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Welcome to the Boreal Summer Intraseasonal Oscillation (BSISO) monitoring website. The BSISO, one of the dominant phenomena over the Asian summer monsoon region, is characterized by northward/northeastward propagation over the Indian summer monsoon region and northward/northwestward propagation over the Western North Pacific-East Asian region, including equatorial eastward propagation. This monitoring information is available from May to October.


Monitoring BSISO index download (1981 ~ )

BSISO Phase Diagram

The BSISO phase diagram illustrates the consecutive development and progression of BSISO for the past 40 days by tracking the BSISO index, which provides the location and strength of BSISO. The eight divided phases represent the location of BSISO convective center. When the index shown is within the center circle, it is indicating a weak BSISO, and when it is outside of the circle, the index is considered to be a strong BSISO.



The time-series depicts the variation of observed BSISO between April and October.


Reconstruction Field(Mode 1-4)

The reconstruction field shows the real-time observed OLR anomaly reconstructed by the first four EOF modes corresponding to the definition of BSISO, which indicates the BSISO activity.


Reconstruction Field(Mode 1,2 & 3,4)

The reconstruction field shows the real-time observed OLR anomaly reconstructed by the BSISO1 (modes 1&2) and BSISO2 (modes 3&4).


BSISO Impact Anomaly

The BSISO impact anomaly shows the local impacts of the most recent BSISO activity over the Asian monsoon region. This is the reconstructed field based on composite of the historical BSISO index (1981-2018) for various variables such as temperature, precipitation, wind field, and other relevant variables.


Anomaly Field

The anomaly field displays how far the current OLR and wind field deviates from the normal state (climate).