A new pliocene dolphin (Cetacea: Pontoporiidae), from the Lee Creek Mine, North Carolina

The typical conditions of the eastern boundary of the subtropical anticyclone [e.g., well-defined marine boundary layer (MBL), equatorward low-level flow] that prevail along the mountainous west coast of subtropical South America are frequently disrupted by shallow, warm-core low pressure cells with alongshore and cross-shore scales of 1000 and 500 km, respectively. These so-called coastal lows (CLs) occur up to five times per month in all seasons, although they are better defined from fall to spring. Marked weather changes along the coast and farther inland are associated with the transition from pressure drop to pressure rise. The mean structure and evolution of CLs is documented in this work, using a compositing analysis of 57 episodes selected from hourly pressure observations at a coastal station at 30°S during the austral winters of 1991, 1993, and 1994, and concurrent measurements from a regional research network of nine automatic weather stations, NCEP–NCAR reanalysis fields and high-resolution visible satellite imagery. Coastal lows tend to develop as a migratory surface anticyclone approaches southern Chile at about 40°S producing a poleward-oriented pressure gradient and geostrophically balanced offshore component in the low-level wind. At subtropical latitudes the transition from negative to positive geopotential anomalies occurs around 850 hPa. Enhanced mid- and low-level subsidence near the coast and downslope flow over the coastal range and Andes Mountains leads to the replacement of the cool, marine air by adiabatically warmed air, lowering the surface pressure at the coast and offshore. As the midlatitude ridge moves to the east of the Andes, the alongshore pressure gradient reverts back and the easterly wind ceases to act. The recovery of the surface pressure toward mean values occurs as the cool, cloud-topped MBL returns to the subtropical coast, although the pressure rise can be attenuated by midlatitude troughing. The return of the MBL resembles a Kelvin wave propagating along the coast from northern Chile (where the MBL eventually thickened) into subtropical latitudes in about a day.

The subtropical west coast of South America is under the influence of the southeast Pacific anticyclone year-round, which induces persistent southerly winds along the coast of north-central Chile. These winds often take the form of a low-level coastal jet, in many aspects similar to the coastal jet existing off the California coast. Extensive diagnostics of mesoscale model results for a case in October 2000 are used here to describe the mean momentum budget supporting the coastal jet. The jet appears to occur when midlatitude synoptic conditions induce a northerly directed pressure gradient force along the coast of north-central Chile. The very steep coastal terrain precludes the development of a significant easterly low-level wind that would geostrophically balance the pressure gradient. Instead, the meridional flow accelerates until turbulent friction in the marine boundary layer balances the meridional pressure gradient. The resulting force balance is semigeostrophic, with geostrophy valid only in the zonal (cross shore) direction. At higher levels, the topographic inhibition of the easterlies relaxes, and a small easterly flow ensues, which turns out to be very important in the temperature and stability budgets of the layer capping the marine boundary layer.

While it is widely accepted that the global mean atmospheric temperature has increased in recent decades, the spatial distribution of global warming has been complex. In this study we comprehensively characterize the spatial pattern, including vertical structure, of temperature trends along the subtropical west coast of South America (continental Chile) for the period 1979–2006 and examine their consistency with expectations based on the CMIP‐3 ensemble of coupled ocean‐atmosphere simulations for the late 20th century. In central and northern Chile (17°–37°S) the most notable feature is a strong contrast between surface cooling at coastal stations (−0.2°C/decade) and warming in the Andes (+0.25°C/decade), only 100–200 km further inland. Coastal radiosonde data imply that the coast‐Andes variation is largely due to strong vertical stratification of temperature trends in the atmosphere west of the Andes. The coastal cooling appears to form part of a larger‐scale, La Niña‐like pattern and may extend below the ocean mixed layer to depths of at least 500 m. Over continental Chile the CMIP‐3 GCM ensemble predicts temperature trends similar to those observed in the Andes. The cooling along the Chilean coast is not reproduced by the models, but the mean SST warming is weaker there than any other part of the world except the Southern Ocean. It is proposed that the intensification of the South Pacific Anticyclone during recent decades, which is also a simulated consequence of global warming, is likely to play a major role in maintaining cooler temperatures off the coast of Chile.

