Atmospheric General Circulation Research Articles

Using statistical downscaling to assess skill of decadal predictions

We test a hypothesis that the signal-to-noise ratio of decadal forecasts improves with larger scales and can be utilised through model output statistics (MOS) involving empirical-statistical downscaling and dependencies to large-scale conditions. Here, we used MOS applied to an ensemble of decadal forecasts to predict local wet-day frequency, the wet-day mean precipitation, and the mean temperature for one to nine year long intervals of forecasts with a one year lead time. Our study involved a set of decadal forecasts over the 1961–2011 period, based on a global coupled ocean-atmosphere model that was downscaled and analysed for the North Atlantic region. The MOS for the decadal forecasts failed to identify aspects that were associated with higher skill for temperature and precipitation over Europe on time scales shorter than five years. A likely explanation for not enhancing skillful parts of the forecasts was that the raw model output had low skill for the general large-scale atmospheric circulation. This was particularly true for the wet-day frequency over Europe, which had a strong connection to the mean sea-level pressure (SLP) anomalies over the North Atlantic. There was a weak connection between large-scale maritime surface temperature anomalies and local precipitation and temperature variability over the European continent. The decadal forecasts for time scale of nine years and longer, on the other hand, exhibited moderate skill. The dependency between temporal and spatial scales was found to differ for the temperature and the mean SLP anomalies, but we found little indication that the decadal predictions for anomalies with large-scale regional extent were associated higher skill than for more local patterns in these forecasts.

气候变化情景下基于最大熵模型的青海云杉潜在分布格局模拟

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化情景下基于最大熵模型的青海云杉潜在分布格局模拟 DOI: 10.5846/stxb201809151999 作者: 作者单位: 甘肃农业大学林学院,兰州大学生命科学学院,甘肃农业大学林学院,甘肃农业大学林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 甘肃农业大学科技创新基金-公招博士科研启动基金项目（GSAU-RCZX01707）；学科建设专项基金项目（GAU-XKJS-2018-099）；国家自然基金项目（31860197） Simulation of the potential distribution patterns of Picea crassifolia in climate change scenarios based on the maximum entropy (Maxent) model Author: Affiliation: Gansu Agricultural University, Lanzhou 730070 Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:青海云杉（Picea crassifolia）是我国青藏高原东北缘特有树种，在维系我国西北地区生态平衡、水土保持、水源涵养和生物多样性等方面发挥着重要作用。基于其分布范围内的69个地理分布样点，利用最大熵（Maxent）模型对现实气候条件下青海云杉的潜在分布及其分布的主导气候因子进行分析，同时结合3种大气环流模型模拟青海云杉在3种气候变化情景（温室气候排放量不同）下未来2050s和2080s潜在分布区的变化。结果表明：Maxent模型对青海云杉潜在分布区的预测具有极高的准确度，所有模型的平均受试者工作特征曲线下面积（AUC测试值）均高于0.99；Jackknife检验和气候因子响应曲线表明年最低降雨量是限制青海云杉分布的主导因子；当前青海云杉的潜在分布区主要集中于青海东部、甘肃东南部、宁夏大部分地区、西藏东部、四川西部山区以及陕西、新疆和内蒙古部分地区。在未来3种增温情景下，青海云杉在2050s和2080s的潜在分布总面积与当前相比变化不明显，但不同适生等级的潜在分布面积变化较大，其中，中度适生区和低度适生区受气候增温影响显著，中度增温下这些区域在2080s的面积明显增大，而高度适生区（核心分布）则在所有增温情景下均呈缩小趋势。同时，在未来3种增温情景下，青海云杉在2050s和2080s的潜在分布区有向北移动趋势，但其心分布区域（高度适生区）仍然以青海东部、甘肃北部为主，无明显变迁趋势。从气候因素角度考虑，本研究表明未来气候变化情景下，青海云杉依然在西部高山地区，特别是作为我国重要生态屏障的祁连山、贺兰山等山区具有重要的经济价值并将持续其生态服务功能。 Abstract:Qinghai spruce (Picea crassifolia) is the endemic tree species in the northeastern margin of the Qinghai-Tibet Plateau (QTP) in China. It plays an important role in maintaining ecological balance, biodiversity, and soil and water conservation in northwestern China. In this study, the current potential distribution of Qinghai spruce and its dominant climatic factors were analyzed firstly based on 69 distributional records via the maximum entropy model (Maxent). Then the distribution patterns of Qinghai spruce under three climate change scenarios (i.e., the lowest, a moderate, and the highest greenhouse gas emission scenarios; RCP2.6, RCP4.5 and RCP8.5) with three general atmospheric circulation models were predicted by Maxent for two future decades:the 2050s and 2080s. The results showed that the accuracy of the Maxent model was pretty high for modeling potential distribution regions of Qinghai spruce, and the average values of the area under the receiver operator characteristic curve (AUC) were higher than 0.99. The results from the Jackknife test and climate factor response curves revealed that the annual lowest precipitation is the key factor that limited the distribution of Qinghai spruce; the current potential distribution regions of Qinghai spruce are mainly concentrated in eastern Qinghai, southeastern Gansu, most of Ningxia, eastern Tibet, mountainous areas of western Sichuan, and parts of Shaanxi, Xinjiang, and Inner Mongolia. The total potential distribution area of Qinghai spruce in the 2050s and 2080s was changed little compared to the current distribution in all three scenarios, but its potential distribution area at different levels of fitness was changed a lot. Among them, the regions with fitness of less than 0.1 and in the range of 0.1-0.3 were significantly affected by the climate changes, and their area was largely increased in the medium emission scenario. In contrast, the regions with fitness in the range of 0.5-0.8 were shrunk in all scenarios. At the same time, the distribution patterns of Qinghai spruce in the 2050s and 2080s had a tendency to move northward in all scenarios, whereas its central distributional regions (more suitable regions) were still kept in eastern Qinghai and northern Gansu, with no obvious trend to change. From the perspective of climatic factors, this study showed that Qinghai spruce would continue to have important economic values and ecological service functions in the western mountains, especially in the Qilian Mountains and Helan Mountains, which are the important ecological barriers in China. 参考文献 相似文献 引证文献

