Search results for "DRY"
showing 10 items of 980 documents
Extreme dry spells over the Mediterranean Basin during the wet season: assessment of HyMeX/Med-CORDEX regional climate simulations (1979-2009).
2018
16 pages; International audience; Exceptional dry spells, in this study referred to as very long dry spells (VLDS), are natural hazards to which the Mediterranean region is extremely vulnerable, with socio‐economic and environmental impacts. In this study, they are characterized in terms of location, spatial extent, duration, temporal variability and associated atmospheric circulations. The main objective is to assess the performance of five HyMeX/Med‐CORDEX regional climate simulations to detect and reproduce VLDS in comparison with the E‐OBS observed daily gridded data. Models accurately reproduce the occurrence of precipitation around the Mediterranean Basin, and therefore the occurrence…
Spatial coherence of monsoon onset over Western and Central Sahel (1950-2000)
2009
Abstract The spatial coherence of boreal monsoon onset over the western and central Sahel (Senegal, Mali, Burkina Faso) is studied through the analysis of daily rainfall data for 103 stations from 1950 to 2000. Onset date is defined using a local agronomic definition, that is, the first wet day (>1 mm) of 1 or 2 consecutive days receiving at least 20 mm without a 7-day dry spell receiving less than 5 mm in the following 20 days. Changing either the length or the amplitude of the initial wet spell, or both, or the length of the following dry spell modifies the long-term mean of local-scale onset date but has only a weak impact either on its interannual variability or its spatial coher…
Prediction of Dry-Season Precipitation in Tropical West Africa and Its Relation to Forcing from the Extratropics
2009
Abstract Precipitation during the boreal winter dry season in tropical West Africa is rare but occasionally results in significant impacts on the local population. The dynamics and predictability of this phenomenon have been studied very little. Here, a statistical evaluation of the climatology, dynamics, and predictions of dry-season wet events is presented for the region 7.5°–15°N, 10°W–10°E. The analysis is based upon Global Precipitation Climatology Project (GPCP) merged satellite–gauge pentad rainfall estimates and 5-day 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) precipitation forecasts, and covers the 23 dry seasons (November–February) during…
Seasonal evolution of boundary layer heat content in the West African monsoon from the NCEP/NCAR reanalysis (1968-1998)
2000
Using the National Center for Environmental Prediction (NCEP)/National Centre for Atmospheric Research (NCAR) dataset over the period 1968–1998, the basic relationships between July and September monsoon circulation variations over West Africa and monthly meridional distribution of moist static energy (MSE) content in the boundary layer are portrayed. Wet minus dry stratified analyses relative to Sudan–Sahel rainfall show that particular April–June meridional patterns of near-surface MSE contents, south of 10°N, could control the amplitude and timing of the monsoon rainy season. Relative to the driest July–September situations, the wettest ones have been, on average, preceded by delayed but…
Impact of very low crop residues cover on wind erosion in the Sahel
2011
International audience; In the Sahel, with average annual precipitation in the order of 500 mm yr− 1, wind erosion occurs mainly on cultivated millet fields whose surfaces are only partially covered by crop residues. The impact of these residues on wind erosion was not clearly established. The objective of this study is thus to quantify the actual amount of crop residues in traditional Sahelian fields and to determine their impacts on wind erosion by reference to a bare surface throughout the seasonal cycle over several years. At the beginning of the year during dry season, Sahelian farmers use to "clean" their fields, i.e. cut and lay flat on the soil surface any millet stalks still standi…
Analysis of climatic data and forecast indices for human fascioliasis at very high altitude
1999
Human infection with Fasciola hepatica has recently been recognized as an important health problem worldwide, and particularly at very high altitudes in South America. The highest prevalences and intensities of human fascioliasis known are those of the northern Bolivian Altiplano, where infected Lymnaea truncatula occur at altitudes of 3800-4100 m. In the present study, the climatic data for this area of the Altiplano, which differ markedly from those of endemic areas in the lowlands, were analysed. There is no marked seasonality in temperature but there are large variations in temperature within a daily, 24-h period. Rainfall is seasonal, with a long dry season, coinciding with the lowest …
Seasonal changes of the infiltration rates in a Mediterranean scrubland on limestone
1997
To investigate the seasonal changes of infiltration rates, measurements by means of simulated rainfall experiments and cylinder infiltrometer were done in a small E–W oriented watershed in Southeast Spain. Data were collected during both the wet seasons (autumn, winter and spring) and the dry season (summer). Infiltration rates were very high in summer, when direct surface runoff is very low. During the wet seasons, the infiltration rates were lower due to the increase in soil moisture. Measurements by means of both ponding as well as simulated rainfall are suitable to study the infiltration process. The former needs more replications, due to the small observation area encompassed for each …
Monitoring of Cueva Larga, Puerto Rico—A First Step to Decode Speleothem Climate Records
2017
This study presents results of an ongoing cave monitoring program at Cueva Larga, Puerto Rico. The monitoring includes monthly analyses of stable isotope ratios of rain and drip water, and trace element ratios of drip water and cave air parameters. Drip sites are above growing speleothems offering the unique chance to calibrate geochemical variations in speleothems in order to reconstruct past climate conditions. Seasonal rainfall patterns above Cueva Larga show characteristic stable isotope values. The wet season is characterized by more negative δ18O and δD values and a maritime deuterium excess (+10‰). The dry season has more positive δ18O and δD values and elevated deuterium excess (>15…
Water Temperature Increasing Caused Mastigias Papua Disappeared in Marine Lake Lenmakana Misool Raja Ampat Regency, West Papua
2020
Mastigias papua is a jellyfish that is trademark of marine lakes. Ongeim’l Tketau Lake in Palau, Hang Du I Lake in Vietnam, Kakaban Lake in Kalimantan, and Lenmakana Lake in Raja Ampat Papua are exotic tourist destinations because of presence of these biota in the lake. Water temperature is very influential on the life of a jellyfish because of its mutual symbiosis with brown algae zooxanthellae. Mastigias has totally disappeared in several places due to water temperature increasing, including Lenmakana Lake in the West Monsoon 2017/2018 and 2018/2019. The absence of Mastigias in this lake will be explained by recorded logger data installed in the lake and at sea. Secondary data from NOAA a…
Extreme dry spell detection and climatology over the Mediterranean Basin during the wet season
2016
The E-OBS precipitation gridded data set v.10.0 is used to detect very long dry spell (VLDS) events over the entire Mediterranean Basin for the 1957–2013 period, during the wet season (September to April). The main objective is to characterize these events as climatic objects, in terms of location, spatial extent, duration, and temporal variability. In this study, 76 VLDS events were detected in the Mediterranean Basin and grouped into four spatial patterns: scattered localized (with 25 events), northeast Mediterranean (11 events), West Mediterranean (15 events), and southeast Mediterranean (25 events). Each pattern shows seasonality in events. Most of the scattered localized, northeast, an…