Peak Emission Rate Research Articles

Retrieval of Airglow Emission Rates in Analytical Form for Limb‐Viewing Satellite Observations at Low Latitudes

AbstractThe observation strategy of the limb‐viewing Imager of Sprites and Upper Atmospheric Lightning (ISUAL) payload aboard the FORMOSAT‐2 spacecraft inspires our development of a method to retrieve the volume emission rates from an array of airglow radiance measurements. The retrieval can be performed simply by evaluation of an analytical formula. The method can be applied to radiation at any wavelength, and its utilities are demonstrated in a reconstructed observation event of the 630.0‐nm OI airglow based on model‐generated emission rates. The simulated observation shows that radiance measurements may underestimate the heights of airglow locations by as much as 20 km. But application of the method to retrieve the emission rate profiles can recover the airglow locations with good accuracy, on average missing the height of the peak emission rate by only 2 km or so, corresponding to only 1–2 grid points in the calculations. The retrieval of airglow locations remains quite accurate even when the effect of noise is incorporated into the array of simulated radiance. Accuracy of the retrieved emission rates improves with the range of the field of view in the vertical direction. The method is also able to resolve the interference between the OI and OH emissions in the radiance data, separating the sources of the two types of emissions at distinctly different altitudes in the retrieved emission rate profiles. Overall, consideration of the reasoning behind this retrieval method could be useful for designing future satellite missions that focus on airglow research.

Synchronous Marine and Terrestrial Carbon Cycle Perturbation in the High Arctic During the PETM

AbstractThe Paleocene‐Eocene Thermal Maximum (PETM; 56 Ma) is considered to be one of the best analogs for future climate change. The carbon isotope composition (δ13C) of n‐alkanes derived from leaf waxes of terrestrial plants and marine algae can provide important insights into the carbon cycle perturbation during the PETM. Here, we present new organic geochemical data and compound‐specific δ13C data from sediments recovered from an early Cenozoic basin‐margin succession from Spitsbergen. These samples represent one of the most expanded PETM sites and provide new insights into the high Arctic response to the PETM. Our results reveal a synchronous ∼−6.5‰ carbon isotope excursion (CIE) in short‐chain n‐alkanes (nC19; marine algae/bacteria) with a ∼−5‰ CIE in long‐chain n‐alkanes (nC29 and nC31; plant waxes) during the peak of the PETM. Although δ13Cn‐alkanes values were potentially affected via a modest thermal effect (1‰–2‰), the relative changes in the δ13Cn‐alkanes remain robust. A simple carbon cycle modeling suggests peak carbon emission rate could be ∼3 times faster than previously suggested using δ13CTOC records. The CIE magnitude of both δ13C n‐C19 and δ13Cn‐C29 can be explained by the elevated influence of 13C‐depleted respired CO2 in the water column and increased water availability on land, elevated pCO2 in the atmosphere, and changes in vegetation type during the PETM. The synchronous decline in δ13C of both leaf waxes and marine algae/bacteria argues against a significant contribution to the sedimentary organic carbon pool from the weathering delivery of fossil n‐alkanes in the Arctic region.

Describing fluctuating indoor aerosol dust measurements with application to house dust mite allergens

Measuring house dust mite aeroallergen concentrations is essential in understanding mite allergen exposure. Physically, the aerolized house dust mite faeces are part of indoor particulate matter. We studied the statistical ways of summarizing measurements of fluctuating mite aeroallergen exposure inside homes through indoor particulate matter. To study emissions from beddings, we measured the time-related airborne dust concentration after shaking a duvet. Analysis was performed both by a method based on the estimated mean and by a non-linear model. Twenty-eight studies reported a sum of concentrations; only one also reported the peak. In our four experiments on shaking a duvet (245 to 275 measurements each), the peak value was two to four times higher than the mean. The mean-based and non-linear models both predicted the sum of concentrations exactly. A 1% upper prediction bound and the non-linear model predicted the peak emission rate moderately well (64 to 92%, and 63 to 93%, respectively). Mean levels of indoor particulate matter measurements differ substantially from peak concentrations. The use of the mean is only sufficient to predict the sum of concentrations. We suggest that, mite aeroallergen measurements should include information on the peak as well as the mean.

