Apparent absence of the quasi-biennial oscillation in sea level pressure in the south indian and south atlantic oceans

2007 ◽  
Vol 107 (452) ◽  
pp. 461-467
Author(s):  
T. G. J. Dyer
Keyword(s):  
Sea Level ◽  
South Atlantic ◽  
The South ◽  
Apparent Absence ◽  
Quasi Biennial Oscillation ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
South Indian ◽  
Biennial Oscillation

scholarly journals The influence of solar variability and the quasi-biennial oscillation on sea level pressure

2010 ◽  
Vol 10 (12) ◽  
pp. 30453-30471
Author(s):  
I. Roy ◽  
J. D. Haigh
Keyword(s):  
Solar Activity ◽  
Sea Level ◽  
The State ◽  
Solar Variability ◽  
The Sun ◽  
High Latitudes ◽  
Quasi Biennial Oscillation ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Biennial Oscillation

Abstract. We investigate an apparent inconsistency between two published results concerning the temperature of the winter polar stratosphere and its dependence on the state of the Sun and the phase of the Quasi-Biennial Oscillation (QBO). We find that the differences can be explained by the use of the authors of different pressure levels to define the phase of the QBO. We identify QBO and solar cycle signals in sea level pressure (SLP) data using a multiple linear regression approach. First we used a standard QBO time series dating back to 1953. In the SLP observations dating back to that time we find at high latitudes that individually the solar and QBO signals are weak but that a temporal index representing the combined effects of the Sun and the QBO shows a significant signal. This is such that combinations of low solar activity with westerly QBO and high solar activity with easterly QBO are both associated with a strengthening in the polar modes; while the opposite combinations coincide with a weakening. This result is true irrespective of the choice of QBO pressure level. By employing a QBO dataset reconstructed back to 1900, we extended the analysis and also find a robust signal in the surface SAM; though weaker for surface NAM. Our results suggest that solar variability, modulated by the phase of QBO, influences zonal mean temperatures at high latitudes in the lower stratosphere and subsequently affect sea level pressure near the poles. Thus a knowledge of the state of the Sun, and the phase of the QBO might be useful in surface climate prediction.

Climatology and variability of jets in the upper troposphere

2020 ◽  
Author(s):  
Clemens Spensberger ◽  
Thomas Spengler
Keyword(s):  
Sea Level ◽  
Storm Track ◽  
South Pacific ◽  
The South ◽  
Continuous Transition ◽  
Sea Level Pressure ◽  
Upper Troposphere ◽  
Level Pressure ◽  
South Indian ◽  
Jet Variability

<p>Jets in the upper troposphere constitute a cornerstone of both synoptic meteorology and climate dynamics, thus providing a direct link between weather and mid-latitude climate variability. Conventionally, jet variability is mostly inferred indirectly through the variability of geopotential or sea-level pressure. Here we use a feature-based jet detection and present a global climatology of upper tropospheric jets as well as their variability for ocean sectors in both Hemispheres. The jet streams on both hemispheres are found to spiral poleward, featuring a continuous transition from subtropical to eddy-driven jets. Most intrinsic patterns of jet variability represent a changeover from a meridional shifting type variability to a pulsing-type variability, or vice-versa, across each ocean basin.</p><p>For the Southern Hemisphere, we find considerable discrepancies between geopotential and jet-based variability. Specifically, we show that SAM cannot be interpreted in terms of mid-latitude variability, as SAM merely modulates the most poleward part of the cyclone tracks and only marginally influences the distribution of other weather-related features of the storm track (e.g., position of jet axes and Rossby wave breaking). Instead, SAM emerges as the leading pattern of geopotential variability due to strong correlations of sea-level pressure around the Antarctic continent. Considering sector-specific variability pattern, we identify modes of consistent geopotential and jet variability in the South Pacific, and, to a lesser extent, the South Indian Ocean. In the South Pacific the leading mode of variability points towards NAO-like variability.</p>

scholarly journals Position of the South Atlantic Anticyclone and Its Impact on Surface Conditions across Brazil

2018 ◽  
Vol 57 (3) ◽  
pp. 535-553 ◽  
Author(s):  
Joshua M. Gilliland ◽  
Barry D. Keim
Keyword(s):  
Wind Speed ◽  
Sea Level ◽  
Surface Wind ◽  
South Atlantic ◽  
Atmospheric Conditions ◽  
Southern Brazil ◽  
The South ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Northern Brazil

