中全新世时期中国地区水循环因子变化的模拟研究

Simulation of hydrological cycle changes over China during Mid-Holocene.

利用全球气候模式CCM3嵌套区域模式MM5模拟了现代和中全新世时的气候,从模拟结果可以发现中全新世有效降水变化中心随季节变化,最大的有效降水增加出现在夏季东北地区和内蒙古东部,最大值超过3mm/d;同时,黄河与长江之间区域降水减少,最大变化超过2mm/d。中国北方地区云量增加,同时,中国东部的长江流域云量减少。高云量变化较小,低云量变化最大,最大变化超过2成。夏季,对应着黄河与长江之间区域的云量减少,这个区域的温度升高最大。从水汽的变化可以看到长江流域地区水汽减少,相对湿度也减少,这与云量的变化一致;华南地区水汽的变化与季节有关;东北地区水汽增加,相对湿度增大,对应云量的增加和降水增多。从结果可以发现相对湿度最大的变化超过15%,不是一个常数。有些地区温度升高,但是水汽却减少。但是,在LGM的温度降低的区域,水汽一致减少。这说明温度降低水汽对应减少,但温度升高不一定对应水汽增加。这与全球尺度水汽相对湿度基本保持常数的结果不同。中全新世时,长江流域除春季外变得干燥、少雨和高温,东北和内蒙古东部变得多雨和潮湿。

Present and Mid-Holocene climates are simulated with a global climate model CCM3 nested with a regional model MM5. From the model results, it is found that in Mid-Holocene, the center of the effective precipitation variation changes with season. A maximum of 3 mm/d effective precipitation variation occurs over Northeast China and the eastern part of Inner Mongolia in summer. Meanwhile, precipitation between the Huanghe River and the Yangtze River decreases with a maximum of 2 mm/d. Cloud cover in North China increases while that over the middle and downstream of the Yangtze River basin reduces. Changes of low cloud amount are the most in three types of clouds with a maximum of more than 0.2, but high cloud changes are the least among them. Temperature between the Huanghe River and the Yangtze River rises the most due to the cloud cover reduction in summer. Water vapor and relative humidity over this region decrease, in accordance with the cloud cover reduction. Water vapor changes in South China are different with seasons. Water vapor and relative humidity in Northeast China increase, which results in cloud cover and precipitation increase. The model results illustrate that the relative humidity isn＇t a conservative factor, the maximum change of which is more than 15%. Moreover, temperature increases in some regions while water vapor decreases. However, in Last Glacial Maximum, when temperature decreases, water vapor consistently reduces. These indicate that temperatures decrease can result in water vapor reduction, but temperature increase does not always bring about water vapor enhancement. This is different from the fact that at the global scale the relative humidity is conserved. In Mid-Holocene, the Yangtze River basin became warmer and drier in all seasons except spring. Meanwhile, Northeast China and the eastern part of Inner Mongolia became more rainy and wetter.