Temporal variability largely explains top-down/bottom-up difference in methane emission estimates from a natural gas production region

This study spatially and temporally aligns top-down and bottom-up methane emission estimates for a natural gas production basin, using multiscale emission measurements and detailed activity data reporting. We show that episodic venting from manual liquid unloadings, which occur at a small fraction of natural gas well pads, drives a factor-of-two temporal variation in the basin-scale emission rate of a US dry shale gas play. The midafternoon peak emission rate aligns with the sampling time of all regional aircraft emission studies, which target well-mixed boundary layer conditions present in the afternoon. A mechanistic understanding of emission estimates derived from various methods is critical for unbiased emission verification and effective greenhouse gas emission mitigation. Our results demonstrate that direct comparison of emission estimates from methods covering widely different timescales can be misleading.

Study of atomic oxygen greenline dayglow emission in thermosphere during geomagnetic storm conditions

The influence of geomagnetic storms on the atomic oxygen greenline (557.7nm) dayglow emission in thermosphere is studied during solar active and solar quiet conditions. This study is primarily based on the photochemical model with inputs obtained from experimental observations and empirical models. The updated rate coefficients, quantum yields and related cross-sections have been used from experimental results and theoretical studies. This study is presented for a low latitude station Tirunelveli (8.7°N, 77.8°E), India. The volume emission rate (VER) has been calculated using densities and temperatures from the empirical models. The modeled VER shows a positive correlation with the Dst index. The VER also shows a negative correlation with the number densities of O, O2, and N2. The VER, calculated at peak emission altitude, exhibits depletion during the main phase of the storm. The altitude of peak emission rate is unaffected by the geomagnetic storm activity. The study also reveals that the peak emission altitude depends on the F10.7 solar index. The peak emission altitude moves upward as the value of F10.7 solar index increases.

The responses of the nightglow emissions observed by the TIMED/SABER satellite to solar radiation

AbstractThe responses of four nightglow emissions, NO emission at 5.3 µm, O2 infrared atmospheric band at 1.27 µm, and OH emissions at 2.0 µm and 1.6 µm (referred to as OH2 and OH1 in this study), to solar radiation are studied and compared based on the data observed by the Sounding of the Atmosphere using Broadband Emission Radiometry instrument over 13 years. The quantitative relationships between the nightglow emissions and solar radiation are obtained by a linear regression fit using the F10.7 index. The intensities and the peak heights of the 13 year average global mean NO, O2, OH2, and OH1 nightglows are 270.0 ± 42.8 kR, 106.9 ± 2.2 kR, 133.2 ± 1.6 kR, 217.5 ± 2.4 kR, 123.6 ± 0.2 km, 89.8 ± 0.05 km, 88.1 ± 0.02 km, and 86.6 ± 0.02 km, respectively. Among the four nightglow emissions, the influence of solar radiation on the ones at lower heights is weaker than the ones higher above. The responses of the global mean NO, O2, OH2, and OH1 nightglow intensities to solar radiation are 176.3 ± 4.8%/100 solar flux units (sfu), 22.2 ± 1.4%/100 sfu, 12.9 ± 1.1%/100 sfu, and 11.4 ± 1.3%/100 sfu, respectively. The intensities and peak emission rates of the four global mean nightglow emissions are highly correlated to solar radiation. The response of the height of the global mean O2 nightglow peak emission rate to solar radiation is 0.51 ± 0.08 km/100 sfu. The responses of NO, OH2, and OH1 nightglow peak heights to solar radiation are not obvious. In addition, the responses of nightglow emissions to solar radiation change with latitude.

Modeling of Na airglow emission and first results on the nocturnal variation at midlatitude

AbstractA model for sodium airglow emission is developed by incorporating all the known reaction mechanisms. The neutral, ionic, and photochemical mechanisms are successfully implemented into this model. The values of reaction rate coefficients are based upon the theoretical calculations as well as from experimental observations. The densities of major species are calculated using the continuity equations, whereas for the minor, intermediating, and short‐lived species steady state approximation method is used. The modeled results are validated with the rocket, lidar, and photometer observations for a branching ratio of 0.04 for the production of Na(2P) in the reaction NaO + O Na(2P, 2S). The inputs have been obtained from other physics‐based models and ground‐ and satellite‐based observations to give the combined volume emission rate (VER) of Na airglow between 80 and 110 km altitude. In the present study, the model is used to understand the nocturnal variation of Na VER during the solstice conditions. The model results suggest a variation of peak emission layer between 85 and 90 km during summer solstice condition, indicating a lower value of peak emission rate during summer solstice. The emission rates bear a strong correlation with the O3 density during summer solstice, whereas the magnitude of VER follows the Na density during winter solstice. The altitude of peak VER shows an upward shift of 5 km during winter solstice.

