A23D-01
New Challenges Threatening the Ozone Layer
Since the beginning of the 1990's when the importation of fairly used Refrigerators, Air-conditioners and propellants that can easily go broken containing chlorofluorocarbon substances that is capable of destroying the Ozone layer started in commercial quantity in Africa, the African refuse mountains began metamorphosing into mountains of dumped broken Refrigerators, Air-conditioners and Propellants which are collectively becoming a threat to the Ozone layer, because of the continuous discharging of the Chlorofluorocarbon gases by the refuse in to the atmosphere in each passing second.. Nobody can actually quantify the numbers of Refrigerators, Air-conditioners and Propellants imported and disposed in Africa over the last fifteen years, but the facts still remains that the numbers of metamorphosing mountains keeps on increasing in both size and numbers in each passing day. They have even become sources of raw materials for the local blacksmiths, children and refrigerators repairers who use parts of the dumped refrigerators, Air-conditioners and Propellants for their constructions, toys and repairs respectively. This explains the reason why despite the global efforts toward protecting the Ozone layer by the United Nations (UN), governments, International Organizations and climatologist among many others, but yet the hole in the Ozone layer keeps on expanding and the global temperature keeps on rising which resulted in the unusual phenomenon like the hurricanes "Katrina" and "Rita" the unusual floods in China, Thailand, Mozambique and to some extent even the Tsunami disaster that claims millions of lives in 2004.The Rapid rising in temperature of the Tropical world countries and increase in the cases of cancer patients among many other unusual happenings over the last eight years. It was in review of the above situation that this research work was conducted and came up with the under listed suggestions/Recommendations: 1. The UN should use its capacity to discourage the importation of fairly used refrigerators, Air-conditioners and propellants to Africa and at the same time assist in the subsidy of the newer ones coming to Africa, so that the average African can afford buying them. 2. The UN through her specialized agencies on climate and meteorology in collaboration with sister related organizations should send their teams of researchers to come and investigate the trend of this ugly situation in other to proffer possible lasting solutions. 3. The African Union (AU), UN and other stakeholders on the World climate change should jointly encourage the companies manufacturing Refrigerator, Air-conditioners and propellants to open their factories in Africa, where their products are needed most, as this will help stop the importation of the fairly used refrigerators, Air conditioners and Propellants. 4. The AU should pass a resolution banning the disposal of these items in the refuse. 5. Special companies in charge of disposing or the recycling of the Refrigerators, Air-conditioners and the propellants should be encourage to come to African countries for their operations. 6. Technicians should also be encourage by the various African governments to retrain the local African black smiths and refrigerator repairers on how to use alternative sources of their raw materials in the absence of the Refrigerators, Air-conditioners and propellants dumped in the refuse. I believe that if the above suggestions/recommendations are adopted and implemented it will help in saving the Ozone Layer in one hand and protect the entire World in the other. Thanks for listening.
A23D-02
QBO and Annual Cycle Variations in Tropical Lower Stratosphere Trace Gases from HALOE and Aura MLS Observations
Using single value decomposition to fit annual and QBO trace gas variations, we analyze thirteen years (1993 to 2005) of HALOE observations and over two years of EOS MLS observations (Sept. 2004 to Dec. 2006). The results reveal annual and QBO variations in tropical H2O, HCl, ozone N2O, CO, HF and CH4. We use these results to develop the theory explaining both Brewer-Dobson circulation (BDC) and QBO driven fluctuations in tropical trace gases. For H2O and CO, tropopause BDC variations drive part of the tropopause annual forcing, and this signal is carried upward by the mean BDC. For ozone, N2O, HCl and other gases, photochemical processes force fluctuations in the trace gases to be synchronized to the zonal mean residual vertical velocity.
A23D-03
Separating ozone from greenhouse gas signals in stratospheric temperature trends
Ozone depletion over the last 3 decades has led to a decrease in stratospheric temperature through decrease of shortwave heating. Greenhouse gases such as carbon dioxide and methane have likewise caused a decrease in stratospheric temperature through longwave radiation to space. Over the next 2-3 decades, ozone should increase in response to the provisions of the Montreal Protocol. Increased ozone and increased carbon dioxide lead to opposite effects on stratospheric temperature. Thus the projection of how stratospheric temperature will change over the next few decades depends on an accurate evaluation of the relative sensitivity of the temperature to ozone change and carbon dioxide change. We have previously evaluated those sensitivities in our chemistry- climate model by time-series analysis of the 140-year simulation. We now extend the analysis to ask how long the data set has to be to achieve a statistically-significant separation of the ozone and greenhouse terms in the temperature time series. We find that in our simulation, the terms can be significantly separated for the upper stratosphere using output from 1979 through 2010. In the lower mid-latitude stratosphere we require output through about 2020 to achieve a significant separation of the terms. We will discuss the implication of these simulation results for determining the causes of trends in measurements of stratospheric temperature.
