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We have developed an empirical model of nitric oxide (NO) number density at altitudes from similar to 73 km to the exobase, as a function of altitude, latitude, day of year, solar zenith angle, solar activity, and geomagnetic activity. The model is part of the NRLMSIS (R) 2.1 empirical model of atmospheric temperature and species densities; this upgrade to NRLMSIS 2.0 consists solely of the addition of NO. MSIS 2.1 assimilates observations from six space-based instruments: UARS/HALOE, SNOE, Envisat/MIPAS, ACE/FTS, Odin/SMR, and AIM/SOFIE. We additionally evaluated the new model against independent extant NO data sets. In this paper, we describe the formulation and fitting of the model, examine biases between the data sets and model and among the data sets, compare with another empirical NO model (NOEM), and discuss scientific aspects of our analysis.

We have developed an empirical model of nitric oxide (NO) number density at altitudes from ∼73 km to the exobase, as a function of altitude, latitude, day of year, solar zenith angle, solar activity, and geomagnetic activity. The model is part of the NRLMSIS® 2.1 empirical model of atmospheric temperature and species densities; this upgrade to NRLMSIS 2.0 consists solely of the addition of NO. MSIS 2.1 assimilates observations from six space-based instruments: UARS/HALOE, SNOE, Envisat/MIPAS, ACE/FTS, Odin/SMR, and AIM/SOFIE. We additionally evaluated the new model against independent extant NO data sets. In this paper, we describe the formulation and fitting of the model, examine biases between the data sets and model and among the data sets, compare with another empirical NO model (NOEM), and discuss scientific aspects of our analysis. © 2022 The Authors.

NRLMSIS® 2.0 is an empirical atmospheric model that extends from the ground to the exobase and describes the average observed behavior of temperature, eight species densities, and mass density via a parametric analytic formulation. The model inputs are location, day of year, time of day, solar activity, and geomagnetic activity. NRLMSIS 2.0 is a major, reformulated upgrade of the previous version, NRLMSISE-00. The model now couples thermospheric species densities to the entire column, via an effective mass profile that transitions each species from the fully mixed region below ~70 km altitude to the diffusively separated region above ~200 km. Other changes include the extension of atomic oxygen down to 50 km and the use of geopotential height as the internal vertical coordinate. We assimilated extensive new lower and middle atmosphere temperature, O, and H data, along with global average thermospheric mass density derived from satellite orbits, and we validated the model against independent samples of these data. In the mesosphere and below, residual biases and standard deviations are considerably lower than NRLMSISE-00. The new model is warmer in the upper troposphere and cooler in the stratosphere and mesosphere. In the thermosphere, N2 and O densities are lower in NRLMSIS 2.0; otherwise, the NRLMSISE-00 thermosphere is largely retained. Future advances in thermospheric specification will likely require new in situ mass spectrometer measurements, new techniques for species density measurement between 100 and 200 km, and the reconciliation of systematic biases among thermospheric temperature and composition data sets, including biases attributable to long-term changes. © 2020. The Authors.

We have investigated the 5 day wave in both temperature and water vapor in the stratosphere and mesosphere as seen in the Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) analysis fields for summer 2007. We have compared these fields and the derived saturation ratios with polar mesospheric cloud (PMC) measurements from the AIM satellite. We find that the 5 day wave is variable in both time and space, with significant amplitudes in the temperature wave in August (up to ~6 K). By contrast, the 5 day wave-induced water vapor anomalies remain at a near-constant level throughout the season. During August, the 5 day wave in the NOGAPS-ALPHA saturation ratio and in the occurrence of clouds in the AIM data shows a clear anticorrelation with bright PMCs forming in the trough of the temperature wave. The analysis shows that the August enhancement in the 5 day wave amplitude acts to extend the PMC season past the time when zonal mean temperatures are saturated with respect to ice. The increased wave amplitude in August is attributed to in situ wave generation and amplification due to baroclinic instability of mean winds at around 0.1-0.01 hPa. The late-season extension of cloud occurrence due to the 5 day wave may explain previous ground-based reports of bright noctilucent cloud displays in August., Published in Jnl. of Geophysical Research, v115 p1-18, 2010. Supported in part by DTRA.

