scholarly journals The Precipitation Imaging Package: Phase Partitioning Capabilities

2021 ◽  
Vol 13 (11) ◽  
pp. 2183
Author(s):  
Claire Pettersen ◽  
Larry F. Bliven ◽  
Mark S. Kulie ◽  
Norman B. Wood ◽  
Julia A. Shates ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Identification ◽  
Near Surface ◽  
Surface Precipitation ◽  
Phase Partitioning ◽  
Thermodynamic Conditions ◽  
Lapse Rates ◽  
Precipitation Phase

Surface precipitation phase is a fundamental meteorological property with immense importance. Accurate classification of phase from satellite remotely sensed observations is difficult. This study demonstrates the ability of the Precipitation Imaging Package (PIP), a ground-based, in situ precipitation imager, to distinguish precipitation phase. The PIP precipitation phase identification capabilities are compared to observer records from the National Weather Service (NWS) office in Marquette, Michigan, as well as co-located observations from profiling and scanning radars, disdrometer data, and surface meteorological measurements. Examined are 13 events with at least one precipitation phase transition. The PIP-determined onsets and endings of the respective precipitation phase periods agree to within 15 min of NWS observer records for the vast majority of the events. Additionally, the PIP and NWS liquid water equivalent accumulations for 12 of the 13 events were within 10%. Co-located observations from scanning and profiling radars, as well as reanalysis-derived synoptic and thermodynamic conditions, support the accuracy of the precipitation phases identified by the PIP. PIP observations for the phase transition events are compared to output from a parameterization based on wet bulb and near-surface lapse rates to produce a probability of solid precipitation. The PIP phase identification and the parameterization output are consistent. This work highlights the ability of the PIP to properly characterize hydrometeor phase and provide dependable precipitation accumulations under complicated mixed-phase and rain and snow (or vice versa) transition events.

scholarly journals An automatic precipitation-phase distinction algorithm for optical disdrometer data over the global ocean

2016 ◽  
Vol 9 (4) ◽  
pp. 1637-1652 ◽  
Author(s):  
Jörg Burdanowitz ◽  
Christian Klepp ◽  
Stephan Bakan
Keyword(s):  
Mixed Phase ◽  
Global Ocean ◽  
Human Observer ◽  
Precipitation Data ◽  
Post Processing ◽  
Atmospheric Measurements ◽  
Data Set ◽  
Surface Precipitation ◽  
Precipitation Phase

Abstract. The lack of high-quality in situ surface precipitation data over the global ocean so far limits the capability to validate satellite precipitation retrievals. The first systematic ship-based surface precipitation data set OceanRAIN (Ocean Rainfall And Ice-phase precipitation measurement Network) aims at providing a comprehensive statistical basis of in situ precipitation reference data from optical disdrometers at 1 min resolution deployed on various research vessels (RVs). Deriving the precipitation rate for rain and snow requires a priori knowledge of the precipitation phase (PP). Therefore, we present an automatic PP distinction algorithm using available data based on more than 4 years of atmospheric measurements onboard RV Polarstern that covers all climatic regions of the Atlantic Ocean. A time-consuming manual PP distinction within the OceanRAIN post-processing serves as reference, mainly based on 3-hourly present weather information from a human observer. For automation, we find that the combination of air temperature, relative humidity, and 99th percentile of the particle diameter predicts best the PP with respect to the manually determined PP. Excluding mixed phase, this variable combination reaches an accuracy of 91 % when compared to the manually determined PP for 149 635 min of precipitation from RV Polarstern. Including mixed phase (165 632 min), an accuracy of 81.2 % is reached for two independent PP distributions with a slight snow overprediction bias of 0.93. Using two independent PP distributions represents a new method that outperforms the conventional method of using only one PP distribution to statistically derive the PP. The new statistical automatic PP distinction method considerably speeds up the data post-processing within OceanRAIN while introducing an objective PP probability for each PP at 1 min resolution.