On the large-scale dynamics of f−plane zonally symmetric circulations

In this study, an f-plane dynamical model for incompressible flows is presented to examine the mechanisms underlying the structure and stability of large-scale zonally symmetric circulations. Analyses based on the Principle of Exchange of Stabilities reveal that this zonally symmetric model possesses a single-cell structure in the absence of the Coriolis force, similar to the single-cell general atmospheric circulation in the absence of the Earth’s rotation as previously hypothesized. The circulation, however, bifurcates into a triple-cell structure in the presence of the Coriolis force if the vertical temperature gradient, the rotational rate, and the momentum eddy coefficients satisfy a certain constraint. Further analyses of this triple-cell structure as a result of the Coriolis force show that this structure is topologically stable, thus offering new insight into the highly resilient structure of the Earth’s atmospheric global circulations.

Relationship between Meteorological Factors and Diffusion of Atmospheric Pollutants

In order to explore the influence of meteorological conditions on the diffusion of atmospheric pollutants, this study takes Linfen City, a key national air pollution city, as an example, and uses the daily air pollution concentration data, wind direction and wind speed observation data and the ground weather observation data from 2016 to 2017 in this area to analyze the distribution characteristic and variation law of the main atmospheric pollutants (PM10, PM2.5, SO2, CO, O3, NO2). The influence of local meteorological conditions and general atmospheric circulation on the diffusion of atmospheric pollutants is discussed. The results show that the air pollution in Linfen City has obvious seasonal difference. The air quality is better in summer and autumn, and the main pollution is concentrated in heating period. The effect of meteorological factors on air quality index (AQI) is significantly different at different periods. In the non-heating period, there is a good negative correlation between precipitation and PM2.5, PM10, SO2 and NO2; the relative humidity, air temperature and cloud cover are negatively correlated with most pollution factors. In the heating period, the air temperature, relative humidity and cloud cover are positively correlated with most pollution factors. The wind speed is less correlated with AQI in the non-heating period, and only has a good negative correlation with NO2. In the heating period, the wind speed is negatively correlated with pollution factors except O3.

