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This is the report for an interlaboratory comparison (ILC) of high voltage measurements performed by ten laboratories in the USA and Canada from 2018-2019. The measurement ranges were 20 kV to 100 kV DC and 15-70 kV RMS at 60 Hz AC. The ILC was designed to verify strengths and reveal weaknesses in high voltage measurements in commercial, military and energy sector calibration laboratories. The ILC was performed among members of NCSL International, with the generous support of National Research Council Canada (NRC).

The publication of the new American high blood pressure guidelines, presented by the American Heart Association and the American College of Cardiology, has caused great controversy; some support them for respect and recognition to the scientists who developed the guidelines and others are extremely critical. To higher blood pressure, there is more cardiovascular risk, lower prevalence in the population, and lower distribution between the hypertensive subjects. Any therapeutic proposal to lower blood pressure goals will result in decreasing the cardiovascular risks. For now, we will use the pattern 140/90 mm Hg in our coast and jungle, and its recently determined equivalent 134/89 mm Hg for chronic adult residents of the Andean heights. La publicación de las nuevas guías americanas de hipertensión arterial, presentadas por la Asociación Americana del Corazón y el Colegio Americano de Cardiología, ha ocasionado una gran polémica universal; algunos la apoyan por respeto y reconocimiento a los científicos que la elaboraron y otros son sumamente críticos. A mayor presión arterial, hay más riesgo cardiovascular, menor prevalencia en la población, y menor distribución porcentual entre los hipertensos. Cualquier propuesta terapéutica a metas menores de presión arterial, llevará consigo a disminuir los riesgos cardiovasculares. Por ahora, usemos el patrón 140/90 mmHg, en nuestra costa y selva, y su equivalente, el rango 134/89 mmHg, recientemente determinada para los residentes adultos crónicos de nuestras alturas andinas.

The climatology of winter anticyclone frequency in the Mediterranean-Black Sea region is studied on the basis of NCEP/NCAR reanalyses for 1951–2012. Time series of average anticyclone frequency are calculated for different parts of the region. It is found that the anticyclone frequency is increased significantly over the Black sea and Western Mediterranean regions while decreased over the Eastern Mediterranean. Regional manifestation of global climate processes in variability of the anticyclone frequency is investigated.

The impact of different boundary layer source regions in Asia on the chemical composition of the Asian monsoon anticyclone, considering its intraseasonal variability in 2012, is analysed by simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS) using artificial emission tracers. The horizontal distribution of simulated CO, O3, and artificial emission tracers for India/China are in good agreement with patterns found in satellite measurements of O3 and CO by the Aura Microwave Limb Sounder (MLS). Using in addition, correlations of artificial emission tracers with potential vorticity demonstrates that the emission tracer for India/China is a very good proxy for spatial distribution of trace gases within the Asian monsoon anticyclone. The Asian monsoon anticyclone constitutes a horizontal transport barrier for emission tracers and is highly variable in location and shape. From the end of June to early August, a northward movement of the anticyclone and, during September, a strong broadening of the spatial distribution of the emission tracer for India/China towards the tropics are found. In addition to the change of the location of the anticyclone, the contribution of different boundary source regions to the composition of the Asian monsoon anticyclone in the upper troposphere strongly depends on its intraseasonal variability and is therefore more complex than hitherto believed. The largest contributions to the composition of the air mass in the anticyclone are found from northern India and Southeast Asia at a potential temperature of 380 K. In the early (mid-June to mid-July) and late (September) period of the 2012 monsoon season, contributions of emissions from Southeast Asia are highest; in the intervening period (early August), emissions from northern India have the largest impact. Our findings show that the temporal variation of the contribution of different convective regions is imprinted in the chemical composition of the Asian monsoon anticyclone. Air masses originating in Southeast Asia are found both within and outside of the Asian monsoon anticyclone because these air masses experience, in addition to transport within the anticyclone, upward transport at the southeastern flank of the anticyclone and in the tropics. Subsequently, isentropic poleward transport of these air masses occurs at around 380 K with the result that the extratropical lowermost stratosphere in the Northern Hemisphere is flooded by the end of September with air masses originating in Southeast Asia. Even after the breakup of the anticyclonic circulation (around the end of September), significant contributions of air masses originating in India/China are still found in the upper troposphere over Asia. Our results demonstrate that emissions from India, China, and Southeast Asia have a significant impact on the chemical composition of the lowermost stratosphere of the Northern Hemisphere, in particular at the end of the monsoon season in September/October 2012.

