2010. aasta augustitormi analüüs: sirgäikesetormi dünaamika modelleerimine HARMONIE mudeliga

http://hdl.handle.net/10062/3055

Atmosfääriaerosoolide otsene kiirguslik mõju meteoroloogilistele tingimustele Euroopas

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Kaasaegse atmosfäärifüüsika tähtsaimateks rakendusteks on lähipäevade ilmaprognoos ja tulevikukliima projitseerimine numbriliste mudelite abil. Täpne ilmaprognoos omab suurt majanduslikku väärtust ning aitab äärmuslikes ilmaoludes kaitsta inimeste elusid ja vara. Kliima modelleerimine aitab välja selgitada antropogeenseid mõjusid kliimasüsteemile ja on aluseks kliimamuutuste leevendamise ja kohanemise strateegiate välja töötamisele. Atmosfääriaerosoolid, õhku pihustunud pisikesed vedelad ja tahked osakesed, mõjutavad nii hetkeilma kui ka Maa kliimat. Kuna tuleviku kliimatingimuste hindamisel on kõige suurem määramatus seotud just nimelt aerosoolide mõjudega, on aerosoolide meteoroloogiliste mõjude uurimine väga oluline. Aerosooliosakesed mõjutavad päikese- ja soojuskiirguse levikut atmosfääris ning lisaks ka pilvede omadusi ja sademete teket, kuna aerosooliosakesed on kondensatsioonituumadeks pilvepiiskade moodustumisel. Aerosoolide summaarne mõju Maa kiirgusbilansile on vastassuunaline kasvuhoonegaaside mõjule, s.t. aerosoolid jahutavad kliimat. Antud doktoritöös uuriti, kuidas tõsta lühiajaliste numbriliste ilmaprognooside täpsust Euroopa kohal tänu aerosoolide otsese kiirgusliku mõju täpsemale arvestamisele. Doktoritöös leiti, et aerosoolidel on oluline mõju aluspinna energiabilansile ning temperatuuri ja niiskuse jaotusele alumises atmosfääris Euroopa kohal ja et neid mõjusid on vaja numbrilises ilmaennustuses prognoosi täpsuse tagamiseks arvesse võtta. Aerosoolide mõju arvestamine tagab päikesekiirguse kiiritustiheduse täpsema prognoosi, mis on vajalik päikeseenergia tootmise planeerimisel. Kui aerosoolide kontsentratsioonid atmosfääris on väga kõrged, tuleks keskmise klimatoloogilise aerosooli mõju arvestamise asemel prognoosi täpsuse tagamiseks arvesse võtta realistlikku (antud hetkele iseloomulikku) aerosooli mõju. Lisaks näidati aerosoolide nõrgendavat mõju üle Balti riikide ja Soome liikunud ekstreemsele konvektiivsele tormile.The most important applications of modern-day atmospheric physics are numerical weather prediction and projections of the future climate. Accurate weather forecasts provide great economic benefits and help to protect human lives and property. Climate modelling helps to determine anthropogenic influences on climate and it forms the basis for climate change mitigation and adaptation strategies. Atmospheric aerosols, tiny solid and liquid particles suspended in the air, influence both short-term weather conditions and the Earth's climate. It is very important to study aerosol impacts on meteorological conditions because in the projections of future climate the largest uncertainty is related to aerosol impacts. Aerosols influence the shortwave and longwave radiative transfer in the atmosphere and the properties of clouds and the formation of precipitation because aerosol particles serve as cloud condensation nuclei. The net effect of aerosols on the Earth's radiative budget is negative and they offset part of the warming induced by greenhouse gases. In this thesis, increasing of the accuracy of short-term numerical weather forecasts over Europe was investigated by improving the representation of the direct radiative effect of aerosols in an atmospheric model. It was found that aerosols have a considerable influence on the energy budget at the Earth's surface and temperature and humidity distributions in the lower atmosphere over Europe and it is necessary to account for the aerosol impacts in order to provide accurate numerical weather forecasts. Including a better representation of the direct radiative effect of aerosols leads to more accurate forecasts of the surface shortwave fluxes which are also necessary for solar energy applications. During periods with very high aerosol concentrations in the atmosphere, the influence of realistic aerosols should be accounted for. In addition, the weakening of a severe convective storm due to the influence of aerosols was demonstrated in this thesis

