Showing papers on "Monsoon published in 1974"

Southwestern United States Summer Monsoon Source—Gulf of Mexico or Pacific Ocean?

Abstract: Moist air from the tropics moves into northwest Mexico and the southwestern portion of the United States during the early part of the summer season. This is analogous to the monsoon circulation in other sections of the globe. The annual change in circulation has been related to the northward and westward development of the large subtropical high pressure system over the southern United States. With this change the moist tropical air over the Gulf of Mexico is believed to be carried across Mexico and into the southwestern United States. The mountains of Mexico provide a formidable barrier for the movement of the Gulf of Mexico moisture westward. It has been shown that half of the precipitable water vapor in the atmosphere over the Arizona deserts in the summer months is below the 800-mb level. This is inconsistent with the idea of the Gulf of Mexico supplying the greatest proportion of the moisture. This paper presents support for the greatest percentage of tropical moisture in the southwest Unite...

Limnological studies on freshwater ponds of Hyderabad — India

Abstract: Seasonal abundance of phytoplankton has been discussed in three tropical ponds of Hyderabad, India during two years of investigation. The observed patterns have been characterized as seasonal maxima and minima during summer, monsoon and winter. The tropical patterns observed in the study ponds were typical but different from those observed in temperate regions. Most of the maxima were observed in winter and the minima during the monsoon or rainy season. Diatomeae dominated the phytoplankton of all the ponds in all seasons. An inverse relationship between Diatomeae and Cyanophyta, and Diatomeae and Euglenineae was observed. The phytoplankters have been grouped as perennial, summer, monsoon and winter species.

Vegetation and Phytogeography of the Western Ghats

Abstract: This chapter attempts to present on outline of the characteristic vegetation and phytogeographical peculiarities of the Western Ghats. The general features of the Western Ghats, the geological structure and tectonic history and the climatic characters of the region are discussed in sufficient detail by specialists in earlier chapters of this book. From the stand point of the present chapter, we may appropriately describe the Western Ghats as an important part of the monsoonland, where the vegetation is influenced more by the abundance and distribution of the seasonal rainfall than the atmospheric temperature. The western side of the Western Ghats is on the threshold of southwest monsoon and receives a rainfall of 203–254 cm, and the eastern side lies in the rain-shadow area of the Peninsula. The main types of soils met with in the Western Ghats are red soils, laterites, black soils and humid soils. The red soils are developed on the Archean crystallines and are brown, grey or black, is deficient in organic matter, phosphoric acid and nitrogen. Evergreen forest of Calophyllum, Dipterocarpus, Hopea, Myristica and Xylia are characteristic of red-soil areas. The laterites consist of 90–95% of iron, aluminium, titanium and manganese oxides and are deficient in lime and organic material, an extend up to 1600 m in the Western Ghats. Shorea and Xylia are the dominant species in lateritic soils of Western Ghats. Black soils, formed out of the basaltic Deccan lava, are deficient in organic matter, nitrogen and phosphoric acid, but generally have enough lime and potash.

Mud Banks of Kerala-Their Formation and Characteristics

Abstract: Mud banks become clearly demarcated as areas of calm water adjoining the Kerala coast, during the roughest SW monsoon conditions prevailing in the Arabian Sea The appearance of mud banks is associated with an increase in the constancy and force of wind towards the east Surface currents at that time run parallel to the coast and record -maximum velocity During June and July, strong swells approach the SW coast Along the continental shelf, between Mangalore and Quilon, the nature of bottom from about 3•5 to 18 m depth is largely muddy Mud banks occur as small elevations of consolidated mud throughout the year

Some aspects of the Arabian sea summer monsoon

Abstract: Some of the observed features of the Arabian sea summer monsoon, such as the formation of a low-level highspeed aircurrent, strengthening of the intertropical convergence zone over northeastern Arabian sea and formation of a secondary convergence zone over southeastern Arabian sea, changing patterns of cloud distributions and formation of double cloud bands over eastern Arabian sea and rainfall discontinuities along the west coast of India between July and August are discussed in relation to possible complex transformations of airmasses that cross the Arabian sea with a continually changing pattern of surface temperature during period May through August. It is hypothesised that following coastal upwelling in Somalia and Arabia during late May or early June, a wedge of cold water is advected across central Arabian sea by the southwestmonsoon current and that it is the feed-back effect of this advection upon the atmosphere that may be largely responsible for the observed monsoon features. DOI: 10.1111/j.2153-3490.1974.tb01624.x

