Earth's Radiation Budget

The proposed work employs a state-of-the-art Earth System Model with comprehensive chemistry that can use horizontal regional refinement to explore the effects of climate change with and without Stratospheric Aerosol Interventions (SAI) on regional climate and air quality. So far, regional and local consequences of climate change and SAI are still very uncertain, and interactions between changes in climate and air quality have not been explored in the context of SAI. This project explores the topic from two different angles; one part focuses on investigating future changes in regional and local climate and air quality over some targeted regions starting with Asia and the Contiguous US. The other part focuses on the additional effects on climate and air quality and the stratospheric aerosol composition, using improved model capabilities that include ammonia and ammonium nitrate particles. Both parts require the development of the model using a sophisticated aerosol model.

Members of the Climate and Chemistry Processes program at the NOAA Chemical Sciences Laboratory will provide real time meteorological forecast for surface conditions in Houston in support of the SABRE high altitude aircraft experiment. They will also prepare flight plans for the mission and interface with the pilots and crew of the WB57 aircraft, and monitor flight conditions in real time during each flight. They will use a combination of both commercial flight software and products produced in house over the past 25 years. Following flights, they will prepare back trajectories for use in post-flight data analysis and provide advice on transport and dynamics.

Earth's radiation budget is changing over time, influenced by internal system variability, climate drivers which include natural and anthropogenic factors (volcanic eruptions, Sun's output; long-lived and short-lived greenhouse gases, aerosols, land-use, contrails), and the rapid interactions with other physical climate processes such as water vapor and clouds. The observed trend reflects an increased discernible imbalance of the Earth's global net radiation over time, and is a prominent indicator of the changes to the climate system (e.g., temperature, sea-level rise). This project will develop a methodology to quantify and map the annual changes in Earth's radiation budget using NOAA's state-of-the-art global climate models, and explain the contributions to the changing solar, longwave, and net radiation budget of the Earth system from anthropogenic and natural drivers, and consequent feedbacks. This understanding will contribute to determining the relative importance of the changing atmospheric constituents to Earth's radiation budget and to the assessment of climate intervention strategies through changes in atmospheric composition.

The University of Wisconsin-Madison Space Science and Engineering Center (SSEC) will provide forecast support for flight planning during the 2022 SABRE Mission using global chemical and aerosol forecasts combined with ensemble trajectory based diagnostics of the histories on flight altitudes covering the range WB-57. SSEC will contribute to the post mission analysis by using global chemical and aerosol analyses combined with ensemble trajectory based diagnostics to characterize the histories of air parcels sampled by the WB-57. These forecast and analysis products will help to interpret the WB-57 measurements by providing estimates of the large-scale distribution of trace gases, aerosol composition, and origin (i.e. stratosphere, free troposphere, continental boundary layer, marine boundary layer) of the atmosphere sampled during SABRE.

Rocket launch rates have more than tripled in the past decade and are expected to accelerate in frequency in the coming decades. Rockets are currently the only source of human- produced particle emissions in the middle atmosphere. Black carbon is of significant interest as it strongly absorbs solar UV radiation and emits longwave radiation which can have impacts ranging from increasing stratospheric temperatures to invigorating the heterogeneous chemistry which controls the concentration of stratospheric ozone. This study we will first develop an inventory of global spaceflight emissions from both rocket launches and space debris reentry. The new emissions inventory will then be used to investigate the stratospheric climate response to possible future spaceflight scenarios. Finally, the project team will calculate the dynamical, chemical and radiative impacts to the stratosphere due to potential increases in space activity over the 50 years.

Numerous ERB-funded efforts require software and in-field instrument support. These needs are consolidated into this one project for simplicity. Software support in FY22 is needed for continued modifications and refinements on the S-CIMS effort, NO/NO₂/NOy and SO₂, O₃, SP2, the ACOS OCS instrument, and B2SAP/OPUS/IBIS. Additional help in the field covers both the ACCLIP and SABRE campaigns.

Ozone measurements are critical to achieving a number of SABRE mission science goals. This project will implement several instrument upgrades and deploy the NOAA CSL UASO3 ozone photometer for measurements during SABRE WB-57 missions.

