Spectral Analysis of the Long-Term Oceanographic Time Series at Ocean Weather Station "P"

1976 ◽  
Vol 33 (10) ◽  
pp. 2203-2212
Author(s):  
C. K. Ross ◽  
G. T. Needler
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Potential Temperature ◽  
Height Anomaly ◽  
Dynamic Height ◽  
The North ◽  
Density Anomaly ◽  
Spectral Estimates ◽  
Order Of Magnitude

Oceanographic observations taken at Ocean Station "P" (50°N, 145°W) provide one of the few long oceanographic time series. The intermittent nature of the sampling program at Station "P," however, presents problems for a standard time-series analysis. In this paper the seriousness of this aspect of the data is discussed and spectral estimates are obtained for the potential temperature, potential density anomaly, and dynamic height anomaly at several depths. We found that the lowest frequency estimates of dynamic height anomaly are approximately an order of magnitude less than those obtained from a similar station in the North Atlantic. This is consistent with a more rapid falloff of energy with depth at Station "P".

scholarly journals Coupled decadal variability of the North Atlantic Oscillation, regional rainfall and karst spring discharges in the Campania region (southern Italy)

2012 ◽  
Vol 16 (5) ◽  
pp. 1389-1399 ◽  
Author(s):  
P. De Vita ◽  
V. Allocca ◽  
F. Manna ◽  
S. Fabbrocino
Keyword(s):  
Time Series ◽  
North Atlantic Oscillation ◽  
Air Temperature ◽  
North Atlantic ◽  
Karst Spring ◽  
The North ◽  
Nao Index ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. Thus far, studies on climate change have focused mainly on the variability of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this variability on the environment, especially with respect to the risks of desertification, droughts and floods. Conversely, the impacts of climate change on the recharge of aquifers and on the variability of groundwater flow have been less investigated, especially in Mediterranean karst areas whose water supply systems depend heavily upon groundwater exploitation. In this paper, long-term climatic variability and its influence on groundwater recharge were analysed by examining decadal patterns of precipitation, air temperature and spring discharges in the Campania region (southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, from 1921 to 2010, using 18 rain gauges and 9 air temperature stations with the most continuous functioning. The time series of the winter NAO index and of the discharges of 3 karst springs, selected from those feeding the major aqueducts systems, were collected for the same period. Regional normalised indexes of the precipitation, air temperature and karst spring discharges were calculated, and different methods were applied to analyse the related time series, including long-term trend analysis using smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes highlighted the existence of long-term complex periodicities, from 2 to more than 30 yr, with differences in average values of up to approximately ±30% for precipitation and karst spring discharges, which were both strongly correlated with the winter NAO index. Although the effects of the North Atlantic Oscillation (NAO) had already been demonstrated in the long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results of this study allow for the establishment of a link between a large-scale atmospheric cycle and the groundwater recharge of carbonate karst aquifers. Consequently, the winter NAO index could also be considered as a proxy to forecast the decadal variability of groundwater flow in Mediterranean karst areas.

scholarly journals Comparison of in situ time-series of temperature with gridded sea surface temperature datasets in the North Atlantic

2009 ◽  
Vol 66 (7) ◽  
pp. 1467-1479 ◽  
Author(s):  
Sarah L. Hughes ◽  
N. Penny Holliday ◽  
Eugene Colbourne ◽  
Vladimir Ozhigin ◽  
Hedinn Valdimarsson ◽  
...  
Keyword(s):  
Time Series ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North Atlantic ◽  
Sea Surface ◽  
The North ◽  
Spatial Coverage ◽  
The North Atlantic

Abstract Hughes, S. L., Holliday, N. P., Colbourne, E., Ozhigin, V., Valdimarsson, H., Østerhus, S., and Wiltshire, K. 2009. Comparison of in situ time-series of temperature with gridded sea surface temperature datasets in the North Atlantic. – ICES Journal of Marine Science, 66: 1467–1479. Analysis of the effects of climate variability and climate change on the marine ecosystem is difficult in regions where long-term observations of ocean temperature are sparse or unavailable. Gridded sea surface temperature (SST) products, based on a combination of satellite and in situ observations, can be used to examine variability and long-term trends because they provide better spatial coverage than the limited sets of long in situ time-series. SST data from three gridded products (Reynolds/NCEP OISST.v2., Reynolds ERSST.v3, and the Hadley Centre HadISST1) are compared with long time-series of in situ measurements from ICES standard sections in the North Atlantic and Nordic Seas. The variability and trends derived from the two data sources are examined, and the usefulness of the products as a proxy for subsurface conditions is discussed.

