Indian Antarctic Station Research Articles

Climatology of blizzards over Schirmacher Oasis, east Antarctica

Weather in Antarctica is subject to frequent and sudden changes. Strong winds and blizzards dominate Antarctic weather. A combination of blowing snow, gale force wind and very low visibility is normally defined as blizzard. Meteorological data recorded at Indian Antarctic Station Maitri, in respect of blizzards recorded during the period 1990-2005 has been studied to find out climatological features of blizzards affecting Schirmacher Oasis.
 
 At Maitri the blizzard is mostly associated with extra-tropical storms and is normally preceded by precipitation. On average during the year about 21 blizzards affects the station for 45 days during the year. During the month of April to August 3 to 4 blizzards affects the station. Maximum number of blizzards occurs in the month of August with about 7 blizzard days. Average wind speed recorded during the blizzard is about 52 kt but it exceeded 100 kt on several occasions. The duration may vary from hours to days with average of 25 hours. Longest duration of 168 hours was recorded in June 1997. There are about 12 such occasions when blizzard lasted more than 72 hours. No correlation has been found between maximum wind speed and temperature rise during blizzard and the speed is also not correlated with pressure departure during the period.

Geomagnetic field variation during winter storm at localized southern and northern high latitude

This paper presents the effect of geomagnetic storm on geomagnetic field components at Southern (Maitri) and Northern (Kiruna) Hemispheres. The Indian Antarctic Station Maitri is located at geom. long. 66.03° S; 53.21° E whereas Kiruna is located at geom. long. 67.52° N; 23.38° E. We have studied all the geomagnetic storms that occurred during winter season of the year 2004–2005. We observed that at Southern Hemisphere the variation is large as compared to the Northern Hemisphere. Geomagnetic field components vary when the interplanetary magnetic field is oriented in southward direction. Geomagnetic field components vary in the main phase of the ring current. Due to southward orientation of vertical component of IMF reconnection takes place all across the dayside that transports plasma and magnetic flux which create the geomagnetic field variation.

The effect of atmospheric blocking high and ridges on weather over Maitri, East Antarctica – A case study

The Indian Antarctic station, Maitri is often experiencing continuous blizzard over a week with strong surface winds and surface temperature anomalies due to atmospheric blocking during winter and spring seasons of Antarctica. One such case during the last week of August 2000 and another case in mid-July 1996 are studied. There is more blocking activity in winter and spring months. The influence of blocking high on weather parameters during the study period is also presented.

IMF BY dependence of the extent of substorm westward electrojet

In this paper the duskward extension of the westward auroral electrojet is investigated for substorm intervals on the basis of magnetograms recorded at the Indian Antarctic station, Maitri. The database comprises three years from 1998–2000. Based on an initial study of the magnetograms, an arbitrary local time of 2030 MLT is fixed to define the early manifestation of the substorm westward electrojet. Using this criterion 12 substorms are identified and the possible causes examined. Many of these events are observed to be associated with a moderate to intense ring current. The hourly average of the GSM BY-component of the interplanetary magnetic field (IMF) for the hour preceding the substorm onset at Maitri is negative for most of the events. It is suggested that the azimuthal shift of the auroral electrojets in the southern hemisphere resulting from a negative BY-component of the IMF influences the extent of the substorm westward electrojet. This finding implies that the IMF may have a role in controlling the longitudinal extent of substorm occurrence.

Hiss-triggered chorus emissions at Indian stations

Some examples of chorus emissions emanating from the upper edge of the underlying hiss events recorded at the Indian Antarctic Station Maitri (geomag. lat.=62°S, long. 57.2° E, L=4.5) and low-latitude station Gulmarg (geomag. lat.=24°26′N, long. 147°09′E) are reported, in which intensity seems to decrease with increase in frequency and also it varies from event to event. It is proposed that resonance interaction of energetic electrons with wavelets present in the upper edge of hiss elements propagating in whistler mode under suitable condition behaves as a backward wave oscillator and generates chorus emissions. The minimum and the maximum value of interaction length, beam modulation period and temporal evolution of emitted wave frequency have been evaluated. Modulation period has been used to explain the periodicity in the recorded events and the temporal evolution of wave frequency has been used to explain the shape of dynamic spectrum of hiss-triggered emissions.

