Large-scale Atmospheric Systems Research Articles

Spatiotemporal changes and background atmospheric factors associated with forest fires in Turkiye.

In this study, spatiotemporal analysis of forest fires in Turkiye was undertaken, with a specific focus on the large-scale atmospheric systems responsible for causing these fires. For this purpose, long-term variations in forest fires were classified based on the occurrence types (i.e. natural/lightning, negligence/inattention, arson, accident, unknown). The role of large-scale atmospheric circulations causing natural originated forest fires was investigated using NCEP/NCAR Reanalysis sea level pressure, and surface wind products for the selected episodes. According to the main results, Mediterranean (MeR), Aegean (AR), and Marmara (MR) regions of Turkiye are highly susceptible to forest fires. Statistically significant number of forest fires in the MeR and MR regions are associated with global warming trend of the Eastern Mediterranean Basin. In monthly distribution, forest fires frequently occur in the MeR part of Turkiye during September, August, and June months, respectively, and heat waves are responsible for forest fires in 2021. As a consequence of the extending summer Asiatic monsoon to the inner parts of Turkiye and the location of Azores surface high over Balkan Peninsula result in atmospheric blocking and associated calm weather conditions in the MeR (e.g. Mugla and Antalya provinces). When this blocking continues for a long time, southerly winds on the back slopes of the Taurus Mountains create a foehn effect, calm weather conditions and lack of moisture in the soil of Antalya and Mugla settlements trigger the formation of forest fires.

The effects of climate warming on large-scale atmospheric systems of the Northern Hemisphere

The effects of climate warming on large-scale atmospheric systems of the Northern Hemisphere

Analysis of extreme wind events in the Weddell Sea region (Antarctica) at Belgrano II Station

The objective of the present work is to analyze the wind pattern (direction and speed) at Belgrano II Station, evaluating the influence of large-scale atmospheric systems on extreme wind speed events. The study area is the Weddell Sea, located at the southern end of the Atlantic Ocean, between latitudes of 83° S and 55° S and longitudes of 84° W and 20° E. Daily meteorological data were used in the period from 1979 to 2015, whose variables are: Sea Level Pres-sure (SLP), Wind Speed (WS), Wind Direction (WD) and Air Temperature at 2 Meters (T2M), collected at Belgrano II Station, under the care of the Ar- gentine Antarctic Institute (AAI). To analyze the anomalies in the fields of air temperature, atmospheric circulation and surface pressure on a large scale, we used the reanalysis data obtained from the ERA-Interim database, which are: air temperature at 2 m (oC), geopotential height (m) at the 500 hPa level, and zonal and meridional components of wind (ms−1) on the surface. The ex-treme event was defined as values above the 95% percentile of each month of the year. The results indicate that the wind direction at Belgrano II Station was predominantly southeast. However, when the wind speed was predominant from the northeast, approximately 20% of the cases presented wind speeds above 16 ms−1. Therefore, when there is a change in synoptic conditions near the Belgrano II station, the predominance of the winds becomes northeasterly, with an intensification in its speed. An extra-tropical cyclone approaching the Belgrano II region caused the wind to become of the northeastern on the days before the extreme event, so that two days beforehand there was an increase in air temperature in surface. When we analyzed the wind speed in Belgrano II, we identified that there was not a marked change and over the years, however, we identified that the seasonality presented changes, with more intense winds between the months of May and September.

Regionalization of Seasonal Precipitation over the Tibetan Plateau and Associated Large-Scale Atmospheric Systems

AbstractPrecipitation over the Tibetan Plateau (TP) has major societal impacts in South and East Asia, but its spatiotemporal variations are not well understood, mainly because of the sparsely distributed in situ observation sites. With the help of the Global Precipitation Measurement satellite product IMERG and the ERA5 dataset, distinct precipitation seasonality features over the TP were objectively classified using a self-organizing map algorithm fed with 10-day averaged precipitation from 2000 to 2019. The classification reveals three main precipitation regimes with distinct seasonality of precipitation: the winter peak, centered at the western plateau; the early summer peak, found on the eastern plateau; and the late summer peak, mainly located on the southwestern plateau. On a year-to-year basis, the winter peak regime is relatively robust, whereas the early summer and late summer peak regimes tend to shift mainly between the central and northern TP but are robust in the eastern and southwestern TP. A composite analysis shows that the winter peak regime experiences larger amounts of precipitation in winter and early spring when the westerly jet is anomalously strong to the north of the TP. Precipitation variations in the late summer peak regime are associated with intensity changes in the South Asian high and Indian summer monsoon. The precipitation in the early summer peak regime is correlated with the Indian summer monsoon together with anticyclonic circulation over the western North Pacific. The results provide a basic understanding of precipitation seasonality variations over the TP and associated large-scale conditions.

