共查询到20条相似文献，搜索用时 30 毫秒
1.
Based on a novel design of coupled model simulations where sea surface temperature (SST) variability in the equatorial tropical Pacific was constrained to follow the observed El Niño—Southern Oscillation (ENSO) variability, while rest of the global oceans were free to evolve, the ENSO response in SSTs over the other ocean basins was analyzed. Conceptually the experimental setup was similar to discerning the contribution of ENSO variability to interannual variations in atmospheric anomalies. A unique feature of the analysis was that it was not constrained by a priori assumptions on the nature of the teleconnected response in SSTs. The analysis demonstrated that the time lag between ENSO SST and SSTs in other ocean basins was about 6 months. A signal-to-noise analysis indicated that between 25 and 50 % of monthly mean SST variance over certain ocean basins can be attributed to SST variability over the equatorial tropical Pacific. The experimental setup provides a basis for (a) attribution of SST variability in global oceans to ENSO variability, (b) a method for separating the ENSO influence in SST variations, and (c) understanding the contribution from other external factors responsible for variations in SSTs, for example, changes in atmospheric composition, volcanic aerosols, etc. 相似文献
2.
Pascal Terray Kakitha Kamala Sébastien Masson Gurvan Madec A. K. Sahai Jing-Jia Luo Toshio Yamagata 《Climate Dynamics》2012,39(3-4):729-754
The impact of diurnal SST coupling and vertical oceanic resolution on the simulation of the Indian Summer Monsoon (ISM) and its relationships with El Ni?o-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events are studied through the analysis of four integrations of a high resolution Coupled General Circulation Model (CGCM), but with different configurations. The only differences between the four integrations are the frequency of coupling between the ocean and atmosphere for the Sea Surface Temperature (SST) parameter (2 vs. 24?h coupling) and/or the vertical oceanic resolution (31 vs. 301 levels) in the CGCM. Although the summer mean tropical climate is reasonably well captured with all the configurations of the CGCM and is not significantly modified by changing the frequency of SST coupling from once to twelve per day, the ISM–ENSO teleconnections are rather poorly simulated in the two simulations in which SST is exchanged only once per day, independently of the vertical oceanic resolution used in the CGCM. Surprisingly, when 2?h SST coupling is implemented in the CGCM, the ISM–ENSO teleconnection is better simulated, particularly, the complex lead-lag relationships between the two phenomena, in which a weak ISM occurs during the developing phase of an El Ni?o event in the Pacific, are closely resembling the observed ones. Evidence is presented to show that these improvements are related to changes in the characteristics of the model’s El Ni?o which has a more realistic evolution in its developing and decaying phases, a stronger amplitude and a shift to lower frequencies when a 2-hourly SST coupling strategy is implemented without any significant changes in the basic state of the CGCM. As a consequence of these improvements in ENSO variability, the lead relationships between Indo-Pacific SSTs and ISM rainfall resemble the observed patterns more closely, the ISM–ENSO teleconnection is strengthened during boreal summer and ISM rainfall power spectrum is in better agreement with observations. On the other hand, the ISM–IOD teleconnection is sensitive to both SST coupling frequency and the vertical oceanic resolution, but increasing the vertical oceanic resolution is degrading the ISM–IOD teleconnection in the CGCM. These results highlight the need of a proper assessment of both temporal scale interactions and coupling strategies in order to improve current CGCMs. These results, which must be confirmed with other CGCMs, have also important implications for dynamical seasonal prediction systems or climate change projections of the monsoon. 相似文献
3.
