21 research outputs found
Winds and windstorms in northern Europe and Finland
Strong winds can cause large impacts and damage to society. Many sectors, such as wind energy, forestry and insurance, are highly affected by winds. Thus, preparedness and adaptation to winds and windstorms is essential in both weather (days) and climate (decades) time scales. The aim of this thesis is to better understand the near surface mean and extreme wind climate in northern Europe and Finland and the role of extratropical cyclones in contributing to the extreme winds.
This thesis investigated the main characteristics of wind and windstorm climate in northern Europe and Finland over a 40-year period. The wind and windstorm climate was found to have large inter-annual and decadal variability and no significant linear trends. The well-known seasonal cycle was detected: winds in northern Europe are up to 30 % stronger in winter than in summer and while there are on average 5â6 windstorms per month in winter in northern Europe there are none in summer months. A more surprising result was that the number of all extratropical cyclones does not vary between seasons. Windstorms were found to be the most frequent over the Barents Sea whereas weaker extratropical cyclones occur over the land areas in northern Europe.
The development and structure of strong winds in windstorms in northern Europe and Finland were examined. The results show that the strongest wind gusts associated with windstorms shift and extend from the warm sector to behind the cold front during the evolution. The cold-season (OctâMar) windstorms are overall stronger and spatially larger than warm-season (AprâSep) windstorms. For example, the central pressure is on average 9 hPa deeper and the maximum wind gust 2 ms-1 stronger in cold-season windstorms than in warm-season windstorms. Analysing a case study of storm Mauri, a damaging windstorm in Finland in September 1982, shows that an individual windstorm development can vary largely from the climateâs general concept. The case study also found that during storm Mauri the wind speeds over land areas in Finland are underestimated in the weather model by 2â13 ms-1 compared to observations, but the location of strong winds is correctly predicted.
Lastly, this thesis investigated what meteorological factors affect the intensity of windstorms in northern Europe. This was studied by using an ensemble sensitivity method. The sensitivities of windstorm intensity to all studied meteorological factors were 20â75 % higher in the cold season than in the warm season. This implies that cold season windstorms are potentially better predictable than warm-season windstorms. The strongest impact to the intensity of northern Europe windstorms is from the low-level temperature gradient which is therefore an important variable to follow when forecasting windstorms. The results from this thesis highlight the importance of examining long-term inter-annual variations, instead of just linear trends, to get a broader understanding of the climate. Moreover, the results emphasize the need of both general conceptual models and individual case studies to better understand the large variety of windstorm development paths.Voimakkaat tuulet voivat aiheuttaa vaikutuksia ja tuhoja yhteiskunnalle. Tuulisuus vaikuttaa moniin aloihin, kuten tuulienergia-, metsĂ€- ja vakuutussektoreihin. Varautuminen ja sopeutuminen tuuliin ja myrskyihin ovat nĂ€in ollen tĂ€rkeitĂ€ sekĂ€ sÀÀn (pĂ€iviĂ€) ettĂ€ ilmaston (vuosikymmeniĂ€) aikaskaaloissa. TĂ€mĂ€n vĂ€itöskirjan tavoitteena on ymmĂ€rtÀÀ paremmin maanpinnan lĂ€heisten keski- ja ÀÀrituulten ilmastoa Pohjois-Euroopassa ja Suomessa sekĂ€ keskileveysasteiden matalapaineiden roolia ÀÀrituulten aiheuttajana.
TĂ€ssĂ€ vĂ€itöskirjassa tutkittiin Pohjois-Euroopan ja Suomen tuuli- ja myrskyilmaston tyypillisiĂ€ piirteitĂ€ 40 vuoden jaksolta. Tuuli- ja myrskyilmastolle havaittiin tyypilliseksi suuri vuosien ja vuosikymmenien vĂ€linen vaihtelu ilman merkitseviĂ€ pitkĂ€najan trendejĂ€. Tutkimuksessa osoitettiin tiedetty kausivaihtelu: tuulet ovat Pohjois Euroopassa jopa 30 % voimakkaampia talvella kuin kesĂ€llĂ€, ja talvikuukausina Pohjois-Euroopassa esiintyy keskimÀÀrin 5â6 myrskyĂ€ kuukaudessa kun taas kesĂ€kuukausina ei yhtÀÀn. YllĂ€ttĂ€vĂ€mpi tulos oli, ettĂ€ kaikkien matalapaineiden mÀÀrĂ€ssĂ€ ei löydetty kausittaista vaihtelua. MyrskyjĂ€ havaittiin esiintyvĂ€n eniten Barentsin meren yllĂ€ kun taas heikommat matalapaineet esiintyvĂ€t Pohjois-Euroopan maa-alueilla.
