High Temperature Intensity and Soil Moisture
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Assess on Agriculture of Extreme High Temperature and Drought in 2003, Jiangxi Province,China WEI Li, DU Xiao-Ling , LIU Wen-ying Jiangxi Meteorological Bureau, Nanchang 330046,China Jiangxi Meteorological Observatory, Nanchang 330046,China Feb.2009 Outline Abstract Soil moisture character High temperature intensity and soil moisture Soil water household in cropland Assessment on agriculture Some measures fighting drought Discussion Abstract Based on field observation data during the period of the extreme high temperature and drought in 2003, high temperature intensity, characteristics of the field evapotranspiration and soil moisture are analyzed by optimizing Penman f ormula. Assess on Agriculture of the extreme high temperature and drought is carried. Brief Introduction to Jiangxi Province Jiangxi province is situated in south of China with sub-tropical monsoon climate, distinctive seasons and rich rainfall. Forest coverage of Jiangxi Province is about 60.05%. But for the features with large areas of mountains, rivers , lakes and complex climate conditions, Jiangxi is also a province with frequent and severe natural d isasters ,which mainly include rainstorm, fl ood, drought, hail, lightning, heat, frozen, landslide, mud-and-rock flow, plant diseases and insect pests, forest fire,etc. Distribution of annual mean precipitation in Jiangxi Province Distribution of annual mean temperature in Jiangxi Province Distribution annual mean solar radiation in Jiangxi Province Remote Sensing Map of Jiangxi Province legend Paddy land Vegetation Water Dry land Trend of flood and drought area from 1950 to 2007, Jiangxi From 1990 to 1999,flood area is lager than that of drought. But since 2000,it is opposite. Drought江西省旱涝灾害的年代际变化情况 area 水灾面积 120.0 Flood area 旱灾面积 100.0 80.0 60.0 40.0 受灾面积(万公顷) 20.0 0.0 1951-1959 1960-1969 1970-1979 1980-1989 1990-1999 2000-2007 年份 Frequency of drought in summer or autumn in Jiangxi Province is 93.2 % Severity 29.5% Light 20.5% Moderate:43.2% In summer 2003, an unprecedented heat wave attracted south of China that l ed to severity drought. It sustains two mo nth hot and drought weather conditions. Comparing to the same period of the history, the influenced areas,the maximum temperature and the continuous days of the disaster set up new records . Located at the heat area, Jiangxi also suffered from e xtreme heat wave and drought which persists until spring in 2004. Several historical records were broke through The day maximum temperature of two-part a third of counties in Jiangxi province exceeded historical record. Day maximum temperature of three-quarter of counties was ≥40℃. A number of days with maximum temperature ≥ 35℃ persists 71 days. There are no soaking rain in two months in more than half of the provincial land. Average temperature from July to September in 2 003 was 28.8℃,which was 1.8℃ higher than historical mean value and broke through passed maximum record value (28.3℃, 1963) since 1951. Mean precipitation in three months was only 287m m that was the minimum value in history (301mm, 1 978), but the evaporation at the same period reached 1009mm that is thirdly lied in history record. Depth of dry soil layer reached 8 to 10cm. 1.Soil moisture characteritics Soil humidity is continuous lower during drought and high temperature in 2003 because of sparse precipitation and strong evaporation. Soil moisture observation data in depth of 0 to 50cm in Hukou and Nankang counties were analyzed, which were observed two times in each ten days. 1.1 Soil weight water amount in each depth. Nankang County .Results shown that soil weight water amount in five depths are continuous lower than 20% from last ten days in June. The minimum value in 0 to 30cm depth in Nankang county appeared in last ten days in July Hukou County which is respective 10.1%, 11.3%,12.3%(chart 1a) ,but the minimum value of soil weight water amount in depth 30 to 50cm happened in first ten days in August that is separately 13.1%, Chart1 Soil weight water changes in each depth in 13.8%(chart 1a). Nankang and Hukou County. .In chart 1b,Hukou observation station, Nankang County the minimum soil weight water amount in each depth layers occurred two times that was 7%,8.1%、11.3%, 12.9%,14.2% in first ten days in August and others Hukou County 7%、8%、9.9%、11.6%、 13.7% in first ten days in November. This results revealed that serious drought in the provincial large area presented in July Chart1 Soil weight water changes in each depth in to August. Nankang and Hukou County. From June to September in 2003, mean soil weight moisture amount in depth 0 to 50cm was only 16.1% in Hukou and 18.3% in Nankang, which showed that soil drought in North of Jiangxi was relatively severity compare to the South. 