青藏高原地面站春季积雪日数的时空演变特征

Temporal and Spatial Variations in the Number of Days with Snow in Spring at the Qinghai-Tibetan Plateau Weather Stations

利用高原地区1962年-2004年64个地面站积雪资料,揭示了该地区春季积雪日数的时空演变特征,结果表明:①高原地区春季积雪日数空间分布局地差异显著,多雪区集中在巴颜喀拉山东段和藏北高原东南部,少雪区主要是藏南谷地、柴达木盆地以及川西干暖河谷地带;②空间分布可以概括为6种类型,青南高原东部型、藏北高原东部型、川西高原南部型、青藏高原东北部型、西藏东北部型以及川西高原东部型;③青南高原东部的春季积雪日数呈显著增长趋势,青藏高原东北部呈减少趋势,川西高原南部基本没有趋势变化,其余分区内各测站的线性变化趋势不完全一致,春季积雪日数仅在青南高原和川西高原东部地区存在由少变多的显著年代际变化,分别出现在1975年和1982年前后;④高原地区的春季积雪日数主要以准2年、准6年以及准10年的周期振荡为主。

In the present research, the authors utilized the data of the number of days with snow from 64 weather stations located in the Qinghai-Tibetan Plateau for the period 1962 to 2004 based on the methods of EOF, REOF, linear regression analysis, running t-test, wavelet analysis and power spectrum analysis. The temporal and spatial variations in the number of days with snow in spring in the Qinghai-Tibetan Plateau were carefully examined. Results suggested that the spatial distribution of the number of days with snow in spring showed a marked difference for different regions of the Plateau. In general, there are two centers of the maximum number of days with snow in spring at the Qinghai-Tibetan Plateau： the mountainous areas in the eastern Bayan Har Range and the southeast of the northern Tibetan Plateau. Also, there are three centers of the minimum number of days with snow in spring in the Qinghai-Tibetan Plateau： the valley in the southern Tibetan Plateau, the Qaidam Basin and the dry-warm valley in the western Sichuan Plateau. Moreover, we classified the anomalous areas of the number of days with snow in spring across the Qinghai-Tibetan Plateau into six major patterns based on the REOF method, i.e., the east of the southern Qinghai Plateau, the east of the northern Tibetan Plateau, the south of the western Sichuan Plateau, the northeast of the Tibetan-Qinghai Plateau, the northeast of the Tibetan Plateau, and the east of the western Sichuan Plateau. Regarding long-term changing trends, the number of days with snow in spring over the east of the southern Qinghai Plateau showed an obvious increasing trend, the northeast of the Tibetan-Qinghai Plateau showed a decreasing trend, and the south of the western Sichuan Plateau was not detected any trend. It was found that the interannual fluctuation of the number of days with snow in spring in the Qinghai-Tibetan Plateau was unstable. By using the running-t test method, an abrupt interdecadal change of number of days with snow in spring was detected over the southern Qinghai Plateau and the east of the western Sichuan Plateau for around 1975 and 1982, respectively. By using the wavelet analysis and power spectrum analysis, it was also found the number of days with snow in spring across the Qinghai-Tibetan Plateau primarily exhibited the quasi-periodicities of two, six and ten years. In general, all regions of the Qinghai-Tibetan Plateau showed a quasi-periodicity of two years. All parts of the Qinghai-Tibetan Plateau except the east of the northern Tibetan Plateau showed a quasi-periodicity of six years. The east of the southern Qinghai Plateau, the east of the northern Tibetan Plateau and the south of the western Sichuan Plateau all showed a quasi-periodicity of ten years.