Coupled carbon, water and heat fluxes over the global land surface

模拟地球能量、水和碳循环的变化是气候和地球系统模型的关键目标。然而，我们需要从观测中更准确地了解这些数量的区域通量和输送，以便为气象局用于气候预测的模型提供强有力的约束，并为更广泛的全球模型界的发展提供信息。IPCC现在认识到了这一点，他们将在下一份评估报告中单独讨论能源、水和碳循环。我们在Thomas等人(2019年)的部门开发了一种能量-水循环耦合的逆方法，该方法使用许多独立观测的卫星数据集及其误差在全球范围内制定封闭的热量和水预算，遵循美国国家航空航天局早些时候的一项能源和水循环研究(新闻)L的厄瓜多尔等人(2015年)，罗德尔等人(2015年)，见www.nasa-news.org。我们通过改进卫星得出的通量的误差，并使用基于船舶测量的额外海洋运输量估计，将新闻研究扩展到海洋上，取得了更好的结果。由国家地球观测中心支持的进一步工作已将该模型扩展到研究2001-11年的年际变化，显示出大陆变暖的更好的季节周期，以及受降水、径流数据和GRACE重力数据的储水量估计所约束的更好的陆地水循环。非洲的年际变化是目前关注的焦点之一。该博士项目将侧重于改善陆地表面过程。在陆地上，土壤水分和植被特性在很大程度上决定了地表在季节性时间尺度上可以储存多少能量，因此产生的陆地表面温度(LST)现在已经通过卫星很好地测量到了。水、阳光和温度也决定了光合作用和生物量的增长，从地球大气中吸收二氧化碳。生物量增长和二氧化碳吸收也可以通过卫星测量进行监测，提供了可以与我们的反方法一起使用的额外数据集。其目的是将土地碳汇与能量和水循环相结合，并在一些关键感兴趣的地区测试由此产生的模型；可能的地区包括非洲和中国。因此，这位博士生将使用新的卫星观测作为约束，以改进地表通量估计。逆方法将被扩展到包括碳收支以及水和能源收支，以产生一个真正耦合的地球系统循环分析，具有许多新的应用，包括测试地球和气候循环模型。学生将探索与大气的能量-水-碳通量交换，并利用来自FLUXNET测量塔的本地观测探索陆地上的存储，然后使用卫星数据寻找更大范围的关系。将使用Jules陆地表面模式的参数化和模拟来探索相互关系，并帮助开发通量不确定性估计。最终目标将是(I)允许EO陆地表面温度测量来限制逆方法中的能量通量和水存储，以及(Ii)扩展逆方法以包括碳收支，其中陆地表面部分受来自卫星数据的植物光合作用/生长测量的约束。学生将探索逆方法对这些附加约束的敏感性。其他碳收支观测数据，例如NASA OCO-2卫星对二氧化碳的大气测量，可能会在稍后阶段带来。

Simulating changes to the Earth's energy, water and carbon cycles is a key goal of climate and earth system models. However we need to know the regional fluxes and transports of these quantities much more accurately from observations to provide strong constraints for models such as those used at the Met Office for climate predictions, and to inform developments across the wider global modelling community. This is now recognized by IPCC who will have separate chapters on the energy, water and carbon cycles in the next Assessment Report.We have developed an energy-water cycle coupled inverse method in the department, Thomas et al (2019), which uses many independently observed satellite datasets and their errors to develop closed heat and water budgets on a global scale following an earlier NASA Energy and Water cycle Study (NEWS) L'Ecuyer et al (2015), Rodell et al (2015), see www.nasa-news.org. We have extended the NEWS study with better results over the oceans by improving the errors used for the satellite derived fluxes, and by using additional ocean transport estimates based on ship measurements. Further work supported by the National Centre for Earth Observations has extended the model to study interannual variability from 2001-11, showing a better seasonal cycle of continental warming and a better land water cycle constrained by precipitation, runoff data and water storage estimates from GRACE gravity data. Interannual variability over Africa is one current focus.This PhD project will focus on improving the land surface processes. On land, soil moisture and vegetation properties largely determine how much energy the surface can store on seasonal timescales, and hence the resultant land surface temperatures (LST), which are now well measured from satellites. Water, sunlight and temperature also determine photosynthesis and biomass growth, taking up CO2 from the Earth's atmosphere. Biomass growth and CO2 uptake can also be monitored from satellite measurements providing additional datasets that can be used with our inverse method. The aim is to couple the land carbon sink to the energy and water cycles, and to test the resulting model in some key regions of interest; possibilities include Africa and China. The PhD student will therefore use new satellite observations as constraints to improve surface flux estimates. The inverse method will be extended to include carbon budgets alongside the water and energy budgets to produce a truly coupled Earth system cycling analysis with many new applications, including testing Earth and Climate circulation models.The student will explore energy-water-carbon flux exchanges with the atmosphere, and storage over land using local observations from Fluxnet measurement towers, and then seek larger scale relationships using satellite data. Parameterizations and simulations with the JULES land surface model will be used to explore relationships and to help in developing flux uncertainty estimates. The ultimate aims will be (i) to allow EO land surface temperature measurements to constrain energy fluxes and water storage within the inverse method, and (ii) to extend the inverse method to include a carbon budget, where the land surface component is constrained by plant photosynthesis/growth measurements from satellite data. The student will explore the sensitivity of the inverse method to these additional constraints. Additional carbon budget observational data e.g. atmospheric measurements of CO2 from the NASA OCO-2 satellite, may be brought in at a later stage.