The Asian summer monsoon (ASM) anticyclone is a dominant feature of the circulation in the upper troposphere-lower stratosphere (UTLS) during boreal summer, which is found to have persistent maxima in carbon monoxide (CO). This enhancement is due to the upward transport of air with high CO from the planetary boundary layer (PBL), and confinement within the anticyclonic circulation. With rapid urbanization and industrialization, CO surface emissions are relatively high in the ASM region, especially in India and East China. To reveal the transport pathway of CO surface emissions over these two regions, and investigate the contribution of these to the CO distribution within the ASM anticyclone, a source sensitivity experiment was performed using the Weather Research and Forecasting (WRF) with chemistry model (WRF-Chem). According to the experiment results, the CO within the ASM anticyclone mostly comes from India, while the contribution from East China is insignificant. The result ismainly caused by the different transportation mechanisms. In India, CO transportation is primarily affected by convection. The surface air with high CO over India is directly transported to the upper troposphere, and then confined within the ASM anticyclone, leading to a maximum value in the UTLS region. The CO transportation over East China is affected by deep convection and large-scale circulation, resulting mainly in transportation to Korea, Japan, and the North Pacific Ocean, with little upward transport to the anticyclone, leading to a high CO value at 215 hPa over these regions.

Positive SST anomalies usually appear in remote ocean such as the China seas during an ENSO event. By analyzing the monthly data of HadISST from 1950 to 2007, it shows that the interannual component of SST anomalies peak approximately 10 months after SST anomalies peak in the eastern equatorial Pacific. As the ENSO event progresses, the positive SST anomalies spread throughout the China seas and eastward along the Kuroshio extension. Atmospheric reanalysis data demonstrate that changes in the net surface heat flux entering into the China seas are responsible for the SST variability. During El Nino, the western north Pacific anticyclone is generated, with anomalous southwester lies prevailing along the East Asian coast. This anticyclone reduces the mean surface wind speed which decreases the surface heat flux and then increases the SST. The delays between the developing of this anticyclone and the south Indian Ocean anticyclone with approximately 3–6 months cause the 2–3 months lag of the surface heat flux between the China seas and the Indian Ocean. The northwestern Pacific anticyclone is the key process bridging the warming in the eastern equatorial Pacific and that in the China seas.

To study the meteorology and chemistry that is associated with the early stages of the North American Monsoon, the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is applied for the first time at high resolution (4 km grid spacing, allowing for explicit representation of convection) over a large region (continental US and northern Mexico) for a multi-week (15 July to 7 August 2006) integration. Evaluation of model results shows that WRF-Chem reasonably represents the large-scale meteorology and strong convective storms, but tends to overestimate weak convection. In the upper troposphere, the WRF-Chem model predicts ozone (O3) and carbon monoxide (CO) to within 10–20% of aircraft and sonde measurements. Comparison of UT O3 and CO frequency distributions between WRF-Chem and satellite data indicates that WRF-Chem is lofting CO too frequently from the boundary layer (BL). This excessive lofting should also cause biases in the WRF-Chem ozone frequency distribution; however it agrees well with satellite data suggesting that either the chemical production of O3 in the model is overpredicted or there is too much stratosphere to troposphere transport in the model. Analysis of different geographic regions (West Coast, Rocky Mountains, Central Plains, Midwest, and Gulf Coast) reveals that much of the convective transport occurs in the Rocky Mountains, while much of the UT ozone chemical production occurs over the Gulf Coast and Midwest regions where both CO and volatile organic compounds (VOCs) are abundant in the upper troposphere and promote the production of peroxy radicals. In all regions most of the ozone chemical production occurs within 24 h of the air being lofted from the boundary layer. In addition, analysis of the anticyclone and adjacent air indicates that ozone mixing ratios within the anticyclone region associated with the North American Monsoon and just outside the anticyclone are similar. Increases of O3 within the anticyclone are strongly coincident with entrainment of stratospheric air into the anticyclone, but also are from in situ O3 chemical production. In situ O3 production is up to 17% greater within the anticyclone than just outside the anticyclone when the anticyclone is over the southern US indicating that the enhancement of O3 is most pronounced over regions with abundant VOCs.

Influence of northwest (NW) Pacific anticyclone on the Indian summer monsoon (ISM), particularly over the head Bay of Bengal and monsoon trough region, is investigated. Strong NW Pacific anticyclone during summer induces negative precipitation anomalies over the head Bay of Bengal and Gangetic Plain region. Westward extension of moisture divergence and dry moisture transport from NW Pacific associated with anticyclone (ridge) and local Hadley cell-induced subsidence are responsible for these negative precipitation anomalies. The impact is maximum when the anticyclone and Indian Ocean basin warming co-occur. This contributes significantly to year-to-year variability of ISM.

The purpose of this study was to assess trends in the intensity of the North American monsoon anticyclone over multiple decades from 1948 to 2010 during July and August, with a focus on the Lower Colorado River Basin (LCRB). The methodology included a 500 hPa geopotential-height regionalization of the monsoon-anticyclone domain (i.e. a large portion of the western United States and northern Mexico), a typing of 500 hPa circulation patterns over the LCRB, and an examination of multi-decadal trends as well as inter-epochal differences in geopotential heights and frequencies of synoptic types. Three regions (i.e. Northwest, Northeast, and South) were revealed that differed based on inter-annual variations in 500 hPa geopotential heights. The Northwest and South regions had significant increases in geopotential heights from 1948–1978 to 1980–2010. The synoptic types reflected the location of the monsoon anticyclone over the LCRB. The monsoon anticyclone intensified primarily over the northwestern region, which includes the LCRB, since the mid- to late 1970s. The anticyclone has thus been expanding over the LCRB. The anticyclone has been in a northern position, specifically a north-central position, over the basin more frequently over the past 30 years; conversely, the anticyclone has been in southern and eastern positions over the basin less frequently.

