SABER Measurements Research Articles

Characteristics Analysis of the Spatial and Temporal Distributions of Stratopause Temperature Based on SABER Measurements

利用SABER探测器2002—2017年超过一个太阳活动周的数据，以大气垂直方向上40～60km的最大温度作为平流层顶温度（<i>T</i>_sp），分析50&#176;S—50&#176;N <i>T</i>_sp的时空分布特征.结果表明：<i>T</i>_sp具有明显的纬度特征和季节特征，在赤道和南北半球夏季温度较高，而在南北半球冬季的40&#176;—50&#176;纬度附近温度有最低值.再利用EOF方法分析<i>T</i>_sp，发现其第一模态的解释率达91%，且时间系数与平流层顶高度相关性最大，为-0.75，与平流层顶臭氧体积混合比相关性约0.49，与日地距离相关性为0.44，与太阳活动性（太阳活动指数，太阳黑子数）的相关性约0.33.依据该相关关系，进一步分析各变量原始场，发现<i>T</i>_sp和平流层顶臭氧体积混合比的纬度变化近似相反；与日地距离的季节变化有明显的负相关，约-0.81，且这种相关性与日地距离有弱的正相关关系；年平均<i>T</i>_sp在2002—2017年的变化约为2K，与<i>F</i>_10.7的相关系数为0.6，在南北纬20&#176;附近与太阳活动指数<i>F</i>_10.7的相关性最大，约0.74.

Investigation of sources of gravity waves observed in the Brazilian equatorial region on 8 April 2005

Abstract. On 8 April 2005, strong gravity wave (GW) activity (over a period of more than 3 h) was observed in São João do Cariri (7.4∘ S, 36.5∘ W). These waves propagated to the southeast and presented different spectral characteristics (wavelength, period and phase speed). Using hydroxyl (OH) airglow images, the characteristics of the observed GWs were calculated; the wavelengths ranged between 90 and 150 km, the periods ranged from ∼26 to 67 min and the phase speeds ranged from 32 to 71 m s−1. A reverse ray-tracing analysis was performed to search for the possible sources of the waves that were detected. The ray-tracing database was composed of temperature profiles from the Naval Research Laboratory Mass Spectrometer Incoherent Scatter (NRLMSISE-00) model and SABER measurements as well as wind profiles from the Horizontal Wind Model (HWM) and meteor radar data. According to the ray tracing result, the likely source of these observed gravity waves was the Intertropical Convergence Zone, which caused intense convective processes to take place in the northern part of the observatory. Also, the observed preferential propagation direction of the waves to the southeast could be explained using blocking diagrams, i.e. due to the wind filtering process.

Ozone and temperature decadal solar-cycle responses, and their relation to diurnal variations in the stratosphere, mesosphere, and lower thermosphere, based on measurements from SABER on TIMED

Abstract. There is evidence that the ozone and temperature responses to the solar cycle of ∼11 years depend on the local times of measurements. Here we present relevant results based on SABER data over a full diurnal cycle, which were not previously available. In this area, almost all satellite data used are measured at only one or two fixed local times, which can differ among various satellites. Consequently, estimates of responses can be different depending on the specific data set. Furthermore, over years, due to orbital drift, the local times of the measurements of some satellites have also drifted. In contrast, SABER makes measurements at various local times, providing the opportunity to estimate diurnal variations over 24 h. We can then also estimate responses to the solar cycle over both a diurnal cycle and at the fixed local times of specific satellite data for comparison. Responses derived in this study, based on zonal means of SABER measurements, agree favorably with previous studies based on data from the HALOE instrument, which only measured data at sunrise and sunset, thereby supporting the analysis of both studies. We find that for ozone above ∼40 km, zonal means reflecting specific local times (e.g., 6, 12, 18, 24 LST – local solar time) lead to different values of responses, and to different responses based on zonal means that are also averages over the 24 h local time period, as in 3-D models. For temperature, the effects of diurnal variations on the responses are not negligible even at ∼30 km and above. We also considered the consequences of local time variations due to orbital drifts of certain operational satellites, and, for both ozone and temperature, their effects can be significant above ∼30 km. Previous studies based on other satellite data do not describe the treatment, if any, of local times. Some studies also analyzed data merged from different sources, with measurements made at different local times. Generally, the results of these studies do not agree very well among themselves. Although responses are a function of diurnal variations, this is not to say that they are the major reason for the differences, as there are likely other data-related issues. The effects due to satellite orbital drift may explain some unexpected variations in the responses, especially above 40 km.

