ISSN 1239-6095
© Boreal Environment Research 2002

Contents of Volume 7 Number 4

The BALETX Theme Issue II

Alestalo, M. 2002. Preface. Boreal Env. Res. 7: 305.
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Roads, J., Raschke, E. & Rockel, B. 2002. BALTEX water and energy budgets in the NCEP/DOE reanalysis II. Boreal Env. Res. 7: 307–317.
Abstract
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Maslowski, W. & Walczowski, W. 2002. Circulation of the Baltic Sea and its connection to the Pan-Arctic region — a large scale and high-resolution modeling approach. Boreal Env. Res. 7: 319–325.
Abstract
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Meier, H.E.M. & Döscher, R. 2002. Simulated water and heat cycles of the Baltic Sea using a 3D coupled atmosphere–ice–ocean model. Boreal Env. Res. 7: 327–334.
Abstract
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Stipa, T. & Vepsäläinen, J. 2002. The fragile climatological niche of the Baltic Sea. Boreal Env. Res. 7: 335–342.
Abstract
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Berger, F.H. 2002. Surface radiant and energy flux densities inferred from satellite data for the BALTEX watershed. Boreal Env. Res. 7: 343–351.
Abstract
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Peters, G., Fischer, B. & Andersson, T. 2002. Rain observations with a vertically looking Micro Rain Radar (MRR). Boreal Env. Res. 7: 353–362.
Abstract
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Stigebrandt, A., Lass, H.-U., Liljebladh, B., Alenius, P., Piechura, J., Hietala, R. & Beszczynska, A. 2002. DIAMIX — An experimental study of diapycnal deepwater mixing in the virtually tideless Baltic Sea. Boreal Env. Res. 7: 363–369.
Abstract
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Brümmer, B., Kirchgäßner, A., Müller, G., Schröder, D., Launiainen, J. & Vihma, T. 2002. The BALTIMOS (BALTEX Integrated Model System) field experiments: A comprehensive atmospheric boundary layer data set for model validation over the open and ice-covered Baltic Sea. Boreal Env. Res. 7: 371–378.
Abstract
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Gryning, S.-E., Halldin, S. & Lindroth, A. 2002. Area averaging of land surface–atmosphere fluxes in NOPEX: challenges, results and perspectives. Boreal Env. Res. 7: 379–387.
Abstract
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Oltchev, A., Cermak, J., Nadezhdina, N., Tatarinov, F., Tishenko, A., Ibrom, A. & Gravenhorst, G. 2002. Transpiration of a mixed forest stand: field measurements and simulation using SVAT models. Boreal Env. Res. 7: 389–397.
Abstract
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Malinin, V.N., Nekrasov, A.V. & Gordeeva, S.M. 2002. Inter-annual variability of Baltic Sea water balance components and sea level. Boreal Env. Res. 7: 399–403.
Abstract
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Lehmann, A. & Hinrichsen, H.-H. 2002. Water, heat and salt exchange between the deep basins of the Baltic Sea. — Boreal Env. Res. 7: 405–415.
Abstract
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Lindau, R. 2002. Energy and water balance of the Baltic Sea derived from merchant ship observations. — Boreal Env. Res. 7: 417–424.
Abstract
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Clemens, M. & Bumke, K. 2002. Precipitation fields over the Baltic Sea derived from ship rain gauge measurements on merchant ships. Boreal Env. Res. 7: 425–436.
Abstract
Full text (pdf format)

Kitaev, L., Kislov, A., Krenke, A., Razuvaev, V., Martuganov, R. & Konstantinov, I. 2002. The snow cover characteristics of northern Eurasia and their relationship to climatic parameters. Boreal Env. Res. 7: 437–445.
Abstract
Full text (pdf format)

Klavins, M., Briede, A., Rodinov, V., Kokorite, I. & Frisk, T. 2002. Long-term changes of the river runoff in Latvia. Boreal Env. Res. 7: 447–456.
Abstract
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Rimkus, E. & Stankunavichius, G. 2002. Snow water equivalent variability and forecast in Lithuania. Boreal Env. Res. 7: 457–462.
Abstract
Full text (pdf format)

Tomingas, O. 2002. Relationship between atmospheric circulation indices and climate variability in Estonia. Boreal Env. Res. 7: 463–469.
Abstract
Full text (pdf format)


Roads, J., Raschke, E. & Rockel, B. 2002. BALTEX water and energy budgets in the NCEP/DOE reanalysis II. Boreal Env. Res. 7: 307–317.

