scholarly journals Quasi-biennial and quasi-triennial oscillations in atmospheric methane

MAUSAM ◽  
2021 ◽  
Vol 51 (1) ◽  
pp. 57-68
Author(s):  
R. P. KANE
Keyword(s):  
Spectral Analysis ◽  
Zonal Wind ◽  
Growth Rates ◽  
Atmospheric Methane

The growth rates of atmospheric methane measured at several locations distributed over the globe during 1983-92 were subjected to spectral analysis. Significant Quasi-biennial (2-3 years) and Quasi-triennial (3-4 years) oscillations were noticed at several locations but not simultaneously at all locations. The periodicities were bunched at 2.10-2.44, 3.1-3.5 and 3.9-4.8 years and, in some cases, matched with the 2.54 year periodicity of 50 hPa equatorial zonal wind and/or ~2.30 year and ~4.5 year periodicities of ENSO.

scholarly journals Transient Growth of Thermodynamically Coupled Variations in the Tropics under an Equatorially Symmetric Mean State*

2010 ◽  
Vol 23 (21) ◽  
pp. 5771-5789 ◽  
Author(s):  
Daniel J. Vimont
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Zonal Wind ◽  
Growth Rates ◽  
Transient Growth ◽  
Propagation Characteristics ◽  
Meridional Mode ◽  
The Tropics

Abstract The dynamics of thermodynamically coupled disturbances in the tropics that bear a strong resemblance to observed meridional mode variations are investigated using two simple linear coupled models. Both models involve an ocean equation coupled to the atmosphere via the linearized effect of zonal wind variations on the surface bulk latent heat flux. The two models differ in their atmospheric components, which consist of (i) a Gill–Matsuno style model of the free troposphere in which atmospheric heating is parameterized to be linearly proportional to sea surface temperature and (ii) a reduced-gravity model of the tropical boundary layer in which SST anomalies are associated with hydrostatic pressure perturbations throughout the boundary layer. Both atmospheric models follow the standard shallow-water equations on an equatorial beta plane. Growth rates and propagation of coupled disturbances are calculated and diagnosed via eigenanalysis of the linear models and singular value decomposition of the Green’s function for each model. It is found that the eigenvectors of either model are all damped, not orthogonal, and not particularly meaningful in understanding observed tropical coupled variability. The nonnormality of the system, however, leads to transient growth over a time period of about 100 days (based on the choice of parameters in this study). The idealized initial and final conditions that experience this transient growth resemble observed tropical meridional mode variations and tend to propagate equatorward and westward in accord with findings from previous theoretical and modeling studies. Instantaneous growth rates and propagation characteristics of idealized transient disturbances are diagnosed via the linearized atmospheric potential vorticity equation and via propagation characteristics of atmospheric equatorial Rossby waves. Constraints on the poleward extent of initial conditions or imposed steady forcing that can lead to tropical meridional mode variations are identified through analysis of the steady coupled equations. Three constraints limit the poleward extent of forcing that can generate tropical meridional mode variations: (i) a dynamical constraint imposed by the damping rate of the temperature equation as well as the propagation speed of the mode along its wave characteristic; (ii) a constraint imposed by the effectiveness of zonal wind variations in generating surface latent heat flux anomalies; and (iii) the surface moisture convergence, which limits the poleward extent and strength of ocean to atmosphere coupling.

scholarly journals Spectrum analysis and prediction possibilities of the onset dates of southwest monsoon over Kerala (India)

MAUSAM ◽  
2022 ◽  
Vol 46 (1) ◽  
pp. 15-24
Author(s):  
R. P. KANE
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Zonal Wind ◽  
Monsoon Rainfall ◽  
Late Onset ◽  
A Priori ◽  
Southwest Monsoon ◽  
Random Component ◽  
Maximum Entropy Spectral Analysis ◽  
Early Late

Maximum Entropy Spectral Analysis of the time series for the onset dates of the southwest monsoon over Kerala (India) revealed several periodicities significant at a 2a a priori level. some at a 3 C a  priori level However these contributed only 40-50% to the total variance thus indicating 50-60% as purely random component. Also many of the significant periodicities observed were in the QBO region (T = 2-3 years) which. due to their variable periodicities and amplitudes, are almost equivalent to a random component. Hence predictions were possible only with a  limit exceeding 5 days which are probably not very useful for any planning purposes agricultural or otherwise. No relationship was found between onset dates of established monsoon rainfall and the 50 hPa mean monthly equatorial zonal wind for the months of March, April, May or June. However there is a possibility that a relationship may exist between westerly (easterly) winds in May and early (late) onset of the first monsoon (or pre-monsoon ?) rainfall in Kerala. Meager or otherwise.    

