Search Results
You are looking at 1 - 3 of 3 items for
- Author or Editor: C. S. Zerefos x
- Refine by Access: All Content x
Abstract
The signal of the Southern Oscillation in the lower half of the Northern Hemisphere stratosphere in winter appears to be as follows: In the extreme of the Southern Oscillation when the trade winds are comparatively weak in the South Pacific Ocean, stratospheric geopotential heights and temperatures tend to be higher over the Arctic and lower in middle latitudes than in the opposite extreme. At the same time, the polar-night stratospheric jetstream tends to be weaker and the subtropical westerlies to be stronger. The conclusions are based on 11 extremes within a 15-year period and on data at standard pressure levels as high as 10 mb.
Abstract
The signal of the Southern Oscillation in the lower half of the Northern Hemisphere stratosphere in winter appears to be as follows: In the extreme of the Southern Oscillation when the trade winds are comparatively weak in the South Pacific Ocean, stratospheric geopotential heights and temperatures tend to be higher over the Arctic and lower in middle latitudes than in the opposite extreme. At the same time, the polar-night stratospheric jetstream tends to be weaker and the subtropical westerlies to be stronger. The conclusions are based on 11 extremes within a 15-year period and on data at standard pressure levels as high as 10 mb.
Abstract
The average areal density of pollutant emissions in Athens is estimated to be two to six times greater than in the Los Angeles basin. Concentration levels of the primary air pollutants, CO and SO2, are several times larger in Athens than in Los Angeles. Concentrations of the photochemical pollutants, NO2 and O3, however, are greater at Los Angeles stations inland 20 or more kilometers from the coast. The relatively lower levels of photochemical pollution in Athens are partially explained by differences in the summer atmospheric-circulation systems and the scale of the basins. Also, the concentration of NO in central Athens is so great as to inhibit the formation of O3.
Abstract
The average areal density of pollutant emissions in Athens is estimated to be two to six times greater than in the Los Angeles basin. Concentration levels of the primary air pollutants, CO and SO2, are several times larger in Athens than in Los Angeles. Concentrations of the photochemical pollutants, NO2 and O3, however, are greater at Los Angeles stations inland 20 or more kilometers from the coast. The relatively lower levels of photochemical pollution in Athens are partially explained by differences in the summer atmospheric-circulation systems and the scale of the basins. Also, the concentration of NO in central Athens is so great as to inhibit the formation of O3.
Abstract
Satellite retrievals of surface evaporation and precipitation from the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS-3) dataset are used to document the distribution of evaporation, precipitation, and freshwater flux over the Mediterranean and Black Seas. An analysis is provided of the major scales of temporal and spatial variability of the freshwater budget and the atmospheric processes responsible for the water flux changes. The satellite evaporation fluxes are compared with fields from three different reanalysis datasets [40-yr ECMWF Re-Analysis (ERA-40), ERA-Interim, and NCEP].
The results show a water deficit in the Mediterranean region that averages to about 2.4 mm day−1 but with a significant east–west asymmetry ranging from 3.5 mm day−1 in the eastern part to about 1.1 mm day−1 in the western part of the basin. The zonal asymmetry in the water deficit is driven by evaporation differences that are in turn determined by variability in the air–sea humidity difference in the different parts of the Mediterranean basin. The Black Sea freshwater deficit is 0.5 mm day−1, with maxima off the northern coast (0.9 mm day−1) that are attributed to both evaporation maxima and precipitation minima there.
The trend analysis of the freshwater budget shows that the freshwater deficit increases in the 1988–2005 period. The prominent increase in the eastern part of the basin is present in the satellite and all three reanalysis datasets. The water deficit is due to increases in evaporation driven by increasing sea surface temperature, while precipitation does not show any consistent trends in the period. Similarly, in the Black Sea, trends in the freshwater deficit are mainly due to evaporation, although year-to-year variability is due to precipitation patterns.
Abstract
Satellite retrievals of surface evaporation and precipitation from the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS-3) dataset are used to document the distribution of evaporation, precipitation, and freshwater flux over the Mediterranean and Black Seas. An analysis is provided of the major scales of temporal and spatial variability of the freshwater budget and the atmospheric processes responsible for the water flux changes. The satellite evaporation fluxes are compared with fields from three different reanalysis datasets [40-yr ECMWF Re-Analysis (ERA-40), ERA-Interim, and NCEP].
The results show a water deficit in the Mediterranean region that averages to about 2.4 mm day−1 but with a significant east–west asymmetry ranging from 3.5 mm day−1 in the eastern part to about 1.1 mm day−1 in the western part of the basin. The zonal asymmetry in the water deficit is driven by evaporation differences that are in turn determined by variability in the air–sea humidity difference in the different parts of the Mediterranean basin. The Black Sea freshwater deficit is 0.5 mm day−1, with maxima off the northern coast (0.9 mm day−1) that are attributed to both evaporation maxima and precipitation minima there.
The trend analysis of the freshwater budget shows that the freshwater deficit increases in the 1988–2005 period. The prominent increase in the eastern part of the basin is present in the satellite and all three reanalysis datasets. The water deficit is due to increases in evaporation driven by increasing sea surface temperature, while precipitation does not show any consistent trends in the period. Similarly, in the Black Sea, trends in the freshwater deficit are mainly due to evaporation, although year-to-year variability is due to precipitation patterns.