Thermal convection over East Antarctica: Potential microorganism dispersal

The Indian Antarctic station, Maitri is in the Schirmacher oasis of east Antarctica. The oasisis covered with snow/ice; except for the local summer season when it gets deglaciated and exposes the small hilly region. During summer, minute microorganisms are observed near water bodies of this rocky terrain. In the year 1996a monostatic acoustic sounder probed planetary boundary layer dynamics over this region. From the data it is observed that the thermal convection (both free and forced) persist for 5.63% of the time in the whole year. The occurrence of free convection predominates in the local summer season around midday, while sporadic cases of forced convection have been recorded during the autumn and winter seasons. The onset of convection is mainly at 0600 hrs to 1200 hrs, while the cessation period is limited within 1400 hrs to 1900 hrs. The cessation of convection is basically governed by the katabatic wind flow around the Schirmacher region and it indicates that the interior of Antarctica or the polar cap ice becomes cooler much faster than the rocky region of Schirmacher oasis.

Physical properties of aerosols at Maitri, Antarctica

Measurements of the submicron aerosol size distribution made at the Indian Antarctic station, Maitri (70‡45′S, 11‡44′E) from January 10th to February 24th, 1997, are reported. Total aerosol concentrations normally range from 800 to 1200 particles cm−3 which are typical values for the coastal stations at Antarctica in summer. Aerosol size distributions are generally trimodal and open-ended with a peak between 75 and 133 nm and two minima at 42 and 420 nm. Size distributions remain almost similar for several hours or even days in absence of any meteorological disturbance. Total aerosol concentration increases by approximately an order of magnitude whenever a low pressure system passes over the station. Based on the evolution of aerosol size-distributions during such aerosol enhancement periods, three types of cases have been identified. The nucleation mode in all three cases has been suggested to result from the photochemical conversion of the DMS emissions transported either by the marine air or by the air from the ice-melt regions around Maitri. Subsidence of midtropospheric air during the weakening of radiative inversion is suggested as a possible source of the nucleation mode particles in the third case. Growth of the nucleation mode particles by condensation, coagulation and/or by cloud processes has been suggested to be responsible for other modes in size distributions.

Observation of very low frequency emissions at Indian Antarctic station, Maitri

Recently, we have succeeded in recording VLF emissions at the Indian Antarctic station, Maitri (geom. lat. 62°S, geom. long. 57.23°E,L = 45) using a T-type antenna, pre/main amplifiers and digital audio tape recorder. VLF hiss in the frequency ranges 11–13 kHz and 13–14.5 kHz and some riser-type emissions in the frequency range 3–5 kHz and magnetospheric lines at about 6.2, 8.0 and 9.2 kHz are reported for the first time. The generation and propagation mechanism of these emissions are discussed briefly.

Diagnostics of magnetosphere-ionosphere coupling over Indian Antarctic station Maitri, from magnetometer and riometer observations during the optical auroral event of 4–5 March 1999

A splendid display of “aurora australis” was observed over the Indian Antarctic station Maitri (geomag. lat. 62°.8 S, long. 52°.8 E; L = 4.8) on the night of 4–5 March 1999. The changes recorded by a fluxgate magnetometer, and a 30 MHz riometer operating at Maitri are interpreted in terms of currently - understood auroral physics. Interplanetary magnetic field and plasma parameters recorded by the WIND satellite indicate very high solar wind velocities (500–600 km/s), and prolonged southward B z of average value (∼ 5 nT), during the auroral event. Ion density is however an average 3–4/cm 3, and Ion pressure only 2–3 nano Pascals during the event.

Velocity of small-scale auroral ionospheric current systems over Indian Antarctic station Maitri

