Total Surface Flux Research Articles

High-Resolution Bayesian Inversion of Carbon Dioxide Flux Over Peninsular India

Accurate estimation of the flux of the most important greenhouse gas, carbon dioxide (CO2), plays a decisive role in designing the policies to reduce the atmospheric CO2 burden to combat climate change. Here we integrate recent (2017–2020) in-situ measurements with a high-resolution particle dispersion model for optimising CO2 flux over peninsular India based on a top-down approach. Using weekly observations of atmospheric boundary layer CO2 from three distinct locations representing peninsular India, the total surface fluxes of CO2 are optimised based on the fluxes from fossil fuel, wildfire, terrestrial biosphere and ocean. Our Bayesian mode inversion using the Lagrangian Particle Dispersion Model FLEXPART suggests that the peninsular Indian region is a slightly stronger source of CO2 (3.34 TgC yr−1) than what is synthesised in the fossil fuel and ecosystem exchanges based on independent estimations. On seasonal scale, the flux corrections to the prior fluxes over peninsular India are 4.68, 6.53, −2.28 and 4.41 TgC yr−1during winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. The CO2 measurements from the stations attempted in the present inversion experiments could capture the footprints of peninsular India, giving better constraints to fluxes in the inversion. However, the data gap, pristineness of the samples, and large variabilities in the observations call for sustained monitoring for a longer term to further reduce the uncertainty of the estimated flux.

Nitrous oxide emissions from trees planted on a closed landfill site

<abstract> <p>Trees growing in natural and managed environments have the capacity to act as conduits for the transport of greenhouse gases produced belowground to the atmosphere. Nitrous oxide (N<sub>2</sub>O) emissions have been observed from tree stems in natural ecosystems but have not yet been measured in the context of forested former landfill sites. This research gap was addressed by an investigation quantifying stem and soil N<sub>2</sub>O emissions from a closed UK landfill and a comparable natural site. Measurements were made by using flux chambers and gas chromatography over a four-month period. Analyses showed that the average N<sub>2</sub>O stem fluxes from the landfill and non-landfill sites were 0.63 ± 0.06 μg m<sup>–2</sup> h<sup>–1</sup> and 0.26 ± 0.05 μg m<sup>–2</sup> h<sup>–1</sup>, respectively. The former landfill site showed seasonal patterns in N<sub>2</sub>O stem emissions and decreasing N<sub>2</sub>O fluxes with increased stem sampling position above the forest floor. Tree stem emissions accounted for 1% of the total landfill N<sub>2</sub>O surface flux, which is lower than the contribution of stem fluxes to the total surface flux in dry and flooded boreal forests.</p> </abstract>

Groundwater-derived U and Ba exports from a coastal acid sulfate soil (CASS) catchment following rain events

Coastal acid sulfate soil (CASS) catchments are regions of enhanced weathering due to sulfur mineral oxidation following drainage of anoxic wetland soils. Heavy rainfall flushes CASS soils, releasing dissolved metals to nearby estuaries and the coastal ocean. The importance of CASS environments on the release of uranium (U) and barium (Ba) to the coastal ocean is not well understood. Here, we discuss daily observations of dissolved Ba and U in an extensively drained CASS system in Australia under contrasting hydrological conditions. Radon-traced groundwater discharge following rain events released trace metals to surface waters. Groundwater fluxes of Ba and U were on average 10% and 30% of the total surface fluxes in the Tuckean Swamp, respectively. The average local surface water fluxes from the Tuckean Swamp were 1692 and 1.6 μmol/m2/yr from the catchment. On a global scale, dissolved Ba and U derived from CASS systems may be equivalent to 1.0% and 2.5% of rivers, respectively, even though CASS cover only ∼0.1% of the global continental area. While CASS may not be a major contributor of dissolved Ba and U to the global ocean, fluxes on a square meter basis indicate that CASS may be highly important to regional U and Ba budgets.

