Meteorological Drivers of Mass and Energy Exchange between Inland Waters and the Atmosphere (MEDIWA)

正确量化内陆水域与大气之间的质量和能量交换对于科学和实际问题都具有重要意义。精确的直接测量是可能的，但昂贵且技术上具有挑战性。因此，不同的梯度方法，如“湍流边界层”（TBL）方法，为利用易于测量的湖泊学和大气变量确定内陆水域的扩散气体通量、能量通量和蒸发率提供了方法基础。然而，这种通量近似的可靠性在很大程度上取决于(i)传递系数的参数化和（ii）输入数据的代表性。为了提高我们确定内陆水域通量的能力，本项目将深入研究交换过程。特别是，我们的目标是(A)提高梯度方法的预测能力，(B)量化气象和湖泊驱动因素的空间和短期变化对通量近似的影响。将在卢萨蒂亚（德国）的bauzzen水库进行两项长期和另外四项短期密集测量实验，以观察不同天气和湖泊条件下以及不同空间和时间尺度下的质量和能量通量。一个装有涡动相关测量系统和若干气象、水化学和水物理传感器的漂浮室外实验室将用于直接连续测量不受陆地表面影响的通量和变量，这些通量和变量代表了纯粹的水-大气相互作用。另外三个简化设置的卫星平台将被用来探测沿线大气和湖泊条件的空间变化。此外，表面膜和微分层在最上层水层的发生和影响将通过额外的水化学现场和实验室实验进行检验。实验野外调查、统计分析和模型研究相结合，以及湖沼学和微气象研究之间的联系，为更好地理解不同时空尺度上质量和能量交换的相关过程提供了基础。我们的分析将集中于发展新的方法，以(a)参数化大气转移系数，特别是在低湍流条件下，(b)评估湖泊现象（如微分层和表面薄膜）的影响，以及(c)量化大气和湖泊非均质性对通量估计的影响。此外(d)，我们将研究大气湍流结构，并开发大气变量谱和共谱的数值描述模型，以改进阻尼损失的校正，从而提高水面以上涡旋相关方差测量的保真度。

The correct quantification of the mass and energy exchange between inland waters and the atmosphere is of great importance for both scientific and practical issues. Exact direct measurements are possible, but expensive and technically challenging. Thus, different gradient approaches, such as the ‘turbulent boundary layer’ (TBL) approach, provide the methodological backbone to determine diffusive gas fluxes, energy fluxes and evaporation rates from inland water utilizing easy–to–measure limnologic and atmospheric variables. However, the reliability of such flux approximations significantly depends on (i) the parameterisation of the transfer coefficient and (ii) the representativeness of input data. In order to enhance our capabilities to determine fluxes from inland waters, exchange processes will be intensively studied in this project. In particular, we aim to (A) improve the predictive power of gradient approaches and (B) quantify effects of spatial and short-term variations of meteorological and limnological drivers on flux approximations.Two long-term and four additional short-term intensive measurement experiments will be performed at Bautzen reservoir in Lusatia (Germany) to observe mass and energy fluxes under different weather and limnic conditions as well as on different scales of space and time. A floating outdoor laboratory equipped with an eddy covariance measurement system and several meteorological, hydro-chemical and hydro-physical sensors will be used for direct continuous measurements of fluxes and variables that are unaffected by land surfaces and are representative for the pure water-atmosphere-interaction. Three additional satellite platforms with a simplified set-up will be utilized to detect the spatial variations of atmospheric and limnic conditions along the fetch. Furthermore, the occurrence and the effects of surface films and micro-stratification in the uppermost water layers will be examined by additional hydro–chemical field and laboratory experiments.The combination of experimental fieldwork, statistical analyses and model–based investigations as well as the nexus between limnological and micrometeorological researches provide the foundations to better understand the processes that are relevant for the mass and energy exchange on different temporal and spatial scales. Our analyses will focus on the development of novel methods to (a) parameterise atmospheric transfer coefficients, especially under low turbulence conditions, (b) evaluate effects of limnological phenomena such as micro-stratification and surface films, and (c) quantify influences of atmospheric and limnologic heterogeneities on flux estimates. Additionally (d), we will examine atmospheric turbulence structures and develop models for the numerical description of spectra and cospectra of atmospheric variables to improve the correction of damping losses and therefore the fidelity of eddy covariance measurements above water surfaces.