An enhanced Warm Arctic-Cold Eurasia(WACE)pattern has been a notable feature in recent winters of the Northern Hemisphere.However,divergent results between model and observational studies of the WACE still remain.This...An enhanced Warm Arctic-Cold Eurasia(WACE)pattern has been a notable feature in recent winters of the Northern Hemisphere.However,divergent results between model and observational studies of the WACE still remain.This study evaluates the performance of 39 climate models participating in the Coupled Model Intercomparison Project Phase 6(CMIP6)in simulating the WACE pattern in winter of 1980-2014 and explores the key factors causing the differences in the simulation capability among the models.The results show that the multimodel ensemble(MME)can better simulate the spatial distribution of the WACE pattern than most single models.Models that can/cannot simulate both the climatology and the standard deviation of the Eurasian winter surface air temperature well,especially the latter,usually can/cannot simulate the WACE pattern well.This mainly results from the different abilities of the models to simulate the range and intensity of the warm anomaly in the Barents Sea-Kara seas(BKS)region.Further analysis shows that a good performance of the models in the BKS area is usually related to their ability to simulate location and persistence of Ural blocking(UB),which can transport heat to the BKS region,causing the warm Arctic,and strengthen the westerly trough downstream,cooling central Eurasia.Therefore,simulation of UB is key and significantly affects the model’s performance in simulating the WACE.展开更多
The existence of outliers can seriously influence the analysis of variational data assimilation.Quality control allows us to effectively eliminate or absorb these outliers to produce better analysis fields.In particul...The existence of outliers can seriously influence the analysis of variational data assimilation.Quality control allows us to effectively eliminate or absorb these outliers to produce better analysis fields.In particular,variational quality control(VarQC) can process gray zone outliers and is thus broadly used in variational data assimilation systems.In this study,governing equations are derived for two VarQC algorithms that utilize different contaminated Gaussian distributions(CGDs): Gaussian plus flat distribution and Huber norm distribution.As such,these VarQC algorithms can handle outliers that have non-Gaussian innovations.Then,these VarQC algorithms are implemented in the Global/Regional Assimilation and PrEdiction System(GRAPES) model-level three-dimensional variational data assimilation(m3 DVAR) system.Tests using artificial observations indicate that the VarQC method using the Huber distribution has stronger robustness for including outliers to improve posterior analysis than the VarQC method using the Gaussian plus flat distribution.Furthermore,real observation experiments show that the distribution of observation analysis weights conform well with theory,indicating that the application of VarQC is effective in the GRAPES m3 DVAR system.Subsequent case study and longperiod data assimilation experiments show that the spatial distribution and amplitude of the observation analysis weights are related to the analysis increments of the mass field(geopotential height and temperature).Compared to the control experiment,VarQC experiments have noticeably better posterior mass fields.Finally,the VarQC method using the Huber distribution is superior to the VarQC method using the Gaussian plus flat distribution,especially at the middle and lower levels.展开更多
Studies on the impact of solar activity on climate system are very important in understanding global climate change. Previous studies in this field were mostly focus on temperature, wind and geopotential height. In th...Studies on the impact of solar activity on climate system are very important in understanding global climate change. Previous studies in this field were mostly focus on temperature, wind and geopotential height. In this paper, interdecadal correlations of solar activity with Winter Snow Depth Index (WSDI) over the Tibetan Plateau, Arctic Oscillation Index (AOI) and the East Asian Winter Monsoon Index (EAWMI) are detected respectively by using Solar Radio Flux (SRF), Total Solar Irradiance (TSI) and Solar Sunspot Number (SSN) data and statistical methods. Arctic Oscillation and East Asian winter monsoon are typical modes of the East Asian atmospheric circulation. Research results show that on inter-decadal time scale over 11-year solar cycle, the sun modulated changes of winter snow depth over the Tibetan Plateau and East Asian atmospheric circulation. At the fourth lag year, the correlation coefficient of SRF and snow depth is 0.8013 at 0.05 significance level by Monte-Carlo test method. Our study also shows that winter snow depth over the Tibetan Plateau has significant lead and lag correlations with Arctic Oscillation and the East Asian winter monsoon on long time scale. With more snow in winter, the phase of Arctic Oscillation is positive, and East Asian winter monsoon is weak, while with less snow, the parameters are reversed. An example is the winter of 2012/2013, with decreased Tibetan Plateau snow, phase of Arctic Oscillation was negative, and East Asian winter monsoon was strong.展开更多
The teleconnection impact of the boreal winter Antarctic Oscillation(AAO) on the Somali Jet(SMJ) intensity in the following spring and summer is examined in this paper.The variability of the boreal winter AAO is p...The teleconnection impact of the boreal winter Antarctic Oscillation(AAO) on the Somali Jet(SMJ) intensity in the following spring and summer is examined in this paper.The variability of the boreal winter AAO is positively related to the SMJ intensity in both spring and summer.The analyses show that the SST in southern high and middle latitudes seems to serve as a bridge linking these two systems.When the AAO is in strong positive phase,SST over the Southern Ocean cools in the high latitudes and warms in the middle latitudes,which persists into summer;however,the variability of SST in southern high and middle latitudes is also closely correlated to SMJ intensity.A possible mechanism that links SST variability with the AAO-SMJ relationship is also discussed.The AAO in boreal winter produces an SST anomaly pattern in southern high and middle latitudes through the air-sea coupling.This AAOrelated SST anomaly pattern modulates the local Ferrel cell anomaly in summer,followed by the regional Hadley cell anomaly in tropics.The anomalous vertical motion in tropics then changes the land-sea thermal contrast between the tropical Indian Ocean and the Asian continent through the variability of low cloud cover and downward surface longwave radiation flux.Finally,the land-sea thermal contrast anomaly between the tropical Indian Ocean and the Asian continent changes the SMJ intensity.The results from Community Atmosphere Model experiments forced by the SST anomaly in southern high and middle latitudes also confirm this diagnostic physical process to some extent.展开更多
