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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 (MC3E) Experiment Final Campaign Report

    SciTech Connect

    Jensen, M; Giangrande, S; Kollias, P

    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.

  3. Cloud and Stability Characteristics of Mid-latitude Continental Convective Snow Events as Determined From Serial Radiosonde Ascents

    NASA Astrophysics Data System (ADS)

    Market, P.; Heymsfield, A.; Bodner, M.; Podzimek, J.; Pettegrew, B.; Melick, C.; Smith, L.

    2005-05-01

    A field experiment is currently underway that seeks to document the evolution of tropospheric stability as well as the microphysical characteristics of the parent cloud during mid-latitude, continental convective snow events. A mobile sounding system, using radiosondes outfitted with an ice crystal replicator, is being deployed in the Midwestern United States during February and March 2005 in support of this study. Intense observing periods (IOP) involve transporting the mobile sounding system to a location where convective snowfall has been predicted. Each IOP features hourly radiosonde ascents for durations of up to 12 hours, with convective snowfall occurring near the middle of this period. Additionally, we expect to launch ice crystal replicators on one or two balloons closest to the time of convective snow occurrence. Data and analysis from these field campaigns will be presented.

  4. 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

  5. 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

  6. Synergistic observations of convective cloud life-cycle during the Mid-latitude Continental Convective Clouds Experiment (MC3E)

    NASA Astrophysics Data System (ADS)

    Jensen, M. P.; Petersen, W. A.; Giangrande, S.; Heymsfield, G. M.; Kollias, P.; Rutledge, S. A.; Schwaller, M.; Zipser, E. J.

    2011-12-01

    The Midlatitude Continental Convective Clouds Experiment (MC3E) took place from 22 April through 6 June 2011 centered at the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Southern Great Plains Central Facility in north-central Oklahoma. This campaign was a joint effort between the ARM and the National Aeronautics and Space Administration's (NASA) Global Precipitation Measurement mission Ground Validation program. It was the first major field campaign to take advantage of numerous new radars and other remote sensing instrumentation purchased through the American Recovery and Reinvestment Act of 2009. The measurement strategy for this field campaign was to provide a well-defined forcing dataset for modeling efforts coupled with detailed observations of cloud/precipitation dynamics and microphysics within the domain highlighted by advanced multi-scale, multi-frequency radar remote sensing. These observations are aimed at providing important insights into eight different components of convective simulation and microphysical parameterization: (1) pre-convective environment, (2) convective initiation, (3) updraft/downdraft dynamics, (4) condensate transport/detrainment/entrainment, (5) precipitation and cloud microphysics, (6) influence on the environment, (7) influence on radiation, and (8) large-scale forcing. In order to obtain the necessary dataset, the MC3E surface-based observational network included six radiosonde launch sites each launching 4-8 sondes per day, three X-band scanning ARM precipitation radars, a C-band scanning ARM precipitation radar, the NASA N-Pol (S-band) scanning radar, the NASA D3R Ka/Ku-band radar, the Ka/W-band scanning ARM cloud radar, vertically pointing radar systems at Ka-, S- and UHF band, a network of over 20 disdrometers and rain gauges and the full complement of radiation, cloud and atmospheric state observations available at the ARM facility. This surface-based network was complemented by aircraft measurements

  7. 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.

  8. 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

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

    NASA Astrophysics Data System (ADS)

    Petersen, W. A.; Jensen, M. P.

    2011-12-01

    The joint NASA GPM - DOE 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 network. As an exploratory effort to examine land-surface emissivity

  10. Dominant factors influencing precipitation efficiency in a continental mid-latitude location

    NASA Astrophysics Data System (ADS)

    Hisham Mohd Anip, Mohd; Market, Patrick S.

    2007-01-01

    The bulk precipitation efficiency (PE) of transient precipitation systems at a continental, mid-latitude location is established as a function of season and dominant cloud type (convective versus stratiform). These results quantify for the first time controls on PE that have long been assumed to be true. Moreover, previous studies have been unable to establish a link between the efficiency of precipitation systems and short-term changes in the warm cloud depth (T > -10°C). These results show that the depth of the warm cloud layer, over which the collision-coalescence process will dominate, is not a short-term control on PE, but a seasonal one.

  11. 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.

  12. Mid-latitude response to geomagnetic storms observed in 630nm airglow over continental United States

    NASA Astrophysics Data System (ADS)

    Bhatt, A.; Kendall, E. A.

    2016-12-01

    We present analysis of mid-latitude response observed to geomagnetic storms using the MANGO network consisting of all-sky cameras imaging 630nm emission over the continental United States. The response largely falls in two categories: Stable Auroral Red (SAR) arc and Large-scale traveling ionospheric disturbances (LSTIDs). However, outside of these phenomena, less often observed response include anomalous airglow brightening, bright swirls, and frozen in traveling structures. We will present an analysis of various events observed over 3 years of MANGO network operation, which started with two imagers in the western US with addition of new imagers in the last year. We will also present unusual north and northeastward propagating waves often observed in conjunction with diffuse aurora. Wherever possible, we will compare with observations from Boston University imagers located in Massachusetts and Texas.

  13. Mid-latitude continental temperatures through the early Eocene in western Europe

    NASA Astrophysics Data System (ADS)

    Inglis, Gordon N.; Collinson, Margaret E.; Riegel, Walter; Wilde, Volker; Farnsworth, Alexander; Lunt, Daniel J.; Valdes, Paul; Robson, Brittany E.; Scott, Andrew C.; Lenz, Olaf K.; Naafs, B. David A.; Pancost, Richard D.

    2017-02-01

    Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are increasingly used to reconstruct mean annual air temperature (MAAT) during the early Paleogene. However, the application of this proxy in coal deposits is limited and brGDGTs have only been detected in immature coals (i.e. lignites). Using samples recovered from Schöningen, Germany (∼48°N palaeolatitude), we provide the first detailed study into the occurrence and distribution of brGDGTs through a sequence of early Eocene lignites and associated interbeds. BrGDGTs are abundant and present in every sample. In comparison to modern studies, changes in vegetation type do not appear to significantly impact brGDGT distributions; however, there are subtle differences between lignites - representing peat-forming environments - and siliciclastic nearshore marine interbed depositional environments. Using the most recent brGDGT temperature calibration (MATmr) developed for soils, we generate the first continental temperature record from central-western continental Europe through the early Eocene. Lignite-derived MAAT estimates range from 23 to 26 °C while those derived from the nearshore marine interbeds exceed 20 °C. These estimates are consistent with other mid-latitude environments and model simulations, indicating enhanced mid-latitude, early Eocene warmth. In the basal part of the section studied, warming is recorded in both the lignites (∼2 °C) and nearshore marine interbeds (∼2-3 °C). This culminates in a long-term temperature maximum, likely including the Early Eocene Climatic Optimum (EECO). Although this long-term warming trend is relatively well established in the marine realm, it has rarely been shown in terrestrial settings. Using a suite of model simulations we show that the magnitude of warming at Schöningen is broadly consistent with a doubling of CO2, in agreement with late Paleocene and early Eocene pCO2 estimates.

  14. Life Cycle of Deep Convective Systems in a Lagrangian Framework: from Mid-latitude to Tropics

    NASA Astrophysics Data System (ADS)

    Feng, Z.; McFarlane, S. A.; Hagos, S. M.; Dong, X.; Xi, B.; Kennedy, A. D.; Lin, B.; Minnis, P.

    2012-12-01

    Deep Convective Systems (DCSs) produce heavy rainfall and large cirrus anvil cloud shields, and they play an important role in the climate system through their impact on the general circulation and cloud radiative feedback. To improve understanding of the life cycle of DCSs, a Lagrangian framework is used to investigate DCSs in the mid-latitudes and the tropics. An automated cloud tracking method is used in conjunction with a multi-sensor hybrid classification to analyze the evolution of DCS structure over the central United States. Composite analysis from 4221 tracked DCSs during two warm seasons shows that stratiform anvil clouds lag behind peak convective intensity and the lag increases linearly from 1-hour for short-lived systems to more than 3-hours for long-lived ones. Longer-lasting systems are associated with up to 60% higher mid-tropospheric relative humidity and up to 40% stronger deep layer wind shear. Areal coverage of anvil clouds is strongly correlated with the size and intensity of convection. Ambient upper tropospheric wind speed and shear also contribute to convective anvil production; for systems with large anvil clouds they are 24% and 20% higher, respectively, than those with small anvil clouds. This Lagrangian framework is then applied to evaluate high-resolution simulations by the Weather Research and Forecasting (WRF) model in the tropical western Pacific. Comparisons from over 50,000 tracked DCSs show that in general, WRF reproduces many satellite observed statistics, but simulated DCSs have shorter lifetimes, grow taller, and their cloud area is smaller due to lack of anvil clouds. Diurnal cycles of DCSs over land agree well with observations. Over the ocean, peak convective activity occurs later and the duration is shorter. For systems with the same lifetime, DCSs over land are initially stronger than over the ocean, although the differences in WRF are smaller than observed. Impacts of the cloud microphysics scheme on DCS life cycle are

  15. The impact of wind shear on mid-latitude convection in convection-allowing WRF simulations.

    NASA Astrophysics Data System (ADS)

    Kennedy, A. D.; Goines, D. C.

    2014-12-01

    Since pioneering studies by Rotunno, Klemp, and Weisman in the 1980s, wind shear has been known to have an important impact on convective storms, controlling mode, strength, and longevity. Despite this knowledge, the impact of wind shear on convection has largely been ignored at the scale of climate models due to a lack of observations. In leiu of these observations, convection-allowing simulations can be used to understand these relationships. Although these simulations are computationally expensive, several institutions maintain large databases of simulations run over the contiguous US in support of the NOAA Hazardous Weather Tesbed (HWT). Multiple years of daily simulations from NSSL and NCEP run in support of this project will be used to understand the relationship between wind shear and convective properties such updraft strength and area. It will be shown that in environments with weak instability, wind shear decreases convective area and strength for areas the size of climate model grids. When sufficient instability is present, however, both of these properties increase with wind shear. Although many of these results are consistent between the NSSL/NCEP simulations, some differences exist. These differences will also be discussed.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Magnetospheric convection effects at mid-latitudes. 2. A coordinated Chatanika/Saint-Santin study of the April 10--14, 1978, magnetic storm

    SciTech Connect

    Blanc, M.; Alcayde, D.; Kelly, J.D.

    1983-01-01

    We analyze simultaneous measurements by the incoherent scatter radars at Saint-Santin (45/sup 0/ latitude) and Chatanika (65/sup 0/ latitude) during a major magnetic storm in April 1978 to examine several disturbance mechanisms operating on the mid-latitude ionosphere during periods of strong magnetospheric and auroral activity. The first type of mechanism, the extension of magnetospheric convection electric fields to mid-latitudes, is illustrated by two large localized departures of the E x B plasma drifts over Saint-Santin that appeared in conjunction with the two storm negative phases. In both cases they were associated with large electric fields in the afternoon sector, within the eastward electrojet region, over Chatanika.

  3. 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

  4. 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

  5. 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

  6. 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

  7. Analysis of convectively sourced water vapor in the overworld stratosphere at northern mid-latitudes: An update with data from SEAC4RS

    NASA Astrophysics Data System (ADS)

    Smith, J. B.; Sargent, M. R.; Wilmouth, D. M.; Anderson, J. G.

    2013-12-01

    The Harvard Water Vapor (HWV) instrument flown aboard NASA's WB-57 and ER-2 high-altitude aircraft has repeatedly observed moist plumes extending well into the stratospheric overworld (>380 K) over the continental United States during the summer. Mixing ratios in these plumes have been observed to be ~12 ppmv above the nominal background. These water vapor enhancements have been unequivocally linked to the direct deposition of ice, associated with summertime deep convective storms, and its subsequent evaporation in the under-saturated stratosphere. Prior to NASA's Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) mission in August and September of 2013, these stratospheric plume events were encountered serendipitously on aircraft missions primarily focused on cirrus sampling. Because these plumes were not intentional targets for study, detailed information on their water vapor content, physical extent vertically and horizontally, and lifetime was limited. Data from targeted encounters with these plumes, acquired during SEAC4RS, is expected to greatly enhance our understanding of the physical and chemical properties of these events, allowing for a more thorough assessment of the contribution of very deep convection to the atmospheric composition of the UT/LS over the continental US. The SEAC4RS mission provides a unique opportunity to target these events with the high-resolution capabilities of a high-altitude aircraft and an unprecedented tracer payload on the ER-2. Additionally, data from the DC-8 aircraft provide constraints on the chemical composition of the boundary layer air, as well as the rapid chemical redistribution throughout troposphere that is associated with these deep convection storms. Finally, satellite data products, including retrieved water vapor profiles, and results from an independent overshooting top detection algorithm that utilizes geostationary satellite infrared imagery and back

  8. 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

  9. Titan's Mid-latitude Clouds

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

    In the first few years of spatially resolved observations of Titan's tropospheric methane clouds (2001-2003) all of the clouds were clustered in the south polar region. This time period coincided with the southern summer solstice (October 2002) and these south polar clouds are almost certainly a seasonal phenomenon. Starting in December 2003 we began seeing clouds in a narrow latitude range centered at 40°S latitude. In Roe et al. (2005a) we published this initial discovery and speculated that the clouds might be due either to changes in the seasonal circulation pattern or a process linked to surface geography. Further observations soon revealed that the clouds were significantly clustered over one region of longitude (near 350°W), strongly suggesting a geographically controlled origin (Roe et al. 2005b), although Cassini observations suggest a circulation-induced convergence origin (Griffith et al. 2005). The actual answer is most likely a combination of geographic surface effects with the atmospheric circulation. We report here on our continuing ground-based observation campaign, including observations on 65 nights in the 2006-2007 apparition with the Gemini 8-m telescope. With two more years of observations since the data shown in Roe et al. (2005b) we now have much firmer conclusions with respect to the spatial distribution and temporal characteristics of the mid-latitude clouds. We will present our latest understanding of Titan's mid-latitude clouds given the entire dataset now available to us. References Griffith, C.A., & 26 co-authors 2005. Science, 310, 474. Roe, H.G., A.H. Bouchez, C.A. Trujillo, E.L. Schaller, & M.E. Brown 2005a. ApJL, 618, 49. Roe, H.G., M.E. Brown, E.L. Schaller, A.H. Bouchez, & C.A. Trujillo 2005b. Science, 310, 477. This work is supported by NASA under Grant #NNX07AK74G issued through the Planetary Astronomy Program.

  10. Impact of Wetlands on Titan's Mid-Latitude Cloudiness

    NASA Astrophysics Data System (ADS)

    Lora, J. M.; Mitchell, J.

    2014-12-01

    Neish and Lorenz [Icarus 228 (2014), 27-34] suggested that Titan's lowest elevations are extensive wetlands based on crater distributions. With a Titan general circulation model (GCM), we examine whether low-lying wetlands at mid-latitudes provide sufficient surface-level moisture to trigger convective cloud formation there, as well as investigate the dynamical processes responsible for different cloud morphologies. GCMs of Titan have shown that the atmospheric circulation transports methane away from low latitudes and into the polar regions on average. Several of these models simulate moist and cloudy conditions over the summer pole, in agreement with observations of convective clouds over the south pole during its summer. However, observations of cloudiness over Titan's southern mid-latitudes that occurred around solstice and persisted until after autumnal equinox are perplexing. GCMs tend to only simulate mid-latitude clouds around equinox, and only when imposing very wet surface conditions. In GCMs where surface moisture is allowed to vary self-consistently, the mid-latitudes are dry and cloud formation is inhibited. However, these models ignore topography. The GCM in this study is three-dimensional and fully simulates Titan's methane cycle, including variable surface moisture, as well as Titan's temperatures and atmospheric superrotation. Comparison of model results to recent obsrvations of the latitudinal humidity distribution of the troposphere will help discriminate between surface distributions. These simulations can therefore begin to constrain the distribution of surface methane, beyond Titan's distinctive lakes and seas, available to the atmosphere.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. A mid-latitude scintillation model

    NASA Astrophysics Data System (ADS)

    Robins, Robert E.; Secan, James A.; Fremouw, E. J.

    1986-10-01

    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.

  16. Mid-latitude hiss and plasmaspheric notch

    NASA Astrophysics Data System (ADS)

    Masson, A.; Inan, U.; Laakso, H.; Décréau, P.; Santolik, O.

    2004-12-01

    A newly identified whistler mode ELF/VLF emission, observed by the Cluster satellites, will be presented. In the vicinity of the plasmapause, around the geomagnetic equator, the four Cluster satellites often observe banded hiss-like electromagnetic emissions (BHE). Their frequency bandwidth is always in between the lower hybrid resonance and the electron gyrofrequency, from 2 kHz to 10 kHz. Based on two years of data measured by three waves experiments on Cluster (WHISPER, STAFF and WBD), the following properties of the BHE waves have been deduced: (i) their location is strongly correlated with the position of the plasmapause, (ii) no MLT dependence has been found, (iii) their spectral width is generally 1 to 2 kHz, and (iv) the central frequency of their emission band varies from 2 kHz to 10 kHz. All these features suggest that BHE are in fact mid-latitude hiss emissions (MLH). MLH have been rarely observed on a regular basis at such altitude. Based on this survey, the central frequency of mid-latitude hiss is shown to be correlated with the Kp index. This suggests either that these banded emissions are generated in a given f/fce range, or that there is a Kp dependent Doppler shift between the satellites and a possible moving source of the MLH Mid-latitude hiss case events observed within density depletion known as plasmaspheric notch (observed by the EUV instrument on IMAGE) will be presented. A recent study showed that plasmaspheric notch plays a crucial role in the generation of higher frequency emissions such as kilometric continuum. The role of plasmaspheric notch in the generation and/or the amplification of mid-latitude hiss will be addressed.

  17. 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.

  18. A Mid-Latitude Scintillation Model.

    DTIC Science & Technology

    1986-10-31

    irregularities • that produce scintillation in the naturally disturbed mid-latitude F layer. The model will be incorporated into Program WBMOD , which includes... WBMOD ) which are operational at USAF Global Weather Central and at several other user locationsiwere based on extensive analysis of scintillation data...Latitudinal Variation 21 4.2.2 Diurnal Variation 23 4.2.3 Sunspot-number Dependence 23 4.2.4 VT Lead Constant 23 5 CONCLUSION 28 5.1 Efficacy of WBMOD 28 5.2

  19. 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.

  20. Using satellite composites to examine transport of gases and aerosols in mid-latitude cyclones

    NASA Astrophysics Data System (ADS)

    Jaegle, L.; Wood, R.

    2007-12-01

    Mid-latitude cyclones have been recognized as an important mechanism for venting polluted air from the continental boundary layer to the free troposphere. Warm conveyor belts, rising airstreams originating at the surface in the warm sector of mid-latitude cyclones, are particularily efficient at transporting pollutants to the middle and upper troposphere. In this study we examine the transport of gases and aerosols in mid-latitude cyclones by using multi-platform remote sensing observations of aerosol optical depth, CO, O3, and NO2 from the MODIS, MLS, OMI, and TES instruments. These atmospheric composition observations are complemented by satellite observations of QuickSCAT surface winds, MODIS clouds, AMSR-E surface rain rate and column water vapor. We first identify mid-latitude cyclones using NCEP sea level pressure, and then composite satellite observations over a 4000 km x 4000 km grid centered over each cyclone. Composites generated over clean regions (South Pacific and South Atlantic) are contrasted to composites downwind of polluted regions (western North Pacific and western North Atlantic). We find a strong signature of surface wind-induced sea-salt generation for each of these regions. The observations downwind of polluted regions exhibit enhanced CO, NO2, and aerosols in the lower troposphere behind the surface cold front, as well as enhanced CO and aerosols at high altitudes ahead of the surface warm front, especially downwind of Asia. In addition, when the warm conveyor belt originates in the clean subtropics, it has a significant dilution effect on the polluted continental outflow. We will use these observations to provide quantitative constraints on the role of mid-latitude cyclones in exporting pollution to the free troposphere.

  1. The ARM-GPM Midlatitude Continental Convective Clouds Experiment (MC3E)

    NASA Astrophysics Data System (ADS)

    Jensen, M. P.; Kollias, P.; Petersen, W. A.; Schwaller, M. R.; Rutledge, S.; Wiscombe, W. J.

    2008-12-01

    The Mid-latitude Continental Convective Clouds Experiment (MC3E) is a joint research collaboration between the Department of Energy's Atmospheric Radiation Measurement (ARM) Program and the National Aeronautics and Space Administration's Global Precipitation Measurement (GPM) Mission's Ground Validation Program. The intensive operational period of MC3E is proposed to be conducted during the late spring/early summer of 2011 over the ARM Southern Great Plains Climate Research Facility site in Oklahoma, United States and includes a multi-scale, multi-frequency surface-based remote sensing approach complemented by aircraft-based observations of precipitating cloud systems. The observational strategy will be aimed at improving our understanding of eight specific elements important for the parameterization of convective cloud processes including: 1) Pre-convective environment, 2) convective initiation, 3) updraft/downdraft dynamics, 4) condensate transport/detrainment, 5) precipitation/cloud microphyics, 6) influence on the environment, 7) influence on radiation and 8) large-scale forcing. These observations over land of cloud and precipitation processes (including latent heating) will further be useful for cloud modeling forcing, validation and development, and the construction of precipitation retrieval algorithms for GPM passive microwave and dual-wavelength precipitation radar systems. The ARM Southern Great Plains Climate Research Facility currently includes long-term, continuous, quality-controlled observations of cloud, precipitation, radiation, aerosol and atmospheric state embedded within the Oklahoma Mesonet and National Weather Service WSR-88D radar network. These routine observations will be complemented by a network of X-band scanning radar systems, a large-scale scanning polarized radar system, a NASA dual- polarization precipitation radar and aircraft in situ and remote sensing observations.

  2. 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.

  3. High Winds in the Jovian Mid-latitudes

    NASA Image and Video Library

    1999-03-06

    A high resolution image of the Jovian mid-latitudes taken by NASA Voyager 1 spacecraft on March 2, 1979, shows distinctly differing characteristics of the planet meteorology. http://photojournal.jpl.nasa.gov/catalog/PIA00360

  4. Change in Mars Mid-Latitude Ionosphere After Comet Flyby

    NASA Image and Video Library

    2014-11-07

    These plots portray data from radar sounding of Mars mid-latitude ionosphere at three times on Oct. 19 and 20, 2014. The data are from the MARSIS instrument on the European Space Agency Mars Express orbiter.

  5. Glacial Ice Deposits in Mid-Latitudes of Mars

    NASA Image and Video Library

    2010-03-02

    NASA Mars Reconnaissance Orbiter has detected widespread deposits of glacial ice in the mid-latitudes of Mars. This map of a region known as Deuteronilus Mensae, in the northern hemisphere, shows locations of the detected ice deposits in blue.

  6. 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.

  7. 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.

  8. Mid-Latitude Thermosphere-Ionosphere Storm Response: An Aeronomy Frontier

    NASA Astrophysics Data System (ADS)

    Sojka, J. J.; Heelis, R.

    2005-12-01

    The primary descriptions of the large scale thermosphere and ionosphere system have been based on micro-scale aeronomy processes, i.e., atomic and molecular chemistry and physical interactions, whose outcomes are then redistributed by macro-scale processes to describe regional morphologies as well as vertical stratification of the plasma environment. To a large extent the redistribution processes are understood but almost always represented by climatological drivers, i.e., neutral atmosphere -"MSIS"; neutral winds -"Hedin HWM"; auroral ionization and energy deposit ion - "Hardy"; convection and joule heating - "Weimer". Even when first principles physics models represent these drivers the models inherent space-time resolution reduces their descriptions to smoothed morphologies. A consequence of these shortcomings is that when the FAA studied mid-latitude ionospheric knowledge to design their WAAS system a major piece of ionosphere extreme weather was missed, with eventual adverse effects. This identifies a significant aeronomy frontier. This presentation emphasizes the mid-latitude regions aeronomy drivers that probably have a significant role to play in resolving our lack of knowledge. Both observations and model results will be presented to highlight why these suggested drivers are geo-effective. The consequence and hence observational requirements will be outlined. Since these conclusions depart significantly from the prevailing explanations of how mid-latitude storm aeronomy operates, specific contrasts will be made between these explanations again using observations and model results.

  9. Map of Martian Iron at Mid-Latitudes

    NASA Image and Video Library

    2003-03-13

    This gamma ray spectrometer map from NASA Mars Odyssey of the mid-latitude region of Mars is based on gamma-rays from the element iron, one of the most abundant elements on Mars and Earth. It is responsible for the red color on the surface of Mars.

  10. 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?

  11. Factors governing the total rainfall yield from continental convective clouds

    NASA Technical Reports Server (NTRS)

    Rosenfeld, Daniel; Gagin, Abraham

    1989-01-01

    Several important factors that govern the total rainfall from continental convective clouds were investigated by tracking thousands of convective cells in Israel and South Africa. The rainfall volume yield (Rvol) of the individual cells that build convective rain systems has been shown to depend mainly on the cloud-top height. There is, however, considerable variability in this relationship. The following factors that influence the Rvol were parameterized and quantitatively analyzed: (1) cloud base temperature, (2)atmospheric instability, and (3) the extent of isolation of the cell. It is also shown that a strong low level forcing increases the duration of Rvol of clouds reaching the same vertical extent.

  12. 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

  13. 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.

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

    PubMed

    Roe, Henry G; Brown, Michael E; Schaller, Emily L; Bouchez, Antonin H; Trujillo, Chadwick A

    2005-10-21

    Observations of Titan's mid-latitude clouds from the W. M. Keck and Gemini Observatories show that they cluster near 350 degrees W longitude, 40 degrees S latitude. These clouds cannot be explained by a seasonal shift in global circulation and thus presumably reflect a mechanism on Titan such as geysering or cryovolcanism in this region. The rate of volatile release necessary to trigger cloud formation could easily supply enough methane to balance the loss to photolysis in the upper atmosphere.

  15. USGS research on three mid-latitude glaciers

    USGS Publications Warehouse

    Green, J.R.; DeWayne, Cecil L.; Naftz, D.L.; Schuster, P.F.

    2000-01-01

    Low- and mid-latitude regions of the earth are home to 80 to 90 percent of the world's population. Because of this, the U.S. Geological Survey (USGS) is conducting a research program to study the geochemistry of precipitation, snow, ice, and runoff samples from mid-latitude glaciers in Kyrghyzstan, Nepal, and the United States, Areas of research, such as ground-water studies, reconstructing paleoclimate records, describing anthropogenic input of chemicals to the environment, and modeling global climate, are important to the well being of the worlds' population and can be supplemented by the collection and chemical analysis of snow and ice cores. Nearly all the constituents that compose snow and ice-core samples contribute vital information, whether it be the microbial communities that flourish in snow, radionuclides present in various amounts in all the samples, or location-specific deposits of mercury and nitrate. This work is hastened by the fact that mid-latitude glaciers, and the information preserved in them, are rapidly disappearing as a result of global warming. Research collaboration for this project includes 12 national and 7 international universities, and 4 government agencies. Funding is provided by the National Science Foundation, the U.S. Department of Energy, and the USGS.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Mid-latitude Spread-F and Large Magnetic Storm-Driven Nighttime Flows

    NASA Astrophysics Data System (ADS)

    Basu, S.; Makela, J. J.; Doherty, P.; Wright, J. W.; Coster, A. J.

    2008-12-01

    Plasma structuring at mid-latitudes causing spread-F on ionograms and VHF/UHF scintillations can have unexpected impacts on GPS signals at L-band if these events occur in a background of large magnetic storm-driven nighttime flows. Two such storm results are presented. The common distinguishing feature of both storms has been the absence of appreciable storm-enhanced density or total electron content (TEC) gradients, which are generally observed in the afternoon sector; rather, the mid-latitude region was enveloped by the auroral oval and the ionospheric trough, within which the sub auroral polarization stream (SAPS) was confined during the local dusk to nighttime hours. The intense flow channel in the ionosphere was revealed by both space and ground-based measurements, through DMSP over-flights and Dynasonde drifts. The competing effects of irregularity amplitude ÄN/N, the background F-region density and the magnitude of SAPS or auroral convection are discussed in establishing the extent of the region which can impact GPS-based navigation systems such as the Wide Area Augmentation System (WAAS) that operates in the North American sector.

  4. The Madden-Julian oscillation and its seasonal impact on mid-latitude weather predictability

    NASA Astrophysics Data System (ADS)

    Kadota, Minoru

    Seasonal influence of the the Madden-Julian oscillation(MJO) activity on weather predictability in the midlatitudes of the Northern Hemisphere and the Southern Hemisphere is investigated. This is accomplished by analyzing a T42 global atmospheric model with an imbedded model of the MJO derived from the observations. The imbedded model uses observed outgoing longwave radiation data from NCEP. Therefore novel features of the present study include a numerical model with realistic representation of the MJO, very large prediction ensembles, and information theoretic techniques to measure potential predictability of midlatitude. Results show that the MJO appears to be potentially able to increase mid-latitude predictability by several days in three important mid-latitude regions. The effect is more pronounced in summer hemisphere than winter hemisphere. The effect is much smaller during winter hemisphere for all three regions. One reason for this difference is that the signal to noise ratio of the remote MJO response is larger during summer. Results also indicate that regions closer geographically to the MJO centre of action around the maritime continent might have bigger effect. Our results also suggest that there appears a strong case for improving the representation of the MJO convection in general circulation models.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Solar correlates of Southern Hemisphere mid-latitude climate variability

    NASA Astrophysics Data System (ADS)

    Thresher, Ronald E.

    2002-06-01

    Atmospheric circulation in the southern mid-latitudes is dominated by strong circum-Antarctic zonal west winds (ZWW) over the latitude range of 35 to 60°S. These winds exhibit coherent seasonal and interannual variability, which has been related both to Antarctic (e.g. polar ice) and low-latitude climate (e.g. El Niño-southern oscillation) parameters. Historical and recent studies suggest that, at its northern margins, variability in the ZWW also has a marked quasi-decadal component. Analysis of sea-level pressure and rainfall data for the Australian region, South Africa and South America confirms frequent indications of quasi-decadal variability in parameters associated with the ZWW, which appears to be in phase around the hemisphere. This variation broadly correlates with the sunspot cycle, and specifically appears to reflect sunspot-correlated, seasonally modulated shifts in the latitude range each year of the sub-tropical ridge over eastern Australia. Sunspot-correlated variability in the southern mid-latitudes is likely to have substantial effects on temperate climate and ecology and is consistent with recent models of solar effects on upper atmospheric climate, though the mechanisms that link these to winds and rainfall at sea level remain obscure.

  10. 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.

  11. Map of Martian Potassium at Mid-Latitudes

    NASA Image and Video Library

    2003-03-13

    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. http://photojournal.jpl.nasa.gov/catalog/PIA04255

  12. Assimilation of observations with models to better understand severe ionospheric weather at mid-latitudes

    NASA Astrophysics Data System (ADS)

    Sojka, Jan J.; Schunk, R. W.; Thompson, D. C.; Scherliess, L.; David, M.

    For many decades, the mid-latitude ionosphere was regarded as well characterized even if not well modeled. As a result, the Federal Aviation Authority's Wide Area Augmentation System (WAAS) was developed to provide augmented GPS positioning information to correct for ionospheric variability. However, over the past 5 years, recurrent superstorms in the ionosphere have forced the WAAS system to go offline for many hours at a time. This report discusses present-day knowledge regarding these conditions and how they are associated with unexpectedly steep horizontal gradients in the mid-latitude ionosphere total electron content (TEC). In a general sense, the possible physical mechanisms are understood, but during a storm the distribution and evolution of the driving forces for these mechanisms are neither understood nor adequately observed, the two main driving forces being the convection electric field and the neutral wind. In this paper a simplified convection electric field pattern is presented and used to drive a physics-based ionospheric model. This demonstrates how the superstorm ionospheric condition could be generated. Data assimilation is a new approach that could exceed present-day empirical and physical model limitations. There are three main expectations for data assimilation: (1) combined with a good ionospheric background model, the data assimilation must provide realistic global specification of the ionosphere; (2) it must also provide additional information about the ionosphere that is not already evident in the observation, that is, altitude profiles of the electron density when only slant TEC integrals of the electron density are available; and (3) with full physics-based models in the assimilation procedure, data assimilation models must also provide the drivers, that is, the neutral wind and electric field patterns. This paper examines the current status of these three expectations with regard to the future for the scientist and the space weather

  13. 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

  14. A Mid-Latitude Geomorphologic Map of Titan

    NASA Astrophysics Data System (ADS)

    Lopes, Rosaly M. C.; Malaska, Michael; Schoenfeld, Ashley; Solomonidou, Anezina; Birch, Samuel; Hayes, Alexander; Williams, David A.; Janssen, Michael A.; Le Gall, Alice; Turtle, Elizabeth P.; Radebaugh, Jani; Cassini RADAR Team

    2016-10-01

    We investigated the geologic history of Titan through mapping and analyzing the distribution of observed geomorphic features using a combination of Cassini data collected by RADAR, VIMS, and ISS. Determining the spatial and superposition relationships between geomorphologic units on Titan leads to an understanding of the likely time evolution of the landscape and gives insight into the process interactions that drive its evolution. We have used all available datasets to extend the mapping initially done by Lopes et al. [1]. We now have the mid-latitudes (60N to 60S) of Titan mapped at 1:800,000 scale in all areas covered by Synthetic Aperture Radar (SAR). A map of the polar regions has been done by Birch et al. [2]. For the mid-latitudes, we have defined five broad classes of terrains following Malaska et al. [3], largely based on prior mapping [1]. These broad classes are: craters, hummocky/mountainous, labyrinth, plains, and dunes. We have found that the hummocky/mountainous terrains are the oldest units on the surface and appear radiometrically cold, indicating icy materials [5]. Dunes are the youngest units and appear radiometrically warm, indicating organic sediments. VIMS analysis shows that compositional variations can also exist within the same class of unit [6, 7]. Future work aims to combine the polar maps of Birch et al. [2] with the mid-latitude maps presented here and harmonize the units at the 60 degrees boundaries. We also plan to extend the map in regions not covered by SAR to produce a 1:1,500,000 scale map compatible with USGS standards.References: [1] Lopes, R.M.C., et al.: Icarus, 205, 540-588, 2010; [2] Birch et al., submitted to Icarus. [3] Malaska, M., et al.: Icarus, 270, 130-161, 2016; [4] Barnes, J., et al.: Pl. Scie., 2:1, 2013; [5] Janssen et al., 2016 Icarus 270, 443-459, 2016. [6] Solomonidou, A., et al. : DPS abstract, 2016. [7] Lopes, R.M.C., et al, Icarus, 270, 162-182, 2016.

  15. Map of Martian Silicon at Mid-Latitudes

    NASA Image and Video Library

    2003-03-13

    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. http://photojournal.jpl.nasa.gov/catalog/PIA04256

  16. 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.

  17. Continental-Scale Convection-Permitting Regional Climate Modeling

    NASA Astrophysics Data System (ADS)

    Prein, A. F.; Rasmussen, R.; Clark, M. P.; Ikeda, K.; Liu, C.

    2015-12-01

    Convection-permitting regional climate models (CPCMs) have proven to be useful for down scaling large-scale climate information to regional and local scales. They add value to the representation of impact relevant parameters such as near surface temperature, precipitation, and the representation of extremes by improving local scale processes such as soil atmosphere interactions, snowpack dynamics, or the representation of deep convection. Due to their high computational costs most CPCM simulations have been restricted to small domains on the order of a few 100 km. On such small domains CPCMs might not reach their full potential because they are restricted by the lateral boundary forcing and may not be able to spin up properly. In this study we investigate the ability of a continental scale CPCM to simulate climate conditions in the Contiguous United States within the period October 2000 to December 2010. We downscale ERA-Interim reanalysis data to a horizontal grid spacing of 4 km with the Weather Research and Forecasting (WRF) Model that allows an explicit treatment of deep convection. The model performance is analyzed in different synoptic-scale weather regimes, which enables a process-oriented evaluation. The significance of model biases in simulated precipitation and temperature is investigated by including observational uncertainties in the analysis. Significant biases are further investigated and possible error sources are discussed. The goal of this study is to provide a benchmark on the state-of-the-art convection-permitting regional climate modeling and to give guidance for future model development.

