AS1.14

Fusion of polarimetric radar observations, atmospheric modelling, and data assimilation for improved cloud and precipitation process understanding, model evaluation and parameterization development

Cloud and precipitation processes are still a main source of uncertainties in numerical weather prediction and climate change projections. During recent years, large progress has been made in implementing those processes in a more realistic way and with a higher level of detail in models. Simultaneously, also our observational capabilities, especially in the field of radar remote sensing, has been substantially improved by the availability of large national networks, improved instrument accuracy, and also new and more affordable technology. Radar polarimetry in particular is known for its high information content of cloud and precipitation processes. Complementary radar observations, such as polarimetric Doppler spectra or multi-frequency cloud radar observations are also increasingly used to further extend our ability to derive characteristic fingerprints of those processes and inform atmospheric models.
This session invites contributions, which combine radar polarimetry or cloud radars with atmospheric models for an improved understanding of moist processes, numerical model evaluation, or parameterization development, as well as studies advancing the direct assimilation of polarimetric measurements or polarimetry-derived information. The combination of radar polarimetry, atmospheric modelling and data assimilation is also the focus of the German research initiative PROM (Polarimetric Radar Observations meet atmospheric Modelling). We invite contributions from all scientists working at the intersection of these fields.

Convener: Silke Troemel | Co-conveners: Andrew Barrett, Stefan Kneifel, Jana Mendrok, Johannes Quaas
Presentations
| Wed, 25 May, 08:30–10:00 (CEST)
 
Room 0.11/12

Presentations: Wed, 25 May | Room 0.11/12

Chairpersons: Silke Troemel, Leonie von Terzi, Giovanni Chellini
08:30–08:33
08:33–08:43
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EGU22-8710
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solicited
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Highlight
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On-site presentation
Toshi Matsui, David Wolff, Stephen Lang, and Karen Mohr

The BiLateral Operational Storm-Scale Observation and Modeling (BLOSSOM) project was initiated in order to establish routine storm-scale polarimetric radar observations and cloud-process modeling at NASA GSFC Wallops Flight Facility (WFF), where various continental and maritime convective systems are being observed. The ultimate goals of BLOSSOM include:

  • Establish a long-term super site to improve understanding of cloud physical states and processes over the WFF site through bilateral storm-scale observations and modeling.
  • Provide routine meteorological large-scale forcing input to support cloud-resolving models (CRMs), large-eddy simulation (LES) models, and single-column models (SCMs) for the improvement of cloud microphysics and convection parameterizations.
  • Provide routine storm-scale cloud-precipitation simulations as well as storm-scale measurements using ground-based polarimetric Doppler radar and in-situ data.
  • Collect and organize value-added data from the cloud-process simulations, ground-based polarimetric radar, and NASA satellite observations for the community.

 

This presentation will highlights a few case studies to test the concept of BLOSSOM, including the creation of ensemble large-scale forcing, configuring and performing cloud-process simulations with different bulk microphysics using the Goddard Cumulus Ensemble (GCE) model, organizing and streaming NASA S-band dual-POLarimetric radar (NPOL) and other WFF instrument data, and validating the ensemble GCE simulations through formulating statistical composites by comparing observed and simulated polarimetric radar signals using the POLArimetric Radar Retrieval and Instrument Simulator (POLARRIS). Different spatial grid spacing (1km vs 250m) of the GCE simulations will be also evaluated to examine resolution impact on representing time-series as well as time-integrated composites of polarimetric radar signals.

How to cite: Matsui, T., Wolff, D., Lang, S., and Mohr, K.: Systematic Validation of Ensemble Cloud-Process Simulations using Polarimetric Radar Observations and Simulator over the NASA Wallops Flight Facility, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8710, https://doi.org/10.5194/egusphere-egu22-8710, 2022.

