Interseismic slip rate of the Garze–Yushu fault belt in the Tibetan Plateau from C-band InSAR observations between 2003 and 2010

InSAR time series techniques can provide high-spatial resolution deformation fields across an active fault belt, even for zones with heavy vegetation coverage. An interseismic deformation map across the Garze–Yushu fault belt in the Tibetan Plateau, ∼300 km by ∼100 km, is derived from C-band Envisat/ASAR imagery collected between 2003 and 2010. Unlike previous research, we obtain a lookup figure which relates the slip rate with the fault locking depth, the dip angle and the rake angle. The estimated slip rate changes significantly with the locking depth and the rake angle, but relatively little with the dip angle. When considering the focal mechanism solutions of historical earthquake along the Garze–Yushu fault, the interseismic slip rate of the Garze–Yushu fault is close to a value of 6.4 mm/yr, which is between the highest (18.2 mm/yr) and the lowest (3.1 mm/yr) slip rate from GPS estimations, but slightly less than the minimum value (∼ 7 mm/yr) from the geological estimations. The earthquake recurrence interval on the Yushu part of Garze–Yushu fault equals 272 yr, and the April 14, 2010 Mw 6.9 earthquake has not completely released the accumulated strain energy between 1738 and 2010.     

Study of the 2013 Lushan M7.0 earthquake coseismic ionospheric disturbances

On April 20, 2013, an earthquake of M7.0 occurred in Lushan, Sichuan province, China. This paper investigates the coseismic ionospheric anomalies using GPS (Global Positioning System) data from 23 reference stations in Sichuan province that are a part of the Crustal Movement Observation Network of China (CMONOC). The recorded results show that a clear ionospheric anomaly occurred within 15 min after the earthquake near the epicenter, and the occurrence time of the anomalies recorded by various stations is related to the distance from the epicenter. The maximum anomaly is 0.25 TECu, with a 2 min duration and the distance of the recording station to the epicenter is 83 km. Acoustic waves generated by the crustal vertical movement during the earthquake propagate up to the height of the ionosphere lead to the ionospheric anomaly, and the propagation speed of the acoustic wave is calculated as 0.72 ± 0.04 km/s based on the propagation time and propagation distance, consistent with the average speed of sound waves within a 0–450 km atmospheric height.     

Investigation of precursory phenomena in the ionosphere,atmosphere and groundwater before large earthquakes of M > 6.5

