scholarly journals B-matrix estimation in the Copernicus European Regional Re-Analysis (CERRA)

2021 ◽  
Author(s):  
Adam El-Said ◽  
Pierre Brousseau ◽  
Roger Randriamampianina ◽  
Martin Ridal
Keyword(s):  
Regime Change ◽  
Forecast Skill ◽  
Specific Humidity ◽  
Limited Area ◽  
Seasonal Component ◽  
Weather Regime ◽  
Skill Scores ◽  
The Impact ◽  
European Regional

<p>A new augmented Ensemble of Data Assimilations (EDA) technique, which estimates background error covariances (B-matrix), has been developed for the new Copernicus European Regional Re-Analysis (CERRA-EDA). CERRA-EDA has 10 members with two main pools of forecast differences: seasonal and daily. The seasonal component is pre-prepared (`offline') at reanalysis-resolution (5.5km). The new augmentation governs the time-dependent mixture of winter and summer differences of this seasonal component with respect to the time of year. The daily component is (`online') and averaged in moving succession over 2.5 days with subsequent B-matrix computation every 2 days. This daily component runs at 11km and the forecasts are interpolated to 5.5km prior to use. The seasonal-daily split is set to a fixed value of 80-20\% for CERRA production. The EDA is cycled 6-hourly while CERRA has a 3-hour analysis cycle. The B-matrix is modelled on a bi-Fourier limited area weather model, where dependence of vertical correlations on horizontal scale (non-separability), horizontal homogeneity and isotropy are assumed. The mass-wind and specific humidity fields are related via vorticity and geopotential and the relationships are estimated via multiple linear regressions enforcing simplified analogues of flow-dependence. </p><p>We demonstrate the potential of CERRA-EDA to estimate rapid changes in weather regime change over Europe by assessing B-matrix statistics and forecast skill scores in a case study. The case study assesses two like-periods bearing different weather regimes, Mar-03 (blocking regime) and Mar-18 (NAO- regime). The aptitude of the B-matrix to reflect weather regime change is shown to be mostly dependent on the observation network in a given year. We also illustrate the impact of: change in observation networks over time, and varying the seasonal-daily split. This is shown through analysing the spatio-temporal evolution of background standard deviations. Finally, analysis and forecast skill scores up to 24-hours are also shown to offer improvements worth considering.</p>

scholarly journals The impact of resolution on meteorological, chemical and aerosol properties in regional simulations with WRF-Chem

2017 ◽  
Vol 17 (2) ◽  
pp. 1511-1528 ◽  
Author(s):  
Paola Crippa ◽  
Ryan C. Sullivan ◽  
Abhinav Thota ◽  
Sara C. Pryor
Keyword(s):  
Spatial Resolution ◽  
Model Performance ◽  
Specific Humidity ◽  
Spatiotemporal Variability ◽  
Limited Area ◽  
Monthly Precipitation ◽  
Regional Models ◽  
Skill Scores ◽  
The Impact ◽  
Aerosol Properties

Abstract. Limited area (regional) models applied at high resolution over specific regions of interest are generally expected to more accurately capture the spatiotemporal variability of key meteorological and climate parameters. However, improved performance is not inevitable, and there remains a need to optimize use of numerical resources and to quantify the impact on simulation fidelity that derives from increased resolution. The application of regional models for climate forcing assessment is currently limited by the lack of studies quantifying the sensitivity to horizontal spatial resolution and the physical–dynamical–chemical schemes driving the simulations. Here we investigate model skill in simulating meteorological, chemical and aerosol properties as a function of spatial resolution, by applying the Weather Research and Forecasting model with coupled Chemistry (WRF-Chem) over eastern North America at different resolutions. Using Brier skill scores and other statistical metrics it is shown that enhanced resolution (from 60 to 12 km) improves model performance for all of the meteorological parameters and gas-phase concentrations considered, in addition to both mean and extreme aerosol optical depth (AOD) in three wavelengths in the visible relative to satellite observations, principally via increase of potential skill. Some of the enhanced model performance for AOD appears to be attributable to improved simulation of meteorological conditions and the concentration of key aerosol precursor gases (e.g., SO2 and NH3). Among other reasons, a dry bias in the specific humidity in the boundary layer and a substantial underestimation of total monthly precipitation in the 60 km simulations are identified as causes for the better performance of WRF-Chem simulations at 12 km.

scholarly journals Value-added by high-resolution regional simulations of climate-relevant aerosol properties

