bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of suitable measurement strategies depending on the scales of atmospheric processes
Authors: Foken Thomas , Beyrich Frank , Wulfmeyer Volker
Published: June 2021

The vertical and horizontal structure of the atmosphere and the typical timescales of atmospheric phenomena and processes largely determine the design and performance of atmospheric measurement techniques. Each meteorological process can be characterized by typical spatial and temporal scales. This is based on the spectral organization of atmospheric turbulence and on wavelike processes, where relevant wavelength ranges (spatial dimensions) relate to distinct durations (frequencies). The development of a suitable measurement strategy for any observational task should therefore be based on a careful consideration of the specific processes to be described and resolved. This should govern the decision on, e.g., the measurement range, the measurement levels / range resolution, the horizontal spacing of sensors or sites, the measurement frequencies and averaging times, and sensor characteristics such as response time, resolution, accuracy, sensitivity etc. When using in-situ technologies, a wide variety of measuring platforms can be used, from the classic weather station arrangements, masts, and towers to balloons or controlled airborne platforms (including both manned and remotely piloted aerial vehicles). With remote sensing technology, various measurement systems (both passive and active) are available in terms of measured variables, pointing and scanning options, altitude range, spatial and temporal resolution. It will be shown that the extensive overview tables in the recently published Springer Handbook of Atmospheric Measurements can provide guidance on how in-situ and remote sensing techniques can be optimally used for both routine observations and process studies (field campaigns) for a large variety of applications and how measurement concepts, strategies and networks can be designed.
Initial results of the project SINOPTICA (Satellite-borne and IN-situ Observations to Predict The Initiation of Convection for ATM) 
Authors: Esbri Laura , Llasat Maria Carmen , Rigo Tomeu , Milelli Massimo , Mazzarella Vincenzo , Lagasio Martina , Parodi Andrea , Temme Marco-Michael , Glushenko Olga , Kerschbaum Markus , Biondi Riccardo , Surian Nicola , Realini Eugenio , Gatti Andrea , Tagliaferro Giulio , Parodi Antonio
Published: June 2021

In the framework of the SINOPTICA project (EU H2020 SESAR, 2020 – 2022), different meteorological forecasting techniques are being tested to better nowcast severe weather events affecting Air Traffic Management (ATM) operations. Short-range severe weather forecasts with very high spatial resolution will be obtained starting from radar images, through an application of nowcasting techniques combined with Numerical Weather Prediction (NWP) model with data assimilation. The final goal is to integrate compact nowcast information into an Arrival Manager to support Air Traffic Controllers (ATCO) when sequencing and guiding approaching aircraft even in adverse weather situations. The guidance-support system will enable the visualization of dynamic weather information on the radar display of the controller, and the 4D-trajectory calculation for diversion coordination around severe weather areas. This meteorological information must be compact and concise to not interfere with other relevant information on the radar display of the controller.

Three severe weather events impacting different Italian airports have been selected for a preliminary radar analysis. Some products are considered for obtaining the best radar approach to characterize the severity of the events for ATM interests. Combining the Vertical Integrated Liquid and the Echo Top Maximum products, hazard thresholds are defined for different domains around the airports. The Weather Research and Forecasting (WRF) model has been used to simulate the formation and development of the aforementioned convective events. In order to produce a more accurate very short-term weather forecast (nowcasting), remote sensing data (e.g. radar, GNSS) and conventional observations are assimilated by using a cycling three-dimensional variational technique. This contribution presents some preliminary results on the progress of the project.
Progress toward a holistic land and marine surface meteorological database and a call for additional contributions.
Authors: Noone Simon , Atkinson Chris , Berry David I. , Dunn Robert J.H. , Freeman Eric , Perez Gonzalez Irene , Kennedy John J. , Kent Elizabeth C. , Kettle Anthony , Mc Neill Shelley , Menne Matthew , Stephens Ag , Thorne Peter W. , Tucker William , Voces Corinne , Willet Kate M.
Published: June 2021

