Classification of Precipitation Types Using Fall Velocity–Diameter Relationships from 2D-Video Distrometer Measurements

Fall velocity–diameter relationships for four different snowflake types（dendrite,plate,needle,and graupel） were investigated in northeastern South Korea,and a new algorithm for classifying hydrometeors is proposed for distrometric measurements based on the new relationships.Falling ice crystals（approximately 40 000 particles） were measured with a two-dimensional video disdrometer（2DVD） during a winter experiment from 15 January to 9 April 2010.The fall velocity–diameter relationships were derived for the four types of snowflakes based on manual classification by experts using snow photos and 2DVD measurements：the coefficients（exponents） for different snowflake types were 0.82（0.24） for dendrite,0.74（0.35） for plate,1.03（0.71） for needle,and 1.30（0.94） for graupel,respectively.These new relationships established in the present study（PS） were compared with those from two previous studies.Hydrometeor types were classified with the derived fall velocity–diameter relationships,and the classification algorithm was evaluated using 3 × 3 contingency tables for one rain–snow transition event and three snowfall events.The algorithm showed good performance for the transition event：the critical success indices（CSIs） were 0.89,0.61 and 0.71 for snow,wet-snow and rain,respectively.For snow events,the algorithm performance for dendrite and plate（CSIs = 1.0 and 1.0,respectively） was better than for needle and graupel（CSIs = 0.67 and 0.50,respectively）.

A critical regulation of Th2 cell responses by RORa in allergic asthma

Allergic asthma is a chronic inflammatory disease of the lung and the airway,which is characterized by aberrant type 2 immune responses to otherwise unharmful aeroallergens.While the central role of Th2 cells and type 2 cytokines in the pathogenesis of allergic asthma is well documented,the regulation and plasticity of Th2 cells remain incompletely understood.By using an animal model of allergic asthma in IL-4-reporter mice,we found that Th2 cells in the lung expressed higher levels of Rora than those in the lymph nodes,and that treatment with an RORa agonist SRI 078 resulted in diminished Th2 cell responses in vivo.To determine the T cell-intrinsic role of RORa in allergic asthma in vivo,we established T cell-specific RORa-deficient^(f/f)fyf(Cd4creRora^(f/f))mice.Upon intranasal allergen challenges,Cd4creRora^(f/f)mice exhibited a significantly increased Th2 cells in the lungs and the airway and showed an enhanced eosinophilic inflammation compared to littermate control mice.Studies with Foxp3^(YFP-cre)Rora^(f/f)mice and CD^(8+)T cell depletion showed that the increased Th2 cell responses in the Cd4creRora^(f/f)mice were independent of Treg cells and CD^(8+)T cells.Our findings demonstrate a critical regulatory role of RORa in Th2 cells,which suggest that RORa agonists could be effective for the treatment of allergic diseases.