Winds in the atmosphere transport chemical constituents like stratospheric ozone to the surface, with impacts on tropospheric ozone and air quality. This project investigates how winds and vertical motion change in response to the climate intervention method termed Stratospheric Aerosol Injection (SAI), and how those changes influence ozone transport. The project team will investigate an ensemble of model runs that use SAI forcing to maintain surface temperature targets for (a) a scenario that allows greenhouse gases to increase through 2040 but then assumes significant emission reductions and net negative emissions after 2070 and (b) a worst-case scenario where greenhouse gas emissions continue to increase substantially. Dynamical mechanisms will be specifically evaluated for circulation changes, and how these changes can then affect ozone transport from the stratosphere to the troposphere. This project is a continuation of the 2021 project to analyze NCAR model output (GLENS) to assess impacts of increased stratospheric aerosol on the climate system.

Marine Cloud Brightening is a form of solar climate intervention that targets shallow, liquid marine clouds in the lowest 1500 m of the Earth's atmosphere. The idea is that an injection of particles into these clouds will create more numerous, smaller cloud droplets, leading to clouds that reflect more solar energy back to space, and a cooling of the planet. The goal of this continued project is twofold: (i) to assess seeding strategies for a number of different cloud targets over the course of a diurnal cycle, and for different perturbation durations; (ii) expand our understanding of the frequency of occurrence, areal coverage, seasonality, and geographical location of susceptible clouds at the global scale.

This project continues twice-monthly instrumented balloon launches at Boulder and quarterly at Lauder, New Zealand. The balloons carry compact, lightweight instruments that measure vertical profiles of water vapor, ozone, and aerosol number and size distribution from the surface to the middle stratosphere (~28 km). These measurements, made since June 2020, are being used to characterize the background state and variability of radiatively important aerosols in Earth's stratosphere. Measurements during the past two years have observed stratospheric air masses affected by strong volcanic eruptions and intense wildfires that injected material directly into the stratosphere. These measurements have helped us to better understand how these natural events alter stratospheric composition, especially the number and size distribution of aerosols, and how the aerosol perturbations evolve with time. During this period of performance, the project team also plans to investigate and likely initiate new ERB sounding programs at Hilo, Hawaii (20°N), Réunion Island (20°S) and Ross Island, Antarctica (78°S) to provide more comprehensive latitudinal coverage of stratospheric composition measurements.

This project provides continued support for a single-particle soot photometer (SP2) operator/analyst focused on black carbon aerosol relevant to ERB-relevant science, including the ACCLIP and SABRE efforts. SP2 provides a unique aerosol data product that is very useful and relevant to stratospheric ERB science as it can quantify black carbon (BC) concentrations even in very clean air. Black carbon (BC) is emitted primarily at the surface, and is only removed from the atmosphere by dry and wet deposition. In other words, BC is inert in the atmosphere, and thus a unique aerosol-phase tracer with relevance to potential changes in condensable materials into and around the stratosphere.

This project continues work started in 2021 to complete the stratospheric chemical ionization mass spectrometer (CIMS) development, and to support deployment and data analysis for the SABRE campaign scheduled for the winter or 2023. Project scientists will also perform post-mission calibrations and analysis of the SABRE results. CIMS instrument measures trace gases that react with particulates and provides new data to better define the current sensitivity of stratospheric ozone to these processes.

The major goals of the project are to evaluate the sampling performance of the low-turbulence inlet (LTI) currently in use by NOAA and design and build a next-generation LTI inlet that is compact and light, and applicable for use. For this next year of support, the project team is focused on simulating particle trajectories to understand particle transport losses in the tube inlet entrance and other possible locations where turbulence can enhance particle loss.

In 2021, the project team extended their work on producing and evaluating short-range (3-24 hour) forecasts of ash and sulfur dioxide (SO₂) for aviation to long-range forecasting up to 16 days and to investigate impacts of alternative mixing schemes, source term characterization, and resolution of mean wind fields and other meteorological data on the accuracy of predicted transport and dispersion of injected materials. This project will continue and improve upon that work by developing a method for empirically determining parameterizations utilizing the satellite retrievals of column mass loading for ash and SO₂.

This project continues work evaluating the impacts of aerosols as implemented in shallow, congestus, and deep convective parameterizations as well as microphysics parameterizations. Results and evaluations ranging from global to high-resolution regional model simulations and simple to complex parameterizations will be compared to observations during intensive field campaigns and Large Eddy Simulations.

This project continues work from 2021 to measure in-situ OCS from aircraft. These measurements will allow us to address a few key aspects to understanding stratospheric aerosols: (1) sources of stratospheric OCS, (2) age of air in the stratosphere and its relationship with aerosol composition and size distributions, (3) influence of convection and anthropogenic emissions on perturbing stratospheric composition. Current work will support SABRE flights planned for 2023 as well as the analysis of measurements.