Precursory phenomena in the ionosphere, atmosphere and groundwater before large earthquakes (M > 6.5) are extensively investigated toward the earthquake prediction. Upward tornado type seismic clouds occurred near the epicenter associated with strong LF-VLF radio noises from lightning discharges in the evening of January 9, 1995 [Yamada, T., Oike, K. On the increase of electromagnetic noises before and after the 1995 Hyogo-Ken Nanbu earthquake. In: Hayakawa M. (Ed.), Atmospheric and Ionospheric Electromagnetic Phenomena Associated with Earthquakes. TERRAPUB, Tokyo, pp. 417–427, 1999] and anomalous foEs increases up to 10 MHz were detected at Shigaraki, 90 km of the epicenter and at Kokubunji, 500 km east of the epicenter [Ondoh, T. Anomalous sporadic-E layers observed before M7.2 Hyogo-ken Nanbu earthquake; Terrestrial gas emanation model. Adv. Polar Upper Atmos. Res. 17, 96–108, 2003; Ondoh, T. Anomalous sporadic-E ionization before a great earthquake, Adv. Space Research 34, 1830–1835, 2004] associated with strong ELF noises from lightning discharges in the daytime on January 15, 1995 [Hata, M., Fujii, T., Takumi, I. EM precursor of large-scale earthquakes in Japan, in: Abstracts of International Workshop on Seismo Electromagnetics (IWSE 2005), Univ. Electro-Communications, Chofu, Tokyo, Japan, March 15–17, pp. 182–186, 2005] before the M7.2 Hyogoken–Nanbu earthquake of January 17, 1995. The anomalous foEs increases occurred at epicentral distances within 500 km that are the same as those of the terrestrial gas emanations along active faults before large earthquakes [King, C.-Y. Gas geochemistry applied to earthquake prediction: An overview. J. Geophys. Res. 91(B12), 12269–12281, 1986]. The anomalous foEs increases seem to be a seismic precursor because geomagnetic and solar conditions were very quiet all day on January 15,1995 and the normal foEs in Japanese winter is below 6 MHz. No significant pre-seismic geomagnetic field variation was detected at epicentral distance of 100 km before this earthquake [Ondoh, T., Hayakawa, M. Anomalous occurrence of sporadic-E layers before the Hyogoken–Nanbu earthquake, M7.2 of January 17, 1995. In: Hayakawa, M. (Ed.), Atmospheric and Ionospheric Electromagnetic Phenomena Associated with Earthquakes, TERRAPUB, Tokyo, pp. 629–639, 1999; Ondoh, T., Hayakawa, M. Seismo discharge model of anomalous sporadic E ionization before great earthquakes. In: Hayakawa, M., O.A. Molchanov, (Eds.), Seismo Electromagnetics: Lithosphere–Atmosphere–Ionosphere Couplings, TERRAPUB, Tokyo, pp. 385–390, 2002; Ondoh. T., Hayakawa, M. Synthetic study of precursory phenomena of the M7.2 Hyogo-ken Nanbu earthquake. Phys. Chem. Earth 31, 378–388, 2006]. The foF2 decrease and h’F increase occurred before the M7.8 Hokkaido Nansei-Oki earthquake of July 12,1993 in a geomagnetic quiet period [Ondoh, T. Ionospheric disturbances associated with great earthquake of Hokkaido southwest coast, Japan of July 12, 1993. Phys. Earth Planet. Interiors. 105, 261–269, 1998; Ondoh, T. Seismo ionospheric phenomena. Adv. Space Res. 26, 8, 1267–1272, 2000]. Characteristic phase changes at terminator times of Omega 10.2 kHz waves passing 70 km of the epicenter extended toward darker local times by 1 h for 3 days before this earthquake due to lowering of the wave reflection height or ion density increases in the D region [Hayakawa, M., Molchanov, O. A., Ondoh, T., Kawai, E. The precursory signature effect of the Kobe earthquake on VLF subionospheric signals. J. Commun. Res. La., 43, 00. 169–180, 1996]. The radon concentration in the atmosphere over Ashiya fault, Kobe [Yasuoka, Y., Shinogi, M. Anomaly in atmospheric radon concentration: a possible precursor of the 1995 Kobe, Japan, earthquake. Health Phys. 72(5), 759–761, 1997] and in the groundwater at 17 m well in Nishinomiya, Japan [Igarashi, G., Saeki, S., Takahata, N., Sumikawa, K., Tasaki, S., Sasaki, Y., Takahashi, M., Sano, Y. Ground-water radon anomaly before the Kobe earthquake in Japan. Science 269, 60–61, 1995] had gradually increased since 2 months before the M7.2 earthquake, increased suddenly in December 1994, and rapidly returned to the normal low level of October, 1994 [Yasuoka, Y., Shinogi, M. 1997. Anomaly in atmospheric radon concentration: a possible precursor of the 1995 Kobe. Japan, earthquake. Health Phys. 72(5), 759–761.]. Radon concentration changes in the groundwater before the M 7.0 Izu-Oshima-kinkai earthquake, Japan on January 14, 1978 [Wakita, H., Nakamura, Y., Notsu, K., Noguchi, M., Asada, T. 1980. Radon anomaly: a possible precursor of the 1978 Izu-Oshima-kinkai earthquake. Science 207, 882–883] and the M6.8 Chengkung earthquake, Taiwan on December 10, 2003 [Kuo, T., Fan, K., Chen, W., Kuochen, H., Han, Y., Wang, C., Chang, T., Lee, Y. Radon anomaly at the Antung Hot Spring before the Taiwan M6.8 Chengkung earthquake. Proceedings, Thirty-First Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, January 30–February 1, 2006, SGP-TR-179, 2006] are also investigated to find common features of the groundwater radon concentration changes before large earthquakes (M > 6.5) in comparison with those before the M7.2 Hyogoken–Nanbu earthquake. Groundwater radon concentrations before the 3 large earthquakes had shown common characteristic changes of gradually initial ones from the normal level since about 2 months before the earthquake onsets, rapid decreases down to the minimum, and quick increases up to the maximum at 7–20 days before the earthquake onsets, respectively. These are very useful characteristics of pre-seismic radon anomaly for the earthquake prediction or warning. Promising observations toward the earthquake prediction are also discussed.     