08:43–08:50
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EGU22-11786
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Highlight
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On-site presentation
Jana Mendrok, Jacob Carlin, Jeffrey Snyder, Silke Trömel, Prabhakar Shrestha, and Ulrich Blahak

Radar observations play a crucial role in detecting and measuring precipitation (QPE, nowcasting) and are useful in various ways to improve numerical weather prediction (NWP) models. Accurate quantitative precipitation estimation remains a challenge as relationships between radar reflectivity and precipitation rate are inheritly ambiguous.Polarimetric observations have the potential to constrain hydrometeor microphysics (size, shape, orientation, etc.) better than conventional ones. Beside improving precipitation measurements, polarimetric observations can be used to evaluate, validate, and improve the representation of hydrometeors in NWP models.Calculating radar observables from prognostic NWP state variables, forward operators (FOs) are a crucial link in comparing radar measurements to NWP output. This requires that the FOs can accurately simulate corresponding observations and that they are consistent with the model(s), e.g. regarding hydrometeor microphysics. However, a wide range of parameters that affect FO output, are not constrained well by the NWP models. This includes, e.g. the melting state, the shape and microstructure, and the orientation of the hydrometeors. Characterization of the uncertainties of an FO, hence, is fundamental to allow its optimal exploitation. Here, we present the revised and polarimetry-extended version of EMVORADO (Efficient Modular VOlume RADar forward Operator) that is coupled to the ICON and COSMO NWP models and applied by DWD in operational weather forecast/data assimilation. Recent developments have focused on enabling polarimetric simulations with computational speed comparable to the Mie-based simulations so far applied in the operational data assimilation as well as to transferability of the code and intermediate calculation results (lookup tables, namely) between different computer architectures. The ability of the FO to reproduce observed polarimetric signatures is evaluated. Uncertainties resulting from weakly or unconstrained assumptions as well as effects of certain techniques and approximations to enhance efficiency are discussed, regarding their impact on analysis of observations and evaluation of NWP models.

How to cite: Mendrok, J., Carlin, J., Snyder, J., Trömel, S., Shrestha, P., and Blahak, U.: An efficient polarimetric radar forward operator for NWP model validation and data assimilation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11786, https://doi.org/10.5194/egusphere-egu22-11786, 2022.

08:50–08:57
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EGU22-11047
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ECS
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Highlight
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Virtual presentation
Velibor Pejcic, Jana Mendrok, Ulrich Blahak, and Silke Trömel

Polarimetric weather radars provide the opportunity to derive spatially and temporally high-resolved hydrometeor distributions to evaluate the representation of hydrometeors in the operational Numerical Weather Prediction (NWP) model ICON-LAM of the German Weather Service (DWD). However, differences in considered hydrometeor types in the model and radar-based hydrometeor classification schemes (HMC) complicate the task. Furthermore, ICON-LAM 2-moment scheme provides number and mass concentration of hail, graupel, rain, snow, cloud ice and cloud water for each model grid-box, while conventional radar-based hydrometeor retrievals indicate only the dominant hydrometeor class in in each radar volume.

In this study, a dual-strategy is proposed for model evaluation. A sophisticated HMC, adapted to the number and types of hydrometeors in the model is developed, which allows to estimate hydrometeor partitioning ratios from radar observations in two steps. First, radar measurements are clustered based on their multidimensional polarimetric signature similarity and afterwards a state-of-the-art HMC is used for the hydrometeor class identification of the resulting clusters. Secondly, the centroids derived from the multidimensional polarimetric clusters and their probability distributions are used for the determination of the hydrometeor partitioning ratios of the individual hydrometeor class. Using ICON's built-in radar polarimetric forward operator (PFO) EMVORADO (Efficient Modular VOlume scan RADar Operator) enables us to simulate synthetic radar observations from modelled hydrometeor distributions. Based on these tools, the dual strategy for model evaluation includes 1) the comparison of hydrometeor distributions derived from the measured and simulated polarimetric moments with the hydrometeor distribution simulated in ICON-LAM, and 2) a direct comparison of the simulated and measured polarimetric moments, which also provides feedback regarding the performance of the PFO and the HMC.

Comparisons of volumetric scans from DWD’s national C-band radars network for stratiform and convective case study days with model simulations revealed e.g. spurious graupel generation around the melting layer (ML). Furthermore, synthetic reflectivity (ZH) and differential reflectivity (ZDR) are too high in rain, most likely caused by raindrop size errors in the model.

