Zonal Wind Shear Index (Webster and Yang, 1992)
Time-series representation of the zonal wind shear index between 200 hPa and 850 hPa averaged over the North Indian Ocean and southern Asia (shown by the rectangle on the bottom: equator – 20°N, 40°E – 110°E). The zonal wind shear index is calculated after Webster and Yang (1992). The thick and thin pink lines indicate seven-day running mean and daily mean values, respectively. The black line denotes the normal (i.e., the 1991 – 2020 average), and the gray shading shows the range of the standard deviation calculated for the time period of the normal.
URL: https://ds.data.jma.go.jp/tcc/tcc/products/clisys/ASIA_TCC/monsoon_index.html
Somali Jet Index (Boos and Emanuel, 2009)
The Somali jet index is a measure of the speed of the Somali jet: the square root of twice the domain mean kinetic energy of the 850 hPa horizontal wind in the region (50 E – 70 E, 5 S – 20 N). Data is from NCEP operational analyses for the current year, and NCEP reanalysis data for the climatology.
URL: http://worldmonsoons.org/vjetindex.html
