scholarly journals Observation-Based Estimates of Global and Basin Ocean Meridional Heat Transport Time Series

2019 ◽  
Vol 32 (14) ◽  
pp. 4567-4583 ◽  
Author(s):  
Kevin E. Trenberth ◽  
Yongxin Zhang ◽  
John T. Fasullo ◽  
Lijing Cheng
Keyword(s):  
Time Series ◽  
Interannual Variability ◽  
Annual Cycle ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Heat Content ◽  
Ocean Basin ◽  
Energy Budgets ◽  
Meridional Heat Transport ◽  
The Mean

Abstract Ocean meridional heat transports (MHTs) are deduced as a residual using energy budgets to produce latitude versus time series for the globe, Indo-Pacific, and Atlantic. The top-of-atmosphere (TOA) radiation is combined with the vertically integrated atmospheric energy divergence from atmospheric reanalyses to produce the net surface energy fluxes everywhere. The latter is then combined with estimates of the vertically integrated ocean heat content (OHC) tendency to produce estimates of the ocean heat divergence. Because seasonal sea ice and land runoff effects are not fully considered, the mean annual cycle is incomplete, but those effects are small for interannual variability. However, there is a mismatch between 12-month inferred surface flux and the corresponding OHC changes globally, requiring adjustments to account for the Earth’s global energy imbalance. Estimates are greatly improved by building in the constraint that MHT must go to zero at the northern and southern extents of the ocean basin at all times, enabling biases between the TOA and OHC data to be reconciled. Zonal mean global, Indo-Pacific, and Atlantic basin ocean MHTs are computed and presented as 12-month running means and for the mean annual cycle for 2000–16. For the Indo-Pacific, the tropical and subtropical MHTs feature a strong relationship with El Niño–Southern Oscillation (ENSO), and in the Atlantic, MHT interannual variability is significantly affected by and likely influences the North Atlantic Oscillation (NAO). However, Atlantic and Pacific changes are linked, suggesting that the northern annular mode (as opposed to NAO) is predominant. There is also evidence of decadal variability or trends.

HHT ANALYSIS OF THE GLOBAL AVERAGE MONTHLY PRECIPITATION DATA

2012 ◽  
Vol 04 (03) ◽  
pp. 1250018 ◽  
Author(s):  
SAMUEL S. P. SHEN ◽  
DAVID NEW ◽  
THOMAS M. SMITH ◽  
PHILLIP A. ARKIN
Keyword(s):  
Time Series ◽  
Annual Cycle ◽  
Climate Models ◽  
Southern Oscillation ◽  
Frequency Variation ◽  
Frequency Change ◽  
Monthly Precipitation ◽  
Precipitation Time Series ◽  
Time Frequency ◽  
The Mean

This paper uses the Hilbert–Huang transform (HHT) method to make time–frequency diagnostic analyses of four monthly time series of the global precipitation: MERG (1900–2008), REOF (1900–2008), GPCP (1979–2009), and CMAP (1979–2009). All these data are the global land and ocean average of precipitation anomalies with respect to the mean of the entire data period. The MERG and REOF are spectral reconstructions based on historical data. The GPCP and CMAP are based on station gauge data and satellite remote sensing data. We have made the following analysis of the four datasets: (a) extract intrinsic mode functions (IMF) by HHT empirical model decomposition (EMD) sifting, (b) calculate the mean frequency and energy of each IMF, (c) calculate the Fourier spectra to compare with the IMF spectral properties, (d) calculate the Hilbert spectra and display the time–frequency variation of the precipitation time series, and (e) calculate the basic statistics of the four datasets, including mean, standard deviation, skewness, kurtosis and inter-correlation among the datasets. Our analysis results indicate the following: (i) IMFs may contain physical signals of MJO (Madden–Julian oscillation), monsoon, annual cycle, and ENSO (El Nino southern oscillation), (ii) Hilbert spectra appears to be an effective tool to display the time-frequency change of a precipitation time series and can help identify critical characteristics for improving data aggregation method and climate models, (iii) among the four datasets, MERG is the smoothest data and has the smallest variance and hence the smallest IMF energies, while the CMAP has the largest, followed by GPCP and REOF, and (iv) the nonlinear and nonstationary annual cycle is the IMF3 for all the four datasets, which is modulated by ENSO signals.

