Search results for "Climate variability"

Social process of adaptation to environmental changes: How eastern african societies intervene between crops and climate

2014

Abstract Studies on climate change can only be conducted on a long time scale, and observing how societies adapt their sowing practices to climate variability is challenging and costly. As an alternative, a space and time substitution design was used, changes in space corresponding to that induced in time by environmental change. On the eastern slope of Mount Kenya, the Tharaka community, originating from the lowlands (750 m), moved up to the midlands (950 m) with their lowland-adapted resources, whereas the Mwimbi, originating from wetter upland (1100 m), moved down to the midlands with their highland-adapted genetic resources. A weather station was installed at 950 and 1100 m, and a logis…

Climate variability and agriculture in Italy: a stochastic frontier analysis at the regional level

2020

In the next future, climate change effects will represent a challenge for Europe and the Mediterranean area. These will have to cope with a rapid increase in climate variability. Although many economic sectors may be affected, agriculture is the most susceptible as climate heavily affects crop production trends, yield variability and the availability of areas suitable for cultivation. Using the stochastic frontier approach, the aim of this work is to analyse the impacts of climate variability on Italian regional technical efficiency in the agricultural sector for a period spanning from 2000 to 2009. Considering that technical inefficiency could be influenced by two main annual meteorologica…

Recent climate variability around the Kerguelen Islands (Southern Ocean) seen through weather regimes

2021

AbstractDaily weather regimes are defined around the Kerguelen Islands (Southern Ocean) based on daily 500 hPa geopotential height anomalies derived from the ERA5 ensemble reanalysis over the period 1979-2018. Ten regimes are retained as significant. Their occurrences are highly consistent across reanalysis ensemble members. Regimes show weak seasonality and non-significant long-term trends in their occurrences. Their sequences are usually short (1-3 days), with extreme persistence values above 10 days. Seasonal regime frequency is mostly driven by the phase of the Southern Annular Mode over Antarctica, mid-latitude dynamics over the Southern Ocean like the Pacific South American mode, and …

How physical parameterizations can modulate internal variability in a regional climate model

2012

Abstract The authors analyze to what extent the internal variability simulated by a regional climate model is sensitive to its physical parameterizations. The influence of two convection schemes is quantified over southern Africa, where convective rainfall predominates. Internal variability is much larger with the Kain–Fritsch scheme than for the Grell–Dévényi scheme at the seasonal, intraseasonal, and daily time scales, and from the regional to the local (grid point) spatial scales. Phenomenological analyses reveal that the core (periphery) of the rain-bearing systems tends to be highly (weakly) reproducible, showing that it is their morphological features that induce the largest internal …

Irrigation water intensity and climate variability: an agricultural crops analysis of Italian regions

2020

This paper examines the relationship between the requirement of water resources for irrigation and climate variability and analyses the ranking of the best and worst performance of irrigation water intensity for each Italian region. To measure water resources demanded by agriculture, the irrigation water intensity (IWI) indicator has been computed as the ratio between volumes of irrigation water and total crop harvested. By applying panel data methodologies to a regional dataset spanning from 2000 to 2009, we may address heterogeneity and omitted variable issues. By merging meteo-climatic with agricultural variables, we may confirm that water precipitations, maximum temperature, irrigation …

Influence of the Madden-Julian Oscillation on Southern African summer rainfall

2007

Rain-causing mechanisms over Southern Africa (south of 15˚S) involve both tropical and temperate dynamics. Most studies focused on the synoptical timescale, while the intraseasonal (20-120 days) variability has more been neglected to date. This study aims at determining whether the dominant mode of intraseasonal variability in the Tropics, namely the Madden-Julian Oscillation (MJO), has a significant impact on Southern African rainfall and associated atmospheric dynamics. The examination of outgoing longwave radiation (OLR) over Southern Africa shows indeed significant intraseasonal fluctuations at the 30-60 day timescale, i.e. in the pe- riods that are typically reminiscent of the MJO. In ord…

Holocene climate variability of the Western Mediterranean: Surface water dynamics inferred from calcareous plankton assemblages

2020

A high-resolution study (centennial scale) has been performed on the calcareous plankton assemblage of the Holocene portion of the Ocean Drilling Program Site 976 (Alboran Sea) with the aim to identify the main changes in the surface water dynamic. The dataset also provided a seasonal foraminiferal sea surface water temperatures (SSTs), estimated using the modern analog technique SIMMAX 28, and it was compared with available geochemical and pollen data at the site. Three main climate shifts were identified as (1) the increase in abundance of Syracosphaera spp. and Turborotalita quinqueloba marks the early Holocene humid phase, during maximum summer insolation and enhanced river runoff. It i…

Paleoclimatic and Paleoceanographic reconstruction of the Pleistocene-Holocene through the study of planktonic foraminifera of two sedimentary cores …

2017

Orbital variations in planktonic foraminifera assemblages from the Ionian Sea during the Middle Pleistocene Transition

2013

Abstract The Middle Pleistocene Transition (1.2–0.7 Ma) is the most recent re-organization of the global climate system which includes variations in the frequency and amplitude of glacial/interglacial cycles, increased ice sheet volume, sea surface temperature cooling and a significant drop in the CO 2 atmospheric levels. Here we present high-resolution planktonic foraminifera data (mean sampling resolution of about 780 years) from core LC10 recovered in the Ionian Sea (eastern Mediterranean), between 1.2 and 0.9 Ma. Selected taxa, among them G. ruber , T. quinqueloba and G. bulloides , show significant periodicities that can be associated to orbital cycles, mainly precession and obliquity.…

From synoptic to interdecadal variability in southern African rainfall: toward a unified view across time scales.

2018

International audience; During the austral summer season (November–February), southern African rainfall, south of 20°S, has been shown to vary over a range of time scales, from synoptic variability (3–7 days, mostly tropical temperate troughs) to interannual variability (2–8 years, reflecting the regional effects of El Niño–Southern Oscillation). There is also evidence for variability at quasi-decadal (8–13 years) and interdecadal (15–28 years) time scales, linked to the interdecadal Pacific oscillation and the Pacific decadal oscillation, respectively. This study aims to provide an overview of these ranges of variability and their influence on regional climate and large-scale atmospheric c…