Laser measurements to space debris from Graz SLR station

In order to test laser ranging possibilities to space debris objects, the Satellite Laser Ranging (SLR) Station Graz installed a frequency doubled Nd:YAG pulse laser with a 1 kHz repetition rate, a pulse width of 10 ns, and a pulse energy of 25 mJ at 532 nm (on loan from German Aerospace Center Stuttgart – DLR). We developed and built low-noise single-photon detection units to enable laser ranging to targets with inaccurate orbit predictions, and adapted our standard SLR software to include a few hundred space debris targets. With this configuration, we successfully tracked – within 13 early-evening sessions of each about 1.5 h – 85 passes of 43 different space debris targets, in distances between 600 km and up to more than 2500 km, with radar cross sections from >15 m² down to <0.3 m², and measured their distances with an average precision of about 0.7 m RMS.     

Response of the mid-latitude D-region ionosphere to the total solar eclipse of 22 July 2009 studied using VLF signals in South Korean peninsula

In this paper, we analyze VLF signals received at Busan to study the the D-region changes linked with the solar eclipse event of 22 July 2009 for very short (∼390 km) transmitter–receiver great circle path (TRGCP) during local noon time 00:36–03:13 UT (09:36–12:13 KST). The eclipse crossed south of Busan with a maximum obscuration of ∼84%. Observations clearly show a reduction of ∼6.2 dB in the VLF signal strength at the time of maximum solar obscuration (84% at 01:53 UT) as compared to those observed on the control days. Estimated values of change in Wait ionospheric parameters: reflection height (h′) in km and inverse scale height parameter (β) in km⁻¹ from Long Wave Propagation Capability (LWPC) model during the maximum eclipse phase as compared to unperturbed ionosphere are 7 km and 0.055 km⁻¹, respectively. Moreover, the D-region electron density estimated from model computation shows 95% depletion in electron density at the height of ∼71 km. The reflection height is found to increase by ∼7 km in the D-region during the eclipse as compared to those on the control days, implying a depletion in the Lyman-α flux by a factor of ∼7. The present observations are discussed in the light of current understanding on the solar eclipse induced D-region dynamics.     

High vertical resolution water vapour profiles in the upper troposphere and lower stratosphere retrieved from MAESTRO solar occultation spectra

An algorithm has been developed that retrieves water vapour profiles in the upper troposphere and lower stratosphere from optical depth spectra obtained by the Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) instrument onboard the SCISAT satellite as part of the Atmospheric Chemistry Experiment (ACE) mission. The retrieval relies on ro-vibrational absorption of solar radiation by water vapour in the 926–970 nm range. During the iterative inversion process, the optical depth spectra are simulated at the spectral resolution and sampling frequency of MAESTRO using the correlated-k approximation. The Chahine inversion updates the water vapour volume mixing ratio (VMR), adjusting all retrieval layers simultaneously, to match the observed differential optical depth due to absorption by water vapour and ozone at each tangent height. This approach accounts for significant line saturation effects. Profiles are typically obtained from ∼22 km down to the cloud tops or to 5 km, with relative precision as small as 3% in the troposphere. In the lower stratosphere, the precision on water vapour VMR is ∼1.3 μmol/mol in an individual retrieval layer (∼1 km thick). The spectral capability of MAESTRO allows for the clear separation of extinction due to water vapour and aerosol, and for the fitting quality to be quantified and used to determine an altitude-dependent convergence criterion for the retrieval. In the middle troposphere, interhemispheric differences in water vapour VMR are driven by oceanic evaporation whereas in the upper troposphere, deep convection dominates and a strong seasonal cycle is observed at high latitudes.     

