Changes in Earth’s Energy Flows and Clouds in 228-Year Simulation with a High-Resolution AGCM

We have examined long-term changes in Earth’s energy flows at top of the atmosphere (TOA) and at Earth’s surface (land and ocean) by using 228-year simulation of a high-resolution global atmosphere model, MRI-AGCM3.2. It is found that the net downward short wave (SW) radiation (absorbed solar radiation, ASR) at TOA significantly increases during twenty-first century in agreement with a previous study. However, in the present study, the reason for the change is an increase in clear sky SW absorption by increased water vapor in the atmosphere, while it is a decrease in cloud amount in the previous study. It is also found that the long wave (LW) cloud radiative forcing for atmosphere is positive and increasing during twenty-first century in agreement with a previous study. The reason for the change in the present study is an increase in absorption by water vapor of the downward LW radiation emitted from clouds, while it is reductions of cloud amount in the middle troposphere in the previous study.     

Dynamical effect of the zonal wind anomalies over the tropical western Pacific on ENSO cycles

The circulation and zonal wind anomalies in the lower troposphere over the equatorial western Pacific and their roles in the developing and decaying processes of the 1982–1983, 1986 –1987, 1991–1992 and 1997–1998 El Ni?o events and the occurrence of La Ni?a events are analyzed by using the observed data in this paper. The results show that before the developing stage of these El Ni?o events, there were cyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies brought the westerly anomalies over the Indonesia and the tropical western Pacific. However, when the El Ni?o events developed to their mature phase, there were anticyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies made the easterly anomalies appear over the tropical western Pacific. A simple, dynamical model of tropical ocean is used to calculate the response of the equatorial oceanic waves to the observed anomalies of wind stress near the sea surface of the equatorial Pacific during the 1997/98 ENSO cycle, which was the strongest one in the 20th century. It is shown that the zonal wind stress anomalies have an important dynamical effect on the devel-opment and decay of this El Ni?o event and the occurrence of the following La Ni?a event.     

The role of cloud height and warming in the decadal weakening of atmospheric heat source over the Tibetan Plateau

The warming over the Tibetan Plateau(TP) is very significant during last 30 years,but the thermal forcing has been weakened.The thermal weakening is attributed mainly to the enhancement of the TOA(top of atmosphere) outgoing radiation.This enhancement is opposite to the greenhouse-gas-induced weakening of the global mean TOA outgoing radiation and is also unable to be explained by the observed decrease of total cloud cover.This study presents the importance of cloud height change and the warming over the TP in modulating the TOA radiation budget and thus the thermal forcing during spring and summer.On the basis of surface observations and satellite radiation data,we found that both the TOA outgoing shortwave radiation and longwave radiation were enhanced during this period.The former enhancement is due mainly to the increase of low-level cloud cover,which has a strong reflection to shortwave radiation,especially in summer.The latter enhancement is caused mainly by the planetary warming,and it is further enhanced by the decrease of total cloud cover in spring,as clouds extinguish outgoing longwave radiation emitted from the land surface.Therefore,the radiative cooling enhancement and thus the thermal weakening over the TP is a response of the earth-atmosphere system to the unique change of cloud cover configuration and the rapid warming of the land surface.However,these trends in cloud cover and TOA outgoing radiation are not well represented in four reanalyses.     

Influences of Indian Ocean interannual variability on different stages of El Nio: A FOAM1.5 model approach

