how ENSO helps to predict the nature of Indian monsoon
Answers
Explanation:
There are many theories proving the significant simultaneous co-variability of ENSO and Indian Monsoon [Rasmusson and Carpenter 1982, Walker 1924 & Webster 1998]. Its the subsiding limb of the walker cell which is shifted over India due to shift in the SST warming regions form West to East and Central Pacific ocean.
As Andy Turner (Sir) told that people have observed a weakening in the relationship in the recent times. Studies by Rajagopalan et al (2006) where they show how the pronounced warming over central Pacific is more likely to produce drought creating subsidence over India as compared to the El-Ninos when warming is more in the eastern Pacific regions. Krishna Kumar et. al (1999) showed that due to the southeast ward shift in the walker circulation for the recent El-Ninos subsidence, weak subsidence was produced over Indian region and That is why ENSO-Monsoon relationship show a weakening in the trend for the recent period.
To me, everything above put together does not give a clean insight of how El-Nino affects Indian monsoon.
Though there are other school of thoughts as well which to me seem more promising as compared to theories given earlier. In a pioneering study done by Goswami and Xavier 2005 (GRL) it was proved that ENSO does affect the Indian monsoon by affecting the troposheric temperature gradient over the Indian monsoon region. Which ends up as the weak lower level monsoon flow and length of the long rainy season (LRS) is also altered by late onset and early withdrawal of Indian monsoon during ENSO years.
Recently (2007) Shaman and Tziperman have shown that ENSO-Indian Monsoon tele-connection comes from the ENSO related dynamics in the upper tropospheric mid-latitude regions. Warming over the central Pacific creates upper tropospheric divergence over the region which is source of the Rossby waves there. These Rossby waves are guided by North-African-Asian jet and associated positive vorticity anomalies do get flooded over the central Asian regions. Effect of these anomalous positive vorticity is pronounced cooling over those regions which ends up as weak temperature gradients in the upper troposphere over Indian region. This disrupts the monsoon flow over Indian region and we get a bad monsoon during EL-Nino years
Answer:
let's se
Explanation:
An El Niño of any strength can reduce the amount of monsoon rainfall and thus have significant local impact. There is increase in both the sea surface temperatures and subsurface ocean temperatures, allowing weak El Nino to persist for at least next several months