Sule Dan-maigona Solomon

We present an alternative method of calculating the historical effective radiative forcing using the observed temperature record and a kernel based on the CMIP5 temperature response. This estimate is the effective radiative forcing time series that the average climate model would need to simulate the observed global mean surface temperature anomali...

A preliminary survey of the risk assessment of selected trace metal (Cd, Cr, Cu, Pb and Zn) levels of castor (Ricinus communis L.) plant growing on refuse dumpsites in Wukari Metropolis, Taraba State was investigated. Duplicate samples each of whole castor plants and decomposed remains of the refuse dumpsites were collected from three locations nam...

Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models consistently showed tropospheric amplification of surface warming in response to human-caused increases in greenhouse gases (GHGs). We revisit such comparisons here using new observational estimates of s...

The ozone hole is an important driver of recent Southern Hemisphere (SH) climate change, and capturing these changes is a goal of climate modeling. Most climate models are driven by offline ozone datasets. Previous studies have shown that there is a substantial range in estimates of SH ozone depletion, but the implications of this range have not be...

Chlorofluorocarbons (CFCs) are the primary cause of ozone depletion, and they also contribute to global climate change. With the global phaseout of CFCs and the coming phaseout of hydrochlorofluorocarbons (HCFCs), the substitute hydrofluorocarbons (HFCs) are increasingly used. While CFCs were originally used mainly in applications such as spray can...

Climate models that do not simulate changes in stratospheric ozone concentrations require the prescription of ozone fields to accurately calculate UV fluxes and stratospheric heating rates. In this study, three different global ozone time series that are available for this purpose are compared: the data set of Randel and Wu (2007) (RW07), Cionni et...

Long-term future warming is primarily constrained by cumulative emissions of carbon dioxide. Previous studies have estimated that humankind has already emitted about 50% of the total amount allowed if warming, relative to pre-industrial, is to stay below 2°C (refs , ). Carbon dioxide emissions will thus need to decrease substantially in the future...

Significant levels of extinction in the upper stratosphere and mesosphere have recently been observed by remote sensing observations. Comparisons are made with observations from SAGE II, the NOAA lidar located in Mauna Loa, HI and model-derived profiles from Whole Atmosphere Community Climate Model (WACCM) coupled with the Community Aerosol and Rad...

Stephen Henry Schneider made a difference in our world. His science, his words, and his actions forever changed the way we think about human influences on climate. Stephen Schneider helped us to realize that we are not just innocent bystanders - we are now active agents of change in the climate system. This lecture has two parts. The first part pro...

We compare global-scale changes in satellite estimates of the temperature of the lower troposphere (TLT) with model simulations of forced and unforced TLT changes. While previous work has focused on a single period of record, we select analysis timescales ranging from 10 to 32 years, and then compare all possible observed TLT trends on each timesca...

In 2010, 25 years of regular, year-round ozone soundings at South Pole station, Antarctica, were completed. These measurements provide unique information about the seasonality, trends, and variability of ozone depletion in the polar stratosphere at high vertical resolution. Here, we focus on the observed loss rates, and their changes since the meas...

Recent measurements demonstrate that the "background" stratospheric aerosol layer is persistently variable rather than constant, even in the absence of major volcanic eruptions. Several independent data sets show that stratospheric aerosols have increased in abundance since 2000. Near-global satellite aerosol data imply a negative radiative forcing...

The Earth is warming on average, and most of the global warming of the past half-century can very likely be attributed to human influence. But the climate in particular locations is much more variable, raising the question of where and when local changes could become perceptible enough to be obvious to people in the form of local warming that excee...

October mean total column ozone data from four Antarctic stations form the basis for understanding the evolution of the ozone hole since 1960. While these stations show similar emergence of the ozone hole from 1960 to 1980, the records are divergent in the last two decades. The effects of long-term changes in vortex shape and location are considere...

The last 10 years of observational temperature records have received considerable public attention. It has been claimed that the relatively muted surface warming trend of the past decade constitutes 'evidence of absence' of a human effect on climate, and that model simulations of historical climate change are incapable of replicating the observed t...

An accurate representation of the global distribution of stratospheric ozone and its temporal evolution is a prerequisite for modeling the impacts of stratospheric change on surface climate. Although it is well known that zonal asymmetries in ozone distributions and trends exist, until now it has not been possible to examine those in vertically res...

We perform the most comprehensive comparison to date of simulated and observed temperature trends. Comparisons are made for different latitude bands, timescales, and temperature variables, using information from a multi-model archive and a variety of observational datasets. Our focus is on temperature changes in the lower troposphere (TLT), the mid...