The relative impacts of Indian and Pacific Ocean processes on Tanzanian rainfall was evaluated using composite and correlation analyses.It was found that the seasonal responses of rainfall to positive Indian Ocean Dip...The relative impacts of Indian and Pacific Ocean processes on Tanzanian rainfall was evaluated using composite and correlation analyses.It was found that the seasonal responses of rainfall to positive Indian Ocean Dipole(pIOD)and El Nino events are substantial from September-October-November(SON)to December-January-February(DJF),whereas the Indian Ocean Dipole(IOD)exerts more control than El Nino-Southern Oscillation(ENSO)in both seasons.The associated relationship with the sea surface temperature(SST)and large-scale atmo-spheric circulations revealed distinct features.For the pure pIOD years,there is above-normal rainfall over the entire country.A strong rainfall condition is evident over the Lake Victoria basin and coastal and northeastern highland parts of the country during SON,while areas of the central and southern highlands exhibit substantial rains during DJF.For the pure El-Nino events,Tanzania has suffered from insignificant,weak,and non-coherent rainfall conditions during SON.However,a contrasting insignificant rainfall signature is found between the north-ern and southern parts of the country during the subsequent DJF season.For the co-occurrence of pIOD and El Nino,significant,excessive rainfall conditions are restricted to over the northern coast and northeastern areas of the country during SON,consistent with the rainfall pattern for pIOD.A weak,positive rainfall condition is observed over the entire country in the following season of DJF.Generally,in terms of Tanzanian rainfall,the IOD/ENSO variability and the associated impacts can be explained by the anomalous SST and circulation anomalies.展开更多
Peracetic acid(CH_(3)C(O)OOH,PAA)-based heterogeneous advanced oxidation process(AOP)has attacked intensive interests due to production of various reactive species.Herein,Co(OH)_(2)nanoparticles decorated biochar(Co(O...Peracetic acid(CH_(3)C(O)OOH,PAA)-based heterogeneous advanced oxidation process(AOP)has attacked intensive interests due to production of various reactive species.Herein,Co(OH)_(2)nanoparticles decorated biochar(Co(OH)_(2)/BC)was fabricated by a simple and controllable method,which was used to degrade tetracycline hydrochloride(TTCH)in water through PAA activation.The results indicated that 100%TTCH(C_(0)=10μmol/L)degradation efficiency was realized within 7 min at pH 7,with a high kinetic rate constant(k_(1))of 0.64 min^(-1)by the optimized Co(OH)_(2)/BC.Material characterizations suggested that Co(OH)_(2)nanoparticle was successfully decorated on biochar,leading to more active sites and electronic structure alteration of biochar,thus greatly promoting the catalytic cleavage of PAA for radicals production.Then,the reactive oxygen species(ROS)quenching experiments and electron paramagnetic resonance(EPR)analysis demonstrated the key species were alkoxyl radicals(R–O^(·),mainly CH_(3)CO_(2)^(·)and CH_(3)CO_(3)^(·)),HO^(·)and^(1)O_(2)in this system.Besides,density functional theory(DFT)calculation on Fukui index further revealed that the vulnerable sites of TTCH and three possible degradation pathways were proposed.This study can provide a new strategy for synthesis functional materials in PAA activation AOPs for removal of antibiotics in water.展开更多
A rainband meridional shift index (RMSI) is defined and used to statistically prove that the East Asian summer monsoon rainband is usually significantly more northward in the early summer of solar maximum years than...A rainband meridional shift index (RMSI) is defined and used to statistically prove that the East Asian summer monsoon rainband is usually significantly more northward in the early summer of solar maximum years than that of solar minimum years. By applying continuous wavelet transform, cross wavelet transform, and wavelet coherence, it is found that throughout most of the 20th century, the significant decadal oscillations of sunspot number (SSN) and the RMSI are phase-locked and since the 1960s, the SSN has led the RMSI slightly by approximately 1.4 yr. Wind and Eliassen-Palm (EP) flux analysis shows that the decadal meridional oscillation of the June rainband likely re- sults from both a stronger or earlier onset of the tropical monsoon and poleward shift of the subtropical westerly jet in high-solar months of May and June. The dynamical responses of the lower tropical monsoon and the upper subtropical westerly jet to the 11-yr solar cycle transmit bottom-up and top-down solar signals, respectively, and the synergistic actions between the monsoon and the jet likely amplify the solar signal at the northern boundary of the monsoon to some extent.展开更多
