4D-Var Assimilation of MIPAS chemical observations: ozone and nitrogen dioxide analyses

International audienceThis paper discusses the global analyses of stratospheric ozone (O3) and nitrogen dioxide (NO2) obtained by the Belgian Assimilation System for Chemical Observations from Envisat (BASCOE). Based on a chemistry transport model (CTM) and the 4-dimensional variational (4D-Var) method, BASCOE has assimilated chemical observations of O3, NO2, HNO3, N2O, CH4 and H2O, made between July 2002 and March 2004 by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the European Space Agency (ESA) Environment Satellite (ENVISAT). This corresponds to the entire period during which MIPAS was operating at its nominal resolution. Our analyses are evaluated against assimilated MIPAS data and independent HALOE (HALogen Occultation Experiment) and POAM-III (Polar Ozone and Aerosol Measurement) satellite data. A good agreement is generally found between the analyses and these datasets, in both cases within the estimated error bars of the observations. The benefit of data assimilation is also evaluated using a BASCOE free model run. For O3, the gain from the assimilation is significant during ozone hole conditions, and in the lower stratosphere. Elsewhere, the free model run is within the MIPAS uncertainties and the assimilation does not provide significant improvement. For NO2, the gain from the assimilation is realized through most of the stratosphere. Using the BASCOE analyses, we estimate the differences between MIPAS data and independent data from HALOE and POAM-III, and find results close to those obtained by classical validation methods involving only direct measurement-to-measurement comparisons. Our results extend and reinforce previous MIPAS data validation efforts by taking account of a much larger variety of atmospheric states and measurement conditions. This study discusses possible further developments of the BASCOE data assimilation system; these concern the horizontal resolution, a better filtering of NO2 observations, and the photolysis calculation near the lid of the model. The ozone analyses are publicly available via the PROMOTE project http://www.gse-promote.org)

The performance of beams and columns continuously braced with diaphragms - I

When properly attached, shear-rigid light-gage metal diaphragms, such as roof decking or wall sheathing, can be very effective as lateral bracing for slender columns and beams. At present, limited design use is made of this fact, because of inadequate information on the effectiveness and reliability of such bracing. In this thesis, previous theory on the stability of Isection beams and columns braced with shear-rigid diaphragms has been extended. Two energy methods are used, one employing the Euler-Lagrange conditions from the calculus of variations, and the other the Rayleigh-Ritz method. The problem initially considered is that of an I-section beam-column eccentrically loaded in the plane of the web. This problem is later reduced to two extreme conditions, a column centrally loaded, and a beam sUbjected to uniform bending moment, for which explicit solutions are obtained. A method for handling the beam-column problem is indicated. For a centrally loaded elastic column with continuous shear-rigid bracing symmetrically disposed with respect to the column centroid, previous investigators have determined the augmented weak-axis buckling load as p = pyy + Q where Pyy is the weak-axis buckling load of the unbraced column, and Q is the effective shear rigidity of the bracing. In this investigation, a theoretical solution is obtained for centrally loaded columns with a single diaphragm at any location, considering possible twist of the column. A solution for the torsional-flexural buckling load for centrally loaded columns symmetrically braced by diaphragms is presented also. In addition, previous results for diaphragm-braced columns buckling into multiple half sine waves are modified, and a solution is obtained for buckling of diaphragm-braced columns with an enforced axis of rotation. For diaphragm-braced beams subjected to uniform bending moment, theoretical results are presented for both simply supported end conditions (ends fixed against rotation about the longitudinal axis only), and for ends fixed also against lateral displacement. Inelastic behavior of diaphragm-braced beams and columns is considered. Theoretical results are compared with 16 tests of concentrically loaded double-column assemblies, and 5 tests of diaphragm-braced dOUble-beam assemblies subjected to uniform bending moment. For columns in the elastic range, test results are consistently about 10 percent below predicted values, while the magnitude of the increase over the unbraced strength is several-fold. It is shown that diaphragm bracing can reliably increase the carrying capacity of slender columns up to the elastic limit load. Above the elastic limit load, the influence of diaphragm bracing is much less pronounced, and somewhat less predictable. For beams in the elastic range, test results exceed predicted values obtained neglecting the cross-bending rigidity of the diaphragms, again with a several-fold increase in carrying capacity. The yield moment of beams appears to be readily attainable using shear-rigid diaphragm bracing

