bluuebunny/crossref_metadata_2025 huggingface dataset:
On the assimilation of dual-polarization radar observations via estimators of hydrometeor mixing ratios in Germany
Authors: Reimann Lucas , Simmer Clemens , Potthast Roland , Trömel Silke
Published: June 2022

Dual-polarization radar (DPR) observations provide additional information about bulk properties of clouds and precipitation such as hydrometeor size, shape, orientation and composition compared to single-polarization radar data. Thus, the use of DPR data for model evaluation and data assimilation has the potential to improve the representation of cloud-precipitation microphysical processes in numerical weather prediction (NWP) models, weather analyses and short-term quantitative precipitation forecasts (QPFs). Two frequently used approaches for radar data assimilation are 1) the use of radar forward operators and 2) the use of radar-estimated microphysical model state variables. Approach 1 is challenging as particle size, shape and orientation distributions and the composition of mixed-phase particles, which all impact polarimetric radar observables, are still rather rudimentarily represented in NWP models. Approach 2 circumvents these difficulties but may suffer from uncertainties in the retrievals. Here, we present first results of the latter approach.

Estimates of liquid water content (LWC) and ice water content (IWC) derived from observations of the operational dual-polarimetric C-band radar network of the German national meteorological service (DWD, Deutscher WetterDienst) are assimilated into DWD’s operational convective-scale NWP model ICON-D2 using the KENDA (Kilometre-sale ENsemble Data Assimilation) system. We compare the results of assimilating A) only conventional observations, B) conventional and radar reflectivity observations (approach 1 for single-polarization radar observations), and C) conventional and radar reflectivity observations as in B) and additionally LWC-/IWC-estimates below/above the melting layer. We focus on predicted hourly precipitation accumulations resulting from the three assimilation configurations for an intense three-day stratiform and a two-day convective precipitation period in summer 2017. Configurations B and C, which include radar observations, clearly improve both the deterministic and ensemble first guess QPFs for both precipitation periods compared to configuration A. Configuration C shows better results than configuration B only in some situations. Results also suggest that the assimilation of LWC is superior to the assimilation of IWC, possibly due to larger observation errors above the melting layer and/or the fact that the LWC estimator has been adjusted to the central European climatology. Investigation of the impact of the LWC/IWC-assimilation on QPFs with longer lead times and more events is in progress.
Comparison of irradiance forecasts from operational NWP model and satellite-based estimates over Fennoscandia
Authors: Kallio-Myers Viivi , Riihelä Aku , Schoenach David , Gregow Erik , Carlund Thomas , Lindfors Anders
Published: June 2022

With the increase of solar power use, the need for solar irradiance forecasts is also increasing. Solar power is a naturally fluctuating energy source, which makes solar irradiance forecasts necessary for e.g. grid integration and management. Both the use of solar energy and the need for forecasts are present also in the Nordic countries, where the sub-Arctic latitude brings its own challenges.

Various methods exist for forecasting solar irradiance. Numerical Weather Prediction (NWP) models have been found superior for forecasting for the following days, while satellite-based models are found suitable for the first few hours of the forecast. The satellite-based model Solis-Heliosat has been found to perform well also in the high latitudes. The current operational NWP models in Finland, however, have not been yet extensively validated for this purpose.

To determine the suitability of the operational NWP models for forecasting solar irradiance in the Nordic countries, we have comparatively validated the MetCoOp Ensemble Model (MEPS), and the MetCoOp Nowcasting Model (MNWC) against in situ irradiance measurements at several stations in Finland and Sweden. We have also included the Solis-Heliosat model in the study, to improve our understanding on the differences and the relative accuracy between the NWP and satellite-based models. As a benchmark, two persistence models are included. The comparison is made for one summer, including all model runs and all MEPS ensemble members, with both hourly and 15 minute output depending on the model.

The results show all models to somewhat under predict irradiance. MEPS shows very good performance in the full length of the forecast, while Solis-Heliosat is better in the first 2-3 hours of the forecast. Solis-Heliosat has some difficulty with the forecasts starting in the morning, whereas MNWC slightly struggles in the afternoon.

Overall we find the NWP models very suitable for forecasting solar irradiance in Finland and Sweden, particularly with the full forecast horizon of MEPS, and the 15-minute time step of MNWC. Nevertheless, Solis-Heliosat brings further value to the beginning of the forecast.

Kallio‐Myers, V., Riihelä, A., Schoenach, D., Gregow, E., Carlund, T., & Lindfors, A. V. (2022). Comparison of irradiance forecasts from operational NWP model and satellite‐based estimates over Fennoscandia. Meteorological Applications, 29(2), e2051.

