Long-Term Wind Speed Trends over Australia

2012 ◽  
Vol 25 (1) ◽  
pp. 170-183 ◽  
Author(s):  
Alberto Troccoli ◽  
Karl Muller ◽  
Peter Coppin ◽  
Robert Davy ◽  
Chris Russell ◽  
...  
Keyword(s):  
Wind Speed ◽  
Atmospheric Circulation ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Long Period ◽  
The Mean ◽  
Strong Winds ◽  
Circulation Changes ◽  
Linear Trends

Abstract Accurate estimates of long-term linear trends of wind speed provide a useful indicator for circulation changes in the atmosphere and are invaluable for the planning and financing of sectors such as wind energy. Here a large number of wind observations over Australia and reanalysis products are analyzed to compute such trends. After a thorough quality control of the observations, it is found that the wind speed trends for 1975–2006 and 1989–2006 over Australia are sensitive to the height of the station: they are largely negative for the 2-m data but are predominantly positive for the 10-m data. The mean relative trend at 2 m is −0.10 ± 0.03% yr−1 (−0.36 ± 0.04% yr−1) for the 1975–2006 (1989–2006) period, whereas at 10 m it is 0.90 ± 0.03% yr−1 (0.69 ± 0.04% yr−1) for the 1975–2006 (1989–2006) period. Also, at 10 m light winds tend to increase more rapidly than the mean winds, whereas strong winds increase less rapidly than the mean winds; at 2 m the trends in both light and strong winds vary in line with the mean winds. It was found that a qualitative link could be established between the observed features in the linear trends and some atmospheric circulation indicators (mean sea level pressure, wind speed at 850 hPa, and geopotential at 850 hPa), particularly for the 10-m observations. Further, the magnitude of the trend is also sensitive to the period selected, being closer to zero when a very long period, 1948–2006, is considered. As a consequence, changes in the atmospheric circulation on climatic time scales appear unlikely.

scholarly journals Anomalies of Central England Temperature Classified by Air Source

2009 ◽  
Vol 22 (5) ◽  
pp. 1069-1081 ◽  
Author(s):  
David E. Parker
Keyword(s):  
Atmospheric Circulation ◽  
Late Nineteenth Century ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Source Regions ◽  
Central England Temperature ◽  
Long Term Changes ◽  
Late Nineteenth ◽  
Circulation Changes

Abstract Daily anomalies of mean central England temperature (CET), relative to daily 1961–90 climatology, are analyzed in terms of the source of the air estimated from fields of mean sea level pressure. The average CET anomaly for a given source and calendar month during 1961–90 is taken as an estimate of the influence of atmospheric circulation for that source and calendar month, and the uncertainty in this influence is provided by the associated standard error. The atmospheric circulation influences are subtracted from the daily CET anomalies since the late nineteenth century to yield “residual anomalies,” which represent the influence of forcings other than atmospheric circulation. The use of air sources captures more circulation-related daily CET variance than the airflow indices used in previous studies. The warming in central England since the 1970s is not predominantly a result of atmospheric circulation changes, and the long-term changes of CET for air from major source regions are on the whole very similar to each other and to the overall long-term changes.

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 North-south asynchrony and long-term variations of sunspot latitudes

2008 ◽  
Vol 4 (S259) ◽  
pp. 237-238 ◽  
Author(s):  
Nadezhda V. Zolotova ◽  
D. I. Ponyavin
Keyword(s):  
Sunspot Area ◽  
Magnetic Equator ◽  
Phase Component ◽  
Long Period ◽  
The North ◽  
Sign Change ◽  
The Mean ◽  
South Asymmetry ◽  
Northern And Southern Hemispheres

AbstractThe long-term records of sunspot area available separately for Northern and Southern Hemispheres have been investigated by means of cross-recurrence technique. Phase component of the north-south asymmetry was extracted. This measure demonstrates long-period systematic variations with the sign change of hemispheric leading in 1930s and 1960s. Moreover phase north-south asynchrony anticorrelates with the so called magnetic equator, which was defined as difference of the mean sunspot latitudes between two hemispheres. Relationships of the phase north-south asynchrony, magnetic equator and butterfly diagrams are presented and discussed.

scholarly journals Celebrating 80 years of the Permanent Service for Mean Sea Level (PSMSL)

2015 ◽  
Vol 365 ◽  
pp. 1-5
Author(s):  
L. Rickards ◽  
A. Matthwes ◽  
K. Gordon ◽  
M. Tamisea ◽  
S. Jevrejeva ◽  
...  
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Tide Gauge Records ◽  
International Union ◽  
Mean Sea Level ◽  
Level Change ◽  
The Mean ◽  
Set Up ◽  
The 19Th Century

