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Q-SAT, a small spherical satellite designed and developed by Tsinghua university, was successfully launched on Aug 6, 2020 at Jiuquan satellite launch center in China. The mission of Q-Sat is the joint measurement of long-wavelength Earth gravity field and upper atmosphere density, which is of great significance for improving spacecraft orbit prediction and promoting the development of satellite gravity measurement technology. The satellite is designed in spherical shape innovatively and deploys high dynamic dual-frequency GPS as the main payload. On-orbit data shows that the atmospheric density detection precision is in the order of 10−14kg/m3 and the gravity recovery precision achieves the level of 30 orders. All mission success criteria and objectives were achieved. This paper presents the design, space mission, key technologies, science capabilities and preliminary results of the satellite. • Q-SAT, a spherical satellite for the joint measurement of long-wavelength Earth gravity field and upper atmosphere density, was launched in 2020. • An electromagnetic separation system with point connection-release structure is designed for the Q-Sat. • As secondary payload a powerful GPU module is implemented to validate artificial intelligence computing capabilities in orbit. • Modifications for the Jacchia-Roberts atmospheric density model are proposed in the paper. [ABSTRACT FROM AUTHOR]

In order to detect the distribution of gravity waves in the middle and upper atmosphere, an all-sky airglow imaging spectrometer is designed to measure the airglow. It has the detection advantages of ultrawide field of view (FOV), large relative aperture and high signal-to-noise ratio (SNR). It can obtain the spectral images of OH (715–850 nm / 880–930 nm) and OI (630 nm) in the height range of 87–250 km. The whole design method of telecentric objective splicing relay zoom group is used to effectively suppress the spectral drift less than 0.2 nm, which meets the requirements of narrow bandwidth filters. The field experiments in northwest China show that the all-sky airglow imaging spectrometer can continuously acquire airglow spectral images with high SNR in both OH channel and OI channel without focusing in the temperature range of 0–45 ℃, and the images obtained in OH channel have obvious gravity wave phenomenon after star point removal and geometric correction. [ABSTRACT FROM AUTHOR]

New particle formation (NPF) is one main source of atmospheric aerosols and plays an important role in global climate by contributing up to two thirds of the atmospheric cloud condensation nuclei. Numerous studies on characteristics and mechanisms of near-surface NPF have been conducted in last decades. However, the characteristics of NPF around the top of the planetary boundary layer (PBL) remains unclear due to the limitations of vertical measurements. In this study, a tethered airship onboard with advanced particle instruments was deployed for directly measurement of the NPF exactly above and under the top of the PBL in the Yangtze River Delta (YRD) of eastern China in December 2017. Coupled with the real time ground Lidar observation, we successfully conducted measurement of aerosol size distribution, chemical components of aerosol and gas pollutants with 100 m above/under the top of the PBL. Despite not being observed within the PBL during the flight and at three ground sites in YRD, NPF event with the growth rate of 3.8 nm/h was detected above the PBL. High oxidizing capacity, enough condensable vapors and low condensation sink above the PBL favor the onset of NPF. Model simulation and the aerosol chemical composition result indicate the important role of gaseous sulfuric acid in NPF and its subsequent growth in the upper atmosphere. Our study highlights the potential mechanism of NPF above the PBL and the need of direct vertical measurements to better understand NPF in the atmosphere and its climate effect. • Tethered airship platform made it possible to understand subtle vertical structure. • Model forecast and online measurements can reduce the risk of experiment. • New particle formation was detected only above the planetary boundary layer. • The growth rate above the planetary boundary layer was about 3.8 nm/h. • High H 2 SO 4 values above planetary boundary layer favor the new particle formation. [ABSTRACT FROM AUTHOR]

