CHAPTER - 17: My Scientific Work in Antarctica and award of Ph.D.

CHAPTER - 17
My Scientific Work in Antarctica and award of Ph.D.
17.1 Introduction
It may be quite appropriate and informative to include in this book a ‘summary and the principal conclusions of scientific work done in Antarctica which is published in many reputed international scientific journals as referred to in the list of publications given its Chapter-20. While his Ph.D. thesis entitled ‘Atmospheric Structure: Exploration over Antarctica and Interhemispheric Comparison’ gives the details of his Antarctic research work carried out at the Physical Research Laboratory (PRL), Ahmedabad, India, a resume of the work done and the principal conclusions drawn from this study are summarized in this Chapter of the book to make it more informative and complete.
17.2 Launching of M-100 Meteorological Rockets from Antarctica
The author participated in the 17th Soviet Antarctic Expedition and carried out the M-100 Meteorological Rocket Soundings at Molodezhnaya in Antarctica. The Soviet M-100 Meteorological Rockets which reach upto about 100 km height probe the atmosphere upto an altitude of about 90 km carrying a payload of about 66.65 kg.
Atmospheric winds are derived from the drift of the trajectory of the descending parachute and chaff while the atmospheric temperatures are measured by resistance thermometers. The upper atmospheric wind and temperature results from these atmospheric soundings have been discussed earlier by the author in his other publications and also compared with the corresponding equatorial results which may be referred to in Chapter-20 of this book.
About 60 ‘M-100’ Meteorological Rockets were launched from the Soviet Antarctic station Molodezhnaya in Antarctica out of which 52 flights were successful and 16 of these carried an additional wind sensor ‘chaff ’ for measuring upper mesospheric winds. The M-100 Rockets were fired from Molodezhnaya in Antarctica on every Wednesday and additionally on every Saturday during the Antarctic winter. The chaff and parachute wind data were obtained simultaneously. Based on all these data, seasonal variations of the winds in the Antarctic troposphere (lower region), stratophere (middle region), and mesophere (upper region) are studied. The results are also compared with the Groves atmospheric model and the corresponding departures in the two hemispheres are worked out.
17.3 Exploration of Atmospheric Structure Over Antarctica
For centuries, the poles have driven hardy men to exploration motivated by curiosity, adventure, promise of rewarding harvests of seals and whales or by the search for shroter trade routes. The annals of early polar exporation tell of daring exploits and killing hardships. Ironically, some of more tragic early expeditions contributed a lot to our knowledge of the polar regions as for example, Shakelton’s remarkable Antarctic odyssey after his ship ‘Endurance’ had been crushed by pack ice in the Weddel Sea, and the ill-fated Franklin expedition into the Arctic. Because survival in the harsh environment demanded so much of the early explorers, their contributions to our knowledge of the polar regions were largely limited to the discovery and mapping of land features.
The polar regions of the Earth are still comparatively less explored. This especially applies to the Antarctic which was discovered just two centuries ago. Scientific investigations of Antarctica started in 1901 when expeditions were sent to the Antarctic continent under various national flags. Polar investigation entered a new era during the International Geophysical Year, (IGY) in 1957-58 which marked the end of random exploration and the beginning of systematic scientific research. Broad features of the polar environment are now known to a reasonable extent. However, some specific significant problems, largely interdisciplinary in nature, that will lead to a better understanding of the total global environment remain yet unsolved.
The polar regions are integral parts of the total global environment and understanding of polar processes and phenomena is essential to the solution of earth-wide problesm. For example, polar atmospheric circulations strongly influence weather and climate at the lower latitiudes, and the polar oceans can be considered the high-latitude portions of the world oceans. Removal of the sea-ice cover of polar seas, either accidently or deliberately, would certainly have a profound effect on the global heat balance and hence on the world’s weather and climate and, consequently, on the atmospheric structure and circulation. We have yet to uncover and explain many of the basic secrets of the polar environment, to relate them to their global counterparts and to weigh the interlocking consequences of environmental modifications. The study of the polar atmospheric structure, particularly over Antarctica which is the last terra incognita on the Earth and the least investigated so far is, therefore, very essential.
17.4 Soviet Antarctic Expedition
Under a joint Indo-Soviet Agreement ratified in 1970, the author participated in the 17th Soviet Antarctic Expedition during the period 1971 to 1973, wintered at the South Poar Ice-Cap and circumnavigated the Antarctic Continent (Caffin, 1975). Some of the stations visited by the author during his Antarctic Odyssey, 1971-73, also include the Amundsen-Scott South Pole station at the geographic South Pole where there is an American station, and the Soviet inland station Vostok. Visit to the station Vostok (78* 28 S, 106*48 E), the pole of cold located at the geomagnetic South Pole at a height of 3488 m above M.S.L. was of special interest because it involved a trekking of about 1500 km with tractor sledge and footsore.
