全球大气再分析实时资料前处理关键技术研制

针对全球实时气象数据,重点研制面向全球大气再分析的观测资料前处理关键技术,主要包括实现大量实时文件快速解析分类的数据分拣技术,实现多类气象观测要素并行解码的信息提取技术,满足同化数据格式需求和实现分级分类有效存储的自定义模板统一编码技术。关键技术已于2019年6月在国家气象信息中心业务应用,为我国第一代全球大气和陆面再分析业务提供着稳定的实时观测数据支撑。     

大气季节内振荡：其全球同步性及其与ENSO的关系

利用美国国家环境预报中心和大气研究中心的大气再分析资料，分析研究了大气季节内振荡的年际变化及其与ＥＮＳＯ的关系。揭示了全球不同纬度带之间存在着的大气季节内振荡年际变化的同步性，以及大气季节内振荡与海温和大气向外长波辐射之关系的复杂性。我们还发现大气季节内振荡与Ｎｉｎｏ３指数的关系存在年代际尺度的变化，即，这种关系有时强时弱的现象。     

Examination of the global lorenz energy cycle using MERRA and NCEP-reanalysis 2

In this study, the global Lorenz atmospheric energy cycle is evaluated using the Modern Era Retrospective analysis for Research and Applications (MERRA) and the National Center for Environmental Prediction and the Department of Energy (NCEP R2) reanalysis datasets over a 30-year period (1979–2008) for the annual, JJA, and DJF means. The energy cycle calculated from the two reanalysis datasets is largely consistent, but the energy cycle determined using the MERRA dataset is more active than that determined from the NCEP R2 dataset. For instance, with regard to the annual mean, the general discrepancy between the energy components in the global integral is about 5 %, whereas the discrepancy between the conversion components is about 16  %, with the exception of C(P_M, K_M), which has a different sign in the global integrals. The latitude-altitude cross-section indicates that the difference in the energy cycle of the two reanalysis datasets is larger in the southern hemisphere than in the northern hemisphere. The conversion rates of mean available potential energy to mean kinetic energy [C(P_M, K_M)] and eddy available potential energy to eddy kinetic energy [C(P_E, K_E)] are also calculated using two formulations (so-called ‘v·grad z’ and ‘ω·α’) for the two reanalysis datasets. The differences in the conversion rate between the two reanalysis datasets for the global integral are not appreciable for the two formulations.     

A high-resolution 44-year atmospheric hindcast for the Mediterranean Basin: contribution to the regional improvement of global reanalysis

A 44-year (1958–2001) high-resolution atmospheric hindcast for the whole Mediterranean Basin was performed within the EU-funded Hindcast of Dynamic Processes of the Ocean and Coastal Areas of Europe (HIPOCAS) Project. The long-term hindcasted data set, which comprises several atmospheric parameters at different levels, was produced by means of dynamical downscaling from the NCEP/NCAR global reanalysis using the atmospheric limited area model REMO. The REMO hindcast has been exhaustively validated. On that score, various hindcasted surface parameters, such as 10-m wind field, 2-m temperature and mean sea level pressure, have been compared to satellite data (ERS-1/2 scatterometer) and in-situ measurements from offshore stations. In addition, two ocean models (waves and sea level) have been forced with REMO hindcasted fields (mean sea level pressure and 10-m wind field). The validation of these ocean runs, performed through comparisons of simulated waves and sea level with oceanographic measurements, allows to evaluate "indirectly" the quality of the REMO hindcasted data used as atmospheric forcing. Once the quality of the hindcasted data was verified, the efficiency of the regional enhancement performed through dynamical downscaling on the NCEP global reanalysis was assessed. The regional improvement was evaluated through comparisons of REMO and NCEP performance in reproducing observations. The important improvement obtained in the characterization of extreme wind events is particularly remarkable.     

Validation of ECMWF and NCEP–NCAR Reanalysis Data in Antarctica

The European Center for Medium-Range Weather Forecast (ECMWF) Re-Analysis (ERA-40) and the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) ECMWF (ERA-40) and NCEP-NCAR reanalysis data were compared with Antarctic station observations, including surface-layer and upper-layer atmospheric observations, on intraseasonal and interannual timescales. At the interannual timescale, atmospheric pressure at different height levels in the ERA-40 data are in better agre...     