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We examine the Earth's energy balance since 1950, identifying results that can be obtained without using global climate models. Important terms that can be constrained using only measurements and radiative transfer models are ocean heat content, radiative forcing by long-lived trace gases, and radiative forcing from volcanic eruptions. We explicitl...

In a recent multimodel detection and attribution (D&A) study using the pooled results from 22 different climate models, the simulated “fingerprint” pattern of anthropogenically caused changes in water vapor was identifiable with high statistical confidence in satellite data. Each model received equal weight in the D&A analysis, despite large differ...

Most current ozone data sets used in general circulation models (GCMs) do not fully represent the magnitude of the decrease in stratospheric ozone over the previous ~30 years. These shortcomings are not limited to polar regions, and also include an under-representation of downward trends at tropical and mid latitudes. As a consequence, the radiativ...

There is increasing evidence that the stratosphere exerts control on tropospheric climate. For example, changes in the Southern Annular Mode (SAM) and Northern Annular Mode (NAM) are thought to be influenced by stratospheric ozone depletion in recent decades. General Circulation Models (GCM) that do not include chemistry must prescribe accurate str...

Weekly cycles have been identified in numerous meteorological parameters, but various analysis methods have been used and interpretations are sometimes contradictory. We will discuss some of the difficulties involved in weekly cycle analyses and describe an approach to test the statistical significance of these cycles that accounts for both the aut...

A recent report of the U.S. Climate Change Science Program (CCSP) identified a ‘ potentially serious inconsistency ’ between modelled and observed trends in tropical lapse rates (Karl et al. , 2006). Early versions of satellite and radiosonde datasets suggested that the tropical surface had warmed more than the troposphere, while climate models con...

This work presents measurements of sulfur dioxide (SO2) emission fluxes from point sources using airborne near-ultraviolet (UV) spectroscopy. A Czerny-Turner spectrograph has been optimized to measure SO2 and the oxygen collision complex (O-4) in the wavelength region of 286-408 nm from an aircraft platform. The spectrograph was deployed aboard the...

The "filling-in" (FI) of Fraunhofer lines, often referred to as the Ring effect, was examined using measurements of near ultraviolet sunlight scattered from the zenith sky above Boulder, Colorado during July and August 2005. The FI of the 344.1 nm Fe I line was directly determined by comparing direct sun and cloud-free zenith sky spectra recorded o...

Accurate chlorocarbon and bromocarbon mixing ratio projections are necessary to make accurate estimates of future stratospheric ozone depletion. As global production of ozone depleting substances (ODSs) continues to decline in response to the Montreal Protocol, the quantity of ODSs in existing products and equipment, referred to as “banks,” has the...

The "filling-in'' (FI) of Fraunhofer lines, often referred to as the Ring effect, was examined using measurements of near ultraviolet sunlight scattered from the zenith sky above Boulder, Colorado during July and August 2005. The FI of the 344.1 nm Fe I line was directly determined by comparing direct sun and cloud-free zenith sky spectra recorded...

A theoretical approach is used to quantify the information available to retrieve cloud physical properties from data taken by a ground-based spectrometer measuring scattered sunlight in the near-infrared wavelength region. Three wavelength regions between 0.9 and 1.7 mum, each containing water vapor, liquid, and ice absorption features, are examine...

1] Tropical ozonesonde measurements display events of substantially reduced or near-zero ozone in the upper troposphere that can be coherent over broad spatial scales. Available observations indicate that these events occur most frequently between about 300 and 100 mbar in the tropical southwest Pacific region. The spatial structure of the events s...

SHADOZ (Southern Hemisphere Additional Ozonesondes) is part of Aura's constellation of validation efforts. Aura's interest in multi-instrument estimates of tropospheric ozone requires high-quality ozone measurements in the UT/LS. Within this region, primarily below 100 hPa, increases in the frequency of very low (< 20 ppbv) and near-zero ozone mixi...

Accurate measurements of sulfur dioxide are important in urban air pollution studies due to the role sulfur dioxide plays in atmospheric processes such as acid rain and particle formation. We will show slant column sulfur dioxide abundances that were derived using the differential optical absorption spectroscopy (DOAS) technique with ultraviolet sp...

The role that aerosols play in changing the radiative properties of clouds is uncertain, with even the sign of the forcing undetermined. The need for remotely sensing clouds is becoming more apparent with the desire to achieve a global estimate of the radiative forcing due to changes in clouds. A new technique of combining microwave and near-infrar...

The microphysical properties of an optically thin (τ ≤ 0.12) cirrus layer formed by dispersing contrails above Boulder, Colorado, have been examined in a ground-based study. Backscatter and depolarization lidar measurements at 0.532 μm were used to characterize the cloud morphology, while near-infrared (0.9 to 1.7 μm) spectroscopy was used to measu...

