion is that

  10. Titan’s mid-latitude surface regions with Cassini VIMS and RADAR

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Lopes, Rosaly M. C.; Coustenis, Athena; Malaska, Michael; Rodriguez, Sebastien; Maltagliati, Luca; Drossart, Pierre; Janssen, Michael; Lawrence, Kenneth; Jaumann, Ralf; Sohl, Frank; Stephan, Katrin; Brown, Robert H.; Bratsolis, Emmanuel; Matsoukas, Christos

    2015-11-01

    The Cassini-Huygens mission instruments have revealed Titan to have a complex and dynamic atmosphere and surface. Data from the remote sensing instruments have shown the presence of diverse surface terrains in terms of morphology and composition, suggesting both exogenic and endogenic processes [1]. We define both the surface and atmospheric contributions in the VIMS spectro-imaging data by use of a radiative transfer code in the near-IR range [2]. To complement this dataset, the Cassini RADAR instrument provides additional information on the surface morphology, from which valuable geological interpretations can be obtained [3]. We examine the origin of key Titan terrains, covering the mid-latitude zones extending from 50ºN to 50ºS. The different geological terrains we investigate include: mountains, plains, labyrinths, craters, dune fields, and possible cryovolcanic and/or evaporite features. We have found that the labyrinth terrains and the undifferentiated plains seem to consist of a very similar if not the same material, while the different types of plains show compositional variations [3]. The processes most likely linked to their formation are aeolian, fluvial, sedimentary, lacustrine, in addition to the deposition of atmospheric products though the process of photolysis and sedimentation of organics. We show that temporal variations of surface albedo exist for two of the candidate cryovolcanic regions. The surface albedo variations together with the presence of volcanic-like morphological features suggest that the active regions are possibly related to the deep interior, possibly via cryovolcanism processes (with important implications for the satellite’s astrobiological potential) as also indicated by new interior structure models of Titan and corresponding calculations of the spatial pattern of maximum tidal stresses [4]. However, an explanation attributed to exogenic processes is also possible [5]. We will report on results from our most recent

  11. Hydrological extremes in the Aksu-Tarim River Basin: Mid-latitude dynamics

    NASA Astrophysics Data System (ADS)

    Borth, Hartmut; Tao, Hui; Fraedrich, Klaus; Schneidereit, Andrea; Zhu, Xiuhua

    2016-04-01

    Analyses of precipitation (1961-2010) from 39 meteorological stations in the Tarim River Basin revealed a trend from dryer towards wetter conditions induced by an increase of the number of wet extremes. A first (1961-1986) and second (1987-2010) period are the basis for a dynamical analysis of changing drought and wetness extremes which are closely related to cyclonic activity over the European continent and circulation anomalies in the Northern Hemisphere mid-latitudes. Wave train, cyclone tracks, water flux and potential vorticity (PV) front analysis of the wet and dry months show the following result: (1) The extreme wet and dry cases in winter and summer are characterized by distinguished wave train patterns upstream of the Tarim River Basin. All wave trains originate in the Atlantic-European sector pointing towards wave train dynamics as one possible mechanism underlying the connection patterns observed. (2) The selected extreme cases show that exceptional precipitation events can be connected to characteristic cyclone tracks and a PV front in the upper troposphere even if cyclone tracks never cross the Tarim Basin. Extremely wet winters are characterized by cyclone tracks close to the western and northern boundary of the Tarim Basin whereas, during extremely dry winters, such cyclone tracks are absent. Wet summers are characterized by long-lived cyclonic anomalies at the north western corner of the Tarim River Basin [see also (3)]. During dry summers such anomalies are absent. (3) On a more local level the hydrological extreme events are linked to special dynamical structures of the upper tropospheric PV front. In winter strong (extreme) precipitation is connected to a strong non-linear wave development or a wave-breaking event over the Tarim River Basin. Together with non-linear wave development moisture and precipitation areas are advected towards the Tarim River Basin. In dry winters the upper tropospheric PV front is much more zonally oriented and wave

  12. Instabilities in the relation between European Weather Types and mid-latitude circulation in the Atlantic

    NASA Astrophysics Data System (ADS)

    Alvarez Castro, Maria del Carmen; Gallego, David; Trigo, Ricardo M.; García-Herrera, Ricardo; Ribera, Pedro

    2015-04-01

    Recently, a new instrumental index (Westerly Index or "WI") measuring the frequency of the westerlies over the English Channel has been developed for the period 1685-1750 (Wheeler et al. 2009) and further extended to the present (Barriopedro et al. 2014). This index holds a climatic signal similar to the North Atlantic Oscillation (NAO) in the temperature and precipitation over large areas of Europe. Nevertheless we are confident that the WI offers two major advantages: first the WI signatures are not restricted to the winter being significant during the entire year and second, the WI does not rely on proxy data and, as such, it is less prone to the uncertainties associated to the calibration process of the NAO reconstructions. During the last decades, regional mid-latitude circulation has also been quantified objectively through the widespread use of so-called Weather Types (WT). WT are used to identify and classify the different patterns of Sea Level Pressure configurations originating particular weather in a given area. In consequence, WT over most Western Europe should be closely related to atmospheric circulation indexes such as the WI. Here we adopted a similar WT classification of the classical WTs developed empirically by Hubert Lamb for the UK and automated by Jones et al. (1993) but centered at the English Channel latitudinal band to be compatible with the window used to define the WI (Wheeler et al., 2009). In this work we compare the long-term (1850-2003) monthly values of WI with the corresponding monthly frequency of directional weather types in the WI area. As expected, we found significant positive (negative) correlation values with WTs dominated by a westerly (easterly) component but interestingly, some quasi periodic intervals of lack of correlation have been found, suggesting an oscillating behaviour on the lack of stationarity between the large-scale north Atlantic circulation and local weather types. Wheeler, D.; García-Herrera, R.; Wilkinson

  13. Simple, novel approaches to investigating biophysical characteristics of individual mid-latitude deciduous trees

    NASA Astrophysics Data System (ADS)

    Kalibo, Humphrey Wafula

    of the twelve trees, while SR worked well for low-foliage trees. The amount of foliage cover affected the accuracy with which the VIs estimated the VF of the various trees. Overall, this study has suggested a simple methodology that combines two distinct sets of data of different spatial scales to examine a vegetation biophysical parameter over a growing season. The findings provide preliminary insights into how individual mid-latitude deciduous trees partition incoming solar radiation at each phenological stage and over the growing season. The research should stimulate more robust inquiry into the use of both remote and in situ sensing tools in the study of vegetation biophysical parameters.

  14. Sub-lithospheric small scale convection - a process for continental collision magmatism

    NASA Astrophysics Data System (ADS)

    Kaislaniemi, Lars; van Hunen, Jeroen; Allen, Mark; Neill, Iain

    2014-05-01

    We have studied the role of sub-lithospheric small scale convection in the generation of collision zone magmatism, using combined geodynamic-petrological models. We compare the results with the collisional magmatism of the Turkish-Iranian plateau, where a number of randomly (in both space and time) distributed volcanic centres on has been produced by the active Arabia-Eurasia collision since initial plate collision at ~27-35 Ma. These volcanic rocks have a highly variable geochemical signature, but commonly point to a lithospheric mantle or asthenospheric source. Major and trace element characteristics span the range from OIB-like, to calc-alkali, shoshonitic and even ultrapotassic. We suggest these spatially, temporally and chemically diverse patterns of volcanism are caused by sub-lithospheric small scale convection (SSC), manifested as small (50 to 300 km) convection cells at the lithosphere-asthenosphere boundary and dripping of the lithospheric mantle into the asthenosphere. SSC is activated by the increased amount of water in the lithospheric and asthenospheric mantle and its rheological weakening effect. The increase in water content is caused by the subduction prior to the collision and/or continental subduction during collision. The mantle convection code CitCom, together with a parameterized melting model, is used to model the SSC process. We relate the water content to the mantle solidus and viscosity, and the amount of depletion to the viscosity and buoyancy of the mantle material. We measure the amount of magmatism taking place by assuming direct and instantaneous percolation of mantle melts to the surface. We mimic the dislocation creep mechanism with a diffusion creep mechanism using low activation energy--either one is needed for the SSC to take place under realistic conditions. Results show that SSC is able to produce small degrees (0-2 %) of melting of the mantle through dripping lithosphere, decompression melting, erosion of the overlying

  15. Two modes of Weddell Sea Bottom Water Production: continental margin gravity currents and open ocean convection, which wins and when?

    NASA Astrophysics Data System (ADS)

    Gordon, Arnold L.

    2014-05-01

    There are 2 processes by which Southern Ocean surface waters may reach into the deep ocean: gravity currents over the continental slope and convection within the open ocean. In February 1977 the Islas Orcadas found clear evidence of the latter process, when it observed the remnants of a convective 'chimney' near Maud Rise, in the Weddell Sea. This observation was key in linking deep ocean convective processes to the "Great Weddell Polynya", a 250,000-km2 area virtually free of sea ice during the winters of 1974-1976. Further research from AWI research vessel Polarstern revealed the vulnerability of central Weddell gyre, particularly in the Maud Rise region, to breakdown of water column stability. Climate forcing related to prolonged period of negative or neutral Southern Annular Mode, as was the situation before the "Great Weddell Polynya", acts to reduce freshwater input to the Weddell Sea and thus serves as a trigger for open ocean convection and Polynya development. Similar condition may be occurred during the1912 Deutschland expedition into the Weddell Sea. We speculate that during glacial times, with sea level 130 m lower and the glacial ice extended to shelf break, with the Southern Annular Mode very much in a prolonged negative mode, open ocean production of Weddell Sea Bottom Water [and perhaps that of the Ross Sea too] was prevalent. The bottom water product during the open ocean convection mode may be expected to be saltier than that produced along the continental margin, which would incorporate glacial melt.

  16. Co-variability of the Atmospheric and Geophysical Parameters in the Mid-latitude Troposphere

    NASA Astrophysics Data System (ADS)

    Morozova, A.; Blanco, J. J.; Ribeiro, P.

    2016-04-01

    The study is based on the analysis of locally measured parameters at the mid-latitude region (Iberian Peninsula). The Principal Component Analysis (PCA) of meteorological parameters (air temperature T and geopotential heights gph) at different pressure levels in troposphere and tropopause regions was used to extract components which strongly resemble variations of the cosmic rays (CR, neutron monitor data) and geomagnetic field (Dst index and locally measure horizontal component of geomagnetic field, COI H). The results of the analysis allowed to make two main conclusions. Firstly, on the time scale of weeks-to-months, the pressure corrected neutron monitor data show variations that correlate with atmospheric conditions in the upper troposphere-tropopause- lower stratosphere - the region where most of the ground level measured neutrons are generated by interacting CR with atmospheric atoms. This co-variability can be explained assuming that the ground neutron monitor data corrected for pressure and efficiency using a standard procedure are not completely free from the atmospheric effect. The principal component analysis of the seasonal trends of the T and the gph series allows to extract not only variations related to the seasonal annual cycle (1st mode explaining 93-97% of the seasonal trends variations), but also modes which anti-correlate with the seasonal trend of the CR series (2nd and the 3rd modes explaining 3-5% of the seasonal trend variability). The obtained co-varying modes have the following features: •they are located in the upper troposphere-tropopause and such co-variability is not seen near the ground; • the data are obtained in mid-latitudes (no effect from the relativistic electron precipitations is expected); •the sign of the correlation correspond to one that is expected for atmospheric effect on the secondary particle production (Alpin et al. 2005). Therefore, we might conclude that this co-variability results rather from a part of the

  17. Depositional environments and cyclo- and chronostratigraphy of uppermost Carboniferous-Lower Triassic -lacustrine deposits, southern Bogda Mountains, NW China - A terrestrfluvialial paleoclimatic record of mid-latitude NE Pangea

    USGS Publications Warehouse

    Yang, W.; Feng, Q.; Liu, Yajing; Tabor, N.; Miggins, D.; Crowley, J.L.; Lin, J.; Thomas, S.

    2010-01-01

    from Sakamarian to Artinskian-Kungurian (?) and from middle Induan to end of Olenekian are in conflict with modern mid-latitude east coast meso- and macrothermal humid climate. Extreme continentality, regional orographic effect, and/or abnormal circulation of Paleo-Tethys maybe are possible causes. Our work serves as a rare data point at mid-latitude NE Pangea for climate modeling to seek explanations on the origin(s) of climate variability in NE Pangea from latest Carboniferous to Early Triassic. ?? 2010 Elsevier B.V.

  18. Precipitation-Lightning Relationships on a Global Basis and a Study of Tropical Continental Convection in TRMM Brazil

    NASA Technical Reports Server (NTRS)

    Williams, Earle R.

    2001-01-01

    This report is concerned with a summary of work completed under NASA Grant NAG5-4778 entitled: "Precipitation-Lightning Relationships on a Global Basis", with a supplement entitled: "A Study of Tropical Continental Convection in TRMM/Brazil". Several areas of endeavor are summarized, some of them concerned directly with the observations from the TRMM satellite, and others focussing on ground based measurements in the NASA TRMM LBA field program in Brazil.

  19. Polarimetric Signatures of Initiating Convection During MC3E

    NASA Technical Reports Server (NTRS)

    Emory, Amber

    2012-01-01

    One of the goals of the Mid-latitude Continental Convective Clouds Experiment (MC3E) field campaign was to provide constraints for space-based rainfall retrieval algorithms over land. This study used datasets collected during the 2011 field campaign to combine radiometer and ground-based radar polarimetric retrievals in order to better understand hydrometeor type, habit and distribution for initiating continental convection. Cross-track and conically scanning nadir views from the Conical Scanning Millimeter-wave Imaging Radiometer (CoSMIR) were compared with ground-based polarimetric radar retrievals along the ER-2 flight track. Polarimetric signatures for both airborne radiometers and ground-based radars were well co-located with deep convection to relate radiometric signatures with low-level polarimetric radar data for hydrometeor identification and diameter estimation. For the time period of study, Z(sub DR) values indicated no presence of hail at the surface. However, the Z(sub DR) column extended well above the melting level into the mixed phase region, suggesting a possible source of frozen drop embryos for the future formation of hail. The results shown from this study contribute ground truth datasets for GPM PR algorithm development for convective events, which is an improvement upon previous stratiform precipitation centered framework.

  20. Evidence for slow periglacial mass wasting in the southern mid-latitudes, Mars.

    NASA Astrophysics Data System (ADS)

    Johnsson, Andreas; Reiss, Dennis; Conway, Susan; Hauber, Ernst; Hiesinger, Harald

    2015-04-01

    Camera (MOC) images [Mangold, 2005]. The first question we ask is hence: what is the distribution of small-scale lobes on southern Mars as seen in HiRISE and CTX datasets. Secondly, is there a link to other mass wasting landforms that have been associated with melting of ice/snow such as gullies? And thirdly, how do the southern small-scale lobes compare to the northern counterparts? Our results show that small-scale lobes are widely distributed across the southern hemisphere of Mars. Particularly well-developed lobes are concentrated in the Charitum Montes region, but well-preserved lobes are also found elsewhere in the mid-latitudes. Their close spatial proximity and superposition relationship to gullies suggests that they may form under similar conditions. Their morphometry and their close proximity to gullies and polygonal terrain are in agreement with terrestrial analogues. Small-scale lobes may therefore be strong indicators of past freeze-thaw activity and be useful sources of paleoclimatic information on Mars. References: Balme et al., 2013. Prog. Phys. Geogr. 1-36. Gallagher et al., 2011. Icarus 211 (1), Gallagher and Balme, 2011. GSL 356. Johnsson et al., 2012. Icarus 218. Kreslavsky et al., 2008. Planet. Space Sci. 56 (2). Mangold, 2005. Icarus 174. Matsuoka, 2001. Earth Sci. Rev. 55. Åkerman, 2005. NJG 59.

  1. Longitudinal dependence of annual cycle of total ozone in the Northern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Milinevsky, Gennadi; Evtushevsky, Oleksandr; Grytsai, Asen

    2015-04-01

    In the Northern mid-latitudes, annual change of the total ozone content (TOC) in terms of zonal means is mainly determined by stratospheric ozone accumulation in winter and spring due to the Brewer-Dobson circulation (BDC) and following photochemical relaxation continuing to autumn. It is known from previous studies that annual TOC cycle in some regions could be close to or differ from the zonal mean one. For example, annual TOC minimum over Eastern Asia is observed two months earlier (August) than over Europe (October). In this work, a consecutive analysis of the TOC seasonality along the latitudinal belt 50-55°N in 36 segments (10°-step in longitude) is analyzed. The latitude range includes northern Ukraine and Kyiv-Goloseyev Dobson station. Analysis is based on the Merged Ozone Data Set (MOD) reanalysis 1979-2011 (http://acd-ext.gsfc.nasa.gov/Data_services/merged/). We use also the NCEP-NCAR reanalysis data (http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl) to estimate seasonal changes in geopotential heights and tropopause heights. It is shown that the seasonal TOC cycle over the cyclonic anomalies (high mean TOC level) is shifted to the beginning of year in comparison with that over the anticyclonic anomalies (low mean TOC level). The largest TOC values over the Aleutian low (around 150°E) are characterized by the earliest seasonal maximum (February-March) and minimum (August). Here, the tropospheric dynamics (winter/summer extremes in the planetary wave activity and stationary pressure anomaly formation/disappearance) and related tropopause effects seem to have dominant influence on the earliest development of the annual TOC cycle. Zonal asymmetry in stratospheric ozone accumulation influences rather the maximum TOC levels in this region than timing of the TOC extremes. In the opposite longitude range (zonal TOC minimum in region of the Azores high influence, 20-30°W), the annual TOC cycle lags by 2-3 months reaching a TOC maximum in May

  2. Possible influence of western North Pacific monsoon on TC activity in mid-latitudes of East Asia

    NASA Astrophysics Data System (ADS)

    Choi, Ki-Seon; Cha, Yumi; Kim, Hae-Dong; Kang, Sung-Dae

    2016-01-01

    This study analyzed the correlation between tropical cyclone (TC) frequency and the Western North Pacific monsoon index (WNPMI), which have both been influential in East Asia's mid-latitude regions during the summer season over the past 37 years (1977-2013). A high positive correlation existed between these two variables, which was not reduced even if El Niño-Southern Oscillation (ENSO) years were excluded. To determine the cause of this positive correlation, the highest (positive WNPMI phase) and lowest WNPMIs (negative WNPMI phase) during a nine-year period were selected to analyze the mean difference between them, excluding ENSO years. In the positive WNPMI phase, TCs were mainly generated in the eastern seas of the tropical and subtropical western North Pacific, passing through the East China Sea and moving northward toward Korea and Japan. In the negative phase, TCs were mainly generated in the western seas of the tropical and subtropical western North Pacific, passing through the South China Sea and moving westward toward China's southern regions. Therefore, TC intensity in the positive phase was stronger due to the acquisition of sufficient energy from the sea while moving a long distance up to East Asia's mid-latitude. Additionally, TCs occurred more in the positive phase. Regarding the difference of the two phases between the 850 and 500-hPa streamlines, anomalous cyclones were strengthened in the tropical and subtropical western North Pacific, whereas anomalous anticyclones were strengthened in East Asia's mid-latitude regions. Due to these two anomalous pressure systems, anomalous southeasterlies developed in East Asia's mid-latitude regions, which played a role in the anomalous steering flows that moved TCs into these regions. Furthermore, due to the anomalous cyclones that developed in the tropical and subtropical western North Pacific, more TCs could be generated in the positive phase. Both the lower and upper tropospheric layers had warm anomalies

  3. Spatio-temporal resolution of autumnal mid-latitude clouds on Titan as probes of waves and instabilities

    NASA Astrophysics Data System (ADS)

    Arias-Young, T. M.; Mitchell, J.; Adamkovics, M.; Caballero, R.

    2013-12-01

    Since mid-2004, the Cassini spacecraft has provided images of clouds on Titan, the largest moon of Saturn. The Cassini Imaging Science Subsystem (ISS) captured images over a period of about 24 hours from Dec. 13 to 14, 2009, that show methane clouds in the troposphere concentrated in a band between 45 and 63 degrees south latitude, a streak-shaped mid-latitude cloud system extending across half the globe, traveling several hundred kilometers during the day-long period of observation. The sequence of images obtained throughout this flyby allowed us to create a movie of clouds moving across the moon's surface background. We present the analysis of this mid-latitude cloud system based on observations of the movie produced from the ISS mapped images and the three-dimensional Titan global circulation model (GCM) developed by the UCLA group [Mitchell et al. 2011], which exhibits streak features similar to those found in the Cassini data. The observed cloud features give us both spatial and temporal information that reveals how the clouds evolve in time, which is then compared to the GCM by evaluating the modeled time series on the same time scale as the observed cloud evolution. The atmosphere on Titan is quite barotropic since there is very little temperature difference from equator to pole, and although the altitude of these clouds is yet to be established, the model suggests that there is enough temperature gradient to drive a weakly unstable extratropical instability, similar to the baroclinic instability driving mid-latitude weather systems on Earth. The results of the simulations and the implications for Titan's atmospheric instabilities will be discussed.

  4. Geomorphological map of the Afekan Crater region, Titan: Terrain relationships in the equatorial and mid-latitude regions

    NASA Astrophysics Data System (ADS)

    Malaska, Michael J.; Lopes, Rosaly M. C.; Williams, David A.; Neish, Catherine D.; Solomonidou, Anezina; Soderblom, Jason M.; Schoenfeld, Ashley M.; Birch, Sam P. D.; Hayes, Alex G.; Le Gall, Alice; Janssen, Michael A.; Farr, Thomas G.; Lorenz, Ralph D.; Radebaugh, Jani; Turtle, Elizabeth P.

    2016-05-01

    We carried out geomorphological mapping in a mid-latitude area surrounding the Afekan Crater region on Titan. We used Cassini RADAR (Synthetic Aperture Radar mode) data as the basemap, supplemented by Cassini RADAR microwave emissivity, Imaging Science Subsystem (ISS) infrared data, Visual and Infrared Mapping Spectrometer (VIMS) spectral images, and topography derived from Synthetic Aperture Radar (SAR). Mapping was done at a spatial scale of 300 m/pixel, which corresponds to a map scale of 1:800,000. We describe multiple terrain units and their spatial relations. We describe five broad classes of units that are in agreement with previous mapping efforts: crater, labyrinth, hummocky/mountainous, plains, and dune terrain classes. We subdivide these into seven crater units, four hummocky/mountainous units, six plains units, and three dunes units. Our results show that plains are the dominant class of terrain unit in Titan's mid latitudes. Of the plains units, the undifferentiated plains are the largest by total areal extent in the mapped region, accounting for over 45% of the mapped area. We developed a stratigraphic sequence that has the hummocky/mountainous and labyrinth terrains as the oldest units. The observed properties of the hummocky/mountainous terrain are consistent with fractured water ice materials, while the labyrinth terrains are consistent with organic materials. The youngest units are the dune units and streak-like plains units, with the undifferentiated plains units being of intermediate age. The microwave emissivity of the undifferentiated plains and dune units are consistent with organic materials. Given their properties and stratigraphic placement, we conclude that the hummocky/mountainous terrains are most consistent with the presumed crustal materials of Titan. The plains materials are consistent with deposits resulting from the transport and emplacement of organic-rich materials predominantly by aeolian mechanisms. Our geomorphological mapping

  5. Interannual, Seasonal and Diurnal Variation of Mid-Latitude Noctilucent Clouds and their Relation with Mesospheric Summer Echos

    NASA Astrophysics Data System (ADS)

    Gerding, M.; Hoffmann, P.; Hoeffner, J.; Kopp, M.; Zecha, M.; Luebken, F.

    2012-12-01

    Noctilucent Clouds (NLC) are observed since 1997 at nighttime by different lidars at our mid-latitude site at Kühlungsborn (54°N, 12°E). Occurrence rates in individual years are up to ~20 %, but typically much smaller. Lowest rates have been observed around years 2000-2002 and highest numbers around year 2009. The year-to-year variation of occurrence rates is in clear anti-correlation with solar activity, upper mesospheric summer temperatures and zonal winds. Up to now there are no indications for additional trends. NLC maximum brightness and centroid altitudes are highly variable and their annual mean parameters do not show any dependence on solar cycle and temperature. Within season, NLC occurrence typically peaks around summer solstice and decreases slowly in the following weeks. Maximum occurrence is in good agreement with highest water vapor saturation while this relation fails for the beginning and end of the season. Until 2009 NLC observations with the RMR lidar have been limited to nighttime conditions. 2009 we build up a new RMR lidar in parallel to the old one at our site, allowing NLC observations with high sensitivity continuously during night and day. From the best of our knowledge this lidar allows for the first time observations of mid-latitude NLC independent of solar elevation. Diurnal variations of NLC occurrence, brightness and altitude have been derived for the seasons 2010 to 2012. E.g., occurrence rates show a diurnal variation with maximum in the early morning and minimum in the late afternoon. This variation is in general agreement with the meridional wind variation but less with temperature, emphasizing the relevance of advection for mid-latitude NLC existence. Daytime NLC soundings enable simultaneous observations with Mesospheric Summer Echoes (MSE) that require a sufficient electron density typically only achieved if the sun is above the horizon. In contrast to higher latitudes, NLC and MSE at mid-latitudes often cover a similar

  6. Ionospheric Response to the 2009 Sudden Stratospheric Warming over the Equatorial, Low- and Mid-Latitudes in American Sector.

    NASA Astrophysics Data System (ADS)

    Fagundes, P. R.; Goncharenko, L. P.; de Abreu, A. J.; Gende, M.; de Jesus, R.; Pezzopane, M.; Kavutarapu, V.; Coster, A. J.; Pillat, V. G.

    2014-12-01

    The equatorial and low-latitude ionosphere/thermosphere system is predominantly disturbed by waves (MSTIDs, tides, and planetary waves), which are generated in the lower atmosphere or in-situ, as well as electric fields and TIDs produced by geomagnetic storm and UV, EUV, and X-ray solar radiation. For many years, it was thought that, during geomagnetic quiet conditions, the equatorial and low-latitude F-layer was mainly perturbed by waves that were generated not far away from the observed location or electric fields generated by the Equatorial Electroject (EEJ). On the contrary, during geomagnetic storms when the energy sources are in high latitudes the waves (TIDs) travel a very long distance from high latitude to equatorial region and electric fields can be mapped via magnetic field lines. However, in the recent times an unexpected coupling between high latitude, mid- latitude, and equatorial/low latitudes was discovered during sudden stratospheric warming (SSW) events. All aspects involved in this process must be explored in order to improve our knowledge about the Earth´s atmosphere. The present study investigates the consequences of vertical coupling from lower to the upper atmosphere in the equatorial and low-latitude ionosphere in Southern Hemisphere during a major SSW event, which took place during January-February 2009 in the Northern Hemisphere. Using seventeen ground-based dual-frequency GPS stations and two ionosonde stations spanning from latitude 2.8oN to 53.8oS and from longitude 36.7oW to 67.8oW over the South American sector, it has been observed that the ionosphere was significantly disturbed by the SSW event from Equator to the mid-latitudes. Using one GPS station located in mid-latitude (South America sector) it is reported for the first time that the mid-latitude in southern hemisphere (American Sector) was disturbed by the SSW event in the Northern hemisphere. The VTEC at all 17 GPS and two ionosonde stations show significant deviations

  7. Effect of electron-density gradients on propagation of radio waves in the mid-latitude trough. Master's thesis

    SciTech Connect

    Citrone, P.J.

    1991-01-01

    Partial contents of this thesis include: (1) Radio-wave propagation and the mid-latitude trough; (2) Ionospheric measurements; (3) Modification of time-dependent ionospheric model output with latitudinal electron-density profiles from digisonde trough depictions; (4) Ray-tracing simulations to examine ground range; and (5) Effects of three-dimensional gradients in electron density on radio-wave propagation in the trough region. Data is tabulated for geophysical conditions, solar activity level, geomagnetic activity level, conditions for vertical ray refraction to surface, and ray-tracing fixed-input conditions.

  8. Atmospheric water parameters in mid-latitude cyclones observed by microwave radiometry and compared to model calculations

    NASA Technical Reports Server (NTRS)

    Katsaros, Kristina B.; Hammarstrand, Ulla; Petty, Grant W.

    1990-01-01

    Existing and experimental algorithms for various parameters of atmospheric water content such as integrated water vapor, cloud water, precipitation, are used to examine the distribution of these quantities in mid latitude cyclones. The data was obtained from signals given by the special sensor microwave/imager (SSM/I) and compared with data from the nimbus scanning multichannel microwave radiometer (SMMR) for North Atlantic cyclones. The potential of microwave remote sensing for enhancing knowledge of the horizontal structure of these storms and to aid the development and testing of the cloud and precipitation aspects of limited area numerical models of cyclonic storms is investigated.

  9. New observations of martian southern mid-latitude recurring slope lineae (RSL) imply formation by freshwater subsurface flows

    NASA Astrophysics Data System (ADS)

    Stillman, David E.; Michaels, Timothy I.; Grimm, Robert E.; Harrison, Keith P.

    2014-05-01

    Southern mid-latitude (SML) recurring slope lineae (RSL) are narrow (0.5-5 m) dark albedo features that emanate from bedrock and incrementally lengthen down steep slopes that preferentially face the equator. We observe that SML RSL begin lengthening prior to southern summer at a solar longitude (Ls) of 245° ± 11° when Mars Global Surveyor Thermal Emission Spectrometer (TES)-derived near-maximum surface temperatures are 296 ± 5 K and Mars Reconnaissance Orbiter Mars Climate Sounder (MCS) - and Mars Odyssey Thermal Emission Imaging System (THEMIS)-derived mid-afternoon surface temperatures are >273 K. SML RSL continue to lengthen for 104 ± 38 sols with an average near-maximum surface temperature of 298 ± 5 K. The SML RSL then stop lengthening at Ls = 314° ± 12° when mid-afternoon surface temperatures drop below 273 K. They remain dark for another 116 ± 41 sols (until Ls = 16° ± 14°) as surface temperatures continue to fall. Although the RSL recharge mechanism remains unknown, our observation that the vast majority of RSL lengthen only when mid-afternoon surface temperatures are >273 K supports the hypothesis that they are formed by shallow subsurface liquid water flows without significant freezing-point depression. The number and length of RSL at multiple sites increased dramatically following the Mars Year 28 globe-encircling dust storm. We interpret this increase to be due to warmer subsurface temperatures created by a dust-laden greenhouse effect that may be unique to the southern mid-latitudes near Ls = 270°. Therefore SML RSL flow is quite sensitive to ground temperature and may only occur under favorable orbital parameters when mean insolation during the RSL lengthening season is above that of the current southern mid-latitude mean insolation value. This value is currently at a peak that has not been attained for the last ∼100 ka. Meanwhile, the RSL-poor northern mid-latitude mean insolation is near a minimum and has a value 27% lower than the

  10. On the stratospheric aerosol budget at Northern mid-latitudes from 21 years of ground-based lidar and satellite observations

    NASA Astrophysics Data System (ADS)

    Khaykin, Sergey; Godin-Beekmann, Sophie; Hauchecorne, Alain; Vernier, Jean-Paul; Jumelet, Julien; Keckhut, Philippe

    2016-04-01

    that sAOD1730km values tend to drop to 0.003 level or below within several months after each eruption-induced aerosol outbreak. The annual cycle of aerosol scattering ratio profile, as seen by both ground-based and satellite observations during both volcanically quiescent and active periods, shows a minimum between 15-19 km altitude during late spring - early summer season. This minimum is argued to be due to quasi-isentropic poleward transport of tropical air processed by overshooting convection, as the latter acts to transport clean tropospheric air into the tropical lower stratosphere. The convective 'cleansing' process, described in detail by Vernier et al. (2011), takes place mainly during the southern tropics convective season, which together with the timescale of poleward transport is compatible with the observed seasonality of aerosol in the mid-latitude stratosphere.

  11. Balloon-borne radiometer measurement of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years

    NASA Astrophysics Data System (ADS)

    Toohey, M.; Quine, B. M.; Strong, K.; Bernath, P. F.; Boone, C. D.; Jonsson, A. I.; McElroy, C. T.; Walker, K. A.; Wunch, D.

    2007-08-01

    Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990-2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and global optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. This suggests that, to within the errors of the 1990 measurements, there has been no significant change in the HNO3 summer mid-latitude profile.

  12. Balloon-borne radiometer measurements of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years

    NASA Astrophysics Data System (ADS)

    Toohey, M.; Quine, B. M.; Strong, K.; Bernath, P. F.; Boone, C. D.; Jonsson, A. I.; McElroy, C. T.; Walker, K. A.; Wunch, D.

    2007-12-01

    Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990-2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. We therefore find no evidence of long-term changes in the HNO3 summer mid-latitude profile, although the uncertainty of our measurements precludes a conclusive trend analysis.

  13. Statistical Analysis of Ionospheric Storms on GPS TEC measurements between 2000 and 2014 in mid-latitude

    NASA Astrophysics Data System (ADS)

    Chung, J. K.

    2015-12-01

    The ionospheric storms that may generate the spatial/temporal gradient or irregularities of electron densities are very interest phenomena for two reasons. First, they occur by the increasing solar EUV/X-ray fluxes as well as by the equatorward or poleward plasma transportations by the global changes of the neutral winds and electric fields responded to geomagnetic storms. Second, they have been the practical interests in the satellite navigations and radio communications, especially in the mid-latitudes of the dense population regions in these days though ionosphere in mid-latitudes is quiet compared with high and low latitudes. In this presentation, the statistical analysis of the occurrences of the ionospheric storms in Korea are presented. They are examined from Korea GPS TEC dataset between 2000 and 2014 over the full-solar cycle coverage. We examine the two super geomagnetic storms cases of 29-31 October 2003 and 8-10 November 2004 to discuss the possible physical mechanisms for ionospheric storm of positive and negative phases and their affection on GPS positioning. The parameters to define the ionospheric storms are suggested to increase our understanding of their physical characteristic and then to apply the practical cases.

  14. Impacts of Atlantic multi-decadal oscillation to summer atmospheric circulation in the northern mid-latitude

    NASA Astrophysics Data System (ADS)

    Lin, Jianshe

    2016-04-01

    Previous studies indicated that Atlantic multi-decadal oscillation (AMO) has significant impacts on regional and global climate. The impacts of the AMO on the summertime atmospheric circulation over the mid latitudes of the Northern Hemisphere and possible mechanisms were investigated througal observational analysis and numerical experiments by AGCMs. The results show that the interdecadal oscillation pattern of land surface temperature in the mid-latitudes are highly associated with the AMO. The eastern Europe, East Asia and the United States were warmer, while central Asia and northwest of the North America were cold during the positive phase of the AMO. Associated geopotential height anomalies is dominated by a barotropic wave train propagating along the jet stream, with zonal wavenumber 4 or 5. Basically, positive (negative) geopotential height anomalies correspond to warm (cold) anomalies of land surface temperature. The wave train pattern is called as interdecadal circumglobal teleconnection pattern Idealized numerical experiment by AGCMs indicates that the AMO-related SST anomalies tend to induce the teleconnection pattern, which was primarily forced by extratropical component of the AMO.

  15. Simulated East-west differences in F-region peak electron density at Far East mid-latitude region

    NASA Astrophysics Data System (ADS)

    Ren, Zhipeng; Liu, Libo; Wan, Weixing; Zhao, Biqiang

    2016-07-01

    In the present work, using Three-Dimensional Theoretical Ionospheric Model of the Earth in Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME3D-IGGCAS), we simulated the east-west differences in F-region peak electron density (NmF2) at Far East mid-latitude region. We found that, after removing the longitudinal variations of neutral parameters, TIME3D-IGGCAS can better represent the observed relative east-west difference (Rew) features. Rew is mainly negative (West NmF2 > East NmF2) at noon and positive (East NmF2 > West NmF2) at evening-night. The magnitude of daytime negative Rew is weak at local winter and strong at local summer, and the daytime Rew show two negative peaks around two equinoxes. With the increasing of solar flux level, the magnitude of Rew mainly become larger, and two daytime negative peaks slight shifts to June Solstice. With the decreasing of geographical latitude, Rew mainly become positive, and two daytime negative peaks slight shifts to June Solstice. Our simulation also suggested that the thermospheric zonal wind combined with the geomagnetic field configuration play a pivotal role in the formation of the ionospheric east-west differences at Far East mid-latitude region.

  16. A Statistical Study of Mid-latitude Thunderstorm Characteristics associated with Acoustic and Gravity Waves

    NASA Astrophysics Data System (ADS)

    Lay, E. H.; Shao, X. M.; Kendrick, A.

    2014-12-01

    Gravity waves with periods greater than 5 minutes and acoustic waves with periods between 3 and 5 minutes have been detected at ionospheric heights (250-350 km) and associated with severe thunderstorms. Modeling results support these findings, indicating that acoustic waves should be able to reach 250-350 km within ~250 km horizontally of the source, and gravity waves should be able to propagate significantly further. However, the mechanism by which the acoustic waves are generated and the ubiquity of occurrence of both types of wave is unknown. We use GPS total electron content measurements to detect gravity and acoustic waves in the ionosphere. We perform a statistical study from 2005 May - July to compare the occurrence rate and horizontal extent of the waves to storm size and convective height from NEXRAD radar measurements. It is found that both gravity waves and acoustic wave horizontal extent is primarily associated with storm size and not convective height.

  17. The Break-up and Drifting of the Continental Plates in 2D Models of Convecting Mantle

    NASA Astrophysics Data System (ADS)

    Dal Zilio, L.; Faccenda, M.; Capitanio, F. A.

    2014-12-01

    Since the early theory of Wegener, the break-up and drift of continents have been controversial and hotly debated topics. To assist the interpretation of the break-up and drift mechanisms and its relation with mantle circulation patterns, we carried out a 2D numerical modelling of the dynamics of these processes. Different regimes of upper plate deformation are studied as consequence of stress coupling with convection patterns. Subduction of the oceanic plate and induced mantle flow propagate basal tractions to the upper plate. This mantle drag forces (FMD) can be subdivided in two types: (1) active mantle drag occurring when the flow drives plate motion (FAD), and (2) passive mantle drag (FPD), when the asthenosphere resists plate motion. The active traction generated by the convective cell is counterbalanced by passive mantle viscous drag away from it and therefore tension is generated within the continental plate. The shear stress profiles indicate that break-up conditions are met where the gradient of the basal shear stress is maximised, however the break-up location varies largely depending on the convection style primarily controlled by slab stagnation on the transition zone, avalanching through or subduction in the lower mantle. We found good correspondence between our models and the evolution of convergent margins on Earth, giving precious insights into the break-up and drifting mechanisms of some continental plates, such as the North and South American plates, Calabria and the Japan Arc.

  18. A study of 3D structure of nighttime electron density enhancement in the mid-latitude ionosphere by GPS tomography

    NASA Astrophysics Data System (ADS)

    Chen, C.; Saito, A.