E-counselling at the University of Johannesburg : a pilot programme case study

With the advent of the Internet and related Web resources and the integration thereof into our everyday life has made it impossible for social work practitioners to ignore the possibilities and challenges that would develop within practice conditions. Practitioners more and more realise that changes due to technological advancement will continue to have a substantial impact on the human services, since information is the key resource used in service delivery. This article reports on some of the results of a PhD study which aimed to design, develop and test an online counselling programme within a naturalised setting via Psychological Services and Career Development (PsyCaD) at the University of Johannesburg. A developmental case study research design, including both exploratory and applied dimensions, was employed and the pilot intervention that ensued was coined the LATS WELL-BeING counselling programme. It encompassed a four session asynchronous e-mail based service and information regarding the experiences of both clients and practitioners were recorded via direct questionnaires and online surveys. The study enabled the researcher to gather information about the application of the online counselling programme and the interaction between the e-counsellors and actual clients within a naturalised setting

The performance of beams and columns continuously-braced with diaphragms

INTRODUCTION Under the general title of Performance of Steel-Framed Buildings and Structural Members Braced with Light-Gage Steel Diaphragms , sponsored at Cornell University by the American Iron and Steel Institute, an investigation has been proceeding in two separate but closely interrelated phases, referred to as: Subproject A - Performance of Steel-Framed Buildings Braced with Light-Gage Steel Diaphragms Subproject B - Performance of Beams and Columns Continuously-Braced with Diaphragms. The investigation now referred to as Subproject B was sponsored by the American Institute of Steel Construction from June, 1961 to June, 1963 after which A.I.S.I. assumed sponsorship with the cooperation of A.I.S.C. The summary report covering the first two years\u27 investigation is The Performance of Beams and Columns Continuously-Braced with Diaphragms , Third Progress Report by Fisher and Pincus, Report No.313, Department of Structural Engineering, School of Civil Engineering, Cornell University, September 1963, hereafter referred to as the Third Progress Report. Investigations to date have covered two general areas: (a) the general characteristics of shear diaphragms, with special reference to shear rigidity, and (b) the performance of diaphragm-braced columns. While a small number of additional double-column tests remain to be performed, Subproject B is essentially at the point of completion of column studies and the initiation of tests on diaphragm-braced beams. Unexpected difficulties in staffing and materials supply have resulted in some unavoidable delays, but there is considerable reason to expect that the beam studies can be substantially completed by the end of the present contract period, May 1965. This present report, to be known as the Fourth Progress Report. covers investigations for the period approximately October 1, 1963 to August 15, 1964. During this reporting period, work has progressed in three related areas: (1) improvement of understanding of diaphragm behavior, (2) inelastic behavior of diaphragm-braced columns, and (3) plans for tests on diaphragm-braced beams. Each of these will be discussed in detail in the following sections of the report. Effective shear modulus of corrugated diaphragms, as determined under Subproject B by means of double-beam assemblies (see Third Progress Report), has been correlated experimentally and, with partial success, theoretically with the shear modulus as determined under Subproject A by means of rectangular frame tests. Practically identical experimental results are obtained by both kinds of tests for small size diaphragms. In addition, the results for the large diaphragms of Subproject A have been correlated also with the small diaphragm results to a substantial degree. Cooperation between the two subprojects, therefore, has provided considerably more generality and certainty of diaphragm behavior than heretofore available. An empirical expression for the shear modulus of standard (and similar) corrugated sheets has been developed. To this end, four additional double-beam shear tests have been performed. Two additional double-column tests have been performed and a better empirical expression for prediction of failure loads of diaphragm-braced columns in the inelastic range has been developed. Planning for the projected diaphragm-braced beam phase of the program is well under way, including studies of suitable beam sections, range of beam slenderness, and details of the test setup