Timo Vihma

Timo Vihma
Finnish Meteorological Institute · Meteorology Unit

Professor

About

257
Publications
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7,159
Citations

Publications

Publications (257)
Preprint
Full-text available
We utilized the global atmospheric reanalysis (ERA5) and reconstructed sea surface temperature (SST) data from 1979 through 2020 to examine the stability of the relationship between the SST oscillations in the southern Indian and the Atlantic Oceans described by the Subtropical Indian Ocean Dipole (SIOD) and the South Atlantic Ocean Dipole (SAOD) i...
Article
Full-text available
In recent decades, the warming in the Arctic has been much faster than in the rest of the world, a phenomenon known as Arctic amplification. Numerous studies report that the Arctic is warming either twice, more than twice, or even three times as fast as the globe on average. Here we show, by using several observational datasets which cover the Arct...
Article
Full-text available
The study provides estimates of summertime evaporation over a glacial lake located in the Schirmacher oasis, Dronning Maud Land, East Antarctica. Lake Zub (alternately named Lake Priyadarshini and referred to throughout as Lake Zub/Priyadarshini) is the second-largest lake in the oasis, and its maximum depth is 6 m. The lake is also among the warme...
Article
Full-text available
Summertime internal melting of Antarctic sea ice is common due to the penetration of solar radiation below the snow and ice surface. We focus on the role of internal melting and heat conduction in generating gap layers within the ice. These often occur approximately 0.1 m below the ice surface. In a small-scale survey over land-fast sea ice in Pryd...
Article
Full-text available
The Antarctic sea ice variability has been linked to tropical sea surface temperature. However, little is known as to whether and how the Indian Ocean Basin Mode (IOBM) influences Antarctic sea ice changes. We revealed the existence of a teleconnection between the IOMB and Antarctic sea ice anomalies, which is much stronger in austral spring and au...
Article
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In March 2013, the Springtime Atmospheric Boundary Layer Experiment (STABLE) was carried out in the Fram Strait region and over Svalbard to investigate atmospheric convection and boundary layer modifications due to interactions between sea ice, the atmosphere, and open water. A major goal was the observation of marine cold-air outbreaks (MCAOs), wh...
Article
Full-text available
The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topic...
Article
Full-text available
On 14 August 2021, rain fell on the peak of Greenland for the first time on record. The atmospheric circulation and water vapour transport responsible for the rain were investigated. A high-pressure ridge favoured southwesterly advection of warm and moist air, the intrusion of which contributed to the rainfall. At the same time, Summit station obse...
Article
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The anticyclonic anomaly over the Ural Mountains, or the Ural high (UH), has recently received much attention as a factor related to weather anomalies across Eurasia. Here we studied how the UH affects the occurrence of cold winter-time episodes over eastern Europe and northern China. By employing three methods to identify the UH, we found that a m...
Article
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Strong offshore wind events (SOWEs) occur frequently near the Antarctic coast during austral winter. These wind events are typically associated with passage of synoptic- or meso-scale cyclones, which interact with the katabatic wind field and affect sea ice and oceanic processes in coastal polynyas. Based on numerical simulations from the coupled F...
Preprint
In March 2013, the Springtime Atmospheric Boundary Layer Experiment (STABLE) was carried out in the region of Fram Strait and over Svalbard to investigate atmospheric convection and boundary layer modifications due to interactions between sea ice, atmosphere, and open water. A major goal was the observation of marine cold-air outbreaks (MCAOs), whi...
Article
Full-text available
Climate change and global warming strongly impact the cryosphere. The rise of air temperature and change of precipitation patterns lead to dramatic responses of snow and ice heat and mass balance. Sustainable field observations on lake air–snow–ice–water temperature regime have been carried out in Lake Orajärvi in the vicinity of the Finnish Space...
Preprint
Full-text available
The water cycle in glacier hydrological networks is not well known in Antarctica. We present the first evaluations of evaporation over a glacial lake located in the Schirmacher oasis, Dronning Maud Land, East Antarctica. Lake Zub/Priyadarshini is a shallow lake of the epiglacial type, and it is ice free for almost two months in summer (December-Feb...