scholarly journals Equatorial annual oscillation with QBO-driven 5-year modulation in NCEP data

2007 ◽  
Vol 25 (1) ◽  
pp. 37-45 ◽  
Author(s):  
H. G. Mayr ◽  
J. G. Mengel ◽  
F. T. Huang ◽  
E. R. Nash
Keyword(s):  
Spectral Analysis ◽  
Zonal Wind ◽  
Lower Stratosphere ◽  
Circumstantial Evidence ◽  
High Latitudes ◽  
Time Intervals ◽  
Quasi Biennial Oscillation ◽  
Temperature Variations ◽  
Environmental Prediction ◽  
Biennial Oscillation

Abstract. An analysis is presented of the stratospheric zonal wind and temperature variations supplied by the National Center for Environmental Prediction (NCEP). The derived zonal-mean variations are employed. Stimulated by modeling studies, the data are separated into the hemispherically symmetric and anti-symmetric components, and spectral analysis is applied to study the 12-month annual oscillation (AO) and the quasi-biennial oscillation (QBO). For data samples that cover as much as 40 years, the zonal wind results reveal a pronounced 5-year modulation of the symmetric AO in the lower stratosphere, which is confined to equatorial latitudes. This modulation is also seen in the temperature variations but extends to high latitudes, qualitatively consistent with published model results. A comparison between different time intervals of the data indicates that the signature of the 5-year oscillation is larger when the QBO of 30 months is more pronounced. Thus there is circumstantial evidence that this particular QBO period is involved in generating the oscillation as was shown in a modeling study (Mayr et al., 2000). In agreement with the model, the spectral analysis also reveals a weak anti-symmetric 5-year oscillation in the zonal wind data, which could interact with the strong anti-symmetric AO to produce the modulation of the symmetric AO. The 30-month QBO is well suited to be synchronized by, and phase-locked to, the equatorial semi-annual oscillation (SAO), and this may explain why this QBO periodicity and its 5-year spin-off are observed to persist for many cycles.

scholarly journals Attribution of the accelerating increase in atmospheric methane during 2010–2018 by inverse analysis of GOSAT observations

2020 ◽  
Author(s):  
Yuzhong Zhang ◽  
Daniel J. Jacob ◽  
Xiao Lu ◽  
Joannes D. Maasakkers ◽  
Tia R. Scarpelli ◽  
...  
Keyword(s):  
Growth Rates ◽  
Inverse Analysis ◽  
Methane Emissions ◽  
Bayesian Optimization ◽  
Atmospheric Methane ◽  
Tropical Wetlands ◽  
Fire Emissions ◽  
Livestock Emissions ◽  
Oil Gas ◽  
Gosat Satellite

Abstract. We conduct a global inverse analysis of 2010–2018 GOSAT satellite observations to better understand the factors controlling atmospheric methane and its accelerating increase over the 2010–2018 period. The inversion optimizes 2010–2018 anthropogenic methane emissions and their trends on a 4º × 5º grid, monthly regional wetland emissions, and annual hemispheric concentrations of tropospheric OH (the main sink of methane) also for individual years. We use an analytical solution to the Bayesian optimization problem that provides closed-form estimates of error covariances and information content for the solution. Our inversion successfully reduces the errors against the independent methane observations from the TCCON network and reproduces the interannual variability of the methane growth rate inferred from NOAA background sites. We find that prior estimates of fuel-related emissions reported by individual countries to the United Nations are too high for China (coal) and Russia (oil/gas), and too low for Venezuela (oil/gas) and the U.S. (oil/gas). We show that the 2010–2018 increase in global methane emissions is mainly driven by tropical wetlands (Amazon and tropical Africa), boreal wetlands (Eurasia), and tropical livestock (South Asia, Africa, Brazil), with no significant trend in oil/gas emissions. While the rise in tropical livestock emissions is consistent with bottom-up estimates of rapidly growing cattle populations, the rise in wetland emissions needs to be better understood. The sustained acceleration of growth rates in 2016–2018 relative to 2010–2013 is mostly from wetlands, while the peak methane growth rates in 2014–2015 are also contributed by low OH concentrations (2014) and high fire emissions (2015). Our best estimate is that OH did not contribute significantly to the 2010–2018 methane trend other than the 2014 spike, though error correlation with global anthropogenic emissions limits confidence in this result.