Ground-based and satellite DC-ULF electric field anomalies around Wenchuan M8.0 earthquake

The ground-based and satellite DC-ULF electric field data were analyzed around Wenchuan M8.0 earthquake on May 12, 2008 in China. The results show that ground electric field anomalies occurred at 3 stations located to the north and south of the epicenter with the amplitude of 3–100 mV/km. The change shapes and their amplitude of ground electric field anomalies are different largely due to their individual underground layer conductivity, water level and so on. The analysis of long time series illustrates that the abnormal geoelectric field started since March 2008. Onboard the DEMETER satellite, the ULF waveforms of electric field were collected and processed by wavelet transform method. The disturbances in the ionosphere were about 3–5 mV/m at a frequency band lower than 0.5 Hz. When the ground and space electric field anomalies were compared, their occurrence time and spatial distribution points are consistent with each other, including the long time anomalies from March 2008 and the short term ones 1–2 days before the Wenchuan earthquake. Finally, the coupling mechanism was discussed.     

Change in refractivity of the atmosphere and large variation in TEC associated with some earthquakes,observed from GPS receiver

The present study reports the analysis of GPS based TEC for our station Surat (21.16°N, 72.78°E) located at the northern crest of equatorial anomaly region in India at times close to some earthquake events (M ? 5) during the year 2009 in India and its neighbouring regions. The TEC data used in the study are obtained from GPS Ionospheric Scintillation and TEC Monitoring (GISTM) system. The TEC data has been analysed corresponding to 11 earthquakes in low solar activity period and quiet geomagnetic condition. We found that, out of 11 cases of earthquakes (M > 5) there were seven cases in which enhancement in TEC occurred on earthquake day and in other four cases there was depletion in TEC on earthquake day. The variation in refractivity prior to earthquake was significant for the cases in which the epicentre lied within a distance of 600 km from the receiving station. By looking into the features on temporal enhancement and depletion of TEC a prediction was made 3–2 days prior to an earthquake (on 28 October 2009 in Bhuj – India). The paper includes a brief discussion on the method of potentially identifying an impending earthquake from ionospheric data.     

Vertical wavenumber spectra of atmospheric ozone measured from ozonesonde observations

Vertical profiles of ozone have been measured at balloon altitudes. Our purpose is to examine the character of vertical wavenumber spectra of ozone fluctuations, to assess the possible roles of gravity wave field in ozone fluctuations, and to determine dominant vertical wavelengths of ozone spectra. Vertical wavenumber spectra of 12 ozone fluctuations obtained during June–August 2003 are presented. Results indicate that mean spectral slopes in the wavenumber range from 4.69 × 10⁻⁴ to 2.50 × 10⁻³ cyc/m are about −2.91 in the troposphere and −2.87 in the lower stratosphere, which is close to the slope of −3 predicted by current gravity wave saturation models. The consistency of the observed spectral slopes with the value of −3 predicted by current gravity wave saturation models suggests that the observed ozone fluctuations are due primarily to atmospheric gravity waves. At m = 1/(1000 m) the mean spectral amplitude is over 30 times larger in the lower stratosphere than in the troposphere. Mean vertical wavenumber spectra in area-preserving form reveal dominant vertical wavelengths of ∼2.6 km in the troposphere and ∼2.7 km in the lower stratosphere, which is consistent with the values varying between 1.5 and 3.0 km estimated from the velocity field and temperature field at these heights.     

