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Dongliang Yuan, Hui Zhou, and Xia Zhao

Abstract

The authors’ previous dynamical study has suggested a link between the Indian and Pacific Ocean interannual climate variations through the transport variations of the Indonesian Throughflow. In this study, the consistency of this oceanic channel link with observations is investigated using correlation analyses of observed ocean temperature, sea surface height, and surface wind data. The analyses show significant lag correlations between the sea surface temperature anomalies (SSTA) in the southeastern tropical Indian Ocean in fall and those in the eastern Pacific cold tongue in the following summer through fall seasons, suggesting potential predictability of ENSO events beyond the period of 1 yr. The dynamics of this teleconnection seem not through the atmospheric bridge, because the wind anomalies in the far western equatorial Pacific in fall have insignificant correlations with the cold tongue anomalies at time lags beyond one season. Correlation analyses between the sea surface height anomalies (SSHA) in the southeastern tropical Indian Ocean and those over the Indo-Pacific basin suggest eastward propagation of the upwelling anomalies from the Indian Ocean into the equatorial Pacific Ocean through the Indonesian Seas. Correlations in the subsurface temperature in the equatorial vertical section of the Pacific Ocean confirm the propagation. In spite of the limitation of the short time series of observations available, the study seems to suggest that the ocean channel connection between the two basins is important for the evolution and predictability of ENSO.

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Xianhua Wu, Zhe Xu, Hui Liu, Ji Guo, and Lei Zhou

Abstract

To investigate the general principle of the impact of tropical cyclones on employment, explore the reason for the divergence among existing research conclusions, and put forward some suggestions for post-disaster reconstruction, this paper employs meta-regression analysis to study the impacts of tropical cyclones on the quantity of labor employed and employee remuneration from four aspects: industry dimension, time dimension, income dimension, and tropical cyclone intensity. The results are as follows: 1) Tropical cyclones create an impact on the intensity of changes in employment remuneration in the primary industry, and the impact in the secondary industry is greater than that in the tertiary industry. 2) In the short term, the impact of tropical cyclones on employment is negative and the impact intensity is strong, whereas in the medium and long terms, the impact is positive and the intensity of impact decreases. 3) Although tropical cyclones increase the quantity of labor employed from low-income groups, they decrease their employment remuneration. In addition, the impact of disasters on the number of employed high-income groups is relatively small compared to that of low-income groups. 4) A higher category of tropical cyclone results in a greater positive impact on the employment of labor force. Accordingly, the following suggestions are made: 1) The government should issue corresponding policies to provide “temporary disaster subsidies” for disaster-stricken low-income groups. 2) Insurance companies should introduce commercial insurance concerning “post-disaster employment” for employers to purchase before any disaster occurs so as to offer disaster-stricken employees compensation.

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Hui Zhou, Dongliang Yuan, Lina Yang, Xiang Li, and William Dewar

Abstract

The meridional geostrophic transport (MGT) in the interior tropical North Pacific Ocean is estimated based on global ocean heat and salt content data. The decadal variations of the zonally and vertically integrated MGT in the tropical North Pacific Ocean are found to precede the Pacific decadal oscillation (PDO) by 1–3 years. The dynamics of the MGT are analyzed based on Sverdrup theory. It is found that the total meridional transport variability (MGT plus Ekman) is dominated by the MGT variability having positive correlations with the PDO index. The Sverdrup transports differ from the total meridional transport significantly and have insignificant correlations with PDO index, suggesting that the MGT variability is not controlled by the Sverdrup dynamics. In comparison, the simulated meridional transport variability in the models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and the Ocean General Circulation Model for the Earth Simulator are dominated by the Sverdrup transports, having insignificant correlations with the simulated PDO indices. The comparison suggests that the non-Sverdrup component in the MGT is important for the predictability of PDO and that significant deficiencies exist in these models in simulating a realistic structure of the tropical ocean gyre variability and predicting the decadal climate variations associated with it.

