A correction of TMI brightness temperatures due to TRMM boost

The satellite orbit of the Tropical Rainfall Measuring Mission (TRMM) was boosted from 350 km to 402 km in August 2001. This caused that the incidence angle of the TRMM Microwave Imager(TMI) was changed, in turn the observed brightness temperature(TB).As a result, the atmospheric parameters retrieved from-TMI TB have shown a spurious jump from the pre-to the post-boost periods. In oder to insure measurements consistency between these two periods so as to establish a dependable dataset for climate research, in this study changes in TB between the pre-and post-boost periods over the ocean are investigated, and their mechanism is analyzed. Based on the MWRT model, the research shows how the various environmental parameters affected the change of brightness temperature related to the boost. Afterwards, the post-boost data are adjusted to match the pre-boost data through linear transformation, and the performance of the correction method is evaluated in several way. The results show that post-boost TB is linearly related to pre-boost TB where TB on vertical polarized channels for the lower frequencies increased by 0.8-1.6 K, while TB on the other channels showed little chang. Through the adjustment, pre- and post-boost TB become consistent,and monthly mean TB bias is reduced significantly Additionally the spurious TB jump in the low frequency polarized channel is removed. This would be helpful to establish reliable and continuous datasets for climate study in the future.