东北地区干旱特征与春玉米生长季干旱主导气象因子

在全球气候变化背景下，东北地区干旱及其主导气象因子呈现出新的态势，并可能对当地农业生产带来不可预见的灾害风险。因此，开展干旱时空规律研究，揭示春玉米生长季干旱发生的气象驱动因子，对于指导当地开展农业防旱减灾工作尤为重要。该研究利用东北地区及其周边105个气象站点数据以及30 m分辨率的DEM，在考虑海拔影响的前提下将逐月气象因子数据空间插值并计算了1989－2018年1、3、6、12、24个月尺度的潜在蒸散量和标准化降水蒸散指数（Standardized Precipitation Evaporation Index，SPEI），分析了干旱的多尺度特征和春玉米生长季各气象因子的变化规律，明确了干旱的高发月份、区域及主导气象因子。结果表明：1）1989－2018年干旱呈现出10 a周期的偏轻-偏重-偏轻规律，其中2000－2010年干旱较为严重。2）干旱高发月份为5月，且在吉林西部、内蒙古东部和黑龙江西南部等地区干旱发生概率较高。3）气象因子变化主要以气温增加为主，且伴随气压下降和风力减弱，平均气温、最高气温、最低气温、气压、风速分别以0.41 ℃/(10 a)、0.42 ℃/(10 a)、0.39 ℃/(10 a)，−0.05 kPa/(10 a)、−0.08 m/(s•10 a)的速度变化。4）各月干旱主导气象因子不尽相同，5月为降水、相对湿度、最高温度和日照时数，6月为降水、相对湿度、日照时数和最低气温，7月为降水、相对湿度和日照时数，8月为降水、最高气温和平均气温，9月为降水、相对湿度和最高气温，生长季平均条件下为降水、最高气温、日照时数和相对湿度，降水对干旱的直接作用远大于其他气象因子。该研究可为全面了解东北地区春玉米生长季干旱特点、以及制定合理的干旱应对措施提供一定的参考和依据。

Drought characteristics and dominant meteorological factors driving drought in spring maize growing season in northeast China

New changing characteristics have emerged in the drought and its dominant meteorological factors in Northeast China, as the ecological impacts of global climate change in recent years. These impacts may bring unpredictable natural disaster risks to local agricultural production. In order to guide the prevention of agricultural drought and mitigation work, it is particularly important to explore the spatial and temporal patterns and evolution trends of drought in Northeast China under the background of climate change, thereby to reveal the meteorological driving factors of drought in the spring maize during growing season. Here, five meteorological factors, including wind speed precipitation, sunshine duration, air temperature, pressure and relative humidity, were interpolated month by month, particularly considering the geographical location and altitude. The data was taken from 105 meteorological stations in Northeast China, where the local DEM data was in the resolution of 30 meters. A Penman-Monteith method was used to calculate the potential evapotranspiration. A IDL program was also used to calculate the Standardized Precipitation Evapotranspiration Index (SPEI) at the 1, 3, 6, 12 and 24-month scales in 1989-2018, further to analyze the multi-scale characteristics of drought. As such, the change characteristic of each meteorological factor was determined in the spring maize during growing season. The high-incidence month and region of drought in the growing season were identified by the SPEI of 1-month scale, thereby to gain the trends of monthly average precipitation and reference evapotranspiration. A stepwise linear regression method was selected to extract the dominant meteorological factors driving drought in each month and the whole growing season. The results indicated that: 1) from 1989 to 2018, a light-serious-light trend of drought was showed in Northeast China in a 10-year cycle, particularly which the worst drought was found in 2000-2010. There was an obvious effect using the SPEI for the drought, as the time scale increased, but there can be a time lag at a certain degree. 2) In the spring maize during growing season, the drought was tend to occur in May, with a high probability in the west of Jilin, the east of Inner Mongolia and the southwest of Heilongjiang. 3) Meteorological variations in the spring maize during growing season in Northeast China were mainly characterized by the increase of air temperature, together with the decrease of air pressure and wind speed. The change rates of average temperature (Tmean), the maximum temperature (Tmax), the minimum temperature (Tmin), the air pressure (APS) and the wind speed (WV) were 0.41 ℃/(10a), 0.42 ℃/(10a), 0.39 ℃/(10a), -0.05 kPa/(10a), and -0.08 m/(s•10 a), respectively. Other meteorological factors did not change significantly. 4) Dominant meteorological factors driving drought varied in the maize growth period in Northeast China. The significant factors were ranked in descend order: the precipitation (PRE), air relative humidity (RHU), Tmax and sunshine duration (SSD) in May, followed by the PRE, RHU, SSD and Tmin in June, the PRE, RHU and SSD in July, the PRE, Tmax and Tmean in August, and the PRE, RHU and Tmax in September. In the whole growth season, the main meteorological factors were the PRE, Tmax, SSD, and RHU. Specifically, the PRE played the most important role in drought in each month, compared with the other factors. The WV and APS showed the minimum influence on drought. This finding can offer a promising potential reference for the drought characteristics of the spring maize during growing season in Northeast China, and further to make the reasonable decisions for drought prevention.