Propagation of normal and faster CMEs in the interplanetary medium

We have analyzed 101 Coronal Mass Ejection (CME) events and their associated interplanetary CMEs (ICMEs) and interplanetary (IP) shocks observed during the period 1997–2005 from the list given by Mujiber Rahman et al. (2012). The aim of the present work is to correlate the interplanetary parameters such as, the speeds of IP shocks and ICMEs, CME transit time and their relation with CME parameters near the Sun. Mainly, a group of 10 faster CME events (V_INT > 2200 km/s) are compared with a list of 91 normal events of Manoharan et al. (2004). From the distribution diagrams of CME, ICME and IP shock speeds, we note that a large number of events tends to narrow towards the ambient (i.e., background) solar wind speed (∼500 km/s) in agreement with the literature. Also, we found that the IP shock speed and the average ICME speed measured at 1 AU are well correlated. In addition, the IP shock speed is found to be slightly higher than the ICME speed. While the normal events show CME travel time in the range of ∼40–80 h with a mean value of 65 h, the faster events have lower transit time with a mean value of 40 h. The effect of solar wind drag is studied using the correlation of CME acceleration with interplanetary (IP) acceleration and with other parameters of ICMEs. While the mean acceleration values of normal and faster CMEs in the LASCO FOV are 1 m/s², 18 m/s², they are −1.5 m/s² and −14 m/s² in the interplanetary medium, respectively. The relation between CME speed and IP acceleration for normal and faster events are found to agree with that of  and  except slight deviations for the faster events. It is also seen that the faster events with less travel time face higher negative acceleration (>−10 m/s²) in the interplanetary medium up to 1 AU.     

Is there an abnormal enhancement of atmospheric aerosol before the 2008 Wenchuan earthquake?

There are extensive reports of ionospheric disturbances before the great 2008 Wenchuan earthquake, which are possibly explained by seismogenic electric field hypotheses linked with the aerosols injected in atmosphere. This paper attempts to investigate the possible change of atmospheric aerosol optical depth (AOD) associated with this earthquake by using MODIS data from both Terra and Aqua satellites. The result shows a clear enhancement of AOD along the Longmenshan faults 7 days before the quake, which is 1 day and 4 days earlier than the reported negative and positive ionospheric disturbances, respectively, and is 1 day earlier than or quasi-synchronism with other reported atmospheric anomalies including air temperature, outgoing longwave radiation and relative humidity. Particularly, the spatial distribution of AOD enhancement is very local and it is correlated well with the active faults and surface ruptures. We suggest that this unique enhancement could be associated with the Lithosphere–Atmosphere–Ionosphere coupling process during the preparation of the Wenchuan earthquake.     

Impact effects from small size meteoroids and space debris

When the impact risk from meteoroids and orbital debris is assessed the main concern is usually structural damage. With their high impact velocities of typically 10–20 km/s millimeter or centimeter sized objects can puncture pressure vessels and other walls or lead to destruction of complete subsystems or even whole spacecraft. Fortunately chances of collisions with such larger objects are small (at least at present). However, particles in the size range 1–100 μm are far more abundant than larger objects and every orbiting spacecraft will encounter them with certainty. Every solar cell (8 cm² area) of the Hubble Space Telescope encountered on average 12 impacts during its 8.25 years of space exposure. Most were from micron sized particles.     

3D Imaging of the OH mesospheric emissive layer

A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645 km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630 m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272 m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3 km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz = 83.5–88.0 km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3 × 10⁻⁴ and 5.4 × 10⁻⁴ J/m³, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude.     

