祁连山2019—2020年面降水量及高山区降水监测意义

获取精确的面降水量是祁连山生态屏障建设以及河西及青海湖水系等水资源估算及合理利用的重要依据,但由于山地地形复杂、高山区监测稀缺等问题,目前相关结果之间差异较大且精度有待证实。为此,在祁连山中、高山区架设了23套T-200BM3、6套TRwS204称重式雨雪量计,两个降水观测误差对比观测场(海拔2980 m和4651 m)、1个不同类型雨量筒对比观测场(海拔2980 m)及其配套观测设施,并结合祁连山及其周边27个国家气象站的中国标准雨量筒和GPM降水数据,估算了祁连山2019年、2020年面降水量。结果表明:各类雨量筒观测误差校正值比实测值平均增加约10%,在高山区降雪观测偏少约30%、总降水量偏少接近20%。世界气象组织推荐的TRwS204雨雪量计可监测“真实”降水量,而T-200BM3在祁连山区无效数据多,且剔除无效数据后其观测值仍偏高约12%。祁连山年降水量总体随海拔升高而增加,但在不同剖面上可能存在微弱的最大降水高度。补充高山区实测数据后,祁连山2019年、2020年降水量分别为565.2 mm和446.3 mm,均比仅利用国家气象站数据增加了约70%。GPM与高山区降水数据融合结果与地面空间插值结果差异较小,可获取祁连山高精度面降水量。祁连山西南高山区缺乏监测以及T-200BM3雨雪量计精度问题仍然是目前祁连山精确面降水量估算中的主要不确定性来源。

高寒山区凝结水研究进展

通过总结高寒山区凝结水的研究现状、梳理近年来的研究进展、归纳凝结水的观测方法,本文阐述了高寒山区凝结水的生态效应及其与冰冻圈水文过程的关系,探讨了未来高寒山区凝结水研究的发展趋势和方向。综述表明:凝结水对高寒山区生态系统有着十分重要的影响,对于维系高寒山区脆弱生态系统有重要意义,在高寒山区生态形成过程中扮演着重要的角色。凝结水是冰冻圈生态水文过程的缓释剂,高寒山区凝结水主要缓解低温造成植被周期性的生理缺水(低温导致土壤水分无法利用),而非干旱胁迫(没有水分);凝结水通过其周期性的水分添加来影响土壤水分有效性,进而影响温度敏感性,从而对土壤呼吸产生周期性影响。凝结水的富集和消散过程,抵消部分蒸发潜热,降低实际蒸散发,对减少蒸发“赤字”有积极作用,间接补给河川径流。在高寒山区,凝结水对海拔的依赖性表明凝结水在高山区可能进一步富集频发,是高寒山区隐形水源的一个潜在探索点,对寒区水汽内循环过程具有显著作用。在我国西北地区暖干向暖湿气候转型中,随着高寒山区水汽含量的增加,造成凝结水量可能呈现增加趋势。

祁连山TRwS204与中国标准雨量筒降水观测对比研究

山区降水类型、过程和气候条件复杂多变,不同雨量筒观测结果均存在一定的误差,亟需了解常用人工和自记雨量筒之间及其与实际降水量之间的差异。针对中国标准雨量筒[无防风措施(CSPG_(UN))和配备单层Alter防风圈(CSPG_(SA))]和在祁连山常用的TRwS204称重式雨雪量计[配备单层Alter防风圈(TRwS_(SA))],于2014年9月至2017年8月在祁连山黑河上游葫芦沟小流域开展了同步降水观测对比试验,以按照世界气象组织推荐的固态降水测量标准安装的中国标准雨量筒的修正值作为标准降水量。结果表明:(1)CSPG_(UN)、CSPG_(SA)和TRwS_(SA)降雨观测的平均动力损失(平均动力损失与平均标准降雨量的百分比)分别为0.21 mm(3.4%)、0.12 mm(1.9%)和0.61 mm(9.8%),雨夹雪分别为0.37 mm(7.6%)、0.16 mm(3.3%)和0.51 mm(10.5%),降雪分别为0.27 mm(10.2%)、0.09 mm(3.4%)和0.57mm(21.4%)。(2)CSPGUN和CSPG_(SA)动力损失的差异主要与防风圈的使用有关,而CSPG_(SA)和TRwS_(SA)动力损失的差异主要与雨量筒形状不同有关,同时本研究结果还可能受到TRwS204特定误差的影响。(3)当风速高于2.0 m·s^(-1)时,各雨量筒降雨捕捉率出现明显的降低。因雨夹雪和降雪期间的平均风速较低,只有CSPGUN降雪捕捉率随风速的增加出现一定的降低。

Adjustment of precipitation measurements using Total Rain weighing Sensor(TRwS)gauges in the cryospheric hydrometeorology observation(CHOICE)system of the Qilian Mountains,Northwest China

