Tracking Tropical Intraseasonal Convective Anomalies: A New Algorithm

A new algorithm based on a multiple object tracking method is developed to identify and track Tropical Intra-seasonal Oscillations (TISO), and classify them on the basis of their direction of propagation. Gridpoint values of daily NOAA Outgoing Long-wave Radiation anomalies (OLRA) from 1979-2013 are Lanczos bandpass filtered for the intra-seasonal time scale (20-100 days) and spatially averaged with eight neighboring points to isolate the appropriate time and space scales. Tracking TISO events is performed by using a two-stage Kalman filter predictor-corrector method.  Two dominant components of TISO events (eastward-propagating and northward-propagating) are classified, and it is found that TISO remains active throughout the year. Eastward propagation of TISO events occurs primarily from November to April with an average speed of ~4 m/s, and northward propagation of TISO events occurs primarily from May to October at ~2 m/s in both the Indian and Pacific Ocean basins