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Russak V.,Tartu Observatory | Niklus I.,Estonian Environment Agency
Proceedings of the Estonian Academy of Sciences | Year: 2015

Solar radiation has been continuously measured in Estonia since 1950, but the recordings of longwave radiation began only about ten years ago. This paper presents the first description of the characteristic features of up- and downwelling longwave radiation in the Baltic Sea region. In the radiation balance the longwave fluxes have an important role. In the annual totals of radiation incident upon the ground surface in Estonia, the longwave atmospheric downwelling radiation L1↓ exceeds the direct solar radiation Eg↓ about three times, and this ratio has an essential seasonal run. In the total upwelling radiation L1↑, the infrared part is still greater, up to 92%. Comparing the measured and calculated (according to the Stefan–Boltzmann law) hourly totals of L1↑ for snow (emissivity ε = 0.85) we found a good linear relationship (R2 = 0.96). However, the measured totals systematically exceeded the calculated values (on average by 18%). Dependence of the downwelling infrared radiation L1↓ on the near-surface water vapour pressure e is approximated by a power function (R2 = 0.73). This is in good accordance with the results of studies carried out at other geographical sites. The influence of clouds on the fitted power function is noteworthy. Separate analysis of the hours with full cloudiness of low clouds and the cloudless hours confirmed the validity of the power function. However, a difference was found in their parameters (for overcast sky the exponent b = 0.20, R2 = 0.91 and for cloudless sky b = 0.25 and R2 = 0.93). © 2015, Estonian Academy Publishers. All rights reserved. Source

Keevallik S.,Tallinn University of Technology | Vint K.,Estonian Environment Agency
Proceedings of the Estonian Academy of Sciences | Year: 2015

Daily maximum and minimum temperatures are analysed from long time series for three Estonian sites: Tallinn on the southern coast of the Gulf of Finland (1920–2013), Tartu in inland Estonia (1894–2013), and Pärnu on the northern coast of the Gulf of Riga (1878–2013). The probabilities of extreme temperatures (defined in the meteorological practice in Estonia as lower than – 30 °C in winter and higher than 30 °C in summer) and their successions (incl. cold and heat waves) are evaluated for the three sites. It is suggested that the thresholds based on upper or lower percentiles of the distributions of daily maxima/minima recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI) are more suitable for the detection of cold and heat waves in Estonian climatic conditions than the current practice. © 2015, Estonian Academy Publishers. All rights reserved. Source

Vali U.,Estonian University of Life Sciences | Vainu O.,Estonian Environment Agency
Ringing and Migration | Year: 2015

The Common Buzzard Buteo buteo is a widespread species whose migration pattern differs by subspecies and regionally. Ring recoveries indicated that Buzzards originating from Estonia move southwest and winter in central and western Europe. This suggests that Estonia is occupied by the nominate subspecies of the Common Buzzard, which is a short-distance migrant. © 2016 British Trust for Ornithology. Source

Iital A.,Tallinn University of Technology | Kloga M.,Tallinn University of Technology | Pihlak M.,Tallinn University of Technology | Pachel K.,Tallinn University of Technology | And 2 more authors.
Agriculture, Ecosystems and Environment | Year: 2014

Several studies have shown that the stream water quality in agricultural catchments could vary according to the changes in land use, production intensities and implemented agri-environmental measures. In present study we investigated the nitrogen content and temporal dynamics in concentration and loss in small streams and catchments in Estonia for the period 1992-2011. The studied catchments represent various agricultural production areas, management practices, soil types, geology and size. A statistical analysis using the Mann Kendall (MK) test was undertaken to discern monotone trends in time series of total nitrogen (TN) and nitrate nitrogen (NO3-N) concentrations for 8 sampling sites and TN loss for five sites, for which at least a data set of 10 years was available. Additionally the partial Mann-Kendall (PMK) test has been adapted to account for the influence of water discharge to the temporal trends in TN loss in five catchments. The MK trend test revealed one statistically significant (p < 0.05; two-sided test) upward trend in TN concentrations and two upward trends in NO3-N concentrations. Less significant (p < 0.08) upward trend in TN content was also noted in two streams. Overall, the TN concentrations were rather high and it ranged with 90% probability from 2.3 to 8.9 mg l-1 in the studied streams. The MK test revealed the statistically significant upward trend in TN loss only at the Räpu (p < 0.001) and Jänijõgi (p < 0.05) catchments (one-sided test). After conditioning on trends in water discharge there was only one (Räpu) statistically significant temporal upward trend in TN loss. Elevated nitrogen concentrations in three other catchments (Rägina, Vodja, Porijõgi) explain only part of the upward trend in nitrogen losses and increasing tendencies in losses could mainly be associated with upward tendency in discharge. The direct (not flow-normalised) unit-area loss of nitrogen from agricultural land reached to 63.1 and 82.5 kg N ha-1 yr-1 in the Räpu and Jänijõgi catchments, respectively, which is higher than seen at the Rägina basin (25 kg ha-1 yr-1) and the River Vodja catchment (21.9 kg ha-1 yr-1). Elevated losses are typical for recent years, particularly after 2007. © 2014 Elsevier B.V. All rights reserved. Source

Toll V.,University of Tartu | Toll V.,Estonian Environment Agency | Pagh Nielsen K.,Danish Meteorological Institute | Rontu L.,Finnish Meteorological Institute | Masek J.,Czech Hydrometeorological Institute
Atmospheric Chemistry and Physics | Year: 2016

The direct shortwave radiative effect of aerosols under clear-sky conditions in the Aire Limitee Adaptation dynamique Developpement InterNational-High Resolution Limited Area Model (ALADIN-HIRLAM) numerical weather prediction system was investigated using three shortwave radiation schemes in diagnostic single-column experiments: the Integrated Forecast System (IFS), acraneb2 and the hlradia radiation schemes. The multi-band IFS scheme was formerly used operationally by the European Centre for Medium Range Weather Forecasts (ECMWF) whereas hlradia and acraneb2 are broadband schemes. The former is a new version of the HIRLAM radiation scheme while acraneb2 is the radiation scheme in the ALARO-1 physics package. The aim was to evaluate the strengths and weaknesses of the numerical weather prediction (NWP) system regarding aerosols and to prepare it for use of real-time aerosol information. The experiments were run with particular focus on the August 2010 Russian wildfire case. Each of the three radiation schemes accurately (within ±4 % at midday) simulates the direct shortwave aerosol effect when observed aerosol optical properties are used. When the aerosols were excluded from the simulations, errors of more than +15 % in global shortwave irradiance were found at midday, with the error reduced to +10 % when standard climatological aerosols were used. An error of-11 % was seen at midday if only observed aerosol optical depths at 550 nm, and not observation-based spectral dependence of aerosol optical depth, single scattering albedos and asymmetry factors, were included in the simulations. This demonstrates the importance of using the correct aerosol optical properties. The dependency of the direct radiative effect of aerosols on relative humidity was tested and shown to be within ± 6% in this case. By modifying the assumptions about the shape of the IFS climatological vertical aerosol profile, the inherent uncertainties associated with assuming fixed vertical profiles were investigated. The shortwave heating rates in the boundary layer changed by up to a factor of 2 in response to the aerosol vertical distribution without changing the total aerosol optical depth. Finally, we tested the radiative transfer approximations used in the three radiation schemes for typical aerosol optical properties compared to the accurate DISORT model. These approximations are found to be accurate to within ±13 % even for large aerosol loads. © 2016 Author(s). Source

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