scholarly journals Transient behavior of the meridional moisture transport across South America and its relation to atmospheric circulation patterns

1999 ◽  
Vol 26 (10) ◽  
pp. 1409-1412 ◽  
Author(s):  
Z. X. Li ◽  
H. Le Treut
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Moisture Transport ◽  
Transient Behavior ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Meridional Moisture Transport

Recent changes in the atmospheric circulation patterns during the dry-to-wet transition season in south tropical South America (1979-2020): Impacts on precipitation and fire season

2021 ◽  
pp. 1-56
Author(s):  
Jhan-Carlo Espinoza ◽  
Paola A. Arias ◽  
Vincent Moron ◽  
Clementine Junquas ◽  
Hans Segura ◽  
...  
Keyword(s):  
South America ◽  
Atmospheric Circulation ◽  
Low Frequency ◽  
Fire Season ◽  
South American ◽  
Low Level ◽  
Atmospheric Circulation Patterns ◽  
Transition Season ◽  
Circulation Patterns ◽  
Tropical South America

AbstractWe analyze the characteristics of atmospheric variations over tropical South America using the pattern recognition framework of weather typing or atmospheric circulation patterns (CPs). During 1979-2020, nine CPs are defined in the region, using a k-means algorithm based on daily unfiltered 850 hPa winds over 0035°N-30°S, 90°W-30°W. CPs are primarily interpreted as stages of the annual cycle of the low-level circulation. We identified three “winter” CPs (CP7, CP8 and CP9), three “summer” CPs (CP3, CP4 and CP5) and three “transitional” CPs (CP1, CP2 and CP6). Significant long-term changes are detected during the dry-to-wet transition season (July-October) over south tropical South America (STSA). One of the wintertime patterns (CP9) increases from 20% in the 1980s to 35% in the last decade while the “transitional” CP2 decreases from 13% to 7%. CP9 is characterized by enhancement of the South American Low-Level Jet and increasing atmospheric subsidence over STSA. CP2 is characterized by southerly cold-air incursions and anomalous convective activity over STSA. The years characterized by high (low) frequency of CP9 (CP2) during the dry-to-wet transition season are associated with a delayed South American Monsoon onset and anomalous dry conditions over STSA. Consistently, a higher frequency of CP9 intensifies the fire season over STSA (1999-2020). Over the Brazilian states of Maranhão, Tocantins, Goiás and São Paulo, the seasonal frequency of CP9 explains around 35%-44% of the interannual variations of fire counts.

scholarly journals Automated classification of the atmospheric circulation patterns that drive regional wave climates

2014 ◽  
Vol 14 (8) ◽  
pp. 2145-2155 ◽  
Author(s):  
J. Pringle ◽  
D. D. Stretch ◽  
A. Bárdossy
Keyword(s):  
Atmospheric Circulation ◽  
Low Pressure ◽  
Wave Climate ◽  
Automated Classification ◽  
Coastal Vulnerability ◽  
Extreme Wave ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Spatially Distributed ◽  
Wave Heights

Abstract. Wave climates are fundamental drivers of coastal vulnerability; changing trends in wave heights, periods and directions can severely impact a coastline. In a diverse storm environment, the changes in these parameters are difficult to detect and quantify. Since wave climates are linked to atmospheric circulation patterns, an automated and objective classification scheme was developed to explore links between synoptic-scale circulation patterns and wave climate variables, specifically wave heights. The algorithm uses a set of objective functions based on wave heights to guide the classification and find atmospheric classes with strong links to wave behaviour. Spatially distributed fuzzy numbers define the classes and are used to detect locally high- and low-pressure anomalies. Classes are derived through a process of simulated annealing. The optimized classification focuses on extreme wave events. The east coast of South Africa was used as a case study. The results show that three dominant patterns drive extreme wave events. The circulation patterns exhibit some seasonality with one pattern present throughout the year. Some 50–80% of the extreme wave events are explained by these three patterns. It is evident that strong low-pressure anomalies east of the country drive a wind towards the KwaZulu-Natal coastline which results in extreme wave conditions. We conclude that the methodology can be used to link circulation patterns to wave heights within a diverse storm environment. The circulation patterns agree with qualitative observations of wave climate drivers. There are applications to the assessment of coastal vulnerability and the management of coastlines worldwide.