Shift of large-scale atmospheric systems over Europe during late MIS 3 and implications for Modern Human dispersal

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.

Charles Henry Brian Priestley. 8 July 1915 — 18 May 1998

Charles Henry Brian Priestley was born and educated in England. After completing the Mathematical Tripos at the University of Cambridge, he joined the Meteorological Office in 1939. For the next seven years he was engaged mostly in wartime work, including a two-year spell in Canada (1941–43) and three years with the Meteorological Office upper-air unit at Dunstable, UK (1943–46). In 1946, aged 31 years, he took up an Australian appointment with the Council for Scientific and Industrial Research (later to become the Commonwealth Scientific and Industrial Research Organization (CSIRO)) to establish and develop a group to undertake research in meteorological physics. Thereafter he was based in Melbourne, Australia, with his career in the CSIRO extending to 1977. Priestley’s own early research focused on large-scale atmospheric systems, including substantial work on global-scale transport, and later on small-scale atmospheric convection and heat transfer, in which he established some significant results. He had a leading role in the development of the atmospheric sciences in Australia, and was strongly involved in international meteorology.

Charles Henry Brian Priestley 1915 - 1998

Charles Henry Brian Priestley (known as Bill) was born and educated in England. After completing the Mathematical Tripos at the University of Cambridge, he joined the Meteorological Office in 1939. In 1946, aged 31 years, he took up an Australian appointment with the Council for Scientific and Industrial Research (CSIR, later to become CSIRO) to establish and develop a group to undertake research in meteorological physics. Thereafter he was based in Melbourne, Australia. The group earned world recognition, particularly for its investigations of turbulent transfer in the lower atmosphere, and evolved to become the CSIRO Division of Atmospheric Research. Priestley's own early research focused on large-scale atmospheric systems, including substantial work on global-scale transport, and later on small-scale atmospheric convection and heat transfer, in which he established some significant results. He had a leading role in the development of the atmospheric sciences in Australia, and was strongly involved in international meteorology. His career with CSIRO extended to 1977, and he finally retired from all professional commitments in the mid-1980s. After several years of declining health, he died on 18 May 1998, seven weeks before he turned 83.

The occurrence of coreless winters in central Spitsbergen and their synoptic conditions

Ten warm-core winters were distinguished in the period 1975/76-2007/08, drawing on data from the Svalbard Airport weather station in central Spitsbergen and using the conditions t m-1 t m+1 ( t is the monthly mean temperature while m-1 , m and m+1 denote subsequent winter months) and the parameter of a coreless rate, c r (the ratio of the second, a ­­ 2 , to the first, a 1 , harmonic of the annual temperature wave). Composite maps of sea-level pressure and z 500-hPa means, as well as anomaly maps, were constructed separately for the mid-winter warm events and for the cold months before and after warming. Using the clustering method, different pressure patterns were recognized among the days of mid-winter warm spells. The occurrence of coreless winters in central Spitsbergen seems to be largely controlled by the position, extent and intensity of large-scale atmospheric systems, mainly the Icelandic Low. When the low spreads to the east and its centre is over the Barents Sea the inflow of air masses from the northern quadrant is observed over central Spitsbergen. This inflow of cold air of Arctic origin to the island takes place during the months preceding and following warm mid-winter events. Different circulation conditions appear when the Icelandic Low gets deeper than usual and shifts northwards, which coincides with warm spells. Sometimes a secondary cyclonic centre is located over Fram Strait and its warm sector encompasses Svalbard. Keywords: Spitsbergen; coreless winters; air temperature; circulation; polar climate (Published: 13 December 2011) Citation: Polar Research 2011, 30 , 12218, DOI: 10.3402/polar.v30i0.12218