Impact of the atmospheric sink and vertical mixing on nitrous oxide fluxes estimated using inversion methods

[1] This study investigates some of the principal errors arising in atmospheric inversion estimates of N2O surface fluxes. Using a synthetic data set of model-generated atmospheric N2O mixing ratio data, representative of the current observation network, we investigate the influence of errors in the stratospheric N2O sink and in vertical transport. Our inversion framework uses a variational formulation of the Bayesian problem, and atmospheric transport is modeled using the global circulation model LMDz. When only optimizing the surface fluxes (with a prescribed sink), bias errors in the sink magnitude translate into substantial bias errors in the retrieved global total surface fluxes. Conversely, we find that errors only in the temporal and horizontal distribution of the N2O sink (nonbiased magnitude) have a very small impact on tropospheric mixing ratios and thus on the retrieved surface fluxes. Bias errors in the modeled vertical transport, however, lead to notable changes in tropospheric N2O and, in particular, in the phase of the seasonal cycle. This also leads to bias errors in the spatial distribution of the derived surface fluxes, although not in the global total. Last, the simultaneous optimization of the surface fluxes and the sink magnitude was tested as a means to avoid biasing the fluxes by incorrect prior assumptions about the N2O lifetime. With this approach, a significant reduction in the error of the sink magnitude was achieved and biases in the surface fluxes were largely avoided, and this result was further enhanced when aircraft data were included in the inversion.

The solar magnetic field since 1700

We have used semi-synthetic records of emerging sunspot groups based on sunspot number data as input for a surface flux transport model to reconstruct the evolution of the large-scale solar magnetic field and the open heliospheric flux from the year 1700 onward. The statistical properties of the semi-synthetic sunspot group records reflect those of the observed Royal Greenwich Observatory photoheliographic results. These include correlations between the sunspot numbers and sunspot group latitudes, longitudes, areas and tilt angles. The reconstruction results for the total surface flux, the polar field, and the heliospheric open flux (determined by a current sheet source surface extrapolation) agree well with the available observational or empirically derived data and reconstructions. We confirm a significant positive correlation between the polar field during activity minimum periods and the strength of the subsequent sunspot cycle, which has implications for flux transport dynamo models for the solar cycle. Just prior to the Dalton minimum, at the end of the 18th century, a long cycle was followed by a weak cycle. We find that introducing a possibly “lost” cycle between 1793 and 1800 leads to a shift of the minimum of the open flux by 15 years which is inconsistent with the cosmogenic isotope record.

What is the Mechanism for the Modification of Convective Cloud Distributions by Land Surface–Induced Flows?

AbstractThe aim of this study is to determine the mechanism that modulates the initiation of convection within convergence zones caused by land surface–induced mesoscale flows. An idealized modeling approach linked quantitatively to observations of vegetation breezes over tropical Benin was used. A large-eddy model was used with a prescribed land surface describing heterogeneities between crop and forest over which vegetation breezes have been observed. The total surface fluxes were constant but the Bowen ratio varied with vegetation type. The heterogeneous land surface created temperature differences consistent with observations, which in turn forced mesoscale winds and convection at the convergence zones over the crop boundaries. At these convergence zones optimum conditions for the initiation of convection were found in the afternoon; the equivalent potential temperature was higher in the convergence zones than over anywhere else in the domain, due to reduced entrainment, and the mesoscale convergence produced a persistent increase in vertical wind velocities of up to 0.5 m s−1 over a 5–10-km region. The relative importance of these two mechanisms depended on the synoptic conditions. When convective inhibition was weak, the thermodynamic conditions at the convergence zone were most important, as the triggering of convection was easily accomplished. However, when the thermodynamic profile inhibited convection, the mesoscale updrafts became essential for triggering in order to break through the inhibiting barrier. At the same time, subsidence over the forest produced a warm capping layer over the boundary layer top that suppressed convection over the forest throughout the afternoon.

On the temporal scale of the turbulent exchange of carbon dioxide and energy above a tropical rain forest in Amazonia

The Large Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA) project has been using the eddy covariance technique since 1998 to monitor energy, water, and carbon surface fluxes over Amazonia. The results obtained up‐to‐date indicate high level of uncertainties, especially regarding the role of the Amazonian ecosystem to the global carbon budget. Besides the problems related to the eddy covariance measuring system (systematic error and nighttime stable conditions), an extremely important factor is associated with the averaging time scale or “time window” used by the scientific community to determine the surface fluxes. This work presents initial efforts to determine the turbulence time scale for long‐term carbon and energy surface fluxes over the Amazon rain forest. A total of 198 nights and 218 days during 2006 were analyzed. The multiresolution decomposition technique was applied to project the signal into several time scales and determine when the spectral and cospectral gap occurred. This technique permitted evaluating and separating the real contribution from turbulent and mesoscale fluxes to the total surface fluxes at both diurnal and nocturnal periods. The average turbulence time scale was below 200 and 1200 s for all scalars at nighttime and daytime, respectively. In all cases, there is seasonal dependence. This result shows that the time scale commonly used to calculate nocturnal surface fluxes (30 min) includes a good portion of mesoscale flux in the estimates. The role of these mesoscale fluxes, in terms of seasonal dependence and the uncertainties they add to the estimates, is then analyzed.

