Similarity and variability of blocked weather-regime dynamics in the Atlantic-European region

Weather regimes govern an important part of the sub-seasonal variability of the mid-latitude circulation. Due to their role in weather extremes and atmospheric predictability, regimes that feature a blocking anticyclone are of particular interest. This study investigates the dynamics of these ''blocked'' regimes in the North Atlantic-European region from a year-round perspective. For a comprehensive diagnostic, we combine wave activity concepts and a piecewise potential-vorticity (PV) tendency framework. The latter essentially quantifies the well-established PV perspective of mid-latitude dynamics. All blocked regimes during the 1979&ndash;2021 period of ERA5 reanalysis are considered. Wave activity characteristics exhibit distinct differences between blocked regimes. After regime onset, one regime (Greenland Blocking) is associated with a suppression of wave activity flux, whereas two other regimes (Atlantic Ridge and European Blocking) are associated with a northward deflection of the flux without a clear net change. During onset, the envelope of Rossby wave activity retracts upstream for Greenland Blocking, whereas the envelope extends downstream for Atlantic Ridge and European Blocking. The fourth regime (Scandinavian Blocking) exhibits intermediate wave activity characteristics. From the perspective of piecewise PV tendencies projected onto the respective regime pattern, the dynamics that govern regime onset exhibit a large degree of similarity: Linear Rossby wave dynamics and nonlinear eddy PV fluxes dominate and are of approximately equal relative importance, whereas baroclinic coupling and divergent amplification make minor contributions. Most strikingly, all blocked regimes exhibit very similar (intra-regime) variability: a retrograde and an upstream pathway to regime onset. The retrograde pathway is dominated by nonlinear PV eddy fluxes, whereas the upstream pathway is dominated by linear Rossby wave dynamics. Importantly, there is a large degree of cancellation between the two pathways for some of the mechanisms before regime onset. The physical meaning of a regime-mean perspective before onset can thus be severely limited. Implications of our results for understanding predictability of blocked regimes are discussed. We further discuss the limitations of projected tendencies in capturing the importance of moist processes, which tend to occur at the fringes or outside of the regime pattern. Finally, we stress that this study investigate the variability of the governing dynamics without prior empirical stratification of data by season or by type of regime transition. We demonstrate, however, that our dynamics-centered approach does not map predominantly on variability that is associated with these factors. The main modes of dynamical variability revealed herein, and the large similarity of the blocked regimes in exhibiting this variability are thus significant results.</p

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Bayesian Retrieval of thermodynamic atmospheric profiles from ground-based microwave radiometer data

