Evapotranspiration is the important process of plant physiological and ecological, estimating and monitoring
evapotranspiration are very useful for evaluation of the influence on the crop growth situation. Determination
evapotranspiration over natural surface, the utilization of satellite remote sensing is indispensable. In this paper, a new
method is established based on high resolution remote sensing data(TM/ETM) combination Penman-Monteith regional
daily evapotranspiration calculation model. The key of the algorithm is used to calculate the Temperature-Vegetation
Coverage Index (TVCI) based on an empirical parameterisation of the relationship between surface temperature (Ts) and
vegetation index (NDVI), Ts and NDVI in combination can provide information on vegetation and moisture conditions
at the surface. Two methods used to calculate the TVCI. The “Universal triangle” method was used to estimate TVCI
according to Carlson et al. (1995). Using a trapezoid (triangle) correlation between surface temperature and fractional
vegetation cover, we constructed an improved ‘Actual triangle’ method to estimate TVCI, then coupling the Penman-
Monteith equation (1998) to estimate daily ET. Daily ET based on the ‘Actual triangle’ methods was compared well with
methods by the ‘soil water lost method’, while daily ET based on the ‘Universal triangle’ methods was underestimated.
So, it is suitable to use ‘Actual triangle’ method to estimate TVCI instead of ‘Universal triangle’ method in the North
China Plain even if the method was applied under different climate conditions. These results indicate that the method is
feasible, and VTCI is a close real-time drought monitoring approach. It is based on satellite derived information and
combination with the meteorology data, and the potential for operational application of the method is therefore large.
The thesis, on the basis of the researches in the past, discusses the researches on agricultural drought
monitoring, forecasting and loss assessment evaluation as well as its application status in China. While
discussing and comparing different soil moisture monitoring methods, the thesis also introduces Gstar-1
which is an automatic soil moisture observer with independent property right, and CSMI which is the
new remote sensing monitoring index for soil moisture on the basis of MODIS data, and gives a
comprehensive introduction to the loss assessment of China. Through the real-time monitoring,
forecasting and assessment of drought occurrence and development, the thesis is dedicated to reducing
the influence of drought to agricultural production to the largest extent. At last, on the basis of the
problems in research, the thesis proposes the future research direction.
Effects of soil water on crop growth and yield are performed on the changes of crop growing conditions and
biomass growth. In this paper, long-term field experiment data at Zhengzhou Experiment Station were used to
statistically analyze the relationships between crop growing conditions and biomass growth at current stage and soil
water at previous stage. And the relationships between soil water and yield were also set up. Subsequently, optimum soil
water and drought indexes were determined for different growth stages of winter wheat. All these results lay the
foundation for dynamic evaluation of drought in winter wheat.
Using datasets of 1991-2004 meteorological and soil data as well as field management from 8 stations in the
summer-sown maize zone over the Huang-Huai River Basin, North China, study is performed of the water deficit in
various phases of growth of the crop impacting on the final yield by means of CERES-Maize of DSSAT Version 4.0,
whose parameters are adjusted for local conditions. Results show that 1) in the jointing stage of vegetative growth and
the filling stage (especially its earlier part) of the reproduction growth, field moisture acts as a key factor affecting the
yield; 2) deficient moisture in the 7-leaf and jointing periods would cause maximum leaf area index to significantly drop,
keeping dry matter from accumulation, leading to appreciable diminution of weight of dry stem and leaves; 3) water
deficit in the earlier (middle) filling stage would result in reduced number of grains per cob (decrease substantially the
weight of 100 grains). The findings in conjunction with measured moisture can be used to implement the "efficient
irrigation with less water" practice in this vast region.
Using experimental data on winter wheat from Bushland, Texas and Zhengzhou, Henan, analysis is performed of the distribution of its root system in 0~50 (50~100) cm soil depth, with the density of root length and its weight making up 57.7% (23.4%) and 66.7% (18.7%), respectively, thereby constructing the model of the roots growth and also by the distribution of the root system and its water absorption, study is undertaken of the appropriate depth of background field
moisture for growing winter wheat.
Using 1994-2006 typical-station agricultural data of the Huang-Huai winter wheat zone for the adjustment and
validation of the DSSAT-CERES Wheat model, which is then used with the IPCC SRES climate scenarios (A2 and B2)
through a stochastic weather generator, simulation is undertaken of effects of the 2050s climate regime on winter wheat
yield, growth/development and water requirement in the Huang-Huai plain. Results suggest that of the two emission
schemes, A2 gives higher negative influence compared to B2; the wheat growth/development period is shortened by 18
days, on average, for the region due to global warming leading to the accelerated growth, the flowering occurring ~20
days in advance, the span from flowering to maturity shortened 1~2 days, and the regional yield reducing by ~10%, on
the average. Enough irrigation will be needed to alleviate the yield decline but the wheat productivity per unit water
volume is to reduce.
The measurements of solar ultraviolet (UV) radiation at eighteen observation sites in Henan province, China
during 2005-2007 are analyzed to investigate the spatial distribution and temporal variation of UV irradiances. The
effects of cloud cover, visibility, and relative humidity on UV radiation are also quantified using regression techniques.
Results show that the annual averages of UV irradiances are high in central and southern Henan province. In winter,
the seasonal averages are high in northwestern Henan, while there are two high regions in the summer, one is resided
in the western part and the other is located in the eastern Henan, where two high centers can be identified. The
seasonal averages in summer and spring are higher than in fall and winter. The intensity of UV radiation is highly
related to total/low cloud cover, relative humidity, and visibility.