scholarly journals Origin of interannual variability in global mean sea level

2020 ◽  
Vol 117 (25) ◽  
pp. 13983-13990
Author(s):  
Benjamin D. Hamlington ◽  
Christopher G. Piecuch ◽  
John T. Reager ◽  
Hrishi Chandanpurkar ◽  
Thomas Frederikse ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Sea Level ◽  
Decadal Variability ◽  
Hydrological Cycle ◽  
Southern Oscillation ◽  
Heat Content ◽  
Scaling Analysis ◽  
Mean Sea Level ◽  
Global Mean Sea Level ◽  
Global Mean

The two dominant drivers of the global mean sea level (GMSL) variability at interannual timescales are steric changes due to changes in ocean heat content and barystatic changes due to the exchange of water mass between land and ocean. With Gravity Recovery and Climate Experiment (GRACE) satellites and Argo profiling floats, it has been possible to measure the relative steric and barystatic contributions to GMSL since 2004. While efforts to “close the GMSL budget” with satellite altimetry and other observing systems have been largely successful with regards to trends, the short time period covered by these records prohibits a full understanding of the drivers of interannual to decadal variability in GMSL. One particular area of focus is the link between variations in the El Niño−Southern Oscillation (ENSO) and GMSL. Recent literature disagrees on the relative importance of steric and barystatic contributions to interannual to decadal variability in GMSL. Here, we use a multivariate data analysis technique to estimate variability in barystatic and steric contributions to GMSL back to 1982. These independent estimates explain most of the observed interannual variability in satellite altimeter-measured GMSL. Both processes, which are highly correlated with ENSO variations, contribute about equally to observed interannual GMSL variability. A theoretical scaling analysis corroborates the observational results. The improved understanding of the origins of interannual variability in GMSL has important implications for our understanding of long-term trends in sea level, the hydrological cycle, and the planet’s radiation imbalance.

scholarly journals Stratospheric ozone interannual variability (1995–2011) as observed by Lidar and Satellite at Mauna Loa Observatory, HI and Table Mountain Facility, CA

2012 ◽  
Vol 12 (11) ◽  
pp. 30825-30867
Author(s):  
G. Kirgis ◽  
T. Leblanc ◽  
I. S. McDermid ◽  
T. D. Walsh
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Stratospheric Ozone ◽  
Montreal Protocol ◽  
Quasi Biennial Oscillation ◽  
Mauna Loa ◽  
Table Mountain ◽  
Biennial Oscillation

Abstract. The Jet Propulsion Laboratory (JPL) lidars, at the Mauna Loa Observatory, Hawaii (MLO, 19.5° N, 155.6° W) and the JPL Table Mountain Facility (TMF, California, 34.5° N, 117.7° W), have been measuring vertical profiles of stratospheric ozone routinely since the early 1990's and late-1980s respectively. Interannual variability of ozone above these two sites was investigated using a multi-linear regression analysis on the deseasonalized monthly mean lidar and satellite time-series at 1 km intervals between 20 and 45 km from January 1995 to April 2011, a period of low volcanic aerosol loading. Explanatory variables representing the 11-yr solar cycle, the El Niño Southern Oscillation, the Quasi-Biennial Oscillation, the Eliassen–Palm flux, and horizontal and vertical transport were used. A new proxy, the mid-latitude ozone depleting gas index, which shows a decrease with time as an outcome of the Montreal Protocol, was introduced and compared to the more commonly used linear trend method. The analysis also compares the lidar time-series and a merged time-series obtained from the space-borne stratospheric aerosol and gas experiment II, halogen occultation experiment, and Aura-microwave limb sounder instruments. The results from both lidar and satellite measurements are consistent with recent model simulations which propose changes in tropical upwelling. Additionally, at TMF the ozone depleting gas index explains as much variance as the Quasi-Biennial Oscillation in the upper stratosphere. Over the past 17 yr a diminishing downward trend in ozone was observed before 2000 and a net increase, and sign of ozone recovery, is observed after 2005. Our results which include dynamical proxies suggest possible coupling between horizontal transport and the 11-yr solar cycle response, although a dataset spanning a period longer than one solar cycle is needed to confirm this result.

