Atmospheric and Oceanic Science Letters最新文献

{"title":"Projection of extreme climate change in the Asian arid region and the Tibetan Plateau in the early and middle 21st century based on NEX-GDDP-CMIP6","authors":"Yankun Sun ,&nbsp;Rui Zhu ,&nbsp;Tao Wang","doi":"10.1016/j.aosl.2024.100534","DOIUrl":"10.1016/j.aosl.2024.100534","url":null,"abstract":"<div><div>In the context of global warming, it is anticipated that both the intensity and the frequency of future global extreme high precipitation (EHP) and extreme high temperature (EHT) events will increase. To evaluate the future extreme climate changes in the Asian arid region and Tibetan Plateau, this study applied the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP-CMIP6) to assess the changes in EHP (Rx5d and R95pTOT) and EHT (TX90p and TXx) under different emission scenarios in the 21st century. Findings suggest that both the frequency and the intensity of the extreme indices will increase, exhibiting accelerated growth under higher emission scenarios, particularly under the SSP5-8.5 emission scenario. It is suggested that the growth of EHT and EHP in the early subperiod of the 21st century (2026–2045) will be relatively moderate, with small differences between different emission scenarios. However, by the middle subperiod of the 21st century (2041–2060), the differences between different emission scenarios will become larger than the 2035s and the growth will become more intense. In western central Asia, TX90p, TXx, Rx5d, and R95pTOT increase by 9.7%–14.2% (13.3%–24.7%), 1.3°C–1.7°C (1.6°C–2.7°C), 6.5%–8.9% (8.2%–8.8%), and 18.1%–27.0% (25.6%–30.0%) by the early (middle) subperiod; in eastern central Asia, TX90p, TXx, Rx5d, and R95pTOT increase 8.1%–12.0% (11.3%–21.1%), 1.4°C–1.8°C (1.9°C–2.9°C), 7.4%–9.7% (10.4%–13.8%), and 20.2%–29.3% (32.0%–40.8%) by the early (middle) subperiod; and over the Tibetan Plateau, TX90p, TXx, Rx5d, and R95pTOT increase 12.5%–17.4% (17.0%–31.0%), 1.2°C–1.5°C (1.6°C–2.5°C), 7.2%–10.0% (9.9%–15.0%), and 26.6%–33.1% (36.1%–55.3%) by the early (middle) subperiod.</div><div>摘要</div><div>近年来, 随着全球变暖, 大部分地区极端气候事件的风险都有所增加. 作为中国一带一路建设核心区域的亚洲干旱区和青藏高原区域面临着严峻的极端气候风险. 本文利用NEX-GDDP-CMIP6数据预估了未来21世纪早期 (2026–2045) 和中期 (2041–2060) 不同排放情景下亚洲干旱区和青藏高原相较气候参考期 (1995–2014) 极端高温指数和极端降水指数的变化. 预估结果显示, 在不同排放情景下极端高温指数和极端降水指数都有所上升, 且在SSP5-8.5情景下增长最多, 其中NEX-GDDP-CMIP6不同模式对极端高温指数的模拟一致性高于极端降水指数. 21世纪中期相比早期极端高温指数和极端降水指数的增长更加严重.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100534"},"PeriodicalIF":2.3,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141398743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of the simulation performance of WRF-Solar for a summer month in China using ground observation network data","authors":"Xin Yue ,&nbsp;Xiao Tang ,&nbsp;Bo Hu ,&nbsp;Keyi Chen ,&nbsp;Qizhong Wu ,&nbsp;Lei Kong ,&nbsp;Huangjian Wu ,&nbsp;Zifa Wang ,&nbsp;Jiang Zhu","doi":"10.1016/j.aosl.2024.100532","DOIUrl":"10.1016/j.aosl.2024.100532","url":null,"abstract":"<div><div>Solar energy is a pivotal clean energy source in the transition to carbon neutrality from fossil fuels. However, the intermittent and stochastic characteristics of solar radiation pose challenges for accurate simulation and prediction. Accurately simulating and predicting solar radiation and its variability are crucial for optimizing solar energy utilization. This study conducted simulation experiments using the WRF-Solar model from 25 June to 25 July 2022, to evaluate the accuracy and performance of the simulated solar radiation across China. The simulations covered the whole country with a grid spacing of 27 km and