TyössĂ€ tutkittiin Pohjois-Euroopan myrskyihin liittyvien voimakkaiden tuulten kehittymistĂ€ ja rakennetta. Tulokset osoittavat, ettĂ€ voimakkaimmat myrskyihin liittyvĂ€t puuskat siirtyvĂ€t ja leviĂ€vĂ€t lĂ€mpimĂ€stĂ€ sektorista kylmĂ€n rintaman taakse myrskyn kehittymisen aikana. KylmĂ€n vuodenajan (lokaâmaaliskuu) myrskyt ovat yleisesti voimakkaampia ja alueellisesti laajempia kuin lĂ€mpimĂ€n vuodenajan (huhtiâsyyskuu) myrskyt. Esimerkiksi myrskyn minimipaine on keskimÀÀrin 9 hPa matalampi ja maksimipuuska 2 ms-1 voimakkaampi kylmĂ€nĂ€ kuin lĂ€mpimĂ€nĂ€ vuodenaikana. Tapaustutkimus Mauri-myrskystĂ€, tuhoisasta myrskystĂ€ Suomessa 22.9.1982, osoittaa, ettĂ€ yksittĂ€isen myrskyn kehitys voi poiketa suuresti ilmaston yleisestĂ€ kehitysmallista. Tapaustutkimuksessa selvisi myös, ettĂ€ sÀÀmalli aliarvioi Suomen maa-alueilla Mauri-myrskyn tuulennopeuksia 2â13 ms-1 havaintoihin verrattuna, mutta voimakkaiden tuulten sijainnit on ennustettu oikein.
ViimeisimpĂ€nĂ€ vĂ€itöskirjassa tutkittiin mitkĂ€ meteorologiset tekijĂ€t vaikuttavat myrskyn voimakkuuteen Pohjois Euroopassa. TĂ€tĂ€ tutkittiin kĂ€yttĂ€mĂ€llĂ€ nk. parviherkkyysmenetelmÀÀ. Myrskyn voimakkuuden herkkyydet kaikkiin tutkittuihin meteorologisiin tekijöihin olivat 20â75 % korkeampia kylmĂ€nĂ€ kuin lĂ€mpimĂ€nĂ€ vuodenaikana. TĂ€mĂ€ viittaa siihen, ettĂ€ kylmĂ€n vuodenajan myrskyt ovat potentiaalisesti paremmin ennustettavissa kuin lĂ€mpimĂ€n vuodenajan myrskyt. Pohjois-Euroopan myrskyjen voimakkuuteen vaikuttaa eniten alailmakehĂ€n vaakasuuntainen lĂ€mpötilaero, joka tĂ€ten on tĂ€rkeĂ€ seurattava muuttuja myrskyjĂ€ ennustettaessa.
TÀmÀn vÀitöskirjan tulokset korostavat tÀrkeyttÀ tarkastella pitkÀnajan vuosien vÀlistÀ vaihtelua pelkkien lineaaristen trendien sijaan, jotta ilmastoa ymmÀrrettÀisiin laajemmin. LisÀksi tulokset korostavat tarvetta sekÀ yleisille kÀsitemalleille ettÀ yksitÀisille tapaustutkimuksille, jotta myrskyjen moninaisia kehityspolkuja ymmÀrrettÀisiin paremmin
Winds and windstorms in northern Europe and Finland
Strong winds can cause large impacts and damage to society. Many sectors, such as wind energy, forestry and insurance, are highly affected by winds. Thus, preparedness and adaptation to winds and windstorms is essential in both weather (days) and climate (decades) time scales. The aim of this thesis is to better understand the near surface mean and extreme wind climate in northern Europe and Finland and the role of extratropical cyclones in contributing to the extreme winds.
