青藏高原冬春多源积雪资料年际变化尺度上的适用性分析

Applicability of Multi-Source Winter-Spring Snow Cover Data over the Qinghai-Xizang(Tibetan)Plateau on the Scale of Interannual Variation

青藏高原冬春积雪变化具有显著的年际变化特征,其对中国东部夏季降水预测具有一定指示意义。由于特殊的复杂地形,青藏高原气象站点分布稀疏且不均匀,再分析数据和卫星数据提供的高原积雪资料的不确定性是影响和制约积雪变化及其天气气候效应研究中的一个关键问题。本文基于青藏高原台站观测、再分析(ERA5和NOAA-V3)和卫星反演(MODIS雪盖以及IMS雪盖)的多源积雪资料,采用偏差分析、均方根误差以及相关分析等多元统计方法重点检验了多源高原积雪数据在描述积雪年际变化特征方面的不确定性。通过比较不同积雪资料的时空分布和变化特征,以期提升多源高原积雪资料适用性的认知,并为相关研究提供有意义的参考。分析结果表明:(1)就再分析数据给出的积雪资料而言,ERA5雪深资料相较NOAA-V3雪深,对高原站点观测雪深的描述效果更好。除了高原中东部分站点外,ERA5雪深数据的平均偏差和平均均方根误差均较小,而NOAA-V3雪深数据的平均偏差和均方根误差在整个高原范围内均存在一定程度的高估;(2)再分析(ERA5和NOAA-V3)和卫星反演(MODIS雪盖以及IMS雪盖)积雪数据和高原站点雪深均在年际变化特征上具有较好的一致性;其中ERA5再分析积雪数据与高原站点观测雪深数据在长期趋势上更为类似;另外,北半球雪盖与站点观测雪深的年代际变化趋势更加类似;(3)再分析资料(ERA5、NOAA-V3)的雪深和雪盖在高原的分布存在空间差异性,其中NOAA-V3在多雪年和少雪年的大值区都位于高原南部、北部边缘以及高原中东部,而ERA5的大值区主要分布在高原的中东部、西部以及南部边缘。然而,每种再分析数据各自的雪深和雪盖之间差异较小,且积雪异常年份的差值分布较为一致,无论是雪深还是雪盖,正异常区都位于高原中部、西部和南部边缘,负异常区则都在高原北部;(4)三种卫星的雪盖在多雪年大值区都位于高原中东部、南部以及西部地区。不同卫星数据在积雪异常增多年份雪盖的差值分布也较为一致,但再分析资料体现出的高原北部边缘的负异常并未在卫星雪盖资料上体现出来,此结果可能与卫星反演积雪数据的涵盖时间短以及处理方式不同有关。

The snow cover in winter and spring on the Qinghai-Xizang(Tibetan)Plateau has a significant interannual variation,which has a certain indicative significance for the prediction of summer precipitation in eastern China.Due to the special complex terrain,the distribution of meteorological stations on the Tibetan Plateau is sparse and uneven.The uncertainty of the plateau snow cover information provided by reanalysis data and satellite data is a key issue affecting and constraining the study of snow variability and its weather-climate effects.Based on the multi-source snow data from station observations,reanalysis(ERA5 and NOAA-V3),and satellite inversion(MODIS snow cover and IMS snow cover)on the Qinghai-Xizang(Tibetan)Plateau,this paper highlights the uncertainties of the multi-source plateau snow data in characterizing the inter-annual variability of the snow cover by means of multivariate statistical methods such as bias analysis,root-mean-square error and correlation analysis.By comparing the spatio-temporal distribution and variation characteristics of various snow data,we aim to improve the knowledge of the applicability of multi-source plateau snow data and provide meaningful references for subsequent related studies.The results show that:(1)In terms of the snow data given by the reanalysis data,the ERA5 snow depth exhibits a better depiction of the observed snow depth at the plateau stations compared to the NOAA-V3 snow depth.The mean bias and root-mean-square error of the ERA5 snow depth data are relatively small,except for some stations in the central-eastern part of the plateau,while NOAA-V3 snow depth is to some extent overestimated throughout the plateau;(2)Both reanalysis(ERA5 and NOAA-V3)and satellite inversion(MODIS as well as IMS snow cover)snow data and the station-observed snow depth on the plateau show good consistency in terms of interannual variability characteristics;Where the ERA5 reanalysis is more similar to the observed snow data on the plateau station in terms of long-term trend;In addition,decadal trend in Northern Hemisphere snow cover and station-observed snow depth appear more similar;(3)The spatial discrepancies in the distribution of snow depth and snow cover on the plateau was observed in the reanalysis data(ERA5,NOAA-V3),in which the large value areas of NOAA-V3 in the years of more and less snow are located in the southern and northern margins of the plateau and in the central-eastern part of the plateau,while the large value of ERA5 are mainly distributed in the central-eastern,western and southern margins of the plateau.However,the differences between the respective snow depth and snow cover for each reanalysis data are relatively small,and the difference distribution between the snow anomalies years is relatively consistent,with the positive anomaly areas located in the central,western and southern margins of the plateau and the negative anomaly areas in the northern part of the plateau for both snow depth and snow cover;(4)The large value areas of snow cover for all three satellites in snowy years are located in the central-eastern and southern part of the plateau as well as in the western region.The difference distribution of snow cover in the increased anomalies years is also consistent for each type of satellite data,but the negative anomalies at the northern edge of the plateau reflected in the reanalysis data are not reflected in the satellite snow cover data,which may be related to the short coverage time of the satellite inversion snow data and different processing methods.