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An Analysis of (Sub-)Hourly Rainfall in Convection-Permitting Climate Simulations Over Southern Sweden From a User's Perspective
No full textTo date, the assessment of hydrological climate change impacts, not least on pluvial flooding, has been severely limited by i) the insufficient spatial resolution of regional climate models (RCMs) as well as ii) the simplified description of key processes, e.g., convective rainfall generation. Therefore, expectations have been high on the recent generation of high-resolution convection-permitting regional climate models (CPRCMs), to reproduce the small-scale features of observed (extreme) rainfall that are driving small-scale hydrological hazards. Are they living up to these expectations? In this study, we zoom in on southern Sweden and investigate to which extent two climate models, a 3-km resolution CPRCM (HCLIM3) and a 12-km non-convection permitting RCM (HCLIM12), are able to reproduce the rainfall climate with focus on short-duration extremes. We use three types of evaluation-intensity-based, time-based and event-based-which have been designed to provide an added value to users of high-intensity rainfall information, as compared with the ways climate models are generally evaluated. In particular, in the event-based evaluation we explore the prospect of bringing climate model evaluation closer to the user by investigating whether the models are able to reproduce a well-known historical high-intensity rainfall event in the city of Malmo 2014. The results very clearly point at a substantially reduced bias in HCLIM3 as compared with HCLIM12, especially for short-duration extremes, as well as an overall better reproduction of the diurnal cycles. Furthermore, the HCLIM3 model proved able to generate events similar to the one in Malmo 2014. The results imply that CPRCMs offer a clear potential for increased confidence in future projections of small-scale hydrological climate change impacts, which is crucial for climate-proofing, e.g., our cities, as well as climate modeling in general
Evaluating the use of Aeolus satellite observations in the regional numerical weather prediction (NWP) model Harmonie-Arome
No full textFramtida isutbredning i svenska farvatten : Analys av isförhållandena runt år 2040 och 2070
No full textSMHI har analyserat hur havsisens utbredning och beskaffenhet i Bottenviken, Bottenhavet, Ålands hav och Norra Östersjön kan komma att förändras i ett perspektiv på 20 respektive 50 år, vilket motsvarar runt år 2040 och 2070. Analyserna utgår från sju indikatorer som beskriver olika aspekter av havsisens förändring. Indikatorerna är framtagna i samråd med Sjöfartsverket och valda både utifrån tillgång till data och med syfte att vara relevanta ur isbrytningsperspektiv.Som underlag för analyserna ligger historiska observationer från SMHI, det Finska Meteorologiska Institutet (FMI) och Sjöfartsverket, samt klimatscenarier framtagna i tidigare projekt.Klimatscenarier som representerar två olika utsläppsscenarier (RCP4,5 och RCP8,5) har analyserats från totalt tio olika klimatmodellsimuleringar. Klimatscenarier baserade på det lägre utsläppsscenariet (RCP2,6) saknas i underlaget eftersom befintliga klimatmodellsimuleringar för detta scenario bedömdes ha för låg kvalité. Tidsramen för denna utredning medgav inte heller framtagande av nya klimatscenarier.Resultatet av analyserna visar att framtidens isvintrar blir lindrigare med avseende på havsisens maximala utbredning jämfört med kontrollperioden (1975–2004). Issäsongens längd blir också kortare, med störst förändring i de södra delområdena. Inget scenario indikerar dock helt isfria vintrar, och åtminstone Bottenviken väntas i medel bli helt istäckt även i framtiden. I södra Bottenviken kommer is tjockare än 10 cm dock att försvinna för RCP8,5. På 20 års sikt är förändringen av den maximala isutbredningen mindre tydlig på grund av en fortsatt stor naturligt förekommande väderdriven mellanårsvariation. På 50 års sikt däremot är signalen tydligare och visar minskad isutbredning och en något mindre mellanårsvariabilitet.Istäcket förväntas bli tunnare i medel i samtliga delområden och utbredningen av tjock deformerad is förväntas minska. Modellerna saknar dock förmågan att simulera så kallade stampisvallar. Dessa vallar bildas då tunnare is pressas upp mot en landfast iskant eller land vid kraftiga vind- och vågförhållanden, och kan utgöra ett problem för sjöfarten även under lindriga isvintrar. Tunnare och glesare is kommer även att leda till ökade isdriftshastigheter i Bottenviken och Bottenhavet.Antalet dagar med utfärdade isrestriktioner till svenska hamnar förväntas minska i takt med att issäsongen blir kortare och isförhållandena lindrigare. Fördelningen av isrestriktioner förändras också, främst i Bottenviken där de högre isklasserna (1A/B) minskar till fördel för de lägre isklasserna (1C/II) som istället ökar.Förändringar i isutbredning, issäsongens längd och jämnisens medeltjocklek bedöms ha en låg osäkerhet eftersom resultatet styrks av