How to cite: Pejcic, V., Mendrok, J., Blahak, U., and Trömel, S.: Polarimetry-based hydrometeor classification from synthetic and measured radar observations for the evaluation of hydrometeor mixtures in numerical weather prediction models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11047, https://doi.org/10.5194/egusphere-egu22-11047, 2022.

08:57–09:04
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EGU22-7667
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ECS
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On-site presentation
Tobias Scharbach and Silke Trömel

Radar polarimetry and novel developed microphysical retrievals offer great potential for evaluating and improving the parameterization of numerical models. In this study, we intend to inform the subgrid parameterizations of the ICON general circulation model (ICON-GCM), more specifically, to assess and improve the spatial heterogeneity of ice water content at ICON subgrid scales. QVPs (Quasi-Vertical Profiles), generated by azimuthal averaging of various polarimetric radar variables from PPIs (Plan Position Indicators) acquired during standard conical scans at antenna elevation angles of 18°, successfully reduce statistical errors or uncertainties, especially in phase-based measurements such as KDP (specific differential phase). The QVP method, with a horizontal resolution of about 50 km and a vertical resolution of 30-300 m, provides the ideal data basis for various robust polarimetric microphysical retrievals of ice water content (IWC), total number concentration (Nt), and mean volume diameter (Dm). Moreover, an attempt is made to improve the specific threshold used in ICON-GCM for the onset of aggregation (particle diameter < 0.1 mm for ice and > 0.1 mm for snow) by using estimated particle size distributions (PSD) assuming an exponential function. Although BoXPol (the polarimetric X-band radar in Bonn, Germany) is not sensitive to the smallest ice particles, this indirect method opens the possibility to determine and analyze the variabilities of ice and snow separately and finally evaluate and improve the parameterizations of ICON-GCM. However, the use of QVPs reduces information on sub-grid scale variability compared to the higher-resolved PPIs. A key question is therefore how much averaging is required for robust estimates of IWC, Nt, and Dm, and how we can separate spatial variability from noise. Statistical errors and spatial variabilities/azimuthal standard deviations of different IWC retrievals are analyzed using measurements from BoXPol. It is assumed that the real spatio-temporal variability equals the difference between the azimuthal standard deviation and the standard error of the mean computed over different ranges/heights. The standard error of the mean is calculated by Gaussian error propagation using Bienaymé's law, and it is investigated to what extent the azimuthal window size of 360° in the QVP methodology can be reduced while still guarantee acceptable statistical errors of the IWC, Dm, and Nt retrievals. Finally, based on a large BoXPol data set, statistics of the real IWC variability as a function of height are presented and compared to simulations of ICON-GCM. A new method is presented in which Shannon's information entropy is used to test the distribution of Zlin (linear reflectivity) for homogeneity within the PPIs.

How to cite: Scharbach, T. and Trömel, S.: Variabilities of ice water content, total number concentration and mean volume diameter for improved parametrizations using polarimetric retrievals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7667, https://doi.org/10.5194/egusphere-egu22-7667, 2022.

09:04–09:11
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EGU22-7623
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ECS
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On-site presentation
Armin Blanke, Andrew Heymsfield, Manuel Moser, and Silke Trömel

Polarimetric microphysical retrievals bear great potential for the evaluation of numerical models and data assimilation. However, a solid database is still lacking to evaluate their accuracy. In order to evaluate these retrievals and assess their accuracy, ground based polarimetric radar measurements are collocated spatially and temporally with airborne in-situ microphysical data collected during the OLYMPEX campaign (Olympic Mountain Experiment). Retrievals for ice water content, total number concentration, and mean volume diameter of ice particles are assessed exploiting both X-band Doppler on Wheels (DOW) measurements and an in-situ measurements obtained by the University of Dakota (UND) Citation aircraft. Vertical profiles of the microphysical retrievals are derived from sector-averaged RHI scans. The comparison of the retrievals with in-situ data above the freezing level reveals new insights into the strengths, weaknesses, and accuracies of the different retrievals, as well as the advantages using polarimetric retrievals rather than non-polarimetric ones. Results clearly demonstrate the superiority of the polarimetric retrievals. Furthermore, the recently introduced hybrid ice water content retrieval exploiting reflectivity ZH, differential reflectivity ZDR and specific differential phase KDP outperforms other retrievals based on either (ZH, ZDR) or (ZH, KDP) or non-polarimetric retrievals in terms of correlations with in-situ measurements and the root mean square error. ZH-based retrievals for the mean volume diameter partly exhibit significant deviations from airborne in-situ measurements, while polarimetric retrievals show a good agreement.