A long-term survey unveils strong seasonal patterns in the airborne microbiome coupled to general and regional atmospheric circulations.

Airborne microbes (bacteria, archaea, protists, and fungi) were surveyed over a 7-y period via high-throughput massive sequencing of 16S and 18S rRNA genes in rain and snow samples collected fortnightly at a high-elevation mountain Long-Term Ecological Research (LTER) Network site (LTER-Aigüestortes, Central Pyrenees, Spain). This survey constitutes the most comprehensive mountain-top aerobiology study reported to date. The air mass origins were tracked through modeled back-trajectories and analysis of rain water chemical composition. Consistent microbial seasonal patterns were observed with highly divergent summer and winter communities recurrent in time. Indicative microbial taxa were unveiled as a forensic signature, and ubiquitous taxa were observed as common atmosphere inhabitants, highlighting aerosols as a potentially successful mechanism for global microbial dispersal. Source-tracking analyses identified freshwater, cropland, and urban biomes as the most important sources for airborne bacteria in summer, while marine and forest biomes prevailed in winter, in agreement with air mass retrotrajectories and the prevailing general and regional atmospheric circulation.

Precipitation Sensitivity to Local Variations in Tropical Sea Surface Temperature

AbstractThe driving of tropical precipitation by the variability of the underlying sea surface temperature (SST) plays a critical role in the atmospheric general circulation. To assess the precipitation sensitivity to SST variability, it is necessary to observe and understand the relationship between precipitation and SST. However, the precipitation–SST relationships from any coupled atmosphere–ocean system can be difficult to interpret given the challenge of disentangling the SST-forced atmospheric response and the atmospheric intrinsic variability. This study demonstrates that the two components can be isolated using uncoupled atmosphere-only simulations, which extract the former when driven by time-varying SSTs and the latter when driven by climatological SSTs. With a simple framework that linearly combines the two types of uncoupled simulations, the coupled precipitation–SST relationships are successfully reproduced. Such a framework can be a useful tool for quantitatively diagnosing tropical air–sea interactions. The precipitation sensitivity to SST variability is investigated with the use of uncoupled simulations with prescribed SST anomalies, where the influence of atmospheric intrinsic variability on SST is deactivated. Through a focus on local precipitation–SST relationships, the precipitation sensitivity to local SST variability is determined to be predominantly controlled by the local background SST. In addition, the strength of the precipitation response increases monotonically with the local background SST, with a very sharp growth at high SSTs. These findings are supported by basic principles of moist static stability, from which a simple formula for precipitation sensitivity to local SST variability is derived.

Impact of a Stochastic Nonorographic Gravity Wave Parameterization on the Stratospheric Dynamics of a General Circulation Model

AbstractThe general circulation of the middle atmosphere, particularly of the mesosphere, is strongly dependent on the forcing arising from gravity wave processes. Their sources in the troposphere are both orographic and nonorographic, the latter being strongly intermittent. In climate models, the effects of gravity waves need to be parameterized, often assuming that their properties are constant. In this work we focus on the changes of the middle atmosphere due to the introduction of intermittency in a parameterization of nonorographic gravity waves, using a stochastic version of the Hines scheme. The stochastic approach is tailored to the diagnosed sensitivity of the model to this forcing, and peculiar changes emerge even if a relatively small amount of intermittency is prescribed. We analyze in detail the changes of the stratospheric dynamics in the tropical region and the global circulation of the middle atmosphere, when the stochastic parameterization is employed in place of the deterministic one. The mean state and variability of the model, realistic also in the default version, are preserved when stochasticity is added. Significant changes are observed in the mesosphere due to an enhanced poleward transport, leading to warming in the winter season. While there are some improvements of the mean state, the interannual variability is not significantly affected in the extratropics. The impacts on the simulated equatorial stratosphere are evident, as the stochasticity reduces the overall period of the quasi‐biennial oscillation but also leads to a net reduction of the variability between cycles.

