tailieunhanh - Climate Change and Variability phần 12

Các chuyên ngành cơ bản của cơ khí bao gồm: động học, tĩnh học, sức bền vật liệu, truyền nhiệt, động lực dòng chảy, cơ học vật rắn, điều khiển học, khí động học, thủy lực, chuyển động học và các ứng dụng nhiệt động lực học. Các kỹ sư cơ khí cũng đòi hỏi phải có kiến thức và năng lực áp dụng những khái niệm trong môi trường kỹ thuật điện và hóa học. Với một mức độ nhỏ, cơ khí còn trở thành kỹ thuật phân tử - một mục tiêu viễn cảnh của nó là tạo. | Simulated potato crop yield as an indicator of climate variability and changes in Estonia 373 The dates of last and first night frosts in the future series are found on the basis of the earlier determined relationships between mean daily air temperature and ground level minimum temperature dependent on the radiation sum of previous day. 3. Results Time series of meteorological resources current climate Series of meteorologically possible yield were compiled for early and late maturing potato varieties in two different Estonian localities. In Table 1 we present long-term mean yields calculated with existing meteorological data series using real and computed both first possible and optimal planting dates the yields thus describe real possible and optimal climatic resources for plant growth during given period. With real planting dates there was practically no difference in average values of the MPY between long and short from 1965 series. As expected the late variety produced higher yields at all locations. Overall the MPY series showed only weak and insignificant trends Fig. 5 although reliable trends are apparent for some shorter periods. The longest period with a significant P decreasing trend was observed in Kuressaare from 1977 to 2006. Generally Anti demonstrated higher variance in yields. For both varieties the variability reached higher in Kuressaare. Variability increases in all cases when using computed planting dates instead of real dates. Closer investigation of the MPY variability showed a significant increase in variance in Tartu since the early 1980s. In the MPY calculations contrived with real meteorological data the standard deviation of MPY was significantly lower for Maret in 1901-1980 compared to 1981-2006 P according to F test for Anti the change was smaller yet significant P . When using shorter time series and optimal planting times the same difference in yield variance was detected both for Maret P and Anti P .