scholarly journals Stable components in extended-range forecasting during the continuous high temperature event in August 2013 over the mid-eastern China

2015 ◽  
Vol 64 (4) ◽  
pp. 049203
Author(s):  
Zeng Yu-Xing ◽  
Ye Tian-Shu ◽  
Wang Kuo ◽  
Shen Qian
Keyword(s):  
High Temperature ◽  
Eastern China ◽  
Extended Range ◽  
Extended Range Forecasting

Robustness of Relations between the MJO and U.S. Tornado Occurrence

2018 ◽  
Vol 146 (11) ◽  
pp. 3873-3884 ◽  
Author(s):  
Michael K. Tippett
Keyword(s):  
Time Scales ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Maritime Continent ◽  
Tropical Variability ◽  
Extended Range ◽  
Leading Mode ◽  
Tornado Outbreaks ◽  
Extended Range Forecasting

Abstract The Madden–Julian oscillation (MJO) is the leading mode of tropical variability on subseasonal time scales and has predictable impacts in the extratropics. Whether or not the MJO has a discernible influence on U.S. tornado occurrence has important implications for the feasibility of extended-range forecasting of tornado activity. Interpretation and comparison of previous studies is difficult because of differing data periods, methods, and tornado activity metrics. Here, a previously described modulation of the frequency of violent tornado outbreaks (days with six or more tornadoes reported rated EF2 or greater) by the MJO is shown to be fairly robust to the addition or removal of years to the analysis period and to changes in the number of tornadoes used to define outbreak days, but is less robust to the choice of MJO index. Earlier findings of a statistically significant MJO signal in the frequency of days with at least one tornado report are shown to be incorrect. The reduction of the frequency of days with tornadoes rated EF1 and greater when MJO convection is present in the Maritime Continent and western Pacific is statistically significant in April and robust across varying thresholds of reliably reported tornado numbers and MJO indices.

scholarly journals Probabilistic Forecast of the Extended Range Heatwave Over Eastern China

2022 ◽  
Vol 9 ◽  
Author(s):  
Wei Zhang ◽  
Jianyun Gao ◽  
Qiaozhen Lai ◽  
Yanzhen Chi ◽  
Tonghua Su
Keyword(s):  
Bayesian Model Averaging ◽  
Grid Point ◽  
Eastern China ◽  
Model Averaging ◽  
Probabilistic Forecast ◽  
Brier Score ◽  
Verification Method ◽  
Pattern Correlation ◽  
Extended Range ◽  
Model Ensembles

Several probabilistic forecast methods for heatwave (HW) in extended-range scales over China are constructed using four models (ECMWF, CMA, UKMO, and NCEP) from the Subseasonal-to-Seasonal (S2S) database. The methods include four single-model ensembles (SME; ECMWF, CMA, UKMO, and NCEP), multi-model ensemble (MME), and Bayesian model averaging (BMA). The construction and verification of reforecasts are implemented by a defined heat wave index (HWI) which is not only able to reflect the actual occurrence of heatwaves, but also to facilitate forecast and verification. The performance is measured by traditional verification method at each grid point of the 105°E to 132°E; 20°N to 45°N domain for the July, August, and September (JAS) of 1999–2010. For deterministic evaluations of HWI forecast, BMA shows a better pattern correlation coefficient than SME and MME and comparable equitable threat score (ETS) with ECMWF and MME. The good performance of ECMWF and MME take advantage of setting the percentile thresholds for forecasting HW. For the probabilistic forecast, the Brier score of BMA is comparable (superior) to that of MME and ECMWF at short (long) lead-time. BMA also demonstrates an improvement on the reliability of probabilistic forecast, indicating that BMA method is a useful tool for an extended-range forecast of HW. Meanwhile, in the real-time extended-range probabilistic forecast, the beginning date, end date, and probability of HW event can be predicted by the HWI probabilistic forecast of BMA.

scholarly journals Summer High Temperature Extremes over China Linked to the Pacific Meridional Mode

2020 ◽  
Vol 33 (14) ◽  
pp. 5905-5917
Author(s):  
Ming Luo ◽  
Ngar-Cheung Lau ◽  
Wei Zhang ◽  
Qiang Zhang ◽  
Zhen Liu
Keyword(s):  
High Temperature ◽  
Land Surface ◽  
Southern China ◽  
Eastern China ◽  
Northern China ◽  
Temperature Extremes ◽  
The Pacific ◽  
Meridional Mode ◽  
High Temperature Extremes ◽  
Pacific Meridional Mode