Both the tropical Indian and tropical Pacific Oceans are active atmosphere-ocean interactive regions with robust interannual variability, which also constitutes a linkage between the two basins in the mode of variability. Using a global atmosphereocean coupled model, we conducted two experiments(CTRL and PC) to explore the contributions of Indian Ocean interannual sea surface temperature(SST) modes to the occurrence of El Ni?o events. The results show that interannual variability of the SST in the Indian Ocean induces a rapid growth of El Ni?o events during the boreal autumn in an El Ni?o developing year. However, it weakens El Ni?o events or even promotes cold phase conversions in an El Ni?o decaying year. Therefore, the entire period of the El Ni?o is shortened by the interannual variations of the Indian Ocean SST. Specifically, during the El Ni?o developing years, the positive Indian Ocean Dipole(IOD) events force an anomalous Walker circulation, which then enhances the existing westerly wind anomalies over the west Pacific. This will cause a warmer El Ni?o event, with some modulations by ocean advection and oceanic Rossby and Kelvin waves. However, with the onset of the South Asian monsoon, the Indian Ocean Basin(IOB) warming SST anomalies excite low level easterly wind anomalies over the west tropical Pacific during the El Ni?o decaying years. As a result, the El Ni?o event is prompted to change from a warm phase to a cold phase. At the same time, an associated atmospheric anticyclone anomaly appears and leads to a decreasing precipitation anomaly over the northwest Pacific. In summary, with remote forcing in the atmospheric circulation, the IOD mode usually affects the El Ni?o during the developing years, whereas the IOB mode affects the El Ni?o during the decaying years.     

2005—2017年两次强ENSO事件对中国区域陆地水储量变化影响的卫星重力观测

近年来极端气候事件的频发对全球和区域性水循环产生了重大影响,特别是2005—2017年间两次强ENSO(El Nino-Southern Oscillation)事件使得全球陆地水储量出现了较大的年际波动.GRACE(Gravity Recovery and Climate Experiment)重力卫星随着数据质量的提高、后处理方法的完善和超过十年的连续观测,捕捉陆地水储量异常的能力明显提高,这为研究2005—2017年间两次强ENSO事件对中国区域陆地水储量变化的影响提供了观测基础.本文综合利用GRACE卫星重力数据、GLDAS水文模型和实测降水资料分析了中国区域陆地水储量年际变化和与ENSO的关系.研究发现:长江流域中、下游地区和东南诸河流域与ENSO存在较高的相关性,与ENSO的相关系数最大值分别为0.55、0.78、0.70,较ENSO分别滞后约7个月、5个月和5个月.其中长江流域下游地区与ENSO的相关性最强,2010/11 La Nina和2015/16 El Nino两次强ENSO事件使得陆地水储量分别发生了约-24.1亿吨和27.9亿吨的波动.在2010/11 La Nina期间,长江流域下游地区和东南诸河流域陆地水储量异常约在2011年4—5月达到谷值,而长江流域中游地区晚1~2月达到谷值.在2015/16 El Nino期间,长江流域中、下游地区和东南诸河流域陆地水储量从2015年9月到2016年7月持续出现正异常信号.其中,2015年秋冬季(2015年9月至2016年1月)陆地水储量异常明显是受此次El Nino同期影响的结果;2016年春季(4—5月)陆地水异常是受到此次厄尔尼诺峰值的滞后影响所致;2016年7月的陆地水储量异常则与西北太平洋存在的异常反气旋环流有关.     

El Niño and La Niña influence on mean river flows of southern South America in the 20th century

The influence of the El Niño Southern Oscillation (ENSO) phenomenon on monthly mean river flows of 12 rivers in the extreme south of South America in the 20th century is analysed. The original dataset of each river is divided into two subsets, i.e. warm ENSO events or El Niño, and cold ENSO events or La Niña. The elements of the subsets are composites of 24 consecutive months, from January of the year when the ENSO event begins to December of the following year. The ENSO signal is analysed by comparing the monthly mean value of each subset to the long-term monthly mean. The results reveal that, in general, monthly mean El Niño (La Niña) river flows are predominantly larger (smaller) than the long-term monthly mean in the rivers studied. The anomalies are more evident during the second half of the year in which the event starts and the first months of the following year.     

不同强度El Ni?o的衰减过程.Ⅱ,中等和较弱El Ni?o的衰减过程

在第二部分,我们研究了中等和较弱El Ni?o的衰减过程. 结果表明,对中等El Ni?o而言,在其发展阶段和盛期,负异常信号在西太平洋产生,但由于强度不足,在El Ni?o盛期之后迅速衰减,这是一种夭折的类西太平洋振子过程. 因此,与强El Ni?o不同,中等El Ni?o衰减进入平常态. 而较弱El Ni?o以截然不同的另一种方式进行位相转换,伴随东南太平洋副高的加强和西移,东风异常和海表温度负异常自赤道东太平洋向西扩展,这是一种平流模态过程,导致较弱El Ni?o衰减进入La Nia.     