    2011-12-01

    The mid-latitude summer nighttime anomaly (MSNA) is a feature that the nighttime electron density larger than that in the daytime mid-latitude ionosphere. This anomaly was first detected in the southern hemisphere five decades ago and observed in the northern hemisphere recently by ionosondes and satellites. Previous studies presented the electron density structure of MSNA by using COSMIC occultation data and found that MSNA is clearly seen around 300 km altitude during local summer. However, due to lack of observation, the day-to-day variation of MSNA was not investigated. A GPS tomography method by SPEL of Kyoto University using the total electron content (TEC) data measured by the ground-based GPS receiver network is employed in this study. The wide coverage and continuous observation of GPS receivers are suitable for investigating the spatial and day-to-day variations of ionospheric electron densities. The algorithm of the GPS tomography developed by SPEL of Kyoto University use a constraint condition that the gradient of election density tends to be smooth in the horizontal direction and steep in the vicinity of the F2 peak, instead of inputting the initial conditions. Therefore, the algorithm is independent of any ionospheric and plasmaspheric electron density distribution models. The dense ground-based GPS receiver network around European region is used to study the three dimensional (3D) structure of MSNA with GPS tomography. Results show that the MSNA usually appear around the geomagnetic mid-latitude region during local summer nighttime. The feature of MSNA is most obvious at the ionospheric F2-peak altitudes. The result also shows a day-to-day variation in the formation of MSNA, in terms of the occurrence time, intensity, and spatial extent. The tomographic results are compared with the ionosondes, satellites, and radar measurements. A theoretical model simulation, SAMI2, is also used to further discuss the mechanism of MSNA. The comparison with other

  19. Abrupt transitions between gyroscopic and internal gravity waves: the mid-latitude case

    NASA Astrophysics Data System (ADS)

    van Haren, Hans

    The large-scale vertical density stratification, represented by buoyancy frequency N, is generally very stable in the upper half of the ocean, and relatively weak in the lower half. However, closer inspection of density profiles demonstrates steps rather than a smooth increase with depth. As is demonstrated here using Richardson number, geostrophic balance and slantwise convective mixing arguments, these layers have a limited set of minimum, weak stratification, N-values Nmin indicating the transition between stably stratified and convective layers. Adopting the viewpoint that the transition occurs for neutral stability in the direction of Earth's rotation ) and (iii) Nmin = 4fh, both under nonlinear stability, where horizontal component fh = 2 sin , because the effect of fh is the tilting of vortex tubes away from the local vertical in the direction of Ω. The above explains very well deep-ocean North-Atlantic and Mediterranean observations on transitions in conductivity-temperature with depth profiles, inertial polarization and near-inertial shear. The latter peaks at sub-inertial 0.97f, which is associated with the lower inertio-gravity wave limit for Nmin = 4fh, thereby stressing the importance of fh for the dominant physics associated with mixing in the ocean.

  20. A two-moment cloud microphysics parameterization for mixed-phase clouds. Part 2: Maritime vs. continental deep convective storms

    NASA Astrophysics Data System (ADS)

    Seifert, A.; Beheng, K. D.

    2006-02-01

    A systematic modeling study investigates the effects of cloud condensation nuclei (CCNs) on the evolution of mixed-phase deep convective storms. Following previous studies the environmental conditions like buoyancy and vertical wind shear are varied to simulate different storm types like ordinary single cells, multicells and supercells. In addition, the CCN characteristics are changed from maritime to continental conditions. The results reveal very different effects of continentality on the cloud microphysics and dynamics of the different storms. While a negative feedback on total precipitation and maximum updraft velocity is found for ordinary single cells and supercell storms, a positive feedback exists for multicell cloud systems. The most important link between CCN properties, microphysics and dynamics is the release of latent heat of freezing.

  1. Precursory enhancement of EIA in the morning sector: Contribution from mid-latitude large earthquakes in the north-east Asian region

    NASA Astrophysics Data System (ADS)

    Ryu, Kwangsun; Oyama, Koh-Ichiro; Bankov, Ludmil; Chen, Chia-Hung; Devi, Minakshi; Liu, Huixin; Liu, Jann-Yenq

    2016-01-01

    To investigate whether the link between seismic activity and EIA (equatorial ionization anomaly) enhancement is valid for mid-latitude seismic activity, DEMETER observations around seven large earthquakes in the north-east Asian region were fully analyzed (M ⩾ 6.8). In addition, statistical analysis was performed for 35 large earthquakes (M ⩾ 6.0) that occurred during the DEMETER observation period. The results suggest that mid-latitude earthquakes do contribute to EIA enhancement, represented as normalized equatorial Ne , and that ionospheric change precedes seismic events, as has been reported in previous studies. According to statistical studies, the normalized equatorial density enhancement is sensitive and proportional to both the magnitude and the hypocenter depth of an earthquake. The mechanisms that can explain the contribution of mid-latitude seismic activity to EIA variation are briefly discussed based on current explanations of the geochemical and ionospheric processes involved in lithosphere-ionosphere interaction.

  2. Model of the mid-latitude ionospheric trough on the base of Cosmos-900 and Intercosmos-19 satellites data

    NASA Astrophysics Data System (ADS)

    Karpachev, A. T.; Deminov, M. G.; Afonin, V. V.

    1996-01-01

    A new model of the mid-latitude ionospheric trough is developed on the base of Intercosmos-19 and Cosmos-900 satellites data (over 1500 orbits). It is valid for the nighttime (18 to 06 MLT), winter and equinox, K_p-indices from 0 to 8. It covers the topside ionosphere up to 1000 km and describes the trough minimum position Lambda_T depending on longitude lambda, altitudeh , local magnetic time MLT and K_p-index. Model is presented in the analytical form, as well as a nomogram versus MLT and K_p and a nighttime segment of a circle (in the polar coordinate system) with the radius depending on the K_p-index. The effective K_p-index taken for preceding 4.4 hours is used in the model. Agreement between the model and other data on the trough and the equatorial boundary of the auroral oval is discussed.

  3. Low- and mid-latitude ionospheric electric fields during the January 1984 GISMOS campaign

    NASA Technical Reports Server (NTRS)

    Fejer, B. G.; Kelley, M. C.; Senior, C.; De La Beaujardiere, O.; Lepping, R.

    1990-01-01

    The electrical coupling between the high-, middle-, and low-latitude ionospheres during January 17-19, 1984 is examined, using interplanetary and high-latitude magnetic field data together with F region plasma drift measurements from the EISCAT, Sondre Stromfjord, Millstone Hill, Saint-Santin, Arecibo, and Jicamarca incoherent scatter radars. The penetration both the zonal and meridional electric field components of high-latitude origin into the low-latitude and the equatorial ionospheres are studied. The observations in the postmidnight sector are used to compare the longitudinal variations of the zonal perturbation electric field with predictions made from global convection models. The results show that the meridional electric field perturbations are considerably more attenuated with decreasing latitude than the zonal fluctuations. It is concluded that variations in the meridional electric field at low latitudes are largely due to dynamo effects.

  4. HF Radar Observations of Space Weather Effects in the Low and Mid-latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Menk, F. W.

    2015-12-01

    The ionosphere is dynamically coupled to the magnetosphere and hence diurnal and seasonal processes in the ionosphere are strongly influenced by space weather effects. These may vary the electron density distribution and cause changes in the reflection and absorption of HF radio signals. Other consequences include the formation of enhanced convective flows and irregularity features which may contribute to Doppler clutter. While there has been much discussion on the ionospheric signatures of magnetic storms at high latitudes, this presentation focuses on effects detected using mid- and low-latitude HF radars which examine field lines mapping to the vicinity of the ring current. Characteristic features include travelling ionospheric disturbances, high velocity flows and sustained irregular and quasi-sinusoidal 5 - 20 mHz waves recorded near the plasmapause. Such observations provide new insight on complex M-I coupling dynamics.

  5. Observational investigation of the possible correlation between medium-scale TIDs and mid-latitude spread F

    NASA Astrophysics Data System (ADS)

    Yu, Shimei; Xiao, Zuo; Aa, Ercha; Hao, Yongqiang; Zhang, Donghe

    2016-08-01

    Global navigation satellite system (GNSS) receivers at two stations, CHAN (43.83°N, 125.27°E) and URUM (43.70°N, 87.60°E) in China, are used to retrieve the total electron content (TEC) from 2001 to 2012, and detect medium-scale traveling ionospheric disturbances (MSTIDs) above the two stations. At either station, MSTIDs occurrence is found to depend on season and solar cycle, that is, lower during equinoctial seasons and low solar activity, in accordance with the general morphological features of mid-latitude spread F (MSF). More interestingly, a significant longitudinal difference exists between the two stations that, both MSTIDs and MSF are more prevalent at CHAN than at URUM over the 12 years. These results imply a strong connection between MSTIDs and MSF, and provide new observational evidences that gravity waves (GWs), manifested in MSTIDs here, might play an important role in triggering MSF in the overhead ionosphere. Since GWs at mid-latitude mostly originate in the lower atmosphere, we infer that the atmospheric background at CHAN is more favorable for generating GWs. This is probably true considering very different surface meteorological conditions for the two stations over such a large longitudinal span (∼38°). CHAN station is near the coast of western Pacific Ocean and URUM station is in the very center of the Europe-Asia continent, and they are in different climate zones. We therefore suggest that the surface meteorological condition is one of the significant factors to be considered in explaining and modeling MSF formation and variations.

  6. Response of equatorial, low- and mid-latitude F-region in the American sector during the intense geomagnetic storm on 24-25 October 2011

    NASA Astrophysics Data System (ADS)

    de Jesus, R.; Sahai, Y.; Fagundes, P. R.; de Abreu, A. J.; Brunini, C.; Gende, M.; Bittencourt, J. A.; Abalde, J. R.; Pillat, V. G.

    2013-07-01

    In this paper, we present and discuss the response of the ionospheric F-region in the American sector during the intense geomagnetic storm which occurred on 24-25 October 2011. In this investigation ionospheric sounding data obtained of 23, 24, 25, and 26 October 2011 at Puerto Rico (United States), Jicamarca (Peru), Palmas, São José dos Campos (Brazil), and Port Stanley, are presented. Also, the GPS observations obtained at 12 stations in the equatorial, low-, mid- and high-mid-latitude regions in the American sector are presented. During the fast decrease of Dst (about ˜54 nT/h between 23:00 and 01:00 UT) on the night of 24-25 October (main phase), there is a prompt penetration of electric field of magnetospheric origin resulting an unusual uplifting of the F region at equatorial stations. On the night of 24-25 October 2011 (recovery phase) equatorial, low- and mid-latitude stations show h'F variations much larger than the average variations possibly associated with traveling ionospheric disturbances (TIDs) caused by Joule heating at high latitudes. The foF2 variations at mid-latitude stations and the GPS-VTEC observations at mid- and low-latitude stations show a positive ionospheric storm on the night of 24-25 October, possibly due to changes in the large-scale wind circulation. The foF2 observations at mid-latitude station and the GPS-VTEC observations at mid- and high-mid-latitude stations show a negative ionospheric storm on the night of 24-25 October, probably associated with an increase in the density of molecular nitrogen. During the daytime on 25 October, the variations in foF2 at mid-latitude stations show large negative ionospheric storm, possibly due to changes in the O/N2 ratio. On the night of 24-25, ionospheric plasma bubbles (equatorial irregularities that extended to the low- and mid-latitude regions) are observed at equatorial, low- and mid-latitude stations. Also, on the night of 25-26, ionospheric plasma bubbles are observed at equatorial

  7. Butterflies, Black swans and Dragon kings: How to use the Dynamical Systems Theory to build a "zoology" of mid-latitude circulation atmospheric extremes?

    NASA Astrophysics Data System (ADS)

    Faranda, D.; Yiou, P.; Alvarez-Castro, M. C. M.

    2015-12-01

    A combination of dynamical systems and statistical techniques allows for a robust assessment of the dynamical properties of the mid-latitude atmospheric circulation. Extremes at different spatial and time scales are not only associated to exceptionally intense weather structures (e.g. extra-tropical cyclones) but also to rapid changes of circulation regimes (thunderstorms, supercells) or the extreme persistence of weather structure (heat waves, cold spells). We will show how the dynamical systems theory of recurrence combined to the extreme value theory can take into account the spatial and temporal dependence structure of the mid-latitude circulation structures and provide information on the statistics of extreme events.

  8. Deformation of "stable" continental interiors by mantle convection: Implications for intraplate stress in the New Madrid Seismic Zone

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Moucha, R.; Simmons, N. A.; Grand, S. P.; Mitrovica, J. X.

    2011-12-01

    The enigmatic origin of large-magnitude earthquakes far from active plate boundaries, especially those occurring in so-called "stable" continental interiors, is a source of continuing controversy that has eluded a satisfactory explanation using past geophysical models of intraplate deformation and faulting. One outstanding case of such major intraplate earthquakes is the 1811-1812 series of events in the New Madrid Seismic Zone (NMSZ). We contend that the origin of some of these enigmatic intraplate events is due to regional variations in the pattern of tectonic stress generated by mantle convective flow acting on the overlying lithosphere and crust. Mantle convection affects the entire surface of the planet, irrespective of the current configuration of surface plate boundaries. In addition, it must be appreciated that plate tectonics is not a 2-D process, because the convective flow that drives the observed horizontal motions of the tectonic plates also drives vertical displacements of the crust across distances as great as 2 to 3 km. This dynamic topography is directly correlated with convection-driven stress field variations in the crust and lithosphere and these stresses can be locally focussed if the mantle rheology below the lithosphere is characterised by sufficiently low viscosities. We have developed global models of convection-driven mantle flow [Forte et al. 2009,2010] that are based on recent high-resolution 3-D tomography models derived from joint inversions of seismic, geodynamic and mineral physics data [Simmons et al. 2007,2008,2010]. These tomography-based mantle convection models also include a full suite of surface geodynamic (postglacial rebound and convection) constraints on the depth-dependent average viscosity of the mantle [Mitrovica & Forte 2004]. Our latest tomography-based and geodynamically-constrained convection calculations reveal that mantle flow under the central US are driven by density anomalies within the lower mantle associated

  9. The noon and midnight mid-latitude trough as seen by Ariel 4

    NASA Technical Reports Server (NTRS)

    Tulunay, Y. K.; Grebowsky, J. M.

    1978-01-01

    The electron density data returned by the polar orbiting satellites Ariel 3 and Ariel 4 revealed that the midlatitude trough is one of the distinct large-scale features of the ionosphere at about 550 km. Recent work (e.g., Tulunay and Grebowsky, 1975) on the data included the investigation of the temporal development of the latitudinal position of the midlatitude electron density trough at dawn and dusk during the large magnetic storms of May 1967 and May 1972. Model calculations which assumed that the equatorial convection E-field varies in step with the Kp index reproduced on the average the observed behavior. In the present paper, trough observations made at noon and midnight during the period, 12-21 December 1971 which encompassed a relatively large magnetic storm are discussed. In this context, model calculations have been employed as a guide of average approximations of the actual situation in predicting the plasmapause location. It is also shown that the trough observed on the noon passes is not generally plasmapause-related as the nightside troughs are expected to be.

  10. Geomagnetic Secular Variation record from a mid-latitude Brazilian speleothem: Preliminary results

    NASA Astrophysics Data System (ADS)

    Jaqueto, P.; Trindade, R. I.; Hartmann, G. A.; Novello, V.; Cruz, F. W.; Feinberg, J. M.

    2013-05-01

    The magnetic study of speleothems is a new way to investigate the continuous record of the geomagnetic field. Recent improvements in magnetic instrumentation and analytical techniques provide the means to accurately measure the magnetic signal of the weakly magnetic speleothems and better characterize their magnetic mineralogy. At the same time, this material is suitable for high-precision U-Th dating and can also be easily correlated through stable isotopes. Continuous geomagnetic records in South America are rare, and the systematic paleomagnetic study of stalagmites could contribute significantly to improve the continent's database. As part of this effort, here we report preliminary magnetic results from a stalagmite located at 14.8°S, 56.4°W, in Mato Grosso State, (Brazil) with ages varying from 500 AD to 1900 AD. Magnetic properties, obtained with Magnetic Property Measurement System (MPMS) and Alternating Gradient Magnetometer (AGM), are very homogeneous throughout the stalagmite comprising partly oxidized PSD magnetite. Magnetic inclinations were obtained after stepwise alternating field (AF) demagnetization with a resolution of 0.5 cm (temporal resolution of ~30 yrs). Our preliminary results agree within error with models CALS3k.3 and SED3K for the well-defined 1700-1900 AD period. For older periods, when models are much less constrained, our data does not match CALS3k.3 and SED3K inclinations. The agreement between our data and the well-constrained recent sector of the model suggests the speleothem is likely recording the geomagnetic field throughout its whole extension. From these preliminary tests we expect the continental record from stalagmites to provide a more refined picture of the spatial and temporal variations of the magnetic field over South America. We are currently working in order to improve the age model of the speleothem through the comparison of its δ180 record with well-dated "sister" speleothems from the same cave.

  11. Vegetation/oceanographic changes in the mid-latitudes of southwestern North Atlantic during the Holocene

    NASA Astrophysics Data System (ADS)

    Naughton, Filipa; Keigwin, Lloyd; Oliveira, Dulce; Desprat, Stephanie; Abrantes, Fatima

    2013-04-01

    The direct correlation between terrestrial (pollen) and marine (planktonic δ18O) proxies from a slope core (KNR 178-2 JPC 32), retrieved in the Cape Hatteras (35°58.58'N, 74°42.77'W, 1006 m), provide substantial information on the Eastern North American vegetation response to the Holocene climate and oceanographic changes of the western North Atlantic. The end of the last glacial-interglacial transition is marked by the gradual replacement of the Boreal forest and herbs by temperate trees reflecting a general warming. Within this overall gradual warming, several abrupt vegetation shifts reveal episodes of relative cool and warm events. The most notorious continental warming of this transition, occurred at around 9650 cal yr BP and is synchronous with the increase of sea surface temperature as revealed by the planktonic foraminifera δ18O. The first maxima of temperate trees expansion, reflecting one of the most warmest events within the Holocene, occurred between 8700 and 7200 cal yr BP. Within this period 4 abrupt vegetation and hydrological changes suggest centennial scale returning cool conditions, being the most extreme detected at around 8400 cal yr BP. Between 7200 and 5300 cal yr BP temperate trees were partially replaced by hemlock suggesting a relative cool episode. The re-expansion of temperate trees marking a climatic warming is detected between 5300 and 2500 cal yr BP. Within this interval it is detected an important change in both vegetation and hydrology, marking a relative long lasting cooling between 4100 and 3550 cal yr BP. Finally the last 2500 cal yr BP is marked by important vegetation and hydrological shifts reflecting important climatic changes.

  12. Airborne lidar observations of cirrus clouds in the Tropics, Mid-latitudes, and the Arctic

    NASA Astrophysics Data System (ADS)

    Ismail, S.; Browell, E.; Ferrare, R.; Grant, W.; Kooi, S.; Brackett, V.; Mahoney, M.

    2003-04-01

    Airborne lidar systems have demonstrated an unsurpassed capability to detect and profile optically thin cirrus. The airborne Lidar Atmospheric Sensing Experiment (LASE) has demonstrated a capability to detect thin cirrus at aerosol scattering levels of <2.0× 10-9 m-1 sr-1 at 815 nm, and this makes it well suited for deriving many cirrus cloud properties. LASE has been operated from high- and medium-altitude aircraft and has participated in 9 major field experiments over the past 8 years. During these missions, data were collected related to optically thin cirrus and moisture in the upper troposphere in the tropics, mid- and high-latitudes. LASE data from these field experiments have been used to characterize the cirrus as thin laminae, thick cirrus, deep convective cirrus, and cirrus anvils. In addition, characteristics including the cloud top height, optical depth, aerosol scattering ratio, lidar extinction-to-backscatter ratio have been derived for optically thin cirrus. During these field experiments, many data sets were available to interpret the cirrus cloud properties including data from satellites, in situ temperature and moisture instruments on aircraft, radiosondes, and during some field experiments, the Microwave Temperature Profiler (MTP). LASE data from long-range flights have been used to derive a relationship between the latitudinal variation of cloud top heights and tropopause locations. These measurements were also used to examine the relationship between relative humidity and the presence of cirrus. LASE observations of cirrus clouds and water vapor fields have also been used to identify dynamical processes like stratosphere-troposphere exchange and to study their characteristics. Examples of these observations and analyses are presented to demonstrate the advantage of using LASE measurements for conducting atmospheric science investigations.

  13. A Decade-long Continental-Scale Convection-Resolving Climate Simulation on GPUs

    NASA Astrophysics Data System (ADS)

    Leutwyler, David; Fuhrer, Oliver; Lapillonne, Xavier; Lüthi, Daniel; Schär, Christoph

    2016-04-01

    The representation of moist convection in climate models represents a major challenge, due to the small scales involved. Convection-resolving models have proven to be very useful tools in numerical weather prediction and in climate research. Using horizontal grid spacings of O(1km), they allow to explicitly resolve deep convection leading to an improved representation of the water cycle. However, due to their extremely demanding computational requirements, they have so far been limited to short simulations and/or small computational domains. Innovations in the supercomputing domain have led to new supercomputer-designs that involve conventional multicore CPUs and accelerators such as graphics processing units (GPUs). One of the first atmospheric models that has been fully ported to GPUs is the Consortium for Small-Scale Modeling weather and climate model COSMO. This new version allows us to expand the size of the simulation domain to areas spanning continents and the time period up to one decade. We present results from a decade-long, convection-resolving climate simulation using the GPU-enabled COSMO version. The simulation is driven by the ERA-interim reanalysis. The results illustrate how the approach allows for the representation of interactions between synoptic-scale and meso-scale atmospheric circulations at scales ranging from 1000 to 10 km. We discuss the performance of the convection-resolving modeling approach on the European scale. Specifically we focus on the annual cycle of convection in Europe, on the organization of convective clouds and on the verification of hourly rainfall with various high resolution datasets.

  14. Improving Representation of Convective Transport for Scale-Aware Parameterization, Part II: Analysis of Cloud-Resolving Model Simulations

    SciTech Connect

    Liu, Yi-Chin; Fan, Jiwen; Zhang, Guang J.; Xu, Kuan-Man; Ghan, Steven J.

    2015-04-27

    Following Part I, in which 3-D cloud-resolving model (CRM) simulations of a squall line and mesoscale convective complex in the mid-latitude continental and the tropical regions are conducted and evaluated, we examine the scale-dependence of eddy transport of water vapor, evaluate different eddy transport formulations, and improve the representation of convective transport across all scales by proposing a new formulation that more accurately represents the CRM-calculated eddy flux. CRM results show that there are strong grid-spacing dependencies of updraft and downdraft fractions regardless of altitudes, cloud life stage, and geographical location. As for the eddy transport of water vapor, updraft eddy flux is a major contributor to total eddy flux in the lower and middle troposphere. However, downdraft eddy transport can be as large as updraft eddy transport in the lower atmosphere especially at the mature stage of 38 mid-latitude continental convection. We show that the single updraft approach significantly underestimates updraft eddy transport of water vapor because it fails to account for the large internal variability of updrafts, while a single downdraft represents the downdraft eddy transport of water vapor well. We find that using as few as 3 updrafts can account for the internal variability of updrafts well. Based on evaluation with the CRM simulated data, we recommend a simplified eddy transport formulation that considers three updrafts and one downdraft. Such formulation is similar to the conventional one but much more accurately represents CRM-simulated eddy flux across all grid scales.

  15. Tropospheric mid-latitude geopotential wave characteristics associated with strong wind events in the North Atlantic/European region

    NASA Astrophysics Data System (ADS)

    Wild, Simon; Simmonds, Ian; Leckebusch, Gregor C.

    2015-04-01

    The variability of strong synoptic scale wind events in the mid-latitudes have long been linked to baroclinic wave activity in the mid troposphere. Previous studies have also shown that greater amplitudes of planetary waves in the mid troposphere are likely to increase the occurrence of regional extremes in temperature and precipitation. In this study we examine whether characteristics of planetary and synoptic mid-latitude waves show systematic anomalies in the North Atlantic/ European region which can be related to the occurrence of a strong surface wind event. We will mainly focus on two questions: 1) Do amplitudes for waves with different wave lengths show a systematic anomaly when a strong wind event occurs? 2) Can phases of the individual wave components be detected that favour strong wind events? In order to decompose the mid-tropospheric flow into longitudinal waves we employ the fast Fourier transform to the meridional mean of the geopotential height in 500hPa between 35° and 60°N for i) the entire latitude belt and ii) for a North Atlantic/European sector (36°W to 36°E). Our definition of strong wind events is based on the Storm Severity Index (SSI) alongside a wind tracking algorithm identifying areas of exceedances of the local 98th percentile of the 10m wind speed. First results using ERA-Interim Reanalysis from 1979 - 2014 for the extended winter season (ONDJFM) for the 50 most intense strong wind systems with respect to the SSI reveal a greater amplitude for all investigated wave numbers. Especially waves with wave lengths below 2000km show an increase of about 25% of the daily standard deviation on average. The distribution of wave phases for the different wave numbers with respect to the location of a strong wind event shows a less homogenous picture. There is however a high proportion of events that can be associated with phases around 3π/4 and 5π/4 of waves with lengths of around 6000km, equivalent to wave number 5 on a planetary scale

  16. Mid-latitude Summer Evening Anomaly (MSEA) in F2 layer electron density and Total Electron Content at solar minimum

    NASA Astrophysics Data System (ADS)

    Klimenko, M. V.; Klimenko, V. V.; Ratovsky, K. G.; Zakharenkova, I. E.; Yasyukevich, Yu. V.; Korenkova, N. A.; Cherniak, I. V.; Mylnikova, A. A.

    2015-11-01

    This paper deals with study of the ionospheric Mid-latitude Summer Evening Anomaly (MSEA) in the F2 layer peak electron density (NmF2) in the Northern Hemisphere and its manifestation in the Total Electron Content (TEC) during the solar activity minimum. The MSEA is identified as an anomaly in the NmF2 diurnal variations when the evening time NmF2 values exceed the daytime NmF2 over a mid-latitude station. For this investigation we used the Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) and observation data of the NmF2 and TEC over Irkutsk (52.3°N, 104.3°E) and Kaliningrad (54.6°N, 20.0°E). We demonstrate that the MSEA is a purely summer feature in the NmF2 diurnal variations. MSEA is found in TEC, but it is less pronounced and it is observed at the earlier hours in comparison with the MSEA appearance in NmF2. The MSEA appearance in TEC is much more distinct over Irkutsk than Kaliningrad. The later sunset and the upward field aligned plasma transport by the thermospheric winds are the main drivers and sources for the MSEA formation. The ratio n(O)/n(N2) contributes also to the MSEA formation. In summer the diurnal variation in the electron content of the altitudinal range near the F2 layer peak height (175-450 km) almost fully determines the diurnal variation and therefore the MSEA formation in TEC. The significant diurnal variation in the electron content of the topside ionosphere and plasmasphere (450-20,200 km) fully coincides with the maxima and minima in the diurnal variations in TEC and the F2 region ionospheric electron content. The contribution of the topside ionosphere and plasmasphere in TEC in the summer of 2009 exceeds 40%. The lower ionosphere (80-175 km) contribution to TEC has a daytime maximum that does not exceed 10%.

  17. Volcanic terrain and the possible periglacial formation of "excess ice" at the mid-latitudes of Utopia Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Soare, R. J.; Horgan, B.; Conway, S. J.; Souness, C.; El-Maarry, M. R.

    2015-08-01

    At the mid-latitudes of Utopia Planitia (UP), Mars, a suite of spatially-associated landforms exhibit geomorphological traits that, on Earth, would be consistent with periglacial processes and the possible freeze-thaw cycling of water. The suite comprises small-sized polygonally-patterned ground, polygon-junction and -margin pits, and scalloped, rimless depressions. Typically, the landforms incise a dark-toned terrain that is thought to be ice-rich. Here, we investigate the dark-toned terrain by using high resolution images from the HiRISE as well as near-infrared spectral-data from the OMEGA and CRISM. The terrain displays erosional characteristics consistent with a sedimentary nature and near-infrared spectra characterised by a blue slope similar to that of weathered basaltic-tephra. We also describe volcanic terrain that is dark-toned and periglacially-modified in the Kamchatka mountain-range of eastern Russia. The terrain is characterised by weathered tephra inter-bedded with snow, ice-wedge polygons and near-surface excess ice. The excess ice forms in the pore space of the tephra as the result of snow-melt infiltration and, subsequently, in-situ freezing. Based on this possible analogue, we construct a three-stage mechanism that explains the possible ice-enrichment of a broad expanse of dark-toned terrain at the mid-latitudes of UP: (1) the dark-toned terrain accumulates and forms via the regional deposition of sediments sourced from explosive volcanism; (2) the volcanic sediments are blanketed by atmospherically-precipitated (H2O) snow, ice or an admixture of the two, either concurrent with the volcanic-events or between discrete events; and, (3) under the influence of high obliquity or explosive volcanism, boundary conditions tolerant of thaw evolve and this, in turn, permits the migration, cycling and eventual formation of excess ice in the volcanic sediments. Over time, and through episodic iterations of this scenario, excess ice forms to decametres of

  18. Convection

    NASA Astrophysics Data System (ADS)

    Britz, Dieter

    Convection has long been coupled with electrochemistry, and the name hydrodynamic voltammetry has become standard. In electroanalytical chemistry we mainly seek reproducible conditions. These are almost always attained by systems in which a steady convective state is achieved, although not always. Thus, the once popular dropping mercury electrode (see texts such as [74, 257]) has convection around it, but is never in steady state; it might be called a reproducible periodic dynamic state.

  19. Convective available potential energy in the environment of oceanic and continental clouds: Correction and comments

    NASA Technical Reports Server (NTRS)

    Lucas, Christopher; Zipser, Edward J.; Lemone, Margaret A.

    1994-01-01

    In 1980, Zipser and LeMone estimated the convective available potential energy (CAPE) for the Thunderstorm Project cumulonimbus environment to be about 3000 J per kg. By assuming the most adiabat reported by Byers and Braham (1949) to be that of an undilute parcel rather than a reference moist adiabat, a significant error was introduced. On the basis of recent calculations made under similar conditions in Oklahoma and Florida, CAPE is now estimated to be considerably lower. These lower CAPE estimates shed doubt on the suggestion that differences in CAPE account for differences in the vertical velocities in convective updrafts over land and over the ocean.

  20. Indirect Radiative Warming Effect in the Winter and Spring Arctic Associated with Aerosol Pollution from Mid-latitude Regions

    NASA Astrophysics Data System (ADS)

    Zhao, Chuanfeng; Garrett, Timothy

    2016-04-01

    Different from global cooling effects of aerosols and aerosol-cloud interactions, anthropogenic aerosols from mid-latitude are found to play an increased warming effect in the Arctic in later winter and early spring. Using four-year (2000-2003) observation of aerosol, cloud and radiation at North Slope of Alaska, it is found that the aerosols can increase cloud droplet effective radius 3 um for fixed liquid water path, and increase cloud thermal emissivity about 0.05-0.08. In other words, aerosols are associated with a warming of 1-1.6 degrees (3-5 W/m2) in the Arctic during late winter and early spring solely due to their first indirect effect. Further analysis indicates that total aerosol climate effects are even more significant (8-10 W/m2), with about 50% contribution from aerosol first indirect effect and another 50% contribution from complicated feedbacks. It also shows strong seasonal distribution of the aerosol indirect radiative effects, with warming effects in seasons other than in summer. However, only the significant warming effect in winter and spring passes through the significance test. The strong warming effect due to aerosol indirect effect could be further strengthened through following feedbacks involving the surface albedo (early ice melting).

  1. A comparison between the current models of mid-latitude spread F and data from the Arecibo Observatory

    NASA Technical Reports Server (NTRS)

    Imel, G.

    1977-01-01

    The current models of mid-latitude F sub s are studied. The assumptions and derivations of the Reid model, the Scannapieco model, and the Perkins model are presented in detail. Incoherent-scatter data of the density profiles and velocity profiles were obtained in order that the models could be evaluated on the basis of experimental data. Initial studies indicated that the Perkins model was most representative of the data from Arecibo, so a detailed comparison of the predictions of the Perkins model and the data was made. Two of four nights studied are nights with F sub s. The Perkins model is derived in a frame of reference moving with the velocity of the neutral wind; the model is transformed to the rest frame to facilitate comparison with data. Several data handling techniques are introduced. In particular, an integration interval that remains constant in length, but follows the vertical motion of the peak of the F layer is used to obtain the field integrated quantities of the Perkins model.

  2. Investigation of the Effects of Solar and Geomagnetic Changes on the Total Electron Content: Mid-Latitude Region

    NASA Astrophysics Data System (ADS)

    Ulukavak, Mustafa; Yalcinkaya, Mualla

    2016-04-01

    The Global Positioning System (GPS) is used as an important tool for ionosphere monitoring and obtaining the Total Electron Content (TEC). GPS satellites, positioned in the Earth's orbit, are used as sensors to investigate the space weather conditions. In this study, solar and geomagnetic activity variations were investigated between the dates 1 March-30 June 2015 for the mid-latitude region. GPS-TEC variations were calculated for each selected International GNSS Service (IGS) station in Europe. GNSS data was obtained from Crustal Dynamics Data and Information System (CDDIS) archive. Solar and geomagnetic activity indices (Kp, F10.7 ve Dst) were obtained from the Oceanic and Atmospheric Administration (NOAA), the Canadian Space Weather Forecast Centre (CSWFC) and Data Analysis Center for geomagnetism and Space Magnetism Graduate School of Science, Kyoto University (WDC) archives. GPS-TEC variations were determined for the quiet periods of the solar and geomagnetic activities. GPS-TEC changes were then compared with respect to the quiet periods of the solar and geomagnetic activities. Global Ionosphere Maps (GIM) IONEX files, obtained from the IGS analysis center, was used to check the robustness of the GPS-TEC variations. The investigations revealed that it is possible to use the GPS-TEC data for monitoring the ionospheric disturbances.

  3. Comparison of Observations of Sporadic-E Layers in the Nighttime and Daytime Mid-Latitude Ionosphere

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Freudenreich, H.; Rowland, D.; Klenzing, J.; Clemmons, J.; Larsen, M.; Kudeki, E.; Franke, S.; Urbina, J.; Bullett, T.

    2012-01-01

    A comparison of numerous rocket experiments to investigate mid-latitude sporadic-E layers is presented. Electric field and plasma density data gathered on sounding rockets launched in the presence of sporadic-E layers and QP radar echoes reveal a complex electrodynamics including both DC parameters and plasma waves detected over a large range of scales. We show both DC and wave electric fields and discuss their relationship to intense sporadic-E layers in both nighttime and daytime conditions. Where available, neutral wind observations provide the complete electrodynamic picture revealing an essential source of free energy that both sets up the layers and drives them unstable. Electric field data from the nighttime experiments reveal the presence of km-scale waves as well as well-defined packets of broadband (10's of meters to meters) irregularities. What is surprising is that in both the nighttime and daytime experiments, neither the large scale nor short scale waves appear to be distinctly organized by the sporadic-E density layer itself. The observations are discussed in the context of current theories regarding sporadic-E layer generation and quasi-periodic echoes.

  4. Radiocarbon Anomalies of Surface Waters in the Glacial-to-Deglacial Low-to-Mid-Latitude Atlantic

    NASA Astrophysics Data System (ADS)

    Sarnthein, M.; Balmer, S.; Mudelsee, M.

    2015-12-01

    14C reservoir ages of surface waters are crucial for dating marine sediment records of the last 40,000 yr. In the low-latitude Atlantic, time series of 14C reservoir ages were reconstructed for five sites using the 14C plateau-tuning technique and supplemented by a reservoir age record from southern mid-latitudes (Skinner et al., 2010). Results suggest small-scale spatial and short-term (multi-centennial-scale) changes in reservoir age over last glacial-to-deglacial times, thus modify previously assigned calendar age chronologies by up to 500-2500 yr. During late peak glacial, enhanced summer winds off South Brazil and strengthened southerly trades off Namibia induced local reservoir ages of up to 900-1100 yr, whereas surface water ages in the Cariaco lagoon fell close to zero, a result of dominant CO2 exchange with the atmosphere. Near 16.05 ka, reservoir ages dropped to a minimum of 170-420 yr all over the South Atlantic, possibly the response to an immediately preceding short-term major rise in atmospheric pCO2 and East Antarctic temperatures. Our 14C reservoir ages provide a first basis for systematic data-model comparisons. They largely confirm model-based estimates for the LGM (Butzin et al., 2012) that have been derived from changes in both atmospheric 14C concentration and reductions in AMOC. Deviations are constrained to coastal upwelling zones in part insufficiently resolved by numerical models.

  5. 18-year variability of ultraviolet radiation penetration in the mid-latitude coastal waters of the western boundary Pacific

    NASA Astrophysics Data System (ADS)

    Kuwahara, Victor S.; Nozaki, Sena; Nakano, Junji; Toda, Tatsuki; Kikuchi, Tomohiko; Taguchi, Satoru

    2015-07-01

    The 18-year time-series shows in situ ultraviolet radiation (UVR) and photosynthetically active radiation (PAR) diffuse attenuation coefficient Kd(λ) have recurrent seasonal variability of high/low attenuation during summer/winter months, respectively, dependent on variability in water column stratification and concentrations of bio-optical properties. The mid-latitude coastal survey station displayed significant seasonality of the mixed layer depth (MLD) between 12 and 82 m which modified the distribution of chlorophyll a (4.6-24.9 mg m-2) and absorption of colored dissolved organic matter [aCDOM(320 nm) 0.043-1.34 m-1]. The median Kd(320 nm) displayed significant seasonality at 0.19-0.74 m-1 (C.V. = 44.1%) and seasonal variability within the euphotic layer [Z10%(320 nm) = 7-20%]. High attenuation of UVR with relatively moderate attenuation of PAR was consistently observed during the summer months when increased concentrations of terrestrially derived CDOM coupled with a shallow MLD were present. The winter season showed the opposite of low UVR and PAR attenuation due to a relatively deeper MLD coupled with low concentrations of bio-optical properties. Although the long term Kd(λ) did not vary significantly during the time-series, analysis of the interannual variability suggests there are positive and negative phases following the Pacific Decadal Oscillation (PDO) vis-a-vis variability in bio-optical properties (p < 0.001).

  6. Objective identification of mid-latitude storms in satellite imagery: determination of an independent storm validation dataset.

    NASA Astrophysics Data System (ADS)

    Delsol, C.; Hodges, K.