Underestimation of the Warming Trend over the Tibetan Plateau during 1998–2013 by Global Land Data Assimilation Systems and Atmospheric Reanalyses

Accurate surface air temperature (T2m) data are key to investigating eco-hydrological responses to global warming. Because of sparse in-situ observations, T2m datasets from atmospheric reanalysis or multi-source observation-based land data assimilation system (LDAS) are widely used in research over alpine regions such as the Tibetan Plateau (TP). It has been found that the warming rate of T2m over the TP accelerates during the global warming slowdown period of 1998–2013, which raises the question of whether the reanalysis or LDAS datasets can capture the warming feature. By evaluating two global LDASs, five global atmospheric reanalysis datasets, and a high-resolution dynamical downscaling simulation driven by one of the global reanalysis, we demonstrate that the LDASs and reanalysis datasets underestimate the warming trend over the TP by 27%–86% during 1998–2013. This is mainly caused by the underestimations of the increasing trends of surface downward radiation and nighttime total cloud amount over the southern and northern TP, respectively. Although GLDAS2.0, ERA5, and MERRA2 reduce biases of T2m simulation from their previous versions by 12%-94%, they do not show significant improvements in capturing the warming trend. The WRF dynamical downscaling dataset driven by ERA-Interim shows a great improvement, as it corrects the cooling trend in ERA-Interim to an observation-like warming trend over the southern TP. Our results indicate that more efforts are needed to reasonably simulate the warming features over the TP during the global warming slowdown period, and the WRF dynamical downscaling dataset provides more accurate T2m estimations than its driven global reanalysis dataset ERA-Interim for producing LDAS products over the TP.     

The influence of atmospheric circulation on the intensity of urban heat island and urban cold island in Poznań, Poland

The study has analyzed influence of an atmospheric circulation on urban heat island (UHI) and urban cold island (UCI) in Poznań. Analysis was conducted on the basis of temperature data from two measurement points situated in the city center and in the ?awica airport (reference station) and the data concerning the air circulation (Nied?wied?’s calendar of circulation types and reanalysis of National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR)). The cases with UHI constitute about 85 % of all data, and UCI phenomena appear with a frequency of 14 % a year. The intensity of UHI phenomenon is higher in the anticyclonic circulation types. During the year in anticyclonic circulation, intensity of UHI is 1.2 °C on average while in cyclonic is only 0.8 °C. The occurring of UHI phenomena is possible throughout all seasons of the year in all hours of the day usually in anticyclonic circulation types. The cases with highest UHI intensity are related mostly to nighttime. The cases of UCI phenomena occurred almost ever on the daytime and the most frequently in colder part of the year together with cyclonic circulation. Study based on reanalysis data indicates that days with large intensity of UHI (above 4, 5, and 6 °C) are related to anticyclonic circulation. Anticyclonic circulation is also promoting the formation of the strongest UCI. Results based on both reanalysis and the atmospheric circulation data (Nied?wied?’s circulation type) confirm that cases with the strongest UHI and UCI during the same day occur in strong high-pressure system with the center situated above Poland or central Europe.     

环北京地区空气污染指数与降水的周循环特征及其影响机制分析

部分气象要素在某些地区表现出明显的周循环特征,其位相和尺度因时因地而异.利用1980～2009年环北京地区地面常规观测气象要素资料、空气污染指数资料(简称API)及NCEP/DOE再分析资料,本文分析了环北京地区API、降水及多种气象要素的周变化特征,并对气溶胶影响降水的可能机制做了初步证明.分析表明:API表现出明显...     

