scholarly journals Universal Frequency Spectra of Surface Meteorological Fluctuations

2011 ◽  
Vol 24 (17) ◽  
pp. 4718-4732 ◽  
Author(s):  
Chikara Tsuchiya ◽  
Kaoru Sato ◽  
Tomoe Nasuno ◽  
Akira T. Noda ◽  
Masaki Satoh
Keyword(s):  
Sea Level ◽  
High Frequency ◽  
Storm Track ◽  
High Frequency Range ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Hourly Data ◽  
Physical Quantities

Statistical characteristics of surface meteorology are examined in terms of frequency spectra. According to a recent work using hourly data over 50 yr in the Antarctic, the frequency spectra have a characteristic shape proportional to two different powers of the frequency in the frequency ranges lower and higher than a transition frequency of (several days)−1. To confirm the universality of the characteristic spectra, hourly data—including surface temperature, sea level pressure, and zonal and meridional winds—collected over 45 yr at 138 stations in Japan were analyzed. Similar spectral shapes are obtained for any physical quantities at all stations. The spectral slopes clearly depend on the latitude, particularly for sea level pressure, which in the high-frequency range are steeper at higher latitudes. Next, the analysis was extended using realistic simulation data over one month with a nonhydrostatic model to examine the global characteristics of the spectra in the high-frequency range. The model spectra accord well with the observations in Japan. The spectral slopes are largely dependent on the latitude—that is, shallow in the low latitudes, and steep in the middle and high latitudes for all the physical quantities. The latitudinal change of the spectral slope is severe around 30°, which may be due to the dynamical transition from nongeostrophy to geostrophy. The longitudinal variations are also observed according to the geography. The variance is large in the storm-track region for surface pressure, on the continents for temperature and over the ocean for winds.

The North Pacific Oscillation–West Pacific Teleconnection Pattern: Mature-Phase Structure and Winter Impacts

2008 ◽  
Vol 21 (9) ◽  
pp. 1979-1997 ◽  
Author(s):  
Megan E. Linkin ◽  
Sumant Nigam
Keyword(s):  
Sea Level ◽  
Pacific Northwest ◽  
Geopotential Height ◽  
Storm Track ◽  
Teleconnection Pattern ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
Mature Phase ◽  
The Pacific

Abstract The North Pacific Oscillation (NPO) in sea level pressure and its upper-air geopotential height signature, the west Pacific (WP) teleconnection pattern, constitute a prominent mode of winter midlatitude variability, the NPO/WP. Its mature-phase expression is identified from principal component analysis of monthly sea level pressure variability as the second leading mode just behind the Pacific–North American variability pattern. NPO/WP variability, primarily on subseasonal time scales, is characterized by a large-scale meridional dipole in SLP and geopotential height over the Pacific and is linked to meridional movements of the Asian–Pacific jet and Pacific storm track modulation. The hemispheric height anomalies at upper levels resemble the climatological stationary wave pattern attributed to transient eddy forcing. The NPO/WP divergent circulation is thermal wind restoring, pointing to independent forcing of jet fluctuations. Intercomparison of sea level pressure, geopotential height, and zonal wind anomaly structure reveals that NPO/WP is a basin analog of the NAO, which is not surprising given strong links to storm track variability in both cases. The NPO/WP variability is influential: its impact on Alaskan, Pacific Northwest, Canadian, and U.S. winter surface air temperatures is substantial—more than that of PNA or ENSO. It is likewise more influential on the Pacific Northwest, western Mexico, and south-central Great Plains winter precipitation. Finally, and perhaps, most importantly, NPO/WP is strongly linked to marginal ice zone variability of the Arctic seas with an influence that surpasses that of other Pacific modes. Although NPO/WP variability and impacts have not been as extensively analyzed as its Pacific cousins (PNA, ENSO), it is shown to be more consequential for Arctic sea ice and North American winter hydroclimate.

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>

On the Summertime Strengthening of the Northern Hemisphere Pacific Sea Level Pressure Anticyclone

2009 ◽  
Vol 22 (5) ◽  
pp. 1174-1192 ◽  
Author(s):  
Sumant Nigam ◽  
Steven C. Chan
Keyword(s):  
Sea Level ◽  
Northern Hemisphere ◽  
Asian Monsoon ◽  
Storm Track ◽  
Hadley Cell ◽  
Winter Storm ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Mascarene High ◽  
The Pacific