    2003-04-01

    Current methods of validating GCMs involve comparing model results with Re-analysis datasets in which observations have been combined with a model. The quality of this approach depends on the observational data distribution in space and time and on the model formulation. We propose to use an automatic and objective technique that can provide efficiently a dataset of “real” data against which the models and re-analysis can be validated based on the identification and tracking of weather systems in satellite imagery. We present results of a boundary finding method based on Fourier Shape Descriptors for the identification of extra-tropical cyclones in the mid-latitudes using NOAA’s AVHRR IR imagery. The boundary-finding method, initially derived for medical image processing, is designed to incorporate model-based information into a boundary finding process for continuously deformable objects. This allows us to work with objects that are diverse and irregular in their shape such as developing weather systems. The method is suited to work in an environment, which may contain spurious and broken boundaries. The main characteristic features of an extra-tropical system such as the vortex and associated frontal systems are identified. This work provides a basis for statistical analyses of extra-tropical cyclones for climatological studies and for the validation of GCMs, making use of the vast amount of satellite archive data available. It is also useful for individual case studies for weather forecast verification.

  7. Interannual variations of the mid-latitude 557.7 nm atmosphere emission within the solar cycle

    NASA Astrophysics Data System (ADS)

    Mikhalev, Alexander

    Variations of the 557.7 nm airglow intensity (emitting layer height is 85-115 km) in the 23- rd solar cycle are analyzed. The experimental data of the 557.7 nm atomic oxygen emission obtained at ISTP Geophysical observatory near Irkutsk (52 N, 103 E) are used. The feature of observed 557.7 nm intensity variations is an infringement of direct correlation dependence between the emission intensity and solar activity level (F10.7) in separate years. Also the results received in the 18th-22d solar cycles at the other mid-latitude stations are analyzed. It is revealed, that the features of the long-term variations of 557.7 nm intensity in the 23-rd and 20-th solar cycles are the most similar. There are some solar cycles in which the phase synchronism of 557.7 nm emission variations with 11-years cycle of solar activity is broken. In these cycles the periods about 4-6 years in 557.7 nm emission variations are dominant. The possible reasons of interannual variations of 557.7 nm atmospheric emission associated with the influence of lower atmosphere are discussed. This work was done under RAS Presidium Program 16 (Part 3) and joint Russian-Bulgarian Atmos project support.

  8. VHF coherent scatter radar observations of mid-latitude F-region field-aligned irregularities over South Korea

    NASA Astrophysics Data System (ADS)

    Kwak, Y.; Yang, T.; Lee, J.; Hwang, J.; Kil, H.; Park, Y.

    2011-12-01

    We examine the mid-latitude F-region field-aligned irregularity (FAI) activity during 2010-2011 by using the VHF coherent scatter radar data in Daejeon (36.2°N, 127.1°E; dip latitude 26.7°N), South Korea. The VHF radar has been operated since December 2009 and provides a unique opportunity to investigate the variability of the FAI activity with local time, season, solar flux, and magnetic activity. Our preliminary results during the solar minimum show that FAIs preferentially occur at post-sunset and pre-sunrise and during the June solstice. The seasonal variation of the FAI occurrence frequency is similar to that of the electron density irregularities observed by the C/NOFS satellite. For one event, we observed the association of the FAIs with a medium-scale traveling ionospheric disturbance (MSTID). Our study extends to the investigation of the correlations between the irregularities in the equatorial region and middle latitudes and between the conjugate F regions, and the causal linkage of the FAIs with the E-region perturbations. For this purpose, we analyze the VHF radar and C/NOFS data during 2010-2011.

  9. Ice Nuclei in Mid-Latitude Cirrus: Preliminary Results from a New Counterflow Virtual Impactor (CVI) Aircraft Inlet

    NASA Astrophysics Data System (ADS)

    Froyd, K. D.; Cziczo, D. J.; Murphy, D. M.; Kulkarni, G.; Lawson, P.

    2011-12-01

    Cirrus cloud properties are strongly governed by the mechanism of ice particle formation and by the number and effectiveness of ambient ice nuclei. Airborne measurements of ice nuclei reveal new nucleation mechanisms, provide constraints on microphysical models, and guide laboratory investigations. For over two decades the Counterflow Virtual Impactor (CVI) inlet has remained the prevailing approach for sampling cloud particles to measure ice nuclei from an aircraft platform. However, traditional CVI inlets have fundamental limitations when operating on high speed aircraft, where only a small fraction of ambient cloud particles are typically sampled. A novel 'folded' CVI was constructed and deployed during the NASA MACPEX 2011 campaign. The flow design of this inlet effectively doubles the CVI length and thereby increases the size range of captured cirrus particles. Additional design elements such as an internal vortex flow, a neon carrier gas, and an infrared laser further improve the capture and evaporation of ice crystals. Preliminary results of ice nuclei composition measured by the PALMS single-particle mass spectrometer are presented from the MACPEX campaign. Examples of ice nuclei from mid-latitude cirrus are shown, including mineral dust, organic-rich aerosol with amine and diacid components, and lead-containing aerosol.

  10. On the Origin of Mid-latitude Fast Wind: Challenging the Two-state Solar Wind Paradigm

    NASA Astrophysics Data System (ADS)

    Stakhiv, Mark; Landi, Enrico; Lepri, Susan T.; Oran, Rona; Zurbuchen, Thomas H.

    2015-03-01

    The bimodal paradigm of solar wind describes a slow solar wind situated near the heliospheric current sheet while a fast wind overexpands from the poles to fill in the remainder of the heliosphere. In this paper, we challenge this paradigm and focus here on mid-latitude wind using three fast-latitude passes completed by the Ulysses spacecraft. Based on its composition and dynamic properties, we discuss how this wind differs from both the fast, polar coronal hole wind and the low latitude, streamer-associated slow solar wind. Using a detailed analysis of ionic and elemental abundances, as well as solar wind dynamic properties, we conclude that there is a third quasi-stationary solar wind state, called the boundary wind. This boundary wind is characterized by a charge-state distribution that is similar to slow wind, but with an elemental composition that is coronal hole like. Based on these data, we present arguments for the location of the origin of this wind. We conclude that the boundary wind is a subset of the fast wind emanating from regions close to the boundaries of coronal holes and is accelerated by a similar process.

  11. A general circulation model simulation of the springtime Antarctic ozone decrease and its impact on mid-latitudes

    SciTech Connect

    Cariolle, D.; Lasserre-Bigorry, A.; Royer, J.F. ); Geleyn, J.F. )

    1990-02-20

    Ozone is treated as an interactive variable calculated by means of a continuity equation which takes account of advection and photochemical production and loss. The ozone concentration is also used to compute the heating and cooling rates due to the absorption of solar ultraviolet radiation, and the infrared emission in the stratosphere. The daytime ozone decrease due to the perturbed chlorine chemistry found at high southern latitudes is introduced as an extra loss in the ozone continuity equation. Results of the perturbed simulation show a very good agreement with the ozone measurements made during spring 1987. The simulation also shows the development of a high-latitude anomalous circulation, with a warming of the upper stratosphere resulting mainly from dynamical heating. In addition, a substantial ozone decrease is found at mid-latitudes in a thin stratospheric layer located between the 390 and the 470 K {theta} surfaces. A significant residual ozone decrease is found at the end of the model integration, 7 months after the final warming and the vortex breakdown. If there is a significant residual ozone decrease in the atmosphere, the ozone trends predicted by photochemical models which do not take into account the high-latitude perturbed chemistry are clearly inadequate. Finally, it is concluded that further model simulations at higher horizontal resolution, possibly with a better representation of the heterogeneous chemistry, will be needed to evaluate with more confidence the magnitude of the mid-latitudinal ozone depletion induced by the ozone hole formation.

  12. Constraints on the Formation of Mid-latitude Valleys from Numerical Modeling of Fluvial Runoff and Erosion

    NASA Astrophysics Data System (ADS)

    Parsons, R.; Moore, J. M.; Howard, A. D.

    2011-12-01

    Mid-latitude valleys (MLVs) are important because they provide constraints on the Martian climate and hydrosphere during the middle of Mars' evolution. In order to assess the time and total sediment and water volumes involved in forming MLVs, we applied a numerical model of fluvial runoff and erosion under Martian gravity based on [1]. Based on the observed number (~10) and length (up to 75 km) of MLVs in Newton basin (40°S, 201°E), their braided or distributary channel morphology, and their valley width to meander wavelength ratios, a significant volume of liquid water must have been released near the basin rim during the late Hesperian to Early Amazonian (2 - 3 Gyr ago), and flowed into the interior - perhaps forming a lake [2]. Valleys incise into a background slope of 5° along the crater wall, and terminate in alluvial deposits at the basin floor, after which, a second set of valleys continue along the 1-2° slopes at the basin floor extending toward the basin center. We ran two simulations using a water-filled channel 1 m deep by 8 m wide, and another for a channel 10 cm deep and 3 m wide flowing over a surface which changes slope from 0.2° to 5° and again to 1° from the rim to the wall to the floor of an idealized crater. The simulations were run until the length of the alluvial fan reached 3 km - comparable to the observed fan extent. Our preliminary results indicate that roughly 4x107 m3 of sediment is contained within alluvial fans deposited by MLVs, and they would require 2 to 140 yrs to form under constant flow conditions for channel dimensions of 1 by 8 m and 0.1 by 3 m. These results are independent of sediment grain size as long as grains are finer than 1/50th the channel depth. Both of these simulations require 1 km3 of water giving a total volume of water of roughly 10 km3 for all of the drainage basins within Newton crater. About 400 km3 of water would be required to fill Newton basin to the elevation at which channels appear to terminate

  13. The effects of springtime mid-latitude storms on trace gas composition determined from the MACC reanalysis

    NASA Astrophysics Data System (ADS)

    Knowland, K. E.; Doherty, R. M.; Hodges, K. I.

    2014-10-01

    The relationship between springtime air pollution transport of ozone (O3) and carbon monoxide (CO) and mid-latitude cyclones is explored for the first time using the Monitoring Atmospheric Composition and Climate (MACC) reanalysis for the period 2003-2012. In this study, the most intense spring storms (95th percentile) are selected for two regions, the North Pacific (NP) and the North Atlantic (NA). These storms (~60 storms over each region) often track over the major emission sources of East Asia and eastern North America. By compositing the storms, the distributions of O3 and CO within a "typical" intense storm are examined. We compare the storm-centered composite to background composites of "average conditions" created by sampling the reanalysis data of the previous year to the storm locations. Mid-latitude storms are found to redistribute concentrations of O3 and CO horizontally and vertically throughout the storm. This is clearly shown to occur through two main mechanisms: (1) vertical lifting of CO-rich and O3-poor air isentropically from near the surface to the mid- to upper-troposphere in the region of the warm conveyor belt; and (2) descent of O3-rich and CO-poor air isentropically in the vicinity of the dry intrusion, from the stratosphere toward the mid-troposphere. This can be seen in the composite storm's life cycle as the storm intensifies, with area-averaged O3 (CO) increasing (decreasing) between 200 and 500 hPa. At the time of maximum intensity, area-averaged O3 around the storm center at 300 hPa is enhanced by 50 and 36% for the NP and NA regions respectively, compared to the background, and by 11 and 7.6% at 500 hPa. In contrast, area-averaged CO at 300 hPa decreases by 12% for NP and 5.5% for NA, and at 500 hPa area-averaged CO decreases by 2.4% for NP while there is little change over the NA region at 500 hPa. From the mid-troposphere, O3-rich air is clearly seen to be transported toward the surface but the downward transport of CO-poor air is

  14. The effects of springtime mid-latitude storms on trace gas composition determined from the MACC reanalysis

    NASA Astrophysics Data System (ADS)

    Knowland, K. E.; Doherty, R. M.; Hodges, K. I.

    2015-03-01

    The relationship between springtime air pollution transport of ozone (O3) and carbon monoxide (CO) and mid-latitude cyclones is explored for the first time using the Monitoring Atmospheric Composition and Climate (MACC) reanalysis for the period 2003-2012. In this study, the most intense spring storms (95th percentile) are selected for two regions, the North Pacific (NP) and the North Atlantic (NA). These storms (∼60 storms over each region) often track over the major emission sources of East Asia and eastern North America. By compositing the storms, the distributions of O3 and CO within a "typical" intense storm are examined. We compare the storm-centered composite to background composites of "average conditions" created by sampling the reanalysis data of the previous year to the storm locations. Mid-latitude storms are found to redistribute concentrations of O3 and CO horizontally and vertically throughout the storm. This is clearly shown to occur through two main mechanisms: (1) vertical lifting of CO-rich and O3-poor air isentropically, from near the surface to the mid- to upper-troposphere in the region of the warm conveyor belt; and (2) descent of O3-rich and CO-poor air isentropically in the vicinity of the dry intrusion, from the stratosphere toward the mid-troposphere. This can be seen in the composite storm's life cycle as the storm intensifies, with area-averaged O3 (CO) increasing (decreasing) between 200 and 500 hPa. The influence of the storm dynamics compared to the background environment on the composition within an area around the storm center at the time of maximum intensity is as follows. Area-averaged O3 at 300 hPa is enhanced by 50 and 36% and by 11 and 7.6% at 500 hPa for the NP and NA regions, respectively. In contrast, area-averaged CO at 300 hPa decreases by 12% for NP and 5.5% for NA, and area-averaged CO at 500 hPa decreases by 2.4% for NP while there is little change over the NA region. From the mid-troposphere, O3-rich air is

  15. Comparison of the decomposition VOC profile during winter and summer in a moist, mid-latitude (Cfb) climate.

    PubMed

    Forbes, Shari L; Perrault, Katelynn A; Stefanuto, Pierre-Hugues; Nizio, Katie D; Focant, Jean-François

    2014-01-01

    The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography--time-of-flight mass spectrometry (GC × GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC × GC-TOFMS were demonstrated

  16. Origin of high-frequency TEC disturbances observed by GPS over the European mid-latitude region

    NASA Astrophysics Data System (ADS)

    Wautelet, Gilles; Warnant, Rene

    2015-10-01

    High-frequency variability of the ionospheric Total Electron Content (TEC) can strongly affect precise positioning with GNSS. The occurrence rate as well as the amplitude of such disturbances has been extensively studied over the last decade. Mainly, one can distinguish disturbances due to space-weather events and the others, qualified as "quiet-time" as they are observed during quiet geomagnetic conditions. The latter, which represent more than 75% of the total number of disturbances over mid-latitudes, are then divided into two categories: the Winter Daytime (WD) and the Summer Nighttime (SN). The first category, representing the bulk of quiet-time disturbances, corresponds to classical Medium-Scale Traveling Ionospheric Disturbances (MSTIDs), that are the result of the interaction of gravity waves and the ionospheric plasma. On the other hand, SN disturbances are generally understood as non-classical MSTIDs of electrical origin. The paper investigates the origin of these two types of disturbance based on GPS measurements, ionospheric soundings and wind speed data at a tropospheric level. If one cannot exclude the solar terminator as a potential source of gravity waves responsible for WD events, it is thought that the major contribution comes from the lower atmosphere. More precisely, tropospheric jetstream is considered as the favorite candidate for daytime MSTIDs. Turning to SN disturbances, our analysis reveals that they are related to spread-F phenomenon, linked to the appearance of sporadic E-layers. The related instabilities are responsible for field-aligned irregularities in the F-region, which are thought to be responsible for noise-like fluctuations of the GPS TEC observed during SN events.

  17. The impact of greenhouse climate change on the energetics and hydrologic processes of mid-latitude transient eddies

    SciTech Connect

    Branscome, L.E.; Gutowski, W.J., JR.

    1991-05-01

    Atmospheric transient eddies contribute significantly to mid-latitude energy and water vapor transports. Changes in the global climate, as induced by greenhouse enhancement, will likely alter transient eddy behavior. Unraveling all the feedbacks that occur in general circulation models (GCMs) can be difficult. The transient eddies are isolated from the feedbacks and are focused on the response of the eddies to zonal-mean climate changes that result from CO{sub 2}-doubling. Using a primitive-equation spectral model, the impact of climate change on the life cycles of transient eddies is examined. Transient eddy behavior in experiments is compared with initial conditions that are given by the zonal-mean climates of the GCMs with current and doubled amounts of CO{sub 2}. The smaller meridional temperature gradient in a doubled CO{sub 2} climate leads to a reduction in eddy kinetic energy, especially in the subtropics. The decrease in subtropical eddy energy is related to a substantial reduction in equatorward flux of eddy activity during the latter part of the life cycle. The reduction in equatorward energy flux alters the moisture cycle. Eddy meridional transport of water vapor is shifted slightly poleward and subtropical precipitation is reduced. The water vapor transport exhibits a relatively small change in magnitude, compared to changes in eddy energy, due to the compensating effect of higher specific humidity in the doubled-CO{sub 2} climate. An increase in high-latitude precipitation is related to the poleward shift in eddy water vapor flux. Surface evaporation amplifies climatic changes in water vapor transport and precipitation in the experiments.

  18. Mid-latitude magnetically conjugate ionospheric F2-layer during magnetic storm periods. Ph.D. Thesis

    SciTech Connect

    Wu, H.Y.

    1993-01-01

    Thermospheric winds and penetrating electric fields play important roles in the complex phenomenon of F2-layer magnetic storms. The combined effect of both on the ionosphere can be inferred using a method based on the nonlinear relationship between the neutral winds and the height of the F2-layer. The F2-layer peak electron density depletion on the storm day generally became more pronounced than quiet-time median values during nighttime. The high to low latitude F2-layer electron density depletion is particularly evident at both hemispheres. A simultaneous enhancement of the eastward electric fields at all latitudes suggests an intimate relationship between the peak electron density depletion and the penetrating electric fields during an onset of storm. The behavior of meridional neutral winds during magnetic storm periods at all latitudes has been shown to differ from their quiet-time patterns. Meridional neutral winds during quiet-time for the months considered are usually equatorward during day and night in the summer season, poleward during the day, and slightly equatorward at night during the winter season for both hemispheres. Meridional neutral winds during storm periods generally become equatorward of quiet time values at night and reach their maximum deviation from the quiet time medians near local midnight. Electric fields can be separated from the effects of neutral air dynamics during the onset of magnetic storms. Simultaneous changes from the quiet-time values of hmF2 occurring at one or more pairs of conjugate stations indicate the penetration of zonal electric fields. Different local times of storm onset were examined to show that the penetration of electric fields to mid-latitudes normally occurs near midnight periods. This may be correlated with the currents flowing into the high latitude ionosphere in the evening sector.

  19. Uniform climate sensitivity in tree-ring stable isotopes across species and sites in a mid-latitude temperate forest.

    PubMed

    Hartl-Meier, Claudia; Zang, Christian; Büntgen, Ulf; Esper, Jan; Rothe, Andreas; Göttlein, Axel; Dirnböck, Thomas; Treydte, Kerstin

    2015-01-01

    Tree-ring stable isotopes, providing insight into drought-induced eco-physiological mechanisms, are frequently used to reconstruct past changes in growing season temperature and precipitation. Their climatic response is, however, still not fully understood, particularly for data originating from non-extreme, mid-latitude environments with differing ecological conditions. Here, we assess the response of δ(13)C, δ(18)O and tree-ring width (TRW) from a temperate mountain forest in the Austrian pre-Alps to climate and specific drought events. Variations in stem growth and isotopic composition of Norway spruce, common beech and European larch from dry, medium and moist sites are compared with records of sunshine, temperature, moisture, precipitation and cloud cover. Results indicate uniform year-to-year variations in δ(13)C and δ(18)O across sites and species, but distinct differences in TRW according to habitat and species. While the climate sensitivity of TRW is overall weak, the δ(13)C and δ(18)O chronologies contain significant signals with a maximum sensitivity to cloud cover changes (r = -0.72 for δ(18)O). The coherent inter-annual isotopic variations are accompanied by substantial differences in the isotopic signatures with offsets up to ∼3‰ for δ(13)C, indicating species-specific physiological strategies and varying water-use efficiencies. During severe summer drought, beech and larch benefit from access to deeper and moist soils, allowing them to keep their stomata open. This strategy is accompanied by an increased water loss through transpiration, but simultaneously enables enhanced photosynthesis. Our findings indicate the potential of tree-ring stable isotopes from temperate forests to reconstruct changes in cloud cover, and to improve knowledge on basic physiological mechanisms of tree species growing in different habitats to cope with soil moisture deficits. PMID:25466725

  20. Comparison of the Decomposition VOC Profile during Winter and Summer in a Moist, Mid-Latitude (Cfb) Climate

    PubMed Central

    Forbes, Shari L.; Perrault, Katelynn A.; Stefanuto, Pierre-Hugues; Nizio, Katie D.; Focant, Jean-François

    2014-01-01

    The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC×GC-TOFMS were demonstrated for

  1. The impact of greenhouse climate change on the energetics and hydrologic processes of mid-latitude transient eddies

    NASA Technical Reports Server (NTRS)

    Branscome, Lee E.; Gutowski, William J., Jr.

    1991-01-01

    Atmospheric transient eddies contribute significantly to mid-latitude energy and water vapor transports. Changes in the global climate, as induced by greenhouse enhancement, will likely alter transient eddy behavior. Unraveling all the feedbacks that occur in general circulation models (GCMs) can be difficult. The transient eddies are isolated from the feedbacks and are focused on the response of the eddies to zonal-mean climate changes that result from CO2-doubling. Using a primitive-equation spectral model, the impact of climate change on the life cycles of transient eddies is examined. Transient eddy behavior in experiments is compared with initial conditions that are given by the zonal-mean climates of the GCMs with current and doubled amounts of CO2. The smaller meridional temperature gradient in a doubled CO2 climate leads to a reduction in eddy kinetic energy, especially in the subtropics. The decrease in subtropical eddy energy is related to a substantial reduction in equatorward flux of eddy activity during the latter part of the life cycle. The reduction in equatorward energy flux alters the moisture cycle. Eddy meridional transport of water vapor is shifted slightly poleward and subtropical precipitation is reduced. The water vapor transport exhibits a relatively small change in magnitude, compared to changes in eddy energy, due to the compensating effect of higher specific humidity in the doubled-CO2 climate. An increase in high-latitude precipitation is related to the poleward shift in eddy water vapor flux. Surface evaporation amplifies climatic changes in water vapor transport and precipitation in the experiments.

  2. Uniform climate sensitivity in tree-ring stable isotopes across species and sites in a mid-latitude temperate forest

    NASA Astrophysics Data System (ADS)

    Hartl-Meier, Claudia; Zang, Christian; Büntgen, Ulf; Esper, Jan; Rothe, Andreas; Göttlein, Axel; Dirnböck, Thomas; Treydte, Kerstin

    2015-04-01

    Tree-ring stable isotopes, providing insight into drought-induced eco-physiological mechanisms, are frequently used to reconstruct past changes in growing season temperature and precipitation. Their climatic response is, however, still not fully understood, particularly for data originating from non-extreme, mid-latitude environments with differing ecological conditions. Here, we assess the response of δ13C, δ18O and tree-ring width (TRW) from a temperate mountain forest in the Austrian pre-Alps to climate and specific drought events. Variations in stem growth and isotopic composition of Norway spruce, common beech and European larch from dry, medium and moist sites are compared with records of sunshine, temperature, moisture, precipitation and cloud cover. Results indicate uniform year-to-year variations in δ13C and δ18O across sites and species, but distinct differences in TRW according to habitat and species. While the climate sensitivity of TRW is overall weak, the δ13C and δ18O chronologies contain significant signals with a maximum sensitivity to cloud cover changes (r = -0.72 for δ18O). The coherent inter-annual isotopic variations are accompanied by substantial differences in the isotopic signatures with offsets up to ˜3‰ for δ13C, indicating species-specific physiological strategies and varying water-use efficiencies. During severe summer drought, beech and larch benefit from access to deeper and moist soils, allowing them to keep their stomata open. This strategy is accompanied by an increased water loss through transpiration, but simultaneously enables enhanced photosynthesis. Our findings indicate the potential of tree-ring stable isotopes from temperate forests to reconstruct changes in cloud cover, and to improve knowledge on basic physiological mechanisms of tree species growing in different habitats to cope with soil moisture deficits.

  3. Electron density and plasma waves in mid-latitude sporadic-E layer observed during the SEEK-2 campaign

    NASA Astrophysics Data System (ADS)

    Wakabayashi, M.; Ono, T.; Mori, H.; Bernhardt, P. A.

    2005-10-01

    The SEEK-2 campaign was carried out over Kyushu Island in Japan on 3 August 2002, by using the two sounding rockets of S310-31 and S310-32. This campaign was planned to elucidate generation mechanisms of Quasi-Periodic Echoes (QPEs) associated with mid-latitude sporadic-E (Es) layers. Electron number densities were successfully measured in the Es layers by using the impedance probe on board two rockets. The plasma waves in the VLF and ELF ranges were also observed on board the S310-32 rocket. Results of electron density measurement showed that there were one or two major peaks in the Es layers along the rockets' trajectories near the altitude of about 10km. There were some smaller peaks associated with the main Es layers in the altitude range from 90 to 120 km. These density peaks were distributed in a very large extent during the SEEK-2 campaign. The Es layer structure is also measured by using the Fixed Bias Probe (FBP), which has a high spatial resolution of several meters (the impedance probe has an altitude resolution of about 400 m). The comparison with the total electron content (TEC) measured by the Dual Band Beacon revealed that the Es layer was also modulated in the horizontal direction with the scale size of 30 40 km. It was shown that the QP echoes observed by the ground-based coherent radar come from the major density peak of the Es layer. The plasma wave instrument detected the enhancement of VLF and ELF plasma waves associated with the operation of the TMA release, and also with the passage of the Es layers. Keywords. Ionosphere (Ionospheric irregularities; Midlatitude ionosphere; Plasma temeperature and density)

  4. Kinematics and thermodynamics of a midlatitude, continental mesoscale convective system and its mesoscale vortex

    NASA Astrophysics Data System (ADS)

    Knievel, Jason Clark

    The author examines a mesoscale convective system (MCS) and the mesoscale convective vortex (MCV) it generated. The MCS, which comprised a leading convective line and trailing stratiform region, traversed Kansas and Oklahoma on 1 August 1996, passing through the NOAA Wind Profiler Network, as well as four sites from which soundings were being taken every three hours during a field project. The unusually rich data set permitted study of the MCS and MCV over nine hours on scales between those of operational rawinsondes and Doppler radars. The author used a spatial bandpass filter to divide observed wind into synoptic and mesoscale components. The environment-relative, mesoscale wind contained an up- and downdraft and divergent outflows in the lower and upper troposphere. The mesoscale wind was asymmetric about the MCS, consistent with studies of gravity waves generated by heating typical of that in many MCSs. According to a scale-discriminating vorticity budget, both the synoptic and mesoscale winds contributed to the prominent resolved sources of vorticity in the MCV: tilting and convergence. Unresolved sources were also large. The author speculates that an abrupt change in the main source of vorticity in an MCV may appear as an abrupt change in its altitude of maximum vorticity. Distributions of temperature and humidity in the MCS were consistent with its mesoscale circulations. In the terminus of the mesoscale downdraft, advection of drier, potentially warmer air exceeded humidifying and cooling from rain, so profiles of temperature and dew point exhibit onion and double-onion patterns. The mesoscale updraft was approximately saturated with a moist adiabatic lapse rate. Mesoscale drafts and convective drafts vertically mixed the troposphere, partially homogenizing equivalent potential temperature. The MCV contained a column of high potential vorticity in the middle troposphere, with a cold core below the freezing level and a warm core above---a pattern

  5. Eocene continental climates and latitudinal temperature gradients

    NASA Astrophysics Data System (ADS)

    Greenwood, David R.; Wing, Scott L.

    1995-11-01

    Global climate during the Mesozoic and early Cenozoic is thought to have been warmer than at present, but there is debate about winter temperatures. Paleontological data indicate mild temperatures even at high latitudes and in mid-latitude continental interiors, whereas computer simulations of continental paleoclimates produce winter temperatures closer to modern levels. Foliar physiognomy and floristic composition of 23 Eocene floras from the interior of North America and Australia indicate cold month means generally >2 °C, even where the mean annual temperature (MAT) was <15 °C. Reconstructed Eocene latitudinal gradients of MAT are curvilinear but are about 0.4 °C per 1° of latitude in continental interiors at mid-latitudes, much less than the 0.8 1.0 °C per 1° of latitude observed in eastern and central North America today, but similar to modern gradients in the Southern Hemisphere mid-latitudes and on the west coast of North America. Latitudinal temperature gradients reconstructed here are broadly representative of Eocene climates, showing that the discrepancy between proxy data and simulations will not be resolved by regional adjustments to paleogeography or reinterpretation of individual fossil assemblages. Similar discrepancies between proxy data and general circulation model simulations for other time periods suggest that there is a basic flaw with the way climate models simulate heat transport to, or loss from, continental surfaces.

  6. Importance of Rain Evaporation and Continental Convection in the Tropical Water Cycle

    NASA Technical Reports Server (NTRS)

    Worden, John; Noone, David; Bowman, Kevin; Beer, R.; Eldering, A.; Fisher, B.; Gunson, M.; Goldman, Aaron; Kulawik, S. S.; Lampel, Michael; Osterman, Gregory; Rinsland, Curtis P.; Rogders, Clive; Sander, Stanley; Shepard, Mark; Webster, Christopher R.; Worden, H. M.

    2007-01-01

    Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur.

  7. The Relation Between Magnetospheric State Parameters and the Occurrence of Plasma Depletion Events in the Night-Time Mid-Latitude F-Region

    NASA Technical Reports Server (NTRS)

    Seker, Ilgin; Fung, Shing F.; Mathews, John D.

    2010-01-01

    Studies using all-sky imagers have revealed the presence of various ionospheric irregularities in the night-time mid-latitude F-region. The most prevalent and well known of these are the Medium Scale Traveling Ionospheric Disturbances (MSTIDs) that usually occur when the geomagnetic activity is low, and mid-latitude spread-F plumes that are often observed when the geomagnetic activity is high. The inverse and direct relations between geomagnetic activity (particularly Kp) and the occurrence rate of MSTIDs and midlatitude plumes, respectively, have been observed by several studies using different instruments. In order to understand the underlying causes of these two relations, it is illuminating to better characterize the occurrence of MSTIDs and plumes using multiple magnetospheric state parameters. Here we statistically compare multiple geomagnetic driver and response parameters (such as Kp, AE, Dst, and solar wind parameters) with the occurrence rates of night-time MSTIDs and plumes observed using an all-sky imager at Arecibo Observatory (AO) between 2003 and 2008. The results not only allow us to better distinguish MSTIDs and plumes, but also shed further light on the generation mechanism and electrodynamics of these two different phenomena occurring at night-time in the mid-latitude F-region.

  8. Convective thinning of the lithosphere - A mechanism for the initiation of continental rifting

    NASA Technical Reports Server (NTRS)

    Spohn, T.; Schubert, G.

    1982-01-01

    A model of lithospheric thinning, in which heat is convected to the base and conducted within the lithosphere, is presented. An analytical equation for determinining the amount of thinning attainable on increasing the heat flux from the asthenosphere is derived, and a formula for lithosphere thickness approximations as a function of time is given. Initial and final equilibrium thicknesses, thermal diffusivity, transition temperature profile, and plume temperature profile are all factors considered for performing rate of thinning determinations. In addition, between initial and final equilibrium states, lithospheric thinning occurs at a rate which is inversely proportional to the square root of the time. Finally, uplift resulting from thermal expansion upon lithospheric thinning is on the order of 10 to the 2nd to 10 to the 3rd m.

  9. Mid-latitude cirrus classification at Rome Tor Vergata through a multi-channel Raman-Mie-Rayleigh lidar

    NASA Astrophysics Data System (ADS)

    Dionisi, D.; Keckhut, P.; Liberti, G. L.; Cardillo, F.; Congeduti, F.

    2013-04-01

    A methodology to identify and characterize cirrus clouds has been developed and applied to the multichannel-multiwavelength Rayleigh-Mie-Raman (RMR) lidar in Rome-Tor Vergata (RTV). A set of 167 cirrus cases, defined on the basis of quasi-stationary temporal period conditions, has been selected in a dataset consisting of about 500 h of nighttime lidar sessions acquired between February 2007 and April 2010. The derived lidar parameters (effective height, geometrical and optical thickness and mean back-scattering ratio) and the cirrus mid-height temperature (estimated from the radiosoundings of Pratica di Mare, WMO site #16245) of this sample have been analyzed by the means of a clustering multivariate analysis. This approach identified four cirrus classes above the RTV site: two thin cirrus clusters in mid and upper troposphere and two thick cirrus clusters in mid-upper troposphere. These results, which are very similar to those derived through the same approach in the lidar site of the Observatoire of Haute Provence (OHP), allows characterizing cirrus clouds over RTV site and attests the robustness of such classification. To have some indications about the cirrus generation methods for the different classes, the analyses of the extinction-to-backscatter ratio (lidar ratio, LReff), in terms of the frequency distribution functions and depending on the mid-height cirrus temperature have been performed. This study suggests that smaller (larger) ice crystals compose thin (thick) cirrus classes. This information, together with the value of relative humidity over ice (110 ± 30%), calculated through the simultaneous WV Raman measurements for the mid-tropospheric thin class, indicates that this class could be formed by an heterogeneous nucleation mechanism. The RTV cirrus results, re-computed through the cirrus classification by Sassen and Cho (1992), shows good agreement to other mid-latitude lidar cirrus observation for the relative occurrence of subvisible (SVC), thin

  10. Structural Variability of Tropospheric Growth Factors Transforming Mid-latitude Cyclones to Severe Storms over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Wild, Simon; Befort, Daniel J.; Leckebusch, Gregor C.

    2015-04-01

    The development of European surface wind storms out of normal mid-latitude cyclones is substantially influenced by upstream tropospheric growth factors over the Northern Atlantic. The main factors include divergence and vorticity advection in the upper troposphere, latent heat release and the presence of instabilities of short baroclinic waves of suitable wave lengths. In this study we examine a subset of these potential growth factors and their related influences on the transformation of extra-tropical cyclones into severe damage prone surface storm systems. Previous studies have shown links between specific growth factors and surface wind storms related to extreme cyclones. In our study we investigate in further detail spatial and temporal variability patterns of these upstream processes at different vertical levels of the troposphere. The analyses will comprise of the three growth factors baroclinicity, latent heat release and upper tropospheric divergence. Our definition of surface wind storms is based on the Storm Severity Index (SSI) alongside a wind tracking algorithm identifying areas of exceedances of the local 98th percentile of the 10m wind speed. We also make use of a well-established extra-tropical cyclone identification and tracking algorithm. These cyclone tracks form the base for a composite analysis of the aforementioned growth factors using ERA-Interim Reanalysis from 1979 - 2014 for the extended winter season (ONDJFM). Our composite analysis corroborates previous similar studies but extends them by using an impact based algorithm for the identification of strong wind systems. Based on this composite analysis we further identify variability patterns for each growth factor most important for the transformation of a cyclone into a surface wind storm. We thus also address the question whether the link between storm intensity and related growth factor anomaly taking into account its spatial variability is stable and can be quantified. While the

  11. A continuous ice-core 10Be record from Mongolian mid-latitudes: Influences of solar variability and local climate

    NASA Astrophysics Data System (ADS)

    Inceoglu, F.; Knudsen, M. F.; Olsen, J.; Karoff, C.; Herren, P.-A.; Schwikowski, M.; Aldahan, A.; Possnert, G.

    2016-03-01

    High-resolution 10Be records used for studies of detailed changes in atmospheric 10Be production rates predominantly derive from polar ice cores. In this study, we present the first 10Be record from a mid-latitude ice core. The ice core derives from the Tsambagarav mountain range located in the Mongolian Altai region. The new 10Be concentration record spans the period from AD 1550 to 2009, while the flux record extends from AD 1816 to 2009. The 10Be concentration in the Tsambagarav ice core ranges between ˜ 1.5 ×104 and ˜ 10 ×104 atomsg-1, whereas the 10Be flux changes from ˜0.02 to ˜0.15 atoms cm-2 s-1. The average 10Be flux at Tsambagarav is four times higher than the average 10Be flux recorded in the NGRIP and Dome Fuji ice cores, which is in accordance with model predictions. In general, the long-term trends observed in the Tsambagarav 10Be concentration and flux records are reasonably similar to those observed in the NGRIP ice core. A comparison between the Tsambagarav 10Be record, group sunspot numbers (GSNs), and solar modulation potentials based on 14C in tree rings suggests that the Maunder Minimum was associated with a prolonged maximum in 10Be concentrations at Tsambagarav, whereas the Dalton Minimum was associated with a minor increase in the 10Be concentration and flux that was delayed relative to the primary minimum in GSNs. The sulphate record from Tsambagarav shows that large positive anomalies in the sulphate concentration are associated with negative anomalies in the 10Be concentration. A concurrent positive sulphate anomaly may explain why the main phase of the Dalton Minimum is subdued in the 10Be record from Tsambagarav. Spectral analysis indicates that the 11-yr solar-cycle signal may have influenced the new 10Be record, but the evidence supporting a direct link is ambiguous. Local and regional climatic changes, such as cyclonic versus anticyclonic conditions and related storm tracks, most likely played a significant role for the 10Be

  12. Observations of reactive nitrogen oxide fluxes by eddy covariance above a mid-latitude mixed hardwood forest

    NASA Astrophysics Data System (ADS)

    Geddes, J. A.; Murphy, J. G.

    2012-12-01

    Human impacts on the global nitrogen cycle have led to many environmental problems including tropospheric ozone and aerosol production, acidification, and eutrophication. However, accelerated nitrogen deposition may also be fertilizing carbon uptake by the world's forests, reducing the impact of global climate change. The observations presented here are part of a long-term interdisciplinary collaboration investigating carbon and nitrogen cycling at a mid-latitude mixed hardwood forest in central Ontario subject to high nitrogen deposition. This project focused on estimating dry deposition rates of reactive nitrogen oxides, as well as the chemical and meteorological controls on their fluxes. Measurements of NOx (= NO + NO2) and NOy (= NOx + NO3 + HNO3 + HONO + volatile p-NO3- + organic nitrates…) were made by a two-channel chemiluminescent analyzer (Air Quality Design, Inc.), where conversion of NO2 to NO was achieved by blue LED converter, and NOy to NO by a heated molybdenum tube. The inlet system was co-located with eddy covariance instrumentation for flux calculations on the top of a 30 m tower extending about 8 m above the forest canopy. The measurements were conducted between July 21 and October 9, 2011. The site is fairly removed from major NOx sources, with campaign average NOx mixing ratio of 550 ppt, although they reached above 2-3 ppb during more polluted events. Average NOy mixing ratios were 1500 ppt. Using meteorological data and back trajectories, we show that airflow from the south brought the highest concentrations of reactive nitrogen, and significant increases in dry deposition to the forest canopy. The magnitude of dry deposition was found to be proportional to NOy mixing ratios, with a small number of high concentration days contributing disproportionately to campaign-long dry deposition. Overall, dry deposition was estimated to contribute approximately 10% of total nitrate deposition to the forest. Diurnal patterns in the fluxes of air with

  13. On the relationship between extreme and mean values in total ozone and atmospheric dynamics and volcanic eruptions at mid-latitudes

    NASA Astrophysics Data System (ADS)

    Holawe, F.; Rieder, H. E.; Frossard, L.; Ribatet, M.; Maeder, J. A.; Staehelin, J.; Peter, T.; Davison, A. C.; Weihs, P.