 
Impact of tropical SSTs on the variability and predictable components of late-winter atmospheric circulation in the North Atlantic-European region
Authors: Ivasić Sara , Herceg Bulić Ivana
Published: June 2022

Atmospheric variability and predictable components over the North Atlantic-European region (NAE) were analysed in the late-winter season using a general circulation model of intermediate complexity (ICTP AGCM). The method of empirical orthogonal functions (EOF) analysis was applied to 200-hPa geopotential heights (GH200) to extract individual modes of variability occurring in the ensemble of numerical simulations. The same variable was selected for the signal-to-noise optimal patterns method, which identifies the patterns maximising the signal-to-noise ratio, following Straus et al. (2003).

Six experiments based on a 35-member ensemble of 156-year long simulations were conducted to detect the potential impact of tropical sea surface temperatures. Each experiment was forced with observed sea surface temperature anomalies prescribed in different ocean areas: globally, in the tropics, in the tropical Atlantic region, in the tropical Pacific, and the tropical Indian Ocean. In late winter, the leading EOF pattern calculated for all individual ensemble members projects onto the North Atlantic Oscillation, while the second EOF pattern projects onto the East Atlantic pattern. However, EOF modes based on the ensemble mean, which should reflect the forced component of the signal, have different spatial characteristics. 

Alongside the classical analysis of signal and noise, results of the signal-to-noise optimal patterns method suggest that the optimal patterns and signal-to-noise ratio are affected by the boundary forcing of the oceans. Relatively high correlations between the first principal component of NOAA SST anomalies in different ocean basins and the principal components of GH200, as well as with the time series of the first optimal pattern, further confirm the connection between remote SSTs and potential predictability of the GH200 over the NAE region in late winter. Furthermore, the resemblance between the first optimal pattern and the EOF1 pattern based on the ensemble mean points toward the vital role of the lower-boundary-forced signal in establishing potential predictability in the NAE region. 
An Available Potential Energy Perspective on North Atlantic Weather Regimes
Authors: Federer Marc , Papritz Lukas , Grams Christian , Sprenger Michael , Wenta Marta
Published: June 2022

The variability of the large-scale flow over the North Atlantic is well described by a set of quasi-stationary recurrent flow patterns, so-called weather regimes. Each weather regime is associated with a characteristic life-cycle and typical large-scale flow configurations, often involving the occurrence of atmospheric blocks in specific regions and particular shifts of the storm track. Due to their relevance for surface weather and, for example, wind energy production, understanding and accurately predicting the weather regime life cycles is highly important. However, the processes leading to the onset and persistence of weather regimes are not well understood. In particular, latent heat release in ascending air streams and air-sea interactions along the Gulf Stream are thought to play a fundamental role in the onset of weather regimes and their mutual transitions.

Here, we focus on a recently introduced diagnostic of available potential energy (APE), which is defined locally for each air parcel and is a measure of the energy that is available for conversion into kinetic energy (baroclinic conversion). APE directly links diabatic processes with the large-scale dynamics, which makes it ideal for the study of latent heat release and air-sea interactions in weather regime life cycles. In a case study of an episode of European blocking - a weather regime associated with an anticyclone over the British Isles and an intensified storm track in the western North Atlantic - in the period between 20 and 27 of February 2019, we study the distribution of APE and its tendencies along the paths of two intense cyclones originating in the Gulf Stream region. Thereby, we elucidate the balance of diabatic and adiabatic contributions to the APE budget of the cyclones. This particular event has been chosen due to its connection with strong air-sea interaction over the Gulf Stream and because it lead to a record-breaking warm spell in the United Kingdom, the Netherlands, and Northern France, where temperatures reached above 20°C. This case study is then complemented by a climatological analysis of the APE tendencies during the various weather regime life cycles.
Trends in temperature and precipitation indices in Croatia, 1961-2020
Authors: Cindric Kalin Ksenija , Patalen Leonardo , Marinovic Ivana , Pasaric Zoran
Published: June 2022

Observed changes in the seasonal and annual air temperature and precipitation amounts, and the corresponding indices of extremes in Croatia are analysed. Daily data from the 1961-2020 period are employed at 37 climatological stations (mean and extreme air temperatures) and 164 rain gauge stations (precipitation amounts) operated by the Croatian Meteorological and Hydrological Service. The trends are estimated using linear regression and the statistical significance of trends is tested by the Mann-Kendall test. The results revealed a consistent warming trend in the whole country. The highest increase in the mean annual air temperature (up to 0.5 °C/10years) is detected in central continental Croatia mostly due to summer and winter positive trends. Observed warming is also evident in positive trends of warm temperature indices (warm days, warm nights and warm spells) and negative trends in cold temperature indices (cold days, cold nights and cold spells). A significant decrease in the summer precipitation amounts is found along the Adriatic coast and in the highlands (5-15 %/10years), in the latter region also in spring. The most prominent feature of precipitation changes is a consistent positive trend in autumn rainfall amounts across the whole country, with the largest increase detected in central parts. The observed trends are associated with an annual increase in dry spell (DS) lengths in the central parts and along the Adriatic coast, and with a significant decrease in DSs in easternmost Croatia. Moreover, in the central, mountainous and northern Adriatic region, a significant increase in precipitation fraction due to very wet days (R95T) and in daily intensity index (SDII) is found. The summer drying is associated with a decrease in the number of moderately wet days along the Adriatic and the highlands but also with an increased number of dry days and DS lengths, and a decrease in the SDII and highest 1-day (Rx1d) and 5- day (Rx5d) precipitation amounts. On the other hand, autumn wetter conditions are mainly associated with an increase in R95T and with shorter DS lengths but also with an increase in SDII and Rx1d and Rx5d. The spring trend pattern is characterised by longer DS lengths in the northern Adriatic and longer wet spells in eastern Croatia.
High-resolution observation of extreme winds at the Sub-Mesoscale with Doppler wind lidars during FESSTVaL
Authors: Steinheuer Julian , Löhnert Ulrich
Published: June 2022