både observationer bakåt i tiden och modellsimuleringarna som ligger förhållandevis nära observationerna. Förändringar i deformation, istjockleksfördelning och isdrift bedöms ha en hög osäkerhet eftersom det saknas eller finns väldigt få observationer som kan styrka resultatet från modellscenarierna.Utredningen begränsas delvis av att data för det lägre strålningsscenariot RCP2,6 och analys av eventuella förändringar i väder- och vindförhållanden saknas. En annan begränsande faktor som kan påverka resultatens tillförlitlighet är det låga antalet regionala klimatmodellsimuleringar med tillförlitliga isparametrar.SMHI has analysed how sea ice conditions in the Bothnian Bay, Bothnian Sea, Åland Sea and northern Baltic Proper may change in a 20 and 50 year perspective relative to 2020. The study is focused on seven indicators describing different aspects of sea ice change. The indicators were identified jointly with the Swedish Maritime Administration (SMA), and chosen based on available data and relevance to ice breaking.The study is based on historical observations from SMHI, the Finnish Meteorological Institute (FMI) and SMA, and climate scenario data from previous projects.Climate scenarios representing two different representative concentration pathways (RCP4.5 and RCP8.5) have been analysed based on a total of ten different climate model simulations. Scenarios based on the lower representative concentration pathway (RCP2.6) are absent because existing datasets for this pathway do not have sufficient quality for sea ice parameters. The time frame for this assignment did not allow for new climate scenario simulations to be produced.The results show that future winters will gradually, on average, have a smaller maximum ice extent compared to the control period (1975-2004). Ice seasons will also get shorter, with the largest differences in the southern areas. None of the scenarios yield ice free winters, and at least Bothnian Bay is expected to become fully ice covered on average, also during future winters. However, in the RCP8.5 scenario, ice with an average thickness of 10 cm or more disappears from the southern Bothnian Bay.In a 20-year perspective, changes in maximum ice extent are less distinct due to large inter-annual variations. In a 50-year perspective the change becomes more distinct and shows decreasing ice extents and smaller inter-annual variations.Level ice is expected to get thinner on average in all analysed areas, and the presence of heavily deformed ice is expected to decrease. However, models lack the ability to simulate brash ice barriers, which are formed when thin ice is pressed against a thicker ice edge or land by wind and waves. These types of barriers can be problematic for ships even in mild winters, and are expected to occur also in the future. Thinner and less dense ice fields also lead to increased ice drift in the Bothnian Bay and Bothnian Sea.The number of days with ice class based traffic restrictions for Swedish harbours are expected to decrease as sea ice thickness become thinner and ice seasons become shorter. The distribution of restrictions will also change, mainly in the Bothnian Bay where days with heavier ice classes (1A/B) decrease and days with lighter ice classes (1C/II) increase.Changes in maximum ice extent, length of ice season and average level ice thickness are judged to have a low uncertainty as the results are supported by both historical observations, and by the fact that model simulations are relatively close to the observations during the historical period. Changes in ice deformation, ice thickness distribution, and ice drift are judged to have a higher degree of uncertainty as there are no or very few observations to support model results.The study is partly limited by the lack of data for the lower RCP2.6 and by lacking analyses of possible changes in meteorological conditions. Another limiting factor is the relatively low number of regional climate model simulations with reliable ice parameters used in the study
What Can We Know About Recent Past Precipitation Over Africa? : Daily Characteristics of African Precipitation From a Large Ensemble of Observational Products for Model Evaluation
No full textThe Assimilation of Temperature and Salinity Profile-Observations For Forecasting the River-Estuary-shelf Waters
No full textBenchmarking an operational hydrological model for providing seasonal forecasts in Sweden
No full textAerosol optics model for black carbon applicable to remote sensing, chemical data assimilation, and climate modelling
No full textAn integrated assessment of the impacts of PM2.5 and black carbon particles on the air quality of a large Brazilian city
