Results for “Stratosphere” — Page 6

NASA NTRS2004

A Long Data Record (1979-2003) of Stratospheric Ozone Derived from TOMS Cloud Slicing: Comparison with SAGE and Implications for Ozone Recovery

It is generally recognized that Stratospheric Aerosols and Gas Experiment (SAGE) stratospheric ozone data have become a standard long-record reference field for comparison with other stratospheric ozone measurements. This study demonstrates that stratospheric column ozone (SCO) derived from total ozone mapping spectrometer (TOMS) Cloud Slicing may be used to supplement SAGE data as a stand-alone long- record reference field in the tropics extending to middle and high latitudes over the Pacific. Comparisons of SAGE I1 version 6.2 SCO and TOMS version 8 Cloud Slicing SCO for 1984-2003 exhibit remarkable agreement in monthly ensemble means to within 1-3 DU (1 - 1.5% of SCO) despite being independently-calibrated measurements. An important component of our study is to incorporate these column ozone measurements to investigate long-term trends for the period 1979-2003. Our study includes Solar Backscatter Ultraviolet (SBW) version 8 measurements of upper stratospheric column ozone (i.e., zero to 32 hPa column ozone) to characterize seasonal cycles and seasonal trends in this region, as well as the lower stratosphere and troposphere when combined with TOMS SCO and total column ozone. The trend analyses suggest that most ozone reduction in the atmosphere since 1979 in mid-to-high latitudes has occurred in the Lower stratosphere below approx. 25 km. The delineation of upper and lower stratospheric column ozone indicate that trends in the upper stratosphere during the latter half of the 1979-2003 period have reduced to near zero globally, while trends in the lower stratosphere have become larger by approx. 5 DU decade%om the tropics extending to mid-latitudes in both hemispheres. For TCO, the trend analyses suggest moderate increases over the 25-year time record in the extra-tropics of both hemispheres of around 4-6 DU (Northern Hemisphere) and 6-8 DU (Southern Hemisphere).

Ziemke, Jerry R.↗

NASA NTRS2004

The Remarkable 2003-2004 Winter and Other Recent Warm Winters in the Arctic Stratosphere Since the Late 1990s

The 2003-2004 Arctic winter was remarkable in the 40-year record of meteorological analyses. A major warming beginning in early January 2004 led to nearly two months of vortex disruption with high-latitude easterlies in the middle to lower stratosphere. The upper stratospheric vortex broke up in late December, but began to recover by early January, and in February and March was the strongest since regular observations began in 1979. The lower stratospheric vortex broke up in late January. Comparison with two previous years, 1984-1985 and 1986-1987, with prolonged mid-winter warming periods shows unique characteristics of the 2003-2004 warming period: The length of the vortex disruption, the strong and rapid recovery in the upper stratosphere, and the slow progression of the warming from upper to lower stratosphere. January 2004 zonal mean winds in the middle and lower stratosphere were over two standard deviations below average. Examination of past variability shows that the recent frequency of major stratospheric warmings (seven in the past six years) is unprecedented. Lower stratospheric temperatures were unusually high during six of the past seven years, with five having much lower than usual potential for PSC formation and ozone loss (nearly none in 1998-1999, 2001-2002 and 2003-2004, and very little in 1997-1998 and 2000-2001). Middle and upper stratospheric temperatures, however, were unusually low during and after February. The pattern of five of the last seven years with very low PSC potential would be expected to occur randomly once every approximately 850 years. This cluster of warm winters, immediately following a period of unusually cold winters, may have important implications for possible changes in interannual variability and for determination and attribution of trends in stratospheric temperatures and ozone.

Manney, Gloria L.↗

NASA NTRS2006

Weather from the Stratosphere?

Is the stratosphere, the atmospheric layer between about 10 and 50 km, important for predicting changes in weather and climate? The traditional view is that the stratosphere is a passive recipient of energy and waves from weather systems in the underlying troposphere, but recent evidence suggests otherwise. At a workshop in Whistler, British Columbia (1), scientists met to discuss how the stratosphere responds to forcing from below, initiating feedback processes that in turn alter weather patterns in the troposphere. The lowest layer of the atmosphere, the troposphere, is highly dynamic and rich in water vapor, clouds, and weather. The stratosphere above it is less dense and less turbulent (see the figure). Variability in the stratosphere is dominated by hemispheric-scale changes in airflow on time scales of a week to several months. Occasionally, however, stratospheric air flow changes dramatically within just a day or two, with large-scale jumps in temperature of 20 K or more. The troposphere influences the stratosphere mainly through atmospheric waves that propagate upward. Recent evidence shows that the stratosphere organizes this chaotic wave forcing from below to create long-lived changes in the stratospheric circulation. These stratospheric changes can feed back to affect weather and climate in the troposphere.

