北京地区上空OH转动温度的季节性变化

在北京东北方向的兴隆天文台,自主搭建的大气辐射观测仪器对OH夜气辉从2011年12月开始进行观测.利用高分辨率的OH(8-3)带的振转光谱计算了转动温度,并与TIMED/SABER探测的温度进行了比较.观测表明,两年(2012—2013)的OH(8-3)带转动温度平均值为203.0±11.2K,有明显的季节变化,冬季高,夏季低,温差可达60K.与SABER观测温度的季节变化一致.对日平均的转动温度进行年振荡和半年振荡分量的拟合分析表明,年振荡强度(10.8K)远大于半年振荡(2.7K).研究还发现,不同夜晚转动温度变化形态差别很大,既有很强的潮汐控制的波动,又有相对短周期的波动.     

Seasonal temperature variations near the mesopause according to the hydroxyl emission measurements in Zvenigorod

The rotational temperatures of hydroxyl molecules with different vibrational excitation, which were used to determine the seasonal variations in the vertical temperature distribution near the mesopause at altitudes of 85–90 km, have been obtained based on the spectral measurements of the atmospheric nightglow at IFA RAN observatory in Zvenigorod. The obtained characteristics of the annual and semiannual harmonics have been compared with their lidar and satellite measurements and model representations.     

The regular nocturnal course of temperature in the midlatitude mesopause region according to hydroxyl airglow measurements

Using ground-based spectral measurements in the near-infrared range at the Zvenigorod scientific station of the Institute of Atmospheric Physics (56° N, 37° E) for 2000–2013, we obtained average nighttime changes in rotational and vibrational temperatures of hydroxyl with its emission layer localized at mesopause heights. The rotational temperature reflects the kinetic temperature of the emission layer of the atmosphere. The analysis made it possible to determine the characteristics of the first three harmonics of diurnal temperature dynamics in the mesopause region both with and without altitudinal oscillations of the OH emission layer. In both cases, the second and third harmonics are statistically significant: their amplitudes are ～1 K and the phases of their first maxima are near 0300 and 0130 local solar time.     

Seasonal and nighttime behaviors of emissions of hydroxyl and the atmospheric system of molecular oxygen of the midlatitude mesopause

Based on observations of mesopause emissions, namely, emissions of hydroxyl (band (6-2)) and molecular oxygen (band (0-1) of the atmospheric system), their systematic nighttime and seasonal variations are determined at Zvenigorod Observatory in 2000–2008. It is shown that the intensity of hydroxyl emission decreases during the entire night or first half-night, probably due to the influence of the chemical sink of atomic oxygen on the nighttime behavior of hydroxyl emission. The nighttime behavior of the intensity of molecular oxygen emission is explained by the action of atmospheric tides. The seasonal behavior of emissions is characterized by two minima, in April–May and December; it is caused by the annual behavior of the atomic oxygen content, temperature, and atmospheric density in the emitting layer. Based on the emission data, we determined the seasonal variations of atomic oxygen at heights of ∼87 km (maximum of hydroxyl emission) and ∼95 km (maximum of molecular oxygen emission).     

Atmospheric temperature profiling by joint Raman,Rayleigh and Fe Boltzmann lidar measurements

Simultaneous and complete temperature profiles from near ground to about 100 km are essential for studying the dynamical coupling between different atmospheric layers. They are acquired by combining three different lidar techniques at Wuhan, China (30.5°N, 114.4°E). The atmospheric temperatures from about 3 to 25 km are calculated from the nitrogen molecule density profiles obtained from the N₂ vibrational Raman backscatter, while the atmospheric temperatures between 30 and ∼75 km are calculated by the standard Rayleigh scattering method. The temperatures in the 80–100 km altitude region are derived from the Fe Boltzmann technique. The temperature profiles measured by our lidar systems exhibit good agreement when compared with the radiosonde and satellite data, as well as the model. A Lomb–Scargle spectral analysis of the normalized temperature perturbations in the altitude range from 4 to 60 km shows that the spectral slopes of the vertical wave number spectra tended to −3 for large vertical wave numbers. This is consistent with the model predictions of saturated gravity wave spectra.     

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.     