Article
Full-text available
Three striking and impactful extreme cold weather events successively occurred across East Asia and North America during the mid-winter of 2020/21. These events open a new window to detect possible underlying physical processes. The analysis here indicates that the occurrences of the three events resulted from integrated effects of a concurrence of...
Article
Full-text available
Near-surface air temperature at the Argentinian research base Esperanza on the northern tip of the Antarctic Peninsula reached 18.3 °C on 6 February 2020, which is the highest temperature ever recorded on the entire Antarctic continent. Here we use weather observations since 1973 together with the ERA5 reanalysis to investigate the circulation that...
Preprint
Full-text available
In recent decades, the warming in the Arctic has been much faster than in the rest of the world, a phenomenon known as Arctic amplification (AA). Numerous studies report that Arctic is warming either twice, more than twice, or even three times as fast as the globe on average. However, the lack of consensus of AA definition precludes its precise qua...
Preprint
Full-text available
The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for sustainable development in the Artic-boreal region. Air quality in China and long-range transport of the atmospheric pollutants was also indicated as one of the most crucial topics o...
Preprint
Full-text available
Climate change and global warming strongly impact the cryosphere. The rise of air temperature and change of precipitation patterns lead to dramatic responses of snow and ice heat and mass balance. Sustainable field observations on lake air-snow-ice-water temperature regime have been carried out in Lake Orajärvi in the vicinity of the Finnish Space...
Article
Full-text available
Plain Language Summary Antarctic sea ice cover has experienced regionally different trends. In austral autumn, sea ice has decreased in the Bellingshausen Sea and increased in the Ross Sea, but reasons for these trends are not well understood. We present an explanation for the observed sea ice concentration trends in the Pacific sector of the South...
Article
Full-text available
Pronounced changes in the Arctic environment add a new potential driver of anomalous weather patterns in midlatitudes that affect billions of people. Recent studies of these Arctic/midlatitude weather linkages, however, state inconsistent conclusions. A source of uncertainty arises from the chaotic nature of the atmosphere. Thermodynamic forcing by...
Article
Atmospheric moisture is a key component in the water cycle and radiative transfer. In this study, a comprehensive picture of air moisture climatology and related physical processes is presented for the first time for the circumpolar area south of 50°S. The results are based on the most modern global reanalysis, ERA-5, which manages reasonably well...
Article
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It is widely recognized that numerical weather prediction (NWP) results for the Antarctic are relatively poor compared to the mid‐latitudes. In this study, we evaluate output from three operational NWP systems: the ECMWF, Global Forecast System (GFS) and Antarctic Mesoscale Prediction System (AMPS), for the Austral winter (June‐August) of 2013 for...
Article
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The rapid polar sea ice retreat and its drivers are challenging and still unresolved questions in climate change research. In particular, the relationship between near-surface wind speed and sea ice extent remains unclear for two main reasons: 1) observed wind speeds over Polar Regions are very sparse, and 2) simulated winds by climate models are d...
Article
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The underlying mechanisms for Arctic sea ice decline can be categories as those directly related to changes in atmospheric circulations (often referred to as dynamic mechanisms) and the rest (broadly characterized as thermodynamic processes). An attribution analysis based on the self-organizing maps (SOM) method is performed to determine the relati...
Article
Full-text available
The rapid polar sea ice retreat and its drivers are challenging and still unresolved questions in climate change research. In particular, the relationship between near-surface wind speed and sea ice extent remains unclear for two main reasons: (1) observed wind speeds over Polar Regions are very sparse, and (2) simulated winds by climate models are...
Article
Full-text available
Oscillations in wind speed and temperature are commonly observed in the atmospheric surface layer due to the ubiquitous presence of submeso-scale motions (SSMs). These motions are of particular importance during stable and low wind conditions as their amplitudes are large compared to the background turbulence. We characterize both SSMs and turbulen...
