The nitrogen isotopic composition of nitrogen oxide (NOx) is useful for estimating its sources and sinks. Several methods have been developed to convert atmospheric nitric oxide (NO) and/or nitrogen ...dioxide (NO2) to nitrites and/or nitrates for collection. However, the collection efficiency and blanks are poorly evaluated for many collection methods. Here, we present a method for collecting ambient NOx (NO and NO2 simultaneously) with over 90% efficiency collection of NOx and low blank (approximately 0.5 μM) using a 3 wt% hydrogen peroxide (H2O2) and 0.5 M sodium hydride (NaOH) solution. The 1σ uncertainty of the nitrogen isotopic composition was ± 1.2 ‰. The advantages of this method include its portability, simplicity, and the ability to collect the required amount of sample to analyze the nitrogen isotopic composition of ambient NOx in a short period of time. Using this method, we observed the nitrogen isotopic compositions of NOx at the Tsukuba and Yoyogi sites in Japan. The averaged δ15N(NOx) value and standard deviation (1σ) in the Yoyogi site was (-2.7 ± 1.8) ‰ and in the Tsukuba site was (-1.7 ± 0.9) ‰ during the sampling period. The main NOx source appears to be the vehicle exhaust in the two sites.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Himawari-8, a new-generation geostationary satellite, can retrieve sub-hourly land surface temperatures (LSTs) with moderate spatial resolution, providing a new scale for monitoring the thermal ...environment in Asia and Oceania. This study evaluated uncertainties of LSTs retrieved by three operational algorithms from Advanced Himawari Imager (AHI) data. We compared two nonlinear split-window algorithms (SOB and WAN algorithms) and one nonlinear three-band algorithm (YAM algorithm). First, the error characteristics of the retrieved LSTs caused by the input parameter errors were simulated under various land-atmospheric conditions using an atmospheric radiative transfer model. Thereafter, retrieved LSTs from actual AHI data were evaluated using in-situ observations from AsiaFlux and OzFlux networks and the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) LSTs. The simulated results showed that the YAM algorithm maintained the highest accuracy, whereas the WAN algorithm had the highest robustness to input errors. The YAM algorithm had the smallest total error including input errors over a wide range of retrieval conditions. Validation of the three algorithms via in-situ LSTs from 12 sites revealed nighttime mean RMSEs for all sites of ∼1.7 °C, and daytime mean RMSEs for semi-arid and humid sites of approximately 3.0 °C and 2.0 °C, respectively. These are comparable to the accuracies reported for LST products with higher spatial resolutions, such as the Moderate Resolution Imaging Spectroradiometer and Landsat. Within the Himawari-8 disk, the estimation error of the YAM algorithm was ∼1.0 °C lower than those of the SOB and WAN algorithms in regions with extremely high viewing angle, temperature, and humidity (e.g., northern China, Australia, and Southeast Asia). Furthermore, AHI LSTs showed closer agreement with ECOSTRESS compared to in-situ LSTs, suggesting the usefulness of ECOSTRESS for assessing the diurnal LSTs derived from geostationary satellites. The resulting LST products and the knowledge of their error characteristics have the potential to improve the collective understanding of terrestrial energy and water cycles based on improved accuracy and robustness.
Seasonality is a key feature of the biosphere and the seasonal dynamics of soil carbon (C) emissions represent a fundamental mechanism regulating the terrestrial–climate interaction. We applied a ...microbial explicit model—CLM‐Microbe—to evaluate the impacts of microbial seasonality on soil C cycling in terrestrial ecosystems. The CLM‐Microbe model was validated in simulating belowground respiratory fluxes, that is, microbial respiration, root respiration, and soil respiration at the site level. On average, the CLM‐Microbe model explained 72% (n = 19, p < 0.0001), 65% (n = 19, p < 0.0001), and 71% (n = 18, p < 0.0001) of the variation in microbial respiration, root respiration, and soil respiration, respectively. We then compared the model simulations of soil respiratory fluxes and soil organic C content in top 1 m between the CLM‐Microbe model with (CLM‐Microbe) and without (CLM‐Microbe_wos) seasonal dynamics of soil microbial biomass in natural biomes. Removing soil microbial seasonality reduced model performance in simulating microbial respiration and soil respiration, but led to slight differences in simulating root respiration. Compared with the CLM‐Microbe, the CLM‐Microbe_wos underestimated the annual flux of microbial respiration by 0.6%–32% and annual flux of soil respiration by 0.4%–29% in natural biomes. Correspondingly, the CLM‐Microbe_wos estimated higher soil organic C content in top 1 m (0.2%–7%) except for the sites in Arctic and boreal regions. Our findings suggest that soil microbial seasonality enhances soil respiratory C emissions, leading to a decline in SOC storage. An explicit representation of soil microbial seasonality represents a critical improvement for projecting soil C decomposition and reducing the uncertainties in global C cycle projection under the changing climate.