  18. 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

  19. The spectral nature of Titan's mid-latitude region

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly; Malaska, Michael; Rodriguez, Sebastien; Drossart, Pierre; Schmitt, Bernard; Philippe, Sylvain; Janssen, Michael; Le Gall, Alice; Lawrence, Kenneth; Hirtzig, Mathieu; Sohl, Frank; Stephan, Katrin; Jaumann, Ralf; Brown, Robert; Villanueva, Edward; Bratsolis, Emmanuel; Matsoukas, Christos; Schoenfeld, Ashley

    2017-04-01

    We infer surface properties, such as surface albedo and atmospheric contributions in the form of haze content, of the mid-latitude region of Titan. In previous studies [1;2] we reported results on two areas presenting indications for possible changes in surface albedo with time [2]. We also investigate the endogenic or exogenic processes linked to the formation of the various mid-latitude geomorphological units. These could be aeolian, fluvial, sedimentary, cryovolcanic, lacustrine, and more. Furthermore, deposition of organics through the atmosphere seems to be predominantly present [1]. We now focus on constraining the chemical composition of the various geomorphological units [5;6] by investigating the lower atmosphere of Titan from Visual and Infrared Mapping Spectrometer (VIMS) spectro-imaging data by use of a recently updated radiative transfer code in the near-IR range. For the distinction of geomorphological units we use RADAR/SAR data [4]. We study the units of interest identified in [1;3] and [4]: mountains, plains, labyrinths, dune fields, and possible cryovolcanic and/or evaporitic features (the latter two are albedo features, [4;5]). Our findings indicate that many of the regions from the same geomorphological unit show compositional variations depending on location, while units of significant geomorphological differences seem to consist of very similar material mixtures. Preliminary results on the chemical composition of the regions that have shown temporal changes (i.e. Tui Regio and Sotra Patera; [6]) are also presented. The albedo differences and similarities among the various geomorphological terrains set constraints on the possible geological processes that govern Titan's surface. References: [1] Lopes, R.M.C., et al.: Icarus, 270, 162-182, 2016; [2] Solomonidou, A., et al.: Icarus, 270, 85-99, 2016; [3] Lopes, R.M.C., et al.: Icarus, 205, 540-558, 2010; [4] Malaska, M., et al.: Icarus, 270, 130-161, 2016; [4] Barnes, J., et al.: Pl. Scie., 2

  20. The Midlatitude Continental Convective Clouds Experiment (MC3E)

    DOE PAGES

    Jensen, M. P.; Petersen, W. A.; Bansemer, A.; ...

    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

  1. The Midlatitude Continental Convective Clouds Experiment (MC3E)

    SciTech Connect

    Jensen, Mark P.; Petersen, Walt A.; Bansemer, Aaron; Bharadwaj, Nitin; Carey, Larry; Cecil, D. J.; Collis, Scott M.; Del Genio, Anthony D.; Dolan, Brenda A.; Gerlach, J.; Giangrande, Scott; Heymsfield, Andrew J.; Heymsfield, Gerald; Kollias, Pavlos; Lang, T. J.; Nesbitt, Steve W.; Neumann, Andrea; Poellot, M. R.; Rutledge, Steven A.; Schwaller, Mathew R.; Tokay, Ali; Williams, C. R.; Wolff, D. B.; Xie, Shaocheng; Zipser, Edward J.

    2016-10-18

    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. 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.

  2. 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.

  3. 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.

  4. Map of Martian Iron 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 iron. Iron, having the chemical symbol Fe, is among of the most abundant elements on the surface of both Mars and Earth. It is responsible for the red color on the surface of Mars. Regions of highest iron content, shown in red, are concentrated in the area spanning from Utopia Planitia to Amazonis Planitia (right and left sides of the map) and within Acidalia Planitia (just left of center). 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.

  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. What Drives the Variability of the Mid-Latitude Ionosphere?

    NASA Astrophysics Data System (ADS)

    Goncharenko, L. P.; Zhang, S.; Erickson, P. J.; Harvey, L.; Spraggs, M. E.; Maute, A. I.

    2016-12-01

    The state of the ionosphere is determined by the superposition of the regular changes and stochastic variations of the ionospheric parameters. Regular variations are represented by diurnal, seasonal and solar cycle changes, and can be well described by empirical models. Short-term perturbations that vary from a few seconds to a few hours or days can be induced in the ionosphere by solar flares, changes in solar wind, coronal mass ejections, travelling ionospheric disturbances, or meteorological influences. We use over 40 years of observations by the Millstone Hill incoherent scatter radar (42.6oN, 288.5oE) to develop an updated empirical model of ionospheric parameters, and wintertime data collected in 2004-2016 to study variability in ionospheric parameters. We also use NASA MERRA2 atmospheric reanalysis data to examine possible connections between the state of the stratosphere & mesosphere and the upper atmosphere (250-400km). A case of major SSW of January 2013 is selected for in-depth study and reveals large anomalies in ionospheric parameters. Modeling with the NCAR Thermospheric-Ionospheric-Mesospheric-Electrodynamics general Circulation Model (TIME-GCM) nudged by WACCM-GEOS5 simulation indicates that during the 2013 SSW the neutral and ion temperature in the polar through mid-latitude region deviates from the seasonal behavior.

  7. Surface changes in mid-latitude regions on Titan

    NASA Astrophysics Data System (ADS)

    Solomonidou, A.; Coustenis, A.; Lopes, R. M. C.; Hirtzig, M.; Rodriguez, S.; Stephan, K.; Sotin, C.; Drossart, P.; Lawrence, K.; Le Mouélic, S.; Bratsolis, E.; Jaumann, R.; Brown, R. H.; Malaska, M.

    2014-04-01

    We present a study focused on the mid-latitude and close to the equator surface regions on Titan that present an interest on their spectral behavior and/or morphology. These are regions where spectroscopic anomalies have been reported in the evolution of the brightness and several interpretations have been proposed (cryovolcanic candidates, evaporates, lacustrine, etc [1;2;5]). Also in our work here we have included analysis of some undifferentiated plains (also referred to as 'blandlands'), which are vast expanses of terrains that appear bland in the radar data [3]. By applying a Radiative transfer code [4;2] we have analyzed these regions to look for evolution with time through their spectral behavior. We use as reference point and calibration tool the surface albedo retrieval of the Huygens Landing site (Titan's ground truth) and we also check the variability of the surface albedo of these regions against areas that are not expected to change with time (e.g. dune fields), by retrieving their albedo differences at all wavelengths [2]. We report here surface albedo changes with time for some of these regions of interest that imply connection to exogenic and/or endogenic processes.

  8. Ionospheric mid-latitude response to solar wind discontinuities

    NASA Astrophysics Data System (ADS)

    Munteanu, Costel; Mosna, Zbysek; Kouba, Daniel; Echim, Marius

    2013-04-01

    We have compiled a database of 356 discontinuities detected by both the Advanced Composition Explorer ACE) and Cluster satellites in the solar wind between 2001-2012 and analyzed their ionospheric response. Each discontinuity of the data base is defined by a change of at least 5 nT in less than 5 min in one or more components of the interplanetary magnetic field (IMF). The discontinuities are observed in January-April every year, when Cluster enters the solar wind. The ionospheric effects of solar wind discontinuities are investigated by checking the variations of critical frequencies foF2, the heights of the F layer and the ionospheric plasma dynamics recorded using ground measurement with a time resolution of 15 minutes from mid-latitude digisondes located in Czech Republic. The time delay between solar wind input and the ionospheric response is analyzed using the characteristics and the shape of the ionograms. The geoeffectiveness of the solar wind discontinuities is expressed as correlation between key plasma parameters (e,g, the solar wind velocity, magnetic jump across the discontinuity) and the ionospheric variations. Solar cycle effects are also discussed.

  9. Map of Martian Thorium at Mid-Latitudes

    NASA Image and Video Library

    2003-03-13

    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. http://photojournal.jpl.nasa.gov/catalog/PIA04257

  10. 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).

  11. 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.

  12. The mid-latitude total ozone trends in the northern hemisphere

    SciTech Connect

    Chandra, S.; Varotsos, C.; Flynn, L.E.

    1996-03-01

    The authors compare trends in column ozone measurements in mid latitudes measured from Nimbus-7 with predictions of 2D photochemical models. They find that the measurements show a larger trended decrease than is predicted by the 2D model. The data shows considerable variability at mid latitudes with longitudinal location.

  13. 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

  14. Impact of interactive radiation on idealized mid-latitude storms

    NASA Astrophysics Data System (ADS)

    Schäfer, Sophia; Voigt, Aiko

    2017-04-01

    The evolution of mid-latitude storms is controlled by the interacting impacts of large-scale advection, vertical motion and diabatic processes. It is widely accepted that understanding and accurately representing the diabatic impact of latent heating is crucial for capturing storm dynamics and their response to climate change. By contrast, little, if any, work has been done to study how radiative heating might impact storms. Here, we address this question by comparing idealized baroclinic lifecycles in the state-of-the-art global atmosphere model ICON in full spherical geometry when radiation is included and when radiative effects are neglected. Following previous work, the level of initial moisture is varied to study possible interactions between latent and radiative impacts. We find that in contrast to latent heating, radiation slows the evolution of the storm and leads to an overall weaker storm. Specifically, including radiation leads to a 10 hPa higher storm central pressure and a 30% to 50% weaker domain-averaged eddy-kinetic energy. The overall weakening impact of radiation is independent of the initial moisture content. However, there is some indication that radiation changes the qualitative evolution of the storm when initial moisture is high. For example, with radiation the low-level eddy-kinetic energy and the storm central pressure are non-monotonic functions in time and show a double peak at day 5 and day 7. This does not occur when radiation is neglected, or when the initial moisture is set to zero. Further simulations will be presented to disentangle the radiative impact of clouds, and to investigate the impact of low-level vs. high-level clouds. Moreover, an analysis of the surface pressure tendency equation will be applied to analyze and compare the impact of adiabatic processes, latent heating and radiative heating. Overall, our results show that radiation, while so far neglected, can play a first-order role for the evolution of individual storms.

  15. Mid-Latitude Circulation and Extremes in a Changing Climate

    SciTech Connect

    Chen, Gang

    2016-08-04

    Mid-latitude extreme weather events are responsible for a large part of climate-related damage. Yet large uncertainties remain in climate model projections of heat waves, droughts, and heavy rain/snow events on regional scales, limiting our ability to effectively use these projections for climate adaptation and mitigation. These uncertainties can be attributed to both the lack of spatial resolution in the models, and to the lack of a dynamical understanding of these extremes. The approach of this project is to relate the fine-scale features to the large scales in current climate simulations, seasonal re-forecasts, and climate change projections in a very wide range of models, including the atmospheric and coupled models of ECMWF over a range of horizontal resolutions (125 to 10 km), aqua-planet configuration of the Model for Prediction Across Scales and High Order Method Modeling Environments (resolutions ranging from 240 km – 7.5 km) with various physics suites, and selected CMIP5 model simulations. The large scale circulation will be quantified both on the basis of the well tested preferred circulation regime approach, and very recently developed measures, the finite amplitude Wave Activity (FAWA) and its spectrum. The fine scale structures related to extremes will be diagnosed following the latest approaches in the literature. The goal is to use the large scale measures as indicators of the probability of occurrence of the finer scale structures, and hence extreme events. These indicators will then be applied to the CMIP5 models and time-slice projections of a future climate.

  16. Statistical Characterization of Stormtime Ionospheric Redistribution At Mid-Latitudes

    NASA Astrophysics Data System (ADS)

    Erickson, P. J.; Foster, J. C.; Miskin, M. Z.; Beroz, F.; Rideout, W.

    2009-12-01

    During major geomagnetic disturbances, dramatic redistribution of ionospheric plasma can occur in the mid-latitude plasmasphere boundary layer, driven by a complex set of interlocked dynamics involving photoionization, magnetospheric influence, ionospheric feedback mechanisms, and the background magnetic field direction. Large amounts of ionospheric material are seen to stream from the dusk sector sunward to the polar cap cusp region, as mesoscale plumes of storm enhanced density (SED) move under the influence of the sub-auroral polarization stream (SAPS) electric field in regions magnetically linked to the region 2 currents associated with the asymmetric ring current. Studies over the last decade have shown that these several degree wide SAPS flow channels, with sunward fluxes delivering over 1E14 ions/m^2/sec to the noontime cusp, are the signatures of processes which can deplete an entire L shell of plasmaspheric material in one hours' time for particularly intense storms. Ground based ionospheric radar measurements of these features lend considerable insight into magnetosphere-ionosphere coupling processes and dynamics. We discuss a statistical study of SAPS/SED region sunward ionospheric flux in the dusk magnetic local time sector using a database of over 1000 Millstone Hill ionospheric radar scans during Kp >= 3 disturbances from 1979-2001. We highlight several persistent features of ionospheric F region velocity and SAPS ion flux magnitude. In particular, sunward F region ion flux is relatively insensitive to magnetic local time and the passage of the dusk solar terminator. Potential explanations focus on the interplay between poleward perpendicular electric field and ionospheric height-integrated Pedersen conductance in the E and F regions as the thermosphere and ionosphere change state from day to night.

  17. Statistical Modeling of Sub-Auroral Polarization Stream (SAPS) Using Observations from Mid-Latitude SuperDARN Radars

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Kunduri, B.; Baker, J. B.

    2016-12-01

    The Sub-Auroral Polarization Stream (SAPS) is a narrow region of sunward directed plasma convection at the sub-auroral latitudes. Before the construction of the new mid-latitude chain of SuperDARN radars, a majority of the SAPS observations presented were limited to a narrow longitudinal sector. However, recent studies have demonstrated the utility of using the mid-latitude SuperDARN radars to provide simultaneous measurements of velocities in a SAPS channel over an extended longitudinal region. These studies have been limited to isolated events. In the current study, data from the mid-latitude SuperDARN radars between January 2011 and August 2012 was used to compile a database of large scale SAPS events. The events were observed during widely varying levels of geomagnetic activity and were divided into different bins based on the Dst-index. We present spatial maps of various parameters of interest such as the probability of occurrence and average velocities for different Dst-index levels. A new empirical model based on the Dst-index to estimate the probability of occurrence of SAPS at a given latitude and MLT is developed using the statistical observations. The results show SuperDARN radars make observations of SAPS channels even during periods of low geomagnetic activity. Moreover the characteristics of SAPS channel exhibit significant differences during periods of low geomagnetic activity as compared to periods with high geomagnetic activity, suggesting the possibility of the SAPS channel being driven by different mechanisms. Furthermore, the SAPS statistical model can be applied to predict SAPS location during the periods mentioned in the CEDAR GRAND challenge and the results compared with theoretical models.

  18. 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

  19. 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

  20. Aspects of wave-particle interactions at mid-latitudes

    NASA Astrophysics Data System (ADS)

    Smith, A. J.

    Arguably the most significant source of particle precipitation into the ionosphere at mid-latitudes (L ~ 2-3), at least for electrons in the tens to hundreds of keV energy range, is that which arises from the interaction between trapped particles and whistler-mode waves in the magnetosphere. Quasi-steady plasmaspheric hiss has long been postulated as a major class of waves contributing to the loss of radiation belt particles but recent studies have suggested that under some conditions, impulsive precipitation caused by interactions with lightning-generated whistlers may be equally important as a loss process. Such lightning-induced electron precipitation (LEP) and its ionospheric signature is the subject of this paper. Although LEP may be detected and studied by a variety of ground-based, balloon-borne and satellite-borne sensors, through optical emissions, X-ray production, enhanced conductivity, or the direct measurement of the precipitating particles themselves, a technique using ground-based narrow-band VLF receivers to measure the Trimpi effect (the transient perturbations in amplitude and/or phase of received narrow-band VLF transmissions) caused by LEP-associated ionisation enhancements has become increasingly popular due to its simple instrumentation and wide field of view. Most work has concentrated on the 2 < L < 3 region where typical whistler spectra, trapped electron energy distributions and magnetospheric plasma densities and magnetic field strengths are most favourable for the Trimpi effect. In order to use the technique to study in detail the characteristics and distribution of LEP (and its importance as a trapped-particle loss mechanism), using a network of intersecting transmitter-receiver great-circle paths (TRGCPs), a consensus on how to interpret the observational data is crucial, though this has recently been the subject of controversy. Whilst most studies suggest that only LEP within ~200 km of the TRGCP gives rise to an observable Trimpi

  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. A Mid-Latitude Skywave Propagation Experiment: Overview and Results

    NASA Astrophysics Data System (ADS)

    Munton, D. C.; Calfas, R. S.; Gaussiran, T., II; Rainwater, D.; Flesichmann, A. M.; Schofield, J. R.

    2016-12-01

    We will describe a mid-latitude HF skywave propagation experiment conducted during 19-27 January, 2014. There were two primary goals to the experiment. First, we wanted to build an understanding of the impact that medium scale traveling ionospheric disturbances have on the angles of arrival of the HF signals. The second goal was to provide a diverse data set that could serve as a baseline for propagation model development and evaluation. We structured individual tests during the experiment to increase the knowledge of temporal and spatial length scales of various ionospheric features. The experiment was conducted during both day and night periods and spanned a wide range of ionospheric states. We conducted the experiment at White Sands Missile Range, New Mexico and in the surrounding area. As part of the experiment, we deployed a number of active HF transmitters, and an array of dipole antennas to provide angle of arrival measurements. We also deployed a smaller array of more novel compact electro-magnetic vector sensors (EMVSs). Other instrumentation specific to the remote sensing of the ionosphere included digisondes, GNSS receivers, beacon satellite receivers, and optical instruments. We will provide a complete description of the experiment configuration and the data products.Finally, we will provide a discussion of experimental results, focusing on ionospheric conditions during the angle-of-arrival determinations, and the impact ionospheric disturbances can have on these measurements. We use the angle-of-arrival determinations to estimate TID properties, including velocity and direction.This research is based upon work supported in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), via US Navy Contract N00024-07-D-6200. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements

  4. 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

  5. A link between high-speed solar wind streams and mid-latitude cyclones

    NASA Astrophysics Data System (ADS)

    Prikryl, Paul; Iwao, Koki; Tsukijihara, Takumi; Muldrew, Donald B.; Rušin, Vojto; Rybanský, Milan; Bruntz, Robert

    2017-04-01

    Mid-latitude cyclone tracks in the northern and southern hemispheres are obtained from meteorological reanalysis datasets to study occurrence of explosively developing extratropical cyclones in the winter season in relation to arrivals of high-speed solar wind streams (HSS) from coronal holes. The new statistical evidence corroborates the previously published results (Prikryl et al., Ann. Geophys., 27, 1-30, 2009). For the northern and southern winters, this evidence shows that explosive extratropical cyclones tend to occur after arrivals of HSS when large amplitude Alfvén waves couple to the magnetosphere-ionosphere system. Solar wind Alfvén waves modulate Joule heating and/or Lorentz forcing of the high-latitude lower thermosphere generating medium-scale atmospheric gravity waves that propagate energy upward and downward from auroral zone through the atmosphere. It is proposed that these gravity waves, in spite of their small amplitudes but subject to amplification upon reflection in the upper troposphere, can trigger instabilities in the troposphere initiating convection to form cloud/precipitation bands. The release of latent heat is known to provide energy for rapid development and intensification of extratropical cyclones.

  6. 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.

  7. Vertical distributions of 230Th in mid-latitude of the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Okubo, A.; Obata, H.; Gamo, T.; Zheng, J.

    2007-12-01

    Thorium is one of the least soluble elements in seawater: its dissolved species is considered as Th(OH)n(4-n)+ [Turner et al., 1981]. Th-232 (t1/2 = 1.4 × 10^10 years) in the oceans is almost entirely contributed by continental weathering, whereas 230Th (t1/2 = 75,200 years) is produced in situ within the water column through the decay of a parent nuclide 234U in the seawater. Vertical distributions of 230Th have been well described by reversible scavenging model in the Pacific Ocean [Nozaki et al., 1981; Bacon and Anderson, 1982; Nozaki, 1983; Nozaki and Nakanishi, 1985; Nozaki et al., 1987]. Scavenging-mixing models have been adopted in regions where horizontal advection is the dominant factor controlling 230Th distribution, such as in the Weddell Sea [Rutgers van der Loeff and Berger, 1993], the Atlantic Ocean [Vogler et al., 1998; Moran et al., 1997; 2001; 2002] and the Andaman Sea [Okubo et al., 2004]. Previous studies on thorium isotopes in seawater have elucidated scavenging processes in water columns in various oceans. Nevertheless, thorium isotope studies have not been performed sufficiently in mid-latitude of the Pacific Ocean. This study clarifies vertical distributions of thorium isotopes, especially 230Th, to study scavenging processes of thorium and trace metals in this region. We investigated the vertical distribution of thorium isotopes in mid-latitudes of the Pacific Ocean especially 230Th as a test case of scavenging of metals, and discuss the control factor of the distribution of 230Th. In comparison with previous studies in the Pacific Ocean [Nozaki et al., 1981; Nozaki and Nakanishi, 1985; Nozaki et al., 1987], the higher latitude stations show lower 230Th concentrations. This tendency corresponds to the primary productivity in surface oceans. The prominent feature is the depletion of 230Th concentrations compared with that estimated by reversible scavenging model calculations in deep water in BO-3 (30o 01'N, 160o 00'W, Depth: 5778 m) and BO-5

  8. Plasma Structuring at Mid-Latitudes during Super-Storms and their Impact on GPS-Based Navigation Systems

    NASA Astrophysics Data System (ADS)

    Basu, S.; Makela, J.; Wright, J.; Sheehan, R.; MacKenzie, E.; Coster, A.; Doherty, P.; Rich, F.; Keskinen, M.; Chua, D.

    2005-12-01

    Two components of ionospheric plasma structuring at mid-latitudes during large magnetic storms have recently been documented (Basu, Su. et al., GRL, 2005). One component is found to be associated with the Storm Enhanced Density (SED) plumes, which have been shown to be ionospheric signatures of plasmaspheric tails (Foster et al., GRL, 2002), and the other with auroral processes. Such was the case for the October 29-30, 2003 and the November 20, 2003 super-storms. During these very magnetically active periods, the Wide Area Augmentation System (WAAS) of the Federal Aviation Administration (FAA), relying on a GPS-based navigation system was in non-operational status throughout the continental United States (CONUS) for several hours on each of the three days mentioned above. During the next super-storm on November 8, 2004, when WAAS problems of such magnitude occurred, very large phase fluctuations were observed within CONUS. The unusual circumstance for this period was that in this case no appreciable SED was observed. However, the entire CONUS was pervaded by a very wide auroral oval which encompassed even Bear Lake Observatory in Utah and a wide mid-latitude trough with an equatorward location near 40 degrees magnetic latitude. This is clearly visible in GPS TEC and DMSP in-situ density and velocity data. In view of these unexpected results and severe impacts on GPS navigation even during a low sunspot period, the need for the LWS Ionosphere-Thermosphere Storm Probe Mission can hardly be overemphasized.

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

    NASA Technical Reports Server (NTRS)

    Volk, C.; Elkins, J.; Fahey, D.; Salawitch, R.; Dutton, G.; Gilligan, J.; Proffitt, M.; Loewenstein, M.; Podolske, J.; Minschwaner, K.; hide

    1996-01-01

    Because exchange with the tropics is slower than multi-dimensional models generally assume, ozone at mid-latitudes apears to be more sensitive to elevated levels of industrial chlorine than currently predicted. Nevertheless, approximately 45% of air in the tropical ascent region at 21 km has been entrained from mid-latitudes, implying that emissions from supersonic aircraft could deplete ozone in the middle stratosphere.

  10. 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

  11. Amplified mid-latitude planetary waves favour particular regional weather extremes

    NASA Astrophysics Data System (ADS)

    Screen, James A.; Simmonds, Ian

    2014-08-01

    There has been an ostensibly large number of extreme weather events in the Northern Hemisphere mid-latitudes during the past decade. An open question that is critically important for scientists and policy makers is whether any such increase in weather extremes is natural or anthropogenic in origin. One mechanism proposed to explain the increased frequency of extreme weather events is the amplification of mid-latitude atmospheric planetary waves. Disproportionately large warming in the northern polar regions compared with mid-latitudes--and associated weakening of the north-south temperature gradient--may favour larger amplitude planetary waves, although observational evidence for this remains inconclusive. A better understanding of the role of planetary waves in causing mid-latitude weather extremes is essential for assessing the potential environmental and socio-economic impacts of future planetary wave changes. Here we show that months of extreme weather over mid-latitudes are commonly accompanied by significantly amplified quasi-stationary mid-tropospheric planetary waves. Conversely, months of near-average weather over mid-latitudes are often accompanied by significantly attenuated waves. Depending on geographical region, certain types of extreme weather (for example, hot, cold, wet, dry) are more strongly related to wave amplitude changes than others. The findings suggest that amplification of quasi-stationary waves preferentially increases the probabilities of heat waves in western North America and central Asia, cold outbreaks in eastern North America, droughts in central North America, Europe and central Asia, and wet spells in western Asia.

  12. 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.

  13. 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, Christophe; 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.

  14. 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.

  15. 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.

  16. The hydrography of the mid-latitude northeast Atlantic Ocean. I: The deep water masses

    NASA Astrophysics Data System (ADS)

    van Aken, Hendrik M.

    2000-05-01

    The circulation of the deep water masses in the mid-latitude northeast Atlantic Ocean was studied by analysis of the distributions of potential temperature, salinity, dissolved oxygen, phosphate, nitrate, and silicate. Pre-formed nutrients were used to allow a quantitative description of the deep water masses, especially the Northeast Atlantic Deep Water, in terms of four local source water types: Iceland-Scotland Overflow Water, Lower Deep Water, Labrador Sea Water, and Mediterranean Sea Water. Over the Porcupine Abyssal Plain between 2500 and 2900 dbar Northeast Atlantic Deep Water appears to be a mixture of mainly Iceland-Scotland Overflow Water and Labrador Sea Water (˜80%), with minor contributions of Lower Deep Water and Mediterranean Sea Water. When the Northeast Atlantic Deep Water re-circulates in the north-eastern Atlantic and flows southwards towards the Madeira Abyssal Plain, contributions of the former two water types of northern origin diminish to about 50% due to diapycnal mixing with the overlying and underlying water masses. The observed meridional and zonal trends of dissolved oxygen and nutrients in the Northeast Atlantic Deep Water appear to be caused both by diapycnal mixing with the underlying Lower Deep Water and by mineralization of organic matter. The eastward decrease of oxygen and increase of nutrients especially require considerable mineralization of organic matter near the European continental margin. At deeper levels (˜4100 dbar), where the nutrient rich Lower Deep Water is found near the bottom, the meridional gradients of oxygen and nutrients are opposite to those found between 2500 and 2900 dbar. Diapycnal mixing cannot explain this change in gradients, which is therefore considered to be a qualitative indication of ageing of the Lower Deep Water when it flows northwards. A considerable part of the Iceland-Scotland Overflow Water and the Lower Deep Water that enter the northeast Atlantic may be removed by deep upwelling in the Bay

  17. The occurrence and chemical implications of geothermal convection of seawater in continental shelves

    NASA Astrophysics Data System (ADS)

    Wilson, Alicia M.

    2003-11-01

    Geothermal convection is an important driving force for fluid flow and diagenesis in carbonate platforms, and the similar shape of continental shelves in general suggests that geothermal convection could occur in continental shelves around the world. Numerical models based on seven transects of the shelf off the east coast of North America were developed to bracket possible fluxes. Simulations assuming relatively permeable sediments (medium-grained carbonates) failed to produce significant thermal variations, suggesting that chemical tracers will be required to detect this flow in the field. Fluxes calculated assuming lower permeabilities (fine grained carbonates) between Cape Fear and the Savannah River were approximately 3 orders of magnitude smaller than river discharge for the area, a difference similar to that between global river discharge and hydrothermal convection at mid-ocean ridges. Sediment diagenesis during geothermal convection in continental shelves thus has the potential to affect ocean chemical budgets, including potassium, calcium, and magnesium.

  18. 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.

  19. 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.

  20. Seasonal Variations of Mid-Latitude Ionospheric Trough Structure Observed with DEMETER and COSMIC

    NASA Astrophysics Data System (ADS)

    Matyjasiak, Barbara; Przepiórka, Dorota; Rothkaehl, Hanna

    2016-12-01

    The mid-latitude ionospheric trough is a depleted region of ionospheric plasma observed in the topside ionosphere. Its behavior can provide useful information about the magnetospheric dynamics, since its existence is sensitive to magnetospherically induced motions. Mid-latitude trough is mainly a night-time phenomenon. Both, its general features and detailed characteristics strongly depend on the level of geomagnetic disturbances, time of the day, season, and the solar cycle, among others. Although many studies provide basic information about general characteristics of the main ionospheric trough structure, an accurate prediction of the trough behavior in specific events is still understood poorly. The paper presents the mid-latitude trough characteristics with regard to the geomagnetic longitude and season during a solar activity minimum, as based on the DEMETER in situ satellite measurements and the data retrieved from FORMOSAT-3/COSMIC radio occultation measurements.

  1. The Relationship Between Recent Arctic Amplification and Extreme Mid-Latitude Weather

    NASA Astrophysics Data System (ADS)

    Cohen, J. L.; Screen, J.; Furtado, J. C.; Barlow, M. A.; Whittleston, D. P.; Coumou, D.; Francis, J. A.; Dethloff, K.; Entekhabi, D.; Overland, J. E.

    2014-12-01

    The Arctic has warmed more than twice as fast as the global average and is refereed to as Arctic amplification. The rapid Arctic warming has contributed to dramatic melting of Arctic sea ice and spring snow cover, at a pace greater than simulated by the climate models. These profound changes to the Arctic system have coincided with a period of ostensibly more frequent events of extreme weather across the Northern Hemisphere (NH) mid-latitudes, including recent severe winters. The possible link between Arctic change and mid-latitude weather can be broadly grouped under three potential dynamical mechanisms—changes in: storm tracks, the jet stream and planetary-waves and their associated energy propagation. I will discuss how less sea ice and increase snow cover separately can force more severe winter weather across the NH continents. I will conclude with a new idea for how it is possible for sea ice and snow cover to jointly influence mid-latitude weather.

  2. Nonlinear response of mid-latitude weather to the changing Arctic

    NASA Astrophysics Data System (ADS)

    Overland, James E.; Dethloff, Klaus; Francis, Jennifer A.; Hall, Richard J.; Hanna, Edward; Kim, Seong-Joong; Screen, James A.; Shepherd, Theodore G.; Vihma, Timo

    2016-11-01

    Are continuing changes in the Arctic influencing wind patterns and the occurrence of extreme weather events in northern mid-latitudes? The chaotic nature of atmospheric circulation precludes easy answers. The topic is a major science challenge, as continued Arctic temperature increases are an inevitable aspect of anthropogenic climate change. We propose a perspective that rejects simple cause-and-effect pathways and notes diagnostic challenges in interpreting atmospheric dynamics. We present a way forward based on understanding multiple processes that lead to uncertainties in Arctic and mid-latitude weather and climate linkages. We emphasize community coordination for both scientific progress and communication to a broader public.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Mid-Latitude Dayside Ionospheric Response to Storm-Time Electric Fields

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    One way in which a geomagnetic storm may impact the ionosphere is through an expansion of the magnetospheric electric field to mid-latitudes. This mechanism was explored in detail by Heelis et al [2009], where it was shown that an electric field with a magnitude of just 1 mV/m at mid-latitudes is sufficient to produce a large increase in TEC on the dayside. This effect is brought about by the lifting of the ionosphere as dayside plasma is transported poleward under the influence of the eastward component of the expanded electric field; the lifting occurs because of the inclination of the magnetic field lines. At the time the above-mentioned article was written, the authors lacked a physics-based modeling capability for the behavior of the storm-time electric field at mid-latitudes, so a simple modified form of the Volland 2-cell model was used. In the present work we use the University of Michigan’s Hot Electron and Ion Drift Integrator (HEIDI) electric field model, along with the Utah State University Time Dependent Ionospheric Model (TDIM). The HEIDI model provides electric potential distributions spanning the northern mid-latitudes with a cadence of 30 minutes; these are used to drive the TDIM in carrying out mid-latitude simulations. The results are compared with model runs for the quiet-time ionosphere, as well as observations from ionosondes and ground-based GPS TEC receivers. ----------------- Heelis, R. A., J. J. Sojka, M. David, and R. W. Schunk (2009), Storm time density enhancements in the middle-latitude dayside ionosphere, J. Geophys. Res., 114, A03315, doi:10.1029/2008JA013690.

  12. Mid-latitude mesospheric clouds and their environment from SOFIE observations

    NASA Astrophysics Data System (ADS)

    Hervig, Mark E.; Gerding, Michael; Stevens, Michael H.; Stockwell, Robert; Bailey, Scott M.; Russell, James M.; Stober, Gunter

    2016-11-01

    Observations from the Solar Occultation For Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite are used to examine noctilucent clouds (NLC) and their environment at middle latitudes ( 56°N and 52°S). Because SOFIE is uniquely capable of measuring NLC, water vapor, and temperature simultaneously, the local cloud environment can be specified to examine what controls their formation at mid-latitudes. Compared to higher latitudes, mid-latitude NLCs are less frequent and have lower ice mass density, by roughly a factor of five. Compared to higher latitudes at NLC heights, mid-latitude water vapor is only 12% lower while temperatures are more than 10 K higher. As a result the reduced NLC mass and frequency at mid-latitudes can be attributed primarily to temperature. Middle and high latitude NLCs contain a similar amount of meteoric smoke, which was not anticipated because smoke abundance increases towards the equator in summer. SOFIE indicates that mid-latitude NLCs may or may not be associated with supersaturation with respect to ice. It is speculated that this situation is due in part to SOFIE uncertainties related to the limb measurement geometry combined with the non-uniform nature of NLCs. SOFIE is compared with concurrent NLC, temperature, and wind observations from Kühlungsborn, Germany (54°N) during the 2015 summer. The results indicate good agreement in temperature and NLC occurrence frequency, backscatter, and height. SOFIE indicates that NLCs were less frequent over Europe during 2015 compared to other longitudes, in contrast to previous years at higher latitudes that showed no clear longitude dependence. Comparisons of SOFIE and the Solar Backscatter Ultraviolet (SBUV) indicate good agreement in average ice water column (IWC), although differences in occurrence frequency were often large.

  13. 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.

  14. 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.

  15. Self-Consistent Generation of Continental Crust in Global Mantle Convection Models

    NASA Astrophysics Data System (ADS)

    Jain, C.; Rozel, A. B.; Tackley, P.

    2016-12-01

    Numerical modelling commonly shows that mantle convection and continents have strong feedbacks on each other (Philips and Coltice, JGR 2010; Heron and Lowman, JGR 2014), but the continents are always inserted a priori while basaltic (oceanic) crust is generated self-consistently in such models (Rolf et al., EPSL 2012). We aim to implement self-consistent generation of continental crust in global models of mantle convection using StagYY (Tackley, PEPI 2008). The silica-rich continental crust appears to have been formed by fractional melting and crystallization in episodes of relatively rapid growth from late Archaean to late Proterozoic eras (3-1 Ga) (Hawkesworth & Kemp, Nature 2006). It takes several stages of differentiation to generate continental crust. First, the basaltic magma is extracted from the pyrolitic mantle. Second, it goes through eclogitic transformation and then partially melts to form Na-rich Tonalite-Trondhjemite-Granodiorite (TTG) which rise to form proto-continents (Rudnick, Nature 1995; Herzberg & Rudnick, Lithos 2012). TTGs dominate the grey gneiss complexes which make up most of the continental crust. Based on the melting conditions proposed by Moyen (Lithos, 2011), we parameterize TTG formation and henceforth, the continental crust. Continental crust can also be destroyed by subduction or delamination. We will investigate continental growth and destruction history in the models spanning the age of the Earth.

  16. Self-consistent generation of continental crust in global mantle convection models

    NASA Astrophysics Data System (ADS)

    Jain, Charitra; Rozel, Antoine; Tackley, Paul

    2017-04-01

    Numerical modeling commonly shows that mantle convection and continents have strong feedbacks on each other (Philips and Coltice, JGR 2010; Heron and Lowman, JGR 2014), but the continents are always inserted a priori while basaltic (oceanic) crust is generated self-consistently in such models (Rolf et al., EPSL 2012). We aim to implement self-consistent generation of continental crust in global models of mantle convection using StagYY (Tackley, PEPI 2008). The silica-rich continental crust appears to have been formed by fractional melting and crystallization in episodes of relatively rapid growth from late Archean to late Proterozoic eras (3-1 Ga) (Hawkesworth & Kemp, Nature 2006). It takes several stages of differentiation to generate continental crust. First, the basaltic magma is extracted from the pyrolitic mantle. Second, it goes through eclogitic transformation and then partially melts to form Na-rich Tonalite-Trondhjemite-Granodiorite (TTG) which rise to form proto-continents (Rudnick, Nature 1995; Herzberg & Rudnick, Lithos 2012). TTGs dominate the grey gneiss complexes which make up most of the continental crust. Based on the melting conditions proposed by Moyen (Lithos, 2011), we parameterize TTG formation and henceforth, the continental crust. Continental crust can also be destroyed by subduction or delamination. We will investigate continental growth and destruction history in the models spanning the age of the Earth.