This study investigates the relationship between North Atlantic sea surface temperatures (SST) and persistent drought in North America using modern observations, proxy paleo-data, and simulations from multiple climate models. The observational results show that persistent droughts in the Great Plains and the southwest North America are closely related to multidecadal variations of North Atlantic SST (Atlantic Multidecadal Oscillations, AMO). During the AMO warm (cold) phases, most of North America is dry (wet). This relationship is persistent since at least 1567 AD, as based on proxy SST for the North Atlantic and the reconstructed drought index for North America. On centennial timescales, proxy SST records from the North Atlantic and proxy drought records for North America suggest that major periods of AMO-like warm (cold) SST anomalies during the last 7.0 ka correspond to dry (wet) conditions in the Great Plains. The influence of North Atlantic SST on North American droughts is examined using simulations made by five global climate models. When forced by warm North Atlantic SST anomalies, all models captured significant drying over North America, despite some regional differences. Specifically, dry summers in the Great Plains and the southwest North America are simulated by all models. The precipitation response to a cold North Atlantic is much weaker and contains greater disagreement among the models. Overall, the ensemble of the five models could well reproduce the statistical relationship between the dry/wet fluctuations in the North America and North Atlantic SST anomalies. Our results suggest that North Atlantic SSTs are likely a major driver of decadal and centennial timescale circulation, including droughts, in North America. Possible mechanisms that connect North Atlantic SST with North American drought, as well as interactions between North Atlantic and tropical Pacific SST and their relative roles on drought are also discussed.

This study revisits the question posed by Hoskins on why the Northern Hemisphere Pacific sea level pressure (SLP) anticyclone is strongest and maximally extended in summer when the Hadley cell descent in the northern subtropics is the weakest. The paradoxical evolution is revisited because anticyclone buildup to the majestic summer structure is gradual, spread evenly over the preceding 4–6 months, and not just confined to the monsoon-onset period, which is interesting, as monsoons are posited to be the cause of the summer vigor of the anticyclone. Anticyclone buildup is moreover found focused in the extratropics, not the subtropics, where SLP seasonality is shown to be much weaker, generating a related paradox within the context of the Hadley cell’s striking seasonality. Showing this seasonality to arise from, and thus represent, remarkable descent variations in the Asian monsoon sector, but not over the central-eastern ocean basins, leads to the resolution of this paradox. Evolution of other prominent anticyclones is analyzed to critique the development mechanisms: the Azores high evolves like the Pacific one, but without a monsoon to its immediate west. The Mascarene high evolves differently, peaking in austral winter. Monsoons are not implicated in both cases. Diagnostic modeling of seasonal circulation development in the Pacific sector concludes this inquiry. Of the three forcing regions examined, the Pacific midlatitudes are found to be the most influential, accounting for over two-thirds of the winter-to-summer SLP development in the extratropics (6–8 hPa), with the bulk coming from the abatement of winter storm-track heating and transients. The Asian monsoon contribution (2–3 hPa) is dominant in the Pacific (and Atlantic) subtropics. The modeling results resonate with observational findings and attest to the demise of winter storm tracks as the principal cause of the summer vigor of the Pacific anticyclone.

The Arctic region in the northern hemisphere presented humans with dietary and temperature challenges and required a maritime sea mammal hunting or sea-ice adaptation. The colonization of this frigid and florally restricted environment occurred earlier than suspected, during the late Pleistocene c .27 000 years ago in northern Eurasia. In geographic terms, only northern Greenland, the coastal margins of Scandinavia, the Taymyr, and Alaska lie beyond the Arctic Circle. By contrast, sustained settlement of the North American High Arctic and Greenland did not occur until late in the Holocene, c .5000 years ago. Complex whaling societies developed in Bering Strait by 2000 years ago. For the most part, Arctic archaeology is synonymous with a single Mongoloid population, the Inuit (formerly Eskimo) who still dominate the region from Alaska to Greenland. A brief incursion between AD 900 and 1400 by the European Norse was renewed by Danish colonists in the early eighteenth century and continues to the present.

The anomalous low-level anticyclone over the western North Pacific presents a link between El Nino and the western North Pacific-East Asian climate. During a La Nina event, however, the low-level wind anomalies over the western North Pacific reverse sign. The low-level wind anomalies move eastward from South Asia and are established over the western North Pacific in the fall of the El Nino (La Nina) developing year. The anomalous low-level anticyclone associated with El Nino is a response to suppressed convection. This suppressed convection is mainly induced by a cooling tendency associated with the vertical average of the anomalous horizontal advection of moist static energy that is defined as the mechanism of the horizontal advection of moist static energy. The El Nino-related sea surface temperature (SST) anomalies, over the eastern Pacific in particular, create negative meridional gradients of temperature and moisture over the western North Pacific. When the winter monsoon starts to dominate the Asian region, the northerly component of the winter monsoon transports low moist static energy air into South Asia that suppresses convection and induces the anomalous low-level anticyclone. Associated with the mean state of temperature and moisture, the meridional components of the anomalous low-level anticyclone transports cold and dry air to the southward branch and warm and moist air to the northward branch of the anomalous low-level anticyclone. This cooling-warming pattern of the anomalous horizontal advections of moist static energy tends to move the anomalous low-level anticyclone eastward. The mechanism of the horizontal advection of moist static energy implies a phase-locking behavior of the anomalous low-level anticyclone with the seasonal cycle of the mean state over the western North Pacific-East Asian region.