Tropical cyclone's activities can affect the ozone pollution characteristics to a certain extent over the Pearl River Delta (PRD) region based on different track types of tropical cyclones. In this study, we utilize the Finite Mixture Model algorithm to classify tropical cyclones which land on the South China coastal area between 2009 and 2018 into 6 track's types, and those types are land on the PRD region directly (A1 type), the east of the PRD region (B1 and B2 types) and the west of the PRD region (C1, C2 and C3 types) respectively. Combined with observation data, the results indicate that the A1 type, B1 type and B2 type tropical cyclones can increase the ozone concentration about 44.9% ∼ 65.3% in the PRD region before landfall accompanied with stagnant meteorological conditions usually, such as high temperature (>27 °C), low humidity (<80%) or weak wind (<3 m/s). And it should be emphasized that, due to the northward or northeastward deflection of the tracks, the ozone concentration in the PRD region does not decrease obviously (<10%) on the landing-day under B1 and B2 types, and ozone pollution maybe persistent longer than other types. By simulating typical cases of each track's type within WRF-Chem model coupled with process analysis method, and the results indicate that tropical cyclone's peripheral subsidence airflow is more obvious over the PRD region under A1, B1 and B2 cases before landfall, and it maybe an external condition which can limit the development of boundary layer and vertical diffusion of ozone, rather than transporting ozone downward from the upper atmosphere to the near surface level. In addition, based on process analysis result, the chemical reaction with strong radiation condition maybe the essential cause of ozone production and pollution, and the physical process can cause the ozone consumption. • Quantifying the influence of tropical cyclones tracks on ozone pollution. • northward deflection could lead to persistent pollution. • Strong radiation before landing is the essential cause of ozone production. [ABSTRACT FROM AUTHOR]

The Global Positioning System (GPS) has been applied in meteorology to monitor the change of Precipitable Water Vapor (PWV) in atmosphere, transformed from Zenith Wet Delay (ZWD). A key factor in converting the ZWD into the PWV is the weighted mean temperature ( T m ), which has a direct impact on the accuracy of the transformation. A number of Bevis-type models, like T m - T s and T m - T s , P s type models, have been developed by statistics approaches, and are not able to clearly depict the relationship between T m and the surface temperature, T s . A new model for T m , called weighted mean temperature norm model (abbreviated as norm model), is derived as a function of T s , the lapse rate of temperature, δ , the tropopause height, h trop , and the radiosonde station height, h s . It is found that T m is better related to T s through an intermediate temperature. The small effects of lapse rate can be ignored and the tropopause height be obtained from an empirical model. Then the norm model is reduced to a simplified form, which causes fewer loss of accuracy and needs two inputs, T s and h s . In site-specific fittings, the norm model performs much better, with RMS values reduced averagely by 0.45 K and the Mean of Absolute Differences (MAD) values by 0.2 K. The norm model is also found more appropriate than the linear models to fit T m in a large area, not only with the RMS value reduced from 4.3 K to 3.80 K, correlation coefficient R 2 increased from 0.84 to 0.88, and MAD decreased from 3.24 K to 2.90 K, but also with the distribution of simplified model values to be more reasonable. The RMS and MAD values of the differences between reference and computed PWVs are reduced by on average 16.3% and 14.27%, respectively, when using the new norm models instead of the linear model. [ABSTRACT FROM AUTHOR]

Abstract: Two lower tropospheric inversion layers (named as LTI1 and LTI2) over Yichang (111°18′E, 30°42′N) were studied by using the data from intensive radiosonde observations in January 2007 on an eight-times-daily basis. Our observations reveal that both the inversion layers are closely related to the intensive inertial gravity waves propagating in winter tropospheric jets. However, their formation mechanisms are likely to be different. Gravity-wave-induced intensive turbulence via convective instability may yield a downward energy transport and finally form the LTI1, while we speculate that the reflection of gravity waves by the strong tropospheric jet is responsible for the LTI2. [Copyright &y& Elsevier]

