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The convective mass flux within tropical convection influences the large-scale circulation, drives cloud radiative forcing, has integral links to the production of fresh water, and impacts extreme weather. CMF forms the focus of the recently selected Investigation of Convective Updrafts (INCUS) mission to be launched in 2026. This NASA mission is comprised of 3 spacecraft, all of which will carry a Ka-band cloud radar. One spacecraft will also carry a passive microwave radiometer. The 3 smallsats are to be separated by time intervals of 30, 90 and 120 seconds, thus allowing for the rapid and systematic sampling of the same storm with all three spacecraft. These time intervals (delta-ts) also facilitate the investigation of the magnitude and evolution of CMF, which will be examined as a function of storm type, storm lifecycle and environmental properties. INCUS will therefore provide the first global systematic investigation into CMF and its evolution within deep tropical convection.A wide range of research tasks have been conducted in preparation for the INCUS mission and the development of the INCUS algorithms including: (1) running and analyzing extensive suites of large-domain, high-resolution model simulations; (2) examining ground-based Doppler radar observations obtained using adaptive scanning techniques during several recent field campaigns; and (3) evaluating anvil characteristics using passive microwave radiometer and geoIR data. This talk will focus on three specific highlights arising from these modeling and observational analyses. First, we will examine the temporal scales of updraft variability. Second, we will analyze the relationship between ice water path cores and convective updrafts. Finally, we will demonstrate proof of the INCUS delta-t concept linking changes in reflectivity to CMF through the use of ground-based radar analyses.

Microwave radiometers and radars in low Earth orbit (LEO) are sensitive to the amount of condensed water in clouds. However, their temporal sampling is quite limited – a single LEO instrument will very rarely observe a weather system more than once during the lifetime of the system. Recent technological advances have enabled the design of miniaturized microwave instruments that are quite capable and, at the same time, inexpensive enough to consider the formation of a convoy of identical radars or radiometers in low-Earth orbit, separated in time by a very short interval, on the order of a minute, the temporal scale required to observe the highly nonlinear cloud dynamics. The time sequences of observations are conceptually similar to the loops that are currently obtained from ground weather radar, as well as geostationary imagery, which readily show the evolution of precipitation (in the radar case) or cloud tops (in the imagery case) over minutes. The satellite convoys overcome the limitations of geostationary images (which are sensitive only to the very top of the clouds), and those of ground radar (with its very limited spatial coverage and its insufficiently short interval between consecutive scans). Because each satellite instrument is sensitive to the 3-dimensional distribution of condensed water within its field of view, the convoy is sensitive to the change in this condensed water over the minute(s) separating the convoy members. NASA’s recently selected INCUS mission will be the first project to demonstrate this new concept, with a convoy of three identical Ka-band reflectivity profiling radars, along with a five-channel microwave radiometer.We have conducted analyses based on simulations – as well as observations from ground-based zenith-pointing profilers – to quantify the ability of a convoy made up of a pair of small Ka-band radars that measures reflectivity only, or a pair of mm-wave radiometers that measures microwave radiances in several mm-wavelength channels, to detect convective updrafts above the freezing level and to quantify their intensity. In the case of a pair of radars, one can retrieve the vertical profile of the vertical transport in the portion of the column where the condensed water concentration is above a minimum threshold (of about 0.05 g/m3 in our analyses) and the vertical velocity exceeds a minimum threshold (of about 2 m/s) with quite low uncertainty (whose characteristics depend on the coarse shape of the vertical velocity as a function of height). These new observation strategies are not only useful to evaluate and improve the model representation of vertical transport in convective storms, they are also uniquely useful to quantify a currently “missing link” in the Hadley circulation, in establishing the potential-energy contribution by an individual convective system to the Upper Troposphere / Lower Stratosphere bubble of high-entropy air mass.Acknowledgement: This research was carried out at Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration

In this two-part study, the relationships between the width of the cloud droplet size distribution and the microphysical processes and cloud characteristics of nonprecipitating shallow cumulus clouds are investigated using large-eddy simulations. In Part I, simulations are run with a bin microphysics scheme and the relative widths (standard deviation divided by mean diameter) of the simulated cloud droplet size distributions are calculated. They reveal that the value of the relative width is higher and less variable in the subsaturated regions of the cloud than in the supersaturated regions owing to both the evaporation process itself and enhanced mixing and entrainment of environmental air. Unlike in some previous studies, the relative width is not found to depend strongly on the initial aerosol concentration or mean droplet concentration. Nonetheless, local values of the relative width are found to positively correlate with local values of the droplet concentrations, particularly in the supersaturated regions of clouds. In general, the distributions become narrower as the local droplet concentration increases, which is consistent with the difference in relative width between the supersaturated and subsaturated cloud regions and with physically based expectations. Traditional parameterizations for the relative width (or shape parameter, a related quantity) of cloud droplet size distributions in bulk microphysics schemes are based on cloud mean values, but the bin simulation results shown here demonstrate that more appropriate parameterizations should be based on the relationship between the local values of the relative width and the cloud droplet concentration.