On June 2nd 2021, WMC-Beijing launches Arctic sea ice and boreal summer intra-seasonal oscillation (BSISO) monitoring products developed by Beijing Climate Center.

The Arctic sea ice cover has rapidly declined in the past three decades, which could exert substantial impact on the remote large-scale atmospheric circulation and surface weather and climate in the extratropical Northern Hemisphere. To measure the Arctic sea ice variability, a sea ice index is defined as the regional-averaged sea ice concentrations over 60°–90°N. The Arctic sea ice index is now updated monthly via the WMC-Beijing website.

BSISO is one of the most prominent short-term climate variability in Asian summer monsoon region. Two-pairs of BSISO indices are designed to measure BSISO variability, which are derived from the first 4 multivariate empirical orthogonal function modes of daily anomalies of outgoing longwave radiation (OLR) and zonal wind at 850 hPa (U850) in the region 10°S–40°N, 40°–160°E. The BSISO1 indicate the northward propagating variability with quasi-oscillating periods of 30–60 days and BSISO2 indicate the north-westward propagating variability with quasi-oscillating periods of 10–30 days. Both BSISO1 and BSISO2 indices are now updated daily via the WMC-Beijing website. (Editor: Lu Bo/Wang Yi)