were compared with ground observation network data from the Chinese Ecosystem Research Network. The results indicated that WRF-Solar can accurately capture the spatiotemporal patterns of global horizontal irradiance over China, but there is still an overestimation of solar radiation, and the model underestimates the total cloud cover. The root-mean-square error ranged from 92.83 to 188.13 <span><math><mrow><mrow><mi>W</mi><mspace></mspace></mrow><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></mrow></math></span> and the mean bias (MB) ranged from 21.05 to 56.22 <span><math><mrow><mrow><mi>W</mi><mspace></mspace></mrow><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></mrow></math></span>. The simulation showed the smallest MB at Lhasa on the Qinghai–Tibet Plateau, while the largest MB was observed in Southeast China. To enhance the accuracy of solar radiation simulation, the authors compared the Fast All-sky Radiation Model for Solar with the Rapid Radiative Transfer Model for General Circulation Models and found that the former provides better simulation.</div><div>摘要</div><div>准确模拟和预测太阳辐射及其变化对于优化太阳能利用至关重要. 本研究使用WRF-Solar模式对中国2022 年 6 月 25 日至 7 月 25 日的太阳辐射情况进行了深入模拟, 模式网格水平分辨率为27 km, 通过与中国生态系统研究网络 (CERN) 的地面观测网络数据的37个观测站点进行对比, 以评估模式性能. 结果表明: WRF-Solar模式能较好地捕捉到中国上空的辐照度GHI (Global Horizontal Irradiance) 的时空分布特征, 但存在高估太阳辐射量, 以及低估总云量的情况. 全国的总辐射模拟均方根误差范围为92.83–188.13 W m⁻², 平均偏差范围为21.05–56.22 W m⁻². 青藏高原拉萨站的偏差最小, 在中国东南部的偏差最大. 为了进一步提升太阳辐射模拟的精确度, 本研究还对比了FARMS与RRTMG辐射方案, 发现FARMS方案的模拟精度更高.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 4","pages":"Article 100532"},"PeriodicalIF":2.3,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141394617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The asymmetry of air temperature: A new potential method to predict precipitation frequency","authors":"Yinan Xie,&nbsp;Fenghua Xie","doi":"10.1016/j.aosl.2024.100531","DOIUrl":"10.1016/j.aosl.2024.100531","url":null,"abstract":"<div><div>There is a significant bias in the precipitation frequency (PF) obtained from numerical model simulations. In this study, the authors use the temperature asymmetry (TA) as an indirect indicator to predict PF. The empirical orthogonal function method is used to analyze the spatiotemporal correlation of TA and PF at interannual and interdecadal time scales. Furthermore, the authors explore using the TA to improve PF prediction in CMIP6 models. Results show that (1) on an interannual time scale, PF and TA show good spatial and temporal correlations; (2) PF and TA exhibit similar modal transitions on interdecadal time scales; and (3) using TA as an indirect indicator can significantly improve the prediction of PF. The TA may be an indirect method for improving precipitation predictions.</div><div>摘要</div><div>在数值模拟中日降水频率具有明显的偏差. 利用EOF方法, 分析了在年际和年代际尺度上降水频率与气温的非对称性的时空相关特征, 并探索使用非对称性改进模式降水频率预测的方法. 得到以下结论: 1) 在年际尺度上, 降水频率和气温的非对称的前两个模态的空间和时间相关系数良好; 2) 在年代际尺度上两者展现出相似的模态转变; 3) 非对称性作为降水频率的间接指标可以明显的改进降水频率的预测.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 4","pages":"Article 100531"},"PeriodicalIF":2.3,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141401487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analyzing uncertainty and constraining projections for future vegetation in mid-to-high-latitude Asia","authors":"Jiangfeng Wei ,&nbsp;Ye Pu ,&nbsp;Xiaocong Liu ,&nbsp;Yufeng Shan ,&nbsp;Botao Zhou","doi":"10.1016/j.aosl.2024.100522","DOIUrl":"10.1016/j.aosl.2024.100522","url":null,"abstract":"<div><div>Mid-to-high-latitude Asia (MHA) is one of the regions most impacted by global warming and is highly vulnerable to