Monsoon and ENSO: Selectively interactive systems

Webster, Peter J.; SONG, YANG,

doi:10.1256/smsqj.50704

Cited by 368 publications

(489 citation statements)

References 0 publications

Supporting

Mentioning

467

Contrasting

Unclassified

Order By: Relevance

“…On interannual time scales the SAM is modulated by El-Niño Southern Oscillation (ENSO) (e.g., Walker 1924;Rasmusson and Carpenter 1983;Webster and Yang 1992;Goswami 1998;Fasullo and Webster 2002). However, the ENSO monsoon relationship has became weaker in the recent decades (Krishna Kumar et al 1999;Torrence and Webster 1999;Kinter et al 2002), and Kucharski et al 2008 linked these deviations in the ENSO monsoon relationship with the sea surface temperature (SST) over the southern equatorial tropical Atlantic.…”

Section: Introductionmentioning

confidence: 99%

Extratropical influences on the inter-annual variability of South-Asian monsoon

et al. 2011

View full text Add to dashboard Cite

The effects of extratropical dynamics on the interannual variations in South-Asian Monsoon (SAM) are examined. Based on NCEP/NCAR reanalysis and CRU precipitation data, a conditional maximum covariance analysis is performed on sea level pressure, 200 hPa geopotential heights and the SAM rainfall by removing the linear effects of El-Niño Southern Oscillation from the fields. It is found that two modes provide a strong connection between the upper-level circulation in the Atlantic/ European region and SAM rainfall: the Circumglobal Teleconnection (CGT) and the Summer North Atlantic Oscillation (SNAO). The structures in the 200 hPa heights of both modes in the Atlantic region are similar in the Atlantic region, and their southeastward extension to South Asia (SA) also corresponds to upper-level ridges (in their positive phases) in slightly different positions. Nevertheless, the influence of both modes on SAM rainfall is distinct. Whereas a positive CGT is related to a widespread increase of rainfall in SAM, a positive SNAO is related to a precipitation dipole with its positive phase over Pakistan and the negative phase over northern India. The physical mechanisms for the influence of CGT and SNAO on SAM are related to the upper-level geopotential anomaly which affects the amplitude and position of the low-level convergence. The small displacements of the centers of these responses and the low level cold advection from the north east of SA in case of SNAO explain the differences in the corresponding SAM rainfall distributions. These findings are confirmed with the relatively high-resolution coupled climate model EC-Earth, which gives confidence in the physical basis and robustness of these extratropical variability modes and their influence on the South-Asian monsoon rainfall.

show abstract

Section: Introductionmentioning

confidence: 99%

Extratropical influences on the inter-annual variability of South-Asian monsoon

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Webster and Yang [9] pointed out that precipitation, temperature and wind field are three important parameters reflecting monsoon activities , and that information about wind fields may provide a better understanding for these. Previous studies on isotopic behaviors have focused on temperature and amount effects but few have been related to the influence of atmospheric wind.…”

Section: Resultsmentioning

confidence: 99%

Positive correlation between δ18O in monsoon precipitation and atmospheric wind speed

Pang

Zhang

2004

Chin. Sci. Bull.