Baldwin, Mark P.↗

NASA NTRS2008

An Overview of the Impact of Energetic Particle Precipitation on the Mesosphere and Stratosphere

Energetic precipitating particles (EPPs) can cause significant constituent changes in the polar mesosphere and stratosphere (middle atmosphere) during certain periods. Both protons and electrons can influence the polar middle atmosphere through ionization and dissociation processes. EPPs can enhance HOx (H, OH, HO2) through the formation of positive ions followed by complex ion chemistry and NOx (N, NO, NO2) through the dissociation of molecular nitrogen. The HO, increases can lead to ozone destruction in the mesosphere and upper stratosphere via several catalytic loss cycles. Such middle atmospheric HOx,-caused ozone loss is rather short-lived due to the relatively short lifetime (hours) of the HOx constituents. The HOx,-caused ozone depletion has been observed during several solar proton events (SPEs) in the past 40 years. HOx enhancements due to SPEs were confirmed by observations in the past solar cycle. A number of modeling studies have been undertaken over this time period that show predictions of enhanced HO, accompanied by decreased ozone due to energetic particles. The NO, family has a longer lifetime than the HOx family and can also lead to catalytic ozone destruction. EPP-caused enhancements of the NOx family can affect ozone promptly, if produced in the stratosphere, or subsequently, if produced in the 1ow.er thermosphere or mesosphere and transported to the stratosphere. NOx enhancements due to auroral electrons, medium and high energy electrons, relativistic electron precipitation (REP) events, and SPEs have been measured and/or modeled for decades Only a small number of SPEs (less than 10) in each solar cycle have sufficient flux of high energy protons (greater than 30 MeV) to produce a significant amount of NOx directly in the stratosphere to cause a measurable ozone destruction. Very high energy electrons (greater than 1500 keV) during REP events can also produce NOx directly in the stratosphere, however, the frequency and intensity of these electrons is uncertain. Indirect stratospheric EPP effects result when NO, is produced in the mesosphere and lower thermosphere and transported to the stratosphere during the late fall or winter. Such EPP-produced NOx may last up to months beyond its initial production. This EPP-produced mesospheric and lower thermospheric NOx primarily results from auroral electrons (approx. 1- 30 keV), medium- and high-energy electrons (approx. 30-1500 keV), and medium energy protons (approx. 1-30 MeV). The EPP-caused direct and indirect effects on the stratosphere are important in the polar regions during particular years, especially near solar maximum. This talk will attempt to provide an overview of several of the EPP-related important processes and their impact on the mesosphere and stratosphere. Much progress has been made in this field in the past several years and it is anticipated that other workshop participants will address aspects of this topic in their presentations.

Jackman, Charles H.↗

NASA NTRS2017

Stratospheric Intrusion-Influenced Ozone Air Quality Exceedences Investigated in MERRA-2

Ozone near the surface is harmful to human health and is a result of the photochemical reaction with both man-made and natural precursor pollutant sources. Therefore, in order to reduce near surface ozone concentrations, communities must reduce anthropogenic pollution sources. However, the injection of stratospheric ozone into the troposphere, known as a stratospheric intrusion, can also lead to concentrations of ground-level ozone exceeding air quality standards. Stratospheric intrusions are dynamical atmospheric features, however, these intrusions have been misrepresented in models and reanalyses until recently, as the features of a stratospheric intrusion are best identified in horizontal resolutions of approximately 50 km or smaller. NASA's Modern-Era Retrospective Analysis for Research and Applications Version-2 (MERRA-2) reanalysis is a publicly-available high-resolution dataset (~50 km) with assimilated ozone that characterizes stratospheric ozone on the same spatiotemporal resolution as the meteorology. We show that stratospheric intrusions that impact surface air quality are well represented in the MERRA-2 reanalysis. This is demonstrated through a case study analysis of stratospheric intrusion events which were identified by the United States Environmental Protection Agency (EPA) to impact surface ozone air quality in spring 2012 in Colorado. The stratospheric intrusions are identified in MERRA-2 by the folding of the dynamical tropopause under the jet stream and subsequent isentropic descent of dry, O3-rich stratospheric air towards the surface where ozone air quality exceedences were observed. The MERRA-2 reanalysis can support air quality agencies for more rapid identification of the impact of stratospheric air on ground-level ozone.