Water and energy budgets from the National Centers for Environmental Prediction/Dept. of Energy (NCEP/DOE) reanalysis II (NCEPRII) are described for the Baltic Sea catchment and sea (BALTEX). Annually, NCEPRII shows 0.7 mm d–1 of atmospheric moisture converged into the land region with a corresponding runoff of 0.7 mm d–1 to the Baltic Sea, consistent with observations. However, precipitation is too low; evaporation is too large; runoff does not have an appropriate winter minimum and spring maximum; the assimilation and surface nudging are too large. Important hydroclimatic characteristics can still be discerned. During summer, atmospheric water vapor, precipitation, evaporation, and surface and atmospheric radiative heating increase and the atmospheric radiative cooling, dry static energy convergence decrease. There are large contrasts between the sea and land; during winter sensible heat is transferred from the sea to the atmosphere and sea evaporation and precipitation are largest during the fall and winter; somewhat opposite behavior occurs over land.
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Maslowski, W. & Walczowski, W. 2002. Circulation of the Baltic Sea and its connection to the Pan-Arctic region — a large scale and high-resolution modeling approach. Boreal Env. Res. 7: 319–325.

The Baltic Sea has traditionally been considered as a semi-enclosed marginal sea with little or no influence on the adjacent oceans. We employ an eddy-permitting, coupled ice-ocean model of the Pan-Arctic region to study the Baltic Sea, especially its circulation and property exchanges with the North Sea and other regions. Using this high-resolution and large scale model we focus here on the freshwater export from the Baltic Sea and its transport by the Norwegian Coastal Current (NCC) into the Norwegian and Barents Sea. We hypothesize that the freshwater outflow from the Baltic Sea plays a significant role in modification of Atlantic Water properties along its northern pathway from the North Atlantic, through the Nordic Seas, and into the Arctic Ocean. Recommendations are made for more realistic model representation of the Baltic Sea circulation to advance understanding of this region's influence on the large-scale northern polar ocean circulation and climate change.
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Meier, H.E.M. & Döscher, R. 2002. Simulated water and heat cycles of the Baltic Sea using a 3D coupled atmosphere–ice–ocean model. Boreal Env. Res. 7: 327–334.

The heat and water cycles of the Baltic Sea are calculated utilizing multi-year model simulations. This is one of the major objectives of the BALTEX program. For the period 1988–1993, results of a 3D ice-ocean model forced with observed atmospheric surface fields are compared with results of a fully coupled atmosphere-ice-ocean model using re-analysis data at the lateral boundaries. The state-of-the-art coupled model system has been developed for climate study purposes in the Nordic countries. The model domain of the atmosphere model covers Scandinavia, Europe and parts of the North Atlantic whereas the ocean model is limited to the Baltic Sea. The annual and monthly mean heat budgets for the Baltic Sea are calculated from the dominating surface fluxes, i.e. sensible heat, latent heat, net longwave radiation and solar radiation to the open water or to the sea ice. The main part of the freshwater inflow to the Baltic is the river runoff. A smaller part of about 11% is added from net precipitation. The heat and water cycles are compared with the results of a long-term simulation (1980–1993) using the stand-alone Baltic Sea model forced with observed atmospheric surface fields. In general, both approaches, using the uncoupled or coupled Baltic Sea model, give realistic estimates of the heat and water cycles and are in good agreement with results of other studies. However, in the coupled model the parameterizations of the latent heat flux and the incoming longwave radiation need to be improved.
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Stipa, T. & Vepsäläinen, J. 2002. The fragile climatological niche of the Baltic Sea. Boreal Env. Res. 7: 335–342.

