RT6 Plenary Prague GA

Examples of FMI’s work Ari Venäläinen, Kirsti Jylhä

Ilmatieteen laitos

RT6 Plenary Prague GA

Change in the number of snow cover days (%) from 1961-1990 to 2071-2100

Ari Venäläinen and Kirsti Jylhä Ari.Venalainen@fmi.fi

RT6 Plenary Prague GA

Observed number of snow cover days

Ari Venäläinen and Kirsti Jylhä Ari.Venalainen@fmi.fi

RT6 Plenary Prague GA

• 12 observing stations

• Variable length of time series

• Monthly data about 100 years, daily about 50 years

• Parameters examined: – monthly, two week, five day, daily and six hour

precipitation

– the length of dry spells (thresholds 10, 50, 100 and 200 mm)

Precipitation extremes in Finland

Ari Venäläinen and Kirsti Jylhä Ari.Venalainen@fmi.fi

RT6 Plenary Prague GA

The variation of return level estimates for dry spell lengths among the studied 12 stations

Ari Venäläinen and Kirsti Jylhä Ari.Venalainen@fmi.fi

RT6 Plenary Prague GA

The variation of return level estimates for monthly, two weeks and daily precipitation among the studied 12 stations.

Ari Venäläinen and Kirsti Jylhä Ari.Venalainen@fmi.fi

RT6 Plenary Prague GA

CONCLUSIONS

•Large differences in the return levels between the 12 stations used in the study, i.e. the level that represents a 10 year return period at one station may be a 500 year level at another location. •These differences may be caused not only by the spatial variation of climate but also by the relatively short measuring periods and the limitations statistical extreme value analyses have. •The physics behind the most rare events may be something that we are not able to take into account.

The changing climate causes further challenges when calculating the return periods. What is past, present and future climate?

Future work; similar kind calculations using climate scenarios.

Ari Venäläinen and Kirsti Jylhä Ari.Venalainen@fmi.fi