ARRIVAL DATES OF MIGRATING BIRDS IN CENTRAL EUROPE AND CLIMATE VARIABILITY

Recently the study of plant and animal phenological observations has contributed much to understand the sensitivity of biosphere to the variability of its atmospheric environment. This study is based on time series of 3 bird phenological phases (‘first barn swallow’, ‘first cuckoo call’ and ‘all swallows have left’) from the archive of the Central Institute for Meteorology and Geodynamics in Vienna, which have been collected at 65 Austrian stations from 1951 – 1999. In contrast to many European countries the arrival times of barn swallow and the cuckoo have predominantly been moving to later dates in Austria. A preliminary analysis points towards dryer conditions in the sub - saharan winter quarters as possible cause for a later departure from the African winter quarters to Europe. About a third of the year to year variability of both spring bird phases can be explained by temperature and wind conditions on the migration route and local temperature

EVALUATION OF THE OPERATIONAL OZONE FORECAST MODEL OF THE ZAMG WITH MEASUREMENTS OF THE AUSTRIAN AIR QUALITY NETWORK

Operational model forecasts of ozone concentrations are compared to the observations of about 150 air quality stations in Austria. Evaluations of the last three summers revealed that exceedances of the information threshold could be predicted quite well by the model. Investigation of a heat period in summer 2006 indicates possible sources of precursors. The Lagrangian particle model LASAT (www.janicke.de) is used additionally to the chemical model CAMx (www.camx.com) to show the dispersion of the plumes of stacks with high emissions of NOx in the vicinity of Vienna. For two months in summer 2007 sensitivity studies with different input parameters were performed. Model runs with different parameterisations for the vertical diffusion coefficient (Kv) are conducted and experiments with different values of the minimum values of Kv in the lower levels show the influence of this parameter on the nocturnal ozone decrease for different sites. Different model runs with variable boundary conditions at the top of the modelling domain as well as variable total ozone column data are performed

Trends of ozone and meteorological parameters

at the alpine GAW-site

An optimal method for validating satellite-derived land surface phenology using in-situ observations from national phenology networks

Satellite-based land surface phenology (LSP) products play an important role in understanding atmosphere-vegetation carbon and energy exchanges. These products have been widely calculated from various satellite observations from local to global scales. However, the quality and accuracy of LSP products are often poorly quantified due to spatial mismatch between satellite observed pixels and in-situ observations. In the present study, we demonstrate an optimal algorithm leveraging the scalability, consistency, and representativeness of rich in-situ observations from national phenology networks to validate LSP products. Specifically, we demonstrate two approaches for validating the phenological timing of greenup onset in the operational Visible Infrared Imaging Radiometer Suite (VIIRS) LSP product developed at NASA using in-situ observations collected from the Pan European Phenological database (PEP725, 9664 site-years) and the USA National Phenology Network (USA-NPN, 3144 site-years) spanning 2013–2020. The first approach assumes that in-situ data contain observations of phenological transitions (e.g., leaf-out) that are directly comparable with satellite detections. Accordingly, in-situ data were aggregated using four upscaling methods (mean, median, 30th percentile, and minimum bias) to directly compare with VIIRS LSP. The second approach assumes that species-specific phenological timing in in-situ data is basically impossible to spatially reconcile VIIRS LSP, but phenological events in a local area are driven by the same or very similar weather conditions. Therefore, interannual variations and long-term trends were applied to compare VIIRS LSP with in-situ data. The result shows first that the 30th percentile method is more promising in aggregating in-situ observations than the commonly used mean method. Second, direct comparison indicates that VIIRS greenup onset has a mean absolute difference of 13.9 ± 9.8 days with PEP725 in-situ observations and 12.3 ± 10.9 days with USA-NPN observations in well-selected deciduous forest sites. Third, the interannual comparison reveals that VIIRS greenup onset exhibits the same directions of multi-year anomalies and long-term trends as those of both PEP725 and USA-NPN observations in over 70% of sample sites. These findings improve our understanding of the scale mismatch and sample representativeness of species-specific phenology and the uncertainties of long-term LSP detections from remote sensing data.National Aeronautics and Space Administration24 month embargo; available online: 17 October 2022This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]