A Climatology of Disdrometer Measurements of Rainfall in Finland over Five Years with Implications for Global Radar Observations

Abstract

To improve the understanding of high-latitude rain microphysics and its implications for the remote sensing of rainfall by ground-based and spaceborne radars, raindrop size measurements have been analyzed that were collected over five years with a Joss-Waldvogel disdrometer located in Jä rvenpä ä , Finland. The analysis shows that the regional climate is characterized by light rain and small drop size with narrow size distributions and that the mutual relations of drop size distribution parameters differ from those reported at lower latitudes. Radar parameters computed from the distributions demonstrate that the high latitudes are a challenging target for weather radar observations, particularly those employing polarimetric and dual-frequency techniques. Nevertheless, the findings imply that polarimetric ground radars can produce reliable ''ground truth'' estimates for space observations and identify dual-frequency radars utilizing a W-band channel as promising tools for observing rainfall in the high-latitude climate.

Climatological characteristics of raindrop size distributions in Busan, Republic of Korea

“…These features are similar to the distribution of D m observed in a high-latitude region at Järvenpää, Finland (Fig. 4 of Leinonen et al, 2012). For D m values > 1.7 mm, the PDF for convective rainfall is higher than stratiform rainfall.…”

“…The shape of the DSD is calculated as the ratio of D m to the standard deviation (SD) of D m (σ m in mm) (Ulbrich and Atlas, 1998;Bringi et al, 2003;Leinonen et al, 2012): …”

Ensemble mean density and its connection to other microphysical properties of falling snow as observed in Southern Finland

“…2. Assuming spheroids (Matrosov, 2007) and taking the typical vertical aspect ratio c/a = 0.6 (Korolev and Isaac, 2003;Matrosov et al, 2005b), we found that D PIP is roughly equal to 0.92 of a volume equivalent diameter. As can be seen, the conversion factor varies between 0.8 and 1.…”

Two months of disdrometer data in the Paris area

“…This approach has been implemented by numerous authors (Jaffrain and Berne, 2012a;Leinonen et al, 2012;Ryzhkov et al , 2005;Verrier et al, 2013;Gires et al, 2015). It should be mentioned that it relies on strong unrealistic hypothesis, notably the homogeneity of the DSD within a radar bin (see Gires et al, 2017b for a discussion of the limitations of this approach).…”