ABSTRACT:The annual and seasonal mean temperature of Finland was calculated for 162 years based on spatially interpolated monthly mean temperature records. The spatial interpolation method, known as kriging, was used with the following forcing parameters: the geographical coordinates, elevation of the terrain, and percentage share of lakes and sea. Homogenised data was used, and thus the most important factor affecting the accuracy of the interpolated data was the uneven distribution of the available observation stations both in time and space. The uncertainty due to the homogenisation adjustments made earlier was notably smaller. In the mid-1800s, the uncertainty in the annual and seasonal mean temperatures was large, with a maximum in winter of over ±2.0°C, but the accuracy improved quickly with time as the number of the observation stations increased. At the beginning of the 20th century, the uncertainty related to the limited station network was less than ±0.2°C, in winter less than ±0.4°C. According to the data, the rise in Finland's annual mean temperature has been statistically significant during the last 100, 50 and 30 years. During the last 100 years the increase in the mean temperature was largest during spring, but during the last 50 years winters have warmed up the most. The temperature time series obtained are compatible with grid point values picked from the global temperature data grids starting from the 1880s, though the global data sets tend to smooth the extremes.

[1] We estimated the magnitude of the radiative forcing (RF) due to changes in albedo following the forestation of peatlands, and calculated the net RF by taking into account the changes in both the albedo and the greenhouse gas (GHG) fluxes during one forest rotation. Data on radiation, tree biomass, and soil GHG fluxes were combined with models for canopy cover, tree carbon accumulation, and the RF due to increased atmospheric GHG concentrations for four typical site cases in Finland covering two soil nutrient levels in the south and north of the country. We also studied the observed long-term surface temperatures to detect any indications of drainage-induced effects. The magnitude of the albedo-induced RF was similar to that caused by the carbon sequestration of the growing trees. At three site cases out of four the drainage induced a cooling or negative RF, the tendency for cooling being higher at sites with a higher nutrient level. The differences in albedo-induced RF mainly arose from the spring season due to (1) the different snow cover duration in the south versus the north, and (2) the different albedos of drained and undrained snow covered peatlands. An increase in the maximum daily temperatures was observed in April in southern Finland, where the most intensive drainage practices have taken place, suggesting that forestry drainage has potentially affected the local climate. Our results show that the decreasing albedo resulting from peatland forestation contributes significantly to the RF, balancing out or even exceeding the cooling effect due to the changing GHG fluxes.Citation: Lohila, A., K. Minkkinen, J. Laine, I. Savolainen, J.-P. Tuovinen, L. Korhonen, T. Laurila, H. Tietäväinen, and A. Laaksonen (2010), Forestation of boreal peatlands: Impacts of changing albedo and greenhouse gas fluxes on radiative forcing,

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ABSTRACT:The atmospheric moisture budget over Antarctica and the Southern Ocean was analysed for the period 1979-2001 on the basis of the ERA-40 reanalysis of the European Centre for Medium-Range Weather Forecasts. Meridional transport by transient eddies makes the largest contribution to the southward water vapour transport. The mean meridional circulation contributes to the northward transport in the Antarctic coastal areas, but this effect is compensated by the southward transport by stationary eddies. The convergence of meridional water vapour transport is at its largest at 64-68°S, while the convergence of zonal transport is regionally important in areas of high cyclolysis. Inter-annual variations in water vapour transport are related to the southern annular mode (SAM). The eastward transport has a significant (95% confidence level) positive correlation with the SAM index, while the northward transport has a significant negative correlation with SAM near 60°S. Hydrological balance is well-achieved in the ERA-40 reanalysis: the difference between the water vapour flux convergence (based on analysis) and the net precipitation (precipitation minus evaporation, based on 24-h forecasts) is only 13 mm yr −1 (3%) over the Southern Ocean and −8 mm yr −1 (5%) over the continental ice sheet. Over the open ocean, the analysis methodology favours the accuracy of the flux convergence. For the whole study region, the annual mean flux convergence exceeded net precipitation by 11 mm yr −1 (3%). The ERA-40 result for the mean precipitation over the Antarctic continental ice sheet in 1979-2001 is 177 ± 8 mm yr −1 , while previous estimates range from 173 to 215 mm yr −1 . For the period 1979-2001, the ERA-40 data do not show any statistically significant trend in precipitation over the Antarctic grounded ice sheet and ice shelves. From the ERA-40 data, the annual average net evaporation (evaporation minus condensation) is positive over the whole continent.

Abstract. The past and projected future precipitation sum in May-September for two areas in Finland, one located in the south-west (SW) and the other in the north-east (NE), is studied using 13 regional climate simulations and three observational datasets. The conditions in the present-day climate for agricultural crop production are far more favourable in the south-western part of the country than the more continental north-eastern Finland. Based on a new high-resolution observational precipitation dataset for Finland (FMI grid), with a resolution of 10×10 km, the only statistically significant past long-term precipitation tendencies in the two study regions are positive. Differences between FMI grid and two other observational datasets during 1961-2000 are rather large in the NE, whereas in the SW the datasets agree better. Observational uncertainties stem from the interpolation and sampling errors. The projected increases in precipitation in the early stage of the growing season would be most favourable for agricultural productivity, but the projected increases in August and September might be harmful. Model projections for the future indicate a statistically significant increase in precipitation for most of the growing season by 2100, but the distribution of precipitation within the growing season is not necessarily the most optimal.