No full textData on airborne fine particle (PM2.5) emissions and concentrations in cities are valuable for traffic and air quality managers, urban planners, health practitioners, researchers, and ultimately for legislators and decision makers. Emissions and ambient concentrations of PM2.5 and black carbon (BC) were assessed in the city of Curitiba, southern Brazil. The methodology combined a month-long monitoring campaign with both fixed and mobile instruments, development of emission inventories, and dispersion model simulations on different scales. The mean urban background PM2.5 concentrations during the campaign were 7.3 mu g m(-3) in Curitiba city center, but three- to fourfold higher (25.3 mu g m(-3)) in a residential area on the city's outskirts, indicating the presence of local sources, possibly linked to biomass combustion. BC concentrations seemed to be more uniformly distributed over the city, with mean urban background concentrations around 2 mu g m(-3), half of which due to local traffic emissions. Higher mean BC concentrations (3-5 mu g m(-3)) were found along busy roads. The dispersion modeling also showed high PM2.5 and BC concentrations along the heavily transited ring road. However, the lack of in situ data over these peripheral areas prevented the verification of the model output. The vehicular emission factors for PM2.5 and BC from the literature were found not to be suitable for Curitiba's fleet and needed to be adjusted. The integrated approach of this study can be implemented in other cities, as long as an open data policy and a close cooperation among regional, municipal authorities and academia can be achieved
Particle shuttling and oxidation capacity of sedimentary organic carbon on the Baltic Sea system scale
No full textContinental margin sediments receive most of the particulate organic carbon (POC) deposited on the global seafloor, making them crucial locations in the carbon cycle. However, the complex environments in coastal oceans make it challenging to predict the fate of sedimentary organic carbon (OC) in these areas. Here we use data from 21 sites in the Baltic Sea, representing different biological and physiochemical regimes, to explore controls on sedimentary OC cycling. To this end, we combine in situ measured benthic fluxes of dissolved inorganic carbon (DIC; proxy for OC oxidation) with data on sediment properties. In the Gulf of Bothnia, low sedimentary OC oxidation capacities (yearly DIC flux divided by sedimentary POC inventory) were likely caused by a large fraction of terrestrial material in the POC pool, indicated by low sedimentary chlorophyll a content and high (> 10) carbon:nitrogen ratios. The highest OC oxidation capacities were measured at shallow, permanently oxic sites in the Baltic Proper, where bioturbation likely stimulates OC oxidation. The other sites in the Baltic Proper and all stations in the Gulf of Finland displayed increasing OC oxidation capacities with increasing normalised water depth (station depth divided by maximal depth in the basin). This pattern suggests that substantial quantities of POC are shuttled, through repeated cycles of resuspension-redeposition, from shallow erosion-transport (ET) areas to deep accumulation (A) areas. This interpretation was supported by decreasing sediment age and increasing sedimentary inventories of POC and chlorophyll a with normalised water depth. Our calculations indicate that particle shuttling redistributes almost half of the deposited export production from ET areas to A areas in the Baltic Proper, and that substantial amounts of terrestrial organic material are transported through particle shuttling to the deeper parts of the Gulf of Finland and Gulf of Bothnia. Depositional setting and POC origin can thus be central factors in predicting the distribution and fate of OC in coastal and shelf sediments
Ecological turnover in neotropical freshwater and terrestrial communities during episodes of abrupt climate change
No full textThe last 85,000 years were characterized by high climate and environmental variability on the Yucatan Peninsula. Heinrich stadials are examples of abrupt climate transitions that involved shifts in regional temperatures and moisture availability. Thus, they serve as natural experiments to evaluate the contrasting responses of aquatic and terrestrial ecosystems. We used ostracodes and pollen preserved in a 75.9-m-long sediment core (PI-6, similar to 85 ka) recovered from Lake Peten Itza, Guatemala, to assess the magnitude and velocity of community responses. Ostracodes are sensitive to changes in water temperature and conductivity. Vegetation responds to shifts in temperature and the ratio of evaporation to precipitation. Ostracodes display larger and more rapid community changes than does vegetation. Heinrich Stadial 5-1 (HS5-1) was cold and dry and is associated with lower ostracode and vegetation species richness and diversity. In contrast, the slightly warmer and dry conditions during HS6 and HS5a are reflected in higher ostracode species richness and diversity. Our paleoecological study revealed the greatest ecological turnover for ostracodes occurred from 62.5 to 51.0 ka; for pollen, it was at the Pleistocene/Holocene transition. Future studies should use various climate and environmental indicators from lake and marine sediment records to further explore late glacial paleoclimate causes and effects in the northern neotropics