Partial Column Research Articles

Comparisons between ground-based FTIR and MIPAS N<sub>2</sub>O and HNO<sub>3</sub> profiles before and after assimilation in BASCOE

Abstract. Within the framework of the Network for Detection of Atmospheric Composition Change (NDACC), regular ground-based Fourier transform infrared (FTIR) measurements of many species are performed at several locations. Inversion schemes provide vertical profile information and characterization of the retrieved products which are therefore relevant for contributing to the validation of MIPAS profiles in the stratosphere and upper troposphere. We have focused on the species HNO3 and N2O at 5 NDACC-sites distributed in both hemispheres, i.e., Jungfraujoch (46.5° N) and Kiruna (68° N) for the northern hemisphere, and Wollongong (34° S), Lauder (45° S) and Arrival Heights (78° S) for the southern hemisphere. These ground-based data have been compared with MIPAS offline profiles (v4.61) for the year 2003, collocated within 1000 km around the stations, in the lower to middle stratosphere. To get around the spatial collocation problem, comparisons have also been made between the same ground-based FTIR data and the corresponding profiles resulting from the stratospheric 4D-VAR data assimilation system BASCOE constrained by MIPAS data. This paper discusses the results of the comparisons and the usefullness of using BASCOE profiles as proxies for MIPAS data. It shows good agreement between MIPAS and FTIR N2O partial columns: the biases are below 5% for all the stations and the standard deviations are below 7% for the three mid-latitude stations, and below 10% for the high latitude ones. The comparisons with BASCOE partial columns give standard deviations below 4% for the mid-latitude stations to less than 8% for the high latitude ones. After making some corrections to take into account the known bias due to the use of different spectroscopic parameters, the comparisons of HNO3 partial columns show biases below 3% and standard deviations below 15% for all the stations except Arrival Heights (bias of 5%, standard deviation of 21%). The results for this species, which has a larger spatial variability, highlight the necessity of defining appropriate collocation criteria and of accounting for the spread of the observed airmasses. BASCOE appears to have more deficiencies in producing proxies of MIPAS HNO3 profiles compared to N2O, but the obtained standard deviation of less than 10% between BASCOE and FTIR is reasonable. Similar results on profiles comparisons are also shown in the paper, in addition to partial column ones.

Severe ozone depletion in the cold Arctic winter 2004–05

During a flight of the M55 Geophysica into the Arctic polar vortex on 7 March 2005, ozone, halogen species, tracers and water vapor were measured. Up to 90% chlorine activation and up to 60% ozone loss were found above 14 km, reflecting the low temperatures and extensive PSC formation prevalent in the Arctic stratosphere over the 2004/05 winter. Observations are generally well reproduced by CLaMS model simulations. The observed levels of active chlorine can only be reproduced by assuming significant denitrification of about 70%. Moderate dehydration up to 0.5 ppm is observed in some locations. We deduce a partial column ozone loss of 62 (+8/−17) DU below 19 km on 7 March.

Seasonal variation of carbon monoxide in northern Japan: Fourier transform IR measurements and source‐labeled model calculations

Tropospheric carbon monoxide (CO) was measured throughout 2001 using ground‐based Fourier transform IR (FTIR) spectrometers at Moshiri (44.4°N) and Rikubetsu (43.5°N) observatories in northern Japan, which are separated by 150 km. Seasonal and day‐to‐day variations of CO are studied using these data, and contributions from various CO sources are evaluated using three‐dimensional global chemistry transport model (GEOS‐CHEM) calculations. Seasonal maximum and minimum FTIR‐derived tropospheric CO amounts occurred in April and September, respectively. The ratio of partial column amounts between the 0–4 and 0–12 km altitude ranges is found to be slightly greater in early spring. The GEOS‐CHEM model calculations generally reproduce these observed features. Source‐labeled CO model calculations suggest that the observed seasonal variation is caused by seasonal contributions from various sources, in addition to a seasonal change in chemical CO loss by OH. Changes in meteorological fields largely control the relative importance of various source contributions. The contributions from fossil fuel (FF) combustion in Asia and photochemical CO production have the greatest yearly averaged contribution at 1 km among the CO sources (31% each). The Asian FF contribution increases from winter to summer, because weak southwesterly wind in summer brings more Asian pollutants to the observation sites. The seasonal variation from photochemical CO production is small (±17% at 1 km), likely because of concurrent increases (decreases) of photochemical production and loss rates in summer (winter), with the largest contribution between August and December. The contribution from intercontinental transport of European FF combustion CO is found to be comparable to that of Asian FF sources in winter. Northwesterly wind around the Siberian high in this season brings pollutants from Europe directly to Japan, in addition to southward transport of accumulated pollution from higher latitudes. The influences are generally greater at lower altitudes, resulting in a vertical gradient in the CO profile during winter. The model underestimates total CO by 12–14% between March and June. Satellite‐derived fire‐count data and the relationship between FTIR‐derived HCN and CO amounts are generally consistent with biomass burning influences, which could have been underestimated by the model calculations.