A23D-04
High Resolution Measurements of the Tropical Tropopause Region by HIRDLS
The High Resolution Dynamics Limb Sounder (HIRDLS) was launched on the Aura satellite in July 2004. It was designed to make measurements of temperature, cloud particles, ozone, water vapor, and 8 other species with higher vertical resolution than previously possible. An unforeseen event occurred during launch that created an obstruction over most of the optical entrance aperture, creating a number of problems. After many months of work, a correction scheme has been developed that will permit much of the original capability to be recovered. The results of initial data validation will be presented, showing that the atmospheric horizontal variations are captured very well. The agreement with correlative data is good, and provides evidence that the vertical resolution of the data is ~1 km. These corrected data show the vertical structure of water vapor, high cirrus and ozone, and their relationship to the temperature structure in the region of the tropical tropopause. The presentation will focus on the response of these quantities to tropical disturbances, especially the Asian Monsoon circulation.
A23D-05
Potential Excited NO2 Chemistry Could Increase Tropospheric O3 Production Rates and Stratospheric NOX/NOY Ratio
Potential reaction of electronically excited NO2 (A,2B1,2B2) with O2, NO2 (A, 2B1,2B2) + O2 → NO + O3 (R1) could increase the probability of NO2 reverting to NO while producing O3 and reduce the probability of being lost to the HNO3 reservoir. This would increase O3 production efficiency and the stratospheric NOX/NOY ratio. It is important to investigate this matter, since air pollution affects climate mostly through the radiative forcing of O3. The reaction NO2+O2 → NO+O3 is expected to occur with a rate coefficient of 5x10-12 exp(-50,550/RT) cm3 s-1, assuming reversibility of reaction holds for the well known reaction NO+O3 → NO2+O2 that occurs with a rate coefficient of 3x10-12 exp(-3,000/RT) cm3 s-1. In the atmosphere in local thermodynamic equilibrium (LTE), therefore, reaction of NO2 (X 2A1) with O2 would be totally insignificant. However, due to the presence of solar photons the atmosphere is not in LTE. Excited NO2 having internal electronic energy in excess of the 50.6 kcal mole-1 activation energy (due, for example, to the absorption of solar photons) could significantly react with O2, especially if it is in the non-dissociative state. The NO2(A, 2B1, 2B2) produced by NO2 (X 2A1) + hν (≤ 500 nm) can therefore drive the reaction (R1). Note that in reaction (R1) the excitation energy is in the reactant that transfers the O atom. Thus, the reaction is more likely than not. Data on the quenching of NO2 fluorescence by N2 and O2 [Myer et al., J. Chem.Phys., 44, 718, 1966] provide some support for the reaction (R1). In Myer et al. experiment fluorescence from electronically excited NO2(A, 2B1, 2B2) was produced by the absorption of &lamda; = 435.8 nm photons by NO2 (X 2A1). The N2 and O2 molecules quenched this fluorescence with rate constant of, respectively, 3.1 x 10-11 cm3 s-1 and 3.4 x 10-11 cm3 s-1. The quenching rate coefficient increases with the molecular complexity of the quencher (such as H2O a polar molecule with many degrees of freedom). However, the more efficient quenching by O2 relative to N2 (which are of comparable complexity) suggests a reactive channel in the case of O2. What fraction of the quenching by O2 is reactive cannot be deduced from the quenching data. However, the previous paragraph supports the conjecture k1 = 5.0 x 10-12 cm3 s-1. Assuming that the conjecture holds for excited NO2 produced by photons 400 ≤ λ ≤ 500 nm, the probability of the reaction (R1) is seen to be about 10% of the photodissociation. Details will be given in the presentation at the meeting. In summary, inclusion of the reaction pair (R1) could increase the O3 production efficiency and rate by about 10%.
