Height Anomalies (height + anomaly)

Distribution by Scientific Domains


Selected Abstracts


Latitudinal height couplings between single tropopause and 500 and 100 hPa within the Southern Hemisphere

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2010
Adrián E. Yuchechen
Abstract In order to provide further insights into the relationships between the tropopause and different mandatory levels, this paper discusses the coupling between standardized tropopause height anomalies (STHAs) and standardized 500-hPa and 100-hPa height anomalies (S5HAs and S1HAs, respectively) within the ,climatic year' for three sets of upper-air stations located approximately along 20°S, 30°S and 45°S. Data used in this research consists in a radiosonde database spanning the period 1973,2007. The mandatory levels are supposed to be included in each radiosonde profile. The tropopause, on the other hand, is calculated from the significant levels available for each sounding using the lapse rate definition. After applying a selection procedure, a basic statistical analysis combined with Fourier analysis is carried out in order to build up the standardized variables. Empirical orthogonal functions (EOFs) in S-mode are used to get the normal modes of oscillation as well as their time evolution, for STHA/S5HA as well as for STHA/S1HA coupling, separately, within the aforementioned latitudes. Overall, there are definite cycles in the time evolution associated with each EOF structure at all three latitudes, the semi-annual wave playing the most important role in most of the cases. Nevertheless, 20°S seems to be the only latitude driven by diabatic heating cycles in the middle atmosphere. Certainly, EOF1 at this latitude has a semi-annual behaviour and seems to be strongly influenced by the tropical convection seasonality. Apparently, the convectively driven release of latent heat in the middle troposphere affects the time evolution of the EOF1 structure. By contrast, the vertical propagation of planetary waves is raised as a possible explanation for the EOF1 and EOF2 behaviour at latitudes beyond 20°S, in view of the close connection existent between the semi-annual oscillation (SAO) and the reversion in the direction of the zonal wind. Copyright © 2009 Royal Meteorological Society [source]


Relationship between atmospheric circulation types over Greece and western,central Europe during the period 1958,97

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 14 2004
Christina Anagnostopoulou
Abstract An attempt is made to examine the relationship of the surface circulation prevailing over Europe with the corresponding surface and 500 hPa over Greece by correlating Lamb weather types for western Europe and Hess and Brezowsky (HB) types for central Europe with those derived from a new classification scheme for the Greek area. It was found that it was difficult to formulate rules controlling the frequency distributions of the circulation types over the Greek area in relation to the circulation over western and central Europe. However, statistically significant correlation was found between certain types with high frequency, which is greater between Lamb and HB types with the surface circulation types over the Greek area, compared with 500 hPa circulation types. For the most correlated pairs, seasonal composites of mean sea-level pressure and 500 hPa geopotential height anomalies demonstrated that the formation of the circulation types over the Greek area depends on the extent, intensity of the anticyclonic or cyclonic centres, air mass characteristics, and stability profile in the lower troposphere over the regions examined, but especially over the central and eastern Mediterranean. Copyright © 2004 Royal Meteorological Society [source]


The El Niño,southern oscillation and Antarctica

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2004
John Turner
Abstract This paper reviews our understanding of how the effects of the El Niño,southern oscillation (ENSO) might be transmitted from the tropical Pacific Ocean to the Antarctic, and examines the evidence for such signals in the Antarctic meteorological, sea ice, ice core and biological records. Many scientific disciples concerned with the Antarctic require an understanding of how the climatic conditions in the tropical and mid-latitude regions affect the Antarctic, and it is hoped that this review will aid their work. The most pronounced signals of ENSO are found over the southeast Pacific as a result of a climatological Rossby wave train that gives positive (negative) height anomalies over the Amundsen,Bellingshausen Sea during El Niño (La Niña) events. However, the extra-tropical signature can sometimes show a high degree of variability between events in this area. In West Antarctica, links between ENSO and precipitation have shown variability on the decadal time scale. Across the continent itself, it is even more difficult to relate meteorological conditions to ENSO, yet analyses of the long meteorological records from the stations do indicate a distinct switch in sign of the pressure anomalies from positive to negative across the minimum in the southern oscillation index. The oceanic signals of ENSO around the Antarctic are less clear, but it has been suggested that the Antarctic circumpolar wave could be forced by the phenomenon. Ice-core data offer the potential to help in understanding the long-term relationship between ENSO and the climate of the Antarctic, but there are difficulties because of the need to smooth the ice-core data to overcome the mixing of snow on the surface. Nevertheless, analysis of methylsulphonic acid in a South Pole core has shown high variability on ENSO time scales. It is clear that some evidence of ENSO can be found in the Antarctic meteorological and ice-core records; however, many of the relationships tend not to be stable with time, and we currently have a poor understanding of the transfer functions by which such signals arrive at the Antarctic from the tropical Pacific. Copyright © 2004 Royal Meteorological Society [source]


Variability of the Northern Hemisphere polar stratospheric cloud potential: the role of North Pacific disturbances

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 641 2009
Yvan J. Orsolini
Abstract The potential of the Arctic stratosphere to sustain the formation of Polar Stratospheric Clouds (PSCs) is a key factor in determining the amount of ozone destroyed each winter, and is often measured as a ,PSC volume'. The latter quantity has been shown to closely follow a near-linear compact relationship with winter-averaged column ozone loss, and displays a high variability from monthly to decadal time-scales. We examine the connection between meteorological conditions in the troposphere and the variability of lower polar stratospheric temperatures over the last four decades, and specifically, conditions leading to a high PSC volume. In addition to the well-established connection between the North Atlantic Oscillation (NAO) and the polar vortex, we demonstrate the large influence of precursory disturbances over the North Pacific and the Far East, the region of maximum climatological upward wave activity flux. Namely, very high monthly PSC volume (in the top 12%) predominantly follows the development of positive tropospheric height anomalies over the Far East, which lead to a weakening of the background planetary wave trough, and lessened upward wave activity flux into the stratosphere. Precursory anomalies over the Far East are reminiscent of East Asian monsoon amplification episodes. Copyright © 2009 Royal Meteorological Society [source]