Fine particulate matter (PM2.5) has been reported to be an important risk factor for asthma. This study was designed to evaluate the relationship between PM2.5 and lung function among children with asthma in Shanghai, China. From 2016 to 2019, a total of 70 Chinese children aged 4 to 14 in Shanghai were recruited for this panel study. The questionnaire was used to collect baseline information, and the lung function covering forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and peak expiratory flow (PEF) were carried out for each child more than twice during follow-up. Meanwhile, the simultaneous daily air atmospheric pollutants and meteorological data were collected. The linear mixed effect (LME) model was used to assess the relationship between air pollutants and lung function. A significantly negative association was found between PM2.5 and lung function in children with asthma. In the single-pollutant model, the largest effects of PM2.5 on lung function were found for lag 0–2, with FVC and FEV1 decreasing by 0.91% [95% confidence interval (CI): −1.75, −0.07] and 1.05% (95% CI: −2.09, 0.00), respectively, for each 10 μg/m3 increase in PM2.5. In the multi-pollution model (adjusted PM2.5 + SO2 + O3), the maximum effects of PM2.5 on FVC and FEV1 also appeared for lag 0–2, with FVC and FEV1 decreasing by 1.57% (95% CI: −2.69, −0.44) and 1.67% (95% CI: −3.05, −0.26), respectively, for each 10 μg/m3 increase in PM2.5. In the subgroup analysis, boys, preschoolers (<6 years old) and hot seasons (May to September) were more sensitive to changes. Our findings may contribute to a better understanding of the short-term exposure effects of PM2.5 on lung function in children with asthma.
Abstract The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide. The autocorrelation function of the received pressure or particle velocity contains both modal autocorrelation component (MAC) and modal cross-correlation component (MCC), with the former part usually treated as interference for source ranging. Because the real part of the vertical intensity flux (RPVIF) only contains MCC, a passive impulsive source ranging method based on the frequency warping transform of RPVIF with a single vector receiver in shallow water is presented. Using a waveguide-invariant-based frequency warping operator, the cross-correlation components of two different modes in the vertical intensity flux are warped into separable impulsive sequences, the time delays of which are subsequently used for source ranging. The advantages of source ranging based on warping the vertical intensity flux compared with warping the pressure autocorrelation function are pointed out, and the experiment results are also presented.
Based on the analysis of soil moisture data in permafrost active layer with three vegetations in the alpine meadow of the Tibetan Plateau,the response of soil moisture in permafrost active layer to the change of vegetation is pronounced.It is found that the soil moisture distributions are similar within the depth of 20 cm in different time during the year for the vegetative coverage of 30% and 65%.After a precipitation,the change in soil moisture for vegetative coverage of 30% is slightly larger than that for vegetative coverage of 65%.The soil moisture for vegetative coverage of 93% is the lowest from the beginning of thawing to the beginning of freezing.The lower the vegetative coverage,the earlier the respond time of soil freezing and thawing,and the shorter the respond duration of soil thawing and freezing in the whole active layer.The dependence of soil thawing and freezing on vegetation will decrease with depth.The decrease of soil moisture for vegetative coverage of 30% and 65% during a freezing process is 10%~26% more than that for vegetative coverage of 93%,while the increase of soil moisture for vegetative coverage of 30% and 65% during a thawing process is 1 5%~80% more than that for vegetative coverage of 93%.The dependence of phase-change water amounts on vegetation is obvious;the lower the vegetative coverage,the more the phase-change water amounts.Soil moisture of the overall profile will redistribute,moving to the upper and bottom sectors of the active layer,and a dry sector appears in the depth range of 60~80 cm during thawing,because of transpiration by vegetation and evapotranspiration.
