Three-dimensional model study of the Arctic ozone loss in 2002/2003 and comparison with 1999/2000 and 2003/2004

We have used the SLIMCAT 3-D off-line chemical transport model (CTM) to quantify the Arctic chemical ozone loss in the year 2002/2003 and compare it with similar calculations for the winters 1999/2000 and 2003/2004. Recent changes to the CTM have improved the model's ability to reproduce polar chemical and dynamical processes. The updated CTM uses σ-θ as a vertical coordinate which allows it to extend down to the surface. The CTM has a detailed stratospheric chemistry scheme and now includes a simple NAT-based denitrification scheme in the stratosphere. In the model runs presented here the model was forced by ECMWF ERA40 and operational analyses. The model used 24 levels extending from the surface to ~55km and a horizontal resolution of either 7.5° x 7.5° or 2.8° x 2.8°. Two different radiation schemes, MIDRAD and the CCM scheme, were used to diagnose the vertical motion in the stratosphere. Based on tracer observations from balloons and aircraft, the more sophisticated CCM scheme gives a better representation of the vertical transport in this model which includes the troposphere. The higher resolution model generally produces larger chemical O3 depletion, which agrees better with observations. The CTM results show that very early chemical ozone loss occurred in December 2002 due to extremely low temperatures and early chlorine activation in the lower stratosphere. Thus, chemical loss in this winter started earlier than in the other two winters studied here. In 2002/2003 the local polar ozone loss in the lower stratosphere was ~40% before the stratospheric final warming. Larger ozone loss occurred in the cold year 1999/2000 which had a persistently cold and stable vortex during most of the winter. For this winter the current model, at a resolution of 2.8° x 2.8°, can reproduce the observed loss of over 70% locally. In the warm and more disturbed winter 2003/2004 the chemical O3 loss was generally much smaller, except above 620K where large losses occurred due to a period of very low minimum temperatures at these altitudes

Aufnahme radioaktiver Stoffe durch Erdbeer· und Rebenblätter

Radioactive strontium in the form of an aqueous solution of 85 5rCl 2 was taken up by the leaves of strawberry plants and grapevines at different rates. Only a limited amount was transported from · the contaminated leaves into other plant organs. However, no strontium was found in the fruit. In contrast, radioactive caesium applied as an aqueous solution of 134CsCI was taken up very quickly from the leaf surface, transported from there to other plant parts and released to some extent into the soil via the roots. In our investigations, strawberry fruit showed a high caesium content. The caesium content in grape berries rose during growth and decreased again in a late phase of maturation and the nuclide was partly redistributed to other plant parts. Caesium reaching the soil may interact with day particles resulting in a very limited availability for plants. First results of investigations with grapevines in hydroculture demonstrated a close relationship between potassium supply and caesium release. The foliar up· take of radioactive strontium into plants is minor and represents therefore a negligible risk for the consumer of fruits. Radio· active caesium nuclides may however reach the human food chain through the leaves of food plants

Uptake and Transport of Radioactive Cesium and Strontium into Strawberry Plants and Grapevines After Leaf Contamination

Radioactive strontium in the form of a carrier-free aqueous solution of 85SrCl2 was taken up by the leaves of strawberry plants and grapevines at different rates. Only a limited amount was transported from the contaminated leaves into other plant organs. However, no strontium was found in the fruit. These findings show that bivalent strontium is mobile in plants only to a very minor extent. In contrast, radioactive cesium applied as an aqueous solution of carrier-free 134CsCl was taken up very quickly from the leaf surface, transported from there to other plant parts and released to some extent into the soil via the roots. In our investigations, strawberry fruit showed a high cesium content. The cesium content in grape berries rose during growth and decreased again in a late phase of maturation and the nuclide was partly redistributed to other plant parts. Cesium reaching the soil may interact with clay particles resulting in a very limited availability for plants. First results of investigations with · grapevines in hydroculture demonstrated a close relationship between potassium supply and cesium release. The foliar uptake of radioactive strontium into plants is minor and represents therefore a negligible risk for the consumer of fruits, berries and nuts. Radioactive cesium nuclides may however reach the hum.an food chain through the leaves of food plants

Development and Airborne Operation of a Compact Water Isotope Ratio Infrared Spectrometer

A sensitive laser spectrometer, named IRIS (water isotope ratio infrared spectrometer), was developed for the in situ detection of the isotopic composition of water vapour in the upper troposphere and the lower stratosphere. Isotope ratio measurements can be used to quantify troposphere stratosphere exchange, and to study the water chemistry in the stratosphere. IRIS is based on the technique of optical feedback cavity-enhanced absorption spectroscopy. It uses a room temperature near-infrared laser, and does not require cryogenic cooling of laser or detectors. The instrument weighs 51 kg including its support structure. Airborne operation was demonstrated during three flights aboard the European M55-Geophysica stratospheric research aircraft, as part of the AMMA/SCOUT-03 (African Monsoon Multidisciplinary Analysis/Stratospheric Climate links with emphasis on the Upper Troposphere and lower stratosphere) campaign in Burkina Faso in August 2006. The data are discussed with reference to a Rayleigh distillation model. As expected, there is no indication of non-mass-dependent fractionation (also known as mass-independent fractionation) in the troposphere. Furthermore, improvements to the thermal management system and a move to a (cryogen-free) longer-wavelength laser source are discussed, which together should result in approximately two orders of magnitude improvement of the sensitivit

Mixing events revealed by anomalous tracer relationships in the Arctic vortex during winter 1999/2000

During the 1999/2000 Arctic winter SAGE III–Ozone Loss and Validation Experiment (SOLVE) campaign, high‐resolution, in situ tracer data measured aboard the NASA ER‐2 high‐altitude aircraft revealed anomalous mixing events within the polar vortex. From January to March 2000 in the 350–500 K potential temperature range, we found mixing events during 15% of the flight time on average with significant maxima at potential temperatures of 450, 410, and 380 K. The events were spread throughout the vortex but showed a distinct minimum at 73° N and a peak at 85°N equivalent latitude. About 60% of the observed mixing events were less than 13 km wide. Based on a case study of tracer‐tracer relationships, an objective simple method is introduced to detect such events using the linear nitrous oxide (N2O):potential temperature relationship observed deep in the vortex. Rigorous analysis and supporting evidence from total water data corroborated the validity of the method. These results suggest mixing across the polar vortex edge occurred preferentially in layers at select altitudes in the Arctic winter 1999/2000