Abstract This study revisits the question posed by Hoskins on why the Northern Hemisphere Pacific sea level pressure (SLP) anticyclone is strongest and maximally extended in summer when the Hadley cell descent in the northern subtropics is the weakest. The paradoxical evolution is revisited because anticyclone buildup to the majestic summer structure is gradual, spread evenly over the preceding 4–6 months, and not just confined to the monsoon-onset period, which is interesting, as monsoons are posited to be the cause of the summer vigor of the anticyclone. Anticyclone buildup is moreover found focused in the extratropics, not the subtropics, where SLP seasonality is shown to be much weaker, generating a related paradox within the context of the Hadley cell’s striking seasonality. Showing this seasonality to arise from, and thus represent, remarkable descent variations in the Asian monsoon sector, but not over the central-eastern ocean basins, leads to the resolution of this paradox. Evolution of other prominent anticyclones is analyzed to critique the development mechanisms: the Azores high evolves like the Pacific one, but without a monsoon to its immediate west. The Mascarene high evolves differently, peaking in austral winter. Monsoons are not implicated in both cases. Diagnostic modeling of seasonal circulation development in the Pacific sector concludes this inquiry. Of the three forcing regions examined, the Pacific midlatitudes are found to be the most influential, accounting for over two-thirds of the winter-to-summer SLP development in the extratropics (6–8 hPa), with the bulk coming from the abatement of winter storm-track heating and transients. The Asian monsoon contribution (2–3 hPa) is dominant in the Pacific (and Atlantic) subtropics. The modeling results resonate with observational findings and attest to the demise of winter storm tracks as the principal cause of the summer vigor of the Pacific anticyclone.

scholarly journals A mean-sea-level pressure time series for Trieste, Italy (1841–2018)

2021 ◽  
Author(s):  
Fabio Raicich ◽  
Renato R. Colucci
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Historical Documents ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Pressure Time ◽  
Hourly Data ◽  
Quality Checks ◽  
Basic Quality

Abstract. A time series of mean-sea-level pressure was built from observations performed in Trieste from 1 January 1841 to 31 December 2018. Original historical documents provided information on the instruments and on the observation sites. Mercury barometers have been always available. Until 1877 they represented the only instruments in operation, while from 1878 onwards barograph records became available. The time series consists of mean daily values, that were computed from 24 hourly data, when possible, or otherwise adjusted to 24-hr means on the basis of climatological daily pressure cycles. The time series was homogenized on the basis of the available metadata, reducing pressure to 0° C and to mean sea level. Basic quality checks were applied, including the comparison with pressure time series from nearby stations. As a result, the data prior to 1865 turned out to be suspect. A mean-sea-level pressure trend of 0.5 ± 0.2 hPa per century was estimated for the 1865–2018 period. The data are available through PANGAEA https://doi.pangaea.de/10.1594/PANGAEA.926896; Raicich and Colucci, 2021).

Reconstructing Sea Level Pressure Variability via a Feature Tracking Approach

2015 ◽  
Vol 72 (1) ◽  
pp. 487-506 ◽  
Author(s):  
Sergey Kravtsov ◽  
I. Rudeva ◽  
Sergey K. Gulev
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Large Fraction ◽  
Storm Track ◽  
Low Frequency ◽  
Time Variability ◽  
Reconstruction Technique ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Wide Range

Abstract The aim of this paper is to quantify the contribution of synoptic transients to the full spectrum of space–time variability of sea level pressure (SLP) in middle latitudes. In previous work by the authors it was shown that tracking cyclones and anticyclones in an idealized atmospheric model allows one to reconstruct a surprisingly large fraction of the model’s variability, including not only synoptic components, but also its large-scale low-frequency component. Motivated by this result, the authors performed tracking of cyclones and anticyclones and estimated cyclone and anticyclone size and geometry characteristics in the observed SLP field using the 1948–2008 NCEP–NCAR reanalysis dataset. The reconstructed synoptic field was then produced via superimposing radially symmetrized eddies moving along their actual observed trajectories. It was found that, similar to earlier results for an idealized model, the synoptic reconstruction so obtained accounts for a major fraction of the full observed SLP variability across a wide range of time scales, from synoptic to those associated with the low-frequency variability (LFV). The synoptic reconstruction technique developed in this study helps elucidate connections between the synoptic eddies and LFV defined via more traditional spatiotemporal filtering. In particular, we found that the dominant variations in the position of the zonal-mean midlatitude jet are synonymous with random ultralow-frequency redistributions of cyclone and anticyclone trajectories and, hence, is inseparable of that in the storm-track statistics.

scholarly journals A mean-sea-level pressure time series for Trieste, Italy (1841–2018)

2021 ◽  
Vol 13 (7) ◽  
pp. 3363-3377
Author(s):  
Fabio Raicich ◽  
Renato R. Colucci
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Historical Documents ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Pressure Time ◽  
Hourly Data ◽  
Quality Checks ◽  
Basic Quality