First detection of meso‐thermospheric Nitric Oxide (NO) by ground‐based FTIR solar absorption spectroscopy

We report the first detection of mesospheric‐lower thermospheric (MLT, 50–130 km) NO from ground‐based FTIR solar absorption spectra using Lorentz‐ and Doppler‐broadened solar absorption lines in the stratosphere and in the MLT, respectively. We present the first characterization of vertical sensitivity in the FTIR NO retrieval and show that MLT NO partial columns can be retrieved with ∼1 independent piece of information using a climatological NO profile extending up to 130 km. The information content analysis also improves the characterization of stratospheric partial column retrievals and is relevant to NO results obtained at other Network for the Detection of Stratospheric Change (NDSC) FTIR sites. We apply our approach to spectra recorded at Complementary NDSC site Toronto (43.66°N, 79.40°W) during the solar storms of Oct–Nov 2003 and at Primary NDSC site Eureka (80.05°N, 86.42°W) during Feb–Mar 2004. MLT NO enhancements are found at Eureka, while possible enhancements at Toronto cannot be attributed to a particular altitude.

Regions containing eigenvalues of a matrix

In this paper, regions containing eigenvalues of a matrixare obtained in terms of partial absolute deleted row sums and column sums. Furthermore, some sufficient and necessary conditions for H-matrices are derived. Finally, an upper bound for the Perron root of nonnegative matrices is presented. The comparison of the new upper bound with the known ones is supplemented with some examples.

Seasonal variations of CO and HCN in the troposphere measured by solar absorption spectroscopy over Poker Flat, Alaska

[1] Tropospheric partial column abundances of CO and HCN have been retrieved from infrared solar spectra observed with a ground-based spectrometer at Poker Flat Alaska (65°N, 147°W) over the time period from 2000 to 2004. From these data we report the transpacific transport induced inter-annual variability of tropospheric CO over Poker Flat. This is the first report of solar infrared data from the Poker Flat station, where the geographical location of the site means that remote sensing measurements are sampling the transport of transpacific air parcels going to Northern America from Eastern Siberia and Asia. The five year time-span of the data also show significant differences in year to year CO and HCN tropospheric column enhancements driven by changes in Siberian/Asian pollution sources.

Whole-column imaging-detection techniques and their analytical applications

We review developments in whole-column detection, including partial column imaging detection and whole-column imaging detection for high-performance liquid chromatography and capillary electrophoresis. We especially discuss recent topics in whole-column imaging detection.

Ground-based measurement of strato–mesospheric CO by a FTIR spectrometer over Poker Flat, Alaska

Abstract Upper atmospheric CO above 24 km has been observed over Poker Flat (147°W, 65°N, altitude 0.61 km), Alaska using ground-based solar absorption infrared spectroscopy. This is the first reported detection of stratospheric–mesospheric CO using this method from the ground. The results clearly indicate that there is a seasonal variation of the CO profile with enhanced abundances in spring while remaining low from May onwards. The Poker Flat Research Range is one of the many measurement sites that constitute the Network for the Detection of Stratospheric Change (NDSC). The method used in this work, estimating the CO partial column abundances above the middle stratosphere, can be applied to spectra observed using FTIR spectrometry at many other NDSC sites. This suggests the availability of this established technique as a new method for CO measurements in the upper atmosphere.