The studies in China on the formation of the summertime subtropical anticyclone on the climate timescale are reviewed. New insights in resent studies are introduced. It is stressed that either in the free atmosphere or in the planetary boundary, the descending arm of the Hadley cell cannot be considered as a mechanism for the formation of the subtropical anticyclone. Then the theories of thermal adaptation of the atmosphere to external thermal forcing and the potential vorticity forcing are developed to understand the formation of the subtropical anticyclone in the three-dimensional domain. Numerical experiments are designed to verify these theories. Results show that in the boreal summer, the formation of the strong South Asian High in the upper troposphere and the subtropical anticyclone over the western Pacific in the middle and lower troposphere is, to a great extent, due to the convective latent heating associated with the Asian monsoon, but affected by orography and the surface sensible heating over the continents. On the other hand, the formation of the subtropical anticyclone at the surface over the northern Pacific and in the upper troposphere over North America is mainly due to the strong surface sensible heating over North America, but affected by radiation cooling over the eastern North Pacific. Moreover, in the real atmosphere such individual thermal forcing is well organized. By considering the different diabatic heating in synthesis, a quadruple heating pattern is found over each subtropical continent and its adjacent oceans in summer. A distinct circulation pattern accompanies this heating pattern. The global summer subtropical heating and circulation may be viewed as “mosaics” of such quadruplet heating and circulation patterns respectively. At last, some important issues for further research in understanding and predicting the variations of the subtropical anticyclone are raised.

In this study the relationship between the North American monsoon, the Californian sea surface temperature (SST) cold pool, the Rocky Mountains and the North Pacific subtropical anticyclone is investigated using the Hadley Centre's atmospheric climate model, HadAM3. In 1996 Hoskins hypothesized that heating in the North American monsoon might be important for the maintenance of the summertime North Pacific subtropical anticyclone, since the monsoon heating may induce descent to the north-west of the monsoon in the descending eastern flank of the subtropical anticyclone. This descent is further enhanced by radiative cooling and is associated with equatorward surface winds parallel to the western coast of North America. These equatorward winds induce oceanic upwelling of cold water and contribute to the formation of the Californian SST cold pool, which may feed back on the anticyclone by further suppressing convection and inducing descent. More recently, Rodwell and Hoskins also investigated the global summer monsoon–subtropical anticyclone relationship. They examined the role that mountains play in impeding the progress of the low-level mid-latitude westerlies, either deflecting the westerlies northwards where they ascend along the sloping mid-latitude isentropes or deflecting them southwards forcing them to descend along the isentropes. In particular, the introduction of the Rockies into a primitive-equation model adiabatically induces descent in the eastern descending flank of the North Pacific subtropical anticyclone. These hypothesized mechanisms have been investigated using HadAM3, focusing on the possible suppression of convection by the Californian SST cold pool, the response of the North Pacific subtropical anticyclone to the strength of the North American monsoon and the ‘blocking’ of the mid-latitude westerlies by the Rocky Mountains. The role of the Rockies is examined by integrating the model with modified orography for the Rocky Mountains. Changing the height of the Rockies alters the circulation in a way consistent with the mechanism outlined above. Higher Rocky mountains force the westerlies southwards, inducing descent in the eastern flank of the subtropical anticyclone as the air descends along the sloping isentropes. The relationship between the North American monsoon and the North Pacific subtropical anticyclone is investigated by suppressing the monsoon in HadAM3. The suppression of the monsoon is accomplished by increasing the surface albedo over Mexico, which induces anomalous ascent on the eastward flank of the subtropical anticyclone and anomalous polewards surface winds along the western coast of the North American continent, also providing support for the above hypothesis. The removal of the Californian SST cold pool, however, has a statistically insignificant effect on the model, suggesting that in this model the feedback of the SST cold pool on the eastern flank of the anticyclone is weak. Copyright © 2002 Royal Meteorological Society.

