Aerosol radiative forcing over a tropical urban site in India

Using collocated measurements of aerosol radiative properties and radiative fluxes, aerosol radiative forcing is estimated at a tropical urban site in India, located between the sub-continent and the Indian Ocean Experiment [INDOEX] sites. Observed sun/sky radiance data are used to derive aerosol spectral optical depth, single scattering albedo [SSA], asymmetry parameter, precipitable water and total column ozone. These serve as inputs to a radiative transfer model, to estimate aerosol forcing at the surface, the top-of-the atmosphere [TOA] and the atmosphere. During the dry season of 2001 and 2002 [November–April], these were found to be −33, 0 and 33 Wm−2, respectively. Using measured radiative fluxes during different aerosol loading conditions yield a surface forcing of −31 Wm−2. The surface forcing efficiency as computed from the two independent methods is found to be −88 and −84 Wm−2, respectively, while mean SSA at 500 nm is found to be 0.8

Remote sensing of aerosol optical characteristics in sub-Sahel, West Africa

We have determined the characteristics of sub-Sahelian aerosols from a 2-year record of continuous ground-based measurements, made at the University of Ilorin, Ilorin (08°19′N, 04°20′E), Nigeria, in cooperation with the Aerosol Robotic Network. Observations of spectral aerosol optical depths during the dusty harmattan season indicate more than a twofold increase, when compared to other seasons. Retrieved columnar volume size distributions show the existence of bimodality with a dominant coarse mode. The retrieved size distributions were grouped according to different ranges of aerosol optical depths to characterize the aerosols for this particular region. Monthly means of retrieved single-scattering albedos show a sharp decrease from ∼0.95 to ∼0.85 at 500 nm from the preharmattan to the harmattan season when biomass burning is also practiced, increasing the presence of absorbing aerosols. On the basis of these comprehensive observations, we propose to augment existing desert aerosol models, as presented in the literature, to better characterize the dust outbreak season in West Africa, which is quite prolonged and overlaps with the biomass burning seaso

The development of the passé composé in lower-intermediate learners of French as a second language

In this study we tracked the development of the passe compose in second-language learners of French whose first language is English. Although the passe compose is a highly used tense among native speakers of French and it appears to present particular difficulty for first-language English speakers, its second-language development has been surprisingly under-researched. In order to trace developmental patterns of the passe compose we obtained a corpus of obligatory context use of this tense by 30 Year-12 (lower-intermediate) students at two time points six months apart and analysed the data both quantitatively and qualitatively. Our findings suggest that these students used remarkably few memorized formulas, that they passed through five distinct stages in their acquisition of the passe compose, that those early stages were characterized by transfer errors, and that the presence of the auxiliary, whether correct or incorrect, formed a crucial stage in the development of the tense. Theoretical explanations for the findings are presented together with some tentative pedagogical implications

Classifying the Arithmetical Complexity of Teaching Models

This paper classifies the complexity of various teaching models by their position in the arithmetical hierarchy. In particular, we determine the arithmetical complexity of the index sets of the following classes: (1) the class of uniformly r.e. families with finite teaching dimension, and (2) the class of uniformly r.e. families with finite positive recursive teaching dimension witnessed by a uniformly r.e. teaching sequence. We also derive the arithmetical complexity of several other decision problems in teaching, such as the problem of deciding, given an effective coding $\{\mathcal L_0,\mathcal L_1,\mathcal L_2,\ldots\}$ of all uniformly r.e. families, any $e$ such that $\mathcal L_e = \{L^e_0,L^e_1,\ldots,\}$, any $i$ and $d$, whether or not the teaching dimension of $L^e_i$ with respect to $\mathcal L_e$ is upper bounded by $d$.Comment: 15 pages in International Conference on Algorithmic Learning Theory, 201

How organizational cognitive neuroscience can deepen understanding of managerial decision-making:a review of the recent literature and future directions