Cross-calibration of ground-based measurement of rotational temperature of OH(3-1) at altitude ∼87 km in Maimaga (63° N, γ = 129.5° E) and SABER/TIMED satellite data

Maimaga (63° N, λ = 129.5° E) is a base point in the meridional station network that we create in East Siberia to monitor changes in the upper mesosphere. Therefore, the comparison of measurements obtained by ground-based instruments and satellite data are relevant. It is known that the rotational temperature of hydroxyl (OH) corresponds to the temperature of the neutral atmosphere at the height of its radiation (∼87 km). The night spectrum of OH(3-1) is measured by a new Shamrock 303i spectrograph since January 2013. The rotational temperature, estimated from the ratio of the P - branches, is compared with the kinetic temperature of the atmosphere at an altitude of 87 km measured with the SABER radiometer installed aboard the TIMED satellite. The v2.0 version of the SABER temperature profiles was used (http://saber.larc.nasa.gov). The SABER measurements obtained within the area (55°N-70°N)×(115°E-135°E) have been selected. The angle of view of the ground-based spectrograph is almost in the center of the selected area. The satellite overpasses the selected area only in September-November and January-March. The spectrograph measurement is considered if the difference in time from the satellite measurement does not exceed a half of hour. The analysis of 328 cases of coincident measurements has shown that the difference in temperatures obtained from the satellite and ground-based spectrograph lies within the errors of both instruments. The correlation coefficient between two databases is equal 0.8. Based on the performed analysis, it has been concluded that a series of hydroxyl rotational temperatures can be used to study temperature variations of different time scales including long-term trends at the OH emission altitude (∼87 km).

A comparison of ground-based hydroxyl airglow temperatures with SABER/TIMED measurements over 23° N, India

Abstract. Ground-based observations of OH (6, 2) Meinel band nightglow were carried out at Ranchi (23.3° N, 85.3° E), India, during January–March 2011, December 2011–May 2012 and December 2012–March 2013 using an all-sky imaging system. Near the mesopause, OH temperatures were derived from the OH (6, 2) Meinel band intensity information. A limited comparison of OH temperatures (TOH) with SABER/TIMED measurements in 30 cases was performed by defining almost coincident criterion of ±1.5° latitude–longitude and ±3 min of the ground-based observations. Using SABER OH 1.6 and 2.0 µm volume emission rate profiles as the weighing function, two sets of OH-equivalent temperature (T1. 6 and T2. 0 respectively) were estimated from its kinetic temperature profile for comparison with OH nightglow measurements. Overall, fair agreement existed between ground-based and SABER measurements in the majority of events within the limits of experimental errors. Overall, the mean value of OH-derived temperatures and SABER OH-equivalent temperatures were 197.3 ± 4.6, 192.0 ± 10.8 and 192.7 ± 10.3 K, and the ground-based temperatures were 4–5 K warmer than SABER values. A difference of 8 K or more is noted between two measurements when the peak of the OH emission layer lies in the vicinity of large temperature inversions. A comparison of OH temperatures derived using different sets of Einstein transition probabilities and SABER measurements was also performed; however, OH temperatures derived using Langhoff et al. (1986) transition probabilities were found to compare well.