This paper uses two subsets of ensemble historical-Nat simulations and pi-Control simulations from CMIP5 as well as observational/reanalysis datasets to investigate responses of the tropical Pacific to the 11-yr solar...This paper uses two subsets of ensemble historical-Nat simulations and pi-Control simulations from CMIP5 as well as observational/reanalysis datasets to investigate responses of the tropical Pacific to the 11-yr solar cycle.A statistically significant 11-yr solar signal is found in the upper-ocean layers above the thermocline and tropospheric circulations.A warming response initially appears in the upper layers of the central equatorial Pacific in the solar maximum years in observations,then increases and shifts into the eastern Pacific at lagged 1-3 yr.Meanwhile,an anomalous updraft arises over the western equatorial Pacific and shifts eastwards in the following years with anomalous subsidence over the Maritime Continent.These lagged responses are confirmed by the historical-Nat simulations,except that the initial signal is located more to the west and all the responses are weaker than the observed.A simplified mixed-layer heat budget analysis based on the historical-Nat simulations suggests that the atmospheric forcing,especially the shortwave radiation,is the major contributor to the initial warming response,and the ocean heat transport effect is responsible for the eastward displacement of the lagged warming responses.In the solar maximum years,the zonal ocean temperature gradient in the western-central Pacific is reduced by the initial warming,and anomalous westerly winds appear over the western equatorial Pacific and extend into the eastern Pacific during the lagged years.These anomalous westerly winds reduce the wind-driven ocean dynamical transport,resulting in the initial warming in the central equatorial Pacific being amplified and the surface warming shifting eastward during the lagged 1-3 yr.展开更多
This study analyzed the changes in precipita- tion over summer and autumn across the Yunnan region of China, and undertook a composite analysis of the atmo- spheric circulations in the troposphere, which included an a...This study analyzed the changes in precipita- tion over summer and autumn across the Yunnan region of China, and undertook a composite analysis of the atmo- spheric circulations in the troposphere, which included an analysis of the interannual and interdecadal variations. This paper examines in detail the circulation backgrounds of the wet and dry periods in summer and autumn and their correlations with the sea surface temperature. The results indicated that the summer and autumn precipitation across Yunnan has significantly decreased over the past 50 years. Furthermore, since the beginning of the century, the summer and autumn precipitation cycle has been in a low precipitation phase. The overlap of two extremely low rain phases has caused frequent droughts in the region. In addition, the atmospheric circulation fields during these wet and dry periods are very different. These are mainly shown as a meridional wind anomaly in eastern China in the low atmosphere, as a cross-equatorial airflow anomaly, a tropical zonal wind anomaly over the Indian Ocean, and as a related South Asia High and Western Pacific Subtropical High. Further analysis suggested that the SST over the Indian Ocean and the Pacific warm pool critically affect the anomalous summer and autumn precipitation over Yunnan by impacting the monsoon circulations. Future projections for greenhouse gas wann- ing suggest a potential anomalous circulation background between 2010 and 2020 which may result in less precipitation during the wet season or even drought events across the Yunnan region.展开更多
A recent version of the Polar Weather Research and Forecasting model(Polar WRF)has been upgraded to the version 4.X era with an improved NoahMP Land Surface Model(LSM).To assess the model performance over the Antarcti...A recent version of the Polar Weather Research and Forecasting model(Polar WRF)has been upgraded to the version 4.X era with an improved NoahMP Land Surface Model(LSM).To assess the model performance over the Antarctic and Southern Ocean,downscaling simulations with different LSM(NoahMP,Noah),WRF versions(Polar WRF 4.1.1 and earlier version 4.0.3,WRF 4.1.1),and driving data(ERA-Interim,ERA5)are examined with two simulation modes:the short-term that consists of a series of 48 h segments initialized daily at 0000 UTC with the first 24 h selected for model spin-up,whereas the long-term component used to evaluate long-term prediction consists of a series of 38-41 day segments initialized using the first 10 days for spin-up of the hydrological cycle and planetary boundary layer structure.Simulations using short-term mode driven by ERA-Interim with NoahMP and Noah are selected for benchmark experiments.The results show that Polar WRF 4.1.1 has good skills over the Antarctic and Southern Ocean and better performance than earlier simulations.The reduced downward shortwave radiation bias released with WRF 4.1.1 performed well with PWRF411.Although NoahMP and Noah led to very similar conclusions,NoahMP is slightly better than Noah,particularly for the 2 m temperature and surface radiation because the minimum albedo is set at 0.8 over the ice sheet.Moreover,a suitable nudging setting plays an important role in long-term forecasts,such as reducing the surface temperature diurnal cycle near the coast.The characteristics investigated in this study provide a benchmark to improve the model and guidance for further application of Polar WRF in the Antarctic.展开更多
As the deep convective clouds(DCCs) over the western Pacific and Indian Ocean warm pool may play different roles in the climate system, variations in DCC properties over these two sectors are investigated and compared...As the deep convective clouds(DCCs) over the western Pacific and Indian Ocean warm pool may play different roles in the climate system, variations in DCC properties over these two sectors are investigated and compared. The DCC intensity and area varies more significantly in the Indian Ocean than the western Pacific sector, while the DCC frequency is comparable in both sectors at the seasonal scale. Although the Indian Ocean sector is strongly dominated by the seasonal evolution, the interannual variations in the two sectors are comparable for all three DCC properties(frequency, intensity, and area). Besides,Walker circulation is closely correlated with the interannual variability of DCCs in both sectors. The Walker circulation strengthens(weakens) as the DCCs shift eastward(westward) over the Indian Ocean sector and westward(eastward) over the western Pacific sector. When more or stronger DCCs occur over the Indian Ocean sector(western Pacific sector), the Walker circulation becomes stronger(weaker) and shifts westward(eastward). Interestingly, the response of the Walker circulation to DCC variability over the warm pool is asymmetry. The asymmetry response of the Walker circulation to the negative and positive DCC anomaly may be related to the non-linearity internal variability of the atmosphere. DCCs over the Indian Ocean sector have a much weaker nonlinear correlation with the Walker circulation than DCCs over the western Pacific sector.展开更多