基于不同资料的影响南海热带气旋环流背景对比北大核心CSCD

利用1981—2020年中国热带气旋最佳路径数据集、中国大气再分析资料(CMA-RA)、欧洲中期天气预报中心ERA5及美国NCEP/NCAR再分析资料(NCEP-Ⅰ),对比不同资料在表征影响南海热带气旋活动环流背景的能力,探讨CMA-RA的适用性。结果表明:不同资料基本刻画出与热带气旋活动密切相关的环流特征,包括南方涛动、菲律宾至南海低层纬向风、热带低层纬向风反向分布型、菲律宾至南海中东部低层涡度、热带西太平洋垂直风切变及南海至菲律宾以东海域中层湿度。它们对南方涛动、关键区纬向风和中层湿度的刻画较相似,CMA-RA和ERA5对南方涛动、低层纬向风及其与热带气旋关系的描述一致性高,较NCEP-Ⅰ密切,但低层经向风、关键物理量差异较大。对极端年环流具有相似的表现能力,但异常程度存在差异,海平面气压、低层纬向风高度一致,以CMA-RA与ERA5最接近;中层湿度CMA-RA与ERA5接近,较NCEP-Ⅰ偏小;关键物理量差异较大。CMA-RA对南海热带气旋环流的刻画具有与ERA5和NCEP-Ⅰ相当的性能,并与ERA5一致性较高,可为相关工作提供可替换的再分析资料集。     

全球大气角动量变化的比较分析

利用日本气象局ＧＳＭ９６０３大气数值模式和客观分析资料以及美国环境预报中心大气再分析数据研究比较全球大气角动量变化。分析表明，三者大气质量再分布角动量东经９０°Ｅ分量的符合程度要好于格林威治方向的分量；而且ＧＳＭ９６０３对大气轴向相对角动量季节变化的强度模拟与其他两者一致，并明显优于第一阶段 ＡＭＩＰ ２３个大气环流模式的平均模拟结果。另外，ＧＳＭ９６０３大气相对角动量的年际变化基本显示了厄尔尼诺变化的主要历程。     

Comparisons of Simulations of Soil Moisture Variations in the Yellow River Basin Driven by Various Atmospheric Forcing Data Sets

Based on station observations, The European Centre for Medium-Range Weather Forecasts reanalysis (ERA40), the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis and Princeton University's global meteorological forcing data set (Princeton), four atmospheric forcing fields were constructed for use in driving the Community Land Model version 3.5 (CLM3.5). Simulated soil moisture content throughout the period 1951-2000 in the Yellow River basin was vali...     

A new assessment of the mid-1970s abrupt atmospheric temperature change in the NCEP/NCAR reanalysis and associated solar forcing implications

Based on the reanalysis data from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP?CNCAR) and solar radio irradiance (SRI) at 10.7?cm wavelength obtained from the National Oceanic and Atmospheric Administration??s Space Weather Prediction center, the abrupt temperature change in the mid-1970s and its possible association with solar irradiance variability have been investigated. The results show that a discontinuous abrupt change in the mid-1970s in the NCEP?CNCAR reanalysis was observed in the tropical lower and middle stratospheric temperature. The shift in temperature and its timing agrees well with the climate regime shift discovered in the radiosonde observations (HadAT), European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40), and many previous studies and manifests a statistically significant change at the 95% confidence level. A corresponding change of the SRI was identified in the mid 1970s although the statistical t test value is not very high. The running correlation with a 21-year moving time window exhibits a strong positive correlation between the solar cycle and atmospheric temperature in the tropical stratosphere during the period of 1948?C2007. However, the positive correlation was broken at the time of the mid-1970s abrupt change and two peak positive correlation points were observed in 1972 and 1982, respectively.     

The simulation of medicanes in a high-resolution regional climate model

Medicanes, strong mesoscale cyclones with tropical-like features, develop occasionally over the Mediterranean Sea. Due to the scarcity of observations over sea and the coarse resolution of the long-term reanalysis datasets, it is difficult to study systematically the multidecadal statistics of sub-synoptic medicanes. Our goal is to assess the long-term variability and trends of medicanes, obtaining a long-term climatology through dynamical downscaling of the NCEP/NCAR reanalysis data. In this paper, we examine the robustness of this method and investigate the value added for the study of medicanes. To do so, we performed several climate mode simulations with a high resolution regional atmospheric model (CCLM) for a number of test cases described in the literature. We find that the medicanes are formed in the simulations, with deeper pressures and stronger winds than in the driving global NCEP reanalysis. The tracks are adequately reproduced. We conclude that our methodology is suitable for constructing multi-decadal statistics and scenarios of current and possible future medicane activities.     

