Spring weather extremes. On how to understand atmospheric phenomena

ekstrema pogodowe

The beginning of April, wrapped in a halo of Saharan dust, gifted Poland with an aura worthy of full summer. Temperatures reached 30°C, the sun sent heat from the sky, and afternoons brought intense thunderstorms – weather extremes unusual for a calendar spring. The scenery was complemented by lilacs already in bloom, heralding not so much the arrival of May, but testifying to the acceleration of the vegetation cycle by a full month. Scientists’ alarming claims of a record warm year in 2023 and a series of record-breaking temperatures in the first months of this year herald an alarming change.

In contrast, Russia is struggling with flooding of unprecedented proportions, and the Alps are astounding with snowfall that is unprecedented for this time of year. We are faced with questions that are impossible to ignore: Is this a new norm to which we must adapt, or merely a temporary deviation from the rule? What are the causes of these unusual atmospheric phenomena? Is El Niño, which hasn’t been coming off the lips of meteorologists lately, responsible for everything, or is it already a direct effect of climate change?

Warmer, warmer, hotter – temperature weather anomalies or already an everyday occurrence?

A new report from the World Meteorological Organization(WMO) shows that in 2023. global records have once again been broken for greenhouse gas levels, air and ocean surface temperatures, glacier retreat and the reduction of the Antarctic ice sheet, and the resulting rise in sea level. According to the WMO report State of the Global Climate 2023 heat waves, floods, droughts, fires and rapidly intensifying tropical cyclones have contributed to a necessary change in the way of life of millions of people and are causing multi-billion dollar losses to the economies of many countries.

The report indicated that the global temperature at the earth’s surface in the previous year was 1.45 degrees Celsius above that of the pre-industrial era, considered the baseline. It was pointed out that we are one step away from crossing the 1.5°C barrier, which will bring catastrophic changes for the Earth. Unfortunately, climate change is much more than just temperature. It’s also the aforementioned intense hurricanes, heat waves that threaten ecosystems, loss of sea ice or frequent extreme weather events.

To make matters worse, according to Copernicus Climate Change Service, after an unusually warm January, February 2024. turned out to be the warmest ever measured. In addition, the average global ocean surface temperature has been rising for more than ten months and in February was the highest ever measured, breaking the record set in August 2023. The end of the previous year and the beginning of this year also brought record high global precipitation. However, their distribution on Earth was very uneven. In North America, Asia and Australia it has brought catastrophic floods and snowstorms, while Africa and South America are facing massive droughts and fires. Tropical cyclones of the highest categories were developing in the Indian Ocean. As we can see from the intense year of 2023, the beginning of the next one brings more extreme weather events around the world.

In Poland, February was also extremely warm. The anomaly of the average air temperature was 5.8°C, with new records being broken at numerous measuring stations. It was also the wettest February since the 1950s. In the 1970s. Rainfall totals were more than double the multi-year average. There are many indications that this past month will be another consecutive month with record high temperatures and the warmest March on record for measurements. Such a weather anomaly contributed to record high temperatures and droughts in southern Europe, and in the last days of March in Poland as well.

Global weather extremes – when the Pacific is ruled by a boy

In addition to global warming, a particularly intense El Niño phenomenon is now responsible for some of these changes. After a three-year reign of La Niña and a neutral period in the Pacific, since last summer the ENSO Southern Oscillation has entered a warmer phase – El Niño. It occurs on average every 2 to 7 years and usually lasts 9 to 12 months. This is a naturally-occurring climate pattern associated with warming ocean surfaces in the central and eastern tropical Pacific. Unfortunately, it usually brings with it hot weather, droughts or unusually heavy rainfall in various parts of the world.

On the one hand, we can expect improved moisture conditions in the eastern part of Africa, on the other hand, we must expect an increase in the intensity of extreme weather events and climatic anomalies in other areas of the world. Also of concern is the fact that despite the frequent occurrence of a cooler La Niña phase in recent times, the last eight years worldwide have been the warmest ever measured. With the current El Niño dominating the Pacific until at least the end of April, experts predict that the current year could be even warmer and with more weather anomalies, with extremes such as heat waves, droughts, fires, torrential rains and floods being intensified.

Weather anomalies in Europe with negative NAO index

Although the influence of the ENSO Southern Oscillation on the occurrence of weather anomalies in Europe has not yet been conclusively confirmed, the occurrence of unusual atmospheric phenomena is certainly related to the NAO North Atlantic Oscillation. With a positive oscillation, when there are large pressure differences between the Azores High and the Icelandic Low, the classic west-to-east flow of air masses for our climate prevails over Europe. During the spring period, relatively moist and cool air masses from over the Atlantic arrive over Poland, bringing moderately warm and rainy weather. Weather conditions reflect multi-year averages.

When there is a negative North Atlantic Oscillation, which is what we are currently in, the pressure differences between the Azores High and the Icelandic Low are smaller than the multi-year average, so the latitudinal inflow is weaker. Humid air masses are headed to the Mediterranean region. Over Europe, however, the meridional influx is stronger. It may contribute to the weather anomalies currently observed in the Old Continent and Poland. Such a circulation, depending on the location of local barric systems, results in the influx of frigid Arctic air masses or humid and hot tropical air. Many times it contributes to intense frost or heat waves in Poland, snowfall in the Alps or flooding in the south of our country.

Hot weather in Poland, and snowstorms in the Alps

In the first half of April, Central and Eastern Europe is experiencing a weather anomaly related to, among other things. With a negative NAO oscillation. As a result of the development of a low-pressure system in the Adriatic region and the expansion of a high-pressure wedge from Spain to Germany, humid air masses from the south arrived over the Alps and came into contact with cool ones from the north. At their junction, there was heavy snowfall, unusual this late, even in this region. The onslaught of winter brought snowfall of 50-80 cm. As long-term models show, this is unlikely to be the last winter touch in the region.

On the other hand, such a pressure system favored the influx of tropical air over Poland and the persistence of high temperatures. Along with the hot air, dust from over the Sahara has arrived over our country. It was visible on satellite images, contributed to reduced visibility and deposited on cars and streets. After an active storm front, unprecedented for this time of year, passed through Poland, the tropical masses receded. The front brought short-lived but very intense rainfall, and also thunderstorms in Pomerania.

Will weather anomalies become an everyday occurrence?

According to the National Oceanic and Atmospheric Administration (NOAA), there is a high probability that 2024. will be the next warmest year on record. July is expected to be particularly hot. Although El Nino has begun to wane, its warming effects will persist for months to come, leading to weather anomalies in the form of prolonged droughts in some areas and intense rainfall and flooding in others. Unusually high ocean temperatures are associated with the development and intensification of hurricanes and storms around the world.

As the national long-term precipitation and temperature forecasting models in Poland show, expect a hot and dry summer. In May, temperature and precipitation should reflect the 1991-2020 multi-year average, but June, July and August will bring temperatures above the multi-year norm. Precipitation will remain at average levels, but its nature may be more localized and episodic. In between periods with heavy rain, prolonged droughts are likely to occur. Rising temperatures could intensify storm events with strong wind gusts and heavy rainfall.

As you can see, changes in the global circulation, combined with factors related to a warming climate, rising ocean temperatures or shrinking ice caps, will contribute to the intensification of atmospheric phenomena. The climate system is a whole, one for the whole world, and no region will escape the consequences of its change. As scientists show, despite attempts by many countries to reduce greenhouse gas emissions, it seems that we must prepare for weather anomalies to become our daily reality.

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