Publications (5)5.05 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: Arctic ice cloud formation during winter is poorly understood mainly due to lack of observations and the remoteness of this region. Their influence on Northern Hemisphere weather and climate is of paramount importance, and the modification of their properties, linked to aerosol-cloud interaction processes, needs to be better understood. Large concentration of aerosols in the Arctic during winter is associated to long-range transport of anthropogenic aerosols from the mid-latitudes to the Arctic. Observations show that sulphuric acid coats most of these aerosols. Laboratory and in-situ measurements show that at cold temperature (
- [Show abstract] [Hide abstract] ABSTRACT: Airborne lidar and in-situ measurements of the aerosol properties were conducted between Svalbard Island and Scandinavia in April 2008. Evidence of aerosol transport from Europe and Asia is given. The analysis of the aerosol optical properties based on a multiwavelength lidar (355, 532, 1064 nm) including depolarization at 355 nm aims at distinguishing the role of the different aerosol sources (Siberian wild fires, Eastern Asia and European anthropogenic emissions). Combining, first aircraft measurements, second FLEXPART simulations with a calculation of the PBL air fraction originating from the three different mid-latitude source regions, and third level-2 CALIPSO data products (i.e. backscatter coefficient, depolarisation and color ratio in aerosol layers) along the transport pathways, appears a valuable approach to identify the role of the different aerosol sources even after a transport time larger than 4 days. Above Asia, CALIPSO data indicate more depolarisation (up to 15%) and largest color ratio (>0.5) for the northeastern Asia emissions (i.e. an expected mixture of Asian pollution and dust), while low depolarisation together with smaller and quasi constant color ratio (≈0.3) are observed for the Siberian biomass burning emissions. A similar difference is visible between two layers observed by the aircraft above Scandinavia. The analysis of the time evolution of the aerosol optical properties revealed by CALIPSO between Asia and Scandinavia shows a gradual decrease of the aerosol backscatter, depolarisation ratio and color ratio which suggests the removal of the largest particles in the accumulation mode. A similar study conducted for a European plume has shown aerosol optical properties intermediate between the two Asian sources with color ratio never exceeding 0.4 and moderate depolarisation ratio being always less than 8%, i.e. less aerosol from the accumulation mode.
- [Show abstract] [Hide abstract] ABSTRACT: Short lived pollutants have been recognized as key species to understand the Arctic climate response to anthropogenic emissions. While the high latitude tropospheric ozone budget has been addressed by previous winter or spring time experiment conducted in the Arctic. Little is known on the summer period when both mid-latitude ozone production and boreal forest fire occurence are maximum. Tropospheric ozone distributions above Greenland are analyzed using airborne observations made by the French ATR-42 during the POLARCAT 2008 summer campaign. The work is based both on ozone lidar and in-situ measurements. Daily profiles are also available from a lidar operated at the aircraft base in Kangerlussuaq (67N, 50W) on the West coast of Greenland. The comparison with ozone vertical profiles measured at Summit (72N, 40W) and by the Canadian ozonesonde stations will be discussed. The data analysis is based on high resolution Lagrangian modelling, ozone/potential vorticity correlation and ozone/aerosol variability. It allows a first estimate of the relative influence of frequent stratospheric intrusions and of summer ozone formation in the North American, Asian and even European plumes.
- [Show abstract] [Hide abstract] ABSTRACT: As part of POLARCAT-FRANCE, an aircraft campaign took place in Kiruna (North Sweden) in March-April 2008. The major objective was to study the impact of transport processes on ozone and aerosol distributions and cloud microphysics in the Arctic region. An ATR-42 equipped with remote sensing instrument (3 wavelength backscatter lidar, radar) and in-situ measurements of gases (O3, CO), aerosol and cloud properties has been used in addition to satellite observation (Aqua-Train, IASI). The 12 aircraft flights occurred during a period characterized by frequent northward transport of European pollution and even the sampling of a Siberian forest fire event across the pole. We will report on 2 case studies: (i) sampling with the aircraft of European outflow with clear signature of the mid-latitude pollution (aerosol, CO), (ii) sampling of an aged forest fire plume which was transported during more than 3 days over the pole. The analysis is based on the vertical lidar meridional cross section between 68N and 72N showing layers of increased aerosol backscatter at 3 wavelengths and correlation with gas (CO) and aerosol in-situ measurements. We have used ECMWF analysis and domain filling backward trajectories using the FLEXPART model in order to characterize the position of the layer with respect to the Arctic front and the origin of the air masses. The time evolution of the polluted layers, i.e. mixing with the background troposphere and the aerosol transformation will be studied by combining the aircraft lidar data with similar measurements made either by other aircraft or by the Calipso lidar. Lagrangian connections between the ATR-42 data and the Calipso lidar have been already established for the Siberian fire forest plume observed on April 11th. The aerosol in-situ measurements will be used to assess the analysis of aerosol properties based on the 3 wavelength and polarized lidar data. This is required for the interpretation of the relative between Calipso and the airborne lidar data.
Pierre and Marie Curie University - Paris 6Lutetia Parisorum, Île-de-France, France
Université de Versailles Saint-QuentinVersailles, Île-de-France, France