Dampening of the Precipitation Response to Aerosol Pollution From Turbulence in Cumulus Clouds
Year: 2025
Type: article
Abstract: The susceptibility of rain formation to aerosol emissions is a key aspect of aerosol-cloud-precipitation interactions. Using aircraft observations and a detailed cloud model with a state-of-the-art particle-based representation of microphysics, it is shown that the enhancement of drop collision-coalescence from turbulent flow in clouds -- which is neglected in current climate models -- leads to earlier onset of rain in warm cumulus clouds and significantly dampens the precipitation susceptibility to aerosol loading. Enhanced drop coalescence from turbulence substantially increases the production of embryonic drizzle drops just above cloud base, which in turn act as seeds that accelerate rain drop growth at mid and upper cloud levels even in highly polluted conditions. In contrast, pollution aerosols strongly inhibit rainfall when the commonly assumed gravitational-only collision kernel is used in the model and turbulent coalescence is neglected. There is also a large impact of turbulent drop coalescence on the mean cloud water amount and optical depth. Overall, turbulence-enhanced drop coalescence strongly influences the response of warm cumulus clouds and precipitation to aerosol loading, suggesting that the effects of turbulent coalescence should be included in climate model representations of aerosol-cloud-precipitation interactions and aerosol indirect radiative forcing.
Source: Geophysical Research Letters
DOI: 10.1029/2025gl118693
Authors: Kamal Kant Chandrakar, Hugh Morrison
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $3,190
Awards: G1286236842, G1335240794, G1632040200, G1863003419, The Management and Operation of the National Center for Atmoshperic Research (NCAR), BUILDING A NEXT-GENERATION MICROPHYSICS SCHEME FOR E3SM: A DATA-DRIVEN, PHYSICALLY CONSTRAINED, SINGLE-CATEGORY APPROACH, G3083819904, G3137522415, G419881185, G42916606, G4501827968, G498139845, BUILDING A NEXT-GENERATION MICROPHYSICS SCHEME FOR E3SM: A DATA-DRIVEN, PHYSICALLY CONSTRAINED, SINGLE-CATEGORY APPROACH, THE IMPACT OF HIGH CONCENTRATIONS OF ANTHROPOGENIC AEROSOLS (E.G. POLLUTION FROM BURNING OF BIOMASS AND/OR FOSSIL FUELS) ON CUMULUS CLOUDS IN SOUTHEAST ASIA MAY HAVE A SIGNIFICANT IMPACT ON THE MAGNITUDE OF PRECIPITATION AND TRANSPORT OF ICE PARTICLES INTO THE UPPER TROPOSPHERE/LOWER STRATOSPHERE (UTLS). PRECIPITATION IS CRITICAL TO AGRICULTURE AND OTHER SOCIAL ECONOMIC DISCIPLINES; THE TRANSPORT OF WATER VAPOR (EVAPORATED ICE) INTO THE UTLS HAS A SERIOUS IMPACT ON GLOBAL CLIMATE CHANGE. WE WILL CONDUCT INTENSIVE IN SITU OBSERVATIONS OF AEROSOLS CLOUD MICROPHYSICS AND UPDRAFT DYNAMICS USING THE NASA P-3B AND SPEC LEARJET RESEARCH AIRCRAFT. SPEC WILL BRING A LEARJET MODEL 35 TO THE FIELD OPERATE IT AND MAINTAIN AND PROCESS DATA FROM ADVANCED CLOUD MICROPHYSICS SENSORS INSTALLED ON BOTH THE P-3B AND LEARJET. THE OBSERVATIONS WILL BE INTEGRATED INTO THREE-DIMENSIONAL (3D) CLOUD