Operational trace gas retrieval algorithm for the Infrared Atmospheric Sounding Interferometer

The Infrared Atmospheric Sounding Interferometer (IASI) is a nadir‐viewing remote sensor due for launch on board the European Metop satellites (to be launched in 2005, 2010, and 2015). It is dedicated to the study of the troposphere and the lower stratosphere to support operational meteorology as well as atmospheric chemistry and climate studies. For this purpose, it will record high resolution atmospheric spectra in the thermal infrared, allowing the measurement of several infrared absorbing species. This paper describes the clear‐sky retrieval scheme developed in the framework of the preparation of the IASI mission for the operational, near real time, retrieval of O3, CH4, and CO concentrations. It includes the inversion module, based on a neural network approach, as well as an error analysis module. The studies undertaken on test simulations have shown that a performance of the order of 1.5%, 2%, and 5% for the retrieval of total columns of O3, CH4, and CO, respectively, can be achieved, and of the order of 28%, 15%, and 9% for the retrieval of partial columns of O3 between the surface and 6, 12, and 16 km high, respectively. The efficiency of the algorithm is demonstrated on the atmospheric measurements provided by the Interferometric Monitor for Greenhouse Gases (IMG)/ADEOS, allowing to obtain the first remote‐sensing simultaneous distributions of ozone and its two precursors, CO and CH4.

Ground-based FTIR measurements of CO from the Jungfraujoch: characterisation and comparison with in situ surface and MOPITT data

Abstract. CO vertical profiles have been retrieved from solar absorption FTIR spectra recorded at the NDSC station of the Jungfraujoch (46.5º N, 8º E and 3580 m a.s.l.) for the period from January 1997 to May 2001. The characterisation of these profiles has been established by an information content analysis and an estimation of the error budgets. A partial validation of the profiles has been performed through comparisons with correlative measurements. The average volume mixing ratios (vmr) in the 3 km layer above the station have been compared with coincident surface measurements. The agreement between monthly means from both measurement techniques is very good, with a correlation coefficient of 0.87, and no significant bias observed. The FTIR total columns have also been compared to CO partial columns above 3580 m a.s.l. derived from the MOPITT (Measurement Of Pollution In The Troposphere) instrument for the period March 2000 to May 2001. Relative to the FTIR columns, the MOPITT partial columns exhibit a positive bias of 8±8% for daytime and of 4±7% for nighttime measurements.

POAM III observations of the anomalous 2002 Antarctic ozone hole

The 2002 southern hemisphere winter was marked by unusually large wave activity, culminating with an unprecedented major warming in late September. This led to an ∼250 DU increase in column ozone near the pole as measured by the Polar Ozone and Aerosol Measurement (POAM) III instrument. POAM measurements of unusually high ozone mixing ratio throughout most of the stratosphere resulted primarily from air from outside the polar vortex being transported to the POAM measurement latitude. In the altitude region where chemical ozone loss from chlorine catalyzed chemistry occurs (below 600 K potential temperature) the 2002 ozone loss was similar to previous years up to the time of the major warming. The ozone loss diminished after this time (about 1 week earlier than usual), resulting in up to 20% less chemical ozone loss within the vortex than in previous winters. This corresponds to partial column ozone values below 600 K inside the polar vortex that were ∼25 DU larger in 2002 than in previous years.

Validation of version 5.20 ILAS HNO3, CH4, N2O, O3, and NO2 using ground‐based measurements at Arrival Heights and Kiruna

Ground‐based measurements of O3 and NO2 columns at Kiruna (68°N) and Arrival Heights (78°S) were used to validate stratospheric profile measurements of the same species by the satellite‐based Improved Limb Atmospheric Spectrometer (ILAS) flown between November 1996 and June 1997. In addition, measurements of HNO3, CH4, and N2O made at Arrival Heights are compared with measurements of these species by ILAS. Even though there were no temporal coincidences in the latter comparison, the ground‐based data provide a climatological context for the ILAS measurements. ILAS profiles measured within 10° of longitude and 2° of latitude of each site were used. For the species with large tropospheric components (CH4 and N2O), ILAS profiles were integrated upward from 12 km and were compared with ground‐based retrievals of partial columns above 12 km. For O3, which is primarily stratospheric but has an appreciable tropospheric component, tropospheric columns (typically to 8–10 km altitude) calculated from ozonesonde climatologies were added to the integrated ILAS profiles to allow comparison with ground‐based total column ozone measurements. Tropospheric columns of HNO3 and NO2 were assumed to be sufficiently small so that ILAS profiles integrated above 8 km could be compared directly with ground‐based total column measurements.

