Climate models

The model weighting method in climate models predicts a larger increase in precipitation change over the Tibetan Plateau

The change in precipitation in the Tibetan Plateau (TP) is likely to have profound effects on the regional ecosystem and on downstream monsoon weather systems.

Researchers from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS) and the Chinese Academy of Meteorological Sciences (CAMS) used the model weighting method in climate models and projected a greater increase in precipitation changes across the TP.

Their study was published in Advances in atmospheric science.

A weighting method in climate modeling refers to statistical adjustments to data that are applied to improve the accuracy of outputs. Considering an independent model simulating competence between CMIP models, they projected a larger increase in TP precipitation by the end of the century.

Climate projections are primarily based on an ensemble mean, or a collective mean of CMIP multi-models, in which each member of the ensemble is given equal consideration, or weight relative to the mean. However, different levels of model skill and independence can reduce the reliability of the projection simply based on the model’s equal weighting method.

To improve TP’s future climate projections and reduce model uncertainty, the researchers recently used a weighting method that assigns models different weights based on their skill and level of independence. They applied this method to 27 members of the CMIP6 model ensemble to see how their weighting method will affect the TP rainfall projection.

“Compared to the traditional equal-weighted projection, we saw a greater increase in precipitation over TP in our model-weighted projection, especially for the spring season and the northwest region of TP,” said the Dr. ZHAO Yin, first author of the study.

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