The Indian Antarctic station Maitri (geog. 70‡45’S, 11‡45’E, geom. 66‡.03S, 53‡.21E) occupies a sub-auroral location during magnetically quiet conditions(Σκρ < 10), but attains an auroral position when the auroral oval shifts equatorwards with increasing strength of magnetic disturbance. At the latter times, triangulation with 3 fluxgate magnetometers located at the vertices of a suitable triangle provides a means of monitoring mobile auroral ionospheric current systems over Maitri. The spacing between the magnetometers is typically kept at 75–200 km, keeping in mind the scale-sizes of ∼ 100 km for these mobile current systems. This work reports the results of two triangulation experiments carried out around Maitri in January 1992 and January 1995, both during Antarctic summer. The velocities estimated for pulsations of the Pc4 and Pc5 type were about 0.59 km/sec in the direction 102‡.7 east of due north, in the first case, and about 1–3 km/sec in the second case in the east-west direction.While several magnetometer arrays exist in the northern auroral regions (e.g., the Alberta array in Canada, the Alaskan array in the U.S. and the IMS Scandinavian array), there is no report in literature of triangulation through arrays in Antarctica, except for a one-day study by Neudegget al 1995 for ULF pulsations of the Pc1 and Pc2 type. The velocities obtained for the Pi3 type of irregular pulsations over Antarctica in the present study tally well with those obtained for northern auroral locations.

Fuel cell power source for a cold region

Electric power generation at Maitri—the Indian Antarctic station is based on a conventional diesel generator. In spite of the high reliability and simplicity of operation, the main disadvantages of this kind of power source are its pollution potential and fuel transportation costs. In a place like Antarctica environmental protection requirements are of prime importance. Apart from gas pollution, they also suffer from various other problems such as degradation of performance due to sub-zero temperature of operation, noise pollution, solidification of lubricants and mechanical wear and tear. Fuel cells find an ideal application for alternate energy solution, and can maintain the pristine nature of Antarctica. With this objective in mind, Research & Development Establishment (Engineers), Pune, Defence Research & Development Organisation, Ministry of Defence, Government of India joined hands with Centre for Electro-Chemical & Energy Research, SPIC Science Foundation, Chennai and developed three prototype 500 W, 12 V, PEMFC fuel cell power sources for this application. PEMFC has been chosen for study and experimentation at Antarctica because the solid electrolyte Nafion-117 is used in this cell and the electro-chemical reaction is exothermic so that the fuel cell can be activated at low temperature. PEMFC was first installed and successfully demonstrated during the XVII Indian Antarctic Expedition. Further studies continued during the XVIII Indian Antarctic Expedition and a series of scientific experiments were conducted in the areas of optimisation of humidification, temperature for reactants (hydrogen and oxygen), elimination of existing humidification system, feasibility of provision of air-cooling system in lieu of water cooling system, humidifcation of gases using membrane as a medium, charging/discharging characteristics of a metal hydride container for hydrogen storage, and performance of a dc–dc converter and static inverter under sub-zero temperature of operation. Based on the results of these experiments, the design of the fuel cell power source for cold region application has been finalised. The paper deals with the design criteria and design factors to be considered for the fuel cell power source for cold region application and details of tests and test results that led to the final design concept for such an application. The paper also deals with a proposed hybrid power plant taking into account the exploitation of wind energy with a fuel cell and generation of hydrogen by an electrolyser and provision of hydrogen storage.

Response of geomagnetic variations and 30 MHz riometer absorption, at Indian Antarctic station MAITRI, to conditions of “zero” and “high” solar wind

Variations in the 30 MHz cosmic radio noise signal, and in the Y, X, Z fluxgate magnetometer traces recorded at the Indian Antarctic station MAITRI (geom. 62°.8 S, 52°.8 E, L = 4.8) are compared for the “zero solar wind” day of 11 May 1999 (ΣKp = 2 0), the very Quiet day 22 Dec 1999 (ΣKp = 1 0), and the very Disturbed day 18 May 1999 (ΣKp = 31 0). Interplanetary magnetic field and solar wind parameters from the WIND satellite for these days are also examined, in order to understand what factors cause Maitri to change from a location influenced by Sq currents, to one influenced by Auroral electrojet currents. It is observed that it is not only negative Bz and high solar wind velocity which play a role in causing pronounced magnetic disturbance at this just-sub-auroral location but also high ion density and high ion dynamic pressure in the solar wind. The observations reflect on the changes which occur in the size of the geomagnetosphere and in the size of the auroral oval as a consequences of changes in the Interplanetary medium.

Environmental status at the Indian Antarctic station — Maitri

A set of procedural guidelines have been developed in 1991 for evaluating the environmental impact of scientific research programs and their associated logistic support facilities in Antarctica. In view of this, an Environmental Impact Assessment (EIA) study of the Indian Antarctic station — Maitri was conducted during the austral summer of 1994–95. Studies covered different components of environment, viz. air, noise, water, wastewater, solid waste and land. Different sources of pollution were identified and the samples were analyzed to assess the current status of environment. The present communication delineates not only the details of the studies undertaken, but also suggests guidelines towards effective Environmental Management Plan (EMP) so as to mitigate the adverse impacts likely to be caused by various activities.

