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Overshooting storms are convective systems with updrafts that penetrate through the tropopause into the overlying stratosphere. These storms can rapidly transport a wide variety of chemical species and aerosols from the boundary layer and free troposphere directly to the stratosphere. The central plains of the U.S. and the Sierra Madre Occidental of Mexico are two of the global hotspots for overshooting convection. While the existence of these storms has been known for several decades, the amount of tropospheric air, including water vapor, trace gases, and aerosols, transported across the tropopause is poorly understood, as is their impact on the dynamics, chemistry, and radiative balance of the stratosphere. Climate models suggest that as Earth’s climate continues to warm, overshooting convection over the U.S. may increase, potentially causing changes to stratospheric composition and transport. To address these scientific questions, the NASA ER-2 high-altitude research aircraft flew 31 missions during the summers of 2021 and 2022 to make observations of the outflow from overshooting storms in the stratosphere over North America and the eastern Pacific Ocean as part of the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) project. The ER-2 carried a payload of 12 instruments to measure meteorological parameters, water and its isotopologues, trace gases, and aerosol properties. Ozone, water vapor, and aerosol sondes were also launched on balloons during the field deployments. This paper describes the science goals of the DCOTSS project, the aircraft measurement strategy, the data produced by the project, and highlights of science results to date.
In this paper, we present high-order boundary procedures for finite-volume and finite-difference schemes. The proposed procedures are deliberately constructed with precomputed derivatives such that they can be implemented without directly accessing cells beyond immediate neighbors and without explicitly setting up ghost cells. These features are expected to benefit unstructured-grid solvers (as well as parallel structured-grid solvers) for applications with smoothly-varying quadrilateral/hexahedral grids. In this paper, we will focus on the basics of the proposed procedures for third- and fourth-order accuracy, deriving and demonstrating the proposed boundary procedures for nonlinear conservation laws in one dimension.
Smoke from agricultural fires is a potentially important source of fine particulate matter (PM2.5) in the US. Sugarcane is burned in Florida to facilitate the harvesting process, with the majority of these fires occurring in the Everglades Agricultural Area (EAA), where there is only one regulatory air quality monitor. During the 2022-2023 sugarcane burning season (October-May), we used public low-cost PurpleAir sensors, regulatory monitors, and 29 PurpleAir sensors deployed for this study to quantify PM2.5 from agricultural fires. We found satellite imagery is of limited use for detecting smoke from agricultural fires in Florida due to the cloud cover, overnight smoke, and the fires being small and short-lived. For these reasons, surface measurements are critical for capturing increases in PM2.5 from smoke, and we used multiple smoke-identification criteria. During the study period, median 24-hour PM2.5 concentrations increased by 2.3-6.9 μg m-3 on smoke-impacted days compared to unimpacted days, with smoke observed on 4%-28% of the campaign days (ranges from the different smoke-identification criteria). Further, short-term PM2.5 increases were observed over 40 μg m-3 during smoke events. We contrast the region near the EAA with large populations of low-income and minoritized groups to the more affluent coastal region. The inland region experienced more smoke-impacted monitor days than the Florida east coast region, and there was a higher study-average smoke PM2.5 concentration in the inland area. These findings highlight the need to increase air quality monitoring near the EAA.
The Hunga eruption (20° S) in January 2022 injected a substantial amount of water vapor and aerosols into the stratosphere, primarily impacting the Southern Hemisphere and tropics. Using a combination of satellite observations and in situ measurements with optical particle counters, we show that a significant portion of the aerosol plume was transported into the Northern Hemisphere (NH) mid-latitudes. This cross-hemispheric transport occurred within the tropically controlled transition zone, within the shallow branch of the Brewer–Dobson circulation. By October 2022, enhanced aerosol concentrations were observed up to 50° N, at altitudes between 17–23 km with some dense plumes at around 21–22 km. In situ observations reveal an effective radius of around 330 nm, comparable to what was observed in the Southern Hemisphere (SH). Aerosol extinction coefficients in the mid-latitudes (30–50° N) were approximately doubled over background levels, corresponding to an aerosol optical depth (AOD) increase of (1–2) × 10−3 across the SAGE III/ISS wavelengths. These enhancements led to a modest, but not negligible, shortwave top-of-atmosphere (TOA) radiative forcing of -0.05±0.01 W m−2 between November 2022 and February 2023. Our results show that the moderate aerosol impact of the Hunga eruption in the SH produced non-negligible radiative impacts in the NH, emphasizing the importance of considering both hemispheres when analysing the total impact.
BACKGROUND:Prescribed burning is a major but poorly characterized source of fine particulate matter (PM2.5) in the southeastern United States. While wildfire-related smoke PM2.5 has been linked to adverse birth outcomes, evidence on prescribed fire-related smoke (PFS) and birth weight remains limited, particularly in the Southeast. OBJECTIVE:This study investigated the association between prenatal exposure to PFS-specific PM2.5 and birth weight in Georgia, USA. METHODS:We analyzed 448,477 singleton term births (37-42 weeks of gestation) with last menstrual period (LMP) dates between January 1, 2013 and December 31, 2016. Daily ZIP code-level PFS PM2.5 concentrations were averaged over early gestation (first 4 and 6 weeks), each trimester, and the entire pregnancy. High-exposure metrics were defined as the number of days exceeding percentile-based thresholds for each exposure window. Linear regression models adjusted for non-PFS PM2.5, LMP date, gestational age, infant sex, and maternal characteristics. RESULTS:Higher PFS PM2.5 exposure was independently associated with lower birth weight. Each 1 µg/m3 increase in average PFS PM2.5 during the first 4 weeks and the first trimester was associated with birth weight decreases of 3.22 g (95 % confidence interval [CI]: 0.82, 5.62) and 4.56 g (95 % CI: 0.12, 9.00), respectively. Each additional day exceeding the 95th percentile (1.21 µg/m3) of PFS PM2.5 during the entire gestation corresponded to an 11.70 g (95 % CI: 0.95, 22.45) reduction. CONCLUSION:Prenatal PFS exposure may reduce birth weight, particularly during early pregnancy, and both exposure intensity and duration are important in evaluating the health impacts of fire-related PM2.5.
