Southern Space Observatory Research Articles

Studies on the propagation dynamics and source mechanism of quasi-monochromatic gravity waves observed over São Martinho da Serra (29° S, 53° W), Brazil

Abstract. A total of 209 events of quasi-monochromatic atmospheric gravity waves (QMGWs) were acquired over 5 years of gravity waves (GWs) observation in southern Brazil. The observations were made by measuring the OH (hydroxyl radical) emission using an all-sky imager hosted by the Southern Space Observatory (SSO) coordinated by the National Institute for Space Research at São Martinho da Serra (RS) (29.44° S, 53.82° W). Using a two-dimensional fast-Fourier-Transform-based spectral analysis, it has been shown that the QMGWs have horizontal wavelengths of 10–55 km, periods of 5–74 min, and phase speeds up to 100 m s−1. The waves exhibited clear seasonal dependence on the propagation direction with anisotropic behavior, propagating mainly toward the southeast during the summer and autumn seasons and mainly toward the northwest during the winter. On the other hand, the propagation directions in the spring season exhibited a wide range from northwest to south. A complementary backward ray-tracing result revealed that the significant factors contributing to the propagation direction of the QMGWs are their source locations and the dynamics of the background winds per season. Three case studies in winter were selected to investigate further the propagation dynamics of the waves and determine their possible source location. We found that the jet stream associated with the cold front and their interaction generated these three GW events.

Case Studies on Concentric Gravity Waves Source Using Lightning Flash Rate, Brightness Temperature and Backward Ray Tracing at São Martinho da Serra (29.44°S, 53.82°W)

AbstractWe relate the spatial and temporal distribution of lightning flash rates and cloud top brightness temperature (CTBT) to concentric atmospheric gravity wave (CGW) events observed at the Southern Space Observatory (SSO) in São Martinho da Serra (29.44°S, 53.82°W, 488.7 m) in southern Brazil. The selected identified cases from 2017 to 2018 were observed by a hydroxyl (OH) all‐sky imager. Backward ray tracing shows that the time of gravity wave excitation agrees with the highest values of lightning flash rates (indicating lightning jump) as well as the coldest brightness temperatures that indicate the time of convective overshoot. Radiosonde measurements show high convective available potential energy (CAPE), associated with a maximum updraft velocity just prior to the wave events. We find that these possible source locations correspond to the positions and times that convective plumes overshot the tropopause (seen in GOES‐16 CTBT images). We also show that higher spatial lightning density (i.e., number of lightning flashes at a given longitude and latitude) agree with the overshoot locations from the GOES satellite. We also find that the overshoot times from the GOES‐16 satellite agree with the times lightning jumps were observed in the lightning flash rate. Finally, we find that the periodicities in the lightning flash rate agree with the periods of the observed CGWs, which further strengthens the result that the CGWs were excited by the deep convective systems determined from backward ray tracing.

A major event of Antarctic ozone hole influence in southern Brazil in October 2016: an analysis of tropospheric and stratospheric dynamics

Abstract. The Antarctic ozone hole is a cyclical phenomenon that occurs during the austral spring where there is a large decrease in ozone content in the Antarctic region. Ozone-poor air mass can be released and leave through the Antarctic ozone hole, thus reaching midlatitude regions. This phenomenon is known as the secondary effect of the Antarctic ozone hole. The objective of this study is to show how tropospheric and stratospheric dynamics behaved during the occurrence of this event. The ozone-poor air mass began to operate in the region on 20 October 2016. A reduction of ozone content of approximately 23 % was observed in relation to the climatology average recorded between 1992 and 2016. The same air mass persisted over the region and a drop of 19.8 % ozone content was observed on 21 October. Evidence of the 2016 event occurred through daily mean measurements of the total ozone column made with a surface instrument (Brewer MkIII no. 167 Spectrophotometer) located at the Southern Space Observatory (29.42∘ S, 53.87∘ W) in São Martinho da Serra, Rio Grande do Sul. Tropospheric dynamic analysis showed a post-frontal high pressure system on 20 and 21 October 2016, with pressure levels at sea level and thickness between 1000 and 500 hPa. Horizontal wind cuts at 250 hPa and omega values at 500 hPa revealed the presence of subtropical jet streams. When these streams were allied with positive omega values at 500 hPa and a high pressure system in southern Brazil and Uruguay, the advance of the ozone-poor air mass that caused intense reductions in total ozone content could be explained. Keywords. Atmospheric composition and structure (middle atmosphere – composition and chemistry)

