pinecone/core-2020-05-10-deduplication huggingface dataset:
State and parameter estimation using Monte Carlo evaluation of path
  integrals

Transferring information from observations of a dynamical system to estimate
the fixed parameters and unobserved states of a system model can be formulated
as the evaluation of a discrete time path integral in model state space. The
observations serve as a guiding potential working with the dynamical rules of
the model to direct system orbits in state space. The path integral
representation permits direct numerical evaluation of the conditional mean path
through the state space as well as conditional moments about this mean. Using a
Monte Carlo method for selecting paths through state space we show how these
moments can be evaluated and demonstrate in an interesting model system the
explicit influence of the role of transfer of information from the
observations. We address the question of how many observations are required to
estimate the unobserved state variables, and we examine the assumptions of
Gaussianity of the underlying conditional probability.Comment: Submitted to the Quarterly Journal of the Royal Meteorological
  Society, 19 pages, 5 figure
On Variational Data Assimilation in Continuous Time

Variational data assimilation in continuous time is revisited. The central
techniques applied in this paper are in part adopted from the theory of optimal
nonlinear control. Alternatively, the investigated approach can be considered
as a continuous time generalisation of what is known as weakly constrained four
dimensional variational assimilation (WC--4DVAR) in the geosciences. The
technique allows to assimilate trajectories in the case of partial observations
and in the presence of model error. Several mathematical aspects of the
approach are studied. Computationally, it amounts to solving a two point
boundary value problem. For imperfect models, the trade off between small
dynamical error (i.e. the trajectory obeys the model dynamics) and small
observational error (i.e. the trajectory closely follows the observations) is
investigated. For (nearly) perfect models, this trade off turns out to be
(nearly) trivial in some sense, yet allowing for some dynamical error is shown
to have positive effects even in this situation. The presented formalism is
dynamical in character; no assumptions need to be made about the presence (or
absence) of dynamical or observational noise, let alone about their statistics.Comment: 28 Pages, 12 Figure
The Water Vapour Intercomparison Effort in the Framework\ud
of the Convective and Orographically-Induced Precipitation\ud
Study: Airborne-to-Ground-based and airborne-to-airborne\ud
Lidar Systems

An intensive water vapour intercomparison effort, involving airborne and ground-based water vapour lidar systems, was carried out in the framework of the COPS experiment. The main objective of this paper is to provide accurate error estimates for these systems.\ud
Comparisons between the ground-based Raman lidar BASIL and the airborne CNRS DIAL indicate a mean relative bias between the two sensors, calculated with respect to the mean\ud
value of -2.13% (-0.034 g/kg) in the altitude region 0.5Ã¢Â�Â�3.5 km, while comparisons between BASIL and the airborne DLR DIAL lead to a mean relative bias of 1.87% (0.018 g/kg) in this same altitude region.\ud
Comparisons between the ground-based UHOH DIAL and the CNRS DIAL indicate a bias of -\ud
3.2% (-0.37x1022 m-3) in the altitude range 1.5-4.5 km, while comparisons between the UHOH DIAL and the DLR DIAL indicate a bias of 0.83% (0.06x1022 m-3) in this same\ud
altitude range. Based on the available comparisons between the ground-based Raman lidar BERTHA and the CNRS DIAL, the mean relative bias is found to be -4.37% (-0.123g/kg) in\ud
the altitude region 0.5Ã¢Â�Â�4.5 km. Comparisons between the ground-based IGN Raman lidar and the CNRS DIAL indicate a bias of 3.18% (0.55 g/kg) in the altitude range from 0.5-4.5 km, while comparisons between the CNRS DIAL and DLR DIAL result in a mean relative bias of 3.93% (1.1x1022 m-3) in the altitude interval 0.5-4.0 km. Based on the available statistics of comparisons, benefiting from the fact that the CNRS DIAL was able to be compared with all other lidar systems, and putting equal weight to the data reliability of each instrument, overall relative values for BASIL, BERTHA, IGN Raman lidar, UHOH DIAL, DLR DIAL, and CNRS DIAL, with respect to the mean value, are found to be -0.38, -2.60, 4.90, -1,43, -2.23 and 1,72%, respectively
Initiation of deep convection at marginal instability in an ensemble of mesoscalemodels: a case-study from COPS