Weather Noise Forcing of Surface Climate Variability

Abstract A model-based method to evaluate the role of weather noise forcing of low-frequency variability of surface properties, including SST, surface currents, land surface temperature, and soil moisture, is presented. In this procedure, an “interactive ensemble” coupled model, in which the ocean and land components are coupled to the mean of an ensemble of atmospheric models, is externally forced by the time-dependent surface fluxes due to the weather noise. The coupling to the ensemble mean atmosphere has the effect of strongly reducing the internally generated atmospheric weather noise so that, for example, observed weather noise forcing can meaningfully be prescribed. The surface flux due to weather noise is determined by removing the ensemble mean surface flux response of an ensemble of atmospheric models to specified surface boundary conditions from the total surface flux. When the system is entirely noise forced and the forcing is specified in this manner, the interactive ensemble model will reproduce the observed evolution of the surface properties. The method is illustrated in the context of two models: 1) a well-known simple coupled model of low-frequency climate variability, which considers the response of a slab thermodynamic surface model coupled to a thermodynamic atmosphere, and 2) a coupled GCM. The simple model is applied to the diagnosis of both observational and model-generated data, while the coupled GCM example illustrates the potential of the method if both model and data are perfect.

Mg II chromospheric radiative loss rates in cool active and quiet stars

The Mg  k emission line is a good indicator of the level of chromospheric activity in late-type stars. We investigate the dependence of this activity indicator on fundamental stellar parameters. To this purpose we use IUE observations of the Mg  k line in 225 late-type stars of luminosity classes I-V, with different levels of chromospheric activity. We first re-analyse the relation between Mg  k line luminosity and stellar absolute magnitude, performing linear fits to the points. The ratio of Mg  surface flux to total surface flux is found to be independent of stellar luminosity for evolved stars and to increase with decreasing luminosity for dwarfs. We also analyse the Mg  k line surface flux-metallicity connection. The Mg  k emission level turns out to be not dependent on metallicity. Finally, the Mg  k line surface flux-temperature relation is investigated by treating separately, for the first time, a large sample of very active and normal stars. The stellar surface fluxes in the k line of normal stars are found to be strongly dependent on the temperature and slightly dependent on the gravity, thus confirming the validity of recently proposed models. In contrast, data relative to RS CVn binaries and BY Dra stars, which show very strong chromospheric activity, are not justified in the framework of a description based only on acoustic waves and uniformly distributed magnetic flux tubes so that they require more detailed models.

An Aerosol Climatology at Kyoto: Observed Local Radiative Forcing and Columnar Optical Properties

Abstract In order to evaluate the radiative effect of the atmospheric aerosol at Kyoto, Japan, surface solar irradiance and columnar aerosol optical properties were observed in the period between September 1998 and December 2001. The aerosol optical thickness, which is an indicator of the columnar mass burden and the overall radiative effect of the aerosol, was on average 0.27 at a wavelength of 500 nm. Springtime aerosol optical thickness was generally higher primarily because of “yellow dust” from the Asian continent. The Angstrom exponent had values ranging from 0.5 to 2.8, with an average value of 1.64, and was found to be low in periods during which the aerosol optical thickness was high. As a first step toward calculating the local climate impact of the atmospheric aerosol at Kyoto, the clear-sky direct radiative forcing is considered in this paper. For an evaluation of the surface aerosol radiative forcing, observed total surface fluxes measured by a pyranometer are subtracted from modeled surface ...

Far‐Ultraviolet Emissions of the Sun in Time: Probing Solar Magnetic Activity and Effects on Evolution of Paleoplanetary Atmospheres