Knowland, K. Emma↗

NASA NTRSDate not supplied

GEOS Constituent Data Assimilation beyond Aura MLS: Assimilating NASA SAGE III/ISS profiles of stratospheric water vapor

Water vapor in the lower stratosphere is an important trace gas for atmospheric chemistry and radiative budget with direct impact on climate. During the last quarter of the 20th century, the Stratospheric Aerosol and Gas Experiment (SAGE) missions were crucial in monitoring the stratospheric ozone loss and the subsequent recovery as well as trends in water vapor linked to surface temperature trends. The SAGE III instrument aboard the International Space Station (ISS) continues the SAGE mission record, with high vertical resolution profiles of water vapor (and other constituents) since mid-2017. The NASA GEOS Earth system model has the capability to assimilate multi-constituents from ground and space-based instruments using the GEOS Constituent Data Assimilation System (CoDAS). Reanalysis products of stratospheric water vapor without data constraints are historically poor, and two recent reanalyses which assimilated stratospheric constituents observed by the Microwave Limb Sounder (MLS) improve the representation of stratospheric composition, including water vapor, when compared against independent observations. The MLS instrument is on NASA's Aura satellite which is expected to be decommissioned in the coming years. Here we demonstrate that while the number of solar occultation observations a day from SAGE III/ISS is about 1 % of the total number of profiles observed globally by MLS, the chemical timescales of water vapor in the lower stratosphere are long enough that the SAGE III/ISS data can provide a useful constraint on the assimilated product. Analyzed water vapor fields from assimilating only SAGE III/ISS water vapor profiles agree well with independent stratospheric observations, including when compared against the frost-point hygrometers at the three NOAA stations. Over the five-year period from 2017 through 2022, the analyzed water vapor using SAGE III/ISS captures many of the features seen with the assimilation of MLS observations. Note, this ability is reduced over regions where the SAGE III/ISS instrument provides infrequent or no observations (associated with the orbit of the ISS), as highlighted in the case study period following the eruption of the tropical underwater volcano Hunga Tonga in early 2022. Nevertheless, there is a clear benefit to the assimilation of stratospheric water vapor from SAGE III/ISS observations, allowing us to continue to monitor stratospheric composition for climate assessments following the impending loss of Aura.

K. Emma Knowland↗

NASA NTRSDate not supplied

GEOS Constituent Data Assimilation Beyond Aura MLS: Assimilating NASA SAGE III/ISS Profiles of Stratospheric Water Vapor

Water vapor in the lower stratosphere is an important trace gas for atmospheric chemistry and radiative budget with direct impact on climate. During the last quarter of the 20th century, the Stratospheric Aerosol and Gas Experiment (SAGE) missions were crucial in monitoring the stratospheric ozone loss and the subsequent recovery as well as trends in water vapor linked to surface temperature trends. The SAGE III instrument aboard the International Space Station (ISS) continues the SAGE mission record, with high vertical resolution profiles of water vapor (and other constituents) since mid-2017. The NASA GEOS Earth system model has the capability to assimilate multi-constituents from ground and space-based instruments using the GEOS Constituent Data Assimilation System (CoDAS). Reanalysis products of stratospheric water vapor without data constraints are historically poor, and two recent reanalyses which assimilated stratospheric constituents observed by the Microwave Limb Sounder (MLS) improve the representation of stratospheric composition, including water vapor, when compared against independent observations. The MLS instrument is on NASA's Aura satellite which is expected to be decommissioned in the coming years. Here we demonstrate that while the number of solar occultation observations a day from SAGE III/ISS is about 1 % of the total number of profiles observed globally by MLS, the chemical timescales of water vapor in the lower stratosphere are long enough that the SAGE III/ISS data can provide a useful constraint on the assimilated product. Analyzed water vapor fields from assimilating only SAGE III/ISS water vapor profiles agree well with independent stratospheric observations, including when compared against the frost-point hygrometers at the three NOAA stations. Over the five-year period from 2017 through 2022, the analyzed water vapor using SAGE III/ISS captures many of the features seen with the assimilation of MLS observations. Note, this ability is reduced over regions where the SAGE III/ISS instrument provides infrequent or no observations (associated with the orbit of the ISS), as highlighted in the case study period following the eruption of the tropical underwater volcano Hunga Tonga in early 2022. Nevertheless, there is a clear benefit to the assimilation of stratospheric water vapor from SAGE III/ISS observations, allowing us to continue to monitor stratospheric composition for climate assessments following the impending loss of Aura.