Accurate monitoring of the wind field is highly relevant in many fields of meteorology. Modern, surface-based in-situ measurement devices are capable of detecting highly, temporally fluctuating wind patterns such as gusts.  However, more and more applications (e.g. air traffic, wind energy, high-resolution modelling, etc.) require temporally highly resolved wind observations throughout the whole atmospheric boundary layer. Doppler wind lidars (DWLs) have the potential to provide these wind observations. Steinheuer et al. 2022 introduce a quick continuous measuring mode (CSM) in combination with a new flexible retrieval, which can be used to produce such high-resolution wind observations. In the framework of the Field Experiment on Sub-Mesoscale Spatio-Temporal Variability in Lindenberg (FESSTVaL) in summer 2021, three boundary layer profiling sites were established at a distance of about 6 km to each other in the area of the Meteorlogical Observatory Lindenberg, specifically at the sites Lindenberg, Falkenberg, and Birkholz. DWLs were placed at these sites and operated in the CSM from May to August 2021. With this setup, one goal was to investigate whether individual gust observations can be considered representative of their surroundings or whether significant differences are already evident on the meso-gamma scale (2-20 km). In addition, the spatial-temporal development of gusts can be observed and weather conditions leading to strong gusts can be investigated. Other measurement instruments have also been deployed at the sites and provide additional parameters to investigate specific processes. These instruments include, for example, ceilometers to determine the cloud base height or microwave radiometers that allow the determination of thermodynamic profiles. We will present different case studies demonstrating the benefits of simultaneously applying the CSM to the DWL and highlighting the differences between the sites. In particular, for small-scale weather phenomena such as cold pools, these are striking and the profiling of the wind, temperature and humidity gives insight about the vertical build up and horizontal variability of the cold pool.

Steinheuer et al. 2022: “A new scanning scheme and flexible retrieval for mean winds and gusts from Doppler lidar measurements”. In: doi: 10.5194/amt-2021-426.
A tool to identify large-scale dynamical precursors to European extreme precipitation
Authors: Dorrington Joshua , Grams Christian , Grazzini Federico , Ferranti Laura , Magnusson Linus , Vitart Frederic
Published: June 2022

Numerical weather prediction models still struggle to accurately forecast extreme precipitation events, both due to their relative rarity and the length-scales of the processes involved, which fall below the grid scale and so must be parameterised. However, extreme precipitation events are by no means decoupled from the large-scale flow: the prevailing winds and wave-structures ‘set the scene’ for amplified or suppressed risk of an extreme, by controlling moisture availability and vertical stability. This is especially true in the mid-latitudes where frontal rainfall is dominant.

The idea that explicitly resolved large-scale circulation patterns, may serve as potentially skilful precursors to extreme precipitation has been explored in a number of studies, investigating precursor patterns to flooding in particular geographical areas, in both process-oriented and regime-based approaches. However, such insights are not yet easily extensible to other regions, or available to the operational meteorologist.

 

We will report on the development of a new flexible tool to identify the precursors of extreme events, assess their usefulness as predictors, and produce statistical forecasts of increased event probability. This will allow the leveraging of physical insight to add value to traditional NWP. We will use results found for UK and Northern Italy extreme precipitation as motivational examples, exploring time-scales ranging from the medium range out to the sub-seasonal. Development of this tool is driven by applications to operational meteorology, but we also see considerable opportunities for application in an academic setting, by streamlining studies of large-scale physical processes and enabling the use of precursor chains in model validation and bias analysis.
The role of warm conveyor belts for the sub-seasonal prediction of blocked weather regimes
Authors: Wandel Jan , Quinting Julian F. , Büeler Dominik , Knippertz Peter , Grams Christian M.
Published: June 2022