The impact of solar activity on climate system is spatiotemporally selective and usually more significant on the regional scale. Using statistical methods and solar radio flux(SRF) data, this paper investigates the im...The impact of solar activity on climate system is spatiotemporally selective and usually more significant on the regional scale. Using statistical methods and solar radio flux(SRF) data, this paper investigates the impact of the solar11-yr cycle on regional climate of Northeast Asia in recent decades. Significant differences in winter temperature,precipitation, and the atmospheric circulation over Northeast Asia are found between peak and valley solar activity years. In peak years, temperature is higher over vast areas of the Eurasian continent in middle and high latitudes, and prone to producing anomalous high pressure there. Northeast Asia is located to the south of the anomalous high pressure, where the easterlies prevail and transport moisture from the western Pacific Ocean to the inland of East Asia and intensify precipitation there. In valley years, temperature is lower over the Eurasian continent and northern Pacific Ocean in middle and high latitudes, and there maintain anomalous low pressure systems in the two regions. Over the Northeast Asian continent, north winds prevail, which transport cold and dry air mass from the high latitude to Northeast Asia and reduce precipitation there. The correlation coefficient of winter precipitation in Northeast China and SRF reaches 0.4, and is statistically significant at the 99% confidence level based on the Student's t-test. The latent heat flux anomalies over the Pacific Ocean caused by solar cycle could explain the spatial pattern of abnormal winter precipitation of China, suggesting that the solar activity may change the climate of Northeast Asia through air–sea interaction.展开更多
To improve the energetics in the life cycle of an ideal baroclinic instability case, we develop a Physical Conserving Fidelity model (F-model), and we compare the simulations from the F-model to those of the traditi...To improve the energetics in the life cycle of an ideal baroclinic instability case, we develop a Physical Conserving Fidelity model (F-model), and we compare the simulations from the F-model to those of the traditional global spectral semi-implicit model (control model). The results for spectral kinetic energy and its budget indicate different performances at smaller scales in the two models. A two-way energy flow emerges in the generation and rapid growth stage of the baroclinic disturbance in the F-model. However, only a downscale mechanism dominates in the control model. In the F-model, the meso- and smaller scales are energized initially, and then an active upscale nonlinear cascade occurs. Thus, disturbances at prior scales are forced by both downscale and upscale energy cascades and by conversion from potential energy. An analysis of the eddy kinetic energy budget also shows remarkable enhancement of the energy conversion rate in the F-model. As a result, characteristics of the ideal baroclinic wave are greatly improved in the F-model, in terms of both intensity and time of formation.展开更多
This study examines the seasonal connections between the interannual variations in LOD (length of day)/ AAMglobe (the relative atmospheric angular momentum for the whole globe) and the ENSO-like SST (El Nifio/ So...This study examines the seasonal connections between the interannual variations in LOD (length of day)/ AAMglobe (the relative atmospheric angular momentum for the whole globe) and the ENSO-like SST (El Nifio/ Southern Oscillation-like sea surface temperature) pattern and corresponding zonal and vertical circulations. Consistent with previous studies, the ENSO-like SST impact the following season LOD/AAMglobe, with the strongest correlations in DJF (December, January, and February), when it is likely to be the peak E1 Nino/La Nifia period. Lag correlations between the interannual variations in LOD/AAMglobe and surface temperature, and the interannual variations in LOD and both zonal circulation and vertical airflow around the equator, consistently indicate that the LOD/AAMglobe reflect the potential impacts of variations in the Earth's rotation rate on the following season's sea surface temperatures (SST) over the tropical central and eastern pattern is located). Pacific (where the ENSO-like SST Moreover, the centers of strongest variation in the AAMcolumn (the relative atmospheric angular momentum for an air column and the unit mass over a square meter) are located over the mid-latitudinal North Pacific in DJF and MAM (March, April, and May), and over the mid-latitudinal South Pacific in JJA (June, July, and August) and SON (September, October, and November). This suggests that the AAMcolumn over the mid-latitudinal Pacific around 30°N (30~S) dominate the modulation of Earth's rotation rate, and then impact the variations in LOD during DJF and MAM (JJA and SON).展开更多
Wind energy is a fluctuating source for power systems, which poses challenges to grid planning for the wind power industry. To improve the short-term wind forecasts at turbine height, the bias correction approach Kalm...Wind energy is a fluctuating source for power systems, which poses challenges to grid planning for the wind power industry. To improve the short-term wind forecasts at turbine height, the bias correction approach Kalman filter (KF) is applied to 72-h wind speed forecasts from the WRF model in Zhangbei wind farm for a period over two years. The KF approach shows a remarkable ability in improving the raw forecasts by decreasing the root-mean-square error by 16% from 3.58 to 3.01 m s−1, the mean absolute error by 14% from 2.71 to 2.34 m s−1, the bias from 0.22 to − 0.19 m s−1, and improving the correlation from 0.58 to 0.66. The KF significantly reduces random errors of the model, showing the capability to deal with the forecast errors associated with physical processes which cannot be accurately handled by the numerical model. In addition, the improvement of the bias correction is larger for wind speeds sensitive to wind power generation. So the KF approach is suitable for short-term wind power prediction.展开更多
基金the National Natural Science Foundation of China(Grant Nos.41790471,42075040,and U1902209)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20100304)the National Key Research and Development Program of China(2018YFA0606203,2019YFC1510400).