K. Emma Knowland↗

NASA NTRSDate not supplied

GEOS Constituent Data Assimilation Beyond Aura MLS: Assimilating NASA SAGE III/ISS Profiles of Stratospheric Water Vapor

Water vapor in the lower stratosphere is an important trace gas for atmospheric chemistry and radiative budget with direct impact on climate. During the last quarter of the 20th century, the Stratospheric Aerosol and Gas Experiment (SAGE) missions were crucial in monitoring the stratospheric ozone loss and the subsequent recovery as well as trends in water vapor linked to surface temperature trends. The SAGE III instrument aboard the International Space Station (ISS) continues the SAGE mission record, with high vertical resolution profiles of water vapor (and other constituents) since mid-2017. The NASA GEOS Earth system model has the capability to assimilate multi-constituents from ground and space-based instruments using the GEOS Constituent Data Assimilation System (CoDAS). Reanalysis products of stratospheric water vapor without data constraints are historically poor, and two recent reanalyses which assimilated stratospheric constituents observed by the Microwave Limb Sounder (MLS) improve the representation of stratospheric composition, including water vapor, when compared against independent observations. The MLS instrument is on NASA's Aura satellite which is expected to be decommissioned in the coming years. Here we demonstrate that while the number of solar occultation observations a day from SAGE III/ISS is about 1 % of the total number of profiles observed globally by MLS, the chemical timescales of water vapor in the lower stratosphere are long enough that the SAGE III/ISS data can provide a useful constraint on the assimilated product. Analyzed water vapor fields from assimilating only SAGE III/ISS water vapor profiles agree well with independent stratospheric observations, including when compared against the frost-point hygrometers at the three NOAA stations. Over the five-year period from 2017 through 2022, the analyzed water vapor using SAGE III/ISS captures many of the features seen with the assimilation of MLS observations. Note, this ability is reduced over regions where the SAGE III/ISS instrument provides infrequent or no observations (associated with the orbit of the ISS), as highlighted in the case study period following the eruption of the tropical underwater volcano Hunga Tonga in early 2022. Nevertheless, there is a clear benefit to the assimilation of stratospheric water vapor from SAGE III/ISS observations, allowing us to continue to monitor stratospheric composition for climate assessments following the impending loss of Aura.

K. Emma Knowland↗

NASA NTRS2013

On the Lack of Stratospheric Dynamical Variability in Low-top Versions of the CMIP5 Models

We describe the main differences in simulations of stratospheric climate and variability by models within the fifth Coupled Model Intercomparison Project (CMIP5) that have a model top above the stratopause and relatively fine stratospheric vertical resolution (high-top), and those that have a model top below the stratopause (low-top). Although the simulation of mean stratospheric climate by the two model ensembles is similar, the low-top model ensemble has very weak stratospheric variability on daily and interannual time scales. The frequency of major sudden stratospheric warming events is strongly underestimated by the low-top models with less than half the frequency of events observed in the reanalysis data and high-top models. The lack of stratospheric variability in the low-top models affects their stratosphere-troposphere coupling, resulting in short-lived anomalies in the Northern Annular Mode, which do not produce long-lasting tropospheric impacts, as seen in observations. The lack of stratospheric variability, however, does not appear to have any impact on the ability of the low-top models to reproduce past stratospheric temperature trends. We find little improvement in the simulation of decadal variability for the high-top models compared to the low-top, which is likely related to the fact that neither ensemble produces a realistic dynamical response to volcanic eruptions.

troposphere↗

NASA NTRS2014

Seasonal Ventilation of the Stratosphere: Robust Diagnostics from One-Way Flux Distributions

We present an analysis of the seasonally varying ventilation of the stratosphere using one-way flux distributions. Robust transport diagnostics are computed using GEOSCCM subject to fixed present-day climate forcings. From the one-way flux, we determine the mass of the stratosphere that is in transit since entry through the tropical tropopause to its exit back into the troposphere, partitioned according to stratospheric residence time and exit location. The seasonalities of all diagnostics are quantified with respect to the month of year (a) when air enters the stratosphere, (b) when the mass of the stratosphere is partitioned, and (c) when air exits back into the troposphere. We find that the return flux, within 3 months since entry, depends strongly on when entry occurred: (34 +/- 10)% more of the air entering the stratosphere in July leaves poleward of 45 deg N compared to air that enters in January. The month of year when the air mass is partitioned is also found to be important: The stratosphere contains about six times more air of tropical origin during late summer and early fall that will leave poleward of 45 deg within 6 months since entering the stratosphere compared to during late winter to late spring. When the entire mass of the air that entered the stratosphere at the tropics regardless of its residence time is considered, we find that (51 +/- 1)% and (39 +/- 2)% will leave poleward of 10 deg in the Northern Hemisphere (NH) and Southern Hemisphere (SH), respectively.