An update on global atmospheric ice estimates from satellite observations and reanalyses

Abstract. This study assesses the global distribution of mean atmospheric ice mass from current state-of-the-art estimates and its variability on daily and seasonal timescales. Ice water path (IWP) retrievals from active and passive satellite platforms are analysed and compared with estimates from two reanalysis data sets, ERA5 (European Centre for Medium-range Weather Forecasts Reanalysis 5, ECMWF) and MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications 2). Large discrepancies in IWP exist between the satellite data sets themselves, making validation of the model results problematic and indicating that progress towards a consensus on the distribution of atmospheric ice has been limited. Comparing the data sets, zonal means of IWP exhibit similar shapes but differing magnitudes, with large IWP values causing much of the difference in means. Diurnal analysis centred on A-Train overpasses shows similar structures in some regions, but the degree and sign of the variability varies widely; the reanalyses exhibit noisier and higher-amplitude diurnal variability than borne out by the satellite estimates. Spatial structures governed by the atmospheric general circulation are fairly consistent across the data sets, as principal component analysis shows that the patterns of seasonal variability line up well between the data sets but disagree in severity. These results underscore the limitations of the current Earth observing system with respect to atmospheric ice, as the level of consensus between observations is mixed. The large-scale variability of IWP is relatively consistent, whereas disagreements on diurnal variability and global means point to varying microphysical assumptions in retrievals and models alike that seem to underlie the biggest differences.

Aerosol versus greenhouse gas impacts on Southern Hemisphere general circulation changes

This study re-examines the possible impacts of anthropogenic aerosols (AERs), which are primarily concentrated in the Northern Hemisphere extratropics, on atmospheric general circulation changes in the Southern Hemisphere (SH). The long-term trends of the SH Hadley Cell edge and Southern Annular Mode (SAM) are evaluated for the historical and single forcing experiments of 12 models archived for the Fifth Coupled Model Inter-comparison Project (CMIP5). The AER-induced temperature changes are typically opposite in sign to that of the greenhouse gas (GHG)-induced changes. However, the zonal-mean circulation changes driven by the AERs are not simply opposite to those due to the GHGs. Depending on the analysis period, they can be either opposite or the same as the GHG-induced ones. It is also found that the inter-model spread of AER-driven circulation changes is primarily dependent on the uncertainty of tropospheric temperature changes, particularly static stability changes in the subtropics, whereas that of GHG-induced changes in the austral summer is influenced by the uncertainty of both the tropospheric and polar lower-stratospheric temperature changes. This accentuates that the AER-induced SH circulation changes are not simply mirroring the GHG-induced ones.

