Fundamental Modes of Atmospheric CFC-11 From Empirical Mode Decomposition

Kobayashi-Kirschvink, Koseki J.; Li, King Fai; Shia, Run‐Lie; Yung, Yuk L.

doi:10.1142/s1793536912500240

Cited by 5 publications

(6 citation statements)

References 22 publications

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“…The 2‐D structure of the 27 day rotational signal in the ionosphere is retrieved using the fast Fourier transform (FFT). A Hanning window with a band‐pass domain from 25 to 35 days is applied to retain the 27 day solar signal; periods below 20 days or above 40 days are damped (Kobayashi‐Kirschvink et al, ). The same FFT filtering window is applied to the F 10.7 index.…”

Section: Resultsmentioning

confidence: 99%

The 11 Year Solar Cycle Response of the Equatorial Ionization Anomaly Observed by GPS Radio Occultation

Lin

Bui

et al. 2018

JGR Space Physics

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We have retrieved the latitudinal and vertical structures of the 11 year solar cycle modulation on ionospheric electron density using 14 years of satellite‐based radio occultation measurements utilizing the Global Positioning System. The densities at the crests of the equatorial ionization anomaly (EIA) in the subtropics near 300 km in 2003 and 2014 (high solar activity with solar 10.7 cm flux, F10.7 ≈ 140 solar flux unit (sfu)) were 3 times higher than that in 2009 (low solar activity F10.7 ≈ 70 sfu). The higher density is attributed to the elevated solar extreme ultraviolet and geomagnetic activity during high solar activity periods. The location of the EIA crests moved ~50 km upward and ~10° poleward, because of the enhanced E × B force. The EIA in the northern hemisphere was more pronounced than that in the southern hemisphere. This interhemispheric asymmetry is consistent with the effect of enhanced transequatorial neutral wind. The above observations were reproduced qualitatively by the two benchmark runs of the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model. In addition, we have studied the impact of the 11 year solar cycle on the 27 day solar cycle response of the ionospheric electron density. Beside the expected modulation on the amplitude of the 27 day solar variation due to the 11 year solar cycle, we find that the altitude of the maximal 27 day solar response is unexpectedly ~50 km higher than that of the 11 year solar response. This is the first time that a vertical dependence of the solar responses on different time scales is reported.

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Section: Resultsmentioning

confidence: 99%

The 11 Year Solar Cycle Response of the Equatorial Ionization Anomaly Observed by GPS Radio Occultation

Lin

Bui

et al. 2018

JGR Space Physics

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“…The harmonic terms define the seasonal and semi-annual cycles, which we compared to results of the same analysis for flask data from La Jolla, CA (Keeling et al, 2005). To determine trends in the C ff time series, derived from the radiocarbon data, we used the empirical mode decomposition (EMD) method (Huang et al, 1998;Kobayashi-Kirschvink et al, 2012). Using this method, nonlinear and nonstationary time series can be broken down into intrinsic mode functions (IMFs) with increasing period lengths and, finally, to a long-term trend with at most only one minimum or maximum with slope of zero.…”

Section: Time Series Analysismentioning

confidence: 99%

Toward consistency between trends in bottom-up CO<sub>2</sub> emissions and top-down atmospheric measurements in the Los Angeles megacity

Xu²,

et al. 2016

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Abstract. Large urban emissions of greenhouse gases result in large atmospheric enhancements relative to background that are easily measured. Using CO2 mole fractions and Δ14C and δ13C values of CO2 in the Los Angeles megacity observed in inland Pasadena (2006–2013) and coastal Palos Verdes peninsula (autumn 2009–2013), we have determined time series for CO2 contributions from fossil fuel combustion (Cff) for both sites and broken those down into contributions from petroleum and/or gasoline and natural gas burning for Pasadena. We find a 10 % reduction in Pasadena Cff during the Great Recession of 2008–2010, which is consistent with the bottom-up inventory determined by the California Air Resources Board. The isotopic variations and total atmospheric CO2 from our observations are used to infer seasonality of natural gas and petroleum combustion. The trend of CO2 contributions to the atmosphere from natural gas combustion is out of phase with the seasonal cycle of total natural gas combustion seasonal patterns in bottom-up inventories but is consistent with the seasonality of natural gas usage by the area's electricity generating power plants. For petroleum, the inferred seasonality of CO2 contributions from burning petroleum is delayed by several months relative to usage indicated by statewide gasoline taxes. Using the high-resolution Hestia-LA data product to compare Cff from parts of the basin sampled by winds at different times of year, we find that variations in observed fossil fuel CO2 reflect seasonal variations in wind direction. The seasonality of the local CO2 excess from fossil fuel combustion along the coast, on Palos Verdes peninsula, is higher in autumn and winter than spring and summer, almost completely out of phase with that from Pasadena, also because of the annual variations of winds in the region. Variations in fossil fuel CO2 signals are consistent with sampling the bottom-up Hestia-LA fossil CO2 emissions product for sub-city source regions in the LA megacity domain when wind directions are considered.