The anomalous variation of the lightning activity in southern China during the 1997/98 El Ni(n~)o event

This paper presents the EOF analysis results of the lightning density (LD) anomalies for the different seasons in southeastern China and Indochina Peninsula by using the OTD/LIS database (June 1995 to Feb. 2003) of the global LD with 2.5°×2.5° resolution offered by Global Hydrology Resource Center. It is shown that the LD positive anomalies in the region occurred at the same time of NINO3 SSTA steep increase in the spring of 1997 and remained to be a higher level till the next spring, as well the corresponding anomaly percent maximum in different seasons was 89%, 30%, 45%, 498% and 55% successively from the beginning to the end of the 1997/98 El Ni(~n)o event (ENSO). The centre of the LD positive anomalies for the spring or winter season is located at southeastern China and the adjacent coastal areas, but it for the summer or autumn season is located at the southern Indochina Peninsula and Gulf of Thailand, whose position for each season in the ENSO as contrasted with the normal years has a westward shift, and especially for winter or spring season a northward shift at the same time. In addition, an analysis of the interannual variations in the LD anomaly percent, convective precipitation and H-CAPE days in southern China shows that each among the three anomaly percents is correlative with the other for the positive anomaly zone and Kuroshio area. The relative variation of LD during the El Ni (~n)o period is the highest among the three rates and is larger than that during the non-El Ni(~n)o period, meaning that the response of lightning activities to the ENSO is the most sensitive in both areas. But the response of lightning activities and precipitation to the ENSO appears to be more complex and diversified either in Kuroshio area or in the Qinghai-Tibet Plateau and northwestern and northeastern China.     

Relationship and its instability of ENSO — Chinese variations in droughts and wet spells

Monthly data of Self-Calibrated Palmer Drought Severity Index (PDSI) from 1951 to 2000 are calculated using historical precipitation and temperature data for Chinese 160 stations. Temporal and spatial patterns of the first empirical orthogonal function (EOF) of the PDSI reveals a fairly linear trend resulting from trends in precipitation and surface temperature, which is similar to the linear PDSI trend during 1951–2000 calculated using all monthly data. The EOF analysis also reveals that the leading mode correlates significantly with ENSO events in time and space. The ENSO EOF shows that during the typical warm phase of ENSO, surface conditions are drier in most regions of China, especially North China, but wetter than normal in the southern regions of Changjiang River, and Northwest China. During the typical cold phase of ENSO, these anomalies reverse sign. From 1951 to 2000, there are large multi-year to decadal variations in droughts and wet spells over China, which are all closely related to strong El Niño events. In other words, when one strong El Niño event happens, there is a possible big variability in droughts and wet spells over China on the multi-year or decadal scale. Studies also suggest that during the last 2–3 decades climate changes over China, especially North China’s drying and northwest China’s wetting, are closely related to the shift in ENSO towards warmer events and global warming since the late 1970s. The instability of the relationship is also studied. It is revealed that there is a good correlation between ENSO and Chinese variations in droughts and wet spells in the 3–8-year band, but the correlation between ENSO and Chinese variations in droughts and wet spells is instable. Studies suggest that there are decadal changes in the correlation: the wavelet coherency between ENSO and Chinese variations in droughts and wet spells is high during 1951–1962 and 1976–1991, but low during 1963–1975 and 1992–2000.     

Solomon Sea circulation and water mass modifications: response at ENSO timescales