Attribution of the accelerating increase in atmospheric methane during 2010–2018 by inverse analysis of GOSAT observations

2021 ◽  
Author(s):  
Yuzhong Zhang ◽  
Daneil J. Jacob ◽  
Xiao Lu ◽  
Joannes D. Maasakkers ◽  
Tia R. Scarpelli ◽  
...  
Keyword(s):  
Growth Rates ◽  
Inverse Analysis ◽  
Methane Emissions ◽  
Bayesian Optimization ◽  
Anthropogenic Emissions ◽  
Atmospheric Methane ◽  
Tropical Africa ◽  
Fire Emissions ◽  
Oil Gas ◽  
The U.S

<p>We conduct a global inverse analysis of 2010–2018 GOSAT satellite observations to better understand the factors controlling atmospheric methane and its accelerating increase over the 2010–2018 period. The inversion optimizes anthropogenic methane emissions and their 2010–2018 trends on a 4º×5º grid, monthly regional wetland emissions, and annual hemispheric concentrations of tropospheric OH (the main sink of methane). We use an analytical solution to the Bayesian optimization problem that provides closed-form estimates of error covariances and information content for the solution. We verify our inversion results with independent methane observations from the TCCON and NOAA networks. Our inversion successfully reproduces the interannual variability of the methane growth rate inferred from NOAA background sites. We find that prior estimates of fuel-related emissions reported by individual countries to the United Nations are too high for China (coal) and Russia (oil/gas), and too low for Venezuela (oil/gas) and the U.S. (oil/gas). We show large 2010–2018 increases in anthropogenic methane emissions over South Asia, tropical Africa, and Brazil, coincident with rapidly growing livestock populations in these regions. We do not find a significant trend in anthropogenic emissions over regions with large production or use of fossil methane, including the U.S., Russia, and Europe. Our results indicate that the peak methane growth rates in 2014–2015 are driven by low OH concentrations (2014) and high fire emissions (2015), while strong emissions from tropical (Amazon and tropical Africa) and boreal (Eurasia) wetlands combined with increasing anthropogenic emissions drive high growth rates in 2016–2018. Our best estimate is that OH did not contribute significantly to the 2010–2018 methane trend other than the 2014 spike, though error correlation with global anthropogenic emissions limits confidence in this result.</p>

Use of spectral analysis to estimate short-term periodicities in growth rates of brook trout Salvelinus frontinalis

1997 ◽  
Vol 54 (7) ◽  
pp. 1532-1541 ◽  
Author(s):  
W Aboul Hosn ◽  
P Dutilleul ◽  
D Boisclair
Keyword(s):  
Growth Rate ◽  
Spectral Analysis ◽  
Growth Rates ◽  
Repeated Measures ◽  
Brook Trout ◽  
Short Term ◽  
Experimental Conditions ◽  
Relative Growth Rates ◽  
Repeated Measures Design ◽  
Periodic Components

We used spectral analysis to investigate the periodic components of relative growth rates (on a mass and length basis) in two groups of six\b young-of-the-year brook trout (Salvelinus fontinalis). Fish were measured every 2 days for 25 days according to a repeated measures design in time. The predominant frequency components were estimated at the end of a stepwise procedure involving the analysis of the multifrequential periodogram. We found mainly two superimposed periodic components that resulted in short rhythms; these had a period of about 5 and 10 days for the growth rate in mass and of about 4 and 6 days for the growth rate in length (R2 = 91% for mass and 90% for length, both including an autocorrelation term). Repeatability of rhythms was assessed by ANOVA of the finite Fourier transform, which showed that the two groups of fish reared under the same experimental conditions exhibited growth rhythms that were not significantly different from each other. On that basis, we present a harmonic model which predicts short-term variation in growth rate of brook trout in mass (R2pred = 0.73, with an autocorrelation term) and in length (R2pred = 0.72).

