基于高分辨率区域气候模式的南极冰盖表面物质平衡模拟与不确定性评估研究

The candidate project focuses on the weakness in the simulation of the Antarctic Ice Sheet. The drifting snow routine will be firstly coupled to Polar WRF with high resolution to improve its assessment of Antarctic surface mass balance. At its lateral boundaries, the coupled Polar WRF will be forced by the best reanalysis through the assessment of the current atmospheric reanalyses including ERA-interim, MERRA, CFSR, and JRA-55, and then be used to assess the surface mass balance and its components (precipitation, surface sublimation, drifting snow sublimation, drifting snow deposition/erosion and runoff due to melt) in recent three decades. The resulting surface mass balance will be evaluated based on snow accumulation rate derived from snow pit, ice core,stake measurements and automatic weather station records. Then, the surface mass balance and its component outputs from the coupled Polar WRF will be compared with the other regional climate models such as MAR and RACMO2 to identify the degree of consistency and inconsistency in their spatial and temporal patterns. The possible reasons will be also detemined. This project will fill in the gap of the Chinese studies on Antarctic surface mass balance simuluation. Our results might have important implications for the improvement of Antarctic mass balance evaluation, and the prediction of future surface mass balance and its impact on the sea level change.

针对当前我国南极冰冻圈模拟研究薄弱的现实，本项目首次将风吹雪物理过程耦合到高分辨率极地区域气候模式（Polar WRF），提高它模拟南极冰盖表面物质平衡性能。在充分评估最新再分析资料ERA-interim、MERRA、CFSR及JRA-55在南极冰盖适用性基础上，确定最适合再分析资料为耦合Polar WRF的初始场和侧边界条件，模拟近30年来南极冰盖表面物质平衡及其各分量（降水、表面蒸发、风吹雪升华、风吹雪引起的积雪侵蚀或沉积和表面消融）时空变化。基于花杆测量、雪坑/冰芯记录及自动气象站记录等积累率资料，定量评估其不确定性，并与已有RACMO2和MAR区域气候模式结果进行对比分析，辨析表面物质平衡及其各分量时空模拟异同，分析其可能原因。该项目的实施将填补我国南极表面物质平衡模拟研究的空白，研究结果有望为提高南极冰盖物质平衡估算精度做出贡献，为南极冰盖未来变化及对海平面变化影响预估奠定基础。

本课题收集整理了南极地面和自动气象站气象数据，对现在流行的再分析资料在南极冰盖适用性进行了全面评估；开展了风吹雪模型与极地区域气候模式耦合试验，对冰盖表面物质平衡进行了模拟，并与其他区域气候模式进行了对比分析。通过4年的研究，课题取得了较好的研究成果。1）明确了当今流行的再分析资料模拟南极冰盖气候变化的能力，辨识了限制模拟能力的主控因子，为区域气候模式边界条件和驱动场选择以及南极气候变化评估奠定了基础；2)首次将风吹雪模型耦合到了Polar WRF模式，通过验证分析表明模拟南极冰盖表面物质平衡的能力大大提高；3) 基于Polar WRF模拟了近30年来南极冰盖气候变化特别是表面物质平衡及分量变化，并与其它区域气候模式MAR和RACMO进行了对比分析，发现均能较好地刻画表面物质平衡空间变化特征，在年际变化模拟能力上RACMO更具优势；4）基于区域气候模式、再分析资料和冰芯数据揭示了西南极冰盖区域表面物质平衡变化呈偶极子型空间型，阐明了其形成机理。