Variability of the large-scale atmospheric circulation in the midlatitudes is characterised by transient extratropical Rossby waves and stationary patterns, such as blocking anticyclones. On sub-seasonal time scales, the extratropical variability can be depicted by weather regimes which are quasi-stationary, persistent, and recurrent flow patterns. Accurate forecasts of the weather regimes are particularly relevant due to their longevity on sub-seasonal time scales and potential socio-economic impact. Research in recent years emphasized the modulation of blocked weather regimes by processes on synoptic scales, in particular by diabatic processes in extratropical cyclones. These diabatic processes are related to latent heat release in the so-called warm conveyor belt (WCB). The WCB is an ascending air stream in the warm sector of an extratropical cyclone and its “diabatic outflow” modulates the upper-level jet, resulting in the amplification of an upper-level ridge and eventually a block. This study systematically investigates the representation of WCBs around the onset of blocked weather regimes over the Atlantic-European region in the sub-seasonal reforecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS). In general, there is a strong link between the flow amplification around blocking onsets and high WCB outflow activity in the region of the incipient block. The analysis of the 11 ensemble members in the extended winter season from 1997 – 2017 shows that the ECMWF’s IFS reforecasts underestimate both the wave amplification and WCB frequencies for regime onsets in forecast week 2 (forecast day 8 – 14). Due to the persistence of the weather regimes, onsets on these time scales typically lead to active life cycles in week 3 and sometimes even week 4. The analysis of the temporal evolution prior to the onset reveals that the reforecasts establish large-scale flow anomalies via WCB outflow differently than observed with a more amplified large-scale flow and high WCB activity upstream of the incipient block. Our findings show that forecast biases in WCB activity might be partly responsible for the relatively poor skill of blocking forecasts in week 2 and 3 and highlight the potential for further improvement of sub-seasonal prediction by improving the representation of WCBs in NWP models.

 
How warm conveyor belt activity across the North Pacific influenced the predictability of the North American heat wave 2021
Authors: Oertel Annika , Pickl Moritz , Quinting Julian F. , Hauser Seraphine , Wandel Jan , Magnusson Linus , Balmaseda Magdalena , Vitart Frederic , Grams Christian M.
Published: June 2022

In June 2021, the western North American continent experienced an intense heat wave with unprecedented temperatures and far-reaching socio-economic consequences. The magnitude of the heat wave was substantially underestimated by probabilistic weather forecasts for lead times beyond seven days. The record-breaking temperature anomaly coincided with a far northward extending upper-level ridge that was unambiguously linked to the intensity of the heat wave. During the 10 days preceeding the heat wave, the upper-level ridge was continuously fed by air masses originating to a substantial fraction from the lower troposphere that ascended in the West, Central, and East Pacific.
We analyze the role of strongly ascending airstreams, so called warm conveyor belts (WCBs), for the upper-level ridge amplitude, and illustrate how the anomalous WCB activity in the North Pacific limits the predictability horizon of this extreme event. We identify footprints of WCBs in operational ensemble forecasts from the European Centre for Medium-Range Weather Forecasts which is enabled through a machine-learning based diagnostic. The 51 member ensemble with lead times up to 15 days is stratified into a subset that best capture the upper-level ridge and potential vorticity anomaly ('good' members), and one with the largest discrepancy in the upper-level flow field ('bad' members). We find that the underestimation of the ridge amplitude over the North American continent in the bad forecasts is associated with a mis-representation of WCB activity across the West and East Pacific. While WCB outflow in the East Pacific maintains the ridge quasi-stationary and re-amplifies the pre-existing PV anomaly, WCB outflow in the West Pacific lifts the tropopause to anomalous heights and strengthens the upper-level jet, which facilitates East Pacific WCB ascent through downstream development. The mis-representation of this chain of synoptic events in the bad members finally results in an erroneous position and amplitude of the upper-level ridge and associated temperature anomaly. We conclude that the chain of synoptic events across the Pacific and their model representation play an essential role for the upper-level ridge position and amplitude and limit the predictability of the magnitude of the heat wave.
Long-term ceilometer/wind-lidar observations of aerosol-layer depth in the Arctic
Authors: Gryning Sven-Erik , Batchvarova Ekaterina , Floors Rogier , Münkel Christoph , Sørensen Lise Lotte , Skov Henrik
Published: June 2022

The depth of the aerosol layer at the Villum Research Station at Station Nord in the high Arctic is analyzed based on eight years of observations from a ceilometer. The depth of the aerosol layer is assigned to the inflection point in the attenuated backscatter profile by two methods; one is based on polynomial approximation of the profile and the other is direct numeric differentiation. The analysis is based on two types of hourly profiles; one consists of averaging the attenuated backscatter observations and the other by computing the median. It is noted that the depth of the aerosol layer in the Arctic might be different from the depth of the turbulent layer near the ground.

Near the ground, the observed backscatter exhibits a pronounced seasonal variation, having low values during the summer and high values during the winter. The strength of the seasonal variability decreases with height and is virtually absent at 1 km.

