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[1] Impact of global warming on the East Asian Winter Monsoon (EAWM) is studied using nine coupled atmosphere-ocean general circulation models (AOGCMs). Models are mostly successful in simulating the basic features of the EAWM with varied location of monsoon northwesterlies (NW). Under the global warming scenario, most models show a weakening of the EAWM accompanied by a strong anticyclonic anomaly over the North Pacific corresponding to a weakened and/or the northern shift of the Aleutian Low (AL). Response in Sea Level Pressure (SLP) also shows the weakening of both the AL and the Siberian High (SH), which gives rise to a weakened pressure gradient along the eastern coast of the Eurasian continent. Among other factors, weakening of the tropical local Hadley circulation was found to substantially weaken the East Asian Jet (EAJ) and the resultant EAWM.

[1] The variability of both the stationary planetary wave activity and the East Asian winter monsoon is strongly associated with the thermal contrast between oceans and landmasses. In this study, we explore the interannual relationship between the monsoon and the wave activity defined by an index of the difference in the divergence of EliassenPalm flux between 50� N at 500 hPa and 40� N at 300 hPa. It is found that, compared to the winters of low wave activity, the equatorward propagation of planetary waves in the middle and upper troposphere is stronger in the high wave activity winters. During these high activity winters, the upward wave propagation from the troposphere into the stratosphere becomes weaker. This is accompanied by a smaller perturbation in the polar vortex, which tends to be colder and stronger. In the meantime, the East Asian westerly jet stream, the East Asian trough, the Siberian high, and the Aleutian low all become weaker apparently. In particular, the weakening of the Siberian high and the Aleutian low decreases the northeasterly wind over East Asia, leading to a warming condition in the region especially in northeastern Asia. A further analysis reveals that the zonal wavenumber-2 pattern of planetary waves contributes dominantly to the variability of the East Asian winter monsoon.

The long-term variability of the Siberian High, the dominant Northern Hemisphere anticyclone during winter, is largely unknown. To investigate how this feature varied prior to the instrumental record, we present a reconstruction of a Dec-Feb Siberian High (SH) index based on Eurasian and North American tree rings. Spanning 1599-1980, it provides information on SH variability over the past four centuries. A decline in the instrumental SH index since the late 1970s, related to Eurasian warming, is the most striking feature over the past four hundred years. It is associated with a highly significant (p < 0.0001) step change in 1989. Significant similar to 3-4 yr spectral peaks in the reconstruction fall within the range of variability of the East Asian winter monsoon (which has also declined recently) and lend further support to proposed relationships between these largescale features of the climate system.

[1] This study assesses how well the East Asian monsoon index (EAMI), developed on the basis of zonal and meridional land–sea thermal contrasts over the Asia-Pacific region, can represent the seasonal and interannual variations of the East Asian summer and winter monsoons (EASM and EAWM). It suggests that the EAMI can be used to estimate the timing of the onset and the relative intensity of the EASM, characterized by dominant meridional circulation and rainfall patterns over the Asia-Pacific region, as well as represent the EAWM, which is dominated by a nearly zonal dipole structure composed of Siberian high and Aleutian low prevailing in the middle and high latitudes. The EAMI is therefore of benefit in understanding the seasonal evolution of the East Asian monsoon circulation and interannual variation of the individual monsoons both in summer and in winter.

The East Asian Winter Monsoon (EAWM) and Siberian High (SH) are inherently related, based on prior studies of instrumental data available for recent decades (since 1958). Here we develop an extended instrumental EAWM index since 1871 that correlates significantly with the SH. These two indices show common modes of variation on the biennial (2-3 year) time scale. We also develop an index of the pressure gradient between the SH and the Aleutian Low, a gradient which critically impacts EAWM variability. This difference series, based on tree-ring reconstructions of the SH and the North Pacific Index (NPI) over the past 400 years, shows that the weakening of this gradient in recent decades has not been unusual in a long-term context. Correlations between the SH series and a tree-ring reconstruction of the El Nino-Southern Oscillation (ENSO) suggest a variable tropical-higher latitude teleconnection.

On the basis of two sedimentary records from the central Sea of Okhotsk, we reconstruct the closely coupled glacial/interglacial changes in terrigenous flux, marine productivity, and sea ice coverage over the past 1.1 Myr. The correspondance of our sedimentary records to the China loess grain size record (China loess particle timescale, CHILOPARTS) suggests that environmental changes in both the Sea of Okhotsk area and in SE Asia were closely related via the Siberian atmospheric high-pressure cell. During full glacial times our records point to a strong Siberian High causing northerly wind directions, the extension of the sea ice cover, and a reduced Amur River discharge. Deglacial maxima of terrigenous flux were succeeded by or synchronous to high-productivity events. Marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing. During interglacials, SE monsoonal winds prevailed, analogous to today's summer situation of a pronounced Mongolian Heat Low and a strong Hawaiian High. Strong freshwater discharge induced by high precipitation rates in the Amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity (although being considerably lower than during the terminations) and a lowered flux of ice-rafted detritus.

The extreme phenomenon of cold-spell events in the Greek region was investigated in this study by using a combined deterministic-stochastic model, along with 31 yr daily minimum temperature data from 16 meteorological stations of the Hellenic National Meteorological Service (HNMS). Trend analysis and the spatio-temporal distribution of cold spells were investigated by applying linear regression and Fourier analysis. The frequency, duration, distribution. timing and intensity of cold spells were successfully filled with Poisson, Gauss and exponential distributions. The features of cold spells were found to vary widely due to the effect of physicogeographical parameters such as latitude, longitude, altitude, and continentality, as well as to the synoptic weather situations, prevailing in the various Greek sub-areas. The relative importance of the physicogeographical peculiarities was assessed: latitude and altitude were evaluated as the most important parameters for determining the features of cold spells in Greece. The highest probability of cold spells in the Greek peninsula exists when a persistent NW European and/or Siberian anticyclone reaches its highest intensity during winter and extends high-pressure ridges to the Balkans, and particularly to the Greek area. Climate Research