Cultural expression is an important site of social andpolitical reproduction. How we imagine, reproduce, and define ourselves, and how we are imagined, reproduced, and defined through culture, are m'tically linked to (and often sustain) struggles for change and freedom. -Tricia Rose ( 1 997:259-60) Seldom is attention focused on the everyday processes whereby people, especially immigrants, are made into subjects of a particular nation-state. -Aihwa Ong ( 1 999:263)

The effects of condensation heating on the formation of the subtropical anticyclone in the Eastern Hemisphere (EH) are studied by means of theoretical analysis and numerical simulation. The complete vorticity equation is employed for the analysis. It is found that, due to the vertical gradient of strong condensation heating, the distribution of cyclone and anticyclone in the upper troposphere is out of phase with that in the middle and lower troposphere. This is confirmed by a series of numerical experiments. The horizontal gradient of the condensation heating also affects the configuration of the subtropical anticyclone. It is concluded that condensation heating is a key factor for the formation and location of the summer subtropical anticyclone in the EH. The latent heating released by the Asian monsoon rainfall contributes to the formation of the 200 hPa South Asian anticyclone on the western side of the heating center and the 500 hPa western Pacific subtropical anticyclone on the eastern side of the center. Such configurations are modified to some extent by surface sensible heating and orography. The circulation in mid-latitudes is also affected by the latent heating in the subtropical area through the propagation of Rossby waves.

The authors investigate the transient behavior of the Asian monsoon anticyclone in the summertime upper troposphere for the four northern summers 1987–90. The evolution of potential vorticity near the tropopause shows the development of westward migrating anticyclones breaking off from the main anticyclone a few times each summer. These disturbances are relatively shallow, being confined to the upper troposphere.

Observational evidence is presented to show a teleconnection between the central Pacific and East Asia during the extreme phases of ENSO cycles. This Pacific‐East Asian teleconnection is confined to the lower troposphere. The key system that bridges the warm (cold) events in the eastern Pacific and the weak (strong) East Asian winter monsoons is an anomalous lower-tropospheric anticyclone (cyclone) located in the western North Pacific. The western North Pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures. The anomalies persist until the following spring or early summer, causing anomalously wet (dry) conditions along the East Asian polar front stretching from southern China northeastward to the east of Japan (Kuroshio extension). Using atmospheric general circulation and intermediate models, the authors show that the anomalous Philippine Sea anticyclone results from a Rossby-wave response to suppressed convective heating, which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central Pacific warming. The development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling. Both the anticyclone and the cooling region propagate slowly eastward. The development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades. The rapid establishment of the Philippine Sea wind and SST anomalies implies the occurrence of extratropical‐tropical interactions through cold surge‐induced exchanges of surface buoyancy flux. The central Pacific warming plays an essential role in the development of the western Pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone‐ SST interaction and midlatitude‐tropical interaction in the western North Pacific.

A new and significant correlation is found between the amplitude of mean-winter atmospheric anomalies over the North Atlantic Ocean and those over the North Pacific Ocean and western North America three winters later. It is as strong as the previously known and much discussed correlation between the ocean temperature in the eastern tropical Pacific (El Nino region) and the North Pacific winter atmospheric anomalies. No physical explanation is given at this time for this correlation. A statistical prediction model for mean-winter conditions is constructed based on the above new and previously known correlations. The prediction model is tested on 36 winters of the past. The model predictions are shown to be of remarkable quality over the North Pacific and western North America.

The semipermanent subtropical anticyclone over the North Atlantic basin (the ‘‘Azores high’’) has a major influence on the weather and climate of much of North America, western Europe, and northwestern Africa. The authors develop a climatology of the Azores high by examining its spatial and temporal changes since 1899. Using gridded surface pressure values, anticyclones are identified when the daily pressure is $1020 mb and frequencies are tabulated for each half month from 1899 to 1990. Principal components analysis is applied to analyze the anticyclone’s spatial variance structure. The Azores high is dominated by two spatial modes: a summer pattern, in which high pressure dominates the Atlantic basin, and a winter pattern, in which anticyclones are present over eastern North America and northwestern Africa. Century-long declines in these two modes indicate that there has been a net removal of atmospheric mass over the subtropical Atlantic. Other modes include a meridional versus zonal circulation pattern and omega blocks. Time series of the mean annual principal component scores indicate that meridional flow has been increasing over the Atlantic and that blocking anticyclones have become more prevalent over west-central Europe and less common over the northeastern Atlantic and the British Isles.

This paper examines the 48-h life cycle of a winter anticyclone occurring over North America from 18 to 20 January 1979 using Goddard Laboratory for Atmospheres FGGE level 3b (SOP 1) global analyses on a 4 deg latitude by 5 deg longitude grid. Applying the relatively new methodology of the Zwack-Okossi equation, results show that anticyclonic vorticity advection and cold-air advection acted to develop the anticyclone, while adiabatic warming in the descending air opposed development. Other forcing processes made only small contributions to anticyclone changes. Vertical profiles of the development quantities reveal that vorticity and temperature advections, as well as the adiabatic warming, maximized in the 200-300-mb layer.

The environment is gaining greater attention as organizations increase efforts to reduce any adverse environmental impact of their operations. These efforts naturally migrate into organizations’ supply chains as much of the energy associated in producing their products is expended by external suppliers and in the need to transport components from suppliers and finished products to markets.