There is growing interest in exploring the potential links between human biology and management and organization studies, which is bringing greater attention to bear on the place of mental processes in explaining human behaviour and effectiveness. The authors define this new field as organizational cognitive neuroscience (OCN), which is in the exploratory phase of its emergence and diffusion. It is clear that there are methodological debates and issues associated with OCN research, and the aim of this paper is to illuminate these concerns, and provide a roadmap for rigorous and relevant future work in the area. To this end, the current reach of OCN is investigated by the systematic review methodology, revealing three clusters of activity, covering the fields of economics, marketing and organizational behaviour. Among these clusters, organizational behaviour seems to be an outlier, owing to its far greater variety of empirical work, which the authors argue is largely a result of the plurality of research methods that have taken root within this field. Nevertheless, all three clusters contribute to a greater understanding of the biological mechanisms that mediate choice and decision-making. The paper concludes that OCN research has already provided important insights regarding the boundaries surrounding human freedom to act in various domains and, in turn, self-determination to influence the workplace. However, there is much to be done, and emerging research of significant interest is highlighted

The impact of sound field systems on learning and attention in elementary school classrooms

Purpose: An evaluation of the installation and use of sound field systems (SFS) was carried out to investigate their impact on teaching and learning in elementary school classrooms. Methods: The evaluation included acoustic surveys of classrooms, questionnaire surveys of students and teachers and experimental testing of students with and without the use of SFS. Students ’ perceptions of classroom environments and objective data evaluating change in performance on cognitive and academic assessments with amplification over a six month period are reported. Results: Teachers were positive about the use of SFS in improving children’s listening and attention to verbal instructions. Over time students in amplified classrooms did not differ from those in nonamplified classrooms in their reports of listening conditions, nor did their performance differ in measures of numeracy, reading or spelling. Use of SFS in the classrooms resulted in significantly larger gains in performance in the number of correct items on the nonverbal measure of speed of processing and the measure of listening comprehension. Analysis controlling for classroom acoustics indicated that students ’ listening comprehension score

Satellite Estimates of Surface Radiative Fluxes for the Extended San Pedro Basin: Sensitivity to Aerosols