The Annual Cycle of the Energy Budget. Part I: Global Mean and Land–Ocean Exchanges

2008 ◽  
Vol 21 (10) ◽  
pp. 2297-2312 ◽  
Author(s):  
John T. Fasullo ◽  
Kevin E. Trenberth
Keyword(s):  
Energy Budget ◽  
Annual Cycle ◽  
Radiant Energy ◽  
Heat Content ◽  
Ocean Heat Content ◽  
Radiation Budget ◽  
Global Ocean ◽  
Net Radiation ◽  
Community Land Model ◽  
The Mean

Abstract The mean and annual cycle of energy flowing into the climate system and its storage, release, and transport in the atmosphere, ocean, and land surface are estimated with recent observations. An emphasis is placed on establishing internally consistent quantitative estimates with discussion and assessment of uncertainty. At the top of the atmosphere (TOA), adjusted radiances from the Earth Radiation Budget Experiment (ERBE) and Clouds and the Earth’s Radiant Energy System (CERES) are used, while in the atmosphere the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis and 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) estimates are used. The net upward surface flux (FS) over ocean is derived as the residual of the TOA and atmospheric energy budgets, and is compared with direct calculations of ocean heat content (OE) and its tendency (δOE/δt) from several ocean temperature datasets. Over land, FS from a stand-alone simulation of the Community Land Model forced by observed fields is used. A depiction of the full energy budget based on ERBE fluxes from 1985 to 1989 and CERES fluxes from 2000 to 2004 is constructed that matches estimates of the global, global ocean, and global land imbalances. In addition, the annual cycle of the energy budget during both periods is examined and compared with ocean heat content changes. The near balance between the net TOA radiation (RT) and FS over ocean and thus with OE, and between RT and atmospheric total energy divergence over land, are documented both in the mean and for the annual cycle. However, there is an annual mean transport of energy by the atmosphere from ocean to land regions of 2.2 ± 0.1 PW (1 PW = 1015 W) primarily in the northern winter when the transport exceeds 5 PW. The global albedo is dominated by a semiannual cycle over the oceans, but combines with the large annual cycle in solar insolation to produce a peak in absorbed solar and net radiation in February, somewhat after the perihelion, and with the net radiation 4.3 PW higher than the annual mean, as it is enhanced by the annual cycle of outgoing longwave radiation that is dominated by land regions. In situ estimates of the annual variation of OE are found to be unrealistically large. Challenges in diagnosing the interannual variability in the energy budget and its relationship to climate change are identified in the context of the episodic and inconsistent nature of the observations.

scholarly journals Characteristics of tropopause parameters as observed with GPS radio occultation

2014 ◽  
Vol 7 (11) ◽  
pp. 3947-3958 ◽  
Author(s):  
T. Rieckh ◽  
B. Scherllin-Pirscher ◽  
F. Ladstädter ◽  
U. Foelsche
Keyword(s):  
Annual Cycle ◽  
Radio Occultation ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Lapse Rate ◽  
Quasi Biennial Oscillation ◽  
Gps Radio Occultation ◽  
Statistical Measures ◽  
The Mean ◽  
Individual Profiles

