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30 June 2026, Volume 38 Issue 2 Previous Issue   

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Analysis of atmosphere vertical structure characteristics over the North Pole and central Arctic Ocean in summer 2023 QI Wei, BIAN Shuangshuang, CHEN Junming, SUN Hulin, DING Minghu 2026, 38 (2):  175-188.  DOI: 10.13679/j.jdyj.20250080 Abstract ( 68 )   PDF (20030KB) ( 139 )   The Arctic region serves as a sensitive zone for global climate change. Understanding its atmospheric vertical structure is crucial for elucidating the Arctic amplification effect. However, our understanding of atmospheric characteristics over the central Arctic Ocean is constrained by the scarcity of radiosonde observation data in this area. Based on radiosonde observations collected during the 13th Chinese National Arctic Research Expedition in summer 2023, this study systematically analyzed atmospheric vertical structure characteristics over the Arctic Ocean region (75.5°N—90°N). The observations are compared with historical data and combined with ERA5 reanalysis data to explore the influence mechanisms of typical weather processes. Results indicate: (1) Inversion phenomena, characterized by a temperature increase with altitude rather than the typical decrease, are widespread in the atmospheric boundary layer. The temperature lapse rate in the lower inversion layer is 0.36 ℃·100 m–1, with a median inversion base height of 250 m, a median inversion thickness of 210 m, and a median inversion strength of 3.2 ℃. (2) In our study, between altitudes of 1 to 10 km, the average temperature lapse rate is 5.44℃·km–1, and the cold-point tropopause is typically found at an altitude of 9.98 km with a corresponding temperature of –48.6 ℃. (3) Near-surface high humidity (relative humidity >90%) and inverted humidity structures lead to frequent sea fog, with 90% of water vapor is concentrated below 5.5 km. (4) Although no distinct regional patterns emerge, frequent low-level jets occur with core heights between 2 and 4 km. (5) Inversion layers and humidity inversions characteristics are particularly pronounced near the North Pole, with an average inversion thickness of 405 m and an average inversion strength of 6.47 ℃. While the strength is significantly higher than at historical drifting stations. Weather-scale analysis indicates that the formation of the warm center and strong inversion at 660 m on September 6 in the North Pole region was closely associated with radiative cooling under the control of a low-level cold high-pressure system and the superposition of warm advection at the 925 hPa level. This study fills a gap in radiosonde observations over the North Pole region in China, providing crucial observational evidence for improving polar numerical models and deepening our understanding of sea-ice-atmosphere coupling mechanisms in the Arctic amplification effect. References | Related Articles | Metrics

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Verification and evaluation of surface meteorological elements from the CMA_GFS model in the Arctic region LI Zhe, SUN Jingzhe, CHEN Junming, LIU Juanjuan, YANG Yi 2026, 38 (2):  189-206.  DOI: 10.13679/j.jdyj.20250077 Abstract ( 52 )   PDF (18606KB) ( 20 )   This study evaluates the forecast performance of the CMA_GFS model in the Arctic using surface observational data and GPM precipitation observations for January, April, July, and October 2023. The model performance for 2 m air temperature, 2 m dew point temperature, surface pressure, 10 m wind speed, and precipitation was systematically assessed. The spatiotemporal characteristics of forecast errors and the model performance under extreme warming events were analyzed, and comparisons were conducted with the GFS and IFS models. The results indicate that the CMA_GFS model exhibits systematic error structures in the prediction of continuous meteorological variables over the Arctic. Specifically, air temperature, surface pressure, and wind speed are generally overestimated, while the dew point temperature shows pronounced seasonal-dependent biases. Forecast errors increase with forecast lead time, and winter errors are significantly larger than those in summer. High-error regions are mainly concentrated over areas with complex underlying surfaces and near coastal boundaries. The precipitation forecasts can reasonably reproduce the overall precipitation structure and show relatively good predictive skill for precipitation events within the 2~5 mm·d–1 range. Under extreme warming events, the forecast errors of thermodynamic variables increase significantly. The comparison results further show that the overall forecast performance of the CMA_GFS model is comparable to that of the GFS model but remains inferior to that of the IFS model. However, the precipitation forecast skill of CMA_GFS is superior to that of both GFS and IFS. This study reveals the error structure characteristics of the CMA_GFS model in the Arctic and identifies their main influencing factors, providing a scientific basis for further model improvement and operational application in polar regions. References | Related Articles | Metrics