MIPAS temperature from the stratosphere to the lower thermosphere: Comparison of vM21 with ACE-FTS, MLS, OSIRIS, SABER, SOFIE and lidar measurements

Abstract. We present vM21 MIPAS temperatures from the lower stratosphere to the lower thermosphere, which cover all optimized resolution measurements performed by MIPAS in the middle-atmosphere, upper-atmosphere and noctilucent-cloud modes during its lifetime, i.e., from January 2005 to April 2012. The main upgrades with respect to the previous version of MIPAS temperatures (vM11) are the update of the spectroscopic database, the use of a different climatology of atomic oxygen and carbon dioxide, and the improvement in important technical aspects of the retrieval setup (temperature gradient along the line of sight and offset regularizations, apodization accuracy). Additionally, an updated version of ESA-calibrated L1b spectra (5.02/5.06) is used. The vM21 temperatures correct the main systematic errors of the previous version because they provide on average a 1–2 K warmer stratopause and middle mesosphere, and a 6–10 K colder mesopause (except in high-latitude summers) and lower thermosphere. These lead to a remarkable improvement in MIPAS comparisons with ACE-FTS, MLS, OSIRIS, SABER, SOFIE and the two Rayleigh lidars at Mauna Loa and Table Mountain, which, with a few specific exceptions, typically exhibit differences smaller than 1 K below 50 km and than 2 K at 50–80 km in spring, autumn and winter at all latitudes, and summer at low to midlatitudes. Differences in the high-latitude summers are typically smaller than 1 K below 50 km, smaller than 2 K at 50–65 km and 5 K at 65–80 km. Differences between MIPAS and the other instruments in the mid-mesosphere are generally negative. MIPAS mesopause is within 4 K of the other instruments measurements, except in the high-latitude summers, when it is within 5–10 K, being warmer there than SABER, MLS and OSIRIS and colder than ACE-FTS and SOFIE. The agreement in the lower thermosphere is typically better than 5 K, except for high latitudes during spring and summer, when MIPAS usually exhibits larger vertical gradients.

Global and long-term comparison of SCIAMACHY limb ozone profiles with correlative satellite data (2002–2008)

Abstract. SCIAMACHY limb scatter ozone profiles from 2002 to 2008 have been compared with MLS (2005–2008), SABER (2002–2008), SAGE II (2002–2005), HALOE (2002–2005) and ACE-FTS (2004–2008) measurements. The comparison is performed for global zonal averages and heights from 10 to 50 km in one km steps. The validation was performed by comparing monthly mean zonal means and by comparing averages over collocated profiles within a zonal band and month. Both approaches yield similar results. For most of the stratosphere SCIAMACHY agrees to within 10% or better with other correlative data. A systematic bias of SCIAMACHY ozone of up to 100% between 10 and 20 km in the tropics points to some remaining issues with regard to convective cloud interference. Statistical hypothesis testing reveals at which altitudes and in which region differences between SCIAMACHY and other satellite data are statistically significant. We also estimated linear trends from monthly mean data for different periods where SCIAMACHY has common observations with other satellite data using a classical trend model with QBO and seasonal terms in order to draw conclusions on potential instrumental drifts as a function of latitude and altitude. Since the time periods considered here are rather short these trend estimates are only used to identify potential instrumental issues with the SCIAMACHY data. As a result SCIAMACHY exhibits a statistically significant negative trend in the range of of about 1–3% per year depending on latitude during the period 2002–2005 (overlapping with HALOE and SAGE II) and somewhat less during 2002–2008 (overlapping with SABER) in the altitude range of 30–40 km, while in the period 2004–2008 (overlapping with MLS and ACE-FTS) no significant trends are observed. Since all correlative satellite instruments do not show to a very large extent statistically significant trends in any of the time periods considered here, the negative trends observed with SCIAMACHY data point at some remaining instrumental artifact which is most likely related to residual errors in the tangent height registration of SCIAMACHY.

Thermosphere–ionosphere coupling in response to recurrent geomagnetic activity

The paper presents the global thermosphere–ionosphere response to the high-speed solar wind streams and the subsequent recurrent geomagnetic variations with a period of 9d during the period of time 1 October 2007–31 March 2009. The COSMIC electron density at fixed heights, as well as the ionospheric parameters foF2 and hmF2, and the two coefficients characterizing the top and bottom side vertical gradients of the electron density profile, are used for investigating the ionospheric 9-d (s=0) wave response. The SABER temperature data are utilized for studying the response of the lower thermosphere to the recurrent auroral heating. The COSMIC and SABER measurements are analyzed by one and the same method where the atmospheric tides and planetary waves which are present in the temperature and electron density measurements are simultaneously extracted from the data. The use of such data analysis approach brings to light additional features of the ionospheric response to a recurrent geomagnetic activity which have not been found before.

