On the Epochal Strengthening in the Relationship between Rainfall of East Africa and IOD

Abstract Variability of the equatorial East Africa "short rains" (EASR) has intensified significantly since the turn of the twentieth century. This increase toward more extreme rainfall events has not been gradual but is strongly characterized by epochs. The rain gauge–based Global Precipitation Climatology Centre (GPCC) monthly precipitation dataset for the period 1901–2009 is used to demonstrate that the epochal changes were dictated by shifts in the Indian Ocean dipole (IOD) mode. These shifts occurred during 1961 and 1997. In the pre-1961 period, there was virtually no significant linear link between the IOD and the EASR. But a relatively strong coupling between the two occurred abruptly in 1961 and was generally maintained at that level until 1997, when another sudden shift to even a greater level occurred. The first principal component (PC1) extracted from the EASR spatial domain initially merely explained about 50% of the rainfall variability before 1961, and then catapulted to about 73% for the period from 1961 to 1997, before eventually shifting to exceed 82% after 1997. The PC1 for each successive epoch also displayed loadings with notably improved spatial coherence. This systematic pattern of increase was accompanied by both a sharp increase in the frequency of rainfall extremes and spatial coherence of the rainfall events over the region. Therefore, it is most likely that the 1961 and 1997 IOD shifts are responsible for the epochal modulation of the EASR in both the spatial and temporal domain

Spring Ozone's Connection to South Africa's Temperature and Rainfall

The Brewer–Dobson circulation (BDC), whose dynamic activity is enhanced from winter to spring, transports stratospheric ozone from the tropical source regions to higher latitudes. But it is the BDC's shallow branch which transfers lower stratospheric ozone (LSO) from the tropics to the subtropics. Hence the accumulation of ozone in the subtropics is at its maximum at the end of spring (October) in the Southern Hemisphere (SH). Here we use observation and observation constrained reanalysis data to investigate the extent to which the interannual variability of this end of spring accumulated LSO is able to impact on the maximum surface air temperature (SATmax) and precipitation of South Africa. This is achieved through contrasting years of high positive and negative October ozone anomalies for the extreme BDC activity, referred to as weak (wBDC) and strong (sBDC) respectively. It is found that the w(s)BDC event composites coincide with significant negative (positive) SATmax anomalies and positive (negative) rainfall over South Africa. We suggest that the wBDC's related LSO surpluses trap the UVB meant to heat the troposphere and surface. This induces the observed negative middle to upper tropospheric air temperatures and geopotential heights resulting in cyclonic circulation anomalies that enhances rainfall and suppresses SATmax. The opposite is true for the sBDC composites where ultimately the elevated geopotential heights result in middle to upper anticyclonic tropospheric anomalies that are accompanied by rainfall deficits and increased SATmax

An Inductive Classification Scheme for Green IT Initiatives

“Green IT” can be loosely described as a set of organizational initiatives undertaken to reduce the environmental impact of Information Technology. Although many trade publications are full of examples of Green IT initiatives, there is a lack of coherence around what constitutes a “Green IT” initiative, which practices could be considered Green IT, and even what the goals and motivations for a Green IT initiative should be. In this paper, we describe a centering resonance text analysis on documentation of the Green IT initiatives undertaken by seven large technology-intensive firms. The findings from the analysis are used to propose a new classification scheme for Green IT initiatives and help bring further clarify to the concepts, goals, and motivations underlying Green IT initiatives

Relative Impacts of ENSO and Indian Ocean Dipole/Zonal Mode on Southern African Rainfall

This thesis investigates the October to December (OND) rainfall variability over the mainland region of southeastern Africa in relation to El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole/Zonal Mode (IODZM) for the period 1950 to 1999. An empirical orthogonal function (EOF) analysis of OND rainfall field revealed that the north-south aligned areas of the eastern SADC are located in different covariability regions. This meridionally aligned dipole rainfall anomaly configuration is captured only in the dominant principal component (PC1) making it possible for the opposing rainfall anomalies of the two regions to have a common trigger. However, ENSO which has typically been invoked as the main cause for significant rainfall variability over this region cannot adequately explain this dipole rainfall anomaly pattern. The results of statistical analyses strongly indicate that positive Indian Ocean Dipole/Zonal Mode (IODZM) phase events lead to a rainfall dipole such that floods occur over the north east of the region (Tanzania) at the same time as droughts over the south east of the region (Zimbabwe, northern South Africa). On the other hand, negative IODZM phase events do not seem to lead to the reverse rainfall anomalies suggesting that the positive and negative rainfall dipoles may have rather different causes. Thus, contrary to conventional knowledge, the ENSO association to this dipole rainfall anomaly pattern is not robust but appears to be the result of the well known ENSO-IODZM connection. However, when analysed over 31-year overlapping segments, the results indicate that the sensitivity of this rainfall pattern to the IODZM is weakening from the 1990s onwards whereas that of ENSO appears to be strengthening

