Abstract: The T42L5 spectral model has been developed on the basis of T42L9 model, with the use of model diagnosed cloud instead of climate cloud. Using EC observed analysis of 12UTC July 1, 1982 as initial field, 5-day medium-range numerical experiments have been carried out in different cloud schemes so as to dynamically investigate the effects of cloud/radiation on the medium-range NMP. The numerical results show that: (1) The model diagnosed cloud can well simulate the real distribution of the cloud in the atmosphere and modify the calculation of radiation, and consequently improve the prediction. (2) The amount of middle and high cloud in the climate cloud is much lower than the real cloud, which results in the weakening of the synoptic system, while the model diagnosed cloud can improve the prediction due to the proper consideration of the effects of cloud and radiation. (3) The model diagnosed cloud scheme is able to successfully simulate the maximum and minimum regions of the middle and high cloud which are responded to the upward and downward areas of the Hadley circulation, respectively. In the meantime, the simulated Hadley circulation of the model diagnosed cloud is much stronger than that of the climate cloud