scholarly journals Analog Ensemble Methods for Improving Satellite-Based Intensity Estimates of Tropical Cyclones

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 830
Author(s):  
William E. Lewis ◽  
Timothy L. Olander ◽  
Christopher S. Velden ◽  
Christopher Rozoff ◽  
Stefano Alessandrini
Keyword(s):  
North Atlantic ◽  
Mean Absolute Error ◽  
Ensemble Methods ◽  
Absolute Error ◽  
Eastern Pacific ◽  
Intensity Maximum ◽  
The North ◽  
The University ◽  
Meteorological Satellite ◽  
Fold Cross Validation

Accurate, reliable estimates of tropical cyclone (TC) intensity are a crucial element in the warning and forecast process worldwide, and for the better part of 50 years, estimates made from geostationary satellite observations have been indispensable to forecasters for this purpose. One such method, the Advanced Dvorak Technique (ADT), was used to develop analog ensemble (AnEn) techniques that provide more precise estimates of TC intensity with instant access to information on the reliability of the estimate. The resulting methods, ADT-AnEn and ADT-based Error Analog Ensemble (ADTE-AnEn), were trained and tested using seventeen years of historical ADT intensity estimates using k-fold cross-validation with 10 folds. Using only two predictors, ADT-estimated current intensity (maximum wind speed) and TC center latitude, both AnEn techniques produced significant reductions in mean absolute error and bias for all TC intensity classes in the North Atlantic and for most intensity classes in the Eastern Pacific. The ADTE-AnEn performed better for extreme intensities in both basins (significantly so in the Eastern Pacific) and will be incorporated in the University of Wisconsin’s Cooperative Institute for Meteorological Satellite Studies (UW-CIMSS) workflow for further testing during operations in 2021.

Stratospheric cirrus clouds related to deep convection over North America observed by satellite measurements

2021 ◽  
Author(s):  
Ling Zou ◽  
Lars Hoffmann ◽  
Sabine Griessbach ◽  
Lunche Wang
Keyword(s):  
North America ◽  
Formation Mechanism ◽  
Great Plains ◽  
Gravity Waves ◽  
North Atlantic ◽  
Deep Convection ◽  
Eastern Pacific ◽  
Western Canada ◽  
The North ◽  
North Eastern

<p>Cirrus clouds in the stratosphere (SCCs) regulate the water vapor budget in the stratosphere, impact the stratosphere and tropopshere exchange, and affect the surface energy balance. But the knowledge of its occurrence and formation mechanism is limited, especially in middle and high latitudes. In this study, we aim to assess the occurrence frequencies of SCC over North America based on The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) instrument during the years 2006 to 2018. Possible driving forces such as deep convection are assessed based on Atmospheric Infrared Sounder (AIRS) observations during the same time. </p><p>Results show that at nighttime, SCCs are most frequently observed during the thunderstorm season over the Great Plains from May to August (MJJA) with maximum occurrence frequency of 6.2%. During the months from November to February (NDJF), the highest SCCs occurrence frequencies are 5.5% over the North-Eastern Pacific, western Canada and 4.4% over the western North Atlantic. Occurrence frequencies of deep convection and strong storm systems from AIRS show similar hotspots like the SCCs, with highest occurrence frequencies being observed over the Great Plains in MJJA (4.4%) and over the North-Eastern Pacific, western Canada and the western North Atlantic in NDJF (~2.5%). Both, seasonal patterns and daily time series of SCCs and deep convection show a high degree of spatial and temporal correlation. As further analysis indicates that the maximum fraction of SCCs generated by deep convection is 74% over the Great Plains in MJJA and about 50% over the western North Atlantic, the North-Eastern Pacific and western Canada in NDJF, we conclude that, locally and regionally, deep convection is a leading factor for the formation of SCCs over North America. Other studies stressed the relevance of isentropic transport, double tropopause events, or gravity waves for the formation of SCCs. </p><p>In this study, we also analyzed the impact of gravity waves as a secondary formation mechanism for SCCs, as the Great Plains is a well-known hotspot for stratospheric gravity waves. In case of SCCs that are not directly linked to deep convection, we found that stratospheric gravity wave observations correlate in as much as 30% of the cases over the Great Plains in MJJA, about 50% over the North-Eastern Pacific, western Canada and maximally 90% over eastern Canada and the north-west Atlantic in NDJF. </p><p>Our results provide better understanding of the physical processes and climate variability related to SCCs and will be of interest for modelers as SCC sources such as deep convection and gravity waves are small-scale processes that are difficult to represent in global general circulation models. </p>