The author wintered at the station Molodezhnaya located at 67*40 S, 45* 51E at a hiehgt of 42 m above M.S.L. and carried out meteorological rocket soundings of the upper atmosphere in addition to other observations. The station Molodezhnaya was formally opened on January 14, 1963 and the atmospheric soundings with meteorological rockets were started from mid 1969. At the station there is a series of east-west ridges made of some exposed bedrocks. The ridges are separated by ice-filled valleys with elevations ranging from about 20 to 200 m along the coast. Some of the ridges terminate in cliffs at the adjacent bay, Alasheyev Bight. The major bedrocks are magmatized, granitized and pegmatized Precambrian gneisses of the crystalline basement of the Antarctic platform. In a narrow zone about 10 km wide parallel to the coast, exposed rock and soil are found in abundance which are, however, very rare inland. Although the station bed itself is confined o erratic and frost-churned mixed materials, yet nearby there are two outlet glaciers, Campbell and Hays, which form active moraines.
Some of the extreme weather conditions at the station Molodezhnaya in Antarctica during the period from 1963-73 are given in the following Table-1 for general reference.

Extreme surface meteorologica results at Molodezhnaya, Antarctica during 1963-1973
S.N Meteorologica parameter Value Date
1. Maximum of the mean temperature recorded during a month
0.8*C

January 1967
2. Minimum of the mean temperature recorded
-22.8*C

July 1965
3. Maximum temperature recoreded 8.5*C
December 30, 1963
4. Minimum temperature recorded -37.5*C
September 8,1965
5. Maximum of the mean atmospheric pressure recorded during a month
997.8 mb
July 1964
6. Minimum of the mean atmospheric pressure recorded during a month
966.0 mb
October 1965
7. Maximum atmospheric pressure recorded
1017.2
June 7, 1964
8. Minimum atmospheric pressure recorded
936.3 mb
September 8, 1969
9. Maximum atmospheric pressure increase during three hours
23.8 mb
Sep. 8, 1969
10. Maximum atmospheric pressure decrease during three hours
22.3 mb
June 27, 1966



Table – 1Continued.
S.No Meteorologica Parameter Value Date
11. Maximum of the mean wind speed recorded during a month
17.0 m/s
April 1966
12. Minimum of the mean wind speed recorded during a month
4.5 m/s
January 1967
13. Maximum of wind speed recorded 39 m/s April 12, 1963
14. Maximum wind thrust (gust) recorded 48 m/s

52 m/s August 24, 1963 & May 1, 1969
October 1972
15. Maximum number of days with wind speed 15 m/s recorded month-wise.

30

May 1968
16. Maximum number of days with wind speed 30 m/s recroded month-wise

6

May 1968
17. Maximum number of clear days 13 December 1964 & July 1966
18. Maximum number of overcast days recorded during a month
23
August 1968
17.5 Some Physical Characteristics of Antartica Meteorology
The weather and climate of Antarctica are the result of several factors, for example its location near the South Pole of the Earth with the implied astronomical influencess, its great elevation which intensifies the polar climate, its perpetual snow cover with strong reflective and radiative characterstics and its complete isolation from all other continents by a completely surrounding ocean of relatively warmer water. The Antarctic atmosphere has the same composition as that of the rest of the world, except that the principal variable gaseous component, water vapour, has only about one-tenth of the average concentration, of what it has in middle latitudes.
Table-1 presents the extreme surface meteorological results at the Antarctic station Molodezhnaya (67* 40* S, 45*51*E, 42 m above M.S.L.) for the period from 1963 to 1973 for general reference. In 1972 the mean annual temperature observed at the station was –10.5*C varying from a lowest minimum of –35.8*C to a highest maximum of 7.0*C. South-east winds prevailed at the surface with frequent gusts of 21-41 m/s. Annual mean relative humidity was 65% and the annual mean precipitation obsereved was 0.14 cm.
The author actually visited and worked at all the Soviet Antarctic stations such as Bellingshausen, Mirny, Molodezhnaya, Leningradskaya, Novolazarevskaya, and the deep inland station ‘Vostok’ situated at the geomagnetic South Pole in the Pole of cold, during the period from 1971 to 1973 in order to collect maximum scientific data from there. Some of these data are for examble, presented in the form of surface meteorological results in Table-2 for general reference. The surface meteorological results collected from the various stations in 1972 during his participation in the Soviet Antarctic Expedition, 1971-1973 are compared in table-2 showing the latitudinal differences in atomospheric pressure, air temperature, wind speed, wind gust, relative huidity and average cloudiness from the Antarctic Peninsula (62*S) to the geomagnetic South Pole (78*S).