文摘An enhanced Warm Arctic-Cold Eurasia(WACE)pattern has been a notable feature in recent winters of the Northern Hemisphere.However,divergent results between model and observational studies of the WACE still remain.This study evaluates the performance of 39 climate models participating in the Coupled Model Intercomparison Project Phase 6(CMIP6)in simulating the WACE pattern in winter of 1980-2014 and explores the key factors causing the differences in the simulation capability among the models.The results show that the multimodel ensemble(MME)can better simulate the spatial distribution of the WACE pattern than most single models.Models that can/cannot simulate both the climatology and the standard deviation of the Eurasian winter surface air temperature well,especially the latter,usually can/cannot simulate the WACE pattern well.This mainly results from the different abilities of the models to simulate the range and intensity of the warm anomaly in the Barents Sea-Kara seas(BKS)region.Further analysis shows that a good performance of the models in the BKS area is usually related to their ability to simulate location and persistence of Ural blocking(UB),which can transport heat to the BKS region,causing the warm Arctic,and strengthen the westerly trough downstream,cooling central Eurasia.Therefore,simulation of UB is key and significantly affects the model’s performance in simulating the WACE.
基金supported jointly by the Strategic Priority Research Program of the Chinese Academy of Sciences[Grant number XDA20060501]the National Natural Science Foundation of China[Grant numbers U1902209 and 91637208]。
基金supported by the China Scholarship Councilprimarily sponsored by the National Key R&D Program of China (Grant No.2018YFC1506702 and Grant No.2017YFC1502000)。
文摘The existence of outliers can seriously influence the analysis of variational data assimilation.Quality control allows us to effectively eliminate or absorb these outliers to produce better analysis fields.In particular,variational quality control(VarQC) can process gray zone outliers and is thus broadly used in variational data assimilation systems.In this study,governing equations are derived for two VarQC algorithms that utilize different contaminated Gaussian distributions(CGDs): Gaussian plus flat distribution and Huber norm distribution.As such,these VarQC algorithms can handle outliers that have non-Gaussian innovations.Then,these VarQC algorithms are implemented in the Global/Regional Assimilation and PrEdiction System(GRAPES) model-level three-dimensional variational data assimilation(m3 DVAR) system.Tests using artificial observations indicate that the VarQC method using the Huber distribution has stronger robustness for including outliers to improve posterior analysis than the VarQC method using the Gaussian plus flat distribution.Furthermore,real observation experiments show that the distribution of observation analysis weights conform well with theory,indicating that the application of VarQC is effective in the GRAPES m3 DVAR system.Subsequent case study and longperiod data assimilation experiments show that the spatial distribution and amplitude of the observation analysis weights are related to the analysis increments of the mass field(geopotential height and temperature).Compared to the control experiment,VarQC experiments have noticeably better posterior mass fields.Finally,the VarQC method using the Huber distribution is superior to the VarQC method using the Gaussian plus flat distribution,especially at the middle and lower levels.
基金funded by the National Science Foundation of China (No. 41575091)the National Basic Research and Development (973) Program of China (Grant No. 2012CB957803 and No. 2012CB957804)
文摘Studies on the impact of solar activity on climate system are very important in understanding global climate change. Previous studies in this field were mostly focus on temperature, wind and geopotential height. In this paper, interdecadal correlations of solar activity with Winter Snow Depth Index (WSDI) over the Tibetan Plateau, Arctic Oscillation Index (AOI) and the East Asian Winter Monsoon Index (EAWMI) are detected respectively by using Solar Radio Flux (SRF), Total Solar Irradiance (TSI) and Solar Sunspot Number (SSN) data and statistical methods. Arctic Oscillation and East Asian winter monsoon are typical modes of the East Asian atmospheric circulation. Research results show that on inter-decadal time scale over 11-year solar cycle, the sun modulated changes of winter snow depth over the Tibetan Plateau and East Asian atmospheric circulation. At the fourth lag year, the correlation coefficient of SRF and snow depth is 0.8013 at 0.05 significance level by Monte-Carlo test method. Our study also shows that winter snow depth over the Tibetan Plateau has significant lead and lag correlations with Arctic Oscillation and the East Asian winter monsoon on long time scale. With more snow in winter, the phase of Arctic Oscillation is positive, and East Asian winter monsoon is weak, while with less snow, the parameters are reversed. An example is the winter of 2012/2013, with decreased Tibetan Plateau snow, phase of Arctic Oscillation was negative, and East Asian winter monsoon was strong.
基金jointly supported by the National Natural Science Foundation of China (Grant Nos. 41175051 and 41490642)the National Basic Research and Development (973) Program of China (Grant No. 2012CB957804)+1 种基金the Postgraduate Science and Technology Innovation Project of Jiangsu Province (Grant No. CXZZ13 0517)the financial support of the China Scholarship Council (CSC)
文摘The teleconnection impact of the boreal winter Antarctic Oscillation(AAO) on the Somali Jet(SMJ) intensity in the following spring and summer is examined in this paper.The variability of the boreal winter AAO is positively related to the SMJ intensity in both spring and summer.The analyses show that the SST in southern high and middle latitudes seems to serve as a bridge linking these two systems.When the AAO is in strong positive phase,SST over the Southern Ocean cools in the high latitudes and warms in the middle latitudes,which persists into summer;however,the variability of SST in southern high and middle latitudes is also closely correlated to SMJ intensity.A possible mechanism that links SST variability with the AAO-SMJ relationship is also discussed.The AAO in boreal winter produces an SST anomaly pattern in southern high and middle latitudes through the air-sea coupling.This AAOrelated SST anomaly pattern modulates the local Ferrel cell anomaly in summer,followed by the regional Hadley cell anomaly in tropics.The anomalous vertical motion in tropics then changes the land-sea thermal contrast between the tropical Indian Ocean and the Asian continent through the variability of low cloud cover and downward surface longwave radiation flux.Finally,the land-sea thermal contrast anomaly between the tropical Indian Ocean and the Asian continent changes the SMJ intensity.The results from Community Atmosphere Model experiments forced by the SST anomaly in southern high and middle latitudes also confirm this diagnostic physical process to some extent.