This thesis investigated the main characteristics of wind and windstorm climate in northern Europe and Finland over a 40-year period. The wind and windstorm climate was found to have large inter-annual and decadal variability and no significant linear trends. The well-known seasonal cycle was detected: winds in northern Europe are up to 30 % stronger in winter than in summer and while there are on average 5â6 windstorms per month in winter in northern Europe there are none in summer months. A more surprising result was that the number of all extratropical cyclones does not vary between seasons. Windstorms were found to be the most frequent over the Barents Sea whereas weaker extratropical cyclones occur over the land areas in northern Europe.
The development and structure of strong winds in windstorms in northern Europe and Finland were examined. The results show that the strongest wind gusts associated with windstorms shift and extend from the warm sector to behind the cold front during the evolution. The cold-season (OctâMar) windstorms are overall stronger and spatially larger than warm-season (AprâSep) windstorms. For example, the central pressure is on average 9 hPa deeper and the maximum wind gust 2 ms-1 stronger in cold-season windstorms than in warm-season windstorms. Analysing a case study of storm Mauri, a damaging windstorm in Finland in September 1982, shows that an individual windstorm development can vary largely from the climateâs general concept. The case study also found that during storm Mauri the wind speeds over land areas in Finland are underestimated in the weather model by 2â13 ms-1 compared to observations, but the location of strong winds is correctly predicted.
Lastly, this thesis investigated what meteorological factors affect the intensity of windstorms in northern Europe. This was studied by using an ensemble sensitivity method. The sensitivities of windstorm intensity to all studied meteorological factors were 20â75 % higher in the cold season than in the warm season. This implies that cold season windstorms are potentially better predictable than warm-season windstorms. The strongest impact to the intensity of northern Europe windstorms is from the low-level temperature gradient which is therefore an important variable to follow when forecasting windstorms. The results from this thesis highlight the importance of examining long-term inter-annual variations, instead of just linear trends, to get a broader understanding of the climate. Moreover, the results emphasize the need of both general conceptual models and individual case studies to better understand the large variety of windstorm development paths.Voimakkaat tuulet voivat aiheuttaa vaikutuksia ja tuhoja yhteiskunnalle. Tuulisuus vaikuttaa moniin aloihin, kuten tuulienergia-, metsĂ€- ja vakuutussektoreihin. Varautuminen ja sopeutuminen tuuliin ja myrskyihin ovat nĂ€in ollen tĂ€rkeitĂ€ sekĂ€ sÀÀn (pĂ€iviĂ€) ettĂ€ ilmaston (vuosikymmeniĂ€) aikaskaaloissa. TĂ€mĂ€n vĂ€itöskirjan tavoitteena on ymmĂ€rtÀÀ paremmin maanpinnan lĂ€heisten keski- ja ÀÀrituulten ilmastoa Pohjois-Euroopassa ja Suomessa sekĂ€ keskileveysasteiden matalapaineiden roolia ÀÀrituulten aiheuttajana.
TĂ€ssĂ€ vĂ€itöskirjassa tutkittiin Pohjois-Euroopan ja Suomen tuuli- ja myrskyilmaston tyypillisiĂ€ piirteitĂ€ 40 vuoden jaksolta. Tuuli- ja myrskyilmastolle havaittiin tyypilliseksi suuri vuosien ja vuosikymmenien vĂ€linen vaihtelu ilman merkitseviĂ€ pitkĂ€najan trendejĂ€. Tutkimuksessa osoitettiin tiedetty kausivaihtelu: tuulet ovat Pohjois Euroopassa jopa 30 % voimakkaampia talvella kuin kesĂ€llĂ€, ja talvikuukausina Pohjois-Euroopassa esiintyy keskimÀÀrin 5â6 myrskyĂ€ kuukaudessa kun taas kesĂ€kuukausina ei yhtÀÀn. YllĂ€ttĂ€vĂ€mpi tulos oli, ettĂ€ kaikkien matalapaineiden mÀÀrĂ€ssĂ€ ei löydetty kausittaista vaihtelua. MyrskyjĂ€ havaittiin esiintyvĂ€n eniten Barentsin meren yllĂ€ kun taas heikommat matalapaineet esiintyvĂ€t Pohjois-Euroopan maa-alueilla.
