Long-Term Measurement Records Related to Global Stratospheric Constituent Change I Posters
Presiding: C H Jackman, NASA Goddard Space Flight Center; E E Remsberg, NASA Langley Research Center
A51A-01 0830h
A Further Look of Decadal Variations of Total Column and Upper Stratospheric Ozone
The most recently reprocessed SBUV(/2) total ozone and ozone profile data (version 8) are used to study decadal ozone variations including trend and solar cycle effect. This improved data set removes many of the problems encountered in the original version 6 and extends the data base to 25 years, about two solar cycles (1979-2004). To utilize this data properly, however, we must still remove systematic inter-satellite differences in the ozone data and examine each satellite for possible drift in the measurements. For this study, all the satellite data (total ozone and profile) are adjusted through comparison with ground-based measurements and using satellite overlap periods. Following this, spectral analyses and multiple regressions are performed to determine the decadal variability of total column and upper stratospheric ozone. The new results are compared with the previous analyses based on shorter time periods as well as with model simulations.
A51A-02 0830h
Solar Cycle Response and Trends in Upper Stratospheric and Lower Mesospheric Ozone From HALOE
Time series of HALOE ozone for the period 1991-2004 were analyzed for their seasonal, interannual, solar cycle (SC), and trend terms. To do this, the HALOE Level 2 ozone profiles were integrated vertically into half-Umkehr pressure layers (about 2.5 km thick) and then averaged zonally for each period when the HALOE sunrise (SR) or sunset (SS) tangent-point measurements cycled through a given 10-degree latitude bin. By conducting analyses within pressure layers, one can separate out the effects of local chemistry and net transport on the ozone from the effects of a cooling or heating of the underlying atmospheric column that contributes to the periodic variations in a time series of ozone on an altitude surface. Analyses were conducted for 9 latitude zones Equatorward of 45S and 45N and 10 pressure layers from about 9.6 mb to 0.35 mb, the upper stratosphere and lower mesosphere. Model terms for each time series were added as they were found to be significant. The 11-yr SC response in ozone is prevalent and generally in-phase throughout this domain. Maximum response occurs in the subtropics at about 1.7 mb in the northern hemisphere (25N), but at about 3.5 mb in the southern hemisphere (15S). Peak amplitude for the SC response is near 1.5% for the NH, but about half that for the SH. Minimum (and nearly non-significant) response amplitudes of about 0.2% were found near the tropical stratopause; they were also out-of-phase with the SC total flux. Tropical SC responses increase to about 0.65% at 0.5 mb and at 4 mb, and they also come back in-phase. It is strongly suggested that this overall pattern of the decadal-scale ozone response across the zonal-mean cross section is not entirely due to photochemistry, but that some kind of dynamical forcing is also affecting the ozone and by a different amount for the two hemispheres. After accounting for the seasonal, interannual, and SC terms, there is no clearly significant loss or recovery for ozone in the upper stratosphere for this recent 13-year period, at least for the low and middle latitudes.
A51A-03 0830h
Decadal Time Series of UV Irradiances at two NDSC Sites
The Network for the Detection of Stratospheric Change (NDSC) comprises a small number of well-instrumented unpolluted measurement sites, selected to represent large geographical areas. Its aim is to better understand the causes and effects of long term changes in atmospheric composition. In order to monitor long term ozone change and its effects, UV spectrometers were installed at the mid-latitude southern hemisphere NDSC site (Lauder New Zealand), and the tropical NDSC site (Mauna Loa Observatory, Hawaii). At NIWA's Lauder site, measurements began in December 1989; while at NOAA's Mauna Loa Observatory, measurements began in June 1995. Since deployment, data have been obtained with a high success rate. The instrumentation and data-processing are similar at both sites, and comply with the exacting standards required by the NDSC. Here we present time series of data products from these spectrometers (e.g., erythemally-weighted UV irradiance) to compare and contrast the results from each site and to illustrate the causes for variabilities, and their influences on validation of radiative transfer models and satellite data products.