Due to sporadic occurrence of outliers in the range between 50 m and 80 m in the ceilometer observations, this part of the profile is not used in this study. Restricting the observations to heights above100 m, the depths of the aerosol layer are found to be typically 230-250 m. It varies little between winter and summer, but the spread in the depth was larger during the winter as compared to summer.

To extend the profile of the attenuated backscatter below 100 m, the ceilometer measurements were combined with Carrier-To-Noise-Ratio observations from a Doppler wind Lidar. Thus, hourly profiles of attenuated backscatter starting at 40 m, are obtained. The results are available for 2018 only and they show aerosol-layer depths below 100 m as well as depths around 230-250 m and they show few observations of aerosol-layer depths between 100 m and 230 m.

Acknowledgement: This article is based upon work from COST Action CA18235 PROBE, supported by COST (European Cooperation in Science and Technology). www.cost.eu.

 
Co-creation of sub-seasonal prediction service for tyre companies in Finland 
Authors: Vajda Andrea , Hyvärinen Otto , Rantanen Mika , Tack Andreas , Mellin Markus
Published: June 2022

Driving safety is strongly weather dependent during the winter season, thus timely installation of winter tyres is essential when temperature falls to near 0 °C and the surface of the roads becomes slippery due to ice and snow. Sub-seasonal forecasts might provide useful information for tyre companies for operational planning of their logistic activities and preparedness. In the EU H2020 E-SHAPE project we co-created a user-oriented climate service providing tailored sub-seasonal predictions for the tyre companies in Finland. To increase the usability and uptake of the forecast products the service was co-created with the tyre and car service chain, Vianor Oy, through an iterative approach. In this study, we provide a short overview of the new sub-seasonal prediction service, emphasizing the challenges emerged during the creation and uptake by the user.

The end-user was engaged through dialog from the beginning of the design and development process to scope and explore their needs in terms of forecast products, and to align the complexity of visualization design and delivery method with their expertise. The user’s purpose was to apply the tailored sub-seasonal forecasts in the operational preparation for the high season, in marketing and in customer communication to facilitate safer driving. Taking this into consideration, a set of sub-seasonal forecast products relevant for winter driving safety were selected and designed with the user, i.e., winter tyre season (onset and offset), probability of snow cover, snow depth and probability of freezing temperature. Air temperature and snow depth variables from the ensemble prediction system from ECMWF were used as input data in the development of the sub-seasonal outlooks. The forecast model data was quality assessed and bias-adjusted using the ERA5 reanalysis as reference. The sub-seasonal outlooks are produced in operational runs, visualized through weekly maps, and disseminated to the users through an online user interface two times a week, on Tuesday and Friday. The service was piloted with Vianor for two winter seasons and improvements are being made based on user’s feedback and forecast product evaluation.

Although the user found beneficial the created climate service in decision making, their capacity and capability to incorporate the sub-seasonal climate information in their line of business proved to be more challenging. This was partly due to the longer time required to understand the potential value of using the forecast products but also in the difficulties of incorporating the new climate information to their workflow. The lessons learnt from this collaboration will contribute to better understanding of users’ engagement and co-production of sustainable and operational climate services.
Exploratory analysis of hourly precipitation data measured by citizen observations over Europe
Authors: Baietti Emma , Lussana Cristian
Published: June 2022

The amount of data observing precipitation near the Earth’s surface today is enormous and is constantly growing. Among the most interesting data sources, which are showing a greater development are the observational networks made up of stations managed by citizens. From the point of view of national meteorological services, this type of data constitutes an opportunity to integrate the networks of traditional weather stations managed by public institutions. For precipitation, especially, the availability of a dense network delivering data at hourly sampling rates, or less, allows for the reconstruction of weather phenomena occurring between the microscale and the mesoscale. Usually, a network of taditional weather stations allow for the reconstruction of atmospheric fields of a variable near the surface with a minimum spatial effective resolution of about 20 km, the use of crowdsourced observations can potentially move this lower limit down to about 2 km.

In this study, we consider the observations of hourly precipitation collected by a network of European citizens from September 2019 to August 2020. All the observations have been measured by Netatmo weather stations. The stations can be purchased in shops and are then installed in private homes for the most varied purposes, including home automation for instance.

We present an exploratory analysis of the data collected aiming at setting up a quality control system for hourly precipitation. In particular, we will show statistics describing the dataset in terms of: data availability over Europe; rain/no-rain probability; (local) variability of precipitation as a function of its intensity; spatial statistics characterizing the length scales of precipitation over time.
Forecasting renewable energy generation: an example of how the private sector adds value
Authors: Finney Isla
Published: June 2022

Lake Street's aim is to help companies 'work with the weather'.  In other words, we look to deliver high value meteorological services that enable the end user to take informed action.  Invariably this means processing weather data alongside datasets from the end user’s sector. 

Using an example from the growing renewable energy sector, we will show how private sector companies are able to identify the relevant datasets – weather and sector specific, translate weather variables to power generation, and present a product that enables informed decision-making. 

