Yangtze-Huaihe River Basin Research Articles

A minor survey of deoxynivalenol in Fusarium infected wheat from Yangtze–Huaihe river basin region in China

Deoxynivalenol (DON) is frequently present in infected cereals such as wheat, barley and maize. Fusarium asiaticum and Fusarium graminearium are the key fungal species which produces DON, when they infect wheat in China. Our present study is to do a minor survey on the presence of DON in the highly infected wheat regions from Jiang su and An hui province, China, harvested during the year 2010. A total of 56 wheat samples which are naturally infected by Fusarium sp., of which 35 samples from Jiang su province and 21 samples from An hui province were taken up for the study. The samples were analyzed for the presence of DON by using high performance liquid chromatography (HPLC) combined with ultraviolet detection. The recoveries of DON from the spiked samples (500–15,000 μg/kg) were obtained in the range of 85.7–90.2%, with the average relative standard deviation of 2.7%. The average percentage of contamination in all the samples was 89.3%, with the DON concentration ranging between 259 and 4975 μg/kg, and with the mean of 1962 μg/kg. According to the Chinese standard limits for DON, nearly 70% of the samples were above the maximum tolerable level of 1000 μg/kg. However, only 44% of the samples exceeded the European commission limits for unprocessed wheat of 1750 μg/kg. Regions where there was higher level of Fusarium sp. contamination due to climatic changes like heavy rainfall with high humidity, showed the presence of higher levels of DON in the samples. Cropping of Fusarium resistant wheat cultivars like Sumai 3 in the regions where the wheat is highly susceptible for the Fusarium contamination could help in the reduction of contamination in wheat.

Assimilation of GPS radio occultation data with the local and non-local op- erators using Backward-4DVar approach

In this paper, the observational operators of local and non-local GPS radio occultation refractivities are added to the Backward-4DVar data assimilation system of the regional heavy rainfall forecast model AREM (AREM-B4DVar), and thereby the assimilation system has the capability to assimilate GPS radio occultation refractivity data. Experiments to predict the heavy rainfall, which occurs on July 4, 2007 to July 5, 2007 in Yangtze-Huaihe river basin of China, with assimilation of the COSMIC GPS radio occultation refractivity data and the radiosonde data, are designed. The results indicate that the quality of initial analysis near the observation and thus the corresponding 24-h rainfall forecast are all improved after the GPS radio occultation data are incorporated into the initial condition using the observational operators of local and non-local in the AREM-B4DVar system. Through the non-local constraints of atmospheric variables, the performance of the assimilation with the non-local operator can further improve the insufficient existing in the assimilation with the local operator. Joining the assimilation based on radiosonde data in the AREM-B4DVar system, the radio occultation refractivity data can further improve the analysis quality of initial condition and the skill of 24-h rainfall forecast, in which the non-local operator plays a better role.

Characteristics and Changes of Extreme Precipitation in the Yellow–Huaihe and Yangtze–Huaihe Rivers Basins, China

Abstract Many works suggest that the intensity of extreme precipitation might be changing under the background of global warming. Because of the importance of extreme precipitation in the Yellow–Huaihe and Yangtze–Huaihe River basins of China and to compare the spatial difference, the generalized Pareto distribution (GPD) function is used to fit the daily precipitation series in these basins and an estimate of the extreme precipitation spatial distribution is presented. At the same time, its long-term trends are estimated for the period between 1951 and 2004 by using a generalized linear model (GLM), which is based on GPD. High quality daily precipitation data from 215 observation stations over the area are used in this study. The statistical significance of the trend fields is tested with a Monte Carlo experiment based on a two-dimensional Hurst coefficient, H2. The spatial distribution of the shape parameter of GPD indicates that the upper reaches of the Huaihe River (HuR) basin have the largest probability of extreme rainfall events, which is consistent with most historical flood records in this region. Spatial variations in extreme precipitation trends are found and show significant positive trends in the upper reaches of Poyang Lake in the Yangtze River (YaR) basin and a significant negative trend in the mid- to lower reaches of the Yellow River (YeR) and Haihe River (HaR) basins. The trends in the HuR basin and the lower reaches of Poyang Lake in the YaR basin are nearly neutral. All trend fields are significant at the 5% level of significance from the Monte Carlo experiments.