Measurements of the total ozone column using a Brewer spectrophotometer and TOMS and OMI satellite instruments over the Southern Space Observatory in Brazil

Abstract. This paper presents 23 years (1992–2014) of quasi-continuous measurements of the total ozone column (TOC) over the Southern Space Observatory (SSO) in São Martinho da Serra, Brazil (29.26° S, 53.48° and 488 m altitude). The TOC was measured by a Brewer spectrometer, and the results are also compared to daily and monthly observations from the TOMS (Total Ozone Mapping Spectrometer) and OMI (Ozone Monitoring Instrument) satellite instruments. Analyses of the main interannual modes of variability computed using the wavelet transform method were performed. A favorable agreement between the Brewer spectrophotometer and satellite datasets was found. The seasonal TOC variation is dominated by an annual cycle, with a minimum of approximately 260 DU in April and a maximum of approximately 295 DU in September. The wavelet analysis applied in the SSO TOC anomaly time series revealed that the Quasi-Biennial Oscillation (QBO) modulation was the main mode of interannual variability. The comparison between the SSO TOC anomaly time series with the QBO index revealed that the two are in opposite phases.

A proposal of a counting and recording system for cosmic ray muon detectors

A multidirecional high energy cosmic ray (muon) telescope is operational at the Southern Space Observatory, in Sao Martinho da Serra, RS, Brazil. This telescope is part of the Global Muon Detector Network (GMDN) and aims to study and forecast Space Weather. This paper proposes a new counting, correlation and recording solution based on an embedded system able to interface observational data by internet for remote monitoring. It is built around a Rabbit 3000 microcontroller with TCP/IP Ethernet 10Base-T connectivity. It is able to detect and count 200 ns pulses generated by the sensor system (scintillator plastics coupled with photomultipliers) during a specified period of time (generally one second). A preliminary version of a monitoring web page was developed and it is able to show the cosmic ray (muon) data of one detector in real time. The current system is an attempt to improve the reliability of the telescope when comparing to the recording system based on a personal computer, currently under operation. One advantage is the easy maintenance, since all the counting and correlation boards currently under operation can be replaced by an embedded system. Besides, as the hardware is off-the-shelf, it is only necessary to develop software routines, which is based on royalty-free libraries.

Temperature effect correction for the cosmic ray muon data observed at the Brazilian Southern Space Observatory in São Martinho da Serra

The negative atmospheric temperature effect observed in the muon intensity measured by surface-level detectors is related to the atmospheric expansion during summer periods. According the first explanation given, the path of muons from the higher atmospheric level (where they are generated) to the ground becomes longer, and more muons decay, leading to a muon intensity decrease. A significant negative correlation, therefore, is expected between the altitude of the equi-pressure surface and the muon intensity. We compared measurements of the altitude of 100 hPa equi-pressure surface and data from the multidirectional muon detector installed at the Brazilian Southern Space Observatory in São Martinho da Serra, RS. Significant correlation coefficient were found (up to 0.95) when using data observed in 2008. For comparison, data from the multidirectional muon detector of Nagoya, located in the opposite hemisphere, is studied and an anti-phase in the cosmic ray variation related with the temperature effect is expected between data from detectors of Nagoya and São Martinho da Serra. The temperature influence is higher for the directional channels of Nagoya than for ones of São Martinho da Serra.