The 1995 and 1996 North Atlantic Hurricane Seasons: A Return of the Tropical-Only Hurricane

1998 ◽  
Vol 11 (8) ◽  
pp. 2062-2069 ◽  
Author(s):  
Todd B. Kimberlain ◽  
James B. Elsner
Keyword(s):  
North Atlantic ◽  
Eastern Pacific ◽  
Tropical Atlantic ◽  
Atlantic Basin ◽  
Local Factors ◽  
North Atlantic Basin ◽  
The North ◽  
Hurricane Activity ◽  
The North Atlantic ◽  
Global And Local

Abstract Hurricane activity over the North Atlantic basin during 1995 and 1996 is compared to the combined hurricane activity over the previous four years (1991–94). The earlier period produced a total of 15 hurricanes compared to a total of 20 hurricanes over the latter period. Despite this similarity in numbers, the hurricanes of 1995 and 1996 were generally of the tropical-only variety, which marks a substantial departure from activity during the early 1990s. The return of tropical-only hurricanes to the Atlantic basin is likely the result of several global and local factors, including cool SST conditions in the equatorial central and eastern Pacific and warm SSTs in the tropical Atlantic. The hurricane activity of 1995 and 1996 is more reminiscent of activity of some seasons during the early and mid-1950s.

Celebrating Greg Donaghy

2020 ◽  
Vol 75 (4) ◽  
pp. 464-470
Author(s):  
Robert Bothwell ◽  
John English ◽  
Norman Hillmer
Keyword(s):  
Foreign Policy ◽  
North Atlantic ◽  
International History ◽  
University Of Toronto ◽  
The North ◽  
Canadian Foreign Policy ◽  
The North Atlantic ◽  
The University ◽  
The Way

Three colleagues pay tribute to Greg Donaghy, who at the time of his death on 1 July 2020 was the co-editor of International Journal and Director of the Bill Graham Centre for Contemporary International History at the University of Toronto. Dr Donaghy’s imaginative international history expanded the canvas of Canadian foreign policy beyond the traditional limits of the North Atlantic Triangle. As an author, editor, and mentor, he redefined the way that Canada’s world looks to its scholars.

scholarly journals Machine learning meets pKa

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 113 ◽  
Author(s):  
Marcel Baltruschat ◽  
Paul Czodrowski
Keyword(s):  
Machine Learning ◽  
Cross Validation ◽  
Mean Squared Error ◽  
Mean Absolute Error ◽  
External Validation ◽  
Absolute Error ◽  
Source Model ◽  
Squared Error ◽  
Fold Cross Validation ◽  
Better Than

We present a small molecule pKa prediction tool entirely written in Python. It predicts the macroscopic pKa value and is trained on a literature compilation of monoprotic compounds. Different machine learning models were tested and random forest performed best given a five-fold cross-validation (mean absolute error=0.682, root mean squared error=1.032, correlation coefficient r2 =0.82). We test our model on two external validation sets, where our model performs comparable to Marvin and is better than a recently published open source model. Our Python tool and all data is freely available at https://github.com/czodrowskilab/Machine-learning-meets-pKa.

scholarly journals The Link between the North Pacific Climate Variability and the North Atlantic Oscillation via Downstream Propagation of Synoptic Waves

2015 ◽  
Vol 28 (10) ◽  
pp. 3957-3976 ◽  
Author(s):  
Marie Drouard ◽  
Gwendal Rivière ◽  
Philippe Arbogast
Keyword(s):  
Wave Propagation ◽  
North Atlantic ◽  
North American ◽  
Eastern Pacific ◽  
Late Winter ◽  
Phase Fluctuations ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
Pacific Climate Variability