ON INDUCED ELECTRICAL POLARIZATION AND GROUNDWATER

Geophysics ◽  
1968 ◽  
Vol 33 (5) ◽  
pp. 805-821 ◽  
Author(s):  
René Bodmer ◽  
S. H. Ward ◽  
H. F. Morrison
Keyword(s):  
Induced Polarization ◽  
Unconsolidated Sediments ◽  
Frequency Effect ◽  
Polarization Method ◽  
Near Surface ◽  
Frequency Effects ◽  
Santa Clara County ◽  
Potential Recharge

Clay horizons and other clay‐bearing unconsolidated sediments are potential sources of induced‐polarization anomalies. If such anomalies may be detected above system noise, the induced‐polarization method may be of value for in‐situ classification of unconsolidated sediments encountered in hydrological projects. One such project exists in Santa Clara County where near‐surface unconsolidated sediments are frequently considered as potential recharge areas. Of four areas surveyed with induced‐polarization apparatus in Santa Clara County, only two yielded significant frequency‐effect anomalies, and in each of these two the frequency effects were of the order of 3 percent. These anomalous frequency effects may be related to clayey gravels. The dipole‐dipole array, with spreads of 10 ft and 20 ft, was typically used in the study.

Antarctic Peninsula warming and precipitation phase transition during atmospheric river events

2021 ◽  
Author(s):  
Irina Gorodetskaya ◽  
Penny Rowe ◽  
Xun Zou ◽  
Anastasia Chyhareva ◽  
Svitlana Krakovska ◽  
...  
Keyword(s):  
Phase Transition ◽  
Antarctic Peninsula ◽  
Moisture Transport ◽  
Large Scale ◽  
The Arctic ◽  
Polar Regions ◽  
Near Surface ◽  
Depth Analysis ◽  
Heat And Moisture ◽  
Precipitation Phase

<p><span lang="en-US">Polar amplification has been pronounced in the Arctic with near-surface air temperatures increasing at more than twice the global warming rate d</span>uring the last several decades<span lang="en-US">. At the same time, over Antarctica temperature trends have exhibited a large regional variability. In particular, the </span>Antarctic Peninsula (AP) <span lang="en-US">stands out as having a </span>warming<span lang="en-US"> rate much higher than</span> the rest of the Antarctic ice sheet and other land areas in the Southern Hemisphere (SH)<span lang="en-US">.</span> <span lang="en-US">F</span>uture projections indicate that <span lang="en-US">warming and ice loss will intensify in both polar regions with important impacts</span> globally. In addition to the warming amplification, there has been also an enhancement of the polar water cycle with increase<span lang="en-US">s</span> <span lang="en-US">in </span>poleward moisture transport and precipitation in both polar regions. An important process linking warming and precipitation enhancement is a shift towards more frequent rainfall compared to snowfall<span lang="en-US">. F</span>uture projections show that the rain fraction will significantly increase in coastal Antarctica, especially in the AP. Atmospheric rivers (ARs), long corridors of intense moisture transport from subtropical and mid-latitude regions poleward, are known for <span lang="en-US">their </span>prominent role in <span lang="en-US">both </span>heat and moisture transport with impacts ranging from intense precipitation to temperature records and major melt events in Antarctica.<span lang="en-US"> Limited observations have hampered process understanding and correct representation of these extreme events in models.</span> <span lang="en-US">This presentation will give an overview of the </span>enhanced observations targeting ARs in the A<span lang="en-US">P</span> (<span lang="en-US">including </span>surface meteorology, radiosonde, cloud and precipitation remote sensing, <span lang="en-US">and </span>radiative fluxes) as part of the <span lang="en-US">Year of Polar Prediction (</span>YOPP<span lang="en-US">)</span>-SH international collaborative effort<span lang="en-US">. </span>In-depth analysis of transport of heat and moisture, <span lang="en-US">atmospheric vertical structure, </span>cloud properties<span lang="en-US"> and precipitation phase transition from snowfall to rainfall </span>during selected <span lang="en-US">AR </span>case<span lang="en-US">s</span> will be<span lang="en-US"> presented and compared with ERA5 reanalysis and high-resolution Polar-WRF model simulations</span>.<span lang="en-US"> We will highlight three different local regimes around the AP: large-scale precipitation over the Southern Ocean north of the AP, orographic enhancement of precipitation in the western AP and the role of foehn, cloud/precipitation clearing and temperature increase in the northeastern AP. </span></p>

scholarly journals Precipitation phase transition in austral summer over the Antarctic Peninsula

2021 ◽  
pp. 32-46
Author(s):  
A. Chyhareva ◽  
◽  
I. Gorodetskaya ◽  
S. Krakovska ◽  
D. Pishniak ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Air Temperature ◽  
Antarctic Peninsula ◽  
Precipitation Amount ◽  
Austral Summer ◽  
Near Surface ◽  
Atmospheric River ◽  
Synoptic Conditions ◽  
Precipitation Phase

