Large scale thermospheric density enhancements in relation to downward Poynting fluxes: Statistics from CHAMP, AMPERE and SuperDARN

2021 ◽  
Author(s):  
Daniel Billett ◽  
Gareth Perry ◽  
Lasse Clausen ◽  
William Archer ◽  
Kathryn McWilliams ◽  
...  
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Mass Density ◽  
Global Scale ◽  
Champ Satellite ◽  
Poynting Flux ◽  
Cusp Region ◽  
F Region ◽  
Primary Driver ◽  
Density Perturbations

<p>Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The CHAMP satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists on statistical timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine-scale Poynting fluxes are associated with the density perturbations on a case-by-case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically.</p><p>In this study, we use nearly 8 years of the overlapping SuperDARN and AMPERE datasets to generate global-scale patterns of the high-latitude and height-integrated Poynting flux into the ionosphere, with a time resolution of two minutes. From these, average patterns are generated based on the IMF orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Mesoscale height-integrated Poynting fluxes thus cannot fully account for the cusp neutral mass density enhancement, meaning energy deposition in the F-region or on fine-scales, which is not captured by our analysis, could be the primary driver.</p>

scholarly journals Comparison of generalized non-data-driven lake and reservoir routing models for global-scale hydrologic forecasting of reservoir outflow at diurnal time steps

2020 ◽  
Vol 24 (5) ◽  
pp. 2711-2729 ◽  
Author(s):  
Joseph L. Gutenson ◽  
Ahmad A. Tavakoly ◽  
Mark D. Wahl ◽  
Michael L. Follum
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Model Performance ◽  
Global Scale ◽  
Army Corps ◽  
Time Step ◽  
Large Spatial Scale ◽  
Reservoir Routing ◽  
Routing Methods ◽  
Improved Model

Abstract. Large-scale hydrologic forecasts should account for attenuation through lakes and reservoirs when flow regulation is present. Globally generalized methods for approximating outflow are required but must contend with operational complexity and a dearth of information on dam characteristics at global spatial scales. There is currently no consensus on the best approach for approximating reservoir release rates in large spatial scale hydrologic forecasting, particularly at diurnal time steps. This research compares two parsimonious reservoir routing methods at daily steps: Döll et al. (2003) and Hanasaki et al. (2006). These reservoir routing methods have been previously implemented in large-scale hydrologic modeling applications and have been typically evaluated seasonally. These routing methods are compared across 60 reservoirs operated by the U.S. Army Corps of Engineers. The authors vary empirical coefficients for both reservoir routing methods as part of a sensitivity analysis. The method proposed by Döll et al. (2003) outperformed that presented by Hanasaki et al. (2006) at a daily time step and improved model skill over most run-of-the-river conditions. The temporal resolution of the model influences model performances. The optimal model coefficients varied across the reservoirs in this study and model performance fluctuates between wet years and dry years, and for different configurations such as dams in series. Overall, the method proposed by Döll et al. (2003) could enhance large-scale hydrologic forecasting, but can be subject to instability under certain conditions.

