Ozone and Tracer Transport Variations in the Summer Northern Hemisphere Stratosphere

Constituent observations from the Upper Atmosphere Research Satellite (UARS) in combination with estimates of the residual circulation are used to examine the transport and chemical budgets of HF, CH4 and O3 in the summer Northern Hemisphere. Budget calculations of HF, CH4 and O3 show that the transport tendency due to the residual circulation increases in magnitude and is largely opposed by eddy motions through the summer months. Ozone budget analyses show that between 100 and 31 hPa, the magnitudes of the mean circulation and eddy transport terms increase through the summer months, producing tendencies that are factors of 2 to 3 times larger than the observed ozone change in the stratosphere. Chemical loss dominates the observed ozone decrease only at the highest latitudes, poleward of about 70°N. A comparison of observations from the Total Ozone Mapping Spectrometer with UARS-calculated total ozone suggests that poleward of 50°N, between 35% and 55% of the seasonal ozone decline during the summer occurs at altitudes below 100 hPa. The overall uncertainties, associated primarily with calculations of the residual circulation and eddy transport, are relatively large, and thus prevent accurate and useful constraints on the ozone chemical rate in the lower stratosphere

Quasifree Pion Electroproduction from Nuclei in the Δ\Delta Region

We present calculations of the reaction $A(e,e^\prime \pi N)B$ in the distorted wave impulse approximation. The reaction allows for the study of the production process in the nuclear medium without being obscured by the details of nuclear transition densities. First, a pion electroproduction operator suitable for nuclear calculations is obtained by extending the Blomqvist-Laget photoproduction operator to the virtual photon case. The operator is gauge invariant, unitary, reference frame independent, and describes the existing data reasonably well. Then it is applied in nuclei to predict nuclear cross sections under a variety of kinematic arrangements. Issues such as the effects of gauge-fixing, the interference of the $\Delta$ resonance with the background, sensitivities to the quadrupole component of the $\Delta$ excitation and to the electromagnetic form factors, the role of final-state interactions, are studied in detail. Methods on how to experimentally separate the various pieces in the coincidence cross section are suggested. Finally, the model is compared to a recent SLAC experiment.Comment: 27 pages in REVTEX, plus 22 PS figures embedded using psfig.sty (included), uuencode