We applied a microbial explicit model – CLM‐Microbe – to evaluate the impacts of microbial seasonality on soil carbon cycling in terrestrial ecosystems. Microbial seasonality overall stimulates microbial activities at an annual scale and leads to higher microbial respiration and thus lower soil carbon storage.
Satellite-based vegetation monitoring provides important insights regarding spatiotemporal variations in vegetation growth from a regional to continental scale. Most current vegetation monitoring ...methodologies rely on spectral vegetation indices (VIs) observed by polar-orbiting satellites, which provide one or a few observations per day. This study proposes a new methodology based on diurnal changes in land surface temperatures (LSTs) using Japan's geostationary satellite, Himawari-8/Advanced Himawari Imager (AHI). AHI thermal infrared observation provides LSTs at 10-min frequencies and ∼ 2 km spatial resolution. The DTC parameters that summarize the diurnal cycle waveform were obtained by fitting a diurnal temperature cycle (DTC) model to the time-series LST information for each day. To clarify the applicability of DTC parameters in detecting vegetation drying under humid climates, DTC parameters from in situ LSTs observed at vegetation sites, as well as those from Himawari-8 LSTs, were evaluated for East Asia. Utilizing the record-breaking heat wave that occurred in East Asia in 2018 as a case study, the anomalies of DTC parameters from the Himawari-8 LSTs were compared with the drying signals indicated by VIs, latent heat fluxes (LE), and surface soil moisture (SM). The results of site-based and satellite-based analyses revealed that DTR (diurnal temperature range) correlates with the evaporative fraction (EF) and SM, whereas Tmax (daily maximum LST) correlates with LE and VIs. Regarding other temperature-related parameters, T0 (LST around sunrise), Ta (temperature rise during daytime), and δT (temperature fall during nighttime) are unstable in quantification by DTC model. Moreover, time-related parameters, such as tm (time reaching Tmax), are more sensitive to topographic slope and geometric conditions than surface thermal properties at humid sites in East Asia, although they correlate with EF and SM at a semi-arid site in Australia. Additionally, the spatial distribution of the DTR anomaly during the 2018 heat wave corresponds with the drying signals indicated as negative SM anomalies. Regions with large positive anomalies in Tmax and DTR correspond to area with visible damage to vegetation, as indicated by negative VI anomalies. Hence, combined Tmax and DTR potentially detects vegetation drying indetectable by VIs, thereby providing earlier and more detailed vegetation monitoring in both humid and semi-arid climates.
•Himawari-8 satellite was used to measure diurnal changes in land surface temperature.•Anomalies in diurnal changes correlated with decreases in surface soil moisture.•Himawari-8 diurnal temperature range indicates drying/heat stress in plants.•This monitoring strategy may be used for drying detection even in humid climates.
We evaluated carbon dioxide (CO2) adsorption on the internal surface of the cylinder and the fractionation of CO2 and air during the preparation of standard mixtures with atmospheric CO2 level ...through multistep dilution. The CO2 molar fractions in the standard mixtures deviated from the gravimetric values by -0.207±0.060 µmolmol-1 on average, which is larger than the compatibility goal (0.1 µmolmol-1) recommended by the World Meteorological Organization. The deviation was consistent with those calculated using two fractionation factors: one was estimated by the mother–daughter transfer experiment in which CO2–air mixtures were transferred from a mother cylinder to an evacuated daughter cylinder, and another was computed by applying the Rayleigh model to the change in CO2 molar fractions in a source gas as its pressure was depleted from 11.5 to 1.1 MPa. The mother–daughter transfer experiments showed that the deviation was caused by the fractionation of CO2 and air during the transfer of the source gas (CO2–air mixture with a higher CO2 molar fraction than that in the prepared gas mixture). The CO2 fractionation was less significant when the transfer speed decreased to less than 3 L min-1, indicating that thermal diffusion mainly caused the fractionation. The CO2 adsorption on the internal cylinder surface was experimentally evaluated by emitting a CO2–air mixture from a cylinder. When the cylinder pressure was reduced from 11.0 to 0.1 MPa, the CO2 molar fractions in the mixture exiting the cylinder increased by 0.16±0.04 µmolmol-1. By applying the Langmuir adsorption–desorption model to the measured data, the amount of CO2 adsorbed on the internal surfaces of a 10 L aluminum cylinder when preparing a standard mixture with atmospheric CO2 level was estimated to be 0.027±0.004 µmolmol-1 at 11.0 MPa.