2016 ◽  
Author(s):  
P. Crippa ◽  
R. C. Sullivan ◽  
A. Thota ◽  
S. C. Pryor
Keyword(s):  
Temporal Variability ◽  
Radiative Forcing ◽  
Model Performance ◽  
Value Added ◽  
Climate Forcing ◽  
Specific Humidity ◽  
Limited Area ◽  
Skill Scores ◽  
Spatio Temporal ◽  
The Impact

Abstract. Despite recent advances in global Earth System Models (ESMs), the current global mean aerosol direct and indirect radiative effects remain uncertain, as does their future role in climate forcing and regional manifestations. Reasons for this uncertainty include the high spatio-temporal variability of aerosol populations. Thus, limited area (regional) models applied at higher resolution over specific regions of interest are generally expected to "add value", i.e. improve the fidelity of the physical-dynamical-chemical processes that induce extreme events and dictate climate forcing, via more realistic representation of spatio-temporal variability. However, added value is not inevitable, and there remains a need to optimize use of numerical resources, and to quantify the impact on simulation fidelity that derives from increased resolution. Here we quantify the value added by enhanced spatial resolution in simulations of the drivers of aerosol direct radiative forcing by applying the Weather Research and Forecasting model with coupled Chemistry (WRF-Chem) over eastern North America at different resolutions. Using Brier Skill Scores and other statistical metrics it is shown that enhanced resolution (from 60 to 12 km) improves model performance for all of the meteorological parameters and gas phase concentrations considered, in addition to both mean and extreme Aerosol Optical Depth (AOD) in three wavelengths in the visible relative to satellite observations, principally via increase of potential skill. Some of the enhanced model performance for AOD appears to be attributable to improved simulation of specific humidity and the resulting impact on aerosol hygroscopic growth/hysteresis.

scholarly journals Impact of additional AMDAR data in the AROME-France model during May 2017

2019 ◽  
Vol 16 ◽  
pp. 215-222
Author(s):  
Alexis Doerenbecher ◽  
Jean-François Mahfouf
Keyword(s):  
Additional Data ◽  
Forecast Skill ◽  
Experimental Methodology ◽  
Scale Model ◽  
Limited Area ◽  
Telecommunication System ◽  
Skill Scores ◽  
Global Telecommunication System ◽  
The Impact ◽  
Aircraft Data

Abstract. From 1 May 2017 until 15 June 2017, the E-AMDAR operational service from EUMETNET disseminated more commercial aircraft data than usual on the Global Telecommunication System (GTS). Météo-France specifically requested the implementation of such a trial. It lead to an increase in the number of aircraft data over France, especially vertical profiles (ascents and descents). Though Météo-France routinely buys additional data with respect to the basic E-AMDAR service, this trial aimed at assessing the potential of French airlines to produce further data in collaboration with E-AMDAR and yield an observation network as dense as possible. This was the opportunity to check the impact of these additional data on forecast skill scores of the limited area and convective scale model AROME-France. A data denial experiment (OSE) was carried out on May 2017, by removing E-AMDAR profiles (about 14 % of data) to mimic the routine observing system. The reference was the operational AROME-France 3D-Var that assimilated all extra data in real-time. However, no dedicated flag allowed to distinguish supplementary data from routine ones. Therefore, a necessary step of the experimental methodology was to identify which data profile could be considered as supplementary. The examination of forecast skill scores from the denial experiment showed that the impact of the removal of the additional observations is rather small and mixed, depending upon the parameter of interest, the atmospheric level, and the forecast range. The case studies done did not exhibit any particular additional skill for the suite with augmented observations. The experimental set-up is described and the results are discussed on the basis of forecast scores, including precipitation scores. Finally, a number of recommendations are given for a more optimal assimilation of AMDAR data in the AROME-France model.

scholarly journals Numerical simulations of June 7, 2020 convective precipitation over Slovakia using deterministic, probabilistic, and convection-permitting approaches

Időjárás ◽  
2021 ◽  
Vol 125 (4) ◽  
pp. 571-607
Author(s):  
André Simon ◽  
Martin Belluš ◽  
Katarína Čatlošová ◽  
Mária Derková ◽  
Martin Dian ◽  
...  
Keyword(s):  
Satellite Imagery ◽  
Weather Prediction ◽  
Severe Weather ◽  
Precipitation Forecast ◽  
Convective Precipitation ◽  
Small Scale ◽  
Limited Area ◽  
Systematic Effect ◽  
The Impact