The role of Lithuania in Russian Civil War in 1919 – 1920

Pirmojo pasaulinio karo metais Lietuva buvo okupuota Vokietijos, todėl abi Rusijos revoliucijos 1917 m. – Vasario ir Spalio, Lietuvos tiesiogiai nepalietė. Vokietijai kapituliavus 1918 m. lapkričio 11 d., Lietuva pradėjo valstybės kūrimo ir nepriklausomybės įtvirtinimo darbus. Nepaisant to, kad Lietuvos premjeras A. Voldemaras tikėjosi, jog Lietuvos nepuls, tačiau gana greitai jam pačiam teko įsitikinti, jog į Lietuvą pretenduoja Rusijos raudonieji ir baltieji, lenkai ir tie patys vokiečiai. Po Spalio revoliucijos Rusijoje įsitvirtino bolševikų režimas, kuris per 1918 m. sutvirtėjo ir dėstė planus įgyvendinti pasaulinę revoliuciją. Bolševikams Lietuva buvo labai geroje strateginėje vietoje. Jie į Lietuvą žiūrėjo ne kaip į buvusios Rusijos imperijos dalį, o kaip į būsimą placdarmą pasaulinei revoliucijai nešti į Lenkiją ir Vokietiją, tuo labiau, kad su pastarąja turėjo bendrą sieną. Tuo tikslu Sovietų Rusijos RA 1919 m. pradžioje įsiveržė į Lietuvą, tačiau buvo sustabdyta lietuvių ir vokiečių savanorių. Nepaisant to buvo suformuota Lietuvos ir Baltarusijos SSR, geriau žinoma Litbelo pavadinimu. Šis hibridas turėjo tapti pasaulinės revoliucijos placdarmu, tačiau 1919 m. vasario mėn. puolimą iš vakarų pradėjo Lenkijos kariuomenė, o iš rytų puolė A. Kolčiako baltieji rusai. Siekdami išsilaikyti valdžioje, bolševikai laikinai atsisakė įgyvendinti pasaulinės revoliucijos planą. Tuo tarpu baltieji rusai žiūrėjo į Lietuvą, kaip į buvusios Rusijos imperijos dalį. Nepaisant to, kad 1919 m. pavasarį Paryžiuje rusų politikai žadėjo Lietuvai nepriklausomybę, tačiau realybėje tai tebuvo taktinis žingsnis siekiant suardyti potencialią buvusios Rusijos imperijos pakraščių tautų vienybę, siekiant atsilaikyti nuo baltųjų rusų spaudimo. Baltieji rusai laikėsi „vieningos ir nedalomos“ Rusijos principo, kurį pabandė įgyvendinti P. Bermontas 1919 m. spalio – lapkričio mėnesiais, pradėjęs karinius veiksmus prieš Latviją ir Lietuvą. Pabaltijo valstybės sugebėjo atremti šį Rusijos imperijos restauracijos bandymą ir sustiprinti savo nepriklausomybę. 1920 m. pradžioje beveik visi baltųjų rusų judėjimai buvo sumušti RA, todėl ir Antantės požiūris į Baltijos valstybes gerėjo. Dėl susidariusių palankių aplinkybių, Lietuva įgijo galimybę sudaryti taikos sutartį su Sovietų Rusija, kuri jau ėmė pripažinti ir „buržuazines“ vyriausybes. Po ilgų ir sunkių derybų 1920 m. liepos 12 d. Lietuva ir Sovietų Rusija pasirašė taikos sutartį, pagal kurią Lietuvai atiteko plačios teritorijos rytuose, įskaitant ir Vilnių. Sovietų Rusija bandė įtraukti Lietuvą, siūlydami pasirašyti karinę sutartį ir tokiu būdu įtraukti į karą su Lenkija. Lietuva sugebėjo atsilaikyti nuo visų bolševikų siūlymu ir tokios sutarties nepasirašė. Lenkijos pergalė kare prieš sovietus, apsaugojo Lietuvą nuo komunistinio perversmo, kuriam aktyviai ruošėsi bolševikai 1920 m. rugpjūčio mėn., tačiau dėl nesėkmių fronte buvo atšauktas paties Lenino įsakymu.During World War I, Lithuania was occupied by Germany. It was the reason why Lithuania did not feel direct influence of both Russian revolutions of 1917, neither the February, neither the October. On 11 November 1918 Germany surrendered to Antanta in WWI and from that moment state building and independence strengthening jobs were started in Lithuania. Lithuanian primier A. Voldemaras expected that nobody will attack Lithuania, but reality showed that many countries – Russian red and whites, poles and germans – claimed parts or all territory of Lithuania. After the October revolution, Bolsheviks established their government in Russia. In 1918 their power increased and they openly stated the importance of worldwide revolution. For Bolsheviks, Lithuania was in very good strategical position. They looked at Lithuania not as to part of former Russian Empire, but as to bridgehead of worldwide revolution. For that reason, Red Army entered Lithuania in early 1919, but it was stopped by Lithuanian and German volunteers. Bolsheviks formed Lithuanian-Bellorussian soviet state, better known as Litbel. That country was suppoused to become bridgehead for worldwide revolution, but in February 1919 Poles and A. Kolchack’s White Russians started attack on Bolsheviks and they had to cancel their revolution plans. White Russians looked at Lithuania as to part of former Russian Empire. In spring 1919, White Russians declared in Paris, that Lithuania might become independent. It was a trick to demolish possible united front of peripheral nations, which declared independence. White Russians officially declared “United and undivided Russian state” principle. In October and November 1919, White Russian colonel P. Bermont tried to realize that principle in Baltic states by attacking them. His army was defeated by Latvian and Lithuanian troops. After liquidation of Whites’ movement in Baltic region, Baltic states strengthened their independence. In the beginning of 1920, nearly all White Russians’ movements were defeated by Red Army. It was the reason why Antanta’s standpoint changed possitivelly towards Baltic states. Lithuania received a real chance to sign peace treaty with Soviet Russia. After long and hard negotiations, both countries signed peace treaty in Moscow on 12 July 1920. Lithuanian borders went very far eastwards, including the capital city Vilnius. Soviets wanted to inveigle Lithuania into war with Poland by signing secret military treaty. Lithuania refused to sign such treaty for many times. In August 1920 Bolsheviks prepared coup de etat in Lithuania, but Poland’s victorious counterattack forced to cancel the plan by Lenin’s order.Humanitarinių mokslų fakultetasVytauto Didžiojo universiteta