Stratosphere-Troposphere Exchange↗

NASA NTRS2018

Evidence for a Continuous Decline in Lower Stratospheric Ozone Offsetting Ozone Layer Recovery

Ozone forms in the Earth's atmosphere from the photodissociation of molecular oxygen, primarily in the tropical stratosphere. It is then transported to the extratropics by the Brewer-Dobson circulation (BDC), forming a protective "ozone layer" around the globe. Human emissions of halogen-containing ozone-depleting substances (hODSs) led to a decline in stratospheric ozone until they were banned by the Montreal Protocol, and since 1998 ozone in the upper stratosphere is rising again, likely the recovery from halogen-induced losses. Total column measurements of ozone between the Earth's surface and the top of the atmosphere indicate that the ozone layer has stopped declining across the globe, but no clear increase has been observed at latitudes between 60degS and 60degN outside the polar regions (60-90deg). Here we report evidence from multiple satellite measurements that ozone in the lower stratosphere between 60degS and 60degN has indeed continued to decline since 1998. We find that, even though upper stratospheric ozone is recovering, the continuing downward trend in the lower stratosphere prevails, resulting in a downward trend in stratospheric column ozone between 60degS and 60degN. We find that total column ozone between 60degS and 60degN appears not to have decreased only because of increases in tropospheric column ozone that compensate for the stratospheric decreases. The reasons for the continued reduction of lower stratospheric ozone are not clear; models do not reproduce these trends, and thus the causes now urgently need to be established.

Stratospheric Ozone↗

NASA NTRS2020

Stratospheric Impact on the Northern Hemisphere Winter and Spring Ozone Interannual Variability in the Troposphere

In this study we use ozone and stratospheric ozone tracer simulations from the high-resolution (0.5°x0.5°) Goddard Earth Observing System, Version 5 (GEOS-5) in a replay mode to study the impact of stratospheric ozone on tropospheric ozone interannual variability (IAV). We use these simulations in conjunction with ozone sonde measurements from 1990 to 2016 during the winter and spring seasons. The simulations include a stratospheric ozone tracer (StratO3) to aid 15in the evaluation of the impact of stratospheric ozone IAV on the IAV of tropospheric ozone at different altitudes and location. The model is in good agreement with the observed interannual variation of tropospheric ozone, except for the post-Pinatubo period(1992-1994)over the region of North America. Ozone sonde data show a negative ozone anomaly in 1992-1994 following the Pinatubo eruption, with recovery thereafter. The simulated anomaly is only half the magnitude of that observed. Our analysis suggests that the simulated Stratosphere-troposphere exchange (STE)flux deduced from the analysis 20might be too strong over the North American (50°N-70°N) region after the Mt. Pinatubo eruption in the early 1990s,maskingthe impact of lower stratospheric ozone concentration on tropospheric ozone. European ozone sonde measurements show a similar but weaker ozone depletion after the Mt. Pinatubo eruption, which is fully reproduced by the model. Analysis based on the stratospheric ozone tracer (StratO3) identifies differences in strength and vertical extent of stratospheric ozone impact on the tropospheric ozone interannual variation (IAV)between North America and Europe. Over NorthAmerica25stations, the StratO3IAV has a significant impact on tropospheric ozone from the upper to lower troposphere and explains about 60% and 66% of the simulated ozone IAV at 400 hPa, and ~11% and 34% at 700 hPa in winter and spring respectively. Over European stations, the influence is limited to the middle to upper troposphere, and becomes much smaller at 700 hPa. The Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2)assimilated fields exhibit strong longitudinal variations over northern hemisphere (NH) mid-high latitudes, with lower tropopause height and 30lower geopotential height over North America than Europe. These variations associated with the relevant variations in the location of tropospheric jet flows are responsible for the longitudinal differences in the stratospheric ozone impact, with stronger effects over North America than over Europe

tropospheric ozone IAV, Model, ozonesonde, stratos↗

DOE OSTI2026

Stratospheric aerosol forcing for CMIP7 – Part 1: optical properties for pre-industrial, historical, and scenario simulations