Response of Atmospheric Energy to Historical Climate Change in CMIP5

Three forms of atmospheric energy, i.e., internal, potential, and latent, are analyzed based on the historical simulations of 32 Coupled Model Intercomparison Project Phase 5(CMIP5) models and two reanalysis datasets(NCEP/NCAR and ERA-40). The spatial pattern of climatological mean atmospheric energy is well reproduced by all CMIP5 models. The variation of globally averaged atmospheric energy is similar to that of surface air temperature(SAT) for most models. The atmospheric energy from both simulation and reanalysis decreases following the volcanic eruption in low-latitude zones. Generally, the climatological mean of simulated atmospheric energy from most models is close to that obtained from NCEP/NCAR, while the simulated atmospheric energy trend is close to that obtained from ERA-40. Under a certain variation of SAT, the simulated global latent energy has the largest increase ratio, and the increase ratio of potential energy is the smallest.     

Thirty-two-year ocean–atmosphere coupled downscaling of global reanalysis over the Intra-American Seas

This study examines the oceanic and atmospheric variability over the Intra-American Seas (IAS) from a 32-year integration of a 15-km coupled regional climate model consisting of the Regional Spectral Model (RSM) for the atmosphere and the Regional Ocean Modeling System (ROMS) for the ocean. It is forced at the lateral boundaries by National Centers for Environmental Prediction-Department of Energy (NCEP-DOE R-2) atmospheric global reanalysis and Simplified Ocean Data Assimilation global oceanic reanalysis. This coupled downscaling integration is a free run without any heat flux correction and is referred as the Regional Ocean–Atmosphere coupled downscaling of global Reanalysis over the Intra-American Seas (ROARS). The paper examines the fidelity of ROARS with respect to independent observations that are both satellite based and in situ. In order to provide a perspective on the fidelity of the ROARS simulation, we also compare it with the Climate Forecast System Reanalysis (CFSR), a modern global ocean–atmosphere reanalysis product. Our analysis reveals that ROARS exhibits reasonable climatology and interannual variability over the IAS region, with climatological SST errors less than 1 °C except along the coastlines. The anomaly correlation of the monthly SST and precipitation anomalies in ROARS are well over 0.5 over the Gulf of Mexico, Caribbean Sea, Western Atlantic and Eastern Pacific Oceans. A highlight of the ROARS simulation is its resolution of the loop current and the episodic eddy events off of it. This is rather poorly simulated in the CFSR. This is also reflected in the simulated, albeit, higher variance of the sea surface height in ROARS and the lack of any variability in the sea surface height of the CFSR over the IAS. However the anomaly correlations of the monthly heat content anomalies of ROARS are comparatively lower, especially over the Gulf of Mexico and the Caribbean Sea. This is a result of ROARS exhibiting a bias of underestimation (overestimation) of high (low) clouds. ROARS like CFSR is also able to capture the Caribbean Low Level Jet and its seasonal variability reasonably well.     

Global Modelling of the Atmospheric Methyl Bromide Budget

A global three-dimensional chemical transport model has been used to identify and evaluate possible candidates for the `missing' surface source required to balance the atmospheric budget of methyl bromide. Both natural and anthropogenic emissions of methyl bromide are `coloured' in the model, thus allowing the global CH₃Br distribution to be broken-down into its source components. These coloured CH₃Br tracers are then combined in various ways to create one base-line emission scenario and five further plausible scenarios. The additional emission scenarios are specifically designed to test whether the geographical distribution and seasonal cycles of additional vegetation and/or increased biomass burning emissions are consistent with atmospheric observations of methyl bromide mixing ratios. Due to an imbalance in our current understanding of the methyl bromide budget, simulated CH₃Br mixing ratios from the base-line emission scenario are significantly lower than atmospheric measurements. Both the inclusion of a vegetation source in the tropics and a double strength biomass burning source substantially improve the agreement between model simulations and atmospheric measurements compared with the base-line emission scenario. While measurement data provides useful information on global fluxes and regional CH₃Br seasonal cycles, small differences between the simulated seasonal cycles of different emission scenarios makes it difficult to distinguish between the relative likelihoods of model scenarios containing a tropical vegetation source or an increased biomass burning source. Further measurements performed in continental mid-to-high northern latitudes, central-southern Africa and South America would be of particular benefit in future attempts to constrain the location and magnitude of the natural terrestrial sources of methyl bromide.     