The present study investigates the initiation of precipitating deep convection in an ensemble of convection-resolving mesoscalemodels. Results of eight differentmodel\ud
runs from five non-hydrostatic models are compared for a case of the Convective andOrographically-induced Precipitation Study (COPS).An isolated convective cell\ud
initiated east of the Black Forest crest in southwest Germany, although convective available potential energy was only moderate and convective inhibition was high.\ud
Measurements revealed that, due to the absence of synoptic forcing, convection was\ud
initiated by local processes related to the orography. In particular, the lifting by\ud
low-level convergence in the planetary boundary layer is assumed to be the dominant process on that day. The models used different configurations as well as different initial and boundary conditions.By comparing the different model performance with each other and with measurements, the processes which need to be well represented to initiate convection at the right place and time are discussed. Besides an accurate specification of the thermodynamic and kinematic fields, the results highlight the role of boundary-layer convergence features for quantitative precipitation forecasts in mountainous terrain
Forecasting summer convection over the Black Forest: A case study from the Convective and Orographically-induced Precipitation Study (COPS) experiment

In the mid-afternoon of 15th July 2007, during the Convective and Orographically-induced Precipitation Study (COPS), in\ud
a very warm and dry environment, an isolated, short-lived, deep convective system developed over the southern Black-Forest. Most of the high-resolution, convection-permitting models involved in COPS were unable to capture this event whereas the Meso-NH forecast was quite skilful. To further assess the Meso-NH performance, the model results were carefully checked against the various\ud
and numerous COPS observations. In full agreement with clear-air radar observations, model results underlined the triggering role of a low-level level convergence line, which developed in the lee of the Feldberg. The main departure from the observations was found\ud
to be in the low-level moisture fields, which appeared significantly moister in the model than in the observations and also slightly moister than in the other models. Sensitivity studies showed that this departure from the observations was strongly controlled by the initial surface moisture conditions. When the surface moisture was reduced by 20% or replaced by the value derived from a different\ud
analysis, the evolution of the planetary boundary layer was more accurately represented while the storm evolution was still correctly captured. These results demonstate that the quality of the initial forecast cannot be ascribed to the moist bias of the model. It could therefore be hypothesized that the key parameters for a satisfactory forecast of this event lay more in the ability of the model to accurately reproduce the dynamical forcing than in the characteristics of the air-mass instability
In situ aerosol measurements taken during the 2007 COPS field campaign at the Hornisgrinde ground site

Copyright @ 2011 Royal Meteorological Society.The Convective and Orographically-induced Precipitation Study (COPS) campaign was conducted during the summer of 2007. A suite of instruments housed at the top of the Hornisgrinde Mountain (1156 m) in the Black Forest region of south-west Germany provided datasets that allow an investigation into the physical, chemical and hygroscopic properties of the aerosol particles sampled during COPS. Organic mass loadings were found to dominate the aerosol composition for the majority of the project, exceeding 8 µg m−3 during a period of high pressure, high temperature, and low wind speed. The ratio of organic:sulphate sub-micron mass concentration exceeds 10:1 during the same time period. Back trajectories show air from this time-frame passing slowly over the local forest and not passing over any local anthropogenic sources. Occasional peaks in nitrate mass loadings were associated with changes in the typical wind direction from south-westerly to north-westerly where air had passed over the Stuttgart region. Size distribution data shows a dominant accumulation-mode when the measurement site was free from precipitation events. A sharp increase in ultrafine particle number concentration was seen during most days commencing around noon. The apparent growth of these particles is associated with an increase in organic mass loading, suggesting condensational growth. For the most part, with the exception of the high pressure period, the aerosol properties recorded during COPS were comparable to previous studies of continental aerosol properties.NER
Spectrum of infrasound radiation from supercell storms