Abstract. The PSMSL was established as a “Permanent Service” of the International Council for Science in 1958, but in practice was a continuation of the Mean Sea Level Committee which had been set up at the Lisbon International Union of Geodesy and Geophysics (IUGG) conference in 1933. Now in its 80th year, the PSMSL continues to be the internationally recognised databank for long-term sea level change information from tide gauge records. The PSMSL dataset consists of over 2100 mean sea level records from across the globe, the longest of which date back to the start of the 19th century. Where possible, all data in a series are provided to a common benchmark-controlled datum, thus providing a record suitable for use in time series analysis. The PSMSL dataset is freely available for all to use, and is accessible through the PSMSL website (www.psmsl.org).

scholarly journals Reconstructing Late Holocene North Atlantic atmospheric circulation changes using functional paleoclimate networks

2017 ◽  
Vol 13 (11) ◽  
pp. 1593-1608 ◽  
Author(s):  
Jasper G. Franke ◽  
Johannes P. Werner ◽  
Reik V. Donner
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Late Holocene ◽  
Dominant Mode ◽  
The North ◽  
The North Atlantic ◽  
Earth’S Climate ◽  
The North Atlantic Oscillation ◽  
Circulation Changes

Abstract. Obtaining reliable reconstructions of long-term atmospheric circulation changes in the North Atlantic region presents a persistent challenge to contemporary paleoclimate research, which has been addressed by a multitude of recent studies. In order to contribute a novel methodological aspect to this active field, we apply here evolving functional network analysis, a recently developed tool for studying temporal changes of the spatial co-variability structure of the Earth's climate system, to a set of Late Holocene paleoclimate proxy records covering the last two millennia. The emerging patterns obtained by our analysis are related to long-term changes in the dominant mode of atmospheric circulation in the region, the North Atlantic Oscillation (NAO). By comparing the time-dependent inter-regional linkage structures of the obtained functional paleoclimate network representations to a recent multi-centennial NAO reconstruction, we identify co-variability between southern Greenland, Svalbard, and Fennoscandia as being indicative of a positive NAO phase, while connections from Greenland and Fennoscandia to central Europe are more pronounced during negative NAO phases. By drawing upon this correspondence, we use some key parameters of the evolving network structure to obtain a qualitative reconstruction of the NAO long-term variability over the entire Common Era (last 2000 years) using a linear regression model trained upon the existing shorter reconstruction.

scholarly journals Chlorophyll in the Eastern Mediterranean Sea: Correlations with Environmental Factors and Trends

Environments ◽  
2019 ◽  
Vol 6 (8) ◽  
pp. 98 ◽  
Author(s):  
Dionysia Kotta ◽  
Dimitra Kitsiou
Keyword(s):  
Wind Speed ◽  
Environmental Factors ◽  
Surface Temperature ◽  
Mediterranean Sea ◽  
Sea Level ◽  
Eastern Mediterranean ◽  
Sea Surface ◽  
Sea Level Pressure ◽  
Eastern Mediterranean Sea ◽  
Mean Sea Level

The research on marine chlorophyll concentrations, as indicators of phytoplankton abundance, their relations with environmental parameters, and their trends is of global interest. It is also crucial when referring to oligotrophic environments where maintenance or increase in primary production is vital. The present study focuses on the Eastern Mediterranean Sea that is in general oligotrophic. Its primary goal is to explore possible relations between surface chlorophyll-a concentrations and environmental factors. The involved parameters are the sea surface temperature, the wind speed, the wave height, the precipitation, and the mean sea level pressure; their relation with chlorophyll is assessed through the calculation of the relevant correlation coefficients, based on monthly satellite-derived and numerical model data for the period 1998–2016. The results show that chlorophyll relates inversely with sea surface temperature; in general positively with wind speed and wave height; positively, although weaker, with precipitation; and negatively, but area and season limited, with mean sea level pressure. These correlations are stronger over the open southern part of the study area and strongly dependent on the season. A secondary aim of the study is the estimation of chlorophyll trends for the same time interval, which is performed separately for the low and the high production periods. The statistically significant results reveal only increasing local chlorophyll trends that, for each period, mainly characterize the eastern and the western part of the area, respectively.

scholarly journals On the Long-Period Variations in the Rate of the Earth's Rotation

1979 ◽  
Vol 82 ◽  
pp. 59-60
Author(s):  
A. I. Emetz ◽  
A. A. Korsun'
Keyword(s):  
Power Spectrum ◽  
Maximum Entropy ◽  
Rotational Speed ◽  
Monthly Data ◽  
Long Period ◽  
Period Variations ◽  
Similar Series ◽  
The Mean ◽  
Using Data ◽  
Linear Trends

The maximum entropy power spectrum (Smylie, et al., 1974) of the Earth's rotational speed was calculated using data from 1900 to 1976. Two series of data were analyzed. The first was a series of δω/ω) determined from annual UT1 - ET data from 1900 to 1976. The second was a similar series derived from the mean monthly data of UT1 - TAI. Linear trends were removed from both series before analysis. Using the second series of data, significant periods of 2.8, 3.7, 7.0, and 10.5 years were found. The first series showed significant periods at 6, 10, 13, 22, and 57 years. Of these periodicities those at 22 and 57 years showed the largest amplitudes (0.454 ± 0.097 × 10−8 and 1.431 ± 0.104 × 10−8 respectively).

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