The South Pacific low latitude western boundary currents (LLWBCs) carry waters of subtropical origin through the Solomon Sea before joining the equatorial Pacific. Changes in their properties or transport are assumed to impact El Niño Southern Oscillation (ENSO) dynamics. At ENSO timescales, the LLWBCs transport tends to counterbalance the interior geostrophic one. When transiting through the complex geography of the Solomon Sea, the main LLWBC, the New Guinea Coastal Undercurrent, cannot follow a unique simple route to the equator. Instead, its routes and water mass properties are influenced by the circulation occurring in the Solomon Sea. In this study, the response of the Solomon Sea circulation to ENSO is investigated based on a numerical simulation. The transport anomalies entering the Solomon Sea from the south are confined to the top 250 m of the water column, where they represent 7.5 Sv (based on ENSO composites) for a mean transport of 10 Sv. The induced circulation anomalies in the Solomon Sea are not symmetric between the two ENSO states because of (1) a bathymetric control at Vitiaz Strait, which plays a stronger role during El Niño, and (2) an additional inflow through Solomon Strait during La Niña events. In terms of temperature and salinity, modifications are particularly notable for the thermocline water during El Niño conditions, with cooler and fresher waters compared to the climatological mean. The surface water at Vitiaz Strait and the upper thermocline water at Solomon Strait, feeding respectively the equatorial Pacific warm pool and the Equatorial Undercurrent, particularly affect the heat and salt fluxes. These fluxes can change by up to a factor of 2 between extreme El Niño and La Niña conditions.     

不同强度El Nino的衰减过程.Ⅰ,强El Nino的衰减过程

将1951～2004年期间的12次El Nino事件分为强、中等、较弱和弱4类,结果发现,强和较弱El Nino衰减进入La Nina,但是中等和弱El Nino衰减进入平常态.因此,El Nino的衰减结果与自身强度之间存在密切的非线性关系.进一步的研究表明,负异常信号自西太平洋向中东太平洋的东传主导了强El Nino事件向La Nina的转变过程,其具体动力过程类似于西太平洋振子理论.热带西北太平洋（WNP）大气异常反气旋在强El Nino位相转变中起核心作用,它的维持和缓慢东移是赤道东风异常维持和发展的原因,而后者通过激发Kelvin波导致了ENSO从El Nino向La Nina的转变.     

南印度洋副热带偶极模在ENSO事件中的作用

南印度洋副热带偶极模（Subtropical Dipole Pattern,SDP）是印度洋存在的另一种很明显的偶极型海温差异现象,在年际和年代际尺度上均有十分明显的表现.而目前有关印度洋海气相互作用的研究主要集中在赤道印度洋地区,针对南印度洋地区的工作还比较少,特别是有关南印度洋海温与ENSO（El NiDo-Southern Oscillation）事件关系的研究.本文初步探讨了年际尺度上南印度洋副热带偶极型海温变化差异与ENSO事件的关系,发现SDP与ENSO事件有密切的联系,SDP事件就像连接正负ENSO位相转换的一个中间环节,SDP事件前后期ENSO的位相刚好完全相反.进一步,本文通过分析SDP事件前后期海温、高低层风、低层辐合辐散、高空云量和辐射等的变化特征研究了南印度洋偶极型海温异常在ENSO事件中的作用,结果表明：SDP在ENSO事件中的作用不仅涉及海气相互作用的正负反馈过程,还与热带和副热带大气环流之间的相互作用有关,特别是与东南印度洋海温变化所引起的异常纬向风由赤道印度洋向赤道太平洋传播的过程等有十分直接的关系;同时,SDP对ENSO事件的影响在很大程度上还依赖于大尺度平均气流随季节的变换.     

Correlation between El Niño–Southern Oscillation (ENSO) and precipitation in South‐east Asia and the Pacific region

The relationship between El Niño–Southern Oscillation (ENSO) events versus precipitation anomalies, and the response of seasonal precipitation to El Niño and La Niña events were investigated for 30 basins that represent a range of climatic types throughout South‐east Asia and the Pacific region. The teleconnection between ENSO and the hydroclimate is tested using both parametric and non‐parametric approaches, and the lag correlations between precipitation anomalies versus the Southern Oscillation Index (SOI) several months earlier, as well as the coherence between SOI and precipitation anomalies are estimated. The analysis shows that dry conditions tend to be associated with El Niño in the southern zone, and part of the middle zone in the study area. The link between precipitation anomalies and ENSO is statistically significant in the southern zone and part of the middle zone of the study area, but significant correlation was not observed in the northern zone. Patterns of precipitation response may differ widely among basins, and even the response of a given river basin to individual ENSO events also may be changeable. Copyright © 2003 John Wiley & Sons, Ltd.     