基金the financial support from the Chinese Academy of Sciences"Belt and Road"Masters Fellowship Programme.
文摘The relative impacts of Indian and Pacific Ocean processes on Tanzanian rainfall was evaluated using composite and correlation analyses.It was found that the seasonal responses of rainfall to positive Indian Ocean Dipole(pIOD)and El Nino events are substantial from September-October-November(SON)to December-January-February(DJF),whereas the Indian Ocean Dipole(IOD)exerts more control than El Nino-Southern Oscillation(ENSO)in both seasons.The associated relationship with the sea surface temperature(SST)and large-scale atmo-spheric circulations revealed distinct features.For the pure pIOD years,there is above-normal rainfall over the entire country.A strong rainfall condition is evident over the Lake Victoria basin and coastal and northeastern highland parts of the country during SON,while areas of the central and southern highlands exhibit substantial rains during DJF.For the pure El-Nino events,Tanzania has suffered from insignificant,weak,and non-coherent rainfall conditions during SON.However,a contrasting insignificant rainfall signature is found between the north-ern and southern parts of the country during the subsequent DJF season.For the co-occurrence of pIOD and El Nino,significant,excessive rainfall conditions are restricted to over the northern coast and northeastern areas of the country during SON,consistent with the rainfall pattern for pIOD.A weak,positive rainfall condition is observed over the entire country in the following season of DJF.Generally,in terms of Tanzanian rainfall,the IOD/ENSO variability and the associated impacts can be explained by the anomalous SST and circulation anomalies.
基金This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences[XDA20060501]the National Natural Science Foundatin of China[91637208].
基金supported by the National Key Research and Development Program of China(Nos.2022YFF1303102 and 2021YFA1202500)Beijing Natural Science Foundation(No.8232035)+2 种基金the National Natural Science Foundation of China(Nos.52270053,52200083 and 52200084)the Beijing Nova Program(No.20220484215)the Key Special Projects for Science and Technology of Inner Mongolia(No.2021EEDSCXSFQZD001)。
文摘Peracetic acid(CH_(3)C(O)OOH,PAA)-based heterogeneous advanced oxidation process(AOP)has attacked intensive interests due to production of various reactive species.Herein,Co(OH)_(2)nanoparticles decorated biochar(Co(OH)_(2)/BC)was fabricated by a simple and controllable method,which was used to degrade tetracycline hydrochloride(TTCH)in water through PAA activation.The results indicated that 100%TTCH(C_(0)=10μmol/L)degradation efficiency was realized within 7 min at pH 7,with a high kinetic rate constant(k_(1))of 0.64 min^(-1)by the optimized Co(OH)_(2)/BC.Material characterizations suggested that Co(OH)_(2)nanoparticle was successfully decorated on biochar,leading to more active sites and electronic structure alteration of biochar,thus greatly promoting the catalytic cleavage of PAA for radicals production.Then,the reactive oxygen species(ROS)quenching experiments and electron paramagnetic resonance(EPR)analysis demonstrated the key species were alkoxyl radicals(R–O^(·),mainly CH_(3)CO_(2)^(·)and CH_(3)CO_(3)^(·)),HO^(·)and^(1)O_(2)in this system.Besides,density functional theory(DFT)calculation on Fukui index further revealed that the vulnerable sites of TTCH and three possible degradation pathways were proposed.This study can provide a new strategy for synthesis functional materials in PAA activation AOPs for removal of antibiotics in water.
基金Supported by the National(Key) Basic Research and Development(973) Program of China(2012CB957804 and 2012CB417205)National Natural Science Foundation of China(41305131,41405146,and 41505079)
文摘A rainband meridional shift index (RMSI) is defined and used to statistically prove that the East Asian summer monsoon rainband is usually significantly more northward in the early summer of solar maximum years than that of solar minimum years. By applying continuous wavelet transform, cross wavelet transform, and wavelet coherence, it is found that throughout most of the 20th century, the significant decadal oscillations of sunspot number (SSN) and the RMSI are phase-locked and since the 1960s, the SSN has led the RMSI slightly by approximately 1.4 yr. Wind and Eliassen-Palm (EP) flux analysis shows that the decadal meridional oscillation of the June rainband likely re- sults from both a stronger or earlier onset of the tropical monsoon and poleward shift of the subtropical westerly jet in high-solar months of May and June. The dynamical responses of the lower tropical monsoon and the upper subtropical westerly jet to the 11-yr solar cycle transmit bottom-up and top-down solar signals, respectively, and the synergistic actions between the monsoon and the jet likely amplify the solar signal at the northern boundary of the monsoon to some extent.