Correlation between the cosmic noise absorption calculated from the SARINET data and the energetic particles measured by MEPED: Simultaneous observations over SAMA region

The cosmic noise absorption is presented in terms of two-dimensional images obtained from the imaging riometers operated at the Southern Space Observatory (geographic coordinate: 29.4°S, 53.1°W), in São Martinho da Serra, Brazil, Concepcion (geographic coordinate: 36.5°S, 73.0°W) and Punta Arenas (geographic coordinate: 53.0°S, 70.5°W) in Chile, which belong to the South American Riometer Network and are located at the central and periphery regions of the South American Magnetic Anomaly. Correlations are performed between the maximum cosmic noise absorption observed at these stations and the energetic electron flux in two energy channels (>30 and >300keV) and the proton flux in three energy channels (80–240, 800–2500 and >6900keV) as measured by the Medium Energy Proton and Electron Detector, during a moderate geomagnetic storm that occurred on September 3, 2008. The results show high correlations between the cosmic noise absorption detected at São Martinho da Serra and the flux of protons with energy between 80 and 240keV, and the flux of electrons with energies higher than 300keV, while an additional ionization at Concepcion was correlated with electrons of energies higher than 30keV. The cosmic noise absorption detected at Punta Arenas was probably caused by the increase of the protons flux with energy between 80 and 240keV.

A comparison of two different techniques for deriving the quiet day curve from SARINET riometer data

Abstract. In this work, an upgrade of the technique for estimating the Quiet Day Curve (QDC) as proposed by Tanaka et al. (2007) is suggested. To validate our approach, the QDC is estimated from data acquired by the Imaging Riometer for Ionospheric Studies (IRIS) installed at the Southern Space Observatory (SSO/CRS/CCR/INPE – MCT, 29°4´ S, 53°8´ W, 480 m a.s.l.), São Martinho da Serra – Brazil. The evaluation was performed by comparing the difference between the QDCs derived using our upgrade technique with the one proposed by Tanaka et al. (2007). The results are discussed in terms of the seasonal variability and the level of magnetic disturbance. Also, the cosmic noise absorption (CNA) images for IRIS data operated at SSO was built using both the techniques aiming to check the implications of the changes in the methods of QDC determination on the CNA that resulted from it.

Reconstruction and searching ozone data periodicities in southern Brazil (29ºS, 53ºW)

Ozone plays a very important role in the nature due its characteristics as a natural filter of ultraviolet solar radiation. Thus, it is pertinent for the scientific community to understand all natural influence factors involving ozone along with a large time series. In this work, a reconstruction of ozone time series obtained by Brewer spectrophotometer from 1994 to 2008 at the Southern Space Observatory (SSO) - 29ºS, 53ºW - Southern Brazil is presented. TOMS-OMI data were used to follow the days without data, where a coefficient of correlation between TOMS-OMI and Brewer is acceptable around r = 0.89. Besides, wavelet analysis to determine the temporal evolution of the frequencies and the amplitudes was applied. Moreover, wavelet analysis aiming to determine the temporal evolution of the frequencies and the amplitudes was performed. The results pointed a period of 365 days (1 yr) for the seasonal variation of ozone, of 600 days attributed for a possible QBO influence and two periods of 2000 and other 4000 days regarding possibly to the second harmonic of the 11-year solar cycle.

Inexpensive Interferometer for Low Frequency Radio Astronomy

An interferometric array similar to the low frequency array (LOFAR) prototype station (LOPES) and to the eight-meter-wavelength transient array (ETA) is being developed to cover the LOFAR frequency range under 100 MHz at the Southern Space Observatory (SSO) (29.4◦ S, 53.8◦ W, 480 m. a. s. l.), in S˜ao Martinho da Serra, RS, Brazil. In accordance with previous observational spectrum results, the SSO site was classified as being suitable to receive sensitive and sophisticated radio interferometers, based on the phased array concept, similar to those employed at the European LOFAR stations. This paper describes the technical details of development and implementation of a low cost elementary radio astronomy interferometer for the frequency range of 20–80 MHz.

