Week 4 Interactive Exercise - Snow
In this exercise we’ll be using NASA’s Worldview tool, and we’ll be using the layers feature to look at snow cover. Snowcover reflects sunlight back into the atmosphere, helping to cool the Earth’s surface. Snowmelt is used for drinking water, water for crop irrigation, and can moisturize soil to reduce the risk of wildfire in many areas in the world. When snow melts in the spring, too much snow can cause springtime flooding.
- Go to NASA Worldview and close the ‘Welcome to Worldview’ box
- Click on the ‘Add layers’ button on the left-handside and type in ‘snow cover’ in the search bar
- Choose the Snow Cover (Normalized DifferenceSnow Index) layer then press the x in the top right corner to close the box.
- You should now be able to see global snow coverdata. This is NASA Terra MODIS Normalized Difference Snow Index (NDSI) snowcover layer which shows the presence of snow cover over land and water bodiesas an index related to the presence of snow. NDSI snow cover is derived fromthe cloud free snow reflectance sensed by the MODIS instrument, and hence thislayer shows presence of snow during daytime and under cloud clear conditiononly.
- Now press the globe symbol on the top right,this is the ‘switch projection’ button, and choose Arctic.
- Press the camera ‘set up animation’ button,which is on the bottom left-hand side, then set the animation start date to 1stJune 2003 and the end date to 1st June 2020. Set the increments to 1year and frames per second to 1.
- Now press the play button. What changes can yousee each year? June is the end of the spring period, and springtime snow coverextent has historically fluctuated over three- or four-year cycles, but recentobservations have shown long-term snow extent declines. What years have the lowest snow cover?
Course topics
The core videos of this course are labelled as topic videos.
We have also provided a range of optional further reading, links, and additional resources to help consolidate your learning. Here is a summary of what is available:
Topic links and resources
In each topic, once you have watched the video and read the accompanying text, you will find the following information:
- Optional Further Reading: These are external links to further reading.
- Featured Images and Animations: Below the text on each video page, you’ll find the featured images and featured animations.
- Interactives: On the 'Interactives' tab on relevent topic pages, you will find a satellite tracking application showing the current location of the satellites, a data viewer from the ESA WEkEO platform, as well as a data viewer, specially created for this course, allowing you to explore a selection of data relevant to the themes and topics in this course. (Please note that due to maintenance, the data viewer is currently unavailable).
Quizzes and comments
- Quizzes: At the end of each week there will be a quizz consisting of around five questions. These will help you consolidate your understanding of new topics, but are not scored. The feedback given with each answer also will also provide you with important information.
Weekly interactive exercises
At the end of each week, we have included a guided exercise, using interactive apps available on other websites, to help you become more familiar with looking at and working with EO datasets. You will be guided through the process of searching for, comparing and drawing conclusions from data relevant to some of the topics covered in that week.