  17. Changing Characteristics of convective storms: Results from a continental-scale convection-permitting climate simulations

    NASA Astrophysics Data System (ADS)

    Prein, A. F.; Ikeda, K.; Liu, C.; Bullock, R.; Rasmussen, R.

    2016-12-01

    Convective storms are causing extremes such as flooding, landslides, and wind gusts and are related to the development of tornadoes and hail. Convective storms are also the dominant source of summer precipitation in most regions of the Contiguous United States. So far little is known about how convective storms might change due to global warming. This is mainly because of the coarse grid spacing of state-of-the-art climate models that are not able to resolve deep convection explicitly. Instead, coarse resolution models rely on convective parameterization schemes that are a major source of errors and uncertainties in climate change projections. Convection-permitting climate simulations, with grid-spacings smaller than 4 km, show significant improvements in the simulation of convective storms by representing deep convection explicitly. Here we use a pair of 13-year long current and future convection-permitting climate simulations that cover large parts of North America. We use the Method for Object-Based Diagnostic Evaluation (MODE) that incorporates the time dimension (MODE-TD) to analyze the model performance in reproducing storm features in the current climate and to investigate their potential future changes. We show that the model is able to accurately reproduce the main characteristics of convective storms in the present climate. The comparison with the future climate simulation shows that convective storms significantly increase in frequency, intensity, and size. Furthermore, they are projected to move slower which could result in a substantial increase in convective storm-related hazards such as flash floods, debris flows, and landslides. Some regions, such as the North Atlantic, might experience a regime shift that leads to significantly stronger storms that are unrepresented in the current climate.

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

    NASA Astrophysics Data System (ADS)

    Spellman, Greg

    2017-05-01

    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.

  19. The effect of solar wind dynamic pressure changes on low and mid-latitude magnetic records

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Ginskey, M.; Petrinec, S.; Le, G.

    1992-06-01

    Magnetic records from low- and mid-latitude stations have been examined to determine their response to solar wind pressure changes. The best correlation between ground level changes and the change in the square root of the solar wind dynamic pressure occurs for stations at latitudes from 15 to 30 deg such as Tahiti, Honolulu, San Juan and Midway. The horizontal component of the field changes on average 16.5 nT for each change of 1(nPa) exp 1/2 of the square root of dynamic pressure. This is 50 percent greater than the vacuum model of Tsyganenko would predict for a nonconducting earth and therefore what would be expected for a perfectly conducting interior. Thus, low- and mid-latitude ground level response to solar wind pressure changes is dominated by the variation of the strength and location of the magnetopause current system and the corresponding induced currents within the earth rather than ionospheric current sources.

  20. Ionospheric frequency spread and its relationship with range spread in mid-latitude regions

    SciTech Connect

    Bowman, G.G. )

    1991-06-01

    The distinction between range spread and frequency spread as seen on mid-latitude ionograms is discussed. A classification of these two types of spread F is proposed in terms of different arrangements of the duplicate traces which provide the basic trace structures of mid-latitude spread F ionograms. Experimental results are presented to support the idea that frequency spread results from multiple ray paths (associated with a shallow ripple structure in the isoionic contours) close to the direction of the zenith position, so that each ray path has a range approximately equal to that of its neighbor. Furthermore, a horizontal gradient of maximum electron density is an additional requirement to create frequency spread. Atmospheric conditions (involving ionospheric F{sub 2} region heights and upper atmosphere neutral particle densities) which seem to favor the generation of frequency spread are discussed.

  1. 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.

  2. Climatology of vTEC at midnight over mid-latitude regions using PCA

    NASA Astrophysics Data System (ADS)

    Natali, M. Paula; Meza, Amalia

    2017-04-01

    At night the content of the electron density at mid-latitude is mainly controlled by loss processes, recombination and electron movement, which are related by the continuity equation. The vertical wind plays an important role in these processes. Global vertical Total Electron Content (vTEC) maps produced by the International Global Navigation Satellite System (GNSS) Service, the Horizontal Wind Model 2007 (HWM07) and the International Reference Ionosphere (IRI) 2012 model are used to describe the climatology at midnight over mid-latitude regions during 2000-2002. In particular, four regions were selected. They are approximately centered in zero magnetic declination, two in the northern hemisphere and two in southern hemisphere. They are located near and far from geomagnetic poles respectively. Principal Components Analysis (PCA) technique highlights the spatial-temporal variations to the overall vTEC variability which can be well represented by an orthogonal base. Indeed, we show for the four selected regions the contributions of the first three modes account for more than 95% of its variability. PCA results show that vTEC variability respond to vertical wind variation with decreasing values of about 10% -15% with the action of a vertical wind lasting for two hours. The Mid-latitude Summer Night Anomaly (MSNA), which is directly related with vertical wind, is present in regions far from geomagnetic poles. A remnant effect of the winter anomaly is also observed, in regions near geomagnetic poles. A longitudinal variation for mid-latitude ionospheric vTEC with maximum values in equinoxes, associated with negative and positive magnetic declination in all regions is observed. For the IRI model, PCA results, are quite similar but the mean values are lower than the obtained with the Global vTEC Maps. These data show the MSNA but not the remnant of the winter anomaly. In all regions the longitudinal variation is present with the same seasonal variation as Global vTEC Maps.

  3. Empirical linkages between Arctic sea ice extents and northern hemisphere, mid-latitude column ozone levels

    SciTech Connect

    Marko, J.R.; Fissel, D.B.

    1993-01-08

    Statistically significant correlations are demonstrated between annual mean column ozone data collected at mid-latitude sites and mean annual and winter sea ice extents east of Greenland and in the Barents and Kara Seas. These results are discussed with reference to the locations of the correlated parameters relative to the Basic Pattern of stratosphere-solar flux correlations. Possibilities for underlying linkage mechanisms are considered and related to recent decreasing hemispheric ozone level trends. 19 refs., 2 figs., 2 tabs.

  4. Synoptic-scale circulation patterns during summer derived from tree rings in mid-latitude Asia

    NASA Astrophysics Data System (ADS)

    Seim, Andrea; Schultz, Johannes A.; Leland, Caroline; Davi, Nicole; Byambasuren, Oyunsanaa; Liang, Eryuan; Wang, Xiaochun; Beck, Christoph; Linderholm, Hans W.; Pederson, Neil

    2017-09-01

    Understanding past and recent climate and atmospheric circulation variability is vital for regions that are affected by climate extremes. In mid-latitude Asia, however, the synoptic climatology is complex and not yet fully understood. The aim of this study was to investigate dominant synoptic-scale circulation patterns during the summer season using a multi-species tree-ring width (TRW) network comprising 78 sites from mid-latitude Asia. For each TRW chronology, we calculated an atmospheric circulation tree-ring index (ACTI), based on 1000 hPa geopotential height data, to directly link tree growth to 13 summertime weather types and their associated local climate conditions for the period 1871-1993. Using the ACTI, three groups of similarly responding tree-ring sites can be associated with distinct large-scale atmospheric circulation patterns: 1. growth of drought sensitive trees is positively affected by a cyclone over northern Russia; 2. temperature sensitive trees show positive associations to a cyclone over northwestern Russia and an anticyclone over Mongolia; 3. trees at two high elevation sites show positive relations to a zonal cyclone extending from mid-latitude Eurasia to the West Pacific. The identified synoptic-scale circulation patterns showed spatiotemporal variability in their intensity and position, causing temporally varying climate conditions in mid-latitude Asia. Our results highlight that for regions with less pronounced atmospheric action centers during summer such as the occurrence of large-scale cyclones and anticyclones, synoptic-scale circulation patterns can be extracted and linked to the Northern Hemisphere circulation system. Thus, we provide a new and solid envelope for climate studies covering the past to the future.

  5. Physical Modeling of the Processes Responsible for the Mid-Latitude Storm Enhanced Plasma Density

    NASA Astrophysics Data System (ADS)

    Fuller-Rowell, T. J.; Maruyama, N.; Fedrizzi, M.; Codrescu, M.; Heelis, R. A.

    2016-12-01

    Certain magnetic local time sectors at mid latitudes see substantial increases in plasma density in the early phases of a geomagnetic storm. The St. Patrick's Day storms of 2013 and 2015 were no exception, both producing large increases of total electron content at mid latitudes. There are theories for the build up of the storm enhanced density (SED), but can current theoretical ionosphere-thermosphere coupled models actually reproduce the response for an actual event? Not only is it necessary for the physical model to contain the appropriate physics, they also have to be forced by the correct drivers. The SED requires mid-latitude zonal transport to provide plasma stagnation in sunlight to provide the production. The theory also requires a poleward drift perpendicular to the magnetic field to elevate the plasma out of the body of the thermosphere to regions of substantially less loss rate. It is also suggested that equatorward winds are necessary to further elevate the plasma to regions of reduced loss. However, those same winds are also likely to transport molecular nitrogen rich neutral gas equatorward, potentially canceling out the benefits of the neutral circulation. Observations of mid-latitude zonal plasma flow are first analyzed to see if this first necessary ingredient is substantiated. The drift observations are then used to tune the driver to determine if, with the appropriate electric field driver, the latest physical models can reproduce the substantial plasma build up. If it can, the simulation can also be used to assess the contribution of the equatorward meridional wind; are they an asset to the plasma build up, or does the enhanced molecular species they carry counteract their benefit.

  6. Synoptic-scale circulation patterns during summer derived from tree rings in mid-latitude Asia

    NASA Astrophysics Data System (ADS)

    Seim, Andrea; Schultz, Johannes A.; Leland, Caroline; Davi, Nicole; Byambasuren, Oyunsanaa; Liang, Eryuan; Wang, Xiaochun; Beck, Christoph; Linderholm, Hans W.; Pederson, Neil

    2016-11-01

    Understanding past and recent climate and atmospheric circulation variability is vital for regions that are affected by climate extremes. In mid-latitude Asia, however, the synoptic climatology is complex and not yet fully understood. The aim of this study was to investigate dominant synoptic-scale circulation patterns during the summer season using a multi-species tree-ring width (TRW) network comprising 78 sites from mid-latitude Asia. For each TRW chronology, we calculated an atmospheric circulation tree-ring index (ACTI), based on 1000 hPa geopotential height data, to directly link tree growth to 13 summertime weather types and their associated local climate conditions for the period 1871-1993. Using the ACTI, three groups of similarly responding tree-ring sites can be associated with distinct large-scale atmospheric circulation patterns: 1. growth of drought sensitive trees is positively affected by a cyclone over northern Russia; 2. temperature sensitive trees show positive associations to a cyclone over northwestern Russia and an anticyclone over Mongolia; 3. trees at two high elevation sites show positive relations to a zonal cyclone extending from mid-latitude Eurasia to the West Pacific. The identified synoptic-scale circulation patterns showed spatiotemporal variability in their intensity and position, causing temporally varying climate conditions in mid-latitude Asia. Our results highlight that for regions with less pronounced atmospheric action centers during summer such as the occurrence of large-scale cyclones and anticyclones, synoptic-scale circulation patterns can be extracted and linked to the Northern Hemisphere circulation system. Thus, we provide a new and solid envelope for climate studies covering the past to the future.

  7. 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.

  8. Observations of mid-latitude planetary waves in the lower atmosphere over America and China

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Ping, Jinsong

    The characteristics of mid-latitude planetary waves (PWs) in the troposphere and lower strato-sphere (TLS) are studied by both statistical and case studies with the data from radiosonde observations at three middle latitude stations (Miramar Nas, 32.9N, 117.2W; Santa Teresa, 31.9N, 106.7W; Fort Worth, 32.8N, 97.3W) in America and Wuhan (30.5N, 114.4E) in China. It is found that mid-latitude PWs exist in two regions. One is in the troposphere, and the other is in the stratosphere. In the troposphere, the amplitudes of the mid-latitude PWs reach maximum round the center of the subtropical jet stream. The subtropical jet stream may be one of the PW excitation sources. However, in the stratosphere, only the lower frequency PWs remain in winter, with the zonal component strongest. Moreover, the PW activities are rather intermittent, and their lifetimes are not longer than two months. In the case study of the 2000/2001 winter, it is found that the quasi 16-day wave in Wuhan around the subtropical jet stream is probable the same quasi 16-day wave at the three American stations, which steadily propagates around the latitude.

  9. Where does subduction initiate and die? Insights from global convection models with continental drift

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Williams, Simon; Coltice, Nicolas; Tackley, Paul

    2017-04-01

    Plate tectonics is a prominent feature on Earth. Together with the underlying convecting mantle, plates form a self-organized system. In order to understand the dynamics of the coupled system, subduction of the lithospheric plates plays the key role since it links the exterior with the interior of the planet. In this work we study subduction initiation and death with respect to the position of the continental rafts. Using thermo-mechanical numerical calculations we investigate global convection models featuring self-consistent plate tectonics and continental drifting employing a pseudo-plastic rheology and testing the effect of a free surface. We consider uncompressible mantle convection in Boussinesq approximation that is basaly and internaly heated. Our calculations indicate that the presence of the continents alterns stress distribution within a certain distance from the margins. Intra-oceanic subudction initiation is favorable during super-continent cycles while the initiation at passive continental margin prevails when continents are dispersed. The location of subduction initiation is additionally controlled by the lithospheric strength. Very weak lithosphere results in domination of intra-oceanic subduction initiation. The subduction zones die more easily in the vicinity of the continent due to the strong rheological contrast between the oceanic and continental lithosphere. In order to compare our findings with subduction positions through time recorded on Earth, we analyse subduction birth in global plate reconstruction back to 410 My.

  10. Mid-latitude Ionospheric Storms Density Gradients, Winds, and Drifts Estimated from GPS TEC Imaging

    NASA Astrophysics Data System (ADS)

    Datta-Barua, S.; Bust, G. S.

    2012-12-01

    Ionospheric storm processes at mid-latitudes stand in stark contrast to the typical quiescent behavior. Storm enhanced density (SED) on the dayside affects continent-sized regions horizontally and are often associated with a plume that extends poleward and upward into the nightside. One proposed cause of this behavior is the sub-auroral polarization stream (SAPS) acting on the SED, and neutral wind effects. The electric field and its effect connecting mid-latitude and polar regions are just beginning to be understood and modeled. Another possible coupling effect is due to neutral winds, particularly those generated at high latitudes by joule heating effects. Of particular interest are electric fields and winds along the boundaries of the SED and plume, because these may be at least partly a cause of sharp horizontal electron density gradients. Thus, it is important to understand what bearing the drifts and winds, and any spatial variations in them (e.g., shear), have on the structure of the enhancement, particularly at its boundaries. Imaging techniques based on GPS TEC play a significant role in study of mid-latitude storm dynamics, particularly at mid-latitudes, where sampling of the ionosphere with ground-based GPS lines of sight is most dense. Ionospheric Data Assimilation 4-Dimensional (IDA4D) is a plasma density estimation algorithm that has been used in a number of scientific investigations over several years. Recently, efforts to estimate drivers of the mid-latitude ionosphere, focusing on electric-field-induced drifts and neutral winds, based on GPS TEC high-resolution imaging have shown promise. Estimating Ionospheric Parameters from Ionospheric Reverse Engineering (EMPIRE) is a tool developed that addresses this kind of investigation. In this work electron density and driver estimates are presented for an ionospheric storm using IDA4D in conjunction with EMPIRE. The IDA4D estimates resolve F-region electron densities at 1-degree resolution at the region

  11. 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

  12. 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).

  13. Storm-time electric fields in the mid-latitude ionosphere observed by ground magnetometers and the Akebono satellite

    NASA Astrophysics Data System (ADS)

    Tsuji, Y.; Shinbori, A.; Kikuchi, T.; Nishimura, Y.; Matsuoka, A.

    2008-12-01

    The mid-latitude ionosphere electromagnetically connected to the inner magnetosphere via magnetic field lines is an important region for understanding storm-time magnetosphere-ionosphere coupling processes. In order to clarify distributions of electric fields and currents in the mid- and low-latitude ionosphere during storms, we investigated latitudinal and local time dependence of magnetic field variations for six storms using a ground magnetometer network covering from high to equatorial latitudes. The analysis results suggested that competition between convection and shielding electric fields controlled characteristics of magnetic disturbances caused by mid-latitude ionospheric currents. However, a quantitative relationship between ground magnetic disturbances and in-situ ionospheric electric fields has not been clarified yet because of difficulties in deducing electric fields from magnetic field variations. Therefore, in this study, we analyzed ground magnetic disturbances and electric field mapped onto the ionosphere observed by the Akebono satellite during the storm occurred on February 21-22, 1994, with a minimum SYM-H value of -152 nT. During the main phase of the storm, the satellite passed through a region from 73 degrees invariant latitude (ILAT) and 10 magnetic local time (MLT) to 49 degrees ILAT and 18 MLT from 0055 to 0148 UT. The poleward electric field changed negative to positive values at 65.5 degrees ILAT (15 MLT). The electric field signature indicates that the center of region-1 field-aligned currents (R-1 FACs) was located at this latitude. Subsequently, the electric field profile showed two peaks at 62-63 degrees ILAT (15.5 MLT) and 55 degrees ILAT (17 MLT). The former corresponds to the auroral oval identified by the lower energy particle instrument of the Akebono. On the other hand, during the same period, we also investigated the latitudinal distribution of the northward magnetic field variation measured on the ground (16.5-19.5 MLT). The

  14. 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.

  15. Two-Way Interactions between the Arctic and Mid-Latitudes Associated with a Wavy Jet Stream

    NASA Astrophysics Data System (ADS)

    Vihma, T. P.

    2015-12-01

    Large-amplitude planetary waves in the eddy-driven jet stream may cause extreme weather in mid-latitudes, for example long-lasting cold spells in winter and heat waves in summer. Such extreme events in mid-latitudes have received a lot of attention, but much less studied are simultaneous anomalous events in the Arctic that occur in different parts of the same wavy jet stream and are governed by thermal advection from mid-latitudes. We analyse cases of high-amplitude waves in the jet stream, and compare their effects in the parts of the jet stream where Arctic air masses are advected towards mid-latitudes and mid-latitude air-masses are advected towards Arctic. We further compare the performance of numerical weather prediction models in the Arctic (northern Canada, Greenland, and Eurasian Arctic archipelago) and mid-latitude regions (U.S. East Coast, northwestern Europe, and eastern Asia) affected by the strong thermal advection.

  16. On the origin of the air between multiple tropopauses in mid-latitudes

    NASA Astrophysics Data System (ADS)

    Gimeno, L.; de la Torre, L.; Añel, J. A.

    2012-04-01

    Double tropopauses (DTs) are a recurrent structure in the mid-latitudes (Añel et al, 2008). Recent studies have relied on the notion of the excursion of tropical air from the upper troposphere into higher latitudes, overlaying the tropopause of the mid-latitudes. Randel et al. (2007) found a coincidence of DT profiles with reduced ozone amounts in the LS, and with regions of enhanced transport from the tropics to higher latitudes above the subtropical jets. Pan et al. (2009) suggested the association of DTs with intrusions of low-latitude air masses with low static stability and low ozone concentrations into the LS of mid-latitudes, related to Rossby wave breaking events. In this work we analyzed the origin and characteristics (ozone, water vapor, vorticity) of the air for Boulder radiosonde station inmediately below/above the first/second tropopause and the air between for both by using a Lagrangian approach based on Flexpart and five years of ERA analysis data 2000-2004. • Añel, J. A., J. C. Antuña, L. de la Torre, J. M. Castanheira, and L. Gimeno (2008), Climatological features of global multiple tropopause events, J. Geophys. Res., 113, D00B08, doi:10.1029/2007JD009697 • Pan, L. L., W. J. Randel, J. C. Gille, W. D. Hall, B. Nardi, S. Massie, V. Yudin, R. Khosravi, P. Konopka, and D. Tarasick (2009), Tropospheric intrusions associated with the secondary tropopause, J. Geophys. Res., 114, D10302, doi:10.1029/2008JD011374. • Randel, W. J., D. J. Seidel, and L. L. Pan (2007b), Observational characteristics of double tropopauses, J. Geophys. Res., 112, D07309, doi:10.1029/2006JD007904.

  17. The response of Northern Hemisphere mid-latitude precipitation to aerosol forcing

    NASA Astrophysics Data System (ADS)

    Osborne, J. M.; Lambert, F. H.

    2013-12-01

    We analyse the relationship between 20th century precipitation, temperature and aerosol forcing in the best observed Northern Hemisphere mid-latitude region. Using CMIP5 model experiments, we find that observed temperature changes are consistent with the IPCC aerosol forcing best estimate of -1.2 Wm-2, but that precipitation changes apparently show little evidence of an aerosol response. It is possible that this is linked to changes in precipitation measurement that increased observed precipitation totals at the same time that aerosol forcing was expected to reduce it. Our physical understanding of regional precipitation is relatively weak. Models and some theoretical considerations suggest that Northern Hemisphere mid-latitude precipitation should change in proportion to changes in the global mean hydrological cycle. Precipitation change is not just a function of temperature change, but also the direct effects of forcings agents driving temperature change. We would expect an evident decrease in precipitation following a significant strengthening in aerosol forcing. Model simulated responses for precipitation and temperature appear to reflect changes in the strength of aerosol forcing over the twentieth-century. Notably, there is no evidence of aerosol forcing in precipitation observations. Investigation of this inconsistency reveals that as little as a 3-4% increase in observed precipitation amounts in the early-twentieth-century would bring precipitation in line with temperature. Biases greater than this have been identified in countries within the Northern Hemisphere mid-latitude region previously, notably the former USSR. These observations are frequently used as a metric for the quality of model simulated precipitation and in wider scientific research. More homogeneity studies would be of huge benefit.

  18. 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.

  19. 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.

  20. Sustainable Arctic observing network for predicting weather extremes in mid-latitudes

    NASA Astrophysics Data System (ADS)

    Inoue, J.; Sato, K.; Yamazaki, A.

    2016-12-01

    Routine atmospheric observations within and over the Arctic Ocean are very expensive and difficult to conduct because of factors such as logistics and the harsh environment. Nevertheless, the great benefit of such observations is their contribution to an improvement of skills of weather predictions over the Arctic and mid-latitudes. The Year of Polar Prediction (YOPP) from mid-2017 to mid-2019 proposed by the World Weather Research Programme - Polar Prediction Project (WWRP-PPP) would be the best opportunity to address the issues. The combination of observations and data assimilation is an effective way to understand the predictability of weather extremes in mid-latitudes. This talk presents the current activities related to PPP based on international special radiosonde observing network in the Arctic, and challenges toward YOPP. Comparing with summer and winter cases, the additional observations over the Arctic during winter were more effective for improving the predicting skills of weather extremes because the impact of the observations would be carried toward the mid-latitudes by the stronger jet stream and its frequent meanderings. During summer, on the other hand, the impact of extra observations was localized over the Arctic region but still important for precise weather forecasts over the Arctic Ocean, contributing to safe navigation along the Northern Sea Route. To consolidate the sustainable Arctic radiosonde observing network, increasing the frequency of observations at Arctic coastal stations, instead of commissioning special observations from ships and ice camps, would be a feasible way. In fact, several existing stations facing the Arctic Ocean have already increased the frequency of observations during winter and/or summer.

  1. Habitat preferences of baleen whales in a mid-latitude habitat

    NASA Astrophysics Data System (ADS)

    Prieto, Rui; Tobeña, Marta; Silva, Mónica A.

    2017-07-01

    Understanding the dynamics of baleen whale distribution is essential to predict how environmental changes can affect their ecology and, in turn, ecosystem functioning. Recent work showed that mid-latitude habitats along migratory routes may play an important role on the feeding ecology of baleen whales. This study aimed to investigate the function of a mid-latitude habitat for blue (Balaenoptera musculus), fin (Balaenoptera physalus) and sei (Balaenoptera borealis) whales occurring in sympatry during spring and summer months and to what extent their environmental niches overlap. We addressed those questions by developing environmental niche models (ENM) for each species and then making pairwise comparisons of niche overlap and relative habitat patch importance among the three species. ENMs were created using sightings from the Azorean Fisheries Observer Program from May to November, between 2004 and 2009, and a set of 18 predictor environmental variables. We then assessed monthly (April-July) overlap among ENMs using a modified Hellinger's distance metric (I). Results show that the habitat niches of blue and fin whales are strongly influenced by primary productivity and sea surface temperature and are highly dynamic both spatially and temporally due to the oceanography of the region. Niche overlap analyses show that blue and fin whale environmental niches are similar and that the suitable habitats for the two species have high degree of spatial coincidence. These results in combination suggest that this habitat may function as a mid-latitude feeding ground to both species while conditions are adequate. The sei whale model, on the other hand, did not include variables considered to be proxies for prey distribution and little environmental niche overlap was found between this species and the other two. We argue that these results suggest that the region holds little importance as a foraging habitat for the sei whale.

  2. Evaluation of the convection-resolving climate modeling approach on continental scales

    NASA Astrophysics Data System (ADS)

    Leutwyler, David; Lüthi, Daniel; Ban, Nikolina; Fuhrer, Oliver; Schär, Christoph

    2017-05-01

    Convection-resolving models allow to explicitly resolve deep convection at horizontal grid spacings of O(1 km). On current supercomputers, refining the grid spacing to the kilometer scale is computationally still extremely demanding, and therefore, climate simulations at this resolution have so far largely been limited to subcontinental computational domains. However, new supercomputers that mix conventional multicore CPUs and accelerators possess properties beneficial for climate codes. Exploiting these capabilities allows expansion of the size of the computational domains to continental scales. Here we present such a convection-resolving climate simulation, using a version of the COSMO model, capable of exploiting GPU accelerators. The simulation has a grid spacing of 2.2 km, 1536 × 1536 × 60 grid points, covers the period 1999-2008, and is driven by the ERA-Interim reanalysis. An assessment of the 10-year-long simulation is conducted using a wide range of data sets, including several rain gauge networks, energy balance stations, and a remotely sensed lightning data set. Substantial improvements are found for the 2 km simulation in terms of the diurnal cycles of precipitation. This confirms results found in studies using smaller computational domains. However, the continental-scale simulations also reveal deficiencies such as substantial performance differences between regions with and without strong orographic forcing. Analysis of the statistical distribution of updrafts and downdrafts shows an increase of the amplitude in seasons with convection and a pronounced asymmetry between updrafts and downdrafts. Furthermore, the analysis of lightning data shows that the convection-resolving simulation is able to reproduce important features of the annual cycle of deep convection in Europe.

  3. US CLIVAR Working Group: Arctic Change and Possible Influence on Mid-latitude Climate and Weather

    NASA Astrophysics Data System (ADS)

    Cohen, J. L.; Zhang, X.

    2015-12-01

    The Arctic has warmed more than twice as fast as the global average, a phenomenon known as Arctic amplification (AA). These profound changes to the Arctic system have coincided with a period of ostensibly more frequent events of extreme weather across the Northern Hemisphere mid-latitudes, including extreme heat and rainfall events and recent severe winters. The possible link between Arctic change and mid-latitude weather has spurred a rush of new observational and modeling studies. These studies have argued that heavy precipitation events and heat waves are at least partially attributable to Arctic warming. A growing number of recent studies even argue that recent extreme winter weather is related to AA. In part due to the high impact of extreme weather on our society, some of these studies linking AA to the increased frequency of extreme weather have garnered public and media attention. At the same time, uncertainties from the large intrinsic variability of the system, the short observational record due to the recentness of AA and the shortcomings of global climate models have also resulted in much skepticism in any argued links between AA and severe weather. This in turn has resulted in a number of workshops trying to frame the problem and laying the groundwork to improve our understanding of Arctic-mid-latitude linkages and accurate attribution of extreme weather events. Although these workshops identified existing problems and difficulties, and provided broad recommendations, they did not synthesize the diversified research results to identify where community consensus and gaps exist. Therefore we have assembled many of the leading scientists researching Arctic-mid-latitude linkages as part of a US CLIVAR working group. Through the three-year efforts of this working group, we will use the outcome of the previous workshops and newly planned activities to guide the synthesis efforts, coordinate on-going research to fill out key gaps, and provide specific

  4. 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.

  5. Near-synchronous interhemispheric termination of the last glacial maximum in mid-latitudes.

    PubMed

    Schaefer, Joerg M; Denton, George H; Barrell, David J A; Ivy-Ochs, Susan; Kubik, Peter W; Andersen, Bjorn G; Phillips, Fred M; Lowell, Thomas V; Schlüchter, Christian

    2006-06-09

    Isotopic records from polar ice cores imply globally asynchronous warming at the end of the last glaciation. However, 10Be exposure dates show that large-scale retreat of mid-latitude Last Glacial Maximum glaciers commenced at about the same time in both hemispheres. The timing of retreat is consistent with the onset of temperature and atmospheric CO2 increases in Antarctic ice cores. We suggest that a global trend of rising summer temperatures at the end of the Last Glacial Maximum was obscured in North Atlantic regions by hypercold winters associated with unusually extensive winter sea ice.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. Layering in halocarbons, methane, nitrous oxide, ozone, and water vapour over mid-latitudes

    NASA Technical Reports Server (NTRS)

    Orsolini, Yvan J.; Karcher, Fernand; Manney, Gloria L.; Engel, Andreas; Ovarlez, Joelle; Claud, Chantal

    1997-01-01

    The purpose of the balloon flights performed in March 1993 from Aire-sur-Adour (France) was to measure trace gases in the polar vortex during a dynamically active period. These balloon flights revealed coincident layering in long-lived tropospheric source gases. A layer of mid-latitude air, enriched in trace gases, was detected at sampled levels near 15 mbar. High resolution advection models, fine scale distributions of ozone, nitrous oxide, methane, and halocarbons were constructed. The calculations showed how air enriched in trace gases is sampled near 15 mbar when a filament of such air is drawn into the outer portion of the vortex.

  11. Layering in halocarbons, methane, nitrous oxide, ozone, and water vapour over mid-latitudes

    NASA Technical Reports Server (NTRS)

    Orsolini, Yvan J.; Karcher, Fernand; Manney, Gloria L.; Engel, Andreas; Ovarlez, Joelle; Claud, Chantal

    1997-01-01

    The purpose of the balloon flights performed in March 1993 from Aire-sur-Adour (France) was to measure trace gases in the polar vortex during a dynamically active period. These balloon flights revealed coincident layering in long-lived tropospheric source gases. A layer of mid-latitude air, enriched in trace gases, was detected at sampled levels near 15 mbar. High resolution advection models, fine scale distributions of ozone, nitrous oxide, methane, and halocarbons were constructed. The calculations showed how air enriched in trace gases is sampled near 15 mbar when a filament of such air is drawn into the outer portion of the vortex.

  12. Observation of HF radio emission bursts of magnetospheric origin at mid latitudes

    NASA Astrophysics Data System (ADS)

    Dudnik, O. V.

    1999-01-01

    Results of the observations of high frequency radio noises of magnetospheric origin at 150 MHz in 1993 are presented. The radio receiving channel for the registration of radio noises at mid latitudes and the method of data processing are described. Perturbations necessary for generation of radio emission are shown to be transported by irregularities of high-speed solar wind streams toward the Earth's magnetosphere. The possible mechanism of radio bursts generation by precipitating energetic electrons from the Earth's radiation belts during the magnetospheric storms is discussed.

  13. 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.

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

    DOE PAGES

    Jensen, M. P.; Toto, T.; Troyan, D.; ...

    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

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

    SciTech Connect

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

    2015-01-01

    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 instrumentation 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.

  16. Magnetic field fluctuations observed by the Swarm constellation in the nighttime mid-latitude topside ionosphere

    NASA Astrophysics Data System (ADS)

    Park, J.; Luhr, H.; Kervalishvili, G.; Rauberg, J.; Michaelis, I.; Stolle, C.; Kwak, Y. S.

    2015-12-01

    Using single-satellite observations on Low-Earth-Orbits (LEO), some previous studies suggested that electric and magnetic field fluctuations observed in the nighttime mid-latitude ionosphere originate from medium-scale traveling ionospheric disturbances (MSTIDs). With the inherently 1-dimensional sampling, however, those studies could not confirm whether (1) the electric and magnetic field fluctuations are spatial structures rather than temporal variations, and (2) horizontal shapes of the field fluctuation regions generally have mirror symmetry with respect to the magnetic equator, just as MSTIDs do. In this presentation we analyze magnetic field data sampled by three identical Swarm satellites. The results support the idea of a close connection between mid-latitude magnetic fluctuations (MMFs) and MSTIDs in the nighttime sector. Combined with the relationship between MMFs and MSTIDs, the MMF climatology can be used for extending that of MSTIDs, which has been poorly investigated over oceans. In addition, we have conducted a scale size analysis and found that coherence lengths of MMFs are typically shorter than 150 km. We also discuss the possibility that the MMF regions are aligned with the background magnetic field.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Green Sahara impact on mid-latitudes during mid-Holocene

    NASA Astrophysics Data System (ADS)

    Gaetani, Marco; Messori, Gabriele; Pausata, Francesco S. R.; Zhang, Qiong

    2017-04-01

    In the mid-Holocene (6 kyr before present), North Africa was characterised by a vegetated Sahara and a stronger summer monsoon, resulting in a wetter climate. These conditions, induced by the different Earth's orbital parameters, and maintained by the precipitation-vegetation feedback, were associated with a substantial change of the regional atmospheric dynamics, with influences extending across the global Tropics and beyond. In this study, we explore the mid-latitude response to the vegetated Sahara in the mid-Holocene. We use the EC-Earth climate model to simulate the North African environment during mid-Holocene, i.e. extensive vegetation over the Sahara, and a consequent reduced dust emission. Vegetation and dust reduction are prescribed both in combination and in isolation, to determine the specific responses to the individual forcings. A significant response at mid-latitudes is simulated during boreal summer, when the precipitation-vegetation feedback is maximum in the Sahara. Results show increased precipitation over Mediterranean and Middle East, and warm anomalies across western Europe. This response is associated with the modification of the atmospheric circulation in the Euro-Atlantic sector. Specifically, the intensification of the subtropical jetstream favours precipitation across the Middle East, while a positive anomaly in the North Atlantic Oscillation leads the warming further west. These results suggest important implications for the understanding of future climate scenarios in the region, since a number of simulations project wetter conditions in North Africa.

  2. The switching between zonal and blocked mid-latitude atmospheric circulation: a dynamical system perspective

    NASA Astrophysics Data System (ADS)

    Faranda, Davide; Masato, Giacomo; Moloney, Nicholas; Sato, Yuzuru; Daviaud, Francois; Dubrulle, Bérengère; Yiou, Pascal

    2016-09-01

    Atmospheric mid-latitude circulation is dominated by a zonal, westerly flow. Such a flow is generally symmetric, but it can be occasionally broken up by blocking anticyclones. The subsequent asymmetric flow can persist for several days. In this paper, we apply new mathematical tools based on the computation of an extremal index in order to reexamine the dynamical mechanisms responsible for the transitions between zonal and blocked flows. We discard the claim that mid-latitude circulation features two distinct stable equilibria or chaotic regimes, in favor of a simpler mechanism that is well understood in dynamical systems theory: we identify the blocked flow as an unstable fixed point (or saddle point) of a single basin chaotic attractor, dominated by the westerlies regime. We also analyze the North Atlantic Oscillation and the Arctic Oscillation atmospheric indices, whose behavior is often associated with the transition between the two circulation regimes, and investigate analogies and differences with the bidimensional blocking indices. We find that the Arctic Oscillation index, which can be thought as a proxy for a hemispheric average of the Tibaldi-Molteni blocking index, tracks unstable fixed points. On the other hand, the North Atlantic Oscillation, representative only for local properties of the North Atlantic blocking dynamics, does not show any trace of the presence of unstable fixed points of the dynamics.

  3. The role of cloud parameterizations on high- and mid-latitude teleconnections

    NASA Astrophysics Data System (ADS)

    Mills, C. M.; Kravitz, B.; Yoon, J.; Rasch, P. J.; Wang, H.

    2016-12-01

    Climate models often overestimate autumn and winter Arctic cloudiness. One method suggested for correcting this bias is known as the "Freezedry" (FD) parameterization (Vavrus and Waliser, 2008), which reduces Arctic cloud cover during episodes of very low humidity. This parameterization is found to amplify teleconnections between Arctic ice loss and mid-latitude winter storm strength and frequency. Here we use a neural network categorization technique to better understand the physical mechanisms of the amplified teleconnections and its implications for real-world responses to sea ice loss associated with Arctic amplification. We find that the FD parameterization reduces wintertime cloud fraction, creating colder wintertime near-surface air temperatures. There are hence stronger upward sensible heat fluxes in areas of open water, which build ridges that propagate downstream into the mid-latitudes. The connections highlight the importance of accurate high-latitude cloud treatments to capture these teleconnections and argue for continued attention to these features as more complex parameterizations of cloud amount and cloud microphysics are introduced in climate models.