How to cite: Blanke, A., Heymsfield, A., Moser, M., and Trömel, S.: Evaluation of state-of-the-art polarimetric ice microphysical retrievals exploiting ground based radar and airborne in-situ measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7623, https://doi.org/10.5194/egusphere-egu22-7623, 2022.

09:11–09:18
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EGU22-6542
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ECS
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Virtual presentation
Eleni Tetoni, Florian Ewald, Martin Hagen, Gregor Köcher, Tobias Zinner, Bernhard Mayer, and Silke Groß

The importance of robust ice microphysics retrievals has been highlighted in the past by several studies. The accurate representation of ice microphysical processes can reduce the uncertainty in numerical weather models which have to deal with the complex nature – various habits, densities, sizes – of ice hydrometeors. To constrain microphysics information, we developed an ice microphysics retrieval algorithm combining measurements from two spatially separated radar instruments. The radar measurements comprise a novel combination of dual-wavelength and polarimetric perspective (i.e., differential radar reflectivity, ZDR) on ice hydrometeors. Exploiting the different scattering behavior (Rayleigh or Mie region) in different radar bands, the dual-wavelength dataset provides information about the ice hydrometeor size within clouds. In addition, ZDR from one of the radar instruments was also used to constrain the shape of ice particles. The measurements were performed with the C-band POLDIRAD (German Aerospace Center, Oberpfaffenhofen) and the Ka-band MIRA-35 (Ludwig-Maximilians-Universität, Munich) using coordinated range-height-indicator (RHI) scans to capture precipitation formation within the 23 km long cross-section between both instruments. To infer microphysical properties, T-matrix scattering simulations were performed in combination with necessary a-priori assumptions about the ice hydrometeors. Due to its versatility, we used the soft spheroid approximation to represent the prevalent ice particles. This approach along with a pre-defined relation between mass and particles dimension (mass-size relation) can help to constrain the prevalent ice particle density, a parameter which is known to be hardly constrained in numerical weather and climate models. In this work, we conducted several sensitivity studies to investigate which assumptions on mass-size relation, particle size distribution and shape (oblate or horizontally aligned prolate) can reproduce our radar observations for the soft spheroid ice model. We also investigated how these assumptions can influence the retrieved median size, the apparent shape and the ice water content of ice particles populations. Our hypotheses were tested for a stratiform precipitation case from a snowfall event over Munich in January 2019. 

How to cite: Tetoni, E., Ewald, F., Hagen, M., Köcher, G., Zinner, T., Mayer, B., and Groß, S.: Ice microphysics retrievals using polarimetric and dual-wavelength radar data – a sensitivity study regarding the assumed ice particle model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6542, https://doi.org/10.5194/egusphere-egu22-6542, 2022.

09:18–09:25
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EGU22-11287
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ECS
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On-site presentation
Leonie von Terzi, Stefan Kneifel, and Jose Dias-Neto

In recent years the dendritic growth zone (DGZ, between -20 and -10°C) has gained a lot of attention. It plays a significant role in the production of precipitation since the ice particle size and number concentration increase significantly in the DGZ. Previous studies have found layers of intense aggregation in the DGZ. Polarimetric radar measurements have revealed that these layers of enhanced aggregation are often accompanied by layers of enhanced differential radar reflectivity (ZDR) and specific differential phase shift (KDP). These observations suggest the growth and increase of concentration of oblate ice crystals at the same height where aggregation is enhanced. Analysis of radar Doppler spectra and mean Doppler velocity (MDV) have further shown a secondary, slow falling peak accompanied by a slow down in the MDV at the same height as the layers of enhanced aggregation and growth of ice particles.  From previous studies it is unclear and often case study dependent where this increase in number concentration of small ice crystals originates and whether it is connected to the enhanced aggregation in the DGZ.

