Direct Measurement of Earth’s Energy Imbalance with Geodetic Satellites – Feasibility Study (EEI-Geodetic)

地球的能量不平衡(EEI)代表地球在大气层顶部吸收和发射的能量之差。其长期全球平均值目前估计为0.9W/m2。最近的几项研究指出，需要在更大的空间尺度上以0.1W/m2的精度测量平均EEI，并检测可能的长期时间变化。目前使用CERES系列卫星辐射计观测到大气层顶部的EEI，但众所周知，这些传感器在长时间尺度上存在校准问题，因此它们的平均值固定在海洋数据的估计值中。然而，由于ARGO等现场数据的稀疏，对海洋热变化的估计也有自己的问题。在这里，我们建议通过用加速度计间接观测太阳和地球的辐射压力或通过卫星激光测距来获得EEI。这是一个非常具有挑战性的目标，因为目前尚不清楚现有的大地测量数据库将允许何种精度以及以何种时间和空间分辨率。我们将开发一个模拟框架，以测试和优化专用EEI大地测量卫星、此类星座或配备改进的加速度计的GRACE-II等未来重力任务。目标将是在大空间尺度(全球平均、陆地-海洋-北极分区、纬度带)以及在年度和更长的时间尺度上验证并可能改进基于CERES的估计

Earth’s Energy Imbalance (EEI) represents the difference between the energy absorbed and emitted by the Earth at the top of the atmosphere. Its long-term global mean is currently estimated to <0.9 W/m2. Several recent studies have pointed out the need to measure mean EEI with an accuracy of 0.1 W/m2 at larger spatial scales, and to detect possible long-term temporal changes. EEI at the top of the atmosphere is currently observed with the CERES family of satellite radiometers, but these sensors are known to have calibration problems at long timescales, so their mean has been anchored inestimates from ocean data. However, estimates of ocean heat change have their own problems due to sparsity of in-situ data such as Argo. Here we suggest to derive EEI from either indirect observation of solar and Earth’s radiation pressure with accelerometers or from satellite laser ranging. This is a very challenging objective, since it is not clear which accuracy the existing geodetic data base will allow for, and at which temporal and spatial resolution. We will develop a simulation framework that will enable testing and optimizing a dedicated EEI geodetic satellite, a constellation of such, or a future gravity mission such as GRACE-II equipped with improved accelerometers. The goal would be to validate, and possibly improve, the CERES-based estimates at large spatial scales (global mean,land-ocean-arctic partitioned, latitudinal bands) and at annual and longer timescales