Tibetan Plateau vortices (TPVs) are major rain-producing systems over the Tibetan Plateau. Some TPVs can move off the plateau under certain conditions and impact rainfall over Eastern China. Accordingly, the eastward propagation distances of the TPVs moving off the plateau (EPDs) are closely related to the areas of rainfall associated with TPVs. In this study, the moving-off TPVs during May-August of 1998–2015 are classified into two groups according to their EPDs, and the circulations and heating fields at the times when the TPVs move off the plateau (i.e. moving-off times) are investigated based on reanalysis data. The dynamic and thermodynamic conditions to the east of the Tibetan Plateau are found to significantly impact the EPDs. In the middle and lower troposphere, the zonal ranges of negative geopotential height anomalies to the east of the Tibetan Plateau are in accordance with the EPDs of the TPVs, indicating that anomalous lows play a favourable role in the eastward movement of TPVs. In addition, the anomalous highs to the northeast of the Tibetan Plateau and over Southeastern China also benefit the maintenance of cyclonic circulation to the east of the plateau. Meanwhile, in the upper troposphere, the jet stream over Northeast Asia is beneficial for divergence at 200 hPa. Accordingly, ascending motion associated with the upper-level divergence and lower-level convergence is observed, with the zonal extent corresponding well to the EPDs in the two situations. The atmospheric thermodynamic factors also show a remarkable effect on the EPDs. The TPVs move farther away when the unstable stratification and water vapour convergence extend further eastward. The heating ranges above 500 hPa coincide with the EPDs of TPVs, implying a close relationship between the heating fields and the EPDs. These results benefit prediction on EPDs and further on rainfall to the east of the Tibetan Plateau.
The sound speed profile plays an important role in shallow water sound propagation. And much attention has been paid on how to obtain it. Concurrences with in-site measurements, many inversion methods have been put forward to estimate sound speed profile from acoustic signals received by a vertical line array. The feasibility and robustness of an acoustic tomography scheme with matched field processing are studied. The acoustic signals from a horizontal line array in South China Sea are analyzed to invert sound speed profiles, in which the sound speed profile is described by the empirical orthogonal functions to reduce the unknown parameters. Parallel genetic algorithm is adopted as the optimization algorithm to increase the inversion speed. The results show that the inverted sound speed profiles are in good agreement with in-site measurements. Moreover, the a posteriori probability analysis is used to verify the validity of the inverted results. [Work supported by the National Natural Science Foundation of China under Grant No. 10974218 and the Knowledge Innovation Program of the Chinese Academy of Sciences, Grant No. KZCX1-YW-12-2.]
The frequency warping transform of the vertical energy flux and a passive impulsive source ranging method with a single acoustic vector sensor are presented in this paper. The cross-correlation component of two different modes in the vertical energy flux is transformed into separable impulsive sequence. With a guide source, the source range is extracted from the relative delay time of the impulsive sequence. Comparing with warping the pressure autocorrelation function, there is no need to delete the modal autocorrelation component for warping the vertical energy flux, especially for its real part. Besides, the source ranging result based on the time delay of the warped vertical energy flux is much better for closer range. The frequency warping transform of the vertical energy flux and the passive source ranging method are verified by experimental data.
Abstract Atmospheric circulation monthly anomalies over the Ural region are key indicators of Eurasian climate anomalies. Here, whether there exists a one-to-two correspondence relationship that generally agrees with the supercritical pitchfork bifurcation model, referred to as a pitchfork-like relationship, between reduced sea ice concentration (SIC) in the Barents-Kara Seas in specific months and the lagging Ural circulation anomalies is explored. Based on the monthly observational SIC data and two reanalyses during 1979/1980 − 2020/2021, two typical examples are found by estimating the joint probability density function. Results show that when the gradually reduced SIC in September (January) passes a critical threshold, the preferred Ural circulation patterns in October (February) exhibit a regime transition from the flat zonal westerlies to wavy westerlies with a Ural trough and wavy westerlies with a Ural ridge. Because both the barotropic and baroclinic conversion of energy from the climatological-mean flow to Ural circulation anomalies exhibit a regime transition from one regime to two regimes. It might be associated with the increased both positive and negative shear vorticity of background westerly wind over the Ural region before the regime transition, contributed by the thermodynamic effect of the SIC reduction. After the regime transition, positive and negative anomaly events of Ural atmospheric circulation occur with equal probability under the same SIC. Our results suggest an increased incidence of both positive and negative anomalies of Ural atmospheric circulation and also the Siberian High, under the recent SIC reduction, which implies a low predictability of Eurasian climate anomalies in October and February.
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