## 4 Results
### Identification of Typical Methane Emission Hotspots in China and the United States
We covered an area of approximately 150 by 200 km in the Shanxi Changzhi area and a similar expanse in the Delaware sub-basin of the Permian Basin, capturing a total of 20 images on various dates, primarily including 5 December 2022, 18 October 2022, 4 May 2022, and 30 March 2023, as detailed in Table 1. We employed the Integrated Methane Enhancement (IME) approach to calculate the emission rates of each plume. Given the relatively small instantaneous methane plumes detected from individual point sources, many do not conform to Gaussian behavior, leading to potential significant errors in flux rate inversion using Gaussian plume modeling. The IME method links the total plume mass to the point source emission rate [39], relying on the effective wind speed and characteristic size of the plume, which results in lower errors. With a spatial sampling of 30 m, our survey enabled the mapping of individual methane plumes and the attributing of emissions to specific infrastructure. Our primary objective was to identify, characterize, and quantify the largest point source emissions in these regions, with the overarching goal of aiding future emission reduction efforts. We successfully detected eight methane emission points in Changzhi, Shanxi, China, and the Permian Basin in the United States, each with an emission rate exceeding 500 kg/h. [PERSON] et al. (2019) estimated the methane point source emission rates in the Changzhi region of Shanxi, China, using the Italian PRISMA hyperspectral imager, to be between 7.7 t/h and 35.5 t/h. For the Permian Basin in the United States, they estimated the methane point source emission rates from oil and natural gas sources to be between 1.7 t/h and 2.8 t/h. Figure 4 illustrates the locations and intensities of the methane plumes detected in Changzhi, Shanxi, after processing the satellite imaging spectroscopy data. On 18 October 2022, the GF5-02-AHSI instrument captured two anomalous methane emission points in Qinyuan County, Changzhi City, as shown in Figure 4e,h. These points were located near the Changxin Coal Mine in Majunyu and the Anda Coal Mine operated by the Tongzhou Group in Shanxi. Analysis of Google Earth imagery and GaoFen-2 satellite images indicated that the detected methane leaks were from gas power plants near these coal mines. The emission rates from these two points were as high as 4.5 \(\pm\) 2.0 t/h and 2.7 \(\pm\) 1.2 t/h, comparable to the emissions detected by [PERSON] et al. (2019) from underground mines in Tunliu District, Changzhi, using PRISMA and WorldView-3 satellites. After processing the satellite imaging spectroscopy dataset, the locations and intensities of the methane plumes detected in the Texas sub-basin of the Permian Basin are shown in Figure 5. The point sources' emission rates (Q) typically ranged between 1700 kg/h (which we assumed as our detection limit and defined as \"extreme emissions\") and 9700 kg/h. This was basically consistent with the research of [PERSON] et al. (2019). They monitored methane emissions in the Permian Basin of the United States using airborne measurements (AVIRIS-NG) and satellite data (TROPOMI). The emission rates were found to be between 2 t/h and 7 t/h. Most plumes were situated in an area spanning from 31.0\({}^{\circ}\) to 32.5\({}^{\circ}\) N latitude and 103.3\({}^{\circ}\) to 104.2\({}^{\circ}\) W longitude. This corresponded with the region of highest methane fluxes identified by [PERSON] et al. in [PERSON] et al. (2019) through top-down estimations, indicating a match between our detected emissions and previously reported high-flux areas, but was less well aligned with the bottom-up emission inventory based on the U.S.