A new method to derive middle atmospheric temperature profiles using a combination of Rayleigh lidar and O&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; 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.

Longitudinal variation of tides in the MLT region: 1. Tides driven by tropospheric net radiative heating

This study demonstrates that the diurnal cycle of net radiative heating in the troposphere accounts for considerable longitudinal variability of diurnal and semidiurnal tidal fields in the mesosphere and lower thermosphere (MLT) (∼80–120 km), whereas previously it was thought that latent heating associated with deep tropical convection is the predominant driver of this variability. The heating rates used for this study are derived from radiative flux products by NASA Goddard Institute for Space Studies (GISS), and the model employed to estimate the corresponding MLT tides is the Global‐Scale Wave Model (GSWM). The radiative flux products by NASA GISS utilize improved International Satellite Cloud Climatology Project (ISCCP) cloud climatology and ancillary data sets and were validated by Earth radiation Budget Experiment (ERBE) and Clouds and the Earth's Radiant Energy System (CERES) radiative flux (0.2–200.0 microns) measurements at the top of the atmosphere and the Earth surface. Typical magnitudes of tidal temperature longitude variations at, e.g., 95 km or 110 km are 20 ± 5 K for the diurnal tide and 6 ± 2 K for the semidiurnal tide. The computed tides and their longitude variability are of comparable amplitude to those derived from TIMED SABER temperature measurements. Part 2 of this study provides new estimates of tidal forcing by latent heating and assesses the total MLT tidal response to these combined heat sources in comparison to tidal climatologies derived from TIMED SABER measurements.

Inferring hydroxyl layer peak heights from ground-based measurements of OH(6-2) band integrated emission rate at Longyearbyen (78° N, 16° E)

Abstract. Measurements of hydroxyl nightglow emissions over Longyearbyen (78° N, 16° E) recorded simultaneously by the SABER instrument onboard the TIMED satellite and a ground-based Ebert-Fastie spectrometer have been used to derive an empirical formula for the height of the OH layer as a function of the integrated emission rate (IER). Altitude profiles of the OH volume emission rate (VER) derived from SABER observations over a period of more than six years provided a relation between the height of the OH layer peak and the integrated emission rate following the procedure described by Liu and Shepherd (2006). An extended period of overlap of SABER and ground-based spectrometer measurements of OH(6-2) IER during the 2003–2004 winter season allowed us to express ground-based IER values in terms of their satellite equivalents. The combination of these two formulae provided a method for inferring an altitude of the OH emission layer over Longyearbyen from ground-based measurements alone. Such a method is required when SABER is in a southward looking yaw cycle. In the SABER data for the period 2002–2008, the peak altitude of the OH layer ranged from a minimum near 76 km to a maximum near 90 km. The uncertainty in the inferred altitude of the peak emission, which includes a contribution for atmospheric extinction, was estimated to be ±2.7 km and is comparable with the ±2.6 km value quoted for the nominal altitude (87 km) of the OH layer. Longer periods of overlap of satellite and ground-based measurements together with simultaneous on-site measurements of atmospheric extinction could reduce the uncertainty to approximately 2 km.

Influence of solar-geomagnetic disturbances on SABER measurements of 4.3 μm emission and the retrieval of kinetic temperature and carbon dioxide

Thermospheric infrared radiance at 4.3 μm is susceptible to the influence of solar-geomagnetic disturbances. Ionization processes followed by ion-neutral chemical reactions lead to vibrationally excited NO + (i.e., NO +(v)) and subsequent 4.3 μm emission in the ionospheric E-region. Large enhancements of nighttime 4.3 μm emission were observed by the TIMED/SABER instrument during the April 2002 and October–November 2003 solar storms. Global measurements of infrared 4.3 μm emission provide an excellent proxy to observe the nighttime E-region response to auroral dosing and to conduct a detailed study of E-region ion-neutral chemistry and energy transfer mechanisms. Furthermore, we find that photoionization processes followed by ion-neutral reactions during quiescent, daytime conditions increase the NO + concentration enough to introduce biases in the TIMED/SABER operational processing of kinetic temperature and CO 2 data, with the largest effect at summer solstice. In this paper, we discuss solar storm enhancements of 4.3 μm emission observed from SABER and assess the impact of NO +(v) 4.3 μm emission on quiescent, daytime retrievals of Tk/CO 2 from the SABER instrument.

