Association of the Indian summer monsoon with the northern hemisphere mid-latitude circulation (original) (raw)
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A prominent pattern of year-to-year variability in Indian Summer Monsoon Rainfall
Proceedings of the National Academy of Sciences, 2012
The dominant patterns of Indian Summer Monsoon Rainfall (ISMR) and their relationships with the sea surface temperature and 850-hPa wind fields are examined using gridded datasets from 1900 on. The two leading empirical orthogonal functions (EOFs) of ISMR over India are used as basis functions for elucidating these relationships. EOF1 is highly correlated with all India rainfall and El Niño–Southern Oscillation indices. EOF2 involves rainfall anomalies of opposing polarity over the Gangetic Plain and peninsular India. The spatial pattern of the trends in ISMR from 1950 on shows drying over the Gangetic Plain projects onto EOF2, with an expansion coefficient that exhibits a pronounced trend during this period. EOF2 is coupled with the dominant pattern of sea surface temperature variability over the Indian Ocean sector, which involves in-phase fluctuations over the Arabian Sea, the Bay of Bengal, and the South China Sea, and it is correlated with the previous winter’s El Niño–Southern...
Dominant impact of South Asian low heat on summer monsoon rainfall over Central India
Arabian Journal of Geosciences, 2011
Although previous literature have considered Southern Oscillation Index (SOI), Indian Dipole, and SST as the major teleconnection patterns to explain the variability of summer monsoon rainfall over India. South Asia low pressure and Indian Ocean high are the centers of action that dominates atmospheric circulations in Indian continent. This paper examines the possible impact of South Asian low pressure distribution on the variability of summer monsoon rainfall of India using centers of action approach. Our analysis demonstrates that the explanation of summer monsoon rainfall variability over Central India is improved significantly if the SOI is replaced by South Asian low heat. This contribution also explains the physical mechanisms to establish the relationships between the South Asian low heat and regional climate by examining composite maps of large-scale circulation fields using NCEP/NCAR Reanalysis data.
Variability of Summer Monsoon Rainfall in India on Inter-Annual and Decadal Time Scales
Indian Summer Monsoon Rainfall (ISMR) exhibits a prominent inter-annual variability known as troposphere biennial oscillation. A season of deficient June to September monsoon rainfall in India is followed by warm sea surface temperature (SST) anomalies over the tropical Indian Ocean and cold SST anomalies over the western Pacific Ocean. These anomalies persist until the following monsoon, which yields normal or excessive rainfall. Monsoon rainfall in India has shown decadal variability in the form of 30 year epochs of alternately occurring frequent and infrequent drought monsoons since 1841, when rainfall measurements began in India. Decadal oscillations of monsoon rainfall and the well known decadal oscillations in SSTs of the Atlantic and Pacific oceans have the same period of approximately 60 years and nearly the same temporal phase. In both of these variabilities, anomalies in monsoon heat source, such as deep convection, and middle latitude westerlies of the upper troposphere over south Asia have prominent roles. Keywords: Indian monsoon rainfall variability, middle latitude westerly winds, Asia Pacific wave, global SST gradient Citation: Joseph, P. V., G. Bindu, A. Nair, et al., 2013: Variability of summer monsoon rainfall in India on inter-annual and decadal time scales, Atmos. Oceanic Sci. Lett., 6, **,
The aim of the present study is to find out the possible linkage between the North Atlantic Oscillation (NAO), a major ocean–atmosphere coupled phenomena believed to be responsible for the variability of Indian Summer Monsoon Rainfall (ISMR) and its relation with Quasi-Biennial Oscillation (QBO) using 60 years (1953–2012) period. Spring North Atlantic Oscillation Index (NAOI) has been found to be inversely correlated with the ISMR, which has been highly enhanced during the east years when the NAOI data have been stratified according to the phases of QBO. The effect of NAOI on the ISMR is shown to be strengthening significant in the later years of the study as compared to that of the initial years of the study. This interesting result provides an input to use it as a predictor of the ISMR.
Climate Dynamics
This observational study during the 29-year period from 1979 to 2007 evaluates the potential role of Eurasian snow in modulating the North East-Indian Summer Monsoon Rainfall with a lead time of almost 6 months. This link is manifested by the changes in high-latitude atmospheric winter snow variability over Eurasia associated with Arctic Oscillation (AO). Excessive wintertime Eurasian snow leads to an anomalous cooling of the overlying atmosphere and is associated with the negative mode of AO, inducing a meridional wave-train descending over the tropical north Atlantic and is associated with cooling of this region. Once the cold anomalies are established over the tropical Atlantic, it persists up to the following summer leading to an anomalous zonal wave-train further inducing a descending branch over NE-India resulting in weak summer monsoon rainfall.
