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M. N. Raphael

Abstract

A 33-yr, numerical dataset of the occurrence of Santa Ana winds for the period 1968–2000 has been created and validated. Daily Weather Maps were examined to identify the days when a surface high pressure system existed over the Great Basin simultaneously with a surface low pressure system offshore of southern California, and the prevailing wind over southern California was from the northeast quadrant. The dates of these occurrences, as well as the wind speed, temperature, and dewpoint temperature among other variables, were extracted and tabulated.

The frequency of Santa Ana events derived from the weather maps was compared to events defined by wind direction only and there is agreement between the two. Preliminary results show that the Santa Ana event is limited to the period September–April and that the month of peak occurrence is December. The average frequency of events is 20 yr–1 and the average duration of an event is 1.5 days. Humidity levels are not uniform across Santa Ana events; the driest months are the months with the highest frequency of events. The frequency of Santa Ana events is usually lower than average during El Niño events.

These preliminary results indicate that the dataset is useful for in depth study of the local phenomenon and its effect on the region within the context of the large-scale circulation.

Full access
Raphaël Rousseau-Rizzi
,
Timothy M. Merlis
, and
Nadir Jeevanjee

Abstract

Tropical cyclone (TC) potential intensity (PI) theory has a well-known form, consistent with a Carnot cycle interpretation of TC energetics, which relates PI to mean environmental conditions: the difference between surface and TC outflow temperatures and the air–sea enthalpy disequilibrium. PI has also been defined as a difference in convective available potential energy (CAPE) between two parcels, and quantitative assessments of future changes make use of a numerical algorithm based on this definition. Here, an analysis shows the conditions under which these Carnot and CAPE-based PI definitions are equivalent. There are multiple conditions, not previously enumerated, which in particular reveal a role for irreversible entropy production from surface evaporation. This mathematical analysis is verified by numerical calculations of PI’s sensitivity to large changes in surface-air relative humidity. To gain physical insight into the connection between the CAPE and Carnot formulations of PI, we use a recently developed analytic theory for CAPE to derive, starting from the CAPE-based definition, a new approximate formula for PI that nearly recovers the previous Carnot PI formula. The derivation shows that the difference in undilute buoyancies of saturated and environmental parcels that determines CAPE PI can in fact be expressed as a difference in the parcels’ surface moist static energy, providing a physical link between the Carnot and CAPE formulations of PI. This combination of analysis and physical interpretation builds confidence in previous numerical CAPE-based PI calculations that use climate model projections of the future tropical environment.

Full access
Rodric Mérimé Nonki
,
André Lenouo
,
Christopher J. Lennard
,
Raphael M. Tshimanga
, and
Clément Tchawoua

Abstract

Potential evapotranspiration (PET) plays a crucial role in water management, including irrigation system design and management. It is an essential input to hydrological models. Direct measurement of PET is difficult, time-consuming, and costly; therefore, a number of different methods are used to compute this variable. This study compares the two sensitivity analysis approaches generally used for PET impact assessment on hydrological model performance. We conducted the study in the upper Benue River basin (UBRB) located in northern Cameroon using two lumped-conceptual rainfall–runoff models and 19 PET estimation methods. A Monte Carlo procedure was implemented to calibrate the hydrological models for each PET input while considering similar objective functions. Although there were notable differences between PET estimation methods, the hydrological model’s performance was satisfactory for each PET input in the calibration and validation periods. The optimized model parameters were significantly affected by the PET inputs, especially the parameter responsible for transforming PET into actual ET. The hydrological model’s performance was insensitive to the PET input using a dynamic sensitivity approach, while it was significantly affected using a static sensitivity approach. This means that the over- or underestimation of PET is compensated by the model parameters during the model recalibration. The model performance was insensitive to the rescaling PET input for both dynamic and static sensitivities approaches. These results demonstrate that the effect of PET input to model performance is necessarily dependent on the sensitivity analysis approach used and suggest that the dynamic approach is more effective for hydrological modeling perspectives.

Full access
P. O. Canziani
,
A. O'Neill
,
R. Schofield
,
M. Raphael
,
G. J. Marshall
, and
G. Redaelli
Full access
Emily L. Schaller
,
J. Ryan Bennett
,
Donald R. Blake
,
Raphael M. Kudela
,
Barry L. Lefer
,
Melissa Yang Martin
,
Dar A. Roberts
,
Richard E. Shetter
,
Bruce A. Tagg
, and
Jack A. Kaye