Presented is the evidence for the actual manifestation of solar variability in climatic characteristics of the Prebaikalye. This influence on surface air temperature was quantified. A high degree of correlation was established between the mean power of a solar activity cycle and the surface air temperature in the Prebaikalye, averaged over a solar cycle period. It is shown that the main meaningful air temperature variations in the region for the period 1881-1960 were caused by solar activity. The temperature variation amplitude for that period was 1°C. Since the 1960s until the present, with the influence of solar variability persisting, there has been an obvious forcing of another factor whose role was steadily increasing so that as recently as in the last decade it exceeded the contribution from solar variability. For the period 1960-1997, the temperature rise that was not associated with solar variability, was 1.7°C. This new factor is most likely to be the global variations of the thermal regime of the atmosphere that are caused by the anthropogenic factor. This assumption is in agreement with model calculations, pointing to the fact that the most significant manifestation of a global warming should be expected in inland regions of Eurasia. An analysis of the seasonal variations in ground temperature showed that the variations that are taking place to date are most clearly pronounced in the winter-spring period and are associated with a reduction of the stationary period of the Siberian anticyclone. This suggests that the mechanism responsible for the realization of variability factors of regional climate is the global atmospheric circulation rather than a local change of the energy balance of the atmosphere.

In the Northern Hemisphere, the land masses are situated much closer to the poles than they are in the Southern Hemisphere. The land not only acts as a source area for cold air, but because of its lower thermal inertia compared to water, it does not modify the cold temperatures nearly as much as does water, even cold Antarctic waters. Thus the middle latitudes are much cooler during winter in the Northern Hemisphere than in the Southern Hemisphere, and snowfall occurs more frequently. Associated with this is the fact that high pressure systems or anticyclones occur less often in the Southern Hemisphere than in the Northern Hemisphere. Because there is less land in the mid latitudes of the Southern Hemisphere, the southern westerlies are stronger than their northern counterpart, and large nearly stationary "high" systems such as the "Siberian High" have a more difficult time becoming established. These large "highs" are important in refrigerating surface air and influencing the strength and tracks of storm systems. Despite these drawbacks, however, snow does occur in the middle latitudes of the southern Hemisphere and occasionally even in the sub-tropics. In this paper SMMR and SSM/I microwave observations made in 1994, 1995 and 1996 are reported.

Within the framework of the Baikal Drilling Project (BDP), a 192 m long sediment core (BDP-96-1) was recovered from the Academician Ridge, a submerged topographic high between the North and Central Basins of Lake Baikal. Sedimentological, clay mineralogical and geochemical investigations were carried out on the core interval between 90 and 124 m depth, corresponding to ca. 2.4–3.4 Ma. The aim was to reconstruct the climatic and tectonic history of the continental region during the intensification of Northern Hemisphere glaciation in Late Pliocene time. A major climate change occurred in the Lake Baikal area at about 2.65 Ma. Enhanced physical weathering in the catchment, mirrored in the illite to smectite ratio, and temporarily reduced bioproduction in the lake, reflected by the diatom abundance, evidence a change towards a colder and more arid climate, probably associated with an intensification of the Siberian High. In addition, the coincident onset of distinct fluctuations in these parameters and in the Zr/Al ratio suggests the beginning of the Late Cenozoic high amplitude climate cycles at about 2.65 Ma. Fluctuations in the Zr/Al ratio are traced back to changes in the aeolian input, with high values in warmer, more humid phases due to a weaker Siberian High. Assuming that the sand content in the sediment reflects tectonic pulses, the Lake Baikal area was tectonically active during the entire investigated period, but in particular around 2.65 Ma. Tectonic movements have likely led to a gradual catchment change since about 3.15 Ma from the western towards the eastern lake surroundings, as indicated in the geochemistry and clay mineralogy of the sediments. The strong coincidence between tectonic and climatic changes in the Baikal area hints at the Himalayan uplift being one of the triggers for the Northern Hemisphere Glaciation.

This letter presents an assessment of winter cloudiness variability over Northern Eurasia regions related to the Siberian High intensity (SHI) variations during 1966‐2010. An analysis of cloud fraction and the occurrence of different cloud types was carried out based on visual observations from almost 500 Russian meteorological stations. The moonlight criterion was implemented to reduce the uncertainty of night observations. The SHI was defined based on sea-level pressure fields from different reanalyses. We found a statistically significant negative correlation of cloud cover with the SHI over central and southern Siberia and the southern Urals with regression coefficients around 3% hPa 1 for total cloud fraction (TCF) for particular stations near the Siberian High center. Cross-wavelet analysis of TCF and SHI revealed a long-term relationship between cloudiness and the Siberian High. Generally, the Siberian High intensification by 1 hPa leads to a replacement of one overcast day with one day without clouds, which is associated mainly with a decrease in precipitating and stratiform clouds. These changes point to a positive feedback between cloudiness and the Siberian High.

An analysis of the interannual variability of surface air temperature during the boreal winter in the East Asian (EA) region from 1960 to 2009 reveals that the East Asian winter monsoon (EAWM) significantly weakens after the mid-1980s. The robust warming over the EA region in the lower and middle troposphere as well as at the surface is caused mainly by changes in circulations over the North Pacific and Eurasian continent. The 300 hPa East Asian jet and 500 hPa trough over the EA region, which are closely linked to cold surges, significantly weaken after the mid-1980s. The weakened northerly wind in the Siberian high region and north of the EA region interfere with cold advection toward the EA region. The anomalous southeasterlies over the East China Sea due to an enhanced North Pacific oscillation (NPO)-like sea level pressure (SLP) pattern lead to anomalous warm advection over the EA region. It is also found that the advection of mean temperature by anomalous wind and the advection of anomalous temperature by mean wind mainly contribute to the anomalous warm advection in the EA region after the mid-1980s. Consequently, these anomalous circulations provide a more favorable environment for weakening of the EAWM.