Solar-induced chlorophyll fluorescence (SIF) emissions were estimated by the "area-ratio Fraunhofer line depth (aFLD) method", a new retrieval methodology in spectra from a low spectral resolution ...(SR) spectroradiometer (MS-700: full width half maximum (FWHM) of 10 nm and spectral sampling interval of 3.3 nm), assisted with a scaling to reference SIF detected from high SR spectrum. The sparse pixels of a spectrum of low SR misses detecting the minimum of the O
2
A absorption band around at 760 nm, which makes the SIF detection by conventional FLD methods lose accuracy considerably. To overcome this, the aFLD method uses the definite integral of spectra over a wide interval between 750 and 780 nm. The integration of the spectrum is insusceptible to the change in shape of the depression curve, leading to higher accuracy of the aFLD method. Daily SIF, calculated by the aFLD method using the spectra obtained with MS-700, was scaled to reference daily SIF calculated by the spectral fitting method using the spectra obtained from August to December 2019 with an ultrafine SR spectroradiometer (QE Pro, FWHM = 0.24 nm). As a result, SIF calculated from MS-700 spectra by aFLD method was strongly correlated with the reference SIF from QE Pro spectra (
r
2
= 0.81) and was successfully scaled. Then, the scaled 11-year SIF from MS-700 at a deciduous broadleaf forest showed the correlation with GPP at multiple time steps: daily, monthly, and yearly, consistently during 2008–2018. The comparison of aFLD-derived SIF with the global Orbiting Carbon Observatory-2 (OCO-2) SIF data set (GOSIF) showed high correlation on monthly values during 2008–2017 (
r
2
= 0.85). The combining approach of the aFLD method with a scaling to reference SIF successfully detected long-term canopy SIF emissions, which has great potential to provide essential information on ecosystem-level photosynthesis.
Systematic measurements of the atmospheric Ar∕N2
ratio have been made at ground-based stations in Japan and Antarctica since
2012. Clear seasonal cycles of the Ar∕N2 ratio with summertime maxima
were ...found at middle- to high-latitude stations, with seasonal amplitudes
increasing with increasing latitude. Eight years of the observed Ar∕N2
ratio at Tsukuba (TKB) and Hateruma (HAT), Japan, showed interannual
variations in phase with the observed variations in the global ocean heat
content (OHC). We calculated secularly increasing trends of 0.75 ± 0.30
and 0.89 ± 0.60 per meg per year from the Ar∕N2 ratio observed at
TKB and HAT, respectively, although these trend values are influenced by
large interannual variations. In order to examine the possibility of the
secular trend in the surface Ar∕N2 ratio being modified significantly
by the gravitational separation in the stratosphere, two-dimensional model
simulations were carried out by arbitrarily modifying the mass stream
function in the model to simulate either a weakening or an enhancement of
the Brewer–Dobson circulation (BDC). The secular trend of the Ar∕N2
ratio at TKB, corrected for gravitational separation under the assumption of
weakening (enhancement) of BDC simulated by the 2-D model, was 0.60 ± 0.30 (0.88 ± 0.30) per meg per year. By using a conversion factor of
3.5 × 10−23 per meg per joule by assuming a one-box ocean with a temperature
of 3.5 ∘C, average OHC increase rates of 17.1 ± 8.6 ZJ yr−1 and 25.1 ± 8.6 ZJ yr−1 for the period 2012–2019 were
estimated from the corrected secular trends of the Ar∕N2 ratio for the
weakened- and enhanced-BDC conditions, respectively. Both OHC increase
rates from the uncorrected- and weakened-BDC secular trends of the Ar∕N2
ratio are consistent with 12.2 ± 1.2 ZJ yr−1 reported by ocean
temperature measurements, while that from the enhanced-BDC is outside of the
range of the uncertainties. Although the effect of the actual atmospheric
circulation on the Ar∕N2 ratio is still unclear and longer-term
observations are needed to reduce uncertainty of the secular trend of the
surface Ar∕N2 ratio, the analytical results obtained in the present
study imply that the surface Ar∕N2 ratio is an important tracer for
detecting spatiotemporally integrated changes in OHC and BDC.