TyössĂ€ tutkittiin Pohjois-Euroopan myrskyihin liittyvien voimakkaiden tuulten kehittymistĂ€ ja rakennetta. Tulokset osoittavat, ettĂ€ voimakkaimmat myrskyihin liittyvĂ€t puuskat siirtyvĂ€t ja leviĂ€vĂ€t lĂ€mpimĂ€stĂ€ sektorista kylmĂ€n rintaman taakse myrskyn kehittymisen aikana. KylmĂ€n vuodenajan (lokaâmaaliskuu) myrskyt ovat yleisesti voimakkaampia ja alueellisesti laajempia kuin lĂ€mpimĂ€n vuodenajan (huhtiâsyyskuu) myrskyt. Esimerkiksi myrskyn minimipaine on keskimÀÀrin 9 hPa matalampi ja maksimipuuska 2 ms-1 voimakkaampi kylmĂ€nĂ€ kuin lĂ€mpimĂ€nĂ€ vuodenaikana. Tapaustutkimus Mauri-myrskystĂ€, tuhoisasta myrskystĂ€ Suomessa 22.9.1982, osoittaa, ettĂ€ yksittĂ€isen myrskyn kehitys voi poiketa suuresti ilmaston yleisestĂ€ kehitysmallista. Tapaustutkimuksessa selvisi myös, ettĂ€ sÀÀmalli aliarvioi Suomen maa-alueilla Mauri-myrskyn tuulennopeuksia 2â13 ms-1 havaintoihin verrattuna, mutta voimakkaiden tuulten sijainnit on ennustettu oikein.
ViimeisimpĂ€nĂ€ vĂ€itöskirjassa tutkittiin mitkĂ€ meteorologiset tekijĂ€t vaikuttavat myrskyn voimakkuuteen Pohjois Euroopassa. TĂ€tĂ€ tutkittiin kĂ€yttĂ€mĂ€llĂ€ nk. parviherkkyysmenetelmÀÀ. Myrskyn voimakkuuden herkkyydet kaikkiin tutkittuihin meteorologisiin tekijöihin olivat 20â75 % korkeampia kylmĂ€nĂ€ kuin lĂ€mpimĂ€nĂ€ vuodenaikana. TĂ€mĂ€ viittaa siihen, ettĂ€ kylmĂ€n vuodenajan myrskyt ovat potentiaalisesti paremmin ennustettavissa kuin lĂ€mpimĂ€n vuodenajan myrskyt. Pohjois-Euroopan myrskyjen voimakkuuteen vaikuttaa eniten alailmakehĂ€n vaakasuuntainen lĂ€mpötilaero, joka tĂ€ten on tĂ€rkeĂ€ seurattava muuttuja myrskyjĂ€ ennustettaessa.