1.2 Soil relative humidity Relative humidity in depth 0 to 20cm in Nankang station was lower than 60％ ,which appeared from middle ten days in July to first ten days in August ,the minimum relative humidity was 48% to 50%. .Soil relative humidity from June to September Nankang County Results showed that there was a time lag of about ten days in the Hukou County lowerest value in North of Jiangxi to the South. 2 High temperature intensity and soil moisture 2.1 Defining high temperature intensity index When day maximum temperature reach 35℃ or more, the high temperature intensity index (HTI) express as follows： when 35.0℃≤Tmax＜36.0℃ K=0.1 36.0℃≤Tmax＜37.0℃ K=0.2 37.0℃≤Tmax＜38.0℃ K=0.3 38.0℃≤Tmax＜39.0℃ K=0.4 39.0℃≤Tmax＜40.0℃ K=0.5 Tmax≥40.0℃ K=0.6 HTI= (∑∑Tmax×K)/N Tmax: day maximum temperature value in a station ∑∑: total value of Tmax×K in all stations in the prefecture. HTI Chart2.Distribution of HTI of the province and eleven pr efectures from June to September in 2003 2.2 Characteristics of HTI and soil moisture content Curve in chart 2 and chart 1 showed that the minimum soil moisture content have a time lag about 10 days to peak value of HTI. 3 Soil water household in cropland 3.1 Crop water requirement Refined Penman equation is used to calculate evapotranspiration. Some factors such as solar radiation, efficiency radiation, dry capacity, are confirmed by experience method . Day evapotranspiration calculation method adapted to regional climate was get , which is as follow: n ET *[0.8 * (B0 B1* S ) 1.9 *T 4 * (0.6259 0.1186 * e ) * (0.1 0.9 * )] K d N * (0.2 0.066 *U ) * (e e ) a d ET is the maximum potential evapotranspiration γ is constant of psychomotor ⊿ is curve slope of saturation air pressure S is sun irradiation hour, Tk is absolute temperature, ed is actual air pressure U is mean wind speed, n/Nis ratio percent of actual irradiation to potential B0\B1 are coefficient between total solar radiation and irritation hour Table one is values of ⊿/（⊿+γ）、γ/（⊿+γ） 3.2 Spatial distribution and anomaly of crop water requirement 3.3 Temporal change of crop water requirement. Chart 5.It is showed that diminishing trend is dominating. Evapotranspiration increased obvious that reached to 727.5mm in 2003, which is the third high value since 1970’s. 3.4 Difference of precipitation and evaporation on cropland. The minimum difference value was -430.3mm in Jian, and the maximum was 450.6 mm in Dingnan of Ganzhou. Water deficit reached 200mm or more. Others region is opposite. 4 Assessment on agriculture of extreme high temperature and drought in 2003 4.1 Assess on grain crop Yield per unit area of single late rice was decreased 5 798 kg/hm2,which decreased 599 kg/hm2 than that in 2002. Yield of double late rice was 4 892 kg/hm2 that decreased 275 kg/hm2 than in 2002. Total yield of fall season was 9,140,000kg which decreased 960,000kg than that of 2002. Total grain yield in 2003 was 1 4,503,000kg which decreased 992,000kg than that in 2002. Paddy land split in Lichuan county Late rice water shortage in Xiajiang county Late rice can cot be plant on schedule , Linchuan county This is a key period to harvest early rice and plant late rice during the end in June to July and abundant water is needed in agriculture. Water levels in rivers and lakes decrease rapidly by the extreme high te mperature and drought. Creeks break off, ponds and reservoirs dry up Water used on agriculture is severe deficiency Drought area increase rapidly at rate of 5 to 6ha and extend to the entire province. Impregnation rate of middle and late rice is only 40% to 60%,which decrease distinctly. Impregnation rate of Jinyou725 only arrived 2 0%. Double rice growth encounters difficulty. It had to form organic matter and weight of grain diminished. Severe drought affects photosynthesis , assimilation of mineral , synthesizing and transportation of matter, which caused increasing of empty rates of grain and decreasing of seeds weight Total drought area： 3,000,000ha Light: 2263800ha moderate：713,000ha severity： 23,200ha Distribution2003年7月26日气象卫星遥感监 of high temperature and 测江西省高温干旱分布drought on 26,July,2003 4.2 Assess on economic crop and fruit. Fruit leaf yellow and rolling Abnormal falling of flower and young fruit. It impact citrus quality, shape and yield , yield decrease 30%. Young citrus trees were damaged, which led to decrease yield in next year. Citrus leaf yellow and rolling in Huichang county,Ganzhou,Jiangxi Province Assess on cotton.