the effects of climate change on its ecosystems. The future vegetation changes in this region are still uncertain, warranting a comprehensive investigation. In this study, the authors conducted a comparative analysis of leaf area index (LAI) projections by models in phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively) under high emission scenarios (RCP8.5 and SSP5–8.5, respectively). It was found that the CMIP6 models offer greater consistency with historical observations and demonstrate reduced prediction uncertainty compared to the CMIP5 models. There are strong linear relationships between the historical and future vegetation characteristics among the CMIP6 models, which enables a constrained projection of future vegetation based on historical vegetation observations. The model projections suggest a prospective overall increase in the mean, interannual variability, and seasonal amplitude of LAI in the MHA region in the future period (2061–2100) in comparison to the historical period (1985–2014). These results underscore the imperative need to enhance the understanding of ecosystem responses to climate extremes in this region.</div><div>摘要</div><div>亚洲中高纬地区是受全球变暖影响最严重的地区之一, 其生态系统高度受到气候变化的影响. 然而, 该地区未来植被变化仍不确定, 需要进行全面调查. 在这项研究中, 作者比较分析了耦合模式比较计划第五和第六阶段 (CMIP5和CMIP6) 中高排放情景 (分别为RCP8.5和SSP5–8.5) 下的叶面积指数 (LAI) 预测. 分析发现, CMIP6模式的LAI结果与历史观测数据更为一致, 并且相比CMIP5模式表现出更小的预测不确定性. CMIP6模式的历史和未来植被特征之间具有强线性关系, 这使得基于历史植被观测进行未来植被预测成为可能. 预测表明, 未来 (2061–2100年) 与历史时期 (1985–2014年) 相比, 亚洲中高纬度地区LAI的平均值, 年际变率和季节振幅将整体增加. 研究结果强调了提高对该地区生态系统应对气候极端事件的理解的重要性.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100522"},"PeriodicalIF":2.3,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141280053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A maximum sea surface salinity tongue in the North Brazil continental shelf","authors":"Maria Cadima ,&nbsp;Paola Castellanos ,&nbsp;Estrella Olmedo ,&nbsp;Joaquim Dias ,&nbsp;Edmo J.D. Campos","doi":"10.1016/j.aosl.2024.100521","DOIUrl":"10.1016/j.aosl.2024.100521","url":null,"abstract":"<div><div>The variability of the sea surface salinity measurements provided by the Soil Moisture and Ocean Salinity mission reveals the presence of a local salinity maximum (a salty tongue) in the northwestern tropical Atlantic. The sea surface salinity positive anomaly starts increasing in July, reaches its maximum in January, and then disappears. The local maximum of salinity appears in the late boreal autumn/winter, when the Amazon discharge is minimal and the salty water from the South Atlantic is transported by the North Brazil Current along the shelf break across the equator. The authors validate the satellite observations in this area and assess the vertical structure of the salinity maximum by using <em>in situ</em> measurements and an <em>in situ</em>-interpolated product.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100521"},"PeriodicalIF":2.3,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improving subseasonal forecasting of East Asian monsoon precipitation with deep learning","authors":"Jiahui Zhou ,&nbsp;Fei Liu","doi":"10.1016/j.aosl.2024.100520","DOIUrl":"10.1016/j.aosl.2024.100520","url":null,"abstract":"<div><div>Accurate subseasonal forecasting of East Asian summer monsoon (EASM) precipitation is crucial, as it directly impacts the livelihoods of billions. However, the prediction skill of state-of-the-art subseasonal-to-seasonal (S2S) models for precipitation remains limited. In this study, the authors developed a convolutional neural network (CNN) regression model to enhance the prediction skill for weekly EASM