Characteristics of raindrop size distribution (DSD) during the Meiyu season are studied using ground-based disdrometer measurements carried out in eastern China (Nanjing) from 2009 to 2011. The observational spectra are divided into convective and stratiform types. The results show that the histograms of the logarithm of the generalized intercept parameter (log10NW) and mass-weighted mean diameter of raindrops (Dm) are negatively and positively skewed, respectively, for both convective and stratiform rain. The absolute value of the skewness coefficient is higher for convective rain than for stratiform rain, in particular for the log10NW distribution. The mean log10NW and Dm values are 3.80 and 1.71 mm for convective rain and 3.45 and 1.30 mm for stratiform rain, respectively. The shape (μ)̶slope (Λ) relationship of the gamma distribution and the radar reflectivity (Z)̶rain rate (R) relationship are also derived for convective rain. The Z̶R relationship is found to be Z = 368R 1.21 . The interpretation of the statistical parameters obtained in this study and possible mechanisms that yield difference and similarity in comparison with those in previous studies are discussed.

[1] Freezing precipitation (i.e., freezing rain or freezing drizzle) is an extremely hazardous weather that can cause severe socioeconomic loss and compromise human safety. To better document and understand the microphysics of this type of precipitation, drop size spectra were collected with an optical disdrometer during a freezing precipitation event on 27 January 2008 in southern China. The drop size distribution (DSD) characteristics, the correlations between the shape (m), slope (L), and intercept (N 0 ) of the gamma distribution, and the relations between the reflectivity (Z) and rainfall rate (R) have been investigated. It was found that the DSDs of freezing precipitation were characterized by weak stratiform rain with a small mass-weighted diameter (D m , 0.63 mm) and a large normalized intercept (N w , 4.25 log 10 mm −1 m −3 ). This indicated that freezing precipitation was not formed by the melting of larger, dry snowflakes but by the melting of smaller, rimed ice particles. Furthermore, the derived m-L, N 0 -m, and Z-R relations are distinctly different from the convective rains or tropical stratiform rains reported in the literature.

A model for water (H 2 O) molecule, the structure of ice, snow and liquid water were presented, and the reasons of formation of their specific characteristics were modeled in good coincidence with observed data. (1) A stable quasi rigid molecule structure may be constructed by dominant trajectories of electrons round and between the H-O-H nucleus according with the laws of Columb's force and Kepler's movement rule. The core of the water molecule is a isosceles triangle with ratio of distances between nucleus: (H-H) 2 /(H-O) 2 =2.5, which would be surrounded by moving electrons and form an equilateral triangular pyramid (ETP Model) with 2 pairs of "+/-" electricity endpoints and edge length of 0.48017nm. (2) The "+/-" endpoint of a water molecule may attract other "-/+" endpoint in distance of less than 0.27 nm. A molecule may joints other molecule to have all their 4 planes parallel each other and the 6 molecules may joint as a hexagon loop with a common plane and then these loops may similarly be formed for each plane of the pyramid and extend to whole space and form the water ice structure with Zigzag Hexagon Tunnel-Vacancy System (ZHTVS Model) with porosity of ≥2.28. (3) A "sheet model" of desublimation like the snowflake is more possible phenomenon below 0°C in air, possessing the self-similarity with the hexagon-sexangle-six needle forms. (4) The liquid water has the same structure of the solid ice, but because there is 1/11 possibility to have an appearance of double electrons at one endpoint of the pyramid with "-" charge, so when the temperature is above 0°C, a part of water molecules on the frame may possess the energy for separating from the frame, and will move into the tunnel/vacancy, being as a "free water molecule". The total volume of the liquid water would decrease until to 4°C to the minimum. The ratio of density of solid water ice and liquid water is 11/12=0.916667. (5) The relationships of the specific characteristics of the water with its construction, such as density, expansibility, compressibility, specific heat capacity, electric and thermal conductivity, solubility for O 2 , H 2 S, NaCl, KCl, etc. were discussed and numerical modeled. The experiments of saturated solution of NaCl audiovisual indicated that there are tunnel/vacancy spaces for storing NaCl molecules/ions, and increasing the volume of 1/11 of water volume after freezing. (6) The surface structure of liquid water and the applications of research results are presented in other papers.

There are complex river-lake systems in the Taihu Lake catchment with total water surface area of 6174.7 km 2 , and population density of 1079/km 2 , including Taihu Lake water surface area of 2338 km 2. The water systems in this catchment have healthy aquaecosystems during long history. However, in some riverlets in this catchment the water quality was estimated as "acute toxicity for higher organisms" and over standards for many heavy metal elements content; there were no any living plants and macro organisms in the water body, because there were developed a series of industry with abundant release of heavy metals and difficult decomposition organic chemical components along the riverlets during last decades. The even more serious situation was observed in sediments of the riverlets. How to restore such riverlet into a healthy aquaeosystem with abound plants and higher organisms? The main strategy and techniques are described in this paper as summarizing a report of engineering in a riverlet in Wuxi New District during last years, which leads to restore the aquaecosystem into a healthy one with abundant surface plant cultured on floating islands and observed living fish, lobster, frog, toad, mollusk and others in the riverlet. The main techniques are: 1) softwall buffer technic; 2) floating eco-island technic by using which can culture any plant which can be cultured in solution; 3) immobilized nitrogen cycle bacteria (INCB) technic; 4) tattering esters and other big-molecule organic chemicals by using electronic pulse technic and photosensitization technic; 5) mist spray facility technic for improving dissolved oxygen in deep water layers; 6) technic for buffering and suppressing H2S release from water; 7) the appropriate portion of surface with cultured plant to the total water surface area is about 1/3; 8) Cress [Oenanthe Ljavanica (Bl.) DC.] and Myriophyllum verticilatum L. may be cultured in Taihu Lake catchment during the whole year as main plants with mosaic combination of other supplement plants in different seasons.

It was revealed that liquid water surfaces, including water drop's surface might generate Negative Water Ions/molecules to air with probability of (1/11) 8 among the water surface molecules by the author's previous paper. Three experiments by spraying water from shower nozzle had been performed on a bathtub covered by soft plastic film with thickness of 10 mm during Aug.-Sep. 2019. The densities of negative ion (DNI) and the atmospheric parameters had been recorded. The experimental results showed that DNI increased immediately after spraying waters in orders with big variations. High DNI up to -190000 ion/cm 3 were recorded under spraying water temperatures about 45°C. The sliding averaged (for 10 instant values) DNI were direct proportion to differences of saturated vapor pressure of spraying water and air vapor pressure, and increasing of relative humidity (under constant air temperature). The liquid water drops become positively charged after evaporation with negative ions. After stopping water spray DNI might keep at high level in a short time interval, then decrease gradually with vibrations by processes of mixing and water phase exchange in a cloud-fog system with -/+ air ions. These experiments proved that neutral liquid water drops may generate air negative water ions/molecules by evaporation and positive charged water drops.