We present and analyze Far Ultraviolet Spectroscopic Explorer (FUSE) observations of six solar analogs. These are single main-sequence G0-G5 stars selected as proxies for the Sun at several stages of its main-sequence lifetime from ~130 Myr to ~9 Gyr. The emission features in the FUSE 920-1180 ? wavelength range allow for a critical probe of the hot plasma over three decades in temperature: from ~104 K for the H I Lyman series to ~6 ? 106 K for the coronal Fe XVIII ?975 line. Using the flux ratio C III ?1176/?977 as diagnostics, we investigate the dependence of the electron pressure of the transition region as a function of the rotation period, age, and magnetic activity. The results from these solar proxies indicate that the electron pressure of the stellar ~105 K plasma decreases by a factor of ~70 between the young fast-rotating (Prot = 2.7 days) magnetically active star and the old, slow-rotating (Prot ~ 35 days) inactive star. We also study the variations in the total surface flux for specific emission features that trace the hot gas in the stellar chromosphere (C II), transition region (C III, O VI), and corona (Fe XVIII). The observations indicate that the average surface fluxes of the analyzed emission features strongly decrease with increasing stellar age and longer rotation period. The emission flux evolution with age or rotation period is well fitted by power laws, which become steeper from cooler chromospheric (~104 K) to hotter coronal (~107 K) plasma. The relationship for the integrated (920-1180 ?) FUSE flux indicates that the solar far-ultraviolet (FUV) emissions were about twice the present value 2.5 Gyr ago and about 4 times the present value 3.5 Gyr ago. Note also that the FUSE/FUV flux of the zero-age main-sequence Sun could have been higher by as much as 50 times. Our analysis suggests that the strong FUV emissions of the young Sun may have played a crucial role in the developing planetary system, in particular, through the photoionization, photochemical evolution, and possible erosion of the planetary atmospheres. Some examples of the effects of the early Sun's enhanced FUV irradiance on the atmospheres of Earth and Mars are also discussed.

Secular variation of the Sun's magnetic flux

We present an extension of the model of Solanki et al. (2000) that allows us to reconstruct the time evolution of both the total and the open magnetic flux at the solar surface since 1700. The flux emerging in large active regions is determined using the sunspot number as a proxy, while the flux emergence in small ephemeral regions is described by an extended cycle whose amplitude and length are related to the corresponding sunspot cycle. Both types of regions contribute to the open flux, which is the source of the heliospheric field. The overlap of the activity cycles of ephemeral regions leads to a secular variation of the total cycle-related magnetic flux (active region flux + ephemeral region flux + open flux). The model results indicate that the total surface flux has doubled in the first half of the last century. The evolution of the open flux is in good agreement with the reconstruction by Lockwood et al. (1999).

A high‐spectral resolution study of the near‐infrared solar flux disposition in clear and overcast atmospheres

The sensitivity of the near‐infrared spectral atmospheric and surface fluxes to the vertical location of clouds is investigated, including a study of factors (drop‐size distribution, drop optical depth, solar zenith angle, cloud geometrical thickness, atmospheric profiles) which govern this dependence. Because of the effects of the above cloud, in‐cloud and below‐cloud water vapor the atmospheric absorbed flux in each spectral band depends critically on the cloud location, with a high cloud resulting in lesser absorption and greater reflection than a low one having the same drop optical depth. The difference between a high and a low cloud forcing of atmospheric absorption increases with drop optical depth. For any optical depth, clouds with larger drops cause a greater forcing of the spectral atmospheric absorption than those with smaller ones, so high clouds can even cause an increase rather than a decrease of the atmospheric absorption relative to clear skies. In contrast, the spectral and total surface fluxes are relatively insensitive to cloud vertical location. Instead, they are determined by the drop characteristics, notably drop optical depth. This near‐invariance characteristic is attributable to the fact that most of the insolation reaching the surface is in the weak water vapor spectral absorption regions; here drops dominate the radiative interactions and thus there is little dependence on cloud height. In addition, the overlap of the drop spectral features with the moderate‐to‐strong vapor absorption bands ensures that insolation in these regimes fails to reach the surface no matter where the cloud is located; instead, these bands contribute the most to atmospheric absorption. The near‐invariant behavior of the spectral and total surface flux holds separately for a wide variety of conditions studied. As a consequence, the difference in reflection, between two columns containing clouds with the same optical depth but located at different altitudes, is approximately balanced in magnitude by the difference in the atmospheric absorption; this holds for every spectral interval whether it be a weak, moderate, or strong vapor/drop absorption band. It also follows that the net fluxes at the top and surface of overcast atmospheres do not have a general, unambiguous relationship; this is in sharp contrast to a linear relation between them in clear skies. However, under certain overcast conditions (e.g., specific vertical location of clouds and solar zenith angle), a simple linear relationship is plausible.