The paper presented is dedicated to the evaluation of the influence of various improvements to the numerical weather prediction (NWP) systems exploited at the Slovak Hydrometeorological Institute (SHMÚ). The impact was illustrated in a case study with multicell thunderstorms and the results were confronted with the reference analyses from the INCA nowcasting system, regional radar reflectivity data, and METEOSAT satellite imagery. The convective cells evolution was diagnosed in non-hydrostatic dynamics experiments to study weak mesoscale vortices and updrafts. The growth of simulated clouds and evolution of the temperature at their top were compared with the brightness temperature analyzed from satellite imagery. The results obtained indicated the potential for modeling and diagnostics of small-scale structures within the convective cloudiness, which could be related to severe weather. Furthermore, the non-hydrostatic dynamics experiments related to the stability and performance improvement of the time scheme led to the formulation of a new approach to linear operator definition for semi-implicit scheme (in text referred as NHHY). We demonstrate that the execution efficiency has improved by more than 20%. The exploitation of several high resolution measurement types in data assimilation contributed to more precise position of predicted patterns and precipitation representation in the case study. The non-hydrostatic dynamics provided more detailed structures. On the other hand, the potential of a single deterministic forecast of prefrontal heavy precipitation was not as high as provided by the ensemble system. The prediction of a regional ensemble system A-LAEF (ALARO Limited Area Ensemble Forecast) enhanced the localization of precipitation patterns. Though, this was rather due to the simulation of uncertainty in the initial conditions and also because of the stochastic perturbation of physics tendencies. The various physical parameterization setups of A-LAEF members did not exhibit a systematic effect on precipitation forecast in the evaluated case. Moreover, the ensemble system allowed an estimation of uncertainty in a rapidly developing severe weather case, which was high even at very short range.

scholarly journals Tropical and Midlatitude Impact on Seasonal Polar Predictability in the Community Earth System Model

2019 ◽  
Vol 32 (18) ◽  
pp. 5997-6014 ◽  
Author(s):  
Edward Blanchard-Wrigglesworth ◽  
Qinghua Ding
Keyword(s):  
Forecast Skill ◽  
Specific Humidity ◽  
The Arctic ◽  
The North ◽  
Perfect Model ◽  
Community Earth System Model ◽  
Free Running ◽  
Skill Improvement ◽  
The Tropics ◽  
The Impact

Abstract The impact on seasonal polar predictability from improved tropical and midlatitude forecasts is explored using a perfect-model experiment and applying a nudging approach in a GCM. We run three sets of 7-month long forecasts: a standard free-running forecast and two nudged forecasts in which atmospheric winds, temperature, and specific humidity (U, V, T, Q) are nudged toward one of the forecast runs from the free ensemble. The two nudged forecasts apply the nudging over different domains: the tropics (30°S–30°N) and the tropics and midlatitudes (55°S–55°N). We find that the tropics have modest impact on forecast skill in the Arctic or Antarctica both for sea ice and the atmosphere that is mainly confined to the North Pacific and Bellingshausen–Amundsen–Ross Seas, whereas the midlatitudes greatly improve Arctic winter and Antarctic year-round forecast skill. Arctic summer forecast skill from May initialization is not strongly improved in the nudged forecasts relative to the free forecast and is thus mostly a “local” problem. In the atmosphere, forecast skill improvement from midlatitude nudging tends to be largest in the polar stratospheres and decreases toward the surface.

scholarly journals Impact of Sea Surface Temperature Forcing on Weeks 3 and 4 Forecast Skill in the NCEP Global Ensemble Forecasting System

2017 ◽  
Vol 32 (6) ◽  
pp. 2159-2174 ◽  
Author(s):  
Yuejian Zhu ◽  
Xiaqiong Zhou ◽  
Malaquias Peña ◽  
Wei Li ◽  
Christopher Melhauser ◽  
...  
Keyword(s):  
North America ◽  
Forecast Skill ◽  
Ensemble Forecasting ◽  
Superior Performance ◽  
Seasonal Forecasts ◽  
Skill Scores ◽  
Short Period ◽  
Forecasting System ◽  
Sst Forcing ◽  
The Impact