    2011-12-01

    We present an analysis of the relationship between mean and extreme values in total ozone and atmospheric dynamics and volcanic eruptions at mid-latitudes. In this work we analyze observational data (NIWA2.7 data, spatial resolution: 1°longitude x 1.5° latitude, temporal resolution: daily values) on large spatial/temporal scale for the northern and southern mid-latitudes. To analyze extremes we apply a so-called r-largest order statistics model, a special case of the Poisson point process model, and compared the results with output from a standard ARMA model for mean values. Spatial analysis of coefficient estimates and related p-values for significance provide interesting results regarding the influence of dynamics (i.e., ENSO, NAO, AAO) on total ozone at mid-latitudes. The results show that ENSO influences ozone extremes in both Northern and Southern mid-latitudes (especially during spring), especially towards low latitudes. This pattern indicates the enhanced transport of ozone from the tropics to the extra tropics during strong El Niño events, a feature described so far only based on data from ground based stations but not shown on large spatial scale. Further, the results provide evidence for a relationship between the thickness of the southern ozone "collar" and the ENSO phase (especially La Niña) during winter at Southern mid-latitudes. Next to ENSO significant influence was found for the NAO and its southern counterpart the AAO. Especially the later one is of importance as at central Southern mid-latitudes highly significant negative coefficient estimates are found which can be related to enhanced wave activity in the tropics leading to enhanced ozone transport from the tropics to the extra-tropics. Further the results indicate that the Mt. Pinatubo eruption was amplified by the dynamical state of the atmosphere in the Northern hemisphere but was strongly weakened/masked in the Southern hemisphere. Here the strength of the ozone hole and ozone "collar

  14. Uplift along passive continental margins, changes in plate motion and mantle convection

    NASA Astrophysics Data System (ADS)

    Japsen, Peter; Green, Paul F.; Chalmers, James A.; Bonow, Johan M.

    2014-05-01

    The origin of the forces that produce elevated, passive continental margins (EPCMs) is a hot topic in geoscience. It is, however, a new aspect in the debate that episodes of uplift coincide with changes in plate motion. This has been revealed, primarily, by studies of the burial, uplift and exhumation history of EPCMs based on integration on stratigraphic landscape analysis, low-temperature thermochronology and evidence from the geological record (Green et al., 2013). In the Campanian, Eocene and Miocene, uplift and erosion affected the margins of Brazil and Africa (Japsen et al., 2012b). The uplift phases in Brazil coincided with main phases of Andean orogeny which were periods of relatively rapid convergence at the Andean margin of South America (Cobbold et al., 2001). Because Campanian uplift in Brazil coincides, not only with rapid convergence at the Andean margin of South America, but also with a decline in Atlantic spreading rate, Japsen et al. (2012b) suggested that all these uplift events have a common cause, which is lateral resistance to plate motion. Because the uplift phases are common to margins of diverging plates, it was also suggested that the driving forces can transmit across the spreading axis; probably at great depth, e.g. in the asthenosphere. Late Eocene, Late Miocene and Pliocene uplift and erosion shaped the elevated margin of southern East Greenland (Bonow et al., in review; Japsen et al., in review). These regional uplift phases are synchronous with phases in West Greenland, overlap in time with similar events in North America and Europe and also correlate with changes in plate motion. The much higher elevation of East Greenland compared to West Greenland suggests dynamic support in the east from the Iceland plume. Japsen et al. (2012a) pointed out that EPCMs are typically located above thick crust/lithosphere that is closely juxtaposed to thinner crust/lithosphere. The presence of mountains along the Atlantic margin of Brazil and in East

  15. DC electric field measurement in the mid-latitude ionosphere by S-520-26 sounding rocket in Japan

    NASA Astrophysics Data System (ADS)

    Ishisaka, K.; Suda, K.; Sugai, M.; Takahashi, T.; Yamamoto, M.; Abe, T.; Watanabe, S.

    2012-12-01

    S-520-26 sounding rocket experiment was carried out at Uchinoura Space Center (USC) in Japan at 5:51 JST on 12 January, 2012. The purpose of this experiment is the investigation of the bonding process between the atmospheres and the plasma in the thermosphere. S-520-26 sounding rocket reached to an altitude of 298 km 278 seconds after a launch. The S-520-26 payload was equipped with Electric Field Detector (EFD) with a two set of orthogonal double probes to measure both DC and AC less than 200 Hz electric fields in the spin plane of the payload by using the double probe method. One of the probes is the inflatable tube structure antenna, called the ITA, with a length of 5 m (tip-to-tip). And ITA is very lightweight (12.5g per one boom). The ITA extended and worked without any problems. It was the first successful use of an inflatable structure as a flight antenna. Another one is the ribbon antenna with a length of 2 m (tip-to-tip). The electrodes of two double probe antennas were used to gather the potentials which were detected with high impedance pre-amplifiers using the floating (unbiased) double probe technique. The potential differences on the two main orthogonal axes were digitized on-board using 16-bit analog-digital converter, sampled at 800 samples/sec with low pass filter at cut-off frequency of 200 Hz. Results of DC electric fields measured by the EFD have the large sine waves that result from the payload rotation at the spin period. The largest contribution to the electric field measurements by double probes moving through the ionosphere at mid-latitudes is that due to the v x B fields created by their motion across the ambient magnetic field, where v is the rocket velocity in the Earth-fixed reference frame and B is the ambient magnetic field. The sum of the squares of the two components represents the magnitude of the DC electric field in the spin plane of the payload. These data reveal abrupt, large-scale variations which can immediately be attributed

  16. Use of Imploding Spheres: An Alternative to Explosives as Acoustic Sources at Mid-Latitude SOFAR Channel Depths

    SciTech Connect

    Harben, P.E.; Boro, C.; Dorman, L.; Pulli, J.

    2000-05-12

    depths (500 meters-1200 meters in mid-latitudes). A much thinner walled sphere, a special order modification of a standard 22 liter laboratory boiling flask made by the Kontes Glass Company, was also tested and found to fail in the desired manner, i.e. catastrophically. A test off the coast of California successfully initiated implosion of a Kontes sphere at 685 meters depth. The recorded signal showed a peak pressure slightly larger than that from 1 lb of high explosive detonated at the same depth. The signal spectra showed relatively broad band higher frequency energy with little signal below about 50 Hz and a broad peak in the amplitude spectra between about 200 and 800 Hz, similar to that from an explosive source detonated at the same depth. Although additional testing and development is needed, an imploding sphere source for hydroacoustic calibrations appears viable. Since the source spectra frequencies are generally higher than the frequency band used for nuclear explosion monitoring, low frequency signals (1-50 Hz) will be absent from the implosion source spectra. Calibration will have to be accomplished with frequencies above 50 Hz unless larger spheres, multiple spheres, or shallower implosion depths are used.

  17. Satellite-based VIS/IR multispectral screening of precipitating clouds: A case study during summer at mid-latitudes

    NASA Astrophysics Data System (ADS)

    Cattani, Elsa; Acquistapace, Claudia; Laviola, Sante; Levizzani, Vincenzo

    2013-04-01

    intensities from the 183-WSL algorithm (Laviola and Levizzani, 2011) to investigate strengths and limitations of the methodology. Despite of the short time span of the evaluation data set, some preliminary conclusions can be drawn. The daytime version of the algorithm exhibits the best skills in identifying PCs with cold tops, optically thick and associated with moderate-intense rain intensities. In addition, it also shows a certain ability to detect stratiform precipitating water clouds. The algorithm has a tendency to slightly overestimate the rainfall areas, but, on the other hand, the missed events are generally associated with low average rain rates (0.6 - 0.8 mm h-1). Finally, a discontinuity in the PC algorithm performances is noted when switching from twilight to daytime conditions and vice versa due to the different algorithm set up for daytime and twilight. Laviola S., and V. Levizzani, 2011: The 183-WSL fast rain rate retrieval algorithm. Part I: Retrieval design. Atmos. Res., 99, 3-4, 443-461. Thies B., T. Nauss, and J. Bendix, 2008: Discriminating raining from non-raining clouds at mid-latitudes using Meteosat Second Generation daytime data. Atmos. Chem. Phys., 8, 2341-2349.

  18. Contribution of Field-Aligned Currents to the Variations of Mid-Latitude Magnetic Field on the Ground: Dayside and Nightside are Compared.

    NASA Astrophysics Data System (ADS)

    Dubyagin, S.; Ganushkina, N. Y.

    2015-12-01

    Field-aligned currents (FACs) are believed to be the main contributors to the asymmetric variation of the magnetic field on the ground at mid-latitudes during geomagnetic storms. However, the contribution from the ionospheric currents can interfere with that from FACs on the dayside where ionospheric conductivity is higher and not concentrated along the auroral oval. We present the results of the comparison of the contribution from the large-scale FAC system with the observations at the mid-latitude observatories during 12 geomagnetic storms. The contribution from the FAC system is estimated using the 10 min resolution data of AMPERE system which provides 2D map of the FAC flowing in and out of the ionosphere reconstructed from the measurements onboard of ~70 Irridium satellites . To estimate the magnetic effect of FAC system, we performed Biot-Savart integration of these currents along IGRF field from the equator to the earth center. Although in reality the FACs close via ionosphere, we generally obtain a good quantitative agreement with observations at the ground observatories on the nighside. On the other hand the agreement is much worse on the dayside. The correlation coefficient between the D-component of the magnetic field measured on the ground and that computed using Biot-Savart integration varies between ~0.65 (21-03h MLT) and < 0.1 (12-18h MLT). In addition, we discuss the closure paths of the large scale FACs during storm periods and the sources of the north-south asymmetry of the ground magnetic field at mid-latitudes.

  19. Patterns of cold-air drainage and microclimate in mid-latitude versus high-latitude mountains: contrasts and implications for climate change (Invited)

    NASA Astrophysics Data System (ADS)

    Pepin, N. C.

    2009-12-01

    Predictions of current spatial patterns of climate are difficult in areas of complex relief in all parts of the world, because of the interweaving influences of topography, elevation and aspect. These influences vary temporally as a result of the seasonal and diurnal cycles in radiation balance. In periods of negative energy balance, surface decoupling can occur as cold air drainage develops low-level temperature inversions, and the surface temperature regime beneath the inversion becomes divorced from free atmospheric forcing. Both the spatial scale and temporal persistence of this decoupling vary according to latitude, and although the physical processes that influence inversion formation are similar in polar areas and mid-latitude mountains, the contrasting seasonal and diurnal forcings make the end results very different. Examples are contrasted from detailed field temperature measurements (~50 sites per field area) taken over several years in areas of complex relief in the eastern Pyrenees (~42.5 deg N), the Oregon Cascades (also ~42.5 deg N) and Finnish Lapland (70 deg N and above the Arctic circle). In the former two locations decoupling is mostly diurnally driven, and small-scale topography is important in mediating the effects. Summer decoupling is brief and spatially limited, whereas winter decoupling can be more spatially extensive. There are strong relationships between synoptic conditions, as measured by objective flow indices at the 700 mb level (derived from NCEP/NCAR reanalysis fields) and the patterns of decoupling, which allow us to assess the effects of past and potential future circulation change on spatial patterns of future climate warming. In Finnish Lapland the decoupling regime most clearly approaches the mid-latitude pattern around the equinoxes when there are clear day and night periods. In winter and summer however (the polar night and polar day) with the muting of the diurnal cycle, processes are more poorly understood. Winter cold

  20. Simulation of the transport of halogen species from the equatorial and mid-latitude stratosphere to the polar stratosphere in a two-dimensional model

    NASA Technical Reports Server (NTRS)

    Yung, Yuk L.; Shia, R. L.; Allen, M.; Zurek, R. W.; Crisp, D.; Wen, J. S.

    1988-01-01

    The bulk of O sub 3 destruction in the Antarctic stratosphere takes place in the lower stratosphere between 15 and 25 km. Both O sub 3 and the halogen reservoir species have their origins in the higher altitude region (20 to 30 km) in the equatorial and mid-latitude stratosphere. Using the Caltech-JPL two-dimensional residual circulation model, researchers investigate the growth of stratospheric halogen due to the increase of CFCl sub 3 and CF sub 2 Cl sub 2.

  1. Kilometer-thick ice-sheets in the northern mid-latitudes of Mars in the Amazonian: Analogs from the East Antarctic Ice Sheet and the Dry Valleys

    NASA Astrophysics Data System (ADS)

    Head, James W.; Marchant, David R.

    2008-09-01

    Introduction. The strong geomorphic similarities between lobate deposits on the northwest flank of the Tharsis Montes [1,2, 12-13] and along the dichotomy boundary between 30° and 50° [3] with terrestrial cold-based glaciers and glacial deposits has led to new hypotheses for geologically recent (Amazonian-age) low and mid-latitude glaciation on Mars [1,4]. A common theme among many of these studies has been to identify individual landscape elements on Mars and match them with terrestrial counterparts from cold polar deserts on Earth [5,6]. Here, we use the documented long-term history of outlet and alpine glaciers along the East Antarctic Ice Sheet in the Dry Valleys of Antarctica as a suitable analog for glaciation along the martian dichotomy boundary. As a guiding principle we note that, just as for terrestrial glacial landsystems, the most recent ice-related deposit/feature along the dichotomy boundary on Mars need not reflect the maximum in ice volume and/or ice configuration. The Antarctic Dry Valleys (ADV). A terrestrial analog for cold-based glaciation across steppedbedrock topography. To a first order, the large-scale bedrock geomorphology of the Antarctic Dry Valleys (Transantarctic mountain rift-margin upwarp) approximates the martian dichotomy boundary: the valleys occur within, and dissect, a series of broad, coast-facing escarpments (total relief of up to 3000 m) separated by isolated inselbergs. In the middle Miocene, sometime between 14.8 and 12.5 Ma [7, 8], all but the highest mountains in the Dry Valleys were overrun by a major expansion of East Antarctic ice. During this time, ice spilled across bedrock escarpments and flowed out across low-lying valleys toward the continental shelf. A modern-day counterpart for the maximum-overriding stage is seen inland of the ADV, where glacier ice still overrides stepped bedrock topography (Fig. 1). Ice expansion was triggered when the Antarctic cryosphere transitioned from relatively warm and wet (fostering

  2. VOC Source and Inflow Characterization during the Deep Convective Cloud and Chemistry (DC3) experiment

    NASA Astrophysics Data System (ADS)

    Blake, N. J.; Hartt, G.; Barletta, B.; Simpson, I. J.; Schroeder, J.; Hung, Y.; Marrero, J.; Gartner, A.; Hirsch, C.; Meinardi, S.; Blake, D. R.; Zhang, Y.; Apel, E. C.; Hornbrook, R. S.; Campos, T. L.; Emmons, L. K.

    2013-12-01

    More than 50 volatile organic compounds (VOCs) were measured during the Deep Convective Clouds and Chemistry Project (DC3) field campaign, which was based out of Salina, KS May 10 - June 30, 2012. DC3 investigated the impact of deep, mid-latitude continental convective clouds on upper tropospheric composition and chemistry. The UCI Whole Air Sampler (WAS) measured VOCs on board the NASA DC-8 aircraft and the NCAR Trace Organic Gas Analyzer (TOGA) measured VOCs on board the NSF GV. Coordinated flights between the two aircraft produced a rich dataset with which to characterize the inflow and outflow of convective events. While probing storm inflow, numerous natural and anthropogenic sources were encountered, including oil and gas wells in Colorado, Texas, and Oklahoma, biomass burning, biogenic VOC emissions, and other anthropogenic sources (urban, feedlots, etc). The significant and widespread influence of oil and gas activities dominated VOC alkane distributions during DC3, in both inflow and outflow, effectively illustrating the connection between emission and fast vertical transport of VOCs into the free troposphere. We present a mass balance analysis of a flight over TX and OK, which allowed us to estimate oil and gas emissions in that region. The results from this analysis will be compared to previous work in the same area, as well as to emissions from other oil and gas regions and to model simulations from the Community Atmosphere Model with Chemistry (CAM-chem).

  3. The impact of Arctic sea ice on the Arctic energy budget and on the climate of the Northern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Semmler, Tido; McGrath, Ray; Wang, Shiyu

    2012-12-01

    The atmospheric general circulation model EC-EARTH-IFS has been applied to investigate the influence of both a reduced and a removed Arctic sea ice cover on the Arctic energy budget and on the climate of the Northern mid-latitudes. Three 40-year simulations driven by original and modified ERA-40 sea surface temperatures and sea ice concentrations have been performed at T255L62 resolution, corresponding to 79 km horizontal resolution. Simulated changes between sensitivity and reference experiments are most pronounced over the Arctic itself where the reduced or removed sea ice leads to strongly increased upward heat and longwave radiation fluxes and precipitation in winter. In summer, the most pronounced change is the stronger absorption of shortwave radiation which is enhanced by optically thinner clouds. Averaged over the year and over the area north of 70° N, the negative energy imbalance at the top of the atmosphere decreases by about 10 W/m2 in both sensitivity experiments. The energy transport across 70° N is reduced. Changes are not restricted to the Arctic. Less extreme cold events and less precipitation are simulated in sub-Arctic and Northern mid-latitude regions in winter.

  4. Electrodynamical response of the Indian low-mid latitude ionosphere to the very large solar flare of 28 October 2003 - a case study

    NASA Astrophysics Data System (ADS)

    Manju, G.; Pant, T. K.; Devasia, C. V.; Ravindran, S.; Sridharan, R.

    2009-10-01

    The electrodynamic effects on the low-mid latitude ionospheric region have been investigated using GPS (global positioning system) data, ionosonde data and ΔH values, during the very large solar flare (X17.2/4B) of 28 October 2003. The results bring out the flare induced unusual behaviour of the equatorial ionosphere on this day just prior to sunset. The important observations are i) Large and prolonged Ne enhancements observed from ionosonde data just after the flare-related peak enhancement in EUV flux. The observed enhancement in Ne is due to the increase in ionization production due to the enhanced EUV flux and the persistence of the enhancement is probably due to the prompt penetration related upliftment of the F layer (just prior to the flare peak phase) to higher altitudes, where recombination rates are lower. ii) A significant enhancement in total electron content (TEC) (~10 TEC units) at regions around the Equatorial Ionization Anomaly (EIA) crest region (Ahmedabad) during the flare in association with the flare related EUV flux enhancement. iii) Similar enhancements seen at stations of Jodhpur and Delhi in the mid latitude sector. iv)The flare related flux enhancements in different longitude sectors in the equatorial electrojet region have been shown to produce positive and negative variations in electrojet strength indicating the presence of current systems having positive and negative polarities in different longitude sectors. Thus the flare effect reveals the longitudinal variation of the counter electrojet events in the Equatorial Electrojet (EEJ) region.

  5. Thermal comfort in Quebec City, Canada: sensitivity analysis of the UTCI and other popular thermal comfort indices in a mid-latitude continental city.

    PubMed

    Provençal, Simon; Bergeron, Onil; Leduc, Richard; Barrette, Nathalie

    2016-04-01

    The newly developed Universal Thermal Climate Index (UTCI), along with the physiological equivalent temperature (PET), the humidex (HX) and the wind chill index (WC), was calculated in Quebec City, Canada, a city with a strong seasonal climatic variability, over a 1-year period. The objective of this study is twofold: evaluate the operational benefits of implementing the UTCI for a climate monitoring program of public comfort and health awareness as opposed to relying on traditional and simple indices, and determine whether thermal comfort monitoring specific to dense urban neighborhoods is necessary to adequately fulfill the goals of the program. In order to do so, an analysis is performed to evaluate each of these indices' sensitivity to the meteorological variables that regulate them in different environments. Overall, the UTCI was found to be slightly more sensitive to mean radiant temperature, moderately more sensitive to humidity and much more sensitive to wind speed than the PET. This dynamic changed slightly depending on the environment and the season. In hot weather, the PET was found to be more sensitive to mean radiant temperature and therefore reached high values that could potentially be hazardous more frequently than the UTCI and the HX. In turn, the UTCI's stronger sensitivity to wind speed makes it a superior index to identify potentially hazardous weather in winter compared to the PET and the WC. Adopting the UTCI broadly would be an improvement over the traditionally popular HX and WC indices. The urban environment produced favorable conditions to sustain heat stress conditions, where the indices reached high values more frequently there than in suburban locations, which advocates for weather monitoring specific to denser urban areas. PMID:26349476

  6. Thermal comfort in Quebec City, Canada: sensitivity analysis of the UTCI and other popular thermal comfort indices in a mid-latitude continental city

    NASA Astrophysics Data System (ADS)

    Provençal, Simon; Bergeron, Onil; Leduc, Richard; Barrette, Nathalie

    2016-04-01

    The newly developed Universal Thermal Climate Index (UTCI), along with the physiological equivalent temperature (PET), the humidex (HX) and the wind chill index (WC), was calculated in Quebec City, Canada, a city with a strong seasonal climatic variability, over a 1-year period. The objective of this study is twofold: evaluate the operational benefits of implementing the UTCI for a climate monitoring program of public comfort and health awareness as opposed to relying on traditional and simple indices, and determine whether thermal comfort monitoring specific to dense urban neighborhoods is necessary to adequately fulfill the goals of the program. In order to do so, an analysis is performed to evaluate each of these indices' sensitivity to the meteorological variables that regulate them in different environments. Overall, the UTCI was found to be slightly more sensitive to mean radiant temperature, moderately more sensitive to humidity and much more sensitive to wind speed than the PET. This dynamic changed slightly depending on the environment and the season. In hot weather, the PET was found to be more sensitive to mean radiant temperature and therefore reached high values that could potentially be hazardous more frequently than the UTCI and the HX. In turn, the UTCI's stronger sensitivity to wind speed makes it a superior index to identify potentially hazardous weather in winter compared to the PET and the WC. Adopting the UTCI broadly would be an improvement over the traditionally popular HX and WC indices. The urban environment produced favorable conditions to sustain heat stress conditions, where the indices reached high values more frequently there than in suburban locations, which advocates for weather monitoring specific to denser urban areas.

  7. Role of Acclimatization in Weather-Related Human Mortality During the Transition Seasons of Autumn and Spring in a Thermally Extreme Mid-Latitude Continental Climate

    PubMed Central

    de Freitas, Christopher R.; Grigorieva, Elena A.

    2015-01-01

    Human mortality is closely related to natural climate-determined levels of thermal environmental stress and the resulting thermophysiological strain. Most climate-mortality research has focused on seasonal extremes during winter and summer when mortality is the highest, while relatively little attention has been paid to mortality during the transitional seasons of autumn and spring. The body acclimatizes to heat in the summer and cold in winter and readjusts through acclimatization during the transitions between the two during which time the body experiences the thermophysiological strain of readjustment. To better understand the influences of weather on mortality through the acclimatization process, the aim here is to examine the periods that link very cold and very warms seasons. The study uses the Acclimatization Thermal Strain Index (ATSI), which is a comparative measure of short-term thermophysiological impact on the body. ATSI centers on heat exchange with the body’s core via the respiratory system, which cannot be protected. The analysis is based on data for a major city in the climatic region of the Russian Far East characterized by very hot summers and extremely cold winters. The results show that although mortality peaks in winter (January) and is at its lowest in summer (August), there is not a smooth rise through autumn nor a smooth decline through spring. A secondary peak occurs in autumn (October) with a smaller jump in May. This suggests the acclimatization from warm-to-cold produces more thermophysiological strain than the transition from cold-to-warm. The study shows that ATSI is a useful metric for quantifying the extent to which biophysical adaptation plays a role in increased strain on the body during re-acclimatization and for this reason is a more appropriate climatic indictor than air temperature alone. The work gives useful bioclimatic information on risks involved in transitional seasons in regions characterized by climatic extremes. This could be handy in planning and managing health services to the public and measures that might be used to help mitigate impacts. PMID:26703633

  8. Role of Acclimatization in Weather-Related Human Mortality During the Transition Seasons of Autumn and Spring in a Thermally Extreme Mid-Latitude Continental Climate.

    PubMed

    de Freitas, Christopher R; Grigorieva, Elena A

    2015-12-01

    Human mortality is closely related to natural climate-determined levels of thermal environmental stress and the resulting thermophysiological strain. Most climate-mortality research has focused on seasonal extremes during winter and summer when mortality is the highest, while relatively little attention has been paid to mortality during the transitional seasons of autumn and spring. The body acclimatizes to heat in the summer and cold in winter and readjusts through acclimatization during the transitions between the two during which time the body experiences the thermophysiological strain of readjustment. To better understand the influences of weather on mortality through the acclimatization process, the aim here is to examine the periods that link very cold and very warms seasons. The study uses the Acclimatization Thermal Strain Index (ATSI), which is a comparative measure of short-term thermophysiological impact on the body. ATSI centers on heat exchange with the body’s core via the respiratory system, which cannot be protected. The analysis is based on data for a major city in the climatic region of the Russian Far East characterized by very hot summers and extremely cold winters. The results show that although mortality peaks in winter (January) and is at its lowest in summer (August), there is not a smooth rise through autumn nor a smooth decline through spring. A secondary peak occurs in autumn (October) with a smaller jump in May. This suggests the acclimatization from warm-to-cold produces more thermophysiological strain than the transition from cold-to-warm. The study shows that ATSI is a useful metric for quantifying the extent to which biophysical adaptation plays a role in increased strain on the body during re-acclimatization and for this reason is a more appropriate climatic indictor than air temperature alone. The work gives useful bioclimatic information on risks involved in transitional seasons in regions characterized by climatic extremes. This could be handy in planning and managing health services to the public and measures that might be used to help mitigate impacts. PMID:26703633

  9. Observations and modeling of northern mid-latitude recurring slope lineae (RSL) suggest recharge by a present-day martian briny aquifer

    NASA Astrophysics Data System (ADS)

    Stillman, David E.; Michaels, Timothy I.; Grimm, Robert E.; Hanley, Jennifer

    2016-02-01

    Recurring slope lineae (RSL) are narrow (0.5-5 m) dark features on Mars that incrementally lengthen down steep slopes, fade in colder seasons, and recur annually. These features have been identified from the northern to southern mid-latitudes. Here, we describe how observations of northern mid-latitude RSL in northern Chryse Planitia and southwestern Acidalia Planitia (CAP) suggest that brines start flowing before northern spring equinox and continue for more than half a Mars-year (490 ± 40 sols, spanning solar longitude 337° ± 11°-224° ± 20°). All CAP RSL are found on the steep slopes of craters and their source zones are at or below the elevation of the surrounding plains. Spacecraft-derived surface temperature observations cannot resolve individual RSL, so thermal modeling was used to determine that CAP RSL have a freezing temperature of 238-252 K, freeze and melt diurnally, and flow only occurs within the top ∼8 cm of the regolith. Furthermore, we calculate that a typical CAP RSL has a water budget of 1.5-5.6 m3/m of headwall. Therefore, such a large water budget makes annual recharge via atmospheric or subsurface diffusion sources unlikely. Alternatively, we hypothesize that the most plausible RSL source is a briny aquifer with a freezing temperature less than or equal to the mean annual CAP surface temperature (220-225 K). The annual cycle is as follows: in late autumn, the shallowest part of the brine feeding the source zone freezes, forming an ice dam. As spring approaches, temperatures rise and the dam is breached. Brine is discharged and the RSL initially lengthens rapidly (>1.86 m/sol), the lengthening rate then slows considerably, to ∼0.25 m/sol. Eventually, the losses equal the discharge rate and the RSL reaches its equilibrium phase. As brine flows in the RSL some of the water is lost to the atmosphere, therefore the freezing temperature of the brine within the RSL is higher (238-252 K) as the brine transitions to a super-eutectic salt

  10. On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes - Part 1: Statistical models and spatial fingerprints of atmospheric dynamics and chemistry

    NASA Astrophysics Data System (ADS)

    Frossard, L.; Rieder, H. E.; Ribatet, M.; Staehelin, J.; Maeder, J. A.; Di Rocco, S.; Davison, A. C.; Peter, T.

    2013-01-01

    We use statistical models for mean and extreme values of total column ozone to analyze "fingerprints" of atmospheric dynamics and chemistry on long-term ozone changes at northern and southern mid-latitudes on grid cell basis. At each grid cell, the r-largest order statistics method is used for the analysis of extreme events in low and high total ozone (termed ELOs and EHOs, respectively), and an autoregressive moving average (ARMA) model is used for the corresponding mean value analysis. In order to describe the dynamical and chemical state of the atmosphere, the statistical models include important atmospheric covariates: the solar cycle, the Quasi-Biennial Oscillation (QBO), ozone depleting substances (ODS) in terms of equivalent effective stratospheric chlorine (EESC), the North Atlantic Oscillation (NAO), the Antarctic Oscillation (AAO), the El Niño/Southern Oscillation (ENSO), and aerosol load after the volcanic eruptions of El Chichón and Mt. Pinatubo. The influence of the individual covariates on mean and extreme levels in total column ozone is derived on a grid cell basis. The results show that "fingerprints", i.e., significant influence, of dynamical and chemical features are captured in both the "bulk" and the tails of the statistical distribution of ozone, respectively described by mean values and EHOs/ELOs. While results for the solar cycle, QBO, and EESC are in good agreement with findings of earlier studies, unprecedented spatial fingerprints are retrieved for the dynamical covariates. Column ozone is enhanced over Labrador/Greenland, the North Atlantic sector and over the Norwegian Sea, but is reduced over Europe, Russia and the Eastern United States during the positive NAO phase, and vice-versa during the negative phase. The NAO's southern counterpart, the AAO, strongly influences column ozone at lower southern mid-latitudes, including the southern parts of South America and the Antarctic Peninsula, and the central southern mid-latitudes. Results

  11. The magnitude and rapidity of the climate change marking the end of the Pleistocene in the mid-latitudes of South America

    USGS Publications Warehouse

    Ashworth, A.C.; Hoganson, J.W.

    1993-01-01

    The chi-squared test of independence and cluster analysis of Otsuka similarity coefficients of fossil beetle assemblages from the Chilean Lake Region in the mid-latitudes of South America support the following conclusions: (1) the mean summer temperature of the glacial climate was 4-5??C lower than today's climate; (2) the climatic change from glacial to interglacial mode was in a single step centered on about 14,000 yr B.P.; (3) the climatic change was rapid, and within 1500 years the biota of a moorland had been completely replaced by a biota of a rain forest; (4) by 12,500 yr B.P., the low elevation beetle fauna of the Chilean Lake Region was similar in composition to that of the present day; and (5) no reversal in the postglacial warming trend, equivalent in age to the Younger Dryas Stade, was detected. ?? 1993.

  12. Mid-Latitude versus Polar-Latitude Transitional Impact Craters: Geometric Properties from Mars Orbiter Laser Altimeter (MOLA) Observations and Viking Images

    NASA Technical Reports Server (NTRS)

    Matias, A.; Garvin, J. B.; Sakimoto, S. E. H.

    1998-01-01

    One intriguing aspect of martian impact crater morphology is the change of crater cavity and ejecta characteristics from the mid-latitudes to the polar regions. This is thought to reflect differences in target properties such as an increasing presence of ice in the polar regions. Previous image-based efforts concerning martian crater morphology has documented some aspects of this, but has been hampered by the lack of adequate topography data. Recent Mars Orbiter Laser Altimeter (MOLA) topographic profiles provide a quantitative perspective for interpreting the detailed morphologies of martian crater cavities and ejecta morphology. This study is a preliminary effort to quantify the latitude-dependent differences in morphology with the goal of identifying target-dependent and crater modification effects from the combined of images and MOLA topography. We combine the available MOLA profiles and the corresponding Viking Mars Digital Image Mosaics (MDIMS), and high resolution Viking Orbiter images to focus on two transitional craters; one on the mid-latitudes, and one in the North Polar region. One MOLA pass (MGS Orbit 34) traverses the center of a 15.9 km diameter fresh complex crater located at 12.8degN 83.8degE on the Hesperian ridge plains unit (Hvr). Viking images, as well as MOLA data, show that this crater has well developed wall terraces and a central peak with 429 m of relative relief. Three MOLA passes have been acquired for a second impact crater, which is located at 69.5degN 41degE on the Vastitas Borealis Formation. This fresh rampart crater lacks terraces and central peak structures and it has a depth af 579 m. Correlation between images and MOLA topographic profiles allows us to construct basic facies maps of the craters. Eight main units were identified, four of which are common on both craters.

  13. Variability of the bottomside (B0, B1) profile parameters of ionospheric electron density over the lower mid-latitude Cyprus and comparisons with IRI-2012 model

    NASA Astrophysics Data System (ADS)

    Panda, Sampad Kumar; Haralambous, Haris; Mostafa, Md Golam

    2016-07-01

    The present study investigates the variations of the bottomside ionospheric electron density profile thickness (B0) and shape (B1) parameters, deduced from the manually scaled digisonde (DPS-4D) ionograms at the lower mid-latitude Cyprus (Geographic 35°N, 33°E) covering the period 2009-2014. The monthly median hourly values of these parameters during different seasons and solar activity conditions are compared with the International Reference Ionosphere model (IRI-2012) estimations using three different options namely: Bil-2000, Gul-1987, and ABT-2009. To ensure the quiet time profile, the ionograms of the geomagnetically disturbed periods are discarded from the datasets and the storm model in the IRI is intentionally turned off. The statistical studies reveal considerable discrepancies in the observed B0 parameters from the model simulations, though the divergences are minimal around the daytime and during the summer solstice seasons. Nevertheless, B0 with the Gul-1987 option apparently shows closer daytime value during the low solar active summer, whereas the ABT-2009 option manifested relatively better agreement during the high solar active summer months. The characteristic morning, evening, as well as nighttime departure in the model derived B0 parameters are conspicuous in all the seasons in spite of unnoticed perturbations in the B1, suggesting that further improvement in the existing model database is essential with additional in-situ experimental data across the lower mid-latitude region. The important extracts from this study may support in the international efforts of determining the best set of profile parameters for the climatological representation of the ionospheric electron density variation across the globe.

  14. Effects of the intense geomagnetic storm of September-October 2012 on the equatorial, low- and mid-latitude F region in the American and African sector during the unusual 24th solar cycle

    NASA Astrophysics Data System (ADS)

    de Jesus, R.; Fagundes, P. R.; Coster, A.; Bolaji, O. S.; Sobral, J. H. A.; Batista, I. S.; de Abreu, A. J.; Venkatesh, K.; Gende, M.; Abalde, J. R.; Sumod, S. G.

    2016-02-01

    The main purpose of this paper is to investigate the response of the ionospheric F layer in the American and African sectors during the intense geomagnetic storm which occurred on 30 September-01 October 2012. In this work, we used observations from a chain of 20 GPS stations in the equatorial, low- and mid-latitude regions in the American and African sectors. Also, in this study ionospheric sounding data obtained during 29th September to 2nd October, 2012 at Jicamarca (JIC), Peru, São Luis (SL), Fortaleza (FZ), Brazil, and Port Stanley (PST), are presented. On the night of 30 September-01 October, in the main and recovery phase, the h´F variations showed an unusual uplifting of the F region at equatorial (JIC, SL and FZ) and mid- (PST) latitude stations related with the propagations of traveling ionospheric disturbances (TIDs) generated by Joule heating at auroral regions. On 30 September, the VTEC variations and foF2 observations at mid-latitude stations (American sector) showed a long-duration positive ionospheric storm (over 6 h of enhancement) associated with large-scale wind circulations and equatorward neutral winds. Also, on 01 October, a long-duration positive ionospheric storm was observed at equatorial, low- and mid- latitude stations in the African sector, related with the large-scale wind circulations and equatorward neutral winds. On 01 and 02 October, positive ionospheric storms were observed at equatorial, low- and mid-latitude stations in the American sector, possibly associated with the TIDs and an equatorward neutral wind. Also, on 01 October negative ionospheric storms were observed at equatorial, low- and mid-latitude regions in the American sector, probably associated with the changes in the O/N2 ratio. On the night of 30 September-01 October, ionospheric plasma bubbles were observed at equatorial, low- and mid- latitude stations in the South American sector, possibly associated with the occurrence of geomagnetic storm.

  15. Dynamic evolution of continental and oceanic lithosphere in global mantle convection model with plate-like tectonics and one sided subduction.

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Coltice, Nicolas; Tackley, Paul

    2015-04-01

    Drifting of continents, spreading of the seafloor and subduction at convergent boundaries shape the surface of the Earth. On the timescales of several hundreds of millions of years, divergent boundaries at mid-ocean ridges are created and destroyed in within the Wilson cycle. This controls the evolution of the Earth as it determines the heat loss out. Presence of floating continents facilitates the Earth-like mobile lid style of convection as convective stresses are concentrated on the rheological boundary between oceanic and continental lithosphere. Subducting slabs allow for the surface material to be buried down into the mantle and have an important effect on surface tectonics. The main feature of the subduction zones observed on Earth is that it is single-sided forming the deep trenches. Recently, different numerical models were successful in reproducing one-sided subduction by allowing for the vertical deformation of the Earth surface (Crameri and Tackley 2014). In the meantime, advances were made in modelling continental break-up and formation (Rolf et al. 2014). In this study we perform numerical simulations of global mantle convection in spherical annulus geometry with strongly depth and temperature dependent rheology using StagYY code (Tackley 2008). In these models plate tectonics is generated self-consistently and features one-sided subduction on ocean-ocean plate boundary as well as floating continents. We focus on determining (1) the influence of one-sided subduction on the dynamics of the system (2) formation and breakup of continents. Rerefences: Crameri, F. and P. J. Tackley, Spontaneous development of arcuate single-sided subduction in global 3-D mantle convection models with a free surface, J. Geophys. Res., 119(7), 5921-5942, 2014. Rolf, T., N. Coltice and P. J. Tackley (2014), Statistical cyclicity of the supercontinent cycle, Geophys. Res. Lett. 41, 2014. Tackley, P. J., Modellng compressible mantle convection with large viscosity contrasts in

  16. Early-Holocene Fire, Vegetation, and Climate Linkages in the Mid-Latitudes of Western North and South America

    NASA Astrophysics Data System (ADS)

    Whitlock, C.; Bartlein, P.; Markgraf, V.; Bianchi, M.

