Measurement report: Immediate impact of the Taal volcanic eruption on atmospheric temperature observed from COSMIC-2 RO measurements

Abstract. For the first time after 43 years of its previous eruption in 1977, the Taal volcano in the Philippines (14° N, 120.59° E) erupted in the afternoon of 12 January, 2020. Interestingly, the Taal volcanic eruption was associated with a strong anticyclonic circulation at the upper levels over the western Pacific region in the northern hemisphere. As a result, the volcanic plumes were carried through the background upper level strong winds to the anticyclone over the Pacific Ocean within a few days following the eruption. In this study, the detailed vertical structure and the day-to-day temperature variability in response to the eruption is delineated by using high-resolution temperature measurements from the recently launched Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)-2 radio occultation (RO) data. We describe the vertical temperature structure near (within 2 degree radius) and away (~ 5 degree radius) from the volcano during its intense eruption day (13 January 2020). A significant temperature inversion at ~ 15 km altitude is observed in the nearest temperature profiles (within 2 degree radius). Multiple tropopauses are evident in the temperature profiles that are available away from the volcano (~ 5 degree radius). The cloud top altitude of 15.2 km detected from the RO bending angle anomaly method is demonstrated. Furthermore, the diurnal temperature and relative humidity anomalies are estimated over ± 5° latitude and longitude radius from the volcano center and over the region of 10–20° N, 160–180° E with respect to the mean temperature of one week before the eruption. A persistent warming layer is observed at 16–19 km altitude range in both regions for several days after the eruption. A strong increase of ~ 50 % relative humidity at 15 km altitude is also noticed just after the eruption in the Taal volcano region. The present work shows the advantages and usefulness of the newly-launched COSMIC-2 data for near real-time temperature monitoring at shorter time scales with sufficient data.