AbstractThis study examines the surface wind characteristics of Brazil on the basis of the location of the maximum high pressure center in the South Atlantic basin (SAB), known as the South Atlantic anticyclone (SAA), from three reanalysis datasets for the period of 1980–2014. Linear wind speed trends determined for Brazil are geographically related to surface and macroscale atmospheric conditions found in the SAB. The daily mean position of the SAA exhibited a latitudinal poleward shift for all seasons, and a longitudinal trend was dependent upon extratropical activity found in the SAB. Results also show that wind speed and sea level pressure for northern Brazil are dependent upon the latitudinal position of the SAA. Consequently, surface wind correlations for southern Brazil tend to be related to changes in the longitudinal position of the SAA, which result from transient anticyclones migrating over the SAB. An examination of positive and negative wind anomalies shows that shifts in the position of the SAA are coupled with changes in sea level pressure for northern Brazil and air temperature for southern Brazil. From these findings, a surface wind analysis was performed to demonstrate how the geographical location of the SAA affects wind speed anomalies across Brazil and the SAB. Results from this study can assist in understanding how atmospheric systems change within the SAB so that forthcoming socioeconomic and climate-related causes of wind for the country of Brazil can be known.

scholarly journals Projected Significant Increase in the Number of Extreme Extratropical Cyclones in the Southern Hemisphere

2017 ◽  
Vol 30 (13) ◽  
pp. 4915-4935 ◽  
Author(s):  
Edmund K. M. Chang
Keyword(s):  
Sea Level ◽  
Southern Hemisphere ◽  
Cmip5 Models ◽  
General Interest ◽  
Extratropical Cyclones ◽  
The South ◽  
Sea Level Pressure ◽  
Near Surface ◽  
Level Pressure ◽  
South Indian

Extratropical cyclones are responsible for much of the extreme weather in the midlatitudes; thus, how these cyclones may change under increasing greenhouse gas forcing is of much general interest. Previous studies have suggested a poleward shift in the location of these cyclones, but how the intensity may change remains uncertain, especially in terms of maximum wind speed. In this study, projected changes in extreme cyclones in the Southern Hemisphere, based on 26 models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5), are presented. Multiple definitions of extreme cyclones have been examined, including intensity exceeding constant thresholds of sea level pressure perturbations, 850-hPa vorticity, and 850-hPa winds, as well as variable thresholds corresponding to a top-5 or top-1 cyclone per winter month in these three parameters and the near-surface winds. Results presented show that CMIP5 models project a significant increase in the frequency of extreme cyclones in all four seasons regardless of the definition, with over 88% of the models projecting an increase. Spatial patterns of increase are also consistent, with the largest increase projected between 45° and 60°S, extending from the South Atlantic across the south Indian Ocean into the Pacific. The projected increases in cyclone statistics are consistent with those in Eulerian statistics, such as sea level pressure (SLP) variance. However, while the projected increase in SLP variance can be linked to increase in the mean available potential energy (MAPE), the increases in cyclone statistics are not well correlated with those in MAPE.

scholarly journals The influence of solar variability and the quasi-biennial oscillation on lower atmospheric temperatures and sea level pressure

2011 ◽  
Vol 11 (22) ◽  
pp. 11679-11687 ◽  
Author(s):  
I. Roy ◽  
J. D. Haigh
Keyword(s):  
Solar Activity ◽  
Sea Level ◽  
Lower Stratosphere ◽  
Solar Variability ◽  
The Sun ◽  
High Latitudes ◽  
Quasi Biennial Oscillation ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Biennial Oscillation

Abstract. Our fundamental aim is to investigate solar cycle signals in sea level pressure. In order to see if these may relate, especially at high latitudes, to the solar influence on the stratosphere we start by investigating the temperature of the winter polar stratosphere and its dependence on the state of the Sun and the phase of the Quasi-Biennial Oscillation (QBO). We find that the choice of pressure level used to define the phase of the QBO is important in determining how the solar and QBO influences appear to act in combination. Informed by this we carry out a multiple linear regression analysis of zonal mean temperatures throughout the lower stratosphere and troposphere. A combined solar*QBO temporal index exhibits strongly in the lower stratosphere, but in much of the troposphere any influence of the QBO, either on its own or coupled to solar effects is much smaller than the pure solar signal. We use a similar approach to analyse sea level pressure (SLP) data, first using a standard QBO time series dating back to 1953. We find at high latitudes that individually the solar and QBO signals are weak but that the compound solar*QBO temporal index shows a significant signal. This is such that combinations of low solar activity with westerly QBO and high solar activity with easterly QBO are both associated with a strengthening in the polar modes; while the opposite combinations coincide with a weakening. By employing a QBO dataset reconstructed back to 1900, we extend the SLP analysis back to that date and also find a robust signal in the surface SAM; though weaker for surface NAM. Our results suggest that solar variability, modulated by the phase of QBO, influences zonal mean temperatures at high latitudes in the lower stratosphere, in the mid-latitude troposphere and sea level pressure near the poles. Thus a knowledge of the state of the Sun, and the phase of the QBO might be useful in surface climate prediction.

scholarly journals Atmospheric forcing of upwelling along the south-eastern Baltic coast

Baltica ◽  
2018 ◽  
Vol 31 (1) ◽  
pp. 73-85 ◽  
Author(s):  
Ewa Bednorz ◽  
Bartosz Czernecki ◽  
Marek Półrolniczak ◽  
Arkadiusz M. Tomczyk
Keyword(s):  
Sea Level ◽  
Coastal Upwelling ◽  
Research Area ◽  
Positive Pressure ◽  
The South ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
South Eastern ◽  
Circulation Types ◽  
Eastern Baltic

