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Cao G.,Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters | Cao G.,Nanjing University of Information Science and Technology | He C.,Nanjing University of Information Science and Technology | Xu W.,Nanjing University of Information Science and Technology
Fluctuation and Noise Letters | Year: 2016

This study investigates the correlation between weather and agricultural futures markets on the basis of detrended cross-correlation analysis (DCCA) cross-correlation coefficients and q-dependent cross-correlation coefficients. In addition, detrended fluctuation analysis (DFA) is used to measure extreme weather and thus analyze further the effect of this condition on agricultural futures markets. Cross-correlation exists between weather and agricultural futures markets on certain time scales. There are some correlations between temperature and soybean return associated with medium amplitudes. Under extreme weather conditions, weather exerts different influences on different agricultural products; for instance, soybean return is greatly influenced by temperature, and weather variables exhibit no effect on corn return. Based on the detrending moving-average cross-correlation analysis (DMCA) coefficient and DFA regression results are similar to that of DCCA coefficient. © 2016 World Scientific Publishing Company. Source

Zhou B.,National Climate Center | Zhou B.,Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters | Wang Z.,National Climate Center
Journal of Geophysical Research Atmospheres | Year: 2015

Using monthly data from the European Centre for Medium-Range Weather Forecasts 40 year Re-Analysis, this study investigated the interannual relationship between the Asian-Pacific Oscillation (APO) and the North Atlantic Oscillation (NAO) for the period of May to August. The NAO is represented by the leading Empirical Orthogonal Function of sea level pressure anomalies over the Atlantic sector. The difference of upper tropospheric eddy air temperature (T′) between Asia and the North Pacific is used to measure the APO. Results clearly show that the APO and the NAO correlated very well on the interannual time scale, with the positive (negative) phase of the APO corresponding to the strong (weak) NAO. Such a relationship is well supported by the atmospheric dynamic process. When the APO is in the positive phase (characterized by the positive T′ anomaly over Asia and the negative T′ anomaly over the North Pacific in the upper troposphere), the upper tropospheric geopotential height increases over Asia and decreases over the North Pacific. Accordingly, anticyclonic circulation and cyclonic circulation anomalies are introduced, respectively, over Asia and south of the North Pacific, and a zonal teleconnection wave train is excited from Asia to the North Atlantic. As a consequence, an anomalous anticyclonic circulation prevails in the low level of the North Atlantic and an anomalous cyclonic circulation appears to its north, which corresponds to the atmospheric pattern of strong NAO. Further study proposes that the quasi-stationary wave pattern emanating from the western North Pacific region may serve as a bridge for this linkage. © 2015. American Geophysical Union. All Rights Reserved. Source

Zhang W.,Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters | Zhao X.,Laboratory of Ocean Circulation and Waves | Zheng F.,CAS Institute of Atmospheric Physics
Journal of Geophysical Research C: Oceans | Year: 2015

The cold tongue mode (CTM) is the second EOF mode of sea surface temperature anomaly (SSTA) variability over the tropical Pacific and represents the out-of-phase relationship in SSTA variability between the Pacific cold tongue region and elsewhere in the tropical Pacific. A positive CTM is characterized by cold SSTA in the Pacific cold tongue region and warm SSTA in the rest of the tropical Pacific, with conditions reversed for a negative CTM. The CTM is a coupled air-sea mode, and its long-term variability is most probably induced by ocean dynamical processes in response to global warming [Zhang et al., 2010]. This study focuses on the specific ocean dynamical processes associated with the CTM and its possible relationship with global warming. A heat budget diagnosis of ocean temperature in the eastern equatorial Pacific shows that the net heat flux plays a damping role and the four ocean advection terms ( -u′∂T-/∂x, -v-∂T′/∂y, -w-∂T′/∂z, and -w′∂T-/∂z) contribute to the temperature change associated with the CTM. Among them, the vertical advection of the anomalous temperature by the mean upwelling ( -w-∂T′/∂z) makes a dominant contribution to the long-term change in the CTM. The long-term change of the term -w-∂T′/∂z is controlled mainly by the decreasing vertical gradient of the ocean temperature anomaly ( ∂T′/∂z). The other three advection terms make a minor contribution to the long-term change in the CTM. © 2015. American Geophysical Union. All Rights Reserved. Source

