Ice crystal number concentration (Ni) is an important parameter for climate change and cloud physical process studies. It may affect precipitation amount, radiative fluxes, and moisture and heat budgets of the Earth's atmosphere. Ice crystal formation may depend on temperature (T), supersaturation with respect to ice (Si), vertical air velocity (w) and the presence of ice nuclei (e.g. aerosols). Earlier studies pointed out that parameterized values of Ni were much lower than that of in-situ observations. In fact, the lack of observations made parameterization in the various environmental conditions very difficult. The present study uses observations from the Beaufort Arctic Storm Experiment (BASE) and the First International Regional Experiment (FIRE III) which took place over the Arctic region of Canada during the fall of 1995, and the spring of the 1998, respectively. Two types of cloud systems were used in the analysis: 1) frontal clouds, and 2) boundary layer stratiform clouds. Cloud systems, representing frontal clouds originating from both the Arctic and Pacific oceans, were used in the analysis of data from BASE. The FIRE III stratiform clouds used in the analysis were mostly boundary layer clouds with no direct effect from the large frontal systems. The T, Ni, size, and shape, aerosol number concentration (Na), liquid water content (LWC), total water content (TWC), and w were obtained from the observations of the Reverse-flow temperature, PMS 2D-C, PCASP, Nevzorov-King-FSSP, and Rosemount 580 probes which were mounted on the National Research Council of Canada (NRCC) Convair. Here, the results from earlier studies and the latest two field projects were included in the analysis. Observations were used to develop relationships among Ni, Si, and T. The importance of w and Na for parameterizations are also discussed with regards to climate model studies