This paper attempts to establish a method for analysing the relationship between the polar and equatorial climate of the Northern Hemisphere. The Arctic Oscillation (AO) is known to have no direct relationship with the monsoon over the Maritime Continent (MC). Thus, an index called the Siberian High(SH)–Maritime Continent(MC) Index (SHMCI) is developed to represent the mean sea level pressure difference between the SH and the warm pool over the MC. This index indicates a strong link with the monsoon circulation. A positive (strong) value of the SHMCI is associated with strong meridional winds and intense and frequent cold surge events over the South China Sea. The correlation between the AO index and the SHMCI is -0.39, which is medium but statistically significant; however, it is not sufficiently conclusive to infer direct correlation. Nevertheless, the SHMCI can be used as a tool to relate the AO with the monsoon over the MC because of the influence demonstrated by the AO towards the SH. Further analysis on the convergence and divergence anomalies over the MC reveals an impact discernible only from the SHMCI. This implies that the SHMCI manifests clearly the relationship between the Arctic and equatorial climate.

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.

The cryosphere consists of water in the solid form at the Earth's surface and includes, among others, snow, sea ice, glaciers and ice sheets. Since the 1990s the cryosphere and its components have often been considered as indicators of global warming because rising temperatures can enhance the melting of solid water (e.g. Barry et al 1993, Goodison and Walker 1993, Armstrong and Brun 2008). Changes in the cryosphere are often easier to recognize than a global temperature rise of a couple of degrees: many locals and tourists have hands-on experience in changes in the extent of glaciers or the duration of winter snow cover on the Eurasian and North American continents. On a more scientific basis, the last IPCC report left no doubt: the amount of snow and ice on Earth is decreasing (Lemke et al 2007). Available data showed clearly decreasing trends in the sea ice and frozen ground extent of the Northern Hemisphere (NH) and the global glacier mass balance. However, the trend in the snow cover extent (SCE) of the NH was much more ambiguous; a result that has since been confirmed by the online available up-to-date analysis of the SCE performed by the Rutgers University Global Snow Lab (climate.rutgers.edu/snowcover/). The behavior of snow is not the result of a simple cause-and-effect relationship between air temperature and snow. It is instead related to a rather complex interplay between external meteorological parameters and internal processes in the snowpack. While air temperature is of course a crucial parameter for snow and its melting, precipitation and radiation are also important. Further physical properties like snow grain size and the amount of absorbing impurities in the snow determine the fraction of absorbed radiation. While all these parameters affect the energy budget of the snowpack, each of these variables can dominate depending on the season or, more generally, on environmental conditions. As a result, the reduction in SCE in spring and summer in the NH was attributed to faster melting because of higher air temperatures, while the winter months (December to February) saw an increase in the SCE due to increased precipitation (Lemke et al >2007). Cohen et al (2012) confirmed these opposing effects in the SCE and showed that on the Eurasian continent the average SCE in October has increased by approximately 3 × 106 km2 in the last two decades; a growth of almost 40%, corresponding to roughly 1.5 times the area of Greenland. For the same period, Cohen et al (2012) found a negligible trend in the average temperatures above the continents of the NH for the winter months despite a significant increase in the annual mean temperature for the same regions. Cohen et al (2012) propose the following link between temperatures and snow: the reduced sea ice cover of the Arctic Ocean and the enhanced air temperatures in fall cause higher evaporation from the Arctic Ocean, leading to increased tropospheric moisture in the Arctic. More moisture results in more snowfall over the Eurasian continent, increasing the SCE. The increased snow cover strengthens the Siberian High, a strong anticyclonic system generally persistent between October and April. This system is strong enough to affect weather patterns in large parts of the NH, resulting in changes in the large-scale circulation of the NH (Panagiotopoulos et al 2005). As a result, outbreaks of cold Arctic air masses into the mid-latitudes are more frequent, leading to low temperatures over the eastern part of North America and Northern Eurasia. According to Cohen et al (2012), these are exactly the same regions that have experienced a cooling trend in the winter temperature over the past twenty years. While this chain of events is plausible (and some are confirmed by observations), existing climate models are not yet capable of reproducing these processes. On the contrary, Cohen et al (2012) showed that they predict a slightly decreasing SCE in October for Eurasia and an increase in winter temperatures over the continents in the NH. This is not surprising because the simulation of snow and its interactions with the atmosphere in global models is imperfect (Armstrong and Brun 2008). Most models have difficulty in simulating successfully the complex behavior of snow cover. A better representation of snow in the models is vital in order to understand the possible far-reaching consequences of changes in the SCE and its effects on the local climate and on large-scale circulations in the atmosphere to utilize snow as a reliable indicator for a changing climate. However, the SCE is only one of many possible snow parameters that can be used (Goodison and Walker 1993). Although omni-present in many regions and during many seasons, there is still much to be learned about snow and how it is linked to the global climate system. References Armstrong R L and Brun E 2008 Snow and Climate: Physical Processes, Surface Energy Exchange and Modeling (Cambridge: Cambridge University Press) Barry R G, Goodison B E and LeDrew E F (ed) 1993 Snow watch '92—detection strategies for snow and ice Glaciological Data Report GD-25 (Boulder, CO: World Data Center A: Glaciology (Snow and Ice)) p 273 Cohen J L, Furtado J C, Barlow M A, Alexeev V A and Cherry J E 2012 Arctic warming, increasing snow cover and widespread boreal winter cooling Environ. Res. Lett. 7 014007 Goodison B E and Walker A E 1993 Use of snow cover derived from satellite passive microwave data as indicator for climate change Ann. Glaciol. 17 137–42 Lemke P et al 2007 Observations: changes in snow, ice and frozen ground Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge: Cambridge University Press) Panagiotopoulos F, Shahgedanova M, Hannachi A and Stephenson D B 2005 Observed trends and teleconnections of the Siberian high: a recently declining center of action J. Clim. 18 1411–22

The prevailing weather processes in winter over East Asia are outbreaks of cold air which, among the most significant weather events of winter over the Northern Hemisphere, are marked by the invasion of extremely dry and cold air over Mongolia, northern China, and Korea. The associated weather includes high winds, an abrupt temperature drop, severe frost, freezing rain, heavy snowfalls and even sandstorms. The severity of these weathers greatly depend upon the coldness of the air masses, patterns of synoptic systems and circulation and the regional or local terrain features.

