A new particle imaging radiosonde “Rainscope” has been developed, and for the first time, particle fall velocity measurement functionality was added to a balloon-borne device. Rainscope can capture a clear still image of precipitation particles in a cloud when they interrupt an infrared beam, using a CMOS camera equipped with an electronic shutter. It can also record the time when a particle passes the upper and lower built-in infrared sensors, enabling measurement of the velocity of falling precipitation particles. For ground testing in rain and snow, a ground-based Rainscope showed raindrop/snowflake size-fall velocity distributions similar to those obtained in previous studies. In a comparison with a Parsivel2 disdrometer in rain, the Rainscope results were in good agreement with the distributions obtained by an adjacent Parsivel2. In a test flight of Rainscope into a stratiform cloud, raindrops, mostly melted particles, snowflakes in the process of melting, graupel, and snowflakes were observed. It was observed that the fall velocity varied depending on the type of solid precipitation particles.

The statistical and dynamical relationships between regional extreme precipitation events (EPEs) during wintertime in five Japanese regions and East-Asian synoptic weather patterns are addressed. 4 Two of the five weather patterns, the southerly flow (SF) and low pressure (LP), are associated with about 50% of EPEs in all the regions. A regional dependency is found, with SF being more likely to cause extreme precipitation in two regions in the south of Japan and LP in the other regions, respectively. The large-scale dynamics leading to EPEs in each region are assessed by a combined Lagrangian and Eulerian analysis. In the two southern regions, EPEs are predominantly associated with direct moisture supply from the subtropical oceans. This is modulated by the large-scale flow pattern of SF. In contrast, EPEs in the northern coastal areas of the Sea of Japan and the Pacific Ocean are influenced by anomalous moisture supply from the cyclone-induced moisture convergence modulated by LP. The eastern coastal region of the Sea of Japan shows a mixture of both these moisture supply mechanisms. The strong link between EPEs and synoptic patterns might help to improve predictions of extreme events, even on the sub-seasonal forecast horizon.

This study proposes a deep learning approach called SolaCam to accurately estimate solar radiation from the images captured by cameras. The proposed SolaCam performs deep learning by utilizing both image features and theoretical maximum solar radiation that vary with time and location. The trained model is capable of accurately estimating solar radiation on the ground surface from sky images captured by smartphones, fixed-point cameras, and other devices. The developed SolaCam can use a remote sensing function, which estimates solar radiation, on inexpensive camera-equipped devices.

We evaluated the mass concentration levels and long-term trends of black carbon (BC) in the historical and future scenario simulations using 12 climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) for East Asia, the region with the largest anthropogenic emissions. By comparing them with surface observations at two regionally representative sites, Fukue and Noto, for the period of 2009-2020, we found that the CMIP6 multi-model mean was approximately two times higher than the observed BC concentrations and did not reproduce the observed decreasing trend before 2014. Sensitivity simulations of emission inventories using a chemical transport model, GEOS-Chem, suggested that the overestimation and increasing trend of Chinese BC emissions in the CMIP6 historical inventory (CEDSv2017-05-18) were responsible for the higher concentrations and opposite trends in the CMIP6 BC simulations. The direct radiative effect of BC for CEDS was estimated to be 72% larger in East Asia than that for the ECLIPSEv6b inventory, which reproduced the observed BC concentrations reasonably well.

An alternative method to estimate the differential reflectivity (ZDR) bias is proposed. The method collects data bins with “weak echo” by the liquid hydrometeor, which theoretically should be spherical (not oblate) to result in a ZDR of ∼0 dB, to calculate the averaged ZDR as the bias. The obtained results are comparable to those from traditional “birdbath” scans in hourly data to prove the validity. The present method can be used to better sample the temporal variation, without operating special scans, such as birdbath scans. The supplemental method for the short-pulse region, when it was difficult for the weak-echo method to directly obtain the valid result, is also demonstrated.