  4. 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

    2016-10-01

    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.

  5. Mid-latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Astrophysics Data System (ADS)

    Minow, J. I.; Willis, E. M.; Parker, L. N.

    2014-12-01

    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 (~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 ~30 degree to ~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.

  6. Longitudinal structure in electron density at mid-latitudes: upward-propagating tidal effects

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Zhang, Kedeng

    2017-01-01

    This work studies the upward-propagating migrating and non-migrating tidal effects from the lower atmosphere on the longitudinal variation of electron density (Δ Ne) in both the E and F regions at mid-latitudes during the 2002 March equinox. A total of 12 runs are conducted using the Thermosphere Ionosphere Electrodynamic General Circulation model for theoretical investigation. The Δ Ne at altitudes above 200 km is affected by upward-propagating tides, with maximum values attained around 300 km. Migrating tides result in reduced longitudinal differences in the Δ Ne over North America and in the Southern Hemisphere, while non-migrating tides induce a wave-4 pattern in both hemispheres. The non-migrating effect is weaker than the migrating effect after penetrating into the F region. The neutral composition (i.e., ratio of atom oxygen to molecular nitrogen) is dominant in regulating the Δ Ne in both the migrating (accounting for approximately 64%) and non-migrating (about 60%) tidal penetration processes. The Δ Ne caused by the tidal meridional wind (accounting for approximately 70%) is stronger than the tidal zonal wind (about 30%) under both the migrating and non-migrating tidal conditions, except in the Southern Hemisphere under migrating tidal input. This work contributes to our understanding of the mechanisms for the longitudinal modulation of the Δ Ne at mid-latitudes.[Figure not available: see fulltext.

  7. Mercury depletion events in the troposphere in mid-latitudes at the Dead Sea, Israel.

    PubMed

    Peleg, Mordechai; Matveev, Valeri; Tas, Eran; Luria, Menachem; Valente, Ralph J; Obrist, Daniel

    2007-11-01

    The occurrence of mercury depletion events (MDE) in the Polar Regions during the spring periods has raised global concern due to the biomagnifications of the deposited mercury into the aquatic food chain. However, it now appears that MDE is not limited to the Polar Regions and can also occur at mid-latitudes. Diurnal cycles of mercury, ozone, and BrO behavior based on short-time resolution measurements are presented for the Dead Sea, Israel, for Summer 2006. The results show that mercury depletion events occur almost daily, accompanied always by the presence of BrO and concurrent ozone destruction. The intensity of the MDE corresponded to increasing BrO levels. Mercury depletions of more than 40% were observed when BrO levels rose above 60-70 ppt. Based on the present measurements and supported bytheoretical considerations, it appears that BrOx (BrO + Br) is the primary species responsible for the mercury depletion at the Dead Sea. The present study also suggests, especially at low ozone levels, that the Br atom may play a major role in conversion of the gaseous elemental mercury to the reactive species, HgBr2. The implications of the present study are that even at low BrO levels (<10 ppt), mercury depletion may well occur at other mid-latitude sites and thus needs to be taken into consideration in the global mercury cycle.

  8. Coherent and incoherent scatter radar observations during intense mid-latitude spread F

    NASA Astrophysics Data System (ADS)

    Swartz, Wesley E.; Kelley, Michael C.; Makela, Jonathan J.; Collins, Stephen C.; Kudeki, Erhan; Franke, Steve; Urbina, Julio; Aponte, Nestor; Sulzer, Michael P.; González, Sixto A.

    2000-09-01

    An intense mid-latitude spread-F event occurred over Puerto Rico during the night of February 17, 1998. Simultaneous observations were made with the Cornell University Portable Radar Interferometer (CUPRI) located near Isabela, PR, the University of Illinois VHF radar located at Salinas, PR, GPS receivers at Isabela and St. Croix, measuring total electron content, the Arecibo incoherent scatter radar, and the Cornell All-Sky imager located at the Arecibo Observatory. This was the first time that such a broad range of complementary instrumentation captured a mid-latitude spread-F space weather event. It was the first (and still only) time that a spread-F event over the Caribbean exhibited large Doppler shifts in the VHF spectra. This event was characterized with multiple filaments that initially produced receding Doppler velocities exceeding 300 m/s as seen by CUPRI and the Illinois radar. The Arecibo incoherent scatter radar recorded line-of-sight velocities exceeding 100 m/s that moved the F-layer peak to over 400-km altitude. Airglow images of 630.0 nm emissions from F-region heights showed depleted structures oriented southeast to northwest. The large velocities observed with the radars suggest that we caught this event in a stage of explosive development. It is interesting that the first fully documented Caribbean event occurred during a magnetically active period.

  9. 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

  10. Temperature beneath continents as a function of continental cover and convective wavelength

    NASA Astrophysics Data System (ADS)

    Phillips, Benjamin R.; Coltice, Nicolas

    2010-04-01

    Geodynamic modeling studies have demonstrated that mantle global warming can occur in response to continental aggregation, possibly leading to large-scale melting and associated continental breakup. Such feedback calls for a recipe describing how continents help to regulate the thermal evolution of the mantle. Here we use spherical mantle convection models with continents to quantify variations in subcontinental temperature as a function of continent size and distribution and convective wavelength. Through comparison to a simple analytical boundary layer model, we show that larger continents beget warming of the underlying mantle, with heating sometimes compounded by the formation of broader convection cells associated with the biggest continents. Our results hold well for purely internally heated and partially core heated models with Rayleigh numbers of 105 to 107 containing continents with sizes ranging from that of Antarctica to Pangea. Results from a time-dependent model with three mobile continents of various sizes suggests that the tendency for temperatures to rise with continent size persists on average over timescales of billions of years.

  11. Representation of Precipitation in a Decade-long Continental-Scale Convection-Resolving Climate Simulation

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The representation of moist convection and the associated precipitation 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. A new version of the Consortium for Small-Scale Modeling weather and climate model (COSMO), capable of exploiting new supercomputer architectures, allows convection-resolving climate simulations on computational domains spanning continents and time period up to one decade. We present results from a decade-long, convection-resolving climate simulation on a European-scale computational domain. The simulation has a grid spacing of 2.2 km, 1536x1536x60 grid points, covers the period 1999-2008, and is driven by the ERA-Interim reanalysis. Specifically we present an evaluation of hourly rainfall using a wide range of data sets, including several rain-gauge networks and a remotely-sensed lightning data set. Substantial improvements are found in terms of the diurnal cycles of precipitation amount, wet-hour frequency and all-hour 99th percentile or in terms of the frequency-intensity distributions. However the results also reveal substantial differences between regions with and without strong orographic forcing. Furthermore we present an index for deep-convective activity based on the statistics of vertical motion. Comparison of the index with lightning data shows that the convection-resolving climate simulations are able to reproduce important features of the annual cycle of deep convection in Europe. Leutwyler, D., Lüthi, D., Ban, N., Fuhrer, O., and Schär, C.: Evaluation of the Convection-Resolving Climate Modeling Approach on Continental Scales, J. Geophys. Res. Atmos., in revision. Leutwyler, D., Fuhrer, O., Lapillonne, X., Lüthi, D., and Schär, C

  12. 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.

  13. 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

  14. TEC differences for the mid-latitude ionosphere in both sides of the longitudes with zero declination

    NASA Astrophysics Data System (ADS)

    Xu, J. S.; Li, X. J.; Liu, Y. W.; Jing, M.

    2014-09-01

    Based on measurements of ground-based GPS station network, differences of the mid-latitude ionospheric TEC in the east and west sides of North America, South America and Oceania have been analyzed in this paper. Results show that for nearly all seasons from 2001 to 2010 and in both sides of the longitudes with zero declination, there exist systematic differences for the mid-latitude ionospheric TEC in the regions mentioned above and the features of these differences markedly depend upon the local time but less depend upon seasons and the level of solar activity. Theory analysis shows that the longitude variations of both declination and zonal thermospheric winds are one of important factors to cause differences of the mid-latitude ionospheric TEC in both sides of the longitudes with zero declination.

  15. 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.

  16. 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.

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

    PubMed

    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

    2005-03-17

    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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Climate change. The weakening summer circulation in the Northern Hemisphere mid-latitudes.

    PubMed

    Coumou, Dim; Lehmann, Jascha; Beckmann, Johanna

    2015-04-17

    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.

  5. 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.

  6. First observations of coherent scatter from the mid-latitude F-region in the Caribbean

    NASA Astrophysics Data System (ADS)

    Swartz, Wesley E.; Makela, Jonathan J.; Kelley, Michael C.

    2000-04-01

    The Cornell University Portable Radar Interferometer (CUPRI) started a new series of measurements of the mid-latitude ionosphere from Puerto Rico in July 1997. On the first day of operation, coherent echoes were obtained from the F region. This was the first detection of such echoes in this longitude sector. This is surprising since the MU radar has seen similar eches over Japan and the presence of related phenomena in the Caribbean suggested they should have been seen in other VHF studies. A number of F-region events were subsequently observed. Some echoes were characterized with very narrow spectra and small mean Doppler shifts. Two events had echoes whose range changed rapidly with time, but only one of these had comparable Doppler velocities. Such differences suggest that we caught the events in different stages of development. In addition to presenting samples of the data, we outline the reasons why these structures were anticipated.

  7. Arctic Change and Mid-latitude Weather Extremes in the CESM Large Ensemble Project

    NASA Astrophysics Data System (ADS)

    Peings, Y.; Cattiaux, J.; Magnusdottir, G.

    2015-12-01

    In this work we explore the linkage between the Arctic amplification (the fact that surface temperature in the Arctic is increasing twice as fast as elsewhere) and atmospheric modes of variability such as the Northern Annular mode (NAM) using the simulations from the CESM large ensemble project. Ensemble members span the 1920-2100 period, using historical forcing (1920-2005) and RCP8.5 forcing (2006-2100). We examine the change in occurrence of extreme events in the mid-latitudes at the end of the 21st century, especially for cold spells in winter. Possible links between trends in the NAM, jet stream variability, storm tracks, atmospheric blocking, etc... and the amplitude of the 21st-century Arctic amplification in each member of the large ensemble are investigated.

  8. Solar activity dependence of low-and mid-latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Chen, Yiding; Liu, Libo; Wan, Weixing

    Solar activity dependence of low-and mid-latitude ionosphere is investigated using ionosonde and the ROCSAT-1 satellite (600 km) observations. The pattern in the solar activity varia-tion of the electron density shows significant local time, seasonal, latitudinal, and altitudinal dependences. Noontime NmF2 saturates with F107 in all seasons in low-latitude regions, while it saturates with F107 in equinoxes and local summer and linearly increases with F107 in local winter in mid-latitude regions. Nighttime NmF2 nearly increases with F107 linearly in equinox seasons and saturates with F107 in local summer, what is peculiar is that there is an amplifica-tion trend of nighttime NmF2 with F107 in local winter. We discussed the possible mechanisms which affect the solar activity variation trend of NmF2 and argued that the changes of neutral atmosphere and ionospheric dynamics are important for the solar activity variation trend of NmF2. Solar activity variations of the plasma density at 600 km present three kinds of patterns (linearity, amplification, and saturation), the pattern depends on local time, season, and lati-tude. That is different from the case at higher altitudes, e.g., 800 km, where the amplification trend prevails. In particular, saturation effect is found in the dip equator region at equinox sunset. Latitudinal distribution of the plasma density at 600 km also depends on local time, season, and solar activity level. Around sunset, a profound double-peak structure is found in the latitudinal distribution of the plasma density in solar maximum equinox and December solstice months. Solar activity dependence of the low-latitude topside ionosphere at 600 km is strongly related to the low-latitude dynamics processes.

  9. 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").

  10. Cluster classification of mid-latitude summer circulation patterns in the CESM1 Large Ensemble

    NASA Astrophysics Data System (ADS)

    Horton, D. E.; Mankin, J. S.; Singh, D.; Diffenbaugh, N. S.; Swain, D. L.

    2016-12-01

    Synoptic- to regional-scale circulation patterns drive daily surface weather conditions, while the occurrence and persistence of particular circulation patterns can have an outsized influence on the likelihood of hot, cold, wet, and/or dry extremes. Recent theoretical work has posited that increasing atmospheric greenhouse gas concentrations may exert some influence on mid-latitude circulation pattern behavior, though detection of such changes in observational analyses is likely to be challenging due to the natural variability of the climate system. To assess the influence of altered levels of radiative forcing on the behavior of atmospheric circulation patterns in the context of internal variability, we utilize pre-industrial, historical, and future simulations from the CESM1 Large Ensemble (LENS) Community Project single-model, multi-realization framework. Using self-organizing map clustering analysis, we classify summer mid-atmospheric circulation patterns over select regional mid-latitude Northern Hemisphere domains in each LENS experiment. For each region in each LENS experiment we calculate and compare the full distribution of summer pattern occurrence and duration, in addition to high-impact extreme (maximum) pattern persistence for each modeled year. Our results indicate little to no change in the left-tails and mean occurrence and duration of circulation patterns as increasing levels of radiative forcing are assessed. However, robust changes in the extreme right-tails of the duration and maximum persistence distributions are prevalent. Patterns in which robust right-tail changes are identified are diverse, with cyclonic, anticyclonic, zonal, and dipole patterns all represented. Our results indicate that in CESM1 LENS circulation changes due to increasing radiative forcing exist, but only in the potentially high impact tails of the distribution.

  11. 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.

  12. 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.

  13. Modelled glacier equilibrium line altitudes during the mid-Holocene in the southern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Bravo, C.; Rojas, M.; Anderson, B. M.; Mackintosh, A. N.; Sagredo, E.; Moreno, P. I.

    2015-03-01

    Glacier behaviour during the mid-Holocene (MH, 6000 year BP) in the Southern Hemisphere provides observational data to constrain our understanding of the origin and propagation of palaeo-climatic signals. We examine the climatic forcing of glacier expansion in the MH by evaluating modelled glacier equilibrium line altitude (ELA) and climate conditions during the MH compared with pre-industrial time (PI, year 1750) in the mid latitudes of the Southern Hemisphere, specifically in Patagonia and the South Island of New Zealand. Climate conditions for the MH are obtained from PMIP2 models simulations, which in turn force a simple glacier mass balance model to simulate changes in equilibrium-line altitude during this period. Climate conditions during the MH show significantly (p ≤ 0.05) colder temperatures in summer, autumn and winter, and significantly (p ≤ 0.05) warmer temperatures in spring. These changes are a consequence of insolation differences between the two periods. Precipitation does not show significant changes, but exhibits a temporal pattern with less precipitation from August to September and more precipitation from October to April during the MH. In response to these climatic changes, glaciers in both analysed regions have an ELA that is 15-33 m lower than PI during the MH. The main causes of this difference are the colder temperature during the MH, reinforcing previous results that mid-latitude glaciers are more sensitive to temperature change compared to precipitation changes. Differences in temperature have a dual effect on mass balance. First, during summer and early autumn less energy is available for melting. Second in late autumn and winter, lower temperatures cause more precipitation to fall as snow rather than rain, resulting in more accumulation and higher surface albedo. For these reasons, we postulate that the modelled ELA changes, although small, may help to explain larger glacier extents observed in the mid Holocene in both South America

  14. Solar Transients Disturbing the Mid Latitude Ionosphere during the High Solar Activity

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Shivangi; Khan, Parvaiz A.; Atulkar, Roshni; Malvi, Bhupendra; Mansoori, Azad Ahmad; Purohit, P. K.

    2016-10-01

    We investigate the effect of solar transients on the mid latitude ionosphere during the high solar activity period of solar cycle 23 i.e 2003 and 2004. A mid latitude station, Guangzhou (23.1N, 113.4E) was selected to carry out the investigation. The ionospheric behaviour at the selected station is characterized by considering the critical frequency of F2 layer (foF2) obtained by using the ground based Ionosonde observations. Then we selected two types of solar transients viz. solar flares and Coronal Mass Ejections (CMEs). To quantify the effect of solar flares we have considered the X-ray flux (1-8 Å) and EUV flux (26-34nm). Similarly to quantify the effect of CMEs, we have considered the geomagnetic storms, because during high solar activity the geomagnetic storms are caused by CMEs. From our analysis we conclude that during the geomagnetic storms the value of foF2 decreases as compared to quiet days thereby showing a negative effect. On the contrary we found that during solar flares there is sudden and intense increase in foF2. We also performed a correlation analysis to access the magnitude of association between changes in flux values and peak values of Dst during flares and storms with the corresponding changes and peak values of foF2. We found that a strong correlation exists between the enhancements/decrements in foF2 and enhancements in flux values and Dst. We conclude, while geomagnetic activity suppresses ionospheric activity the flares enhance the same.

  15. Spatial Distribution of the Errors in Modeling the Mid-Latitude Critical Frequencies by Different Models

    NASA Astrophysics Data System (ADS)

    Kilifarska, N. A.

    There are some models that describe the spatial distribution of greatest frequency yielding reflection from the F2 ionospheric layer (foF2). However, the distribution of the models' errors over the globe and how they depend on seasons, solar activity, etc., are unknown till this time. So the aim of the present paper is to compare the accuracy in describing the latitudinal and longitudinal variation of the mid-latitude maximum electron density, of CCIR, URSI, and a new created theoretical model. A comparison between the above mentioned models and all available from Boulder's data bank VI data (among 35 deg and 70 deg) have been made. Data for three whole years with different solar activity - 1976 (F_10.7 = 73.6), 1981 (F_10.7 = 20.6), 1983 (F_10.7 = 119.6) have been compared. The final results show that: 1. the areas with greatest and smallest errors depend on UT, season and solar activity; 2. the error distribution of CCIR and URSI models are very similar and are not coincident with these ones of theoretical model. The last result indicates that the theoretical model, described briefly bellow, may be a real alternative to the empirical CCIR and URSI models. The different spatial distribution of the models' errors gives a chance for the users to choose the most appropriate model, depending on their needs. Taking into account that the theoretical models have equal accuracy in region with many or without any ionosonde station, this result shows that our model can be used to improve the global mapping of the mid-latitude ionosphere. Moreover, if Re values of the input aeronomical parameters (neutral composition, temperatures and winds), are used - it may be expected that this theoretical model can be applied for Re or almost Re-time mapping of the main ionospheric parameters (foF2 and hmF2).

  16. Solar ultraviolet doses and vitamin D in a northern mid-latitude.

    PubMed

    Serrano, Maria-Antonia; Cañada, Javier; Moreno, Juan Carlos; Gurrea, Gonzalo

    2017-01-01

    Solar ultraviolet (UV) radiation is one of the most important factors in the development of skin cancer in human, solar erythema and skin aging. Nevertheless, numerous studies have shown the benefits of UV solar radiation in moderate doses, such as the reduction of blood pressure and mental health, treatment of various diseases, and the synthesis of vitamin D in the skin. This paper analyses data from solar ultraviolet erythemal (UVER) irradiance in W/m(2) measured in a northern mid-latitude as Valencia (Spain) for the period 2003-2010. To estimate effective solar UV radiation in the production of vitamin D (UVD) we used the relationship proposed by McKenzie et al. (2009). It was obtained for one month for each season the minimum exposure time needed around solar noon and at 9 UTC and 15 UTC (Coordinated Universal Time) to obtain the recommended daily dose of 1000IU. Also, it has been calculated time for erythema induction around solar noon for the same months. The median UVER daily dose during the summer months was 4000J/m(2)day, and 700J/m(2)day in winter. With regard to UVD, the median UVD daily dose in summer season was 7700J/m(2)day, and in winter it was 1000J/m(2)day. Around noon in January it takes more than two hours of solar exposure to obtain the recommended daily dose of vitamin D, whereas the rest of the year range between 7min on July and 31min on October. For the same months around noon, exposure times to produce erythema were obtained, these being of higher value to the previous. The results show that it is difficult to obtain the recommended vitamin D doses in winter in a northern mid-latitude, as the human body is almost entirely covered in this season.

  17. 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

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

    SciTech Connect

    Seager, Richard

    2014-09-20

    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.

  19. 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.

  20. Explaining darker deep convective clouds over the western Pacific in comparison to tropical continental regions

    NASA Astrophysics Data System (ADS)

    Sohn, B.; Choi, M.

    2013-12-01

    A recent study, based on analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) solar channel measurements, reports that deep convective clouds (DCCs) over the western Pacific are found to be darker than DCCs over continental tropical regions such as Africa and South America. This phenomenon is quite interesting although an immediate attempt to explain the reason may be the different cloud microphysics within the deep convective clouds between land and ocean. However, in fact, attempt has not made what causes such difference. In this study, aiming at understanding why DCCs over the western Pacific show generally lower reflectivity in comparison to tropical African and South American regions, regional differences in optical properties of DCCs are examined using Cloud Profile Radar (CPR) onboard CloudSat and Cloud Aerosol Lidar Infrared Pathfinder Satellite Observation (CALIPSO) measurements. Analysis of four January months of 2007-2010, demonstrates that there are distinct difference in ice water path (IWP) between the western Pacific and other two continental regions. Also found is small but meaningful differences in the effective radius. Results lead to a conjecture that smaller IWP over the western Pacific is the main cause inducing smaller reflectance. Radiative transfer experiments investigating what optical parameters of DCCs are responsible for the darker clouds over the western Pacific make it clear that smaller ice water content available in the western Pacific is the main cause.

  1. 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

  2. Stagnant lid convection and carbonate metasomatism of the deep continental lithosphere

    NASA Astrophysics Data System (ADS)

    Sleep, Norman H.

    2009-11-01

    The current (and past) mantle adiabat beneath continents is hot enough that ascending carbonate-rich domains partially melt liberating kimberlites. Over the last 2 Ga, most of these kimberlites have been trapped and frozen in the deep continental lithosphere, forming a massive CO2 reservoir. Geochemical studies of kimberlites that reached the surface indicate the pervasiveness of their effects within the deep lithosphere. These magmas extensively reacted with the deep lithosphere on the way up. Conversely, studies of deep mantle xenoliths brought up in kimberlites detect repeated episodes of metasomatism by these fluids. The heat balance between convection and conduction through the lithosphere provides gross constraints on the cumulative global effects of this process. Stagnant lid (including chemical lid) convection supplies heat to the base of continental lithosphere in equilibrium with the conductive heat flow. The thermal gradient beneath continents is constrained by xenolith geotherms and mantle heat flow q is ˜20 mW m-2. The upwelling velocity V at the base of the thermal boundary layer is ˜q/TηρC, where ρC is volume specific heat, 4 MJ m-3 and Tη is the temperature to change viscosity by a factor of e, ˜60 K. The upwelling velocity is thus ˜2 km per million years; the mass of the mantle circulates beneath continents over ˜2 Ga. The rate that plate tectonics recirculates the mantle is comparable and limits the supply carbonate-rich undepleted material to the melting zone of upwelling stagnant lid convection and thus the production of kimberlites. Overall the amount of CO2 emplaced by kimberlites into continental lithosphere is a significant fraction (˜1/2) of that in the convecting mantle, resulting in a major deep lithospheric reservoir of CO2 of ˜5000 × 1018 moles, an equivalent thickness of ˜2 km carbonatized rock. This process, however, is insufficient to affect the overall density of deep lithosphere. The observed linearity of the xenolith

  3. 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

  4. Post-rift influence of small-scale convection on the landscape evolution at divergent continental margins

    NASA Astrophysics Data System (ADS)

    Sacek, Victor

    2017-02-01

    After decades of geological and geophysical data acquisition along with quantitative modeling of the long-term evolution of the landscape at divergent continental margins, the search for an explanation for the formation and evolution of steep escarpments bordering the coast is still a challenging task. One difficult aspect to explain about the evolution of these escarpments is the expressive variability of denudation rate through the post-rift phase observed in many margins. Here I propose that the interaction of small-scale convection in the asthenosphere with the base of the continental lithosphere can create intermittent vertical displacements of the surface with magnitude of a few hundreds of meters at the continental margin. These topographic perturbations are sufficient to produce an expressive variability in the rate of erosion of the landscape through the post-rift phase similar to the exhumation history observed along old divergent margins. I show that the vertical motion of the surface is amplified when a mobile belt is present at the continental margin, with lithospheric mantle less viscous than the cratonic lithosphere and, consequently, more prone to be partially eroded by the convective asthenosphere. I conclude that the influence of small-scale convection is not the primary explanation for the formation of high topographic features at divergent continental margins, but can be an important component contributing to sustain a preexistent escarpment. The present results are based on numerical simulations that combine thermochemical convection in the mantle, flexure of the lithosphere and surface processes of erosion and sedimentation.

  5. 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.

  6. 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

  7. 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

  8. New evidence for geothermal controls upon recent basal melting of mid-latitude glaciers on Mars

    NASA Astrophysics Data System (ADS)

    Butcher, Frances; Gallagher, Colman; Arnold, Neil; Balme, Matthew; Conway, Susan; Lewis, Stephen; Hagerman, Axel

    2017-04-01

    Diagnostic evidence for past melting of putative debris-covered glaciers (DCGs) in Mars' mid-latitudes [e.g. 1-2] is extremely rare. As such, it is widely believed that these DCGs have been perennially frozen to their beds in cold-based thermal regimes [e.g. 3] since their formation 40 Ma to 1 Ga [4-8]. Here, we present a geomorphic map and propose a landsystem model that challenges this paradigm. We identify a sinuous ridge emerging from the terminus of a DCG in the broad rift zone NE of the Tharsis volcanic province. We interpret this ridge as an esker formed by deposition of sediment within a subglacial meltwater conduit. This is only the second esker-like ridge to be identified in association with a mid-latitude DCG. Recent work [9] identified a complex of esker-like ridges on the foreland of an extant DCG in Phlegra Montes, for which high-resolution analysis is ongoing [10]. Significantly, both candidate eskers are located within graben. Graben are topographic troughs formed by crustal extension and are commonly associated with elevated geothermal heat flux [e.g. 11]. A paucity of meltwater morphologies associated with DCGs elsewhere in Mars' mid-latitudes implies that atmospheric warming alone was insufficient for widespread basal melting. We argue that, during deglaciation, atmospheric warming supplemented enhanced geothermal heat flux within graben such that the basal temperature threshold for basal melting of DCGs was surpassed in these locations [9]. This has implications for the search for recent life on Mars, as it helps constrain the likely regions of recent meltwater production within protected subglacial environments. As eskers are exposed relicts of subglacial drainage systems, they are accessible to landed missions without the high-risk requirement to drill through remnant decametre-thick debris-mantled ice. FEGB is funded by STFC grant ST/N50421X/1 [1] Head, J.W. et al. (2010), Earth Planet. Sc. Lett. 294, 306-320. [2] Levy, J.S. et al. (2014), J

  9. 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

  10. Historical deforestation increased the risk of heat extremes in northern mid-latitudes

    NASA Astrophysics Data System (ADS)

    Lejeune, Quentin; Davin, Edouard; Gudmundsson, Lukas; Winckler, Johannes; Seneviratne, Sonia

    2017-04-01

    During the industrial period, large areas in the world have experienced a reduction in forest cover and an expansion of agricultural areas. Some modelling studies showed that this has significantly affected the intensity of temperature extremes through changes in biophysical land surface properties (Christidis et al. 2013, Pitman et al. 2012), however they exhibit a low level of agreement about its overall climate impact. Besides, even if they generally point toward an albedo-induced cooling over deforested mid-latitudes, this does not align with recent observational evidence suggesting that deforestation has a local daytime warming effect, especially in summer (Lee et al. 2011). Here, for the first time we intend to constrain CMIP5 models with observations in order to assess the contribution of historical deforestation to changes in the risk of warm extreme events. To do so, we have selected five models from the CMIP5 ensemble that can reproduce the observed local warming effect of deforestation during daytime in summer. Our results indicate that deforestation played a primary role in the evolution of hot extremes since preindustrial time. We quantify that a decrease in tree cover by at least 15% locally increased the intensity of the 99th percentile of daily maximum temperature (corresponding to the 3-4 hottest days of the year) by 0.6°C over northern mid-latitudes, accounting for 30-40% of their total warming. Moreover, it amplified the increase in their frequency due to the greenhouse gas forcing by 30%. Our results imply that land-cover changes need to be considered when studying past and future changes in heat extremes, in particular for regional-scale detection and attribution purposes. References: Christidis, N., P. A. Stott, G. C. Hegerl, and R. A. Betts, The role of land use change in the recent warming of daily extreme temperatures (2013), Geophysical Research Letters, 40, 589-594 Pitman, A. J., et al., Effects of land cover change on temperature and

  11. 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.

  12. Young Mid-latitude Martian Valleys: Evidence from Newton and Gorgonum Basins

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    The mid-latitudes of Mars feature distinctive landforms, including extensive mantling deposits, glacial and periglacial landforms, very young gullies on steep slopes, and sparse, shallowly-incised, fresh-appearing valleys discussed here. These mid-latitude valleys (MLVs) are distinct from the older, late Noachian to early Hesperian valley systems which are deeply dissected, generally of much larger spatial extent and which feature multiple tributaries. The older valley systems extend from equatorial to near-polar latitudes and are much more degraded than the MLVs. Although some MLVs involve rejuvenation of older valley networks, many MLVs are eroded into smooth or rolling slopes and intercrater terrain. The MLVs range from a few meters to more than 300 m in width, with nearly parallel valley walls and planforms that are locally sinuous. Valley floors appear to be nearly flat, sometimes exhibiting faint lineations. These features suggest that the MLVs in many cases are incised channels that were occupied at least intermittently by flows over the entire valley bottom. Particularly diagnostic MLVs occupy parts of the floors of the ~ 300 km Newton and the ~240 km Gorgonum basins on the southern highlands. In Newton basin the MLVs are sourced from the upper basin walls and flow radially inwards towards the basin center, extending across the smooth basin floor (which may have been the site of an earlier paleolake). Incised and depositional sections sometimes alternate in response to variations in basin slope. The valleys terminate in small fans. In some places the valleys appear to anastomose, but it is likely that the multiple valleys record successive flow diversions. There is no evidence that the valleys terminated in standing water in the basin center. MLVs in Gorgonum basin likewise are sourced from the upper basin walls and flow inward, but in this case the valleys disappear at the edge of what has previously been hypothesized to be a late stage, ice-covered lake

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

    NASA Astrophysics Data System (ADS)

    DeWayne Cecil, L.; Vogt, Stephan

    1997-03-01

    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 1994-1995, 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.

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. Impact of radiosonde data over the Arctic ice on forecasting winter extreme weather over mid latitude

    NASA Astrophysics Data System (ADS)

    Sato, Kazutoshi; Inoue, Jun; Yamazaki, Akira; Kim, Joo-hong; Maturilli, Marion; Dethloff, Klaus; Hudson, Stephen

    2016-04-01

    In February 2015, the Arctic air outbreak caused extreme cold events and heavy snowfall over the mid latitude, in particular over the North America. During the winter, special radiosonde observations were made on the Norwegian RV Lance around the north of Svalbard under the N-ICE2015 project. We investigated the impact of the radiosonde data on forecasting of a cold extreme event over the eastern North America using the AFES-LETKF experimental ensemble reanalysis version2 (ALERA2) data set. ALERA2 was used as the reference reanalysis (CTL) while the observing-system experiment (OSE) assimilated the same observational data set, except for the radiosonde data obtained by the RV Lance. Using these two reanalysis data as initial values, ensemble forecasting experiments were conducted. Comparing these ensemble forecasts, there were large differences in the position and depth of a predicted tropopause polar vortex. The CTL forecast well predicted the southward intrusion of the polar vortex which pushed a cold air over the eastern North America from the Canadian Archipelago. In the OSE forecast, in contrast, the trough associated with southward intrusion of the polar vortex was weak, which prevented a cold outbreak from Arctic. This result suggested that the radiosonde observations over the central Arctic would improve the skill of weather forecasts during winter.

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

    PubMed

    Francis, Jennifer; Skific, Natasa

    2015-07-13

    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.

  1. Modification of the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation

    NASA Astrophysics Data System (ADS)

    Head, James W.; Nahm, Amanda L.; Marchant, David R.; Neukum, Gerhard

    2006-03-01

    Restoration of the dichotomy boundary to its original position to assess its origin requires a thorough knowledge of processes responsible for its degradation and retreat. The unique fretted terrain, located along the Deuteronilus-Protonilus Mensae northern mid-latitude portion of the boundary, has been long held to provide clues to dichotomy degradation processes. We use new spacecraft data to show that fretted valleys display a multitude of characteristics typical of integrated valley glacial systems on Earth (multiple theater-headed, alcove-like accumulation areas; sharp arete-like ridges typical of glacial erosion; converging patterns of downslope valley flow; valley lineation patterns typical of folding and shear; wrap-around features indicative of flow around obstacles; and broad piedmont-like lobes as the valley fill extends out into the northern lowlands). The single integrated system containing these features covers about 30,000 km2, and is one of dozens of fretted valleys along the dichotomy boundary in this region. These relationships suggest that the boundary area was subjected to very large-scale regional glaciation during the Amazonian. Recognition and documentation of this important late-stage process provides information critical to reconstructing the original dichotomy boundary.

  2. Mastodon herbivory in mid-latitude late-Pleistocene boreal forests of eastern North America

    NASA Astrophysics Data System (ADS)

    Teale, Chelsea L.; Miller, Norton G.

    2012-07-01

    Skeletal remains of the extinct American mastodon have often been found with deposits of short, decorticated twigs intermixed with plant fragments presumed to be gastrointestinal or fecal material. If such deposits are digesta, paleobotanical evidence may be used to analyze mastodon foraging strategy, with implications for assessing habitat selection, ecological roles, and response to environmental change. To identify components of mastodon diet in mid-latitude late-Pleistocene boreall forests of eastern North America, plant macrofossils and pollen from a molar socket (Hyde Park site, New York) were compared with dispersed deposits associated with skeletal remains (Hiscock and Chemung sites, New York). Similar macrofossil condition and twig morphology among samples, but difference from a modern boreal fen analog, confirmed the deposits were digesta. Comparison of twigs with material from other paleontological sites and modern elephants suggested dimensions generally indicative of digesta. Picea formed the bulk of each sample but Pinus may have been locally important. Wintertime browsing of Salix and Populus, and springtime consumption of Alnus, were indicated. Evidence for Cyperaceae, Gramineae, and Compositae was ambiguous. If conifers, broadleaf trees, shrubs, and herbs were necessary to fulfill dietary requirements, mastodons would have been nutritionally stressed by rapid late-Pleistocene decrease in vegetational diversity.

  3. Simulation experiments with late quaternary carbon storage in mid-latitude forest communities

    SciTech Connect

    Solomon, A.M.; Tharp, M.L.

    1984-01-01

    The assumption was tested that forest biomass in communities on the modern landscape is equivalent to that in similar communities on the late-Quaternary landscape. Forest carbon storage dynamics during the past 16,000 years were derived from a mathematical model of forest processes and individual tree species behavior. Modern pollen and climate data sets provided pollen-climate transfer functions to generate model driving variables from fossil pollen records. Climate variables were estimated from fossil pollen stratigraphies in Tennessee, Ohio, and Michigan. Only simulated early postglacial warming produced the large carbon gains one would expect in mixed deciduous-coniferous forests from unglaciated regions. The simulated mid-Holocene warming generated little carbon storage response by temperate deciduous forests and large carbon gains in northern hardwood-conifer forests, unlike the linear relationship expected when equivalence is assumed between modern and prehistoric forests. Late-glacial, mid-latitude forests may have contained more biomass than would be expected from equivalent forests on the modern landscape. Simulations of alternate hypotheses to explain the enhanced late-glacial cannot distinguish effects of reduced seasonal temperature extremes from effects of changing species' temperature tolerances. 84 references, 5 figures, 2 tables.

