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20 March 2022, Volume 43 Issue 03

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Spatiotemporal Variation of Climate Dry-Wet Condition and Its Potential Trend in the Yellow River Basin from 1960 to 2020

GONG Jie, GAO Bing-li, LI Yan, JIN Tian-tian, ZHANG Yun-xia, ZHU Yue-hua

2022, 43(03):  165-176.  doi:10.3969/j.issn.1000-6362.2022.03.001

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Based on the humidity index, using the daily climate data of 113 meteorological stations in and adjacent the Yellow River Basin(YRB) from 1960 to 2020, climate trend rate, Morlet wavelet, simple correlation analysis, and Hurst index were used to analysis the spatiotemporal characteristics of dry-wet condition in the YRB in the latest 61 years and to predict the future trend of dry-wet changes in the YRB, to provide scientific basis for drought prevention and mitigation and rational utilization of climate resources in the YRB. The results showed that: (1) among all the geographic zones, the annual and seasonal humidity index in the YRB was high in the southeastern YRB and low in the northwestern YRB. Spatially, the climate of the annual, spring and autumn in the YRB was mainly dry, the proportions of stations with significant decrease of humidity index of the total stations were 5.31%, 7.96% and 6.19%, respectively. The climate of summer and winter was mainly wet, the proportions of stations with significant increase of humidity index were 10.62% and 13.27%, respectively. (2) As for the interannual change, the annual and seasonal humidity index of the YRB from 1960 to 2020 showed no significant change. Semi-humid, semi-drought, semi-humid, semi-humid, semi-drought were found in entire year, spring, summer, autumn, and winter, respectively. The annual and seasonal humidity index of the YRB had periodic oscillation characteristics at multiple time scales, and the first main period was 3 years, 26 years, 14 years, 3 years and 15 years, respectively. (3) The change of humidity index in the YRB was extremely significantly positively correlated with precipitation and relative humidity. There was a extremely significant negative correlation between sunshine duration and humidity index. Precipitation, relative humidity, and sunshine duration were the main factors affecting the change of humidity index in the YRB. (4) The Hurst index of annual and seasonal humidity index in the YRB were larger than 0.50, indicating that the climate of annual, spring, and autumn of the YRB would continue to be drying, the summer and winter climate would continue to be wetting.

Study on “Cold Chamber Effect” of Red Plum Apricot Frost Proof Shed Based on Dynamic Analysis of Heat Balance and Heat and Moisture Parameters

JIANG Rui-yang, ZHANG Wei-jiang, MA Yi, MA Fang, FENG Na, LI Wei-jian, JIANG Chang

2022, 43(03):  177-193.  doi:10.3969/j.issn.1000-6362.2022.03.002

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A frost-proof shed was designed to prevent perennial frost disaster suffered by red plum apricots in the southern area of Ningxia. During the tests at night, the ambient temperature in the shed was always lower than that outside the shed, resulting in a "cold chamber effect”, and the desired effect was not achieved. Therefore, there was a test that needed to probe into the mechanism of the “cold chamber effect” in the frost-proof shed to provide a theoretical basis for improving the design of the frost-proof shed accurately and prevent frost disaster effectively. According to the principle of mass and heat balance, the test was researched the heat budget of the cover layer, the moist air in the shed, and the soil layer respectively then studied the heat accumulation in the whole system of the frost-proof shed during the period after the covering of the shed cloth to the time before its folding on the next day. Finally, the test explored the influence of relative humidity and the changes of moist air on phase transition latent heat by analyzing the dynamic process of main heat and humidity parameters in the shed. The study results show that: (1) when the “cold chamber effect” occurs at night in spring and autumn, both the soil layer and the cover layer become the part losing heat due to more heat loss, while the moist air in the shed becomes the part gaining heat due to more heat gain. (2) In spring and autumn, the accumulated heat gain is lower than the accumulated heat loss in the shed during the period after the covering of the shed cloth to the time before its folding on the next day, resulting in the heat imbalance in the shed. (3) There is a significant difference in the heat and humidity parameters of the moist air in the shed and those outside the shed (except the saturated water vapor pressure in the shed in spring); The dynamic changes of the water vapor density and the dew point temperature in the shed at night can reflect the change rules of latent heat caused by evaporation and condensation; The low temperature and higher water vapor density in the shed make the saturated water vapor pressure infinitely close to the actual water vapor pressure, resulting in the relative humidity in the shed persistently on the high side. The accumulated heat gain of the frost-proof shed for red plum apricots is always less than the accumulated heat loss at night, and the soil layer and the cover layer are the most important parts losing heat, and thus the “cold chamber effect” appears in the case of heat imbalance.

