Mesospheric Temperature Profiles Research Articles

The second Venus flyby of BepiColombo mission reveals stable atmosphere over decades

Studies of the Venusian mesosphere provide important information about the current state of the entire Venusian atmosphere. This includes information about the dense cloud structure, its vertical thermal profile, temperature fields, and the resulting dynamical and meteorological processes that contribute to a deeper understanding of the climatologically different evolutionary paths of Earth and Venus. However, the last measurements were acquired in 1983 during Venera-15 mission. In this paper, results of mid-infrared spectral measurements of the Venusian atmosphere are presented. Here we show Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) measurements of the Venusian atmosphere during the second flyby of BepiColombo mission on its way to Mercury. Our Venus measurements provide reliable retrievals of mesospheric temperature profiles and cloud parameters between 60 and 75 km altitude, although MERTIS was only designed to operate in Mercury environment. Our results are in good agreement with the Venera-15 mission findings. This indicates the stability of the Venusian atmosphere on time scales of decades.

The Fusion of ERA5 and MERRA-2 Atmospheric Temperature Profiles with Enhanced Spatial Resolution and Accuracy

Accurate high-resolution atmospheric temperature profiles are essential for precisely characterizing the evolution of the atmosphere and developing numerical forecasts. Atmospheric datasets, such as ERA5 (the fifth-generation ECMWF Reanalysis) and MERRA-2 (the Modern-Era Retrospective Analysis for Research and Applications, Version 2), provide global and continuous temperature profiles, with fine vertical distribution and horizontal resolution. RAOB (Radiosonde Observation) sounding data have high confidence and representativeness and are usually used for data accuracy verification. Due to the difficulty of updating existing products, and the scarcity of research on mesospheric temperature profiles, this work maximizes the high observation accuracy of RAOB data, combines the benefits of ERA5’s horizontal resolution and MERRA-2’s vertical distribution, and employs the optimal interpolation method to combine the data, in order to produce a fused result with high spatial resolution. After converting all of the data to the same spatial distribution, the optimal interpolation method was used to combine the two datasets from separate places and different pressure layers in order to produce the fused results, which had a vertical distribution of 45 layers and a spatial resolution of 0.25°. The fused data’s RMSE and MAE were 6.0 K and 5.0 K lower than those of the MERRA-2 temperature profile data, respectively, and 0.3 K and 0.4 K lower than those of the ERA5 temperature profile data, respectively. The validation, using data from 2019, showed that the fused data exhibits better correlation and data accuracy than the other two datasets, which demonstrated that the fused algorithm can potentially be used to generate reliable datasets for future meteorological research.

Mesospheric anomalous diffusion during noctilucent cloud scenarios

Abstract. The Andenes specular meteor radar shows meteor trail diffusion rates increasing on average by about 10 % at times and locations where a lidar observes noctilucent clouds (NLCs). This high-latitude effect has been attributed to the presence of charged NLC after exploring possible contributions from thermal tides. To make this claim, the current study evaluates data from three stations at high, middle, and low latitudes for the years 2012 to 2016 to show that NLC influence on the meteor trail diffusion is independent of thermal tides. The observations also show that the meteor trail diffusion enhancement during NLC cover exists only at high latitudes and near the peaks of NLC layers. This paper discusses a number of possible explanations for changes in the regions with NLCs and leans towards the hypothesis that the relative abundance of background electron density plays the leading role. A more accurate model of the meteor trail diffusion around NLC particles would help researchers determine mesospheric temperature and neutral density profiles from meteor radars at high latitudes.

Investigation of the mesospheric temperature over Fort Collins region

The nightly mean mesospheric temperature profiles between 80 and 107 km, observed by Na lidar, over Fort Collins, Colorado (41°N, 105°W) from 1990 to 2010, are employed to research the temporal and spatial variations and mesopause. We find that the maximum mean temperature is in summer months above 95 km, but reverse below 95 km, and there is a cooler region below 185 K around 97 km in August. The largest seasonal variation is 39.2 K at 81 km, and the minimum is 6.5 K at 96.5 km. The maximum standard derivation in spring and autumn months are larger than other seasons above 105 km, but the temperatures in March, June and September are lower than the other months between 82 km and 100 km where winter is the largest season. Moreover, the seasonal variations of the temperature are about 36, 8 and 21 K at 85, 95 and 105 km, respectively. winter is colder and summer is warmer above 97.5 km, but reverse below 92 km. The mesopause height is around 102 km in winter, but 84 km in summer, and the mean speed of decreasing or increasing of the mesopause height is about 5 km/month in spring and autumn months which are about 90 km. The lasting time of the mesopause in winter is near 6 months, longer than other seasons, and the mesopause temperature is about 165 K in cool summer, and 185 K in warm winter.