scholarly journals Coupled decadal variability of the North Atlantic Oscillation, regional rainfall and spring discharges in the Campania region (Southern Italy)

2011 ◽  
Vol 8 (6) ◽  
pp. 11233-11275
Author(s):  
P. De Vita ◽  
V. Allocca ◽  
F. Manna ◽  
S. Fabbrocino
Keyword(s):  
Time Series ◽  
Air Temperature ◽  
North Atlantic ◽  
Campania Region ◽  
The North ◽  
Nao Index ◽  
Groundwater Circulation ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract. Climate change is one of the issues most debated by the scientific community with a special focus to the combined effects of anthropogenic modifications of the atmosphere and the natural climatic cycles. Various scenarios have been formulated in order to forecast the global atmospheric circulation and consequently the variability of the global distribution of air temperature and rainfall. The effects of climate change have been analysed with respect to the risks of desertification, droughts and floods, remaining mainly limited to the atmospheric and surface components of the hydrologic cycle. Consequently the impact of the climate change on the recharge of regional aquifers and on the groundwater circulation is still a challenging topic especially in those areas whose aqueduct systems depend basically on springs or wells, such as the Campania region (Southern Italy). In order to analyse the long-term climatic variability and its influence on groundwater circulation, we analysed decadal patterns of precipitation, air temperature and spring discharges in the Campania region (Southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, in the period from 1921 to 2010, choosing 18 rain gauges and 9 air temperature stations among those with the most continuous functioning as well as arranged in a homogeneous spatial distribution. Moreover, for the same period, we gathered the time series of the winter NAO index (December to March mean) and of the discharges of the Sanità spring, belonging to an extended carbonate aquifer (Cervialto Mount) located in the central-eastern area of the Campania region, as well as of two other shorter time series of spring discharges. The hydrogeological features of this aquifer, its relevance due to the feeding of an important regional aqueduct system, as well as the unique availability of a long-lasting time series of spring discharges, allowed us to consider it as an ideal test site, representative of the other carbonate aquifers in the Campania region. The time series of regional normalised indexes of mean annual precipitation, mean annual air temperature and mean annual effective precipitation, as well as the time series of the normalised annual discharge index were calculated. Different methods were applied to analyse the time series: long-term trend analysis, through smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes has highlighted long-term complex periodicities, strongly correlated with the winter NAO index. Moreover, we also found robust correlations among precipitation indexes and the annual discharge index, as well as between the latter and the NAO index itself. Although the effects of the North Atlantic Oscillation had already been proved on long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results obtained appear original because they establish a link between a large-scale atmospheric cycle and the groundwater circulation of regional aquifers. Therefore, we demonstrated that the winter NAO index can be considered as an effective proxy to forecast the decadal variability of groundwater circulation in Mediterranean areas and in estimating critical scenarios for the feeding of aqueduct systems.

Consistency of Towing Speed and Sampling Depth for the Continuous Plankton Recorder

1993 ◽  
Vol 73 (4) ◽  
pp. 967-970 ◽  
Author(s):  
G. C. Hays ◽  
A. J. Warner
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
Data Sets ◽  
Sampling Depth ◽  
The North ◽  
The North Sea ◽  
The Mean ◽  
Towing Speed ◽  
Term Data

The mean annual towing speed of the Continuous Plankton Recorder (CPR) varied systematically between 1946 and 1991. By mounting a pressure transducer on the CPR to record towing depth, it was shown, however, that changes in towing speed did not cause a significant change in towing depth, although the mean towing depth (6–7 m, SD=l-7 m, N=77) was shallower than the previously assumed towing depth of 10 m. Thus the observed changes in towing speed are unlikely to have caused discontinuities in the CPR time-series by affecting sampling depth.Long-term data sets play an important role in attempts to understand the causes of fluctua- tions in plankton abundance. The Continuous Plankton Recorder (CPR) survey provides multi- decadal information on plankton abundance in the North Sea and North Atlantic (McGowan, 1990), and is one of the longest standing marine plankton abundance time-series. However, while the CPR time-series has great potential, as with all other data sets spanning many years, questions may be asked regarding the consistency with which the data have been collected and hence the true continuity of the time-series.