Stratospheric aerosols, most of which originate from explosive volcanic sulfur emissions into the stratosphere, are a key natural driver of climate variability. They are thus a forcing provided by the Coupled Model Intercomparison Project (CMIP) Climate Forcings Task Team to climate modelling groups participating in phase 7 of CMIP. For the historical period, we provide two datasets covering 1750–2023: (i) a volcanic upper tropospheric-stratospheric sulfur emission dataset, documented in a companion paper; and (ii) a stratospheric sulfate aerosol optical property dataset, documented in this paper. For the satellite era (from 1979 onwards), stratospheric aerosol optical properties are derived from the Global Space-based Stratospheric Aerosol Climatology (GloSSAC) dataset. For the pre-satellite era (1750–1978), optical properties are derived from our volcanic SO 2 emission dataset using a new version of the reduced-complexity volcanic aerosol model Easy Volcanic Aerosol (Height) (EVA_H v2). A background, non-volcanic stratospheric aerosol climatology is derived from the 1998–2001 period with a trend over 1850–1978 accounting for increasing anthropogenic aerosols. A monthly stratospheric aerosol climatology is derived from the 1850–2021 average for both pre-industrial and scenario (future) simulations, with a 9-year ramp over 2022–2030 for scenario simulations to ensure a smooth transition from the historical period. CMIP7 simulations should use version 2.2.1 of our pre-industrial and historical datasets, and version 2.2.2 of our scenario dataset. Our methodology to produce historical aerosol optical properties significantly differs from CMIP6 for the pre-satellite era, and the resulting forcings in turn largely differ. In particular, the CMIP6 dataset was mostly based on the sparse and uncertain pyrheliometer record, which resulted in strongly underrepresented emissions from small-to-moderate magnitude eruptions. The resulting bias is addressed in CMIP7, which is entirely emission-derived in the pre-satellite era and uses more recent ice-core-based volcanic sulfur emission inventories than CMIP6. Our approach results in an overall larger volcanic aerosol forcing for CMIP7, with the 1850–2014 mean mid-visible global mean stratospheric aerosol optical depth (SAOD) in CMIP7 (0.0138) being 29 % higher than in CMIP6 (0.0107). The pre-industrial mean of the same variable is 26 % higher in CMIP7 (0.0135, derived from the historical 1850–2021) than CMIP6 (0.0107, derived from the historical 1850–2014 mean). Using a reduced-complexity climate model, we simulate a global mean surface temperature that is 0.07 °C colder for 1850–1900 when using the CMIP7 dataset instead of CMIP6, whereas 2000–2014 is 0.03 °C warmer in CMIP7. Our dataset also exhibits lower forcing for 1960–1980, resulting in temperatures 0.06 °C warmer when averaged over 1960–1990, a period for which CMIP6 climate models exhibit a cold bias. Given the large uncertainties characterizing the dataset, in particular for the pre-satellite era, we advise against treating the CMIP7 or CMIP6 dataset as uniquely superior for any specific year and highlight the need for further evaluation. We conclude the study by discussing sources of uncertainty for the dataset, future research avenues to improve it, as well as requirements to operationalize the production of the dataset, i.e. extend it and update it on an annual basis instead of every 5–7 years following CMIP cycles.

Aubry, Thomas J. [Univ. of Exeter, Devon (United K↗

DOE OSTI2025

A process-based evaluation of biases in extratropical stratosphere–troposphere coupling in subseasonal forecast systems

Abstract. Two-way coupling between the stratosphere and troposphere is recognized as an important source of subseasonal-to-seasonal (S2S) predictability and can open windows of opportunity for improved forecasts. Model biases can, however, lead to a poor representation of such coupling processes; drifts in a model's circulation related to model biases, resolution, and parameterizations have the potential to feed back on the circulation and affect stratosphere–troposphere coupling. We introduce a set of diagnostics using readily available data that can be used to reveal these biases and then apply these diagnostics to 22 S2S forecast systems. In the Northern Hemisphere, nearly all S2S forecast systems underestimate the strength of the observed upward coupling from the troposphere to the stratosphere, downward coupling within the stratosphere, and the persistence of lower-stratospheric temperature anomalies. While downward coupling from the lower stratosphere to the near surface is well represented in the multi-model ensemble mean, there is substantial intermodel spread likely related to how well each model represents tropospheric stationary waves. In the Southern Hemisphere, the stratospheric vortex is oversensitive to upward-propagating wave flux in the forecast systems. Forecast systems generally overestimate the strength of downward coupling from the lower stratosphere to the troposphere, even as most underestimate the radiative persistence in the lower stratosphere. In both hemispheres, models with higher lids and a better representation of tropospheric quasi-stationary waves generally perform better at simulating these coupling processes.

