8: Satellites and Radar
- Page ID
- 9581
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)To understand and predict the weather, we first must measure it. In-situ or direct weather instruments must physically touch, or be exposed to, the air being measured. Examples include thermometers (temperature), barometers (pressure), hygrometers (humidity), anemometers (wind speed), wind vanes (wind direction), pyranometers (solar radiation), and rain gauges (precipitation).
Remote sensors infer the weather conditions by detecting the characteristics of waves propagating from distant regions. The waves can be electromagnetic (light, infrared, microwaves, etc.) or sound. Active remote instrument systems such as radar (RAdio Detection And Ranging) transmit their own waves toward the object and then receive the signal bounced back to the sensors. Passive ones, such as some satellite sensors, receive waves naturally emanating from the object.
Clouds, precipitation, and air molecules can totally or partially absorb electromagnetic radiation (Fig. 8.1a), scatter it into many directions (Fig. 8.1b), or reflect it (Fig. 8.1c). Objects also emit radiation (Fig. 8.1d) according to Planck’s law. Interactions of radiation with the Earth, air, and clouds create the signals that satellites and radar use.
This chapter covers the basics of weather satellites and radar. Other remote-sensor systems, not covered here, include lidar (LIght Detection And Ranging), and sodar (SOund Detection And Ranging).
- 8.0: Radiative Transfer for Satellites
- This page covers essential concepts in remote sensing using weather satellites, focusing on the role of radiometers in detecting varying wavelengths of electromagnetic radiation affected by atmospheric conditions. It discusses Planck’s law, blackbody radiance, and the radiative transfer equation, highlighting temperature influences and the significance of transmittance.
- 8.1: Weather Satellites
- This page covers satellite orbits and their mechanics, focusing on artificial satellites like weather and polar-orbiting satellites. It explains geostationary concepts, sun-synchronous orbits, and modern weather satellite imaging capabilities using infrared and water-vapor imagery. The interpretation of satellite data for cloud observation and temperature retrieval is addressed, along with radiative transfer equations for estimating temperature profiles through iterative methods.
- 8.2: Weather Radars
- This page covers various aspects of weather radar technology, including the use of microwaves, radar display types, beam propagation, and the radar equation for measuring reflectivity and precipitation. It highlights the principles of Doppler radar for tracking hydrometeor velocities, challenges like velocity folding, and the importance of dual-Doppler setups.
- 8.3: Review
- This page discusses passive sensors on weather satellites that detect electromagnetic radiation, providing cloud imagery and atmospheric data, particularly over oceans. It outlines the two primary satellite orbits: geostationary and sun-synchronous. Additionally, it covers active sensors like weather radars that use microwaves for precipitation analysis, wind profiling via the Doppler effect, and polarimetric techniques for improved rainfall estimation.
- 8.4: Homework Exercises
- This page covers web-based research tasks to improve understanding of remote sensing, satellite imagery, and radar technology, fostering critical thinking and practical applications in meteorology. It includes evaluations of satellite data, blackbody radiance, orbital mechanics, and radar interpretation, while analyzing effects like temperature errors and gravitational variations on satellite mechanics.
Thumbnail: Infrared image of storms over the central United States from the GOES-17 satellite. (Public Domain; NOAA)