基金Supported by the National Key Basic Research and Development(973)Program of China(2012CB957804)Project from State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences(LTO1916)+1 种基金National Natural Science Foundation of China(42075040)Science and Technology Project of State Grid Corporation of China(SGCC,NY71-19-013)。
文摘This paper uses two subsets of ensemble historical-Nat simulations and pi-Control simulations from CMIP5 as well as observational/reanalysis datasets to investigate responses of the tropical Pacific to the 11-yr solar cycle.A statistically significant 11-yr solar signal is found in the upper-ocean layers above the thermocline and tropospheric circulations.A warming response initially appears in the upper layers of the central equatorial Pacific in the solar maximum years in observations,then increases and shifts into the eastern Pacific at lagged 1-3 yr.Meanwhile,an anomalous updraft arises over the western equatorial Pacific and shifts eastwards in the following years with anomalous subsidence over the Maritime Continent.These lagged responses are confirmed by the historical-Nat simulations,except that the initial signal is located more to the west and all the responses are weaker than the observed.A simplified mixed-layer heat budget analysis based on the historical-Nat simulations suggests that the atmospheric forcing,especially the shortwave radiation,is the major contributor to the initial warming response,and the ocean heat transport effect is responsible for the eastward displacement of the lagged warming responses.In the solar maximum years,the zonal ocean temperature gradient in the western-central Pacific is reduced by the initial warming,and anomalous westerly winds appear over the western equatorial Pacific and extend into the eastern Pacific during the lagged years.These anomalous westerly winds reduce the wind-driven ocean dynamical transport,resulting in the initial warming in the central equatorial Pacific being amplified and the surface warming shifting eastward during the lagged 1-3 yr.
基金This research was supported by the National Natural Science Foundation of China (Grant Nos. 41175051 and 41101045), and the National Science Foundation of China-Yunnan Province Joint Grant (U1133603).
文摘This study analyzed the changes in precipita- tion over summer and autumn across the Yunnan region of China, and undertook a composite analysis of the atmo- spheric circulations in the troposphere, which included an analysis of the interannual and interdecadal variations. This paper examines in detail the circulation backgrounds of the wet and dry periods in summer and autumn and their correlations with the sea surface temperature. The results indicated that the summer and autumn precipitation across Yunnan has significantly decreased over the past 50 years. Furthermore, since the beginning of the century, the summer and autumn precipitation cycle has been in a low precipitation phase. The overlap of two extremely low rain phases has caused frequent droughts in the region. In addition, the atmospheric circulation fields during these wet and dry periods are very different. These are mainly shown as a meridional wind anomaly in eastern China in the low atmosphere, as a cross-equatorial airflow anomaly, a tropical zonal wind anomaly over the Indian Ocean, and as a related South Asia High and Western Pacific Subtropical High. Further analysis suggested that the SST over the Indian Ocean and the Pacific warm pool critically affect the anomalous summer and autumn precipitation over Yunnan by impacting the monsoon circulations. Future projections for greenhouse gas wann- ing suggest a potential anomalous circulation background between 2010 and 2020 which may result in less precipitation during the wet season or even drought events across the Yunnan region.
基金supported by the Chinese Academy of Sciences(No.XDA20060501)the National Natural Science Foundation of China(Grant No.91937000)to the first two authorsThe other co-authors were supported by the Office of Naval Research(ONR)(No.N00014-18-1-2361).
文摘A recent version of the Polar Weather Research and Forecasting model(Polar WRF)has been upgraded to the version 4.X era with an improved NoahMP Land Surface Model(LSM).To assess the model performance over the Antarctic and Southern Ocean,downscaling simulations with different LSM(NoahMP,Noah),WRF versions(Polar WRF 4.1.1 and earlier version 4.0.3,WRF 4.1.1),and driving data(ERA-Interim,ERA5)are examined with two simulation modes:the short-term that consists of a series of 48 h segments initialized daily at 0000 UTC with the first 24 h selected for model spin-up,whereas the long-term component used to evaluate long-term prediction consists of a series of 38-41 day segments initialized using the first 10 days for spin-up of the hydrological cycle and planetary boundary layer structure.Simulations using short-term mode driven by ERA-Interim with NoahMP and Noah are selected for benchmark experiments.The results show that Polar WRF 4.1.1 has good skills over the Antarctic and Southern Ocean and better performance than earlier simulations.The reduced downward shortwave radiation bias released with WRF 4.1.1 performed well with PWRF411.Although NoahMP and Noah led to very similar conclusions,NoahMP is slightly better than Noah,particularly for the 2 m temperature and surface radiation because the minimum albedo is set at 0.8 over the ice sheet.Moreover,a suitable nudging setting plays an important role in long-term forecasts,such as reducing the surface temperature diurnal cycle near the coast.The characteristics investigated in this study provide a benchmark to improve the model and guidance for further application of Polar WRF in the Antarctic.
基金supported by the National Natural Science Foundation of China (Grants Nos. 91637208 & 41405146)the Key Project of Science Foundation of Yunnan Province (Grant No. 2016FA041)the Key Research Program of Frontier Sciences of CAS (Grant No. QYZDB-SSW-DQC2017)
文摘As the deep convective clouds(DCCs) over the western Pacific and Indian Ocean warm pool may play different roles in the climate system, variations in DCC properties over these two sectors are investigated and compared. The DCC intensity and area varies more significantly in the Indian Ocean than the western Pacific sector, while the DCC frequency is comparable in both sectors at the seasonal scale. Although the Indian Ocean sector is strongly dominated by the seasonal evolution, the interannual variations in the two sectors are comparable for all three DCC properties(frequency, intensity, and area). Besides,Walker circulation is closely correlated with the interannual variability of DCCs in both sectors. The Walker circulation strengthens(weakens) as the DCCs shift eastward(westward) over the Indian Ocean sector and westward(eastward) over the western Pacific sector. When more or stronger DCCs occur over the Indian Ocean sector(western Pacific sector), the Walker circulation becomes stronger(weaker) and shifts westward(eastward). Interestingly, the response of the Walker circulation to DCC variability over the warm pool is asymmetry. The asymmetry response of the Walker circulation to the negative and positive DCC anomaly may be related to the non-linearity internal variability of the atmosphere. DCCs over the Indian Ocean sector have a much weaker nonlinear correlation with the Walker circulation than DCCs over the western Pacific sector.