scholarly journals Attribution of the accelerating increase in atmospheric methane during 2010–2018 by inverse analysis of GOSAT observations

2021 ◽  
Vol 21 (5) ◽  
pp. 3643-3666 ◽  
Author(s):  
Yuzhong Zhang ◽  
Daniel J. Jacob ◽  
Xiao Lu ◽  
Joannes D. Maasakkers ◽  
Tia R. Scarpelli ◽  
...  
Keyword(s):  
Growth Rates ◽  
Inverse Analysis ◽  
Oil And Gas ◽  
Methane Emissions ◽  
Bayesian Optimization ◽  
Anthropogenic Emissions ◽  
Atmospheric Methane ◽  
Tropical Africa ◽  
Fire Emissions ◽  
The Us

Abstract. We conduct a global inverse analysis of 2010–2018 GOSAT observations to better understand the factors controlling atmospheric methane and its accelerating increase over the 2010–2018 period. The inversion optimizes anthropogenic methane emissions and their 2010–2018 trends on a 4∘×5∘ grid, monthly regional wetland emissions, and annual hemispheric concentrations of tropospheric OH (the main sink of methane). We use an analytical solution to the Bayesian optimization problem that provides closed-form estimates of error covariances and information content for the solution. We verify our inversion results with independent methane observations from the TCCON and NOAA networks. Our inversion successfully reproduces the interannual variability of the methane growth rate inferred from NOAA background sites. We find that prior estimates of fuel-related emissions reported by individual countries to the United Nations are too high for China (coal) and Russia (oil and gas) and too low for Venezuela (oil and gas) and the US (oil and gas). We show large 2010–2018 increases in anthropogenic methane emissions over South Asia, tropical Africa, and Brazil, coincident with rapidly growing livestock populations in these regions. We do not find a significant trend in anthropogenic emissions over regions with high rates of production or use of fossil methane, including the US, Russia, and Europe. Our results indicate that the peak methane growth rates in 2014–2015 are driven by low OH concentrations (2014) and high fire emissions (2015), while strong emissions from tropical (Amazon and tropical Africa) and boreal (Eurasia) wetlands combined with increasing anthropogenic emissions drive high growth rates in 2016–2018. Our best estimate is that OH did not contribute significantly to the 2010–2018 methane trend other than the 2014 spike, though error correlation with global anthropogenic emissions limits confidence in this result.

Influence of latitude and moisture effects on the barotropic instability of an idealized ITCZ

2021 ◽  
Author(s):  
Eric Bembenek ◽  
Timothy M. Merlis ◽  
David N. Straub
Keyword(s):  
Zonal Wind ◽  
Growth Rates ◽  
Water Model ◽  
Latent Heat Release ◽  
Barotropic Instability ◽  
Shallow Water Model ◽  
Moisture Effects ◽  
Latitudinal Position ◽  
Poleward Shift ◽  
Wind Profiles

AbstractA large fraction of tropical cyclones (TCs) are generated near the intertropical convergence zone (ITCZ), and barotropic instability of the related wind shear has been shown to be an important generation mechanism. The latitudinal position of the ITCZ shifts seasonally and may shift poleward in response to global warming. Aquaplanet GCM simulations have shown TC-generation frequency to vary with position of the ITCZ. These results, and that moisture plays an essential role in the dynamics, motivate the present study on the growth rates of barotropic instability in ITCZ-like zonal wind profiles. Base-state zonal wind profiles are generated by applying a prescribed forcing (representing zonally-averaged latent heat release in the ITCZ) to a shallow-water model. Shifting the latitudinal position of the forcing alters these profiles, with a poleward shift leading to enhanced barotropic instability. Next, an examination of how latent release impacts the barotropic breakdown of these profiles is considered. To do this, moisture is explicitly represented using a tracer variable. Upon supersaturation, precipitation occurs and the related latent heat release is parameterized as a mass transfer out of the dynamically active layer. Whether moisture serves to enhance or reduce barotropic growth rates is found to depend on how saturation humidity is represented. In particular, taking it to be constant or a function of the layer thickness (related to temperature) leads to a reduction, whereas taking it to be a specified function of latitude leads to an enhancement. Simple arguments are given to support the idea that moisture effects should lead to a reduction in the moist shallow water model and that a poleward shift of the ITCZ should lead to an enhancement of barotropic instability.

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