We investigated the bonding mechanism of single-layered Cu2O nanospheres (NSs) on Cu thin films. When near-infrared femtosecond laser pulses were focused and irradiated on the Cu2O NS films ...containing the NSs and reducing agents on Cu thin film-coated Si substrates, single-layered NSs were bonded just above the substrates after rinsing the non-bonded NSs. The minimum pulse energy for the single bonding on the Cu thin film-coated Si substrates was smaller than that on Si substrates. The electromagnetic enhancement was calculated between the Cu2O NSs and Cu thin films by simulating the finite element method. The enhancement was estimated using a transverse mode of the linear polarization of the incident femtosecond laser pulses. The experimental and simulation results indicated that the single-layered NSs were bonded on the Cu thin films by femtosecond laser pulse-induced local heating and melting due to the localized plasmon enhancement between the Cu2O NSs and substrates.
A high precision continuous measurement system has been developed for analysis of the atmospheric O
2
/N
2
and Ar/N
2
ratios based on a mass spectrometry method. Sample and reference air flows ...through an inlet system and only a miniscule amount of each is transferred to the ion source of the mass spectrometer through thermally insulated thin fused silica capillaries. The measured O
2
/N
2
and Ar/N
2
values are experimentally corrected for the effects of pressure imbalance between the sample air and reference air during their introduction into the mass spectrometer, as well as for the influence of CO
2
concentration and O
2
/N
2
ratio of the sample air. Standard deviations of the measured O
2
/N
2
and Ar/N
2
ratios of standard air are ±3.2 and ±6.5 per meg, respectively, for our normal measurement time of 62 seconds. Our standard air is prepared by drying natural air and then stored in 48-L high-pressure cylinders; its O
2
/N
2
and Ar/N
2
ratios are stable to within ±1.1 and ±5.8 per meg, respectively, over a period of 11 months. The CO
2
/N
2
ratio is also simultaneously measured by this system, and converted to CO
2
concentration with a precision better than ±0.3 ppm using an experimentally determined relationship. This system has been field tested in Tsukuba, Japan since February 2012. Preliminary results show clear seasonal cycles of atmospheric potential oxygen (APO=O
2
+1.1×CO
2
), as well as of Ar/N
2
. If we ignore the fossil fuel influence, then that part the seasonal APO cycle driven by the air-sea heat flux accounts for 23% of the observed seasonal APO cycle, as estimated from the seasonal cycle of Ar/N
2
; any residuals are attributed to ocean biology and ventilation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Growing complexity in ecosystem structure and functions, under impacts of climate and land-use changes, requires interdisciplinary understandings of processes and the whole-system, and accurate ...estimates of the changing functions. In the last three decades, observation networks for biodiversity, ecosystems, and ecosystem functions under climate change, have been developed by interested scientists, research institutions and universities. In this paper we will review (1) the development and on-going activities of those observation networks, (2) some outcomes from forest carbon cycle studies at our super-site “Takayama site” in Japan, and (3) a few ideas how we connect in-situ and satellite observations as well as fill observation gaps in the Asia-Oceania region. There have been many intensive research and networking efforts to promote investigations for ecosystem change and functions (e.g., Long-Term Ecological Research Network), measurements of greenhouse gas, heat, and water fluxes (flux network), and biodiversity from genetic to ecosystem level (Biodiversity Observation Network). Combining those in-situ field research data with modeling analysis and satellite remote sensing allows the research communities to up-scale spatially from local to global, and temporally from the past to future. These observation networks oftern use different methodologies and target different scientific disciplines. However growing needs for comprehensive observations to understand the response of biodiversity and ecosystem functions to climate and societal changes at local, national, regional, and global scales are providing opportunities and expectations to network these networks. Among the challenges to produce and share integrated knowledge on climate, ecosystem functions and biodiversity, filling scale-gaps in space and time among the phenomena is crucial. To showcase such efforts, interdisciplinary research at ‘Takayama super-site’ was reviewed by focusing on studies on forest carbon cycle and phenology. A key approach to respond to multidisciplinary questions is to integrate in-situ field research, ecosystem modeling, and satellite remote sensing by developing crossscale methodologies at long-term observation field sites called “super-sites”. The research approach at ‘Takayama site’ in Japan showcases this response to the needs of multidisciplinary questions and further development of terrestrial ecosystem research to address environmental change issues from local to national, regional and global scales. KCI Citation Count: 0
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