This project continues laboratory studies supported by ERB in 2021 focused on either limestone (CaCO₃) or dimethyl sulfate (CH₃SCH₃ aka DMS) The experimental studies of CaCO₃, and related minerals, radiative properties and chemical transformations will enable climate models to establish the impacts of CaCO₃ as a climate intervention (SRM) material. The DMS oxidation studies will enable improvement in climate-chemistry modeling of marine boundary layer sulfate aerosol formation and its impact on cloud formation.

A low-cost alternative approach to observing stratospheric trace gases was developed at CIRES and NOAA/GML with the balloon-borne AirCore whole-air sampling system. CIRES/GML routinely uses the AirCore to collect and retrieve mole fraction profiles of CO₂, CH₄, and CO from the stratosphere, recently extending to include N₂O. In 2021, the project team adapted a custom gas chromatograph coupled with electron capture detectors to measure the mole fraction profiles of SF₆, N₂O, CFC-12, CFC-113, CFC-11, and H-1211 in AirCores, demonstrating the ability to analyze an enhanced suite of long-lived stratospheric trace gases in these samples. They also re-designed the AirCore (called the StratoCore) with a larger sampling volume and enhanced sampling efficiency in the stratosphere. In 2022, the team will strengthen the CIRES & GML stratospheric sampling program by conducting monthly StratoCore flights in Boulder, CO as well as interpreting routine multispecies StratoCore profiles collected to monitor and detect trends and potential changes in baseline stratospheric composition and dynamics.

For this project, CSL is working with World View Enterprises to make stratospheric size distribution measurements onboard a World View Stratollite commercial, navigable, long-endurance stratospheric balloon platform. Measurements from the POPS Stratollite Mission will help us better understand stratospheric aerosol under background conditions, as well following natural injections of sulfur gases and aerosols and aerosol precursors from explosive volcanic eruptions and very large fires. POPS flights on the Stratollite will also demonstrate the potential of using new observing platforms to acquire scientific data in the stratosphere for extended periods over large geographic regions. Continued support for this project allows for new launch opportunities and data collection following engineering improvements designed after the POPS instrument underwent rigorous testing in 2021.

ERB is participating in, and supporting, several airborne field campaigns in 2022 and 2023 including SABRE, SABRE, and ACCLIP. These projects are designed to improve understanding of the stratospheric aerosol layer, how particles formed from ocean emissions of gases affect the reflectivity of marine clouds, and how particles from different sources scatter and absorb sunlight. Measurements of aerosol extinction and absorption and of the number of aerosol particles as a function of their size, are vital to understanding all of these processes. These measurements are considered mission-critical for the planned field campaigns. This project provides continued airborne field campaign support for these measurements by hiring additional staff to improve and test instruments, install them on the research aircraft, participate in field measurements, and lead analysis, interpretation, and publication of the results.

Nitrogen oxides (e.g. NO, NO₂) and halogen oxides (e.g. ClO, BrO, etc.) are key species for stratospheric chemistry, acting as radical chain propagators and ozone destruction catalysts. Understanding their contributions to stratospheric chemistry requires measurements of these species and their photolysis frequencies. This project provides support for development and operation of instrumentation to provide measurements of nitrogen oxides and NO₂ photolysis frequencies on the WB-57 during ERB research flights in the stratosphere. Through these measurements, we will provide insight into radical chemistry in the stratosphere, and the chemical effects of aerosols on stratospheric ozone.

The Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN) was established in 2008 to be an international network of sites making reference-quality measurements of essential climate variables above Earth's surface, designed to fill an important gap in the current global observing system. GRUAN measurements are providing long-term, high-quality climate data records from the upper troposphere into the lower stratosphere. These data are being used to determine trends, constrain and calibrate data from more spatially-comprehensive observing systems including satellites and current operational radiosonde networks, and provide important data for studying atmospheric processes. This project continues support for and supplies new instrumentation to the three US GRUAN sites in Boulder, CO; Beltsville, MD; and Lamont, OK; as well as the GRUAN station in Lauder, New Zealand.

The Particle Analysis by Laser Mass Spectrometry (PALMS) instrument measures the composition of single aerosol particles. By flying this instrument on the WB-57F aircraft, we can learn about the sources, sinks, and climate properties of particles in the lower stratosphere. This project continues support for the PALMS instrument which will fly on the WB-57F aircraft during ERB missions in 2022-2023.

This project continues support for Uncrewed Aerial System flights measuring vertical profiles of aerosol and cloud properties in the marine boundary layer. The overall goal is to further our understanding of the impacts of aerosol on direct radiative forcing and cloud properties in the marine boundary layer.