Sub-millimeter observations of the terrestrial atmosphere during an Earth flyby of the MIRO sounder on the Rosetta spacecraft

Sub-millimeter spectra recorded by the MIRO sounder aboard the Rosetta spacecraft have been used at the time of an Earth flyby (November 2007) to check the consistency and validity of the instrumental data. High-resolution spectroscopic data were recorded in 8 channels in the vicinity of the strong water line at 557GHz, and in a broad band continuum channel at 570GHz. An atmospheric radiative transfer code (ARTS) and standard terrestrial atmospheres have been used to simulate the expected observational results. Differences with the MIRO spectra suggest an anomaly in the behavior of four spectroscopic channels. Further technical investigations have shown that a large part of the anomalies are associated with an instability of one of the amplifiers. The quality of the MIRO data has been further tested by inverting the spectra with an atmospheric inversion tool (Qpack) in order to derive a mesospheric temperature profile. The retrieved profile is in good agreement with the one inferred from the Earth Observing System Microwave Limb Sounder (EOS-MLS). This work illustrates the interest of validating instruments aboard planetary or cometary spacecraft by using data acquired during Earth flybys.

Identification of large‐scale billow‐like structure in the neutral sodium layer over Arecibo

We present a rare event that was recorded over Arecibo using sodium (Na) lidar. Billow‐like structures with periods of ∼60 min were seen in the Na layer above 102 km on the night of 7–8 July 2010. The absence of any high‐altitude structure was noted on the following night. Spectral analysis using the Lomb‐Scargle technique reveals periods with larger power on the first night as compared to the adjacent one. The keograms derived from a sequence of 557.7 nm airglow images show the passage of a large frontal wave on 7–8 July 2010. Further investigation on the occurrence of neutral instabilities was carried out using mesospheric temperature and horizontal wind obtained from the Sounding of Atmosphere using Broadband Emission Radiometry (SABER) and TIMED Doppler Interferometer (TIDI) instruments onboard the TIMED satellite. A good agreement is observed between the temperatures derived from SABER and ground‐based airglow instruments. The mesospheric temperature and horizontal wind profiles allowed the determination of square of the Brunt‐Väisälä frequency and Richardson number to quantitatively evaluate the possible role of different instabilities in generating this structure. The profile of the former entity reveals that the region is convectively stable during the time when the event was observed. However, the presence of strong shears in the region, where billow‐like structures are observed on 7–8 July 2010, is noted along with a Richardson number of 0.22, indicating the likely occurrence of dynamical instability. Thus, the present work suggests that dynamical instability make conditions conducive for billow‐like structures in the Na layer above 102 km. The possible role of plasma processes in generating these structures is also discussed.

A new method to derive middle atmospheric temperature profiles using a combination of Rayleigh lidar and O<sub>2</sub> airglow temperatures measurements

Abstract. The vertical temperature profiles in a typical Rayleigh lidar system depends on the backscatter photon counts and the CIRA-86 model inputs. For the first time, we show that, by making simultaneous measurements of Rayleigh lidar and upper mesospheric O2 temperatures, the lidar capability can be enhanced to obtain mesospheric temperature profile up to about 95 km altitudes. The obtained results are compared with instantaneous space-borne SABER measurements for a validation.

Simultaneous lidar observations of a noctilucent cloud and an internal wave in the polar mesosphere

Lidar and radar observations of the upper mesosphere and lower thermosphere were conducted in interior Alaska (65°N, 147°W) during the summer of 2001. Lidar observations of a noctilucent cloud (NLC) were made on the night of 20–21 August 2001 during a visible noctilucent cloud display when the midnight solar depression angle was 12°. These nighttime lidar observations in late August have yielded measurements of both the NLC at 82.7 km and the mesospheric temperature profile below the cloud (∼40–80 km). Analysis of the temperature profile indicates the presence of a wave with a vertical wavelength of 7.9 km. The altitude of the NLC coincides with the cold phase of the temperature wave. Located approximately 50 km from the lidar, radar observations yielded measurements of polar mesosphere summer echoes (PMSEs) during daytime on 21 August 2001. The PMSE layer occurs just above the NLC layer and also shows structural characteristics associated with the passage of gravity waves through the layer. The presence of NLCs in late August supports recent reports that the late summer Arctic mesosphere is colder and wetter than represented in “standard” models. These NLC observations are discussed in terms of earlier lidar observations over Alaska, observations at other sites, and current models.

