Vertical profiles of atmospheric constituents describe the distribution of gases such as water vapor and trace gases with altitude, like a "layered map" of the atmosphere. These profiles are important for studying atmospheric processes and environmental change.

In a study published in Optics Letters, a research team led by Prof. ZHAO Weixiong from the Hefei Institute of Physical Science of the Chinese Academy of Sciences developed a compact spectroradiometer based on a virtually imaged phased array (VIPA), and demonstrated its first application in retrieving vertical profiles of atmospheric water vapor.

Researchers developed this miniaturized spectroradiometer which combines broadband spectral coverage with high spectral resolution. The spectroradiometer achieves a resolution of 0.023 cm^-1 over a 145 cm^-1 range (7535 - 7680 cm^-1), while maintaining a compact size of about 40 x 28 x 12 cm and a weight of approximately 8.5 kg.

With this spectroradiometer, researchers obtained high-resolution atmospheric transmittance spectra and retrieved vertical water vapor profiles using a selected absorption window and an optimal estimation method. The results allowed them to "see" how water vapor is distributed from the lower to the upper atmosphere, layer by layer.

This study shows that the VIPA-based spectroradiometer can enable high-precision atmospheric profiling, and has potential for building low-cost, distributed observation networks.

Schematic diagram of the water vapor profile measurement experiment using a VIPA spectrometer. (Image by TANG Tu)