Abstract The Global Ensemble Forecasting System (GEFS) is being extended from 16 to 35 days to cover the subseasonal period, bridging weather and seasonal forecasts. In this study, the impact of SST forcing on the extended-range land-only global 2-m temperature, continental United States (CONUS) accumulated precipitation, and MJO skill are explored with version 11 of the GEFS (GEFSv11) under various SST forcing configurations. The configurations consist of 1) the operational GEFS 90-day e-folding time of the observed real-time global SST (RTG-SST) anomaly relaxed to climatology, 2) an optimal AMIP configuration using the observed daily RTG-SST analysis, 3) a two-tier approach using the CFSv2-predicted daily SST, and 4) a two-tier approach using bias-corrected CFSv2-predicted SST, updated every 24 h. The experimental period covers the fall of 2013 and the winter of 2013/14. The results indicate that there are small differences in the ranked probability skill scores (RPSSs) between the various SST forcing experiments. The improvements in forecast skill of the Northern Hemisphere 2-m temperature and precipitation for weeks 3 and 4 are marginal, especially for North America. The bias-corrected CFSv2-predicted SST experiment generally delivers superior performance with statistically significant improvement in spatially and temporally aggregated 2-m temperature RPSSs over North America. Improved representation of the SST forcing (AMIP) increased the forecast skill for MJO indices up through week 2, but there is no significant improvement of the MJO forecast skill for weeks 3 and 4. These results are obtained over a short period with weak MJO activity and are also subject to internal model weaknesses in representing the MJO. Additional studies covering longer periods with upgraded model physics are warranted.

scholarly journals Case study of a moisture intrusion over the Arctic with the ICOsahedral Non-hydrostatic (ICON) model: resolution dependence of its representation

2022 ◽  
Vol 22 (1) ◽  
pp. 173-196
Author(s):  
Hélène Bresson ◽  
Annette Rinke ◽  
Mario Mech ◽  
Daniel Reinert ◽  
Vera Schemann ◽  
...  
Keyword(s):  
High Resolution ◽  
Temporal Structure ◽  
Specific Humidity ◽  
The Arctic ◽  
Limited Area ◽  
Turbulent Heat ◽  
Strong Impact ◽  
Downward Longwave Radiation ◽  
Spatio Temporal

Abstract. The Arctic is warming faster than the global average and any other region of a similar size. One important factor in this is the poleward atmospheric transport of heat and moisture, which contributes directly to the surface and air warming. In this case study, the atmospheric circulation and spatio-temporal structure of a moisture intrusion event is assessed, which occurred from 5 to 7 June 2017 over the Nordic seas during an intensive measurement campaign over Svalbard. This analysis focuses on high-spatial-resolution simulations with the ICON (ICOsahedral Non-hydrostatic) model which is put in context with coarser-resolution runs as well the ERA5 reanalysis. A variety of observations including passive microwave satellite measurements is used for evaluation. The global operational ICON forecasts from the Deutscher Wetterdienst (DWD) at 13 km horizontal resolution are used to drive high-resolution Limited-Area Mode (LAM) ICON simulations over the Arctic with 6 and 3 km horizontal resolutions. The results show the skilful capacity of the ICON-LAM model to represent the observed spatio-temporal structure of the selected moisture intrusion event and its signature in the temperature, humidity and wind profiles, and surface radiation. In several aspects, the high-resolution simulations offer a higher accuracy than the global simulations and the ERA5 reanalysis when evaluated against observations. One feature where the high-resolution simulations demonstrated an advanced skill is the representation of the changing vertical structure of specific humidity and wind associated with the moisture intrusion passing Ny-Ålesund (western Svalbard); the humidity increase at 1–2 km height topped by a dry layer and the development of a low-level wind jet are best represented by the 3 km simulation. The study also demonstrates that such moisture intrusions can have a strong impact on the radiative and turbulent heat fluxes at the surface. A drastic decrease in downward shortwave radiation by ca. 500 W m−2 as well as an increase in downward longwave radiation by ca. 100 W m−2 within 3 h have been determined. These results highlight the importance of both moisture and clouds associated with this event for the surface energy budget.

Case study of an Arctic atmospheric river with the ICON model

2021 ◽  
Author(s):  
Hélène Bresson ◽  
Annette Rinke ◽  
Vera Schemann ◽  
Mario Mech ◽  
Susanne Crewell ◽  
...  
Keyword(s):  
Temporal Structure ◽  
Horizontal Resolution ◽  
Added Value ◽  
Arctic Climate ◽  
The Arctic ◽  
Limited Area ◽  
Polar Regions ◽  
Relative Role ◽  
The Impact