Comparison of empirically derived ozone losses in the Arctic vortex

A number of studies have reported empirical estimates of ozone loss in the Arctic vortex. They have used satellite and in situ measurements and have principally covered the Arctic winters in the 1990s. While there is qualitative consistency between the patterns of ozone loss, a quantitative comparison of the published values shows apparent disagreements. In this paper we examine these disagreements in more detail. We choose to concentrate on the five main techniques (Match, Système d'Analyse par Observation Zénithale (SAOZ)/REPROBUS, Microwave Limb Sounder (MLS), vortex average descent, and the Halogen Occultation Experiment (HALOE) ozone tracer approach). Estimates of the ozone losses in three winters (1994/1995, 1995/1996 and 1996/1997) are recalculated so that the same time periods, altitude ranges, and definitions of the Arctic vortex are used. This recalculation reveals a remarkably good agreement between the various estimates. For example, a superficial comparison of results from Match and from MLS indicates a big discrepancy (2.0 ± 0.3 and 0.85 ppmv, respectively, for air ending at ∼460 K in March 1995). However, the more precise comparisons presented here reveal good agreement for the individual MLS periods (0.5 ± 0.1 versus 0.5 ppmv; 0.4 ± 0.2 versus 0.3–0.4 ppmv; and 0.16 ± 0.09 ppmv versus no significant loss). Initial comparisons of the column losses derived for 1999/2000 also show good agreement with four techniques, giving 105 DU (SAOZ/REPROBUS), 80 DU (380–700 K partial column from Polar Ozone and Aerosol Monitoring (POAM)/REPROBUS), 85 ± 10 DU (HALOE ozone tracer), and 88 ± 13 (400–580 partial column from Match). There are some remaining discrepancies with ozone losses calculated using HALOE ozone tracer relations; it is important to ensure that the initial relation is truly representative of the vortex prior to the period of ozone loss.

Cracked Column Flanges in Steel Moment Frame Buildings: Considerations for Their Repair including Report on Tests on Volumetric Weld Repairs

This paper presents recommendations on the repair of cracked columns based upon the writers' experiences, found from repair of cracked column flanges following the 1994 Northridge Earthquake. This paper also describes tests carried out using volumetric weld repairs on thick plates to evaluate acceptable procedures for the repair of column flanges with partial cracks damaged from earthquakes. Cracks were often found in the bottom flange of welded joints. In some cases, cracks propagated into column flanges, and in a few cases into their webs. Repairs of cracked welded joints are discussed at some length in other documents and thus are not part of the scope of this paper. One method for the repair of cracked columns involves replacement of the column flange with a new plate. Another method of repair involves the use of volumetric welds to replace the cracked portion of the column flange. This paper includes a description of the development of procedures and limited testing to assess the adequacy of the volumetric repair method of partial column cracks.

Plinian pumice fall deposit of the Campanian Ignimbrite eruption (Phlegraean Fields, Italy)

A plinian pumice fall deposit associated with the Campanian Ignimbrite eruption (36 ka, Phlegraean Fields caldera, Italy) occurs at the base of the distal grey ignimbrite in 15 localities spread over an area exceeding 1500 km 2 between Benevento and the Sorrentina peninsula. In the thickest stratigraphic section at Voscone (130 cm), 45 km east of the Phlegraean caldera centre (Pozzuoli), the deposit consists of two units: the lower fall unit (LFU) is well sorted, exhibits reverse size grading and is composed of equidimensional light-grey pumice clasts with very subordinate accidental lithics; the upper fall unit (UFU) is from well to poorly sorted, crudely stratified, richer in lithics and composed of both equidimensional and prolate pumice clasts. The two fall units show slightly different dispersal axis: N90° for the LFU and N95° for the UFU. Volumes calculated with the method of Pyle (1989) are about 8 km 3 for the LFU and 7 km 3 for the UFU. The maximum height of the eruptive columns are estimated, using the model of the maximum lithic clasts dispersal, at 44 km for the LFU and 40 km for the UFU, classifying both fall units as ultraplinian in character. Reverse size grading within the LFU suggests an increase of the height of the column and magma discharge rate with time. Moderate sorting and crude stratification of the UFU are consistent with short-period oscillation of the column, possibly associated with repeated partial column collapses. Sharp increases in lithic content at the transition to UFU and within the UFU suggest that changes in the eruptive behaviour was produced by a dramatic increase in conduit/vent erosion. The phase of column instability preceded the emplacement of widely dispersed pyroclastic flow. The ultraplinian nature of the fall fits well with the wide dispersal of the Campanian Ignimbrite with an estimated aspect ratio of 3–4×10 −4 (LARI).