Historical observational climate records are crucial in understanding climatic variability, extreme past weather and climate events and allowing us to make informed decisions for better societal adaptation to climate change. Historical observations are also a key component to derive reanalysis products and evaluate climate models.The management of both marine and land historical datasets has been highly fragmented, leading to diverse data holdings held by multiple institutions. Consequently, it is necessary to confront the challenges of: a plethora of distinct data formats; gross duplication of records with differing identifiers, names; and in many cases varying geo-location information. Within available land and marine data holdings there are greatly differing levels of completeness, data quality checks and data processing applied. There are further issues with limited data discovery metadata and sometimes a distinct lack of traceability to the underlying original data source. In light of these issues, we have produced The C3S Global Land and Marine Observations Database which is part of the Copernicus Climate Change Service, making climate data and information more easily accessible to support adaptation and mitigation policies of the European Union and the wider global community  This talk outlines progress of the Global Land and Marine Observations Database service in securing data sources and introduces the data deposit component. We present details of land based data holdings inventoried, highlighting priority needs in terms of periods, regions and Essential Climate Variables (ECVs) where additional land based data could bring most benefit. These holdings are being iteratively merged and integrated to best meet user needs and are served to the user via the Copernicus Climate Data Store (CDS). Details of the current land based data release are also presented in this talk. The secure Data Deposit Service enables any data provider to share additional data and metadata with the service. We encourage all data owners to share their data with the C3S service via our Data Upload Server. All unique and relevant data acquired or submitted will be also archived at the NOAA National Centers for Environmental Information World Data Center for Meteorology, Asheville, North Carolina, USA and used in their data base curation efforts which are being jointly developed.
Stratosphere-Troposphere Coupling and Global Warming
Authors: Manzini Elisa
Published: June 2021

The atmospheric circulation response to the anthropogenic increase of CO2 is known to generally involve a number of pathways of change, often leading to contrasting responses, the so called “tug of wars”. Multiple pathways of change in atmospheric dynamics are due to the development of direct and indirect dynamical responses to global warming, the latter being the thermodynamical response to the anthropogenic increase of CO2. The most known direct dynamical response to global warming is the strengthening and poleward shift of the tropospheric eddy-driven jets, a direct consequence of the tropical upper troposphere warming. During Northern Hemisphere winter, where and when the two-way dynamical stratosphere-troposphere coupling is active, stratosphere-troposphere coupling has been shown to provide for indirect dynamical responses, which are relevant to regional circulation changes, over the North Atlantic and Eurasia, for instance affecting the European precipitation changes. However, it has been found that the dynamical response of the stratospheric vortex is highly uncertain. Changes from ensemble of models (such as the CMIP intercomparisons) show a spread in the stratospheric responses, although the stratospheric response can be significant by model. This spread in the stratospheric responses in turn leads to uncertainty in the impact on surface climate of the stratospheric change. For instance, a stratospheric vortex weakening with global warming will counteract to some extend in some regions, the strengthening and poleward shift of the tropospheric eddy-driven jets. However, a polar vortex strengthening will feedback positively on the strengthening and poleward shift of the tropospheric eddy-driven jets. Here we review our knowledge and include new selected results, based on CMIP6, on the role of dynamical stratosphere-troposphere coupling in providing for pathway of atmospheric circulation changes in response to global warming.
Analysis of Long-Term Solar Resource Variability Using NSRDB Version 3
Authors: Sengupta Manajit , Habte Aron
Published: June 2021

Understanding long-term solar resource variability is essential for planning and deployment of solar energy systems. These variabilities occur due to deterministic effects such as sun cycle and nondeterministic such as complex weather patterns. The NREL’s National Solar Radiation Database (NSRDB) provides long term solar resource data covering 1998- 2019 containing more than 2 million pixels over the Americas and gets updated on an annual basis. This dataset is satellite-based and uses a two-step physical model for it’s development. In the first step we retrieve cloud properties such as cloud mask, cloud type, cloud optical depth and effective radius. The second step uses a fast radiative transfer model to compute solar radiation.  This dataset is ideal for studying solar resource variability. For this study, NSRDB version 3 which contains data from 1998-2017 on a half hourly and 4x4 km temporal and spatial resolution was used. The study analyzed the spatial and temporal trend of solar resource of global horizontal irradiance (GHI) and direct normal irradiance (DNI) using long-term 20-years NSRDB data. The coefficient of variation (COV) was used to analyze the spatio-temporal interannual and seasonal variabilities. The spatial variability was analyzed by comparing the center pixel to neighboring pixels. The spatial variability result showed higher COV as the number of neighboring pixels increased. Similarly, the temporal variability for the NSRDB domain ranges on average from ±10% for GHI and ±20% for DNI. Furthermore, the long-term variabilities were also analyzed using the Köppen-Geiger climate classification. This assisted in the interpretation of the result by reducing the originally large number of pixels into a smaller number of groups. This presentation will provided a unique look at long-term spatial and temporal variability of solar radiation using high-resolution satellite-based datasets.
The Swiss National Centre for Climate Services (NCCS) – accomplishments and future perspectives
Authors: Fischer Andreas , Hama Angela Michiko , Croci-Maspoli Mischa
Published: June 2021

In response to the Global Framework for Climate Services’ (GFCS) call for the establishment of national coordination mechanisms, Switzerland founded its National Centre for Climate Services (NCCS) in late 2015. The Centre is organized as a network of nine Federal Offices and Institutes as well as partners from academia. Based on a federally agreed national adaptation strategy and plan for action, the NCCS is organized in the sense of a nationwide network. All members are on a par and have an equal say. Attention is given to both pure climate information as well as downstream applications along the climate services value chain.

