Assessing water availability under pastoral livestock systems in drought-prone Isiolo District, Kenya

Water availability / Water demand / Surface water / Groundwater / Wells / Salinity / Livestock / Grazing / Land use / Water supply / Drainage / GIS / Databases / Cost recovery

UV Aerosol Indices from SCIAMACHY: introducing the SCattering Index (SCI)

The Absorbing Aerosol Index (AAI) is a useful tool for detecting aerosols that absorb UV radiation – especially in cases where other aerosol retrievals fail, such as over bright surfaces (e.g. desert) and in the presence of clouds. The AAI does not, however, consider contributions from scattering (hardly absorbing) aerosols and clouds: they cause negative AAI values and are usually disregarded. In this paper, we demonstrate the use of the AAI's negative counterpart, the SCattering Index (SCI) to detect scattering aerosols. Consideration of the full UV Aerosol Index scale is of importance if the Aerosol Index is to be used for the quantification of aerosol absorption in the future. <br><br> Maps of seasonally averaged SCI show significantly enhanced values in summer in Southeast USA and Southeast Asia, pointing to a high production of scattering aerosols (presumably mainly sulphate aerosols and secondary organic aerosols) in this season. The application of a cloud filter makes the presence of scattering aerosols even more clear. Radiative transfer calculations were performed to investigate the sensitivity of AAI and SCI to cloud parameters, and it is demonstrated that clouds cause significant SCI, in some special cases even small AAI values. The results from cloud modelling imply that cloud effects need to be taken into account when AAI and SCI are used in a quantitative manner. <br><br> The paper concludes with a comparison of aerosol parameters from AERONET and our Aerosol Indices (AAI and SCI) from SCIAMACHY, where reasonable agreement was found for six AERONET stations in Southeast USA, Southeast Asia, and Africa. These findings corroborate the suitability of SCI as a tool to detect scattering aerosols

Intensifying agricultural sustainability: an analysis of impacts and drivers in the development of ‘bright spots’

Food security / Farming systems / Sustainable agriculture / Productivity / Investment / Thailand / Palestine / Latin America / Africa

Integrated land and water management for food and environmental security

Water resource management / Food security / Environmental effects / Soil degradation / Water pollution / Watersheds / Urbanization / Public policy / Water quality / Ecosystems / Land resources / Water scarcity / Developing countries / Poverty / Households / Food supply / Economic aspects / Social aspects / Groundwater depletion / Salinity / Wetlands / Investment / Land use / Water use / Training needs assessment / Research priorities

Shared Perceptions of Supervisor Support: What Processes Make Supervisors and Employees See Eye to Eye?

This paper aims to find out what processes contribute to horizontal (between employees) and vertical (between employees and their supervisor) shared perceptions of supervisor support by public frontline supervisors. Informed by a multilevel qualitative study among supervisors and teachers in public secondary schools, we develop theoretical propositions regarding these processes. We propose that employees’ expectations based on experiences with previous supervisors can decrease horizontal shared perceptions. Subsequently, a contingent or consistent approach to supporting employees contribute to the development of horizontal and vertical shared perceptions, depending on the legitimacy attributed by employees to the reason behind this approach. Over time, supervisor support experienced by employees at meaningful work-life events contributes to the emergence of horizontal and vertical shared perceptions. This research shows that instead of merely looking for correlates of shared perceptions, scrutinizing the processes that contribute to horizontal and vertical shared perceptions increases our understanding of this complex phenomenon

Clip Correction in Wireless LAN receivers

Abstract-OFDM signals suffer from a large Peak to Average Power Ratio, which requires large power back-offs in the transmit and receive chains. This paper presents a digital postprocessing method that mitigates clipping by the analog-to-digital converter (ADC) in the receiver. Clipped peaks cause spurious signals on empty subcarriers, which can be used to eliminate clipping artifacts and to recover the original signal. Simulations show that a significant reduction of 3 dB in the headroom of the A/D converter (ADC) is possible, when an elaborate MMSE clip correction algorithm is used. A simple algorithm still allows for 1 dB reduction of the headroom. As the ADC is consuming an ever increasing fraction of the total receiver power, the results are believed to be relevant for low-power design of OFDM receivers, for instance to prolong battery life of laptops and other portable WLAN devices

Theoretical production ecology: reflections and prospects.

This book gives an impression of the field of Theoretical Production Ecology, its development and its position as an interdisciplinary subject. Revised versions of the papers presented at the symposium Theoretical Production Ecology: hindsight and perspectives, organized on the occasion of the retirement of Professor C.T. de Wit from Wageningen Agricultural University, are presented. Professor de Wit's valedictory address is included. The papers have been arranged according to the four scientific themes covered by the Department of Theoretical Production Ecology: soil and climate; plant growth and development; pests, diseases and weeds; agricultural production systems. During his scientific career of more than 40 years, Professor de Wit made substantial innovative contributions in each of these four areas. Together the papers give an overview of the major developments during de Wit's inspiring involvement in production ecology and indicate the directions in which it may proceed in the years to come

Political innovation as ideal and strategy: the case of aleatoric democracy in the City of Utrecht

Political innovations aim to strengthen democracy but few connect well to the institutionalized democratic context. This paper explores how political innovations can be successfully embedded in existing democratic systems. It builds upon both the literature on political innovation and on new democratic arrangements and studies a practice of aleatoric democracy – using the lottery instead of elections to select representatives – in the Dutch City of Utrecht. The case study shows how the idealist logic of improving democracy and the realist logic of realizing specific political goals intertwine to get the political innovation accepted by the institutionalized democratic system

Global Monitoring of Atmospheric Trace Gases, Clouds and Aerosols from UV/vis/NIR Satellite Instruments: Currents Status and Near Future Perspectives

A new generation of UV/vis/near‐IR satellite instruments like GOME (since 1995), SCIAMACHY (since 2002), OMI (since 2004), and GOME‐2 (since 2006) allows to measure several important stratospheric and tropospheric trace gases like O_3, NO_2, OClO, HCHO, SO_2, BrO, and H_2O as well as clouds and aerosols from space. Because of its extended spectral range, the SCIAMACHY instrument also allows the retrieval of Greenhouse gases (CO_2, CH_4) and CO in the near IR. Almost all of the tropospheric trace gases are observed by these instruments for the first time. From satellite data it is possible to investigate the temporal and spatial variation. Also different sources can be characterised and quantified. The derived global distributions can serve as input and for the validation of atmospheric models. Here we give an overview on the current status of these new instruments and data products and their recent applications to various atmospheric and oceanic phenomena