Research ArticleATMOSPHERIC SCIENCE

Reducing the aerosol forcing uncertainty using observational constraints on warm rain processes

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Science Advances  29 May 2020:
Vol. 6, no. 22, eaaz6433
DOI: 10.1126/sciadv.aaz6433
  • Fig. 1 Warm rain and warm drizzle fraction from the satellite climatology and the reference model configuration.

    The model strongly overestimates the warm precipitation fractions over land and extratropical oceans but slightly underestimates warm drizzle over the northeastern Pacific. Dark lines indicate the 10 and 80% warm precipitation fraction contours in the satellite climatology.

  • Fig. 2 Change in model bias in warm precipitation fraction relative to the reference configuration.

    The reduced scale factor strongly decreases the warm rain fraction but leaves warm drizzle largely unaffected, whereas the re threshold decreases warm drizzle but leaves warm rain largely unaffected.

  • Fig. 3 The relationship between the (observable) bias in warm rain fraction and the (emergent) rapid adjustment under scale factor and effective radius threshold tuning strategies.

    The relationship between warm rain fraction (fwarm) and normalized rapid adjustment (F/FNd) is multivalued, which presents an apparent obstacle to an observational constraint. Distinguishing between rain (solid line), which responds strongly to the Qaut scale factor tuning but weakly to the re threshold tuning, and drizzle (dashed line), with the opposite responses, breaks the degeneracy and removes the obstacle to formulating an observational constraint.

Supplementary Materials

  • Supplementary Materials

    Reducing the aerosol forcing uncertainty using observational constraints on warm rain processes

    Johannes Mülmenstädt, Christine Nam, Marc Salzmann, Jan Kretzschmar, Tristan S. L’Ecuyer, Ulrike Lohmann, Po-Lun Ma, Gunnar Myhre, David Neubauer, Philip Stier, Kentaroh Suzuki, Minghuai Wang, Johannes Quaas

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