Abstract. A time series of mean-sea-level pressure was built from observations performed in Trieste from 1 January 1841 to 31 December 2018. Original historical documents provided information on the instruments and on the observation sites. Mercury barometers have always been available. Until 1877 they represented the only instruments in operation, while from 1878 onwards barograph records became available. The time series consists of mean daily values that were computed from 24-hourly data, when possible, or otherwise adjusted to 24 h means on the basis of climatological daily pressure cycles. The time series was homogenized on the basis of the available metadata, reducing pressure to 0 ∘C and to mean sea level. Basic quality checks were applied, including the comparison with pressure time series from nearby stations. As a result, the data prior to 1865 turned out to be suspect. A mean-sea-level pressure trend of 0.5 ± 0.2 hPa per century was estimated for the 1865–2018 period. The data are available through PANGAEA (https://doi.org/10.1594/PANGAEA.926896; Raicich and Colucci, 2021).

scholarly journals A DRP–4DVar Data Assimilation Scheme for Typhoon Initialization Using Sea Level Pressure Data

2012 ◽  
Vol 140 (4) ◽  
pp. 1191-1203 ◽  
Author(s):  
Ying Zhao ◽  
Bin Wang ◽  
Juanjuan Liu
Keyword(s):  
Data Assimilation ◽  
Sea Level ◽  
Mesoscale Model ◽  
Storm Track ◽  
Initial Step ◽  
State University ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Fifth Generation ◽  
Typhoon Track

In this study, a new data assimilation system based on a dimension-reduced projection (DRP) technique was developed for the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) modeling system. As an initial step to test the newly developed system, observing system simulation experiments (OSSEs) were conducted using a simulated sea level pressure (SLP) field as “observations” and assimilation experiments using a specified SLP field to evaluate the effects of the new DRP–four-dimensional variational data assimilation (4DVar) method, initialization, and simulation of a tropical storm—Typhoon Bilis (2006) over the western North Pacific. In the OSSEs, the “nature” run, which was assumed to represent the “true” atmosphere, was simulated by the MM5 model, which was initialized with the 1.0° × 1.0° NCEP final global tropospheric analyses and integrated for 120 h. The simulated SLP field was then used as the observations in the data assimilation. It is shown that the MM5 DRP–4DVar system can successfully assimilate the (simulated) model output (used as observations) because the OSSEs resulted in improved storm-track forecasts. In addition, compared with an experiment that assimilated the SLP data fixed at the end of a 6-h assimilation window, the experiment that assimilated the SLP data every 3 min in a 30-min assimilation window further improved the typhoon-track forecasts, especially in terms of the initial vortex location and landfall location. Finally, the assimilation experiments with a specified SLP field have demonstrated the effectiveness of the new method.

A multivariate assessment of climate change projections over South America using CMIP5 models

2020 ◽  
Author(s):  
Paul Loikith ◽  
Valerie Thaler ◽  
Luana Albertani Pampuch ◽  
C. Roberto Mechoso ◽  
Armineh Barkhordarian ◽  
...  
Keyword(s):  
Climate Change ◽  
South America ◽  
Sea Level ◽  
Storm Track ◽  
Northeastern Brazil ◽  
Cmip5 Models ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Poleward Shift ◽  
Model Agreement

<p>A multivariate assessment of climate model projections over South America from the CMIP5 archive is presented. Change in near-surface temperature, precipitation, evapotranspiration, integrated water vapor transport (IVT), sea level pressure, and wind at multiple pressure levels is quantified across the multi-model suite and an assessment of model-to-model agreement on projected change performed. All models project warming by the mid- and late-21<sup>st</sup> century throughout the continent, with the highest magnitude projected over tropical regions. The CMIP5 models are in strong agreement that precipitation will decrease in all seasons over portions of Patagonia, especially along the northern portions of the current-climate mid-latitude storm track. This is consistent with a robustly projected poleward shift of the Pacific extratropical high and mid-latitude storm track indicated by a systematic increase in sea level pressure and decrease in westerly wind over Patagonia. Decreased precipitation for the months of September, October, and November is also projected, with strong model agreement, over portions of northern and northeastern Brazil, coincident with decreases in sea level pressure and increases in evapotranspiration. IVT is broadly projected to decrease over southern South America, coincident with the projected poleward shift of the mid-latitude storm track indicators, with increases projected in the vicinity of the South Atlantic Convergence Zone in austral spring and summer. Further decomposition of the thermodynamic and dynamic components to this change in IVT indicate that the projected decreases in the mid-latitudes are primarily driven by changes in circulation (i.e. dynamic) while the sub-tropical and tropical changes have a predominantly thermodynamic origin. Results provide a comprehensive picture of climate change across South America and highlight where projections should be interpreted with the most confidence.</p>

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.

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