Abstract Surface downwelling and upwelling radiative fluxes are important inputs into hydrologic models that evaluate water budgets, and into land surface data assimilation schemes which are driven with radiative fluxes. For large-scale needs, only remote sensing methods can provide such information. The accuracy of the derived fluxes depends on the inference schemes and on the quality of auxiliary input parameters. At present, information on surface short-wave radiative fluxes over the United States is produced in real time by the National Oceanic and Atmospheric Administration (NOAA)/National Environmental Satellite Data and Information Service (NESDIS) at 0.5 degree resolution, at hourly time intervals, using independently derived auxiliary inputs. Information on aerosol properties and their temporal variability is not available, and at best, is only estimated. During 1997 information on aerosol optical properties was collected at the USDA-Agricultural Research Service Walnut Gulch Experimental Watershed, Arizona, in preparation for future validation efforts in support of new satellite observations (e. g., ADEOS-II). This data set was used to test the sensitivity of a radiation inference scheme to aerosols, in particular, on the determination of clear sky fluxes and the surface albedo. Data from the Arizona Meteorological Network (AZMET) have been utilized to evaluate the satellite estimates for 1997. It was found that the current satellite estimates are within 70 Wm -2 of the ground observations on an hourly time scale and within 24 Wm -2 on a daily time scale. In the latter case this is less than 10% of the mean. Use of actual observations of aerosols, as compared to climatological values, reduces the bias substantially, while less significant changes in the rms were found. Keywords: radiative fluxes, aerosols, remote sensing 2 1. Background Site and history The Semi-Arid Land-Surface-Atmosphere (SALSA) Program seeks to evaluate the consequences of natural and human-induced changes in semi-arid environments (this issue; also see the SALSA home-page at http://www.tucson.ars.ag.gov/salsa/salsahome.html). Information on remote sensing activities in this region is presented in Surface downwelling and upwelling radiative fluxes play an important role as inputs into hydrologic models aimed at evaluating water budgets. Therefore, it is important to determine how well such fluxes can be derived from satellite observations. First estimates of short-wave (SW) surface radiative fluxes (global irradiance) by satellite methods for this region were attempted during the Monsoon '90 experiment Linkage to related activities The Upper San Pedro Basin has been established as the North American semi-arid site for assessing the impacts of climatic variation and for calibrating and validating algorithms and process-based models to be implemented with NASA EOS observations. For example, the basin was selected by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument team as a semi-arid validation site as well as a NASA Global Land Cover Test Site. It was also selected as the primary focus site for the EOS interdisciplinary science hydrology team at the University of Arizona and Centre d'Etudes Spatiales de la Biosphere (CESBIO), France. Two Sonora research groups have been involved in research in the USPB: Instituto del Medio Ambiente y Desarrollo Sustentable del Estado de Sonora (IMADES), and Instituto Tecnológico de Sonora (ITSON). Numerous proposals have been funded for research as well as for remotely sensed data acquisition in the basin, which range from ERS-2, SPOT4, ADEOS-II, and for a mesoscale meteorological modeling initiative. Modeling activity focuses on exploring the potential of coupling parameters derived by methods of remote sensing to mesoscale atmospheric models, to aid in diagnosing the spatial distribution of surface fluxes over the entire San Pedro Basin at a 4 x 4 kilometer grid spacing (Toth, 1997). 4 Radiative fluxes used in this study Remotely sensed data The estimated surface SW radiative fluxes (global irradiance) used in this study are produced by NOAA/NESDIS, using the University of Maryland methodology The full archive maintained at the University of Maryland contains additional parameters, that as yet, are not distributed. Specifically, the following types of information are archived: • satellite based information, used to drive the model; • auxiliary data used to drive the model; • Eta model output products relevant for hydrologic modeling; and, • independently derived satellite products. It is planned to expand the number of parameters currently distributed via the World Wide Web to include,e. g., cloud amounts). Validation data Radiative fluxes A comprehensive evaluation of the model was done using data for the entire year of 1996 from several sources (Pinker et al., 2000). Data available from the Surface Radiation Monitoring Network (SURFRAD) (Hicks et al., 1996), the Illinois State Water Survey (Hollinger et al., 1994) and the Arizona Meteorological Network (AZMET) (Brown, 1989) were used. In this study, only AZMET stations, as illustrated in Aerosol observations at Walnut Gulch In December of 1996 a CIMEL sunphotometer was installed at the USDA-ARS Walnut Gulch Experimental Watershed to provide information on aerosol optical depths and other aerosol optical parameters Aerosol sensitivity experiments Issues Satellite inference schemes that use physical models require information on radiances as observed by the satellite sensor in relevant spectral channels, as well as information on the state of the atmosphere and the surface. Such information has been available for some of the needed parameters from numerical weather prediction models (e. g., on water vapor) or from independently derived satellite quantities (e. g., ozone). Typically the least amount of information in known about aerosols. Therefore, most inference schemes use some type of aerosol climatology. We have followed a two-step approach in the process of inferring surface SW radiative fluxes. Initially, we use an average value of clear sky radiance as derived from about two weeks of clear sky observations. We assume a climatological value of aerosol optical depth 6 Subsequently, we use each clear sky pixel from the beginning of the retrieval time interval (one month segments at a time) and the initially derived surface albedo to subsequently derive an aerosol optical thickness from each clear sky pixel. The corresponding flux at the surface will be