We consider the generation of acoustic waves by turbulent convection and
perform spectral analysis of a monopole source of sound related to the heat
production by condensation of moisture. A quantitative explanation of the
correlation between intensity of infrasound generated by supercell storms and
later tornado formation is given. It is shown that low lifting condensation
level (LCL) and high values of convective available potential energy (CAPE),
which are known to favor significant tornadoes, also lead to a strong
enhancement of supercell's low frequency acoustic radiation.Comment: 11 pages, Submitted to QJRM
Radar climatology of the COPS region

A climatology of convection initiation (CI) and convective enhancements (CE) has been developed using radar reflectivity data in southwestern Germany and eastern\ud
France over the period of MayÃ¢Â�Â�August of 2000Ã¢Â�Â�2006 and 2008. The study region included the Vosges Mountains of France, the Rhine Valley which straddles France and Germany, the Black ForestMountains and the SwabianMountains of Germany.\ud
Convection occurred frequently during the summer months throughout the study region. The CI density (number of initiations per square km) illustrates preferential formation in the mountain regions while the CE events spanned both mountains and valleys nearly equally. There is a strongmid-day peak of the CI events suggesting that diurnal heating is critical for CI in the region. The very strong thunderstorms (>46 dBZ) first occurred in the mountains and Ã¢Â�Â¼2 h later in the Rhine Valley.\ud
During the summer of 2007, the Convective and Orographically-induced Precipitation Study (COPS) field campaign was conducted with the objective\ud
of obtaining improved understanding of convective processes and short-term quantitative precipitation forecasting in low-mountain regions. Comparisons were\ud
made between the radar climatology results and the COPS summer. The COPS summer exhibited preferential CI density in the mountainous regions but not as pronounced as the climatology. The COPS summer had a similar diurnal peak of CI events as climatology but the ratio of daytime to nighttime CI (1.7), or amplitude of the diurnal cycle, was less than that of climatology (3.0). While both the 8-year climatology and COPS summer were dominated by daytime, locally-forced CI\ud
occurrences, the broad distribution of daytime CI events and increase in nighttime events observed during COPS indicate a more active synoptic pattern in 2007
Development of ice particles in convective clouds observed over the Black Forest mountains during COPS

A combination of modelling studies and ground-based and aircraft measurements is used to examine the development of ice particles in convective clouds observed over the Black Forest mountains during the Convective and Orographically-induced Precipitation Study (COPS). High concentrations of relatively small ice particles were observed in the weaker northern cell that developed on convergence lines over the mountains in the much-studied 15 July 2007 case. The conditions in the cloud were not conducive for the HallettÃ¢Â�Â�Mossop process. Instead, the explanation for such high concentrations of ice is likely associated with the type of ice nuclei ingested into the cloud. Biological nuclei, oxidised organic aerosol particles in the polluted air vented from the Murg valley into the cloud base, and desert dust are all possible candidates. A model sensitivity test with biological nuclei produced similar concentrations of ice particles to the observations. In contrast, the high concentration of ice particles measured in clouds that advected over the Black Forest mountains on 11 July 2007 were likely due to the HallettÃ¢Â�Â�Mossop process.\ud
The deep convective cell at the southern end of the COPS domain on 15 July 2007 developed in less polluted air than the shallower northern cloud. A model sensitivity test with lower aerosol loading produced a more vigorous cloud with a higher top, more precipitation, and greater reflectivity, more similar to the radar observations. The results suggest that aerosol particles vented out of the valleys could have a significant impact on orographically induced precipitation
The Convective and Orographically-induced Precipitation Study (COPS): the scientific strategy, the field phase, and research highlights

Within the framework of the international field campaign COPS (Convective and Orographically-induced Precipitation Study), a large suite of state-of-the-art meteorological instrumentation was operated, partially combined for the first time. This includes networks of in situ and remote-sensing systems such as the Global Positioning System as well as a synergy of multi-wavelength passive and active\ud
remote-sensing instruments such as advanced radar and lidar systems. The COPS field phase was performed from 01 June to 31 August 2007 in a low-mountain\ud
area in southwestern Germany/eastern France covering the Vosges mountains, the Rhine valley and the Black Forest mountains. The collected data set covers\ud
the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase until their decay. Eighteen\ud
Intensive Observation Periods with 37 operation days and eight additional Special Observation Periods were performed, providing a comprehensive data set covering\ud
different forcing conditions. In this article, an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS research provides new insight into key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of quantitative precipitation forecasting by the assimilation of new observations,\ud
and in the performance of ensembles of convection-permitting models in complex\ud
terrain
Latent Heat Flux Measurements over Complex Terrain by Airborne Water Vapour and Wind Lidars

