Our Slog (Ships Log) with a Satelite View
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Eric & Sherrell
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Posted on Sunday Sep 21, 2014
In attempt to take my mind off current events, I'm going to geek out and talk about something exciting to me, RapidScat. First off, RapidScat isn't something an animal does on the run. It refers to scatterometry where radio waves are scattered on the surface of something then the result is measured. In this case, scattering microwaves on the ocean reveals the wind direction and strength at the surface.
Back in 2009 the old QuickScat satellite antennas stopped rotating. This means that it stopped sending data consistently back to Earth. Well, most of the ocean is not monitored with surface instruments and QuickScat was absolutely the best space based tool for measuring the winds in critical places where dangerous winds can form (think hurricanes or Tehuantepec).
So in 2009 the ocean wind forecast accuracy took a punch to the gut and NASA scrambled to find a way to fix it. In just too years they cobbled together a great idea. They took QuickScat gear and found a way to mount it to the ISS and the ISS-RapidScat was born.
The RapidScat system launched today, 9/21/14 (along with the much hyped 3-d printer). Soon this instrument, the first pointed at the Earth from the ISS, will be spewing data to help calibrate and measure winds in all those remote parts of the world that are critical to sailors and people who model world-wide weather (NOAA).
We can expect to finally get highly accurate data on katabatic, thermal and storm generated winds. With this new accuracy NOAA is going to start a new study of the diurnal and semi-diurnal winds in the open ocean. Something many sailors experience but hard to believe. Thermal winds in the middle of the ocean?! Where's the land to heat it up?
It is well know from buoy observations that winds in the tropics can exhibit strong diurnal and semi-diurnal cycles, forced by solar heating or tidal effects respectively (Deser and Smith, 1998; Dai and Deser, 1999; Ueyama and Deser, 2008). In the tropical Pacific, semi-diurnal variations account for 68% of the mean daily variance of the zonal wind component, while diurnal variations account for 82% of the mean daily variance of the meridional wind component (Deser and Smith, 1998). These cyclic processes are known to be important in influencing the diurnal cycle of cloud formation and precipitation in the tropics, a key component of the Earth's water and energy cycles.
RapidScat will collect data over the course of years and this will be used to look at daily, weekly, monthly, and yearly wind patterns. Surprisingly this has never been done before and sailors rely on "Pilot Charts" which are averages from ships traveling the ocean averaged over decades. RapidScat will measure the entire planet every 2 days instead of just a point. It will reveal many hidden patterns of weather and winds.
This will be a revolution in understanding wind patterns and hopefully we can all through out those old Pilot Charts and update them with a much more accurate understanding of surface winds.