Recent observations provide evidence that variations in the Northern Hemisphere stratospheric polar vortex are strongly coupled to similarly signed variations in the tropospheric circulation. Anomalous examination of the Southern Hemisphere (SH) circulation reveals that similar coupling occurs in the SH as well. These results support previous resea...

Ground-based visible absorption spectroscopy of zenith-scattered sky light was used to measure changes in the column abundance of NO2 during the passage of a thunderstorm over Boulder, Colorado, on September 12, 2002. The measurements showed a 10-fold rise in slant column NO2 within the thunderstorm cell, consistent with an increase of about 7 ppbv...

We present a novel application of the GPS meteorology technique for investigating various problems in atmospheric radiative transfer. Tropospheric water vapor is the dominant absorber of solar radiation in the visible and near infrared spectral region. Errors in modeling absorption by water vapor in this region are suspected to contribute to the pr...

1] We carried out a spectroscopic field experiment designed to measure water vapor continuum absorption in the visible and near-infrared spectral regions. Atmospheric spectra at $1 nm resolution were recorded using direct sunlight at high solar zenith angles during sunrise. Simultaneously radiosonde soundings and a network of geodetic Global Positi...

[1] The ability to retrieve key information about clouds from observations of atmospheric absorption by molecular oxygen along with the O2-O2 collision complex is examined. Specifically, the fractional absorption of scattered solar radiation in the oxygen A and B bands and the 477 nm O2-O2 absorption band at moderate resolution (0.5–6.0 nm) is show...

We report the results of a field experiment designed to study atmospheric water vapor absorption in the visible and near-infrared spectral regions between 550 and 1000 nm. We carried out spectroscopic ground measurements of direct solar radiation under clear-sky conditions in Boulder, Colorado. The data with a spectral resolution of approximately 1...

Estimates of annual‐mean stratospheric temperature trends over the past twenty years, from a wide variety of models, are compared both with each other and with the observed cooling seen in trend analyses using radiosonde and satellite observations. The modelled temperature trends are driven by changes in ozone (either imposed from observations or c...

Accurate measurements of nitrogen dioxide (NO2), a key trace gas in the formation and destruction of tropospheric ozone, are important in studies of urban pollution. Nitrogen dioxide column abundances were measured during the Texas Air Quality Study 2000 using visible absorption spectroscopy from an aircraft. The method allows for quantification of...

The impact of radiative transfer processes on MM5 air-quality forecasts during the Nashville Southern Oxidants Experiments is addressed. We find that an incorrect specification of aerosol scattering, aerosol absorption, and ozone absorption in the model can lead to positive errors in the instantaneous total solar irradiance at the surface of 100 W...

A new technique is presented for the simultaneous measurement of water vapor, liquid water, and water ice in clouds using spectral observations of scattered sunlight between 0.865 and 1.065 mum. A nonlinear least squares approach is used to fit the measurements with the absorption spectral signatures of the vapor, liquid, and solid phases of water....

Climate change can be driven by changes in the atmospheric concentrations of a number of radiatively active gases and aerosols. We have clear evidence that human activities have affected concentrations, distributions and life cycles of these gases. These matters, discussed in this chapter, were assessed at greater length in IPCC WGI report ""Radiat...

Several techniques to directly measure the absorption of solar radiation in clouds in the visible and near-IR spectral regions are discussed. Ground based and airborne measurements taken with several spectrographs covering 400-1000 nm are used. The fact that the cloud scattering properties are nearly constant over this spectral interval is exploite...

Cloudy sky average photon path lengths were measured using the gamma band of oxygen near 628 nm on many days over Boulder, Colorado, using a zenith-looking spectrograph with a resolution of 0.8 nm. The approach allows accurate measurement of the average photon path length. Days characterized by relatively extensive cloud cover are examined here, wh...

Liquid aerosol particles and ice crystals in subvisible cirrus clouds in the tropopause region are investigated in terms of microphysical, chemical, and optical properties. These particle properties are examined by means of a thermodynamic equilibrium model and are related to satellite extinction measurements. .

Near-global time series of Halogen Occultation Experiment (HALOE) derived total Cl, F, and the Cl/F ratio were evaluated and compared with data from two ground-based CFC measurement programs and United Nations Environment Programme (UNEP) best-case scenarios for CFC emissions. The HALOE Cl profiles confirm that the chlorine burden near the stratopa...