A51A-04 0830h
Improvements to SAGE II Level 1 Transmission Product
In recent years, advances in the SAGE II processing in versions 6.0, 6.1, and 6.2 have produced increasingly robust measurements of stratospheric ozone, nitrogen dioxide, water vapor and aerosol extinction. The processing algorithms continue to be refined, resulting in impressive noise reduction in stratospheric transmission measurements. Most of the new changes relate to the I-zero calibration, which is the normalization of observations of the atmosphere to exo-atmospheric observations. In the enhanced algorithm, more scans are combined to create a finer spatial resolution calibration curve. In addition, an entirely new algorithm has been developed which addresses a previously neglected time dependence of the I-zero function; the time dependence is attributed to rotation of the scan plane over the course of each event. These and other algorithm updates decrease the noise in the unbinned transmission by 40 to 50 percent in the stratosphere. The improvements to the unbinned transmission are expected to generate a more robust binned transmission profile and better species profile products for the next version.
A51A-05 0830h
Aerosol and Gases Data Available For Long-term Stratospheric Constituent Studies
The Atmospheric Sciences Data Center (ASDC) at NASA Langley Research Center archives data from the Stratospheric Aerosol and Gas Experiment (SAGE) I, II, and III and Stratospheric Aerosol Measurement (SAM) II projects. These data span approximately 27 years and can be used to study long term trends of stratospheric constituents such as the effects of volcanic eruptions and changes in ozone levels. The SAGE I, II, and III projects cover the time span February 1979 through the present. These data provide vertical distributions of nitrogen dioxide, ozone, water vapor and aerosols. The SAGE I instrument provided nearly global measurements of aerosol extinction profiles and ozone and nitrogen dioxide concentration profiles using four spectral channels centered at wavelengths of 1000, 600, 450, and 385 nanometers (nm). SAGE II data contain profiles of aerosol extinction at 1020, 525, 453, and 385 nm and contains number density profiles of ozone and nitrogen dioxide. The ASDC continues to receive and archive the SAGE II data. SAGE III collects measurements during both solar and lunar occultation events. Solar event species are water vapor, nitrogen dioxide, ozone, temperature and pressure, and aerosol extinction at wavelengths of 1550, 1019, 868, 754, 676, 596, 521, 448, and 385 nm. Cloud occurrence are also collected during solar events. Lunar event species are chlorine dioxide, nitrogen dioxide, nitrogen trioxide, and ozone. In addition to the SAGE data, the NASA Langley ASDC archives data from the SAM II which contains the vertical distribution of stratospheric aerosols in the polar regions and covers the time span October 1978 through December 1993. These data along with documentation, tools, and read software are available from the NASA Langley ASDC at http://eosweb.larc.nasa.gov.
http://eosweb.larc.nasa.gov
A51A-06 0830h
Ozonesonde measurements at Lauder, New Zealand, and the search for ozone recovery
As part of the Network for Detection of Stratospheric Change (NDSC), ozonesonde flights at Lauder (45.04°S, 169.68°E) have been made approximately weekly from August 1986 to the present. In earlier years, flights were made twice weekly from September to December. These data have been subjected to a range of data quality control procedures including homogenization of the data set; ozonesondes before August 1996 were flown with a 1% KI cathode solution, while later flights were made with a 0.5% KI cathode solution1. A brief discussion of the ozonesonde data quality control procedures developed at Lauder will be presented. Ozone number densities and ozone mixing ratios from these flights from August 1986 to December 2004 were interpolated onto 100 pressure levels from the surface (969.6 hPa, 370m) to 12.1 hPa (~30.1 km) and ~300 geopotential meters apart. These were then used as input to a linear least squares regression model to quantify the drivers of trends and variability in the vertical distribution of ozone over New Zealand. The regression model includes basis functions for a seasonally dependent long-term trend, a mean annual cycle, the Quasi-biennial Oscillation (QBO), the El Niño Southern Oscillation (ENSO), the solar cycle, the influence of tropopause height variability, and the influence of the Mt. Pinatubo volcanic eruption2. The seasonal structure in the ozone trends derived using this statistical model provides constraints on the potential sources of the trends and is also a good test for models of southern hemisphere ozone change. A cumulative sum of residuals diagnostic3 was then applied to the residuals from the regression analysis to look for evidence of turnaround in ozone trends over New Zealand and/or the timing of minimum ozone levels over New Zealand. References 1) Boyd, I.S., G.E. Bodeker, B.J. Connor, D.P.J. Swart, and E.J. Brinksma, An assessment of ECC ozonesondes operated using 1% and 0.5% KI cathode solutions at Lauder, New Zealand, Geophysical Research Letters, 25 (13), 2409-2412, 1998. 2) Bodeker, G.E., I.S. Boyd, and W.A. Matthews, Trends and variability in vertical ozone and temperature profiles measured by ozonesondes at Lauder, New Zealand: 1986-1996, Journal of Geophysical Research, 103 (D22), 28661-28681, 1998. 3) Reinsel, G.C., Trend analysis of upper stratospheric Umkehr ozone data for evidence of turnaround, Geophysical Research Letters, 29 (10), 10.1029/2002GL014716, 2002.
