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Based on nearly 4.6 million radio occultation (RO) ionospheric profile data from Constellation Observing System for Meteorology, Ionosphere, and Climate satellites in 2006–2020, a global three‐dimensional ionospheric electron density model was constructed with a new concept. The global 3D ionosphere structure was divided into total 338,661 grids with longitude intervals of 10°, latitude intervals of 2°, and height intervals of 5 km. On each grid, the electron density is modeled as a function of solar activity, geomagnetic activity, local time, and season variation using 21 coefficients. Then all grid models are combined to form a global ionospheric model. This method makes full use of all ionospheric electron density data. The spatial resolution of the model is high with 10° in longitude, 2° in latitude, and 5 km in height, which can effectively model the fine ionospheric spatial structure like the longitudinal wavenumber‐4 structure in low latitudes. The model also takes into account the influence of both solar and geomagnetic activities on the ionosphere. At the altitude below the F2 peak, the RO electron density observation suffers from an artificial meridional maximum between the double peaks of the equatorial ionization anomaly, referred hereafter as the three‐peak error. By combining our model with the International Reference Ionospheric electron density results of the E layer below 140 km, the problem of three‐peak error is effectively solved. Compared the with other data sources such as the ZH01 and the ROCSAT‐1, the modeling ability of model in fine spatial structure is verified. Plain Language Summary: With the increas of human space activities, the monitoring and prediction of the space environment, especially the ionospheree, is in increasingly high demand. Observations of the ionosphere are becoming more abundant, such as radio occultation, which allows us to get observations of global ionosphere without space constraints. Based on large number data of Constellation Observing System for Meteorology, Ionosphere, and Climate, we propose a novel ionospheric modeling method. The global ionospheric structure is divided into sufficiently fine grids. Each grid is modeled separately and then all grid models are combined to form a global ionospheric model. This method makes full use of all ionospheric electron density data without spatial smoothing, and can effectively simulate fine spatial structures such as the wavenumber‐four structures. The model also considers the influence of solar and geomagnetic activities on the ionosphere. It can reflect the climate change of ionospheric electron density with geomagnetic activity. In addition, combined with the international reference ionospheric electron density results of the E layer below 140 km, the three‐peak error problem of occultation data of F2 layer below peak height in middle and low latitude. Comparison of other observation data, such as the ZH01 and the ROCSAT‐1, further verifies the simulation ability of the model under fine spatial structure. Key Points: A global 3D Grid Modeling method of ionosphere empirical model is proposedThe global model consists of a large number of independent models at fixed grid pointsThis model is combined with the IRI‐2012 model to deal with the artificial three‐peak structure at low heights in radio occultation data [ABSTRACT FROM AUTHOR]

Many studies have investigated the spatial variations of the ionosphere, but the quantitative characteristics of the ionosphere are rarely reported. In this paper, we utilize the total electron content (TEC) data to evaluate the latitudinal gradient of the ionosphere within 10°-50° N over the China sector. It is found that the magnitudes of latitudinal gradient are significantly higher within 10°-40° N and 45°-50° N, respectively. The database of TEC from 1 November 2018 to 31 October 2022 is processed to figure out the local time, seasonal, and solar activity dependency of the latitudinal gradient. The results suggest that the gradient within 10°-40° N is higher in the daytime and during high solar activity period. They are more noticeable in the spring and autumn, and least visible in the summer. Conversely, the gradient within 45°-50° N strengthens in the nighttime and under lower solar activity, and has larger values in the summer months. Furthermore, the International Reference Ionosphere (IRI-2020) model is assessed in terms of the reproducibility of latitudinal gradient. The IRI-2020 basically represents the latitudinal gradient within 10°-40° N, whereas it overestimates the gradient in the low solar activity period and misses the gradient features near 45°–50° N. [ABSTRACT FROM AUTHOR]