摘要:本文利用1980～2019年美国NOAA系列卫星观测的向外长波辐射（OLR）月平均资料和欧洲中心ERA5月平均地表热通量资料，研究青藏高原（以下简称高原）地区OLR与对流活动的时空分布及其演变特征，以及地表热通量与高原夏季对流活动之间的关系。结果表明：高原地区平均OLR强度由高原周边地区向中部递减，高原东部OLR低于西部，高原东部对流活动显著强于西部；近40年高原OLR总体呈较平稳的增强趋势，存在显著的6年与2～3年的周期特征，对流活动总体呈缓慢减弱趋势，但不同区域不同季节对流活动的变化趋势存在差异，其中夏季高原对流活动呈增强趋势，其他季节则以减弱趋势为主。各季节在高原三江源地区附近对流活动均呈减弱趋势，在高原南部喜马拉雅山脉北侧地区，对流活动则呈一致的增强趋势。夏季高原地表潜热通量普遍强于地表感热通量，且二者分布型近似相反。高原对流活动演变与地表感热、潜热通量均有关，且与地表感热通量的关系更为密切，二者之间普遍存在负相关关系，且在高原西部最为显著；地表潜热通量与高原东西部对流活动间相关呈东西向偶极型分布，在高原西部二者之间存在正相关关系，在高原东部则表现为负相关。
关键词:青藏高原/
向外长波辐射/
对流特征/
地表热通量
Abstract:Based on the monthly mean NOAA outgoing longwave radiation (OLR) data and surface heat fluxes derived from ERA-5 reanalysis data from 1980 to 2019, the spatial and temporal distributions of OLR and convection over the Tibetan Plateau (TP) and the relationship between surface heat fluxes and convection were investigated. Results showed that the minimum value of OLR was located in the middle of the TP and increased outward. The OLR (convection) was lower (stronger) in the eastern plateau than in the western region. In the past 40 years, the OLR (convection) increased (decreased) gradually with a period of 6 a and 2–3 a over the TP. However, the tendency for convective activity had significant differences among different regions and seasons. A growing trend of convective activity occurred in boreal summer, while it weakened in the other seasons. The convection had a weakening trend in the vicinity of the Three Rivers’ Headstream region but increased in the north of the Himalayas on the TP. In the boreal summer, the surface latent heat flux was generally stronger than the surface sensible heat flux. The evolution of convection was significantly related to both surface sensible and latent heat fluxes. The surface sensible heat flux was highly negatively correlated to the evolution of convective activity, while there was an east-west dipole pattern of correlation between the surface latent heat flux and convection. A positive correlation between the surface latent heat flux and the evolution of the convection in the western plateau was observed, while a negative correlation was evident with that in the eastern region.
Key words:Tibetan Plateau/
Outgoing longwave radiation (OLR)/
Characteristics of the convection/
Surface heat flux
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