基金Supported by the National Natural Science Foundation of China(41575091)National(Key)Basic Research and Development(973)Program of China(2012CB957803)Natural Science Foundation of Jiangsu Province(BK20171230)
文摘The impact of solar activity on climate system is spatiotemporally selective and usually more significant on the regional scale. Using statistical methods and solar radio flux(SRF) data, this paper investigates the impact of the solar11-yr cycle on regional climate of Northeast Asia in recent decades. Significant differences in winter temperature,precipitation, and the atmospheric circulation over Northeast Asia are found between peak and valley solar activity years. In peak years, temperature is higher over vast areas of the Eurasian continent in middle and high latitudes, and prone to producing anomalous high pressure there. Northeast Asia is located to the south of the anomalous high pressure, where the easterlies prevail and transport moisture from the western Pacific Ocean to the inland of East Asia and intensify precipitation there. In valley years, temperature is lower over the Eurasian continent and northern Pacific Ocean in middle and high latitudes, and there maintain anomalous low pressure systems in the two regions. Over the Northeast Asian continent, north winds prevail, which transport cold and dry air mass from the high latitude to Northeast Asia and reduce precipitation there. The correlation coefficient of winter precipitation in Northeast China and SRF reaches 0.4, and is statistically significant at the 99% confidence level based on the Student's t-test. The latent heat flux anomalies over the Pacific Ocean caused by solar cycle could explain the spatial pattern of abnormal winter precipitation of China, suggesting that the solar activity may change the climate of Northeast Asia through air–sea interaction.
基金This research was supported by the National Basic Research Program of China (No. 2012CB957804) and the National Natural Science Foundation of China (Grant Nos. 41275109, 41075078 and 41175051).
文摘To improve the energetics in the life cycle of an ideal baroclinic instability case, we develop a Physical Conserving Fidelity model (F-model), and we compare the simulations from the F-model to those of the traditional global spectral semi-implicit model (control model). The results for spectral kinetic energy and its budget indicate different performances at smaller scales in the two models. A two-way energy flow emerges in the generation and rapid growth stage of the baroclinic disturbance in the F-model. However, only a downscale mechanism dominates in the control model. In the F-model, the meso- and smaller scales are energized initially, and then an active upscale nonlinear cascade occurs. Thus, disturbances at prior scales are forced by both downscale and upscale energy cascades and by conversion from potential energy. An analysis of the eddy kinetic energy budget also shows remarkable enhancement of the energy conversion rate in the F-model. As a result, characteristics of the ideal baroclinic wave are greatly improved in the F-model, in terms of both intensity and time of formation.
文摘This study examines the seasonal connections between the interannual variations in LOD (length of day)/ AAMglobe (the relative atmospheric angular momentum for the whole globe) and the ENSO-like SST (El Nifio/ Southern Oscillation-like sea surface temperature) pattern and corresponding zonal and vertical circulations. Consistent with previous studies, the ENSO-like SST impact the following season LOD/AAMglobe, with the strongest correlations in DJF (December, January, and February), when it is likely to be the peak E1 Nino/La Nifia period. Lag correlations between the interannual variations in LOD/AAMglobe and surface temperature, and the interannual variations in LOD and both zonal circulation and vertical airflow around the equator, consistently indicate that the LOD/AAMglobe reflect the potential impacts of variations in the Earth's rotation rate on the following season's sea surface temperatures (SST) over the tropical central and eastern pattern is located). Pacific (where the ENSO-like SST Moreover, the centers of strongest variation in the AAMcolumn (the relative atmospheric angular momentum for an air column and the unit mass over a square meter) are located over the mid-latitudinal North Pacific in DJF and MAM (March, April, and May), and over the mid-latitudinal South Pacific in JJA (June, July, and August) and SON (September, October, and November). This suggests that the AAMcolumn over the mid-latitudinal Pacific around 30°N (30~S) dominate the modulation of Earth's rotation rate, and then impact the variations in LOD during DJF and MAM (JJA and SON).
基金supported by National Key R&D Program of China(Technology and application of wind power/photovoltaic power prediction for promoting renewable energy consumption,2018YFB0904200)eponymous Complement S&T Program of State Grid Corporation of China(SGLNDKOOKJJS1800266).
文摘Wind energy is a fluctuating source for power systems, which poses challenges to grid planning for the wind power industry. To improve the short-term wind forecasts at turbine height, the bias correction approach Kalman filter (KF) is applied to 72-h wind speed forecasts from the WRF model in Zhangbei wind farm for a period over two years. The KF approach shows a remarkable ability in improving the raw forecasts by decreasing the root-mean-square error by 16% from 3.58 to 3.01 m s−1, the mean absolute error by 14% from 2.71 to 2.34 m s−1, the bias from 0.22 to − 0.19 m s−1, and improving the correlation from 0.58 to 0.66. The KF significantly reduces random errors of the model, showing the capability to deal with the forecast errors associated with physical processes which cannot be accurately handled by the numerical model. In addition, the improvement of the bias correction is larger for wind speeds sensitive to wind power generation. So the KF approach is suitable for short-term wind power prediction.