A study of OI 844.6 nm dayglow emission under geomagnetic storm conditions

A comprehensive model is developed to study 844.6nm dayglow emission. The Solar2000 EUV (extreme ultraviolet) flux model, neutral atmosphere model (NRLMSISE-00) and latest available cross-sections are incorporated in this model. The present model is used to study the effects of geomagnetic storm on the 844.6nm dayglow emission at a low latitude station Tirunelveli (8.7°N, 77.8°E). Three geomagnetic storms which occurred during 23rd–27th August 2005, 13th–17th April 2006 and 1st–5th February 2008 are chosen in the present study. It is found that the volume emission rate (VER) shows a negative correlation with the Dst index for all the three geomagnetic storms. The present study also shows that the altitude of the peak emission rate does not vary with the activity of geomagnetic storm. The model predicts a positive correlation between the zenith intensity of 844.6nm dayglow emission and atomic oxygen number density. The consistency of atomic oxygen number density obtained from the NRLMSISE-00 model during a geomagnetic storm is checked using the satellite measurements of Earle et al. (2013). It is found that the atomic oxygen number density given by NRLMSISE-00 model is significantly lower than the measured values. Consequently, the effect of atomic oxygen number density abundance on 844.6nm dayglow emission is further studied by treating the atomic oxygen number density as a variable parameter in the present model. An increase of more than 50% in the zenith intensity above the normal level (before the onset of the storm) is found when the atomic oxygen number density which is obtained from NRLMSISE-00 model is doubled (under the limits of measurements).

A study of 732.0 nm dayglow emission at the equator under varying atomic oxygen density conditions for equinox and solstice cases

AbstractA comprehensive model is developed to compute the volume emission rate of O+(2P) 732.0 nm dayglow emission. The modeled volume emission rates are compared with the measurements as provided by Atmosphere Explorer C satellite and Dynamics Explorer 2 spacecraft. It is found that the model explains quite well the measured emission profiles. The present model is used to study the effect of atomic oxygen abundance on the volume emission rate of 732.0 nm dayglow emission at the equator for equinox and solstice. To study the effect of atomic oxygen abundance on 732.0 nm dayglow emission, the atomic oxygen number densities obtained from the NRLMSISE‐00 model are increased (or decreased) in an increment (or decrement) of 20% and are incorporated into the model to compute volume emission rate profiles. The present study shows that the peak emission rate (PER) varies linearly below the reference level of atomic oxygen number density and does not vary linearly above the reference level of atomic oxygen number density. The atomic oxygen number density at reference level corresponds to that value which is obtained from the NRLMSISE‐00 model. It is found that the altitude of peak emission rate moves upward as the F10.7 solar index increases. On average the upward movement of altitude of PER is about 9 km for both the equinox and solstice cases. The upward movement of the altitude of peak emission rate is due to the enhancement in atomic oxygen number density with increase in F10.7 solar index.