Granger Causality of Coupled Climate Processes: Ocean Feedback on the North Atlantic Oscillation

2006 ◽  
Vol 19 (7) ◽  
pp. 1182-1194 ◽  
Author(s):  
Timothy J. Mosedale ◽  
David B. Stephenson ◽  
Matthew Collins ◽  
Terence C. Mills
Keyword(s):  
Time Series ◽  
North Atlantic Oscillation ◽  
Granger Causality ◽  
North Atlantic ◽  
General Circulation ◽  
Careful Examination ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract This study uses a Granger causality time series modeling approach to quantitatively diagnose the feedback of daily sea surface temperatures (SSTs) on daily values of the North Atlantic Oscillation (NAO) as simulated by a realistic coupled general circulation model (GCM). Bivariate vector autoregressive time series models are carefully fitted to daily wintertime SST and NAO time series produced by a 50-yr simulation of the Third Hadley Centre Coupled Ocean–Atmosphere GCM (HadCM3). The approach demonstrates that there is a small yet statistically significant feedback of SSTs on the NAO. The SST tripole index is found to provide additional predictive information for the NAO than that available by using only past values of NAO—the SST tripole is Granger causal for the NAO. Careful examination of local SSTs reveals that much of this effect is due to the effect of SSTs in the region of the Gulf Steam, especially south of Cape Hatteras. The effect of SSTs on NAO is responsible for the slower-than-exponential decay in lag-autocorrelations of NAO notable at lags longer than 10 days. The persistence induced in daily NAO by SSTs causes long-term means of NAO to have more variance than expected from averaging NAO noise if there is no feedback of the ocean on the atmosphere. There are greater long-term trends in NAO than can be expected from aggregating just short-term atmospheric noise, and NAO is potentially predictable provided that future SSTs are known. For example, there is about 10%–30% more variance in seasonal wintertime means of NAO and almost 70% more variance in annual means of NAO due to SST effects than one would expect if NAO were a purely atmospheric process.

scholarly journals About the seasonal and fortnightly variabilities of the Mediterranean outflow

Ocean Science ◽  
2011 ◽  
Vol 7 (3) ◽  
pp. 421-428 ◽  
Author(s):  
C. Millot ◽  
J. Garcia-Lafuente
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Internal Tide ◽  
Atlantic Water ◽  
Strait Of Gibraltar ◽  
The North ◽  
Mediterranean Outflow ◽  
The Mediterranean

Abstract. CTD time series from the HYDRO-CHANGES programme and INGRES projects have been collected simultaneously (2004–2008) on the shelf of Morocco and at the sills of Camarinal and Espartel in the strait of Gibraltar. They provide information that supports results recently obtained from the analysis of the two former time series, as well as from a reanalysis of GIBEX CTD profiles (1985–1986). The outflow of Mediterranean Waters, which does not show a clear seasonal variability before entering the strait, strongly mixes within the strait, due mainly to the internal tide, with the seasonally variable inflow of Atlantic Water. The outflow thus gets marked seasonal and fortnightly variabilities within the strait. Furthermore, since the outflowing waters entering the strait display marked spatial heterogeneity and long-term temporal variabilities, accurately predicting the characteristics of the Mediterranean outflow into the North Atlantic Ocean appears almost impossible.

Preaching and Sermons

2017 ◽  
Author(s):  
Robert H. Ellison
Keyword(s):  
Eighteenth Century ◽  
North Atlantic ◽  
Religious Revival ◽  
Early Nineteenth Century ◽  
Denominational Identity ◽  
The North ◽  
The North Atlantic ◽  
The One ◽  
The Impact

Prompted by the convulsions of the late eighteenth century and inspired by the expansion of evangelicalism across the North Atlantic world, Protestant Dissenters from the 1790s eagerly subscribed to a millennial vision of a world transformed through missionary activism and religious revival. Voluntary societies proliferated in the early nineteenth century to spread the gospel and transform society at home and overseas. In doing so, they engaged many thousands of converts who felt the call to share their experience of personal conversion with others. Though social respectability and business methods became a notable feature of Victorian Nonconformity, the religious populism of the earlier period did not disappear and religious revival remained a key component of Dissenting experience. The impact of this revitalization was mixed. On the one hand, growth was not sustained in the long term and, to some extent, involvement in interdenominational activity undermined denominational identity; on the other hand, Nonconformists gained a social and political prominence they had not enjoyed since the middle of the seventeenth century and their efforts laid the basis for the twentieth-century explosion of evangelicalism in Africa, Asia, and South America.

scholarly journals A Regime View of the North Atlantic Oscillation and Its Response to Anthropogenic Forcing

2010 ◽  
Vol 23 (6) ◽  
pp. 1291-1307 ◽  
Author(s):  
Tim Woollings ◽  
Abdel Hannachi ◽  
Brian Hoskins ◽  
Andrew Turner
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Anthropogenic Forcing ◽  
The Third ◽  
The North ◽  
Nao Index ◽  
Future Behavior ◽  
Real Change ◽  
The North Atlantic Oscillation

