We present a methodology adopted to extract planetary wave information from a set of interferomet... more We present a methodology adopted to extract planetary wave information from a set of interferometric data. The data set represent information collected by a Bomem interferometer from 1993 until 1995 in Stockholm, Sweden. We also discuss several procedures other than that adopted for the analysis of this unevenly spaced data and provide the rationale for the adopted procedure. New results
<p>Solar, auroral, and radiation belt electrons enter the atmosphere at pol... more <p>Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models with interactive chemistry in the upper atmosphere, such as WACCM-X or EDITh, usually parametrize this ionization and calculate the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra. These satellites provide in-situ measurements of the particle populations at the satellite altitude, but require interpolation and modelling to infer the actual input into the upper atmosphere.</p><p>Here we use the electron energy and flux data products from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of currently three operating satellites observes both auroral zones in the far UV from (115--180 nm) with a 3000 km wide swath and 10 x 10 km (nadir) pixel resolution during each orbit. From the N<sub>2</sub> LBH emissions, the precipitating electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate auroral ionization rates in the lower thermosphere (≈ 90–150 km), which have been validated previously against ground-based electron density measurements from EISCAT. We present an empirical model of these ionization rates derived for the entire satellite operating time and sorted according to magnetic local time and geomagnetic latitude and longitude. The model is based on geomagnetic and solar flux indices, and a sophisticated noise model is used to account for residual noise correlations. The model will be particularly targeted for use in climate models that include the upper atmosphere, such as the aforementioned WACCM-X or EDITh models. Further applications include the derived conductances in the auroral region, as well as modelling and forecasting E-region disturbances related to Space Weather.</p>
<p>The middle atmospheric circulation is driven by atmospheric waves, which carry energy an... more <p>The middle atmospheric circulation is driven by atmospheric waves, which carry energy and momentum from their source to the area of their dissipation and thus providing an energetic coupling between different atmospheric layers. A comprehensive understanding of the wave-wave or wave-mean flow interactions often requires a spatial characterization of these waves. Multistatic meteor radar observations provide an opportunity to investigate the spatial and temporal variability of mesospheric/lower thermospheric winds on regional scales. We apply the 3DVAR+div retrievals to observations from the Nordic Meteor Radar Cluster and the Chilean Observation Network De Meteor Radars (CONDOR). Here we present preliminary results of a new 3DVAR+div retrieval to infer the vertical wind variability using spatially resolved observations. The new retrieval includes the continuity equation in the forward model to ensure physical consistency in the vertical winds. Our preliminary results indicate that the vertical wind variability is about +/-2m/s. The 3DVAR+div algorithm provides spatially resolved winds resolves body forces of breaking gravity waves, which are typically indicated by two counterrotating vortices. Furthermore, we infer horizontal wavelength spectra for all 3 wind components to obtain spectral slopes indicating a transition of the vertical to the divergent mode at scales of about 80-120 km at the mesosphere.</p>
Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ion... more Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the rela...
The atmospheric winds, density and temperature of the region between 80 and 100 km, known as the ... more The atmospheric winds, density and temperature of the region between 80 and 100 km, known as the mesosphere and lower thermosphere (MLT), are subject to the effects of solar and particle precipitation from above as well as to tidal and gravity-wave forcing from below (Fritts and Alexander 2003). Additionally, the solar heating of ozone and chemical heating due to oxygen recombination chemistry in this region compete with long-term cooling of the upper atmosphere caused by increases in greenhouse gases (Robel and Dickenson 1989; Akmaev et al. 2006; Hervig et al. 2016). However, naturally occurring fluctuations associated with variations in ozone, solar or wave forcing can mask, or even mimic, the evidence of secular change in measurements of the temperature, density and winds of the MLT. Thus, these naturally occurring variations, their mechanisms and their seasonal and solar cycle behaviour must be quantified along with the driving forces associated with small-scale wave activity th...
&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp... more &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;We present electron energy and flux measurements from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) satellite instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of now four satellites observes the auroral zone in the UV from which electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate ionization rates and electron densities in the upper mesosphere and lower thermosphere (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8776; 70&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;200 km). We present an initial comparison of these rates to other models and compare the electron densities to those measured by the EISCAT radar. This comparison shows that with the current standard parametrizations, the SSUSI inferred auroral (90&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;120 km) electron densities are larger than the ground-based measured ones by a factor of 2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;5. It is still under investigation if this difference is due to collocation (in space and time) and EISCAT mode characteristics or caused by incompletely modelling the ionization and recombination in that energy range.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;
Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral... more Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral temperatures near the mesopause. Correct Einstein coefficients for the various transitions in the OH airglow are needed to calculate accurate temperatures. However, studies from some studys showed experimentally and theoretically that the most commonly used Einstein spontaneous emission transition probabilities for the Q-branch of the OH Meinel (6,2) transition are overestimated. Extending their work to several Δv = 2 and 3 transitions from v′ = 3 to 9, we have determined Einstein coefficients for the first four Q-branch rotational lines. These have been derived from high resolution, high signal to noise spectroscopic observations of the OH airglow in the night sky from the Nordic Optical Telescope. The Q-branch Einstein coefficients calculated from these spectra show that values currently tabulated in the HITRAN database overestimate many of the Q-branch transition probabilities. The i...