The Baltic Sea is governed by the same physical laws as any other sea. Yet since it lies in a very different part of the temperature and salinity range than most other waters of the World Ocean, these laws result in dynamics that is not found elsewhere in the same extent. Here some consequences of this fact are discussed in light of recent observational and theoretical advances. We show that heat fluxes are almost negligible for restratification in this regime, and combine this idea with what is expected about the climatic warming to give a forecast of a substantial, non-linear change in the way the seasonal stratification and the vernal bloom in the Baltic Sea are formed. This discussion should also provide a conceptual framework for the discussion of the impacts of climate change on vernal bloom dynamics there, and in boreal estuaries in general.
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Berger, F.H. 2002. Surface radiant and energy flux densities inferred from satellite data for the BALTEX watershed. Boreal Env. Res. 7: 343–351.

To study the energy and water cycle at different spatial and temporal scales, the satellite data analysis scheme SESAT (Strahlungs- und Energieflüsse aus SATellitendaten) has been developed for passive remotely sensed data, like NOAA-AVHRR, ERS-1/2 ATSR, Envisat AATSR and MSG SEVIRI data. SESAT consists of several modules to compute cloud properties (types as well as geometrical, optical and microphysical properties), land surface properties (radiometrical and bio-geophysical properties), surface radiant and energy flux densities. SESAT could be applied to different data sets, especially for the BALTEX watershed, to infer surface radiant flux densities and also, as a first estimation, surface energy flux densities with sufficient accuracy. Most of the parameters needed for this computation can be derived from meteorological satellite data. Comparisons of net radiation, inferred from satellite data and measured at the surface, do show sufficient accuracy, but for energy flux densities more observations at the ground will have to be carried out to quantify the achievable accuracy.
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Peters, G., Fischer, B. & Andersson, T. 2002. Rain observations with a vertically looking Micro Rain Radar (MRR). Boreal Env. Res. 7: 353–362.

Measurements of rain were obtained with a vertically pointing micro radar (MRR) with 1 min time resolution and 50(100) m height resolution at the German Baltic coast on the Zingst peninsula (54.43°N, 12.67°E). The comparison with a conventional rain gauge (30 min integration time) for a five months summer period show a correlation coefficient of [[rho][eta][omicron]] = 0.87 for the rainrate and agreement within 5% for the total rainfall integrated over the whole period. Single measurements with 30 min integration time showed deviations up to a factor of 2 between MRR and rain gauge. Classification of the measurements into rainrate intervals shows that rainrates around 0.2 mm h–1 provide the highest contribution per rainrate interval to the total rainfall. Typical distributions of number-concentration, liquid-water- concentration and rainrate versus drop size, retrieved with the MRR, are presented. Simultaneous estimates of rainrate and reflectivity factor with data of a C-band (frequency 6 GHz) weather radar suggest that the MRR may be used to support quantitative rainrate estimates with weather radars. The weather radar used for comparison is operated by the German Weather Service and is situated 51 km from the MRR.
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Stigebrandt, A., Lass, H.-U., Liljebladh, B., Alenius, P., Piechura, J., Hietala, R. & Beszczynska, A. 2002. DIAMIX — An experimental study of diapycnal deepwater mixing in the virtually tideless Baltic Sea. Boreal Env. Res. 7: 363–369.

