scholarly journals Empirical Modeling and Stochastic Simulation of Sea Level Pressure Variability

2016 ◽  
Vol 55 (5) ◽  
pp. 1197-1219 ◽  
Author(s):  
Sergey Kravtsov ◽  
Natalia Tilinina ◽  
Yulia Zyulyaeva ◽  
Sergey K. Gulev
Keyword(s):  
Sea Level ◽  
Diurnal Cycle ◽  
Empirical Model ◽  
Empirical Modeling ◽  
Statistical Prediction ◽  
Main Step ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Statistical Measures ◽  
Wide Range

AbstractThe scope of this work is stochastic emulation of sea level pressure (SLP) for use in error estimation and statistical prediction studies. The input SLP dataset whose statistics are to be emulated was taken from the 1979–2013 ERA-Interim dataset at full 6-hourly temporal and 0.75° spatial resolutions over the Northern Hemisphere. Upon subtracting the monthly climatological mean value and mean diurnal cycle, the SLP anomalies (SLPA) were projected onto the subspace of 1000 leading empirical orthogonal functions of the daily-mean SLPA, which account for the vast majority (>99%) of the full 6-hourly fields’ variance for each season. The main step of this method is the estimation of a linear autoregressive moving-average empirical model for the daily SLPA principal components (PCs) via regularized multiple linear regression; this model was driven, at the stage of simulation, by state-dependent (multiplicative) noise. Last, a diagnostic statistical scheme has been developed and implemented for accurate interpolation of simulated daily SLPA to 6-hourly temporal resolution. Upon transforming the simulated 6-hourly SLPA PCs into the physical space and adding a seasonal climatological mean and mean diurnal cycle, the resulting SLP variability was compared with the actual variability in the ERA-Interim dataset. It is shown that this empirical model produces independent realizations of SLP variability that are nearly indistinguishable from the observed variability over a wide range of statistical measures; these measures include, among others, spatial patterns of bandpass- and low-pass-filtered variability, as well as diverse characteristics of midlatitude cyclone tracks.

scholarly journals Spatial and Temporal Variability of Nonfreezing Drizzle in the United States and Canada

2006 ◽  
Vol 19 (15) ◽  
pp. 3629-3639 ◽  
Author(s):  
Addison L. Sears-Collins ◽  
David M. Schultz ◽  
Robert H. Johns
Keyword(s):  
United States ◽  
Sea Level ◽  
The United States ◽  
Seasonal Migration ◽  
Eastern United States ◽  
Eastern Canada ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Wind Speeds ◽  
Wide Range

Abstract A climatology of nonfreezing drizzle is created using surface observations from 584 stations across the United States and Canada over the 15-yr period 1976–90. Drizzle falls 50–200 h a year in most locations in the eastern United States and Canada, whereas drizzle falls less than 50 h a year in the west, except for coastal Alaska and several western basins. The eastern and western halves of North America are separated by a strong gradient in drizzle frequency along roughly 100°W, as large as about an hour a year over 2 km. Forty percent of the stations have a drizzle maximum from November to January, whereas only 13% of stations have a drizzle maximum from June to August. Drizzle occurrence exhibits a seasonal migration from eastern Canada and the central portion of the Northwest Territories in summer, equatorward to most of the eastern United States and southeast Canada in early winter, to southeastern Texas and the eastern United States in late winter, and back north to eastern Canada in the spring. The diurnal hourly frequency of drizzle across the United States and Canada increases sharply from 0900 to 1200 UTC, followed by a steady decline from 1300 to 2300 UTC. Diurnal drizzle frequency is at a maximum in the early morning, in agreement with other studies. Drizzle occurs during a wide range of atmospheric conditions at the surface. Drizzle has occurred at sea level pressures below 960 hPa and above 1040 hPa. Most drizzle, however, occurs at higher than normal sea level pressure, with more than 64% occurring at a sea level pressure of 1015 hPa or higher. A third of all drizzle falls when the winds are from the northeast quadrant (360°–89°), suggesting that continental drizzle events tend to be found poleward of surface warm fronts and equatorward of cold-sector surface anticyclones. Two-thirds of all drizzle occurs with wind speeds of 2.0–6.9 m s−1, with 7.6% in calm wind and 5% at wind speeds ⩾ 10 m s−1. Most drizzle (61%) occurs with visibilities between 1.5 and 5.0 km, with only about 20% occurring at visibilities less than 1.5 km.

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 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.

scholarly journals Analysis of Atmospheric and Ionospheric Variations Due to Impacts of Super Typhoon Mangkhut (1822) in the Northwest Pacific Ocean

2021 ◽  
Vol 13 (4) ◽  
pp. 661
Author(s):  
Mohamed Freeshah ◽  
Xiaohong Zhang ◽  
Erman Şentürk ◽  
Muhammad Arqim Adil ◽  
B. G. Mousa ◽  
...  
Keyword(s):  
Wind Speed ◽  
Pacific Ocean ◽  
Tropical Cyclone ◽  
Sea Level ◽  
Northwest Pacific ◽  
Northwest Pacific Ocean ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Super Typhoon ◽  
The Northwest Pacific Ocean

The Northwest Pacific Ocean (NWP) is one of the most vulnerable regions that has been hit by typhoons. In September 2018, Mangkhut was the 22nd Tropical Cyclone (TC) over the NWP regions (so, the event was numbered as 1822). In this paper, we investigated the highest amplitude ionospheric variations, along with the atmospheric anomalies, such as the sea-level pressure, Mangkhut’s cloud system, and the meridional and zonal wind during the typhoon. Regional Ionosphere Maps (RIMs) were created through the Hong Kong Continuously Operating Reference Stations (HKCORS) and International GNSS Service (IGS) data around the area of Mangkhut typhoon. RIMs were utilized to analyze the ionospheric Total Electron Content (TEC) response over the maximum wind speed points (maximum spots) under the meticulous observations of the solar-terrestrial environment and geomagnetic storm indices. Ionospheric vertical TEC (VTEC) time sequences over the maximum spots are detected by three methods: interquartile range method (IQR), enhanced average difference (EAD), and range of ten days (RTD) during the super typhoon Mangkhut. The research findings indicated significant ionospheric variations over the maximum spots during this powerful tropical cyclone within a few hours before the extreme wind speed. Moreover, the ionosphere showed a positive response where the maximum VTEC amplitude variations coincided with the cyclone rainbands or typhoon edges rather than the center of the storm. The sea-level pressure tends to decrease around the typhoon periphery, and the highest ionospheric VTEC amplitude was observed when the low-pressure cell covers the largest area. The possible mechanism of the ionospheric response is based on strong convective cells that create the gravity waves over tropical cyclones. Moreover, the critical change state in the meridional wind happened on the same day of maximum ionospheric variations on the 256th day of the year (DOY 256). This comprehensive analysis suggests that the meridional winds and their resulting waves may contribute in one way or another to upper atmosphere-ionosphere coupling.

A reconstruction of Madras (Chennai) mean sea-level pressure using instrumental records from the late 18th and early 19th centuries

2002 ◽  
Vol 22 (9) ◽  
pp. 1119-1142 ◽  
Author(s):  
Rob J. Allan ◽  
Chris J. C. Reason ◽  
Penny Carroll ◽  
Phil D. Jones
Keyword(s):  
Sea Level ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Instrumental Records

Solar influence on North Atlantic mean sea level pressure

Nature ◽  
1977 ◽  
Vol 269 (5626) ◽  
pp. 320-322 ◽  
Author(s):  
P. M. KELLY
Keyword(s):  
Sea Level ◽  
North Atlantic ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Level Pressure ◽  
Solar Influence
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