Abstract The North Atlantic Oscillation (NAO) response to the northeast Pacific climate variability is examined using the ERA-40 dataset. The main objective is to validate a mechanism involving downstream wave propagation processes proposed in a recent idealized companion study: a low-frequency planetary-scale ridge (trough) anomaly located in the eastern Pacific–North American sector induces more equatorward (poleward) propagation of synoptic-scale wave packets on its downstream side, which favors the occurrence of anticyclonic (cyclonic) wave breakings in the Atlantic sector and the positive (negative) NAO phase. The mechanism first provides an interpretation of the canonical impact of the El Niño–Southern Oscillation on the NAO in late winter. The wintertime relationship between the Pacific–North American oscillation (PNA) and the NAO is also investigated. For out-of-phase fluctuations between the PNA and NAO indices (i.e., the most recurrent situation in late winter), the eastern Pacific PNA ridge (trough) anomaly modifies the direction of downstream wave propagation, triggering more anticyclonic (cyclonic) wave breakings over the North Atlantic. For in-phase fluctuations, the effect of the eastern Pacific PNA anomalies is cancelled out by the North American PNA anomalies. The latter anomalies being deeper and more centered in the latitudinal band of downstream wave propagation, they are able to reverse the direction of wave propagation just before waves enter the Atlantic domain. The contrasting relationship between the PNA and NAO is similar to what occurs for the two leading hemispheric EOFs of geopotential height: the northern annular mode (NAM) and the cold ocean–warm land (COWL) pattern. The proposed mechanism provides a physical meaning for the NAM and COWL patterns.

scholarly journals 10 años de historia fundacional de la URACCAN Siuna-Las Minas

2012 ◽  
Vol 10 (1) ◽  
pp. 22-40
Author(s):  
Fredy Leonel Valiente Contreras ◽  
Víctor Manuel Del Cid Lucero
Keyword(s):  
Identity Development ◽  
North Atlantic ◽  
Atlantic Coast ◽  
Caribbean Coast ◽  
Autonomous Region ◽  
The North ◽  
The Caribbean ◽  
Group Interviews ◽  
The University

La Universidad de las Regiones Autónomas de la Costa Caribe Nicaragüense (URACCAN), tiene presencia en 4 Recintos Universitarios del Caribe. En la Región Autónoma Atlántico Norte en Siuna y Bilwi; en la Región Autónoma Atlántico Sur en Bluefields y Nueva Guinea, se asimilan en relación a la estructura orgánica y líneas de trabajo: extensión, docencia e investigación. El Recinto Siuna-Las Minas surge en 1995, para dar respuesta a una demanda histórica de siglos de exclusión económica, política, cultural y social por parte del Estado nacional nicaragüense. El objeto de esta sistematización fue rescatar la historia y la generación de propuestas alternativas en la construcción de la autonomía de la Costa Atlántica. Es de tipo longitudinal de 1995-2005 y se realizó en el 2007 a partir de un enfoque cualitativo básicamente con entrevistas In situ individuales y grupales, además se estudiaron las memorias de los talleres, actas, resúmenes de los debates, datos estadísticos, evaluaciones y diagnósticos institucionales. Con un enfoque sistémico se ha concluido que en el ámbito nacional la URACCAN por su perfil multiétnico, intercultural bilingüe y su praxis de acompañamiento comunitario con­tribuye al desarrollo identitario en la forja de la Autonomía de la Costa Caribe donde conviven seis culturas: miskitu, sumu-mayangna, rama, garífuna, creol y los pueblos del mestizaje. SUMMARY The University of the Autonomous Regions of the Caribbean Coast of Nicaragua (URACCAN), is present in four Campuses. In the North Atlantic Autonomous Region in Siuna and Bilwi; and in the South Atlantic Autonomous Region in Bluefields and Nueva Guinea, as they are treated in relation to the organizational structure and working lines: extension, teaching and research. The Siuna Campus was founded in 1995, in response to a historical demand of centuries of economic, political, cultural and social exclusion by the Nicaraguan national state. The purpose of this systematization was to rescue the history and the generation of alternative proposals for the construction of the autonomy of the Atlantic Coast. It’s a longitudinal study from 1995-2005 and it was carried-out in 2007 from a primarily qualitative approach with individual and group interviews in situ; we also examined the reports of the workshops, the minutes, summaries of discussions, statistics, evaluations and institutional diagnostics. It was concluded -using a systemic approach- that URACCAN at a national context and due to its multiethnic and intercultural-bilingual profile, as well as it community accompaniment praxis contributes to identity development in forging the autonomy of the Caribbean Coast where six cultures coexist: Miskitu, Sumu-Mayangna, Rama, Creole, Garifuna, and Mestizo.