Atmosphere sounding by GPS radio occultation: First results from TanDEM-X and comparison with TerraSAR-X

On 21 June 2010 the TerraSAR-X satellite was joined by the TanDEM-X satellite. A Global Positioning System (GPS) radio occultation (RO) experiment using the twin satellites has been carried out to estimate the precision of GPS atmospheric soundings. For the Day Of Year (DOY) 330–336, 2011, we analyze phase and amplitude data recorded by GPS receivers separated by a few hundred meters in a low earth orbit and derive collocated atmospheric refractivity profiles. In the altitude range 10–20 km the standard deviation between TerraSAR-X and TanDEM-X refractivity does not exceed 0.15%. The standard deviation is rapidly increasing for lower and higher altitudes; close to the surface and at an altitude of 30 km the standard deviation reaches 0.8% and 0.5%, respectively. Systematic deviations between TerraSAR-X and TanDEM-X refractivity in the considered altitude range (0–30 km) are negligible. The results confirm the anticipated high precision of the GPS RO technique. However, the difference in the retrieved refractivity in the lower troposphere for different Open Loop (OL) signal tracking parameters, altered onboard TanDEM-X for DOY 49–55, 2012, calls for an in depth analysis. At the moment we can not exclude that a potential bias in the OL Doppler model introduces a bias in our retrieved refractivity at altitudes <8$<8$ km.     

Precursory signature of several major earthquakes studied using 40 kHz low frequency signal

To investigate the precursory signature of earthquakes on low frequency (LF) signal propagation, six earthquakes, having magnitude greater than equal to 6.5 and depth less than equal to 30 km, are being studied. The base line level of 40 kHz signal, transmitted from JJY station, Japan, is analysed with respect to V_d statistical parameter. Results show that the V_d parameter values starts fluctuating from its ambient levels before and during the days of the earthquakes, with significant variation starting 1–3 days prior to the earthquake concerned. This present study is an approach for identifying the precursory signatures of earthquakes on LF signal propagation using a new methodology with V_d parameter.     

GSFC DORIS contribution to ITRF2008

The NASA GSFC DORIS analysis center has provided weekly DORIS solutions from November 1992 to January 2009 (839 SINEX files) of station positions and Earth Orientation Parameters for inclusion in the DORIS contribution to ITRF2008. The NASA GSFC GEODYN orbit determination software was used to process the orbits and produce the normal equations. The weekly SINEX gscwd10 submissions included DORIS data from Envisat, TOPEX/Poseidon, SPOT-2, SPOT-3, SPOT-4, SPOT-5. The orbits were mostly seven days in length (except for weeks with data gaps or maneuvers). The processing used the GRACE-derived EIGEN-GL04S1 gravity model, updated modeling for time-variable gravity, the GOT4.7 ocean tide model and tuned satellite-specific macromodels for SPOT-2, SPOT-3, SPOT-4, SPOT-5 and TOPEX/Poseidon. The University College London (UCL) radiation pressure model for Envisat improves nonconservative force modeling for this satellite, reducing the median residual empirical daily along-track accelerations from 3.75 × 10⁻⁹ m/s² with the a priori macromodel to 0.99 × 10⁻⁹ m/s² with the UCL model. For the SPOT and Envisat DORIS satellite orbits from 2003 to 2008, we obtain average RMS overlaps of 0.8–0.9 cm in the radial direction, 2.1–3.4 cm cross-track, and 1.7–2.3 cm along-track. The RMS orbit differences between Envisat DORIS-only and SLR & DORIS orbits are 1.1 cm radially, 6.4 cm along-track and 3.7 cm cross-track and are characterized by systematic along-track mean offsets due to the Envisat DORIS system time bias of ±5–10 μs. We obtain a good agreement between the geometrically-determined geocenter parameters and geocenter parameters determined dynamically from analysis of the degree one terms of the geopotential. The intrinsic RMS weekly position repeatability with respect to the IDS-3 combination ranges from 2.5 to 3.0 cm in 1993–1994 to 1.5 cm in 2007–2008.     