Boden-basierte Mikrowellenradiometer werden in den Atmosphärenwissenschaften zunehmend verwendet um vertikale Informationen über Temperatur, Feuchte und Wolken zu erfassen. Solche Informationen sind für Grenzschichtforschung und Wettervorhersage wertvoll und es werden Anstrengungen unternommen, Beobachtungen von Mikrowellenradiometern in numerische Wettervorhersagemodelle zu assimilieren. Mehrere Methoden existieren um solche Information zu erhalten. Sie unterscheiden sich in Anforderungen an die Ausgangsdaten, der Benutzerfreundlichkeit und Flexibilität Messungen anderer Sensoren zu integrieren. Eine lineare Regressions- und Optimale Abschätzungstechnik wurden als Teil dieser Arbeit implementiert. Sie werden von einem Bayesschen Standpunkt hergeleitet und wichtige Merkmale dieser Methoden werden diskutiert. Schließlich wird deren Genauigkeit anhand von Radiosondendaten und Radiometermessungen aus Innsbruck evaluiert. Standardabweichungen von Temperaturprofilen aus optimaler Abschätzung, welche Vorhersagen eines numerischen Wettervorhersagemodells integrieren, betragen weniger als 1.2 K in der gesamten Troposphäre. Die ungenauste Region befindet sich zwischen 1.5 und 3 km über Grund. In diesen Höhen sind die numerischen Vorhersagen nicht so genau wie in der oberen Troposphäre und der Informationsgehalt des Radiometers hat im Vergleich zur unteren Atmosphäre schon substantiell abgenommen. Die Methode hat daher Probleme in dieser Region hohe Genauigkeit zu erreichen. Zwei Fallstudien zeigen, dass das optimale Abschätzungsschema vielversprechend zur Erfassung von Temperaturinversionen ist, welche ein häufig studiertes Problem in der Mikrowellenradiometerliteratur sind. Ein Experiment zeigt, dass die Qualität der Ausgangsinformationen, insbesondere deren Vermögen die Grundzüge des Zustands der Atmosphäre abzubilden, großen Einfluss auf die Genauigkeit der Methode hat. Die Ausgansinformationen sind daher ein guter Ausgangspunkt für die Verbesserung der Genauigkeit. In der Arbeit wird auch ein Prototyp eines numerischen Strahlungstransportmodells für die Mikrowellenregion präsentiert. Dieser ist eine minimalistische Implementation in einer höheren Programmiersprache und fähig Linearisierungen von sich selbst mithilfe von automatischem Differenzieren zu berechnen. Das Modell wird als ausreichend genau für die Nutzung mit den vorgestellen Methoden befunden.Ground-based microwave radiometers are increasingly used in the atmospheric sciences to retrieve vertical temperature, humidity and cloud information. Such information is valuable for boundary layer research and weather forecasting and efforts are undertaken to assimilate microwave radiometer observations into numerical weather prediction models. Multiple methods exist to perform the retrieval, differing in their data requirements, ease of use and flexibility to include measurements from sensors other than the radiometer. A linear regression and an optimal estimation technique have been implemented as part of this thesis. They are derived from a Bayesian standpoint and important properties of these methods are discussed. Finally, their accuracy is evaluated with data from radiosoundings and radiometer measurements in Innsbruck. Standard deviations of temperature retrievals from an optimal estimation scheme incorporating forecasts from a numerical weather prediction model are found be be less than 1.2 K throughout the troposphere. The least accurate region is located between 1.5 and 3 km above ground level. At these heights the numerical forecasts are not as accurate as in the upper troposphere and the information content of the radiometer has already decreased substantially compared to the lower atmosphere therefore the retrieval scheme struggles to perform well. Two case studies reveal that the optimal estimation scheme is promising for the retrieval of temperature inversions which are an often studied problem of microwave radiometer retrieval. An experiment shows that the quality of a-priori information, particularly its capability of providing a description of the features that an atmospheric state exhibits, has much influence on the accuracy of retrieved vertical profiles. The a-priori information are therefore a good place to start when trying to improve the retrieval performance. Also presented in this thesis is a prototype of a numerical radiative transfer model for the microwave region. It is a minimalistic implementation in a high-level programming language and able to calculate linearizations of itself by utilizing automatic differentiation. The model is found to be sufficiently accurate for use in retrieval applications.by Christopher PolsterUniversität Innsbruck, Masterarbeit, 2016(VLID)147180

Design and development of a catalyst microsystem for the detection of carbon monoxide in hydrogen fuels

The viability and fabrication of a catalytic micro-system for the detection of CO in H2 fuel is discussed in detail. Technology utilizing the measurement of temperature changes from the exothermic oxidation of CO as a transduction method is proposed. CuOx-CeO2 is shown as a suitable catalyst substrate for selective CO detection, showing 100% selectivity to CO oxidation (relative to H2 oxidation) down to 200 ppm CO at 333 K. The high selectivity of CuOx-CeO2 is shown to be a result of both competitive adsorption effects as well as the ability of the oxidized catalyst to inhibit H2 dissociation. Pt/CeO2 is studied as another potential catalyst substrate for CO detection due to its higher activity per gram, but is found to have substantial selectivity losses at low CO concentrations (∼20% selective at 333 K for 100 ppm CO). Selectivity loss in Pt/CeO2 catalysts is explained by a loss of CO coverage at low concentrations, and also the ability of Pt to dissociate H2 at a very fast rate. Device design and fabrication are discussed. The micro-system functions properly as a calorimeter, showing a very clear signal for the oxidation of H2 on a Pt/CeO2 catalyst. However, CO detection with CuOx-CeO2 proves to challenge the device sensitivity, and potential improvements on device sensitivity are discussed

