Investigation of the seasonal variations of PM10 concentrations with EOF/REOF analysis across Türkiye

Air pollution is one of the main environmental issues and air pollutants like PM10 is widely identified as an important atmospheric pollutant posing a serious threat to human health, environment, the ecosystem as well as influences the climate system. To unearth the mechanism involved in its sources and circulation behavior in environment, this study focuses on seasonal variability of PM10 over Türkiye by applying rotated empirical orthogonal functions (REOF) analysis to the daily PM10 observations for 80 stations for the period 2010-2020, that are homogenously distributed over Türkiye. As a result of the implementation of REOF to the daily PM10 data for 80 air quality stations throughout the study period 2010–2020, the first REOF mode (REOF1 44.9% in winter, 43.2% in spring, 39.5% in summer and 31.6% in fall) for all the four seasons indicated the role of local emission sources on the variations of PM10, which show high PM10 values in different geographical regions located in distant proximities from each other (e.g for winter REOF1 the identified significant stations are Adana Meteoroloji, Canakkale, Erzincan, Giresun, Kastamonu, and Sinop. Same is with spring, summer and fall seasons). The results of the second mode (REOF2, 17.9% in winter, 14.0% in spring, 14.0% in summer and 16.3% in fall) indicate the role of large-scale atmospheric circulations on the values of PM10. From the REOF2 analysis and extracted synoptic composite maps, it was observed that the strength of southerly winds and the presence of southwesterly winds at low levels are very important in transporting dust pollutants from the Arabian Peninsula and Northern Africa, respectively, to the eastern (EAR) and southeastern (SEAR) regions of Türkiye during winter. In spring, sand particles in the interior terrestrial part of the country are carried to the northern regions by the effect of large-scale southerly winds, which cause above-normal PM10 concentrations in the Black Sea region of Türkiye. In summer, dust particles together with warm dry air intrusion to the eastern region of Türkiye by strong easterly winds are sourced by Caspian Sea and result in high PM10 values. Our findings emphasize that the long-term variations in air quality over Türkiye are affected secondary by the variations in the large-scale atmospheric circulations with primary contributions from the changes in local emission sources. Keywords: EOF, NCEP/NCAR reanalysis, PM10 , Synoptic composites, Türkiye