Excluding the Antarctic Peninsual, the monthly mean teperature during the warmest month is around 0*C in the coastal region and from –34 to -20*C in the interior. The water vapour concentration can be higher than about 4.8 and 0.2 grams respectively. In winter, the coldest monthly mean temperature is from about –30 to -20*C in the coastal region and from –70 to -40*C in the interior, while the water vapour concentration is less than 0.3 and 0.003 grams respectively. The carbon dioxide content is between 310 and 315 parts the author also visited and worked at some American stations in antarctica including the ‘Ammudsen-Scott South Pole station’ located at the geogzaplic South Pole during 1971-1973 for an indepth exploration of Antarctica. indepth exploration of per million, about the same as other parts of the world. Total atmospheric ozone is at a maximum in spring, usually November, while the limited dark-season data indicate minimum during the winter. Dust and other pollutants are practically unknown.
The total of the incoming direct and diffuse solar radiation reahes values of 75-85 % of the solar constant depedning on the altitude of the station. The high values are partly due to the Earth’s being at perihelion (point of its orbit nearest the sun) during the Southern Hemisphere summer, but the clear and dry atmosphere and high elevation of Antarctica are important factors. However, as much as 80-90% of the incoming short wave radiation is reflected by the snow surface. Only the upper 1-1.5 metres of the snow-cover absorb appreciable amounts of the solar enrergy and it is quickly lost again in the dark season because the dry atmosphere has little blanketing effect. Small amounts of cloud do not appreciably reduce the total amount of solar radiation reaching the surface, since there is a high multiple reflection caused by the snow surface and the underside of the clouds. In some cases this can even raise the total of the direct and diffuse radiation reaching the surface to a value higher than that of the solar constant, i.e., the amount of radiation from the sun reaching the top of the atmosphere. The albedo, or reflectivity of the snow surface varies from about 75 to 90% and the values tend to be lowest after periods of ablation (e.g. sublimation, melting, evaporation) and wind erosion, and highest after fresh snow-fall. The albedo has a seasonal as well as shorter period variation.
The mean annual temperature isotherms over Antarctica generally approximate the terrain contours with warmer temperatures near the low-lying coast and the coldest temperatures on the high plateau in the interior of East Antarctica, which averages between 790-1100 metres higher than the South Pole elevation of 2800 metres. The annual mean on the plateau is about -56*C and tempeatures below -80*C are very common as is obvious from the lowest temperature ever observed in the world equivalent to –89.3*C which was recorded at the Soviet Antarctic station Vostok (78*28 S, 106*48 E, 3488 m above M.S.L.), the geomagnetic South Pole. Although it is the world’s coldest continent, Antarctica is not uniformly cold. Variations in the atmospheric circulation bring about considerable differences in temperatures, both in time and in space. The minimum temperatures at one place do not always occur during the same month from one year to another, and places several hundred miles apart may be under completely different temperature regimes at the same time. A rise and fall of as much as 8*C in the monthly mean temperature can take place in successive months during the winter. Under conditions of large-scale flow of air from the oceans to the continent, a rise of as much as 14*C in one day can occur. Increased cloudiness inhibits the loss of heat by radiation from the snow surface as well as increases the amount of heat radiated downward to the snow surface.
The main supply of heat to Antarctica in winter is the warm air carried by the atmospheric currents. The first strong radiational cooling in winter causes an early winter teperature minimum, but the atmosphere reacts to it by changing its circulation to bring in the warmer air. Finally, at the end of the winter radiational cooling again becomes dominant and late winter minimum teperatures are noted usually just before the return of the sun. The cyclonic storms that move around Antarctica often pass through the West Antarctica highland and even across the South Pole, but only rarely over the higher plateau of East Antarctica. The exchange of air horizontally in the levels from about 2440-4570 m is such that a temperature fall of only about 8*C is noted in the monthly mean values from summer to winter. The very lowest layers of the atmosphere lose heat by radiation and by contact with the snow surface. The result in these cases is inversion i.e. the temperature increases with height and a gradient of 28*C in 305 m is not uncommon.
The air trajectory and the contrast between ocean and continental underlying surface are the principal factors in the development of weather at a given spot as a result of which cyclones on the polar front attain great intensity and size. The great storms and blizzards of long duration are related to deep disturbances extending in many cases from sea level to the tropopause (located at about 10 km). Storms of blowing snow accompany the disturbances and even persist for some hours after the passage of initial storms. The shallow storms tend to move quickly around the periphery of the continent and are not related to the large-scale planetary waves in the atmosphere. The large storms move in arc-like, clockwise trajectories, generally from the north-west to the southeast and remain north of the coastline in most cases. The high level of the continent, the strong gravitational outflow of the cold air in contanct with the surface and the procession of stroms act against the formation of large polar anticyclones, alothough the sea level pressure at some coastal stations has gone above 1035 milibars. Some of the cold anticyclones have provided sufficient cold air both from West Antarctica and from East Antarctica to reach other Southern Hemisphere continents, although much modified by over water trajectories of several thousand kilometres.
