Fig. 1.
(a) Mean 850 hPa wind of monsoon season (JJAS) for the period 1979 to 2010 showing the zonal flows and the cross equatorial meridional flows. The six representative regions (as marked by boxes) of the LLJ of Asian summer monsoon are (1) Equatorial Indian-Ocean EIm (box 5°S–5°N, 35°E–55°E), (2) Central Arabian-sea CAz (box 10°N–20°N, 55°E–65°E), (3) Peninsular India PIz (box 10°N–20°N, 70°E–85°E), (4) west Pacific-Ocean WPm (box 5°S–5°N, 100°E–140°E), (5) northwest Pacific (box 5°N–15°N, 120°E–160°E) and (6) Indian-Ocean Trades ITz (box 20°S–5°S, 60°E–90°E).Suffixes z and m represent zonal and meridional components of wind (b) Mean OLR (Watts per sq, metre) of the monsoon season (JJAS) for the period 1979–2010. The two active convection zones of the monsoon season A and B are marked.
Table 1a.
Correlation between interannual components of pairs of LLJ box parameters and ISMR / N3.4 Red, green and blue colours represents 99.9, 99 and 95% levels of statistical significance.
Table 1b.
The PCC in the inter-annual component among six parameters of LLJ using JRA55 and NCEP (marked top left) data. Red, green and blue colours represents 99.9, 99 and 95% levels of statistical significance.
Fig. 2.
(a) Trend of 850 hPa zonal wind and (b) 850 hPa meridional wind during 1958–2010 using JRA-55 reanalysis data. Shading shows 95% level of statistical significance.
Fig. 2c.
Trend of outgoing longwave radiation (OLR) during 1979–2010 Shading shows 95% level of statistical significance.
Fig. 3.
Schematic diagram representing inter-annual correlations among ISMR, Nino 3.4 and LLJ components (positive PCC by red arrows and negative PCC by green). All the PCCs marked are at 99.9% level of statistical significance. A one way relation that is statistically significant is marked by an arrow with single head. If there is a high and significant PCC between two parameters with two way interaction, it is represented by lines with arrows on both ends.
Fig. 4.
(a) Mean JJAS SST anomaly of El Nino years during 1958–2010 over west Pacific. (b) same as (a) but for 850 hPa wind anomaly (JRA-55). Years with N3.4 index equal to and greater than 1 of the season October to December is taken as El Nino years (1965, 1972, 1977, 1982, 1986, 1987, 1991, 1994, 1997, 2002, 2006, 2009).