The streamflow timings of the Euphrates and Tigris, two important snow-fed rivers in the Middle East, are found to be shifting to earlier days in the year. Six out of eight stations indicate statistically significant shifts between two consecutive 17-year periods (i.e. 1972-88 and 1990-2006). Among these stations, the average shift to earlier times is over 5 days, suggesting earlier spring melting of snowpack due to increased temperatures in the second period. A striking increase in the discharges takes place during the first half of March, and it is observed at all stream gauging sites considered in this study. An analysis based on the NCEP/NCAR reanalysis data indicates that warming which results in this increase is associated with the switching from the northeasterly flow to southwesterly flow over the Black Sea and western Anatolia caused by the weakening of the Siberian High over eastern Europe. These changes in the circulation features from the first to second periods are found to be very consistent with the positive and negative phases of the North Sea-Caspian pattern.

Aggregate annual discharge from the six largest Arctic-draining Eurasian rivers achieved an all-time record high in 2007, accentuating a long-term upward trend that argues for intensification of the Arctic hydrologic cycle. This record discharge was due in part to strong positive anomalies in late winter snow water equivalent across much of northern Eurasia. These anomalies arose in response to an unusual pattern of atmospheric circulation in late 2006 and early 2007, characterized by an extreme northeastward extension of the Icelandic Low and a contraction of the Siberian High. Positive net precipitation anomalies then continued into summer, further contributing to discharge.

For the past few decades, daily winter temperatures over East Asia have been higher and less variable. Generally, these simple temperature-distribution shifts should lead to a decrease in the occurrence of cold extremes, but observations of the changes in the extremes are often complicated. In the present study, the change in the occurrence of relatively cold events (daily temperature anomaly, _?T_n-2_ã_nfor that season) in each winter monsoon over East Asia was examined using ground observations of daily temperature for the period 1954 - 2006. The time-mean temperature for each winter was subtracted to remove the interannual variability and long-term trend. Our analyses reveal that the intraseasonal temperature distribution over East Asia has changed with a negative skew, and the frequency of the relatively cold events has slightly increased (by 0.09 days per decade) over the past few decades, on an average, for the entire analysis domain (east of 105°E, 122 stations). In particular, the increase occurs me dominantly (82% of the total stations) in regions north of 40°N where a stronger warming has progressed. The frequency of relatively cold events is found to be significantly correlated with the variance of the Siberian high and the mean of the Arc tic Oscillation. The increasing trend in the frequency of relatively cold events may serve to partly countervail the decrease (-1.12 days per decade) in the frequency of absolute cold events (daily temperature anomaly, _?T_n2_ã_noverall) across the entire observation period.

General circulation model experiments test the geologically based correlation of high monsoon rainfall over interior Australia with Northern Hemisphere insolation and evaluate the sensitivity of the Australian Monsoon to ecosystem change. Our results suggest that Northern Hemisphere insolation control on the intensity of the Siberian High, rather than summer insolation over the Australian continent, determines the strength of the Australian Monsoon on millennial time scales, unlike a classic monsoon regime. Additional simulations show that the penetration of monsoon moisture into the interior is sensitive to biosphere-atmosphere feedbacks linked to vegetation type and soil properties. This sensitivity offers a resolution to the observed failure of the Australian Monsoon to penetrate the interior in the Holocene. Postulated regular burning practiced by early humans may have converted a tree-shrub-grassland mosaic across the semiarid zone to the modern desert scrub, thereby weakening biospheric feedbacks and resulting in long-term desertification of the continent.

The relationship between the Arctic Oscillation (AO) and daily temperature variance of 150 Chinese stations are investigated in the present study for wintertime (1November through 31 March) in the period of 1954–2001. Results show that the temperature variance significantly decreases during the high AO years, and increases in low AO cases. A key factor connecting them is the Siberian High, particularly the high-frequency fluctuations of the High. Within the seasonal time scale, the frequency of low-temperature extremes (daily temperature anomaly below −2σ, σ is the standard deviation of daily temperature for a given winter and a given station) displays an odd relation to the variance: a larger (smaller) variance is found to be associated with smaller (greater) frequency of low-temperature events. That is due to the non-normal distribution of the temperatures, and also influenced by the phases of AO. During the last 50 years or so, AO experiences a significant increasing trend, meanwhile the variance of daily sea level pressure (SLP) in the central region of Siberian High has decreased at a rate of −10.7%/10 a. These result in a significant weakening of the daily temperature variance in China with a trend of −4.1%/10 a, and a significant increase in the intra-seasonal low-temperature extremes at a rate of 0.16d/10 a.

The first volume in Springer's Regional Climate Studies series focuses on the Mediterranean Basin. This is a climatically interesting and diverse region, subject to the influences of the Mediterranean Sea and the large-scale circulation patterns associated with the south Asian monsoon, Siberian high pressure system, southern oscillation, and North Atlantic oscillation. All of these influences are modified by the complex local topography and characterized by regional processes such as Mediterranean cyclogenesis. It is also a sensitive region, with a long and rich human history where the impacts of past, present, and future climate variability on the rate of desertification, for example, are potentially large. Thus, the recent research into many facets of the climate of the Mediterranean Basin is welcome and timely. For researchers and students unfamiliar with the region, a standard overview textbook has not been available, so Mediterranean Climate—Variability and Trends has the potential to fill an important gap.