This study uses experiments with an atmospheric general circulation model (AGCM) to address the role of the oceans and the effect of land–atmosphere coupling on the predictability of summertime rainfall over northern Argentina focusing on interdecadal time scales during 1901–2006. Ensembles of experiments where the AGCM is forced with historical sea surface temperature (SST) in the global, Pacific and tropical-North Atlantic domains are used. The role of land–atmosphere interaction is assessed comparing the output of simulations with active and climatological soil moisture. A maximum covariance analysis between precipitation and SST reveals the impact of the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation and the equatorial–tropical South Atlantic on rainfall over northern Argentina. Model simulations further show that while the dominant influence comes from the Pacific basin, the Atlantic influence can explain a large transition from dry to wet decades over northern Argentina during the beginning of the 1970s. Analysis of anomalies before and after the transition reveals an upper level anticyclonic circulation off the Patagonian coast with barotropic structure. This circulation enhances the moisture transport and convergence in northern Argentina and, together with enhanced evaporation, increased the rainfall after 1970. The SST pattern is dominated by cold conditions in the equatorial Atlantic and warm eastern Pacific and South Atlantic. We also found that land–atmosphere interaction leads to a representation of the long term rainfall evolution over northern Argentina that is closer to the observed one. Moreover, it leads to a smaller dispersion among ensemble members, thus resulting in a larger signal-to-noise ratio. 相似文献
4.
Wei Zhou Mengyan Chen Wei Zhuang Fanghua Xu Fei Zheng Tongwen Wu Xin Wang 《大气科学进展》2016,33(2):208-220
The second-generation Global Ocean Data Assimilation System of the Beijing Climate Center(BCC_GODAS2.0) has been run daily in a pre-operational mode.It spans the period 1990 to the present day.The goal of this paper is to introduce the main components and to evaluate BCC_GODAS2.0 for the user community.BCC_GODAS2.0 consists of an observational data preprocess,ocean data quality control system,a three-dimensional variational(3DVAR) data assimilation,and global ocean circulation model[Modular Ocean Model 4(MOM4)].MOM4 is driven by six-hourly fluxes from the National Centers for Environmental Prediction.Satellite altimetry data,SST,and in-situ temperature and salinity data are assimilated in real time.The monthly results from the BCC_GODAS2.0 reanalysis are compared and assessed with observations for 1990-2011.The climatology of the mixed layer depth of BCC-GODAS2.0 is generally in agreement with that of World Ocean Atlas 2001.The modeled sea level variations in the tropical Pacific are consistent with observations from satellite altimetry on interannual to decadal time scales.Performances in predicting variations in the SST using BCC_GODAS2.0 are evaluated.The standard deviation of the SST in BCC-GODAS2.0 agrees well with observations in the tropical Pacific.BCC-GODAS2.0 is able to capture the main features of E1 Nino Modoki I and Modoki Ⅱ,which have different impacts on rainfall in southern China.In addition,the relationships between the Indian Ocean and the two types of E1 Nino Modoki are also reproduced. 相似文献
5.
A coupled climate–carbon cycle model composed of a process-based terrestrial carbon cycle model, Sim-CYCLE, and the CCSR/NIES/FRCGC atmospheric general circulation model was developed. We examined the multiple temporal scale functions of terrestrial ecosystem carbon dynamics induced by human activities and natural processes and evaluated their contribution to fluctuations in the global carbon budget during the twentieth century. Global annual net primary production (NPP) and heterotrophic respiration (HR) increased gradually by 6.7 and 4.7%, respectively, from the 1900s to the 1990s. The difference between NPP and HR was the net carbon uptake by natural ecosystems, which was 0.6 Pg C year?1 in the 1980s, whereas the carbon emission induced by human land-use changes was 0.5 Pg C year?1, largely offsetting the natural terrestrial carbon sequestration. Our results indicate that monthly to interannual variation in atmospheric CO2 growth rate anomalies show 2- and 6-month time lags behind anomalies in temperature and the NiNO3 index, respectively. The simulated anomaly amplitude in monthly net carbon flux from terrestrial ecosystems to the atmosphere was much larger than in the prescribed air-to-sea carbon flux. Fluctuations in the global atmospheric CO2 time series were dominated by the activity of terrestrial vegetation. These results suggest that terrestrial ecosystems have acted as a net neutral reservoir for atmospheric CO2 concentrations during the twentieth century on an interdecadal timescale, but as the dominant driver for atmospheric CO2 fluctuations on a monthly to interannual timescale. 相似文献
6.