A preliminary experimental simulation on the heating effect of the tibetan plateau on the general circulation over eastern asia in summer

Abstract: In summer the Tsinghai-Tibetan Plateau is a giant heat source. It has important influence on the circulation over Eastern Asia. This has been studied synoptically in many aspects. In the present paper we simulate this effect in a rotating annulus. A semi-ellipsoidal body is used for simulating the Tsinghai-Tibetan Plateau. The rcsistance wires are buried under its surface for hcating the plateau.Our experiments show that some of the important features of the summer circulation over Eastern Asia such as the heat low and the huge high in the lower and upper levels respectively over the plateau, northward retreat of the strong westerlies therc in summcr, the building of the easterlies in the upper troposphere and the monsoon meridional circulation (in revcrsed direction of Hadley circulation) to the south of it, are all internally related. The key-point in their relation is the heat source of the plateau. It is also seen in our expcriment that the southwest monsoon and even the northward push of rainfall belt in summer over China may also be related to this heat source.The main agents for the upward transport of heat from the heat source are the strong convective wcather systems. Thcre is also some indication in our experiment that these medium and small-scale convective systems are responsible for the maintenance of the large-scale circulation over the platcau.urther, the synoptic experience of the slowing down of the long trough as well as its cut-off by the plateau has also been simulated in our experiment.

Monsoonal Influences on the Annual Variation of Tropical Cyclone Development over the Indian and Pacific Oceans

Abstract: Except for parts of the northwest Pacific, Indian Ocean and Pacific Ocean hurricanes always begin to develop in troughs located at high enough latitudes for low-level westerly winds to be observed on their equatorial sides. These near-equatorial troughs coincide with axes of maximum sea surface temperature, and in this respect they resemble continental heat troughs. Oceanic near-equatorial troughs follow the march of the sun. Generally, the farther they are from the equator the more often do hurricanes begin to form in them. The meridional rate of trough movement depends on the rate of ocean surface heating. Seas east and equatorward of the continents. Through the spring, continental heating rapidly diminishes the equatorward winds of winter, reducing evaporational cooling of the sea surface and mixed-layer depth. The consequent sea surface temperature rise brings the near-equatorial troughs poleward and starts the hurricane season only. In the height of summer, monsoon winds by increasing evapor...

Southwestern United States Summer Monsoon Source—Gulf of Mexico or Pacific Ocean?

Abstract: Moist air from the tropics moves into northwest Mexico and the southwestern portion of the United States during the early part of the summer season. This is analogous to the monsoon circulation in other sections of the globe. The annual change in circulation has been related to the northward and westward development of the large subtropical high pressure system over the southern United States. With this change the moist tropical air over the Gulf of Mexico is believed to be carried across Mexico and into the southwestern United States. The mountains of Mexico provide a formidable barrier for the movement of the Gulf of Mexico moisture westward. It has been shown that half of the precipitable water vapor in the atmosphere over the Arizona deserts in the summer months is below the 800-mb level. This is inconsistent with the idea of the Gulf of Mexico supplying the greatest proportion of the moisture. This paper presents support for the greatest percentage of tropical moisture in the southwest Unite...

Radon concentration of air over the Eastern Arabian Sea

Abstract: The radon concentrations of air samples collected during the South West monsoon period at altitudes up to 4 km over the Arabian Sea at two locations,i.e., 0–50 km and 300–400 km west of Bombay, are reported. Radon was extracted from air, using a simple single stage apparatus. The concentration of radon in the monsoon air mass was found to range around 80–100 dpm/m3 STP, indicative of its recent continental origin. The results suggest that the coastal monsoon air mass, up to 400 km west of Bombay coast, is generally homogeneous and vertically well mixed.