Journal of Climate, 2015
A diagnostic analysis reveals that on the interannual time scale the southeast–northwest movement is a dominant feature of the South Asian high (SAH), and it is closely related to the Indian and East Asian summer monsoon rainfall. The southeastward (northwestward) shift of the SAH is closely related to less (more) Indian summer monsoon rainfall and more (less) rainfall in the Yangtze River valley (YRV) over the East Asian summer monsoon region. An anomalous AGCM is utilized to examine the effect of latent heat anomalies associated with the Asian summer monsoon rainfall on the SAH. The negative latent heat anomalies over the northern Indian Subcontinent associated with a weak Indian summer monsoon stimulates an anomalous cyclone to its northwest and an anticyclone to its northeast over the eastern Tibetan Plateau and eastern China in the upper troposphere, which is responsible for the east–west shift of the SAH and more rainfall in the YRV. The positive latent heat release associated...
Land surface conditions over Eurasia and Indian summer monsoon rainfall
Journal of Geophysical Research, 2003
1] Using observations of snow cover, soil moisture, surface air temperature, atmospheric circulation, and Indian summer monsoon precipitation from 1870 to 2000, we examine the relationship between interannual variations of the strength of the monsoon and land surface conditions over Eurasia. For the periods 1870-1895 and 1950-1995, strong Indian summer monsoon precipitation was preceded by warmer than normal temperatures over Europe and North America in the previous winter and over western Asia in the previous spring but colder temperatures over Tibet. The European temperature anomalies were related to the positive phase of the North Atlantic Oscillation (NAO). Related negative snow cover anomalies in Europe in winter and central Asia in spring were produced by circulation and temperature anomalies. The snow-albedo feedback is always operating, but the snow by itself did not physically control the monsoon. Anomalous snow cover impacts on temperature were not prolonged by soil moisture feedbacks because of its short time memory, and there was no obvious relationship between soil moisture and the monsoon. Strong Indian summer monsoon precipitation was actually preceded by higher than normal Tibetan snow cover in winter and spring in contrast to the suggestion of Blanford [1884] more than a century ago. The correlation between Indian summer monsoon rainfall and winter land temperatures and snow cover only exists when interannual variation of the NAO is very strong, and therefore NAO is not a robust predictor of the monsoon. Climate models show that the relationship between NAO and monsoon is random. Land surface conditions over Eurasia and Indian summer monsoon rainfall,
Indian summer monsoon rainfall and its link with ENSO and Indian Ocean climate indices
International Journal of Climatology, 2007
We examine the relationship between the state of the equatorial Indian Ocean, ENSO, and the Indian summer monsoon rainfall using data from 1881 to 1998. The zonal wind anomalies and SST anomaly gradient over the equatorial Indian Ocean are used as indices that represent the condition of the Indian Ocean. Although the index defined by the zonal wind anomalies correlates poorly with Indian summer monsoon rainfall, the linear reconstruction of Indian summer monsoon rainfall on the basis of a multiple regression from the NINO3 and this wind index better specifies the Indian summer monsoon rainfall than the regression with only NINO3. Using contingency tables, we find that the negative association between the categories of Indian summer monsoon rainfall and the wind index is significant during warm years (El Niño) but not during cold years (La Niña). Composite maps of land precipitation also indicate that this relationship is significant during El Niño events. We conclude that there is a significant negative association between Indian summer monsoon rainfall and the zonal wind anomalies over the equatorial Indian Ocean during El Niño events. A similar investigation of the relationship between the SST index and Indian summer monsoon rainfall does not reveal a significant association.
Climate Dynamics, 2012
Variability of the Indian summer monsoon is decomposed into an interannually modulated annual cycle (MAC) and a northward-propagating, intraseasonal (30-60-day) oscillation (ISO). To achieve this decomposition, we apply multichannel singular spectrum analysis (M-SSA) simultaneously to unfiltered daily fields of observed outgoing long-wave radiation (OLR) and to reanalyzed 925-hPa winds over the Indian region, from 1975 to 2008. The MAC is essentially given by the year-to-year changes in the annual and semi-annual components; it displays a slow northward migration of OLR anomalies coupled with an alternation between the northeast winter and southwest summer monsoons. The impact of these oscillatory modes on rainfall is then analyzed using a 1-degree gridded daily data set, focusing on Monsoonal India (north of 17°N and west of 90°E) during the months of June to September. Daily rainfall variability is partitioned into three states using a Hidden Markov Model. Two of these states are shown to agree well with previous classifications of "active" and "break" phases of the monsoon, while the third state exhibits a dipolar east-west pattern with abundant rainfall east of about 77°E and low rainfall to the west. Occurrence of the three rainfall states is found to be an asymmetric function of both the MAC and ISO components.