[1] The Transport and Chemical Evolution over the Pacific (TRACE-P) experiment was conducted between February and April 2001. It included extensive chemical sampling by two aircraft based primarily in Hong Kong and Yokota Air Base, Japan. TRACE-P examined pathways for the outflow of chemically and radiatively important gases and aerosols and their precursors from eastern Asia to the western Pacific and explored the chemical evolution of Asian outflow. This paper describes meteorological conditions and transport pathways over the Pacific Basin during TRACE-P. Meteorological conditions changed rapidly during the period due to the seasonal winter to spring transition and the decay of prolonged ENSO cold phase (La Nina) conditions. To document these changes, TRACE-P was divided into two halves, and mean flow patterns during each half are presented and discussed. Important circulation features are the semipermanent Siberian anticyclone and transient middle latitude cyclones that form near eastern Asia and then move eastward over the northern Pacific. Five-day backward trajectories from the various flight tracks show that air sampled by the aircraft had been transported from a variety of locations. Some parcels remained over the tropical western North Pacific during the entire period, while other important origins were Southeast Asia, Africa, and central Asia. Specifically, lower tropospheric flight segments out of Hong Kong sampled both prefrontal maritime air as well as postfrontal air from the Asian continent. Conversely, low-level flight segments out of Yokota, Japan mostly sampled postfrontal Asian air. Southern portions of middle and upper tropospheric flight segments from Hong Kong sampled air previously in the deep tropics, while the more northerly flight segments sampled air that originated from the west (e.g., passing over central Africa and India). Most upper level flight segments from Yokota sampled air arriving from the west. Patterns of satellite-derived precipitation and lightning are described. TRACE-P occurs during a neutral to weak La Nina period of relatively cold sea surface temperatures in the tropical Pacific. Compared with climatology, the TRACE-P period exhibits deep convection located west of its typical position; however, tropospheric flow patterns do not exhibit a strong La Nina signal. Circulation patterns during TRACE-P are found to be generally similar to those during NASA's PEM WEST-B mission that occurred in the same region during February–March 1994.

[1] In this note, we investigate the impacts of the winter Arctic Oscillation (AO) and Siberian High (SH) on the East Asia winter monsoon (EAWM). It is found that the winter AO and the SH are relatively independent of each other in influencing the EAWM. The winter AO influences directly surface air temperature (SAT), sea level pressure (SLP) and the East Asian Trough at 500 hPa over the region northwards of 35°N in East Asia rather than through its impact on the SH. Compared with influences of the winter AO, the SH shows more direct and significant influences on the EAWM, particularly on SLP and northerly wind along the East Asian Coast. Impacts of the SH on the SAT occur primarily in the southwards of 50°N over East Asia, the northwestern Pacific and the South China Sea, because the AO suppresses the SH's influences in high latitudes of Asian Continent and the some subarctic regions.

The Alpert and Getenio (1988) modification of the Mass and Dempsey (1985) one-level sigma-surface model was used to study four synoptic events that included two winter cases (a Cyprus low and a Siberian high) and two summer cases. Results of statistical verification showed that the model is not only capable of diagnosing many details of surface mesoscale flow, but might also be useful for various applications which require operative short-range prediction of the diurnal changes of high-resolution surface flow over complex terrain, for example, in locating wildland fires, determining the dispersion of air pollutants, and predicting changes in wind energy or of surface wind for low-level air flights.

Romania's climatic and hydrographical characteristics are due to its position in east central Europe and to the Carpathian arc at its centre. The influence of baric centres, the subtropical Azores anticyclone and the Siberian anticyclone, is to be noticed in climatic parameters in all seasons. In its turn, the Carpathian arc brings about vertical variation and an obvious gradation in the distribution of temperature, precipitation drainage and other geographical features (soils, vegetation, fauna, etc.). On the background of these characteristics of general circulation and local relief, the climate and the hydrography show differently various aspects: humid in the west, south-Mediterranean in the south-west and continental in the south and east. The hydrographic net is affected by the Carpathian arc which causes all morphometric and hydrologic particularities, and is almost completely collected by the Danube. The synopsis of climatic and hydrogeographical regions reflects the conditions of the continental temperate zone in which Romania lies.

A space-time spectral analysis is applied to the Northern Hemisphere winter of an 11-layer GFDL general circulation model with seasonal variation. A statistical study is made of the stationary and transient ultra-long waves and transient long waves with respect to their wave characteristics, three-dimensional structure and energetics. The stratospheric stationary waves attain their maximum amplitude in geopotential at the latitudes of the stratospheric jet in agreement with observations and theories, although their amplitude is too large. The tropospheric stationary waves corresponding to the Siberian high and the Aleutian low are characterized by large eddy available potential energy which is mainly converted from zonal available potential energy. On the other hand, the tropospheric stationary wave corresponding to the local intensification of the subtropical jet is characterized by large eddy kinetic energy which is supplied by the energy flux from the region of large eddy energy conversion occ...

In this study spatial and temporal relationships involving Southern Hemisphere (SH) sea level pressure (SLP) were examined using a 25-year data set assembled for this purpose, with special emphasis on discovering inter-hemispheric teleconnections in the seasonal SLP field. Principal component and correlation analysis was employed. The most important findings include: 1 Season-to-season autocorrelation of SLP is at least as large in the SH as in the Northern Hemisphere (NH), though the amount of area of significant autocorrelation is not great in either hemisphere (i.e. a total global area of 17-24 per cent). 2 Principal component (PC) analysis performed on SH SLP in conjunction with Monte Carlo tests of significance showed that three or four PCs, explaining 40 to 58 per cent of the variance, represent the climatic signal in the data set. 3 Field significance tests applied to each teleconnection map, produced for each grid point in the SH, implied that there is a strong likelihood of real inter-hemispheric relationships in NH winter. There was much less certainty in the other seasons. Examination of significant teleconnection maps suggested SH links to the Southern Oscillation, the North Atlantic Oscillation, Siberian High strength, and the ‘West Pacific pattern’ described by Wallace and Gutzler (1981).

Twenty occasions in the period 1968–1972 when the Siberian anticyclone extended westwards over southeast Europe are considered in terms of mean surface, 500 mbar and 1000/500 mbar thickness charts. These means were compared with normal values based on the period 1950–1972 and statistically significant anomaly patterns over the northern hemisphere were drawn. The mean and anomaly patterns are used to show the development and subsequent break-up of the extension of the Siberian anticyclone over the Balkans.

The global distribution of the forcing of the time-mean flow due to large-scale, horizontal Reynolds stresses (u′ u′, v′ v′, u′ v′) is determined from upper wind statistics for the period 1968–73. The role of this forcing in the maintenance of the vorticity and enstrophy of the time-mean flow is discussed. The most striking effect of transient eddy stresses is the tendency to shift the subtropical maxima in the time-mean flow and the associated vorticity patterns poleward. However, significant longitudinal Variations in forcing occur, also. Calculations of the dominant terms in vorticity budgets of the North Pacific Low, the North Atlantic Low, and the Siberian High, which may he called the centers of action of winter-time circulation at sea level in the Northern Hemisphere, are presented. In all three cases, transient eddies are found to be important in maintaining the centers against the dissipative action of surface friction. In terms of the enstrophy budget, the hemispheric and global-mean ef...