    2005-12-01

    High-resolution fire history data from temperate forests of western North and South America permit examination of regional and hemispheric linkages between Holocene climate, fire, and ecosystem response. Both regions show striking differences in the seasonality of precipitation that influence fire regimes at present, and evidence from the paleorecord suggests that the intensity of these precipitation regimes was affected by large-scale changes in the climate system. At present, summer-dry areas in both hemispheres are dominated by subtropical high pressure systems, and subsidence in these areas suppresses summer precipitation. Summer-wet areas are influenced by onshore flow of moisture from the subtropical Pacific and Atlantic, and monsoonal precipitation increases convectional activity and fire activity east of the Rockies and Andes. In the western U.S., paleoenvironmental data, including vegetation, fire, and lake-level records, suggest that the summer-dry area became drier in the early Holocene with the expansion of the subtropical high-pressure system. Fire and pollen records from summer-wet areas, in contrast, are consistent with wetter-than-present conditions, presumably because summer insolation strengthened summer monsoonal circulation. The network of South American fire records show: (1) an abrupt increase in fire activity at the Pleistocene/Holocene transition at high-latitudes; (2) widespread fire activity and drought in the early Holocene despite the summer-insolation minimum; (3) north-south differences in fire activity in the mid-Holocene suggesting the onset of the current dipole climate, and (4) locally variable fire signals and a shift to smaller surface fires in the late Holocene consistent with cooler conditions and greater interannual variability. Widespread fire activity in southern South America in the early Holocene is consistent with recent model simulations that suggest warmer SSTs, a weakened pole-to-equator temperature gradient, and a

  17. The ages of pedestal craters on Mars: Evidence for a late-Amazonian extended period of episodic emplacement of decameters-thick mid-latitude ice deposits

    NASA Astrophysics Data System (ADS)

    Kadish, Seth J.; Head, James W.

    2014-02-01

    There is significant geomorphologic evidence for the past presence of longitudinally widespread, latitudinally zoned deposits composed of ice-rich material at the northern and southern mid latitudes on Mars (lobate debris aprons, lineated valley fill, concentric crater fill, pedestal craters, etc.). Among these features, pedestal craters (Pd) are impact craters interpreted to have produced a protective layer on top of decameters-thick ice deposits now missing in intercrater regions. The time during which these various deposits were present is still highly debated. To address this question we have analyzed the distribution and characteristics of pedestal craters; here, we use a population of 2287 pedestal craters (Pd) to derive a crater retention age for the entire population, obtaining a minimum timescale of formation of ~90 Myr. Given that the ice-rich deposit has not been continuously present for this duration, the timescale of formation is necessarily longer than ~100 Myr. We then compiled impact crater size-frequency distribution dates for 50 individual pedestal craters in both hemispheres to further assess the frequency distribution of individual ages. We calculated pedestal crater ages that ranged from ~1 Myr to ~3.6 Gyr, with a median of ~140 Myr. In addition, 70% of the pedestal ages are less than 250 Myr. During the 150 Myr period between 25 Ma and 175 Ma, we found at least one pedestal age every 15 Myr. This suggests that the ice-rich paleodeposit accumulated frequently during that time period. We then applied these results to the relationship between obliquity and latitudinal ice stability to suggest some constraints on the obliquity history of Mars over the past 200 Myr. Atmospheric general circulation models indicate that ice stability over long periods in the mid latitudes is favored by moderate mean obliquities in the ~35° range. Models of spin-axis/orbital parameter evolution predict that the average obliquity of Mars is ~38°. Our data represent

  18. Large scale variability, long-term trends and extreme events in total ozone over the northern mid-latitudes based on satellite time series

    NASA Astrophysics Data System (ADS)

    Rieder, H. E.; Staehelin, J.; Maeder, J. A.; Ribatet, M.; Davison, A. C.

    2009-04-01

    Various generations of satellites (e.g. TOMS, GOME, OMI) made spatial datasets of column ozone available to the scientific community. This study has a special focus on column ozone over the northern mid-latitudes. Tools from geostatistics and extreme value theory are applied to analyze variability, long-term trends and frequency distributions of extreme events in total ozone. In a recent case study (Rieder et al., 2009) new tools from extreme value theory (Coles, 2001; Ribatet, 2007) have been applied to the world's longest total ozone record from Arosa, Switzerland (e.g. Staehelin 1998a,b), in order to describe extreme events in low and high total ozone. Within the current study this analysis is extended to satellite datasets for the northern mid-latitudes. Further special emphasis is given on patterns and spatial correlations and the influence of changes in atmospheric dynamics (e.g. tropospheric and lower stratospheric pressure systems) on column ozone. References: Coles, S.: An Introduction to Statistical Modeling of Extreme Values, Springer Series in Statistics, ISBN:1852334592, Springer, Berlin, 2001. Ribatet, M.: POT: Modelling peaks over a threshold, R News, 7, 34-36, 2007. Rieder, H.E., Staehelin, J., Maeder, J.A., Ribatet, M., Stübi, R., Weihs, P., Holawe, F., Peter, T., and Davison, A.C.: From ozone mini holes and mini highs towards extreme value theory: New insights from extreme events and non stationarity, submitted to J. Geophys. Res., 2009. Staehelin, J., Kegel, R., and Harris, N. R.: Trend analysis of the homogenized total ozone series of Arosa (Switzerland), 1929-1996, J. Geophys. Res., 103(D7), 8389-8400, doi:10.1029/97JD03650, 1998a. Staehelin, J., Renaud, A., Bader, J., McPeters, R., Viatte, P., Hoegger, B., Bugnion, V., Giroud, M., and Schill, H.: Total ozone series at Arosa (Switzerland): Homogenization and data comparison, J. Geophys. Res., 103(D5), 5827-5842, doi:10.1029/97JD02402, 1998b.

  19. Evidence for Amazonian northern mid-latitude regional glacial landsystems on Mars: Glacial flow models using GCM-driven climate results and comparisons to geological observations

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.; Forget, Francois; Madeleine, Jean-Baptiste; Marchant, David R.

    2011-11-01

    A fretted valley system on Mars located at the northern mid-latitude dichotomy boundary contains lineated valley fill (LVF) with extensive flow-like features interpreted to be glacial in origin. We have modeled this deposit using glacial flow models linked to atmospheric general circulation models (GCM) for conditions consistent with the deposition of snow and ice in amounts sufficient to explain the interpreted glaciation. In the first glacial flow model simulation, sources were modeled in the alcoves only and were found to be consistent with the alpine valley glaciation interpretation for various environments of flow in the system. These results supported the interpretation of the observed LVF deposits as resulting from initial ice accumulation in the alcoves, accompanied by debris cover that led to advancing alpine glacial landsystems to the extent observed today, with preservation of their flow texture and the underlying ice during downwasting in the waning stages of glaciation. In the second glacial flow model simulation, the regional accumulation patterns predicted by a GCM linked to simulation of a glacial period were used. This glacial flow model simulation produced a much wider region of thick ice accumulation, and significant glaciation on the plateaus and in the regional plains surrounding the dichotomy boundary. Deglaciation produced decreasing ice thicknesses, with flow centered on the fretted valleys. As plateaus lost ice, scarps and cliffs of the valley and dichotomy boundary walls were exposed, providing considerable potential for the production of a rock debris cover that could preserve the underlying ice and the surface flow patterns seen today. In this model, the lineated valley fill and lobate debris aprons were the product of final retreat and downwasting of a much larger, regional glacial landsystem, rather than representing the maximum extent of an alpine valley glacial landsystem. These results favor the interpretation that periods of mid-latitude

  20. Measurements of mid-latitude E-region, sporadic-E, and TID-related drifts using HF Doppler-sorted interferometry

    NASA Astrophysics Data System (ADS)

    Parkinson, M. L.; Dyson, P. L.

    1998-03-01

    Modern HF digital ionosondes have been used for Doppler-sorted interferometry (DSI) to automatically measure F-region plasma drifts by detecting the Doppler shift and angle-of-arrival of echoes. We report on the use of a Digisonde 256 receiving on a seven-element antenna array located at the Australian mid-latitude station Beveridge (37.5° S, 144.9° E, -48.0°CGM latitude) to extend the routine application of drift measurements to the E-region, and especially sporadic-E (Es). Obtaining good quality E-region drift measurements required many more soundings independent in the frequency and time domains than are usually made for F-region measurements. This is because the E-region isoionic surfaces were usually more horizontally stratified than those in the more disturbed F-region, and so did not return as many of the oblique echoes upon which the accuracy of the technique depends. Smoothness of the ionosphere was less of a problem when performing Es measurements because of the patchy, cloud-like property of the layers. When making F-region drift measurements the motions are usually thought of as being uniform throughout the volume of ionosphere sampled for echoes. Application of the technique to E-region measurements is interesting because of the enhanced irregular neutral winds associated with gravity waves which grow in amplitude with height. These irregular winds control the motion of the plasma via high collision frequencies, and lead to the formation of Es layers at mid-latitudes. Therefore, the possibility of sharp vertical gradients in plasma drifts must be considered when making and analysing measurements. During numerous campaigns conducted throughout 1994/95, horizontal drifts in the range of ≈ 30-250 m/s were measured for Es patches lasting up to 6 h. The drift measurements sometimes indicated the presence of wave-like motions in the ionosphere with periods in the range 5-90 min. A TID was observed to propagate towards the station from the south, and

  1. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    DOE PAGESBeta

    Fridlind, Ann M.; Atlas, Rachel; van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-06-10

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette massesmore » are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5–2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by  ∼  0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from  ∼ 0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.« less

  2. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    DOE PAGESBeta

    Fridlind, Ann M.; Atlas, Rachel; van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-06-10

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette massesmore » are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5–2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by ~0.2 and 0.05, respectively. Furthermore, a model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from ~0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.« less

  3. On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes - Part 1: Statistical models and spatial fingerprints of atmospheric dynamics and chemistry

    NASA Astrophysics Data System (ADS)

    Frossard, L.; Rieder, H. E.; Ribatet, M.; Staehelin, J.; Maeder, J. A.; Di Rocco, S.; Davison, A. C.; Peter, T.

    2012-05-01

    We use models for mean and extreme values of total column ozone on spatial scales to analyze "fingerprints" of atmospheric dynamics and chemistry on long-term ozone changes at northern and southern mid-latitudes. The r-largest order statistics method is used for pointwise analysis of extreme events in low and high total ozone (termed ELOs and EHOs, respectively). For the corresponding mean value analysis a pointwise autoregressive moving average model (ARMA) is used. The statistical models include important atmospheric covariates to describe the dynamical and chemical state of the atmosphere: the solar cycle, the Quasi-Biennial Oscillation (QBO), ozone depleting substances (ODS) in terms of equivalent effective stratospheric chlorine (EESC), the North Atlantic Oscillation (NAO), the Antarctic Oscillation (AAO), the El~Niño/Southern Oscillation (ENSO), and aerosol load after the volcanic eruptions of El Chichón and Mt. Pinatubo. The influence of the individual covariates on mean and extreme levels in total column ozone is derived on a grid cell basis. The results show that "fingerprints", i.e., significant influence, of dynamical and chemical features are captured in both the "bulk" and the tails of the ozone distribution, respectively described by means and EHOs/ELOs. While results for the solar cycle, QBO and EESC are in good agreement with findings of earlier studies, unprecedented spatial fingerprints are retrieved for the dynamical covariates.

  4. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    NASA Astrophysics Data System (ADS)

    Fridlind, Ann M.; Atlas, Rachel; van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-06-01

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5-2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by ˜ 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from ˜ 0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  5. Statistical characteristics of nighttime mid-latitude F-region field-aligned irregularities observed by Daejeon VHF coherent scattering radar in South Korea

    NASA Astrophysics Data System (ADS)

    Yang, T. Y.; Kwak, Y. S.; Kil, H.; Lee, Y.; Lee, W. K.; Park, Y. D.

    2014-12-01

    We report statistical characteristics of mid-latitude nighttime F-region field-aligned irregularities (FAIs) based on more than three-year observations by Daejeon VHF coherent backscatter radar. This radar has built at Daejeon (36.18°N, 127.14°E, dip lat. 26.7°N) in 2009 with 40.8 MHz operating frequency for continuous monitoring of the behavior of electron density irregularities in the middle latitude. By using long-term observations from January 2010 to December 2013, we obtained the annual, diurnal and seasonal characteristics of a variety of a percentage occurrence, signal-to-noise ratio, and Doppler velocities from the nighttime F-region irregularities over Korea peninsular. From almost four-year observations, the F-region nighttime irregularities occurred most frequently during post-sunset period. These nighttime irregularities usually appeared with occupying different height levels according to local time. This height variation of F-region FAIs was correlated with hmf2 of ionosonde in Icheon, South Korea. The irregularities were least active near the winter solstice and most active near summer solstice. From the annual occurrence variations, F-region nighttime irregularities seem to have tendency with solar activity.

  6. Model study of the mid-latitude atmospheric interaction with energetic O/sup +/ and He/sup +/ (< 20 keV) precipitation during a storm

    SciTech Connect

    Ishimoto, M.

    1986-01-01

    The purpose of this study is to use a model computation to investigate the mid-latitude atmospheric interaction with energetic O/sup +/ and He/sup +/ (<20 keV) precipitation during a storm. The steady-state continuity equations for the fluxes are formulated as a system of first-order ordinary differential equations. The model, consisting of three components, O, N/sub 2/ and He, computes the upward and downward fluxes resulting from energetic ion precipitation by solving sets of this system of equations. The model computes the heating, the ion production, the N/sub 2//sup +/ first negative (O-O) band and N/sub 2/ second-positive (O-O) band emission intensities in the atmosphere, and the escape fluxes to the magnetosphere. Energetic O/sup +/ deposit 80% of their energy for heating and a few percent for ionization below 200 km, and bring 20% of their incident energy back to the magnetosphere together with 30 O and 5 N/sub 2/ particles from the ionospheres for each incident O/sup +/. Energetic He/sup +/ dissipate by ionization (50%) instead of atmospheric heating (10%). He/sup +/ are reflected at an altitude of about 200 km back to the magnetosphere without losing much energy. He/sup +/ precipitation does not bring the ionospheric neutrals back to the magnetosphere.

  7. Impact of the ocean diurnal cycle on the intraseasonnal variability of Sea Surface Temperatures in the mid-latitudes Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Guemas, V.; Salas-Mélia, D.; Kageyama, M.; Giordani, H.; Voldoire, A.

    2009-04-01

    Some recent studies have shown that the ocean diurnal cycle could increase the intraseasonal variability of the Sea Surface Temperatures (SST) in the tropics (Shinoda and Hendon, 1998; Bernie et al, 2005; Shinoda, 2005). This study aims at extending these analyses to the mid-latitudes. To conduct these analyses, the CNRMOM1D 1-dimensional ocean model is forced with ERA40 reanalysis data with a 1 hour frequency in solar heat flux ( 6h hours for the other forcing fields ). The turbulent vertical mixing scheme (Gaspar et al., 1988) is based on the parameterisation of the second-order turbulent moments expressed as a function of the turbulent kinetic energy. The model has 124 vertical levels with a vertical resolution of 1m near the surface and 500m at the bottom. This high vertical resolution combined with a high temporal forcing resolution allows to simulate a realistic diurnal cycle of the oceanic upper-layers. This experiment is compared with one forced on a daily time-step. By comparing both experiments, the impact of the ocean diurnal cycle on the intraseasonnal variability of sea surface temperature anomalies is assessed. We show that the phase of the SST variability is affected and this impact is strongly associated with the non-linear interactions between the diurnal cycle in mixed layer depth and surface forcings.

  8. Dusk-to-nighttime enhancement of mid-latitude NmF2 in local summer: inter-hemispheric asymmetry and solar activity dependence

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Liu, L.; Le, H.; Wan, W.; Zhang, H.

    2015-06-01

    In this paper ionosonde observations in the East Asia-Australia sector were collected to investigate dusk-to-nighttime enhancement of mid-latitude summer NmF2 (maximum electron density of the F2 layer) within the framework of NmF2 diurnal variation. NmF2 were normalized to two solar activity levels to investigate the dependence of the dusk-to-nighttime enhancement on solar activity. The dusk-to-nighttime enhancement of NmF2 is more evident at Northern Hemisphere stations than at Southern Hemisphere stations, with a remarkable latitudinal dependence. The dusk-to-nighttime enhancement shows both increasing and declining trends with solar activity increasing, which is somewhat different from previous conclusions. The difference in the dusk-to-nighttime enhancement between Southern Hemisphere and Northern Hemisphere stations is possibly related to the offset of the geomagnetic axis from the geographic axis. hmF2 (peak height of the F2 layer) diurnal variations show that daytime hmF2 begins to increase much earlier at low solar activity level than at high solar activity level at northern Akita and Wakkanai stations where the dusk-to-nighttime enhancement is more prominent at low solar activity level than at high solar activity level. That implies neutral wind phase is possibly also important for nighttime enhancement.

  9. Precipitation characteristics of CAM5 physics at mesoscale resolution during MC3E and the impact of convective timescale choice

    SciTech Connect

    Gustafson, William I.; Ma, Po-Lun; Singh, Balwinder

    2014-12-17

    The physics suite of the Community Atmosphere Model version 5 (CAM5) has recently been implemented in the Weather Research and Forecasting (WRF) model to explore the behavior of the parameterization suite at high resolution and in the more controlled setting of a limited area model. The initial paper documenting this capability characterized the behavior for northern high latitude conditions. This present paper characterizes the precipitation characteristics for continental, mid-latitude, springtime conditions during the Midlatitude Continental Convective Clouds Experiment (MC3E) over the central United States. This period exhibited a range of convective conditions from those driven strongly by large-scale synoptic regimes to more locally driven convection. The study focuses on the precipitation behavior at 32 km grid spacing to better anticipate how the physics will behave in the global model when used at similar grid spacing in the coming years. Importantly, one change to the Zhang-McFarlane deep convective parameterization when implemented in WRF was to make the convective timescale parameter an explicit function of grid spacing. This study examines the sensitivity of the precipitation to the default value of the convective timescale in WRF, which is 600 seconds for 32 km grid spacing, to the value of 3600 seconds used for 2 degree grid spacing in CAM5. For comparison, an infinite convective timescale is also used. The results show that the 600 second timescale gives the most accurate precipitation over the central United States in terms of rain amount. However, this setting has the worst precipitation diurnal cycle, with the convection too tightly linked to the daytime surface heating. Longer timescales greatly improve the diurnal cycle but result in less precipitation and produce a low bias. An analysis of rain rates shows the accurate precipitation amount with the shorter timescale is assembled from an over abundance of drizzle combined with too little heavy

  10. Precipitation characteristics of CAM5 physics at mesoscale resolution during MC3E and the impact of convective timescale choice

    DOE PAGESBeta

    Gustafson, William I.; Ma, Po-Lun; Singh, Balwinder

    2014-12-17

    The physics suite of the Community Atmosphere Model version 5 (CAM5) has recently been implemented in the Weather Research and Forecasting (WRF) model to explore the behavior of the parameterization suite at high resolution and in the more controlled setting of a limited area model. The initial paper documenting this capability characterized the behavior for northern high latitude conditions. This present paper characterizes the precipitation characteristics for continental, mid-latitude, springtime conditions during the Midlatitude Continental Convective Clouds Experiment (MC3E) over the central United States. This period exhibited a range of convective conditions from those driven strongly by large-scale synoptic regimesmore » to more locally driven convection. The study focuses on the precipitation behavior at 32 km grid spacing to better anticipate how the physics will behave in the global model when used at similar grid spacing in the coming years. Importantly, one change to the Zhang-McFarlane deep convective parameterization when implemented in WRF was to make the convective timescale parameter an explicit function of grid spacing. This study examines the sensitivity of the precipitation to the default value of the convective timescale in WRF, which is 600 seconds for 32 km grid spacing, to the value of 3600 seconds used for 2 degree grid spacing in CAM5. For comparison, an infinite convective timescale is also used. The results show that the 600 second timescale gives the most accurate precipitation over the central United States in terms of rain amount. However, this setting has the worst precipitation diurnal cycle, with the convection too tightly linked to the daytime surface heating. Longer timescales greatly improve the diurnal cycle but result in less precipitation and produce a low bias. An analysis of rain rates shows the accurate precipitation amount with the shorter timescale is assembled from an over abundance of drizzle combined with too

  11. Electron density fluctuations resulted from turbulent mixing in the mid-latitude sporadic-E: A possible variability of the 1D spectrum in rocket measurements

    NASA Astrophysics Data System (ADS)

    Kyzyurov, Yu.

    Motions of neutral gas play the important role in creating irregularities of different scales in the ionospheric plasma. In particular, experimental data reveal that mid-latitude sporadic-E layer is formed by a vertical shear in the horizontal east-west wind due to tides or gravity waves. Below the homopause level (100-120 km) turbulent motions of neutral gas exhibit an essential influence on the layer. Neutral turbulence is responsible for the many-cloud structure of spread sporadic-E layers. This report is devoted to small-scale electron-density fluctuations produced by the turbulence in sporadic-E. Length-scales of the fluctuations correspond to the inertial range of turbulence and are small compared with the local scale of mean plasma-density gradient. We discuss an expected shape of the 1D fluctuation spectrum that can be measured during rocket experiments. The discussion is based on an analytical expression for the spectrum. The main steps necessary for obtaining the expression within the framework of macroscopic description are outlined too. Possible parabolic trajectories of two rockets which can be used for measurements of the sporadic-E electron-density fluctuations in the mid-latitude ionosphere (a magnetic dip angle of 45°) are chosen for a comparison. Parameters of the hypothetical flights were the following: (1) an apogee hmax=180 km, a distance between start and final points R=280 km; and (2) hmax=125 km, R=67 km. Mean values of characteristics for the sporadic-E and the neutral turbulence were fixed at around 97 km in this consideration. We have chosen the layer with a thickness of 2 km, a maximum electron density of 2\\cdot1010 m-3, and concentration of Fe^+ ions of 80 % (i.e. the mean ion mass is about 51 AMU). The mean rate of the turbulent energy dissipation was about 0.1 m^2s-3. Under these circumstances, the rms level of relative fluctuations in electron density may be about 10 % in the range of length-scales 10-400 m. The shape of

  12. Butyltins, polyaromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls in sediments and bivalve mollusks in a mid-latitude environment from the Patagonian coastal zone.

    PubMed

    Commendatore, Marta G; Franco, Marcos A; Gomes Costa, Patricia; Castro, Italo B; Fillmann, Gilberto; Bigatti, Gregorio; Esteves, José L; Nievas, Marina L

    2015-12-01

    Butyltins (BTs), polyaromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) were assessed in a mid-latitude environment of the Patagonian coast, distant from significant pollutant sources. Bioaccumulation processes through bottom sediment resuspension were suggested by BTs level (expressed as ng of tin [Sn] g(-1) dry wt) found in surface sediment (

  13. Statistical study of possible pre-, co- (coeval to) and post- earthquake effects in the near-equatorial, low and mid latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Gousheva, Mariyana; Danov, Dimitar; Hristov, Plamen; Georgieva, Katya

    This paper presents the quasi-static electric field disturbances in the upper ionosphere observed from the satellite INTERCOSMOS-BULGARIA-1300 over earthquakes' source regions at different latitudes. The earthquake data were obtained from United State Geological Survey (USGS) website. In the present paper, an attempt of a statistical stady of ionospheric effects during seismic activity in August- November 1981 is presented. Present study focuses on four main areas- (i) satellite and seismic data selection, (ii) data processing and observations of some most important experimental results, (iii) comparison of observational new data with the results in our previous studies, (iiii) statistical study of possible pre-, co- (coeval to) and postearthquake effects in the near-equatorial, low and mid latitude ionosphere. After review of observational results we analyze an increase of about 5-10-15 mV/m in the vertical component of the quasi-static electric field observed by INTERCOSMOS-BULGARIA-1300 in the upper ionosphere above earthquakes sources during seismic activity. The obtained results strengthen our previous studies (Gousheva et al., 2005a, b; 2006a, b; 2007a, b).The paper discusses the observed effects. The main goal of this study is to generalize our results of possible connection between anomalous vertical electric fields penetrating from the earthquake zone into the ionosphere, and seismic activity. An additional goal of this study is to evaluate some morphological peculiarities of quasi-static electric field disturbances such as their appearance time before and after the main shock, sensitivity, amplitude and time duration.

  14. The study of variability of TEC over mid-latitude American regions during the ascending phase of solar cycle 24 (2009-2011)

    NASA Astrophysics Data System (ADS)

    Asmare Tariku, Yekoye

    2016-08-01

    This paper deals with the pattern of the variability of the Global Positioning System vertical total electron content (GPS VTEC) and the modeled vertical total electron content (IRI 2012 TEC) over American mid-latitude regions during the rising phase of solar cycle 24 (2009-2011). This has been conducted employing ground-based dual frequency GPS receiver installed at Mississippi County Airport (geographic lat. 36.85°N and long. 270.64°E). In this work, the monthly and seasonal variations in the measured VTEC have been analyzed and compared with the VTEC inferred from IRI-2012 model. It has been shown that the monthly and seasonal mean VTEC values get decreased mostly between 05:00 and 10:00 UT and reach their minimal nearly at around 10:00 UT for both the experimental and the model. The VTEC values then get increased and reach the peak values at around 20:00 UT and decrease again. Moreover, it is depicted that the model better estimates both the monthly and seasonal mean hourly VTEC values mostly between 15:00 and 20:00 UT. The modeled monthly and seasonal VTEC values are smaller than the corresponding measured values as the solar activity decreases when all options for the topside electron density are used. However, as the Sun goes from a very low to a high solar activity, the overestimation performance of the VTEC values derived from the model increases. The overall results show that it is generally better to use the model with IRI-2000 option for the topside electron density in estimating the monthly and seasonal VTEC variations, especially when the activity of the Sun decreases.

  15. Emission ratios of anthropogenic volatile organic compounds in northern mid-latitude megacities: Observations versus emission inventories in Los Angeles and Paris

    NASA Astrophysics Data System (ADS)

    Borbon, Agnes; Gilman, J. B.; Kuster, W. C.; Grand, N.; Chevaillier, S.; Colomb, A.; Dolgorouky, C.; Gros, V.; Lopez, M.; Sarda-Esteve, R.; Holloway, J.; Stutz, J.; Petetin, H.; McKeen, S.; Beekmann, M.; Warneke, C.; Parrish, D. D.; Gouw, J. A.

    2013-02-01

    Ground-based and airborne volatile organic compound (VOC) measurements in Los Angeles, California, and Paris, France, during the Research at the Nexus of Air Quality and Climate Change (CalNex) and Megacities: Emissions, Urban, Regional and Global Atmospheric Pollution and Climate Effects, and Integrated Tools for Assessment and Mitigation (MEGAPOLI) campaigns, respectively, are used to examine the spatial variability of the composition of anthropogenic VOC urban emissions and to evaluate regional emission inventories. Two independent methods that take into account the effect of chemistry were used to determine the emission ratios of anthropogenic VOCs (including anthropogenic isoprene and oxygenated VOCs) over carbon monoxide (CO) and acetylene. Emission ratios from both methods agree within ±20%, showing the reliability of our approach. Emission ratios for alkenes, alkanes, and benzene are fairly similar between Los Angeles and Paris, whereas the emission ratios for C7-C9 aromatics in Paris are higher than in Los Angeles and other French and European Union urban areas by a factor of 2-3. The results suggest that the emissions of gasoline-powered vehicles still dominate the hydrocarbon distribution in northern mid-latitude urban areas, which disagrees with emission inventories. However, regional characteristics like the gasoline composition could affect the composition of hydrocarbon emissions. The observed emission ratios show large discrepancies by a factor of 2-4 (alkanes and oxygenated VOC) with the ones derived from four reference emission databases. A bias in CO emissions was also evident for both megacities. Nevertheless, the difference between measurements and inventory in terms of the overall OH reactivity is, in general, lower than 40%, and the potential to form secondary organic aerosols (SOA) agrees within 30% when considering volatile organic emissions as the main SOA precursors.

  16. Influence of Tree Proximity on Simulated Sub-Canopy Incoming Longwave Radiation to the Snow Surface in Mid-Latitude Boreal Forests

    NASA Astrophysics Data System (ADS)

    Webster, C.; Rutter, N.; Jonas, T.; Zahner, F.

    2014-12-01

    Snowmelt in boreal forest environments contributes substantially to spring surface runoff and is largely controlled by the local surface radiation budget. In mid-latitude forested regions, the shading, absorption and emission of incoming radiation causes significant spatial and temporal variation in the surface energy balance within forests of variable canopy densities. Canopy gaps and edges in particular have been shown to have markedly different radiative regimes compared to continuous forests and open areas due to heightened exposure to solar radiation and increased emission of longwave radiation. Improved simulation of the sub-canopy energy fluxes will reduce uncertainty in snowmelt modelling in these areas. Simulated incoming longwave radiation can be partitioned between that from the sky and the canopy, i.e. a two part model, using estimates of emissivity and temperatures. Hemispherical photography allows objective partitioning into sky-view fraction (SVF) and forest fraction (1 - SVF). While air temperature may be used as a proxy for canopy temperature in these models, explicit representation of variability of canopy temperatures have been shown to improve the simulations of longwave emission from the canopy to the snow surface. Simulated incoming longwave radiation, within close proximity to tree trunks, was evaluated at edges of gaps in a discontinuous forest of predominantly spruce and larch trees in Davos, Switzerland (46°50'N 9°52'E) between January and April 2014. Measurements were made of long- and shortwave radiation at increasing distances from tree trunks, tree trunk and air temperatures, SVF using hemispherical photography, and both closed and above canopy radiation. Results show that the simulation bias of incoming longwave radiation estimates are related to proximity of the nearest tree and the sky-view fraction at the modelled point. This suggests a greater complexity to modelling incoming longwave radiation along forest gaps and edges than a

  17. East Asia monsoon's influence on seasonal changes of beryllium-7 and typical POPs in near-surface atmospheric aerosols in mid-latitude city Qingdao, China

    NASA Astrophysics Data System (ADS)

    Yang, Yong-Liang; Gai, Nan; Geng, Cun-Zhen; Zhu, Xiao-Hua; Li, Yong; Xue, Yuan; Yu, Han-Qing; Tan, Ke-Yan

    2013-11-01

    Near-surface atmospheric aerosols were collected at sampling frequency of 3 d per week for one year from August 2009 to July 2010 in Laoshan District, Qingdao, located in the mid-latitude coastal region of East Asia monsoon region. The samples were analyzed for cosmogenic nuclide beryllium-7 (7Be), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs). The annual average 7Be concentration was 6.83 ± 0.40 mBq m-3, with the variation range from 1.52 to 14.58 mBq m-3. The maximum and minimum levels were observed in September and May, respectively. Autumn and spring were the seasons with high 7Be concentrations and summer was the lowest 7Be season. Enhanced wet precipitation may have caused lower 7Be observed in summer when southeasterlies were prevailing. Higher 7Be concentrations in autumn 2009 were caused by the abnormal atmospheric circulation. Concentrations of HCHs, DDTs, and PCBs followed a trend of being lower in summer and higher in winter. Higher chlorinated PCB isomers were predominant in winter and lower chlorinated PCB isomers were predominant in summer. ∑OCPs generally showed positive correlations with 7Be but were interrupted by the “spring leak maximum” episode for 7Be in the atmosphere in April when the stratosphere-troposphere exchange was enhanced, and in December when abnormally high HCHs were observed. No significant correlation was found between 7Be and PCBs except for PCB28. Seasonal oscillations in 7Be and the ratios of POP/7Be were observed.

  18. Relationship between the trajectory of mid-latitude cyclones in the eastern Pacific Ocean and the isotopic composition of snowfall in the Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Vasquez, K. T.; Sickman, J. O.; Heard, A.; Lucero, D.

    2013-12-01

    Diatoms, preserved in lake sediments, provide a potential archive of snowfall variability in the Sierra Nevada through their sensitivity to changes in water chemistry (a proxy for runoff volume) and by recording the isotopic composition of snow-melt (potentially a proxy for sources of atmospheric moisture). In the Sierra Nevada, we hypothesize that the oxygen isotopic composition of diatom silica is principally controlled by snow and that the isotopic composition of snow varies as a function of the tracks of mid-latitude cyclonic storms in the eastern Pacific Ocean. Snow samples from discrete storms were collected from December 2012 to March 2013 at 2042 meters a.s.l. in Sequoia National Park. The δ18O and δ2H values of the snow samples were measured using a temperature-conversion elemental analyzer coupled to a Delta V isotope ratio mass spectrometer. The isotopic measurements were then coupled to 3, 5 and 7-day air mass back trajectories using the NOAA HYSPLIT model. The measured δ18O values ranged from -17.6 to -7.8 per mil and the δ2H ranged from -119.8 to -73.3 per mil. Both δ18O and δ2H were inversely related to the latitude of the storm origin (R^2 values of 0.67 and 0.57, respectively). Winter storms from the Gulf of Alaska were the most isotopically depleted while storms originating in the subtropical/tropical Pacific were the most isotopically enriched, reflecting the overall latitudinal pattern of ocean-water isotope composition in the Pacific Ocean. Our results suggest that the isotopic composition of Sierra Nevada snowfall is influenced by storm track trajectory and this relationship could be useful in interpreting the climatic significance of δ18O of diatom silica preserved in lake cores.

  19. Ice and liquid partitioning in mid-latitude and artic mixed-phase clouds: how common is the real mixed-phase state

    NASA Astrophysics Data System (ADS)

    Meyer, Jessica; Krämer, Martina; Afchine, Armin; Gallagher, Martin; Dorsey, James; Brown, Phil; Woolley, Alan; Bierwirth, Eike; Ehrlich, Andre; Wendisch, Manfred; Gehrmann, Martin

    2013-04-01

    The influence of mixed-phase clouds on the radiation budget of the earth is largely unknown. One of the key parameters to determine mixed-phase cloud radiative properties however is the fraction of ice particles and liquid droplets in these clouds. The separate detection of liquid droplets and ice crystals especially in the small cloud particle size range below 50 µm remains challenging though. Here, we present airborne NIXE-CAPS mixed-phase cloud particle measurements observed in mid-latitude and Arctic low-level mixed-phase clouds during the COALESC field campaign in 2011 and the Arctic field campaign VERDI in 2012. NIXE-CAPS (Novel Ice EXpEriment - Cloud and Aerosol Particle Spectrometer, manufactured by DMT) is a cloud particle spectrometer which measures the cloud particle number, size as well as their phase for each cloud particle in the diameter range 0.6 to 945 µm. The common understanding in mixed-phase cloud research is that liquid droplets and ice crystals in the same cloud volume are rather sparse, but instead either liquid droplets or ice crystals are present. However, recently published model studies (e.g. Korolev, A. & Field, P., The effect of dynamics on mixed-phase clouds: Theoretical considerations. J. Atmos. Sci. 65, 66-86, 2008) indicate that a cloud state containing both liquid droplets and ice crystals can be kept up by turbulence. Indeed, our particle by particle analyses of the observed mixed-phase clouds during COALESC and VERDI indicate that the real mixed-phase state is rather common in the atmosphere. The spatial distribution of the mixed-phase ice fraction and the size of the droplets and ice crystals however vary substantially from case to case. The latter parameters seem to be influenced not only by concentration of ice nuclei but also - to a large degree - by cloud dynamics.

  20. Effects of rotation and mid-troposphere moisture on organized convection and convectively coupled gravity waves

    NASA Astrophysics Data System (ADS)

    Majda, Andrew J.; Khouider, Boualem; Frenkel, Yevgeniy

    2015-02-01

    Atmospheric convection has the striking capability to organize itself into a hierarchy of cloud clusters and super-clusters on scales ranging from the convective cell of a few kilometres to planetary scale disturbances such as the Madden-Julian oscillation. It is widely accepted that this phenomenon is due in large part to the two-way coupling between convective processes and equatorially trapped waves and planetary scale flows in general. However, the physical mechanisms responsible for this multiscale organization and the associated across-scale interactions are poorly understood. The two main peculiarities of the tropics are the vanishing of the Coriolis force at the equator and the abundance of mid-level moisture. Here we test the effect of these two physical properties on the organization of convection and its interaction with gravity waves in a simplified primitive equation model for flows parallel to the equator. Convection is represented by deterministic as well as stochastic multicloud models that are known to represent organized convection and convectively coupled waves quite well. It is found here that both planetary rotation and mid-troposphere moisture are important players in the diminishing of organized convection and convectively coupled gravity wave activity in the subtropics and mid-latitudes. The meridional mean circulation increases with latitude while the mean zonal circulation is much shallower and is dominated by mid-level jets, reminiscent of a second baroclinic mode circulation associated with a congestus mode instability in the model. This is consistent with the observed shallow Hadley and Walker circulations accompanied by congestus cloud decks in the higher latitude tropics and sub-tropics. Moreover, deep convection activity in the stochastic model simulations becomes very patchy and unorganized as the computational domain is pushed towards the subtropics and mid-latitudes. This is consistent with previous work based on cloud resolving

  1. Improving Representation of Convective Transport for Scale-Aware Parameterization – Part I: Convection and Cloud Properties Simulated with Spectral Bin and Bulk Microphysics

    SciTech Connect

    Fan, Jiwen; Liu, Yi-Chin; Xu, Kuan-Man; North, Kirk; Collis, Scott M.; Dong, Xiquan; Zhang, Guang J.; Chen, Qian; Ghan, Steven J.

    2015-04-27

    The ultimate goal of this study is to improve representation of convective transport by cumulus parameterization for meso-scale and climate models. As Part I of the study, we perform extensive evaluations of cloud-resolving simulations of a squall line and mesoscale convective complexes in mid-latitude continent and tropical regions using the Weather Research and Forecasting (WRF) model with spectral-bin microphysics (SBM) and with two double-moment bulk microphysics schemes: a modified Morrison (MOR) and Milbrandt and Yau (MY2). Compared to observations, in general, SBM gives better simulations of precipitation, vertical velocity of convective cores, and the vertically decreasing trend of radar reflectivity than MOR and MY2, and therefore will be used for analysis of scale-dependence of eddy transport in Part II. The common features of the simulations for all convective systems are (1) the model tends to overestimate convection intensity in the middle and upper troposphere, but SBM can alleviate much of the overestimation and reproduce the observed convection intensity well; (2) the model greatly overestimates radar reflectivity in convective cores (SBM predicts smaller radar reflectivity but does not remove the large overestimation); and (3) the model performs better for mid-latitude convective systems than tropical system. The modeled mass fluxes of the mid latitude systems are not sensitive to microphysics schemes, but are very sensitive for the tropical case indicating strong microphysics modification to convection. Cloud microphysical measurements of rain, snow and graupel in convective cores will be critically important to further elucidate issues within cloud microphysics schemes.