The DIAMIX (DIApycnal MIXing) project aims at investigating wind-driven vertical mixing below the pycnocline. Since tides are exceedingly weak in the Baltic an area east of Gotland was chosen as the study area. Two pilot surveys and two main experiments were conducted between June 1997 and September 2000. The joint effort is motivated to cover as many scales as possible of the distribution of kinetic and potential energy. This paper describes the main features found in the field measurements. Inertial currents, near-inertial waves and internal seiches are the bulk features in the mooring data. Acting against topography these currents may generate strong clockwise and anti-clockwise rotating eddies as well as up- and down-welling which has been observed mainly from ship-borne measurements. From turbulent dissipation measurements the stabilizing effect of the stratification can clearly be seen. Dissipation measurements at the slope indicate a much higher dissipation rate there as compared to the deeper station. All these effects have to be taken into account to add up the power needed to explain the turbulent dissipation and work against buoyancy forces connected to diapycnal mixing in the deepwater as estimated from long-term modeling.
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Brümmer, B., Kirchgäßner, A., Müller, G., Schröder, D., Launiainen, J. & Vihma, T. 2002. The BALTIMOS (BALTEX Integrated Model System) field experiments: A comprehensive atmospheric boundary layer data set for model validation over the open and ice-covered Baltic Sea. Boreal Env. Res. 7: 371–378.

A comprehensive atmospheric boundary layer (ABL) data set was collected in eight field experiments (two during each season) over open water and sea ice in the Baltic Sea during 1998–2001 with the primary objective to validate the coupled atmospheric-ice-ocean-land surface model BALTIMOS (BALTEX Integrated Model System). Measurements were taken by aircraft, ships and surface stations and cover the mean and turbulent structure of the ABL including turbulent fluxes, radiation fluxes, and cloud conditions. Measurement examples of the spatial variability of the ABL over the ice edge zone and of the stable ABL over open water demonstrate the wide range of ABL conditions collected and the strength of the data set which can also be used to validate other regional models.
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Gryning, S.-E., Halldin, S. & Lindroth, A. 2002. Area averaging of land surface–atmosphere fluxes in NOPEX: challenges, results and perspectives. Boreal Env. Res. 7: 379–387.

The NOPEX experimental campaigns dealt with the land-surface-atmosphere exchange of momentum, heat, water and CO2 on local and regional scales. In this paper emphasis is put on the NOPEX experiences with respect to the spatial integration of fluxes of momentum, heat, humidity and CO2 over the mosaic of forest, agricultural land, lakes and mires that make up the southern part of the NOPEX area. It is found that the forest dominates both the regional momentum and heat fluxes but in very different ways. Furthermore, results from a NOPEX experiment in the northern zone of the boreal forest in Finnish Lapland highlights the very unique processes associated with the energy exchange within a forest in wintertime. The interaction of the forest canopy with sunshine provides a considerable energy source, particularly at low solar angles. A considerable improvement in model simulations of fluxes and surface temperature was achieved when this effect and the heat storage of the canopy were taken into account.
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Oltchev, A., Cermak, J., Nadezhdina, N., Tatarinov, F., Tishenko, A., Ibrom, A. & Gravenhorst, G. 2002. Transpiration of a mixed forest stand: field measurements and simulation using SVAT models. Boreal Env. Res. 7: 389–397.

Transpiration of a mixed spruce-aspen-birch forest at the Valday Hills in Russia was determined using sap flow measurements and two different SVAT (Soil–Vegetation–Atmosphere-Transfer) models. The more sophisticated Mixed Forest multi-layer SVAT model (MF-SVAT) considers water uptake and transpiration of each tree species individually, and the simple Multi-Layer (ML-SVAT) describes the forest stand using averaged effective parameters of canopy structure and tree physiology. Comparisons of modelled and measured transpiration rates under sufficient soil moisture conditions did not show any significant differences between two models. Under limited soil moisture conditions MF-SVAT described forest transpiration still realistically whereas ML-SVAT overestimated it by up to 50%. Drought in the upper soil layers reduced transpiration of spruces more than of deciduous trees due to differences in physiological properties and vertical root distribution. Individual regulation of the transpiration of different tree species is typical for mixed forests and cannot be accurately described with averaged parameterisation such as used in ML-SVAT.
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Malinin, V.N., Nekrasov, A.V. & Gordeeva, S.M. 2002. Inter-annual variability of Baltic Sea water balance components and sea level. Boreal Env. Res. 7: 399–403.