A51A-07 0830h
Long-Term Observations of BrO at Lauder, New Zealand and Arrival Heights, Antarctica
As part of the Network for Detection of Stratospheric Change (NDSC) ground-based measurements of BrO (bromine oxide) have been made using zenith-sky UV/vis absorption spectroscopy at Lauder, New Zealand (45°S, 170°E), and at Arrival Heights, Antarctic (78°S, 167°E). These BrO column measurements have been made continuously since 1995 and are the only two decadal Southern Hemisphere ground-based data sets. A knowledge of long-term changes in BrO is important since in the lower stratosphere during winter and spring the ClO+BrO ozone loss cycle can be as important as the ClO dimer cycle (up to 40% each) over the Antarctic, and can account for up to 20% of ozone loss between 40°S and 50°S (1). Furthermore, while stratospheric concentrations of chlorine containing compounds are expected to decrease in the future, concentrations of bromine containing compounds, and in particular methyl bromide (CH3Br), are changing little. Therefore, compared to ClO, the relative contribution of BrO to ozone depletion could increase in the future. To this end we have analyzed our BrO column measurements at both locations for long-term variability and trends. Recent studies have shown that although existing models are able to approximately predict the amount of BrO in the atmosphere, the distribution of BrO in the stratosphere-troposphere layers could be misrepresented and the inorganic bromine (Bry) at and above the tropopause could be 4-8 ppt greater than currently assumed in models used in past ozone trend assessments. Intercomparisons between model results and measurements provide a very sensitive test of the model and can highlight model inadequacies. We have therefore compared our measurements with output from two models to assess the ability of the models to reproduce the long-term trends and variability in our data. In polar regions, BrO concentrations in the lower troposphere can be rapidly elevated through non-linear chemistry thought to involve sea-salt particles deposited onto the sea-ice; so called `BrO explosion events'. To better diagnose these events and their impact on tropospheric ozone at Arrival Heights, in 1999 the zenith-sky measurements were complemented with measurements made using a multi-axis viewing geometry. In addition, during spring 2002, direct-sun BrO measurements were made. The latter two types of observation provide more accurate information on the tropospheric component of the BrO column. All three BrO data sets were investigated for sudden strong increases in BrO and concomitant decreases in surface ozone typical of a BrO explosion event. References (1) Lee, A.M., R.L. Jones, I. Kilbane-Dawe, and J.A. Pyle, Diagnosing ozone loss in the extratropical lower stratosphere, Journal of Geophysical Research, 107 (D11), 10.1029/2001JD000538, 2002.
A51A-08 0830h
Updated Studies in the Trends of Stratospheric Water Vapor Using SAGE II and HALOE Multi-year Measurements
The SPARC Water Vapor Assessment (2000) reported that water vapor trends from HALOE satellite instrument (Version 19) exhibited positive trends (.02 to .03 ppmv/year) at altitudes 20-34 km in the northern mid latitudes for the period 1993-1997. Our trend analyses for a lower portion of this layer (16-25km), but same latitude region indicate significant negative trends varying from -.02ppmv/year to -.04ppmv/year when evaluated over the period 1994-2004. For the upper layer (26-34km), the trends were either insignificant or slightly negative. Very similar results were found for periods 1995-2004, 1996-2004, 1997-2004, 1995-2003, 1996-2003, and 1997-2003. The SAGE II (Version 6.2) data record revealed the same general results for same periods and regions. Examination of HALOE time series found relatively low water vapor mixing ratios in 1992 and 1993 when elevated aerosols abundance was present from the eruption of Mt. Pinatubo. It is speculated that this feature may be the primary cause for the postive trends reported in the SPARC Assessment. This study will elaborate on these findings and will provide additional information on derived trends over longer periods in the SAGE II record and in the southern hemisphere.