The thirty year simulation of the coupled global atmosphere-tropical Pacific Ocean general circulation model of the Laboratoire
de Métérologie Dynamique and the Laboratoire d’Océanographie Dynamique et de Climatologie presented in Part I is further investigated
in order to understand the mechanisms of interannual variability. The model does simulate interannual events with ENSO characteristics;
the dominant periodicity is quasi-biennial, though strong events are separated by four year intervals. The mechanism that
is responsible for seasonal oscillations, identified in Part I, is also active in interannual variability with the difference
that now the Western Pacific is dynamically involved. A warm interannual phase is associated with an equatorward shift of
the ITCZ in the Western and Central Pacific. The coupling between the ITCZ and the ocean circulation is then responsible for
the cooling of the equatorial subsurface by the draining mechanism. Cold subsurface temperature anomalies then propagate eastward
along the mean equatorial thermocline. Upon reaching the Eastern Pacific where the mean thermocline is shallow, cold subsurface
anomalies affect surface temperatures and reverse the phase of the oscillation. The preferred season for efficient eastward
propagation of thermocline depth temperature anomalies is boreal autumn, when draining of equatorial waters towards higher
latitudes is weaker than in spring by a factor of six. In that way, the annual cycle acts as a dam that synchronizes lower
frequency oscillations.
Received: 7 April 1997 / Accepted: 15 July 1998 相似文献
7.
Alessandro Attanasio 《Theoretical and Applied Climatology》2012,110(1-2):281-289
In this paper, we analyze the Granger causality from natural or anthropogenic forcings to global temperature anomalies. The lag-augmented Wald test is performed, and its robustness is also evaluated considering bootstrap method. The results show there is no-evidence of Granger causality from natural forcings to global temperature. On the contrary, a detectable Granger causality is found from anthropogenic forcings to global temperature confirming that greenhouse gases have an important role on recent global warming. 相似文献
8.
Since the World War II, many economies have transitioned from an agrarian, biomass-based to an industrial, minerals-based metabolic regime. Since 1950, world population grew by factor 2.7 and global material consumption by factor 3.7–71 Gigatonnes per year in 2010. The expansion of the resource base required by human societies is associated with growing pressure on the environment and infringement on the habitats of other species. In order to achieve a sustainability transition, we require a better understanding of the currently ongoing metabolic transition and its potential inertia. In this article, we present a long-term global material flow dataset covering material extraction, trade, and consumption of 177 individual countries between 1950 and 2010. We trace patterns and trends in material flows for six major geographic and economic country groupings and world regions (Western Industrial, the (Former) Soviet Union and its allies, Asia, the Middle East and Northern Africa, Latin America and the Caribbean, and Sub-Saharan Africa) as well as their contribution to the emergence of a global metabolic profile during a period of rapid industrialization and globalization. Global average material use increased from 5.0 to 10.3 tons per capita and year (t/cap/a) between 1950 and 2010. Regional metabolic rates range from 4.5 t/cap/a in Sub-Saharan Africa to 14.8 t/cap/a in the Western Industrial grouping. While we can observe a stabilization of the industrial metabolic profile composed of relatively equal shares of biomass, fossil energy carriers, and construction minerals, we note differences in the degree to which other regions are gravitating toward a similar form of material use. Since 2000, Asia has overtaken the Western Industrial grouping in terms of its share in global resource use although not in terms of its per capita material consumption. We find that at a sub-global level, the roles of the world regions have changed. There are, however, no signs yet that this will lead to stabilization or even a reduction of global resource use. 相似文献
9.
10.