Emissions Variability Processor (EMVAP): Design, evaluation, and application

Emissions of pollutants such as SO2 and NOx from external combustion sources can vary widely depending on fuel sulfur content, load, and transient conditions such as startup, shutdown, and maintenance/malfunction. While monitoring will automatically reflect variability from both emissions and meteorological influences, dispersion modeling has been typically conducted with a single constant peak emission rate. To respond to the need to account for emissions variability in addressing probabilistic 1-hr ambient air quality standards for SO2 and NO2, we have developed a statistical technique, the Emissions Variability Processor (EMVAP), which can account for emissions variability in dispersion modeling through Monte Carlo sampling from a specified frequency distribution of emission rates. Based upon initial AERMOD modeling of from 1 to 5 years of actual meteorological conditions, EMVAP is used as a postprocessor to AERMOD to simulate hundreds or even thousands of years of concentration predictions. This procedure uses emissions varied hourly with a Monte Carlo sampling process that is based upon the user-specified emissions distribution, from which a probabilistic estimate can be obtained of the controlling concentration. EMVAP can also accommodate an advanced Tier 2 NO2 modeling technique that uses a varying ambient ratio method approach to determine the fraction of total oxides of nitrogen that are in the form of nitrogen dioxide. For the case of the 1-hr National Ambient Air Quality Standards (NAAQS, established for SO2 and NO2), a “critical value” can be defined as the highest hourly emission rate that would be simulated to satisfy the standard using air dispersion models assuming constant emissions throughout the simulation. The critical value can be used as the starting point for a procedure like EMVAP that evaluates the impact of emissions variability and uses this information to determine an appropriate value to use for a longer term (e.g., 30-day) average emission rate that would still provide protection for the NAAQS under consideration. This paper reports on the design of EMVAP and its evaluation on several field databases that demonstrate that EMVAP produces a suitably modest overestimation of design concentrations. We also provide an example of an EMVAP application that involves a case in which a new emission limitation needs to be considered for a hypothetical emission unit that has infrequent higher-than-normal SO2 emissions.ImplicationsEmissions of pollutants from combustion sources can vary widely depending on fuel sulfur content, load, and transient conditions such as startup and shutdown. While monitoring will automatically reflect this variability on measured concentrations, dispersion modeling is typically conducted with a single peak emission rate assumed to occur continuously. To realistically account for emissions variability in addressing probabilistic 1-hr ambient air quality standards for SO2 and NO2, the authors have developed a statistical technique, the Emissions Variability Processor (EMVAP), which can account for emissions variability in dispersion modeling through Monte Carlo sampling from a specified frequency distribution of emission rates.

Effect of severe geomagnetic storm conditions on atomic oxygen greenline dayglow emission in mesosphere

Severe geomagnetic storms and their effects on the 557.7nm dayglow emission are studied in mesosphere. This study is primarily based on photochemical model with the necessary input obtained from a combination of experimental observations and empirical models. The model results are presented for a low latitude station Tirunelveli (8.7°N,77.8°E). The volume emission rates are calculated using MSISE-90 and NRLMSISE-00 neutral atmospheric models. A comparison is made between the results obtained from these two models. A positive correlation amongst volume emission rate (VER), O, O2 number densities and Dst index has been found. The present results indicate that the variation in emission rate is more for MSISE-90 than in NRLMSISE-00 model. The maximum depletion in the VER of greenline dayglow emission is found to be about 30% at 96km during the main phase of the one of the geomagnetic storms investigated in the case of MSISE-90 (which is strongest with Dst index −216nT). The O2 density decreases about 22% at 96km during the main phase of the same geomagnetic storm.The NRLSMSISE-00 model does not show any appreciable change in the number density of O during any of the two events. The present study also shows that the altitude of peak emission rate is unaffected by the geomagnetic storms. The effect of geomagnetic storm on the greenline nightglow emission has also been studied. It is found that almost no correlation can be established between the Dst index and variations in the volume emission rates using the NRLMSISE-00 neutral model atmosphere. However, a positive correlation is found in the case of MSISE-90 and the maximum depletion in the case of nightglow is about 40% for one of the storms. The present study shows that there are significant differences between the results obtained using MSISE-90 and NRLMSISE-00.

Effect of solar activity on the latitudinal variation of peak emission rate of 557.7 nm dayglow emission under equinox conditions

In the present study a comprehensive model has been developed to study the 557.7nm dayglow emission using Solar2000 EUV flux model. This study presents the model results of diurnal variation of 557.7nm dayglow emission under equinox conditions. The effect of varying solar activity on this emission is studied for a period of 5years (2001–2005) at a fixed date of April 3. These date are chosen due to the fact of large variations in the solar activity during the period of 5 years. An analytical formula for peak emission rate in thermosphere (E- and F-region peaks) is obtained from the model results. This analytical formula gives the first ever latitudinal variation of peak emission rate under equinox conditions. The earlier analytical formula obtained by Zhang and Shepherd (2005) from WINDII observations only provides the variation of peak emission rate as a function of solar zenith angle and F10.7 solar index.