  2. Aerosol transport and wet scavenging in deep convective clouds: a case study and model evaluation using a multiple passive tracer analysis approach

    SciTech Connect

    Yang, Qing; Easter, Richard C.; Campuzano-Jost, Pedro; Jimenez, Jose L.; Fast, Jerome D.; Ghan, Steven J.; Wang, Hailong; Berg, Larry K.; Barth, Mary; Liu, Ying; Shrivastava, ManishKumar B.; Singh, Balwinder; Morrison, H.; Fan, Jiwen; Ziegler, Conrad L.; Bela, Megan; Apel, Eric; Diskin, G. S.; Mikoviny, Tomas; Wisthaler, Armin

    2015-08-20

    The effect of wet scavenging on ambient aerosols in deep, continental convective clouds in the mid-latitudes is studied for a severe storm case in Oklahoma during the Deep Convective Clouds and Chemistry (DC3) field campaign. A new passive-tracer based transport analysis framework is developed to characterize the convective transport based on the vertical distribution of several slowly reacting and nearly insoluble trace gases. The passive gas concentration in the upper troposphere convective outflow results from a mixture of 47% from the lower level (0-3 km), 21% entrained from the upper troposphere, and 32% from mid-atmosphere based on observations. The transport analysis framework is applied to aerosols to estimate aerosol transport and wet-scavenging efficiency. Observations yield high overall scavenging efficiencies of 81% and 68% for aerosol mass (Dp < 1μm) and aerosol number (0.03< Dp < 2.5μm), respectively. Little chemical selectivity to wet scavenging is seen among observed submicron sulfate (84%), organic (82%), and ammonium (80%) aerosols, while nitrate has a much lower scavenging efficiency of 57% likely due to the uptake of nitric acid. Observed larger size particles (0.15 - 2.5μm) are scavenged more efficiently (84%) than smaller particles (64%; 0.03 - 0.15μm). The storm is simulated using the chemistry version of the WRF model. Compared to the observation based analysis, the standard model underestimates the wet scavenging efficiency for both mass and number concentrations with low biases of 31% and 40%, respectively. Adding a new treatment of secondary activation significantly improves simulation results, so that the bias in scavenging efficiency in mass and number concentrations is reduced to <10%. This supports the hypothesis that secondary activation is an important process for wet removal of aerosols in deep convective storms.

  3. Snow nitrate photolysis in polar regions and the mid-latitudes: Impact on boundary layer chemistry and implications for ice core records

    NASA Astrophysics Data System (ADS)

    Zatko, Maria C.

    The formation and recycling of nitrogen oxides (NOx=NO+NO 2) associated with snow nitrate photolysis has important implications for air quality and the preservation of nitrate in ice core records. This dissertation examines snow nitrate photolysis in polar and mid-latitude regions using field and laboratory based observations combined with snow chemistry column models and a global chemical transport model to explore the impacts of snow nitrate photolysis on boundary layer chemistry and the preservation of nitrate in polar ice cores. Chapter 1 describes how a global chemical transport model is used to calculate the photolysis-driven flux and redistribution of nitrogen across Antarctica, and Chapter 2 presents similar work for Greenland. Snow-sourced NOx is most dependent on the quantum yield for nitrate photolysis as well as the concentration of photolabile nitrate and light-absorbing impurities (e.g., black carbon, dust, organics) in snow. Model-calculated fluxes of snow-sourced NOx are similar in magnitude in Antarctica (0.5--7.8x108 molec cm-2 s -1) and Greenland (0.1--6.4x108 molec cm-2 s-1) because both nitrate and light-absorbing impurity concentrations in snow are higher (by factors of 2 and 10, respectively) in Greenland. Snow nitrate photolysis influences boundary layer chemistry and ice-core nitrate preservation less in Greenland compared to Antarctica largely due to Greenland's proximity to NOx-source regions. Chapter 3 describes how a snow chemistry column model combined with chemistry and optical measurements from the Uintah Basin Winter Ozone Study (UBWOS) 2014 is used to calculate snow-sourced NOx in eastern Utah. Daily-averaged fluxes of snow-sourced NOx (2.9x10 7--1.3x108 molec cm-2 s-1) are similar in magnitude to polar snow-sourced NO x fluxes, but are only minor components of the Uintah Basin boundary layer NOx budget and can be neglected when developing ozone reduction strategies for the region. Chapter 4 presents chemical and optical

  4. Surface Water Hydrography in the Mid-Latitude North Atlantic (IODP Site U1313) from 480-355 ka: Observations from Calcareous Nannoplankton

    NASA Astrophysics Data System (ADS)

    Kulhanek, D. K.; Voelker, A. H.; Gruetzner, D. J.

    2009-12-01

    Integrated Ocean Drilling Program Site U1313 cored thick sequences of Pleistocene sediments in the mid-latitude North Atlantic during Expedition 306. This site is located near the region of steepest sea-surface temperature gradients during the last glacial maximum, and is also on the southern margin of the ice-rafted debris (IRD) belt, making it an ideal location to study millennial-scale climate variability during the Pleistocene. Calcareous nannoplankton assemblages from 480-355 ka record changes in surface water conditions during this interval, which spans the end of Marine Isotope Stage (MIS) 13 to the beginning of MIS 10, thus including a complete glacial/interglacial cycle. The assemblage data are compared to the oxygen and carbon isotope records, lithics abundance, x-ray fluorescence measurements, and alkenone data to interpret changes in surface water hydrography. The nannoplankton assemblage is dominated by family Noelaerhabdaceae, and spans a single biostratigraphic event, the last occurrence of Pseudoemiliania, dated to 427 ka at this site. Most species indicate paleoecological preferences similar to those found in the literature, although Gephyrocapsa oceanica is more abundant during glacial MIS 12, even though it is thought to prefer warmer waters. Similarly, Helicosphaera, another warm-water taxon, is also more abundant during MIS 12. Both are generally considered eutrophic species, preferring higher nutrient conditions that occur during glacial stages at this site. The first factor of a CABFAC factor analysis explained nearly 92% of the variability in the assemblage. This factor is dominated by G. oceanica, and the varimax factor scores correlate well with the alkenone-based temperature record, suggesting that the distribution of G. oceanica at Site U1313 is mostly controlled by temperature. The N ratio, based on the ratio of lower photic zone dweller Florisphaera profunda to upwelling indicators, shows deep stratification during much of MIS 12

  5. Extensive Middle Amazonian mantling of debris aprons and plains in Deuteronilus Mensae, Mars: Implications for the record of mid-latitude glaciation

    NASA Astrophysics Data System (ADS)

    Baker, David M. H.; Head, James W.

    2015-11-01

    The mid-latitudes of Mars are host to a record of recent episodes of accumulations of ice-rich materials. The record includes debris aprons, interpreted to be debris-covered glaciers, that may represent the preserved remnants of a much more extensive ice sheet. We assessed the possibility of former glacial extents by examining debris aprons and the surrounding plains in Deuteronilus Mensae. Geomorphic units and stratigraphic relationships were mapped and documented from Mars Reconnaissance Orbiter (MRO) Context (CTX) and High Resolution Imaging Science Experiment (HiRISE) camera images, and crater retention ages were estimated from crater size-frequency distributions. Three major units are observed within the study area: debris aprons, lower plains, and upper plains. Debris aprons exhibit characteristics typical for these features documented elsewhere and in previous studies, including integrated flow lineations and patterns, convex-upward profiles, and knobby and brain terrain surface textures. A lower bound on the age for debris aprons is estimated to be 0.9 Ga. Debris aprons are superposed on a lower plains unit having a lower bound age of 3.3-3.5 Ga. A 50-100 m thick upper plains unit superposes both debris apron landforms and lower plains units and has a best-fit minimum age of 0.6 Ga. The upper plains unit exhibits characteristics of atmospherically-emplaced mantle material, including fine-grained nature, sublimation textures, cyclic layering, draping character, and widespread spatial distribution. Fracturing and subsequent sublimation/erosion of upper plains on debris aprons has contributed to many of the surface textures on debris aprons. The upper plains unit has also been eroded from the lower plains and plateaus, evidenced by isolated blocks of upper plains in the interiors of craters and on the walls and tops of plateaus. While no conclusive evidence diagnostic of former cold-based ice sheets are observed in the plains within the study region, such

  6. A spectral study of the mid-latitude sporadic E layer characteristic oscillations comparable to those of the tidal and the planetary waves

    NASA Astrophysics Data System (ADS)

    Pignalberi, A.; Pezzopane, M.; Zuccheretti, E.

    2015-01-01

    In this paper different spectral analyses are employed to investigate the tidal and planetary wave periodicities imprinted in the following two main characteristics of the sporadic E (Es) layer: the top frequency (ftEs) and the lowest virtual height (h‧Es). The study is based on ionograms recorded during the summertime of 2013, and precisely in June, July, August and September, by the Advanced Ionospheric Sounder by Istituto Nazionale di Geofisica e Vulcanologia (AIS-INGV) ionosondes installed at Rome (41.8°N, 12.5°E) and Gibilmanna (37.9°N, 14.0°E), Italy. It was confirmed that the diurnal and semidiurnal atmospheric tides play a fundamental role in the formation of the mid-latitude Es layers, acting through their vertical wind-shear forcing of the long-living metallic ions in the lower thermosphere, and at the same time it was found that the planetary atmospheric waves might affect the Es layers acting through their horizontal wind-shear forcing with periods close to the normal Rossby modes, that is 2, 5, 10 and 16 days. The wavelet analysis shows also that the ftEs and h‧Es tidal oscillations undergo a strong amplitude modulation with periods of several days and with important differences between the two parameters. This amplitude modulation, characterizing markedly the first thirty days of the ftEs spectrogram, suggests that Es layers are affected indirectly by planetary waves through their nonlinear interaction with the atmospheric tides at lower altitudes. This study wants to be a continuation of the Haldoupis et al. (2004) work in order to verify their results for the foEs characteristic and on the other hand to extend the study also to the h‧Es characteristic not yet shown so far. Anyhow, the study confirms that ionosonde data, especially those registered in summertime, represent a powerful tool for studying tidal and planetary waves properties and their climatology in the mesosphere-low-thermosphere region.

  7. Ten-year trends of atmospheric mercury in the high Arctic compared to Canadian sub-Arctic and mid-latitude sites

    NASA Astrophysics Data System (ADS)

    Cole, A. S.; Steffen, A.; Pfaffhuber, K. A.; Berg, T.; Pilote, M.; Poissant, L.; Tordon, R.; Hung, H.

    2013-02-01

    Global emissions of mercury continue to change at the same time as the Arctic is experiencing ongoing climatic changes. Continuous monitoring of atmospheric mercury provides important information about long-term trends in the balance between transport, chemistry, and deposition of this pollutant in the Arctic atmosphere. Ten-year records of total gaseous mercury (TGM) from 2000 to 2009 were analyzed from two high Arctic sites at Alert (Nunavut, Canada) and Zeppelin Station (Svalbard, Norway); one sub-Arctic site at Kuujjuarapik (Nunavik, Québec, Canada); and three temperate Canadian sites at St. Anicet (Québec), Kejimkujik (Nova Scotia) and Egbert (Ontario). Five of the six sites examined showed a decreasing trend over this time period. Overall trend estimates at high latitude sites were: -0.9% yr-1 (95% confidence limits: -1.4, 0) at Alert and no trend (-0.5, +0.7) at Zeppelin Station. Faster decreases were observed at the remainder of the sites: -2.1% yr-1 (-3.1, -1.1) at Kuujjuarapik, -1.9% yr-1 (-2.1, -1.8) at St. Anicet, -1.6% yr-1 (-2.4, -1.0) at Kejimkujik and -2.2% yr-1 (-2.8, -1.7) at Egbert. Trends at the sub-Arctic and mid-latitude sites agree with reported decreases in background TGM concentration since 1996 at Mace Head, Ireland, and Cape Point, South Africa, but conflict with estimates showing an increase in global anthropogenic emissions over a similar period. Trends in TGM at the two high Arctic sites were not only less negative (or neutral) overall but much more variable by season. Possible reasons for differences in seasonal and overall trends at the Arctic sites compared to those at lower latitudes are discussed, as well as implications for the Arctic mercury cycle. The first calculations of multi-year trends in reactive gaseous mercury (RGM) and total particulate mercury (TPM) at Alert were also performed, indicating increases from 2002 to 2009 in both RGM and TPM in the spring when concentrations are highest.

  8. Ten-year trends of atmospheric mercury in the high Arctic compared to Canadian sub-Arctic and mid-latitude sites

    NASA Astrophysics Data System (ADS)

    Cole, A. S.; Steffen, A.; Aspmo Pfaffhuber, K.; Berg, T.; Pilote, M.; Poissant, L.; Tordon, R.; Hung, H.

    2012-08-01

    Global emissions of mercury continue to change at the same time as the Arctic is experiencing ongoing climatic changes. Continuous monitoring of atmospheric mercury provides important information about long-term trends in the balance between transport, chemistry, and deposition of this pollutant in the Arctic atmosphere. Ten-year records of total gaseous mercury (TGM) were analyzed from two high Arctic sites at Alert (Nunavut, Canada) and Zeppelin Station (Svalbard, Norway); one sub-Arctic site at Kuujjuarapik (Nunavik, Québec, Canada); and three temperate Canadian sites at St. Anicet (Québec), Kejimkujik (Nova Scotia) and Egbert (Ontario). Five of the six sites examined show a decreasing trend over this time period. Overall trend estimates at high latitude sites were: -0.9% yr-1 (95% confidence limits: -1.4, 0) at Alert and no trend (-0.5, +0.7) at Zeppelin Station. Faster decreases were observed at the remainder of the sites: -2.1% yr-1 (-3.1, -1.1) at Kuujjuarapik, -1.9% yr-1 (-2.1, -1.8) at St. Anicet, -1.6% yr-1 (-2.4, -1.0) at Kejimkujik and -2.2% yr-1 (-2.8, -1.7) at Egbert. Trends at the sub-Arctic and mid-latitude sites agree with reported decreases in background TGM concentration since 1996 at Mace Head, Ireland, and Cape Point, South Africa, but conflict with estimates showing an increase in global anthropogenic emissions over a similar period. Trends in TGM at the two high Arctic sites were not only less negative (or neutral) overall but much more variable by season. Possible reasons for differences in seasonal and overall trends at the Arctic sites compared to those at lower latitudes are discussed, as well as implications for the Arctic mercury cycle. The first calculations of multi-year trends in reactive gaseous mercury (RGM) and total particulate mercury (TPM) at Alert were also performed, indicating increases from 2002 to 2009 in both RGM and TPM in the spring when concentrations are highest.

  9. Effects of local microclimates on the surface sensible heat flux on a mid-latitude alpine valley glacier using Large-Eddy Simulations

    NASA Astrophysics Data System (ADS)

    Sauter, Tobias; Galos, Stephan

    2016-04-01

    While the large-scale climate conditions play an important role in shaping the environment in which glaciers exist, the mass and energy balance of each individual glacier are dictated by local conditions. Given the complex mountain topography around alpine glaciers, it is not trivial to find a direct link between the large-scale atmospheric motions and the local-scale weather conditions at an individual glacier. Non-local dynamic effects due to the surrounding complex topography can significantly modify the spatial variability of exchange processes, either by small scale circulations or episodic entrainment of heat and momentum by burst events. Motivated by the fact that distributed glacier models strongly rely on the quality of high resolution forcing data to adequately represent the glacier wide ablation and accumulation processes, the present study investigates (i) whether non-local topographic effects have a significant impact on the spatial distribution of turbulent sensible heat fluxes (local microclimates) over alpine glaciers, and (ii) how much variability is smoothed out when using linearly interpolated fields together with the commonly used bulk approach. To answer these questions, we perform highly resolved and properly designed case experiments by Large-Eddy Simulations with real topography to determine the impact of topographic flow features on the spatial variability of the surface sensible heat flux and compare the fields with those derived with the bulk approach. The analysis shows that there is a significant spatial variability of the mean fluxes with values ranging from -10 Wm‑2 to -120 Wm‑2. Since the sensible heat flux can make up to 40% of the total melting on mid-latitude alpine valley glaciers, the heterogeneity of the fluxes can substantially dictate the local melting rates. When estimating the glacier-wide surface heat fluxes on the basis of point-measurements and the bulk approach, a considerable amount of spatial information is lost

  10. The role of large-scale eddies in the nonlinear equilibration of a multi-level model of the mid-latitude troposphere

    NASA Astrophysics Data System (ADS)

    Solomon, Amy Beth

    The role of waves in maintaining the mid-latitude tropospheric climate is investigated in a dry high resolution quasi-geostrophic β-plane channel model which is coupled to an equation for the horizontally averaged static stability tendency. This coupling allows for the feedback between vertical eddy heat fluxes and the vertical temperature structure, which is typically neglected in quasi-geostrophic models. It is important to include this process in order to understand the dynamical balance in the boundary layer. The model includes simple parameterizations of heating, surface friction and fluxes by turbulent eddies. Studies of the impact of vertical resolution on the model's equilibrated climate and fluxes show that, given the standard set-up of the model, decreasing the resolution stabilizes the eddies. Coupling the model to an equation for the surface air temperature tendency eliminated this dependence on the vertical resolution. The model's climate is found to be separated into two dynamical regimes, one within the boundary layer and the other within the free troposphere. In the free troposphere the potential vorticity gradients are relatively independent of the parameters and parameterizations used to define the boundary layer, although the equilibrated static stability and meridional temperature gradients are not. The potential vorticity gradients are essentially eliminated in the mid troposphere, in agreement with observations. The complete homogenization of pv occurs in the region where the baroclinic waves have a critical layer. The dynamics in the boundary layer are determined by the tropopause potential vorticity structure and the parameterization of the turbulent fluxes of heat and momentum in the atmospheric boundary layer. Thermal diffusion in the boundary layer prevents the modification of the mean temperature structure by damping temperature fluctuations. This result is consistent with the recent observational study by Swanson and Pierrehumbert

  11. Prediction of convective activity using a system of parasitic-nested numerical models

    NASA Technical Reports Server (NTRS)

    Perkey, D. J.

    1976-01-01

    A limited area, three dimensional, moist, primitive equation (PE) model is developed to test the sensitivity of quantitative precipitation forecasts to the initial relative humidity distribution. Special emphasis is placed on the squall-line region. To accomplish the desired goal, time dependent lateral boundaries and a general convective parameterization scheme suitable for mid-latitude systems were developed. The sequential plume convective parameterization scheme presented is designed to have the versatility necessary in mid-latitudes and to be applicable for short-range forecasts. The results indicate that the scheme is able to function in the frontally forced squallline region, in the gently rising altostratus region ahead of the approaching low center, and in the over-riding region ahead of the warm front. Three experiments are discussed.

  12. El Nino, from 1870 to 2014, and other Atmospheric Circulation Forcing by Extreme Apparitions of the Eight Annual, Continental Scale, Aerosol Plumes in the Satellite Era which Point to a Possible Cause for the Current Californian Drought

    NASA Astrophysics Data System (ADS)

    Potts, K. A.

    2015-12-01

    Eight continental scale aerosol plumes exist each year as the enclosed image shows. Apparitions of seven plumes only exist for a few months in the same season each year whilst the East Asian Plume is visible all year. The aerosol optical depth (AOD) of all the plumes varies enormously interannually with two studies showing the surface radiative forcing of the South East Asian Plume (SEAP) as -150W/m2 and -286W/m2/AOD. I show that the SEAP, created by volcanic aerosols (natural) and biomass burning and gas flares in the oil industry (anthropogenic), is the sole cause of all El Nino events, the greatest interannual perturbation of the atmospheric circulation system. The SEAP creates an El Nino by absorbing solar radiation at the top of the plume which heats the upper atmosphere and cools the surface. This creates a temperature inversion compared to periods without the plume and reduces convection. With reduced convection in SE Asia, the Maritime Continent, the Trade Winds blowing across the Pacific are forced to relax as their exit into the Hadley and Walker Cells is constrained and the reduced Trade Wind speed causes the Sea Surface Temperature (SST) to rise in the central tropical Pacific Ocean as there is a strong negative correlation between wind speed and SST. The warmer SST in the central Pacific creates convection in the region which further reduces the Trade Wind speed and causes the Walker Cell to reverse - a classic El Nino. Having established the ability of such extreme aerosol plumes to create El Nino events I will then show how the South American, West African, Middle East and SEAP plumes create drought in the Amazon, Spain, Darfur and Australia as well as causing the extremely warm autumn and winter in Europe in 2006-07. All these effects are created by the plumes reducing convection in the region of the plume which forces the regional Hadley Cells into anomalous positions thereby creating persistent high pressure cells in the mid latitudes. This

  13. Nitrogen Oxides and Ozones from B-747 Measurements (NOXAR) during POLINAT 2 and SONEX: Overview and Case-Studies on Continental and Marine Convection

    NASA Technical Reports Server (NTRS)

    Jeker, Dominique; Pfister, Lenny; Brunner, Dominik; Boccippio, Dennis J.; Pickering, Kenneth E.; Thompson, Anne M.; Wernli, Heini; Selkirk, Rennie B.; Kondo, Yutaka; Koike, Matoke; Zhao, Yongjing; Staehelin, Johannes

    1999-01-01

    In the framework of the project POLINAT 2 (Pollution in the North Atlantic Flight Corridor) we measured NO(x) (NO and NO2) and ozone on 98 flights through the North Atlantic Flight Corridor (NAFC) with a fully automated system permanently installed aboard an in-service Swissair B-747 airliner in the period of August to November 1997. The averaged NO, concentrations both in the NAFC and at the U.S. east coast were similar to that measured in autumn 1995 with the same system. The patchy occurrence of NO(x), enhancements up to 3000 pptv over several hundred kilometers (plumes), predominately found over the U.S. east coast lead to a log-normal NO(x) probability density function. In three case-studies we examine the origins of such plumes by combining back-trajectories with brightness temperature enhanced (IR) satellite imagery, with lightning observations from the U.S. National Lightning Detection Network (NLDN) or with the Optical Transient Detector (OTD) satellite. For frontal activity above the continental U.S., we demonstrate that the location of NO(x) plumes can be well explained with maps of convective influence. For another case we show that the number of lightning flashes in a cluster of marine thunderstorms is proportional to the NO(x) concentrations observed several hundred kilometers downwind of the anvil outflows and suggest that lightning was the dominant source. From the fact that in autumn the NO, maximum was found several hundred kilometers off the U.S. east coast, it can be inferred that thunderstorms triggered over the warm Gulf Stream current are an important source for the regional upper tropospheric NO(x) budget in autumn.

  14. Long-term changes and trends in total ozone over the northern mid-latitudes: Influence of atmospheric dynamics and chemistry and contribution from extreme events

    NASA Astrophysics Data System (ADS)

    Rieder, H. E.; Staehelin, J.; Maeder, J. A.; Ribatet, M.; di Rocco, S.; Frossard, L.; Jancso, L. M.; Peter, T.; Davison, A. C.

    2010-12-01

    Downward trends in global stratospheric ozone during recent decades have been shown to be directly linked to increasing surface UV-radiation. In the past, long-term ozone trends were determined from homogenized data series by fitting with multiple linear regression models, in which suitable independent variables (so-called explanatory variables) were used to represent atmospheric variability, such as the Quasi-Biennial Oscillation (QBO), the 11-year solar cycle, and a linear trend attributed to anthropogenic ozone depletion. Previous studies have identified a number of other processes influencing total ozone at mid-latitudes, such as synoptic-scale meteorological variability, decadal or long-term climate variability, described e.g. by the Northern Atlantic Oscillation (NAO), the Arctic Oscillation (AO), atmospheric circulation indices ENSO, temperature at the 470-K isentrope level, and volcanic eruptions. Due to the successful implementation of the Montreal Protocol the discussion about a recovery or possible “super recovery” started within the scientific community. Here we address long-term changes and trends in a different framework. As statistical analysis showed that previously used concepts assuming a Gaussian distribution of total ozone data do not address the internal data structure concerning extremes adequately methods from extreme value theory are applied on local (various long-term ground based total ozone records) and regional (high resolution homogenized satellite data) scale. Within the extreme value theory framework days with extreme low (ELOs) and high (EHOs) total ozone are analyzed and their frequency is linked to changes in atmospheric chemistry and dynamics. The results show: (i) an increase in ELOs and (ii) a decrease in EHOs during the last decades and (iii) that the overall trend during the 1970s and 1980s in total ozone is strongly dominated by changes in these extreme events. After removing the extremes, the different time series show a

  15. Extreme events in total ozone over the northern mid-latitudes: A case study based on long-term data sets from 5 ground-based stations

    NASA Astrophysics Data System (ADS)

    Rieder, Harald E.; Jancso, Leonhardt M.; Staehelin, Johannes; Maeder, Jörg A.; Ribatet, Mathieu; Peter, Thomas; Davison, Anthony C.

    2010-05-01

    In this study we analyze the frequency distribution of extreme events in low and high total ozone (termed ELOs and EHOs) for 5 long-term stations in the northern mid-latitudes in Europe (Belsk, Poland; Hradec Kralove, Czech Republic; Hohenpeissenberg and Potsdam, Germany; and Uccle, Belgium). Further, the influence of these extreme events on annual and seasonal mean values and trends is analysed. The applied method follows the new "ozone extreme concept", which is based on tools from extreme value theory [Coles, 2001; Ribatet, 2007], recently developed by Rieder et al. [2010a, b]. Mathematically seen the decisive feature within the extreme concept is the Generalized Pareto Distribution (GPD). In this analysis, the long-term trends needed to be removed first, differently to the treatment of Rieder et al. [2010a, b], in which the time series of Arosa was analysed, covering many decades of measurements in the anthropogenically undisturbed stratosphere. In contrast to previous studies only focusing on so called ozone mini-holes and mini-highs the "ozone extreme concept" provides a statistical description of the tails in total ozone distributions (i.e. extreme low and high values). It is shown that this concept is not only an appropriate method to describe the frequency and distribution of extreme events, it also provides new information on time series properties and internal variability. Furthermore it allows detection of fingerprints of physical (e.g. El Niño, NAO) and chemical (e.g. polar vortex ozone loss) features in the Earth's atmosphere as well as major volcanic eruptions (e.g. El Chichón, Mt. Pinatubo). It is shown that mean values and trends in total ozone are strongly influenced by extreme events. Trend calculations (for the period 1970-1990) are performed for the entire as well as the extremes-removed time series. The results after excluding extremes show that annual trends are most reduced at Hradec Kralove (about a factor of 3), followed by Potsdam

  16. Space Weather Effects on Mid-Latitude Railways: a Statistical Study of Anomalies observed in the Operation of Signaling and Train Control Equipment on the East-Siberian Railway

    NASA Astrophysics Data System (ADS)

    Kasinskii, V. V.; Ptitsyna, N. G.; Lyahov, N. N.; Dorman, L. I.; Villoresi, G.; Iucci, N.

    The end result of a long chain of space weather events beginning on the Sun is the induction of currents in ground-based long conductors as power lines pipelines and railways Intense geomagnetically induced currents GIC can hamper rail traffic by disturbing signaling and train control systems In few cases induced voltages were believed to have affected signaling equipment in Sweden Jansen et al 2000 and in the North of Russia Belov et al 2005 GIC threats have been a concern for technological systems at high-latitude locations due to disturbances driven by electrojet intensifications However other geomagnetic storm processes such as SSC and ring current enhancement can also cause GIC concerns for the technological systems Objective of this report is to continue our research Ptitsyna et al 2005 on possible influence of geomagnetic storms on mid-latitude railways and to perform a statistical research in addition to case studies This will help in providing a basis for railway companies to evaluate the risk of disruption to signaling and train control equipment and devise engineering solutions In the present report we analyzed anomalies in operation of automatic signaling and train control equipment occurred in 2004-2005 on the East-Siberian Railway located at mid-latitudes latitudes 51N-56N longitudes 96E-114E The anomalies consist mainly in unstable functioning and false operations in traffic automatic control systems rail chain switches locomotive control devices etc often resulting in false engagement of railway

  17. Effects of Model Resolution and Subgrid-Scale Physics on the Simulation of Daily Precipitation in the Continental United States

    SciTech Connect

    Duffy, P B; Iorio, J P; Govindasamy, B; Thompson, S L; Khairoutdinov, M; Randall, D

    2004-07-28

    spatial patterns of seasonal-mean precipitation compared to models at the same resolution using traditional parameterizations. Thus, our results suggest that using an embedded ''Cloud Resolving Model'' in a high-resolution GCM might provide the best representation of spatial and temporal variability of mid-latitude continental precipitation.

  18. A coccolithophore based view on paleoenvironmental changes in the open ocean mid-latitude North Atlantic between 130 and 48 ka BP with special emphasis on MIS 5e

    NASA Astrophysics Data System (ADS)

    Schwab, C.; Kinkel, H.; Weinelt, M.; Repschläger, J.

    2013-12-01

    As oceanographic changes in the North Atlantic are known to modulate global climate, they are key to the understanding of past and future climate changes. Especially the mid-latitudes of the open ocean North Atlantic may be of interest, regarding the large area covered. We therefore reconstructed past changes in productivity and hydrography from a new sediment core (MD08-3179Cq) taken in the open ocean mid-latitude North Atlantic in the vicinity of the Azores Current System. Concomitant to the reorganizations of environmental conditions in the North Atlantic between 130 and 48 ka BP, changes in coccolithophore assemblages and changes in the abundance of siliceous plankton (diatoms) indicate a southward shift of the Azores Front (AzF), and hence a southward retreat of the North Atlantic subtropical gyre, as well as an increased productivity, during glacial Marine Isotope Stage (MIS) 4, Termination II and during cold substages of MIS 5. Furthermore we hypothesize that the ecological changes led to distinct evolutionary patterns of coccolithophores, resulting e.g. in a dominance of Gephyrocapsaornata between 76 and 105 ka BP. Additionally, high-resolution analysis of MIS 5e indicate a short reversal towards cool conditions during MIS 5e, corresponding to a basin-wide cooling event. Full interglacial conditions are reached only late in the Azores region. During MIS 5e an increased advection of Subantarctic Mode Water (SAMW), and/or the possibility to occupy new habitats after glacial conditions, result in a distinct coccolithophore productivity peak. As global temperature during MIS 5e are assumed to be similar to the expected future global climate change, MIS 5e serves as a possible scenario for future changes. Taking MIS 5e as a possible analogue for expected future climate change, our results indicate that an expected decrease in marine primary productivity, due to the expansion of the oligotrophic gyres, may be attenuated by increased coccolithophore productivity.

  19. Long-Term Changes in Lower Tropospheric Baseline Ozone Concentrations:. [Comparing Chemistry-Climate Models and Observations at Northern Mid-Latitudes

    NASA Technical Reports Server (NTRS)

    Parrish, D. D.; Lamarque, J.-F.; Naik, V.; Horowitz, L.; Shindell, D. T.; Staehelin, J.; Derwent, R.; Cooper, O. R.; Tanimoto, H.; Volz-Thomas, A.; Gilge, S.; Scheel, H.-E.; Steinbacher, M.; Frohlich, M.

    2014-01-01

    Two recent papers have quantified long-term ozone (O3) changes observed at northernmidlatitude sites that are believed to represent baseline (here understood as representative of continental to hemispheric scales) conditions. Three chemistry-climate models (NCAR CAM-chem, GFDL-CM3, and GISS-E2-R) have calculated retrospective tropospheric O3 concentrations as part of the Atmospheric Chemistry and Climate Model Intercomparison Project and Coupled Model Intercomparison Project Phase 5 model intercomparisons. We present an approach for quantitative comparisons of model results with measurements for seasonally averaged O3 concentrations. There is considerable qualitative agreement between the measurements and the models, but there are also substantial and consistent quantitative disagreements. Most notably, models (1) overestimate absolute O3 mixing ratios, on average by approximately 5 to 17 ppbv in the year 2000, (2) capture only approximately 50% of O3 changes observed over the past five to six decades, and little of observed seasonal differences, and (3) capture approximately 25 to 45% of the rate of change of the long-term changes. These disagreements are significant enough to indicate that only limited confidence can be placed on estimates of present-day radiative forcing of tropospheric O3 derived from modeled historic concentration changes and on predicted future O3 concentrations. Evidently our understanding of tropospheric O3, or the incorporation of chemistry and transport processes into current chemical climate models, is incomplete. Modeled O3 trends approximately parallel estimated trends in anthropogenic emissions of NO(sub x), an important O3 precursor, while measured O3 changes increase more rapidly than these emission estimates.

  20. Latitudinal trends in fluxes and congener patterns of PCBs inferred from lake sediment cores from mid-latitude and Arctic Lakes

    SciTech Connect

    Muir, D.; Omelchenko, A.; Grift, N.; Lockhart, L.; Wilkinson, P.; Brunskill, G.; Robbins, J.A.

    1995-12-31

    Sediment cores collected from 9 remote lakes in central and Arctic Canada (49{degree}N to 82{degree}N and from 71{degree} to 136{degree}W) were analyzed for PCBs with the objective of examining latitudinal and temporal trends in deposition. Core slices (1--1.3 cm) were dated with {sup 210}Pb and {sup 137}Cs using the Robbins rapid steady-state mixing model and sediment focusing factors were determined with the aid of soil cores or predictions of historical radionuclide deposition. Slices were freeze-dried, Soxhlet extracted with DCM and chromatographed on Florisil, then analyzed by high resolution GC-ECD with confirmation by GC-HRMS. {Sigma}PCB concentrations in surface sediments were low ranging from 8 to 40 ng{center_dot}g{sup {minus}1} (dry wt) in southern mid-continental sites (49--63{degree}N) to 2 ng{center_dot}g{sup {minus}1} in Lake Hazen, the most northerly location (82{degree}N). Highest concentrations were found in the most recent slices (1980s) of cores from high Arctic lakes (at 75 and 82{degree}N) whereas peak concentrations were reached earlier (in the 1970s) at more southerly locations. Principal components analysis revealed that sediments from high Arctic lakes could be distinguished by greater proportions of lower chlorinated PCBs in comparison with published results for Lakes Ontario and Superior. Focus corrected {Sigma}PCBs fluxes ranged from 305 to 920 ng{center_dot}m{sup 2}{center_dot}yr{sup {minus}1} in the 9 lakes and were negatively correlated with latitude (r{sup 2} = 0.53). Fluxes of Cl{sup 8} CBs had a strong negative correlation with latitude (r2 = 0.88) while Cl{sup 3} CBs showed no latitudinal trend. The results generally support several of the predictions of the cold condensation hypothesis.

  1. Debris flows in a young mid-latitude crater on Mars: Evidence for recent water-bearing mass wasting and efficient insolation-controlled slope modification within the last

    NASA Astrophysics Data System (ADS)

    Johnsson, Andreas; Reiss, Dennis; Hauber, Ernst; Hiesinger, Harald; Zanetti, Michael

    2013-04-01

    Debris flows are moving masses of loose debris of varying grain sizes, water and air that travels down a slope under the influence of gravity. Terrestrial debris flows are mainly studied and monitored because of their hazardous nature. On Mars they may serve as important geomorphologic indicators of transient liquid water. The discovery of well-developed debris flow deposits within a very young southern mid-latitude crater (~0.2 Ma) highlights the impact of periglacial slope processes during recent climate conditions on Mars. We compared the morphology of debris flows on Svalbard as possible analogues to the observed deposits on Mars in order to infer possible formation mechanisms. Within our study crater on Mars, high-resolution imagery obtained by the HiRISE instrument (High Resolution Imaging Science Experiment) revealed typical debris-flow attributes such as overlapping terminal lobes, debris tongues, debris-flow fans, scoured channels with medial deposits (debris plugs), and well-defined lateral deposits (levées). Collectively, these attributes are found on studied debris flows on Svalbard. Additionally, our study crater's interior walls display mass-wasting with strong aspect-dependence, ranging from debris-flow dominated pole-facing slopes, to east-and-west-facing single channel gullies, and north-facing talus cones (grain flow). Our findings suggest that the debris flows are neither related to impact induced heating and release of meltwater or melting of an ice-rich mantling deposit since the latter is absent in the study crater. Instead, we propose that the debris flows are formed by melting of very recent snow deposits after the termination of the last Martian ice-age. As such it may represent one of the most recent geomorphological indicators of transient liquid water in the Martian mid-latitudes. Our study crater further illustrates the importance of regolith differences and micro-climate variability (e.g., insolation) in debris flow initiation on Mars

  2. HIBISCUS and SCOUT-AMMA: Water vapour and ice particles in the tropical lower stratosphere above overshooting continental convective systems. Part B. Moistening of lowest stratosphere by ice particles.

    NASA Astrophysics Data System (ADS)

    Nielsen, J. K.; Larsen, N.; Christensen, T.; Khaykin, S.; Korshunov, L.; Pommereau, J.; Cairo, F.; di~Donfrancesco, G.

    2006-12-01

    Two series of balloon-borne backscatter soundings performed over two different tropical continental sites are presented. The sounding instrument is the 480nm/940nm Wyoming Backscatter Sonde. The first series, recorded in Bauru, Brazil (49.03W 22.36S, February 2004) includes one event where solid particles are observed well above the TTL at temperatures up to at least 10K above the expected frost point temperature. This observation is supported by previous observations with a ground based 532nm lidar at the same site. The second series, recorded in Niamey, Niger (2.17E, 13.49N, August 2006) also includes an event where particles are observed above the TTL. This observation is confirmed by a simultaneous LABS-backscatter flight, and further supported by an on board Lyman-alpha Flash-B hygrometer. It is concluded that the observed particles originate from local overshooting convective events, and that these convective events must have mixed with stratospheric air and caused a moistening of the local stratosphere.

  3. Model Evaluation of Aerosol Wet Scavenging in Deep Convective Clouds Based on Observations Collected during the DC3 Campaign

    NASA Astrophysics Data System (ADS)

    Yang, Q.; Easter, R. C.; Fast, J. D.; Wang, H.; Ghan, S. J.; Campuzano Jost, P.; Barth, M. C.; Fan, J.; Morrison, H.; Jimenez, J. L.; Bela, M. M.; Markovic, M. Z.

    2014-12-01

    Deep convective storms greatly influence the vertical distribution of aerosols by transporting aerosols from the boundary layer to the upper troposphere and by removing aerosols through wet scavenging processes. Model representation of wet scavenging is a major uncertainty in simulating the vertical distribution of aerosols due partly to limited constraints by observations. The effect of wet scavenging on ambient aerosols in deep mid-latitude continental convective clouds is studied for a severe storm case in the vicinity of the ARM Southern Great Plains site on May 29, 2012 during the Deep Convective Clouds and Chemistry Project (DC3) field campaign. A new budget analysis approach is developed to characterize the convective transport to the upper troposphere based on the vertical distribution of several slowly reacting and nearly insoluble trace gases (i.e., CO, acetone, and benzene). A similar budget framework is applied to aerosols combined with the known transport efficiency to estimate wet-scavenging efficiency. The chemistry version of the Weather Research and Forecasting model (WRF-Chem) simulates the storm initiation timing and structure reasonably well when compared against radar observations from the NSSL national 3-D reflectivity Mosaic data. Simulated vertical profiles of humidity and temperature also closely agree with radiosonde measurements before and during the storm. High scavenging efficiencies (~80%) for aerosol number (Dp < 2.5μm) and mass (Dp < 1μm) are obtained from the observations. Both observation analyses and the simulation show that, between the two dominant aerosol species, organic aerosol shows a slightly higher scavenging efficiency than sulfate aerosol, and higher scavenging efficiency is found for larger particle sizes (0.15 - 2.5μm versus 0.03 - 0.15μm). However, the model underestimates the wet scavenging efficiency (by up to 50%), in general, for both mass and number concentrations. The effect of neglecting secondary

  4. Long-term monthly statistics of the mid-latitude ionospheric E-layer peak electron density in the Northern geographic hemisphere during geomagnetically quiet and steadily low solar activity conditions

    NASA Astrophysics Data System (ADS)

    Pavlov, Anatoli; Pavlova, Nadezhda

    2016-07-01

    Long-term hourly values of the ionospheric E-layer peak electron density, NmE, measured during the time period of 1957-2014 by 4 mid-latitude ionosondes (Wallops Island, Boulder, de l'Ebre, and Rome) in the Northern geographic hemisphere were processed to select periods of geomagnetically quiet and low solar activity conditions to calculate several descriptive statistics of NmE close to noon for each month in a year, including the mathematical expectation of NmE, the standard deviations of NmE from the mathematically expected NmE, and the NmE variation coefficient. The month-to-month variability of these descriptors allowed us to identify months of a year when they reach their extremes (maxima, minima). We found that the most probable NmE cannot be considered as the best statistical parameter among the most probable NmE and the mathematically expected NmE in statistical studies of month-to-month variations of NmE. Depending on a choice of an ionosonde and a month, the calculated NmE variation coefficient changes from 5 to 12 %.