Abstract

NASA’s Student Airborne Research Program (SARP) has completed 13 years of airborne student research since its inception in 2009. The 8-week summer internship program provides students, typically rising undergraduate seniors, with an opportunity to get hands-on experience in making Earth system measurements using NASA’s airborne science platforms. Students also make complementary surface-based measurements, analyze airborne and surface data in the context of related data (e.g. coincident satellite measurements or prior-year SARP data), and present results to peers, program leadership, agency management, and the community. The program splits its time between the NASA Armstrong flight facility in Palmdale, California, and the University of California, Irvine. It is implemented with participation of faculty advisors (who provide many of the instruments used) and graduate student mentors, under the overall leadership of the NASA Earth Science Division. Disciplinary foci include atmospheric gases and aerosols, ocean biology, and terrestrial ecology using both in situ and remote sensing instruments. Students are also taken on site visits to nearby laboratories and facilities and attend lectures from visiting faculty and NASA agency personnel. The program engages approximately 30 students per year, with overall approximate gender balance. The program has a high rate of STEM retention, and its alumni are actively engaged in graduate and postgraduate programs in Earth system science and other disciplines. A summary of scientific and programmatic outcomes and a description of how the program has evolved will be presented.

Full access
M. N. Raphael
,
G. J. Marshall
,
J. Turner
,
R. L. Fogt
,
D. Schneider
,
D. A. Dixon
,
J. S. Hosking
,
J. M. Jones
, and
W. R. Hobbs

Abstract

The Amundsen Sea low (ASL) is a climatological low pressure center that exerts considerable influence on the climate of West Antarctica. Its potential to explain important recent changes in Antarctic climate, for example, in temperature and sea ice extent, means that it has become the focus of an increasing number of studies. Here, the authors summarize the current understanding of the ASL, using reanalysis datasets to analyze recent variability and trends, as well as ice-core chemistry and climate model projections, to examine past and future changes in the ASL, respectively. The ASL has deepened in recent decades, affecting the climate through its influence on the regional meridional wind field, which controls the advection of moisture and heat into the continent. Deepening of the ASL in spring is consistent with observed West Antarctic warming and greater sea ice extent in the Ross Sea. Climate model simulations for recent decades indicate that this deepening is mediated by tropical variability while climate model projections through the twenty-first century suggest that the ASL will deepen in some seasons in response to greenhouse gas concentration increases.

Full access
Judy Shamoun-Baranes
,
Silke Bauer
,
Jason W. Chapman
,
Peter Desmet
,
Adriaan M. Dokter
,
Andrew Farnsworth
,
Hans van Gasteren
,
Birgen Haest
,
Jarmo Koistinen
,
Bart Kranstauber
,
Felix Liechti
,
Tom H. E. Mason
,
Cecilia Nilsson
,
Raphael Nussbaumer
,
Baptiste Schmid
,
Nadja Weisshaupt
, and
Hidde Leijnse

Abstract

Weather radar networks have great potential for continuous and long-term monitoring of aerial biodiversity of birds, bats, and insects. Biological data from weather radars can support ecological research, inform conservation policy development and implementation, and increase the public’s interest in natural phenomena such as migration. Weather radars are already used to study animal migration, quantify changes in populations, and reduce aerial conflicts between birds and aircraft. Yet efforts to establish a framework for the broad utilization of operational weather radar for biodiversity monitoring are at risk without suitable data policies and infrastructure in place. In Europe, communities of meteorologists and ecologists have made joint efforts toward sharing and standardizing continent-wide weather radar data. These efforts are now at risk as new meteorological data exchange policies render data useless for biodiversity monitoring. In several other parts of the world, weather radar data are not even available for ecological research. We urge policy makers, funding agencies, and meteorological organizations across the world to recognize the full potential of weather radar data. We propose several actions that would ensure the continued capability of weather radar networks worldwide to act as powerful tools for biodiversity monitoring and research.