Garfinkel, Chaim I. (ORCID:000000017258666X)↗

NASA NTRS1991

The Cl-36 in the stratosphere

Initial measurements of the cosmogenic radionuclide, Cl-36, in the lower stratosphere were made by accelerator mass spectrometry. Samples were obtained using the large volume LASL air sampling pods on a NASA WB-57F aircraft. Untreated (for collection of particulates only) and tetrabutyl ammonium hydroxide treated (for collection of particulates and HCl) IPC-1478 filters were flown on three flights in the lower stratosphere. Chlorine (Cl) and Cl compounds are important trace constituents for stratospheric chemistry, in particular with respect to O3 destruction. Stratospheric Cl chemistry has recently received increased attention with the observation of strong O3 depletion in the Antarctic winter vortex and in the weaker and more complex Arctic winter vortices. Cosmogenic (Cl-36) is produced by spallation reactions from Ar mainly in the stratosphere, and has had several applications as a geochemical tracer. The large amounts of Cl-36 introduced by nuclear weapon testing have been removed from the stratosphere by now, and measurements in the stratosphere to obtain cosmogenic production rates and concentration distributions is now possible. The use of cosmogenic Cl-36 as a tracer for stratospheric Cl chemistry and for stratospheric/tropospheric exchange processes is investigated. A first attempt to determine stratospheric and tropospheric production rates, the partitioning of Cl-36 among particulate and gaseous Cl compounds, and the respective inventories and removal rates is being made. Results from a flight at 13.7 km, 30-33 degrees N, 97-107 degrees W, and from a second flight at 17.7 km, 43-45-36 degrees N, 92-94 degrees W, for the untreated and treated filters respectively are presented.

Deck, Bruce↗

NASA NTRS1994

Simulations of the February 1979 stratospheric sudden warming: Model comparisons and three-dimensional evolution

The evolution of the stratopsheric flow during the major stratospheric sudden warming of February 1979 is studied using two primitive equation models of the stratosphere and mesosphere. The United Kingdom Meteorological Office Stratosphere-Mesosphere Model (SMM) uses log pressure as a vertical coordinate. A spectral, entropy coordinate version of the SMM (entropy coordinate model, or ECM) that has recently been developed is also used. Comparison of SMM simulations with forecasts performed using the University of California, Los Angeles general circulation model confirms the previously noted sensitivity of stratospheric forecasts to tropospheric forecasts and emphasizes the importance of adequate vertical resolution in modeling the stratosphere. The ECM simulations provide a schematic description of the three-dimensional evolution of the polar vortex and the motion of air through it. During the warming, the two cyclonic vortices tilt westward and equatorward with height. Strong upward velocities develop in the lower stratosphere on the west (cold) side of a baroclinic zone as it forms over Europe and Asia. Strong downward velocities appear in the upper stratosphere on the east (warm) side, strengthening the temperature gradients. After the peak of the warming, vertical velocities decrease, downward velocities move into the lower stratosphere, and upward velocities move into the upper stratosphere.

Manney, G. L.↗

NASA NTRS1996

Stratospheric Heterogeneous Chemistry and Microphysics: Model Development, Validation and Applications

