A COMPARISON BETWEEN TRANSILIENT TURBULENCE THEORY AND THE EXCHANGE COEFFICIENT MODEL APPROACHES

The transilient turbulence model of Stull and Driedonks (1987) and the exchange coefficient model of Bougeault and Lacarrere (1989) are inte rcompared on four convective days of the HAPEX-MOBILHY experiment. We show that the numerical formulations of the models are very close to e ach other, despite their totally different theoretical backgrounds. Bo th models describe the mixing effect of the turbulence via matrices ha ving the same general characteristics. The results of the models are a lso found to be very similar in general, although the transilient appr oach requires more computations. Some systematic differences are noted and discussed in detail. We argue that similar work should be conduct ed on non-convective cases before deciding on the superiority of one o r the other approach.