  4. Evaluating hydrological influences on mid-latitude δ18Op in the Middle East

    NASA Astrophysics Data System (ADS)

    Reuter, Justin; Buenning, Nikolaus; Yoshimura, Kei

    2017-07-01

    The oxygen isotope ratio of precipitation (δ18Op) in the mid-latitudes varies in response to multiple climate influences imposing significant challenges to the interpretation of climate proxies such as the oxygen isotope ratio of lake and speleothem calcite (δ18Oc) that incorporates an isotopic finger print of precipitation. This challenge is particularly acute for pre-historic time periods when climate forcings differed significantly from modern and consequently, internal feedbacks altered the transport of moisture as well as the rate of fractionation that determine the isotopic composition of atmospheric moisture. Here we investigate how δ18Op from the mid-Holocene was influenced by internal feedbacks in the Holocene with an isotope-enabled climate model that simulates the atmospheric response to changing boundary conditions and different climatic forcing. We find that δ18Op during the Mid-Holocene was lower than present day consistent with published proxy records. However, this lower value cannot be simply explained by basic isotope drivers such as precipitation amount or seasonality. Rather, we find that the combination of changes in local surface temperature, precipitation amount, upstream isotopic composition of vapor as well as the season can quantitatively explain the isotopic differences between the mid-Holocene and present day.

  5. Testing the water hypothesis: Quantitative morphological analysis of terrestrial and martian mid-latitude gullies

    NASA Astrophysics Data System (ADS)

    Hobbs, S. W.; Paull, D. J.; Clarke, J. D. A.

    2017-10-01

    Although Martian gullies resemble terrestrial counterparts, two conflicting hypotheses exist for their formation still invoke fluvial processes on the one hand or lubricated CO2 flows on the other. In this work we compared the quantitative morphology of terrestrial gullies, known to have formed by liquid water, and mid-latitude Martian gullies in the Martian southern hemisphere. We also compared these results with measurements of Martian dry ravines adjacent to the gullies. Our results show a similarity between Martian and terrestrial gully formation, supporting the hypothesis that liquid water was involved in their erosion. Our results show dry ravines differ morphologically from gullies, further suggesting fluidised flows as a likely origin of the latter. Variations in the relationships across various terrestrial and Martian gullies indicate the significance of local environmental and geological conditions. Our work supports the idea that Martian gullies may not have been formed by just one single process but may have evolved through a more complex interaction of processes and environment.

  6. Pitted Terrain on Dwarf Planet Ceres: Morphological Evidence for Shallow Volatiles at Low and Mid Latitudes

    NASA Astrophysics Data System (ADS)

    Sizemore, H. G.; Platz, T.; Prettyman, T. H.; Schorghofer, N.; Mest, S. C.; Crown, D. A.; Yingst, R. A.; Schenk, P.; Bland, M. T.; Schmidt, B. E.; De Sanctis, M. C.; Schmedemann, N.; Tosi, F.; Hughson, K.; Raymond, C. A.; Russell, C. T.

    2016-12-01

    The Dawn spacecraft entered orbit around Ceres, the largest body in the asteroid belt, on March 5, 2015. Over its first 16 months at Ceres, the spacecraft obtained morphological, topographical, mineralogical, elemental, and gravity data through a series of successively lower orbits. Framing Camera (FC) images from High Altitude Mapping Orbit (HAMO) and Low Altitude Mapping Orbit (LAMO) have provided global coverage of Ceres' morphology at pixel scales of 140 m/px and 35 m/px respectively. In the FC dataset we have identified distinct pitted terrains, characterized by clusters of round-to-irregular, rimless or low-rimmed pits in smooth crater materials. We describe the morphology, setting, and geographic distribution of these pitted materials, which exhibit striking similarities to pitted materials previously discovered by Dawn at Vesta1, and pitted materials identified in low-and mid-latitude martian craters2. We discuss likely production mechanisms for the cerean pitted materials, as well as implications for the geographic distribution and concentration of shallow volatiles on Ceres. 1Denevi, et al. 2012. Science, 338, 246-249. 2Tornabene, et al. 2012. Icarus, 220, 348-368.

  7. 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.

  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. 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.

  10. 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

  11. 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.

  12. 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.

  13. Seasonal and interannual variability of mesospheric gravity wave activity at high and mid-latitudes

    NASA Astrophysics Data System (ADS)

    Hoffmann, Peter; Singer, Werner; Becker, Erich; Latteck, Ralph; Keuer, Dieter

    The seasonal variation and interannual variability of the gravity wave activity in the mesosphere/lower thermosphere (MLT) region at high and mid-latitudes is investigated. Variations of the gravity wave activity are examined in relation to the filtering processes due to the changes of the background winds, tides and planetary waves. Our studies are basing on wind measurements from meteor and MF radars at Andenes (69° N, 16° E) and Juliusruh (55° N, 13° E). These measurements are supplemented by mesospheric temperatures derived from meteor decay times. Additionally, turbulent energy dissipation rates have been estimated from spectral width measurements using a 3 MHz Doppler radar near Andenes. Particular attention is directed to the influence of the solar activity on the gravity wave activity during the summer months when the mesospheric winds show the strongest correlation with the solar activity. Possible dependencies between the occurrence rates of polar mesospheric summer echoes (PMSE) and the gravity wave activity are discussed. Furthermore, the activity of gravity waves and their dissipation are investigated in winter in relation with wind changes during sudden stratospheric warming (SSW) events. The summer/ winter behavior of the gravity wave activity will be compared to simulations with the simple general circulation model KMCM (K¨hlungsborn Mechanistic u Circulation Model) that extends up to 100 km. In all cases, the percentage rates of the kinetic energy of defined period ranges in relation to the total variances of the horizontal wind fluctuations are estimated.

  14. 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.

  15. 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 (

  16. Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene

    NASA Astrophysics Data System (ADS)

    Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.

    2014-12-01

    Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.

  17. 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.

  18. Substantial stores of sedimentary carbon held in mid-latitude fjords

    NASA Astrophysics Data System (ADS)

    Smeaton, Craig; Austin, William E. N.; Davies, Althea L.; Baltzer, Agnès; Abell, Richard E.; Howe, John A.

    2016-10-01

    Quantifying marine sedimentary carbon stocks is key to improving our understanding of long-term storage of carbon in the coastal ocean and to further constraining the global carbon cycle. Here we present a methodological approach which combines seismic geophysics and geochemical measurements to quantitatively estimate the total stock of carbon held within marine sediment. Through the application of this methodology to Loch Sunart, a fjord on the west coast of Scotland, we have generated the first full sedimentary carbon inventory for a fjordic system. The sediments of Loch Sunart hold 26.9 ± 0.5 Mt of carbon split between 11.5 ± 0.2 and 15.0 ± 0.4 Mt of organic and inorganic carbon respectively. These new quantitative estimates of carbon stored in coastal sediments are significantly higher than previous estimates. Through an area-normalised comparison to adjacent Scottish peatland carbon stocks, we have determined that these mid-latitude fjords are significantly more effective as carbon stores than their terrestrial counterparts. This initial work supports the concept that fjords are important environments for the burial and long-term storage of carbon and therefore should be considered and treated as unique environments within the global carbon cycle.

  19. 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.

  20. Enhanced stratospheric water vapor over the summertime continental United States and the role of overshooting convection

    NASA Astrophysics Data System (ADS)

    Herman, Robert L.; Ray, Eric A.; Rosenlof, Karen H.; Bedka, Kristopher M.; Schwartz, Michael J.; Read, William G.; Troy, Robert F.; Chin, Keith; Christensen, Lance E.; Fu, Dejian; Stachnik, Robert A.; Bui, T. Paul; Dean-Day, Jonathan M.

    2017-05-01

    The NASA ER-2 aircraft sampled the lower stratosphere over North America during the field mission for the NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS). This study reports observations of convectively influenced air parcels with enhanced water vapor in the overworld stratosphere over the summertime continental United States and investigates three case studies in detail. Water vapor mixing ratios greater than 10 ppmv, which is much higher than the background 4 to 6 ppmv of the overworld stratosphere, were measured by the JPL Laser Hygrometer (JLH Mark2) at altitudes between 16.0 and 17.5 km (potential temperatures of approximately 380 to 410 K). Overshooting cloud tops (OTs) are identified from a SEAC4RS OT detection product based on satellite infrared window channel brightness temperature gradients. Through trajectory analysis, we make the connection between these in situ water measurements and OT. Back trajectory analysis ties enhanced water to OT 1 to 7 days prior to the intercept by the aircraft. The trajectory paths are dominated by the North American monsoon (NAM) anticyclonic circulation. This connection suggests that ice is convectively transported to the overworld stratosphere in OT events and subsequently sublimated; such events may irreversibly enhance stratospheric water vapor in the summer over Mexico and the United States. A regional context is provided by water observations from the Aura Microwave Limb Sounder (MLS).

  1. The Role of Overshooting Convection in Elevated Stratospheric Water Vapor over the Summertime Continental United States

    NASA Astrophysics Data System (ADS)

    Herman, R. L.; Ray, E. A.; Rosenlof, K. H.; Bedka, K. M.; Schwartz, M. J.; Read, W. G.; Troy, R. F.

    2016-12-01

    The NASA ER-2 aircraft sampled the UTLS region over North America during the NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission. On four flights targeting convectively-influenced air parcels, in situ measurements of enhanced water vapor in the lower stratosphere over the summertime continental United States were made using the JPL Laser Hygrometer (JLH Mark2). Water vapor mixing ratios greater than 10 ppmv, twice the stratospheric background levels, were measured at pressure levels between 80 and 160 hPa. Through satellite observations and analysis, we make the connection between these in situ water measurements and overshooting cloud tops. The overshooting tops (OT) are identified from a SEAC4RS OT detection product based on satellite infrared window channel brightness temperature gradients. Back-trajectory analysis ties enhanced water to OT one to seven days prior to the intercept by the aircraft. The trajectory paths are dominated by the North American Monsoon (NAM) anticyclonic circulation. This connection suggests that ice is convectively transported to the overworld stratosphere in OT events and subsequently sublimated; such events may irreversibly enhance stratospheric water vapor in the summer over Mexico and the United States. Regional context is provided by water observations from the Aura Microwave Limb Sounder (MLS).

  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. 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)

  4. The life cycle of continental rifts: Numerical models of plate tectonics and mantle convection.

    NASA Astrophysics Data System (ADS)

    Ulvrova, Martina; Brune, Sascha; Williams, Simon

    2017-04-01

    Plate tectonic processes and mantle convection form a self-organized system whose surface expression is characterized by repeated Wilson cycles. Conventional numerical models often capture only specific aspects of plate-mantle interaction, due to imposed lateral boundary conditions or simplified rheologies. Here we study continental rift evolution using a 2D spherical annulus geometry that does not require lateral boundary conditions. Instead, continental extension is driven self-consistently by slab pull, basal drag and trench suction forces. We use the numerical code StagYY to solve equations of conservation of mass, momentum and energy and transport of material properties. This code is capable of computing mantle convection with self-consistently generated Earth-like plate tectonics using a pseudo-plastic rheology. Our models involve an incompressible mantle under the Boussinesq approximation with internal heat sources and basal heating. Due to the 2D setup, our models allow for a comparably high resolution of 10 km at the mantle surface and 15 km at the core mantle boundary. Viscosity variations range over 7 orders of magnitude. We find that the causes for rift initiation are often related to subduction dynamics. Some rifts initiate due to increasing slab pull, others because of developing trench suction force, for instance by closure of an intra-oceanic back-arc basin. In agreement with natural settings, our models reproduce rifts forming in both young and old collision zones. Our experiments show that rift dynamics follow a characteristic evolution, which is independent of the specific setting: (1) continental rifts initiate during tens of million of years at low extension rates (few millimetres per year) (2) the extension velocity increases during less than 10 million years up to several tens of millimetres per year. This speed-up takes place before lithospheric break-up and affects the structural architecture of rifted margins. (3) high divergence rates

  5. Spectrum analysis of short-period K index behaviour at high and mid-latitudes

    NASA Astrophysics Data System (ADS)

    Kotzé, P. B.

    2015-01-01

    Geomagnetic activity levels during the declining phase and solar minimum period of the solar cycle are considerably different from those during the solar maximum phase. Previous studies revealed variations in the pattern of recurrent activity from cycle to cycle as well as variations in the average geomagnetic activity levels during a solar cycle. During the declining phase of a solar cycle (and solar minimum), the solar and interplanetary causes of geomagnetic activity are substantially different from those during the solar maximum phase. Co-rotating fast solar wind streams originating from large polar coronal holes, extending towards the Sun's equator, interact with the Earth's magnetosphere, resulting in recurrent geomagnetic activity particularly during solar cycle minimum periods. This is a well-known phenomenon with respect to 27.0- and 13.5-day recurrence geomagnetic activity, and it is well-known to be related to sectorial (non-axial) poloidal magnetic field structure in the Sun. Published results of the recent solar-cycle-23 minimum showed that the presence of 9.0- and 6.7-day recurrent geomagnetic activities can be attributed to the sectorial spherical harmonic structure present in the solar magnetic field. In this study we performed a wavelet and Lomb-Scargle analysis of the geomagnetic activity K index at Lerwick (LER), Hermanus (HER) and Canberra (CNB) for the period between 1960 and 2010, overlapping with solar cycles 20 to 23. Daily mean K indices are used to identify how several harmonics of the 27.0-day recurrent period change during each solar cycle when comparing high and mid-latitude geomagnetic activity, applying a 95% confidence level. In particular the behaviour of the second (13.5-day), third (9.0-day) and fourth (6.7-day) harmonics are investigated by doing a wavelet analysis of each individual year's K indices at each location. Results obtained show that particularly during solar minima the 27.0-day period is no longer detectable above the

  6. Characteristics of mid-latitude planetary waves in the lower atmosphere derived from radiosonde data

    NASA Astrophysics Data System (ADS)

    Wang, R.; Zhang, S. D.; Yang, H. G.; Huang, K. M.

    2012-10-01

    The activities of mid-latitude planetary waves (PWs) in the troposphere and lower stratosphere (TLS) are presented by using the radiosonde data from 2000 to 2004 over four American stations (Miramar Nas, 32.9° N, 117.2° W; Santa Teresa, 31.9° N, 106.7° W; Fort Worth, 32.8° N, 97.3° W; and Birmingham, 33.1° N, 86.7° W) and one Chinese station (Wuhan, 30.5° N, 114.4° E). Statistically, strong PWs mainly appear around subtropical jet stream in the troposphere and lower stratosphere. In the troposphere, the activities of the mid-latitude PWs are strong around the centre of the subtropical jet stream in winter and become small near the tropopause, which indicates that the subtropical jet stream may strengthen the propagation of PWs or even be one of the PW excitation sources. Among the three disturbance components of temperature, zonal and meridional winds, PWs at Wuhan are stronger in the temperature component, but weaker in the zonal wind component than at the other four American stations. While in the meridional wind component, the strengths of PW spectral amplitudes at the four American stations decrease from west to east, and their amplitudes are all larger than that of Wuhan. However, the PWs are much weaker in the stratosphere and only the lower frequency parts remain. The amplitudes of the PWs in the stratosphere increase with height and are strong in winter with the zonal wind component being the strongest. Using the refractive index, we found that whether the PWs could propagate upward to the stratosphere depends on the thickness of the tropopause reflection layer. In the case study of the 2000/2001 winter, it is observed that the quasi 16-day wave in the troposphere is a quasi standing wave in the vertical direction and propagates upward slowly with vertical wavelength greater than 24 km in the meridional component. It propagates eastward with the zonal numbers between 5 and 8, and the quasi 16-day wave at Wuhan is probably the same quasi 16-day

  7. Investigation of the Accuracy of Ionospheric Models at Mid-Latitudes: Examining Ionospheric Metrics

    NASA Astrophysics Data System (ADS)

    Eccles, V.; Sojka, J. J.; Gonzalez, S.; Fuller-Rowell, T. J.; Howsden, M.

    2004-12-01

    The electron density specification of the ionosphere is the key parameter supporting many operational products. To assess the accuracy of tools based on space weather models of the ionosphere one must know the accuracy of the underlining models. We are developing a software/database package to assess the accuracy of ionospheric models. The package will be placed at the Community Coordinated Modeling Center (CCMC). Initial focus is on the mid-latitude ionosphere as observed by the Arecibo Incoherent Scatter Radar (ISR). This ISR database has extensive ionospheric coverage over variability in solar cycle, season, local time, and geomagnetic activity. The assessments of models need to be based on careful constructed metric definitions to compare the model specifications with the ISR "ground truth." Our goals for the assessment tool are (1) to provide reliable, metric assessment of models for users represented by agencies of the Nation Space Weather Program and, (2) to provide the scientific community with an assessment of conditions when models are adequate and inadequate. The second implementation plan of the NSWP (2000) has established the priority of metrics and has specified these metrics. We begin with the NSWP ionospheric metrics as a reasonable starting place, but examine other strategies to assess ionosphere weather specifications through several new metric definitions for the F region. We present our initial studies on the weaknesses and benefits of several different metric definitions for F region profile accuracy. Three models will be use in the metric assessment (1) the physics-based Ionospheric Forecast Model (IFM), (2) the physics-based and Coupled Thermospheric-Ionospheric-Plasmasphere-electrodynamics Model (CTIPe), and (3) the empirical International Reference Model (IRI). Central to creating reliable metric results is the need to quantify the quality and accuracy of the "ground truth" ISR database. Metric issues associated with ISR operational modes

  8. 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.

  9. 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.

  10. 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.

  11. Changes of benthic fauna in the Kattegat - An indication of climate change at mid-latitudes?

    NASA Astrophysics Data System (ADS)

    Göransson, Peter

    2017-07-01

    Several predictions point to changes in the marine benthic macrofauna associated with climate change, but so far only a few and minor changes have been reported. This study relates observed changes in the species composition to climate change by looking on the past decades in the Kattegat between Denmark and Sweden. A reduction of the total number species and a reduction of species with a northern range parallel to an increase of species with a southern range have been observed. The most likely explanation of the changes is the increase in temperature of the bottom water. Increased temperature could change the species distributions but also decrease primary production which impacts recruitment and growth. Hypoxia and bottom trawling could also act synergistic in this process. A sparse occurrence of previously encountered Arctic-Boreal species and critical foundation species, which gives the area its special character, suggests a change in biodiversity and might therefore be designated as early warning signals of a warmer climate. The northern fauna below the halocline with limited capacity of dispersal and low reproduction potential, can be considered as sensitive with low adaptive capacity to climate change. Therefore, not only tropical and high-latitude species, but also benthos on deep bottoms at mid-latitudes, could be vulnerable to warming. As many species live at the edge of their range in the Kattegat, and also are dependent of distant recruitment, large scale changes will probably be detected here at an early stage. It is important to protect relatively undisturbed reference areas in the Kattegat for future studies, but also for preserving a large number of ecosystem services, biotopes, habitats, and fish species.

  12. Ice supersaturated regions and cirrostratus observations at northern mid latitudes and the tropics

    NASA Astrophysics Data System (ADS)

    Immler, F. J.; Vömel, H.; Schrems, O.

    2009-04-01

    Cirrostratus (Cs) clouds were observed with the mobile Lidar systems MARL and ComCAL during field campaigns in the mid latitudes in 2003 (Lindenberg/Germany, 53∘N, 15∘E) and in the tropics in 2004-2006 (Paramaribo/Suriname, 6∘N, 55∘W). The lidar system MARL and ComCAL are capable of detecting thin cirrus including extremely thin clouds with optical depth below 10-3. This study is based on lidar observations and meteorological data obtained from radiosondes as well as the analysis of the European centre for medium range weather forecast (ECMWF). Cirrostratus are ubiquitous in the midlatitudes (55% coverage) and even more so in the tropics (88% coverage). Humidity measurements in the upper troposphere are difficult to conduct and need careful consideration with respect to systematic errors. We discuss the reliability of radiosonde data based on the data obtained during the Lindenberg Upper Air Method Intercomparison (LUAMI) campaign (Nov 2008) where a number of commercial radiosondes was launched together with reference instruments including the NOAA crygenic frostpoint hygrometer (CFH). Relating the humidity profiles obtained from radiosondes to concurrent lidar observations reveals a close correlation between ice supersaturation and the occurrence of Cs. This leads us to the conclusion that on synoptic scales ice particles are almost always present in supersaturated conditions. The ECMWF cloud parametrization reproduces the observed cirrus clouds consistently and a close correlation between the ice water path in the model and the measured optical depth of cirrus is observed.

  13. Intercomparison of mid latitude storm diagnostics (IMILAST) - synthesis of project results

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2017-04-01

    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, e.g. data transformation, metrics used for cyclone identification, cyclone identification procedures or tracking methods. The project IMILAST systematically compares different cyclone detection and tracking methods, with the aim to comprehensively assess the influence of different algorithms on cyclone climatologies, temporal trends of frequency, strength or other characteristics of cyclones and thus quantify systematic uncertainties in mid-latitudinal storm identification and tracking. The three main intercomparison experiments used the ERA-interim reanalysis as a common input data set and 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 the third experiment, the intercomparison period has been 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) or specific phenomena like splitting and merging of cyclones. In addition, the representation of storms and their characteristics in reanalysis data sets is examined to further enhance the knowledge on uncertainties related to storm occurrence. This poster presents a synthesis of the main results from the intercomparison activities within IMILAST.

  14. Jetstream Influences on Landfalling Atmospheric Rivers in the Mid-latitudes

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Atmospheric rivers (ARs) serve as key players in the globe's hydrological cycle by transporting large amounts of moisture and link the subtropics to the mid-latitudes. Extratropical cyclones provide the basis for the dynamical component while the oceans influence moisture content. Coastal regions that fall within the AR track experience multi-day extreme precipitation events that ultimately contributes to regional water resources. However, not all ARs are created equal. ARs have different flavors around the globe. For example, the U.S. West Coast (Pineapple Express) and Atlantic Basin ARs (both the UK and Iberian peninsula) have dynamical characteristics such as the role of mean circulations and local jets. How the atmospheric circulation changes in a warming world will dictate how ARs change. Here, we analyze ARs using the half-degree fully coupled Community Climate System Model, Version4, CCSM4, in an ensemble suite of historical and RCP8.5 (Representative Concentration Pathway) simulations. The higher resolution in the atmosphere and land components provides important improvements in the climatology of ARs and associated extreme precipitation. Our AR tracking algorithm uses a unique moisture threshold calculated for each time step using maximum and mean values for each latitude band; an important requirement that uses a relative tracking method thus accounting for increases in moisture simply due to the Clausius-Claperyon relationship. Changes to the subtropical and eddy-driven jets in a warming world, their variance with season, and their influences on AR climatology, will be presented for a variety of regions (e.g., U.S. West Coast, UK, Iberian Peninsula). Modes of natural atmospheric variability, such as PNA and AO, will also be considered in the context landfalling ARs.

  15. 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.

  16. Progressive Mid-latitude Afforestation: Impacts on Clouds, Circulation, and the Global Energy Budget

    NASA Astrophysics Data System (ADS)

    Lague, M.; Swann, A. L. S.

    2015-12-01

    Vegetation influences the atmosphere in complex and non-linear ways. Large-scale changes in vegetation can drive changes in climate on both local and global scales. Interactions between the land and atmosphere are controlled by shifts between terms controlling the surface energy budget. Depending on the magnitude and location of land surface changes, imbalances in energy at large spatial scales can be introduced which shift atmospheric circulation on a global scale. Various studies have explored the impacts of large area changes in vegetation, but how the climate response scales with the area of vegetation change has not been demonstrated. Here, we systematically evaluate the response of climate to linearly increasing the area of forest cover over the northern mid-latitudes. We show that global circulation changes the atmospheric cross-equatorial energy transport in a linear fashion with respect to the area of afforestation (a relationship which has not previously been demonstrated). We also identify how vegetation-induced changes in cloud cover further feedback on changes in the global energy balance - a concept that has been largely ignored in most large-scale vegetation manipulation experiments. The changes in atmospheric energy transport induced by vegetation changes result in remote shifts in precipitation; the relationship between the change in energy transport and the shift in tropical precipitation is shown to be model dependent. Our results highlight the importance of considering both local and remote effects of large-scale vegetation change, and explore how the effects of vegetation change on climate scale with the area of land surface changed. We demonstrate how vegetation changes can modify the surface energy budget both directly and through impacts on cloud cover through land-atmosphere interactions.

  17. A study of the daytime E-F sub 1 region ionosphere at mid-latitudes

    SciTech Connect

    Buonsanto, M.J. )

    1990-06-01

    A photochemical equilibrium daytime model is used to study the ionosphere between 110 and 180 km at mid-latitudes. The model includes the latest photoionization and photoabsorption cross sections, extreme untraviolet (EUV) fluxes in 37 wavelength bands, and all reactions believed to be important in this region. Model results are compared with (1) noon-time E layer critical frequency (foE) at Boulder and Wallops Island over a full solar cycle; (2) Millstone Hill incoherent scatter radar observations of electron density at 180 km (N{sub 180}) for a wide variety of seasons and solar geophysical conditions; (3) selected Millstone Hill incoherent scatter profiles of electron density between 110 and 180 km which included E-F{sub 1} valley minima; and (4) the ratio of the molecular ion concentration to the total ion concentration at 180 km for noon throughout the solar cycle as given by both the IRI-86 ion composition model and the semiempirical ion composition model of Oliver. Best agreement between the photochemical model documented in this paper and the observations and ion composition models is generally obtained if (1) the EUV fluxes in the photochemical model are increased by 25-30% above values derived from published reference spectra; (2) neutral densities used in the photochemical model are decreased by 25% below those given by MSIS-86 at equinox, with larger decreases in winter, and smaller or no decreases in summer. The results show that this region of the ionosphere can be modeled with reasonable success given the current state of knowledge. Modeling this region of the ionosphere is important for resolving ambiguities in true height analysis of ionograms and reduction of incoherent scatter spectra. Improved modeling requires more accurate values of aeronomical parameters, i.e., ionizing fluxes, cross sections, reaction rates, composition and temperature.

  18. Daytime Observations of Mid-latitude Sporadic-E and QP Radar Echoes

    NASA Astrophysics Data System (ADS)

    Pfaff, R. F.; Liebrecht, C.; Urbina, J.; Kudeki, E.

    2007-12-01

    Although sporadic-E layers and quasi-periodic (QP) radars are typically detected during nighttime conditions at mid-latitudes, they also may exist in the daytime lower ionosphere as well. We present observations of ionosonde observations of daytime sporadic-E layers gathered at the Wallops Flight Facility, Virginia, in the late morning to noon local times. The data reveal sporadic-E characteristics similar to nighttime observations including considerable variations in frequency and altitude. For one event, observed on 23 July 1999 near 14 U.T. (10 L.T.), we present coincident strong Wallops ionosonde sporadic-E observations and 50MHz backscatter radar observations of quasi-periodic echoes gathered with the University of Illinois radar situated at Ft. Macon, N.C., whose beam was perpendicular to the magnetic field in the lower E-region over Wallops. The radar data show daytime QP structuring that is very similar to the nighttime observations, suggesting a similar driving mechanism. A statistical survey of the daytime ionogram data at Wallops shows a preponderance of daytime sporadic-E events occurring during the local summer months, a seasonal dependence that is well-established for nighttime sporadic-E conditions in the northern hemisphere. No clear correlation is observed between the daytime sporadic-E events and magnetic storms, suggesting that the daytime sporadic-E events are not necessarily driven by the disturbance dynamo. Rather, we speculate that the same large wind shears that are believed to be the main engine for the nighttime sporadic-E and QP echoes, may also be at work during the daytime. The existence of enhanced plasma density layers during the daytime and their role in generating QP- echoes during the day remain open questions.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Using Carbon Isotopes in Cenozoic Soil Carbonates to Quantify Primary Productivity from Mid-Latitude Regions

    NASA Astrophysics Data System (ADS)

    Caves, J. K.; Kramer, S. H.; Ibarra, D. E.; Chamberlain, C. P.

    2015-12-01

    The carbon isotope composition of pedogenic carbonates (δ13Ccarb) from paleosols has been extensively used as a proxy to estimate atmospheric pCO2 over the Phanerozoic. However, a number of other factors - including the concentration of plant-respired CO2 and the isotopic composition of both atmospheric and plant-respired carbon - influence the δ13C of pedogenic carbonates. For example, δ13Ccarb records from the mid-latitudes in central Asia and western North America show increasing trends in δ13Ccarb despite decreasing pCO2 during the late Cenozoic, which suggests that other factors play an important role in determining the isotopic composition of pedogenic carbonates. Instead, we suggest that these records are primarily recording changes in primary productivity rather than changes in atmospheric pCO2 and therefore propose a novel use of paleosol carbonate records to understand paleo-ecosystem dynamics. Here, we compile existing paleosol carbonate records, and present three new records from Wyoming, to estimate soil respiration and primary productivity in western North America during the Paleogene and early Neogene. We observe both an overall increase in δ13Ccarb after the early Eocene, and spatially heterogeneous δ13Ccarb values across western US basins. We combine this δ13Ccarb data with compilations of atmospheric pCO2 to estimate soil respiration and plant productivity. The long-term increase in δ13Ccarb indicates a decrease in plant productivity as conditions became more arid across much of the western US, congruent with both records of regional uplift and of global cooling. Furthermore, significant spatial heterogeneity in δ13Ccarb indicates that regional factors, such as the presence of paleolakes and/or local paleotopography may have provided a second-order control on local and regional productivity. Thus, our results provide a first-order estimate linking changes in primary productivity with regional tectonics and global climatic change.

  4. Mid-Latitude Lightning NOx Production from OMI and WWLLN Data

    NASA Astrophysics Data System (ADS)

    Bucsela, E. J.; Pickering, K. E.; Allen, D. J.; Holzworth, R.; Krotkov, N. A.

    2015-12-01

    Mid- and upper- tropospheric NOx (NO + NO2) is a trace gas important in atmospheric radiative forcing through its regulation of ozone concentrations. Changes in NOx and ozone result in indirect effects on other greenhouse gases such as methane. Lightning is the dominant source of NOx in the free troposphere, and most estimates of the concentration of lightning NOx (LNOx) require knowledge of the amount of this species produced per lightning flash. We present the largest spatial- and temporal-scale investigation of LNOx to date that combines satellite-based NOx estimates and lightning flash data. The data comprise five northern-hemisphere (NH) summers, including much of the mid-latitude regions in North America and Asia and adjacent waters. NO2 measurements from the Ozone Monitoring Instrument (OMI), selected from cloudy areas, are converted to LNOx and compared with flashes preceding OMI overpass by 1 - 4 hours. The flash counts are derived from ground-based World Wide Lightning Location Network (WWLLN) data that are adjusted for detection efficiency by comparing them with Optical Transient Detector and Lightning Imaging Sensor satellite data. We find reasonable correlation between the number of lightning flashes and the amount of LNOx produced and estimate mean efficiencies for the production of LNOx in various NH regions. Overall results indicate mole/flash values near the low end of those reported in previous LNOx studies, as well as a possible dependence of production efficiency on flash rate. These findings have potential implications for upper tropospheric trace gases and the global NOx budget.

  5. Phlegra Montes - Spatio-Temporal Distribution of Ice and Debris at Martian Mid-Latitudes

    NASA Astrophysics Data System (ADS)

    Schulz, J.; van Gasselt, S.; Orgel, C.

    2014-04-01

    Mars hosts an abundance of landforms indicative of near-subsurface ice. Lobate debris aprons belong to a group of well-studied but still enigmatic ice-related landforms which have been identified at mid-latitudes between 30o and 50o in both hemispheres. While nature and origin of ice in these aprons are still controversially debated there is a general consensus that these features are sensitive to climate variability and, consequently, a potential indicator of past climate conditions, and potential water reservoirs today. The northern hemisphere hosts three populations of debris aprons: the Tempe Terra/Mareotis Fossae(TT) region [2, 5], the Deuteronilus/Protonilus Mensae (DPM) [1, 4, 9], and the Phlegra Montes region (PM) [3]. In southern latitudes the impact-basins rims of Argyre (AP) and Hellas Planitiae/Promethei Terra (HP) host a similar, albeit less well-pronounced set of features [1, 2, 6]. While most research is being concentrated on the HP, TT and DPM areas, studies discussing the population of the PM (located at 165o E, 30-50o N, see figure 1) are rather sparse [3, 14, 15, 16] although features are generally well-developed, representative due to their spatial distribution and wellimaged by high-resolution instruments. We performed an integrated spatio-temporal analysis of the PM population and focus on the age distribution of debris aprons in order to constrain their formation age. Our research is motivated by the assumption that if young-Amazonian climate variations have controlled formation and appearance of geomorphic landforms on Mars, we should observe traces of this process in PM as latitudinal trends and variations should provide measurable characteristics. If so, and if surface ages based on crater-frequency analysis are consistent with these assumptions, the exact timing of climate shifts may be assessable.

  6. Ionospheric variations during sudden stratospheric warming in the high- and mid-latitude regions

    NASA Astrophysics Data System (ADS)

    Yasyukevich, Anna; Voeykov, Sergey; Mylnikova, Anna

    2017-04-01

    The ionospheric dynamic in the high- and middle-latitude regions during the periods of sudden stratospheric warmings (SSW) was studied by using the international network of phase dual-frequency GPS/GLONASS receivers and the vertical sounding data. Twelve SSW events that occurred in the Northern Hemisphere 2006 through 2013 were considered. In order to identify the possible response of the ionosphere to SSW events, we carried out the analysis of the total electron (TEC) and the F2-layer maximum electron density (NmF2) deviations from the background level. We have also studied changes of the level of total electron content (TEC) wave-like variations characterized by a special index WTEC. The index reflects the intensity of medium- and large-scale traveling ionospheric disturbances. The dynamics of the high- and middle-latitude ionosphere at the points near the SSW areas was found to differ from the regular. For a large number of events, it is shown that, despite quiet geomagnetic conditions, a noticeable decrease in the NmF2 and TEC values (by 5-10% relative to the background level) is observed during the SSW evolution and maximum stages. On the contrary, for 10-20 days after the SSW maxima, NmF2 and TEC significantly exceed the monthly averaged values. Moreover, these electron density changes are observed for both strong and weak stratospheric warmings, and are recorded mainly during daytime. The observed SSW effects in the polar and mid-latitude ionosphere are assumed to be probably associated with the changes in the neutral composition at the thermospheric heights that affect the F2-layer electron density. The study is supported by the Russian Foundation for Basic Research under Grant No. 16-35-60018, as well as by the RF President Grant of Public Support for RF Leading Scientific Schools (NSh-6894.2016.5).

  7. 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.

  8. 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.

  9. 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.

  10. Intercomparison of mid latitude storm diagnostics (IMILAST) - overview of project results

    NASA Astrophysics Data System (ADS)

    Neu, Urs

    2016-04-01

    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, e.g. data transformation, metrics used for cyclone identification, cyclone identification procedures or tracking methods. The project IMILAST systematically compares different cyclone detection and tracking methods, with the aim to comprehensively assess the influence of different algorithms on cyclone climatologies, temporal trends of frequency, strength or other characteristics of cyclones and thus quantify systematic uncertainties in mid-latitudinal storm identification and tracking. The three main intercomparison experiments used the ERA-interim reanalysis as a common input data set and 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 the third experiment, the intercomparison period has been 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) or specific phenomena like splitting and merging of cyclones. In addition, the representation of storms and their characteristics in reanalysis data sets is examined to further enhance the knowledge on uncertainties related to storm occurrence. This poster presents an overview of some of the main results from the intercomparison activities within IMILAST.

  11. 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.

  12. 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.

  13. Examining The Effects of Huge Sunspots of 7 January 2014 over Local TEC Variation in Mid-Latitudes

    NASA Astrophysics Data System (ADS)

    Ulukavak, Mustafa; Yalçınkaya, Mualla

    2014-05-01

    The ionosphere is the major contributor of errors in Global Positioning System (GPS). The activity of the Sun is associated with the sunspot cycle and solar flares. Solar activity rises and falls periodically, repeated every 11 years known as a solar cycle. Hence, the ionosphere is the major contributor of errors in Global Positioning System (GPS), especially during the 11-year sunspot cycle. One of the largest sunspots in the last nine years, named AR1944, was captured by NASA's Solar Dynamics Observatory in 01/07/2014. As an important parameter, Total Electron Content (TEC) is appropriate for the study of the Sun-Ionosphere connection. In this study, the mid-latitude IGS stations RINEX observation data was used to determine the local TEC variations. This study monitors the local TEC changes on the effects of sunspots over mid-latitude region in January 7th 2014.

  14. A formula for comparing annual damaging ultraviolet DUV radiation doses at tropical and mid-latitude sites

    NASA Astrophysics Data System (ADS)

    Cutchis, P.

    1980-06-01

    A simple formula is developed in this paper for the relative annual damaging ultraviolet radiation (DUV) dose at different tropical and mid-latitude sites. The formula consists of six multiplicative factors which include the effects of amount of ozone, latitude, altitude, cloudiness, ground albedo, and amount of aerosols. A seasonal ozone variation factor is introduced to modify the tropical relative DUV formula for application to mid-latitude sites. The approach involves correlations of sometimes sparse data, and remains to be validated in the general sense. The formula should be useful, where more exact data are not available, in studies of the effects of solar ultraviolet radiation, and its possible increase from a reduction in stratospheric ozone on land and marine ecological systems and skin cancer incidence in white Caucasian populations.