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Construction and evaluation of an Arctic regional atmospheric reanalysis system based on Polar WRF-Gridpoint Statistical Interpolation (GSI) CHEN Junming, LI Zhe, CHENG Wei, DING Minghu, ZHANG Lei 2026, 38 (2):  207-228.  DOI: 10.13679/j.jdyj.20260019 Abstract ( 40 )   PDF (49130KB) ( 20 )   This study developed a high-resolution regional atmospheric reanalysis system for the Arctic using the Polar WRF mesoscale numerical model and the Gridpoint Statistical Interpolation (GSI) variational data assimilation system. The system assimilates multi-source observations, including surface observations, radiosonde data, and satellite remote sensing data, to generate a 10 km-resolution Arctic regional atmospheric reanalysis dataset for 2012–2016. The system was evaluated using surface and radiosonde observations, ERA5 reanalysis data, and GPM precipitation products. The results show that: (1) for near-surface variables, WRF performs better than ERA5 in simulating 2 m air temperature and 10 m wind speed, with root mean square error (ERMSE) values of 2.008 ℃ and 1.707 m·s–1, respectively, lower than the corresponding ERA5 values of 2.196 ℃ and 2.018 m·s–1; however, the ERMSE values for 2 m dew-point temperature and sea-level pressure are 1.984 ℃ and 1.303 hPa, respectively, higher than those of ERA5. (2) For upper-air variables, WRF shows advantages in geopotential height and relative humidity, with relative humidity ERMSE values of 11.5%~12.4%, lower than the ERA5 values of 18.0%~19.5%; however, the ERMSE values for temperature and wind speed are slightly higher than those of ERA5. (3) For precipitation, WRF can reproduce the spatial pattern characterized by higher precipitation over the peripheral seas and lower precipitation over the central Arctic Basin. The smallest errors occur in July, with mean error (EME) and ERMSE values of 0.04 mm·d–1 and 0.57 mm·d–1, respectively; the ERMSE values in January and October are 1.11 mm·d–1 and 1.03 mm·d–1, respectively, indicating larger precipitation magnitude errors in winter and autumn. (4) A case study of the strong Arctic cyclone in August 2012 shows that WRF can capture the 500 hPa low-pressure center, cold-core structure, humidity distribution, and peripheral high-wind-speed belt. Overall, the system demonstrates good applicability in reconstructing the atmospheric state and precipitation spatial structure over the Arctic. References | Related Articles | Metrics

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Seasonal applicability evaluation of boundary layer parameterization schemes in typical regions of the Arctic shipping route based on the Polar-WRF model GU Chunli, MA Shupo, SUN Jiaqing, BIAN Shuangshuang, LIANG Mingjie 2026, 38 (2):  229-241.  DOI: 10.13679/j.jdyj.20250076 Abstract ( 43 )   PDF (2921KB) ( 156 )   To support the construction of a numerical weather prediction system for the Arctic shipping route, Ny-Ålesund, a typical region of the Arctic shipping route, was selected as the study area. Using the Polar-WRF V4.1.1 model, we conducted winter and summer numerical simulations with four planetary boundary layer parameterization schemes (MYNN, MYJ, YSU, QNSE). Based on surface automatic weather station observations and radiosonde data in Ny-Ålesund, the applicability of these schemes was evaluated in terms of near-surface meteorological elements and atmospheric vertical structure. The results show significant seasonal differences in simulation performance, with larger discrepancies in near-surface elements than in the vertical structure. The MYNN scheme achieved the highest accuracy in simulating near-surface elements in both seasons, with controllable errors in vertical structure simulation. The YSU and QNSE schemes performed adequately only for certain elements, while the MYJ scheme exhibited the largest overall errors. Thus, the MYNN scheme is recommended for planetary boundary layer and surface layer processes in this region, providing a scientific basis for selecting planetary boundary layer schemes in the Arctic shipping route numerical weather prediction system. References | Related Articles | Metrics

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The pole problem: A persistent challenge in spherical harmonic applications LI Huijun, CHENG Wei, CAI Qifa, GUO Bing, GE Panze , LI Fei, YANG Hongyang, YU Qian 2026, 38 (2):  242-252.  DOI: 10.13679/j.jdyj.20250082 Abstract ( 35 )   PDF (7395KB) ( 20 )   Since the inception of spherical harmonic theory, the pole problem has been an inescapable companion in its many applications. A prevailing misconception holds that local corrections outside the standard framework can resolve it. However, our analysis reveals that the mapping from the spherical harmonic polynomial space to its tangent space disrupts completeness at the poles, demonstrating that the pole problem is fundamentally global in nature. Quantitative calculations further confirm that no representation on the tangent space can be constructed while preserving the completeness of spherical harmonic expansions. Despite this, spherical harmonics remain widely—and paradoxically—employed in fields such as planetary gravimetry and geomagnetic field modeling, where they are used to derive tensor representations of gravitational and magnetic fields. This amounts to an unjustifiable persistence: a practice sustained for 240 years in direct violation of representation theory’s completeness requirements. The time has come to abandon this deeply entrenched but mathematically flawed approach. References | Related Articles | Metrics