The NCCS pursues three main goals: 1) bundle the existing climate services of the Swiss Confederation, 2) foster dialogue among stakeholder communities, and 3) co-produce new tailored solutions. The co-creation and dissemination of climate services is vital for effective climate mitigation, adaptation and societal transformation. Thus, the NCCS supports policymakers from the national to local level as well as the private sector and society at large in minimizing their risks, maximizing opportunities and optimizing costs.

Since its foundation in 2015, several accomplishments have been made through the NCCS’ priority themes, such as the release of the Swiss climate scenarios (CH2018) in 2018 and hydrological scenarios (Hydro-CH2018) in 2021 as a downstream application. Other accomplishments include novel insights into climate-sensitive disaster risk reduction as well as the elaboration of a new hail climatology serving multiple stakeholders in the insurance sector. Moreover, the NCCS web portal www.nccs.ch has been online for more than two years, serving as a one stop-shop for the provision of tailored climate services, best practices and guidance.

This presentation will give an overview of the NCCS and its first milestones as well as discuss lessons learnt and current challenges. This also includes new perspectives from a new NCCS programme on cross-sectoral climate impacts and the development of respective decision-support tools to be launched in 2021.

 
Analysis of the observed and modelled budburst dates of grapevine in Croatia
Authors: Omazić Branimir , Telišman Prtenjak Maja , Prša Ivan , Karoglan Marko
Published: June 2021

Since changes in temperatures and precipitation significantly affect the biosphere, viticulture as an important economic branch in the moderate latitudes (e.g., mainly between 35°N and 55°N) is strongly influenced by climate change. The most commonly analysed/modelled phenological phases of grapevines are budburst (beginning of grapevine seasonal growth), flowering (crucial for the reproductive cycle) and veraison (initiation of the ripening). Resent studies indicate that budburst is greatly regulated by temperature. Due to climate change and temperature increase, budburst dates show trends in earlier occurrences at several available stations throughout Croatia which increases the vulnerability of the grapevine to the spring frost.

The aim of this study is to determine trends and changes in budburst date, their statistical characteristics at available stations in period 1961-2020 in Croatia. We focus on four grapevine varieties, two white (Graševina and Chardonnay) and two red (Merlot and Plavac Mali) and performance of statistical models (GDD, Riou’s model and BRIN model) that predict budburst dates in the present climate. For this purpose an effect of the dormancy period and base temperature on the simulated budburst date have been explored. The study is further extended to future climatic conditions using statistical and numerical climate models. Therefore, a daily output from three CORDEX Regional Climate Models’ (RCMs) simulations (CLMcom-CCLM4-8-17, SMHI-RCA4, CNRM-ALADIN5.3) for Croatian domain are used. All RCMs are forced by Global Climate Models (GCMs) with a moderate (RCP4.5) and a high-end (RCP8.5) green-house gass (GHG) scenario(s) and all the simulations have horizontal grid spacing of 0.11°. Results indicate further earlier appearance of budburst regardless of varieties.
From open data to global digital public good
Authors: Futsæter Håvard
Published: June 2021

MET Norway has had an open data policy for many years. A permissive open data license, and a freely accessible service through which to gain access to the dataset is the first step. However, the data is not useful before it is understood and used in decision-making.

MET Norway serves many user groups, many of which have very different needs for open meteorological data. To cater for the different user needs, MET Norway provides multiple distribution services. One of our most important open data data services is MET Norway Weather API, a global location based time series forecast service. (https://developer.yr.no/featured-products/forecast/)

MET Norway has recently joined the Digital Public Goods Alliance, to help reach the Sustainable Development Goals(SDG) (https://sdgs.un.org/goals)  by leveraging our MET Norway Weather API service as a digital public good.

“The Digital Public Goods Alliance is a multi-stakeholder initiative with a mission to accelerate the attainment of the sustainable development goals in low- and middle-income countries by facilitating the discovery, development, use of, and investment in digital public goods.” (https://digitalpublicgoods.net/about/)

Moving from open data to a digital public good has meant taking a more active part in identifying, exploring and understanding the needs that low -and middle-income countries have. The needs considered are both end-user needs and gaps/tools/competency needs across the value chain. And we are trying to find ways our data and services can help fill those needs in an operational sustainable way by co-creating applications built on top of our services.

In this presentation we will first describe our experience with serving open and free weather forecast data. Then describe the challenges in moving from open data to working with our data as an SDG.