We present a statistical analysis of DGZ observations collected during a three-month-long winter campaign in Jülich, Germany. For our analysis we use observations from a polarimetric W-band Doppler radar and zenith pointing X-, Ka- and W-Band Doppler radars. This unique setup allows us to simultaneously look at the aggregate size, as well as ice crystal shape and concentration. We can therefore look at the described increase of aggregation and ice crystal size and concentration in more detail and see if these signatures can be found in general in mid-latitude clouds.  

Similar to previous studies, our statistical analysis shows a strong increase of aggregation within the DGZ. This increase in aggregation is correlated to a slow down in MDV just below -15°C. The larger the particles in the DGZ, the larger is also the slow down of the MDV. The strong temperature dependence of the slow down and an analysis of the Doppler spectra allowed us to narrow down the origin to an increase in the concentration of small ice crystals in this region as well as enhanced depositional growth leading to a buoyancy effect. Due to the Doppler capabilities of our polarimetric W-band radar, we can derive the maximum of spectral ZDR (sZDRmax), which is not affected by the low ZDR of aggregates. sZDRmax starts to increase at just above -15°C, showing an increase in size of ice crystals at this height. Interestingly, sZDRmax stays constantly elevated until -4°C. KDP shows that the concentration of ice crystals is continuously increasing in the DGZ. This is in contrast to the KDP layers found in previous studies, where KDP was enhanced only around -15°C. We also find KDP to stay constantly elevated until -4°C. Given strong aggregation in the DGZ as a sink for small ice crystals, a source for this continuous increase in ice crystal concentration has to be found. 

 

How to cite: von Terzi, L., Kneifel, S., and Dias-Neto, J.: Aggregation in the Dendritic Growth Zone: A statistical analysis combining multi-frequency Doppler  and  polarimetric Doppler cloud radar observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11287, https://doi.org/10.5194/egusphere-egu22-11287, 2022.

09:25–09:32
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EGU22-5159
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ECS
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Virtual presentation
Jan-Niklas Welß, Leonie von Terzi, Stefan Kneifel, Axel Seifert, and Christoph Siewert

The dendritic growth zone (DGZ) plays a significant role in the production of precipitation and life cycle of clouds. Previous studies have shown that the DGZ is the region where the ice particle size first starts to increase through aggregation. This increase in ice particle size immensely influences the precipitation on the ground. In-situ cloud observations as well as polarimetric and Doppler radar observations of the DGZ have also shown an increase of ice particle number above the available ice nucleating particles concentration. It is unclear and often case study specific where this large number of new ice particles originates from and if this increase in ice particle concentration influences or even triggers the strong increase in particle size in the DGZ. 

In our work, we combine multi-frequency Doppler and polarimetric Doppler cloud radar observations with Monte-Carlo Lagrangian particle modeling linked by a polarimetric forward operator to test these hypotheses. While polarimetric radar observations are sensitive to small, asymmetric ice particles, the multi-frequency approach can provide information about aggregation and riming. This observational setup allows us to look at the size and shape of ice particles. However, detailed evolution of the particle’s properties and the interaction between ice microphysical processes, such as the aggregation of ice particles and generation of new particles in the DGZ, are difficult to identify using only remote-sensing observations. 

The Lagrangian super-particle model McSnow allows us to describe the microphysical process on the detailed particle level and with that track their individual history.   The newly implemented habit prediction scheme includes ice shape effects that represent various aspects of the particle properties and growth, such as a shape-dependent depositional growth rate, fall velocity, and density evolution, more realistically. Ice habit, fall velocity, and density are core information for radar forward simulations, facilitating the comparison with polarimetric observations.

This setup enables us to test observation-based hypotheses such as an increase in number concentration of small, asymmetric ice crystals in the DGZ due to secondary ice or seeder-feeder processes. First results show that the temperature at which the particle is first nucleated is crucial for the particle's habit development. To match the polarimetric radar observations around -15°C, the particles need to be nucleated within the plate-like growth regime at temperatures warmer than -20°C. Particles nucleated at colder temperatures and falling into the plate-like growth regime do not reach the expected habit and the needed aspect ratios to explain the polarimetric radar observations. It is therefore likely that the small particles that cause the distinct polarimetric features at -15°C do not stem from seeder-feeder processes but rather are generated close to the -15°C level. One possible generation process is ice fragmentation which has been found in previous studies to be particularly enhanced at this temperature regime.