The jet stream, the core of winds of maximum velocity, found usually just below the tropopause and in regions of maximum horizontal temperature gradient, tends to broaden its latitudinal extent and strengthen in winter and tends to narrow and weaken in summer. Surface winds frequently attain speeds of 160 km per hour (about 45 m/s) or more during the passage of storms along the coast of East Antarctica as is obvious from and Table-1, Table-2. The temperature field along the steep slopes of the continent affects he horizontal temperature gradient and thus modifies the winds in these cases. Along low-lying coastlines, the maximum force of wind is usually less. The extension of the ‘effective’ continent as much as 6* of latitude farther north of its summer coastline comes about through the freezing of the surface layers of the ocean in winter. This inhibits the vertical exchange of heat between ocean and atmosphere and also provides a longer continental trajectory for the air of oceanic origin that reaches the continent. This is one reason for lower average cloudiness in winter than in summer.
The condensation of water vapour carried in the air not only adds to the snow cover but also contributes about 14% of the net heat energy transported by the atmosphere. It is estimated that on an average about 12-20 cm of water equivalent are deposited in the form of snow over Antarctica in one year. The coastal regions have up to ten or more times the 2-inch snow fall (water equivalent) deposited on the interior of Antarctica, the polar ice-cap. During the winter lot of snow is accumulated over the South Polar Ice-Cap and the camps of the wintering teams are often burried under the snow. It is due to the frequent blizzards and snow drift.
17.6 Atmospheric Wind Structure in Antarctica
The analysis of the Antarctic M-100 rocketsonde data was carried out for the southern summer (December to February), autumn (March to May), winter (June to August) and spring (September to November). The Antarctic summer was characterised by light easterly winds increasing in strength with altitude. The winter exhibited strong westerly winds of speed about 50 to 100 m/s increasing in magnitude as the season progressed. The accuracy of wind measurements was about 5 to 10 m/s. The autumn and spring were found to be the wind reversal periods marked by the change of summer easterly winds to the winter westerlies and vice versa.
It may be noted that in the Southern Hemisphere including Antarctica, the summer, autumn, winter and spring periods are opposite to those in the Northern Hemishphere including the Arctic, i.e., when it is summer in one, it is winter in the other and vice versa, etc.
The zonal (east-west) winds over Molodezhnaya, Antarctica were predominantly easterly (blowing from the east) in the southern summer and westerly (blowing from the west) in the winter with reversal of winds from easterly to westerly during the autumn (period after the summer and before the winter), and from westerly to easterly during the spring (period after the winter and before the summer). The Antarctic winter westerly winds increased in strength as the season advanced and attained jet speed of about 90 metres per second (m/s). Complete reversal of winds from easterlies to westerlies occurred in the first week of February in the stratosphere and in February end in the trophosphere. The reversal from westerlies to easterlies occurred in the third week of November in the stratosphere. It was found that the reversal first occurred in the upper layers and subsequently in the lower layers indicating a downward propagation of the disturbance.
It is found that the summer to winter shift was a relatively rapid change while the winter to summer shift was slow and gradual. Also, the most unsettled period in the south polar region was the winter and early spring which was marked by large perturbations in wind and thermal structures accompanied by stratospheric and mesopheric warmings and coolings.
It is found that in the southern summer (December to February), average zonal flow over Antarctica was easterly throughout the atmosphere from surface up to about 80 km. The flow had a speed less than 13 m/s in the tropsophere and the stratosphere. It became stronger in the mesosphere and attained a speed of 41 m/s at 70 km with a standard deviation of about 7 m/s. In an altitude region from about 10 to 20 km the zonal winds were very weak and calm with speeds less than 3 m/s indicating that there was no turbulence at the boundary of the troposphere and the stratosphere in the summer.
Average wind profile for the southern winter (June to August) over Antarctica shows that in the winter the zonal winds were stong westerly throughout the atmosphere from about 5 to 80 km with weak easterly winds of speed less than 8 m/s in the lower troposphere below 5 km. The winter westerly flow attained jet speed in the stratosphere and the mesosphere which had a maximum of 90 m/s at 64 km with a secondary maximum of 71 m/s at 44 km. The winter westerly flow persisted in the spring with the stratospheric maximum of 39 m/s at 28 km and mesospheric maximum of 56 m/s at 61 km. It is found that the meridional (north-south) wind components were variable throughout the atmosphere with weaker winds from surface up to the lower mesosphere and relatively stronger aloft.
17.7 Atmospheric Thermal Structure in Antarctica
The atmospheric temperatures (thermal structure) over Antarctica were obtained up to an altitude of about 80 km. The results showed that the variation of the Antarctic temperatures was smaller in the troposphere and larger in the stratosphere and the mesosphere. The summer polar tropopause (end of the troposphere and the beginning of the startosphere) was located between 8 and 11 km with the temperature varying from –50 to -60*C. The accuracy and mean square error in temperature measurements was about 3 to 10*C. However, the winter tropopause was not found to be well defined due to its multiple occurrence between 10 and 25 km caused by a differential cooling.