TÀmÀn vÀitöskirjan tulokset korostavat tÀrkeyttÀ tarkastella pitkÀnajan vuosien vÀlistÀ vaihtelua pelkkien lineaaristen trendien sijaan, jotta ilmastoa ymmÀrrettÀisiin laajemmin. LisÀksi tulokset korostavat tarvetta sekÀ yleisille kÀsitemalleille ettÀ yksitÀisille tapaustutkimuksille, jotta myrskyjen moninaisia kehityspolkuja ymmÀrrettÀisiin paremmin
Climatology, variability, and trends in near-surface wind speeds over the North Atlantic and Europe during 1979-2018 based on ERA5
This study presents the monthly 10âm wind speed climatology, decadal variability and possible trends in the North Atlantic and Europe from ERA5 reanalysis from 1979 to 2018 and investigates the physical reasons for the decadal variability. Additionally, temporal time series are examined in three locations: the central North Atlantic, Finland and Iberian Peninsula. The 40âyear mean and the 98th percentile wind speeds emphasize a distinct landâsea contrast and a seasonal variation with the strongest winds over the ocean and during winter. The strongest winds and the highest variability are associated with the storm tracks and local wind phenomena such as the mistral. The extremeness of the winds is examined with an extreme wind factor (the 98th percentile divided by mean wind speeds) which in all months is higher in southern Europe than in northern Europe. Mostly no linear trends in 10âm wind speeds are identified in the three locations but large annual and decadal variability is evident. The decadal 10âm wind speeds were stronger than average in the 1990s in northern Europe and in the 1980s and 2010s in southern Europe. These decadal changes were largely explained by the positioning of the jet stream and storm tracks and the strength of the northâsouth pressure gradient in the North Atlantic. The 10âm winds have a positive correlation with the North Atlantic Oscillation in the central North Atlantic and Finland on annual scales and during cold season months and a negative correlation in Iberian Peninsula mostly from July to March. The Atlantic Multiâdecadal Oscillation has a moderate negative correlation with the winds in the central North Atlantic but no correlation in Finland and Iberian Peninsula. Overall, our results emphasize that while linear trends in wind speeds may show a general longâterm trend, more information on the changes is obtained by analysing longâterm variability.This study presents the monthly 10-m wind speed climatology, decadal variability and possible trends in the North Atlantic and Europe from ERA5 reanalysis from 1979 to 2018 and investigates the physical reasons for the decadal variability. Additionally, temporal time series are examined in three locations: the central North Atlantic, Finland and Iberian Peninsula. The 40-year mean and the 98th percentile wind speeds emphasize a distinct land-sea contrast and a seasonal variation with the strongest winds over the ocean and during winter. The strongest winds and the highest variability are associated with the storm tracks and local wind phenomena such as the mistral. The extremeness of the winds is examined with an extreme wind factor (the 98th percentile divided by mean wind speeds) which in all months is higher in southern Europe than in northern Europe. Mostly no linear trends in 10-m wind speeds are identified in the three locations but large annual and decadal variability is evident. The decadal 10-m wind speeds were stronger than average in the 1990s in northern Europe and in the 1980s and 2010s in southern Europe. These decadal changes were largely explained by the positioning of the jet stream and storm tracks and the strength of the north-south pressure gradient in the North Atlantic. The 10-m winds have a positive correlation with the North Atlantic Oscillation in the central North Atlantic and Finland on annual scales and during cold season months and a negative correlation in Iberian Peninsula mostly from July to March. The Atlantic Multi-decadal Oscillation has a moderate negative correlation with the winds in the central North Atlantic but no correlation in Finland and Iberian Peninsula. Overall, our results emphasize that while linear trends in wind speeds may show a general long-term trend, more information on the changes is obtained by analysing long-term variability.Peer reviewe
Characteristics of extratropical cyclones and precursors to windstorms in northern Europe
Peer reviewe
Salamahavainnot 2016 - Lightning observations in Finland, 2016
Ilmatieteen laitos on koonnut ja julkaissut salamanlaskijoiden havainnot vuosilta 1960â1997. Vuodesta 1998 lĂ€htien kaikki jĂ€rjestelmĂ€lliset maasalamahavainnot perustuvat salamanpaikantimeen, jonka nykyinen malli aloitti toimintansa elokuussa 1997. Se kĂ€sitti 2016 kahdeksan anturia, pohjoisin Lokassa. Vuodesta 2002 mukana ovat olleet lisĂ€ksi Norjan ja Ruotsin anturit, joiden ansiosta koko Lappi on katettu ja suorituskyky on parantunut myös muualla Suomessa, sekĂ€ yksi anturi Virossa (mukaan vuonna 2005) ja kolme anturia Liettuassa (mukaan 2014). Laitteisto paikantaa maasalamoista erikseen jokaisen osaiskun ja ryhmittelee ne kokonaisiksi salamoiksi. Paikannettu
salama voi sisÀltÀÀ 1-15 iskua; keskiarvo Suomessa on vajaa kaksi iskua/salama. Tilastoinnin pohjana kÀytetÀÀn salama- eikÀ iskumÀÀriÀ, koska salama on ilmastollisesti edustavampi suure. KesÀn 2016 aikana paikannettiin Suomen noin 115 000 maasalamaa, joka on hieman alle keskimÀÀrÀisen
(138 000). Suurin osa salamoista esiintyi heinÀkuussa (80 000), ja touko-, kesÀ- ja elokuussa mÀÀrÀt olivat noin puolet keskimÀÀrÀisestÀ
Review on winds, extratropical cyclones and their impacts in Northern Europe and Finland
Strong winds caused by powerful extratropical cyclones are one of the most dangerous and damaging weather phenomena in Northern Europe. Stormy winds can generate extreme waves and rise the sea level, which leads occasionally to storm surges in coastal areas. In land areas, strong winds can cause extensive forest damage. In general, windstorms induce annually significant damage for society. Moreover, due to climate change, the frequency and the impacts caused by the windstorms is changing.
