An Empirical Relationship among Characteristics of Severe Convective Storms, Their Cloud-Top Properties and Environmental Parameters in Northern Eurasia

Severe convective storms that produce tornadoes and straight-line winds usually develop under particular environmental conditions and have specific signatures on the cloud tops associated with intense updrafts. In this study, we performed a comparative analysis of satellite-derived characteristics, with a focus on cloud-top properties, and ERA5-based environmental parameters of convective storms in forested regions of the western part of Northern Eurasia in 2006–2021. The analyzed sample includes 128 different convective storms that produced 138 tornadoes and 143 linear windstorms. We found most tornadoes and linear windstorms are generated by quasi-linear convective storms or supercells. Such supercells form under lower convective instability and precipitable water content compared to those for other types of storms. We found a significant negative correlation of minimum temperature on the storm cloud top with instability parameters. In turn, the longevity of convective storms significantly correlates with wind shear and storm-relative helicity. About half of the tornadoes and 2/3 of linear windstorms are associated with the presence of cloud-top signatures, such as overshooting tops, cold-ring or cold U/V features. The events associated with such signatures are formed under high values of instability parameters. Our results can be used for further analysis of peculiarities of tornado and linear windstorm formation and to enhance the predictability of such severe events, especially in regions with a lack of weather radar coverage

Climatology of Total Cloudiness in the Arctic: An Intercomparison of Observations and Reanalyses

Total cloud fraction over the Arctic (north of 60°N) has been evaluated and intercompared based on 16 Arctic cloud climatologies from different satellite and surface observations and reanalyses. The Arctic annual-mean total cloud fraction is about 0.70±0.03 according to different observational data. It is greater over the ocean (0.74±0.04) and less over land (0.67±0.03). Different observations for total cloud fraction are in a better agreement in summer than in winter and over the ocean than over land. An interannual variability is higher in winter than in summer according to all observations. The Arctic total cloud fraction has a prominent annual cycle according to most of the observations. The time of its maximum concurs with the time of the sea ice extent minimum (early summer–late autumn) and vice versa (late spring). The main reason for the discrepancies among observations is the difference in the cloud-detection algorithms, especially when clouds are detected over the ice/snow surface (during the whole year) or over the regions with the presence of strong low-tropospheric temperature inversions (mostly in winter). Generally, reanalyses are not in a close agreement with satellite and surface observations of cloudiness in the Arctic

An Empirical Relationship among Characteristics of Severe Convective Storms, Their Cloud-Top Properties and Environmental Parameters in Northern Eurasia

Severe convective storms that produce tornadoes and straight-line winds usually develop under particular environmental conditions and have specific signatures on the cloud tops associated with intense updrafts. In this study, we performed a comparative analysis of satellite-derived characteristics, with a focus on cloud-top properties, and ERA5-based environmental parameters of convective storms in forested regions of the western part of Northern Eurasia in 2006–2021. The analyzed sample includes 128 different convective storms that produced 138 tornadoes and 143 linear windstorms. We found most tornadoes and linear windstorms are generated by quasi-linear convective storms or supercells. Such supercells form under lower convective instability and precipitable water content compared to those for other types of storms. We found a significant negative correlation of minimum temperature on the storm cloud top with instability parameters. In turn, the longevity of convective storms significantly correlates with wind shear and storm-relative helicity. About half of the tornadoes and 2/3 of linear windstorms are associated with the presence of cloud-top signatures, such as overshooting tops, cold-ring or cold U/V features. The events associated with such signatures are formed under high values of instability parameters. Our results can be used for further analysis of peculiarities of tornado and linear windstorm formation and to enhance the predictability of such severe events, especially in regions with a lack of weather radar coverage

The linkage between POLar air-sea ice-ocean interaction, Arctic climate change and Northern hemisphere weather and climate EXtremes (POLEX).

First results of the POLEX project will be presented. The objectives of our project comprise: 1) An improvement of the representation of atmosphere-sea ice-ocean interaction in climate models by developing and implementing a suite of advanced turbulence parametrizations for polar conditions 2) Performance of present day and future climate change simulations for the 21st century using the new suite of parametrizations 3) Understanding the dynamical linkages between Arctic climate change, mid-latitude atmospheric circulation changes and subsequent changes in extreme events 4) Determination of recent and future changes in extreme events over the Arctic, Middle Europe and Russia and assessment of their impact on Northern Sea route, wildfire and vegetation over the key regions Arctic and Russia Our project will strongly enhance the climate models capability to represent Arctic processes that are known to be critical for simulating linkages between the Arctic and mid-latitudes

Winter cloudiness variability over Northern Eurasia related to the Siberian High during 1966–2010