Atmospheric ray path modeling for radiative transfer algorithms

A new method for the determination of ray paths as well as resulting path segments and partial gas columns within a layered atmosphere is presented. Any singularity at the tangent point is avoided. No use is made of the gross spherical symmetry of the Earth's atmosphere. Using this approach we examine the impact of the Earth's oblate shape and horizontal atmospheric inhomogeneities on infrared limb spectra.

Analytical Evaluation of Retrofit Strategies for Multicolumn Bridges

The objective of the work of this paper was to investigate analytically the feasibility and advantages of applying various combinations of steel jacket retrofit measures developed for single-column bent bridges to multicolumn bent bridges. To achieve the objective, an existing nonlinear dynamic bridge analysis program with elastic–perfectly plastic column behavior and a conventional hysteresis model was modified in order to include softening behavior from column damage and a more realistic hysteresis rule for cyclic loading. A 2D structural model of an actual bridge was used to evaluate column retrofitting measures by applying a typical seismic record. Both partial and full column retrofit strategies were shown to result in decreased maximum earthquake response and decreased plastic deformation of columns for the bridge bent compared to the case without retrofitting, but to varying degrees. However, for some partial retrofit strategies, the plastic hinge rotation at the unretrofitted columns was deemed to be unacceptable. Therefore, it was concluded that partial column retrofit strategies are viable only if combined with an evaluation of the ductility capacity of the bridge.

Nitrogen species in the post‐Pinatubo stratosphere: Model analysis utilizing UARS measurements

We present an analysis of the impact of heterogeneous chemistry on the partitioning of nitrogen species measured by the Upper Atmosphere Research Satellite (UARS) instruments. The UARS measurements utilized include N2O, HNO3, and ClONO2 from the cryogenic limb array etalon spectrometer (CLAES), version 7 (v.7), and temperature, methane, ozone, H2O, HCl, NO and NO2 from the halogen occultation experiment (HALOE), version 18. The analysis is carried out for the UARS data obtained between January 1992 and September 1994 in the 100‐ to 1‐mbar (∼17–47 km) altitude range and over 10° latitude bins from 70°S to 70°N. The spatiotemporal evolution of aerosol surface area density (SAD) is adopted from analysis of the Stratospheric Aerosol and Gas Experiment (SAGE) II data. A diurnal steady state photochemical box model, constrained by the temperature, ozone, H2O, CH4, aerosol SAD, and columns of O2 and O3 above the point of interest, has been used as the main tool to analyze these data. Total inorganic nitrogen (NOy) is obtained by three different methods: (1) as a sum of the UARS‐measured NO, NO2, HNO3, and ClONO2; (2) from the N2O‐NOy correlation, and (3) from the CH4‐NOy correlation. To validate our current understanding of stratospheric heterogeneous chemistry for post‐Pinatubo conditions, the model‐calculated monthly averaged NOx/NOy ratios and the NO, NO2, and HNO3 profiles are compared with the UARS‐derived data. In general, the UARS‐constrained box model captures the main features of nitrogen species partitioning in the post‐Pinatubo years, such as recovery of NOx after the eruption, their seasonal variability and vertical profiles. However, the model underestimates the NO2 content, particularly in the 30‐ to 7‐mbar (∼23–32 km) range. Comparisons of the calculated temporal behavior of the partial columns of NO2 and HNO3 and ground‐based measurements at 45°S and 45°N are also presented. Our analysis indicates that ground‐based and HALOE v. 18 measurements of the NO2 vertical columns are consistent within the range of their uncertainties and are systematically higher (up to 50%) than the model results at midlatitudes in both hemispheres. Reasonable agreement is obtained for HNO3 columns at 45°S, suggesting some problems with nitrogen species partitioning in the model. Outstanding uncertainties are discussed.