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Xiao-Hui Zhou, Dong-Ping Wang, and Dake Chen

Abstract

The altimetry wavenumber spectra of sea surface height (SSH) provide a unique dataset for testing of geostrophic turbulence. While SSH spectral slopes of k −11/3 and k −5 are expected from theories and numerical simulations, the altimetry spectra from the original unfiltered and instrument noise–corrected data often are too shallow, falling between k −2 and k −3. In this study, the possibility that the flattened spectral slopes are partly due to contamination by unresolved high-frequency (<10 days) motions is tested. A spatiotemporal filter based on empirical orthogonal function expansion (EOF) is used to remove the temporally incoherent signals. The resulting spectral slopes are much steeper than in the previous studies. Over 70% of the revised global spectral estimates, excluding the tropics, are above k −3. Moreover, in high energy regions like the Gulf Stream and Kuroshio, the spectral slopes are about k −5, which is consistent with the classical quasigeostrophic (QG) turbulence. The spectral slopes are validated with the eddy kinetic energy (EKE) spectra from shipboard acoustic Doppler current profiler (ADCP) measurements in the high and low energy regions.

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Xianhua Wu, Lei Zhou, Ji Guo, and Hui Liu

Abstract

What impacts do typhoons have on local labor markets? Few empirical researches have been conducted in China. By collecting the data of 23 quarters (3-month intervals) of Guangdong province from 2009 to 2014 and using the generalized method of moments (GMM), this paper analyzes the impacts of typhoons on labor markets from the perspectives of general effect, regional effect, intensity effect, and time effect. In addition, a comparative analysis is carried out between this study and similar studies of developed countries. The results show that 1) massive typhoons resulted in a 12.5% increase in employment but did not have a significant impact on Guangdong’s per capita employee remuneration, and 2) there are periodic features to typhoons’ impacts on employment. Typhoons influence employment in a four-quarter cycle. In the quarter affected by a typhoon, the first quarter, the number of employees increased by 17.4%. The quantity of labor employed in the subsequent two quarters shows no significant change. In the last quarter, the number of employed people decreases by 17.0%, which returns to predisaster levels. Additionally, 3) the results of this study are different from those of studies involving developed countries, which may be caused by the distinctiveness of China’s labor market. Finally, conclusions and corresponding suggestions are presented.

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An-Zhou Cao, Hui Chen, Wei Fan, Hai-Lun He, Jin-Bao Song, and Ji-Cai Zhang

Abstract

Previous studies have shown that strong tidal currents can cause intense turbulent mixing near the seafloor in continental shelf areas. To quantify the turbulent mixing, the eddy viscosity coefficient is generally used. In this study, an estimation scheme is proposed to evaluate the eddy viscosity profile (EVP) in the bottom Ekman boundary layer based on the adjoint method. The estimation scheme is composed of the bottom Ekman boundary layer model and its adjoint model, and a minimization algorithm. The feasibility and effectiveness of the proposed scheme are validated by a series of twin experiments, where the proposed scheme is compared with three other schemes in previous studies. When large measurement errors exist, the proposed scheme performs better than the three other schemes. When large Ekman balance errors exist, the proposed scheme is better than two of the other schemes. The selection of components of the steady current and tidal constituents also influences the performance of the proposed scheme. Successful estimation of the EVP requires the usage of intense components of the steady current and tidal constituents. With the usage of the intense components, increasing the number of tidal constituents cannot lead to a more accurate estimation of the EVP.

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Dongliang Yuan, Jing Wang, Tengfei Xu, Peng Xu, Zhou Hui, Xia Zhao, Yihua Luan, Weipeng Zheng, and Yongqiang Yu

Abstract

Controlled numerical experiments using ocean-only and ocean–atmosphere coupled general circulation models show that interannual sea level depression in the eastern Indian Ocean during the Indian Ocean dipole (IOD) events forces enhanced Indonesian Throughflow (ITF) to transport warm water from the upper-equatorial Pacific Ocean to the Indian Ocean. The enhanced transport produces elevation of the thermocline and cold subsurface temperature anomalies in the western equatorial Pacific Ocean, which propagate to the eastern equatorial Pacific to induce significant coupled evolution of the tropical Pacific oceanic and atmospheric circulation. Analyses suggest that the IOD-forced ITF transport anomalies are about the same amplitudes as those induced by the Pacific ENSO. Results of the coupled model experiments suggest that the anomalies induced by the IOD persist in the equatorial Pacific until the year following the IOD event, suggesting the importance of the oceanic channel in modulating the interannual climate variations of the tropical Pacific Ocean at the time lag beyond one year.

