Geomagnetic jerk extraction based on the covariance matrix

We normalize data from 43 Chinese observatories and select data from ten Chinese observatories with most continuous records to assess the secular variations(SVs)and geomagnetic jerks by calculating the deviations between annual observed and CHAOS-6 model monthly means.The variations in the north,east,and vertical eigendirections are studied by using the covariance matrix of the residuals,and we find that the vertical direction is strongly affected by magnetospheric ring currents.To obtain noise-free data,we rely on the covariance matrix of the residuals to remove the noise contributions from the largest eigenvalue or vectors owing to ring currents.Finally,we compare the data from the ten Chinese observatories to seven European observatories.Clearly,the covariance matrix method can simulate the SVs of Dst,the jerk of the northward component in 2014 and that of the eastward component in 2003.5 in China are highly agree with that of Vertically downward component in Europe,compare to CHAOS-6,covariance matrix method can show more details of SVs.

Evolution in physiochemical and cloud condensation nuclei activation properties of crop residue burning particles during photochemical aging

As a main form of biomass burning in agricultural countries, crop residue burning is a significant source of atmospheric fine particles. In this study, the aging of particles emitted from the burning of four major crop residues in China was investigated in a smog chamber.The particle size distribution, chemical composition and cloud condensation nuclei(CCN)activity were simultaneously measured. The properties of crop residue burning particles varied substantially among different fuel types. During aging, the particle size and mass concentration increased substantially, suggesting condensational growth by formation of secondary aerosols. The particle composition was dominated by organics. Aging resulted in considerable enhancement of organics and inorganics, with enhancement ratios of 1.24–1.44 and 1.33–1.76 respectively, as well as a continuous increase in the oxidation level of organics. Elevated CCN activity was observed during aging, with the hygroscopicity parameter κ varying from 0.16 to 0.34 for fresh particles and 0.19 to 0.40 for aged particles.Based on the volume mixing rule, the hygroscopicity parameter of organic components(κorg) was derived. κorgexhibited an increasing tendency with aging, which was generally consistent with the tendency of the O:C ratio, indicating that the oxidation level was related to the hygroscopicity and CCN activity of organic aerosols from crop residue burning. Our results indicated that photochemical aging could significantly impact the CCN activation of crop burning aerosols, not only by the production of secondary aerosols, but also by enhancing the hygroscopicity of organic components, thereby contributing to the aerosol indirect climate forcing.