沼泽湿地小气候效应的观测与模拟

【作者】 拱秀丽；

【导师】 王毅勇；

【作者基本信息】 中国科学院研究生院(东北地理与农业生态研究所) ， 环境科学， 2012， 硕士

【摘要】 本文以三江平原洪河国家级自然保护区沼泽湿地及周边农田为研究对象，采用野外定位观测和数值模拟相结合的方法，对沼泽湿地冷湿小气候效应的时空分布特征进行了统计分析和数值模拟研究，结果表明：在生长季的6—9月，沼泽湿地地上0.5—5m高度范围内，气温低，相对湿度大；在空间上，贴地层0.5m高度冷湿效应最强，随着高度的增加，冷湿效应逐渐减弱；不同月份中，7月份冷湿效应最显著。在一日之内，白天的午后时段（12:00–14:00），湿地与旱田的气温和相对湿度差异最大。在夏季的7、8月份，沼泽湿地和旱田0–10cm地温日变化规律相似，均呈正弦曲线。湿地地温日变化波动幅度小于旱田；在相同土壤深度上，湿地的地温低于旱田。通过WRF模式对洪河国家级湿地自然保护区及周边农田夏季晴朗天气的数值模拟发现：WRF模式能够比较精确的反应出研究区域湿地和农田地表2m高度温度和比湿的差异。在夏季晴朗天气的白天时段，湿地边缘的气温高于湿地中心，但低于周围农田，从湿地边缘地带向中心区域气温逐渐降低，沼泽湿地在白天表现出“冷岛”效应，午后14:00“冷岛”效应最显著，到夜间22:00湿地的“冷岛”效应基本消失。日间“冷岛”效应在高度上随时间发生变化，清晨6:00时，湿地的“冷岛”范围可影响到200m高度，午后14:00时，湿地的“冷岛”效应可延伸至600m的高度。无论白天还是夜间，地表2m高度处，湿地上空相对湿度始终都高于农田，湿地表现出“湿岛”效应。从农田到湿地边缘再到湿地中心，其相对湿度的分布规律是：农田<湿地边缘<湿地中心。在一天之内，湿地上空夜间相对湿度大于白天，夜间2:00时最大，白天14:00最低；农田相对湿度日变化的幅度大于湿地，二者在夜间相对湿度差异最小，在午后14:00时差异最大。沼泽湿地和农田上空的相对湿度均随高度递减，在距地面200m高度范围内，湿地上空的相对湿度均大于农田。更多还原

【Abstract】 Relying on the Honghe National Nature Reserve of the Sanjiang Plain, this studyinvestigated the temporal-spatial variations of microclimate effects (i.e., cold-humideffect) in marsh wetland. Temperature and humidity from marsh wetlands andsurrounding farmlands were measured in the field and simulated at regional scale bythe model of Weather Research and Forecasting (WRF).Compared to surrounding farmlands, the temperature was lower and relativehumidity (RH) was higher at three heights (0.5,2and5m) in marsh wetlands duringthe growing season (from June to September). This indicates the cold-humid effect ofmarsh wetland. The cold-humid effect was most significant at0.5cm, and graduallydecreased with the increasing height. During the non-growing season, the mostsignificant cold-humid effect occurred in July. The biggest differences of temperatureand humility between marsh wetland and farmland were found from12:00to14:00based on daily measurements.The daily variations of soil temperatures (0,5and10cm) at marsh wetland andfarmland were similar in July and August, with a sinusoidal change. During a day, thechange range of soil temperature in marsh wetland was less than that in farmland. Atthe same depth, soil temperature in marsh wetland was lower than that in farmland.The simulations from WRF model show that: WRF model provided comparablevalues of temperature and RH at the height of2m from wetland underlying surface insummer sunny day as compared to that measured in the field.During the summer sunny day, air temperature measured at the edge of wetlandwas higher than at the center of wetland, but was lower than that at surroundingfarmland. There was a decreasing trend of air temperature from the edge to the centerof wetland. The marsh wetland represented a significant cold-island effect, withmaximum effect at14:00and gradually decreased during the night, with minimumeffect at22:00. Our study showed that the cold-island effect of marsh wetland couldbe found at the height of200m at6:00, and the height could extend to600m at14:00. The RH of marsh wetland was higher than that in farmland during both thedaytime and nighttime at the height of2m, indicating the ‘wet-island effect’ inwetland. The value of RH was highest at the center of wetland, followed at the edgeof wetland and lowest at farmland. Similar diurnal variations of RH were determinedin both wetland and farmland. The RH of marsh wetland was higher in the daytimethan that in the nighttime, with the maximum values at2:00and minimum values at14:00. The change range of RH in a day was higher in farmland then that in marshwetland. The difference of RH between wetland and farmland is biggest during thenighttime, whereas lowest at14:00. At both marsh wetland and farmland, the RHvalues decreased with increasing height. Within the range of200m height, RH valuesin marsh wetland were higher than surrounding farmland.更多还原