scholarly journals Cloud Inhomogeneity from MODIS

2005 ◽  
Vol 18 (23) ◽  
pp. 5110-5124 ◽  
Author(s):  
Lazaros Oreopoulos ◽  
Robert F. Cahalan
Keyword(s):  
Optical Thickness ◽  
Large Scale ◽  
Spatial Scales ◽  
Temporal Variations ◽  
Global Scale ◽  
Time Of Day ◽  
Wide Range ◽  
Level 3 ◽  
Inhomogeneity Parameter ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Two full months (July 2003 and January 2004) of Moderate Resolution Imaging Spectroradiometer (MODIS) Atmosphere Level-3 data from the Terra and Aqua satellites are analyzed in order to characterize the horizontal variability of vertically integrated cloud optical thickness (“cloud inhomogeneity”) at global scales. The monthly climatology of cloud inhomogeneity is expressed in terms of standard parameters, initially calculated for each day of the month at spatial scales of 1° × 1° and subsequently averaged at monthly, zonal, and global scales. Geographical, diurnal, and seasonal changes of inhomogeneity parameters are examined separately for liquid and ice phases and separately over land and ocean. It is found that cloud inhomogeneity is overall weaker in summer than in winter. For liquid clouds, it is also consistently weaker for local morning than local afternoon and over land than ocean. Cloud inhomogeneity is comparable for liquid and ice clouds on a global scale, but with stronger spatial and temporal variations for the ice phase, and exhibits an average tendency to be weaker for near-overcast or overcast grid points of both phases. Depending on cloud phase, hemisphere, surface type, season, and time of day, hemispheric means of the inhomogeneity parameter ν (roughly the square of the ratio of optical thickness mean to standard deviation) have a wide range of ∼1.7 to 4, while for the inhomogeneity parameter χ (the ratio of the logarithmic to linear mean) the range is from ∼0.65 to 0.8. The results demonstrate that the MODIS Level-3 dataset is suitable for studying various aspects of cloud inhomogeneity and may prove invaluable for validating future cloud schemes in large-scale models capable of predicting subgrid variability.

scholarly journals Time-dependent responses of the neutral mass density to magnetospheric energy inputs into the cusp region in the thermosphere: A high-resolution two-dimensional local modeling

2020 ◽  
Author(s):  
Tomokazu Oigawa ◽  
Hiroyuki Shinagawa ◽  
Satochi Taguchi
Keyword(s):  
High Resolution ◽  
Electric Fields ◽  
Mass Density ◽  
Satellite Observation ◽  
Two Dimensional ◽  
Additional Energy ◽  
Champ Satellite ◽  
Cusp Region ◽  
Energy Inputs ◽  
Density Enhancement

Abstract Remarkable enhancements of the thermospheric mass density around the 400-km altitude in the cusp region have been observed by the CHAllenging Minisatellite Payload (CHAMP) satellite. We employed a high-resolution two-dimensional local model to gain insights into the extent to which the neutral-ion drag process controls the mass density’s enhancements under the energy inputs typical of the cusp. We expressed those energy inputs by quasi-static electric fields and electron precipitation. We compared two cases and calculated the thermospheric dynamics with and without neutral-ion drags. We found that in the more realistic case containing the neutral-ion drag, the calculated mass density enhancement was 10% at most, which is dramatically smaller than the observations by the CHAMP satellite (33% on average). The results also showed that the neutral-ion drag process suppresses Joule heating and neutral mass density enhancements, as well as the chemical reaction process. The discrepancy between our modeling result and the satellite observation suggests the existence of additional energy sources, such as Alfvén waves propagating from the magnetosphere, which play an important role in the cusp’s density enhancement.

Dependence of spatial periods of travelling ionospheric disturbances on their relative amplitudes

2020 ◽  
Vol 26 (6) ◽  
pp. 38-59
Author(s):  
Yu.P. Fedorenko ◽  
Keyword(s):  
Linear Approximation ◽  
Large Scale ◽  
Spatial Scales ◽  
Global Scale ◽  
Relative Amplitude ◽  
Spatial Period ◽  
Ionospheric Disturbances ◽  
Radio Waves ◽  
Traveling Ionospheric Disturbances ◽  
National University

The relationship between the horizontal spatial period L and the relative amplitude Ad of traveling ionospheric disturbances (TID) at various levels of solar (SA) and geomagnetic (GA) activity is experimentally studied. In the vast majority of cases, the TIDs observed during our study were generated by high-latitude sources. It was found that the period L and amplitude Ad of the medium-scale (MS) TIDs (L = 100 – 800 km) are related by a linear dependence, which does not depend upon the SA level. For large-scale (LS) TID with L = 1000 – 4000 km, the linear approximation of the function L(Ad) at low and high SA levels are increasing or decreasing functions, respectively. For global-scale (GM) TIDs with L = 5000 – 35000 km at low SA levels, the linear approximation L(Ad) is an increasing function. The function L(Ad) for TIDs of all spatial scales does not depend upon the GA level. The data were collected at the radio-physical observatory of V. N. Karazin Kharkiv National University (j = 49.63°N, l = 36.32°E) in 1999—2010 with the ionosphere radio sounding by using coherent radio waves at frequencies of about 150 and 400 MHz radiated by low-orbit navigation satellites Parus and Cicada orbiting at circular near-polar orbit with a height of about 1000 km. The experimental dependence of the horizontal period L of TID upon their relative amplitude Ad is explained based on the global prognostic semi-empirical model of the generation and propagation of acoustic-gravitational waves and traveling ionospheric disturbances.