Probabilistic seasonal prediction of summer rainfall over East China based on multi-model ensemble schemes

The skill of probability density function (PDF) prediction of summer rainfall over East China using optimal ensemble schemes is evaluated based on the precipitation data from five coupled atmosphere-ocean general circulation models that participate in the ENSEMBLES project. The optimal ensemble scheme in each region is the scheme with the highest skill among the four commonly-used ones: the equally-weighted ensemble (EE), EE for calibrated model-simulations (Cali-EE), the ensemble scheme based on multiple linear regression analysis (MLR), and the Bayesian ensemble scheme (Bayes). The results show that the optimal ensemble scheme is the Bayes in the southern part of East China; the Cali-EE in the Yangtze River valley, the Yangtze-Huaihe River basin, and the central part of northern China; and the MLR in the eastern part of northern China. Their PDF predictions are well calibrated, and are sharper than or have approximately equal interval-width to the climatology prediction. In all regions, these optimal ensemble schemes outperform the climatology prediction, indicating that current commonly-used multi-model ensemble schemes are able to produce skillful PDF prediction of summer rainfall over East China, even though more information for other model variables is not derived.

Relationship between the Meiyu over the Yangtze-Huaihe River Basins and the Frequencies of Tropical Cyclone Genesis in the Western North Pacific

The relationship between the Meiyu precipitation over the Yangtze-Huaihe River Basins (YHRB) and the frequencies of tropical cyclone (TC) genesis in the western North Pacific (WNP) for the period 1951-2006 has been investigated in the present paper. The results have shown that there exists a significant negative correlation between them, which is due to the fundamental changes in monsoonal airflows and associated moisture transports over East Asia and the WNP. In the years with fewer TCs genesis, the location of the main body of the subtropical high over the WNP is farther west and south, and its intensity is abnormally stronger. The monsoon trough also shifted farther west, with a weaker intensity. Under this condition, the monsoon flow and the corresponding moisture transport can not extend eastward down to the WNP, but turns to the East Asian region along the western flank of the subtropical anticyclone over the South China Sea (SCS). Meanwhile, the westerlies at mid-latitudes are located farther south with a stronger intensity. This kind of circulation conditions is favorable for the convergence of the dry and cold air from the mid- and high latitudes and the warm and moist air from the low latitudes over the YHRB, and leads to more precipitation there.In the years with more TCs, the subtropical high over the WNP is located farther north and east, with its intensity being weaker. The monsoon trough zonally extends eastward down to the open sea of the WNP. Most of the monsoon flow and the associated moisture transport from the tropical Indian Ocean can all the way reach the WNP, with a smaller proportion turning northward to the East Asian Meiyu region over the SCS, which is favorable for the genesis and development of TC in the WNP. At the same time, the location of the mid-latitude westerlies is farther north and its intensity is weaker, which is unfavorable for the occurrence of the precipitation over the YHRB. This kind of negative correlation relationship will be conducive to the seasonal forecast of the TC and the Meiyu during the rainy season in China.

A summer weather index in the East Asian pressure field and associated atmospheric circulation and rainfall

AbstractUsing the daily rainfall from rain gauge stations in China and the daily data from the National Centers for Environmental Prediction‐National Center for Atmospheric Research (NCEP‐NCAR) reanalysis for each year of 1981–2008, a relationship between daily rainfall over the Yangtze‐Huaihe River basin (YHB) and surface pressure over East Asia was statistically investigated and a summer weather index (ISW) was defined from surface pressure for describing the daily variations of the atmospheric circulation and rainfall over the monsoon region of eastern China. The results show that the daily ISW is significantly correlated with the YHB rainy weather during summer. In higher‐ISW days, there is usually more YHB rainfall. This link may be explained by the East Asian atmospheric circulation well. When ISW is higher, a low‐pressure system frequently occurs over the land of southern China and an enhanced ridge appears over the South China Sea (SCS)–subtropical western Pacific region, which strengthens the seaward pressure gradient and southwesterly winds over southern China. Accordingly, the transport of water vapour toward the YHB and the ascending motion over the YHB strengthen remarkably. These variations in the daily atmospheric circulation finally lead to the frequent occurrence of the YHB rainy weather. Thus, ISW can represent the variations of the atmospheric circulation and rainy weather for most of the years of 1981–2008. For some extremely dry years over the YHB, however, ISW does not indicate the local large‐scale rainfall well. This suggests an asymmetric descriptive ability of this index. Copyright © 2010 Royal Meteorological Society