Drought is the serious agrometeorological disaster influences the growth of winter wheat in Henan Province, China.
The main causes of drought formation in the province was preliminarily described based on factors such as
geographical, monsoon circulation and the global climate background and then drought patterns that happened during
last more than 40 years were analyzed in terms of negative departure percentage from averaged precipitation as
indicators. Results show that heavy droughts are centralized in northeast part of the province and light droughts
centralized in southwest part. The light ones took place every 3 years, medium ones did every 7 years and heavy ones
every 10 years. This study is beneficial to winter wheat cropping planning and drought-prevention in Henan Province.
Shortage of water supply in the growing season is the key condition to form a drought in the winter wheat
production. Knowledge of risks brought about by the drought in winter wheat production is helpful in agricultural
management. In this work, we investigated the intensities of droughts and probability of their occurrence as well as their
impacts on the wheat yield based on water requirement by the crop and the nature of precipitation. Various techniques to
comprehensively assess the risks of droughts in winter wheat production are exploited to develop the model of risk
assessment of climatic droughts, the model of risk assessment of crop droughts, and the model of comprehensive risk
assessment of crop-climatic droughts. The models are used in regional comprehensive risk assessment of droughts in
winter wheat production in Northern China. A regionalization of risk levels is performed for this area. The results are
helpful in adjusting the cropping arrangement and in carrying out agricultural managements to minimize or prevent the
risk of droughts.
The characteristic of climate in North China is short of precipitation in winter and spring. Insufficient supply of water is a major factor affecting yield of winter wheat. The variation of yield caused by irrigation or drought at different stages is not alike. The relationship between them can be represented with water-yield reaction coefficient. Based on the experiment conducted in 2001 through 2004, yield of winter wheat has a marked positive correlation with precipitation at different stages after winter. The water-yield reaction coefficients increase with crop development, especially in turning green stage. The maximum occurs at head sprouting stage. Then it decreases slightly at milking stage. In order to raise water use efficiency of winter wheat, it is necessary to practice irrigation at elongating and head sprouting stages first and milking stage next.
From the dependence of winter wheat on water for growth a study is conducted of drought intensity and probability as well as their impacts upon the yield, whereupon are developed models for venture evaluation of drought damage to the crop grown in Henan province, with which to make the venture evaluation and regionalization of drought effects to provide scientific basis for modifying crop structure and preparing countermeasures for preventing and alleviating drought loss.
Determination the regional land surface parameters and components of surface radiation balance over heterogeneous landscape is very important and not an easy problem, in such researches, the utilization of satellite remote sensing is indispensable. In this study, a parameterization method based on Landsat-7 ETM+ data and 22 weather stations data is described for deriving the regional distributions of land surface parameters and components of surface radiation balance over the South Ningxia area. The distribution figs and straight-bar charts of the parameters and components are given out. Further more, the South Ningxia area is classified into five surface types, regional distributions are discussed according to each type. The main results indicate: All the regional distributions are characteristic by their terrain nature and the regional distributions are obvious and regular. The figures of the mountains and rivers are very clear, cause there is a great deal vegetation growing over the mountains and rivers edge. It is seen that the derived regional distributions of land surface parameters and components of surface radiation balance for the whole mesoscale area are in good accordance with the land surface status.
KEYWORDS: Meteorology, Climatology, Atmospheric modeling, Data processing, Sun, Lithium, Statistical analysis, Information science, Information technology, Information security
As a major agrometeorological disaster of winter wheat in Henan, drought is a big contributing factor to the steady rise of the yield. To make risk assessment of the drought-caused yield decline is of much significance to rational choice of culvars and putting forth measures against drought loss. Based on interannual meteorological and yield records, analysis is undertaken of yearly drought probability, percentage yield decline and yield coefficient of variation, whereupon is constructed a model for comprehensive risk assessment of wheat yield and regionalized is the risk happening. Evidence suggests that the indices of the risk assessment range over 1.23 ~ 4.88, with the high-value zones making up 12.5%, distributed mainly in eastern, and northeastern Henan, the middle-value zones accounting for 36.5% in southwest, southeast, eastern, northeast and northwest Henan and the low-value zones (51.0%) in the extensive region, with Lushi - Xiangcheng (Beijing to Guangzhou railway in Henan) as the axis line in the east - west (south - north) Henan province.
Drought is one of the major meteorological disasters to agriculture in north China so that the development of methods for effectively monitoring droughts is of great significance to dry land crops. This paper makes analysis of products of energy and water balances retrieved from LAS (Large Aperture Scintillometer) measurements, indicating that the structural parameter of LAS refractive index shows regular difference in daily variation between different weather backgrounds and remarkable difference in sensible heat flux on a seasonal basis, with higher negative correlation between such flux and soil humidity at 0 ~ 50 cm depth.
Drought is a principal agrometeorological disaster to winter wheat zones in North China. From the correlation of wheat yield to rainfall the drought indices are determined that correspond to varying levels of severities on an agricultural basis. In wheat growing season, when rainfall displays its negative anomalies of <15, 15-35, 36-55 and <55%, there occurs a slight, moderate, heavy and extreme drought, leading to yield drop by <10, 10-20, 21-30 and <30%, respectively. The economic loss consists of yield reduction and drought-fighting input like irrigation. A drought-caused loss model is presented from historical meteorological and wheat yield datasets, with which to make the distribution of economic losses in the last 30 years over the province of Henan. Evidence suggests that in years of heavy droughts the loss was between 450 to 675 (<250) RMB yuans per hectare in the NE (west − SW) segment of the province.
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