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Summer Monsoon Rainfall (summer + monsoon_rainfall)

Distribution by Scientific Domains

Earth and Environmental Science	87%

Selected Abstracts

Large-scale summer monsoon rainfall over India and its relation to 850 hPa wind shear

HYDROLOGICAL PROCESSES, Issue 15 2007
V. S. Prasad
Abstract The daily variations of the horizontal wind shear at the 850 hPa level between a southern region (5,15°N, 40,80°E; Zone 1) and a northern region (20,30°N, 70,90°E; Zone 2) during the period 1979,2002 were investigated. Investigations revealed that the changes of this wind shear on a daily basis are directly related to the large-scale rainfall over the Indian region during the monsoon season. The wind shear of zonal wind together with Zone 2 is useful for determining active, weak and break periods of the Indian summer monsoon (ISM). Thus, the Horizontal Wind Shear can be used as a dynamical circulation Index (HWSI) for studying ISM variability. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A study on the effect of Eurasian snow on the summer monsoon circulation and rainfall using a spectral GCM

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2006
S. K. Dash
Abstract Many studies based on observed data indicate the inverse relationship between the Eurasian snow cover/depth and the Indian summer monsoon rainfall (ISMR). The purpose of this study is to confirm the inverse snow,ISMR relationship by using the observed snow depth data as boundary conditions in the spectral general circulation model (GCM) of Indian Institute of Technology, Delhi (IITD), and to examine the influence of Eurasian snow depth on the monsoon circulation. The original model belonging to the European Centre for Medium range Weather Forecasts (ECMWF) at resolution T21 has been modified extensively to a higher resolution of T80L18 at IITD. A two-dimensional Lanczos digital filter has been used to represent the orography realistically. The Historical Soviet Daily Snow Depth (HSDSD) version II data set has been used for conducting sensitivity experiments using the above model. Two sensitivity experiments have been designed, corresponding to two contrasting cases: one with high Eurasian snow depth in spring followed by deficient ISMR and the second with low snow depth followed by excess ISMR. The difference fields of mean monsoon circulation simulated in the above two experiments are examined in detail in order to confirm the influence of Eurasian snow depth on ISMR and to examine the Asian summer monsoon circulation and rainfall. Copyright © 2006 Royal Meteorological Society [source]

Lagged teleconnections between snow depth in northern Eurasia, rainfall in Southeast Asia and sea-surface temperatures over the tropical Pacific Ocean

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2001
Hengchun Ye
Abstract This study shows that above-(below-)normal winter snow depth over European Russia and corresponding below-(above-)normal snow depth over central Siberia is associated with reduced (increased) summer monsoon rainfall over southern and western India and eastern Pakistan, and above-(below-)normal sea-surface temperatures (SSTs) over the eastern and central tropical Pacific Ocean during the following winters. The connection is slightly stronger when snow depth over European Russia is above normal than below normal. These results are derived from an examination of 60 years (1936,1995) of winter snow depth data and SSTs, and 45 years (1951,1995) of summer precipitation records. The results of this study suggest that winter snow depth over the western rather than the eastern portion of Eurasia is critical to Southeast Asian summer monsoon rainfall and eastern tropical Pacific SSTs during the following seasons. Copyright © 2001 Royal Meteorological Society [source]

Ocean-atmosphere-land feedbacks in an idealized monsoon

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 576 2001
C. Chou
Abstract An intermediate-complexity atmospheric model coupled with a simple land-surface model and a mixed-layer ocean model is used to investigate the processes involved in an idealized monsoon occurring on a single rectangular continent. Idealized divergences of ocean heat transports are specified as an annual average ,Q-flux'. In this simple coupled configuration, the mechanisms that affect land-ocean contrast and, in turn, the seasonal movement of the continental convergence zones are examined. These include soil-moisture feedbacks: cooling of tropical oceans by ocean transpoit; ventilation, defined as the import into continental regions of low moist static-energy air from ocean regions where heat storage opposes summer warming; and the ,interactive Rodwell-Hoskins mechanism', in which Rossby-wave-induced subsidence to the west of monsoon heating interacts with the convection zone. The fixed ocean transports have a substantial impact on the continental convection. If Q-flux is set to zero, subtropical subsidence and ventilation tend to substantially limit the poleward movement of summer monsoon rainfall. When land hydrology feedbacks are active, the drying of subtropical continents disfavours continental convection even in the tropics. When ocean transports are included, tropical oceans are slightly disfavoured as regions for producing convection which, by contrast, favours continental convection. The monsoon circulation then produces moisture transport from the ocean regions that allows substantial progression of convection into the subtropics over the eastern portion of the continent. The western portion of the continent tends to have a dry region of characteristic shape. This east-west asymmetry is partly due to the interactive Rodwell-Hoskins mechanism. The ventilation is of at least equal importance in producing east-west asymmetry and is the single most important process in limiting the poleward extent of the continental convection zone. [source]

Trend analysis of Indian summer monsoon rainfall at different spatial scales

ATMOSPHERIC SCIENCE LETTERS, Issue 4 2009
Subimal Ghosh
Abstract The results obtained from a conventional trend analysis of the Indian summer monsoon rainfall over a larger region are contradicted when analysis is performed at a finer resolution because of spatial variability and heterogeneity in the rainfall pattern. The present study analyzes the trend of summer monsoon rainfall all over India at a finer spatial resolution (1° latitude × 1° longitude) to identify the places that have a significant trend in terms of both rainfall amount and occurrence. The results obtained from this study are compared with those of a recent study by Goswami et al. (2006), where trend analysis is performed over a larger region [Central India (CI); 10° latitude × 12° longitude; assumed to be homogeneous in that study]. The increasing trend of occurrence of heavy rainfall and decreasing trend of occurrence of moderate rainfall, as concluded from that study, are contradicted by the present results for some places in CI. The present analysis shows spatially varying mixed responses of global warming toward rainfall occurrence and amounts all over India. The perception of increase in daily rainfall amount and occurrence due to climate change is found to be not correct for some of the regions in India. The possible reason may be the spatial variability of local changes such as rapid urbanization, industrialization and deforestation. Copyright © 2009 Royal Meteorological Society [source]