  15. 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).

  16. Progressive Mid-latitude Afforestation: Local and Remote Climate Impacts in the Framework of Two Coupled Earth System Models

    NASA Astrophysics Data System (ADS)

    Lague, Marysa

    Vegetation influences the atmosphere in complex and non-linear ways, such that large-scale changes in vegetation cover can drive changes in climate on both local and global scales. Large-scale land surface changes have been shown to introduce excess energy to one hemisphere, causing a shift in atmospheric circulation on a global scale. However, past work has not quantified how the climate response scales with the area of vegetation. Here, we systematically evaluate the response of climate to linearly increasing the area of forest cover over the northern mid-latitudes. We show that the magnitude of afforestation of the northern mid-latitudes determines the climate response in a non-linear fashion, and identify a threshold in vegetation-induced cloud feedbacks - a concept not previously addressed by large-scale vegetation manipulation experiments. Small increases in tree cover drive compensating cloud feedbacks, while latent heat fluxes reach a threshold after sufficiently large increases in tree cover, causing the troposphere to warm and dry, subsequently reducing cloud cover. Increased absorption of solar radiation at the surface is driven by both surface albedo changes and cloud feedbacks. We identify how vegetation-induced changes in cloud cover further feedback on changes in the global energy balance. We also show how atmospheric cross-equatorial energy transport changes as the area of afforestation is incrementally increased (a relationship which has not previously been demonstrated). This work demonstrates that while some climate effects (such as energy transport) of large scale mid-latitude afforestation scale roughly linearly across a wide range of afforestation areas, others (such as the local partitioning of the surface energy budget) are non-linear, and sensitive to the particular magnitude of mid-latitude forcing. Our results highlight the importance of considering both local and remote climate responses to large-scale vegetation change, and explore the

  17. Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

    NASA Astrophysics Data System (ADS)

    Dabas, R. S.; Kersley, L.

    2003-12-01

    Nighttime enhancements in ionospheric electron content (IEC)/peak electron density (NmF2) have been studied by various workers in the equatorial anomaly and mid-latitude regions. Such studies give an idea about their enhancement over that location only. In the present study tomographic images over the UK, which give a latitudinal versus height distributions of ionospheric electron density in a much wider area, have been used to study the anomalous increases in nighttime F-region electron density at mid-latitudes. From the analysis of four seasonal representative months (November 1997, March, June and October 1998) data it was noted that the majority of the cases of nighttime enhancements were observed after local midnight, with a maximum between 03:00 04:00 LT in the month of November 1997. Enhancements were observed mostly between 45 50° N latitudes, and their positions are not affected by magnetic activity (Kp ) variations, whereas the separation between the mid-latitude trough and enhancement decreases with increases in magnetic activity. This finding shows that only the trough moves equatorward with the increase in magnetic activity. It is also noted that the electron density gradient from the trough to the enhancement increases with an increase in Kp. Results are discussed in terms of downward plasma transport from the protonosphere to the ionosphere and the nighttime neutral winds.

  18. 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.

  19. An Optical Atmospheric Phenomenon Observed in 1670 over the City of Astrakhan Was Not a Mid-Latitude Aurora

    NASA Astrophysics Data System (ADS)

    Usoskin, I. G.; Kovaltsov, G. A.; Mishina, L. N.; Sokoloff, D. D.; Vaquero, J.

    2017-01-01

    It has recently been claimed (Zolotova and Ponyavin Solar Phys., 291, 2869, 2016; ZP16 henceforth) that a mid-latitude optical phenomenon, which took place over the city of Astrakhan in July 1670, according to Russian chronicles, were a strong aurora borealis. If this were true, it would imply a very strong or even severe geomagnetic storm during the quietest part of the Maunder minimum. However, as we argue in this article, this conclusion is erroneous and caused by a misinterpretation of the chronicle record. As a result of a thorough analysis of the chronicle text, we show that the described phenomenon occurred during the daylight period of the day ("the last morning hour"), in the south ("towards noon"), and its description does not match that of an aurora. The date of the event was also interpreted incorrectly. We conclude that this phenomenon was not a mid-latitude aurora, but an atmospheric phenomenon, the so-called sundog (or parhelion), which is a particular type of solar halo. Accordingly, the claim of a strong mid-latitude aurora during the deep Maunder Minimum is not correct and should be dismissed.

  20. Parameterization of convective clouds, mesoscale convective systems, and convective-generated cirrus

    SciTech Connect

    Cotton, W.R.

    1992-03-03

    A level 2.5w deep convection updraft/downdraft parameterization scheme has been refined and tested against 3D simulations of sea-breeze generated convection over S. Florida. Cases for explicit simulation of MCSs in mid-latitudes and tropics have been encouraging. After a few refinements in those cases, fine resolution explicit simualtions of deep convection and mesoscale, stratiform clouds will be begun.

  1. Geomorphological map of the South Belet region of Titan: An exploration of Mid-Latitude-to-Pole transition zones

    NASA Astrophysics Data System (ADS)

    Schoenfeld, Ashley Marie; M. C Lopes, Rosaly; Malaska, Michael; Solomonidou, Anezina; Birch, Samuel; Hayes, Alexander; Williams, David A.; Janssen, Michael A.; Le Gall, Alice; Turtle, Elizabeth P.; Cassini RADAR Team

    2016-10-01

    We carried out detailed geomorphological mapping of Titan's mid-latitude region south of the Belet Sand Sea. We used radar data collected by Cassini's Synthetic Aperture Radar (SAR) as our basemap, supplemented by spectro-images from VIMS, images from ISS, SARtopo, and microwave emissivity datasets. We mapped at a scale of 1:800,000 in all areas of the South Belet region covered by SAR swaths, taking into consideration the 300 m/pixel resolution of the swaths. For the mid-latitudes, we have defined five broad classes of terrains following Malaska et al. (2016). These terrain classes are craters, hummocky/mountainous, labyrinth, plains, and dunes. We have found that the hummocky/mountainous terrains are the oldest, with a radiometric signature consistent with icy materials. Dunes are the youngest units and return a radiometric signature consistent with organic sediments. The South Belet region of Titan is primarily covered by the dune and plain units (specifically the undifferentiated plains) typical of the mid-latitudes (Malaska et al. 2016). Previous mapping efforts of the mid-latitude regions of Titan (Lopes et al. 2016; Malaska et al. 2016) have indicated that these regions are predominately modified and influenced by aeolian activities. A plain unit designated "scalloped plains" is prominently featured between the 50°S and 60°S latitudes of this region. In this area we also find a terrain unit (dark irregular plains) that has been interpreted as damp materials saturated with liquid hydrocarbons (Malaska et al 2016; Hayes et al. 2008). We also note a higher identification of fluvial channels starting at this latitude zone and extending poleward. We suggest that these features demark the transition zone between mid-latitude/equatorial aeolian-dominated processes and fluvial-dominated processes prevailing at the poles.References: Lopes, R.M.C., et al.: Icarus, 270, 162-182, 2016; Malaska, M., et al.: Icarus, 270, 130-161, 2016; Hayes, A. et al.: Geophys. Res

  2. 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

  3. 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.

  4. Mid-latitude Ionospheric Irregularity Diagnostic Results From Dynasonde Observations at Bear Lake, Utah

    NASA Astrophysics Data System (ADS)

    Zabotin, N. A.; Wright, B.

    2004-12-01

    We use the available time series (11 Feb. 2003 to present) of dynasonde recordings from a mid-latitude (Bear Lake, Utah) location, for a climatological study of small-scale irregularity parameters using our "Phase Structure Function" and "Anomalous Attenuation" methods. Real-time data transfer to NGDC, automatic processing, and display of the data is a result of a shared effort with observatory managers and is supported under NSF project ATM 0125297 and a USAF SBIR project F19628-03-C-0019. The Phase Structure Function method is based on precision measurements of short-period phase variations in totally-reflected radio echoes, as statistically summarized in the temporal structure function, SF. We relate parameters of the SF to the irregularity spectrum parameters by means of diffraction theory. Another diagnostic approach, based on the theory of multiple scattering, predicts a significant level of anomalous attenuation (tens of dBs) of totally-reflected echoes arising from their specific mode of interaction with ionospheric irregularities. Our study of about one year's data yields the following results: a) Characteristic (and different) average diurnal variations are found for E and F regions, and for the seasons. We find evident cause-effect relations between, for example, the sunrise/sunset processes in the ionosphere and irregularity amplitude. b) We have found evidence that the electron density irregularity absolute-amplitude, Δ N, is of more fundamental significance than the relative amplitude Δ N/N for small scales. Clearly, Δ N is less dependent on diurnal variations of average electron density and we find that it has a distinct tendency to preserve its value (on the average) along a magnetic tube, even between E and F regions. c) There is an evident correlation between irregularity amplitude and plasma gradient, in both E and F regions. d) Irregularity amplitude is well correlated with the local magnetic K index at higher latitudes, but not at Bear Lake

  5. 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

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

    NASA Astrophysics Data System (ADS)

    Solomonidou, A.; Lopes, R.; Coustenis, A.; Malaska, M.; Rodriguez, S.; Drossart, P.; Janssen, M. A.; Le Gall, A. A.; Schmitt, B.; Hirtzig, M.; Maltagliati, L.; Sohl, F.; Stephan, K.; Jaumann, R.; Brown, R. H.; Villanueva, E.; Matsoukas, C.; Bratsolis, E.

    2016-12-01

    We investigate the surface of 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 the surface composition [1;2;3]. We examine here the mid-latitude zones extending from 60ºN to 60ºS, which include key geological features identified in [4;5] and [6]: 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, possibly suggesting the presence of surface activity, while a number of other regions such as Hotei Regio and the undifferentiated plains remain unchanged [3]. The surface albedo variations, together with the presence of volcanic-like morphological features, suggest that the active regions are probably 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 [7]. Previous studies [3;5] showed that a variety of surface processes could be linked to the formation of the different geomorphological units (aeolian, fluvial, sedimentary, lacustrine) as well as of the deposition of atmospheric products through the process of photolysis and sedimentation of organics. The surface albedo differences and similarities among the various geomorphological terrains constrain the implications for the geological processes that govern Titan's surface and

  7. Impacts of Climate Change on Permafrost in Mid-Latitude Mountain Regions

    NASA Astrophysics Data System (ADS)

    Frauenfelder, R.; Kaeaeb, A.; Roer, I.; Gruber, S.; Noetzli, J.

    2005-12-01

    Global Climate Models (GCMs) predict significant warming through the 21st Century, with the amplitude of change generally increasing at higher latitudes and higher altitudes. Periglacial permafrost in the European mountains occupies today an area about twice as large as the glacierized area. In order to be able to anticipate and quantify the possible impact of forecast climatic change, it is important to investigate and understand the current conditions and dominant processes in these periglacial areas. In this presentation, we review latest findings about the impact of atmospheric warming in mid-latitude mountain regions, focussing on impacts on creeping debris-ice bodies (i.e. rockglaciers) and on the stability of steep rock faces. In debris covered areas, the reaction to warming temperatures is filtered and occurs through the increase in active layer thickness and melting at the top of the permafrost over periods of years. A warming of the temperature profile within permafrost occurs over the span of decades to centuries. Upward displacement of the base of permafrost to reach a new equilibrium thickness takes centuries to millennia. Spatial modelling of the distribution of permafrost suggest a rise of the lower limit of discontinuous Alpine permafrost of around 100 m during the last 150 years. Borehole measurements show a warming of the permafrost in the upper tens of meters of up to 0.5-0.8°C during recent decades. Rising of the permafrost limit leads to climatic inactivation of creeping bodies presently below the lower limit of permafrost. Warming of the permafrost temperature seems to increase creep rates of active rockglaciers. In comparison with debris-covered slopes, rock faces react quickly to climate change. This is due to the absence of a blocky layer and corresponding direct coupling of surface and sub-surface conditions, combined with a low water content and a small transfer of latent heat during melt. Rising temperatures or the complete thaw of

  8. 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

  9. 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

  10. Impact on Space-Based Navigation Systems of Large Magnetic Storm-Driven Nighttime Flows in the Mid-latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Basu, S.; Makela, J.; Doherty, P.; Wright, J.; Coster, A.

    2008-05-01

    Multi-technique ground and space-based studies conducted during the intense magnetic storm of 7-8 November 2004 yielded a hitherto little-recognized means of impacting space-based navigation systems such as the Federal Aviation Administration's Wide Area Augmentation System (WAAS) that operates in the North American sector. During this superstorm, no appreciable storm-enhanced density gradients were observed. Rather the mid-latitude region was enveloped by the auroral oval and the ionospheric trough within which the sub auroral polarization stream (SAPS) was confined during the local dusk to nighttime hours. This shows that such processes can partially disable GPS-based navigation systems for many hours even in the absence of appreciable TEC gradients, provided an intense flow channel is present in the ionosphere during nighttime hours, as revealed by DMSP and Dynasonde drift results. The competing effects of irregularity amplitude ΔN/N, the background F-region density and the magnitude of SAPS or auroral convection are discussed in establishing the extent of the region of impact on the WAAS system. In order to provide inputs to operational space weather models, the current GPS network used for measuring the total electron content in North America and elsewhere should be augmented by instruments that can measure ionospheric drifts.

  11. 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.

  12. 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

  13. Climate change and Elevational Dependence at a Mid-Latitude Mountain System, Niwot Ridge, Colorado Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Williams, M. W.; Kittel, T.; Hartman, M.; Ackerman, T.; Losleben, M.

    2007-12-01

    Mid-latitude mountain systems are critically sensitive to recent and projected climate change under an elevated greenhouse gas world. It is often taken that climatic change at high elevation sites will reflect those at lower sites - regional warming is assumed to be consistently played out in mountains, or even amplified by the snow-albedo feedback. The anticipated outcome is that the alpine will eventually be "pushed off the top of mountains." There are several reasons why this might not be the case, or at least considerably delayed - one is whether high elevation climates reasonably reflect regional lowland trends or if they are decoupled from them as a result of mountain climatic processes. We evaluated standard climatological variables (minimum & maximum temperature, precipitation) and derived variables [diurnal temperature range, growing season length (using both 0° & -3°C thresholds), and growing degree days (0°C base)] from subalpine (C1, 3048m) and high alpine (D1, 3749m) sites from 1953 to 2006 at Niwot Ridge in Colorado, the longest high- elevation climate record in the US. Over the last 54 years, mean maximum temperature (Tmax) increased through much of the year in the subalpine (trend in annual Tmax=+0.4°C/decade), but in the alpine decreased in early winter (-0.4 to -0.6°C/decade). These patterns resulted in altered seasonal cycles for the two sites, but in different ways: a positive offset in the subalpine (C1) and amplification in the alpine. Precipitation increased at the alpine site from October through April (trend in annual ppt=+100mm/decade), but not during any season in the subalpine. At both sites, summer onset is later and termination earlier, so that the "growing season" has shortened - this reflects long-term tendencies in minimum temperatures. An apparent contradiction is that growing degree-days have gone up at the subalpine site; this due to the positive trend in maximum temperatures. The alpine showed no corresponding trend. An

  14. 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

    semiarid–subhumid conditions 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.

  15. 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.

  16. A case study of subdaily simulated and observed continental convective precipitation: CMIP5 and multiscale global climate models comparison

    NASA Astrophysics Data System (ADS)

    Rosa, D.; Collins, W. D.

    2013-11-01

    We analyze subdaily continental convective precipitation data relative to the Southeastern U.S. from gridded rain gauge measurements, conventional global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive, and a multiscale GCM. GCMs react too quickly to local convective instability and, therefore, overestimate the incidence of middle rainfall events and underestimate the incidence of no, little, and heavy rainfall events. Moreover, GCMs overestimate the persistence of heavy precipitation and underestimate the persistence of no and light precipitation. In general, GCMs with suppression mechanisms in the treatments of convective precipitation compare best with rain gauge derived data and should be trusted more than the others when assessing the risk from extreme precipitation events. The multiscale GCM has the best estimate of the diurnal cycle and a good estimate of heavy rainfall persistence.

  17. 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.

  18. 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

  19. Comparison of Mid-latitude Cyclones in Sea Level Pressure, Gepotential Height and Vorticity Fields

    NASA Astrophysics Data System (ADS)

    Raible, Christoph C.; Blender, Richard; Fraedrich, Klaus

    2013-04-01

    The mid-latitudes are dominated by diurnal variability, which is related to traveling high- and low-pressure systems. The lows or cyclones are a major source of natural hazards. This has led to growing interest in the scientific community to develop Eulerian and Lagrangian measures and to analyze the atmospheric high-frequency variability. One important issue is that there is no straight forward definition of cyclones resulting in a large variety of so-called cyclone detection and tracking methods. Each of these methods relies on different input fields which are related to specific features of a cyclone, e.g., sea level pressure (SLP), which specifically focuses on the mass aspect of the velocity field. Recently, the available methods have been compared with respect to climatology and life cycles using the ERA interim data set (Neu et al. 2013). Based on this study we investigate different fields as input for one specific method. We focus on the three mostly used input data, sea level pressure (SLP), 1000-hPa gepotential height (Z1000) and 850-hPa vorticity (850VOR). The cyclone detection and tracking method developed by Blender et al. (1997) is used and we apply it to ERA interim data in the 1.5 x 1.5 resolution. The method was mainly applied for Z1000 and the Northern Hemisphere (e.g., Blender et al. 1997; Raible et al. 2008). To compare the tracks and cyclone characteristics obtained from the different input data we need to adapt critical parameters of the method in such a way that comparable numbers of cyclone centers are identified in either field. The target is set to the number of cyclone centers in northern hemispheric winter. This enables us to assess the seasonal and hemispheric dependence. Preliminary results show that the agreement between cyclones based on SLP and Z1000 varies between roughly 70 to 80% depending on the season and the hemisphere. Spatially, most of the differences are found around orographic features like Greenland. An interesting

  20. 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

  1. Dissected Mantle Terrain on Mars: Formation Mechanisms and the Implications for Mid- latitude Near-surface Ground Ice

    NASA Astrophysics Data System (ADS)

    Searls, M. L.; Mellon, M. T.

    2008-12-01

    Determining the present and past distribution of surface and subsurface ice on Mars is critical for understanding the volatile inventory and climatic history of the planet. An analysis of a latitude-dependent layer of surface material known as the dissected mantle terrain can provide valuable insight into the distribution of ice in the recent past. The dissected mantle terrain is a surface unit that occurs globally in the mid-latitude of Mars. This unit is characterized by a smooth mantle of uniform thickness and albedo that is draped over the existing topography. This smooth mantle is disaggregated and dissected in places resulting in a hummocky pitted appearance. We propose that the mid-latitude dissected terrain results from collapse of a dusty mantle into the void left from desiccation of an underlying ice-rich (pure or dirty ice) layer. During period(s) of high obliquity, it is possible for ice to become stable at lower latitudes. Due to lack of direct solar insolation, surface ice deposits will preferentially accumulate on pole-ward facing slopes first. A mantle of dust and dirt is then deposited on top of these ice-rich deposits. As the climate changes, desiccation of the now buried ice leads to collapse of the overlying dusty layer resulting in a hummocky pitted appearance. This theory is supported by the pole-ward preference for the dissection pits as well an increase in dissection with increasing latitude. A study of the global distribution of the mid-latitude dissected terrain can provide invaluable clues towards unlocking the distribution of ice in the recent past. An analysis of HiRISE images and MOLA data indicate that the distribution of dissection pits varies from one region to the next. Knowing the distribution of ice in conjunction with ice stability modeling can provide a global view of the climate and orbital history of Mars at the time these features formed.

  2. 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.

  3. New insights into the relationship between mid latitude North Atlantic hydrography and productivity during the intensification of northern hemisphere glaciation

    NASA Astrophysics Data System (ADS)

    Bolton, C. T.; Koch, M. C.; Friedrich, O.; Bailey, I.; Tachikawa, K.; de Garidel-Thoron, T.; Ermini, M.; Marino, G.; Rohling, E. J.; Vidal, L.; Sonzogni, C.; Cooper, M. J.; Wilson, P. A.

    2015-12-01

    In the North Atlantic Ocean today, the North Atlantic Current (NAC) transports warm salty water to high northern latitudes, with key feedbacks on global climate. The mean latitudinal position of the NAC dictates whether the mid-latitude North Atlantic is dominated by warm, nutrient-poor subtropical surface waters (as it is during Late Pleistocene interglacials) or cold, nutrient-rich Arctic surface waters (as it is during Late Pleistocene glacials). The origin of this glacial-interglacial pattern in North Atlantic productivity is hypothesised to be linked to the onset of southward deflections of the NAC into the mid latitude North Atlantic after 2.7 Ma, during the late Pliocene intensification of northern hemisphere glaciation (iNHG). Yet, changes in wind-driven Ekman divergence and the upwelling of nutrient-rich thermocline waters are also hypothesised to influence surface water productivity in this region from this time. To shed new light on the origin of these large-amplitude productivity cycles, we present new suborbital-resolution records of surface and thermocline water properties from IODP Site U1313 (41°N), a benchmark mid-latitude drillsite at which this transition in productivity is recorded, during iNHG (MIS G11 to 95, ~2.82-2.41 Ma). We reconstruct surface and thermocline temperatures using Mg/Ca ratios of the tests of two species of planktic Foraminifera with distinct depth habitats, Globigerinoides ruber (surface mixed layer) and Globorotalia crassaformis (500-800 m water depth), and upper water column stratification using co-registered thermocline-surface water δ18O and δ13C gradients. With these new data and other published proxy records from Site U1313, we compare competing hypotheses to explain drivers of the large export productivity changes previously documented at this site during iNHG.

  4. Changes on Mid-Latitude Cyclones due to Global Warming Simulated by a Global 20-km-mesh Atmospheric Model

    NASA Astrophysics Data System (ADS)

    Miyamoto, K.

    2005-12-01

    I investigate how the intensity and the activity of mid-latitude cyclones change as a result of global warming, based on a time-slice experiment with a super-high resolution Atmospheric General Circulation Model (20-km mesh TL959L60 MRI/JMA AGCM). The model was developed by the RR2002 project "Development of Super High Resolution Global and Regional Climate Models" funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology. In this context, I use a 10-year control simulation with the climatological SST and a 10-year time-slice global warming simulation using the SST anomalies derived from the SRES A1B scenario run with the MRI-CGCM2.3 (T42L30 atmosphere, 0.5-2.0 x 2.5 L23 ocean) corresponding to the end of the 21st century. I have analyzed the sea-level pressure field and the kinetic energy field of the wind at the 500 hPa pressure level associated with mid-latitude transients from October through April. According to a comparison of 10-day average fields between present and future in the North Pacific, some statistically significant changes are found in a warmer climate for the both of sea-level pressure and the kinetic energy fields. In particular, from late winter through early spring, the sea-level pressure decreases on many parts of the whole Pacific. The kinetic energy of the wind becomes higher on center of the basin. Therefore, I suppose the Aleutian Low is likely to settle in longer by about one month than the present. Hereafter, I plan to investigate what kind of phenomena may accompany the changes on mid-latitude transients.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Active and passvie microwave remote sensing of springtime near-surface soil that at mid-latitudes

    NASA Astrophysics Data System (ADS)

    Han, L.; Tsunekawa, A.; Tsubo, M.

    2010-12-01

    Springtime near-surface soil thaw event is important for understanding the near-surface earth system. Previous researches based on both active and passive microwave remote sensing technologies have paid scant attention, especially at mid-latitudes where the near-surface earth system has been changed substantially by climate change and human activities, and are characterized by more complex climate and land surface conditions than the permafrost areas. SSM/I brightness temperature and QuikSCAT Ku-band backscatter were applied in this study at a case study area of northern China and Mongolia in springtime. The soil freeze-thaw algorithm was employed for SSM/I data, and a random sampling technique was applied to determine the brightness temperature threshold for 37 GHz vertically polarized radiation: 258.2 and 260.1 K for the morning and evening satellite passes, respectively. A multi-step method was proposed for QuikSCAT Ku-band backscatter based on both field observed soil thaw events and the typical signature of radar backscatter time series when soil thaw event occurred. The method is mainly focuses on the estimated boundary of thaw events and detection of primary thaw date. Finally, based on those results, a theoretical method by applying both active and passive microwave remote sensing was proposed for understanding different types of frozen grounds and their specific characters (e.g. initial and end date of springtime soil freeze-thaw transition period) in mid-latitudes.

  11. First evidence of anisotropy of GPS phase slips caused by the mid-latitude field-aligned ionospheric irregularities

    NASA Astrophysics Data System (ADS)

    Afraimovich, E. L.; Ishin, A. B.; Tinin, M. V.; Yasyukevich, Yu. V.; Jin, S. G.

    2011-05-01

    The mid-latitude field-aligned irregularity (FAI) along the magnetic field line is a common phenomenon in the ionosphere. However, few data reveal the field-aligned ionospheric irregularities. They are insufficient to identify FAIs effects so far, particularly effect on global positioning system (GPS) signals. In this paper, the mid-latitude FAIs by line-of-sight angular scanning relative to the local magnetic field vector are investigated using the denser GPS network observations in Japan. It has been the first found that total GPS L2 phase slips over Japan, during the recovery phase of the 12 Feb 2000 geomagnetic storm were caused by GPS signal scattering on FAIs both for the lines-of-sight aligned to the magnetic field line (the field of aligned scattering, FALS) and across the magnetic field line (the field of across scattering, FACS). The FALS results are also in a good agreement with the data of the magnetic field orientation control of GPS occultation observations of equatorial scintillation during thorough low earth orbit (LEO) satellites measurements, e.g. Challenging Minisatellite Payload (CHAMP) and Satellite de Aplicaciones Cientificas-C (SAC-C). 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.

  12. The effects of March 20 2015 solar eclipse on the F2 layer in the mid-latitude

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    This paper studied the effects of solar eclipse of March 20, 2015 on the F2 layer in the mid-latitude. The diurnal changes in the NmF2 and hmF2 in mid-latitude stations during the spectacular event, as recorded by the ionosonde situated along the path of solar eclipse, which are within the obscuration percentage of 59-90% were investigated. The estimation of the percentage of solar ionizing radiation that remains unmasked during the eclipse window was carried out. The high uncertainty level (i.e. the error is ⩽±0.2), indicates that variation in electron density during eclipse window can be used as proxy parameter for solar ionizing radiation. The NmF2 decreased during the eclipse window, as a consequence of the variation in the local solar radiation. The variation of F2 plasma was dominated by diffusion mechanisms which determine the height at which the F2 peak formed and were related to the changes in thermospheric composition. The downward/upward movements of the plasma correspond with the drifting of the diffusion mechanisms and undergone a comparable variation with the solar ionizing radiation. Our result indicates that eclipse effects increase with increase in latitude and the time lag (the time delay ranges from 11 to 21 min) decreases with increase in latitude.

  13. 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.

  14. 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.

  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. 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.

  17. Impacts of solar activity on performance of the IRI-2012 model predictions from low to mid latitudes

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Tan, Eng Leong; Murti, Dhimas Sentanu

    2015-03-01

    This study investigates the impacts of solar activity on the performance of the latest release of International Reference Ionosphere (IRI) model version 2012 (IRI-2012) predictions during the ascending phase of solar activity from 2009 to 2013. The study is based on the data of total electron content (TEC) retrieved from the Global Positioning System (GPS) at Singapore (NTUS) (geographic latitude 01.34°N, longitude 103.67°E, geomagnetic latitude 8.4°S), Thailand (CUSV) (geographic latitude 13.73°N, longitude 100.54°E, geomagnetic latitude 3.96°N), China (KUNM) (geographic latitude 25.02°N, longitude 102.79°E, geomagnetic latitude 15.15°N), Mongolia (ULAB) (geographic latitude 47.67°N, longitude 107.05°E, geomagnetic latitude 37.73°S), and Russia (IRKM) (geographic latitude 52.21°N, 104.31°E, geomagnetic latitude 42.28°S). The GPS-TEC has been compared with the IRI-2012 model TEC for three different options, namely, IRI-NeQ, IRI01-corr, and IRI-2001, for topside Ne over all the above five stations lying at different latitudes from equatorial-equatorial ionization anomaly (EIA) to mid-latitude regions but at around the same longitude line (104° ± 3°E). The study showed that the IRI model predictions for different topside options are different and significant in low-latitude region but insignificant in mid-latitude regions (except during winter season of high solar activity year 2012). During the period from 2009 to 2013, upon moving from low to high solar activity, the prediction nature (overestimation/underestimation) of IRI-2012 model changes significantly at EIA station KUNM of low-latitude region. The discrepancy in IRI-2012 model TEC as compared to GPS-TEC in low-latitude region is found to be larger and significant than in mid-latitude region (Mongolia and Russia). The discrepancy in the IRI-2012 model TEC with IRI-2001 topside is found to be maximum at equatorial station CUSV (RMSD 99%) during the solar minimum year 2009 and decreases moving

  18. Large-scale simulations and in-situ observations of mid-latitude and Arctic cirrus clouds

    NASA Astrophysics Data System (ADS)

    Rolf, Christian; Grooß, Jens-Uwe; Spichtinger, Peter; Costa, Anja; Krämer, Martina

    2017-04-01

    Cirrus clouds play an important role by influencing the Earth's radiation budget and the global climate (Heintzenberg and Charlson, 2009). The formation and further evolution of cirrus clouds is determined by the interplay of temperature, ice nuclei (IN) properties, relative humidity, cooling rates and ice crystal sedimentation. Thus, for a realistic simulation of cirrus clouds, a Lagrangian approach using meteorological wind fields is the best way to represent complete cirrus systems as e.g. frontal cirrus. To this end, we coupled the two moment microphysical ice model of Spichtinger and Gierens (2009) with the 3D Lagrangian model CLaMS (McKenna et al., 2002). The new CLaMS-Ice module simulates cirrus formation by including heterogeneous and homogeneous freezing as well as ice crystal sedimentation. The boxmodel is operated along CLaMS trajectories and individually initialized with the ECMWF meteorological fields. From the CLaMS-Ice three dimensional large scale cirrus simulations, we are able to assign the formation mechanism - either heterogeneous or homogeneous freezing - to specific combinations of temperatures and ice water contents. First, we compare a large mid-latitude dataset of in-situ measured cirrus microphysical properties compiled from the ML-Cirrus aircraft campaign in 2014 to ClaMS-Ice model simulations. We investigate the number of ice crystals and the ice water content with respect to temperature in a climatological way and found a good and consistent agreement between measurement and simulations. We also found that most (67 %) of the cirrus cloud cover in mid-latitude is dominated by heterogeneously formed ice crystals. Second, CLaMS-Ice model simulations in the Arctic/Polar region are performed during the POLSTRACC aircraft campaign in 2016. Higher ice crystal number concentrations are found more frequently in the Arctic region in comparison to the mid-latitude dataset. This is caused by enhanced gravity wave activity over the mountainous

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Future C loss in mid-latitude mineral soils: climate change exceeds land use mitigation potential in France

    PubMed Central

    Meersmans, Jeroen; Arrouays, Dominique; Van Rompaey, Anton J. J.; Pagé, Christian; De Baets, Sarah; Quine, Timothy A.

    2016-01-01

    Many studies have highlighted significant interactions between soil C reservoir dynamics and global climate and environmental change. However, in order to estimate the future soil organic carbon sequestration potential and related ecosystem services well, more spatially detailed predictions are needed. The present study made detailed predictions of future spatial evolution (at 250 m resolution) of topsoil SOC driven by climate change and land use change for France up to the year 2100 by taking interactions between climate, land use and soil type into account. We conclude that climate change will have a much bigger influence on future SOC losses in mid-latitude mineral soils than land use change dynamics. Hence, reducing CO2 emissions will be crucial to prevent further loss of carbon from our soils. PMID:27808169

  6. Deep depletions of total electron content associated with severe mid-latitude gigahertz scintillations during geomagnetic storms

    SciTech Connect

    Ogawa, T.; Kumagai, H.

    1985-07-01

    Using 136-MHz Faraday rotation data obtained at three closely spaced stations, we present evidence that severe nightime gigahertz scintillations, which appear rarely at mid-latitudes around Japan only during geomagnetic storm conditions, are closely associated with deep depletions of total electron content (TEC). The TEC depletions amount to 2--8 x 10/sup 16/ el/m/sup 2/ (10--30% of the background TEC), and their durations range from 10 min to 1 hour. These depletions move northeastward or eastward with velocities between 60 and 260 m/s. The depletions are probably not counterparts of the equatorial bubbles but seem to be formed in localized regions around Japan under complicated and peculiar ionospheric conditions. There is an indication that the oscillation of the F region caused by large-scale TID's propagating from north to south (approx.600 m/s) may initiate the generation of the depletion.

  7. Future C loss in mid-latitude mineral soils: climate change exceeds land use mitigation potential in France

    NASA Astrophysics Data System (ADS)

    Meersmans, Jeroen; Arrouays, Dominique; van Rompaey, Anton J. J.; Pagé, Christian; de Baets, Sarah; Quine, Timothy A.

    2016-11-01

    Many studies have highlighted significant interactions between soil C reservoir dynamics and global climate and environmental change. However, in order to estimate the future soil organic carbon sequestration potential and related ecosystem services well, more spatially detailed predictions are needed. The present study made detailed predictions of future spatial evolution (at 250 m resolution) of topsoil SOC driven by climate change and land use change for France up to the year 2100 by taking interactions between climate, land use and soil type into account. We conclude that climate change will have a much bigger influence on future SOC losses in mid-latitude mineral soils than land use change dynamics. Hence, reducing CO2 emissions will be crucial to prevent further loss of carbon from our soils.

  8. Reverse relationship between drought of mid-latitudes in East Asia and Northwest Pacific tropical cyclone genesis frequency in summer

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Won; Cha, Yumi; Kim, Jeoung-Yun

    2016-12-01

    This study found that there is a significant negative correlation between summer drought in Korea, China and Japan and the frequency of tropical cyclone (TC) in the subtropical western North Pacific (SWNP) using effective drought index (EDI). The frequency of TCs that affect Korea is low (high) in a year of summer drought (non-drought). As a case study, in 1994 when there is extremely severe summer drought in Korea, there was high frequency of TCs while in 2003 when there was least severe summer drought, the frequency of TCs is the lowest. Changes in the anomalous secondary circulation, namely anomalous upward (downward) flow in the SWNP and anomalous downward (upward) flow in the mid-latitudes of East Asia, are one of the causes of drought (non-drought).

  9. Future C loss in mid-latitude mineral soils: climate change exceeds land use mitigation potential in France.

    PubMed

    Meersmans, Jeroen; Arrouays, Dominique; Van Rompaey, Anton J J; Pagé, Christian; De Baets, Sarah; Quine, Timothy A

    2016-11-03

    Many studies have highlighted significant interactions between soil C reservoir dynamics and global climate and environmental change. However, in order to estimate the future soil organic carbon sequestration potential and related ecosystem services well, more spatially detailed predictions are needed. The present study made detailed predictions of future spatial evolution (at 250 m resolution) of topsoil SOC driven by climate change and land use change for France up to the year 2100 by taking interactions between climate, land use and soil type into account. We conclude that climate change will have a much bigger influence on future SOC losses in mid-latitude mineral soils than land use change dynamics. Hence, reducing CO2 emissions will be crucial to prevent further loss of carbon from our soils.

  10. The association between ionospheric and geomagnetic pulsations in the Pc3-4 range at mid-latitudes

    NASA Astrophysics Data System (ADS)

    Tedd, B. L.; Cole, K. D.; Dyson, P. L.

    1989-09-01

    The response of the ionosphere to hydromagnetic waves in the Pc3-4 range has been investigated using an induction magnetometer and a digital ionosonde at Beveridge, Australia. Doppler shift measurements on four space radio frequencies have been made to monitor simultaneously the response of the E- and F-regions. E-region fluctuations correlated with P-3 activity have been observed for the first time. Excellent correlation is sometimes observed between magnetic pulsations and both E- and F-region fluctuations. The lack of correlation more often observed is probably caused by ionospheric irregularities which produce RF interference effects in the Doppler measurements. Nine events exhibiting particularly high correlation have been analyzed in detail. The phase differences between the magnetic and ionospheric data varied from event to event, such that different events are consistent with different theoretical mechanisms. This indicates the complex nature of the interaction of hydromagnetic waves with the ionosphere at mid-latitudes.

  11. Estimate of Low/Mid-Latitude Conductances, Electric Potential and Neutral Winds using IDA4D and EMPIRE

    NASA Astrophysics Data System (ADS)

    Bust, G. S.; Makela, J. J.; Harding, B. J.; Heelis, R. A.; Bishop, R. L.