Abstract. Characteristics of the lapse rate tropopause are analyzed globally for tropopause altitude and temperature using global positioning system (GPS) radio occultation (RO) data from late 2001 to the end of 2013. RO profiles feature high vertical resolution and excellent quality in the upper troposphere and lower stratosphere, which are key factors for tropopause determination, including multiple ones. RO data provide measurements globally and allow examination of both temporal and spatial tropopause characteristics based entirely on observational measurements. To investigate latitudinal and longitudinal tropopause characteristics, the mean annual cycle, and inter-annual variability, we use tropopauses from individual profiles as well as their statistical measures for zonal bands and 5° × 10° bins. The latitudinal structure of first tropopauses shows the well-known distribution with high (cold) tropical tropopauses and low (warm) extra-tropical tropopauses. In the transition zones (20 to 40° N/S), individual profiles reveal varying tropopause altitudes from less than 7 km to more than 17 km due to variability in the subtropical tropopause break. In this region, we also find multiple tropopauses throughout the year. Longitudinal variability is strongest at northern hemispheric mid latitudes and in the Asian monsoon region. The mean annual cycle features changes in amplitude and phase, depending on latitude. This is caused by different underlying physical processes (such as the Brewer–Dobson circulation – BDC) and atmospheric dynamics (such as the strong polar vortex in the southern hemispheric winter). Inter-annual anomalies of tropopause parameters show signatures of El Niño–Southern Oscillation (ENSO), the quasi–biennial oscillation (QBO), and the varying strength of the polar vortex, including sudden stratospheric warming (SSW) events. These results are in good agreement with previous studies and underpin the high utility of the entire RO record for investigating latitudinal, longitudinal, and temporal tropopause characteristics globally.

scholarly journals The mean state and variability of the North Atlantic circulation: a perspective from ocean reanalyses

2020 ◽  
Author(s):  
Laura Jackson ◽  
Clotilde Dubois ◽  
Gael Forget ◽  
Keith Haines ◽  
Matt Harrison ◽  
...  
Keyword(s):  
North Atlantic ◽  
Decadal Variability ◽  
Heat Content ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
The North ◽  
Ocean Reanalyses ◽  
The Mean ◽  
The North Atlantic ◽  
Mean State

<p>The observational network around the North Atlantic has improved significantly over the last few decades with the advent of Argo and satellite observations, and the more recent efforts to monitor the Atlantic Meridional Overturning Circulation (AMOC) using arrays such as RAPID and OSNAP. These have shown decadal timescale changes across the North Atlantic including in heat content, heat transport and the circulation. </p><p>However there are still significant gaps in the observational coverage, and significant uncertainties around some observational products. Ocean reanalyses integrate the observations with a dynamically consistent ocean model and are potentially tools that can be used to understand the observed changes. However the suitability of the reanalyses for the task must also be assessed.<br>We use an ensemble of global ocean reanalyses in comparison with observations in order to examine the mean state and interannual-decadal variability of the North Atlantic ocean since 1993. We assess how well the reanalyses are able to capture different processes and whether any understanding can be inferred. In particular we look at ocean heat content, transports, the AMOC and gyre strengths, water masses and convection. </p><p> </p>

scholarly journals A Comparison of the Variability and Changes in Global Ocean Heat Content from Multiple Objective Analysis Products During the Argo Period

2021 ◽  
pp. 1-47
Author(s):  
Xinfeng Liang ◽  
Chao Liu ◽  
Rui M. Ponte ◽  
Don P. Chambers
Keyword(s):  
Southern Ocean ◽  
Interannual Variability ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Heat Content ◽  
Global Scale ◽  
Ocean Heat Content ◽  
Objective Analysis ◽  
Global Ocean ◽  
Ocean Measurements