The presentation will be focused both on user needs and on technical challenges connected to running a global freely available open data service.
The Swiss Alpine zero degree line: methods, past evolution, sensitivities
Authors: Scherrer Simon C. , Gubler Stefanie , Wehrli Kathrin , Fischer Andreas M. , Kotlarski Sven
Published: June 2021

The near-surface zero degree line (ZDL) is a key isotherm in mountain regions worldwide, but a detailed analysis of methods for the ZDL determination, their properties and applicability in a changing climate is missing. We here test different approaches to determine the near-surface ZDL on a monthly scale in the Swiss Alps. A non-linear profile yields more robust and more realistic ZDLs than a linear profile throughout the year and especially in the winter-half year when frequent inversions disqualify a linear assumption. In the period 1871-2019, the Swiss ZDL has risen significantly in every calendar month: In northern Switzerland, the monthly ZDL increases generally amount to 300-400 m with smaller values in April and September (200-250 m) and a larger value in October (almost 500 m). The largest increases of 600-700 m but also very large uncertainties (±400 m, 95% confidence interval) are found in December and January. The trends have accelerated in the last decades especially in spring and summer. The ZDL has increased by ~160 m per °C warming in the summer-half year and up to 340±45 m/°C in winter months. In southern Switzerland, ZDL trends and temperature scalings are somewhat smaller, especially in winter. Sensitivity analyses using a simple shift of the non-linear temperature profile suggest that the winter ZDL-temperature scalings are at a record high today or will reach it in the near future, and are expected to decrease with a strong future warming. Nevertheless, the cumulative ZDL increase for strong warming is considerably larger in winter than in summer. Based on a few key criteria, we also present best practises to determine the ZDL in mountain regions worldwide. The outlined methods lay a foundation for the analysis of further isotherms and to study the future ZDL evolution based on climate scenario data.
Case Study: Planning a low-cost X-band radar network from scratch in Austria
Authors: Peštová Zuzana , Najman Michal
Published: June 2021

A Start-Up company (Meteosense, a subsidiary of Meteopress, Czech republic, and Idokep, Hungary)  in collaboration with a National Meteorological Office in Austria (ZAMG) is preparing and deploying a radar network consisting of affordable X-band weather radars. With a minimum team of three people and based on Lean methodology (Build-Measure-Learn) the plan was set-up with milestones along the way. 

The presentation will describe Stage Zero - radar site selection criteria, planning and simulating, Stage One - upgrading existing radar in Vienna to 2.4 meters antenna and Stage Two - planning and deployment of second radar in Austria. Currently, Stage Two is on the way. Stages Three and further will be also briefly described and mistakes and lessons learned will be revealed. 

In Stage Zero we will describe how we chose locations for new radars and how we plan the expansion of our radar network in Austria with the help of our radar simulators and experience from building weather radar network in the Czech Republic, Slovakia, Hungary and Croatia.

In Stage One we will describe how we upgraded previously installed radar in Vienna from 1.2-meters antenna to 2.4-meters antenna. We will show the problems that occurred during installation and lessons learned will be revealed. We will also show the results and data from this radar.

In Stage Two we will describe the planning and deployment of our second radar in Austria and this stage will also include how we plan and prepare radar installation in general.

Stages Three and further will include our future plans in Austria.
Spatial analysis of extreme hourly and daily precipitation return levels – Borrowing information over space in spite of complex topography
Authors: Frei Christoph , Fukutome Sophie
Published: June 2021

Knowledge of the magnitude of rare precipitation extremes is important for civil protection and infrastructure design. But the preparation of related datasets is methodologically complex. The estimation of, say, the 100-year return value at a location without measurement crucially depends on how much information can be drawn from instrumented locations nearby. Are there prospects for this “borrowing information over space”, when the climate of the region is spatially complex? In this presentation we illustrate that a method of spatial extreme value analysis has great potential, if it can be carefully configured and equipped with climatological knowledge. We also illustrate that spatial integration may be less efficient when the modelling is limited by poor observational coverage. In both cases, it is highly desirable to quantify uncertainties reliably.

Here, we focus on the domain of Switzerland, with a complex topography and climatology. A Bayesian Hierarchical Model, combining the GEV model for block maxima and the Gaussian Random Fields model for spatial dependence, is used to derive km-scale maps of return levels for 24-hour and 1-hour precipitation extremes. The observational coverage is very different between the two durations, with more than 400 stations over 60 years for the 24-hour, but less than 100 stations over 40 years for the 1-hour case. Accordingly, the model configuration for the data-rich case can involve numerous and verifiably informative covariates, whereas the modelling for the data-sparse case is left to be more scrimpy. Our results illustrate the difference in the information gain over space using a set of independent test stations. An additional finding of this study is, that efficient information gain over space is not a given from rich data alone, but depends on a careful model configuration. Advanced methods of data science do not replace a knowledgeable climatologist and patience with simple data exploration.
Summer drought in Switzerland 1981‒2020: Events, trends and drivers
Authors: Scherrer Simon C. , Spirig Christoph , Hirschi Martin , Maurer Felix , Kotlarski Sven
Published: June 2021