MUSICA - Modeling for Chemistry, Weather and Climate

2020 ◽  
Author(s):  
Gabriele Pfister ◽  
Andrew Conley ◽  
Mary Barth ◽  
Louisa Emmons ◽  
Forrest Lacey ◽  
...  
Keyword(s):  
Air Quality ◽  
Atmospheric Chemistry ◽  
Large Scale ◽  
Spatial Scales ◽  
Spectral Element ◽  
Global Scale ◽  
Earth System ◽  
Early Results ◽  
Consistent Manner ◽  
Model Components

<p>Current chemical transport models inadequately account for the two-way coupling of atmospheric chemistry with other Earth System components over the range of urban/local to regional to global scales and from the surface up to the top of the atmosphere.  To meet future challenges, future modeling systems need to have the ability to (1) change spatial scales in a consistent manner, (2) resolve multiple spatial scales in a single simulation, (3) couple model components which represent different Earth system processes, and (4) easily mix-and-match model components. This is the motivation behind MUSICA - the Multi-Scale Infrastructure for Chemistry and Aerosols, which we develop together with the atmospheric chemistry community. MUSICA will allow simulation of large-scale atmospheric phenomena while still resolving chemistry at scales relevant for representing societal and scientific critical phenomena (e.g. urban air quality, or convection in monsoon regions) and also enable connections to other components of the earth system by fully coupling to land and ocean models. MUSICA objectives will be achieved through development of a global modeling system capable of regional refinement and the new Model Independent Chemistry Module (MICM). We will discuss the infrastructure and show preliminary results of atmospheric chemistry simulations being conducted in a global model with regional refinement: the Community Atmosphere Model with chemistry using spectral element grids that refine from one-degree resolution to ~14 km resolution over the conterminous United States. These early results confirm that model resolution does matter for representing regional air quality and that the two-way feedback between the local and global scale can play an important role.</p>

scholarly journals Reef Cover: a coral reef classification to guide global habitat mapping from remote sensing

2020 ◽  
Author(s):  
Emma Kennedy ◽  
Chris Roelfsema ◽  
Mitchell Lyons ◽  
Eva Kovacs ◽  
Rodney Borrego-Acevedo ◽  
...  
Keyword(s):  
Coral Reef ◽  
Large Scale ◽  
Spatial Scales ◽  
Global Scale ◽  
Habitat Mapping ◽  
Ecological Knowledge ◽  
Observation Data ◽  
Reef Management ◽  
Global Mapping ◽  
Earth Observation Data

AbstractCoral reef management and conservation stand to benefit from improved high-resolution global mapping. Yet classifications employed in large-scale reef mapping to date are typically poorly defined, not shared or region-specific. Here we present Reef Cover, a new coral reef geomorphic zone classification, developed to support global-scale coral reef habitat mapping in a transparent and version-based framework. We developed scalable classes by focusing on attributes that can be observed remotely, but whose membership rules also reflect knowledge of reef formation, growth and functioning. Bridging the divide between earth observation data and geo-ecological knowledge of reefs, Reef Cover maximises the trade-off between applicability at global scales, and relevance and accuracy at local scales. We use the Caroline and Mariana Island chains in the Pacific as a case study to demonstrate use of the classification scheme and its scientific and conservation applications. The primary application of Reef Cover is the Allen Coral Atlas global coral reef mapping project, but the system will support bespoke reef mapping conducted at a variety of spatial scales.

scholarly journals A new method for studying the thermospheric density variability derived from CHAMP/STAR accelerometer data for magnetically active conditions