The “wave turbopause”

The “wave turbopause” is defined as the mesospheric altitude level where the temperature fluctuation field indicates a substantial increase in wave amplitudes in the vertical direction. The turbopause altitude is analyzed on the basis of four years of SABER data (2002–2005, Version 1.06). Substantial seasonal and latitudinal variations are found, with some interannual variability also present. Seasonal changes are annual at high latitudes, semi-annual at low latitudes, and a mixture of both at middle latitudes. Southern hemisphere data are similar as in the North if shifted by half a year. Latitudinal variations show a minimum in the tropics and two relative maxima at middle latitudes. The “wave turbopause” is found near to zero-wind lines or low-wind zones (zonal wind). It is compared to rocket and other measurements, and interesting similarities are obtained. The wave turbopause can also be found in the HAMMONIA GCM. A preliminary analysis shows results similar to those of the SABER measurements.

Monthly tidal temperatures 20–120 km from TIMED/SABER

The SABER instrument on the TIMED satellite provides unprecedented geographical coverage for the determination and study of atmospheric tides. However, the slow local time precession rate of TIMED can cause longer‐term temperature variations to alias into the tidal signals. A new method of analyzing satellite data for tides has been developed to circumvent this difficulty, but at the expense of temporal resolution of the tidal fields, i.e., 120‐day mean tidal structures are obtained. In this work, we apply this method to SABER temperature data to derive a series of 120‐day mean tidal structures, extending between 20 and 120 km altitude, 50°S–50°N latitude, and centered on each month from September 2003 to September 2004. In addition to the migrating (Sun‐synchronous) diurnal and semidiurnal tides, a number of nonmigrating tides are revealed in the SABER measurements. Some of these waves are thought to originate via nonlinear coupling between the migrating tides and the stationary planetary wave with zonal wave number s = 1. Other nonmigrating tidal components appear to be forced by latent heating due to deep tropical convection. Of the latter, the eastward propagating diurnal tide with s = 3 is dominant and is as large as the migrating diurnal tide during some months. Of particular interest is the wave‐4 structure with respect to longitude that characterizes both the diurnal and semidiurnal total tidal fields. This feature is a result of the predominant wave‐4 topography/land‐sea longitude dependence at the surface, which is reflected in the diurnal and semidiurnal components of the latent heating rates due to deep tropical convection. The ability of the global‐scale wave model (GSWM) to approximate the observed tidal fields, including the wave‐4 total tidal structures, is also assessed.

Stratospheric and mesospheric temperature variations for the quasi-biennial and semiannual (QBO and SAO) oscillations based on measurements from SABER (TIMED) and MLS (UARS)

