Search results for "Atlantic"
showing 10 items of 307 documents
Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence
2008
[1] We present a new Lagrangian diagnostic for identifying the sources of water vapor for precipitation. Unlike previous studies, the method allows for a quantitative demarcation of evaporative moisture sources. This is achieved by taking into account the temporal sequence of evaporation into and precipitation from an air parcel during transport, as well as information on its proximity to the boundary layer. The moisture source region diagnostic was applied to trace the origin of water vapor for winter precipitation over the Greenland ice sheet for 30 selected months with pronounced positive, negative, and neutral North Atlantic Oscillation (NAO) index, using the European Centre for Medium-…
The Pre-Depression Investigation of Cloud-Systems in the Tropics (PREDICT) Field Campaign: Perspectives of Early Career Scientists
2012
The Pre-Depression Investigation of Cloud-systems in the Tropics (PREDICT) field experiment successfully gathered data from four developing and four decaying/nondeveloping tropical disturbances over the tropical North Atlantic basin between 15 August and 30 September 2010. The invaluable roles played by early career scientists (ECSs) throughout the campaign helped make possible the successful execution of the field program's mission to investigate tropical cyclone formation. ECSs provided critical meteorological information— often obtained from novel ECS-created products—during daily weather briefings that were used by the principal investigators in making mission planning decisions. Once a…
Analysis of winter dust activity off the coast of West Africa using a new 24-year over-water advanced very high resolution radiometer satellite dust …
2006
A 24-year (1982-2005) winter daytime advanced very high resolution radiometer (AVHRR) data set has been processed utilizing a new over-water dust detection algorithm. The dust data are for the oceanic regions surrounding West Africa and provide a long-term remotely sensed continuous record of dustiness in the region. These AVHRR dust observations are comparable to dust records produced via the Total Ozone Mapping Spectrometer and Meteosat instruments. Strong positive correlations between the wintertime Jones North Atlantic Oscillation index and this dust record are observed across the entire oceanic region, corroborating earlier studies on the relationship between the two. Also consistent w…
Time evolution of observed July–September sea surface temperature-Sahel climate teleconnection with removed quasi-global effect (1900–2008)
2011
[1] Using sea surface temperature (SST), precipitation, and atmospheric information, this statistical study revisits the questions of the July–September SST-Sahel teleconnection variability after removing impact of quasi-global SSTs over the period 1900–2008. The eastern Mediterranean and the Indian Ocean dominate the relationship, both in terms of intensity and time stability, with significant values in 52% and 47% of years, respectively. More than two thirds of the rainy seasons classified as dry (wet) and 16 out of 18 (12 out of 15) of those classified as very dry (very wet) are concomitant of negative (positive) differences between the Mediterranean and the Indian Ocean. Correlations wi…
Emission of iodine-containing volatiles by selected microalgae species
2014
In this study we present the results of an emission study of different phytoplankton samples in aqueous media treated with elevated ozone levels. Halocarbon measurements show that the samples tested released bromoform and different iodocarbons, including iodomethane, iodochloromethane and diiodomethane. Iodide and iodate levels in the liquid phase were representative of concentrations of surface water in a natural environment. Measurement of volatile iodine (I2) emissions from two diatom samples (Mediopyxis helysia and Porosira glacialis) and the background sample (F/2 medium from filtered natural seawater) showed that the quantity of evolved I2 depends on the ozone concentration in the air…
Influence of climate change on phenological phases in Latvia and Lithuania
2009
To investigate the impact of recent climatic changes on plant development, this study used phenological data of the volunteer networks in Latvia and Lithuania from the 1971-2000 period. The phenological calendar method was applied. Phenological seasons were described using data on 6 phenological phases at 10 stations. The growing season was described using birch Betula pendula as an example. Correlation analysis, linear regression and non-parametric Mann-Kendall trend tests were applied to establish the relationship between phenological phases and meteorological factors (temperature, precipitation) and the North Atlantic Oscillation (NAO). The results indicate a statisti- cally significant …
Summer Sahel-ENSO teleconnection and decadal time scale SST variations
2001
The correlation between Sahel rainfall and El Nino–Southern Oscillation (ENSO) in the northern summer has been varying for the last fifty years. We propose that the existence of periods of weak or strong relationship could result from an interaction with the global decadal scale sea surface temperature (SST) background. The main modes of SST variability have been extracted through a principal component analysis with Varimax rotation. The correlations between a July-September Sahel rainfall index and these SST modes have been computed on a 20-year running window between 1945 and 1993. The correlations with the interannual ENSO-SST mode are negative, not significant in the 1960s during the tr…
Seasonality and atmospheric dynamics of the teleconnection between African rainfall and tropical sea-surface temperature: Atlantic vs. ENSO
2001
A 47-year record (1951-1997) of gridded data covering Africa south of the Sahara was used to document the spatial and seasonal patterns of the correlation between precipitation and sea-surface temperatures (SST) in key tropical areas, as depicted by the NIN O3, South Atlantic and North Atlantic indices. El Nino -Southern Oscillation (ENSO) is confirmed as playing a dominant part in northeastern, eastern and southern Africa. However, its impact is also found over the Sahel during the northern summer, and other parts of the Gulf of Guinea region outside this season, a hitherto poorly documented feature. Over these two areas, ENSO and Atlantic SST (predominantly South Atlantic) contribute to d…
Trends of mean temperatures and warm extremes in northern tropical Africa (1961-2014) from observed and PPCA-reconstructed time series
2016
Trends in daily maximum (TX) and minimum (TN) temperatures and indices of warm extremes are studied in tropical North Africa, west of the eastern African highlands, from 1961 to 2014. The analysis is based on the concatenation and cross-checking of two observed databases. Due to the large number of missing entries (~25%), a statistical infilling using probabilistic principal component analysis was applied. Averaged over 90 stations, the linear trends of annual mean TX and TN equal respectively +0.021 °C/yr and +0.028 °C/yr. The frequency of very hot days (TX > 35°C) and tropical nights (TN > 20°C), as well as the frequency of daily TX and TN above the 90th percentile (p90) (“warm days” and …
Sea-surface temperature co-variability in the Southern Atlantic and Indian Oceans and its connections with the atmospheric circulation in the Souther…
2003
The relationship between sea-surface temperature (SST) inter-annual variability at the subtropical and midlatitudes of the southern Atlantic and Indian Oceans and its links with the atmospheric circulation in the Southern Hemisphere are investigated over the 1950–1999 period. Exploratory analysis using singular value decomposition and further investigations based on simple indices show that a large part of regional SST variability is common between the southwestern parts of both basins at subtropical and midlatitudes during the austral summer. Interestingly, these areas are also significantly associated with the far southwestern Pacific (Tasman Sea area). The patterns and time series of co-…