The variations of neutral temperature in the mesosphere and lower thermosphere (MLT) region, during the 7–8 September 2017 intense geomagnetic storm, are studied using observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. They are also studied using simulations by the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM). The neutral temperature data cover the altitudes from 80 km to 110 km between 83° N and 52° S latitude, obtained from both SABER observations and model simulations. The SABER observations reveal that temperature increases (the maximum increase is larger than 35 K at ~108 km) and decreases (the maximum decrease is larger than 20 K at ~105 km) during the geomagnetic storm. The storm effects penetrate down to ~80 km. In observations, temperature variations corresponding to the storm show hemispheric asymmetry. That is, the variations of temperature are more prominent in the northern hemisphere than in the southern hemisphere. Conversely, the TIMEGCM outputs agree with the observations in general but overestimate the temperature increases and underestimate the temperature decreases at high and middle latitudes. Meanwhile, the simulations show stronger temperature decreases and weaker temperature increases than observations at low latitudes. After analyzing the temperature variations, we suggest that vertical winds may play an important role in inducing these significant variations of temperature in the MLT region.

Observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and simulations by the Whole Atmosphere Community Climate Model‐eXtended (WACCM‐X) are used to analyze the impacts of the January 2012 solar proton events (SPEs) on mesospheric ozone at high latitudes. The mesospheric ozone at high latitudes decreased evidently with the increasing proton flux and ionization rates during SPEs. The results of SABER and WACCM‐X both showed that maximum mesospheric ozone depletion reached 100% in the North Hemispheric (NH) high latitudes during SPEs while only 40% in the South Hemispheric (SH) high latitudes. The SPEs‐caused ozone changes simply occurred below 85 km and the ozone changes observed by SABER above 85 km may be associated with day‐to‐day variations. WACCM‐X simulations showed NO_x (N, NO, and NO₂) increased over 600% in both the northern and southern high latitudes during SPEs, while HO_x (H, OH, and HO₂) increased over 300% in the NH high latitudes and only over 30% in the SH high latitudes. HO_x is the main ozone‐depleting substance because the reactions of NO_x are less capable of depleting ozone than the reactions of HO_x. Due to the difference in sunlight between the northern and southern hemispheres, ozone, HO_x, and NO_x exhibited significant northern and southern hemispheric asymmetries. Meanwhile, an increase in ozone after the SPEs was reported but not explained by previous studies. Here it is shown that the decreases in the HO_x caused the increases in ozone after the SPEs.

The Yunnan–Kweichow Plateau serves as a critical ecological security barrier in southwest China. The region has witnessed substantial transformations in land use patterns due to rapid urban expansion, economic development, and population growth. These changes have significantly impacted the structure and services of regional ecosystems. Conducting a quantitative analysis of the influence of land-use changes on ecosystem service value (ESV) proves to be invaluable for guiding regional land planning and environmental conservation efforts. Utilizing land use data, we calculated ESV variations linked to dynamic land-use changes spanning the period from 1980 to 2020. This comprehensive study delved into the spatiotemporal fluctuations and regional disparities in ESV. To enhance the reliability of our evaluation, we applied a regional coefficient to adjust the equivalent factor of ecosystem service value. Over the 40 years, the total ESV exhibited a decrease from USD 122,215.03 million to USD 121,838.82 million. Notably, water supply experienced the most significant decline, while hydrological regulation witnessed the largest increase. The continuous decline in water supply service capacity raises concerns about exacerbating water resource shortages in the region. Spatially, the ESVs in the study region primarily concentrated within the medium-low to medium-high value range. However, except for regions with medium values, the area of other level regions is expanding, and is particularly evident in the increase in low-value regions. The reduction of forestland, grassland, and cultivated land, coupled with the expansion of built-up land, emerged as the primary contributors to the overall ESV decrease. In particular, the negative ecological contribution rate of built-up land reached 37.97%, and the ESV decreased by USD 866.64 million, underscoring that the expansion of water bodies could not compensate for this loss. The study highlights the increasing sensitivity of ESV to land-use changes in the region. As a response, there is a pressing need for managers to reinforce the implementation of ecological engineering and engage in rational planning for production, living, and ecological spaces. This research serves as a crucial reference for establishing an ecological security pattern system and fostering the sustainable development and utilization of land resources in the region.

Using the temperature data observed from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), we investigate the response of the mesosphere and lower thermosphere (MLT) to two medium geomagnetic storms with disparate durations, on 20 April 2018 and 10 April 2022. The high-latitude MLT temperature increase in the Southern hemisphere can reach 40 K during April 2018 geomagnetic storm with a longer duration (Kp values greater than 4 for 15 h), while the temperature variations are less than 10 K for the April 2022 event (Kp values greater than 4 for 6 h). To investigate the different temperature responses to disparate geomagnetic storm durations and understand what physical process results in this difference, we simulated the two events using the thermosphere ionosphere mesosphere electrodynamics general circulation model (TIMEGCM). The simulations show that more particles and energy input in longer-duration geomagnetic storms produce larger ion drag force and pressure gradient force at ~130 km, and then the enhanced two forces cause faster horizontal wind, leading to larger horizontal divergence. Subsequently, the stronger downward vertical wind is transported to the MLT region (below 110 km) and ultimately makes greater temperature increases through adiabatic heating/cooling and vertical advection. Therefore, the effects of the storm’s duration on the MLT temperature are also important.