![]() The Loess Plateau of China is regarded as the most intensively eroded region in the world and soil erosion caused by raindrop impact is a common occurrence on agricultural land within this region. The algorithm is then used to simulate polarimetric X-band radar observations, which might mitigate uncertainties in the surface rainfall retrievals due to evaporation at far distances from the radars and in the case of beam blocking.Ībstract. A retrieval scheme for estimating the evaporation-related cooling rate and surface precipitation from polarimetric radar observations below the bright band is derived based on MRR observations. ![]() The second event is characterized by a lower initial ZDR < 0.5 dB with all raindrops evaporating before reaching the ground. During the first event, which exhibits an initial ZDR > 1.5 dB in the upper rain column, raindrops undergo relatively weak evaporation as deduced from the decrease of the small raindrop fraction observed by the MRR. Two events with significant rain evaporation, observed simultaneously by a polarimetric X-band radar and a K-band Micro Rain Radar (MRR), offer quite detailed insight into the evaporation process. The latter effect, however, can be reduced because of the increasing temperature toward the surface and may even lead to a decrease of ZDR toward the surface. Raindrop evaporation leads to a decrease of Z and an increase of ZDR toward the surface because of the depletion of small raindrops that evaporate first and thus enhance the mean raindrop size. A 1D model is used to examine the impact of raindrop evaporation on the evolution of the initial raindrop size distribution (DSD), the resulting reflectivity (Z), and differential reflectivity (ZDR) and surface rain rates. (2001a,b) developed algorithms for retrieving rain rate (R) as well as Do, Nw and m using βe f f in combination with the measurement pair (Zh, Zdr).AbstractThis study analyzes radar observations of evaporation in rain and investigates its impact on surface rainfall and atmospheric cooling rates. The slope of βe f f such that the same relation between Kdp /Nw and Do is preserved on average. Instead it pulls apart when it grows to around 4 millimeters or more. This time, the surface tension loses and the large raindrop ceases to exist. Once the size of a raindrop gets too large, it will eventually break apart in the atmosphere back into smaller drops. The surface tension at the top allows the raindrop to remain more spherical while the bottom gets more flattened out.Įven as a raindrop is falling, it will often collide with other raindrops and increase in size. ![]() At the top, small air circulation disturbances create less air pressure. The reason is due to their speed falling through the atmosphere.Īir flow on the bottom of the water drop is greater than the airflow at the top. Flattened on the bottom and with a curved dome top, raindrops are anything but the classic tear shape. ![]() The raindrop becomes more like the top half of a hamburger bun. The reason is the flow of air around the drop.Īs the raindrop falls, it loses that rounded shape. On smaller raindrops, the surface tension is stronger than in larger drops. The cause is the weak hydrogen bonds that occur between water molecules. This surface tension is the "skin" of a body of water that makes the molecules stick together. Raindrops start to form in a roughly spherical structure due to the surface tension of water. High in the atmosphere, water collects on dust and smoke particles in clouds.
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