scholarly journals Empirical evidence for deep convection related stratospheric cirrus clouds over North America

2021 ◽  
Author(s):  
Ling Zou ◽  
Lars Hoffmann ◽  
Sabine Griessbach ◽  
Reinhold Spang ◽  
Lunche Wang
Keyword(s):  
North America ◽  
Great Plains ◽  
Gravity Waves ◽  
North Atlantic ◽  
Deep Convection ◽  
Cirrus Clouds ◽  
Eastern Pacific ◽  
Western Canada ◽  
The North ◽  
North Eastern

Abstract. Cirrus clouds in the lowermost stratosphere affect stratospheric water vapor and the Earth's radiation budget. The knowledge of its occurrence and driving forces is limited. To assess the distribution and possible formation mechanisms of stratospheric cirrus clouds (SCCs) over North America, we analyzed SCC occurrence frequencies observed by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) instrument during the years 2006 to 2018. Possible driving forces such as deep convection are assessed based on Atmospheric Infrared Sounder (AIRS) observations during the same time. Results show that at nighttime, SCCs are most frequently observed during the thunderstorm season over the Great Plains from May to August (MJJA) with a maximum occurrence frequency of 6.2 %. During the months from November to February (NDJF), the highest SCCs occurrence frequencies are 5.5 % over the North-Eastern Pacific, western Canada and 4.4 % over the western North Atlantic. Occurrence frequencies of deep convection from AIRS, which includes storm systems, fronts, mesoscale convective systems and mesoscale convective complexes at mid- and high latitude, show similar hotspots like the SCCs, with highest occurrence frequencies being observed over the Great Plains in MJJA (4.4 %) and over the North-Eastern Pacific, western Canada and the western North Atlantic in NDJF (~2.5 %). Both, seasonal patterns and daily time series of SCCs and deep convection show a high degree of spatial and temporal relation. Further analysis indicates that the maximum fraction of SCCs related to deep convection is 74 % over the Great Plains in MJJA and about 50 % over the western North Atlantic, the North-Eastern Pacific and western Canada in NDJF. We conclude that, locally and regionally, deep convection is the leading factor related to occurrence of SCCs over North America. In this study, we also analyzed the impact of gravity waves as another important factor related to the occurrence SCCs, as the Great Plains is a well-known hotspot for stratospheric gravity waves. In the cases where SCCs are not directly linked to deep convection, we found that stratospheric gravity wave observations correlate with SCCs in as much as 30 % of the cases over the Great Plains in MJJA, about 50 % over the North-Eastern Pacific, western Canada and up to 90 % over eastern Canada and the north-west Atlantic in NDJF. Our results provide better understanding of the physical processes and climate variability related to SCCs and will be of interest for modelers as SCC sources such as deep convection and gravity waves are small-scale processes that are difficult to represent in global general circulation models.

scholarly journals Cenozoic Biostratigraphy and Global Change

1991 ◽  
Vol 9 (2) ◽  
pp. 117-117
Author(s):  
Brian M. Funnell
Keyword(s):  
Global Change ◽  
North Atlantic ◽  
Ocean Drilling Program ◽  
East Anglia ◽  
Ongoing Research ◽  
Ocean Drilling ◽  
The North ◽  
History Of ◽  
The North Atlantic ◽  
The University