    2015-12-01

    In this talk we will focus on the current ability of the ionosphere-thermosphere data assimilative models, Ionospheric Data Assimilation Four Dimensional (IDA4D) and Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE), to estimate low and mid latitude ionosphere-thermosphere (IT) state variables at altitudes of 200 km and less. In particular we focus on the estimation of Pederson and Hall conductances, equatorial electric potential, and neutral winds. We will characterize the current state of IDA4D and EMPIRE in terms of data available to be assimilated and geophysical conditions. We will discuss the accuracy expected for given conditions, current limitations, and to what degree data assimilative models can be used to advance our understanding of the low/mid latitude physics at 200 km and below. We will use three case study events to help elucidate the current capabilities of IDA4D and EMPIRE: The March, 2013 storm, the March 2015 storm, and the March 2014 time period, which was relatively quiet. In additional to the normal data sets ingested by IDA4D and EMPIRE we intend to ingest observation from the C/NOFS satellite including radio occultations, in-situ measurements of plasma density and ion drifts. We will also ingest other measurements related to electric fields from coherent scatter radars and magnetometers when available. Finally, we will ingest neutral wind measurements from FPI's. We will conclude with a discussion of the future of IT data assimilation algorithms, the advantages of coupling to first principle models, and what future satellite missions such as ICON, GOLD and COSMIC 2 will contribute to improved IT data assimilation estimates.

  12. Modeling the Impact of Climate Change on Lake Thermal Structure for Small Inland Lakes in the Mid-latitudes

    NASA Astrophysics Data System (ADS)

    Reinl, K. L.; Wagenbrenner, J. W.; Urban, N. R.

    2016-02-01

    Lakes in the mid-latitudes are subject to large seasonal variations in temperature that have been impacted by climate change. The focus of this study is to determine the impacts of climate change on the thermal structure of small inland lakes in the mid-latitudes. Small lakes comprise more than double the amount of the land surface than large lakes, and have gone largely underrepresented in lakes research regarding climate change. With this knowledge, we can better understand the effects of climate change on small inland lakes' physical processes and develop more holistic mitigation and management practices for these resources. We identified 517 inland lakes in Michigan based on data availability with surface areas between 0.03 and 81 km2, and subdivided this sample into 27 groups based on climate, lake surface area, and trophic state. The F-Lake model was tested using five Wisconsin lakes with varying surface areas and trophic states in two of the climate groups to determine its ability to predict observed lake temperatures. The average root mean squared error for the predicted surface and mean water temperature was 4.8 and 3.8 °C, respectively. We then applied the model to 3 lakes from each of the 27 groups under recently observed and future climate conditions from the regionally downscaled MPI ECHAM5 climate model (A2 emissions scenario) to assess the impacts of climate change on lake thermal structure. We hypothesize that small, eutrophic lakes located in warmer climates will be most strongly impacted, and this represents 20% of the lake resource in our sample. From these results, we will determine the susceptibility of lakes within and among the various climate, size, and trophic classes to the impacts of climate change as well as identify possible threats to aquatic organisms.

  13. 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.

  14. 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.

  15. A numerical study of aerosol effects on the dynamics and microphysics of a deep convective cloud in a continental environment

    NASA Astrophysics Data System (ADS)

    Cui, Zhiqiang; Carslaw, Kenneth S.; Yin, Yan; Davies, Stewart

    2006-03-01

    The effects of aerosols on a deep convective cloud in a midlatitude continental environment are studied using an axisymmetric cloud model with a sectional treatment of aerosol and hydrometeor microphysical processes. Simulations are conducted using observations from the Cooperative Convective Precipitation Experiments (CCOPE). The isolated cloud occurred in an environment with low wind shear and with relatively dry air in the midtroposphere and upper troposphere. By varying the concentration of aerosol particles in the accumulation mode within realistic limits for a continental environment, the simulated cloud exhibited different properties. The overall impact as the aerosol concentration increased is that (1) the cloud development was inhibited; (2) the precipitation was suppressed; (3) the maximum values of liquid water content decreased, but the maximum values of droplet number concentration increased before the dissipating stage; (4) a clear tendency was found for ice crystals to be larger and less numerous in the anvil cloud; and (5) there was a significant reduction of the inflow in the lower 2 km of the atmosphere. In the relatively dry environment in the midtroposphere, the latent heat changes associated with the Wegener-Bergeron-Findeisen mechanism played an important role in the upper part of the cloud at altitudes below the homogeneous freezing level. In particular, immersion freezing and latent heat release were much more rapid in the base simulation than in the increased aerosol simulation. Less latent heat release and insufficient inflow together impeded the development of the cloud with the higher aerosol loading. Our simulations suggest that continental clouds existing below the homogeneous freezing level could show an opposite response of cloud top height and anvil crystal concentrations to changes in aerosol to what has previously been reported for clouds ascending to higher levels.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Performance of a compact elastic 355 nm airborne lidar in tropical and mid-latitude clouds

    NASA Astrophysics Data System (ADS)

    Baibakov, Konstantin; Wolde, Mengistu; Nguyen, Cuong; Korolev, Alexei; Wang, Zhien; Wechsler, Perry

    2016-10-01

    In 2014 a new AECL (Airborne Elastic Cloud Lidar) lidar system was installed on-board the NRC Convair-580. AECL is a single wavelength elastic lidar which operates at 355nm and can supply vertical profiles of clouds and aerosols at high vertical and temporal resolution (1.5m and 0.05s). AECL is also equipped with a polarization channel and can provide information on particle phase (i.e. liquid or glaciated). The NRC AECL lidar was flown briefly on March 28, 2014 near Ottawa, Canada. In May of 2015 it was also deployed during the multi-week international HAIC (High Altitude Ice Crystals) - HIWC (High Ice Water Content) campaign near Cayenne, French Guinea. During the midlatitude flight near Ottawa, a convective cloud with cloud top extending to 4000 m was sampled by AECL. The on board in-situ cloud microphysics probes showed that the aircraft climbed through rain below 2 km reaching a mixedphase cloud above the melting layer and finally going through a supercooled layer. The lidar depolarization data from the AECL clearly identified the shallow supercooled layer near the cloud top and ice crystals with high depolarization ratio between the melting layer and the supercooled layer. In the regions of HIWC near Cayenne, the AECL laser beam was generally completely extinguished within the first 200 m. The lidar extinction coefficient, estimated using the Klett inversion technique and taken at 50 m above the aircraft showed a very good qualitative agreement with the measured in-situ extinction at flight level. The lidar extinction values had to be scaled by a factor of 5.88 to match the in-situ data. The discrepancies between the lidar estimated extinction and the direct measurements were explained, in part, by insufficient overlap correction and/or the error in the initial parameters used for the Klett inversion. In general, AECL showed promising initial results and in conjunction with other instrumentation, supplied valuable insight into the cloud optical and

  1. 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.

  2. 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.

  3. 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.

  4. 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%.

  5. 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

  6. The Next-Generation Goddard Convective-Stratiform Heating Algorithm: New Model Simulations for Tropical and Continental Summertime Environments

    NASA Astrophysics Data System (ADS)

    Lang, S. E.; Tao, W. K.; Wu, D.

    2016-12-01

    The Goddard Convective-Stratiform Heating (or CSH) algorithm is used to retrieve estimates of cloud heating over the global Tropics using TRMM rainfall data and a set of look-up-tables (LUTs) derived from a series of multi-week cloud-resolving model (CRM) simulations using the Goddard Cumulus Ensemble model (or GCE). These simulations link satellite observables (i.e., surface rainfall and stratiform fraction) with cloud heating profiles, which are not directly observable. The strength of the algorithm relies in part on the representativeness of the simulations; more realistic simulations provide a stronger link between the observables and simulated heating profiles. The current "TRMM" version of the CSH algorithm relies on 2D GCE simulations using an improved version of the Goddard 3-class ice scheme (3ICE), a moderate-sized domain, and 1-km horizontal resolution. Updating the LUTs, which are suitable for tropical and continental summertime environments requires new, more realistic GCE simulations. New simulations are performed using a new, improved 4-class ice scheme, which has been shown to outperform the 3ICE scheme, especially for intense convection. Additional grid configurations are also tested and evaluated to find the best overall setup to for re-deriving and updating the CSH tropical/summertime LUTs.

  7. 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.

  8. 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).

  9. Statistical analysis of ionospheric mid-latitude trough over the Northern Hemisphere derived from GPS total electron content data

    NASA Astrophysics Data System (ADS)

    Yang, Na; Le, Huijun; Liu, Libo

    2015-12-01

    This study statistically investigated the seasonal variation, magnetic local time (MLT) variation, geomagnetic activity dependence, and solar activity dependence of the mid-latitude trough using GPS total electron content (TEC) data from 2000 to 2014. The daily median Kp index was used to characterize the daily geomagnetic activity level. The results showed that the trough minimum position depended primarily on the geomagnetic activity, MLT, and the season. The trough depth depended primarily on the solar flux index (F107) and, to a lesser degree, on MLT. The trough depth increased as F107 increased and as the incidence angle of solar flux decreased. The trough equatorward half-width decreased as the geomagnetic activity increased. These variations in the GPS-TEC trough minimum position were compared with the variations in the TEC trough derived from the International Reference Ionosphere (IRI)-2007 model. The GPS-TEC trough minimum position changed little with respect to F107, whereas the IRI-TEC trough minimum position showed a strong F107 dependence.

  10. 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.

  11. 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.

  12. Influence of the St. Patrick's Day geomagnetic storm on the mid-latitude E and F regions.

    NASA Astrophysics Data System (ADS)

    Garnett Marques Brum, C.; Raizada, S.; Hajra, R.; Echer, E.

    2016-12-01

    We will discuss the impact of St. Patrick's Day geomagnetic storm that occurred between 17 -19 March 2015 on the E and F-region of the ionosphere. During the initial phase of this event the foF2 increases about 3 MHz in respect to the quiet period followed by a sharp decrease in foF2 values of about 10 MHz, reaching -6 MHz in the end of the main phase (Dst dropped to -225 nT on 17th March) as observed using Incoherent Scatter Radar and ionosonde located in Puerto Rico. However, during the rest of the disturbance, the F-region showed an increase in the electron concentration, in particular during the nighttime periods. Large fluctuations were observed in hmF2 with variations up to 150 km relative to quiet time period. This paper will also investigate the coupling between high and mid latitudes along with E and F region of the ionosphere over Arecibo.

  13. 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.

  14. 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.

  15. Temperatures in the Mid-Latitude Mesosphere During Sudden Stratospheric Warmings as Determined from Rayleigh Lidar Data

    NASA Astrophysics Data System (ADS)

    Sox, L.; Wickwar, V. B.; Fish, C. S.; Heron, J. P.

    2013-12-01

    The original Rayleigh-scatter lidar that operated at the Atmospheric Lidar Observatory (ALO; 41.7°N, 111.8°W) in the Center for Atmospheric and Space Sciences (CASS) on the campus of Utah State University (USU), collected temperature data for 11 years, from 1993 through 2004. The temperatures derived from these data extended over the mesosphere, from 45 to 90 km. Recently, they were combined with other observations to examine the mid-latitude mesosphere's behavior during Sudden Stratospheric Warmings (SSWs). Other data utilized in this study include Imaging Doppler Interferometry (IDI) data from a dynasonde at Bear lake Observatory (BLO), a meteor wind radar at BLO, a Na lidar from Colorado State University (now at ALO), and the SABER instrument aboard the TIMED satellite. Extensive Rayleigh lidar observations were made during fourteen SSW events. In order to determine the characteristics of the mesospheric temperatures during SSWs, comparisons were made between the temperature profile on an individual night during a SSW event and the climatological (11-year average) temperature profile for that night. An overall disturbance pattern was observed in the mesospheric temperatures during these SSWs. It included coolings (sometimes very significant) in the upper mesosphere and warmings in the lower mesosphere.

  16. 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.

  17. A study of the undisturbed mid-latitude ionosphere using simultaneous multiple site ionosonde measurements during the Sundial-86 campaign

    SciTech Connect

    Sica, R.J. ); Schunk, R.W. ); Willkinson, P.J. )

    1990-06-01

    The Sundial-86 campaign obtained simultaneous ionosonde measurements of N{sub m}F2 from 41 mid-latitude sites geographically dispersed around the world from September 21 to October 5, 1986. A three-dimensional, time-dependent model of Earth's ionoshpere has been used to fit the variations in N{sub m}F2 obtained from these sites. The model successfully reproduced the measurements in both the northern and southern hemispheres using the vertical plasma drift as a free parameter. During geomagnetically quiet conditions this drift is primarily due to the meridional neutral wind. The vertical plasma drift required to fit the data is consistent from location to location and the deduced meridional neutral wind is also consistent with previous neutral wind measurements and models. However, it is shown that a lack of knowledge of the variation of the O{sup +} flux at the top of the atmosphere introduces a large uncertainty in the deduced thermospheric winds.

  18. Multi-model assessment of the impact of soil moisture initialization on mid-latitude summer predictability

    NASA Astrophysics Data System (ADS)

    Ardilouze, Constantin; Batté, L.; Bunzel, F.; Decremer, D.; Déqué, M.; Doblas-Reyes, F. J.; Douville, H.; Fereday, D.; Guemas, V.; MacLachlan, C.; Müller, W.; Prodhomme, C.

    2017-02-01

    Land surface initial conditions have been recognized as a potential source of predictability in sub-seasonal to seasonal forecast systems, at least for near-surface air temperature prediction over the mid-latitude continents. Yet, few studies have systematically explored such an influence over a sufficient hindcast period and in a multi-model framework to produce a robust quantitative assessment. Here, a dedicated set of twin experiments has been carried out with boreal summer retrospective forecasts over the 1992-2010 period performed by five different global coupled ocean-atmosphere models. The impact of a realistic versus climatological soil moisture initialization is assessed in two regions with high potential previously identified as hotspots of land-atmosphere coupling, namely the North American Great Plains and South-Eastern Europe. Over the latter region, temperature predictions show a significant improvement, especially over the Balkans. Forecast systems better simulate the warmest summers if they follow pronounced dry initial anomalies. It is hypothesized that models manage to capture a positive feedback between high temperature and low soil moisture content prone to dominate over other processes during the warmest summers in this region. Over the Great Plains, however, improving the soil moisture initialization does not lead to any robust gain of forecast quality for near-surface temperature. It is suggested that models biases prevent the forecast systems from making the most of the improved initial conditions.

  19. Taking the Chill off: Future Arctic Sea-Ice Loss Reduces Severity of Cold Air Outbreaks in Mid-Latitudes

    NASA Astrophysics Data System (ADS)

    Ayarzagüena, B.; Screen, J.

    2016-12-01

    The effects of Arctic sea-ice loss on cold air outbreaks (CAOs) in midlatitudes remains unclear. Previous studies have defined CAOs relative to present-day climate, but changes in CAOs, defined in such a way, may reflect changes in mean climate and not in weather variability, and society is more sensitive to the latter. Here we revisit this topic but applying changing temperature thresholds relating to climate conditions of the time. CAOs do not change in frequency or duration in response to projected sea-ice loss. However, they become less severe, mainly due to advection of warmed polar air, since the dynamics associated with the occurrence of CAOs are largely not affected. CAOs weaken even in mid-latitude regions where the winter-mean temperature decreases in response to Arctic sea-ice loss. These results are robustly simulated by two atmospheric models in time-slice simulations where we have prescribed differing future sea ice states and in transient runs where external forcings are included. Additionally, sensitivity experiments with prescribed regional sea ice loss are used to isolate the effects of sea ice loss over specific areas.

  20. A long-lived band of plasma density enhancement at mid-latitudes during the 2003 Halloween magnetic storm

    NASA Astrophysics Data System (ADS)

    Park, Jaeheung; Lühr, Hermann; Jakowski, Norbert; Gerzen, Tatjana; Kil, Hyosub; Jee, Geonhwa; Xiong, Chao; Wook Min, Kyoung; Noja, Max

    2012-05-01

    During the magnetic storm recovery phase between 08 and 13 UT on 30th October 2003 (so-called Halloween Storm), CHAMP, GRACE and TIMED satellites encountered an unusual post-midnight streak of high plasma density. The streak was latitudinally narrow (∼0.5° GLAT), zonally elongated (>10° GLON), and vertically extended for several hundred kilometers. Inside the streak, as observed by CHAMP, the deviation of the magnetic field from the background is greater in the zonal component than in the meridional component. This observation is consistent with the zonally extended nature of the streak, as confirmed by TIMED/GUVI optical observations. The field-aligned current (FAC) direction is generally upward (downward) at the equatorward (poleward) edge of the streak. We discuss the time history of observed features. We suggest the following scenario of the streak formation. A storm-enhanced density (SED) was generated before 19 h local time by a sub-auroral polarization stream (SAPS). The SED gradually separated from the poleward-retreating region of strong westward plasma drift and turned into an electron density enhancement fossil (EDEF). This EDEF at mid-latitude (about 40°S MLAT) practically co-rotated with the Earth for more than 10 h through the night till dawn. We suggest that the enhanced plasma pressure was counter-balanced by magnetic pressure gradient and kept stable over many hours.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    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 Fregion 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 midlatitude region.

  2. 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.

  3. Parameterization of convective clouds, mesoscale convective systems, and convective-generated cirrus. Year 2 technical progress report, September 15, 1991--September 14, 1992

    SciTech Connect

    Cotton, W.R.

    1992-03-03

    A level 2.5w deep convection updraft/downdraft parameterization scheme has been refined and tested against 3D simulations of sea-breeze generated convection over S. Florida. Cases for explicit simulation of MCSs in mid-latitudes and tropics have been encouraging. After a few refinements in those cases, fine resolution explicit simualtions of deep convection and mesoscale, stratiform clouds will be begun.

  4. First detection of a seasonality of stratomesospheric CO above mid-latitudes via solar FTIR measurements. Analysis of one decade of observations at the NDACC Primary Station Zugspitze

    NASA Astrophysics Data System (ADS)

    Borsdorff, T.; Sussmann, R.; Rettinger, M.

    2009-04-01

    Model studies revealed that stratomesospheric CO exhibits considerable seasonal and latitudinal variations caused by the competition between downward transport from the thermospheric production region and photochemical loss processes. A sharp latitudinal gradient with highest abundances at the North Pole was found which implies that the mid-latitude region can exhibit strong enhancements of stratomesospheric CO under conditions of large-scale planetary wave activity displacing CO enriched vortex air from North to South. Unfortunately, until now there are not enough continuous long-term measurements of stratomesospheric CO at mid-latitudes to prove this assumption. Velazco et al. [2007] reported ground-based FTIR measurements of stratomesospheric CO partial columns from several sites in the Arctic, northern and southern mid-latitudes, and Antarctica. Unfortunately, this study concluded that, generally, the mid-latitude stations show no significant annual variability of stratomesospheric CO columns. However, already early microwave observations indicated that stratomesospheric CO is about twice as large in mid-latitude winter as in summer [Clancy et al., 1982]. Obviously, there was a technical difficulty with the FTIR inversion of mid-latitude mesospheric CO in the early study by Velazco et al. [2007]. It is one aim of this paper to present a solution to this problem. Therefore, this paper describes an improved retrieval approach for ground-based FTIR stations, that is capable to derive a significant seasonal cycle of stratomesospheric CO at mid-latitudes. Coincident measurements at Zugspitze (2964 m a.s.l.) and Garmisch (744 m a.s.l.) show perfect agreement (R = 0.94) which proves that the new retrieval approach is not limited to high altitude stations, and is thus applicable to all mid-latitude stations. The first long-term series of stratomesospheric CO at mid-latitudes (42.42°N, 10.98°E) derived from ground-based FTIR spectrometry is presented (1999 to 2008

  5. 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

  6. A new climate modeling framework for convection-resolving simulation at continental scale

    NASA Astrophysics Data System (ADS)

    Charpilloz, Christophe; di Girolamo, Salvatore; Arteaga, Andrea; Fuhrer, Oliver; Hoefler, Torsten; Schulthess, Thomas; Schär, Christoph

    2017-04-01

    Major uncertainties remain in our understanding of the processes that govern the water cycle in a changing climate and their representation in weather and climate models. Of particular concern are heavy precipitation events of convective origin (thunderstorms and rain showers). The aim of the crCLIM project [1] is to propose a new climate modeling framework that alleviates the I/O-bottleneck in large-scale, convection-resolving climate simulations and thus to enable new analysis techniques for climate scientists. Due to the large computational costs, convection-resolving simulations are currently restricted to small computational domains or very short time scales, unless the largest available supercomputers system such as hybrid CPU-GPU architectures are used [3]. Hence, the COSMO model has been adapted to run on these architectures for research and production purposes [2]. However, the amount of generated data also increases and storing this data becomes infeasible making the analysis of simulations results impractical. To circumvent this problem and enable high-resolution models in climate we propose a data-virtualization layer (DVL) that re-runs simulations on demand and transparently manages the data for the analysis, that means we trade off computational effort (time) for storage (space). This approach also requires a bit-reproducible version of the COSMO model that produces identical results on different architectures (CPUs and GPUs) [4] that will be coupled with a performance model in order enable optimal re-runs depending on requirements of the re-run and available resources. In this contribution, we discuss the strategy to develop the DVL, a first performance model, the challenge of bit-reproducibility and the first results of the crCLIM project. [1] http://www.c2sm.ethz.ch/research/crCLIM.html [2] O. Fuhrer, C. Osuna, X. Lapillonne, T. Gysi, M. Bianco, and T. Schulthess. "Towards gpu-accelerated operational weather forecasting." In The GPU Technology

  7. 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; hide

    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.

  8. 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.

  9. Mid-Holocene paleoclimatic changes and solar activity in San'in District, mid-latitude North Pacific Region

    NASA Astrophysics Data System (ADS)

    Okazaki, Y.; Seto, K.; Sakai, T.; Ooki, A.; yamada, K.; Dettman, D. L.

    2011-12-01

    Evidence shows that solar activity influences climate on a global scale. In the mid-latitude region, climate change is expected to change precipitation patterns. Concurrently, variation in solar activity may influence phytoplankton productivity. It seems that these changes should be recorded in sediment and organic matter deposits in coastal lagoons. In this study, we discuss the relationship between climate change and solar activity in the mid-Holocene in the northern hemisphere mid-latitude region based on grain size analysis, total organic carbon (TOC) content and organic carbon accumulation rates (Corg A.R.) in coastal lagoon sediment core samples. The INB core was drilled to produce a high resolution record of Holocene paleoenvironmental change in the San'in District, western Japan. The core is 19.17m in total length and is divided into Unit I~VII by lithofacies. Holocene sediment, primarily organic silt, forms Unit III and above in this core. Unit III was deposited from 8.4 to 5.4 ka, when sea level rose during the Jomon transgression; its depositional environment is a coastal lagoon. Progradation of the river mouth during the sea level rise lead to an increase in the C/N ratio of organic matter. Unit IV contains the volcanic Shigaku pyroclastic flow (the sixth stage of volcanic activity of the Sanbe volcano), and Unit V reflects deposition in a freshwater lake or swamp. Above this aggredational sediments were deposited by small rivers. This study focused on the coastal lagoon sediments of Unit III (8.4 to 5.4 ka); we carried out CNS elemental analysis and grain size analysis with a resolution of approximately five years. TOC content is variable and increases from 0.5 to 5%. Variation in TOC content is relatively well correlated with atmospheric radiocarbon 14C (Delta 14C) and therefore with solar activity, although the relationship is unclear in the upper portion of Unit III. The trend in Corg A.R. is different than TOC contents, about 40g/m/yr at ~8ka and

  10. The effects of thunderstorm-generated atmospheric gravity waves on mid-latitude F-region drifts

    NASA Astrophysics Data System (ADS)

    Kumar, V. V.; Parkinson, M. L.; Dyson, P. L.; Burns, G. B.

    2009-12-01

    Superposed epoch analysis (SEA) was used to examine ionospheric drift velocities measured by a digital ionosonde located at the mid-latitude station Bundoora (145.1°E, 37.7°S geographic), near Melbourne. The control times for the SEA were the times of cloud-to-ground (CG) lightning strokes measured from August 2003 to August 2004 by the World Wide Lightning Location Network (WWLLN). Statistically, regions of concentrated lightning activity migrated from west to east across Bundoora, and the stroke frequency was higher the day prior the activity reached the station, and lower on the day after it passed to the east. For the SEA, CG strokes were separated into four directional quadrants centred on north, south, east and west. No SEA results are shown for the south quadrant due to the relatively low detection frequency of strokes across the Southern Ocean (6% of all events). The strongest downward vertical perturbations in F-region drifts, -4.5 m s-1, were found for lightning located towards the west during -30 to -16 h (i.e., the afternoon prior the activity passed near the station at t=0 h). The downward perturbation decreased in amplitude to -1.5 m s-1 for lightning located towards the north during -6-+6 h, and was weakest (-0.7 m s-1) for lightning located towards the east during +16-+28 h (i.e., the next afternoon). There were directionally consistent perturbations in the drift azimuths associated with the lightning located in their respective quadrants; lightning located to the west of the station caused eastward azimuth enhancements, northward lightning caused southward enhancements, and eastward lightning caused westward enhancements. Velocity magnitudes and fluctuations tended to increase during the passage of lightning. The observed responses were stronger when the SEA was performed with data selected using time windows of <2 min on either side of each lightning stroke. However, they persisted at longer time scales and were strong when thunderstorm onsets

  11. Temporal variation in methane emissions in a shallow lake at a southern mid latitude during high and low rainfall periods.

    PubMed

    Fusé, Victoria S; Priano, M Eugenia; Williams, Karen E; Gere, José I; Guzmán, Sergio A; Gratton, Roberto; Juliarena, M Paula

    2016-10-01

    The global methane (CH4) emission of lakes is estimated at between 6 and 16 % of total natural CH4 emissions. However, these values have a high uncertainty due to the wide variety of lakes with important differences in their morphological, biological, and physicochemical parameters and the relatively scarse data from southern mid-latitude lakes. For these reasons, we studied CH4 fluxes and CH4 dissolved in water in a typical shallow lake in the Pampean Wetland, Argentina, during four periods of consecutive years (April 2011-March 2015) preceded by different rainfall conditions. Other water physicochemical parameters were measured and meteorological data were reported. We identified three different states of the lake throughout the study as the result of the irregular alternation between high and low rainfall periods, with similar water temperature values but with important variations in dissolved oxygen, chemical oxygen demand, water turbidity, electric conductivity, and water level. As a consequence, marked seasonal and interannual variations occurred in CH4 dissolved in water and CH4 fluxes from the lake. These temporal variations were best reflected by water temperature and depth of the Secchi disk, as a water turbidity estimation, which had a significant double correlation with CH4 dissolved in water. The mean CH4 fluxes values were 0.22 and 4.09 mg/m(2)/h for periods with low and high water turbidity, respectively. This work suggests that water temperature and turbidity measurements could serve as indicator parameters of the state of the lake and, therefore, of its behavior as either a CH4 source or sink.

  12. 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.

  13. Draining a ditch irrigated area to mitigate low flows in a small lowland catchment of the mid-latitudes

    NASA Astrophysics Data System (ADS)

    Gliege, Steffen; Thomas, Björn D.; Steidl, Jörg; Hohenbrink, Tobias L.; Dietrich, Ottfried

    2017-04-01

    Decreasing groundwater levels in many parts of the federal state of Brandenburg and decreasing low flows in Central Europe have created a need for adaption measures to stabilize the water balance and to increase low flows. The objective of this study was to estimate the impact of ditch water level management on stream-aquifer interactions by analyzing a ditch structure already existing in a small lowland catchment of the mid- latitudes. At the investigated ditch system water levels, runoff and precipitation was monitored between 2010 and 2012. The water balance of the ditch irrigated area and fluxes between the subsurface and the adjacent stream were modeled for three runoff recession periods using the Hydrus-2D software package. Five scenarios of different antecedent water levels in the ditch irrigation system were examined. The results showed that subsurface flow to the stream was closely related to the difference between the water level in the ditch system and the stream. Evapotranspiration during the growing season additionally reduced base flow. It was crucial to stop irrigation during a recession period to decrease water withdrawal from the stream and enhance base flow by draining the irrigated area. Mean fluxes to the stream were between 0.04 and 0.64 ls-1 for the first 20 days of the low-flow periods. This only slightly increased the flow in the stream, which was in mean 57 ls-1 during the period with the lowest flows. Larger areas where ditch irrigation is adapted or a combination with other measures are necessary in order to effectively increase flows in mesoscale catchments. Ditch water levels should be increased as much as possible to assure high base flow during subsequent low flow periods. Clearly, this contradicts current land use and environmental protection. Thus, this study can be used as basis for a discussion on possible fluctuations in water levels in such areas and subsequently possible effects considering current land use have to be evaluated

  14. Space Shuttle Exhaust Modifications of the Mid-Latitude Ionospheric Plasma As Diagnosed By Ground Based Radar

    NASA Astrophysics Data System (ADS)

    Lind, F. D.; Erickson, P. J.; Bhatt, A.; Bernhardt, P. A.

    2009-12-01

    The Space Shuttle's Orbital Maneuvering System (OMS) engines have been used since the early days of the STS program for active ionospheric modification experiments designed to be viewed by ground based ionospheric radar systems. In 1995, the Naval Research Laboratory initiated the Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) Program using dedicated Space Shuttle OMS burns scheduled through the US Department of Defense's Space Test Program. SIMPLEX objectives include generation of localized ion-acoustic turbulence and the formation of ionospheric density irregularities for injections perpendicular to the local magnetic field, creating structures which can scatter incident UHF radar signals. We discuss radar observations made during several recent SIMPLEX mid-latitude experiments conducted over the Millstone Hill incoherent scatter radar system in Westford, Massachusetts. OMS engine firings release 10 kg/s of CO2, H2, H2O, and N2 molecules which charge exchange with ambient O+ ions in the F region, producing molecular ions and long lived electron density depletions as recombination occurs with ambient electrons. Depending on the magnetic field angle, the high velocity of the injected reactive exhaust molecules relative to the background ionosphere can create longitudinal propagating ion acoustic waves with amplitudes well above normal thermal levels and stimulate a wide variety of plasma instability processes. These effects produce high radar cross section targets readily visible to the Millstone Hill system, a high power large aperture radar designed to measure very weak scatter from the quiescent background ionosphere. We will survey the plasma instability parameter space explored to date and discuss plans for future SIMPLEX observations.

  15. The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study

    NASA Astrophysics Data System (ADS)

    Timmreck, C.; Graf, H.-F.

    2006-01-01

    The chemistry climate model MAECHAM4/ CHEM with interactive and prognostic volcanic aerosol and ozone was used to study the initial dispersal and radiative forcing of a possible Northern Hemisphere mid-latitude super eruption. Tropospheric climate anomalies are not analysed since sea surface temperatures are kept fixed. Our experiments show that the global dispersal of a super eruption located at Yellowstone, Wy. is strongly dependent on the season of the eruption. In Northern Hemisphere summer the volcanic cloud is transported westward and preferentially southward, while in Northern Hemisphere winter the cloud is transported eastward and more northward compared to the summer case. Aerosol induced heating leads to a more global spreading with a pronounced cross equatorial transport. For a summer eruption aerosol is transported much further to the Southern Hemisphere than for a winter eruption. In contrast to Pinatubo case studies, strong cooling tendencies appear with maximum peak values of less than -1.6 K/day three months after the eruption in the upper tropical stratosphere. This strong cooling effect weakens with decreasing aerosol density over time and initially prevents the aerosol laden air from further active rising. All-sky net radiative flux changes of less than -32 W/m2 at the surface are about a factor of 6 larger than for the Pinatubo eruption. Large positive flux anomalies of more than 16 W/m2 are found in the first months in the tropics and sub tropics. These strong forcings call for a fully coupled ocean/atmosphere/chemistry model to study climate sensitivity to such a super-eruption.

  16. Climatology of Mid-Latitude Mstid Events Observed by the Demeter Satellite in the Period 2005-2010.

    NASA Astrophysics Data System (ADS)

    Berthelier, J. J.; Nguyen, C. T.; Amory-Mazaudier, C. C.; Petitdidier, M.

    2015-12-01

    Using plasma measurements from the CNES DEMETER micro-satellite, we have performed a global survey of ionospheric disturbances observed at middle and low latitudes on the nightime part of the DEMETER orbit in the local time sector 21.30-22.30 LT. This study encompasses the 6 years of the satellite operations, from 2005 to 2010, including years of moderate magnetic activity of solar cycles 23 and 24 and the deep solar minimum in 2009-2010. We report in this poster a statistical analysis of MSTID events characterized by quasi-periodic variations of the O+ density observed below ~ 40° geomagnetic latitudes with wavelengths ranging from 350 to 700 km. Although detected in both hemispheres they occur predominantly at southern latitudes with a rather strong peak over the Pacific ocean. A detailed analysis has shown that these events may be sorted in 4 categories according to their latitudinal extent. Most of them are restricted to a latitude band between ~ 15° and 40° geomagnetic in North or South but some of them extend from mid latitudes in one hemisphere to low latitude in the other hemisphere, thus spanning equatorial regions up to 5-10°. The apparent negative correlation with magnetic activity seems to indicate that most of these events are driven by AGW originating from low altitude atmospheric levels and not triggered by auroral phenomena. We shall present the seasonal and inter-annual variations showing significant changes associated with solar activity. Our results will be compared to other ground-based or satellite observations and our investigation pointed out a strong effect of these MSTID and their parent AGW on the electrodynamics of the low latitude ionosphere.

  17. 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

  18. 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

  19. 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.

  20. Stability of the seasonal variations in diurnal and semidiurnal components of mid-latitude F2 layer parameters

    NASA Astrophysics Data System (ADS)

    Zolotukhina, N.; Polekh, N.; Romanova, E.; Polyakova, A.

    2014-08-01

    We report work utilizing 15-min resolution ionospheric data obtained with DPS-4 digisonde in 2003-2011 to study the seasonal variations in amplitudes and phases of the most powerful spectral components of the F2 layer critical frequency (foF2) and peak height (hmF2) fluctuations over Irkutsk (52.5°N, 104.0°E). We show that fluctuations of both parameters contain quasi-harmonic components with periods of Tn = 24/n h (n = 1-7). The number of distinct spectral peaks varies from 3 in summer to 7 in winter. Amplitude and phase characteristics of the diurnal (n = 1) and semidiurnal (n = 2) components is studied using the data sets extracted from the original data sets with band-pass filter. It has been found that the amplitudes of diurnal/semidiurnal foF2 and diurnal hmF2 components are maximum in winter and minimum in summer. Amplitudes of the diurnal components vary gradually; those of the foF2 semidiurnal one, abruptly, thus forming a narrow winter maximum in November-January. The phase (local time of maximum) of the diurnal foF2 component increases gradually by 4-6 h from winter to summer. The phase of the semidiurnal foF2 component is nearly stable in winter/summer and sharply decreases (increases) by 2-3 h near the spring (autumn) equinox. The phase of the diurnal component of hmF2 (local time of minimum) varies slightly between 1130 and 1300 LT; that of the semidiurnal one decreases (increases) by 4-6 h from January to March (from September to November). The results obtained show that the main features of seasonal variations in the diurnal and semidiurnal components of the mid-latitude F2 layer parameters recur consistently during the solar activity growth and decline phases.

  1. 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.

  2. A MU radar-based study of mid-latitude F region response to a geomagnetic disturbance

    SciTech Connect

    Reddy, C.A.; Fukao, S.; Takami, T.; Yamamoto, M.; Tsuda, T.; Nakamura, T.; Kato, S. )

    1990-12-01

    During the night of January 20-21, 1989, ionospheric incoherent scatter power measurements were made with the MU (middle and upper atmosphere) radar at Shigaraki (geographic latitude 34.85 N, longitude 136.10 E; geomagnetic latitude 24.9{degree}, longitude 204.3{degree}). Japan, and the electron density profiles in the 180- to 1,000-km height range were derived at 8-min intervals. The observations showed the presence of three F region disturbances during the night. During the very large first disturbance, which lasted from 2,300 to 0240 LT approximately, the height of maximum electron density N{sub m} increased by 220 km in 2 hours to reach an altitude of 600 km. The other two, smaller disturbances occurred during 0300-0500 LT and 0530-0700 LT approximately. A detailed interpretation of the above F region disturbances is given. Examination of some high- and middle-latitude magnetograms showed the beginning of an intense geomagnetic substorm at auroral latitudes at the start of the first F region disturbance, and a less intense substorm around the starting time of the second F region disturbance. On the basis of this evidence, the first two F region disturbances are interpreted as the result of large vertical drifts of F region ionization due to the substorm-generated east-west electric fields appearing at mid-latitudes. The patterns of h{prime}F variations during this night at five ionospheric stations in Japan support the above interpretation. Additionally, during the second disturbance the possible presence of a wind perturbation due to the equatorward propagation of a wave disturbance, generated probably by the first major substorm, is indicated by the MU radar data and the ionosonde data. The third F region disturbance is attributed to a neutral wind perturbation associated with a gravity wave traveling equatorward, the wave being generated most plausibly by the Joule heating during the first major substorm.

