Jennifer M. Collins

Temperature Variability over Africa

AbstractThe variation of near-surface air temperature anomalies in Africa between 1979 and 2010 is investigated primarily using Microwave Sounding Unit (MSU) total lower-tropospheric temperature data from the Remote Sensing Systems (RSS) and the University of Alabama in Huntsville (UAH) datasets. Significant increasing temperature trends were found in each of the following regions examined: all of Africa, Northern Hemisphere Africa, Southern Hemisphere Africa, tropical Africa, and subtropical Africa. Considering the months June–August, regions in both North and South Africa saw significantly warmer temperatures in the most recent period 1995–2010 than in the period 1979–94. However, for the months December–February, the significant warming was concentrated in the north of Africa. When the two most recent decades are compared with the period 1979–90, warming is observed over these same regions and is concentrated in the most recent decade, from 2001 to 2010. The results presented here indicate that the cli...

Coming to America: Challenges for Faculty Coming to United States' Universities

‘Coming to America’ is a journey filled with obstacles for some new faculty from abroad. This paper reports the findings of surveys conducted with foreign-born faculty and their students in order to explore the key issues these faculty face at US institutions. They identify substantial concerns about cultural differences, including relations with students, feelings of loneliness and the difficult process of obtaining permanent residency rights. The paper concludes with recommendations of strategies that could ease the transition into US academe for foreign-born faculty in the future. These include improving mentoring, networking and training opportunities for foreign-born faculty and providing more information and training for chairs so that they are better able to help foreign-born colleagues.

Temperature Variability over South America

Abstract The variation of air temperature at 2 m above the earth’s surface in South America (SA) between 1948 and 2007 is investigated primarily using the NCEP–NCAR reanalysis. In December–February (austral summer), the majority of SA has a mean temperature between 21° and 24°C during 1948–75, and for 1976–2007 the mean temperature is above 24°C. In June–August (austral winter), warmer temperatures are observed in the tropical region in the recent period. The results indicate that Northeast Brazil (NEB) and central Brazil are warmer in the more recent period. In the last seven years (2001–07) compared to the earlier periods, greater warming is noted in the tropical SA region, mainly in NEB and over the North Atlantic Ocean, and cooling is observed in part of the subtropical SA region. Supporting evidence for the warming in Brazil is given through analyses of station data and observational data. The results presented here indicate that the climate change over SA is likely not predominantly a result of vari...

Spatiotemporal Snowfall Trends in Central New York

AbstractCentral New York State, located at the intersection of the northeastern United States and the Great Lakes basin, is impacted by snowfall produced by lake-effect and non-lake-effect snowstorms. The purpose of this study is to determine the spatiotemporal patterns of snowfall in central New York and their possible underlying causes. Ninety-three Cooperative Observer Program stations are used in this study. Spatiotemporal patterns are analyzed using simple linear regressions, Pearson correlations, principal component analysis to identify regional clustering, and spatial snowfall distribution maps in the ArcGIS software. There are three key findings. First, when the long-term snowfall trend (1931/32–2011/12) is divided into two halves, a strong increase is present during the first half (1931/32–1971/72), followed by a lesser decrease in the second half (1971/72–2011/12). This result suggests that snowfall trends behave nonlinearly over the period of record. Second, central New York spatial snowfall pa...

The 2009 Hurricane Season in the Eastern North Pacific Basin: An Analysis of Environmental Conditions

AbstractDespite the presence of an intensifying El Nino event, the 2009 eastern North Pacific hurricane season was near normal when considering overall hurricane activity. This is in contrast to the relative lull in activity observed between 1998 and 2008. Previous research has noted that the eastern North Pacific should be subdivided into two development regions, the western development region (WDR; 10°–20°N, 116°W–180°) and the eastern development region (EDR; 10°–20°N, North American coastline to 115.9°W), when examining interannual hurricane variability. In 2009, the EDR saw below average numbers of tropical cyclones of all intensities, while the WDR saw near-normal activity. However, activity in both regions varied sharply from month to month with periods of high activity in August and October and lower activity in July and September. This monthly variability was also observed in primary environmental forcing factors such as total precipitable water, tropospheric vertical wind shear, and low-level re...

The record-breaking 2015 hurricane season in the eastern North Pacific: An analysis of environmental conditions

The presence of a near-record El Nino and a positive Pacific Meridional Mode provided an extraordinarily warm background state that fueled the 2015 eastern North Pacific hurricane season to near-record levels. We find that the western portion of the eastern North Pacific, referred to as the Western Development Region (WDR; 10°–20°N, 116°W–180°), set records for named storms, hurricane days, and Accumulated Cyclone Energy in 2015. When analyzing large-scale environmental conditions, we show that record warm sea surface temperatures, high midlevel relative humidity, high low-level relative vorticity, and record low vertical wind shear were among the environmental forcing factors contributing to the observed tropical cyclone activity. We assess how intraseasonal atmospheric variability may have contributed to active and inactive periods observed during the 2015 hurricane season. We document that, historically, active seasons are associated with May–June El Nino conditions, potentially allowing for predictability of future active WDR seasons.