Radiative forcings, preindustrial to present, are presented due to changes in both tropospheric and total ozone. Unlike previous studies, we use a combination of present-day satellite data, ozonesondes, and a chemistry model to produce a hybrid monthly mean ozone data set from 1870 to 1990. We calculate the radiative forcing due to the prescribed o...

Liquid aerosol particles and ice crystals in subvisible cirrus clouds in the tropopause region are characterized in terms of size distributions, chemical composition, and optical extinction. These particle properties are studied by means of simple models and are related to satellite extinction measurements, particularly for midlatitudes. Sulfuric a...

The relative effectiveness of bromine compared to chlorine for destroying stratospheric ozone is explored. Two definitions previously used to quantify this relative effectiveness, typically referred to as alpha, are compared and a definition is presented to calculate alpha values applicable for column and global ozone loss. Calculations of alpha ar...

Recent isotopic studies have suggested that the trace gas N2O has a missing stratospheric sink of potentially major significance. While these studies have raised interesting questions, the constraints on N2O photochemistry imposed by correlations between N2O, total reactive nitrogen, and other tracers measured in situ in the lower stratosphere also...

For several years NO2 and OClO, two species important to understanding ozone destruction in the Antarctic stratosphere, have been measured at Arrival Heights, Antarctica by two groups: New Zealand's National Institute of Water and Atmospheric Research (NIWA) and the NOAA Aeronomy Laboratory in Boulder, Colorado. Using data independently collected b...

We present ground-based spectral measurements of downward direct and diffuse solar intensities between 624 and 686 nm. Using the rising Sun as a light source, it is shown that the water dimer does not absorb significantly in this wavelength region. Over Boulder, Colorado, on July 10, 1998, the upper limit to the dimer vertical optical depth at thes...

Direct measurements of the absorption of downwelling visible radiation by nitrogen dioxide are presented. The data show that this gas can contribute significantly to local radiative forcing under certain conditions. The observed enhancements in nitrogen dioxide absorption are likely to be due both to pollution and to production by lightning in conv...

The response of stratospheric O3 to changes in NOx and HOx is tested in a two-dimensional model with the goal of exploring photochemical buffering mechanisms. The model tests are performed under background aerosol conditions at both current (1996) and preindustrial levels of stratospheric halogens. The tests are prompted in part by comparisons to o...

Observations inside the November 1994 Antarctic stratospheric vortex and inside the April 1993 remnant Arctic stratospheric vortex by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer are reported. In both instances, elevated volume mixing ratios (VMRs) of carbon monoxide (CO) were measured. A peak Antarctic CO VMR...

Satellite observations of total ozone at 40-60 deg N are presented from a variety of instruments over the time period 1979-1997. These reveal record low values in 1992-3 (after Pinatubo) followed by partial but incomplete recovery. The largest post-Pinatubo reductions and longer-term trends occur in spring, providing a critical test for chemical th...

Absorption of solar radiation by collision pairs of oxygen is a small but significant part of the total budget of incoming shortwave radiation. It is shown that the 1.26-gm band of 04 and O2oN2 is likely to contribute 0.64-1.55 W m -2 to the total atmospheric absorption for overhead Sun, clear sky conditions, bringing the total estimated absorption...

Satellite observations of cloud optical depths and occurrence frequencies are used as input to a two-dimensional numerical model of the chemistry and dynamics of the atmosphere to study the effects of heterogeneous reactions on cloud surfaces upon chemical composition and ozone depletion in the tropopause region. Efficient reactions of CIONO2 with...

The tracer species nitrous oxide, N2O, and the reactive nitrogen reservoir, NOy, were measured in situ using instrumentation carried aboard the NASA ER-2 high altitude aircraft as part of the NASA Airborne Southern Hemisphere Ozone Expedition/Measurements for Assessing the Effects of Stratospheric Aircraft (ASHOE/MAESA) and Stratospheric Tracers of...

The mechanisms responsible for latitudinal and seasonal variations in the stratospheric NOy/N2O correlation, represented by the effective NOy yield from N2O loss, or FNOy, are explored using the Garcia-Solomon two-dimensional model. The model is run with and without Antarctic denitrification. Model results are compared to in situ NOy/N2O measuremen...

The radiative forcing of the Earth's climate system due to tropical tropospheric ozone is estimated using ozonesonde profiles and maps of the tropospheric ozone column derived from satellite data. The forcing is estimated using several different techniques in order to place bounds on its likely magnitude and to elucidate the role of biomass burning...

Stratospheric NOy profiles from the Garcia-Solomon two-dimensional model are compared to observed profiles from the Upper Atmosphere Research Satellite (UARS) and the Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS). The model consistently overestimates NOy in the upper stratosphere beyond the range of uncertainty in the satellite data. T...