Investigating precipitation phase transitions is crucial for improving our understanding of precipitation formation processes and impacts, particularly in Polar Regions. This study uses observational data and numerical modelling to investigate precipitation phase transitions in the western and northern Antarctic Peninsula (AP) during austral summer. The analysis is based on the ERA5 reanalysis product, dynamically downscaled using the Polar-WRF (Polar Weather Research and Forecasting) model, evaluated using regular meteorological observations and additional measurements made during the Year of Polar Prediction special observing period. We analyse three cases of extra-tropical cyclones bringing precipitation with phase transitions, observed at the Chilean station Professor Julio Escudero (King George Island, north of the AP) and the Ukrainian Antarctic Akademik Vernadsky station (western side of the AP) during the first week of December 2018. We use observed and modelled near-surface air temperature and pressure, precipitation amount and type, and vertical temperature profiles. Our results show that precipitation type (snow or rain) is well-represented by ERA5 and Polar-WRF, but both overestimate the total amount of precipitation. The ERA5 daily variability and vertical air temperature profile are close to the observed, while Polar-WRF underestimates temperature in the lower troposphere. However, ERA5 underestimates the temperature inversion, which is present during the atmospheric river event, while Polar-WRF represents that inversion well. The average weekly temperature, simulated with Polar-WRF, is lower compared to ERA5. The Polar-WRF fraction of snow in the total precipitation amount is higher than for ERA5; nevertheless, Polar-WRF represents the precipitation phase transition better than ERA5 during the event, associated with an atmospheric river. These case studies demonstrated a relationship between specific synoptic conditions and precipitation phase transitions at the AP, evaluated the ability of the state-of-the-art reanalysis and regional climate model to represent these events, and demonstrated the added value of combined analysis of observations from the western and northern AP, particularly for characterizing precipitation during synoptic events affecting the entire AP.

scholarly journals Rain or Snow: Hydrologic Processes, Observations, Prediction, and Research Needs

2016 ◽  
Author(s):  
Adrian A. Harpold ◽  
Michael Kaplan ◽  
P. Zion Klos ◽  
Timothy Link ◽  
James P. McNamara ◽  
...  
Keyword(s):  
Complex Terrain ◽  
Hydrological Modeling ◽  
Atmospheric Modeling ◽  
Hydrological Models ◽  
Near Surface ◽  
Surface Precipitation ◽  
Hydrologic Processes ◽  
Wide Range ◽  
Precipitation Phase ◽  
Observation Networks

Abstract. The phase of precipitation as snow or rain controls numerous hydrologic processes that are fundamental to effective hydrological modeling. Despite its foundational importance to terrestrial hydrology, typical phase prediction methods (PPM) use overly simplistic estimates based on near-surface air temperature. The review conveys the diversity of tools available for PPM in hydrological modeling and the advancements needed to improve predictions in complex terrain characterized by large spatiotemporal variations in precipitation phase. Initially, we review the processes and physics that control precipitation phase as relevant to hydrologists, focusing on the importance of processes occurring aloft. There are a wide range of options for field observations of precipitation phase, but a lack of a robust observation networks in complex terrain. New remote sensing observations have the potential to increase PPM fidelity, but generally require underlying assumptions and field validation before they are operational. We review the types and accuracy of common PPM to show accuracy is generally increased at finer time steps and by including humidity. One important tool for PPM development is atmospheric modeling, which offers numerous models and microphysical schemes that have not been effectively linked to hydrological models or validated against near-surface precipitation phase observations. One important tool for PPM development is atmospheric modeling, which offers numerous models and microphysical schemes that have not been effectively linked to hydrological models or validated against near-surface precipitation phase observations. The review concludes by describing key research gaps and recommendations to improve PPM. Recommendations include incorporate humidity information and atmospheric information into models, develop observation networks at high temporal resolutions, compare and validate different PPM, develop spatially resolved products, and characterize regional variability. PPM is a critical research frontier in hydrology that requires scientific cooperation between hydrological and atmospheric modelers with field hydrologists.

scholarly journals An automatic precipitation phase distinction algorithm for optical disdrometer data over the global ocean