A51A-09 0830h
Instrument Drift Uncertainties and the Long-Term TOMS/SBUV Total Ozone Record
Long-term climate records from satellites are often constructed from the measurements of a sequence of instruments launched at different times. Each of these instruments is calibrated prior to launch. After launch they are subjected to potential offsets and slow drifts in calibration. We illustrate these issues in the construction of a merged total ozone record from 2 TOMS and 3 SBUV instruments. This record extends from late 1978 through the present. The question is "How good are these records?". We have examined the uncertainty in determining the relative calibration of two instruments during an overlap period in their measurements. When comparing a TOMS instrument, such as that on Nimbus 7, with an SBUV instrument, also on Nimbus 7, we find systematic differences and random differences. We have combined these findings with estimates of individual instrument drift into a monte-carlo uncertainty propagation model. We estimate an instrument drift uncertainty of a little larger than 1 percent per decade over the 25-year history of the TOMS/SBUV measurements. We make an independent estimate of the drift uncertainty in the ground-based network of total ozone measurements and find it to be of similar, but slightly smaller magnitude. The implications of these uncertainties for trend and recovery determination will be discussed.
A51A-10 0830h
Long-Term HALOE Observations of HCl and HF
The Halogen Occultation Experiment (HALOE) instrument on-board the Upper Atmosphere Research Satellite has provided unprecedented temporal and spatial information on the near-global distribution of hydrogen chloride (HCl) and hydrogen fluoride (HF) since October, 1991. Stratospheric HCl is central to the gas phase chemistry of ozone depletion. Stratospheric HF is a photodissociation product of anthropogenic CFCs, HCFCs, halons, and HFCs and it has no known appreciable natural sources. Near the stratopause, HCl comprises greater-than 93 percent of the total inorganic chlorine while HF comprises greater-than 85 percent of the total inorganic fluorine. We present updated near-global time series of HALOE derived total inorganic Cl and F at 55 km and compare these with time series derived from ground-based measurement programs, a United Nations Environment Programme scenario for CFC emissions, and mean-age theory. In addition, we will present updated time series of stratospheric column abundances and compare these with those measured at various Network for Detection of Stratospheric Change sites.
A51A-11 0830h
Simulating Ozone in the Near Tropopause Region with the NASA Global Modeling Initiative Combined Model of the Stratosphere and Troposphere
We use monthly mean, tropopause-referenced ozone climatologies constructed from multiple years of ozonesonde and SAGE II satellite data to evaluate near-tropopause ozone mixing ratios and vertical gradients generated by the NASA Global Modeling Initiative (GMI) three-dimensional chemistry and transport model. Most of the sonde station data sets exceed 10 years in length, and the SAGE II climatology was constructed from observations made between December, 1984, and November, 2002. The model includes a full description of stratospheric and tropospheric physicochemical processes extending from the surface to above the stratopause with a vertical resolution near the tropopause of approximately1 km. This "combined" CTM can be driven with several sets of meteorological data; here we focus on results using meteorological data from the NASA GEOS-4 AGCM. The GEOS-4 AGCM has been shown to have good stratosphere-to-troposphere mass and ozone fluxes. Preliminary results indicate that tropical profiles of modeled and observed ozone mixing ratios and vertical gradients agree best, with larger discrepancies at higher latitudes. We investigate the various factors causing these discrepancies and compare results of simulations using other meteorological data sets to drive the CTM.