This letter presents an assessment of winter cloudiness variability over Northern Eurasia regions related to the Siberian High intensity (SHI) variations during 1966–2010. An analysis of cloud fraction and the occurrence of different cloud types was carried out based on visual observations from almost 500 Russian meteorological stations. The moonlight criterion was implemented to reduce the uncertainty of night observations. The SHI was defined based on sea-level pressure fields from different reanalyses. We found a statistically significant negative correlation of cloud cover with the SHI over central and southern Siberia and the southern Urals with regression coefficients around 3% hPa ^−1 for total cloud fraction (TCF) for particular stations near the Siberian High center. Cross-wavelet analysis of TCF and SHI revealed a long-term relationship between cloudiness and the Siberian High. Generally, the Siberian High intensification by 1 hPa leads to a replacement of one overcast day with one day without clouds, which is associated mainly with a decrease in precipitating and stratiform clouds. These changes point to a positive feedback between cloudiness and the Siberian High

Observed changes in convective and stratiform precipitation in Northern Eurasia over the last five decades

Long-term changes in convective and stratiform precipitation in Northern Eurasia (NE) over the last five decades are estimated. Different types of precipitation are separated according to their genesis using routine meteorological observations of precipitation, weather conditions, and morphological cloud types for the period 1966–2016. From an initial 538 stations, the main analysis is performed for 326 stations that have no gaps and meet criteria regarding the artificial discontinuity absence in the data. A moderate increase in total precipitation over the analyzed period is accompanied by a relatively strong growth of convective precipitation and a concurrent decrease in stratiform precipitation. Convective and stratiform precipitation totals, precipitation intensity and heavy precipitation sums depict major changes in summer, while the relative contribution of the two precipitation types to the total precipitation (including the contribution of heavy rain events) show the strongest trends in transition seasons. The contribution of heavy convective showers to the total precipitation increases with the statistically significant trend of 1%–2% per decade in vast NE regions, reaching 5% per decade at a number of stations. The largest increase is found over the southern Far East region, mostly because of positive changes in convective precipitation intensity with a linear trend of more than 1 mm/day/decade, implying a 13.8% increase per 1 °C warming. In general, stratiform precipitation decreases over the majority of NE regions in all seasons except for winter. This decrease happens at slower rates in comparison to the convective precipitation changes. The overall changes in the character of precipitation over the majority of NE regions are characterized by a redistribution of precipitation types toward more heavy showers

A Dynamic Analysis of the Role of the Planetary- and Synoptic-Scale in the Summer of 2010 Blocking Episodes over the European Part of Russia

During the summer of 2010, an unusually persistent blocking episode resulted in anomalously warm dry weather over the European part of Russia. The excessive heat resulted in forest and peat fires, impacted terrestrial ecosystems, greatly increased pollution in urban areas, and increased mortality rates in the region. Using the National Centers for Atmospheric Research (NCAR), National Centers for Environmental Prediction (NCEP) reanalysis datasets, the climatological and dynamic character of blocking events for summer 2010 and a precursor May blocking event were examined. We found that these events were stronger and longer lived than typical warm season events. Using dynamic methods, we demonstrate that the July 2010 event was a synoptic-scale dominant blocking event; unusual in the summer season. An analysis of phase diagrams demonstrated that the planetary-scale did not become stable until almost one week after block onset. For all other blocking events studied here and previously, the planetary-scale became stable around onset. Analysis using area integrated regional enstrophy (IRE) demonstrated that for the July 2010 event, synoptic-scale IRE increased at block onset. This was similar for the May 2010 event, but different from case studies examined previously that demonstrated the planetary-scale IRE was prominent at block onset

Hydrological Changes: Historical Analysis, Contemporary Status, and Future Projections

This chapter looks at several aspects of the hydrological regime across Siberia using long-term historical data and model simulation results to provide a better understanding of ongoing changes and future directions. It begins with a survey of the major components of water balance: river flow, precipitation, and evapotranspiration. This is followed by the primary focus on the Siberian river systems with emphasis on annual variability and the anomalously high river discharge in 2007, the seasonality of river flow with increases in winter discharge, and changes in magnitude of minimum river flow and the temporal shifts in maximum river flow. Other components related to the river systems are also explored, including the thermal regime showing a lack of widespread evidence for increasing river temperature while the ice cover over the major rivers is decreasing in terms of both the duration of ice cover and ice thickness. Related hydrological conditions (e.g., groundwater hydrology) demonstrate an increase in both levels and temperatures; however, there is evidence for some local decreases in groundwater level. Additionally, increases in groundwater runoff from the taiga zone are observed. Total thermokarst lake area is changing, depending on the landscape zone. Northern zones of tundra are gaining lake area, while the southern tundra and taiga regions are losing lake area. This chapter concludes with a look at possible future changes in the region’s hydrology. River discharge in the major Siberian watersheds is expected to rise, and this result is consistent across a majority of the global climate models’ projections for the twenty-first century

Special issue: 10th anniversary of atmosphere: climatology and meteorology

During the last decade, the number of open access science journals has increased, and these have become an avenue for publishing quality science in a relatively fast and economical way [...