India and the Indian Ocean

Abstract: security system is the vulnerability of her coast. The weakness emerged with the decay of the ancient Hindu maritime tradition ending with the Cholas in the 12th Ccntury. Islam, did nothing to sustain the curiosity of the Indian people about lands beyond her coast. The Moghuls always feared overland invasion from Persia. Imperial Britain found no European naval power strong enough to disturb them. The

China's Claim to South China Sea Islands

Abstract: IN LATE JANUARY this year the Chinese military engaged South Vietnamese forces in combat over control of the Paracel Islands in the South China Sea. Subsequently Peking reiterated and underscored its claim to these as well as other islands in the area. It also proclaimed its ownership to a large area of the sea extending west to the Philippines and south to Brunei and Malaysia. Peking’s actions seem bizarre in view of the fact that China seeks leadership of the small, underdeveloped countries of the world and criticizes &dquo;big power chauvanism.&dquo; China has cultivated an image of friend,

Cloud Cover over the Intertropical Indian Ocean

Abstract: Satellite observations of cloud cover have been used to compile average daily cloud charts for the intertropical Indian Ocean in 1967 and 1968. Annual, semiannual, seasonal and monthly averages have been examined to identify the major features of cloud distributions. Trend surface coefficients for average cloud cover have also been calculated, partly to aid comparisons between different periods, and partly as an experiment to determine their applicability to such problems. The greatest variations in cloud cover have been found to occur over the northern part of the Indian Ocean; three relatively cloud-free zones persisted throughout both years, as did a broad corss-equatorial belt of relatively large cloud amounts; considerable variations were apparent in cloud cover associated with the south-west monsoon; and there was evidence for inter-hemispheric linkages both before and during the south-west monsoon season.

Major climatological discontinuities in the monthly activity of the summer monsoon over Asia

Abstract: It is well known that the activity of the summer monsoon, as measured by rainfall, undergoes variations from one month to another. In this study, the monsoon activity has been examined in detail to find if any major climatological discontinuities in the activity exist in the field of the Asian summer monsoon. From amongst the possible criteria for major discontinuity, the criterion based on the lower and the upper quartiles has been selected. The study brings out that major climatological discontinuities do exist over some parts of Asia. These are (i) a marked decrease in activity from July to August, right in the middle of the monsoon season, over the west coast of India, between Bombay and Trivandrum; (ii) a marked decrease from August to September over a small portion of the Indian west coast in the neighbourhood of Mangalore; (iii) a marked decrease from August to September over the Arakan coast; and (iv) a marked increase from August to September over the Viet Nam coast. Possible causes of these discontinuities have been discussed.

Seasonal Variation of Ichthyoplankton in the Arabian Sea in Relation to Monsoons

Abstract: The seasonal variation of ichthyoplankton of the Arabian Sea based on the 694 Zooplankton samples collected during the International Indian Ocean Expedition has been discussed in the light of the hydrographical features caused by monsoons. The pattern of distribution of total fish eggs showed that the highest degree of concentration was at the northeastern and southwestern parts of Socotra Island, areas off Kutch and Gujarat, Kerala coast, south of Ceylon and Chagos archipelago. The lowest concentration was noticed in the central part of the Arabian Sea. During the southwest monsoon season there was a slight reduction in these areas of high concentration. During the northeast monsoon, however, the northeastern half of the Arabian coast was changed into an area of lowest density. The areas of high concentration along the west coast of India were retained without much change. In the case of total fish larvae the highest density was noticed in the middle of the Red Sea, also near Aden, around Socotra Island, the Arabian and southern Somali coasts, off Kutch and Bombay, along the Malabar coast, south of southern India and Ceylon, in addition to a few places along the equatorial region. The lowest density was noticed in the central part of the Arabian Sea.

