Relating forest damage data to the wind field from high-resolution RCM simulations: Case study of Anatol striking Sweden in December 1999

Abstract

Forestry is of major economical importance in Europe, and recent devastating windstorms have pinpointed the vulnerability of this economic sector to windstorms. Forest damage is an important economic issue at a country level and may become even of larger concern under future conditions following global warming. An underlying question is to what extent the storm damage is due to changes in the wind climate compared to the effect of changes in forest management practices? In this paper, the first part of this rather complex problem is tackled.By using the Canadian Regional Climate Model, CRCM, including a physically based gust parameterisation scheme, NCEP-NCAR reanalysis wind fields for the windstorm Anatol, on December 3-4, 1999, were downscaled, into a nested set-up, to 2 km resolution. The aim is to relate the simulated storm wind field to the observed distribution of storm damaged forests in Scania in southern Sweden, as a first methodological step towards analysing the effect of future windstorms in Swedish forests at the highest spatial resolution one can afford nowadays.Our results show that the CRCM produced realistic wind field simulations, compared to station observations, of the windstorm event in 1999. The simulated winds were underestimated at the coasts, but in congruence with inland observations. Most of the damaged forest stands were located on south-westerly (SW) slopes, which indicated a south-westerly wind during the wind throw process. This SW wind direction was evident in the early phase of the simulated storm, but then changed into a westerly flow, at an earlier stage than the true observations specified. Further, most damage occurred in the areas of simulated maximum wind speed greater than 30 m s − 1 .To conclude, the CRCM has proven to be a useful tool to realistically simulate a forest damaging storm event. Hence, the model could be used for further study cases, preferably driven by a GCM, in order to reveal a greater understanding about recent storms, which in turn helps us evaluate future climate change driven storm conditions.

Climate change impacts on stand structure and competitive interactions in a southern Swedish spruce–beech forest

“…7) matches the main south-westerly wind direction during the storm maximum (33 m s -1 at Vaxjö, 08/01/05, 7-9 p.m. SMHI 2005). Nilsson et al (2007) identified from storm analyses based on the 'Anatol' storm in 1999 a threshold of 30 m s -1 for critical wind speed that was exceeded only for about two hours (SMHI 2005). Recent wind simulation of the model-system WINDA using regionally downscaled climate change scenarios (Blennow and Olofsson 2008) exhibits a high future probability of exceeding critical wind speed from south-westerly directions at Växjö region.…”

The Role of Highly-Resolved Gust Speed in Simulations of Storm Damage in Forests at the Landscape Scale: A Case Study from Southwest Germany

“…This means that the proposed methodology opens up the possibility to embed damage caused by exceptional storms like Wiebke and Lothar into the regional chronic damage pattern. In the context of empirical-statistical storm damage modeling this is an important achievement, because consideration of single storm events might bias the assessment of storm damage predictor importance since every storm event is unique concerning intensity, spatial extent and duration [23]. Including high-resolution statistical gust speed fields [27] into storm damage modeling process clearly improves model accuracy in comparison to previous studies when only lower resolution gust speed fields were available [17,19].…”

Development of a model-based high-resolution extreme surface wind climatology for Switzerland

“…The same methodology may be applied over other countries and regions and this may lead to a different position of the averaged cyclones responsible for strong winds; a particular example is given by the Anatol storm that struck southern Scandinavia in early December 1999 (Nilsson et al 2006). …”

“…Cyclonic activity is particularly strong during winters when frequent storms bring adverse conditions in western European countries (Nilsson et al 2006;Schüepp et al 1994;Beniston and Innes 1998;Dorland et al 1999;Dobbertin 2002]. In Switzerland, the number of station recordings with hourly maximum wind speeds exceeding 30 m s À1 (i.e.…”

“…Although computationally resource intensive, multiple nesting techniques driven by reanalysis data has shown genuine skill in resolving a number of specific strong wind events over the Alps such as the Feb 27, 1990 Vivian, and the Dec. 26, 1999 Lothar storms (Goyette et al 2001;Goyette et al 2003). A recent study using a similar methodology showed that the CRCM produced realistic wind field simulations compared to station observations over Southern Sweden during the windstorm Anatol in early December 1999 (Nilsson et al 2006). The simulated winds were in congruence with inland observations.…”