Estimations of precipitable water and its characteristics during the HUBEX/IOP 1998

GMS-5 satellite data at channels of infrared split windows and water vapor are analyzed to retrieve the precipitable water (PW) distributions under cloud-free conditions. Radiosonde data and surface station data are applied to estimate the PW distributions under cloudy conditions. These two methods are then merged to obtain the PW distributions under all-weather conditions during the Huaihe River Basin Energy and Water Cycle Experiment (HUBEX). The results of the all-weather PW distributions from these methods demonstrate that this new merging technique may be applied to derive large-scale or global maps of PW. It is revealed that the atmospheric water vapor over the Yangtze-Huaihe River Basins came mainly from the southwest during the 1998 prevailing period of Meiyu. Sufficient atmospheric PW is a necessary condition for ground rainfall. Under certain dynamic conditions, it can be partially transformed into surface precipitation. Several types of rain are displayed and their PW conditions and characteristics, as well as atmospheric dynamic conditions, are analyzed. It is demonstrated that surface precipitation centers usually appear not at the high PW centers but on their downwind sides.

Analysis of the Large-Scale Circulation Features and Synoptic Systems in East Asia During the Intensive Observation Period of GAME/HUBEX.

An analysis of the large-scale circulation features, major synoptic systems, precipitation, and atmospheric heating fields during the intensive observation period (IOP) of the GAME/HUBEX identified eight features. 1) The beginning and maintenance of the Meiyu season over the Yangtze-Huaihe River Basin in both 1998 and 1999 occurred under the condition of the northward advance and enhancement of the East Asian summer monsoon. 2) The circulation features characterized with two ridges in the region to west of the Baikal Lake and the Sea of Okhotsk, respectively, and one trough in between (in the region of the Baikal Lake) in the middle and high latitudes set a stage for the development of Meiyu seasons. Especially, the quasi-stationary Okhotsk blocking high and the upper-level vortex over East China/the Sea of Japan was a couplet of circulation systems under which the Meiyu front over the Yangtze-Huaihe River Basins was stably maintained. 3) The subtropical high in the western Pacific assumed a significant westward and northward shift before arrival of Meiyu seasons in 1998 and 1999. During the concentrating period of Meiyu precipitation for 1998, its meridional oscillation was closely related to variations of episodes of heavy rainfalls in this region. 4) The low-level easterly aircurrent to the north of the low-level southerly jet played an important role in maintenance of the frontal zone, which is also one of major factors leading to the persistent heavy rainfalls in middle and lower reaches of the Yangtze River. 5) The formation of the low-level jets is different in the synoptic conditions for 1998 and 1999. This difference mainly resulted from the different zonal positions of the subtropical high and activities of the summer monsoon. 6) There existed a succession of meso-scale disturbances (at least 2 and 3 meso-scale vortices for 1998 and 1999, respectively) along the Meiyu frontal zones, which mostly originated in the eastern flank of the Tibetan plateau and migrated eastward, with vortex centers located to the north of the low-level jet axis and heavy rainfalls in the southeast of the disturbances. 7) Along the Meiyu front, there was a high humidity and lower temperature conditions, while relatively dry and higher temperature conditions existed to south and north of the Meiyu front. This kind of sandwich-like temperature and humidity condition is important for the Meiyu maintenance; Zonally, the temperature field was characterized by lower temperature in the west and higher temperature in the east along the Meiyu frontal zone. 8) During the processes of heavy rains in 1998 and 1999, the patterns and the magnitudes of Q1 and Q2 are nearly similar to each other, indicating that the heating over the heavy rain regions was created by the moisture condensation process, due mainly to convective activities. However, it is now not clear how this prosess of energy and water cycle may in turn affect events of heavy rainfalls through feedback effect. The above indications of the large-scale circulation features and synoptic systems provide a starting point for further investigation of the energy and water cycle over the Huaihe River Basin.