Related Experiment Video
Updated: Jun 16, 2026

13:31
High Speed Sub-GHz Spectrometer for Brillouin Scattering Analysis
Published on: December 22, 2015
Spectral band passes for a high precision satellite sounder
Applied Optics
|February 20, 2010
Summary
High-resolution atmospheric temperature soundings are achievable using specific carbon dioxide (CO2) band measurements. This method enhances vertical resolution in the troposphere and works even with broken clouds.
Area of Science:
- Atmospheric science
- Remote sensing
- Spectroscopy
Background:
- Accurate atmospheric temperature profiles are crucial for weather forecasting and climate modeling.
- Existing remote sensing techniques have limitations in vertical resolution and cloud penetration.
Purpose of the Study:
- To develop a method for high-vertical-resolution atmospheric temperature soundings.
- To demonstrate the feasibility of retrieving temperature and water vapor profiles, even under cloudy conditions.
Main Methods:
- Utilizing narrow band-pass measurements in the 4.3-micrometer band of carbon dioxide (CO2).
- Leveraging the pressure and temperature dependence of CO2 absorption coefficients and weighting functions.
- Identifying specific channels in the 4.2-micrometer region for enhanced resolution.
Main Results:
- Achieved approximately 2-km vertical resolution in the troposphere.
- Demonstrated the capability to obtain high-resolution temperature and water vapor profiles.
- Showcased the system's effectiveness in the presence of broken clouds.
Conclusions:
- Narrow band-pass measurements in the CO2 4.3-micrometer band offer superior vertical resolution for atmospheric sounding.
- The proposed system provides a robust method for temperature and water vapor retrievals, including surface and cloud top temperatures, under challenging cloud conditions.
Related Concept Videos
Bandpass Sampling
In signal processing, bandpass sampling is an effective technique for sampling signals that have most of their energy concentrated within a narrow frequency band. This type of signal is known as a bandpass signal. The key principle of bandpass sampling involves sampling the signal at a rate that is greater than twice the signal's bandwidth to prevent aliasing.
A bandpass signal has a spectrum with a lower frequency limit, denoted as ω1, and an upper frequency limit, denoted as ω2. The spectrum...
A bandpass signal has a spectrum with a lower frequency limit, denoted as ω1, and an upper frequency limit, denoted as ω2. The spectrum...
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
IR Frequency Region: X–H Stretching
In IR spectroscopy, signals produced by the X−H bonds (such as C−H, O−H, or N−H) can be observed in the frequency range of 2700–4000 cm–1. The C−H stretching vibration forms sharp bands in the region 2850–3000 cm–1. The presence of the O−H stretching vibration leads to the forming of an absorption band in the frequency range 3650–3200 cm−1. At the same time, N−H stretching can be confirmed by absorption bands in the 3500–3100 cm−1 range. Even though both O−H and N−H bonds vibrate at a similar...
IR Spectrum
When infrared (IR) radiation passes through a molecule, the bonds stretch or bend by absorbing the radiation. This absorption creates the molecule's absorption spectrum, which is the plot of its percentage transmittance versus wavenumber.
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
IR Spectrometers
There are two main infrared (IR) spectrophotometers: dispersive IR spectrometers and Fourier transform infrared (FTIR) spectrometers. In a dispersive IR spectrometer, a beam of infrared radiation produced by a hot wire is divided into two parallel equal-intensity beams using mirrors. One beam passes through the sample, while another is a reference beam. The beams then move through the monochromator, which separates the radiations into a continuous spectrum of different frequencies. The...