View full text Add to dashboard Cite

Analyzed results of the atmospheric wind speed and stable isotopic data (6 18 0) in summer precipitation at Bangkok, Bombay, New Delhi, Kunming and Lhasa, the IAEAlWMO stations, indicate that 6 18 0 in monsoon precipitation correlate positively to wind speed and that there exists a monsoonal vapor layer over these monsooncontrolled areas during monsoon seasons. The isotopic exchange happens between monsoon vapors and falling raindrops in the layer, resulting in this correlation between 6 18 0 and wind speed. This suggests that wind speed is probably one of key factors affecting the 6 18 0 variation besides air temperature and rainfall in the southwest monsoon domain.Stable isotopic contents in precipitation have widely varied at most IAEAIWMO stations. Dansgaard[l] suggested that the amount effect, a negative correlation between isotopic ratio and precipitation amount, is apparent in low tropical regions, whereas the isotopic variations in high-latitude regions are ascribed to the temperature effect, a positive correlation between air temperature and isotopic composition. However, both effects exist in mid-latitude regions. In the past a few decades, much attention has been paid to the amount effect in mid-latitude monsoonal regions where the intense atmospheric convective processes are prevailing [l,2]. Because the 5 18 0 value in accumulatively condensed waters in cloud is the weighted mean value from different vapor-condensation stages [3,4], precipitation amount can reflect vapor's condensation conditions in cloud, resulting in an amount effect. However, the southwestern monsoon is a typical coupled air-land-sea system caused by exterior forcing factors (e.g. landform, thermal discrepancy between land and sea, ENSO, sun activities, etc.) and interior oscillation system in the atmosphere [5]. Because monsoonal activities result in the complex meteorological conditions for a single precipitation event, amount effect or temperature effect may not be an only explanation for isotopic variation in monsoon precipitation in mid-latitude regions, where isotopes 938 may vary in some particular mamIers under the monsoonal climatic condition.Studies on stable isotopes in relation to the hydro-cyclic system started in early 1950s [6]. Isotopic investigations in precipitation have been made since 1961, on the basis of worldwide network of hydrogen and oxygen isotopes in precipitation established by the International Atomic Energy Agency (lAEA) and World Meteorological Organization (WMO), with about 550 IAEAlWMO stations in different parts of the world. The network has provided reliable evidence for studying global and local hydro-cyclic systems and given a new angle to study isotopic variation in precipitation under the background of monsoonal climate. In order to reveal the relation between atmospheric wind speed and isotopic variation under monsoonal circumstance, the data of wind speeds and 5 18 0 in summer precipitation at the IAEAlWMO stations, Bangkok, Bombay, New Delhi, Kumning and Lhasa (Fig. 1), is collected and ...

show abstract

“…Various monsoon indices and their correlation with IMR for JJAS seasonal means. A. WEBSTER-YANG defined originally in Webster and Yang (1992); statistics above from WANG and FAN (1999 the NINO3 SST index and IMR, but is stronger. Both show modest (but significant) negative correlation when NINO3 leads PC-1 (or IMR) by one-two months, and stronger negative correlations when PC-1 (or IMR) leads NINO3.…”

Section: Discussionmentioning

confidence: 99%

The Preferred Structure of the Interannual Indian Monsoon Variability

Straus

Krishnamurthy

2007

Pure appl. geophys.

View full text Add to dashboard Cite

The leading empirical orthogonal function (EOF) of the June-Sept. mean, rotational horizontal wind at 850 hPa and 200 hPa (over the region 12.5°S-42.5°N, 50°E-100°E) from 56 years of reanalysis (from the National Centers for Environmental Prediction) shows strong anticyclonic circulation at upper levels, strong Indian Ocean cross-equatorial flow and on-shore flow over western India at lower levels . The associated principal component (PC) is correlated at the 0.75 level with the seasonal mean observed Indian Monsoon rainfall (IMR). Composite differences of vertically integrated divergence (surface to 800 hPa) and vorticity (surface to 500 hPa) between ''strong'' years (PC-1 exceeds one standard deviation r) and ''weak'' years (PC-1 less than ) r) suggest increased rising motion and storminess over the Bay of Bengal and central India. Composite difference maps of station rainfall from the India Meteorological Department (IMD) between strong years and normal years (weak years and normal years) are statistically significant over central India, with strong (weak) years associated with increased (decreased) precipitation. In both cases the maps of rainfall anomalies are of one sign throughout India. The correlation of PC-1 with global seasonal mean SST is strong and negative over the eastern equatorial Pacific, but positive in a surrounding horse-shoe like region. Significant negative correlation occurs in the northwestern Indian Ocean. The lag/lead correlation between the NINO3 SST index and PC-1 is similar to but stronger than the NINO3/IMR correlation. Modest (but significant) negative correlation is seen when NINO3 leads PC-1 (or IMR) by one-two months. Strong negative correlation is seen when PC-1 (or IMR) leads NINO3. The projections of running five-day means of horizontal rotational winds at 850 and 200 hPa onto EOF-1 (after removing the seasonal mean for each year) were pooled for strong, normal and weak years. The strong and normal year probability distribution functions (pdfs) are nearly indistinguishable, but the weak year pdf has more weight for moderate negative values and in both extreme tails and shows some hint of bi-modality.

show abstract

Monsoon and ENSO: Selectively interactive systems

Cited by 368 publications

References 0 publications

Extratropical influences on the inter-annual variability of South-Asian monsoon

Extratropical influences on the inter-annual variability of South-Asian monsoon

Positive correlation between δ18O in monsoon precipitation and atmospheric wind speed

The Preferred Structure of the Interannual Indian Monsoon Variability

Contact Info

Product

Resources

About