Abstract. INTRODUCTIONIn May 1989 a British Micropalaeontological Society Symposium Meeting was held at the University of East Anglia under the title “Cenozoic Biostratigraphy and Global Change”. Fourteen lectures were given on this theme, many of them originating from investigations of DSDP/IPOD and ODP (Ocean Drilling Program) samples. All addressed the potential of micropalaeontological observations for interpreting the history of global and regional oceanographic and climatic change. Many results of this type of investigation are currently appearing in science journals such as “Paleoceanography” and “Palaeogeography, Palaeoclimatology, Palaeoecology” as well as in the “Proceedings of the Ocean Drilling Program”. British micropalaeontologists are taking an active part in this research, but relatively few of the resultant papers have so far appeared in the Journal of Micropalaeontology.Many of the lectures given at the May 1989 Symposium represented work already recently published, or due to be subsequently published in the Proceedings of the Ocean Drilling Program. Four papers, representing ongoing research not then due to be published, have been brought together here as a small thematic set, illustrating a variety of approaches to “Cenozoic Biostratigraphy and Global Change”. They range across Ostracoda, Coccolithophorida, Planktonic and Benthic Foraminifera, through the entire Cenozoic, including the latest Quaternary, and they include results from both the North Atlantic and Pacific oceans.TITLES“Global Change and the Biostratigraphy of North Atlantic Cenozoic deep water Ostracoda” - Robin C. Whatley and Graham P. Coles.“Palaeoclimatic control of Upper Pliocene Discoaster assemblages in the North Atlantic” - Alex. Chepstow-Lusty, Jan Backman. . .

Future projections in tropical cyclone activity over multiple CORDEX domains from RegCM4 CORDEX-CORE simulations

2020 ◽  
Author(s):  
Abraham Torres ◽  
Russell Glazer ◽  
Erika Coppola ◽  
Xuejie Gao ◽  
Kevin Hodges ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
North Atlantic ◽  
North Indian Ocean ◽  
Eastern Pacific ◽  
Northwest Pacific ◽  
Future Projections ◽  
The North ◽  
The Future

<p>Under the Coordinated Regional Downscaling Experiment (CORDEX) initiative, simulations of tropical cyclones were performed using the latest version of the International Centre for Theoretical Physics (ICTP) Regional Climate Model 4 (RegCM4) at a spatial resolution of 25 km over four domains (Australasia, Central America, Western Pacific and South Asia). These simulations cover the 130-year period, 1970-2099, for two Representative Concentration Pathways, 2.6 (RCP2.6) and 8.5 (RCP8.5) emission scenarios and were driven by three General Circulation Models (GCMs) from phase 5 of the Coupled Model Inter-comparison Project (CMIP5). In these simulations, the potential changes in TC activity for future climate conditions over five areas of tropical cyclone formation (North Indian Ocean, the Northwest Pacific, North Atlantic, Australasia and Eastern Pacific) are investigated, using an objective algorithm to identify and track them. The RegCM4 simulations driven by GCMs are evaluated for the period of 1995–2014 by comparing them with the observed tropical cyclone data from the International Best Track Archive for Climate Stewardship (IBTrACS); then the changes in two future periods (2041-2016 and 2080–2099), relative to the baseline period (1995–2014), are analyzed for RegCM4 simulations driven by GCMs. Preliminary results show that RegCM4 simulations driven by GCMs are capable of most of the features of the observed tropical cyclone climatology, and the future projections show an increase in the number of tropical cyclones over the North Indian Ocean, the Northwest Pacific and Eastern Pacific regions. These changes are consistent with an increase in mid-tropospheric relative humidity. On the other hand, the North Atlantic and Australasia regions show a decrease in tropical cyclone frequency, mostly associated with an increase in wind shear. We also find a consistent increase in the future storm rainfall rate and the frequency of the most intense tropical cyclones over almost all the domains. Our study shows robust and statistically significant responses, often, but not always, in line with previous studies. This implies that a robust assessment of tropical cyclone changes requires analyses of ensembles of simulations with high-resolution models capable of representing the response of different characteristics of different key atmospheric factors.</p>

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