A51A-12 0830h
Regression Analysis of Long-term Profile Ozone Data Set from BUV Instruments
We have produced a profile merged ozone data set (MOD) based on the SBUV/SBUV2 series of nadir-viewing satellite backscatter instruments, covering the period from November 1978 - December 2003. In 2004, data from the Nimbus 7 SBUV and NOAA 9, 11, and 16 SBUV/2 instruments were reprocessed using the Version 8 (V8) algorithm and most recent calibrations. More recently, data from the Nimbus 4 BUV instrument, which operated from 1970 - 1977, were also reprocessed using the V8 algorithm. As part of the V8 profile calibration, the Nimbus 7 and NOAA 9 (1993-1997 only) instrument calibrations have been adjusted to match the NOAA 11 calibration, which was established from comparisons with SSBUV shuttle flight data. Given the level of agreement between the data sets, we simply average the ozone values during periods of instrument overlap to produce the MOD profile data set. We use statistical time-series analysis of the MOD profile data set (1978-2003) to estimate the change in profile ozone due to changing stratospheric chlorine levels. The Nimbus 4 BUV data offer an opportunity to test the physical properties of our statistical model. We extrapolate our statistical model fit backwards in time and compare to the Nimbus 4 data. We compare the statistics of the residuals from the fit for the Nimbus 4 period to those obtained from the 1978-2003 period over which the statistical model coefficients were estimated.
A51A-13 0830h
Long-Term Measurements of NO2 at Lauder, New Zealand
Daily NO2 column measurements have been made at Lauder, New Zealand (45S, 170E) since 1980. The measurement technique utilizes the highly structured absorptions by NO2 which are present in sunlight scattered from the zenith sky at twilight (dawn and dusk). The site is well suited to stratospheric observations because of the very clear troposphere and negligible amounts of NO2 in the boundary layer. The importance of nitrogen oxides, in particular the so called NOx species (NO and NO2), in determining stratospheric ozone concentrations has long been recognized. The NOx species catalytically destroy ozone but in the anthropogenically perturbed lower stratosphere, they can inhibit ozone depletion by converting active halogen and hydrogen compounds into their unreactive reservoirs (e.g. ClONO2 and HNO3). The dominant variation in the measured NO2 values at Lauder is the photochemically induced diurnal and annual cycles, with the El Chichon and Pinatubo volcanic eruptions producing significant episodic reductions. Longer-term patterns have also been identified which suggest that NO2 variation may be predicted by major atmospheric cycles: the solar cycle, quasi-biennial oscillation and southern oscillation index. Based on the current estimates of the influence of these atmospheric cycles and volcanic eruptions, the secular trend in the measurements is estimated to be 5% per decade. Convergence of the trend only occurs after a relatively long period of measurement (>15 years). A range of different models have been used to help elucidate aspects of the observed changes in NO2 over Lauder. Results from these studies will be summarized.
A51A-14 0830h
Long-term Stratospheric Measurements at Lauder, New Zealand, and Arrival Heights, Antarctica, using Fourier Transform Spectrometers
Ground-based remote measurements of selected stratospheric trace species using Fourier transform spectrometers (FTS) at mid-infrared wavelengths (2-14 microns) began in Lauder, New Zealand (45 ° S), in the 1980s. These have been expanded and improved over many years, to include more trace gases, and to derive some information of the vertical profile of the measured gases. The initial focus was on gases that are important in stratospheric ozone chemistry, such as HCl and HNO3 . Measurements of these species were also carried out on a campaign basis at Arrival Heights, Antarctica, (78 ° S) from the late 1980s and continuously from the early 1990s with the support of the New Zealand Antarctic programme and collaborating groups. In addition to chemically active species, gases that are useful as stratospheric tracers are also measured. Both Lauder and Arrival Heights are part of the international Network for the Detection of Stratospheric Change (NDSC) and several of the time series are now over 10 years in length. A consistent reanalysis of these longer time series, to be submitted to the NDSC database, will be presented. This presentation will examine some of the principal results from these data sets, including the long-term trends and variability of the measured trace gases, and the influence of anthropogenic changes and natural events in the atmosphere. It will also look at the way the programme of FTS measurements is evolving to meet new challenges. In particular, there is a new emphasis on tropospheric species, including biomass burning products and greenhouse gases, which has prompted an expansion of the programme to near-IR and visible wavelengths.