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Magnetic field disturbance in the polar region during the upstream energetic ion event GE Panze, CHENG Wei, XU Xiaojun, LI Huijun, GUO Bing, LYU Jiakun 2026, 38 (2):  253-264.  DOI: 10.13679/j.jdyj.20250079 Abstract ( 32 )   PDF (8293KB) ( 17 )   On January 14, 2018, the MMS4 satellite located outside the Earth’s bow shock observed an upstream energetic ion event, during which energetic ions moved from the bow shock along the interplanetary magnetic field toward the Sun. This study analyzes the changes in the Earth’s polar magnetic field during the upstream ion event using the ionospheric equivalent current method. The conclusions are as follows: Before the occurrence of the upstream energetic ion event, the polar magnetic field exhibited intense disturbances, with a delay of several hours between the two. Prior to the event, the ionospheric current disturbances showed a significantly enhanced negative current vortex on the dayside, with curl-free component currents flowing from the dayside to the nightside. The active ionospheric currents in the polar region provided energy for the acceleration of oxygen ions, transforming them into energetic oxygen ions. These energetic oxygen ions subsequently outflowed from the magnetosphere, reached the bow shock, and finally moved upward along the interplanetary magnetic field. Upstream energetic ions may impact future manned space activities in outer space. This study provides insights for the forecasting of future upstream ion events. References | Related Articles | Metrics

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Auroral oval intensity modeling based on FA-GAN HAN Bing, ZHAO Weixiong, HU Zejun 2026, 38 (2):  265-274.  DOI: 10.13679/j.jdyj.20250075 Abstract ( 43 )   PDF (4200KB) ( 156 )   The auroral intensity of the auroral oval directly reflects the distribution characteristics of auroral particle precipitation. It serves as a critical physical parameter for investigating magnetospheric dynamics and the space environment, playing a vital role in understanding the coupling mechanisms between the magnetosphere, ionosphere, and thermosphere. Recent studies have demonstrated that specific space physical parameters are closely correlated with auroral intensity; however, their explicit mathematical relationships remain poorly defined. Neural networks offer a robust alternative by modeling these complex non-linear associations through learned mapping relationships. In this study, an auroral oval intensity dataset spanning from December 1996 to January 1997 was constructed using ultraviolet auroral imagery from the Polar satellite, integrated with six key space physical parameters retrieved from the NASA OMNI database. A prediction model mapping physical parameters to auroral oval intensity was developed based on the Feature-Aware Generative Adversarial Network (FA-GAN), a text-to-image synthesis framework. The performance of the proposed model was evaluated using four metrics: Kullback-Leibler (KL) divergence, Structural Similarity (SSIM), Structural Inception Score (SIS), and Denoising Feature Inception Distance (DFID). The experimental results indicate that the FA-GAN-based prediction model significantly outperforms existing auroral intensity models in terms of SSIM, SIS, and DFID. References | Related Articles | Metrics

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Research on ionospheric convection dawn-dusk asymmetry based on SuperDARN GAO Bingjie, LIU Erxiao, CHEN Xuan, HU Zejun , WANG Zilei, LIU Junliang 2026, 38 (2):  275-288.  DOI: 10.13679/j.jdyj.20250084 Abstract ( 40 )   PDF (5420KB) ( 155 )   Based on ionospheric convection data measured by the Super Dual Auroral Radar Network (SuperDARN) in 2024, we analyze the effects of the Interplanetary Magnetic Field (IMF) components (Bx, By, Bz), solar wind velocity (Vx), dynamic pressure (Pd), and geomagnetic activity index AE on the morphology and intensity of ionospheric convection under northward and southward IMF Bz conditions. The slope of the inter-vortex line (Ks), Cross Polar Cap Potential (CPCP), and vortex spacing are selected as characteristic indices of ionospheric convection. We analyze their correlations with the six near-Earth space parameters (Bx, By, Bz, Vx, Pd, AE) to evaluate the influence of these near-Earth space parameters on dawn-dusk asymmetry and convection intensity. The results indicate that, under northward IMF conditions, the overall coupling is weak. The linear response of the three characteristic indices to driving parameters is weak, and ionospheric convection exhibits considerable randomness and structural complexity. Under southward IMF conditions, the coupling is enhanced. Bz plays a dominant role in variations of CPCP and vortex spacing. By is the primary factor controlling dawn–dusk asymmetry, and Bx has a modulating effect on that asymmetry. Meanwhile, higher AE typically leads to increasing CPCP and larger vortex spacing (AE varies synchronously with both CPCP and vortex spacing), while Vx and Pd show weak linear correlations with the three characteristic indices. This study provides a reference for further research on the dawn–dusk asymmetry of ionospheric convection in solar wind-magnetosphere-ionosphere coupling. References | Related Articles | Metrics

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Development and sensitivity analysis of an ionospheric conductivity adjoint model YANG Hongyang, YU Qian, NIU Zhuang, GUO Bing, LYU Jiakun, LI Huijun, CHENG Wei 2026, 38 (2):  289-303.  DOI: 10.13679/j.jdyj.20250086 Abstract ( 40 )   PDF (11244KB) ( 15 )   References | Related Articles | Metrics