Space Weather and the Global Muon Detector Network – GMDN

The main objective of this work is to present an overview of the space weather and its relation with the global network of ground-based multi-directional muon detectors (GMDN). The GMDN is an international collaboration consisting of 10 institutions from 6 countries in 5 continents. A multi-directional muon detector for measuring high-energy galactic cosmic rays (GCRs) was installed in 2001 and expanded in its detection area in 2005, through an international cooperation between Brazil, Japan and USA, and has been in operation since then at the Southern Space Observatory - SSO/CRS/INPE -MCT, (29,4o S, 53,8o W, 480 m a.s.l), Sao Martinho da Serra, RS, in southern Brazil, as an important component of the GMDN. The observations conducted by this detector are used for forecasting the arrival of the interplanetary coronal mass ejections (ICMEs) and the geomagnetic storms at the Earth. The detector measures high-energy GCRs by detecting secondary muons produced from the hadronic interactions of primary GCRs (mostly protons) with atmospheric nuclei. While muons have a relatively short life-time (about 2.2 microseconds at rest), they can reach the detector at ground level because of the relativistic effect of the time dilation with heir high speed (~0.96c), preserving the incident direction of primary particles. The multi-directional detector can measure the GCR intensity in various directions at a single location, such as SSO in Brazil. ICMEs accompanied by a strong shock often forms a GCR depleted region behind the shock. The Forbush decrease is observed when the Earth enters in this depleted region. Some particles from this depleted region leak into the downstream, traveling with almost the speed of light, much faster than the approaching shock, and creating the precursory loss-cone anisotropy around the sunward IMF direction at the Earth. Loss-cones are typically visible 4-8 hours prior to the shock arrival and the onset of major geomagnetic storm at the Earth. This cosmic-ray precursor can be detected sometimes as early as ten hours prior to the shock arrival at the Earth. With the real time data from the upgraded GMDN, its methodology and data reduction techniques permits accurate Space Weather forecasting.

Influence of the Antarctic Ozone Hole over the South of Brazil in 2008 and 2009

The Antarctic Ozone Hole is a cyclical phenomenon which occurs over the Antarctic region from August to November each year. The polar vortex turns it into a restricted characteristic dynamics for this region. However, when the polar vortex begins to weaken in October, air masses with low ozone concentration could escape and reach regions of lower latitudes. This study presents the influence of the Antarctic Ozone Hole over the South of Brazil in the years 2008 and 2009. To verify the events of influence, data of ozone total column from Brewer Spectrophotometer installed at the Southern Space Observatory (29.42° S, 53.87° W), in Sao Martinho da Serra, South of Brazil was used, and OMI Spectrometer overpass data for the same location. In addition to Brewer and OMI data, potential vorticity maps using GrADS (Grid Analysis and Display System) generated with the NCEP data reprocessed, and backward trajectories of air masses, using the HYSPLIT model of NOAA, were analysed. Ozone total column for the days with lower ozone were compared with the climatological average of twenty years for September and October. For statistical reasons, only the days with ozone total column lower than climatological monthly average minus 1.5 times the standard deviation, were analysed. Considering only the days with less ozone, increased absolute potential vorticity and backward trajectories indicating the origin of polar air masses, 3 events in 2008 and 2 events in 2009, with an average decreased about 9.7 ± 3.3% when compared with climatological means, were observed.

Dosimetria esporular: Bacillus subtilis TKJ6312 como biossensor de radiação solar biologicamente ativa

Since 2000, spore dosimetry and spectral photometry have been performed in parallel at the Southern Space Observatory, Sao Martinho da Serra (Southern Brazil). A comparative study involving data from Punta Arenas - Chile (53.2o S), Sao Martinho da Serra (29.5o S), Padang - Indonesia (0.9oS), Brussels - Belgium (50.9o N) and Kiyotake - Japan (31.9o N) from 2000 to 2006 is presented. The Spore Inactivation Doses presented the higher values in summer (973 ± 73 for Punta Arenas and 4,369 ± 202 for Sao Martinho da Serra, as well 1,402 ± 170 and 3,400 ± 1,674 for Brussels and Kiyotake, respectively). The simplicity, robustness and high resistance of bacterial spores makes the biosensor an potential biological tool for UV-B monitoring.