Article
Full-text available
The Arctic winter seasonal sea ice (WSSI) concentration from 1979 to 2019 is derived from passive microwave data. Based on Empirical Orthogonal Function (EOF) analysis, the WSSI time series includes regionally different trends, abrupt shifts and interannual variations. The time series of the first EOF mode (PC1) mainly represents the WSSI trend, wh...
Article
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The Innovative Strategies for Observations in the Arctic Atmospheric Boundary Layer Program (ISOBAR) is a research project investigating stable atmospheric boundary layer (SBL) processes, whose representation still poses significant challenges in state-of-the-art numerical weather prediction (NWP) models. In ISOBAR ground-based flux and profile obs...
Article
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The greatest impacts of climate change on ecosystems, wildlife and humans often arise from extreme events rather than changes in climatic means. Northern high latitudes, including the Arctic, experience a variety of climate-related extreme events, yet there has been little attempt to synthesize information on extreme events in this region. This rev...
Article
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The Svalbard Archipelago has undergone rapid warming in the recent decades leading to warmer and wetter winter conditions. This study relates the present (2013–2018) 2 m temperature, precipitation, and rain‐on‐snow (ROS) climate in Svalbard to different atmospheric circulation (AC) types utilizing the high‐resolution numerical weather prediction mo...
Article
Full-text available
Snow and ice were monitored by thermistor-string-based Snow and Ice Mass Balance Array (SIMBA) in Lake Orajärvi in northern Finland. An existing automatic SIMBA-algorithm was further developed to derive air/snow, snow/ice and ice/water interfaces based on the SIMBA environment temperature (ET) profiles. The identified interfaces agreed with in situ...
Article
Full-text available
A Fast Ice Prediction System (FIPS) was constructed and is the first regional land-fast sea-ice forecasting system for the Antarctic. FIPS had two components: (1) near-real-time information on the ice-covered area from MODIS and SAR imagery that revealed, tidal cracks, ridged and rafted ice regions; (2) a high-resolution 1-D thermodynamic snow and...
Article
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Public attention has recently focused on high-impact extreme weather events in midlatitudes that originate in the sub-Arctic. We investigate movements of the stratospheric polar vortex (SPV) and related changes in lower atmospheric circulation during the February-March 2018 “Beast from the East” cold winter event that dramatically affected much of...
Article
Along with the amplified warming and dramatic sea ice decline, the Arctic has experienced regionally and seasonally variable moistening of the atmosphere. Based on reanalysis data, this study demonstrates that the regional moistening patterns during the last four decades, 1979– 2018, were predominantly shaped by the strong trends in horizontal mois...
Article
Full-text available
The relative importance of the factors contributing to Arctic spring sea ice decline remains an open question. Here we suggest a new major factor. In spring the North Pacific Gyre Oscillation (NPGO) shows a significantly increasing trend during 1998‐2016, in contrast to the insignificant trend of the Pacific Decadal Oscillation (PDO) index. Nearly...
Article
Full-text available
Weather forecasting in the Southern Ocean and Antarctica is a challenge above all due to the rarity of observations to be assimilated in numerical weather prediction (NWP) models. As observations are expensive and logistically challenging, it is important to evaluate the benefit that additional observations could bring to NWP. Atmospheric soundings...
Conference Paper
Full-text available
Arctic sea ice retreat is expected to widen the average late summer and autumn window of navigability of the Northern Sea Route (NSR). However, the impacts on navigation are complicated by the large inter-annual and spatial variability and limited predictability of ice conditions along the NSR. Major investments in Polar Code ships is likely to pic...
Chapter
The scales of dynamical processes in the Arctic atmosphere range from turbulence in the atmospheric boundary layer (ABL) via interactive mesoscale processes, such as orographic flows and Polar lows, to synoptic-scale cyclones, and further to hemispherical-scale circulations characterized by the Polar front jet stream and planetary waves. Specific b...