Raudonosios armijos Vilniaus ir Kauno gubernijų karinių komisariatų veikla okupuotose Lietuvos teritorijose 1919 m

Humanitarinių mokslų fakultetasVytauto Didžiojo universiteta

The Remarkable 2003-2004 Winter and Other Recent Warm Winters in the Arctic Stratosphere Since the Late 1990s

The 2003-2004 Arctic winter was remarkable in the 40-year record of meteorological analyses. A major warming beginning in early January 2004 led to nearly two months of vortex disruption with high-latitude easterlies in the middle to lower stratosphere. The upper stratospheric vortex broke up in late December, but began to recover by early January, and in February and March was the strongest since regular observations began in 1979. The lower stratospheric vortex broke up in late January. Comparison with two previous years, 1984-1985 and 1986-1987, with prolonged mid-winter warming periods shows unique characteristics of the 2003-2004 warming period: The length of the vortex disruption, the strong and rapid recovery in the upper stratosphere, and the slow progression of the warming from upper to lower stratosphere. January 2004 zonal mean winds in the middle and lower stratosphere were over two standard deviations below average. Examination of past variability shows that the recent frequency of major stratospheric warmings (seven in the past six years) is unprecedented. Lower stratospheric temperatures were unusually high during six of the past seven years, with five having much lower than usual potential for PSC formation and ozone loss (nearly none in 1998-1999, 2001-2002 and 2003-2004, and very little in 1997-1998 and 2000-2001). Middle and upper stratospheric temperatures, however, were unusually low during and after February. The pattern of five of the last seven years with very low PSC potential would be expected to occur randomly once every approximately 850 years. This cluster of warm winters, immediately following a period of unusually cold winters, may have important implications for possible changes in interannual variability and for determination and attribution of trends in stratospheric temperatures and ozone

The extraordinarily strong and cold polar vortex in the early northern winter 2015/16

The Arctic polar vortex in the early winter 2015/16 was the strongest and coldest o f the la st 68 years. Using global reanalysis data, satellite observations, and mesospheric radar wind measurements over northern Scandinavia we investigate the characteristics of the early sta g e polar vortex and relate them to previous winters. We found a correlation between the planetary wave (PW) activity and the strength and temperature of the northern polar vor- tex in the stratosphere and mesosphere. In Nov/D ec 2015, a reduced PW generation in the troposphere and a stronger PW filtering in the troposphere and stratosphere, caused by stronger zonal winds in mid-latitudes, resulted in a stronger polar vortex. Thi s effect was strengthened by the equator ward shift of PWs due to the strong zonal wind in polar latitudes resulting in a southward shift of the Eliassen-Palm flux divergence and hence inducinga decreased deceleration of th e polar vortex by PWs

Simulations of Dynamics and Transport during the September 2002 Antarctic Major Warming

A mechanistic model simulation initialized on 14 September 2002, forced by 100-hPa geopotential heights from Met Office analyses, reproduced the dynamical features of the 2002 Antarctic major warming. The vortex split on approx.25 September; recovery after the warming, westward and equatorward tilting vortices, and strong baroclinic zones in temperature associated with a dipole pattern of upward and downward vertical velocities were all captured in the simulation. Model results and analyses show a pattern of strong upward wave propagation throughout the warming, with zonal wind deceleration throughout the stratosphere at high latitudes before the vortex split, continuing in the middle and upper stratosphere and spreading to lower latitudes after the split. Three-dimensional Eliassen-Palm fluxes show the largest upward and poleward wave propagation in the 0(deg)-90(deg)E sector prior to the vortex split (coincident with the location of strongest cyclogenesis at the model's lower boundary), with an additional region of strong upward propagation developing near 180(deg)-270(deg)E. These characteristics are similar to those of Arctic wave-2 major warmings, except that during this warming, the vortex did not split below approx.600 K. The effects of poleward transport and mixing dominate modeled trace gas evolution through most of the mid- to high-latitude stratosphere, with a core region in the lower-stratospheric vortex where enhanced descent dominates and the vortex remains isolated. Strongly tilted vortices led to low-latitude air overlying vortex air, resulting in highly unusual trace gas profiles. Simulations driven with several meteorological datasets reproduced the major warming, but in others, stronger latitudinal gradients at high latitudes at the model boundary resulted in simulations without a complete vortex split in the midstratosphere. Numerous tests indicate very high sensitivity to the boundary fields, especially the wave-2 amplitude. Major warmings occurred for initial fields with stronger winds and larger vortices, but not smaller vortices, consistent with the initiation of wind-deceleration by upward-propagating waves near the poleward edge of the region where wave 2 can propagate above the jet core. Thus, given the observed 100-hPa boundary forcing, stratospheric preconditioning is not needed to reproduce a major warming similar to that observed. The anomalously strong forcing in the lower stratosphere can be viewed as the primary direct cause of the major warming