This paper discusses some estimates of the Baltic Sea water balance components for the period 1951–1990. A considerable discrepancy is found resulting from different causes. The features of the trends in the inter-annual variations of the vertical water exchange components are also discussed. Particular emphasis is placed on the inter-annual oscillations of sea level. The most important large-scale regularities of these oscillations are demonstrated for the period 1892–1994.
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Lehmann, A. & Hinrichsen, H.-H. 2002. Water, heat and salt exchange between the deep basins of the Baltic Sea. — Boreal Env. Res. 7: 405–415.

From numerical model simulations, fluxes of volume, heat and salt have been calculated for different hydrographical sections in areas which are important for the deep water exchange in the Baltic Sea. The calculated deep water flow in the Arkona basin is in accordance with independent estimations obtained from profile data. Model results reveal strong seasonal and inter-annual variability in the calculated fluxes. The variability is governed by the prevailing atmospheric conditions. It is found that the strength of the upper layer low saline flow in the Arkona Basin which on average is directed to the west, opposite to the mean wind direction, is compensated by a high saline flow in deeper layers. The upper layer flow is a combination of a flow forced by the fresh water surplus directed to the west, and a wind-driven part. In dependence on the prevailing wind conditions the resulting flow is either increased or decreased. Furthermore, increasing upper layer flow results in an increased lower layer flow in opposite direction. The annual mean flow is weakly correlated with the annual mean runoff to the Baltic Sea. In accordance with the mean circulation, the flow through the Bornholm Channel is on average directed to the east, and south of Bornholm to the west indicating an import of heat and salt to the Bornholm Basin through the Bornholm Channel and an export south of Bornholm. Flux characteristics change further downstream in the Stolpe Channel. The volume flow in the upper layer shows a strong seasonal signal. During autumn to spring the flow is mainly directed to the east, in summer, the flow direction is reversed. Flow in westerly directions is related to increased lower layer flow in easterly directions. On average, the net flow through the Stolpe channel is directed to the east which is in accordance with the mean circulation. Calculated fluxes show high intra- and inter-annual variability with no obvious trend during the simulation period. The variability of the deep water stratification in the deep basins of the Baltic Sea is directly controlled by the changing flux characteristics.
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Lindau, R. 2002. Energy and water balance of the Baltic Sea derived from merchant ship observations. — Boreal Env. Res. 7: 417–424.

Individual merchant ship observations from COADS (Comprehensive Ocean Atmosphere Data Set) were used to determine the energy and water budget of the Baltic Sea for the period 1980 to 1995. On a monthly time scale these ship reports provide reasonable estimates for the radiative and turbulent fluxes and the precipitation despite their concentration on narrow shipping routes, because of the large correlation lengths for monthly means. In order to take into account the effects of sea ice on evaporation and albedo, the ice-covered parts of the Baltic Sea are treated separately, where we applied a simple thermodynamic ice model using ice information from the GISST (Global sea Ice coverage and Sea Surface Temperature) data set. As the overall result we found a small surplus of rain compared to evaporation (5 mm per month) and a quasi-balanced energy budget (1 W m–2 energy loss of the sea surface).
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Clemens, M. & Bumke, K. 2002. Precipitation fields over the Baltic Sea derived from ship rain gauge measurements on merchant ships. Boreal Env. Res. 7: 425–436.

Precipitation over the Baltic Sea has been estimated from satellite measurements, ground-based weather radars and synoptic observations made at coastal and island stations. The obtained estimates do not use any in situ measurements over the Baltic Sea. Thus, a validation of the estimates over the sea proper is required. Here we present a method to analyse precipitation measurements over the Baltic Sea from the ship observations for the period 1996–2000. In order to measure precipitation over the Baltic Sea, several merchant ships have been equipped with specially designed ship rain gauges. The measurements are stored at 8-minute intervals. More than 20000 instrumental measurements were collected during several months. An interpolation scheme based on the kriging method has been used to estimate spatial precipitation distributions on a 1° [xi] 1° grid. This method is particularly used to minimise sampling errors due to the low data density. All estimations are presented on a seasonal time resolution. The estimated spatial rain fields give reasonable results, especially in areas along the main shipping routes characterised by a high data density.
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Kitaev, L., Kislov, A., Krenke, A., Razuvaev, V., Martuganov, R. & Konstantinov, I. 2002. The snow cover characteristics of northern Eurasia and their relationship to climatic parameters. Boreal Env. Res. 7: 437–445.