Polarization of measurement for microwave temperature sounding of the mesosphere

This paper examines microwave measurement polarization for mesospheric temperature profile retrieval on a global basis, for which forthcoming satellite instruments are tasked. Retrieval performances at circular, horizontal, and vertical polarization are mapped across the range of geomagnetic conditions (field strength and view orientation) and are related to the impact of Zeeman line splitting on temperature channel weighting functions. Retrieval performance is hampered by conditions that cause clusters and gaps with respect to the heights at which the weighting functions peak, and this may be a greater detriment to sounding performance than the double-peaking of weighting functions that has been previously identified as a pitfall of sounding in linear polarization. Each of the measurement polarizations was better than the other two under some of the geomagnetic conditions. An orbit simulator was used to document the frequency of occurrence of each of the geomagnetic viewing conditions. With respect to overall global performance, circular polarization was found to be the best choice, regardless whether conical or cross-track scanning is used. Between the linear polarizations, vertical was preferable to horizontal for conical sounding at fine spectral resolution.

Procedures for recovering mesospheric and stratospheric temperatures from OSIRIS scattered-sunlight measurements

Procedures for recovering mesospheric and stratospheric temperature profiles from scattered-sunlight limb radiance measurements made by the OSIRIS (optical spectrograph and infrared imager system) instrument on the Odin satellite are described. We assess various approaches to the problem and show that temperature recoveries based on an analysis of inferred volume-scattering rates are significantly more accurate than those based on direct analysis of the observed limb radiances. A forward model for the OSIRIS instrument is used to test temperature recovery algorithm performance in the presence of realistic instrument noise and to assess the expected accuracy of the OSIRIS temperature recoveries. It is shown that, for radiances measured in the near-infrared region, temperatures can be reliably recovered over the altitude range 40 km to 80 km with an accuracy of better than ±1 K. PACS Nos.: 42.68Mj, 94.10Dy

The mechanism of formation of inversion layers in the mesosphere

Mesospheric temperature profiles obtained by Rayleigh lidar in the south of France frequently show winter temperature inversions, with an amplitude up to 40K in a few km. A 2D dynamic model, developed to interpret these observations, showed that the mesospheric inversions were mainly due to the vertical circulation induced by the breaking of gravity waves in the upper mesosphere.

Vertical Profiles of Temperature and Ozone Observed during DYANA Campaign with the NIES Ozone Lidar System at Tsukuba.

Temperature and ozone profiles were observed with the NIES ozone lidar system during the DYANA campaign from January 15th to March 15th at Tsukuba (36°E, 140°N). Temperature profiles from 30km to 90km and ozone profiles from 20km to 45km were obtained. The mesospheric temperature profiles were highly variable and deviations from the NASA88 model atmosphere were large in January and February, but the deviations were small in March 1990. Especially, conspicuous variations of the mesospheric temperature profiles, rapid increase around 55km and rapid decrease around 75km, were observed during the period from January 24th to 26th. We also observed layers with large vertical temperature gradients close to the adiabatic lapse rate above clear inversion layers in the middle mesosphere on January 17th and February 17th. The observed ozone number densities were>10% lower than the ozone sonde data averaged over 22 years at 25km and 30km on January 17th, 25th, 26th. The deviations from the averaged ozone sonde data were small on February 5th, March 8th, 10th and 13th.

Long-term (1979–1990) changes in the thermal, dynamical, and compositional structure of the Venus Mesosphere as inferred from microwave spectral line observations of [formula omitted], [formula omitted], and C 18O

Microwave spectral line observations of 12CO (1.3, 2.6 mm) and 13CO (1.4 mm) were obtained for Venus near inferior conjunctions in 1982, 1985, 1986, 1988, and 1990. Detailed analyses of these whole-disk spectra were performed to derive low to midlatitude average CO mixing profiles (75–105 km) and temperature profiles (85–100 km) for the nightside Venus mesosphere. Mesospheric temperatures determined for the 1982, 1988, and 1990 periods are in good agreement with those returned by Pioneer Venus spacecraft observations in 1979. However, the 1985 and 1986 observations indicate 20–40 K increases in low to midlatitude atmospheric temperatures at 85- to 100-km altitude, relative to the 1979 Pioneer-Venus measurements. The 1985–1986 temperature profiles are similar to the mesospheric temperature profile returned by Venera 10 in 1975. Comparisons with 60- to 90-km temperatures observed between 1978 and 1987 by Pioneer-Venus radio occultations indicate a reversal in the latitudinal gradient of atmospheric pressure within the Venus mesosphere in late 1984, early 1985. Cyclostrophic balance appears to persist throughout the Venus mesosphere at this time, as opposed to the breakdown of cyclostrophic balance above 80-km altitude observed by Pioneer Venus in 1979. Mesospheric CO abundances inferred from the microwave observations also exhibit large changes in 1985–1986. The CO mixing ratio at 80-km altitude increased by several hundred percent between 1982 and 1985. The CO column density above 1 mbar (∼86 km) presented a similar increase between 1985 and 1986. Furthermore, the appearance of an extreme solar-zenith-angle gradient in the nightside distribution of mesospheric CO is inferred from the 1986 observations. We suggest that these 1985–1986 perturbations in mesospheric CO and temperatures, the 5- to 10-year cyclical variations in cloud top dynamics, and the 1979 decay of cloud top SO 2 are all related phenomena of interannual variations in the global-scale dynamics within and above the cloud layers of the Venus atmosphere. We also present a 1.4-mm spectrum of C 18O observed in 1986 which, combined with analysis of the 1986 13CO spectrum, yields a terrestrial ratio (5.6 ± 0.8) for 13CO/C 18O in the Venus mesosphere.

