Comment on acp-2021-249

Abstract

This study reveals that haze pollution (HP) over the North China Plain (NCP) in winter can persist to following spring during most years. The persistence of HPNCP is attributed to maintenance of an anticyclonic anomaly (AA) over northeast Asia and southerly wind anomalies over the NCP. Southerly wind anomalies over the NCP reduce surface wind speed and increase relative humidity, which are conducive to above-normal HPNCP both in winter and spring. However, there exist several years when above-normal HPNCP in winter are followed by below-normal HPNCP in the following spring. The reversed HPNCP in winter and spring in these years is due to the inverted atmospheric anomalies over northeast Asia. In particular, AA over northeast Asia in winter is replaced by a cyclonic anomaly (CA) in the following spring. The resultant spring northerly wind anomalies over NCP are conducive to below-normal HPNCP. These two distinctive evolutions of HPNCP and atmospheric anomalies over northeast Asia from winter to spring are attributed to the different evolutions of sea surface temperature anomalies (SSTA) in the North Atlantic. In the persistent years, warm North Atlantic SSTA in winter maintains to following spring via positive air-sea interaction process and induces a negative spring North Atlantic Oscillation (NAO)-like pattern, which contributes to the AA over northeast Asia via atmospheric wave train. By contrast, in the reverse years, cold SSTA in the North Atlantic is maintained from winter to spring, which induces a positive spring NAO-like pattern and leads to CA over northeast Asia via atmospheric wave train. The findings suggest that North Atlantic SSTA plays crucial roles in modulating the distinct evolutions of HPNCP from winter to succedent spring, which can be served as an important preceding signal for haze pollution evolution over the North China Plain.