Having accurate weather information enables efficient dispatch of fossil-fuel generators when required to match demand, and so helps nations work towards net zero.  This includes information about temporal and spatial correlations that are not immediately obvious from raw weather model output. 

Different models are best for varying timeframes (think within day compared to next week) making no single weather model sufficient on its own.  Further, the timetable of the network operator determines the cut off time for model information, and so influences model choice.

Weather forecasts are not exact and model errors can be considerable.  Knowledge of uncertainties aids decision-making, yet this information is often one of the greatest challenges to calculate.     

Private sector companies act as the translator, and add value at the last step, but could not do this work alone.  They draw on the work of national and international bodies and academia, and in turn feedback observations about forecast error enabling model improvement.  With collaboration, we increase the value of meteorological services and their usefulness to society.
Does the performance of different physical parameterizations in the WRF regional climate model depend on the synoptic weather pattern in the large-scale driving fields?
Authors: Varga Ákos János , Breuer Hajnalka
Published: June 2022

It has been indicated by multiple studies that the performance of a particular physical parameterization scheme in a numerical model is determined by several factors and displays high spatial and temporal variability. One factor that could potentially lead to distinctive behavior for the different schemes is the large-scale weather situation. Here we aim to answer the following questions: does the performance of the WRF regional climate model with different physical parameterizations depend on the synoptic weather situation? Can simulation results be improved with the utilization of different physics schemes depending on the synoptic weather situation?

To answer these questions, we produce 5-year (2006–2010) regional climate simulations with the WRF model. First, a 50-km simulation is performed using the ERA5 reanalysis as input data. Then, this coarse-resolution run is further downscaled to a set of 10 km simulations with daily re-initialization utilizing different planetary boundary layer (PBL), surface layer, and deep convection schemes. A simulation with the cumulus convection turned off is also included in the analysis.

The weather pattern in the 50-km run for each day is determined based on model-derived relative vorticity at the 500 and 950 hPa isobaric levels (i.e., cyclonic or anticyclonic flow in the upper and lower levels of the atmosphere). Then, we evaluate the performance of the 10-km simulations separately for periods with a specific synoptic pattern prevailing in the driving fields, using the E-OBS dataset as reference. This way, it can be deduced if a physical parameterization is superior to the other for a particular large-scale weather situation. Finally, based on the results of this sensitivity study, we produce further 10-km simulations in which we initialize the 10-km model with different physics schemes each day based on the dominant synoptic pattern in the outer domain.
Destination Earth: Digital Twins of the Earth System
Authors: Wedi Nils , Quintino Tiago , Modigliani Umberto , Baousis Vasileios , Geenen Thomas , Sandu Irina , Bauer Peter , Hoffmann Joern , Thiemert Daniel
Published: June 2022

The talk describes ongoing efforts to create digital replicas of the Earth as part of the the European Commission's Destination Earth programme.

Global, coupled storm-resolving simulations are feasible and can contribute to building such information systems and are no longer a dream thanks to recent advances in Earth system modelling, supercomputing and the adaptation of weather and climate codes for novel computing architectures. Such simulations for example explicitly represent essential climate processes, such as deep convection and mesoscale ocean eddies, that today need to be parametrised even at the highest resolution used in global weather and climate information production. These simulations, combined with novel data-driven deep learning advances, thus offer a window into the future, with a promise to significantly increase the realism of Earth system information. Despite the significant compute and data challenges, there is a real prospect to better support global to local climate change mitigation and adaptation efforts, and complement the existing information derived with today's operational simulations in the range of 10-100 km.

Digital Twins of Earth thus encapsulate both the latest science as well as technology advances to provide near-real time information on Extremes and climate change in a wider digital environment. Here users can interact, modify and ultimately create their own tailored information. This is facilitated through complex workflows managed by ECMWF's digital twin engine that closely connects EuroHPC resources for the production of digital twin data, manages diverse data access patterns through cloud-based ancilliary systems such as Eumetsat's Data Lake, and provides a diverse range of tools to faciliate user interaction and data-driven applications creating new information through ESA's user service platform. The underlying system architecture and design choices will be described and justified.
Homogenized Sunshine duration data for the Austrian domain
Authors: Chimani Barbara , Paul Anita , Olefs Marc , Haslinger Klaus , Tilg Anna-Maria
Published: June 2022

The measurement of sunshine duration has experienced a number of changes since the operational observation by the national meteorological service ZAMG in Austria. With the automatization of the stations the Campbell-Stokes sunshine recorders were replaced by Haenni Solar 111 instruments and later partly with Meteoservice SD6. While no calibration was/is necessary for Campbell-Stokes and Meteoservice SD6 (using a threshold of 120W/m2 as proposed by WMO), calibration was regularly done for the different versions of Haenni (in metadata the name of the company changed multiple times). First inquiries indicated that in the beginning they were calibrated to 200 W/m2 and that later on - during one of the service cycles around the year 2000 - the threshold was changed to 50 W/m2.

