The top-down thermodynamic control of atmospheric blockings on the magnitude of surface heat waves

Atmospheric blocking introduces a warm anomaly in the free troposphere. This warm anomaly comes from latent heat release in warm conveyor belts upstream of the blocking as well as from adiabatic warming due to subsidence within the blocking (e.g., Neal et al., 2022; Papritz & Röthlisberger, 2023). Neal et al. (2022) proposed that the warm anomaly in the free troposphere can control the magnitude of a subsequent surface heat wave by suppressing the height of the convective boundary layer.
In this study, we investigate the impact of a warm anomaly aloft on maximum surface temperature using an idealized column model of the dry atmosphere that is coupled to the surface via the sensible heat flux. During the daytime, the convective boundary layer temperature and height are determined by encroachment (Stull, 1988). Introducing a warm anomaly of 10 K in the free troposphere increases our model’s convective boundary layer temperature by more than 5 K. Model parameters can be adjusted to investigate the magnitude of boundary layer warming under a variety of conditions including low soil moisture. In addition, we examine boundary layer behavior during significant blocking events and their subsequent surface heat waves over the past 40 years.

References:

[1] Neal, E., Huang, C. S., & Nakamura, N. (2022). The 2021 Pacific Northwest heat wave and associated blocking: Meteorology and the role of an upstream cyclone as a diabatic source of wave activity. Geophysical Research Letters, 49(8), e2021GL097699.
[2] Papritz, L., & Röthlisberger, M. (2023). A novel temperature anomaly source diagnostic: Method and application to the 2021 heatwave in the Pacific Northwest. Geophysical Research Letters, 50(23), e2023GL105641.
[3] Stull, R. B. (1988). An introduction to boundary layer meteorology (Vol. 13). Springer Science & Business Media.