Anatoly I. Semenov

On rotational temperature of the hydroxyl emission

The method for determining the rotational temperature of the hydroxyl emission of the upper atmosphere is analyzed. It is shown that a discrepancy of up to 14 K appears in the temperature values determined for the region of OH emission (∼87 km) since different researchers use the intensity factors (line strengths) of the lines of the rotational structure of hydroxyl bands based on various theoretical calculations. This discrepancy considerably exceeds the error (2–3 K) of direct temperature measurements. The use of the set of such data in the analysis of the time and spatial temperature regime can lead to a distortion of the character of the long-term changes in the mesopause temperature. Analytical expressions are obtained making it possible to calculate a systematic correction for the temperatures determined with the use of various intensity factors. One should also take into account considerable seasonal variations in the dependence of rotational temperature values on the level of the hydroxyl vibrational excitation.

Dependencies of the amplitude of the temperature enhancement maximum and atomic oxygen concentrations in the mesopause region on seasons and solar activity level

Abstract Long term temperature measurements of the mesopause and lower thermosphere give a possibility to obtain altitude profiles of the mean annual temperature and to reveal a regular occurrence of the temperature maximum for heights of 85–95 km, the amplitude of which correlates with the solar activity level. Distributions with height of the atomic oxygen concentration for low and high solar activity conditions have been calculated on the basis of an empirical model of 557.7 nm emission variations and its photochemical theory. It is shown that there is the distinct correlation between an increment of the temperature and the density of the atomic oxygen. Apparently, a reaction of CO2 with O2 causes this phenomenon.

The spatial distribution of gravity wave energy influx into the mesopause over a mountain lee

Abstract The vertical influx of gravity wave energy into the mesosphere, generated by gusts of wind over a mountain chain has been calculated. There is a satisfactory agreement between the spatial distributions of the calculated energy flux and the measured temperature increments over the mountain lee region. It is necessary to take into account the fluctuations of direction of the local wind and gusts of wind. These fluctuations have anisotropic distributions.

Empirical model of variations in the emission of the molecular oxygen atmospheric system. 1. Intensity

The data on regular variations in the emission intensity of the molecular oxygen Atmospheric system excited in the region of the lower thermosphere have been systematized based on the long-term studies. The empirical approximations of the emission behavior are presented.

Comparison of ground-based OH temperature data measured at Irkutsk (52°N, 103°E) and Zvenigorod (56°N, 37°E) stations with Aura MLS v3.3

Data about the variations of mesopause temperature (∼87 km) obtained from ground-based spectrographic measurements of the OH emission (834.0 nm, band (6-2)) at Irkutsk and Zvenigorod observatories were compared with satellite data on vertical temperature distribution in the atmosphere from Aura MLS v3.3. We analyzed MLS data for two geopotential height levels: 0.005 hPa (∼84 km) and 0.002 hPa (∼88 km) as the closest to OH height (∼87 km).We revealed that Aura MLS temperature data have lower values than ground-based (cold bias). In summer periods, that difference increases. Aura cold biases compared with OH(6-2) at Irkutsk and Zvenigorod were calculated. For the 0.002 hPa height level, the biases are 10.1 and 9.4 K, and for 0.005 hPa they are 10.5 and 10.2 K at Irkutsk and Zvenigorod, respectively. When the bias is accounted for, an agreement between Aura MLS and OH(6-2) data obtained at both Irkutsk and Zvenigorod is remarkable.

Empirical model of the OI 630 nm emission variations. 3. Emitting layer height

The empirical model of variations in the emitting layer height and parameters has been developed based on an analysis of the rocket measurements of the vertical distributions in the 630 nm intensity. The dependences on the solar zenith angle during a day are most substantial. This dependence is responsible for the character of seasonal variations at different latitudes. The height of the emitting layer increases with increasing solar activity, reflecting a temperature rise in the upper atmosphere. The negative trend—0.35 km yr−1 in the interval 1964–1990—has been revealed.

Model of the latitudinal, seasonal, and vertical variations in the long-term temperature trend of the middle atmosphere

Based on the data of the rocket sounding of the middle atmosphere (25–75 km) in the Northern and Southern hemispheres during 1964–1994, the average monthly vertical distributions of the long-term temperature trend have been obtained for the low, middle, and high latitudes. These distributions have been approximated by the series of the harmonic functions describing the latitudinal, seasonal, and vertical variations in the temperature trend. The characteristics of the obtained harmonics are presented.

Empirical Model of Variations in the 630 nm Atomic Oxygen Emission. 2. Temperature

A model of the temperature variations of the atomic oxygen 630 nm emission for the nighttime conditions is created on the basis of the ground-based interferometer measurements of the Doppler temperature by Fabry-Pérot interferometers. On the basis of these measurements, various regular variations and their approximations for temperature evaluations for the given solar and geophysical conditions in the nighttime period of the day are obtained.

Spatio-temporal variations in characteristics of the IR emissions of atomic oxygen and of carbon dioxide in the upper atmosphere

We analyzed and systemized the published data on satellite and rocket long-term measurements of the oxygen atom O(3P) (63 μm) and of the СО2 molecule (15 μm) infrared (IR) emissions in the upper atmosphere. We revealed and presented empirical ratios describing the diurnal, seasonal, and latitudinal variations in the intensities of these emissions, their height distribution, as well as their dependence on solar activity. We analyzed photochemical atmospheric processes leading to the emergence of O(3P) (63 μm) and of СО2 (15 μm) emissions in the upper atmosphere.