冰川特殊下垫面对高山区降水的影响研究

The relationship between glacier and climate is a scientific research hot spot. Alpine glaciers may act as condensers which increasing the amount of precipitation in the glacial zone via the glacial cooling effect. Most studies about the glacial cooling effect on precipitation were limited to theoretical derivation and qualitative description at present. Systematic observation, onsite confirmation and study on the mechanism of glacial cooling effect were seldom involved. Focusing on the influence of glacial surface on alpine precipitation and taking the Laohugou No.12 glacier in the Qianlian Mountain for example, this study will systematically observe the microclimate around the glacier and quantitatively describe their influence on alpine precipitation and expound the mechanism. Combining the meteorological observation data, a downscaling mesoscale weather forecast model WRF3.3 will be used to simulate the weather process in the glacier region and precipitable water and the height of local convective cloud base will be exported. Also sensitivity experiments of whether the glacier surface exist or not will be performed and the simulated results will compare the observations to calculate the contribution of glacier cooling effect to local precipitation amount. The result of this study may extrapolate to similar glacial zone in the west Qianlian Mountain and give a estimated contribution of glaciers to regional precipitation. This study has scientific significance for alpine glacier mass balance research and practical utilities for optimal use of glacier water resources in the arid region.

冰川与气候的关系是当前研究的热点之一。山地冰川作为一种特殊性质的下垫面通过其致冷效应形成独特的冰川小气候，起到了类似水汽"冷凝器"的作用，对高山区的小气候尤其是冰川区降水产生了不容忽视的影响。目前该方面的研究仅限于理论上的推定和定性描述，有针对性地系统观测、验证并从机理上阐述其形成机制的研究却少有涉及。本研究拟针对冰川特殊性质下垫面对高山区小气候，特别是对高山区降水的影响这一特定研究目标，以祁连山老虎沟12号冰川为例，通过实地观测定量化描述冰川特殊下垫面对局地小气候的影响，阐明其对冰川区降水产生影响的机理。结合气象观测资料，通过理论推算与数值模拟的方法定量评估冰川下垫面致冷作用对高山区降水的可能贡献量。最终尝试将该条冰川的研究结果外推到中国西部更多的类似冰川区来估算冰川下垫面对区域降水的贡献量。本研究对于山地冰川的物质平衡研究及干旱区冰川水资源的合理利用都具有较重要的科学意义和实用价值。

通过对祁连山老虎沟12号冰川地区连续4年实地观测，获得了大量冰川区气象观测资料，针对冰川这种特殊下垫面对局地小气候的影响，特别是对高山区降水的影响这一特定研究目标，进行了系统研究。初步结果表明：高山冰川作为一种特殊性质的下垫面通过其致冷效应形成独特的冰川小气候，对高山区的小气候尤其是冰川区降水产生了不容忽视的影响：冰川表面全天大部分时间都存在非常明显的逆温现象，非冰川表面主要在夜间才出现逆温；冰川和非冰川表面之间的气温垂直递减率显著大于自由大气的气温垂直递减率，越接近交界面气温垂直递减率越大；总降水量随海拔高度变化不明显，但微量降水(本研究定义为<=10mm的日降水量，大部分为局地对流性降水)随着冰川距离的接近而增大，冰川特殊下垫面很可能在其中起到较大的作用；局地地形也对降水起到一定作用，但需要通过理论推算与数值模拟的方法定量评估冰川下垫面致冷作用对高山区降水的可能贡献量。下一步将深入分析气象数据，阐明其对冰川区降水产生影响的机理，定量评估冰川下垫面致冷作用对高山区降水的可能贡献量。