The onset of the summer monsoon in early June over India heralds the rainly season after a long period of almost no rainfall. The thermodynamic and dynamic structure of the atmosphere experiences a step change during monsoon onset, that retreats back after its withdrawal. Thus, in many sence, a theory for the onset of summer monsoon is similar to a theory for monsoon itself.
CAOS faculty initiated, and have actively been involved in establishing a theoretical framework for summer monsoon onset using numerical models and observations. A framework based on energetics of the atmosphere is proposed for onset of monsoon that confronts the land-sea thermal contrast theory.
An important component of the monsoon studies is its forcast. To have a skillful forecast, it is necessary to understand the interannual variations well. Study from CAOS proposes a physical mechanism for early and late onset of summer monsoon over central India, a region of vast agriculture where onset of monsoon matters the most. This theory is based on observations of surface pressure over west central Asia about a month befor the onset. The application of this theory is establishment of statitical model for real-time prediction of monsoon onset.
El Nino Southern Oscillation (ENSO) is a coupled ocean-atmosphere phenomenon manifested by warming or cooling of sea surface temperature (SST) primarily over the eastern equatorial Pacific Ocean. During El Nino, the warm phase of the ENSO, monsoon rainfall over India is typically less than normal. How does warming of ocean half a globe apart impact rainfall over India?
At CAOS, we have research projects to understand the global teleconnection of the Indian summer monsoon. Apart from looking at the role of global east-west Walker circulation or mid-latitude Rossby Waves in 'transferring' the impact of ENSO far away over India instantly, we investigate delayed impact of ENSO. We look at coupled atmosphere-ocean models to understand their prediction skill and physical mechanisms of global teleconnection.