A small group of Kirisitan (Christian) has miraculously survived in Japan despite the severe oppression in Tokugawa Period. While the majority of Japanese used a lunar calendar, only these Kirisitan fishers knew Gregorian Calendar introduced by Portugese missionaries. During the oppression time their christianity has transformed into a polytheistic religion. Even so they have kept and used their calendar until today for their services with a day's delay from the Gregorian Calendar.Through this solar calendar, they have experienced that on their Christmas Eve, 23 rd of December, heavy storms often began, followed by calm days on 26th and 27th. These storms are confirmed by Fig. 1 to be the winter monsoon from Siberia and the calm days to be the result of the weakening of the Siberian High (Fig. 2).A problem arises whether these Kirisitans have discovered this “Christmas Storm” by themselves or they have learnt it from Portugese missionaries four hundred years ago. For it is possible that the Portugese missionaries knew something about the Portugese weather on these days of which equivalent is known in Germany as Wheinachtstauwetter (Christmas Bad Weather).Such a oversea spread of weather knowledge seems to be possible through a case study on the west coat of South America, where fishers know Viento de San Juan (Wind of St. John) etc which are not supported by the local meteorogical observations. In this case a spread from Spain seems to be probable.On the other hand, some of Japanese fishers have used a lunar calendar even until today with several knowledges on lunar singularities such as “8 th's Storm” etc. Against my working hypothesis that such knowledges reflect local weather differences, the distributions of lunar weather knowledges are almost uniform throughout Japan except “Daishiko Storm” and “Daishiko Calm” on 23rd of XI Month (Fig. 3 and 4).This uniformity may indicate that a spreading played more important role in the aquirment of weather knowledges than discovery. Since some similarities in lunar weather knowledges are found in Korea and Taiwan a spread from the mainland of China is possible.By such considerations a spread of “Christmas Storm” from Portugal still remains a possible guess. Informations from Portugal are most welcomed.

The heat budget of the Siberian high is investigated by using a compositing method. Ninteen cases of strong Siberian highs that moved over China from the northwest were selected from datasets covering five winters (December through February of 1980–1984). The apparent heat source (Q1)and the apparent moisture sink (Q2) were estimated via budget calculations. The diabatic heating terms were also calculated via direct use of physical parameterization schemes. The vertical transports of sensible and latent heat from subgrid-scale of motions were estimated as residuals from the thermodynamic energy equation. Over the region of the region of the Siberian high, strong radiative cooling and large-scale descending motion (with large-scale mass convergence over the upper and middle tropospheric and divergence over the lower troposphere) contributes to a rapid buildup of the Siberian high. Heating in the upper troposphere due to subgrid-scale sensible heat transfer is also an important factor in the mainte...

Biological distributions and fish migrations during the spring and summer in the mid-latitude N Pacific are believed to be affected by the large-scale wind systems during the preceding winter. These wind systems are related to the field of atmospheric pressure which, on a monthly or quarterly time scale, show pronounced interannual variations. This exploratory investigation is concerned with measures of the large-scale wind systems that are indicative of their intensity, location, and size, and that can be derived from monthly or quarterly sea-level pressure distributions. Of interest are the NW, W, and SW wind systems which are related to the pressure gradients between the Siberian High and Aleutian Low, the Aleutian Low and the N Pacific Subtropical High, and the Aleutian Low and the N American High, respectively. Interannual changes in the winter sea-level pressure distribution pattern are primarily the result of changes in the pressure and zonal displacements of the Aleutian Low near 50°N. This property permitted simple derivation of wind indices from grid values of N hemisphere mean winter pressures distributions for the years 1947 to 1985. Indices, presented as normalized anomalies, are for the meridional component of the wind system at 50°N over the ocean W and E of the Aleutian Low, for the westerlies S of the Aleutian Low and for the longitude of this Low. The paper concludes with a discussion of the limitations of the indices in terms of reflecting characteristic atmospheric pressure distribution patterns, an examination of the relationship between wind anomalies and El Nino events, and a discussion of the results in terms of oceanographic, climate, and biological implications.

A more complete and new formulation of the orographic forcing and new thermal forcings are included in a steady state model of the Northern Hemisphere planetary waves. When both forcings are included, the simulation produces excellent results which are compared in detail with observations. In particular, the Siberian high, the tropospheric East Asian trough and subtropical tropospheric East Asian jet stream maxima are well reproduced even though the forcing is primarily extratropical in origin. The modes uses a lower boundary condition in which the orographic forcing is determined by the effects of the total flow, not just the zonal mean basic state. Consequently, the net orographic forcing changes when thermal forcing is added and the tow solution is not equal to the linear sum of the solutions with orographic and thermal forcings separately. The thermally induced orographic forcing is found to be very significant and, in the troposphere, there is strong interaction between the two forcings with...

Spatial patterns of circulation variability over the Northern Hemisphere and their changes during the past 70 yr (1899–1969) are examined using eigenvector analyses of mean January and July sea-level pressure maps. The first several eigenvectors display variability associated with the major centers of action (the subpolar oceanic Lows, the subtropical oceanic Highs, the winter Siberian High, and the summer Asiatic Low). The pattern of the first eigenvector of January suggests that the intensity and latitudinal position of the major circulation features over the North Atlantic are associated with the intensity and position of the Aleutian Low over the North Pacific. The time series of the coefficients of the hemispheric eigenvectors are used to identify intervals of change in the hemispheric circulation associated with features on the scale of thc major centers of action. These time series provide a more general description of circulation change than that obtained from local or regional indices; b...

