Atmospheric boundary layer height and its relationship with PM2.5 concentrations in Almaty, Kazakhstan

On June 7, 2022, the scientific journal Aerosol and Air Quality Research (Q3 WoS) published an article "Planetary Boundary Layer and its Relationship with PM2.5 Concentrations in Almaty, Kazakhstan", in which researchers Tursumbayeva M., Kerimray A., Karaca F., and Permadi D. analyzed the seasonal variations of the planetary boundary layer height and its impact on PM2.5 concentrations.

The height of the planetary boundary layer (PBLH) is one of the most important meteorological factors limiting the vertical mixing of air pollutants, including PM2.5, near the earth's surface.

The radiosonde data used in this study were obtained from the Almaty aerological station. PM2.5 data were obtained from the US Embassy station in Almaty (AirNow.gov) starting February 4, 2020, with a temporal resolution of 1 hour.
Throughout the annual cycle, PM2.5 concentrations in Almaty were highest in the winter months. During the heating period (from October to March), daily concentrations did not meet the daily standards set by WHO (92.8% of days) and Kazakhstan's national air quality standards (65.3% of days). In total, 23.2% of days during this period were characterized by concentrations above 100 µg/m3.

In winter, the increase in PM2.5 emissions may be associated with coal burning at large sources (CHP plants) and small heat sources (stoves, boilers), contributing to the deterioration of air quality. Meteorological and geographical conditions may also contribute to winter peak PM2.5 concentrations.

The PBLH analysis results showed that throughout the year, the lowest boundary layer heights (393 m) occurred in the winter period when PM2.5 concentrations were highest (94.0 µg/m3), and conversely, high boundary layer heights (1970 m) in the summer period corresponded to low PM2.5 concentrations (9.9 µg/m3). The results showed a clear negative relationship between the average daily PM2.5 concentration and PBLH in the cold season (from October to March).

Considering the highest and lowest PM2.5 concentrations in the cold half-year, the researchers concluded that the highest PM2.5 concentrations corresponded to lower PBLH values and lower average wind speeds within the boundary layer and, consequently, a lower ventilation coefficient.

The work was carried out within the framework of a grant project of the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (grant № AP09260359).