<p>The Arctic climate changes faster than the ones of other regions, but the relative role of the individual feedback mechanisms contributing to Arctic amplification is still unclear. Atmospheric Rivers (ARs) are narrow and transient river-style moisture flows from the sub-polar regions. The integrated water vapour transport associated with ARs can explain up to 70% of the precipitation variance north of 70°N. However, there are still uncertainties regarding the specific role and the impact of ARs on the Arctic climate variability. For the first time, the high-resolution ICON modelling framework is used over the Arctic region. Pan Arctic simulations (from 13 km down to ca. 6 and 3 km) are performed to investigate processes related with anomalous moisture transport into the Arctic. Based on a case study over the Nordic Seas, the representation of the atmospheric circulation and the spatio-temporal structure of water vapor, temperature and precipitation within the limited-area mode (LAM) of the ICON model is assessed, and compared with reanalysis and in-situ datasets. Preliminary results show that the moisture intrusion is relatively well represented in the ICON-LAM simulations. The study also shows added value in increasing the model horizontal resolution on the AR representation.</p>

scholarly journals Case study of a moisture intrusion over the Arctic with the ICON model: resolution dependence of its representation

2021 ◽  
Author(s):  
Hélène Bresson ◽  
Annette Rinke ◽  
Mario Mech ◽  
Daniel Reinert ◽  
Vera Schemann ◽  
...  
Keyword(s):  
High Resolution ◽  
Temporal Structure ◽  
Specific Humidity ◽  
The Arctic ◽  
Limited Area ◽  
Turbulent Heat ◽  
Strong Impact ◽  
Downward Longwave Radiation ◽  
Spatio Temporal

Abstract. The Arctic is warming faster than the global average and any other region. One important factor for this is the poleward atmospheric transport of heat and moisture, which contributes directly to the surface and air warming. In this case study, the atmospheric circulation and spatio-temporal structure of a moisture intrusion event is assessed, which occurred during the 5th to 7th June 2017 over the Nordic Seas during an intensive measurement campaign over Svalbard. This analysis focuses on high-spatial resolution simulations with the ICON (ICOsahedral Non-hydrostatic) model which is put in context with coarser resolution runs as well the ERA5 reanalysis. A variety of observations including passive microwave satellite measurements is used for evaluation. The global operational ICON forecasts from the German Weather Service DWD at 13 km horizontal resolution are used to drive high resolution Limited Area Mode (LAM) ICON simulations over the Arctic with 6 km and 3 km horizontal resolutions. The results show the skillfull capacity of the ICON-LAM model to represent the observed spatio-temporal structure of the selected moisture intrusion event and its signature in the temperature, humidity and wind profiles, and surface radiation. The high resolution simulations offer a higher accuracy than the global simulations and the ERA5 reanalysis, compared to observations. This is especially demonstrated in the representation of the changing vertical structure of specific humidity and wind associated with the moisture intrusion passing Ny-Ålesund (western Svalbard). Namely, the humidity increase in 1–2 km height topped by a dry layer and the development of a low-level wind jet is best represented by the 3 km simulation. The study also demonstrates that such moisture intrusions can have a strong impact on the radiative and turbulent heat fluxes at the surface. A drastic decrease of downward shortwave radiation by ca. 500 W m−2 and an increase of downward longwave radiation by ca. 100 W m−2 within 3 hours are determined, which highlight the importance of both moisture and clouds associated with this event for the surface energy budget.

scholarly journals Impact of Doppler Radar Wind Observations on Australian High-Resolution Numerical Weather Prediction

2020 ◽  
Vol 35 (2) ◽  
pp. 309-324
Author(s):  
Susan Rennie ◽  
Lawrence Rikus ◽  
Nathan Eizenberg ◽  
Peter Steinle ◽  
Monika Krysta
Keyword(s):  
High Resolution ◽  
Data Assimilation ◽  
Numerical Weather Prediction ◽  
Doppler Radar ◽  
Weather Prediction ◽  
Limited Area ◽  
Observation Error ◽  
Numerical Weather ◽  
Skill Scores ◽  
The Impact

Abstract The impact of Doppler radar wind observations on forecasts from a developmental, high-resolution numerical weather prediction (NWP) system is assessed. The new 1.5-km limited-area model will be Australia’s first such operational NWP system to include data assimilation. During development, the assimilation of radar wind observations was trialed over a 2-month period to approve the initial inclusion of these observations. Three trials were run: the first with no radar data, the second with radial wind observations from precipitation echoes, and the third with radial winds from both precipitation and insect echoes. The forecasts were verified against surface observations from automatic weather stations, against rainfall accumulations using fractions skill scores, and against satellite cloud observations. These methods encompassed verification across a range of vertical levels. Additionally, a case study was examined more closely. Overall results showed little statistical difference in skill between the trials, and the net impact was neutral. While the new observations clearly affected the forecast, the objective and subjective analyses showed a neutral impact on the forecast overall. As a first step, this result is satisfactory for the operational implementation. In future, upgrades to the radar network will start to reduce the observation error, and further improvements to the data assimilation are planned, which may be expected to improve the impact.

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