THE year 1954 will be remembered for a variety of unpleasant reasons. It produced the wettest autumn in Scotland since general records began in 1869. In England, the summer was probably the drabbest within memory, owing to the combination of wetness, coolness and lack of sunshine, though no new records were set up. 1954's combined summer and autumn rainfall was surpassed in England and Wales in 1872, but not since ; in Scotland only the 1872 and 1938 figures were higher. The late winter of 1953-54 w a s severe and followed what is believed to be the commonest pattern of severe winters, marked by a northwestward shift of the Siberian anticyclone towards Scandinavia after the turn of the year. February was the coldest month, as usual in such cases. This was a short winter, however, since December 1953 was exceptionally mild. Easterly winds set in on 22nd January, and from then until after mid-February all parts of Britain partook to some extent in the exceptionally severe weather affecting the rest of Europe. — 2O°G (—4°F) was reported at Welshpool. Roads were blocked and villages isolated by snowdrifts, notably in Kent. Rivers, canals and lakes froze. During February the Atlantic depressions came east in 5O-55°N and crossed England, causing increasingly changeable weather, excessive rainfall, more snow in many districts and a deficit of sunshine over all. The month was particularly foggy in the English midlands and east. The greatest monthly temperature anomaly for February in Britain was — 2-7°G at Eskdalemuir, but the deviations exceeded —5°C over the European plain east of io°E and in central Sweden. It was a noteworthy feature of 1954 that all five ' natural seasons ' (Lamb 1950) were marked by long spells of set weather type

Regeneration of shallow secondaries, stationary near Cyprus for some time, is brought about by the approach of a stream of polar air from eastern Europe, or Asia Minor. The process is quite marked and common, and represents the main mechanism underlying the development of deep depressions in the eastern Mediterranean in winter. Successive cold fronts become traceable on the charts, and shallow thundery depressions, which travel with the general circulation round the main barometric minimum, sometimes develop in the polar air over Egypt; but the system of isobars and fronts is not Norwegian, and while the low can be regarded as orographic in origin, the associated weather is generally analogous to squall phenomena rather than to the development of a depression, and can be treated on the lines suggested by Margules. These regenerated lows are usually accompanied by the occurence of a strong south-east current over Iraq. This phenomenon has, however, been regarded as a topographical effect; the current being mainly induced to flow parallel to the general run of the plateau of Iran under the effect of convergence into the Cyprus Iows. The present work also endeavours to show that the known seasonal features of the Mediterranean, which are associated directly with the southward extension from summer to winter of the zone of barometric depressions and accompanying westerly winds over the Atlantic and Europe, and with the formation in summer of the great continental low of Asia, are also influenced, at least in the eastern areas, by the Sudan low in the transitional seasons, and by the Siberian anticyclone in winter.

Through the rhythmic change of the decade means of Dec., Jan. and Feb. air temperature in the middle and south-western part of Japan, a rising trend of winter air temperature with longer period is observed as shown in Fig. 1, in which it will be seen that the eight points of the decadal means of air temperatures change inversely with these of the pressure difference, Irkutsk (52°16'N, 104°19'E) - Nemuro 43°20'N, 145°35'E), which was taken as an index of the Far East monsoons strength, and, notwithstanding the inverse parallelism of the decade means, the secular rising trend of Japanese winter temperature is running parallel with that of the Far East monsoon strength.The same relation can be seen in the case of rainfalls. In Fig. 2, 10-year running mean curve of January precipitations on the Japan Sea side indicates the same increasing trend with that of the Pacific side, though the 10-year running mean in itself change in parallel with opposite signs.These facts lead us to the conclusion that the secular trend of the winter climate in Japan through centuries must be due to some longer period change in the general circulation other than the change in the Far East monsoons.A comparison of the two mean December, January and February pressure charts averaged for the periods 1899/1900-1928/29 (n=30) and of 1929/30-1959/60 (n=27) is shown in Fig. 3. The pressure of the Siberian High increased from the first half period to the second period, while the Pacific Low decreased, and the position of the center of the Siberian High has shifted significantly to the northwest (about 3.5° northwards and 5.0° westwards) and that of the Pacific Low appears to have moved to the northwest too.It is my opinion that the secular trends observed in the winter climate of Japan must be a reflection of the northwest-wards shift of the climatic zone which was seen in Fig. 3.The summer climate of Japan in the past 80 years can be broadly divided into three epochs, basing on the facts which is seen in Fig. 4 and Table 3 (A) and (B).(i) 1891-1910 (20 years) cool-rainy epoch(ii) 1911-1950 (40 years) hot-dry epoch(iii) 1951-1970 (20 years) cool-rainy epochBy using all the northern hemisphere monthly mean chart on hand, the secular change of July pressure in the central part of the North Pacific High is investigated in Fig. 5, in which the area enclosed by 1026 mb isobar averaged for (ii) period is remarkably large compared with those before and after the period, and the center of the North Pacific High is situated moving to the northwest in comparison with those before and after the period. The patterns of the July pressure distribution in the neighborhood of the Japan Island are also investigated respectively for (i), (ii) and (iii) period. In Fig. 6, it will be seen that the North Pacific High bulges out strongly towards the south-western part of Japan in the period of (ii).The geographical distributions of correlation coefficient of July air temperature with July monsoon strength, taking the pressure difference between Choshi (35°43'N, 140°51'E) and Asahikawa (43°46'N, 142°22'E) as an index of the monsoon intensity in the neighborhood of Japan, are shown for each period in Table 1, in which the region of maximum correlation coefficient goes northwards, or southwards, corresponding to the north-south oscillation of the center of the North Pacific High.The July pressure difference between Bo-so Peninsula in Japan and the northeastern part of Korea or the Maritime Province in Siberia is taken as an index of the intensity of bulging of the North Pacific High and the correlation coefficient of the index with amount of July precipitation are computed at various places or district in the Far East.

Historical data from oceanographic expeditions and remotely sensed data on outgoing longwave radiation, temperature, wind speed and ocean color in the western Arabian Sea (1950–2010) were used to investigate decadal trends in the physical and biochemical properties of the upper 300 m. 72 % of the 29,043 vertical profiles retrieved originated from USA and UK expeditions. Increasing outgoing longwave radiation, surface air temperatures and sea surface temperature were identified on decadal timescales. These were well correlated with decreasing wind speeds associated with a reduced Siberian High atmospheric anomaly. Shoaling of the oxycline and nitracline was observed as well as acidification of the upper 300 m. These physical and chemical changes were accompanied by declining chlorophyll-a concentrations, vertical macrofaunal habitat compression, declining sardine landings and an increase of fish kill incidents along the Omani coast.