AbstractOcean heat content (OHC) is key to estimating the energy imbalance of the earth system. Over the past two decades, an increasing number of OHC studies were conducted using oceanic objective analysis (OA) products. Here we perform an intercomparison of OHC from eight OA products with a focus on their robust features and significant differences over the Argo period (2005-2019), when the most reliable global scale oceanic measurements are available. For the global ocean, robust warming in the upper 2000 m is confirmed. The 0-300 m layer shows the highest warming rate but is heavily modulated by interannual variability, particularly the El Niño–Southern Oscillation. The 300-700 m and 700-2000 m layers, on the other hand, show unabated warming. Regionally, the Southern Ocean and mid-latitude North Atlantic show a substantial OHC increase, and the subpolar North Atlantic displays an OHC decrease. A few apparent differences in OHC among the examined OA products were identified. In particular, temporal means of a few OA products that incorporated other ocean measurements besides Argo show a global-scale cooling difference, which is likely related to the baseline climatology fields used to generate those products. Large differences also appear in the interannual variability in the Southern Ocean and in the long-term trends in the subpolar North Atlantic. These differences remind us of the possibility of product-dependent conclusions on OHC variations. Caution is therefore warranted when using merely one OA product to conduct OHC studies, particularly in regions and on timescales that display significant differences.

scholarly journals Comparison of GTO-ECV and adjusted MERRA-2 total ozone columns from the last 2 decades and assessment of interannual variability

2020 ◽  
Vol 13 (3) ◽  
pp. 1633-1654
Author(s):  
Melanie Coldewey-Egbers ◽  
Diego G. Loyola ◽  
Gordon Labow ◽  
Stacey M. Frith
Keyword(s):  
Interannual Variability ◽  
Total Ozone ◽  
Southern Oscillation ◽  
Mean Difference ◽  
Tropical Region ◽  
Ozone Monitoring Instrument ◽  
Spatial And Temporal Patterns ◽  
Quasi Biennial Oscillation ◽  
The Mean ◽  
Ozone Monitoring

Abstract. In this study we compare the satellite-based Global Ozone Monitoring Experiment (GOME)-type Total Ozone Essential Climate Variable (GTO-ECV) record, generated as part of the European Space Agency's Climate Change Initiative (ESA-CCI) ozone project, with the adjusted total ozone product from the Modern Era Retrospective Analysis for Research and Applications version 2 (adjusted MERRA-2) reanalysis, produced at the National Aeronautics and Space Administration (NASA) Global Modeling and Assimilation Office (GMAO). Total ozone columns and associated standard deviations show a very good agreement in terms of both spatial and temporal patterns during their 23-year overlap period from July 1995 to December 2018. The mean difference between adjusted MERRA-2 and GTO-ECV 5∘×5∘ monthly mean total ozone columns is -0.9±1.5 %. A small discontinuity in the deviations is detected in October 2004, when data from the Ozone Monitoring Instrument (OMI) were ingested in the GTO-ECV and adjusted MERRA-2 data records. This induces a small overall negative drift in the differences for almost all latitude bands, which, however, does not exceed 1 % per decade. The mean difference for the period prior to October 2004 is -0.5±1.7 %, whereas the difference is -1.0±1.1 % for the period from October 2004 to December 2018. The variability in the differences is considerably reduced in the period after 2004 due to a significant increase in data coverage and sampling. In the tropical region, the differences indicate a slight zonal variability with negative deviations over the Atlantic, Africa, and the Indian Ocean and positive deviations over the Pacific. Ozone anomalies and the distribution of their statistical moments indicate a very high correlation among both data records as to the temporal and spatial structures. Furthermore, we evaluate the consistency of the data sets by means of an empirical orthogonal function (EOF) analysis. The interannual variability is assessed in the tropics, and both GTO-ECV and adjusted MERRA-2 exhibit a remarkable agreement with respect to the derived patterns. The first four EOFs can be attributed to different modes of interannual climate variability, and correlations with the Quasi-Biennial Oscillation (QBO), the El Niño–Southern Oscillation (ENSO) signal, and the solar cycle were found.