Full access
Stefan Brönnimann
,
Rob Allan
,
Linden Ashcroft
,
Saba Baer
,
Mariano Barriendos
,
Rudolf Brázdil
,
Yuri Brugnara
,
Manola Brunet
,
Michele Brunetti
,
Barbara Chimani
,
Richard Cornes
,
Fernando Domínguez-Castro
,
Janusz Filipiak
,
Dimitra Founda
,
Ricardo García Herrera
,
Joelle Gergis
,
Stefan Grab
,
Lisa Hannak
,
Heli Huhtamaa
,
Kim S. Jacobsen
,
Phil Jones
,
Sylvie Jourdain
,
Andrea Kiss
,
Kuanhui Elaine Lin
,
Andrew Lorrey
,
Elin Lundstad
,
Jürg Luterbacher
,
Franz Mauelshagen
,
Maurizio Maugeri
,
Nicolas Maughan
,
Anders Moberg
,
Raphael Neukom
,
Sharon Nicholson
,
Simon Noone
,
Øyvind Nordli
,
Kristín Björg Ólafsdóttir
,
Petra R. Pearce
,
Lucas Pfister
,
Kathleen Pribyl
,
Rajmund Przybylak
,
Christa Pudmenzky
,
Dubravka Rasol
,
Delia Reichenbach
,
Ladislava Řezníčková
,
Fernando S. Rodrigo
,
Christian Rohr
,
Oleg Skrynyk
,
Victoria Slonosky
,
Peter Thorne
,
Maria Antónia Valente
,
José M. Vaquero
,
Nancy E. Westcott
,
Fiona Williamson
, and
Przemysław Wyszyński
Full access
Stefan Brönnimann
,
Rob Allan
,
Linden Ashcroft
,
Saba Baer
,
Mariano Barriendos
,
Rudolf Brázdil
,
Yuri Brugnara
,
Manola Brunet
,
Michele Brunetti
,
Barbara Chimani
,
Richard Cornes
,
Fernando Domínguez-Castro
,
Janusz Filipiak
,
Dimitra Founda
,
Ricardo García Herrera
,
Joelle Gergis
,
Stefan Grab
,
Lisa Hannak
,
Heli Huhtamaa
,
Kim S. Jacobsen
,
Phil Jones
,
Sylvie Jourdain
,
Andrea Kiss
,
Kuanhui Elaine Lin
,
Andrew Lorrey
,
Elin Lundstad
,
Jürg Luterbacher
,
Franz Mauelshagen
,
Maurizio Maugeri
,
Nicolas Maughan
,
Anders Moberg
,
Raphael Neukom
,
Sharon Nicholson
,
Simon Noone
,
Øyvind Nordli
,
Kristín Björg Ólafsdóttir
,
Petra R. Pearce
,
Lucas Pfister
,
Kathleen Pribyl
,
Rajmund Przybylak
,
Christa Pudmenzky
,
Dubravka Rasol
,
Delia Reichenbach
,
Ladislava Řezníčková
,
Fernando S. Rodrigo
,
Christian Rohr
,
Oleg Skrynyk
,
Victoria Slonosky
,
Peter Thorne
,
Maria Antónia Valente
,
José M. Vaquero
,
Nancy E. Westcottt
,
Fiona Williamson
, and
Przemysław Wyszyński

Abstract

Instrumental meteorological measurements from periods prior to the start of national weather services are designated “early instrumental data.” They have played an important role in climate research as they allow daily to decadal variability and changes of temperature, pressure, and precipitation, including extremes, to be addressed. Early instrumental data can also help place twenty-first century climatic changes into a historical context such as defining preindustrial climate and its variability. Until recently, the focus was on long, high-quality series, while the large number of shorter series (which together also cover long periods) received little to no attention. The shift in climate and climate impact research from mean climate characteristics toward weather variability and extremes, as well as the success of historical reanalyses that make use of short series, generates a need for locating and exploring further early instrumental measurements. However, information on early instrumental series has never been electronically compiled on a global scale. Here we attempt a worldwide compilation of metadata on early instrumental meteorological records prior to 1850 (1890 for Africa and the Arctic). Our global inventory comprises information on several thousand records, about half of which have not yet been digitized (not even as monthly means), and only approximately 20% of which have made it to global repositories. The inventory will help to prioritize data rescue efforts and can be used to analyze the potential feasibility of historical weather data products. The inventory will be maintained as a living document and is a first, critical, step toward the systematic rescue and reevaluation of these highly valuable early records. Additions to the inventory are welcome.

Open access
Kyle R. Clem
,
Marilyn N. Raphael
,
Susheel Adusumilli
,
Rebecca Baiman
,
Alison F. Banwell
,
Sandra Barreira
,
Rebecca L. Beadling
,
Steve Colwell
,
Lawrence Coy
,
Rajashree T. Datta
,
Jos De Laat
,
Devon Dunmire
,
Ryan L. Fogt
,
Natalie M. Freeman
,
Helen Amanda Fricker
,
Alex S. Gardner
,
Bryan Johnson
,
Linda M. Keller
,
Natalya A. Kramarova
,
Matthew A. Lazzara
,
Jan L. Lieser
,
Michael MacFerrin
,
Graeme A. MacGilchrist
,
Michelle L. MacLennan
,
Robert A. Massom
,
Matthew R. Mazloff
,
Thomas L. Mote
,
Eric R. Nash
,
Paul A. Newman
,
Taylor Norton
,
Irina Petropavlovskikh
,
Michael Pitts
,
Phillip Reid
,
Michelle L. Santee
,
Ted A. Scambos
,
Jia-Rui Shi
,
Sharon Stammerjohn
,
Susan E. Strahan
,
Andrew F. Thompson
,
Jonathan D. Wille
, and
Earle Wilson
Free access