Conditions for the Onset of Monsoon
The necessary conditions for onset of monsoon are as follows:
Rainfall
The onset of the monsoon is declared if at least 60% of 14 designated meteorological stations in Kerala and Lakshadweep record at least 2.5 mm of rain for two consecutive days after May 10. The onset over Kerala is declared on the second day, provided specific wind and temperature criteria are also met.
Wind Field
According to the IMD, the depth of westerlies should extend up to 600 hectopascal (hPa) in the area bounded by the equator to 10ºN latitude, and from longitude 55ºE to 80ºE. The zonal wind speed over the region bound by 5-10ºN latitude (Maldives to Kochi) and 70-80ºE longitude (Arabian Sea to Chennai) should be around 15-20 knots (28-37 kph) at 925 hPa.
Heat
The INSAT-derived Outgoing Longwave Radiation (OLR) value should be below 200 watts per square meter (wm2) in the area between 5ºN and 10ºN latitudes, and 70ºE and 75ºE longitudes.
‘Onset’ of the Monsoon| Class 11 Geography Notes
Class 11 Geography ‘Onset’ of the Monsoon Notes: These notes are helpful for Class 11 students learning about the onset of the monsoon. It covers important topics such as what causes the monsoon to begin, how pressure systems affect it, and what happens in different regions when the monsoon arrives.
By studying these notes, students can gain a better understanding of how the monsoon influences weather patterns, farming, and people’s lives in India. The explanations are clear and easy to follow, making it easier for students to grasp this important concept.
‘Onset’ of the Monsoon| Class 11 Geography Notes