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OBSERVER: Evapotranspiration in the spotlight: how Copernicus helps | |
admin | |
2021-03-04 | |
发布年 | 2021 |
语种 | 英语 |
国家 | 欧洲 |
领域 | 气候变化 |
正文(英文) | OBSERVER: Evapotranspiration in the spotlight: how Copernicus helpsEvapotranspiration, or water released from the earth into the air through evaporation and transpiration (water lost from plants), is an important indicator when it comes to monitoring water needs and vegetation productivity of an area. This is very useful for agriculture: as a sector that is highly vulnerable to climate change, it needs accurate estimations of evapotranspiration rates to be able to react to changes and control water consumption. However, estimating evapotranspiration is anything but easy - and this is where Copernicus products and data can help. Links between water and evapotranspirationThe UN's World Water Report from March 2020 stated that global water use has increased by a factor of six over the past 100 years, and continues to grow at a rate of about 1% per year. There are many causes for this: the effects of climate change, increasing population, economic development or shifts in the patterns of consumption (e.g. high protein diet). This situation is expected to worsen in the future not only in places that already lack water, but also in places where water is plentiful today. Global food and water security are underpinned by water and energy cycles. Quantification of those cycles is critical for many applications in the fields of climatology, meteorology, hydrology and agronomy. Food security and economic growth depend on the availability of water and are threatened by both droughts and floods. Therefore, understanding the behaviour of water is of utmost importance to mitigate and manage climate risks in climate-sensitive sectors such as agriculture and is key to securing a sustainable future. Evapotranspiration and surface soil moisture rates are important parameters in understanding the natural processes driving the global hydrological cycle. The spatial-temporal variations of those two parameters are of key significance. Easy access to their reliable estimations is needed for efficient and sustainable natural resource management. However, it is not easy to accurately estimate evapotranspiration. There are many factors determining the evapotranspiration rate – for example land cover, vegetation type, humidity, temperature or wind speed. Satellites can provide spatially distributed information about these properties at regular time intervals. And the Copernicus programme provides products focused on these variables. Copernicus steps inThe global component of the Copernicus Land Monitoring Service provides a range of global products used to estimate evapotranspiration. Land cover maps give information about different types of physical coverage of the Earth’s surface. Several products can be used to estimate vegetation type and condition - for example Normalized Difference Vegetation Index (NDVI), Leaf Area Index (LAI), or Fraction of Absorbed Photosynthetically Active Radiation (FAPAR). They also provide information about the Land Surface Temperature, which is estimated from Top-of-Atmosphere brightness temperatures together with albedo, vegetation cover and soil moisture. Evapotranspiration is also one of the indicators in the Copernicus Climate Change Service (C3S). The AgERA5 9sa version of ERA5 with a set of indicators specifically relevant to agriculture, water resource indicators, such as those for soil moisture and water availability and also an indicator for evapotranspiration produced for four crops - wheat, maize, soybean and rice. Evapotranspiration and Land Surface Temperature monitoring will become even easier in the future. The new Copernicus Land Surface Temperature Monitoring mission will add high spatial-temporal resolution Thermal Infrared (TIR) observations to current Sentinel observation capabilities in support of agricultural management. This mission, which is currently in the preparatory phase, aims to complement the existing LST estimations currently provided globally by Sentinel-3. The 1 km spatial scale is however not sufficient to capture field-scale variability required for irrigation, crop growth modelling and crop water productivity reporting. The primary objective of the future mission is therefore to monitor the LST variability on the field scale across Europe and thus estimate evapotranspiration rates on the same scale. Two satellites teaming up to estimate evapotranspirationLooking at the Earth’s surface from space, we see that plots and fields differ not only in their geographical position, but also in shape or crop type. Those differences also affect the evapotranspiration rate. Parcel-specific estimates of evapotranspiration are key for sustainable agriculture and water management. With more exact knowledge of evapotranspiration rates, farmers can easily identify crops under water stress even before they show any visible signs of damage. At the same time, evapotranspiration rates can be used for irrigation and water consumption monitoring to make sure that irrigation water is not wasted. The ESA’s Sentinels for Evapotranspiration project (or Sen-ET for short) aimed to develop a methodology for estimating evapotranspiration at the scale of tens of meters, which would enable parcel-specific rates to be obtained. The trick is in combining optical and thermal data from two satellite missions from the Copernicus Sentinel family - Sentinel-2 and Sentinel-3. The sea and land surface temperature radiometer on Sentinel-3 acquires thermal images at a resolution of around 1 km