We retrieve nitric monoxide (NO) number densities from measurements from the SCanning Imaging Abs... more We retrieve nitric monoxide (NO) number densities from measurements from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY, on Envisat) nominal limb mode (0–91 km). We derive the NO number densities from atmospheric emissions in the gamma bands in the range 230–300 nm, measured by the SCIAMACHY ultra-violet (UV) channel 1. We adapt the NO retrieval from the mesosphere and lower thermosphere mode (MLT, 50–150 km) (Bender et al., 2013), including the same 3-D ray tracing, 2-D retrieval grid, and regularisations with respect to altitude and latitude. <br><br> Since the nominal mode limb scans extend only to about 91 km, we use NO densities in the lower thermosphere (above 92 km) derived from empirical models as a priori input. As priors we use the NOEM model (Marsh et al., 2004) and a regression model derived from the MLT NO data comparison (Bender et al., 2015). Our algorithm yields mea...
Physics and Chemistry of the Earth, Parts A/B/C, 2002
ABSTRACT Using ground-based measurements of the hydroxyl (OH) Meinel (3,1) band nightglow near 15... more ABSTRACT Using ground-based measurements of the hydroxyl (OH) Meinel (3,1) band nightglow near 1500 nm, nightly means of mesospheric temperature and OH radiance from 1991 to 1998 have been derived over Stockholm (59.5°N, 18.2°E). Time-series analysis techniques applied both to the eight-year data set as well as to an annual superposed epoch revealed several statistically significant periodic components. A trend analysis that included these periodic components revealed a small positive trend over the eight-year temperature time series. However, examining the trends on a month-to-month basis revealed positive trends during winter, small negative trends during equinox, and no significant trend during summer. This seasonal variability indicates that dynamic feedbacks, rather than radiative forcing of the mesosphere by infrared active gases, may dominate the response of the mesosphere to greenhouse gas emissions. In support of this an examination of the variability in the superposed epoch of OH temperature and radiance showed strong impulses near equinox. A simple gravity-wave transmission and dissipation model indicates that these are due in part to seasonal increases in the gravity-wave transmission of the lower atmosphere, and enhanced wave heating and mixing in the mesosphere.
We present a methodology adopted to extract planetary wave information from a set of interferomet... more We present a methodology adopted to extract planetary wave information from a set of interferometric data. The data set represent information collected by a Bomem interferometer from 1993 until 1995 in Stockholm, Sweden. We also discuss several procedures other than that adopted for the analysis of this unevenly spaced data and provide the rationale for the adopted procedure. New results
&amp;lt;p&amp;gt;Solar, auroral, and radiation belt electrons enter the atmosphere at pol... more &amp;lt;p&amp;gt;Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models with interactive chemistry in the upper atmosphere, such as WACCM-X or EDITh, usually parametrize this ionization and calculate the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra. These satellites provide in-situ measurements of the particle populations at the satellite altitude, but require interpolation and modelling to infer the actual input into the upper atmosphere.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Here we use the electron energy and flux data products from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of currently three operating satellites observes both auroral zones in the far UV from (115--180 nm) with a 3000 km wide swath and 10 x 10 km (nadir) pixel resolution during each orbit. From the N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; LBH emissions, the precipitating electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate auroral ionization rates in the lower thermosphere (&amp;amp;#8776; 90&amp;amp;#8211;150 km), which have been validated previously against ground-based electron density measurements from EISCAT. We present an empirical model of these ionization rates derived for the entire satellite operating time and sorted according to magnetic local time and geomagnetic latitude and longitude. The model is based on geomagnetic and solar flux indices, and a sophisticated noise model is used to account for residual noise correlations. The model will be particularly targeted for use in climate models that include the upper atmosphere, such as the aforementioned WACCM-X or EDITh models. Further applications include the derived conductances in the auroral region, as well as modelling and forecasting E-region disturbances related to Space Weather.&amp;lt;/p&amp;gt;
<p>The middle atmospheric circulation is driven by atmospheric waves, which carry energy an... more <p>The middle atmospheric circulation is driven by atmospheric waves, which carry energy and momentum from their source to the area of their dissipation and thus providing an energetic coupling between different atmospheric layers. A comprehensive understanding of the wave-wave or wave-mean flow interactions often requires a spatial characterization of these waves. Multistatic meteor radar observations provide an opportunity to investigate the spatial and temporal variability of mesospheric/lower thermospheric winds on regional scales. We apply the 3DVAR+div retrievals to observations from the Nordic Meteor Radar Cluster and the Chilean Observation Network De Meteor Radars (CONDOR). Here we present preliminary results of a new 3DVAR+div retrieval to infer the vertical wind variability using spatially resolved observations. The new retrieval includes the continuity equation in the forward model to ensure physical consistency in the vertical winds. Our preliminary results indicate that the vertical wind variability is about +/-2m/s. The 3DVAR+div algorithm provides spatially resolved winds resolves body forces of breaking gravity waves, which are typically indicated by two counterrotating vortices. Furthermore, we infer horizontal wavelength spectra for all 3 wind components to obtain spectral slopes indicating a transition of the vertical to the divergent mode at scales of about 80-120 km at the mesosphere.</p>
Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ion... more Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the rela...
