15 research outputs found
Thermal seasons in northern Europe in projected future climate
Global warming acts to prolong thermal summers and shorten winters. In this work, future changes in the lengths and timing of four thermal seasons in northern Europe, with threshold temperatures 0 and 10 degrees C, are derived from bias-adjusted output data from 23 CMIP5 global climate models. Three future periods and two Representative Concentration Pathway (RCP) scenarios are discussed. The focus is on the period 2040-2069 under RCP4.5, which approximately corresponds to a 2 degrees C global warming relative to the preindustrial era. By the period 2040-2069, the average length of the thermal summer increases by nearly 30 days relative to 1971-2000, and the thermal winter shortens by 30-60 days. The timing of the thermal springs advances while autumns delay. Within the model ensemble, there is a high linear correlation between the modelled annual-mean temperature increase and shifts in the thermal seasons. Thermal summers lengthen by about 10 days and winters shorten by 10-24 days per 1 degrees C of local warming. In the mid-21st century, about two-thirds of all summers (winters) are projected to be very long (very short) according to the baseline-period standards, with an anomaly greater than 20 days relative to the late-20th century temporal mean. The proportion of years without a thermal winter increases remarkably in the Baltic countries and southern Scandinavian peninsula. Implications of the changing thermal seasons on nature and human society are discussed in a literature review.Peer reviewe
Communicating the amount of windstorm induced forest damage by the maximum wind gust speed in Finland
Windstorms are natural disturbance agents in forests playing a role in
natural forest regeneration. In Finland, the most severe individual
windstorms have commonly damaged 2â4Â million m3 of timber. In addition
to financial losses caused to forest owners, windthrown trees have in many
cases seriously disrupted the functionality of the national power grid.
Communicating windstorm risks in duty forecasting is difficult. In this
study, we aimed at developing windstorm impact estimates for forest damage in
Finland to help the forecaster to improve communication of the risks of
windstorms. We have compared the volume of forest damage caused by the most
intense windstorms in Finland during the recent decade to the observed
maximum inland wind gust speeds associated with the same windstorms. It was
found out that the volume of forest damage follows approximately a power
relation as a function of wind gust speed with a power of âŒ10. This is
a tentative estimate because of a short time series and small number of
inspected windstorms. Moreover, also wind direction, location of the affected
area and soil properties among other factors have an impact to the amount of
damage as illustrated in our inspection. Despite the shortness of the time
series, we believe that our results demonstrating the steep increase in the
impacts of windstorms with an increasing windstorm intensity are valuable.
However, more detailed investigations with longer time series are needed in
order to more specifically communicate the windstorm risks and their impacts
in boreal forests.</p
The 10-Year Return Levels of Maximum Wind Speeds under Frozen and Unfrozen Soil Forest Conditions in Finland
Reliable high spatial resolution information on the variation of extreme wind speeds under frozen and unfrozen soil conditions can enhance wind damage risk management in forestry. In this study, we aimed to produce spatially detailed estimates for the 10-year return level of maximum wind speeds for frozen (>20 cm frost depth) and unfrozen soil conditions for dense Norway spruce stands on clay or silt soil, Scots pine stands on sandy soil and Scots pine stands on drained peatland throughout Finland. For this purpose, the coarse resolution estimates of the 10-year return levels of maximum wind speeds based on 1979−2014 ERA-Interim reanalysis were downscaled to 20 m grid by using the wind multiplier approach, taking into account the effect of topography and surface roughness. The soil frost depth was estimated using a soil frost model. Results showed that due to a large variability in the timing of annual maximum wind speed, differences in the 10-year return levels of maximum wind speeds between the frozen and unfrozen soil seasons are generally rather small. Larger differences in this study are mostly found in peatlands, where soil frost seasons are notably shorter than in mineral soils. Also, the high resolution of wind multiplier downscaling and consideration of wind direction revealed some larger local scale differences around topographic features like hills and ridgelines
Spatial and temporal variation in weather events critical for boreal agriculture: III Frost and winter time fluctuation
201
Spatial and temporal variation in weather events critical for boreal agriculture: III Frost and winter time fluctuation
In the boreal zone of Europe, differences between the four seasons are considerable. Also, the within-season variation in climatic conditions is substantial. This has many impacts on agriculture that are exceptional when compared to any other environmental zone in Europe. All the meteorological data were based on weather observations made by the Finnish Meteorological Institute. Likelihood (%) for soil frost (†0 °C at 20 cm soil depth) at nine weather stations, and late snow cover (> 1 cm) (10 km Ă 10 km grid) were estimated for late spring. Probabilities (%) of night frost at the ground surface (March-September) were calculated at nine weather stations by frequencies of the lowest observed night-time temperature: a) between â2 and â5 °C (mild), b) †â5 °C (moderate) and c) †â9 °C (severe). Also, the probabilities (%) of night frost in mid-summer were estimated (†â1 °C for at least five hours). Furthermore, a significant shift from mild to below-freezing conditions was measured in winter as a period of at least ten days with daily maximum temperatures above 0°C followed by at least a 10-day period with daily mean temperatures below â5°C in order to characterize high fluctuating winter conditions. All these except late snow cover constitute high risks to crop production. Deep soil frost may postpone sowings, while in advanced springs, night frost may cause damage. For winter crops and perennials, shifts from mild to cold spells outside the growing season are particularly detrimental. Again the data may have many other applications beyond the assessments highlighted in this paper
Estimation of the high-spatial-resolution variability in extreme wind speeds for forestry applications
The bioeconomy has an increasing role to play in climate
change mitigation and the sustainable development of national economies. In Finland, a forested country, over 50âŻ% of the current bioeconomy
relies on the sustainable management and utilization of forest resources.
Wind storms are a major risk that forests are exposed to and high-spatial-resolution analysis of the most vulnerable locations can produce risk
assessment of forest management planning. In this paper, we examine the
feasibility of the wind multiplier approach for downscaling of maximum wind
speed, using 20âŻm spatial resolution CORINE land-use dataset and high-resolution digital elevation data. A coarse spatial resolution estimate of
the 10-year return level of maximum wind speed was obtained from the
ERA-Interim reanalyzed data. Using a geospatial re-mapping technique the data
were downscaled to 26 meteorological station locations to represent very
diverse environments. Applying a comparison, we find that the downscaled 10-year return levels represent 66âŻ% of the observed variation among the stations
examined. In addition, the spatial variation in wind-multiplier-downscaled
10-year return level wind was compared with the WAsP model-simulated wind.
The heterogeneous test area was situated in northern Finland, and it was
found that the major features of the spatial variation were similar, but in
some locations, there were relatively large differences. The results indicate
that the wind multiplier method offers a pragmatic and computationally
feasible tool for identifying at a high spatial resolution those locations
with the highest forest wind damage risks. It can also be used to provide
the necessary wind climate information for wind damage risk model
calculations, thus making it possible to estimate the probability of
predicted threshold wind speeds for wind damage and consequently the
probability (and amount) of wind damage for certain forest stand
configurations
Spatial and temporal variation in weather events critical for boreal agriculture: III Frost and winter time fluctuation
Harmfulness of weather events and the adaptive capacity of farmers at high latitudes of Europe
Harmfulness of weather events and the adaptive capacity of farmers at high latitudes of Europe
201