Diurnal and Seasonal Variation of Planetary Boundary Layer Height  over East Asia and Its Climatic Change as Seen in the ERA-5 Reanalysis Data

Abstract

The diurnal/seasonal structure of the boundary layer height (BLH) is investigated over East Asia by using the hourly synoptic monthly ERA5 reanalysis variables from 1979–2019. Sensible heat flux (SHF) is the major factor in the temporal and spatial variation of the BLH. Although BLH, in general, is positively correlated with SHF throughout the year, BLH-SHF relationship varies significantly based on the surface type, latitude and time of the year. Analysis also reveals that stability is an important parameter controlling the diurnal maximum BLH. The growth of BLH is strongly limited by the presence of a stable layer. On the other hand, BLH increases abruptly in the presence of a weakly stratified residual layer. In addition, regional warming tends to increase the BLH in the mid- to high-latitude continental area. In the low-latitude continental area, the sign of SHF differs seasonally and regionally. Stability plays only a minor role in the BLH change except over the Tibetan Plateau, where the increased stability at the top of boundary layer due to warming reduces BLH rather significantly.

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“…We obtained the PBLH at SHT from the nearest ERA5 gridded reanalysis data (Hersbach et al, 2020) (https://cds.climate.copernicus.eu/cdsapp#!/ dataset/reanalysis-era5-single-levels?tab=form, last access: 27 November 2022). The ERA PBLH is calculated utilizing a bulk Richardson method, which is widely used for both convective and stable boundary layers (Kim, 2022). According to Wang et al (2018), the ERA data tend to overestimate the PBLH at nighttime but underestimate the PBLH during daytime in eastern China by comparing it with the PBLH calculated from radiosonde sounding data.…”