Weak average liquid-cloud-water response to anthropogenic aerosols

The cooling of the Earth’s climate through the effects of anthropogenic aerosols on clouds offsets an unknown fraction of greenhouse gas warming. An increase in the amount of water inside liquid-phase clouds induced by aerosols, through the suppression of rain formation, has been postulated to lead to substantial cooling, which would imply that the Earth’s surface temperature is highly sensitive to anthropogenic forcing. Here we provide direct observational evidence that, instead of a strong increase, aerosols cause a relatively weak average decrease in the amount of water in liquid-phase clouds compared with unpolluted clouds. Measurements of polluted clouds downwind of various anthropogenic sources—such as oil refineries, smelters, coal-fired power plants, cities, wildfires and ships—reveal that aerosol-induced cloud-water increases, caused by suppressed rain formation, and decreases, caused by enhanced evaporation of cloud water, partially cancel each other out. We estimate that the observed decrease in cloud water offsets 23% of the global climate-cooling effect caused by aerosol-induced increases in the concentration of cloud droplets. These findings invalidate the hypothesis that increases in cloud water cause a substantial climate cooling effect and translate into reduced uncertainty in projections of future climate

Volcano and ship tracks indicate excessive aerosol-induced cloud water increases in a climate model

Aerosol-cloud interaction is the most uncertain mechanism of anthropogenic radiative forcing of Earth’s climate, and aerosol-induced cloud water changes are particularly poorly constrained in climate models. By combining satellite retrievals of volcano and ship tracks in stratocumulus clouds, we compile a unique observational dataset and confirm that liquid water path (LWP) responses to aerosols are bidirectional, and on average the increases in LWP are closely compensated by the decreases. Moreover, the meteorological parameters controlling the LWP responses are strikingly similar between the volcano and ship tracks. In stark contrast to observations, there are substantial unidirectional increases in LWP in the Hadley Centre climate model, because the model accounts only for the decreased precipitation efficiency and not for the enhanced entrainment drying. If the LWP increases in the model were compensated by the decreases as the observations suggest, its indirect aerosol radiative forcing in stratocumulus regions would decrease by 45%

Large-scale industrial cloud perturbations confirm bidirectional cloud water responses to anthropogenic aerosols

Aerosols offset a poorly quantified fraction of anthropogenic greenhouse gas warming, and the aerosol impact on clouds is the most uncertain mechanism of anthropogenic climate forcing. Here, observations of a relatively weak average response of liquid cloud water to aerosol perturbations are extended to much larger areas than in previous studies, with the polluted cloud areas covering hundreds by hundreds of kilometers. Polluted clouds detected in satellite images at the global anthropogenic air pollution hot spot of Norilsk, Russia, and at other various major aerosol source regions show close compensation between aerosol-induced cloud water increases and decreases. In the sampled Norilsk cloud perturbations the decrease in LWP offsets 3% of the radiative forcing through the Twomey effect on average. Weak cloud water response on average in large polluted areas is in very good agreement with previous results based on observations of small-scale ship-track-likeindustrial cloud perturbations, helping to reduce the uncertainty associated with the anthropogenic aerosol impacts on clouds

Sensitivity of radiative fluxes to aerosols in the ALADIN-HIRLAM numerical weather prediction system

The direct radiative effect of aerosols is taken into account in many limited-area numerical weather prediction models using wavelength-dependent aerosol optical depths of a range of aerosol species. We studied the impact of aerosol distribution and optical properties on radiative transfer, based on climatological and more realistic near real-time aerosol data. Sensitivity tests were carried out using the single-column version of the ALADIN-HIRLAM numerical weather prediction system, set up to use the HLRADIA simple broadband radiation scheme. The tests were restricted to clear-sky cases to avoid the complication of cloud–radiation–aerosol interactions. The largest differences in radiative fluxes and heating rates were found to be due to different aerosol loads. When the loads are large, the radiative fluxes and heating rates are sensitive to the aerosol inherent optical properties and the vertical distribution of the aerosol species. In such cases, regional weather models should use external real-time aerosol data for radiation parametrizations. Impacts of aerosols on shortwave radiation dominate longwave impacts. Sensitivity experiments indicated the important effects of highly absorbing black carbon aerosols and strongly scattering desert dust

