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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Field-aligned current associated with a distorted two-cell convection pattern during northward interplanetary magnetic field

The influence of the ionospheric conductance on the field-aligned current associated with a distorted two-cell convection pattern during northward IMF was investigated using the Heppner-Maynard (1987) convection model and the Utah State University conductivity model described by Rasmussen and Schunk (1987). Results show that the variation of the ionospheric conductivity distribution can significantly affect the features of the field-aligned current for northward IMF, where matching or mismatching between the conductance gradient and the convection electric field plays a key role. It was found that the increase of the field-aligned current in the polar cap observed during summer is mainly due to the increasing contribution from the Pedersen current, and that the increase of the field-aligned current in both the oval region and the evening-midnight sector during the active aurora period is mainly due to the increasing contribution from the Hall current.

Zhu, L.↗
NASA NTRS1976

Convection cells in the early lunar magma ocean - Trace-element evidence

A method was proposed for recognizing suites of samples which are related to the differentiation of distinct and regionally separated magmas in the early lunar surface ocean. The sample suites were identified by three Cl-P2O5 compositional groups. New experimental data continue to add samples to these groups. Each magma was associated with a convection cell the boundaries of which are proposed. Independent geochemical evidence supporting a limited number of early magmas is cited. Two new possible Cl-P2O5 groups are identified. Samples not indigenous to a given site and their possible source regions are identified. It is proposed that many Apollo 17 basalts are not locally derived.

Jovanovic, S.↗
NASA NTRS2010

Do the Tallest Convective Cells Over the Tropical Ocean Have Slow Updrafts?

Far from continents, a few storms lift precipitation-size ice particles into the stratosphere, 17 to 18 km above the tropical ocean. This study is the first to examine the observed properties of a large sample of these extremely tall convective storm cells. The central questions in this study are whether the unusually tall ocean cells have the slow updrafts known to be typical of oceanic convection, and if so, how can these tall cells reach such extreme heights. The precipitation radar on the Tropical Rainfall Measuring Mission (TRMM) satellite observed 174 extremely tall oceanic cells from 1998 to 2007. Relative updraft intensity is inferred from 17-km-tall oceanic cells having, on average, a 7-km lower 40-dBZ radar reflectivity height and an order of magnitude less lightning than do equally tall cells over the Sahel region of Africa, a region known for vigorous convective updrafts. Despite some ambiguity, the potential temperature and lapse rate of the NCEP reanalysis suggest that the environment in which these oceanic cells form is conducive to modest updrafts reaching extreme heights. Extrapolating based on the limited coverage of the TRMM satellite radar, it is likely that such extremely tall cells occur more often than once each day somewhere over the tropical ocean.

Kelley, Owen A.↗
DOE OSTI2025

TRACER-MAP: Mapping Aerosol Processes Across Houston During Convective Cell Events

The Houston, TX Metropolitan area was selected for the 2022 Tracking Aerosol Convection Interactions Experiment (TRACER) due to its high convective storm activity and broad range of polluted aerosol conditions. With the overall TRACER project in mind, we planned TRACER-MAP, a related investigation of the impacts of convective storms on atmospheric composition, chemistry and aerosol processing in Houston. Because the Houston metroplex is large and has a wide range of atmospheric conditions, this project has “MAP-ped” the air chemistry conditions across Houston while atmospheric scientists working in the TRACER project monitor convective storm activity overhead. Specifically, we conducted a series of aerosol, gas, and meteorological measurements in the summer of 2022 that matches measurements from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Mobile Facilities. The TRACER-MAP campaign extended from Jul 1 – Sept 3, 2022. TRACER-MAP included two urban sites: Aldine and University of Houston (UH); two industrial sites: San Jacinto Battleground and the main DOE TRACER site at the La Porte Municipal Airport (ARM/La Porte AMF); and one background site in WG Jones State Forest north of Houston.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Observed Variability in Convective Cell Characteristics and Near-Storm Environments across the Sea- and Bay-Breeze Fronts in Southeast Texas