Surface Flux Variability over the North Pacific and North Atlantic Oceans

Daily fields obtained from a 17-yr atmospheric GCM simulation are used to study the surface sensible and latent heat flux variability and its relationship to the sea level pressure (SLP) field. The fluxes are analyzed over the North Pacific and Atlantic Oceans during winter. The leading mode of interannual SLP variability consists of a single center associated with the Aleutian low in the Pacific, and a dipole pattern associated with the Icelandic low and Azores high in the Atlantic. The surface flux anomalies are organized by the low-level atmospheric circulation associated with these modes in agreement with previous observational studies. The surface flux variability on all of the timescales examined, including intraseasonal, interannual, 3‐10 day, and 10‐30 day, is maximized along the north and west edges of both oceans and between Japan and the date line at ;358N in the Pacific. The intraseasonal variability is approximately 3‐5 times larger than the interannual variability, with more than half of the total surface flux variability occuring on timescales of less than 1 month. Surface flux variability in the 3‐10-day band is clearly associated with midlatitude synoptic storms. Composites indicate upward (downward) flux anomalies that exceed |30 W m 22| occur to the west (east) of storms, which move eastward across the oceans at 108‐158 per day. The SLP and surface flux anomalies are also strong and coherent in the 10‐30-day band but are located farther north, are broader in scale, and propagate ;3‐4 times more slowly eastward than the synoptic disturbances. The sensible and latent heat flux are proportional to the wind speed multiplied by the air‐sea temperature and humidity difference, respectively. The anomalous wind speed has the greatest influence on surface flux anomalies in the subtropics and western Pacific, while the air temperature and moisture anomalies have the greatest impact in the northeast Pacific and north of 408N in the Atlantic. The covariance between the wind speed and the air temperature or humidity anomalies, while generally small, is nonnegligible on synoptic timescales.

Seasonal variation of surface radiation budget derived from International Satellite Cloud Climatology Project C1 data

Surface radiation budget data are presented for the midseasonal months of July and October of 1983 and January and April of 1984. These data allow examination for the first time of geographical and seasonal variations of the entire surface radiation budget from pole to pole. The latest flux estimation techniques have been used along with data from the International Satellite Cloud Climatology Project (ISCCP) and the Earth Radiation Budget Experiment (ERBE). Regional, zonal, and hemispheric distributions of the downward and net components of both shortwave and longwave fluxes and of the net total surface fluxes are determined. Seasonal flux variation per region, expressed as flux range, is illustrated for these components also. The estimated fluxes appear to be accurate to about 16 W m−2 on a global average, based on sensitivity analyses and comparisons with ground data. An analysis of flux errors showed that most of the error was attributable to errors in input data.

Outer atmospheres of cool stars. II - MG II flux profiles and chromospheric radiative loss rates

view Abstract Citations (95) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Outer atmospheres of cool stars. II. MG II flux profiles and chromospheric radiative loss rates. Basri, G. S. ; Linsky, J. L. Abstract International Ultraviolet Explorer high-resolution spectra of the Mg II lines at 2796, 2803 A in 15 stars of spectral type G2-M2 including a wide range of luminosities are presented. These spectra are calibrated in absolute flux units at earth and at the stellar surface, and the chromospheric radiative loss rates in the Mg II lines are compared with corresponding rates in the Ca II H, K, and 8542 lines. The ratio of Mg II surface flux to total surface flux is found to be independent of stellar luminosity and thus gravity; may decrease slowly with decreasing effective temperature, and increases with decreasing period among RS Canum Venaticorum binaries. The factor of 10 range in this ratio at each effective temperature may be due to differences in the fractional surface area covered by plages and may indicate that stars of all luminosity classes have chromospheric plages. In this small data sample no evidence is found that the Mg II line surface fluxes indicate whether a star possesses a transition region and hot corona. Publication: The Astrophysical Journal Pub Date: December 1979 DOI: 10.1086/157586 Bibcode: 1979ApJ...234.1023B Keywords: Binary Stars; Chromosphere; Cool Stars; Emission Spectra; Late Stars; Line Spectra; Ultraviolet Spectra; High Resolution; Iue; Magnesium; Spaceborne Astronomy; Stellar Atmospheres; Stellar Gravitation; Stellar Luminosity; Ultraviolet Astronomy; Astrophysics full text sources ADS | data products SIMBAD (56) MAST (1) INES (1) Related Materials (14) Part 1: 1979ApJ...229L..27L Part 3: 1980ApJ...235...76A Part 4: 1980ApJ...235..519H Part 5: 1980ApJ...241..279A Part 6: 1980ApJ...237...72S Part 7: 1980ApJS...44..383S Part 8: 1981ApJ...251..162B Part 9: 1981ApJ...247..545A Part 10: 1982ApJ...254..168A Part 11: 1982ApJ...256..550A Part 12: 1982ApJ...260..670L Part 13: 1983ApJ...272..223A Part 14: 1983ApJ...272..665E Part 15: 1983ApJ...274..784A