This paper describes CHEM2D-H2O, a new parameterization of H2O photochemical production and loss based on the CHEM2D photochemical-transport model of the middle atmosphere. This parameterization accounts for the altitude, latitude, and seasonal variations in the photochemical sources and sinks of water vapor over the pressure region from 100-0.001 hPa (~16-90 km altitude). A series of free-running NOGAPS-ALPHA forecast model simulations offers a preliminary assessment of CHEM2D-H2O performance over the June 2007 period. Results indicate that the CHEM2D-H2O parameterization improves global 10-day forecasts of upper mesospheric water vapor compared to forecasts using an existing one-dimensional (altitude only) parameterization. Most of the improvement is seen at high winter latitudes where the one-dimensional parameterization specifies photolytic H2O loss year round despite the lack of sunlight in winter. The new CHEM2D-H2O parameterization should provide a better representation of the downwelling of dry mesospheric air into the stratospheric polar vortex in operational analyses that do not assimilate middle atmospheric H2O measurements., Published in Atmospheric Chemistry and Physics, v8 p7519-7532, 2008.

Meteoric material entering Earth's atmosphere ablates in the mesosphere and is then expected to recondense into tiny so-called "smoke particles." These particles are thought to be of great importance for middle atmosphere phenomena like noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. Commonly used one-dimensional (1-D) meteoric smoke profiles refer to average global conditions and yield of the order of a thousand nanometer sized particles per cubic centimeter at the mesopause, independent of latitude and time of year. Using the first two-dimensional model of both coagulation and transport of meteoric material we here show that such profiles are too simplistic, and that the distribution of smoke particles indeed is dependent on both latitude and season. The reason is that the atmospheric circulation, which cannot be properly handled by 1-D models, efficiently transports the particles to the winter hemisphere and down into the polar vortex. Using the assumptions commonly used in 1-D studies results in number densities of nanometer sized particles of around 4000/cc at the winter pole, while very few particles remain at the Arctic summer mesopause. If smoke particles are the only nucleation kernel for ice in the mesosphere this would imply that there could only be of the order of 100 or less ice particles per cc at the Arctic summer mesopause. This is much less than the ice number densities expected for the formation of ice phenomena (noctilucent clouds and polar mesospheric summer echoes) that commonly occur in this region. However, we find that especially the uncertainty of the amount of material that is deposited in Earth's atmosphere imposes a large error bar on this number, which may allow for number densities up to 1000/cc near the polar summer mesopause., Published in Journal of Geophysical Research, v113 D03202 p1-15, 2008.

On March 9, 2007, the first ultraviolet spectrometer using the innovative optical technique known as spatial heterodyne spectroscopy was launched into low Earth orbit from Cape Canaveral, FL. The Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER) is a deskjet printer-sized rugged spectrometer designed to measure solar resonance fluorescence of hydroxyl (OH) in the Earth's middle atmosphere between 30 and 100 km altitude. It is optimized for high spectral resolution, low mass, low power, low volume, and high sensitivity with no moving parts. SHIMMER is performing as expected and has already returned several hundred thousand atmospheric OH measurements. SHIMMER also detects mesospheric clouds (MCs) at their equatorward edge region, around 55 degrees latitude, where they are believed to be most sensitive to mesospheric change. SHIMMER's unprecedented local time coverage allows the investigation of how atmospheric dynamics influence MCs and their environment and thus potentially bias the interpretation of multi-decadal cloud frequency and brightness trends. To date, SHIMMER data have already led to three significant science results, discussed briefly here., Performed in collaboration with St. Cloud State University, St. Cloud, MN; Computational Physics, Inc., Fairfax, VA; and the University of Wisconsin, Madison, WI. Sponsored in part by the Department of Defense (DoD) Space Test Program and the National Aeronautics and Space Administration (NASA). Published in the Naval Research Laboratory (NRL) Review, p131-133, 2008.

Meteoric material entering Earth's atmosphere ablates in the mesosphere and is then expected to recondense into tiny so-called “smoke particles.” These particles are thought to be of great importance for middle atmosphere phenomena like noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. Commonly used one-dimensional (1-D) meteoric smoke profiles refer to average global conditions and yield of the order of a thousand nanometer sized particles per cubic centimeter at the mesopause, independent of latitude and time of year. Using the first two-dimensional model of both coagulation and transport of meteoric material we here show that such profiles are too simplistic, and that the distribution of smoke particles indeed is dependent on both latitude and season. The reason is that the atmospheric circulation, which cannot be properly handled by 1-D models, efficiently transports the particles to the winter hemisphere and down into the polar vortex. Using the assumptions commonly used in 1-D studies results in number densities of nanometer sized particles of around 4000 cm−3 at the winter pole, while very few particles remain at the Arctic summer mesopause. If smoke particles are the only nucleation kernel for ice in the mesosphere this would imply that there could only be of the order of 100 or less ice particles cm−3 at the Arctic summer mesopause. This is much less than the ice number densities expected for the formation of ice phenomena (noctilucent clouds and polar mesospheric summer echoes) that commonly occur in this region. However, we find that especially the uncertainty of the amount of material that is deposited in Earth's atmosphere imposes a large error bar on this number, which may allow for number densities up to 1000 cm−3 near the polar summer mesopause. This efficient transport of meteoric material to the winter hemisphere and down into the polar vortex results in higher concentrations of meteoric material in the, Part of urn:nbn:se:su:diva-7734