The differential cooling was set in the atmosphere beginning early autumn which weakened the South polar tropopause and at times wiped it out thus forming a quasi-tropopause during the winter regime. The differential cooling might be due to the ventilation of the Antarctic atmosphere by warm marine air with intense horizontal advection in the troposphere and a weak advection through the strong stratospheric jet stream encircling Antarctica,
The average polar stratopause (end of the stratosphere and the beginning of the mesosphere) over Antarctica was located at 47 km and the winter stratopause was colder than its summer counterpart by about 19*C. The Antarctic stratosphere was colder in the southern winter because there was very little warm air advection through the strong stratospheric jet-stream encircling Antarctica thus permitting the average stratospheric temperature to fall steadily at the rate of about 0.25*C per day. The Antarctic upper stratosphere and the lower mesosphere appears to gain energy through radiative processes in the southern summer and to lose it during the winter regime.
The mesosphere over Antarctica in an altitude region from about 64 to 80 km in the summer was found colder than its winter counterpart. The average summer and winter temperature departures from the annual mean were found to be in a range of about -22*C to 7*C. The polar winter mesosphere in the Southern Hemisphere may be warmer due to a large-scale meridional transport of heat in one form or another by the atmosphere resulting from a mean meridional circulation or from large-scale eddy diffusion (mixing) processes.
17.8 Upper Atmospheric Warmings and Coolings in Antarctica
The investigation of the Antarctic atmosphere shows that the most unsettled period in the South Polar regions was the winter and the early spring which was marked by large perturbations in the wind and thermal structures. The rapid shifts in both zonal and meridional components of the upper atmospheric winds, particularly during the period from May to July, were accompanied by sudden changes in the temperature distribution as revealed by the stratospheric and mesospheric warming and cooling. During Spetember when the winter westerlies changed to the summer easterlies the upper atmosphere experienced a warming of about 40*C at 40 km. Apart from the general warmings and coolings of the Antarctic stratosphere and mesosphere, there were a few occasions in May and July when sudden warmings were also obsereved.
The Antarctic upper atmosphere was subjected to large thermal perturbations during the winter regime causing significant warmings and coolings in the stratosphere and the mesosphere with larger amplitudes at higher altitudes. Apart from this, there were a few instances when sudden warmings also occurred, e.g., on May 17 and July 5 1972. The polar warmings might be due to an increase in the supply of energy caused by radiative processes.
As noted by the author, in the southern winter there were significant disturbances of temperature and wind velocity distribution in the Antarctic mesosphere exceeding similar variations at lower levels. The period of oscillations at heights of 60-70 km ranged from one to three weeks and changes of temperture were from about 20*C to 70*C. The strengthening of westerly flows in the middle and upper mesosphere as well as in the upper stratosphere were accompanied by warming, while the weakening of a westerly flow, the increase of meridional components and the appearance of easterly components coincided with cooling.
A rather interesting fact is that in the uper mesosphere easterly wind components are predominant for about 8-9 months and these periods of easterly winds correspond to a period of low tempertures. Periods of westerly flow correspond to short duration mid-winter warmings in the upper mesosphere.
17.9 Atmospheric Gravity Waves in Antarctica
A remarkable wave like structure was detected in the vertical profiles of wind components both over the South polar and the equatorial regions. These observations indicate that the recurrent wave structure might have been caused by the wind fluctuations due to atmospheric gravity waves. It is also found that these irregular waves were predominantly horizontal, had amplitudes that increased with height and also the dominant scale size of the vertical wave length increased with height which may be due to gravity waves.
The amplitude of the irregular waves increased rapidly with height owing to the rapid decrease in atmospheric density. Turbulent motions causing the irregular waves over rough terrain and about local circulations such as clouds, as a result of local instabilities can be expected to make their influence felt at remote points in the atmosphere. Thus it appears that both the processes, i.e., internal manifestations in the wind field due to atmostpheric gravity waves and irregular fluctuations set up due to turbulent motions might cause the wave like structures in the vertical wind profiles.
17.10 Comparison between the Antarctic and the Equatorial Atmospheric Structure
The summer polar tropopause and stratopause in the Southern Hemisphere over Antarctica were found to be about 27*C and 13*C warmer than the corresponding equatorial tropopause and stratopause while the Antarctic mesopause (end of the mesosphere) was apparently about 25*C colder. Also, the South polar tropopause and stratopause were located at altitudes of about 8 km and 2 km lower than their corresponding equatorial counterparts while the Antarctic mesopause seemed to be located at an altitude of about 5 km higher than the corresponding equatorial mesopause in the southern summer. The primary reason of the warmer polar tropopause and stratopause is the availabilty of more solar radiation in Antarctica due to almost continuous sunight.