Factors affecting marine debris deposition at French Frigate Shoals, Northwestern Hawaiian Islands Marine National Monument, 1990-2006

Data on the amount and type of small debris items deposited on the beaches of the Hawaiian Islands National Wildlife Refuge Tern Island station, French Frigate Shoals were collected over 16 years. We calculated deposition rates and investigated the relationship among deposition and year, season, El Ni?o and La Ni?a events from 1990 to 2006. In total 52,442 debris items were collected with plastic comprising 71% of all items collected. Annual debris deposition varied significantly (range 1116-5195 items) but was not influenced by season. Debris deposition was significantly greater during El Ni?o events as compared to La Ni?a events. Although often deduced to influence floating marine pollution, this study provides the first quantitative evidence of the influence of El Ni?o/La Ni?a cycles on marine debris deposition.     

Influence of the El Niño/Southern Oscillation on South Korean streamflow variability

Deciphering the mechanisms through which the El Niño/Southern Oscillation (ENSO) affects hydrometeorological parameters in the tropics and extratropics is of great interest. We investigate climatic teleconnections between warm or cold phases of ENSO and streamflow patterns over South Korea using an empirical methodology designed to detect regions showing a strong and consistent hydroclimatic signal associated with ENSO. We calculate not only spatial coherence values by monthly streamflow composite formed over 2‐year ENSO cycle and the first harmonic fit to detect candidate regions but also temporal consistency rates by aggregate composite and index time series to determine core regions. As a result, the core regions, namely, the Han river basin and the Nakdong river basin, are detected with a high level of response of ENSO phenomena to streamflow patterns. The ENSO composites for both core regions indicate drier (wetter) conditions in early autumn of the warm (cold) episode years and wetter (drier) conditions from winter to spring of the following year. For both regions, the spatial coherences are over 92% (82%) and the temporal consistencies are 71% (75%) during the El Niño (La Niña) events. In addition, for the core regions identified by composite‐harmonic analysis for both extreme episodes, the results of comparative analyses by using correlation, annual cycle, and Wilcoxon rank sum test indicate that 2 opposite phases‐streamflow relationships have a tendency of sign reversal of the streamflow anomaly. Also, the positive departures during the El Niño years show more coherent and strong responses than the negative anomalies in the La Niña events. In conclusion, South Korea experiences climatic teleconnection between ENSO forcing and midlatitude streamflow patterns.     

Evolution of the 2015/16 El Nio and historical perspective since 1979

The 2015/16 El Nio developed from weak warm conditions in late 2014 and NINO3.4 reached 3℃ in November 2015. We describe the characteristics of the evolution of the 2015/16 El Nio using various data sets including SST, surface winds,outgoing longwave radiation and subsurface temperature from an ensemble operational ocean reanalyses, and place this event in the context of historical ENSO events since 1979. One salient feature about the 2015/16 El Nio was a large number of westerly wind bursts and downwelling oceanic Kelvin waves(DWKVs). Four DWKVs were observed in April-November 2015 that initiated and enhanced the eastern-central Pacific warming. Eastward zonal current anomalies associated with DWKVs advected the warm pool water eastward in spring/summer. An upwelling Kelvin wave(UWKV) emerged in early November 2015 leading to a rapid decline of the event. Another outstanding feature was that NINO4 reached a historical high(1.7℃), which was 1℃(0.8℃) higher than that of the 1982/83(1997/98) El Nio . Although NINO3 was comparable to that of the 1982/83 and 1997/98 El Nio , NINO1+2 was much weaker. Consistently, enhanced convection was displaced 20 degree westward, and the maximum D20 anomaly was about 1/3.1/2 of that in 1997 and 1982 near the west coast of South America.     

EDITORIAL

Abstract

Net radiation at the surface of the Earth, when estimated from relationships employed in the equation of Penman, is found to be greater than the values of net radiation that are measured. Since the net short-wave (solar) radiation is well estimated when derived from Penman relationships, the problem is identified as an overestimate of the net long-wave radiation and primarily as an underestimate of the outgoing long-wave radiation from the surface of the Earth.     

