The Impact of Arid Climate Change on Agriculture of Dry Valley in Southwest China and Its Adaptive Countermeasures

The eco-environmental vulnerability and underdevelopment of the agriculture in Southwest China would strengthen its disadvantage conditions further on the condition of arid climate change.It is necessary to deal with the relations between resource utilization and eco-environment finely and ascertain the adaptive principles on the dry valley agriculture to the arid climate change in order to change the extensive utilization of the special agricultural resources.The paper gave some adaptive countermeasures that develop modern rangeland husbandry,strengthening the special agriculture and agricultural industrialization,emphasis on the ecological agriculture development,constructing the extension system of water-saving modern agriculture,encouraging the service industry related to ＂agriculture,peasants and the countryside＂,constructing water utilization facilities,and exploiting the renewable energies.

Possible Impacts of Climate Change on Agricultural Production in China and Its Adaptation Countermeasures

Global climate warming has discernable impacts on various natural systems and biological systems. As the most fragile ecosystem,agriculture is subjected to the most direct impacts from climate change. Of these impacts,the first one is the change in agricultural climate resources,which directly affects agricultural cultivation structure and crop variety distribution and finally results in the change in crop yield. Here,we review the advances in the impacts of climate change on crop yield,agricultural climate resources and China＇s agricultural cropping system and crop variety distribution pattern,and prospect the countermeasures for agricultural production in order to meet the future climate change,and several issues must be given high priority.

Scenario Analysis on the Adaptation of Different Maize Varieties to Future Climate Change in Northeast China

Based on gridded meteorological data for the period 1981-2100 from the RegCM3 regional model, the changing trends of climatic resources in Northeast China are analyzed, and the distributions of maize va-rieties are accordingly adjusted. In order to explore the eff ects of diff erent adaptation countermeasures on climatic productivity and meteorological suitability in the future, maize cultivars with resistance to high temperatures and/or drought are selected. The results show that, in the future, there is likely to be a sig-nifi cant increase in thermal resources, and potential atmospheric evaporation will increase correspondingly. Meanwhile, radiation is predicted to increase signifi cantly during 2041-2070 in the growing season. How-ever, changes in precipitation are unlikely to be suffi cient enough to off set the intensifi cation in atmospheric evaporation caused by the temperature increase. Water resources and high temperatures are found to be the two major factors constraining grain yield. The results also show that the warming climate will be favorable for maize production where thermal resources are already limited, such as in central and northern Heilongjiang Province and eastern Jilin Province; while in areas that are already relatively warm, such as Liaoning Province, climatic productivity will be reduced. The climatic productivity and the meteorological suitability of maize are found to improve when the planting of resistant varieties is modeled. The utilization of agricultural climatic resources through the adaptation countermeasures of maize varieties is to increase obviously with time. Specifi cally, maize with drought-resistant properties will have a marked infl uence on meteorological suitability during 2011-2070, with suitable areas expanding. During 2071-2100, those maize varieties with their upper limit of optimum temperature and maximum temperature increased by 2℃, or water requirement reduced to 94%, or upper limit of optimum temperature and maximum temperature in-creased by 1℃and water requirement reduced to 98%, all exhibit signifi cant diff erences in climatic potential productivity, compared to the present-day varieties. The meteorological suitability of maize is predicted to increase in some parts of Heilongjiang Provine, with the eastern boundary of the“unavailable”area shifting westward.

An approach for parameter estimation of combined CPPM and LFM radar signal

In this paper, the problem of parameter estimation of the combined radar signal adopting chaotic pulse position modulation （CPPM） and linear frequency modulation （LFM）, which can be widely used in electronic countermeasures, is addressed. An approach is proposed to estimate the initial frequency and chirp rate of the combined signal by exploiting the second-order cyclostationarity of the intra-pulse signal. In addition, under the condition of the equal pulse width, the pulse repetition interval （PRI） of the combined signal is predicted using the low-order Volterra adaptive filter. Simulations demonstrate that the proposed cyclic autocorrelation Hough transform （CHT） algorithm is theoretically tolerant to additive white Gaussian noise. When the value of signal noise to ratio （SNR） is less than 4 dB, it can still estimate the intra-pulse parameters well. When SNR = 3 dB, a good prediction of the PRI sequence can be achieved by the Volterra adaptive filter algorithm, even only 100 training samples.