Ice state evolution during spring in Richardson crater, Mars

The Martian climate is governed by an annual cycle, that results in the condensation of CO2 ice during winter, up to a meter thick at the pole and thousands of kilometers in extension. Water and dust may be trapped during the condensation and freed during the sublimation. In addition, ice may be translucent or granular depending on the deposition process (snow vs direct condensation), annealing efficiency, and dust sinking process. The determination of ice translucency is of particular interest to confirm or reject the cold jet model (also known as Kieffer model).This work is focused on the dune field of Richardson Crater (72° S, 180° W)in which strong interactions between the water, dust and CO2 cycles are observed. We analyzed CRISM hyperspectral images in the near IR using radiative transfer model inversion. We demonstrate that among the states of CO2 ice, the translucent state is observed most frequently. The monitoring of surface characteristics shows a decrease in the thickness of the ice during the spring consistently with climate models simulations. We estimate a very low dust content of a few ppmv into the CO2 ice, consistent with the formation scenario of cold jets. The water impurities is around 0.1%v, almost stable during the spring, suggesting a water escape from the surface of subliming CO2 ice layer. The water ice grain size varies in a range 1 to 50 microns. From these results, we propose the following new mechanism of small water ice grain suspension: as a cold jet occurs, water ice grains of various sizes are lifted from the surface. These jets happen during daytime, when the general upward gas flux from the subliming CO2 ice layer is strong enough to carry the smaller grains, while the bigger fall back on the CO2 ice layer. The smaller water grains are carried away and integrated to the general atmospheric circulation.

Subtropical hydroclimate during Termination V (∼430-422 ka): Annual records of extreme precipitation, drought, and interannual variability from Santa Barbara Basin

Hydroclimate extremes are expected to become more frequent and intense with anthropogenic climate forcing, but future El Niño-Southern Oscillation (ENSO) behavior is unclear. Understanding of extreme hydroclimate variability and magnitude prior to human-influences is limited by short instrumental records, however, continuous sedimentary archives of past hydroclimate variability can complement and extend these records. Laminated Santa Barbara Basin (SBB) sediment cores MV0508-33JPC, −21JPC, and −29JPC preserve annually-resolved, multi-centennial-scale precipitation records from Termination V (TV), the transition from glacial Marine Isotope Stage (MIS) 12 to interglacial MIS 11 at 424 ka. These records provide insights into the subtropical hydroclimate response to warming. Foraminiferal δ18O variations indicate rapid warming and/or salinity changes, and were used to verify the TV age assignment. A paleoprecipitation proxy was developed using the first principal component of scanning XRF elemental counts (PC1), which has high loadings for siliciclastic sediment-associated elements K, Ti, and Si. Sedimentary laminae couplets identified in PC1 were annually-tuned to investigate TV paleoprecipitation variability, as modern SBB laminae represent annual deposits. Extreme flooding and decadal-to-centennial droughts were identified, with magnitudes exceeding modern observations. ENSO-like (2–7 year) paleoprecipitation periodicities coincide with wetter intervals, but ENSO variability is reduced during droughts. A 1500-year arid interval may be related to poleward shifting of general atmospheric circulation as ice sheets melted, such that the subtropical dry zone intersected California. Southern California paleoprecipitation reconstructions from past warm climates provide insight into precipitation variability and magnitude on interannual timescales, and can reduce uncertainties in predictions of interannual climate, including ENSO.

Vertical Helicity Flux as an Index of General Atmospheric Circulation

As an index of the general atmospheric circulation over the hemisphere, it is proposed to calculate the hemisphere-area-averaged (poleward of the latitude 20°) product of the Coriolis parameter by the wind velocity squared at the upper boundary of the planetary boundary layer. In practical calculations, data on the wind velocity at an isobaric level of 850 hPa were used. Control calculations for the 900 hPa level gave similar results. It is shown that the index introduced adequately characterizes the seasonal and interannual variability of the general atmospheric circulation over both hemispheres.

Multifractal Detrended Fluctuation Analysis of Regional Precipitation Sequences Based on the CEEMDAN-WPT