2015 ◽  
Vol 8 (12) ◽  
pp. 13645-13691
Author(s):  
J. Burdanowitz ◽  
C. Klepp ◽  
S. Bakan
Keyword(s):  
A Priori ◽  
Particle Diameter ◽  
Mixed Phase ◽  
Global Ocean ◽  
Human Observer ◽  
Post Processing ◽  
Atmospheric Measurements ◽  
Surface Precipitation ◽  
Precipitation Phase

Abstract. The lack of high quality in situ surface precipitation data over the global ocean so far limits the capability to validate satellite precipitation retrievals. The first systematic ship-based surface precipitation dataset OceanRAIN (Ocean Rainfall And Ice-phase precipitation measurement Network) aims at providing a comprehensive statistical basis of in situ precipitation reference data from optical disdrometers at 1 min resolution deployed on various research vessels (RVs). Deriving the precipitation rate for rain and snow requires a priori knowledge of the precipitation phase (PP). Therefore, we present an automatic PP distinction algorithm using available data based on more than four years of atmospheric measurements onboard RV Polarstern that covers all climatic regions of the Atlantic Ocean. A time-consuming manual PP distinction within the OceanRAIN post-processing serves as reference, mainly based on 3 hourly present weather information from a human observer. For automation, we find that the combination of air temperature, relative humidity and 99th percentile of the particle diameter predicts best the PP with respect to the manually determined PP. Excluding mixed-phase, this variable combination reaches an accuracy of 91 % when compared to the manually determined PP for about 149 000 min of precipitation from RV Polarstern. Including mixed-phase (165 000 min), 81.2 % accuracy are reached with a slight snow overprediction bias of 0.93 for two independent PP distributions. In that respect, a method using two independent PP distributions outperforms a method based on only one PP distribution. The new statistical automatic PP distinction method significantly speeds up the data post-processing within OceanRAIN while introducing an objective PP probability for each PP at 1 min resolution.

scholarly journals The α–β phase transition in volcanic cristobalite

2014 ◽  
Vol 47 (4) ◽  
pp. 1205-1215 ◽  
Author(s):  
David E. Damby ◽  
Edward W. Llewellin ◽  
Claire J. Horwell ◽  
Ben J. Williamson ◽  
Jens Najorka ◽  
...  
Keyword(s):  
Phase Transition ◽  
Ambient Temperature ◽  
Volcanic Ash ◽  
Phase Identification ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
The Stability ◽  
First Time

Cristobalite is a common mineral in volcanic ash produced from dome-forming eruptions. Assessment of the respiratory hazard posed by volcanic ash requires understanding the nature of the cristobalite it contains. Volcanic cristobalite contains coupled substitutions of Al3+ and Na+ for Si4+; similar co-substitutions in synthetic cristobalite are known to modify the crystal structure, affecting the stability of the α and β forms and the observed transition between them. Here, for the first time, the dynamics and energy changes associated with the α–β phase transition in volcanic cristobalite are investigated using X-ray powder diffraction with simultaneous in situ heating and differential scanning calorimetry. At ambient temperature, volcanic cristobalite exists in the α form and has a larger cell volume than synthetic α-cristobalite; as a result, its diffraction pattern sits between ICDD α- and β-cristobalite library patterns, which could cause ambiguity in phase identification. On heating from ambient temperature, volcanic cristobalite exhibits a lower degree of thermal expansion than synthetic cristobalite, and it also has a lower α–β transition temperature (∼473 K) compared with synthetic cristobalite (upwards of 543 K); these observations are discussed in relation to the presence of Al3+ and Na+ defects. The transition shows a stable and reproducible hysteresis loop with α and β phases coexisting through the transition, suggesting that discrete crystals in the sample have different transition temperatures.

scholarly journals North polar trough formation due to in-situ erosion as a source of young ice in mid-latitudinal mantles on Mars

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Alexis P. Rodriguez ◽  
Kenneth L. Tanaka ◽  
Ali M. Bramson ◽  
Gregory J. Leonard ◽  
Victor R. Baker ◽  
...  
Keyword(s):  
Katabatic Wind ◽  
Spiral Pattern ◽  
Near Surface ◽  
Valuable Source ◽  
History Of ◽  
North Polar ◽  
Human Exploration ◽  
Erosional Event

