Constraining Cloud Lifetime Effects of Aerosols using A-Train Satellite Observations
journal contributionposted on 15.08.2012, 00:00 by M. Wang, S. Ghan, Xiaohong Liu, T. S. L'Ecuyer, K. Zhang, H. Morrison, M. Ovchinnikov, R. Easter, R. Marchand, D. Chand, Y. Qian, J. E. Penner
Aerosol indirect effects have remained the largest uncertainty in estimates of the radiative forcing of past and future climate change. Observational constraints on cloud lifetime effects are particularly challenging since it is difficult to separate aerosol effects from meteorological influences. Here we use three global climate models, including a multi-scale aerosol-climate model PNNL-MMF, to show that the dependence of the probability of precipitation on aerosol loading, termed the precipitation frequency susceptibility (Spop), is a good measure of the liquid water path response to aerosol perturbation (λ), as both Spop and λ strongly depend on the magnitude of autoconversion, a model representation of precipitation formation via collisions among cloud droplets. This provides a method to use satellite observations to constrain cloud lifetime effects in global climate models. Spop in marine clouds estimated from CloudSat, MODIS and AMSR-E observations is substantially lower than that from global climate models and suggests a liquid water path increase of less than 5% from doubled cloud condensation nuclei concentrations. This implies a substantially smaller impact on shortwave cloud radiative forcing over ocean due to aerosol indirect effects than simulated by current global climate models (a reduction by one-third for one of the conventional aerosol-climate models). Further work is needed to quantify the uncertainties in satellite-derived estimates of Spop and to examine Spop in high-resolution models.
PublisherUniversity of Wyoming. Libraries
Journal titleGeophysical Research Letters
CollectionFaculty Publications - Atmospheric Science
A-trainAerosol effectAerosol indirect effectAerosol loadingAutoconversionCloud condensation nucleiCloud dropletsCloud radiative forcingCloudSatFuture climateGlobal climate modelHigh-resolution modelsLiquid water pathsMeteorological influenceModel representationMultiscalesPrecipitation formationPrecipitation frequencyRadiative forcingsSatellite observationsAtmospheric aerosolsAtmospheric radiationClimate changeClimate modelsLoadingSatellite imageryUncertainty analysisPrecipitation (meteorology)aerosol propertyAMSR-Eclimate changeclimate modelingcloud condensation nucleuscloud dropletglobal climatemeteorologyMODISobservational methodradiative forcingresolutionsatellite imageryshortwave radiationuncertainty analysisEngineering