rehan

[nasa]

How Do Hurricanes Form?

Hurricanes are the most violent storms on Earth. People call these storms by other names, such as typhoons or cyclones, depending on where they occur.

The scientific term for ALL of these storms is tropical cyclone. Only tropical cyclones that form over the Atlantic Ocean or eastern and central Pacific Ocean are called “hurricanes.”

Whatever they are called, tropical cyclones all form the same way.

Tropical cyclones are like giant engines that use warm, moist air as fuel. That is why they form only over warm ocean waters near the equator. This warm, moist air rises and condenses to form clouds and storms.

As this warmer, moister air rises, there’s less air left near the Earth’s surface. Essentially, as this warm air rises, this causes an area of lower air pressure below.

This starts the ‘engine’ of the storm. To fill in the low pressure area, air from surrounding areas with higher air pressure pushes in. That “new” air near the Earth’s surface also gets heated by the warm ocean water so it also gets warmer and moister and then it rises.

As the warm air continues to rise, the surrounding air swirls in to take its place. The whole system of clouds and wind spins and grows, fed by the ocean’s heat and water evaporating from the surface.

As the storm system rotates faster and faster, an eye forms in the center. It is vey calm and clear in the eye, with very low air pressure.

Tropical cyclones usually weaken when they hit land, because they are no longer being “fed” by the energy from the warm ocean waters. However, when they move inland, they can drop many inches of rain causing flooding as well as wind damage before they die out completely. 

There are five types, or categories, of hurricanes. The scale of categories is called the Saffir-Simpson Hurricane Scale and they are based on wind speed.

How Does NASA Study Hurricanes?

Our satellites gather information from space that are made into pictures. Some satellite instruments measure cloud and ocean temperatures. Others measure the height of clouds and how fast rain is falling. Still others measure the speed and direction of winds.

We also fly airplanes into and above hurricanes. The instruments aboard planes gather details about the storm. Some parts are too dangerous for people to fly into. To study these parts, we use airplanes that operate without people. 

Learn more about this and other questions by exploring NASA Space Place and the NASA/NOAA SciJinks that offer explanations of science topics for school kids.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

Credits: NASA Space Place & NASA/NOAA SciJinks

[programming]

Introducing Graywater for Android

[engineering]

Introducing Graywater, Tumblr’s framework for decomposing complex items in a RecyclerView list in order to improve scroll performance, reduce memory usage, and lay a foundation for a more composition-oriented approach to building lists. With Graywater, the app now scrolls faster and crashes less often, and it also gives us a solid foundation for building new features faster and better than before.

On screens that display posts, such as the dashboard, the Tumblr Android app customizes one adapter across multiple screens. This approach results in a complex adapter, and over time, our previous solution became difficult to manage and hard to reason about since there was no consistent place for screen-specific behavior.

Furthermore, each post type had its own layout and viewholder, which meant that once a user encountered a post type they hadn’t seen on that screen before, the entire post had to go through the inflate, layout, and draw process. Once offscreen, the post would take up large chunk of memory in the RecyclerView pool.

Graywater solves this by rendering only the parts of a post that are visible and reusing the parts of a post that appear in other posts, such as the header and footer. By breaking up a large post into smaller components, the UI thread has to do less on each scroll. Even though there are more view types, each individual view type is smaller, so memory usage is lower.

For example, a photoset post may be composed of ten photos, one after another. In the previous architecture, a photoset layout with headers and footers would be inflated and the photo views added in afterwards. If the viewholder is recycled and the next photoset post only has one photo, the extra photo views are discarded. With Graywater, each individual photo view is recycled separately, which allows RecyclerView to reuse the photo views that appeared earlier in the photoset.

This idea is based off of Facebook’s post on a faster news feed and Components for Android, which have been open-sourced as Litho.

Graywater differs from other RecyclerView libraries by being small (a single file!) and flexible enough to work within your model architecture. For libraries like Epoxy and Groupie to accomplish sub-item recycling, complex items like posts need to be decomposed into smaller viewmodels beforehand. For Litho to flatten view hierarchies and perform fine-grained recycling, existing XML layouts need to be converted to layout specs.

By converting to Graywater, we’ve been able to reduce OutOfMemory errors by 90% and dramatically improve scroll performance. It is now much easier to add new item types that are composed of preexisting post components. We have also migrated screen-specific logic to the screen itself by injecting the customized component into the adapter. By open-sourcing Graywater, we’re hoping the Android community will achieve similar performance and architecture gains, and we’re excited to hear what the community builds next!

- @dreamynomad

[theislandofewan]

Mark Renton now and then ( 2016 - 1996 )