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Hui Zhou, Hengchang Liu, Shuwen Tan, Wenlong Yang, Yao Li, Xueqi Liu, Qiang Ren, and William K. Dewar

Abstract

The structure and variations of the North Equatorial Countercurrent (NECC) in the far western Pacific Ocean during 2014–16 are investigated using repeated in situ hydrographic data, altimeter data, Argo data, and reanalysis data. The NECC shifted ~1° southward and intensified significantly with its transport exceeding 40 Sv (1 Sv ≡ 106 m3 s−1), nearly double its climatology value, during the developing phase of the 2015/16 El Niño event. Observations show that the 2015/16 El Niño exerted a comparable impact on the NECC with that of the extreme 1997/98 El Niño in the far western Pacific Ocean. Baroclinic instability provided the primary energy source for the eddy kinetic energy (EKE) in the 2015/16 El Niño, which differs from the traditional understanding of the energy source of EKE as barotropic instability in low-latitude ocean. The enhanced vertical shear and the reduced density jump between the NECC layer and the North Equatorial Subsurface Current (NESC) layer renders the NECC–NESC system baroclinically unstable in the western Pacific Ocean during El Niño developing phase. The eddy–mean flow interactions here are diverse associated with various states of El Niño–Southern Oscillation (ENSO).

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Hui Yu, Guomin Chen, Cong Zhou, Wai Kin Wong, Mengqi Yang, Yinglong Xu, Peiyan Chen, Rijin Wan, and Xinrong Hu

Abstract

The annual-mean position errors (PE) of tropical cyclone (TC) track forecasts from three forecast agencies [WMO Regional Specialized Meteorological Center in Tokyo (RSMC-Tokyo), China Meteorological Administration (CMA), and Joint Typhoon Warning Center of the United States (JTWC)] are analyzed to document the past improvements and project future tendency in track forecast accuracy for TCs in the western North Pacific. An improvement of 48 h (2 days) in lead time has been achieved in the past 30 years, but with noticeable stepwise periods of improvements with superposed short-term fluctuations. The stepwise improvement features differ among the three forecast agencies, but are highly related to the development of objective forecast guidance and the application strategy. As demonstrated by an exponential model for the growth of PEs with lead time for TCs of tropical storm category and above, the improvements in the past 10 years have mainly been due to the reduction in analysis errors rather than the reduction in the error growth rate. If the current trend continues, a further 2-day improvement in TC track forecast lead times may be projected for the coming 15 years up to 2035, and we certainly have not reached yet the limit of TC track predictability in the western North Pacific.

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Hui Shao, John Derber, Xiang-Yu Huang, Ming Hu, Kathryn Newman, Donald Stark, Michael Lueken, Chunhua Zhou, Louisa Nance, Ying-Hwa Kuo, and Barbara Brown

Abstract

With a goal of improving operational numerical weather prediction (NWP), the Developmental Testbed Center (DTC) has been working with operational centers, including, among others, the National Centers for Environmental Prediction (NCEP), National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), and the U.S. Air Force, to support numerical models/systems and their research, perform objective testing and evaluation of NWP methods, and facilitate research-to-operations transitions. This article introduces the first attempt of the DTC in the data assimilation area to help achieve this goal. Since 2009, the DTC, NCEP’s Environmental Modeling Center (EMC), and other developers have made significant progress in transitioning the operational Gridpoint Statistical Interpolation (GSI) data assimilation system into a community-based code management framework. Currently, GSI is provided to the public with user support and is open for contributions from internal developers as well as the broader research community, following the same code transition procedures. This article introduces measures and steps taken during this community GSI effort followed by discussions of encountered challenges and issues. The purpose of this article is to promote contributions from the research community to operational data assimilation capabilities and, furthermore, to seek potential solutions to stimulate such a transition and, eventually, improve the NWP capabilities in the United States.

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