Acoustic sounder measurements of the planetary boundary layer at Maitri, Antarctica

The planetary boundary layer (PBL) over the Indian Antarctic station, Maitri (70.7° S; 11.7° E; 120 m asl) has been studied using a monostatic acoustic sounder. Acoustic sounder records reveal that the Antarctic PBL remains stably stratified throughout the year except for some periods in the peak summer months. The summertime PBL exhibits a diurnal variation with ground-based inversions developing at night and the convective plumes occurring during the peak sunlight hours. The cyclonic inflow of warm oceanic air towards the continent's interior from the coast helps in the development of the elevated layers and the Kelvin-Helmholtz waves observed on the sodar records.

Evaluation of turbulent fluxes over Maitri, Antarctica

Turbulent fluxes have been evaluated for clear sunny days over the Indian Antarctic station, Maitri, using the basic meteorological data recorded at four levels of a 28 m tower. The data are supplemented with radiation data. The surface layer over Maitri remains thermally stratified during the hours of minimum solar insolation, the so-called nighttime period. The surface winds during this period are generally very strong resulting in high momentum fluxes. In particular, for high winds (>12 m s−1), the temperature gradient is found to be less positive than for moderate winds (4 to 7 m s−1). Solar insolation provided the daytime heating necessary for the diurnal variation of atmospheric stability, and hence, for the turbulent fluxes. Thus, on clear days daytime conditions are marked by upward transport of heat with reduced momentum flux, while stable nighttime conditions are marked by a downward heat flux with increased momentum fluxes.

Microanalysis of uranium in Antarctica soil samples using fission track method

Soil samples collected at the Indian Antarctic station Maitree, situated at the Schirmachar Oasis and belonging to the East Antarctic charnockite provinces have been analysed to determine trace uranium concentrations. The fission track technique using Makrofol-KG as the track detector was used for the analyses. Finely powdered samples and pellets were irradiated with thermal neutrons from a nuclear reactor. Uranium concentrations were obtained from the tracks of the detector. Uranium concentrations were found to vary from 0.036 to 0.364 ppm in the samples investigated. The low levels of uranium indicate the absence of human intervention with the lithosphere in this region.

Characteristics of atmospheric turbulence in the surface layer over Antarctica

This paper presents meteorological measurements made during the antarctic summer period, on two 9 m and 3 m towers, on the rocky and ice shelf terrains of the Indian antarctic stations Maitri and Dakshin Gangotri, respectively. The measurements of fluctuations in temperature and wind speed made with relatively lesser precision instrumentation pertain to smaller wave numbers ~10-2 m-1 appropriate to outer scale L 0 of the atmospheric turbulence spectrum. Autocorrelation analysis of the fluctuations in temperature and wind speed has been performed. A new autoregressive scheme has been developed to represent the computed autocorrelation functions by a Yule statistical model, and to estimate the correlation period T 0 of the turbulent medium. Height profiles of outer scale L 0 of turbulence may be given in terms of T 0 and mean wind speed u. Further, the similarity theory of Monin-Obukhov has been used to compute height profiles of temperature structure parameter C T 2. At Maitri, values of L 0 and C T 2 are higher between 03–22 h local time than between 22–03 h. Values of L 0 and C T 2 are smaller over the ice shelf terrain of the Dakshin Gangotri station, compared to those over the rocky terrain of the Maitri station.

Criteria for Selection of Site for Co~lstruction of Structures on a Floating Ice Shelf in Antarctica-A Case Stucty

The coastal regions of Antarctica, where substantial deposits of oil and (other minerals are reported, consist of a number of ice shelves. Such areas encounter severe weather conditions and flow of the ice shelf which severely affect the life of the structure/installations. The Indian Antarctic station Dakshin Gangotri located in east Antarcticaat 70 degrees S 12 degrees 05' E lies on one of such ice shelves. The paper brings out the criteria which should be kept in niind while selecting the site of a structure on an ice shelf and a case study for selection of site of Indian research station Diikshin Gangotri 'in December 1983 of which the author was the leader of the first wintering party.