Showing papers on "Monsoon published in 1970"

An analysis of four tropical rain forest sites in new guinea

Abstract: 1966). Two of these forest types, forest on mid-slopes and forest on plateaux, were selected to investigate the interrelationship of structure, floristics and habitat in more detail by means of sample plots. Further objectives were to investigate the presence or absence of layering using detailed height and crown measurements, and to test the usefulness of profile diagrams. The results are thought to merit publication, firstly because quantitative information on tropical rain forest is rather scarce in the literature, and secondly because the findings are probably of more than local interest. The area visited lies in the Northern District of Papua, 100 miles (160 km) north-east of Port Moresby and about 18 miles (30 km) inland from the coast (Fig. 1). It comprises the southern foothills of the Hydrographers Range in the north, the northern foothills of the Sibium Range in the south, and a large central volcanic plateau, the Managalase. The area has a tropical rain forest climate and is subject to the north-west monsoon from December to March, and to south-east trade winds from May to October. Due to its position to leeward of the high east-south-east to west-north-west trending Owen Stanley Range in the centre of New Guinea, the area receives most rain during the north-west season. The nearest rainfall station, Popondetta, 12 miles (19 km) inland from the coast and about 500 ft (150 m) altitude, has a mean annual rainfall of 94 in. (2380 mm). As there is a general increase in rainfall with altitude and distance from the coast, the area under study probably has a higher rainfall. Monthly averages are most probably in excess of 4 in. (100 mm) even during the dry season. The area lies outside the zone of severe tropical storms but strong squall winds of up to 40 knots (74 km/h) have been observed (Fitzpatrick 1964).

The monsoon regime of the currents in the Indian Ocean

Abstract: : All hydrographic data collected during the International Indian Ocean Expedition from 1960 to 1965, and additional data from previous years, have been compiled at the University of Hawaii so that an atlas of the physical oceanography of the Indian Ocean can be prepared. The present investigation, which is based on these data, is limited to a discussion of the effects of the monsoonal winds on the surface circulation north of 20 degrees S. Although the accumulated data is the most comprehensive material on the Indian Ocean, it is still very heterogeneous; hence, it was necessary to apply statistical criteria in order to remove errors and variations that were introduced partly by nonsynoptic observations. The first part of this investigation presents the dynamic topographies of the sea surface for spring, early summer, late summer, fall, and winter. The second part presents a theoretical model in an attempt to interpret the peculiarities of the monsoonal circulation.

Mid-Tropospheric Cyclones of the Southwest Monsoon

Abstract: Mid-tropospheric cyclones are an important part of the tropical general circulation of the summer season. These are synoptic-scale disturbances which appear in the daily and monthly mean circulation maps with greatest intensity at levels near 500 mb. The structure and energetics of this type over southeast Asia are discussed in this paper. Interesting features include a warm anomaly above the cyclone and a cold anomaly below. A five-level non-geostrophic balanced model is used in this study to obtain the distribution of vertical motion. The model includes a parameterization of cumulus-scale convection. In the middle levels, rising motions are found west of the cyclone and sinking motions to the east. This is primarily due to the thermal structure of the atmosphere and associated advection of colder air from the oceanic regions and warmer air from land areas. A marked diurnal change in the vertical velocity is noted in the computations; magnitudes are large at 0700 local time compared to 1900. Thi...

Zonal anomaly of sea surface temperature in equatorial Indian ocean and its possible effect upon monsoon circulation

Abstract: The paper calls attention to the existence of a well-defined zonal anomaly of sea surface temperature between the equatorial west and east Indian ocean. The effect of this anomaly on ocean-atmosphere exchange and low-level air circulation in the equatorial Indian ocean as well as the Arabian Sea are discussed. It is shown that phenomena like the equatorial westerlies, the double intertropical convergence zone, and the Somali Jet receive plausible explanation on the basis of the observed zonal anomaly of ocean temperature. The effect of upwelling and its eastward advance in the Arabian Sea during the southwest monsoon are discussed in detail and it is suggested that this effect through air-sea interaction may change the low-level air circulation over the Arabian sea in a manner which may affect the distribution of rainfall along the west coast of India as well as inland during August and also explain frequent occurrence of feeble low pressure troughs in the southeast Arabian Sea during this period. Vertical circulation cells attributable to the observed anomalies of ocean temperature and their possible effect upon monsoon circulation and rain are discussed. DOI: 10.1111/j.2153-3490.1970.tb00506.x