2007 ◽  
Vol 25 (9) ◽  
pp. 1949-1958 ◽  
Author(s):  
M. Menvielle ◽  
C. Lathuillère ◽  
S. Bruinsma ◽  
R. Viereck
Keyword(s):  
Geomagnetic Activity ◽  
Large Scale ◽  
Singular Vector ◽  
Temporal Variations ◽  
Global Scale ◽  
Magnetic Activity ◽  
Accelerometer Data ◽  
Champ Satellite ◽  
Time Variations ◽  
The Impact

Abstract. Thermospheric densities deduced from STAR accelerometer measurements onboard the CHAMP satellite are used to characterize the thermosphere and its response to space weather events. The STAR thermospheric density estimates are analysed using a Singular Value Decomposition (SVD) approach allowing one to decouple large scale spatial and temporal variations from fast and local transients. Because SVD achieves such decomposition by using the reproducibility of orbital variations, it provides more meaningful results than any method based upon data smoothing or filtering. SVD analysis enables us to propose a new thermosphere proxy, based on the projection coefficient of the CHAMP densities on the first singular vector. The large scale spatial variations in the density, mostly related to altitude/latitude variations are captured by the first singular vector; time variations are captured by the associated projection coefficient. The study presented here is focused on time dependent global scale variations in the thermospheric density between 50 N and 50 S geographic latitudes. We show that the time variations in the projection coefficient do in fact represent those in the global density that are associated with magnetic activity as well as with solar EUV radiations. We also show that the NRLMSISE-00 empirical model better accounts for the density forcing by Solar radiations when tuned using Mg II indices. Using the so modified model with an additional geomagnetic parameterization corresponding to quiet geomagnetic situation enables one to define time reference values which are then used to evaluate the impact of geomagnetic activity. The ratio of CHAMP density projection coefficient to the quiet model projection coefficient is a global quantity, independent of altitude and latitude, which quantifies the thermospheric density response to auroral energy deposition. It will serve as a proxy of the response of thermospheric density to geomagnetic activity forcing.

scholarly journals Climatology of zonal wind and large-scale FAC with respect to the density anomaly in the cusp region: seasonal, solar cycle, and IMF <i>B</i><sub><i>y</i></sub> dependence

2014 ◽  
Vol 32 (3) ◽  
pp. 249-261 ◽  
Author(s):  
G. N. Kervalishvili ◽  
H. Lühr
Keyword(s):  
Solar Cycle ◽  
Relative Density ◽  
Wind Velocity ◽  
Zonal Wind ◽  
Large Scale ◽  
Solar Maximum ◽  
Mass Density ◽  
Cusp Region ◽  
Density Anomaly ◽  
The Imf

Abstract. We investigate the relationship of the thermospheric density anomaly (ρrel) with the neutral zonal wind velocity (Uzonal), large-scale field-aligned current (FAC), small-scale FAC, and electron temperature (Te) using the superposed epoch analysis (SEA) method in the cusp region. The dependence of these variables on the sign of the interplanetary magnetic field (IMF) By component and local season is of particular interest. Also, the conditions that lead to larger relative density enhancements are investigated. Our results are based on CHAMP satellite data and OMNI online data of IMF for solar maximum (March 2002–March 2007) and minimum (March 2004–March 2009) conditions in the Northern Hemisphere. In the cusp region the SEA technique uses the time and location of the mass density anomaly peaks as reference parameters. On average, the amplitude of the relative density anomaly, ρrel, does not depend on the solar cycle phase, local season, and IMF By sign. Also, it is apparent that the amplitude of IMF By does not have a large influence on ρrel, while the negative IMF Bz amplitude prevailing about half an hour earlier is in good correlation with ρrel. Both the zonal wind velocity and the large-scale FAC (LSFAC) distribution exhibit a clear dependence on the IMF By sign. Uzonal is directed towards dawn for both positive and negative IMF By at all local seasons and for solar maximum and minimum conditions. There is a systematic imbalance between downward (upward) and upward (downward) large-scale FACs peaks equatorward and poleward of the reference point, respectively, for the IMF By+ (By−) case. Relative density enhancements appear halfway between region 1 and region 0 currents in closer proximity to the upward FAC region. FAC densities and mass density anomaly amplitudes are not well correlated, but it is apparent that there is a close spatial relationship between ρrel and LSFAC. At this point we cannot offer any simple functional relation between these two variables, because there seem to be additional quantities controlling this relation.