Vertical profiles of the latent heat flux in a convective boundary layer (CBL) are obtained for the first time over complex terrain with airborne water vapour differential absorption lidar and Doppler wind lidar. During the Convective and Orographically-induced Precipitation Study (COPS) over the Black Forest Mountains in south-western Germany both lidars were installed nadir-viewing onboard the Falcon research aircraft of the Deutsches Zentrum fÃ�Â¼r Luft- und Raumfahrt (DLR). On 30 July 2007, additional in-situ measurements by the Karlsruhe Institute of Technology (KIT) were performed with a Dornier-128 aircraft that flew below the Falcon. This unique instrument configuration allows to validate the lidar-derived fluxes and to assess lidar-specific issues such as instrument noise and data gaps that impinge on the results. The cospectra of in-situ humidity and vertical velocity peak at wavelengths between 1 - 3 km and reveal that the dominant scales of turbulent transport are larger than 700 m in space. Consequently the airborne lidarsÃ¢Â�Â� horizontal and vertical resolution of ~200 m is sufficient to seize most of the flux. The lidar and in-situ fluxes of five collocated 45-km flight legs agree within Ã�Â±20 %, the average difference over the total distance of 225 km is 3 %. A flux comparison with ground-based water vapour Raman and wind lidars shows agreement within the instrumentsÃ¢Â�Â� accuracies under low-wind conditions. All latent heat fluxes vary between 100 - 500 W/mÃ�Â² in the CBL and have small vertical divergences. Vertical velocity spectra in the mid-CBL enable to estimate the dissipation rate of turbulent kinetic energy that amounts to 5Ã¢Â�Â¢10-4 m2 s-3 in the Rhine Valley and 10-3 m2 s-3 over the Black Forest Mountains. This new airborne lidar instrumentation proves to be a valuable tool for the study of CBL processes and variability, particularly over complex terrain
Observation of convection initiation processes with a suite of\ud
state-of-the-art research instruments during COPS IOP 8b

In the afternoon of15 July 2007, a thunderstormwas initiatedwithin a line ofcumulus\ud
clouds which formed parallel to the crest of the Black Forest mountains during the\ud
Intensive Observation Period (IOP) 8b of the Convective and Orographicallyinduced\ud
Precipitation Study (COPS). This paper extends the analysis of processes that led to convection initiation (CI), i.e. the transition from shallow to deep\ud
convection, on this day with the data from several COPS instruments that have not been considered in previous studies. In particular, the boundary-layer structure,\ud
lids and the water-vapour field in the pre-convective environment of the event are discussed. For this purpose, we investigated measurements of water-vapour lidars, temperature lidars and wind lidars, profiles from radiosondes, in situ aircraft data\ud
and gridded data of weather stations as well as GPS integrated-water-vapour data and satellite imagery. Thermally driven circulation systems formed over both the Black Forest and the Vosges mountain ranges which resulted in local convergence zones. These superimposed with the large-scale convergence in the Black Forest area. In the presence of sufficient moisture and updraught, clouds formed close to\ud
the mountain crests. The related latent-heat release allowed larger thermals to be\ud
produced, which may have had a positive feedback on stabilizing these convergence zones as a whole. We believe that differences in the moisture field explain why convection remained shallow and sparse over the Vosges mountains because these differences were responsible for differences in convective inhibition (CIN). The stationary location of the convergence zone over the southern Black Forest was probably decisive for CI because it constantly transported sensible and latent heat into the area inwhich CI took place
Process-oriented large-eddy simulations of a midlatitude cirrus\ud
cloud system based on observations

