CCN concentration in troposphere over China

CCN concentration in the middle-lower troposphere over northern China was observed using a cloud condensation nucleus counter, MEE-130, installed on an IL-14 aircraft in the summer of 1983 and 1984. More than 60 sets of data (each flight as one set) were collected. The main results are: (1) in northern China, CCN concentration is 10²-10⁴/ cm³ near ground, decreases with increasing height and follows exponential distribution; (2) the local CCN concentration and its distribution with altitude are influenced by some meteorological factors: such as inversion, cloud and precipitation, wind and land—sea breeze etc. The inversion makes CCN significantly accumulate just below the inversion level; CCN concentration is lower inside clouds than outside clouds at same level; wind plays an important role of transporting CCN horizontally; (3) the CCN concentration is higher above the land than above the sea at same level; CCN concentration is one order of magnitude lower over the coastal cities like Qingdao than over the continental cities like Zhengzhou; (4) all these suggest that CCN in northern China comes mainly from continental surface layer. Densely—populated areas and industrial areas may produce more CCN.