The ecology of hydromedusae from the Cochin area

Abstract: A survey has been made of medusae found in plankton samples taken fortnightly over a period of a year at 2 fixed stations in the waters near Cochin, Kerala, India Twenty two species were identified, 8 of them were recorded for the first time in this region The 2 stations were found to be controlled by different hydrographical regimes; that at Aroor is entirely characterised by backwater conditions, with salinity afternating from fresh water to 32‰ S according to the monsoon cycle; the station at Fairway Buoy is also dominated by the monsoon cycle, with mixed, low-salinity (11 to 13‰) waters at the surface, and upwelled Arabian Sea water in the bottom layer during the Southwest monsoon Life cycles are discussed and the population dynamics of Eutima commensalis at Aroor are analysed A mathematical model is proposed for more detailed population dynamics studies of plankton species in the Cochin Backwaters, taking E commensalis as an example

Notes on the Somali Current System during the Southwest Monsoon

Abstract: Four hydrographic sections by the vessels Ob, Vityaz, and Atlantis 2 off the Somali coast during or just after the southwest monsoon season are discussed. Each section indicates a strong relative geostrophic current with a northward or northeastward component just off the coast (Somali current) and, to the right of this current, a current in the opposite direction. It is suggested that the currents are part of an anticyclonic circulation that may be formed by early June and that persists at least until late October after the cessation of the southwest monsoon winds.

Using natural radon for delineating monsoon circulation

Abstract: The presence of a major continental component in the monsoon air mass has been detected from radon observations made over the Arabian Sea and the Indian Ocean. The concentrations of radon in equatorial maritime surface air are found to be low (2–3 dpm/m3); in the monsoon air over the west Arabian Sea they are similar, but values gradually increase (∼20 dpm/m3) as the monsoon approaches the west coast of India. This result can be interpreted in terms of mixing between the lower maritime air and the continental air above. The usefulness of vertical radon profiles in further delineating some aspects of monsoon circulation is pointed out.

Interhemispheric mixing of fallout debris in the monsoon regions

Abstract: Striking evidence for interhemispheric mixing of the air masses in the Indian Ocean region during the period July-September has been obtained from the measurements of airborne radioactivity at a network of stations in India following the French tests in the South Pacific region from 1966 to 1968. This is based on the early detection of tropospheric activity at the sampling stations after the different tests, particularly after the medium-yield tests of 1968. Measurements of cesium 137 and zirconium 95 showed a minimum arrival time of 17 days at the southern stations in India. It is found that the most likely mode of travel for air masses of the southern hemisphere during the period July–September is by way of the summer monsoon in the Indian Ocean region. The importance of this study in understanding the classical Indian monsoon and the associated circulation patterns is also discussed.

Transfer of nuclear debris from southern to northern troposphere during 1968

Abstract: Debris from the French nuclear explosions at Mururoa (22°S, 140°W) during the period July-September 1968 circulated in the southern hemisphere in the same and adjacent zones of latitude. Traces of the debris have been followed across the equator, into the northern hemisphere at Bombay, Hong Kong, and middle latitudes. The transit times of the early debris from the first explosion, from Mururoa to Pretoria, Aspendale (Melbourne), and Bombay are consistent with the average wind fields in the upper troposphere. In particular, rapid interhemispheric transfer is indicated in the lower troposphere over the Indian Ocean. It is not possible to present a unique explanation, supported by plausible meteorological evidence, of the passage of the debris observed at the more northerly stations. This work documents incursions of southern tropospheric debris into the northern hemisphere. It appears that this transfer is favored at this season in the region of the Indian Ocean and the south-west monsoon. More generally, interhemispheric transfer in the troposphere (including the transfer in reverse direction), could possibly be inferred from the wind fields over this and other regions, according to season.

Misconceptions about the use of monsoons by dhows in East African waters

Abstract: The East African coast has had maritime contacts with the peripheral lands of the Arabian Sea from time immemorial, and although dhows have been superseded by steamships since the latter part of the nineteenth century, a few still visit East Africa every year. Unless they are equipped with engines, movement of these sailing craft is dependent upon the monsoonal regime of the western Indian Ocean. However, popular ideas about monsoons constitute major misconceptions. These relate to the southern extent of the reliable northeast monsoon employed for the outward journey to East Africa, and the use of the southwest monsoon for the homeward passage to Arabia, Iran and India. This article seeks to correct these misconceptions on the basis of meteorological conditions in the western Indian Ocean, substantiated where possible by empirical evidence, contemporary and historical.

Reversal of pressure gradients and wind circulation across India and the southwest monsoon

Abstract: This paper describes some features of the climatology of the free atmosphere over India which are related to the onset and withdrawal of the monsoon.

Hydrobiological features of the Kerala backwaters during premonsoon and monsoon months

Abstract: The hydrobiological features like temperature, salinity, phytoplankton, zooplankton and bottom fauna at twelve stations in the Vembanad lake during pre-monsoon and monsoon months were studied and the results communicated in this paper.

The structure of sea surface temperatures in monsoonal areas.

