This is a two-part technical report that considers the short-time statistical modeling of atmospheric noise at VLFLF frequencies and applies a new noise model to the performance evaluation of various generic VLFLF communication modems. In Part One atmospheric noise is examined mainly from a statistical point of view. Next, various statistical models for this type of noise are examined finally, a new model is developed and compared with available data. In Part Two this noise model is applied to the evaluation of the error probability calculations of various generic VLFLF modems. Much of Part Two, particularly in regard to a receiver system employing no clipping, is based on classical white Gaussian noise analysis applied in generic modems of interest. When nonlinear clipping is applied, the detailed statistical behavior of atmospheric noise becomes more important, and results depend on the detailed structure of the noise.