10.26165/JUELICH-DATA/4BRLEM Kachula, Oleh(Forschungszentrum Jülich GmbH) Jülich DATA 2025 This data set is part of the study by Kachula et. al (2025). It includes time series of the Montgomery streamfunction contour level from May to September for each day at 12:00 UTC during the period 1980-2023 at 350 K, 370 K, 390 K and 410 K, representing the boundary of the Asian Summer Monsoon Anticyclone as calculated by the proposed method. In addition, we provide the Montgomery streamfunction data defined on a regular 1° × 1° grid. Kachula, Oleh(Forschungszentrum Jülich GmbH)