Dreary state of precipitation in global models

TLDR

Global ocean liquid precipitation differs markedly from that simulated by global weather and climate models, raising concerns about model realism. New definitive measures of precipitation frequency from CloudSat are used to assess the realism of global model precipitation. Five state‑of‑the‑art weather, climate, and high‑resolution cloud‑resolving models are compared. Observed precipitation differs from model output: while global accumulations agree, models generate about twice the frequency and lighter rainfall, a discrepancy beyond observational or sampling errors.

Abstract

New, definitive measures of precipitation frequency provided by CloudSat are used to assess the realism of global model precipitation. The character of liquid precipitation (defined as a combination of accumulation, frequency, and intensity) over the global oceans is significantly different from the character of liquid precipitation produced by global weather and climate models. Five different models are used in this comparison representing state‐of‐the‐art weather prediction models, state‐of‐the‐art climate models, and the emerging high‐resolution global cloud “resolving” models. The differences between observed and modeled precipitation are larger than can be explained by observational retrieval errors or by the inherent sampling differences between observations and models. We show that the time integrated accumulations of precipitation produced by models closely match observations when globally composited. However, these models produce precipitation approximately twice as often as that observed and make rainfall far too lightly. This finding reinforces similar findings from other studies based on surface accumulated rainfall measurements. The implications of this dreary state of model depiction of the real world are discussed.