Interactions between the tropical and subtropical northern Pacific at decadal time scales are examined using uncoupled oceanic and atmospheric simulations. An atmospheric model is forced with observed Pacific sea surface temperatures (SST) decadal anomalies, computed as the difference between the 2000–2009 and the 1990–1999 period. The resulting pattern has negative SST anomalies at the equator, with a global pattern reminiscent of the Pacific decadal oscillation. The tropical SST anomalies are responsible for driving a weakening of the Hadley cell and atmospheric meridional heat transport. The atmosphere is then shown to produce a significant response in the subtropics, with wind-stress-curl anomalies having the opposite sign from the climatological mean, consistent with a weakening of the oceanic subtropical gyre (STG). A global ocean model is then forced with the decadal anomalies from the atmospheric model. In the North Pacific, the shallow subtropical cell (STC) spins down and the meridional heat transport is reduced, resulting in positive tropical SST anomalies. The final tropical response is reached after the first 10 years of the experiment, consistent with the Rossby-wave adjustment time for both the STG and the STC. The STC provides the connection between subtropical wind stress anomalies and tropical SSTs. In fact, targeted simulations show the importance of off-equatorial wind stress anomalies in driving the oceanic response, whereas anomalous tropical winds have no role in the SST signal reversal. We further explore the connection between STG, STC and tropical SST with the help of an idealized model. We argue that, in our models, tropical SST decadal variability stems from the forcing of the Pacific subtropical gyre through the atmospheric response to ENSO. The resulting Ekman pumping anomaly alters the STC and oceanic heat transport, providing a negative feedback on the SST. We thus suggest that extratropical atmospheric responses to tropical forcing have feedbacks onto the ocean dynamics that lead to a time-delayed response of the tropical oceans, giving rise to a possible mechanism for multidecadal ocean-atmosphere coupled variability. 相似文献
11.
What drives national adaptation? A global assessment 总被引：1，自引：1，他引：0
Lea Berrang-Ford James D. Ford Alexandra Lesnikowski Carolyn Poutiainen Magda Barrera S. Jody Heymann 《Climatic change》2014,124(1-2):441-450
That the climate is changing and societies will have to adapt is now unequivocal, with adaptation becoming a core focus of climate policy. Our understanding of the challenges, needs, and opportunities for climate change adaptation has advanced significantly in recent years yet remains limited. Research has identified and theorized key determinants of adaptive capacity and barriers to adaptation, and more recently begun to track adaptation in practice. Despite this, there is negligible research investigating whether and indeed if adaptive capacity is translating into actual adaptation action. Here we test whether theorized determinants of adaptive capacity are associated with adaptation policy outcomes at the national level for 117 nations. We show that institutional capacity, in particular measures of good governance, are the strongest predictors of national adaptation policy. Adaptation at the national level is limited in countries with poor governance, and in the absence of good governance other presumed determinants of adaptive capacity show limited effect on adaptation. Our results highlight the critical importance of institutional good governance as a prerequisite for national adaptation. Other elements of theorized adaptive capacity are unlikely to be sufficient, effective, or present at the national level where national institutions and governance are poor. 相似文献
12.
A preindustrial climate experiment was conducted with the third version of the CNRM global atmosphere–ocean–sea ice coupled
model (CNRM-CM3) for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4). This experiment is
used to investigate the main physical processes involved in the variability of the North Atlantic ocean convection and the
induced variability of the Atlantic meridional overturning circulation (MOC). Three ocean convection sites are simulated,
in the Labrador, Irminger and Greenland–Iceland–Norwegian (GIN) Seas in agreement with observations. A mechanism linking the
variability of the Arctic sea ice cover and convection in the GIN Seas is highlighted. Contrary to previous suggested mechanisms,
in CNRM-CM3 the latter is not modulated by the variability of freshwater export through Fram Strait. Instead, the variability
of convection is mainly driven by the variability of the sea ice edge position in the Greenland Sea. In this area, the surface
freshwater balance is dominated by the freshwater input due to the melting of sea ice. The ice edge position is modulated
either by northwestward geostrophic current anomalies or by an intensification of northerly winds. In the model, stronger
than average northerly winds force simultaneous intense convective events in the Irminger and GIN Seas. Convection interacts
with the thermohaline circulation on timescales of 5–10 years, which translates into MOC anomalies propagating southward from
the convection sites. 相似文献
13.
