Modeling of middle atmosphere dynamics with LIMA
Modeling of middle atmosphere dynamics with LIMA
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DOI：
10.1016/j.jastp.2008.02.004
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发表时间：
2008-06
影响因子：
1.9
通讯作者：
U. Berger
中科院分区：
文献类型：
--
作者：
U. Berger
本文介绍了一种新的中层大气环流模式LIMA（莱布尼兹-研究所中层大气模式），该模式专门用于模拟中顶高度附近的热结构。LIMA是一个从地面延伸到低层热层（0-150km）的全非线性、全局三维欧拉网格点模式，考虑了辐射、化学和输运等主要过程。与之前的COMMA/IAP相比，LIMA的主要改进是采用三角形水平网格结构，每个水平层（Δx ~ Δy ~ 110km）有41804个网格点，并同化了来自ECMWF/ERA-40的对流层和平流层下层数据。利用LIMA，我们可以在不使用任何重力波参数化的情况下，模拟大气中喷流和夏季冷中层顶的现场风逆转。在夏季，西向风的中间层风反转在+ 5-10m /s量级，这意味着涡场的分解和由此产生的ep通量散度被低估了大约两倍，而ep通量散度决定了中间层区域的动量收支。另一方面再现了夏季中间层顶的热结构，因此至少再现了夏季中间层顶区域的能量收支平衡。例如，7月初在阿罗马尔（69°N, 16°E）上空进行的火箭（落球）实验观测到的中流层温度在88公里处为131K，而相应的模式温度在88公里处为133K。我们的数值模拟结果表明(1)中间层的内在变异性确实是由低层大气变异性决定的，(2)模拟的涡流场可能被解释为模型（λxy小于500km， 2h≤T≤12h）解决的惯性重力波的一部分。
This paper describes a new circulation model of the middle atmosphere called LIMA (Leibniz-Institute middle atmosphere model) which especially aims to model the thermal structure around mesopause altitudes. LIMA is a fully non-linear, global, and 3-d Eulerian grid-point model which extends from the ground to the lower thermosphere (0–150km) taking into account major processes of radiation, chemistry, and transport. The major improvements of LIMA compared to its predecessor COMMA/IAP are the implementation of a triangular horizontal grid structure with 41804 grid points in every horizontal layer (Δx∼Δy∼110km), and the assimilation of tropospheric and lower stratospheric data from ECMWF/ERA-40. Applying LIMA we are able to simulate in situ wind reversals of the mesospheric jets and cold summer mesopause states without applying any gravity wave parametrization. In the summer season the mesospheric wind reversal of the westward zonal wind is in the order of +5–10m/s which implies that the resolved eddy fields and hence EP-flux divergences, determining the momentum budget of the mesopause region, are underestimated by approximately a factor of two. On the other hand the thermal structure of the summer mesopause, and hence at least the balance of the energy budget in the summer mesopause region, is reproduced. E.g. during early July the observed mesopause temperature from rocket (falling spheres) experiments over ALOMAR (69∘N, 16∘E) is 131K at 88km compared to corresponding model temperature of 133K at 88km. The results of our numerical simulations suggest (1) that the intrinsic variability of the mesosphere is indeed determined by the lower atmosphere variability, and (2) that the simulated eddy fields may be interpreted as some fraction of inertia gravity waves resolved by the model (λxy⩾500km, 2h⩽T⩽12h).