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Above the Clouds: Why Millimeter Wave Radar Is the Best Tool for Exploring Clouds?
As climate change and the frequency of extreme weather events increase, the scientific community is paying more and more attention to the study of clouds. The nature and dynamics of clouds directly affect the accuracy of weather predictions and climate models. In this regard, millimeter-wave radar is considered one of the best tools for exploring cloud structure and its dynamics. This high-tech radar system provides unprecedented resolution, allowing researchers to analyze the microphysical properties of clouds and even track their evolution.
How millimeter wave radar works
Millimeter wave radar is a radar system specially designed to monitor clouds. Its operating frequency range is generally between 24 and 110 GHz. Compared with traditional S-band radar, its wavelength is shorter, about 1 mm to 1.11 centimeter. This characteristic allows millimeter-wave radar to more sensitively detect smaller water droplets or ice crystals in clouds.
With its high temporal and range resolution, millimeter-wave radar can accurately identify the boundaries of clouds and their microphysical properties, thereby helping scientists better understand the process of cloud reflection, absorption and conversion of radiant energy.
Millimeter wave radar typically operates in the Ka-band at 35 GHz and the W-band at 94 GHz, the two frequencies with the best atmospheric transmission. Its high time domain and distance resolution allows researchers to obtain data between 1 and 10 seconds and observe different characteristics of clouds with an accuracy of several meters.
Diverse applications of millimeter wave radar
These radars are not only used to measure the physical properties of clouds, but are also widely used to study other important topics such as fog, insects and aerosols. Because millimeter-wave radar can detect almost all insect targets on a cloudless day, it has demonstrated its unique value in entomological research. In addition, these radars can also detect large aerosols, helping scientists understand the distribution and intensity of aerosols.
For example, the Cloud Profile Radar (CPR) operating on the CloudSAT satellite since 2006 is a successful application example of millimeter wave radar.
Technical characteristics of millimeter wave radar
Millimeter wave radar has a variety of advanced technologies, including polarization measurement capabilities, which can measure the size and shape of water droplets and ice crystals in clouds. The development of this technique is particularly important for the study of mixed-phase clouds in the atmosphere, since the shape of ice crystals is an important factor leading to errors in size and number concentration retrieval in vertically combined lidar and radar observations.
In addition, the diversity of millimeter wave radars is also reflected in their installation forms, including systems on the ground, in the air, and in space. For example, many scientific research aircraft are equipped with millimeter-wave radar, such as the HALO aircraft and Wyoming's KingAir research aircraft, which allows researchers to make cloud measurements at different altitudes and environments.
Future development and challenges
Although millimeter-wave radar has demonstrated excellent capabilities in cloud research, it still faces various challenges. For example, how to improve the resolution of radar data to accurately capture small changes and cope with the uncertainty of the atmospheric environment is still a difficult problem that the scientific community needs to overcome.
The Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission, which will be launched in March 2023, will also push this technology to new heights. This is the first space cloud profile radar with Doppler capabilities.
Final Thoughts
The development and application of millimeter-wave radar continues to advance our understanding of clouds, helping to improve the accuracy of weather forecasts and climate predictions. However, in the face of ever-changing weather systems, whether it is technology or methods, can we continue to make breakthroughs in exploration and pave the way for future climate research?