东亚夏季风降水年代际变异模态及其与太平洋年代际振荡的关系

利用全球陆地月平均降水资料、英国气象局哈德莱中心的月平均海表温度距平(SSTA)资料及NCEP/NCAR再分析大气环流资料,探讨东亚夏季风降水年代际变率及其与太平洋年代际振荡(PDO)的联系。研究指出:东亚夏季风降水年代际变异模态以及PDO均在1976年前后呈现显著的年代际转折,并且东亚夏季风降水与PDO在年代际尺度上具有较好的相关关系。PDO能够在对流层低层激发出与年代际东亚夏季风环流较为相似的大气环流异常特征,表明东亚夏季风环流的年代际变化可能受大气外强迫因子PDO在对流层低层的外源强迫作用影响,最终导致东亚夏季风降水发生年代际变化。     

ENSO对印度洋偶极子非对称性的影响及机制研究北大核心

利用海表温度再分析资料、NCEP/NCAR大气环流再分析资料以及MPI-ESM1-2-LR气候模式PI-Control试验输出数据等,通过对不同强度的厄尔尼诺-南方涛动(El Nino-Southern Oscillation, ENSO)事件所对应的印度洋偶极子(Indian Ocean Dipole, IOD)事件的分析,探讨了ENSO对IOD偏度的调制作用。结果表明,伴随着赤道中东太平洋明显的正海温偏度,秋季印度洋海表温度存在西正东负的偏度。IOD与ENSO之间呈现出较强的非线性关系,且大部分强的正IOD事件对应着强El Nino事件。强El Nino位相下,IOD事件相关的海温与风场表现出很强的响应,强于La Nina事件产生的响应,表现为强的非对称性;相比较而言,弱El Nino事件与La Nina事件下引起的印度洋海温和风场的强度相当,并没有显著的非对称性。因此,ENSO可通过激发非对称的大气遥相关对IOD强度非对称性产生调制作用,印度洋海表温度偏度很大程度上是由强El Nino事件导致的强正IOD事件所贡献。     

基于多套再分析数据的全球山脉力矩计算及比较分析

山脉力矩是地球与大气角动量交换的重要途径之一,为了深刻地理解全球的大气环流变化,比较了NCEP再分析数据、欧洲中心中尺度天气预报的ECMWF再分析数据和NASA的MERRA再分析数据计算的1979-2012年的全球山脉力矩的时、空分布及其年际变化。研究发现三套数据计算的山脉力矩空间分布基本一致,均显示北半球的青藏高原、落基山脉以及南半球的安第斯山脉是对全球山脉力矩贡献最大的三个区域。NCEP再分析数据计算的山脉力矩空间差异和多年变化标准差明显高于其他两套数据,其在纬向上的积分廓线与其他两套数据也差异较大,但是全球积分以后其平均值与标准差与其他两套数据基本一致,而且其在欧亚、南美和北美区域的积分与其他两套数据也没有明显差别,因此,NCEP再分析数据适用于大尺度的山脉力矩模拟。在研究空间尺度较小的山脉力矩变化时,建议优先考虑ECMWF和MERRA再分析数据。三套数据对北美地区山脉力矩计算的一致性较高,其次是欧亚地区,对南美区域山脉力矩计算的一致性则较差,表明北美地区气象数据质量要高于亚洲,南美洲气象数据质量较差。欧亚地球山脉力矩与大西洋-欧洲环流有很强的相关,北美山脉力矩与太平洋区极涡面积关系密切。