The Alpine region has recently experienced several dry summers with negative impacts on the economy, society and ecology. Here, soil water, evapotranspiration and meteorological data from several observational and model-based data sources is used to assess events, trends and drivers of summer drought in Switzerland in the period 1981‒2020. 2003 and 2018 are identified as the driest summers followed by somewhat weaker drought conditions in 2020, 2015 and 2011. We find clear evidence for an increasing summer drying in Switzerland. The observed climatic water balance (-39.2 mm/decade) and 0-1 m soil water from reanalysis (ERA5-Land: -4.7 mm/decade; ERA5: -7.2 mm/decade) show a clear tendency towards summer drying with decreasing trends in most months. Increasing evapotranspiration (potential evapotranspiration: +21.0 mm/decade; ERA5-Land actual evapotranspiration: +15.1 mm/decade) is identified as important driver which scales excellently (+4 to +7%/K) with the observed strong warming of about 2°C. An insignificant decrease in precipitation further enhanced the tendency towards drier conditions. Most simulations of the EURO-CORDEX regional climate model ensemble underestimate the changes in summer drying. They underestimate both, the observed recent summer warming and the small decrease in precipitation. The changes in temperature and precipitation are negatively correlated, i.e. simulations with stronger warming tend to show (weak) decreases in precipitation. However, most simulations and the reanalysis overestimate the correlation between temperature and precipitation and the precipitation-temperature scaling on the interannual time scale. Our results emphasize that the analysis of the regional summer drought evolution and its drivers remains challenging especially with regional climate model data but considerable uncertainties also exist in reanalysis data sets.
The Zilitinkevich Scale in Life and Science
Authors: Esau Igor
Published: June 2021

A prominent scientist, a leader in environmental turbulence and planetary boundary layer research Sergej Zilitinkevich passed away on February 15, 2021.  His scientific  contribution is of a remarkably large scale, and so was his life. In fact, one of his most commonly referred research achievements is now widely known as The Zilitinkevich scale - a length scale of a rotation-stratification turbulent mixing in stably stratified planetary boundary layers. In fact, one of his most significant life achievements can be characterized as organizing large international consortiums to advance the boundary layer research into new territories of non-local turbulence, organized structures, and extreme stratifications. Many of his discoveries are now in textbooks, often cited as classical common knowledge without references. Sergej Zilitinkevich was passionate for truly large-scale international science that combined the best of multidisciplinary approaches and multicultural research schools. In the last decade, he has been leading international efforts to develop an energetically consistent turbulence theory that could be applied to strongly stratified, very-high-Reynolds-number environmental flows. He and collaborators obtained ground-breaking results in the studies of key mechanisms controlling both the stably stratified and convective turbulence. Until present, turbulence in strongly stratified flows such as those found in the free atmosphere and hydrosphere has been parameterized only heuristically; the theoretical and experimental basis behind the computing schemes was rather fragmented. Convective turbulence is still parameterized only heuristically. These and other theoretical advances open opportunities for a novel class of parametrizations for modelling and forecasting of climate, weather, wind-energy potential, and air and water quality. His last project - the Pan-Eurasian experiment - connects more than 100 research groups from 20 countries. It aims to solve interlinked challenges of global warming, atmospheric pollution, biodiversity loss, energy production, and fresh water recognizing the increasing role of the cold climate areas in the context of global change. This presentation commemorates the life and work of our collegue and friend.
Coupled parameter perturbations in the SPP scheme of the HarmonEPS
Authors: Tsiringakis Aristofanis , de Rooy Wim , van der Veen Sibbo , Barkmeijer Jan
Published: June 2021

In an ensemble prediction system (EPS) the uncertainty in the initial atmospheric conditions is usually represented via perturbation of the initial atmospheric state and different boundary conditions at the beginning and throughout the duration of the forecast. These approaches exclude the uncertainty due to the representation of physical processes within the parameterization schemes of a numerical weather prediction model (NWP). Much of the uncertainty in the presentation of physical process arises from uncertain parameter values regulating key physical processes in the boundary-layer and microphysics schemes. This uncertainty can be represented with a Stochastically Perturbed Parameterization (SPP) scheme, where parameter values for the different model grid points are randomly selected from a defined probability density function. The SPP scheme can improve model performance and increase ensemble spread, but may lead to unrealistic parameter values, which can introduce additional model bias. A potential solution is to use coupled/correlated perturbations for relevant SPP parameters to increase the model performance and ensemble spread, while maintaining physically realistic ranges for the parameters. In this study, we investigate the impact of coupled perturbations in key parameters within the boundary-layer and microphysics schemes of the HarmonEPS model using the new SPP scheme. The performance of the coupled perturbations experiment is evaluated against HarmonEPS experiments using independent parameter perturbations, and perturbations in the initial atmospheric state and boundary conditions for both a winter and a summer period.  We find that coupled perturbations in the SPP scheme can decrease model bias and increase the ensemble spread for the 2m temperature and relative humidity, 10m-wind speed and total cloud cover.
Future climate data for the building sector
Authors: Wehrli Kathrin , Gubler Stefanie , Fischer Andreas M. , Kotlarski Sven
Published: June 2021

