The intense plasma irregularities within the ionospheric sporadic E (Es) layers at 90–130 km altitude have a significant impact on radio communications and navigation systems. As a result, the modeling of the Es layer is very important for the accuracy, reliability, and further applications of modern real‐time global navigation satellite system precise point positioning. In this study, we have constructed an empirical model of the Es layer using the multivariable nonlinear least‐squares‐fitting method, based on the S4max from Constellation Observing System for Meteorology, Ionosphere, and Climate satellite radio occultation measurements in the period 2006–2014. The model can describe the climatology of the intensity of Es layers as a function of altitude, latitude, longitude, universal time, and day of year. To validate the model, the outputs of the model were compared with ionosonde data. The correlation coefficients of the hourly foEs and the daily maximum foEs between the ground‐based ionosonde observations and model outputs at Beijing are 0.52 and 0.68, respectively. The model can give a global climatology of the intensity of Es layers and the seasonal variations of Es layers, although the Es layers during the summer are highly variable and difficult to accurately predict. The outputs of the model can be implemented in comprehensive models for a description of the climatology of Es layers and provide relatively accurate information about the global variation of Es layers.
In this study, the effects of the Madden‐Julian oscillation (MJO) on the northern stratosphere during boreal winter are investigated, especially in cases with the absence of a stratospheric sudden warming (SSW) event. During the wintertime, the polar cap temperature is expected to increase following MJO phase 2 (P2), P3, P4, and P7. However, the responses after P2 and P3 are much weaker if the dates from 50 days before to 50 days after the SSW central days are excluded from the composite. This result implies that the stratospheric polar warming following MJO P2 and P3 is sensitive to the occurrence of SSWs. After excluding the SSW events from the composite, the subsequent temperature anomalies strengthen and become more significant approximately 30 days after MJO P4 and 10 days after MJO P7. Planetary wave (PW) anomalies are enhanced in the midlatitudes of the upper troposphere, lagging MJO P4 by 15–25 days and lagging MJO P7 by 5–15 days. Thus, the upward propagation and dissipation of PWs in the stratosphere are significantly enhanced, further strengthening the Brewer‐Dobson circulation in the Northern Hemisphere stratosphere. The WN1, which is induced by the MJO in the stratosphere, is the dominant component of PW perturbation. The enhanced PW dissipation in the high latitudes of the stratosphere is weaker in terms of lagging MJO P4, so the zonal wind and temperature anomalies after MJO P4 are less significant in the polar region, especially in the lower stratosphere.
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