We apply a cloud-resolving model with explicit aerosol and ice microphysics and Lagrangian ice particle tracking to simulate the evolution of a cirrus cloud field\ud
observed during the US Atmospheric Radiation Measurement Program Intensive Operational Period in March 2000. This comprehensive data set includes remote\ud
sensing, radiosonde, and aircraft measurements of a midlatitude cirrus cloud system, supported by estimates of the dynamical cloud forcing. The dataset allows\ud
us to evaluate and study in great detail the process-oriented representation of the microphysical processes relevant to the formation and evolution of deep,\ud
stratiform cirrus (in particular ice crystal sedimentation and aggregation). The suite of explicitly resolved physical processes in our model enables us to better understand\ud
the sensitivity of the simulated cirrus properties on a large number ofmicrophysical and environmental parameters.\ud
The evolution of the domain-integrated cloud optical depth is largely dominated by homogeneous freezing processes.Wefind that the evolution of the observed cirrus\ud
cloud system is most dependent on updraught speed and ice supersaturation and that homogeneous freezing leads to a total, cloud-averaged ice crystal concentration\ud
of 0.1 cmÃ¢Â�Â�3 of air. It is not necessary to invoke heterogeneous ice nuclei to explain most of the data, but we cannot rule out that a small concentration (up to\ud
0.002 cmÃ¢Â�Â�3) of such particles may have affected the cirrus cloud field in nature.\ud
Cloud-averaged ice particle size distributions are bimodal, separating two distinct growth regimes in the developed cloud. The small mode (ice particle sizes below a\ud
few 100Ã�Â¼m) forms by homogeneous freezing of supercooled aerosol droplets and grows by deposition of water molecules from the gas phase. The large mode (sizes up to several 1000Ã�Â¼m) forms and grows by aggregation. We demonstrate that the formation of the largest crystals by aggregation in deep cirrus is controlled in part by the nucleation of new ice crystals in dynamically active, highly supersaturated upper cloud regions. Furthermore, a pronounced increase in the number of aggregation events is predicted in sublimation zones. The combined effect of sublimation and sedimentation leads to the formation of a very thin (vertical extension Ã¢Â�Â¼ 100 m) sublimation microlayer mainly composed of aggregated ice crystals, containing relatively high total ice crystal number concentrations (Ã¢Â�Â¼ 0.02 cmÃ¢Â�Â�3) comparable to those generated locally by homogeneous freezing in the upper cloud layers
Ocean ensemble forecasting. Part I: Ensemble Mediterranean winds from a Bayesian hierarchical model

A Bayesian hierarchical model (BHM) is developed to estimate surface vector
wind (SVW) fields and associated uncertainties over the Mediterranean Sea. The
BHM–SVW incorporates data-stage inputs from analyses and forecasts of the
European Centre for Medium-Range Weather Forecasts (ECMWF) and SVW
retrievals from the QuikSCAT data record. The process-model stage of the
BHM–SVW is based on a Rayleigh friction equation model for surface winds.
Dynamical interpretations of posterior distributions of the BHM–SVW parameters
are discussed. Ten realizations from the posterior distribution of the BHM–SVW
are used to force the data-assimilation step of an experimental ensemble ocean
forecast system for the Mediterranean Sea in order to create a set of ensemble
initial conditions. The sequential data-assimilation method of the Mediterranean
forecast system (MFS) is adapted to the ensemble implementation. Analyses
of sample ensemble initial conditions for a single data-assimilation period in
MFS are presented to demonstrate the multivariate impact of the BHM–SVW
ensemble generation methodology. Ensemble initial-condition spread is quantified
by computing standard deviations of ocean state variable fields over the ten ensemble
members. The methodological findings in this article are of two kinds. From the
perspective of statistical modelling, the process-model development is more closely
related tophysicalbalances than inpreviousworkwithmodels for the SVW.Fromthe
ocean forecast perspective, the generation of ocean ensemble initial conditions via
BHM is shown to be practical for operational implementation in an ensemble ocean
forecast system. Phenomenologically, ensemble spread generated via BHM–SVW
occurs on ocean mesoscale time- and space-scales, in close association with strong
synoptic-scale wind-forcing events. A companion article describes the impacts of
the BHM–SVW ensemble method on the ocean forecast in comparisons with more
traditional ensemble methods