  5. Chlorine-36 in Water, Snow, and Mid-Latitude Glacial Ice of North America: Meteoric and Weapons-Tests Production in the Vicinity of the Idaho National Engineering and Environmental Laboratory, Idaho

    SciTech Connect

    L. DeWayne; J. R. Green; S. Vogt, P. Sharma; S. K. Frape; S. N. Davis; G. L. Cottrell

    1999-01-01

    Measurements of chlorine-36 (36Cl) were made for 64 water, snow, and glacial-ice and -runoff samples to determine the meteoric and weapons-tests-produced concentrations and fluxes of this radionuclide at mid-latitudes in North America. The results will facilitate the use of 36Cl as a hydrogeologic tracer at the Idaho National Engineering and Environmental Laboratory (INEEL). This information was used to estimate meteoric and weapons-tests contributions of this nuclide to environmental inventories at and near the INEEL. The data presented in this report suggest a meteoric source 36Cl for environmental samples collected in southeastern Idaho and western Wyoming if the concentration is less than 1 x 10 7 atoms/L. Additionally, concentrations in water, snow, or glacial ice between 1 x 10 7 and 1 x 10 8 atoms/L may be indicative of a weapons-tests component from peak 36Cl production in the late 1950s. Chlorine-36 concentrations between 1 x 10 8 and 1 x 10 9 atoms/L may be representative of re-suspension of weapons-tests fallout airborne disposal of 36Cl from the INTEC, or evapotranspiration. It was concluded from the water, snow, and glacial data presented here that concentrations of 36Cl measured in environmental samples at the INEEL larger than 1 x 10 9 atoms/L can be attributed to waste-disposal practices.

  6. Studying the impact of overshooting convection on the tropopause tropical layer (TTL) water vapor budget at the continental scale using a mesoscale model

    NASA Astrophysics Data System (ADS)

    Behera, Abhinna; Rivière, Emmanuel; Marécal, Virginie; Claud, Chantal; Rysman, Jean-François; Geneviève, Seze

    2016-04-01

    Water vapour budget is a key component in the earth climate system. In the tropical upper troposphere, lower stratosphere (UTLS), it plays a central role both on the radiative and the chemical budget. Its abundance is mostly driven by slow ascent above the net zero radiative heating level followed by ice crystals' formation and sedimentation, so called the cold trap. In contrast to this large scale temperature driven process, overshooting convection penetrating the stratosphere could be one piece of the puzzle. It has been proven to hydrate the lower stratosphere at the local scale. Satellite-borne H2O instruments can not measure with a fine enough resolution the water vapour enhancements caused by overshooting convection. The consequence is that it is difficult to estimate the role of overshooting deep convection at the global scale. Using a mesoscale model i.e., Brazilian Regional Atmospheric Modelling System (BRAMS), past atmospheric conditions have been simulated for the full wet season i.e., Nov 2012 to Mar 2013 having a single grid with horizontal resolution of 20 km × 20km over a large part of Brazil and South America. This resolution is too coarse to reproduce overshooting convection in the model, so that this simulation should be used as a reference (REF) simulation, without the impact of overshooting convection in the TTL water budget. For initialisation, as well as nudging the grid boundary in every 6 hours, European Centre for Medium-Range Weather Forecasts (ECMWF) analyses has been used. The size distribution of hydrometeors and number of cloud condensation nuclei (CCN) are fitted in order to best reproduce accumulated precipitations derived from Tropical Rainfall Measuring Mission (TRMM). Similarly, GOES and MSG IR mages have been thoroughly compared with model's outputs, using image correlation statistics for the position of the clouds. The model H2O variability during the wet season, is compared with the in situ balloon-borne measurements during

  7. Hotspots and sunspots - Surface tracers of deep mantle convection in the earth and sun

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1993-01-01

    The evolution of the hot-spot distribution on earth in time and space is investigated using available age data. The statistics of continental flood basalt eruptions suggests the formation of a total of about 40 hot spots worldwide during the Cenozoic and Mesozoic, with no true antipodal pairs found. It was found that hot spots tend to concentrate mainly in mid-latitudes, but the pattern of new appearances of hot spots may migrate from high to low latitudes in both hemispheres in long cycles, and may also drift in longitude, although much more slowly prograde.

  8. Modeling the Dynamical Coupling of Solar Convection with the Radiative Interior

    NASA Astrophysics Data System (ADS)

    Brun, Allan Sacha; Miesch, Mark S.; Toomre, Juri

    2011-12-01

    The global dynamics of a rotating star like the Sun involves the coupling of a highly turbulent convective envelope overlying a seemingly benign radiative interior. We use the anelastic spherical harmonic code to develop a new class of three-dimensional models that nonlinearly couple the convective envelope to a deep stable radiative interior. The numerical simulation assumes a realistic solar stratification from r = 0.07 up to 0.97R (with R the solar radius), thus encompassing part of the nuclear core up through most of the convection zone. We find that a tachocline naturally establishes itself between the differentially rotating convective envelope and the solid body rotation of the interior, with a slow spreading that is here diffusively controlled. The rapid angular momentum redistribution in the convective envelope leads to a fast equator and slow poles, with a conical differential rotation achieved at mid-latitudes, much as has been deduced by helioseismology. The convective motions are able to overshoot downward about 0.04R into the radiative interior. However, the convective meridional circulation there is confined to a smaller penetration depth and is directed mostly equatorward at the base of the convection zone. Thermal wind balance is established in the lower convection zone and tachocline but departures are evident in the upper convection zone. Internal gravity waves are excited by the convective overshooting, yielding a complex wave field throughout the radiative interior.

  9. MODELING THE DYNAMICAL COUPLING OF SOLAR CONVECTION WITH THE RADIATIVE INTERIOR

    SciTech Connect

    Brun, Allan Sacha; Toomre, Juri

    2011-12-01

    The global dynamics of a rotating star like the Sun involves the coupling of a highly turbulent convective envelope overlying a seemingly benign radiative interior. We use the anelastic spherical harmonic code to develop a new class of three-dimensional models that nonlinearly couple the convective envelope to a deep stable radiative interior. The numerical simulation assumes a realistic solar stratification from r = 0.07 up to 0.97R (with R the solar radius), thus encompassing part of the nuclear core up through most of the convection zone. We find that a tachocline naturally establishes itself between the differentially rotating convective envelope and the solid body rotation of the interior, with a slow spreading that is here diffusively controlled. The rapid angular momentum redistribution in the convective envelope leads to a fast equator and slow poles, with a conical differential rotation achieved at mid-latitudes, much as has been deduced by helioseismology. The convective motions are able to overshoot downward about 0.04R into the radiative interior. However, the convective meridional circulation there is confined to a smaller penetration depth and is directed mostly equatorward at the base of the convection zone. Thermal wind balance is established in the lower convection zone and tachocline but departures are evident in the upper convection zone. Internal gravity waves are excited by the convective overshooting, yielding a complex wave field throughout the radiative interior.

  10. Mid-Latitude Sedimentary Rock: Spallanzani Crater

    NASA Technical Reports Server (NTRS)

    2001-01-01

    [figure removed for brevity, see original site]

    Although most of the best examples of layered sedimentary rock seen on Mars are found at equatorial and sub-tropical latitudes, a few locations seen at mid- and high-latitudes suggest that layered rocks are probably more common than we can actually see from orbit. One extremely good example of these 'atypical' layered rock exposures is found in the 72 km-diameter (45 miles) crater, Spallanzani (58.4oS, 273.5oW). Located southeast of Hellas Planitia, the crater is named for the 18th Century Italian biologist, Lazzaro Spallanzani (1729-1799). Picture A presents a composite of the best Viking orbiter image (VO2-504B55) of the region with 4 pictures obtained June 1999 through January 2001 by the Mars Global Surveyor Mars Orbiter Camera (MOC). Each MOC narrow angle image is 3 km across. Taken in the MOC's 'survey mode,' all four images were acquired at roughly 12 meters (39 ft) per pixel. Picture B zooms-in on the portion of the composite image that includes the 4 MOC images (the 100%-size view is 20 m (66 ft) per pixel). Other craters in the region near Spallanzani show features--at Viking Orbiter scale--that are reminiscent of the layering seen in Spallanzani. Exactly what these layers are made of and how they came to be where we see them today are mysteries, but it is possible that they are similar to the materials seen in the many craters and chasms of the equatorial latitudes on Mars.

  11. Unveiling Titan's Mid-Latitude Surface Regions

    NASA Astrophysics Data System (ADS)

    Solomonidou, A.; Coustenis, A.; Lopes, R. M. C.; Rodriguez, S.; Hirtzig, M.; Stephan, K.; Sotin, C.; Drossart, P.; Le Mouelic, S.; Lawrence, K. J.; Malaska, M. J.; Jaumann, R.; Brown, R. H.; Bratsolis, E.

    2014-12-01

    Titan's extended, dense, and hazy N2-CH4 dominated atmosphere shields its surface from direct optical observations except at certain frequencies where the methane absorption is weak. These "methane windows" are exploited by the VIMS instrument on Cassini. After accounting for the atmospheric contribution to the VIMS data, we use a Radiative Transfer code (RT) that includes the most recent evaluations of the aerosol and methane opacity characteristics [1;2] in order to simulate the spectra and to infer the surface properties as well as any possible evolution with time. We focus on some equatorial regions that have been identified as possibly subject to changes, having particular spectral properties and possibly being the strongest cryovolcanic candidate regions, that is: Sotra Patera, Hotei Regio and Tui Regio [3;4;5]. In addition, we examine some test cases and a vast expansion of terrain called the 'Blandlands', which are all not expected to change with time as confirmed by our results. The only changes with time we find are for Tui Regio darkening from 2005-2009 while Sotra Patera brightens from 2005-2006 at all wavelengths, indicating that dynamical processes control the regions, compatible with their complex morphology. We also use a despeckle filtering technique [6] on RADAR data in order to retrieve more revealing information on the morphology of these regions. We also associate radiometric and topographic data with the compositional information from VIMS to derive constraints on the chemical composition and the geology of the surface and the nature of these regions [5]. [1] Hirtzig, M., et al.: Icarus, 226, 470-486, 2013. [2] Solomonidou, A., et al.: JGR, accepted, 2014 [doi: 10.1002/2014JE004634]. [3] Lopes, R.M.C., et al.: JGR, 118, 416-435, 2013; [4] Moore, J.M., and Howard, A.D.: GRL, 37, L22205, 2010; [5] Solomonidou, A., et al.: in prep. (2014b); [6] Bratsolis, E., et al.: PSS, 61, 108-113, 2012.

  12. Moist convection in hydrogen atmospheres and the frequency of Saturn’s giant storms

    NASA Astrophysics Data System (ADS)

    Li, Cheng; Ingersoll, Andrew P.

    2015-05-01

    A giant storm erupted on Saturn in December 2010. It produced intense lightning and cloud disturbances and encircled the planet in six months. Six giant storms--also called Great White Spots--have been observed on Saturn since 1876, recurring every 20 to 30 years and alternating between mid-latitudes and the equator. Here we use thermodynamic arguments to demonstrate that the quasi-periodic occurrence of Saturn’s giant storms can be explained by a water-loading mechanism, in which moist convection is suppressed for decades owing to the relatively large molecular weight of water in a hydrogen-helium atmosphere. We find that the interaction between moist convection and radiative cooling in the troposphere above the cloud base produces an oscillation that leads to giant storm generation with a period of approximately 60 years for either mid-latitudes or the equator, provided the mixing ratio of water vapour in the troposphere exceeds 1.0%. We use a two-dimensional axisymmetric dynamic model and a top-cooling convective adjustment scheme to apply our conceptual model to Saturn. For a water vapour mixing ratio of 1.1%, simulated storms show a recurrence interval, ammonia depletion and tropospheric warming that are consistent with 2010 observations. Jupiter’s atmosphere is more depleted in water than Saturn, which may explain its lack of planet-encircling storms.

  13. Continental aggregation, subduction initiation, and plume generation

    NASA Astrophysics Data System (ADS)

    Heron, P. J.; Lowman, J. P.

    2013-12-01

    Several processes unfold during the supercontinent cycle, more than one of which might result in an elevation in subcontinental mantle temperatures through the generation of mantle plumes. Paleogeographic plate reconstructions have indicated that sub-continental mantle upwellings appear below large continents that are extensively ringed by subduction zones. Moreover, several numerical simulations of supercontinent formation and dispersal attribute the genesis of sub-continental plumes to the generation of subduction zones on the edges of the supercontinent, rather than resulting from continental insulation. However, the role of the location of downwellings in producing a return-flow upwelling, and on increasing sub-continental mantle temperatures, is not fully understood. In this mantle convection study, we examine the evolution of mantle dynamics after supercontinent accretion over a subduction zone (analogous to the formation of Pangea) for a range of continental coverage. We present 2D and 3D Cartesian geometry mantle convection simulations, featuring geotherm- and pressure-dependent viscosity with thermally and mechanically distinct oceanic and continental plates. Through changing the size of the continent we are able to analyze the factors involved in the generation of mantle plumes in purely thermal convection. Furthermore, we change the upper and lower mantle viscosity to determine their relation to plume formation in vigorous mantle convection simulations. Elevated sub-continental temperatures are analyzed in relation to continental coverage to further understand the influence of continental tectonics on the thermal evolution of the mantle.

  14. Parameterizing deep convection using the assumed probability density function method

    SciTech Connect

    Storer, R. L.; Griffin, B. M.; Hoft, Jan; Weber, J. K.; Raut, E.; Larson, Vincent E.; Wang, Minghuai; Rasch, Philip J.

    2015-01-06

    Due to their coarse horizontal resolution, present-day climate models must parameterize deep convection. This paper presents single-column simulations of deep convection using a probability density function (PDF) parameterization. The PDF parameterization predicts the PDF of subgrid variability of turbulence, clouds, and hydrometeors. That variability is interfaced to a prognostic microphysics scheme using a Monte Carlo sampling method.The PDF parameterization is used to simulate tropical deep convection, the transition from shallow to deep convection over land, and mid-latitude deep convection.These parameterized single-column simulations are compared with 3-D reference simulations. The agreement is satisfactory except when the convective forcing is weak. The same PDF parameterization is also used to simulate shallow cumulus and stratocumulus layers. The PDF method is sufficiently general to adequately simulate these five deep, shallow, and stratiform cloud cases with a single equation set. This raises hopes that it may be possible in the future, with further refinements at coarse time step and grid spacing, to parameterize all cloud types in a large-scale model in a unified way.

  15. Parameterizing deep convection using the assumed probability density function method

    DOE PAGESBeta

    Storer, R. L.; Griffin, B. M.; Höft, J.; Weber, J. K.; Raut, E.; Larson, V. E.; Wang, M.; Rasch, P. J.

    2014-06-11

    Due to their coarse horizontal resolution, present-day climate models must parameterize deep convection. This paper presents single-column simulations of deep convection using a probability density function (PDF) parameterization. The PDF parameterization predicts the PDF of subgrid variability of turbulence, clouds, and hydrometeors. That variability is interfaced to a prognostic microphysics scheme using a Monte Carlo sampling method. The PDF parameterization is used to simulate tropical deep convection, the transition from shallow to deep convection over land, and mid-latitude deep convection. These parameterized single-column simulations are compared with 3-D reference simulations. The agreement is satisfactory except when the convective forcing ismore » weak. The same PDF parameterization is also used to simulate shallow cumulus and stratocumulus layers. The PDF method is sufficiently general to adequately simulate these five deep, shallow, and stratiform cloud cases with a single equation set. This raises hopes that it may be possible in the future, with further refinements at coarse time step and grid spacing, to parameterize all cloud types in a large-scale model in a unified way.« less

  16. On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes - Part 2: The effects of the El Niño/Southern Oscillation, volcanic eruptions and contributions of atmospheric dynamics and chemistry to long-term total ozone changes

    NASA Astrophysics Data System (ADS)

    Rieder, H. E.; Frossard, L.; Ribatet, M.; Staehelin, J.; Maeder, J. A.; Di Rocco, S.; Davison, A. C.; Peter, T.; Weihs, P.; Holawe, F.

    2013-01-01

    We present the first spatial analysis of "fingerprints" of the El Niño/Southern Oscillation (ENSO) and atmospheric aerosol load after major volcanic eruptions (El Chichón and Mt. Pinatubo) in extreme low and high (termed ELOs and EHOs, respectively) and mean values of total ozone for the northern and southern mid-latitudes (defined as the region between 30° and 60° north and south, respectively). Significant influence on ozone extremes was found for the warm ENSO phase in both hemispheres during spring, especially towards low latitudes, indicating the enhanced ozone transport from the tropics to the extra-tropics. Further, the results confirm findings of recent work on the connection between the ENSO phase and the strength and extent of the southern ozone "collar". For the volcanic eruptions the analysis confirms findings of earlier studies for the northern mid-latitudes and gives new insights for the Southern Hemisphere. The results provide evidence that the negative effect of the eruption of El Chichón might be partly compensated by a strong warm ENSO phase in 1982-1983 at southern mid-latitudes. The strong west-east gradient in the coefficient estimates for the Mt. Pinatubo eruption and the analysis of the relationship between the AAO and ENSO phase, the extent and the position of the southern ozone "collar" and the polar vortex structure provide clear evidence for a dynamical "masking" of the volcanic signal at southern mid-latitudes. The paper also analyses the contribution of atmospheric dynamics and chemistry to long-term total ozone changes. Here, quite heterogeneous results have been found on spatial scales. In general the results show that EESC and the 11-yr solar cycle can be identified as major contributors to long-term ozone changes. However, a strong contribution of dynamical features (El Niño/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Antarctic Oscillation (AAO), Quasi-Biennial Oscillation (QBO)) to ozone variability and

  17. On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes - Part 2: The effects of the El Niño/Southern Oscillation, volcanic eruptions and contributions of atmospheric dynamics and chemistry to long-term total ozone changes

    NASA Astrophysics Data System (ADS)

    Rieder, H. E.; Frossard, L.; Ribatet, M.; Staehelin, J.; Maeder, J. A.; Di Rocco, S.; Davison, A. C.; Peter, T.; Weihs, P.; Holawe, F.

    2012-05-01

    We present the first spatial analysis of "fingerprints" of the El Niño/Southern Oscillation (ENSO) and atmospheric aerosol load after major volcanic eruptions (El Chichón and Mt. Pinatubo) in extreme low and high (termed ELOs and EHOs, respectively) and mean values of total ozone for the northern and southern mid-latitudes (defined as the region between 30° and 60° north and south, respectively). Significant influence on ozone extremes was found for the warm ENSO phase in both hemispheres during spring, especially towards low latitudes, indicating the enhanced ozone transport from the tropics to the extra-tropics. Further, the results confirm findings of recent work on the connection between the ENSO phase and the strength and extent of the southern ozone "collar". For the volcanic eruptions the analysis confirms findings of earlier studies for the northern mid-latitudes and gives new insights for the Southern Hemisphere. The results provide evidence that the negative effect of the eruption of El Chichón might be partly compensated by a strong warm ENSO phase in 1982-83 at southern mid-latitudes. The strong west-east gradient in the coefficient estimates for the Mt. Pinatubo eruption and the analysis of the relationship between the AAO and ENSO phase, the extent and the position of the southern ozone "collar" and the polar vortex structure provide clear evidence for a dynamical "masking" of the volcanic signal at southern mid-latitudes. The paper also analyses the contribution of atmospheric dynamics and chemistry to long-term total ozone changes. Here, quite heterogeneous results have been found on spatial scales. In general the results show that EESC and the 11-yr solar cycle can be identified as major contributors to long-term ozone changes. However, a strong contribution of dynamical features (El Niño/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Antarctic Oscillation (AAO), Quasi-Biennial Oscillation (QBO)) to ozone variability and

  18. Nitrogen Oxides and Ozone from B-747 Measurements (NOXAR) During POLINAT-2 and SONEX: Overview and Case Studies on Continental and Marine Convection

    NASA Technical Reports Server (NTRS)

    Jeker, Dominique P.; Pfister, Lenny; Brunner, Dominik; Boccippio, Dennis J.; Pickering, Kenneth E.; Thompson, Anne M.; Wernli, Heini; Selkirk, Rennie B.; Kondo, Yutaka; Koike, Matoke

    1997-01-01

    In the framework of the project POLINAT 2 (Pollution in the North Atlantic Flight Corridor) we measured NO(x) (NO and NO2) and ozone on 85 flights through the North Atlantic Flight Corridor (NAFC) with a fully automated system permanently installed aboard an in-service Swissair B-747 airliner in the period of August to November 1997. The averaged NO(x) concentrations both in the NAFC and at the U.S. east coast were similar to that measured in autumn 1995 with the same system. The patchy occurrence of NO(x) enhancements up to 3000 pptv over several hundred kilometers (plumes), predominately found over the U.S. east coast lead to a log-normal NO(x) probability density function. In three case studies we examine the origins of such plumes by combining back-trajectories with brightness temperature enhanced (IR) satellite imagery, lightning observations from the U.S. National Lightning Detection Network (NLDN) and the Optical Transient Detector (OTD) satellite. We demonstrate that the location of NO(x) plumes can be well explained with maps of convective influence. We show that the number of lightning flashes in cluster of marine thunderstorms is proportional to the NO(x) concentrations observed several hundred kilometers downwind of the anvil outflows. From the fact that in autumn the NO(x) maximum was found several hundred kilometers off the U.S. east coast, it can be inferred that thunderstorms triggered over the warm Gulf Stream current are major sources for the regional upper tropospheric NO(x) budget in autumn.

  19. UV dosage levels in summer: increased risk of ozone loss from convectively injected water vapor.

    PubMed

    Anderson, James G; Wilmouth, David M; Smith, Jessica B; Sayres, David S

    2012-08-17

    The observed presence of water vapor convectively injected deep into the stratosphere over the United States can fundamentally change the catalytic chlorine/bromine free-radical chemistry of the lower stratosphere by shifting total available inorganic chlorine into the catalytically active free-radical form, ClO. This chemical shift markedly affects total ozone loss rates and makes the catalytic system extraordinarily sensitive to convective injection into the mid-latitude lower stratosphere in summer. Were the intensity and frequency of convective injection to increase as a result of climate forcing by the continued addition of CO(2) and CH(4) to the atmosphere, increased risk of ozone loss and associated increases in ultraviolet dosage would follow. PMID:22837384

  20. A three-dimensional model of moist convection for the giant planets II: Saturn's water and ammonia moist convective storms

    NASA Astrophysics Data System (ADS)

    Hueso, Ricardo; Sánchez-Lavega, Agustín

    2004-11-01

    Moist convective storms constitute a key aspect in the global energy budget of the atmospheres of the giant planets. Among them, Saturn is known to develop the largest scale convective storms in the Solar System, the Great White Spots (GWS) which occur rarely and have been detected once every 30 years approximately. On the average, Saturn seems to show much less convective storms than Jupiter with smaller size and reduced frequency and intensity. Here we present detailed simulations of the onset and development of storms at the Equator and mid-latitudes of Saturn. These are the regions where most of the recent convective activity of the planet has been observed. We use a 3D anelastic model with parameterized microphysics (Hueso and Sánchez-Lavega, 2001, Icarus 151, 257) studying the onset and evolution of water and ammonia moist convective storms up to sizes of a few hundred km. Water storms, while more difficult to initiate than in Jupiter, can be very energetic, arriving to the 150 mbar level and developing vertical velocities on the order of 150 m s -1. Ammonia storms develop easier but with a much smaller intensity unless very large abundances of ammonia (10 times solar) are present in Saturn's atmosphere. The Coriolis forces play a major role in the morphology and properties of water based storms.

  1. Meridional Circulation in Solar and Stellar Convection Zones

    NASA Astrophysics Data System (ADS)

    Featherstone, Nicholas A.; Miesch, Mark S.

    2015-05-01

    We present a series of 3D nonlinear simulations of solar-like convection, carried out using the Anelastic Spherical Harmonic code, that are designed to isolate those processes that drive and shape meridional circulations (MCs) within stellar convection zones. These simulations have been constructed so as to span the transition between solar-like differential rotation (DR; fast equator/slow poles) and “anti-solar” DR (slow equator/fast poles). Solar-like states of DR, which arise when convection is rotationally constrained, are characterized by a very different convective Reynolds stress (RS) than anti-solar regimes, wherein convection only weakly senses the Coriolis force. We find that the angular momentum transport by convective RS plays a central role in establishing the meridional flow profiles in these simulations. We find that the transition from single-celled to multi-celled MC profiles in strong and weak regimes of rotational constraint is linked to a change in the convective RS, which is a clear demonstration of gyroscopic pumping. Latitudinal thermal variations differ between these different regimes, with those in the solar-like regime conspiring to suppress a single cell of MC, whereas the cool poles and warm equator established in the anti-solar states tend to promote single-celled circulations. Although the convective angular momentum transport becomes radially inward at mid-latitudes in anti-solar regimes, it is the MC that is primarily responsible for establishing a rapidly rotating pole. We conclude with a discussion of how these results relate to the Sun, and suggest that the Sun may lie near the transition between rapidly rotating and slowly rotating regimes.

  2. MAGNETIC CYCLES IN GLOBAL LARGE-EDDY SIMULATIONS OF SOLAR CONVECTION

    SciTech Connect

    Ghizaru, Mihai; Charbonneau, Paul; Smolarkiewicz, Piotr K.

    2010-06-01

    We report on a global magnetohydrodynamical simulation of the solar convection zone, which succeeds in generating a large-scale axisymmetric magnetic component, antisymmetric about the equatorial plane and undergoing regular polarity reversals on decadal timescales. We focus on a specific simulation run covering 255 years, during which 8 polarity reversals are observed, with a mean period of 30 years. Time-latitude slices of the zonally averaged toroidal magnetic component at the base of the convecting envelope show a well-organized toroidal flux system building up in each solar hemisphere, peaking at mid-latitudes and migrating toward the equator in the course of each cycle, in remarkable agreement with inferences based on the sunspot butterfly diagram. The simulation also produces a large-scale dipole moment, varying in phase with the internal toroidal component, suggesting that the simulation may be operating as what is known in mean-field theory as an {alpha}{Omega} dynamo.

  3. Magnetic Cycles in Global Large-eddy Simulations of Solar Convection

    NASA Astrophysics Data System (ADS)

    Ghizaru, Mihai; Charbonneau, Paul; Smolarkiewicz, Piotr K.

    2010-06-01

    We report on a global magnetohydrodynamical simulation of the solar convection zone, which succeeds in generating a large-scale axisymmetric magnetic component, antisymmetric about the equatorial plane and undergoing regular polarity reversals on decadal timescales. We focus on a specific simulation run covering 255 years, during which 8 polarity reversals are observed, with a mean period of 30 years. Time-latitude slices of the zonally averaged toroidal magnetic component at the base of the convecting envelope show a well-organized toroidal flux system building up in each solar hemisphere, peaking at mid-latitudes and migrating toward the equator in the course of each cycle, in remarkable agreement with inferences based on the sunspot butterfly diagram. The simulation also produces a large-scale dipole moment, varying in phase with the internal toroidal component, suggesting that the simulation may be operating as what is known in mean-field theory as an αΩ dynamo.

  4. Gravity shear waves atop the cirrus layer of intense convective storms

    NASA Technical Reports Server (NTRS)

    Stobie, J. G.

    1975-01-01

    Recent visual satellite photographs of certain intense convective storms have revealed concentric wave patterns. A model for the generation and growth of these waves is proposed. The proposed initial generating mechanism is similar to the effect noticed when a pebble is dropped into a calm pond. The penetration of the tropopause by overshooting convection is analogous to the pebble's penetration of the water's surface. The model for wave growth involves instability due to the wind shear resulting from the cirrus outflow. This model is based on an equation for the waves' phase speed which is similar to the Helmholtz equation. It, however, does not assume an incompressible atmosphere, but rather assumes density is a logarithmic function of height. Finally, the model is evaluated on the two mid-latitude and three tropical cases. The data indicate that shearing instability may be a significant factor in the appearance of these waves.

  5. Convection and the Soil-Moisture Precipitation Feedback

    NASA Astrophysics Data System (ADS)

    Schar, C.; Froidevaux, P.; Keller, M.; Schlemmer, L.; Langhans, W.; Schmidli, J.

    2014-12-01

    interannual variability over mid-latitude summer climates, both over Europe and North America. It is argued that parameterized convection may contribute towards such biases by overemphasizing a positive SMP feedback.

  6. Growth of continental-scale metro-agro-plexes, regional ozone pollution, and world food production

    SciTech Connect

    Chameides, W.L.; Kasibhatla, P.S. ); Yienger, J.; Levy, H. II )

    1994-04-01

    Three regions of the northern mid-latitudes, the continental-scale metro-agro-plexes, presently dominate global industrial and agricultural productivity. Although these regions cover only 23 percent of the Earth's continents, they account for most of the world's commercial energy consumption, fertilizer use, food-crop production, and food exports. They also account for more than half of the world's atmospheric nitrogen oxide (NO[sub x]) emissions and, as a result, are prone to ground-level ozone (O[sub 3]) pollution during the summer months. On the basis of a global simulation of atmospheric reactive nitrogen compounds, it is estimated that about 10 to 35 percent of the world's grain production may occur in parts of these regions where ozone pollution may reduce crop yields. Exposure to yield-reducing ozone pollution may triple by 2025 if rising anthropogenic NO[sub x] emissions are not abated.

  7. Growth of Continental-Scale Metro-Agro-Plexes, Regional Ozone Pollution, and World Food Production

    NASA Astrophysics Data System (ADS)

    Chameides, W. L.; Kasibhatla, P. S.; Yienger, J.; Levy, H., II

    1994-04-01

    Three regions of the northern mid-latitudes, the continental-scale metro-agro-plexes, presently dominate global industrial and agricultural productivity. Although these regions cover only 23 percent of the Earth's continents, they account for most of the world's commercial energy consumption, fertilizer use, food-crop production, and food exports. They also account for more than half of the world's atmospheric nitrogen oxide (NO_x) emissions and, as a result, are prone to ground-level ozone (O_3) pollution during the summer months. On the basis of a global simulation of atmospheric reactive nitrogen compounds, it is estimated that about 10 to 35 percent of the world's grain production may occur in parts of these regions where ozone pollution may reduce crop yields. Exposure to yield-reducing ozone pollution may triple by 2025 if rising anthropogenic NO_x emissions are not abated.

  8. Orographic effects related to deep convection events over the Andes region

    NASA Astrophysics Data System (ADS)

    Hierro, R.; Pessano, H.; Llamedo, P.; de la Torre, A.; Alexander, P.; Odiard, A.

    2013-02-01

    In this work, we analyze a set of 39 storms which took place between 2006 and 2011 over the South of Mendoza, Argentina. This is a semiarid region situated at mid-latitudes (roughly between 32S and 36S) at the east of the highest Andes tops which constitutes a natural laboratory where diverse sources of gravity waves usually take place. We consider a cultivated subregion near San Rafael district, where every summer a systematic generation of deep convection events is registered. We propose that the lift mechanism required to raise a parcel to its level of free convection is partially supplied by mountain waves (MWs). From Weather Research and Forecasting (WRF) mesoscale model simulations and radar network data, we calculate the evolution of convective available potential energy and convective inhibition indices during the development of each storm. Global Final Analysis is used to construct initial and boundary conditions. Convective inhibition indices are compared with the vertical kinetic energy capable of being supplied by the MWs, in order to provide a rough estimation of this possible triggering mechanism. Vertical velocity is chosen as an appropriate dynamical variable to evidence the presence of MWs in the vicinity of each detected first radar echo. After establishing a criterion based on a previous work to represent MWs, the 39 storms are split into two subsets: with and without the presence of MWs. 12 cases with considerable MWs amplitude are retained and considered. Radar data differences between the two samples are analyzed and the simulated MWs are characterized.

  9. Supergranular Convection

    NASA Astrophysics Data System (ADS)

    Udayashankar, Paniveni

    2015-12-01

    Observation of the Solar photosphere through high resolution instruments have long indicated that the surface of the Sun is not a tranquil, featureless surface but is beset with a granular appearance. These cellular velocity patterns are a visible manifestation of sub- photospheric convection currents which contribute substantially to the outward transport of energy from the deeper layers, thus maintaining the energy balance of the Sun as a whole.Convection is the chief mode of transport in the outer layers of all cool stars such as the Sun (Noyes,1982). Convection zone of thickness 30% of the Solar radius lies in the sub-photospheric layers of the Sun. Here the opacity is so large that heat flux transport is mainly by convection rather than by photon diffusion. Convection is revealed on four scales. On the scale of 1000 km, it is granulation and on the scale of 8-10 arcsec, it is Mesogranulation. The next hierarchial scale of convection , Supergranules are in the range of 30-40 arcsec. The largest reported manifestation of convection in the Sun are ‘Giant Cells’or ‘Giant Granules’, on a typical length scale of about 108 m.'Supergranules' is caused by the turbulence that extends deep into the convection zone. They have a typical lifetime of about 20hr with spicules marking their boundaries. Gas rises in the centre of the supergranules and then spreads out towards the boundary and descends.Broadly speaking supergranules are characterized by the three parameters namely the length L, the lifetime T and the horizontal flow velocity vh . The interrelationships amongst these parameters can shed light on the underlying convective processes and are in agreement with the Kolmogorov theory of turbulence as applied to large scale solar convection (Krishan et al .2002 ; Paniveni et. al. 2004, 2005, 2010).References:1) Noyes, R.W., The Sun, Our Star (Harvard University Press, 1982)2) Krishan, V., Paniveni U., Singh , J., Srikanth R., 2002, MNRAS, 334/1,2303) Paniveni

  10. Hydroclimatic Assessment of West Nile Virus Occurrence Across Continental US

    NASA Astrophysics Data System (ADS)

    Billian, H. E.; Jutla, A.; Colwell, R. R.

    2014-12-01

    West Nile virus (WNV) is the most widely infections from arbovirus in mid-latitudes, having reached the Western Hemisphere in 1999. As a vector-borne disease, WNV is primarily spread by mosquitoes; the disease is predominantly found in tropical and temperate regions of the world, and is now considered an endemic pathogen in the United States, Africa, Asia, Australia, the Middle East, and Europe. Environmental processes play a vital role in the trigger of WNV. Here, using logistical regression models, we quantified relationships between hydroclimatic processes and mosquito abundance for WNV across the continental USA using precipitation and temperature at different spatial and temporal scales. It will be shown that reported cases of this disease are more prevalent during spring and summer months in the entire country, when there is more precipitation and higher surface air temperatures for 2003 to 2013. The key impacts of this research are those related to the improvement of human health, and a means to predict mosquito breeding patterns long term as they relate to the prevalence of vector-borne illnesses.

  11. Continental Rifts

    NASA Astrophysics Data System (ADS)

    Rosendahl, B. R.

    Continental Rifts, edited by A. M. Quennell, is a new member of the Benchmark Papers in Geology Series, edited in toto by R. W. Fairbridge. In this series the individual volume editors peruse the literature on a given topic, select a few dozen papers of ostensibly benchmark quality, and then reorder them in some sensible fashion. Some of the original papers are republished intact, but many are chopped into “McNuggets™” of information. Depending upon the volume editor, the chopping process can range from a butchering job to careful and prudent pruning. The collecting, sifting, and reorganizing tasks are, of course, equally editor-sensitive. The end product of this series is something akin to a set of Reader's Digest of Geology.

  12. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1994-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air and of generating electricity utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity. Other embodiments may also provide fresh water, and operate in an updraft mode.

  13. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1996-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

  14. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1995-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

  15. Convection towers

    DOEpatents

    Prueitt, M.L.

    1996-01-16

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water. 6 figs.

  16. Modeling Convection

    ERIC Educational Resources Information Center

    Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda

    2004-01-01

    Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…

  17. Microphysical Effects Determine Macrophysical Response for Aerosol Impacts on Deep Convective Clouds

    SciTech Connect

    Fan, Jiwen; Leung, Lai-Yung R.; Rosenfeld, Daniel; Chen, Qian; Li, Zhanqing; Zhang, Jinqiang; Yan, Hongru

    2013-11-26

    Deep convective clouds (DCCs) play a crucial role in the general circulation and energy and hydrological cycle of our climate system. Anthropogenic and natural aerosol particles can influence DCCs through changes in cloud properties, precipitation regimes, and radiation balance. Modeling studies have reported both invigoration and suppression of DCCs by aerosols, but none has fully quantified aerosol impacts on convection life cycle and radiative forcing. By conducting multiple month-long cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macro- and micro-physical properties of summer convective clouds in the tropics and mid-latitudes, this study provides the first comprehensive look at how aerosols affect cloud cover, cloud top height (CTH), and radiative forcing. Observations validate these simulation results. We find that microphysical aerosol effects contribute predominantly to increased cloud cover and CTH by inducing larger amount of smaller but longer lasting ice particles in the stratiform/anvils of DCCs with dynamical aerosol effects contributing at most ~ 1/4 of the total increase of cloud cover. The overall effect is a radiative warming in the atmosphere (3 to 5 W m-2) with strong surface cooling (-5 to -8 W m-2). Herein we clearly identified mechanisms more important than and additional to the invigoration effects hypothesized previously that explain the consistent signatures of increased cloud tops area and height by aerosols in DCCs revealed by observations.

  18. Convection towers

    DOEpatents

    Prueitt, M.L.

    1994-02-08

    Convection towers which are capable of cleaning the pollution from large quantities of air and of generating electricity utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity. Other embodiments may also provide fresh water, and operate in an updraft mode. 5 figures.

  19. Extremely tall convection: characteristics and controls

    NASA Astrophysics Data System (ADS)

    Nesbitt, S. W.; Rasmussen, K. L.

    2015-12-01

    Tall continental convective structures are observed in several climatological regions, and have been shown to be related with severe weather and extreme hydrologic events. Recent work has defined tall convection as regions with precipitation structures observed with spaceborne radar echo extending into the upper troposphere/lower stratosphere. While these climatological regions are known for these tall convective structures (subtropical South America, equatorial Africa, southcentral USA, South Asia), not all observed convective eventsin these regions contain strong structures, and the characteristics of the meteorological environments, including sounding profiles, that dictate the strength of the spectrum of convective systems are poorly constrained. In this study, precipitation radar (PR) data from the Tropical Rainfall Measuring Mission (TRMM) and dual-frequency precipitation radar (DPR) from the Global Precipitation Measurement (GPM) satellites will be examined alongside composites of atmospheric reanalysis data to examine the structural and meteorological environments surrounding observed tall convective systems. Environments of convective systems of various vertical extents will be contrasted with less extreme convection to infer physical causal mechanisms and to examine issues of predictability of these events.