On the Interannual Variability of the Indonesian Throughflow and Its Linkage with ENSO

2005 ◽  
Vol 18 (9) ◽  
pp. 1435-1444 ◽  
Author(s):  
Matthew H. England ◽  
Fei Huang
Keyword(s):  
Interannual Variability ◽  
Heat Transport ◽  
Ocean Circulation ◽  
Large Scale ◽  
Southern Oscillation ◽  
Heat Content ◽  
Global Ocean ◽  
Enso Cycle ◽  
Indonesian Throughflow ◽  
Tropical Ocean

Abstract The Indonesian Throughflow (ITF) variability is assessed using a retrospective analysis of the global ocean based on the Simple Ocean Data Assimilation (SODA) experiment spanning the period 1950–99. A comparison between the 1983–95 observed ITF, and the simulated ITF suggests a reasonably accurate reconstruction of ocean circulation in the vicinity of the ITF during the available measurement record. A wavelet analysis shows that once the seasonal cycle is removed, the dominant variation of the ITF anomaly is an interannual oscillation with a period of about 4–7 yr. This interannual variability is significantly correlated with the El Niño–Southern Oscillation (ENSO) pattern, with the ITF lagging the ENSO cycle by 8–9 months. This suggests that large-scale tropical ocean–atmosphere interaction plays an important role in the interannual variability of the ITF. Regional upper-ocean heat content variability might also play a role in controlling interannual fluctuations of the ITF transport via geostrophic flows, though it could equally be ITF variations that establish heat content anomalies downstream of the Indonesian archipelago. The model heat transport associated with the ITF is in good agreement with the limited observational record available. Resultant variability in annual mean ITF heat transport is in the range 0.4–1.2 PW, which is significantly correlated with ITF and ENSO indices.

scholarly journals Interannual variability in Antarctic krill (Euphausia superba) density at South Georgia, Southern Ocean: 1997–2013

2014 ◽  
Vol 71 (9) ◽  
pp. 2578-2588 ◽  
Author(s):  
Sophie Fielding ◽  
Jonathan L. Watkins ◽  
Philip N. Trathan ◽  
Peter Enderlein ◽  
Claire M. Waluda ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Interannual Variability ◽  
Antarctic Krill ◽  
Southern Oscillation ◽  
Euphausia Superba ◽  
Target Strength ◽  
South Georgia ◽  
Key Species ◽  
The Mean ◽  
Antarctic Krill Euphausia Superba

Abstract Antarctic krill (Euphausia superba) are a key species in Southern Ocean ecosystems, maintaining very large numbers of predators, and fluctuations in their abundance can affect the overall structure and functioning of the ecosystems. The interannual variability in the abundance and biomass of krill was examined using a 17-year time-series of acoustic observations undertaken in the Western Core Box (WCB) survey area to the northwest of South Georgia, Southern Ocean. Krill targets were identified in acoustic data using a multifrequency identification window and converted to krill density using the Stochastic Distorted-Wave Born Approximation target strength model. Krill density ranged over several orders of magnitude (0–10 000 g m−2) and its distribution was highly skewed with many zero observations. Within each survey, the mean krill density was significantly correlated with the top 7% of the maximum krill densities observed. Hence, only the densest krill swarms detected in any one year drove the mean krill density estimates for the WCB in that year. WCB krill density (µ, mean density for the area) showed several years (1997/1998, 2001–2003, 2005–2007) of high values (µ > 30 g m−2) interspersed with years (1999/2000, 2004, 2009/2010) of low density (µ < 30 g m−2). This pattern showed three different periods, with fluctuations every 4–5 years. Cross correlation analyses of variability in krill density with current and lagged indices of ocean (sea surface temperature, SST and El Niño/Southern Oscillation) and atmospheric variability (Southern Annular Mode) found the highest correlation between krill density and winter SST (August SST) from the preceding year. A quadratic regression (r2 = 0.42, p < 0.05) provides a potentially valuable index for forecasting change in this ecosystem.

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