Solar influence on the redline dayglow emission under equinox conditions

In the present paper the results of the modeled emission rates of redline dayglow emission are presented under equinox conditions as a function of F10.7 solar index. The Solar2000 EUV (extreme ultra violet) flux model is used in the model. It is for the first time that the Solar2000 EUV flux model is being used in the modeling of redline dayglow emission. The model is tested with the WINDII (wind imaging interferometer) observations of redline dayglow emission. It has been found that the modeled emission rates are in good agreement with WINDII observations over a wide range of altitudes. The model is also tested for peak emission rate using the empirical formula of Zhang and Shepherd (2004). The volume emission rate is calculated at various locations and local times under varying solar activity conditions using this model. An analytical formula which gives the latitudinal variation of peak emission rate is obtained from the modeled volume emission rates under equinox conditions. The redline dayglow emission intensities are studied under equinox conditions as a function of F10.7 solar index. It is found that the intensity does not vary linearly with F10.7 index and becomes more or less saturated when the F10.7 index is greater than 200.

Seasonal and QBO variations in the OH nightglow emission observed by TIMED/SABER

Using TIMED/SABER observations, we present global distribution of the semiannual oscillation (SAO), annual oscillation (AO), and quasi‐biennial oscillation (QBO) in the OH nightglow peak emission rate and height as well as the intensity. The latitudinal variations of the SAO, AO, and QBO in the peak emission rate are similar to those in the intensity. For the peak emission rate and the intensity, the SAO and QBO amplitudes have three peaks (one at the equator and others at about 35°S and 35°N). The AO amplitude peaks at about 20°S and 20°N, respectively. The SAO phase is delayed poleward from the equinoxes at the equator to the solstices at 50°S/N; in addition, the phases of the AO are delayed poleward from 30°S. For the peak height, the SAO and QBO amplitudes have three peaks (around the equator, 40°S, and 40°N). Its AO amplitudes at 50°S and 50°N are larger than those at other latitudes; the phase of the SAO shifts from the solstice at the equator to near the equinoxes at 50°S/N. The airglow QBO is stronger in tropics than midlatitude and is likely the real QBO oscillation at the equator. In addition, the emission in the Southern Hemisphere is weaker than that in the Northern Hemisphere. The SAO and QBO are hemispherically symmetrical, and the AO is hemispherically antisymmetrical at some latitudes. The peak emission rate and peak height SAOs are generally in antiphase. The peak emission rate and intensity SAOs are generally in phase.

Characterisation of an (S)-linalool synthase from kiwifruit (Actinidia arguta) that catalyses the first committed step in the production of floral lilac compounds

Kiwifruit (Actinidia spp. Lindl.) flowers and fruit contain many compounds of interest to the flavour and fragrance industries. In particular, Actinidia arguta (Sieb. et Zucc.) Planch. ex Miq. flowers produce β-linalool and important derivatives thereof, including linalool oxides, lilac aldehydes, alcohols and alcohol epoxides. Dynamic headspace sampling of whole A. arguta flowers showed that the peak emission rate of linalool, lilac alcohols and lilac aldehydes occurred around 0800 hours. After solvent extraction, linalool levels remained constant throughout the day and night, but lilac alcohol levels peaked at noon. In whole flowers, linalool was found predominantly in pistils and petals, and the lilac compounds were found mainly in petals. Two highly homologous (96.6% nucleotide identity) terpene synthase cDNA sequences, AaLS1 and ApLS1, were isolated from A. arguta and Actinidia polygama (Sieb. et Zucc.) Maxim flower EST libraries respectively. Real-time PCR analysis revealed that AaLS1 was expressed constitutively throughout the day and night, and primarily in petal tissue. Functional analysis in Escherichia coli showed that AaLS1 and ApLS1 each encoded a linalool synthase which was confirmed by transient expression in planta. Enantioselective gas chromatography revealed that both terpene synthases produced only (S)-(+)-linalool. AaLS1, therefore, is likely to be the key enzyme producing the (S)-linalool precursor of the lilac alcohols and aldehydes in A. arguta flowers.