Abstract The distribution of the daily wintertime North Atlantic Oscillation (NAO) index in the 40-yr ECMWF Re-Analysis (ERA-40) is significantly negatively skewed. Dynamical and statistical analyses both suggest that this skewness reflects the presence of two distinct regimes—referred to as “Greenland blocking” and “subpolar jet.” Changes in both the relative occurrence and in the structure of the regimes are shown to contribute to the long-term NAO trend over the ERA-40 period. This is contrasted with the simulation of the NAO in 100-yr control and doubled CO2 integrations of the third climate configuration of the Met Office Unified Model (HadCM3). The model has clear deficiencies in its simulation of the NAO in the control run, so its predictions of future behavior must be treated with caution. However, the subpolar jet regime does become more dominant under anthropogenic forcing and, while this change is small it is clearly statistically significant and does represent a real change in the nature of NAO variability in the model.

Planetary Wave Breaking and Tropospheric Forcing as Seen in the Stratospheric Sudden Warming of 2006

2009 ◽  
Vol 66 (2) ◽  
pp. 495-507 ◽  
Author(s):  
Lawrence Coy ◽  
Stephen Eckermann ◽  
Karl Hoppel
Keyword(s):  
North Atlantic ◽  
Wave Breaking ◽  
Potential Temperature ◽  
Polar Vortex ◽  
Stratospheric Polar Vortex ◽  
Stratospheric Sudden Warming ◽  
Advanced Level ◽  
Earth Observing System ◽  
The North ◽  
Temperature Surface

Abstract The major stratospheric sudden warming (SSW) of January 2006 is examined using meteorological fields from Goddard Earth Observing System version 4 (GEOS-4) analyses and forecast fields from the Navy Operational Global Atmospheric Prediction System–Advanced Level Physics, High Altitude (NOGAPS-ALPHA). The study focuses on the upper tropospheric forcing that led to the major SSW and the vertical structure of the subtropic wave breaking near 10 hPa that moved low tropical values of potential vorticity (PV) to the pole. Results show that an eastward-propagating upper tropospheric ridge over the North Atlantic with its associated cold temperature perturbations (as manifested by high 360-K potential temperature surface perturbations) and large positive local values of meridional heat flux directly forced a change in the stratospheric polar vortex, leading to the stratospheric subtropical wave breaking and warming. Results also show that the anticyclonic development, initiated by the subtropical wave breaking and associated with the poleward advection of the low PV values, occurred over a limited altitude range of approximately 6–10 km. The authors also show that the poleward advection of this localized low-PV anomaly was associated with changes in the Eliassen–Palm (EP) flux from equatorward to poleward, suggesting an important role for Rossby wave reflection in the SSW of January 2006. Similar upper tropospheric forcing and subtropical wave breaking were found to occur prior to the major SSW of January 2003.

Meridional Tripole Mode of Winter Precipitation over the Arctic and Continental North Africa–Eurasia

2021 ◽  
pp. 1
Author(s):  
Xiaolin Liu ◽  
Jianhua Lu ◽  
Yimin Liu ◽  
Guoxiong Wu
Keyword(s):  
Time Series ◽  
North Africa ◽  
North Atlantic ◽  
Hadley Cell ◽  
The Arctic ◽  
Positive Phase ◽  
The North ◽  
Ferrel Cell ◽  
The North Atlantic ◽  
Westerly Jets

AbstractWintertime precipitation is vital to the growth of glaciers in the northern hemisphere. We find a tripole mode of precipitation (PTM), with each pole of the mode extending zonally over the eastern hemisphere roughly between 30°W and 120°E, and the positive/negative/positive structure for its positive phase extending meridionally from the Arctic to the continental North Africa–Eurasia. The large-scale dynamics associated with the PTM is explored. The positive phase of the PTM is associated with the negative while eastward-shifted phase of the North Atlantic Oscillation (NAO) and a zonal band of positive SST anomaly in the tropics, together with a narrowed Hadley cell and weakened Ferrel cell. While being north-eastward tilted and separated from their North Africa-Eurasia counterpart in the climatological mean, the upper-tropospheric westerly jets over the east Pacific and north Atlantic become extending zonally and shifting southward and hence form a circumpolar subtropical jet as a whole by connecting with the westerly jets over the North Africa-Eurasia. The enhanced zonal winds over the north Atlantic promote more synoptic-scale transient eddies which are waveguided by the jet streams. The polar vortex weakens and cold air dips southward from the North Pole. Further diagnosis of the E-vectors suggests that transient eddies have a positive feedback on the weakening of Ferrel cell. Opposite features are associated with the negative phase of the PTM. The reconstructed time series using multiple linear regression on the NAO index and the tropical SST averaged over 20°S– 20°N, can explain 62.4% of the variance of the original the original precipitation time series.

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