A dropsonde is a weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

 reconnaissance device created by the National Center for Atmospheric Research
National Center for Atmospheric Research
The National Center for Atmospheric Research has multiple facilities, including the I. M. Pei-designed Mesa Laboratory headquarters in Boulder, Colorado. NCAR is managed by the nonprofit University Corporation for Atmospheric Research and sponsored by the National Science Foundation...

 (NCAR), designed to be dropped from an aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 at altitude to more accurately measure (and therefore track) tropical storm conditions as the device falls to the surface. The dropsonde contains a GPS receiver, along with pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

, temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

, and humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...

 (PTH) sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...

s to capture atmospheric profiles and thermodynamic data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

. It typically relays these data to a computer in the aircraft by radio transmission. The device's descent is usually slowed by a parachute, allowing for more readings to be taken before it reaches the water beneath.


Dropsondes are commonly used by Hurricane Hunters
Hurricane Hunters
The Hurricane Hunters are aircraft that fly into tropical cyclones in the North Atlantic Ocean and Northeastern Pacific Ocean for the specific purpose of directly measuring weather data in and around those storms. In the United States, the Air Force, Navy, and NOAA units have all participated in...

 to obtain data on hurricane
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

s, and these data are then fed into supercomputers for numerical weather prediction
Numerical weather prediction
Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic...

, enabling forecasters to track and predict what will happen to the hurricane. To obtain the data, an aircraft, either operated by NOAA or the U.S. Air Force flies into the hurricane. The dropsonde is released when the plane reaches the eye (center) of the hurricane, normally at around 10,000 feet (approx. 3,000 meters). The dropsonde sends back coded data, which includes:
  1. The date and time of the drop. Time is always in UTC.
  2. Location of the drop, indicated by the latitude
    In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

    , longitude
    Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

    , and Marsden Square
    Marsden square
    Marsden square mapping or Marsden squares is a system that divides a chart of the world with latitude-longitude gridlines between 80°N and 70°S latitudes into grid cells of 10° latitude by 10° longitude, each with a unique, numeric identifier...

  3. Standard isobaric surfaces: the height, temperature, dewpoint depression, wind speed
    Wind speed
    Wind speed, or wind velocity, is a fundamental atmospheric rate.Wind speed affects weather forecasting, aircraft and maritime operations, construction projects, growth and metabolism rate of many plant species, and countless other implications....

    , and wind direction
    Wind direction
    Wind direction is reported by the direction from which it originates. For example, a northerly wind blows from the north to the south. Wind direction is usually reported in cardinal directions or in azimuth degrees...

     at the surface, and at where the following air pressures are found as the dropsonde is descending: 1000, 925, 850, 700, 500, 400, 300, 250 hectopascals (hPa).
  4. Significant isobaric surfaces: the temperature and dewpoint depression of other levels of atmospheric pressure deemed significant
  5. Air pressure, temperature, dewpoint depression, wind speed and wind direction of the tropopause
    The tropopause is the atmospheric boundary between the troposphere and the stratosphere.-Definition:Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry...


Also included in the report is information on the aircraft, the mission, the dropsonde itself, and other remarks.


A driftsonde is a high altitude, durable weather balloon holding a transmitter and a bank (35 in the first models) of miniature dropsonde capsules. These water-bottle-sized transmitters have enough power to send information on their parachuted fall to the balloon, and then the balloon holds a transmitter powerful enough to relay readings to a satellite. The sensor packages are relatively inexpensive ($400 each), and the entire package is very cheap compared to a Hurricane Hunter plane. After being introduced in April 2007, around a thousand a year are expected to be used to track winds in hurricane breeding grounds off of West Africa, which are too far for practical operation of Hurricane Hunter planes.

Related articles

  • Aerology
  • Weather balloon
    Weather balloon
    A weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde...

  • Radiosonde
    A radiosonde is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required...

External links

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