In this paper, we simulate the negative ion evolution shape considering 151 different ions, 66 trace gases and 493 ion-molecule reactions. The main attention is paid to the evolution interval from 30 ms to 3 s where the knowledge is most limited., The connections between the evolution shape and temperature have been studied. The simulated results have been compared with the relevant measurements, and the ions most likely responsible for a certain ion evolution shape observed by Nagato and Ogawa (J. Geophys. Res. 103(D12) (1998) 13917) have been revealed. Also, the composition of trace gases likely responsible for the observed shape can be derived. In the studied evolution interval the transformation O-2(-)(H2O)(n) --> CO3-(H2O)(m) --> NO3- x X x Y prevails. At the higher temperature, the ions CO3-(H2O)(m) are less abundant. In the respective steady (natural) state the most abundant ions are NO3- x X x Y x (HCl)(n) and NO3-(H2O)(m) At the higher temperature, the ions NO3-(H2O)(m) are dominant. (C) 2002 Elsevier Science Ltd. All rights reserved.