scholarly journals Spring Extreme Precipitation Days in North China and Their Reliance on Atmospheric Circulation Patterns During 1979–2019

2022 ◽  
pp. 1-41
Keyword(s):  
Climate Variability ◽  
Atmospheric Circulation ◽  
Extreme Precipitation ◽  
Interannual Variation ◽  
North China ◽  
Circulation Pattern ◽  
Southerly Wind ◽  
Atmospheric Circulation Patterns ◽  
Rain Gauges ◽  
Circulation Patterns

Abstract The interannual variation of springtime extreme precipitation (SEP) days in North China (NC) and their reliance on atmospheric circulation patterns are studied by using the continuous daily record of 396 rain gauges and the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis during 1979–2019. The SEP days are defined as the days when at least 10% of rain gauges in NC record daily precipitation no less than 10.5 mm. Results show that the number of SEP days shows large interannual variability but no significant trend in the study period. Using the objective classification method of the obliquely rotated principal analysis in T-mode, we classify the atmospheric circulation into five different patterns based on the geopotential height at 700 hPa. Three circulation patterns all have fronts and are associated with strong southerly wind, leading to 88% of SEP days in NC. The strong southerly wind may provide moisture and dynamic forcing for the frontal precipitation. The interannual variation of SEP days is related with the number of the three above-mentioned dominant circulation patterns. Further analysis shows that the West Pacific pattern could be one of the possible climate variability modes related to SEP days. This study reveals that the daily circulation pattern may be the linkage between SEP days and climate variability modes in NC.

scholarly journals Extreme Temperature Events in Serbia in Relation to Atmospheric Circulation

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1584
Author(s):  
Ivana Tošić ◽  
Suzana Putniković ◽  
Milica Tošić ◽  
Irida Lazić
Keyword(s):  
Atmospheric Circulation ◽  
Heat Waves ◽  
Extreme Temperature ◽  
Daily Maximum ◽  
Absolute Maximum ◽  
Extreme Temperature Events ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Maximum Temperatures ◽  
The Relationship

In this study, extremely warm and cold temperature events were examined based on daily maximum (Tx) and minimum (Tn) temperatures observed at 11 stations in Serbia during the period 1949–2018. Summer days (SU), warm days (Tx90), and heat waves (HWs) were calculated based on daily maximum temperatures, while frost days (FD) and cold nights (Tn10) were derived from daily minimum temperatures. Absolute maximum and minimum temperatures in Serbia rose but were statistically significant only for Tx in winter. Positive trends of summer and warm days, and negative trends of frost days and cold nights were found. A high number of warm events (SU, Tx90, and HWs) were recorded over the last 20 years. Multiple linear regression (MLR) models were applied to find the relationship between extreme temperature events and atmospheric circulation. Typical atmospheric circulation patterns, previously determined for Serbia, were used as predictor variables. It was found that MLR models gave the best results for Tx90, FD, and Tn10 in winter.

scholarly journals Aerosol reductions outweigh circulation changes for future improvements in Beijing haze

2021 ◽  
Author(s):  
Liang Guo ◽  
Laura J. Wilcox ◽  
Massimo Bollasina ◽  
Steven T. Turnock ◽  
Marianne T. Lund ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Atmospheric Circulation ◽  
Greenhouse Gas Emission ◽  
Weather Patterns ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Main Driver ◽  
Emission Changes ◽  
Aerosol Emissions ◽  
Circulation Changes

Abstract. Despite local emission reductions, severe haze events remain a serious issue in Beijing. Previous studies have suggested that both greenhouse gas increases and aerosol decreases are likely to increase the frequency of weather patterns conducive to haze events. However, the combined effect of atmospheric circulation changes and aerosol and precursor emission changes on Beijing haze remains unclear. We use the Shared Socioeconomic Pathways (SSPs) to explore the effects of aerosol and greenhouse gas emission changes on both haze weather and Beijing haze itself. We confirm that the occurrence of haze weather patterns is likely to increase in future under all SSPs, and show that even though aerosol reductions play a small role, greenhouse gas increases are the main driver, especially during the second half of the 21st century. However, the severity of the haze events decreases on decadal timescales by as much as 70 % by 2100. The main influence on the haze itself is the reductions in local aerosol emissions, which outweigh the effects of changes in atmospheric circulation patterns. This demonstrates that aerosol reductions are beneficial, despite their influence on the circulation.

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