A New Atmospheric Background State to Diagnose Local Waveguidability

Abstract A new procedure to obtain a longitudinally varying and slowly evolving atmospheric background state for the analysis of Rossby waveguides is described and discussed. The procedure is a rolling zonalization scheme, redistributing Ertel potential vorticity in a moving window to separate waves from the background. Waveguides are subsequently diagnosed from the gradient of the logarithm of potential vorticity. The effectiveness of the wave‐background separation, even in large‐amplitude conditions, is illustrated with reanalysis data. Established climatological‐mean waveguide structures are recovered from the rolling‐zonalized state in the limit of long‐term aggregation. Two contrasting episodes of Rossby wave packet propagation demonstrate how the evolution of waveguides derived from rolling zonalization can correspond to the development of superposed wave packets. The ability of the procedure to work with snapshots of the atmosphere provides new opportunities for waveguide research

csyhuang/hn2016_falwa: Bugfix release v1.2.0: inconsistency in differential area computation in reference state calculation

&lt;p&gt;&lt;strong&gt;Important:&lt;/strong&gt; This release fix a bug in computing the reference states #102 : the differential area to compute reference states, $a^2 \cos\phi \Delta\phi \Delta\lambda$ , was miscomputed as $a^2 \cos\phi (\Delta\phi)^2$ . This has not caused issues in results presented in our previous publications because we have been using ERA5 datasets with $\Delta\phi = \Delta\lambda$. Great thanks to Pragallva Barpanda for fixing the issue and also sharing her working example to preprocess model output for consumption of &lt;code&gt;QGField&lt;/code&gt; downstream.&lt;/p&gt; &lt;p&gt;Summary of changes:&lt;/p&gt; &lt;ol&gt; &lt;li&gt;$\Delta\phi$ and $\Delta\lambda$ are precomputed in &lt;code&gt;QGField&lt;/code&gt; object and passed into the F2PY modules as parameters&lt;/li&gt; &lt;li&gt;Pragallva has included an example in &lt;code&gt;scripts/pre_process_data_in_hybrid_coordinates/&lt;/code&gt; how to preprocess climate model output in hybrid coordinate for consumption of &lt;code&gt;QGField&lt;/code&gt; downstream by (1) transforming the fields to pressure coordinates, and (2) do gridfill over underground&quot; gridpoints using poisson solver (as how Clare did in MDTF project)&lt;/li&gt; &lt;li&gt;Added &lt;code&gt;CONTRIBUTING.md&lt;/code&gt; to include instructions for potential contributors.&lt;/li&gt; &lt;/ol&gt

csyhuang/hn2016_falwa: v1.1.0 Fix bug in processing input with even number of grid points

&lt;h1&gt;Release: &lt;code&gt;falwa&lt;/code&gt; v1.1.0&lt;/h1&gt; &lt;h2&gt;Bug being fixed&lt;/h2&gt; &lt;p&gt;This release fix the bug occuring in &lt;code&gt;QGField&lt;/code&gt;/&lt;code&gt;QGDataset&lt;/code&gt; when processing latitude grid with even number of grid points - the dimension of latitude grid is recorded inconsistently, leading the code to crash. With this fix, computed variables are returned with original dimension (or original dimension / 2 if &lt;code&gt;northern_hemisphere_results_only=False&lt;/code&gt;).&lt;/p&gt; &lt;h2&gt;Additional unit tests&lt;/h2&gt; &lt;p&gt;There are two additional unit tests demostrating the fix:&lt;/p&gt; &lt;ul&gt; &lt;li&gt;&lt;code&gt;tests/test_output_results.py::test_offgrid_data_input&lt;/code&gt;&lt;/li&gt; &lt;li&gt;&lt;code&gt;tests/test_output_results.py::test_offgrid_data_input_xarrayinterface&lt;/code&gt;&lt;/li&gt; &lt;/ul&gt

csyhuang/hn2016_falwa: Bugfix release v1.2.1 wrong values of u_baro in Southern Hemisphere

&lt;p&gt;This is fixing the issue reported in #108 that the barotropic component of zonal wind in southern hemisphere was wrongly computed using the data in the northern hemisphere. Other barotropic quantities computed were not affected.&lt;/p&gt; &lt;p&gt;Thanks @chpolste for figuring out the fix.&lt;/p&gt