By mid-Century the Swiss Climate Scenarios CH2018 project an additional warming of 2-3 degree Celsius in Switzerland if greenhouse emissions continue unabatedly. In consequence, heatwaves become longer, more intense and more frequent, whereas coldwaves will be less common. Changes in the outdoor climate also affect the indoor climate in buildings where people spend a substantial part of their day to work, study, and live. Buildings are designed to last for several decades with limited possibility to update heating and cooling systems. Hence, the climate a building will face during its lifetime has to be considered in the planning process. In general, it can be expected that the heating demand will decrease whereas the cooling demand will increase in the near future. However, a holistic and quantitative assessment of the effect of climate change on the energy demand in buildings is still missing. For the use in building simulations, climate data at hourly resolution with physical consistency for a number of key variables such as temperature, humidity and radiation are required. To ensure that the use of the data is feasible in practice, the climate of the future needs to be condensed into a single year, representing typical mean conditions as well as typical deviations from the mean. In addition to the typical year, the assessment of an extreme year can provide information on the level of comfort during a once in a lifetime event and the performance at maximum capacity of the installations. Users of this data are practitioners in the building sector as well as officials from federal offices.

Our project aims to provide future climate data for the building sector at station level. For this, we make use of observations as well as climate change information from the Swiss climate scenarios CH2018.  Together with the users, we define criteria that shall be represented by the future typical and extreme years. We design different methods to create this years based on observations and scenarios and under consideration of existing standards and regulations. The methods are compared in a climatological assessment and sensitivities to emission scenario and time horizon are explored using building simulations. The results of this project support decision-making to optimize national and international norms and regulations and to design adaptation measures. The climate data will be made available to practitioners who can use them to plan the buildings of the future.
Aerosol optical depth prediction using machine learning techniques
Authors: Logothetis Stavros Andreas , Salamalikis Vasileios , Kazantzidis Andreas
Published: June 2021

Aerosol optical depth (AOD) describes adequately aerosols’s burden and extinction within an atmospheric column. AOD can be retrieved using remote sensing instruments such as ground-based sun photometers. Despite the very good quality of ground based AOD measurements, their spatiotemporal coverage is restricted. In this study, an alternative approach of AOD estimation is proposed with the synergy of ground-based measurements and machine learning (ML) techniques, in order to expand and complement the existing spatiotemporal capabilities of AOD data. The ML algorithms which are implemented are: Random Forests, Gradient Boosting Machines, Extreme Gradient Boosting Machines, Support Vector Regression, K-nearest Neighbors Regression, and Multivariate Adaptive Regression Splines. Each model receives as input information the Global Horizontal Irradiance (GHI) as well as water vapor (WV) content in hourly basis and under clear skies. A randomized cross-validation search scheme is implemented to obtain the optimal hyperparameters and avoid overfitting for each ML algorithm. GHI and WV are retrieved from Baseline Surface Radiation Network (BSRN) and NASA’s Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA-2) reanalysis product respectively. AOD estimations are evaluated against AOD from AErosol RObotic NETwork (AERONET) inversion product, using the Level 2.0 Version 3 (L2V3) which provides cloud-screened and quality assured measurements. In total, 29 collocated AERONET-BSRN stations are used spanning from 2000 to 2019. Since, the aerosol pattern is different at each site, the effect of various aerosol types is further investigated. ML-based AOD predictions are adequately good, highlighting the feasibility of ML algorithms on producing AOD data. The results of this study could be useful for direct normal irradiance estimations as well as aerosols radiative effect calculations and climate projections.
Linking Large-scale Circulation Descriptors to Precipitation Variability in the Northern French Alps
Authors: Blanc Antoine , Blanchet Juliette , Creutin Jean-Dominique
Published: June 2021

This work analyses the link between Western Europe large-scale circulation and precipitation variability in the Northern French Alps from 1950 to 2017. We consider simple descriptors characterizing the daily 500hPa geopotential height fields. They are the Maximum Pressure Difference - representing the range of geopotential heights over Western Europe -, and the singularity - representing the mean distance between a geopotential shape and its closest analogs, i.e. the way this geopotential shape is reproduced in the climatology. These descriptors are compared to the occurrence of different atmospheric influences - Atlantic, Mediterranean, Northeast, Anticyclonic - and to the leading mode of large-scale circulation variability over Europe - the North Atlantic Oscillation (NAO) - for explaining precipitation variability in the Isère River catchment from one day to 10 years. We show that the Maximum Pressure Difference and the singularity of geopotential shapes explain a significant part of precipitation variability in the Northern French Alps from 10 days to 10 years, especially in winter (correlation values of 0.7). These descriptors provide much better performance than NAO and the same performance as the occurrence of the Atlantic influence, which is the best performing atmospheric influence. This means that simple characteristics of large-scale circulation - that are easy to implement - provide as much information as weather pattern classification to explain precipitation variability over a medium size mountainous catchment. Furthermore, we show that NAO does not drive the pressure gradient in a domain spreading from the Iberic Peninsula to Southern Great Britain and weakly explains precipitation variability in the Northern French Alps.
Hyper-local extreme temperature and wind modeling in the Basque Country
Authors: R. Gelpi Ivan , Pedruzo Xabier , Diaz de Arcaya Aurelio , Gomez de Segura Jose Daniel , Gaztelumendi Santiago
Published: June 2021