Abstract. We present the zonal mean temperature variations for the quasi-biennial oscillation (QBO) and the semiannual oscillation (SAO) based on data from SABER on the TIMED spacecraft (years 2002 to 2004) and from MLS on the UARS mission (1992 to 1994). The SABER measurements provide the rare opportunity to analyze data from one instrument over a wide altitude range (15 to 95 km), while MLS data were taken in the 16 to 55 km altitude range a decade earlier. The results are presented for latitudes from 48° S to 48° N. New results are obtained for the QBO, especially in the upper stratosphere and mesosphere, and at mid-latitudes. At Equatorial latitudes, the QBO amplitudes show local peaks, albeit small, that occur at different altitudes. From about 20 to 40 km, and within about 15° of the Equator, the amplitudes can approach 3.5° K for the stratospheric QBO (SQBO). For the mesospheric QBO (MQBO), we find peaks near 70 km, with temperature amplitudes reaching 3.5° K, and near 85 km, the amplitudes approach 2.5° K. Morphologically, the amplitude and phase variations derived from the SABER and MLS measurements are in qualitative agreement. As a function of latitude, the QBO amplitudes tend to peak at the Equator but then increase again pole-ward of about 15° to 20°. The phase progression with altitude varies more gradually at the Equator than at mid-latitudes. Many of the SAO results presented are also new, in part because measurements were not previously available or were more limited in nature. At lower altitudes near 45 km, within about 15° of the Equator, the temperature amplitudes for the stratospheric SAO (SSAO) reveal a local maximum of about 5° K. At higher altitudes close to the Equator, our results show separate peaks of about 7° K near 75 and 90 km for the mesospheric SAO (MSAO). In the SAO results, significant inter-annual differences are evident, with the amplitudes being largest in 2002 relative to 2003 and 2004. As in the case for the QBO, the SAO temperature amplitudes go through minima away from the Equator, and then increase towards mid latitudes, especially at altitudes above 55 km. We compare our findings with previously published empirical results, and with corresponding results from the numerical spectral model (NSM). Although not a focus of this study, we also show results for the inter-annual variations (which appear to be generated at least in part by the QBO) of the migrating diurnal tide. In the upper mesosphere, their amplitudes can approach 20° K, and they are derived jointly with the zonal-mean components.

Zonal‐mean temperature variations inferred from SABER measurements on TIMED compared with UARS observations

In the zonal mean meridional winds of the upper mesosphere, oscillations with periods between 1 and 4 months have been inferred from UARS measurements and independently predicted with the Numerical Spectral Model (NSM). The wind oscillations tend to be confined to low latitudes and appear to be driven, at least in part, by wave‐mean‐flow interactions. Winds across the equator should generate, due to dynamical heating and cooling, temperature oscillations with opposite phase in the two hemispheres. Investigating this phenomenon, we have analyzed SABER temperatures from TIMED in the altitude range between 55 and 95 km to delineate with an empirical model, the year‐long variability of the migrating tides and zonal mean components. The inferred seasonal variations of the diurnal tide, characterized by amplitude maxima near equinox, are in substantial agreement with UARS observations and results from the NSM. For the zonal mean, the dominant seasonal variations in the SABER temperatures, with annual (12 months) and semiannual (6 months) periodicities, agree well with those derived from UARS measurements. The intraseasonal variations with periods between 2 and 4 months have amplitudes close to 2 K, almost half as large as those for the dominant seasonal variations. Their amplitudes are in qualitative agreement with the corresponding values inferred from UARS during different years. The SABER and UARS temperature variations reveal pronounced hemispherical asymmetries, consistent with meridional wind oscillations across the equator. The phase of the semiannual temperature oscillations from the NSM agrees with the observations from UARS and SABER. However, the amplitudes are systematically smaller, which may indicate that planetary waves are more important than is allowed for in the model. For the shorter‐period intraseasonal variations, which can be generated by gravity wave drag, the model results are generally in better agreement with the observations.

Planetary wave coupling from the stratosphere to the thermosphere during the 2002 Southern Hemisphere pre‐stratwarm period

Temperature observations between 20 and 120 km from the SABER instrument on the TIMED spacecraft are used to investigate the nature of planetary wave activity during the 60 days prior to the midwinter stratospheric warming that commenced on 26 September, 2002 in the Southern Hemisphere. The primary wave components consist of eastward‐propagating quasi‐10‐day waves with zonal wave numbers s = 1 and s = 2, and a stationary planetary wave with s = 1. The waves are found to extend from the lower stratosphere to the 100–120 km height region with surprisingly little amplitude attenuation, although wave amplitudes oscillate with altitude like a standing wave pattern. Time evolution of the waves is also addressed with emphasis on 86 km altitude, where temperature observations from three Antarctic stations at Davis (69°S, 78°W), Rothera (68°S, 68°W) and Syowa (69°S, 40°E) are available during the same period. We demonstrate that the temporal evolution of temperature obtained by superposition of the waves derived from SABER measurements accounts for nearly all the temperature variability observed at the longitudes of the three Antarctic stations.