数十年周期変動と東アフリカ・南アフリカ気候への影響

学位の種別:論文博士University of Tokyo(東京大学

Elementary Statistics (GHC)

This Grants Collection for Elementary Statistics was created under a Round Eleven ALG Textbook Transformation Grant. Affordable Learning Georgia Grants Collections are intended to provide faculty with the frameworks to quickly implement or revise the same materials as a Textbook Transformation Grants team, along with the aims and lessons learned from project teams during the implementation process. Documents are in .pdf format, with a separate .docx (Word) version available for download. Each collection contains the following materials: Linked Syllabus Initial Proposal Final Reporthttps://oer.galileo.usg.edu/mathematics-collections/1039/thumbnail.jp

Climate and southern Africa's water-energy-food nexus

In southern Africa, the connections between climate and the water-energy-food nexus are strong. Physical and socioeconomic exposure to climate is high in many areas and in crucial economic sectors. Spatial interdependence is also high, driven for example, by the regional extent of many climate anomalies and river basins and aquifers that span national boundaries. There is now strong evidence of the effects of individual climate anomalies, but associations between national rainfall and Gross Domestic Product and crop production remain relatively weak. The majority of climate models project decreases in annual precipitation for southern Africa, typically by as much as 20% by the 2080s. Impact models suggest these changes would propagate into reduced water availability and crop yields. Recognition of spatial and sectoral interdependencies should inform policies, institutions and investments for enhancing water, energy and food security. Three key political and economic instruments could be strengthened for this purpose; the Southern African Development Community, the Southern African Power Pool, and trade of agricultural products amounting to significant transfers of embedded water

Modeling the climate impact of Southern Hemisphere ozone depletion:the importance of the ozone dataset

The ozone hole is an important driver of recent Southern Hemisphere (SH) climate change, and capturing these changes is a goal of climate modeling. Most climate models are driven by off-line ozone data sets. Previous studies have shown that there is a substantial range in estimates of SH ozone depletion, but the implications of this range have not been examined systematically. We use a climate model to evaluate the difference between using the ozone forcing (Stratospheric Processes and their Role in Climate (SPARC)) used by many Intergovernmental Panel on Climate Change Fifth Assessment Report (Coupled Model Intercomparison Project) models and one at the upper end of the observed depletion estimates (Binary Database of Profiles (BDBP)). In the stratosphere, we find that austral spring/summer polar cap cooling, geopotential height decreases, and zonal wind increases in the BDBP simulations are all doubled compared to the SPARC simulations, while tropospheric responses are 20–100% larger. These results are important for studies attempting to diagnose the climate fingerprints of ozone depletion

Solar ultraviolet radiation and ozone depletion-driven climate change: Effects on terrestrial ecosystems

In this assessment we summarise advances in our knowledge of how UV-B radiation (280-315 nm), together with other climate change factors, influence terrestrial organisms and ecosystems. We identify key uncertainties and knowledge gaps that limit our ability to fully evaluate the interactive effects of ozone depletion and climate change on these systems. We also evaluate the biological consequences of the way in which stratospheric ozone depletion has contributed to climate change in the Southern Hemisphere. Since the last assessment, several new findings or insights have emerged or been strengthened. These include: (1) the increasing recognition that UV-B radiation has specific regulatory roles in plant growth and development that in turn can have beneficial consequences for plant productivity via effects on plant hardiness, enhanced plant resistance to herbivores and pathogens, and improved quality of agricultural products with subsequent implications for food security; (2) UV-B radiation together with UV-A (315-400 nm) and visible (400-700 nm) radiation are significant drivers of decomposition of plant litter in globally important arid and semi-arid ecosystems, such as grasslands and deserts. This occurs through the process of photodegradation, which has implications for nutrient cycling and carbon storage, although considerable uncertainty exists in quantifying its regional and global biogeochemical significance; (3) UV radiation can contribute to climate change via its stimulation of volatile organic compounds from plants, plant litter and soils, although the magnitude, rates and spatial patterns of these emissions remain highly uncertain at present. UV-induced release of carbon from plant litter and soils may also contribute to global warming; and (4) depletion of ozone in the Southern Hemisphere modifies climate directly via effects on seasonal weather patterns (precipitation and wind) and these in turn have been linked to changes in the growth of plants across the Southern Hemisphere. Such research has broadened our understanding of the linkages that exist between the effects of ozone depletion, UV-B radiation and climate change on terrestrial ecosystems