Correlations of mesospheric variability and their relation to the large-scale circulation during polar winter

WINDII data from the Upper Atmosphere Research Satellite show an integrated OH emission rate systematically increasing with decreasing airglow peak altitude. A Spectral Airglow Temperature Imager (SATI) at 74°N shows strong positive correlations between the integrated emission rate and the rotational OH temperature. Taken together, the two correlations are consistent with vertical motions of the mesopause region, over periods from hours to winter to winter. SABER data are consistent with these correlations. The O₂ atmospheric band shows much weaker correlations. The SATI mesospheric temperatures also correlate with Resolute Bay temperatures for the 22.5 km level, a mesosphere–stratosphere relationship.     

Planetary waves observed by TIMED/SABER in coupling the stratosphere–mesosphere–lower thermosphere during the winter of 2003/2004: Part 1—Comparison with the UKMO temperature results

Part 1 of the present paper is focused on the types of planetary wave seen in the TIMED/SABER and UK Met Office (UKMO) temperature data in the Northern Hemisphere (NH) (0–50°N) stratosphere (30–60 km) during the Arctic winter of 2003/2004, as the emphasis is on their spatial structure (latitude and altitude) and temporal evolution particularly in relation to the stratospheric warmings. A new method for analysis of satellite data is presented in this study where the migrating and nonmigrating tides and planetary waves (stationary, zonally symmetric and travelling) are simultaneously extracted from the satellite data. The comparison between the altitude and latitude structure of the SABER and UKMO planetary waves in the temperature field of the NH stratosphere indicates a high degree of qualitative and quantitative resemblance and in this way the validity of the new data analysis method is verified as well.     

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.     

Inter-hemispheric asymmetry in polar mesosphere summer echoes and temperature at 69° latitude

An inter-hemispheric asymmetry is found in the characteristics of polar mesosphere summer echoes (PMSE) and upper mesosphere temperatures at conjugate latitudes (～69°) above Antarctica and the Arctic. The second complete mesosphere–stratosphere–troposphere (MST) radar summer observation season at Davis (68.6°S) revealed that PMSE occur less frequently, with lower strength and on average 1 km higher compared with their northern counterparts at Andenes (69.3°N). We consider the thermodynamic state of the mesosphere for conjoining hemispheric summers based on satellite and ground-based radar measurements, and show the mesopause region near ～80–87 km of the Southern Hemisphere (SH) to be up to 7.5 K warmer than its Northern Hemisphere (NH) counterpart. We show that this is consistent with our observation of asymmetries in the characteristics of PMSE and demonstrate how the mesosphere meridional wind field influences the existence and strength of the echoes in both hemispheres.     

Semidiurnal thermal tide in the mesopause region over Yakutia

The study is based on measuring fluctuations of the intensity and rotational temperatures of the molecular emissions of hydroxyl OH(6,2) and the first atmospheric band of oxygen O₂(0–1), excited at approximately 87 and 95 km, respectively. The measurements are conducted at Maimaga station (63°N, 129.5°E), located 150 km north of Yakutsk. The semidiurnal tide parameters were obtained using the database compiled from 1999 to 2005. The data obtained from October to March were analyzed. The measurements conducted during 214 nights were used to determine the semidiurnal tide parameters. The wave amplitude at the height of the molecular oxygen emission (～95 km) is 8 K, which is larger than the amplitude at the height of the hydroxyl emission (～87 km) by approximately 2 K. Except November, the 12-h oscillation at the height of molecular oxygen excitation leads the oscillation at the height of hydroxyl excitation. On average, the phase is ～5.7 h at the OH emission height and ～6.4 h at the O₂ emission height. We note that an abrupt increase in the tide amplitude in March at the molecular oxygen height can be related to a seasonal decrease in the so-called “wave” turbopause height.     

Detection of solar activity signatures in OH* temperature fluctuations possibly related to the differential rotation of the Sun

Measurements of the hydroxyl rotational temperatures at about 87 km altitude above Wuppertal (51.3°N, 7.2°E), Germany, are analysed. The time series covers the time interval from 1987 until 2005 and consists of more than 4000 night mean temperature data. Seasonal and longer-term trends are removed from the data set and OH* temperature fluctuations on temporal scales of about 3–40 days are derived. Various spectral analysis techniques (harmonic analysis, maximum entropy method and wavelet transform) are applied. Can – due to the Sun's rotation – the irregular pattern of sunspots on the solar disc lead to OH* temperature fluctuations? Pronounced spectral components in the OH* temperature fluctuations around a period from 27 to 31 days are frequently observed. We tentatively attribute these signatures to the differential rotation of the Sun: Sun's equatorial regions rotate faster (taking only about 27 days) than the polar regions. Sunspots occur at heliographic latitudes at about ±40°, which correspond to a rotation rate of about 27–31 days. The OH* temperature fluctuations within this period range show a long-term modulation of 11 years. Thus, tracking the spectral intensity of the 27- to 31-day component should allow the indirect monitoring of the solar sunspot cycle.     