Global warming exerts a lengthening effect on the growing season, with observational evidences emerging from different regions over the world. However, the difficulty for a global overview of this effect for the last century arises from limited availability of the long-term daily observations. In this study, we find a good linear relationship between the start (end) date of local growing season (LGS) and the monthly mean temperature in April (October) using the global gridded daily temperature dataset for 1960–1999. Using homogenized daily temperature records from nine stations where the time series go back to the beginning of the twentieth century, we find that the rate of change in the start (end) date of the LGS for per degree warming in April (October) mean temperature keeps nearly constant throughout the time. This enables us to study LGS changes during the last century using global gridded monthly mean temperature data. The results show that during the period 1901–2009, averaged over the observation areas, the LGS length has increased by a rate of 0.89 days decade?1, mainly due to an earlier start (?0.58 days decade?1). This is smaller than those estimates for the late half of the twentieth century, because of multidecadal climate variability (MDV). A MDV component of the LGS index series is extracted by using Ensemble Empirical Mode Decomposition method. The MDV exhibits significant positive correlation with the Atlantic Multi–decadal Oscillation (AMO) over most of the Northern Hemisphere lands, but negative in parts of North America and Western Asia for start date of LGS. These are explained by analyzing differences in atmospheric circulation expressed by sea level pressure departures between the warm and cool phases of AMO. It is suggested that MDV in association with AMO accelerates the lengthening of LGS in Northern Hemisphere by 53 % for the period 1980–2009. 相似文献
14.
Jinbao Li Edward R. Cook Rosanne D’arrigo Fahu Chen Xiaohua Gou 《Climate Dynamics》2009,32(7-8):1173-1186
Moisture variability across China and Mongolia (hereafter, CM) during 1951–2005 was investigated using the recently developed monthly Palmer Drought Severity Index (PDSI) dataset. In total there are 206 PDSI grid points across CM, based on a 2.5° × 2.5° gridding system. For CM as a whole a significant decreasing trend in mean moisture availability was observed during 1951–2005, but with strong decadal (17.1-year) and interannual (5.0-year, 3.2-year, 2.4–2.8 year) variations. The areas affected by moderate and severe moisture deficit over CM have increased significantly since the mid-1950s. In contrast, there is a significant decreasing trend for areas affected by moderate wetness since the mid-1950s, and no significant trend was found for the areas affected by severe wetness. Ten moisture-related spatial patterns were objectively defined for CM using rotated Empirical Orthogonal Function (REOF) analysis. These patterns are related to distinct geographical areas and are associated with distinct temporal variations. Four of these patterns, in Northeast China (NE), North China (NC), Central China (CC), and East China (EC), generally demonstrate a significant decreasing trend in moisture availability. Two patterns located in western areas of Northwest China (NW) and the Tibetan Plateau (TP) show a significant moisture increase, while four patterns in Mongolia (MN), far western China (FW), South China (SC), and Southwest China (SW) do not have significant moisture trends during 1951–2005. Based on REOF results we propose that CM should be divided into ten coherent moisture divisions. Moisture variations within each division are generally coherent, but may show either similar or contrasting covariability with adjacent divisions. 相似文献
15.
Proxy and instrumental records reflect a quasi-cyclic 50–80-year climate signal across the Northern Hemisphere, with particular presence in the North Atlantic. Modeling studies rationalize this variability in terms of intrinsic dynamics of the Atlantic Meridional Overturning Circulation influencing distribution of sea-surface-temperature anomalies in the Atlantic Ocean; hence the name Atlantic Multidecadal Oscillation (AMO). By analyzing a lagged covariance structure of a network of climate indices, this study details the AMO-signal propagation throughout the Northern Hemisphere via a sequence of atmospheric and lagged oceanic teleconnections, which the authors term the “stadium wave”. Initial changes in the North Atlantic temperature anomaly associated with AMO culminate in an oppositely signed hemispheric signal about 30?years later. Furthermore, shorter-term, interannual-to-interdecadal climate variability alters character according to polarity of the stadium-wave-induced prevailing hemispheric climate regime. Ongoing research suggests mutual interaction between shorter-term variability and the stadium wave, with indication of ensuing modifications of multidecadal variability within the Atlantic sector. Results presented here support the hypothesis that AMO plays a significant role in hemispheric and, by inference, global climate variability, with implications for climate-change attribution and prediction. 相似文献
16.