The summer polar mesopause in the Southern Hemisphere may be colder than its equatorial counterpart due to strong adiabatic cooling in the Antarctic mesosphere. It is because upward motions exist to some degree in summer polar areas due to the expansion of stratospheric regions. Initial phases of upward motions of this meridional current at the stratopause could well be supported by ozone heating in that region. As the air lifts towards the mesopause, adiabatic cooling would become a very strong effect and consequently the polar mesopause becomes colder and also shifted somewhat upwards.
During the southern winter, the South polar tropopause and stratopause were found to be 5*C and 8*C colder and at higher altitudes, about 3 km and 2 km, respectively than the corresponding equatorial tropopause and stratopause. The situation is reversed because of the absence of sunlight over Antarctica during the southern winter.
17.11 Atmospheric Structure over the Antarctic and the Arctic Regions and Comparison with the Groves Atmospheric Model
Departures of the actual zonal winds from the corresponding Groves atmospheric model over Antarctica varied from –14 to 8 m/s in January and -34 to 36 m/s in February while the corresponding equatorial departures ranged from -30 to 5 m/s and -9 to 27 m/s between the two months. The temperature departures of the actuals form the Groves profiles were -30*C to 10*C over the South polar region and -25*C to 2*C over the equatorial region in the southern summer.
The departures over Antarctica are apparently because the Groves atmospheric model is based on the data from the Northern Hemisphere which differs form the Southern Hemisphee in many respects. Antarctica is as continental as the Arctic at the surface, but the dominant water surface outside the polar regions in the Southern Hemisphere and the extensive areas of land surrounding the Arctic emerge as the important factors controlling various changes in the atmospheric winds and temperaturs in the Southern and the Northern Hemispheres. The higher albedo over Antarctica than over the Arctic explains the much lower summer temperatures of the Antarctic. The coldness of the air at middle southern latitudes in summer, compared with the same northern latitudes, owes more to the physical properties of the immense southern oceans than to the presence of an ice-covered polar continent.
The departures may also be due to the reasons that the Southern Hemisphere is more symmetric and has a vigorous general circulation and that the Antarctic continent is located at a higher elevation than the Arctic. Likewise for the Thumba latitude in the Eastern Hemisphere, the Groves Model is based on data from all longitudes mostly from the Western Hemisphere. Departures of the equatorial actuals from the Groves profiles may, therefore, be the evidence of longitudinal asymmetries between the Eastern and the Western Hemispheres. Thus the discrepancy between the actuals and the Groves Model may be largely attributed to the specificity of geographical locations of the sounding stations.
17.12 Interhemispheric Comparison of Atmospheric Structure
In addition to the Antarctic exploration, and equatorial study, an interhemispheric comparison of the atmospheric structure is also carried out employing meridional cross section analysis. Data were taken from the meteorological rocket soundings along two meridional zones : 40*E to 90*E in the Eastern Hemisphere and 35*W to 95*W in the Western Hemisphere. The results obtained from the Eastern Meridional Network of stations from the 'M-100’ rocket soundings in 1972 at Heiss Island (80*37 N), Volgograd (48*41 N), Thimba (8*32 N), Mobile ships in the Indian Ocean and Molodezhnaya (67*40 S) are presented as mean profiles, time-height cross sections and lateral cross sections. Rocketsonde data for the Western Meridional Network are taken from the stations Thule (76*33 N), Fort Churchill (58*44 N), Wallops Island (37*50 N), Cape Kennedy (28* 27 N), Antigua (17* 09 N), Fort Sherman (9*20 N), Natal (5*55 S), and Mar Chiquita (37*45 S).
The meridional cross section analysis carried out using the data from the Eastern and the Western Hemispheres shows that the main differences between hemispheres in the intensity of various physical processes in the upper atmosphere occurred in the winter period. Frequent break-up of mid-winter zonal circulation accompanied by warmings have been observed in the stratosphere of the Northern Hemisphere. In the Southern Hemisphere these processes were relatively less. In 1972, the wind and thermal field over Antarctica were subjected to sizeable perturbations accompanied by significant warmings and coolings including a few cases of sudden explosive warming.
The latitude-height cross sections of the atmospheric winds and temperatures in the Eastern and the Western meridional networks during the periods December to February and June to August provide a valuable information on the relative symmetry between phenomena of the Northern and the Southern hemispheres. For example, the spring time transition from westerlies to easterlies outside the tropics appeared to take place in a more regular fashion in the Southern Hemisphere. This is in no doubt related to differences in dynamic and radiational warming patterns between the two hemispheres. It may be due to differences in topographical characteristics.
In both hemispheres there is a marked tendency for the westerlies to replace the easterlies before the autumnal equinox and to persist after the vernal equinox. Both wintertime westerlies and summertime easterlies appear to be stronger on the average between 20 and 60 km over the Southern Hemisphere than over the Northern Hemisphere. The above analysis shows that the winter polar vortex and the summer anticyclones spread up to the mesosphere while tropical anticyclones are confined to the stratosphere. It is noted that large-scale disturbances of the thermal field and circulation caused by winter warmings of planetary scale appear most significant in the mesosphere.