A classification scheme for cold surges occurring along the Front Range of the Rocky Mountains has been developed using NMC surface and upper air data. A separation is seen in the data between cases with “parent” anticyclones that moved from Canada south into the United States (Northern type) and those which moved from the Eastern Pacific Ocean east into the central US (Western type). The Northern surges are further broken down into three types, A, B and B′, when the degree of southward motion of the anticyclone and the leading edge of the cold air is considered. An anticyclone movement south of 40°N distinguishes type A, while anticyclone tracks remaining north of 40°N characterize types B and B′. The leading edge of the surge (the surge line) associated with the type A anticyclone travels south of 25δN, while the type B anticyclones produce two distinct surge line movements, one remaining north of 25°N and the other moving south of 25°N. It is not possible to break down the Western surges into distinct types. As a rule, the anticyclones associated with Western surges remain between 50°N and 30°N, with the surge line moving south to ∼18°N on average.

The National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) monthly mean reanalysis dataset has been used to analyze spatial variations of summertime subtropical anticyclones over the Asia–Africa region. The geopotential height and zonal wind components of 1000, 500, 200, and 100 hPa in a 30-year period (1971–2000) have been used to determine the spatial and temporal variations of the anticyclone centres, their monthly frequency and latitudinal axis variations during April–October. The results revealed that there is a clear difference in the location of the summer anticyclone centres in lower, middle and upper levels of the troposphere. In the lower levels, the Azores subtropical anticyclone is located at the east of North Atlantic. In the middle levels, the frequencies of anticyclone centre are concentrated over the northwest of Africa, Arabian Peninsula and Iranian Plateau. In the upper troposphere, the geographical location of the anticyclone centres and their frequencies in the summer season exhibit a scattered pattern from south of China up to western Iran at 200 hPa, and a bimodal pattern over the Tibetan and the Iranian Plateaus at 100 hPa. In fact, in the entire study domain, the Iranian Plateau is a preferable location of the middle and upper troposphere anticyclones. The highest observed latitude of the subtropical anticyclone at 100, 200 and 500 hPa levels have been seen over north of Tibetan plateau, a large area from east to west of Asia and Iran during August, July–August and July, respectively. The maximum monthly variation in the latitude of the ridgeline is seen at 500, 200, and 100 hPa from June to July which goes even up to 10 degrees at some longitudes. Copyright © 2009 Royal Meteorological Society

The South Atlantic anticyclone is a major feature of the austral winter climatology. An atmospheric general circulation model (AGCM) is used to study the dynamics of the South Atlantic anticyclone by means of control simulations and experiments to investigate sensitivity to prescribed orography, sea surface temperatures, and soil wetness. The South Atlantic anticyclone in the first control simulation is unrealistically zonally elongated and centered too far west—errors typical of coupled ocean–atmosphere GCMs. Results of the sensitivity experiments suggest that these deficiencies are associated with another family of systematic model errors: the overprediction of convection over the tropical land surfaces, particularly over eastern tropical Africa and India, and the concurrent large-scale westward shift in the divergence center at upper levels and the convergence center at lower levels. The results also confirm the important role of South American and African orography in localizing the South Atlantic anticyclone over the ocean. Other factors, however, like the regional zonal gradients of sea surface temperatures, are found to have only a minor impact on the anticyclone. To further substantiate these findings, the wintertime anticyclone is examined using a revised version of the atmospheric GCM. Improvements are found in both the anticyclone as well as the Asia–African summer monsoon circulations. The results demonstrate the existence of links between intensity and structure of the wintertime South Atlantic anticyclone and the major summer monsoons in the Northern Hemisphere.

A case study of a transitory anticyclone is conducted as part of the Genesis of Atlantic Lows Experiment (GALE) for the Intensive Observing Period (IOP) of 7–9 March 1986. The special GALE data networks were activated in anticipation of possible Appalachian cold air damming. Cold air damming did not occur and the purpose of the case study is to diagnose a nonevent so that processes associated with cold air damming can be better isolated. An important finding is that the configuration of the antecedent synoptic-scale flow is crucial in determining whether cold air damming will evolve and be sustained. In the 7–9 March 1986 case a surface anticyclone moved steadily southeastward from west of the Great Lakes to the Middle Atlantic coast and offshore as part of a progressive westerly flow regime aloft. The typical cold air damming signature consisting of 1) a slow moving surface anticyclone along the United States-Canada border with a “U” shaped pressure ridge in the sea level isobars east of the App...

This paper reports on Long Range Transport (LRT) of ozone and related species over the North Atlantic ocean and its impact on Europe. Measurements of NO2 and O3 columns from the GOME and MOPITT satellite instruments are first used in conjunction with the GEOS-CHEM global model of transport and tropospheric chemistry to identify the major events of LRT that reach Europe over the course of the summer 2000. Model simulations are then used to examine surface O3 observations at a European mountain site and O3 vertical profiles over several European cities to quantify the impact of the LRT events on the European ozone distributions. Over the course of summer 2000, we identified nine major episodes of pollution transport between North America and Europe, which are in majority associated with WCB/post-frontal outflow (7 events) and zonal transport (2 events). We find that on average three episodes occur per month with the strongest ones being in June. The number and frequency of LRT events that reach Europe after leaving North America is strongly driven by the position and strength of the Azores anticyclone. After leaving North America, the plumes can either i) travel in the North American cyclones, mostly in the Warm Conveyor Belt (WCB), tracking poleward and thus reach Europe at high latitudes; ii) be transported zonally between 40° and 55° N directly to Europe; iii) be incorporated into the Azores anticyclone and reach Europe at mid-latitudes. Based on model sensitivity simulation it can be concluded that on average the North American sources of ozone contribute between 2–8 ppb in PBL and 10–13 ppb in FT. During particular episodes the North American sources resulted in O3 enhancement up to 25–28 ppb in the layer between 800–600 hPa and 10–12 ppb in PBL. For some episodes a substantial North American contribution (30% or higher) does not translate into a well marked enhancement of the total O3.