First results of warm mesospheric temperature over Gadanki (13.5°N, 79.2°E) during the sudden stratospheric warming of 2009

Rayleigh lidar observations at Gadanki (13.5°N, 79.2°E) show an enhancement of the nightly mean temperature by 10–15 K at altitudes 70–80 km and of gravity wave potential energy at 60–70 km during the 2009 major stratospheric warming event. An enhanced quasi-16-day wave activity is observed at 50–70 km in the wavelet spectrum of TIMED–SABER temperatures, possibly due to the absence of a critical level in the low-latitude stratosphere because of less westward winds caused by this warming event. The observed low-latitude mesospheric warming could be due to wave breaking, as waves are damped at 80 km.     

High-altitude data assimilation system experiments for the northern summer mesosphere season of 2007

A global numerical weather prediction system is extended to the mesosphere and lower thermosphere (MLT) and used to assimilate high-altitude satellite measurements of temperature, water vapor and ozone from MLS and SABER during May–July 2007. Assimilated temperature and humidity from 100 to 0.001 hPa show minimal biases compared to satellite data and existing analysis fields. Saturation ratios derived diagnostically from these assimilated temperature and water vapor fields at PMC altitudes and latitudes compare well with seasonal variations in PMC frequency measured from the aeronomy of ice in the mesosphere (AIM) satellite. Synoptic maps of these diagnostic saturation ratios correlate geographically with three independent transient mesospheric cloud events observed at midlatitudes by SHIMMER on STPSat-1 and by ground observers during June 2007. Assimilated temperatures and winds reveal broadly realistic amplitudes of the quasi 5-day wave and migrating tides as a function of latitude and height. For example, analyzed winds capture the dominant semidiurnal MLT wind patterns at 55°N in June 2007 measured independently by a meteor radar. The 5-day wave and migrating diurnal tide also modulate water vapor mixing ratios in the polar summer MLT. Possible origins of this variability are discussed.     

Microwave measurements of the ozone content in winter arctic stratosphere

As a result of the long-term observations lead in region of Kola Peninsula, connection between character of variations of the ozone content in a stratosphere of Arctic regions and behavior and structure of a winter polar vortex is established. During winter seasons with well developed cyclone and duration of stable existence not less than 1.5–2 months were observed extremely low ozone number density at heights 20–25 km connected, apparently, with its chemical destruction. On the other hand, during disturbances of the vortex, accompanied strong stratospheric warming, was registered almost double increase of ozone amount in a high-altitude interval from 20 up to 40 km. Comparison of results of ground-based microwave monitoring of an ozone layer to data of the satellite instrument EOS MLS installed on satellite AURA is lead. In most cases comparison has shown satisfactory within the limits of an error of measurements coincidence of results. However in conditions of atmospheric disturbances when arose significant spatial heterogeneity, the discrepancy of results of comparison was marked. The possible reasons which cause the detected disagreement in results are discussed.     

Auroral electron precipitation when the trapped radiation region collapsed during the main phase of the geomagnetic storm of May 15, 2005

The simultaneous measurements of the boundary of the trapped radiation region, where auroral electrons precipitate, on the Meteor-3M satellite (the circular polar orbit at an altitude of ∼1000 km) and the westward electrojet dynamics during the main phase of a strong (Dst = −263 nT) magnetic storm that occurred on May 15, 2005, are analyzed. At the end of the first hour of the storm main phase, the nightside boundary of the trapped radiation region and the peak of the precipitating electron fluxes with a energies of ∼1 keV shifted toward the Earth to L ∼ 3. The westward electrojet center approached the same L shell. Near the boundary of the trapped radiation region, the auroral electron spectrum had the shape of typical inverted V. The differential spectrum maximum shifted to an energy of ∼100 eV, when the latitude decreased by ∼1°. The nightside boundary of the trapped radiation region, the electron precipitation equatorward boundary, and the westward electrojet center are compared with the known empirical dependences of the position of these structures on the Dst variation amplitude.     