Daily Weather Forecast-Based Reference Crop Evapotranspiration Estimation in Wheat Growing Season

LIU Xiao-fei, WANG Jing-lei, LIU Zu-gui, SONG Ni, FANG Wen-song

2022, 43(03):  194-203.  doi:10.3969/j.issn.1000-6362.2022.03.003

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In order to accurately estimate the reference crop evapotranspiration (ETc) of wheat using incomplete meteorological elements, three verification and analysis processes in estimation of some meteorological elements were carried out by using daily forecast weather data and the corresponding daily measured meteorological data of Xinxiang during winter wheat growing seasons from 2014 to 2016, as well as modified solar radiation parameters and adjustment coefficients. First, the accuracy of forecast air temperature was verified. Then, the actual water vapor pressure and solar radiation were estimated based on forecast air temperature. Finally, the forecast air temperature and averaged wind speed were adopted to estimate the reference ETc based on the Penman-Monteith formula. The results showed that the daily forecast air temperature could replace the daily observed air temperature, water vapor pressure and solar radiation using the forecast maximum and minimum temperature, which met the requirements of Penman-Monteith formula, and the accuracy of the radiation estimated using weather forecast data was higher than that of the aerodynamics. Generally, the accuracy of the radiation in the daily reference ETc estimated by weather forecast data was higher than that of the aerodynamics, the estimated values by weather forecast was relatively lower, and the underestimate rate was below 7%. Through statistical analysis, there was a high correlation between daily ETc estimated by weather forecast and that estimated by Penman-Monteith equation (R2=0.77). Therefore, it was feasible to use the daily meteorological data from weather forecast to estimate the reference ETc, and it was suggested to use the radiation method to estimate ETc in arid and semi-arid areas, which provided theoretical and methodological guarantee for agricultural irrigation forecast and had reference significance for guiding the optimal allocation of local agricultural water resources.

Impacts of Barnyard Grass on Photosynthesis and Physiology of Rice under Elevated Atmospheric CO2 Concentration

JIN Dian-yu, XIE Li-yong, ZHAO Hong-liang, LI Ying, HAN Xue, HE Yu-tong, LIN Er-da

2022, 43(03):  204-214.  doi:10.3969/j.issn.1000-6362.2022.03.004

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Barnyard grass is one of the vicious weeds in rice field, which affects seriously the growth and development of rice and reduces the yield of rice. In order to clarify the effect of barnyard grass on rice growth and development and yield formation under the condition of elevated atmospheric carbon dioxide (CO2) concentration, the experiment was conducted with the Free-Air CO2 Enrichment system (FACE system), taking rice Jijing 88 as material. The experiment included 4 treatments: atmospheric CO2 concentration (400µmol·mol−1) without barnyard grass, rice planting and barnyard grass together with atmospheric CO2 concentration, elevated CO2 concentration (550µmol·mol−1) without barnyard grass, rice planting and barnyard grass together with elevated CO2 concentration. Physiological indicators were measured and analyzed at the tillering stage, jointing stage, heading stage, and mature stage of rice. The results showed that elevated CO2 concentration increased significantly the number of rice ears per hole and the seed setting rate, and eventually increased the rice yield. Barnyard grass significantly reduced the rice seed setting rate, and reduced rice yield ultimately. Interaction of elevated CO2 concentration and barnyard grass increased significantly thousand-grain weight of rice, yet, the interaction did not affected rice yield significantly. Elevated CO2 concentration increased significantly the dry matter of rice, and barnyard grass reduced significantly the dry matter of rice. However, the interaction of elevated CO2 concentration and the barnyard grass had no significant difference. Elevated CO2 concentration increased significantly the net photosynthetic rate of the flag leaf of rice, the concentration of intercellular CO2 of the flag leaf, and the Soil and Plant Analyzer Developrnent (SPAD) value of rice flag leaf. Barnyard grass treatment reduced significantly the net photosynthetic rate of the flag leaf of rice, the concentration of intercellular CO2 in the flag leaf, the stomatal conductance, the transpiration rate, the instantaneous water use efficiency, and the SPAD value. The interaction of elevated CO2 concentration and barnyard grass reduced the net photosynthetic rate of rice flag leaves at early stage, and increased it at later stage. In conclusion, Elevated CO2 concentration after heading stage had a greater impact on rice photosynthesis than barnyard grass on rice photosynthesis.

Climatic Suitability Analysis of Millet Growing Season in Northern China Region in the Context of Climate Warming

YANG Yue-ting , LI Kai-wei , ZHANG Ji-quan , WEI Si-cheng , LIU Cong , WANG Chun-yi