precipitation by utilizing the more reliably predicted circulation fields from dynamic models. The outcomes of the CNN model are promising, as it led to a 14 % increase in the anomaly correlation coefficient (ACC), from 0.30 to 0.35, and a 22 % reduction in the root-mean-square error (RMSE), from 3.22 to 2.52, for predicting the weekly EASM precipitation index at a leading time of one week. Among the S2S models, the improvement in prediction skill through CNN correction depends on the model's performance in accurately predicting circulation fields. The CNN correction of EASM precipitation index can only rectify the systematic errors of the model and is independent of whether the each grid point or the entire area-averaged index is corrected. Furthermore, u200 (200-hPa zonal wind) is identified as the most important variable for efficient correction.</div><div>摘要</div><div>东亚夏季风(EASM)降水的准确次季节预报至关重要, 因为它直接影响着数十亿人的生计. 然而, 最先进的次季节-季节(S2S)预测模型的预测技巧仍然有限. 本研究开发了一种卷积神经网络(CNN)回归模型, 通过利用动力预测模型预测的更可靠的环流场来提高EASM周降水的预测技巧. 经过CNN模型的订正, 在提前一周预测EASM降水指数时, 11个S2S模式的平均距平相关系数从增加了14 %, 从0.30增加到0.35; 均方根误差减少了22 %, 从3.22减少到2.52. 在这些S2S模式中, 通过CNN订正对预测技巧的提高程度取决于模式在准确预测大气环流变量方面的表现. 对EASM降水指数的CNN订正只能订正模式的系统误差, 与逐个网格订正还是整个区域平均指数订正无关, 并且在不同的提前期内CNN的订正效果基本不变. 此外, 200hPa纬向风被认为是有效订正的最重要变量.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100520"},"PeriodicalIF":2.3,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Upper-ocean cooling rate of the South China Sea in response to extreme cold surges and weak cold-air invasions","authors":"Weiwei Zhang ,&nbsp;Dongxiao Wang ,&nbsp;Marco Y.-T. Leung ,&nbsp;Lin Wang ,&nbsp;Jinchi Xie ,&nbsp;Wen Zhou","doi":"10.1016/j.aosl.2024.100517","DOIUrl":"10.1016/j.aosl.2024.100517","url":null,"abstract":"<div><div>Cold-surge events can lead to temperature drops and strong winds, which then leads to upper-ocean cooling and deepening of the mixed-layer depth, as illustrated in previous studies. In this study, based on the temperature drop of Shanwei meteorological station, two extreme cold surges and five weak cold invasions in the South China Sea are simulated using an ocean–atmosphere coupled model to investigate their different impacts on the upper-ocean temperature. The diffusion term contributes to the difference in temperature tendency of the upper 20 m, while the advection term contributes to the positive difference from 20 to 80 m of the offshore region and negative difference from 80 to 160 m. In addition, the significant differences are attributed primarily to the influence of the upper-ocean temperature gradient, which subsequently impacts the advection term and results in notable differences in temperature tendency at depths from 80 to 160 m.</div><div>摘要</div><div>前人的研究揭示了寒潮事件导致近地气温下降和强风, 也导致上层海洋冷却和混合层深度加深. 本研究根据汕尾气象站的气温变化, 并利用海气耦合模型模拟了南海的两次极端寒流和五次弱冷空气入侵, 研究它们对上层海洋温度变化的不同影响. 研究结果说明了扩散项对上层20米的温度变化差异的贡献, 平流项是导致20至80米的正温度变化差异的主要原因, 平流项也导致80至160米的负温度变化差异. 此外, 这种显著差异主要归因于上层海洋温度梯度的影响, 进而影响平流项, 使80至160米深度的温度变化存在显著差异.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100517"},"PeriodicalIF":2.3,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141134621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of ocean wave spectra on the polarized bidirectional reflectance distribution function matrix at Ku‐band and its implications on satellite backscattering simulations","authors":"Lingli He ,&nbsp;Fuzhong Weng","doi":"10.1016/j.aosl.2024.100518","DOIUrl":"10.1016/j.aosl.2024.100518","url":null,"abstract":"<div><div>A polarized bidirectional reflectance distribution function (pBRDF) matrix is developed from two-scale roughness theory with the aim of