A climatology of aerosol surface area inferred from satellite measurements is used as input in a two-dimensional model to study the long-term evolution of polar ozone depletion, especially the Antarctic ozone hole. It is found that volcanic aerosol inputs very likely modulate the severity of the ozone hole. In particular, the rapid deepening of the...

Stratospheric volume mixing ratio profiles of carbon tetrafluoride, CF4, obtained with the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during the ATLAS (Atmospheric Laboratory for Applications and Science) -3 mission of 1994 are reported. Overall the profiles are nearly constant over the altitude range 20 to 50 km, indicative of the...

The sunrise column abundance of NO3 has been measured at Fritz Peak, Colorado (40°N, 105°W), using visible absorption spectroscopy with scattered sky light as the light source. Measurements were made in the ``off-axis'' configuration, viewing the sky near the horizon. This is a convenient alternative to direct Moon measurements, and the tropospheri...

We estimate the average transport time from the tropical tropopause to various regions of the northern hemisphere lower stratosphere (stratospheric age) using simultaneous mixing ratio measurements of CFC-115 and CO2 measured by the Whole Air Sampler (WAS) during Airborne Arctic Stratospheric Expedition II (AASE II). Our inferred ages are consisten...

The rate coefficient for the reaction OH + CF3CH2CF3 (1,1,1,3,3,3-hexafluoropropane, HFC236fa) was measured between 269 and 413 K using the pulsed photolysis-laser induced fluorescence technique to be k1 = (1.60 ± 0.40) × 10-12 exp (-(2450 ± 150)/T) cm3 molecule-1 s-1. The rate coefficient, k2b, for the destruction of CF3CH2CF3 via reaction with O(...

The sunset/sunrise NOx ratios measured in 1994 by the Halogen Occultation Experiment (HALOE) onboard the Upper Atmosphere Research Satellite (UARS) peak at up to 2.8 in the tropics around 30 km and decrease to 1 at the stratopause. These ratios are interpreted by using a fully diurnal one-dimensional model, which considers gas phase reactive nitrog...

Emission indices of reactive gases and particles were determined from measurements in the exhaust plume of a Concorde aircraft cruising at supersonic speeds in the stratosphere. Values for NOx (sum of NO and NO2) agree well with ground-based estimates. Measurements of NOx and HOx indicate a limited role for nitric acid in the plume. The large numbe...

The Garcia-Solomon two-dimensional model was used to study the effect of doubled carbon-dioxide on the middle atmosphere. The model has been improved to include non-LTE CO2 cooling in the 15 micron band above 70 km and new chemical heating and heating efficiencies. The effect of doubling CO2 on the temperature is found to be large at the stratopaus...

Aircraft sampling has provided extensive in situ and flask measurements of organic chlorine species in the lower stratosphere. The recent Airborne Arctic Stratospheric Expedition II (AASE II) included two independent measurements of organic chlorine species using whole air sample and real-time techniques. From the whole air sample measurements we d...

Visible absorption spectroscopy was employed for stratospheric measurements at McMurdo Station, Antarctica, during the summer and fall seasons in 1990, 1991, 1992, and 1993. Observed column amounts of NO2 were as much as 50% smaller in 1992 and 1993 than in 1990 and 1991. The measured decreases in NO2 are believed to be due to the hydrolysis of N2O...

The column abundance of BrO has been measured at 40°N throughout the period from January 22 to May 24, 1993, providing the first remote sensing observations of this key molecule at midlatitudes. The near-ultraviolet BrO absorption bands at 349 and 355 nm have been clearly identified in the measured scattered sky spectra, with additional confirmatio...

The amount of organic chlorine and bromine entering the stratosphere have a direct influence on the magnitude of chlorine and bromine catalyzed ozone losses. Twelve organic chlorine species and five organic bromine species were measured from 12 samples collected near the tropopause between 23.8 deg N and 25.3 deg N during AASE 2. The average mixing...

Simultaneous in situ measurements of stratospheric ClO and HCl have been made for the first time, during numerous flights of the ER-2 aircraft covering latitudes 24-90 deg N from October 1991 through March 1992. The ClO/HCl ratio is identified as a key indicator of heterogeneous processing both outside and within the Arctic polar vortex. For ClO mi...

The UV absorption spectrum of Cl2O3 between 220 and 320 nm was measured using time-resolved transient absorption. Cl2O3 was produced following 193-nm pulsed laser photolysis of N2O/Cl2/OClO/He or Cl2-Cl2/OClO/N2 gas mixtures by reaction 1: ClO + OClO + M --> Cl2O3 + M. The absorption spectrum peaks at 267 nm with a cross section of (1.60(-0.22)+0.3...