ABSORPTION CROSS-SECTIONS OF OZONE IN THE 590-NM TO 610-NM REGION AT T = 230-K AND T = 299-K

Measurements of the ozone absorption cross section in the 590- to 610-nm region of the Chappuis bands have been carried out at the temperatures T = 230 K and T = 299 K. Ozone is produced with an electrical discharge and stored cryogenically. Differential absorption measurements are obtained in a slowly evolving mixture of ozone and molecular oxygen. Previous results by other authors indicate a certain disagreement on the temperature dependence of the absorption cross section. Our data at each wavelength show no significant dependence of the absorption coefficient on the temperature, within experimental errors. The statistical consistency of the results is discussed

Variability of mineral dust deposition in the western Mediterranean basin and south-east of France

International audiencePrevious studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than 1 year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie in French) have been deployed in the western Mediterranean region during 1 to 3 years depending on the station. The sites include, from south to north, Lampedusa, Majorca, Corsica, Frioul and Le Casset (southern French Alps). Deposition measurements are performed on a common weekly period at the five sites. The mean dust deposition fluxes are higher close to the northern African coasts and decrease following a south-north gradient, with values from 7.4 g m −2 year −1 in Lampe-dusa (35 • 31 N, 12 • 37 E) to 1 g m −2 year −1 in Le Casset (44 • 59 N, 6 • 28 E). The maximum deposition flux recorded is of 3.2 g m −2 wk −1 in Majorca with only two other events showing more than 1 g m −2 wk −1 in Lampedusa, and a maximum of 0.5 g m −2 wk −1 in Corsica. The maximum value of 2.1 g m −2 year −1 observed in Corsica in 2013 is much lower than existing records in the area over the 3 previous decades (11-14 g m −2 year −1). From the 537 available samples, 98 major Saharan dust deposition events have been identified in the records between 2011 and 2013. Complementary observations provided by both satellite and air mass trajectories are used to identify the dust provenance areas and the transport pathways from the Sahara to the stations for the studied period. Despite the large size of African dust plumes detected Published by Copernicus Publications on behalf of the European Geosciences Union. 8750 J. Vincent et al.: Variability of mineral dust deposition by satellites, more than 80 % of the major dust deposition events are recorded at only one station, suggesting that the dust provenance, transport and deposition processes (i.e. wet vs. dry) of dust are different and specific for the different de-position sites in the Mediterranean studied area. The results tend to indicate that wet deposition is the main form of de-position for mineral dust in the western Mediterranean basin, but the contribution of dry deposition (in the sense that no precipitation was detected at the surface) is far from being negligible, and contributes 10 to 46 % to the major dust de-position events, depending on the sampling site

Aerosol and tropospheric ozone direct radiative impacts

This chapter describes the direct radiative effect (RE) over the Mediterranean region exerted by aerosols and tropospheric ozone. Recent results on the regional direct aerosol RE at the surface and at the top-of-the-atmosphere (TOA) are presented, together with trends in surface solar radiation. Absorption by aerosol particles within the troposphere affects heating rates and atmospheric stability, therefore playing a key role in the regional radiative impact of aerosols. In addition, the impact of aerosols on photochemistry and solar energy production over the Mediterranean region is also discussed with a focus on recent advances on the impact of the aerosol dimming on photovoltaic (PV) panels. Finally, the last section describes the regional RE of tropospheric ozone and drivers of its uncertainty

ABSOLUTE DETERMINATION OF THE CROSS-SECTIONS OF OZONE IN THE WAVELENGTH REGION 339-355 NM AT TEMPERATURES 220-293-K

Absolute measurements of the ozone absorption coefficient in the Huggins bands at different temperatures have been carried out. Ozone is produced by an electrical discharge and stored cryogenically; differential absorption measurements are subsequently obtained in a slowly evolving mixture of ozone and molecular oxygen. High resolution (to 0.012 nm) measurements cover a spectral range (339–355 nm) where the ozone absorption shows a strong dependance on temperature. Results at 293 and 220 K are reported; they are particularly interesting in view of the utilization of this spectral region as a low-absorption reference channel for the observation of atmospheric ozone profiles by active probing techniques. Coherent radiation at two wavelengths, around 355 and 353 nm, respectively, can be obtained as third harmonic of the fundamental output of a Nd:YAG laser and by H2 Raman shifting of a XeCl excimer laser output

Aerosol and tropospheric ozone direct radiative impacts

This chapter describes the direct radiative effect (RE) over the Mediterranean region exerted by aerosols and tropospheric ozone. Recent results on the regional direct aerosol RE at the surface and at the top-of-the-atmosphere (TOA) are presented, together with trends in surface solar radiation. Absorption by aerosol particles within the troposphere affects heating rates and atmospheric stability, therefore playing a key role in the regional radiative impact of aerosols. In addition, the impact of aerosols on photochemistry and solar energy production over the Mediterranean region is also discussed with a focus on recent advances on the impact of the aerosol dimming on photovoltaic (PV) panels. Finally, the last section describes the regional RE of tropospheric ozone and drivers of its uncertainty

Aerosol and tropospheric ozone direct radiative impacts

This chapter describes the direct radiative effect (RE) over the Mediterranean region exerted by aerosols and tropospheric ozone. Recent results on the regional direct aerosol RE at the surface and at the top-of-the-atmosphere (TOA) are presented, together with trends in surface solar radiation. Absorption by aerosol particles within the troposphere affects heating rates and atmospheric stability, therefore playing a key role in the regional radiative impact of aerosols. In addition, the impact of aerosols on photochemistry and solar energy production over the Mediterranean region is also discussed with a focus on recent advances on the impact of the aerosol dimming on photovoltaic (PV) panels. Finally, the last section describes the regional RE of tropospheric ozone and drivers of its uncertainty

Aerosol and tropospheric ozone direct radiative impacts

This chapter describes the direct radiative effect (RE) over the Mediterranean region exerted by aerosols and tropospheric ozone. Recent results on the regional direct aerosol RE at the surface and at the top-of-the-atmosphere (TOA) are presented, together with trends in surface solar radiation. Absorption by aerosol particles within the troposphere affects heating rates and atmospheric stability, therefore playing a key role in the regional radiative impact of aerosols. In addition, the impact of aerosols on photochemistry and solar energy production over the Mediterranean region is also discussed with a focus on recent advances on the impact of the aerosol dimming on photovoltaic (PV) panels. Finally, the last section describes the regional RE of tropospheric ozone and drivers of its uncertainty