天山科其喀尔冰川区复杂下垫面CO2通量贡献区分析

doi:10.13866/j.azr.2018.06.30

摘要/Abstract

摘要： 大气湍流交换过程中CO₂有效源(汇)区域即CO₂通量贡献区，在冰川作用区不仅受到水化学侵蚀强度的影响，还受区域微气候的影响，另外，动态的下垫面和复杂地形也增加了实际监测的不确定性。为了评估冰川区CO₂通量监测结果的空间代表性，在西天山南坡科其喀尔冰川表碛区利用涡度协方差观测系统进行观测，同时，结合基于KM足迹模型基础上开发的ART Footprint Tool足迹软件对通量贡献区进行分析，结果表明：①积雪积累期主风向以NW为主，风向频率占53.31%；积雪消融期和冰川消融初期NW向主风减少，偏北的NNW风逐渐增多，但冰川消融峰期后又逐渐过渡为NW向风。②积雪积累期雪冰融水几乎消失，但大气CO₂通量平均为-0.07 g•m^-2•d^-1，尤其是白天为-0.88 g•m^-2•d^-1，仍呈没收现象，是由于白天较强辐射下，少量积雪融水引起可溶性物质淋溶过程中水化学反应没收大气CO₂所致；而夜间冰川消融峰期CO₂通量值平均为0.33 g•m^-2•d^-1，呈释放CO₂现象，这可能与夜间区域降温及降水过程中溶解的CO₂因地表蒸发返回大气所致。③通量贡献率80%以上的各期0.5 h数据占比依次为：积雪积累期（95.80%）＞积雪消融期（93.28%）＞冰川消融峰期（86.13%）＞冰川消融初期（81.88%），而足迹最远点分布距离顺序与前者几乎相反，但均分布在主风向下的冰川中流线上，说明对CO2通量监测值有显著影响的贡献区比较集中，也意味着冰川末端及两侧山脊草地CO₂通量变化的影响可以忽略。④白天在大气稳态条件下，贡献区解释的CO₂通量为(78.55±2.08)%，略高于夜间的(77.72±1.41)%，但显著低于非稳定条件下白天(89.86±0.22)%和夜间(89.45±0.57)%的解释结果，进一步验证了CO2通量贡献区比较集中。

关键词: CO2通量, 贡献区, 涡动相关系统, 主风向, 科其喀尔冰川, 天山

Abstract: At some flux sites, the alpine zone surrounding the measuring tower is affected by complex topography and strong wind, which results in the distortion of atmospheric CO₂flux. The goal of this study was to carry out a numerical experiment with the eddy covariance system in moraine area of the Koxkar Glacier in the Tianshan Mountains, and to evaluate the integral of footprint function over the considered domain and distance of the corresponding farthest point from the sensor with the ART (Agroscope Reckenholz Tanikon) Footprint Tool base on the Kormann Meixner method. Results are as follows: ①The prevailing wind direction in snow accumulation period was NW, and its frequency accounted for 53.31%. NW wind evolved gradually into NNW one in snow melting season and early ice-glacial ablation season; ② Atmospheric CO₂sank during the majorly typical period and even snow accumulation period, because soluble substances reacted chemically under snow-ice melting; ③ Temporally, the proportion of more than 80% 0.5h CO₂ flux data of footprint function in each period was in an order of > snow accumulation period (95.96%) > snow melting period (93.75%) > intense glacial ablation season (86.30%) > early glacial ablation season (82.35%). The footprint distance to the farthest point was almost in reverse order, which meant that the major areas of CO₂ flux contribution were relatively concentrated, and the effect of CO₂ flux change at the glacial terminal and on the ridges could be ignored; ④ Under the stable atmosphere in the daytime, the CO₂ flux (78.55±2.08)% was slightly higher than that under the unstable atmosphere (77.72±1.41)% at night, but they were significantly lower than the interpretated ones.

Key words: CO₂ flux, flux footprint, eddy covariance system, prevailing wind direction, Koxkar Glacier, Tianshan Mountains

王建，丁永建，许民，许君利 . 天山科其喀尔冰川区复杂下垫面CO2通量贡献区分析[J]. 干旱区研究, 2018, 35(6): 1512-1520.

WANG Jian, DING Yong-jian, XU Min, XU Jun-li. CO₂ Carbon Flux over Moraine Area of the Koxkar Glacier in the Tianshan Mountains[J]. , 2018, 35(6): 1512-1520.

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