51 research outputs found
Changes in aerosol properties during spring-summer period in the Arctic troposphere
The change in aerosol properties during the transition from the more polluted spring to the clean summer in the Arctic troposphere was studied. A six-year data set of observations from Ny-Ă
lesund on Svalbard, covering the months April through June, serve as the basis for the characterisation of this time period. In addition four-day-back trajectories were used to describe air mass histories. The observed transition in aerosol properties from an accumulation-mode dominated distribution to an Aitken-mode dominated distribution is discussed with respect to long-range transport and influences from natural and anthropogenic sources of aerosols and pertinent trace gases. Our study shows that the air-mass transport is an important factor modulating the physical and chemical properties observed. However, the air-mass transport cannot alone explain the annually repeated systematic and rather rapid change in aerosol properties, occurring within a limited time window of approximately 10 days. With a simplified phenomenological model, which delivers the nucleation potential for new-particle formation, we suggest that the rapid shift in aerosol microphysical properties between the Arctic spring and summer is mainly driven by the incoming solar radiation in concert with transport of precursor gases and changes in condensational sink
Moisture transport and Antarctic sea ice: austral spring 2016 event
In austral spring 2016 the Antarctic region experienced anomalous sea ice
retreat in all sectors, with sea ice extent in October and November 2016
being the lowest in the Southern Hemisphere over the observational period
(1979âpresent). The extreme sea ice retreat was accompanied by widespread
warming along the coastal areas as well as in the interior of the Antarctic
continent. This exceptional event occurred along with a strong negative phase
of the Southern Annular Mode (SAM) and the moistest and warmest spring on
record, over large areas covering the Indian Ocean, the Ross Sea and the
Weddell Sea. In October 2016, the positive anomalies of the totally
integrated water vapor (IWV) and 2âm air temperature (T2m) over the Indian
Ocean, western Pacific, Bellingshausen Sea and southern part of Ross Sea were
unprecedented in the last 39 years. In October and November 2016, when the
largest magnitude of negative daily sea ice concentration anomalies was
observed, repeated episodes of poleward advection of warm and moist air took
place. These results suggest the importance of moist and warm air intrusions
into the Antarctic region as one of the main contributors to this exceptional
sea ice retreat event.</p
Arctic smoke - aerosol characteristics during a record smoke event in the European Arctic and its radiative impact
In early May 2006 a record high air pollution event was observed at Ny-Ă
lesund, Spitsbergen. An atypical weather pattern established a pathway for the rapid transport of biomass burning aerosols from agricultural fires in Eastern Europe to the Arctic. Atmospheric stability was such that the smoke was constrained to low levels, within 2 km of the surface during the transport. A description of this smoke event in terms of transport and main aerosol characteristics can be found in Stohl et al. (2007). This study puts emphasis on the radiative effect of the smoke. The aerosol number size distribution was characterised by lognormal parameters as having an accumulation mode centered around 165â185 nm and almost 1.6 for geometric standard deviation of the mode. Nucleation and small Aitken mode particles were almost completely suppressed within the smoke plume measured at Ny-Ă
lesund. Chemical and microphysical aerosol information obtained at Mt. Zeppelin (474 m a.s.l) was used to derive input parameters for a one-dimensional radiation transfer model to explore the radiative effects of the smoke. The daily mean heating rate calculated on 2 May 2006 for the average size distribution and measured chemical composition reached 0.55 K dayâ1 at 0.5 km altitude for the assumed external mixture of the aerosols but showing much higher heating rates for an internal mixture (1.7 K dayâ1). In comparison a case study for March 2000 showed that the local climatic effects due to Arctic haze, using a regional climate model, HIRHAM, amounts to a maximum of 0.3 K dayâ1 of heating at 2 km altitude (Treffeisen et al., 2005)
September Arctic sea ice minimum prediction â a skillful new statistical approach
Sea ice in both polar regions is an important indicator of the
expression of global climate change and its polar amplification.
Consequently, broad interest exists on sea ice coverage, variability and
long-term change. However, its predictability is complex and it depends
strongly on different atmospheric and oceanic parameters. In order to
provide insights into the potential development of a monthly/seasonal signal
of sea ice evolution, we applied a robust statistical model based on
different oceanic and atmospheric parameters to calculate an estimate of the
September sea ice extent (SSIE) on a monthly timescale. Although previous
statistical attempts of monthly/seasonal SSIE forecasts show a relatively
reduced skill, when the trend is removed, we show here that the September
sea ice extent has a high predictive skill, up to 4Â months ahead, based on
previous months' oceanic and atmospheric conditions. Our statistical model
skillfully captures the interannual variability of the SSIE and could
provide a valuable tool for identifying relevant regions and oceanic and
atmospheric parameters that are important for the sea ice development in the
Arctic and for detecting sensitive/critical regions in global coupled
climate models with a focus on sea ice formation.</p
Arctic smoke ? record high air pollution levels in the European Arctic due to agricultural fires in Eastern Europe
International audienceIn spring 2006, the European Arctic was abnormally warm, setting new historical temperature records. During this warm period, smoke from agricultural fires in Eastern Europe intruded into the European Arctic and caused the most severe air pollution episodes ever recorded there. This paper confirms that biomass burning (BB) was indeed the source of the observed air pollution, studies the transport of the smoke into the Arctic, and presents an overview of the observations taken during the episode. Fire detections from the MODIS instruments aboard the Aqua and Terra satellites were used to estimate the BB emissions. The FLEXPART particle dispersion model was used to show that the smoke was transported to Spitsbergen and Iceland, which was confirmed by MODIS retrievals of the aerosol optical depth (AOD) and AIRS retrievals of carbon monoxide (CO) total columns. Concentrations of halocarbons, carbon dioxide and CO, as well as levoglucosan and potassium, measured at Zeppelin mountain near Ny Ă