The North Atlantic is one of the world’s most utilised ocean bodies, most strategic militarily and commercially, and one of the most marine-resource rich. The North Pacifiic is probably its closest rival in these respects. The North Atlantic has a rich history of political and economic development both among its littoral states and in comparison with other ocean regions around the world. With the break-up of the Soviet Union and the growing economic integration of eastern and central Europe, the geopolitical structure of the North Atlantic is changing somewhat; however, its status as an economic force is still great.

Until recently, the first Americans were thought to be fluted-point spear-hunters from the Siberian steppes. Near the end of the Ice Age, they followed big-game herds over the Bering land bridge into the open, upland habitats of the interior of North America about 12,000 years ago. Rapidly extinguishing the big game herds with their deadly hunting methods, they pressed southward in search of new herds and reached the tip of South America about a thousand years later. Today, nearly 70 years after the first excavations at Clovis, New Mexico, the type site for this culture, new sites and new dates from both North and South America are forcing a revision of the earlier picture of the migrations and adaptations of the first Americans. But despite recurring claims that human colonization of the Western Hemisphere began as early as 20,000 or more years ago with the arrival of generalized foragers lacking a projectile-point tradition, no definitive data gives empirical support for a human presence before c. 12,000 before the present (B.P.). All supposed pre-Clovis cultures except one in Alaska have failed to withstand careful scrutiny of their data. In addition, despite recent claims for cultural and biological links of the migrants to Europe or the Pacific Islands, the skeletons and cultural assemblages of Paleoindians throughout the hemisphere point consistently to a northeast Asian origin. According to new data, Paleoindian ancestors in Beringia c. 12,000 years ago were not specialized, fluted-point hunters of large game, but broad-spectrum hunter-gatherers using triangular or bipointed, lanceolates. Diverse cultures descended from these ancestors, not only the big-game hunting Clovis culture of the North American high plains. And just as Clovis did not set the cultural pattern for the hemisphere, it was not the earliest culture. Fully contemporary with the earliest possible Clovis dates of c. 11,200, in South America there already were maritime foragers on the Pacific coast, small-game hunters in the southern pampas, and tropical forest riverine foragers in the eastern tropical lowlands. The Clovis culture thus was just one of several regional cultures developed in the millennium after the initial migration. It could not have been the ancestor of the other early Paleoindian cultures. This new picture of Paleoindian cultures changes understanding of initial human adaptive radiation in the Americas and has implications for general theories of human evolution and behavioral ecology.

This wireless access system for the 1.9 GHz PCS is derived from the existing North American 900-MHz CDMA cellular standard referred to as the IS-95 standard[2].

Extreme cold winter weather events over Eurasia have occurred more frequently in recent years in spite of a warming global climate. To gain further insight into this regional mismatch with the global mean warming trend, we analyzed winter cyclone and anticyclone activities, and their interplay with the regional atmospheric circulation pattern characterized by the semi-permanent Siberian high. We found a persistent weakening of both cyclones and anticyclones between the 1990s and early 2000s, and a pronounced intensification of anticyclone activity afterwards. It is suggested that this intensified anticyclone activity drives the substantially strengthening and northwestward shifting/expanding Siberian high, and explains the decreased midlatitude Eurasian surface air temperature and the increased frequency of cold weather events. The weakened tropospheric midlatitude westerlies in the context of the intensified anticyclones would reduce the eastward propagation speed of Rossby waves, favoring persistence and further intensification of surface anticyclone systems.

In the past two decades, a major change has occurred in the way Paleo-Indian researchers view flaked stone artifacts. No longer are “finished tools” simply classified and compared. Gone are the days of simple functional typologies. It is now generally accepted that flaked stone artifacts became part of the archaeological record as the result of manufacture, use, reuse, discard, and natural site formation processes. Flaked stone assemblages from the High Plains have been increasingly analyzed within the concept of these dynamic systems. Indeed, it is the systems themselves that are being used to characterize cultural norms.

The most recent paleoecological data indicate that the last glacial maximum in North America occurred about 20,000 to 18,000 years ago. At this time, the continental ice sheets covered all of present-day Canada and extended a short distance into the northern tier of the Plains states in the western United States to about 48° north latitude. South of the continental ice sheets, there were valley glaciers in the higher elevations of the Rocky Mountains that reached their maximum advance at the same time as the continental glaciers. The Yellowstone Plateau in northwest Wyoming, southwest Montana, and southeast Idaho contained the largest mass of ice south of the continental ice sheets. Consequently, periglacial conditions affected climates, faunal, and floral resources over the entire Northern Plains area (see Porter 1988).