Abstract During the DOE Atmospheric Radiation Measurement (ARM) Tracking Aerosol Convection Interactions Experiment (TRACER) IOP spanning June–September 2022, two fixed ARM sites and a mobile team concurrently sampled the airmass heterogeneity across sea- and bay-breeze fronts around the greater Houston metropolitan region. Here, we quantify the spatiotemporal variability between maritime (coastal/bay side of breeze fronts) and continental (inland side of breeze fronts) air masses over 15 IOP days characterized by strong sea-breeze forcing. We analyze environmental profile data from 177 radiosondes and use S- and C-band radar data to track and quantify the variability in attributes of more than 2300 shallow and transitioning cells across different air masses. The composite analysis of environmental profiles indicates that during the early afternoon, the sea-breeze maritime air mass exhibits lower convective available potential energy (CAPE) than the bay-breeze maritime air mass. As the sea breeze advances inland with time, CAPE within the maritime air mass exceeds that of the continental air mass to the north of the breeze fronts. In general, maritime cells have a larger mean composite reflectivity and cell widths than continental cells; however, the response varies between shallow and transitioning cells. Mean composite 20-dB Z echo-top heights, however, are similar across air masses for both shallow and transitioning cells. The continental and maritime inflow air mass for transitioning cells has significantly different mean values for mixed-layer entrainment CAPE, lifted condensation level, level of free condensation, boundary layer depth, and diluted equilibrium level. For shallow cells, only total precipitable water shows a significant difference. Significance Statement The greater Houston metropolitan area is a natural laboratory for understanding the individual impacts of background meteorology and aerosols on convective clouds. Due to its proximity to the Gulf Coast and Galveston Bay, the Houston region experiences a diurnal precipitation cycle in the summer, driven by convection triggered from sea- and bay-breeze fronts. These fronts act as a boundary between air masses with distinct thermodynamic and environmental characteristics. Convergence along these fronts and interactions between storm outflow and the fronts facilitate convection initiation in different mesoscale air masses. This study quantifies the heterogeneity among these air masses while investigating their influence on cloud microphysics. We find that the effect of airmass heterogeneity is more pronounced for the bulk microphysical properties in shallow clouds.

Sharma, Milind↗
NASA NTRS1974

Cloud top height variability of strong convective cells

Cloud top height variability of cloud domes above the cirrostratus anvil was investigated for two severe local storm occurrences over Texas on May 12 and 13, 1972. Twenty-three domes were monitored and the average maximum height was 1.6 km above the anvil. It was estimated that a dome would take a maximum of about 6 min to grow from the anvil level to peak altitude based on measurements over the last 2 min of the growth period when the upward vertical velocity averaged 4 m/sec. The extreme vertical growth rate was 27 m/sec for a 30-sec period. This vertical growth rate compared with a range of 11.4-19.4 m sec determined from a method of estimating vertical motions based on laboratory measurements. Average dome collapse was at the same rate as the average ascent for the first 90 sec after the maximum altitude was reached.

Shenk, W. E.↗
NASA NTRS1980

A search for large-scale convection cells in the solar atmosphere

Mount Wilson magnetograph velocity observations are used to search for east-west motions resulting from hypothetical cellular patterns extending over one or two hemispheres in the latitude direction. No such solar patterns were found. Upper limits established by this analysis depend on the cell lifetime and the pattern stability, but in all cases they are no more than about 10 m/s.

Howard, R.↗
NASA NTRS1981

An improved search for large-scale convection cells in the solar atmosphere

A reanalysis of Mount Wilson solar velocity observations was made to search for giant cellular patterns. The reanalysis avoids several errors made in a previous search. No cells are detected with sensitivity of 3 to 12 m/s depending upon wavenumber. The observed amplitudes do not conflict with recent model predictions.

Labonte, B. J.↗
NASA NTRS1991

Dynamical buoyancy of hydrodynamic eddies

The dynamical pressure reduction within a vortex tube produces both a tension along the tube and a general buoyancy, analogous to magnetic flux tubes. The dynamical buoyancy causes convective cells to rise at speeds comparable to the rms fluid velocity within the cell. Consequently, the convective cells in a stratified atmosphere are more active than indicated by the standard anelastic approximation. The coherent convective cells at each level actively crowd upward into the convective cells above, elbowing weaker cells out of the way and flattening themselves and others against the upper surface of the convective region. These effects can be seen in the recent SOUP observations of the solar granulation. Deeper in the convective zone the inhomogeneity of the buoyancy may explain the random character of the convective motions that turns up in recent numerical simulations.

Parker, E. N.↗
NASA NTRS1972

Finite-amplitude thermal convection within a self-gravitating fluid sphere.

