St Petersburg University scientists study how planetary waves affect atmospheric dynamics
Physicists at St Petersburg University have studied planetary waves and discovered that they can generate disturbances in the stratosphere causing extreme warming and cooling in the Arctic and mid-latitudes. Numerical modelling of global atmospheric circulation was carried out by researchers at the Ozone Layer and the Upper Atmosphere Research Laboratory at St Petersburg University. The Laboratory was established within the framework of the mega-grant programme of the Ministry of Science and Higher Education of the Russian Federation.
Planetary waves are large-scale variations in the hydrodynamic parameters of the Earth’s atmosphere, namely: pressure; density; temperature; and wind. This phenomenon is similar to the Earth’s oceanic tides, where the ocean water level fluctuates over the course of a day, with differences of up to several metres. Similar ‘tides’ exist in the atmosphere, but they are not visible to human eyes and can occur not only within a period of one day, but within time periods of up to 30 days.
The research findings are published in the international scientific journal Atmospheric Chemistry and Physics (ACP).
Planetary waves are generated in the lower atmosphere and propagate to its uppermost layers. The amplitudes of planetary waves increase due to a decrease in the density of the atmosphere when they propagate from their sources in the troposphere. In the upper layers of the atmosphere, waves are the dominant form of motion, causing transfer of energy and momentum. Additionally, planetary waves are the main driving force of meridional circulation, which transports air masses between the equator and the poles. Due of its global nature, the meridional circulation is considered the most important mechanism affecting the transport of aerosol, atmospheric gases and, consequently, the composition of the atmosphere.
According to the physicists from St Petersburg University, changes in the meridional circulation can affect the behaviour of the ozone layer. The state of the ozone layer has attracted increased attention in the recent years due to global ozone depletion. Notably, the ozone layer acts as a ‘guard’ of life on Earth by shielding it from the Sun’s harmful ultraviolet radiation, consequently affecting the climate and biosphere in general.
The researchers from the Ozone Layer and the Upper Atmosphere Research Laboratory at St Petersburg University have developed an online course "Space Weather: Environmental Impact Assessment". The course will help you learn more about: the Sun and solar activity; the Earth’s atmosphere and the processes that occur in it; and about the impact of energetic particles and electromagnetic radiation on the processes in the Earth’s atmosphere and the ozone layer.
Earlier, researchers from the Ozone Layer and the Upper Atmosphere Research Laboratory at St Petersburg University revealed that powerful magnetic storms can destroy the ozone layer in the polar mesosphere, at an altitude of about 75 kilometres, by 25% per day.
The physicists from St Petersburg University have studied various planetary-wave impacts with periods in the range of 3 to 16 days on the general atmospheric circulation. Additionally, they studied the contribution of the 16-day planetary wave, which is regularly observed in the atmosphere, especially intensifying in winter in the northern hemisphere. Previously, such waves were studied using satellite and radar observations data. Yet, no one until now has estimated the contribution of the 16-day wave to changes in wind speed and temperature on the planet.
‘Such work requires a number of numerical experiments and modelling of atmospheric circulation. We conducted such experiments and showed that the impact of just one 16-day planetary wave in an average month can change the speed of the circulation flows (winds) by up to 5%. It may seem a very small percentage, but we are talking about a global, ongoing process that has a significant impact on climate conditions, including the Earth’s surface temperatures,’ stressed Andrey Koval, Associate Professor in the Department of Atmospheric Physics at St Petersburg University, Doctor of Physics and Mathematics.
St Petersburg University, the oldest university in Russia, was founded on 28 January (8 February) 1724. This is the day when Peter the Great issued a decree establishing the University and the Russian Academy of Sciences. Today, St Petersburg University is an internationally recognised centre for education, research and culture. In 2024, St Petersburg University will celebrate its 300th anniversary.
The plan of events during the celebration of the anniversary of the University was approved at the meeting of the Organising Committee for the celebration of St Petersburg University’s 300th anniversary. The meeting was chaired by Dmitry Chernyshenko, Prime Minister of the Russian Federation. Among the events are: the naming of a minor planet in honour of St Petersburg University; the issuance of bank cards with a special design; the creation of postage stamps dedicated to the history of the oldest university in Russia; and the branding of the aircraft of the Rossiya Airlines to name just a few. The University has launched a website dedicated to the upcoming holiday. The website contains information about outstanding University staff, students, and alumni; scientific achievements; and details of preparations for the anniversary.
Andrey Koval noted that a detailed research of planetary waves is very important because the research findings provide not only scientifically-based but also practically relevant insights about the mechanisms of large-scale atmospheric interactions. For example, the combined contribution of several planetary waves, under certain conditions, can generate such powerful wind and temperature disturbances in the stratosphere that their ‘echoes’ travel down to the Earth’s surface, leading to periods of extreme cooling or heating in the Arctic and mid-latitudes. Such events are also referred to as cold and heat waves. Basic research like this enables better prediction of such changes, thus significantly reducing the potential damage from the effects of such waves.