西南地区夏季降水变化与青藏高原大气热源的关系

Relationship between Summer Precipitation Change in Southwest China and Atmospheric Heat Source in Qinghai-Tibet Plateau

摘要: 为进一步研究青藏高原大气热源对西南地区夏季降水的影响，用NCEP/NCAR1961~2022年的月平均再分析资料，网格距2.5˚ × 2.5˚、采用点相关分析、SVD分解、合成分析法及热源计算倒算法对西南地区62年夏季降水的时空分布特征及其与青藏高原大气热源的关系进行了详细研究，结果表明：1) 62年来，整个西南地区的夏季降水有减小的趋势，且西南地区的夏季降水存在三个高值区，高值区分别位于云南的南部地区、四川东部地区和贵州东南部地区，并且在降水高值区附近降水量的梯度也更大。降水量自东向西，自南向北逐渐减少，可以明显看出海拔较高的地区降水量较少。这与西南季风、复杂的地形地貌以及影响西南地区的环流系统等因素有关。2) 在青藏高原在1961~2022年均为大气热源，可以看出大气热源在1961年开始时较弱，随着时间逐渐增强，在70年代中期和80年代末期分别达到强度的最大值，之后大气热源逐渐减弱呈下降趋势，在2020年达到最低值。总体来看，从1961到2022年，青藏高原的大气热源强度呈现由强到弱的变化趋势，且存在一定的年际变化特征。3) 青藏高原地区(26˚00'~39˚47'N，73˚19'~104˚47'E)，除东北部的少部分地区为较强冷源外和北部地区为较弱冷源之外，其余大部分地区全年平均均为大气热源，中部地区为较强的大气热源。4) 在青藏高原范围内，与西南地区夏季降水存在显著正相关的地区是高原东部地区的大气热源和高原西部地区大气热源，与西南地区夏季降水存在显著负相关的地区是高原北部地区。总体来说西南地区夏季降水与青藏高原大气热源存在显著的相关性且西南地区夏季降水与青藏高原大气热源具有较高的年际线性相关性。5) 青藏高原大气热源的异常增加会影响西南地区夏季降水的不均变化，部分地区夏季降水量异常增多且存在大值区，部分地区夏季降水量异常减少且存在大值区；而青藏高原大气热源的异常减小时，西南地区夏季降水的增加较均匀。

Abstract: To further investigate the impact of atmospheric heat sources on summer precipitation in the southwestern region of the Qinghai Tibet Plateau, monthly average reanalysis data from NCEP/ NCAR 1961~2022 were used with a grid distance of 2.5˚ × 2.5˚. A detailed study was conducted on the spatiotemporal distribution characteristics of summer precipitation in Southwest China for 62 years and its relationship with atmospheric heat sources over the Qinghai Tibet Plateau using point correlation analysis, SVD decomposition, Synthetic analysis method and inverse heat source calculation algorithms at 2.5˚. The results show that: 1) In the past 62 years, the summer precipitation in the entire southwestern region has shown a decreasing trend, and there are three high value areas for summer precipitation in the southwestern region. The high value areas are located in the southern region of Yunnan, the eastern region of Sichuan, and the southeastern region of Guizhou, and the gradient of precipitation near the high value areas is also greater. The precipitation gradually decreases from east to west and from south to north, indicating that areas with higher elevations have less precipitation. This is related to factors such as the southwest monsoon, complex terrain, and the circulation system that affects the southwest region. 2) In the Qinghai Tibet Plateau, from 1961 to 2022, it can be seen that the atmospheric heat source was weak at the beginning of 1961 and gradually strengthened over time, reaching its maximum intensity in the mid-1970s and late 1980s, respectively. Afterwards, the atmospheric heat source gradually weakened and showed a downward trend, reaching its lowest value in 2020. Overall, from 1961 to 2022, the intensity of atmospheric heat sources in the Qinghai Tibet Plateau showed a trend of change from strong to weak, with certain interannual variation characteristics. 3) In the Qinghai Tibet Plateau region (latitude 26˚00'~39˚47' N, longitude 73˚19'~104˚47' E), except for a few areas in the northeast that are strong cold sources and the northern region that are weak cold sources, most of the remaining areas are atmospheric heat sources on average throughout the year, while the central region is a strong atmospheric heat source. 4) Within the range of the Qinghai Tibet Plateau, the regions with significant positive correlation with summer precipitation in the southwest region are the atmospheric heat sources in the eastern region of the plateau and the atmospheric heat sources in the western region of the plateau, while the regions with significant negative correlation with summer precipitation in the southwest region are the northern region of the plateau. Overall, there is a significant correlation between summer precipitation in the southwest region and atmospheric heat sources in the Qinghai Tibet Plateau, and there is a high interannual linear correlation between summer precipitation in the southwest region and atmospheric heat sources in the Qinghai Tibet Plateau. 5) The abnormal increase in atmospheric heat sources on the Qinghai Tibet Plateau will affect the uneven changes in summer precipitation in the southwest region. Some regions have abnormally increased summer precipitation with high value areas, while others have abnormally decreased summer precipitation with high value areas; The anomalous decrease in atmospheric heat sources on the Qinghai Tibet Plateau results in a more uniform increase in summer precipitation in the southwestern region.