Finite-difference calculations have been carried out to determine the structure of finite-amplitude thermal convection within a self-gravitating fluid sphere with uniform heat release. For a fixed-surface boundary condition, single-cell convection breaks up into double-cell convection at a Rayleigh number of 30,000, at a Rayleigh number of 500,000 four-cell convection is observed. With a free-surface boundary condition only single cell convection is obtained up to a Rayleigh number of 5,000,000.

Hsui, A. T.↗
DOE OSTI2022

The Behaviors of Intraseasonal Cloud Organization During DYNAMO/AMIE

This study investigates the organization of tropical convection associated with the Madden-Julian Oscillation (MJO) during the Dynamics of the MJO/Atmospheric Radiation Measurement MJO Investigation Experiment field campaign. While it is known that tropical clouds can organize and impact the large-scale environment, how this occurs, and its underlying mechanism are not fully understood. Application of several existing cloud organization indices showed inconsistent evolutions in the measured degree of organization with the MJO. The inconsistency arises from the varying definitions and assumptions of cloud organization behaviors that are applied to each index. While these indices often combine different properties of clouds, such as their number density, size, and distance between them, the analysis of these properties separately provided further understanding of how clouds organize with the MJO. Using the rainfall clusters identified from the S-Polka radar, we find that deep convective rainfall clusters begin to increase their number density before the arrival of MJO enhanced convective center, which is accompanied by increased proximity (shorter distance to each other) and followed by growth in their size. However, the nonrandomness in the spatial distribution of rainfall clusters maximizes as MJO convection decays. Deep convective clusters become the least randomly distributed as the clusters decay because of the suppression and decay of isolated deep convective cells, while clustered deep convective cells exist longer. This evolution of cloud organization is analogous to mesoscale convective systems, indicating that the duration and frequency of their organization stages are altered by the large-scale environmental perturbations associated with the MJO.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

CSAPR2 cell-tracking data collected during TRACER

One of the challenges of analyzing convective cell properties is quick evolution of the individual convective cells. While the operational radar data provide great a data set to analyze the evolution of radar observables of convective precipitation clouds statistically, previous studies also suggested that, because of the quick evolution of cell life cycle, conventional radar volume scan strategies taking ~5-7 minutes might not capture the detailed evolution. The TRACER campaign deployed CSAPR2, which performed frequent update of RHI and sector PPI scans to track convective cells every < 2 minutes guided by a new cell-tracking framework, Multisensor Agile Adaptive Sampling (MAAS; Kollias et al. 2020). This allows for capturing fast-evolving radar observables. The submitted data files are CSAPR2 data in CfRadial format collected during the TRACER field campaign from June to September 2020. The data files include processed radar variables including: noise-masked reflectivity and differential reflectivity corrected for rain attenuation and systematic biases, noise-masked dealiased radial velocity, specific differential phase, locations of target cells (latitude, longitude, radar range), and radar-echo classification.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Model Intercomparison of the Impacts of Varying Cloud Droplet–Nucleating Aerosols on the Life Cycle and Microphysics of Isolated Deep Convection

The microphysical impacts of aerosol particles on scattered isolated deep convective cells near Houston, Texas, on 19 June 2013, are examined using multiple cloud-resolving model (CRM) simulations initialized with vertical profiles of low and high concentrations of cloud droplet–nucleating aerosols. These simulations formed part of the Model Intercomparison Project (MIP) conducted by the Deep Convective Working Group of the Aerosol, Cloud, Precipitation and Climate (ACPC) initiative. Each CRM generated a field of convective cells representing those observed during the case study with varying degrees of accuracy. The Tracking and Object-Based Analysis of Clouds (tobac) cell-tracking algorithm was applied to each MIP CRM simulation to track relatively long-lived convective cells (20–60 min). Most of the CRMs produced similar aerosol loading impacts on the warm phase of tracked cell properties with reduced autoconversion and accretion growth of rain, increased cloud water, reduced rainfall, and reduced near-surface evaporation of rain. The sign of aerosol impacts on the warm-phase properties of the convective cells was also quite consistent over cell lifetimes with the greatest magnitude of influence in the first half of the life cycle in most CRMs. In contrast, the ice-phase response to aerosol loading was highly variable among CRMs and included increases or decreases in ice amounts at inconsistent stages of the cell life cycle and midlevel versus upper-level changes in ice. This intermodel variability in ice is indicative both of the complex indirect interactions between aerosols and ice-phase processes in deep convection and their associated parameterizations.

Aerosol-cloud interaction↗