providing more accurate simulations of microwave emissions and scattering required for ocean–atmosphere coupled radiative transfer models. The potential of the pBRDF matrix is explored for simulating the ocean backscatter at Ku-band. The effects of ocean wave spectra including the modified Durden and Vesecky (DV2), Elfouhaily, and Kudryavtsev spectra on the pBRDF matrix backscatter simulations are investigated. Additionally, the differences in backscattering normalized radar cross-section (NRCS) simulations between the Ku-band geophysical model function and pBRDF matrix are analyzed. The results show that the pBRDF matrix can reasonably reproduce the spatial distribution of ocean surface backscattering energy, but the distribution pattern and numerical values are influenced by ocean wave spectra. The DV2 spectrum is the best one for the pBRDF matrix to simulate horizontally polarized NRCSs, with the exception of scenarios where the incidence angle is below 35°, the wind speed is less than 10 m s⁻¹, and in the cross-wind direction. Also, the DV2 spectrum effectively characterizes the wind speed and relative azimuth angle dependence for vertically polarized NRCSs. The Elfouhaily spectrum is suitable for simulating vertically polarized NRCSs under conditions of low wind speed (below 5 m s⁻¹) and incidence angles under 40°. The Kudryavtsev spectrum excels in simulating vertically polarized NRCSs at high incidence angles (&gt; 40°) and horizontally polarized NRCSs at low incidence angles (&lt; 35°).</div><div>摘要</div><div>为提供微波海洋-大气耦合辐射传输模型所需的精确发射和散射, 基于双尺度粗糙度理论发展了极化双向反射分布函数 (pBRDF) 矩阵. 本研究探讨了pBRDF矩阵是否能够表征ku波段洋面后向散射, 对比了三种常用海浪谱模型对pBRDF矩阵后向散射模拟的影响, 分析了ku波段地球物理模型函数 (GMF) 与pBRDF矩阵在后向散射归一化雷达截面 (NRCS) 模拟中的差异. 结果表明, pBRDF矩阵能够准确再现洋面后向散射能量的空间分布, 但后向散射能量分布受海浪谱影响较大.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100518"},"PeriodicalIF":2.3,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141145335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long-term variations of the solar energy in different subregions of Northwest China and associated mechanisms","authors":"Junhui Yu ,&nbsp;Hui Ma ,&nbsp;Shen-Ming Fu ,&nbsp;Xiaoling Su ,&nbsp;Xiqiang Chang ,&nbsp;Yanan Fu","doi":"10.1016/j.aosl.2024.100515","DOIUrl":"10.1016/j.aosl.2024.100515","url":null,"abstract":"<div><div>As a type of clean and pollution-free energy source, solar energy plays an important role in achieving the goals of carbon neutrality and global sustainable development. Northwest China occupies an important position in the national energy strategy due to its rich solar energy. Clarifying the long-term variations of Northwest China's solar energy and understanding the associated mechanisms are crucial to improving the layout of new energy sources and the usage efficiency of solar energy within China. In this study, the authors first divide Northwest China into northwestern and southeastern sections by conducting a rotated empirical orthogonal function analysis on the surface solar radiation (SSR) from 1993 to 2022, and then explore the SSR's variation trends and associated mechanisms within these subregions. It is found that the two subregions, both of which show a significant feature of decadal change, differ notably in their long-term trends: the northwestern section shows a significant increasing trend of ∼8.1 kJ m⁻² yr⁻¹ in the annual mean SSR, and in each season the SSR increases significantly, with a maximum/minimum increasing rate of ∼11.2/∼4.6 kJ m⁻² yr⁻¹ appearing in summer/autumn. A possible mechanism for the SSR's increasing trend is that global warming results in a lower relative humidity within the northwestern section, which decreases the total cloud cover, as it is harder for the atmosphere to reach saturation state. A decreasing total cloud cover results in an increasing SSR within the northwestern section. In contrast, the southeastern section shows no significant trend in annual mean SSR, as the SSRs in summer and autumn show significant decreasing trends, whereas the trends in spring and winter are not significant.