Variazioni delle latitudini terrestri e fenomeni geofisici

Riassunto Esposti brevemente i fondamenti teorici dello spostamento dell'asse istantaneo di rotazione terrestre nella massa della Terra, ed accennato alle prove sperimentali che hanno condotto a stabilire la realtà del fenomeno, sono analizzate le variazioni delle latitudini terrestri, che comprendono una variazionepolare ed una variazionenon polare. La variazione non polare appare dovuta principalmente ad anomalie rifrazionali, aventi sede nell'atmosfera terrestre e caratteristiche locali. La variazione polare comprende due oscillazioni essenziali: una avente origine meccanica (nutazione culeriana), modificata dall'elasticità terrestre; l'altra avente origine geofisica, e dipendente da spostamenti annuali dell'asse di massimo momento d'inerzia della Terra (asse di figura). L'analisi della variazione polare mostra perturbazioni strettamente connesse con la costituzione della Terra e con fenomeni geofisici. In tutti i suoi aspetti il problema della variazione delle latitudini terrestri implica la considerazione di fenomeni geofisici aventi sede nell'atmosfera, alla superficie e all'interno della Terra.

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Summary Having briefly set forth the theoretical principles of the displacement of the istantaneous axis of rotation of the Earth in the interior of the same, and made reference to the experimental tests that have shown the reality of the phenomenon, the variations of the terrestrial latitudes, which include apolar and anon polar variation, are analyzed. The non polar variation seems to have its origin mainly in refractional anomalies, that have their place in the atmosphere and local characteristics. The polar variation includes two fundamental oscillations: one having mechanical origin (Eulerian nutation), modified by the elasticity of the Earth, and another having geophysical origin and depending on annual displacements of the axis of the maximum momentum of inertia of the Earth (axis of figure). The analysis of the polar motion shows perturbations hightly connected with the constitution of the Earth and with geophysical phenomena. In all its appearances the problem of the variation of the terrestrial latitudes implies the consideration of geophysical phenomena occurring in the atmosphere, at the surface, and in the interior of the Earth.

     

Aquifer responses to El Niño-Southern Oscillation, Southwest British Columbia

We used climatological composite analysis to investigate El Ni?o-Southern Oscillation (ENSO) signals in long-term shallow ground water level observations from four wells in the lower Fraser Valley of British Columbia. Significance of differences between warm-phase, cold-phase, and neutral climate states was assessed with a Monte Carlo bootstrap technique. We also considered time series of local precipitation and streamflow for comparison. Composite annual hyetographs suggest that ENSO precipitation impacts are largely limited to winter and spring, with higher and lower rainfall occurring, respectively, under cold-phase and warm-phase episodes. This is consistent with prior work in the region and is found to be directly reflected in both streamflow and ground water level data. The mean magnitude of ENSO terrestrial hydrologic anomalies can be up to approximately 50% of the average seasonal cycle amplitude. ENSO does not appear to systematically affect annual hydrometeorological cycle timing in this study area. However, relative to the surface hydrologic systems considered, aquifers are observed to retain a stronger memory of seasonal ENSO-related precipitation anomalies, with changes potentially extending through the following summer, presumably reflecting storage effects. Most responses appear to be somewhat nonlinear.     

Analysing the influences of ENSO and PDO on water discharge from the Yangtze River into the sea

The El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) are two important climate oscillations that affect hydrological processes at global and regional scales. However, few studies have attempted to identify their single and combined influences on water discharge variability at multiple timescales. In this study, we examine temporal variation in water discharge from the Yangtze River into the sea and explore the influence of the ENSO and the PDO on multiscale variations in water discharge over the last century. The results of the wavelet transform analysis of the water discharge series show significant periodic variations at the interannual timescale of 2 to 8 years and the decadal timescale of 15 to 17 years. Water discharge tended to be higher during the La Niña–PDO cold phase and lower during the El Niño–PDO warm phase. The results of the cross wavelet spectrum and wavelet coherence analyses confirm the relationship between the interannual (i.e., 2 to 8 years) and decadal (i.e., 15 to 17 years) periodicities in water discharge with the ENSO and the PDO, respectively. As an important large‐scale climate background, the PDO can modulate the influence of the ENSO on water discharge variability. In general, the warm PDO enhances the influence of El Niño events, and the cold PDO enhances the influence of La Niña events. Our study is helpful in understanding the influencing mechanism of climate change on hydrological processes and provides an important scientific guideline for water resource prediction and management.