2022, 43(03):  215-228.  doi:10.3969/j.issn.1000-6362.2022.03.005

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Millet shows a strong tolerance to drought and barren soil during the process of planting. Millet is also an important strategic reserved crop for sustainable agricultural development in China in the future. It is of great practical significance to discuss the regional adaptability of millet in the context of climate change. Based on the climate suitability model, Anusplin software was used to interpolate the climate resources and climate suitability of 314 meteorological stations in millet growing area in Northern China Region by 1km×1km. The spatial distribution and temporal variation characteristics of climate resources and climate suitability in millet growing season were analyzed in 1960-1989 and 1990-2019. The results showed that: (1) the climate resources in millet growing season in Northern China Region showed that sunshine duration increased from east to west and from south to north; Cumulative precipitation increased from north to south and from west to east. The spatial distribution of mean temperature was higher in the south and lower in the north. With the warming of climate, the mean temperature in millet growing season showed an increasing trend, while sunshine duration and accumulated precipitation showed a decreasing trend. (2) The climate suitability in millet growing season presented a trend of "temperature suitability decreased from east to west and from south to north, precipitation suitability increased from northwest to southeast, and sunshine suitability decreased from northwest to southeast". Due to climate warming, the high value areas of temperature suitability and precipitation suitability increased, while the high value areas of sunshine suitability decreased greatly. (3) According to the calculation results of comprehensive climate suitability, the method of natural break was used to divide it into four grades: most suitable, suitable, sub-suitable and unsuitable. About 21.5% of Northern China Region was the most suitable area for millet planting in 1960-1989 (the first 30 years). As the climate warms, about 10.5% areas changed from the suitable area to the most suitable area in 1990-2019(the last 30 years), mainly in Shandong and Shanxi. In the future, it can be considered to expand the planting area in this region according to the actual situation.

An Outliers Detection Method for Automatic Soil Moisture Observation Data Based on Characteristic Curve

ZHOU Xiao-tian, CHEN Yi-ling, LI Yun, LI Chang-jun, ZHANG Ping, ZHANG Qian-ru

2022, 43(03):  229-239.  doi:10.3969/j.issn.1000-6362.2022.03.006

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A new outliers detection method for automatic soil moisture observation data based on characteristic curve is proposed. The main and basic idea of this method was feature extraction and the morphological matching between two soil moisture time series, and the detailed operation processes were as follows: firstly, the method took X as the expected checking time series and took Y as the corrected template time series, and also gave the range and elements of these two series. Secondly, the method decomposed series X and Y by empirical mode decomposition (EMD) method to obtain the recomposition series C and Q respectively. In this process, series C was the total accumulation of IMFs of series X and series Q was the total accumulation of IMFs of series Y. Thirdly, the method obtained series C' and Q' by using dynamic time warping (DTW) algorithm which was designed to align series C and Q. Fourthly, the method obtained the variation series D' whose elements were calculated by the variation coefficient between series C' and Q', and then, the method also traversed each element of series D' and marked the elements whose value was greater than threshold as overruns. The threshold was obtained by comprehensive calculating the standard deviation of series X and Y. Finally, the outliers in the checking series X could be found through the mapping relationships between series X and series D'. The example showed that: (1) the method did not need to introduce external factors such as soil physical constants and meteorological conditions, and avoided adding relevant parameters such as high and low boundary and slope in the calculation process. (2) The method used the continuous soil moisture data of the same depth from the same station instead of multi-station data comparison, and had no strict length consistency requirements for series X and series Y, so the calculation was more flexible and applicable. (3) The routine of the method was clear, and all of the input processes and output processes in this method were specific. The method was suitable for computer programming and business operation. The technical route of this method might be provided for other agrometeorological data quality control research.

Influence Report of Weather on Agricultural Production in Autumn 2021

WANG Chun-zhi, ZHAO Xiu-lan

2022, 43(03):  240-243.  doi:10.3969/j.issn.1000-6362.2022.03.007

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Based on the daily national meteorological data in autumn in 2021, relationships between meteorological factors and agricultural production in China were analyzed using statistical methods. The results showed that the national average air temperature in autumn in 2021 was 10.5℃, which was warmer than the same period from 1981 to 2010. The national average precipitation in autumn in 2021 was 157.9mm, which was the most since 1961. Additionally, the average precipitation in northwest China, north China and Huanghuai region was also the most respectively since 1961. The national average sunshine was 564.9 hours, which was the ninth from the bottom since 1961. The early frost in most of the agricultural areas of northeast China significantly occurred later than the normal year. The suitable sunshine and temperature in the most of autumn harvesting area in China were favorable for crop grain-filling, maturing, harvesting and drying. However, continuous rainy and cloudy weather in the early autumn in the eastern part of northwest China, most of north China and northern Huanghuai region disrupted the autumn crop harvesting. Therefore, the sowing date of winter wheat was delayed for 7−15 days due to delay of maize harvesting. The weather turned better in the middle and late autumn. Thus, the sowing speed of winter wheat was accelerated. At the end of autumn, the date of phenological stage of winter wheat in north China, Huanghuai and the east of northwest China was later for generally 7−25 days than the normal year, where the percentage of tillering stage for winter wheat was lower than that in the same period in the normal year and last year. The proportion of weak winter wheat seedling in China was higher than the same period in the normal year and last year. The soil moisture was suitable for autumn sowing in most of agricultural areas in south China, in which winter wheat and rapeseed sowing progressed well and was close to the normal year.