Chapter
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Observations over the last decades showed large changes in the Arctic regions with a strong warming of the Arctic, which is about twice that of the global mean warming. The largest warming rates with up to 10 K since 1980 are reached near the surface in the Chukchi Sea in autumn and in the Barents Sea in winter. Changes in Arctic climate are a resu...
Article
Full-text available
Evaporation plays an important role in the global water and energy cycles and, hence, in climate change. Evaporation over the Southern Ocean, where the Antarctic sea ice coverage has a large annual cycle, is poorly quantified. In this study, daily evaporation is estimated for the Southern Ocean with a sea‐ice‐specific algorithm, using surface tempe...
Article
Full-text available
Applying the daily ERA-interim reanalysis data from 1979 to 2016, we found that widespread cold (warm) wintertime extreme events in Northern Europe occurred most frequently in winter 1984–1985 (2006–2007). These events often persisted for multiple days, and their primary drivers were the pattern of atmospheric large-scale circulation, the direction...
Article
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Surface layer and upper‐air in situ observations from two research vessel cruises and an ice station in the Weddell Sea from 1992 and 1996 are used to validate four current atmospheric reanalysis products: ERA‐Interim, CFSR, JRA‐55, and MERRA‐2. Three of the observation data sets were not available for assimilation, providing a rare opportunity to...
Article
Full-text available
The Arctic has warmed more than twice as fast as the global average since the late twentieth century, a phenomenon known as Arctic amplification (AA). Recently, there have been considerable advances in understanding the physical contributions to AA, and progress has been made in understanding the mechanisms that link it to midlatitude weather varia...
Article
Full-text available
We report an increase in winter (DJF) cyclone densities in the areas around Svalbard and in northwestern Barents Sea and a decrease in cyclone densities in southeastern Barents Sea during 1979–2016. Despite of high inter‐annual variability, the trends are significant at the 90% confidence level. The changes appear as a result of a shift into a more...
Article
This study gives a comprehensive picture of how atmospheric large-scale circulation is related to moisture transport and to distributions of moisture, clouds, and surface downward longwave radiation in the Arctic in winter. Anomaly distributions of the abovementioned variables are compared in 30 characteristic wintertime atmospheric circulation reg...
Article
Full-text available
Arctic trends of integrated water vapor were analyzed based on four reanalyses and radiosonde data over 1979–2016. Averaged over the region north of 70°N, the Arctic experiences a robust moistening trend that is smallest in March (0.07 ± 0.06 mm decade ⁻¹ ) and largest in August (0.33 ± 0.18 mm decade ⁻¹ ), according to the reanalyses’ median and o...
Article
NCEP CFSR reanalysis 6-hourly fields from 1979 to 2015 were used to investigate the relationships of sea ice concentration (SIC), atmospheric stratification, surface roughness, and wind speed at 10-m height (W10) and 850-hPa level (W850). We found that in autumn (September–November), winter (December–February), and spring (March–May) a lower SIC fa...
Article
Full-text available
The observed snow depth and ice thickness on landfast sea ice in Prydz Bay, East Antarctica, were used to determine the role of snow in (a) the annual cycle of sea ice thickness at a fixed location (SIP) where snow usually blows away after snowfall and (b) early summer sea ice thickness within the transportation route surveys (TRS) domain farther f...
Article
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Plain Language Summary The radiosounding network is a crucial part of the atmospheric observing system, because radiosoundings provide accurate direct information on vertical profiles of temperature, humidity and winds. However, the radiosounding network is sparse in the Arctic; 76 sounding stations are located on continents and islands north of 60...
Article
Future changes in geostrophic winds over Europe and the North Atlantic region were studied utilizing output data from 21 CMIP5 global climate models (GCMs). Changes in temporal means, extremes, and the joint distribution of speed and direction were considered. In concordance with previous research, the time mean and extreme scalar wind speeds do no...
Article
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We investigate factors influencing European winter (DJFM) air temperatures for the period 1979‐2015 with the focus on changes during the recent period of rapid Arctic warming (1998‐2015). We employ meteorological reanalyses analysed with a combination of correlation analysis, two pattern clustering techniques, and back‐trajectory airmass identifica...