Climate simulations for the Last Glacial Maximum using general circulation models typically show a glacial anticyclone that produced an easterly wind anomaly south of the North American ice sheets. Evidence of this phenomenon has not been found in eolian sedimentary deposits that record surface wind patterns. Luminescence ages of loess and accompanying paleoecologic records from opal phytoliths and paleosol units across the Columbia Plateau, Washington State, United States, document a decrease, up to fivefold, in regional dust production and accumulation from 35 ka to 15 ka. This interval corresponds to simulations indicating that a glacial anticyclone weakened prevailing south-southwesterly winds that have shaped the eolian landscape of the Columbia Plateau since at least 75 ka. At the same time that the glacial anticyclone suppressed dust production and accumulation, enhanced cold and dry conditions resulted in soil formation dominated by intense bioturbation in periglacial steppe accompanied by shallow calcium carbonate precipitation. This is the first evidence from eolian deposits in North America verifying that the glacial anticyclone altered surface wind patterns and affected eolian systems during the Last Glacial Maximum.

Evidence for a cooling event synchronous with the Younger Dryas (12,000 calendar years before present) has been found in the North Pacific Ocean north of 30° N in records of surface1–5 and subsurface water properties6,7. These changes may be related to a temporary shut-down of North Atlantic Deep Water formation and associated surface cooling over the North Atlantic. It has remained unclear, however, whether this North Atlantic cooling was communicated to the North Pacific Ocean through the atmosphere or the ocean. Here we report results of a sensitivity experiment with a coupled ocean–atmosphere general circulation model that support a primarily atmospheric forcing of North Pacific climate variations. Changes in wind strongly affect coastal upwelling at the North American west coast, and surface cooling by the atmosphere causes better ventilation of the thermocline waters of the northeast Pacific. This effect is amplified by oceanic progagation to the Pacific of the signal arising from collapse of North Atlantic Deep Water formation. These teleconnections may also explain earlier North Pacific and western North American millenial-scale cooling events of a similar nature8–12.

Monthly North American anticyclone climatology for the period 1950-79 is examined. Preferred tracks are evident for each of the 12 calendar months, and three general types can be recognized. The winter pattern is oriented southeastward from northwestern Canada into the contiguous United States; the spring pattern is similar but is displaced eastward, extending southward across western Hudson Bay into the Great Lakes area. The summer pattern develops abruptly in July and has a more zonal orientation east-southeastward from British Columbia along the U.S.-Canadian border. The monthly total of individual anticyclone paths in the study area declined significantly through the period.

A detailed case study has been made of a cyclone/anticyclone couplet over North America during early winter, 11–18 November 1969. The anticyclone was the dominant member of the couplet in this case. Objective analyses of the wind and mass fields were carried out in both the isobaric and isentropic coordinate systems. Calculated quantities which are discussed include quasi-geostrophic vertical velocity and height tendency, potential vorticity, and quasi-Lagrangian kinetic energy budgets. The movement of the cold, polar anticyclone out of its source region in Alaska southeastward to the Gulf of Mexico is seen to be thermally steered. During this stage the anticyclone moves toward the region of descent forced by the low level cold advection. As the anticyclone recurves and begins to move northeastward along the cut coast of the United States, it becomes a warm, dynamic system. The forcing directing the movement is that of differential vorticity advection. The static stability structure of the anticy...

Two hypotheses for the orientation of autumnal migration over the western North Atlantic Ocean, proposed by Williams and Richardson, were tested by simulating the flight of birds from North to South America through calculated wind fields in the western North Atlantic Ocean. Use of a constant compass heading proved to be a tenable strategy for birds departing from the North American coast as far north as Nova Scotia. The range of successful headings, however, became increasingly restricted at northern latitudes. Airspeed, heading, altitude, and point of departure all had major effects on migratory success. Time required for successful non-stop migration was found to lie between 70 and 100 h for passerines and 40 to 60 h for shorebirds.

Results are presented for a synoptic-dynamic investigation of certain polar anticyclones originating in northwestern Canada.. A composite, consisting of three similar high pressure systems, is constructed. This cold anticyclone weakens while it moves southeastward towards the Gulf of Mexico. Along the Gulf Coast it curves northeastward and reintensifies as it becomes a warm, dynamic anticyclone. During a second composite case the high moves rapidly southeastward before dissipating quickly over the warm waters of the Gulf of Mexico. No further intensification or recurvature occurs. In both instances, cold air penetrates deeply into the southern latitudes. An upper tropospheric ridge over northwestern Canada and Alaska appears important in strengthening the polar anticyclone. The center of the high moves southward if uninterrupted northwesterly flow is established aloft. The cold air preceding the high pushes towards the Gulf of Mexico as the trough downstream of the Canadian ridge deepens. The eve...