In this paper, the complete ensemble empirical mode decomposition with the adaptive noise (CEEMDAN) algorithm is introduced into the complexity research of precipitation systems to improve the traditional complexity measure method specific to the mode mixing of the Empirical Mode Decomposition (EMD) and incomplete decomposition of the ensemble empirical mode decomposition (EEMD). We combined the CEEMDAN with the wavelet packet transform (WPT) and multifractal detrended fluctuation analysis (MF-DFA) to create the CEEMDAN-WPT-MFDFA, and used it to measure the complexity of the monthly precipitation sequence of 12 sub-regions in Harbin, Heilongjiang Province, China. The results show that there are significant differences in the monthly precipitation complexity of each sub-region in Harbin. The complexity of the northwest area of Harbin is the lowest and its predictability is the best. The complexity and predictability of the middle and Midwest areas of Harbin are about average. The complexity of the southeast area of Harbin is higher than that of the northwest, middle, and Midwest areas of Harbin and its predictability is worse. The complexity of Shuangcheng is the highest and its predictability is the worst of all the studied sub-regions. We used terrain and human activity as factors to analyze the causes of the complexity of the local precipitation. The results showed that the correlations between the precipitation complexity and terrain are obvious, and the correlations between the precipitation complexity and human influence factors vary. The distribution of the precipitation complexity in this area may be generated by the superposition effect of human activities and natural factors such as terrain, general atmospheric circulation, land and sea location, and ocean currents. To evaluate the stability of the algorithm, the CEEMDAN-WPT-MFDFA was compared with the equal probability coarse graining LZC algorithm, fuzzy entropy, and wavelet entropy. The results show that the CEEMDAN-WPT-MFDFA was more stable than 3 contrast methods under the influence of white noise and colored noise, which proves that the CEEMDAN-WPT-MFDFA has a strong robustness under the influence of noise.

Actinometric System Aboard the Yak-42D “Roshydromet” Research Aircraft

The actinometric system installed aboard the Yak-42D "Roshydromet" research aircraft is presented. It is designed to study radiation processes in the troposphere. The system is based on standard Kipp&Zonen actinometric instruments for measuring solar, thermal, and ultraviolet radiation fluxes as well as on specially developed radiation models with high-precision methods for solving radiative transfer equations (Monte Carlo, k-distribution, and line-by-line calculations). The combination of actinometric measurements and detailed simulation of radiative transfer in the atmosphere allows examining the radiation balance components throughout the troposphere using in situ measurements at the aircraft location. Some results of studying radiation fluxes obtained during the flights over the Arctic region of the Russian Federation are presented. The data of measurements carried out using the presented system are useful for validating radiation codes utilized in general atmospheric circulation models and for processing satellite remote sensing data.

Cyclonic circulation of Saturn’s atmosphere due to tilted convection

Saturn displays cyclonic vortices at its poles and the general atmospheric circulation at other latitudes is dominated by embedded zonal jets that display cyclonic circulation. The abundance of small-scale convective storms suggests that convection plays a role in producing and maintaining Saturn’s atmospheric circulation. However, the dynamical influence of small-scale convection on Saturn’s general circulation is not well understood. Here we present laboratory analogue experiments and propose that Saturn’s cyclonic circulation can be explained by tilted convection in which buoyancy forces do not align with the planet’s rotation axis. In our experiments—conducted with a cylindrical water tank that is heated at the bottom, cooled at the top and spun on a rotating table—warm rising plumes and cold sinking water generate small anticyclonic and cyclonic vortices that are qualitatively similar to Saturn’s convective storms. Numerical simulations complement the experiments and show that this small-scale convection leads to large-scale cyclonic flow at the surface and anticyclonic circulation at the base of the fluid layer, with a polar vortex forming from the merging of smaller cyclonic storms that are driven polewards. Saturn’s cyclonic atmospheric circulation may be explained by the dynamics of small-scale convection, suggest laboratory analogue experiments.

Peculiarities of Thunderstorms’ Occurrences on the Border of the Western Siberia Plains and Altai Mountains

Mountains of Altai are characterized by the greatest elevation in the Siberian region, creating an obstacle for Western air masses transfer. This fact determines the diversity of micro-climatic conditions. Complex climatic and geomorphologic factors create the variety of storms in certain regions of the mountainous country. At the same time, the climate and the weather in the mountains of Altai is the product of processes of general atmospheric circulation. Any economic activity feels the risk during storms. The airport on the territory of the Altai Republic which receives a lot of passengers, especially in the summer, operates again. Therefore, it is rational to conduct the study of the relationship of thunderstorm activity with cyclonic activity, which was the purpose of the study, on the Northern slopes of the Altai, where the airport and the weather station are situated. The results of the study allowed identifying the periods of thunderstorms’ manifestation on the border of the plains of Western Siberia and the Altai Mountains, as well as their confinement to the frontal phenomena.