The sustainability of economic development and living conditions depends to a large extent on our ability to manage the risks associated with extreme events. In that sense, many practical problems require knowledge of the behaviour of extreme meteo-climatic variables at a high level of spatial and temporal detail. This is particularly true around highly populated areas where most part of the socio-economic activity takes place. Those metropolitan areas seem to be more vulnerable to extreme meteo-climatic conditions in the coming decades.

 

In this paper, we present some results of the implementation of operational high-resolution tools (down to 100m) for temperature and wind analysis at local level. Here we focus on different systems we have developed for its applications at local level in the Basque Country based on WRF and CALMET but we also include a brief descriptive analysis of some others available tools for thermal and wind analysis at high spatial resolution.

In order to test their operational capabilities, the behaviour of the different systems is analysed in diverse experiments corresponding to high impact weather scenarios, affecting the three largest metropolitan areas of the Basque Country, i.e. the metropolitan areas of Bilbao, Donostia-San Sebastian and Vitoria-Gasteiz, where more than half of the Basque population lives.  

The aim of this study is to evaluate and provide plausible tools and methodologies for very high resolution meteo-climatic analysis in the Basque Country area, focusing on wind and temperature extremes. With the final objective of identifying the benefit of hyperlocal modelling, finding under which conditions and spatio-temporal resolutions these highly computation demanding tools for wind and thermal characterisation are fully useful and provide sufficient added value. It is important to note that some results and main conclusions are of a general nature and could be extrapolated to other areas.
Boundary Layer Height Estimated and dynamic parameter comparison  using Radiosounding Observations around globe at mid-latitude region.
Authors: Summa Donato , Madonna Fabio , Franco Noemi , Di Girolamo Paolo , De Rosa Benedetto , Wang Yuanzu , Rosoldi Marco
Published: June 2021

The exchange processes between the Earth and the atmosphere play a crucial role in the development of the Planetary Boundary Layer (PBL). Vertical profiles of atmospheric thermodynamic variables, i.e. temperature and humidity, or wind speed, clouds and aerosols can be used as proxy to retrieve the PBL height and other dynamic variables  at different vertical and temporal resolutions. [1].The present work aims to correlate the PBL height variability  with other factors determining or interacting with the PBL, such as the mixing-ratio and CAPE . The study is focused on the mid-latitudes observations ( 30 ° N and 50 ° N). Radiosounding profiles from the Integrated Global Radiosounding Archive (IGRA) are used to estimate the PBL height, while the European Center for Medium-Range Weather Forecasts (ECMWF) Re-Analysis v5 (ERA5) and the GCOS Reference Upper-Air Network (GRUAN) Lindenberg station radiosounding data are used as intercomparison datasets for the study uncertainties in the trend analysis. [2][3][4].

The results of these comparisons will be summarized and discussed at the conference.

 

[1] Summa, D.; Di Girolamo, P.; Stelitano, D.; Cacciani, M. Characterization of the planetary boundary layer height and structure by Raman lidar: Comparison of different approaches. Atmos. Meas. Tech. 2013, 6, 3515–3525.

[2] Madonna F., Summa D., Di Girolamo P., Marra F. ,Wang Y. and Rosoldi  M. Assessment of Trends and Uncertainties in the Atmospheric Boundary Layer Height Estimated Using Radiosounding Observations over Europe Atmosphere 2021, 12, 301. https://doi.org/10.3390/atmos12030301.

[3] Sy, S.; Madonna, F.; Rosoldi, M.; Tramutola, E.; Gagliardi, S.; Proto, M.; Pappalardo, G. Sensitivity of trends to estimation methods and quantification of subsampling effects in global radiosounding temperature and humidity time series. Int. J. Climatol. 2020, 41.

