The relationship between black carbon and atmospheric boundary layer height

Abstract Black carbon (BC) has a significant influence on regional climate and human health. Variations of BC aerosol and atmospheric boundary layer height (BLH) were investigated in an urban site over Wuhan from November 2014 to November 2016. The annual average BC concentration and BLH were approximately 3.01 ± 1.97 μg/m 3 and 892 ± 389 m, respectively. The variation of BC is opposite to that of BLH. The maximum monthly mean BC was 4.32 ± 2.3 μg/m 3 in December, and the minimum monthly mean BC was 1.94 ± 1.9 μg/m 3 in July. The maximum monthly mean BLH was approximately 1211 ± 308 m in July, and the minimum monthly mean BLH was approximately 668 ± 342 m in January. Moreover, the high BC mass concentration days have relatively higher relative humidity (RH) values than the clean days, and the high RH values were usually accompanied by low BLH. The relationship between the BC concentrations and BLH exhibits a negative correlation. The correlation coefficient was R 2  = 0.424 on the polluted days, whereas the R 2 coefficient was approximately 0.0037 during the clean periods. The PM 2.5 and BLH have no evident relationship in low (R 2  = 0.0097) or high (R 2  = 0.058) BC concentrations. Results indicate that the BC mass concentration would suppress the BLH on the polluted days. The increased BC aerosol concentration resulted in lower BLH and led to poor air quality.