Contrasting High North-East Pacific Tropical Cyclone Activity with Low North Atlantic Activity

Teleconnections between different basins have previously been examined in the literature and that research shows no evidence of a significant inter-basin relationship between North-East Pacific (NE Pacific) and North Atlantic (N Atlantic) tropical cyclone frequency. However, it has been suggested that the NE Pacific basin should be divided into two sub-regions, east and west of 116°W, to gain increased understanding of the factors which influence tropical cyclone formation in the NE Pacific. Using this subdivision to examine the period 1972–2006, it is observed that significant negative relationships are found between tropical cyclone frequency in the west region of the NE Pacific and tropical cyclone frequency in the N Atlantic, i.e. less tropical cyclones in the west region of the NE Pacific are associated with more tropical cyclones in the N Atlantic. The causes of these relationships are examined.

Weather, Ocean, and Social Aspects Associated with Rip Current Deaths in the United States

ABSTRACT Paxton, C.H. and Collins, J.M., 2014. Weather, ocean, and social aspects associated with rip current deaths in the United States. The purpose of this research is to provide a better understanding of the physical and social aspects of rip currents in ocean areas that will lead to better forecasts, better governmental policies in beach areas, and ultimately to save lives. The primary factors associated with rip current formation on beaches are variations in the local beach bathymetry, wind-generated waves of significant wave height typically 1 m or higher, and lower tidal stages. The methodology followed for this study included a review of demographics from over 500 rip current drowning reports along the Atlantic Ocean, Pacific Ocean and Gulf of Mexico coasts of the United States. This research indicated that tourists are often the victims and rescuers often become the victims. For each state or sub-state area where rip current drownings are prevalent, an analysis of social aspects and associated ocean and weather patterns was conducted using buoy and tide data and composite weather patterns. It is important to understand the evolution of these fatal events with respect to the trends of wave height, period, and pressure patterns and resulting surface wind fields that produce the waves.

Recent Advances in the Emerging Field of Paleotempestology

Roughly 35 % of the world’s 7.4 billion people are in the path of tropical cyclones, and coastal populations are expected to increase in the coming century. To understand the future damage that tropical cyclones could impose on an ever-growing coastal population, it is critically important to better understand the relationships between tropical cyclones and climate. Large-scale features of the climate system have been shown to affect tropical cyclone activity, for example, the El Nino Southern Oscillation (ENSO) has been shown to influence tropical cyclone frequency in all oceanic basins on seasonal, yearly, and decadal timescales. However, the relatively short observational record (<160 years) is inadequate for identifying the climatic influences on tropical cyclones over centennial to millennial timescales. Paleotempestology, a relatively new science, helps to resolve this issue by extending the instrumental record back several thousands of years. Over the past two decades, the number of paleotempestology records has increased substantially for sites along the Northwest Atlantic Ocean, Gulf of Mexico and Caribbean Sea, the South Pacific Ocean, and the Northwest Pacific and Indian Ocean regions. The most obvious characteristic of these records is that they reveal extended alternating periods of either greater or lesser tropical cyclone activity over centennial and millennial timescales. In these studies, researchers have shown that large-scale climatic features such as ENSO, sea surface temperatures (SSTs), the latitudinal position of the intertropical convergence zone (ITCZ), and the North Atlantic Oscillation (NAO) are likely driving the alternating long-term behavior of tropical cyclones in global oceanic basins. This review paper will focus on recent paleotempestology studies from multiple global sites and endeavor to synthesize the results and interpretations.

The 2016 North Atlantic Hurricane Season: A Season of Extremes

The 2016 North Atlantic hurricane season had an early start with a rare and powerful storm for January impacting the Azores at hurricane force. Likewise, the end of season heralded Otto which was record breaking in location and intensity being a high-end Category 2 storm at landfall over southern central America in late November. We show that high precipitable water, positive relative vorticity, and low sea level pressure allowed for conducive conditions. During the season, few storms occurred in the main development region. While some environmental conditions were conducive for formation there (such as precipitable water, relative vorticity, and shear), the midlevel relative humidity was too low there for most of the season, presenting very dry conditions in that level of the atmosphere. We further find that the October peak in the accumulated cyclone energy was related to environmentally conducive conditions with positive relative humidity, precipitable water, relative humidity, and low values of sea level pressure. Overall 2016 was notable for a series of extremes, some rarely, and a few never before observed in the Atlantic basin, a potential harbinger of seasons to come in the face of ongoing global climate change.