An investigation into the conditions leading to monsoon onset over Kerala
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Monsoon onset over the Kerala (MOK) coast has been studied using the recently released high resolution Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data (HOAPS 3). Columnar water vapour content, sea surface temperature and evaporation have been utilised to examine the conditions leading to MOK from −7 pentads. The role of monsoon hadley cell (MHC) has also been assessed using the NCEP/NCAR Reanalysis dataset. In addition the role of the cross-equatorial flow and low level jet at 850 hPa has also been explored, as has the importance of the Madden Julian Oscillation in initiating the MOK, the latter using outgoing longwave radiation data. An analysis of sea surface temperature over the Arabian Sea (AS) and Bay of Bengal for contrasting MOKs, showed that the AS warm pool plays a crucial role in MOK. Contrary to the popular notion that moisture builds up only 2–3 weeks in advance of MOK, our study has shown that the integrated columnar water peaks around 35–40 days (almost around the same time as that of the pre-monsoon rainfall peak) prior to MOK and can be a potential predictor of MOK. The 850 hPa winds strengthen over the extreme southern peninsula and Sri Lanka about 3 pentads prior to MOK, and the evaporation rates over the southern Arabian Sea show a dramatic increase with onset of MOK. The MHC can be a useful predictor for extreme monsoon onsets (early or delayed).
KeywordsIndian Ocean Madden Julian Oscillation Outgoing Longwave Radiation Warm Pool Monsoon Onset
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- Ananthakrishnan, R, Soman, MK 1991The Onset of the southwest monsoon in 1990Curr Sci61447453Google Scholar
- Ananthakrishnan R, Acharya UR, Ramakrishnan AR (1967) On the criteria for declaring the onset of southwest monsoon over Kerala. IMD Forecasting Manual No. IV-18.1. India Meteorological Department, Pune, India, 52 ppGoogle Scholar
- Andersson A, Bakan S, Fennig K, Grassl H, Klepp C-P, Schulz J (2007) Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data – HOAPS-3-5-days mean. (doi: 10.1594/WDCC/HOAPS3_PENTAD)Google Scholar
- Joseph, PV 1990Monsoon variability in relation to equatorial trough activity over Indian and Western Pacific OceansMausam41291296Google Scholar
- Joseph, PV, Sooraj, KP, Rajan, CK 2003Conditions leading to monsoon over Kerala and associated Hadley cellMausam54155164Google Scholar
- Kalnay, EM, Kanamitsu, M, Kistler, R, Collins, W, Deaven, D, Gandin, L, Iredell, M, Saha, S, White, G, Woollen, J, Zhu, Y, Leetma, A, Reynolds, R, Chelliah, M, Ebisuzaki, , Higgins, W, Janowiak, J, Mo, KC, Ropelewski, C, Wang, J, Jenne, R, Joseph, D 1996The NCEP/NCAR 40 year Reanalysis ProjectBull Amer Meteor Soc77437471CrossRefGoogle Scholar
- Sadler JC, Lander MA, Hori AM, Oda LK (1987) Tropical Marine Climatic Atlas., Vol. 1. Atlantic and Indian Oceans, Vol. 2. Pacific Ocean. Department of Meteorology, University of Hawaii, USAGoogle Scholar
- Schleussel, P 1996Satellite remote sensing of evaporation over seaRaschke, E eds. Radiation and water in the climate system: remote measurementsSpringerHeidelberg431461Google Scholar