Abstract: : Time-dependent fluctuations of structure sizes of sea surface temperatures in the Indian Ocean and the Atlantic Ocean were determined by using three different methods of analysis: (a) graphical integration of isothermal structures, (b) computation of the structure function of temperature distributed along zonal bands across both oceans and (c) computation of energy spectra for temperatures distributed along these bands. Table 1 summarizes the main results of the investigation. Mean values of 156, 420, and 1190 km characterize structure sizes occurring most frequently in the Indian Ocean. The structure size of 420 km compares well with other independent observations: The dynamic topographies of the surface in the Arabian Sea exhibit cellular structures of similar dimensions. Satellite observations of sea surface temperatures off the Somali coast reveal isothermal structures with a diameter of approximately 450 km. Structures in the Atlantic Ocean possess mean values of 133, 370, and 1190 km, hence, do not deviate much from those in the Indian Ocean. The results for both oceanic areas not only display a high degree of similarity in structure sizes, but also indicate that large peaks in the energy spectra occur only during winter time. (Author)

Studies on precipitable water over tropical stations in relation to monsoon flow

Abstract: The mean monthly precipitable water at four tropical stations Madras (13°00′N, 80°11′E), Waltair (17°42′N, 83°18′E), Bombay (18°54′N, 72°49′E) and Nagpur (21°06′N, 79°03′E) are evaluated for the layer surface to 500 mb (0–5.4 km) of the atmosphere using radiosonde data available for seven years period (1959–1965). The mean monthly precipitable water for the above four stations is also estimated from dew point temperature. The precipitable water in the air column at any station is examined in relation to monsoon flow. The higher values of precipitable water are found to occur over the regions when there is good supply of moisture by the monsoon flow as well as low level convergence. These studies are believed to provide useful information in forecasting the monsoon circulation over the country.

Strontium 90 concentrations in surface air: North America versus Atlantic Ocean from 1966 to 1969

Abstract: Strontium 90 in surface air has been measured continually for three years, February 1966 to January 1969, at four North Atlantic Ocean weather stations to compare fallout processes over the ocean with those over land. Between 35°N and 55°N, concentrations over land were an average 1.1 times greater than those over the ocean. The relative concentration varied with both season and latitude, being greater in the north and during the summer. This variation seems to correlate better with monsoonal meteorological processes than with the suggested process of aerosol scavenging by ocean spray.

Climatological wave data for colombo, ceylon

Abstract: : Deep-water wave statistics for Colombo on the west coast of Ceylon have been compiled using the Sverdrup-Munk-Bretschneider wave-hindcast method applied to 12-hourly weather maps of the West Indian and South Atlantic Oceans for the one-year period from June 1968 through May 1969. Results of the wave- hindcast analysis are presented in the form of monthly and annual height-period- direction frequency distributions. The predominant waves are in the one to three foot height range, have periods centered about 13-14 seconds, and arrive from westerly to south-southwesterly directions. Wave action is most frequent in May through September and least in December. The wind waves and local swell on the west coast of Ceylon strongly reflect the seasonal Monsoons. The principal source of distant swell for this coast is the prevailing westerly wind belt of the Southern Hemisphere between Argentina and the longitude of Ceylon (80 degrees E). The subtropical anticyclone in the central Indian Ocean is a relatively quiet source region for swell compared to the Moonsoon belt and the prevailing westerlies.

Seasonal march of surface pressure gradients across India and the southwest monsoon

Abstract: It is well known that the seasonal weather features of Indian sub-continent are associated with corresponding changes in the pressure gradients across the country.

Nimbus 3 satellite observations of ozone associated with the easterly jet stream over India during the 1969 summer monsoon

Abstract: Nimbus 3 satellite observations of ozone associated with easterly jet stream over India during 1969 summer monsoon

The Monsoon Lands: India, East Pakistan and Ceylon

Abstract: The ‘monsoon lands’ is a term commonly used to describe a major world region which includes Pakistan, India, Ceylon, South-east Asia, China and Japan. This area contains half the world’s population and has a distinctive way of life marking it off from Europe and Africa, from which it is separated by a belt of arid lands. But although this may be a justifiable region on a world scale in terms of its agricultural way of life, in which paddy farming is predominant, it has little unity as an ecological region. Over much of the area the seasonal reversal of wind direction gives a marked concentration of rainfall in the summer and a virtually rainless winter and spring. But although monsoons determine the climate throughout the region, the climatic consequences are by no means uniform. In much of South-east Asia the dry season is very short, rainfall heavy and the natural vegetation tropical rain forest. This area has been discussed in Chapter 7, on the humid tropics. The monsoon lands, as commonly defined, stretch from 7°N. to 40°N. and show marked variations in temperature. Although summers are hot throughout the region, winters in northern China and Japan are cold.