Northern and southern hemisphere ground‐based infrared spectroscopic measurements of tropospheric carbon monoxide and ethane

Time series of CO and C2H6measurements have been derived from high‐resolution infrared solar spectra recorded in Lauder, New Zealand (45.0°S, 169.7°E, altitude 0.37 km), and at the U.S. National Solar Observatory (31.9°N, 111.6°W, altitude 2.09 km) on Kitt Peak. Lauder observations were obtained between July 1993 and November 1997, while the Kitt Peak measurements were recorded between May 1977 and December 1997. Both databases were analyzed with spectroscopic parameters that included significant improvements for C2H6relative to previous studies. Target CO and C2H6lines were selected to achieve similar vertical samplings based on averaging kernels. These calculations show that partial columns from layers extending from the surface to the mean tropopause and from the mean tropopause to 100 km are nearly independent. Retrievals based on a semiempirical application of the Rodgers optimal estimation technique are reported for the lower layer, which has a broad maximum in sensitivity in the upper troposphere. The Lauder CO and C2H6partial columns exhibit highly asymmetrical seasonal cycles with minima in austral autumn and sharp peaks in austral spring. The spring maxima are the result of tropical biomass burning emissions followed by deep convective vertical transport to the upper troposphere and long‐range horizontal transport. Significant year‐to‐year variations are observed for both CO and C2H6, but the measured trends, (+0.37±0.57)% yr−1and (−0.64±0.79)% yr−1, 1 sigma, respectively, indicate no significant long‐term changes. The Kitt Peak data also exhibit CO and C2H6seasonal variations in the lower layer with trends equal to (− 0.27±0.17)% yr−1and (−1.20±0.35)% yr−1, 1 sigma, respectively. Hence a decrease in the Kitt Peak tropospheric C2H6column has been detected, though the CO trend is not significant. Both measurement sets are compared with previous observations, reported trends, and three‐dimensional model calculations.

The Pomici di Base plinian eruption of Somma-Vesuvius

The Pomici di Base eruption represents the first of a series of plinian eruptions which occurred at Somma-Vesuvius in the period 20,000 yr B.P.–79 A.D. These eruptions led to substantial demolition of the Mt. Somma stratovolcano and the formation of the 4.9×3.4 km E–W-elongated summit caldera. New 14 C datings and previous radiometric data constrain the age of the Pomici di Base eruption to between 18,000 and 19,000 yr B.P. Deposits of the Pomici di Base eruption comprise from base to top: (1) plinian fallout with minor surge deposits and (2) a succession of volcanic landslide and lithic-rich fallout, surge and flow deposits. Ballistic block distribution and thickness of tephra deposits indicate that the vent was located in a 50° wide western sector within a distance of 1–2.5 km from the present Vesuvius crater, in a fairly eccentric position with respect to the ancestral Somma cone. The plinian fallout likely blanketed an eastwards elliptical area of 2600 km 2 within the 20-cm isopach. Reconstruction of isopachs yields an approximate volume calculation of 4.4 km 3. Comparison of maximum thickness of the fallout deposit with other plinian deposits of Somma-Vesuvius suggests that the PB eruption was the largest explosive event of the volcano. The mass discharge rate deduced from clast dispersal models is estimated in the range of 2–2.5×10 7 kg/s, corresponding to a column height of 16–17 km. Part of the plinian phase was characterized by pulsatory behaviour with repeated partial column collapses (surge emplacement) and concurrent oscillation of the height of the plume (stratified fallout). The plinian phase was followed by a limited slope failure of the Somma cone and by several explosive episodes with a prominent phreatomagmatic nature. We proposed that this activity occurred in connection with a phase of substantial demolition of the Somma edifice due to caldera collapse. The plinian fallout is dominated by strong compositional zoning from white trachytic pumice (SiO 2 63.0 wt.%) to black latitic scoriae (SiO 2 53.7 wt.%), coupled with a marked decrease of vesicularity of juvenile clasts from 70–80% to 45–55%. The compositional variation reflects strong pre-eruptive zoning of the magma chamber probably associated with volatile zonation.