The research presented in this paper was based on snow depth data over the former Soviet Union territory for the period 1936–1995 and snow water equivalent data for the period 1966–1990. These data were averaged for the territories of different scales. The errors associated with such averaging were estimated. Positive trends in the snow amount were revealed. They coincide with positive trends in the winter precipitation and air temperature. A relationship between the distribution of observed snow depth anomalies and the spatial distribution of precipitation and air temperature was established. During the last 60 years, the role of low air temperatures in the formation of the snow cover formation has diminished, while that of high precipitation has increased. The relation of the snow cover in the former Soviet Union to the NAO and SOI indices and monsoon intensify was examined.
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Klavins, M., Briede, A., Rodinov, V., Kokorite, I. & Frisk, T. 2002. Long-term changes of the river runoff in Latvia. Boreal Env. Res. 7: 447–456.

The study of changes in river discharge is important for the development of efficient water resource management systems, as well as for the development and validation of climate change impact models. The discharge regime of rivers and their long-term changes in Latvia were investigated. Four major types of river discharge regimes, which depend on climatic and physico-geographic factors, were characterized. These factors are linked to the changes observed in river discharge. Periodic oscillations of discharge intensity, and low- and high-water flow years are common for the major rivers in Latvia. A main frequency of about 20 and 13 years was estimated for the studied rivers.
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Rimkus, E. & Stankunavichius, G. 2002. Snow water equivalent variability and forecast in Lithuania. Boreal Env. Res. 7: 457–462.

Atmosphere circulation is the most important modulator of snow cover parameters. This study deals with the relation between the dominant Northern Hemisphere circulation mode, called the Arctic Oscillation (AO), and the spatial distribution of the snow water equivalent (SWE) within the territory of Lithuania. The results indicate an inverse relation between the extreme AO phase and the SWE. However, the largest spatial differences are seen in the positive AO phase. The absolute altitude and slopes expositions play a more significant role in that case. During the extreme negative AO phase, a decreasing temperature as a function of distance from the seacoast from west to east becomes more significant to the accumulation of snow cover. The study also includes a climatic forecast for changes in the snow water equivalent based on the outputs of five climate models. Under an increasing winter air temperature and rain fraction in winter precipitation, the SWE will decrease distinctly causing a change in river feeding regime.
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Tomingas, O. 2002. Relationship between atmospheric circulation indices and climate variability in Estonia. Boreal Env. Res. 7: 463–469.

A simple method for calculating circulation indices by using gridded data of mean sea level pressure is applied to Estonia. The main objective of the research is to analyse the relationship between the developed indices and climate variability in Estonia. The results indicated that correlation between the indices and air temperature varies significantly between different months and seasons. The air temperature is positively correlated with the zonal circulation index during the period from September to March and has no correlation from April to August. The meridional index (positive values correspond to the higher-than-normal southerly airflow) has a positive correlation with the air temperature from April to September and no significant correlation in other months. In case of the higher-than-normal zonal and SW–NE index, the duration of the snow cover in Estonia is shorter than normal because the snow cover duration is related to air temperature conditions. The correlation between the indices and precipitation is low. Several statistically significant trends in monthly and seasonal circulation indices were detected using a linear regression analysis and a non-parametric Mann-Kendall test for trend. During 1946–1997, the mean zonal circulation has intensified in February and winter (DJF), and decreased in April, June and September. The southerly airflow has increased in March. The southwesterly circulation has increased in February and March and decreased in April, June, September, summer (JJA) and autumn (SON). The airflow from southeast has intensified in spring (MAM).
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