The Changing Climate through the Period of Meteorological Records and the Historical Past in Japan and Some Conciderations about the Cold Climate in the Alluvial Epoch

Abstract: The Far East monsoon regime is a consequence of the interaction of both planetary and regional factors. When the westerlies over the Eastern Hemisphere are weak in winter, the stational trough of the planetary wave, which is located normally in the neighborhood of the Japanese islands, tends to retreat in the Japan Sea side, producing the monsoonal climate, that is to say, the lower air temperatures in the south-western Japan and more snowy winter in the Hokuriku District. On the contrary, when the westerlies become stronger, the trough moves across the Japan Island to the Pacific side, resulting the non-monsoonal winter climate, warm winter in the southwestern Japan, less snowy in the Hokuriku District and more rainy in the Pacific coast. In summer, the trough, which is normally located farther west in the Japan Sea, moves westwards or eastwards, corresponding to the weaker or stronger westerlies, and produces hot-dry summers or cool-rainy summers in Japan. In other words, the winter and summer monsoons in the Far East change their vigor in contrast with the intensity of the prevailing westerlies throughout the year, and this is the reasons why the cold-snowy (warm-less snowy) winters correspond to hot-dry (cool-rainy) summers, and the curve of 11-year running means of the annual means of wind speeds at the summit of Mt. Fuji (3782m) changes opposite to those of the annual amplitude of air temperatures at various points in the central Japan.Through the rhythm of the decade means of summer air temperatures in the north-eastern Japan and the running means of the amount of January precipitations on the Japan Sea coast, a significant trend of long-term change is noticable, which must be attributed to the north-southward displacement of the climatic zone. The northward shift or the southward retreat of the climatic zone generally appears in company with the weak or vigorous state of the prevailing westerlies.Consequently, in the case of Japanese climate, the effect of the Far East monsoons on the winter climate, for instance, the lowering or rising air temperatures due to the change of the Far East monsoon, objects to the effect influenced by the north-southward displacement of climatic zone, while, in summer, both effects cooperate with each other.However, in the estreme cases of the displacement of the climatic zone, the global effect exceeds the regional effect of the Far East monsoons, producing the extreme case of“Little Climatic Optimum” with warm-less snowy winters and hot-dry summers and the extreme case of“Little Ice Age”with cold-snowy winters and cool-rainy summers.It is beyond question that the most favorable condition for the accumulation of snow and ice must be the extreme case of“Little Ice Age”distinguished with much snowfalls, lower air temperature in all seasons, and rainy summers associated by the reduced durations of sunshine. The climate in the first half of XV Century, for instance, is estimated to be the extreme case of“Little Ice Age”from the various records of decuments. In accord with the estimation, the 14C dating test on the wood which was discovered by Horie (1968) in the outwash deposit of Shirouma Kitamata (1620M) gives 520±80 years B. P. Howeve, the duration of extreme period of“Little Ice Age”is not so long as far as it concerns within historical times. The climate of (warm-winter)-(cool-summer), which is caused by the predominant westerlies and distinguished with the intensified activities of Lows in the surroundings of the Japan Island, is also favorable, to a certain exextent, for the accumulation of snow.

Spectrum analysis of tropical waves in the Indian Ocean.

Abstract: An attempt has been made to identify tropical waves with periods less than 20 days in the Indian Ocean by spectrum analysis of radiosonde data for five stations, widely scattered over the Indian Ocean area. The data used is for the period from January to September, 1973, which was further divided into two five-month seasons, overlapping in May due to consideration of the monsoonal shift in the mean flow. Three spectral peaks in the 10-17 day, 6-7 and 4-5 day ranges have been detected. However, only the 10-17 day fluctuations seem to be prominent and appear consistently at all stations in both seasons. Cross-spectrum analysis reveals a basically in-phase structure in the vertical in the lower troposphere and reversed phase at upper levels. Evidences also indicate a northwest-southeast tilt in the Northern Hemisphere and a northeast-southwest tilt in the Southern Hemisphere. Inter-station cross-spectra and theoretical considerations suggest an estimated horizontal wavelength of approximately 3,000 km with a westward propagation direction. Due to the limited number of available stations and the quality of data, these results are considered tentative and further study in this area is suggested.