Risk Assessemt, Remote Sensing Monitoring,and Loss Assessment Of Cold Damage Of Double Cropping Rice In South China

The production of double cropping rice in south China has a special contribution to ensure national food security, but due to climate fluctuation, it’s often influenced by cold damage. This research selected double cropping rice area in south China as research area. To use satellites and ground multi-source data, risk assessment, dynamic monitoring and loss assessment of cold damage were researched for double cropping rice in south China. Mainly in the following work:1. The extraction of possible area for double cropping rice.First, agricultural statistics is used to determine the scope of the study area, the scope include Hubei, Anhui, Zhejiang, Jiangxi, Hunan, Fujian, Guangdong, Guangxi, Hainan nine provinces(area), the nine provinces(area) sum of double cropping rice sown area and output account for the vast majority of China total double cropping rice sown area and output. The percentage of both reached more than99%, respectively; Then using daily mean temperature of meteorological stations from1954-2011, the annual accumulated temperature (≥10℃) was calculated for each meteorological stations, the annual accumulated temperature was averaged for each station, annual average accumulated temperature was obtained. Taking annual average accumulated temperature for each meteorological station as the dependent variable, longitude, latitude, altitude et al. geographical factors as the independent variable, the accumulated temperature prediction model was established, and according to the model, the spatial distribution map of accumulated temperature was obtained. Using accumulated temperature threshold of5300℃.d for double cropping rice, the area that average accumulated temperature less than5300℃.d was removed from research area. Finally the10years distribution of grain crops was obtained by using the classification products of MODIS MCD12Q1from2001-2010. Then, the two steps results were overlay and intersected, the information of double cropping rice was obtained. The result has been clear about the research space for risk assessment and monitoring of double cropping rice cold damage.2. Dynamic simulation of main development phase of double cropping rice. In the southern double cropping rice area, rice cold damage mainly include late spring coldness happening in seeding to raising seedling stage of double season early rice, May low temperature happening in tillering to panicle primordium differentiation stage of double season early rice, and cold dew wind happening in heading and flowering stage of double season later rice. Therefore, it is necessary for cold damage remote sensing monitoring and early warning of the southern double cropping rice to determine the development phase of different region rice. This research used development phase data of167agricultural meteorological observation stations in the south double cropping rice area from1981to2011, to calculate many year average date of each station main development phase of double cropping rice, to analysis the correlation between many year average date of main development phase and longitude, latitude and altitude, to establish the spatial distribution model of many year average date of each main development phase, and obtained the regression fitting distribution map of each main development phase; To calculate error between simulation value of the spatial distribution model and the measured values, the residual spatial distribution map was obtained to use geological statistics method. By superposition of two images, the results of each main development phase of double cropping rice were obtained; then, to draw the spatial distribution maps of each main development phase of double cropping rice based on GIS, the results showed that there was no significant difference between estimated and measured values. The maps of dynamic development phase were produced by using two static maps before and after through EVNI+IDL programming.3. Risk assessment of double cropping rice cold damage in south China.In the risk assessment of double cropping rice cold damage, this paper focused on May low temperature and cold drew wind. Each station cold damage annual frequency and average annual intensity of cold damage was calculated by using1951-2011station daily mean temperature and simple cold damage identification index (The May low temperature of early rice is that daily mean temperature is≤20℃and consecutive5days. Cold dew wind is that daily mean temperature is≤20℃and consecutive3days). On this basis, average annual cold damage risk index was obtained by their product. In order to cold damage annual frequency as the standard, critical threshold level of average annual cold damage risk index for double-season early rice (DSER) and double-season later rice (DSLR) were respectively determined by the correlative equation of cold damage annual frequency and average annual intensity of cold damage. The spatial analysis models of cold damage risk index about DSER and DSLR were established respectively by the correlation of average annual cold damage risk index and its geographic factors. Through the map of average annual cold damage risk index obtained by model, using the critical threshold of index, combining with extraction result of double cropping rice area in south China, the risk assessment of cold damage was completed finally. The results showed that there was no significant difference between estimated and measured values. The results have quite accuracy.4. Dynamic monitoring of double cropping rice cold damage in south China.In the dynamic monitoring of cold damage, the monitoring is mainly focused on seeding to raising seedling stage of double-season early rice, tillering to panicle primordium differentiation stage of double-season early rice, and heading and flowering stage of double-season later rice. Using the ascending orbit and the descending orbit bright temperature data of AMSR E L2A89GHZ, the2010daily mean bright temperature data was obtained by data preprocessing. The data have strong correlation with daily mean temperature. Multivariate regression model is established by using the correlation between bright temperature, geological factors and daily mean temperature of meteorological stations, as a result to complete the calculation of daily mean temperature. The roor mean square error is1.57℃between regression value and real value. The estimation precision meets the needs of cold damage monitoring. Finally, the dynamic monitoring of cold damage of double cropping rice was achieved by combing with dynamic development phase maps built, extraction result of double cropping rice area and monitoring index of cold damage. Monitoring results highly corresponds to reported content in time and space. The method has better real-time performance than traditional monitoring method. It is advantage for the agricultural production department to make quick response to cold damage, and to help to make up for the loss caused by cold damage.5. Loss assessment of double cropping rice cold damage in south China.In the loss assessment of cold damage, DSSAT crop model can be used to simulate crop potential output on the basis of rice parameter correction of regionalization. The loss only caused by cold damage was calculated by comparing the yield difference between average temperature light condition and cold damage condition. The results of cold damage loss assessment using model to simulate is more scientific and accurate than conventional method.Finally, the main conclusions and innovations were summarized, and to point out the difficulty of cold damage research and the future development direction.