青藏高原东部强降温过程阈值的探讨及其气候特征

为解决青藏高原东部强降温的气象预报和服务问题,利用青藏高原东北部68个气象站1961-2017年逐日最低气温数据,辅以趋势分析及相关分析等方法,本文探讨了近57年青藏高原东北部强降温的阈值及气候特征,并利用NECP/NCAR(2.5°×2.5°)海温场、高度场建立了预报诊断模型。研究发现 (1) 应用改进的强降温指标统计寒潮发生的特征更符合高原实际情况。(2)受地形地貌及山脉阻挡的影响,青藏高原东部强降温次数的地域分布存在明显差异,海拔较高的山区和东部地区强降温次数明显多于盆地。南部山区24h寒潮发生的次数多于48h、72h。(3)近57年区域寒潮频次总体呈下降趋势,南部和北部的降速分别为-0.5次/10a、-0.4次/10a,并通过显著性检验；西北部盆地区降速分别为-0.1次/10a,未通过显著性检验。(4)高冷空气的移动路径是强降温预测的关键信号。研究结果为青藏高原相关部门开展农牧业资源的和旅游资源的相关决策服务提供科学依据。

Steep Descent of Temperature in the Northeastern Qinghai-Tibet Plateau: Threshold Values and Climatic Characteristics

Aiming at the meteorological forecast and corresponding service for steep descent of temperature in the northeastern Qinghai-Tibet Plateau, based on the daily minimum temperature data of 68 meteorological stations from 1961 to 2017, we discussed the threshold values in the process of steep descent of temperature and its climate characteristics by employing the means of trend analysis and correlation analysis, and built a forecast diagnostic model with NECP/NCAR (2.5°×2.5°) SST field and height field. The results showed that: (1) it was more in line with the actual situation to use the improved steep descent of temperature indexes to summarize the characteristics of the occurrence of cold wave; (2) due to the influence of landform and mountain barriers, there were obvious differences in the regional distribution of the times of steep descent of temperature in the northeastern Qinghai-Tibet Plateau, and the times of steep descent of temperature in the mountainous areas and eastern areas at higher altitudes were significantly more than those in the basins, the times of 24- hour cold wave in the southern mountain areas were more than those of 48-hour and 72-hour; (3) in recent 57 years, the frequency of regional cold waves showed a general downward trend, and the deceleration rate in the south and the north was -0.5 times/10 a and -0.4 times/10 a, respectively; which passed the significance test, the deceleration rate in the northwestern basin area was -0.1 times/10 a, which failed to pass the significance test; (4) the moving path of high cold air was a key signal for the prediction of steep descent of temperature. The research results could provide a basis for the decision-making concerning agricultural and animal husbandry resources and tourism resources.