Properties of traveling atmospheric disturbances (TADs) inferred from CHAMP accelerometer observations

Densities derived from accelerometer measurements on the CHAMP satellite near 400 km are used to statistically establish characteristics of large-scale (>1000 km) traveling atmospheric disturbances (TADs). Only TADs that at least propagate from the auroral zone to the equator are analyzed here, and a total of 21 identifiable events are found over the years 2001–2007. The average speed of all TADs, regardless of local time, is 646 ± 122 ms⁻¹. The average speeds on the dayside and nightside are 595 ± 127 ms⁻¹ and 685 ± 106 ms⁻¹, respectively, i.e., the speed appears to be 10% higher on average on the nightside. On six occasions TADs were only detected on the night side; however, TADs on the dayside often appear more distinctly in the data. Moreover, contrary to some theoretical expectations, dayside TADs do not dissipate more readily than night side TADs, although much less are detected between 8–20 solar local time. No clear dependence of TAD amplitude or phase speed with respect to Kp, or rate of increase of Kp, is found.     

Lower-mesospheric inversion layers over brazilian equatorial region using TIMED/SABER temperature profiles

Lower-mesospheric inversion layers (MILs) were studied using the temperature profiles observed by TIMED/SABER over Cariri (7.5°S, 36.5°W), Brazil, in 2005. A total 175 MILs were identified with the maximum occurrence in April and October and the minimum in January and July. The lower MIL is located in a height region from 70 to 90 km, with the peak at around 83 ± 4 km with the temperature of 205 ± 5 K, and the thickness of 4–10 km. The results show large amplitudes of MILs during equinoxes and minimum in solstices, with a clear semiannual variation. A general feature of lower MIL in monthly mean profile was observed twice a year, one from February to May, and the other from August to October with a downward shift of the top level. These results suggest that formation and long persistence of MIL is an important factor to investigate propagation of atmospheric gravity waves in the mesosphere-lower thermosphere (MLT) region.     

CRISTA-NF measurements of water vapor during the SCOUT-O3 Tropical Aircraft Campaign

The new remote sensing experiment CRISTA-NF (Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere – New Frontiers) successfully participated in the SCOUT-O3 Tropical Aircraft Campaign in November and December 2005. CRISTA-NF operated aboard the high-altitude research aircraft M-55 Geophysica. Mid-infrared spectra (4–15 μm) were measured in the limb sounding geometry with high spatial resolution (250 m vertical sampling, 5–15 km along track sampling). Measurements were carried out during transfer flights between Oberpfaffenhofen, Germany, and Darwin, Australia, as well as during several local flights near Darwin. Water vapor volume mixing ratios in the upper troposphere and lower stratosphere were derived from the CRISTA-NF radiance measurements by utilizing a rapid radiative transfer forward model and the optimal estimation retrieval approach. CRISTA-NF water vapor measurements below the hygropause have a total retrieval error of 15–40% (i.e. root mean square of accuracy and precision). The systematic terms are dominating in the retrieval error budget. The contributions of a priori information to the retrieval results are less than 5–10%. The vertical resolution of the observations is about 250–500 m when permitted by instrument sampling. In this paper we present first results for three transfer flights of the campaign. Being generally in good agreement with corresponding ECMWF operational analyzes, the CRISTA-NF measurements show significantly higher variability and local structures in the upper tropospheric water vapor distributions.     

Electrostatic gravity gradiometer design for the future mission

Satellite gravity gradiometry has been applied in GOCE mission to obtain higher harmonics of the Earth’s gravity mapping. In-orbit results showed that the precision of GOCE gradiometry achieved a level of 10–20 mE/Hz^1/2 in the bandwidth of 38–100 mHz, and the major error source came from the intrinsic noise of the core sensor electrostatic accelerometer. Two schemes for improving sensitivity of such accelerometer are presented by optimizing the parameters to reduce the dynamic range and choosing the heavier proof mass to suppress the thermal noise limited by the discharging gold wire. As a result, an accelerometer with a better resolution of 6.6×$6.6\times$10⁻¹³ m/s²/Hz^1/2 could be developed, and then a precision of 3 mE/Hz^1/2, corresponding to a spatial resolution of about 78 km half wavelength, is achievable for the future satellite gradiometric mission.