lesund, were used to further corroborate the BB source of the smoke at Spitsbergen. The ozone (O3) and CO concentrations were the highest ever observed at the Zeppelin station, and gaseous elemental mercury was also enhanced. A new O3 record was also set at a station on Iceland. The smoke was strongly absorbing ? black carbon concentrations were the highest ever recorded at Zeppelin ?, and strongly perturbed the radiation transmission in the atmosphere: aerosol optical depths were the highest ever measured at Ny Ă
lesund. We furthermore discuss the aerosol chemical composition, obtained from filter samples, as well as the aerosol size distribution during the smoke event. Photographs show that the snow at a glacier on Spitsbergen became discolored during the episode and, thus, the snow albedo was reduced. Samples of this polluted snow contained strongly enhanced levels of potassium, sulphate, nitrate and ammonium ions, thus relating the discoloration to the deposition of the smoke aerosols. This paper shows that, to date, BB has been underestimated as a source of aerosol and air pollution for the Arctic, relative to emissions from fossil fuel combustion. Given its significant impact on air quality over large spatial scales and on radiative processes, the practice of agricultural waste burning should be banned in the future
Deriving evaluation indicators for knowledge transfer and dialogue processes in the context of climate research
Knowledge transfer and dialogue processes in the field of climate
science have captured intensive attention in recent years as being an
important part of research activities. Therefore, the demand and pressure to
develop a set of indicators for the evaluation of different activities in
this field have increased, too. Research institutes are being asked more and more to build up structures in order to map these activities and, thus, are
obliged to demonstrate the success of these efforts. This paper aims to
serve as an input to stimulate further reflection on the field of evaluation
of knowledge transfer and dialogue processes in the context of climate sciences.
The work performed in this paper is embedded in the efforts of the German
Helmholtz Association in the research field of earth and environment and is
driven by the need to apply suitable indicators for knowledge transfer and
dialogue processes in climate research center evaluations. We carry out a
comparative analysis of three long-term activities and derive a set of
indicators for measuring their output and outcome by balancing the wide
diversity and range of activity contents as well as the different tools to
realize them. The case examples are based on activities which are part of
the regional Helmholtz Climate Initiative Regional Climate Change (REKLIM) and the Climate Office for Polar Regions and Sea Level Rise at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research. Both
institutional units have been working on a wide range of different knowledge
transfer and dialogue processes since 2008/2009. We demonstrate that
indicators for the evaluation must be based on the unique objectives of the
individual activities and the framework they are embedded in (e.g., research
foci which provide the background for the performed knowledge transfer and
dialogue processes) but can partly be classified in a principle
two-dimensional scheme. This scheme might serve as a usable basis for
climate research center evaluation in the future. It, furthermore,
underlines the need for further development of proper mechanisms to evaluate
scientific centers, in particular with regard to knowledge transfer and
dialogue processes
Arctic smoke ? aerosol characteristics during a record air pollution event in the European Arctic and its radiative impact
International audienceIn early May 2006 a record high air pollution event was observed at Ny-Ă
lesund, Spitsbergen. An atypical weather pattern established a pathway for the rapid transport of biomass burning aerosols from agricultural fires in Eastern Europe to the Arctic. Atmospheric stability was such that the smoke was constrained to low levels, within 2 km of the surface during the transport. A description of this smoke event in terms of transport and main aerosol characteristics can be found in Stohl et al. (2007). This study puts emphasis on the radiative effect of the smoke. The aerosol size distribution was characterized as having an accumulation mode centered at 165?185 nm and almost 1.6 for geometric standard deviation of the mode. Nucleation and small Aitken mode particles were almost completely suppressed within the smoke plume measured at Ny-Ă
lesund. Chemical and microphysical aerosol information obtained at Mt. Zeppelin (474 m.a.s.l) was used to derive input parameters for a one-dimensional radiation transfer model to explore the radiative effects of the smoke. The daily mean heating rate calculated on 2 May 2006 for the average size distribution and measured chemical composition reached 0.55 K day?1 at 0.5 km altitude for the assumed external mixture of the aerosols but showing much higher heating rates for an internal mixture (1.7 K day?1). In comparison a case study for March 2000 showed that the local climatic effects due to Arctic haze, using a regional climate model, HIRHAM, amounts to a maximum of 0.3 K day?1 of heating at 2 km altitude (Treffeisen et al., 2005)
Springtime Arctic aerosol: Smoke versus Haze, a case study for March 2008
During March 2008 photometer observations of Arctic aerosol were performed both at a Russian ice-floe drifting station (NP-35) at the central Arctic ocean (56.7e42.0 E, 85.5e84.2 N) and at Ny-Ă
lesund, Spitsbergen (78.9 N, 11.9 E). Next to a persistent increase of AOD over NP-35, two pronounced aerosol events have been recorded there, one originating from early season forest fires close to the city of Khabarovsk (âArctic Smokeâ), the other one showed trajectories from central Russia and resembled more the classical Arctic Haze. The latter event has also been recorded two days later over Ny-Ă
lesund, both in photometer and lidar. From these remote sensing instruments volume distribution functions are derived and discussed. Only subtle differences between the smoke and the haze event have been found in terms of particle microphysics. Different trajectory analysis, driven by NCEP and ECMWF have been performed and compared. For the data set presented here the meteorological field, due to sparseness of data in the central Arctic, mainly limits the precision of the air trajectories
Social and Environmental Risk Factors for Atopy in a Low-Income Urban Immigrant Pediatric Population
- âŠ