In this report, we introduce a literature review on the occurrence of strong winds, extratropical cyclones and their impacts in Northern Europe. We present the most important findings on both past trends and current climate on wind speeds and extratropical cyclones based on in-situ measurements and reanalysis data. We also briefly analyse impacts caused by extreme convective weather. Furthermore, we aim to respond to the question on how the wind climate in Northern Europe is going to change in the future under climate change.
The decadal changes in the frequency of extratropical cyclones in Northern Europe follows the changes in the storm track regions. Regarding the past climate, confident estimates of the past trends are difficult to make due to inhomogeneities in the number and type of assimilated wind speeds into reanalysis data. Based on homogenized in-situ observations, the wind climatology in 1959-2015 in Finland shows a slight downward trend, but no trend is evident in the number of potential forest damage days in Finland. Possible change points are however detected for wind speeds and the impacts. Forest damage is not only a function of wind speeds but also the environmental factors, such as the amount of frost in the ground, play a role.
In the future, the strongest signal in Northern Europe for slightly increasing wind speeds is in the autumn while other seasons do not show remarkable trends. It has been shown that the total number of the strongest windstorms are projected to decrease in the North Atlantic and Europe, but regional differences are likely to appear due to changes in the storm tracks. The strong wind gusts associated with thunderstorms in parts of Northern Europe will likely increase in frequency by the end of the 21st century.Voimakkaista keskileveysasteiden matalapaineista johtuvat myrskytuulet ovat yksi eniten vaaraa ja vahinkoa aiheuttavista sÀÀilmiöistÀ Pohjois-Euroopassa. Myrskytuulet aiheuttavat korkeita aaltoja ja nostavat meriveden pintaa, mikÀ johtaa toisinaan merivesitulviin. SisÀmaassa voimakkaat myrskytuulet aiheuttavat ajoittain laajoja metsÀtuhoja. MyrskyistÀ koituu vuosittain merkittÀviÀ vahinkoja yhteiskunnalle. Ilmastonmuutoksen myötÀ myrskyjen toistuvuus ja tuulista johtuvat tuhot muuttuvat.
Raportissa kÀydÀÀn kirjallisuuden pohjalta lÀpi voimakkaiden tuulien ja myrskyjen esiintyvyyttÀ Pohjois-Euroopassa. Raportissa esitellÀÀn tÀrkeimmÀt havaintoihin ja uusanalyyseihin perustuvat tutkimustulokset tuulista, myrskyistÀ ja niiden vaikutuksista. LisÀksi esitellÀÀn lyhyesti muutoksia konvektiivisten sÀÀhÀiriöiden aiheuttamissa tuulissa. Lopuksi pyritÀÀn vastaamaan kysymykseen, miten tuulisuus tulee muuttumaan Pohjois-Euroopassa ilmastonmuutoksen myötÀ.