</div><div>摘要</div><div>作为一种清洁无污染的新能源, 太阳能对于实现碳中和及可持续发展的目标至关重要. 西北地区太阳能资源丰富, 在我国能源战略中占据着重要地位. 厘清西北地区太阳能的长期变化趋势并揭示其可能的内在机理有助于改善我国的新能源布局并提高太阳能的利用效率. 鉴于此, 作者首先对1993年至2022年的地表太阳辐射 (SSR) 进行了旋转经验正交函数分析, 将西北地区划分为西北和东南两个分区, 然后分别研究了这些分区内SSR的变化趋势和相关机制. 研究发现, 在西北地区的两个分区内, SSR均表现出显著的年代际变化特征, 但两个分区内的SSR趋势存在显著不同. 对于西北分区而言, 其年平均SSR呈现出显著的增长趋势 (增速约为8.1 kJ m⁻² yr⁻¹), 在每个季节, 其季节平均的SSR都显著增加, 最大与最小增速分别为11.2 (夏季) 和4.6 kJ m⁻² yr⁻¹ (秋季). 该区域内SSR增加趋势的一个可能机制是, 全球变暖导致该区域内相对湿度较低, 所以大气更难达到饱和状态, 这直接导致该区域内的总云量减少; 总云量的减少使得云对太阳短波辐射的反射, 散射和吸收减弱, 因此, 该区域内SSR增加. 对于东南分区而言, 由于其夏季和秋季的SSR呈显著的下降趋势, 而春季和冬季的SSR趋势并不显著, 所以该区域内年平均的SSR没有显著的线性趋势.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100515"},"PeriodicalIF":2.3,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141034397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Construction and characteristic analysis of background error covariance coupled with land surface temperature","authors":"Qihang Yang ,&nbsp;Yaodeng Chen ,&nbsp;Luyao Qin ,&nbsp;Yuanbing Wang ,&nbsp;Deming Meng ,&nbsp;Xusheng Yan ,&nbsp;Xinyao Qian","doi":"10.1016/j.aosl.2024.100512","DOIUrl":"10.1016/j.aosl.2024.100512","url":null,"abstract":"<div><div>Land surface temperature (LST) is the key variable in land–atmosphere interaction, having an important impact on weather and climate forecasting. However, achieving consistent analysis of LST and the atmosphere in assimilation is quite challenging. This is because there is limited knowledge about the cross-component background error covariance (BEC) between LST and atmospheric state variables. This study aims to clarify whether there is a relationship between the error of LST and atmospheric variables, and whether this relationship varies spatially and temporally. To this end, the BEC coupled with atmospheric variables and LST was constructed (LST-BEC), and its characteristics were analyzed based on the 2023 mei-yu season. The general characteristics of LST-BEC show that the LST is mainly correlated with the atmospheric temperature and the correlation decreases gradually with a rise in atmospheric height, and the error standard deviation of the LST is noticeably larger than that of the low-level atmospheric temperature. The spatiotemporal characteristics of LST-BEC on the heavy-rain day and light-rain day show that the error correlation and error standard deviation of LST and low-level atmospheric temperature and humidity are closely related to the weather background, and also have obvious diurnal variations. These results provide valuable information for strongly coupled land–atmosphere assimilation.</div><div>摘要</div><div>地表温度 (LST) 是涉及陆气相互作用的关键变量, 对天气气候预报具有重要影响. 不过在同化中实现LST与大气的协调分析却并不容易. 这是因为目前对跨陆气圈层的背景误差协方差 (BEC) 的了解较少. 本文旨在探究LST与大气的背景误差是否存在联系, 以及这种联系是否存在时空变化. 为此, 本研究构建了耦合大气变量和LST的BEC, 并基于2023年梅雨季分析了其特征. 总体特征表明: LST误差主要与大气温度相关; 随着大气高度的上升, 误差相关性逐渐减小; LST误差的标准差明显大于低层大气温度. “多雨日”和“少雨日”的时空特征表明, LST与低层大气温湿度误差的相关性及标准差均与天气背景密切相关, 且具有明显的昼夜变化. 上述结果可为后续陆气强耦合同化提供参考.</div></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"18 3","pages":"Article 100512"},"PeriodicalIF":2.3,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143868400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}