AbstractThis study investigates the association between summer high temperature extremes (HTEs) over China and the Pacific meridional mode (PMM) that is characterized by an anomalous north–south sea surface temperature gradient and an anomalous surface circulation over the northeastern subtropical Pacific. It is found that the HTE activities over most parts of southern China (particularly eastern China) are prominently intensified during the positive PMM phase and weakened during the negative phase. Further examinations suggest that the PMM is linked with HTEs in China through processes that entail both eastward and westward development of signals emanating from the PMM site. The westward development is associated with the formation of an anomalous low-level cyclone over the western North Pacific (WNP), which may be viewed as a Matsuno–Gill-type response to the off-equatorial heating in the eastern Pacific. This circulation change is accompanied by anomalous ascent over WNP and northern China, and subsidence over eastern China. On the other hand, the eastward development process is linked to the PMM-induced displacement of the East Asian jet stream and the generation of a midlatitude Rossby wave train. In the positive PMM phase, the above circulation changes are accompanied by anomalous air subsidence and enhanced adiabatic heating, reduced precipitation, anomalous lower-level anticyclone, and rising surface pressure over the eastern part of China. Moreover, the land surface of that region receives more solar radiation. Opposite changes are discernible over northern China. These changes are favorable for the occurrence and persistence of HTEs over eastern China and tend to suppress HTEs over northern China.

Dynamical Extended Range Forecasting (DERF) at the National Meteorological Center

1989 ◽  
Vol 117 (7) ◽  
pp. 1604-1635 ◽  
Author(s):  
M. Steven Tracton ◽  
Kingtse Mo ◽  
Wilbur Chen ◽  
Eugenia Kalnay ◽  
Robert Kistler ◽  
...  
Keyword(s):  
Extended Range ◽  
Extended Range Forecasting

Climate Change, High-Temperature Stress, Rice Productivity, and Water Use in Eastern China: A New Superensemble-Based Probabilistic Projection

2013 ◽  
Vol 52 (3) ◽  
pp. 531-551 ◽  
Author(s):  
Fulu Tao ◽  
Zhao Zhang
Keyword(s):  
Climate Change ◽  
High Temperature ◽  
Temperature Stress ◽  
Eastern China ◽  
Extreme Temperature ◽  
High Temperature Stress ◽  
Crop Model ◽  
Large Area ◽  
Rice Productivity ◽  
Probabilistic Projection

AbstractThe impact of climate change on rice productivity in China remains highly uncertain because of uncertainties from climate change scenarios, parameterizations of biophysical processes, and extreme temperature stress in crop models. Here, the Model to Capture the Crop–Weather Relationship over a Large Area (MCWLA)-Rice crop model was developed by parameterizing the process-based general crop model MCWLA for rice crop. Bayesian probability inversion and a Markov chain Monte Carlo technique were then applied to MCWLA-Rice to analyze uncertainties in parameter estimations and to optimize parameters. Ensemble hindcasts showed that MCWLA-Rice could capture the interannual variability of the detrended historical yield series fairly well, especially over a large area. A superensemble-based probabilistic projection system (SuperEPPS) coupled to MCWLA-Rice was developed and applied to project the probabilistic changes of rice productivity and water use in eastern China under scenarios of future climate change. Results showed that across most cells in the study region, relative to 1961–90 levels, the rice yield would change on average by 7.5%–17.5% (from −10.4% to 3.0%), 0.0%–25.0% (from −26.7% to 2.1%), and from −10.0% to 25.0% (from −39.2% to −6.4%) during the 2020s, 2050s, and 2080s, respectively, in response to climate change, with (without) consideration of CO2 fertilization effects. The rice photosynthesis rate, biomass, and yield would increase as a result of increases in mean temperature, solar radiation, and CO2 concentration, although the rice development rate could accelerate particularly after the heading stage. Meanwhile, the risk of high-temperature stress on rice productivity would also increase notably with climate change. The effects of extreme temperature stress on rice productivity were explicitly parameterized and addressed in the study.

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