The effect of the Eastern Mediterranean Transient on the hydrographic characteristics in the Strait of Sicily and in the Tyrrhenian Sea

Recent studies have definitively shown the high sensitivity of the Mediterranean Sea to the effects produced by the large-scale atmospheric systems. The rapid response of this basin, when compared with the ocean time scales, makes the interannual variability of the circulation an important signal that, in some regions, may prevail over the annual cycle. We have also to consider that the distinct sub-basins, often subjected to different atmospheric and dynamic regimes, produce specific water masses that can reach all the Mediterranean regions as far as the adjacent Atlantic Ocean by a connecting network provided by the internal straits and channel. In this scenario an important role is played by the Strait of Sicily dividing the two principal sub-basins, the eastern and the western Mediterranean. A long-term monitoring of the hydrographic properties of water masses across this strait, initiated in the second half of the 1980s, permitted the identification of the principal interannual variations in the water exchange between the Ionian Sea and the Tyrrhenian Sea. It was possible to follow the evolution of the water mass characteristics under the influence of the climatic transient, which modified the production of both the intermediate and the deep water in the eastern Mediterranean. A consequence was an increase of density in the Sicily westward outflow, which produced a cascade in the deep Tyrrhenian with a remarkable deep injection of heat and salt. Furthermore, moving from the impact on the Tyrrhenian Sea, the possible effects on the western Mediterranean basin are discussed.

A study on the convective structure of the atmosphere over the West Coast of India during ARMEX-I

Onset of south west monsoon (SWM) over Kerala is associated with intense convection followed by heavy rainfall over the west-coast of India. The intense rainfall events are usually associated with meso-scale convective systems embedded in large scale synoptic system over the Arabian Sea. Such deep and intense cumulus convection can have an important effect on the dynamics and energetics of large-scale atmospheric systems, because of the large magnitudes of the energy transformations associated with changes of phase of water in precipitating cumulus clouds as well as the strong updrafts and downdrafts in the troposphere.
 The prime objective of this study is to understand the convective structure (active/suppressed) of the atmosphere over the west-coast of India during ARMEX-I (Arabian Sea Monsoon Experiment). This study uses an approach to obtain the average structure of a cloud cluster and its interaction with the environment that enables in distinguishing the variation of kinematic and convective parameters from suppressed to convectively active process. Upper air observations obtained from four coastal land stations viz., Bombay, Goa, Mangalore and Trivandrum, alongwith that obtained over ORV Sagar Kanya are used to calculate both the convective and the kinematic parameters at the centre of the polygon formed by these observation locations. Time averaged circulation kinematic parameters and vertical velocity during active and suppressed convective phases off the west coast of India were discussed. The apparent heating and the apparent moisture sink are also estimated through residuals of the thermodynamic equations during intense and weak phases of SWM.

Northern hemispheric NDVI variations associated with large-scale climate indices in spring

Large-scale atmospheric systems, such as the Southern Oscillation, North Atlantic Oscillation, and so on, are important climatic change indicators over the northern hemisphere. These systems play essential roles in regional-to-continental scale climate fluctuation and vegetation activity in response to global change. Using the Pathfinder AVHRR NDVI (Advanced Very High Resolution Radiometer Normalized Difference Vegetation Index) data for the period 1982-2000, the authors investigated the relationship of the inter-annual variations of spring NDVI to nine large-scale climate indices. On average, 57.2% of the satellite-sensed NDVI variance was explained. These climate indices also accounted for a large portion of the trends in NDVI as observed in five regions, namely, north-west North America (climate-related trend was 18.2%/10 years), south-eastern North America (5.8%/10 years), Europe (6.9%/10 years), high-latitude Asia (12.4%/10 years), and East Asia (8.0%/10 years). The results are useful for understanding and predicting the regional-to-continental NDVI variations in response to global climate change.

Vorticity, Rossby number, and geostrophy in the atmosphere of Jupiter

Recent observations of spots moving around the Great Red Spot are used to calculate circulation, vorticity and a Rossby number at this scale of atmospheric motions. The results are quite comparable to values applying to large-scale atmospheric systems on Earth and indicate that geostrophy obtains on Jupiter.