The present research and investigation gives an indication of the development of ascending motions in the tropical strtosphere of both the hemispheres during the period of warming in middle and high latitudes. As warmings are generally more frequent and intense during the winter period of the Northern Hemisphere, ascending motions in low latitudes may be supposed to attain greater intensity in January or February (northern winter) than in July or August (southern winter). The resulting effect would be decrease of temperature over the equator at the beginning and end of a year and increase in the middle of it.
17.13 Need to Collect More Scientific Data Over the South Polar Region Including Antarctica
Ad finem, it may be added that it is very essential to collect more meteorological data particularly in the relatively less explored South Polar region including Antarctica and fill up the data gaps over oceanic areas in the Southern Hemisphere in order to fully understand the physical processes influencing the weather and climate all over the globe and solve the intricate problems connected with weather forecasting. The first GARP Global Experiment (FGGE) of the Global Atmospheric Research Programme (GARP) carried out during 1978-79 is one of the most complex and ambitious international projects ever conceived to solve these problems.
The World Meteorological Organization (WMO) of the United Nations Organization (UNO) in Geneva, Switzerland, in which the author of this book has worked as a WMO/UN Expert for several years is organising such international programmes quite often. The author thus hopes to continue making significant scientific contributions in this field on a regular basis in future also.
17.14 Letter of Reference from the PRL regarding Ph.D.
Physical Research Laboratory
TELEGRAM : “RESEARCH” NAVRANGPURA TELEPHONES
TELEX : 012-397 AHMEDABAD-380009 76242 TO 46
(INDIA)
July 10, 1974
TO WHOM IT MAY CONCERN
This is to certify that Mr. Parmjit Singh Sehra joined the Physical Research Laboratory (PRL) as Research Scholar on 7th July 1969 and has been engaged in research work in atmospheric physics since then. He has been working with Professor P.R. Pisharoty on the Studies of the Atmospheric Structure and Circulation for his Ph. D. Degree. The title of his Ph.D. thesis is ‘Atmospheric Structure : Exploration over Antarctica and Interhemispheric Comparison’.
He is carrying out his research work here at the PRL and has registered for his Ph.D dgree with the Gujarat University, Ahmedabad, India under the guidance of Prof. P.R. Phisharoty as a regular Research Scholar since he joined the PRl in 1969. He will now be working here as an Honorary Research Scholar after his appointment in the Space Applications Centre, ISRO as a Research Associate.
The scientific objectives of the meteorological rocket investigations are to study the properties and processes which characterise the physical state of the stratosphere and mesosphere. He has been engaged in research work in atmospheric physics with special reference to meteorology for the last five years.
Mr. Parmjit Singh Sehra was deputed to participate in the 17th Soviet Antarctic Expedition from 1971 to 1973 by the Government of India. There he worked on meterological rocket soundings of the upper atmosphere. He is the first Indian ever to have wintered over Antarctica and to have worked there during its harsh winter from 1971 to 1973 as a Project Scientist. He is also the first Indian ever to winter over the South Pole and circumnavigate and explore the Antarctic continent.
He has been awarded the prestigious Soviet Antarctic medal, Ribbon and Polar Watch for his active participation in the 17th Soviet Antarctic Expedition from 1971 to 1973.
Mr. Parmjit Singh Sehra has been one of the best Research Scholars of PRL. He has first class academic career with high ranks in all his college and university examinations.
During his tenure with us he has been found to be sincere, reliable and social. He has a great stamina and zeal for work. He has been working diligently and intelligently. He possesses excellent moral character.
Sd/- S.R. THAKORE
DEPUTY DIRECTOR (ADMN.)
17.15 Letter of Appointment from SAC/ISRO while still continuing as an Honorary Research Scholar at PRL
SPACE APPLICATION CENTER
(SAC)
TELPHONE : 837715-19-26-29 AHMEDABAD 380015
TELEGRAM : ANTARIX : TELEX : 012-261 INDIA
SAC/PER/8.48/74 July 18, 1974
MEMORANDUM
Shri Parmjit Singh Sehra is appointed as Research Associate in the Space Applications Centre (SAC) with effect from the forenoon of July 4, 1974 on a basic pay of Rs. 400/- per month in the grade of Rs. 400-40-800-50-950, plus allowances as admissible under the Indian Space Research Organisation (ISRO) rules from time to time.
Shri Sehra will become a member of the ISRO Employees’ Contributory Provident Fund Scheme after suceessful completion of the probationary period.
His appointment is made subject to the terms and conditions of service stipulated in this office Offer of Appointment No. SAC/PER/8.48/74 dated June 12, 1974, accepted by him vide his letter dated July 4, 1974.
He is posted to Remote Sensing and Meteorology Applications Division (RSMD).