[4] Seidel, D.J.; Ao, C.O.; Li, K. Estimating climatological planetary boundary layer heights from radiosonde observations: Comparison of methods and uncertainty analysis. J. Geophys. Res. Space Phys. 2010, 115, 16113.
Impact of ocean–atmosphere coupling on future projectionof Medicanes in the Mediterranean sea
Authors: Gutiérrez-Fernández Jesús , González-Alemán Juan Jesús , de la Vara Alba , Cabos William , Sein Dmitry V. , Gaertner Miguel Angel
Published: June 2021

The Mediterranean basin is one of the main cyclogenetic regions in the world. This is likely due to the orographic conditions, as well as the thermodynamic
characteristics found over the Mediterranean. Among the large amount of cyclones that develop in this area, cyclones with tropical characteristics called medicanes (“Mediterranean Hurricanes”) eventually develop in the Mediterranean Sea. They have large harmful potential and a correct simulation of their evolution in climate projections is important for an adequate adaptation to climate change. Different studies suggest that ocean–atmosphere coupled models provide a better representation of medicanes, especially in terms of intensity and frequency. In this work, we use the regionally coupled model ROM and its stand-alone atmospheric component (REMO) that in this work is used as uncoupled model to study how air-sea interactions affect the evolution of medicanes in future climate projections. We find that under the RCP8.5 scenario our climate simulations show an overall frequency decrease which is more pronounced in the coupled than in the uncoupled configuration, whereas the intensity displays a different behaviour depending on the coupling. These changes could be explained due to the decrease in the number of extratropical cyclones and the increase of atmospheric stability conditions. In the coupled run, the relative frequency of higher-intensity medicanes increases, but this is not found in the uncoupled simulation. Also, this study indicates that the coupled model simulates better the summer minimum in the occurrence of medicanes, avoiding the reproduction of unrealistically intense events that can be found in summer in the uncoupled model.
Comparative verification in complex topography
Authors: Bhend Jonas , Orain Jean-Christophe , Schönenberger Vera , Spirig Christoph , Moret Lionel , Liniger Mark
Published: June 2021

Verification is a core activity in weather forecasting. Insights from verification are used for monitoring, for reporting, to support and motivate development of the forecasting system, and to allow users to maximize forecast value. Due to the broad range of applications for which verification provides valuable input, the range of questions one would like to answer can be very large. Static analyses and summary verification results are often insufficient to cover this broad range. To this end, we developed an interactive verification platform at MeteoSwiss that allows users to inspect verification results from a wide range of angles to find answers to their specific questions.

We present the technical setup to achieve a flexible yet performant interactive platform and two prototype applications: monitoring of direct model output from operational NWP systems and understanding of the capabilities and limitations of our pre-operational postprocessing. We present two innovations that illustrate the user-oriented approach to comparative verification adopted as part of the platform. To facilitate the comparison of a broad range of forecasts issued with varying update frequency, we rely on the concept of time of verification to collocate the most recent available forecasts at the time of day at which the forecasts are used. In addition, we offer a matrix selection to more flexibly select forecast sources and scores for comparison. Doing so, we can for example compare the mean absolute error (MAE) for deterministic forecasts to the MAE and continuous ranked probability scores of probabilistic forecasts to illustrate the benefit of using probabilistic forecasts.
First results of a promising Doppler lidar configuration to derive wind gusts within the FESSTVaL campaign
Authors: Detring Carola , Steinheuer Julian , Päschke Eileen , Leinweber Ronny , Kayser Markus , Beyrich Frank
Published: June 2021

A central aspect of the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL, www.fesstval.de) is the investigation of wind gusts with Doppler lidar measurements. Compared to meteorological tower observations, they have the advantage of being able to probe higher altitudes of the atmosphere, they thus offer the possibility to record a vertical profile of wind gusts with a resolution of about 30 m in the atmospheric boundary layer. Nevertheless, it is difficult to capture wind gusts with these instruments as it is challenging to measure fluctuations of short duration with an instrument which needs a certain time for one complete measurement.

Based on the research of Suomi et al. (2017), different configurations were tested in a pre-campaign in autumn 2019 to identify a suitable measurement mode for Halo Photonics Stream Line Scanning Doppler LiDAR systems. Different lidars were operated in parallel to compare configurations against each other. A promising mode was tested during the FESST@MOL campaign in summer 2020 for a three month period. This is a continous scan mode (CSM) configuration that takes about 3.4 seconds per circulation and performs measurements in 10-11 directions.

The derived wind gusts and mean wind speeds are compared with high resolution sonic anemometer measurements at 90.3 m to verify the quality of the lidar measurements. In a first comparison good agreement is shown despite the different measuring principles. In addition, various parameters are tested to identify optimal thresholds that allow a reliable derivation of wind gusts.

In summer 2021 this fast CSM mode will be operated and further tested in the FESSTVaL campaign in parallel with UAS measurements. Moreover lidars will be installed at different locations to analyse the spatial characteristics of wind gusts with this scanning configuration.

Reference

Suomi, I., Gryning, S.‐E., O'Connor, E.J. and Vihma, T. (2017), Methodology for obtaining wind gusts using Doppler lidar. Q.J.R. Meteorol. Soc., 143: 2061-2072. https://doi.org/10.1002/qj.3059