on a daily basis. Sentinel-2 can, on the other hand, acquire images at a resolution of 10–20 m every three to five days thanks to its multispectral instrument. By using innovative machine learning data fusion, the companies involved in the Sen-ET project (Denmark’s DHI GRAS, Spain’s Institute of Agrifood Research and Technology (IRTA) and Denmark’s Sandholt) were able to create a tool to merge data from both missions to produce maps of evapotranspiration at a smooth 20 m resolution. The tool is available via an open source license. High-resolution land-surface temperature. Source: esa.int “By combining machine-learning sharpening methods and physical models of land-surface processes, we are able to optimally fuse the unique characteristics of the Copernicus Sentinel-2 and Sentinel-3 satellites. The resulting evapotranspiration maps, which cannot be produced by relying on one satellite type alone, show that the Sentinel constellation is larger than the sum of its parts,” said Radoslaw Guzinski from DHI GRAS. The final methodology was implemented as an open-source plugin to SNAP software and is available free to all users. Sen-ET imagery for Po Valley in Italy. Source: esa-sen4et.org A follow-up project to SEN-ET, called “Increasing Crop Water Use Efficiency at Multiple Scales Using Sentinel Evapotranspiration – ET4FAO”, aims to show how the developed method can be used for monitoring water use efficiency in the context of UN Sustainable Development Goal 6. The project is funded by ESA and implemented in collaboration with the Food and Agriculture Organization (FAO). The main objective of ET4FAO is to provide knowledge and tools that will enable FAO (and the general international development community) to accurately and consistently monitor agricultural water use at continental, national and local scales using primarily Copernicus data sources, thus enabling global improvements in water use efficiency As the custodian of SDG indicators 6.4.1 and 6.4.2, FAO is maintaining - under Dutch funding - the WaPOR portal which provides evapotranspiration estimates at multiple time and spatial scales. The ET4FAO project aims to evaluate the feasibility of improving WaPOR monitoring with Copernicus data sources including Sentinel-2, Sentinel-3 satellites and climate data from the Copernicus Climate Data Store. Furthermore, in the updated version of WaPOR, the Copernicus Global Land Cover product is used as a basis for the WaPOR Land Cover maps. SafeGuarding vineyards and orchards with FruitLookThe efficient use of water resources is of utmost importance, especially in regions already facing water scarcity and droughts. One of those regions is the Western Cape of South Africa, which is experiencing one of the longest and hardest-hitting droughts in living memory. The local agricultural sector is extremely vulnerable to this ongoing drought. Local farmers are facing many problems caused by it: inability to grow crops, financial distress, loss of jobs, etc. Drought is also affecting fruit and wine production in the area. Those two sectors represent almost a third of the province’s exports and are therefore a crucial part of the area’s economy. Production optimisation and the improved use of freshwater in these industries is being addressed by FruitLook, a platform which was developed by the Western Cape Department of Agriculture together with a Dutch company eLEAF. The first thing that is needed to optimise water use is to know how much water is consumed by crop production. This is described by actual evapotranspiration, which is quite difficult to obtain because in-situ measurements are costly, complicated, and do not show any spatial variation. This information gap is addressed by FruitLook, which uses Sentinel-2 data for their weekly data products. The platform provides users with diverse spatially distributed data to monitor crop development, detect and locate growth problems, and evaluate and improve water management. Farmers can therefore analyse crop growth and water consumption over time and space which helps them to make better informed decisions. FruitLook platform provides information about actual evapotranspiration, evaporation deficit and the efficiency of water use. Source: fruitlook.co.za FruitLook users have increased their water efficiency by between 10% and 30% in the time period between the launch of the platform in 2010 and the Copernicus Market Report published in 2019. You can find out more about FruitLook in the Copernicus4Regions 2018 publication (pp. 68-69). Spatial variation of actual evapotranspiration in the area of Stellenbosch Dryland White Wine vineyard. Source: fruitlook.co.za Copernicus supports stakeholders to better manage water resourcesSatellites have become a crucial ally and tool to address the complicated and challenging task of estimating evapotranspiration rates. Decision-makers, managers and farmers all around the world are realising the importance of having accurate and up-to-date information on evapotranspiration. Copernicus data and products are enabling projects and applications that are helping these stakeholders in their everyday struggle against drought and water overconsumption. Moreover, the precision and resolution of the data obtained are constantly improving with the development of even more sophisticated methods and technologies. |
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来源平台 | The Copernicus Programme |
文献类型 | 新闻 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/318182 |
专题 | 气候变化 |
推荐引用方式 GB/T 7714 | admin. OBSERVER: Evapotranspiration in the spotlight: how Copernicus helps. 2021. |
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