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“…The uncertainties of the IMFs can be estimated by creating an ensemble of IMFs that are obtained by a set of white noise to the raw time series, a procedure known as the ensemble EMD (EEMD) (Wu and Huang, 2009). The EEMD can better detach climate signals of different time scales naturally without prior information than the EMD (Kobayashi-Kirschvink et al, 2012;Shi et al, 2013;Newman et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Solar 11-Year Cycle Signal in Stratospheric Nitrogen Dioxide—Similarities and Discrepancies Between Model and NDACC Observations

Wang¹,

Zhu

et al. 2020

Sol Phys

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NOx (NO2 and NO) plays an important role in controlling stratospheric ozone. Understanding the change in stratospheric NOx and its global pattern is important for predicting future changes in ozone and the corresponding implications on the climate. Stratospheric NOx is mainly produced by the reaction of N2O with the photochemically produced O( 1 D) and, therefore, it is expected to vary with changes in solar UV irradiance during the solar cycle. Previous studies on this topic, often limited by the relatively short continuous data, show puzzling results. The effect of the 1991 Pinatubo eruption might have caused interference in the data analysis. In this study, we examine the NO2 vertical column density (VCD) data from the Network for the Detection of Atmospheric Composition Change (NDACC). Data collected at 16 stations with continuous longterm observations covering the most recent Solar Cycles 23 and 24 were analyzed. We found positive correlations between changes in NO2 VCD and solar Lyman-α over nine stations (mostly in the Northern Hemisphere) and negative correlations over three stations (mostly in the Southern Hemisphere). The other four stations do not show significant NO2 solar-cycle signal.The varying NO2 responses from one location to another are likely due to different geo-locations (latitude and altitude). In particular, two high-altitude stations show the strongest positive NO2 solar-cycle signals. Our 1D chemical-transport model calculations help explain the altitude dependence of NO2 response to the solar cycle. NO2 solar-cycle variability is suggested to play an important role controlling O3 at an altitude range from 20 km to near 60 km, while OH solarcycle variability controls O3 at 40 -90 km. While observations show both positive and negative NO2 responses to solar forcing, the 1D model predicts negative NO2 responses to solar UV changes throughout the middle atmosphere. 3D global model results suggest complex roles of

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Fundamental Modes of Atmospheric CFC-11 From Empirical Mode Decomposition

Cited by 5 publications

References 22 publications

The 11 Year Solar Cycle Response of the Equatorial Ionization Anomaly Observed by GPS Radio Occultation

The 11 Year Solar Cycle Response of the Equatorial Ionization Anomaly Observed by GPS Radio Occultation

Toward consistency between trends in bottom-up CO<sub>2</sub> emissions and top-down atmospheric measurements in the Los Angeles megacity

Solar 11-Year Cycle Signal in Stratospheric Nitrogen Dioxide—Similarities and Discrepancies Between Model and NDACC Observations

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Fundamental Modes of Atmospheric CFC-11 From Empirical Mode Decomposition

Cited by 5 publications

References 22 publications

The 11 Year Solar Cycle Response of the Equatorial Ionization Anomaly Observed by GPS Radio Occultation

The 11 Year Solar Cycle Response of the Equatorial Ionization Anomaly Observed by GPS Radio Occultation

Toward consistency between trends in bottom-up CO&lt;sub&gt;2&lt;/sub&gt; emissions and top-down atmospheric measurements in the Los Angeles megacity

Solar 11-Year Cycle Signal in Stratospheric Nitrogen Dioxide—Similarities and Discrepancies Between Model and NDACC Observations

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Toward consistency between trends in bottom-up CO<sub>2</sub> emissions and top-down atmospheric measurements in the Los Angeles megacity