The atmospheric winds, density and temperature of the region between 80 and 100 km, known as the ... more The atmospheric winds, density and temperature of the region between 80 and 100 km, known as the mesosphere and lower thermosphere (MLT), are subject to the effects of solar and particle precipitation from above as well as to tidal and gravity-wave forcing from below (Fritts and Alexander 2003). Additionally, the solar heating of ozone and chemical heating due to oxygen recombination chemistry in this region compete with long-term cooling of the upper atmosphere caused by increases in greenhouse gases (Robel and Dickenson 1989; Akmaev et al. 2006; Hervig et al. 2016). However, naturally occurring fluctuations associated with variations in ozone, solar or wave forcing can mask, or even mimic, the evidence of secular change in measurements of the temperature, density and winds of the MLT. Thus, these naturally occurring variations, their mechanisms and their seasonal and solar cycle behaviour must be quantified along with the driving forces associated with small-scale wave activity th...
&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp... more &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;We present electron energy and flux measurements from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) satellite instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of now four satellites observes the auroral zone in the UV from which electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate ionization rates and electron densities in the upper mesosphere and lower thermosphere (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8776; 70&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;200 km). We present an initial comparison of these rates to other models and compare the electron densities to those measured by the EISCAT radar. This comparison shows that with the current standard parametrizations, the SSUSI inferred auroral (90&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;120 km) electron densities are larger than the ground-based measured ones by a factor of 2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#8211;5. It is still under investigation if this difference is due to collocation (in space and time) and EISCAT mode characteristics or caused by incompletely modelling the ionization and recombination in that energy range.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;
Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral... more Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral temperatures near the mesopause. Correct Einstein coefficients for the various transitions in the OH airglow are needed to calculate accurate temperatures. However, studies from some studys showed experimentally and theoretically that the most commonly used Einstein spontaneous emission transition probabilities for the Q-branch of the OH Meinel (6,2) transition are overestimated. Extending their work to several Δv = 2 and 3 transitions from v′ = 3 to 9, we have determined Einstein coefficients for the first four Q-branch rotational lines. These have been derived from high resolution, high signal to noise spectroscopic observations of the OH airglow in the night sky from the Nordic Optical Telescope. The Q-branch Einstein coefficients calculated from these spectra show that values currently tabulated in the HITRAN database overestimate many of the Q-branch transition probabilities. The i...
We retrieve nitric monoxide (NO) number densities from measurements from the SCanning Imaging Abs... more We retrieve nitric monoxide (NO) number densities from measurements from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY, on Envisat) nominal limb mode (0–91 km). We derive the NO number densities from atmospheric emissions in the gamma bands in the range 230–300 nm, measured by the SCIAMACHY ultra-violet (UV) channel 1. We adapt the NO retrieval from the mesosphere and lower thermosphere mode (MLT, 50–150 km) (Bender et al., 2013), including the same 3-D ray tracing, 2-D retrieval grid, and regularisations with respect to altitude and latitude. <br><br> Since the nominal mode limb scans extend only to about 91 km, we use NO densities in the lower thermosphere (above 92 km) derived from empirical models as a priori input. As priors we use the NOEM model (Marsh et al., 2004) and a regression model derived from the MLT NO data comparison (Bender et al., 2015). Our algorithm yields mea...
Physics and Chemistry of the Earth, Parts A/B/C, 2002
ABSTRACT Using ground-based measurements of the hydroxyl (OH) Meinel (3,1) band nightglow near 15... more ABSTRACT Using ground-based measurements of the hydroxyl (OH) Meinel (3,1) band nightglow near 1500 nm, nightly means of mesospheric temperature and OH radiance from 1991 to 1998 have been derived over Stockholm (59.5°N, 18.2°E). Time-series analysis techniques applied both to the eight-year data set as well as to an annual superposed epoch revealed several statistically significant periodic components. A trend analysis that included these periodic components revealed a small positive trend over the eight-year temperature time series. However, examining the trends on a month-to-month basis revealed positive trends during winter, small negative trends during equinox, and no significant trend during summer. This seasonal variability indicates that dynamic feedbacks, rather than radiative forcing of the mesosphere by infrared active gases, may dominate the response of the mesosphere to greenhouse gas emissions. In support of this an examination of the variability in the superposed epoch of OH temperature and radiance showed strong impulses near equinox. A simple gravity-wave transmission and dissipation model indicates that these are due in part to seasonal increases in the gravity-wave transmission of the lower atmosphere, and enhanced wave heating and mixing in the mesosphere.
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