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Unresolved Model Biases in Cloud Climatology

Paper Reviewed
Wang, H. and Su, W. 2015. The ENSO effects on tropical clouds and top-of-atmosphere cloud radiative effects in CMIP5 models. Journal of Geophysical Research: Atmospheres 120: 4443-4465.

Focusing on projected El Niño-Southern Oscillation (ENSO) effects, Wang and Su (2015) evaluated their impacts on tropical clouds and their top-of-atmosphere (TOA) cloud radiative effects (CREs) in Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models by evaluating their projections as compared to (1) satellite-based observations and (2) International Satellite Cloud Climatology Project satellite simulator output. And what did this work reveal?

The two researchers report that "most CMIP5 models produce [1] considerably less total cloud amount with [2] higher cloud top and [3] notably larger reflectivity than observations in [the] tropical Indo-Pacific." In addition, they state that "during ENSO, most CMIP5 models strongly underestimate [4] TOA, [5] CRE and [6] cloud changes over the western tropical Pacific." And they further note that the multi-model mean [7] "notably overestimates cloud top pressure (CTP) decreases."

Continuing, Wang and Su write that "in a fully coupled ocean-atmosphere model system, such model cloud biases over the western tropical Pacific can [8] easily lead to biases in tropical SST whose effects can [9] subsequently propagate into regions worldwide through atmospheric teleconnection." And they thus conclude that (10) "much modeling work is needed to correct this model bias," because, as they continue, "only when these issues are alleviated can there be a stronger confidence in the model simulations of climate variability and projection of future climate change."

Posted 19 October 2015