The meteorological forcing on the occurrence of upwelling along the south-eastern Baltic Sea coast (Lithuanian-Latvian sector) is analysed in this study. The sea level pressure patterns and the locations of pressure centres inducing and inhibiting upwelling were identified. The research was performed for the years 1982–2017, for the months of May–September, when the sea waters are thermally stratified and the phenomenon is detectable. The frequency of upwelling is the highest in June (approximately 15%), July and August (11–13%) and the lowest in September (7%). The central and northern part of the Lithuanian–Latvian coast is most favourable for upwelling occurrence (frequency up to 20% in summer months). The main features of the sea level pressure patterns that induce upwelling in the research area are positive pressure anomalies spreading over Northern Europe and the Norwegian Sea, while negative anomalies encompass Southern Europe. Airflow around the anticyclonic centres gives a north-eastern component to the wind direction over the Lithuanian-Latvian shore. Two circulation types were recognized as inducing the occurrence of upwelling along the Lithuanian–Latvian coast. Both of them are characterized by the anticyclonic centres located west or northwest of the study area and intensify the northerly or north-easterly airflow over the research area. Different pressure patterns with the negative anomalies of sea level pressure spreading over the North Sea and the positive anomalies underlying Central Europe inhibit upwelling along the Lithuanian–Latvian coast. Such pressure conditions, bring about the western airflow component. More constant western winds restrain the upwelling process and bring about normal thermal stratification of coastal waters. A detailed analysis allowed the recognition of two circulation types inhibiting coastal upwelling in the study area. They reveal dipole patterns of sea level pressure anomalies, but the two inhibiting patterns differ substantially in the intensities and locations of the pressure centres and in wind conditions.

scholarly journals Complex network approach for detecting tropical cyclones

2021 ◽  
Author(s):  
Shraddha Gupta ◽  
Niklas Boers ◽  
Florian Pappenberger ◽  
Jürgen Kurths
Keyword(s):  
Sea Level ◽  
Tropical Cyclones ◽  
Complex Network ◽  
Time Scales ◽  
Southern Oscillation ◽  
Volcanic Eruptions ◽  
Network Approach ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Climate Networks

AbstractTropical cyclones (TCs) are one of the most destructive natural hazards that pose a serious threat to society, particularly to those in the coastal regions. In this work, we study the temporal evolution of the regional weather conditions in relation to the occurrence of TCs using climate networks. Climate networks encode the interactions among climate variables at different locations on the Earth’s surface, and in particular, time-evolving climate networks have been successfully applied to study different climate phenomena at comparably long time scales, such as the El Niño Southern Oscillation, different monsoon systems, or the climatic impacts of volcanic eruptions. Here, we develop and apply a complex network approach suitable for the investigation of the relatively short-lived TCs. We show that our proposed methodology has the potential to identify TCs and their tracks from mean sea level pressure (MSLP) data. We use the ERA5 reanalysis MSLP data to construct successive networks of overlapping, short-length time windows for the regions under consideration, where we focus on the north Indian Ocean and the tropical north Atlantic Ocean. We compare the spatial features of various topological properties of the network, and the spatial scales involved, in the absence and presence of a cyclone. We find that network measures such as degree and clustering exhibit significant signatures of TCs and have striking similarities with their tracks. The study of the network topology over time scales relevant to TCs allows us to obtain crucial insights into the effects of TCs on the spatial connectivity structure of sea-level pressure fields.

scholarly journals Tropical cyclone simulations over Bangladesh at convection permitting 4.4 km & 1.5 km resolution

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hamish Steptoe ◽  
Nicholas Henry Savage ◽  
Saeed Sadri ◽  
Kate Salmon ◽  
Zubair Maalick ◽  
...  
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Sea Level ◽  
Tropical Cyclones ◽  
Weather Forecasting ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Medium Range ◽  
Gust Speed

AbstractHigh resolution simulations at 4.4 km and 1.5 km resolution have been performed for 12 historical tropical cyclones impacting Bangladesh. We use the European Centre for Medium-Range Weather Forecasting 5th generation Re-Analysis (ERA5) to provide a 9-member ensemble of initial and boundary conditions for the regional configuration of the Met Office Unified Model. The simulations are compared to the original ERA5 data and the International Best Track Archive for Climate Stewardship (IBTrACS) tropical cyclone database for wind speed, gust speed and mean sea-level pressure. The 4.4 km simulations show a typical increase in peak gust speed of 41 to 118 knots relative to ERA5, and a deepening of minimum mean sea-level pressure of up to −27 hPa, relative to ERA5 and IBTrACS data. The downscaled simulations compare more favourably with IBTrACS data than the ERA5 data suggesting tropical cyclone hazards in the ERA5 deterministic output may be underestimated. The dataset is freely available from 10.5281/zenodo.3600201.

Sign in / Sign up

Export Citation Format

Share Document