An Evaluation of Ice Nuclei Characteristics from the Long-term Measurement Data over North China

An attempt was made to delineate the characteristics of ice nuclei (IN) over North China using the ground-based measurement data from 1963-2003. The results show that: (1) the IN concentrations increased during the period from 1963-1996, but decreased after 2000; (2) the average IN concentrations range from 1.0 to 26.3, 3.6 to 78.9, 19.2 to 627.3, and 92.9 to 5285.0 L-1 at temperature -15, -20, -25, and -30 degrees C, with the overall average of 7.8, 20.6, 167.7, and 890.6 L-1, respectively; and (3) the number concentration of active IN increased nearly exponentially with decreasing temperature, with the slope (ranging from 0.11 to 0.42A degrees C-1) being of a narrow range in a log-linear coordinate; the regression equations for the western central China and the eastern central China can be expressed as N(T) = 0.0396 exp (-0.317 Delta T) and N(T) = 0.1496 exp (-0.299 Delta T), respectively. The present study may be useful toward applications in models for predicting IN effects on the cloud, precipitation and climate over North China.