Preventive control of odor emissions through manipulation of operational parameters during the active phase of composting

Better understanding of the effects of key operational parameters or environmental factors on odor emission is of critical importance for minimizing the generation of composting odors. A series of laboratory experiments was conducted to examine the effects of various operating conditions on odor emissions. The results revealed that airflow rates that were too high or too low could result in higher total odor emissions. An optimal flowrate for odor control would be approximately 0.6 L/min.kg dry matter with intermittent aeration and a duty cycle of 33%. Temperature setpoint at 60°C appeared to be a turning point for odor emission. Below this point, odor emissions increased with increasing temperature setpoint; conversely, odor emissions decreased with increasing temperature setpoint above this point. With regard to the composting material properties, odor emissions were greatly affected by the initial moisture content of feedstock. Both peak odor concentration and emission rate generally increased with higher initial moisture content. Odor emission was significant only at moisture levels higher than 65%. An initial moisture level below 45% is not recommended due to concern with the resulting lower degree of biodegradation. Biodegradable volatile solids content (BVS) of feedstock had pronounced effect on odor emissions. Peak odor concentration and emission rate increased dramatically as BVS increased from 45% to 65%, thus, total odor emission increased exponentially with BVS.

Warming caused by cumulative carbon emissions towards the trillionth tonne

Global efforts to mitigate climate change are guided by projections of future temperatures. But the eventual equilibrium global mean temperature associated with a given stabilization level of atmospheric greenhouse gas concentrations remains uncertain, complicating the setting of stabilization targets to avoid potentially dangerous levels of global warming. Similar problems apply to the carbon cycle: observations currently provide only a weak constraint on the response to future emissions. Here we use ensemble simulations of simple climate-carbon-cycle models constrained by observations and projections from more comprehensive models to simulate the temperature response to a broad range of carbon dioxide emission pathways. We find that the peak warming caused by a given cumulative carbon dioxide emission is better constrained than the warming response to a stabilization scenario. Furthermore, the relationship between cumulative emissions and peak warming is remarkably insensitive to the emission pathway (timing of emissions or peak emission rate). Hence policy targets based on limiting cumulative emissions of carbon dioxide are likely to be more robust to scientific uncertainty than emission-rate or concentration targets. Total anthropogenic emissions of one trillion tonnes of carbon (3.67 trillion tonnes of CO(2)), about half of which has already been emitted since industrialization began, results in a most likely peak carbon-dioxide-induced warming of 2 degrees C above pre-industrial temperatures, with a 5-95% confidence interval of 1.3-3.9 degrees C.

The Contribution of Reaction HO2+0 → OH+O2 to OH Nightglow

AbstractThe photochemical model for the OH Meinel bands nightglow emission is discussed. Both the expression for the number densities of OH(v ≤ 9) and the expression for the OH vibrational bands nightglow emission rates are derived from the photochemical model. The impact of chemical reaction, HO2+O → OH(v ≤ 6)+O2, on the number densities of OH(v ≤ 6) and on the OH(v'—v'')(v' ≤ 6) (v' represents the higher vibrational levels and v'' represents the lower vibrational levels) vibrational bands emission are studied detailedly. The results indicate that the contribution of the reaction to the number densities increases with decreasing v and the contribution to the OH(v'—v'') bands emission increases with decreasing v'. The calculations for vernal equinox, local midnight at (0°E, 45°N) show that the reaction makes the peak density at level v = 1 and the peak emission rate of the OH(1—0) vibrational band increase by about 33%, the peak density at level v = 6 and the peak emission rates of the OH(6—v'') vibrational bands increase by about 7%, the OH(1—0) band intensity increase by about 30%, and the OH(6—v'') bands intensities increase by about 11%. Furthermore, the reaction can make the widths of the altitude profiles of both the number densities and the vibrational bands emission rates increase, and the peak altitudes of these profiles lower by about 1 km. The contribution of the reaction is sensitive to the atomic oxygen density and temperature. It increases almost linearly with decreasing atomic oxygen density, and with increasing temperature. And it is the strongest at the summer solstice and the weakest at the winter solstice.