selected from a look-up table as the one that is appropriate for all the derived values of input parameters, as well as the inferred aerosol optical depth. This approach was used to produce the surface fluxes presented in Aerosol experiments We have performed an experiment to evaluate the sensitivity of surface SW radiative flux parameters to aerosol information. An off-line version of the GCIP/SRB model was run for the entire year of 1997. All the satellite input parameters, as well as the atmospheric and surface parameters were the same as used by NOAA/NESDIS in the real time runs for 1997 and as archived at the University of Maryland. The only difference was that the climatological aerosol optical depth values used to initialize the retrieval process were replaced by the monthly mean observed values, as presented in Results Surface fluxes In A comparison of hourly mean estimated global irradiance with ground truth as obtained from the control run, is presented in Figures 6 for all sky (a) and clear sky (b) cases independently. In for clear sky). Surface albedo The GCIP/SRB model produces surface downwelling and upwelling SW radiative fluxes (global and reflected radiation), and their ratio is termed "albedo". At instantaneous time scales, the albedo represents the value at the time of the observation. In order to derive a daily value, the downwelling and upwelling fluxes are averaged and their ratio is taken. Since the surface fluxes are computed independently for clear and cloudy pixels, it is possible to produce "clear sky" albedos and all-sky albedos. Preliminary evaluations show that these two values are quite close to each other. In Discussion Radiative fluxes at the earth's surface determine the surface energy budget, and therefore, the rate of evapotranspiration (Dickinson, 1986; Avissar and Verstraete, 1990; Henderson-Sellers, 1993; Sellers et al., 1996; In addition to better aerosol information, there is a need for improved calibration of satellite sensors. It is believed that some degradation of satellite instruments might have occurred. Preliminary estimates of such degradation are as high as 15%. Experiments were performed to evaluate the possible impact of such degradation on the derived surface fluxes Summary Regions classified as semi-arid or arid constitute about one-third of the total global land cover. Often these regions are subjected to soil erosion, wind-storms, and variable aerosol loading. Aerosols are important in altering the radiation that reaches the surface and therefore, they are a source of error in the interpretation of satellite signals. This is particularly true in the visible region of the spectrum. Routine and continuous information on atmospheric aerosol content is lacking. However, such data are becoming available on regional scales under observational initiatives like the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) (Russel et al., 1999), AERONET (Holben et al., 1998), SKYNET (Takamura, 1996); and will become available on global scale under new satellite observational programs like MODIS (King et al., 1999), ADEOS and ADEOS-II (http://www.eorc.nasda.go.jp/index.html); and under integrating initiatives like the Global Aerosol Climatology Project (GACP) (Curran et al., 1998; Curran, 1999). Many landscapes in the southwest United States and northern Mexico are being altered from activities such as groundwater mining and overgrazing. Lack of information on aerosols can therefore introduce errors in our ability to estimate from space how much the surface has changed. In the framework of the SALSA Program objectives for long-term monitoring of human-induced change on the hydrological and ecological resources of semi-arid regions, we have conducted an experiment to assess the current uncertainties in aerosol optical depths on such parameters as surface short-wave fluxes and surface albedos. This is important because these parameters influence the modeling of hydrological processes that control the exchange of heat, water vapor and CO2. It was found that using observed aerosol climatology improved radiative flux retrieval from satellite observations and subsequent computation of flux estimates. In addition, it was found that using measured values to initialize the aerosol optical depth in the retrieval of surface global irradiance, the surface albedo increased by about 0.02 on the average. Comparison of satellite estimates of radiative flux were made with data from the Arizona Meteorological Network (AZMET) for 1997 to evaluate the procedures described. It was found that the current satellite estimates are within 70 Wm -2 of the ground observations on an hourly time scale and within 24 Wm -2 on a daily time scale. In the latter case this is less than 10% of the mean. 10 Use of actual observations of aerosols, as compared to climatological values, reduces the bias substantially, while less significant changes in the rms were found. In summary, this study demonstrated that on a local scale, characterizations of aerosols, based even on a limited observational periods is preferred to estimates based on large-scale climatologies

Using Synchronic and Diachronic Relations for Summarizing Multiple Documents Describing Evolving Events

In this paper we present a fresh look at the problem of summarizing evolving events from multiple sources. After a discussion concerning the nature of evolving events we introduce a distinction between linearly and non-linearly evolving events. We present then a general methodology for the automatic creation of summaries from evolving events. At its heart lie the notions of Synchronic and Diachronic cross-document Relations (SDRs), whose aim is the identification of similarities and differences between sources, from a synchronical and diachronical perspective. SDRs do not connect documents or textual elements found therein, but structures one might call messages. Applying this methodology will yield a set of messages and relations, SDRs, connecting them, that is a graph which we call grid. We will show how such a grid can be considered as the starting point of a Natural Language Generation System. The methodology is evaluated in two case-studies, one for linearly evolving events (descriptions of football matches) and another one for non-linearly evolving events (terrorist incidents involving hostages). In both cases we evaluate the results produced by our computational systems.Comment: 45 pages, 6 figures. To appear in the Journal of Intelligent Information System