A23D-06
Indirect Global Warming Potentials of Halons Using Atmospheric Models
Emission of bromochlorofluorocarbons, or Halons, results in stratospheric ozone depletion. This leads to cooling of the climate system in the opposite direction to direct warming contribution of the Halons as greenhouse gases. This cooling is a key indirect effect of Halons on radiative forcing or climate. The Global Warming Potential (GWP) is a relative index used to compare the climate impact of an emitted greenhouse gas, relative to an equal amount of carbon dioxide. Until now, indirect GWPs have been calculated based on the concept of Equivalent Effective Stratospheric Chlorine (EESC), which oversimplifies the complex processes in the atmosphere. As a step towards obtaining indirect GWPs through a more robust approach, 2-D and 3-D global chemical transport models (CTM) were used as the computational tool to derive more realistic ozone changes caused by pulse perturbation of Halons at the surface. Indirect GWPs of Halon-1211 and -1301 for a 100-year time horizon were explicitly calculated based on the University of Illinois at Urbana-Champaign (UIUC) 2-D global CTM and radiative transport model (RTM) and the 3-D CTM, MOZART-3.1. The 2-D and 3-D model simulations show acceptable temporal variations in the atmosphere as well as derived lifetimes and direct GWP values of the Halons. The 2-D model-based indirect GWPs for a 100-year horizon are -16,294 for Halon-1211 and -33,648 for Halon-1301. 3-D indirect GWP for Halon-1211 is -18,216. The indirect GWPs for Halon-1211 presented here are much smaller than previous published results using the previous simplified appraoch.
A23D-07
Changes in Ozone and UV Index of Australian Cities (1958-2004)
Ground-based total ozone data sets are compared with ERA40 and TOMS and then used to estimate the total ozone variations for several Australian cities over the period 1958 to 2004. The data sets are deseasonalized and the differences with the pre-ozone-hole period 1970-1980 are calculated. All data sets show changes in the rate of the total ozone decline during the 80's while the ozone decline during the 90's is fairly constant. Ozone decline may have an important impact in the amount of surface UV radiation, if all other factors remain constant. Consideration of the changes in UV levels is particularly important for this region as Australia has one of the highest rates of skin cancer in the world. UV Index distributions within the period 1958-2004 are calculated using the ground-based total ozone as input to the "single column model version" of the Australian Ozone and UV forecasting system. The UV Index is also compared with the occurrence of non-melanoma skin cancer rate over Australia.
A23D-08
Why Modelling on Different Scales is Necessary to Understand the Balance of Mercury in the Atmosphere
Two apparently conflicting facts concerning atmospheric mercury have prompted debate and an intensification of
research activity over the last five years. The first is that global background atmospheric mercury concentrations
are extremely uniform, with a slightly lower in the southern hemisphere compared to the northern hemisphere.
This indicates that the atmospheric residence time pf mercury is long enough for it to be transported from its
main emission source areas. The second is the by now well established presence of oxidised mercury
compounds in the marine BL, far from anthropogenic sources. Oxidised mercury compounds make up a fairly
small component of anthropogenic emissions, but are much more readily scavenged or deposited than
elemental mercury and therefore not expected to be transported over any great distance. The presence of these
compounds in the MBL therefore suggests that in-situ production occurs, which would also infer in-situ
deposition thereby reducing the local concentration of mercury. However, as stated previously background
concentrations are hemisperically extremely uniform. In order to investigate the atmospheric transport and
transformation of mercury, modelling studies at different scales are required. Complex photochemical box
models are used to study chemical processes in detail. Regional transport models with less complex chemistry
but including anthropogenic and natural emission sources and a parameterised description of deposition
processes are used to study source receptor relationships and estimate Hg exchange budgets between the
atmosphere and terrestrial and marine receptors. Global transport models (with simplified chemistry) are used to
investigate long-distance (intercontinental) transport pathways and the uniformity of hemispherical background
concentrations. Results from the photochemical box model studies indicate that the atmospheric lifetime of
mercury due to reactions with Br and OH may be shorter than previously thought, while the regional models
indicate that emission and deposition processes may actually act to maintain the uniformity of the background
concentration away from emission sources. The role of oceans and the reactions which occur in the atmospheric
boundary layer and the surface layer of seas and oceans merit further investigation.
http:www.cs.iia.cnr.it