The intensity of the winter Siberian High has significantly negative correlations with Arctic sea ice concentration anomalies from the previous autumn to winter seasons in the Eastern Arctic Ocean and Siberian marginal seas. Our results indicate that autumn-winter Arctic sea ice concentration and concurrent sea surface temperature anomalies are responsible for the winter Siberian High and surface air temperature anomalies over the mid-high latitudes of Eurasia and East Asia. Numerical experiments also support this conclusion, and consistently show that the low sea ice concentration causes negative surface air temperature anomalies over the mid-high latitudes of Eurasia. A mechanism is proposed to explain the association between autumn-winter sea ice concentration and winter Siberian High. Our results also show that September sea ice concentration provides a potential precursor for winter Siberian High that cannot be predicted using only tropical sea surface temperatures. In the last two decades (1990–2009), a strengthening trend of winter Siberian High along with a decline trend in surface air temperature in the mid-high latitudes of the Asian Continent have favored the recent frequent cold winters over East Asia. The reason for these short-term trends in winter Siberian High and surface air temperature are discussed.

The Arctic Oscillation (AO), which depicts a most dominant large-scale seesaw between the mid-latitudes and Arctic atmospheric mass, influences climate over Eurasia, North America, eastern Canada, North Africa, and the Middle East, especially during boreal winter. This review, with a special focus on the East Asian region, summarizes the climatic impact of AO. It begins with a description of the spatial structure of AO and the related climatic anomalies. The relationship of winter AO with the simultaneous East Asian winter climate (e.g. the East Asian winter monsoon (EAWM), cold surges/cold waves, and precipitation) and its instability are then followed. It is generally accepted that, through impacting the Siberian high, westerly wind, blocking frequency, Rossby wave activities etc., a positive phase of winter AO is associated with a weaker-than-normal EAWM, warmer conditions in East Asia, less frequency of cold surges/cold waves, increasing (decreasing) of winter precipitation in south (north) parts of East Asia; and vice versa. Notably, the pathways that the winter AO exerts impact are different. Besides, the AO-EAWM and the AO-cold surges/cold wave linkages have spatial and temporal variations. Subsequently, an overview of the inter-seasonal linkages between the East Asian summer monsoon with the preceding spring/winter AO is presented. There is a generally accepted knowledge that a positive spring AO is followed by significant positive summer precipitation anomalies in southern China and western Pacific as well as negative ones in the lower valley of Yangtze River and southern Japan. Finally, this review synthesizes the impact of winter/spring AO on the East Asian spring climate (e.g. dust storm, temperature, and precipitation) and discusses the potential predictive value of AO. The projection of AO and its impact on the East Asian climate in future has been barely explored. We conclude that, along with the long-term observation data, the linkage between AO and the East Asian climate on the sub-seasonal and decadal time scales, how tropical and extratropical forcing modulates the linkage and how the linkage evolves under future warming conditions should be more investigated. Notably, the change of AO during 1990–2013 winters could explain the Eurasian cooling but failed to explain the Arctic warming. In the future, the effect of Ural blocking on Arctic and Eurasian climate and their connection might be a hot topic.

The average strength of the Siberian Anticyclone is defined. Daily values of average strength of this anticyclone have been computed for each day for the period of 1st November 1967 to 30th April 1968 from the daily 12 GMT, NHAC (New Delhi) charts. A power spectra of this data has been computed. A significant 5 day periodicity is observed. A possible connection of this anticyclone and western disturbances is discussed. DOI: 10.1111/j.2153-3490.1972.tb01565.x

Understanding the past dynamics of large-scale atmospheric systems is crucial for our knowledge of the palaeoclimate conditions in Europe. Southeastern Europe currently lies at the border between Atlantic, Mediterranean, and continental climate zones. Past changes in the relative influence of associated atmospheric systems must have been recorded in the region’s palaeoarchives. By comparing high-resolution grain-size, environmental magnetic and geochemical data from two loess-palaeosol sequences in the Lower Danube Basin with other Eurasian palaeorecords, we reconstructed past climatic patterns over Southeastern Europe and the related interaction of the prevailing large-scale circulation modes over Europe, especially during late Marine Isotope Stage 3 (40,000–27,000 years ago). We demonstrate that during this time interval, the intensification of the Siberian High had a crucial influence on European climate causing the more continental conditions over major parts of Europe, and a southwards shift of the Westerlies. Such a climatic and environmental change, combined with the Campanian Ignimbrite/Y-5 volcanic eruption, may have driven the Anatomically Modern Human dispersal towards Central and Western Europe, pointing to a corridor over the Eastern European Plain as an important pathway in their dispersal.

Asian mineral dust has been studied extensively for its role in affecting regional-to global-scale climate and for its deposits, which enable reconstructing Asian atmospheric circulation in the past. However, the timing and origin of the dust deposits remain debated. Numerous loess records have been reported across the Asian continent with ages varying from the Miocene to the Eocene and linked to various mechanisms including global cooling, Tibetan Plateau uplift and retreat of the inland proto-Paratethys Sea. Here, we study the Eocene terrestrial mudrocks of the Xining Basin in central China and use nonparametric end-member analysis of grain-size distributions to identify a loess-like dust component appearing in the record at 40 Ma. This is coeval with the onset of high-latitude orbital cycles and a shift to predominant steppe-desert vegetation as recognized by previous studies in the same record. Furthermore, we derive wind directions from eolian dune deposits which suggest northwesterly winds, similar to the modern-day winter monsoon which is driven by a high pressure system developing over Siberia. We propose that the observed shifts at 40 Ma reflect the onset of the Siberian High interacting with westerly derived moisture at obliquity timescales and promoting dust storms and aridification in central China. The timing suggests that the onset may have been triggered by increased continentality due to the retreating proto-Paratethys Sea.