Empirical model of variations in the emission of the Infrared Atmospheric system of molecular oxygen: 3. Temperature

Rotational temperatures of the 1.58-μm (0–1) band of the Infrared Atmospheric system of molecular oxygen (IRAO₂), measured in Zvenigorod (56° N, 36° E), are systematized and analyzed. An empirical dependence of variations in the temperature of the 1.58-μm emission on the solar zenith angle is derived. The use of parameters of the altitude distribution of emission intensity 1.27 μm of middle atmosphere temperature profiles, received from the AURA satellite, allowed for the study of daily variations in the temperature of the 1.58-μm emission. It is revealed that the behavior of these variations corresponds to daily variations in the atmospheric temperature at altitudes of the radiating layer of IRAO₂, received from the AURA satellite.     

临近空间大气扰动变化特性的定量研究

本文利用TIMED/SABER 2002年1月至2013年1月共11年的卫星温度探测数据,通过全球网格化及在网格内作数学统计的方法,得到了20~100km高度上全球网格点上温度的平均值和标准差,实现了对临近空间全球大气扰动进行定量刻画的目的.通过定量分析温度标准差的分布特性,文中得到了临近空间大气扰动的全球分布规律,并讨论了与这些分布规律相关的物理过程.结果表明,在20~70km高度上,温度标准差为1~10K,有显著的冬季/夏季的差异,冬季的温度标准差比夏季大;大气重力波扰动是最主要来源,同时大气传播性行星波引起的扰动也是来源之一.在70~100km高度上,温度标准差常年较强,量值为10~30K,冬季/夏季的差异小,低纬地区的温度标准差高于中高纬度地区,呈现许多局地化的小结构.大气重力波是引起该区域大气总扰动量的主要扰动来源,大气潮汐波、传播性行星波(准2天、准6.5天)也有重要贡献.     

A comparison of field- and satellite-derived thermal flux at Piton de la Fournaise: implications for the calculation of lava discharge rate

We present thermal measurements made by high spatial resolution ground-based (a hand-held thermal camera) and low spatial resolution space-based (MODIS) instruments for a lava flow field active during the last phase of the May–July 2003 eruption at Piton de la Fournaise (La Réunion). Multiple oblique ground-based thermal images were merged to provide full coverage of the flow-field. These were then corrected for path length attenuation and orthorectified, allowing the at-surface radiance emitted by the flow-field to be estimated. Comparison with the radiance recorded by the MODIS sensors during the eruption reveals that, for clear-sky conditions and moderate-to-low viewing angles (satellite zenith <40°), the satellite measurements represent ∼90% of the at-surface radiance, and thus represent valuable data for quantifying volcanic thermal anomalies. Nevertheless, extreme viewing geometries and the presence of clouds strongly affect the radiance reaching the sensor and affected data from 94% of the overpasses. Ground-based thermal data were used to investigate an empirical relationship between the radiant heat flux and lava discharge rate during the emplacement of pahoehoe flows. While the average radiation temperature for flow surface that were 6–24 h old ranged between 500 K and 625 K, the ratio between radiative heat flux and Time-Averaged lava Discharge Rate (TADR) ranged between 1.5 × 10⁸ J m⁻³ and 3.5 × 10⁸ J m⁻³. This relationship was used to estimate TADR values from optimal MODIS data and produced results in line with those obtained from GPS surveys (Coppola et al. 2005). Our results underscore the importance of ground-based thermal analysis for the interpretation of satellite measurements, particularly in terms of calculating discharge rate trends.     

Nocturnal temperature changes over tropics during CAWSES-III campaign: Comparison with numerical models and satellite data

In the frame of the third CAWSES tidal campaign in June–August 2007, lidar and satellite data were collected and compared with numerical models. Continuous nocturnal middle atmospheric temperature measurements performed with a Rayleigh lidar located at La Reunion Island (20.8°S–55.5°E) were obtained for three subsequent nights. The results clearly show the presence of tidal components with a downward phase propagation. Comparisons with SABER satellite data show good agreement on tidal amplitude; however, some differences on the structures are reported probably due to the zonal nature of the retrieval provided by the SABER data. The observed tidal components are compared with two different numerical models such as the 2D global scale wave model and the 3D-GCM LMDz-REPROBUS. Both models reveal good agreement with temperature lidar patterns, while simulated tidal amplitudes are smaller by a factor of around 2–2.5 K.