We investigate the solar cycle modulation of the quasi-biennial oscillation (QBO) in stratospheric zonal winds and its impact on stratospheric ozone with an updated version of the zonally averaged CHEM2D middle atmosphere model. We find that the duration of the westerly QBO phase at solar maximum is 3 months shorter than at solar minimum, a more robust result than in an earlier CHEM2D study due to reduced Rayleigh friction drag in the present version of the model. The modeled solar cycle ozone response, determined via multiple linear regression, is compared with observational estimates from the combined Solar Backscattered Ultraviolet (SBUV/2) data set for the period 1979 2003. We find that a model simulation including imposed solar UV variations, the zonal wind QBO, and an imposed 11-year variation in planetary wave 1 amplitude produces a lower stratospheric ozone response of approx. 2.5% between 0 and 20 deg S and an upper stratospheric ozone response of approx. 1% between 45 and 55 km, in good agreement with the SBUV-derived ozone response. This simulation also produces an (enhancement/reduction) in the (lower/upper) stratospheric temperature response at low latitudes compared to the effects of solar UV variations alone, which are consistent with model vertical velocity anomalies produced by the solar-modulated QBO and imposed changes in planetary wave forcing., Published in the Journal of Geophysical Research, v112 Article D16109 p1-17, 2007. Supported in part by ONR.

The new CHEM2D-Ozone Photochemistry Parameterization (CHEM2D-OPP) for high-altitude numerical weather prediction (NWP) systems and climate models specifies the net ozone photochemical tendency and its sensitivity to changes in ozone mixing ratio, temperature and overhead ozone column based on calculations from the CHEM2D interactive middle atmospheric photochemical transport model. We evaluate CHEM2D-OPP performance using both short-term (6-day) and long-term (1-year) stratospheric ozone simulations with the prototype high-altitude NOGAPS-ALPHA forecast model. An inter-comparison of NOGAPS-ALPHA 6-day ozone hindcasts for 7 February 2005 with ozone photochemistry parameterizations currently used in operational NWP systems shows that CHEM2D-OPP yields the best overall agreement with both individual Aura Microwave Limb Sounder ozone profile measurements and independent hemispheric (10 90 N) ozone analysis fields. A 1-year free-running NOGAPS-ALPHA simulation using CHEM2D-OPP produces a realistic seasonal cycle in zonal mean ozone throughout the stratosphere. We find that the combination of a model cold temperature bias at high latitudes in winter and a warm bias in the CHEM2D-OPP temperature climatology can degrade the performance of the linearized ozone photochemistry parameterization over seasonal time scales despite the fact that the parameterized temperature dependence is weak in these regions., The original document contains color images. Pub. in Atmospheric Chemistry Physics, v6, p4943-4972, 2006.

We used temperature data from the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) on the NASA TIMED satellite to quantify the connection between temperatures in the stratosphere and in the mesosphere and lower thermosphere. Specifically, we studied three winter periods where stratospheric temperatures were dynamically disturbed: February 2002, August, 2002, and February 2003. The SABER temperatures show a clear signature of mesospheric coolings in concert with stratospheric warmings. Mesospheric temperatures between 0.7 hPa and 0.01 hPa show a significant anticorrelation with stratospheric temperatures. For pressures less than 0.01 hPa, this anticorrelation breaks down, in disagreement with recent model results from a thermosphere-ionosphere-mesosphere general circulation model that suggest mesospheric coolings persist up to 110 km. Also, the lack of a clear correlation between stratospheric temperatures and those at 83 90 km suggests that measurements of the OH Meinel band temperatures at those altitudes may not be representative of the entire mesosphere., Published in the Journal of Geophysical Research Letters, v32, L09804, p1-4, 2005.

Hindcasts of the Southern Hemisphere minor stratospheric warming and mesospheric cooling event of August 2002, made with a new high altitude version of the Navy's operational forecast model, are compared with temperatures acquired by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry). Results show realistic hemispheric evolution of both the stratospheric warming and mesospheric cooling over a 10-day time period. Use of Rayleigh friction to model mesospheric gravity wave drag shows improvement in the upper mesosphere over a hindcast without Rayleigh friction. The limited vertical extent of the main mesospheric cooling signature disagrees with the Liu and Roble model results but is supported by SABER temperature observations. Examination of 3D EP-flux vectors over the 10-day forecast suggests that the planetary wave responsible for the warming/cooling event originated from a horizontally localized region of the troposphere., Published in Geophysical Research Letters, v32 article L07808, 2005.