The objectives of this project are to: define the chemical and physical processes leading to stratospheric ozone change that involve polar stratospheric clouds (PSCS) and the reactions occurring on the surfaces of PSC particles; study the formation processes, and the physical and chemical properties of PSCS, that are relevant to atmospheric chemistry and to the interpretation of field measurements taken during polar stratosphere missions; develop quantitative models describing PSC microphysics and heterogeneous chemical processes; assimilate laboratory and field data into these models; and calculate the extent of chemical processing on PSCs and the impact of specific microphysical processes on polar composition and ozone depletion. During the course of the project, a new coupled microphysics/physical-chemistry/ photochemistry model for stratospheric sulfate aerosols and nitric acid and ice PSCs was developed and applied to analyze data collected during NASA's Arctic Airborne Stratospheric Expedition-II (AASE-II) and other missions. In this model, detailed treatments of multicomponent sulfate aerosol physical chemistry, sulfate aerosol microphysics, polar stratospheric cloud microphysics, PSC ice surface chemistry, as well as homogeneous gas-phase chemistry were included for the first time. In recent studies focusing on AASE measurements, the PSC model was used to analyze specific measurements from an aircraft deployment of an aerosol impactor, FSSP, and NO(y) detector. The calculated results are in excellent agreement with observations for particle volumes as well as NO(y) concentrations, thus confirming the importance of supercooled sulfate/nitrate droplets in PSC formation. The same model has been applied to perform a statistical study of PSC properties in the Northern Hemisphere using several hundred high-latitude air parcel trajectories obtained from Goddard. The rates of ozone depletion along trajectories with different meteorological histories are presently being systematically evaluated to identify the principal relationships between ozone loss and aerosol state. Under this project, we formulated a detailed quantitative model that predicts the multicomponent composition of sulfate aerosols under stratospheric conditions, including sulfuric, nitric, hydrochloric, hydrofluoric and hydrobromic acids. This work defined for the first time the behavior of liquid ternary-system type-1b PSCS. The model also allows the compositions and reactivities of sulfate aerosols to be calculated over the entire range of environmental conditions encountered in the stratosphere (and has been incorporated into a trajectory/microphysics model-see above). Important conclusions that derived from this work over the last few years include the following: the HNO3 content of liquid-state aerosols dominate PSCs below about 195 K; the freezing of nitric acid ice from sulfate aerosol solutions is likely to occur within a few degrees K of the water vapor frost point; the uptake and reactions of HCl in liquid aerosols is a critical component of PSC heterogeneous chemistry. In a related application of this work, the inefficiency of chlorine injection into the stratosphere during major volcanic eruptions was explained on the basis of nucleation of sulfuric acid aerosols in rising volcanic plumes leading to the formation of supercooled water droplets on these aerosols, which efficiently scavenges HCl via precipitation.

Turco, Richard P.↗

NASA NTRS1982

NASA Experiment on Tropospheric-Stratospheric Water Vapor Transport in the Intertropical Convergence Zone

The following six papers report preliminary results obtained from a field experiment designed to study the role of tropical cumulo-nimbus clouds in the transfer of water vapor from the troposphere to the stratosphere over the region of Panama. The measurements were made utilizing special NOAA enhanced IR satellite images, radiosonde-ozonesondes and a NASA U-2 aircraft carrying. nine experiments. The experiments were provided by a group of NASA, NOAA, industry, and university scientists. Measurements included atmospheric humidity, air and cloud top temperatures, atmospheric tracer constituents, cloud particle characteristics and cloud morphology. The aircraft made a total of eleven flights from August 30 through September 18, 1980, from Howard Air Force Base, Panama; the pilots obtained horizontal and vertical profiles in and near convectively active regions and flew around and over cumulo-nimbus towers and through the extended anvils in the stratosphere. Cumulo-nimbus clouds in the tropics appear to play an important role in upward water vapor transport and may represent the principal source influencing the stratospheric water vapor budget. The clouds provide strong vertical circulation in the troposphere, mixing surface air and its trace materials (water vapor, CFM's sulfur compounds, etc.) quickly up to the tropopause. It is usually assumed that large scale mean motions or eddy scale motions transport the trace materials through the tropopause and into the stratosphere where they are further dispersed and react with other stratospheric constituents. The important step between the troposphere and stratosphere for water vapor appears to depend upon the processes occurring at or near the tropopause at the tops of the cumulo-nimbus towers. Several processes have been sugested: (1) The highest towers penetrate the tropopause and carry water in the form of small ice particles directly into the stratosphere. (2) Water vapor from the tops of the cumulonimbus clouds is transported somehow through the tropopause, the vapor pressure being controlled by the temperature at the tops of the clouds; the dryness of the stratosphere could be explained if most of the transport occurs in connection with very high clouds in regions with very high and cold tropopause. (3) Cumulo-nimbus anvils act as terrestrial-radiation shields allowing the ice particle temperatures near cloud tops to cool radiatively below the supersaturation point; this cooling would cause a vapor deposition on the ice particles which will settle out and thus act as water scavengers. The experiment was designed to collect information on these detailed physical processes near and above the tropopause in order to assess their importance and the role they play in controlling stratospheric water vapor humidity.

Page, William A.↗