中全新世全球极端温度响应:基于MPI-ESM-P模拟试验

中全新世是北半球轨道时间尺度距今最近的温暖期,是当前全球变暖的历史相似型之一,研究该阶段极端温度的变化有助于理解典型温暖期极端温度的响应和机制。利用MPI-ESM-P海气耦合模式中全新世暖期试验与工业革命前试验数据,分析中全新世暖期全球极端温度的响应。结果表明:由于北半球夏季轨道日射量的增加,与工业革命前相比,中全新世平均温度在极地海洋以及夏季北半球中高纬度陆地地区升高,其余区域温度降低;平均温度升高的区域,极端高温与极端低温也将上升,暖事件频率增加;陆地区域日最高温相关指标比日最低温相关指标的变化幅度更大;相对于极端高温事件的响应,极地海洋地区极端低温事件的响应更为显著,冷事件频率显著减少,全年高于0℃的天数显著增加。

Response of global temperature extremes in mid-Holocene: results from MPI-ESM-P experiments

Background, aim, and scope Compared to the modern warming period, mid-Holocene is the most recent warm period during summer over north hemisphere on the orbital time scale, which is resulted from higher orbital insolation. To evaluate the response of temperature extremes in mid-Holocene will help to better understand how temperature extremes change in future warming scenarios. This paper aims to evaluate the response of temperature extremes in mid-Holocene by numerical experiments under the Coupled Model Intercomparison Project 5 (CMIP5) framework. Materials and methods We adopt the outputs of mid-Holocene experiment and pre-industrial experiment by the coupled climate model MPI-ESM-P in this paper. Indices based on daily mean temperature, daily maximum temperature (T _max ) and daily minimum temperature (T _min ) are analyzed, respectively. Extreme temperature indices are defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). Results In mid-Holocene, summer extreme temperature increases over boreal continents and polar oceans but decreases over the tropic. Warm events and cold events become more frequent over extratropical continents. Cold events decrease significantly over polar oceans especially where close to the mainland. Discussion In mid-Holocene, responses of extreme temperature indices show features that are different from greenhouse gases-induced warming. Extreme temperature indices based on T _max changes more than indices based on T _min over continents, because insolation heats the globe in the daytime but greenhouse gas heats it more during the night. However, over the polar oceans, monthly minimum temperature changes faster than monthly maximum temperature, which is consistent with the response under greenhouse gases-induced warming. Both warm events and cold events become more frequent over extratropical continents, which leads to high seasonal temperature variance. Conclusions Extreme temperature increases (decreases) and extreme warm (cold) events become more frequent in summer (winter) over extratropical continent, and temperature differences between seasons increase. As extreme temperature increases, frequency of cold events decreases significantly over polar oceans. Indices based on T _max changes more pronounced than indices based on T _min over mainland, which is different from responses of temperature extremes in warm periods induced by greenhouse gases. Recommendations and perspectives Responses of temperature extremes are different between mid-Holocene and greenhouse gases-induced warm period. Whether such differences lead to different responses of other climatic variables such as precipitation is worth to be explored in following studies.