THORpex
Application
This page shows a simulation using stratospheric balloons
to achieve THORpex objectives. THORpex
is a loose acronym for "The Hemispheric Observing
system Research and Predictability Experiment".
This simulation demonstrates a possible targeting test
mission scenario that takes advantage of trajectory
control for observations. The goal is to obtain multiple
dropsonde samples in regions of high sensitivity for
2- to 10-day weather forecasts in the western U.S. This
region of high sensitivity is the Pacific Ocean in Northern
Hemisphere winter.
In this simulation, the Red trajectory shows an uncontrolled
balloon floating at 35 km. The Green trajectory represents
a "simple control" balloon at 35 km whose
trajectory is being controlled by a StratoSail®
BGS at 20 km. The objective of the simple trajectory
control algorithm for the Green balloon is to maintain
45°-north longitude at all times. Thus, if the balloon
is south of 45°, the BGS pushes the balloon north
if possible, and vice versa. The Blue trajectory shows
a balloon at 35 km with the same 20-km StratoSail®
BGS as the green balloon. However, the Blue balloon
uses a sophisticated trajectory control algorithm. At
various times throughout the flight, the Blue balloon
is commanded to maintain latitude or to move toward
or away from the center of an observed vortex. Control
actions are taken based on the structure of the wind
field at the time the control decision is made. No forecast
information is utilized.
This simulation begins at November 1, 2000 and ends
on March 1, 2001, 120 days in duration. Only 15 days
of the trajectories (starting from December 1, 2000)
are shown for clarity. The arrows on the trajectories
indicate direction of travel and are spaced at 6-hour
intervals to demonstrate locations of possible sonde
drops. Real stratospheric winds from the time of the
flight are used for calculating balloon trajectories.
The table below gives the number of sonde observations
in the region of interest over the 120 days of simulation.
Trajectory |
Number of
Sonde Drops in High-Sensitivity Region |
Uncontrolled (Red) |
12 |
Simple Control (45°) (Green) |
107 |
Sophisticated (Blue) |
175 |
These simulations demonstrate the effectiveness of
trajectory control capabilities for targeted balloon
observations.
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