During the last years, six sun-tracking devices equipped with pyrheliometers have been installed in the Austrian network (ARAD station network - one BSRN site). By using those data the influence of the different sunshine recorder thresholds could be estimated and the meta information on the changes evaluated. For homogenization, ACMANT was used. The use of different choices for reference series have been analyzed and evaluated. Finally, additional to station data, satellite data from the EUMETSAT SARAH dataset from 1983 to 2015 was included in the final homogenization process of those time series.

The presentation will include information on the stations history, the correction and homogenisation methods explored and evaluated, information on the final homogenization procedure using ACMANT as well as the impact of the homogenization on the  analyses of sunshine duration.
The Importance of Anticyclonic Transient Eddies for Atmospheric Block Persistence
Authors: Suitters Charlie , Martinez-Alvarado Oscar , Hodges Kevin , Schiemann Reinhard , Ackerley Duncan
Published: June 2022

Atmospheric blocking is often responsible for high-impact surface weather conditions such as heatwaves, cold spells, and droughts. Very long blocking events are particularly problematic due to the persistence of hazardous surface conditions. Despite their many impacts, understanding the dynamical behaviour of blocking events is still incomplete despite recent progress. Here, the relationship between block persistence and anticyclonic eddies contributing towards these blocks is investigated. Anticyclonic eddies that contribute to blocking are defined as large positive 500 hPa geopotential height (Z500) anomalies, obtained by filtering in both space and time, that pass through a blocked region. These features are then followed using an objective feature tracking algorithm. It emerges that stationary blocking conditions are often the result of more than one transient anticyclonic eddy entering the block itself, which is a reflection of the selective absorption mechanism (SAM) for block maintenance, proposed by Yamazaki and Itoh (2013). A relationship is found between the number of anticyclonic eddies contributing to a block and the persistence of the block itself, with longer-lasting blocks typically absorbing more eddies than less persistent events; this behaviour is particularly noticeable in winter. The contribution of the smaller eddies to the blocks via the SAM is also observed as the anomalies speed up slightly just before entering the blocking region, before intensifying, becoming slow-moving, and sometimes reversing in direction inside the block itself. In addition to this climatological viewpoint, case studies have also been analysed to obtain a more detailed view of the process. From these, it is observed that some of the Z500 anomalies that contribute to blocking events originate from a long way upstream and travel along the wave guide until they are absorbed into a block, and this is again most evident in winter. The results from this work suggest there is an inherent link between repeated block maintenance and the persistence of block events, and also provides evidence that block maintenance processes may differ according to time of year.
Simulating the effects of regional forest cover on mid-latitude boundary-layer clouds
Authors: Noual Gaëtan , Brunet Yves , Le Moigne Patrick , Lac Christine
Published: June 2022

It has been observed repeatedly that the presence of forests at regional scale can affect cloud formation and precipitation, but the direction and extent of this effect is highly variable. It primarily depends on the differences in albedo and roughness length with the surrounding areas, leading to contrasted water and energy balances, and also depends on the water availability and the possibility for secondary atmospheric circulations. In contrast with Amazonia where cloud enhancement has been reported over deforested areas, recent satellite observations have shown that temperate European forests promote summertime cloud formation. This is notably the case of the Landes forest in South-West France, where the destruction of 40% of the pine trees by storm Klaus in 2009 produced a sharp drop in the positive cloudiness anomaly.

To better understand these effects, the atmospheric Meso-NH model coupled with the SURFEX platform has been used at 500 m horizontal resolution at the scale of the region with advanced physical parametrizations. Two complementary study cases were selected, with significantly different soil moisture conditions. Both present summer situations of cloud cover over the Landes forest in contrast to its surroundings. After a validation step using satellite observations, near surface measurements and radiosoundings, simulated fields were compared with pre-Klaus and post-Klaus surface conditions.

In both cases, deforestation tends to decrease cloud top height or reduce the occurrence of the highest clouds. The surface flux partitioning appears as a key factor: the wet case shows a significant decrease in cloud cover, while the dry one shows a slight increase in cloud lifetime. This is in agreement with previous research using satellite data, showing that deforestation generally decreases cloud cover in temperate regions, while having a somewhat contrasting role. The atmospheric budgets of wind velocity components, TKE, temperature and air moisture have been analysed to understand the physical processes at play. A further study with a larger number of simulated case studies and a variety of meteorological situations will allow us to move towards a climatological approach.
Drivers of extreme Antarctic ice extents in summer over the period 1979-2022 
Authors: Mezzina Bianca , Goosse Hugues , Klein François , Massonnet François
Published: June 2022

The Antarctic sea ice variability and its underlying drivers remain overall unsettled, particularly since the sea ice extent (SIE) during the last two decades has first exhibited a slight increase, somewhat in contrast with the global warming trend, followed by a rapid reduction in the more recent years. The unprecedented SIE minimum registered in February 2022 has received great attention and already constitutes an important case study, as the prior record low in 2017. However, other extreme anomalous events are present in the observational record, and a comprehensive analysis of both minima and maxima in the summer SIE is essential to identify and separate potential common drivers from event-specific dynamics, ultimately advancing our general understanding of the Antarctic sea ice and climate variability.

