Yong-jia LU

Research Interests:

• Extreme weather
• Marine heat waves
• Air-sea coupling

Recent Research Projects:

Marine heatwaves (MHWs) are defined as the prolonged warm sea surface temperature (SST) events that are above the climatological seasonally varying 90th percentile for at least five consecutive days, which can have a substantial negative impact on marine ecosystems and economies. In the boreal summer (June-August) of 2020, the North Arabian Sea experienced a record-breaking MHW event since 1982 with the duration of 84 days and the intensity of 1.9°C, followed by another comparably strong MHW event with the duration of 47 days in September and early October. Using satellite data and reanalysis products, we explored the relative contributions of different physical processes to these two consecutive MHW events by performing a mixed layer heat budget analysis.

The first extreme MHW was initiated by suppressed evaporation and surface wind, which were related to anomalous atmospheric circulation due to southwest tropical Indian Ocean warming. After its peak, enhanced total cloud cover and evaporative cooling led to the decay of this MHW event. However, in early September there was a revival of MHW in the same region, because of strengthened (suppressed) convection over southeastern part of the Arabian Sea (Northern Bay of Bengal) and low-level wind anomalies that were associated with the northward propagation of the boreal summer intraseasonal oscillation (BSISO) over northern Indian Ocean. It was found that, in additional to surface heat fluxes, mixed layer depth variation and ocean temperature advection were also important in shaping the MHW evolution. The roles of various climate modes, in particular the 2019 super Indian Ocean Dipole and the active BSISO over eastern Indian Ocean in 2020 were discussed.

Fig 1. Different terms of mixed layer budget equation in four different phases.