Public Abstract

DE-SC0020056: Interactions Between Aerosols, Meteorology, and Early Convective Cloud Lifecycle as Measured During CACTI

Award Status: Expired

Institution: University of Utah, Salt Lake City, UT
UEI: LL8GLEVH6MG3
DUNS: 009095365

Most Recent Award Date: 01/28/2022
Number of Support Periods: 2
PM: Nasiri, Shaima

Current Budget Period: 08/15/2020 - 08/14/2023
Current Project Period: 08/15/2019 - 08/14/2023
PI: Zipser, Edward

Supplement Budget Period: N/A

Public Abstract

Interactions Between Aerosols, Meteorology, and Early Convective Cloud Lifecycle as Measured During CACTI PI: Edward Zipser, University of Utah PROJECT SUMMARY / ABSTRACT This proposal addresses convective cloud processes with a specific focus on (1) the interactions between convective dynamics and microphysics, and the initiation, growth, and organization of convective systems. These deep convective systems are important because they often contain severe, damaging thunderstorms, and/or flash flooding. We shall take full advantage of the comprehensive database produced by the DOE/ARM Cloud, Aerosol, and Complex Terrain Interactions (CACTI) program in 2018-19 in Argentina, because of the huge advantages afforded by concentrating surface, radar, and aircraft observations in a location well-known for the high frequency of convective initiation, often growing into deep, intense storms nearby. Research questions to be addressed include (1) How predictable is the transition from clouds of moderate depth to deep storms, and (2) Which combinations of environmental variables, specifically including aerosols, are the best predictors of this transition? The project will proceed in three distinct but eventually overlapping and complementary tasks. First will be primarily observational, characterizing the relationship between atmospheric variables (including aerosols on which cloud droplets form) and properties of early stage convection. The 6-week period when data from instrumented aircraft made spiral ascents over the surface site will be used to decide when the surface-based data are representative of air actually entering the convective clouds, with the aid of sounding data, for the full CACTI 7-month period. Cloud top heights from frequent satellite data will be used to supplement the comprehensive radar data at the observing site on the mountain slopes, enabling knowledge of which convective initiation days led to deep, rapidly growing storms. Second, we will use rigorous statistical analysis to identify robust relationships between the effects of aerosols on growth of storms over the full CACTI experimental period. Third, we will conduct a series of high-resolution numerical simulations in which all variables can be controlled. Because the convective clouds of greatest interest are not large initially, we shall use 100 meter resolution in the inner grid, and we will also be able to choose well-observed cases, one with high observed aerosol concentrations and one with low concentrations. We anticipate the following outcomes. (1) Comprehensive analysis of observed initial conditions for the 7-month CACTI period that will be used for study of the relationship between aerosols and convective growth. (2) By weeding out inappropriate periods for such work, e.g., periods when multiple cloud bases exist such that air near the surface would not enter the convection, any relationships found should be robust and well-documented. (3) By a series of high-resolution experiments, rigorously test any relationships found, including the chain of events by which the hypothesized convective invigoration occurs, especially in the region of the clouds unsafe for direct aircraft penetration because of the threat of wing icing, but accessible to examination by dual-polarized radars at the observing site during CACTI.

Interactions Between Aerosols, Meteorology, and Early Convective Cloud Lifecycle as Measured During CACTI

PI: Edward Zipser, University of Utah

PROJECT SUMMARY / ABSTRACT

This proposal addresses convective cloud processes with a specific focus on (1) the interactions between convective dynamics and microphysics, and the initiation, growth, and organization of convective systems. These deep convective systems are important because they often contain severe, damaging thunderstorms, and/or flash flooding. We shall take full advantage of the comprehensive database produced by the DOE/ARM Cloud, Aerosol, and Complex Terrain Interactions (CACTI) program in 2018-19 in Argentina, because of the huge advantages afforded by concentrating surface, radar, and aircraft observations in a location well-known for the high frequency of convective initiation, often growing into deep, intense storms nearby. Research questions to be addressed include (1) How predictable is the transition from clouds of moderate depth to deep storms, and (2) Which combinations of environmental variables, specifically including aerosols, are the best predictors of this transition?

The project will proceed in three distinct but eventually overlapping and complementary tasks. First will be primarily observational, characterizing the relationship between atmospheric variables (including aerosols on which cloud droplets form) and properties of early stage convection. The 6-week period when data from instrumented aircraft made spiral ascents over the surface site will be used to decide when the surface-based data are representative of air actually entering the convective clouds, with the aid of sounding data, for the full CACTI 7-month period. Cloud top heights from frequent satellite data will be used to supplement the comprehensive radar data at the observing site on the mountain slopes, enabling knowledge of which convective initiation days led to deep, rapidly growing storms. Second, we will use rigorous statistical analysis to identify robust relationships between the effects of aerosols on growth of storms over the full CACTI experimental period. Third, we will conduct a series of high-resolution numerical simulations in which all variables can be controlled. Because the convective clouds of greatest interest are not large initially, we shall use 100 meter resolution in the inner grid, and we will also be able to choose well-observed cases, one with high observed aerosol concentrations and one with low concentrations.

We anticipate the following outcomes. (1) Comprehensive analysis of observed initial conditions for the 7-month CACTI period that will be used for study of the relationship between aerosols and convective growth. (2) By weeding out inappropriate periods for such work, e.g., periods when multiple cloud bases exist such that air near the surface would not enter the convection, any relationships found should be robust and well-documented. (3) By a series of high-resolution experiments, rigorously test any relationships found, including the chain of events by which the hypothesized convective invigoration occurs, especially in the region of the clouds unsafe for direct aircraft penetration because of the threat of wing icing, but accessible to examination by dual-polarized radars at the observing site during CACTI.