Knowledge Resource Center for Ecological Environment in Arid Area
| 夏季不同源地水汽对我国西北区降水影响的数值模拟 | |
| 其他题名 | Simulation on Impact of Water Vapor in Various Source Areas on NWC Precipitation Summer |
| 周建琴 | |
| 出版年 | 2009 |
| 学位类型 | 硕士 |
| 导师 | 蔡英 |
| 学位授予单位 | 中国科学院寒区旱区环境与工程研究所 |
| 中文摘要 | 水汽是降水的物质基础，某地降水的水汽又常与外来的水汽输送有关，特别是深入内陆的西北干旱荒漠区。为客观地讨论夏季不同源区水汽对我国西北区降水影响的相对重要性，本研究选择了西北区全区性湿月1979年7月作为积分模拟对象，划分了东南沿海、孟加拉湾、青藏高原、西风带等4个西北区的水汽源区，利用NCAR MM5中尺度模式和NCEP再分析值作初、侧边界条件，对该月分别执行了检验模式性能的控制性试验及减、增各源区水汽对西北区降水影响的敏感性试验等13个试验。\n 得出的主要结论如下：\n （1）对某天气气候事件的事后模拟，若积分时间超过10天，采用分段积分模拟方案，可部分提高模式的模拟效果。\n（2）夏季东南沿海源区水汽的减（增）变化常通过西伸的西太副高西南侧的东南风，西侧的南风，连同西南涡或高原涡东部的南风等的“干（湿）平流”输送，使西北区东部降水减少（增加）。这种影响一般在减少（增加）该源区水汽后第2天就能到达西北区东部，日雨量变化可以达到25-50mm。继之，若遇河西走廊低层较强偏东风，SE源区水汽的影响还可进一步扩及到河西走廊、乃至南疆地区。即东南沿海源区是直接影响西北区东部夏季降水的最重要水汽源区，但是，其具体的影响还与西太副高等相关天气系统的位置、强度及相伴的低层输送气流情况有关。\n（3）孟加拉湾源区水汽的减（增）变化可通过高原槽、涡东部的偏南气流和源区的偏西气流，兵分两路分别经高原东北传，或沿20°N附近东传再折向北，共同影响西北区降水。在减少（增加）该源区水汽后第2天，两路“干（湿）平流”就能会合，共同影响青海、西北区东部和华北区的降水，日降水变化量可以达到5-25mm；第3-4天后，“干（湿）平流”的影响进一步扩大，并经青海影响到南疆南缘地区。即孟加拉湾源区将直接影响青海及河西走廊中东部的降水，另外也可间接影响西北区东部及南疆的降水。\n（4）东南沿海和孟加拉湾共同减少（增加）水汽后，在西北及华北区引起更大范围的降水减少（增加），减少（增加）的雨量值比减（增）单一源区的试验都更大。在西北区东部3天的总雨量变化可以达到75-100mm，在河西走廊及青海地区的也达到了25-50mm。显然，两源区同时减少（增加）水汽后，对西北地区降水的影响明显比单一源区试验加强了。\n（5）相对来说，青藏高原及西风带源区因本身水汽少，青藏高原区主要影响青海及河西走廊中、东部的降水，对西北区东部也有一定影响；而西风带源区主要影响北疆及南疆地区的降水；而南疆地区的强降水常与河西走廊及柴达木盆地西部的低层偏东风有关，也即受东南沿海及孟加拉湾源区的间接影响。\n（6）作西北区夏季降水预测时，要特别关注其上游孟加拉湾区，特别是东南沿海源区水汽及沿途低空急流的变化。 |
| 英文摘要 | The water vapor is the material base of precipitation and the water vapor of precipitation is often associated with external water vapor transportation in a certain place, especially the Northwest arid and desert area. To objectively test the relative importance of water vapor in various source areas in summer precipitation over Northwest China(hereafter NWC), first, a typically wet month over nearly NWC around July, 1979 was chosen; then the likely water vapor source areas of NWC such as Off the Southeast Coast of China(SE), The Bay of Bengal(BB), Qinghai-Xizang Plateau(QXP) and Westerly Zone(WZ) were drawn; and again then, a set of thirteen numerical experiments totally, including two control ones testing MM5 modeling performance and eleven sensitive ones changing respectively water vapor over each source area, have been designed and integrated for whole July of 1979, utilizing the PSU/NCAR MM5 v3.7 model and the NCEP reanalyzed data as the initial and lateral boundary conditions.\nFrom the analyses above the main conclusions can be drawn as follows:\n(1) As a post event modeling analysis, if the integrated time is to exceed ten days, using the pentad-by-pentad integration scheme may partly improve the modeling behavior.\n (2)With decreasing (increasing) the water vapor over SE source area and through the “dried (wetted) advection” from the source area of southeasterly and southerly on the SW and W sides of West Pacific Subtropic High extended westward, the main precipitation decreasing (increasing) regions in east part of NWC(including east Qinghai) will be occurred after two days, The range of variation of daily rainfall could be 25-50mm.After then, the decreased (increased) rain regions can be extended westward further if there exists the easterly in lower-levels in Gansu Corridor. Thus the SE source area is the most important one for summer precipitation in east part of NWC. But, the influence also has relationship with position and strength of West Pacific Subtropic High and the transport condition of low-level of water vapor.\n(3)After decreasing (increasing) the water vapor over the BB source area, there are usually two ways for the “dried (wetted) advection” transported both the north-and east-ward, then meet together and influence common the precipitation of NWC and NC. The range of variation of daily rainfall could be 5-25mm.After three or four days, the influence of the “dried (wetted) advection” also can reach Qinghai and south Rim of southern Xinjiang. Namely the BB source area affects mainly the precipitation in Qinghai and the central and east of Gansu Corridor; partly, the one in east part of NWC; occasionally, the one in South Xinjiang.\n(4) With decreasing (increasing) the water vapor over both SE and BB source areas, the precipitation decreasing (increasing) region and the range of variation of rainfall are more than the signal SE or BB numerical experiments. The range of variation of three days rainfall could be 75-100mm in east part of NWC and also could be 25-50mm in Gansu corridor and Qinghai. Obviously, the influence of decreasing (increasing) the water vapor over both SE and BB source areas is reinforced. \n(5) Because the QXP and WZ source area (especially the latter) have a little water vapor, the former affects mainly the rain in Qinghai and mid-and east- Gansu Corridor; partly, the one in east part of NWC, and the latter influences mainly precipitation in Xinjiang .\n(6) For the summer precipitation forecast in NWC, it is needed to pay more attention to the water vapor changes in BB, especially SE source area in the upstream of NWC and the conditions and changes of the major rain-producing systems and the lower-level jet on the way from the source areas to NWC. |
| 中文关键词 | MM5模式 ; NCEP再分析资料 ; 我国西北地区夏季降水 ; 东南沿海、孟加拉湾、青藏高原及西风带等水汽源区 |
| 英文关键词 | MM5 model NCEP reanalyzed data Summer precipitation in NWC of China The SE source area The BB source |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 气象学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286761 |
| 推荐引用方式 GB/T 7714 | 周建琴. 夏季不同源地水汽对我国西北区降水影响的数值模拟[D]. 中国科学院寒区旱区环境与工程研究所,2009. |
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