Abrupt Change in Sahara Precipitation and the Associated Circulation Patterns

This study investigates the changes in inter-annual summer precipitation and the relationship with the atmospheric general circulation in the Sahara Desert occurred in the last 40 years (1971-2010). The results show that the summer precipitation undergone in drought recovery with a strong abrupt change at the end of 20th century. This change in Sahara precipitation is subsequently accompanied with the changes in the atmospheric circulation. The Sahara drought recovery is associated with a significant warming in the tropical and extratropical sea surface temperature, which led to the increase in moisture budget of the tropical African monsoon. The remarkable features such as the strengthening in Arctic high and mid-latitude upper level westerly wind, weakening in subpolar low and upper tropospheric zonal wind over North Africa have shown a distinct relationship with the Sahara precipitation changes.

Effective parameterizations of biologically active UV radiation absorption by atmospheric ozone

A method for parameterization of the UV radiation absorption by atmospheric ozone is described. Parameterizations are suggested for computer simulation of tropospheric fluxes of UV–A and UV–B radiations and modified fluxes of biologically active UV radiation in medical applications (for the analysis of vitamin D formation and risk of erythema, cancer, and cataract). The parameterizations allow the solution of the UV radiation transfer equations at a single effective spectral point for obtaining integral fluxes in the 280–400 nm range (taking into account the spectral factors characterizing biological effects). When using the parameterizations, the characteristic errors in the calculations of the fluxes in a clear and cloudy troposphere are ~3–5%. The use of these parameterizations is relevant for fast radiation models, for example, on-line simulation of UV radiation fluxes for medical purposes. This method can be used to improve the accuracy of radiation codes in general atmospheric circulation models, radiation-chemical models, etc.

The 2015/16 “Super” El Niño Event and Its Climatic Impact

Climatic monitoring shows that 2015 has been the warmest year around the globe since the first modern observation was conducted in1880. Asia has witnessed its average land surface temperature reaching the highest level since 1901; China has seen the warmest year since 1951 when it had completed the meteorological records; the CO2 concentration in the atmosphere exceeds 400[Formula: see text]ppm; the ocean thermal capacity sets a new record high; and the global sea surface temperature has also been the highest since 1870. Against the backdrop of global warming, the incidence of strong El Niño and the duration of El Niño in the central and eastern equatorial Pacific Ocean have both significantly increased, while the time interval between El Niño and La Niña has shortened. The 2015/16 “Super” El Niño event exceeds previous two “Super” El Niño events in several indexes (e.g. durative event and peak intensity), although the 1982/83 El Niño event keeps the record in terms of the intensity of atmospheric response to the ocean. Influenced by the 2015/16 “Super” El Niño event, the general atmospheric circulation was significantly abnormal with extreme climate events frequently occurring in many places worldwide.

Estimation of uncertainty in surface air temperature climatic trends related to the internal dynamics of the atmosphere

The variability of zonal trends of surface air temperature for the period 1979–2012 is analyzed using ensemble simulations with a general atmospheric circulation model (AGCM) with identical prescribed conditions at the lower boundary of the atmosphere and different initial conditions. It is shown that the dependence of the variability of intra-ensemble zonal temperature trends on the variability of zonal fluctuations of temperature anomalies (associated with the internal variability of atmospheric circulation in the AGCM) is described quite well in terms of the stationary stochastic process model. In such a model, the dependence of the standard deviation of intra-ensemble trends can be approximated by a linear function of the standard deviation of temperature fluctuations, which agrees well with the AGCM results.