How to cite: Welß, J.-N., von Terzi, L., Kneifel, S., Seifert, A., and Siewert, C.: Exploring the origin of increasing ice particle number in the dendritic growth zone combining polarimetric radar observations and novel Lagrangian particle modeling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5159, https://doi.org/10.5194/egusphere-egu22-5159, 2022.

09:32–09:39
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EGU22-11528
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ECS
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On-site presentation
Gregor Köcher, Florian Ewald, Martin Hagen, Christoph Knote, Eleni Tetoni, and Tobias Zinner

The representation of microphysical processes in numerical weather prediction models remains a main source of uncertainty until today. To evaluate the influence of cloud microphysics parameterizations on numerical weather prediction, a convection permitting regional weather model setup has been established using 5 different microphysics schemes of varying complexity (double-moment, spectral bin, particle property prediction (P3)). A polarimetric radar forward operator (CR-SIM) has been applied to simulate radar signals consistent with the simulated particles. The performance of the microphysics schemes is analyzed through a statistical comparison of the simulated radar signals to radar measurements on a dataset of 30 convection days. 

The observational data basis is provided by two polarimetric research radar systems in the area of Munich, Germany, at C- and Ka-band frequencies and a complementary polarimetric C-band radar operated by the German Meteorological Service.  By measuring at two different frequencies, the dual-wavelength ratio that facilitates the investigation of the particle size evolution is derived. Polarimetric radars provide in-cloud information about hydrometeor type and asphericity by measuring, e.g., the differential reflectivity ZDR.

Within the DFG Priority Programme 2115 PROM, we compare the simulated polarimetric and dual-wavelength radar signals with radar observations of convective clouds. Deviations are found between the schemes and observations in ice and liquid phase, related to the treatment of particle size distributions. Apart from the P3 scheme, simulated reflectivities in the ice phase are too high. Statistical distributions of simulated and observed polarimetric and dual-wavelength radar signals demonstrate the challenge to correctly represent ice and rain particle size distributions. The polarimetric information is further exploited by applying a classification algorithm to obtain dominant hydrometeor classes. By comparing the simulated and observed distribution of hydrometeors, as well as the frequency, intensity and area of high impact weather situations (e.g., hail or heavy convective precipitation), the influence of cloud microphysics on the ability to correctly predict high impact weather situations is examined.

How to cite: Köcher, G., Ewald, F., Hagen, M., Knote, C., Tetoni, E., and Zinner, T.: Evaluation of convective cloud microphysics in numerical weather prediction models with dual-wavelength polarimetric radar observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11528, https://doi.org/10.5194/egusphere-egu22-11528, 2022.

09:39–09:46
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EGU22-12147
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On-site presentation
Prabhakar Shrestha, Jana Mendrok, Velibor Pejcic, Silke Trömel, Ulrich Blahak, and Jacob Carlin

Polarimetric observation operators generate virtual observations from the models, which enable a direct comparison of observed and simulated radar signatures of microphysical processes. However, differences in polarimetric fingerprints between observations and models may result both from model deficiencies and faulty assumptions in observation operators. Using the Bonn Polarimetric Radar forward Operator (B-PRO), the evaluation of the German weather forecast model COSMO in radar observation space revealed deficiencies in the ice-snow partitioning and spurious graupel production near the melting layer. Follow-up sensitivity experiments with the model and forward operator (FO) guided the improvement of model parameters, namely the critical diameter of particles for ice-to-snow conversion by aggregation (Dice) and the threshold temperature responsible for graupel production by riming (Tgr), pushing the synthetic radar variables closer to the observations. However, the model still exhibited a low bias (lower magnitude than observation) in simulated polarimetric moments at lower levels above the melting layer (  -3 to   -13 ° C), where snow was found to dominate. Sensitivity experiments with the FO also could not explain this bias indicating shortcoming in the FO or missing cloud microphysical processes in the 2-moment cloud microphysical scheme of the model.