Precipitation is one of the most important indicators of climate data,but there are many errors in precipitation measurements due to the influence of climatic conditions,especially those of solid precipitation in alpine mountains and at high latitude areas.The measured amount of precipitation in those areas is frequently less than the actual amount of precipitation.To understand the impact of climatic conditions on precipitation measurements in the mountainous areas of Northwest China and the applicability of different gauges in alpine mountains,we established a cryospheric hydrometeorology observation(CHOICE)system in 2008 in the Qilian Mountains,which consists of six automated observation stations located between 2960 and 4800 m a.s.l.Total Rain weighing Sensor(TRwS)gauges tested in the World Meteorological Organization-Solid Precipitation Intercomparison Experiment(WMO-SPICE)were used at observation stations with the CHOICE system.To study the influence of climatic conditions on different types of precipitation measured by the TRwS gauges,we conducted an intercomparison experiment of precipitation at Hulu-1 station that was one of the stations in the CHOICE system.Moreover,we tested the application of transfer functions recommended by the WMO-SPICE at this station using the measurement data from a TRwS gauge from August 2016 to December 2020 and computed new coefficients for the same transfer functions that were more appropriate for the dataset from Hulu-1 station.The new coefficients were used to correct the precipitation measurements of other stations in the CHOICE system.Results showed that the new parameters fitted to the local dataset had better correction results than the original parameters.The environmental conditions of Hulu-1 station were very different from those of observation stations that provided datasets to create the transfer functions.Thus,root-mean-square error(RMSE)of solid and mixed precipitation corrected by the original parameters increased significantly by the averages of 0.135(353%)and 0.072 mm(111%),respectively.RMSE values of liquid,solid and mixed precipitation measurements corrected by the new parameters decreased by 6%,20% and 13%,respectively.In addition,the new parameters were suitable for correcting precipitation at other five stations in the CHOICE system.The relative precipitation(RP)increment of different types of precipitation increased with rising altitude.The average RP increment value of snowfall at six stations was the highest,reaching 7%,while that of rainfall was the lowest,covering 3%.Our results confirmed that the new parameters could be used to correct precipitation measurements of the CHOICE system.

基于延时数字摄影测量的积雪过程4D监测技术研究

为实现4D(时间+空间)多目标、高精度的积雪监测,本次试验研究采用单台相机延时拍摄结合运动结构重建算法(Structure from motion,SfM),分别获取了祁连山黑河上游站裸露山坡坡面尺度单次降雪的雪深、逐日积雪空间分布和面积,以及祁连山八一冰川1.5m×1.5m的斑块尺度全年雪深及雪面特征数据。坡面尺度积雪观测研究表明:本方法可以准确获取积雪分布信息,但其雪深空间分布获取精度较差。斑块尺度雪深监测研究表明:本方法能够很好地获取连续的雪面特征信息和雪深,且获取雪深与SR50观测雪深的绝对误差小于3.4cm。在不同季节,本方法对积雪监测能力略有差异:春季快速积累期雪面纹理少,照片组对齐并获取点云数据和DEM数据的成功率较低,而冬季和消融季雪面纹理丰富,相应的对齐成功率比例和精度较高。本研究表明基于单台相机的4D摄影测量方法能够实现小范围、连续、高精度、多目标的积雪监测,未来应用前景广泛。

西北干旱区融雪洪水灾害预报预警技术:进展与展望

针对全球变化背景下极端升温、暴雪和雪面雨等事件增多以及我国西北干旱区融雪洪水灾害风险增大问题,简要概述了干旱区融雪洪水预报预警系统及其关键技术的研究进展,重点阐述了近年来发生频率增加、灾害风险大,但在干旱区未引起重视的雪面雨洪水的研究进展,提出了西北干旱区融雪洪水高精度预报预警所面临的关键科学问题,指出需在揭示干旱区融雪洪水灾害致灾机理、成灾机制及其演化规律基础上,研发干旱区融雪洪水灾害监测预警装置并构建立体监测体系,研究雨雪冰混合洪水形成及演进过程并建立模型,构建洪水风险评估指标体系,建成干旱区融雪洪水智能化预报预警决策支持平台,动态展示流域实时、潜在及未来超标准融雪洪水的淹没范围,评估风险程度,并提出防洪技术和工程方案以及洪水资源化利用途径等应对措施。

祁连山高寒山区降水观测网络及其数据应用

降水是地表及地下水资源的根本补给源,直接影响水资源的时空分布格局以及山地冰冻圈的分布和发育。祁连山高寒山区是降水和产流高值区,降水特征受地形影响较大,但现有的降水观测网络还无法合理反映降水特征在地形垂直梯度上的变化。为了确定降水变化如何影响高寒山区的水文和生态过程,需要从流域垂直梯度观测降水形态和降水量的变化。本文概述了由T-200BM3组成的祁连山高山区降水格网化、梯度化、自动化观测网络,并在八一冰川冰缘区建立高寒山区降水标准校正场,采用世界气象组织(WMO)推荐的降水/降雪观测标准(DFIR)校正八一冰川区域降水量。在八一冰川区域对地面降水数据产品作初步分析,并利用高海拔站点数据评估了GPM和TRMM降水数据产品在祁连山区的适用性。该降水观测网络的建设对进一步认识高寒山区不同海拔雨雪和水汽变化规律,精细化评估高寒山区降水资源具有重要意义,并可为全国的降水资源综合观测和评估提供方法和降水数据产品。

How do GPM and TRMM precipitation products perform in alpine regions?A case study in northwestern China's Qilian Mountains

Satellite technologies provide valuable areal precipitation datasets in alpine mountains.However,coarse resolution still limits the use of satellite precipitation datasets in hydrological and meteorological research.We evaluated different time scales and precipitation magnitudes of Tropical Rainfall Measurement Mission 3B43 V7(TRMM)and Global Precipitation Measurement(GPM)products for alpine regions using ground precipitation datasets from January 2015 to June 2019 obtained from 25 national meteorological stations and 11 sets of T-200B weighing precipitation gauges in the Qilian Mountains.The results indicated that GPM outperformed TRMM at all temporal scales at an elevation<3500 m with a higher probability of detection(POD),false alarm ratio(FAR),and frequency bias index(FBI)and performed best at 3000 m;TRMM performed better than GPM at an elevation>3500 m,with the best performance at 4000 m.GPM and TRMM had the best estimation accuracy in areas with monthly precipitation of 30 mm and 40 mm,respectively.Both TRMM and GPM products underestimated mid to large daily precipitation and overestimated light daily precipitation averaging<2 mm/d.This research not only emphasizes the superiority of GPM/TRMM in different regions but also indicates the limitations of precipitation algorithms.