Central Chile is a densely populated region along the west coast of subtropical South America (30°–36°S), limited to the east by the Andes. Precipitation is concentrated in austral winter, mostly associated with the passage of cold fronts. The freezing level over central Chile is typically between 1500 and 2500 m when precipitation is present. In about a third of the cases, however, precipitation occurs accompanied by warm temperatures and freezing levels above 3000 m, leading to a sizeable increment in the pluvial area of Andean basins and setting the stage for hydrometeorological hazards. Here, warm winter storms in central Chile are studied, including a statistical description of their occurrence and an estimate of their hydrological impacts. Remote-sensed data and high-resolution reanalysis are used to explore the synoptic-scale environment of a typical case, generalized later by a compositing analysis. The structure of warm storms is also contrasted with that of the more recurrent cold cases. Precipitation during warm events occurs in the warm sector of a slow-moving cold front because of the intense moisture flux against the mountains in connection with a land-falling atmospheric river. This is in turn driven by a strong zonal jet aloft and reduced mechanical blocking upstream of the Andes. On a broader scale, a key element is the presence of a slowly moving anticyclone over the south Pacific, fostering advection of cold air into midlatitudes. The intense and persistent zonal jet stretches a moist-air corridor from the central Pacific to the west coast of South America.

Andean uplift, ocean cooling and Atacama hyperaridity: A climate modeling perspective

Subsynoptic, warm core low pressure areas are frequently observed along the west coast of subtropical South America during austral winter. These so-called coastal lows (CLs) tend to develop as an upper-air, midlatitude ridge is approaching the subtropical Andes and, therefore, while pressure is increasing aloft and farther to the south. These CLs have a profound impact in the coastal weather associated with a rapid transition from clear skies and stronger than average equatorward low-level flow to overcast conditions and relaxed equatorward (or even poleward) flow. Weather conditions inland mostly reflect the associated changes in the strength and height of the base of the subsidence inversion. In this work, a mesoscale simulation of a typical CL episode is performed using a numerical weather prediction model [the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5)] Comparison with observations reveals that the model simulation properly captures the large-scale pattern as we...

Simulated interface elevation anomalies with a reduced gravity model forced by observed wind stress are used to investigate the origin of thermocline depth fluctuations in the eastern tropical and South Pacific at interdecadal timescales. It is found that interdecadal thermocline depth fluctuations in the eastern equatorial Pacific and along the western coast of the Americas are fundamentally driven by zonal wind fluctuations in the western equatorial Pacific. Thus positive (negative) interface elevation anomalies, which correspond to shallower (deeper) thermocline depths, in the eastern tropical Pacific and along the west coast of Central and South America are related to easterly (westerly) anomalies in the western sector of the equatorial Pacific. However, off‐equatorial wind fluctuations maintain and reinforce the interdecadal variability observed along the eastern equatorial Pacific and along the west coast of South America. In the latter region, equatorial (off‐equatorial) wind forcing is relatively more important equatorward (poleward) of 30°S. In the eastern equatorial Pacific, interface elevation anomalies are negatively correlated with sea surface temperature (SST) at interdecadal timescales. According to our results the SST interdecadal anomalies are in part (50–60%) driven by wind fluctuations likely through the modulation of vertical advection of cold waters which depends primarily on the thermocline depth forced remotely or locally by winds. This relationship was especially strong during the 1970s and 1980s, a period characterized by the larger zonal wind stress interdecadal fluctuations observed in the western equatorial Pacific.

Walter Rathbone Bacon Traveling Scholarship Expeditions to the East and West Coasts of South America, 1925-1927 : photographs of Faulklands (2 of 3)

Walter Rathbone Bacon Traveling Scholarship Expeditions to the East and West Coasts of South America, 1925-1927 : photographs of Brazil (2 of 2)

We have applied a wavelet analysis technique on the quiet-time equatorial magnetic field perturbation measurements (signature of the equatorial electrojet) from Sao Luis (Brazil) and Jicamarca (Peru), to study longitudinal, seasonal, and solar cycle variabilities of the equatorial electrojet over the East and West coasts of South America.

In further reply to yours of June 21st beg to say that i 9 e are in receipt of letter from the Pacific Stetim Navigation Company, New York, sending us their sailings between t'hristobal

Walter Rathbone Bacon Traveling Scholarship Expeditions to the East and West Coasts of South America, 1925-1927 : photographs (3 of 5)

Walter Rathbone Bacon Traveling Scholarship Expeditions to the East and West Coasts of South America, 1925-1927 : station data, typed copy

Walter Rathbone Bacon Traveling Scholarship Expeditions to the East and West Coasts of South America, 1925-1927 : Photographs of Uruguay

Walter Rathbone Bacon Traveling Scholarship Expeditions to the East and West Coasts of South America, 1925-1927 : reports on the expeditions by Waldo LaSalle Schmitt