The HARMONIE–AROME Model Configuration in the ALADIN–HIRLAM NWP System

The aim of this article is to describe the reference configuration of the convection-permitting numerical weather prediction (NWP) model HARMONIE-AROME, which is used for operational short-range weather forecasts in Denmark, Estonia, Finland, Iceland, Ireland, Lithuania, the Netherlands, Norway, Spain, and Sweden. It is developed, maintained, and validated as part of the shared ALADIN–HIRLAM system by a collaboration of 26 countries in Europe and northern Africa on short-range mesoscale NWP. HARMONIE–AROME is based on the model AROME developed within the ALADIN consortium. Along with the joint modeling framework, AROME was implemented and utilized in both northern and southern European conditions by the above listed countries, and this activity has led to extensive updates to themodel’s physical parameterizations. In this paper the authors present the differences inmodel dynamics and physical parameterizations compared with AROME, as well as important configuration choices of the reference, such as lateral boundary conditions, model levels, horizontal resolution, model time step, as well as topography, physiography, and aerosol databases used. Separate documentation will be provided for the atmospheric and surface data-assimilation algorithms and observation types used, as well as a separate description of the ensemble prediction system based on HARMONIE–AROME, which is called HarmonEPS

Kliimamuutuste ABC: põhjused, mõjud, lahendused. Teaduspõhine õppematerjal kliimamuutustest