Sd/-
(S. R. Thakore)
Dy. Director (Admn.)
Shri Parmjit Singh Sehra
Research Associate
RSMD, SAC, ISRO

and Honorary Research Scholar
Physical Research Laboratory (PRL)
Ahmedabad-380009, India.
17.16 News entitled Dr. Parmjit Sehra honoured with the award of Ph.D. which appeared in The Indian Express on Friday, 20th May 1977
Dr. Parmjit Sehra honoured
By Our Staff Reporter
AHEMDABAD, May 19. Dr. Parmjit Singh sehra who participated in the 17th Soviet Antarctic Expedition during 1971-73 to the South Pole, has been awarded Ph.D. by the Gujarat University for his thesis “Atmospheric Structure: Exploration over Antarctica and Interhemispheric Comparison”.
Dr. Sehra, at present working at the Space Applications Centre here, participated in the Expedition under an agreement between the Indian Space Research Organisation and the Hydrometeorological Service of the U.S.S.R.
His research and investigations showed for the first time that sizeable perturbations occur in the South Polar atmospheric structure during winter.
17.17 Acceptance of Doctoral Thesis by the Gujarat University for the award of Ph.D. Degree.
Tele- {phones40341-42-43-41344
GUJARAT UNIVERSITY
DO.PG/PH/D. No./ 11632 Of 1977
OFFICE OF THE GUJARAT UNIVERSITY
POST BOX NO. 4010
AHMEDABAD-380009 (INDIA)
DATE 18 - 5 -1977
Dear Shri Sehra,
It gives me great pleasure, indeed, in informing you that your thesis entitled ‘Atmospherio Structure: Exploration over Antarctica and Interhemispheric Comparison’ has been accepted for the award of the Ph. D. Degree of this University. I am, in this connection, enclosing a formal communication of the University in this behalf.
May I take this opportunity of offering my congratulations on this occassion.
With best regards
Yours sincerely
Sd/-
K.C.Parikh
Encl : as above. (REGISTRAR.)
To
Shri Parmjit Singh Sehra
c/o. Prof. P.R. Pisharoty
Physical Research Laboratory
Ahmedabad-380 009, India.
Sdc/-18.5.
17.18 Official Communication of the Gujarat University for the award of
Ph. D. Dgree
1008-500-2-76 tele- Phone : 40341-42-43-44
grams : UNIVERSITY
GUJARAT UNIVERSITY
No. /P.G./Ph.D/11633 of 1977
OFFICE OF THE GUJARAT UNIVERSITY
AHMEDABAD-380009 ( INDIA)
Date : 18-8-1977.
To :
Shri Parmjit Singh Sehra
c/o P.R. Pisharoty
Physical Research Laboratory
Ahemdabad-380009, India.
Sir,
With reference to the thesis in Physics (Meteorology & Atmospheric Science) by you for the degree of Ph.D., I have the honour to inform you that you have been declared elegible for the said dgree which will be formally conferred upon you at the Convocation on your applying for it in the prescribed form at the proper time.
Yours faithfully,
Sd/-
K.C. Parikh
(University Registrar)
17.19 Award of Ph. D. Degree in Antarctic Explorations by the Gujarat University for the Thesis entitled “Atmospheric Structure : Exploration over Antarctica and Interhemispheric Comparison”
We, the Chancellor, Vice-Chancellor and Members
of the Court of the Gujarat University certify
that the Degree of
Doctor of Philosophy
(Science)
has been conferred on the eighteenth day of the month of October in the year one thousand nine hundred and seventy seven at Ahmedabad, India, on Parmjit Singh Sehra who has been found duly qualified for the same.
In Testimony whereof are set the Seal of the said University and the Signature of the said Vice Chancellor.
Sd/-
Vice Chancellor.
17.20 News entitled ‘Gujarat Varsity honours Scientist’ about the award of Ph.D. Degree which appeared in The National Herald on Friday, 20th May 1977
NATIONAL HERALD, Friday, May 20, 1977
Gujarat Varsity honours Scientist
AHMEDABAD. May 19 (Samachar ) - A young Scientist Mr. Parmjit Singh Sehra (27) who participated in the 17th Soviet Antarctic Expedition during 1971-1973 and wintered over the South Polar Ice-Cap as the First Indian has been awarded Ph.D. by the Gujarat University for his thesis “ Atmospheric Structure: Exploration over Antarctica and Interhemispheric Comparison”.
Dr. Sehra Participated in the Expedition under an agreement between the Indian Space Research Organisation and the Hydrometeorological Service of the USSR.
His research and investigation showed for the first time that sizable perturbations occur in the South Polar atmospheric structure during the winter regime. The most unsettled period over the South Polar region, according to him, was from May to September, which was marked by rapid shifts in both zonal and meridional components of the stratospheric and mesospheric winds accompanied by changes in the upper atmospheric temperature distribution