China will launch the Atmospheric Environment Monitoring Satellite, which is equipped with a CO2-IPDA LIDAR. It is of great significance to explore the feasibility and effectiveness of this novel technique and to identify potential differences among its CO2 concentration products and the passive remote sensing technique. In this work, we developed an initial data-processing procedure for an airborne CO2-IPDA LIDAR, which is the minified prototype of the forthcoming space-borne LIDAR. We tested the effectiveness of this procedure and evaluated the performance of the minified prototype in a flight test over ocean, urban and mountainous terrain. The column-weighted xCO2 (XXCO2) retrievals obtained by the airborne IPDA-LIDAR were considerably more sensitive to the gradients of the dry-air mixing ratio of CO2 (xCO2), compared with both the XCO2 products of OCO-2 and in-situ measurements of point xCO2. The mean XXCO2 over the ocean, urban and mountainous area are 412.02, 438.32 and 433.08 ppm with STDs of 1.35, 0.75 and 0.91 ppm, respectively. We also used altitude-dependent xCO2 obtained by a decline-climb flight to calculate a reference for XXCO2 over the ocean. The difference between XXCO2 obtained via two means was less than 0.5 ppm. Moreover, our performance evaluation model predicted that a relative random error of less than 0.3% would be very likely for the forthcoming satellite mission over land. However, measuring CO2 concentrations precisely over oceans is identified as a very challenging work. Thus, developing dedicated algorithms to address CO2 measurement over oceans by using the IPDA-LIDAR is necessary.

The impacts of haze emphasized significance of hazards for human activities and importance of observations of aerosol vertical distribution. This study aimed to analyze the aerosol vertical distribution during a haze case at temporal and spatial aspects, using space-borne and ground-based Lidar observations over Jinhua Basin, Zhejiang province, as well as the Hybrid Single-Particle Lagrangian Integrated Trajectory (HSPLIT) model and optical situ monitoring at Jinhua site. The results highlight three pollution peaks above the surface located in the upper and lower boundary layer in Jinhua Basin. The trajectory analysis shows the pollutants inside and outside the planetary boundary layer from different sources. Planetary boundary layer height (PBLH) obtained from the space-borne Lidar observations was compared with that from ground-based Lidar observations. The absolute error between the two instruments is about 0.193 km. It is illustrated that the space-borne Lidar is an effective instrument for obtaining regional aerosol pollution in vertical section. Pollution transport near the ground is closely related with the terrain condition.

The successive tidal force (TF) at the epicenter of the Jiashi M6.6 earthquake in Xinjiang, China, was calculated for the period from 13 December 2019 to 10 February 2020. With periodic changes in tide-generating forces, the variations in the electron density (Ne) data recorded by the China Seismo-Electromagnetic Satellite (CSES) and outgoing longwave radiation (OLR) data provided by NOAA on a large scale at N25°–N55°, E65°–E135° were studied. The results show that (1) in the four cycles during which the TF changes from trough to peak, the earthquake occurred during one peak time when the OLR changed around the epicenter via calm–rise processions and in other similar TF phases, and neither an increase in the OLR nor earthquake occurred. (2) With a change in the TF, the spatiotemporal evolution of the OLR from seismogenic processes to its occurrence was as follows: microenhancement–enhancement–microattenuation–enhancement–calmness; this is consistent with the evolution of outward infrared radiation when rocks break under stress loading: microrupture–rupture–locking–accelerated rupture–rupture. (3) Ne increased significantly during the seismogenic period and was basically consistent with OLR enhancement. The results indicate that as the TF increases, the Earth’s stress accumulates at a critical point, and the OLR increases and transfers upward. The theoretical hypothesis underlying the conducted study is that the accumulated electrons on the surface cause negatively charged electrons in the atmosphere to move upward, resulting in an increase in ionospheric Ne near the epicenter, which reveals the homology of seismic stress variations in the spatial coupling process. The quasi-synchronous change process of these three factors suggests that the TF changed the process of the stress accumulation–imbalance in the interior structure of this earthquake and has the effect of triggering the earthquake, and the spatiotemporal variations in the OLR and ionospheric Ne could be indirect reflections of in situ stress.

Surface albedo plays a significant role in Earth’s energy budget and global climate change. The spaceborne remote sensing technique is efficient for deriving and monitoring long-term surface albedo over large regions. Numerous satellite surface albedo products have been established and used for climate change research. However, the surface daily mean albedo is not regularly produced from satellite observations, even though it is more critical than instantaneous albedo for calculating daily shortwave radiation budget. Compared to polar-orbiting satellites, the geostationary satellites offer greater potential for mapping daily albedo with more diurnal observations. This study proposes an innovative multi-sensor combined direct estimation algorithm, which takes advantage of multiple clear-sky observations from new-generation geostationary satellite sensors FengYun-4 Advanced Geostationary Radiation Imager (AGRI) and Himawari-8 Advanced Himawari Imager (AHI) taken during the same day to improve the surface albedo estimation. Compared to albedo estimates derived from a single sensor, the root mean squared error (RMSE) decreases from 0.030 to 0.022 at OzFlux sites and from 0.040 to 0.031 at Heihe sites. Moreover, an information index of top-of-atmosphere (II_TOA) reflectance was proposed to quantify the amount of information that multiangular TOA observations carry in the surface albedo estimation. As a result, combining observations from two sensors increases such information by 20%, as compared to observations from a single sensor. This study demonstrated the combined multi-sensor direct estimation method has significant potential for improving surface albedo estimation.