Myrskyjen lukumÀÀrÀn alueelliset muutokset ovat sidoksissa myrskyratojen muutoksiin. Menneiden myrskytrendien tutkiminen uusanalyysien avulla on kuitenkin osoittautunut ongelmalliseksi, koska eri uusanalyyseihin on assimiloitu vaihteleva mÀÀrÀ ilmakehÀn havaintoja ja siten aineisto on epÀhomogeenista. YksittÀisten uusanalyysien pohjalta ei nÀin ollen voida tehdÀ varmoja johtopÀÀtöksiÀ menneistÀ myrskytrendeistÀ. Kirjallisuuden mukaan voimakkaat tuulet ovat olleet Suomessa laskusuunnassa vuosina 1959-2015, mutta potentiaaliset metsÀtuhopÀivÀt Suomessa eivÀt nÀytÀ vÀhentyneen. MetsÀtuhojen mÀÀrÀÀn vaikuttaa tuulisuuden lisÀksi myös muun muassa maaperÀn roudan mÀÀrÀ. MetsÀtuhojen ja tuulisuuden trendeissÀ on lisÀksi havaittu viime vuosina mahdollisia kÀÀnnekohtia.
Tutkimusten mukaan Pohjois-Euroopassa ei ole odotettavissa suurta muutosta tuulisuudessa, joskin syksyisin keskimÀÀrÀisen tuulisuuden odotetaan hieman lisÀÀntyvÀn. Voimakkaiden myrskyjen kokonaislukumÀÀrÀ Pohjois-Atlantilla tulee todennÀköisesti laskemaan, mutta alueellisia eroja voi ilmetÀ myrskyratojen muutoksista johtuen. KesÀn rajuilmoihin liittyviÀ voimakkaita tuulenpuuskia voi vuosisadan loppuun mennessÀ Pohjois-Euroopassa esiintyÀ useammin kuin nykyilmastossa
Monoterpenesâ oxidation capacity and rate over a boreal forest : temporal variation and connection to growth of newly formed particles
Peer reviewe
Storm Aila : An unusually strong autumn storm in Finland
Satellite image of storm Aila on 17 September 2020 at 0900 utc. Storm Aila was a high-impact autumn storm in Finland which was well predicted by medium-range forecasts. The extreme winds caused by Aila established new Finnish records for the month of September. (Source: Finnish Meteorological Institute/EUMETSAT.)Peer reviewe
Thunderstorm Activity and Extremes in Vietnam for the Period 2015â2019
Within a meteorological capacity building project in Vietnam, lightning location data and manual (human-observed) thunderstorm day observations were analyzed for the period 2015â2019. The lightning location dataset, based on the global lightning detection system Vaisala GLD360, consists of a total of 315,522,761 lightning strokes. The results indicate that, on average, 6.9 million lightning flashes per year occur in the land areas of Vietnam; this equals a lightning flash density
of 20 flashes kmâ2 yrâ1. The largest average annual flash density values occur in three regions in North, Central and South Vietnam. The majority of lightning occurs in the monsoon season (AprilâSeptember), peaking in May, while in OctoberâMarch, the lightning activity is very modest. During individual intense thunderstorm days, the flash density may exceed 12 flashes kmâ2 dayâ1. Thunderstorms in Central Vietnam are generally more intense, i.e., more lightning is expected on average per one thunderstorm day in Central Vietnam than in other regions. This study is
a continuation of several years of meteorological capacity building in Vietnam, and the results suggest that large socio-economic benefits can be received by understanding the local thunderstorm climatology in high detail, especially in a country such as Vietnam, where lightning causes substantial socio-economic losses annually
The Impact of Serial Cyclone Clustering on Extremely High Sea Levels in the Baltic Sea
In the Baltic Sea, sea level variations are often very pronounced. During the winter season, storm surges caused by strong extratropical cyclones (ETCs) can have major societal impacts on coastal cities. In this study, using reanalysis-based cyclone tracks and in-situ tide gauge records, we show that serial cyclone clustering (SCC) leads to higher sea levels in the Baltic Sea than situations where only one ETC passes the tide gauge. Consequently, almost half of extreme sea level events in the Baltic Sea are associated with cyclone clustering periods. For example, in Helsinki, 45% of the extreme sea level events coincided with SCC periods of three or more ETCs, while only 6% of the events coincided with a single ETC. Our study represents a significant advance in the understanding of the factors influencing sea level variations in the Baltic Sea.Peer reviewe