scholarly journals Large-scale recovery of an endangered amphibian despite ongoing exposure to multiple stressors

2016 ◽  
Vol 113 (42) ◽  
pp. 11889-11894 ◽  
Author(s):  
Roland A. Knapp ◽  
Gary M. Fellers ◽  
Patrick M. Kleeman ◽  
David A. W. Miller ◽  
Vance T. Vredenburg ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Large Scale ◽  
Multiple Stressors ◽  
Spatial Scales ◽  
Large Fraction ◽  
Regional Scale ◽  
Global Scale ◽  
Amphibian Declines ◽  
Active Management ◽  
Introduced Fish

Amphibians are one of the most threatened animal groups, with 32% of species at risk for extinction. Given this imperiled status, is the disappearance of a large fraction of the Earth’s amphibians inevitable, or are some declining species more resilient than is generally assumed? We address this question in a species that is emblematic of many declining amphibians, the endangered Sierra Nevada yellow-legged frog (Rana sierrae). Based on >7,000 frog surveys conducted across Yosemite National Park over a 20-y period, we show that, after decades of decline and despite ongoing exposure to multiple stressors, including introduced fish, the recently emerged disease chytridiomycosis, and pesticides, R. sierrae abundance increased sevenfold during the study and at a rate of 11% per year. These increases occurred in hundreds of populations throughout Yosemite, providing a rare example of amphibian recovery at an ecologically relevant spatial scale. Results from a laboratory experiment indicate that these increases may be in part because of reduced frog susceptibility to chytridiomycosis. The disappearance of nonnative fish from numerous water bodies after cessation of stocking also contributed to the recovery. The large-scale increases in R. sierrae abundance that we document suggest that, when habitats are relatively intact and stressors are reduced in their importance by active management or species’ adaptive responses, declines of some amphibians may be partially reversible, at least at a regional scale. Other studies conducted over similarly large temporal and spatial scales are critically needed to provide insight and generality about the reversibility of amphibian declines at a global scale.

Towards a 3-D model for large-scale glacier simulations

2020 ◽  
Author(s):  
Harry Zekollari ◽  
Heiko Goelzer ◽  
Frank Pattyn ◽  
Bert Wouters ◽  
Stef Lhermitte
Keyword(s):  
Large Scale ◽  
Temporal Evolution ◽  
Spatial Scales ◽  
Global Scale ◽  
Ice Flow ◽  
Surface Mass ◽  
Mass Redistribution ◽  
Glacier Changes ◽  
Minimal Data ◽  
D Model

&lt;p&gt;Glaciers outside the two major ice sheets are key contributors to sea level rise, act as important sources of freshwater, and have great touristic value. To simulate the temporal evolution of these ice masses at regional- to global scale, simplified models are typically used that rely on volume scaling approximations or parameterizations based on observed glacier changes. These approaches rely on minimal data and are fast, but they do not account for mass redistribution through ice flow. More recently, efforts have been undertaken to represent ice dynamical processes in flowline models that can be applied at large spatial scales. These flowline approaches represent the mass transfer within a glacier in a more realistic way, but fail at reproducing the evolution of large glaciers, which are typically not confined by the local topography and do not have a pronounced elongated shape as represented in flowline models.&lt;/p&gt;&lt;p&gt;Here we present our first efforts to develop a 3D coupled surface mass balance &amp;#8211; ice flow model that can be used to model the temporal evolution of an ensemble of glaciers. The main goal of such a model is to be able to simulate the temporal evolution of glaciers with distinct shapes and situated in various climatic regimes in an automated way. By relying on a 3D model architecture we aim to better represent processes crucial for glacier evolution, such as glacier calving and convergent flow from several tributaries. Here, we will present first tests with a prototype version of the model by reproducing steady state geometries of selected glaciers, and by simulating the evolution of these ice bodies under idealised forcing scenarios.&lt;/p&gt;

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