SIMULATIONS USING A BIN MICROPHYSICS SCHEME IN CONJUNCTION WITH A NOVEL MICROPHYSICAL PIGGYBACKING APPROACH TO SHED LIGHT ON THE MECHANISM(S) RESPONSIBLE FOR CLOUD MODIFICATION DUE TO ENHANCED AEROSOL LOADING. THE MAIN IDEA OF MICROPHYSICAL PIGGYBACKING IS TO APPLY TWO SETS OF THERMODYNAMIC VARIABLES (THE POTENTIAL TEMPERATURE WATER VAPOR MIXING RATIO AND ALL VARIABLES DESCRIBING AEROSOL CLOUD AND PRECIPITATION PARTICLES) IN A SINGLE CLOUD FIELD SIMULATION. THE FIRST SET IS COUPLED TO THE DYNAMICS AND DRIVES THE SIMULATION AND THE SECOND SET PIGGYBACKS THE SIMULATED FLOW AND DOES NOT AFFECT IT. THE METHODOLOGY ALLOWS FOR ASSESSING THE IMPACTS WITH AN UNPRECEDENTED ACCURACY AND IT IS CAPABLE OF DETECTING EVEN MINUSCULE IMPACTS ON BULK CLOUD PROPERTIES SUCH AS THE CLOUD COVER LIQUID AND ICE WATER PATH AND SURFACE PRECIPITATION. THE IMPACT ON THE DYNAMICS IS ASSESSED BY PERFORMING A SECOND SIMULATION WITH MICROPHYSICAL SETS SWAPPED SO THE DRIVER SET BECOMES THE PIGGYBACKING SET AND VICE VERSA. IF THE DIFFERENCES BETWEEN RESULTS FROM DRIVER AND PIGGYBACKING SETS IN THE TWO SIMULATIONS (I.E. IN THE ORIGINAL SIMULATION AND IN THE ONE WITH SETS SWAPPED) ARE THE SAME EXCEPT FOR THE SIGN THEN THE CLOUD DYNAMICS IS ARGUABLY INSIGNIFICANTLY AFFECTED BY THE CLOUD MICROPHYSICS. WE EMPHASIZE THAT THIS IS AN INTERPRETIVE MODELING COMPONENT AND NOT STAND-ALONE; THE MODEL WILL BE INTEGRATED WITH THE OBSERVATIONS TO QUANTIFY MICROPHYSICAL AND DYNAMICAL IMPACTS OF AEROSOLS AS A PART OF OUR DATA ANALYSIS APPROACH AND TO ASSESS RADIATIVE IMPACTS. THE LEAR 35 PROPOSED FOR CAMP2EX HAS TURBOFAN ENGINES AND IS AN UPGRADE FROM SPEC S LEAR 25 THAT HAS TURBOJET ENGINES. THE LEAR 35 HAS A 2 000 NMI RANGE AND WILL BE CAPABLE OF WORKING WITH THE P-3B UP TO ABOUT 400 NMI OFFSHORE. THE BASIC MEASUREMENT APPROACH IS FOR THE P-3B TO MAKE SUBCLOUD MEASUREMENTS OF AEROSOLS AND AIR MOTIONS BEFORE CLIMBING INTO WARM CLOUD TO MAKE MICROPHYSICS MEASUREMENTS. THE LEARJET WILL FIRST PENETRATE CLOUD NEAR THE FREEZING LEVEL AND THEN CONTINUE TO CLIMB AND PENETRATE THE UPDRAFT CORE UNTIL THE CLOUD IS GLACIATED. THE ABILITY OF THE LEARJET TO CLIMB AT RATES UP TO 5 000 FPM (21 M S-1) ALLOWS IT TO CLIMB AND PENETRATE THE SAME REGION OF THE UPDRAFT CORE PRODUCING A QUASI-LANGRANGIAN DOCUMENTATION OF THE UPDRAFT. ANALYSIS OF P3-B AND LEARJET MICROPHYSICAL DATA WILL BE CONDUCTED BY AN EXPERIENCED COMPLEMENT OF SPEC SCIENTISTS (DRS. LAWSON WOODS GURGANUS MO AND RODEN). DRS. MORRISON AND GRABOWSKI FROM NCAR PLAY A MAJOR (FUNDED) ROLE IN DATA ANALYSIS AND INTEGRATION OF THE NOVEL PIGGYBACKING MODEL METHODOLOGY. DR. ROELOF BRUINTJES FROM NCAR AND PRECIPITATION PHYSICS CONSULTANTS WILL PARTICIPATE AS FLIGHT SCIENTIST AND DATA ANALYSIS. DR. SEBASTIAN SCHMIDT FROM THE UNIVERSITY OF COLORADO (CU) AND DR. MELODY AVERY FROM NASA LANGLEY RESEARCH CENTER ARE COLLABORATORS ON THIS PROPOSAL., UNTANGLING DYNAMICAL AND MICROPHYSICAL CONTROLS OF CONVECTIVE UPDRAFT VERTICAL VELOCITY: INSIGHTS FROM A LAGRANGIAN PERSPECTIVE, G969889393
OpenAlex ID: W4417037933