  20. Uranium-series dating of sediments from Searles Lake: Differences between continental and marine climate records

    USGS Publications Warehouse

    Bischoff, J.L.; Rosenbauer, R.J.; Smith, G.I.

    1985-01-01

    One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial ??18O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 ?? 106 years. Uranium-series dates on the salt beds range from 35 ?? 103 to 231 ?? 103 years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record.

  1. Uranium-series dating of sediments from searles lake: differences between continental and marine climate records.

    PubMed

    Bischoff, J L; Rosenbauer, R J; Smith, G I

    1985-03-01

    One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial delta(18)O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 x 10(6) years. Uraniumseries dates on the salt beds range from 35 x 10(3) to 231x 10(3) years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record. PMID:17757864

  2. Linking Late Pleistocene alpine glacial erosion and continental margin sedimentation: Insights from 40Ar/39Ar dating of silt-sized sediment, Canterbury Basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Villaseñor, Tania; Jaeger, John M.; Foster, David A.

    2016-01-01

    Quaternary climatic and eustatic cycles in mid-latitude regions have led to more extensive alpine glaciations and continental shelf progradation, respectively. However, the glacial influence on sediment fluxes to the ocean creating continental margin strata is poorly documented. This contribution analyzes the provenance of fine sediment accumulating on the continental shelf during the Late Pleistocene to evaluate the influence of glacial cycles on sediment erosion and routing to the continental shelf. Taking advantage of the contrasting bedrock ages exposed across the Southern Alps, New Zealand, we perform 40Ar/39Ar incremental heating on the bulk silt-size sediment from three drill sites of IODP Expedition 317, Canterbury Basin, New Zealand. The results suggest that a large proportion of sediment accumulating on the continental shelf results from erosion within the Main Divide fault zone of the Southern Alps. Sediment 40Ar/39Ar age fluctuations over this time period suggest that bedrock with various 40Ar/39Ar cooling ages has been differentially eroded in the upper Waitaki River catchment and mixed in the Waitaki-Canterbury sediment-routing system. Across-shelf variations in sediment 40Ar/39Ar age reflect changing modes of sediment dispersal on the continental shelf. Fluvial material, likely derived from the main drainage divide zone, preferentially accumulates in the middle continental shelf, whereas material representing erosion of older bedrock (Torlesse Terrane), located lower in the drainage basin, is dispersed uniformly across the shelf. The age signature of the muddy sediment accumulating on the continental shelf reflects Late Pleistocene landscape evolution of the Southern Alps and its influence on sediment dispersal to the continental shelf.

  3. Studies of Tropical/Mid-Latitude Exchange Using UARS Observations

    NASA Technical Reports Server (NTRS)

    Avallone, Linnea

    2001-01-01

    At the time this proposal was submitted, recent publications had suggested an important role for transport of midlatitude air into the tropical lower stratosphere. Most of these studies had employed data that gave only a time-averaged picture, making it difficult to determine the nature of the transport processes responsible for the observed behavior. We proposed to analyze observations of long-lived trace gases, such as nitric acid, methane, nitrous oxide, and chlorofluorocarbons, made from the Upper Atmosphere Research Satellite, to investigate the seasonal behavior of mixing between the midlatitudes and tropics. We planned to construct probability distributions of the concentrations of these species over small altitude ranges and to compare them to expectations based on modeled mean concentrations and knowledge of instrument precision. Differences from expectation were to be analyzed with respect to meteorological parameters to determine whether wave activity may have induced apparent mixing.

  4. Aerosol studies in mid-latitude coastal environments in Australia

    NASA Technical Reports Server (NTRS)

    Young, S. A.; Cutten, D.; Lynch, M. J.; Davies, J. E.

    1986-01-01

    The results of the evaluation of several inversion procedures that were used to select one which provides the most accurate atmospheric extinction profiles for small aerosol extinction coefficients (that often predominate in the maritime airmass) are presented. Height profiles of atmospheric extinction calculated by a two component atmospheric solution to the LIDAR equation will be compared with corresponding in-situ extinction profiles based on the size distribution profiles obtained in Western Australia. Values of the aerosol backscatter to extinction ratio obtained from multi-angle LIDAR measurements will be used in this solution.

  5. THE MID-LATITUDE BIODIVERSITY RIDGE IN TERRESTRIAL CAVE FAUNA

    EPA Science Inventory

    The world's obligate cave-dwelling fauna holds considerable promise for biogeographic analysis because it represents a large number of independent evolutionary experiments in isolation in caves and adaptation to subterranean life. We focus on seven north temperate regions of at l...

  6. The ozone layer is recovering in mid-latitudes?

    NASA Astrophysics Data System (ADS)

    Casiccia, Claudio; Zamorano, Felix; Viana, Roberta; Paes Lema, Neusa; Quel, Eduardo; Wolfram, Elian

    2010-05-01

    During the recent decades there has been an increasing concern related to ozone layer and solar ultraviolet radiation, UV-B (280-320 nm), reaching the surface of the earth. The Antarctic Ozone Hole (AOH) is a phenomenon of strong ozone depletion in the Antarctic stratosphere, this is a consequence of heterogeneous chemical reactions and dynamical processes which enhance ozone losses by reactions with chlorine. Punta Arenas (53.0S,70.9W) is the southernmost city in Chile with a population of approximately 120000. Due to its location, well within the area affected by the Antarctic Ozone Hole. Systematic observation of ozone and UV-B with a Brewer spectrophotometer have been made in order study during the ozone hole conditions. In addition, the vertical distribution using ozosonde has been investigated during campaigns in spring time and in 2009 started regularly ECC-ozonesonde measurements, also since 2002 measurements of the ozone vertical distribution using Umkehr technique have been carry out. Intercomparisons with different ozone measurement platforms were presented. Particularly we compared a DIAL ozone vertical profile in Rio Gallegos (Argentina) with an ozonesonde measurement launched in Punta Arenas. The results were in good agreement over the 16-32 km altitude range. Also, here we present measurements of column ozone, vertical distribution of ozone and ultraviolet radiation UV-B made in Punta Arenas and Magallanes region to period 1992-2009. To analyze the behavior of the stratospheric ozone layer over Magallanes was used the reference AVE-CLI-TOMS minus twice the standard deviation of the reference mean (TOMS;1978-1987, mean monthly - 2SD). The number of days per year shows an interesting cycle of 8 to 10 years, but monthly variations did not show a significant decrease, especially during September-October period.

  7. IMF-By effect on the mid-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Jin, Hidekatsu

    The primary factor that controls ionospheric total electron content (TEC) variations is solar UV/EUV radiations through the ionization of the thermospheric neutral particles and through the modification of the thermosphere. Changes in temperature and composition of the neutral atmosphere and the atmospheric circulation greatly affect the ionospheric electron density. Because such a relationship between the solar spectral irradiance and the ionospheric TEC is highly complex, we applied an artificial neural network (ANN) technique that has a great capability of function approximation of complex systems to model solar irradiance effects on TEC. Three solar proxies, F_{10.7}, SOHO_SEM_{26-34} EUV emission index, and MgII_c-w-r were chosen as input parameters to the ANN-TEC model. Another channel of energy flow from the sun to the earth’s ionosphere is the solar wind. The am index and several solar wind magnetosphere coupling functions were chosen as additional inputs to the ANN to model the effects of magnetic disturbances. Somewhat minor but interesting effects on TEC variations emerged when the major effects of solar irradiance and magnetic disturbances were removed. We analyzed the time series of the residual error in TEC prediction by using a wavelet transformation, which revealed a periodic increase in error approximately every 27 days in the summer. Possible origins of the error are (1) insufficient modeling of the solar activity effect, (2) lunar tidal forcing, (3) coupling with planetary waves in the lower atmosphere, and (4) solar wind effects. Examinations refused the first three possibilities. We investigated solar wind parameters that are not concerned in geomagnetic disturbances. The 27-day periodic error during the summer disappeared when the IMF-By component and the solar wind velocity were included in the input space of the ANN. Possible explanation of the IMF-By effect is discussed in terms of changes in the thermospheric general circulation pattern.

  8. HIGH METHANE EMISSIONS FROM A MID-LATITUDE AGRICULTURAL RESERVOIR

    EPA Science Inventory

    To assess the magnitude of methane (CH4) emissions from reservoirs in agricultural regions, we measured CH4 emission rates from William H. Harsha Lake, located in southwestern Ohio, USA, over a thirteen month period. The reservoir was a strong source of CH4¬ throughout the year,...

  9. Particulate emissions from a mid-latitude prescribed chaparral fire

    NASA Technical Reports Server (NTRS)

    Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Winstead, Edward L.; Riggin, Philip J.; Brass, James A.; Ambrosia, Vincent G.

    1988-01-01

    Particulate emission from a 400-acre prescribed chaparral fire in the San Dimas Experimental Forest was investigated by collecting smoke aerosol on Teflon and glass-fiber filters from a helicopter, and using SEM and EDAX to study the features of the particles. Aerosol particles ranged in size from about 0.1 to 100 microns, with carbon, oxygen, magnesium, aluminum, silicon, calcium, and iron as the primary elements. The results of ion chromatographic analysis of aerosol-particle extracts (in water-methanol) revealed the presence of significant levels of NO2(-), NO3(-), SO4(2-), Cl(-), PO4(3-), C2O4(2-), Na(+), NH4(+), and K(+). The soluble ionic portion of the aerosol was estimated to be about 2 percent by weight.

  10. Are tropical cirrus brighter than mid-latitude cirrus?

    NASA Technical Reports Server (NTRS)

    Mitchell, David L.; Arnott, W. Patrick; Sassen, Kenneth; Dong, Yayi; Hallett, John

    1993-01-01

    Recent measurements during FIRE II, in the tropics and elsewhere, support an emerging hypothesis about the role of stratospheric mixing in determining the microphysical and radiative properties of cirrus clouds. This is only a working hypothesis, and may change as new measurements become available. This report reviews the conditions under which certain types of ice crystals form.

  11. Mid-Latitude Plasma Density Irregularities and Electromagnetic Wave Scattering

    NASA Astrophysics Data System (ADS)

    Sotnikov, V.; Kim, T.; Mishin, E.; Rose, D.; Paraschiv, I.

    2015-11-01

    Ionospheric irregularities cause scintillations of electromagnetic signals that can severely affect navigation and transionospheric communication, in particular during space storms. At midlatitudes, such space weather events are caused mainly by subauroral electric field structures (SAID/SAPS) SAID/SAPS -related shear flows and plasma density troughs point to interchange and Kelvin-Helmholtz type instabilities as a possible source of plasma irregularities. A model of nonlinear development of these instabilities based on the two-fluid hydrodynamic description with inclusion of finite Larmor radius effects will be presented. The high-resolution simulations with continuous density and velocity profiles will be driven by the ambient conditions corresponding to the in situ Defense Meteorological Satellite Program (DMSP) satellite low-resolution data during UHF/GPS L-band subauroral scintillation events. These types of density irregularities play important roles in refraction and scattering of high frequency electromagnetic signals propagating in the Earth's ionosphere, inside the plasma sheath of reentry and hypersonic vehicles, and in many other applications.

  12. Length measurements of mid-latitude scintillation irregularities

    SciTech Connect

    Macdougall, J.W. )

    1992-04-01

    The lengths of irregularities which produce 150-MHz amplitude scintillations have been measured at 43 deg N, 81 deg W (geographic) using arrays of receivers with large spacings. The average length (major axis radius) of the irregularities was 6.1 km. This is much shorter than expected and implies that the measurements are of 'young' irregularities, less than 1 minute old. These irregularities appear to be a large, 25-50-percent perturbation of the background density. 8 refs.

  13. Mid-latitude wind forced ocean circulation studies

    NASA Technical Reports Server (NTRS)

    Harrison, D. E.

    1981-01-01

    A simple barotropic vorticity equation model was developed to study some of the various modeling factors that affect the characteristics of strong western boundary currents like the Gulf Stream and Kuroshio. Successful prediction of sea surface temperature, both in the climatological mean and over periods as short as 1 month requires that the heating tendency, due to horizontal advection of heat by these currents, be accurately modeled. Conventional, coarse resolution ocean models do not satisfactorily reproduce the dominant features of these currents. It is concluded that it is important to understand why they do not and what must be done to do so in the future.

  14. Low/Mid-latitude Ionospheric irregularities and scintillation climatology

    NASA Astrophysics Data System (ADS)

    Abdallah, Amr; Groves, K. M.; Mahrous, Ayman; Hussein, Fayrouz

    Ionospheric scintillation occur when radio signals propagate through an irregular ionosphere (e.g., plasma bubbles). Since plasma bubbles are regions of depleted ion and electron densities, a plasma bubble located on the satellite-to-ground signal path will cause radio signals to fluctuate in phase and amplitude. Ionospheric scintillation data were analyzed in the magnetic latitudinal field-of-view 29° N -13.4° N, observed by a stand-alone SCINDA (Scintillation Network Decision Aid) - GPS receiver at Helwan, Egypt (29.86° N, 31.32° E). A minimum 20° elevation cut off angle has been set in order to minimize the multipath effect. During the enhancing phase of the current solar cycle 24 (years 2010, 2011, 2012 and 2013), the behaviour of the scintillation occurrence were characterized. The seasonal, annual and solar cycle variation of scintillation occurrence is investigated together with the Total Electron Content (TEC), to put in evidence the relation between the electron density gradients and the ionospheric irregularities causing scintillation. This study considers a first step to develop a scintillation climatology over Northern Africa.

  15. Synopsis of Mid-latitude Radio Wave Absorption in Europe

    NASA Technical Reports Server (NTRS)

    Torkar, K. M.; Friedrich, M.

    1984-01-01

    Radio wave absorption data covering almost two years from Europe to Central Asia are presented. They are normalized by relating them to a reference absorption. Every day these normalized data are fitted to a mathematical function of geographical location in order to obtain a daily synopsis of radio wave absorption. A film of these absorption charts was made which is intended to reveal movements of absorption or absorption anomaly. In addition, radiance (temperature) data from the lower D-region are also plotted onto these charts.

  16. HIBISCUS and SCOUT-AMMA: Water Vapor And Ice Particles In The Tropical Lower Stratosphere Above Overshooting Continental Convective Systems. Part A. Evidence Of Water Injection Above The Tropopause

    NASA Astrophysics Data System (ADS)

    Khaikin, S.; Korshunov, L.; Pommereau, J.; Nielsen, J.; Christensen, T.; Larsen, N.

    2006-12-01

    The possible impact of meso-scale convective systems (MCS) on water vapor in the lower stratosphere has been explored by a series of six backscatter / ozone / H2O soundings in August 2006 from Niamey (13N, 2E) in West Africa using the backscatter instrument of the University of Wyoming, an ECC ozone cell and a FLASH Lyman alpha hygrometer, all flown on the same balloon. All profiles downwind or next to MCS show saturation, sometimes supersaturation (5-6 ppm H2O), and cirrus clouds at the tropopause at 16-16.5 km around 78°C, surmounted by highly variable H2O layers up to 19 km, a broad minimum between of 4.2 ppm 19-21 km and then almost constant mixing ratio (5.5-6 ppm) from 22 to 31 km. The frequent moist layers between the tropopause and 19 km suggest that water could penetrate the stratosphere up to at least 450 K potential temperature levels. The locations of the MCS potentially responsible for water injection upwind are explored from satellite pictures combined with backward trajectories.

  17. Zoned mantle convection.

    PubMed

    Albarède, Francis; Van Der Hilst, Rob D

    2002-11-15

    We review the present state of our understanding of mantle convection with respect to geochemical and geophysical evidence and we suggest a model for mantle convection and its evolution over the Earth's history that can reconcile this evidence. Whole-mantle convection, even with material segregated within the D" region just above the core-mantle boundary, is incompatible with the budget of argon and helium and with the inventory of heat sources required by the thermal evolution of the Earth. We show that the deep-mantle composition in lithophilic incompatible elements is inconsistent with the storage of old plates of ordinary oceanic lithosphere, i.e. with the concept of a plate graveyard. Isotopic inventories indicate that the deep-mantle composition is not correctly accounted for by continental debris, primitive material or subducted slabs containing normal oceanic crust. Seismological observations have begun to hint at compositional heterogeneity in the bottom 1000 km or so of the mantle, but there is no compelling evidence in support of an interface between deep and shallow mantle at mid-depth. We suggest that in a system of thermochemical convection, lithospheric plates subduct to a depth that depends - in a complicated fashion - on their composition and thermal structure. The thermal structure of the sinking plates is primarily determined by the direction and rate of convergence, the age of the lithosphere at the trench, the sinking rate and the variation of these parameters over time (i.e. plate-tectonic history) and is not the same for all subduction systems. The sinking rate in the mantle is determined by a combination of thermal (negative) and compositional buoyancy and as regards the latter we consider in particular the effect of the loading of plates with basaltic plateaux produced by plume heads. Barren oceanic plates are relatively buoyant and may be recycled preferentially in the shallow mantle. Oceanic plateau-laden plates have a more pronounced

  18. CONVECTION REACTOR

    DOEpatents

    Hammond, R.P.; King, L.D.P.

    1960-03-22

    An homogeneous nuclear power reactor utilizing convection circulation of the liquid fuel is proposed. The reactor has an internal heat exchanger looated in the same pressure vessel as the critical assembly, thereby eliminating necessity for handling the hot liquid fuel outside the reactor pressure vessel during normal operation. The liquid fuel used in this reactor eliminates the necessity for extensive radiolytic gas rocombination apparatus, and the reactor is resiliently pressurized and, without any movable mechanical apparatus, automatically regulates itself to the condition of criticality during moderate variations in temperature snd pressure and shuts itself down as the pressure exceeds a predetermined safe operating value.

  19. How cold pool triggers deep convection?

    NASA Astrophysics Data System (ADS)

    Yano, Jun-Ichi

    2014-05-01

    The cold pool in the boundary layer is often considered a major triggering mechanism of convection. Here, presented are basic theoretical considerations on this issue. Observations suggest that cold pool-generated convective cells is available for shallow maritime convection (Warner et al. 1979; Zuidema et al. 2012), maritime deep convection (Barnes and Garstang 1982; Addis et al. 1984; Young et al. 1995) and continental deep convection (e.g., Lima and Wilson 2008; Flamant 2009; Lothon et al. 2011; Dione et al. 2013). Moreover, numerical studies appear to suggest that cold pools promote the organization of clouds into larger structures and thereby aid the transition from shallow to deep convection (Khairoutdinov and Randall 2006, Boing et al. 2012, Schlemmer and Hohenegger, 2014). Even a cold--pool parameterization coupled with convection is already proposed (Grandpeix and Lafore 2010: but see also Yano 2012). However, the suggested link between the cold pool and deep convection so far is phenomenological at the best. A specific process that the cold pool leads to a trigger of deep convection must still to be pinned down. Naively, one may imagine that a cold pool lifts up the air at the front as it propagates. Such an uplifting leads to a trigger of convection. However, one must realize that a shift of air along with its propagation does not necessarily lead to an uplifting, and even if it may happen, it would not far exceed a depth of the cold pool itself. Thus, the uplifting can never be anything vigorous. Its thermodynamic characteristics do help much either for inducing convection. The cold-pool air is rather under rapid recovering process before it can induce convection under a simple parcel-lifting argument. The most likely reason that the cold pool may induce convection is its gust winds that may encounter an air mass from an opposite direction. This induces a strong convergence, also leading to a strong uplifting. This is an argument essentially developed

  20. Tropical Cyclone Signatures in Atmospheric Convective Available Potential Energy

    NASA Astrophysics Data System (ADS)

    Studholme, Joshua; Gulev, Sergey

    2016-04-01

    Tropical cyclones play an important role in the climate system providing transports of energy and water vapor, forcing the ocean, and also affecting mid-latitude circulation phenomena. Tropical cyclone tracks experience strong interannual variability and in addition, longer term trend-like changes in all ocean basins. Analysis of recent historical data reveal a poleward shift in the locations of tropical cyclone tracks in both the Northern and Southern Hemispheres (Kossin et al. 2014, Nature, 509, 349-352). The physical consequences of these alterations are largely unconstrained. For example, the increasing encroachment of tropical cyclone activity into the extra-tropical environment presents a novel and still poorly understood paradigm for tropical-extratropical interactions. In this respect, the role that the atmospheric convective available potential energy (CAPE) plays in the dynamics of tropical cyclones is highly interesting. The two characteristic global-scale spatial patterns in CAPE are identified using EOF analysis. The first pattern shows an abundance of CAPE in the centre of the Pacific and corresponds to the El Nino Southern Oscillation. The second one is capturing positive CAPE anomalies in the oceanic tropics and negative anomalies over equatorial Africa. Associated with these buoyancy patterns, alterations in tropical cyclone activity occur in all basins forming both zonal and meridional patterns. Atmospheric buoyancy is the trigger for deep convection, and subsequently cyclone genesis. This is the mechanism of impact upon location at the start of cyclone tracks. It is found to have less impact upon where cyclones subsequently move, whether or not they undergo extratropical transition and when and where they experience lysis. It is shown that CAPE plays a critical role in the general circulation in the tropics which in turn is the larger steering context for embedded systems within the Walker and Hadley cells. So this lack of `latter life' impact

  1. Assessing the sensitivity of moist convection to climate change within an idealized cloud-resolving modeling framework

    NASA Astrophysics Data System (ADS)

    Schlemmer, Linda; Schmidli, Juerg; Schär, Christoph

    2014-05-01

    The use of parametrization schemes for the representation of moist convection implies major uncertainties in current climate projections. Here we introduce an idealized cloud-resolving modeling (CRM) framework for the study of mid-latitude diurnal convection over land. The framework is used to assess the sensitivity of the soil-moisture precipitation feedback and associated heavy precipitation events from first principles. The model is run for 30 days. Using a relaxation strategy, approximate equilibrium is reached after about 16 days. In this state, termed "diurnal equilibrium", the diurnal cycle of moist convection repeats itself more or less from day to day. Using this framework we investigate the sensitivity of the diurnal convection and resulting cloud development to changes in atmospheric temperature, lapse-rate and soil moisture content that could result from anthropogenic climate change. We find that the temperature stratification of the environment has a dominant influence on the depth and intensity of convection. If the background profile is more stably stratified, more clouds develop and the intensity of convection increases considerably. More unstable profiles in contrast lead to deeper convection that continues over a longer time span. For warmer atmospheres, the increase of water vapor enhances moreover cloud amount. A decrease of soil moisture reduces precipitation amounts and leads to the development of very localized precipitation patches. Concerning the distribution of precipitation intensities, we find an increase of heavy precipitation events if a warming of the atmosphere goes together with a stabilization of the atmosphere as is projected by many climate models. These increases are however smaller than expected from Clausius Clapeyron scaling. Reductions of soil moisture on the other hand decrease precipitation over all intensities.

  2. Convective heater

    DOEpatents

    Thorogood, R.M.

    1983-12-27

    A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation. 14 figs.

  3. Convective heater

    DOEpatents

    Thorogood, Robert M.

    1986-01-01

    A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation.

  4. Convective heater

    DOEpatents

    Thorogood, Robert M.

    1983-01-01

    A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation.

  5. Urban Heat Island phenomenon in extreme continental climate (Astana, Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Konstantinov, Pavel; Akhmetova, Alina

    2015-04-01

    Urban Heat Island (UHI) phenomenon is well known in scientific literature since first half of the 19th century [1]. By now a wide number of world capitals is described from climatological point of view, especially in mid-latitudes. In beginning of XXI century new studies focus on heat island of tropical cities. However dynamics UHI in extreme continental climates is insufficiently investigated, due to the fact that there isn't large cities in Europe and Northern America within that climate type. In this paper we investigate seasonal and diurnal dynamics UHI intensity for Astana, capital city of Kazakhstan (population larger than 835 000 within the city) including UHI intensity changes on different time scales. Now (since 1998) Astana is the second coldest capital city in the world after Ulaanbaatar, Mongolia [3] For this study we use the UHI investigation technology, described in [2]. According to this paper, we selected three stations: one located into city in high and midrise buildings area (including extensive lowrise and high-energy industrial - LCZ classification) and two others located in rural site (sparsely built or open-set and lightweight lowrise according LCZ classification). Also these stations must be close by distance (less than 100 km) and altitude. Therefore, first for Astana city were obtained numerical evaluations for UHI climate dynamics, UHI dependence of synoptic situations and total UHI climatology on monthly and daily averages. References: 1.Howard, L. (1833) The Climate of London, Deduced from Meteorological Observations. Volume 2, London. 2.Kukanova E.A., Konstantinov P.I. An urban heat islands climatology in Russia and linkages to the climate change In Geophysical Research Abstracts, volume 16 of EGU General Assembly, pages EGU2014-10833-1, Germany, 2014. Germany. 3.www.pogoda.ru.net

  6. Helicity inversion in spherical convection as a means for equatorward dynamo wave propagation

    NASA Astrophysics Data System (ADS)

    Duarte, Lúcia D. V.; Wicht, Johannes; Browning, Matthew K.; Gastine, Thomas

    2016-02-01

    We discuss here a purely hydrodynamical mechanism to invert the sign of the kinetic helicity, which plays a key role in determining the direction of propagation of cyclical magnetism in most models of dynamo action by rotating convection. Such propagation provides a prominent, and puzzling constraint on dynamo models. In the Sun, active regions emerge first at mid-latitudes, then appear nearer the equator over the course of a cycle, but most previous global-scale dynamo simulations have exhibited poleward propagation (if they were cyclical at all). Here, we highlight some simulations in which the direction of propagation of dynamo waves is altered primarily by an inversion of the kinetic helicity throughout much of the interior, rather than by changes in the differential rotation. This tends to occur in cases with a low Prandtl number and internal heating, in regions where the local density gradient is relatively small. We analyse how this inversion arises, and contrast it to the case of convection that is either highly columnar (i.e. rapidly rotating) or locally very stratified; in both of those situations, the typical profile of kinetic helicity (negative throughout most of the Northern hemisphere) instead prevails.

  7. Moist convection in hydrogen atmospheres and the frequency of Saturn's giant storms

    NASA Astrophysics Data System (ADS)

    Li, C.; Ingersoll, A. P.

    2015-12-01

    A giant planet-encircling storm occurred on Saturn on Dec. 5th, 2010 at planetographic latitude 37.7 N. It produced intense lightning, created enormous cloud disturbances and wrapped around the planet in 6 months. Six such storms, called Great White Spots, have erupted since 1876. They have alternated between mid-latitudes and the equator at intervals ranging from 20 to 30 years. The reason for the intermittent explosion is not clear and there are no similar storms on brother Jupiter. Here we describe the water-loading mechanism, which could suppress moist convection for decades due to the larger molecular weight of water in a hydrogen-helium atmosphere. We show that this mechanism requires the deep water vapor mixing ratio to be greater than 1.0%, which implies O/H at least 10 times the solar value. Observations imply that Saturn's atmosphere is more enriched in water than Jupiter, which could explain why Saturn has such storms and Jupiter does not. We further use a two-dimensional axisymmetric dynamic model and a top-cooling convective adjustment scheme to connect our theory to observation. We show that for a deep water vapor mixing ratio of 1.1%, the ammonia vapor is depleted down to 6 bars, the tropospheric warming is ~6 K, and the interval between two consecutive storms at one latitude is ~70 years. These values are consistent with observations.

  8. MERIDIONAL CIRCULATION DYNAMICS FROM 3D MAGNETOHYDRODYNAMIC GLOBAL SIMULATIONS OF SOLAR CONVECTION

    SciTech Connect

    Passos, Dário; Charbonneau, Paul; Miesch, Mark

    2015-02-10

    The form of solar meridional circulation is a very important ingredient for mean field flux transport dynamo models. However, a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work, we use results from three-dimensional global simulations of solar convection to infer the dynamical behavior of the established meridional circulation. We make a direct comparison between the meridional circulation that arises in these simulations and the latest observations. Based on our results, we argue that there should be an equatorward flow at the base of the convection zone at mid-latitudes, below the current maximum depth helioseismic measures can probe (0.75 R{sub ⊙}). We also provide physical arguments to justify this behavior. The simulations indicate that the meridional circulation undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation which involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.

  9. A continuous and prognostic convection scheme based on buoyancy, PCMT

    NASA Astrophysics Data System (ADS)

    Guérémy, Jean-François; Piriou, Jean-Marcel

    2016-04-01

    A new and consistent convection scheme (PCMT: Prognostic Condensates Microphysics and Transport), providing a continuous and prognostic treatment of this atmospheric process, is described. The main concept ensuring the consistency of the whole system is the buoyancy, key element of any vertical motion. The buoyancy constitutes the forcing term of the convective vertical velocity, which is then used to define the triggering condition, the mass flux, and the rates of entrainment-detrainment. The buoyancy is also used in its vertically integrated form (CAPE) to determine the closure condition. The continuous treatment of convection, from dry thermals to deep precipitating convection, is achieved with the help of a continuous formulation of the entrainment-detrainment rates (depending on the convective vertical velocity) and of the CAPE relaxation time (depending on the convective over-turning time). The convective tendencies are directly expressed in terms of condensation and transport. Finally, the convective vertical velocity and condensates are fully prognostic, the latter being treated using the same microphysics scheme as for the resolved condensates but considering the convective environment. A Single Column Model (SCM) validation of this scheme is shown, allowing detailed comparisons with observed and explicitly simulated data. Four cases covering the convective spectrum are considered: over ocean, sensitivity to environmental moisture (S. Derbyshire) non precipitating shallow convection to deep precipitating convection, trade wind shallow convection (BOMEX) and strato-cumulus (FIRE), together with an entire continental diurnal cycle of convection (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of convection. Then, a 3D LAM validation is presented considering an AMMA case with both observations and a CRM simulation using the same initial and lateral conditions as for the parameterized one. Finally, global

  10. Reanalysis Study of the North American Monsoon and its Effect on Convective Injection of Water Vapor from the Troposphere to the Stratosphere

    NASA Astrophysics Data System (ADS)

    Clapp, C.; Leroy, S. S.; Anderson, J. G.

    2014-12-01

    The presence of elevated stratospheric water vapor concentrations poses significant consequences for stratospheric ozone. With high concentrations of water vapor at low temperatures, inorganic chlorine can enter a heterogeneous chemical regime in which it becomes processed into the chlorine radical. The chlorine radical drives the catalytic destruction of ozone in the stratosphere. Historically the intersection of low temperatures and high water vapor concentrations has been isolated to the polar vortexes. However, convection over the mid-latitude United States has been observed in isotopic data to inject water vapor from the troposphere into the stratosphere (Hanisco et al. 2007). The consequent elevated levels of stratospheric water vapor may lead to catalytic destruction of stratospheric ozone in the mid-latitudes thereupon resulting in increased UV exposure at the Earth's surface and increased risk to public health (Anderson et al. 2012). It is therefore critical to identify the climatology of the stratosphere that may exacerbate or mitigate the elevated water vapor conditions. Specifically we investigate the North American monsoon and its effect on perpetuating conditions of high water vapor concentrations. An analysis of relative vorticity from the ERA-interim and MERRA reanalyses over the United States from 2000 to 2013 reveal the consistent formation of the monsoon during the months of July and August and frequently June. An examination of circulation during the same time period allows us to estimate the monsoon's stability. Furthermore, using potential vorticity as a tracer we see further evidence of the monsoon's effect on keeping moist air masses over the United States. Finally, the analyzed dynamics of the North American Monsoon may explain the fact that NEXRAD observations of convective injection of water occur most strongly in the Spring months while the EOS MLS instrument detects the majority of high water vapor observations during the Summer months.

  11. ON THE MODE OF DYNAMO ACTION IN A GLOBAL LARGE-EDDY SIMULATION OF SOLAR CONVECTION

    SciTech Connect

    Racine, Etienne; Charbonneau, Paul; Ghizaru, Mihai; Bouchat, Amelie; Smolarkiewicz, Piotr K.

    2011-07-01

    In this paper, we examine the mode of dynamo action in the implicit large-eddy magnetohydrodynamical simulation of solar convection reported upon in Ghizaru et al. Motivated by the presence of a strong and well-defined large-scale axisymmetric magnetic component undergoing regular polarity reversals, we define the fluctuating component of the magnetic field as the difference between the total field and its zonal average. The subsequent analysis follows the physical logic and mathematical formulation of mean-field electrodynamics, whereby a turbulent electromotive force (EMF) is computed by the suitable averaging of cross-correlations between fluctuating flow and field components and expressed in terms of the mean field via a linear truncated tensorial expansion. We use singular value decomposition to perform a linear least-squares fit of the temporal variation of the EMF to that of the large-scale magnetic component, which yields the components of the full {alpha}-tensor. Its antisymmetric component, describing general turbulent pumping, is also extracted. The {alpha}-tensor so calculated reproduces a number of features already identified in local, Cartesian simulations of magnetohydrodynamical rotating convection, including an {alpha}{sub {phi}{phi}} component positive in the northern solar hemisphere, peaking at high latitudes, and reversing sign near the bottom of the convection zone; downward turbulent pumping throughout the convecting layer; and significant equatorward turbulent pumping at mid latitudes, and poleward at high latitudes in subsurface layers. We also find that the EMF contributes significantly to the regeneration of the large-scale toroidal magnetic component, which from the point of view of mean-field dynamo models would imply that the simulation operates as an {alpha}{sup 2}{Omega} dynamo. We find little significant evidence of {alpha}-quenching by the large-scale magnetic field. The amplitude of the magnetic cycle appears instead to be

  12. On the Mode of Dynamo Action in a Global Large-eddy Simulation of Solar Convection

    NASA Astrophysics Data System (ADS)

    Racine, Étienne; Charbonneau, Paul; Ghizaru, Mihai; Bouchat, Amélie; Smolarkiewicz, Piotr K.

    2011-07-01

    In this paper, we examine the mode of dynamo action in the implicit large-eddy magnetohydrodynamical simulation of solar convection reported upon in Ghizaru et al. Motivated by the presence of a strong and well-defined large-scale axisymmetric magnetic component undergoing regular polarity reversals, we define the fluctuating component of the magnetic field as the difference between the total field and its zonal average. The subsequent analysis follows the physical logic and mathematical formulation of mean-field electrodynamics, whereby a turbulent electromotive force (EMF) is computed by the suitable averaging of cross-correlations between fluctuating flow and field components and expressed in terms of the mean field via a linear truncated tensorial expansion. We use singular value decomposition to perform a linear least-squares fit of the temporal variation of the EMF to that of the large-scale magnetic component, which yields the components of the full α-tensor. Its antisymmetric component, describing general turbulent pumping, is also extracted. The α-tensor so calculated reproduces a number of features already identified in local, Cartesian simulations of magnetohydrodynamical rotating convection, including an αphiphi component positive in the northern solar hemisphere, peaking at high latitudes, and reversing sign near the bottom of the convection zone; downward turbulent pumping throughout the convecting layer; and significant equatorward turbulent pumping at mid latitudes, and poleward at high latitudes in subsurface layers. We also find that the EMF contributes significantly to the regeneration of the large-scale toroidal magnetic component, which from the point of view of mean-field dynamo models would imply that the simulation operates as an α2Ω dynamo. We find little significant evidence of α-quenching by the large-scale magnetic field. The amplitude of the magnetic cycle appears instead to be regulated primarily by a magnetically driven

  13. The bog landforms of continental western Canada in relation to climate and permafrost patterns

    SciTech Connect

    Vitt, D.H.; Halsey, L.A. ); Zoltai, S.C. )

    1994-02-01

    In continental western Canada, discontinuous permafrost is almost always restricted to ombrotrophic peatlands (bogs). Bogs occur mostly as islands or peninsulas in large, often complex fens or are confined to small basins. Permafrost may be present in extensive peat plateaus (or more locally as palsas) and was preceded by a well-developed layer of Sphagnum that served to insulate the peat and lower the pore water temperatures. Air photo interpretation reveals the occurrence of bogs with five types of surface physiography. Concentrated to the south are bogs without internal patterns that have never had permafrost. Dominating the mid-latitudes are bogs with internal lawns and fens with internal lawns (mostly representing former bogs) that had permafrost lenses in the past that have recently degraded. Concentrated in the northwest are peat plateaus without internal lawns or distinct collapse scars, but with permafrost; dominating in the northernmost area are peat plateaus with extensive permafrost and collapse scars. Relationships are apparent between the current - 1[degrees]C isotherm and the southern occurrence of peat plateaus and between the 0[degrees]C isotherm and the southern edge of bogs and fens with internal lawns. We interpret bogs and fens with internal lawns to represent areas where permafrost degradation is currently occurring at a greater rate than aggradation, seemingly in response to warmer regional climate, although fire frequency may also be of local importance. 54 refs., 21 figs., 2 tabs.

  14. Deep continental margin reflectors

    USGS Publications Warehouse

    Ewing, J.; Heirtzler, J.; Purdy, M.; Klitgord, Kim D.

    1985-01-01

    In contrast to the rarity of such observations a decade ago, seismic reflecting and refracting horizons are now being observed to Moho depths under continental shelves in a number of places. These observations provide knowledge of the entire crustal thickness from the shoreline to the oceanic crust on passive margins and supplement Consortium for Continental Reflection Profiling (COCORP)-type measurements on land.

  15. Freshly brewed continental crust

    NASA Astrophysics Data System (ADS)

    Gazel, E.; Hayes, J. L.; Caddick, M. J.; Madrigal, P.

    2015-12-01

    Earth's crust is the life-sustaining interface between our planet's deep interior and surface. Basaltic crusts similar to Earth's oceanic crust characterize terrestrial planets in the solar system while the continental masses, areas of buoyant, thick silicic crust, are a unique characteristic of Earth. Therefore, understanding the processes responsible for the formation of continents is fundamental to reconstructing the evolution of our planet. We use geochemical and geophysical data to reconstruct the evolution of the Central American Land Bridge (Costa Rica and Panama) over the last 70 Ma. We also include new preliminary data from a key turning point (~12-6 Ma) from the evolution from an oceanic arc depleted in incompatible elements to a juvenile continental mass in order to evaluate current models of continental crust formation. We also discovered that seismic P-waves (body waves) travel through the crust at velocities closer to the ones observed in continental crust worldwide. Based on global statistical analyses of all magmas produced today in oceanic arcs compared to the global average composition of continental crust we developed a continental index. Our goal was to quantitatively correlate geochemical composition with the average P-wave velocity of arc crust. We suggest that although the formation and evolution of continents may involve many processes, melting enriched oceanic crust within a subduction zone, a process probably more common in the Achaean where most continental landmasses formed, can produce the starting material necessary for juvenile continental crust formation.