A study into the effects of gravity wave activity on the diurnal tide and airglow emissions in the equatorial mesosphere and lower thermosphere using the Coupled Middle Atmosphere and Thermosphere (CMAT) general circulation model

Momentum deposition by gravity wave breaking is known to affect the amplitude and phase of the diurnal tide. Modelling studies of this interaction have produced some conflicting results and as yet, the exact nature of this interaction is not fully understood. In this study, the effects of parameterised gravity wave momentum deposition on the diurnal tide and subsequently on green line airglow from atomic oxygen during equinox are investigated using the Coupled Middle Atmosphere and Thermosphere (CMAT) general circulation model. The effects of gravity wave drag calculated by two different parameterisations, Meyer [1999. Gravity wave interactions with the diurnal propagating tide. Journal of Geophysical Research 104, 4223–4239] and Medvedev and Klaassen [2000. Parameterisation of gravity wave momentum deposition based on non-linear wave interactions: basic formulation and sensitivity tests. Journal of Atmospheric and Terrestrial Physics 62, 1015–1033], are compared in the low latitude MLT region between 70 and 120 km, where the amplitude of the diurnal tide and green line volume emission rates maximise. Results indicate that momentum sources from both gravity wave parameterisations act to reduce the mid-latitude zonal jets and advance the phase of the diurnal tide, such that the peak amplitude at a given height occurs at an earlier time of day. Gravity wave momentum deposition as parameterised by Meyer [1999. Gravity wave interactions with the diurnal propagating tide. Journal of Geophysical Research 104, 4223–4239] results in a reduction of the amplitude of the diurnal tide in the MLT region, whereas the tidal amplitude is increased when the Medvedev and Klaassen [2000. Parameterisation of gravity wave momentum deposition based on non-linear wave interactions: basic formulation and sensitivity tests. Journal of Atmospheric and Terrestrial Physics 62, 1015–1033] parameterisation is used. Both parameterisations affect the local time variability of the simulated airglow, and the magnitude of the peak emission rate. When using gravity wave momentum sources from the Medvedev and Klaassen [2000. Parameterisation of gravity wave momentum deposition based on non-linear wave interactions: basic formulation and sensitivity tests. Journal of Atmospheric and Terrestrial Physics 62, 1015–1033] parameterisation, the magnitude and morphology of CMAT tidal winds and O( 1S) 557.7 nm emission rates are in agreement with recent satellite observations.

On the response of the O(1S) dayglow emission rate to the Sun's energy input: An empirical model deduced from WINDII/UARS global measurements

More than 520,000 emission rate profiles of the O(1S) dayglow (557.7 nm, the atomic oxygen green line) were measured by the Wind Imaging Interferometer (WINDII) on the Upper Atmospheric Research Satellite (UARS) during 1991–1997, providing an unprecedented and unique resource for studying the O(1S) emission layer, its related physics and chemistry, and the response of the mesosphere and thermosphere to the solar input. The daytime O(1S) emission is one of the most remarkable and persistent phenomena in the Earth's atmosphere between 80 and 280 km. The emission has two components, peaking at 140–180 km and 94–104 km. WINDII measurements show that both components are sensitively correlated with the Sun in the sense that (1) for a given day, the peak emission rates in both the F‐region and the E‐region increase with increasing cosine of the solar zenith angle, the height of the peak emission rate in the F‐region decreases with increasing peak emission rate but that in the E‐region does not have a clear relationship with the peak emission rate; (2) both the peak emission rate and its height in the F‐region as well in the E‐region increase with increasing solar irradiance, i.e., they follow the solar cycle. For the first time an empirical model of the green line emission rate and height of the peak emission are derived from WINDII global measurements over six years as functions of the solar zenith angle and the solar irradiance using the daily solar F10.7 cm flux as a proxy. This model provides a baseline for the unperturbed daytime green line emission for any time and any location. Owing to the direct effect of the solar zenith angle, the emission rate is symmetrical with respect to local noon; and globally, it is symmetrical with respect to the equator at equinox, and is much larger in the summer hemisphere than in the winter hemisphere at solstice. As a result, for a constant solar irradiance, the emission rate has an annual oscillation at mid and high latitudes, and a semiannual oscillation at the equator. In the solar cycle 22, for an overhead Sun, the max/min ratio of the F10.7 cm flux is about four, and the max/min ratio of the integrated O(1S) emission rate is about three. Some unsolved problems regarding the mechanism of the green line emission are reported.