Evidence for an OH≠ N2≠CO2(ν3) → CO2 +hν (4.3 μm) mechanism for 4.3‐μm airglow

Prior to the study we report here it had been thought that the sole undisturbed nighttime mechanisms for producing CO2 vibrationally excited in the ν3 mode were (1) vibrational excitation by thermal collisions and (2) absorption of 4.3‐µm earthshine by CO2. In this paper we show detailed evidence that the mechanism OH(υ) + N2 → OH(υ ‐ 1) + N2≠, followed by N2≠ + CO2 → N2 + CO2(ν3), may be the dominant excitation mechanism for producing CO2(ν3) in the 85‐km altitude region. The evidence is based on 4.3‐µm zenith radiance data obtained on April 11, 1974, via a rocket‐borne liquid N2 nitrogen cooled circular variable‐filtered radiometer. The rocket was launched at night from the Poker Flat Research Range, Alaska. The data were obtained under conditions of essentially zero auroral activity. There is a feature in these data near 85‐km altitude which can be explained by the mechanism . A column transfer of 0.12 ± 0.025 erg/cm² s from OH≠ to N2 is required to explain the feature. An alternate explanation on the basis of just the mechanisms 1 and 2 which are cited above requires that there existed a very unlikely mesospheric temperature profile on the evening of April 11, 1974. A similar nonauroral feature appears consistently near 85 km in preliminary 4.3‐µm zenith data obtained on March 27, 1973, February 25, 1974, March 6, 1975, and March 12, 1975, thus providing further evidence that the feature most likely results from the OH mechanism rather than a strange mesopheric temperature profile. These data were obtained from the Air Force Geophysics Laboratory and Utah State University as part of the Infrared Chemistry Experiments, Coordinated Auroral Program supported by the Defense Nuclear Agency. In this article we confine our attention to analysis of the April 11, 1974, data.

The winter anomaly in ionospheric absorption and the D-region ion chemistry

A detailed analysis of the D-region ion composition measurements performed by Zbinden et al. (1975), during a winter day of high ionospheric absorption, has been carried out. The study examines the interactive mesosphere- D-region processes which occur in such anomalous conditions and their implication for water cluster ion chemistry. Two clustering regimes for NO + have been observed in the data. Association with N 2 is identified as the dominant process below 76 km. Between 76 and 78 km altitude the effective loss rate of NO + drops by two orders of magnitude. Above 77 km, the three-body reaction NO + + CO 2+M→NO +CO 2+M seems to be the main NO + loss. A mesospheric temperature profile could be derived from the ion composition data. This indicates the presence of a strong inversion above 76 km altitude. The wavelike structure obtained, is shown to be consistent with in situ winter temperature measurements. The sharp suppression of the N 2 association reaction could, thus, be explained by an increase in the collisional break-up of the NO +N 2 ion because of the enhanced temperature. In conclusion, our study indicates that, besides the increase in the production of NO + and O 2 +, due to an enhancement in the minor ionizable constituents, an additional thermal mesosphere- D-region interaction seems necessary to explain this winter anomalous ion composition data.

Microwave spectrum of molecular oxygen in the mesosphere

The potential of using the 5-mm resonance lines of O2 to remotely probe the mesospheric temperature profile is analyzed in detail, and specific experiments are proposed. An absorption matrix, which includes the complete Zeeman effect, is used in a tensor equation of radiative transfer to compute the microwave spectrum near the resonance lines as it would be seen from space. The conclusion is that such techniques do afford a means of remotely determining the mesospheric temperature profile to heights of approximately 80 km, and that this is possible with available 5-mm hardware. The two specific experiments that are described in detail would sound the mesosphere in the 60-km and 73-km regions. Radiometric sensitivities of 1.5–5°K are possible for these experiments, with a horizontal resolution of 100–300 km along the direction of motion.