Tao W.,CAS Institute of Atmospheric Physics | Tao W.,Chengdu University of Information Technology | Huang G.,CAS Institute of Atmospheric Physics | Huang G.,Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters | And 4 more authors.
International Journal of Climatology | Year: 2015

On the basis of Coupled Model Intercomparison Project phase 5 (CMIP5) models, this study have examined the ability of models to capture the El Niño/Southern Oscillation (ENSO)-Indian Ocean Basin Mode (IOBM) relationship, and investigated the characteristics of interdecadal change of ENSO-IOBM relationship as well as the response of the ENSO-IOBM relationship to the global warming. Among 23 CMIP5 models, the capability of models in representing the IOBM depends largely on the simulation of ENSO. Moreover, half of the models can reproduce the unstable ENSO-IOBM relationship. Considering the simulations of ENSO, ENSO-IOBM relationship and interdecadal change, 6 of 23 CMIP5 models are chosen for further investigation. The interdecadal change of ENSO-IOBM relationship is relative to the three ENSO-related processes. During the high correlation (HC) period, the tropospheric temperature (TT) mechanism, oceanic Rossby waves and antisymmetric wind pattern are strong, prolonging the persistence of IOBM. In comparison, during the low correlation (LC) period, the three processes are weak. The results show that the shallow thermocline in the southwestern Indian Ocean (SWIO), increased interannual variability and prolonged periodicity of ENSO are all responsible for the interdecadal change. Furthermore, the possible changes of ENSO-IOBM relationship in the future are investigated. The ENSO-related tropical Indian Ocean (TIO) warming is strengthened under global warming. Despite the deepened thermocline over SWIO and unchanged ENSO activity, the ENSO-related TIO warming is strengthened by the enhanced TT mechanism, which is caused by the increased saturated specific humidity. The results reveal that there is more downward net heat flux (NHF) over the TIO, which is conducive to the TIO warming, and the latent heat flux (LHF) change makes a great contribution to the NHF change. The weakened upward or strengthened downward LHF is possibly due to the decreased anomalous sea-air temperature difference by strengthened TT mechanism. © 2014 Royal Meteorological Society. Source

Gao Y.,Nanjing University of Information Science and Technology | Chen Y.,Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters | Zhang L.,China Meteorological Administration Training Center | Peng T.,Institute of Heavy Rain CMA
Journal of the Meteorological Society of Japan | Year: 2016

From July 1 to 13, 2007, a widespread heavy rainfall event occurred in the Huaihe River Basin (HB) in China, with an average rainfall of nearly 465 mm in the area. The main purpose of this study is to integrate a rainfall estimate by the China New Generation Weather Radar S-band radar (CINRAD-SB) into the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and analyze the CINRAD-SB rainfall estimation and its impact on the runoff simulation of this type of rare flood event in a region with complex terrain. For the CINRAD-SB rainfall estimation four methods are considered: (1) Z = 300R1.4 (Z: radar reflectivity, R: rainfall intensity); (2) a rainfall estimation error adjustment by using a Kalman Filter (KF); (3) Optimal Interpolation (OI); and (4) the Union method, which is composed of KF and OI. The HEC-HMS is used to investigate the spatial and temporal distribution of the CINRAD-SB rainfall and its impact on the hydrological simulation of the event. Rainfall estimations from the four methods are compared with rain gauge observations. The four methods underestimate the precipitation amounts, while for the Union method the values of the relative bias are closer to zero. The relative bias values of the four methods vary with different rainfall intensity, those of the Union method vary the least among the four methods. This evaluation indicates that runoff simulations based on radar-rainfall could reproduce similar overall patterns to the observed streamflow. The peak discharge contains obvious improvements – for instance, the skill score is 0.6 – in model runs with forcing that is provided by the Union method vs. rain gauge data. These results might guide the improvement of hydrological predictions that are driven by radar rainfall. © 2016, Meteorological Society of Japan. Source

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