Carbonyl sulfide (OCS) and dimethyl sulfide (DMS) are important trace gases contributing to sulfate aerosol formation in the lower and upper atmosphere and hence greatly impacting global radiative balance. In the present study the exchange of OCS and DMS between rice (Oryza sativa L.) paddy fields and the atmosphere was studied in subtropical China from November 2004 to July 2005. OCS and DMS fluxes were compared between the planted and non-planted paddy fields, and between dry and waterlogged soils. The rice paddy fields were found to be a net sink for OCS and a source for DMS, with an uptake rate of 12.1±16.0pmolm−2 s−1 for OCS and an emission rate of 25.9±35.2pmolm−2 s−1 for DMS. OCS fluxes varied significantly between non-planted dry and waterlogged soils, with an uptake rate of 11.4±7.1pmolm−2 s−1 for non-planted dry soils and an emission rate of 9.0±5.4pmolm−2 s−1 for non-planted waterlogged soils. For DMS the variation between non-planted dry and waterlogged soils was not significant. Both OCS and DMS fluxes showed significant differences between the planted and non-planted waterlogged soils. For OCS, the planted waterlogged soil acted as a sink with an uptake rate of 29.0±25.7pmolm−2, but the non-planted waterlogged soil acted as a source with an emission rate of 9.0±5.4pmolm−2 s−1. For DMS, both the planted and non-planted waterlogged soils acted as sources, with an emission rate of 51.2±37.5pmolm−2 s−1 for the planted waterlogged soil, which was significantly higher than that for the non-planted waterlogged soil (3.8±2.8pmolm−2 s−1). OCS and DMS exchange rates differed significantly at different rice growth stages, with the highest fluxes at the jointing-booting stage. The potential factors causing the variations between the different treatments are also discussed. This work revealed that rice paddy field in subtropical China acts as a sink for OCS and an emission source for DMS as a whole and further investigation on the influence of soil microorganisms and soil redox potential on the OCS and DMS fluxes in rice paddy field are needed. [Copyright &y& Elsevier]

In this paper, the ionospheric characteristic parameters obtained from ionograms recorded by the DPS-4 digisonde at Hainan (19.4°N, 109.0°E), China are used to analyze the diurnal and seasonal behavior of the ionospheric variability at low latitude. Data used for the present study are hourly interval resolution data of the F2 layer critical frequency foF2, the F2 layer peak height hmF2, the thickness parameter B0 and the shape parameter B1. Time period coverage of the data used for the present study is from March 2002 to June 2003. The monthly inter-quartiles (ΔIntQT) and monthly ranges (ΔRange) as well as their percentage ratios to the monthly medians (ΔIntQT (%), ΔRange (%)) are used as quantitative measurements of the variability of the ionospheric parameters in the present study. Seasonal averages of these quantities are also obtained for summer, winter and equinox. Our study showed that: (1) for the foF2 parameter, the variability is much lower during daytime hours than during nighttime hours, with the maximum variability occurring at pre-sunrise hours – in terms of percentage inter-quartile values. The seasonal averages of ΔIntQT (%) are less than 15% by day and fluctuate between 12% and 40% at night; (2) for the hmF2 parameters, the variability has a minimum value at hours after sunrise and sunset, whereas it has a maximum value at about 4:00LT. The seasonal averages of ΔIntQT (%) fluctuate between 6.9% and 19.2%, with a slightly lower value at equinox than in the other two seasons; (3) for the B0 parameter, for the winter and equinox seasons, the variability has a minimum value at hours after sunrise and sunset, whereas it has maximum values at about 02:00–03:00LT and post-noon hours; for the summer season, the occurrence time of the maximum and minimum shifts to later compared with those observed in the other two seasons. The seasonal averages of ΔIntQT (%) range between 21% and 46.2% for winter and between 18.2% and 37.6% for the other two seasons; (4) for the B1 parameter, in terms of the absolute monthly inter-quartiles and monthly ranges, except for the hours near 06:00–07:00LT when the variability reaches a maximum value, it changes within a very limited extent. In terms of the percentage ratios to the monthly medians, the variability of B1 is higher during daytime than during nighttime. The seasonal averages of ΔIntQT (%) change between 11.6% and 33.2%, showing in general slightly higher values in the solstices (23.4–32.9%) than at equinox (15.0–23.1%) in the time period between 02LT and 15LT. [Copyright &y& Elsevier]