AbstractThe clockwise spiral of troughs marking the Martian north polar plateau forms one of the planet’s youngest megastructures. One popular hypothesis posits that the spiral pattern resulted as troughs underwent poleward migration. Here, we show that the troughs are extensively segmented into enclosed depressions (or cells). Many cell interiors display concentric layers that connect pole- and equator-facing slopes, demonstrating in-situ trough erosion. The segmentation patterns indicate a history of gradual trough growth transversely to katabatic wind directions, whereby increases in trough intersections generated their spiral arrangement. The erosional event recorded in the truncated strata and trough segmentation may have supplied up to ~25% of the volume of the mid-latitude icy mantles. Topographically subtle undulations transition into troughs and have distributions that mimic and extend the troughs’ spiraling pattern, indicating that they probably represent buried trough sections. The retention of the spiral pattern in surface and subsurface troughs is consistent with the megastructure’s stabilization before its partial burial. A previously suggested warm paleoclimatic spike indicates that the erosion could have occurred as recently as ~50 Ka. Hence, if the removed ice was redeposited to form the mid-latitude mantles, they could provide a valuable source of near-surface, clean ice for future human exploration.

Strategies of In Situ Generated Magnesium Catalysis in Asymmetric Reactions

Synlett ◽  
2021 ◽  
Author(s):  
Dongxu Yang ◽  
Linqing Wang
Keyword(s):  
Asymmetric Synthesis ◽  
Alkaline Earth ◽  
Earth Metal ◽  
Asymmetric Reactions ◽  
Chiral Ligands ◽  
Alkaline Earth Metal ◽  
Enantioselective Reactions ◽  
Earth's Crust

AbstractMagnesium (Mg) is a cheap, non-toxic, and recyclable alkaline earth metal that constitutes about 2% weight in the Earth’s crust. The use of magnesium catalysts to forge chiral moieties in molecules is highly attractive. Based on our work in recent years, we describe the current progress in the development of in situ generated magnesium catalysts and their application in asymmetric synthesis. In this perspective, a critically concise classification of in situ generated magnesium catalytic modes, with relevant examples, is presented, and representative mechanisms of each category are discussed. Building on the established diverse strategies, one can foresee that more innovative and structurally creative magnesium catalysts that are generated in situ will be developed to overcome more formidable challenges of catalytic enantioselective reactions.1 Introduction2 Magnesium Catalysts Generated in Situ from Chiral Ligands Containing Dual Reactive Hydrogens3 Magnesium Catalysts Generated in Situ from Monoanionic Chiral Ligands4 Bimetallic and Polymetallic Magnesium Catalysts Assembled in Situ5 Summary and Outlook

scholarly journals Phase Transition and Coefficients of Thermal Expansion in Al2−xInxW3O12 (0.2 ≤ x ≤ 1)

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4021
Author(s):  
Andrés Esteban Cerón Cerón Cortés ◽  
Anja Dosen ◽  
Victoria L. Blair ◽  
Michel B. Johnson ◽  
Mary Anne White ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Thermal Shock ◽  
Monoclinic Phase ◽  
Ceramic Materials ◽  
Precipitation Method ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
Co Precipitation

Materials from theA2M3O12 family are known for their extensive chemical versatility while preserving the polyhedral-corner-shared orthorhombic crystal system, as well as for their consequent unusual thermal expansion, varying from negative and near-zero to slightly positive. The rarest are near-zero thermal expansion materials, which are of paramount importance in thermal shock resistance applications. Ceramic materials with chemistry Al2−xInxW3O12 (x = 0.2–1.0) were synthesized using a modified reverse-strike co-precipitation method and prepared into solid specimens using traditional ceramic sintering. The resulting materials were characterized by X-ray powder diffraction (ambient and in situ high temperatures), differential scanning calorimetry and dilatometry to delineate thermal expansion, phase transitions and crystal structures. It was found that the x = 0.2 composition had the lowest thermal expansion, 1.88 × 10−6 K−1, which was still higher than the end member Al2W3O12 for the chemical series. Furthermore, the AlInW3O12 was monoclinic phase at room temperature and transformed to the orthorhombic form at ca. 200 °C, in contrast with previous reports. Interestingly, the x = 0.2, x = 0.4 and x = 0.7 materials did not exhibit the expected orthorhombic-to-monoclinic phase transition as observed for the other compositions, and hence did not follow the expected Vegard-like relationship associated with the electronegativity rule. Overall, compositions within the Al2−xInxW3O12 family should not be considered candidates for high thermal shock applications that would require near-zero thermal expansion properties.

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