How to cite: Shrestha, P., Mendrok, J., Pejcic, V., Trömel, S., Blahak, U., and Carlin, J.: Evaluation of the COSMO model in polarimetric radar space – impact of uncertainties in model microphysics, retrievals and forward operators, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12147, https://doi.org/10.5194/egusphere-egu22-12147, 2022.

09:46–09:53
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EGU22-11309
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Virtual presentation
Woosub Roh and Masaki Satoh

It is important to evaluate and improve the cloud properties in global non-hydrostatic models like a Nonhydrostatic ICosahedral Atmospheric Model (NICAM, Satoh et al. 2014) using observation data. There are intensive observation stations over the Tokyo metropolitan area in Japan. The ULTIMATE (ULTra sIte for Measuring Atmosphere of Tokyo metropolitan Environment) is proposed to verify and improve high-resolution numerical simulations based on these observation data.

The C-band Polarimetric radars are in Haneda and Narita airports. A polarimetric radar can observe the additional information of hydrometeors related to the shapes and retrieve the hydrometeor identification based on polarimetric variables. 
In this study, we used the Joint simulator, which is developed for The EarthCARE satellite, which has Cloud Profiling Radar (CPR, 94 GHz) and High Spectral Resolution Lidar (HSRL). The EarthCARE Active Sensor Simulator (EASE, Okamoto et al. 2007, 2008; Nishizawa et al. 2008) in the Joint simulator can simulate signals of CPR and HSRL on the ground. POLArimetric Radar Retrieval and Instrument Simulator (POLARRIS, Matsui et. al. 2019) were implemented in the Joint simulator for the polarimetric radar. 

We introduced our evaluation method and results of our microphysics using polarimetric radars and the CPR.

 

How to cite: Roh, W. and Satoh, M.: Evaluations of microphysics in NICAM using a polarimetric radar and a 94 GHz Doppler radar in Japan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11309, https://doi.org/10.5194/egusphere-egu22-11309, 2022.

09:53–10:00
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EGU22-13008
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ECS
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Highlight
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On-site presentation
Kaveh Patakchi Yousefi and Stefan Kollet

Numerical weather prediction and climate models provide important information on essential atmospheric variables and extreme events. However, due to model uncertainties arising from initial value and model errors, the simulation results do not match in-situ or remotely sensed measured observations to an arbitrary accuracy. Machine Learning (ML) and/or Deep Learning (DL) methods have shown to be successful tools in closing the gap between models and observations due to high generalization skills and better representation of non-linear and complex relationships. This study focused on using UNet encoder-decoder Convolutional Neural Network (CNN) for extracting spatiotemporal features from model simulations and predicting the actual mismatches between the simulations results and a reference data set. Here, the model simulations serving as input to the CNN were obtained from climate simulations over Europe with the Terrestrial Systems Modeling Platform (TSMP-G2A). The reference data set representing observations was obtained from the COSMO-REA6 reanalysis. The proposed mismatch learning framework was applied to precipitation and surface pressure representing more and less chaotic variables, respectively. The study shows that UNet is able to learn the precipitation and surface pressure mismatches with a daily average correlation coefficient of 0.68 between the actual against predicted mismatches. Seasonal and regional intercomparisons of various precipitation types (e.g., stratiform rainfall, convective rainfall, and snowfall) reveal that the UNet faces challenges in learning the convective-type precipitation mismatches, which may be due to higher random uncertainties in model-based data. After training the UNet network, the reference data is no longer needed for generating the mismatch information. Thus, the UNet weights may be used online during the simulation or as a post-processor to correct predicted variables, which is useful in impact studies. In the first validation experiments, the corrected precipitation data show a strong improvement over the original simulated model data in mean error (47 % on average), correlation coefficient (37 % on average), and root mean square error (22 % on average).

How to cite: Patakchi Yousefi, K. and Kollet, S.: Closing the Gap between Models and Observations: Deep Learning from Mismatches , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13008, https://doi.org/10.5194/egusphere-egu22-13008, 2022.