Kliimamuutused kujutavad endast ökosüsteemidele ja inimestele suurt ohtu. Teadus on selge: me peame tegutsema, et inimtekkelistest kliimamuutustest tingitud riske vähendada. Siin astub vahele aga kliimamuutustealase kirjaoskuse laialdane puudumine Eestis. Kliima kirjaoskus lihtsalt seletatuna, sisaldab endas mõistmist, kuidas kliima mõjutab mind ja kogu ühiskonda, aga ka seda, kuidas mina ja meie mõjutame kliimat. Selles sisaldub ka arusaam kuidas vähendada kliimamõju (ehk kliimamuutusi leevendada) ja suurendada vastupanuvõimet kliimamuutustele (ehk kliimamuutustega kohaneda). Eesti inimeste suur kliimaskeptilisus püstitab väga suured tõkked kliimamuutustega kohanemiseks ja nende leevendamiseks. Tegutsemiseks ei piisa üksnes teadmistest, vaid tarvis on ka teadmistele tuginevaid väärtusi, hoiakuid ning oskusi. Siit tulebki vajadus selge riikliku poliitika järele, kuidas inimesi kliimamuutuste vallas harida. Euroopa majanduspiirkonna rahastatavas projektis „KLIIMATEADLIK - Kliimateadlikkus koolist ühiskonda: laste, noorte ja õpetajate võimestamine kliimamuutuste mõjude vähendamiseks“ keskendume kliimahariduse edendamisele Eestis. Teeme seda nii formaalses kui ka mitteformaalses hariduses, et suurendada kliimamuutuste leevendamiseks ja nendega kohanemiseks vajalikke pädevusi. Meie eesmärk on luua Eestis kliimamuutuste haridusprogramm, mis hõlmab kõiki haridustasandeid. Selleks arendame haridusstrateegiaid, loome õppematerjale ja toetame õpetajaid. Esiteks selgitasime välja praeguse kliimahariduse olukorra. Vaatasime läbi riikliku õppekava ning ainekavad. Selgus, et kliimamuutusi käsitletakse iseseisva teemana ainult mõningates loodusainetes. Kuid siingi tutvustatakse kliimat ekslikult kui pelgalt üht osa kohalikest keskkonnatingimustest. Puudub globaalse kliimasüsteemi terviklik käsitlus, mistõttu on kliimamuutuste teemade teistesse ainetesse lõimimine keeruline. Järgmine samm oli õpetamise olukorra väljaselgitamine. Analüüsisime Eestis kasutatavaid õpikuid ja korraldasime õpetajate küsitluse. Selgus, et kahjuks ei sisalda kooliõpikud tänapäevast teaduslikku arusaama kliimamuutustest. Õppematerjalides puuduvad selgitused kliimamuutuste põhjuste ja mõjude kohta. Pealegi ei käsitleta üldse kliimamuutuste leevendamist ja kohanemist. Õpetajate küsitlus andis ühelt poolt väga positiivse vastukaja, sest valdav osa õpetajatest pidas kliimamuutusi oluliseks teemaks ning oli ka nõus end neil teemadel harima. Teiselt poolt kurdavad õpetajad, et puudu on tänapäevased eestikeelsed õppevahendid kliimamuutuste käsitlemiseks. Eriti just mitteloodusainete õpetajad nendivad, et neil puuduvad teadmised, kuidas kliimaprobleeme õppesse lõimida. Projekti KLIIMATEADLIK esimene õppevahend „Kliimamuutuste ABC“ püüab neid tühikuid täita. Siin on kokku võetud tänapäevased teaduspõhised arusaamad kliimamuutustest. Õppematerjal tugineb Valitsustevahelise kliimamuutuste paneeli (IPCC) ja teiste organisatsioonide kliimaraportitele, kus on sünteesitud eelretsenseeritud kliimateadust. Õppematerjal hõlmab kliimamuutuste põhjuseid ja mõjusid koos kliimamuutuste leevendamise ja kohanemisega. Õppevahendi lõid projektipartnerid ühistöös ning seda katsetati 2023. aasta märtsis neljal koolitusel Tartus, Pärnus, Narvas ja Tallinnas, samuti Moodle’i e-õppekeskkonnas. „Kliimamuutuste ABC“ on kättesaadav kõigile huvilistele projekti KLIIMATEADLIK õppevahendite lehel kliimatarkused.ut.ee. See on mõeldud kogu Eesti rahvale. Õppevahend sisaldab mõtlemapanevaid ülesandeid, videoid ning kokkuvõtlikku teksti, milles on rohkelt viiteid. Teksti saab ka soovi korral välja printida. Suur tänu kõigile, kes on selle õppevahendi valmimisel kaasa löönud. Rõõmsat õppimist! Kliimateadlik muudab ühiskonda, mitte kliimat. Piia Post ja Velle Toll. September 2023Trükis valmis projekti “Kliimateadlikkus koolist ühiskonda: laste, noorte ja õpetajate võimestamine kliimamuutuste mõjude vähendamiseks” raames.Projekti rahastatakse Euroopa Majanduspiirkonna Finantsmehhanismi 2014−2021 programmi „Kliimamuutuste leevendamine ja nendega kohanemine“ avatud taotlusvoorust „Kliimateadlikkuse suurendamine

Opportunistic experiments to constrain aerosol effective radiative forcing

Aerosol–cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due to human activities. The nonlinearity of cloud-state changes to aerosol perturbations make it challenging to attribute causality in observed relationships of aerosol radiative forcing. Using correlations to infer causality can be challenging when meteorological variability also drives both aerosol and cloud changes independently. Natural and anthropogenic aerosol perturbations from well-defined sources provide “opportunistic experiments” (also known as natural experiments) to investigate ACI in cases where causality may be more confidently inferred. These perturbations cover a wide range of locations and spatiotemporal scales, including point sources such as volcanic eruptions or industrial sources, plumes from biomass burning or forest fires, and tracks from individual ships or shipping corridors. We review the different experimental conditions and conduct a synthesis of the available satellite datasets and field campaigns to place these opportunistic experiments on a common footing, facilitating new insights and a clearer understanding of key uncertainties in aerosol radiative forcing. Cloud albedo perturbations are strongly sensitive to background meteorological conditions. Strong liquid water path increases due to aerosol perturbations are largely ruled out by averaging across experiments. Opportunistic experiments have significantly improved process-level understanding of ACI, but it remains unclear how reliably the relationships found can be scaled to the global level, thus demonstrating a need for deeper investigation in order to improve assessments of aerosol radiative forcing and climate change