A very active sprite‐producing storm observed over Argentina

During the night of 22–23 February 2006, more than 400 middle‐atmospheric optical discharges were observed above one large thunderstorm system over northeastern Argentina. These transient luminous events (TLEs) were imaged during the Southern Brazil Sprite Campaign, the first campaign to focus on TLEs over southern Brazil, northeastern Argentina, and Uruguay. All of the TLEs were imaged from the Brazilian Southern Space Observatory (SSO) near Santa Maria, which is nearly in the center of the southernmost Brazilian state of Rio Grande do Sul. Although the fields of view of the imaging cameras were too narrow to view the entire storm, the more than 400 confirmed TLEs imaged indicate that this storm ranks as the third most active TLE producer ever reported. Hence, storms in this region of South America might be some of the leading TLE generators on Earth.

Estimativa para cálculo de ozônio total usando dados de UVB E UVA do observatório espacial do sul, Brasil

A obtenção da coluna total de ozônio a partir de detectores de radiação ultravioleta (UV) como Radiômetros e Espectroradiômetros é de grande importância, visto que os medidores de ozônio como o Espectrofotômetro Brewer são muito caros e, portanto, de difícil obtenção. Este trabalho tem como objetivo encontrar modelos matemáticos que relacionem a razão entre as radiações UVB/UVA do Espectroradiômetro MS 701, dos Radiômetros UV-B MS 212 W e UV-A MS 212 A e as medidas de ozônio efetivo obtidas a partir do Espectrofotômetro Brewer MKIII #167, instalados no Observatório Espacial do Sul, no Sul do Brasil. Os períodos selecionados para análise foram o ano de 2003 para o Espectroradiômetro e o de 2005 para os Radiômetros, onde foram utilizados apenas dias sem interferências de nuvens. Os modelos matemáticos encontrados foram funções exponenciais com coeficiente de correlação R = 0,85 para a relação com o Espectroradiômetro e de R = 0,99 para a relação com os Radiômetros. Os dados de ozônio efetivo obtidos a partir dos detectores UV foram ajustados aos seus respectivos modelos e comparados com a coluna total de ozônio fornecida pelo Espectrofotômetro Brewer e pelo TOMS. A diferença média entre os valores obtidos da coluna total de ozônio do Espectroradiômetro e o Brewer foi de 0,7% e com o TOMS foi de 3,1% enquanto a comparação para a coluna total de ozônio fornecida pelos Radiômetros com o Brewer apresentou diferença média de 2% e com o TOMS de 4,3%. Estes resultados comprovam a eficiência do método utilizado e uma boa aproximação das funções encontradas.

Analysis of geomagnetic storm variations and count-rate of cosmic ray muons recorded at the Brazilian southern space observatory

An analysis of geomagnetic storm variations and the count rate of cosmic ray muons recorded at the Brazilian Southern Space Observatory -OES/CRS/INPE-MCT, in São Martinho da Serra, RS during the month of November 2004, is presented in this paper. The geomagnetic measurements are done by a three component low noise fluxgate magnetometer and the count rates of cosmic ray muons are recorded by a Muon Scintilator Telescope - MST, both instruments installed at the Observatory. The fluxgate magnetometer measures variations in the three orthogonal components of Earth magnetic field, H (North-South), D (East-West) and Z (Vertical), with data sampling rate of 0.5 Hz. The Muon Scintilator Telescope records hourly count rates. The arrival of a solar disturbance can be identified by observing the decrease in the muon count rate. The goal of this work is to describe the physical morphology and phenomenology observed during the geomagnetic storm of November 2004, using the H component of the geomagnetic field and vertical channel V of the multi-directional muon detector in South of Brazil.