Lower Stratospheric Temperature Differences Between Meteorological Analyses in two cold Arctic Winters and their Impact on Polar Processing Studies

A quantitative intercomparison of six meteorological analyses is presented for the cold 1999-2000 and 1995-1996 Arctic winters. The impacts of using different analyzed temperatures in calculations of polar stratospheric cloud (PSC) formation potential, and of different winds in idealized trajectory-based temperature histories, are substantial. The area with temperatures below a PSC formation threshold commonly varies by approximately 25% among the analyses, with differences of over 50% at some times/locations. Freie University at Berlin analyses are often colder than others at T is less than or approximately 205 K. Biases between analyses vary from year to year; in January 2000. U.K. Met Office analyses were coldest and National Centers for Environmental Prediction (NCEP) analyses warmest. while NCEP analyses were usually coldest in 1995-1996 and Met Office or NCEP[National Center for Atmospheric Research Reanalysis (REAN) warmest. European Centre for Medium Range Weather Forecasting (ECMWF) temperatures agreed better with other analyses in 1999-2000, after improvements in the assimilation model. than in 1995-1996. Case-studies of temperature histories show substantial differences using Met Office, NCEP, REAN and NASA Data Assimilation Office (DAO) analyses. In January 2000 (when a large cold region was centered in the polar vortex), qualitatively similar results were obtained for all analyses. However, in February 2000 (a much warmer period) and in January and February 1996 (comparably cold to January 2000 but with large cold regions near the polar vortex edge), distributions of "potential PSC lifetimes" and total time spent below a PSC formation threshold varied significantly among the analyses. Largest peaks in "PSC lifetime" distributions in January 2000 were at 4-6 and 11-14 days. while in the 1996 periods, they were at 1-3 days. Thus different meteorological conditions in comparably cold winters had a large impact on expectations for PSC formation and on the discrepancies between different meteorological analyses. Met Office. NCEP, REAN, ECMWF and DAO analyses are commonly used for trajectory calculations and in chemical transport models; the choice of which analysis to use can strongly influence the results of such studies

Diagnostic Comparison of Meteorological Analyses during the 2002 Antarctic Winter

Several meteorological datasets, including U.K. Met Office (MetO), European Centre for Medium-Range Weather Forecasts (ECMWF), National Centers for Environmental Prediction (NCEP), and NASA's Goddard Earth Observation System (GEOS-4) analyses, are being used in studies of the 2002 Southern Hemisphere (SH) stratospheric winter and Antarctic major warming. Diagnostics are compared to assess how these studies may be affected by the meteorological data used. While the overall structure and evolution of temperatures, winds, and wave diagnostics in the different analyses provide a consistent picture of the large-scale dynamics of the SH 2002 winter, several significant differences may affect detailed studies. The NCEP-NCAR reanalysis (REAN) and NCEP-Department of Energy (DOE) reanalysis-2 (REAN-2) datasets are not recommended for detailed studies, especially those related to polar processing, because of lower-stratospheric temperature biases that result in underestimates of polar processing potential, and because their winds and wave diagnostics show increasing differences from other analyses between similar to 30 and 10 hPa (their top level). Southern Hemisphere polar stratospheric temperatures in the ECMWF 40-Yr Re-analysis (ERA-40) show unrealistic vertical structure, so this long-term reanalysis is also unsuited for quantitative studies. The NCEP/Climate Prediction Center (CPC) objective analyses give an inferior representation of the upper-stratospheric vortex. Polar vortex transport barriers are similar in all analyses, but there is large variation in the amount, patterns, and timing of mixing, even among the operational assimilated datasets (ECMWF, MetO, and GEOS-4). The higher-resolution GEOS-4 and ECMWF assimilations provide significantly better representation of filamentation and small-scale structure than the other analyses, even when fields gridded at reduced resolution are studied. The choice of which analysis to use is most critical for detailed transport studies (including polar process modeling) and studies involving synoptic evolution in the upper stratosphere. The operational assimilated datasets are better suited for most applications than the NCEP/CPC objective analyses and the reanalysis datasets