  3. 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.

  4. 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.

  5. Continental-scale convection-permitting modeling of the current and future climate of North America

    NASA Astrophysics Data System (ADS)

    Liu, Changhai; Ikeda, Kyoko; Rasmussen, Roy; Barlage, Mike; Newman, Andrew J.; Prein, Andreas F.; Chen, Fei; Chen, Liang; Clark, Martyn; Dai, Aiguo; Dudhia, Jimy; Eidhammer, Trude; Gochis, David; Gutmann, Ethan; Kurkute, Sopan; Li, Yanping; Thompson, Gregory; Yates, David

    2017-07-01

    Orographic precipitation and snowpack provide a vital water resource for the western U.S., while convective precipitation accounts for a significant part of annual precipitation in the eastern U.S. As a result, water managers are keenly interested in their fate under climate change. However, previous studies of water cycle changes in the U.S. have been conducted with climate models of relatively coarse resolution, leading to potential misrepresentation of key physical processes. This paper presents results from a high-resolution climate change simulation that permits convection and resolves mesoscale orography at 4-km grid spacing over much of North America using the Weather Research and Forecasting (WRF) model. Two 13-year simulations were performed, consisting of a retrospective simulation (October 2000-September 2013) with initial and boundary conditions from ERA-interim and a future climate sensitivity simulation with modified reanalysis-derived initial and boundary conditions through adding the CMIP5 ensemble-mean high-end emission scenario climate change. The retrospective simulation is evaluated by validating against Snowpack Telemetry (SNOTEL) and an ensemble of gridded observational datasets. It shows overall good performance capturing the annual/seasonal/sub-seasonal precipitation and surface temperature climatology except for a summer dry and warm bias in the central U.S. In particular, the WRF seasonal precipitation agrees with SNOTEL observations within a few percent over the mountain ranges, providing confidence in the model's estimation of western U.S. seasonal snowfall and snowpack. The future climate simulation forced with warmer and moister perturbed boundary conditions enhances annual and winter-spring-fall seasonal precipitation over most of the contiguous United States (CONUS), but suppresses summertime precipitation in the central U.S. The WRF-downscaled climate change simulations provide a high-resolution dataset (i.e., High-Resolution CONUS

  6. Continental-scale convection-permitting modeling of the current and future climate of North America

    NASA Astrophysics Data System (ADS)

    Liu, Changhai; Ikeda, Kyoko; Rasmussen, Roy; Barlage, Mike; Newman, Andrew J.; Prein, Andreas F.; Chen, Fei; Chen, Liang; Clark, Martyn; Dai, Aiguo; Dudhia, Jimy; Eidhammer, Trude; Gochis, David; Gutmann, Ethan; Kurkute, Sopan; Li, Yanping; Thompson, Gregory; Yates, David

    2016-08-01

    Orographic precipitation and snowpack provide a vital water resource for the western U.S., while convective precipitation accounts for a significant part of annual precipitation in the eastern U.S. As a result, water managers are keenly interested in their fate under climate change. However, previous studies of water cycle changes in the U.S. have been conducted with climate models of relatively coarse resolution, leading to potential misrepresentation of key physical processes. This paper presents results from a high-resolution climate change simulation that permits convection and resolves mesoscale orography at 4-km grid spacing over much of North America using the Weather Research and Forecasting (WRF) model. Two 13-year simulations were performed, consisting of a retrospective simulation (October 2000-September 2013) with initial and boundary conditions from ERA-interim and a future climate sensitivity simulation with modified reanalysis-derived initial and boundary conditions through adding the CMIP5 ensemble-mean high-end emission scenario climate change. The retrospective simulation is evaluated by validating against Snowpack Telemetry (SNOTEL) and an ensemble of gridded observational datasets. It shows overall good performance capturing the annual/seasonal/sub-seasonal precipitation and surface temperature climatology except for a summer dry and warm bias in the central U.S. In particular, the WRF seasonal precipitation agrees with SNOTEL observations within a few percent over the mountain ranges, providing confidence in the model's estimation of western U.S. seasonal snowfall and snowpack. The future climate simulation forced with warmer and moister perturbed boundary conditions enhances annual and winter-spring-fall seasonal precipitation over most of the contiguous United States (CONUS), but suppresses summertime precipitation in the central U.S. The WRF-downscaled climate change simulations provide a high-resolution dataset (i.e., High-Resolution CONUS

  7. Pre-sunrise uplift and sunrise downward excursion in the F-region vertical plasma drift: Observations from the mid-latitude station Nicosia

    NASA Astrophysics Data System (ADS)

    Mathew, Tiju Joseph; Haralambous, Haris; Oikonomou, Christina

    2017-04-01

    The characteristics of mid-latitude vertical plasma drift, with a focus on pre-sunrise hours for Nicosia station, Cyprus, based on digital ionosonde measurements, have been investigated and are reported for the first time. The pre-sunrise vertical plasma drift is defined by an uplift prior to sunrise, followed by a downward drift, which is referred to as sunrise downward excursion (SDE). The pre-sunrise uplift at mid-latitudes seems to be apparent due to 'thinning' of the F- layer bottom side. The observed uplift is followed by a sudden descend which is also 'apparent' and is attributed to the downward movement of the ionisation peak during sunrise. The pre-sunrise uplift is more significant in winter but the downward drift is observed irrespective of the season.

  8. Impacts of Geomagnetic storms on the mid-latitude mesosphere and lower thermosphere observed by a Na lidar and TIMED/GUVI

    NASA Astrophysics Data System (ADS)

    Yuan, T.; Zhang, Y.

    2015-12-01

    In this paper, we report our findings on the correlation between the neutral temperature (around the mesopause) and thermospheric column density O/N2 ratio, along with their response to geomagnetic storms above mid-latitude of North America. A temperature/wind Doppler Na lidar, operating at Fort Collins, CO (41°N, 105°W) and later at Logan, UT (42°N and 112°W), observed significant temperature increases (temperature anomaly) above 95 km (as much as 55 K at 105 km altitude) during four geomagnetic storms (April 2002, Nov. 2004, May 2005 and Oct. 2012). Coincident TIMED/GUVI observations indicate significant depletion in the thermospheric O/N2 ratio at the lidar locations. These observations suggest that the local mesopause warming seen by the lidar is due to transport of the high-latitude Joule and particle heated neutrals at the E and F layers to the mid-latitude region.

  9. 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.

  10. Four Years of Simultaneous Observations of Noctilucent Clouds and Mesospheric Summer Echoes at a Mid-Latitude Site (Kühlungsborn/Germany, 54°N)

    NASA Astrophysics Data System (ADS)

    Gerding, M.; Zoellner, J.; Zecha, M.; Luebken, F. J.

    2015-12-01

    Occurrence of ice particles in the polar summer mesopause region is an intriguing phenomenon that can be observed either optically as Noctilucent Clouds (NLC) / Polar Mesospheric Clouds (PMC) or by radar as (Polar) Mesosphere Summer Echoes ((P)MSE). The relation of both phenomena is well understood and allows insights into atmospheric properties like temperature, humidity, winds, turbulence and electron density. Simultaneous observations of NLC and PMSE require sufficient electron density (for the radar observation) and therefore daylight conditions that may hinder optical observations by lidar. Up to now, simultaneous observations of NLC and PMSE are mainly limited to polar latitudes, while data from mid-latitudes are lacking. Since 2010 we operate a new RMR lidar at our site at Kühlungsborn/Germany (54°N, 12°E). From the best of our knowledge this lidar allows for the first time observations of mid-latitude NLC independent of solar elevation, i.e. during night and day. With our new RMR lidar and the co-located OSWIN radar we are for the first time able to compare the occurrence and altitude structure of NLC and MSE at mid-latitudes. It turns out that the lower edges of simultaneously observed NLC/MSE typically agree, as expected from higher latitudes. Though, the top edge of MSE is observed about 500 m above the NLC edge, indicating the presence of particles being too small to be observed by lidar. Nevertheless, height difference is small compared to the typical layer widths and smaller than observed at higher latitudes. This hints at different size distributions and, by this, different growing conditions at mid-latitudes. We will present a statistical overview on the comparison of simultaneously observed NLC and MSE layers and their main characteristics. Simultaneous NLC and MSE are of additional importance if observed during twilight conditions. The onset or disappearance of MSE during morning and evening twilight is directly related with changing electron

  11. 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

  12. Assessing and evaluating urban VOC emissions in mid-latitude megacities from intensive observations in Paris and Los Angeles

    NASA Astrophysics Data System (ADS)

    Borbon, A.; Gilman, J. B.; Kuster, W. C.; McKeen, S. A.; Holloway, J. S.; Gros, V.; Gaimoz, C.; Beekmann, M.; De Gouw, J. A.

    2011-12-01

    Volatile Organic Compounds (VOC) affect urban air quality and regional climate change by contributing to ozone formation and the build-up of Secondary Organic Aerosols (SOA). Quantification of VOC emissions is a first critical step to predict VOC environmental impacts and to design effective abatement strategies. Indeed, the quality of ozone and SOA forecasts strongly depends on an accurate knowledge of the primary VOC emissions. However, commonly used bottom-up approaches are highly uncertain due to source multiplicity (combustion processes, storage and distribution of fossil fuels, solvent use, etc.) because of numerous controlling factors (driving conditions, fuel type, temperature, radiation, etc.), and their great variability in time and space. Field observations of VOC and other trace gases can provide valuable top-down constraints to evaluate VOC emission inventories at urban scales. In addition, the implementation of emission reduction measures raises the question of the increasing importance of VOC sources other than traffic. Here, we will evaluate VOC emissions of two mid-latitude megacities in the Northern Hemisphere: the Greater Paris area (Europe) and Los Angeles (USA). In 2009 and 2010, three intensive field campaigns took place in Paris and Los Angeles in the framework of the MEGAPOLI (EU FP7) and CalNex-2010 projects, respectively. Very detailed measurements of aerosol composition and properties, and their gaseous VOC precursors were carried out at ground-based sites (urban center and suburban) and on various mobile platforms. This contribution uses a comprehensive suite of VOC measurements collected by GC-MS/FID techniques at ground-based sites in both cities by a source-receptor methodology. First, emission ratios were estimated from the observations (uncertainty of ± 20%) and compared regarding regional characteristics and European vs. Californian control policies. Then, determined emission ratios were used to assess the accuracy of up

  13. 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

  14. 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 10

  15. Interaction of polar and tropical influences in the mid-latitudes of the Southern Hemisphere during the Mi-1 deglaciation

    NASA Astrophysics Data System (ADS)

    Fox, B. R. S.; D'Andrea, W. J.; Wilson, G. S.; Lee, D. E.; Wartho, J.-A.

    2017-08-01

    It is well-known from geologic archives that Pleistocene and Holocene climate is characterised by cyclical variation on a wide range of timescales, and that these cycles of variation interact in complex ways. However, it is rarely possible to reconstruct sub-precessional (< 20 kyr) climate variations for periods predating the oldest ice-core records (c. 800 ka). Here we present an investigation of orbital to potentially sub-precessional cyclicity from an annually resolved lake sediment core dated to a 100-kyr period in the earliest Miocene (23.03-22.93 Ma) and spanning a period of major Antarctic deglaciation associated with the second half of the Mi-1 event. Principal component analysis (PCA) of sediment bulk density, magnetic susceptibility (MS), and CIELAB L* and b* with a resolution of 10 years indicates two major environmental processes governing the physical properties records, which we interpret as changes in wind strength and changes in precipitation. Spectral analysis of the principal components indicates that both processes are strongly influenced by obliquity (41 kyr). We interpret this 41-kyr cycle in wind strength and precipitation as related to the changing position and strength of the Southern Hemisphere westerly winds. Precipitation is also influenced by an 11-kyr cycle. The 11-kyr periodicity is potentially related to orbital cyclicity, representing the equatorial semi-precessional maximum insolation cycle. This semi-precession cycle has been identified in a number of records from the Pleistocene and Holocene and has recently been suggested to indicate that insolation in low-latitude regions may be an important driver of millennial-scale climate response to orbital forcing (Feretti et al., 2015). This is the first time this cycle has been identified in a mid-latitude Southern Hemisphere climate archive, as well as the first identification in pre-Pleistocene records. The 11-kyr cycle appears at around 23.01 Ma, which coincides with the initiation of

  16. Constraining mass-diameter relations from hydrometeor images and cloud radar reflectivities in tropical continental and oceanic convective anvils

    NASA Astrophysics Data System (ADS)

    Fontaine, E.; Schwarzenboeck, A.; Delanoë, J.; Wobrock, W.; Leroy, D.; Dupuy, R.; Protat, A.

    2014-01-01

    In this study the density of hydrometeors in tropical clouds is derived from a combined analysis of particle images from 2-D-array probes and associated reflectivities measured with a Doppler cloud radar on the same research aircraft. The mass-diameter m(D) relationship is expressed as a power law with two unknown coefficients (pre-factor, exponent) that need to be constrained from complementary information on hydrometeors, where absolute ice density measurement methods do not apply. Here, at first an extended theoretical study of numerous hydrometeor shapes simulated in 3-D and arbitrarily projected on a 2-D plane allowed to constrain the temporal evolution of the exponent of the mass-diameter relationship with that of the exponent of the surface-diameter relationship that is measured by the 2-D-array probes. The pre-factor is then constrained from theoretical simulations of the radar reflectivities matching the measured reflectivities along the aircraft trajectory. The study has been performed as part of the Megha-Tropiques satellite project, where two types of mesoscale convective systems (MCS) have been investigated: (i) above the African Continent and (ii) above the Indian Ocean. In general, both mass-diameter coefficients (pre-factor and exponent) decrease with decreasing temperature, the decrease is more pronounced for oceanic MCS. The condensed water contents (CWC) calculated from particle size distributions (PSD) and m(D) also decrease with altitude while the concentrations of the hydrometeors increase with altitude. The calculated values of CWC are largest for continental MCS.

  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. Scaling Anisotropy in Cloud Satellite Images at Mid-Latitudes: Directional Structure Function Measurements and Exponents Determination

    NASA Astrophysics Data System (ADS)

    Addor, J.

    2004-05-01

    Motivation We investigate scaling anisotropy in cloud images. Even if these images look pretty much the same in all directions, we can observe details at different scales. For instance, small (13 km) bands of clouds tend to be East-West oriented and larger sized (130 km) bands tend to be more North-South. Moreover, bands of clouds can have any orientation, so we have to be able to measure if the scaling anisotropy is aligned with the cardinal directions or not. Data MODIS satellite images are used to measure scaling anisotropy on cloud fields. Two bands available at a resolution of 250 m are used; the image are 1250 by 2000 km (5000 x 8000 pixels) wide. The quantization depth of the pixels is 12 bits. The two bands available at that resolution have been used; they are designed for a primary use in land, cloud and aerosols boundaries. Band 1 (visible) has a bandwidth of 620-670 nm and is sensitive to land cover and vegetation (chlorophyll). Band 2 (near infra-red) has a bandwidth of 841-876 nm and is sensitive to cloud amount, vegetation and, land cover. The selected images were located over the southern Atlantic, mostly in mid-latitude. Islands, continents, and icebergs have been avoided (to lower the effect of topography on cloud statistics) and bad pixels have been ignored. Scaling anisotropy measurement method We propose a simple method to visualize and measure basic exponents of scaling anisotropy in all directions, assuming weak anisotropy. Considering the fact that very few anisotropic analyses have been done to this date it is better to analyse nearly isotropic data first, before going to highly anisotropic cases. This way, isotropic scaling analysis methods can be used for determining the scaling range and anisotropic scaling analysis will show if there is any weak anisotropy. Main results A smooth variation of the structure function exponent with the geographic direction has been observed and the behavior of the function corresponds to what is

  19. 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.

  20. 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.

  1. NmF2 trends at low and mid latitudes for the recent solar minima and comparison with IRI-2012 model

    NASA Astrophysics Data System (ADS)

    Perna, L.; Pezzopane, M.; Ezquer, R.; Cabrera, M.; Baskaradas, J. A.

    2017-07-01

    The ionospheric electron density peak (NmF2) is analyzed for the recent minima of solar activity for two mid-latitude stations, Rome (41.8°N, 12.5°E, geomagnetic latitude 41.7°N, Italy) and Gibilmanna (37.9°N, 14.0°E, geomagnetic latitude 37.6°N, Italy), and for the low-latitude station of Tucumán (26.9°S, 294.6°E, geomagnetic latitude 17.2°S, Argentina), located in the south ridge of the equatorial ionization anomaly. An inter-minima comparison reveals that from an ionospheric point of view the last minimum of solar activity (minimum 23/24) was peculiar, with values of NmF2 lower than those recorded during the previous minima for all the stations and all the hours of the day. A more pronounced decrease is observed at Tucumán than at Rome and Gibilmanna. The study of the winter and semi-annual anomaly shows that at mid-latitude stations the winter anomaly is not visible only for the years 2008 and 2009, which represent the deeper part of the prolonged and anomalous last solar minimum. The same is for the semi-annual anomaly. A comparison with the version 2012 of the International Reference Ionosphere model (IRI) is also carried out. The results reveal that for low solar activity the model works better at mid latitudes than at low latitudes, confirming the problems of IRI in correctly representing the low-latitude ionosphere. Nevertheless, using as input updated values of the solar and geomagnetic indices, no loss of accuracy is detected in the IRI performances for the last solar minimum with respect to the previous ones, both at mid and low latitudes.

  2. 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.

  3. Seasonal variations of long period oscillations in the mesosphere at high- and mid-latitudes and their relation to mesospheric summer echoes

    NASA Astrophysics Data System (ADS)

    Zeller, Olof; Hoffmann, Peter; Bremer, Juergen; Singer, Werner

    Continuous MF and meteor radar observations allow detailed studies of the wind field in the mesosphere and lower thermosphere, which is characterized by a high variability due to the presence of gravity and tidal waves as well as planetary waves. Here the seasonal variation of long period oscillations (periods of few days) is used to indicate the presence of transient planetary waves in the mesosphere at high and mid-latitudes. Our studies are based on wind measurements from meteor and MF radars at Andenes (69° N, 16° E) and Juliusruh (55° N, 13° E). These measurements are supplemented by mesospheric temperatures derived from meteor decay times. For investigations of wind and temperature oscillations wavelet analyses have been performed showing the seasonal varations of their preferred periods and amplitudes. The activity of oscillations with a period in the range 2 - 4 d have their maximum during summer while the long period ones (˜10 d) occur preferably in winter. Oscillations with periods of 4 - 7 d occur in every season. Such periods are not only observed in wind and temperature variations, but also in variations of (polar) mesosphere summer echos (P)MSE observed by VHF radars in Kuehlungsborn (54° N, 12° E) and Andenes. (P)MSE are connected with very cold temperatures where ice particles can exist. Due to an equatorward directed meridional temperature gradient variations of meridional wind and temperature are positively correlated. Generally radar echoes at mid latitudes are strongly affected by meridional wind variations due to a mean temperature around the frost point of water vapour. In contrast there is mostly no significant impact of the meridional wind on radar echoes at polar latitudes. A mean temperature well below the frost point and a weaker meridional temperature gradient than at mid latitudes are reasons for this reduced impact. But because of higher temperatures in 2002 long period temperature and meridional wind variations impact the PMSE

  4. 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

  5. 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

  6. COPT 81: A Field Experiment Designed for the Study of Dynamics and Electrical Activity of Deep Convection in Continental Tropical Regions.

    NASA Astrophysics Data System (ADS)

    Sommeria, Gilles; Testud, J.

    1984-01-01

    During May and June 1981 several French research organizations, the University of Abidjan (Ivory coast) and the Agency for security of Aeronautical Navigation (ASECNA), participated in the observational field program called "Convection Profonde Tropicale 1981" (COPT 81). COPT 81 was directed toward developing a better understanding of the dynamical and electrical features of precipitating convection in continental tropical regions.The observational network was designed to study the development and evolution of diurnal convection and squall lines over the northern part of the Ivory Coast, which is an example of a tropical savanna region at the southern edge of the Sahel. It consisted of two Doppler radars, a central meteorological station equipped for the reception of satellite data, rawin sounding and interrogation of remote targets, an acoustic sounder, a central electrical and electro-magnetical station, and a set of remote ground meteorological and electrical stations.Some experimental results are presented to characterize the main features of a tropical continental squall line. The evolution of the boundary layer during its passage, its precipitation pattern and associated dynamical field, its surface trace and the modification it produces on the thermodynamical state of the atmosphere, as well as some of its associated electrical features, are given.

  7. Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for Late Amazonian obliquity-driven climate change

    NASA Astrophysics Data System (ADS)

    Head, J. W.; Marchant, D. R.; Agnew, M. C.; Fassett, C. I.; Kreslavsky, M. A.

    2006-01-01

    Understanding spin orbital parameter-driven climate change on Mars prior to ˜ 20 Ma ago requires geological evidence because numerical solutions for that period are chaotic and non-unique. We show geological evidence that lineated valley fill at low mid-latitudes in the northern hemisphere of Mars (˜ 37.5° N) originated through regional snow and ice accumulation and underwent glacial-like flow. Breached upland craters and theater-headed valleys reveal features typical of erosion in association with terrestrial glaciers. Parallel, converging and chevron-like lineations in potentially ice-rich deposits on valley floors indicate that flow occurred through constrictions and converged from different directions at different velocities. Together, these Martian deposits and erosional landforms resemble those of intermontaine glacial systems on Earth, particularly in their major morphology, topographic shape, planform and detailed surface features. An inferred Late Amazonian age, combined with predictions of climate models, suggest that the obliquity of Mars exceeded a mean of 45° for a sustained period. During this time, significant transfer of ice occurred from ice-rich regions (e.g., the poles) to mid-latitudes, causing prolonged snow and ice accumulation there and forming an extensive system of valley glaciers.

  8. 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.

  9. Impact of propagation uncertainties on the potential dark matter contribution to the Fermi LAT mid-latitude {gamma}-ray data

    SciTech Connect

    Cumberbatch, Daniel T.; Tsai, Yue-Lin Sming; Roszkowski, Leszek

    2010-11-15

    We investigate the extent to which the uncertainties associated with the propagation of Galactic cosmic rays impact upon estimates for the {gamma}-ray flux from the mid-latitude region. We consider contributions from both standard astrophysical background (SAB) processes as well as resolved point sources. We have found that the uncertainties in the total {gamma}-ray flux from the mid-latitude region relating to propagation parameter values consistent with local B/C and {sup 10}Be/{sup 9}Be data dominate by 1-2 orders of magnitude. These uncertainties are reduced to less than an order of magnitude when the normalizations of the SAB spectral components are fitted to the corresponding Fermi LAT data. We have found that for many propagation parameter configurations (PPCs) our fits improve when an extragalactic background (EGB) component is simultaneously fitted to the data. We also investigate the improvement in our fits when a flux contribution from neutralino dark matter (DM), described by the minimal supersymmetric standard model, was simultaneously fitted to the data. We consider three representative cases of neutralino DM for both Burkert and Einasto DM density profiles, in each case simultaneously fitting a boost factor of the DM contribution together with the SAB and EGB components. We have found that for several PPCs there are significant improvements in our fits, yielding both substantial EGB and DM components, where for a few of these PPCs the best-fit EGB component is consistent with recent estimates by the Fermi Collaboration.

  10. 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.

  11. 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.

  12. 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

  13. 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

    2015-11-26

    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.

  14. Periods of active permafrost layer formation during the geological history of Mars: Implications for circum-polar and mid-latitude surface processes

    NASA Astrophysics Data System (ADS)

    Kreslavsky, Mikhail A.; Head, James W.; Marchant, David R.

    2008-02-01

    Permafrost is ground remaining frozen (temperatures are below the freezing point of water) for more than two consecutive years. An active layer in permafrost regions is defined as a near-surface layer that undergoes freeze-thaw cycles due to day-average surface and soil temperatures oscillating about the freezing point of water. A "dry" active layer may occur in parched soils without free water or ice but significant geomorphic change through cryoturbation is not produced in these environments. A wet active layer is currently absent on Mars. We use recent calculations on the astronomical forcing of climate change to assess the conditions under which an extensive active layer could form on Mars during past climate history. Our examination of insolation patterns and surface topography predicts that an active layer should form on Mars in the geological past at high latitudes as well as on pole-facing slopes at mid-latitudes during repetitive periods of high obliquity. We examine global high-resolution MOLA topography and geological features on Mars and find that a distinctive latitudinal zonality of the occurrence of steep slopes and an asymmetry of steep slopes at mid-latitudes can be attributed to the effect of active layer processes. We conclude that the formation of an active layer during periods of enhanced obliquity throughout the most recent period of the history of Mars (the Amazonian) has led to significant degradation of impact craters, rapidly decreasing the steep slopes characterizing pristine landforms. Our analysis suggests that an active layer has not been present on Mars in the last ˜5 Ma, and that conditions favoring the formation of an active layer were reached in only about 20% of the obliquity excursions between 5 and 10 Ma ago. Conditions favoring an active layer are not predicted to be common in the next 10 Ma. The much higher obliquity excursions predicted for the earlier Amazonian appear to be responsible for the significant reduction in

  15. 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

  16. Attribution of recent ozone changes in the Southern Hemisphere mid-latitudes using statistical analysis and chemistry-climate model simulations

    NASA Astrophysics Data System (ADS)

    Zeng, Guang; Morgenstern, Olaf; Shiona, Hisako; Thomas, Alan J.; Querel, Richard R.; Nichol, Sylvia E.

    2017-09-01

    Ozone (O3) trends and variability from a 28-year (1987-2014) ozonesonde record at Lauder, New Zealand, have been analysed and interpreted using a statistical model and a global chemistry-climate model (CCM). Lauder is a clean rural measurement site often representative of the Southern Hemisphere (SH) mid-latitude background atmosphere. O3 trends over this period at this location are characterised by a significant positive trend below 6 km, a significant negative trend in the tropopause region and the lower stratosphere between 9 and 15 km, and no significant trend in the free troposphere (6-9 km) and the stratosphere above 15 km. We find that significant positive trends in lower tropospheric ozone are correlated with increasing temperature and decreasing relative humidity at the surface over this period, whereas significant negative trends in the upper troposphere and the lower stratosphere appear to be strongly linked to an upward trend of the tropopause height. Relative humidity and the tropopause height also dominate O3 variability at Lauder in the lower troposphere and the tropopause region, respectively. We perform an attribution of these trends to anthropogenic forcings including O3 precursors, greenhouse gases (GHGs), and O3-depleting substances (ODSs), using CCM simulations. Results indicate that changes in anthropogenic O3 precursors contribute significantly to stratospheric O3 reduction, changes in ODSs contribute significantly to tropospheric O3 reduction, and increased GHGs contribute significantly to stratospheric O3 increases at Lauder. Methane (CH4) likely contributes positively to O3 trends in both the troposphere and the stratosphere, but the contribution is not significant at the 95 % confidence level over this period. An extended analysis of CCM results covering 1960-2010 (i.e. starting well before the observations) reveals significant contributions from all forcings to O3 trends at Lauder - i.e. increases in GHGs and the increase in CH4 alone

  17. Airborne measurements of single particle refractory black carbon over the continental U.S. during the Deep Convective Clouds and Chemistry (DC3) field study

    NASA Astrophysics Data System (ADS)

    Markovic, M. Z.; Perring, A. E.; Schwarz, J. P.; Gao, R.; Holloway, J. S.; Watts, L. A.; Fahey, D. W.; Diskin, G. S.; Sachse, G. W.; Fried, A.; Weibring, P.; Richter, D.; Walega, J.; Wisthaler, A.; Mikoviny, T.

    2012-12-01

    The Deep Convective Clouds and Chemistry (DC3) campaign was a large-scale, collaborative project, which took place in the continental U.S. in May and June of 2012. The goal of the campaign was to investigate the impacts of continental convection on the composition and chemistry of the upper troposphere and lower stratosphere through a series of aircraft and ground-based measurements of atmospheric gases and particles. During DC3, a NOAA Single Particle Soot Photometer (SP2) instrument was utilized onboard NASA's DC8 research aircraft for measurements of refractory black carbon (rBC) in atmospheric particles with 1 second time resolution. Particles containing rBC are emitted into the atmosphere by incomplete combustion of fossil and bio fuel and hence are strongly linked to anthropogenic sources. These particles are of great importance because, among other effects, they increase the radiative forcing of the Earth's system through absorption of shortwave solar radiation in the troposphere, accelerate the rate of melting of arctic ice and snow by changing the albedo, and pose a respiratory and cardiovascular health risk in the boundary layer. Removal processes and timescales for rBC-containing particles are poorly constrained, which leads to high uncertainty in modeling of regional and global distributions. In this work, an overview of the NOAA SP2 measurements during DC3 is presented. Geographical variations in mass loadings and size distributions of rBC over the continental U.S. are discussed. Vertical profiles of rBC concentrations are generated and, in conjunction with carbon monoxide (CO) and formaldehyde (HCHO) mixing ratios, are used to investigate the impacts of cloud convection and storm processing on the removal of rBC-containing particles from convected air masses. Comparisons of rBC mass loadings with acetonitrile (CH3CN) and CO mixing ratios are made to identify biomass burning plumes from wild fires originating in Colorado and New Mexico, and to

  18. 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.

  19. 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

  20. Mid-latitude ionospheric plasma temperature climatology and model based on Saint Santin incoherent scatter radar data from 1966-1987

    NASA Astrophysics Data System (ADS)

    Zhang, S. R.; Holt, J. M.; Zalucha, A. M.; Amory-Mazaudier, C.

    Zhang and Holt (2003, Ionospheric plasma temperatures during 1976-2001 over Millstone Hill, Adv. Space Res.) have reported the ionospheric plasma temperature variation based on incoherent scatter radar (ISR) observations between 1976 and 2001 at Millstone Hill, a typical sub-auroral mid-latitude site in North America. The French Saint Santin ISR, with a geographic latitude slightly higher but an apex latitude 7 degress lower than Millstone, collected bistatic and quadristatic measurements for 2 solar cycles beginning in September 1965.A database of these data from 1966 and 1987 has been used in this study in order to establish the mid-latitude ionospheric climatology, in particular that of the upper atmosphere thermal status, as well as empirical models for space weather applications. This paper presents, in comparison with the Millstone results, the variation of ion and electron temperature (Ti and Te) with solar activity, season, time of the day, and altitude. It is found that the F2 region Te at St Santin is not as high as in Millstone between May and September, when electron density (Ne) is relatively higher. The midday Te increases below 300 km with F107, as at Millstone Hill. However, above 300 km it tends to decrease with F107 at St Santin and increases between May and September at Millstone Hill. Ti between 250-350 km peaks not in summer but around May. Based on this database, Saint Saintin ionospheric models for Ne, Te, and Ti have also been created using a bin-fit technique similar to that used for the Millstone Hill models. Comparisions with corresponding IRI predications indicate good agreement in Ti at high solar activity, and IRI tends to give Te above the F2 peak higher than both the Saint Santin and Millstone Hill models.

  1. 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.

  2. Detection of the mid-latitude Sporadic-E signal using GNSS/TEC and ALOS2 InSAR data

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Maeda, J.; Furuya, M.; Heki, K.

    2016-12-01

    Sporadic E (Es) is known to generate unusual propagation of VHF waves over long distances, which is caused by a layer of ionization that irregularly appears within the E region of the ionosphere. However, the generation mechanism of Es remains unclear, because the conventional ionosonde observation of Es has limited spatial resolution. Maeda et al. (2016) succeeded in capturing mid-latitude Es signal over Japan two-dimensionally as an image, using InSAR, and demonstrated the detailed spatial structure of Es. As InSAR is clearly useful for capturing Es, we aim to detect mid-latitude Es over Japan by InSAR, following Maeda et al. (2016). First, we chose the dates whose critical frequencies of Es (foEs) were more than 15MHz at ionosonde in Kokubunji, Wakkanai and Yamagawa in the morning and noon in 2016 from May to June; Es is known to be frequent in the local daytime of summer season. Secondly, we chose the ALOS-2/PALSAR-2 data sets whose observation area, dates and time matches the data above as closely as possible. Thirdly, we generated Global Navigation Satellite System - Total Electron Content (GNSS-TEC) map whose areas, dates and time become the same as the above and if Es appeared in GNSS-TEC map, we generate interferogram. We could detect interesting phase changes in the pair of February 17, 2016 (Master) and May 25, 2016 (Slave) along a track from Tottori to Okayama. The location of the phase shift is close to the Es on the GNSS-TEC image. Therefore, we can consider the phase shift as the edge of Es. This is the second successful detection of Es signals, using InSAR. Also, we are going to separate the Es signal from other non-dispersive signals, using split-band InSAR technique.

  3. Evidence for very recent melt-water and debris flow activity in gullies in a young mid-latitude crater on Mars

    NASA Astrophysics Data System (ADS)

    Johnsson, A.; Reiss, D.; Hauber, E.; Hiesinger, H.; Zanetti, M.

    2014-06-01

    Terrestrial debris flows and their deposits are mainly studied and monitored because of their hazardous nature. On Mars they may serve as geomorphologic indicators of transient liquid water. We compared the morphology of debris flow-like deposits within a young (˜0.2 Ma) mid-latitude crater on Mars with debris flow fans on Svalbard as possible terrestrial analogues. It was our objective to constrain whether dry granular flow or processes related to water-saturation at or close to the surface were responsible for the formation of the deposits within the crater. We found that the morphological attributes of the deposits on Mars are very similar to debris flows in Svalbard and include overlapping terminal lobes, debris tongues and snouts, debris-flow fans, scoured channels with medial deposits (debris plugs), and clearly defined lateral deposits (levées). Furthermore, the interior crater walls display a range of landforms indicating aspect-dependent degradation, ranging from debris flow-dominated pole-facing slopes, to east-and-west-facing single channel gullies and north-facing talus cones (granular flow). Our findings suggest that the debris flows are not related to impact-induced heating and release of meltwater. We further suggest that degradation of a latitude dependent dust-ice mantling unit may only have played a minor role in this youthful terrain. Instead, we propose that the debris flows are mainly formed by melting of very recent snow deposits after the termination of the last martian ice-age. As such they may represent some of the most recent geomorphological indicators of transient liquid water in the martian mid-latitudes. The distinct north-south asymmetry in degradation further demonstrates that insolation-controlled slope processes are surprisingly efficient on Mars during the last <1 Myr.

  4. Comparison of terdiurnal tidal oscillations in mesospheric OH rotational temperature and Na lidar temperature measurements at mid-latitudes for fall/spring conditions

    NASA Astrophysics Data System (ADS)

    Taylor, M. J.; Pendleton, W. R., Jr.; Gardner, C. S.; States, R. J.

    1999-07-01

    Results from two different instrumental techniques, an Na Wind/Temperature Lidar and an OH Mesospheric Temperature Mapper, have been combined to investigate the occurrence and properties of the mid-latitude terdiurnal (8-hr) tide at near mesopause altitudes (80-105 km). High-resolution Na lidar measurements were taken throughout the diurnal and annual cycle (1996-98) at Urbana, Illinois (40°N, 88°W) to characterize the seasonal behavior of the 24, 12, 8 and 6-hr tides. Complementary measurements using a recently developed CCD imager capable of mapping OH temperature (at ˜87 km altitude) were made from Bear Lake Observatory, Utah (41.9°N, 111.6°W) and Ft. Collins, Colorado (40.6°N, 105°W) within the same time period. The "mean day" lidar data for the spring and fall periods investigated here each indicate an average amplitude variation of ˜2-5 K over the depth of the OH layer but distinct phases of <1-hr LST and ˜7-hr LST, respectively, for the 8-hr component. The Temperature Mapper data are in excellent agreement with these findings but in addition have shown that the amplitude of this tidal component can vary by as much as an order of magnitude (1.5-15 K) on a night-by-night basis resulting in an apparent 8-hr dominance of the nocturnal variation during investigated portions of the spring and fall seasons with little or no diurnal and semi-diurnal variability evident. Reports of terdiurnal tidal measurements in the mid-latitude nightglow emissions are exceptionally rare and have yet to be modeled. These innovative joint measurements pave the way for new research in this important area.

  5. 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 m