First estimations of the aerosol optical thickness using Langley Method at Southern Brazil (29.4°S, 53.8°W)

The first estimations of the aerosol optical thickness (AOT) using Langley Method at Southern Space Observatory (SSO) at Southern Brazil (29.4°S, 53.8°W) are presented. In addition to ozone and sulphur dioxide columns, AOT can be obtained using Brewer Spectrophotometer at specific wavelengths: 306.3, 310.1, 313.5, 316.8 and 320.1 nm. The AOT was obtained for the period from November/2002 to May/2003. Very low AOT averages were obtained, whose values were about 0.21 ± 0.03 at 306.3 nm, 0.21 ± 0.02 at 310.1 nm, 0.19 ± 0.02 at 313.5 nm, 0.20 ± 0.02 at 316.8 nm and 0.20 ± 0.02 at 320.0 nm for all period analysed. Different behaviour of AOT were obtained at two daily specific periods of aerosol accumulation, one in the afternoons from November/2002 to February/2003, caused mainly by a mild biomass burning season’s in the region and other in the mornings from March to May/2003, due the high relative humidity presented in the region studied.

Comparisons of biologically effective doses of solar UV-radiation determined with spore dosimetry and spectral photometry in 2000–2003 at Southern Space Observatory, Brazil

In order to assess the impact of solar-UV radiation on biosphere and human health, spore dosimetry and spectral photometry have been performed in parallel at the Southern Space Observatory, São Martinho da Serra in the State of Rio Grande do Sul (southern region of Brazil, latitude 29.44°S, longitude 53.8°W). Daily and monthly cumulative doses obtained from spore dosimeters were compared with the doses derived from the integration of the daily effectiveness spectra obtained by multiplications of the spectral irradiance from Brewer spectrophotometers with the action spectra for spore inactivation and erythema induction. For daily exposures performed on 24 days in 2002–2003, the values of the observed spore inactivation doses (SID) and the calculated ones were closely correlated with a mean ratio (observed SID/calculated SID) of 0.7 ± 0.3, while the values of the observed SID were regressed to the erythemal doses (MED) by a power function with a correlation coefficient r 2 ∼ 0.9. For cumulative monthly doses, the values of calculated SID and MED were regressed to the observed values of SID by power functions for each year with r 2 = 0.5–0.9 and r 2 = 0.5–0.9, respectively. The applicability of the spore dosimetry for continuous long-term monitoring of biologically effective doses of solar-UV radiation has been verified in this work.

A study of the anticorrelations between ozone and UV-B radiation using linear and exponential fits in southern Brazil

The aim of this work was to study the anticorrelation between ozone and UV-B radiation. The data were collected at the Southern Space Observatory (OES/CRSPE/INPE – MCT), located in the southern part of Brazil, and analyzed by linear and first order exponential fits. The UV-B radiation (280–315 nm) was measured by the UV-B radiometer (Eko Instruments – model MS-210W) and the total ozone column was measured by the Total Ozone Mapping Spectrometer (TOMS) installed on board of NASA's Earth Probe satellite. The UV-B radiation measurements employed for correlation analysis (from July 1999 to December 2001) had fixed solar zenith angles and were taken on days with clear sky. The mathematical behavior of correlations at different angles was observed and correlation coefficients were determined by linear and first order exponential fits. High correlation coefficient values were obtained for both fits studied and the differences between them can be considered small. The values for linear fits varied from R 2 =0.64 (SZA 55°) to 0.90 (SZA 30° and 35°) and for exponential fits varied from R 2 =0.63 (SZA 55°) to 0.85 (SZA 30° and 35°).

A commercial radio receiver for lower ionosphere monitoring: Initial results

A commercial computer controlled radio receiver has been used to measure signal strength of High Frequency (HF) signals in order to study the effects of geophysical events on radio communications and to test the system for ionospheric monitoring. The system was installed at the Southern Space Observatory (OES/CRSPE/INPE) in Sāo Martinho da Serra, Brazil (29.43°S, 53.8°W, B = 23350 nT). Initial results show that this system is able to detect ionospheric radio absorption events. The commercial radio receiver has a computer serial interface, to control the reception frequency in order to acquire the values of the received signal strength. We describe the system and some initial results on radio absorption events associated to C and M classes of x-ray solar flares. The results suggest the possibility of using this low-cost system to study the daily variation of the lower ionosphere ionization and to stuy events of ionospheric absorption. Long period measurements give statistical information about the magnitude and time scale of fading, that can be used for planning radio links.doi: sin doi