In this work, we aim at assessing the relative roles of atmospheric and oceanic processes in the summer SIE extremes and at disentangling the dynamic contributions to sea ice changes - such as wind-driven transport and divergence - from the thermodynamic part (freezing and melting). Furthermore, we identify the key regions at play during such events, the local dominant mechanisms, and the mutual interactions that result in a total maximum or minimum. The timing and persistence of the sea ice, atmosphere and ocean anomalies in the prior months are also examined to clarify the time scales of the processes during the melting season that lead to the summer extremes.

We use observations and reanalysis data over the satellite period (1979-2022) and compare our main findings with results obtained from an ocean-sea ice model (NEMO-LIM) driven by prescribed atmospheric fields from ERA5 on the same period. While the model may not be able to capture all the extremes in the observational record, examining its own variability provides valuable insights on the dynamics of the Antarctic sea ice extremes.

 
GRAPEVINE project: Operational weather forecasting in HPC managed by an orchestrator in Kubernetes cluster. 
Authors: Vourlioti Paraskevi , Kotsopoulos Stylianos , Mamouka Theano , Agrafiotis Apostolos , Sánchez Carlos Fernández , Llerena Cecilia Grela , Nieto Francisco Javier , García Sergio
Published: June 2022

To promote cloud and HPC computing, GRAPEVINE* project objectives include using these tools along with open data sources to provide a reusable IT service. In this service a predictive model based on Machine learning (ML) techniques is created with the aim of preventing and controlling grape vine diseases in the wine cultivation sector. Aside from the predictive ML, meteorological forecasts are crucial input to train the ML models and on a second step to be used as input for the operational prediction of grapevine diseases. To this end, the Weather and Research Forecasting model (WRF) has been deployed in CESGA’s HPC infrastructure to produce medium-range and sub-seasonal forecasts for the targeted pilot areas (Greece and Spain). The data assimilation component of WRF – WRFDA-   has been also introduced for improving the initial conditions of the WRF model by blending in observations from weather stations and satellite precipitation products (Integrated Multi-satellitE Retrieval for GPM – [IMERG]). The operational production of the aforementioned forecasts is achieved by the cloudify orchestrator on a Kubernetes cluster. The connection between the Kubernetes cluster and the HPC infrastructure, where the model resides, is achieved with the croupier plugin of cloudify. Blueprints that encapsule the workflows of the meteorological model and its dependencies were created. The instances of the blueprints (deployments) were created automatically to produce operationally weather forecasts and they were made available to the ML models via a thredds server.  Valuable lessons were learned with regards the automation of the process and the coupling  with the HPC in terms of reservations and operational production.  

*hiGh performAnce comPuting seRvices for preVention and coNtrol of pEsts in fruit crops
The RCC Network – climate services for WMO Members in Europe
Authors: Bissolli Peter , Rösner Stefan , Roebeling Maarit , Körber Maya , Kreis Andrea
Published: June 2022

Regional Climate Centres (RCCs) are regional, operational entities of the Global Framework for Climate Services (GFCS) Climate Services Information System (CSIS). As such they are serving the members of the World Meteorological Organization (WMO) through their respective National Meteorological and Hydrological Services (NMHSs). Thus, RCCs are supporting NMHSs in meeting their national climate-related duties and better serving their users. RCCs are formally designated by WMO and are recognized as WMO Regional Specialized Meteorological Centres (RSMCs) in the WMO Manual on the Global Data-processing and Forecasting System (GDPFS).

WMO RCCs provide climate data sets, climate monitoring products, including climate watches, and long-range forecasting products. The details of the services provided by RCCs are developed jointly with the WMO Members in the region, based on their needs, and regularly reviewed. The RCC in Europe (WMO Regional Association (RA) VI) has been established in 2009 and designated in 2012 as a network of three nodes i.e. for climate data, climate monitoring and long-range forecasting. Each of these nodes is led by a NMHS, supported by a consortium of agencies providing regional or sub-regional contributions. A website (www.rccra6.org) allows access to the network, with links to the websites of the individual nodes. While most of the information is accessible without restriction, some content, like the Climate Watch Advisories (CWAs) is password protected, and may only be accessed with permission of the home country’s NMHS.

The presentation will demonstrate the many services offered by the WMO RA VI RCC Network through its members, lessons learned, and challenges ahead. It will be a kind of update to the information provided in the EMS/ ECAC 2012. 