17.
18.
[No abstract available] 相似文献
19.
Global hydroclimatic changes from 1950 to 2018 are analyzed using updated data of land precipitation, streamflow, and an improved form of the Palmer Drought Severity Index. The historical changes are then compared with climate model-simulated response to external forcing to determine how much of the recent change is forced response. It is found that precipitation has increased from 1950 to 2018 over mid-high latitude Eurasia, most North America, Southeast South America, and Northwest Australia, while it has decreased over most Africa, eastern Australia, the Mediterranean region, the Middle East, and parts of East Asia, central South America, and the Pacific coasts of Canada. Streamflow records largely confirm these precipitation changes. The wetting trend over Northwest Australia and Southeast South America is most pronounced in austral summer while the drying over Africa and wetting trend over mid-high latitude Eurasia are seen in all seasons. Coupled with the drying caused by rising surface temperatures, these precipitation changes have greatly increased the risk of drought over Africa, southern Europe, East Asia, eastern Australia, Northwest Canada, and southern Brazil. Global land precipitation and continental freshwater discharge show large interannual and inter-decadal variations, with negative anomalies during El Niño and following major volcanic eruptions in 1963, 1982, and 1991; whereas their decadal variations are correlated with the Interdecadal Pacific Oscillation (IPO) with IPO’s warm phase associated with low land precipitation and continental discharge. The IPO and Atlantic multidecadal variability also dominate multidecadal variations in land aridity, accounting for 90 % of the multidecadal variance. CMIP5 multi-model ensemble mean shows decreased precipitation and runoff and increased risk of drought during 1950–2018 over Southwest North America, Central America, northern and central South America (including the Amazon), southern and West Africa, the Mediterranean region, and Southeast Asia; while the northern mid-high latitudes, Southeast South America, and Northwest Australia see increased precipitation and runoff. The consistent spatial patterns between the observed changes and the model-simulated response suggest that many of the observed drying and wetting trends since 1950 may have resulted at least partly from historical external forcing. However, the drying over Southeast Asia and wetting over Northwest Australia are absent in the 21st century projections.
相似文献20.
The oceanic and atmospheric conditions and the related climate impacts of the 2015/16 ENSO cycle were analyzed, based on the latest global climate observational data, especially that of China. The results show that this strong El Niño event fully established in spring 2015 and has been rapidly developing into one of the three strongest El Niño episodes in recorded history. Meanwhile, it is also expected to be the longest event recorded, attributable to the stable maintenance of the abnormally warm conditions in the equatorial Pacific Ocean since spring 2014. Owing to the impacts of this strong event, along with climate warming background, the global surface temperature and the surface air temperature over Chinese mainland reached record highs in 2015. Disastrous weather in various places worldwide have occurred in association with this severe El Niño episode, and summer precipitation has reduced significantly in North China, especially over the bend of the Yellow River, central Inner Mongolia, and the coastal areas surrounding Bohai Bay. Serious drought has occurred in some of the above areas. The El Niño episode reached its peak strength during November-December 2015, when a lower-troposphere anomalous anticyclonic circulation prevailed over the Philippines, bringing about abnormal southerlies and substantially increased precipitation in southeastern China. At the same time, a negative phase of the Eurasia-Pacific teleconnection pattern dominated over the mid-high latitudes, which suppressed northerly winds in North China. These two factors together resulted in high concentrations of fine particulate matter (PM2.5) and frequent haze weather in this region. Currently, this strong El Niño is weakening very rapidly, but its impact on climate will continue in the coming months in some regions, especially in China. 相似文献